RECYCLING OF SPENT LITHIUM NICKEL-COBALT

BATTERIES THROUGH LEACHING OF NICKEL AND

COBALT FROM CATHODE MATERIAL

By

Kristian Monteiro

An honours research thesis submitted to Murdoch University

In fulfilment of the requirements for the Degree of

Bachelor (Hnrs) in Chemical and Metallurgical Engineering

Department of Chemical and Metallurgical Engineering Murdoch University 2018 Supervisor: Dr Aleks Nikoloski

ii | P a g e Author’s Declaration

I declare that the following work presented is my own, unless otherwise specified, and the research carried out was under the supervision of Dr Aleks Nikoloski and Dr. Asem Mousa during the years of 2017-2018. This thesis is submitted as part of the requirements for the Bachelor (Hnrs) of Chemical and Metallurgical Engineering degree to the school of Engineering and Information Technology, Murdoch University, Western Australia. This thesis has not previously been submitted for a degree at any tertiary education institution.

Kristian Monteiro 7th June, 2018

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iv | P a g e Abstract

This research paper investigates a hydrometallurgical approach that includes the leaching of spent lithium-ion battery cathode material. The targeted elements to be recovered are cobalt and nickel which are identified to be the cost drivers in the lithium-ion battery to date. The observation of parameters surrounding the leaches give a brief but excellent understanding into the recovery mechanisms and extraction stages of nickel and cobalt in a sulphuric acid and hydrogen peroxide medium.

The recycling of lithium ion batteries is trending to become one of the major processes in the recycling industry heading forward. As more appliances and technologies look to lithium ion batteries for an energy storage system, it is crucial that the supply is not hindered with the increase in demand for the battery. The eventual commercialization of a hydrometallurgical process will most likely be based around the leaching of the spent lithium ion batteries and the recovery of valuable metals.

Although further test work is necessary to achieve credible and reliable results, this thesis demonstrates the effect of the change in parameters within the test work which leads to the recovery of nickel and cobalt from waste lithium ion batteries. 113.2 % cobalt and 98.6 % nickel were recovered with the leaching of cathode material while 109.6 % cobalt and 100.5 % nickel were extracted with the leaching of separator material. The increased recovery at a lower cost will generally lead to a commercialised process that will in the future be used to process all spent lithium- ion batteries.

This thesis looks at the broader scope of the energy storage system market, identifies the cost driver and looks to decrease that cost driver for a viable and cost effective process.

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vi | P a g e

Acknowledgements

As I look back on the last four and a half years of this degree, it is staggering to see how much has changed. It is a reminder of the good people who have made all of this possible. I firstly would like to thank Dr Aleks Nikoloski for his ongoing support in not only this thesis but also throughout the degree. Having a supervisor with so much knowledge and willingness to guide allowed the process of this last step to be relatively smooth. The enthusiasm expressed in each meeting will not be forgotten, thank you. I would also like to thank Dr Asem Mousa for his willingness to give up time and valuable knowledge that helped with the research. Dr Mousa’s extensive knowledge into battery systems helped me with the initial stages right through to the test work of this thesis. I would like to thank the tutors and lecturers I have had the privilege of studying under throughout my time in this degree. Notably associate professor Gamini Senanyake for his teachings throughout the years. To my friends who I have met pre-university and friends I have made in university, thank you for supporting and encouraging throughout these years. Bryce, Mike, Shannon, Lia and Daniel, thank you for the laughs and hangouts over the last couple of years. My girlfriend Raquel, thank you for the unwavering support over the last 4 years. Thank you for your patience and guidance, without you this would not have been possible. Thank you for your sacrifice at times to put your life on hold for me. Last but not least to my family. Mum, Dad, Josh, Luke and George, it is not possible to thank you enough for the support, wisdom and encouragement through some of the hardest times in my life. I hope that in some way, shape or form I have made you proud. I could not have asked for better people to be by my side through my university life. For this, thank you God.

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Contents

Chapter 1 – Introduction ...... 1

1.1 Overview ...... 1 1.2 Motivation for Study ...... 2 1.3 Leaching Using Hydrogen Peroxide and Sulfuric Acid...... 3 1.4 Scope and Objectives ...... 4 Chapter 2 – Literature Review ...... 5

2.1 Introduction ...... 5 2.2 Background ...... 5 2.2.1 Lithium – Ion Batteries ...... 6 2.2.2 Zinc - Bromine Batteries ...... 7 2.2.3 Nickel Metal – Hydride ...... 8 2.2.4 Vanadium Redox Flow ...... 9 2.2.5 Lead – Acid ...... 10 2.3 Battery Operation and Chemistry ...... 11 2.3.1 Lithium – Ion ...... 11 2.3.2 Zinc – Bromine ...... 12 2.3.3 Vanadium Redox Flow ...... 13 2.3.4 Nickel Metal – Hydride ...... 14 2.3.5 Lead – Acid ...... 15 2.4 Leading Developers ...... 17 2.5 Battery Materials & Chemicals ...... 19 2.5.1 Chemical Compositions and Concentrations ...... 20 2.5.2 Varied Materials ...... 20 2.6 Processing ...... 23 2.7 Major Ore Deposits and Mineralogy ...... 24 2.7.1 Vanadium ...... 24 2.7.2 Nickel ...... 25 2.7.3 Lead ...... 26 2.7.4 Lithium ...... 26 2.7.5 Zinc ...... 27 2.7.6 Cobalt ...... 27 2.7.7 Reserve and Production Summary ...... 27

ix | P a g e 2.8 Processing Options ...... 29 2.8.1 Nickel ...... 29 2.8.2 Lead ...... 29 2.8.3 Vanadium ...... 30 2.8.4 Cobalt ...... 30 2.8.5 Zinc ...... 31 2.8.6 Lithium ...... 31 2.8.7 Processing Summary ...... 31 2.9 Battery Effectivity & Efficiency...... 32 2.9.1 Operational Cell Voltage ...... 32 2.9.2 Specific Capacities ...... 33 2.9.3 Recharge Time ...... 34 2.9.4 Operable Temperatures ...... 34 2.9.5 Battery/Cycle Life ...... 35 2.9.6 Effectivity and Efficiency Summary ...... 35 2.10 Cost Comparisons ...... 36 2.10.1 Lithium Ion Battery ...... 36 2.10.2 Vanadium Redox Flow Battery ...... 38 2.11 Critical Cost Drivers ...... 39 2.11.1 Sensitivity Analysis ...... 40 2.12 Summary ...... 41 Chapter 3 – Experimental Methods ...... 43

3.1 Introduction ...... 43 3.2 Sample Source, Reagents and Equipment ...... 43 3.2.1 Lithium ion batteries ...... 43 3.2.2 Acids ...... 45 3.2.3 Catalyst ...... 45 3.2.4 Equipment ...... 46 3.3 Method ...... 47 3.3.1 Battery Discharge ...... 47 3.3.2 Battery Deconstruction ...... 48 3.3.3 Material Cleaning ...... 50 3.3.4 Small-Scale Leaches ...... 51 3.3.5 AAS & ICP-MS Analysis ...... 54 Chapter 4 - Cathode Characterisation ...... 56

x | P a g e 4.1 External Cathode Characterisation Assays ...... 56 Chapter 5 - Leach Results ...... 58

5.1 Time Variable Results ...... 58 5.1.1 Change of pH on Time Leach ...... 60 5.2 Temperature Variable Results ...... 62 5.2.1 Change of pH on Temperature Leach ...... 63 5.3 Acid Concentration Variable Results ...... 64 5.3.1 Change of pH on Acid Leach ...... 65 5.4 Hydrogen Peroxide Concentration Variable Results ...... 66 5.4.1 Change of pH on Peroxide Leach ...... 68 5.5 Leach Optimization ...... 69 Chapter 6 – Conclusions and Recommendations ...... 72

6.1.1 Conclusions ...... 72 6.1.2 Recommendations ...... 73 Chapter 7 - References ...... 76

xi | P a g e Tables, Equations and Figures

Table 2.2. 1: Cathodic and anodic reactions of the most promising battery systems ...... 9 Table 2.3. 1: Positive electrode materials with given capacities (Linden 2002) ...... 11 Table 2.3. 2: Conductivity in mS/cm for 1 M of LiFP6 in different solvents (Linden 2002) ..... 12 Table 2.3. 3: Molecular weight and solubility data of the electrolytes (Zabavchik n.d.) ...... 12 Table 2.3. 4: Properties of sulphuric Acid Solutions and change in Ah (Linden 2002)...... 16 Table 2.5. 1: Materials for anodes, cathodes and electrolytes for the investigated battery systems (Linden 2002)...... 19 Table 2.5. 2: Sodium alanates used as metal-hydride cathodic materials (Sakintuna 2006). . 22 Table 2.7. 1: Elemental reserves and production for 2016 (USGS 2016)...... 24 Table 2.9. 1: Characteristics of each battery system compared to each other (Linden 2002)...... 32 Table 2.10. 1: Cost breakdown of lithium ion battery (cobalt cathode) (Novo 2016)...... 37 Table 2.10. 2: Cost Breakdown of the vanadium redox flow battery (VRFB) (Moore 2013)... 38 Table 3.2. 1: Battery weight breakdown for a lithium ion battery ...... 45 Table 3.3. 1: Mass Percentage for components of batteries ...... 51 Table 3.3. 2: Variable Time Leach Variables ...... 51 Table 3.3. 3: Variable Temperature Leach Variables ...... 51 Table 3.3. 4: Variable Acid Concentration Leach Variables ...... 52 Table 3.3. 5: Variable H2O2 Concentration Leach Variables ...... 52 Table 3.3. 6: Optimisation Leach Variables...... 52 Table 4.1. 1: Cathode, Anode and Separator characterisations via ICP-MS in standard ppm concentrations ...... 56 Table 5.5. 1: Optimisation parameters for both cathode and separator material...... 69 Table 5.5. 2: Cobalt and nickel recoveries in both cathode and separator materials...... 70

[1] Leaching Rate Equation……………………..………………………………………………………………………… 46 [2] Chemical Reaction For Hydrogen Peroxide…………………………………….……………………….…….46 [3] pH Equation…………………………………………………………………………………………………………………..61 [4] Arrhenius Equation ……………………………………………………………………………………………………….62

xii | P a g e Figure 1. 1.1: Rechargeable battery powered car sourced by Wikimedia Commons ...... 1 Figure 2.2. 1: Operation of the lithium-ion cell showing charge and discharge adapted from Roy Poulomi 2015 ...... 6 Figure 2.2. 2: The operation of the zinc-bromine cell showing charge and discharge adapted from BSEF 2017 ...... 7 Figure 2.2. 3: Operation of nickel metal-hydride cells showing charge/discharge adapted from Kawasaki 2017 ...... 8 Figure 2.2. 4: Operation of the lead-acid cell showing charge and discharge adapted from Kuphaldt 2010 ...... 10 Figure 2.3. 1: The vanadium redox flow battery operation adapted from Australian Vanadium Limited 2017 ...... 14 Figure 2.3. 2: Alkaline electrolyte (NaOH and KOH) conductivities adapted by Rand 2011 ... 15 Figure 2.3. 3: Cell voltage and rated capacity data in the lead-acid battery adapted by Vincent 1984 ...... 16 Figure 2.7. 1: World selected element reserves as of 2016...... 25 Figure 2.7. 2: World elemental production of each investigated element in 2016...... 26 Figure 2.7. 3: Major lithium processing operations adapted from British Geological Surveys 2008 ...... 28 Figure 2.8. 1: Sphalerite mineral containing zinc sourced by Wikimedia Commons ...... 30 Figure 2.9. 1: Sumitomo’s redox flow battery shown as a grid scale adapted from Sumitomo Electric 2017 ...... 33 Figure 2.9. 2: Projected installed capacity for three different batteries adapted from MSE Supplies 2015 ...... 34 Figure 2.10. 1: Lithium ion battery cost breakdown into cathodic elements adapted from Berger 2012 ...... 36 Figure 2.10. 2:Capital cost fractions pie chart showing distribution of costings for lithium ion...... 37 Figure 2.10. 3: Capital cost fractions pie chart showing distribution of costings for VRFB. .... 38 Figure 2.11. 1: Sensitivity web diagram for the fluctuation of each vanadium battery component ...... 40 Figure 2.11. 2: Sensitivity web diagram for the fluctuation of each lithium-ion battery component ...... 41

xiii | P a g e Figure 3.2. 1: Lithium ion battery breakdown (Physics Central 2017) ...... 44 Figure 3.3. 1: Discharging mechanism for battery ...... 47 Figure 3.3. 2: 18650 lithium ion battery outer-shell components ...... 48 Figure 3.3. 3: Inner-battery components ...... 49 Figure 3.3. 4: Separated components showing cathode, separator and anode material respectively ...... 49 Figure 3.3. 5: Aluminium foil with attached cobalt and nickel material ...... 50 Figure 3.3. 6: Event tree showing the method for leaching of spent lithium ion battery cathode material ...... 53 Figure 3.3. 7: Nickel standard curve 1 showing error and equation ...... 54 Figure 3.3. 8: Cobalt standard curve 1 showing error and equation ...... 54 Figure 3.3. 9: Nickel standard curve 2 showing error and equation ...... 55 Figure 3.3. 10: Cobalt standard curve 2 showing error and equation ...... 55 Figure 5.1. 1: Pink leach liquor with 40-minute time leach ...... 58 Figure 5.1. 2: Time vs Co & Ni Extraction ...... 59 Figure 5.1. 3: pH variation of solution during precipitation (Sohn 2006) ...... 60 Figure 5.1. 4: Time vs Delta pH ...... 61 Figure 5.2. 1: Leach temperature vs leach liquor concentration of nickel and cobalt ...... 62 Figure 5.2. 2: Temperature vs Delta pH ...... 63 Figure 5.3. 1: H2SO4 Concentration Vs Leach Liquor concentration of nickel and cobalt ...... 64 Figure 5.3. 2: H2SO4 Concentration Vs Leach Liquor concentration of various elements (Nayl 2017)...... 65 Figure 5.3. 3: H2SO4 concentration Vs Delta pH ...... 65 Figure 5.4. 1: Hydrogen Peroxide addition % (H2O2) Vs cobalt and nickel concentration in leach liquor ...... 66 Figure 5.4. 2: Hydrogen Peroxide Addition Vs Leaching Percentage of various elements (Nayl 2017) ...... 67

Figure 5.4. 3: H2O2 % Vs Delta pH ...... 68

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Chapter 1 – Introduction

1.1 Overview

As the demand for advances in technology presents itself, supply is critical in sustaining this advancement. Renewable energy is crucial to sustain modern day technology as shown by multiple upcoming innovative products. The electric car is most likely to be the biggest ‘new’ technology which is made possible through the use of rechargeable batteries and renewable energy. These rechargeable batteries now power a lot of modern day technology such as mobile phones and portable computers. As population increases at a rapid rate, the demand for this technology is also increasing at a rapid rate suggesting a shortage of rechargeable batteries may be a factor into stopping civilization in progressing.

The objective of this research was to reduce the costing of a significant battery by the method of cost driver identification and process optimization. By reducing the cost of processing of energy storage components, the particular battery system has a higher chance of being sustainable for the future and may even prove some batteries to be valid for particular uses in technology.

Figure 1. 1.1: Rechargeable battery powered car sourced by Wikimedia Commons 2018

1 | P a g e Finding a more efficient technique of processing may reduce tailings hence increasing production, increase production through a faster processing method or reducing cost of the processing through a cheaper and more affordable process. The minimization of any of these factors may lead to the commercialization of a battery or make it more viable and sustainable.

Once a cost driver is determined for the most applicable energy storage system, test work can begin into the minimizing in cost of that component which would ideally lead to advances in the battery production.

In this research project, it was found that the cathode component in the Lithium ion battery was the cost driver. A total of 27 % of the total battery cost was accountable to the cathode consisting of mainly nickel and cobalt. As this was the largest component by percent within the battery systems studied and also the battery that is ideal in most rechargeable battery applications, it was chosen to be researched. The vanadium battery also had a large cost driver being the vanadium electrolyte, this battery however is still in relative early development in terms of processing and is not as widely used as the lithium ion battery.

1.2 Motivation for Study

As the lithium ion battery was predicted to have the biggest impact on the energy storage system market, decreasing the cost driver was the selected point of research. A similar process has already been conducted in 2017 by Nayl et al. It was interesting to see a recycling process used to decrease the major cost driver in the lithium ion battery. Using spent lithium ion batteries seemed quite relevant as the demand for lithium ion batteries is increasing and the spent cathode is still relatively unchanged after discharge.

As the lithium electrolyte decreases in capacity and electrical conductivity characteristics over its long life, the important matter was the cathode. If the cathode can be recovered, the costliest part of the battery may be recycled. Nayl et al (2017) used a leaching process with hydrogen peroxide and sulfuric acid which seemed relevant to the metallurgy and process side of the production or recycling of lithium ion batteries.

A similar process of recycling is the intention for the test work however using conditions that will prove even less costly may be the difference between a useable and non-useable process.

2 | P a g e 1.3 Leaching Using Hydrogen Peroxide and Sulfuric Acid

A cheap yet effective type of acid needs to be used to recover the cobalt and nickel into solution. It is important that the conditions in the leach are relatively cost effective to make the process successful and relevant. Using an inorganic acid is usually cheaper and can prove to be very effective in recovery of metals (Yan, 2014). Although the inorganic acid may achieve less recovery, it could be the difference between a successful or non-successful recycling process due to its low cost.

High recoveries of cobalt and nickel were recorded by Nayl et al (2017). Using the process of a hydrogen peroxide and sulfuric acid leach, up to 97% recovery was achieved. This high recovery shows that the process is effective however if conditions can be tweaked to achieve similar recoveries at a lower cost, it may make it a viable process.

Using hydrometallurgy processes to recycle battery materials is not a new idea and has already been used in nickel metal hydride battery recycling (Holmberg, 2017). Using a similar process for lithium ion batteries is the next step to decrease overall costings for the battery which proves to be a large factor in modern day technology.

Decreasing the demand for primary cobalt and nickel deposits and stockpiles, the cobalt and nickel used in lithium ion batteries can be recycled which makes it a much more sustainable and cheap energy storage system.

3 | P a g e 1.4 Scope and Objectives

The recovery of cobalt and nickel from a spent lithium ion battery’s cathode material in a cost effective process in turn decreasing overall production cost of the lithium ion battery is the sole aim of this report. Having this clear scope in mind, setting out basic objectives is a good method to achieve success. These objectives include the following process variables;

• Altering hydrogen peroxide concentration to achieve the best recovery to cost ratio • Finding optimal time for leach to achieve maximum recovery • Finding optimal temperature for maximum recovery • Finding optimal sulfuric acid concentration to achieve the highest recovery • Combining all optimal variables to achieve the highest recovery possible in a sulfuric acid - hydrogen peroxide leach

4 | P a g e Chapter 2 – Literature Review 2.1 Introduction

Identifying cost drivers associated with different batteries allows for advances in the reduction of production costs for relevant energy storage systems. Chapter 2 studies the exploration of the largest cost driver in the given batteries investigated to find the biggest influence on the market. The literature review will be the guideline for the test work needed to locate and reduce the largest cost driver. A process of elimination technique not only identifies cost driver objectives but also ore reserves and battery relevance in terms of efficiency in today’s context. By completing this compact study and investigating each energy storage system individually, comparisons can be made to further the research in a positive and useful direction.

It was critical that the energy storage systems explored needed to be broad and an open minded study was undertaken. The batteries and their given uses proved it to be a difficult selection process therefore all systems needed to be characterized in topics to identify the most relevant battery to be further researched.

2.2 Background

Some batteries that will be studied include lithium-ion, zinc- bromine, nickel metal hydride, lead-acid and also the vanadium redox flow battery. These batteries have been developed to be the most practical, efficient and cost effective for modern day applications. Development of these batteries have included substitution and alteration of given materials, chemicals and conditions. The batteries investigated have been chosen due to their market demand for energy storage considering integration of wind and solar energy (ESA, 2015).

5 | P a g e 2.2.1 Lithium – Ion Batteries

Lithium-ion batteries are one of the latest batteries to take over the market and be used in a wide range of applications. Sony Energytec Incorporated developed the battery in 1991 after findings from John Goodenough at Oxford University suggested that lithium-cobalt oxides and lithium-nickel oxides could create rechargeable batteries (Brodd, 2012). Rechargeable batteries and electric car batteries are two of the main applications that lithium is processed for, taking over conventional lead-acid batteries (Hecimovich, 2015).

As lithium-ion batteries continue to grow in market value and usage around the world, one of the main questions that need to be asked is; how long will the lithium reserves last? Stanford University suggested that if all cars were to be replaced with electric engines using the lithium ion rechargeable battery, 82 % of the world’s lithium reserves (economically viable to process) would be ‘consumed’ (Eason, 2010). This suggests that lithium reserves may be sustainable now however may not be with an increased process rate, this is shown in table 2.7.1. With this figure not accounting for population increase, lithium shows to be a short term solution. This underlying problem shows that lithium will not be able to keep up with the world’s supply and demand and therefore alternative energy storage systems should be investigated. Although lithium production won’t be able to sustain human needs after a period of time, the lithium- ion battery may be the bridging between current or previous technologies to future technologies that are more sustainable and viable in the long term.

Figure 2.2. 1: Operation of the lithium-ion cell showing charge and discharge adapted from Roy Poulomi (2015)

6 | P a g e 2.2.2 Zinc - Bromine Batteries

Zinc-bromine batteries are energy storage systems that utilize a redox flow technique that allows for plating of zinc onto anode plates. The zinc – bromine batteries were patented in the late 1800’s but not thoroughly researched until the 1970’s by Exxon. The reason for this was due to the highly volatile chemical nature of bromine that was not suitable for battery systems as it posed as a severe risk and also due to its high discharge rate. It was not until the 70’s that a new electrolyte was considered (being zinc-bromide). The zinc-bromine battery was effective with the use of the zinc-bromide electrolyte as the regeneration of zinc-bromide could occur through reactions with the introduction of a charge (Rand, 2001). The zinc- bromine flow battery is effective in that it can discharge large amounts of energy and also can be scaled up depending on its application relatively easily, however its downfall is the toxicity of the zinc bromide electrolyte and its high costing of materials (ESA, 2017). Figure 2.2.2 shows the operation and reactions occurring in a zinc-bromine battery.

Figure 2.2. 2: The operation of the zinc-bromine cell showing charge and discharge adapted from BSEF (2017)

7 | P a g e 2.2.3 Nickel Metal – Hydride

Nickel metal-hydride batteries are another energy storage system that have been used extensively in the last 50 years. As a replacement for nickel-cadmium batteries, nickel metal- hydride batteries use a similar battery mechanism to NiCd however they don’t contain the toxic element of cadmium. Toxicity of cadmium was not the only disadvantage of the nickel- cadmium battery, the discharge rate was much too high for consumer use and interest which urged developers to invent an alternative battery with longer shelf life, hence the invention of the NIMH battery (Rosch, 2001). Stanford Ovshinsky was the inventor of the NiMH battery in 1992 (Lambert, 2016). The battery technology incorporates hydrogen stored in the alloys which can act as a cathode. This change with the energy storage system increased the shelf life for the battery which aided in the eventual commercialization. Although the shelf life of the battery increases, compared to other batteries, nickel metal-hydride cell systems still are at a disadvantage with service life when deep discharge occurs. This is one of the main problems of the nickel metal-hydride battery and is crucial to the battery operation as consumers want batteries with longevity (Green Ion, 2016). This battery configuration is now used in car batteries and also many portable devices such as phones, PC’s and televisions.

Figure 2.2. 3: Operation of nickel metal-hydride cells showing charge/discharge adapted from Kawasaki (2017)

8 | P a g e 2.2.4 Vanadium Redox Flow

Vanadium redox flow batteries (VRB) are one of the newer batteries that show extremely high potential to become commercialized worldwide. The battery runs off of a vanadium electrolyte which has the ability to move charges without a change in capacity which means a high battery life is able to be achieved (Energy Storage Association, n.d.). Maria Skyllas- Kazacos and co-workers invented the vanadium battery at The University of New South Wales in 1985 (UNSW, n.d.). Some of the main advantages of the battery include its long battery life (longer than most current batteries) and its ability to power large scale grids by a high energy efficiency (Wang, 2012). The downfall for vanadium currently is the costing of vanadium electrolyte as the processing is quite complex. Although the vanadium battery is not used world-wide currently, an in depth analysis can be carried out to find the cost driver of this developing battery and in time aid in the commercialisation of this exciting and innovative technology.

Table 2.2. 1: Cathodic and anodic reactions of the most promising battery systems

References Battery System Anode (Anolyte) Reaction + Potential Cathode (Catholyte) Reaction + Potential

+ - + - Lithium – Ion Li0.55CoO2 + 0.45Li + 0.45e ⇋ LiCoO2 LixC6 ⇋ 6C + xLi + xe (Cobalt) E° = +1.00 E° = -3.00 (S.-C. S. Wang 2011)

+ - + - Lithium – Ion Li0.35NiO2 + 0.5Li + 0.5e ⇋ Li0.85NiO2 LixC6 ⇋ 6C + xLi + xe (Nickel) E° = +0.70 E° = -3.00 (S.-C. S. Wang 2011)

2+ - + 3+ 2+ - Vanadium VO +e +2H ⇋ V + H2O, E° = +0.34 V + 2e ⇋ V, E° = -1.13

+ + - 2+ 3+ - 2+ Redox-Flow VO2 +2H +e ⇋ VO + H2O, E° = +1.00 V + e ⇋ V , E° = -0.26 (Skyllas-Kazacos 2012)

- - 2+ - Zinc-Bromine Br2 + 2e ⇋ 2Br Zn ⇋ Zn + 2e E° = +1.065 * E° = -0.76 * (Rajarathnam 2016)

- - - - Nickel metal- NiOOH + H2O + e ⇋ Ni(OH)2 + OH MHx + OH ⇋ MHx-1 + H2O + e hydride E° = +0.83 E° = -0.52 (Power Stream 2017)

- + - - + - Lead - Acid PbO2 + HSO4 + 3H + e → PbSO4 + 2H2O Pb + HSO4 → PbSO4 + H + 2e E° = +1.685 E° = -0.356 (Engineers Edge 2017)

* = Potentials taken from potassium hydroxide electrolyte and nickel oxyhydroxide cathode

9 | P a g e 2.2.5 Lead – Acid

Lead-acid batteries are unarguably one of the most used rechargeable energy storage systems used in the last century. These batteries use the reaction of lead (II) sulphate and sulphuric acid to store the energy in the electrodes as electrons are transferred between the cells. The commercialization and eventual success of the battery was due to its robustness, cheap cost and reliability of the energy storage system (Electropaedia, 2017). Gaston Planté was the French physicist who invented the lead-acid battery in 1859 before being tweaked to be the popular battery that it is today (Vincent, 1984). One of the main factors that make the lead- acid battery appealing to the motor industry is the power to weight ratio. The large supply currents within the relatively small battery makes it favourable with cars and automotive vehicles along with its low cost (Evolving Energy, n.d.). Some disadvantages and problems for the lead acid battery include its weight and size (although robust, can be quite bulky), it has the ability to overheat during charging and also for a battery in the 21st century has a relatively small service life of around 400-500 cycles (Linden, 2002). Main applications of the lead acid battery include automotive, lighting, high current drainage applications and also backup energy storage (Sunlight, 2012).

Figure 2.2. 4: Operation of the lead-acid cell showing charge and discharge adapted from Kuphaldt (2010)

10 | P a g e 2.3 Battery Operation and Chemistry

2.3.1 Lithium – Ion

Lithium-ion batteries operate with three main components, a positive and negative electrode with a lithium electrolyte. The positive electrode is made of an aluminium foil that is usually coated with either LiCoO2 or LiNiO2. Many different electrode compounds have been used however the LiCoO2 and LiNiO2 compounds have proven to be the most effective. Table 2.3.1 shows the specific capacity of the different positive electrode materials. Only the LiCoO2 or

LiNiO2 electrode compounds will be investigated to find cost drivers as they are most widely used in the market. Initially, the lithium-nickel positive electrode was the preferred material due to its low toxicity however was found to be too reactive with the electrolyte. This high reactivity caused safety hazards and also reduced the battery life after multiple cycles (Brodd, 2012). The negative electrode is usually a copper foil that is coated with powdered graphite or carbon. Between the two electrodes is a membrane film that acts as a separator between the two electrodes that is usually super saturated with the electrolyte salt (LiPF6). Table 2.3.2 shows the effect of solvent used and how the temperature affects conductivity. As the cell runs, the electrodes attract or repel the charged lithium ion which results in the build-up of charge as electrons transfer. The movement of lithium ion across the cells to one electrode or another determines the charging or discharging of the battery and hence the reason why it is called the lithium-ion battery. As shown in Table 2.3.3 one problem associated with the lithium-ion battery is the solubility of the LiPF6 as it is quite low at around 1 g/L in water at standard temperatures. The three materials used in the lithium-ion battery need to be studied to find the cost driver within the useful battery storage system (Brodd, 2012).

Table 2.3. 1: Positive electrode materials with given capacities (Linden 2002)

Material Specific Capacity (mAh/g) Advantages and Disadvantages LiCoO2 155 Most Common Commercially LiNi0.7Co0.3O2 190 Intermediate Cost LiNi0.8Co0.2O2 205 Intermediate Cost LiNi0.9Co0.1O2 220 Highest Specific Capacity LiNiO2 200 Most Exothermic Decomposition LiMn2O4 120 Least Exothermic Decomposition

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Table 2.3. 2: Conductivity in mS/cm for 1 M of LiFP6 in different solvents (Linden 2002)

Solvent -40 C -20 C 0 C 20 C 40 C 60 C 80 C diethyl carbonate - 1.4 2.1 2.9 3.6 4.3 4.9 ethyl methyl carbonate 1.1 2.2 3.2 4.3 5.2 6.2 7.1 propylene carbonate 0.2 1.1 2.8 5.2 8.4 12.2 16.3 dimethyl carbonate - 1.4 4.7 6.5 7.9 9.1 10 ethylene carbonate - - - 6.9 10.6 15.5 20.6 methyl acetate 8.3 12 14.9 17.1 18.7 20 - methyl formate 15.8 20.8 25 28.3 - - -

Table 2.3. 3: Molecular weight and solubility data of the electrolytes (Zabavchik n.d.)

Electrolyte Molecular Weight (g/mol) Solubility in Water (25° C)

V2O5 181.9 Low Solubility

LiPF6 151.9 Low Solubility

H2SO4 98.07 Soluble

ZnBr2 225.19 Soluble NaOH 39.99 Soluble KOH 56.11 Soluble Soluble – More than 1 g/ 100 g of water Low Solubility – 0.01 to 0.1 grams per 100 grams of water

2.3.2 Zinc – Bromine

The zinc – bromine battery operates by the flow of electrolyte through a cell stack. The electrolyte that consists of the zinc – bromide which is dissolved in salt water passes through the cell stack from one tank where zinc is plated onto the cathode and the bromine is oxidised at the anode. This solution is then transferred into the opposite tank where it is stored until a recharge occurs. The reaction of zinc plating occurs on the negative electrode where the zinc ions attaches onto carbon-plastic electrodes. The charging occurs when bromine solution is loaded by dissolved zinc ions from the plate. The amount of electrodes can be increased to increase the cell stack size. Increasing the cell stack size by simply increasing the carbon- plastic electrode count suggests that the battery size is determined by the amount of

12 | P a g e electrolyte in the tanks and also the electrode sizes, making the battery a viable energy storage solution (Rand, 2001).

2.3.3 Vanadium Redox Flow

The vanadium redox flow battery essentially also has four main sections. The catholyte, anolyte, membrane filter and electrodes are all the essential key aspects that make up the vanadium flow battery. The battery works by the movement of electrolyte from one cell to another. The distinctive characteristic that vanadium contains is that it has the ability to gain and lose charges (electrons) without a lasting effect on the electrolyte solution. Compared to lead acid and lithium-ion, the vanadium battery therefore has an ‘infinite’ time life if the

2+ + vanadium electrolyte is being inspected (Kim, 2015). In the catholyte, VO is oxidised to VO2 where V3+ is reduced to V2+ in the anolyte for the charging of the battery. The opposite occurs for the discharge of the battery and this is why the redox reaction is so important in this cell. The membrane that divides the catholyte and anolyte is primarily to stop the mixing of electrolyte as they will have different charges and vanadium ions. As the mechanism is similar to lithium-ion batteries, it is important to note the key differences in that the vanadium redox flow battery runs off of a much simpler mechanism and reaction that has an increased electrolyte life. The electrolyte however does have a problem with solubility. It is found that

V2O5 has a low solubility of around 1 g/L of water which poses to be a problem to be dissolved in water or sulphuric acid. Further refining of V2O5 to V2O4 gives better solubility allowing for increased electrolyte performance however, cost is a factor. Finding the cost drivers of the vanadium redox flow battery would help in the commercialization of the battery and reduce cost factors that may pose an issue (Rand, 2001). Figure 2.3.1 shows a component breakdown of the vanadium flow battery clearly showing the main sections with reactions.

13 | P a g e

Figure 2.3. 1: The vanadium redox flow battery operation adapted from Australian Vanadium Limited (2017)

2.3.4 Nickel Metal – Hydride

The nickel metal-hydride battery uses a similar energy transfer mechanism to the lead acid battery. The ‘hydrogen’ component is in the form of the metal hydride at the negative electrode. Nickel oxide is the material used at the positive electrode with an alkaline electrolyte used to transfer the charge. The alkaline electrolyte is usually a potassium hydroxide or sodium hydroxide. Both electrolytes are shown to be effective however potassium hydroxide proves to have a better conduction. Figure 2.3.2 shows the conductivity effected by concentration of electrolyte. The alkaline electrolyte reacts with the metal- hydride electrode and discharges electrons with the production of water at the negative electrode. The positive electrode reacts with the H2O molecules which allow for the ‘reduction’ stage. These reactions are also reversible so charging the battery can be done by the reverse reactions. This two stage process at the positive and negative electrodes allows the battery to have multiple advantages over other batteries such as a high storage capacity and low battery costs (Rand, 2001).

14 | P a g e 0.7

0.65

0.6

1 - 0.55

0.5

0.45 NaOH KOH

0.4 Conductance / cm S 0.35

0.3

0.25 0 2 4 6 8 10 Concentration / mol l-1

Figure 2.3. 2: Alkaline electrolyte (NaOH and KOH) conductivities adapted by Rand (2011)

2.3.5 Lead – Acid

The lead-acid battery is similar to the lithium-ion battery in that is contains two electrodes and a solution. The positive electrode is a lead dioxide (PbO2) material while the negative electrode is of a lead sponge material. Both of these electrodes are submerged in diluted sulphuric acid that plays a similar role which is to transfer electrons from the negative electrode to the positive electrode however, the sulphuric acid also takes part in the reaction between the electrodes and is not merely a form of transport for the ions in solution. As the cell discharges, the sulphuric acid is converted to water which means for good indication of battery charge. Figure 2.3.3 shows the indication of capacity and voltage constraints as sulphuric acid is depleted (decrease in density). The charging mechanism from the lead-acid battery occurs when the lead sulphate (PbSO4) reacts with the lead electrodes to form sulphuric acid under reverse current. The lead sulphate is reconverted at the appropriate electrodes and hence is why the charging is possible in the lead-acid battery (Vincent, 1984). Table 2.3.4 shows the effect on sulphuric acid concentration in water and how the electrochemistry is affected. Even though this battery storage system has been used industrially for a lengthy amount of time, it is still important to understand the mechanisms of the battery and find cost drivers that may have not been found before.

15 | P a g e

2.2 1.4

) 3 1.3 2.1

1.2

2

1.1

Open Circuit Cell Voltage Voltage Open Circuit (V) Cell ElectrolyteDensity /dm (kg

1.9 1 0 20 40 60 80 100 Percentage of Rated Capacity

Figure 2.3. 3: Cell voltage and rated capacity data in the lead-acid battery adapted by Vincent (1984)

Table 2.3. 4: Properties of sulphuric Acid Solutions and change in Ah (Linden 2002).

Specific Gravity H2SO4 Electrochemical Equivalent At 15° C At 25° C Wt % Vol % mol/L Ah 1 1 0 0 0 0 1.05 1.049 7.3 4.2 0.82 22 1.1 1.097 14.3 8.5 1.65 44 1.15 1.146 20.9 13 2.51 67 1.2 1.196 27.2 17.7 3.39 90 1.25 1.245 33.2 22.6 4.31 115 1.3 1.295 39.1 27.6 5.26 141 1.35 1.345 44.7 32.8 6.23 167 1.4 1.395 50 38 7.21 - 1.45 1.445 55 43.3 8.2 - 1.5 1.495 59.7 48.7 9.2 -

16 | P a g e 2.4 Leading Developers

It is important to recognise the companies that are focused on creating new energy storage systems and also the companies that are innovating current batteries. These companies are usually large users of the given battery and therefore make it a priority to innovate current energy storage systems to gain profit and improve technological potential.

• As lithium – ion batteries are the most popular trend in battery systems, Tesla has been a leading developer of recent as it uses the rechargeable battery in electric vehicles. Some other leading developers of the lithium ion battery include AESC, Alevo (who developed the first inorganic lithium battery), Amprius and Electrovaya (Shahan 2015). LG Chem is also another company that is focused on creating lithium ion hybrid batteries. Producing lithium-ion polymer batteries capable of grid scale and electric vehicle application, the company aims to improve battery capacity and efficiency through change in components (LG Chem, 2017).

• Imergy is one of the leading developers for the vanadium redox flow battery as the company aims to find more effective stationary energy storage systems. The company has already implemented the redox flow batteries in several countries including Australia (Bridges, 2016). Sumitomo is a Japanese company who have also implemented a major redox flow battery in Japan. Small towns in Japan are being powered by the battery systems and has proven to be an effective investment (Stone, 2014). Maria Skyllas - Kazacos although inventing the battery system has continued researching on the battery and proves to be one of the leading researches into the reduction of cost and improving efficiency.

17 | P a g e • Primus Power have developed a zinc - bromine battery that is capable of large grid scale deployment and use. It utilizes a stronger membrane filter as well as a single tank. The grid-scale batteries are being deployed in multiple countries and is appealing to consumers due to its ‘endless’ battery life similar to the vanadium redox flow (Primus Power, 2017). Redflow is also a company that is promoting growth as the zinc- bromine energy storage producers have supplied to over 100 projects worldwide (Stone, 2014). The company is currently implementing the zinc-bromine battery into telecommunications, grid scale, commercial and residential applications. (RedFlow, 2017).

• Ecoult which is a lead-acid battery developing company from Australia have been granted funding to aid in the developing of the lead-acid battery in India with a sole focus on decreasing costings for the widely used energy storage system. It is important to notice that batteries are still being investigated and developed to cut costings or increase battery efficiency after a long period of time (Financial Review, 2017).

18 | P a g e 2.5 Battery Materials & Chemicals

As observing multiple energy storage systems can be quite complex, it is useful to form a material matrix that can be used to examine the various materials in each battery which will help in the costing analysis. Finding the cost driver is the objective to achieve the aim of finding a method to reduce the costing of a particular battery. As the battery systems include multiple components, the material matrix can be broken down into cathodes, anodes and electrolytes. As the batteries being investigated nearly all contain these components, it can be a crucial piece of data that helps in finding the cost driver. The cost drivers of each battery system are usually related to the cathodes, anodes or electrolytes.

Table 2.5. 1: Materials for anodes, cathodes and electrolytes for the investigated battery systems (Linden 2002).

Battery System Material Anode Cathode Electrolyte (Anolyte) (Catholyte) Lithium – Ion Lithium Nickel – Oxide Carbon Graphite Lithium Hexafluorophosphate

(Nickel Complex) (LiPF6) Lithium – Ion Lithium Cobalt - Oxide Carbon Graphite Lithium Hexafluorophosphate

(Cobalt Complex) (LiPF6)

Vanadium Redox Carbon Graphite Carbon Graphite Vanadium (V) Oxide (V2O5)

Flow Nickel Metal - Nickel (II) Oxide Metal-Hydride Potassium Hydroxide OR Hydride Sodium Hydroxide (NaOH)

Zinc Bromine Bi-polar Carbon Bi-polar Carbon Plastic Zinc Bromide (ZnBr2) Plastic Electrode Electrode

Lead - Acid Lead Dioxide Lead Sponge Sulfuric Acid (H2SO4)

19 | P a g e Although there are various materials that can be substituted for each major component of the investigated batteries, these materials and chemicals are the most commonly used. Table 2.5.1 will eventually be the basis that a cost driver will be taken from as the battery systems are further investigated. The vanadium flow battery has multiple vanadium states in the catholyte and anolyte as the reactions take place which affects the composition of the double cell system.

2.5.1 Chemical Compositions and Concentrations

Various materials and chemicals also have a mixture composition to maintain a cost effective material while still achieving the desired battery potential. Electrolytes particularly can be diluted or mixed with a different chemical if costing is too great or effectivity is greater in the electrolyte complex. It is therefore important to take this into account especially with the costing analysis of each electrolyte as diluted electrolytes are very common in batteries.

Vanadium(V) oxide used as an electrolyte in the VRB is a mixture of V2O5 and sulphuric acid mixture which is used in concentrations that maintain battery efficiency while being a relatively cost effective electrolyte. For the VRB and zinc- bromide batteries, concentrations of 2 – 3 mol/L of the major chemical is standard (Hashimoto, 1993). The nickel metal-hydride electrolyte of either potassium hydroxide or sodium hydroxide is normally around 30% by volume with water (Linden, 2002).

2.5.2 Varied Materials

Nickel metal – hydride batteries can use various cathode materials. Different cathodic materials may hinder performance or costing so it is suited to the task of the battery. According to Dell and Rand, the metal-hydride cathode should; have high storage capacity, prove to be safe, have good corrosion resistance, repeat cycles without change in pressure and temperature characteristics, and also form and decompose at any appropriate rate (Rand 2001). To make a useful analysis for the nickel metal-hydride batteries, some common cathode materials can be analysed. Table 2.5.2 shows just a small list of cathodic materials that can be used in the nickel metal-hydride battery.

20 | P a g e It is important to analyse each component and the most common material that is used. The availability of the material, costing for processing, the mineral reserves and also the effectivity of the materials should be taken into consideration as various effective materials may be used at a cheaper cost. Assessing all of these factors in each case will develop a method to find the cost driver for each energy storage system.

21 | P a g e Table 2.5. 2: Sodium alanates used as metal-hydride cathodic materials (Sakintuna, 2006).

Temperature Cycling Max wt % Materials Method Pressure (bar) Kinetics (min) (C ) stability of H2 Mechano- Na3AlH6 chemical Tdes: 200 Pdes: 1 Tdes: 150 No Data 2.5 synthesis

Na2LiAlH6 BM Tabs: 211 Pabs: 45 Tabs: 100 No Data 2.5

NaAlH4-2 Tabs and Tdes: Pabs & Pdes: 5 cyc.: not BM Tabs: 60 mol % 125-165 101-202 stable 3 Ti(Obun)4- 2 mol % BM - - Tdes: 180 stable Zr(Opri)4

Tabs: 120 Pabs: 120 Tabs: 60 NaAlH4-4 8 cyc.: not BM 3.3 mol% Ti stable Tdes: 150 Pdes: 1 Tdes: 600

Tdes: 25-160 Pabs: 20-120 Tabs: 300 - 720 NaAlH4-2 BM No data 3.8 mol % Ti Tabs: 25-193 Pdes: 1 Tdes: 40

NaAlH4-2 Tabs: 120 Tabs: 1020 Pabs and Pdes: 25 cyc.: not mol % Mixing 4 n 60-150 stable (Ti(Obu )4 Tdes: 180-260 Tdes: 120-300

NaAlH4-2 Tabs: 135 - 120 Tabs:330 Pabs and Pdes: 33 cyc.: not mol % Mixing 4 n 150-130 stable Ti(Obu )4 Tdes: 180-160 Tdes:90

NaAlH4-2 5 cyc.: not mol % BM Tdes: 125-100 Pdes: 83-91 Tdes:20 4 stable TiCl3 NaAlH4-2 3 cyc.: stable mol % Mixing Tdes: 200 Pdes: 1 No Data 3 after 4 Zr(OPr)4 second cyc NaAlH4-2 3 cyc.: stable mol % Mixing Tabs: 104 Pabs:88 Tabs: 1020 after second 4 n Ti(Obu )4 cycle

Mechano- Tabs: 120-300 2 cyc.: not Tabs and Tdes: Pabs and Pdes: NaAlH4 chemical stable 5 80-180 76-91 synthesis Tdes:300

NaAlH4-2 mol % n Mixing Tdes: 200 Pdes: 1 No Data Not Stable 5 Ti(Obu )4- C 25 cycle: NaAlH4-2 BM Tabs: 104-170 Pabs: 115-140 Tdes:30-1200 stable after 5 mol % TiN 17th cycle

Tdes: Desorption time

22 | P a g e 2.6 Processing

The cost analysis for the studied energy storage systems can be broken down into four major parts including;

• Sustainability • Applicability • Performance • Materials and individual components

Studying the materials and the individual components may lead to cost drivers of which can be reduced. Some sections that can be changed within the battery to reduce the overall cost and make a battery a more viable option include;

• Material cost reduction • Chemical cost reduction (electrolyte) • Changing the design of the battery • Additions that may aid in the performance of the battery such as reagent or conditional changes (temperature and pressure)

As the material costing tends to be the cost driver in most applications, observing processing techniques is a critical method that could lead to the reduction of cost. Many energy storage system elements are processed and produced in different methods so it is important to find which elements are expensive to produce starting at the mining processes.

Ore bodies and reserves are also an important factor to analyze the sustainability of the battery and to achieve battery viability estimates assuming the energy storage systems are commercialized. Materials are produced all over the world through different processes due to the mineralogy so it is crucial to understand trends to find costing figures.

23 | P a g e 2.7 Major Ore Deposits and Mineralogy

2.7.1 Vanadium

Vanadium is usually mined as a by-product and is not typically mined from individual mineral sources. Found in over 65 minerals, vanadium resources have found to exceed well over 63 Mt. The majority of vanadium is found in phosphate rocks, titaniferous magnetite, uraniferous sandstone, siltstone as well as carboniferous materials such as crude oil, coal, oil shale and tar sands (USGS, 2016). Vanadium processing is largely associated with titaniferous magnetite as it accounts for 85% of vanadium production (Investing News, 2016). As vanadium is mined as a by-product and is found in various different minerals, it is best to recognize vanadium product by country. China, South Africa, Russia and Brazil are the four leading producers of the vanadium resource V2O5 that can be further processed to be used in the vanadium redox flow battery system. At 0.042 Mt of vanadium produced in 2016, China poses to be a large contributor to the vanadium stocks however large vanadium sources can be found in Australia. This suggests that Australia may be a future major producer of the sustainable battery (Australian Shares, 2016).

Table 2.7. 1: Elemental reserves and production for 2016 (USGS, 2016).

Element Reserves (Mt) Production (Mt) 2016 Sustainability (years)

Vanadium 63 0.076 829

Lithium 40 0.035 1143

Cobalt 25 0.123 203

Nickel 130 2.25 58

Lead 2000 4.82 415

Zinc 1900 11.9 160

24 | P a g e 2.7.2 Nickel

Nickel used in the nickel metal – hydride batteries as well as the anodic material for the lithium – ion battery is in abundance in various countries. Estimated nickel reserves are approximated at around 130 Mt with 2.25 Mt of that being processed in 2016 alone. Leading nickel producers include the Philippines, Canada, Russia and Australia respectively, although the largest amount of nickel reserves by country is Australia (USGS, 2016). Major minerals that contain the nickel include pentlandite, millerite, niccolite, garnierite and also the nickel replacement in pyrrhotite. The high amount of nickel being processed in a single year show the world wide processing and availability of nickel (British Geological Surveys, 2008).

2100

1800

1500

1200

900 Reserves Reserves (Mt)

600

300

0 Vanadium Lithium Cobalt Nickel Lead Zinc

Figure 2.7. 1: World selected element reserves as of 2016.

25 | P a g e 2.7.3 Lead

Lead which is used in the lead – acid battery has a large reserve of over 2000 Mt. Australia, China, Russia and Peru are the leaders in lead reserves respectively as of 2016 (Statista, 2016). Galena is the main mineral that contains the lead at high amounts. Cerussite and anglesite also make up large amounts of the lead reserve as an oxidized lead mineral (Government of South Australia, n.d.). Of this 2000 Mt reserve, 4.82 Mt of lead was produced in 2016 alone. This larger amount of lead reserve also shows a large production of the lead. The supply and demand of lead is the main contributor to the large process (USGS, 2016).

2.7.4 Lithium

Lithium resources used to create the anode and electrolyte for the lithium ion battery is on high demand as renewable energies are being pursued. With a reserve of over 40 Mt, lithium is being produced predominately by Chile, China, Argentina and Australia respectively at around 0.035 Mt in 2015 (USGS, 2016). Although found in over 100 minerals, major lithium bearing minerals that are economically viable to process include spodumene, lepidolite, petalite, eucryptite and jadarite. Lithium can also be processed from brines which is a fluid that contains the dissolved lithium element. Although in small concentrations, large amounts of lithium can be processed from these fluid bodies. With major deposits in Australia, South America and China, Figure 2.7.3 shows the various major lithium ore deposits including major brine processes for the production of lithium (British Geological Survey 2016).

14 0.14

12 0.12

10 0.1

8 0.08

6 0.06 Production(Mt) 4 0.04 Production(Mt)

2 0.02

0 0 Nickel Lead Zinc Cobalt Vanadium Lithium

Figure 2.7. 2: World elemental production of each investigated element in 2016.

26 | P a g e 2.7.5 Zinc

Zinc is used for the electrolyte in the zinc-bromine battery. As of 2011, zinc reserves estimated around 1900 Mt. Majority of the zinc reserve was found in Australia, China and Peru. Of the three countries with major zinc reserves, China is the world’s leading producer of zinc at nearly 5 Mt of zinc in 2011 (Asian Minerals, 2013). Zinc minerals that are economically viable to process are sphalerite, smithsonite and willemite (MEC n.d.).

2.7.6 Cobalt

Cobalt is used in the lithium ion (cobalt complex) battery. Used as one of the main elements of the anode, it is a large determinant as to whether the lithium ion battery is viable in terms of sustainability. As of 2016, found cobalt reserves accumulated to approximately 25 Mt. The amount of cobalt mined in 2016 is around 0.123 Mt world-wide. These reserve and production figures are based primarily off terrestrial ore deposits. Cobalt has also been found in manganese nodules on the crusts of the oceanic floor that account for some 120 Mt. These nodules that contain the cobalt however are not included in the overall reserve as mining processes have not been used. Some leading producers of cobalt include China, Canada and Congo, who produced the largest amount of cobalt at 0.066 Mt in 2016. Majority of cobalt is found in sediment hosted copper ores (USGS, 2017).

2.7.7 Reserve and Production Summary

As shown in Figure 2.7.2, although small compared to zinc and lead, vanadium has quite a large reserve and exceeds lithium which suggests that vanadium redox flow batteries can be sustainable for the future. Having large sources of vanadium and small production shows that the battery may contain large future potential. Lithium although not as abundant as vanadium also has considerable amount of deposits that can be used to sustain lithium ion batteries into the future. Sustainability figures can approximate element life if production was to continue at the 2016 rate with no new reserves found. As shown lithium and vanadium are the most sustainable elements currently.

27 | P a g e

)

2008

(

Major lithium processing operations adapted from British Geological Surveys Geological British operations from adapted processing Majorlithium

: :

3 Figure2.7.

28 | P a g e 2.8 Processing Options

2.8.1 Nickel

Nickel can be processed by hydrometallurgical or pyrometallurgical processes. The difference in processes usually depends on the mineral composition. Nickel sulphide ores usually undergo crushing, flotation, thickening, smelting and refining where a high purity nickel product is formed. The sulphide ores that undergo pyrometallurgical processing can also incorporate hydrometallurgical processing, where solvent extraction is used to separate the nickel-cobalt matte into nickel and cobalt (usually in sulphide ores). Electro refining is then used to produce the nickel on the cathode. A high pressure acid leach can also be used to recover the nickel using high concentrations of sulfuric acid and high pressures. This high pressure acid leach has been used for over 60 years. (Metalpedia, 2016).

2.8.2 Lead

Lead sulphide ores are usually concentrated by flotation (as sulphides are generally easy to float). The concentrate is then roasted and then smelted for reduction purposes. In this indirect smelting process, impurities are skimmed from the top to produce high grade lead. Direct smelting is also an option as no coke is required and also pollution is quite minimal. The remaining impurities from the lead bullion can be removed by electro refining or further pyrometallurgical processes (Ponikvar, 2016).

29 | P a g e

Figure 2.8. 1: Sphalerite mineral containing zinc sourced by Wikimedia Commons

2.8.3 Vanadium

Vanadium is produced by various methods as the element exists in many forms. Hot sulphuric acid is used to leach carnotite over a 24-hour period. The leached solution which consists of both uranium (as uranium is usually a co-product with vanadium) and vanadium are extracted by solvent extraction in two different stages. Ferrovanadium is processed by the electric arc furnace. The oxidation reduction reaction that takes place within the furnace allows for the separation and hence production of the vanadium pentoxide (Moskalyk, 2003).

2.8.4 Cobalt

Cobalt is processed through a number of different methods. Copper-cobalt ores account for quite a large amount of cobalt reserve. The ore is usually floated to separate the minerals into a concentrate. The use of an electric-arc furnace reduces the cobalt in the copper-cobalt complex ores. After the electric-arc furnace, the compound is then leached to extract the cobalt and nickel from ore. The cobalt is then removed from the leach solution by electrolysis. (Taylor, 2017). Both pyrometallurgical and hydrometallurgical processes can be used to extract the cobalt.

30 | P a g e 2.8.5 Zinc

Zinc sulfides are concentrated usually through the flotation process. Once concentrated, the zinc sulfides undergo roasting, smelting and then electrolysis. Fluidized bed roasters are typically used to remove the sulfur before the blast furnace is used to reduce the zinc sulfides and in some cases separate concentrates such as lead and zinc. Electrolysis is used to produce the zinc sulfate solution and purify for electrowinning (Richards, 2011). The sphalerite mineral shown in Figure 2.8.1 contains the zinc element.

2.8.6 Lithium

Spodumene is the main lithium bearing mineral. The spodumene is usually first floated to produce a concentrate. The concentrate is then dried and sent to a roaster which is standard practice. The redox process is followed by a leaching circuit to extract the lithium. Once leached the solution is extracted and undergoes electrowinning to produce lithium. Brines that contain lithium (large source) undergoes an evaporation process that goes over long periods of time (18 months) (Bohlsen, 2016). The evaporation followed by leaching produces a lithium concentrate for purification.

2.8.7 Processing Summary

Observing sustainability factors in relation to each battery element, it is deduced that Lithium- ion, lead acid and vanadium redox flow are the most sustainable batteries that need to be examined. This deduction was made from considering both elemental reserves and elemental production. Although vanadium, lithium and cobalt do not have a large reserve, production rates are small compared to nickel, lead and zinc. Lead however has a large reserve which suggests that even though production is high, the element can be produced in the future. Not accounting for production and reserve fluctuations, the lithium ion battery has abundance of lithium and cobalt while the vanadium redox flow also has high amounts of vanadium to be processed. Although nickel and zinc have large reserves, production suggests that within 58 - 160 years, both nickel and zinc will be depleted (not considering reserve fluctuations). These three batteries will be investigated further.

31 | P a g e 2.9 Battery Effectivity & Efficiency

The process of elimination can aid in the selection of a battery once a cost driver has been found. To select a battery that will be worth-while to investigate however is the main problem. Observing battery characteristics can be a useful tool in comparing batteries to find which batteries are most suited to the markets and customer demand. Some main characteristics that can have major influence on battery efficiency and effectivity include cell voltage, capacity, recharge time, amount of cycles, self-discharge rate, operable temperature and energy density. These characteristics however must be compared to each other in context with the usability of the battery.

Table 2.9. 1: Characteristics of each battery system compared to each other (Linden, 2002).

Lithium-Ion Lithium-Ion Vanadium Redox Lead-Acid Characteristic (Nickel Cathode) (Cobalt Cathode) Flow Operational Cell Voltage (V) 3 - 4 3 - 4 1.4 2.1 Specific Capacity (Ah/kg) - 100 21 120 Specific Energy (Wh/kg) 150 360 29 252 Recharge Time (hr) 2.5 - 6 - 10 8 - 24 Cycle Life (Cycles) 400 600 3000 500 Self-Discharge Rate (%/Month) <3.5 - 5 - 10 3 Operable Temperature (C°) -20 - 45 -20 - 60 10 - 50 -20 - 50 Energy Density (Wh/L) 400 410 10 80

2.9.1 Operational Cell Voltage

The open circuit cell voltage for the lithium ion batteries are the highest in comparison to the redox flow and lead acid. Vanadium redox flow battery although significantly smaller in capacity, energy and voltage does have some factors associated. The vanadium redox flow battery is much more applicable to scaling than other batteries. Increasing the size of the battery requires more electrolyte and carbon electrodes while lithium-ion and lead acid require much more components to upsize. These low energy capacities and voltages are then countered with the easy increase in size of the vanadium redox flow.

32 | P a g e 2.9.2 Specific Capacities

For Lithium ion and lead-acid batteries, energy capacities and voltages need to be quite high due to the use of the battery. Primarily used in portable batteries for motors and automotive vehicles, the batteries need to be able to operate at high voltages to supply the demand of energy. The high energy capacities of both lithium-ion and lead-acid are linked to the amount of energy needed for it to be useful to the automotive industry and attract marketable value. Vanadium redox flow batteries are used for grid scale application which suggests that although characterised as a low capacity and voltage battery, larger scale systems can in the future provide varying energy outputs with varying sizes.

Figure 2.9. 1: Sumitomo’s redox flow battery shown as a grid scale adapted from Sumitomo Electric (2017)

33 | P a g e 2.9.3 Recharge Time

Recharge time is mainly applicable to portable batteries. The lead-acid and lithium-ion batteries need to have relatively low recharge times to maintain viability towards portable batteries for automotive applications. As the lithium-ion battery has quite a low recharge time it becomes very applicable to the automotive industry as the battery usage is quite high. The vanadium redox flow battery is used mainly on a grid scale where it can constantly be charged with minimal battery deterioration. This suggests that self-discharge rate is also not heavily applicable to the vanadium redox flow battery as constant charging can be done. Lithium-ion batteries and lead-acid batteries have similar self-discharge rates which are quite minimal.

2.9.4 Operable Temperatures

As the vanadium redox flow battery is mainly composed of vanadium electrolyte, it is important to note the operable temperatures of the cell system. The flow battery has a lower operable temperature due to precipitation and freezing of electrolyte. This is a problem for low temperature climates however heating systems can be implemented especially for large grid systems. The Li-ion and Lead acid batteries can be used in multiple applications including portable batteries due to the characteristic of having large operable temperature ranges. This large temperature range means that the portable batteries can be used widely around the world in a variety of climates.

1600

1400

1200

1000

800

600 Capacity(MW) 400

200

0 2013 2014 2015 2016 2017 2018 2019 2020 2021

Advanced Flow Battery Advanced Li-ion Battery Advanced Lead-Acid Battery

Figure 2.9. 2: Projected installed capacity for three different batteries adapted from MSE Supplies (2015)

34 | P a g e 2.9.5 Battery/Cycle Life

Battery life is a major factor in the determinant of an energy storage system viability. The main advantage that the vanadium redox flow battery has over other energy storage systems is the long battery life through cycles. The flow battery can go through above 3000 cycles without having an effect on electrolyte and capacity which means the life of electrolyte is ‘infinite’. Compared to the lithium-ion and lead-acid the flow battery is far superior in terms of battery life which makes it more applicable to large scale systems as it won’t have to be replaced often. Small scale portable batteries can be replaced relatively easy and thus smaller battery life is acceptable. Increasing the amount of cycles with the lithium-ion could be a driver that would increase applicability of the lithium – ion battery.

2.9.6 Effectivity and Efficiency Summary

The two main advantages that can be taken from the energy, capacity and durability data in Table 2.9.2 is; the vanadium redox flow battery has a large cycle amount meaning it is useful to large scale systems and also that the lithium – ion battery has great energy efficiency making it applicable to portable energy storage and automotive applications. By observing the differences in lithium ion cobalt and lithium ion nickel batteries, conclusions can be made about the use of cobalt. As shown, the cobalt cathodes do have an effect on the efficiency of the battery system with an increased amount of cycles, an increased energy density and increased energy capacity.

As batteries with the most potential in terms of sustainability and battery efficiency have a higher chance of change in cost driver, these batteries will be further investigated; the lithium ion with cobalt cathode, the lithium ion with the nickel cathode and the vanadium redox flow.

35 | P a g e 2.10 Cost Comparisons

By observing a cost breakdown for each battery, it is possible to find cost drivers that may affect the overall marketability of the battery. Batteries come in different variations with a wide range of elements, suggesting that a comparison between them is quite difficult. Overall battery breakdowns however can be compared to find which batteries are the most efficient under a single unit. As the aim of this investigation is to find the cost drivers behind multiple batteries to identify potential changes that decrease costs in batteries, the cost comparison is a crucial factor.

2.10.1 Lithium Ion Battery

The lithium ion battery with the different cathodes and the vanadium redox flow battery will be compared in capital costings.

Figure 2.10. 1: Lithium ion battery cost breakdown into cathodic elements adapted from Berger (2012)

Figure 2.10.1 shows the lithium ion battery breakdown in capital costings. This particular cell is assumed to be using a 96 Wh PHEV cell with an NCM622 cathode (use of cobalt). Elemental material prices are; US 7.00 $/lb nickel, US 12.00 $/lb cobalt, US 1.00 $/lb manganese and US 6.50 $/lb lithium.

36 | P a g e

Table 2.10. 1: Cost breakdown of lithium ion battery (cobalt cathode) (Novo 2016).

Lithium - Ion (Cobalt Cathode) Component Cost (US$/kWh) Material Costs (US$/kWh) Percentage (%) Overhead 64.23 - - Labour 9.52 - - Cathode 40.48 40.48 27 Anode 21.43 21.43 14 Electrolyte 21.43 21.43 14 Separator 19.05 19.05 13 Other Materials 50.00 50.00 33 Total Cost 226.14 152.39 100

33% 27%

14%

13%

14%

Cathode Anode Electrolyte Separator Other Materials

Figure 2.10. 2:Capital cost fractions pie chart showing distribution of costings for lithium ion.

As shown, the capital costs supplied by Novo and Berger (2016 & 2012) are very similar. Cathode costing is heavily weighted in capital cost with the focus on nickel and cobalt. Accounting for approximately 78 % of the cost of the cathode material and 39 % of the overall cost of battery, Berger’s model gives indication that nickel and cobalt are large cost drivers in the lithium-ion battery. Berger’s model suggests around US 240 $/kWh while the Novo data suggests around 226 $/kWh. With fluctuations in price as a factor, it is very similar and therefore is a reliable estimate.

37 | P a g e 2.10.2 Vanadium Redox Flow Battery

Table 2.10. 2: Cost Breakdown of the vanadium redox flow battery (VRFB) (Moore 2013).

Vanadium Flow Battery Component Cost (US$/kWh) Percentage (%) Total Cost of Stack 117.10 31 Pump Costs and Heat Exchangers 11.33 3 Cost of Electrolyte Tanks 30.22 8 Total Cost of Vanadium 139.76 37 PCS, Transformer, etc. 79.32 21 Total Cost 377.73 100

21 % 31 %

3 %

37 % 8 %

Total Cost of Stack Pump Costs and Heat Exchangers

Cost of Electrolyte Tanks Total Cost of Vanadium

PCS, Transformer, etc.

Figure 2.10. 3: Capital cost fractions pie chart showing distribution of costings for VRFB.

Table 2.10.2 and Figure 2.10.3 show the overall distribution for cost breakdown of the vanadium redox flow battery. Suggested by the pie chart, the vanadium electrolyte accounts for a large portion of the overall capital cost of the vanadium battery, 37 % to be exact.

38 | P a g e Observing total capital cost for both batteries shows large differences. US 377.73 $/kWh compared to US 226.14 $/kWh shows just where the two batteries are in terms of development. The VRFB is grossly expensive compared to the lithium battery, however in context the extra cost is justifiable. The cycle life for the VRFB is nearly 4 times that of the lithium ion battery which suggests that although an expensive battery is costed, it makes up for it in battery life and cycle amount. As of 2017, the two batteries have different applications in the world. One battery poses to be a grid scale energy storage system, while the other is best suited currently to portable devices for relatively short use and high energy throughputs.

2.11 Critical Cost Drivers

Following the cost analysis, the critical cost drivers can be found which provides avenues to minimize costs. In the lithium – ion battery with cobalt used as the cathode, the cathode showed to have the highest expense in comparison to other materials and parts. The cathode alone accounts for 39 % of the overall expenditure suggesting that the critical cost driver is certainly the cobalt and nickel in the cathode.

The vanadium redox flow battery’s critical cost driver is the vanadium electrolyte, which accounts for 37 % of the total cost. To decrease the market value of the battery, it is necessary to decrease the cost of vanadium production.

By comparing the cost drivers, vanadium electrolyte is considerably more expensive than the cobalt cathode, which indicates a large potential for reduction of costing.

39 | P a g e 2.11.1 Sensitivity Analysis

A sensitivity analysis has been used to examine the critical drivers for supporting evidence. By exposing the individual component costs of both the lithium-ion and vanadium redox flow to fluctuations in increments, the critical cost drivers can be deduced from the largest price change. Figure 2.11.1 shows that the critical cost driver of the vanadium redox flow battery is the vanadium electrolyte, indicated by the largest price changes at 10 and 20 % fluctuations. Costing of stacks also accounts for large amounts of the vanadium redox flow battery cost.

Figure 2.11.2 shows the fluctuation in price for the lithium ion battery. Eliminating ‘other materials’ as it is comprised of multiple small components; the cathode has the largest cost influence on the lithium ion battery. An increase or decrease of 20 % for the cathodic material in price will lower the overall cost of the lithium ion battery immensely.

30

20

10

0 -25% -20% -15% -10% -5% 0% 5% 10% 15% 20% 25%

-10

-20 Difference Difference in cost (US$/kWh)

-30 Input Fluctuation Cost of Stack Pump and Heat Exchangers Electrolyte Tanks Vanadium Electrolyte PCS, Transformers, etc.

Figure 2.11. 1: Sensitivity web diagram for the fluctuation of each vanadium battery component

40 | P a g e 10

8

6

4

2

0 -25% -20% -15% -10% -5% 0% 5% 10% 15% 20% 25% -2

-4

-6 Difference in cost(US$/kWh) Difference

-8

-10 Input Fluctuation

Cathode Anode Electrolyte Separator Other Materials

Figure 2.11. 2: Sensitivity web diagram for the fluctuation of each lithium-ion battery component

2.12 Summary

The investigative study to obtain cost drivers in various energy storage systems has been achieved. By analyzing economical, sustainability and efficiency factors for the zinc bromide, lithium ion, lead acid, vanadium redox flow and nickel metal-hydride batteries, cost drivers were found that would have the biggest impact in the renewable energy storage market.

It was found that through a sustainability analysis, the nickel-metal hydride and zinc bromine batteries were found to be less sustainable compared to the lithium ion, lead acid and vanadium redox flow batteries. Being produced at 11.9 and 2.25 Mt per year respectively, zinc and nickel are less sustainable compared to the other investigated batteries. Elemental reserves and production rates were taken into consideration to achieve a general ‘element life’ which aided in the investigation of the most sustainable, economic and efficient battery for cost driver findings.

41 | P a g e Comparing efficiency, cycle life and capacity data allowed for good conclusions to be made of the lithium ion battery and the vanadium redox flow batteries, given the current applications. The vanadium redox flow battery poses to be a long term grid scale energy storage system due to the 3000 cycles for the electrolyte life, while the lithium ion battery proved to be applicable for portable devices and high energy output systems due to its high operational cell voltage of around 3 – 4 volts. These two factors a marginally higher than the other investigated batteries therefore were chosen to be cost analyzed further.

The economic analysis was based around the batteries with the largest potential, being lithium ion and VRFB. The analysis concluded that the cost drivers in the VRFB was the vanadium electrolyte with a 37 % cost composition of the overall battery, while the lithium ion cost drivers was the cobalt and nickel in the cobalt cathode with a cost weight of 39%.

A decrease in vanadium electrolyte process cost will have a larger effect on the market than the reduction in cost of processing cobalt. Reasoning is due to the cost breakdown of both batteries, which suggests the vanadium electrolyte has a higher cost weight compared to the cobalt cathode.

Solubility data suggests that refining vanadium increases the overall solubility of electrolyte which increases efficiency of the vanadium battery. Refining the V2O5 with a cost effective method will decrease the costing of the vanadium energy storage system. Specialized leaching and electro-refining techniques are avenues that may be able to obtain the vanadium from ore at a lesser cost. As carnotite is a major vanadium bearing mineral, flotation on the uranium – vanadium mineral may be an option to produce a concentrate for leaching. If a concentrate can be produced that contains a higher grade of uranium and vanadium, sequential processing will be vastly cheaper. Studying conditions around the selective flotation of uranium and vanadium would be an interesting avenue.

Extracting nickel or cobalt from ore with a cheaper process will reduce overall costing of the battery remarkably. As electric arc furnaces heavily influence the cost of processing the cobalt, reducing the cobalt by cheaper methods may introduce a decrease in costings. Flotation of cobalt can be examined to alter conditions which has potentials of decreasing operational cost of processing. The flotation of copper-cobalt ores may reduce costings by decreasing throughput and increasing grade for the electric arc furnace.

42 | P a g e Chapter 3 – Experimental Methods

3.1 Introduction

Finding a methodical approach into this investigation in regards to test work is quite complicated and technical. In this chapter, these methods are clearly outlined and discussed to prove relativity and accuracy within the results. From how the test work was conducted to the materials and resources used, the lithium ion battery recycling test work needed to be accurate in order for the results to be valid. Points of error are discussed and room for development within the research test work. For test work replication, it was necessary to clearly define the test work procedure to create a recycling process that may be of use in the future.

3.2 Sample Source, Reagents and Equipment

3.2.1 Lithium ion batteries

Lithium batteries are constructed from materials that are specific to its use. It is therefore important to choose a battery that is composed of the materials selected for leaching. The alteration of battery components is directly linked to its performance and cost. The anode material is generally similar in most lithium ion batteries, being carbon graphite. The electrolyte is varied from one battery to another to increase or decrease capacity, costing, storage life and performance. As the lithium electrolyte was not of importance in the leaching stage, this component was disregarded.

43 | P a g e

Figure 3.2. 1: Lithium ion battery breakdown (Physics Central 2017)

The cathode was the sole factor in the choice of lithium ion battery. As nickel and cobalt were found to be the costliest elements in the lithium ion battery, the cathode needed to be composed of cobalt and nickel to be leached. A safe battery was mandatory as the disassembly posed to be a dangerous factor. The lithium ion ICR - 18650 was the battery of choice as it was quite small and relatively easy to disassemble. The ICR has high amounts of cobalt in the cathode which means that a cobalt leach can be achieved (Battery Bro, 2015). A generally low voltage of 3.7 V could easily be discharged which meant that time taken to disassemble and discharge multiple batteries would be made possible in a short period of time.

According to research into the cleaning of lithium-ion cathodes, a large portion of the battery weight is attributed to the cathode. This reflected to be useful as the amount of cathode powder extracted from the lithium ion could be used in the leaches. The greater the weight of cathode material, the less batteries needed for the test work. Although all batteries are different in terms of composition and weights, the test work by Toma can be used as a relative reference guide as to how many batteries were needed, in this case 20 seemed sufficient (Toma, 2017). Table 3.2.1 represents the battery weight breakdown and shows the high amount of cathode material.

44 | P a g e

Table 3.2. 1: Battery weight breakdown for a lithium ion battery

Component Weight %

LiCoO2 (Cathode) 27.5 Steel/Ni 24.5 Cu/Al 14.5 Carbon 16 Electrolyte 3.5 Polymer 14

3.2.2 Acids

As the aim of this research is to find a cost effective method in the recycling of spent lithium ion batteries, it is important to keep the process cost and reagent cost low. Many different acids can be used in the leaching of nickel and cobalt however choosing a cost effective acid that will achieve high recovery is necessary. Sulfuric acid (H2SO4) was used in this test work as the inorganic acid proves to be effective with many leaching procedures and is also cost effective.

Metals have been extracted and leached into solution with the use of sulfuric acid in a wide range of cases. Nickel and cobalt which are the desired elements to be leached from the spent lithium ion battery cathode material have both been leached with the use of sulfuric acid (Ognyanova, 2009) (Sohn, 2006). In both cases cobalt and nickel recoveries were above 90 % showing the effectivity of sulfuric acid on the leaching mechanism.

A solution of 96 % v/v sulfuric acid was used and diluted to the given concentrations of acid needed for the test work. Nayl et al. (2017) tested multiple sulfuric acid concentrations and found that 2 M was optimum suggesting that not a high concentration is necessary for extraction (Nayl, 2017).

3.2.3 Catalyst

Hydrogen peroxide (H2O2) is commonly used with the dissolution of cyanide however in this case, it is used to create cobalt 2+ ions. The cobalt (II) ions are readily leached into solution making it a faster method than common oxidation from air. As the reaction rate is dependent

45 | P a g e on diffusion coefficient of cobalt ions, it makes sense that the cobalt 2+ ions increase the reaction rate and create a faster leaching mechanism (Deng, 2007).

The equation for reaction rate of leaching is;

2푏푀퐷퐶 푘 = where D = diffusion co-efficient of cobalt ions. [1] 푝 푝푟2

A solution of 30 % w/v hydrogen peroxide was used in liquid state and this was key to keeping the costs low and also testing to see if extraction would still remain high. Nayl et al. (2017) used 4 % H2O2 obviously at a higher w/v however keeping costs low was crucial for the commercialization of the process (Nayl, 2017).

The chemical reaction taking place with the addition of H2O2 is;

2퐿푖퐶표푂2(푠) + 3퐻2푆푂4(푙) + 퐻2푂2(푙) → 2퐶표푆푂4(푙) + 퐿푖2푆푂4(푙) + 4퐻2푂(푙) + 푂2(푔) [2]

3.2.4 Equipment

Some pieces of equipment were quite minor in the process and some major. It is important to outline the equipment as replication of results can be made easier or even optimized with more effective equipment types and specifications.

• X-Ray Diffraction (XRD) – Used to characterize the material found in the lithium ion batteries and produce findings into specific elements for the leach feed. • Atomic Absorption Spectroscopy (AAS) –Used to find concentration of elements within leach liquor to determine effectivity of test work. The AAS machine used was a 55B AA Agilent Technology system. • Inductively Coupled Plasma Mass Spectrometry (ICP-MS) – Used for characterisation of leach feed material and also concentrations of leach liquors. This machine was used by Nagrom Metallurgical for feed leach concentrations. • Fume Hood – Extraction of harmful vapors and mitigation of odors from lithium electrolyte material during battery decomposition and also vapors from leaches. • Heated Bath – Used to maintain leaches at desired temperature and keep solids in suspension to optimize surface reaction with acids. • Beakers, flasks, measuring cylinders, sample bottles, pipettes etc.

46 | P a g e 3.3 Method

3.3.1 Battery Discharge

To safely disassemble a battery, it is mandatory to ensure it is fully discharged. Batteries that still contain charge have the ability to short, explode or catch on fire. A well investigated process was needed to discharge the 18650 lithium ion batteries.

A few options were considered such as the discharging through salt water, short circuiting, a lightbulb circuit configuration, laptop discharge and also a resistor circuit. In many case studies, the pre – treatment of lithium ion batteries was made simple as the batteries were recycled meaning that they had no charge. The batteries purchased however were fully charged at 3.7 V. In 2017, Chen et al used an electrolyte solution to discharge the batteries to 0.0 V (Chen 2017). The ions in solution allow for the complete discharge of the battery however the process is quite long for batteries with full charge.

Short circuiting was an option however due to the large amount of current flowing through the battery, the lithium ion battery started to smoke suggesting that there was not enough resistance. A resistor circuit was the easiest method to discharge the batteries safely. Using multiple 1 ohm resistors in series due to the 3.7 V voltage, the batteries would deplete in charge within 20 – 30 minutes. The voltage however would remain at approximately 1.7 V as a safety mechanism built inside the battery faults the discharge when going below a certain voltage. Although the resistors were very hot, it was a safe and relatively fast method to discharge the 20 batteries. The battery packaging was used to hold the battery during discharge. This is shown in Figure 3.3.1.

Figure 3.3. 1: Discharging mechanism for battery

47 | P a g e At 1.7 V, the batteries carried no charge and were safe enough to dismantle. Multiple checks were done on the battery before it was dismantled to make certain that little to no charge was in the lithium ion 18650 battery.

3.3.2 Battery Deconstruction

The lithium ion 18650 batteries needed to be dismantled very carefully as residual energy may cause shorting. The tools necessary to deconstruct the batteries were a fume hood for electrolyte vapors and also a pair of pliers to pry the casing open.

The batteries showed to be quite simple to disassemble and the technique made it easy. By prying open the top of the battery and removing the ‘cap’ or protector, the casing could slowly be pulled away into a spiral to reveal the inner layers. Below is a breakdown of the outer casing of the 18650 lithium ion batteries.

Figure 3.3. 2: 18650 lithium ion battery outer-shell components

48 | P a g e After removing the outer shell casing of the 18650 batteries, the inner roll of cathode, anode and separator could be found. Unraveling the roll showed the copper sheet coated with carbon graphite, the aluminum sheet coated with cathode material and the separators which had both carbon and cathode material attached. A current distributor rod was inserted into the middle of the roll to transfer current from one terminal to another.

Figure 3.3. 3: Inner-battery components

The three components of the inner battery were separated into beakers for further processing and cleaning. It was important that all test work was performed under a fume hood to decrease lithium electrolyte vapor contact. The electrolyte was very odorous and in some cases very hot when shorted.

Figure 3.3. 4: Separated components showing cathode, separator and anode material respectively

49 | P a g e 3.3.3 Material Cleaning

Removing the leach feed material from the cathode and anode was quite strenuous as the material had coated the copper and aluminum. The copper sheet was soaked in DI water to rinse off carbon graphite material, vacuum filtered and then dried under a heat lamp to remove excess moisture. Similar processes were repeated for the separator and aluminum sheet however the nickel-cobalt material was much more difficult to remove and needed to be scraped off of the surface. The aluminum sheet full clean was not possible as the metal material was too weak to be scraped. The aluminum sheet with attached LiCoO2 is shown in Figure 3.3.5.

Figure 3.3. 5: Aluminium foil with attached cobalt and nickel material

Recording weights of material extracted from the battery was quite interesting and showed little significance with literature findings. Anode material accounted for around 39 % of the total mass of the battery disregarding the aluminum anode. This finding was not representative of the whole battery composition as only small amount of cathode material could be extracted (10%). Although this does not support literature suggested in earlier sections, it is still possible that more material could be extracted from the aluminum sheets via better cleaning methods. A cleaning method that could be used is the ultrasonic bath with

50 | P a g e the use of acetic acid. Toma et al. used this process to release the strongly bound nickel and cobalt material from the sheets (Toma, 2017). Separator material also contains high amounts of the nickel-cobalt material with the carbon graphite. The separator material can also be leached for extractive purposes.

Table 3.3. 1: Mass Percentage for components of batteries

Battery Composition (20 Batteries) Component Mass (g) Mass Percentage % Cathode Material 31.72 10.37 Anode Material 118.52 38.76 Separator Material 67.25 21.99 Copper Sheet 88.27 28.87 Aluminium Sheet - -

3.3.4 Small-Scale Leaches

The following leaches were undertaken to check for recoveries of cobalt and nickel from spent lithium ion battery material. The leaching mechanisms of the sulfuric acid can be shown in the results and discussion component of this thesis. Obtaining the correct parameters was mandatory to show relevance and also provide a base case for the optimization leach.

Table 3.3. 2: Variable Time Leach Conditions

H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)

2 M 4 % 70 50:1 VARIABLE*

VARIABLE* = 50, 60, 70, 120 and 180 minutes

Table 3.3. 3: Variable Temperature Leach Conditions

H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)

2 M 4 % VARIABLE* 50:1 70

VARIABLE* = 30, 40, 50, 60, 80 C°

51 | P a g e Table 3.3. 4: Variable Acid Concentration Leach Conditions

H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)

VARIABLE* 4 % 70 50:1 70

VARIABLE* = 1, 4 and 6 M

Table 3.3. 5: Variable H2O2 Concentration Leach Conditions

H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)

2 M VARIABLE* 70 50:1 70

VARIABLE* = 0, 2, 4 and 6 %

Once all of the variables have been considered and tested for optimization, an optimization leach can be conducted to achieve the best possible process for the extraction of cobalt and nickel material from spent lithium ion batteries using a leaching method.

Table 3.3. 6: Optimisation Leach Conditions

H2SO4 Concentration H2O2 Concentration Temp (C°) L/S mass ratio Time (min)

Optimised Optimised Optimised 50:1 Optimised

Figure 3.3.6 shows the eventual breakdown of the full method with concentrations and mass percentages for majority of streams. If results are to be replicated or furthermore improved, it is important to follow a similar method to show relativity.

52 | P a g e

erial

Event tree showing the method for leaching of spent lithium ion battery ion lithium mat spent themethod leaching of for cathode showing Eventtree

: :

6

Figure3.3.

53 | P a g e 3.3.5 AAS & ICP-MS Analysis

AAS analysis was carried out on the leach liquors and wash solutions to analyze for cobalt and nickel extraction. Below are the standard graphs which were used to show accuracy within results. As shown by each graph, R2 figures were recorded and are kept relatively high to assure accuracy. As the leaches were analyzed in two separate dates, two different graphs are presented for both nickel and cobalt trends.

1 0.9 0.8 0.7 y = 0.0101x 0.6 R² = 0.9974

0.5 Abs 0.4 0.3 0.2 0.1 0 0 10 20 30 40 50 60 70 80 90 100 Concentration (ppm)

Figure 3.3. 7: Nickel standard curve 1 showing error and equation

0.14

0.12

0.1

0.08 y = 0.0014x

Abs R² = 0.9997 0.06

0.04

0.02

0 0 10 20 30 40 50 60 70 80 90 100 Concentration (ppm)

Figure 3.3. 8: Cobalt standard curve 1 showing error and equation

54 | P a g e 1 0.9 0.8 0.7 0.6 0.5 y = 0.0095x + 0.0463 Abs R² = 0.9866 0.4 0.3 0.2 0.1 0 0 10 20 30 40 50 60 70 80 90 100 Concentration (ppm)

Figure 3.3. 9: Nickel standard curve 2 showing error and equation

0.12

0.1

0.08 y = 0.0012x + 0.002 R² = 0.9988

0.06 Abs

0.04

0.02

0 0 10 20 30 40 50 60 70 80 90 100 Concentration (ppm)

Figure 3.3. 10: Cobalt standard curve 2 showing error and equation

55 | P a g e Chapter 4 - Cathode Characterisation

Characterizing the cathode material is important to understand the leach mechanisms taking place. Obtaining baseline elemental results in the feed will give indication of how efficient and effective the leaching was. Multiple assays can bring out an average in elemental composition which decreases error and shows accuracy in lab results.

4.1 External Cathode Characterisation Assays

The cathode characterisation was carried out through external test work. The initial feed cathode sample was assayed externally by Nagrom Metallurgical. Nagrom is a local laboratory operating out of Western Australia that specialize in assaying and metallurgy (Nagrom, 2018). Triplicate samples were assayed via ICP-MS through the Nagrom laboratory to determine the elemental composition of feed material to be leached. Obtaining accurate results for the elemental composition of the cathode material would allow comparisons to be drawn from the leaches and also gives clear indication of what material is being leached from the feed material. The samples were extracted from the initial leach feed material by a riffle splitter to achieve a relatively homogenous sample.

Table 4.1. 1: Cathode, Anode and Separator characterisations via ICP-MS in standard ppm concentrations

Al Co Cu Li Li2O Mn Ni

Units ppm ppm ppm ppm ppm ppm ppm

Cathode 4350 238500 <100 40075 86270 24500 46550

Anode 700 700 300 <100 <100 100 100

Separator 200 279225 200 48000 103340 29900 56400

56 | P a g e Table 4.1.1 shows the composition of each assayed material. The assays were completed in triplicate samples to assure representative results and accurate compositions. It was interesting to assay the separator and anode materials as some notable compositions were found, shown in table 4.4.1. The two elements to be leached from feed were cobalt and nickel. Cobalt in both cathode and anode were as expected as the cathode material would have been predominately LiCoO2, while the anode would have contained more graphite. The given concentration of 700 ppm in the anode would have most likely been contamination through the cleaning process.

The nickel concentration in the anode was expected to be quite low however the cathode nickel concentration was notably low. With cobalt concentration being over 5 times that amount of nickel concentration, it is evident that the cathode composition was more cobalt based than nickel based.

The separator findings were also unexpected. Taking the battery apart, it would be expected to find that the separator material’s cobalt and nickel concentration would be less than that of the cathode material. This however was proved wrong as both nickel and cobalt concentrations were higher in the separator material than in the cathode material. This is most likely due to the inefficient cleaning methods or the discharging method. If the cleaning methods were the reason for the higher concentrations in the separator than the cathode, it would most likely be because of the contamination between the two samples. As the powders within the battery cell were very fine, it was easy to mix the two cobalt and nickel concentrated powders. Another reason could have been the discharge methods in order to take the battery apart. As the lithium-ion batteries contained safety mechanisms to stop the battery from discharging to 0 V, it would have been possible that the ‘cathode’ material was still being transferred to the aluminum foil, however was stopped by the discharge safety mechanism. This would mean that a great deal of cobalt and nickel ions would have been forming on the separator.

In the literature review section of this thesis, it discusses that all batteries have a cycle life and this produces an irreversible process that disallows the battery to charge, in this case, this is why the separator contains more nickel and cobalt than the aluminum cathode.

57 | P a g e Chapter 5 - Leach Results

5.1 Time Variable Results

Using the various leach times, it was possible to draw conclusions into the kinetics and extraction of each leach. Observing the colors of leach liquor is the first form of noticeable extraction. The leaches all under various times produced reddish-pink leach liquors suggesting large amount of cobalt has been leached from the feed solids (Flett, 2004).

Figure 5.1. 1: Pink leach liquor with 50-minute time leach

The time variable leaches were carried out at 50, 60, 70, 120 and 180 minutes. These times were set to find a general extraction curve with the focus on getting an optimum time. Figure 5.1.2 shows the cobalt and nickel extraction over the given set of times. As shown, nickel concentration is drastically less than cobalt concentration however a trend is shown. Initial timings (50, 60 and 70 minutes) show slight decreases in extraction however both elements are shown to have the highest concentration with the two hour leaches. Cobalt achieves 5.29 g/L into solution while nickel achieves 1.56 g/L into solution.

58 | P a g e 6.00 1.8

1.6 5.00 1.4

4.00 1.2

1 3.00 Cobalt 0.8 Nickel 2.00 0.6

0.4

1.00 LeachLiquor Concentration Nickel (g/L LeachLiquor CobaltConcentration (g/L) 0.2

0.00 // // 0 0 50 60 70 120 180 Time [min] Figure 5.1. 2: Time vs Co & Ni Extraction

As shown, equilibrium for cobalt and nickel in solution occurs in the first 50 minutes of the leaches. This is shown by the plateau in both elements and only the slight decrease and increase in concentration of liquor through to the 180-minute test. This gives indication that the solution is either supersaturated with cobalt and nickel ions and the pulp density needs to decrease (below 1:50) or all of the cobalt and nickel in the leach feed has been extracted into solution. Increasing the acid volume to a ratio of 1:75 would increase the capacity for ions in solution however keeping costs low was a factor. If the leach feed cobalt and nickel has been fully extracted, increasing the pulp density may be a method in the increase of concentration of cobalt and nickel in solution. A time leach below 50 minutes could also be undertaken to find the general curve of the rate of extraction before equilibrium however cathode material for testing was limited. For optimization purposes however, 2 hour leaches achieve the greatest concentration of cobalt and nickel ions.

59 | P a g e 5.1.1 Change of pH on Time Leach

The change of pH can be linked to the extraction of the leach mechanism. As time increases the change in pH also increases. These results can be compared to a similar study on the leaching of cobalt in sulfuric acid solution. Although a longer length of time is trialed, latter pH changes are similar to test work in that a decrease in pH is found (Sohn 2006). Sohn (2006) attributed the initial increase in pH of solution to the mixing of acid, showing the initial increase. After this increase however, pH steadily decreases. Very similar conditions were used however pulp density does play a key factor into the high recoveries. pH similarities however can be drawn.

100 0.29

90 0.27

80 0.25

70 0.23 pH 60 0.21

50 0.19 PrecipitationRate (efficiency) (%)

40 0.17

30 // // // // 0.15 0 1 2 3 4 5 6 7 13 25 46 70 Time [hr]

Figure 5.1. 3: pH variation of solution during precipitation (Sohn, 2006)

60 | P a g e 0.14

0.12

0.1

0.08 Delta pH Delta

0.06

0.04

0.02 50 70 90 110 130 150 170 190 Time [min]

Figure 5.1. 4: Time vs Delta pH

The reason for the decrease in pH over time is due to hydrogen ions into solution. The pH equation is given below; pH = -log[H+] [3]

This equation shows the relationship between hydrogen ions and pH. An increase in hydrogen ions in solution is due to the sulfuric acid reacting with the cobalt oxide material causing a dissolution of hydrogen ions (Yakusheva, 2010). This suggests that as time increases with the leaching mechanism, increased amount of hydrogen ions accumulate to decrease pH levels within solution.

61 | P a g e 5.2 Temperature Variable Results

Temperature can heavily effect leaching activity which is shown through the Arrhenius equation below.

−퐸푎 푘 = 퐴푒 푅푇 [4]

The rate constant (k) is effected by temperature (T) shown. This is good indication that the change in temperature will have a positive or negative impact on the leach recovery. This claim is supported by Figure 5.2.1 in which both nickel and cobalt show change in liquor concentration with the change in temperature. Cobalt extraction with temperature shows logarithmic growth as temperature increases shown in figure 5.2.1, this is good indication that the rate of leach reaction (k) is increasing with the increasing temperature.

6.00 1.60

1.50 5.00

1.40 4.00

1.30

3.00 Cobalt 1.20 Nickel 2.00

1.10

LeachLiquor Concentration Nickel (mg/L) LeachLiquor CobaltConcentration (mg/L)

1.00 1.00 40 50 60 70 80 Temperature [C°]

Figure 5.2. 1: Leach temperature vs leach liquor concentration of nickel and cobalt

62 | P a g e Nickel concentration in leach has only slight increases over 50°C. This is most likely due to the nickel being the limiting factor in the reaction. If all nickel has been leached into solution at 50°C the concentration will not increase. Changing the solid/liquid ratio could be a mechanism to increase this nickel concentration. Cobalt loss however could be a factor as the cobalt in feed material is obviously still able to be leached above the 50-degree temperature. Having a low concentration of nickel in the feed mass is the reason why low nickel concentrations in solution are found. Cobalt concentration achieved approximately 5.1 g/L while nickel concentration achieved approximately 1.5 g/L. Although the leaching mechanism is similar for both leach reactions, limiting factors are the reason for the difference in trend. In conclusion, an increased in temperature has a positive impact on the recovery of nickel and cobalt.

5.2.1 Change of pH on Temperature Leach

Effect of temperature on the pH of solution is not as expected. With the increase in hydrogen ions, pH decreases. This is not evident with Figure 5.2.2 as the decrease in pH is less at 80 °C than the 60 and 70°C temperature’s respective pH decrease. This suggests that there is an equilibrium point between 60 – 70°C where dissociation is maximal. Above these temperatures, hydrogen ions are being drawn from solution suggesting the formation of precipitation maybe occurring. Although no precipitation was noticeable at 80°C, the decrease in hydrogen ions in solution suggest a cobalt or nickel complex was most likely forming.

0.12

0.1

0.08

0.06 Delta pH Delta 0.04

0.02

0 40 45 50 55 60 65 70 75 80 Temperature (C)

Figure 5.2. 2: Temperature vs Delta pH

63 | P a g e 5.3 Acid Concentration Variable Results

Leach liquor concentration of both nickel and cobalt is only slightly effected by the concentration of sulfuric acid. 1, 2, 4 and 6 M solutions of H2SO4 were made up to identify the relationship between extraction and sulfuric acid concentration. As shown in Figure 5.3.1, leach extraction for both elements do not differ greatly over the various concentrations. The greatest recoveries of both nickel and cobalt were achieved at sulfuric acid concentrations of 4 M. Above 4 M, extraction mechanisms look to diminish as suggested by the 6 M concentration.

5.00 1.45

1.40 4.00

1.35

3.00

Cobalt 1.30 Nickel 2.00

1.25

LeachLiquor Concentration Nickel (g/L) LeachLiquor CobaltConcentration (g/L)

1.00 // // 1.20 1 2 4 6 [H2SO4], M Figure 5.3. 1: H2SO4 Concentration Vs Leach Liquor concentration of nickel and cobalt

By observing Figure 5.3.1, it is quite possible to see that the extraction equilibrium is achieved between 1 to 6 M. This gives indication that to find the correct acid molarity vs extraction curve, sulfuric acid concentrations below 1 M would have to be trialed. This is supported by literature where most extraction change occurs before 1.5 M shown in Figure 5.3.2 (Nayl 2017). Sulfuric acid solutions with a higher concentration than 3.5 M also shows to decline in extraction for both nickel and cobalt. Concentrations below 1 M could have been trialed however cathode and separator material was limited.

64 | P a g e 100 90 80 70 Mn 60 Li 50 Co 40 Ni 30

Leaching Percentage E) (% 20 10 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 [H2SO4], M

Figure 5.3. 2: H2SO4 Concentration Vs Leach Liquor concentration of various elements (Nayl 2017).

5.3.1 Change of pH on Acid Leach

The effect of sulfuric acid concentration on the change of pH is negligible shown in figure 5.3.3. As leach extraction decreases after 4 M, a notable difference in pH increase is recorded. This is contradictory to what was previously related between extraction and dissolution in equation [4]. To identify the errors, it would be important to increase the amount of intervals to display accurate results that are backed through multiple tests.

0.14

0.12

0.1

0.08 Delta pH Delta 0.06

0.04

0.02 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

[H2SO4], M

Figure 5.3. 3: H2SO4 concentration Vs Delta pH

65 | P a g e 5.4 Hydrogen Peroxide Concentration Variable Results

Hydrogen peroxide as an additive does show to effect extraction of both nickel and cobalt logarithmically. With the trend identified in Figure 5.4.1, both nickel and cobalt increase with a similar leach rate. Although nickel and cobalt concentration in leach feed are very different, it is interesting to find that both have the same leach characteristics. These similar leach characteristics can be an advantage into the identification of a leach process for spent Li-ion battery cathodes as only a single process needs to be used. If nickel and cobalt were both leached at different conditions or rates, designing a process would become more complex and may introduce a higher cost for processing.

5.50 1.60

1.40 4.50 1.20

1.00 3.50

0.80 Cobalt 2.50 Nickel 0.60

0.40

1.50 LeachLiquor Concentration Nickel (g/L LeachLiquor CobaltConcentration (g/L) 0.20

0.50 0.00 0 2 4 6

[H2O2], %

Figure 5.4. 1: Hydrogen Peroxide addition % (H2O2) Vs cobalt and nickel concentration in leach liquor

The hydrogen peroxide % that produces the best recovery of both cobalt and nickel was 6 %, which was the highest test for H2O2. This however does not give clear indication of the optimal hydrogen peroxide concentration needed to optimise the leach. To find this optimum hydrogen peroxide to sulphuric acid ratio, a higher test range would need to be completed. For the given test range, maximum cobalt in solution is approximately 5.1 g/L while nickel in solution is approximately 1.5 g/L. Increasing the hydrogen peroxide in intervals up to 20 %, a

66 | P a g e clear optimised additive content could be deduced. Above this optimised percentage, it would be realistic to find a decrease in nickel and cobalt recovery due to the acid concentration decrease.

100

90

80 Mn Ni 70 Co Li 60

Leaching Percentage (%E) 50

40

30 0 1 2 3 4 5 6 [H2O2], %

Figure 5.4. 2: Hydrogen Peroxide Addition Vs Leaching Percentage of various elements (Nayl 2017)

Figure 5.4.2 shows the relationship between peroxide and leaching recovery of various elements. It shows that at around 4 % hydrogen peroxide, the highest recovery is achieved and in fact tends to decrease above this concentration of additive (Nayl 2017). This test work however was conducted with ~ 100 % w/v H2O2 additive whereas 30 % w/v H2O2 solution was used for the purpose of decreasing costs of the process.

67 | P a g e 5.4.1 Change of pH on Peroxide Leach

As shown in Figure 5.4.3, the pH is not effected by the addition of H2O2. As multiple peroxide tests were completed, it is clearly evident that there is no effect on pH. This is an interesting finding as the change in cobalt and nickel extraction was clearly effected by the addition of hydrogen peroxide, however no noticeable change in pH was noted with the change in hydrogen peroxide.

1

0.9

0.8

0.7

0.6

0.5

DeltapH 0.4

0.3

0.2

0.1

0 0 1 2 3 4 5 6

[H2O2], %

Figure 5.4. 3: H2O2 % Vs Delta pH

68 | P a g e 5.5 Leach Optimization

Leach optimizations were carried out to achieve maximum recoveries possible with the given conditions while limiting costs of the process. The leach parameters used were taken from the maximum recoveries within each leach test and are shown in Table 5.5.1.

Table 5.5. 1: Optimisation parameters for both cathode and separator material

Temperature (°C) Time (min) Solid/Liquid Ratio H2O2 Conc (%) H2SO4 Conc (M) 80 120 50:1 4 M 6 %

Optimization leaches were carried out on both cathode and separator materials. Although the baseline leaches were completed on the cathode material to find optimization results, it was important to also test these parameters on the separator material as a high concentration of targeted metal to be extracted was discovered. If the same parameters could be used for the extraction of nickel and cobalt on both separator and cathode materials, it would reduce the cost as both materials could be leached together. Ideally, a concentrated leach feed of high grade is the best material for leaching hence separating the components of a lithium-ion battery does provide to produce a higher concentrated feed of nickel and cobalt. Cost factors however need to be considered as it may be cheaper to leach all of the battery including anode, casing etc.

The cathode optimization leach was quite successful however results tend to show a large amount of error. As the cathode composition revealed an average of 238500 ppm cobalt, this suggests approximately 23.85 % of the 1-gram sample was cobalt. The cobalt extraction in the cathode optimization leach revealed an optimum of 5 g/L. This suggests that using 1 gram in 54 mL as a reference, 0.27 grams of cobalt was found to be leached into solution. These values show subsequent error as the recovery of cobalt in the optimization leach is approximately 113.2 %. More cobalt is being extracted from the feed material than the amount of cobalt that is in the feed material. This error is most likely attributed to the feed characterisation. As only two tests were assayed on the leach feed material, it may be likely that a higher concentration Co-Ni leach feed was leached or a lower concentration Co-Ni sample was assayed.

69 | P a g e The nickel concentration in solution with the cathode material achieved 0.849 g/L. Again using 1 gram and 54 mL as a reference, 0.0459 grams of nickel was found to have leached. With the characterisation of the leach feed cathode material, 4.655 % of the material was Ni. This is clear indication of good leach recovery as 98.6 % recovery was achieved.

Although high recoveries were achieved with the leach optimization, it is important however to note the decrease in extraction with the optimization parameters. As the optimization was imposed to find the best possible parameters to achieve the highest nickel and cobalt recovery, it has not been the case in this instance. A lower cobalt and nickel concentration was found in both optimization leaches for the cathode material. This is most likely because even though one parameter may be optimized for leach recovery, it may come into conflict with the leach mechanism of a different parameter. To overcome this problem, it would be important to observe all leach conditions at different parameters as adverse or negative leach reactions can occur. For example, if the extraction is greatest at 2 hours and in a separate test at 80 °C, it may not necessarily mean the extraction will be the greatest at 2 hours and 80 °C in the same test.

Table 5.5. 2: Cobalt and nickel recoveries in both cathode and separator materials.

Co Feed [%] Ni Feed [%] Co Opt [g] Ni Opt [g] Co Recovery Ni Recovery

Cathode 23.8500 4.6550 0.2700 0.0459 113.2% 98.6%

Anode 0.0007 0.0001 - - - -

Separator 27.9225 5.6400 0.3060 0.0567 109.6% 100.5%

Table 5.5.2 shows the nickel and cobalt recoveries for the cathode as well as separator. As indicated, cobalt recovery in the optimization cathode leach is approximately 109.6 % which is less than the cathode optimization leach. Again these results tend to show high % error and it supports the argument that the feed mass was not indicative of the overall sample. As both separator and cathode recoveries are above 100 %, it suggests that the main reason for error is the non-representative sample. The nickel recovery if compared to the cathode leach is actually higher, at 100.5 % however this suggests there is some error.

70 | P a g e These results can be used to conclude that the given parameters achieve better cobalt recoveries in the cathode material leach while the nickel recovery is increased with the separator material. It is difficult to draw conclusions with recoveries when the feed sample is not representative, therefor it is crucial to re-assay the samples and perhaps decrease particle size for a more representative sample which can be used to find more accurate recoveries.

An interesting point of discussion was the change in pH pre and post leach for both cathode and separator materials. While the greatest pH change was a 0.13 decrease in the standard leaches, the optimization leaches shows to have a 0.49 and 0.59 pH drop for the cathode and separator materials respectively. This suggests that an increase in H+ ions are in solution which is representative of the reaction taking place. This however is not supported by extraction results as higher recoveries of both nickel and cobalt took place at different parameters.

71 | P a g e Chapter 6 – Conclusions and Recommendations

6.1.1 Conclusions

The demand for lithium-ion batteries into the future will continue to rise as technology advances and the advantages of lithium – ion energy storage systems are needed. To ensure this demand is supplied, it is crucial to find alternative and more efficient processes to not only extract lithium-ion battery components from the source (mineral) but also recycling. This thesis identified the cost drivers surrounding the lithium-ion battery, constructed a formal method in decreasing the cost drivers through recycling and also presented the results to be further investigated. As similar investigations and reports have been published into the recycling of lithium-ion energy storage systems, it is important to further those studies to produce and make more effective already trialed processes.

The literature review section of this thesis identified that the cost drivers surrounding lithium- ion batteries were nickel and cobalt metals used in the cathode material. These metals proved to be the costliest component of the battery and showed that the reduction of these components would dramatically reduce the overall battery cost. The reduction of this cost would mean that the battery would be even more viable in the energy storage market than it already is.

Observing cobalt and nickel reserves, it was evident that there will come a time when a different energy storage system will have to be commercially available as reserves deplete. The recycling of the cobalt and nickel within the battery cathode would be a way to decrease demand on the raw mineral processing which would lead to the reduction in overall process cost for the lithium-ion battery. Finding an effective recycling process was made easy through literature and already published methods. The method that provided the highest concentrations at a relatively low cost was the hydrometallurgical process of leaching through the use of sulfuric acid (Nayl, 2017).

Through the alteration of certain cost factors in regards to the leach process, the aim was to increase recovery while decreasing the cost component for the hydrometallurgical process.

72 | P a g e The parameters that were tested for reduction were time, temperature, sulfuric acid concentration, hydrogen peroxide concentration and also the battery component material.

This test work differed to other literature in that the leach material that was used was highly concentrated through the manual breakdown of 20, 18650 – ICR lithium-ion batteries. This high concentration of both nickel and cobalt in material could be compared to standard lithium-ion battery recycling techniques which usually consists of lower concentrations due to the high impurities in the feed. A cost analysis could be completed to find if it is more or less cost effective to breakdown the battery components and leach the concentrate. This would depend on recovery and time factors.

It was concluded that although high recoveries were achieved within the leach optimizations for both nickel and cobalt, the results are inconclusive with the high amount of error. Achieving recoveries over 100 % brings about speculation in research and is usually accounted for in accountabilities and repetition in testing. Multiple recommended technical changes can be made to decrease the error in the results and is discussed in the following section 6.1.2.

6.1.2 Recommendations

To further the investigation into the recycling of lithium ion batteries by a hydrometallurgical approach, it is important to recommend different aspects of which should be considered. These aspects from a test-work point of view may make the results more valid or decrease error within achieved results. Broadening the test work schematic may also lead to the increase in development into the process and therefore aids in the commercialization of the leaching of cathodes from spent lithium ion batteries.

Accountability throughout the test work is pivotal into the reliability of data and results. It is crucial that when performing leach studies, whatever is input into the leach cell is taken out and tested. This will assure that all mass and compositions have been accounted for which confirms results and decreases error. As assays are relatively expensive when completed externally, it was not possible to retrieve all accountability data. This data however would have been helpful to support presented arguments surrounding compositions and leach recoveries.

73 | P a g e Internal characterisation could have been completed on the feed and residue samples. This characterisation includes Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). These machines could have been used to further study the structures and compositions on a microscopic and angular level. The SEM could have identified new methods into the processing of the leach feed as microscopic imagery can enhance understanding by showing certain characteristics about the material that is not seen by the naked eye. XRD could have been used to identify pre and post leach material compositions which would have supported arguments made about leaching recovery and efficiency. As the SEM machine was not operational in the time the test work was being carried out, it was not possible to obtain the information and imagery.

As shown in Table 3.3.1, the battery cathode cleaning suffers in that not a large amount of cathode material was recovered. As the cathode material was the subject material to be leached in the test work, it was disadvantageous to the results as only small leaches could be carried out. If larger amounts of cathode material were recovered, increased sized leaches could have been undertaken which would have decreased the amount of error. It was difficult to draw conclusions between test work battery material compositions and literature battery compositions as the cathode material was unable to be retrieved. A better cleaning method that may be able to extract this valuable material is acetic acid usage in ultrasonic baths (Toma 2017).

An increased amount of parameters could have been tested to increase recovery. Such parameters that could have been tested and measured includes pH change of solution with the use of NaOH, measurement of Eh, leaching of certain apertures and sizing and also the different liquid/solid mass ratios. All of these factors most likely would have made a large difference to the final recovery of the leach and therefore should be investigated to achieve a worthwhile process. The increase in surface area of a material increases the rate of dissolution and therefore increases the recovery and rate of leach (Peelman 2016). This suggests that the use of a mill or pulverizer would decrease the particle sizes and increase the surface area for leaching, thus increasing extraction.

Increasing the peroxide concentration range will most likely also increase the extraction of nickel and cobalt. As shown in Figure 5.4.1, extraction shows logarithmic increase and is most likely to increase even past 6 %.

74 | P a g e Increasing the amount of feed characterisation assays would have been helpful in the composition make up of feed material. Decreasing the error is a critical to achieve credible results. As displayed in the optimization section of this thesis, it is evident that there is error within the leach feed compositions. If this feed material was averaged over an extended amount of assays as well as large sample sizes, the composition data would have minimal error. Further homogenization of the feed material would also achieve credibility towards accuracy and data reliability.

A drop in pH was unexpectedly recorded for all tests. This was most likely due to the excess acid converting to H+ ions. As the liquid/solid mass ratio was approximately 50:1, the reaction allowed for the sulfuric acid to be in excess. Test work allowed for such high doses of sulfuric acid as the liquid/solid mass ratio was approximately 10:1. This would have made a large difference on the acid usage and allowed for H+ ions to be drawn from solution hence increasing pH. A free acid test could have been used to identify this excess usage of acid however time was a constraint. As the material used for the leaches was manually taken from spent lithium ion batteries, the material usage was also a limiting constraint that hindered pH results and correct parameters.

75 | P a g e Chapter 7 - References

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