Automotive Batteries 101

AUTOMOTIVE BATTERIES 101

JULY 2018 WMG, University of Warwick Professor David Greenwood, Advanced Propulsion Systems The battery is the defining component of an electrified vehicle Cost Power Range

Package Life

Ride and Handling

ENGINE MOTOR ‘BATTERY’ BATTERY FUNCTION

CONVENTIONAL 100kW Starter motor 12V Engine starting (ICE) Full transient Stop/start 3kW, 1kWh (3kW, 2-5Wh) Ancillary loads (400W average, 4kW peak, ~1kWh)

MILD HYBRID 90-100kW 3-13kW 12-48V Absorb regenerated (MHEV) Full transient Torque boost/re-gen 5-15kW, 1kWh braking energy

FULL HYBRID 60-80kW 20-40kW 100-300V Support acceleration (HEV) Less transient Limited EV mode 20-40kW, 2kWh

PLUG-IN HYBRID 40-60kW 40-60kW 300-600V Provide primary power (PHEV) Less transient Stronger EV mode 40-60kW, 5-20kWh and energy Increasing power to energy ratio power to energy Increasing RANGE-EXTENDED 30-50kW 100kW 300-600V Provide primary power (REEV) No transient Full EV mode 100kW, 10-30kWh and energy

ELECTRIC VEHICLE No Engine 100kW 300-600V Provide sole power (EV) Full EV mode 100kW, 30-80kWh and energy source

COMPONENT COSTS FOR ELECTRIFICATION OF POWERTRAIN BATTERY Conventional COST IS THE SINGLE MHEV BIGGEST FACTOR

HEV Engine/Transmission Battery Power Electronics Motor PHEV Charger E-ancillaries

0 2000 4000 6000 8000 10000 12000

Bill-of-Materials Component Cost €

• Costs have fallen dramatically due to technology, production volume and market dynamics 4000 • Pack cost fallen from $1,000/kWh to <$250/kWh in less than 8 years 3000

2,000 95% conf interval whole industry 1,900 95% conf interval market leaders 2000 1,800 Publications, reports and journals 1,700 News items with expert statements 1,600 Log fit of news, reports, and journals: 12 ± 6% decline 1,500 Additional cost estimates without clear method 1,400 1000 Market leader, Nissan Motors, Leaf 1,300 Market leader, Tesla Motors, Model S 1,200 Other battery electric vehicles 1,100 Log fit of market leaders only: 8 ± 8% decline 1,000 Log fit of all estimates: 14 ± 6% decline 900 0 Future costs estimated in publications 800

2014 US$ per kWh

Graph credit: Nkyvist et al 2014

Lithium-ion cell Module Pack

e.g. pouch or cylindrical cell e.g. module for pouch cells (Nissan Leaf) e.g. pack for pouch cells (Nissan Leaf)

As a single unit, a ‘cell’ performs the A ‘module’ is formed by connecting A ‘pack’ is formed by connecting primary functions of a rechargeable multiple ‘cells’, providing them with multiple ‘modules’ with sensors ‘battery’. Cells come in varied formats: a mechanical support structure and and a controller and then thermal interface and attaching housing the unit in a case. • Cylindrical Cells terminals. Modules are designed Electric vehicles are equipped • Pouch Cells according to cell format, target pack with batteries in a ‘pack’ state voltage and vehicle requirements. which are connected to • Prismatic Cells the powertrain.

Cathode Charge Anode • Lithium-ion (Li-ion) is a negative electrode to the Discharge general term for a variety of positive through the outer + - batteries whose properties circuit (the power supply). Li e rely on lithium as the When no more lithium-ions Li e- Li+ charge carrier. Li-ion offers will flow, the battery is advantages over other fully charged Cathode Material Anode Material e.g. LiCoO2 e.g. graphite chemistries such as weight • During discharge, the and voltage. For automotive lithium-ions flow back purposes, rechargeable through the electrolyte/ Anode/cathode materials: specific capacities and cells are used separator to the cathode. operating voltages vs pure lithium • There are many types of Electrons flow back to the Different chemistries suit specific requirements Li-ion battery depending anode through the outer 5 LiMn Ni O on the exact combination circuit. When all ions have 1.5 0.5 4 ENERGY DENSITY 4.5 LiMn1/3Co1/3Ni1/3O2 of materials used for the moved back, the battery is LiMn2O4 4 Cathode anode and cathode fully discharged and needs LiNiO2 3.5 LiCoO2 recharging 2.8V Anode • During charging, the 3 LiFePO 3.7V 4 3.5V positively charged lithium- • A motor converts the 2.5 Li2FeS2 ions flow from the cathode, electrical energy from the 2 3.2V

Voltage vs Li(V) Voltage LTO 2.0V through the electrolyte/ battery into mechanical 1.5 TiO -B 2 Hard Carbons separator, to the anode energy to turn the wheels 1 Metal Nitrides 3.8V Silicon where they are stored. Graphite Lithium • Electricity from the grid is M alloys Electrons flow from the 0 used to charge the battery 0 200 400 600 3500 4200 141 mAh/g Specific Capacity (mAh/g) 3.7 V x 141 Ah/kg = 512 Wh/kg

CATHODE/ANODE MATERIAL STRENGTHS WEAKNESSES

Lithium Cobalt Oxide • High energy • Thermally unstable (LCO) Cathode • High power • Relatively short life span • Limited load capabilities

Lithium Manganese Oxide Spinel • High power and thermal stability • Low capacity compared to other cathode materials (LMO) Cathode • Enhanced safety • Limited life cycle • Low cost • Need advanced thermal management

Lithium Nickel Cobalt Aluminium • High specific energy • Safety issues Oxide (NCA) Cathode • Good specific power • Cost • Long life cycle Cathode Lithium Nickel Manganese Cobalt • Ni has high specific energy; Mn adds low • Nickel has low stability Oxide (NMC) Cathode internal resistance • Manganese offers low specific energy • Can be tailored to offer high specific energy or power

Lithium Iron Phosphate • Inherently safe; tolerant to abuse • Lower energy density due to low operating (LFP) Cathode • Acceptable thermal stability voltage and capacity • High current rating • Long cycle life

Graphite/Carbon-based • Good mechanical stability • Low volumetric capacity Anode • Good conductivity and Li-ion transport • Good gravimetric capacity

Lithium Titanate • Withstands fast charge/discharge rates • Lower energy density compared to (LTO) Anode • Inherently safe graphitic anodes

Anode • Long cycle life • Cost

Silicon Alloy • High gravimetric/volumetric capacity • High degree of mechanical expansion (Si) Anode • Low cost on charging • Chemical stability

CHEMISTRY* PROPERTIES/BENEFITS RESEARCH CHALLENGES

Solid State Batteries • Solid electrolyte and separator components; no concerns over • Improving poor conductivity ‘leakage’ • High volume manufacturing at • Improved safety due to lack of liquid electrolyte acceptable cost • High operating voltages increase potential energy density • Lighter and more space efficient; less need for cooling

Metal Air Batteries • Pure metal anode and ambient air/O2 cathode • Short life cycle e.g. Li, Al, Zn, Na • Very high theoretical capacity • Issues with practical rechargeability • Increased safety vs Li-ion • Air handling • No use of heavy metals • Energy density reduces at high power

Lithium Sulphur • High theoretical gravimetric energy density • Poor volumetric energy density (Li-S) • Sulphur is a low cost, abundant material • Issues with power density and • Improved safety discharge rate • Issues with cycle life stability

Sodium-ion • Sodium is a low cost, abundant material • Issues of volumetric/gravimetric energy (Na-ion) • Improved safety for battery transportation density compared to Li-ion

Silicon-based Electrodes • Si has ~x10 gravimetric capacity compared to graphite • Does not offer long cycle life (Si) • Could be lighter and/or store more energy • Practical application constraints

*Promising chemistries included are those demonstrating suitable application potential for automotive requirements at lab scale.

Active electrodes: Thinly wound or stacked into alternating sheets of material following a pattern: cathode – separator – anode. Quality and purity of material has an impact on charge efficiency and battery life. • Cathode: Positively charged electrode in the battery cell, often made of a lithium metal oxide and coated on to a current collecting aluminium (Al) foil. Metallised • Anode: Negatively charged electrode in the battery cell, often made of foil pouch graphite and coated on to a current collecting copper (Cu) foil. Anode • Terminals: positive and negative contacts to connect the cells and module. Separator Cathode • Separator: Thin layer of polymer electrically isolates the cathode and anode from one another to prevent short circuit. Its structure allows lithium ions to pass through, allowing current to flow through the cell (microporosity) +ve/-ve Electrolyte Terminals • Electrolyte: A liquid transport medium which surrounds the electrodes and soaks into the separator, allowing lithium ions to flow freely • Additives: Electrode and electrolyte properties can be improved by adding small amounts of other components, e.g. conductive additives • Current Interrupt Device: A pressure valve disables the cell in case of Metal case over-charge/over-heating Anode Separator Cathode

Powder Mixing Coating Drying Calendering Slitting

Electrode manufacturing

Cell stacking Tab welding Packaging Electrolyte Filling Formation/ageing EoL Testing

Cell assembly/electrical formation

Cylindrical cells Pouch cells Prismatic cells

• Highly developed • Highest power and energy • Benefits lie part-way between density at cell level cylindrical and pouch cells • Standard sizes • Needs volume for • Layered approach improves • Used widely in consumer commercialisation space utilisation goods (well standardised) • Relatively lightweight and easy to • Allows highly flexible module • Mechanically self-supporting package for effective use of space design for differing requirements • High volumes and price competitive market Challenges: Challenges: • Little standardisation of format (VDA) • Little standardisation of format Challenges: • Requires supporting structure within (VDA) • Relatively heavy a module • Can be expensive to manufacture • Shape reduces packaging • Some cooling constraints • Large format cells contain high density • Large format cells contain high energy (safety issues if damaged) energy (safety issues if damaged) Image credit: Panasonic

Breakdown by relative weight and cost of cell materials shows the value is spread across components, not just from the primary electrochemical materials.

TYPICAL MATERIAL VOLUME (CYLINDRICAL CELL) MATERIAL COMPONENT COST BREAKDOWN (CYLINDRICAL CELL) Cathode Electrolyte 12% Material Electrolyte 9% e.g. NCA 42%

Separator 2% Separator 14% Anode Current Collector (Cu) 9% Anode Current Collector (Cu) Anode 5% Binders Anode 1% Binders 1%

Anode Material Cathode e.g. graphite 29% Binder 0% Cathode Conductors 1% Cathode Current Cathode Material Anode Material Cathode Current Collector Collector (Al) 1% e.g. NCA 53% e.g. graphite 29% (Al) 4% Cathode Binder 0% Cathode Conductors 0%

Cathode Material e.g. NCA Cathode Current Collector (Al) Anode Binders Separator Figures source: Cathode Conductors Anode Material e.g. Graphite Anode Current Collector (Cu) Electrolyte ITRI, Taiwan

Image credit: Institut francais des relations internationales (ifri)

1 Casing: Metal casing provides mechanical support to the cells and holds them under slight compression for best performance 2 Clamping frame: Steel clamping frames secure the modules to the battery case 3 Temperature sensors: Sensors in the modules 3 4 6 5 monitor the cell temperatures to allow the battery management system to control cooling and power Pouch cell module (Nissan Leaf) delivery within safe limits 4 Cells: Each module in a pack contains the same 1 3 4 6 7 number of cells. The number of cells varies by format and usage requirements 5 Terminals: Two terminals on the module allow it to be electrically connected to other modules via the bus bars 6 Cell interconnects: Each cell has two tabs – one 5 positive and one negative. These are welded together in series then connected to the terminals 7 Cooling channels: Liquid coolant runs between rows of cells to withdraw heat and avoid thermal runaway. Other packs, such as Nissan Leaf, instead use air cooling Cylindrical cell module (Tesla)

MODULE ASSEMBLY LINE

Module BoL Cell Module Welding Contact Welding Module EoL Test Insertion Welder Verification Welder Verification Test Cell Delivery Storage

Storage Module Delivery

Handling Assembly Test

Primary tasks: • Assembling the cells into a carrier • Installing the module control unit with • Testing the system • Joining the conductors in voltage and temperature sensors functionality architecture (typically welded) • Inserting cooling system components Lower cost achieved through if required increased automation.

© 2018 16 Automotive battery: 3 pack components 1 4 2 1 Upper case: Provides fire protection 5 Fusing: Fuses protect expensive and watertight casing for the components from damage due to battery components and protects power surges and faults it from dirt ingress. Also shields 6 Disconnect: Used to electrically service personnel from high voltage isolate the battery from the vehicle components during servicing or maintenance 2 Battery modules: A ‘module’ is 7 Cooling: Modules require formed by connecting multiple cooling. Packs may be cooled ‘cells’, supporting those cells in using air, water or vehicle air a structural frame and then conditioning system attaching terminals. Modules are designed according to cell format 8 Battery management system and vehicle requirements (BMS): The BMS ensures the cells remain within their safe operating 3 Bus bars: Electrically connect temperatures and voltages. It the battery modules together, measures the remaining charge and connect the modules to 9 8 7 6 5 in the battery and reports on the contactors state of health. It also ensures 4 Contactors: Electrically isolate the battery is correctly connected the battery pack from the vehicle. and isolated before closing Closed upon completion of safety the contactors tests and opened in the event of a 9 Lower case: Structural casing crash or battery fault supports the mass of the battery pack and protects it from damage Image credits: Nissan UK

Cells need to be monitored and controlled, e.g. temperature, voltage. The BMS is an electronic system that key off: store data

manages cells in a battery pack. key on: initialize • The BMS monitors and controls: Meas. voltage Estimate state Estimate state Balance Compute - State of charge (SOC) current of health of charge (SOC) cells power limits temperature (SOH) - State of health (SOH)

- State of function (SOF) Loop each measurement interval while pack is active - Safety and critical safeguards - Load balancing/individual BATTERY MANAGEMENT SYSTEM cell efficiency • Advances in BMS can provide Traction CAN Vehicle CAN Battery improved cell usage and efficiency Inverter Controller Charger and reduce the amount of battery CAN content required Interface Module • Requires highly skilled electronics CAN CAN and software engineering talent BMM Core Module BMM Core Module CAN BMM Core Module Current Sensor

8 Cell Stack 8 Cell Stack 8 Cell Stack Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell

Battery Pack

The primary function of the EDS is to provide +VE sensor the electrical conduction path through the HV Main Fuse Connector battery pack. MCB

It also: MCB Pre-CH Fuse Pre-CHARGE Contactor • Isolates the conduction path Pre-CH registor MCB • Measures current and voltage in the HV +VE Manual Service Battery high voltage (HV) line Disconnect Management System • Provides pre-charge function when MCB (BMS) HV -VE energising HV line MCB LV • Fuses the HV line in case of over-current Connector MCB • Provides manual disconnect of the HV line for vehicle servicing Current sensor +VE Contactor • Monitors effectiveness of the electrical insulation • The Low Voltage (LV) wiring also provides • The BMS receives inputs from • External connectors enable power for the battery control functions and voltage and temperature robust and safe connection allows communication between the battery sensors in the modules. In between the battery pack and and vehicle (CAN protocol). The LV wiring some packs, the BMS may also other vehicle systems. These also carries a signal (HVIL) to confirm all provide outputs to drive other are typically split into HV and LV external connectors are correctly in place components such as fans, connectors and potentially other and to ensure that HV conductors can not pumps or valves for the battery auxiliary connectors (to chargers be contacted externally cooling system or HV accessories)

PACK ASSEMBLY LINE

Module Module Module Lower Case Module Delivery BoL Test Acceptance Pre-assembly Insertion

Bus bar Assembly

Handling Electrical Assembly Integrity Test

Test Cooling System Assembly

BMS/EDS Connection

Battery EoL Acceptance Cooling Case Top Cover Shipping Testing System Test Pressure Test Assembly

Primary tasks: • Assembling the modules into • Connecting and testing power • Testing pack quality and the pack electronics system functionality • Joining the modules in pack • Inserting cooling system Lower cost achieved through architecture components if required increased automation.

New chemistries at proof of concept stage in the lab will take typically 10 years to emerge as market products.

MATERIAL PROOF OF MATERIAL INDUSTRIAL OEM PLANT PRODUCT CONCEPT SCALE UP DEVELOPMENT DEVELOPMENT RESEARCH DEVELOPMENT VALIDATION CYCLE

• Investigating new • Developing • Scale up of • Proving out • Validation of • OEM ready to chemistries promising promising at-volume cell R&D at the cell bring technology materials at materials manufacturing stage into 3-year • Understanding gram scale from lab to application development properties and commercially • At-volume cycle characterisation • Testing and viable cell • Supply chain testing of cells analysing validation of to industrial • OEM led activity • Chemical lab- properties for • Testing and R&D standards based/university application analysis of -led activity impact of scale • Optimisation of • OEM • Lab-based/ up on chemistry industrial scale validation • No limit to university-led manufacturing of required potential timescale activity • Validation of quality, for breakthrough manufacturing • Industry and reliability and to occur • Timescale processes university led safety levels dependent upon activity chemistry maturity • University and/ • Industry-led or industry led activity/OEM activity

Min. 3 Years ? ? ? 2 Years 3 Years 1-1.5 Years 2-3 Years decades

UKBIC is part of the UK Government’s Faraday Battery Challenge. UK BIC: SCHEMATIC VISION The establishment of this new facility is being led by Coventry City Council, Coventry and Warwickshire Local Enterprise Electrodes Partnership, and WMG, at Electrodes in the University of Warwick. The consortium out were awarded £80 million, through Anode coating a competition led by the Advanced lines Cylinder cell assembly Powders Electrode Formation

Propulsion Centre and supported by in mixing Cathode coating Drying Pouch cell assembly Innovate UK. lines Cells out UKBIC will be an open access facility, Cell EoL opening early 2020 in the Coventry/ testing Cells Warwickshire area. Module BoL in testing The UK Battery Industrialisation Centre will: • Be a ‘Learning factory’ for high speed, Packs Pack assembly Module assembly high quality manufacturing of cells, out modules and packs at GWh/year scale

• Enable users to develop and prove Modules Modules in out manufacturing processes, and train staff • Be capable of bespoke cell development /prototype/low volume manufacture

Newcastle Belfast

Dublin Manchester Liverpool Nottingham

Birmingham

Coventry

Leamington Spa

Cardiff

London DOI number: 10.31273/978-0-9934245-5-7

APC Electric Energy Storage Spoke WMG, International Manufacturing Centre, University of Warwick, Coventry, CV4 7AL www.wmg.warwick.ac.uk