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Home , Voltaic pile

This unit is aligned with 30 – Unit B: Electrochemical Changes.

1 Start your discussion on EV’s by introducing what they are.

Electric vehicles are an emission free form of transportation. These vehicles use an electric motor in place of an internal combustion engines (ICE) – what you find in gasoline cars. These vehicles are essentially large, rechargeable batteries. The description here is for an all-electric vehicle (meaning no gas is used). There are also plug-in hybrids, and hybrid vehicles. Plug-in hybrid cars run on and gas to increase the range. Hybrids run on gas and use electricity to offset the car.

Reference: https://www.drive.com.au/motor-news/everything-you-need-to-know-about-electric- cars-119469

2 https://www.plugndrive.ca/electric-cars-available-in-canada/

Image source: https://www.nspower.ca/your-home/energy-products/electric- vehicles/types

Hybrids do not travel as far on electricity as an all-electric vehicle does on a single charge. However, hybrids use gasoline to further the distance they travel once the battery runs out of power. All-electric cars do not burn gasoline, do not have gears or a transmission, and do not require oil for the parts (there are no moving parts). On average, all-electric cars can travel 200 – 250 km on a single charge.

3 The very first battery, called the Voltaic Pile, was invented by in 1799. This battery was composed of multiple and cooper , and the was a -soaked paper.

This invention was revolutionary as at the time, people believed that only living beings could make electricity. This theory was debunked with the invention of the Voltaic Pile.

Although revolutionary, the Voltaic Pile was not perfect. It was prone to producing bubbles, which would collect at the zinc . This decreased the lifespan and usage of the battery.

60 years later, the first rechargeable, lead acid battery was invented. https://www.visualcapitalist.com/evolution-of-battery-technology/

4 Electric Vehicles (EV) are a large battery that stores chemical energy, which is then converted to electrical energy. The electrical energy is used to turn the wheels of the car and make it move. In another lesson, we learn about energy storage. Electric vehicles are considered a form of energy storage in the sense that they store energy to be used later.

Electrons are the basis of batteries. The flow of is what creates electricity.

In a voltaic battery (one that produces electricity), electrons flow from the positive terminal to the negative terminal.

An easy way to remember the way electrons flow is with the saying “LEO the lion says GER” LEO = lose electrons, oxidation (start) GER = gain electrons, reduction (end)

Another saying is “OIL RIG” OIL = oxidation is loss (start) RIG = Reduction is gain (end)

It is up to you which saying you use to remember. Can you think of another saying?

5 These sayings lead to the next topic: https://www.youtube.com/watch?v=9OVtk6G2TnQ

5 Every battery undergoes electrochemistry within the cells. By taking a closer look at the chemistry within each cell, we can better understand how electricity is created.

Electrochemistry is the study of chemical reactions that result in the movement of electrons. Moving electrons creates a current, which creates electricity. The chemical reactions in electrochemistry are called reactions. Redox reactions are made up of two half reactions (oxidation and reduction). The next slide will discuss redox reactions in more detail.

Electrochemistry Crash Course: https://www.youtube.com/watch?v=IV4IUsholjg

6 Redox reactions are the basis of electrochemistry. This type of reaction is made up of two half reactions. One half reaction undergoes oxidation and the other undergoes reduction. Together, the reactions combine and a net flow of electrons occurs.

An example of a oxidation half reaction is (Na). We know this is oxidation because the oxidation state (the charge) of the species is neutral to start, then is +1. This is a net loss of electrons. A species becomes more negative if electrons are gained. Na is also called an donor

Chlorine (Cl) is an example of a reduction reaction. The oxidation state of Cl is neutral to begin, then becomes -1, which is in line with a gain of electrons. Cl is called an electron acceptor.

You can also tell which species is reduced and oxidized based on where the electron is expressed in the half reaction. In the case of Cl, is it on the left hand side. This means the electron acts as a reactant and is added to Cl to form the new Cl- (the electron is consumed). If the electron is on the right hand side, as seen with Na, it is a product and therefore removed from Na. https://www.youtube.com/watch?v=lQ6FBA1HM3s

7 Now that we understand the chemistry that occurs in a battery, we can take a look at the three types of batteries associated with electric cars.

The three batteries to note are as follows: - Lead-acid batteries - Nickel metal Hydride batteries - Lithium-ion batteries

In the next slides, we will take a deeper dive into the chemistry of each.

8 Lead-acid batteries are a type of , invented in 1859 by a French physicist named Gaston Planté. This type of battery is commonly used as an automobile starter motor, found in internal combustion engines, but was also used in early electric vehicles. They are usually rated at 12 . Their low cost and efficiency make them a popular option. However, one of the major downfalls of a lead-acid battery is that they discharge on their own. If you were to let the battery sit unused for months, the total efficiency would slowly deplete; approximately 5% per month. However; a lead acid battery is more efficient than other alternatives.

Lead acid batteries are best suited for high loads for short periods of time (i.e., starting an engine).

9 Here is an example of one cell contained in a lead acid battery. This battery was used in the early models of electric cars. They are still the most common battery used in ICE cars.

Each cell has a metal conductor used to transfer electrons and create electricity.

There are 6 plates in a lead acid battery. Each are 2.1 volts, the whole battery is 12.6 volts. One plate is spongy lead and the other is lead dioxide (the active material where the electrochemical reaction takes place).

Lead acid batteries are composed of multiple layers of “plates” (one plate shown on the slide), all of which are submerged in an electrolyte solution. The electrolyte solution is made up of dilute Sulfuric Acid (H2SO4 and water). When the sulfuric acid comes into contact with the lead plates, a chemical reaction occurs, which results in the transfer of electrons to produce a . These electrons move from the negative electrode to the positive electrode. This occurs because the negative electrode has a surplus of electrons (and repels the electrons), while the positive electrode is lacking electrons. This means that the positive electrode has more affinity to electrons; in other words, it wants electrons more than the negative electrode and has a stronger pull. The discharge is a spontaneous reaction whereas charging requires an external power source.

10 During the reaction, the electrolyte depletes and coats the plates. The plates eventually become fully coated and the battery is fully discharged. When the battery is charged, this process is reversed and the electrolyte is returned to solution.

These batteries are heavy and are less stable that the newer batteries (nickel and lithium based batteries).

Since this battery creates electricity, it is called a galvanic (or voltaic) cell. In these batteries, the electrons flow from the negative to the positive . As the chemical process continues, the anode becomes less negative, and then cathode becomes less positive.

A key feature of the lead-acid battery is the electrolyte solution that was not present in the prior battery. The electrolyte solution reacts with both electrodes to transfer the electrons.

Watch this video for an explanation on how these cells work: https://www.youtube.com/watch?v=7b34XYgADlM

Some more information on lead acid batteries: https://batteryuniversity.com/learn/article/lead_based_batteries

10 This is how a lead-acid battery discharges.

Blue boxes are the reactants, orange are the intermediates, pink are the products ** Note at the negative electrode, the H is not shown in the graphic, but is expressed in the reaction. This is because the H breaks apart from HSO4 and remains in solution as a hydrogen ion. It is apart of the reaction, but is omitted from the graphic for simplicity.

We can examine a lead acid battery in three parts: the electrolyte, the positive electrode and the negative plate.

Electrolyte: The electrolyte solution is dilute sulfuric acid (H2SO4 and water). This graphic shows the solution as to help understand how the chemical reaction proceeds. This is a fairly accurate representation as when a substance is mixed with water it dissociates into its ionic forms.

Positive Electrode: The positive electrode exists as PbO2 (lead oxide) to start. The electrode reacts with 2- + SO4 , H and two electrons. The resulting product is PbSO4 which forms on the electrode.

11 Negative Electrode: At the negatively charged plate, Pb(s) will give off two electrons. At this point, the Pb 2+ 2- becomes positively charged (Pb ). The SO4 the reacts with the lead cation (positively charged ion) and forms PbSO4 in solution.

11 This is the chemical process that occurs during charging. An external source is required to recharge. The sources returns the electrons to the starting point so that the spontaneous reaction can proceed during discharge.

This is called a galvanic (or voltaic) cell. In these batteries, the electrons flow from the negative anode to the positive cathode. As the chemical process continues, the anode becomes less negative, and then cathode becomes less positive.

Watch this video for an explanation on how these cells work: https://www.youtube.com/watch?v=7b34XYgADlM

Picture source: https://www.itacanet.org/a-guide-to-lead-acid-battries/part-1-how-lead-acid- batteries-work/

12 In 1967, research on Nickel-metal hybrid batteries took off. It’s discovery is credited to Stanford Ovshinsky. The first rendition was highly unstable due to the hydride in the battery. Nickel-hydrogen batteries were invented instead. By 1980, a hydride alloy was discovered, which was more stable and resulted in the NiMH battery having 40 percent more specific energy (energy per unit mass) than the former NiCd.

13 NiCd was originally invented in 1899 by Waldemar Jungner. NiCd had some advantages over the lead acid batteries, such as high cycle count. However, NiCd was much more expensive than lead acid ($400 per kWh as of 2018), and the cadmium was toxic if the battery leaked. NiCd underwent many renditions in the following years to improve the efficiency and capacity.

https://batteryuniversity.com/learn/article/nickel_based_batteries https://www.sciencedirect.com/topics/engineering/nickel-metal-hydride-battery

13 Here are some advantages and disadvantages to NiMH Batteries. NiMH was invented to replace NiCd (Nickel Cadmium), so NiCd is used as a comparison.

Memory: the memory effect is when a battery must be fully discharged before recharging or the capacity will be reduced. The new NiMH batteries can be recharged at any point in the cycle without adverse effects.

14 The double arrow shown means the reactions are reversible. This means that the charging and discharging cycles are the same process, but in reverse. https://www.sciencedirect.com/topics/engineering/nickel-metal-hydride

15 Modified from Science Direct (https://www.sciencedirect.com/topics/engineering/nickel-metal-hydride),this is the charge and discharge process. Charging is denoted by the solid arrows and discharge is denoted by the dashed arrows.

While charging, electrons flow from the positive to negative electrode. During discharge, electrons flow from the negative electrode to the positive electrode.

The positive plates of NiMH batteries are made of NiOOH (nickel oxyhydroxide) – the active material. The active material at the negative plate is hydrogen-absorbing intermetallic alloy – a metal that will uptake hydrogen ions. • An alloy is a mixture of metals

The electrolyte is a mixture of concentrated hydroxide. The charge and discharge process is essentially electron and proton transfers. Protons (hydrogen) is transferred between the electrode and electrolyte.

The metal alloy can be of form AB5 or AB2.

• AB5: a rare earth element that forms stable hydrides is bonded with Ni (sometimes doped in cobalt, aluminum or tin). The rare earth elements is lanthanum, cerium, neodymium, praseodymium, or yttrium.

16 • AB2: The A element is titanium, vanadium or zirconium mixed with zirconium or nickel. The B element is manganese, chromium , cobalt, vanadium or iron.

16 17 Lithium-ion batteries are used in a wide range of applications, are are arguably the most advanced rechargeable battery. However, this does not mean it is perfect. Like many batteries, there are some safety risks to be aware of. Lithium-ion batteries are highly prone to fire. More discussion on Li-ion fire hazard is found on the next slide. https://www.electronics-notes.com/articles/electronic_components/battery- technology/li-ion-lithium-ion-advantages-disadvantages.php

18 Like everything, there is a degree of risk associated to the use of the product. Lithium-ion batteries in particular have a history of short-circuiting. A short-circuit occurs when components of the battery come into contact unintentionally, which results in an unintended current. This can be dangerous because it can cause a fire or explosion.

Scientist have worked to improve this fault. https://batteryuniversity.com/learn/article/safety_concerns_with_li_ion https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_problems

19 An animation of this image is on the US Department of Energy’s website (go to the website to see how the electrons flow). The animation is interactive – you can hover over regions for explanations on what is happening during charge and discharge.

A Lithium-ion battery is made of a separator, electrolyte solution and positive (cathode) and negative (anode) electrode terminals. The electrolyte is responsible for transporting lithium ions from the anode to the cathode. Lithium becomes an ion when it gives up an electron (which is carried through the wires to the positive terminal). The electrolyte then transports the positively charged lithium between the anode and cathode, across the separator. The separator only allows the passage of ions, and prevents the passage of electrons.

During charging, the cathode releases the lithium ions and the electrons flow back to the negative electrode.

Click on this link to view the animation, or watch the clip on the following slide. https://www.energy.gov/eere/articles/how-does-lithium-ion-battery-work

20 Watch this video to understand the flow of electrons and ions in a lithium-ion cell. https://www.energy.gov/eere/articles/how-does-lithium-ion-battery-work

21 During discharge, the electrons and the lithium atoms move from the negative terminal to the positive terminal. The movement of the electrons creates electricity that is used by the EV. The electrons travel outside the cell through wires.

Inside the cell, lithium atoms exist on the graphite. They donate their electrons, and are transported as ions across the separator (dashed line) by the electrolyte. The ions interact with the CoO2 at the positive electrode and accept the electrons. In this process, Li is oxidized at the negative terminal, and reduced at the positive terminal. https://www.explainthatstuff.com/how-lithium-ion-batteries-work.html

22 The opposite process occurs when the cell is charged. Here the lithium atoms donate their electrons and are transported across the separator from the positive electrode to the negative electrode. When electricity is created, electrons flow from (-) to (+). In this case, electricity is not created for an external source. Therefore the process is opposite. The Li ions therefore accept electrons at negative electrons and interact with the graphite. Once all the Li ions are moved, the cell is ready to discharge.

23 Depending on the battery use, the composition of the cathode changes. All are made of lithium, a metal or two, and oxygen. Even within electric cars, there are different cathode chemistries. Take a look at the Tesla Model S and the Nissan Leaf. How do these batteries differ?

The radar graph on the left shows the features of each Li-ion types. Take a look and figure out which battery is the best and worst in each of the six categories (specific energy, specific power, safety, performance, life span, and cost). https://www.visualcapitalist.com/explaining-surging-demand-lithium-ion-batteries/ https://batteryuniversity.com/learn/article/types_of_lithium_ion

24 This visual shows how the cost of the lithium-ion battery has decreased significantly in 10 years. The cost is anticipated to decrease even more https://www.visualcapitalist.com/explaining-surging-demand-lithium-ion-batteries/

25 Here is a visualization of where the majority of the materials required for lithium-ion batteries are sourced. https://www.visualcapitalist.com/critical-ingredients-fuel-battery-boom/

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