Lithium-ion electric vehicle batteries: what are they and how do they work?
EV batteries are integral components in an electric vehicle. They not only function as the “heart” of an electric vehicle by distributing the electrical energy needed to power up the car, but they also serve as a storage system for this same energy.
Because of these functions, electric vehicle batteries need to possess a number of key characteristics; among them are having high voltage and charge storage. The current drive for “green” energy also requires that these batteries not only have zero to low gas emissions, but also be recyclable so that electronic waste does not end up polluting the environment.
At present, lithium-ion EV batteries meet these high standards. This article serves as your introduction to these batteries, how they work, and how they are produced and eventually recycled.
What is a lithium-ion EV battery?
Lithium-ion electric vehicle batteries are considered as an advanced form of battery technology. Most people are familiar with these batteries because they are commonly found in smartphones, laptops, and other electronic devices. But because of the characteristics that we have mentioned earlier, they have been further developed for use as EV batteries.
The lithium-ion EV battery is so-named for the lithium ions that are present in the components of the battery. It is the electrochemical reaction of these lithium ions which result in the generation of electricity that powers the electric vehicle.
How do lithium-ion EV batteries work?
The cathode contains positively charged particles called ions. When you turn your EV on (“Discharge”), these ions flow through the electrolyte and separator from the cathode to the anode. It is this chemical reaction or flow of ions that generates the electrical power for your car to run.
Now, when you turn off your car and plug the battery into an electrical outlet (“Charge”), the reverse happens. The ions now flow from the anode to the cathode. This chemical reaction transforms power back into electrical energy which is stored in the cathode.
Battery charging cycles
How do lithium-ion electric vehicle batteries work? To better answer this question, we need to take a look at the four main components of the lithium-ion EV battery, namely the cathode, anode, separator, and electrolyte. The chemical compositions of these components will be discussed in a later section.
Inside these lithium-ion EV batteries, the cathode (positive electrode) is installed apart from the anode (negative electrode) by a micro-permeable separator. These two electrodes both contain lithium ions, although it is more abundant in the cathode when the battery isn’t running. The cathode and anode are immersed in an electrolyte solution, the medium through which the lithium ions will flow.
When you turn on your EV, your battery is in a state of DISCHARGING. A chemical reaction occurs which results in lithium ions flowing from the cathode to the anode. This flow is what generates the electrical energy that is distributed throughout the EV.
When you turn off your EV and plug the battery in an electrical outlet, it is now in a state of charging. The chemical reaction now happens in reverse. The lithium ions now flow from the anode to the cathode, where it is stored.
This reverse reaction also occurs when you slow down or step on the brakes (also known as “regenerative braking”). The excess kinetic energy that is produced by the EV also results in the flow of lithium ions from the anode to the cathode, so that more energy is stored.
How are lithium-ion EV batteries manufactured?
Most people erroneously believe that their cars contain a single battery, same as their favorite electronic gadgets. However, to generate sufficient energy to power an entire electrical vehicle, it needs a large number of EV batteries.
The manufacturing of lithium-ion EV batteries follows a strict design to ensure high voltage, high storage capacity, and safety.
Lithium-ion EV battery design begins with the individual cell. As mentioned earlier, a single cell is assembled so that you have the anode and cathode apart from each other by means of a separator and then immersed in an electrolyte solution. This simple assembly is then encased in a metal housing. Tests are done to check for electrolyte leaks and prevention of moisture seepage within the battery.
These battery cells are then assembled into modules, also having a sturdy metal housing to protect the cells from external shocks. Finally, the modules are placed inside the large battery pack and installed in an electric vehicle.
If you want to have an idea on how many cells and modules there are in an electric vehicle, let’s take a look at the Tesla Model S Plaid. This EV’s battery pack contains 7,920 lithium-ion 1865-type cylindrical cells. The cells are divided into five modules, with each module containing 1,584 cells each. This battery pack gives the Tesla Model S Plaid a total capacity of 99 kWh.
How long does a lithium-ion EV battery last?
How long does an EV battery last? The lifespan of lithium-ion EV batteries makes it ideal for electric vehicles. On average, this type of EV batteries is built to last for 10-20 years with proper usage and care. Like the lithium-ion batteries in your electronic gadgets, these batteries should not undergo extreme charging cycles (such as depleting the battery to 0 and then charging it to 100%). It is best to maintain the battery’s state of charge (SOC) at 20-80%.
Are Lithium-ion EV batteries sustainable?
The U.S. Environmental Protection Agency defines “sustainability” as the ability to meet the needs of the present without compromising the ability of the next generations to meet their needs. This involves taking the necessary steps to protect the environment “in ways that are economically viable, beneficial to human health and well-being, and socially just in the long term.”
This brings us to the question: are lithium-ion EV batteries sustainable? To answer this, we need to take a look at the lithium EV battery components. The most important chemical components in these EV batteries are found in the cathode, and these are lithium, manganese, nickel, and cobalt.
Both lithium and manganese are not scarce. In a report by BloombergNEF, the current reserves of lithium, in particular, is at 21 million tonnes, sufficient for the projected ambitious conversion to electric vehicles from 2030s to 2050s. However, lithium mining has environmental issues because it requires large amounts of energy to extract the metal from rock and large volumes of water for extraction from brine.
The more problematic ones are nickel and especially cobalt, with two-thirds of the world’s supply being mined in the Democratic Republic of the Congo. A heavy metal, cobalt, is highly toxic. As the demand for these metals increases, there is a danger of experiencing shortages for EV battery manufacturing.
Future EV battery technology is currently geared toward eliminating cobalt and/or nickel from cathodes without compromising battery performance. One way is by using small quantities of other metals while maintaining the integrity of the cathode’s crystal structure that is the same as cobalt-oxide. Another method is the use of disordered lithium-rich rock salts that allow for easy flow of lithium ions with repeated charging, even in the absence of nickel or cobalt.
Can you recycle lithium-ion EV batteries?
Because there is a potential for future shortages of lithium EV battery components, in particular, nickel and cobalt, recycling of EV batteries plays a big role in possibly addressing these deficits.
How are lithium-ion EV batteries recycled? The umbrella term used to describe the processes for recycling lithium-ion batteries is “destructive dismantling”. Whether it’s smelting, direct recovery, or intermediate processes between the two previous procedures, recycling of lithium-ion batteries involves destroying the batteries themselves in order to recover the valuable metals and other elements, which can be reused in new batteries or for other purposes. These recycling processes are essential for recovering lithium, cobalt, and other precious metals because of the limited availability from extraction and dwindling of existing supply chains.
The latest technologies in electric vehicle batteries material recycling, particularly wet-chemistry extraction, allows for more efficient recovery of lithium and other valuable materials. These technologies are vital now as more EVs are reaching their end-of-life. In a projection by the US Department of Energy, they state that “recycled material could potentially provide one-third of United States cathode material needs for lithium-ion batteries by 2030.”