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EV Batteries 101: The Basics

Learn about types of EV batteries, how they’re made, and how they work.

This article is the first in a series about EV batteries and the EV battery supply chain.

In the United States, transportation contributes more climate-warming emissions and air pollution than any other sector. To reduce transportation-related climate pollution and avoid the worst effects of climate change, we must rapidly improve infrastructure for non-motorized ways of moving, and we must transition vehicle transportation to use electricity instead of fossil fuels. We must electrify the way we move.

The good news is that we are making progress — an increasing number of people are buying electric vehicles (EVs) and many governments and employers are replacing their gas-powered trucks, vans, and buses with ones powered by electricity.

However, to speed up EV adoption, we’ll need to improve the ways we mine, process, and assemble the materials that go into an EV battery. Understanding how an EV battery works can help policymakers make informed decisions, help people choose an EV that best meets their needs, guide investor resources, and equip the private and public sectors with the tools they need to develop efficient and effective technologies.

This article answers four common questions about EV batteries.

1. What kind of batteries do EVs use?

Most electric vehicles are powered by lithium-ion batteries and regenerative braking, which slows a vehicle down and generates electricity at the same time. The types of EVs that use batteries include:

  • All-electric vehicles, also known as battery electric vehicles (BEVs), are completely powered by electricity. To recharge, the vehicle can be plugged into a wall outlet or charger.
  • Plug-in hybrid electric vehicles (PHEVs) are powered by both electricity and an internal combustion engine (ICE). Unlike older hybrid electric vehicles, PHEVs can be operated on electricity alone. The gas-powered engine is available for longer trips when charging is unavailable or unreliable.
  • Hybrid electric vehicles (HEVs), like PHEVs, are powered by electricity and an ICE. However, an HEV cannot be plugged in to charge the battery. Since they cannot operate on electricity alone, they are not nearly as efficient as BEVs and PHEVs.

There are several types of lithium-ion batteries, with lithium nickel manganese cobalt oxide (NMC) and lithium iron phosphate (LFP) batteries being the most common ones used in EVs. Like all batteries, both NMCs and LFPs have their strengths and shortcomings:

All batteries have their own unique chemistry, each of which has its tradeoffs. There’s no overall “best” battery for all EVs.

2. Why are lithium-ion batteries used in EVs?

Lithium-ion batteries are used in EVs because they:

  • Have high energy density: They can store a relatively large amount of electrical energy into a smaller and more lightweight package than other battery technologies.
  • Perform well at high temperatures and can withstand low temperatures without being damaged.
  • Have a low self-discharge rate, meaning that the battery holds its energy well even if it’s not used for days or weeks.
  • Are able to withstand many charge cycles while retaining almost all of their original capacity.
3. How do lithium-ion batteries work?

Lithium-ion batteries, like all batteries, store energy and convert it to electrical energy when in use. This electricity is produced by the movement of electrons, which are small particles with a negative charge that are found in all atoms.

Chemical reactions within the battery move these electrons from one electrode to another. There are two electrodes in a battery: the anode (a negative electrode) and the cathode (a positive electrode). Electrons start off in the anode and then move to the cathode through an electrolyte medium, which can be either liquid or solid.

When the battery is in use, the electrons move from the anode electrode to the cathode electrode; when the battery is charging, they move from the cathode to the anode.

To explain this movement, imagine that an electron is a person taking a bus to the grocery store. The anode is the person’s home while the cathode is the grocery store. The electrolyte medium is the bus itself, the tool that gets the person from point A to point B. The food the person buys at the grocery store is the electricity.

Another key component of a battery is the separator, a thin, porous membrane that, as the name implies, separates the anode and cathode electrodes while enabling the lithium ions to move from one to the other. It also prevents short circuiting, which happens when an electric current flows down a wrong or unintended path.

4. What minerals are used in lithium-ion batteries?

Lithium-ion batteries usually include lithium, cobalt, manganese, nickel, and graphite. There is considerable concern about the effects of mining these minerals on local communities and landscapes. Some mines use child labor, lack safety measures to protect workers, and negatively impact the surrounding environment.

The rest of this 101 series will explore where these critical minerals come from and how we can source these minerals in a just, equitable, and safe manner.