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Why are lithium-ion batteries, and not some other kind of battery, used in electric cars and grid-scale energy storage?

Lithium-ion batteries hold a lot of energy for their weight, can be recharged many times, have the power to run heavy machinery, and lose little charge when they're just sitting around.

July 16, 2024

Many fast-growing technologies designed to address climate change depend on lithium, including electric vehicles (EVs) and big batteries that help wind and solar power provide round-the-clock electricity. This has led to a spike in lithium mining: from 2017 to 2022, demand for lithium tripled, mostly driven by the energy sector.¹

Why is lithium so desirable for these applications? Lithium-ion batteries hold energy well for their mass and size, which makes them popular for applications where bulk is an obstacle, such as in EVs and cellphones. They have also become cheap enough that they can be used to store hours of electricity for the electric grid at a rate utilities will pay.

Two of the most important features of a battery are how much energy it can store, and how quickly it can deliver that energy. On both counts, lithium-ion batteries greatly outperform other mass-produced types like nickel-metal hydride and lead-acid batteries, says Yet-Ming Chiang, an MIT professor of materials science and engineering and the chief science officer at Form Energy, an energy storage company. Lithium-ion batteries have higher voltage than other types of batteries, meaning they can store more energy and discharge more power for high-energy uses like driving a car at high speeds or providing emergency backup power.

Charging and recharging a battery wears it out, but lithium-ion batteries are also long-lasting. Today’s EV batteries can be recharged at least 1,000 times and sometimes many more without losing their capacity, says Chiang. Plus, unused lithium-ion batteries lose their charge at a much slower rate than other types of batteries.

So it’s no surprise lithium-ion batteries are playing the dominant role in today’s early transition to a clean energy economy. Still, they do have drawbacks that leave an opening for other types of batteries to contribute. Though the cost of lithium-ion batteries has dropped swiftly over the last decade, they are still relatively expensive, at around $140 per kilowatt-hour for an EV battery pack. (Lead-acid batteries, by comparison, cost about the same per kilowatt-hour, but their lifespan is much shorter, making them less cost-effective per unit of energy delivered.)² Lithium mining can also have impacts for the environment and mining communities. And recycling lithium-ion batteries is complex, and in some cases creates hazardous waste.³

Though rare, battery fires are also a legitimate concern. “Today's lithium-ion batteries are vastly more safe than those a generation ago,” says Chiang, with fewer than one in a million battery cells and less than 0.1% of battery packs failing. “Still, when there is a safety event, the results can be dramatic.” Physically damaged, overheated, or defective batteries can spark fires, which have occurred at large battery installations supporting the electric grid and in apartments where people stowed electric scooters.

For all these reasons, scientists keep experimenting with new battery chemistries to fill various niches in the race to replace climate-warming fossil fuels. Chiang’s company, Form Energy, is working on iron-air batteries, a heavy but very cheap technology that would be a poor fit for a car but a promising one for storing extra solar and wind energy. Some new types of batteries, like lithium metal batteries or all-solid-state batteries that use solid rather than liquid electrolytes, “are pushing the energy density frontier beyond that of lithium-ion today,” says Chiang. Other energy storage technologies—such as thermal batteries, which store energy as heat, or hydroelectric storage, which uses water pumped uphill to run a turbine—are also gaining interest, as engineers race to find a form of storage that can be built alongside wind and solar power, in a power-plus-storage system that still costs less than climate-warming coal or natural gas.

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