Dash of potassium could help make long-lasting electric car batteries

By Layal Liverpool

Adding small amounts of potassium salt to lithium-metal batteries could make them safer and boost their charging efficiency.

Lithium-metal batteries are lighter and can store more energy compared with the more commonly used lithium-ion batteries, but their widespread use has been limited by safety concerns, says Lauren Marbella at Columbia University in New York.

Unlike lithium-ion batteries, which contain an electrode typically made of graphite, lithium-metal batteries contain an electrode made of lithium.

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Because of the way lithium-metal batteries charge, this can lead to a build-up of tiny lithium deposits on the electrode surface that can cause the battery to short circuit.

Short-circuiting can result in explosions, says Marbella. “Basically the whole system just goes into runaway failure,” she says. “It’s a recipe for disaster.”

Marbella and her team discovered that adding a small amount of potassium salt to lithium-metal batteries prevents this dangerous build-up of deposits on the electrode. “Whenever we had the potassium in the battery, we had less of these microstructures growing and we also had a higher efficiency battery,” she says.

The researchers found that the addition of potassium boosted the charging efficiency of the batteries from 84 to 88 per cent. Small increases in charging efficiency can go a long way, says Marbella, particularly in applications such as electric vehicles.

A big barrier in the transition to electric vehicles is their limited range, says Marbella. “You’re limited in how far you can go before you have to charge your battery again,” she says. “The development of lithium-metal batteries would help eliminate some of the range anxiety because they last longer.”

Marbella says the next step will be to investigate how the addition of potassium salt works to limit the formation of deposits on the lithium electrode and to potentially optimise this further.

“This research will be important for the discovery of next-generation battery chemistries that will offer improvements in energy density and safety,” says Shahid Rasul at Northumbria University in the UK, such as lithium-sulphur and lithium-air batteries. “[This] is critical for electrifying the transportation and aviation sectors,” he says.

Journal reference: Cell Reports Physical Science, DOI: 10.1016/j.xcrp.2020.100239