Adding small amounts of potassium salt to lithium metal batteries could make them safer and increase their charging efficiency.
Lithium metal batteries are lighter and can store more energy compared to the commonly used lithium ion batteries. However, their widespread use has been limited by safety concerns, says Lauren Marbella of Columbia University in New York.
Unlike lithium-ion batteries, which contain an electrode that is typically made of graphite, lithium-metal batteries contain an electrode made of lithium.
Due to the way lithium metal batteries charge, this can lead to tiny lithium deposits on the electrode surface that can short circuit the battery.
Short circuits can lead to explosions, says Marbella. “Basically the whole system just goes into one out of control bug,” 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 prevented this dangerous buildup of debris on the electrode. “Whenever we had the potassium in the battery, fewer of these microstructures grew and we also had a battery with higher efficiency,” she says – although it is currently not entirely clear why.
The researchers found that adding potassium increased the charging efficiency of the batteries from 84 to 88 percent. Small increases in charging efficiency can go a long way, according to Marbella, especially in applications like electric vehicles.
One of the major obstacles in the transition to electric vehicles is limited range, Marbella says. “You are limited in how far you can go before you have to recharge your battery,” she says. “The development of lithium metal batteries would help eliminate range anxiety as they last longer.”
Marbella says the next step will be to study how adding potassium salt limits the build-up of deposits on the lithium electrode, and potentially optimizes it further.
“This research will be important in discovering next-generation battery chemistries that offer improvements in energy density and safety,” says Shahid Rasul of Northumbria University in the UK, such as lithium-sulfur and lithium-air batteries. “[This] is critical to electrifying the transportation and aviation sectors, ”he says.
Journal reference: Cell Reports Physical Science, DOI: 10.1016 / j.xcrp.2020.100239
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