Most batteries spend more than 70% of their lifetime at rest. Yet few studies have examined calendar aging, which is how a battery degrades when it is neither charging nor being used.

Now, a pair of complementary papers published in Joule and Nature Communications, both led by chemical engineers at the UCLA Samueli School of Engineering, has found that many next-generation metal-anode batteries can lose significant capacity during calendar aging. Across the two studies, the researchers compared losses for various metals and designed strategies to reduce them, providing new pathways to extend battery life.

Metals such as zinc, sodium and magnesium are being explored as alternatives to lithium-ion batteries for their potential to store more energy. To evaluate their performance, most studies have focused on cycling efficiency — how efficiently the battery recovers charge over repeated use. It is often assumed that if a battery cycles well, it will also remain stable while idle. But cycling performance alone does not tell the full story of how a battery holds up in real-world use.

“We understand very little about how next-generation metal batteries degrade during rest,” said Yuzhang Li, an associate professor of chemical and biomolecular engineering at UCLA Samueli and the corresponding author on both papers. “These two papers further our understanding and present new concepts on how to improve battery aging during rest.”

Read more at the UCLA Samueli website.