Charging lithium-ion cells at different rates boosts the lifetimes of battery packs

Charging lithium-ion cells at different rates boosts the lifetimes of battery packs
Stanford University researchers have devised a new way to make lithium-ion battery packs last longer and suffer less deterioration from fast charging.

The research, published in IEEE Transactions on Control Systems Technology, shows how actively managing the amount of electrical current flowing to each cell in a pack, rather than delivering charge uniformly, can minimise wear and tear. The approach effectively allows each cell to live its longest life.

According to Stanford professor and senior study author Simona Onori, initial simulations suggest batteries managed with the new technology could handle at least 20% more charge-discharge cycles, even with frequent fast charging, which puts extra strain on the battery.

Most previous efforts to prolong battery life have focused on improving the design, materials, and manufacturing of single cells, based on the premise that, like links in a chain, a battery pack is only as good as its weakest cell. The new study begins with an understanding that while weak links are inevitable – because of manufacturing imperfections and because some cells degrade faster than others as they’re exposed to stresses like heat – they needn’t bring down the whole pack. The key is to tailor charging rates to the unique capacity of each cell to stave off failure.

“If not properly tackled, cell-to-cell heterogeneities can compromise the longevity, health, and safety of a battery pack and induce an early battery pack malfunction,” said Onori, who is an assistant professor of energy science engineering at the Stanford Doerr School of Sustainability. “Our approach equalises the energy in each cell in the pack, bringing all cells to the final targeted state of charge in a balanced manner and improving the longevity of the pack.”



image: shutterstock/Parilov

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