Lithium-ion batteries with bumpy components may hold charge better in freezing cold temperatures.
Rechargeable lithium-ion batteries are used in many electronic devices ranging from iPhones to electric vehicles. However, at temperatures below freezing, such batteries can take days to fully recharge or they store a lot less energy. For example, very cold weather can decrease an electric vehicle’s range by 30 per cent.
Xi Wang at Beijing Jiaotong University in China and his colleagues have found that changing the shape of a lithium-ion battery’s anode could make it work better at low temperatures.
Anodes are involved in the charging and discharging of a battery and are normally flat in shape, but the team engineered a battery with a curved and bumpy one.
The researchers found that their bumpy battery retained around 86 per cent of its energy at -20°C compared with at room temperature. A similarly sized conventional lithium-ion battery could only hold around 3 per cent of its energy at the same cold temperature. Overall, batteries with the new anodes lasted longer than standard lithium-ion batteries at temperatures between -20°C and 25°C.
Charging and discharging a battery relies on charged particles flowing to and from the anode. Near freezing, most of the particles don’t have enough energy to make the trip, so the battery fails to power devices or recharge.
Making the anode bumpy and rounded puts charged particles closer to each other, meaning they cluster and interact, lowering the overall amount of energy they need to move.
So far, the method has only been tested in small, coin-shaped batteries like those used in watches. The researchers’ next challenge is to devise a way to reliably make many bumpy anodes for larger batteries.
Creating batteries that perform well at cold temperatures may also help researchers engineer one that works better at room temperature as well, says Ping Liu at the University of California, San Diego.