A metal-free battery working at –80 °C

Abstract With the rapidly expanded applications of rechargeable batteries, more requirements have been generated, and low-temperature operation of battery has gained increasing concern because of the specified use in extreme weather condition and frequently-occurred extreme weather. However, the battery performance under ultralow temperature of below –40 °C has so far been rarely reported because of the electrolyte freezing as well as retarded reaction kinetics. Herein, we propose a novel low-temperature and metal-free battery, in which the pseudocapacitive electrochemical behavior of organic electrode has been fully utilized. With the sophisticatedly optimized ternary electrolyte of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) in acetonitrile (AN) and methyl acetate (MA), the high ionic conductivity, sufficient oxidation resistance, and enough-low freezing point is obtained. The PI5/1 M EMITFSI in MA/AN (1/2, v/v)/PTPAn cell is capable of delivering 79% of the theoretical capacity under 1 C-rate when the temperature was down to –80 °C, and longer than 2000-cycling under 5 C with slight capacity decay, 65% capacity release at 100 C-rate at –60 °C. The work sheds new lights on the unique organic-cation storage behavior of the organics in ionic liquid electrolyte and provides a new avenue for developing efficient and sustainable low-temperature batteries.