Liquefied gas electrolytes for electrochemical energy storage devices.

Rustomji, Cyrus S; Yang, Yangyuchen; Kim, Tae Kyoung; Mac, Jimmy; Kim, Young Jin; Caldwell, Elizabeth; Chung, Hyeseung; Meng, Y Shirley · Science · 2017

basic_science · Level V

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Abstract

Electrochemical capacitors and lithium-ion batteries have seen little change in their electrolyte chemistry since their commercialization, which has limited improvements in device performance. Combining superior physical and chemical properties and a high dielectric-fluidity factor, the use of electrolytes based on solvent systems that exclusively use components that are typically gaseous under standard conditions show a wide potential window of stability and excellent performance over an extended temperature range. Electrochemical capacitors using difluoromethane show outstanding performance from -78° to +65°C, with an increased operation voltage. The use of fluoromethane shows a high coulombic efficiency of ~97% for cycling lithium metal anodes, together with good cyclability of a 4-volt lithium cobalt oxide cathode and operation as low as -60°C, with excellent capacity retention.