Enable rechargeable carbon fluoride batteries with ultra-high rate and ultra-long life by electrolyte solvation structure and interface design

Abstract

The primary lithium-fluorinated carbon batteries, with high energy density, long shelf life, and low self-discharge, have been employed in some specialized fields such as aerospace and deep-sea exploration. Nevertheless, this system has been deemed to be non-rechargeable since its inception. In our previous research, despite oxygen doping into electrode reduced the charging difficulty, the degradation of cathode interface led to rapid failure of this system. Here, we propose a rechargeable carbon fluoride battery with an unprecedented long life through the design of electrolyte solvation structure and interface. The addition of ethyl isothiocyanate (EITC) with an electronegative terminal facilitates the neutralization of positive charge on Li⁺, mitigating the polarization of solvent and enhancing its oxidative stability at cathode. EITC with the higher reactivity than solvent preferentially polymerizes at cathode, thus hindering the side reactions and solvent degradation. The oxygen-doped carbon fluoride battery, mediated by EITC-based electrolyte, demonstrates an ultra-long life for at least 2000 cycles (with a reversible capacity as high as 425 mAh/g) even at a ultra-high current density of 20 A/g. Even at a low temperature of −20 °C, the reversible capacity still surpasses 300 mAh/g. This electrolyte formulation endows the fluorinated graphite cathode with a high power density of 40892 W/kg and a high energy density of 1140 Wh/kg.