An all-fluorinated electrolyte based on a fluorinated cosolvent toward a high-voltage LRMO cathode

Abstract

Lithium-rich manganese-based oxides (LRMOs) have been considered as a promising candidate among various cathode materials for next-generation high-energy-density battery systems due to their high specific capacity (>250 mAh g⁻¹) and high working voltage. However, their practical application remains challenging due to the voltage/capacity decay caused by the structural degradation of the LRMO cathode during long-term cycling and the undesirable decomposition of conventional carbonate-based electrolytes under high cut-off voltages. Electrolyte engineering is a promising strategy for constructing a robust electrode–electrolyte interphase and enhancing the cycling stability of the LRMO cathode under high cut-off voltage. Herein, we develop an all-fluorinated electrolyte using 4-fluorobenzotrifluoride (FBTF) as a cosolvent to regulate the solvation structure of the electrolyte, thus greatly enhancing the Li⁺ transfer kinetics at the interface of the electrode and electrolyte. Benefiting from the formation of a thin and robust cathode–electrolyte interphase (CEI) and a LiF-rich solid electrolyte interphase (SEI), the degradation of the LRMO cathode and the growth of lithium dendrites are significantly suppressed. Consequently, the developed electrolyte enables a capacity retention of 86.26% after 200 cycles at a rate of 0.5C for the Li/LRMO battery, compared to only 52.12% for the conventional carbonate-based electrolyte. This work provides a feasible fluorinated electrolyte strategy toward high-voltage LRMO cathodes.