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

Lithium-rich manganese-based oxide (LRMO) has been considered as a promising candidate among various cathode materials for next generation high energy density battery systems due to its 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 structural degradation of LRMO cathode during long-term cycling and undesirable decomposition of conventional carbonate-based electrolyte under high cut-off voltage. Electrolyte engineering is a promising strategy to construct a robust electrode electrolyte interphase and enhance the cycling stability of LRMO cathode under high cut-off voltage. Herein, we develop an all-fluorinated electrolyte by using 4-fluorobenzotrifluoride (FBTF) as a cosolvent to regulate the solvation structure of electrolyte, thus greatly enhancing the Li+ transfer kinetics at the interface of 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 LRMO cathode and the growth of lithium dendrites are significantly suppressed. Consequently, the developed electrolyte enables capacity retention of 86.26% after 200 cycles at the rate 0.5 C for Li/LRMO battery, compared to only 52.12% for conventional carbonate-based electrolyte. This work provides a feasible fluorinated electrolyte strategy toward high voltage LRMO cathode.