Temperature-Responsive Solvation of Deep Eutectic Electrolyte Enabling Mesocarbon Microbead Anode for High-Temperature Li-Ion Batteries

Deep eutectic electrolytes (DEEs) provide a safe solutionfor high-temperaturebatteries. While promising, the DEEs/electrode interphase chemistryand the underlying temperature mechanism remain unclear. Herein, theDEE is formulated with succinonitrile (SCL) and lithium bis(fluorosulfonyl)imide (LiFSI) to promote the mesocarbon microbead (MCMB) anode inhigh-temperature Li-ion batteries. The temperature-sensitive mechanismof solid electrolyte interphase (SEI) evolution on the MCMB is deciphered,the core of which is temperature-regulated solvation chemistry. Specifically,high temperature can result in the enhanced interaction between Li+ and FSI- anions in the solvation structure,thus elevating the LiF content in the SEI. Due to the synergy of DEE(featuring rapid ion conduction and thermal stability) and high-temperatureoptimized interphase, MCMB/Li and LiFePO4/MCMB cells exhibitimproved cycling stability at high temperature. This work promotesa fundamental understanding of the intrinsic relationship betweenthe temperature factor and SEI evolution, illuminating the futureof DEEs in high-temperature batteries.