A novel trimethylsilyl 2-(fluorosulfonyl)difluoroacetate additive for stabilizing the Ni-rich LiNi0.9Co0.05Mn0.05O2/electrolyte interface

Abstract A stabilized cathode electrolyte interphase (CEI) formed on the cathode electrode by virtue of effective electrolyte additives is crucial for prolonging the lifespan of lithium-ion battery adopting high energy density Ni-rich cathode materials. Here, we report a novel multifunctional additive trimethylsilyl 2-(fluorosulfonyl)difluoroacetate (TMSFS) for LiNi0.9Co0.05Mn0.05O2 (NCM90). By adding 0.5% TMSFS, the NCM90 electrode shows an enhanced capacity retention of 85.1% at 1C up to 200 cycles, superior over that of 73.1% for baseline electrolyte. The improvement on cycling performance can be also achieved at harsh testing conditions (e.g., 60 °C and even a high voltage of 4.4 V), along with fast electrode kinetics in the presence of TMSFS. It's demonstrated that TMSFS additive could scavenge the undesired H2O, PF5 and HF species in electrolyte, alleviating the subsequent damages to both cathode-electrolyte interface and NCM90 cathode structure. More importantly, a compact, inorganics-enriched CEI layer formed in TMSFS-added electrolyte is further revealed, rationalizing the impressive improvement in electrochemical performance. Furthremore, we also prove the effectiveness of TMSFS additive for graphite||NCM90 full cells.