Advanced low-flammable electrolytes for stable operation of high-voltage lithium-ion batteries

Despite being an effective flame retardant, trimethyl phosphate (TMP${}_a$) is generally considered as an unqualified solvent for fabricating electrolytes used in graphite (Gr)-based lithium-ion batteries as it readily leads to Gr exfoliation and cell failure. In this work, by adopting the unique solvation structure of localized high-concentration electrolyte (LHCE) to TMP${}_a$ and tuning the composition of the solvation sheaths via electrolyte additives, excellent electrochemical performance can be achieved with TMP${}_a$-based electrolytes in Gr∥LiNi${}_{0.8}$Mn${}_{0.1}$Co${}_{0.1}$O${}_2$ cells. After 500 charge/discharge cycles within the voltage range of 2.5-4.4 V, the batteries containing the TMP${}_a$-based LHCE with a proper additive can achieve a capacity retention of 85.4 %, being significantly higher than cells using a LiPF${}_6$-organocarbonates baseline electrolyte (75.2 %). Meanwhile, due to the flame retarding effect of TMP${}_a$, TMP${}_a$-based LHCEs exhibit significantly reduced flammability compared with the conventional LiPF${}_6$-organocarbonates electrolyte. (© 2021 Wiley‐VCH GmbH)