Electrolyte tailoring and interfacial engineering for safe and high-temperature lithium-ion batteries

Abstract

The deployment of lithium-ion batteries, essential for military and space exploration applications, faces restrictions due to safety issues and performance degradation stemming from the uncontrollable side reactions between electrolytes and electrodes, particularly at high temperatures. Current research focuses on interfacial modification and non-flammable electrolyte development, which fails to simultaneously improve both safety and cyclic performance. This work introduces a synergistic approach by incorporating weakly polar methyl 2,2-difluoro-2-(fluorosulfonyl)acetate (MDFSA) and non-flammable 2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphospholane 2-oxide (TFP) to achieve a localized high-concentration electrolyte (LHCE) that can stabilize both anode and cathode interfaces and thus improve the cycling life and safety of batteries, particularly at evaluated temperatures. As a result, the NCM811|Gr pouch cell with MDFSA-containing LHCE exhibits a high capacity retention rate of 79.6% at 60 °C after 1200 cycles due to the formation of thermally and structurally stable interfaces on the electrodes, outperforming pouch cells utilizing commercial carbonate-based (capacity retention: 23.7% after 125 cycles). Additionally, pouch cells in the charging state also exhibit commendable safety performance, indicating potential for practical applications.