Controlled hydrolysis of LiPF₆-based electrolytes with trace dual-unsaturated additives for high-temperature lithium-ion pouch batteries

Lithium-ion batteries (LIBs) have emerged as the predominant electrochemical energy storage devices in contemporary applications. However, the uncontrollable lithium (Li) plating on graphite (Gr) anodes and the structural deterioration of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) cathodes in conventional carbonate electrolytes—particularly at high operating voltages and elevated temperatures—are the primary factors contributing to capacity decay and short circuits in LIBs. Herein, we elucidate the regulation of the lithium hexafluorophosphate (LiPF₆) decomposition pathway with a 1.15 M LiPF₆ by incorporating trace dual-unsaturated additives, 0.5 wt.% vinylene carbonate (VC) and 0.3 wt.% prop-1-ene-1,3-sultone (PES), resulting in LiF-enriched cathode electrolyte interphase and polymeric C–F and S–F species. The influences of the VC and PES serve to deactivate the Lewis acid phosphorus pentafluoride (PF₅), thereby impeding the formation of the byproduct Li_xPOF_y. Furthermore, the radical copolymerization of VC with PES through electrochemical initiation engenders a spatially adaptable polymeric solid electrolyte interphase on the Gr anode, significantly mitigating Li plating during cycling. Consequently, Gr|NCM523 pouch cells containing 0.5% VC and 0.3% PES additives exhibit a remarkable capacity retention of 97.54% after 500 cycles at 45 °C. This work offers a new insight into tuning the interphasial chemistry of anode/cathode at elevated temperatures through strategic dual-unsaturated electrolyte additives.