Trifluoromethyl-free anion for highly stable lithium metal polymer batteries

With the blooming of energy storage systems in e-mobility applications, the research activities of rechargeable lithium metal (Li degrees) batteries (LMBs) using solid-state electrolytes have been rekindled in recent years in light of stringent demands in terms of safety and energy density which are far beyond the capability of the contemporary lithium-ion batteries (LIBs). Lithium metal polymer (LMP) batteries utilizing solid polymer electrolytes (SPEs) are inherently safe and easy to process, thus becoming in the spotlights of solid-state lithium metal batteries (SSLMBs) technologies. However, the widely used electrolyte salts generally contain the trifluoromethyl (-CF3) group which has very low chemical and biochemical degradability, despite its strong electron-withdrawing ability which is essential for the dissolution and transport of ions in SPEs. In this work, a trifluoromethyl-free anion, bis(difluoromethanesulfonyl)imide {[N(SO2CF2H)(2)](-), DFSI-}, as an environmentally benign and interfacially favourable anion for high-performance SSLMB is reported. In contrast to the popular bis(trifluoromethanesulfonyl)imide anion {[N(SO2CF3)(2)](-), TFSI-}, the DFSI-based salt shows more rapid chemical degradation and its SPEs possess higher Li-only conductivity, significantly enhanced stability against Li degrees electrode, and better cell performance of LMP batteries. The results conveyed in this work may inspire the design of better SPEs, thus enabling a wider practical deployment of SSLMBs.