A solid-like dual-salt polymer electrolyte for Li-metal batteries capable of stable operation over an extended temperature range

Abstract

Solid polymer electrolytes (SPEs) and gel polymer electrolytes (GPEs) show great promise for the realization of commercial, high performance Li-metal batteries (LMBs). However, the interfacial and high-temperature instability of GPEs, and the low room-temperature ionic conductivity of SPEs still limit their practical implementation. This article presents a solid-like dual-salt polymer electrolyte (DSPE), consisting of coordinated solvents and thermally stable Li-salts within a temperature-resistant polymer matrix, as a promising new strategy for addressing these issues. The developed DSPE demonstrates high ionic conductivity of 0.16, 0.73, and 1.93 mS cm−1 at −20, 20, and 100 °C, respectively. Li|DSPE|LiFePO4 batteries using this DSPE deliver an initial discharge capacity of 151 mAh g−1 at 0.5C, a rate performance of 123 mAh g−1 at 3C, and excellent long-term stability with a retained capacity of 143 mAh g−1 after 500 cycles at 0.5C and 23 °C. Further, the battery shows stable cycling between −10 °C and 80 °C. This impressive electrochemical performance is ascribed to the high Li+ conductivity of the membrane, the stabilization of the Al current collector, and the formation of a robust, LiF-rich solid-electrolyte interphase containing conductive Li-B-O-based species.