A multifunctional polymer to enhance SEI stability and Li utilization for efficient lithium metal batteries

Abstract

The development of lithium (Li) metal anodes is severely hindered by the unstable solid electrolyte interphase (SEI) layer. Herein, we explore a novel polymer that can promote stable SEI formation and maintain high Li utilization in different electrolyte systems. In an ether-based electrolyte, the polymer can be applied to modify a polypropylene separator to enhance anion-derived SEI formation so that Li/Li symmetric batteries can perform robustly for 12 500 hours at a current density of 5 mA cm⁻². Moreover, in a carbonate-based electrolyte, the polymer can work as an additive to be involved in stable SEI construction, which efficiently eliminates the side effects of electrolyte decomposition and results in an average coulombic efficiency of 99.87% after 500 cycles in a half battery with a carbon-paper current collector. Remarkably, at a negative/positive electrode capacity ratio of approximately 1.4, the battery can operate stably for 1000 cycles at 1C with a capacity retention of >90%. The design and synthesis of functional polymers reported in this work can pave the way for their high-performance applications in Li metal batteries.