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 construction and maintain high Li utilization in different electrolyte systems. In an ether-based electrolyte, the polymer can be applied to modify polypropylene separator to enhance the anion-derived SEI formation, so that the Li/Li symmetric battery can perform robustly for 12,500 hours at a current density of 5 mA/cm2. In a carbonate-based electrolyte, moreover, the polymer can work as an additive to involve in the stable SEI construction, which efficiently eliminates the side effect 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 the negative/positive electrode capacity ratio of ca. 1.4, the battery can operate stably for 1000 cycles at 1C with capacity retention above 90%. The design and synthesis of functional polymers in this work can pave the way for their applications in Li metal batteries of high performance.