Lithium (Li) metal is one of the most promising anodes for next-generation energy storage systems.However,the Li dendrite formation and unstable solid-electrolyte interface (SEI) have hindered its further application.Lithium nitrate (LiNOa) is extensively used as an effective electrolyte additive in ether-based electrolytes to improve the stability of lithium metal.Nevertheless,it is rarely utilized in carbonate electrolytes due to its low solubility.Here,a novel gel polymer electrolyte (GPE) consisting of poly(vinylidene fluoride) (PVDF),poly(methyl methacrylate) (PMMA),poly(ethylene oxide) (PEO) with LiNO3 additive is proposed to solve this issue.In this GPE,polyether-based PEO serves as a matrix for dissolving LiNO3 which can be decomposed into a fast Li-ion conductor (Li3N) in conventional carbonate electrolytes to enhance the stability and Li+ conductivity of the SEI film.As a result,dendrite formation is effectively suppressed,and a significantly improved average Coulombic efficiency (CE) of 97.2％ in Li-Cu cell is achieved.By using this novel GPE coupled with Li anode and LiNi0.5Mn0.3Co0.2O2 (NMC532),excellent capacity retention of 94.1％ and high average CE of over 99.2％ are obtained after 200 cycles at 0.5 C.This work presents fresh insight into practical modification strategies on high-voltage Li metal batteries.