Nonflammable in situ PDOL‐based gel polymer electrolyte for high‐energy‐density and high safety lithium metal batteries

Abstract Due to its high energy density and low interface impedance, in situ polymerized gel electrolytes were considered as a promising electrolyte candidate for lithium metal batteries (LMBs). In this work, a new flame‐retardant gel electrolyte was prepared via in situ ring‐opening polymerization of DOL and TEP. The PDOL–TEP electrolyte exhibits excellent room temperature ionic conductivity (0.38 mS cm −1 ), wide electrochemical window (4.4 V), high Li + transference number (0.57), and enhanced safety. Thus, the NCM811||Li cells with PDOL–TEP electrolyte exhibit excellent cycle stability (82.7% of capacity retention rate after 300 cycles at 0.5 C) and rate performance (156 and 119 mAh g −1 at 0.5 and 1 C). Furthermore, phosphorus radicals decomposed from TEP can combine with hydrogen radicals to block the combustion reaction. This work provides an effective method for the preparation of solid‐state LMBs with high voltage, high energy density, and high safety.