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

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.