Revealing the mechanism on HF-induced degradation of PDOL-based electrolytes for high-temperature solid-state lithium metal batteries

Poly (1,3-dioxolane)-based (PDOL-based) solid polymer electrolytes have attracted much attention in solid-state lithium metal batteries (LMBs) due to their high ionic conductivity and excellent lithium anode compatibility. However, practical application of PDOL-based electrolytes is hindered by poor thermal stability and irreversible degradation caused by hydrofluoric acid (HF) at high temperatures. Herein, we introduce a multifunctional cross-linking agent glycerol triglycidyl ether (TASG) to improve the ionic conductivity and thermal stability of the electrolyte. The stable three-dimensional network structure of PDOL-TASG enhances the thermal stability of the electrolyte. The epoxy group in TASG effectively captures the HF generated by the electrolyte at high temperatures, preventing irreversible degradation of PDOL chains. This capture elevates the thermal stability of the PDOL-based electrolyte from 70 °C to 120 °C. LMBs employing PDOL-TASG electrolyte demonstrate an initial specific discharge capacity of 169 mAh g⁻¹ with 96.4 % capacity retention after 120 cycles at 90 °C at 1C rate. Even at 100 °C, the Li|PDOL-TASG|LFP batteries demonstrate exceptional cyclability, surpassing most reported batteries using solid polymer electrolytes. This work elucidates the mechanism of HF-induced PDOL degradation and provides a strategy to increase high-temperature durability of LMBs using solid polymer electrolytes.