Molecular Engineering Enabled In Situ 3D Cross‐Linked and Thermo‐Electrochemically Stable Poly(1,3‐dioxolane) Solid Polymer Electrolyte

Abstract The narrow electrochemical stability window (ESW) and poor thermal stability of poly(1,3‐dioxolane) (PDOL) solid polymer electrolyte severely restrict its application. In this study, poly(1,3‐dioxolane) dimethacrylate (PDOL‐DMA) is designed and synthesized to replace the unstable terminal hydroxyl groups with unsaturated C═C double bond. The cross‐linked quasi‐solid electrolyte (CPDOL‐DMA QSE) demonstrates a wide ESW of 4.5 V versus Li + /Li and a high Li + transference number of 0.64. This crosslinked network facilitates lithium salt dissociation, weakens Li + ‐polymer interactions, and achieves the reversibility of lithium metal anode disolution/deposition. For CPDOL‐DMA QSE, capacity retention is 83% after the 400th cycle at 25 °C. Moreover, it can perform stable cycling with 82% retention after 200 cycles at an elevated temperature of 80 °C. Due to the high oxygen content of the repeating units in CPDOL‐DMA, microcalorimetry and accelerated calorimetry results further confirm the high safety of the CPDOL‐DMA QSE. This work provides insights into the design of polyether polymer electrolytes with high oxygen contents, realizing thermo‐electrochemical stability in lithium metal batteries.