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

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.