Tailored Stereo-Configuration of Crosslinkable Polyester-Based Solid Polymer Electrolytes for All-Solid-State and...

By harnessing stereoisomerism in unsaturated polyesters, we elucidate how subtle structural variations impact Li⁺ solvation structures by modulating free volume, Li⁺ diffusivity, and lithium salt dissociation within solid polymer electrolytes (SPEs). The intrinsic reactivity of C═C bonds along the polymeric backbones is further exploited via a facile UV-curing approach to construct robust three-dimensional polymeric networks that impart mechanical robustness and preferential restriction of TFSI^- mobility relative to Li⁺ transport. The distorted conformation of poly(n-pentyl maleate) (PPM) leads to sparsely crosslinked structures, preserving efficient Li⁺ transport pathways. Furthermore, end-group fluorination enhances interfacial stability by facilitating the formation of a LiF-rich solid electrolyte interphase. These synergistic design strategies culminate in a crosslinked PPM-based SPE (XL-PPM-3F-Li) featuring one CF₃ end-capping group, which exhibits remarkable electrochemical durability in both Li||Li symmetric and LFP full-cell configurations. Furthermore, this advantage is extended to the device level by integrating binder, electrolyte, and separator into a single ultrathin (∼"5 µm-thick") crosslinked SPE that conformally interfaces with the electrode microstructure. This integrated configuration markedly lowers interfacial and charge-transfer resistance, enabling 65% of the initial reversible capacity at 2 C and 93.6% retention after 100 cycles at 0.5 C (60°C). Overall, this crosslinking-enabled unified architecture establishes a robust strategy for ultra-stable solid-state lithium-metal batteries.