Extended Segmental Structures Regulate Li⁺ Solvation in 1,3-Dioxane-Based Cross-Linked Polymer Electrolytes for...

Cross-linked polymer electrolytes based on 1,3-dioxolane (DOL) are attractive for lithium metal batteries, but their application in high-voltage systems remains limited. 1,3-dioxane (DOX) has emerged as an effective substitute for DOL in high-voltage polymer electrolytes, yet the structural origin of its advantage remains unclear. Here, we construct a pair of closely related cross-linked polymer electrolytes, DOL-3-methylglutaric anhydride (MA) and DOX-MA, within the same anhydride framework to uncover the structural basis of the DOL-to-DOX effect. Compared with DOL-MA, DOX-MA exhibits more extended segmental structural characteristics, which weaken polymer-dominated Li⁺ coordination and reconstruct the local solvation environment toward anion-enriched configurations. This segmental-structure-mediated solvation reconstruction further drives the formation of a robust LiF-rich interphase, thereby enabling faster Li⁺ transport and improved interfacial stability. As a result, DOX-MA delivers an ionic conductivity of 8.73 × 10^-4 S cm^-1, a Li⁺ transference number of 0.79, and an electrochemical stability window up to 5.3 V. Li||Li symmetric cells exhibit stable cycling for 4000 h with low polarization, and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)||Li full cells show excellent cycling stability with 89.1% capacity retention at a cutoff voltage of 4.5 V. This work highlights the extended segmental structure as a key factor governing the superior solvation and interfacial behavior of DOX-based cross-linked polymer electrolytes.