"Armor Polymerization" Unlocks Polymer Electrolytes With Simultaneous Rapid Li⁺ Conduction and High Solidification

Polymer electrolytes offer significant promise for high-performance quasi-solid-state batteries due to their simple processing and excellent electrode compatibility. Nevertheless, they are intrinsically constrained by a critical compromise: while mobile solvents enable higher ionic conductivity (σ), these solvents inherently weaken solidification and therefore undermine intrinsic safety. Herein, we propose an innovative "armor polymerization" strategy to simultaneously achieve rapid Li conduction and robust solidification. Employing a functionalized ionic covalent organic framework (iCOF) as structural "armor" for in situ polymerization, our strategy creates hierarchical, low-energy-barrier ion‑transport pathways with weakened Li⁺-polymer interactions, while immobilizing solvent molecules via hydrogen‑bond networks. The resulting electrolyte exhibits a σ of 7.6 × 10^-4 S cm^-1 at 25°C, an elevated Li⁺ transference number (t_Li+) of 0.66, and solid‑state characteristics with high solidification. Remarkably, Li||LiFePO₄ cells deliver a long cycling life with a high-capacity retention of 92.2% and a nearly 100% Coulombic efficiency after 1500 cycles at 1C, as well as a 83.8% capacity retention after 2200 cycles at 2C. Furthermore, Li||NCM523 maintains an extremely high-capacity retention of 99.7% after 210 cycles at 0.5C. This strategy provides a novel pathway for designing high-performance, safe quasi-solid-state batteries through advanced electrolyte engineering.