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

ABSTRACT

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||LiFePO ₄ 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.