In-situ Radiation-synthesized UiO-66/Poly(Ionic Liquid) Gel Electrolyte with High Conductivity, Wide Electrochemical Window and Flame Retardancy for High Performance Lithium Metal Batteries

Lithium metal batteries exhibit ultrahigh theoretical capacity but face critical challenges in cycling stability and safety due to lithium dendrite growth and dead lithium formation. Herein, a UiO-66/imidazolium-based poly(ionic liquid) (UiO/PPV-Li) gel electrolyte was synthesized through γ-ray radiation-induced in-situ polymerization and crosslinking using 1-vinyl-3-ethylimidazolium hexafluorophosphate ionic liquid ([VEIm]PF 6 ) monomer, pentaerythritol tetraacrylate (PET4A) crosslinker, and UiO-66 dispersed in liquid electrolyte. Enhanced Li + transport was achieved through dipole-ion interactions between [VEIm] + cations and carbonyl groups of PET4A and complemented by dynamic coupling between PET4A and anions. The optimized UiO/PPV-Li exhibited an ionic conductivity of 9.12 mS·cm –1 at ambient temperature. The electrochemical stability window was extended to 5.31 V (vs. Li⁺/Li) through coordination of PF 6 – with Zr–O clusters in the UiO-66 structure. The desolvation energy barrier of solvated Li + was effectively reduced by UiO-66 and optimized hopping sites for Li⁺ transport provided by polymer chains were identified through theoretical calculation. Li ‖ UiO/PPV-Li ‖ LiNi 0.8 Co 0.1 Mn 0.1 O 2 exhibited discharge specific capacity of 154 mAh·g −1 at 1 C (75.7% retention), enhanced cycle stability at 4.8 V and superior high-rate discharge capacities compared to liquid electrolytes. Significant safety improvements were exhibited through flame retardancy and structural integrity of UiO/PPV-Li. The graphite ‖ UiO/PPV-Li ‖ LiCoO 2 pouch batteries exhibited high safety under calendering and nail penetration. The UiO/PPV-Li in-situ synthesized through γ-ray radiation-induced polymerization and crosslinking is a novel strategy for the development of next-generation lithium metal batteries.