In-situ cross-linked polyurethane networks: Leveraging active hydrogen for enhanced ion transport in stable lithium metal batteries

Herein, we report a strategy by introducing active hydrogen-containing polyurethane (PU) architectures into GPEs via a rapid, room-temperature in-situ cross-linking process. Contrary to the general understanding that the presence of labile hydrogen compromises electrochemical stability, our PU-based GPE demonstrates a broad electrochemical window and a significantly enhanced lithium-ion transference number t L i + of 0.74, attributed to the unique coordination environment provided by the polar carbamate groups. This exceptional selectivity stems from a synergistic mechanism enabled by the active-hydrogen-bearing carbamate groups: the N–H groups immobilize fluorine-containing anions via N–H···F hydrogen bonding, while simultaneously establishing competitive N–H···O interactions with ethylene oxide (EO) units to free the Li + ions from polyether chains. This in-situ polymerization of PEG and PM-200 monomers ensures a conformal interface with electrodes while forming a robust 3D covalent network that overcomes the inherent frailty of traditional linear polymers in the presence of solvents. Consequently, the GPE achieves a high ionic conductivity of 3.06 × 10 − 4 Scm −1 at room temperature, and enables superior cycling stability for LiFePO 4 | Li 0 batteries, maintaining a discharge capacity of 119 mAh g −1 after 200 cycles at 0.5C with high coulombic efficiency (>98.67%).