Microenvironment Regulation Unlocks High Li⁺ Conduction in Polyether Electrolytes for High‐Performance Quasi‐Solid‐State Batteries

Polyether electrolytes (PEs) have attracted significant research and industrial interest for high‐performance lithium metal batteries (LMBs). However, traditional PEs are limited by their low lithium‐ion (Li+) conductivity primary due to strong Li⁺–polymer interactions (i.e. Li+‐oxygen coordination). Current approaches of modifying polymer molecular structures are largely challenged by the inherent molecular structural constraints of specific polymers and the complexity of the required structural engineering processes. Herein, a novel and straightforward strategy i proposed to reduce the Li+−polymer interaction, increase free‐Li+ concentration, and introduce ion‐channels by regulating the microenvironment of PEs through introducing Ge4+ sites with weak Lewis acidity during in situ polymerization. In this way, the microenvironment regulates PE with a high ionic conductivity of 1.83 mS cm−1 at 25 °C and a Li+ transference number of 0.8 is achieved. Remarkably, the electrolyte exhibits extraordinary cycling stability in Li||Li symmetric cells for over 2000 h, demonstrating dendrite‐free Li metal deposition during prolonged cycling. Moreover, the assembled Li||LiFePO4 cells achieve an impressive capacity retention of 92.1% and ≈100% Coulombic efficiency after a long‐term stability of 2190 cycles at 5 C. This work provides new insight into the design of polymer electrolytes for high‐performance LMBs through microenvironment regulation.