The Regulation of Local Li⁺ Coordination Environment for High-Performance Quasi-Solid-State Polymer Electrolyte

Quasi-solid-state polymer electrolytes (QSPEs) have attracted significant attention for their good flexibility and superior interfacial contact with electrodes, while their low room temperature ionic conductivity remains challenging. Polymer structure design and plasticizers introduction are reported to be effective in enhancing the ionic conductivity of QSPEs. However, current research predominantly focuses on enhancing lithium-ion conductivity via improved polymer chain mobility, yet critically overlooks how plasticizer/polymer-modulated Li⁺ coordination environments govern ion transport heterogeneity, ultimately constraining the achievable upper limits of ionic conduction efficiency. Herein, this work designed a hyperbranched polymer structure associated with plasticizer with different structure (fluoroethylene carbonate (FEC) and ethylene carbonate (EC)) to regulate the Li⁺ coordination environment inside the QSPEs and further revealed the enhanced Li⁺ transportation mechanism. The weaker solvation ability of FEC with Li⁺ compared with EC makes the polymer matrix more likely to coordinate with Li⁺, resulting in an accelerated Li⁺ transmission pathway. The QSPE with FEC addition shows superior ionic conductivity (8.8 × 10^-4 S cm^-1, room temperature) and improved compatibility with Li anode. The correspondent Li||LiFePO₄ battery exhibits a high capacity retention of 83.79% after 2000 cycles at 1 C, which is much better than that with EC (79.65% after 1000 cycles).