Molecule Crowding Strategy in Polymer Electrolytes Inducing Stable Interfaces for All‐Solid‐State Lithium Batteries

Abstract All‐solid‐state lithium batteries with polymer electrolytes suffer from electrolyte decomposition and lithium dendrites because of the unstable electrode/electrolyte interfaces. Herein, a molecule crowding strategy is proposed to modulate the Li + coordinated structure, thus in situ constructing the stable interfaces. Since 15‐crown‐5 possesses superior compatibility with polymer and electrostatic repulsion for anion of lithium salt, the anions are forced to crowd into a Li + coordinated structure to weaken the Li + coordination with polymer and boost the Li + transport. The coordinated anions prior decompose to form LiF‐rich, thin, and tough interfacial passivation layers for stabilizing the electrode/electrolyte interfaces. Thus, the symmetric Li–Li cell can stably operate over 4360 h, the LiFePO 4 ||Li full battery presents 97.18% capacity retention in 700 cycles at 2 C, and the NCM811||Li full battery possesses the capacity retention of 83.17% after 300 cycles. The assembled pouch cell shows excellent flexibility (stand for folding over 2000 times) and stability (89.42% capacity retention after 400 cycles). This work provides a promising strategy to regulate interfacial chemistry by modulating the ion environment to accommodate the interfacial issues and will inspire more effective approaches to general interface issues for polymer electrolytes.