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

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 LiFePO₄||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.