Regulation of Interphase Layer by Flexible Quasi‐Solid Block Polymer Electrolyte to Achieve Highly Stable Lithium Metal Batteries

Abstract Low safety, unstable interfaces, and high reactivity of liquid electrolytes greatly hinder the development of lithium metal batteries (LMBs). Quasi‐solid‐state electrolytes (QGPEs) with superior mechanical properties and high compatibility can meet the demands of LMBs. Herein, a biodegradable polyacrylonitrile/polylactic acid‐block‐ethylene glycol polymer (PALE) as membrane skeleton for GPEs is designed and systematically investigated by regulating the length and structure of the cross‐linked chain. Benefiting from the enriched affinitive sites of polar functional groups (CO, COC, CN, and OH) in highly cross‐linked polymer structure, the designed PALE membrane skeleton exhibits flame‐retardant property and ultrahigh liquid electrolyte uptake property, and the derived quasi‐solid‐state PALE GPEs deliver enhanced stretchability and a higher electrochemical stable window of 5.11 V. Besides, the PALE GPEs effectively protect cathodes from corrosion while allowing uniform and fast transfer of Li + ions. Therefore, the Li||Li symmetrical battery and LFP or NCM811||Li full‐cell using PALE GPEs exhibit excellent cycling stability coupled with compact and flat inorganic/organic interface layers. And the excellent cycling stability of pouch cells under harsh operating conditions indicates the application possibilities of PALE GPEs in flexible devices with high‐energy‐density.