Interpenetrating Interface Engineering via Competitive Coordination in Ultrathin Asymmetric Solid‐State Electrolytes for High‐Energy Lithium Metal Batteries

ABSTRACT Asymmetric solid‐state electrolytes (ASEs) have been proven to achieve simultaneous compatibility with high‐voltage cathodes and lithium metal anodes, making them attractive for high‐energy‐density solid‐state lithium metal batteries (SSLMBs). However, conventional ASE configuration typically introduces an additional electrolyte/electrolyte interface, which results in high Li‐ion (Li + ) migration resistance and compromised electrochemical performance. Herein, we propose an interpenetrating interface engineering strategy to construct a seamless and integrated ASE. The unique interface layer is formed by a reduction‐resistant poly(1,3‐dioxolane) (PDOL) penetrating into an oxidation‐tolerant poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) polymer layer. In addition to achieving synchronized interfacial stability at both the cathode and the anode, the competitive coordination of PDOL with Li + in the interpenetrating interface layer promotes efficient Li + transport along PDOL chains, effectively reducing the Li + cross‐interface transport energy barrier and lowering the total interfacial resistance. The resulting ASE, with an ultra‐thin thickness of 10 µm, enables a pouch cell incorporating an ultrathin Li metal anode and high‐loading Li‐rich Mn‐based oxide cathode (7 mAh cm −2 ) to achieve a high energy density of 521.6 Wh kg −1 and 1161.4 Wh L −1 . This interpenetrating interface design strategy provides a new pathway for developing next‐generation SSLMBs with high energy density.