An Inorganic Layered Coordination Polymer as High‐Performance Solid‐State Electrolyte for Stable Lithium Metal Batteries

Limited ionic conductivity, heterogeneous Lithium‐ion flux, and interfacial instability in solid‐state electrolytes (SSEs) hinder the development of high‐energy‐density solid‐state lithium metal batteries (SSLMBs). Herein, we report a new Li + conducting SSE derived from an inorganic coordination polymer, specifically a two‐dimensional Hofmann‐type framework material (HFM). By varying the solvent types used as interlayer guest molecules, we can modulate the interlayer spacing of the HFM. Specifically, when methoxymethane (DME) serves as the guest, it orchestrates highly selective Li + transport pathways within the structure, achieving a high ionic conductivity of 1.51 mS cm −1 . The coordination between metal centers and solvent molecules leads to the reconstruction of the local Li + solvation structure, effectively immobilizing solvent molecules and lowering the energy barriers for the desolvation process. More importantly, a Li 3 N‐rich solid electrolyte interphase forms on the lithium anode, stabilizing the Li–electrolyte interface. As a result, Li||Li symmetric cells demonstrate stable cycling for over 3000 h, while LiFePO 4 ||Li full cells show a capacity retention of 96.3% after 500 cycles at 1C. This work establishes a structurally nanoconfined electrolyte system that bridges ion‐selective nanochannels with a stabilized interphase, offering a promising platform for next‐generation high‐energy‐density SSBs.