A Metal–Organic‐Framework‐Based Electrolyte with Nanowetted Interfaces for High‐Energy‐Density Solid‐State Lithium Battery

Abstract Solid‐state batteries (SSBs) are promising for safer energy storage, but their active loading and energy density have been limited by large interfacial impedance caused by the poor Li + transport kinetics between the solid‐state electrolyte and the electrode materials. To address the interfacial issue and achieve higher energy density, herein, a novel solid‐like electrolyte (SLE) based on ionic‐liquid‐impregnated metal–organic framework nanocrystals (Li‐IL@MOF) is reported, which demonstrates excellent electrochemical properties, including a high room‐temperature ionic conductivity of 3.0 × 10 ‐4 S cm ‐1 , an improved Li + transference number of 0.36, and good compatibilities against both Li metal and active electrodes with low interfacial resistances. The Li‐IL@MOF SLE is further integrated into a rechargeable Li|LiFePO 4 SSB with an unprecedented active loading of 25 mg cm ‐2 , and the battery exhibits remarkable performance over a wide temperature range from −20 up to 150 °C. Besides the intrinsically high ionic conductivity of Li‐IL@MOF, the unique interfacial contact between the SLE and the active electrodes owing to an interfacial wettability effect of the nanoconfined Li‐IL guests, which creates an effective 3D Li + conductive network throughout the whole battery, is considered to be the key factor for the excellent performance of the SSB.