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|LiFePO₄ 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.

A novel solid-like electrolyte featuring a high ionic conductivity with nanowetted interfaces and good Li-metal compatibility is created by impregnating a Li⁺-containing ionic liquid into a metal–organic framework host. On this basis, the Li|LiFePO₄ solid-state battery with an unprecedented areal active loading exhibits good capacity retention over a wide temperature range.

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