MXene‐Modulated Garnet Electrolyte Interface for Uniform Li Flux and Dendrite‐Free Solid‐State Lithium Metal Batteries

Garnet‐type solid electrolytes hold great promise for solid‐state Li‐metal batteries owing to their high ionic conductivity, large shear modulus, and excellent Li metal stability. However, their air instability and poor interfacial contact cause high Li/garnet interfacial resistance and Li dendrite growth. Herein, an ionic/electronic mixed‐conductive artificial interlayer (denoted as MLPL), consisting of MXene nanosheets, Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZT) particles, and a poly(ethylene oxide)/lithium salt (PEO/LiTFSI) matrix, is fabricated at the LLZT/Li interface to address these issues. Incorporating MXene and LLZT suppresses PEO crystallization, enhances segmental motion, and efficiently boosts ionic conductivity. The as‐obtained MLPL interlayer is thin (15 μm) and exhibits excellent chemical/electrochemical stability and high ionic conductivity (1.48 × 10 −4 S cm −1 at 60°C). Furthermore, it homogenizes interlayer electric field distribution, mitigates electron‐induced garnet attack, improves interfacial contact, accelerates Li + transport, and suppresses dendrite growth, as confirmed by field‐emission scanning electron microscopy, electrochemical measurements and COMSOL simulations. Consequently, LiFePO 4 /LLZT@MLPL/Li cells exhibit excellent rate performance (95.4 mA h g −1 at 2.0C) and cycling stability (124.2 mA h g −1 after 100 cycles at 0.1C, 135.6 mA h g −1 after 70 cycles at 0.5C, 60°C). This work offers a universal and feasible strategy for interfacial engineering toward high‐performance solid‐state batteries.