High‐Entropy Strategy Flattening Lithium Ion Migration Energy Landscape to Enhance the Conductivity of Garnet‐Type Solid‐State Electrolytes

Abstract Garnet‐type solid‐state electrolytes with exceptional stability are believed to promote the commercialization of all solid‐state lithium metal batteries. However, the extensive application of garnet‐type solid‐state electrolytes is greatly impeded on account of their low ionic conductivity. Herein, a high‐entropy fast lithium‐ion conductor Li₇(La,Nd,Sr)₃(Zr,Ta)₂O₁₂ (LLNSZTO) with high lattice distortion is designed. It is found that the enhanced ionic conductivity of the high entropy garnet‐type solid‐state electrolyte LLNSZTO is achieved by introducing disorder in the lattice, which creates fast ion penetration paths with flattened energy landscapes within the pristine ordered lattice. Thus, the prepared high‐entropy garnet‐type solid electrolyte LLNSZTO exhibits low activation energy for Li⁺ migration (0.34 eV) and elevated ionic conductivity (6.26 × 10⁻⁴ S cm⁻¹). Full cells assembled with LLNSZTO electrolyte, lithium metal anode, and LiFePO₄ (LFP) cathode exhibit excellent capacity retention of 86.81% after 200 cycles at room temperature. Moreover, the superior ionic conductivity of LLNSZTO enables all solid‐state battery with high‐loading LFP cathode (>12 mg cm⁻²), achieving stable cycling exceeding 120 cycles. The large area pouch cell (5.5 cm × 8 cm) exhibits stable long‐term cycling performance, showing a capacity retention of 96.50% after 50 cycles.