In Situ Grain Boundary Engineering Enabling Ultralong Stable Cycling Garnet-Based Solid-State Electrolytes

Solid-state lithium metal batteries (SSLMBs) are promising next-generation energy storage due to their high safety and energy density, but lithium dendrite growth in solid electrolytes hinders their application. We propose an in situ grain boundary (GB) modification strategy using LiTaO₃ (LTO) reacting with Ta-doped garnet electrolyte to form a pseudocrystal Li₃TaO₄/Zr₃O (LZT) phase at GBs. The LZT phase reduces electronic conductivity, inhibits abnormal grain growth, strengthens GBs bonding, and enhances fracture toughness, effectively suppressing dendrite formation. The modified electrolyte (2LTaO) achieves an ultralow electronic conductivity of 8.58 × 10^-9 S cm^-1. Symmetrical Li | 2LTaO | Li cells demonstrate a high critical current density of 2.2 mA cm^-2 and stable cycling for 12,000 h at 0.3 mA cm^-2. Full cells exhibit excellent cycling stability and rate performance. This strategy provides a promising approach for the development of high-performance SSLMBs.