Ultrafast One‐Step Synthesis of Garnet‐Type Solid Electrolytes With Modified Surface and Microstructure for Solid‐State Lithium‐Metal Batteries

Abstract

Garnet‐type Li6.5La3Zr1.5Ta0.5O12 (LLZTO) solid electrolytes provide the necessary electrochemical stability and ionic conductivity for solid‐state lithium‐metal batteries (SSLMBs). However, their wider application is hindered by their high interfacial resistance with electrodes and a lengthy synthesis process. This study presents the synthesis of densified LLZTO electrolytes using unconventional Li2O and Li2ZrO3 precursors through an ultrafast (≈60 s) Joule heat‐assisted synthesis approach in a single‐step process. The lower sintering temperature of Li2ZrO3 compared to traditional ZrO2 precursor yields LLZTO with larger grains, resulting in enhanced Li+ conductivity (7.0 × 10−4 S cm−1 at 25 °C), reduced electronic conductivity (1.7 × 10−10 S cm−1), and higher density (94.2%). Applying a 52–80 nm Sn:SnF2 coating on the LLZTO surface using a melt‐quenching approach produces a uniform interlayer that chemically converts to Li‐Sn alloy and LiF upon contact with lithium, resulting in a near‐zero interfacial resistance and a critical current density of 4.2 mA cm−2 at 25 °C. The SSLMBs, incorporating Sn:SnF2‐coated LLZTO electrolyte with NMC811 cathode, demonstrate remarkable initial capacity (181.1 mAh g−1) and cycle performance (88.63% capacity retention at 3000th cycle). The results indicate that this approach has the potential to advance the commercial fabrication technology for high‐performance solid electrolytes for SSLMBs.