Garnet-type oxide Li₇La₃Zr₂O₁₂ (LLZO) has attracted considerable attention as promising solid-state electrolyte (SSE) owing to the exceptional bulk ion conduction. However, the Li⁺ transfer capacity of most LLZO-based solid electrolytes remains inadequate, primarily due to the presence of extensive grain boundaries and excessive thickness. Herein, we report the fabrication of a LLZO-based lamellar composite inorganic solid electrolyte (LLZO/LIC LISE) by in-situ sintering Li₃InCl₆ (LIC) in LLZO lamellar framework. LIC can act as an effective Li⁺-conductive grain boundary modifier within the electrolyte, leading to a remarkable reduction in grain boundary resistance of LLZO/LIC LISE (<9.2 Ω cm²), which is much lower than that of LLZO lamellar framework (827.2 Ω cm²). Together with the reduced internal grain boundary of LLZO nanosheet, a high ionic conductivity of 3.22 × 10⁻⁴ S cm⁻¹ at 25 °C is obtained for LLZO/LIC LISE. In addition, combining with the thin thickness of 29 μm, LLZO/LIC LISE obtains high ionic conductance of 223 mS and exceptional energy density of 246 Wh kg⁻¹, surpassing most developed SSEs. As a result, the cell assembled with LLZO/LIC LISE achieves superior cycling performance of 144.2 mAh g⁻¹ after 200 cycles at 0.5C with a capacity decay of only 0.055% per cycle. This study may present a facile approach to effectively eliminate the grain boundary resistance of inorganic solid electrolytes toward high-performance all-solid-state lithium batteries.

石榴石型氧化物Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO)由于具有优异的体离子传导性，作为有前景的固态电解质(SSE)而引起了广泛关注。然而，大多数LLZO基固体电解质的Li ^{+传输能力仍然不足，这主要是由于存在广泛的晶界和过大的厚度。}在此，我们报道了通过在LLZO层状骨架中原位烧结Li ₃ InCl _{6 (LIC} )来制备LLZO基层状复合无机固体电解质(LLZO/LIC LISE)。LIC可以充当有效的Li ⁺-电解质中的导电晶界改性剂，导致LLZO/LIC LISE的晶界电阻显着降低（<9.2 Ω cm ²），远低于LLZO层状骨架的晶界电阻（827.2 Ω cm ² ）。加上LLZO纳米片内部晶界的减少，  LLZO/LIC LISE在25℃下获得了3.22×10 ^-4  S cm ^{-1的高离子电导率。}此外，结合29μm的薄厚度，LLZO/LIC LISE获得了223 mS的高离子电导和246 Wh kg -1 的出色能量密度^，超越了大多数开发的SSE。结果，用LLZO/LIC LISE组装的电池实现了144.2 mAh g ^{-1的优异循环性能}在 0.5C 下循环 200 次后，每个循环容量衰减仅为 0.055%。这项研究可能为高性能全固态锂电池提供一种有效消除无机固体电解质晶界电阻的简便方法。