A highly self-textured Ga2O3-substituted Li7La3Zr2O12 (LLZO-Ga) solid electrolyte with a nominal composition of Li6.55Ga0.15La3Zr2O12 is obtained by a simple and low-cost solid-state reaction technique, requiring no seed crystals to achieve grain orientation. The as-prepared self-textured LLZO-Ga shows a strong (420) preferred orientation with a high Lotgering factor of 0.91. Coherently, a terrace-shaped microstructure consisting of many parallel layers, indicating a two-dimensional-like growth mode, is clearly observed in the self-textured sample. As a result, the highly self-textured garnet-type lithium-ion conducting solid electrolyte of LLZO-Ga exhibits an extremely high ionic conductivity, reaching a state-of-the-art level of 2.06 × 10−3 S cm−1 at room temperature (25 °C) and thus shedding light on an important strategy for improving the structure and ionic conductivity of solid electrolytes.

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A large number of pores and a low relative density that are frequently observed in solid electrolytes reduce severely their ionic conductivity and thus limit their applicability. Here, we report on the use of hot isostatic pressing (HIP) for ameliorating the garnet-type lithium-ion conducting solid electrolyte of Ga2O3-doped Li7La3Zr2O[Formula: see text] (Ga-LLZO) with nominal composition of Li[Formula: see text]Ga[Formula: see text]La3Zr2O[Formula: see text]. The Ga-LLZO pellets were conventionally sintered at 1075[Formula: see text]C for 12[Formula: see text]h, and then were followed by HIP treatment at 120[Formula: see text]MPa and 1160[Formula: see text]C under an Ar atmosphere. It is found that the HIP-treated Ga-LLZO shows an extremely dense microstructure and a significantly enhanced ionic conductivity. Coherent with the increase in relative density from 90.5% (untreated) to 97.5% (HIP-treated), the ionic conductivity of the HIP-treated Ga-LLZO reaches as high as [Formula: see text][Formula: see text]S/cm at room temperature (25[Formula: see text]C), being two times higher than that of [Formula: see text][Formula: see text]S/cm for the untreated one.

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