Lithium lanthanum titanate (LLTO) is one of the most promising solid electrolytes for next generation batteries owing to its high ionic conductivity of ∼1 × 10 − 3 S/cm at room temperature. To comprehensively understand the microstructure and ion diffusion mechanism of LLTO, recent research in diffraction and spectroscopy techniques as well as computational study have been reviewed in this paper. The extremely low ionic conductivity at grain boundary as well as the increased electronic conductivity related to the direct contact with metallic lithium has impeded the practical application of LLTO for the solid-state batteries. Various studies including substitution, the introduction of grain boundary layer modifier, high temperature sintering, and synthesis of amorphous LLTO have been applied to solve these major challenges and their effectiveness are discussed in this review. Moreover, different types of synthesis methodologies of LLTO thin films are reviewed and compared in detail. In the end, the recent reports of solid-state battery system are reviewed and discussed.

中文翻译：

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钛酸锂镧钛酸盐对全固态锂离子二次电池的研究进展

钛酸锂镧（LLTO）是下一代电池最有希望的固体电解质之一，因为它在室温下的离子电导率高达〜1×10-3 S / cm。为了全面了解LLTO的微观结构和离子扩散机理，本文对衍射和光谱技术以及计算研究的最新进展进行了综述。晶界的极低离子电导率以及与金属锂直接接触相关的增加的电子电导率阻碍了LLTO在固态电池中的实际应用。各种研究，包括替代，引入晶界层改性剂，高温烧结，非晶态LLTO的合成和合成已用于解决这些主要挑战，并且在本文中讨论了它们的有效性。此外，对LLTO薄膜的不同类型的合成方法进行了综述和详细比较。最后，对固态电池系统的最新报道进行了回顾和讨论。