石榴石固体电解质Li7La3Zr2O12（LLZO），因其良好的对锂稳定性、高离子电导率和宽电化学窗口的特点被认为是最有潜力的固体电解质材料之一。过去十多年中关于LLZO的研究取得了巨大进步，但LLZO基固态电池的应用依旧面临界面问题的挑战。本文针对LLZO基固态电池的界面问题，开展主要工作如下：1）高离子电导率Ta掺杂LLZO（LLZTO）固体电解质制备与工艺优化。用Ta在Zr位进行元素掺杂，当分子式中Ta掺杂量大于0.6时可以得到稳定的立方相LLZTO。采用热压陶瓷烧结工艺，制备得到了一致性好、厚度可控的LLZTO固体电解质陶瓷片，其相对密度大于98 %，电导率0.79 S cm-1。高离子电导率的固体电解质，是实现高性能LLZTO基固态电池的前提。2）LLZTO在液态电解液中的不稳定性及界面动力学特征。以新鲜解离的热压陶瓷断面作为界面稳定性的研究对象，观察到了LLZTO在电解液中的副反应过程。通过系统地研究“固-液”界面的理化特征，总结了LLZTO在液态电解液中的不稳定性的原因及界面相形成机理。界面相主要成分为LiF，电解液中的H2O对LiF的生成起了重要作用，降低水份含量能抑制界面反应的发生。这部分研究有望为LLZO基“半固态”电池、“准固态”电池的设计提供借鉴和指导意义。3）LLZTO的空气稳定性研究及优化、改性策略。通过系统的理化性质表征确认了空气钝化层的主要成分为Li2CO3、LiOH·xH2O层和Li6.4-xHxLa3Zr1.4Ta0.6O12中间层，LLZTO空气不稳定性的根源在于H+/Li+置换反应。空气钝化层界面电阻高达1670 Ω，热处理工艺可减轻空气钝化层的负面影响。在24 d位掺杂Ga3+，可以抑制H+/Li+置换反应的发生，提升固体电解质空气稳定性。这部分研究拓展了对LLZTO空气稳定性的认识，提出了可供借鉴的优化和改性策略。4）开发低成本湿化学法用于原位构筑稳定LLZTO/Li界面。异丙醇对LLZTO具有很强亲和性，是一种理想的界面改性溶剂。当分别选用InCl3和Zn(NO3)2作为界面改性材料时，负极界面稳定性得到明显提升。当采用InCl3改性时，在0.45 mA cm-2的电流密度下，对称电池循环寿命超1000 h，LiFePO4全电池在0.5 C电流密度下循环475周容量保持率97.8 %。电池性能的提升归因于修饰层将不亲锂的LLZTO界面变为亲锂界面，亲锂界面可以实现更好的界面接触。这种有效、简便且成本低廉的策略可以为各种固体电池的界面改性提供一定的借鉴参考意义。

Li7La3Zr2O12 (LLZO) with the characteristics of a garnet solid electrolyte is considered one of the most promising solid electrolyte materials due to its advantages in lithium stability, high ion conductivity, and wide electrochemical window. Research on LLZO has made great strides over the past decades, but the application of LLZO-based solid-state batteries is still challenged by interface issues. Aiming at the above issues, the main work of this paper is as follows: 1) Preparation and process optimization of Ta-doped LLZO solid electrolyte (LLZTO) with high ion conductivity. When doping with Ta in the Zr sites, a stable cubic phase LLZTO can be obtained when the amount of Ta doped is greater than 0.6. LLZTO ceramic plates with good consistency and controllable thickness were obtained by hot pressing sintering process. The relative density of solid electrolyte was 98% and the conductivity was 0.79 s cm-1. Obtaining solid electrolyte with high ionic conductivity is the premise of practical application of LLZTO based solid-state cells.2) The interfacial side reaction mechanism and kinetic characteristics of LLZTO in liquid electrolyte. The instability of the solid-liquid interface reaction in fresh hot-pressed ceramic sections was studied. By systematically studying the physicochemical characteristics of the "solid-liquid" interface, the reasons for the instability of LLZTO in the liquid electrolyte are summarized. The main component of the interface phase is LiF, and the H2O in the electrolyte plays an important role in the formation of LiF. Reducing the moisture content can inhibit interfacial reactions. This part of the research is expected to provide guidance for the design of LLZO-based "semi-solid-state" cells and "quasi-solid-state" cells.3) Air stability, optimization and modification strategy of LLZTO. The properties are characterized to confirm that the root cause of air instability in LLZTO lies in spontaneous H+/Li+ displacement reaction. The main components of the air passivation layer are Li2CO3, LiOH·xH2O and Li6.4-xHxLa3Zr1.4Ta0.6O12 intermediate layer. The air passivation layer has an interfacial resistance up to 1670 Ω. The heat treatment process can mitigate the negative impacts of the air passivation layer. Doping Ga3+ in the 24d sites can inhibit the occurrence of H+/Li+ displacement reaction and improve the air stability of solid electrolytes. This section expands the understanding of LLZTO air stability and proposes optimization strategies that can be used as references.4) Low-cost wet chemistry to construct a stable LLZTO/Li interface in situ. Propanol has a strong affinity for LLZTO and it can improve interfacial film formation which is an ideal interfacial modification solvent. Using InCl3 and Zn(NO3)2 as interface modification materials can significantly improve interface stability. When modified with InCl3, the Li||Li symmetrical cells deliver a long-lifespan cycle exceeding 1000 h at a current density of 0.45 mA cm-2. The LiFePO4 full cell exhibits a high capacity retention of 97.8 % after 475 cycles at a current density of 0.5C. The elevated electrochemical performance is attributed to the enhance of lithiophilicity at LLZTO interface which can significantly improve the physical contact between electrolyte and metal lithium in the process of lithium plating/stripping. These effective, simple and low-cost modification strategies can provide some reference for the interface modification of solid-state batteries.