含锂石榴石薄膜材料的制备和离子传导研究

A safe, stable and ionically fast solid electrolyte material has become the key and bottleneck to develop all-solid-state lithium-ion batteries. In recent years, lithium garnets as solid-state lithium-ion electrolyte has attracted much attention thanks to the relatively high room-temperature ionic conductivity (~0.0003 S/cm). However, this conductivity value is still well below the widely accepted practical value for lithium-ion electrolyte, i.e. 0.01 S/cm. Our strategy to address this issue is to introduce thin-film materials. Based on our experience in complex oxide thin-film ion conductors, we propose 1) to fabricate thin-film lithium garnets through RF magnetron sputtering deposition, investigating the effect of sputtering parameters on the material features (order/disorder transfer, stoichiometry, grain size, grain boundary impurities, and texture) of the thin film; 2) to study the ionic property of thin-film lithium garnets and shed lights on the influence of "space charge" effect and interface impurities on ionic conductance. This work will develop a fabrication process for thin-film lithium garnets, deepen the understanding of ion transport in thin-film ion conductors and provide experimental and theoretical insights to develop novel fast thin-film lithium-ion electrolyte.

研发一种安全、稳定、高离子传导率的固态锂离子电解质是开发全固态锂离子电池的关键与难点。近年来含锂石榴石以其较高的室温离子传导率（~0.0003 S/cm）成为固态锂离子电解质的热门备选材料。本项目针对此离子传导率仍低于业界公认的实用值0.01 S/cm的问题，提出引入薄膜材料的策略。基于前期在多元氧化物离子薄膜导体上的研究基础，我们计划采用RF磁控溅射沉积技术制备含锂石榴石薄膜，通过考察沉积条件和后续处理对薄膜材料的材料学特性如晶体的有序/无序转变、化学计量、晶粒尺寸、晶界杂质和生长取向的影响，以制得致密、形稳、缺陷少的薄膜材料。同时通过采用电化学交流阻抗法测量其离子传导性能，揭示含锂石榴石薄膜材料中"空间电荷"效应和晶界杂质对锂离子传导过程的影响机理。本研究可以加深对薄膜离子导体中离子传导机制的理解，可研发含锂石榴石薄膜材料的制备流程，为研制新型快速锂离子电解质薄膜提供理论和实验依据。

研发一种安全、稳定、高离子传导率的固态锂离子电解质是开发全固态锂离子电池的关键与难点。近年来含锂石榴石以其较高的室温离子传导率（~0.0003 S/cm）成为固态锂离子电解质的热门备选材料。本项目主要研究内容包括含锂石榴石固体电解质的可控制备、空气稳定性机理、固体电解质/锂界面改性、以及在新型锂离子储能器件中的初步应用等方面。目前实验室制备的含锂石榴石电解质室温离子电导率在4~8 × 10^-4 S/cm范围内；同时阐明该固体电解质材料在空气中离子传导率下降源自表面形成的高阻杂质相如Li2CO3，此杂质想的形成与固体电解质材料特性、空气中水汽及相关的质子交换过程直接相关；同时固体电解质的引入对抑制锂硫电池多硫化物的穿梭效应效果明显。通过本项目的执行，一方面为含锂石榴石固体电解质的进一步研发打下了坚实基础；另一方面我们坚信随着含锂石榴石化学稳定性和电极/电解质界面性能的改善，此材料将成为新型储能器件固体电解质的有力备选。