Garnet型Li7La3Zr2O12固体电解质基全固态锂离子电池中电解质/电极界面的调控及离子输运特性研究

Conventional lithium-ion batteries using organic liquid electrolytes suffer from limited energy density and safety risks. To obtain both the optimized energy density and safety, all-solid-state lithium battery will be developed using solid electrolytes. The garnet-type solid electrolyte, Li7La3Zr2O12 (LLZO) will be chosen as the study material, and co-sintered with cathodes and anodes, respectively. Furthermore, all-solid-state lithium-ion battery will be assembled. Chemical stability between the LLZO electrolyte and electrodes during the co-sintering will be studied to confirm the compatible electrodes for co-sintering with the LLZO electrolyte. Aiming to overcome the poor ion-conducting performance of the solid electrolyte/electrode interfaces in the all-solid-state battery, an ion-conducting layer will be added between the electrolyte and electrode to improve the interfacial ionic conductivity and stability. Thus, the efficient and stable solid electrolyte/electrode interfaces will be obtained. The mechanism of structure modification for the electrolyte/electrode interfaces will be investigated to obtain an effective method that optimizes the interfacial ionic conductivity via structure modification. The evolutions of composition, phase and morphology of the interfaces during electrochemical process will be studied, and the relationship between structure and ionic conductivity will be established to confirm the key factors that affect interfacial ion-conducting. These studies will provide theoretical and experimental basis for applications of all-solid-state lithium-ion batteries based on the LLZO electrolyte.

现有锂离子电池采用有机电解液体系，能量密度难以进一步提升，同时存在一定的安全隐患。采用固体电解质构建全固态锂离子电池，在提高电池能量密度同时可兼顾安全性问题。本项目选用Garnet型Li7La3Zr2O12（LLZO）固体电解质作为研究材料，将其与正负极材料共烧，构建全固态锂离子电池。探讨在共烧过程中电解质与电极之间的化学稳定性，找到与LLZO电解质相匹配的电极材料。针对电池中固体电解质/电极界面离子输运性能不佳的问题，在电解质和电极之间引入离子导电层，提高界面的离子电导率和稳定性，获得高效稳定的离子输运界面。研究电解质/电极界面的结构调控机制，找到通过结构调控优化界面离子传导性能的有效方法。分析在电化学过程中电解质/电极界面处组分、物相、形貌等结构因素的演变，构建界面结构与离子导电率的科学联系，揭示影响离子传输的关键因素，为LLZO固体电解质基全固态锂离子电池的实用化提供理论和实验基础。

现有锂离子电池采用有机电解液体系，能量密度难以进一步提升，同时存在一定的安全隐患。采用固体电解质构建全固态锂金属电池，在提高电池能量密度同时可兼顾安全性问题。本项目开发了各种固体电解质材料的批量制备工艺，材料体系涵盖了Garnet型Li6.4La3Zr1.4Ta0.6O12（LLZTO）、Li6.4La3Zr1.4Nb0.6O12（LLZNO），NASICON型Li1.3Al0.3Ti1.7(PO4)3（LATP），Perovskite型Li0.33La0.56TiO3（LLTO），Argyrodite型Li6PS5Cl（LPSCl）、Li6PS5Br（LPSBr）和Halide型Li3InCl6（LInCl）。这些材料在室温30 oC下的离子电导率均高于10-3 S cm-1，具有优异的离子导电性，为课题的研究提供了重要的材料基础。选用Garnet型Li7La3Zr2O12（LLZO）基固体电解质作为研究材料，构建固态锂金属电池。在固态锂离子电池方面，基于厚度为200 μm的Garnet型固体电解质流延片构建了Li/Garnet/LiFePO4电池，基于Garnet型固体电解质陶瓷片构建了Li/Garnet/Si薄膜电池，并获得了优异的电池性能。针对电池中固体电解质/电极界面离子输运性能不佳的问题，在电解质和电极之间引入离子导电层，如Li-Sn合金层、LixSn+Li2O复合层、LiF-石墨烯离子电子混合导电层，提高界面的离子电导率和稳定性，获得高效稳定的离子输运界面。在固态锂氧气电池方面，提出了多孔框架渗透（PFI）的概念，通过在Garnet型固体电解质表面进行酸刻蚀，形成多孔框架结构。多孔结构增加了固体电解质和电极之间的接触面积，能降低界面电阻并提高倍率性能。在孔内渗入少量液体电解质，该框架依然具有不可燃性。此外，项目还系统分析了在电化学过程中电解质/电极界面处组分、物相、形貌等结构因素的演变，构建了界面的构效关系，为LLZO固体电解质基全固态锂金属电池的实用化提供了重要的理论和实验基础。