全固态锂电池中石榴石型电解质/电极功能层一体化设计及界面离子传输研究

All-solid-state lithium-ion batteries have been considered as the ideal optional for the power batteries and energy storage batteries due to its high security and capacity. However, the high interface impedance between the electrolyte and the electrode layers restrict its business application. In this project, all-solid-state lithium-ion batteries based on Li7-xLa3Zr2-xTaxO12 (LLZTaO, x=0.2~1.0) electrolyte are designed and investigated combined with several electrode materials and Li3BO3 fluxing agent. After carefully optimizing the composition of the electrode and electrolyte, the integrated electrode functional layer /electrolyte double-layer specimens with dense interface structure, good chemical stability and high lithium ionic conductivity are prepared through SPS and co-sintering process at lower temperature. Microstructure analysis, AC impedance spectroscopy as well as the internal friction technology will be used to investigate the relationship between the conduction mechanism and the synthesis conditions, including the composition of the electrode function layer, sintering pressure and temperature. This project is expected to develop a new preparation technique of integrated electrode functional layer /electrolyte double-layer specimens, reveal the mechanism of the interface migration of the lithium ions, and provide the scientific basis for the performance optimization and application of the LLZTaO based all-solid-state lithium-ion batteries.

全固态锂离子电池具有高安全性和大容量，是动力电池和储能电池的理想选择之一，但其电解质/电极界面的高阻抗问题限制了其商业化应用。对此，本项目将以Li7-xLa3Zr2-xTaxO12为电解质（LLZTaO，x=0.2~1.0），以Li3BO3为助熔剂，与多种电极材料匹配来制备全固态锂离子原型电池，通过优化设计电极功能层组成，并基于先进放电等离子体烧结工艺和低温一体化共烧技术制备具有界面致密、化学稳定性好的电解质/电极功能层双层结构模块，达到提高离子传输率，降低界面阻抗的目的；采用微结构分析、交流阻抗谱及内耗谱等技术，阐明电极功能层及其电解质/电极界面的锂离子电导率随制备工艺参数（电极功能层组成、烧结压力和烧结温度等）的变化规律及迁移机理。项目预期将发展LLZTaO基无机固体电解质/电极功能层低温一体化制备技术，为LLZTaO基全固态锂电池的界面性能优化和最终应用提供科学依据。

为提高锂电池的安全性、实现全固态电池的应用，该项目通过设计电极功能层，通过共压共烧工艺将其与电解质层一起制备成界面紧密结合的多层结构块材，并对界面锂离子迁移机理进行分析。主要研究内容包括：1）石榴石型固态电解质低温致密化，2）电极功能层内活性电极钴酸锂、石榴石型固态电解质以及电子导体银的组成比例调整，3）具有平整界面结构的电解质/电极功能层双层结构块材的制备及性能表征，4）全固态电池的制备及性能表征以及5）固态电解质在空气中的稳定型分析。通过固相法实现了在较低温度下（800oC）制备Ca/Ta共掺杂的Li6.55La2.95Ca0.05Zr1.5Ta0.5O12电解质，借助硼酸锂（Li3BO3，LBO）作为助熔剂，实现了电解质的低温致密化，30oC时锂离子电导率为1.33 × 10-4 S/cm，为后续电极功能层的实验设计和实施提供了基础。在电极功能层组成中，我们加入了Ag作为电子导体，改善了电极功能层内电子电导，有利于电极参与电化学反应，同时通过对称结构烧结方法，解决了共压共烧过程中，不同层间热收缩不匹配问题，实现了具有平整界面结构的多层块材制备，并在此基础上组装了全固态电池，所制备电池可实现对LED灯的供电。以上工作均按照基金计划执行，互为基础，循序渐进，所得成果与经验可为后续研究展开提供帮助，具有十分重要的基础科学价值，待其性能进一步改善之后，具有重要的实际应用前景。