锂离子电池层状锰基正极材料\碳酸酯基电解质溶液界面性质的理论和实验研究

In order to meet the energy and power density requirement of lithium ion batteries for electric vehicles, it is necessary to develop new cathode materials with high voltage and high lithium-inserted capacity. However, the cathode materials and electrolytes are unstable under high voltage. A new solution to this problem, building up a solid electrolyte interphase (SEI), is proposed in this project through theoretical and experimental investigations on the interfacial properties between layered manganese-based cathode materials and organic carbonate-based electrolytes. A series of cathode materials with well defined structure, composition and grain size will be synthesized. The natures of the cathode materials, the electrolytes and the interfacial properties between the cathode materials and the electrolytes, the design and optimization on the molecule structure of the additives for SEI formation, and the formation process and properties of the SEIs will be investigated. With these investigations, it is hoped to understand the mechanisms on the cathode material and electrolyte solution decompositions, the SEI formation and the influence of SEI on lithium insertion/deinsertion process, and to obtain the methods to build up the SEIs with good stability, ability to inhibit the decompositions of cathode materials and electrolytes. The obtained results will not only help to solve the instability of high voltage cathode materials-electrolyte systems and thus to promote the application of lithium ion batteries with high energy density, but also widen the research on lithium ion battery and enrich the electrochemical science.

为满足电动汽车用锂离子电池能量和功率密度要求，必须发展高压高嵌锂容量的正极材料。但高电压下电极材料及电解质溶液不稳定，阻碍了材料的实际应用。本项目以高压层状锰基嵌锂材料和有机碳酸酯基电解质溶液为研究对象，结合理论计算和实验方法，研究电极\溶液界面性质，提出界面膜解决方案。研究内容涉及：制备结构、组成和颗粒尺度确定的高压层状锰基嵌锂材料；研究电极材料、电解质溶液以及电极\溶液界面性质；设计和优选界面膜添加剂分子结构，研究界面膜形成过程及性质。阐明电极材料及电解质溶液不稳定机理，以及添加剂分子结构对界面膜组成和性质的影响规律。获得具有良好化学稳定性、能抑制材料和电解质溶液分解、有利于锂离子传输及电荷交换的界面膜构建方法。研究结果不仅为高压嵌锂材料\电解质溶液体系不稳定性问题的解决提供新方法，促进锂离子电池向高能量密度发展，也拓展锂离子电池的研究视野，并丰富电化学科学的内容。

项目以层状锰基嵌锂材料和有机碳酸酯基电解质溶液为研究对象，结合理论计算和实验方法，开展了材料制备、电极和电解液分解机理、电解液添加剂优选、以及添加剂作用机理的研究。取得的主要成果包括：制备出多种结构、组成和粿粒尺度可控的层状锰基嵌锂材料；发现表面掺杂少量的尖晶石相、提高锂含量、减小粒径等材料控制措施，均对层状锰基嵌锂材料的充放电循环稳定性有改善作用；提出多种能够提高层状锰基嵌锂材料循环稳定性的电解液添加剂；明确了添加剂的作用机理，添加剂优先于电解液氧化形成界面膜，该界面膜保护层状锰基嵌锂材料的结构完整性以及抑制电解液分解，从而提高了材料的循环稳定性。以上结果为解决层状锂锰嵌锂材料循环不稳定性的问题提供了新的解决方案。. 项目累计发表论文56篇，在国内外重要学术会议上做特邀报告9次；申请发明专利19件，其中获授权2件。