石墨烯基锂离子电池的原位构建及皮米分辨下电极微结构演变的动态表征与机理研究

Exploring the essential microcosmic mechanisms of electrode materials during the charging and discharging in lithium-ion batteries (LIBs) is of great importance for developing next-generation high-performance LIBs. Aiming at the fact that the electrochemical process of lithiation and delithiation in LIBs mainly happens within the anode and cathode, this project combines picometer-resolution Cs-corrected transmission electron microscope (TEM) and in situ manipulation technique to construct the single nanoscale LIB for studying extensively the microstructure and crystal phase evolution of graphene-based and other materials' electrodes. Simultaneously, the dynamic evolution process of electrode microstructure, solid electrolyte interphase (SEI) film, and lithium dendrite during the charging and discharging in LIBs can be inspected in real time as well as dynamic changes in electrode materials' morphology induced by the lithiation and delithiation. In the full use of the sub-angstrom resolution of the Cs-corrected TEM and in situ dynamic manipulation ability, it is possible to have an insight into the electrode microstructure evolution law, SEI film formation mechanism, and the lithium ion transport mode down to atomic level, which could help us solve some key scientific problems existed presently in LIBs. By virtue of the in situ electrical measurement and in situ heating technique, high and low temperature performances and cycle performance of the electrode materials used in LIBs can be evaluated. In addition, other device performance parameters in LIBs can be further optimized. All these provide the potential in developing high-reliability and highly efficient LIBs in the future.

从根本上探寻锂离子电池电极材料充放电的基本微观机制已成为研发新一代高性能锂离子电池的有效途径。本项目基于原位电子显微学技术，针对锂离子电池充放电过程中脱锂、嵌锂的电化学反应发生在电极内部的客观事实，以石墨烯基及其他电极材料微结构演化为研究对象，采用皮米分辨的球差校正透射电子显微镜(TEM)和原位操纵手段实现纳米尺度下的电池原位构建，并结合原位电学测试，开展充放电状态下电极微结构、固体电解质界面(SEI)膜和锂枝晶演化的动态表征。充分利用球差校正TEM的高分辨与原位操纵的本领，从原子尺度层面探索石墨烯基及其他电极材料微结构演变规律和SEI膜成膜机理，明确锂离子传递通道，以解决电池器件中的关键基础科学问题；同时借助于原位电学测试和原位加热方法，开展电极材料高低温特性和循环性能等指标评价，进行电池其他构成要素的优化研究，对提升电池可靠性和研发高效电池具有重要的指导意义。

本项目在透射电镜中对石墨烯及其复合材料作为锂离子电极材料进行电学性能研究。首先，采用原位化学合成方法，制备高质量石墨烯-纳米金属颗粒(Ag-石墨烯纳米复合电极、Co3O4-石墨烯纳米复合电极等)复合材料电极，将此电极材料用作负极材料和正极材料，研究其充电过程中嵌锂时电极结构的晶体结构变化和脱锂时对电极结构的破化作用。其次，基于原位透射电子显微学技术，针对锂离子电池充放电过程中脱锂、嵌锂的电化学反应发生在电极内部的客观事实，以石墨烯基及其他电极材料微结构演化为研究对象，采用透射电子显微镜(TEM)和原位操纵手段实现纳米尺度下的电池原位构建，并结合原位电学测试，开展充放电状态下电极微结构演化的动态表征。最后，建立石墨烯基锂离子电池的原位构建及皮米分辨下电极微结构演变的动态表征的微纳平台，构建新型的高精度纳米加工、原位性能测试与结构表征的多功能一体化的研究平台，为研发具有自主知识产权的透射电镜原位操作设备积累经验。