皮米分辨下石墨烯基锂离子电池电极微结构演化的原位动态表征与嵌/脱锂机制研究

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 for 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型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嵌/脱锂电化学过程发生在电极内部的客观事实，以石墨烯及其他电极材料微结构演化为研究对象，采用配备单色器的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，从原子尺度层面探索石墨烯及其他电极材料微结构演化规律和SEI膜成膜机制，明确嵌脱锂通道，以解决电池器件失效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，并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。

石墨烯和黑磷烯等二维材料在能源应用领域得到广泛关注，尤其在二次电池储能领域。本项目首先着力新兴二维材料的可控制备，成功开发出利用常规水热合成和机械剥离技术制备二维材料纳米结构的新途径，继而将其引入到锂离子电池储能应用领域。采用原位透射电子显微学方法，原位研究了锂离子电池充放电过程中嵌/脱锂电化学过程，观察石墨烯及其他电极材料微结构演化，从原子尺度层面解释了黑磷烯等二维电极材料微结构演化规律，明确了嵌脱锂通道，确认了二维材料的限域作用。同时基于本课题的研究技术手段，进一步拓展课题研究广度，研究了一维隧道结构的正极电池材料，首次观察到纳米材料个体之间的界面传输行为，深化了锂离子在材料内部传输的动力学新认知，并运用能量损失谱从表面缺陷角度解释这一发现。项目成果有效解决了电池器件失效的关键基础科学问题，对提升电池可靠性和研发高效电池具有重要的指导意义。