锂离子电池富锂层状正极材料的结构调控与电化学性能研究

It is getting more and more essential in Li-ion battery to research the cathode materials with high energy and power density. This work is focus on the Li-rich layer structure materials to reseach and deplore, taking advantage of their high theory capacity. Nowsdays, there exist really some problems for this kind of materials,such as low coulombic efficiency and the release of oxygen in the first charge, poor rate charge-discharge performance and the further improvement of discharge capapcity. In order to opptomise this kind of new cathode mateials for Li-ion battery with high energy and power density and good cycle performance, some technical ways, such as bulk-doping , surface coating and the treatment of corrision , will be introduced to reseach the structure of bulk and interface, the function machanism of bulk and interface with each other, the electrochemical diffusion character of Li-ion in bulk and interface and the properties of surface/interface includeing structure and electrochemistry. The purpose of this king of works is to offer the technical service for the application of next generation cathode materials with high energy density in Li-ion. There is no doubt that the reseach of thix kind of cathode materials is far more important in terms of application value.

研发高容量和高功率的正极材料成为目前锂离子电池领域的研究重点与关键。本项目基于具有高比容量富锂层状化合物的优势，进行重点研究。针对该材料存在的首周库伦效率低及充电析氧，倍率性能差及放电容量有待进一步提高等问题，围绕优化设计具有高比能量，高功率特征及良好循环稳定性的锂离子电池新型正极材料这一总体目标，采用体相掺杂，表面包覆与腐蚀处理等技术途径，从材料体相及界面结构的调控，体相及界面作用机制，电化学体相及界面扩散特征及表面/界面性质等方面进行较为系统的探索研究，为下一代高比能量锂离子电池正极材料的开发与应用提供技术储备，这无疑具有广阔的应用前景和潜在的实际应用价值。

本项目研究实施完成的创新点和主要特征体现在以下几个方面：（1）运用简单的氯化钠熔盐法合成富锂层状氧化物,探究了前驱体的质量比对材料形貌、结构和电化学性能的影响。（2）采用碳酸盐共沉淀法合成了梯度结构的富锂层状氧化物。合成的富锂层状氧化物材料从核表面到接近于壳，过渡金属元素组分含量连续均匀地呈线性变化，材料形貌为类球形，材料具有良好的循环稳定性。（3）采用模板法结合共沉淀法制备了具有孔状结构的富锂层状氧化物。材料具有的中孔特殊结构有利于电解液的渗入，缩短锂离子的穿梭路径并降低材料在充放电循环中的电化学阻抗，从而提高了富锂层状氧化物的倍率性能。（4）在富锂层状材料表面包覆硅酸铝锂，磷酸钒锂，铝酸锂，硅酸锂等，提供快离子通道的同时，能有效抑制活性电极材料与电解液接触界面上的副反应，提高正极材料的活性物质利用率和电化学性能。（5）采用溶胶凝胶法合成了铝部分替代锰的富锂层状材料。改性材料结构稳定性和电化学循环稳定性都得到有效改善。