富锂锰基层状氧化物的阴离子电荷补偿行为机制及异质结构设计

富锂锰基层状氧化物具有高比容量和能量密度，且成本低廉、对环境友好，极具潜力成为新一代锂离子电池正极材料。其独特的阴离子氧化还原反应为实现多电子转移过程及提高材料比容量创造了条件，然而提高该材料的本征稳定性、保持良好的循环性能仍存在挑战，同时其首次充放电行为不一致且性能随循环而衰减，需深入研究阴离子行为机制，并针对性地设计局域异质结构来增强阴离子电荷补偿能力并稳定晶体结构。本项目拟解析首次4.5V平台处氧的电子态变化规律及其与金属阳离子迁移的拓扑关联，明确在电极反应过程中的结构演变及失效机制，研究材料内部、表层及界面处的电化学行为。通过表面均匀修饰富含氧空穴的催化材料及四面体间隙位非金属原子掺杂，提高富锂材料阴离子的电荷补偿能力并钉扎过渡金属元素，同时探索新型O3@O2型异质结构及拓宽参与氧化还原的阴离子的多元性，从结构和机理上解决富锂材料存在的不可逆容量损失、相结构转变等一系列科学问题。

Lithium-rich manganese-based layered oxides have the potential to become a new generation of cathode materials for lithium-ion batteries, exhibiting high specific capacity and energy density, low cost and environmentally friendliness. Its unique anionic redox reaction creates conditions for multi-electron transfer processes and increasing specific capacity of materials. However, there are huge challenges to improve the intrinsic stability of the materials and maintain excellent cycle performance. What’s more, the initial charge behavior is not consistent with the discharge behavior, and the performance deteriorates accompanied by the subsequent cycle. It is necessary to study the anion charge compensation behavior mechanism of the material in depth, and targetedly design the local heterostructure to enhance the anion charge compensation ability and stability of the material structure. This project intends to analyze the evolution of the electronic state of oxygen at the first 4.5V platform and the topological correlation with the migration of metal cations, define the local structure evolution and failure mechanism during the electrode reaction process, and study the electrochemical behavior at the interior, surface and interface of the material. Improve the charge compensation ability of the anion and pin the transition metal by uniformly modifying the catalytic material with abundant oxygen vacancy on the surface and doping non-metal atom at the tetrahedral interstitial. Meanwhile, explore the novel O3@O2 heterostructure and broaden the diversity of the anions participating in redox. These will solve a series of scientific problems such as irreversible capacity loss and phase structure transformation of lithium-rich materials from the structure and mechanism.