缺陷构筑提升富锂锰基正极材料的电化学性能

富锂锰基层状材料具有比容量高、工作电压高和成本低等优点，是极具潜力的下一代锂离子电池新型正极材料。然而，循环过程中电极材料首次库仑效率低、倍率性能差、容量与电压衰减严重的缺点限制了其实际应用。本申请项目拟在理解缺陷、构筑缺陷和利用缺陷的核心思路指导下，通过锂、氧双空位缺陷与表面保护协同提升首次循环锂离子的电化学可逆性，提高其库伦效率；通过本征锂空位缺陷构筑与非本征高离子导率复合相修饰协同增强电极材料体相与界面处锂离子扩散速率，增强其倍率性能；通过体相掺杂和表面Li-M-O异质结构一体化构筑来调控电极材料的缺陷结构，抑制晶格氧过度氧化与相转变，提高容量与电压稳定性。在此基础上，建立缺陷与电化学性能的构效关系，理清不同缺陷间的内在联系，实现不同缺陷的协调与统一，并通过锂层超量锂空位的科学设计与合理构筑全面提升电极材料的电化学性能，考察其在全电池中的应用，为其商业化应用提供实验基础和理论依据。

Li-rich manganese-based layered oxide (LLO) cathodes are among the most promising cathodes in the next generation lithium ion batteries due to their high specific capacity, high operation voltage and low cost. However, they always suffer from severe disadvantages, such as low initial Coulombic efficiency, poor rate capability, rapid capacity and voltage decay, which greatly prohibit their practical application. Under the guideline of understanding, constructing and utilizing defects, this project will combine the lithium-vacant and oxygen-vacant defects associated by surface coating to improve the irreversibility of lithium ions at the activated electrochemical process and thus the initial Coulombic efficiency, construct intrinsic lithium-vacant defects and extrinsic modified phase with high ionic conductivity to promote the electrochemical kinetics of lithium ions in the bulk and at the interface and thus the rate consequently, construct doping in the bulk and Li-M-O heterostructures on the surface to tailor the defect structure in the electrode materials to suppress the excessive oxidization of lattice oxygen and phase transition, and thus improve the capacity and voltage retentions. Then, the relationship between defects and electrochemical performances will be investigated to understand the internal relationship among different defects. The scientific design and rational construction of excessive lithium-vacant defects in lithium sites of electrode materials will be carried out to improve the overall electrochemical performances of LLO cathodes and then their application in full cells will be investigated, which will provide the experimental and theoretical foundations for high energy density lithium ion battereis from the experimental study to the practical application.