The lithium-ion battery has mitigated the reliance on fossil fuels and alleviated the increasing pressure on environment as a new form of energy storage.Compared with other conventional cathodes,lithium-rich layered oxide is considered to be one of the most potential candidates for the next generation cathode materials due to its low cost and higher reversible capacity,which is a promising application especially in the fields of electric vehicles and large-scale energy storage grids.In this review,we start from the point of the structures of lithium-rich layered oxides then mainly focus on the differences of lattice configuration between a solid solution structure and a " composite" structure.Various characterization methods which are used to identify these differences are introduced as well.The origins of the 4.5 V plateau and several representative mechanisms proposed in recent years are summarized.From different perspective,these mechanisms explain the origin of the abnormal capacity of lithium-rich layered oxides when they are charged-discharged at the first cycle.According to the current research,the validity of these mechanisms is elaborated.Meanwhile,some major problems which hinder the further development of lithium-rich layered oxides,including irreversible capacity loss at first cycle,cycle performance,rate capability,are introduced.At the same time,the effects generated by the surface spinel phase and several typical modification methods are elaborated.Finally,the future development and the prospects of lithium-rich layered oxides as cathode materials for lithium-ion batteries are also proposed.%锂离子电池作为新型的储能形式,缓解了人们对化石燃料的依赖和日益严峻的环境压力.富锂层状氧化物相比于传统正极材料,由于其低成本和大可逆容量的特性,被誉为最具发展潜力的下一代锂离子电池正极材料之一,尤其是在电动汽车和大规模储能电网领域的应用前景十分广阔.本文从材料的结构类型出发,主要介绍了固溶体结构和复合结构在晶格排布上的差异以及在鉴别这种差异时所采用的一系列表征手段.本文还总结了近年来提出的最具代表性的几种4.5V电压平台产生机理,从不同角度解释了富锂层状氧化物在首次循环过程中表现出异常容量的现象,并结合现有研究阐述了各种机理.此外,也对阻碍富锂层状氧化物进一步发展的重大问题,包括首次不可逆容量损失、循环性能和倍率性能等进行了分析,讨论了表面尖晶石相对材料性能的影响,介绍了几种最典型的改性手段.最后,对富锂层状氧化物正极材料未来的研究方向进行了概述,展望其研究前景.
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