摘要/Abstract

钠离子电池凭借分布广泛和低成本的钠资源在大规模电化学能量存储领域受到广泛关注. 层状过渡金属氧化物作为一种重要的钠离子电池正极材料, 具有比容量高、电化学可逆性相对较好和化学组成丰富且可调的特征, 得到广泛关注. 其中钴酸钠是一种典型层状过渡金属氧化物, 自20世纪80年代就得到大量研究. 由于钴酸钠含有丰富的电化学信息, 基于其充放电过程进行的机理研究对理解钠离子电池层状氧化物体系具有重要意义. 因此在介绍钴酸钠的常见结构类型与合成相图的基础上, 本文着重综述了不同结构钴酸钠在充放电过程中结构变化和电荷补偿机理的研究进展, 同时讨论了上述机制对电化学性能的影响. 本综述旨在为深入研究并建立层状过渡金属氧化物正极材料电化学过程中的构效关系提供支持.
关键词: 钠离子电池, 正极材料, 钴酸钠, 结构变化, 电荷补偿机理, 构效关系
Sodium ion batteries have regained widespread attention in the field of large-scale electrochemical energy storage by virtue of their widely distributed and low-cost sodium resources. Among many of the cathode materials (layered, tunnel-like, polyanionic type and Prussian-blue type, etc.), layered transition metal oxide materials have received extensive research attention due to the features of high specific capacity, relatively good electrochemical reversibility, and rich and adjustable chemical composition. Sodium cobalt oxide is one of the most typical layered transition metal oxides. A lot of research has been done about sodium cobalt oxide since the 1980s. Although compared with other energy storage systems (such as lithium cobalt oxide materials which has the similar composition), sodium cobalt oxide does not take more advantage in electrochemical performance (like rate performance, cycle performance, etc.), but it can be observed from the charge and discharge curve that sodium cobalt oxide has undergone complex electrochemical processes, which means that it has a bunch of information on the degradation mechanisms during the charge and discharge processes. The correlation studies of the failure mechanism during the charging and discharging processes of sodium cobalt oxide (including the structure changes and the charge compensation mechanisms) are of great significance for the deep understanding of the layered oxide systems in sodium ion batteries. Therefore, on the basis of introducing the common crystal structure types and the synthesis phase diagram of sodium cobalt oxides, this article focuses on reviewing the structure changes (including phase transition and Na⁺/ vacancy ordering) and charge compensation mechanisms of sodium cobalt oxides with different crystal structures during the charging and discharging. At the same time, the correlation between the mechanisms above and electrochemical performance is discussed. This review aims to provide support for the in-depth study and establishment of the structure-activity relationship in the electrochemical processes of layered transition metal oxide cathode materials.
Key words: sodium ion battery, cathode material, sodium cobalt oxide, structure change, charge compensation mechanism, structure-activity relationship


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