过渡金属空位耦合钠位Mg/Al掺杂构建高稳定性基于氧变价的钠离子电池正极材料

开发高性能的正极材料是发展室温钠离子电池的关键。在层状正极材料中诱发可逆的阴离子氧化还原被认为是提高正极材料容量的有效途径。近期研究表明，在过渡金属位引入空位能有效提高阴离子氧化还原的可逆性，但空位的引入会造成正极材料结构稳定性的显著降低，尤其在高电压区间会发生不可逆相变，从而严重影响材料的长循环性能。为了在过渡金属层中引入空位的同时，还能保证正极材料在循环过程中的结构稳定性，本项目提出“过渡金属空位耦合钠位掺杂”的协同优化策略，通过在过渡金属位引入空位，诱发阴离子氧化还原提高容量的同时，在钠位引入惰性主族金属离子（Mg, Al），提高层状材料的结构稳定性，从而提高其循环性能。本项目将系统研究不同掺杂元素、掺杂剂量、空位浓度对其电化学行为、结构演变、电荷补偿机制的影响，分析过渡金属空位和钠位掺杂的耦合作用机制，研究成果有望为开发高性能的钠离子电池正极材料提供新思路和理论指导。

Exploring high performance cathode materials is the key step for developing room temperature sodium-ion batteries. Triggering reversible anion redox in layered cathode materials is considered to be an effective way to increase their capacity. Recently, introducing transition metal vacancies has been proved to be able to improve the reversibility of anion redox. However, the vacancies will decrease the structure stability of the cathodes, resulting in irreversible phase transition in high voltage region, thus deteriorating long-term cycle performance. In order to ensure the structure stability of the cathode materials with transition metal vacancies, a synergic strategy of transition metal vacancy coupled with Na-site doping is proposed in this project. When the transition metal vacancies are introduced to trigger anion redox, Mg/Al ions are doped into the Na sites in the layered cathode materials, to strengthen the structure stability, and improve cycle performance. The impacts of doping elements, doping amount and vacancy density on the electrochemical behavior, structure evolution and charge compensation mechanisms will be investigated systematically. The coupling effect of transition metal vacancies and Na-site doping will be analyzed. The results are expected to provide new ideas and theoretical guidance for developing high performance cathode materials for sodium-ion batteries.