Na2MnPO4F-Na3V2(PO4)2F3/C复合纳米纤维高效电子/离子导电网络的构建及性能调控

With the depletion of lithium resources, sodium-ion batteries have been considered as promising candidates for large-scale applications because of the advantages such as abundance of sodium resources, low cost and high safety, etc. The development of cathodes with excellent performances is the key to the application of sodium-ion batteries. Na2MnPO4F shows high development potentiality because of its high theoretical capacity, high working potential and excellent thermo-stability. However, the low electronic and ionic conductivities, and Jahn-Teller effect hinder its practical application. In this project, we introduce electrospining method to build a high conductive network for electron and ion, and thus to improve the performance of Na2MnPO4F. Firstly, the ionic conductivity can be enhanced through building of nano porous hollow fiber network and in-situ synthesizing Na3V2(PO4)2F3 fast ion conductor and Na2MnPO4F composite. Secondly, the in-situ coating of nano carbon and the mutual doping of V and Mn will increase the electronic conductivity of the composite material. Thirdly, Jahn-Teller effect can be restrained by V-doping. The study shows the mechanism of the synergistic effect of Na2MnPO4F-Na3V2(PO4)2F3 composite, the mechanism of restaining Jahn-Teller effect, and "structure-performance" relationship between the structure of nano porous hollow fiber and electrochemical properties. These all can provide new ideas for the development and application of the electrode materials for sodium-ion battery.

随着锂资源迅速枯竭，钠离子电池因其资源丰富、价格低廉和安全性能好等优点而展现出广阔的应用前景，其应用的关键是开发高性能正极材料。Na2MnPO4F因其理论容量高、工作电位高、热稳定性好等优点成为最具发展潜力的正极材料之一，但较低的电子/离子电导率及Mn的Jahn-Teller效应制约了其有效应用。本项目拟采用静电纺丝法构建高效电子/离子混合导电网络来对Na2MnPO4F进行改性：利用中空多孔纳米纤维网络以及原位复合Na3V2(PO4)2F3快离子导体来提高离子电导率；利用V、Mn相互掺杂及原位包覆纳米碳提高电子电导率；利用V掺杂抑制Jahn-Teller效应。通过本项目研究，揭示Na2MnPO4F-Na3V2(PO4)2F3复合协同改性的作用机理及Jahn-Teller效应的抑制机理，明晰中空多孔纳米纤维结构与性能之间的“构效关系”，从而为钠离子电池电极材料的开发应用提供新思路。

随着锂资源迅速枯竭，钠离子电池因其资源丰富、价格低廉和安全性能好等优点而展现出广阔的应用前景，其应用的关键是开发高性能正极材料。Na2MnPO4F因其理论容量高、工作电位高、热稳定性好等优点成为最具发展潜力的正极材料之一，但较低的电子/离子电导率及Mn的Jahn-Teller效应制约了其有效应用。本项目采用静电纺丝法构建高效电子/离子混合导电网络来对Na2MnPO4F进行改性：利用中空多孔纳米纤维网络以及原位复合Na3V2(PO4)2F3快离子导体来提高离子电导率；利用V、Mn相互掺杂及原位包覆纳米碳提高电子电导率；利用V掺杂抑制Jahn-Teller效应。通过本项目研究，揭示了Na2MnPO4F-Na3V2(PO4)2F3复合协同改性的作用机理及Jahn-Teller效应的抑制机理，明晰了中空多孔纳米纤维结构与性能之间的“构效关系”，最终获得了电化学性能优异的钠离子电池复合正极材料Na2MnPO4F-Na3V2(PO4)2F3。上述成果为新型二次电池电极材料的开发应用提供了新思路。在本项目实施过程中共发表学术论文17篇，其中SCI检索12篇，有2篇论文入选ESI 1%高被引论文；共申请发明专利13项，其中已授权7项；培养了博士研究生2人，硕士研究生5人。