Na3V2(PO4)3/(N-RGO)双重修饰Na2Fe1-xMnxPO4F复合材料的设计合成、储钠性能及作用机理

The cathode material Na2Fe1-xMnxPO4F possesses higher operating potential than Na2FePO4F, and better electrochemical activity than Na2MnPO4F. However, there are some shortcomings such as the low electronic conductivity, low diffusivity coefficient of Na+, Jahn-Teller effect, and the dissolution of Mn in electrolyte. In this project, we introduce solvothermal method to synthesize Na2Fe1-xMnxPO4F nanocrystal, and realize the double modification with fast ion conductor Na3V2(PO4)3 and conductive agent (N-RGO) . Firstly, the excellent electric conductivity of (N-RGO), and the mutual doping of core and shell will increase the electronic conductivity of Na2Fe1-xMnxPO4F. Secondly, the diffusivity coefficient of Na+ can be enhanced owing to the nanorization of the material and the modified layer of fast ion conductor Na3V2(PO4)3. Moreover, the dissolution of Mn can be decreased and Jahn-Teller effect can be restrained due to the double- modified layers. Consequently, the structure stability and electrochemical performanceof Na2Fe1-xMnxPO4F can be remarkably improved. The study shows the law and mechanism how double-modified layers influence the Na+ transport and electronic conductivity, restrain Jahn-Teller effect and the Mn dissolution, and enhance interface stability of the composite. These all can provide new ideas for the development and application of the electrode materials for sodium ion battery.

Na2Fe1-xMnxPO4F具有工作电位比Na2FePO4F高，电化学活性比Na2MnPO4F好的优点，但存在较低的电子电导率和钠离子传输速率、锰的溶解以及Jahn-Teller效应等问题。本项目通过溶剂热法制备Na2Fe1-xMnxPO4F纳米晶，采用Na3V2(PO4)3快离子导体和氮掺杂石墨烯(N-RGO)对其进行双重修饰，利用内核和修饰层的相互掺杂以及(N-RGO)表面修饰共同提高材料的电子电导率；利用纳米化以及Na3V2(PO4)3快离子导体修饰共同提高钠离子传输速率，利用双重修饰抑制锰的溶解和减小Jahn-Teller效应，从而达到提高Na2Fe1-xMnxPO4F结构稳定性和改善电化学性能的目的。通过项目研究，揭示双重修饰改善钠离子传输速率和电子电导率、抑制锰的溶解和减小Jahn-Teller效应、以及提高界面稳定性的作用机理，为钠离子电池电极材料的开发应用提供新的思路。

Na2Fe1-xMnxPO4F具有工作电位比Na2FePO4F高，电化学活性比Na2MnPO4F好的优点，但存在较低的电子电导率和钠离子传输速率、锰的溶解以及Jahn-Teller效应等问题。本项目通过合成Na2Fe1-xMnxPO4F纳米晶，采用Na3V2(PO4)3快离子导体和氮掺杂石墨烯(N-RGO)对其进行双重修饰，利用内核和修饰层的相互掺杂以及(N-RGO)表面修饰共同提高材料的电子电导率；利用纳米化以及Na3V2(PO4)3快离子导体修饰共同提高钠离子传输速率，利用双重修饰抑制锰的溶解和减小Jahn-Teller效应，从而达到提高Na2Fe1-xMnxPO4F结构稳定性和改善电化学性能的目的。通过项目研究，揭示双重修饰改善钠离子传输速率和电子电导率、抑制锰的溶解和减小Jahn-Teller效应、以及提高界面稳定性的作用机理，为钠离子电池电极材料的开发应用提供新的思路。上述成果为二次电池的修饰改性提供了新思想。在项目实施过程中，公开发表学术论文18篇，其中SCI收录论文14篇，中文核心论文4篇，其中一篇论文入选ESI 1%高被引论文，参加学术会议9次，申请中国发明专利14项，其中授权专利5项。