石墨烯/NixCo2-xS4复合电极材料制备及其界面电荷传输与复合机制研究

The nickel and cobalt sulfide (NixCo2-xS4) with spinel structure holds a significant promise as electrode materials for supercapacitors, while the electrochemical performance is ultimately limited by its poor electrical conductivity. It’s therefore the aim of this work to fully exploit the potential of NixCo2-xS4-based electrode materials. In-situ growth of NixCo2-xS4 with spinel structure on the graphene can promote the formation of interface with good connection between graphene and NixCo2-xS4. Possessing interconnected 3D porous network, the graphene/NixCo2-xS4 composites can take full advantage of both high conductivity of graphene and fast 3D ion diffusion channel of spinel structure, which benefit to the optimization of charge transport pathway and accelerate the electron diffusion. However, the mechanism for the improvement of Ni-Co pseudocapacitance performance is still not clear so far. Especially, the mechanism of electron transport and recombination in the interface of graphene/NixCo2-xS4 composites still needs next further study. This project aims at the preparation of graphene/NixCo2-xS4 composite electrode with high specific capacity through material design and microstructure control. Firstly, the influences of the synthesis technology on the microstructure of graphene/NixCo2-xS4 composites are investigated. Then, the close relationship between synthesis technology, microstructure and the electrochemical properties will be explored in detail. Finally, the mechanism of charge transport and recombination in the interfaces of graphene/NixCo2-xS4 composites is investigated as the theoretical guidance and practice basis for developing high-performance supercapacitors.

尖晶石结构的镍钴硫化物是一种极具潜力的超级电容器电极材料，但其较差的电导率，导致电荷传输困难，限制了其电化学性能的发挥。在石墨烯上原位生长尖晶石结构镍钴硫化物，能够促使石墨烯和镍钴硫化物之间形成良好的连接界面，进而通过其内部互相连通的多孔网络，充分发挥石墨烯良好的导电性和尖晶石结构互通的三维离子扩散通道的优势，优化电荷传输路径，加速电子传递。然而，其改善镍钴赝电容性能的机理目前还不清楚，特别是复合材料界面的电荷传输与复合机制尚需进一步深入研究。本项目拟通过材料设计和微结构调控，制备高比电容量的石墨烯/NixCo2-xS4复合材料，研究制备工艺、微观结构和电化学特性之间的联系，揭示石墨烯/NixCo2-xS4复合材料的界面电荷传输与复合机制，以优化其电荷传输路径，抑制电子复合，改善电极性能。研究成果有助于深入理解复合材料的界面电荷传输与复合机理，为开发高性能的超级电容器电极材料提供理论指导。

尖晶石结构的镍钴硫化物是一种极具潜力的超级电容器电极材料，但其较差的电导率，导致电荷传输困难，限制了其电化学性能的发挥。在石墨烯上原位生长尖晶石结构镍钴硫化物，能够在石墨烯和镍钴硫化物之间形成良好的连接界面，进而通过其内部互相连通的多孔网络，充分发挥石墨烯良好的导电性和尖晶石结构互通的三维离子扩散通道的优势，优化电荷传输路径。然而，其改善镍钴赝电容性能的机理目前还不清楚。本项目首先将GO还原为RGO，然后在RGO表面原位沉积镍钴硫代尖晶石，制备了石墨烯/NixCo3-xS4复合材料，并系统研究了复合材料电极的制备工艺、微观结构和电化学特性之间的联系，探索了石墨烯/NixCo3-xS4复合材料的界面电荷传输与复合机制，改善电极性能。研究结果包括：1)对FeI2水溶液在不同pH条件下还原所得RGO薄膜体电导率和碳氧比进行了系统的研究，向FeI2水溶液中加酸以抑制FeI2的水解来实现石墨烯的高导电性，并且对还原机理进行了深入地讨论；2）以石墨氧化物的水溶液为溶剂，采用原位水热合成的方法利用前驱体直接在RGO表面形成了NixCo3-xS4颗粒，从而得到NixCo3-xS4-RGO杂化物。相对于中空的NiCo2S4微球，石墨烯/NixCo3-xS4在5 A/g的电流密度下，比容量达到1270 F/g；在经历2000次循环后，比容量仍然保持在1209 F/g的水平上，容量损失仅为4.8%，远远小于的NiCo2S4的损失。研究成果有助于深入理解复合材料的界面电荷传输与复合机理，为开发高性能的超级电容器电极材料提供理论指导。同时本项目制备的石墨烯/NixCo3-xS4复合电极材料也可以用作热电池阴极材料，更适合于发展高功率密度和能量密度的热电池，是代替二硫化铁的理想阴极材料之一。.以通讯作者发表SCI论文8篇，授权国家发明专利4项。