三维有序介孔石墨烯复合材料的制备及其在储能方面的应用研究

Due to the strong Van der Waals force between layer and layer, two-dimensional graphene tended to restack together again in the process of storage, processing and application, which will lead to reduce the effective specific surface area of graphene, and be difficult to form efficient and uniform composites with other materials. Aim to resolve this problem, this project proposed a new method to prepare a highly ordered, three-dimensional continuous mesoporous graphene skeleton microspheres. This method started from nanocrystalline superlattice microspheres, combined with carbonization ligand at a low temperature, acid etching to remove superlattice, graphitization at a high temperature, to get three-dimensional ordered mesoporous graphene microspheres (3D-graphene). And then, using this 3D-graphene as a platform, metal oxide (such as tin oxide, germanium oxide, etc.) or sulfur were loaded in the 3D mesoporous pores to construct composite electrode materials with a high capacity. The performance of these composites in lithium-ion battery were studied. We also planed to further studied the influence of microsphere size, pore size, thickness of graphene layers, degree of graphitization, percent of nitrogen atoms doped, to the morphology and the electrochemical properties of the resultant composites. This will be favorable to guide us to optimize the structure of composite materials, develop high-performance electrode materials based on 3D-graphene skeleton.

二维石墨烯层与层之间较强的范德华力导致其在储存、加工和使用过程中容易重新堆叠在一起，从而引起有效比表面积降低，与其他材料难以高效、均匀复合的问题。针对这一问题，本项目提出了一种制备高度有序、三维连续介孔石墨烯骨架微球的新方法。该方法从纳米晶超晶格微球出发，结合低温配体碳化、酸刻蚀超晶格、高温石墨化等一系列过程得到三维有序介孔石墨烯微球。进而以该三维有序介孔石墨烯微球为平台，在三维介孔孔道内负载金属氧化物（如氧化锡、氧化锗等）或硫等构筑高容量复合电极材料，并研究它们在锂离子电池中的应用性能。深入研究三维有序介孔石墨烯微球尺寸、介孔孔径、石墨烯层厚、石墨化程度、氮原子掺杂等对复合材料形貌、电化学性能等的影响，并以此为指导优化复合材料结构，发展高性能基于三维石墨烯骨架结构的电极材料。

通过本项目的研究，我们发展了一种制备有序三维石墨烯骨架微球的新方法。通过对自组装反应条件的调控实现了对超晶格微球形貌的控制，获得了空心和实心两种不同形貌的超晶格微球。进而以该有序三维石墨烯骨架微球为平台，负载了硫和二硫化钼，构筑高容量复合电极材料。介孔石墨烯骨架微球可以高效负载硫，载量>70%，并有效抑制多硫化合物穿梭，也能够实现较快的电子离子传输，S@M-MGCSs-20表现出优异的电化学性能，高的可逆容量（在0.1C时为1122mAh/g），出色的倍率性能（在10和12C时分别为340和300mAh/g），良好的循环稳定性（1C循环300次后，仍有702mAh/g）。MoS2@OMGSs由介孔石墨烯骨架构筑的三维碳网络为材料的电荷传输提供了优秀的介质，提高了MoS2的导电性。同时，三维连通的有序介孔结构提供了足够的空间用于电化学过程中的物料传输和材料的体积膨胀。在作为锂离子电池负极材料时也表现出了高比容量、长循环稳定性和优异的倍率性能。