纳米孔石墨烯/氧化锰复合材料的可控制备及其在高性能锂离子电容器中的应用

Lithium-ion capacitors (LICs) is a new type of advanced energy storage devices, which integrates the advantages of lithium ion batteries and supercapacitors. Design and preparation ofFinding suitable materials is are a key issues in fabricating LICs with high energy density and long cyclic stability, which areis also the hot and difficult problem of the field. As anode materials, manganese oxides have attracted tremendous attentions due to its high specific capacity. However, the drastic volume change during the charge and discharge process, which causes the instability of electrode structure, interfacial and charge transfer, has severely restricted the practical applications of the manganese oxide anodes. Our previous study has confirmed that the graphene wrapping on manganese dioxide nanowires improved the electrochemical performance of the electrode. In this project, an innovative idea is proposed, that is by improving the mass transfer between the graphene layers to improve the performance of electrode material. Starting from the controllable preparation of porous graphene, we will study the formation mechanism of the nanoporous on the graphene sheets prepared by thermal treatment method; clarifying study the impact of the amounts and sizes of porous on the electrical conductivity of the electrode; revealing the mechanism of nanoporous graphene in the composite electrode. The success of this project can effectively settle the problems faced by the anode materials of LICs, and provide theoretical and experimental approaches for the practical applications of the nanoporous graphene/metal oxide composite materials. Meanwhile, the theoretical and practical guidance for the preparation nanoporous graphene and its related applications will be provided as well.

锂离子电容器（LICs）是一种兼具锂离子电池和超级电容器优点的新型储能器件。而电极材料的开发是发展高能量密度和长循环寿命LICs的关键，也是当前研究的热点和难点。作为负极材料，氧化锰材料因具有极高的理论比容量而备受瞩目，但是在充放电过程中其剧烈的体积变化导致电极结构、表界面、电荷传输等的不稳定性，严重制约了其实际应用。申请人在前期研究中，证实了石墨烯包覆二氧化锰纳米线能够提高电极的电化学性能。本项目创新性地提出通过提高石墨烯层间传质来提高电极材料性能的思路，将从多孔石墨烯可控制备的角度出发，阐明热处理法制备纳米孔石墨烯的孔形成机理；研究孔数量与尺寸对电极导电性能的影响；揭示石墨烯的多孔结构在复合材料电极中的作用机制。相信本项目的实施可以有效解决LIC负极目前存在的问题；为多孔石墨烯/金属氧化物复合负极材料的实用化研究提供理论与实验依据；同时对纳米孔石墨烯的制备及相关应用提供理论与实践指导。

石墨烯具有优异的导电性和机械强度，在电化学电容器的电极结构中容易形成良好的导电网络，从而能够大幅提高电极材料在大电流密度下的性能，因此在高性能电化学电容器中具有很好的应用前景。然而，石墨烯是一种致密的二维材料，阻碍了石墨烯片层两侧的物质传递。纳米孔石墨烯是片层具有纳米级孔结构的石墨烯衍生材料，其表面上的多孔结构有助于提高物质传递，从而可以提高其电化学性能。同时，将纳米孔石墨烯与金属氧化物进行复合，制备复合电极材料，既可以一定程度上减少石墨烯的团聚，又可以同时利用双电层电容和法拉第准电容的优势，提高电容器的整体性能。本项目研究了纳米孔石墨烯的可控制备技术，采用H2O2、KOH和混酸（H3PO4/HNO3）处理的方法制备了多孔石墨烯，并研究了不同试剂对最终产物的电化学性能影响规律，最终确定了用混酸处理的方法制备多孔石墨烯。同时，制备了多孔石墨烯/氧化锰复合材料，研究了复合材料作为超级电容器电极材料的电化学性能，探讨了其可能的电化学性能增强机制。在本项目的资助下，还研究了石墨烯/金属硫化物、石墨烯/有机金属框架复合材料的制备方法与电化学性能，为石墨烯基复合材料的制备与应用奠定了实验基础。