面向非对称超级电容器的石墨烯插层钴基双金属氢氧化物复合电极材料的设计及合成

Aqueous asymmetric supercapacitior is a high effective energy-storage device that integrate electric double layer and surface redox charge storage modes, which have many advantages including potentially large operational voltage window, high energy density and low cost. Co-based layered double hydroxide (LDH) has significant application value for asymmetric supercapacitor owing to its similar layered structure with graphene and high redox property. However, similar to many psedocapacitance materials, the poor electrical conductivity of Co-based layered double hydroxid seriously affects its energy storage properties and application. Therefore, we expect to combine the advantages of the good redox property and high sepicific capacitance of Co-based LDH and the large area and high conductivity of RGO, to design the sandwich structure of reduced graphene oxide-intercalated co-based layered double hydroxide Composites through a charge-bearing self-assembly approach using positively charged LDH nanosheets and negatively charged graphene oxide nanosheets as the raw materials. On this basis, asymmetric supercipacitors were constructed with the as-prepared Co-based LDH/RGO electrode material as the positive electrode and carbon-based material as negative electrode to enhance energy density. The project will systematically study the structure-activity relationship between the morphology and microstructure of the electrode and its electrochemical properties, and try to clarify the energy storage mechanism of the electrode material, providing theoretical guidance and practical basis for the development and wide application of electrode materials of asymmetric supercapacitiors.

水系非对称超级电容器是集物理和化学储能于一体的高效储能器件，它具有电压窗口宽、能量密度大和成本低等特点。钴基双金属氢氧化物（LDH）具有与石墨烯类似的层状结构，拥有高的电化学活性，因此其在非对称超级电容器中具重要的应用价值。然而与多数赝电容材料类似，电导性差的缺点严重影响了钴基LDH的储能性能及应用。本课题拟结合钴基LDH高电化学活性和高比容量与石墨烯高电导率和大比表面积的优点，以剥离带正电荷的钴基LDH纳米片为赝电容单元，以带负电的层状氧化石墨烯为微观集流体，在分子水平上进行三维异质组装，形成具有“三明治”结构的石墨烯插层LDH复合电极材料。并将所制材料与炭材料进一步组装非对称电容器，增大电容器的工作电压，进而有效提高其储能密度。本项目将系统研究复合电极材料表面形貌、微观结构与电化学特性之间的构效关系，努力阐明储能机制，为非对称超级电容器电极材料的开发与应用推广提供理论和实践基础

商业化超级电容器偏低的能量密度极大地限制了其更为广泛的应用。而如何在保持超级电容器高功率密度的同时提高其能量密度是亟待突破的关键问题。非对称超级电容器是对称式电容器的一种改进，一极使用电化学反应来储存和转化能量，另一极则通过双电层来储存能量，由于两种电极材料在同一种电解液中发生可逆循环时对应的电化学电势范围不同，通过组合可以有效地提高整个电容器的工作电压。可见，电极材料结构、成分和电化学性能的调控和优化对高性能非对称电容器的发展是非常关键的。在本项目中，探索了不同插层阴离子对钴基氢氧化物纳米片稳定性的影响；考察剥离条件（分散液浓度、膨润时间、超声时间及功率）对钴基氢氧化物纳米片结构、形貌以及剥离效果的影响，最终实现硝酸根插层钴基氢氧化物在水中的有效剥离。利用剥离得到的带电荷的纳米片作为组装单元构建了周期性堆叠的超晶格材料。本研究中进一步关注合成方法－材料结构－电化学性能三者的相互关系，阐明其中的材料科学问题，最终为电化学储能技术发展更高效的材料方案。