异质复合多壳层结构金属氧化物超级电容器材料的创制及规律研究

Supercapaictors(SCs)or Electrochemical capacitors(ECs) have gained enoumous attention due to their higher power density and longer cycle life.Metal oxides as electrode materials exhibit much higher specific capacitance and better electrochemical stability. Facing the questions of the current electrode materials, transtition-metal oxides with multi-shelled heterostructure composed of nanoparticles are designed in this case.Electrochemical activity could be improved by these nanoparticles and the available specific surface, and the volume change and stress during discharge-charge process could be buffered and the tranfer rate of electrylote ions could be accelerated due to the hollow structue. Importantly, the structure could be mainteined by the different shells,thereby the stability cycle and life-span could be enhanced.Moreover,different component can bridge the performance gap between these materials and the high energy density could be gained as well as the high power density.Here, electrode materials of SCs will obtained with high specific capacitance and long spanlife. The relationship of structure, design and properties will be discussed. During the synthesis process, all factors affecting the structures and components (including the structure of the spheres, the thickness and component of the shells, pore structure and so on) will be controlled as much as possible. In order to raise the electron conductivity of materials, the preparation and properties of the oxides/cabon nanocomposite will be studied. The charge storage mechanism during the charge-discharge process will be carried out.

本项目针对超级电容器电极材料存在的问题，从提高活性位点的有效利用和结构稳定的原则出发，以功能为导向进行结构和组成设计，采用模板法和表面调控技术相结合，实现异质多壳层结构金属氧化物(如MnO2-SnO2\Co2O3、NiO-Co2O3等)电极材料的可控合成，研究结构和组成对电容器性能的增强作用，实现最优电极材料的创制。通过多壳层结构，提高电极材料的有效比表面积和单位体积的有效活性位点，实现比容量、功率密度的最大化；利用不同壳层彼此支撑，保持材料结构的稳定，提高其循环寿命；通过不同金属氧化物的合理组合，充分发挥材料的协同效应，在保持功率密度的前提下提高材料的能量密度；通过中空结构，促进电解液离子在界面的传输能力；系统研究多壳层电极材料/电解质界面上电荷存储机理及关键影响因素，从而开发出一种兼具功率密度和能量密度、能够快速充放电、结构稳定、循环寿命好的超级电容器电极材料，为同类研究奠定基础。

在结构和组成设计的基础上，基于次序模板法，结合外场调控和表面技术，实现了异质多壳层结构金属氧化物电极材料的可控合成，成功制备了中空多壳层结构的(Co2/3Mn1/3)(Co5/6Mn1/6)2O4及多种组成和结构的CoxMnyO4二元金属氧化物、内外异质的TiO2-CuxO多壳层结构、多壳层Fe 2TiO5/TiO2复合空心球等多种异质中空多壳层结构金属氧化物及其复合材料。通过对碳球模板表面基团研究，明确了阴离子竞争吸附机制，拓展了中空多壳层结构的合成方法。将中空多壳层结构作为电极材料应用，表现出优异的电化学性能，例如，四壳层MnO2空心球在电流密度为0.5 A/g时，可逆容量达到1457 F/g，5A/g大电流密度下，连续循环4000次后容量保持率依然可以高达91.2%；七壳层结构(Co2/3Mn1/3)(Co5/6Mn1/6)2O4在三电极体系1 A/g电流密度下，可逆容量高达1891F/g，与活性炭构成非对称体系，在0.5 A/g电流密度下比容量达到106.85 mAh/g，当电流密度为4 A/g时，仍然能够保持62.67 mAh/g的比容量，在电流密度为1 A/g下展现了良好的循环寿命，循环3000次，仍然能够保持84.17%的初始容量。系统研究了结构和组成对超级电容器性能的增强作用，深入探究了多壳层电极材料/电解质界面上电荷存储机理及关键影响因素，基本建立了材料结构与性能之间的规律性关系，研究成果表明：通过构筑中空多壳层结构，能够有效缓冲充放电过程中的材料体积变化和应力应变，保持结构和性能的稳定；多壳层结构增加了材料有效的比表面积，能够提高材料的反应活性，大大提高比容量；通过多壳层中空结构和壳层上的孔道，能够有效促进物质的传输，显著提高了倍率性能，而且，不同组分的复合和异质实现了性质互补，大力推动了功率密度和能量密度大、能够快速充放电、结构稳定、循环寿命好的超级电容器电极材料的开发和研制。