Ni-Y层状双氢氧化物/石墨烯纳米复合材料3D结构的构筑设计及电化学机理研究

Haze phenomenon is becoming more and more serious in some cities in China. Therefore, the development of electric vehicles is an important strategic measure to effectively deal with the challenges of energy and environment. The popularization of pure electric vehicles demands to greatly improve the energy density of nickel-metal hydride batteries, and the development of high-capacity, high-activity nickel hydroxide cathode materials has become a key issue for high-specific energy storage devices with significant commercial and scientific value. α-Ni(OH)2 is considered to be a very promising electrode active material due to its high discharge potential, flat discharge platform, high electrochemical activity, and insusceptible expansion of the electrode, but in the strong alkaline solution of poor stability and low bulk density has become a bottleneck restricting their practical application. In this project, one-step hydrothermal method and microwave-assisted method are used to replace part of the nickel ions with high-valence metal cations Y3+ to form layered double hydroxides. Anisotropic nanosheets are stacked and aggregated to form α-Ni(OH)2 with a flower-like structure. And then which is combined with graphene to form a three-dimensional composite electrode material with high conductivity and high structural stability. Also the construction and assembly can be finished in one step by in situ synthesis.. The mechanism of rare earth doping is clarified to provide a reference for the design, development and practical application of high bulk density and high activity nickel hydroxide electrode active materials.

中国部分城市雾霾现象越来越严重，大力发展电动汽车是有效应对能源与环境挑战的重要战略举措。纯电动汽车的普及需要大幅度提升镍氢电池的能量密度，开发高容量、高活性氢氧化镍正极材料，已成为具有重大商业和科学价值的高比能储能器件的关键问题。α-Ni(OH)2因其具有高的放电电位、平坦的放电平台、高的电化学活性以及电极不易膨胀等优点被认为是一种非常有前景的电极活性材料，但其在强碱性溶液中稳定性差且堆积密度低等问题已成为制约其实际应用的瓶颈。本课题以一步水热法和微波辅助法通过高价金属阳离子Y3+取代部分镍离子形成层状双氢氧化物，生成各向异性的纳米片相互堆叠聚集组装成具有花状结构的α-Ni(OH)2后与石墨烯复合形成高导电性高结构稳定性三维复合电极材料。通过原位合成，实现结构构建和组装一步进行。阐明稀土元素掺杂作用机制，以期为高堆积密度、高活性氢氧化镍电极活性材料的设计开发和实际应用提供参考。

基于稀土元素钇可以改善电极材料的固有导电性，设计了镍钇双金属氢氧化物/石墨烯复合材料。最佳Y(OH)3（Y3+/Ni2+的摩尔比为10%）含量下，1 A g-1的电流密度时比电容达到了1876 F g-1，远高于未加入Y(OH)3的256 F g-1。经过2000圈循环后，其容量保持率为71.32%。将钇作为掺杂剂，在最佳掺杂量(Y3+/Ni2+摩尔比为10%)下合成的Y-Ni(OH)2材料在电流密度为1.5 A/g下获得的最佳比容量为735.46 C g-1，远高于未掺杂样品的279.7 C g-1。经过3000个循环后，显示出良好的电化学稳定性，其容量保持率为80.39%。Y的引进加速了电极体系内部的反应动力学并提高了电荷转移效率。.通过简单的水热法分别制得丝绒状的MWCNTs-GONRs/Ni(OH)2电极、纳米针阵列的MWCNTs-GONRs/Co3O4电极和松树状核壳阵列结构的MWCNTs-GONRs/Co3O4/Ni(OH)2电极。在1 A g-1时比电容分别为1713.2、846.2和2654.7 F g-1。组装器件后分别具有41.23、38.23和74.85 Wh kg-1的最大能量密度及在大电流密度下的高循环稳定性。.通过选取不同的组氨酸功能化碳材料并采用微波法一步合成了花球状His-GQD/ Co-Ni LDH和His-MW/Co-Ni LDH复合材料。组氨酸功能化碳材料和LDH的协同作用可以有效增加复合材料的比表面积和电导率，从而赋予His-GQD/LDH和His-MW/LDH高的比电容（1 A g-1时分别具有1526和1674 F g-1）和循环稳定性（82.36％和83.33％的电容保持率）。而组装成器件后分别具有48.89和39.47 W h kg-1的最大能量密度，在10 A g-1的大电流下历经6000次循环后器件的电容保持率未曾有较大损耗，仍能保持90％以上。