类松果状NiMoO4/MnO2复合材料的合成及超级电容性能

Preparation and supercapacitive performance of pinecone-like NiMoO4/MnO2 composite material

  • 摘要: 以Na2MoO4·2H2O、NiSO4·6H2O和MnO2为原料, 采用水热法成功制备了类松果状NiMoO4/MnO2复合材料.通过X射线衍射、扫描电子显微镜、恒电流充放电、循环伏安和交流阻抗对材料进行表征.结果表明, MnO2的最佳质量分数为10%, 所得NiMoO4/MnO2复合材料具有类松果状形貌, 其颗粒直径为200~600 nm, 且表面粗糙、多孔; 在1 A·g-1的电流密度下, MnO2质量分数为0、5%、10%、15%、20%时, 所得复合材料NM0、NM5、NM10、NM15和NM20的放电比电容分别为260、248、650、420和305 F·g-1.在电流密度为10 A·g-1下, 最佳样品NM10复合材料的首次放电比容量为102 F·g-1, 经过100次循环后, 其放电比电容稳定在147 F·g-1.该性能的提高, 主要是由于MnO2的引入弥补了NiMoO4单一材料存在的不足, 从而达到协同增效的作用.

     

    Abstract: Supercapacitors, also called electrochemical capacitors or ultracapacitors, have attracted increasing attention owing to their high specific capacitance, high power density, long lifecycle, fast charge-discharge ability, wide working temperature range, and environmental friendliness for mobile electronics, power grids, and hybrid electric vehicles. The electrode is the most important part of supercapacitors; therefore, the electrode material is the chief factor that determines the properties of supercapacitors. To enhance the performance of a supercapacitor, particularly its specific energy while retaining its intrinsic high specific power, several researchers have focused mainly on improving the properties of electrode materials. The major classes of materials applied for supercapacitors include various forms of carbon, transition metal oxides, and conductive polymers. Compared to the carbon materials and conducting polymer materials, transition metal oxides can achieve a much higher specific capacitance because of their high theoretical capacitance, well-defined electrochemical redox activity, low cost, and abundant resources. In particular, binary metal oxides, such as NiMoO4, MnMoO4, and CoMoO4, have been extensively studied as pseudocapacitor electrode materials because of their good electronic conductivity and rich redox reactions. In this study, pinecone-like NiMoO4/MnO2 composite materials were successfully synthesized using a facile hydrothermal method. Na2MoO4·2H2O, NiSO4·6H2O, and MnO2 were used as raw materials. The as-products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results show that when the optimal content of MnO2 reaches 10%, the obtained NiMoO4/MnO2 composite materials exhibits a pinecone-like porous morphology, with the particle size ranging from 200 to 600 nm. The results show that NiMoO4/MnO2 composite materials have excellent electrochemical properties. The discharge specific capacitance of NM0, NM5, NM10, NM15, and NM20 composites with corresponding MnO2 contents of 0%, 5%, 10%, 15%, and 20% are 260, 248, 650, 420, and 305 F·g-1, respectively, at a current density of 1 A·g-1. When the current density is up to 10 A·g-1, the initial discharge specific capacitance is 102 F·g-1. After 100-week cycles, the discharge specific capacitance of the NM10 sample is still 147 F·g-1. The improvements can be mainly attributed to the introduction of MnO2 in the NiMoO4/MnO2 composite materials to overcome the shortcomings of single NiMoO4.

     

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