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類松果狀NiMoO4/MnO2復合材料的合成及超級電容性能

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

  • 摘要: 以Na2MoO4·2H2O、NiSO4·6H2O和MnO2為原料, 采用水熱法成功制備了類松果狀NiMoO4/MnO2復合材料.通過X射線衍射、掃描電子顯微鏡、恒電流充放電、循環伏安和交流阻抗對材料進行表征.結果表明, MnO2的最佳質量分數為10%, 所得NiMoO4/MnO2復合材料具有類松果狀形貌, 其顆粒直徑為200~600 nm, 且表面粗糙、多孔; 在1 A·g-1的電流密度下, MnO2質量分數為0、5%、10%、15%、20%時, 所得復合材料NM0、NM5、NM10、NM15和NM20的放電比電容分別為260、248、650、420和305 F·g-1.在電流密度為10 A·g-1下, 最佳樣品NM10復合材料的首次放電比容量為102 F·g-1, 經過100次循環后, 其放電比電容穩定在147 F·g-1.該性能的提高, 主要是由于MnO2的引入彌補了NiMoO4單一材料存在的不足, 從而達到協同增效的作用.

     

    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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