| Supercapacitors as a new type of energy storage devices have the advantages of high energy density, high coulombic efficiency and long cycle life. Ni(OH)2 and NiO have been studied as electrode materials for supercapacitors, because of their excellent electrochemical properties, abundant resource and low price.Ni(OH)2 was prepared by hydrothermal method, and the effects of different preparation conditions on capacitor properties of Ni(OH)2 were investigated by cyclic voltammetry,constant-current charge-discharge and electrochemical impedance spectrum. When raw material is NiSO4·6H2O, pH is 12, hydrothermal reaction temperature is 180℃and the reaction lasts out for 12 h, the maximum specific capacitance is 303.7 F·g-1, the reaction resistance is 0.1Ω.NiO was prepared by several different methods and the effects of different preparation conditions on capacitor properties of NiO were studied. NiO prepared by direct depositing method exhibits good supercapacitor properties, when the precursor was prepared at pH of 11～12, depositing at 30℃, and intensively milling the mixed solution for 3 h, the specific capacitance of the resulting NiO reached 346.0 F·g-1 at 3 mA·cm-2, the reaction resistance is 0.24Ω, the resistance related to conductivity of the electrode and electrolyte is 0.085Ω, and NiO have a long cycle life. NiO prepared by precipitation -transformation method has the highest specific capacitance of 383.8 F·g-1 when the precursor was prepared under the following conditions: with 20 mL/L surfactant, the temperature of precipitation -transformation is 70℃. The reaction resistance of NiO obtained is 0.25Ω, the resistance related to conductivity of the electrode and electrolyte is 0.21Ω, and it exhibits steady cycling performance after numbers of cycles. NiO was prepared by hydrothermal-transformation method and its electrochemical properties were investigated. The results indicated that the optimal pH is 9 and hydrothermal reaction temperature is 240℃. The highest specific capacitance of NiO prepared at the optimal conditions is 517.6 F·g-1, the reaction resistance is 0.45Ωand the resistance related to conductivity of the electrode and electrolyte is 0.39Ω. The specific capacitance of NiO prepared by sol-gel method is 199.3 F·g-1 and the specific capacitance of NiO prepared by coordinated precipitation method is 117.8 F·g-1.NiO was prepared by solid state grinding method under the following conditions, the proportion of Ni(Ac)2·4H2O and NaOH is 1: 2, calcining temperature is 300℃. The resulting NiO shows a specific capacitance of 258.6 F·g-1, the reaction resistance is 0.25Ωand the resistance related to conductivity of the electrode and electrolyte is 0.21Ω.
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