The Preparation, Activation And Supercapacitance Of Cobalt Compounds

The supercapacitor, also known as the electrochemical capacitor, is a kind of new energy storage device by the insertion and extraction (adsorption and desorption) of electrolyte ions in the electrode material surfaces, with high power density, long cycle life. As a kind of active materials of supercapacitor, cobalt compounds have attached more and more attention for its high theoretical capacity, easy preparation and high electrochemical stability.In this paper, we introduce the history and status of the supercapacitor. Then, the beta-Co(OH)2 and Co3O4 hollow microspheres grown with nanosheets on the surface have been synthesized as supercapacitor electrode materials. The electrodes exhibited high specific capacitance of 781.5F/g and 755F/g at lA/g, when we run them at 10A/g,the electrodes still have 460F/g and 431F/g , and after 5000 cycles, the capacitance of these two electrode both only decreased about 5%. The result showing the high electrochemical stability of beta-Co(OH)2 and Co3O4,and the hollow microsphere grown with nanosheets is a very suitable nano structure as supercapacitors.On the basis of above, a new method without changing the microstructure was proposed for improving the performances of Co3O4 electrodes by heating dihydrogen phosphate under it, in this paper. At the current density of 1 A/g, it exhibited high specific capacitance of 1250F/g, which has increased by 65.56%, and still keep 68% of the maximum specific capacitance at a current density of 30A/g, after 5000 cycles, the specific capacitance did not decline, showed high stability. In addition, the reaction mechanism of the activation process was proposed based on the chemical properties of the related materials.