Preparation And Electrochemical Capacitive Performance Of Co₃O₄ And Its Composites

As a new type of electrochemical energy storage device, supercapacitors have the capacities to be charged and discharged rapidly, and perform high power output, wide range of operating temperatures and ultralong cycle lifetime. It is important to develop electrode materials with high performance to improve the energy desity of supercapacitors. In recent years, some transition metal oxides and their binary materials, such as Co₃O₄, Ni Co₂O₄, Mn O2, have attracted intensive attention owing to their low-cost, easy-to-get, simple and controllable method, high specific capacitance and excellent stability. In this paper, the preparation, morphology structure and electrochemical properties of Co 3O4 and its composite electrode materials would be studied.?1? By changing the fill fraction, Co₃O₄ of the same phase and different morphologies were prepared by thydrothermal-pyrolysis mothod with six water cobalt nitrate as the raw material, urea as the precipitator, Scanning electron microscopy?SEM? analysis showed that Co₃O₄ of 70% filling fraction were uniform and regular nanoclusters. The electrochemical performances of Co₃O₄ under different filling fractions indicated Co₃O₄ of 70% filling fraction exhibited a high capacitance of 961 F/g at 1 A/g of the current density and the capacitance retention rate was 76% when the current density was up to 20 A/g. The capacitance loss rate is only 10% after 500 cycles. Ac impedance results revealed that Co₃O₄ electrode of 70% filling fraction owned small charge transfer resistance and outstanding supercapacitor impedance characteristics.?2?Co₂O₄/Co₃O₄ composite materials were prepared through the green environmental electrochemical deposition while Co₃O₄/nickel foam and Co₃O₄/carbon fiber were used as the substrate materials, respectively. SEM images indicated that an uniform nanoscale flake structures could be presented on both of the Nickel foam and carbon fiber substrate materials. And this structure made the nickel cobalt acid possessed large specific surface area and fast electron ion transfer rate. The electrochemical tests showed that electrodes based on the carbon fiber had faster transfer rate between ion and electron,,shorter diffusion path and stronger electrochemical activity of Ni Co 2O4 than that on the nickel foam. The charging and discharging test showed that the discharging time of electrode based on the carbon fiber was obviously longer than that on the nickel foam. The capacitance response value of Ni Co₂O₄/Co₃O₄/carbon fiber electrode was high up to 1880 F/g at 1 A/g. AC impedance indicated that the Ni Co₂O₄/Co₃O₄/carbon fiber composite materials had the smallest resistance.