Preparation And Electrochemical Properties Of Nickel-based Supercapacitor Materials

As a new type of environmentally friendly and efficient energy storage device,supercapacitors have received special attention from researchers in the field of energy storage.Electrode materials,which largely determine the performance of supercapacitors,have become the focus of research.Nickel hydroxide materials are inexpensive with high specific capacitance and electrochemical activity.However,due to their own structural limitations,they often suffer from poor conductivity and low electrochemical stability.Obtaining nanometer morphology with high specific surface area and doping them with metal ions are two effective methods to improve the conductivity and rate performance of nickel hydroxide electrode materials.In this paper,using the confinement effect of glucose "molecular cage",Co2+/Ni(OH)2 ultrafine nanoparticles with different Co2+content were synthesized in an aqueous solution of glucose.When the Ni/Co molar ratio in the raw material is 5:1,the average particle size of the sample(Denoted as 3Co-Ni(OH)2)was 5-15 nm.The specific capacitance of this sample at current density of 1 A g-1 is 669.57 F g-1,while the specific capacitance of pure Ni(OH)2 at the same current density is only 259.56 F g-1.After 500 charge-discharge cycles,the specific capacitance retention rate reached 94%and the coulombic efficiency remained at 98.1%for 3Co-Ni(OH)2 electrode.Obviously,this sample has excellent cycle stability and redox reversibility.In addition,the mechanism of 3Co-Ni(OH)2 samples showing excellent electrochemical performance was analyzed.The ultrafine particle size increased the specific surface area of the material,allowing the electrode redox reaction to proceed sufficiently.Doping Co2+ improved the charging efficiency and the depth of discharge,thereby improving the specific capacitance and the utilization rate of the active material.In addition,commercial graphene oxide was reduced by chemical reduction method while doped with S and N elements to synthesize sulfur and nitrogen co-doped three-dimensional graphene materials in this paper.On this basis,Ni2+/three-dimensional graphene composites were prepared innovatively by immersion adsorption method.The effects of adsorption time on the electrochemical performance of the composites were studied.After electrochemical tests,the sample with the adsorption time for 16 h had the highest specific capacitance of all,reaching 1053.2 F g-1,and had high cycle stability with the specific capacitance retention rate of 92%after 500 charge and discharge cycles.Ni element in this sample was evenly distributed with the atomic percentage of 20.2%,indicating that it was feasible to synthesize composite materials by immersion adsorption method,which opened up a new idea for the preparation method for composite materials.