Application Of Transition Metal Borate/selenide Electrode Materials In Supercapacitor Fiel

Excessive exploitation and utilization of coal,oil,natural gas and other non-renewable resources have led to the depletion of resources and the worsening of environmental pollution.Human beings pay more and more attention to the development of new renewable energy such as wind energy,water energy and solar energy,thus increasing the demand for energy storage equipments that can store and convert energy.Therefore,it is urgent to develop supercapacitors with high power density and long cycle life.The rational development of electrode materials is the key to the excellent performance of supercapacitors,so it is very important to explore and prepare excellent electrode material.In this thesis,Ni₃（BO₃）₂ nanospheres were prepared by simple electrochemical deposition on titanium mesh（Ti）.In addition,in order to further improve the energy density of asymmetric supercapacitor devices,Mn Se₂@Ni Co₂Se₄heterogeneous structure materials were prepared on nickel foam（NF）by a two-step hydrothermal method.The details are as follows:1.Nickel borate has an important prospect in electrochemical catalytic applications,but its energy storage performance in supercapacitors is rarely reported.Ni₃（BO₃）₂ nanospheres（NSs）were prepared on Ti by a simple and scalable electrodeposition technique,and Ni₃（BO₃）₂NSs@Ti was obtained.With the help of modern characterization methods and electrochemical tests,Ni₃（BO₃）₂NSs@Ti was studied in detail as electrode materials for supercapacitors.Among them,Ni₃（BO₃）₂NSs@Ti-1.2V obtained by electrodeposition at 1.2 V for 24h shows a mass capacitance of 663 F g^-1 at the current density of 0.5 A g^-1,because of its uniform morphology distribution.In addition,all solid state asymmetric supercapacitors（ASC）prepared with Ni₃（BO₃）₂NSs@Ti-1.2V as positive electrode and activated carbon material（AC）as negative electrode show an energy density of 30.6 W h kg^-1 and a power density of 400 W kg^-1.In addition,three of the ASC devices are connected in series to light a small bulb.Therefore,Ni₃（BO₃）₂NSs,which is easy to be electrodeposited,has practical application voltage in the field of energy storage.2.Mn Se₂@Ni Co₂Se₄ heterogeneous structural materials consisting of Ni Co₂Se₄nanosheets and Mn Se₂ nanorods were uniformly generated on NF substrate by a two-step hydrothermal process.By adjusting the supply of selenium in the process of selenization,the microstructure of samples was characterized and the formation mechanism of Mn Se₂@Ni Co₂Se₄ heterogeneous structure was studied.The three-electrode system of the electrochemical workstation was tested to analyze its electrochemical performance.The results show that Mn Se₂@Ni Co₂Se₄-2 electrode has remarkable electrochemical performance,at a current density of 1 A g^-1,its specific capacitance is 1078 C g^-1.In addition,Mn Se₂@Ni Co₂Se₄-2 also shows excellent cyclic stability.At the same time,Mn Se₂@Ni Co₂Se₄-2 and AC are used as positive and negative electrodes respectively to develop ASC devices with power density of 396 W kg^-1 and energy density of 63.2 W h kg^-1,which makes Mn Se₂@Ni Co₂Se₄ material have broad voltage in the field of supercapacitors.