Fabrication Of Porous Nickel Based On Redox Method And Its Application For Supercapacitors

With the excessive use of traditional fossil fuels and unclean energy,environmental pollution problems are becoming more and more serious.Scientists all over the world are focusing on how to develop an energy that can be recycled without any damage to the environment.As a new type of energy storage device,supercapacitor has high power density and long service life,which has attracted extensive attention from scientists all over the world.Manganese dioxide material is considered to be one of the most promising supercapacitor electrode materials because of its extremely high theoretical energy density(1370 F g^-1)and low cost and environmentally friendly.But the conductivity of manganese dioxide is poor,which limits its application in some aspects requiring rapid charge and discharge.It usually requires a load to form a composite electrode material on the current collector.In this thesis,a three-dimensional porous nickel sheet was prepared by oxidation-reduction approach,which was used as a current collector.Electrochemical-ly deposit of manganese dioxide on porous nickel to form a manganese dioxide/porous nickel composite electrode material.The high-performance supercapacitor electrode materials were explored by adjusting the microscopic pore structure of the current collector porous nickel and the microstructure of the composite electrode.In this thesis,the commercial nickel sheet is firstly treated by gas phase oxidation-reduction method,and the pore structure is effectively regulated by adjusting the oxidation-reduction parameters?mainly time and treatment temperature?.The results show that the porous nickel sheet obtained by oxidation of nickel sheet at 1000°C for 24h in air and 650°C for 10 min in hydrogen has the best comprehensive performance in terms of porous structure,specific surface area and mechanical strength.The MnO₂ active material was electrodeposited on the porous nickel substrate by pulse electrodeposition,and a manganese dioxide/porous nickel sheet composite electrode was constructed.The effect of deposition of different masses of manganese dioxide active material on the specific capacitance of the electrode was studied.The electrochemical performance of the manganese dioxide/porous nickel sheet composite electrode show that:by reasonably optimizing the electrodeposition quality.The mass specific capacitance of the composite electrode material can reach 1305 F g^-1 at a scanning speed of 2 mV s^-1.With the increase of electrodeposited mass,the mass-to-capacitance ratio of manganese dioxide electrode material shows a significant decline.In this thesis,a new method for preparing three-dimensional porous nickel metal with nickel oxide as precursor is proposed,which is a gas phase reduction induction method.Three-dimensional porous nickel is used as a self-supporting electrode in a supercapacitor.Through the research related preparation parameters of the system,we found that the low temperature reduction is beneficial to reduce the size of the pores on the porous nickel and increase the pore density.Finally,by optimizing the relevant parameters,the three-dimensional porous nickel reduced by hydrogen at 400°C for 30min,its area specific capacitance and volume specific capacitance as a self-supporting electrode can reach 4.5 F cm^-2 and 90 F cm^-3 at a scanning speed of 2 mV s^-1.