Fabrication And Modification Of Three-dimensional Porous Nickel And Its Performance As Composite Electrodes

As a rapid development type of energy storage device in the field of new energy,supercapacitor has long service life,outstanding charge-discharge ability and excellent temperature adaptability meanwhile its power density is much higher than traditional batteries.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),low cost and environmentally friendly.But the conductivity of manganese dioxide is poor,which limits its application.It usually requires a load to form a composite electrode in the current collector.However,as the main current collector,commercial Ni foam still has some problems,such as larger pore size,small specific surface area,and the smooth surface of the ligament,which is not suitable for the attachment of active materials.Based on hereinbefore problems,a three-dimensional porous structure was prepared on the smooth skeleton of commercial Ni foam by oxidation-reduction approach,and then a self-combustion method was used to make a new current collector with three-dimensional porous structure in this thesis.The microporous structures were explored and regulated by adjusting the experimental conditions,and the prepared porous current collector was applied to create the high performance composite electrode of supercapacitor.For the problem of smooth surface on ligament,the commercial Ni foam is firstly treated by high temperature oxidation-reduction method in this thesis,and the pore structure is effectively regulated by systematically adjusting the oxidation-reduction parameters?time and treatment temperature?.The results show that the porous Ni foam obtained by oxidation of Ni foam at 750°C for 36 h in air and 650°C for 10 min in hydrogen has the best comprehensive performance in terms of porous structure.The Mn O₂ active material was electrodeposited on the porous Ni substrate by anodic electrodeposition.The mass specific capacitance of the composite electrode material can reach 1108 F g^-1 at a scanning speed of 2 m V s^-1.For the problem of larger pore size of the commercial Ni foam,a self-combustion method for preparing three-dimensional porous Ni metal as precursor is proposed in this thesis.The microporous structure is regulated by changing the proportion of reagent and pore former.The results show when the molar ratio of Ni?NO?₃ to C₃H₈O₂ is 1:5 and without pore former,the porous Ni has the best comprehensive porous structure.Three-dimensional porous Ni was used as a composite electrode through electrodepositing Mn O₂ active material by pulse electrodeposition.Finally,the area specific capacitance of the manganese dioxide/porous Ni composite electrode can reach 0.12 F/cm^-2 at a scanning speed of2 m V s^-1,which is 2.5 times than the area specific capacitance of the manganese dioxide/Ni foam composite electrode(0.048 F/cm^-2).With the increase of electrodeposited mass,the mass-to-capacitance ratio of manganese dioxide electrode material shows a significant decline.