Preparation Of Porous Nickel Film By Electrodeposition And Its Application For Supercapacitors

With the change of lifestyle,the demand for energy,which is a mainstay of people's lives,is growing daily.New renewable energy can relax the energy crises and high-performance energy storage devices are the key to the utilization of these energy.Supercapacitor has high power density and good cycle stability,but the low energy density limits its application in energy storage.Electrode is the core component of the supercapacitors.Electrode is mainly composed of current collectors and active materials.One of the main ways to improve the performance of supercapacitors is to prepare high-performance current collector.Nickel foam is widely used due to its low cost,high specific surface and corrosion resistance.However,the pore of the nickel foam is large and the utilization efficiency of the volume is low.Furthermore,nikel foam can not be applied to flexible devices.This thesis aims at preparing the porous nickel thin films by electrodeposition using templates.The application of the porous nikel films as the current collectors for supercapacitors is investigated.The main work and results are as follows:Metal templates with insulating arrays were prepared by laser drilling and subsequent pore filling with insulating material.The effects of laser drilling and pore-filling process on the preparation of templates were investigated.The results indicate that the stainless steel with thickness of 0.15 mm works best.The smallest pore diameter and distance between two adjacent pores are 20 ?m and 50 ?m,respectively,for obtaining uinform and flat templates.In order to make the pore rounder and the surface smoother,electrochemical polishing was applied on the drilled stainless templates.In order to make insulating arrays,insulating ink was filled into the pores.Porous nickel films were prepared by electrodepositing of nickel on the templates.It is indicated that peeling can be prevented when the current density is less than 0.16mA/cm2.Pinholes decrease when the pH value is kept between 3-4.Sufficient stirring of the electrodeposition bath favors the uniform deposition of the nickel films.MnO₂ films were deposited on the porous nickel films.The effects of the nickel film structure and electrodeposition parameters on the electrochemical properties of the MnO₂ films were investigated.The results indicated that interfacial strength between MnO₂ and nickel film substrates can be improved due to the surface roughness increase of nickel films arising from the porous stucture.Nickel films with small pores?20 ?m in diameter?have better performance than that without pores,which is because the nickel films with small pores possess higher surface area,increasing the utilization efficiency of the MnO₂.Compared to these prepared by galvanostatic electrodeposition,the MnO₂ films prepared by potentiostatic deposition are loose and have better performance.When the voltage is 0.5 V,the MnO₂ possesses nanosheet structure,which possesses the best performance.With increasing deposition time,the electrodes prepared by the two deposition methods show the same changing tendency that mass specific capacitance decreases and area specific capacitance increases.