Ni-Based Electrode Material Prepared By Electrodeposition And Its Application In Supercapacitor

As an efficient electrochemical energy storage device,supercapacitors are widely used in the fields of renewable energy and assist with mobile energy storage due to their advantages of fast charging and discharging speed,long cycle life,and environmentally friendly.Electrode materials are the key point to determining the capacitive performance of supercapacitors.Among various transition metal electrode materials,Ni is cheap,easy to obtain,and has low toxicity.Ni-based electrode materials have always attracted a lot of attention due to their high theoretical capacity.However,single-metal Ni-based compounds have disadvantages such as low electrical conductivity and few active sites,which make the actual discharge capacity much lower than the theoretical value.So carbon material modification,metal element doping modification,and heat treatment modification are commonly used for overcome its shortcomings.The main contents of the research are as follows:(1)NiCo-LDH electrode material was prepared by the electrodeposition method.The effects of raw material types,deposition current density,frequency and duty cycle on the properties of the obtained electrode materials were investigated respectively.The results showed that the best preparation conditions were as follows: using nickel nitrate and cobalt nitrate as the nickel source and cobalt source,the deposition current density is 20 m A/cm2,the frequency is 30 Hz,and the duty cycle is 90%.The NiCo-LDH electrode materials prepared under these conditions formed two morphological structures: one is a flocculent formed by agglomeration of fold-like structures,and the other is a sheet-like structure.These two structures are intertwined to form a network structure.When the samples are at 1,4,7,and 10 A/g,their discharge capacitances can reach 1480,1401,1337,and 1283 F/g,respectively.(2)Preparation and properties of NiCo-LDH/C composites.Two carbon materials,graphene and carbon nanotubes,were used for modification: the effects of graphene concentration,carbon nanotube treatment,and carbon nanotube concentration on the performance of electrode materials were researched by a single-factor variable method.The preparation conditions are as follows:carbon nanotubes are pretreated with concentrated hydrochloric acid,and the concentration of carbon nanotubes is 0.3 mg/m L.The electrode materials prepared under these conditions exhibited two morphologies,flocculent and sheet-like structures formed by agglomeration of wrinkled structures,and two structures were intertwined to form a 3D network structure.When the samples are at 1,4,7,and 10 A/g,the specific capacitance can reach 1481,1371,1284,and 1213 F/g,respectively.(3)Preparation and properties of NiCo Zn-LDH electrode materials.The NiCo Zn-LDH electrode material was directly prepared on the foamed nickel substrate by electrodeposition method,and the influence of the type of raw material and its ratio on the capacitance performance of the obtained electrode material was studied.The results show that the best preparation conditions are: sulfate as raw material,Zn:Ni:Co=0.3:1:1.The electrode material prepared under this condition exhibits a granular structure composed of interlaced sheet-like structures.Electrochemical test results show that the specific capacitances of NiCo Zn-LDH composites at 1,4,7,and 10 A/g are 1992,1585,1416,and 1259 F/g,respectively.At a current density of 4 A/g,the specific capacitance of the sample material is 459 F/g after 2000 charge-discharge cycles,which is28.9% of the initial capacitance.(4)In order to further improve the cycling stability of the material,the NiCo-LDH material was modified by heat treatment.The effects of heat treatment temperature and time on the properties of electrode materials were tested by the single-factor variable method.The results show that the best heat treatment conditions are: heat temperature is 400 ?,heat time is 3 h.The electrode material prepared under this condition exhibits a bark-like structure with interlaced ravines,and 3D porous structures of different sizes are distributed on the bark-like structure.The specific capacitances of the samples at 1,4,7,and 10 A/g can reach 1151,987,936,and 908 F/g,respectively.Under the condition of 7 A/g,the NiCo2O4 sample material obtained by heat treatment at 400 ? for 3 h was tested by GCD.After 5000 charge-discharge cycles,its specific capacitance was 854 F/g,which was 91.2% of the initial capacitance.