Preparation And Properties Of Cobalt-carbon-based Porous Nanocomposite Materials

Supercapacitors,also known as electrochemical capacitors,have attracted much attention due to their high power density and long cycle life.As a material for electric double-layer capacitor electrodes in supercapacitors,porous carbon is favored by researchers due to its rich raw materials and excellent cycle performance.However,the low capacitance and low energy density caused by the huge surface area are in urgent need of improvement.Pseudocapacitance electrode materials such as metal oxides and sulfides can make up for the deficiencies of porous carbon materials and effectively increase their energy density,but their inherent poor conductivity greatly reduces the power density of capacitors.Therefore,preparing a composite of two materials is an effective way to improve the overall performance of the capacitor.In this paper,using cobalt nanoparticles generated in situ as a catalyst,monodisperse carbon nanotubes are introduced into the porous carbon system,followed by vulcanization to obtain Co₃S₄pseudocapacitance electrode materials,and high energy density C/CNT/Co₃S₄ nanocomposites are prepared.In the experiment,the high nitrogen content biomass material(black beans)is used as the carbon source,and cobalt chloride is used as the cobalt source.Through high-temperature carbonization,a one-step method is used to obtain nitrogen in-situ doped porous carbon and carbon nanotube composite materials(CNT/C),In which cobalt nanoparticles(?20 nm)generate in situ are the catalysts for carbon nanotubes.Furthermore,L-cysteine(molecular formula)is used as a vulcanizing agent to convert cobalt nanoparticles into cobalt tetrasulfide nanoparticles,thus successfully introducing pseudocapacitors in-situ into the porous carbon system to prepare C/CNT/Co₃S₄nanocomposites.As an electrode material for supercapacitors,the material exhibits extremely high energy density.When combined with self-made activated carbon materials to form an asymmetric capacitor,the power density is 629.9 W kg^-1 and the energy density is as high as 46.4 Wh kg^-1.When the power density increases to 4852.2 W kg^-1(7.7 times),the energy density is still as high as 33.7 Wh kg^-1.In addition,the material has a capacity retention rate of 100%after 5000 cycles at a current density of 5 A g^-1.