Preparation Of NiCo₂S₄ And Porous Carbon Electrode Materials For Asymmetric Supercapacitors

The precipitous decline of non-renewable energy reserves and the unstable characteristics of new energy urge researchers to develop new energy storage devices for new energy storage.Compared with traditional energy storage devices,supercapacitors have attracted wide attention in the field of energy storage because of their advantages such as high power density,long cycle life and fast charging and discharging.Compared with chemical power sources such as lithium-ion batteries,ultracapacitors have a lower energy density.According to the energy density calculation formula E=CV²/2,increasing the specific capacitance of electrode material and widening the voltage window of capacitor are the key to increase the energy density.In this paper,porous carbon materials were prepared by self-template method,bimetallic sulfide was prepared by two-step hydrothermal method,and the materials were characterized and electrochemical test,and the two materials were assembled into asymmetric supercapacitors to study their electrochemical performance.Zinc phytate was synthesized from phytic acid and zinc acetate and used as self template and carbon source to prepare porous carbon for supercapacitors.Nitrogen adsorption analysis showed that the prepared carbon materials had a multi-stage pore structure,with pore size concentrated in 1～10 nm and specific surface area of 1125 m² g^-1.In addition,the introduction of KOH in the phytate preparation process can effectively regulate the porous structure of the prepared carbon material,and significantly increase the content of micropores.The material characterization analysis of carbon precursors showed that there was no KOH in the precursors,K and Zn were uniformly distributed in the form of bimetallic phytates,and the increase in the content of porous carbon was due to in situ K activation rather than KOH activation.The electrochemical test of the system shows that the supercapacitor performance is significantly improved with the increase of micropore content of carbon material:the porous carbon specific capacitance increases from 195 to294 F g^-1 in KOH electrolyte and from 187 to 247 F g^-1 in H₂SO₄ electrolyte.Nickel-cobalt bimetallic sulfides（NCS）were prepared by a two-step hydrothermal method using nickel salts and cobalt salts containing different anionic groups as raw materials,and the obtained materials were characterized and electrochemical tested.The morphologies of Ni-Co bimetallic sulfide synthesized from different anionic materials can be obtained by characterization.Tests show that NCS-C with perfect sea urchin-like morphology has excellent electrochemical performance.NCS nanonuclides are tightly anchored in sea urchin-like shape,with abundant redox active sites and excellent electrochemical performance,and the specific capacitance can reach 1112 F g^-1 when the current density is 6 A g^-1.Based on the experiment of the first item,carbon source was added to improve the yield of carbon materials,porous carbon was prepared and NCS-C was used as the positive electrode,and the material after carbon source was added（PC-K4-DH）was used as the negative electrode to assemble an asymmetric supercapacitor,and its electrochemical performance was tested.The suitable voltage window of the asymmetric supercapacitor is tested and the energy and power density of the asymmetric supercapacitor are measured under the 1.6 V voltage window.When the power density is 400 W kg^-1,the energy density can reach 23.4 Wh kg^-1.