Preparation And Study On Supercapacitor Performance Of MOFs-Derived Cobalt Compound/carbon Nanotubes Composites

Supercapacitor is an energy storage device developed in the 1970s and 1980s,which is also called Farad capacitor.In order to actively respond to the dual carbon policy,supercapacitors have attracted the attention of scientists because of their fast charging and discharging rate,safety,high power density and long cycle life in energy storage equipment.At present,the most advanced HSC（Asymmetric Supercapacitor）has the problems of insufficient energy density and poor cycle stability,and the cathode material is the main limiting factor.In order to solve this problem,metal organic framework（MOF）ZIF-67 with high specific surface area,high porosity and structural diversity is selected as precursor,MWCNT with different ratios is added,and Co₃O₄and MWCNT composites（MWCNT@Co₃O₄）are obtained by calcination and oxidation,and then obtained the composite of Co P and MWCNT（MWCNT@Co P）by phosphating.And the electrochemical characteristics of the composites were investigated by using it as the cathode material of supercapacitor.1.The MWCNT_x@ZIF-67 precursor is calcined in one step to obtain diamond dodecahedron structure MWCNT_x@Co₃O₄compound material.The specific capacitance of the MWCNT₃@Co₃O₄composite is 206.89 F/g（much higher than the specific capacitance of Co₃O₄、MWCNT₁@Co₃O₄、MWCNT₂@Co₃O₄and MWCNT₄@Co₃O₄is 129.26 F/g、132.73 F/g、194.64 F/g and 89.36 F/g when the current density is 1 A/g）.In addition,The specific capacitance of MWCNT₃@Co₃O₄//AC asymmetric capacitor reaches 50.0 F/g,which has excellent electrochemical performance.2.The MWCNT_x@Co P is successfully prepared by one-step chemical vapor deposition（CVD）by MWCNT_x@Co₃O₄as the precursor.The experimental results show that the optimum MWCNT addition is 60mg.According to GCD test,the specific capacitance of MWCNT₃@Co P is up to 747.27 F/g when the current density is 1 A/g.In addition,After 1400 charge discharge cycles,the capacity of MWCNT₃@Co P//AC asymmetric supercapacitor still maintains 85.8%of the initial specific capacitance（the current density is 1 A/g）,so it has excellent cycle characteristics.