Preparation Of Cobalt-based Compound Electrode Materials And Supercapacitor Performance

Supercapacitors have fast charge/discharge rates,ultra-long cycle stability,and high specific power characteristics,so people have begun to use them as energy storage devices to replace batteries.Carbon-based supercapacitors have excellent stability,but their specific capacity is low;transition metal oxide-based supercapacitors mainly provide pseudocapacitance through the Faradaic reaction,but they cannot be widely used due to the poor conductivity of oxide materials.In this paper,the highly conductive material MXene or carbon material is selected as the substrate,and the transition metal oxide or hydroxide is used as the load material.It is hoped that high specific capacitance can be obtained while improving the stability.Electrode materials with excellent properties,the specific work is as follows:（1）Accordion-like structure V₂CT_x-MXene was obtained by etching the bulk V₂AlC-MAX in an acidic solution,and the V₂CT_x-MXene was compounded with NiCoFe-LDH by a hydrothermal method,and a microstructure with a three-dimensional interconnected porous network was successfully prepared.The NiCoFe-LDH/V₂CT_x-MXene heterostructure with a specific capacitance of 1305 F g^-1 at 1 A g^-1 was used as the positive electrode and activated carbon as the negative electrode to fabricate an asymmetric supercapacitor,which showed Excellent electrochemical performance.In this work,not only nickel and cobalt metals are selected,but also cheap iron metals are selected as components.With the help of the growth platform and excellent conductivity provided by MXene materials,the specific capacitance advantages of metal hydroxides are fully utilized.（2）The low-cost melamine was selected as the raw material and carbonized at high temperature.To further enhance the conductivity of the base material,silver nanoparticles were also introduced during the carbonization process.Interestingly,the nitrate ions in silver nitrate changed the pore structure of the nanosheets during the carbonization process,so that the sheet carbon nanosheets were transformed into porous carbon,which created very favorable conditions for the subsequent growth of metal oxides.Under the synergistic effect of Co₃O₄ nanoclusters,silver nanoparticles and porous carbon,the electrode material exhibits excellent electrochemical activity.The three-electrode system can obtain a specific capacitance of 1045 F g^-1 at 1 A g^-1,and after 5000 times of charging and discharging,it still maintains a performance retention rate of 89%.After assembling the MP@Ag/Co₃O₄//AC,the specific capacitance is 157.5 F g^-1 at 1 A g^-1,and the power density of 56 Wh kg^-1 can be achieved at the energy density of 800 W kg^-1.（3）Biomass-derived carbon mangosteen husks were carbonized,and porous carbon materials were prepared by chemical activation,and then cobalt salts and nickel salts were introduced into the surface by hydrothermal methods,and finally the growth on the surface of porous carbon materials was obtained.And cobalt-nickel metal oxide with nanosheet morphology.The low-cost biomass carbon material mangosteen husk lays the foundation for industrial production.The three-dimensional interconnected porous carbon ensures the continuity of the material and provides enough active sites for the growth of metal oxides on its surface,which is beneficial to the electron transfer of the electrochemical reaction.The electrochemical measurement of PC-3/Co₃O₄-NiO in the three-electrode system shows that the specific capacitance of 894 F g^-1 can be obtained at 1 A g^-1,and the performance can be maintained at 80.1%after 5000 times of charge and discharge.Assembled into PC-3/Co₃O₄-NiO//PC-3 devices,the specific capacitance is 137 F g^-1 at 1 A g^-1 and the power density is48.7 Wh kg^-1 at an energy density of 800 W kg^-1.