Construction And Electrochemical Properties Of Co/Mn Carbonate Based Micro-Nano Structure Aggregates

The adoption of clean energy technology is one of the important means to solve the national"dual carbon"strategic goal.Supercapacitors are sensitive to electrical signals and can effectively stabilize the peak of charge and discharge.As an electrochemical device for fast storage and release of energy,they have very important applications in the field of clean energy storage.The cathode material of supercapacitor,as the"energy storage core"of electrochemical energy storage device,should have both high specific capacitance performance and high cycle stability.In principle,charge storage of positive electrode materials is based on Faraday REDOX process on the surface,so improving the specific capacitance performance of electrode materials can be adjusted by reducing the size of electrode materials（nano scale）,while improving the cyclic stability requires increasing the size of electrode materials（micron scale）.In order to solve the contradiction between large specific capacitance performance and cyclic stability of electrode materials,this paper selects transition metal-based micro-nano structures(Mn_xCo_yCO₃nanosheets,Co（CO₃）_0.5（OH）·0.11H₂O nanowires)as monomers to further construct complex micro-nano structures.The energy storage behavior of supercapacitor electrode materials is systematically studied.The research contents are as follows:（1）Mn_xCo_y（CO₃）₂nanosheets were synthesized by simple hydrothermal method,and the structure of Mn_xCo_y（CO₃）₂nanosheets aggregate（NPs）was successfully controlled by controlling the concentration of Mn.At 1 A/g current density,the mass specific capacitance of the synthesized material can reach 654.9 F/g,and at 4 A/g current density,the retention rate of specific capacitance is 118.12%after 29,000 cycles.In this experiment,Mn_xCo_y（CO₃）₂NPs structure was used as positive electrode and activated carbon as negative electrode to assemble asymmetric supercapacitor.Under the condition of 0.5 A/g current density,the mass specific capacitance can reach 60.91 F/g,and at 6 A/g current density maintains the initial specific capacitance performance of 58.92%at 1 A/g.The maximum energy density of asymmetric supercapacitor is 23.03Wh kg^-1,and the specific capacitance retention rate is 91.93%after 60000 electrochemical cycles.（2）The Co（CO₃）_0.5（OH）·0.11H₂O nanowire aggregates（NWs）were synthesized by introducing surfactant as a template and using electrostatic force to drive the ordered assembly of inorganic ions.At the current density of 1 A/g,the mass specific capacitance of the synthesized material can reach 719.05 F/g.At 2 A/g current density,the specific capacitance retention rate is about 100%after 10000 cycles.In this experiment,the asymmetric supercapacitor was assembled by using the nanowire aggregate structure as positive electrode and activated carbon as negative electrode.At 0.5 A/g current density,the mass specific capacitance performance is 131.30 F/g,and the maximum energy density is 47.17 Wh/kg.After 14000 electrochemical cycles,the specific capacitance performance increased steadily until 24000 cycles began to decay.The supercapacitor assembly was able to drive 38 red LED bulbs for up to two minutes and twenty seconds.