Co-Sn Based Composite Oxide/Hydroxide Microstructure-Control Of Capacitance Performance Control Study

Supercapacitor is a new type of energy storage and conversion system,which has the advantages of fast charging and discharging,high efficiency,long cycle life,high power density,so has attracted much attention.However,the lower energy density hinders the commercial application of supercapacitors.By adjusting and designing the morphology and structure of electrode materials,preparing multi-element metal compounds by doping with metallic elements and non-metallic elements,and preparing self-supporting electrodes that integrate current collectors and electrode materials are effective ways to solve this problem.In this paper,one-step hydrothermal method was used to prepare Co₃O₄@SnO₂-SnO electrode materials with core-shell structure.The temperature of hydrothermal influence the morphology,structure and chemical composition of the electrode materials,and electrochemistry was studied.Secondly,using foam nickel as the current collector substrate,using two ligands,potassium sodium tartrate and sodium citrate,to construct a Co(OH)₂/SnO_x/C nanosheet array self-supporting electrode,and assemble Co(OH)₂/SnO_x/C//AC solid supercapacitors further studied its supercapacitance performance.Finally,based on the research of foam nickel self-supporting electrodes,sodium phosphite and thiourea are used to provide P and S sources,and the surface of the foam nickel is modified in the inert argon protection to further prepare high-performance P&S-SnO₂/Co(OH)₂ nanosheet array supercapacitor self-supporting electrode,and assembled P&S-SnO₂/Co(OH)₂//AC solid supercapacitor,showing excellent supercapacitor energy storage performance.The main research contents and results are as follows:(1)The Co₃O₄@SnO₂-SnO core-shell hybrid metal oxide electrode material was synthesized by a simple one-step hydrothermal method.The influence of hydrothermal synthesis temperature on the morphology,structure and electrochemical performance of Co₃O₄@SnO₂-SnO was studied.The gauze-like SnO₂-SnO nanosheets are coated with Co₃O₄ nanoparticles,showing an unusual dumpling shape.This core-shell structure promotes the separation and transfer of charges,shortens the ion transport path,and increases the electrochemical reaction rate,making it exhibit significant pseudo-capacitance characteristics.The hydrothermal temperature affects the microscopic morphology of the electrode material,and further affects its electrochemical performance.By optimizing the conditions:when the water is heated at 250?,the specific capacitance of Co₃O₄@SnO₂-SnO at a current density of 1 A g^-1 is 325 F g^-1,and the specific capacity at 20 A g^-1 is 77.9%.The retention rate of specific capacitance is as high as 100%under 5000 cycles of charge and discharge test at a current density of 5 A g^-1.(2)The Co(OH)₂/SnO_x/C hybrid nanosheet array self-supporting electrode was synthesized on the foam nickel substrate by one-step hydrothermal method.Among them,the hybrid nanosheets have a special petal-like shape.XPS analysis shows that Co(OH)₂/SnO_x/C introduces abundant oxygen vacancies to increase the carrier concentration and promote the charge transport in the electrochemical reaction of the electrode.,Thus showing better electrochemical performance:1 A g^-1 when the specific capacitance is 806.4 F g^-1.The assembled Co(OH)₂/SnO_x/C//AC solid supercapacitor has a power density of 399.9 W kg^-1 at an energy density of 12.4 Whkg^-1.The capacitance retention rate after 20,000 cycles of 1 A g^-1 64.4%.(3)Sodium phosphite and thiourea are used as P source and S source,the surface of nickel foam is modified in inert medium argon to improve the conductivity of the foam nickel current collector substrate,and then a one-step hydrothermal process is carried out to prepare high-performance P&S-SnO₂/Co(OH)₂(PSSC)nanosheet array supercapacitor self-supporting electrode,and further assembly of P&S-SnO₂/Co(OH)₂//AC solid supercapacitor.SnO₂/Co(OH)₂ grows vertically and covers the nickel foam substrate.Numerous tiny nanosheets are connected to each other,cross-linked and supported,and have stable pores,showing excellent electrochemical performance:1 A g^-1 The specific capacitance is as high as 2608.9 F g^-1.The P&S-SnO₂/Co(OH)₂//AC supercapacitor has a high energy density of28.8 Whkg^-1 and a power density of 180.1 W kg^-1.The capacitance retention rate after 6000cycles of charge and discharge at a current density of 1 A g^-1 is 57.4%.