Research On The Supercapacitors Based On Bimetal Cobalt-vanadium Hydroxide Electrode Materials

In the 21st century,the relationship between energy and human society is increasingly close.With the rapid development of human society and world economy,energy and environmental problems are becoming increasingly serious.Sustainable development is the common aspiration of all mankind.Nowadays,to solve the problem of energy exhaustion and ecological environmental pollution is not only the requirement of science and technology,but also the challenge of energy storage field.Supercapacitors?SCs?,also known as electrochemical capacitors,are a new type of energy storage device between traditional capacitors and batteries.In recent years,they have become a focus of research due to their large capacity,low resistance,high charge-discharge efficiency,high power density,green environment protection and other advantages.With the progress and development of science and technology,people's understanding of SCs continues to deepen,and various electrode materials and electrolytes with special properties have emerged.According to the energy storage model and structure,SCs can be divided into three types:double-layer capacitor?EDLCs?,pseudocapacitor?PCs?and hybrid supercapacitor?HSCs?.Layered double hydroxides?LDHs?are typical new inorganic functional materials due to their special structure?their layered structure can provide multiple platforms and active sites?,which have great potential in the field of electrochemistry.However,the material's ability to charge and discharge is limited by its relatively low electron transfer rate,so it needs to be assembled into a hybrid supercapacitor to improve performance.In this paper,LDHs electrode material was prepared from bimetallic cobalt-vanadium,and the relationship between its morphology and surface information and electrochemical properties was investigated.The electrode material was applied to the SCs field,mainly including the following three aspects:?1?Preparation of CoV-LDH electrode material by one-step hydrothermal methodThrough simple one-step hydrothermal method,CoV-LDH electrode was prepared by using CoCl2·6H2O and VCl3 as raw materials,its morphology was characterized,its elemental composition and chemical state were understood,and its electrochemical performance was tested.In A typical three-electrode electrochemical system,the electrode material had A high specific capacitance of 3540 F·g^-1 at 1 A·g^-1.After the assembly of CoV-LDH and activated carbon?AC?electrode into an asymmetric supercapacitor?ASC?,the working voltage window is widened to 0-1.6v,the specific capacitance of the CoV-LDH//AC ASC reaches 114.13 F·g^-1 at 1 A·g^-1,and the energy density is 40.6 Wh·kg^-1 at the power density of 800.4 W·kg^-1.After10,000 cycles,CoV-LDH/AC ASC has a capacitance retention rate of 87.5%.?2?Prepared rare earth Yb³⁺doped CoV-LDH electrode material by one-pot hydrothermal methodUse of rare earth elements unique electronic structure,the use of one-pot hydrothermal method to doped with rare earth Yb³⁺to CoV-LDH materials in the preparation of Yb-doped CoV-LDH electrode materials,through the study of the characterization test and analysis of electrode materials,rare earth elements Yb doped into the electrode material increased the specific surface area,reducing the grain size and improve the electrochemical performance of electrode materials.In electrochemical tests,the Yb-doped CoV-LDH electrode material with a doping of 10%has a specific capacitance of up to 4184.4 F·g^-1 at 1 A·g^-1,and has a smaller diffusion resistance than CoV-LDH.Assembled with AC as 10%Yb-doped CoV-LDH//AC ASC,its specific capacitance reaches 134.72 F·g^-1 at 1 A·g^-1,and its energy density is47.78 Wh·kg^-1 at the power density of 800.04 W·kg^-1.After 10,000 cycles,10%Yb-doped CoV-LDH/AC ASC had a capacitance retention rate of 89.4%.?3?Preparation of Yb-doped CoV-LDS electrode material by two-step methodYb-doped CoV-LDS electrode was obtained by curing Yb-doped CoV-LDH with sodium sulfide as curing agent.This material has better surface morphology and electrochemical properties than Yb-doped CoV-LDH.In the electrochemical system,the specific capacitance of Yb-doped CoV-LDS electrode material under 1 A·g^-1reached 4817.5 F·g^-1.When assembled with AC as Yb-doped CoV-LDS//AC ASC,the specific capacitance under 1 A·g^-1 was 161.71 F·g^-1,the energy density was 57.5Wh·kg^-1 when the power density was 800.03 W·kg^-1,and the capacitance retention rate was 91.4%after 10,000 charge/discharge cycles.