Preparation And Study Of Cobalt-Based Spinel Structure Supercapacitor Electrode Materials

Supercapacitors have the dual characteristics of traditional capacitors and batteries:high rate performance,high energy density and excellent cycle stability.At present,the material of the cobalt-based spinel structure in the positive electrode material of the supercapacitor is widely studied due to the low cost,but the following problems still exist:1.Since the powder material is used as an electrode,it is necessary to add a conductive agent and a binder.The impedance increases.2.Metal oxides have the main problem of battery type materials:phase transition is easy to occur during charge and discharge,resulting in a decrease in material rate performance and stability.3.The single cobalt-based material has a lower specific capacity than the composite material.At present,the above problems can be solved mainly by reducing the intrinsic impedance of the electrode,increasing the high active site of the electrode material,preparing a multi-layered surface-active material,and doping of a hetero atom.The main work of this paper mainly includes the following aspects:1.Using PVP as a surfactant to synthesize the loose grass-like Co₃O₄ composed of nanowires grown on a foamed nickel substrate by hydrothermal coprecipitation,and study the active agent content and growth time for this special The effect of the growth process is to convert the hydrothermally converted hydroxide to black tricobalt tetroxide by heat treatment.The phase composition of the prepared product was determined by XRD powder diffraction and Raman analysis.The specific surface area of the material obtained by BET was 121.3 m²g^-1.The SEM test results showed that the structure had no grass morphology.The TEM test analysis showed that the material was porous inside.structure.The CV test shows that it has good reversible performance at 100mV/s.The GCD test has a capacity retention ratio of 75%at a current density of 893Fg^-11 at 1Ag-1,and has a good rate performance at a current density of 20Ag^-1.At the current density of 10Ag^-1,the specific capacity is maintained at 91.2%after 3000 cycles,which has good cycle stability.2.The morphology of NiCo₂O₄ was investigated by introducing different surfactants.At the same time,the synergistic effect of double-specific surfactants?PVP and NH₄F?in different hydrothermal time,different active agents and composite active agents was studied in detail.The influence of NiCo₂O₄ growth process and electrochemical performance.Experiments show that PVP can reduce the nucleation of crystals and the morphology from the initial single tiny particles to the final spherical radial shape,while NH₄F can accelerate the material growth rate and gradually transform from the initial sheet structure to a dense tree structure.The results of active agent content indicated that PVP assisted the conversion to a needle-like structure only when the content was 0.2g,while the BET test of the electrode material of NH₄F with a PVP of 0.2g and a hydrothermal time of 10h and a NH4F of 0.2 hydrothermal time of 4h.It shows that the former surface area reaches 112m²g^-1,and the latter is 87.5m²g^-1.The material prepared by the former has a specific capacity of 1410.9Fg^-1 at 1Ag^-1,and can maintain the initial value of 75.6 at the current density of 20Ag^-1.%,the latter is 1220.7Fg^-1 at a current density of 1Ag^-1,but 20Ag^-1 has a retention rate of only54%,and after 3000 cycles,it has a maximum value of 74.5%.When the double surfactant is introduced together,a flower-like structure which is assembled into a two-dimensional shape by one-dimensional needle assembly and assembled into a three-dimensional structure is prepared,and a high specific capacitance of a mass ratio capacitance of 2048 Fg^-1 is realized,and PVP and When the NH₄F composite active agent is introduced,the possibility of assembling a low-dimensional structure to a high-dimensional structure is prepared,and a relatively high specific capacitance is realized.3.By using a Mn and Ni bimetal atom to replace a part of the cobalt atom in Co₃O₄,the specific capacitance is increased while the cycle stability is improved.The MNCO ternary metal oxides with needle-like structure grown on foamed nickel were realized by a hydrothermal method.The effect of absolute ethanol on the growth of MNCO was also explored.It was confirmed by XRD and EDS that the prepared product was a product of spinel structure and Mn and Ni successfully replaced part of Co atoms.The SME pattern showed that the prepared product was needle-like structure,and the BET test showed that the material had mesoporous characteristics.The pore size distribution is mainly concentrated between 5 and10 nm,and the specific surface area is 96.53 m²g^-1.The CV test results show that there is still good reversibility at the scan rate of 40mV/s.The GCD test results of the three electrodes show that the ultra-high specific capacitance is 2238.2Fg^-1,20Ag^-1 at the current density of 1Ag^-1.At current density,it is still close to 1683Fg^-1.After circulating 2000 turns at the current density of 8Ag-1,the specific capacitance is1662Fg^-1,which is close to the highest value of 88.6%.The above results indicate a higher specific capacitance and cycle stability of MNCO relative to tricobalt tetroxide.