Preparation Of Hierarchical Structure Nickel-cobalt Carbonate Hydroxide Composite Electrode And Study On Its Capacitive Performance

As a new type of energy storage device,supercapacitor has the advantages of high power density,superior cycle stability and fast charge performance,etc.Electrode material is one of the keys to determine the performance of supercapacitor.In recent years,the application of carbonate hydroxide as energy storage materials for pseudocapacitor in the electrode materials of supercapacitor has attracted much attention.By combining electrode materials of different dimensions to construct electrode materials with multistage structure,the transport and transfer efficiency of electrons and ions can be effectively increased,and the stability of the structure can be effectively increased in the charging and discharging process of the device.Therefore,it has a broad application prospect in the realization of high specific capacitance,high-rate performance and good cycle stability of the energy storage devices.Based on nickel-cobalt carbonate hydroxide materials,this paper investigates the trimetallic carbonate hydroxide and its composite electrode materials from the aspects of crystal structure,morphology and electrochemical performance.The main research contents are as follows:Part 1.Nickel-cobalt-copper trimetallic carbonate hydroxide（Ni Co Cu CH）with nanoneedle structure was synthesized on nickel foam（NF）base by one-step hydrothermal method by adjusting hydrothermal time,temperature and reactant ratio.It was found that the optimal reaction condition was 160℃for 4 h through micro-morphology characterization and electrochemical performance evaluation.The optimal ratio is Ni（NO₃）₂·6H₂O:Co（NO₃）₂·6H₂O:Cu（NO₃）₂·3H₂O=3:2:1.After depositing PPy on NF by electrodeposition,the electrode material with the above optimal ratio was combined with NF@PPy by hydrothermal method,and the NF@PPy/Ni Co Cu CH electrode material with similar shape of"green lawn"was constructed on NF.The specific capacitance is 1371.9F/g at 1 A/g.The capacitance retention rate is 92.8%at 20 A/g.When the current density is 10 A/g,after 5000 cycles of charge-discharge test,the capacitance retention rate is138.4%of the initial capacitance.The electrochemical test of the asymmetric supercapacitor（NF@PPy/Ni Co Cu CH//AC/NF）shows that the maximum energy density and power density provided by the device are 27.6 Wh/kg and 8000.0 W/kg.After 10000cycles at the current density of 5 A/g,the capacitance retention rate is 116.4%of the initial capacitance,showing good electrochemical stability.Part 2.Ni Co Cu CH/δ-Mn O₂/NF was synthesized by a two-step hydrothermal method on NF,and the electrode material with"flower"morphology is constructed by nanoneedles and nanosheets.The optimal composite ratio was explored by controlling the input of KMn O₄.The specific capacitance of Ni Co Cu CH/δ-Mn O₂/NF is 4162.9 F/g at 1 A/g,and the capacity retention rate is 86.1%at 20 A/g.After 5000 charge-discharge cycles at a current density of 10 A/g,the capacitance retention rate is 93.0%of the initial capacitance.The asymmetric supercapacitor（Ni Co Cu CH/δ-Mn O₂/NF//AC/NF）has a maximum energy density of 54.6 Wh/kg and a maximum power density of 8000.0 W/kg.After 10000 cycles at 5 A/g,its capacitor retention rate is 96.8%,which shows good cyclic stability.Part 3.Carbon quantum dots（CQDs）were prepared by pyrolysis.Ni Co Cu CH/CQDs/NF composite electrode material was prepared by one-step hydrothermal method using CQDs,nitrate and urea as raw materials in ethanol:ultra-pure water=1:1 solvent.Under the influence of CQDs,the electrode material with honeycomb morphology was constructed.The electrochemical performance test of Ni Co Cu CH/CQDs/NF composite electrode material shows that the specific capacitance is2111.1 F/g at 1 A/g,and the capacitance retention rate is 75.3%at 20 A/g.After 5000cycles at 10 A/g current density,the capacitance retention rate is 84.4%.Asymmetric supercapacitors（Ni Co Cu CH/CQDs/NF//AC/NF）have a maximum energy density of 53.6Wh/kg and a maximum power density of 7959.0 W/kg.Showing excellent cycle stability,after 10000 cycles charge-discharge tests at a current density of 5 A/g,the capacitance retention rate can reach 95.7%.