Construction And Research Of Supercapacitor Based On Nickel-Cobalt Carbonate Hydroxide Electrode Materials

With the rapid economic growth of the world,the pollution produced by human society has affected the ecological health of the whole earth.Therefore,the new green energy storage device-supercapacitors has attracted the attention of scholars.In supercapacitors,pseudocapacitor type electrode materials have higher theoretical specific capacitance and higher energy density than double-layer capacitors.With them as the electrodes,supercapacitors have more application prospects,so pseudocapacitor materials have become the current research hotspot.Nickel carbonate hydroxide and cobalt carbonate hydroxide are typical pseudocapacitive electrode materials,which have high theoretical specific capacitance.However,their low conductivity and low rate performance prevent them from being used as supercapacitor electrodes.In order to construct supercapacitors with high energy storage capacity and large current working capacity,this paper starts from nickel carbonate hydroxide and cobalt carbonate hydroxide,and uses nickel and cobalt doping to prepare cobalt-nickel carbonate hydroxide as the electrode material of supercapacitor.The synergistic effect of nickel-cobalt was used to improve its electrochemical performance,and the composite with MnO₂ was further used to improve its specific capacitance and conductivity.Finally,the prepared material was assembled into supercapacitors as electrodes and its performance was studied.The research contents are as follows:（1）Co₂（OH）₂CO₃ and Ni₂（OH）₂CO₃ nanowire electrode materials were prepared by hydrothermal method on Ni Foam.The irregular arrangement of the nanowires provides a large amount of pore structure for the electrode,which can provide a large number of active reaction sites during the charge and discharge process and enhance the efficiency of ion transport of the electrode.The specific capacitance of Co₂（OH）₂CO₃ and Ni₂（OH）₂CO₃ is 247 F g^-1 and 457 F g^-1,respectively,which is higher than that of common double-layer materials.But the specific capacitance has not reached the expectation and needs to be further improved.（2）In order to improve the specific capacitance of the electrode,the nanowire Co Ni（OH）₂CO₃ electrode material was prepared by doping Co and Ni elements.Electrochemical test results show that the specific capacitance of Co Ni（OH）₂CO₃electrode material is up to 926 F g^-1,which is much higher than that of Co₂（OH）₂CO₃and Ni₂（OH）₂CO₃,but the rate capability is still insufficient.（3）The Ni Foam@Co Ni-OCN@MnO₂ core-shell electrode was constructed in order to improve the rate capability and electrical conductivity of the materials for the Co Ni（OH）₂CO₃ electrode.The overall conductivity of the electrode was improved by composited with MnO₂ material with higher conductivity,and the electrochemical performance was enhanced by adding REDOX reaction channels with more complex core-shell structure.The electrochemical tests show that the specific capacitance of material up to 1366.5 F g^-1,and the equivalent resistance also dropped to 1.9Ω.The whole electrochemical properties of electrode is at a high level,satisfying the requirements of assembly of supercapacitor.（4）The prepared Ni Foam@Co Ni-OCN@MnO₂ electrode was used as the positive electrode and the Ni Foam@Activated Carbon electrode was used as the negative electrode to assemble an asymmetric supercapacitor,and its performance was tested.The ASC device delivers an energy density of 117.9 Wh·kg^-1 at a power density of 786W·kg^-1 and the equivalent series resistance is 3.0Ω.After 10000 cycles,88.1%of the specific capacitance is retained,revealing the excellent cycling performance.And it successfully acts as a power source to light up a small LED bulb,proving its practical application.In conclusion,the supercapacitor based on Ni Foam@Co Ni-OCN@MnO₂ has good energy storage capacity and large current discharge capacity,as well as good cycle stability,which reflects the value of practical application and provides experimental data and theoretical support for the development and research of supercapacitor.