Preparation And Electrochemical Properties Of Nickel Cobalt Oxide And Its Composites

Supercapacitor as a hot research of new energy storage equipment,the properties of the electrode material plays a decisive role on the performance of the super capacitor,so the electrode material research is the key of the research.The transition metal oxide has the advantages of abundant resources,environmental friendly and outstanding electrochemical performance.In this paper,nickel and cobalt metal oxides were used as the research object to explore the synthesis conditions,different nickel and cobalt ratios and carbon materials for composite,and the Metalorganic frameworks ZIF-67 was used as template to synthesize the anisotropic special structure affect the material structure,electrochemical properties,magnification performance and cycle stability,as follows:1.NiCo₂O₄ were synthesized by a facile hydrothermal method followed by an annealing treatment,to explore the effect of synthesis conditions on the structure and morphology of NiCo₂O₄ and study the electrochemical performance,magnification performance and cyclic stability.The results show that deionized water and ethylene glycol as solvent,using hexamethylene tetramine（HMT）to release OH-slowly at the high temperature to prepared hierarchical mesoporous spinel NiCo₂O₄ nanowires.NiCo₂O₄ nanowires exhibit a high specific capacitance of 2876 F·g^-1 at a current density of A·g^-1.As the current density increases to 10.0 A·g^-1,the specific capacitance can still be maintained at 1290 F·g^-1,which means that the electrode material have the excellent large current discharge capacity.In addition,the capacitance retention rate reached 84.7% after 500 cycles,this indicates that the electrode material has excellent cycle performance.The excellent electrochemical performance of the hierarchical mesoporous NiCo₂O₄ nanowires indicates its potential as an electrode material for the supercapacitor.2.NiCo₂O₄/N-rGO nanocomposites can be prepared by using solvothermal method and hydrothermal method.PVP as surfactant and hexamethylene tetramine（HMT）can not only provide nitrogen source,but also can be used as precipitant and reducing agent.After the thermal annealing,the structure does not change,the specific surface area of the composite material can reach 99.38 m2 g^-1,and the high specific capacitance of 2090 F·g^-1 at a current density of 1 A·g^-1,and when the current density reaches 10 A·g^-1 still maintains the specific capacitance of 1257.5 F·g^-1,showing the high rate performance of the material,and the capacitance retention rate is 60.16% after 2000 cycles.This study shows that NiCo₂O₄/ N-rGO nanocomposites have high activity,large specific capacitance and good rate performance as electrode materials for supercapacitors.3.The NiCo₂O₄@ ZnCo₂O₄@Co₃O₄ hollow Nanocages were prepared by the metal organic frameworks ZIF-67 was used as template and the coprecipitation of the metal ion.The use of the organic ligand in the metal organic frameworks could effectively prevent the agglomeration of the metal by high temperature calcination,which can obtain the uniform size metal oxide nanocages composites,this unique structure of the composite material has a complex shell,the surface showing a porous network-like structure,can provide more active sites,and promote the redox reaction of electrode material redox reaction.At a current density of 1 A·g^-1 and 10 A·g^-1 exhibited the specific capacitance of 1892.5 F·g^-1 and 1135 F·g^-1,respectively,which show the high rate properties of the material.After the 2000 cycles shows 66% of the capacitance retention rate,and good cycle stability.This study provides insight into the synthesis of other composites,providing more possibilities for constructing more desirable electrode materials.