Preparation Of Cobalt-based Electrode Materials For Supercapacitor Application And Its Electrochemical Performance

Supercapacitors have attracted considerable interest due to the superior capacitance,excellent power density,good cycling stability,and low maintenance cost.In the development process of supercapacitor electrode materials,cobalt-based materials have been studied by researchers as an important supercapacitor material because of its advantages of theoretical specific capacitance and multiple oxidation.Firstly,the method of precursor conversion was used in this paper.Cobalt oxalate as precursor is prepared by a facile route under room temperature.L-ascorbic acid?AA?as structure-directing agent and the origin of oxalate(C₂O₄^2-)plays a key role in the reaction of compounding the precursor.Co₃O₄ with hollow coral-shaped nanostructure is synthesized by calcining cobalt oxalate precursor in air.The unique Co₃O₄ nanostructures are used as electrode materials in supercapacitors Co₃O₄ nanostructures exhibit noticeable pseudocapacitive properties with a capacitance of 626.5 F/g at 5 mV/s.They also show superior charge-discharge stability?capacity retention of 99%?and outstanding coulombic efficiency?¹00%?after 5000 GCD cycles at a current density of 10 A/g.Then,precursor conversion method is also used on the synthesis of cobalt-nickel oxide.Four kinds of nickel-cobalt oxide with different ratios of elements?nickel and cobalt?were synthesized by the same way as above.The element ratios of the four cobalt-nickel oxides are 1:0,3:1,1:1 and 1:3.1:1 sample showed the best electrochemical performance.It exhibits noticeable pseudocapacitive properties with a capacitance of 782.8 F/g at 5 mV/s.The capacity retention is 99%at 50 mV/s.It shows good coulombic efficiency?¹00%?.And its capacity retention is 100%after 10 000 GCD cycles.Finally the solvothermal process is utilized.Five kinds of samples were synthesized through changing the composition ratio of the two solvents(V_water:V_{ethylene glycol}=1:0,1:1,1:2,1:3,and 1:4).It exhibits pseudocapacitive properties with a capacitance of 782.8F/g 49.68,202.3,321.79,262.8 and 239.79 at 5 mV/s,respectively.1:2 sample showed the best electrochemical performance.And its capacity retention is 100%after 10 000GCD cycles.It also shows outstanding coulombic efficiency?¹00%?during 10 000 GCD cycles.