Preparation And Electrochemical Properties Of Cobalt-based Electrode Materials

The rapid developments of human society is indispensable from energy source,the most of which are from fossil fuel exploitation.But the storage of fossil energy source on earth is limited,and the uncontrolled use of fossil fuels has caused the negative influence to the ecological environment.Thus scientist try their best to develop clean,green and renewable energy source to meet human needs,such as wind,solar and tidal energy and so on.But there are many intermittent and unevenly distributed problems existing above energy sources.So,how to store and utilize the electricity generated by these natural and green energy resources has become a research hotspot naturally.Supercapacitor is a kind of electrochemical energy storage devices,which are favored by researchers due to their advantages such as high power density,long cycle life and environmental friendly.But low energy density is deficiency of supercapacitor,constructing electrode materials with high energy density is the key to solve the problem.Cobalt is low in price and abundant in nature and cobalt-based materials as electrode in supercapacitors have been focused widely,which also showed superior electrochemical performance.But it still existing some disadvantages,such as unsatisfactory specific capacitance and cycle life.Therefore,the single and binary cobalt base compounds were designed and prepared in this paper.And we characterized their microscopic morphology and structure through multifold physical means,and their electrochemical performance as supercapacitor electrode materials was also tested.The specific work is as follows:?1?First of all,Co?NO₃?₂ and?NH₂?₂CO were used as cobalt source and precipitator respectively to synthesize series of Co₃O₄ products via simple one-step solvothermal method,following by the subsequent thermal treatment.SEM and TEM measurements revealed that the as-prepared Co₃O₄ was a porous and hollow microsphere consisting of sheet.Electrochemical test results show that Co₃O₄-600delivers the highest specific capacitance 922.7 F g^-1 at current density of 1 A g^-1,and shows long cycle life.?2?On the basis of optimizing the preparation process of Co₃O₄ electrode material,gallium was introduced into the component.So hierarchical mesoporous CoGa₂O₄microspheres were synthesized via a facile template-free solvothermal approach with a following calcination treatment.Effects of different calcination temperature on electrochemical performance and microstructure were also analyzed.CoGa₂O₄-400shows the highest specific capacitance and excellent cycle stability(specific capacitance do not decay after 20000 cycles at high current density of 20 A g^-1).?3?Hierarchical CoGa-LDH?cobalt gallium layered double hydroxide?was in situ gown on Ni foam via a facile and one-step hydrothermal method directly.When feeding ratio of Co/Ga source is 1 the as-prepared CoGa-LDH show the highest specific capacitance 2862.8 F g^-11 at current density 1 A g^-1.Assembling hybrid supercapacitor also deliver high energy density 68.07 Wh kg^-1.