The Preparation And Electrochemical Properties Of Cobalt Molybdate Nanocomposite For Supercapacitors

Modern society is increasingly dependent on energy.With the increasingly depleted fossil energy,advanced storage technologies have been imminent.Efficient charge and discharge capacity,high power density,high energy density,good reversibility,high cycle life and a series of advantages over supercapacitor have been widely concerned by researchers.Electrode materials are the key of supercapacitor,the present researchers who engaged in the field of energy storage suffer from the development of high performance electrode materials.This paper is focused on the preparation of CoMoO₄ composites with metal oxides and carbon materials.We designed and prepared electrode materials with special morphology and studies its property.The following main topics are included in this dissertation:(1)Hydrothermal method was used to synthesize CoMoO₄nanomaterials by different temperature and time.The CoMoO₄-X were prepared under the conditions of different reaction temperatures of 140?,160?,180?and 200?(reaction for 6 h);The CoMoO₄-Y were prepared under the conditions of reaction temperatures of 180?and reaction for 4 h,6 h,8 h,and 10 h.The structure and surface morphology of the materials were characterized by scanning electron microscope(SEM)and X-ray diffraction(XRD)respectively.All the samples prepared are nanorod-like structures,which are?-CoMoO₄.The electrochemical performance test results showed that the CoMoO₄ material,prepared by the hydrothermal reaction under the conditions of reaction,has the best supercapacitor performance.The specific capacitance of CoMoO₄-6 is 770 F/g(the discharge current density of 1 A/g).After 5000 charge/discharge cycles,the capacitance retention is 91.6%.(2)The ILs-RGO(Ionic liquid modified graphene)was prepared.The CoMoO₄/ILs-RGO nanocomposites were fabricated through hydrothermal method.The ILs-RGO nanosheets has a good bonding force between the Ni foam substrate and the CoMoO₄.This structure is highly stable during charge/discharge processes.Among the samples,the CoMoO₄-6/ILs-RGO has the best pseudocapacitance performance and high cycle stability.The specific capacitance of the CoMoO₄-6/ILs-RGO is 1464 F/g(the current density of 1 A/g).After 5000 charge/discharge cycles,the capacitance retention is 103.1%.The CoMoO₄/ILs-RGO has more excellent performance compared with pure CoMoO₄nanomaterials.The ILs-RGO is similar to a conductive network in the nanocomposite to improve the conductivity.The network reduces the diffusion path of ions and accelerates the electrode reaction kinetics.Secondly,the CoMoO₄/ILs-RGO has a larger surface area after mixed with the ILs-RGO.The contact area between active material and the electrolyte became larger,with a large number of ion reactive site,improves the utilization of the active material.(3)The optimized CoMoO₄@MnO₂-20 composite electrode exhibited a high specific capacitance of 1168 F/g(the current density of 1 A/g).After 5000 charge/discharge cycles,the CoMoO₄@MnO₂-20 had an excellent cycling stability with 97.1%retention rate.(4)The Ni(OH)₂ nanomaterials grown on Ni foam substrate with good electrochemical properties have been synthesized by hydrothermal method.The combination of Ni(OH)₂ and CoMoO₄ showed a synergistic effect for supercapacitors with greatly enhanced performance.The CoMoO₄@Ni(OH)₂-6 composite electrode exhibited a high specific capacitance of 1875F/g(the current density of 1 A/g).After 5000 charge/discharge cycles,the CoMoO₄@Ni(OH)₂-6 had an excellent cycling stability with 96.4%retention rate.