Study Of Electrochemical Performance Of Nickel Cobalt Oxide Supercapacitor By Surface Modification

As an innovative,efficient and environment-friendly energy storage device,super capacitor has broad development space and application prospect in many fields.Compared with the traditional battery,the supercapacitor has the advantages of high power density,long cycle life,high stability,wide application temperature,energy saving and environment-friendly.But the lower energy density is a disadvantage for humans.Therefore,developing a kind of electrode material that has high energy density has become a major challenge.In many metal oxides,spinel NiCo₂O₄/TiO₂ is well known because of its low cost,abundant reserves and friendly environment.This transition metal oxide has good conductivity and theoretical specific capacity up to3300 F/g.It is an excellent pseudo capacitance electrode material.In this paper,we study the effect of different surface modification methods on the performance of NiCo₂O₄/TiO₂ electrode material.The main contents of this article are as follows:?1?With cobalt nitrate and nickel foam as raw material,urea and ammonium fluoride as the catalyst,a nickel cobalt oxygen nanowire precursor with excellent properties was prepared on the nickel foam substrate by one step hydrothermal method.Then a layer of ultra-thin TiO₂ thin film was deposited evenly on the surface of nickel cobalt oxygen nanowires by atomic layer deposition,and NiCo₂O₄/TiO₂nanocomposites were obtained after air annealing.The morphology and structure of NiCo₂O₄/TiO₂ nanocomposites were characterized by XRD,EDS,SEM and TEM.The results showed that the top of nickel cobalt oxide nanosheets was dispersed into several nanowires,and a thin layer of TiO₂ thin film was visible on the surface of nanowires through EDS.By comparing the NiCo₂O₄ and NiCo₂O₄/TiO₂ electrode materials in the three electrode test system,it is found that the specific capacity of NiCo₂O₄/TiO₂ nanocomposites at the current density of 2 mA/cm² has reached the highest value 2.94 F/cm²,which is significantly higher than that of the initial sample at the same current density of the capacity 1.1 F/cm².At the current density of 10mA/cm²,the specific capacity of the NiCo₂O₄/TiO₂ nanocomposite as the electrode of the supercapacitor remained high after the 4000 cycles.The retention rate is 63%.?2?With cobalt nitrate and nickel foam as raw material,urea and ammonium fluoride as the catalyst,a nickel cobalt oxygen nanowire precursor with excellent properties was prepared on the nickel foam substrate by one step hydrothermal method.Then the graphene oxide was coated on the precursor of nickel cobalt oxygen nanowire by hydrothermal method,and the samples were annealed in the reducing atmosphere,and the NiCo₂O₄/graphene nanocomposites were obtained.The morphology and structure of NiCo₂O₄/graphene nanocomposites were characterized by XPS,SEM and TEM.The results show that the tip of nickel cobalt oxygen nanoscale is dispersed into several nanowires,and the redox graphene film is dispersed evenly at the top of the nanowire.This structure can greatly increase the contact area between the electrode material and the electrolyte.The electrochemical properties of NiCo₂O₄ and NiCo₂O₄/graphene nanomaterials before and after the composite were respectively tested in the three electrode system.It was found that the specific capacity of the NiCo₂O₄/graphene nanocomposites reached the maximum 3.7F/cm² at the current density of 2 mA/cm²,and was 336%higher than that of the initial sample at the same current density capacity of 1.1 F/cm².Under the current density of 10 mA/cm²,the specific capacitance of NiCo₂O₄/graphene nanocomposite as an electrode remains high after 4000 cycles.The retention rate is 64%.