Preparation Of Nickel Bimetallic Oxides For Electrochemical Energy Storage

A facile,cost-effective,and eco-friendly method has been developed to the preparation of electrode materials with excellent electrochemical energy storage performances,then the stuctuctures and morphologies of the materials were investigated by X-ray diffraction(XRD),X-ray photoelectronic spectroscopy(XPS),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-resolution transmission electron microscope(HRTEM),the electrochemical performances were evaluated by cyclic voltammetry(CV),galvanostatic charge-discharge(GCD),and electrochemical impedance spectroscopy(EIS)tests,the detailed researches are summarized as follows:1.A one-step hydrothermal method was taken to fabricate porous Co1.29Ni1.71O4 nanosheets on Ni foam(NF),isopropanol was used as solvent.The morphologies of the material was investigated by SEM,irregular Co1.29Ni1.71O4 nanosheets fully covered on NF,there are many pores between the Co1.29Ni1.71O4 nanosheets.Electrochemical performances were evaluated,NF@Co1.29Ni1.71O4 was directly used as working electrode,it reached a high areal capacitance of 6.75 F cm-2 at 5 mA cm-2,when the current density reached 50 m A cm-2,74.4% areal capacitance was still maintained,which was much higher than most reported papers.2.Three dimentional(3D)graphene foam was prepared by a facile,cost-effective,and eco-friendly one-step hydrothermal method(NF@rGO),then ultrathin NiMoO4 nanosheets was in-situ grown on graphene foam(NF@rGO@NiMoO4).The morphologies of the nanocomposite were investigated by SEM and TEM,we can clearly see the ultrathin NiMoO4 nanosheets on rGO and the wrinkles of rGO.Electrochemical performances tests were evaluated,it showed batter rate capability(56% from 1 to 20 m A cm-2),and exellent cycle stability(93.1%,1000 cycles).3.A facile hydrothermal and annealing method was used to synthesis Co2NiO4,NiMn2O4,and Co2NiO4@NiMn2O4 nanocomposite which were directly grown on NF.We can see the multilayered nanosheets of Co2NiO4 and flower-like ultrathin nanosheets of Ni Mn2O4 from the SEM images,as to Co2NiO4@NiMn2O4nanocomposite,layerd nanosheets of Co2NiO4 was fully covered by the flower-like ultrathin nanosheets of NiMn2O4,we can clearly see the boundary of the two composites from TEM analysis.Their electrochemical performances were tested and found that NF@Co2NiO4@NiMn2O4 demonstrated much higher areal capacitance(13.35 F cm-2,30 m A cm-2).An asymmetric supercapacitor(ASC)was assembled with NF@Co2NiO4@NiMn2O4 as positive electrode and graphene pasted on NF as nagetive electrode(NF@Co2NiO4@NiMn2O4//rGO),demonstrating wide potential range(0-1.8 V),a high energy density of 1.38 mWh cm-2 was obtained at a power density of 292.2 mW cm-2.