Synthesis And Electrochenical Properties Of Nickel-Cobalt-Manganese-based Hydroxide As Electrode Materials For Supercapacitor

As we all know, micron-scale Ni Co Mn ternary material is one of important commercialized positive electrode materials in rechargeable lithium ion batteries so that the Ni-Co-Mn hydroxides if they were used as high specific capacitance electrode materials for supercapacitors possess the special chance of going into industrialization, In this paper, Ni-Co-Mn hydroxide is used as electrode materials for supercapacitor, and though doping graphene and cation-exchange treatment two different processing to improve the electrical conductivity of material, and then to improve the rate performance, the main contents are as follows;(1)Hierarchical sphere-shaped Ni-Co-Mn ternary hydroxides with hierarchical microstructure are employed for supercapacitors displaying high and tunable specific capacitances depending on the composition. When the molar ratio reaches to Ni : Co : Mn = 8 : 1 : 1(named as 811), the maximum specific capacitance reaches 1884.53 F/g at discharge current density of 0.5 A/g, and with the increasing of current density, the specific capacitance is decreasing severely. When the current density reach up to 10 A/g, 977.38 F/g is only got. For current densities beyond 10 A/g, the discharge time drop is too large to permit an accurate calculation of the specific capacitance.(2) In order to improve the rate performance of 811, through introducing two-dimention flexible conductive graphene, the partly open longan-shaped Ni0.8Co0.1Mn0.1(OH)2/graphene(811/G) composite is obtained. The chemical composition and morphology are characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscope(TEM), X-ray photoelectron spectroscopy(XPS) and so on. The electrochemical performance of samples are examined by cyclic voltammetry, impedance and galvanostatic charge–discharge measurements. The results show that 811/G maintaines the structure of initial precursor 811 and exhibits the good electrochemical characteristics. The specific capacitance is 1712.13, 1658.74, 1622.08, 1603.08, 1535.43 F/g at 0.5, 1, 2, 5, and 10 A/g, respectively. Even the current density reaches up to 20 A/g, the electrode can also retain 79.8% of its original specific capacitance.(3)Besides, through cation-exchange treatment Ni0.8-xCo0.1Mn0.1(OH)2@Co OOH composite is successfully built under the condition of oxidant. A asymmetrical supercapacitor is fabricated using Ni0.8-xCo0.1Mn0.1(OH)2@Co OOH anode material and activated carbon cathode materials to investigate whether Cation-exchange treatment can improve the electrical conductivity, rate performance and cycle performance of the hybrid supercapacitor. The results show the specific capacitances of Ni0.8-xCo0.1Mn0.1(OH)2@Co OOH and Ni0.8Co0.1Mn0.1(OH)2 are nearly at discharge current density of 0.5 A/g. With the increase of current density, difference as more. When the current density reach up to 7.5 A/g, the specific capacitances of Ni0.8-xCo0.1Mn0.1(OH)2@Co OOH is 67.09 F/g more than the 811.