The Fabrication Of Versatile Ultrathin Ni/Co-based Nanocomposites And The Research About Their Supercapacitive Performance

In our work,three-dimensional porous foam nickel served as matrix,we utilized facial hydrothermal reaction to fabricate nickel/cobalt-based?Ni/Co-based?nanocomposites with different morphology and structure.Meanwhile,these as-prepared materials directly used for electrode materials,can avoid the use of binder and greatly enhance their electrochemical activity.Ultra-thin Ni/Co hydroxides?Ni1Co2?with a sheet-like structure are successfully grown on the surface of conductive nickel foam via a one-pot hydrothermal reaction,avoiding the need for binders and conducting agents.In the reaction,NO₃^-ions from reactants release OH^-ions partially with Co2+ ions turning into Co3+ ions and then OH^-ions can react with Ni2+,Co2+ or Co3+ in a mixed solvent of water and ethanol,without the necessary addition of an extra alkali source.The as-prepared Ni1Co2 composites display a ultrathin sheet-like structure,and their thickness mainly focuses on a range of 5 to 13 nm.When used for supercapacitors,the resulting free-standing Ni1Co2 composites exhibit an impressive specific capacitance of 2654.9 F g-1 at a current density of 1 A g-1 and a favorable cycling stability with 77% retention even at a high current density of 10 A g-1 after 1500 cycles.In order to do research into the electrochemical properties of Ni1Co2 composites,a simple asymmetric supercapacitor?ASC?is constructed,using the Ni1Co2 nanosheets as the positive electrode and activated carbon?AC?as the negative electrode,then the ASC is marked as Ni Co-10//AC.This ASC with an extended voltage window of 0–1.6 V presents an outstanding energy density of 42.4 W h kg-1?at a power density of 823.2 W kg-1?and still retains 24.8 W h kg-1?at 10170.8 W kg-1?.Meanwhile,the excellent cycling stability of this ASC device has been revealed via a great specific capacitance retention of 94% after 3000 cycles?at a current density of 5 A g-1?.A rational Co-doped Ni?OH?₂/Ni₃S₂ hybrid was designed and grown in situ on Nifoam via a one-pot hydrothermal reaction with two-step temperature control,avoiding the utilization of complicated production processes or high-end technology.Interestingly,the as-prepared Ni Co-10 presents a distinct one-dimensional serpent-cactus-like?1D SL?structure consisting of ultrathin internal nanosheets.We chose different reaction stages?90 for 4 h,90 for 4 h and 110 for 5 h,90 for 4 h and 110 for 10 h?as comparisons,and obtained the entire transformation process.We can conclude that original nanosheets gradually turned into the 1D SL structure and the Co content is much lower than that of Ni and gradually increases in the later reaction.As a supercapacitor electrode,the hinder-free Ni Co-10 exhibits an ultrahigh specific capacitance value of 3023.4 F g-1 at 1 A g-1 and excellent rate performance?capacitance retention of 82.9% up to 20 A g-1?,owing to the distinct and available ultrathin serpent-cactus-like structure.Meanwhile,an asymmetric supercapacitor is developed,wherein Ni Co-10 is utilized as positive electrode and activated carbon as negative electrode.The asymmetric device could exhibit a high specific capacitance value of 136.2 F g-1?at 1 A g-1?,high energy densities of 51.5 W h kg-1?at 0.825 k W kg-1?and 23.0 W h kg-1?even at 8.25 k W kg-1?,and appropriate cycling stability.The versatile advantages of facile fabrication,eco-friendliness,high efficiency and low cost makes them become promising electrode materials in the energy storage field.