Morphology Control And Electrochemical Performance Of A Nanoporous Nickel/Cobalt Double Hydroxide

Electrochemical supercapacitors have attracted significant attention due to their long cycle life and high energy density.Nickel-cobalt hydroxides have great application prospects in the field of energy storage materials,due to their excellent electrochemical performance,rich storage of resources.However,their large electron and ion transfer resistance have limited its development.In this paper,the internal resistance of the material is successfully reduced and the electrochemical performance is optimized,by controlling the synthesis of nickel-cobalt double hydroxides with a simpler,cheaper method.(1)Nickel/cobalt double hydroxides with sphere-like nanoflowers and nanoporous structures were controllably prepared by introducing halide ions into the reaction system.The morphology and structure of the composites were characterized by X-ray diffraction,scanning electron microscope,infrared spectra and Brunauer-Emmett-Teller method.Halides,especially bromide,can dramatically affect the morphology of the crystal aggregates,and some morphology-dependent electrochemical properties are found.Nickel/cobalt double hydroxide,prepared in the presence of potassium bromide,exhibits excellent electrochemical performance.The composite's specific capacitance can reach 2630 F g-1 at a current density of 1 Ag-1.Even at 8 Ag-1,the composite can still retain 80.7% of its capacitance,which is much higher than that of nickel/cobalt double hydroxide prepared in the absence of bromide.(2)The strong acid alkali salt was introduced into the reaction system and the nano-spherical porous nickel/cobalt double hydroxide particles were successfully synthesized by co-precipitation method.The physical properties of the prepared material were characterized by SEM and XRD.It was found that the prepared material have a rich pore size structure and a small particle size(200 nm).This structure greatly improves the electrochemical performance of the nickel/cobalt double hydroxide.The effect can be attributed to the intercalation effect of the acid ions.The acid ions can be inserted between the layers of the nickel/cobalt double hydroxides,the interlayer spacing is enlarged,more pores are formed,the internal resistance of the material is reduced,and the capacitance is increased.In particular,the potassium nitrate added nickel/cobalt double hydroxide has a specific capacitance of up to 2162 F g-1 at a current density of 1 Ag-1.The capacitance can retain 92.4% even at a current density of 8 Ag-1.