Preparation and electrochemical performances of flower-like Co–Ni double hydroxide electrode materials

To obtain the hydroxide electrode materials with excellent capacitance and cycling performance, the cobalt-nickel double hydroxide electrode materials doped by nickel were prepared by in-situ growth method on nickel foams using cobaltous nitrate and ammonium hydroxide as the raw materials and using ammonium nitrate as the promoters.X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the crystal phases and microstructures of Co–Ni double hydroxide electrode materials.The tests of cycling voltammetry (CV), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS) were conducted to analyze the electrochemical properties of electrode materials.The results show that, the nickel doping results in the crystal phase transform from Co (OH) ₂ single-phase to Co (OH) ₂ and Ni (OH) ₂ bi-phase, and changes the microstructures of electrode materials from cluster-like to flower-like, which is in favor of ion diffusion.Importantly, the flower-like cobalt-nickel double hydroxide electrode material with a Co/Ni mole ratio of 3:1 exhibits the best electrochemical performance, it has a specific capacitance value of 3674.7 F·g ^-1 at a scan rate of 5 m V·s^-1 and that of 1450.0 F·g^-1 at a current density of 5 A·g^-1, as well as a capacitance retention of 77.1%at 20 A·g^-1 after 5000 cycles.