Boosting discharge capability of α-Ni(OH)2 by cobalt doping based on robust spherical structure

Abstract

α-Ni(OH)2 is a promising candidate of the currently commercialized β-Ni(OH)2 due to its higher theoretical discharge capacity in alkaline solution; however, its instability and poor conductivity plague the practical application. Herein, we propose α-Ni(OH)2 with Co doping and spherical structure to strengthen the stability and enhance the conductivity and use it as the cathode for nickel-metal hydride batteries. Studies show that proper Co doping promotes the electrochemical reaction between the active materials and the electrolyte due to the spherical α-Ni(OH)2 with enlarged interlayer distance and abundant hole channels, as well as high conductivity of Co, therefore, the obtained spherical α-Ni(OH)2 with 7 mol% Co doping delivers significantly improved discharge capability, which is 384.6 mAh g−1 at 70 mA g−1 (0.2 C), increased by 54.3 mAh g−1 compared with pure α-Ni(OH)2, and at a high current of 5 C, it still gives 269.4 mAh g−1, in contrast 218.5 mA g−1 for the pure α-Ni(OH)2. Besides, the cycling stability of the α-Ni(OH)2 with 7 mol% Co doping maintains 340 cycles at a capacity retention of 80% (1C), which is extended 110 cycles in contrast to the pure α-Ni(OH)2. These results provide the underpinning platform of α-Ni(OH)2 for battery applications with high discharge ability and cycle life.