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

alpha-Ni(OH)(2) is a promising candidate of the currently commercialized beta-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 alpha-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 alpha-Ni(OH)(2) with enlarged interlayer distance and abundant hole channels, as well as high conductivity of Co, therefore, the obtained spherical alpha-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 alpha-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 alpha-Ni(OH)(2). Besides, the cycling stability of the alpha-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 alpha-Ni(OH)(2). These results provide the underpinning platform of alpha-Ni(OH)(2) for battery applications with high discharge ability and cycle life. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Doping with cobalt and adopting a spherical structure can enhance the stability and conductivity of alpha-Ni(OH)(2), resulting in significantly improved discharge capability and cycling stability for its application as a cathode material in nickel-metal hydride batteries.