β-Ni(OH)2 nanosheets coating on 3D flower-like α-Ni(OH)2 as high-performance electrodes for asymmetric supercapacitor and Ni/MH battery

β-Ni(OH) 2 with good crystallinity is grown on the surface of the flower-like α-Ni(OH) 2 to form a 3D α@β-Ni(OH) 2 material by a two-step hydrothermal method . The synthesized β-Ni(OH) 2 is nanometer size and strong alkali stability, while the α-Ni(OH) 2 has a large specific surface, high specific capacity and good electrical conductivity , so there are multiple synergistic effects between the β-Ni(OH) 2 coating and the α-Ni(OH) 2 core. Coupled with a 3D flower-like structure, the obtained α@β-Ni(OH) 2 electrode shows a high capacity of 431 mAh g −1 at a current density of 1 A g −1 . Furthermore, we use the α@β-Ni(OH) 2 electrode and the activated carbon (AC) electrode to assemble an asymmetric supercapacitor (ASC) device. This ASC shows the excellent energy density of 53 Wh kg −1 at a power density of 875 W kg −1 and capacity retention rate of 78% after 5000 cycles. Finally, metal hydride (MH) is used to replace the AC negative electrode, and a cell with a high energy density of 100.17 Wh kg −1 at a power density of 424.75 W kg −1 is obtained. The results show that α@β-Ni(OH) 2 electrode has better electrochemical performance than commercial electrodes and has application prospects in energy storage.