3D Co‐Doping α‐Ni(OH)2 Nanosheets for Ultrastable, High‐Rate Ni‐Zn Battery

Abstract The α‐Ni(OH) 2 is regarded as one promising cathode for aqueous nickel‐zinc batteries due to its high theoretical capacity of ≈480 mAh g −1 , its practical deployment however suffers from the poor stability in strong alkaline solution, intrinsic low electrical conductivity as well as the retarded ionic diffusion. Herein, a 3D (three dimensional) macroporous α‐Ni(OH) 2 nanosheets with Co doping is designed through a facile and easily scalable electroless plating combined with electrodeposition strategy. The unique micrometer‐sized 3D pores come from Ni substrate and rich voids between Co‐doping α‐Ni(OH) 2 nanosheets can synergistically afford facile, interconnected ionic diffusion channels, sufficient free space for accommodating its volume changes during cycling; meanwhile, the Co‐doping can stabilize the structural robustness of the α‐Ni(OH) 2 in the alkaline electrolyte during cycling. Thus, the 3D α‐Ni(OH) 2 shows a high capacity of 284 mAh g −1 at 0.5 mA cm −2 with an excellent retention of 78% even at 15 mA cm −2 , and more than 2000 stable cycles at 6 mA cm −2 , as well as the robust cycling upon various flexible batteries. This work provides a simple and efficient pathway to enhance the electrochemical performance of Ni‐Zn batteries through improving ionic transport kinetics and stabilizing crystal structure of cathodes.