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

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.