Yttrium doping stabilizes the structure of Ni 3 (NO 3 ) 2 (OH) 4 cathodes for application in advanced Ni-Zn batteries.

Ni 3 (NO 3 ) 2 (OH) 4 has a high theoretical specific capacitance, low cost, and environmental friendliness, making it a promising electrode material. Specifically, Ni 3 (NO 3 ) 2 (OH) 4 electrodes have a larger layer spacing ( c = 6.898 Å) than Ni(OH) 2 electrodes since NO 3 - has a much larger ionic radius than OH - . The larger layer spacing stores more electrolyte ions, significantly improving the electrochemical activity of the electrodes. Additionally, the interlayer NO 3 - can enhance the structural stability of Ni 3 (NO 3 ) 2 (OH) 4 . However, since Ni 3 (NO 3 ) 2 (OH) 4 has a higher molar mass than Ni(OH) 2 , it has a lower theoretical specific capacity. Consequently, Ni 3 (NO 3 ) 2 (OH) 4 has not been used in zinc-based alkaline batteries. Studies showed that doping could enhance the electrochemical performance of electrode materials. Therefore, this study used a simple solvothermal reaction to synthesize yttrium-doped Ni 3 (NO 3 ) 2 (OH) 4 (Y-Ni 3 (NO 3 ) 2 (OH) 4 ), assembling a Y-Ni 3 (NO 3 ) 2 (OH) 4 //Zn battery for electrochemical testing. Y-Ni 3 (NO 3 ) 2 (OH) 4 served as the cathode in the battery. The analysis of Y-Ni 3 (NO 3 ) 2 (OH) 4 showed that yttrium (Y) doping increased the specific surface area and pore size of Ni 3 (NO 3 ) 2 (OH) 4 significantly. The increased specific surface area improved the active material utilization, and the abundant mesopores facilitated OH - transport, substantially enhancing the battery's specific capacity and energy density. Ultimately, the specific discharge capacity of the advanced Y-Ni 3 (NO 3 ) 2 (OH) 4 //Zn battery reached 177.97 mA h g -1 at a current density of 4 A g -1 , nearly doubling the capacity of the earlier Ni 3 (NO 3 ) 2 (OH) 4 //Zn battery (103.59 mA h g -1 ).