Preparation And Modification Of Positive Electrode For Alkaline Aqueous Nickel Zinc Battery

With the continuous development of wearable electronic devices in the field of healthcare and sensor monitoring,there is an urgent need to design energy storage units with high energy/power density,small size,light weight,high mechanical flexibility,and safe operation.Nickel zinc batteries using non combustible aqueous electrolyte and low-cost zinc anode are considered potential candidates in the field of flexible energy storage due to their high output voltage（about 1.7 V）,high theoretical energy density,high safety,and low cost.However,due to poor conductivity,delayed ion diffusion kinetics,and severe crystal structure collapse of nickel based positive electrodes during cycling,their low actual energy density and poor cycling performance have hindered their large-scale application.Therefore,in this paper,the positive electrode of nickel zinc battery was modified from the aspects of microstructure design and ion doping modification.The main research results are as follows:（1）Electrodeposition of Co doping based on reactions(NO₃^-+H₂O+e^-→NO₂^-+2OH^-,and Ni²⁺+Co²⁺+2OH^-→Ni_1-xCo_x（OH）₂)on three-dimensional porous nickel prepared by electroless plating using hydrogen bubbles as a templateα-Ni（OH）₂ nanosheet array.The unique micrometer-sized 3D pores come from Ni substrate and rich voids between Co-dopingα-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 theα-Ni（OH）₂ in the alkaline electrolyte during cycling.Thus,the 3Dα-Ni（OH）₂ shows a high capacity of 284m Ah g^-1 at 0.5 m A cm^-2 with an excellent retention of 78%even at 15 m A cm^-2,and more than 2000 stable cycles at 6 m A cm^-2,as well as the robust cycling upon various flexible bat-teries.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.（2）Based on the reaction of 3Ni+2Na₂S₂O₃→Ni₃S₂+2Na₂SO₃,a three-dimensional porous nickel substrate prepared by electroless plating using hydrogen bubbles as a template was grown by hydrothermal method in its pores.The rich voids between the Ni₃S₂ nanosheet arrays not only provide a fast transfer channel for OH^-,but also alleviate the volume change of the Ni₃S₂ electrode during the cycling process,ensuring the integrity of the active material;The three-dimensional porous structure can provide sufficient active reaction sites and fast ion/electron transport channels,which improves the charging and discharging performance of the battery under high current conditions;With the surface modification of indium,the electrical conductivity of the material is enhanced,and the stability of the material is enhanced,further improving the electrochemical performance of the material.Under the synergistic effect of 3D porous structure,nano chip array structure,and indium surface modification,3D Ni₃S₂@In Shows high capacity(267 m Ah g^-1 at 0.5 m A cm^-2)and excellent magnification performance(124 m Ah g^-1 capacity at 15 m A cm^-2),with more than 900 cycles at 6 m A cm^-2.