The Energy Storage Performance Of Nickel/Cobalt-based Materials In Alkaline Aqueous Zinc Battery

In recent years,due to its high theoretical capacity(820 m Ah g^-1/5855 m Ah cm^-3),low redox potential,abundant crustal reserves and environmental friendliness,aqueous zinc batteries have shown extremely high application potential,which has attracted more and more attention.At present,the research on the aqueous zinc battery mainly focuses on the near-neutral electrolyte（Zn SO₄,Zn（CF₃SO₃）₂,etc.）,but the zinc negative electrode in the alkaline electrolyte has a lower redox potential（-1.26 V vs.SHE）,which can make the whole battery have a higher output voltage.Therefore,zinc battery has wide application prospects in energy storage systems,electric vehicles and portable equipment.Nickel-cobalt-based electrode material,as the cathode of alkaline aqueous zinc battery,has attracted more and more attention from researchers in recent years.It has the advantages of high safety,high capacity and low production cost,but its low energy density and low-rate characteristics are the limiting factors for its application.Therefore,it is necessary to design reasonable structure and components to improve the properties of cathode materials.In this thesis,we designed and synthesized three nickel-based nanomaterials as the positive electrodes of alkaline aqueous zinc batteries,and the main research results are as follows:（1）A cobalt element-doped nickel sulfide nanosheet arrays（Co-Ni₃S₂）were prepared by one-step solvent thermal method,and then the precursor was treated by Na BH₄ solution reduction method to synthesize cobalt-rich sulfur vacancy-doped nickel sulfide.The doping of cobalt optimizes the adsorption energy of OH^-,thus improving the conductivity,and the abundant sulfur vacancies lead to rapid ion diffusion and electron transfer rates with good structural stability.These results are validated by the density functional theory（DFT）calculations.The electrochemical testing（CV,GCD,EIS,etc.）and characterization technique analysis（SEM,TEM,XRD,XPS,etc.）confirm that the Co-Ni₃S₂ electrode has a high specific capacity(At the current density of 1 A g^-1,the capacity is 458.95 m Ah g^-1).The study of the assembled Co-Ni₃S_2-x/NF//Zn battery finds that it has excellent specific capacity(The capacity is 183.9 m Ah g^-1 at the current density of 1 A g^-1),energy density of 442.754 Wh kg^-1,and a long cycle life(At a current density of 10 A g^-1,its capacity remains at 72.9%after 6000 cycles).（2）Co-MOF nanosheets were grown on nickel foam as the skeleton template,and nickel cobalt oxide nanomaterials（AM-O_v-NCO/NF）with amorphous oxygen-rich vacancy were successfully synthesized by ion exchange and air calcination,serving as the positive electrode of alkaline aqueous zinc battery.The ion-rich diffusion channels of the amorphous compounds improve the electrochemical properties of the AM-O_v-NCO/NF electrode.The nanosheet structure is conducive to the penetration of the electrolyte,promotes the full contact of the active material in the reaction,and effectively improves the conductivity of the material and the number of active sites.The capacity of the AM-O_v-NCO/NF electrode can reach 350.83 m Ah g^-1 at the current density of 1 A g^-1,and even at the high current density of 30 A g^-1,the AM-O_v-NCO/NF electrode can still show the good rate performance of the electrode material.The assembled AM-O_v-NCO/NF//Zn battery has a high energy density(539.08 Wh kg^-1,the corresponding power density is 1.68 k W kg^-1),excellent cycle stability(Its capacity remains91.9%after 2000 cycles at 10 A g^-1 current density),and excellent low-temperature performance(At low temperatures of-25℃,it has a capacity of 238.5 m Ah g^-1).The assembled alkaline aqueous zinc battery has the characteristics of high safety,good super durability and excellent low temperature performance,which can be applied to flexible electronic devices and has great application potential.（3）Ni_xB nanoparticles adhered to the surface of reduced graphene oxide were synthesized by a simple chemical precipitation method to serve as the positive electrode for alkaline nickel-zinc batteries.Amorphous Ni_xB nanoparticles are rich in unsaturated active sites and synergistic electronic effects,facilitating the adsorption of OH^-.The addition of r GO improves the electron transfer rate and conductivity of Ni_xB,and greatly increases the specific capacity of the Ni_xB/r GO electrode(The capacity can reach 241.9 m Ah g^-1 at the current density of 2 A g^-1).Furthermore,the assembled Ni_xB/r GO//Zn battery has a high energy density of 399.7 Wh kg^-1(the power density was 3.5 k W kg^-1)and a long cycle life(It maintains 93.7%of the initial capacity after 1000 cycles at the current density of 10 A g^-1).Therefore,the Ni_xB/r GO electrode is an excellent cathode material for nickel-zinc batteries.