Anionic And Cationic Co-Doped Nickel-cobalt Compounds And Study On Properties Of Aqueous Zinc-ion Batteries

With the progress of society and the improvement of people’s living standards,the consumption of fossil energy increases rapidly,leading to environmental pollution and resource shortage.As the country vigorously promotes the construction of an environment-friendly society,how to promote the large-scale use of new energy has become an urgent problem to be solved.Because the distribution of new energy is not uniform,energy storage has become a problem that restricts the development of new energy.Water zinc ion battery is considered as an ideal energy storage device because of its high energy density and good safety.As an indispensable part of zinc ion battery,positive electrode material determines the energy density and cycle life of zinc ion battery.Nickel-cobalt cathode materials have attracted much attention because of their high theoretical capacity and energy density.However,the inherent poor multiplier performance and short cycle life of nickel-cobalt base limit its further application.However,the current doping modification method（anionic and cationic doping）can only improve the performance of a certain aspect of the material,but can not achieve many aspects or even the overall strengthening.In this paper,the overall electrochemical performance of nickel-cobalt compounds was improved by means of ionizing and ionizing doping and composite modification.Hope to make a contribution to the development of zinc ion battery positive electrode,the specific research content is as follows:（1）Construction of N/Mn-Ni Co₂O₄ nanosheets and study on properties of aqueous zinc ion batteries:N/Mn-Ni Co₂O₄ nanosheets were obtained by hydrothermal reaction followed by calcination in air and NH₃,based on anionic and cationic co-doping method.Firstly,the oxygen vacancy introduced in the N/Mn co-doping process can be used as the active site of chemical reaction,which improves the specific capacity and multiplier performance of the material.Secondly,due to the synergistic action between Ni/Co/Mn elements,the band gap can be adjusted to improve the electron conductivity and ion migration rate of the material.The third interconnected vertically arranged N/Mn-Ni Co₂O₄ nanosheets have dense electrochemically active sites and high specific surface area,providing many pathways for electrolyte ion penetration,charge storage and transport.The N/Mn-Ni Co₂O₄ electrode can provide a maximum specific capacity of 382 m A h g^-1.Even if the current density increases to 3 times,the specific capacity can still retain 86.1%,showing the outstanding charge storage and multiplier performance of the material.After further assembling it into N/Mn-Ni Co₂O4//Zn battery with zinc sheets,it can provide 606 Wh kg^-1 energy density at 6.893 k W kg^-1 and maintain 92.3%initial capacity after 10,000 charge and discharge cycles.It is proved that N/Mn co-doping can improve the overall electrochemical performance of the material.（2）Synthesis of S-Ni/Co/Mn/（OH）_x composites and study on properties of aqueous zinc ion batteries:S-Ni/Co/Mn/（OH）_x composites were prepared by two-step hydrothermal method based on anion exchange.Firstly,the oxygen vacancy and heterojunction generated in the partial vulcanization process will regulate the electronic structure of the material and form ion superhighway on the heterogeneous interface,promoting electron transport and ion diffusion rate.Secondly,the synergistic action between Ni/Co/Mn elements can improve the conductivity and structural stability of the sulfide,thus improving the material rate performance and cycle life.The electrochemical performance test showed that S-Ni/Co/Mn（OH）_x electrode could provide the maximum specific capacity of 372.2 m A h g^-1,and when the current density was increased to14 A g^-1,the specific capacity remained 84%,showing high specific capacity and excellent rate performance of the material.When it is assembled into S-Ni/Co/Mn（OH）_x//Zn battery with zinc sheet,it can contribute the maximum energy density of 618.39 Wh kg^-1 with the power density of 6.85 k W kg^-1,and still retain 96.7%of the initial capacity after 10,000 cycles.It is proved that the partial vulcanization composite modification method can improve the electrochemical properties of the materials.