Research On Transition Metal Oxide/Hydroxide As Aqueous Zinc Ion Battery Cathode Materials

Aqueous zinc ion batteries（ZIBs）combine the high safety and low cost of water-based batteries,as well as the advantages of high theoretical capacity and low redox potential.ZIBs is a promising electrochemical energy storage device.However,at present,ZIBs lacks a cathode material that can fully take advantage of the zinc anode.The research carried out in this paper aims to synthesize ZIBs cathode materials and study their performance.The researches on transition metal oxides（Zn O）and transition metal hydroxides,which are rarely reported in this research direction,are carried out,mainly covering the following two parts:（1）A temperature adjustment method was used to prepare manganese-doped zinc oxide microspheres with rough surface.The microsphere structure is rich in ultrafine nanoparticles and internal mesopores,which can provide more ion diffusion channels and reduce the stress and strain in the electrochemical process.At the same time,doping Mn into the Zn O structure can not only adjust the electronic structure of the material,but also increase its electrical conductivity,thereby improving the reaction kinetics of the electrode material.The DFT calculation proves that the doping of Mn can reduce the diffusion barrier of Zn²⁺.The Mn-doped Zn O is used as cathode of ZIBs has good rate performance.The specific capacity can reach 268.1 m A h g^-1at 1A g^-1,while it still retains 163.8 m A h g^-1at 5 A g^-1.In addition,high energy density(206.9 Wh kg^-1),power density(6896.7 W kg^-1)and excellent cycle stability（compared to the first cycle,after 10,000 cycles,the capacity retention rate is about146.7%）.This material has more energy storage potential.（2）Transition metal hydroxide materials are synthesized through simple hydrothermal reaction and used in ZIBs cathode materials for electrochemical performance research.La（OH）₃/Ni Mn LDH is a composite structure of nanosheets and nanoparticles.In the electrochemical process,different structures support and restrict each other,which improves the stability of the structure while also buffering the volume shrinkage/expansion during the electrochemical process.The combination of Ni Mn LDH and La（OH）₃also improves the conductivity of the material.The La（OH）₃/Ni Mn LDH composite structure has better electrochemical performance than the single structure of other control hydroxides.The specific capacity of the electrode can reach 284.2 m A h g^-1at 1 A g^-1.At 5 A g^-1,106.3 m A h g^-1is retained.At the same time,the hydroxyl on the surface of the hydroxide and the water molecules in the aqueous electrolyte will undergo surface remodeling,stabilizing H⁺at the electrode/electrolyte interface,and promote the diffusion of H⁺into the material,thereby improving the electrochemical performance of the material.