Preparation Of Layered Manganese Dioxide Cathode Material And Its Performance In Aqueous Zinc Ion Battery

Water-based zinc ion secondary battery has become a research hotspot because of its high safety and easy to manufacture.layered MnO₂,as a representative layered structure of zinc cathode material,can provide more abundant electrochemical active sites and ion diffusion channels.However,its limited interlayer spacing and electronic conductivity limit its rate performance.in addition,the serious problem of structural collapse in the cycle also limits its cycle performance.Based on the above problems,this paper will modify layered MnO₂ by the following methods.From the starting point of improving the transport efficiency of layered MnO₂ zinc ions,the interlayer spacing is gradually expanded by protonation and macromolecular reagent intercalation.Through regulation and control,the layer spacing of layered MnO₂is expanded from 7.04?to 7.5?.Because of the expansion of layer spacing,the maximum charge and discharge current intensity of layered Mn O2 is increased from 0.4A/g to 10 A/g,and the discharge capacity retention of 0.1 A/g is increased from 74%of65 laps to 90%of 200 laps,and the electrochemical properties of the materials can be greatly improved.In order to make up for the electrical conductivity of layered Mn O2,graphene was directly added into the hydrothermal solution as the nucleation center to make layered MnO₂ grow in situ on its surface,and the poor electronic conductivity of layered MnO₂ was compensated by the synergistic effect between them.Thanks to this method,the maximum discharge intensity of the material has been increased from 0.4 A/g to 13 A/g,and the rate performance has been greatly improved.At the same time,the capacity retention rate of 160 cycles under 0.2A/g current intensity is 75%,and the cycle performance has also been significantly improved.By calculating and comparing the reactant diffusion coefficients of the materials prepared by the above two modification methods,it is known that the electrochemical reaction process of layered MnO₂ tends to be controlled by electrochemical steps.In order to improve the structural collapse of layered MnO₂ during the cycle,polypyrrole was coated on the surface by using the oxidizability of layered MnO₂itself.The electrochemical performance test results show that the capacity retention of the modified material is 94%under the current intensity of 0.2 A/g,which is greatly improved compared with the cycle performance of 72 cycles and 35%before modification.In addition,the maximum discharge intensity of the material reached 8 A/g,the capacity is restored to 91%of the original 91%when it is changed to 1 A/g after the end of high current discharge,which proves that the material has good stability under the impact of high current.This paper systematically studies the electrochemical energy storage characteristics of the obtained materials,and reveals the influence law and internal relationship of the structural characteristics of the materials on the energy storage characteristics,which provides a new idea and valuable reference for the design of a new type of high-performance chemical power supply.