Study On Preparation And Electrochemical Properties Of High Performance Aqueous Zinc Ion Battery Electrode Materials

With the progress of technology,energy storage equipment has become an indispensable part of people's lives.Although lithium ion battery(LIBs)has the advantages of high energy density,long cycle life and Wide range of operating temperatures,it has been widely used.but lithium metal is scarce and expensive,and the scientific community has to study other system batteries to meet future energy storage applications.Because of its high safety,friendly environment,abundant zinc resources and low cost,water system zinc ion battery(ZIBs)is regarded as a competitive substitute for large-scale application of lithium ion battery in the future.As an important part of battery,electrode material has great influence on battery performance.Nowadays,the scientific research on zinc electricity mainly focuses on the positive electrode,such as Prussian blue analogues,manganese series materials,vanadium series materials and organic materials,and has made remarkable progress.However,the series of problems of zinc metal negative electrode have not been solved well.Mainly reflected in the occurrence of side reactions,aggravated electrode corrosion,resulting in low Coulomb efficiency(<90%);zinc dendrite production,resulting in shorter life;and zinc deposition potential(-0.76 V vs.standard hydrogen electrode)lower than hydrogen evolution potential,resulting in electrolyte instability.In view of the problems existing in the above zinc negative electrode,the researchers are mainly through electrolyte modification and modification of zinc metal surface to achieve uniform zinc deposition and stripping,reduce dendrite production and improve cycle life.However,this can not fundamentally solve the problem.Based on this,the first experimental part of this paper is the first time to use mixed valence Cu_2-xSe materials as negative electrode of zinc ion battery.The material was characterized by XRD,SEM,TEM,Roman and other tests,and was assembled into a half cell as cathode material to analyze its performance.Cu_2-xSe electrode with nanorod morphology was observed to have extremely strong cycling stability.At 5A g^-1high current density,30000 cycles can be stabilized.To commercialize the Cu_2-xSe as negative electrode matching Mn O₂positive electrode assembly water rocking chair full battery,It has well electrochemical performance.Especially at a current density of 2 A g^-1,With 20000 cycles of long cycle life.the Zn²⁺insertion Cu_2-xSe structure is also revealed as an embedding/extraction reaction mechanism.Advantages of intercalation Cu_2-xSe anode,In order to solve the problem of zinc metal negative electrode in water zinc ion battery,It provides a new way.The proposed battery is ideal for long cycle life and high safety,expected for future large-scale energy storage applications.In addition,the circulation performance of manganese based materials is unstable due to the dissolution of manganese.In the second part of this paper,the positive electrode of zinc ion battery was studied by synthesizing nitrogen-doped Na₂Mn₃O₇(N-NMO)material.It is found that the successful doping of nitrogen and the provision of oxygen vacancies can increase the electron density and reduce the band gap ratio of the material.At the same time,adding a small amount of Mn²⁺in the electrolyte can effectively inhibit the dissolution of manganese.This series of measures plays an obvious role in improving the electrochemical properties of manganese materials.The results show that the discharge capacity of the N-NMO positive electrode is 308 m Ah g^-1at the current density of 0.5 A g^-1,and 100 m Ah g^-1at 10 A g^-1,showing superior rate performance.At 2 A g^-1,the capacity can still reach 150m Ah g^-1after 550 cycles.Compared with the unmodified NMO cathode,N-NMO cathode has more outstanding performance in terms of cycling performance and magnification performance.Finally,we use CV and GITT to reveal that the system is a process of diffusion effect and pseudocapacitance effect.