Nowadays,lithium ion batteries(LIBs)have been widely used in convenient energy storage equipment,new energy vehicles,power grid energy storage and other fields,but the shortage of lithium resources,safety and other problems,hinder the further development of LIBs.Because of the advantages of abundant natural resources and high safety,aqueous Zinc ion batteries(ZIBs)are considered as an alternative to LIBs and can be widely used in large-scale power grid energy storage.Zinc ions have a higher charge density than lithium ions,and the ions are more difficult to be intercalated/extracted from the crystal lattice of cathode materials,which makes the available cathode material very limit.ZIBs are currently facing two major problems:first,electrode materials are mainly limited to manganese/vanadium based materials,Prussian blue analogue,and so on,but these electrode materials are affected by some factors,restricting the further development of ZIBs;Second,the electrochemical energy storage mechanism of manganese/vanadium based materials has not been clearly explored,and remain elusive.The key to the development of ZIBs is to find suitable new zinc ion electrode materials and explore the charge storage mechanism.This paper focuses on the study of zinc ion battery electrode materials,starting from the synthesis and modification of different kinds of materials,to understand the electrochemical properties of materials,explore the zinc storage mechanism of the synthesized materials.The research contents are as follows:In the first part,PbO was synthesized from waste lead-acid battery by wet chemical conversion method,and PbO was used as the electrode material of zinc ion battery.The materials and electrodes were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and electrochemical characterization methods.Electrochemical tests show that the designed Zn/PbO electrochemical system has a specific capacity of 136m Ah/g at the current density of 0.1A/g.By systematically exploring the energy storage mechanism of the system,it is found that(ZnSO4)[Zn(OH)2]3·5H2O(ZHS)nanosheets can spontaneously from on the PbO surface as solid interface layer(SEI)passivation layer to prevent the dissolution of active materials.With the help of ZHS,the reversible phase transition occurs between Pb SO4 and Pb.The synergetic two-phase reaction mechanism produces an ultra-flat voltage platform during charging and discharging.In the second part,bismuth sulfide(Bi2S3)and reduced graphene oxide(RGO)composites with different graphene contents were prepared by hydrothermal reaction,which were used as cathode materials for ZIBs.XRD,Raman,SEM and XPS characterizations show that the prepared Bi2S3nanoparticles successfully incorporates with RGO.Compared with bare Bi2S3 and the mixed components,Bi2S3-RGO20,the Bi2S3 mixed with 20 mg of RGO(~10 wt.%)has the best electrochemical performance.At the current density of 0.1A/g,the initial discharge capacity of Bi2S3-RGO20 is as high as 313.2m Ah/g,while the bare Bi2S3 only delivered 209.4m Ah/g.Besides,the pseudocapacitive effect in Bi2S3-RGO20 is greater than the other samples,and the electrochemical performance is significantly improved.Furthermore,the electrochemical charge storage of Bi2S3/RGO composite was explored by ex-situ XRD and XPS.The experiment show that Bi2S3/RGO composite provides abundance diffusion channel for zinc ions,enabling zinc ions to be reversibly inserted/extracted during charge and discharge,accompanied by the reversible formation and dissolution of ZHS. |