High Performance Zinc Anode Modified By Conjugated Organic Porous Materials

Zinc ion batteries have attracted people'extensive attention due to the rich zinc resources,low cost and high safety.Zinc is considered as a competitive negative electrode because of its high theoretical specific capacity,low reduction potential,and environmental friendliness.However,zinc anode still suffers from uncontrollable growth of zinc dendrite and surface corrosion,which reduces its cycle life and hinders the application of zinc ion battery seriously.In this paper,different conjugated organic porous materials are designed and coated for zinc anode protection.The research contents are as follows:(1)Conjugated porous organic polymers(POPs)containing triazine ring and OH group were used for zinc anode protection,and a highly reversible and stable zinc anode was developed.The conjugated polymers(named TM-OH)were prepared by liquid phase polymerization of 2,5-dihydroxy-terephthalic acid formaldehyde and 2,4,6-trimethyl-1,3,5-triazine.The results showed that TM-OH was spherical in shape and had good thermal stability and hydrophilicity.It was found that TM-OH had the following advantages:1.The triazine ring group in fully conjugated TM-OH could provide Zn²⁺coordination sites and inhibit the growth of zinc dendrites;2.The rich OH groups in TM-OH ensure good electrolyte wettability and ionic conductivity.The electrochemical properties and mechanism of the system show that the zinc deposits of TM-OH@Zn anode grow horizontally,while the pure Zn anode grows as vertical dendrite.The symmetrical batteries with TM-OH@Zn anode exhibited highly reversible stripping/electroplating behavior and extremely low polarization potential(28 m V at 1 m A cm^-2).The TM-OH@Zn and?-Mn O₂ water-based zinc ion batteries showed good cycle stability(1200cycles at 0.5 A g^-1).(2)Design and synthesis of conjugated fluorinated organic skeleton(COFs)and its mechanism as a protective layer for zinc anode.2,3,5,6-tetrafluoro-terephthalaldehyde and 2,4,6-trimethyl-1,3,5-triazine were used to prepare fluorinated organic framework materials(named FCOFs)with specific surface area of 532.14 m² g^-1.When the FCOFs was applied as a zinc anode coating,the contact angle of the electrode surface decreased,which indicated that the FCOFs@Zn surface could ensure good electrolyte wettability.Excellent structural stability of TM-OH can provide“Protective wall”for zinc anode.The electrochemical results show that the FCOFS@Zn symmetric cell exhibits an extremely low polarization potential(2 m A cm^-2,25 m V),highly reversible stripping/plating behavior with excellent cycle stability(running well after 2000h cycle at 0.1 m A cm^-2)and better corrosion resistance.The enhancement of these electrochemical behaviors is closely related to the porous structure,stable conjugate structure and fluorine-containing functional groups of FCOFs.On this basis,the zinc ion batteries FCOFs@Zn//V₂O₅ and FCOFs@Zn//Mn O₂ have better comprehensive electrochemical properties than Zn//V₂O₅and Zn//Mn O₂ respectively,which proves the potential application of FCOFs@Zn.It is expected that the development of the zinc anode with no dendrite,corrosion resistance and long cycle life can be realized by properly designing the interface protective layer of porous organic polymer materials containing special functional groups,in this paper,hydrophilic conjugated POPs(TM-OH)and fluorinated COFs(FCOFs)were used for zinc anode protection.The structure-activity relationship of interface layer,functional groups and electrochemical properties of zinc anode was studied systematically,the growth of Zinc dendrite and the corrosion resistance of Zinc anode were improved,which laid a foundation for the development of high performance zinc anode and zinc ion battery.