Design Of Sulfonate Functionalized Gel Electrolytes And Study On Protection Mechanism Of Zinc Negative Electrode

Recently,rechargeable aqueous zinc-ion batteries（ZIBs）have garnered significant attention as a promising energy storage device to supplant lithium-ion batteries,owing to their low cost,high safety,environmental friendliness,high theoretical specific capacity of zinc metal(820 m Ah g^-1),low redox potential（-0.762 V vs.SHE）,and high abundance.However,the development of ZIBs is impeded by several issues such as zinc dendrites,hydrogen precipitation,corrosion,and side reactions during the cycling process.Utilizing gel electrolytes in ZIBs can effectively resolve these issues,and the excellent flexibility of the electrolyte can find applications in smart wear.Nonetheless,the gel electrolytes that are currently examined have certain insufficiencies pertaining to ionic conductivity,mechanical properties,chemical stability,and interfacial contact.As a result,this research focuses on resolving these deficiencies by designing the structure of the gel electrolyte for ZIBs and improving its performance.The results obtained are outlined as follows.（1）In order to improve the ionic conductivity and mechanical properties of the gel electrolyte,the method of adding inorganic clay to the polymer was adopted in this paper,making full use of the complementary advantages of organic and inorganic components,and the gel electrolyte with excellent properties was obtained to the maximum extent.In this system,PVA,CNC-C and sepiolite were used to design an organic-inorganic composite gel electrolyte.The sulfonic acid group in the polymer forms a hydrogen bond with the hydroxyl group in the sepiolite.The presence of these hydrogen bonds enhances the binding force between organic and inorganic components,thus improving the ionic conductivity and mechanical properties of the electrolyte.Moreover,the sulfonic acid groups in this gel electrolyte facilitate the uniform deposition of Zn²⁺,whereas the pores between the multilayer structures in the sepiolite further optimize the ion transfer channels and improve the transfer kinetics of Zn²⁺.Owing to the synergistic effect of organic-inorganic components,the Zn/Zn symmetric cell operates for a duration of more than 2000 hours,and the Zn/I₂full cell exhibits an ultra-stable lifetime of 10,000 cycles.（2）To overcome the issue of too much interfacial resistance,we developed a copolymer gel electrolyte with high adhesion,utilizing two monomers sodium allyl sulfonate and acrylamide and a free radical polymerization technique.The high adhesion of this copolymer gel electrolyte effectively resolved the interfacial contact problem between the gel electrolyte and the zinc anode,leading to a significant improvement in the interfacial dynamics.The sulfonic acid group in this gel electrolyte has a high affinity for Zn²⁺,which effectively improves the ionic conductivity and enables the polymer chain to re-regulate the flow of Zn²⁺at the micro-scale,facilitating the controlled deposition of Zn²⁺on the anode.The results exhibit that the AS-1.5 gel electrolyte attains an ultra-stable Zn deposition/exfoliation lifetime of over 1000 h,suppressing side reactions and enabling parallel Zn deposition,and a high cycle stability of over 500 cycles for Zn/Mn VO full cell and over 2500 cycles for Zn/HATN full cell.The molecular modulation was engineered to obtain a gel electrolyte with high ionic conductivity and good interfacial adhesion ability using the sulfonic acid group as a Zn²⁺transfer medium.In conclusion,this research devised novel gel electrolytes to address the aforementioned issues of existing gel electrolytes,leading to marked enhancements in ionic conductivity,mechanical properties,and interfacial contact,as well as remarkable electrochemical properties.Thus,these outcomes offer fresh concepts in the production of gel electrolytes for ZIBs.