Preparation And Modification Research Of Hydrogel Electrolyte For Flexible Zinc Ion Battery

Due to their advantages of high energy efficiency,long cycle life and high energy density,Lithium ion batteries（LIBs）are widely used in portable electronics,electric cars and energy storage.However,the lack of lithium resources and the increasing price of lithium salt have aroused people’s concerns about the sustainable development of lithium-ion batteries.At the same time,LIBs also exhibit poor safety,flammable and explosive electrolytes,and other shortcomings.In recent years,flexible and wearable electronic devices,such as smart clothing,implantable medical devices,artificial electronic skin,electronic bracelets and other new flexible wearable electronic products have developed rapidly,which put forward higher requirements for the flexibility and safety of energy storage equipment.So it is necessary to consider and develop non-rigid ZIBs with light,thin,safety and integrated configurations.Because of the high theoretical capacity（820 m Ah/g and 5855 m Ah/cm³）,low redox potential（-0.76 V vs.SHE）,low cost and decent safety of zinc anode,aqueous Zn-ion batteries（ZIBs）have shown great potential in the above application fields,attracting research and development booms worldwide.In this work,flexible Zn-ion batteries were assembled by preparing and modifying polyacrylamide（PAM）hydrogel electrolyte.The main research contents include:The PAM hydrogel electrolyte was prepared by a method of free radical polymerization.After optimization experiments,the water absorption of PAM hydrogel electrolyte can reach 1325.58%.The tensile property is relatively good,it can be stretched to 1500% deformation,and its ionic conductivity is as high as 3.75×10^-2 S/cm.At 1 C,after 200 cycles,the capacity retention rate of the flexible battery assembled with this electrolyte is 56.94%.Aiming at the problem of poor cycle performance of PAM-based flexible zinc ion batteries,by introducing carboxymethyl cellulose（CMC）into the PAM hydrogel electrolyte to form a double network structure to modify it,the physical properties and electrochemical performance of the electrolyte were improved.After the introduction of the double network structure,the tensile property of the hydrogel electrolyte has increased from 1500% to 3000%,the water absorption rate has increased from 1325.58% to 2138.03%,and the ionic conductivity is 1.303×10^-2 S/cm.The study also found that the carboxyl group in CMC can regulate the deposition process of zinc ions on the surface of the zinc electrode,and effectively inhibit the growth of zinc dendrites.Thus,the flexible zinc-ion battery assembled with this electrolyte exhibits a competitive electrochemical performance: a capacity retention rate of 90.18% after 500 cycles at 1 C.The flexible zinc ion batteries also have excellent bending resistance.