Preparation Of Gel Polymer Electrolyte And Its Performance For Aqueous Zinc Ionic Batteries

As commonly used energy storage devices,batteries play a significant role in various fields which need energy source supply.As recyclable secondary batteries,conventional lithium-ion batteries have been widely used in energy conversion and various large-scale energy storage applications.Due to the shortcomings such as explosion,high production cost and harsh assembly requirements,the sustainable development of lithium-ion batteries has been greatly challenged.The ensuing water-based rechargeable secondary battery has become a research topic,mainly because of easy preparation process,low cost,safe working process and environmental friendly.Among them,aqueous zinc-ion batteries are emerging secondary batteries developed in recent years.Due to the high abundance of zinc,environmental friendliness,low cost,high safety,high theoretical specific capacity,and simultaneous Zn²⁺/Zn low redox potential,aqueous zinc-ion batteries have attracted much attention.In recent years,kinds of electronic products have occupied the market,and the demand for miniature portable flexibility has increased.Therefore,the design and application of energy storage equipment are also confronted with higher requirements.Gel polymer electrolytes,which are flexible and liquid retaining,can play the dual role of electrolyte and membrane in batteries.They are considered as intelligent materials with many applications.However,there are still some problems such as the limited flexibility of battery electrolytes and the unavoidable freezing of aqueous electrolytes at low temperatures exist in batteries,so it is particularly vital to develop new electrolyte materials.In this paper,a new GPE with the environmental friendly biomass material sodium alginate（SA）was prepared:（1）introducing graphene oxide to the double networks formed by SA and polyacrylamide.The SAG-assembled aqueous zinc-ion battery exhibited better electrochemical stability and performance than the conventional aqueous liquid electrolyte（LE）.After 500 cycles at a rate of 1 C,the battery assembled with SAG exhibited a discharge specific capacity retention rate of 63.3%and a Coulomb efficiency about 100%,while the capacity retention rate of the LE battery was only 33.2%.The anode zinc foil of the cycled SAG was relatively flat.SEM and EDS images proved that SAG could effectively suppress zinc dendrites.（2）The acrylamide monomer and zwitterionic monomer were copolymerized and grafted onto the main chain of SA as an antifreeze gel electrolyte（SAS）for zinc-ion batteries,which showed stable and excellent electrochemical performance.The strong hydration of the zinc salt and the chloride salt reduced the condensation temperature of the gel electrolyte,and the gel electrolyte can be charged and discharged normally without being frozen at-20°C.The addition of zwitterions promoted the ion migration,and showed a high ionic conductivity(10.38 m S cm^-1)at-20°C.The practical application of aqueous zinc-ion batteries equipped with SAS as a flexible energy storage device at-20°C was further explored.Results illustrated that the superb low temperature performance and the broaden applications of SAS in batteries.