Preparation And Performance Study Of Polyvinyl Alcohol-based Battery Separators Containing Metal Ions

In recent years,with the continuous development of modern industry,polymer materials such as plastics,rubber,and synthetic fibers have been widely used.However,most polymer materials are flammable,which causes fires in countries around the world.Moreover,the polymer material used for the battery separator is easily destroyed by heat,resulting in spontaneous combustion of the battery.These have seriously affected personal safety.Nowadays,PVA is widely used as a synthetic material because of its good biocompatibility,harmless to human body and low cost.But this synthetic material has the disadvantage of being flammable.Therefore,polyvinyl alcohol is modified to improve its flame retardant performance and understand its flame retardant mechanism.Finally,it is applied according to the principle.In this paper,polyvinyl alcohol is used as the main raw material in combination with metal ions to prepare polyvinyl alcohol polymers containing acrylates.The flame retardant properties and mechanism of metal ion-containing polyvinyl alcohol materials are discussed,as well as their application in battery separators.(1).Polyvinyl alcohol is used as a raw material for crosslinking with acrylate to prepare a polyvinyl alcohol/calcium acrylate polymer containing metal ions.Infrared analysis,ICP,LOI,thermogravimetry,XRD,pyrolysis product(Py-GC-MS)analysis and SEM characterization of the product and its gel were carried out.The characterization results showed that the acrylate was successfully cross-linked on the polyvinyl alcohol.The limit oxygen index and thermogravimetric test of the gel substance confirmed that the metal ion plays a role in improving the thermal stability of the polymer.The dried gel was then analyzed by thermal cracking products(Py-GC-MS),and the products obtained at different temperatures after sintering were tested by infrared,XRD and SEM.The mechanism shows that metal ions can promote the formation of carbon layers,and the formation of carbonates or oxides plays a protective role in the interior of the material,showing significant flame retardant properties.(2)It is further applied to prepare a polyvinyl alcohol fiber battery separator with good thermal stability to improve the safety performance of the battery.The polyvinyl alcohol fiber battery separator containing monovalent metal ions and divalent metal ions was prepared by grafting acrylate,and the product was subjected to infrared analysis,LOI,thermogravimetric analysis,SEM and electrochemical performance characterization.The characterization results indicate success acrylates grafted with different ionic valences.And it shows that the monovalent metal ion and the divalent metal ion have the same thermal stabilization effect.It is proved that the monovalent metal ion also produces the effect of the carbon layer and the carbonate covering the surface of the material.Through electrochemical characterization of polyvinyl alcohol fiber battery separators containing metal ions of different valence states,lithium iron phosphate half-cells composed of monovalent lithium ion separators have higher discharge capacity,better long cycle and rate performance,which helps to improve the capacity and safety performance of the battery.