| Being a new type of energy storage products,lithium-ion secondary battery?for short called lithium-ion battery?has been widely used in electric vehicles,aircrafts,base station backup power and other large projects.In our daily life,mobile phones,tablet PCs,laptops and cameras also use lithium-ion battery as a power source.Comparing with the traditional nickel-metal hydride batteries and lead-acid batteries,lithium-ion battery have some advantages themselves,such as long cycle life,no memory effect and high energy density.One of the issues of the lithium battery that the separator must have the function of block positive and negative,conducting ions.At present,lithium-ion battery usually uses polyolefin as separators,but those separators'porosities aren't high and liquid absorption are weak relatively.However,the separator obtained by electros-pinning method has lots of advantages,such as high porosity,high liquid absorption capacity and so on.Choosing the materials with high mechanical strength&barrier properties and low processing difficulty are very promising as lithium ion battery separator.Whereas,the common problem with electros-pinning films is their mechanical properties not good enough,which is a barrier for applicating the electrospinning separators to lithium-ion battery.The purpose of this paper is to improve the mechanical properties of the electrospinning separator.EVOH was used as raw material to prepare Ionic polymer EVOH-SO3Li.EVOH-SO3Li separator was fabricated by electros-pinning.Polydopamine?PDA?was used to modify electrospinning separator,and then we obtained PDA modified separator.FTIR test result showed that PDA existed on the surface of the fibers;SEM test result showed the fibers'surface change from smooth to rough,and the diameter of fibers was increased.those suggested the fibers were covered by PDA.Tensile test result showed that compared to pure separator,modified separator's maximum tensile strength increased by 760%;TGA test result showed that the initial thermal decomp-osition temperature of modified separator increased,the decomposition temperature at 10%weight loss was 343?,comparing with pure separator,PDA modified separator increased by30%.The porosity of PDA modified separator declined slightly,meanwhile the liquid absorption rate improved greatly.And Dimensional stability&Anti-electrolyte corrosion performance kept the same.PDA modified separator was assembled into button battery,the electrochemical stability window of PDA modified membrane was 4.3 V;and after high rate discharge,the capacity of the battery remained at 97%;Ion conductivity was3.434×10-33 S/cm;After 50 times cycle charge and discharge,the capacity of the battery kept at 95.2%. |
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