The Study Of PPEK And PVDF Composite Membrane As Separator For Lithium Ion Battery

Lithium-ion batteries have received considerable attention for its high energy density.The separator is one of the core material in lithium-ion batteries.20% of the costs of production for the whole battery is spent on the separator.Meanwhile,most of the safety problem for Lithium-ion batteries is induced by the separator.Polyolefin(polyethylene and polypropylene)is the main commercial separator material.However,the commercial separators have some shortcoming for example: low thermal deformation temperature,low electrolyte uptake,low porosity.These shortcomings limit its application in high power application field,such as electric vehicles,hybrid electric vehicles and robots.Non-woven membrane with high porosity and electrolyte uptake produced by electrospining,has been applied in various fields.Poly(phthalazione ether ketone)(PPEK)has high thermal stability up to 400 ?.Consequently,the combination of non-woven membrane and PPEK is expected to be used for Lithium-ion batteries separators to overcome the weakness of commercial separator material.The contents of this study are as follows:1.Prepare PPEK/PVDF electrospinning fiber.Study the mechanical properties,pore structure and wettability of the composite membrane.Test the electrochemical property,cycle and C-rate performance of the lithium-ion battery.The results show that the Young's modulus of composite membrane is 185 MPa,the porosity is 73.6 %,the electrolyte uptake is 490 %,and the cycle and C-rate performance are better than commercial PP membrane.2.Make another layer of PVDF non-woven membrane on PPEK/PVDF electrospinning fiber to prepare double layer of non-woven membrane.Study the mechanical properties,pore structure and wettability of the composite membrane.Test the electrochemical property,cycle and C-rate performance of the lithium-ion battery.The results indicate that the Young's modulus of composite membrane is 200 MPa,the porosity is 63.1 %,the electrolyte uptake is337 %,and the cycle and C-rate performance are better than commercial PP membrane.Meanwhile,the composite separator has the shut-down function,the shut-down temperature is180 ?.