| Poly-m-phenylene isophthalamide(PMIA) fiber is a special high-performance synthetic fibers with excellent performances of high strength and modulus, outstanding temperature and chemical resistance. Therefore, it will have great potential for development while the PMIA fibers is applied on high temperature resistant battery separator with its excellent thermal stability and mechanical properties.As the Lithium-ion battery has advantages of high voltage and specific energy, long cycle life, no memory effect, fast charging, lower self-discharge rate and environmental friendly, etc., it had became the most widely used battery in recent years.This experiment mainly adopts the polymerization at low temperature to be suitable for the preparation of aramid fiber type, it is m-phenylene diamine (MPD) and isophthalic formyl chloride (IPC) as raw materials, in polar organic solvents (DMAC) as the reaction system, with the medium of nitrogen protection and at the reaction temperature (-20 ℃), obtains liquid quality fraction is 25wt%, and organic fluorine modified doping in the solution (F-PMIA). This study discusses the PMIA and F-PMIA optimal spinning process parameters. The results show that:its molar ratio of optimum reaction is MPD:IPC:neutralizer=0.28:0.2805:0.28, the PMIA optimal spinning process parameters:concentration 14wt%, voltage 27kV,receive distance 19cm. F-PMIA fiber morphology of nanofiber membrane status analysis, the mass ratio of F-PMIA-organic fluorine:PMIA:DMAC=0.15:0.675:6.875 is the optimum proportion F-PMIA nanofibrous membrane, voltage 30kV, receive distance 19cm, the fluid ratio 0.2L/h.It adopts SEM-EDX, pore size distribution, FTIR, TG tests to study PMIA and F-PMIA nanofiber membrane, and researches thermoshrinking, permittivity, water contact angle and electrolyte contact angle performances. The results showed that:In relative to PMIA nanofibrous membrane, F-PMIA nanofibrous surface contains a lot of C, O, Cl, Na and F element, and possesses average pore size 0.37μm, narrower pore size distribution than PMIA membrane. Both of membranes show good thermal stability performance, The addition of organic fluorine slightly reduces the initial thermal weightless temperature F-PMIA membrane, so that the weightless temperature drops from 426 ℃ to 409 ℃. The membrane’s electrolyte contact angle of F-PMIA membrane is 9°, meanwhile, water contact angle reaches up to 111°, which expressions good performance of water repellency and hydrophilic electrolyte.The PMIA, F-PMIA membrane and commercial PE separator were assembled to lithium-ion battery to test the charge and discharge cycle performance of battery. The ionic conductivity and interfacial properties of the separators were tested by AC impedance methods, and the electrochemical stability of the separators were tested by Linear sweep voltammetry methods. The results show that:the PMIA separator and separator had the interfacial impedance of 195 Ω and 200 Ω respectively, the ion conductivity of 0.6mS/cm and 0.54 mS/cm, the decomposition voltage of 4.7V and 5.7V and the electrochemical stability window of 0～5V and 0～6V. F-PMIA and PMIA electrolyte separators have good compatibility of the interface with anode (lithium).The initial discharge specific capacity of the Li-ion batteries with three kinds of PE, PMIA and F-PMIA separators was 131mAh/g,145mAh/g and 140mAh/g respectively, the capacity of PMIA and F-PMIA separator is slightly higher than PE separator.The charge-discharge efficiency of the battery was almost higher than 98% in 20 cycles. Thus PMIA nanofibrous membrane and F-PMIA nanofibrous membrane has good prospects as a kind of lithium-ion battery separator material.
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