Polytetrafluoroethyllithium lithium-ion battery separator and preparation methodTechnical field
The present invention relates to a kind of polytetrafluoroethyllithium lithium-ion battery separator and preparation method
Background technology
Lithium ion battery has the characteristic of high-energy-density, long circulation life, memory-less effect; Harmful substances such as not leaded, cadmium, free from environmental pollution, belong to the environmental protection battery; Have again safety, reliable and can fast charging and discharging etc. advantage, thereby become the focus of novel power supply technical research in recent years.Lithium ion battery can be widely used in portable type electronic product, as: required rechargeable batteries such as mobile phone, notebook computer, Video Camera also can be used as the required electrical source of power of electric automobile and hybrid vehicle etc.The lithium ion battery development is exceedingly fast, and paid attention to by various countries deeply.Lithium ion battery mainly is made up of positive and negative electrode material, electrolyte and barrier film.One membrane material is arranged between lithium ion cell positive and negative pole, be commonly referred to barrier film, it is the important component part of lithium ion battery.The main effect of barrier film is: (1), isolate positive and negative electrode and the electronics in the battery can not be passed freely through; (2), can allow ion (in the electrolyte solution) between both positive and negative polarity, freely pass through.The quality of the quality decision battery performance of lithium ion battery septation performance, the development of barrier film and the raising of performance are promoting the development of battery and the raising of performance.
The diaphragm material of commercialization lithium ion battery mainly still adopts the composite membrane of polyethylene, microporous polypropylene membrane or the material modified formation of coating on polyethylene, microporous polypropylene membrane basis at present.As certificate " Chinese science and technology industry " the 1st phase in 2003, it is primary raw material that China has developed with the polypropylene, through technologies such as fusion, stretching, thermal finalizations, prepares capillary polypropylene lithium ion battery separator material.As publication number is that the patent " a kind of nothing extraction composition polymer lithium ion battery separator and preparation method " of CN1481036A promptly is that the composite membrane that matrix forms is filled in coating on polyethylene, microporous polypropylene membrane rack.And for example publication number is the patent " lithium ion battery separator and preparation method thereof " of CN101271965A, publication number is the patent " method for preparing polyolefin micro-porous " of CN 1978037A, and publication number is that patent " a kind of thermo-stable lithium ion battery septum " of CN 101271967A etc. all is to be that material of main part prepares lithium ion battery separator with polyethylene or polypropylene.Yet though China has grasped the technology of producing barrier film, the investment of membrane apparatus needs more than one hundred million funds.So up to the present form industrial-scale production also seldom.Simultaneously, show that according to data also there are many shortcomings in polyethylene, polypropylene lithium ion battery film, relatively poor such as absorbency, be unfavorable for the lithium ion migration, cause battery large current density difficulty; Polypropylene is difficult to bonding, and it is not tight that barrier film is combined with positive/negative plate, influences specific energy; The production cost height, the equipment complexity, price is more high.
Domestic production polytetrafluoroethylene micro-filtration membrane production technology reaches its maturity at present, as publication number be the patent " polytetrafluoroethylporous porous membrane and manufacture method thereof " of CN1102748A introduce with polytetrafluoroethylene not sintered body under specified temp, stretch, the polytetrafluoroethylporous porous membrane of making mainly is applicable to the suspended particulates in the gases such as air that use in the clean room that is captured in semi-conductor industry etc.What and for example two patents of invention of " manufacture method of polytetrafluoroethylporous porous membrane " of application number 941120570 " using porous membrane preparation with polytetrafluorethylene " and application number 951133470 were introduced expands film forming with the polyflon process, the made film of typing is mainly used in the compound fabric of processing waterproof and breathable under specified temp and time.Polytetrafluoroethylene is commonly called as the plastics king, has high-and low-temperature resistance; Anti-strong acid, alkali and organic solvent; Characteristics such as oxidation resistance is strong.The micro-filtration membrane made from polytetrafluoroethylene, has the required higher porosity of battery diaphragm, lower resistance, high tear resistance, performances such as better elastic, but also have good chemical stability and thermal stability, stable performance in 125 ℃ of strong acid, highly basic and strong redox environment, than polyethylene, microporous polypropylene membrane more excellent performance, especially its good anti-oxidant reducing property has more superiority to useful life and the safety in utilization that improves lithium ion battery.But because the fusing point of polytetrafluoroethylene is higher than polyethylene, polypropylene, thus overheated molten certainly at battery, close micropore, stopping the discharge aspect need solve by the composite low melting point polymer.
Summary of the invention
The objective of the invention is to disclose a kind of polytetrafluoroethyllithium lithium-ion battery separator and preparation method, it is to do base material with polytetrafluoroethylporous porous membrane, at one or two surface impregnation, coating or the spraying one layer of polymeric of polytetrafluoroethylporous porous membrane, dry thermocompression forming forms composite membrane.Polytetrafluoroethylporous porous membrane has high tear resistance, and good chemical stability, thermal stability and non-oxidizability can improve the useful life and the safety in utilization of lithium ion battery.Polymer coating is met high temperature can fusion close fenestra, makes barrier film become insulator, prevents that electrolyte from passing through, thereby reaches the purpose that breaking current stops discharge, improves the safety in utilization of battery.
Method of the present invention adopts following technical scheme to realize:
Polytetrafluoroethyllithium lithium-ion battery separator disclosed by the invention and preparation method, earlier with polyflon by the biaxial tension masking technique, making thickness is 10 μ m～50 μ m, average pore size is at the perforated membrane of 0.1 μ m～15 μ m, then in its one side or two coated polymer material suspension, dry fixing back forms composite diaphragm with the hot-forming back of 80 ℃～100 ℃ warm-up mill, prepared barrier film, film thickness is 15 μ m～60 μ m, its average aperture is at 0.01 μ m～10 μ m, 100 ℃～140 ℃ of the self-closing temperature of fenestra.
Embodiment
The following examples can make those skilled in the art more fully understand the present invention, but do not limit the present invention in any way.
Embodiment 1:
To account for barrier film gross mass 80% (mass percent, as follows) polyflon to become thickness through biaxial tension be that 20 μ m, average pore size are the perforated membrane of 3 μ m, simultaneously apply at it again and account for barrier film gross mass 20% (dry meter, as follows) solid content be 40% polyethylene suspension, dry fixing back is with the hot-forming back formation of 90 ℃ warm-up mill composite diaphragm.The finished film performance: the thickness of film is 25 μ m, and average pore size is 0.3 μ m, 115 ℃ of the self-closing temperature of fenestra.
Embodiment 2:
It is that 30 μ m, average pore size are the perforated membrane of 0.4 μ m that the polyflon that accounts for barrier film gross mass 70% is become thickness through biaxial tension, the solid content that accounts for barrier film gross mass 30% in its coated on both sides is 40% polyethylene, polypropylene (mass ratio is 1: 1) mixing suspension again, and dry fixing back is with the hot-forming back formation of 100 ℃ warm-up mill composite diaphragm.The finished film performance: the thickness of film is 40 μ m, and average pore size is 0.05 μ m, 135 ℃ of the self-closing temperature of fenestra.
Embodiment 3:
It is that 30 μ m, average pore size are the perforated membrane of 0.4 μ m that the polyflon that accounts for barrier film gross mass 80% is become thickness through biaxial tension, simultaneously applying the solid content that accounts for barrier film gross mass 20% at it again is 40% Tissuemat E, the mixing suspension of polypropylene wax (mass ratio is 3: 1), and dry fixing back forms composite diaphragm with the hot-forming back of 100 ℃ warm-up mill.The finished film performance: the thickness of film is 35 μ m, and average pore size is 0.1 μ m, 125 ℃ of the self-closing temperature of fenestra.
Embodiment 4:
It is that 35 μ m, average pore size are the perforated membrane of 0.2 μ m that the polyflon that accounts for barrier film gross mass 75% is become thickness through biaxial tension, simultaneously applying the solid content that accounts for barrier film gross mass 25% at it again is 45% polyethylene, the mixing suspension of Kynoar (mass ratio is 5: 1), and dry fixing back forms composite diaphragm with the hot-forming back of 90 ℃ warm-up mill.The finished film performance: the thickness of film is 45 μ m, and average pore size is 0.05 μ m, 120 ℃ of the self-closing temperature of fenestra.