CN100565975C - A kind of polyalkylene microporous diaphragm for lithiam ion battery and manufacture method thereof - Google Patents
A kind of polyalkylene microporous diaphragm for lithiam ion battery and manufacture method thereof Download PDFInfo
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- CN100565975C CN100565975C CNB2006101379491A CN200610137949A CN100565975C CN 100565975 C CN100565975 C CN 100565975C CN B2006101379491 A CNB2006101379491 A CN B2006101379491A CN 200610137949 A CN200610137949 A CN 200610137949A CN 100565975 C CN100565975 C CN 100565975C
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Abstract
Patent disclosure of the present invention a kind of polyalkylene microporous diaphragm for lithiam ion battery and manufacture method thereof, it is by one polyethylene layer, the multilayer material that one deck polypropylene layer etc. overlap mutually, the overall structure of the microporous polyolefin laminated diaphragm that thermally induced phase separation technology manufactures after the application enhancements, having one deck in adjacent polyethylene and polypropylene layer at least is to contain a certain amount of ethylene-propylene copolymer, to improve their compatibility.Its advantage is: 1) overall structure of this microporous polyolefin laminated diaphragm has improved the fail safe of barrier film under the situation that does not influence other performance and realized lower closed pore temperature and than higher broken film temperature, improved the thermal endurance of barrier film; 2) barrier film is difficult for curling, outer damage being had high resistance and high mechanical properties, the reliability that has improved barrier film processing and used; 3) manufacturing process is simple, only needs just can realize to improve a little on the basis of general thermally induced phase separation.
Description
Technical field
Patent of the present invention relates to the exploitation and the manufacturing field of lithium ion battery, especially a kind of polyalkylene microporous diaphragm for lithiam ion battery and manufacture method thereof.
Background technology
The release of SONY success in 1991 first business-like lithium ion battery, caused developing rapidly of chargeable battery of new generation.Compare nickel-cadmium cell and Ni-MH battery, lithium ion battery has the energy density height, the life-span is long and the voltage advantages of higher.Lithium ion battery is widely used on automobile, motorcycle, the electric bicycle, particularly portable electronic product at present, as the product of aspects such as notebook computer, mobile phone, gamma camera, mp3, mp4.The composition of lithium ion battery comprises: the positive level of cobalt acid lithium, carbon negative pole, electrolyte and barrier film.Wherein, the barrier film between anode and negative pole is a kind of membrane for polymer with little porous, and it is the important component part of lithium ion battery, and it mainly acts on and is: (1) separates positive and negative electrode, and the electronics in the battery can not be passed freely through; (2) can allow the electrolyte solution intermediate ion between between both positive and negative polarity, freely pass through.The micro-porous amount of barrier film, mechanical performance and temperature variant performance quality are determining the interfacial structure of battery, the internal resistance of battery, and then affect the key characteristic such as capacity, cyclicity, battery charging and discharging current density of battery, therefore the quality of membrane properties plays an important role for the combination property that improves lithium ion battery, is the vitals of lithium ion battery.
At present, lithium ion battery separator mainly is the little porous membrane of TPO, and manufacture method commonly used can be divided into substantially extends port-creating method (also claiming dry method) and thermally induced phase separation (also claiming wet method), and it is different fully that little porous of these two kinds of methods forms mechanism.
The dry process principle be earlier with crystalline polymer (as PP, PE) melt at heavily stressed film extrusion after the match, obtain to have lamellar structure then through Overheating Treatment, promptly so-called hard elastics material perpendicular to extruding direction and being arranged in parallel.After the polymer film with hard elastics that makes thus carried out longitudinal stretching, separate between the platelet, and a large amount of fentos occur, produce the network structure in a kind of slit-shaped space, form a large amount of microcellular structures therefrom, promptly make micro-porous film through thermal finalization again.The patent and the prior art of this respect have:
1, the micro-porous film of the poly mixing of different molecular weight or polyethylene and polyacrylic mixing, be expressed in EP-A-336170, Japan Patent No.H2-21559, No.H2-334309, No.H5-331306, patent CN1057873C, CN1329638A, United States Patent (USP) 5385777 and 5480745.
2, the micro-porous film that forms of the perforated membrane lamination of different materials is expressed in USP4650730, Japan Patent No.62-10857, No.62-53813, No.63-308866, No.H6-20671.
3, by binder and utilize heat and pressure in conjunction with laminated multilayer micro-porous film of two-layer perforated membrane etc.
Dry process is fairly simple and pollution-free, but the difficult control of product thickness, aperture and porosity, mechanical strength is relative relatively poor with endurable thorn intensity, particularly can't produce thin film, as the product below the 20 μ m, so this method can't satisfy the requirement of more and more slimming trend of lithium ion battery separator.
Wet method is a kind of method for preparing micro-porous film that development in recent years is got up, and it is to utilize thermoplastic, crystalline high polymer and some high boiling micromolecular compound at high temperature (the melting temperature T that generally is higher than polymer
m) following blend formation homogeneous phase solution, then this solution is extruded and formed certain thin slice, thin slice brought out with certain speed or quenching be separated, carry out biaxial tension then, the back employing solvent wash method that stretches is washed low-molecular material off, carry out drying then cleaning solvent is vapored away, then can be made into the micro-porous film material.The patent and the prior art of this respect have:
Thermoplastic resin such as polyethylene, polypropylene individual layer micro-porous film are expressed in GB1180066, USP3679538, USP4190707, USP5173235, Japanese patent laid-open publication gazette No.46-40119, No.55-32531, No.59-37292 etc.
This method can be controlled thickness, aperture and the porosity of product preferably, has mechanical strength and endurable thorn intensity preferably, and can produce relatively thinner film, the thickness of barrier film can reach below the 20 μ m, can satisfy the requirement of more and more slimming trend of lithium ion battery separator, be a kind of up-and-coming manufacture method, use commonplace at present.
The shortcoming of this method is, up to now, the lithium ion battery separator of wet production still all is that the micro-porous film by individual layer constitutes, and this individual layer micro-porous film performance can not be satisfactory in some field.The barrier film that it can not satisfy lithium ion battery strengthens and safe requirement.
Use the electronic product miniaturization constantly of lithium ion battery and use more and more universal, and during products such as notebook computer, mobile phone, gamma camera and the explosion accident that occurs, people are had higher requirement to the fail safe of lithium ion battery, and the fail safe that therefore improves lithium ion battery separator has become the focus content of research.
At first lithium ion battery separator should have suitable closed pore temperature.This is because externally in the short circuit, the Joule heat that forms owing to battery short circuit makes the battery heating temp raise, at this moment battery diaphragm is out of shape owing to temperature raises, the aperture of micro-porous film dwindles gradually, ion is by difficulty, being equivalent to resistance increases, all disappearing up to micropore is diaphragm closed pore, at this moment ion can not pass through fully, so just can prevent the rising of internal temperature of battery, thereby can not make internal temperature of battery reach the point of ignition of the fusing point of lithium electrode or electrolyte and cause the generation of fire and explosion accident, thereby reach purpose of safety.Be referred to as closed pore temperature with the corresponding temperature of diaphragm closed pore.So the closed pore temperature of lithium ion battery separator is very important, closed pore temperature is low more, so just can under lower temperature, stop ion to pass through, so just can prevent the rising of internal temperature of battery, but closed pore temperature can not be too low, when too low, when the temperature tip has rising, will upset ion flow, this phenomenon can influence the operate as normal of battery.If closed pore temperature is too high, will cause serious problems such as lithium battery blast on fire.Generally should be in 120-140 ℃ scope.
Lithium ion battery separator also should have heat resistance, and promptly barrier film should be able to be kept closed pore state always and be indeformable up to certain higher temperature after closed pore.In detail, raise distortion and after micropore being disappeared be diaphragm closed pore, it will intercept the electric current of battery, have the effect that stops the temperature rising as lithium ion battery separator Yin Wendu.If but at this moment barrier film does not have enough heat resistances, the barrier film temperature behind the closed pore continues to rise, and when reaching a higher temperature range, barrier film further melts, and membrane ruptures then takes place, and at this moment Dui Ying temperature is referred to as broken film temperature.If membrane ruptures, positive and negative electrode will directly contact and explode, and this also is breakneck.So lithium ion battery separator should have enough heat resistances, make barrier film keep its shape more than the melt temperature, to keep closed pore situation to a high as far as possible temperature at it as far as possible.This barrier film begins until the temperature difference between the broken film temperature is big more from closed pore temperature, the time that then stops ion to pass through is also long more, and still can keep its integrality than higher temperature lower diaphragm plate at this, make breaking fast of barrier film with regard to having prevented Yin Wendu from rising really like this, thereby have very high security performance.
At present, the closed pore temperature of individual layer micro-porous polypropylene film is at 170 ℃ or higher, and the shortcoming of this temperature is the fusing point near lithium, and obviously this is unsafe.And the closed pore temperature of the little porous polyethylene membrane of individual layer relatively low be 135 ℃, more suitable, but its broken film temperature is also low, near 145 ℃, just the temperature difference between closed pore temperature and the broken film temperature only has 10 ℃, the heat resistance that is it is poor, this is very unsafe, and, the elastic return of the little porous polyethylene membrane of individual layer is poor, easily produces when causing packing into battery to stretch, so its production performance and serviceability all are very low, therefore thermoplastic resin individual layer micro-porous film all needs to improve aspect security reliability.
In a word, though dry process, or wet processing, and it is low and microporous polyolefin separator product that broken film temperature is high has become important exploration content to study and produce closed pore temperature.
Summary of the invention
A kind of polyalkylene microporous diaphragm for lithiam ion battery of patent of the present invention and manufacture method thereof are in order to overcome the shortcoming that current microporous polyolefin film barrier film exists, and are intended to improve the fail safe of lithium ion battery microporous polyolefin barrier film and a kind of new technique scheme of designing.It is to make on the basis of microporous polyolefin barrier film at thermally induced phase separation (also claiming wet method), has adopted new membrane configuration and new process, thereby has produced a kind of high performance microporous polyolefin barrier film that has.Design feature and manufacturing process aspect from product is described below below:
This polyalkylene microporous diaphragm for lithiam ion battery of the present invention, it is with thermoplastic, crystalline high polymer and some high boiling micromolecular compound adopt thermally induced phase separation to make the microporous polyolefin barrier film of mutual perforation, it is characterized in that: this microporous polyolefin barrier film is the overall structure that adopts the microporous polyolefin laminated diaphragm that multilayer material and structure manufacture, be that it is by one polyethylene layer, one deck polypropylene layer, one polyethylene layer, the multilayer material of one deck polypropylene layer etc., overlap mutually and form, wherein, minimumly to form overall structure by three strata alkene layer coextrusion, recommend to adopt the two layers of polypropylene film to clip the sandwich construction of layer of polyethylene film, and have one deck (being polyethylene layer or polypropylene layer) at least in every adjacent polyethylene and polypropylene layer is the blend that contains a certain amount of ethylene-propylene copolymer, the ratio that adds ethylene-propylene copolymer is the 5-50% of blend unit of weight, and recommending the ratio of adding ethylene-propylene copolymer is the 20-40% of blend unit of weight.Because polyethylene and polyacrylic compatibility are relatively poor, the main purpose that adds a certain amount of ethylene-propylene copolymer is exactly to improve their compatibility, makes to have realized between this sandwich construction that little porous connects the compatibility of heat resistance.
The polypropylene that constitutes polypropylene layer is to adopt high isotacticity, and polyethylene layer is to adopt high density polyethylene (HDPE).When two or more polypropylene layers are attached in the polyene layer integral body, each polypropylene layer can have different molecular weight and characteristic, when two or more polyethylene layers are attached in the polyene layer integral body, each polyethylene layer can have different molecular weight and characteristic, can adjust corresponding performance like this.Can contain surfactant, antioxidant and other additives in polypropylene and the polyethylene.
Generally, the thickness of lithium ion battery separator depends primarily on mechanical strength in the scope of 12～50um, the minimized needs of performance and battery.
In this patent product, each polyethylene or polypropylene single thin film can reach 3um to the 20um scope in final products.The integrally-built thickness of this patent product microporous polyolefin laminated diaphragm can reach below the 20 μ m, until 10 μ m.In drawing process, the thickness of the little porous multilayer barrier film that obtains can be measured, and can obtain different-thickness.The final thickness of little porous multilayer barrier film is as the criterion with its final instructions for use.
Recommend to adopt the two layers of polypropylene film to clip the sandwich construction of layer of polyethylene film, also be because after this little porous multilayer barrier film formation overall structure, except having high heat resistance, it is difficult for curling, outer damage had high resistance and high mechanical strength, therefore, it is a kind of lithium ion battery separator of high reliability from the fail safe that mechanical properties has also improved little porous multilayer barrier film.
This microporous polyolefin laminated diaphragm patented product has following performance:
1, porosity
Porosity recommends to adopt 40-60% at 35-80%.If less than 35%, it is too little that the ion of barrier film passes ability; If greater than 80%, the insufficient strength of barrier film itself, its mechanical property and anti-perforate degradation.
2, puncture intensity
In the battery pack process of assembling, barrier film directly contact has the positive pole and the negative pole of crust, or stands the charging and the discharge of repetition in actual use, when inside battery forms skeleton, can form the flaw that causes short circuit in barrier film inside.Therefore in order to stop the generation of this situation, the puncture intensity of barrier film should be best, and the puncture intensity of the patented product of this little porous multilayer barrier film is greater than 400g.
3, pore size
Barrier film is thin more, just can improve the impedance of energy content of battery density and reduction battery, but along with barrier film is more and more thinner, its aperture and pore-size distribution is extremely important for the both positive and negative polarity short circuit that prevents lithium battery.In wet processing, the size and the distribution in aperture are relevant with quantity, extrusion temperature and the stretching condition of second component that adds.The aperture of this little porous multilayer barrier film patented product is between 0.01-0.1 μ m, and during less than 0.01 μ m, the ability of passing of lithium ion is too little, and promptly permeability is low excessively; During greater than 0.1 μ m, because inside battery forms the generation of skeleton, the easy short circuit of battery.
4, air penetrability
Air penetrability is by decision such as the connectivity in the pore size of barrier film, pore-size distribution, porosity and hole.Can adopt the gurley index to characterize air penetrability, it is meant that under certain pressure certain volume gas is by the needed time of barrier film.Because the tortuosity of micropore is different in the micro-porous film, although microporous barrier aperture and porosity are approaching, but its air penetrability is not exclusively approaching, so in order to guarantee that battery has enough lithium ion penetration powers, the air penetrability of this little porous multilayer barrier film patented product is below 400s/cc, can improve the ion transfer ability of barrier film, export due performance.
5, hot strength
In length and breadth to hot strength all greater than 50MPa, when guaranteeing to be used for lithium ion battery separator, under the hot strength that has more than the 50MPa, barrier film can not rupture.
6, elongation at break
Elongation at break is greater than 50%, and it can avoid because distortion, the electrode shape of battery be irregular etc. factor to cause the short circuit of battery.
7, percent thermal shrinkage
Laterally percent thermal shrinkage is less than 3%, and vertically percent thermal shrinkage should be less than 5%, and this can be avoided causing when battery heats up suddenly electrode exposed.
8, closed pore temperature and broken film temperature
Closed pore temperature is 130-140 ℃, and broken film temperature is 160 ℃ more than-170 ℃, and the difference of broken film temperature and closed pore temperature reaches more than 30 ℃, and the closed pore temperature that has satisfied lithium ion battery separator well is low, the security requirement that broken film temperature is high.Just its low-melting polyethylene layer is with the rising of internal temperature of battery, and fusion makes the micropore closure, and isolated effectively electric current passes through, and dystectic polypropylene layer still can provide the integrality of barrier film under higher temperature, thereby has realized good security performance.
The manufacture method of this patent product microporous polyolefin laminated diaphragm:
As previously mentioned, so-called thermally induced phase separation (being also referred to as wet method usually), it is to utilize thermoplastic, crystalline high polymer and some high boiling micromolecular compound blend at high temperature to form homogeneous phase solution, then this solution is extruded and formed certain thin slice, thin slice brought out with certain speed or quenching be separated, carry out biaxial tension then, the back employing solvent wash method that stretches is washed low-molecular material off, carrying out drying then vapors away cleaning solvent, pass through thermal finalization again, then can be made into the micro-porous film material.
The manufacture method of this patent product microporous polyolefin laminated diaphragm is exactly on the basis of general general thermally induced phase separation, has done corresponding improvement according to the sandwich construction of this patent product and the characteristics that add different materials and has formed. and concrete production procedure comprises: (1) is the ethylene-propylene copolymer mixing granulation of blend unit of weight 5-50% with polyethylene or polypropylene and content at first; (2) with polyethylene and the polypropylene blend that has added ethylene-propylene copolymer, or polypropylene and the polyethylene blend that added ethylene-propylene copolymer respectively on double screw extruder separately and high boiling micromolecular compound solvent extrude, plastifying fusion is a homogeneous phase solution; The ratio of the two, polyene or polyene mixture content are the 10-35% of unit of weight, high boiling micromolecular compound solvent is the 90-65% of unit of weight; If the content of polyene is less than 10%, then not only production cost improves, and fluctuation appears in melt easily when going out die head, can't keep the good casting sheet processability and the integrality of diaphragm; If the content of polyene is greater than 35%, then the porosity of film forming is low also little with the aperture, can't satisfy the requirement of micro-porous film.So the air penetrability of controlling micro-porous film by the content that changes polyene in above-mentioned scope is fine; Solvent can be fat or cyclic hydrocarbon, as: nonane, decane, hendecane, atoleine etc. and other mineral oil, as long as can at high temperature fully compatiblely with polyene just can adopt, liquid flux is to join in the polyene of fusion at the middle part of double screw extruder; The temperature of extruder depends on the type of the polyene and the solvent of use, suggestion; The extruder temperature of polyethylene and solvent is 170-230 ℃, and the extruder temperature of polypropylene and solvent is 190-250 ℃; (3) several homogeneous phase solutions of extruding are according to layer of polyethylene (or one deck polypropylene), one deck polypropylene (or layer of polyethylene), layer of polyethylene (or one deck polypropylene), one deck polypropylene (or layer of polyethylene) ... be staggered order on the multilayer die head extruder respectively by behind each layer die head coextruded multilayer film, be coextruded into compound film sheet again; The die head interlabial gap normally 0.6 arrives 2mm, and the heating-up temperature of die head is 160-220 ℃; (4) will on slab roller, draw by the compound film sheet that the multilayer die head is extruded and get flakiness, with auxiliary pasters such as air knife or pressure rollers; (5) obtain the gel diaphragm by the cold bath chilling, suggestion is cooled to 30-50 ℃ with the speed greater than 60 ℃/min, otherwise the degree of crystallinity of diaphragm improves, and is difficult to form the suitable gel diaphragm that stretches.In addition, by control cooldown rate and chilling temperature, can adjust the aperture of microporous barrier; (6) the gel diaphragm is carrying out biaxial tension after preheating, and draft temperature is 115-150 ℃, and the draw ratio suggestion is more than 3, and biaxial tension can be biaxial tension simultaneously or substep biaxial tension; (7) film after stretching is washed solvent in the film off by sink, and the solution that is used for cleaning solvent can be volatile, comprises hexane, heptane, chlorinated hydrocabon etc.; (8) through removing wash solution with mode of heating, air-dry mode etc. with the film behind the solution washing; (9) dried film is to carry out thermal finalization under 120-150 ℃ in temperature, and the shrinkage in width that makes it is below 8%, thereby improves the elongation at break of film.
This patent product microporous polyolefin laminated diaphragm has the following advantages: 1, the integrally-built advantage of microporous polyolefin laminated diaphragm, it at first is the excellent properties of having realized being equal to single-layer septum at aspect of performances such as porosity, puncture intensity, pore size, air penetrability, hot strength, elongation at breaks equally, and the while has remedied the weak point of single-layer septum, the fail safe that has promptly improved barrier film.This is because after adopting the overall structure of this microporous polyolefin laminated diaphragm, had lower closed pore temperature and than higher broken film temperature, improved the temperature difference between closed pore temperature and the broken film temperature, this temperature difference can reach more than 30 ℃, improved the thermal endurance of barrier film, can prevent that lithium ion battery from catching fire and explosion accident takes place.2, after the overall structure with this microporous polyolefin laminated diaphragm, barrier film is difficult for curling, outer damage being had high resistance and high mechanical properties, therefore also improved the reliability of barrier film processing and use from mechanical properties, thereby the overall structure of the little porous multilayer barrier film of this polyene kind will become a kind of lithium ion battery separator of high reliability.3, manufacturing process is simple, only need just be improved and can realize by the tip on the basis of general thermally induced phase separation.
Embodiment
Here general thought according to the present invention provides three specific embodiment, in these three examples, adopted different embodiments all to obtain effect preferably respectively, and their performance parameter and two comparison example are contrasted, see table 1 for details, they have all adopted following identical method of testing:
1, film thickness: adopt vertical optical meter or other suitable calibrators to measure
2, air penetrability: measure according to JIS P8117 method
3, porosity: depend on the thickness of Mechanical Method calibrator measurement and the thickness of gravimetric method
4, hot strength and elongation at break: depend on the situation of the sample that is about 200mm, wide 15 ± 1mm, test according to ASTM D822
5, puncture intensity: depend on that diameter is that the syringe needle of 1mm moves to sample with 50mm/min speed, pierce through the record full-scale reading until test.
6, thermal contraction: depend on the film vertical and horizontal, in 85 ℃ baking oven, keep 8h.Aperture: the absorptivity that depends on nitrogen
7, closed pore temperature and broken film temperature: film sample is whole to be fixed on the fixture of diameter 60mm, heating is after one minute in hot blast is heated to the baking oven of preset temperature, the taking-up heated sample is cooled off, and detects the air penetrability (measuring according to JIS P8117 method) of film when room temperature again.
Embodiment 1
At polypropylene (M
w=4.8 * 10
5Melt index is 2.1,170 ℃ of fusing points) ethylene-propylene copolymer of adding 30% carries out the blend granulation in, this blend with 25% unit of weight ratio adds wherein double screw extruder (Φ 58mm then, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by in double screw extruder, making polypropylene blend fusion and mixed atoleine under 250 ℃ and 200rpm condition, form polypropylene blend solution, the solution that obtains is extruded from two top layers of three layers of die head by measuring pump, and every layer thickness is approximately 170 μ m.
Simultaneously with the high density polyethylene (HDPE) (ρ=0.968g/cm of 25% unit of weight ratio
3, M
w=3.5 * 10
5) add another double screw extruder (Φ 58mm, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by in double screw extruder, making polyethylene fusion and mixed atoleine under 220 ℃ and 200rpm condition, form polyethylene solution, the solution that obtains is extruded from the sandwich layer of three layers of die head by measuring pump, thickness 150 μ m.
After three layers of melt go out by the die head composite co-extruding, on the slab roller of 35 ℃ of maintenances, draw and get flakiness,, obtain the gel diaphragm of 480-520 μ m then by the cold bath chilling with auxiliary pasters such as air knife or pressure rollers.Diaphragm is then 5 * 5 times of 115-150 ℃ of following biaxial tensiones, and the film after the stretching obtains the little porous multilayer barrier film of 20 μ by washing (washed with heptane), drying and thermal finalization 10 seconds, and the performance of barrier film sees Table 1.
Embodiment 2
Polypropylene (M with 25% unit of weight ratio
w=4.8 * 10
5Melt index is 2.1,170 ℃ of fusing points) add wherein double screw extruder (Φ 58mm, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by in double screw extruder, making polypropylene fusion and mixed atoleine under 250 ℃ and 200rpm condition, form polypropylene solution, the solution that obtains is extruded from two top layers of three layers of die head by measuring pump, every layer thickness 170 μ m.
Simultaneously at high density polyethylene (HDPE) (ρ=0.958g/cm
3, M
w=6.8 * 10
5) in add 35% ethylene-propylene copolymer and carry out the blend granulation, this mixture with 25% unit of weight ratio adds double screw extruder (Φ 58mm then, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by in double screw extruder, making polyethylene fusion and mixed atoleine under 220 ℃ and 200rpm condition, form polyethylene solution, the solution that obtains is extruded from the sandwich layer of three layers of die head by measuring pump, thickness 150 μ m.
After three layers of melt go out by the die head composite co-extruding, on the slab roller of 35 ℃ of maintenances, draw and get flakiness,, obtain the gel diaphragm of 480-520 μ m then by the cold bath chilling with auxiliary pasters such as air knife or pressure rollers.Diaphragm is then 5 * 5 times of 115-150 ℃ of following biaxial tensiones, and the film after the stretching obtains the little porous multilayer barrier film of 20 μ by washing (washed with heptane), drying and thermal finalization 10 seconds, and the performance of barrier film sees Table 1.
Embodiment 3
Polypropylene (M with 25% unit of weight ratio
w=4.8 * 10
5Melt index is 2.1,170 ℃ of fusing points) add wherein double screw extruder (Φ 58mm, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by in double screw extruder, making polypropylene fusion and mixed atoleine under 250 ℃ and 200rpm condition, form polypropylene solution, the solution that obtains is extruded from two top layers of three layers of die head by measuring pump, every layer thickness 170 μ m.
Simultaneously at high density polyethylene (HDPE) (ρ=0.958g/cm
3, M
w=6.8 * 10
5) in add 30% ethylene-propylene copolymer and carry out the blend granulation, this mixture with 25% unit of weight ratio adds double screw extruder (Φ 58mm then, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by in double screw extruder, making polyethylene fusion and mixed atoleine under 220 ℃ and 200rpm condition, form polyethylene solution, the solution that obtains is extruded from the sandwich layer of three layers of die head by measuring pump, thickness 150 μ m.
After three layers of melt go out by the die head composite co-extruding, on the slab roller of 35 ℃ of maintenances, draw and get flakiness,, obtain the gel diaphragm of 480-520 μ m then by the cold bath chilling with auxiliary pasters such as air knife or pressure rollers.Diaphragm is then 5 * 5 times of 115-150 ℃ of following biaxial tensiones, and the film after the stretching obtains the little porous multilayer barrier film of 20 μ by washing (washed with heptane), drying and thermal finalization 10 seconds, and the performance of barrier film sees Table 1.
Control examples 1
High density polyethylene (HDPE) (ρ=0.958g/cm with 25% unit of weight ratio
3, M
w=6.8 * 10
5) adding double screw extruder (Φ 58mm, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by in double screw extruder, making polyethylene fusion and mixed atoleine under 220 ℃ and 200rpm condition, form polyethylene solution, the solution that obtains is extruded from die head by measuring pump.Melt draws on the slab roller of 35 ℃ of maintenances and gets flakiness by after the die head coextrusion, with auxiliary pasters such as air knife or pressure rollers, obtains the gel diaphragm of 480-520 μ m then by the cold bath chilling.Diaphragm is then 5 * 5 times of 115-130 ℃ of following biaxial tensiones, and the film after the stretching obtains the little porous single-layer septum of polyethylene of 20 μ by washing (washed with heptane), drying and thermal finalization 10 seconds, and the performance of barrier film sees Table 1.
Control examples 2
Polypropylene (M with 25% unit of weight ratio
w=4.8 * 10
5Melt index is 2.1,170 ℃ of fusing points) add double screw extruder (Φ 58mm, L/D=48, the high shear form), and the atoleine of 75% unit of weight ratio joins double screw extruder by the side direction feeding, by make polypropylene fusion and mixed atoleine under 250 ℃ and 200rpm condition in double screw extruder, form polypropylene solution, the solution that obtains is extruded from single layer die by measuring pump.After melt is extruded by die head, on the slab roller of 35 ℃ of maintenances, draw and get flakiness,, obtain the gel diaphragm of 480-520 μ m then by the cold bath chilling with auxiliary pasters such as air knife or pressure rollers.Diaphragm is then 5 * 5 times of 120-150 ℃ of following biaxial tensiones, and the film after the stretching obtains the little porous single-layer septum of polypropylene of 20 μ by washing (washed with heptane), drying and thermal finalization 10 seconds, and the performance of barrier film sees Table 1.
The performance comparison table of the barrier film of three examples of implementation of table 1 and two comparison example
Claims (7)
1, a kind of polyalkylene microporous diaphragm for lithiam ion battery, it is with thermoplastic, the fat of crystalline high polymer and high boiling micromolecular compound or cyclic hydrocarbon solvents adopt thermally induced phase separation to make the microporous polyolefin barrier film of mutual perforation, it is characterized in that: this microporous polyolefin barrier film is the overall structure that adopts the microporous polyolefin laminated diaphragm that multilayer material and structure manufacture, be that it is by one polyethylene layer, one deck polypropylene layer, one polyethylene layer, multilayer materials such as one deck polypropylene layer, overlap mutually and form, and have one deck (being polyethylene layer or polypropylene layer) at least in every adjacent polyethylene and polypropylene layer is the blend that contains a certain amount of ethylene-propylene copolymer, and the proportion that adds ethylene-propylene copolymer is the 5-50% of blend unit of weight.
2, a kind of polyalkylene microporous diaphragm for lithiam ion battery according to claim 1, the overall structure that it is characterized in that microporous polyolefin laminated diaphragm be minimum be that two layers of polyethylene film folder one deck polypropylene screen or the coextrusion of two layers of polypropylene film folder layer of polyethylene film form overall structure by three strata alkene layers.
3,, it is characterized in that the overall structure of microporous polyolefin laminated diaphragm recommends to adopt the two layers of polypropylene film to clip the three-decker of layer of polyethylene film according to claim 1 and 2 described a kind of polyalkylene microporous diaphragm for lithiam ion battery.
4, a kind of polyalkylene microporous diaphragm for lithiam ion battery according to claim 1 is characterized in that the ratio of adding ethylene-propylene copolymer in polyethylene layer or polypropylene layer is the 20-40% of blend unit of weight.
5, a kind of polyalkylene microporous diaphragm for lithiam ion battery according to claim 1 and 2, it is characterized in that constituting in the overall structure of microporous polyolefin laminated diaphragm, polypropylene layer is the polypropylene that adopts high isotacticity, and polyethylene layer is to adopt highdensity polyethylene.
6, a kind of polyalkylene microporous diaphragm for lithiam ion battery according to claim 1 and 2 is characterized in that the microporous polyolefin laminated diaphragm overall structure, has 130-140 ℃ closed pore temperature and 160-170 ℃ broken film temperature simultaneously.
7, a kind of manufacture method of making the described polyalkylene microporous diaphragm for lithiam ion battery of claim 1, concrete processing step is as follows: (1) is the ethylene-propylene copolymer mixing granulation of blend unit of weight 5-50% with polyethylene or polypropylene and content at first; (2) with polyethylene and the polypropylene blend that has added ethylene-propylene copolymer, or polypropylene and the polyethylene blend that added ethylene-propylene copolymer respectively on double screw extruder separately and high boiling micromolecular compound solvent extrude, plastifying fusion is a homogeneous phase solution; The two mixed proportion, polyene or polyene mixture content are the 10-35% of unit of weight, high boiling micromolecular compound solvent is the 90-65% of unit of weight; Solvent is fat or cyclic hydrocarbon, adopts nonane, decane, hendecane or atoleine; The temperature of extruder: the extruder temperature of polyethylene and solvent is 170-230 ℃, and the extruder temperature of polypropylene and solvent is 190-250 ℃; (3) several homogeneous phase solutions of extruding are according to layer of polyethylene (or one deck polypropylene), one deck polypropylene (or layer of polyethylene), layer of polyethylene (or one deck polypropylene), one deck polypropylene (or layer of polyethylene) ... be staggered order on the multilayer die head extruder respectively by behind each layer die head coextruded multilayer film, be coextruded into compound film sheet again; The die head interlabial gap is 0.6 to 2mm, and the heating-up temperature of die head is 160-220 ℃; (4) will on slab roller, draw by the compound film sheet that the multilayer die head is extruded and get flakiness, with auxiliary pasters such as air knife or pressure rollers; (5) by the cold bath chilling, be cooled to 30-50 ℃ with speed greater than 60 ℃/min, obtain the gel diaphragm; (6) the gel diaphragm is carrying out biaxial tension after preheating, and draft temperature is 115-150 ℃, and draw ratio is more than 3; (7) film after stretching is washed solvent in the film off by sink, and the solution that is used for cleaning solvent adopts volatile hexane, heptane or chlorinated hydrocabon; (8) remove wash solution with the film behind the solution washing with mode of heating or air-dry mode; (9) dried film is to carry out thermal finalization under 120-150 ℃ in temperature, and the shrinkage in width that makes it is below 8%.
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| CNB2006101379491A CN100565975C (en) | 2006-11-02 | 2006-11-02 | A kind of polyalkylene microporous diaphragm for lithiam ion battery and manufacture method thereof |
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| CNB2006101379491A CN100565975C (en) | 2006-11-02 | 2006-11-02 | A kind of polyalkylene microporous diaphragm for lithiam ion battery and manufacture method thereof |
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| CN100565975C true CN100565975C (en) | 2009-12-02 |
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