CN106328860A

CN106328860A - Heat-shrinkage-resistant lithium ion battery diaphragm and pore-forming agent composition adopted by same

Info

Publication number: CN106328860A
Application number: CN201510348902.9A
Authority: CN
Inventors: 张汉鸿
Original assignee: LIAOYUAN HONGTU LI-ION BATTERY DIAPHRAGM TECHNOLOGY Co Ltd
Current assignee: LIAOYUAN HONGTU LI-ION BATTERY DIAPHRAGM TECHNOLOGY Co Ltd
Priority date: 2015-06-23
Filing date: 2015-06-23
Publication date: 2017-01-11
Anticipated expiration: 2035-06-23
Also published as: CN106328860B

Abstract

The invention discloses a heat-shrinkage-resistant lithium ion battery diaphragm and a pore-forming agent composition adopted by the same. The pore-forming agent composition comprises an organic pore-forming agent and an inorganic pore-forming agent, wherein the organic pore-forming agent is high-boiling-point low molecular weight organic matter preferably; the inorganic pore-forming agent is water-soluble inorganic nanoparticles preferably; and the pore-forming agent and the optional additive are jointly added to a film-forming material to form a lithium ion battery diaphragm with three kinds of microporous structures through processing of casting pieces. In addition, the heat-shrinkage-resistant lithium ion battery diaphragm has relatively low closed-hole temperature, high heat shrinkage resistance, high tensile strength, high puncture strength and relatively high diaphragm-rupture temperature, thereby ensuring safety in preparation and usage of the lithium ion battery.

Description

The lithium ion battery separator of a kind of resistance to thermal contraction and the pore former combination thing used

Technical field

The present invention relates to the preparation technology of battery diaphragm, be specifically related to the lithium of a kind of resistance to thermal contraction Pore former combination thing used in ion battery barrier film and its preparation process.

Background technology

Lithium ion battery is widely used in the fields such as telecommunications, energy storage and electrical source of power, main Will be made up of positive pole, negative pole, electrolyte and battery diaphragm, wherein, battery diaphragm is not lead Electricity, between positive pole and negative pole, prevent the two short circuit because of contact, allow electricity simultaneously Solving matter ion to pass through, thus produce electric current, current battery diaphragm mostly is has microcellular structure Polyolefin film, its performance determines the interfacial structure of battery, internal resistance etc., directly affects electricity The characteristics such as the capacity in pond, circulation and security performance, the battery diaphragm of excellent performance is to raising The combination property of battery has important function.

The performance of battery diaphragm mainly characterizes by following index: the property cut off requires battery diaphragm There is partition property and electronic isolation, it is ensured that effective mechanical isolation of positive and negative electrode；Porosity Require that barrier film has certain aperture and porosity, it is ensured that low resistance and high ion migration Rate, has good permeability to lithium ion；Chemical stability and electrical stability require barrier film tool Standby moisture-proof and electrolyte resistance corrosivity；Wellability requires the barrier film wellability to electrolyte Good, and there is preferable imbibition moisture-retaining capacity and ion permeability；Mechanical strength requires barrier film Enough mechanical properties and shock resistance is ensured, including puncturing while thickness is the least Intensity and hot strength；Security requirement barrier film heat stability to be had and automatically shut down protection Performance, including closed pore temperature and broken film temperature.It is phase between the multinomial performance index of battery diaphragm Mutual correlation, it is desirable to take into account multinomial performance, obtain indices all preferably battery diaphragm mesh Before still there is bigger difficulty.

Existing polyolefin battery separation film preparation method is broadly divided into wet method and dry method, the wettest The preparation process of method includes: add in polyolefin using little for high boiling point molecule as pore former, Heating is melt into homogeneous system, and then cooling occurs to be separated, with organic after biaxial tension Solvent extraction goes out little molecule, can prepare the micro-pore septum being mutually communicated.

There are some defects in traditional battery diaphragm wet method preparation process, including: in slab mistake Generally using a slab roller with refrigerating function to carry out one side cooling in journey, pore former seals Close not exclusively, easily flow out, cause micropore skewness；Extruding in different production steps Equipment is different, causes product quality pattern different, is difficult to control concordance；Generally extruding sets Standby, stretcher roller smooth surface, the membrane surface produced is smooth, with other material Adhesive power is poor, is unfavorable for researching and developing novel battery barrier film；After extraction, drying equipment generally uses Hydraulic giant and air gun two ways are carried out simultaneously, cause the surface of barrier film generally to have water wave, and flat Whole degree is the best.

Above-mentioned condition based on prior art, the preparation technology of battery diaphragm is entered by the present inventor Row research, it is therefore an objective to the preparation method of the battery diaphragm of resistance to thermal contraction is provided and uses the party's legal system The battery diaphragm with resistance to thermal contraction obtained.

Summary of the invention

In order to overcome the problems referred to above, the preparation method of battery diaphragm has been carried out sharp by the present inventor Meaning research, found that: by using organic pore former and the Inorganic pore forming agents of specific proportioning The pore former combination thing combined, adds with high-molecular polythene and ultra high molecular polyethylene For in the mixture of film-forming components, and optionally add other additive, through specific device After processes, it is possible to had simultaneously relatively low closed pore temperature, higher broken film temperature and Good mechanical strength and the lithium ion battery separator of good thermal shrinkage, thus complete this Bright.

It is an object of the invention to provide following aspect:

First aspect, the present invention provide a kind of lithium ion battery for preparing resistance to thermal contraction every The pore former combination thing of film, it is characterised in that said composition includes that organic pore former is with inorganic Pore former,

Preferably,

Described organic pore former is selected from high boiling point small organic molecule；

Described Inorganic pore forming agents is selected from water-soluble inorganic nano-particle.

Second aspect, the present invention also provides for above-mentioned pore former combination thing, it is characterised in that

Described high boiling point small organic molecule is that boiling point is higher than 200 DEG C, and number-average molecular weight is little In the liquid state organics of 500；

Described water-soluble inorganic nano-particle be particle diameter be the particles of inorganic material of 1～200nm.

The third aspect, the present invention also provides for above-mentioned pore former combination thing, it is characterised in that institute State high boiling point small organic molecule and be preferably selected from mineral oil, C_6-15Alkane, C_8-15Aliphatic carboxylic acid, C_1-4Alkyl ester, C_2-6One or more in halogenated alkane, it is highly preferred that

Described mineral oil is white oil；Described C_6-15Alkane selected from heptane, naphthalane, decane, ten One alkane and dodecane；Described C_8-15Aliphatic carboxylic acid is selected from capric acid, hendecoic acid and lauric acid； Described C_1-4Alkyl ester selected from methyl caprate, ethyl caprate, capric acid propyl ester, capric acid N-butyl, Hendecoic acid methyl ester, hendecoic acid ethyl ester, hendecoic acid propyl ester, hendecoic acid N-butyl, Lauric acid methyl ester, dodecanoate, lauric acid propyl ester, lauric acid N-butyl； Described C_2-6Halogenated alkane is selected from dichloroethanes, dichloropropane, chlorofluoroethane and fluorine chloropropane； And/or

Described water-soluble inorganic nano-particle is selected from water-soluble nano sulfate, water-soluble nano One or more in nitrate, water-soluble nano hydrochlorate, it is highly preferred that

Described water-soluble nano sulfate is selected from nanometer sodium sulfate, nanometer potassium sulfate and nano-sulfur Acid ammonium etc.；Described water-soluble nano nitrate is selected from nanometer sodium nitrate, nanometer potassium nitrate, receives Rice ammonium nitrate, nanometer magnesium nitrate and nanometer copper nitrate etc.；Described water-soluble nano hydrochlorate selects From nanometer sodium chloride, nanometer potassium chloride, nanometer ammonium chloride, nanometer magnesium chloride, nanometer chlorination Calcium and nanometer copper chloride etc..

Fourth aspect, the present invention also provides for above-mentioned pore former combination thing, it is characterised in that institute The weight ratio stating organic pore former and described Inorganic pore forming agents is (30～60): (1～10), It is preferably (35～55): (2～8), more preferably (40～50): (4～6).

5th aspect, the present invention also provides for above-mentioned pore former combination thing, it is characterised in that institute Stating organic pore former and be preferably white oil, described Inorganic pore forming agents is preferably nanometer magnesium chloride, excellent Selecting described pore former is white oil and the compositions of nanometer magnesium chloride.

6th aspect, the present invention also provides for above-mentioned pore former combination thing, it is characterised in that institute State pore former to add in polyolefin, it is preferable that be 100 weight portions with polyolefinic weight Meter, the addition of pore former is 20～70 weight portions, preferably 30～60 weight portions, more preferably It is 50 weight portions.

7th aspect, the present invention also provides for above-mentioned pore former combination thing, it is characterised in that institute State pore former to be preferably dividedly in some parts in polyolefin.

Eighth aspect, the present invention provides the preparation of the lithium ion battery separator of a kind of resistance to thermal contraction Method, it is characterised in that the method includes:

Step 1), by polyethylene or a combination thereof thing, above-mentioned pore former combination thing and optional its Its additive melting mixing, extrudes casting films；

Step 2), step 1) casting films extruded flows through the first slab roller and the second slab roller Between space, cast sheet；

Step 3), step 2) the most preheated roller of sheet, draw roll and the chill roll that obtain Carry out longitudinal stretching；

Step 4), step 3) the thin film both sides that obtain fix, successively through the first preheating zone, First drawing zone and the first cooling zone carry out cross directional stretch；

Step 5), step 4) thin film that obtains processes through extractant, is then dried；Preferably Ground, described being dried in drying device is carried out, and described drying device includes that multiple one-tenth broken line is arranged The transfer roller of cloth, is provided with for dry gas in the position that thin film contacts with transfer roller Rifle, the jet direction of the most described air gun preferably with the plane tangent of described transfer roller or with thin The direction of transfer of film is parallel；

Step 6), step 5) the thin film both sides that obtain fix, successively through the second preheating zone, Second drawing zone and the second cooling zone carry out second time cross directional stretch, obtain the electricity of resistance to thermal contraction Pond barrier film.

9th aspect, the lithium of resistance to thermal contraction that the present invention also provides for using said method to prepare from Sub-battery diaphragm, it is characterised in that this battery diaphragm include the first outer layer, the second outer layer and Being clipped in internal layer therebetween, described first outer layer, the second outer layer and internal layer have different Microcellular structure,

The average pore size of the most described first outer layer is 20～100nm, the second outer layer average Aperture is 30～140nm, and the aperture of internal layer is 50～180nm.

Another object of the present invention also resides in offer and a kind of implements what above-mentioned preparation method was used Device, it includes extrusion device, cooling roller device and drying device, wherein,

Described extrusion device includes machine barrel, is disposed in parallel in two poly-second of described machine barrel one end Ene compositions charging aperture and be respectively arranged on described machine barrel to enter away from described polyethylene composition Material mouth is two pore former charging apertures at 1/3 and 2/3 barrel length, and/or

Described cooling roller device includes the first slab roller and second that spacing is 180～580 μm Slab roller, the diameter of described first slab roller and the second slab roller is than for 1:(1～6), described First slab roller and the second slab roller rotate in opposite directions, it is preferable that the roller of described first slab roller The roller linear velocity numerical value of cylinder linear velocity and described second slab roller is equal, and/or

Described drying device includes the transfer roller that multiple one-tenth broken line is arranged, at thin film and transfer roller The position contacted is provided with for dry air gun, the jet direction of the most described air gun with The plane tangent of described transfer roller.

The present invention described below.

According to the present invention first is to the 7th aspect, it is provided that a kind of for preparing resistance to thermal contraction The pore former combination thing of battery diaphragm, it is characterised in that said composition includes organic pore former With Inorganic pore forming agents, it is preferable that

Described organic pore former is high boiling point small organic molecule, it is preferable that little point of high boiling point Sub-Organic substance is that boiling point is higher than 200 DEG C, and the liquid state organics that number-average molecular weight is less than 500, It is preferably mineral oil, C_6-15Alkane, C_8-15Aliphatic carboxylic acid, C_1-4Alkyl ester, C_2-6Halogenated alkane In one or more, wherein,

Described C_6-15Alkane is selected from heptane, naphthalane, decane, hendecane and dodecane, described C_8-15Aliphatic carboxylic acid is selected from capric acid, hendecoic acid and lauric acid, described C_1-4Alkyl ester is selected from Methyl caprate, ethyl caprate, capric acid propyl ester, capric acid N-butyl, hendecoic acid methyl ester, ten One ethyl carbonate, hendecoic acid propyl ester, hendecoic acid N-butyl, lauric acid methyl ester, ten Two ethyl carbonates, lauric acid propyl ester, lauric acid N-butyl, described C_2-6Halogenated alkane Selected from dichloroethanes, dichloropropane, chlorofluoroethane and fluorine chloropropane.

Described organic pore former is more preferably white oil.

Described Inorganic pore forming agents be selected from water-soluble inorganic nano-particle, it is preferable that water solublity without Machine nano-particle is 1～200nm selected from particle diameter, preferably 3～100nm, more preferably The water-soluble nano sulfate of 5～20nm, water-soluble nano nitrate, water-soluble nano salt One or more in hydrochlorate etc., wherein,

Described water-soluble nano sulfate is selected from nanometer sodium sulfate, nanometer potassium sulfate and nano-sulfur Acid ammoniums etc., described water-soluble nano nitrate is selected from nanometer sodium nitrate, nanometer potassium nitrate, receives Rice ammonium nitrate, nanometer magnesium nitrate and nanometer copper nitrate etc., described water-soluble nano hydrochlorate selects From nanometer sodium chloride, nanometer potassium chloride, nanometer ammonium chloride, nanometer magnesium chloride, nanometer chlorination Calcium and nanometer copper chloride etc..

Described Inorganic pore forming agents is more preferably nanometer magnesium chloride.

It is highly preferred that the compositions that described pore former is white oil and nanometer magnesium chloride.

In pore former, described organic pore former with the weight ratio of described Inorganic pore forming agents is (30～60): (1～10), are preferably (35～55): (2～8), more preferably (40～50): (4～6).

It is highly preferred that the compositions that described pore former is white oil and nanometer magnesium chloride, wherein, White oil is (30～60) with the weight ratio of nanometer magnesium chloride: (1～10), is preferably (35～55): (2～8), more preferably (40～50): (4～6), such as 45:5.

In the present invention, described pore former adds to polyolefin, it is preferable that with polyolefin Weight be 100 weight portion meters, the addition of pore former is 20～70 weight portions, be preferably 30～60 weight portions, more preferably 50 weight portions.

The inventors discovered that, when preparing lithium ion battery separator, add in preparation system Described pore former, described pore former can be uniform with the form of fine droplet and solid granule It is scattered in film forming matter, particularly polyolefin, the molten state combination that especially polyethylene is formed In thing, after its cooling film forming, pore former remains able in film with fine droplet and solid Short grained form is present in the slab of film, forms " occupy-place " effect, when the slab quilt of film After stretching, pore former is extracted membrane, then it can leave correspondingly micropore on film, makes The lithium ion battery separator prepared has microcellular structure, thus when lithium ion battery works, The lithium ion of abjection positive electrode can pass battery diaphragm.

The present inventors have additionally discovered that, described pore former is added from different pore former charge doors in batches Entering in film forming matter molten state compositions, pore former degree of scatter in preparation system is higher, More uniformly spreading of microwave drop and solid granule, so that the lithium ion battery prepared The aperture of every layer of microporous layers of barrier film all ratios are more uniform.

Additionally, the present inventor also has surprisingly found that, Inorganic pore forming agents is preparing lithium ion battery The mixing process of barrier film has stronger plasticising thickening power, makes the particle diameter of aggregated particle become Little, it is possible to suppression occurs big gathering, thus improves the puncture of the lithium ion battery separator prepared Intensity.

In the present invention, it is preferred to, described pore former is added and includes following weight proportion In polyethylene or a combination thereof thing,

High-molecular polythene 93～98 weight portion,

Ultra high molecular polyethylene 2～7 weight portion,

It is preferably,

High-molecular polythene 94～96 weight portion

Ultra high molecular polyethylene 4～6 weight portion,

More preferably,

High-molecular polythene 95 weight portion

Ultra high molecular polyethylene 5 weight portion.

In a preferred embodiment of the present invention, described pore former can also with include with The interpolation of lower weight proportion with the use of,

It is preferably,

More preferably,

Wherein,

Described antioxidant is selected from 4,4-thiobis (6-tert-butyl-m-cresol), dibutyl hydroxy Toluene, phosphite ester, tert-butylhydroquinone, preferably 4,4-thiobis is (between the 6-tert-butyl group Cresol), tert-butylhydroquinone, wherein, described dibenzylatiooluene is 3, the tertiary fourth of 5-bis- Base-4-hydroxy-methylbenzene, described antioxidant is more preferably 4,4-thiobis (first between the 6-tert-butyl group Phenol).

The inventors discovered that, antioxidant can suppress high-molecular polythene and supra polymer to gather The oxidative degradation of ethylene so that it is maintain higher number-average molecular weight, thus ensure that prepared The function admirable of lithium ion battery separator.

Described anti ultraviolet agent is selected from salicylic acid esters, benzophenone class, benzotriazole, replacement third Alkene nitrile, triazines and hindered amines, as oxybenzoic acid phenyl ester, 2-(2-hydroxyl-5- Aminomethyl phenyl) BTA, 2,4-DihydroxyBenzophenone, 2-hydroxyl-4-methoxyl group two Benzophenone, Octabenzone, 2-(the tertiary phenyl of 2'-hydroxyl-3', 5'-bis-)-5- Chlorination benzotriazole, single benzoic acid resorcinol, three (1,2,2,6,6-five first piperazines Piperidinyl) phosphite ester, 4-benzoyloxy-2,2,6,6-tetramethyl piperidines, 2,4,6- Three (2' n-butoxyphenyl)-1,3,5-triazines and HMPA etc..

The inventors discovered that, anti ultraviolet agent can absorb ultraviolet, reduces ultraviolet to preparing The radiolysis of lithium ion battery separator, strengthens its ageing resistace, extends lithium ion The service life of battery diaphragm.

Described antistatic additive is selected from cationic antistatic agent, anionic antistatic agents and nonionic Antistatic additive, preferably quaternary ammonium salt, ethoxy alkylation aliphatic alkyl amine, such as 18 Quaternary ammonium alkyl sodium.

Described antifoggant is selected from the ester of xylitol, sorbitol palmitate, lauric acid, span Series of surfactants, TWEEN Series surfactant or animi resin monoglyceride, preferably For span series and TWEEN Series surfactant.

According to a further aspect in the invention, described pore former be applied to one prepare have heat-resisting In the preparation method of the lithium ion battery separator shunk, the method comprises the following steps:

Step 1), extrusion: by above-mentioned polyethylene or a combination thereof thing, pore former and optional adding Add agent melting mixing, extrude casting films.

In a preferred embodiment in accordance with the present invention, described polyethylene or a combination thereof thing are preferred From high-molecular polythene and ultra high molecular polyethylene, more preferably high-molecular polythene and superelevation Molecular polyethylene is by weight (93～98): (2～7), more preferably (94～96): (4～6), the compositions of more preferably 95:5 composition, the number of described high-molecular polythene is divided equally Son amount is 100,000～600,000, preferably 200,000～500,000, and more preferably 300,000～400,000 are described The number-average molecular weight of ultra high molecular polyethylene is 1,200,000～1,500,000, preferably 1,300,000～140 Ten thousand.

In a preferred embodiment in accordance with the present invention, described pore former includes organic pore former And Inorganic pore forming agents, wherein, described organic pore former is high boiling point small organic molecule, excellent Selection of land, described high boiling point small organic molecule is that boiling point is higher than 200 DEG C, and number-average molecular weight Liquid state organics less than 500, preferably mineral oil, C_6-15Alkane, C_8-15Aliphatic carboxylic acid, C_1-4Alkyl ester, C_2-6One or more in halogenated alkane, wherein,

Described mineral oil is preferably white oil, described C_6-15Alkane selected from heptane, naphthalane, decane, Hendecane and dodecane, described C_8-15Aliphatic carboxylic acid is selected from capric acid, hendecoic acid and 12 carbon Acid, described C_1-4Alkyl ester is selected from methyl caprate, ethyl caprate, capric acid propyl ester, the positive fourth of capric acid Ester, hendecoic acid methyl ester, hendecoic acid ethyl ester, hendecoic acid propyl ester, the positive fourth of hendecoic acid Ester, lauric acid methyl ester, dodecanoate, lauric acid propyl ester, the positive fourth of lauric acid Ester, described C_2-6Halogenated alkane is selected from dichloroethanes, dichloropropane, chlorofluoroethane and fluorine chlorine Propane,

Described organic pore former more preferably mineral oil, more preferably white oil.

Described Inorganic pore forming agents is water-soluble inorganic nano-particle, it is preferable that described water solublity Inorganic nanoparticles be particle diameter be 1～200nm, preferably 3～100nm, more preferably The water-soluble nano sulfate of 5～20nm, water-soluble nano nitrate, water-soluble nano salt One or more in hydrochlorate, wherein,

Compared to organic pore former, the Inorganic pore forming agents of described solid granular has bigger Particle diameter and fixing form, thus there is higher occupy-place effect, can in battery diaphragm shape Become the microcellular structure that aperture is bigger, the formation size of micropore, shape can be better controled over and divide Cloth, and be conducive to improving porosity and the air permeability of battery diaphragm, such as: can be by selecting not The battery diaphragm that micropore size is different is prepared with the Inorganic pore forming agents of particle diameter.

It is in terms of 100 weight portions by the weight of polyethylene or the weight sum of a combination thereof thing, described The addition of pore former is 20～70 weight portions, preferably 30～60 weight portions, more preferably 50 Weight portion, wherein, described organic pore former with the weight ratio of described Inorganic pore forming agents is (30～60): (1～10), are preferably (35～55): (2～8), more preferably (40～50): (4～6).

In a preferred embodiment in accordance with the present invention, described melting mixing the process extruded Extruder or extrusion device are carried out, described extruder or extrusion device include machine barrel and Row are arranged on two polyethylene composition charging apertures of described machine barrel one end and are respectively arranged at On described machine barrel away from described polyethylene composition charging aperture be at 1/3 and 2/3 barrel length two Individual pore former charging aperture.

After polyethylene composition, Inorganic pore forming agents and optional additive being pre-mixed uniformly Extruder is put into, preferably by Inorganic pore forming agents and polyphosphazene polymer through polyethylene composition charging aperture Ethylene is pre-mixed uniformly, optional additive and ultra high molecular polyethylene is pre-mixed all Even, put into extruder through two different polyethylene composition charging apertures, then add heat fusing, The extrusion direction of the polyethylene composition of extruder inner molten adds organic pore former, Described organic pore former is separately added into crowded from two different pore former charging apertures the most in batches Go out machine, extrude casting films after melted also mix homogeneously, use above-mentioned preferred mode to add institute State Inorganic pore forming agents and organic pore former, can avoid polyethylene composition and pore former that phase occurs Separate and cause mixing inequality and with pressure oscillation in extruder so that polyethylene composition Being sufficiently mixed uniformly with pore former, pore former is uniformly distributed in polyethylene composition, favorably The aperture preparing micropore in subsequent step and the battery diaphragm being more evenly distributed.

In a preferred embodiment in accordance with the present invention, it is optionally added into following weight proportion Additive,

In a preferred embodiment in accordance with the present invention, described polyethylene or a combination thereof thing, one-tenth Hole agent and optional additive can first mix, and are again heated to molten condition, it is also possible to first divide Not adding heat fusing, then mixed by melted above-mentioned substance, the present invention is the most first by institute State polyethylene or a combination thereof thing, pore former and optional additive mix homogeneously respectively, then add Enter extruder is heated to molten condition and stir mixing, mix homogeneously, and easy and simple to handle, Energy consumption is low.

In a preferred embodiment in accordance with the present invention, extrusion temperature and the direct shadow of rate of extrusion Ring step 2) in prepare the character of sheet and thickness, and determine finally to prepare each of barrier film Item physicochemical property.Extrusion temperature is the highest, and the mobility of casting films is the best, molecule confusion degree The highest, the crystallinity preparing barrier film is the poorest；Extrusion temperature is the lowest, and the mobility of casting films is more Difference, molecule confusion degree is the lowest, and degree of molecular orientation is the highest, and the crystallinity preparing barrier film is the best, In the present invention, extrusion temperature is 150～250 DEG C, preferably 170～240 DEG C.Rate of extrusion is too fast, Casting films is piled up too much between the first slab roller 3 and the second slab roller 4, is likely to result in local Cool down hardening and affect slab and carry out；Rate of extrusion is the slowest, is likely to result in prepared sheet thick Spending uneven or the thinnest, in the present invention, rate of extrusion is 800～2000g/min, is preferably 1000～1500g/min.

Step 2), slab: step 1) casting films extruded flows through the first slab roller and second Space between slab roller, casts sheet.

Described cooling roller device includes the first slab roller and second that spacing is 180～580 μm Slab roller, the diameter of described first slab roller and the second slab roller is than for 1:(1～6), described First slab roller and the second slab roller rotate in opposite directions, it is preferable that the roller of described first slab roller The roller linear velocity numerical value of cylinder linear velocity and described second slab roller is equal.

In a preferred embodiment in accordance with the present invention, as in figure 2 it is shown, described first slab Roller and the second slab roller opposite direction rotating, from the casting films of extruder die head extrusion in the first slab Formed between roller and the second slab roller and pile up, be then passed through gap therebetween and squeeze Pressure, cooling, cast sheet, reduce that rate of extrusion is uneven and extruder machinery concussion etc. because of The element impact on sheet character, thus prepare the sheet that thickness is uniform, character is stable.

In a preferred embodiment in accordance with the present invention, described first slab roller 3 and the second casting The surface temperature of sheet roller 4 is 5～40 DEG C, preferably 10～35 DEG C, more preferably 12～33 DEG C, The casting films of extrusion flows through during the gap between the first slab roller and the second slab roller two-sided cold But molding, casts sheet, meanwhile, is uniformly distributed pore former therein and polyethylene group There is thermotropic being separated in compound, pore former is closed therein by the sheet of two-sided cooling, Compared with the sheet of one side cooling in traditional handicraft, pore former is less susceptible to ooze out, and is conducive to system Obtain the more uniform battery diaphragm of the aperture of micropore, distribution.

In a preferred embodiment in accordance with the present invention, optionally by described first slab roller or the The surface of two slab rollers is processed into rough plane, can prepare the electricity that single or double is coarse Pond barrier film, improves the membrane surface bonding to other material (such as: coating, film etc.) Ability, lays a good foundation for research and development novel battery barrier film.

In a preferred embodiment in accordance with the present invention, the thickness of described sheet directly affects Preparing the thickness of barrier film eventually, in general, sheet is the thickest, and the barrier film prepared is the thickest, can lead to Overregulate the gap length between the first slab roller and the second slab roller to regulate the thickness of sheet Degree, the thickness of heretofore described sheet is 200～600 μm, preferably 250～550 μm, More preferably 300～500 μm.

Step 3), longitudinal stretching: step 2) obtain the most preheated roller of sheet, stretching Roller and chill roll carry out longitudinal stretching.

In a preferred embodiment in accordance with the present invention, the most preheated roller of described sheet is with relatively Low temperature preheats, and softens sheet, prepares for stretching, prevents sheet because of unexpected high-temperature heating And cause character cataclysm；Then, the draw roll that described sheet gradually rises through multiple rotating speeds exists Longitudinal stretching is carried out under high temperature；Finally, cooled roller sub-cooled is shaped, and obtains character solid Fixed thin film.After longitudinal stretching, thin film elongates compared with sheet in the vertical, and thickness becomes Thin, and longitudinal mechanical strength is improved, meanwhile, the micropore of its internal pore former occupy-place is indulged To being elongated to elongate.

In a preferred embodiment in accordance with the present invention, the temperature of described pre-hot-rolling is 40～130 DEG C, preferably 50～120 DEG C, more preferably 60～110 DEG C, preheat sheet, for drawing Stretch and prepare；

The temperature of described draw roll is 70～150 DEG C, preferably 80～140 DEG C, more preferably 90～130 DEG C, while ensureing the good tensile property of sheet, make the micropore of pore former occupy-place Reach suitable aperture；

The temperature of described chill roll is 3～50 DEG C, preferably 5～45 DEG C, more preferably 8～40 DEG C, Make the rapid cooling and shaping of the thin film after drawing by high temperature, keep the length after longitudinal stretching, thickness Degree and aperture.

In a preferred embodiment in accordance with the present invention, the rotating speed of the plurality of draw roll exists In the range of 2～40m/min, gradient raises so that stretching is uniform, by turning of regulation draw roll Speed regulates the longitudinal stretching degree of thin film, obtains different ratios of elongation.

The ratio of elongation of described longitudinal stretching is 3～10, preferably 3.5～9.5, more preferably 4～9, Obtain that there is suitable thickness, aperture and the thin film of longitudinal mechanical strength.

Step 4), cross directional stretch for the first time: step 3) the thin film both sides that obtain fix, depend on Secondary carry out cross directional stretch through the first preheating zone, the first drawing zone and the first cooling zone.

In a preferred embodiment in accordance with the present invention, described thin film both sides are used fixture respectively Fixing, first pass around the first preheating zone and preheat, soften thin film, prepare for stretching； Then, at high temperature carry out cross directional stretch through the first drawing zone, symmetrical spacing jig from by Cumulative greatly；Finally, through the first cooling zone sub-cooled sizing, the thin film that character is fixing is obtained. After first time cross directional stretch, thin film elongates in the horizontal, lower thickness, and laterally machinery Intensity is improved, and meanwhile, the micropore horizontal elongation of its internal pore former occupy-place becomes similar circle Shape.

In a preferred embodiment in accordance with the present invention, the temperature of described first preheating zone is 60～150 DEG C, preferably 70～140 DEG C, more preferably 75～135 DEG C, preheated film, for drawing Stretch and prepare；

The temperature of described first drawing zone is 80～150 DEG C, preferably 85～145 DEG C, more preferably It is 90～140 DEG C, while ensureing the good tensile property of thin film, makes the micro-of pore former occupy-place Hole reaches suitable aperture；

The temperature of described first cooling zone is 60～150 DEG C, preferably 70～140 DEG C, more preferably It is 75～135 DEG C so that the rapid cooling and shaping of thin film after drawing by high temperature, keeps the most horizontal Length, thickness and aperture after stretching.

In a preferred embodiment in accordance with the present invention, described thin film the most at the uniform velocity moves Dynamic, regulate the cross directional stretch degree of thin film by regulating the distance between horizontal fixture, obtain Different ratios of elongation.

The ratio of elongation of described first time cross directional stretch is 3～11, and preferably 3.5～10.5 are more excellent Elect 4～10 as, obtain that there is suitable thickness, aperture and the thin film of horizontal mechanical strength.

Step 5), extraction: step 4) thin film that obtains processes through extractant, then successively It is dried.

In a preferred embodiment in accordance with the present invention, described extractant preferably includes the first extraction Taking agent and the second extractant, step 4) thin film that obtains is successively through the first extractant and second Extractant immersion treatment.

In a preferred embodiment in accordance with the present invention, the most at twice pore former is extracted Take, first extract the organic pore former component in pore former with the first extractant, then extract with water Take out the Inorganic pore forming agents component in pore former.Soak with the first extractant and the second extractant During thin film, be evenly distributed on the pore former within thin film be dissolved extract, originally by pore-forming Position that agent occupies forms microcellular structure, the distribution of micropore and aperture the most uniformly and pore creating material It is distributed the most dispersed directly related in thin film；Described first extractant is to pore former In organic pore former component dissolubility good, and polyethylene composition in insoluble thin film and The reagent of additive, the present invention preferably selects the mixing of dichloromethane and phosphate ester composition Thing, described phosphate ester is preferably one or more in trimethyl phosphate and triethyl phosphate, Wherein, dichloromethane is 10:1～40:1, preferably 15:1～30:1 with the weight ratio of phosphate ester, Described organic extractant is better than simple dichloromethane to organic pore former effect of extracting, extraction More complete, pore former residual is few；Described second extractant is to the inorganic pore-forming in pore former Agent component dissolubility is good, and the polyethylene composition in insoluble thin film and the examination of additive Agent, the present invention preferably selects water, more preferably high purity water.

Drying device is dried.Described drying device includes what multiple one-tenth broken line was arranged Transfer roller.In a preferred embodiment in accordance with the present invention, contact with transfer roller at thin film Position be provided with for dry air gun, the jet direction of the most described air gun and described biography Send the plane tangent of roller.

Use air gun that the thin film after extraction is dried, to remove the extraction of film surface residual Taking agent, prevent stain mark, described air gun drying effect is good, and effectively prevent thin film The generation of surface water wave stricture of vagina, meanwhile, by the position of Reasonable adjustment air gun Yu thin film so that The vertical impact forces of thin film is obviously reduced by air gun, significantly improves final prepared battery diaphragm The bad phenomenon such as outward appearance fold, scollop, scallop.

Step 6), cross directional stretch for the second time: step 5) the thin film both sides that obtain fix, depend on Secondary through the second preheating zone, the second drawing zone and the second cooling zone carry out second time cross directional stretch, Obtain the battery diaphragm of resistance to thermal contraction.

In a preferred embodiment in accordance with the present invention, the both sides fixture of described thin film is solid Fixed, first pass around the second preheating zone and preheat, soften thin film, prepare for stretching；So After, at high temperature carry out small size cross directional stretch through the second drawing zone, symmetrical spacing jig from It is gradually increased；Finally, through the second cooling zone sub-cooled sizing, obtain fixing resistance to of character The battery diaphragm of thermal contraction.Cross directional stretch is compared with first time cross directional stretch for the second time, stretching Degree substantially reduces, and after second time cross directional stretch, has the thin film of microcellular structure laterally On slightly elongate or keep constant, make its mechanical strength, ventilative by heating-cooling process Degree, thermal contraction performance improve further, meanwhile, its internal micropore horizontal elongation, aperture Increase, obtain the battery diaphragm with the resistance to thermal contraction of good character.

In a preferred embodiment in accordance with the present invention, the temperature of described second preheating zone is 70～160 DEG C, preferably 80～150 DEG C, more preferably 90～140 DEG C, preheated film, for drawing Stretch and prepare；

The temperature of described second drawing zone is 100～155 DEG C, preferably 105～150 DEG C, more excellent Elect 110～145 DEG C as, make micropore reach to close while ensureing the good tensile property of thin film Suitable aperture；

The temperature of described second cooling zone is 60～130 DEG C, preferably 65～135 DEG C, more preferably It is 70～130 DEG C so that the rapid cooling and shaping of thin film after drawing by high temperature, keeps second time horizontal Length, thickness and aperture after stretching.

The ratio of elongation of described second time cross directional stretch is 0.5～5, preferably 0.7～4, more preferably It is 0.8～3, obtains that there is the resistance to of suitable thickness, aperture, mechanical strength and thermal contraction performance The battery diaphragm of thermal contraction.

According to the present invention, it is provided that use the battery of such as resistance to thermal contraction prepared by said method every Film, it is characterised in that as it is shown in figure 5, this barrier film include the first outer layer, the second outer layer and Being clipped in internal layer therebetween, described first outer layer, the second outer layer and internal layer have different Microcellular structure.

In a preferred embodiment in accordance with the present invention, the aperture of described first outer layer is 20～100nm, the aperture of the second outer layer is 30～140nm, and the aperture of internal layer is 50～180 nm。

In a preferred embodiment in accordance with the present invention, the performance of described barrier film is as follows:

Thickness is 5～25 μm, preferably 8～22 μm, more preferably 10～18 μm；

Porosity is 40～90%, preferably 42～80%, more preferably 44～75%；

Venting quality is 200～400sec, preferably 220～380sec, more preferably 250～350 sec；

Longitudinal tensile strength is 1800～2200kgf/cm², preferably 1850～2150 kgf/cm², more preferably 1900～2100kgf/cm²；

Transverse tensile strength is 1800～2500kgf/cm², preferably 1900～2450 kgf/cm², more preferably 2000～2400kgf/cm²；

Puncture strength is 600～1000gf, preferably 640～950gf, more preferably 660～900 gf；

Longitudinal extension rate is 160～220%, preferably 170～210%, more preferably 180～200%；

Horizontal expansion rate is 150～210%, preferably 160～200%, more preferably 170～195%；

Longitudinal percent thermal shrinkage is not more than 3%, and preferably no greater than 2.8%, more preferably no more than 2.5%；

Laterally percent thermal shrinkage is not more than 1%, and preferably no greater than 0.5%, more preferably no more than 0.1%；

Closed pore temperature is 120～150 DEG C, preferably 130～148 DEG C, more preferably 138～142 DEG C；

Broken film temperature is 160～180 DEG C, preferably 163～175 DEG C, more preferably 166～172 DEG C.

The battery diaphragm that the pore former using the present invention to provide prepares is while thickness is relatively low There is higher hot strength and puncture strength, can be used for preparing the battery that volume is less, and Higher mechanical force, not cracky can be born in battery assembling process；It addition, porosity And venting quality is high, low with its internal resistance of cell prepared, capacitance improves relatively；And thermal contraction Rate is low, reduces and causes battery open circuit because of barrier film heat shrinkable during the use of battery Etc. problem；Meanwhile, having relatively low closed pore temperature and higher broken film temperature, safety is high.

According to the present invention, the preparation method of three kinds of microcellular structure battery diaphragms described above is made Device include extrusion device, cooling roller device and drying device.

Described extrusion device includes machine barrel, is disposed in parallel in two poly-second of described machine barrel one end Ene compositions charging aperture and be respectively arranged on described machine barrel to enter away from described polyethylene composition Material mouth is two pore former charging apertures at 1/3 and 2/3 barrel length.

Described cooling roller device includes the first slab roller and second that spacing is 180～580 μm Slab roller, the diameter of described first slab roller and the second slab roller is than for 1:(1～6), described First slab roller and the second slab roller rotate in opposite directions, it is preferable that the roller of described first slab roller The roller linear velocity numerical value of cylinder linear velocity and described second slab roller 4 is equal.

As fully visible, the pore former provided according to the present invention and the resistance to thermal contraction prepared with it Lithium ion battery separator, the present invention is had the advantage that to include:

(1) heretofore described pore former includes organic pore former and Inorganic pore forming agents, can Better control over the formation size of micropore, shape and distribution, be conducive to improving battery diaphragm Porosity and venting quality；

(2) lithium ion battery separator prepared has good thermal shrinkage simultaneously, draws Stretch intensity, puncture strength, there is relatively low closed pore temperature and higher broken film temperature；

(3) lithium ion battery separator prepared has three-decker, and the micropore shape of every layer Shape, aperture are the most different, and micropore is evenly distributed, and porosity is high；

(4) each Component Source is extensive, with low cost.

Accompanying drawing explanation

Fig. 1 illustrates the extruder feed arrangement schematic diagram according to one embodiment of the present invention；

Fig. 2 illustrates the cooling roller device schematic diagram according to one embodiment of the present invention；

Fig. 3 illustrates the drying device schematic diagram according to one embodiment of the present invention；

Fig. 4 illustrates the drying mode schematic diagram in traditional processing technology；

Fig. 5 illustrates that the battery diaphragm side of the resistance to thermal contraction according to one embodiment of the present invention is cut Face schematic diagram.

Drawing reference numeral explanation

1-polyolefin charging aperture

2-pore former charging aperture

3-the first slab roller

4-the second slab roller

5-extruder die head

6-transfer roller

7-air gun

8-hydraulic giant

9-the first outer layer

10-the second outer layer

11-internal layer

Detailed description of the invention

Below by drawings and Examples, the present invention is described in more detail.Said by these Bright, the features and advantages of the invention will become more apparent from clearly.

According to the present invention, the preparation method of three kinds of microcellular structure battery diaphragms of preparation uses specific Device, this device includes extrusion device, cooling roller device and drying device, specific as follows:

Extrusion device

As it is shown in figure 1, described extrusion device includes polyethylene composition charging aperture 1 and pore former Charging aperture 2.

In a preferred embodiment in accordance with the present invention, described extrusion device preferably includes two Polyethylene composition charging aperture 1 and two pore former charging apertures 2.

Described extrusion device also includes machine barrel, and said two polyethylene composition charging aperture 1 is also Row are arranged at one end of described machine barrel, and said two pore former charging aperture 2 is respectively arranged at institute State on machine barrel away from described polyethylene composition charging aperture 1 be at 1/3 and 2/3 barrel length.

In a preferred embodiment in accordance with the present invention, polyethylene or a combination thereof thing, inorganic one-tenth Hole agent and optional additive enter through said two polyethylene composition after being pre-mixed uniformly Material mouth 1 adds described extrusion device, preferably by Inorganic pore forming agents with high-molecular polythene in advance Mix homogeneously, is pre-mixed uniformly by optional additive and ultra high molecular polyethylene, above-mentioned Two kinds of mixture add described extrusion dress through said two polyethylene composition charging aperture 1 respectively Put, be more easy to mix homogeneously.

Said mixture is heated to molten condition and along described machine barrel in described extrusion device Extrusion, adds organic pore former through said two pore former charging aperture 2 in extrusion direction, Extrude casting films after melted also mix homogeneously, polyethylene composition and pore former can be avoided to occur It is separated and causes mixing inequality and with pressure oscillation in extruder so that polyethylene composition Thing and pore former are sufficiently mixed uniformly, and pore former is uniformly distributed in polyethylene composition mixture In, the aperture beneficially preparing micropore in subsequent step and the battery that is more evenly distributed every Film.

Cooling roller device

As in figure 2 it is shown, described cooling roller device includes that axis is positioned in same level One slab roller 3 and the second slab roller 4, between described first slab roller 3 and the second slab roller 4 Spacing is 180-580 μm, preferably 230-530 μm, more preferably 280-480 μm.

In a preferred embodiment in accordance with the present invention, described first slab roller 3 and the second casting Sheet roller 4 opposite direction rotating, from the casting films of extruder die head 5 extrusion at the first slab roller 3 and the Formed between two slab rollers 4 and pile up, be then passed through space extruding therebetween, cooling, Casting sheet, the factors such as rate of extrusion inequality, extruder machinery concussion that reduce are to sheet The impact of shape, thus prepare the sheet that thickness is uniform, character is stable.

In a preferred embodiment in accordance with the present invention, described first slab roller 3 and the second casting The diameter of sheet roller 4 is than for 1:(1～6), preferably 1:(2～5), more preferably 1:(3～4), A diameter of 300-600mm of the most described first slab roller 3, the second slab roller 4 a diameter of 500-900mm。

At the chiller that is internally provided with of described first slab roller 3 and the second slab roller 4, use In controlling the first slab roller 3 and temperature on the second slab roller 4 surface, thus the curtain coating to extrusion Film cools down, and the temperature of the most described first slab roller 3 and the second slab roller 4 is 5～40 DEG C, preferably 10～35 DEG C, more preferably 12～33 DEG C, the casting films of extrusion flows through Two-sided cooling molding during space between one slab roller 3 and the second slab roller 4, casts sheet, Meanwhile, being uniformly distributed pore former therein occurs thermotropic phase to divide with polyethylene composition From, pore former is closed therein by the sheet of two-sided cooling, cold with one side in traditional handicraft But sheet is compared, and pore former is less susceptible to ooze out, and is conducive to preparing the aperture of micropore, distribution More uniform battery diaphragm.

In a preferred embodiment in accordance with the present invention, optionally by described first slab roller 3 or The surface of the second slab roller 4 is processed into rough plane, can prepare single or double coarse Battery diaphragm, improve membrane surface to other material (such as coating, film etc.) Adhesive power, lays a good foundation for research and development novel battery barrier film.

Drying device

As it is shown on figure 3, described drying device includes the transfer roller 6 that multiple one-tenth broken line is arranged, The position that thin film contacts with transfer roller 6 is provided with for dry air gun 7.

In a preferred embodiment in accordance with the present invention, the jet direction of described air gun 7 and institute State the plane tangent of transfer roller 6.

In a preferred embodiment in accordance with the present invention, the thin film after extraction is through multiple transfer rollers 6 advance along broken line, and the position contacted with each transfer roller 6 at thin film is provided with for being dried Air gun 7, with remove film surface residual extractant, prevent stain mark, described gas The jet direction of rifle 7 and the plane tangent of transfer roller, i.e. parallel with the direction of transfer of thin film, Drying effect is good, and effectively prevent the generation of film surface water ripples, meanwhile, air gun The vertical impact forces of 7 pairs of thin film is obviously reduced, and significantly improves final preparing outside battery diaphragm See the bad phenomenon such as fold, scollop, scallop；And in traditional processing technology.

Different from foregoing of the present invention, as shown in Figure 4, the thin film after extraction linearly passes Sending, and use hydraulic giant 8 and air gun 7 mixing to be dried, the film surface prepared easily occurs Water ripples, cause the final battery diaphragm uneven thickness prepared or injustice, and hydraulic giant 8 are gentle Rifle 7 injects directly on the surface of thin film the most at a certain angle, and impulsive force is big, outside battery diaphragm See the phenomenon such as fold, scollop, scallop serious, affect use and the rolling of battery diaphragm.

According in another embodiment of the present invention, as it is shown in figure 5, described heat-resisting receipts The battery diaphragm of contracting includes first outer layer the 9, second outer layer 10 and is clipped in internal layer therebetween 11, described first outer layer the 9, second outer layer 10 and internal layer 11 have different microcellular structures.

The aperture of described first outer layer 9 is 20～100nm, and the aperture of the second outer layer 10 is 30～140nm, the aperture of internal layer 11 is 50～180nm.

Embodiment

Embodiment 1

For prepare the polyethylene composition of the lithium ion battery separator of resistance to thermal contraction include with The component of lower weight proportion:

Wherein,

The number-average molecular weight of high-molecular polythene is 500,000,

The number-average molecular weight of ultra high molecular polyethylene is 1,400,000,

The mean molecule quantity of white oil is 200,

The particle diameter of described nanometer magnesium chloride is 50～70nm.

Above-mentioned composition is made in accordance with the following methods lithium ion battery separator:

Step 1), extrusion: by high-molecular polythene and nanometer magnesium chloride melting mixing, by the One charging aperture add extruder, by ultra high molecular polyethylene, 4,4-thiobis is (between the 6-tert-butyl group Cresol), 2,4-DihydroxyBenzophenone, octadecyl quaternary ammonium sodium and Tween 80 enter by second Material mouth adds extruder, by white oil by the first pore former charging aperture and the second pore former charging aperture Adding extruder, be 210～240 DEG C at extrusion temperature, rate of extrusion is the bar of 1200g/min Under part, above-mentioned composition is extruded, form casting films；

Step 2), slab: step 1) casting films that is extruded into flows through the first slab roller (3) (smooth surface, surface temperature is 20 DEG C) and the second slab roller (4) (smooth surface, table Surface temperature is 20 DEG C) between gap, cast the sheet that thickness is 400 μm；

Step 3), longitudinal stretching: step 2) the most preheated roller of the sheet (surface that obtains Temperature is 80 DEG C), draw roll (ratio of elongation of every grade is 6, and surface temperature is 110 DEG C) and Chill roll (surface temperature is 20 DEG C) carries out longitudinal stretching；

Step 4), cross directional stretch for the first time: step 3) thin film that obtains is in the direction of the width Both sides be individually fixed on clamping device, through the first preheating zone, (surface temperature is successively 100 DEG C), the first drawing zone (ratio of elongation of every grade is 7, and surface temperature is 115 DEG C) and During one cooling zone (surface temperature is 95 DEG C), under the effect of described clamping device, carry out horizontal stroke To stretching；

Step 5), extraction: step 4) thin film that obtains is through the first extractant (dichloromethane The mixture formed by weight 22:1 with trimethyl phosphate) and the second extractant (high purity water) Soak 6h, be then dried with air gun, obtain thin film；

Step 6), cross directional stretch for the second time: step 5) thin film that obtains is in the direction of the width Both sides be individually fixed on clamping device, through the second preheating zone, (surface temperature is successively 115 DEG C), the second drawing zone (ratio of elongation of every grade is 1.2, and surface temperature is 125 DEG C) and Second cooling zone (surface temperature is 95 DEG C) carries out second time cross directional stretch, and obtaining thickness is The battery diaphragm of the 16.2 resistance to thermal contractions of μm.

Embodiment 2

The component of following weight proportion is included for preparing the compositions of lithium ion battery separator:

Wherein,

The number-average molecular weight of high-molecular polythene is 300,000.

The number-average molecular weight that ultra high molecular polyethylene is is 1,300,000.

The mean molecule quantity of white oil is 180；

The particle diameter of nanometer magnesium chloride is 60～90nm.

Above-mentioned composition is prepared in accordance with the following methods lithium ion battery separator:

Step 1), extrusion: by high-molecular polythene and nanometer magnesium chloride melting mixing, by the One charging aperture add extruder, by ultra high molecular polyethylene, 3,5-di-t-butyl-4-hydroxyl first Benzene, 4 benzoyloxy 2,2,6,6 tetramethyl piperidine, octadecyl quaternary ammonium sodium and lauric acid Extruder is added, by white oil by the first pore former charging aperture and the second pore-forming by the second charging aperture Agent charging aperture is separately added into extruder, is 210～240 DEG C at extrusion temperature, and rate of extrusion is Under conditions of 1200g/min, above-mentioned composition is extruded, form casting films；

Step 2), slab: step 1) casting films that is extruded into flows through the first slab roller (3) (surface roughness is 0.1, and surface temperature is 20 DEG C) and the second slab roller (4) (surface Roughness is 0.2, and surface temperature is 20 DEG C) between gap, casting thickness is 400 μm Sheet；

Step 4), cross directional stretch for the first time: step 3) thin film that obtains is in the direction of the width Both sides be individually fixed on clamping device, through the first preheating zone, (surface temperature is successively 100 DEG C), the first drawing zone (ratio of elongation of every grade is 7, and surface temperature is 115 DEG C) and During one cooling zone (surface temperature is 95 DEG C), under the effect of described clamping device, carry out horizontal stroke To stretching, obtain thin film；

Embodiment 3

The present embodiment method therefor is similar to embodiment 2 method therefor, differs only in poly-second Ene compositions includes the component of following weight proportion:

Wherein,

The number-average molecular weight of high-molecular polythene is 400,000.

The number-average molecular weight of ultra high molecular polyethylene is 1,400,000.

Comparative example

Comparative example 1

This comparative example is identical with embodiment 1 method therefor, differs only in polyethylene composition In be added without white oil.

The battery diaphragm micropore size prepared is excessive and uneven, is preparing lithium ion battery Time cracky.

Comparative example 2

Use the preparation of battery diaphragm described in embodiment 6 in patent CN201210454073.9 Method, it may be assumed that the polyethylene that number-average molecular weight is 800,000 g/mol is heated to 180 DEG C and melts, Add in double screw extruder with 54kg/h feed rate.White oil is heated to 95 DEG C, with 2,6- Di-tert-butyl-4-methy phenol mix and blend 3h, injects mixture twin screw at twice and squeezes Go out in machine.Temperature within extruder is 200 DEG C, and extrusion temperature is 190 DEG C, extruded material The sheet that thickness is 1.4mm is cast in space extruding between 15 DEG C of chill rolls and adjustable roller. Polyethylene is 1:2.4 with the mass ratio of white oil, and the quality of 2,6-di-tert-butyl-4-methy phenols is The 1.0% of white oil quality.

Sheet obtained above is carried out successively longitudinal stretching and first time cross directional stretch, longitudinally The temperature of stretching is 100 DEG C, and stretching ratio is 5.78, and the temperature of cross directional stretch is for the first time 120 DEG C, stretching ratio is 4.41, after dichloromethane extracts, obtains medial septum.

Medial septum obtained above is carried out second time cross directional stretch, for the second time cross directional stretch Temperature be 132 DEG C, stretching ratio is 1.6, and rolling is cut, 50 DEG C of Ageing Treatment 18h, To battery diaphragm.

Experimental example

To embodiment 1～3 and the battery diaphragm for preparing of comparative example 1 and 2 test as follows, survey Test result is shown in Table 1:

(1) thickness of battery diaphragm is measured；

(2) use electronic scanner microscope to observe the microcellular structure of battery diaphragm, and measure Aperture；

(3) press pump instrument is used to measure the porosity of battery diaphragm；

(4) venting quality tester is used to measure the venting quality of battery diaphragm；

(5) tension tester is used to measure the longitudinal tensile strength of battery diaphragm and laterally draw Stretch intensity；

(6) electronic tensile machine is used to measure the puncture strength of battery diaphragm, longitudinal extension rate With horizontal expansion rate；

(7) the longitudinally heat using battery diaphragm percent thermal shrinkage tester to measure battery diaphragm is received Shrinkage and horizontal percent thermal shrinkage；

(8) battery septum closed pore temperature and broken film temperature tester is used to measure battery diaphragm Closed pore temperature and broken film temperature.

Table 1. battery diaphragm the performance test results

Above in association with preferred implementation, embodiment and comparative example, the present invention is carried out in detail Explanation.But it is to be understood that, these detailed description of the invention are only the elaborations to the present invention Property explain, not to protection scope of the present invention constitute any restriction.Without departing from the present invention In the case of spirit and scope, the technology of the present invention content and embodiment thereof can be entered The various improvement of row, equivalencing or modification, these each fall within protection scope of the present invention. Protection scope of the present invention is as the criterion with claims.

Claims

1. the pore former group being used for preparing the lithium ion battery separator of resistance to thermal contraction Compound, it is characterised in that said composition includes organic pore former and Inorganic pore forming agents,

Preferably,

Pore former combination thing the most according to claim 1, it is characterised in that

Described high boiling point small organic molecule is that boiling point is higher than 200 DEG C, and number-average molecular weight Liquid state organics less than 500；

Described water-soluble inorganic nano-particle be particle diameter be the inorganic matter of 1～200nm Grain.

3. according to the pore former combination thing of claim 1 or 2, it is characterised in that described High boiling point small organic molecule is preferably selected from mineral oil, C_6-15Alkane, C_8-15Aliphatic series carboxylic Acid, C_1-4Alkyl ester, C_2-6One or more in halogenated alkane, it is highly preferred that

Described mineral oil is white oil；Described C_6-15Alkane selected from heptane, naphthalane, decane, Hendecane and dodecane；Described C_8-15Aliphatic carboxylic acid is selected from capric acid, hendecoic acid and ten Two carbonic acid；Described C_1-4Alkyl ester selected from methyl caprate, ethyl caprate, capric acid propyl ester, Capric acid N-butyl, hendecoic acid methyl ester, hendecoic acid ethyl ester, hendecoic acid propyl ester, Hendecoic acid N-butyl, lauric acid methyl ester, dodecanoate, lauric acid third Ester, lauric acid N-butyl；Described C_2-6Halogenated alkane is selected from dichloroethanes, dichloro Propane, chlorofluoroethane and fluorine chloropropane；And/or

Described water-soluble inorganic nano-particle is selected from water-soluble nano sulfate, water solublity One or more in nanometer nitrate, water-soluble nano hydrochlorate, it is highly preferred that

Described water-soluble nano sulfate is selected from nanometer sodium sulfate, nanometer potassium sulfate and receives Rice ammonium sulfate etc.；Described water-soluble nano nitrate is selected from nanometer sodium nitrate, nanometer nitre Acid potassium, nanometer ammonium nitrate, nanometer magnesium nitrate and nanometer copper nitrate etc.；Described water solublity Nm salt hydrochlorate is selected from nanometer sodium chloride, nanometer potassium chloride, nanometer ammonium chloride, nanometer Magnesium chloride, nanometer calcium chloride and nanometer copper chloride etc..

4., according to the pore former combination thing one of claims 1 to 3 Suo Shu, its feature exists In, described organic pore former is (30～60) with the weight ratio of described Inorganic pore forming agents: (1～10), are preferably (35～55): (2～8), more preferably (40～50): (4～6).

5., according to the pore former combination thing one of Claims 1-4 Suo Shu, its feature exists In, described organic pore former is preferably white oil, and described Inorganic pore forming agents is preferably nanometer Magnesium chloride, the most described pore former is white oil and the compositions of nanometer magnesium chloride.

6., according to the pore former combination thing one of claim 1 to 5 Suo Shu, its feature exists In, described pore former adds to polyolefin, it is preferable that with polyolefinic weight be 100 weight portion meters, the addition of pore former is 20～70 weight portions, preferably 30～60 Weight portion, more preferably 50 weight portions.

7., according to the pore former combination thing one of claim 1 to 6 Suo Shu, its feature exists In, described pore former is preferably dividedly in some parts in polyolefin.

8. a preparation method for the lithium ion battery separator of resistance to thermal contraction, its feature exists In, the method includes:

Step 1), by poly-polyethylene or a combination thereof thing, according to one of claim 1 to 7 Described pore former combination thing and other optional additive melting mixing, extrusion curtain coating Film；

Step 2), step 1) casting films extruded flows through the first slab roller and the second slab Space between roller, casts sheet；

Step 3), step 2) the most preheated roller of sheet, draw roll and the cooling that obtain Roller carries out longitudinal stretching；

Step 5), step 4) thin film that obtains processes through extractant, is then dried；Excellent Selection of land, described being dried in drying device is carried out, and described drying device includes multiple one-tenth Broken line arrangement transfer roller, be provided with in the position that thin film contacts with transfer roller for The air gun being dried, the jet direction of the most described air gun preferably with the table of described transfer roller Tangent or with thin film the direction of transfer in face is paralleled；

Step 6), step 5) the thin film both sides that obtain fix, successively through the second preheating zone, Second drawing zone and the second cooling zone carry out second time cross directional stretch, obtain resistance to thermal contraction Battery diaphragm.

The battery diaphragm of resistance to thermal contraction prepared by method the most according to claim 8, It is characterized in that, this battery diaphragm includes the first outer layer, the second outer layer and is clipped in the two Between internal layer, described first outer layer, the second outer layer and internal layer have different micropores Structure,

The average pore size of the most described first outer layer is 20～100nm, the second outer layer Average pore size is 30～140nm, and the aperture of internal layer is 50～180nm.