CN106328858A

CN106328858A - Lithium ion battery diaphragm with three kinds of microporous structures, and polyethylene composition adopted by same

Info

Publication number: CN106328858A
Application number: CN201510346310.3A
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: CN106328858B

Abstract

The invention discloses a lithium ion battery diaphragm with three kinds of microporous structures, and a polyethylene composition adopted by the same. The composition comprises high-molecular polyethylene, ultra-high-molecular polyethylene and an optional additive. The lithium ion battery diaphragm prepared from the composition has integrally-formed three kinds of microporous structures; and in addition, the lithium ion battery diaphragm has relatively low closed-hole temperature, high heat resistance shrinkage, high tensile strength, high puncture strength and relatively high membrane-rupture temperature, thereby ensuring safety in preparation and usage of the lithium ion battery.

Description

The lithium ion battery separator of three kinds of microcellular structures and the polyethylene composition used

Technical field

The present invention relates to lithium ion battery separator field, particularly to one, there are three kinds of micropores The lithium ion battery separator of structure and polyolefin (especially polyethylene) combination used Thing.

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 short circuit because of contact of both positive and negative electrodes, with Time allow electrolyte ion to pass through, thus produce electric current, current battery diaphragm mostly is to be had The polyolefin film of microcellular structure, its performance determines the interfacial structure of battery, internal resistance etc., directly Connect characteristics such as affecting the capacity of battery, cycle performance and security performance, the electricity of excellent performance Pond barrier film has important function to the combination property improving battery.

The performance of battery diaphragm mainly characterizes by following index: (1) cut off property, battery every Film needs have partition property and electronic isolation, it is ensured that the effective mechanical isolation to both positive and negative polarity； (2) porosity, battery diaphragm to have certain aperture and porosity, it is ensured that low electricity Resistance and high ionic mobility, have good permeability simultaneously to lithium ion；(3) chemistry is steady Qualitative and electrical stability, battery diaphragm needs possess moisture-proof and electrolyte resistance corrosivity；(4) Wellability, the wellability of electrolyte to be got well, and be had preferable imbibition moisturizing by battery diaphragm Ability and ion permeability；(5) mechanical strength, battery diaphragm is the least same of thickness Time to ensure enough mechanical properties and shock resistance, with including puncture strength and hot strength etc. Characterize；(6) safety, battery diaphragm heat stability to be had and automatically shut down protectiveness Can, with including that closed pore temperature and broken film temperature etc. characterize.

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, tensile stress device roller smooth surface, the membrane surface produced is smooth, with other thing The adhesive power of matter is poor, is unfavorable for researching and developing novel battery barrier film；After extraction, drying equipment is usual Use hydraulic giant and air gun two ways to carry out simultaneously, cause the surface of barrier film generally to have water wave, And flatness is the best.

At present, prior art exists by multi-layer polyolefin thin film by lamination method make MULTILAYER COMPOSITE lithium ion battery separator, not only operates complexity, unstable product quality, and The equipment used generally requires particular design.

For problems of the prior art, the present inventor is to preparing lithium ion battery separator Raw material study, be desirably to obtain and a kind of use existing equipment simplicity preparation to have resistance to Thermal contraction performance, do not lose simultaneously hot strength, puncture strength, higher broken film temperature and The compositions of the lithium ion battery separator of relatively low closed pore temperature.

Summary of the invention

In order to solve the problems referred to above, present inventor has performed and study with keen determination, found that: tool There are the high-molecular polythene of specified weight proportioning and the compositions of ultra high molecular polyethylene, optionally Be added thereto to include high boiling point small organic molecule and water-soluble inorganic nano-particle Pore former, and optionally add antioxidant, anti ultraviolet agent, antistatic additive and antifoggant etc. Additive, the lithium ion battery separator prepared with the polyethylene composition obtained has relatively low Closed pore temperature does not lose hot strength, puncture strength, higher broken film temperature and heat-resisting simultaneously Contractility, thus complete the present invention.

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

First aspect, a kind of lithium ion battery separator for preparation with three kinds of microcellular structures Polyethylene composition, it is characterised in that said composition includes the component of following weight proportion:

High-molecular polythene 88～92 weight portion

Ultra high molecular polyethylene 8～12 weight portion.

Second aspect, the present invention also provides for above-mentioned composition, it is characterised in that

The number-average molecular weight of described high-molecular polythene is 100,000～600,000, preferably 200,000～50 Ten thousand, more preferably 300,000～400,000, and/or,

The number-average molecular weight of described ultra high molecular polyethylene is 1,200,000～1,500,000, preferably 130 Ten thousand～1,400,000.

The third aspect, the present invention also provides for above-mentioned composition, it is characterised in that described combination Thing also includes the component of following weight portion,

Pore former 20～70 weight portion,

Preferably, described pore former includes organic pore former and Inorganic pore forming agents, it is preferable that Described organic pore former is high boiling point small organic molecule, and described Inorganic pore forming agents is water solublity Inorganic nanoparticles, wherein, described high boiling point small organic molecule is that boiling point is higher than 200 DEG C, And the liquid state organics that number-average molecular weight is less than 500, described water-soluble inorganic nano-particle grain Footpath is 1～200nm；

Preferably, described high boiling point small organic molecule is preferably mineral oil, C6-15 One or more in alkane, C8-15 aliphatic carboxylic acid, C1-4 alkyl ester, C2-6 halogenated alkane；

Preferably, described water-soluble inorganic nano-particle preferably is selected from water-soluble nano sulphuric acid One or more in salt, water-soluble nano nitrate, water-soluble nano hydrochlorate.

Fourth aspect, the present invention also provides for above-mentioned composition, it is characterised in that described pore-forming Agent includes white oil and nanometer magnesium chloride,

The most 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).

5th aspect, the present invention also provides for above-mentioned composition, it is characterised in that described combination Thing also includes the component of following weight proportion,

The most described antioxidant is selected from 4,4-thiobis (6-tert-butyl-m-cresol), two fourths Base hydroxy-methylbenzene, phosphite ester, tert-butylhydroquinone, and/or

Described anti ultraviolet agent is selected from salicylic acid esters, benzophenone class, benzotriazole, takes For vinyl cyanide, triazines and hindered amines, and/or

Described antistatic additive is selected from cationic antistatic agent, anionic antistatic agents and non- Ionic antistatic agent, and/or

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

6th aspect, the present invention also provides for above-mentioned composition, it is characterised in that described combination Thing includes the component of following weight proportion,

Wherein,

The number-average molecular weight of described high-molecular polythene is 400,000～600,000；And/or

The number-average molecular weight of described ultra high molecular polyethylene is 1,400,000～1,500,000；And/or

The particle diameter of described nanometer magnesium chloride is 5～20nm.

7th aspect, the present invention also provides for above-mentioned composition, it is characterised in that described combination Thing includes the component of following weight proportion,

Wherein,

The particle diameter of described nanometer magnesium chloride is 5～20nm, and/or

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), and/or

Described anti ultraviolet agent is selected from salicylic acid esters, benzophenone class, benzotriazole, replacement third Alkene nitrile, triazines and hindered amines, preferably oxybenzoic acid phenyl ester, 2-(2-hydroxyl Base-5-aminomethyl phenyl) BTA, 2,4-DihydroxyBenzophenone, 2-hydroxyl-4-first Epoxide benzophenone, Octabenzone, 2-(2'-hydroxyl-3', 5'-bis- Tertiary phenyl)-5-chlorination benzotriazole, single benzoic acid resorcinol, three (1,2,2,6, 6-pempidine base) phosphite ester, 4-benzoyloxy-2,2,6,6-tetramethyl piperidines, 2,4,6-tri-(2' n-butoxyphenyl)-1,3,5-triazines and HMPA etc., And/or

Described antistatic additive is selected from quaternary ammonium salt, ethoxy alkylation aliphatic alkyl amine, as Octadecyl quaternary ammonium sodium, and/or

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

Eighth aspect, the present invention also provides for a kind of lithium ion battery with three kinds of microcellular structures The preparation method of barrier film, it is characterised in that said method comprising the steps of:

1), extrusion: by according to the polyethylene composition described in above-mentioned one to eight aspect, pore-forming Agent and optional additive melting mixing, extrude casting films；

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

3), longitudinal stretching: step 2) obtain the most preheated roller of sheet, draw roll and Chill roll carries out longitudinal stretching；

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

5), extraction: step 4) thin film that obtains processes through extractant, is then dried；

6), cross directional stretch for the second time: step 5) the thin film both sides that obtain fix, warp successively Second preheating zone, the second drawing zone and the second cooling zone carry out second time cross directional stretch, obtain There is the battery diaphragm of three kinds of microcellular structures.

9th aspect, the present invention also provides for said method, it is characterised in that in step 5) In, 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.

Tenth aspect, the present invention also provides for according to method system described in above-mentioned 8th or the 9th aspect The lithium ion battery separator obtained, it is characterised in that described battery diaphragm has three kinds of micropores knots Structure.

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.

It is to be mutually related between the multinomial performance index of battery diaphragm, such as: the electricity that thickness is less Pond barrier film tends to stretch out intensity and puncture strength is relatively low, easily breaks in battery installation process Damage；The general fusing point of polyolefine material that the barrier film that mechanical strength is higher uses is higher, therefore closes Hole temperature is higher, poor stability.Although raw materials for production or the working condition of barrier film can be changed Significantly improve some performance indications, but want to take into account multinomial performance, obtain indices All preferably battery diaphragm still has great difficulty.

According to the first aspect of the invention, it is provided that a kind of for preparing lithium ion battery separator Polyethylene composition, said composition includes the component of following weight proportion,

High-molecular polythene 88～92 weight portion,

Ultra high molecular polyethylene 8～12 weight portion,

It is preferably,

High-molecular polythene 89～91 weight portion

Ultra high molecular polyethylene 9～11 weight portion,

More preferably,

High-molecular polythene 90 weight portion

Ultra high molecular polyethylene 10 weight portion,

Wherein,

The number-average molecular weight of described high-molecular polythene is 100,000～600,000, preferably 200,000～50 Ten thousand, more preferably 300,000～400,000.

The inventors discovered that, when high-molecular polythene and ultra high molecular polyethylene in compositions Weight ratio is (88～92): (8～12), is preferably (89～91): (9～11), more preferably During for 90:10, the lithium ion battery separator prepared by said composition has relatively low closed pore temperature Degree, its carry out at 150 DEG C 60 minutes overcharge test, remain to keep form good, no Breakdown, thus ensure that lithium ion battery safety in use.

Additionally, the present inventors have additionally discovered that, when high-molecular polythene and supra polymer in compositions When polyethylene is combined according to above-mentioned weight proportion, the lithium-ion electric prepared by said composition Pond barrier film remains in that stronger hot strength and puncture strength so that assembling prepare lithium from During sub-battery, prepared battery diaphragm is difficult to be torn, and is not easy to by conductive fiber in battery Damage Deng other material, thus ensure that the preparation efficiency of battery and the certified products of battery produce Rate, and then ensure the safety of the lithium ion battery prepared.

In a preferred embodiment of the present invention, be used for described in preparing lithium ion battery every The compositions of film also includes the component of following weight proportion,

Pore former 20～70 weight portion,

It is preferably,

Pore former 30～60 weight portion,

More preferably,

Pore former 50 weight portion,

Wherein, described pore former includes organic pore former and Inorganic pore forming agents, wherein,

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, C6-15 alkane, C8-15 aliphatic carboxylic acid, C1-4 alkyl ester, C2-6 halo One or more in alkane, wherein,

Described C6-15 alkane is selected from heptane, naphthalane, decane, hendecane and dodecane, institute State C8-15 aliphatic carboxylic acid selected from capric acid, hendecoic acid and lauric acid, described C1-4 alkyl 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 C2-6 alkyl halide Hydrocarbon is selected from dichloroethanes, dichloropropane, chlorofluoroethane and fluorine chloropropane,

Described organic pore former is more preferably white oil.

Described Inorganic pore forming agents is water-soluble inorganic nano-particle, it is preferable that water-soluble inorganic Nano-particle is 1～200nm selected from particle diameter, preferably 3～100nm, more preferably 5～20nm Water-soluble nano sulfate, water-soluble nano nitrate, in water-soluble nano hydrochlorate etc. One or more, 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..

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).

The inventors discovered that, after adding pore former in the composition, preparing lithium ion battery During barrier film, pore former can be dispersed in height with the form of fine droplet and solid granule In the molten state compositions that molecular polyethylene and ultra high molecular polyethylene are formed, it is cooled at it After film, pore former remains able in film presented in fine droplet and solid granule In the slab of film, form " occupy-place " effect, after the slab of film is stretched, pore former quilt Extraction membrane, then it can leave corresponding micropore on film, makes the lithium ion battery prepared Barrier film has microcellular structure, thus when lithium ion battery works, the lithium of abjection positive electrode Ion can pass battery diaphragm.

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 embodiment being more highly preferred to of the present invention, described in be used for preparing lithium ion The compositions of battery diaphragm also includes the component of following weight proportion,

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.

In the embodiment being more highly preferred to of the present invention, described in be used for preparing lithium ion The compositions of battery diaphragm, including the component of following weight proportion,

Wherein,

The number-average molecular weight of described high-molecular polythene is 400,000～600,000；

The number-average molecular weight of described ultra high molecular polyethylene is 1,400,000～1,500,000；

The particle diameter of described nanometer magnesium chloride is 5～20nm.

In the embodiment being more highly preferred to of the present invention, described in be used for preparing lithium ion The polyethylene composition of battery diaphragm, including the component of following weight proportion,

Wherein,

The particle diameter of described nanometer magnesium chloride is 5～20nm,

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),

Described anti ultraviolet agent is selected from salicylic acid esters, benzophenone class, benzotriazole, replacement third Alkene nitrile, triazines and hindered amines, preferably oxybenzoic acid phenyl ester, 2-(2-hydroxyl Base-5-aminomethyl phenyl) BTA, 2,4-DihydroxyBenzophenone, 2-hydroxyl-4-first Epoxide benzophenone, Octabenzone, 2-(2'-hydroxyl-3', 5'-bis- Tertiary phenyl)-5-chlorination benzotriazole, single benzoic acid resorcinol, three (1,2,2,6, 6-pempidine base) phosphite ester, 4-benzoyloxy-2,2,6,6-tetramethyl piperidines, 2,4,6-tri-(2' n-butoxyphenyl)-1,3,5-triazines and HMPA etc.,

Described antistatic additive is selected from quaternary ammonium salt, ethoxy alkylation aliphatic alkyl amine, as Octadecyl quaternary ammonium 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 of the invention, described polyethylene composition be applied to prepare one have In the method for the lithium ion battery separator of three kinds of microcellular structures, described method includes following step Rapid:

Step 1), extrusion: by above-mentioned polyethylene composition, pore former and optional additive Melting mixing, extrudes casting films.

In a preferred embodiment in accordance with the present invention, the preferred high score of described polyethylene composition Sub-polyethylene and ultra high molecular polyethylene are by weight (88～92): (8～12), are preferably (89～91): (9～11), the compositions of more preferably 90:10 composition, described polyphosphazene polymer The number-average molecular weight of ethylene is 100,000～600,000, preferably 200,000～500,000, more preferably 30 Ten thousand～400,000, the number-average molecular weight of described ultra high molecular polyethylene is 1,200,000～1,500,000, preferably It is 1,300,000～1,400,000.

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, C6-15 alkane, C8-15 aliphatic series carboxylic One or more in acid, C1-4 alkyl ester, C2-6 halogenated alkane, wherein,

Described mineral oil is preferably white oil, and described C6-15 alkane is selected from heptane, naphthalane, the last of the ten Heavenly stems Alkane, hendecane and dodecane, described C8-15 aliphatic carboxylic acid selected from capric acid, hendecoic acid and Lauric acid, described C1-4 alkyl ester is selected from methyl caprate, ethyl caprate, capric acid propyl ester, the last of the ten Heavenly stems Acid N-butyl, hendecoic acid methyl ester, hendecoic acid ethyl ester, hendecoic acid propyl ester, 11 carbon Acid N-butyl, lauric acid methyl ester, dodecanoate, lauric acid propyl ester, 12 carbon Acid N-butyl, described C2-6 halogenated alkane is selected from dichloroethanes, dichloropropane, chlorofluoroethane With fluorine chloropropane,

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 100 weight portions with the weight sum of high-molecular polythene and ultra high molecular polyethylene Meter, the addition of described pore former is 20～70 weight portions, preferably 30～60 weight portions, more It is preferably 50 weight portions, wherein, described organic pore former and the weight of described Inorganic pore forming agents Than being (30～60): (1～10), it is 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 composition, pore former Can first mix with optional additive, be again heated to molten condition, it is also possible to add the most respectively Heat fusing, more melted above-mentioned substance is mixed, the present invention is the most first by described poly- Vinyl composition, pore former and optional additive mix homogeneously respectively, adds extruder In be 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 with three kinds of microcellular structures.

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 that character is fixing three Plant the battery diaphragm of microcellular structure.Cross directional stretch is compared with first time cross directional stretch for the second time, Level of stretch substantially reduces, and after second time cross directional stretch, the thin film with microcellular structure exists The most slightly elongate or keep constant, by heating-cooling process make its mechanical strength, Air permeability, thermal contraction performance improve further, meanwhile, and its internal micropore horizontal elongation, Aperture increases, and obtains the battery diaphragm with three kinds of microcellular structures 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 three of suitable thickness, aperture, mechanical strength and thermal contraction performance Plant the battery diaphragm of microcellular structure.

According to the present invention, it is provided that the battery of three kinds of microcellular structures prepared by employing such as said method Barrier film, it is characterised in that as it is shown in figure 5, this barrier film includes the first outer layer, the second outer layer With the internal layer being clipped in therebetween, described first outer layer, the second outer layer and internal layer have difference 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 method using the present invention to provide prepares has while thickness is relatively low There are higher hot strength and puncture strength, can be used for preparing the battery that volume is less, and Battery assembling process can bear higher mechanical force, not cracky；It addition, porosity and Venting quality is high, and low with its internal resistance of cell prepared, capacitance improves relatively；And percent thermal shrinkage Low, reduce during the use of battery, cause battery open circuit etc. because of barrier film heat shrinkable 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 polyethylene composition provided according to the present invention and the tool prepared with it The lithium ion battery separator having three kinds of microcellular structures has the advantages that

(1) in the polyethylene composition that the present invention provides, each Component Source is extensive, and component Kind few, with low cost；

(2) in polyethylene composition, the weight ratio of each component is easily controllable, easily realizes；

(3) lithium ion battery separator prepared by said composition has good having simultaneously Relatively low closed pore temperature, thermal shrinkage, hot strength, puncture strength and higher rupture of membranes Temperature；

(4) in the present invention, 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；

(5) lithium ion battery separator prepared by said composition has a three-decker, and often The micro-pore shape of layer, aperture are the most different, and micropore is evenly distributed, and porosity is high.

Accompanying drawing explanation

Fig. 1 illustrates the extrusion device 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 the battery diaphragm of three kinds of microcellular structures according to one embodiment of the present invention Representative side section view.

Drawing reference numeral explanation

1-polyethylene composition 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 the present invention is described in detail, the features and advantages of the invention will be along with These illustrate and 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.

Different from foregoing of the present invention, and in traditional processing technology, as shown in Figure 4, Thin film after extraction linearly transmits, and uses hydraulic giant 8 and air gun 7 mixing to be dried, system Easily there are water ripples in the film surface obtained, causes the final battery diaphragm uneven thickness prepared Or uneven, and hydraulic giant 8 and air gun 7 inject directly on the surface of thin film the most at a certain angle, punching Power of hitting is big, and the phenomenon such as battery diaphragm outward appearance fold, scollop, scallop is serious, affects battery diaphragm Use and rolling.

According in another embodiment of the present invention, as it is shown in figure 5, described three kinds micro- The battery diaphragm of pore structure includes first outer layer the 9, second outer layer 10 and is clipped in therebetween Internal layer 11, described first outer layer the 9, second outer layer 10 and internal layer 11 have different micropore knots Structure.

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

There is the polyethylene composition of the lithium ion battery separator of three kinds of microcellular structures for preparation Thing includes the component of following 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 16.2 μm have the battery diaphragm of three kinds of microcellular structures.

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 high-molecular polythene.

The lithium ion battery separator hardness and the density that prepare are excessive, and lithium ion cannot pass through.

Comparative example 2

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

The battery diaphragm mechanical strength prepared is too low, the cracky when preparing lithium ion battery.

Comparative example 3

This comparative example is identical with embodiment 2 method therefor, differs only in polyethylene composition Middle high-molecular polythene is as follows with the weight proportion of ultra high molecular polyethylene:

The battery diaphragm micropore skewness prepared, in irregular shape.

Comparative example 4

This comparative example is identical with embodiment 3 method therefor, differs only in polyethylene composition Middle high-molecular polythene is as follows with the weight proportion of ultra high molecular polyethylene:

The battery diaphragm mechanical strength prepared is low, and poor air permeability, aperture is uneven.

Comparative example 5

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

The battery diaphragm preparing embodiment and comparative example is tested as follows, and 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 test result

Above in association with detailed description of the invention and exemplary example, the present invention is carried out specifically Bright, but these explanations can not be interpreted as limitation of the present invention.Those skilled in the art Understand, without departing from the spirit and scope of the invention, can be to the technology of the present invention side Case and embodiment thereof carry out multiple equivalencing, modify or improve, and these each fall within this In bright scope.Protection scope of the present invention is as the criterion with claims.

Claims

1. the polyethylene for three kinds of microcellular structure lithium ion battery separators of preparation Compositions, it is characterised in that said composition includes the component of following weight proportion:

High-molecular polythene 88～92 weight portion

Ultra high molecular polyethylene 8～12 weight portion.

Compositions the most according to claim 1, it is characterised in that

The number-average molecular weight of described high-molecular polythene is 100,000～600,000, preferably 20 Ten thousand～500,000, more preferably 300,000～400,000, and/or,

The number-average molecular weight of described ultra high molecular polyethylene is 1,200,000～1,500,000, preferably It is 1,300,000～1,400,000.

Compositions the most according to claim 1 and 2, it is characterised in that described group Compound also includes the component of following weight portion,

Pore former 20～70 weight portion,

The most described pore former includes organic pore former and Inorganic pore forming agents, it is preferable that Described organic pore former is high boiling point small organic molecule, and described Inorganic pore forming agents is water Insoluble inorganic nano-particle, wherein, described high boiling point small organic molecule is that boiling point is high In 200 DEG C, and number-average molecular weight less than 500 liquid state organics, described water solublity without Machine nano particle diameter is 1～200nm；

Preferably, described high boiling point small organic molecule is preferably mineral oil, C_6-15Alkane Hydrocarbon, C_8-15Aliphatic carboxylic acid, C_1-4Alkyl ester, C_2-6One or more in halogenated alkane； And/or

Preferably, described water-soluble inorganic nano-particle selected from water-soluble nano sulfate, One or more in water-soluble nano nitrate, water-soluble nano hydrochlorate etc..

4. according to the compositions one of claims 1 to 3 Suo Shu, it is characterised in that institute State pore former and include white oil and nanometer magnesium chloride,

The most 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).

5. according to the compositions one of Claims 1-4 Suo Shu, it is characterised in that institute State compositions and also include the component of following weight proportion,

Described antifoggant selected from the ester of xylitol, sorbitol palmitate, lauric acid, Span series, TWEEN Series surfactant or animi resin acid glycerol list Ester.

6. according to the compositions one of claim 1 to 5 Suo Shu, it is characterised in that institute State compositions and include the component of following weight proportion,

Wherein,

The particle diameter of described nanometer magnesium chloride is 5～20nm.

7. according to the compositions one of claim 1 to 6 Suo Shu, it is characterised in that institute State compositions and include the component of following weight proportion,

Wherein,

Described antioxidant is selected from 4,4-thiobis (6-tert-butyl-m-cresol), dibutyl hydroxyl Base toluene, phosphite ester, tert-butylhydroquinone, preferably 4,4-thiobis (uncle 6- Butyl metacresol), and/or

Described anti ultraviolet agent is selected from salicylic acid esters, benzophenone class, benzotriazole, takes For vinyl cyanide, triazines and hindered amines, preferably oxybenzoic acid phenyl ester, 2-(2-hydroxyl-5-aminomethyl phenyl) BTA, 2,4-DihydroxyBenzophenone, ESCALOL 567, Octabenzone, 2-(2'- The tertiary phenyl of hydroxyl-3', 5'-bis-)-5-chlorination benzotriazole, single benzoic acid resorcinol, Three (1,2,2,6,6-pempidine base) phosphite ester, 4-benzoyloxy-2,2, 6,6-tetramethyl piperidines, 2,4,6-tri-(2' n-butoxyphenyl)-1,3,5-triazines With HMPA etc., and/or

Described antistatic additive is selected from quaternary ammonium salt, ethoxy alkylation aliphatic alkyl amine, Such as octadecyl quaternary ammonium sodium, and/or

Described antifoggant selected from the ester of xylitol, sorbitol palmitate, lauric acid, Span series and TWEEN Series surfactant or animi resin acid glycerol list Ester, is preferably, span series and TWEEN Series surfactant.

8. a preparation method for three kinds of microcellular structure lithium ion battery separators, its feature It is, said method comprising the steps of:

1), by the polyethylene composition according to one of claim 1 to 8, pore former and Other optional additive melting mixing, extrudes casting films；

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

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

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

5), step 4) thin film that obtains processes through extractant, is then dried；

6), step 5) the thin film both sides that obtain fix, successively through the second preheating zone, Two drawing zones and the second cooling zone carry out second time cross directional stretch, obtain having three kinds micro- The battery diaphragm of pore structure.

Method the most according to claim 8, it is characterised in that in step 5) in, 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 in the position that thin film contacts with transfer roller Air gun, the jet direction of the most described air gun preferably with the plane tangent of described transfer roller Or parallel with the direction of transfer of thin film.

The lithium ion battery separator that the most according to claim 8 or claim 9, method prepares, It is characterized in that, described battery diaphragm has three kinds of microcellular structures.