WO2013097311A1 - 具有热压粘合特性的聚乙烯基复合材料微多孔隔膜 - Google Patents

具有热压粘合特性的聚乙烯基复合材料微多孔隔膜 Download PDF

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WO2013097311A1
WO2013097311A1 PCT/CN2012/070487 CN2012070487W WO2013097311A1 WO 2013097311 A1 WO2013097311 A1 WO 2013097311A1 CN 2012070487 W CN2012070487 W CN 2012070487W WO 2013097311 A1 WO2013097311 A1 WO 2013097311A1
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separator
molecular weight
membrane
polyvinyl
composite
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PCT/CN2012/070487
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English (en)
French (fr)
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李鑫
李建华
焦永军
李龙
陈卫
邓新建
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天津东皋膜技术有限公司
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Publication of WO2013097311A1 publication Critical patent/WO2013097311A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/261—Polyethylene
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/494—Tensile strength
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a polyolefin microporous separator for a lithium ion battery and a method for producing the same, and particularly to a polyvinyl composite microporous separator having a thermocompression bonding property by controlling an amorphous content, which is suitable for high safety and long cycle life.
  • Lithium battery field such as lithium ion power battery or energy storage battery.
  • the polyolefin microporous membrane has a three-dimensional network-like nano-scale microporous penetrating, is resistant to high voltage oxidation, and is stable to an organic electrolyte of a lithium ion battery.
  • As a separator material it has been widely used in lithium ion batteries for mobile phones, notebook computers, etc., typical Commercialized polyolefin microporous membranes are "dry"
  • PP/PE/PP three-layer composite separator and single-layer "wet" high molecular weight PE separator.
  • a porous physical gel membrane which is lyotropic phase separation method, which is typically manufactured by Bellcore process.
  • PVDF-HFP Copolymer Porous Physical Gel Membrane due to its low strength, is usually laminated by a lamination process and a pole piece by hot pressing to form an integral pole group, PVDF-HFP copolymer porous gel absorption electrolysis After the liquid, it can be swelled, with a certain degree of elasticity, and the liquid repellency of the pole piece is good, the cycle life of the battery is high, the safety and the consistency are good; but the pore diameter of the PVDF-HFP gel membrane is slightly larger, close to 0. 5- 2 Micron and separator have not been strengthened by thermal stretching, and the mechanical strength is low, which cannot meet the process requirements of battery winding.
  • the diaphragm has insufficient toughness and is easy to tear in the transverse direction; the transverse elongation at break is less than 20%; 2.
  • the intermediate microporous layer uses PE which is turned off at a high temperature of 135-145 ° C, the PP microporous layer having a limited melting point and being thermally stretched and strengthened has a large heat shrinkage at a high temperature of 130 ° C or higher. Shortcomings of insufficient high temperature resistant membrane breakage;
  • the Chinese invention patent application 02152444. 0 proposes blending less than 10% thermoplastic polyolefin elastomer (diethylene propylene rubber) in the polyolefin matrix. , EPDM), and then stretched into pores; however, the nature and toughness of the thermoplastic polyolefin elastomer determine its effect on the formation and distribution of silver streaks in the polyolefin matrix during cold drawing, ie, affecting the polyolefin matrix.”
  • the dry method has the ability to stretch into pores, and a suitable porosity is not obtained. Therefore, the proportion of the thermoplastic olefin elastomer mixed therein must be less than 10%, so that the mechanical properties of the separator are limited and the practicality is insufficient.
  • the other is the "wet method” process, the “wet method” is also called the thermal phase separation method.
  • the high molecular weight polyolefin resin and the “high temperature compatibilizer” are used as the main raw materials, and the high temperature compatibilizer is conventionally used as the paraffin oil.
  • High-boiling alkane liquid which dissolves in a thermodynamic sense at a high temperature with a polyolefin resin, can achieve molecular-level mixing, and is phase-separated at a low temperature.
  • the high-temperature compatibilizer is also a process solvent for pore-forming, heating and kneading.
  • the uniform high-temperature melt rapidly solidifies on the surface of the chill roll, phase separation occurs during the cooling process, and the sheet is stretch-strengthened by stepwise biaxial stretching or simultaneous biaxial stretching, and then the semi-finished film is extracted by a volatile cleaning solvent.
  • the high-temperature compatibilizer in the sheet is further subjected to further thermal stretching strengthening, heat setting, and cooling to prepare a nano-scale microporous separator material which is internally interpenetrated.
  • the common method is a single-layer PE separator, which is compared with the dry diaphragm. Due to the use of biaxial stretching reinforcement, the weight of the raw materials The molecular weight is generally above 500,000, and the wet film has improved tensile strength and elongation at break.
  • the main disadvantages of the existing "wet method" PE separator include:
  • high-molecular-weight powdered high-density polyethylene is mixed with liquid paraffin oil high-temperature compatibilizer, and then heated and mixed. Due to the difference in density between the two, the solid content of the slurry tends to fluctuate, feed stability and Poor consistency of melt composition; product stability and consistency are affected;
  • the existing "wet method" PE membrane and the pole piece also lack the thermocompression bonding ability; the thickness direction is also lack of elasticity, lack of stress absorption ability, and safety. Sex and battery cycle life can not meet the high-end requirements of power batteries.
  • the diaphragm is required to have the following characteristics:
  • the diaphragm When the internal accidental heating of the battery is at a high temperature of 130-200 °C, the diaphragm should have a melt-off characteristic and a small heat-shrinkage; a high temperature resistant membrane, even if molten, has mechanical integrity;
  • the thickness direction has good compressive elasticity, that is, the diaphragm has appropriate elastic deformation ability when it is subjected to compressive stress in the thickness direction to meet the needs of the expansion of the negative electrode, and prevents the pole piece from being bucked by uneven deformation stress and deformation; At the same time, the porosity is not reduced much. Even the micropores are closed and the internal resistance is too high, which affects the normal discharge of the battery. After the pressure is released, it has the elastic recovery ability, ensuring uniform and close contact between the positive and negative electrodes and the diaphragm, and no local poor liquid.
  • the existing polyolefin separator is basically an inert material, the adhesion between the coating and the coating is insufficient, the coating is thick and easy to peel off, and the heat shrinkage effect of the polyolefin membrane is not obvious;
  • the micropores of the polyolefin separator have capillary action.
  • the colloid in the slurry easily enters the micropores of the polyolefin separator, which may affect the separator after the solvent is evaporated and dried to form a film.
  • the pore size distribution and gas permeability, the consistency of the coating method for mass production is difficult to control, and the coating method composite membrane is expensive to manufacture.
  • Chinese Patent Application No. 0112218. 8 proposes mixing a monomer polymer which can be thermally crosslinked to form a gel in an electrolyte.
  • the gel is used to increase the bonding strength between the separator and the positive electrode tab.
  • the gel forms a gel in the micropores of the separator during the formation of the thermal crosslink, thereby affecting the permeability of the separator, and the reaction. Incomplete monomers may also oxidize on the positive side, produce gas, etc., and may even affect the cycle performance of the battery.
  • the viscous commercial film material such as stretch-wound film, inspires the inventors.
  • Poly-isobutylene and other tackifying resins are used to modify PP and PE to obtain a non-porous and adhesive film for packaging.
  • the inventors Based on the analysis of the defects of the polyolefin separator for lithium ion batteries and the understanding of the diaphragm manufacturing process and formulation analysis, based on the understanding of the relationship between the safety and service life of the battery and the separator material, in order to improve the existing single layer and multilayer Disadvantages of the separator, the inventors made a completely new design in the raw material and process of the separator, and the structure of the separator product, and obtained a polymer which has the above-mentioned characteristics and can improve the safety performance and the cycle performance of the lithium ion battery.
  • Olefin microporous membrane In addition to the various deficiencies of the prior art, the following inventions are specifically proposed.
  • the polyvinyl composite composite microporous membrane of the present invention is characterized in that it has a weight percentage of 10-25%, a weight average molecular weight of 900,000 to 250,000, a suitable high temperature viscosity, and a dynamic viscosity at 100 Torr of 50 to 2000 Pa's.
  • the rubber composition is modified by high-crystallinity high-density polyethylene HDPE, and the flash point is 210 ° C by controlling the amorphous content in the polyethylene matrix and the principle of "liquid-liquid phase separation" by thermally induced phase separation.
  • the above aliphatic dibasic acid ester is used as a process solvent and a pore-forming agent for the polyvinyl composite composite microporous separator, and an asymmetric microporous polyvinyl composite microporous membrane is obtained, and the composite microporous membrane and the positive electrode tab
  • Paraffin oil as a compatibilizer the general commercial wet PE microporous membrane generally has an average pore diameter of less than 70 nm, and has substantially no thermocompression bonding ability with the pole piece. If the high temperature is too strong, the hot pressure becomes smaller due to the diaphragm diameter, the battery The internal resistance is unacceptably high. Therefore, the present invention adopts an asymmetric microporous, relatively large average pore diameter polyvinyl composite microporous membrane structure, and uses a liquid phase separation principle of thermally induced phase separation, and the high temperature compatibilizer does not.
  • the paraffin oil is preferably an aliphatic dibasic acid ester preferably selected from a flash point of 21 CTC or more, including dioctyl sebacate DOS, dioctyl sebacate D0Z, diisodecyl adipate DIDA, or the like, or a combination thereof.
  • the aliphatic dibasic acid ester is thermodynamically compatible with polyethylene at a high temperature of 180-210 ° C, and the concentration segregation and phase separation behavior of the melt during the gradual cooling and cooling of the melt above the melting point of the polyethylene is "liquid-liquid phase separation".
  • High temperature compatibilizers for aliphatic diesters can also be avoided with a high flash point When the diaphragm is manufactured, large pores and bubbles are generated in the high-temperature melt, and the production is relatively safe; fat.
  • the dibasic acid ester is compatible with polyisobutylene and ethylene-propylene rubber at 90-12 CTC.
  • the high temperature and the conditions are kneaded together to form a uniform hot melt adhesive.
  • the hot melt adhesive and the high molecular weight polyethylene powder and the liquid high temperature compatibilizer have a certain viscosity after being uniformly dispersed at a high temperature of 90-120 ° C. ,: It can form a liquid-solid two-phase flow slurry which is not easy to settle, and is convenient for feeding stability and product consistency in the extruder when the wet diaphragm is produced.
  • the melt phase separation is also necessary to control the melt phase separation by controlling the different cooling conditions on both sides of the melt by using a special process of asymmetric cooling casting, common film casting.
  • the film is often cooled by a large single mirror roll.
  • the melt is rapidly solidified into a sheet on the surface of the chill roll by at least two-roller asymmetric cooling process, and the control sheet is cooled on both sides, and the side of the melt can be controlled.
  • the wrapping length of the secondary chilling roll is smaller than the winding length of the other side of the melt and the cooling tempering roller of the No.
  • the membrane has an average pore diameter of 80-300 nm and a porosity of 40-75%.
  • the porosity is preferably between 50 and 65%, and the initial GURLEY value is between 30 and 400 S/100 cc.
  • the resistance of the composite membrane is still treated even after 110-120 ° C, 1-2. 5 MPa hot pressing. Little.
  • the latent heat of fusion of the wet PE microporous separator is generally 220 J/g or more.
  • the present invention The amorphous-based rubber-modified polyethylene can regulate the content of amorphous therein, thereby controlling the polyethylene.
  • the latent heat of fusion of the composite separator is controlled to 150-195 J/g. Since it is a polyethylene matrix, the separator of the present invention has a melting point of 130-145 ° C; a thickness of 20-50 ⁇ m, more preferably controlled at 25 -35 microns, combined with a suitably large average pore size and a suitably high porosity, the porosity is preferably between 50 and 65%, even after heat treatment, the internal resistance of the battery is still small; When the content of the crystalline rubber is 10% or more and 25% or less, the contradiction between the thermocompression bonding ability and the tensile strength can be achieved, and if the polyethylene matrix and the rubber are used in an excessively low rubber ratio, the thermocompression bonding ability is insufficient.
  • the main material of the separator is 4 to 7 times hot stretching in the MD direction at 105-128 ° C, and 2-6 times in the TD direction, and the longitudinal tensile strength of the separator is controlled to be greater than 70 MPa, and the transverse elongation at break is greater than 100%, the diaphragm has strong resistance to extrusion and needle punching, and the diaphragm is safe.
  • a method for producing the above-mentioned polyvinyl composite composite microporous separator having thermocompression bonding property characterized in that the polyvinyl composite composite microporous membrane crucible is produced by a thermally induced phase separation method, more preferably a liquid phase Made by separation method, using high-density high-density polyethylene HDPE as the base material, using amorphous polyisobutylene and/or ethylene-propylene rubber compatible with polyethylene at high temperature to provide heat for the polyethylene composite diaphragm
  • the pressure-adhesive ability is obtained by controlling the cooling speed of the two sides when the cast piece is different to obtain a porous film having asymmetric micropores on both sides, and the main steps of manufacturing the polyethylene-based composite microporous separator having thermocompression bonding characteristics include:
  • the medium molecular weight rubber and the aliphatic dibasic acid ester high temperature compatibilizer are kneaded and kneaded uniformly at 90-12CTC to form a hot melt adhesive A;
  • high molecular weight polyethylene powder and high temperature compatibilizer in 90-120 ⁇ swell and swell for 1-24 hours, mixing and mixing into slurry B;
  • Asymmetric cooling of the cast piece the melt is rapidly solidified into a sheet on the surface of the chill roll by at least two-roller asymmetric cooling process, and the sheet is cooled on both sides to control the side of the melt and the secondary chilling of No. 1
  • the wrapping length of the roller is smaller than the wrapping length of the other side of the melt and the temperature and flow rate of the cooling medium inside the primary and secondary chill rolls;
  • the second hot stretching adjusts the porosity, pore size, thickness of the microporous film, and heat-set and then cools to obtain a polyvinyl composite composite microporous separator having thermocompression bonding properties.
  • a lithium ion battery using the above-described polyvinyl composite microporous separator having thermocompression bonding property comprising a positive electrode tab, a negative electrode tab, an electrolyte, and the above-mentioned thermocompression bonding property
  • the polyethylene micro-composite microporous separator before the liquid injection, the battery pole set of the positive pole piece, the separator and the negative electrode piece is pressed at a temperature of 110-125 ° C for 1-15 minutes by using a pressure of 1-2. 5 MPa. After hot pressing, the concavo-convex particles on the surface of the separator and the pole piece can form a mechanical fitting effect to prevent heat shrinkage of the separator at 130 Torr or higher, and the battery is safe.
  • polyvinyl composite microporous separators with thermocompression bonding properties have the same bonding ability as PVDF-HFP copolymer gel membranes, overcoming Heat shrinkage defects characteristic of heat-stretched polyolefin separators, amorphous in polyvinyl-based composite microporous separators Rubber has a certain ability to absorb and swell, and the battery's consistency and cycle life will benefit.
  • the rubber raw material adopts a medium molecular weight polyisobutylene rubber, a binary ethylene propylene rubber or a weight average molecular weight of 190,000 to 20,000, 10 CTC, and a dynamic viscosity of 50 to 2000 Pa's.
  • the composition of the rubber such a design is to take into account the need to prepare hot melt adhesive, the molecular weight of the rubber is too small and the viscosity is too low, the liquid-solid two-phase flow after mixing with the polyethylene powder is unstable, the powder is easy to settle, not Conducive to the consistency of the production of the membrane; another disadvantage of the molecular weight of the rubber raw material is that it is easily extracted and extracted together with the high-temperature compatibilizer during the membrane extraction and pore-forming process; the molecular weight of the rubber raw material is too small, the viscosity is too high or too high The rubber content will cause the polyethylene separator to be closed at 105-128 ° C during the hot tensile strengthening process; if the rubber material uses too high molecular weight and too high viscosity, it will affect the hot melt adhesive at 90-12 CTC.
  • Figure 1 is a side view of the side of the orifice of the diaphragm of the present invention.
  • Figure 2 is a view showing the macroporous side of the other side of the diaphragm of the present invention.
  • the embodiment of the present invention will be described in detail. Further, the present invention is not limited to the embodiments described below, and various modifications can be made within the scope of the invention.
  • microporous membrane was tested for gas permeability in accordance with JIS P8117.
  • the pore size distribution and average pore diameter of the separator were measured using a mercury intrusion meter at a pressure of 20-2000 psi.
  • Example 1 Polyethylene Composite Diaphragm Formulation:
  • the temperature setting range is: 175 ⁇ -210 ⁇ ; the melt is extruded through the flat die and quenched and cast, the cast piece adopts three-roll cooling process, No. 1 cooling press roll, No. 2 sub-cooling roll, No. 3 main cooling roll
  • the melt is cut at a zero angle between the 1/2 rolls. After the surface of the No. 2 roll is wrapped at a 90 degree angle to cool the side of the melt, it is transferred to the other side of the No. 3 main cooling roll to cool the melt, and the main cooling roll No. 3 5 ⁇ ;
  • the thickness of the slab is controlled to 1. 5mm;
  • the heat-stretching temperature is 125 ° C; the longitudinal hot-stretching is 1. 3 times, the transverse hot-stretching is 1.5 times, the hot stretching temperature is 125 ° C, and the pre-heated film is preheated by 115-125 O.
  • the pole group Before the liquid injection, the pole group is pressurized at 118 ° C / l MPa for 10 min, after cooling
  • the peel strength of the test separator and the positive electrode tab was 0.1 N/20 ⁇ , and the composite of the separator and the positive electrode sheet was heat-shrinked at 13 CTC, cooled to room temperature, and the separator was kept in a complete shape, and the heat shrinkage ratio in both the longitudinal direction and the transverse direction was measured. Less than 8%; Gurley value is greater than 2000S/100CC.
  • the thickness of the separator was 24 ⁇ m, and the thickness of the test membrane was 26 ⁇ m after 5 minutes of pressure release, and the Gurley value was 228 S/100 cc. .
  • the battery was fabricated in the same manner as in Example 1, except that the separator was made of a dry PP/PE/PP film of a company, thickness 25 ⁇ m, porosity 40%, Gurley value 600-630S/100CC, tensile strength: MD direction 165 MPa, TD direction 13 MPa The transverse elongation at break is 15%.
  • the battery was fabricated in the same manner as in Example 1, except that the separator was made of a company's wet single-layer PE separator, thickness 25 ⁇ m, porosity 49%, Gurley value 185 S/100 CC, tensile strength: MD direction 143 MPa, TD direction 21 MPa, longitudinal fracture extension The growth rate is 42% and the transverse elongation at break is 344%.

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Abstract

具有热压粘合特性的聚乙烯基复合材料微多孔隔膜，采用中分子量的二元乙丙、聚异丁烯橡胶对高结晶度的高密度聚乙烯进行改性，采用闪点210°C以上的脂肪族二元酸酯作为隔膜的工艺溶剂和造孔剂，得到具备热压粘合特性的隔膜，该隔膜与正极极片热压贴合后粘接成一体，隔膜热收缩得到抑制，该隔膜具备高强度、耐高温，可用于锂离子动力电池。

Description

具有热压粘合特性的聚乙烯基复合材料微多孔隔膜 技术领域
本发明涉及锂离子电池用聚烯烃微多孔隔膜及其制造方法， 尤其涉及通 过控制非晶含量具有热压粘合特性的聚乙烯基复合材料微多孔隔膜，适用于 高安全性、 长循环寿命的锂离子动力电池或储能电池等锂电池领域。
背景技术
聚烯烃微多孔膜具有贯穿的三维网络状纳米级微孔，耐高电压氧化、 对 锂离子电池的有机电解质稳定， 作为隔膜材料目前己广泛应用于手机、 笔记 本电脑等用的锂离子电池， 典型的商品化聚烯烃微多孔隔膜为 "干法"
PP/PE/PP三层复合隔膜和单层 "湿法"高分子量 PE隔膜， 除此两大类外还 有一种是溶致相分离法的多孔物理凝胶隔膜,典型的如 Bellcore工艺制造的 PVDF-HFP共聚物多孔物理凝胶隔膜，由于该隔膜强度低、 使用时通常采用叠 片工艺与极片间通过热压工艺粘结成为一个整体极组， PVDF-HFP共聚物多孔 凝胶吸收电解液后可以溶胀，有一定弹性、 极片保液性较好， 电池循环寿命 较高、 安全性、 一致性较好；但是 PVDF-HFP 凝胶隔膜微孔孔径略大， 接近 0. 5- 2微米、 隔膜未有经过热拉伸强化， 机械强度低， 不能适应电池卷绕等 工艺要求。
现有聚烯烃微多孔隔膜在电池安全性和电池的循环寿命等方面目前均 满足不了动力电池以及消费电子等长寿命、 安全的高端要求，主要技术分析 如下:现有 "干法" PP/PE/PP三层隔膜的主要缺点是：
1. 隔膜的强韧性不足， 横向易撕裂;横向断裂伸长率小于 20%; 2. 虽然中间微多孔层采用了 135- 145°C高温下关断的 PE，但是熔点有限 并经过热拉伸强化的 PP微多孔层在 130°C以上的高温下仍存在热收 缩偏大、 耐高温破膜不足的缺点；
3. 与 PVDF-HFP物理凝胶隔膜或涂层隔膜相比， 干法隔膜与极片间缺乏 , 热压粘合能力。
为提高 "干法" PP/PE/PP 隔膜的横向抗撕裂性能， 中国发明专利申请 02152444. 0 提出了在聚烯烃基体中共混入低于 10%的热塑性聚烯烃弹性体 (二元乙丙橡胶、 三元乙丙橡胶）， 然后再拉伸成孔的方法； 但是热塑性聚 烯烃弹性体的本性和韧性决定了其影响冷拉时聚烯烃基体中银纹的形成和 分布， 即影响聚烯烃基体 "干法"拉伸成孔的能力， 得不到合适的孔隙率， 因此其中热塑性烯烃弹性体混入的比例必须低于 10%， 所以对隔膜的力学性 能提高有限， 实用性不足。
另外一种是 "湿法"工艺， "湿法"又称热致相分离法， 将高分子量的 聚烯烃树脂与 "高温相容剂"作为主要原料， 高温相容剂常规多采用石蜡油 类高沸点烷烃液体， 该溶剂与聚烯烃树脂在高温下在热力学意义上相互溶 解、 可以达到分子级别的混合， 低温下分相， 高温相容剂其实也是一种造孔 的工艺溶剂， 加热混炼均匀的高温熔体在冷辊表面快速凝固， 降温过程中发 生相分离， 再以分步双向拉伸或同步双向拉伸对薄片做拉伸强化处理， 然后 用易挥发的清洗溶剂去萃取半成品膜片中的高温相容剂，经进一步热拉伸强 化、 热定型、 冷却可制备出内部相互贯通的纳米级微孔隔膜材料， 该法常见 的为单层 PE隔膜， 与干法隔膜相比， 由于采用双向拉伸强化、 原料的重均 分子量一般在 50万以上， 湿法隔膜在横向拉伸强度和断裂伸长率均有所提 高， 现有 "湿法" PE隔膜主要缺点包括：
1、 制造时采用高分子量的粉状高密度聚乙烯与液态的石蜡油类高温相 容剂混合后加热混炼， 由于二者密度差异， 料浆的固含量易存在波动， 喂料 稳定性和熔体成分一致性不佳； 产品稳定性、 一致性受影响；
2、 由于采用了热拉伸强化工艺， 120°C以上的高温下热收缩偏大； 电池 安全性不足；
3、 与 PVDF-HFP物理凝胶隔膜或涂层隔膜相比， 现有"湿法" PE隔膜与 极片间同样缺乏热压粘合能力；厚度方向同样缺乏弹性、缺乏应力吸收能力， 在安全性和电池的循环寿命等方面均满足不了动力电池的高端要求。
在有关动力电池等要求较高的市场应用， 要求隔膜兼具以下特性：
1. 厚度均匀、 纳米级孔径、 低内阻、 具有合适、 均匀分布的孔隙率；
2. 在机械性能方面要求纵向具有高的拉伸强度、 横向具有高的韧性、 厚度方向耐挤压和针刺， 防止物理短路；
3.电池内部意外发热处于 130-200°C高温时，隔膜应具有熔融关断特性、 高温热收缩小； 耐高温破膜、 即使熔融仍具备机械完整性；
4. 厚度方向具备良好的压缩弹性，即在厚度方向受到压应力时隔膜具 备适当的弹性变形能力以适应负极膨胀的需要， 防止极片受不均匀压应力失 稳变形而皱曲；受压变形的同时不致于孔隙率降低很多甚至微孔闭合而内阻 过高影响电池的正常放电； 压力释放后具备弹性回复能力， 保证正、 负极片 与隔膜间均匀紧密地接触、 不存在局部贫液。 为提高和弥补现有聚烯烃微孔隔膜的耐高温收缩及耐高温破膜性能， 中 国发明专利申请 200480034190. 3提出在聚烯烃微孔隔膜表面涂布可以凝胶 化的氟树脂形成涂层的技术方案； 主要不足之处在于：
1.由于现有聚烯烃隔膜基本属惰性材料， 与涂层之间粘接力不够、 涂层 厚了易剥离， 太薄抑制聚烯烃隔膜热收缩作用不明显；
2.采用电晕处理后， 聚烯烃隔膜的微孔存在毛细作用， 在实施上述涂层 方案时料浆中的胶体容易进入聚烯烃隔膜的微孔中， 在溶剂挥发干燥成 膜后可能影响隔膜的孔径分布和透气性， 涂层方法批量生产的一致性难 以控制， 另外涂层法复合隔膜制造成本高。
为提高隔膜与正极极片的粘接强度从而提高锂电池耐过充等方面的安 全性， 中国发明专利申请 01112218. 8提出在电解液中混合加入可以热交联 形成凝胶的单体聚合物， 利用该凝胶提高隔膜与正极极片的粘接强度， 同样 的该凝胶在热交联形成过程中会同样在隔膜的微孔中形成凝胶， 从而影响隔 膜的透过能力， 另外反应不完全的单体还可能会在正极侧氧化、 产气等， 甚 至会影响电池的循环性能。
带粘性的商业薄膜材料如拉伸缠绕膜给发明者带来启发， 采用聚异丁烯 等增粘树脂对 PP、PE改性，可以得到无孔的有粘接能力的薄膜用于包装； 经 过对现有锂离子电池用聚烯烃隔膜的缺点分析和隔膜制造工艺及配方分析 理解的基础上， 基于对电池的安全性及使用寿命与隔膜材料之间的关系理 解， 为改善现有单层、 多层隔膜的缺点，本发明人在隔膜的制造原料和工艺 方法及其隔膜产品的结构作全新的设计， 得到同时具备前述诸特性并能够使 锂离子电池在安全性能和循环性能均有所改善的聚烯烃微多孔隔膜,从而弥 补了现有技术的种种不足， 特提出以下发明内容。
发明内容
本发明的聚乙烯基复合材料微多孔隔膜特征在于， 通过采用重量百分 比介于 10-25%、 重均分子量 9-25万、 具备合适的高温粘度、 100Ό下的动力 粘度在 50- 2000Pa'S、 可以与高温相容剂配制成热熔胶、 具备热压粘合特性、 与聚乙烯和高温相容剂均相容的非晶态、 中分子量的聚异丁烯橡胶 PIB、 二 元乙丙橡胶 EPM或两种橡胶的组合物对高结晶度的高密度聚乙烯 HDPE进行 改性，通过控制聚乙烯基体中的非晶含量和采用热致相分离的"液液相分离" 原理， 采用闪点 210°C以上的脂肪族二元酸酯作为聚乙烯基复合材料微多孔 隔膜的工艺溶剂和造孔剂， 得到非对称微孔的聚乙烯基复合材料微多孔隔膜, 该复合材料微多孔隔膜与正极极片可以在 110-120°C、 1-2. 5MPa、 l-15min 的热压贴合后将隔膜与极片粘接成一体， 剥离强度大于 0. 03N/20隱、 130°C /30min热收缩小于 10%。
石蜡油作为相容剂的普通商业化湿法 PE微多孔隔膜平均孔径一般小于 70纳米， 与极片间基本不具备热压粘合能力， 如果高温勉强热压由于隔膜孔 径变得更小， 电池内阻高的不可接受， 因此本发明采用非对称微孔、 相对大 平均孔径的聚乙烯基复合材料微多孔隔膜组织结构， 釆用热致相分离的液液 相分离原理， 高温相容剂不采用石蜡油而是优选自闪点 21CTC以上的脂肪族 二元酸酯，包括癸二酸二辛酯 D0S、壬二酸二辛酯 D0Z、己二酸二异癸酯 DIDA 等或其组合物，脂肪族二元酸酯与聚乙烯在 180-210°C的高温下热力学相容、 熔体在聚乙烯的熔点以上高温逐步冷却降温过程中存在浓度偏析分相行为 即 "液液相分离"， 高温相容剂的脂肪族二元酸酯釆用高的闪点还可以避免 隔膜制造时高温熔体中产生大的气孔和气泡等缺陷， 生产也比较安全； 脂肪. '： 族二元酸酯与聚异丁烯、二元乙丙橡胶在 90- 12CTC下也相容，可以在此高温 · 条件下捏合在一起配制成均匀的热熔胶使用， 热熔胶与高分子量的聚乙烯粉 体及液态的高温相容剂在 90- 120°C高温下混合分散均匀后具有一定粘度，：可 以构成不易沉降的液固两相流料浆，便于湿法隔膜生产时向挤出机中喂料的 稳定性和产品一致性。
除采用本发明的高闪点脂肪族二元酸酯作为高温相溶剂外， 还要通过釆 用不对称冷却铸片特殊工艺控制熔体两面的冷却条件不同来控制熔体分相， 普通薄膜铸片常采用大的单只镜面辊冷却，本发明将熔体在激冷辊表面至少 采用双辊不对称冷却工艺快速凝固成片材， 控制片材两面冷却不同，可以控 制熔体的一面与 1号副激冷辊的包绕长度小于熔体的另一面与 2号主激冷辊 的包绕长度或控制主副急冷辊内部的冷却介质的温度和流量不同，得到两面 具有不同孔径的微孔隔膜形貌， 其中一面的微孔形貌呈细密分布，另一面的 微孔形貌呈树枝状粗大孔分布， 优选隔膜的平均孔径介于 80-300纳米， 孔 隙率介于 40-75%， 孔隙率优选介于 50-65%， 初始 GURLEY 值介于 30-400S/100CC , 这样的隔膜产品结构即使经过 110- 120°C、 1-2. 5MPa热压 处理， 复合材料隔膜的阻力仍然不大。
由于高密度聚乙烯容易结晶具有相对较高的结晶度， 在热拉伸时容易形 成微纤化组织所以 PE隔膜远较未拉伸强化的 PVDF-HFP凝胶隔膜的拉伸强度 高， 普通商品湿法 PE微多孔隔膜的熔融潜热一般在 220 J/g .以上， 本发明. 采用非晶为主的橡胶改性聚乙烯可以调控其中非晶的含量、从而控制聚乙烯 . 基微多孔隔膜的结晶度、 利用隔膜表面非晶区的橡胶部分提供热压粘合能 力， 复合材料隔膜的熔融潜热控制为 150- 195J/g，由于是聚乙烯基体， 本发 明的隔膜其熔点仍介于 130- 145°C ; 厚度介于 20-50 微米， 更优选控制在 25-35微米， 与适当大的平均孔径及适当高的孔隙率结合， 孔隙率优选介于 50-65%， 即使经过热压处理后电池的内阻仍不大； 通辻控制复合材料隔膜中 非晶橡胶的含量在 10%以上、 25%以下可以兼顾热压粘合能力和拉伸强度的矛 盾，聚乙烯基体和橡胶二者中如果采用过低的橡胶占比，热压粘合能力不足， 过高的橡胶占比则降低微孔膜的机械强度， 另外由于其中橡胶未釆用交联处 理存在热塑性流动还会导致隔膜热拉伸后存在局部闭孔。采用熔融潜热介于 200-250J/g的高结晶度、 重均分子量介于 50- 500万， 优选重均分子量介于 100-300万的特高分子量 HMWPE或超高分子量高密度聚乙烯 UHMWPE作为隔膜 的主体材料， 通过 105- 128°C下 MD方向 4- 7倍的热拉伸， TD方向 2-6倍的 热拉伸， 控制隔膜的纵向拉伸强度大于 70MPa、 横向断裂伸长率大于 100%， 隔膜的抗挤压、 针刺短路能力较强， 隔膜安全性高。
一种制造上述具有热压粘合特性的聚乙烯基复合材料微多孔隔膜的方 法， 其特征在于， 该聚乙烯基复合材料微多孔隔膜釆用热致相分离法制造， 更优选采用液液相分离法制造， 采用高结晶度的高密度聚乙烯 HDPE为基体 材料,采用与聚乙烯高温下相容的非晶态的聚异丁烯和 /或二元乙丙橡胶为 聚乙烯基复合材料隔膜提供热压粘合能力，通过控制铸片时两面的冷却速度 不同得到两面具备非对称微孔的多孔膜，具有热压粘合特性的聚乙烯基复合 材料微多孔隔膜的制造主要步骤包括：
( 1 ) 中分子量橡胶与脂肪族二元酸酯高温相容剂在 90-12CTC捏合混炼均匀, 成热熔胶 A;. (2 ) 高分子量聚乙烯粉体与高温相容剂在 90-120Ό溶胀搅拌溶胀 1-24 小 时， 混合均匀成料浆 B;
( 3 )将热熔胶 A和料浆 B在 90- 120°C下混合均匀后，计量喂料给双螺杆挤出 机， 经 180-210Ό加热混炼成热力学均匀溶液后挤出铸片；
( 4.) 不对称冷却铸片， 将熔体在激冷辊表面至少采用双辊不对称冷却工艺 快速凝固成片材， 片材两面冷却不同，可以控制熔体的一面与 1 号副激冷辊 的包绕长度小于熔体的另一面与 2号主激冷辊的包绕长度或控制主副急冷辊 内部的冷却介质的温度和流量不同；
( 5 ) 双向热拉伸成膜，冷却后的片材在 105-128Ό预热后双向热拉伸， 纵向 拉伸倍率 4-7倍， 横向热拉伸倍率 2- 6倍；
( 6 ) 萃取， 采用第二溶剂萃取掉高温相容剂；
( 7 ) 第二次热拉伸调整微孔膜的孔隙率、 孔径、 厚度、 热定型后冷却即得 具有热压粘合特性的聚乙烯基复合材料微多孔隔膜。
一种使用上述具有热压粘合特性的聚乙烯基复合材料微多孔隔膜的锂 离子电池， 其特征在于， 含有正极极片、 负极极片、 电解液以及采用上述的 具有热压粘合特性的聚乙烯基复合材料微多孔隔膜，在注液前先对正极极 片、 隔膜、 负极极片的电池极组在 110- 125°C下采用 1-2. 5MPa 的压力热压 1-15分钟，热压后隔膜与极片表面的凹凸颗粒可以形成机械嵌合效应进而阻 止隔膜在 130Ό甚至更高温度下的热收缩， 电池安全性好。 与常规湿法 PE 隔膜或干法 PP/PE/PP 隔膜相比， 具有热压粘合特性的聚乙烯基复合材料微 多孔隔膜具有类似 PVDF-HFP共聚物凝胶隔膜的粘接能力， 克服了热拉伸聚 烯烃隔膜所特有的热收缩缺陷， 聚乙烯基复合材料微多孔隔膜中的非晶态的 橡胶具备一定的吸液溶胀能力， 电池的一致性、 循环寿命均会受益。
为更好地理解本发明做进一步解释，橡胶原料采用重均分子量介于 9-25 万， 10CTC下的动力粘度介于 50-2000Pa'S的中分子量的聚异丁烯橡胶、二元 乙丙橡胶或两种橡胶的组合物， 这样的设计是要兼顾配制热熔胶的需要， 橡 胶的分子量太小和粘度太低， 与聚乙烯粉体混合后的液固两相流不稳定， 粉 体容易沉降， 不利于隔膜生产的一致性； 橡胶原料分子量太小后另外一个缺 点是在隔膜萃取成孔工艺时容易与高温相容剂一起被萃取抽提出来；橡胶原 料分子量太小、 较小的粘度或过高的橡胶含量均会导致聚乙烯基隔膜在 105-128°C热拉伸强化过程中闭孔； 橡胶原料如果采用过高的分子量和过高 的粘度则影响在 90-12CTC下配置热熔胶，工艺性不好， 另外采用过高分子量 或过高粘度的橡胶改性的聚乙烯基复合材料微多孔隔膜则需要 128°C以上更 高的热压温度， 容易导致聚乙烯基体熔融关断， 也影响聚乙烯基复合材料微 多孔隔膜与极片的热压贴合工艺， 粘接力不够。
附图说明
图 1为本发明隔膜一面的小孔侧形貌。
图 2为本发明隔膜另一面的大孔侧形貌。
具体实 式
以下， 关于本发明的具体实施方式 （以下简称 "实施方式"） 进行详细 说明。 而且本发明不限于下述实施方式的限定， 可以在要点范围内做各种 变形。
隔膜特性评价方法
( 1 ) 膜厚 （ πι) 使用济南兰光机电技术有限公司生产的 CHY-C2型精密测厚仪 进行测定， 从多孔膜剪切 50mmX 50mm的样品， 用测厚仪在样品表 面均匀地进行 5点测量， 然后对膜厚的测定值进行平均。 .
( 2 ) 透气度
按照 JIS P8117的标准对微孔隔膜进行透气度测试。
( 3 ) 拉伸强度、 以及断裂伸长率
按照 GB/T 1040. 1-2006标准，使用宽为 25匪的长条状薄膜样片， 采用 MTS公司的 CMT4000型电子测试机进行测定。
(4) 平均孔径
按照 IS015901. 1-2006标准， 采用压汞仪在 20-2000Psi压力下 测试隔膜的孔径分布和平均孔径。
( 5 ) 孔隙率
测试隔膜的假体密度 (g/cm3) =隔膜重量 / (厚度 *面积）， 与理论值. 93 g/cm3相除后用 1减， 即视为微孔隔膜的孔隙率。
( 6 ) 热关断温度、 热收缩及耐高温破膜测试
将隔膜与正极极片热压后重新压在光滑不锈钢平板中间， 在厚度方 向施加 0. 35MPa静态压縮应力，从 90- 15CTC对隔膜以 C/min速率加热， 到 150°C并保持 5分钟后冷却至室温后测试 Gurley值，大于 2000S/100CC 即视为热关断温度小于 150°C ; 从 90到 150°C对隔膜以 rC/min.速率加 热， 到 150°C并保持 5分钟后冷却至室温， 测试 Gurley值及观察冷却后 的隔膜物理形态保持完整，测试热缩后隔膜在纵向和横向的长度，热收縮 率= (初始长度 -缩后长度） /初始长度 *100%。 ( 7 ) 剥离强度
釆用 180度拉脱试验测试隔膜与正极极片热压合后的粘接强度。 . 实施例 1- 聚乙烯基复合材料隔膜配方：
重均分子量（Mw) 150万的超高分子量聚乙烯 UHMWPE: 20份； 重均分子 量 12万、 100°C下 Brookfield动力粘度 150Pa*S的中分子量聚异丁烯 PIB: 4份， 癸二酸二辛酯 DOS: 80份； 抗氧剂 1010: 0. 5份；
隔膜加工方法：
( 1 ) 配料、 铸片： 将上述 4份聚异乙烯 PIB和 20份的癸二酸二辛 酯 DOS两种原料在捏合机中于 120°C捏合 2小时配制成热熔胶 A; 将上 述 20份超高分子量聚乙烯 UHMWPE和 60份的癸二酸二辛酯 DOS两种原 料在真空搅拌釜中于 105°C溶胀混合处理 12小时， 配制料桨 B; 热熔胶 A和料浆 B继续在真空搅拌釜中于 105°C混合分散处理 5小时， 然后通 过计量泵将料浆喂料输入长径比 1 : 52的平行同向双螺杆挤出机中进行 熔融混炼， 挤出机的温度设置范围为： 175Ό-210Ό之间； 熔体经平模 头挤出并急冷铸片， 铸片采用三辊冷却工艺， 1号冷却压辊， 2号副冷 却辊， 3号主冷却辊， 熔体在 1/2号辊之间零度角切入， 在 2号辊表面 包角 90度冷却熔体的一面后转入 3号主冷却辊冷却熔体的另一面，在 3 号主冷却辊表面包角 180速度， 铸片厚度控制为 1. 5mm;
( 2 ) 同步双向热拉伸： 将上述铸片的片材经 1Ί5-125Ό预热后进行 同步拉伸， 纵向拉伸倍率 5倍，，横向拉伸倍率为 3倍； ( 3 ) 液相高压萃取： 将复合成卷的产品放入萃取釜中进行清洗， 清 洗工艺为：清洗温度： 55Ό，清洗压力： 4. OMPa,分离压力为 1. 5-1. 8MPa， 分离温度为 65°C， 萃取溶剂采用 R125， 在整个系统中循环对产品清洗;
( 4 ) 分步热拉伸， 对上述萃取后的半成品膜经 115-125O预热后先 纵向热拉伸 1. 3倍， 横向热拉伸 1. 5倍， 热拉伸温度 125°C ;
( 5 ) 热定型处理， 横拉后的膜在 120-128°C在宽度方向保持 20-4Q 秒；
(6 ) 冷却收卷，将上述经过热定型的膜冷却至 40°C以后收卷即得成 品聚乙烯基复合材料微多孔隔膜；
隔膜具备以下特性：
产品厚度 30 微米； 平均孔径 160 纳米； 孔隙率 55°/。； Gurley值： 95S/100CC; 拉伸强度： MD方向 118MPa， TD方向 75MPa; 断裂伸长率： 纵向 55%， 横向 173%; DSC测试隔膜的熔融潜热为 176J/g， 熔点为 138° (： 。 采用该隔膜， 其 2号辊侧一面与电池的负极极片接触， 另一侧与电池的 正极极片接触， 在注液前将极组在 118°C/lMPa下加压 10min，冷却后测 试隔膜与正极极片的剥离强度为 0. 1N/20匪， 在 13CTC测试隔膜与正极片 的复合体的热收缩， 冷却至室温， 隔膜保持形态完整，其在纵向和横向的热 收缩率均小于 8%; Gurley值大于 2000S/100CC。
在 80°C温度下， 将隔膜单独在厚度方向施加 0.35MPa静态压缩应力并 保持 5分钟后， 隔膜的厚度为 24微米， 压力释放 5分钟后测试隔膜的厚度 为 26微米， Gurley值 228S/100CC。
经干燥后注入电解液做成锂离子电池， 测试 150°C热箱、 针剌、 短 路、 挤压， 室温 25°C下的 1C循环， 电池安全性试验全部合格， 循环寿.. 命： 1250次。
对比例 1
电池制作同实施例 1， 仅隔膜采用某公司的干法 PP/PE/PP膜， 厚 度 25微米， 孔隙率 40%, Gurley值 600-630S/100CC, 拉伸强度： MD 方向 165MPa, TD方向 13MPa， 横向断裂伸长率 15%。
室温 25°C下的 1C循环寿命： 635次， 安全性试验针刺、 短路测试 合格， 150°C热箱 /30min、 挤压测试电池着火、 爆炸。
对比例 2
电池制作同实施例 1， 仅隔膜采用某公司的湿法单层 PE隔膜， 厚 度 25微米， 孔隙率 49%, Gurley值 185S/100CC, 拉伸强度： MD方向 143MPa, TD方向 21MPa， 纵向断裂伸长率 42%， 横向断裂伸长率 344%。
室温 25°C下的 1C电池循环寿命： 876次；安全性试验针剌合格， 150°C热箱、 短路不合格。

Claims

权利要求书
1、 具有热压粘合 ^^性的聚乙烯基复合材料微多孔隔膜，其特征在于， 通过采 用重量百分比介于 10-25%、 10CTC下的动力粘度在 50- 2000Pa'S、 重均分子量 9-25万的中分子量聚异丁烯橡胶 PIB、二元乙丙橡胶 EPM或两种橡胶的组合物. 对高结晶度的高密度聚乙烯进行改性， 采用热致相分离法的 "液液相分离 "原 理， 釆用闪点 21CTC以上的脂肪族二元酸酯， 包括癸二酸二辛酯 D0S、 壬二酸 二辛酯 D0Z、 己二酸二异癸酯 DIDA或其组合物， 作为聚乙烯基复合材料微多 孔隔膜的工艺溶剂和造孔剂，得到两面具有非对称微孔的具备热压粘合特性的 聚乙烯基复合材料微多孔隔膜，该隔膜与正极极片可以在 110- 120 °C、 1-2. 5MPa、 l-15min 的热压贴合后粘接成一体， 剥离强度大于 0. 03N/20mm、 130°C/30min 热收缩小于 10°/。， 该隔膜的熔融潜热为 150-195J/g，熔点介于 133- 145°C，平均孔径介于 80-300纳米， 孔隙率介于 40-75%， 其中一面的微孔 形貌呈细密分布，另一面的微孔形貌呈树枝状粗大孔分布，初始 GURLEY值介于 30-400S/100CC , 厚度介于 20-50微米， 纵向拉伸强度大于 70MPa， 横向断裂 伸长率大于 100%。
2、 根据权利要求 1所述的聚乙烯基复合材料微多孔隔膜， 其特征在于该隔膜 的聚乙烯基体材料采用熔融潜热介于 200-250J/g、 重均分子量介于 50-500万 的特高分子量或超高分子量高密度聚乙烯。
3、 根据权利要求 1所述的聚乙烯基复合材料微多孔隔膜， 其特征在于， 其中 的橡胶原料优选重均分子量 12-20万、 10CTC下的动力粘度在 150- lOOOPa'S的 聚异丁烯橡胶 PIB。
4、 根据权利要求 1所述的聚乙烯基复合材料微多孔隔膜， 其特征在于， 其中 的橡胶原料优选重均分子量 12-20万、 10CTC下的动力粘度在 120- 9.00Pa'S的' 二元乙丙橡胶 EPM。 .
5、 根据权利要求 1所述的聚乙烯基复合材料微多孔隔膜， 其特征在于， 其中 的聚乙烯优选重均分子量介于 100-300万的高密度聚乙烯。 . .
6、 根据权利要求 1所述的聚乙烯基复合材料微多孔隔膜， 其特征在于， 隔膜 的厚度优选 25-35微米、 孔隙率优选介于 50-65%。
7、 一种制造具有热压粘合特性的聚乙烯基复合材料微多孔隔膜的方法， 其特 征在于， 该隔膜采用热致相分离法制造，采用高结晶度的高密度聚乙烯作为基 体材料，采用与聚乙烯相容的非晶态的聚异丁烯和 /或二元乙丙橡胶提供热压 粘合能力， 高温相容剂选自闪点 210°C以上的脂肪族二元酸酯， 包括癸二酸二 辛酯 D0S、壬二酸二辛酯 D0Z、 己二酸二异癸酯 DIDA或其组合物， 通过控制铸 片时两面的冷却速度不同得到两面具备非对称微孔的多孔膜，制造主要步骤包 括：
( 1 ) 中分子量橡胶与高温相容剂在 90- 120°C捏合混炼均匀成热熔胶 A;
( 2 )聚乙烯与高温相容剂在 90- 120Ό溶胀搅拌 1-24小吋；混合均匀成料浆 B;
( 3 )将热熔胶 A和料浆 B在 90-120Ό下混合均匀后，计量喂料给双螺杆挤出 机， 经 180-21CTC加热混炼成热力学均匀溶液后挤出铸片；
(4) 不对称冷却铸片， 将熔体在激冷辊表面至少采用双辊不对称冷却工艺快 速凝固成片材， 片材两面冷却不同，熔体的一面与 1号副繳冷辊的包绕长度小 于熔体的另一面与 2 号主激冷辊的包绕长度或控制主副急冷辊内部的冷却介 · 质的温度和流量不同； 权利要求书
( 5 )双向热拉伸成膜，冷却后的片材在 105- 128Ό预热后双向热拉伸， 纵向拉 伸倍率 4-7倍， 横向热拉伸倍率 2- 6倍；
( 6 ) 萃取， 采用第二溶剂萃取掉高温相容剂；
( 7 ) 第二次热拉伸调整微孔膜的孔隙率、 孔径、 厚度、 热定型后冷却即得具 有热压粘合特性的聚乙烯基复合材料微多孔隔膜。
8、 一种锂离子电池， 其特征在于， 含有正极极片、 负极极片、 电解液以及采 用权利要求 1-7所述的具有热压粘合特性的聚乙烯基复合材料微多孔隔膜，在 注液前对正极极片 /隔膜 /负极极片的电池极组在 110- 125°C下采用 1-2. 5MPa 的压力热压 1-15分钟。
PCT/CN2012/070487 2011-12-28 2012-01-17 具有热压粘合特性的聚乙烯基复合材料微多孔隔膜 WO2013097311A1 (zh)

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