WO2013185335A1 - 一种锂离子电池复合隔膜 - Google Patents

一种锂离子电池复合隔膜 Download PDF

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Publication number
WO2013185335A1
WO2013185335A1 PCT/CN2012/076958 CN2012076958W WO2013185335A1 WO 2013185335 A1 WO2013185335 A1 WO 2013185335A1 CN 2012076958 W CN2012076958 W CN 2012076958W WO 2013185335 A1 WO2013185335 A1 WO 2013185335A1
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Prior art keywords
separator
battery
composite
composite membrane
layer
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PCT/CN2012/076958
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English (en)
French (fr)
Inventor
荆正军
申向宇
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新乡市中科科技有限公司
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Priority to PCT/CN2012/076958 priority Critical patent/WO2013185335A1/zh
Publication of WO2013185335A1 publication Critical patent/WO2013185335A1/zh

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • 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
    • H01M50/417—Polyolefins
    • 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
    • H01M50/426—Fluorocarbon polymers
    • 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
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • 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
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • 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 invention relates to a novel lithium ion battery composite diaphragm and a production method thereof.
  • a lithium ion secondary battery generally consists of a positive and negative electrode, a separator, an electrolyte, and an outer casing.
  • the separator is an important component of the battery and has a unique property of being non-conductive and allowing ions to pass.
  • the role of the separator in a lithium-ion battery is to isolate the positive and negative electrodes to prevent short circuits and to ensure that lithium ions can pass freely, thereby causing the battery to generate current.
  • the lithium ion battery separator is usually a polyolefin film having a microporous structure, which has long-term stability with an electrolyte.
  • lithium-ion batteries have the characteristics of large capacity, large charge and discharge current, and high safety performance.
  • the production of lithium ion battery separators is mainly polyolefin.
  • polyolefin films have better mechanical properties and chemical stability, but their own properties are still insufficient to ensure the high safety of lithium ion batteries.
  • Lithium-ion batteries using a polyolefin microporous membrane as a separator have the following problems in terms of safety and service life:
  • the strength is not high enough.
  • overshooting causes lithium to precipitate as a metal in the negative electrode, and it is easy to grow dendritic lithium dendrites.
  • the lithium dendrite grows to a certain extent, it will pierce the diaphragm, causing a short circuit of the battery, which not only increases the risk of overheating of the battery but also greatly reduces the service life of the lithium ion battery.
  • the strength of the separator In the current state of the art, there is still no good solution to control the growth of lithium dendrites, so in order to increase the safety and life of the battery, it is necessary to increase the strength of the separator.
  • In order to increase the strength when the material is constant it is necessary to increase the thickness of the separator and reduce the porosity, which will increase the internal resistance of the battery and affect the normal use of the battery.
  • Thermal stability is limited. Lithium-ion battery in the process of use, on the one hand due to the diaphragm The defect is short-circuited, releasing a large amount of heat; on the other hand, the precipitated metal lithium reacts with the electrolyte because a large amount of heat is generated. Both polyethylene and polypropylene melt as the battery heats up, causing the entire membrane to melt at the melting temperature and thus cause a large area short circuit, so that the battery is often destroyed by fire or even explosion. The power lithium-ion battery is tantamount to a time bomb because of its high capacity.
  • the polyolefin is a non-polar material, it has poor compatibility with the polar organic solvent of the electrolyte solution, and only plays a mechanical isolation between the positive and negative electrodes in the battery, and has no affinity for the electrolyte, so that the electrolyte solution is The free state exists in the battery.
  • the free electrolyte inevitably undergoes a redox side reaction with the positive and negative materials, consuming the electrolyte in the battery, causing the battery to be poor, thereby causing the battery
  • the increase in polarization makes it easy to reduce lithium ions into metallic lithium and cause lithium deposition to crystallize into lithium dendrites, resulting in membrane puncture.
  • the main difference of the invention of CN1514501A is that the substrate of the present invention is a biaxially stretched polyolefin film having a microporous structure, and both sides of the film are coated with a porous inorganic particle layer and a porous polymeric organic layer, respectively.
  • Another object of the present invention is to provide a method of manufacturing the above composite separator which is simple in process and can manufacture separator materials of various thicknesses.
  • the invention has the advantages of high strength, high temperature resistance and low heat shrinkage. It can greatly reduce the probability of short circuit of the battery, effectively extend the life of the battery, and increase the safety performance of the battery.
  • the invention is characterized in that the base layer of the composite membrane is a polyolefin microporous membrane prepared by biaxial stretching. On the basis of the microporous membrane, the organic polymer layer is coated on the front side and the inorganic oxide particles are coated on the reverse side.
  • It is a schematic structural view of the composite separator of the present invention. When the composite membrane is fabricated into a lithium ion battery, the front side of the diaphragm is in contact with the positive electrode of the lithium ion battery, and the reverse side is in contact with the negative electrode of the lithium ion battery.
  • Fig. 2 is a schematic cross-sectional view showing a battery made of a composite separator of the present invention.
  • the front surface of the composite separator of the present invention is a high temperature resistant organic polymer layer, and the layer is made of a polymer having a relatively high melting point, such as a copolymer of polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene, and polyethylene terephthalate.
  • a copolymer of polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene and polyethylene terephthalate.
  • a vinyl fluoride polymer is preferred.
  • the polyolefin is a non-polar polymer
  • a layer of a polar polymer layer is coated on the surface, so that the separator can be better infiltrated with the electrolyte, and the contact with the positive electrode is also tighter, thereby avoiding uneven local current distribution. The resulting overheating and short circuit occur.
  • the heat release is basically generated at the negative electrode, the high temperature resistance and wear resistance of the coating layer polymer also improve the performance of the separator, thereby improving the safety performance of the lithium ion battery.
  • the organic polymer layer is prepared by dissolving the polymer resin in an organic solvent, adding a pore former and other additives, dissolving into a uniform transparent solution as a casting solution, and coating the casting solution on the polyolefin separator to remove After drying the solvent and pore former, the coating is obtained.
  • the concentration of the casting liquid polymer is 8% ⁇ 18%, preferably 9% ⁇ 12%
  • the solvent used is acetone, tetrahydrofuran (THF), N, N-dimethylacetamide (DMAC), N, N-dimethyl Formamide (DMF), N-methylpyrrolidone (leg P), dimethyl sulfoxide (DMS0), triethyl phosphate (TEP) or other solvent which can dissolve the polymer.
  • the porogen is an organic solvent which is miscible with the solvent of the dissolved polymer but does not dissolve the polymer, such as ethanol, ethylene glycol, 1-butanol, methanol, and the like.
  • Other additives may include plasticizers, leveling agents, and the like.
  • the reverse side of the composite separator of the present invention is an inorganic oxide layer whose main components are inorganic oxide nanoparticles and a binder.
  • the inorganic oxide nanoparticles are selected from oxide particles of Si, Al, Ti and/or Zr.
  • the binder is an organic polymer having good electrochemical properties, thermal stability and chemical stability, such as poly(m-phenylene isophthalamide), polyvinylidene fluoride. Ethylene, polyethylene oxide, polymethyl methacrylate, polyethylene terephthalate, polyvinyl chloride, polyacrylonitrile, but not limited to the above.
  • the oxide layer formed by coating according to the invention has high hardness and is in contact with the negative electrode of the lithium ion battery, which can effectively prevent the separator from being pierced by the lithium dendrite and short-circuit; and at the same time, due to the presence of the oxide layer, the composite The thermal contraction of the diaphragm is reduced, reducing the probability of diaphragm failure due to wrinkling.
  • the presence of the coating increases the ability of the separator to absorb and retain the electrolyte, thereby increasing the uniform distribution of the charge and discharge current, resulting in improved cycle performance of the lithium ion battery.
  • the anode is heated, and the presence of the inorganic coating improves the heat resistance of the separator and increases the melting temperature of the separator.
  • the thermal inertia causes the temperature of the battery to continue to rise, eventually causing the diaphragm to blow and the battery short-circuit is dangerous.
  • the presence of the inorganic layer allows the membrane to melt only without melting, ensuring safe use of the battery.
  • Inorganic nano-oxide particles have unique surface effects, volumetric effects, and chemical properties. They have high hardness and are easily chemically modified so that the formed inorganic layer is tightly bonded to the polymer layer; its microporous structure makes it formed.
  • the coating has good permeability.
  • the present invention employs oxide particles of Si, Al, Ti and/or Zr in view of stable performance, inexpensive and readily available raw materials, and mature modification modification methods.
  • the inorganic oxide layer is prepared by dissolving the binder in an organic solvent, adding the inorganic nanoparticles, and uniformly dispersing under the action of strong shearing force, adding a pore former and other additives; and applying the obtained dispersion to the separator On the top, the solvent and the pore former are removed and dried to obtain an inorganic coating.
  • the solvent used was acetone, tetrahydrofuran (THF), N, N-dimethylacetamide (DMAC), N, N-dimethylformamide (DMF), N-methylpyrrolidone (leg P), dimethyl One of sulfone (DMS0) and triethyl phosphate (TEP).
  • the porogen is an organic solvent which is miscible with the solvent of the dissolved polymer but does not dissolve the polymer, such as ethanol, ethylene glycol, 1-butanol, methanol, and the like.
  • Other additives may include a silane coupling agent, a leveling agent, and the like.
  • the thickness of the composite separator intermediate layer polyolefin separator is 10 ⁇ 60 ⁇ ⁇ , preferably 20 ⁇ 40 ⁇ m; the thickness of the single layer coating is 2 ⁇ 10 ⁇ ⁇ , preferably 4 ⁇ 6 ⁇ ⁇ ; the thickness of the composite membrane is 14 ⁇ 80 ⁇ ⁇ , preferably 30 ⁇ 50 ⁇ ⁇ .
  • Composite membrane permeability (Gurley value, 100ml) is 200 ⁇ 800s, preferred 300 ⁇ 500s.
  • Figure 1 is a schematic view showing the structure of a composite separator of the present invention.
  • FIG. 2 is a schematic cross-sectional view showing a battery made of a composite separator of the present invention.
  • Figure 3 is a scanning electron micrograph of an organic layer made of PVDF. It can be seen from the figure that the layer is porous and porous, the pore distribution is relatively uniform, the polyolefin layer of the substrate is not exposed, and the local denseness is not observed.
  • Figure 4 is a scanning electron micrograph of an inorganic layer made of silica. It can be seen from the figure that the inorganic particle layer is more evenly distributed, and a brush-like binder can be seen in the gap to ensure that the inorganic particles do not fall off; the particles are loosely arranged, and the electrolyte is easily infiltrated and permeated.
  • Figure 5 is a schematic view of a composite membrane production line based on a biaxially oriented film production line.
  • the production method of the composite membrane of the invention can adopt the method of directly modifying the production line of the polyolefin production line, or the production line can be separately established by the separate unwinding system.
  • Figure 3 is a schematic view of a composite membrane production line based on a biaxially oriented film production line. The following non-limiting examples illustrate the invention.
  • Polyvinylidene fluoride, NMP, and ethylene glycol are mixed at a ratio of 10:100:30, and dissolved in a uniform transparent solution as a casting solution, coated on a polyolefin separator, left for 10 minutes, and immersed in a volume at room temperature.
  • the mixture of ethanol and water in a ratio of 1:2 was taken for 2 minutes, taken out and placed in an oven at a temperature of 60 for 1 hour to remove the remaining NMP and ethylene glycol.
  • Polyvinylidene fluoride, NMP, and ethylene glycol are mixed at a ratio of 10:100:30, and dissolved in a uniform transparent solution as a casting solution, coated on a polyolefin separator, left for 10 minutes, and immersed in a volume at room temperature.
  • the mixture of ethanol and water in a ratio of 1:2 was taken for 2 minutes, taken out and placed in an oven at a temperature of 60 for 1 hour to remove the remaining NMP and ethylene glycol.
  • Polyvinylidene fluoride, DMAC, and ethylene glycol are mixed in a ratio of 10:100:30, and dissolved in a uniform transparent solution as a casting solution, coated on a polyolefin separator, left for 10 minutes, and immersed in a volume at room temperature.
  • the mixture of ethanol and water in a ratio of 1:2 was taken for 2 minutes, taken out and placed in an oven at a temperature of 60 for 1 hour to remove the remaining DMAC and ethylene glycol.
  • Polyvinylidene fluoride, dimethyl sulfoxide, and ethylene glycol are mixed at a ratio of 10:100:30, and dissolved in a uniform transparent solution as a casting solution, coated on a polyolefin separator, and left for 10 minutes.
  • the mixture was immersed in a 1:2 ratio of ethanol to water at room temperature for 2 minutes, taken out and placed in an oven at a temperature of 60 for 1 hour to remove the remaining dimethyl sulfoxide and ethylene glycol.
  • Copolymer of vinylidene fluoride and hexafluoropropylene, DMAC, 1-butanol are mixed in a ratio of 10:100:30, and dissolved in a uniform transparent solution as a casting solution, coated on a polyolefin separator, placed 10 After a minute, it was immersed in a mixture of ethanol and water in a volume ratio of 1:2 at room temperature for 2 minutes, taken out and placed in an oven at a temperature of 60 for 1 hour to remove the remaining DMAC and 1-butanol.
  • Copolymer of vinylidene fluoride and hexafluoropropylene, DMAC, nano-silica, 1-butanol are mixed in a ratio of 5:20:100:30, and heated to dissolve into a uniform transparent solution as a casting solution, coated on The reverse side of the dried membrane of the previous step was allowed to stand for 10 minutes, immersed in an ethanol bath for 2 minutes at room temperature, taken out and placed in an oven at a temperature of 60 for 1 hour to remove the remaining leg P and 1-butanol.
  • a 40 ⁇ ⁇ thick polypropylene separator of a company was used as a base layer, and coated with the above method to obtain a sample separator, and these samples were tested; and a battery was prepared by using a sample separator to perform thermal shock detection.
  • the results are shown in Table 1. Shown. The data in this table is intended to illustrate the performance improvement of the composite membrane of the present invention relative to the original base membrane, the value of which depends on the performance of the substrate separator and the process parameters of the coating process and does not represent the absolute performance of the present invention.
  • Example 1 Example 2 Example 3
  • Example 4 Example gas permeability (S) 337.4 548.69 524.32 562.17 496.05 542.45 Longitudinal tensile strength (N) 134.45 153.466 147.25 159.62 143.61 154.18 Lateral tensile strength (N) 33.49 35.42 34.61 32.67 35.09 32.34 Puncture strength 0 5.07 6.162 5.58 6.2 6.21 5.89 Average pore diameter (nm) 201.8 146.2 157.6 150.7 165.3 152.7 Heat shrinkage 00 Landscape 7.56 1.87 1.76 1.74 2.21 1.86

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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

本发明为一种新型的锂离子电池复合隔膜及其生产方法。该隔膜以聚烯烃微孔膜为基体，在膜的正反两面分别涂布形成有机聚合物层和无机颗粒层。此复合隔膜的涂层在保证隔膜的离子导通性能的同时可提高隔膜的强度和热稳定性，降低隔膜的热收缩率，从而降低电池发生内部短路的概率，提高电池的安全性，增加电池的寿命。

Description

一种锂离子电池复合隔膜
技术领域
本发明涉及一种新型的锂离子电池复合隔膜及其生产方法。
背景技术
锂离子电池由于具有电压高、 比能量高、 循环寿命长且不污染环 境的优点， 已经成为广泛应用的新一代电池。 锂离子二次电池一般由 正负极、 隔膜、 电解质和外壳组成。 隔膜是电池中重要的组成部分， 其具有独特的不导电而允许离子通过的特性。 隔膜在锂离子电池中的 作用是将正负极隔离开来， 防止发生短路， 同时保证锂离子能够自由 的通过， 从而使电池产生电流。 锂离子电池隔膜通常为具有微孔结构 的聚烯烃薄膜， 其对与电解液具有长期稳定性。
随着新能源产业的发展， 尤其是电动汽车的快速发展， 动力型锂 离子电池也得到了快速发展与应用。 与普通锂离子电池相比， 动力型 锂离子电池有着容量大、 充放电电流大、 安全性能要求高等特点。 目 前用于锂离子电池隔膜制造的主要为聚烯烃， 与其他材料相比， 聚烯 烃薄膜虽然有着较好的力学性能和化学稳定性， 但其自身性能仍然不 足以保证锂离子电池较高的安全性要求， 尤其是动力型锂电池。 以聚 烯烃微孔膜为隔膜的锂离子电池在安全性和使用寿命上还存在如下问 题：
强度不够高。 以钴酸锂为正极的锂离子电池在使用中， 过冲会造 成锂以金属的形式在负极析出， 进而容易生长出枝杈状的锂枝晶。 当 锂枝晶生长到一定程度就会刺穿隔膜， 导致电池的短路， 这不但会增 加电池过热的风险还会大大降低锂离子电池的使用寿命。 以目前的技 术而言， 控制锂枝晶的生长仍然没有很好的解决办法， 所以要想增加 电池的安全性和寿命， 就必须提高隔膜的强度。 在材料一定时要想提 高强度就必须增加隔膜的厚度、降低孔隙率，这样会增加电池的内阻， 影响电池的正常使用。
热稳定性有限。 锂离子电池在使用的过程中， 一方面会由于隔膜 的缺陷出现短路， 放出大量的热； 另一方面， 析出的金属锂会与电解 液反应因为生成大量的热。 无论聚乙烯还是聚丙烯都会随着电池的升 温而熔融，致使整个隔膜将在熔化温度熔融并因此而发生大面积短路， 以致常常因起火甚至爆炸而摧毁电池。 而动力型锂离子电池由于具有 较高的容量， 无异于一个定时炸弹。
发生热收缩。 由于聚烯烃隔膜拉伸工艺和高分子的固有特性， 隔 膜在高温时会发生热收缩现象。 收缩导致隔膜起皱， 进而使电极和隔 膜之间难以获得紧密和均匀的接触。 在电池的使用过程中， 难以在电 极的整个表面上进行均相电极反应因此很难获得均匀的电池性能导致 电极在局部过度损耗， 降低了电池的寿命。 此外， 当电极的这种不均 匀状态变得严重时， 电极反应可能仅在局部发生， 因此可能发生锂金 属的局部沉淀， 导致安全性降低。
与电解液浸润性能差。 由于聚烯烃属于非极性材料， 它与电解质 溶液的极性有机溶剂相容性差， 在电池中只起到正负极间机械的隔离 作用， 而对电解液没有亲和作用， 使得电解质溶液以游离状态存在于 电池中， 在电池充放电循环使用中， 这种游离的电解液不可避免地与 正负极材料发生氧化还原副反应， 消耗电池中的电解液， 造成电池贫 液， 从而使得电池极化增大， 易使锂离子还原成金属锂并产生锂沉积 结晶成锂枝晶， 导致隔膜穿刺现象。
以上这些缺点制约了动力型锂离子电池的推广应用。 发明内容
本发明的目的是提供一种增强的锂离子电池隔膜， 与公开号为
CN1514501A 的发明的主要不同之处在于本发明基材为双向拉伸的具 有微孔结构的聚烯烃薄膜， 薄膜两面分别涂覆有多孔无机颗粒层和多 孔聚合有机物层。
本发明的另一个目的是提供制造上述复合隔膜的方法， 此方法工 艺简单， 可以制造各种厚度的隔膜材料。
本发明的优点在于具有较高的强度、耐高温性和较低的热收缩性， 可以大大降低电池发生短路的概率， 有效延长电池的寿命， 增加电池 的安全性能。
本发明的特征为复合隔膜的基层为经双向拉伸制成的聚烯烃微孔 膜， 在此微孔膜的基础上， 正面涂覆有机聚合物层， 反面涂覆无机氧 化物颗粒， 图 1为本发明复合隔膜的结构示意图。 当此复合隔膜被制 造成锂离子电池时， 隔膜的正面与锂离子电池的正极接触， 反面与锂 离子电池的负极接触。 图 2为本发明的复合隔膜制成电池的剖面示意 图。
本发明复合隔膜的正面为耐高温的有机聚合物层，本层采用熔点 较高的聚合物制造， 如聚偏氟乙烯、 偏氟乙烯和六氟丙烯的共聚物、 聚对苯二甲酸乙二醇酯、 聚氧化乙烯、 聚甲基丙烯酸甲酯、 聚间苯二 甲酰间苯二胺、 聚氯乙烯、 聚丙烯腈， 但不限于以上。 优选氟乙烯类 聚合物。 由于聚烯烃为非极性聚合物， 在其表面涂覆一层极性的聚合 物层， 可使隔膜更好的与电解液浸润， 与正极的接触也更加紧密， 避 免了局部电流分布不均而导致的过热、 短路现象的发生。 此外， 因为 放热基本都是在负极产生， 涂覆层聚合物良好的耐高温性能和耐磨性 也使隔膜的性能得到提升， 进而提高锂离子电池的安全性能。
有机聚合物层的制造方法为将聚合物树脂溶于有机溶剂中， 加入 成孔剂和其他添加剂， 溶解为均匀透明的溶液作为铸膜液， 将铸膜液 涂覆于聚烯烃隔膜上， 除去溶剂及成孔剂后烘干即得涂层。 铸膜液聚 合物浓度为 8% ~ 18%，优选 9% ~ 12%，所用溶剂为丙酮、四氢呋喃（THF)、 N, N-二甲基乙酰胺（DMAC)、 N, N-二甲基甲酰胺（DMF)、 N-甲基吡咯烷 酮（腿 P)、 二甲基亚砜（DMS0)、 磷酸三乙酯（TEP)或其他可以溶解聚合 物的溶剂。 成孔剂为可以和溶解聚合物的溶剂互溶， 但不能溶解聚合 物的有机溶剂， 如乙醇、 乙二醇、 1-丁醇、 甲醇等。 其他添加剂可包 括增塑剂、 流平剂等。 本发明复合隔膜的反面为无机氧化物层， 其主 要成分为无机氧化物纳米颗粒和粘结剂。 无机氧化物纳米颗粒选用 Si、 Al、 Ti和 /或 Zr的氧化物颗粒。 粘结剂为电化学性能、 热稳定性 和化学稳定性较好的有机聚合物， 如聚间苯二甲酰间苯二胺、 聚偏氟 乙烯、 聚氧化乙烯、 聚甲基丙烯酸甲酯、 聚对苯二甲酸乙二醇酯、 聚 氯乙烯、 聚丙烯腈， 但不限于以上。 本发明涂覆形成的氧化物层具有 较高的硬度， 与锂离子电池的负极相接触， 可以有效地防止隔膜被锂 枝晶刺破进而发生短路； 同时， 由于氧化物层的存在， 使得复合隔膜 的热收缩下降， 降低了隔膜因起皱发生故障的概率。 此外， 涂层的存 在使隔膜对电解液的吸液、 保液能力得到提高， 进而提高了充放电电 流的均匀分布， 导致锂离子电池的循环性能得到提高。
在锂离子电池使用过程中， 负极发热， 无机涂层的存在可提高隔 膜的耐热性，提高隔膜的熔断温度。 当电池温度上升到隔膜的熔点后， 虽然隔膜发生闭孔效应会使电池关闭， 但热惯性会使电池的温度继续 升高， 最终导致隔膜熔断， 电池短路发生危险。 无机层的存在使隔膜 只熔融而不熔断， 保证了电池的安全使用。
无机纳米氧化物颗粒具有独特的表面效应、 体积效应、 和化学性 质， 具有较高的硬度， 易于进行化学修饰， 从而使形成的无机层与聚 合物层紧密结合； 其微孔结构使其形成的涂层具有较好的透过性。 考 虑到性能稳定、 原料廉价易得、 改性修饰方法成熟， 本发明采用 Si、 Al、 Ti和 /或 Zr的氧化物颗粒。
无机氧化物层的制造方法为将粘结剂溶于有机溶剂中， 加入无机 纳米颗粒，在强剪切力的作用下分散均匀后加入成孔剂和其他添加剂； 将所得分散液涂覆于隔膜上，除去溶剂及成孔剂后烘干即得无机涂层。 所用溶剂为丙酮、 四氢呋喃（THF)、 N, N-二甲基乙酰胺（DMAC)、 N, N- 二甲基甲酰胺（DMF)、 N-甲基吡咯烷酮（腿 P)、 二甲基亚砜（DMS0)和磷 酸三乙酯（TEP)其中的一种。 成孔剂为可以和溶解聚合物的溶剂互溶， 但不能溶解聚合物的有机溶剂， 如乙醇、 乙二醇、 1-丁醇、 甲醇等。 其他添加剂可包括硅烷偶联剂、 流平剂等。
复合隔膜中间层聚烯烃隔膜的厚度为 10 ~ 60 μ ηι， 优选 20 ~ 40 μ m; 单层涂层厚度为 2 ~ 10 μ ηι， 优选 4 ~ 6 μ ηι; 复合隔膜厚度为 14 ~ 80 μ ηι， 优选 30 ~ 50 μ ηι。
复合隔膜透气性（Gurley仪数值， 100ml )为 200 ~ 800s， 优选 300 ~ 500s。
本发明通过图 3-图 7和表 1的非限定性实施方案进一步说明。 附图说明
图 1为本发明复合隔膜的结构示意图。
图 2为本发明的复合隔膜制成电池的剖面示意图。
图 3为以 PVDF为原料制成的有机层得扫描电镜照片。由图可以看 出本层呈多孔疏松的状态， 孔分布较为均 ， 没有暴露出基底的聚烯 烃层， 也没有出现局部致密不透的情况。
图 4为采用二氧化硅为原料制成的无机层的扫描电镜照片。 从图 上可以看出，无机颗粒层分布较为均 ，缝隙处可见拉丝状的粘结剂， 保证了无机颗粒不发生脱落； 颗粒排布较为疏松， 易于电解液的浸润 和透过
图 5为以双轴拉伸薄膜生产线为基础的复合隔膜生产线示意图。
本发明复合隔膜生产方法可采用直接改造聚烯烃生产线在线生产 的方式， 也可以另配放卷系统单独建立生产线。
图 3为以双轴拉伸薄膜生产线为基础的复合隔膜生产线示意图。 以下非限定性实施例说明本发明。
【实施例 1】
将聚偏氟乙烯、 NMP、 乙二醇按 10: 100: 30的比例混合， 加热溶解 为均一透明的溶液作为铸膜液，涂覆在聚烯烃隔膜上，放置 10分钟后， 室温下浸入体积比为 1 : 2的乙醇与水的混合液中 2分钟，取出后放入 温度为 60 的烘箱中 1小时， 除去剩余的 NMP和乙二醇。
将聚偏氟乙烯、 纳米二氧化硅、 NMP、 乙二醇按 5: 20: 100: 30的比 例混合， 加热溶解为均一透明的溶液作为铸膜液， 涂覆于上一步干燥 好的隔膜的反面， 放置 10分钟后， 室温下浸入体积比为 1 : 2的乙醇 与水的混合液中 2分钟， 取出后放入温度为 60 的烘箱中 1小时， 除 去剩余的腿 P和乙二醇。 【实施例 2】
将聚偏氟乙烯、 NMP、 乙二醇按 10: 100: 30的比例混合， 加热溶解 为均一透明的溶液作为铸膜液，涂覆在聚烯烃隔膜上，放置 10分钟后， 室温下浸入体积比为 1 : 2的乙醇与水的混合液中 2分钟，取出后放入 温度为 60 的烘箱中 1小时， 除去剩余的 NMP和乙二醇。
将聚间苯二甲酰间苯二胺、 无水氯化钙、 纳米二氧化硅、 腿 P、 乙 二醇按 5: 1: 20: 100: 30 的比例混合，加热溶解为均一透明的溶液作为 铸膜液， 涂覆于上一步干燥好的隔膜的反面， 放置 10分钟后， 室温下 浸入乙醇浴中 2分钟， 取出后放入温度为 60 的烘箱中 1小时， 除去 剩余的 NMP和乙二醇。
【实施例 3】
将聚偏氟乙烯、 DMAC、 乙二醇按 10: 100: 30的比例混合， 加热溶 解为均一透明的溶液作为铸膜液，涂覆在聚烯烃隔膜上，放置 10分钟 后， 室温下浸入体积比为 1: 2的乙醇与水的混合液中 2分钟， 取出后 放入温度为 60 的烘箱中 1小时， 除去剩余的 DMAC和乙二醇。
将聚偏氟乙烯、 纳米二氧化硅、 NMP、 乙二醇按 5: 20: 100: 30的比 例混合， 加热溶解为均一透明的溶液作为铸膜液， 涂覆于上一步干燥 好的隔膜的反面， 放置 10分钟后， 室温下浸入体积比为 1 : 2的乙醇 与水的混合液中 2分钟， 取出后放入温度为 60 的烘箱中 1小时， 除 去剩余的腿 P和乙二醇。
【实施例 4】
将聚偏氟乙烯、 二甲基亚砜、 乙二醇按 10: 100: 30的比例混合， 加热溶解为均一透明的溶液作为铸膜液， 涂覆在聚烯烃隔膜上， 放置 10分钟后， 室温下浸入体积比为 1: 2的乙醇与水的混合液中 2分钟， 取出后放入温度为 60 的烘箱中 1小时， 除去剩余的二甲基亚砜和乙 二醇。
将聚间苯二甲酰间苯二胺、 无水氯化钙、 纳米二氧化硅、 腿 P、 乙 二醇按 5: 1: 20: 100: 30 的比例混合，加热溶解为均一透明的溶液作为 铸膜液， 涂覆于上一步干燥好的隔膜的反面， 放置 10分钟后， 室温下 浸入乙醇浴中 2分钟， 取出后放入温度为 60 的烘箱中 1小时， 除去 剩余的 NMP和乙二醇。
【实施例 5】
将偏氟乙烯和六氟丙烯的共聚物、 DMAC、 1-丁醇按 10: 100: 30的 比例混合， 加热溶解为均一透明的溶液作为铸膜液， 涂覆在聚烯烃隔 膜上， 放置 10分钟后， 室温下浸入体积比为 1 : 2的乙醇与水的混合 液中 2分钟，取出后放入温度为 60 的烘箱中 1小时，除去剩余的 DMAC 和 1-丁醇。
将偏氟乙烯和六氟丙烯的共聚物、 DMAC、 纳米二氧化硅、 1-丁醇 按 5: 20: 100: 30的比例混合，加热溶解为均一透明的溶液作为铸膜液， 涂覆于上一步干燥好的隔膜的反面，放置 10分钟后， 室温下浸入乙醇 浴中 2分钟，取出后放入温度为 60 的烘箱中 1小时，除去剩余的腿 P 和 1-丁醇。
实施例样品性能对比
以某公司 40 μ ηι厚的聚丙烯隔膜为基层， 分别以上述实施例方法 进行涂覆， 得到样品隔膜， 对这些样品进行检测； 并用样品隔膜制成 电池， 进行热冲击检测， 结果如表 1所示。 本表中数据目的为说明本 发明复合隔膜相对于原基层隔膜的性能提升， 其数值取决于基层隔膜 的性能和涂覆过程的工艺参数， 不代表本发明的绝对性能。
表 1
涂覆隔膜
未涂覆隔膜
实施例 1 实施例 2 实施例 3 实施例 4 实施例 透气性（S) 337.4 548.69 524.32 562.17 496.05 542.45 纵向抗拉强度 (N) 134.45 153.466 147.25 159.62 143.61 154.18 横向抗拉强度 (N) 33.49 35.42 34.61 32.67 35.09 32.34 穿刺强度 0 5.07 6.162 5.58 6.2 6.21 5.89 平均孔径（nm) 201.8 146.2 157.6 150.7 165.3 152.7 热收缩 00 横向 7.56 1.87 1.76 1.74 2.21 1.86
130Ό, 30
纵向 3.02 2.47 2.23 2.31 2.52 2.12 分钟
130(Ό) 通过 通过 通过 通过 通过 通过 热冲击
150(Ό) 失敗 通过 通过 通过 通过 通过

Claims

权 利 要 求
1.一种复合隔膜， 其包含：
双向拉伸的具有微孔结构的聚烯烃薄膜， 薄膜两面分别涂覆有无 机颗粒层和聚合有机物层。
2.权利要求 1的复合隔膜， 其中无机颗粒层是多孔无机颗粒层。
3.权利要求 1的复合隔膜， 其中无机颗粒层是多孔无机颗粒层。
4.前述权利要求任一项的复合隔膜， 其中所述有机聚合物层采用 高熔点的聚合物制造。
5.前述权利要求任一项的复合隔膜， 其中所述有机聚合物选自聚 偏氟乙烯、 偏氟乙烯和六氟丙烯的共聚物、 聚对苯二甲酸乙二醇酯、 聚氧化乙烯、 聚甲基丙烯酸甲酯、 聚间苯二甲酰间苯二胺、 聚氯乙烯、 聚丙烯腈、 或它们的混合物。
6.前述权利要求任一项的复合隔膜， 其中所述有机聚合物为氟乙 烯类聚合物。
7.前述权利要求任一项的复合隔膜， 其中所述聚烯烃薄膜的厚度 为 10 ~ 60 μ m， 优选 20 ~ 40 μ m。
8.前述权利要求任一项的复合隔膜， 其中所述复合隔膜厚度为 14 ~ 80 μ ηι, 优选 30 ~ 50 μ ηι。
9.前述权利要求任一项的复合隔膜， 其中所述复合隔膜的透气性 ( Gurley仪数值， 100ml )为 200 ~ 800s， 优选 300 ~ 500s。
10.前述权利要求任一项的复合隔膜用于锂离子电池的用途。
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CN104916802A (zh) * 2015-04-09 2015-09-16 厦门大学 一种复合隔膜及其应用
CN114597588A (zh) * 2020-12-07 2022-06-07 比亚迪股份有限公司 一种锂离子电池隔膜及锂离子电池
CN114058054A (zh) * 2021-10-27 2022-02-18 四川华能氢能科技有限公司 基于制氢工艺可提升离子迁移性能的非石棉复合隔膜材料
CN114284633A (zh) * 2021-12-16 2022-04-05 国科广化精细化工孵化器(南雄)有限公司 一种相变材料复合隔膜及其制备方法与应用
CN114824648A (zh) * 2022-03-18 2022-07-29 扬州大学 Pw12@pdadmac/wmcnt修饰聚丙烯隔膜及其在锂硫电池中的应用

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