WO2022155959A1 - 叠层多孔膜、二次电池以及电子装置 - Google Patents

叠层多孔膜、二次电池以及电子装置 Download PDF

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WO2022155959A1
WO2022155959A1 PCT/CN2021/073618 CN2021073618W WO2022155959A1 WO 2022155959 A1 WO2022155959 A1 WO 2022155959A1 CN 2021073618 W CN2021073618 W CN 2021073618W WO 2022155959 A1 WO2022155959 A1 WO 2022155959A1
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porous layer
laminated porous
laminated
porous
film
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PCT/CN2021/073618
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English (en)
French (fr)
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张龙
郭东阳
杨晓兵
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宁德新能源科技有限公司
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Priority to PCT/CN2021/073618 priority Critical patent/WO2022155959A1/zh
Priority to CN202180002978.XA priority patent/CN113728505A/zh
Publication of WO2022155959A1 publication Critical patent/WO2022155959A1/zh

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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • 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
    • H01M50/409—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
    • H01M50/449—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
    • H01M50/489—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
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/24—All layers being polymeric
    • B32B2250/242—All polymers belonging to those covered by group B32B27/32
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/306—Resistant to heat
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/10—Batteries
    • 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 application relates to the field of energy storage, and in particular, to a laminated porous film, a secondary battery and an electronic device.
  • Secondary ion batteries are mainly composed of positive electrodes, negative electrodes, electrolytes and battery separators.
  • the separator is located between the positive electrode and the negative electrode, which can prevent the electrons from passing through, so as to prevent the positive electrode and the negative electrode from being short-circuited due to contact, while the separator allows the electrolyte ions to pass through, thereby generating electric current.
  • the closed cell temperature and membrane rupture temperature of the separator are the primary considerations to ensure safety.
  • the diaphragm is usually provided with a microporous structure for the passage of electrolyte ions.
  • a violent chemical reaction will occur inside it to generate a large amount of Joule heat.
  • the separator will block the passage of lithium ions by shrinking and closing the pores, cutting off the chemical reaction in the battery, thereby avoiding further thermal runaway, such as explosion.
  • its normal operating temperature is 0-60°C
  • the closed-cell temperature of the existing separator is relatively high.
  • separators with lower closed-cell temperature are required.
  • the membrane rupture temperature refers to the temperature at which rupture of the separator occurs.
  • the separator needs to have a high film breaking temperature, that is, high film breaking property. When the internal temperature of the battery rises sharply due to an abnormality such as a short circuit, the separator will not rupture.
  • the method of adding high melting point or/or low melting point raw material is generally adopted, so that the diaphragm has the above functions at the same time.
  • high melting point raw materials often affect the closed cells of the diaphragm
  • low melting point raw materials often make the diaphragm unable to be processed into a film because of low melting point and small molecular weight (high melting index). Therefore, the existing method affects the reduction of the closed cell temperature of the diaphragm, and The increase of the film breaking temperature.
  • the surface layer is usually made of polypropylene material
  • the core layer is made of high-density polyethylene, and the effect of improving the safety performance of the actual cell is poor.
  • the primary purpose of the present application is to propose a laminated porous membrane, so as to reduce the closed cell temperature of the separator and increase the membrane breaking temperature of the separator.
  • the purpose of the second application of the present application is to propose a secondary battery to improve the safety of the secondary battery.
  • the purpose of the third application of the present application is to provide an electronic device to improve the security of the electronic device.
  • the present application relates to a laminated porous membrane, comprising a first porous layer and a second porous layer disposed on at least one side of the first porous layer, wherein the first porous layer and the second porous layer
  • a laminated porous membrane comprising a first porous layer and a second porous layer disposed on at least one side of the first porous layer, wherein the first porous layer and the second porous layer
  • Tm 1 is the melting point of the first porous layer, °C
  • MI 1 is the melt flow rate of the first porous layer, g/10min
  • Tm 2 is the melting point of the second porous layer, °C
  • MI 2 is the first porous layer Melt flow rate of two porous layers, g/10min.
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the melting point Tm 1 of the first porous layer satisfies: 120°C ⁇ Tm 1 ⁇ 135°C; the melting point Tm 2 of the second porous layer satisfies: 135°C ⁇ Tm 2 ⁇ 145°C.
  • the melting point Tm 2 of the second porous layer and the melting point Tm 1 of the first porous layer satisfy: Tm 2 -Tm 1 >0°C.
  • the laminated porous membrane of the present application satisfies at least one of the following characteristics: the melt flow rate MI 1 of the first porous layer satisfies: 0.2 g/10min ⁇ MI 1 ⁇ 20g/10min; the second porous layer The melt flow rate MI 2 satisfies: 0.2g/ 10min ⁇ MI2 ⁇ 20g /10min.
  • the thickness of the laminated porous film is 5 to 30 ⁇ m.
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the thickness of the first porous layer accounts for 20% to 80% of the thickness of the laminated porous film; the thickness of the second porous layer accounts for the thickness of the laminated porous film 20% to 80% of film thickness.
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the closed-cell temperature of the laminated porous film is less than or equal to 133° C.; the film breaking temperature of the laminated porous film is greater than or equal to 143° C.; In the state, the ionic impedance of the laminated porous membrane is greater than or equal to 1000 ⁇ .
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the closed cell temperature of the laminated porous film is 120°C to 133°C; the film breaking temperature of the laminated porous film is 143°C to 180°C; When the layered porous membrane is in a closed-cell state, the ionic impedance of the laminated porous membrane is greater than or equal to 1000 ⁇ .
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the material of the first porous layer includes high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, linear branch At least one of polyethylene or metallocene polyethylene; the material of the second porous layer includes ultra-high molecular weight polyethylene, high-density polyethylene, polypropylene, polyimide, poly-4methyl-1-pentene , at least one of polystyrene or polyvinylidene fluoride.
  • the present application provides a secondary battery, comprising a positive electrode, a negative electrode, and the laminated porous film of the first aspect of the present application between the positive electrode and the negative electrode.
  • the present application provides an electronic device including the secondary battery of the second aspect of the present application.
  • the laminated porous membrane proposed in this application by defining the relationship between the melting point and the melt flow of the first porous layer and the second porous layer, allows the porous layers to act synergistically, so that the laminated porous membrane can not only operate at a lower temperature
  • the downflow closed cell can also not break the film at high temperature, which can better improve the safety performance of the battery cell.
  • the first porous layer closes the pores at a lower temperature, which can provide a higher internal resistance of the diaphragm, and the second porous layer can keep the membrane at a higher temperature and continue to isolate the positive electrode and the negative electrode, so that no short circuit occurs. Therefore, the synergistic effect between the first porous layer and the second porous layer can better improve the safety of the cell.
  • FIG. 1 is a schematic structural diagram of a laminated porous membrane according to an embodiment of the present application.
  • FIG. 2 is a schematic structural diagram of a laminated porous membrane according to a second embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of a laminated porous membrane according to a third embodiment of the present application.
  • the laminated porous film, the secondary battery, and the electronic device according to the present application are described in detail below.
  • the present application provides a laminated porous membrane, the laminated porous membrane includes a first porous layer and a second porous layer, wherein the first porous layer and the second porous layer satisfy the formula
  • the relationship between I and formula II is shown:
  • Tm 1 is the melting point of the first porous layer, °C
  • MI 1 is the melt flow rate of the first porous layer, g/10min
  • Tm 2 is the melting point of the second porous layer, °C
  • MI 2 is the first porous layer Melt flow rate of two porous layers, g/10min.
  • the melting point Tm 2 of the second porous layer is greater than the melting point Tm 1 of the first porous layer, and the first porous layer achieves a certain temperature. Close the pores to prevent further chemical reactions in the secondary battery.
  • the second porous layer can provide the laminated porous film with high film breaking performance, so that the secondary battery has better safety performance.
  • the laminated porous membrane can not only flow and close the pores at lower temperature, but also The film will not be broken at high temperature, which can better improve the safety performance of the cell.
  • the strength of the casting melt during the processing is suitable, which can also meet the processing requirements.
  • the melting point Tm 1 and melt flow rate MI 1 of the first porous layer, and the melting point Tm 2 and melt flow rate MI 2 of the second porous layer satisfy 0.3 ⁇ ( When Tm 2 -Tm 1 )/MI 1 ⁇ 40, 0.2 ⁇ (Tm 2 -Tm 1 )/MI 2 ⁇ 70, the first porous layer closes pores at a lower temperature, which can provide a higher internal resistance of the separator , the second porous layer can not break the film at a higher temperature, and continue to isolate the positive electrode and the negative electrode, so that no short circuit occurs. Therefore, the synergistic effect between the first porous layer and the second porous layer can better improve the safety of the cell.
  • FIG. 1 is a schematic structural diagram of a laminated porous membrane according to an embodiment of the application.
  • the laminated porous membrane 1 is composed of a first porous layer 11 and a second porous layer 12 .
  • the first porous layer 11 and the second porous layer 12 are stacked and provided.
  • FIG. 2 is a schematic structural diagram of a laminated porous membrane according to another embodiment of the application.
  • the laminated porous membrane 1 of this embodiment consists of a first porous layer 11 and two second porous layers 12, and two second porous layers 12 are respectively disposed on both sides of the first porous layer 11.
  • FIG. 3 is a schematic structural diagram of a laminated porous membrane according to a third embodiment of the application.
  • the laminated porous membrane 1 of this embodiment consists of two first porous layers 11 and one second porous layer 12 The second porous layer 12 is sandwiched between the two first porous layers 11 .
  • FIGS. 1 to 3 are only several exemplary embodiments of the laminated porous membrane provided by the present application.
  • the laminated porous membrane of the present application may also include other The laminated porous membrane of the structure, which includes at least one first porous layer and at least one second porous layer, and the specific number of the first porous layer and the second porous layer is not limited, the first porous layer is not limited.
  • the relationship between the porous layer and the second porous layer only needs to satisfy 0.3 ⁇ (Tm 2 ⁇ Tm 1 )/MI 1 ⁇ 40, and 0.2 ⁇ (Tm 2 ⁇ Tm 1 )/MI 2 ⁇ 70.
  • the laminated porous membrane provided by the present application innovatively constructs the relationship between the melting point and the melt flow rate between the first porous layer and the second porous layer.
  • the melting point and melt flow rate of the porous layer and the second porous layer are combined to make the interaction between the layers, so that the laminated porous film can both close the pores at a lower temperature and provide a higher resistance value at high temperature. It does not break the membrane under it, which can better improve the safety performance of the battery core.
  • it when it is used as a diaphragm, it can also meet the processing requirements of the diaphragm.
  • the lower limit of (Tm 2 -Tm 1 )/MI 1 can be, for example, 0.3, 0.5, 0.8, 1, 1.2, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or a number greater than 10;
  • the upper limit of (Tm 2 -Tm 1 )/MI 1 can be, for example: 40 , 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25 or a number below 25.
  • the lower limit of (Tm 2 -Tm 1 )/MI 2 can be, for example, 0.2, 0.3, 0.5, 0.8, 1, 1.5, 2, 3, 4, 5, 5.5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a number greater than 15;
  • the upper limit of (Tm 2 -Tm 1 )/MI 2 can be, for example: 70, 69, 67, 65, 63, 62, 61, 60, 59 , 57, 55, 53, 51, 50 or a number less than 50.
  • test conditions for the melt flow rate of the first porous layer and the second porous layer of the laminated porous film of the present application are 21.6kg pressure molding pressure and 190°C temperature conditions.
  • the material of the first porous layer includes, but is not limited to, high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear branched polyethylene, or polyvinyl chloride At least one of metallic polyethylene.
  • high density polyethylene (high density polyethylene, HDPE) is a non-polar thermoplastic resin with high crystallinity, and the density is in the range of 0.940-0.976 g/cm 3 .
  • MDPE Medium density polyethylene
  • methyl or ethyl branches per 1000 carbon atoms
  • Low density polyethylene Low density Polyethylene (Low DensityPolyethylene, LDPE), the density is in the range of 0.910-0.925g/ cm3 .
  • Linear low density polyethylene is a copolymer of ethylene and a small amount of ⁇ -olefins (such as 1-butene, 1-octene, etc.), with a narrower molecular weight distribution than general LDPE, while Having a linear structure gives it different rheological properties.
  • Linear branched polyethylene is graft-modified linear polyethylene.
  • Ultra-high molecular weight polyethylene is an unbranched linear polyethylene with a molecular weight of more than 600,000, molecular formula: —(—CH 2 —CH 2 —)—n—, density: 0.920 ⁇ 0.964g/cm 3 .
  • the material of the second porous layer includes, but is not limited to, ultra-high molecular weight polyethylene, high-density polyethylene, polypropylene, polyimide, poly4methyl-1 - At least one of pentene, polystyrene or polyvinylidene fluoride.
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the melting point Tm 1 of the first porous layer satisfies: 120° C ⁇ Tm1 ⁇ 135 °C; the second porous layer satisfies: The melting point Tm 2 of the layer satisfies: 135° C ⁇ Tm2 ⁇ 145 °C.
  • the film-forming performance during processing can be further optimized, and at the same time, the obtained laminated porous film has better low closed-cell performance and high rupture membrane properties.
  • the melting point Tm1 of the first porous layer can be, for example, 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, 131°C, 132°C, 133°C, 134°C or 135°C.
  • the value of the melting point Tm 2 of the second porous layer includes but is not limited to 135°C, 136°C, 137°C, 138°C, 139°C, 140°C, 141°C, 142°C, 143°C, 144°C or 145°C.
  • the melting point Tm 2 of the second porous layer and the melting point Tm 1 of the first porous layer satisfy: Tm 2 -Tm 1 >0°C.
  • the laminated porous membrane of the present application satisfies at least one of the following characteristics: the melt flow rate MI 1 of the first porous layer satisfies: 0.2g/ 10min ⁇ MI1 ⁇ 20g / 10min; the melt flow rate MI2 of the second porous layer satisfies: 0.2g/ 10min ⁇ MI2 ⁇ 20g /10min.
  • the first porous layer and the second porous layer satisfy the above-mentioned melt flow rate index, and can quickly realize closed pores after the temperature of the secondary battery is increased, so as to improve the safety of the secondary battery.
  • the thickness of the laminated porous membrane is 5 to 30 ⁇ m.
  • the resistance, shrinkage rate, strength and other characteristics of the laminated porous film can be further improved, so that it can meet the use requirements of the secondary battery for the separator.
  • the thickness of the laminated porous film may be, for example, 5 ⁇ m, 7 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 17 ⁇ m, 20 ⁇ m, 22 ⁇ m, 25 ⁇ m, 27 ⁇ m or 30 ⁇ m.
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the thickness of the first porous layer accounts for 20% to 80% of the thickness of the laminated porous film; the second porous layer The thickness of the layer is 20% to 80% of the thickness of the laminated porous membrane.
  • the laminated porous film can have a certain high resistance after the pores are closed, so as to prevent the progress of side reactions in the secondary battery.
  • the laminated porous film can have higher strength at high temperature, and the laminated porous film can be prevented from breaking at high temperature.
  • the laminated porous film of the present application satisfies at least one of the following characteristics: the closed cell temperature of the laminated porous film is ⁇ 133°C, preferably, the closed cell temperature is 120°C to 133°C ;
  • the film breaking temperature of the laminated porous film is ⁇ 143°C, preferably, the film breaking temperature is 143°C to 180°C; in the closed-cell state, the ionic impedance of the laminated porous film is ⁇ 1000 ⁇ .
  • the laminated porous membrane in the closed-cell state, is in a blocking state for electrolyte ions. In the closed-cell state, the reaction in the secondary battery is stopped, and the electrons and electrolyte ions between the positive electrode and the negative electrode are in a non-conducting state.
  • the laminated porous membrane provided in the embodiments of the present application has a lower closed-cell temperature, a higher membrane breaking temperature, and a higher ionic impedance in a closed-cell state, so as to prevent the battery from thermal runaway and other problems. Improve the safety of the secondary battery.
  • the preparation method of the laminated porous film of the present application may include the following steps:
  • the ratio of each layer is controlled by adjusting the extrusion volume of the extruder and the lip opening of the multilayer die.
  • the laminated porous film is composed of two layers
  • one layer of the laminated porous film is composed of the raw material added to the first extruder
  • the other layer is composed of the raw material added to the second extruder
  • the laminated porous film is composed of
  • the two outer layers are extruded by the first extruder
  • the middle layer is extruded by the second extruder.
  • Step S12) After the raw material is extruded, it is cooled by a casting roll at 50°C to 120°C to form a film, and then longitudinally stretched at a temperature of 80°C to 130°C, and then transversely stretched, and then extracted with dichloromethane. Hot air is used for drying, secondary heat setting, and winding to prepare the desired laminated porous film.
  • the laminated porous membrane of the present application will be specifically explained below based on specific experimental examples and comparative examples.
  • Table 1 lists the specific raw materials of the laminated porous films provided in Experimental Examples 1 to 12 and Comparative Examples 1 to 7, as well as the processing parameters used in the specific processing and preparation process.
  • the preparation process of the laminated porous membrane provided in Examples 1 to 12 and Comparative Examples 1 to 7 refers to the preparation method of the second aspect of the present application.
  • the raw material and the paraffin oil plasticizer are added to one of the extruder systems and extruded through a three-layer T-die.
  • Test 1 Test of Laminated Porous Membrane
  • test methods of each performance are as follows.
  • a laminated porous membrane sample with a length of 100 mm and a width of 20 mm was cut. First, take a piece of double-sided tape to bond and fix the first surface of the laminated porous film on the platform; then cut a piece of tape with a thickness of 50 ⁇ m, and fix one end of the laminated porous film on the platform to prevent the end part during the peeling process. Then, a 50 ⁇ m thick adhesive tape was cut to adhere to the second surface of the separator, and the laminated porous film was 180° peeled and delaminated by using the adhesive force of the adhesive tape.
  • the thickness of 10-15 points of the laminated porous film was uniformly measured by a "LITEMATIC" VL-50 model of 10,000 thickness gauge (measurement accuracy is 0.01N), and the average value was taken as the total thickness of the laminated porous film.
  • Each layer of the laminated porous film was peeled off according to the method for measuring the interlayer peeling force, and the thickness of each layer was measured by the same method.
  • the temperature was increased from 25 °C to 300 °C at a rate of 10 °C/min, the first melting peak T1 of the sample was measured, and then the temperature was quickly cooled to room temperature, and then the temperature was 10 °C/min. The temperature was increased to 300°C, and the second melting peak T2 of the sample was measured. T2 was recorded as the melting point of the sample.
  • melt flow rate tester (model MFI-1211)
  • the melt flow rate tester was heated to 190 ° C, put into a standard die ⁇ 2.095 ⁇ 0.005 mm, and the raw materials were compacted and placed in a barrel for about 10 minutes.
  • a sample with a length of 30mm and a width of 30mm was cut and sealed in a metal chamber connected with a positive electrode and a negative electrode. Then, the test electrolyte (A_E5068) was injected and sealed, and the metal chamber was connected to a resistance recorder (TH2830 LCR Meter). Put the metal bin into an oven at 200°C, and record the change of the resistance of the sample inside the metal bin with temperature. The temperature at which the resistance of the sample was increased to 1000 ohms was recorded as the closed cell temperature. With the increase of temperature, the temperature corresponding to the resistance of the sample dropped to 1000 ohms was recorded as the film breaking temperature.
  • the closed-cell temperature of the laminated porous film can be effectively reduced
  • the closed-cell temperature of the laminated porous membrane in the embodiment of the present application can be reduced to about 130°C, and some can even reach 129°C.
  • the film breaking temperature of the laminated porous membranes in the embodiments of the present application can all reach above 143°C, among which, the film breaking temperature of some laminated porous films can reach above 160°C, or even 170°C.
  • the laminated porous membranes in Comparative Examples 1-7 cannot meet the requirements of low closed cell temperature and high membrane breaking temperature at the same time.
  • the laminated porous membranes of Comparative Examples 1-7 either have low closed cell temperature or high membrane breaking temperature.
  • the film breaking temperature cannot be effectively unified. From the relevant test data of Examples 1-12 and Comparative Examples 1-7, it can be seen that the laminated porous membranes of the examples of the present application can also achieve the performance of high membrane breaking temperature under the condition of low closed cell temperature.
  • the lithium ion battery was assembled by using the laminated porous membrane provided in each experimental example and the comparative example, and the pass rate of the battery under overcharge adjustment was tested.
  • the test results are listed in Table 3. Among them, the assembled lithium ion batteries are the same except for the separators, other materials and assembly methods.
  • the 4.8V pass rate refers to the ratio of the number of lithium-ion batteries that pass the test to the total number of lithium-ion batteries at 4.8V. The same method is used to calculate the pass rates of other voltages.
  • the lithium-ion batteries prepared by using the laminated porous membranes provided in Examples 1-12 of the present application as separators have a pass rate of 100% at voltages from 4.8V to 6V, and at 8V The pass rate under the voltage also reaches more than 50%, and some can even reach 100%.
  • the lithium ion battery using the laminated porous film provided in Comparative Examples 1-7 as the separator has already begun to decline in the 5V pass rate, and the 5.5V pass rate is all 0. It can be seen that the laminated porous membrane of the embodiment of the present application has better safety.

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Abstract

本申请涉及储能技术领域，具体讲，涉及一种叠层多孔膜、二次电池以及电子装置。该叠层多孔膜包括第一多孔层和设置在第一多孔层至少一面的第二多孔层，其中，第一多孔层和第二多孔层满足式Ⅰ和式Ⅱ所示关系: 0.3≤(Tm 2-Tm 1)/MI 1≤40式Ⅰ，0.2≤(Tm 2-Tm 1)/MI 2≤70式Ⅱ; 其中: Tm 1为所述第一多孔层的熔点; MI 1为所述第一多孔层的熔体流动速率; Tm 2为所述第二多孔层的熔点; MI 2为所述第二多孔层的熔体流动速率。该叠层多孔膜具有较低的闭孔温度以及较高的破膜温度。

Description

叠层多孔膜、二次电池以及电子装置 技术领域
本申请涉及储能领域，具体讲，涉及一种叠层多孔膜、二次电池以及电子装置。
背景技术
随着电动汽车和储能行业的发展，对二次电池的要求越来越高，要求二次电池具有更高的安全性和更高的能量密度。二次离子电池主要由正极、负极、电解质和电池隔膜构成。其中，隔膜位于正极和负极之间，其能够阻止电子通过，以防止正极、负极二者因接触而短路，同时隔膜允许电解质离子通过，从而产生电流。在锂电池的安全性中，隔膜的闭孔温度和破膜温度是保障安全性的首要考虑指标。
其中，隔膜上通常设有微孔结构，以用于电解质离子的通过，当电池异常反应时，其内部会发生剧烈的化学反应从而产生大量的焦耳热，当电池内部温度达到隔膜的闭孔温度时，隔膜会通过收缩闭孔阻碍锂离子的通过，切断电池内的化学反应，进而避免进一步热失控，例如爆炸的发生。以锂离子电池为例，其正常工作温度为0～60℃，而现有的隔膜的闭孔温度较高，当锂离子电池温度失控，达到隔膜的闭孔温度时，此时的温度已经能够引起其他零件异常或损坏，造成一定损失。为了进一步提高锂离子电池的安全性能，需要闭孔温度更低的隔膜。
另外，破膜温度是指隔膜发生破裂的温度。为了保证电池的使用安全性，需要隔膜具有高的破膜温度，即具有高破膜性，当电池发生短路等异常导致其内部温度急剧升高后，也不会导致隔膜发生破裂。
现有的隔膜中，为了使隔膜具有高破膜温度和低闭孔功能，在隔膜加工过程中，一般采用添加高熔点或/或低熔点原料的方式，使隔膜同时具备 上述功能。但是，高熔点原料往往会影响隔膜的闭孔，低熔点原料往往因为熔点低、分子量小(熔指高)，使隔膜无法加工成膜，因此，现有方式影响隔膜闭孔温度的降低，以及破膜温度的提升。例如，目前的隔膜，其表层通常采用聚丙烯材料，芯层采用高密度聚乙烯，实际电芯安全性能改善效果差。
发明内容
本申请的首要申请目的在于提出一种叠层多孔膜，以降低隔膜的闭孔温度以及提高隔膜的破膜温度。
本申请的第二申请目的在于提出一种二次电池，以提高二次电池的安全性。
本申请的第三申请目的在于提出一种电子装置，以提高电子装置的安全性。
为了完成本申请的目的，采用的技术方案为：
第一方面，本申请涉及一种叠层多孔膜，包括第一多孔层和设置在第一多孔层至少一面的第二多孔层，其中，第一多孔层和第二多孔层满足式Ⅰ和式Ⅱ所示关系：
0.3≤(Tm 2-Tm 1)/MI 1≤40    式Ⅰ
0.2≤(Tm 2-Tm 1)/MI 2≤70    式Ⅱ，
其中：Tm 1为第一多孔层的熔点，℃；MI 1为第一多孔层的熔体流动速率，g/10min；Tm 2为第二多孔层的熔点，℃；MI 2为第二多孔层的熔体流动速率，g/10min。
进一步地，本申请的叠层多孔膜满足以下特征中的至少一者：第一多孔层的熔点Tm 1满足：120℃≤Tm 1≤135℃；第二多孔层的熔点Tm 2满足：135℃≤Tm 2≤145℃。
进一步地，第二多孔层的熔点Tm 2与第一多孔层的熔点Tm 1满足：Tm 2-Tm 1＞0℃。
进一步地，本申请的叠层多孔膜满足以下特征中的至少一者：第一多孔层的熔体流动速率MI 1满足：0.2g/10min≤MI 1≤20g/10min；第二多孔 层的熔体流动速率MI 2满足：0.2g/10min≤MI 2≤20g/10min。
进一步地，叠层多孔膜的厚度为5至30μm。
进一步地，本申请的叠层多孔膜满足以下特征中的至少一者：第一多孔层的厚度占叠层多孔膜厚度的20％至80％；第二多孔层的厚度占叠层多孔膜厚度的20％至80％。
进一步地，本申请的叠层多孔膜满足以下特征中的至少一者：叠层多孔膜的闭孔温度≤133℃；叠层多孔膜的破膜温度≥143℃；叠层多孔膜处于闭孔状态下，叠层多孔膜的离子阻抗≥1000Ω。
进一步地，本申请的叠层多孔膜满足以下特征中的至少一者：叠层多孔膜的闭孔温度为120℃至133℃；叠层多孔膜的破膜温度为143℃至180℃；叠层多孔膜处于闭孔状态下，叠层多孔膜的离子阻抗≥1000Ω。
进一步地，本申请的叠层多孔膜满足以下特征中的至少一者：第一多孔层的材料包括高密度聚乙烯、中密度聚乙烯、低密度聚乙烯、线性低密度聚乙烯、线性枝化聚乙烯或茂金属聚乙烯中的至少一种；第二多孔层的材料包括超高分子量聚乙烯、高密度聚乙烯、聚丙烯、聚酰亚胺、聚4甲基-1-戊烯、聚苯乙烯或聚偏氟乙烯中的至少一种。
第二方面，本申请提出一种二次电池，包括正极、负极以及介于正极与负极之间的本申请第一方面的叠层多孔膜。
第三方面，本申请提出一种电子装置，包括本申请第二方面的二次电池。
采用本申请提出的技术方案所到达的有益效果如下：
本申请提出的叠层多孔膜，通过限定第一多孔层和第二多孔层的熔点和熔体流动的关系，让多孔层之间协同作用，使得叠层多孔膜既能在较低温度下流动闭孔，也能在高温下不破膜，更好地改善电芯的安全性能，同时加工过程中的流延熔体强度合适，也能满足加工要求。第一多孔层在较低温度下闭孔，可提供一个较高的隔膜内阻，第二多孔层可以在较高温度下不破膜，继续隔离正极和负极，使其不发生短路。由此，第一多孔层和第二多孔层之间协同作用，可以起到更好改善电芯安全的作用。
下面结合具体实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。实施例中的配方、比例等可因地制宜作出选择而对结果并无实质性影响。
附图说明
图1为本申请一种实施例的叠层多孔膜的结构示意图；
图2为本申请第二种实施例的叠层多孔膜的结构示意图；
图3为本申请第三种实施例的叠层多孔膜的结构示意图。
附图标号：1-叠层多孔膜；11-第一多孔层；12-第二多孔层。
具体实施方式
下面详细说明根据本申请的叠层多孔膜、二次电池和电子装置。
根据本申请的一个方面，本申请提供一种叠层多孔膜，该叠层多孔膜包括第一多孔层和第二多孔层，其中，第一多孔层和第二多孔层满足式Ⅰ和式Ⅱ所示关系：
0.3≤(Tm 2-Tm 1)/MI 1≤40    式Ⅰ
0.2≤(Tm 2-Tm 1)/MI 2≤70    式Ⅱ，
其中：Tm 1为第一多孔层的熔点，℃；MI 1为第一多孔层的熔体流动速率，g/10min；Tm 2为第二多孔层的熔点，℃；MI 2为第二多孔层的熔体流动速率，g/10min。
可以理解的是，将该叠层多孔膜用作二次电池的隔膜时，第二多孔层的熔点Tm 2大于第一多孔层的熔点Tm 1，第一多孔层在一定温度下实现闭孔，以阻止二次电池进一步的化学反应。第二多孔层可为该叠层多孔膜提供高破膜性能，以使二次电池具有较好的安全性能。
当0.3≤(Tm 2-Tm 1)/MI 1≤40并且0.2≤(Tm 2-Tm 1)/MI 2≤70时，叠层多孔膜既能在较低温度下流动闭孔，也能在高温下不破膜，更好地改善电芯的安全性能，同时加工过程中的流延熔体强度合适，也能满足加工要求。
当(Tm 2-Tm 1)/MI 1＜0.3，在满足第一多孔层与第二多孔层存在一定的熔点差异的条件下，第一多孔层的熔体流动速率如果过低，即MI 1过大， 叠层多孔膜加工过程中的流延熔体强度太差，无法正常成膜，叠层多孔膜会出现外观不良、厚度不均等情况。
当(Tm 2-Tm 1)/MI 1＞40，在满足第一多孔层与第二多孔层存在一定的熔点差异的条件下，第一多孔层的熔体流动速率如果过高，即MI 1过小，第一多孔层高温下流动性差，难以有效闭孔，不能起到改善二次电池安全性的作用。
当(Tm 2-Tm 1)/MI 2＜0.2，在满足第一多孔层与第二多孔层存在一定的熔点差异的条件下，第二多孔层的熔体流动速率如果过低，即MI 2过大，叠层多孔膜加工过程中的流延熔体强度太差，无法正常成膜，叠层多孔膜会出现外观不良、厚度不均等情况。
当(Tm 2-Tm 1)/MI 2＞70，在满足第一多孔层与第二多孔层存在一定的熔点差异的条件下，第二多孔层的熔体流动速率如果过高，即MI 2过小，第二多孔层的原料高温下流动性差，会抑制和它接触的第一多孔层闭孔，使第一多孔层难以有效闭孔，也不能起到改善电芯安全的作用。
由此，本申请提供的叠层多孔膜，第一多孔层的熔点Tm 1和熔体流动速率MI 1，以及第二多孔层的熔点Tm 2和熔体流动速率MI 2满足0.3≤(Tm 2-Tm 1)/MI 1≤40，0.2≤(Tm 2-Tm 1)/MI 2≤70时，第一多孔层在较低温度下闭孔，可提供一个较高的隔膜内阻，第二多孔层可以在较高温度下不破膜，继续隔离正极和负极，使其不发生短路。由此，第一多孔层和第二多孔层之间协同作用，可以起到更好改善电芯安全的作用。
图1为本申请一种实施例的叠层多孔膜的结构示意图，如图1所示，该叠层多孔膜1由一层第一多孔层11和一层第二多孔层12组成。第一多孔层11和第二多孔层12叠层设置。
图2为本申请另一种实施例的叠层多孔膜的结构示意图，如图2所示，该实施例叠层多孔膜1由一层第一多孔层11和两层第二多孔层12组成，两层第二多孔层12分别设置在第一多孔层11的两侧表面。
图3为本申请第三种实施例的叠层多孔膜的结构示意图，如图3所示，该实施例叠层多孔膜1由两层第一多孔层11和一层第二多孔12层组成，第二多孔层12夹设在两层第一多孔层11之间。
可以理解的是，图1至图3仅为本申请提供的叠层多孔膜的几种示例性实施例，除图1至图3所示结构外，本申请的叠层多孔膜还可包括其他结构的叠层多孔膜，其中，至少包括一层第一多孔层和至少一层第二多孔层，而第一多孔层和第二多孔层的具体设置数量不做限制，第一多孔层和第二多孔层之间只要满足0.3≤(Tm 2-Tm 1)/MI 1≤40，0.2≤(Tm 2-Tm 1)/MI 2≤70即可。
由此，本申请提供的叠层多孔膜，创新性地构建了第一多孔层和第二多孔层之间熔点和熔体流动速率的关系式，通过对叠层多孔膜中第一多孔层和第二多孔层熔点和熔体流动速率进行组合，以使各层之间相互作用，使叠层多孔膜既能在较低温度下闭孔，提供一个较高的阻值，高温下不破膜，更好的改善电芯的安全性能，同时其作为隔膜时，也能满足隔膜的加工要求。
其中，本申请提供的叠层多孔膜中，(Tm 2-Tm 1)/MI 1的下限值例如可以为：0.3、0.5、0.8、1、1.2、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、6.5、7、7.5、8、8.5、9、9.5、10或大于10的数；(Tm 2-Tm 1)/MI 1的上限值例如可以为：40、39、38、37、36、35、34、33、32、31、30、29、28、27、26、25或低于25的数。
(Tm 2-Tm 1)/MI 2的下限值例如可以为：0.2、0.3、0.5、0.8、1、1.5、2、3、4、5、5.5、6、7、8、9、10、11、12、13、14、15或大于15的数；(Tm 2-Tm 1)/MI 2的上限值例如可以为：70、69、67、65、63、62、61、60、59、57、55、53、51、50或小于50的数。
其中，需要说明的是，本申请的叠层多孔膜的第一多孔层和第二多孔层的熔体流动速率的测试条件为21.6kg压力成型压力，190℃温度条件。
在本申请一种可选实施例中，第一多孔层的材料包括但不限于高密度聚乙烯、中密度聚乙烯、低密度聚乙烯、线性低密度聚乙烯、线性枝化聚乙烯或茂金属聚乙烯中的至少一种。
其中，高密度聚乙烯(high densitypolyethylene，HDPE)是一种结晶度高、非极性的热塑性树脂，密度在0.940～0.976g/cm 3范围内。
中密度聚乙烯(medium density polyethylene，MDPE)，平均每1000 个碳原子中引入少量甲基支链或乙基支链，MDPE的相对密度为0.926-0.953g/cm 3。
低密度聚乙烯(Low DensityPolyethylene，LDPE)，密度在0.910～0.925g/cm 3范围内。
线性低密度聚乙烯(Linear low density polyethylene，LLDPE)，是乙烯与少量的α-烯烃(如1-丁烯、1-辛烯等)的共聚物，具有比一般LDPE更窄的分子量分布，同时具有线性结构使其有着不同的流变特性。
线性枝化聚乙烯为接枝改性的线性聚乙烯。
超高分子量聚乙烯(ultra-high molecular weight polyethylene，UHMWPE)，是分子量60万以上的无支链的线性聚乙烯，分子式：—(—CH 2-CH 2—)—n—，密度：0.920～0.964g/cm 3。
另外，在本申请另一种可选实施例中，第二多孔层的材料包括但不限于超高分子量聚乙烯、高密度聚乙烯、聚丙烯、聚酰亚胺、聚4甲基-1-戊烯、聚苯乙烯或聚偏氟乙烯中的至少一种。
在本申请的一种实施例中，本申请的叠层多孔膜满足以下特征中的至少一者：第一多孔层的熔点Tm 1满足：120℃≤Tm 1≤135℃；第二多孔层的熔点Tm 2满足：135℃≤Tm 2≤145℃。
当第一多孔层或第二多孔层的熔点满足上述关系时，可以进一步优化加工过程中的成膜性能，同时，使得到的叠层多孔膜具有更好的低闭孔性能和高破膜性能。
其中，第一多孔层的熔点Tm 1例如可以为120℃、121℃、122℃、123℃、124℃、125℃、126℃、127℃、128℃、129℃、130℃、131℃、132℃、133℃、134℃或135℃。第二多孔层的熔点Tm 2的取值包括但不限于135℃、136℃、137℃、138℃、139℃、140℃、141℃、142℃、143℃、144℃或145℃。
在本申请的一种实施例中，第二多孔层的熔点Tm 2与第一多孔层的熔点Tm 1满足：Tm 2-Tm 1＞0℃。
在本申请的一种实施例中，本申请的叠层多孔膜满足以下特征中的至少一者：第一多孔层的熔体流动速率MI 1满足：0.2g/10min≤MI 1≤ 20g/10min；第二多孔层的熔体流动速率MI 2满足：0.2g/10min≤MI 2≤20g/10min。
第一多孔层和第二多孔层满足上述熔体流动速率指标，可在二次电池温度提高后，快速实现闭孔，以提高二次电池的安全性。
在本申请的一种实施例中，叠层多孔膜的厚度为5至30μm。
通过优化叠层多孔膜的厚度，可进一步提高叠层多孔膜的电阻、收缩率以及强度等特性，使其满足二次电池对隔膜的使用要求。
其中，叠层多孔膜的厚度例如可以为5μm、7μm、10μm、12μm、15μm、17μm、20μm、22μm、25μm、27μm或30μm。
在本申请的一种实施例中，本申请的叠层多孔膜满足以下特征中的至少一者：第一多孔层的厚度占叠层多孔膜厚度的20％至80％；第二多孔层的厚度占叠层多孔膜厚度的20％至80％。
其中，通过优化第一多孔层的厚度占比，可使该叠层多孔膜闭孔后具有一定较高的电阻，以阻止二次电池内副反应的进行。通过优化第二多孔层的厚度占比，可使该叠层多孔膜在高温下具有较高的强度，防止叠层多孔膜在高温下破裂。
在本申请的一种实施例中，本申请的叠层多孔膜满足以下特征中的至少一者：叠层多孔膜的闭孔温度≤133℃，优选地，闭孔温度为120℃至133℃；叠层多孔膜的破膜温度≥143℃，优选地，破膜温度为143℃至180℃；闭孔状态下，叠层多孔膜的离子阻抗≥1000Ω。其中，闭孔状态下，叠层多孔膜对于电解质离子处于阻隔状态。在闭孔状态下，二次电池内的反应停止，正极与负极间的电子和电解质离子均处于不导通状态。
由此，本申请实施例提供的叠层多孔膜具有较低的闭孔温度，较高的破膜温度，以及在闭孔状态下具有较高的离子阻抗，以防止电池发生热失控等问题，提高二次电池的使用安全性。
根据本申请第二方面，在本申请一种实施例中，本申请的叠层多孔膜的制备方法可包括如下步骤：
步骤S11)在制备本申请实施例的叠层多孔膜时，向两个独立的挤出机系统(第一挤出机和第二挤出机)分别添加不同的原材料和石蜡油增塑 剂，经过多层T型口模挤出。通过调整挤出机挤出量和多层模头膜唇开度来控制各层的比例。
当叠层多孔膜由两层构成时，叠层多孔膜的其中一层采用添加至第一挤出机的原料构成，另一层采用第二挤出机的原料构成；当叠层多孔膜由三层膜组成时，两个外层由第一挤出机挤出，中间层由第二挤出机挤出。
步骤S12)原料挤出后经过在50℃-120℃流延辊冷却成膜，然后在80℃-130℃的温度下进行纵向拉伸，然后进行横向拉伸，再经过二氯甲烷萃取、用热风进行干燥、二次热定型、收卷，制备得到所需叠层多孔膜。
以下将根据具体实验例和对比例对本申请的叠层多孔膜做具体解释说明。
表1列出了实验例1至12以及对比例1至7提供的叠层多孔膜的具体原料，以及具体加工制备过程中所使用的加工参数。其中，实施例1至12以及对比例1至7提供的叠层多孔膜的制备工艺过程参照本申请第二方面的制备方法。另外，在制备对比例的单层结构的多孔膜时，向其中一个挤出机系统添加原材料和石蜡油增塑剂，经过三层T型口模挤出即可。
表1
Figure PCTCN2021073618-appb-000001
Figure PCTCN2021073618-appb-000002
测试一：叠层多孔膜的测试
分别测试不同实验例和对比例的叠层多孔膜的各项性能参数，测试结果列于表2。其中，测试的性能参数有：各层膜厚、熔点、熔融指数、闭 孔温度以及破膜温度。
其中，各项性能的测试方法如下。
1、叠层多孔膜的层间剥离的方法
裁取长100mm、宽20mm的叠层多孔膜样品。先取一截双面胶将叠层多孔膜的第一表面粘结固定在平台上；然后再截取一段50μm厚的胶带，将叠层多孔膜的一端固定在平台上，防止剥离过程中该端部发生移动；然后再截取一段50μm厚的胶带贴合隔离膜的第二表面，利用胶带的粘结力对叠层多孔膜进行180°剥离分层。
2、厚度的测试方法
采用“LITEMATIC”VL-50型号的万分测厚仪(测试精度为0.01N)均匀测试叠层多孔膜的10-15个点的厚度，取平均值作为叠层多孔膜的总厚度。根据测量层间剥离力的方法剥离叠层多孔膜的各层，并采用相同的方法测试各层的厚度。
3、熔点的测试方法
采用同步热分析仪(型号STA449F3)，以10℃/分钟的速率从常温25℃升温至300℃，测得样品的第一次熔融峰T1，然后迅速降温至常温，再以10℃/分钟的速度升温至300℃，测得样品的第二次熔融峰T2。将T2记为样品的熔点。
4、熔体流动速率的测试方法
采用熔体流动速率测定仪(型号MFI-1211)，将熔体流动速率测定仪升温至190℃，放入标准口模Φ2.095±0.005毫米，将原料压实放入料筒中保温约10min，设定样条裁切时间，加压(21.6kg)将原料挤出，计算原料熔体流动速率：MFR＝t*m/T；其中，t为样条裁切时间，m为样条重量，T为600s。
5、闭孔温度和破膜温度的测试方法
裁取长30mm、宽30mm的样品，将其密封在连有正极和负极的金属仓内，然后注入测试用电解液(A_E5068)并密封，将金属仓连接电阻记录仪(TH2830 LCR Meter)。将金属仓放入200℃烘箱内，记录金属仓内部样品电阻随温度的变化。将样品电阻增加至1000欧姆所对应的温度记为闭 孔温度。随温度的升高，将样品电阻重新降为1000欧姆所对应的温度记为破膜温度。
表2
Figure PCTCN2021073618-appb-000003
从表2的数据可以看出，当第一多孔层和第二多孔层的熔点和熔体流动速率满足本申请实施例限定的范围内时，可以有效降低叠层多孔膜的闭孔温度，本申请实施例的叠层多孔膜的闭孔温度可降到130℃左右，有的甚至可达到129℃。另外，本申请实施例的叠层多孔膜的破膜温度均可达到143℃以上，其中，有的叠层多孔膜的破膜温度可达到160℃以上，甚至可以达到170℃。而对比例1-7中的叠层多孔膜，并不能同时满足低闭孔温度和高破膜温度的要求，对比例1-7的叠层多孔膜，要么具有低闭孔温度，要么具有高破膜温度，两者不能有效统一。通过实施例1-12与对比例1-7的相关测试数据可以看出，本申请实施例的叠层多孔膜，在具有低 闭孔温度的情况下，还可达到高破膜温度的性能。
测试二：电池测试
电池过充通过率测试
利用各实验例和对比例提供的叠层多孔膜组装成锂离子电池，测试过充调节下的电池的合格通过率，测试结果列于表3。其中，组装成的锂离子电池除隔膜不同外，其他材料以及组装方法均相同。
过充通过率测试方法：取100个锂离子电池样品，在常温下以0.25C倍率恒定电流放电至额定电压2.8V，再以2C倍率的额定电流充电至指定电压mV(m＝4.8、5.0、5.5…)，然后恒压充电7h，锂离子电池若没有发生冒烟、起火、爆炸，则记为通过，反之则记为不通过。4.8V通过率是指4.8V电压下通过测试的锂离子电池数量与锂离子电池总数的比值，采用相同方法计算其他电压通过率。
表3
隔膜序号 4.8V 5V 5.5V 6V 8V
实施例1 100％ 100％ 100％ 100％ 60％
实施例2 100％ 100％ 100％ 100％ 80％
实施例3 100％ 100％ 100％ 100％ 90％
实施例4 100％ 100％ 100％ 100％ 80％
实施例5 100％ 100％ 100％ 100％ 60％
实施例6 100％ 100％ 100％ 100％ 100％
实施例7 100％ 100％ 100％ 100％ 100％
实施例8 100％ 100％ 100％ 100％ 100％
实施例9 100％ 100％ 100％ 100％ 90％
实施例10 100％ 100％ 100％ 100％ 90％
实施例11 100％ 100％ 100％ 100％ 50％
实施例12 100％ 100％ 100％ 100％ 80％
对比例1 100％ 90％ 0％ 0％ 0％
对比例2 100％ 20％ 0％ 0％ 0％
对比例3 100％ 10％ 0％ 0％ 0％
对比例4 100％ 0％ 0％ 0％ 0％
对比例5 100％ 20％ 0％ 0％ 0％
对比例6 100％ 0％ 0％ 0％ 0％
对比例7 100％ 20％ 0％ 0％ 0％
由表3的数据可以看出，利用本申请实施例1-12提供的叠层多孔膜作 为隔膜制备的锂离子电池，其在4.8V至6V电压下的通过率均为100％，并且在8V电压下的通过率也均达到50％以上，有的甚至可以达到100％。而利用对比例1-7提供的叠层多孔膜作为隔膜的锂离子电池，5V通过率就已经开始下降，5.5V通过率均为0。由此可见，利用本申请实施例的叠层多孔膜具有更好的安全性。
本申请虽然以较佳实施例公开如上，但并不是用来限定权利要求，任何本领域技术人员在不脱离本申请构思的前提下，都可以做出若干可能的变动和修改，因此本申请的保护范围应当以本申请权利要求所界定的范围为准。

Claims (11)

  1. 一种叠层多孔膜，包括第一多孔层和设置在所述第一多孔层至少一面的第二多孔层，其特征在于，所述第一多孔层和所述第二多孔层满足式Ⅰ和式Ⅱ所示关系：
    0.3≤(Tm 2-Tm 1)/MI 1≤40  式Ⅰ
    0.2≤(Tm 2-Tm 1)/MI 2≤70  式Ⅱ，
    其中：Tm 1为所述第一多孔层的熔点，℃；MI 1为所述第一多孔层的熔体流动速率，g/10min；
    Tm 2为所述第二多孔层的熔点，℃；MI 2为所述第二多孔层的熔体流动速率，g/10min。
  2. 根据权利要求1所述的叠层多孔膜，其特征在于，满足以下特征中的至少一者：
    所述第一多孔层的熔点Tm 1满足：120℃≤Tm 1≤135℃；
    所述第二多孔层的熔点Tm 2满足：135℃≤Tm 2≤145℃。
  3. 根据权利要求2所述的叠层多孔膜，其特征在于，所述第二多孔层的熔点Tm 2与所述第一多孔层的熔点Tm 1满足：Tm 2-Tm 1＞0℃。
  4. 根据权利要求1-3任一项所述的叠层多孔膜，其特征在于，满足以下特征中的至少一者：
    所述第一多孔层的熔体流动速率MI 1满足：0.2g/10min≤MI 1≤20g/10min；
    所述第二多孔层的熔体流动速率MI 2满足：0.2g/10min≤MI 2≤20g/10min。
  5. 根据权利要求1-3任一项所述的叠层多孔膜，其特征在于，所述叠层多孔膜的厚度为5至30μm。
  6. 根据权利要求5所述的叠层多孔膜，其特征在于，满足以下特征中的至少一者：
    所述第一多孔层的厚度占所述叠层多孔膜厚度的20％至80％；
    所述第二多孔层的厚度占所述叠层多孔膜厚度的20％至80％。
  7. 根据权利要求1-3任一项所述的叠层多孔膜，其特征在于，满足以下特征中的至少一者：
    所述叠层多孔膜的闭孔温度≤133℃；
    所述叠层多孔膜的破膜温度≥143℃；
    所述叠层多孔膜处于闭孔状态下，所述叠层多孔膜的离子阻抗≥1000Ω。
  8. 根据权利要求1-3任一项所述的叠层多孔膜，其特征在于，满足以下特征中的至少一者：
    所述叠层多孔膜的闭孔温度为120℃至133℃；
    所述叠层多孔膜的破膜温度为143℃至180℃；
    所述叠层多孔膜处于闭孔状态下，所述叠层多孔膜的离子阻抗≥1000Ω。
  9. 根据权利要求1-3任一项所述的叠层多孔膜，其特征在于，满足以下特征中的至少一者：
    第一多孔层的材料包括高密度聚乙烯、中密度聚乙烯、低密度聚乙烯、线性低密度聚乙烯、线性枝化聚乙烯或茂金属聚乙烯中的至少一种；
    所述第二多孔层的材料包括超高分子量聚乙烯、高密度聚乙烯、聚丙烯、聚酰亚胺、聚4甲基-1-戊烯、聚苯乙烯或聚偏氟乙烯中的至少一种。
  10. 一种二次电池，其特征在于，包括正极、负极以及介于所述正极与所述负极之间的如权利要求1-9任一项所述的叠层多孔膜。
  11. 一种电子装置，其特征在于，包括如权利要求10所述的二次电池。
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102791485A (zh) * 2010-03-18 2012-11-21 三菱树脂株式会社 聚烯烃树脂多孔膜及电池用隔板
CN108039443A (zh) * 2017-11-21 2018-05-15 新纶复合材料科技（常州）有限公司 一种锂电池用复合隔膜及其制备方法
CN109192902A (zh) * 2018-07-10 2019-01-11 深圳中兴新材技术股份有限公司 一种多级安全防护锂电池隔膜的制备方法及锂电池隔膜

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102791485A (zh) * 2010-03-18 2012-11-21 三菱树脂株式会社 聚烯烃树脂多孔膜及电池用隔板
CN108039443A (zh) * 2017-11-21 2018-05-15 新纶复合材料科技（常州）有限公司 一种锂电池用复合隔膜及其制备方法
CN109192902A (zh) * 2018-07-10 2019-01-11 深圳中兴新材技术股份有限公司 一种多级安全防护锂电池隔膜的制备方法及锂电池隔膜

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