WO2022002094A1 - Séparateur et son procédé de fabrication, batterie, dispositif électronique et dispositif mobile - Google Patents

Séparateur et son procédé de fabrication, batterie, dispositif électronique et dispositif mobile Download PDF

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Publication number
WO2022002094A1
WO2022002094A1 PCT/CN2021/103351 CN2021103351W WO2022002094A1 WO 2022002094 A1 WO2022002094 A1 WO 2022002094A1 CN 2021103351 W CN2021103351 W CN 2021103351W WO 2022002094 A1 WO2022002094 A1 WO 2022002094A1
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WIPO (PCT)
Prior art keywords
polyethylene
diaphragm
coating
separator
polyolefin composition
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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PCT/CN2021/103351
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English (en)
Chinese (zh)
Inventor
阳东方
张新枝
谢封超
徐凡
王志豪
陶晶
张�雄
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CHONGQING YUNTIANHUA NEWMI-TECH Co Ltd
Huawei Technologies Co Ltd
Original Assignee
CHONGQING YUNTIANHUA NEWMI-TECH Co Ltd
Huawei Technologies Co Ltd
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Priority claimed from CN202010922459.2A external-priority patent/CN113964448B/zh
Application filed by CHONGQING YUNTIANHUA NEWMI-TECH Co Ltd, Huawei Technologies Co Ltd filed Critical CHONGQING YUNTIANHUA NEWMI-TECH Co Ltd
Publication of WO2022002094A1 publication Critical patent/WO2022002094A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • 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
    • 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
    • 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 technical field of lithium ion batteries, and in particular, to a separator and a method for manufacturing the same, a battery, an electronic device, and a mobile device.
  • Lithium-ion batteries are currently commercialized and widely used secondary power sources.
  • the separator is a porous, electrochemically inert medium between the positive electrode and the negative electrode, which does not participate in the electrochemical reaction but is critical to the safety performance of the cell.
  • Currently commonly used polyolefin separators may have some drawbacks. For example, the ductility of the separator is poor, which can cause the separator to be punctured when the cell is mechanically abused.
  • the closed-cell temperature of the separator is high, so that when the cell is overheated, it is difficult to cut off the electrochemical path.
  • the membrane breaking temperature of the diaphragm is low, so that the diaphragm melts when the cell is overheated.
  • the present application provides a separator and a manufacturing method thereof, a battery, an electronic device, and a mobile device.
  • a separator and a manufacturing method thereof By controlling the mechanical properties of the separator, reducing the closed-cell temperature of the separator, etc., the safety of the cell is improved.
  • a separator for use in batteries which is characterized by comprising a separator base material containing a polyolefin composition, the polyolefin composition comprising a plurality of polyethylenes with different viscosity-average molecular weights, and the separator has The thickness is 0.5-12um, the bidirectional elongation of the diaphragm is greater than or equal to 130%, the closed cell temperature of the diaphragm is less than or equal to 142°C, and the membrane breaking temperature of the diaphragm is greater than or equal to 150°C.
  • the diaphragm satisfies at least one of the following:
  • the thickness is 0.5 ⁇ 7um
  • Bidirectional elongation is greater than or equal to 150%
  • the film breaking temperature is greater than or equal to 155°C.
  • the polyolefin composition includes a first polyethylene and a second polyethylene, and the viscosity average molecular weight of the first polyethylene is greater than that of the second polyethylene
  • the viscosity-average molecular weight of the first polyethylene and the viscosity-average molecular weight of the second polyethylene are greater than 40 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition ratio is greater than the second polyethylene.
  • the diaphragm satisfies at least one of the following:
  • the viscosity-average molecular weight of the first polyethylene is greater than or equal to 90 ⁇ 10 4 ;
  • the viscosity average molecular weight of the second polyethylene is less than or equal to 30 ⁇ 10 4 .
  • the diaphragm satisfies at least one of the following:
  • the viscosity average molecular weight of the first polyethylene is greater than or equal to 110 ⁇ 10 4 ;
  • the viscosity average molecular weight of the second polyethylene is less than or equal to 20 ⁇ 10 4 .
  • the proportion of the first polyethylene in the polyolefin composition is 70-100 wt %, and the second polyethylene in the polyolefin composition The proportion of the material is 0-30 wt%.
  • increasing the proportion of the first polyethylene in the polyolefin composition of the diaphragm substrate is conducive to further increasing the proportion of polyethylene Olefin Microporous Film Continuous Processing Efficiency and Improved Melt Index.
  • increasing the proportion of the second polyethylene in the polyolefin composition of the diaphragm substrate is beneficial to reduce the It can reduce the possibility of poor plasticization of the material, reduce the number of melt crystal points in the diaphragm substrate, and help improve the quality of the diaphragm substrate.
  • it is also beneficial to reduce the closed cell temperature of the separator substrate.
  • the polyolefin composition further includes polypropylene or a derivative of polypropylene.
  • polypropylene may be interspersed with polyethylene to form relatively fine crystals rather than large platelets. This is beneficial to improve the comprehensive performance of the diaphragm substrate.
  • adding polypropylene to the diaphragm is beneficial to control the membrane breaking temperature of the diaphragm within a relatively appropriate range, thereby improving the thermal stability of the diaphragm.
  • the enthalpy ⁇ H m of the polypropylene or the derivative of polypropylene is 55-85 J/g.
  • the thermal stability of the polyolefin microporous membrane by optimizing the enthalpy ⁇ H m of polypropylene, it is beneficial to improve the thermal stability of the polyolefin microporous membrane. For example, it is beneficial to improve the tensile strength and improve the problem of excessive flexibility and low stiffness of the film surface; in the process of cutting or attaching the coating, it is beneficial to reduce the possibility of edge protrusion, winding deviation, bending, wrinkling, etc. sex.
  • the polypropylene accounts for 2-10 wt % in the polyolefin composition.
  • the diaphragm satisfies at least one of the following:
  • the tensile modulus is 900 ⁇ 1500MPa
  • the closed cell temperature is 110 ⁇ 142°C;
  • the ratio of longitudinal tensile modulus to transverse tensile modulus is 0.9 to 1.2;
  • the bidirectional heat shrinkage rate of the heat shrinkage test at 130°C is less than or equal to 25%;
  • the ratio of longitudinal tensile strength to transverse tensile strength is 0.9 to 1.2;
  • the crystallinity of the first heating is less than or equal to 72%, and the crystallinity of the second heating is less than or equal to 55%;
  • the porosity is 20% to 85%;
  • the puncture strength is greater than or equal to 150gf;
  • the tensile strength in at least one direction is 1000 ⁇ 3000kgf/cm 2 ;
  • Air permeability is less than or equal to 250s/100cc/5um.
  • the diaphragm satisfies at least one of the following:
  • the closed cell temperature is 130 ⁇ 140°C;
  • the ratio of longitudinal tensile modulus to transverse tensile modulus is 0.91 to 1.1;
  • the bidirectional heat shrinkage rate of the heat shrinkage test at 130°C is less than or equal to 22%;
  • the ratio of longitudinal tensile strength to transverse tensile strength is 0.95 to 1.16;
  • the crystallinity of the first heating is 60-70%, and the crystallinity of the second heating is 40-55%;
  • the porosity is 20% to 40%
  • the puncture strength is greater than or equal to 180gf;
  • the tensile strength in at least one direction is 1000 ⁇ 2500kgf/cm 2 ;
  • Air permeability is less than or equal to 220s/100cc/5um.
  • the polyolefin composition comprises at least one of the following: polyethylene-propylene copolymers, derivatives of polyethylene-propylene copolymers, polyethylene-butene Copolymers, derivatives of polyethylene-butene copolymers, polyethylene-hexene copolymers, derivatives of polyethylene-hexene copolymers, derivatives of polyethylene-octene copolymers, derivatives of polyethylene-octene copolymers polystyrene-ethylene-styrene copolymers, derivatives of polystyrene-ethylene-styrene copolymers, polystyrene-ethylene-butylene-styrene copolymers, polystyrene-ethylene-butylene- Derivatives of styrene copolymers, polyethylene-hydrogenated oligocyclopentadiene, polyethylene-hydrogenated oligo
  • copolymers may have problems such as unstable film formation and difficult control of molecular weight distribution.
  • the propylene copolymer may comprise ethylene-propylene block copolymers and/or random copolymers.
  • the proportion of the ethylene-propylene block copolymer in the propylene copolymer is higher than the proportion of the random copolymer in the propylene copolymer. Specific reasons may include that the melting point of ethylene-propylene block copolymers is generally higher than that of random copolymers.
  • polypropylene or propylene copolymer may contain ethylene molecules.
  • the membrane further includes a coating layer, and the coating layer is provided on one side or both sides of the substrate.
  • setting the separator coating is beneficial to make the separator have properties such as high thermal stability, high film breaking temperature, and low closed cell temperature.
  • the separator coating may also have other properties, such as relatively high adhesion and the like.
  • the coating includes one or more of an organic coating, an inorganic coating, and an organic-inorganic composite coating.
  • the inorganic coating includes a ceramic coating
  • the ceramic coating includes at least one of the following: aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, oxide Zinc, barium oxide, magnesium oxide, beryllium oxide, calcium oxide, thorium oxide, aluminum nitride, titanium nitride, boehmite, apatite, aluminum hydroxide, magnesium hydroxide, barium sulfate, boron nitride, silicon carbide , silicon nitride, cubic boron nitride, hexagonal boron nitride, mesoporous molecular sieve (MCM-41, SBA-15), pearl mica layer.
  • the organic coating includes at least one of the following: polyvinylidene fluoride coating, vinylidene fluoride-hexafluoropropylene copolymer coating, polystyrene coating, aramid coating, polyacrylate or its modified coating, polyester coating, polyarylate coating, polyacrylonitrile coating, aramid coating, polyimide coating, Polyethersulfone coating, polysulfone coating, polyetherketone coating, polyetherimide coating, polybenzimidazole coating, polydopamine.
  • a battery including a positive electrode, a negative electrode, an electrolyte, and the separator as described in any one of the implementation manners of the above-mentioned first aspect.
  • an electronic device including a housing, a display screen, a circuit board assembly and a battery according to any one of the implementation manners of the second aspect, which are accommodated in the housing.
  • a battery powers the display screen and the circuit board assembly.
  • a mobile device in a fourth aspect, includes the battery as described in any one of the implementation manners of the second aspect above.
  • a fifth aspect provides a method for manufacturing a diaphragm, comprising:
  • the polyolefin composition including a plurality of polyethylenes with different viscosity average molecular weights
  • the heat-setting including low-magnification stretching and retracting operations
  • the gel sheet is wound and slit to form the separator.
  • a diaphragm with high elongation properties, low closed cell temperature, high film breaking temperature, and high puncture strength can be formed;
  • the membrane may have an elongation greater than 100%, even greater than 150%.
  • the membrane provided in the embodiments of the present application has a relatively high bidirectional elongation.
  • the separator has a relatively high tensile modulus, which is beneficial to the processing of the separator in the cell process (for example, it is beneficial to avoid problems such as edge protrusion, winding deviation, bending, and wrinkling caused by high elongation characteristics) .
  • the separator provided by the present application is beneficial to improve the mechanical abuse resistance and thermal abuse resistance of the battery.
  • the parameters of the manufacturing method include at least one of the following:
  • the longitudinal stretching ratio in the biaxial stretching process is 2-4 times;
  • the transverse stretching ratio in the biaxial stretching process is 5-7 times;
  • the temperature of the biaxial stretching process is 60-110°C;
  • the stretching ratio of the low-magnification stretching is 1 to 3 times
  • the temperature of the heat setting process is 105-135°C.
  • FIG. 1 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.
  • FIG. 2 is a schematic structural diagram of a lithium ion secondary battery provided in an embodiment of the present application.
  • FIG. 3 is an exploded view of a fixture in a test device for closed-cell temperature and film-breaking temperature provided by an embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of a testing device for closed-cell temperature and membrane-breaking temperature provided in an embodiment of the present application.
  • Separator It can refer to the medium used to separate the positive and negative electrodes of the cell and prevent the positive and negative electrodes from directly contacting and short-circuiting.
  • the essential properties of separators are their porosity (which provides channels for ion transport) and insulation (which prevents electrical leakage).
  • the membrane may include a membrane substrate and a membrane coating.
  • Base separator It can refer to the polyolefin microporous membrane part in the separator.
  • the separator substrate can be used alone in the cell.
  • the separator substrate can provide the aforementioned porosity and the aforementioned insulating properties.
  • Separator coating layer can refer to a thin layer attached to a separator substrate.
  • the membrane coating can be attached to the membrane substrate by coating.
  • the separator coating can be used to enhance the performance of the separator, such as improving the heat resistance, adhesion, etc. of the separator.
  • the core or cell can refer to the part of the battery that has the function of storing electricity.
  • the cells may include positive and negative electrodes.
  • Heat abuse It can refer to the abuse of the battery cell in terms of heat (or high temperature). Cells can be tested for thermal abuse using a hot box (such as using high temperature ( ⁇ 130°C) to bake cells).
  • Mechanical abuse It can refer to the mechanical abuse of batteries. Cells can be tested for mechanical abuse using needle stick tests, bump tests, etc.
  • Elongation Also known as elongation at break, it can refer to the percentage of the length increment relative to the initial length when the separator is pulled off.
  • the separator can be tensile tested under specific conditions, and the increase in the length of the separator divided by the initial length of the separator when the separator is just pulled apart can be used to characterize the elongation. The larger the elongation value is, the less likely the separator is to be broken, and the better the elongation is.
  • the elongation can be divided into longitudinal (MD, ie, along the long side of the membrane) elongation and transverse (TD, perpendicular to MD, ie, along the short side of the membrane) elongation.
  • Tensile modulus It can refer to the tensile strength under certain tensile conditions, that is, the ratio of the force per unit length required by the diaphragm along the tensile direction to the cross-sectional area of the diaphragm.
  • Tensile modulus can be divided into machine direction (MD, ie along the long side of the separator) tensile modulus and transverse (TD, perpendicular to MD, ie along the short side of the separator) tensile modulus.
  • Tensile strength It can refer to the critical strength value of the plastic deformation of the diaphragm, which can characterize the maximum bearing capacity of the diaphragm under uniform tensile conditions.
  • Tensile strength can refer to the stress obtained by dividing the maximum load force on the diaphragm by the initial cross-sectional area of the diaphragm when the diaphragm is just pulled apart.
  • Tensile strength is divided into machine direction (MD, ie along the long side of the separator) tensile strength and transverse (TD, perpendicular to MD, ie along the short side of the separator) tensile strength.
  • Puncture strength It can refer to the use of a spherical steel needle with a diameter of 1.0mm to pierce the diaphragm at a speed of 300 ⁇ 10mm/min.
  • the force required for the steel needle to penetrate the diaphragm is the puncture strength of the diaphragm.
  • Heat shrinkage It can refer to the dimensional change of the separator in the longitudinal/horizontal (longitudinal MD, i.e. along the long side of the separator; transverse TD, perpendicular to MD, i.e. along the short side of the separator) before and after heating Rate.
  • the test method for thermal shrinkage may include: measuring the dimension of the separator in the longitudinal/transverse (MD/TD) direction; placing the diaphragm with a certain size in the longitudinal/transverse (MD/TD) direction in a constant temperature box; heating at a constant temperature oven to a specific temperature; measure the dimensions of the membrane in the longitudinal/transverse (MD/TD) direction after heating.
  • Viscosity-average Molecular Weight It can be one of the common methods of expressing the molecular weight of polymers. Polymers can have polydispersity, and polymer molecular weight generally refers to the average molecular weight of the polymer. Various types of average molecular weights can be obtained by various molecular weight averaging methods. The molecular weight of the polymer obtained by the dilute solution viscosity method can be the viscosity average molecular weight.
  • Molecular weight distribution (distribution of molecular weight): the ratio of weight average molecular weight to number average molecular weight or the ratio of viscosity average molecular weight to weight average molecular weight.
  • Porosity It can refer to the percentage of pore volume in the diaphragm to the total volume of the diaphragm.
  • the porosity P satisfies: where V can be the total volume of the membrane, m can be the mass of the membrane, and ⁇ can be the skeletal density (or true density) of the membrane.
  • Air permeability (Gurley): Can refer to the degree to which the diaphragm allows gas to pass through. Air permeability can be obtained by measuring the time required for a unit gas volume (100 cc) to permeate a membrane at a specific pressure (0.05 MPa).
  • Hole size It can refer to the diameter of the straight hole in the diaphragm.
  • the pore size is measured by a pore size analyzer.
  • Crystallinity It can be obtained by differential scanning calorimetry (differential scanning calorimetry, DSC).
  • the crystallinity of the polyolefin separator can be obtained by: calculating the melting endothermic curve of the polyolefin separator during the process from the start of heating to the generation of the heat transition enthalpy to obtain the melting enthalpy value (unit: Joule (J)); The enthalpy of fusion value was divided by the mass of the sample (g) to obtain the mass-normalized enthalpy of fusion ( ⁇ Hs) of the polyolefin separator.
  • the mass-normalized enthalpy of fusion ( ⁇ Hs) was then divided by the enthalpy of fusion ( ⁇ Hf) of 100% crystalline polyolefin to obtain the crystallinity X (%) of the polyolefin separator.
  • Obturator temperature It can refer to the temperature at which the diaphragm begins to melt and block a part of the originally formed pores during the heating process.
  • Rupture temperature It can refer to the temperature at which the diaphragm melts to a certain extent and ruptures, resulting in a partial or comprehensive short circuit.
  • FIG. 1 is a schematic structural diagram of an electronic device 100 provided by an embodiment of the present application.
  • the electronic device 100 may be a terminal consumer product or a 3C electronic product (computer, communication, consumer electronic product), such as a mobile phone, a power bank, a portable computer, a tablet computer, an e-reader, Laptops, digital cameras, in-vehicle devices, wearable devices, earphones, etc.
  • a mobile phone such as a mobile phone, a power bank, a portable computer, a tablet computer, an e-reader, Laptops, digital cameras, in-vehicle devices, wearable devices, earphones, etc.
  • a mobile phone such as a mobile phone, a power bank, a portable computer, a tablet computer, an e-reader, Laptops, digital cameras, in-vehicle devices, wearable devices, earphones, etc.
  • FIG. 1 is described by taking the electronic device 100 as a mobile phone as an example.
  • Electronic device 100 includes housing 10 , display screen 20 and circuit board assembly 30 .
  • the casing 10 includes a frame and a back cover.
  • the frame surrounds the periphery of the display screen 20 and the periphery of the back cover.
  • the cavity formed between the display screen 20 , the frame, and the back cover can be used to place the circuit board assembly 30 .
  • both the display screen 20 and the circuit board assembly 30 may be disposed on the housing 10 .
  • the electronic device 100 may also include a power supply 40 for powering the circuit board assembly 30 .
  • the power source 40 may be, for example, a lithium-ion secondary battery.
  • FIG. 2 is a schematic structural diagram of a lithium ion secondary battery provided in an embodiment of the present application.
  • the core components of the lithium ion secondary battery may include a positive electrode material 101, a negative electrode material 102, an electrolyte 103, and a separator 104 (corresponding communication accessories and circuits, etc. are not shown).
  • the positive electrode material 101 and the negative electrode material 102 can deintercalate lithium ions to achieve energy storage and release. As shown in Figure 2, Li+ moves to the left (positive electrode) as an energy release process, and Li+ moves to the right (negative electrode) as an energy storage process.
  • the electrolyte 103 may be a transport carrier for lithium ions between the positive electrode material 101 and the negative electrode material 102 .
  • the positive electrode material 101 and the negative electrode material 102 are the main energy storage parts of the lithium ion secondary battery, and can reflect the energy density, cycle performance and safety performance of the battery cell.
  • the separator 104 is permeable to lithium ions, but the separator 104 itself is not conductive, so that the separator 104 can separate the positive electrode material 101 and the negative electrode material 102 to prevent short circuit between the positive electrode material 101 and the negative electrode material 102.
  • the positive electrode material 101 may include a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector.
  • Positive active materials include but are not limited to lithium composite metal oxides (such as nickel cobalt lithium manganate, etc.), polyanion lithium compound LiMx(PO4)y (M is Ni, Co, Mn, Fe, Ti, V, 0 ⁇ x ⁇ 5, 0 ⁇ y ⁇ 5) and so on.
  • the negative electrode material 102 may include a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector.
  • Negative active materials include but are not limited to at least one of the following: lithium metal, lithium alloy, lithium titanate, natural graphite, artificial graphite, MCMB, amorphous carbon, carbon fiber, carbon nanotube, hard carbon, soft carbon, graphene, oxide Graphene, silicon, silicon carbon compounds, silicon oxide compounds and silicon metal compounds.
  • the performance of the separator 104 itself should be beneficial for the lithium-ion secondary battery to achieve good charge-discharge performance.
  • the separator 104 should have certain strength and ductility to avoid being punctured, that is, the separator 104 should have certain mechanical abuse resistance.
  • the lithium-ion secondary battery itself may generate heat during charging and discharging.
  • the membrane 104 should also have relatively high stability, that is, the membrane 104 should have some heat resistance or heat abuse resistance.
  • the membrane breaking temperature of the diaphragm 104 can be relatively high, and it is not easy to melt when the cell is overheated.
  • the closed-cell temperature of the separator 104 can be relatively low, and the electrochemical path between the positive electrode material 101 and the negative electrode material 102 can be relatively easily cut off by the separator 104 when the cell is overheated.
  • the membrane 104 may include a membrane substrate.
  • the membrane substrate may be a porous insulating material.
  • the pores on the separator substrate can permeate lithium ions (the pores on the separator substrate can be transport channels for lithium ions).
  • the membrane substrate may include, for example, a polyolefin-based material.
  • the membrane substrate may also be referred to as a polyolefin porous membrane substrate.
  • the polyolefin-based material provides the separator 104 with chemical inertness, electrochemical inertness, porosity, electrical insulation, and the like.
  • the separator base material as the main component of the separator 104, needs to have properties such as high ductility, high film breaking temperature, and low closed cell temperature.
  • the polyolefin-based material may include polyethylene (PE), for example.
  • the membrane 104 may also include a membrane coating where the properties of the membrane substrate are insufficient or to be improved.
  • the membrane coating can be attached to one or both sides of the membrane substrate, so as to facilitate the membrane 104 to have properties such as high ductility, high membrane breaking temperature, and low closed cell temperature.
  • the separator coating may also have other properties, such as relatively high adhesion and the like.
  • Separator coatings may include organic coatings, inorganic coatings, and/or organic-inorganic composite coatings.
  • Inorganic coatings may include ceramic coatings.
  • the ceramic coating may include at least one of the following: aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, zinc oxide, barium oxide, magnesium oxide, beryllium oxide, calcium oxide, thorium oxide, aluminum nitride, titanium nitride, boehm Stone, Apatite, Aluminum Hydroxide, Magnesium Hydroxide, Barium Sulfate, Boron Nitride, Silicon Carbide, Silicon Nitride, Cubic Boron Nitride, Hexagonal Boron Nitride, Graphite, Graphene, Mesoporous Molecular Sieve (MCM-41 , SBA-15) and so on.
  • the organic coating may include at least one of the following: polyvinylidene fluoride coating, vinylidene fluoride-hexafluoropropylene copolymer coating, polystyrene coating, aramid coating, polyacrylate or its modification coating layer, polyester coating, polyarylate coating, polyacrylonitrile coating, aramid coating, polyimide coating, polyethersulfone coating, polysulfone coating, polyetherketone coating, Polyetherimide coating, polybenzimidazole.
  • the organic-inorganic composite coating can be prepared by mixing the above-mentioned inorganic coating and organic coating.
  • the embodiments of the present application provide a membrane substrate.
  • the membrane substrate can be a microporous film, including a polyolefin composition.
  • the membrane substrate may include a first polyethylene and a second polyethylene, wherein the viscosity average molecular weight of the first polyethylene is greater than the viscosity average molecular weight of the second polyethylene.
  • first polyethylene and the second polyethylene is beneficial to optimize the mechanical properties and heat resistance of the diaphragm base material.
  • the first polyethylene and the second polyethylene have different strengths and extensibility due to the difference in viscosity average molecular weight. Since the viscosity average molecular weight of the first polyethylene is higher than that of the second polyethylene, the strength of the first polyethylene may be higher than that of the second polyethylene, and the elongation of the first polyethylene may be lower than that of the second polyethylene.
  • the first polyethylene may have good toughness and processability. Therefore, the polyolefin composition comprising the first polyethylene and the second polyethylene can have a relatively high elongation relative to the first polyethylene.
  • the polyolefin composition comprising the first polyethylene and the second polyethylene may have relatively high strength relative to the second polyethylene. When the first polyethylene and the second polyethylene are used, the high strength of the first polyethylene and the high elongation of the second polyethylene can be combined to provide suitable strength and elongation for the membrane substrate.
  • the first polyethylene and the second polyethylene have different film breaking temperature and closed cell temperature.
  • the heat resistance of the first polyethylene and the heat resistance of the second polyethylene can be combined, so that the membrane substrate has a suitable film breaking temperature and closed cell temperature.
  • the crystal growth time can be relatively long, which is conducive to fully releasing the stress in the crystallization stage and slowing down the subsequent Stress concentration in the stretching process.
  • first polyethylene and the second polyethylene will be described in detail from various aspects by taking the polyolefin including the first polyethylene and the second polyethylene as an example.
  • the difference between the viscosity average molecular weight of the first polyethylene and the viscosity average molecular weight of the second polyethylene may be greater than a preset threshold.
  • the viscosity average molecular weight of the first polyethylene is greater than or equal to 90 ⁇ 10 4
  • the viscosity average molecular weight of the second polyethylene is less than or equal to 30 ⁇ 10 4
  • the preset threshold may be, for example, 60 ⁇ 10 4 .
  • the viscosity average molecular weight of the first polyethylene is greater than or equal to 100 ⁇ 10 4 .
  • the viscosity average molecular weight of the first polyethylene is greater than or equal to 110 ⁇ 10 4 .
  • Increasing the viscosity-average molecular weight of the first polyethylene is beneficial to improving the strength of the diaphragm base material.
  • the viscosity average molecular weight of the second polyethylene is ⁇ 25 ⁇ 10 4 .
  • the viscosity average molecular weight of the second polyethylene ranges from 15 ⁇ 10 4 to 30 ⁇ 10 4 .
  • the viscosity average molecular weight of the second polyethylene is ⁇ 20 ⁇ 10 4 . Increasing the viscosity average molecular weight of the second polyethylene is beneficial to reduce the difficulty of processing the separator.
  • the viscosity average molecular weight of the first polyethylene is ⁇ 200 ⁇ 10 4
  • the viscosity average molecular weight of the second polyethylene can be in the range of 20 ⁇ 10 4 to 30 ⁇ 10 4 . This is beneficial to improve the uniformity of nuclei growth and the uniformity of refractive index at the macroscopic scale.
  • the phase separation temperature of polyethylene with high viscosity average molecular weight is relatively high, and the phase separation temperature of polyethylene with low viscosity average molecular weight is relatively low.
  • Shortening the difference between the viscosity-average molecular weight of the first polyethylene and the viscosity-average molecular weight of the second polyethylene is beneficial to reducing the phase separation temperature difference between the two. If the phase separation temperature difference is relatively large, voids and supports are likely to be formed during the formation of the diaphragm, and the crystallization conditions in the diaphragm are inconsistent, which will eventually lead to poor uniformity of refractive index at the macro scale, and there may be light and dark differences.
  • the viscosity-average molecular weight of the first polyethylene is ⁇ 110 ⁇ 10 4
  • the viscosity-average molecular weight of the second polyethylene can be in the range of 20 ⁇ 10 4 to 30 ⁇ 10 4
  • Polyethylenes of high viscosity average molecular weight generally have relatively good thermal stability.
  • the first polyethylene and the second polyethylene may also be used in a blend of various species each within the above-mentioned viscosity-average molecular weight range.
  • the viscosity-average molecular weight and molecular weight distribution can be measured by gel permeation chromatography (GPC).
  • GPC gel permeation chromatography
  • the proportion of the first polyethylene in the membrane substrate may be greater than that of the second polyethylene.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm substrate or in the diaphragm substrate may be greater than 50 wt % (wt % may be a weight percentage).
  • the first polyethylene is the main component in the separator base material.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 70 wt % or more.
  • the proportion of the second polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 30 wt % or less. This is beneficial to improve the continuous processing efficiency of polyolefin microporous film and improve the melt index.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 75 wt % or more.
  • the proportion of the second polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 25 wt % or less.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm substrate or in the diaphragm substrate may preferably be 80wt% to 90wt%, and the second polyethylene in the polyolefin composition of the diaphragm substrate or The proportion in the separator base material may preferably be 10wt% to 20wt%.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 85 wt % or more.
  • the proportion of the second polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 15 wt % or less.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm substrate or in the diaphragm substrate may preferably be 85wt% to 95wt%, and the second polyethylene in the polyolefin composition of the diaphragm substrate or The proportion in the separator substrate may preferably be 5wt% to 15wt%.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 95 wt % or more.
  • the proportion of the second polyethylene in the polyolefin composition of the diaphragm base material or in the diaphragm base material may preferably be 5 wt % or less.
  • Increasing the proportion of the first polyethylene in the polyolefin composition of the diaphragm substrate is conducive to further improving the continuity of the polyolefin microporous membrane. Processing efficiency and improved melt index.
  • it is also beneficial to prevent the diaphragm base material from wrinkling and creep, and is beneficial to improve the tensile modulus of the diaphragm base material.
  • Increasing the proportion of the second polyethylene in the polyolefin composition of the diaphragm substrate is beneficial to reduce the problem of poor plasticization of the diaphragm substrate. It is possible to reduce the number of melt crystal points in the diaphragm substrate, which is beneficial to improve the quality of the diaphragm substrate. In addition, it is also beneficial to reduce the closed cell temperature of the separator substrate.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm base material may preferably be 95 wt % or less, and more preferably 90 wt % or less.
  • the proportion of the second polyethylene in the polyolefin composition of the diaphragm base material may preferably be 5 wt % or more, more preferably 7 wt % or more, and further preferably 10 wt % or more.
  • the elongation rate of the diaphragm substrate can be further influenced by changing the crystallinity of the diaphragm substrate at the first temperature rise and the crystallinity at the second temperature increase.
  • the crystallinity of the membrane substrate at one temperature increase may preferably be 55-72%.
  • the crystallinity of the membrane substrate at one temperature increase may more preferably be 60-70%.
  • the crystallinity of the membrane substrate at one temperature increase may further preferably be 66-70%.
  • the crystallinity of the diaphragm base material may preferably be 40-55% during the second temperature rise.
  • the crystallinity of the diaphragm base material may be more preferably 45-55% at the second temperature rise.
  • the crystallinity of the diaphragm base material may be further preferably 47-53% at the second temperature rise.
  • the crystallinity of the membrane substrate at one temperature increase may be less than or equal to 72%.
  • the secondary temperature rise crystallinity of the membrane substrate may be less than or equal to 55%.
  • the crystallinity of the membrane substrate at one temperature rise may be less than or equal to 65%.
  • the secondary temperature rise crystallinity of the membrane substrate may be greater than or equal to 45%.
  • reducing the crystallinity of the diaphragm substrate is conducive to improving the elongation of the diaphragm substrate; increasing the crystallinity of the diaphragm substrate is conducive to increasing the strength.
  • the molecular weight distribution of the one-component polyolefin composition is preferably 5-25, more preferably 6-12, further preferably 7-10. This facilitates the optimization of the blending process.
  • the blending process can be performed. More preferably, when the molecular weight distribution of the blended polyolefin is 10-65, the blending process can be performed. This facilitates the optimization of the blending process.
  • the molecular weight distribution can be determined by gel permeation chromatography (GPC).
  • the melting point of the first polyethylene may be 133-139°C. More preferably, the melting point of the first polyethylene may be 133-136°C.
  • the melting point of the second polyethylene may be less than or equal to 130°C. More preferably, the melting point of the second polyethylene may be less than or equal to 126°C.
  • the polyethylene component in the polyolefin composition is preferably a homopolymer, but may also be a polyethylene-propylene copolymer, a derivative of a polyethylene-propylene copolymer, a polyethylene-butene copolymer, or a polyethylene-butene copolymer.
  • polyethylene-hexene copolymers derivatives of polyethylene-hexene copolymers, polyethylene-octene copolymers, derivatives of polyethylene-octene copolymers, polystyrene-ethylene-styrene copolymers Polystyrene-ethylene-butylene-styrene copolymer derivatives, polystyrene-ethylene-butylene-styrene copolymers, polystyrene-ethylene-butylene-styrene copolymer derivatives, polyethylene- Hydrogenated oligocyclopentadiene, polyethylene-derivatives of hydrogenated oligocyclopentadiene, polyethylene oxide, derivatives of polyethylene oxide, polypentene-ethylene copolymers, derivatives of polypentene-ethylene copolymers, Polyhexene-ethylene copolymers, derivatives of polyhexene-ethylene copolymers, polymethylpentene-
  • the membrane substrate may also include at least one of the following: antioxidants: such as phenols, amines, phosphites, thiodipropionates, etc.; stabilizers: such as sodium stearate, hard Calcium stearate, magnesium stearate, zinc stearate, etc.; antistatic agent, radiation absorber, light stabilizer, nucleating agent, inorganic particles, etc.
  • antioxidants such as phenols, amines, phosphites, thiodipropionates, etc.
  • stabilizers such as sodium stearate, hard Calcium stearate, magnesium stearate, zinc stearate, etc.
  • antistatic agent such as sodium stearate, hard Calcium stearate, magnesium stearate, zinc stearate, etc.
  • the membrane substrate may also include thermoplastic resins other than polyolefins.
  • the membrane substrate may also include at least one of the following: linear low density polyethylene, branched polyethylene, polymethyl methacrylate, polyvinylidene fluoride, polyacrylonitrile, and the like.
  • the embodiments of the present application provide another membrane substrate.
  • the membrane substrate can be a microporous film, including a polyolefin composition.
  • This membrane substrate can also be referred to as a polyolefin microporous membrane.
  • the membrane substrate may include a first polyethylene, a second polyethylene, and polypropylene (PP), wherein the viscosity average molecular weight of the first polyethylene is greater than the viscosity average molecular weight of the second polyethylene.
  • PP polypropylene
  • the polyethylene in the polyolefin composition can be blended with polypropylene, and the polypropylene can be interspersed with the polyethylene to form relatively fine crystals rather than large platelets. This is beneficial to improve the comprehensive performance of the diaphragm substrate.
  • the enthalpy ⁇ Hm of the polypropylene is in the range of 55-85 J/g.
  • the enthalpy ⁇ Hm of the polypropylene is in the range of 60-80 J/g.
  • the first polyethylene polyethylene with relatively high viscosity average molecular weight
  • the first polyethylene can be cut and inserted between polypropylene molecular chains, which is beneficial to improve the incompatibility between polyethylene and polypropylene.
  • relatively consistent phase separation characteristics can be formed, which is beneficial to prevent the thickness deviation of the membrane from being too large.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm base material may preferably be 70 wt% or more, and the second polyethylene in the polyolefin composition of the diaphragm base material
  • the proportion of polypropylene in the polyolefin composition of the separator substrate may preferably be 20 wt % or less.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm substrate may preferably be more than 80 wt%, and the second polyethylene in the polyolefin composition of the diaphragm substrate
  • the proportion of polypropylene in the polyolefin composition of the separator substrate may preferably be 20 wt % or less, and the proportion of polypropylene in the polyolefin composition of the separator substrate may preferably be 15 wt % or less.
  • the proportion of the first polyethylene in the polyolefin composition of the diaphragm substrate may preferably be 85-95 wt %, and the proportion of the second polyethylene in the polyolefin composition of the diaphragm substrate may preferably be 5%. ⁇ 15wt%, the proportion of polypropylene in the polyolefin composition of the diaphragm substrate may preferably be 10wt% or less.
  • Polypropylene may include propylene copolymers.
  • the propylene copolymer may comprise ethylene-propylene block copolymers and/or random copolymers.
  • the proportion of the ethylene-propylene block copolymer in the propylene copolymer is higher than the proportion of the random copolymer in the propylene copolymer. Specific reasons may include that the melting point of ethylene-propylene block copolymers is generally higher than that of random copolymers.
  • polypropylene or propylene copolymer may contain ethylene molecules.
  • the ethylene content may be above 5 wt %, preferably the ethylene content is above 7 wt %, and more preferably the ethylene content is above 10 wt %.
  • the compatibility of polyethylene with polypropylene can be changed.
  • optimizing the density of polyethylene is also beneficial to optimizing the degree of delamination of polyethylene or polypropylene.
  • the density of polyethylene is preferably 0.85 to 0.99 g/cm 3 , more preferably 0.91 to 0.97 g/cm 3 , still more preferably 0.92 to 0.95 g/cm 3 .
  • the polypropylene density is preferably 0.9 g/cm 3 or more, and more preferably 0.91 g/cm 3 or more.
  • the tensile strength of the separator base material is preferably 1500 to 2000 kgf/cm 2 .
  • the ratio of the longitudinal/transverse (MD/TD) tensile strength of the diaphragm substrate is preferably 0.9-1.2, more preferably 0.95-1.2, and further preferably 0.96-1.16.
  • the tensile modulus of the separator base material is preferably 900 to 1500 Mpa.
  • the ratio of the longitudinal/transverse (MD/TD) tensile modulus of the diaphragm substrate is preferably 0.9-1.2, more preferably 0.91-1.1.
  • the puncture strength of the diaphragm base material is preferably 200 to 350 gf, and more preferably 210 to 300 gf.
  • improving the puncture strength of the diaphragm substrate is conducive to improving the safety of the diaphragm substrate (for example, the puncture strength of the diaphragm substrate can be above 200 gf), and is conducive to winding batteries and processing coatings. Reducing the puncture strength of the diaphragm substrate is beneficial to avoid the obvious decrease in the bidirectional elongation of the diaphragm substrate under the condition of excessive stretching (the puncture strength of the diaphragm substrate can be, for example, 350 gf or less).
  • Air permeability can refer to the time it takes for a volume of air to pass through the membrane. The lower the air permeability, the easier it is for air to pass through the diaphragm. Low air permeability often means that the separator has large pores, low porosity, etc.
  • the air permeability of the diaphragm base material is preferably 100-300s/100cc/5um, more preferably 150-250s/100cc/5um, still more preferably 150-230s/100cc/5um.
  • the air permeability of the separator substrate is beneficial to reduce the self-discharge defect rate (the air permeability of the separator substrate can be, for example, 100s/100cc/5um or more). Reducing the air permeability of the diaphragm substrate is beneficial to improve the transmission efficiency of ions in the cell (the air permeability of the diaphragm substrate can be, for example, below 300s/100cc/5um).
  • the thickness of the diaphragm base material is preferably 0.5um to 12um, more preferably 3um to 7um, further preferably 3um to 6um.
  • the thickness of the separator substrate is conducive to improving the transmission efficiency of ions in the cell, and is conducive to improving the energy density of the battery (the thickness of the separator substrate can be, for example, 7um or less).
  • Increasing the thickness of the diaphragm substrate is beneficial to reduce the self-discharge inside the cell, improve the isolation capability of the diaphragm substrate, and further improve the safety of the battery (the thickness of the diaphragm substrate can be, for example, more than 3um).
  • the biaxial elongation at break of the separator base material is preferably 100 to 250%, more preferably 150 to 220%, and further preferably 180 to 220%.
  • the bidirectional elongation at break of the separator substrate is beneficial to reduce safety problems caused by the expansion and contraction of the battery winding body during charging and discharging (the bidirectional elongation at break of the separator substrate can be, for example, 100%). above). Reducing the biaxial elongation at break of the diaphragm substrate is beneficial to improve the mechanical strength and thermal stability of the diaphragm substrate (the biaxial elongation at break of the diaphragm substrate can be, for example, 250% or less).
  • the ratio of the elongation at break in the machine direction/transverse direction is preferably 0.9 to 1.2, and more preferably 0.94 to 1.2.
  • the ratio of the elongation at break in the machine direction/transverse direction is close to 1 (the elongation at break is equal in all directions), which is beneficial to make the membrane substrate have uniform pores.
  • the closed cell temperature of the separator base material is preferably 90 to 145°C, more preferably 110 to 142°C, further preferably 130 to 140°C.
  • the closed-cell temperature of the diaphragm substrate is beneficial to prevent the battery from melting during normal use, thereby improving the thermal stability of the battery (the closed-cell temperature of the diaphragm substrate is preferably above 90°C, more preferably 110°C or higher, more preferably 130°C or higher). Reducing the closed cell temperature of the separator substrate is beneficial to improve the safety of the battery (the closed cell temperature of the separator substrate is preferably 145°C or lower, more preferably 142°C or lower, and even more preferably 140°C or lower)
  • the membrane breaking temperature of the diaphragm base material is preferably 150°C or higher, more preferably 152°C or higher, and further preferably 155°C or higher.
  • the film breaking temperature of the separator substrate is beneficial to improve the safety of the battery under high temperature conditions (for example, in a thermally abnormal environment, the film breaking temperature of the separator substrate is preferably 150°C or higher).
  • the separator provided in the embodiments of the present application can be applied to a battery (eg, a flexible battery) as a separator of the battery.
  • the diaphragm provided in the embodiments of the present application can also be applied to capacitors.
  • the membrane provided in the embodiments of the present application can be applied as a permeable membrane, a filtration membrane, or an ultrafiltration membrane.
  • the embodiments of the present application provide a method for manufacturing a diaphragm substrate.
  • the polyolefin composition may also include polypropylene.
  • Step (1) is described in detail below.
  • Step (1) can be simply referred to as extrusion casting process.
  • the extrusion casting step may be a step of kneading, extruding, and casting a mixture containing a polyolefin composition and a plasticizer with a screw extruder, and cooling to form a gel sheet.
  • the mixture may be mixed by a counter-current mixer, a twin-shaft blade mixer, a double-boiler mixer, or the like.
  • the mixture can be kneaded at high temperature by a single-screw extruder or a twin-screw extruder.
  • a twin-screw extruder is preferred.
  • the temperature of the extruder is preferably 150 to 300°C, more preferably 160 to 260°C, still more preferably 170 to 230°C.
  • the temperature of the extruder is beneficial to improve the melt plasticization efficiency (the temperature of the extruder is preferably 150°C or higher, more preferably 160°C or higher, and further preferably 170°C or higher). Lowering the temperature of the extruder is beneficial to prevent oxidative decomposition of the polyolefin composition (the temperature of the extruder is preferably 300°C or lower, more preferably 260°C or lower, and further preferably 230°C or lower).
  • the method of forming the cast sheet may be, for example, a rolling method, a free die method, or the like.
  • the thickness of the gel sheet is preferably 200 to 700 um, more preferably 250 to 550 um.
  • the thickness of the gel sheet is beneficial to increase the mechanical strength of the separator substrate (the thickness of the gel sheet is preferably 200 um or more, more preferably 250 um or more). Reducing the thickness of the gel sheet is beneficial to increase the elongation properties of the separator substrate (the thickness of the gel sheet is preferably 700 um or less, more preferably 550 um or less).
  • the high temperature melt casting cooling method can be, for example, a direct contact cooling method such as air cooling, water cooling, oil cooling, and contacting a casting sheet with a cooling roll. From the viewpoint of controlling the thickness of the gel sheet and improving the uniformity of the separator substrate, the embodiment of the present application preferably adopts a method of cooling by contact with a cooling roller.
  • the plasticizer may include at least one of the following: hydrocarbon organic solvent (such as paraffin, etc.), 2-ethylhexyl phthalate, dibutyl phthalate, alkyl sulfonate, phthalate Butyl benzyl formate, diisononyl phthalate.
  • hydrocarbon organic solvent such as paraffin, etc.
  • 2-ethylhexyl phthalate dibutyl phthalate
  • alkyl sulfonate phthalate Butyl benzyl formate, diisononyl phthalate.
  • liquid paraffin is preferred.
  • the plasticizer can be miscible with the polyolefin composition in any ratio (ie, a homogeneous organic solvent is formed).
  • the proportion of the polyolefin composition in the mixture is preferably 10-50 wt %, more preferably 12-30 wt %, further preferably 15-25 wt %.
  • the proportion of the polyolefin composition in the mixture is beneficial to improve the moldability and processability of the mixture (for example, the proportion of the polyolefin composition in the mixture may be more than 15wt%). Reducing the proportion of the polyolefin composition in the mixture is beneficial to improve the porosity of the mixture (for example, the proportion of the polyolefin composition in the mixture may be below 95 wt %).
  • the proportion of plasticizer in the mixture is preferably 50-90 wt %, more preferably 75-85 wt %.
  • adding a plasticizer to the mixture is also beneficial to provide a relatively complete pore structure.
  • the mixture further includes inorganic particles.
  • the inorganic particle can be a porogen.
  • inorganic particles are used in step (1), and at least part of the inorganic particles are removed in the final product, it is beneficial to obtain a relatively high porosity, thereby improving the ion transport efficiency.
  • the way to remove the inorganic particles can be, for example, the use of a liquid in which the inorganic particles can be dissolved.
  • inorganic particles are used in step (1), and at least part of the inorganic particles are retained in the final product, it is beneficial to improve the stability of the diaphragm substrate (for example, improve the mechanical properties, heat resistance, etc. of the diaphragm substrate) and improve the stability of the diaphragm substrate. properties (that is, to improve the affinity of the separator substrate and the electrolyte).
  • Inorganic particles may include, for example, at least one of the following: aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, zinc oxide, barium oxide, magnesium oxide, beryllium oxide, calcium oxide, thorium oxide, aluminum nitride, titanium nitride, boehmium Stone, Apatite, Aluminum Hydroxide, Magnesium Hydroxide, Barium Sulfate, Boron Nitride, Silicon Carbide, Silicon Nitride, Cubic Boron Nitride, Hexagonal Boron Nitride.
  • the size of the inorganic particles can affect the uniformity of mixing.
  • the particle diameter of the inorganic particles is preferably in the range of 5 to 300 nm, more preferably in the range of 10 to 100 nm, and still more preferably in the range of 20 to 50 nm.
  • the mixture may also include antioxidants.
  • antioxidants can be added to the polyolefin composition. That is, the mixture containing the polyolefin composition and the antioxidant is kneaded and extruded in a screw extruder.
  • the proportion of antioxidants in the mixture is preferably 0.1-5 wt %, more preferably 0.2-2 wt %.
  • Step (2) can be simply referred to as a stretching process.
  • the stretching step may be a step of biaxially stretching the gel sheet.
  • the method of biaxial stretching can be, for example, asynchronous stretching (sequential biaxial stretching using a combination of a speed difference roll stretching machine and a guide chain tenter frame, that is, stretching in the first axis first, and then stretching in the second axis upward stretching), simultaneous stretching (simultaneous stretching using a biaxial tenter, that is, stretching in the first axial direction and the second axial direction at the same time).
  • asynchronous stretching is beneficial to improve the efficiency of stretch forming.
  • the surface draw ratio in the stretching step is preferably 10 to 50 times, more preferably 12 to 40 times, and further preferably 15 to 15 times. 30 times.
  • lowering the area draw ratio in the stretching step is advantageous in increasing the elongation of the separator base material (for example, the separator base material may be 50 times or less).
  • Increasing the area draw ratio of the stretching process is beneficial to increase the porosity or pore transmittance, and is beneficial to improve the thickness uniformity of the diaphragm substrate (for example, the diaphragm substrate may be 10 times or more).
  • the stretching temperature in the stretching process should be selected with reference to the solid content of the polyolefin composition (the solid content can be the mass percentage of the remaining part of the polyolefin composition after drying under specified conditions to the total amount).
  • the stretching temperature in the stretching step is preferably 60 to 110°C, more preferably 63 to 108°C, further preferably 65 to 106°C.
  • stretching temperature in the stretching process is beneficial to prevent the stretching temperature from being too low to cause cold stretching, which in turn causes insufficient activation of the molecular chain (that is, the degree of solidification is relatively large), resulting in relatively large stress concentration (
  • the stretching temperature in the stretching step may be, for example, 60° C. or higher).
  • Lowering the stretching temperature in the stretching process is beneficial to improve the pore structure of the separator (the stretching temperature in the stretching process can be, for example, 110° C. or lower).
  • the step (3) can be simply referred to as the process of removing the plasticizer.
  • the plasticizer in the gel sheet can be removed by the extraction agent.
  • the extractant can dissolve the plasticizer (the extractant can be a good solvent for the plasticizer), but is incompatible with the polyolefin material (ie, the extractant cannot dissolve the polyolefin material).
  • the extractant may include, for example, at least one of the following: halogenated hydrocarbons (eg, dichloromethane, n-hexane, cyclohexane, etc.), acetone, tetrahydrofuran, ethanol, N-methylpyrrolidone, and the like.
  • the extractant is preferably dichloromethane.
  • the method for removing the plasticizer may be to immerse the gel sheet in the extractant, or spray the gel sheet with the extractant to extract the plasticizer, and finally dry the extracted gel sheet.
  • Step (4) can be simply referred to as a heat setting process.
  • the heat setting process can refer to performing low-rate stretching and retracting operations on the gel sheet under a certain temperature condition to release the stress accumulated in the gel sheet in the previous process, thereby helping to improve the gel sheet. of thermal stability.
  • the low-magnification stretching (ie, the stretching in the heat-setting step) may refer to stretching with a stretching ratio of 3.0 times or less.
  • the stretching ratio in the heat-setting step is advantageous in improving the elongation properties of the gel sheet (the stretching ratio in the heat-setting step is preferably 2.5 times or less, more preferably 2 times or less).
  • Increasing the stretching ratio in the heat-setting process is advantageous to improve the pore structure of the gel sheet (the stretching ratio in the heat-setting process is preferably 1 times or more, more preferably 1.2 times or more).
  • the stretching temperature (setting temperature) of the low-magnification stretching is preferably 105 to 135°C, more preferably 105 to 130°C, and still more preferably 108 to 129°C.
  • the stretching temperature in the heat-setting process is advantageous in reducing the crystallinity of the gel sheet (the stretching temperature in the heat-setting process is preferably 135° C. or lower).
  • Increasing the stretching temperature in the heat-setting process is advantageous in order to prevent stress concentration and microcracks from being generated in the gel sheet (the stretching temperature in the heat-setting process is preferably 105°C or higher).
  • the retracting operation may specifically refer to relaxing the gel sheet through the retracting track, so that the gel sheet is relaxed or in a semi-free state.
  • Reducing the retraction ratio of the retraction operation is beneficial to prevent excessive relaxation, which in turn is beneficial to increase the pores of the gel sheet, and is beneficial to improve the transmission efficiency of ions (the retraction ratio of the retraction operation is preferably 10% or less, more preferably 4.5% or less, more preferably 3% or less).
  • thermal shrinkage can refer to the shrinkage phenomenon that occurs under the action of diaphragm stress at high temperature
  • the shrinkage ratio of is preferably 0.5% or more, more preferably 1% or more).
  • the step (5) may specifically be: winding and slitting the gel sheet.
  • step (5) the membrane substrate or membrane provided in the embodiments of the present application can be obtained.
  • This embodiment of the present application may not limit the execution order and execution times of the foregoing steps (1) to (5).
  • the execution sequence of steps (1)-(5) may be: (1)-(2)-(3)-(4)-(5).
  • step (2) before step (3) is beneficial to improve the pore structure of the diaphragm and improve the mechanical strength of the diaphragm.
  • execution sequence of steps (1)-(5) may be: (1)-(3)-(2)-(4)-(5).
  • execution sequence of steps (1)-(5) may be: (1)-(3)-(2)-(3)-(4)-(5).
  • Step (2) ie, the stretching process
  • step (3) ie, the plasticizer removal process
  • Embodiments of the present application also provide a method for manufacturing a lithium ion battery.
  • the principle is that the above-mentioned separator is arranged between the positive electrode material and the negative electrode material (for example, the assembly is performed in the order of positive electrode material-diaphragm-negative electrode material or negative electrode material-diaphragm-positive electrode material);
  • the layered member is wound to obtain a winding body; the winding body is put into a battery casing; and an electrolyte solution is injected.
  • the positive electrode material can be obtained by combining the positive electrode active material (such as lithium cobalt oxide), a conductive agent (such as conductive carbon black, Super-P, SP), a binder (such as polyvinylidene fluoride) , polyvinylidene fluoride, PVDF), mixed in a solvent (such as N-methyl pyrrolidone, N-methyl pyrrolidone, NMP) in a mass ratio of 97:1.5:1.5 to form a positive electrode slurry; It is evenly coated on both sides of the plate (such as aluminum foil); the positive electrode slurry on the plate is dried in an oven to remove the solvent; the positive electrode material on the plate is cold-pressed, slit, and pole-ear welded. Finally, the cathode material shown in Figure 2 can be obtained.
  • the positive electrode active material such as lithium cobalt oxide
  • a conductive agent such as conductive carbon black, Super-P, SP
  • a binder such as polyvinylidene fluoride
  • the negative electrode material can be obtained by combining negative electrode active materials (such as artificial graphite), thickeners (such as carboxymethyl cellulose, CMC), and binders (such as styrene-butadiene rubber). , styrene butadiene rubber, SBR), mixed in a solvent (such as deionized water) in a mass ratio of 97:1.3:1.7 to form a negative electrode slurry; through coating equipment, the negative electrode slurry is uniformly coated on the plate (such as copper foil); drying the negative electrode slurry on the plate by an oven to remove the solvent; cold pressing, slitting and tab welding the negative electrode material on the plate.
  • the negative electrode material shown in Figure 2 can be obtained.
  • the membrane can be obtained by applying a membrane coating on the surface of the membrane substrate.
  • the thickness of the separator coating may be, for example, 0.5 ⁇ m-10 ⁇ m.
  • the separator coating may include an inorganic coating (eg, a ceramic coating) and an organic coating (eg, an oil-based PVDF coating) disposed on the inorganic coating.
  • the ceramic coating is beneficial to improve the heat resistance of the separator.
  • the PVDF coating has certain bonding properties, which can improve the bonding force between the separator and the positive electrode material (or between the separator and the negative electrode material), so that the separator can be more closely bonded with the positive electrode material or the negative electrode material, thereby improving the battery cell. hardness, and improve the pass rate of the acupuncture test of the cell. If there is a bonding gap between the separator and the positive electrode material or the negative electrode material, it is not conducive to the hardness of the cell and the pass rate of the acupuncture test of the cell.
  • the separator coating may only include an organic coating or an organic/inorganic hybrid coating, that is, it may be directly coated on the surface of the separator substrate.
  • the above-mentioned positive electrode material, separator and negative electrode material are wound together to form a bare cell.
  • the storage capacity of the bare cell can reach 3.8Ah, for example, and the working voltage of the bare cell can be 3.0-4.43V.
  • the above-mentioned bare cell is packaged, baked, liquid injected, chemically formed, etc., to produce a finished lithium-ion battery.
  • the membrane provided in Example 1 may include a membrane substrate, and the membrane substrate may include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • the polyolefin composition may exclude polypropylene.
  • Antioxidants include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate.
  • the proportion of antioxidants in the separator substrate may be 0.3 wt %.
  • the separator provided in Example 1 can be obtained through the steps (1) to (5) described above.
  • step (1) includes: using a biaxial blade mixer, premixing the above-mentioned polyolefin composition and antioxidant to obtain a premix; premixing in the feeder and the twin-screw extruder Introduce nitrogen gas, and then send the premix to the twin-screw extruder through the feeder; preheat the liquid paraffin by the oil pump (the preheating temperature of the liquid paraffin is 40°C, wherein the liquid paraffin is heated at 40°C.
  • step (2) includes: setting the gel sheet in an asynchronous stretching machine to perform biaxial stretching (for the specific parameters of biaxial stretching, please refer to Table 1 below).
  • step (3) includes: extracting the stretched gel sheet with dichloromethane to remove the liquid paraffin in step (1).
  • step (4) includes: heat-setting the gel sheet after extraction (for the specific parameters of heat-setting, please refer to Table 1 below).
  • step (5) includes: continuously slitting and winding the heat-set gel sheet.
  • the membrane provided in Example 2 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • Antioxidants include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • the separator provided in Example 2 can be obtained through the above-mentioned steps (1)-step (4) and the following step (6).
  • step (1)-step (4) For the specific content of step (1)-step (4), reference may be made to the above-mentioned Embodiment 1, and details are not repeated here.
  • step (6) a membrane coating is provided on the rolled gel sheet (ie, the membrane substrate).
  • the specific content of step (6) may include: sending the diaphragm base material into a coating device, and applying a microgravure coating method to coat a heat-resistant coating on the diaphragm base material (that is, performing one coating), the heat-resistant coating
  • the coating can include Al 2 O 3 ; send the diaphragm containing the heat-resistant coating into a drying box, and use hot air to dry the diaphragm (ie, perform primary drying);
  • the surface of the heat-resistant coated diaphragm is coated with an adhesive coating (ie, secondary coating), and the adhesive coating can include oil-based PVDF; the diaphragm containing the adhesive coating is sent to a drying oven, and hot air is used for Drying (that is, performing secondary drying); placing the (secondary) dried diaphragm into a winding device for winding to obtain a finished diaphragm.
  • the membrane provided in Example 3 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 90wt% , the proportion of the second polyethylene in the polyolefin composition may be 10 wt %.
  • Antioxidants include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 2 For the manufacturing method and other specific parameters of the diaphragm provided in Example 3, reference may be made to Example 2 and Table 1, and it is unnecessary to repeat them in detail here.
  • the membrane provided in Example 4 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 95wt% , the proportion of the second polyethylene in the polyolefin composition may be 5 wt %.
  • Antioxidants include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 2 For the manufacturing method and other specific parameters of the diaphragm provided in Example 4, reference may be made to Example 2 and Table 1, and it is unnecessary to repeat them in detail here.
  • the membrane provided by Example 5 can include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition may be 100 wt %.
  • Antioxidants include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate.
  • the proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 2 For the manufacturing method and other specific parameters of the diaphragm provided in Example 5, reference may be made to Example 2 and Table 1, and it is unnecessary to repeat them in detail here.
  • the membrane provided by Example 6 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • Antioxidants include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may comprise waterborne PVDF.
  • Example 6 For the manufacturing method and other specific parameters of the diaphragm provided in Example 6, reference may be made to Example 2 and Table 1, and it is unnecessary to repeat them in detail here. It should be noted that the specific processing parameters of Example 6 may be different from those of Example 2 (for example, including the use of single-sided heat-resistant coating and the use of water-based PVDF microgravure coating, etc.).
  • the membrane provided in Example 7 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include boehmite.
  • the bond coat may comprise waterborne PVDF.
  • Example 7 For the manufacturing method and other specific parameters of the diaphragm provided in Example 7, reference may be made to Example 6 and Table 2, and it is unnecessary to repeat them in detail here.
  • the membrane provided by Example 8 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition comprises a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 , a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and a polypropylene with a thermal enthalpy ⁇ Hm of 65.
  • the proportion of the composition may be 80 wt %
  • the proportion of the second polyethylene in the polyolefin composition may be 15 wt %
  • the proportion of polypropylene in the polyolefin composition may be 5 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate.
  • the proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 2 For the manufacturing method and other specific parameters of the diaphragm provided in Example 8, reference may be made to Example 2 and Table 2, and it is unnecessary to repeat them in detail here.
  • the membrane provided by Example 9 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 9 For the manufacturing method and other specific parameters of the diaphragm provided in Example 9, reference may be made to Example 2 and Table 2, and it is unnecessary to repeat them in detail here. It should be noted that the specific processing parameters of Example 9 may be different from those of Example 2 (for example, including extrusion amount, thickness of gel sheet, stretching ratio of biaxial stretching, etc.).
  • the membrane provided by Example 10 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 10 For the manufacturing method and other specific parameters of the diaphragm provided in Example 10, reference may be made to Example 2 and Table 2, and it is unnecessary to repeat them in detail here. It should be noted that the specific processing parameters of Example 10 may be different from those of Example 2 (for example, including polymer solid content, etc.).
  • the membrane provided by Example 11 may include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a third polyethylene with a viscosity average molecular weight of 60 ⁇ 10 4 , and the proportion of the third polyethylene in the polyolefin composition may be 100 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate.
  • the proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 11 For the manufacturing method and other specific parameters of the diaphragm provided in Example 11, reference may be made to Example 2 and Table 2, and it is unnecessary to repeat them in detail here. It should be noted that the specific processing parameters of Example 11 may be different from those of Example 2 (for example, including extrusion amount, thickness of gel sheet, stretching ratio of biaxial stretching, etc.).
  • the membrane provided by Example 12 can include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 12 For the manufacturing method and other specific parameters of the diaphragm provided in Example 12, reference may be made to Example 11 and Table 2, and details are not repeated here.
  • the membrane provided by Example 13 can include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a third polyethylene with a viscosity average molecular weight of 60 ⁇ 10 4 , and the proportion of the third polyethylene in the polyolefin composition may be 100 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate.
  • the proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 13 For the manufacturing method and other specific parameters of the diaphragm provided in Example 13, reference may be made to Example 2 and Table 3, and details are not repeated here.
  • the membrane provided by Example 14 can include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 85wt% , the proportion of the second polyethylene in the polyolefin composition may be 15 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include water-based PMMA.
  • Example 14 For the manufacturing method and other specific parameters of the diaphragm provided in Example 14, reference may be made to Example 6 and Table 3, and it is unnecessary to repeat them in detail here.
  • the membrane provided by Example 15 can include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition comprises a first polyethylene with a viscosity average molecular weight of 130 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 83 wt % , the proportion of the second polyethylene in the polyolefin composition may be 17 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 15 For the manufacturing method and other specific parameters of the diaphragm provided in Example 15, reference may be made to Example 2 and Table 3, and it is unnecessary to repeat them in detail here.
  • the membrane provided by Example 16 can include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a first polyethylene with a viscosity average molecular weight of 90 ⁇ 10 4 and a second polyethylene with a viscosity average molecular weight of 25 ⁇ 10 4 , and the proportion of the first polyethylene in the polyolefin composition can be 87wt% , the proportion of the second polyethylene in the polyolefin composition may be 13 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate. The proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Membrane coatings may include heat resistant coatings and bond coats.
  • the heat resistant coating may include Al 2 O 3 .
  • the bond coat may include oil-based PVDF.
  • Example 2 For the manufacturing method and other specific parameters of the diaphragm provided in Example 16, reference may be made to Example 2 and Table 3, which need not be described in detail here.
  • the membrane provided by Example 17 can include a membrane substrate and a membrane coating.
  • the membrane substrate can include a polyolefin composition and an antioxidant.
  • the polyolefin composition includes a second polyethylene with a viscosity average molecular weight of 20 ⁇ 10 4 , and the proportion of the second polyethylene in the polyolefin composition may be 100 wt %.
  • Antioxidants may include isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate.
  • the proportion of the antioxidant in the mixture comprising the polyolefin composition and the antioxidant may be 0.3 wt%.
  • Example 17 For the manufacturing method and other specific parameters of the diaphragm provided in Example 17, reference may be made to Example 2 and Table 3, and details are not repeated here.
  • Example 14 From Examples 6-7 and Example 14, it can be seen that the coating process of the separator (such as adjusting the coating material, system and other conditions) can affect the cell performance index of the separator and improve the consistency of the separator performance.
  • Example 8 It can be seen from Example 8 that adding polypropylene to the diaphragm is beneficial to control the membrane breaking temperature of the diaphragm within a relatively appropriate range, thereby improving the thermal stability of the diaphragm.
  • Example 9 It can be seen from Example 9 and Example 10 that the processing technology of the diaphragm (such as adjusting the extrusion amount, polymer solid content, gel sheet thickness, biaxial stretching conditions, heat setting conditions) can affect the basic physical properties of the diaphragm (such as porosity, pore size, air permeability, elongation, etc.).
  • the processing technology of the diaphragm such as adjusting the extrusion amount, polymer solid content, gel sheet thickness, biaxial stretching conditions, heat setting conditions
  • the basic physical properties of the diaphragm such as porosity, pore size, air permeability, elongation, etc.
  • Example 11 It can be seen from Example 11 that only using polyethylene with a medium viscosity average molecular weight may not be able to obtain a separator with relatively high comprehensive properties.
  • Example 12 It can be seen from Example 12 that under the condition that the blending synergistic effect of polyethylene with high viscosity average molecular weight and polyethylene with low viscosity average molecular weight is good, if the processing technology of the diaphragm is not suitable, it may be difficult to obtain relatively comprehensive performance. high diaphragm.
  • Example 13 It can be seen from Example 13 that only using polyethylene with a medium viscosity average molecular weight (60 ⁇ 10 4 ) cannot obtain a separator with high elongation characteristics, and the tensile strength and modulus are relatively low.
  • Example 17 It can be seen from Example 17 that only the use of polyethylene with a low viscosity average molecular weight cannot carry out the processing and molding of the separator. Specifically, polyethylene with a low viscosity average molecular weight has a relatively large melt index, and the quality of the cast sheet obtained in the stretch casting stage is poor, so that a stable gel sheet cannot be formed in the subsequent process, and other coagulation processes cannot be carried out. glue processing.
  • a diaphragm with high elongation properties, low closed cell temperature, high film breaking temperature, and high puncture strength can be formed;
  • the membrane may have an elongation greater than 100%, even greater than 150%.
  • the membrane provided in the embodiment of the present application has a relatively high bidirectional elongation and a relatively wide closed-cell membrane rupture platform.
  • the separator has a relatively high tensile modulus, which is beneficial to the processing of the separator in the cell process (for example, it is beneficial to avoid problems such as edge protrusion, winding deviation, bending, and wrinkling caused by high elongation characteristics) .
  • the separator provided by the present application is beneficial to improve the mechanical abuse resistance and thermal abuse resistance of the battery.
  • the embodiments of the present application also provide testing methods for specific parameters.
  • the viscosity average molecular weight of polypropylene can be calculated according to the following formula:
  • the polyolefin material can be tested multiple times, and the arithmetic mean value can be calculated (calculating the arithmetic mean value is beneficial to reduce the variation caused by the measurement system).
  • the area of the sample can also be ⁇ 1.5 ⁇ 10 3 mm 2
  • the number of test points depends on the condition of the diaphragm (usually not less than 10 points).
  • Test Test by ten thousandth thickness measuring instrument under the condition of 23 ⁇ 2°C.
  • test points For products with a width less than 200mm: determine a point every 40mm ⁇ 5mm along the longitudinal (MD) direction, and the number of test points shall not be less than 10.
  • the number of test points can be determined according to the width of the diaphragm, among which, the distance between the measurement starting point and the edge is not less than 20mm;
  • test points For products with a width of ⁇ 200mm: determine a point every 80mm ⁇ 5mm along the transverse (TD) direction, and the number of test points is not less than 10.
  • the number of test points can be determined according to the width of the diaphragm, among which, the distance between the starting point of measurement and the edge is not less than 20mm.
  • Test Test each test point with a thickness measuring instrument at 23 ⁇ 2°C. The diameter of the measuring surface should be between 2.5mm and 10mm, and the load applied to the sample should be between 0.5N and 1.0 between N.
  • the overall porosity P of the sample can be calculated by the following formula:
  • m can be the mass of the sample (for example, obtained by an analytical balance)
  • skeletal density ⁇ can be the true density of the material of the sample
  • V can be the volume of the sample.
  • a. Sampling Cut out a rectangular sample with a 237 ⁇ 170mm sampler. When cutting the sample, it should be as far away as possible from the edge of the diaphragm (for example, more than 50mm from the edge of the diaphragm).
  • Test use the density method to measure the porosity, including measuring n (n may be greater than or equal to 9) points of the sample, and the n points may be distributed in an equidistant lattice.
  • Porosity P i of each point can be calculated by the following equation:
  • m i is the mass of each point, a sample of skeletal density [rho] (ratio of materials can be obtained according to the calculation), V i is the total volume of each dot (which can be obtained according to the length, width, thickness of sample is calculated );
  • the overall porosity P of the sample can be calculated by the following formula:
  • Test Test according to the method specified in the standard JIS P8117-2009. Specifically, it can include: setting the pressure of the cylinder to drive the pressure reducing valve to 0.25MPa, the test pressure to 0.05MPa, and selecting "JIS" as the test standard.
  • a. Sampling Cut out 6 square samples through a 100 ⁇ 100mm sampler. When cutting the sample, it should be as far away as possible from the edge of the diaphragm (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the membrane (ie, the full width of the membrane is evenly divided to obtain 6 zones, and 1 sample is cut from each of these 6 zones).
  • Test Test according to the method specified in the standard JIS P8117-2009. Specifically, it may include: setting the pressure of the cylinder-driven pressure reducing valve to 0.25MPa, the test pressure to 0.05MPa, and selecting "JIS" as the test standard.
  • test Fix the sample in the center on the fixture, and the test needle is a sphere with a diameter of 1mm (the material is ruby), make sure that the sample extends to or exceed the edge of the clamping plate in all directions, and confirm that the sample is completely fixed in the ring fixture. , there is no slippage.
  • the diaphragm is punctured, the speed of the machine is set at 300 ⁇ 10mm/min, until the puncture ball completely breaks the sample, and the puncture resistance is the maximum force recorded during the test.
  • a. Sampling Cut out 6 rectangular samples through a 237 ⁇ 170mm sampler. When cutting the sample, it should be as far away as possible from the edge of the diaphragm (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the membrane (ie, the full width of the membrane is evenly divided to obtain 6 zones, and 1 sample is cut from each of these 6 zones).
  • Test according to the method specified in the standard ASTMD4833-07. Specifically, it can include: the test needle is a spherical needle with a diameter of 1mm (the material is sapphire); the sample is centered and fixed on the clamp, to ensure that the sample extends to or beyond the edge of the clamping plate in all directions, and to confirm that the sample is completely fixed in the ring There is no slippage on the fixture; during the test, the speed of the machine is set to 300 ⁇ 10mm/min, and the diaphragm is punctured until the test needle completely breaks the sample; the puncture resistance is the maximum force recorded during the test.
  • a. Sampling On the overall width sample, cut the diaphragm according to the MD and TD directions, respectively, to obtain a plurality of long strip samples with a length of ⁇ 50mm and a width of about 15 ⁇ 0.1mm (for the MD test, the sample The width of the sample can be along the TD direction of the separator, and the length of the sample can be along the MD direction of the separator; for TD testing, the width of the sample can be along the MD direction of the separator, and the length of the sample can be along the TD direction of the separator).
  • the clamp spacing can be 100 ⁇ 5mm, until the sample is pulled off, and the stretching speed can be 100 ⁇ 1mm/min.
  • a. Sampling Cut out 6 rectangular samples through a 237 ⁇ 170mm sampler. When cutting the sample, it should be as far away as possible from the edge of the diaphragm (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the diaphragm (that is, along the MD and TD directions of the diaphragm, the entire width of the film is separated to obtain 6 areas, and one sample is cut from each of these 6 areas). After that, the sampler was used to cut long strip samples with a length of ⁇ 150mm and a width of 15 ⁇ 0.1mm.
  • Test measure according to the method specified in GB/T1040.3-2006. Specifically, the distance between the clamps can be 100 ⁇ 5mm, and the stretching speed can be 100 ⁇ 1mm/min.
  • a. Sampling On the overall width sample, cut the diaphragm according to the MD and TD directions, respectively, to obtain a plurality of long strip samples with a length of ⁇ 50mm and a width of about 15 ⁇ 0.1mm (for the MD test, the sample The width of the sample can be along the TD direction of the separator, and the length of the sample can be along the MD direction of the separator; for TD testing, the width of the sample can be along the MD direction of the separator, and the length of the sample can be along the TD direction of the separator).
  • the clamp spacing can be 100 ⁇ 5mm
  • the stretching speed can be 25 ⁇ 1mm/min
  • the starting point strain can be set to 0.05%
  • the ending point strain can be set to 0.5%.
  • the tensile modulus can be calculated by the regression slope method, and the value of the tensile modulus can be equal to the least square regression linear fitting of the stress-strain curve in the strain range of 0.05%-0.25% The slope of , in Mpa (refer to GB/T 1040.1-2018).
  • a. Sampling Cut out 6 rectangular samples through a 237 ⁇ 170mm sampler. When cutting the sample, it should be as far away as possible from the edge of the diaphragm (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the diaphragm (that is, along the MD and TD directions of the diaphragm, the entire width of the film is separated to obtain 6 areas, and one sample is cut from each of these 6 areas). After that, the sampler was used to cut long strip samples with a length of ⁇ 150mm and a width of 15 ⁇ 0.1mm.
  • the clamp spacing can be 100 ⁇ 5mm
  • the stretching speed can be 25 ⁇ 1mm/min
  • the starting point strain can be set to 0.05%
  • the ending point strain can be set to 0.5%.
  • the tensile modulus can be calculated by the regression slope method, and the value of the tensile modulus can be equal to the least square regression linear fitting of the stress-strain curve in the strain range of 0.05%-0.25% The slope of , in Mpa (refer to GB/T 1040.1-2018).
  • Sampling Take a circular sample with a diameter of 15mm with the corresponding tool, and then use tweezers to soak the sample in a glass dish containing the test solution.
  • Test use the bubble point method to test. Put the sample into the sample cover and test according to the standard ASTM F316-2011, according to the operating procedure of the pore size analyzer. Compressed air can be used at low pressure, and the pressure can be 80 psi; low-purity nitrogen can be used at high pressure, and the pressure can be ⁇ 350 psi.
  • Figure 3 shows an exploded view of the fixture in a test device for closed-cell temperature and film-breaking temperature.
  • the test device may include a test fixture, a locking device, and a measurement assembly.
  • the test fixture may include a lock nut 301 , lead-out pins 302 , spacers 303 and lead-out wires 304 .
  • the insulating block 308 and the insulating block 320 are disposed opposite to each other, and the insulating block 308 and the insulating block 320 are connected by a locking device.
  • the locking device may include a leaflet 314 and a locking screw 312 .
  • the loose leaf 314 is connected to one end of the insulating block 308 and the insulating block 320
  • the locking screw 312 is connected to the other end of the insulating block 308 and the insulating block 320 .
  • the measurement assembly may include measurement electrodes 309 and measurement electrodes 319 .
  • the measurement electrode 309 and the measurement electrode 319 may be disposed between the insulating block 308 and the insulating block 320 .
  • the measuring electrode 309 is fixed on the fixing block 306 through the insulating block 308 .
  • the measuring electrode 319 is fixed on the fixing block 322 through the insulating block 320 .
  • the measurement electrode 309 and the measurement electrode 319 are disposed opposite to each other, and a temperature probe 327 is connected to the measurement electrode 309 and the measurement electrode 319 respectively.
  • FIG 4 shows another test device for closed cell temperature and film breaking temperature.
  • the testing device includes a temperature control device 331 , an internal resistance measurement device 330 , a control device 328 and a fixture 332 .
  • the temperature control device 331 is used to heat the jig 332 .
  • the internal resistance measuring device 330 is electrically connected between the measuring electrode 309 and the measuring electrode 319 for monitoring the internal resistance between the measuring electrode 309 and the measuring electrode 319 .
  • the control device 328 is used to record temperature and internal resistance data.
  • Fixing clamp the diaphragm to be measured between the measuring electrode 309 and the measuring electrode 319, drop the electrolyte solution, and then lock the insulating block 308 and the insulating block 320 tightly.
  • Test The fixture 332 is heated by the temperature control device 331, and the internal resistance between the measurement electrode 309 and the measurement electrode 319 is measured by the internal resistance measurement device 330; the control device 328 can record temperature data and internal resistance data.
  • the heating rate of the temperature control device is controlled at ⁇ 5°C, the test temperature range is raised from room temperature to 200°C, and the internal resistance test is performed with a 1000Hz AC internal resistance meter.
  • the initial resistance value is less than or equal to 10 ⁇
  • the temperature at which the internal resistance value of the microporous film rises to 100 ⁇ for the first time is defined as the closed cell temperature
  • the temperature when the internal resistance value reaches the closed cell resistance value for the second time is defined as the film breaking temperature
  • the initial resistance value at which the internal resistance value of the microporous film rises to 10 times the initial resistance value for the first time is defined as the closed cell temperature
  • the temperature when the internal resistance value reaches the closed cell resistance value for the second time is defined as is the membrane breaking temperature.
  • Sampling 6 samples are randomly cut from the full width.
  • the specific sampling of each sample can include: cutting 100mm along the MD direction of the diaphragm; when the TD direction of the diaphragm is greater than 100mm, the length of the test sample in the TD direction can be 100mm; when the TD direction of the microporous membrane is less than 100mm , the length of the test sample in the TD direction can be subject to the actual.
  • Test mark the vertical and horizontal marks of the sample, measure and record the vertical and horizontal dimensions of each sample; heat the electric thermostat to 130°C; place the sample flat in the paper jacket layer, the sample is not folded, Wrinkling, adhesion, etc.; put the paper sleeve with the sample (for example, the number of layers can be 10 layers) into the middle of the constant temperature oven (for example, the door opening time does not exceed 3s); heat the sample to 130 through the electric heating constant temperature box °C, the heating time is 1h; after taking out the sample, it is cooled to room temperature, and the longitudinal and transverse lengths are measured.
  • T can be the thermal shrinkage rate (%) of the sample
  • L 0 can be the length (mm) of the sample before heating
  • L can be the length (mm) of the sample after heating.
  • Test use a differential scanning calorimeter (DSC) and conduct the test under N 2 atmosphere. The temperature is raised to within 30°C above the melting point of the polyolefin for the first time at 10°C/min, and the temperature is kept for 3 minutes to obtain the polyolefin. The crystallinity is heated up once, then cooled to ⁇ 40°C at 10°C/min and kept for 3 minutes, and then heated for the second time at 10°C/min to within 30°C above the melting point of the polyolefin to obtain the crystallinity of the polyolefin after the second temperature rise, And read the melting point temperature directly.
  • DSC differential scanning calorimeter
  • Crystallinity X (%) mass-normalized melting enthalpy of the sample ( ⁇ H s )/melting enthalpy of 100% crystalline polyethylene ( ⁇ H f ) ⁇ 100%,
  • the embodiment of the present application provides a separator applied to a battery, and the separator has the characteristics in any of the above embodiments.
  • the embodiment of the present application provides a battery, the battery has the characteristics in any of the above-mentioned embodiments.
  • An embodiment of the present application also provides an electronic device, the electronic device includes the above-mentioned battery.
  • the electronic device may be a mobile phone, a tablet, or the like.
  • An embodiment of the present application further provides a mobile device, where the mobile device includes the above-mentioned battery.
  • the mobile device may be a car or the like.
  • At least one means one or more, and “plurality” means two or more.
  • At least one item(s) below” or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s).
  • at least one (a) of a, b, or c or, “at least one (a) of a, b, and c” can mean: a, b, c, ab( That is, a and b), ac, bc, or abc, where a, b, and c may be single or multiple, respectively.
  • first, second, third, etc. may be used in the embodiments of the present application to describe various messages, requests and terminals, these messages, requests and terminals should not be limited to these terms. These terms are only used to distinguish messages, requests and terminals from one another.
  • the first terminal may also be referred to as the second terminal, and similarly, the second terminal may also be referred to as the first terminal.
  • the words “if” or “if” as used herein may be interpreted as “at” or “when” or “in response to determining” or “in response to detecting.”
  • the phrases “if determined” or “if detected (the stated condition or event)” can be interpreted as “when determined” or “in response to determining” or “when detected (the stated condition or event),” depending on the context )” or “in response to detection (a stated condition or event)”.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Cell Separators (AREA)

Abstract

La présente invention concerne un séparateur et son procédé de fabrication, ainsi qu'une batterie, un dispositif électronique et un dispositif mobile. Le séparateur comprend un substrat de séparateur contenant une composition de polyoléfine, la composition de polyoléfine comprenant une variété de polyéthylènes ayant différents poids moléculaires moyens en viscosité. Le séparateur a une épaisseur comprise entre 0,5 et 12 µm, un allongement bidirectionnel supérieur ou égal à 130 %, une température d'élément fermé inférieure ou égale à 142 °C et une température de rupture de séparateur supérieure ou égale à 150 °C. En régulant les propriétés mécaniques du séparateur, en réduisant la température de l'élément fermé du séparateur, etc. la sécurité de l'élément de batterie peut être améliorée.
PCT/CN2021/103351 2020-07-01 2021-06-30 Séparateur et son procédé de fabrication, batterie, dispositif électronique et dispositif mobile Ceased WO2022002094A1 (fr)

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CN202010922459.2 2020-09-04
CN202010922459.2A CN113964448B (zh) 2020-07-01 2020-09-04 隔膜及其制造方法、电池、电子设备、移动装置

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CN115636993A (zh) * 2021-07-20 2023-01-24 华为技术有限公司 聚烯烃粉末、挤出成型材料，隔膜，电池、电子设备及移动装置
CN116169434A (zh) * 2023-04-23 2023-05-26 宁德新能源科技有限公司 一种隔膜、电化学装置及电子装置
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CN115636993A (zh) * 2021-07-20 2023-01-24 华为技术有限公司 聚烯烃粉末、挤出成型材料，隔膜，电池、电子设备及移动装置
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WO2025130380A1 (fr) * 2023-12-19 2025-06-26 宁德新能源科技有限公司 Batterie secondaire et appareil électronique

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