WO2023115898A1 - 一种电池隔离膜及其制备方法和二次电池 - Google Patents

一种电池隔离膜及其制备方法和二次电池 Download PDF

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WO2023115898A1
WO2023115898A1 PCT/CN2022/103158 CN2022103158W WO2023115898A1 WO 2023115898 A1 WO2023115898 A1 WO 2023115898A1 CN 2022103158 W CN2022103158 W CN 2022103158W WO 2023115898 A1 WO2023115898 A1 WO 2023115898A1
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Prior art keywords
battery separator
conductive particles
heat
battery
coating
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PCT/CN2022/103158
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English (en)
French (fr)
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白麟
王连广
刘淑真
高飞飞
汤晓
秦文娟
张绪杰
刘杲珺
白耀宗
郑蕾
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中材锂膜有限公司
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Publication of WO2023115898A1 publication Critical patent/WO2023115898A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • 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
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • 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 disclosure relates to the technical field of batteries, in particular to a battery separator, a preparation method thereof, and a secondary battery.
  • the secondary battery is mainly composed of four parts, namely the positive electrode, the electrolyte, the separator, and the negative electrode.
  • the main function of the separator is to separate the positive and negative electrodes and prevent the direct contact between the positive and negative electrodes to cause a short circuit.
  • the through-hole structure in the separator can play the role of allowing the positive and negative ions to pass through.
  • the performance of the separator It will directly affect important performances such as battery equipment yield, capacity, internal resistance and cycle.
  • the traditional inorganic filler coating can maintain a certain shape at high temperature, the hardness of the inorganic material is high, and it is easy to scratch the substrate during the coating process, resulting in a high short circuit rate during the battery assembly process; polymer polymerization
  • the material has a high melting point, but it is coated on the surface of the substrate as a coating, which is loosely bonded to the substrate, and the heat resistance is reduced, causing a short circuit of the battery and causing a safety accident.
  • the purpose of the present disclosure is to provide a battery separator, a preparation method thereof, and a secondary battery. Solve the problems of poor coating uniformity, poor heat resistance, high short-circuit rate during battery equipment, diaphragm soaked in electrolyte, and electrical performance attenuation in the later stage of the cycle. Select non-conductive particles with specific requirements to make a uniform porous coating layer, high temperature resistance and excellent electrochemical stability, greatly improving the assembly yield, electrical performance and safety performance of the battery.
  • the secondary battery prepared from the separator has excellent electrical properties and high safety.
  • the first aspect of the present disclosure provides a battery separator, the battery separator includes:
  • a substrate having a porous structure and a heat-resistant polymer coating applied to at least one side of the substrate;
  • the heat-resistant polymer coating includes a heat-resistant resin and non-conductive particles
  • the particle diameter D97 of the non-conductive particles ⁇ thickness of the heat-resistant polymer coating is the particle diameter D97 of the non-conductive particles ⁇ thickness of the heat-resistant polymer coating
  • the particle size distribution of the non-conductive particles satisfies: 0.5 ⁇ (D90-D10)/D50 ⁇ 3.0;
  • the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 0 ⁇ S/D50 ⁇ 5 ⁇ 10 7 m/g.
  • the particle size D97 of the non-conductive particles is 0.5-1.5 ⁇ m, and the thickness of the heat-resistant polymer coating is 1.5-6 ⁇ m;
  • the particle size distribution of the non-conductive particles satisfies: 0.8 ⁇ (D90-D10)/D50 ⁇ 2.8;
  • the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 2 ⁇ 10 7 m/g ⁇ S/D50 ⁇ 4 ⁇ 10 7 m/g.
  • the peel strength of the battery separator is above 10 N/m, and after the battery separator is placed in an environment of 130° C. for 1 hour, its shrinkage rate in both the longitudinal direction and the transverse direction is less than 15%, and The ratio of the shrinkage rate in the longitudinal direction to the transverse direction is greater than 1.
  • the battery separator is soaked in the electrolyte at 25°C. After 60 days, the acupuncture strength retention rate is above 60%. The rate is above 40%.
  • the peel strength of the battery separator film is above 50 N/m; after the battery separator film is placed in an environment of 130°C for 1 hour, its longitudinal shrinkage rate is 0-5%, and its transverse shrinkage rate is 0-5%. 0-5%, and the ratio of longitudinal shrinkage to transverse shrinkage is greater than 1; the battery separator is soaked in electrolyte at 25°C, and after 60 days, the acupuncture strength retention rate is 70-100%, and after 500 cycles of the equipped battery, The needle-punched strength retention rate of the diaphragm is 50-100%.
  • the peel strength of the battery separator is 50-80 N/m; after the battery separator is placed in an environment of 130°C for 1 hour, its longitudinal shrinkage rate is 1.2-2.1%, and its transverse shrinkage rate is 1.2-2.1%. 0.8 to 1.2%; the battery separator is soaked in electrolyte at 25°C, and after 60 days, the acupuncture strength retention rate is 92% to 96%. %.
  • the present disclosure also provides a battery separator, the peel strength of the battery separator is above 10N/m, and the shrinkage rate of the battery separator in the longitudinal and transverse directions after the battery separator is placed in an environment of 130°C for 1 hour All below 15%, and the ratio of the shrinkage rate in the longitudinal direction to the transverse direction is greater than 1.
  • the battery separator is soaked in the electrolyte at 25°C. After 60 days, the acupuncture strength retention rate is above 60%, and the battery is equipped with a cycle of 500 cycles. After that, the needle punch strength retention rate of the diaphragm was above 40%.
  • the battery separator includes: a substrate having a porous structure and a heat-resistant polymer coating coated on at least one side of the substrate;
  • the heat-resistant polymer coating includes a heat-resistant resin and non-conductive particles
  • the particle diameter D97 of the non-conductive particles ⁇ thickness of the heat-resistant polymer coating is the particle diameter D97 of the non-conductive particles ⁇ thickness of the heat-resistant polymer coating
  • the particle size distribution of the non-conductive particles satisfies: 0.5 ⁇ (D90-D10)/D50 ⁇ 3.0;
  • the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 0 ⁇ S/D50 ⁇ 5 ⁇ 10 7 m/g.
  • the peel strength of the battery separator film is above 50 N/m; after the battery separator film is placed in an environment of 130°C for 1 hour, its longitudinal shrinkage rate is 0-5%, and its transverse shrinkage rate is 0-5%. 0-5%, and the ratio of longitudinal shrinkage to transverse shrinkage is greater than 1; the battery separator is soaked in electrolyte at 25°C, and after 60 days, the acupuncture strength retention rate is 70-100%, and after 500 cycles of the equipped battery, The needle-punched strength retention rate of the diaphragm is 50-100%.
  • the peel strength of the battery separator is 50-80 N/m; after the battery separator is placed in an environment of 130°C for 1 hour, its longitudinal shrinkage rate is 1.2-2.1%, and its transverse shrinkage rate is 1.2-2.1%. 0.8 to 1.2%; the battery separator is soaked in electrolyte at 25°C, and after 60 days, the acupuncture strength retention rate is 92% to 96%. %.
  • the particle size D97 of the non-conductive particles is 0.5-1.5 ⁇ m, and the thickness of the heat-resistant polymer coating is 1.5-6 ⁇ m;
  • the particle size distribution of the non-conductive particles satisfies: 0.8 ⁇ (D90-D10)/D50 ⁇ 2.8;
  • the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 2 ⁇ 10 7 m/g ⁇ S/D50 ⁇ 4 ⁇ 10 7 m/g.
  • the particle size D97 of the non-conductive particles is 0.7-1.5 ⁇ m, and the thickness of the heat-resistant polymer coating is 3-3.2 ⁇ m;
  • the particle size distribution of the non-conductive particles satisfies: 0.8 ⁇ (D90-D10)/D50 ⁇ 2.6;
  • the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 3 ⁇ 10 7 m/g ⁇ S/D50 ⁇ 4 ⁇ 10 7 m/g.
  • the substrates include polyolefin substrates, non-woven fabric substrates and substrates prepared by coating inorganic particles or polymer functional coatings thereon.
  • the thickness of the substrate is 1-30 ⁇ m, preferably 5-20 ⁇ m; the porosity of the substrate is 10-70%, preferably 20-60%; the heat-resistant polymer coating The thickness is 1.5-10 ⁇ m.
  • the heat-resistant resin is selected from nitrogen-containing aromatic polymers, polyimide polyamides, polyamideimides, polyimides, polyetherimides, polyvinylidene fluoride, polyvinylidene fluoride One or more of ethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, polysulfone, polyketone, polyetherketone, polycarbonate, and polyoxymethylene;
  • the nitrogen-containing aromatic polymer includes aromatic polyamide, Aromatic polyimides, aromatic polyamideimides, preferably aromatic polyamides, particularly preferably para-aromatic polyamides;
  • the para-aramid has an intrinsic viscosity of 1.2-6.5 g/l, preferably 2-6 g/l, more preferably 3-5 g/l;
  • the viscosity-average molecular weight of the para-aramid is 10,000-100,000, preferably 20,000-80,000.
  • the non-conductive particles include silica, alumina, magnesia, zirconia, titania, calcia, boehmite, magnesium hydroxide, aluminum nitride, boron nitride, barium sulfate, fluoride One or more of calcium and barium fluoride; preferably aluminum oxide, boehmite, magnesium oxide, silicon dioxide, particularly preferably aluminum oxide;
  • the shape of the non-conductive particles includes plate, rod, scale, needle, column, sphere, block, polyhedron, preferably plate, polyhedron, column, and rod;
  • the non-conductive particles may also contain particles capable of transferring lithium ions, including one of lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium nitride, lithium carbonate, lithium chloride, lithium sulfide, and lithium hexafluorophosphate or several.
  • the second aspect of the present disclosure provides a method for preparing a battery separator according to the first aspect of the present disclosure, comprising the following steps:
  • step (3) using the slurry prepared in step (2) to coat at least one side of the substrate to obtain a coating film;
  • step (4) washing the coating film obtained in step (4) with water, and drying to obtain a battery separator.
  • the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and tetramethylurea .
  • coating includes coating method or dipping method; coating method includes doctor blade method, dipping method, reverse roll method, direct roll method, micro gravure roll method, extrusion method, preferably micro gravure Roller method, scraper method;
  • the drying methods include hot air, low humidity air, vacuum drying, spray drying, and freeze drying.
  • the third aspect of the present disclosure provides a secondary battery, including the battery separator described in the first aspect of the present disclosure.
  • the invention makes the thickness and pore diameter of the porous polymer coating uniform by screening the particle size and distribution of the non-conductive particles, the ratio of the specific surface area to the average particle size, and improves the assembly yield of the secondary battery and the cycle performance of the secondary battery , enhance the force between the particles and the stability of the slurry.
  • the diaphragm can better build a three-dimensional skeleton structure, inhibit the shrinkage of the diaphragm at high temperature, and the excellent potential energy between the particles can significantly improve the liquid absorption and storage of the diaphragm. Liquid capacity, thereby improving the battery cycle performance and needle strength retention rate.
  • the peel strength of the separator obtained by the present invention is more than 10N/m, especially more than 50N/m, such as 50-80N/m; after the separator is placed in an environment of 130°C for 1 hour, its shrinkage in the longitudinal and transverse directions Both are below 15%, and the ratio of shrinkage in the longitudinal direction to the transverse direction is greater than 1, especially the shrinkage rate in the longitudinal direction is 0-5%, such as 1.2-2.1%, and the shrinkage rate in the transverse direction is 0-5%, such as 0.8-1.2 %; when the separator is soaked in the electrolyte at 25°C, the acupuncture strength retention rate after 60 days is 60%, especially 70% to 100%, such as 92 to 96%. The rate is above 40%, especially 50-100%, such as 85-95%.
  • FIG. 1 is an electron microscope image of a battery separator prepared in Example 1 of the present invention.
  • the first aspect of the present disclosure provides a battery separator, comprising a substrate with a porous structure and a heat-resistant polymer coating coated on at least one side of the substrate, the heat-resistant polymer coating includes a heat-resistant non-conductive resin and non-conductive particles;
  • the particle size D97 of the non-conductive particles ⁇ thickness of the heat-resistant polymer coating is the particle size D97 of the non-conductive particles ⁇ thickness of the heat-resistant polymer coating
  • the particle size distribution of non-conductive particles satisfies: 0.5 ⁇ (D90-D10)/D50 ⁇ 3.0;
  • the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 0 ⁇ S/D50 ⁇ 5 ⁇ 10 7 m/g.
  • the substrate can be any material known in the art that can be used as a membrane substrate, such as a polyolefin porous membrane, a non-woven membrane, an electrospun membrane, and inorganic particles coated on the above membrane or Separator prepared by polymer functional coating.
  • the material of polyolefin porous diaphragm can be polyethylene (PE) or polypropylene (PP), it can be a single-layer PE layer or PP layer structure, or it can be a composite multi-layer structure of polyethylene (PE) and polypropylene (PP), From the viewpoint of film-forming properties, polyethylene and its copolymers are preferred, and polyethylene can be obtained by one-step polymerization or multi-step polymerization.
  • the molecular weight (viscosity-average molecular weight) of the polyethylene can be 50-4 million, for example, the viscosity-average molecular weight of the polyethylene is 500,000, 550,000, 600,000...1 million, 2 million, 3 million, 4 million, According to a specific embodiment of the present disclosure, the polyethylene has a viscosity-average molecular weight of 600,000-3 million, particularly preferably 800,000-3 million; the particle size of the polyethylene is ⁇ 100 ⁇ m.
  • the inorganic particles may be selected from silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), magnesium oxide (MgO), zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), calcium oxide (CaO), etc.
  • Oxide particles hydroxides such as boehmite (AlOOH) and magnesium hydroxide (Mg(OH) 2 ), nitride particles such as aluminum nitride (AlN) and boron nitride (BN), and barium sulfate (BaSO 4 ), calcium fluoride (CaF 2 ), barium fluoride (BaF 2 ) and other insoluble ionic crystal particles.
  • the polymer functional coating material can be selected from one or more of PMMA or PVDF.
  • the thickness of the substrate can be 1-30 ⁇ m, such as 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m...29 ⁇ m, 30 ⁇ m. According to a specific embodiment of the present disclosure, the thickness of the substrate is 5-20 ⁇ m.
  • the porosity of the substrate may be 10-70%, such as 10%, 12%, 15%...69%, 70%. According to a specific embodiment of the present disclosure, the porosity of the substrate is between 20-70%. 60%.
  • Heat-resistant polymer coatings include heat-resistant resins and non-conductive particles.
  • the heat-resistant resin material may be selected from nitrogen-containing aromatic polymers, polyimide polyamides, polyamideimides, polyimides, polyetherimides, polyvinylidene fluoride, polyvinylidene fluoride Ethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, polysulfone, polyketone, polyether ketone, polycarbonate, polyoxymethylene; nitrogen-containing aromatic polymers include aromatic polyamide, aromatic polyamide Imine, aromatic polyamideimide, etc. are preferably resins composed of aromatic polyamides, and para-type aromatic polyamides excellent in physical properties, heat resistance, and low thermal shrinkage properties are particularly preferable.
  • the intrinsic viscosity of the para-position aromatic polyamide can be 1.2-6.5g/l, such as 1.2g/l, 1.3g/l...6.4g/l, 6.5g/l, according to a specific implementation of the present disclosure
  • the intrinsic viscosity of the para-aramid is 2-6 g/l, more preferably 3-5 g/l.
  • the molecular weight (viscosity average molecular weight) of the para-position aromatic polyamide can be 10000-100000, such as 10000, 10100...99999, 100000. According to a specific embodiment of the present disclosure, the para-position aromatic polyamide The molecular weight is 20,000-80,000. It should be noted that the molecular weight is calculated according to the Maglis formula after measuring the intrinsic viscosity value with an Ubbelohde viscometer.
  • the non-conductive particles may include, but are not limited to, silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), magnesium oxide (MgO), zirconium oxide (ZrO 2 ), titanium oxide ( Oxide particles such as TiO 2 ) and calcium oxide (CaO), hydroxides such as boehmite (AlOOH) and magnesium hydroxide (Mg(OH) 2 ), aluminum nitride (AlN), boron nitride (BN), etc.
  • Nitride particles and one or more of barium sulfate (BaSO 4 ), calcium fluoride (CaF 2 ), barium fluoride (BaF 2 ) and other insoluble ion crystal particles.
  • the non-conductive particles may be selected from one of the above, or two or more of the above in any proportion. Among these particles, oxide particles are preferable in view of stability and potential in the electrolytic solution.
  • non-conductive particles need to have high thermal decomposition temperature (decomposition temperature higher than 200°C), low water absorption, preferably alumina, boehmite, magnesia, silica, especially alumina.
  • the shape of non-conductive particles is not particularly limited, such as plate, rod, scale, needle, column, sphere, block, polyhedron, etc., and a variety of particles having the above shapes can also be used in combination.
  • Inorganic filler From the viewpoint of improving permeability, plate-like, polyhedral, columnar, and rod-like shapes including a plurality of surfaces are preferable.
  • the non-conductive particles can also contain particles with lithium ion transfer ability, thereby improving the conductivity of lithium ions.
  • the particles with lithium ion transfer can be selected from any one of the following inorganic particles or a mixture of at least two inorganic particles: phosphoric acid Lithium (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 3), lithium aluminum titanium phosphate, lithium nitride, lithium carbonate, chlorine Lithium chloride, lithium sulfide, lithium hexafluorophosphate.
  • the non-conductive particles have the following requirements:
  • the particle size of non-conductive particles is D97 ⁇ a, where D97 means that particles with a particle size smaller than D97 account for 97% of the total, and those larger than D97 account for 3%; a means that the heat-resistant polymer coating of the battery separator thickness.
  • the particle size D97 of the non-conductive particles is 0.5-1.5 ⁇ m, especially 0.7-1.5 ⁇ m, and the thickness of the heat-resistant polymer coating is 1.5-6 ⁇ m, especially 3-3.2 ⁇ m.
  • the thickness and pore size of the porous polymer coating are uniform, thereby improving the assembly yield of the secondary battery and the cycle performance of the secondary battery.
  • the particle size of the non-conductive particles satisfies the above range, the formed slurry is not easy to settle, so that a uniform pore structure and particle distribution are formed during the coating process; when the particle size D97 of the non-conductive particles is larger than that of the heat-resistant polymer coating Thickness, the formed slurry is easy to settle, resulting in poor thickness consistency, and the D97 is too large, which affects the tightness of the aramid fiber film to the substrate, resulting in poor peel strength of the aramid fiber separator.
  • the particle size distribution of the non-conductive particles satisfies 0.5 ⁇ (D90-D10)/D50 ⁇ 3.0, such as 0.6, 0.8, 1.0, 1.2, 1.5, 1.6, 1.8, 2.0, 2.5, 3.0. According to a specific embodiment of the present disclosure, the particle size distribution of the non-conductive particles satisfies 0.8 ⁇ (D90-D10)/D50 ⁇ 2.8, especially 0.8 ⁇ (D90-D10)/D50 ⁇ 2.6.
  • the particle size distribution of non-conductive particles is within this range, the van der Waals force between particles is enhanced, and the formed slurry has good uniformity, strong stability and is not easy to settle; during the coating process, non-conductive particles are evenly distributed in the coating, The thickness of the formed coating has good consistency.
  • the three-dimensional skeleton formed by the non-conductive particles can inhibit the shrinkage of the diaphragm at high temperature, and during the coating and baking process, the non-conductive particles can be closely attached to the surface of the substrate, forming Dense micropores and channels, which are conducive to the transportation of Li + during charge and discharge and the storage of electrolyte, thereby improving the cycle and needle strength retention of the battery.
  • the distribution of non-conductive particles is greater than 3, the morphology difference between particles is large, resulting in poor thickness uniformity of the coating, and affecting the pore-forming effect, resulting in different lithium ion migration rates during the battery cycle, thereby affecting the battery cycle performance.
  • the particle size distribution of non-conductive particles is less than 0.5, the particle size difference between particles is small, and secondary agglomeration between particles is easy to form, which increases the difficulty and cost of slurry making.
  • the ratio of the specific surface area of non-conductive particles to the average particle diameter D50 satisfies 0 ⁇ S/D50 ⁇ 5 ⁇ 10 7 m/g, such as 0.1 ⁇ 10 7 , 0.5 ⁇ 10 7 , 1 ⁇ 10 7 , 1.5 ⁇ 10 7 , 2 ⁇ 10 7 , 2.5 ⁇ 10 7 , 3 ⁇ 10 7 , 3.5 ⁇ 10 7 , 4 ⁇ 10 7 , 4.5 ⁇ 10 7 , 5 ⁇ 10 7 m/g.
  • the ratio of the specific surface area of the non-conductive particles to the average particle diameter D50 satisfies 2 ⁇ 10 7 m/g ⁇ S/D50 ⁇ 4 ⁇ 10 7 m/g, especially 3 ⁇ 10 7 m /g ⁇ S/D50 ⁇ 4 ⁇ 10 7 m/g.
  • Non-conductive particles have excellent surface action potential, which can better build a three-dimensional skeleton structure and inhibit the diaphragm at high temperature. Shrinkage, and the excellent interaction potential energy between particles significantly improves the liquid absorption and wetting ability of the separator, thereby improving the cycle performance of the battery.
  • the non-conductive particles meet the above range.
  • the non-conductive particles have excellent surface potential, which can improve the ability of the coating to store the electrolyte. Maintain high mechanical properties, reduce the chance of insolubles produced by side reactions piercing the separator, thereby reducing battery self-discharge and improving battery life.
  • the non-conductive particles absorb too much water during the coating process, react with the electrolyte lithium hexafluorophosphate, and release gas, resulting in a decrease in battery voltage and capacity.
  • the present invention selects non-conductive particles that meet the requirements of the above three conditions, and the coating thickness and pore diameter of the porous polymer are uniform, which improves the assembly yield of the secondary battery and the cycle performance of the secondary battery, and strengthens the interaction between the particles and the cyclic performance of the secondary battery.
  • the stability of the slurry, after coating, can better build a three-dimensional skeleton structure, inhibit the shrinkage of the diaphragm at high temperature, and the excellent interaction potential energy between the particles can significantly improve the liquid absorption and storage capacity of the diaphragm, thereby improving the cycle performance of the battery and acupuncture strength retention.
  • the peel strength of the obtained battery separator is above 10N/m, for example, the peel strength is 10N/m, 11N/m...79N/m, 80N/m...; and the separator is placed at 130°C
  • its shrinkage in the longitudinal direction (MD) and transverse direction (TD) is below 15%, and the ratio of the shrinkage in the longitudinal direction (MD) to the transverse direction (TD) is greater than 1, such as MD shrinkage 1%, 2%...14%, 15%, TD shrinkage rate 1%, 2%...14%, 15%
  • the retention rate is above 60%, for example, the acupuncture strength retention rate is 70%, 80%, ...
  • the retention rate of the separator’s acupuncture strength is above 40%, such as the 500 cycles of the equipped battery After one week, the acupuncture strength retention rate of the septum was 45%, 55%, ... 90%, 95%.
  • the peel strength of the battery separator is more than 50 N/m; after the battery separator is placed in an environment of 130°C for 1 hour, its longitudinal shrinkage rate is 0-5%, The transverse shrinkage rate is 0-5%, and the ratio of the longitudinal shrinkage rate to the transverse shrinkage rate is greater than 1; the battery separator is soaked in electrolyte at 25°C, and the acupuncture strength retention rate is 70-100% after 60 days, and the battery cycle is equipped with After 500 weeks, the needle-punched strength retention rate of the diaphragm was 50-100%.
  • the peel strength of the battery separator film is 50-80 N/m; after the battery separator film is placed in an environment of 130° C. for 1 hour, its longitudinal shrinkage rate is 1.2-2.1%, The lateral shrinkage rate is 0.8-1.2%.
  • the battery separator is soaked in the electrolyte at 25°C. After 60 days, the acupuncture strength retention rate is 92-96%. After 500 cycles of the equipped battery, the separator acupuncture strength retention rate is 85-95%.
  • Thermal shrinkage rate in TD direction (%) (length in TD direction before heating ⁇ length in TD direction after heating)/length in MD direction before heating ⁇ 100.
  • the puncture strength is tested according to the requirements of ASTM D4833-00e1.
  • ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were formulated into organic solvents in a mass ratio of 1:1:1, and Put the bulk diaphragm to be tested in the prepared organic solvent, soak for 60 days at 25°C, take out the bulk diaphragm, put it in a fume hood to dry naturally, measure the acupuncture strength once at intervals of 2 cm, and measure it five times
  • the average value of the results is recorded as the acupuncture strength c 1 after soaking in the electrolyte, and the retention rate of the acupuncture strength is: c 1 /c 0 .
  • the puncture strength is tested according to the requirements of ASTM D4833-00e1.
  • the acupuncture strength d 0 before assembling the battery, equip the battery with the coated separator (the positive electrode material of the battery is lithium iron phosphate, the negative electrode material is graphite, and the electrolyte solute is lithium hexafluorophosphate), and the battery is continuously charged and discharged , when the battery has cycled to 500 cycles, disassemble the battery again, take out the diaphragm, and put it in a fume hood to dry naturally.
  • the needling strength d 1 of the needling strength retention rate is: d 1 /d 0 .
  • the second aspect of the present disclosure provides a method for preparing a battery separator according to the first aspect of the present disclosure, the method comprising the following steps:
  • step (3) using the slurry prepared in step (2) to coat at least one side of the substrate to obtain a coating film;
  • step (4) washing the coating film obtained in step (4) with water, and drying to obtain a battery separator.
  • the preparation method of the base material is not particularly limited, and dry uniaxial stretching, bidirectional synchronous or asynchronous stretching, and wet biaxial synchronous or asynchronous stretching can be used, and wet biaxial synchronous stretching is preferably used for preparation.
  • the organic solvents include N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), tetramethylurea (TMU ) at least one of.
  • the coating method of the slurry there is no fixed limitation on the coating method of the slurry, and methods such as coating method and dipping method can be selected for coating.
  • the coating method include methods such as a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a micro gravure roll method, an extrusion method, a spray method, and a spot coating method.
  • the micro-gravure roll method and the doctor blade method are preferred for coating.
  • drying methods such as hot air, low humidity air, vacuum drying, spray drying, and freeze drying can be selected.
  • a third aspect of the present disclosure provides a secondary battery, including the battery separator described in the first aspect of the present disclosure.
  • the secondary battery may include a lithium ion battery, a sodium ion battery.
  • the raw materials, reagents, and methods used in the examples are conventional raw materials, reagents, and methods in the art.
  • the prepared coating film was shaped in an NMP coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the prepared coating film was shaped in an NMP coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the prepared coating film was shaped in a DMF coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the prepared coating film was shaped in a DMF coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the prepared coating film was shaped in an NMP coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the prepared coating film was shaped in an NMP coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the prepared coating film was shaped in a DMF coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the prepared coating film was shaped in a DMF coagulation bath with a mass concentration of 30% for 20s, then washed in a pure water tank for 70s, and finally dried in an oven at 75°C to obtain a battery separator.
  • the test method is as described above.
  • the obtained diaphragm has uniform coating thickness and pore size, good electrolyte resistance and high safety performance, while for The inorganic particles of ratio 1-4 are made into slurry and coated with separator, the uniformity of thickness is poor, the holes of aramid fibers are uneven, and the electrolyte resistance of the separator and the battery cycle are lower than those of Examples 1-4, and the shrinkage rate is uniform. Obviously higher than embodiment 1-4.

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Abstract

一种电池隔离膜及其制备方法和二次电池，隔离膜包括具有多孔结构的基材和涂覆于基材至少一面的耐热性聚合物涂层；耐热性聚合物涂层包括耐热性树脂和非导电粒子；非导电粒子的粒径D97≤耐热性聚合物涂层的厚度；非导电粒子的粒径分布满足：0.5≤(D90-D10)/D50<3.0；非导电粒子的比表面积 S 与平均粒径 D50之比满足：0<S/D50≤5×10 7m/g。隔离膜具有较高的耐温性能和优异的电化学稳定性，大大提升了电池的装配良率、电性能、安全性能。

Description

一种电池隔离膜及其制备方法和二次电池
优先权信息
本公开请求于2021年12月23日向中国国家知识产权局提交的、专利申请号为202111591247.1、申请名称为“一种电池隔离膜及其制备方法、二次电池”的中国专利申请的优先权，并且其全部内容通过引用结合在本公开中。
技术领域
本公开涉及电池技术领域，具体涉及一种电池隔离膜及其制备方法和二次电池。
背景技术
随着新能源技术的发展，二次电池因其高能量密度、长寿命、高安全性能应用到数码产品、电动车和储能装置中。二次电池主要由四大部分组成，分别是正极、电解液、隔离膜、负极。其中，隔离膜的主要作用是将正负极隔开，防止正负极直接接触引发短路，此外隔离膜中的通孔结构能够起到使正负极离子通过的作用，隔离膜性能的优劣将直接影响到电池装备良率、容量、内阻及循环等重要性能。
目前商用电池隔离膜的基底大多为聚烯烃材质，但因聚烯烃本身熔点较低，隔离膜在100℃以上时会发生严重收缩，引发正负极接触，从而易导致电池起火爆炸。为改善上述问题，通常会在聚烯烃基材表面涂覆一层或多层功能性涂层，常见的涂层主要有无机填料涂层、高分子聚合物材料涂层及无机填料和高分子聚合物材料混合涂层，传统的无机填料涂层虽然能在高温下保持一定的形态，但无机材料硬度大，涂覆过程中容易划伤基材，导致电池装配过程中短路率高；高分子聚合物材料熔点高，但作为涂层涂覆在基材表面上，与基材贴合疏松，耐热性能降低，造成电池短路，引发安全事故。
发明内容
本公开的目的是提供一种电池隔离膜及其制备方法和二次电池。解决了涂覆涂层均匀性差、耐热性不良、电池装备过程中短路率高、隔膜浸泡电解液和循环后期电性能衰减等的问题，选择特定要求的非导电粒子，使具有均匀的多孔涂层、较高的耐温性能和优异的电化学稳定性，大大提升了电池的装配良率、电性能、安全性能。由该隔离膜制备的二次电池具有优异的电性能和高安全性。
为了实现上述目的，本公开第一方面：提供一种电池隔离膜，所述电池隔离膜包括：
具有多孔结构的基材和涂覆于所述基材至少一面的耐热性聚合物涂层；
所述耐热性聚合物涂层包括耐热性树脂和非导电粒子；
其中，所述非导电粒子的粒径D97≤耐热性聚合物涂层的厚度；
所述非导电粒子的粒径分布满足：0.5≤(D90-D10)/D50≤3.0；
所述非导电粒子的比表面积S与平均粒径D50之比满足：0<S/D50≤5×10 7m/g。
根据本公开实施例，所述非导电粒子的粒径D97在0.5～1.5μm，耐热性聚合物涂层的厚度在1.5～6μm；
所述非导电粒子的粒径分布满足：0.8≤(D90-D10)/D50≤2.8；
所述非导电粒子的比表面积S与平均粒径D50之比满足：2×10 7m/g<S/D50≤4×10 7m/g。
根据本公开，所述电池隔离膜的剥离强度在10N/m以上，将所述电池隔离膜放置于130℃环境下1小时后，其在纵向和横向上的收缩率均在15％以下，且纵向与横向上的收缩率之比大于1，所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率在60％以上，装备电池循环500周后，隔膜针刺强度保持率在40％以上。
根据本公开实施例，所述电池隔离膜的剥离强度为50N/m以上；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为0～5％，横向收缩率为0～5％，且纵向与横向收缩率之比大于1；所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率为70～100％，装备电池循环500周后，隔膜针刺强度保持率在50～100％。
根据本公开实施例，所述电池隔离膜的剥离强度为50～80N/m；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为1.2～2.1％，横向收缩率为0.8～1.2％；所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率为92～96％，装备电池循环500周后，隔膜针刺强度保持率在85～95％。
本公开还提供了一种电池隔离膜，所述电池隔离膜的剥离强度在10N/m以上，将所述电池隔离膜放置于130℃环境下1小时后，其在纵向和横向上的收缩率均在15％以下，且纵向与横向上的收缩率之比大于1，所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率在60％以上，装备电池循环500周后，隔膜针刺强度保持率在40％以上。
根据本公开，所述电池隔离膜包括：具有多孔结构的基材和涂覆于所述基材至少一面的耐热性聚合物涂层；
所述耐热性聚合物涂层包括耐热性树脂和非导电粒子；
其中，所述非导电粒子的粒径D97≤耐热性聚合物涂层的厚度；
所述非导电粒子的粒径分布满足：0.5≤(D90-D10)/D50≤3.0；
所述非导电粒子的比表面积S与平均粒径D50之比满足：0<S/D50≤5×10 7m/g。
根据本公开实施例，所述电池隔离膜的剥离强度为50N/m以上；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为0～5％，横向收缩率为0～5％，且纵向与横向收缩率之比大于1；所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率为70～100％，装备电池循环500周后，隔膜针刺强度保持率在50～100％。
根据本公开实施例，所述电池隔离膜的剥离强度为50～80N/m；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为1.2～2.1％，横向收缩率为0.8～1.2％；所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率为92～96％，装备电池循环500周后，隔膜针刺强度保持率在85～95％。
根据本公开实施例，所述非导电粒子的粒径D97在0.5～1.5μm，耐热性聚合物涂层的厚度在1.5～6μm；
所述非导电粒子的粒径分布满足：0.8≤(D90-D10)/D50≤2.8；
所述非导电粒子的比表面积S与平均粒径D50之比满足：2×10 7m/g<S/D50≤4×10 7m/g。
根据本公开实施例，所述非导电粒子的粒径D97在0.7～1.5μm，耐热性聚合物涂层的厚度在3～3.2μm；
所述非导电粒子的粒径分布满足：0.8≤(D90-D10)/D50≤2.6；
所述非导电粒子的比表面积S与平均粒径D50之比满足：3×10 7m/g<S/D50≤4×10 7m/g。
根据本公开，所述基材包括聚烯烃基材、无纺布基材和在其上涂覆无机颗粒或聚合物功能性涂层制备出的基材。
根据本公开，所述基材的厚度为1-30μm，优选为5-20μm；所述基材的孔隙率为10-70％，优选为20-60％；所述耐热性聚合物涂层的厚度为1.5-10μm。
根据本公开，所述耐热性树脂选自含氮芳香族聚合物、聚酰亚胺聚酰胺、聚酰胺酰亚胺、聚酰亚胺、聚醚酰亚胺、聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物、聚四氟乙烯、聚砜、聚酮、聚醚酮、聚碳酸酯、聚甲醛中的一种或几种；其中含氮芳香族聚合物包括芳香族聚酰胺、芳香族聚酰亚胺、芳香族聚酰胺酰亚胺，优选为芳香族聚酰胺，特别优选对位芳香族聚酰胺；
优选地，对位芳香族聚酰胺的特性粘度为1.2-6.5g/l，优选为2-6g/l，更优选为3-5g/l；
优选地，对位芳香族聚酰胺的粘均分子量为10000-100000，优选为20000-80000。
根据本公开，所述非导电粒子包括二氧化硅、氧化铝、氧化镁、氧化锆、氧化钛、氧化钙、勃姆石、氢氧化镁、氮化铝、氮化硼、硫酸钡、氟化钙、氟化钡中的一种或几种；优选为氧化铝、勃姆石、氧化镁、二氧化硅，特别优选为氧化铝；
所述非导电粒子的形状包括板状、棒状、鳞片状、针状、柱状、球状、块体状、多面体状，优选板状、多面体状、柱状、棒状；
所述非导电粒子还可以含有具有锂离子转移能力的粒子，包括磷酸锂、锂钛磷酸盐、锂铝钛磷酸盐、锂氮化物、碳酸锂、氯化锂、硫化锂、六氟磷酸锂中的一种或几种。
本公开第二方面：提供一种本公开第一方面所述电池隔离膜的制备方法，包括以下步骤：
(1)提供基材；
(2)将非导电粒子投入到有机溶剂中，分散均匀后，加入耐热性树脂继续进行分散，得到浆料；
(3)使用步骤(2)制备出的浆料涂覆在基材的至少一面上，得到涂覆膜；
(4)将涂覆膜经过凝固浴或者饱和蒸汽，耐热性树脂多孔涂层形成网状纤维结构，非导电粒子均匀分布在多孔涂层中；
(5)将步骤(4)得到的涂覆膜经过水洗，干燥，得到电池隔离膜。
根据本公开，步骤(2)中，有机溶剂包括N-甲基吡咯烷酮、N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、四甲基脲中的一种或几种。
根据本公开，步骤(3)中，涂覆包括涂布法或浸渍法；涂布法包括刮刀法、浸渍法、逆转辊法、直接辊法、微凹版辊法、挤压法，优选微凹版辊法、刮刀法；
根据本公开，步骤(5)中，干燥方式包括热风、低湿风、真空干燥、喷雾干燥、冷冻干燥。
本公开第三方面：提供一种二次电池，包括本公开第一方面所述的电池隔离膜。
本发明技术方案相对于现有技术具有以下有益效果：
本发明通过对非导电粒子粒径及分布、比表面积与平均粒径之比的筛选，使多孔聚合物涂层厚度和孔径均匀，提高了二次电池的装配良率和二次电池的循环性能，增强粒子间的作用力和浆料的稳定性，涂覆后隔膜能够更好的搭建三维骨架结构，抑制隔膜在高温下的收缩，并且颗粒间的优异作用势能显著提高隔膜的吸液和储液能力，从而提高电池的循环性能和针刺强度保持率。
本发明获得的隔离膜的剥离强度在10N/m以上，特别是50/m以上，例如50～80N/m；将隔膜放置于130℃环境下1小时后，其在纵向和横向上的收缩率均在15％以下，且纵向与横向上的收缩率之比大于1，特别是其纵向收缩率为0～5％，例如1.2～2.1％，横向收缩率为0～5％，例如0.8～1.2％；隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率在60％，特别是70％～100％，例如92～96％；装备电池循环500周后，隔膜针刺强度保持率在40％ 以上，特别是50～100％，例如85～95％。
本公开的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本公开的实践了解到。
附图说明
附图是用来提供对本公开的进一步理解，并且构成说明书的一部分，与下面的具体实施方式一起用于解释本公开，但并不构成对本公开的限制。在附图中：
图1是本发明实施例1制备的电池隔离膜的电镜图。
具体实施方式
以下结合附图对本公开的具体实施方式进行详细说明。应当理解的是，此处所描述的具体实施方式仅用于说明和解释本公开，并不用于限制本公开。
本公开第一方面，提供了一种电池隔离膜，包括具有多孔结构的基材和涂覆于所述基材至少一面的耐热性聚合物涂层，耐热性聚合物涂层包括耐热性树脂和非导电粒子；
其中，非导电粒子的粒径D97≤耐热性聚合物涂层的厚度；
非导电粒子的粒径分布满足：0.5≤(D90-D10)/D50≤3.0；
非导电粒子的比表面积S与平均粒径D50之比满足：0<S/D50≤5×10 7m/g。
基材
根据本公开，所述基材可以为本领域已知的任何可用作隔膜基底的材料，例如聚烯烃多孔隔膜、无纺布隔膜、静电纺丝隔膜和在上述隔膜上涂覆的无机颗粒或聚合物功能性涂层制备出的隔膜。聚烯烃多孔隔膜材质可以为聚乙烯(PE)或聚丙烯(PP)，可以为单层PE层或PP层结构，也可以为聚乙烯(PE)和聚丙烯(PP)的复合多层结构，从成膜性能角度来看，优选聚乙烯及其共聚物，聚乙烯可以通过一步聚合法或者多步聚合法得到。
所述聚乙烯的分子量(粘均分子量)可以在50-400万，例如所述聚乙烯的粘均分子量为50万、55万、60万……100万、200万、300万、400万，根据本公开的一个具体实施例，所述聚乙烯的粘均分子量在60-300万，特别优选在80-300万；所述聚乙烯的粒径≤100μm。
所述无机颗粒可以选自二氧化硅(SiO 2)、氧化铝(Al 2O 3)、氧化镁(MgO)、氧化锆(ZrO 2)、氧化钛(TiO 2)、氧化钙(CaO)等氧化物粒子，勃姆石(AlOOH)、氢氧化镁(Mg(OH) 2)等氢氧化物，氮化铝(AlN)、氮化硼(BN)等氮化物粒子，以及硫酸钡(BaSO 4)、氟化钙(CaF 2)、氟化钡(BaF 2)等难溶性离子结晶粒子中的一种或几种。
所述聚合物功能性涂层材质可以选自PMMA或者PVDF的一种或多种。
根据本公开，基材的厚度可以在1-30μm，例如1μm、2μm、3μm、4μm、5μm……29μm、30μm，根据本公开的一个具体实施例，基材的厚度在5-20μm。
根据本公开，基材的孔隙率可以在10-70％，例如10％、12％、15％……69％、70％，根据本公开的一个具体实施例，基材的孔隙率在20-60％。
耐热性聚合物涂层
耐热性聚合物涂层包括耐热性树脂和非导电粒子。
根据本公开，耐热性树脂材料可以选自含氮芳香族聚合物、聚酰亚胺聚酰胺、聚酰胺酰亚胺、聚酰亚胺、聚醚酰亚胺、聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物、聚四氟乙烯、聚砜、聚酮、聚醚酮、聚碳酸酯、聚甲醛；其中含氮芳香族聚合物，可举出芳香族聚酰胺、芳香族聚酰亚胺、芳香族聚酰胺酰亚胺等，优选为由芳香族聚酰胺构成的树脂，特别优选物理特性、耐热性、低热收缩特性优异的对位系芳香族聚酰胺。
所述对位系芳香族聚酰胺的特性粘度可以在1.2-6.5g/l，例如1.2g/l、1.3g/l……6.4g/l、6.5g/l，根据本公开的一个具体实施例，所述对位系芳香族聚酰胺的特性粘度在2-6g/l，更优选在3-5g/l。
所述对位系芳香族聚酰胺的分子量(粘均分子量)可以在10000-100000，例如10000、10100……99999、100000，根据本公开的一个具体实施例，所述对位系芳香族聚酰胺的分子量在20000-80000，需要特别说明的是，所述分子量采用乌式粘度计测量特性粘度数值后，并根据马格里斯公式计算而来。
根据本公开，对非导电粒子的种类没有特别限制，只要电化学性能稳定。根据本公开的一个具体实施例，非导电粒子可以包括但不限于二氧化硅(SiO 2)、氧化铝(Al 2O 3)、氧化镁(MgO)、氧化锆(ZrO 2)、氧化钛(TiO 2)、氧化钙(CaO)等氧化物粒子，勃姆石(AlOOH)、氢氧化镁(Mg(OH) 2)等氢氧化物，氮化铝(AlN)、氮化硼(BN)等氮化物粒子，以及硫酸钡(BaSO 4)、氟化钙(CaF 2)、氟化钡(BaF 2)等难溶性离子结晶粒子中的一种或几种。非导电粒子可以选自上述的一种，也可以选自以任何比例的上述两种或者两种以上。在这些粒子中，考虑到在电解液中的稳定性和电位，优选氧化物粒子。另外，非导电粒子需有较高的热分解温度(分解温度高于200℃)，低吸水性，优选氧化铝、勃姆石、氧化镁、二氧化硅，特别优选氧化铝。
根据本公开，对非导电粒子形状没有特别限制，如可以举出板状、棒状、鳞片状、针状、柱状、球状、块体状、多面体状等，也可以组合使用多种具有上述形状的无机填料。从提高透过性的观点出发，优选包含多个面的板状、多面体状、柱状、棒状。
非导电粒子中还可以含有具有锂离子转移能力的粒子，从而提高了锂离子的导电性能， 具有锂离子转移的粒子选自以下的任一一种无机粒子或至少两种无机粒子的混合物：磷酸锂(Li 3PO 4)、锂钛磷酸盐(Li xTi y(PO 4) 3,0＜x＜2,0＜y＜3)，锂铝钛磷酸盐、锂氮化物、碳酸锂、氯化锂、硫化锂、六氟磷酸锂。
根据本公开，对非导电粒子具有以下要求：
1、非导电粒子的颗粒粒径D97≤a，其中D97表示粒径小于D97的颗粒占总量的97％，大于D97的占3％；a表示电池隔离膜的耐热性聚合物涂层的厚度。根据本公开的一个具体实施例，非导电粒子的粒径D97在0.5～1.5μm，特别在0.7～1.5μm，耐热性聚合物涂层的厚度在1.5～6μm，特别在3～3.2μm。
D97≤a时，多孔聚合物涂层厚度和孔径均匀，从而提高了二次电池的装配良率和二次电池的循环性能。非导电粒子的粒径满足以上范围时，形成的浆料不易沉降，从而在涂覆过程中，形成均匀的孔结构和粒子分布；当非导电粒子粒径D97大于耐热性聚合物涂层的厚度，形成的浆料容易沉降，导致厚度一致性差，且D97过大，影响了芳纶成膜时与基材贴合的紧密程度，导致芳纶隔膜的剥离强度较差。
2、非导电粒子的粒径分布满足0.5≤(D90-D10)/D50≤3.0，例如0.6、0.8、1.0、1.2、1.5、1.6、1.8、2.0、2.5、3.0。根据本公开的一个具体实施例，非导电粒子的粒径分布满足0.8≤(D90-D10)/D50≤2.8，特别是0.8≤(D90-D10)/D50≤2.6。
非导电颗粒粒径分布位于此区间范围内，粒子之间的范德华力作用增强，形成的浆料均匀性好、稳定性强不易沉降；涂覆过程中，非导电粒子在涂层中分布均匀，形成的涂层厚度一致性好，非导电粒子形成的三维骨架，能够抑制隔膜的在高温下的收缩，且在涂覆烘烤过程中，非导电粒子能紧密的贴合于基材表面，形成致密的微孔洞和通道，这些通道有利于Li +在充放电过程中的运输及电解液的储存，从而提高电池的循环和针刺强度保持率。当非导电粒子分布大于3时，颗粒间形貌差异较大，导致涂层的厚度均匀性差，且影响成孔效果，导致在电池循环中锂离子迁移速率不同，从而影响电池循环性能。当非导电粒子粒径分布小于0.5时，颗粒之间的粒径相差较小，粒子之间容易形成二次团聚，增加了浆料的制浆难度和成本。
3、非导电粒子的比表面积与平均粒径D50之比满足0<S/D50≤5×10 7m/g，例如0.1×10 7、0.5×10 7、1×10 7、1.5×10 7、2×10 7、2.5×10 7、3×10 7、3.5×10 7、4×10 7、4.5×10 7、5×10 7m/g。根据本公开的一个具体实施例，非导电粒子的比表面积与平均粒径D50之比满足2×10 7m/g<S/D50≤4×10 7m/g，特别是3×10 7m/g<S/D50≤4×10 7m/g。
非导电粒子的比表面积采用氮吸附法进行测量，非导电颗粒S/D50位于此区间范围内，非导电粒子具有优异的表面作用势，能够更好的搭建三维骨架结构，抑制隔膜在高温下的 收缩，并且颗粒间的优异作用势能显著提高隔膜的吸液和浸润能力，从而提高电池的循环性能。非导电粒子满足以上范围，非导电粒子具有优异的表面作用势，能够提高涂层储存电解液的能力，同时，抑制电解液在循环和高温存储等等使用中副反应的发生，使得隔膜仍能够维持较高的力学性能，降低副反应生产的不溶物刺穿隔膜的几率，从而降低电池的自放电和提高电池的使用寿命。当所述非导电粒子不在以上范围，非导电粒子在涂覆过程中吸附过多的水分，与电解质六氟磷酸锂发生反应，释放出气体，导致电池压降和容量降低。
本发明选择满足上述三个条件要求的非导电粒子，多孔聚合物的涂层厚度和孔径均匀，提高了二次电池的装配良率和二次电池的循环性能，增强了粒子间的作用力和浆料的稳定性，涂覆后能够更好的搭建三维骨架结构，抑制隔膜在高温下的收缩，并且颗粒间的优异作用势能显著提高隔膜的吸液和储液能力，从而提高电池的循环性能和针刺强度保持率。
根据本公开，获得的电池隔离膜的剥离强度在10N/m以上，例如剥离强度为10N/m、11N/m……79N/m、80N/m……；并且将所述隔膜放置于130℃环境下1小时后，其在纵向(MD)和横向(TD)上的收缩率均在15％以下，且纵向(MD)与横向(TD)上的收缩率之比大于1，例如MD收缩率为1％、2％……14％、15％，TD收缩率为1％、2％……14％、15％；并且所述隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率在60％以上，例如针刺强度保持率为70％、80％……90％、95％，装备电池循环500周后，隔膜针刺强度保持率在40％以上，例如装备电池循环500周后隔膜针刺强度保持率为45％、55％……90％、95％。
根据本公开的一个具体实施例，所述电池隔离膜的剥离强度为50以上N/m；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为0～5％，横向收缩率为0～5％，且纵向与横向收缩率之比大于1；所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率为70～100％，装备电池循环500周后，隔膜针刺强度保持率在50～100％。
根据本公开的一个具体实施例，所述电池隔离膜的剥离强度为50～80N/m；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为1.2～2.1％，横向收缩率为0.8～1.2％；所述电池隔离膜在25℃下浸泡电解液，60天之后针刺强度保持率为92～96％，装备电池循环500周后，隔膜针刺强度保持率在85～95％。
剥离强度测试方法：
使用2.5cm×30cm模具裁切试样，将试样平整粘贴到贴完双面胶的短钢尺上，用压辊来回滚动三次，手动剥离1cm后夹到拉力机上进行180°测试，其中拉伸速度为50mm/min，测量三次结果取均值。
收缩率测试方法：
取15cm×15cm的块状隔离膜，按照纵向和横向画两条相互垂直的线段(一般为10cm×10cm)，用钢直尺(或投影仪)分别量取试样纵向和横向的长度；将试样平展放在两张A4纸中，随后放在130℃的烘箱中，保持1h；加热结束后，取出样品，待恢复室温后，再次测量纵向和横向标记长度，按照下式分别计算收缩率，最后取几个样品的平均值作为收缩率。
MD方向热收缩率(％)＝(加热前MD方向长度-加热后MD方向长度)/加热前MD方向长度×100。
TD方向热收缩率(％)＝(加热前TD方向长度-加热后TD方向长度)/加热前MD方向长度×100。
浸泡电解液前后针刺强度测试方法：
穿刺强度按ASTM D4833-00e1的要求进行测试。其中针头形状为Ф＝1.0mm的半球，针头运行速度为1mm/s，裁取15cm×15cm的块状隔离膜，每间隔2cm，按上述方法测量一次针刺强度，五次测量结果取均值，记录为浸泡电解液前的针刺强度c 0，将碳酸乙烯酯(EC)、碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)按照质量比1:1:1配成有机溶剂，将待测的块状隔膜放入配成的有机溶剂中，25℃，浸泡60day后，取出块状隔膜，放在通风橱自然风干，每间隔2cm，按上述方法测量一次针刺强度，五次测量结果取均值，记录为浸泡电解液后的针刺强度c 1，则针刺强度保持率为：c 1/c 0。
循环前后针刺强度测试方法：
穿刺强度按ASTM D4833-00e1的要求进行测试。其中针头形状为Ф＝1.0mm的半球，针头运行速度为1mm/s，裁取15cm×15cm的块状隔离膜，每间隔2cm，按上述方法测量一次针刺强度，五次测量结果取均值，记录为装配电池前的针刺强度d 0，将涂覆完成的隔离膜装备电池(电池正极材料为磷酸铁锂，负极材料为石墨，电解液溶质为六氟磷酸锂)，对电池进行不断的充放电测试，当电池循环到500周后，再次拆解电池，取出隔膜，放在通风橱自然风干，每间隔2cm，按上述方法测量一次针刺强度，五次测量结果取均值，记录为浸泡电解液后的针刺强度d 1，则针刺强度保持率为：d 1/d 0。
本公开第二方面，提供一种本公开第一方面所述电池隔离膜的制备方法，所述方法包括以下步骤：
(1)提供基材；
(2)将非导电粒子投入到有机溶剂中，分散均匀后，加入耐热性树脂继续进行分散，得到浆料；
(3)使用步骤(2)制备出的浆料涂覆在基材的至少一面上，得到涂覆膜；
(4)将涂覆膜经过凝固浴或者饱和蒸汽，耐热性树脂多孔涂层形成网状纤维结构，非导电粒子均匀分布在多孔涂层中；
(5)将步骤(4)得到的涂覆膜经过水洗，干燥，得到电池隔离膜。
步骤(1)
对基材的制备方法不做特别限定，可采用干法单向拉伸、双向同步或异步拉伸以及湿法双向同步或异步拉伸，优选的采用湿法双向同步拉伸方法进行制备。
步骤(2)
根据本公开，所述有机溶剂包括N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAC)、四甲基脲(TMU)中的至少一种。
步骤(3)
对于所述浆料的涂覆方式并无固定限制，可以选择涂布法、浸渍法等方法进行涂覆。作为涂布法，可以举出刮刀法、浸渍法、逆转辊法、直接辊法、微凹版辊法、挤压法、喷涂法、点涂法等方法。考虑到多孔膜厚度的均匀性，优选微凹版辊法和刮刀法进行涂覆。
步骤(5)
对于涂覆膜的干燥方式并无固定的限制，可以选择利用热风、低湿风、真空干燥、喷雾干燥、冷冻干燥等干燥方法。
本公开第三方面，提供一种二次电池，包括本公开第一方面所述的电池隔离膜。
根据本公开，二次电池可以包括锂离子电池、钠离子电池。
隔离膜的制备方法制备得到的隔离膜和二次电池具有与上述隔离膜相同的优势，在此不再赘述。
下面参考具体实施例，对本公开进行描述，需要说明的是，这些实施例仅仅是描述性的，而不以任何方式限制本公开。
除特殊说明外，在实施例中所采用的原料、试剂、方法等均为本领域常规的原料、试剂、方法。
定义：α＝(D90-D10)/D50；β＝S/D50。
实施例1
(1)向100份NMP中添加4份的氧化铝粉，通过高速分散乳化机搅拌20min，而后添加2份对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位芳纶浆料，其中氧化铝粒径D97＝1.125μm，粒径分布α＝2.31，β＝3.85×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3.1μm；
(3)制备的涂覆膜在的经过质量浓度为30％的NMP凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
实施例2
(1)向100份NMP中添加4份氧化铝粉，通过高速分散乳化机搅拌20min，而后添加2份对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位芳纶浆料，其中氧化铝粒径D97＝1.032μm，粒径分布α＝2.59，β＝3.53×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3.0μm；
(3)制备的涂覆膜在的经过质量浓度为30％的NMP凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
实施例3
(1)向100份DMF中添加4份勃姆石粉，通过高速分散乳化机搅拌20min，而后添加2份对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位芳纶浆料，其中勃姆石粒径D97＝0.785μm，粒径分布α＝0.82，β＝3.24×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3.2μm；
(3)制备的涂覆膜在的经过质量浓度为30％的DMF凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
实施例4
(1)向100份DMF中添加4份勃姆石粉，通过高速分散乳化机搅拌20min，而后添加2份对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位芳纶浆料，其中勃姆石粒径D97＝1.3μm，粒径分布α＝1.63，β＝2.16×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3μm；
(3)制备的涂覆膜在的经过质量浓度为30％的DMF凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
对比例1
(1)向100份NMP中添加4份氧化铝粉，通过高速分散乳化机搅拌20min，而后添加2份对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位 芳纶浆料，其中氧化铝粒径D97＝4.128，粒径分布α＝5.23，β＝5.17×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3.8μm；
(3)制备的涂覆膜在的经过质量浓度为30％的NMP凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
对比例2
(1)向100份NMP中添加4份氧化铝粉，通过高速分散乳化机搅拌20min，而后添加对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位芳纶浆料，其中氧化铝粒径D97＝3.78，粒径分布α＝5.28，β＝1.14×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3.8μm；
(3)制备的涂覆膜在的经过质量浓度为30％的NMP凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
对比例3
(1)向100份DMF中4份勃姆石粉，通过高速分散乳化机搅拌20min，而后添加对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位芳纶浆料，其中勃姆石粒径D97＝4.428，粒径分布α＝4.58，β＝0.96×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3.5μm；
(3)制备的涂覆膜在的经过质量浓度为30％的DMF凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
对比例4
(1)向100份DMF中4份勃姆石粉，通过高速分散乳化机搅拌20min，而后添加对位芳纶，高速分散乳化机继续搅拌20min，在1000目滤网过滤后得到均匀的对位芳纶浆料，其中勃姆石粒径D97＝3.886，粒径分布α＝3.17，β＝0.83×10 7m/g；
(2)选取规格厚度为9μm的聚乙烯基膜，孔隙率为38％，透气度为150s/100cc，采用凹版涂覆方式在基膜一侧涂覆上述对位芳纶浆料，涂层厚度3.4μm；
(3)制备的涂覆膜在的经过质量浓度为30％的DMF凝固浴进行定型20s，随后进入纯水槽水洗70s，最后进入75℃的烘箱干燥得到电池隔离膜。
测试例
实施例和对比例隔膜参数和性能如下表：
测试方法如上文所述。
Figure PCTCN2022103158-appb-000001
如实施例1-4所示，通过选用D97,α和β满足要求标准的无机粒子，得到的隔膜具有涂层厚度和孔径均匀，较好的耐电解液性能和较高的安全性能，而对比例1-4的无机粒子制成浆料后涂覆隔膜，厚度均匀性差，芳纶纤维成孔不均，且隔膜的耐电解液性能和电池循环后低于实施例1-4，收缩率均明显高于实施例1-4。
尽管上面已经示出和描述了本公开的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本公开的限制，本领域的普通技术人员在本公开的范围内可以对上述实施例进行变化、修改、替换和变型。

Claims (15)

  1. 一种电池隔离膜，其特征在于，包括：具有多孔结构的基材和涂覆于所述基材至少一面的耐热性聚合物涂层；
    所述耐热性聚合物涂层包括耐热性树脂和非导电粒子；
    其中，所述非导电粒子的粒径D97≤耐热性聚合物涂层的厚度；
    所述非导电粒子的粒径分布满足：0.5≤(D90-D10)/D50≤3.0；
    所述非导电粒子的比表面积S与平均粒径D50之比满足：0<S/D50≤5×10 7m/g。
  2. 根据权利要求1所述的电池隔离膜，其特征在于，所述非导电粒子的粒径D97在0.5～1.5μm，耐热性聚合物涂层的厚度在1.5～6μm；
    所述非导电粒子的粒径分布满足：0.8≤(D90-D10)/D50≤2.8；
    所述非导电粒子的比表面积S与平均粒径D50之比满足：2×10 7m/g<S/D50≤4×10 7m/g。
  3. 根据权利要求1或2所述的电池隔离膜，其特征在于，所述电池隔离膜的剥离强度在10N/m以上；将所述电池隔离膜放置于130℃环境下1小时后，其在纵向和横向上的收缩率均在15％以下，且纵向与横向上的收缩率之比大于1；所述电池隔离膜25℃下浸泡电解液，60天之后针刺强度保持率在60％以上，装备电池循环500周后，隔膜针刺强度保持率在40％以上。
  4. 根据权利要求3所述的电池隔离膜，其特征在于，所述电池隔离膜的剥离强度为50N/m以上；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为0～5％，横向收缩率为0～5％，且纵向与横向收缩率之比大于1；所述电池隔离膜25℃下浸泡电解液，60天之后针刺强度保持率为70～100％，装备电池循环500周后，隔膜针刺强度保持率在50～100％。
  5. 根据权利要求1所述的电池隔离膜，其特征在于，所述基材包括聚烯烃基材、无纺布基材和在其上涂覆无机颗粒或聚合物功能性涂层制备出的基材。
  6. 根据权利要求1所述的电池隔离膜，其特征在于，所述基材的厚度为1-30μm；所述基材的孔隙率为10-70％；
    所述耐热性聚合物涂层的厚度为1.5-10μm。
  7. 根据权利要求1所述的电池隔离膜，其特征在于，所述耐热性树脂选自含氮芳香族聚合物、聚酰亚胺聚酰胺、聚酰胺酰亚胺、聚酰亚胺、聚醚酰亚胺、聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物、聚四氟乙烯、聚砜、聚酮、聚醚酮、聚碳酸酯、聚甲醛中的一种或几种；其中含氮芳香族聚合物包括芳香族聚酰胺、芳香族聚酰亚胺、芳香族聚酰胺酰亚胺。
  8. 根据权利要求1所述的电池隔离膜，其特征在于，所述非导电粒子包括二氧化硅、氧化铝、氧化镁、氧化锆、氧化钛、氧化钙、勃姆石、氢氧化镁、氮化铝、氮化硼、硫酸钡、氟化钙、氟化钡中的一种或几种；
    所述非导电粒子的形状包括板状、棒状、鳞片状、针状、柱状、球状、块体状、多面体状；
    所述非导电粒子还可以含有具有锂离子转移能力的粒子，包括磷酸锂、锂钛磷酸盐、锂铝钛磷酸盐、锂氮化物、碳酸锂、氯化锂、硫化锂、六氟磷酸锂中的一种或几种。
  9. 一种电池隔离膜，其特征在于，所述电池隔离膜的剥离强度为50/m以上；将所述电池隔离膜放置于130℃环境下1小时后，其纵向收缩率为0～5％，横向收缩率为0～5％，且纵向与横向收缩率之比大于1；所述电池隔离膜25℃下浸泡电解液，60天之后针刺强度保持率为70～100％，装备电池循环500周后，隔膜针刺强度保持率在50～100％。
  10. 根据权利要求9所述的电池隔离膜，其特征在于，所述电池隔离膜包括：具有多孔结构的基材和涂覆于所述基材至少一面的耐热性聚合物涂层；
    所述耐热性聚合物涂层包括耐热性树脂和非导电粒子；
    其中，所述非导电粒子的粒径D97≤耐热性聚合物涂层的厚度；
    所述非导电粒子的粒径分布满足：0.5≤(D90-D10)/D50≤3.0；
    所述非导电粒子的比表面积S与平均粒径D50之比满足：0<S/D50≤5×10 7m/g。
  11. 根据权利要求9所述的电池隔离膜，其特征在于，所述非导电粒子的粒径D97在0.5～1.5μm，耐热性聚合物涂层的厚度在1.5～6μm；
    所述非导电粒子的粒径分布满足：0.8≤(D90-D10)/D50≤2.8；
    所述非导电粒子的比表面积S与平均粒径D50之比满足：2×10 7m/g<S/D50≤4×10 7m/g。
  12. 一种权利要求1-8任一项所述的电池隔离膜或权利要求9-11任一项所述的电池隔离膜的制备方法，其特征在于，包括以下步骤：
    (1)提供基材；
    (2)将非导电粒子投入到有机溶剂中，分散均匀后，加入耐热性树脂继续进行分散，得到浆料；
    (3)使用步骤(2)制备出的浆料涂覆在基材的至少一面上，得到涂覆膜；
    (4)将涂覆膜经过凝固浴或者饱和蒸汽，耐热性树脂多孔涂层形成网状纤维结构，非导电粒子均匀分布在多孔涂层中；
    (5)将步骤(4)得到的涂覆膜经过水洗，干燥，得到电池隔离膜。
  13. 根据权利要求12所述的制备方法，其特征在于，步骤(2)中，有机溶剂包括N-甲基吡咯烷酮、N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、四甲基脲中的一种或几种。
  14. 根据权利要求12所述的制备方法，其特征在于，步骤(3)中，涂覆包括涂布法或浸渍法；涂布法包括刮刀法、浸渍法、逆转辊法、直接辊法、微凹版辊法、挤压法；
    步骤(5)中，干燥方式包括热风、低湿风、真空干燥、喷雾干燥、冷冻干燥。
  15. 一种二次电池，其特征在于，包括权利要求1-8任一项所述的电池隔离膜或权利要求9-11任一项所述的电池隔离膜。
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