WO2024007863A1 - 一种隔膜和电池 - Google Patents

一种隔膜和电池 Download PDF

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Publication number
WO2024007863A1
WO2024007863A1 PCT/CN2023/101847 CN2023101847W WO2024007863A1 WO 2024007863 A1 WO2024007863 A1 WO 2024007863A1 CN 2023101847 W CN2023101847 W CN 2023101847W WO 2024007863 A1 WO2024007863 A1 WO 2024007863A1
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Prior art keywords
weight
monomer
separator
layer
polymer
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PCT/CN2023/101847
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English (en)
French (fr)
Inventor
张祖来
刘建明
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珠海冠宇电池股份有限公司
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Publication of WO2024007863A1 publication Critical patent/WO2024007863A1/zh

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/497—Ionic conductivity
    • 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 field of battery technology, and in particular to a separator and a battery including the separator.
  • the purpose of the present disclosure is to overcome the above-mentioned problems existing in the prior art and provide a separator and a battery including the separator.
  • the separator of the present disclosure has higher wettability and can achieve a lower ion conductivity deviation ratio; the battery obtained by the separator of the present disclosure has lower resistance, thereby having better cycle performance and higher safety.
  • the separator can be modified with specific compounds to form more "ion channels" on the separator without relying on the inherent properties of the separator.
  • the pore structure conducts ions; these "ion channels” guide ions, which on the one hand increases the speed of ions passing through the diaphragm, and on the other hand improves the consistency of the ions conducted by the diaphragm, making the ion conductivity on the diaphragm higher. Evenly.
  • the inventor of the present disclosure has screened out specific compounds that have a better modification effect on the separator through extensive and in-depth research.
  • a first aspect of the present disclosure provides a separator, the separator contains a first monomer and/or a first polymer, the first polymer is obtained by polymerizing the first monomer;
  • the first monomer has a structure represented by formula (I) or formula (II),
  • a second aspect of the present disclosure provides a battery, and the separator of the battery is the separator described in the first aspect of the present disclosure.
  • the present disclosure has at least the following advantages compared with the prior art:
  • the separator of the present disclosure has good wettability and fast ion conduction speed
  • the battery of the present disclosure has low internal resistance
  • the battery of the present disclosure has a high capacity retention rate and a long cycle life
  • the battery of the present disclosure has good safety performance
  • a first aspect of the present disclosure provides a separator, the separator contains a first monomer and/or a first polymer, the first polymer is obtained by polymerizing the first monomer;
  • the first monomer has a structure represented by formula (I) or formula (II),
  • R 1 and R 2 are each independently selected from H, -C n NR 3 and -C n NR 4 R 5 , n is an integer of 0-4; NR 3 is a 4-7 membered heterocycle, and R 3 contains 0 -2 oxygen atoms and/or 0-2 nitrogen atoms, the rest are carbon atoms; the presence or absence of the graft group R 6 on R 3 , R 6 is -C m OH, m is an integer from 0 to 2; R 4 and R 5 are each independently a C1-C4 aliphatic chain.
  • the separator by adding the first monomer of the above-mentioned specific structure and/or the first polymer obtained by polymerization thereof into the separator, the separator can achieve a lower ion conductivity deviation ratio than the prior art, and a more Good wettability and lower battery internal resistance. In order to further improve the effect, one or more of the technical features can be further optimized.
  • the first polymer is obtained by polymerizing the first monomer.
  • the polymerization can be a homopolymerization of the first monomer, or it can be a combination of the first monomer and other monomers. Get together.
  • the first polymer refers to a polymer obtained by homopolymerizing the first monomer.
  • the polymer obtained by copolymerizing the monomers of conventional materials used in battery separators and the first monomer is also within the protection scope of the first polymer of the present disclosure.
  • the separator may contain only the first monomer, only the first polymer, or both the first monomer and the first polymer.
  • the first monomer has a structure of formula (I) or a structure of formula (II). It can be seen from the structural formula that the first monomer has two centrosymmetric benzene rings and at least four hydroxyl groups.
  • R 1 and R 2 are the same or different, and are each independently selected from H, -C n NR 3 and -C n NR 4 R 5 .
  • n represents the number of carbon atoms connecting the benzene ring and the nitrogen atom, and n can be an integer from 0 to 4 (such as 0, 1, 2, 3), preferably 1 or 2.
  • the N atom and R 3 group in -C n NR 3 together form a ring structure, which can be a 4-7-membered heterocyclic ring (such as four-membered, five-membered, six-membered, or seven-membered), preferably a five-membered heterocyclic ring or a six-membered heterocyclic ring. Heterocycle.
  • the R 3 group can be composed entirely of carbon atoms (hydrogen atoms are not counted), or it can contain 0-2 (such as 0, 1, 2) oxygen atoms and/or 0-2 (such as 0, 1, 2) nitrogen atoms atom.
  • the R 3 group consists entirely of carbon atoms.
  • a graft group R 6 may also exist on R 3 , R 6 is -C m OH, and m is an integer from 0 to 2 (such as 0, 1, 2).
  • the grafting site of the graft group R 6 is in the opposite position to the N atom in the NR 3 heterocyclic ring.
  • -C n NR 3 includes, but is not limited to, the following structures:
  • R 4 and R 5 are each independently selected from methyl and ethyl.
  • the first monomer includes but is not limited to the following structures:
  • any position where the first monomer and/or the first polymer is present in the separator falls within the scope of the present disclosure.
  • the separator includes a base material layer and an optional heat-resistant layer and/or an optional glue layer (the term “optionally” means that it may or may not be present); the heat-resistant layer Cover one or both sides of the base material layer; the glue coating layer covers the surface of the heat-resistant layer, and/or the glue coating layer covers the surface of the base material layer.
  • the separator includes a glue coating layer, a heat-resistant layer, a base material layer, a heat-resistant layer and a glue coating layer arranged in sequence.
  • the separator includes a glue coating layer, a base material layer, a heat-resistant layer and a glue coating layer arranged in sequence.
  • At least one layer among the base material layer, the heat-resistant layer and the glue coating layer contains the first monomer and/or the first polymer.
  • the base material layer, the heat-resistant layer and the glue coating layer may all contain the first monomer and/or the first polymer, or only one or more of the layers may contain the first monomer and/or the first polymer. first monomer and/or said first polymer. Therefore, the inclusion of the first monomer and/or the first polymer in at least one layer of the base material layer, the heat-resistant layer and the glue coating layer falls within the protection scope of the present disclosure, and can be achieved The purpose of this disclosure is to have better technical effects.
  • the term "one layer" in this article refers to a layer rather than a type of layer. For example, when the glue layer contains the first monomer and/or the first polymer, it does not require two upper and lower layers. Contained in the glue layer.
  • At least the base material layer contains the first monomer and/or the first polymer.
  • the first monomer and/or the first polymer are contained in the base material layer and the heat-resistant layer and/or the glue coating layer.
  • the base material layer contains the first monomer and/or the first polymer.
  • the heat-resistant layer contains the first monomer and/or the first polymer.
  • the glue layer contains the first monomer and/or the first polymer.
  • the base material layer and the heat-resistant layer contain the first monomer and/or the third A polymer.
  • the heat-resistant layer and the glue coating layer contain the first monomer and/or the first polymer.
  • the base material layer, the heat-resistant layer and the glue coating layer all contain the first monomer and/or the first polymer.
  • the same layer may contain only one structure of the first monomer and/or the first polymer, or may contain multiple structures of the first monomer and/or the first polymer. .
  • the form in which the first monomer and/or the first polymer is present in the separator may not be particularly limited.
  • it may be present in the separator in the form of doping (blending), grafting, partial coating, etc. in the diaphragm.
  • the material of the base material layer is a material obtained by graft-modifying the base material with the first monomer.
  • the content of the first monomer may be 0.1 parts by weight to 10 parts by weight (for example, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight), preferably 0.5 parts by weight to 5 parts by weight.
  • the base material can be a material conventional in the art as a separator base material, for example, selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride, polyimide, polyethylene terephthalate, and polyterephthalate.
  • a separator base material for example, selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride, polyimide, polyethylene terephthalate, and polyterephthalate.
  • the material of the base material layer is obtained by the following graft modification method:
  • step (a2) subjecting the material obtained in step (a1) to a first oxygen treatment
  • step (a3) In the first solvent, under a protective atmosphere, the material obtained in step (a2) and the first monomer are subjected to a first contact reaction.
  • the conditions for the first plasma activation treatment include: the time is 3min-10min (for example, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min), preferably 5min -8min.
  • the first oxidation treatment process includes placing the material obtained in step (a1) in oxygen, and the control conditions include: the temperature is 30°C-60°C (for example, 30°C, 35°C °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C), preferably 40-50 °C; the time is 100min-250min (for example, 100min, 120min, 150min, 180min, 200min, 220min, 250min), preferably 120min-200min.
  • the control conditions include: the temperature is 30°C-60°C (for example, 30°C, 35°C °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C), preferably 40-50 °C; the time is 100min-250min (for example, 100min, 120min, 150min, 180min, 200min, 220min, 250min), preferably 120min-200min.
  • the first contact reaction method may include: converting the obtained product from step (a2) The material is soaked in a solution containing the first monomer and the first solvent.
  • the conditions for the first contact reaction include: the temperature is 50°C-80°C (for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C ), preferably 55°C-65°C; the time is 6h-10h (for example, 6h, 7h, 8h, 9h, 10h), preferably 7h-9h.
  • the first solvent is selected from acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, methanol, ethanol, One or more of isopropyl alcohol and water.
  • a substrate layer graft-modified with the first monomer of a preferred embodiment can be obtained.
  • the heat-resistant layer may also contain the first monomer and/or the first polymer, and the first monomer and/or the first polymer may exist in the heat-resistant layer in various forms.
  • the heat-resistant layer includes ceramic particles, the ceramic particles have a core-shell structure, wherein the shell material of the ceramic particles is the first polymer, and the core material of the ceramic particles is selected from One or more of alumina, boehmite, magnesium oxide, boron nitride and magnesium hydroxide.
  • the heat-resistant layer may also contain other conventional components, for example, the heat-resistant layer may also contain a first adhesive.
  • the heat-resistant layer can be obtained by mixing modified ceramic particles and a first binder, then applying and curing the mixture.
  • the shell material of the ceramic particles is a homopolymer of the first monomer.
  • the content of the shell material of the ceramic particles may be 5% to 50% by weight (for example, 5% by weight, 10% by weight, 15% by weight, 20% by weight, 25% by weight). %, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%), the content of the core material of the ceramic particles is 50 wt%-95 wt% (for example, 95 wt%, 90 wt% , 85 wt%, 80 wt%, 75 wt%, 70 wt%, 65 wt%, 60 wt%, 55 wt%, 50 wt%).
  • step (b1) in order to avoid losses during the process, the dosage of the first monomer can be excessive.
  • the dosage of the first monomer is more than the actual amount of shell formation, and the dosage is such that the above core-shell ratio requirement can be achieved, that is, Can.
  • step (b1) the second contact is, for example, stirring and mixing.
  • step (b2) the drying is, for example, vacuum heating drying or spray drying.
  • modified ceramic particles having a core structure of a shell (the first monomer is homopolymerized into a shell) are obtained.
  • the heat-resistant layer may also include a first adhesive.
  • the first binder in the heat-resistant layer is selected from polytetrafluoroethylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, polyimide, polyacrylonitrile, polymethacrylic acid One or more of methyl ester, polyacrylic acid, and polyacrylate.
  • the heat-resistant layer is obtained by mixing modified ceramic particles with a first binder, then coating and curing.
  • the content of the ceramic particles can be selected within a wide range. Based on the total weight of the heat-resistant layer, the content of the ceramic particles may be 20% by weight to 99% by weight (for example, 20% by weight, 30% by weight, 40% by weight, 50% by weight, 60% by weight, 70% by weight, 80% by weight, 90% by weight, 99% by weight), the content of the first binder may be 1% by weight - 80% by weight (for example, 1% by weight, 10% by weight, 20% by weight, 30% by weight, 40% by weight, 50% by weight, 60% by weight, 70% by weight, 80% by weight); preferably, the content of the ceramic particles can be 50% by weight - 95% by weight, and the first bonding
  • the content of the agent may range from 5% to 50% by weight.
  • the first binder may not contain the first monomer and/or the first polymer.
  • the first binder may also contain the first monomer and/or the first polymer, which can be obtained by referring to the modification method of the second binder below.
  • the thickness of the heat-resistant layer may be 0.5 ⁇ m-4 ⁇ m, such as 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, or 4 ⁇ m.
  • the first monomer and/or first polymer may also be contained in the glue coating layer, and the first monomer and/or first polymer may be present in the glue coating layer in various forms.
  • the glue coating layer is formed by combining a modified second binder and a third solvent. It is obtained by coating and solidifying the mixed slurry of the agent (that is, the glue layer includes a modified second binder and a third solvent), and the modified second binder is obtained by adding the third binder. A monomer and/or a first polymer is grafted onto a base binder.
  • the third solvent is selected from one or more of N-methylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, acetone and water.
  • the usage ratio of the modified second binder and the third solvent is 1: (5-50) (for example, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50), more preferably 1: (6-20).
  • the modified second binder is obtained by the following graft modification method:
  • step (c2) subjecting the material obtained in step (c1) to a second oxidation treatment
  • step (c3) In the fourth solvent, under a protective atmosphere, the material obtained in step (c2) and the first monomer are subjected to a third contact reaction.
  • the conditions for the plasma activation treatment include: the time is 3min-10min (for example, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min), preferably 5min-8min .
  • the third contact reaction method may include: soaking the material obtained in step (c2) in a solution containing the first monomer and the fourth solvent.
  • the conditions for the third contact reaction include; the temperature is 50°C-80°C (for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C ), preferably 55°C-65°C; the time is 6h-10h (for example, 6h, 7h, 8h, 9h, 10h), preferably 7h-9h.
  • the fourth solvent is selected from acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, methanol, ethanol, One or more of isopropyl alcohol and water.
  • the base binder is, for example, selected from polytetrafluoroethylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, polyimide, polyacrylonitrile, polymethylmethacrylate, polyacrylic acid and polyacrylic acid One or more of the esters.
  • the thickness of the glue coating layer may be 0.5 ⁇ m to 2 ⁇ m. For example, it is 0.5 ⁇ m, 1 ⁇ m or 2 ⁇ m.
  • the content of the first monomer and/or first polymer in the separator can be selected within a wide range according to the number of distributed layers and demand targets. For example, relative to the total weight of the separator, the content of the first monomer and/or the first polymer can be selected within a wide range.
  • the content of a monomer and/or the first polymer may be 0.1% by weight to 20% by weight (for example, 0.1% by weight, 0.5% by weight, 1% by weight, 5% by weight, 10% by weight, 15% by weight, 20% by weight %), preferably 0.5% by weight to 10% by weight.
  • the ion channels of the separator are increased, the consistency of conduction of ions by the separator is improved, the wettability of the separator and the electrolyte is improved, and the speed and speed of ions passing through the separator are accelerated. Uniformity.
  • a second aspect of the present disclosure provides a battery, and the separator of the battery is the separator described in the first aspect of the present disclosure.
  • the materials and preparation methods of the battery other than the battery separator can all be carried out in accordance with the methods in the art, and can achieve the effects of reducing internal resistance, improving cycle performance and improving safety performance.
  • the battery is preferably a lithium ion battery.
  • the battery also includes a positive electrode sheet, a negative electrode sheet and a non-aqueous electrolyte.
  • the positive electrode sheet may be a conventional positive electrode sheet in the art.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector.
  • the positive active material layer may include a positive active material, a conductive agent, and a binder.
  • the mixing mass ratio of the positive electrode active material, conductive agent and binder is (97-99): (0.5-1.5): (0.5-1.5).
  • the positive active material is selected from lithium cobalt oxide (LiCoO 2 ) or lithium cobalt oxide (LiCoO 2 ) that has been doped and coated with two or more elements among Al, Mg, Mn, Cr, Ti, and Zr.
  • the chemical formula of lithium cobalt oxide that has been doped and coated with two or more elements among Al, Mg, Mn, Cr, Ti, and Zr is LixCo 1-y1-y2-y3-y4 A y1 B y2 C y3 D y4 O 2 ; 0.95 ⁇ x ⁇ 1.05, 0.01 ⁇ y1 ⁇ 0.1, 0.01 ⁇ y2 ⁇ 0.1, 0 ⁇ y3 ⁇ 0.1, 0 ⁇ y4 ⁇ 0.1, A, B, C, D are selected from Al, Mg, Two or more elements among Mn, Cr, Ti and Zr.
  • the positive active material is also selected from a ternary material (NCM or NCA) or a ternary material that has been doped and coated with two or more elements among Al, Mg, W, Sr, Mo, and Zr.
  • NCM or NCA the chemical formula of the ternary material that has been doped and coated with two or more elements among Al, Mg, W, Sr, Mo, and Zr is LiNix Co y Mn z M 1-xyz O 2 ; 0.33 ⁇ x ⁇ 0.96, 0 ⁇ y ⁇ 0.33, 0.03 ⁇ Z ⁇ 0.33, 0 ⁇ 1-xyz ⁇ 0.005
  • M is selected from Al, Mg, W, Sr, Mo, Zr of two or more elements.
  • the positive active material is also selected from lithium iron phosphate (LFP) or lithium iron phosphate (LFP) that has been doped and coated with two or more elements among Ti, W, V, Na, Mn, and Co.
  • the chemical formula of lithium iron phosphate that has been doped and coated with two or more elements among Ti, W, V, Na, Mn, and Co is LiFe x PN 1-x O 2 ; 0.095 ⁇ x ⁇ 1, 0.0001 ⁇ 1-X ⁇ 0.005, N is selected from two or more elements among Ti, W, V, Na, Mn and Co.
  • the conductive agent in the positive electrode active material layer is selected from acetylene black.
  • the binder in the positive active material layer is selected from polyvinylidene fluoride (PVDF).
  • the negative electrode sheet may be a conventional negative electrode sheet in the art.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector.
  • the negative electrode active material layer may include Negative active material, conductive agent and binder.
  • the negative active material is selected from graphite.
  • the negative active material optionally contains SiO x /C or Si/C, where 0 ⁇ x ⁇ 2.
  • the negative active material also contains 1wt% to 15wt% SiO x /C or Si/C, examples are 1wt.%, 2wt.%, 5wt.%, 8wt.%, 10wt.%, 12wt.%, 15wt.% or any point value within the range of the aforementioned pairs of values.
  • the battery of the present disclosure contains the separator of the present disclosure, the internal resistance of the battery is reduced, thereby improving the long-term cycle performance and improving the safety performance; and the required aging time is reduced, thereby improving the production efficiency and reducing the cost.
  • the base material polyolefin with a thickness of 5 ⁇ m is activated by plasma treatment for 6 minutes, it is treated in oxygen at a temperature of 45°C for 150 minutes to obtain a peroxide-rich base material; the peroxide-rich base material is soaked In the first monomer solution (the solvent is acetone, the amount is such that the weight ratio of the first monomer to the base material is 2:100), in the presence of a protective atmosphere, control the temperature to 60°C, and react for 8 hours to obtain the modified base material. layer.
  • the solvent is acetone, the amount is such that the weight ratio of the first monomer to the base material is 2:100
  • the first monomer is dissolved in an acetone solvent by stirring to form an acetone solution containing the first monomer and the first polymer, and alumina is added to the acetone solution containing the first monomer and the first polymer.
  • Ceramic particles stir and mix for 2 hours, so that the first monomer polymerizes on the surface of the ceramic particles to form a shell; the resulting material is spray-dried to obtain modified ceramic particles.
  • the weight ratio of shell to core of the modified ceramic particles is 20:100.
  • the modified ceramic particles (60% by weight), polyvinylidene fluoride (PVDF) (40% by weight) and acetone were mixed and stirred to obtain a slurry.
  • PVDF polyvinylidene fluoride
  • the obtained slurry is applied to the upper and lower surfaces of the base material layer and cured respectively to form a first heat-resistant layer and a second heat-resistant layer.
  • the coating material PVDF is activated by plasma treatment for 6 minutes, it is treated in oxygen at a temperature of 45°C for 150 minutes to obtain peroxide-rich PVDF; the peroxide-rich PVDF is soaked in the first monomer solution (The solvent is acetone, the amount is such that the weight ratio of the first monomer to the coating material is 10:100), in the presence of protective gas, the temperature is controlled to 60°C, and after 8 hours of reaction, the modified PVDF is obtained.
  • the modified PVDF and dimethylacetamide (DMAC) were stirred at a stirring speed of 1500 rpm for 120 min at a solid content ratio of 6% to obtain a slurry.
  • the obtained slurry is coated on the surfaces of the first heat-resistant layer and the second heat-resistant layer to form first glue layers and second glue layers.
  • a separator which consists of the first glue layer, the first heat-resistant layer, the base material layer, the second heat-resistant layer and the second glue layer from bottom to top.
  • the thickness of each layer is 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 2 ⁇ m, 1 ⁇ m.
  • the separator prepared in this comparative example does not contain modified monomers.
  • the base material layer uses polyethylene material (denoted as D j );
  • a layer of alumina ceramic slurry is coated on both sides of the base material layer to obtain a heat-resistant layer (denoted as D n ).
  • the alumina ceramic slurry is prepared with reference to Example I1, except that the alumina ceramic is not modified. ;
  • a layer of sizing material is applied to the upper and lower surfaces respectively to obtain a sizing layer (marked as D t ).
  • the sizing material is prepared with reference to Example I1, except that the PVDF is not modified.
  • a separator which consists of the first glue layer, the first heat-resistant layer, the base material layer, the second heat-resistant layer and the second glue layer from bottom to top.
  • the thickness of each layer is 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 2 ⁇ m, 1 ⁇ m.
  • Group I embodiments are used to represent the embodiments modified with structural monomers of formula (I);
  • Group II embodiments are Examples are used to represent examples of modification using structural monomers of formula (II);
  • Group III examples are used to represent examples of modification using structural monomers of formula (I) and formula (II) together. These combinations are only examples, and each structural unit of the present disclosure can be combined with each other.
  • the separators obtained in the examples were used to prepare batteries in the following manner:
  • the artificial graphite anode material with a mass proportion of 97%, the single-walled carbon nanotube (SWCNT) conductive agent with a mass proportion of 0.1%, the conductive carbon black (SP) conductive agent with a mass proportion of 0.8%, and the mass proportion of to 1% Sodium carboxymethylcellulose (CMC) binder and styrene-butadiene rubber (SBR) binder with a mass ratio of 1.1% are made into a slurry by a wet process, and coated on the negative electrode current collector with a thickness of 6 ⁇ m on the copper foil. The surface was dried (temperature: 85°C, time: 5h), rolled and die-cut to obtain the negative electrode sheet.
  • SWCNT single-walled carbon nanotube
  • SP conductive carbon black
  • SBR styrene-butadiene rubber
  • the above-prepared positive electrode sheet, separator, and negative electrode sheet are wound to obtain a bare cell without liquid injection; the bare cell is placed in the outer packaging foil, and the electrolyte prepared above is injected into the dried bare cell, and then vacuumed Processes such as packaging, standing, formation, second sealing, and sorting are used to obtain the required lithium-ion batteries.
  • the separators obtained in the above examples and comparative examples were placed in an environment of (25 ⁇ 2)°C, a circular sample with a diameter of 40mm was prepared, and the sample was allowed to stand for 2 hours in an electrolyte with an ionic conductivity of 10 ⁇ 2ms/cm. Take a completely dried conductivity cell, rinse it three times with electrolyte, then add the standard electrolyte into the conductivity cell with a dropper, and use tweezers to pick up a layer of the soaked separator and put it into the conductivity cell.
  • the prepared samples were tested for impedance using an electrochemical workstation with a scanning frequency of 1KHz-100KHz. According to the above test method, the impedance of the 1st to 5th layer separators is tested in order to obtain the ionic conductivity of the separator.
  • Ion conductivity deviation ratio (%) maximum value/minimum value ⁇ 100%.
  • the batteries obtained in the above examples and comparative examples are placed in an environment of (25 ⁇ 2)°C and left for 2-3 hours.
  • the cut-off current of the battery is 0.05C according to 1C constant current charging.
  • the battery After the battery is fully charged, leave it aside for 5 minutes, then discharge it at a constant current of 1C to a cut-off voltage of 3.0V.
  • the number of cycles reaches 1000
  • record the last discharge capacity Q1 of the battery Record the initial thickness T of the battery core.
  • the thickness after 1000 cycles is recorded as T1.
  • Table 2 The recording results are shown in Table 2.

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Abstract

本公开涉及电池技术领域，具体涉及一种隔膜以及包括该隔膜的电池。隔膜中含有第一单体和/或第一聚合物；第一单体具有式(I)或式(II)所示结构，其中，R1和R2各自独立地选自H、-CnNR3和-CnNR4R5，n为0-4的整数；NR3为4-7元杂环，R3含0-2个氧原子和/或0-2个氮原子，其余为碳原子；R3上存在或不存在接枝基团R6，R6为-CmOH，m为0-2的整数；R4和R5各自独立地为C1-C4的脂肪链。隔膜具有较高的浸润性，能够实现更低的离子电导率偏离比例；隔膜所得的电池具有更低的电阻，从而具有更好的循环性能和更高的安全性。

Description

一种隔膜和电池 技术领域
本公开涉及电池技术领域，具体涉及一种隔膜以及包括该隔膜的电池。
发明背景
近年来，电池在智能手机、平板电脑、智能穿戴、电动工具和电动汽车等领域得到了广泛的应用。随着电池的广泛应用，消费者对电池的使用寿命、应用安全性的需求不断提高，这就要求电池能够具有长循环寿命，同时兼具高安全性能。
目前，电池在使用过程中存在诸多安全隐患，例如电池在使用一段时间后，在循环过程中，尤其是高倍率循环过程中，会存在因为电池内阻过高，引起电池内部温升过高，进而容易引发严重的安全事故，起火甚至爆炸的问题。
因此，发明一种内阻更低的，从而更安全且循环性能好的电池是非常重要的。
发明内容
本公开的目的在于克服现有技术存在的上述问题，提供一种隔膜以及包括该隔膜的电池。本公开的隔膜具有较高的浸润性，能够实现更低的离子电导率偏离比例；本公开的隔膜所得的电池具有更低的电阻，从而具有更好的循环性能和更高的安全性。
本公开的发明人发现，通过增加隔膜的浸润性能够降低电池内阻。
本公开的发明人通过进一步深入研究后发现，为了增加隔膜的浸润性，可以通过用特定的化合物对隔膜进行改性，在隔膜上形成更多的“离子通道”而不再依赖于隔膜中固有的孔结构来传导离子；这些“离子通道”对离子具有导向作用，从而一方面提升了离子通过隔膜的速度，另一方面提升了隔膜导通离子的一致性，使得隔膜上离子导通率更均匀。本公开的发明人经过大量深入研究筛选出了对隔膜有较好改性效果的特定化合物。
为了实现上述目的，本公开第一方面提供了一种隔膜，所述隔膜中含有第一单体和/或第一聚合物，所述第一聚合物由所述第一单体聚合得到；
所述第一单体具有式(I)或式(II)所示结构，
其中，R1和R2各自独立地选自H、-CnNR3和-CnNR4R5，n为0-4的整数；NR3为4-7元杂环，R3含0-2个氧原子和/或0-2个氮原子，其余为碳原子；R3上存在或不存在接枝基团R6，R6为-CmOH，m为0-2的整数；R4和R5各自独立地为C1-C4的脂肪链。
本公开第二方面提供了一种电池，该电池的隔膜为本公开第一方面所述的隔膜。
通过上述技术方案，本公开与现有技术相比至少具有以下优势：
(1)本公开的隔膜的浸润性好，离子导通速度快；
(2)本公开的隔膜的导通离子的一致性好，离子电导率偏离比例低；
(3)本公开的电池的内部电流密度的一致性好；
(4)本公开的电池的内阻低；
(5)本公开的电池的容量保持率高，循环寿命长；
(6)本公开的电池的安全性能好；
(7)由于隔膜的浸润性的提升，还缩短了陈化时间，从而本公开的电池的生产效率高，生产成本低。
本公开的其它特征和优点将在随后的具体实施方式部分予以详细说明。
具体实施方式
以下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隔膜，所述隔膜中含有第一单体和/或第一聚合物，所述第一聚合物由所述第一单体聚合得到；
所述第一单体具有式(I)或式(II)所示结构，
其中，R1和R2各自独立地选自H、-CnNR3和-CnNR4R5，n为0-4的整数；NR3为4-7元杂环，R3含0-2个氧原子和/或0-2个氮原子，其余为碳原子；R3上存在或不存在接枝基团R6，R6为-CmOH，m为0-2的整数；R4和R5各自独立地为C1-C4的脂肪链。
在本公开中，通过将上述特定结构的第一单体和/或其聚合得到的第一聚合物加入到隔膜中，已经能够使隔膜实现比现有技术更低的离子电导率偏离比例，更好的浸润性和更低的电池内阻。为了进一步提高效果，可以对其中一个或多个技术特征做进一步优选。
在本公开中，所述第一聚合物是由所述第一单体聚合得到，所述聚合可以为所述第一单体进行均聚，也可以为所述第一单体与其它单体共聚。在本公开的某具体方式中，当未提及其它单体时，所述第一聚合物指的是所述第一单体进行均聚得到的聚合物。但可以理解的是，电池隔膜中使用到的常规材料的单体与所述第一单体共聚所得的聚合物也在本公开的所述第一聚合物的保护范围内。
所述隔膜可以只含有所述第一单体，也可以只含有所述第一聚合物，还可以同时含有所述第一单体和所述第一聚合物。
所述第一单体具有式(I)结构或具有式(II)结构，从结构式可以看出，所述第一单体具有呈中心对称的两个苯环和至少四个羟基基团。
R1和R2相同或不同，各自独立地选自H、-CnNR3和-CnNR4R5。
其中，n表示连接苯环与氮原子的碳原子个数，n可以为0-4的整数(如0，1，2，3)，优选为1或2。
-CnNR3中N原子与R3基团共同构成环结构，可以为4-7元杂环(如四元、五元、六元、七元)，优选为五元杂环或六元杂环。
R3基团中可以全部由碳原子组成(氢原子不计)，也可以含有0-2(如0，1，2)个氧原子和/或0-2(如0，1，2)个氮原子。
在一种具体实施方式中，R3基团由多个碳原子和一个氧原子组成。
在另一种具体实施方式中，R3基团全部由碳原子组成。
R3上可以没有接枝基团。
根据一种具体实施方式，R3上还可以存在接枝基团R6，R6为-CmOH，m为0-2(如0，1，2)的整数。
优选地，所述接枝基团R6的接枝位点为NR3杂环中与N原子对位。
列举地，-CnNR3包括但不限于以下结构：
-CnNR4R5中不含有环结构，R4和R5相同或不同，各自独立地为C1-C4的脂肪链。
在一种具体实施方式中，R4和R5各自独立地选自甲基和乙基。
列举地，所述第一单体包括但不限于以下结构：

所述第一单体和/或所述第一聚合物存在于所述隔膜中的任意位置都属于本公开的保护范围。
根据一种具体实施方式，所述隔膜包括基材层以及任选的耐热层和/或任选的涂胶层(术语“任选地”表示可以有也可以没有)；所述耐热层覆盖所述基材层一侧或两侧表面；所述涂胶层覆盖在所述耐热层的表面，和/或，所述涂胶层覆盖在所述基材层的表面。在一实例中，所述隔膜包括依次设置的涂胶层、耐热层、基材层、耐热层和涂胶层。在另一实例中，所述隔膜包括依次设置的涂胶层、基材层、耐热层和涂胶层。
所述基材层、所述耐热层和所述涂胶层中的至少一层中含有所述第一单体和/或所述第一聚合物。所述基材层、所述耐热层和所述涂胶层中可以都含有所述第一单体和/或所述第一聚合物，也可以仅其中一层或多层中含有所述第一单体和/或所述第一聚合物。因此所述基材层、所述耐热层和所述涂胶层的至少一层中含有所述第一单体和/或所述第一聚合物即属于本公开的保护范围，且能够实现本公开的目的，具有较好的技术效果。在本文中术语“一层”指的是一个层而不是一类层，例如当涂胶层中含有所述第一单体和/或所述第一聚合物时，并不要求上下两层涂胶层中均含有。
在一实例中，至少所述基材层中含有所述第一单体和/或所述第一聚合物。
在一实例中，所述基材层中以及所述耐热层和/或所述涂胶层中含有所述第一单体和/或所述第一聚合物。
在一实例中，所述基材层中含有所述第一单体和/或所述第一聚合物。
在一实例中，所述耐热层中含有所述第一单体和/或所述第一聚合物。
在一实例中，所述涂胶层中含有所述第一单体和/或所述第一聚合物。
在一实例中，所述基材层和所述涂胶层中含有所述第一单体和/或所述第一聚合物。
在一实例中，所述基材层和所述耐热层中含有所述第一单体和/或所述第 一聚合物。
在一实例中，所述耐热层和所述涂胶层中含有所述第一单体和/或所述第一聚合物。
在一实例中，所述基材层、所述耐热层和所述涂胶层中均含有所述第一单体和/或所述第一聚合物。
在同一层中，可以只含有一种结构的所述第一单体和/或所述第一聚合物，也可以含有多种结构的所述第一单体和/或所述第一聚合物。
所述第一单体和/或所述第一聚合物存在于所述隔膜中的形式可以没有特别的限定，例如可以以掺杂(共混)、接枝、部分包覆等形式存在于所述隔膜中。
在一种具体实施方式中，所述基材层的材料为用所述第一单体对基体材料进行接枝改性所得的材料。
在一实例，相对于100重量份的所述基体材料，所述第一单体的含量可以为0.1重量份-10重量份(例如1重量份、2重量份、3重量份、4重量份、5重量份、6重量份、7重量份、8重量份、9重量份、10重量份)，优选为0.5重量份-5重量份。
所述基体材料可以为本领域常规的作为隔膜基材的材料，例如选自聚乙烯、聚丙烯、聚偏氟乙烯、聚酰亚胺、聚对苯二甲酸乙二酯、聚对苯二甲酸丁二酯、聚苯乙烯、聚萘体系聚合物、聚酰胺、聚对苯撑苯并二唑和芳纶中的一种或多种。
在一实例中，基材层的材料通过以下接枝改性的方法而得到：
(a1)将基体材料进行第一等离子体活化处理；
(a2)将步骤(a1)所得材料进行第一氧气处理；
(a3)在第一溶剂中，在保护气氛下，将步骤(a2)所得材料与所述第一单体进行第一接触反应。
在步骤(a1)中，优选地，所述第一等离子体活化处理的条件包括：时间为3min-10min(例如，3min、4min、5min、6min、7min、8min、9min、10min)，优选为5min-8min。
在步骤(a2)中，优选地，所述第一氧化处理的过程包括将步骤(a1)所得材料置于氧气中，并控制条件包括：温度为30℃-60℃(例如，30℃、35℃、40℃、45℃、50℃、55℃、60℃)，优选为40-50℃；时间为100min-250min(例如，100min、120min、150min、180min、200min、220min、250min)，优选为120min-200min。经过该步骤(a2)，得到富含过氧化物的基体材料。
在步骤(a3)中，所述第一接触反应的方式可以包括：将步骤(a2)所得 材料浸泡于含有第一单体和第一溶剂的溶液中。
在步骤(a3)中，优选地，所述第一接触反应的条件包括：温度为50℃-80℃(例如，50℃、55℃、60℃、65℃、70℃、75℃、80℃)，优选为55℃-65℃；时间为6h-10h(例如，6h、7h、8h、9h、10h)，优选为7h-9h。
在步骤(a3)中，优选地，所述第一溶剂选自丙酮、四氢呋喃、二氯甲烷、氯仿、二甲基甲酰胺、N-甲基-2-吡咯烷酮、环己烷、甲醇、乙醇、异丙醇和水中的一种或多种。
由此可以得到用一种优选实施方式的第一单体接枝改性的基材层。
本领域技术人员采用其它方法使第一单体进入基材层的实施方式也均属于本公开的保护范围。
所述基材层的厚度可以为2μm-20μm，例如为2μm、3μm、4μm，5μm，6μm，7μm，8μm，9μm，10μm，12μm，16μm，18μm，20μm。
所述耐热层中也可以含有所述第一单体和/或第一聚合物，所述第一单体和/或第一聚合物可以以各种形式存在于所述耐热层中。
在一种具体实施方式中，所述耐热层中包括陶瓷颗粒，该陶瓷颗粒具有核壳结构，其中所述陶瓷颗粒的壳材料为所述第一聚合物，所述陶瓷颗粒的核材料选自氧化铝、勃姆石、氧化镁、氮化硼和氢氧化镁中的一种或多种。
所述耐热层中还可以含有其它常规的成分，例如所述耐热层中还含有第一粘结剂。所述耐热层可以通过将改性后的陶瓷颗粒与第一粘结剂混合后涂敷并固化得到。
在一实例中，所述陶瓷颗粒的壳材料为所述第一单体的均聚物。
以所述陶瓷颗粒的总重量为基准，所述陶瓷颗粒的壳材料的含量可以为5重量％-50重量％(例如为5重量％、10重量％、15重量％、20重量％、25重量％、30重量％、35重量％、40重量％、45重量％、50重量％)，所述陶瓷颗粒的核材料的含量为50重量％-95重量％(例如为95重量％、90重量％、85重量％、80重量％、75重量％、70重量％、65重量％、60重量％、55重量％、50重量％)。可以理解的是，所述陶瓷颗粒的壳材料的含量可以在5重量％-50重量％范围内取值，所述陶瓷颗粒的核材料的含量可以在50重量％-95重量％内取值，但需要满足的是，所述陶瓷颗粒的壳材料的含量与所述陶瓷颗粒的核材料的含量之和为100重量％。
根据一种具体实施方式，以所述陶瓷颗粒的总重量为基准，所述陶瓷颗粒的壳材料的含量为15重量％-25重量％，所述陶瓷颗粒的核材料的含量为75重量％-85重量％。
根据一种具体实施方式，所述陶瓷颗粒的壳通过以下方法制备得到：
(b1)在第二溶剂中，将核材料与第一单体进行第二接触，得到固液混合物；
(b2)将所述固液混合物进行干燥。
在步骤(b1)中，优选地，所述第二溶剂选自丙酮、四氢呋喃、二氯甲烷、氯仿、二甲基甲酰胺、N-甲基-2-吡咯烷酮、环己烷、甲醇、乙醇、异丙醇和水中的一种或多种。
在步骤(b1)中，为了避免过程中的损失，第一单体的用量可以是过量的，第一单体的用量多于实际成壳的量，用量使得能实现上述核壳比的要求即可。
在步骤(b1)中，所述第二接触例如为搅拌混合。
在步骤(b1)中，所述固液混合物中第一单体已经发生部分和/或全部聚合。所述固液混合物中含有第一单体和/或第一聚合物。
在步骤(b2)中，所述干燥例如为真空加热干燥或喷雾干燥。
由此，得到具有壳(第一单体均聚成壳)核结构的改性后的陶瓷颗粒。
所述耐热层中还可以包括第一粘结剂。
优选地，所述耐热层中的第一粘结剂选自聚四氟乙烯、聚偏氟乙烯、六氟丙烯-偏氟乙烯共聚物、聚酰亚胺、聚丙烯腈、聚甲基丙烯酸甲酯、聚丙烯酸、聚丙烯酸酯中的一种或多种。
根据一种具体实施方式，所述耐热层通过将改性陶瓷颗粒与第一粘结剂混合后涂敷并固化得到。根据对耐热性能的需求，所述陶瓷颗粒的含量可以在较大范围内选择。以所述耐热层的总重量为基准，所述陶瓷颗粒的含量可以为20重量％-99重量％(例如，20重量％、30重量％、40重量％、50重量％、60重量％、70重量％、80重量％、90重量％、99重量％)，所述第一粘结剂的含量可以为1重量％-80重量％(例如，1重量％、10重量％、20重量％、30重量％、40重量％、50重量％、60重量％、70重量％、80重量％)；优选地，所述陶瓷颗粒的含量可以为50重量％-95重量％，所述第一粘结剂的含量可以为5重量％-50重量％。
所述第一粘结剂中可以不含有所述第一单体和/或第一聚合物。
所述第一粘结剂中也可以含有所述第一单体和/或第一聚合物，可以参考下文第二粘结剂的改性方法得到。
所述耐热层的厚度可以为0.5μm-4μm，例如为0.5μm，1μm，1.5μm，2μm，2.5μm，3μm，4μm。
所述涂胶层中也可以含有所述第一单体和/或第一聚合物，所述第一单体和/或第一聚合物可以以各种形式存在于所述涂胶层中。
在一种具体实施方式中，所述涂胶层通过将改性后的第二粘结剂和第三溶 剂的混合浆料涂敷固化而得到(即，所述涂胶层包括改性后的第二粘结剂和第三溶剂)，所述改性后的第二粘结剂通过将所述第一单体和/或第一聚合物接枝在基础粘结剂上而得到。
优选地，所述第三溶剂选自N-甲基吡咯烷酮、N、N-二甲基乙酰胺、N、N-二甲基甲酰胺、丙酮和水中一种或多种。
优选地，所述改性后的第二粘结剂和所述第三溶剂的用量比为1：(5-50)(例如，1:5、1:10、1:15、1:20、1:25、1:30、1:35、1:40、1:45、1:50)，更优选为1：(6-20)。
在一实例中，所述改性后的第二粘结剂通过以下接枝改性的方法而得到：
(c1)将基础粘结剂进行第二等离子体活化处理；
(c2)将步骤(c1)所得材料进行第二氧化处理；
(c3)在第四溶剂中，在保护气氛下，将步骤(c2)所得材料与所述第一单体进行第三接触反应。
在步骤(c1)中，优选地，所述等离子体活化处理的条件包括：时间为3min-10min(例如，3min、4min、5min、6min、7min、8min、9min、10min)，优选为5min-8min。
在步骤(c2)中，优选地，所述第二氧化处理的过程包括将步骤(c1)所得材料置于氧气中，并控制条件包括：温度为30℃-60℃(例如，30℃、35℃、40℃、45℃、50℃、55℃、60℃)，优选为40℃-50℃；时间为100min-250min(例如，100min、120min、150min、180min、200min、220min、250min)，优选为120min-200min。经过该步骤(a2)，得到富含过氧化物的基础粘结剂。
在步骤(c3)中，所述第三接触反应的方式可以包括：将步骤(c2)所得材料浸泡于含有第一单体和第四溶剂的溶液中。
在步骤(c3)中，优选地，所述第三接触反应的条件包括；温度为50℃-80℃(例如，50℃、55℃、60℃、65℃、70℃、75℃、80℃)，优选为55℃-65℃；时间为6h-10h(例如，6h、7h、8h、9h、10h)，优选为7h-9h。
在步骤(c3)中，优选地，所述第四溶剂选自丙酮、四氢呋喃、二氯甲烷、氯仿、二甲基甲酰胺、N-甲基-2-吡咯烷酮、环己烷、甲醇、乙醇、异丙醇和水中的一种或多种。
所述基础粘结剂例如选自聚四氟乙烯、聚偏氟乙烯、六氟丙烯-偏氟乙烯共聚物、聚酰亚胺、聚丙烯腈、聚甲基丙烯酸甲酯、聚丙烯酸和聚丙烯酸酯中的一种或多种。
优选地，相对于100重量份的所述基础粘结剂，所述第一单体的用量为0.1重量份-20重量份(例如，0.1重量份、0.5重量份、1重量份、5重量份、 10重量份、15重量份、20重量份)，更优选为1重量份-15重量份，进一步优选为8重量份-12重量份。
所述涂胶层的厚度可以为0.5μm～2μm。例如为0.5μm、1μm或2μm。
以上对基材层、耐热层和涂胶层的改性方式分别予以了示例性说明。
所述隔膜中所述第一单体和/或第一聚合物的含量可以根据分布的层数和需求目标在较大的范围内选择，例如，相对于所述隔膜的总重量，所述第一单体和/或第一聚合物的含量可以为0.1重量％-20重量％(例如，0.1重量％、0.5重量％、1重量％、5重量％、10重量％、15重量％、20重量％)，优选为0.5重量％-10重量％。
通过将第一单体/第一聚合物引入隔膜中，增加了隔膜的离子通道，提高了隔膜导通离子的一致性，提升了隔膜与电解液的浸润性，加快了离子通过隔膜的速度和均一性。
本公开第二方面提供了一种电池，该电池的隔膜为本公开第一方面所述的隔膜。
所述电池除电池隔膜以外的材料和制备方法均可以按照本领域的方式进行，均能够实现内阻降低，循环性能提高和安全性能提高的效果。
所述电池优选为锂离子电池。
所述电池还包括正极片、负极片和非水电解液。
所述正极片可以为本领域常规的正极片，例如，所述正极片包括正极集流体和涂覆在正极集流体一侧或两侧表面的正极活性物质层。
所述正极活性物质层可以包括正极活性物质、导电剂和粘结剂。
在一实例中，所述正极活性物质、导电剂和粘结剂的混合质量比为(97-99):(0.5-1.5):(0.5-1.5)。
在一实例中，所述正极活性物质选自钴酸锂(LiCoO2)或经过Al、Mg、Mn、Cr、Ti、Zr中两种或多种元素掺杂包覆处理的钴酸锂(LiCoO2)，所述经过Al、Mg、Mn、Cr、Ti、Zr中两种或多种元素掺杂包覆处理的钴酸锂的化学式为LixCo1-y1-y2-y3-y4Ay1By2Cy3Dy4O2；0.95≤x≤1.05，0.01≤y1≤0.1，0.01≤y2≤0.1，0≤y3≤0.1，0≤y4≤0.1，A、B、C、D选自Al、Mg、Mn、Cr、Ti、Zr中两种或多种元素。
在一实例中，所述正极活性物质还选自三元材料(NCM或者NCA)或经过Al、Mg、W、Sr、Mo、Zr中两种或多种元素掺杂包覆处理的三元材料(NCM或者NCA)，所述经过Al、Mg、W、Sr、Mo、Zr中两种或多种元素掺杂包覆处理的三元材料的化学式为LiNixCoyMnzM1-x-y-zO2；0.33≤x≤0.96，0≤y≤0.33，0.03≤Z≤0.33，0≤1-x-y-z≤0.005，M选自Al、Mg、W、Sr、Mo、Zr 中两种或多种元素。
在一实例中，所述正极活性物质还选自磷酸铁锂(LFP)或经过Ti、W、V、Na、Mn、Co中两种或多种元素掺杂包覆处理的磷酸铁锂(LFP)，所述经过Ti、W、V、Na、Mn、Co中两种或多种元素掺杂包覆处理的磷酸铁锂的化学式为LiFexPN1-xO2；0.095≤x≤1，0.0001≤1-X≤0.005，N选自Ti、W、V、Na、Mn、Co中两种或多种元素。
在一实例中，所述正极活性物质层中的导电剂选自乙炔黑。
在一实例中，所述正极活性物质层中的粘结剂选自聚偏氟乙烯(PVDF)。
所述负极片可以为本领域常规的负极片，例如，所述负极片包括负极集流体和涂覆在负极集流体一侧或两侧表面的负极活性物质层，所述负极活性物质层可以包括负极活性物质、导电剂和粘结剂。
在一实例中，所述负极活性物质选自石墨。
在一实例中，所述负极活性物质还任选地含有SiOx/C或Si/C，其中0<x<2。例如，所述负极活性物质还含有1wt％～15wt％SiOx/C或Si/C，示例性为1wt.％、2wt.％、5wt.％、8wt.％、10wt.％、12wt.％、15wt.％或者是前述两两数值组成的范围内的任一点值。
本公开的电池由于含有本公开所述隔膜，电池内阻降低，进而长期循环性能提高，安全性能提高；且需要的陈化时间减少，从而生产效率提高且成本降低。
以下将通过实施例对本公开进行详细描述。本公开所描述的实施例仅是本公开一部分实施例，而不是全部的实施例。基于本公开中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本公开保护的范围。
实施例I1
本实施例使用(I-1)所示结构的第一单体进行改性。
按照以下步骤制备隔膜。
(1)改性基材层
将厚度为5μm的基体材料聚烯烃经等离子体处理6min活化后，在温度为45℃的氧气中处理150min，得到富含过氧化物的基体材料；将所述富含过氧化物的基体材料浸泡于第一单体溶液(溶剂为丙酮，用量使第一单体与基体材料的重量比为2：100)中，在保护气氛存在下，控制温度60℃，反应8h得到改性后的基材层。
(2)改性陶瓷颗粒并形成耐热层
将第一单体通过搅拌的方式溶解于丙酮溶剂中，形成含有第一单体和第一聚合物的丙酮溶液，在所述含有第一单体和第一聚合物的丙酮溶液中加入氧化铝陶瓷颗粒，搅拌混合2小时，使得第一单体在陶瓷颗粒表面聚合成壳；将所得物料进行喷雾干燥，得到改性陶瓷颗粒。该改性陶瓷颗粒的壳核重量比为20：100。
将所述改性陶瓷颗粒(60重量％)、聚偏氟乙烯(PVDF)(40重量％)和丙酮混合搅拌，得到浆料。
将所得浆料在基材层的上下表面分别涂敷并固化，形成第一耐热层和第二耐热层。
(3)改性并形成涂胶层
将涂胶材料PVDF经等离子体处理6min活化后，在温度为45℃的氧气中处理150min，得到富含过氧化物的PVDF；将所述富含过氧化物的PVDF浸泡于第一单体溶液(溶剂为丙酮，用量使第一单体与涂胶材料的重量比为10：100)中，在保护气体存在下，控制温度为60℃，反应8h后，得到改性的PVDF。将所述改性的PVDF与二甲基乙酰胺(DMAC)按照6％固含量的比例在1500rpm的搅拌速度下搅拌120min，得到浆料。将所得浆料涂覆在第一耐热层和第二耐热层的表面，形成第一涂胶层和第二涂胶层。
最终得到自下到上依次为第一涂胶层、第一耐热层、基材层、第二耐热层和第二涂胶层的隔膜，各层的厚度依次为1μm、2μm、5μm、2μm、1μm。
对比例1
本对比例制备的隔膜中不含有改性单体。
基材层使用聚乙烯基材(记为Dj)；
在基材层双面涂覆一层氧化铝陶瓷浆料，得到耐热层(记为Dn)，该氧化铝陶瓷浆料参照实施例I1制备，所不同的是不对氧化铝陶瓷进行改性；
在上下表面分别涂覆一层胶料，得到涂胶层(记为Dt)，该胶料参照实施例I1制备，所不同的是不对PVDF进行改性。
最终得到自下到上依次为第一涂胶层、第一耐热层、基材层、第二耐热层和第二涂胶层的隔膜，各层的厚度依次为1μm、2μm、5μm、2μm、1μm。
其它实施例
各实施例参照实施例I1进行，所不同的是，基材层、耐热层和涂胶层分别改变第一单体的具体选择或不进行改性，具体如表1所示。
其中，I组实施例用于表示用式(I)结构单体进行改性的实施例；II组实 施例用于表示用式(II)结构单体进行改性的实施例；III组实施例用于表示用式(I)和式(II)结构单体共同进行改性的实施例。这些组合方式仅用于示例，本公开的各结构单体之间均可以进行组合。
表1
将实施例所得隔膜分别按照以下方式制备电池：
(1)正极片制备
将正极活性物质LiCoO2、粘结剂聚偏氟乙烯(PVDF)、导电剂乙炔黑按照重量比98:1.0:1.0进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌，直至混合体系成均一流动性的正极浆料；将正极浆料均匀涂覆于厚度为10μm的铝箔上；将上述涂覆好的铝箔在5段不同温度梯度的烘箱烘烤后，再将其在120℃的烘箱干燥8h，然后经过辊压、分切得到所需的正极片。
(2)负极片制备
将质量占比为97％的人造石墨负极材料，质量占比为0.1％的单壁碳纳米管(SWCNT)导电剂、质量占比为0.8％的导电炭黑(SP)导电剂、质量占比为1％ 的羧甲基纤维素钠(CMC)粘结剂及质量占比为1.1％的丁苯橡胶(SBR)粘结剂以湿法工艺制成浆料，涂覆于负极集流体厚度6μm铜箔的表面，经烘干(温度：85℃，时间：5h)、辊压和模切得到负极片。
(3)非水电解液制备
在充满氩气的手套箱(水分<10ppm，氧分<1ppm)中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、丙酸丙酯(PP)以2:1.5:2质量比混合均匀，在混合溶液中缓慢加入基于非水电解液总质量14wt.％的LiPF6、基于非水电解液总质量5～60wt.％的丙酸乙酯，搅拌均匀得到非水电解液。
(4)隔膜
隔膜分别使用上述各实施例和对比例所得隔膜。
(5)锂离子电池的制备
将上述准备的正极片、隔膜、负极片通过卷绕得到未注液的裸电池；将裸电池置于外包装箔中，将上述制备好的电解液注入到干燥后的裸电池中，经过真空封装、静置、化成、二封、分选等工序，获得所需的锂离子电池。
测试例
将所得隔膜和电池分别进行以下测试：
(1)对隔膜进行离子电导率的测试
将上述实施例和对比例所得隔膜置于(25±2)℃环境中，制备直径为40mm的圆形样品，将样品在离子电导率为10±2ms/cm的电解液中静置2h。取完全烘干的电导池，用电解液润洗3次，然后用滴管将标准电解液加入电导池中，用镊子将浸泡好的隔膜夹取一层放入电导池内。将制备好的样品用电化学工作站进行阻抗测试，扫描频率在1KHz-100KHz。按照以上测试方法依次测试1层至5层隔膜的阻抗得到隔膜的离子电导率。
记录100组数据，计算离子电导率偏离比例。离子电导率偏离比例(％)＝最大值/最小值×100％。
(2)对电池进行电化学性能测试
将上述实施例和对比例所得电池置于(25±2)℃环境中，静置2-3h，待电池本体达到(25±2)℃时，电池按照1C恒流充电截止电流为0.05C，电池充满电后搁置5min，再以1C恒流放电至截止电压3.0V，记录前3次循环的最高放电容量为初始容量Q，当循环次数达到1000次时，记录电池最后一次的放电容量Q1；记录电芯初始厚度T，当循环至1000次的厚度记为T1，记录结果如表2。
其中用到的计算公式如下：容量保持率(％)＝Q1/Q×100％。
将所得结果记于表2中。
表2
*对比例1由常规隔膜制得的电池，在对其进行电池容量保持率测试时，循环608周后，电池容量保持率骤降至60％，之后电池容量保持率下降迅速，无法完成1000周测试。
通过表2可以看出，通过对比例和实施例可以看出，实施例的隔膜的离子电导率偏离比例明显降低，实施例的隔膜制得的电池的容量保持率明显提升，说明本公开的第一单体和/第一聚合物的引入，提升了隔膜的导通离子的一致性，降低了电池的内阻，增长了电池的循环寿命，提高了电池的安全性能。
以上详细描述了本公开的优选实施方式，但是，本公开并不限于此。在本公开的技术构思范围内，可以对本公开的技术方案进行多种简单变型，包括各个技术特征以任何其它的合适方式进行组合，这些简单变型和组合同样应当视为本公开所公开的内容，均属于本公开的保护范围。

Claims (14)

  1. 一种隔膜，其特征在于，所述隔膜中含有第一单体和/或第一聚合物，所述第一聚合物由所述第一单体聚合得到；
    所述第一单体具有式(I)或式(II)所示结构，
    其中，R1和R2各自独立地选自H、-CnNR3和-CnNR4R5，n为0-4的整数；NR3为4-7元杂环，R3含0-2个氧原子和/或0-2个氮原子，其余为碳原子；R3上存在或不存在接枝基团R6，R6为-CmOH，m为0-2的整数；R4和R5各自独立地为C1-C4的脂肪链。
  2. 根据权利要求1所述的隔膜，其中，n为1或2；NR3为五元或六元杂环，R3含0-1个氧原子，其余为碳原子；R3上存在或不存在接枝基团R6，R6为OH；R4和R5各自独立地选自甲基和乙基；
    优选地，-CnNR3选自以下结构：
  3. 根据权利要求1或2所述的隔膜，其中，所述第一单体选自以下结构：
  4. 根据权利要求1-3中任意一项所述的隔膜，其中，所述隔膜包括基材层以及任选的耐热层和/或任选的涂胶层；所述耐热层覆盖所述基材层一侧或两侧表面；所述涂胶层覆盖在所述耐热层的表面，和/或，所述涂胶层覆盖在所述基材层的表面。
  5. 根据权利要求4所述的隔膜，其中，所述基材层、所述耐热层和所述涂胶层中至少一层含有所述第一单体和/或所述第一聚合物；
    优选地，至少所述基材层中含有所述第一单体和/或所述第一聚合物；
    优选地，所述基材层中以及所述耐热层和/或所述涂胶层中含有所述第一单体和/或所述第一聚合物；
    优选地，所述耐热层和所述涂胶层中含有所述第一单体和/或所述第一聚合物；
    优选地，所述基材层、所述耐热层和所述涂胶层中均含有所述第一单体和/或所述第一聚合物。
  6. 根据权利要求4或5所述的隔膜，其中，所述基材层的材料为用所述第一 单体对基体材料进行接枝改性所得的材料；
    和/或，所述基体材料选自聚乙烯、聚丙烯、聚偏氟乙烯、聚酰亚胺、聚对苯二甲酸乙二酯、聚对苯二甲酸丁二酯、聚苯乙烯、聚萘体系聚合物、聚酰胺、聚对苯撑苯并二唑和芳纶等中的一种或多种；
    和/或，100重量份的所述基体材料，所述第一单体的含量为0.1重量份-10重量份；
    和/或，所述基材层的厚度为2μm-20μm。
  7. 根据权利要求4-6中任一项所述的隔膜，其中，所述耐热层中包括陶瓷颗粒和第一粘结剂，该陶瓷颗粒具有核壳结构，其中所述陶瓷颗粒的壳材料为所述第一聚合物，所述陶瓷颗粒的核材料选自氧化铝、勃姆石、氧化镁、氮化硼和氢氧化镁中的一种或多种；
    和/或，以所述陶瓷颗粒的总重量为基准，所述壳材料的含量为5重量％-50重量％，所述核材料的含量为50重量％-95重量％；
    和/或，以所述耐热层的总重量为基准，所述陶瓷颗粒的含量为20重量％-99重量％，所述第一粘结剂的含量为1重量％-80重量％；
    和/或，所述耐热层的厚度为0.5μm-4μm。
  8. 根据权利要求7所述的隔膜，其中，所述第一粘结剂中含有所述第一单体和/或第一聚合物。
  9. 根据权利要求4-8中任一项所述的隔膜，其中，所述涂胶层包括改性后的第二粘结剂和第三溶剂，所述改性后的第二粘结剂通过将所述第一单体和/或第一聚合物接枝在基础粘结剂上而得到；
    优选地，所述第三溶剂选自N-甲基吡咯烷酮、N、N-二甲基乙酰胺、N、N-二甲基甲酰胺、丙酮和水中一种或多种。
  10. 根据权利要求9所述的隔膜，其中，所述改性后的第二粘结剂和所述第三溶剂的用量比为1：(5-50)，优选为1：(6-20)。
  11. 根据权利要求9或10所述的隔膜，其中，相对于100重量份的所述基础粘结剂，所述第一单体的用量为0.1重量份-20重量份，优选为1重量份-15重量份，进一步优选为8重量份-12重量份；
    和/或，所述涂胶层的厚度为0.5μm～2μm。
  12. 根据权利要求1-11中任意一项所述的隔膜，其中，相对于所述隔膜的总重量，所述第一单体和/或第一聚合物的含量为0.1重量％-20重量％，优选为0.5重量％-10重量％。
  13. 一种电池，其特征在于，该电池的隔膜为权利要求1-12中任意一项所述的隔膜。
  14. 根据权利要求13所述的电池，其中，所述电池为锂离子电池。
PCT/CN2023/101847 2022-07-08 2023-06-21 一种隔膜和电池 WO2024007863A1 (zh)

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