WO2024065367A1 - 隔离膜及其制备方法、二次电池和用电装置 - Google Patents

隔离膜及其制备方法、二次电池和用电装置 Download PDF

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WO2024065367A1
WO2024065367A1 PCT/CN2022/122476 CN2022122476W WO2024065367A1 WO 2024065367 A1 WO2024065367 A1 WO 2024065367A1 CN 2022122476 W CN2022122476 W CN 2022122476W WO 2024065367 A1 WO2024065367 A1 WO 2024065367A1
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material layer
mixed material
substrate layer
lithium
layer
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PCT/CN2022/122476
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English (en)
French (fr)
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范玉磊
刘锋
钟韡
葛销明
欧阳楚英
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/122476 priority Critical patent/WO2024065367A1/zh
Publication of WO2024065367A1 publication Critical patent/WO2024065367A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to an isolation membrane, a method for preparing the isolation membrane, a secondary battery and an electrical device.
  • batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • the isolation membrane used in the battery is easily punctured by lithium dendrites or sodium dendrites on the negative electrode sheet, thereby causing a short circuit problem in the battery, which seriously affects the service life of the battery; in addition, the electrolyte wettability of the existing isolation membrane is poor, resulting in low lithium ion or sodium ion conduction rate, which affects the charge and discharge rate of the battery; in addition, the existing isolation membrane is prone to severe shrinkage when heated, which can easily lead to serious safety problems.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a separator, a method for preparing a separator, a secondary battery and an electrical device.
  • the separator of the present application can delay the occurrence of lithium dendrites or sodium dendrites piercing the separator, thereby delaying the occurrence of short circuits in the battery and extending the battery life;
  • the separator of the present application can improve the wettability of the separator to the electrolyte, increase the transmission rate of sodium ions or lithium ions, and increase the charge and discharge rate of the battery;
  • the separator of the present application can also improve the thermal shrinkage performance of the battery and improve the battery safety; and the separator of the present application can prevent the inorganic material from reacting with the negative electrode to consume lithium or sodium metal, thereby improving the first coulomb efficiency of the battery.
  • the first aspect of the present application provides an isolation film, comprising a first substrate layer, a mixed material layer and a second substrate layer; the mixed material layer is arranged between the first substrate layer and the second substrate layer; the mixed material layer comprises an inorganic material and a dispersant; wherein,
  • the electronic conductivity ⁇ of the isolation membrane satisfies: 1 ⁇ 10 -13 mS/cm ⁇ 1 ⁇ 10 -1 mS/cm.
  • the holes and electrons in the inorganic material move in a directed manner, making the inorganic material electronically conductive; inorganic materials have different crystal forms in their structures, and different crystal forms have different effects on electronic conductivity, which causes the same type of inorganic materials to exhibit a wide range of electronic conductivity distribution due to structural differences; when the isolation membrane contains inorganic materials, the electronic conductivity of the isolation membrane also presents a wide range of variation.
  • the present application adopts an isolation membrane that meets a certain electronic conductivity to make the inorganic material in the mixed material layer react with the lithium dendrites or sodium dendrites on the negative electrode sheet, thereby delaying the occurrence of lithium dendrites or sodium dendrites piercing the membrane, delaying the occurrence of internal short circuits in the battery, and extending the service life of the battery.
  • it can reduce the deposition of lithium ions on the surface of the isolation membrane, thereby reducing the self-discharge and internal short circuits in the battery.
  • the present application improves the wettability of the isolation membrane to the electrolyte through the mixed material layer, increases the transmission rate of sodium ions or lithium ions, and increases the charge and discharge rate of the battery.
  • the present application improves the thermal shrinkage performance of the battery and improves the safety of the battery by adopting a mixed material layer. Moreover, when the negative electrode is lithium metal or sodium metal, the present application separates the mixed material layer from the negative electrode through the first substrate layer or the second substrate layer, thereby avoiding the reaction of the mixed material layer with the negative electrode and consuming lithium or sodium metal in advance, thereby ensuring the first coulomb efficiency of the battery.
  • the inorganic material is selected from one or more of the following (1)-(3):
  • the inorganic material is one or more selected from silicon dioxide, silicon monoxide, silicon, zinc oxide, tin oxide, copper oxide, iron phosphate, barium titanate, cobalt oxide, manganese oxide, iron oxide, copper nitride and lithium aluminum titanium phosphate.
  • the mixed material layer using the above-mentioned inorganic materials can react with lithium dendrites or sodium dendrites, further delaying the occurrence of lithium dendrites or sodium dendrites piercing the isolation membrane, delaying the occurrence time of short circuit in the battery, and extending the service life of the battery; the mixed material layer using the above-mentioned inorganic materials further improves the wettability of the isolation membrane to the electrolyte, improves the transmission rate of sodium ions or lithium ions, and improves the battery charge and discharge rate; the mixed material layer containing the above-mentioned inorganic materials further improves the thermal shrinkage performance of the battery and improves the battery safety.
  • the mass content of the inorganic material is 75%-99.7%, and the mass content of the dispersant is 0.1%-15%, and optionally 0.1%-5%.
  • the above-mentioned mass content is conducive to promoting the reaction between the mixed material layer and lithium dendrites or sodium dendrites, further delaying the occurrence of lithium dendrites or sodium dendrites piercing the diaphragm, delaying the occurrence of short circuit in the battery caused by this, and extending the service life of the battery. At the same time, it can keep the inorganic material uniformly dispersed in the mixed material layer to ensure the normal function of the mixed material layer.
  • the ratio of the particle size D v 50 of the inorganic material to the average pore size of the first substrate layer is 1:1-243:1; and/or,
  • the ratio of the particle size D v 50 of the inorganic material to the average pore size of the second substrate layer is 1:1-243:1.
  • the above-mentioned ratio range is conducive to the contact between lithium dendrites or sodium dendrites and inorganic material particles after piercing the substrate layer, and is also conducive to better reaction kinetics between the mixed material layer and lithium dendrites or sodium dendrites; and the above-mentioned ratio range reduces the blockage of the pores on the substrate layer by inorganic material particles.
  • the dispersant is selected from one or more of sodium polyacrylate, ammonium polyacrylate, sodium hexafluorophosphate, sodium carboxymethyl cellulose, hydrolyzed polymaleic anhydride, acrylic block polymers, polyester block polymers, polyethylene glycol-type polyols, polyvinyl alcohol and polyethyleneimine derivatives.
  • the thickness of the mixed material layer is 0.5-10 ⁇ m
  • the isolation film has a thickness of 11-24 ⁇ m.
  • the mixed material layer can react with the lithium dendrites or sodium dendrites on the negative electrode sheet to delay the occurrence of lithium dendrites or sodium dendrites piercing the diaphragm and delay the occurrence of battery short circuit caused by lithium or sodium precipitation; on the other hand, it reduces the volume occupied by the isolation membrane and improves the energy density of the battery cell.
  • the mixed material layer further comprises a polymer, and the polymer is selected from one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB);
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA ethylene-vinyl acetate copolymer
  • PAA polyacrylic acid
  • CMC carboxymethyl cellulose
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • the mass content of the polymer is 0.1%-20%.
  • the polymer helps the components of the hybrid material layer to adhere to each other.
  • a protective layer is further provided on the surface of the first substrate layer away from the mixed material layer and/or on the surface of the second substrate layer away from the mixed material layer; optionally, the protective layer comprises one or more selected from alumina and boehmite.
  • the wettability of the separator to the electrolyte and the high-voltage resistance of the separator can be further improved.
  • the second aspect of the present application also provides a method for preparing an isolation film, comprising the following steps:
  • the isolation membrane includes a first substrate layer, a mixed material layer and a second substrate layer; the mixed material layer is arranged between the first substrate layer and the second substrate layer; the mixed material layer contains an inorganic material, a dispersant and an optional polymer; the electronic conductivity ⁇ of the isolation membrane satisfies: 1 ⁇ 10-13 mS/cm ⁇ 1 ⁇ 10-1 mS/cm; the definitions of the inorganic material, the dispersant and the polymer are as in the first aspect of the present application.
  • the present application delays the occurrence of lithium dendrites or sodium dendrites piercing the diaphragm by allowing the mixed material layer to react with the lithium dendrites or sodium dendrites on the negative electrode sheet, delays the occurrence of short circuit in the battery, and extends the service life of the battery.
  • the amount of lithium ion deposition on the surface of the isolation membrane can be reduced, thereby reducing the self-discharge and internal short circuit in the battery.
  • the present application improves the wettability of the isolation membrane to the electrolyte through the mixed material layer, increases the transmission rate of sodium ions or lithium ions, and increases the charge and discharge rate of the battery.
  • the present application improves the thermal shrinkage performance of the battery and improves the safety of the battery by adopting the mixed material layer. Moreover, when the negative electrode is lithium metal or sodium metal, the present application separates the mixed material layer from the negative electrode through the first substrate layer or the second substrate layer, thereby avoiding the reaction of the mixed material layer with the negative electrode and consuming lithium or sodium metal in advance, thereby ensuring the first coulomb efficiency of the battery.
  • a third aspect of the present application provides a secondary battery, comprising the isolation membrane of the first aspect of the present application or the isolation membrane prepared by the method of the second aspect of the present application.
  • the positive electrode active material includes one or more selected from lithium iron phosphate, nickel-cobalt-manganese ternary material, lithium manganese oxide, lithium cobalt oxide and lithium nickel oxide; and/or, the negative electrode active material includes one or more selected from graphite, silicon-carbon compounds, silicon-oxygen compounds and lithium metal.
  • a fourth aspect of the present application provides an electrical device, comprising the secondary battery of the third aspect of the present application.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • “Scope” disclosed in the present application is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range.
  • the scope defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can continue to be used by recharging to activate the active materials after the battery is discharged.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • active ions such as lithium ions and sodium ions
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.
  • the electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct active ions.
  • One embodiment of the present application provides a separation film, comprising a first substrate layer, a mixed material layer, and a second substrate layer; the mixed material layer is disposed between the first substrate layer and the second substrate layer; the mixed material layer comprises an inorganic material and a dispersant; wherein,
  • the electronic conductivity ⁇ of the isolation membrane satisfies: 1 ⁇ 10 -13 mS/cm ⁇ 1 ⁇ 10 -1 mS/cm; optionally, 1 ⁇ 10 -11 mS/cm ⁇ 1 ⁇ 10 -3 mS/cm, more optionally, 1.5 ⁇ 10 -11 mS/cm ⁇ 9 ⁇ 10 -4 mS/cm, for example, 10 -10 mS/cm, 10 -9 mS/cm, 10 -8 mS/cm, 10 -6 mS/cm, 10 -5 mS/cm, 10 -4 mS/cm, and a range consisting of any two of the above values as endpoints.
  • the holes and electrons in the inorganic material move in a directed manner, making the inorganic material electronically conductive; inorganic materials have different crystal forms in their structures, and different crystal forms have different effects on electronic conductivity, which causes the same type of inorganic materials to exhibit a wide range of electronic conductivity distribution due to structural differences; when the isolation membrane contains inorganic materials, the electronic conductivity of the isolation membrane also presents a wide range of variation.
  • the applicant unexpectedly found that: first, when the ends of the lithium dendrites or sodium dendrites on the negative electrode sheet pierce the first substrate layer or the second substrate layer and contact the mixed material layer, and the electronic conductivity ⁇ of the separator is greater than 1 ⁇ 10 -13 mS/cm, it is conducive to the reaction between the inorganic material in the mixed material layer and the lithium dendrites or sodium dendrites, thereby delaying the occurrence time of the lithium dendrites or sodium dendrites piercing the separator, delaying the occurrence of short circuit in the battery, and extending the service life of the battery; and, when the electronic conductivity ⁇ of the separator is less than 1 ⁇ 10 -1 mS/cm, which can reduce the amount of lithium ion deposition on the surface of the isolation membrane, thereby reducing the self-discharge and internal short circuit in the battery; secondly, the mixed material layer of the present application has a strong affinity for the electrolyte, which
  • the electronic conductivity ⁇ of the isolation membrane may be measured by conventional methods in the art, for example, by the following specific method:
  • a thermal pressure resistance meter is used to perform impedance testing under certain pressure and voltage.
  • the test area of the isolation membrane is S, and the resistance value R of the isolation membrane is measured; the electronic conductivity ⁇ of the isolation membrane is calculated according to the following formula;
  • H H ⁇ (1-porosity)
  • H the initial thickness of the isolation membrane
  • l the thickness of the isolation membrane after the pores are eliminated under the above pressure
  • the thickness and area of the diaphragm are measured, and the apparent volume V of the diaphragm is calculated.
  • the weight M of the diaphragm is measured, and ⁇ represents the theoretical density of the substrate in the diaphragm.
  • the porosity P of the diaphragm is calculated according to the following formula.
  • the inorganic material is selected from one or more of the following (1)-(3):
  • the inorganic material is one or more selected from silicon dioxide, silicon monoxide, silicon, zinc oxide, tin oxide, copper oxide, iron phosphate, barium titanate, cobalt oxide, manganese oxide, iron oxide, copper nitride and lithium aluminum titanium phosphate.
  • the mixed material layer using the above-mentioned inorganic materials can react with lithium dendrites or sodium dendrites, further delaying the occurrence of lithium dendrites or sodium dendrites piercing the isolation membrane, delaying the occurrence time of short circuit in the battery, and extending the service life of the battery; the mixed material layer using the above-mentioned inorganic materials further improves the wettability of the isolation membrane to the electrolyte, improves the transmission rate of sodium ions or lithium ions, and improves the battery charge and discharge rate; the mixed material layer containing the above-mentioned inorganic materials further improves the thermal shrinkage performance of the battery and improves the battery safety.
  • the mass content of the inorganic material is 75%-99.7%, for example 98.5%, 94%, 90%, 85%, 80%, 76%; the mass content of the dispersant is 0.1%-15%, optionally 0.1%-5%, for example 0.5%, 1%, 4%, 5%, and a range consisting of any two of the above values as endpoints.
  • the above-mentioned mass content is conducive to promoting the reaction between the mixed material layer and lithium dendrites or sodium dendrites, further delaying the occurrence of lithium dendrites or sodium dendrites piercing the diaphragm, delaying the occurrence of short circuit in the battery caused by this, and extending the service life of the battery. At the same time, it can keep the inorganic material uniformly dispersed in the mixed material layer to ensure the normal function of the mixed material layer.
  • the ratio of the particle size D v 50 of the inorganic material to the average pore size of the first substrate layer is 1:1-243:1, for example 4:1, 5:1, 8:1, 10:1, 11:1, 12:1, 14:1, 15:1, 16:1, 19:1, 20:1, 27:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 100:1, 120:1, 140:1, 160:1, 180:1, 200:1, 220:1 and ranges consisting of endpoints of any two of the above values; and/or,
  • the ratio of the particle size D v 50 of the inorganic material to the average pore size of the second substrate layer is 1:1-243:1, for example, 4:1, 5:1, 8:1, 10:1, 11:1, 12:1, 14:1, 15:1, 16:1, 19:1, 20:1, 27:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 100:1, 120:1, 140:1, 160:1, 180:1, 200:1, 220:1, and ranges having any two of the above values as endpoints.
  • the above-mentioned ratio range is conducive to the contact between lithium dendrites or sodium dendrites and inorganic material particles after piercing the substrate layer, and is also conducive to better reaction kinetics between the mixed material layer and lithium dendrites or sodium dendrites; and the above-mentioned ratio range reduces the blockage of the pores on the substrate layer by inorganic material particles.
  • the dispersant is selected from one or more of sodium polyacrylate, ammonium polyacrylate, sodium hexafluorophosphate, sodium carboxymethyl cellulose, hydrolyzed polymaleic anhydride, acrylic acid block polymer, polyester block polymer, polyethylene glycol type polyol, polyvinyl alcohol and polyethyleneimine derivatives.
  • the thickness of the mixed material layer is 0.5-10 ⁇ m, for example 3 ⁇ m;
  • the thickness of the isolation film is 11-24 ⁇ m, for example, 14 ⁇ m, 15 ⁇ m, 17 ⁇ m, 19 ⁇ m, and a range consisting of any two of the above values as endpoints.
  • the mixed material layer can react with the lithium dendrites or sodium dendrites on the negative electrode sheet to delay the occurrence of lithium dendrites or sodium dendrites piercing the diaphragm and delay the occurrence of battery short circuit caused by lithium or sodium precipitation; on the other hand, it reduces the volume occupied by the isolation membrane and improves the energy density of the battery cell.
  • the mixed material layer further comprises a polymer, and the polymer is selected from one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB);
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA ethylene-vinyl acetate copolymer
  • PAA polyacrylic acid
  • CMC carboxymethyl cellulose
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • the mass content of the polymer is 0.1%-20%, for example, 0.2%, 1%, 1.4%, 10% and a range consisting of any two of the above values as endpoints.
  • the polymer helps the components in the mixed material layer to bond to each other.
  • the polymer meets the conventional requirements of the art for the molecular weight and distribution of polymers having bonding effects.
  • the weight average molecular weight of the polymer is 300,000-10 million, for example 500,000.
  • a protective layer is further provided on the surface of the first substrate layer away from the mixed material layer and/or on the surface of the second substrate layer away from the mixed material layer; optionally, the protective layer comprises one or more selected from alumina and boehmite.
  • the wettability of the separator to the electrolyte and the high-voltage resistance of the separator can be further improved.
  • the first substrate layer and the second substrate layer comprise a substrate
  • the substrate in the first substrate layer and the second substrate layer is independently selected from one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
  • the use of the above substrate is conducive to separating the mixed material layer from the negative electrode, avoiding the reaction between the mixed material layer and the negative electrode to consume lithium or sodium metal in advance, thereby improving the first coulombic efficiency of the battery.
  • the present application provides a method for preparing an isolation film, comprising the following steps:
  • the isolation membrane includes a first substrate layer, a mixed material layer and a second substrate layer; the mixed material layer is arranged between the first substrate layer and the second substrate layer; the mixed material layer contains an inorganic material, a dispersant and an optional polymer; the electronic conductivity ⁇ of the isolation membrane satisfies: 1 ⁇ 10-13 mS/cm ⁇ 1 ⁇ 10-1 mS/cm; optionally, 1 ⁇ 10-11 mS/cm ⁇ 1 ⁇ 10-3 mS/cm, more optionally, 1.5 ⁇ 10-11 mS/cm ⁇ 9 ⁇ 10-4 mS/cm, for example, 10-10 mS/cm, 10-9 mS/cm, 10-8 mS/cm, 10-6 mS/cm, 10-5 mS/cm, 10-4 mS/cm and a range consisting of any two of the above values as endpoints; the definitions of inorganic material, dispersant and polymer are as in [Isolation membrane].
  • the present application improves the wettability of the isolation membrane to the electrolyte through the mixed material layer, improves the transmission rate of sodium ions or lithium ions, and improves the charge and discharge rate
  • the positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material for a battery known in the art.
  • the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333 ), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ) , LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, and the like.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • Secondary batteries include battery cells, battery modules, and battery packs.
  • battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 is a battery module 4 as an example.
  • a plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes a secondary battery provided by the present application.
  • the secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery can be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are dissolved in the solvent N-methylpyrrolidone (NMP) in a mass ratio of 0.9:0.05:0.05, and the mixture is fully stirred and evenly mixed to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode collector aluminum foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet.
  • NMP N-methylpyrrolidone
  • the negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water in a mass ratio of 90%:5%:4%:1%, and the mixture is fully stirred and mixed to prepare a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector copper foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.
  • Elemental silicon particles with a particle size D v 50 of 1 ⁇ m, polyvinylidene fluoride (PVDF, weight average molecular weight 500,000) and dispersant polyvinyl alcohol are mixed in N-methylpyrrolidone at a mass ratio of 0.985:0.01:0.005 to obtain a mixed slurry with a solid mass content of 50%; the mixed slurry is scraped on the surface of a first substrate layer (PP material, average pore size 50 nm) with a thickness of 7 ⁇ m to obtain a mixed material layer arranged on the first substrate layer, and while the mixed slurry is not dry, the surface of the mixed material layer away from the first substrate layer is compounded with a second substrate layer (PP material, average pore size 50 nm) with a thickness of 7 ⁇ m by a roller pressing method, and an isolation membrane is obtained after drying; wherein the thickness of the mixed material layer is 3 ⁇ m.
  • PVDF weight average molecular weight 500,000
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of LiPF 6 is 1 mol/L.
  • the positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is added. After packaging, standing, forming, aging and other processes, a secondary battery is obtained.
  • Lithium sheets with a diameter of ⁇ 18 mm and a thickness of 500 ⁇ m were used as positive and negative electrodes, and the intermediate layer between the positive and negative electrodes was the above-mentioned isolation membrane. Electrolyte was added dropwise to assemble into a 2430 model button battery. The electrolyte was EC/DMC containing 1 mol/L LiPF 6 (the volume ratio of EC and DMC was 1:1).
  • Examples 2-34 and Comparative Examples 1-5 are similar to Example 1, and the different parameters are detailed in Table 1.
  • the positive electrode uses a lithium iron phosphate electrode (surface density of 0.025g/ cm2 , aluminum foil thickness of 60 ⁇ m), the negative electrode uses a graphite electrode (surface density of 0.012g/ cm2 , copper foil thickness of 8 ⁇ m), the middle interlayer is the isolation membrane to be tested, and the impedance test is carried out using a thermal pressure resistance meter with a voltage of 200V and a pressure of 600kgf to measure the resistance value of the isolation membrane; the electronic conductivity ⁇ of the isolation membrane is calculated according to the following formula;
  • R is the resistance value of the isolation membrane
  • S is the test area of the isolation membrane, that is, the area of a circle with a diameter of ⁇ 14 mm
  • l H ⁇ (1-porosity)
  • l is the thickness of the isolation membrane after the pores are eliminated under a pressure of 600 kgf
  • H is the initial thickness of the isolation membrane
  • the thickness of the diaphragm is measured with a micrometer, the length and width of the diaphragm are measured with a ruler and the area of the diaphragm is calculated, and then the apparent volume V of the diaphragm is calculated.
  • the weight M of the diaphragm is tested with a balance with a precision of ten thousand micrometers.
  • ⁇ represents the theoretical density of the substrate.
  • the porosity P of the diaphragm is calculated according to the following formula.
  • Determination method Add a certain amount of deionized water to the sample, ultrasonicate it for 10 minutes, and after the sample is completely dispersed, use a laser particle size analyzer to determine the particle size D v 50 of the sample.
  • Determination method After the sample is flattened, use a micrometer to measure the thickness at more than ten different locations, and take the average value to get the thickness of the sample.
  • Determination method Using the mercury intrusion method, a certain amount of sample is placed in the mercury intrusion instrument and the average pore size is obtained through testing.
  • Experimental method Flatten the isolation film and cut it into samples of 100mm ⁇ 100mm size. Set the oven to 120°C, put the samples in after keeping warm for 1h, continue to keep warm for 4h, then take out the samples, cool them, test the size of the samples, calculate the heat shrinkage ratio in two directions respectively, and then take the average value of the two directions.
  • the button cell was charged and discharged using a Xinwei charge and discharge tester. First, it was left to stand for 10 minutes, charged at a current density of 4mA/ cm2 for 1 hour, left to stand for 10 minutes, and then discharged at a current density of 4mA/ cm2 for 1 hour, and then the above operation was repeated for multiple cycles.
  • the maximum voltage minus the minimum voltage in the first charge and discharge process was taken as the normal voltage distribution.
  • the isolation membrane was judged to be in a short-circuit state, the cycle was stopped, and the running time at this time was recorded as the short-circuit time.
  • the isolation membrane of the present application delays the occurrence time of lithium dendrites piercing the diaphragm, delays the occurrence of short circuit in the secondary battery, and extends the service life of the battery; compared with comparative examples 1-3, the present application improves the wettability of the isolation membrane to the electrolyte, increases the transmission rate of lithium ions, increases the battery charge and discharge rate, the isolation membrane has better thermal shrinkage performance, and improves the safety of the secondary battery.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and embodiments having substantially the same structure as the technical idea and exerting the same effects within the technical solution of the present application are all included in the technical scope of the present application.
  • various modifications that can be thought of by those skilled in the art to the embodiments, and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

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Abstract

本申请提供了一种隔离膜、制备隔离膜的方法、二次电池和用电装置。隔离膜包括第一基材层、混合材料层和第二基材层；混合材料层设置在第一基材层与第二基材层之间；混合材料层包含无机材料和分散剂；其中，隔离膜的电子电导率σ满足：1×10 -13mS/cm<σ<1×10 -1mS/cm。本申请隔离膜能够延缓锂枝晶或钠枝晶刺破隔膜的发生，延缓电池内短路的发生，延长电池使用寿命，提高隔离膜对电解液的浸润性，提高电池充放电速率，改善电池的热收缩性能，提高电池安全性，提高电池的首次库伦效率。

Description

隔离膜及其制备方法、二次电池和用电装置 技术领域
本申请涉及电池技术领域，尤其涉及一种隔离膜、制备隔离膜的方法、二次电池和用电装置。
背景技术
近年来，随着电池的应用范围越来越广泛，电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。目前，电池所采用的隔离膜容易被负极片上的锂枝晶或钠枝晶刺破，从而引起电池内短路问题，严重影响了电池的使用寿命；并且，现有隔离膜的电解液浸润性差，导致锂离子或钠离子传导速率低，影响了电池的充放电速率；另外，现有隔离膜受热容易严重收缩，易导致严重的安全问题。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种隔离膜、制备隔离膜的方法、二次电池和用电装置。采用本申请的隔离膜能够延缓锂枝晶或钠枝晶刺破隔膜现象的发生，从而延缓电池内短路的发生，延长了电池使用寿命；采用本申请隔离膜能提高隔离膜对电解液的浸润性，提高钠离子或锂离子的传输速率，提高电池的充放电速率；本申请隔离膜还能够提高电池的热收缩性能，改善电池安全性；并且，本申请隔离膜能避免无机材料与负极反应消耗锂或钠金属，从而提高电池的首次库伦效率。
为了达到上述目的，本申请第一方面提供了一种隔离膜，包括第一基材层、混合材料层和第二基材层；混合材料层设置在第一基材层与第二基材层之间；混合材料层包含无机材料和分散剂；其中，
隔离膜的电子电导率σ满足：1×10 -13mS/cm<σ<1×10 -1mS/cm。
在电场作用下，无机材料内的空穴和电子发生定向移动，使无机材料具有电子导电性；无机材料在结构上具有不同的结晶形态，不同结晶形态对电子电导率的影响不同，这导致同种类的无机材料因结构差异而呈现出跨度范围较大的电子电导率分布；当隔离膜包含有无机材料时，隔离膜的电子电导率同样呈现跨度较大的变化范围。
由此，本申请采用满足一定电子电导率的隔离膜使混合材料层中的无机材料与负极片上的锂枝晶或钠枝晶发生反应，延缓了锂枝晶或钠枝晶刺破隔膜现象的发生，延缓了电池 内短路的发生，延长了电池的使用寿命，并且，能够减少锂离子在隔离膜表面的沉积，从而减少电池内部的自放电和内短路的发生；本申请通过混合材料层提高了隔离膜对电解液的浸润性，提高了钠离子或锂离子的传输速率，提高了电池的充放电速率；本申请通过采用混合材料层提高了电池的热收缩性能，改善了电池的安全性；并且，当负极为锂金属或钠金属时，本申请通过第一基材层或第二基材层将混合材料层与负极相互隔开，避免了混合材料层与负极发生反应而提前消耗锂或钠金属，从而保证了电池的首次库伦效率。
在任意实施方式中，无机材料选自如下的(1)-(3)项中的一种或多种：
(1)单质硅；
(2)选自硅、铝、铁、钛、钴、镍、锰、锡、锌、钡和铜中一种或多种元素的氧化物、氮化物及氟化物；
(3)选自铝、铁、钛、钴、镍、锰、锡、锌、钡和铜中一种或多种元素的磷酸盐。
在任意实施方式中，无机材料为选自二氧化硅、氧化亚硅、硅、氧化锌、氧化锡、氧化铜、磷酸铁、钛酸钡、氧化钴、氧化锰、氧化铁、氮化铜和磷酸钛铝锂中的一种或多种。
采用上述无机材料的混合材料层能够与锂枝晶或钠枝晶进行反应，进一步延缓锂枝晶或钠枝晶刺破隔离膜现象的发生，延缓电池内短路的发生时间，延长电池的使用寿命；采用上述无机材料的混合材料层进一步提高了隔离膜对电解液的浸润性，改善了钠离子或锂离子的传输速率，提高了电池充放电速率；包含上述无机材料的混合材料层机进一步提高了电池的热收缩性能，改善了电池安全性。
在任意实施方式中，以混合材料层的总质量为基准计，无机材料的质量含量为75％-99.7％，分散剂的质量含量为0.1％-15％、可选为0.1％-5％。
上述质量含量有利于促进混合材料层与锂枝晶或钠枝晶的反应，进一步延缓锂枝晶或钠枝晶刺破隔膜的发生，延缓由此引发的电池内短路的发生，延长电池的使用寿命，同时，能保持无机材料在混合材料层中均匀分散，以保证混合材料层作用的正常发挥。
在任意实施方式中，无机材料的粒径D v50与第一基材层的平均孔径的比例为1:1-243:1；和/或，
无机材料的粒径D v50与第二基材层的平均孔径的比例为1:1-243:1。
上述比例范围有利于锂枝晶或钠枝晶刺穿基材层后与无机材料颗粒相接触，也有利于混合材料层与锂枝晶或钠枝晶的反应动力学较好；并且，上述比例范围减少了无机材料颗粒对基材层上孔道的堵塞。
在任意实施方式中，分散剂选自聚丙烯酸钠、聚丙烯酸铵、六氟磷酸钠、羧甲基纤维素钠、水解聚马来酸酐、丙烯酸嵌段聚合物、聚酯嵌段聚合物、聚乙二醇型多元醇、聚乙 烯醇和聚乙烯亚胺衍生物中的一种或多种。
由此，有利于无机材料在混合材料层中的均匀分布，有助于混合材料层与锂枝晶或钠枝晶正常进行反应，延缓锂枝晶或钠枝晶刺破隔膜，延缓析锂或析钠所引起的电池短路的发生，延长电池的使用寿命。
在任意实施方式中，混合材料层的厚度为0.5-10μm；
可选地，隔离膜的厚度为11-24μm。
采用上述的混合材料层厚度和隔离膜厚度，一方面能够保证混合材料层能与负极片上的锂枝晶或钠枝晶发生反应，以延缓锂枝晶或钠枝晶刺破隔膜的发生，延缓析锂或析钠所引发的电池短路的发生，另一方面减少了隔离膜占用的体积，提高了电芯的能量密度。
在任意实施方式中，混合材料层还包含聚合物，聚合物选自丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚丙烯酸(PAA)、羧甲基纤维素(CMC)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的一种或多种；
可选地，以混合材料层的总质量为基准计，聚合物的质量含量为0.1％-20％。
聚合物有助于混合材料层中各成分的相互粘结。
在任意实施方式中，在第一基材层远离混合材料层的表面和/或在第二基材层远离混合材料层的表面还设置有保护层；可选地，保护层包含选自氧化铝和勃姆石中的一种或多种。由此，能够进一步提高隔离膜对电解液的浸润性和隔离膜的耐高压性能。
本申请的第二方面还提供一种制备隔离膜的方法，包括如下步骤：
将包含无机材料、分散剂及可选的聚合物的浆料涂覆在第一基材层上，得到设置有混合材料层的第一基材层；
在混合材料层远离第一基材层的表面复合上第二基材层，得到隔离膜；
隔离膜包括第一基材层、混合材料层和第二基材层；混合材料层设置在第一基材层与第二基材层之间；混合材料层包含无机材料、分散剂及可选的聚合物；隔离膜的电子电导率σ满足：1×10 -13mS/cm<σ<1×10 -1mS/cm；无机材料、分散剂和聚合物的定义如本申请第一方面中。
由此，本申请通过使混合材料层与负极片上的锂枝晶或钠枝晶发生反应，延缓了锂枝晶或钠枝晶刺破隔膜现象的发生，延缓了电池内短路的发生，延长了电池的使用寿命，并且，能够减少锂离子在隔离膜表面的沉积量，从而减少电池内部的自放电和内短路的发生；本申请通过混合材料层提高了隔离膜对电解液的浸润性，提高了钠离子或锂离子的传输速率，提高了电池的充放电速率；本申请通过采用混合材料层提高了电池的热收缩性能，改 善了电池的安全性；并且，当负极为锂金属或钠金属时，本申请通过第一基材层或第二基材层将混合材料层与负极相互隔开，避免了混合材料层与负极发生反应而提前消耗锂或钠金属，从而保证了电池的首次库伦效率。
本申请的第三方面提供一种二次电池，包括本申请第一方面的隔离膜或通过本申请第二方面的方法制备的隔离膜。
在任意实施方式中，电池中，正极活性材料包括选自磷酸铁锂、镍钴锰三元材料、锰酸锂、钴酸锂和镍酸锂中的一种或多种；和/或，负极活性材料包括选自石墨、硅碳化合物、硅氧化合物和锂金属中的一种或多种。
本申请的第四方面提供一种用电装置，包括本申请的第三方面的二次电池。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的隔离膜及其制备方法、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为 60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子(例如锂离子、钠离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
[隔离膜]
本申请的一个实施方式提供一种隔离膜，包括第一基材层、混合材料层和第二基材层；混合材料层设置在第一基材层与第二基材层之间；混合材料层包含无机材料和分散剂；其中，
隔离膜的电子电导率σ满足：1×10 -13mS/cm<σ<1×10 -1mS/cm；可选地，1×10 -11mS/cm<σ<1×10 -3mS/cm，更可选地，1.5×10 -11mS/cm<σ<9×10 -4mS/cm，例如为10 -10mS/cm、10 -9mS/cm、10 -8mS/cm、10 -6mS/cm、10 -5mS/cm、10 -4mS/cm以及以上述任意两个值为端点构成的范围。
在电场作用下，无机材料内的空穴和电子发生定向移动，使无机材料具有电子导电性；无机材料在结构上具有不同的结晶形态，不同结晶形态对电子电导率的影响不同，这导致同种类的无机材料因结构差异而呈现出跨度范围较大的电子电导率分布；当隔离膜包含有无机材料时，隔离膜的电子电导率同样呈现跨度较大的变化范围。
虽然机理尚不明确，但本申请人意外地发现：首先，负极片上的锂枝晶或钠枝晶的端部刺破第一基材层或第二基材层后与混合材料层相接触，隔离膜的电子电导率σ大于1×10 -13mS/cm时，有利于混合材料层中的无机材料与锂枝晶或钠枝晶发生反应，由此延缓了锂枝晶或钠枝晶刺破隔膜的发生时间，延缓了电池内短路的发生，延长了电池的使用寿命；并且，隔离膜的电子电导率σ小于1×10 -1mS/cm，能够减少锂离子在隔离膜表面的沉积量，从而减少电池内部的自放电和内短路的发生；其次，本申请的混合材料层对电解液的亲和性强，提高了隔离膜对电解液的浸润性，提高了钠离子或锂离子的传输速率，从而提高了电池的充放电速率；再次，本申请混合材料层受热不容易收缩，提高了电池的热收缩性能，改善了电池的安全性；而且，当负极为锂金属或钠金属时，本申请通过第一基材层或第二基材层将混合材料层与负极相互隔开，避免了混合材料层与负极发生反应而提前消耗掉锂或钠金属，从而保证了电池的首次库伦效率。
在一些实施方式中，隔离膜的电子电导率σ可通过所属技术领域的常规方法测定，例如可通过如下的具体方法测定：
以磷酸铁锂为正极，以石墨为负极极片，中间夹层为待测的隔离膜，在一定的压力和电压下采用热压电阻仪进行阻抗测试，隔离膜的测试面积S，测得隔离膜的电阻值R；按照如下的公式计算隔离膜的电子电导率σ；
R＝S/(σ×l)
其中，l＝H×(1-孔隙率)，H为隔离膜的初始厚度，l为隔离膜在上述压力下孔隙被消除后对应的厚度，；
上述的孔隙率的测试方法：
测量隔膜的厚度和面积，计算出隔膜的表观体积V，测量隔膜的重量M，ρ表示隔膜 中基材的理论密度，根据如下公式计算隔膜的孔隙率P。
Figure PCTCN2022122476-appb-000001
在一些实施方式中，无机材料选自如下的(1)-(3)项中的一种或多种：
(1)单质硅；
(2)选自硅、铝、铁、钛、钴、镍、锰、锡、锌、钡和铜中一种或多种元素的氧化物、氮化物及氟化物；
(3)选自铝、铁、钛、钴、镍、锰、锡、锌、钡和铜中一种或多种元素的磷酸盐。
在一些实施方式中，无机材料为选自二氧化硅、氧化亚硅、硅、氧化锌、氧化锡、氧化铜、磷酸铁、钛酸钡、氧化钴、氧化锰、氧化铁、氮化铜和磷酸钛铝锂中的一种或多种。
采用上述无机材料的混合材料层能够与锂枝晶或钠枝晶进行反应，进一步延缓锂枝晶或钠枝晶刺破隔离膜现象的发生，延缓电池内短路的发生时间，延长电池的使用寿命；采用上述无机材料的混合材料层进一步提高了隔离膜对电解液的浸润性，改善了钠离子或锂离子的传输速率，提高了电池充放电速率；包含上述无机材料的混合材料层机进一步提高了电池的热收缩性能，改善了电池安全性。
在一些实施方式中，以混合材料层的总质量为基准计，无机材料的质量含量为75％-99.7％、例如98.5％、94％、90％、85％、80％、76％，分散剂的质量含量为0.1％-15％、可选为0.1％-5％、例如0.5％、1％、4％、5％以及以上述任意两个值为端点构成的范围。
上述质量含量有利于促进混合材料层与锂枝晶或钠枝晶的反应，进一步延缓锂枝晶或钠枝晶刺破隔膜的发生，延缓由此引发的电池内短路的发生，延长电池的使用寿命，同时，能保持无机材料在混合材料层中均匀分散，以保证混合材料层作用的正常发挥。
在一些实施方式中，无机材料的粒径D v50与第一基材层的平均孔径的比例为1:1-243:1、例如4:1、5:1、8:1、10:1、11:1、12:1、14:1、15:1、16:1、19:1、20:1、27:1、30:1、40:1、50:1、60:1、70:1、80:1、100:1、120:1、140:1、160:1、180:1、200:1、220:1以及以上述任意两个值为端点构成的范围；和/或，
无机材料的粒径D v50与第二基材层的平均孔径的比例为1:1-243:1、例如4:1、5:1、8:1、10:1、11:1、12:1、14:1、15:1、16:1、19:1、20:1、27:1、30:1、40:1、50:1、60:1、70:1、80:1、100:1、120:1、140:1、160:1、180:1、200:1、220:1以及以上述任意两个值为端点构成的范围。
上述比例范围有利于锂枝晶或钠枝晶刺穿基材层后与无机材料颗粒相接触，也有利于混合材料层与锂枝晶或钠枝晶的反应动力学较好；并且，上述比例范围减少了无机材料颗 粒对基材层上孔道的堵塞。
在一些实施方式中，分散剂选自聚丙烯酸钠、聚丙烯酸铵、六氟磷酸钠、羧甲基纤维素钠、水解聚马来酸酐、丙烯酸嵌段聚合物、聚酯嵌段聚合物、聚乙二醇型多元醇、聚乙烯醇和聚乙烯亚胺衍生物中的一种或多种。
由此，有利于无机材料在混合材料层中的均匀分布，有助于混合材料层与锂枝晶或钠枝晶正常进行反应，延缓锂枝晶或钠枝晶刺破隔膜，延缓析锂或析钠所引起的电池短路的发生，延长电池的使用寿命。上述分散剂中的部分属于聚合物，其满足所属技术领域常规的聚合物型分散剂的分子量大小及分布的要求。
在一些实施方式中，混合材料层的厚度为0.5-10μm，例如3μm；
可选地，隔离膜的厚度为11-24μm，例如14μm、15μm、17μm、19μm以及以上述任意两个值为端点构成的范围。
采用上述的混合材料层厚度和隔离膜厚度，一方面能够保证混合材料层能与负极片上的锂枝晶或钠枝晶发生反应，以延缓锂枝晶或钠枝晶刺破隔膜的发生，延缓析锂或析钠所引发的电池短路的发生，另一方面减少了隔离膜占用的体积，提高了电芯的能量密度。
在一些实施方式中，混合材料层还包含聚合物，聚合物选自丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚丙烯酸(PAA)、羧甲基纤维素(CMC)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的一种或多种；
可选地，以混合材料层的总质量为基准计，聚合物的质量含量为0.1％-20％，例如0.2％、1％、1.4％、10％以及以上述任意两个值为端点构成的范围。
聚合物有助于混合材料层中各成分的相互粘结。上述聚合物满足所属技术领域对起粘结作用的聚合物的分子量及分布的常规要求，可选地，聚合物的重均分子量为30-1000万、例如50万。
在一些实施方式中，在第一基材层远离混合材料层的表面和/或在第二基材层远离混合材料层的表面还设置有保护层；可选地，保护层包含选自氧化铝和勃姆石中的一种或多种。由此，能够进一步提高隔离膜对电解液的浸润性和隔离膜的耐高压性能。
在一些实施方式中，第一基材层和第二基材层包含基材，第一基材层和第二基材层中的基材独立地选自聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺、聚酰胺、聚酯和天然纤维中的一种或多种。
采用上述基材有利于将混合材料层与负极相互隔开，避免了混合材料层与负极发生反应提前消耗锂或钠金属，从而提高了电池的首次库伦效率。
[制备隔离膜的方法]
本申请实施方式提供一种制备隔离膜的方法，包括如下步骤：
将包含无机材料、分散剂及可选的聚合物的浆料涂覆在第一基材层上，得到设置有混合材料层的第一基材层；
在混合材料层远离第一基材层的表面复合上第二基材层，得到隔离膜；
隔离膜包括第一基材层、混合材料层和第二基材层；混合材料层设置在第一基材层与第二基材层之间；混合材料层包含无机材料、分散剂及可选的聚合物；隔离膜的电子电导率σ满足：1×10 -13mS/cm<σ<1×10 -1mS/cm；可选地，1×10 -11mS/cm<σ<1×10 -3mS/cm，更可选地，1.5×10 -11mS/cm<σ<9×10 -4mS/cm，例如为10 -10mS/cm、10 -9mS/cm、10 -8mS/cm、10 -6mS/cm、10 -5mS/cm、10 -4mS/cm以及以上述任意两个值为端点构成的范围；无机材料、分散剂和聚合物的定义如[隔离膜]中。
由此，负极片上的锂枝晶或钠枝晶的端部刺破第一基材层或第二基材层后与混合材料层相接触，隔离膜的电子电导率σ大于1×10 -13mS/cm时，有利于混合材料层与锂枝晶或钠枝晶发生反应，由此延缓了锂枝晶或钠枝晶刺破隔膜的发生时间，延缓了电池内短路的发生，延长了电池的使用寿命；并且，隔离膜的电子电导率σ小于1×10 -1mS/cm，能够减少锂离子在隔离膜表面的沉积量，从而减少电池内部的自放电和内短路的发生；本申请通过混合材料层提高了隔离膜对电解液的浸润性，提高了钠离子或锂离子的传输速率，提高了电池的充放电速率；采用混合材料层提高了电池的热收缩性能，改善了电池的安全性；并且，当负极为锂金属或钠金属时，本申请通过第一基材层或第二基材层将混合材料层与负极相互隔开，避免了混合材料层与负极发生反应而提前消耗锂或钠金属，从而保证了电池的首次库伦效率。
[正极极片]
正极极片通常包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银 及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。作为示例，粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质为液态的，且包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。作为示例，添加剂可以包括负极成 膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
二次电池包括电池单体形式、电池模块形式、电池包形式。在一些实施方式中，电池单体可以组装成电池模块，电池模块所含电池单体的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个电池单体5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个电池单体5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，用电装置包括本申请提供的二次电池。二次电池可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为用电装置，可以根据其使用需求来选择二次电池。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
[实施例]
以下说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
1、正极极片的制备：
将正极活性材料磷酸铁锂、粘结剂聚偏氟乙烯(PVDF)、导电剂乙炔黑按照质量比为0.9:0.05:0.05溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后制备成正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，之后经过烘干、冷压、分切，得到正极极片。
2、负极极片的制备：
将负极活性材料人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为90％:5％:4％:1％溶于去离子水中，充分搅拌混合均匀后制备成负极浆料；将负极浆料涂覆在负极集流体铜箔上，之后经过烘干、冷压、分切，得到负极极片。
3、隔离膜的制备：
将粒径D v50为1μm的单质硅颗粒、聚偏氟乙烯(PVDF，重均分子量50万)和分散剂聚乙烯醇以0.985:0.01:0.005质量比在N-甲基吡咯烷酮中混合，得到固体质量含量为50％的混合浆料；将混合浆料刮涂在厚度为7μm的第一基材层(PP材质，平均孔径为50nm)的表面，得到设置在第一基材层上的混合材料层，趁混合浆料未干，将混合材料层远离第 一基材层的表面与厚度为7μm的第二基材层(PP材质，平均孔径为50nm)通过压辊方式进行复合，经干燥得到隔离膜；其中，混合材料层的厚度为3μm。
4、电解液的制备：
将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
5、二次电池的制备：
将上述正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述制备的电解液，经封装、静置、化成、老化等工序后，得到二次电池。
6、扣式电池的制备：
采用Φ18mm、厚度为500μm的锂片作为正负极，正负极的中间夹层为上述隔离膜，滴加电解液，组装成2430型号扣式电池，电解液为包含1mol/L LiPF 6的EC/DMC(EC和DMC体积比为1:1)。
实施例2-34和对比例1-5与实施例1相似，不同的参数详见表1。
Figure PCTCN2022122476-appb-000002
Figure PCTCN2022122476-appb-000003
Figure PCTCN2022122476-appb-000004
材料及电池性能测试
(1)隔离膜的电子电导率测定：
测定方法：正极使用磷酸铁锂极片(面密度为0.025g/cm 2，铝箔的厚度为60μm)，负极使用石墨极片(面密度为0.012g/cm 2，铜箔的厚度为8μm)，中间夹层为需测试的隔离膜，采用热压电阻仪进行阻抗测试，电压为200V，压力为600kgf，测得隔离膜的电阻值；按照如下的公式计算隔离膜的电子电导率σ；
R＝S/(σ×l)
其中，R为隔离膜的电阻值；S为隔离膜的测试面积，即直径Φ14mm的圆面积；l＝H×(1-孔隙率)，l为隔离膜在600kgf压力下孔隙被消除后对应的厚度，H为隔离膜的初始厚度；
上述孔隙率的测试方法：
采用万分尺测量隔膜的厚度，采用尺测量隔膜的长和宽并计算隔膜的面积，进而计算出隔膜的表观体积V，采用万分精度的天平测试隔膜的重量M，ρ表示基材的理论密度，根据如下公式计算隔膜的孔隙率P。
Figure PCTCN2022122476-appb-000005
(2)粒径D v50的测定：
测定方法：向样品中加入一定量的去离子水，通过超声装置超声10min，样品完全分散后，采用激光粒度仪测定样品的粒径D v50。
(3)厚度的测定：
测定方法：样品铺平后，使用万分尺测量十个以上不同位置的厚度，取平均值即得到样品的厚度。
(4)平均孔径的测定：
测定方法：利用压汞法，将一定量的样品放置到压汞仪中，测试得出其平均孔径。
(5)隔离膜的电解液吸收性实验：
实验方法：将隔离膜在100℃下烘烤6小时以上，保证样品充分干燥，将干燥后的隔离膜裁剪成固定大小的样品，测量其厚度(d)；固定在样品台上，使用端口平齐的毛细管，吸取指定高度h的电解液(密度为ρ)，打开显微镜，调节镜头倍数，至清晰看到毛细管和样品。使毛细管端口与样品接触，毛细管液面下降的同时使用秒表计时，当液面下降完毕后，读取吸液时间t，记录数据。根据公式计算隔离膜的平均吸液速率v。
v＝π×(d/2) 2×h×ρ/t
(6)隔离膜的热收缩实验：
实验方法：将隔离膜铺平，裁剪成100mm×100mm尺寸的样品，将烘箱设置为120℃， 保温1h后放入样品，继续保温4h，然后取出样品，冷却，测试样品的尺寸，分别计算出两个方向的热收缩比率，然后取两个方向的平均值。
(7)短路时间的测定：
对扣式电池采用新威充放电测试机进行充放电测试，首先，静置10min，以电流密度为4mA/cm 2充电1h，静置10min，再以电流密度为4mA/cm 2放电1h，然后继续重复上述操作进行多次循环。以第一次充放电过程中的最大电压减去最小电压作为正常电压分布，当后续充放电循环中的电压分布(同一次循环中的最大电压减去最小电压)<0.3倍的正常电压分布时，则判定隔离膜为短路状态，停止循环并记录此时的运行时间作为短路时间。
以上结果见表2。
表2：实施例1-34与对比例1-5的性能测试结果
Figure PCTCN2022122476-appb-000006
Figure PCTCN2022122476-appb-000007
根据上述结果可知：与对比例1-5相比，本申请隔离膜延缓了锂枝晶刺破隔膜的发生时间，延缓了二次电池内短路的发生，延长了电池的使用寿命；与对比例1-3相比，本申请提高了隔离膜对电解液的浸润性，提高了锂离子的传输速率，提高了电池充放电速率，隔离膜的热收缩性能更好，改善了二次电池的安全性。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而 构筑的其它方式也包含在本申请的范围内。

Claims (13)

  1. 一种隔离膜，包括第一基材层、混合材料层和第二基材层；所述混合材料层设置在所述第一基材层与所述第二基材层之间；所述混合材料层包含无机材料和分散剂；其中，
    所述隔离膜的电子电导率σ满足：1×10 -13mS/cm<σ<1×10 -1mS/cm。
  2. 根据权利要求1所述的隔离膜，其中，所述无机材料选自如下的(1)-(3)项中的一种或多种：
    (1)单质硅；
    (2)选自硅、铝、铁、钛、钴、镍、锰、锡、锌、钡和铜中一种或多种元素的氧化物、氮化物及氟化物；
    (3)选自铝、铁、钛、钴、镍、锰、锡、锌、钡和铜中一种或多种元素的磷酸盐。
  3. 根据权利要求1或2所述的隔离膜，其中，所述无机材料为选自二氧化硅、氧化亚硅、硅、氧化锌、氧化锡、氧化铜、磷酸铁、钛酸钡、氧化钴、氧化锰、氧化铁、氮化铜和磷酸钛铝锂中的一种或多种。
  4. 根据权利要求1至3中任一项所述的隔离膜，其中，以所述混合材料层的总质量为基准计，所述无机材料的质量含量为75％-99.7％，所述分散剂的质量含量为0.1％-15％、可选为0.1％-5％。
  5. 根据权利要求1至4中任一项所述的隔离膜，其中，所述无机材料的粒径D v50与所述第一基材层的平均孔径的比例为1:1-243:1；和/或，
    所述无机材料的粒径D v50与所述第二基材层的平均孔径的比例为1:1-243:1。
  6. 根据权利要求1至5中任一项所述的隔离膜，所述分散剂选自聚丙烯酸钠、聚丙烯酸铵、六氟磷酸钠、羧甲基纤维素钠、水解聚马来酸酐、丙烯酸嵌段聚合物、聚酯嵌段聚合物、聚乙二醇型多元醇、聚乙烯醇和聚乙烯亚胺衍生物中的一种或多种。
  7. 根据权利要求1至6中任一项所述的隔离膜，其中，所述混合材料层的厚度为0.5-10μm；
    可选地，所述隔离膜的厚度为11-24μm。
  8. 根据权利要求1至7中任一项所述的隔离膜，其中，所述混合材料层还包含聚合物，所述聚合物选自丁苯橡胶、水性丙烯酸树脂、聚偏二氟乙烯、聚四氟乙烯、乙烯-醋酸乙烯酯共聚物、聚丙烯酸、羧甲基纤维素、聚乙烯醇和聚乙烯醇缩丁醛中的一种或多种；
    可选地，以所述混合材料层的总质量为基准计，所述聚合物的质量含量为0.1％-20％。
  9. 根据权利要求1至8中任一项所述的隔离膜，其中，在所述第一基材层远离所述混合材料层的表面和/或在所述第二基材层远离所述混合材料层的表面还设置有保护层；可选地，所述保护层包含选自氧化铝和勃姆石中的一种或多种。
  10. 一种制备隔离膜的方法，包括如下步骤：
    将包含无机材料、分散剂及可选的聚合物的浆料涂覆在第一基材层上，得到设置有混合材料层的第一基材层；
    在所述混合材料层远离所述第一基材层的表面复合上第二基材层，得到隔离膜；
    所述隔离膜包括所述第一基材层、所述混合材料层和所述第二基材层；所述混合材料层设置在所述第一基材层与所述第二基材层之间；所述混合材料层包含所述无机材料、所述分散剂及可选的所述聚合物；所述隔离膜的电子电导率σ满足：1×10 -13mS/cm<σ<1×10 -1mS/cm；
    其中，所述无机材料和分散剂如权利要求1至9任一项中所述，所述聚合物如权利要求8中所述。
  11. 一种二次电池，包括权利要求1至9中任一项所述的隔离膜或通过权利要求10所述的方法制得的隔离膜。
  12. 根据权利要求11所述的二次电池，其中，
    正极活性材料包括选自磷酸铁锂、镍钴锰三元材料、锰酸锂、钴酸锂和镍酸锂中的一种或多种；和/或，
    负极活性材料包括选自石墨、硅碳化合物、硅氧化合物和锂金属中的一种或多种。
  13. 一种用电装置，包括权利要求11或12所述的二次电池。
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