WO2023184443A1 - 一种二次电池及包含该电池的装置 - Google Patents

一种二次电池及包含该电池的装置 Download PDF

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Publication number
WO2023184443A1
WO2023184443A1 PCT/CN2022/084668 CN2022084668W WO2023184443A1 WO 2023184443 A1 WO2023184443 A1 WO 2023184443A1 CN 2022084668 W CN2022084668 W CN 2022084668W WO 2023184443 A1 WO2023184443 A1 WO 2023184443A1
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coating
polymer
secondary battery
battery
battery according
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PCT/CN2022/084668
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English (en)
French (fr)
Inventor
冯波
魏增斌
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宁德新能源科技有限公司
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Priority to PCT/CN2022/084668 priority Critical patent/WO2023184443A1/zh
Priority to CN202280005581.0A priority patent/CN116157945A/zh
Publication of WO2023184443A1 publication Critical patent/WO2023184443A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0583—Construction or manufacture of accumulators with folded construction elements except wound ones, i.e. folded positive or negative electrodes or separators, e.g. with "Z"-shaped electrodes or separators
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of energy storage, and specifically to a secondary battery and a device containing the battery.
  • lithium-ion batteries have the characteristics of high energy density, high operating voltage, low self-discharge rate, small size, and light weight. They are widely used in various fields such as electrical energy storage, portable electronic devices, and electric vehicles.
  • the negative electrode continues to expand during the cycle, causing the space between the positive electrode and the negative electrode to be continuously squeezed, and the electrolyte transmission space becomes smaller and smaller, ultimately causing Electrolyte transmission disorder.
  • the electrolyte transmission is most severely hindered.
  • the bending part is prone to insufficient electrolyte replenishment, causing electrolyte bridge breakage, resulting in insufficient lithium insertion and lithium precipitation in the bending part, thus affecting the performance of the battery.
  • the present invention provides a secondary battery, which includes a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode.
  • the positive electrode, The separator and the negative electrode are stacked and rolled in sequence to form a rolled structure containing a curved part and a straight part.
  • the separator includes a base material, and the base material has a first surface and a second surface opposite to the first surface.
  • the first surface is provided with a first coating
  • the first coating includes a first polymer
  • the second surface is provided with a second coating, wherein in the curved portion, adjacent The distance between the negative electrode and the positive electrode is d1, and in the straight part, the distance between adjacent negative electrodes and positive electrodes is d2, where 1 ⁇ d1/d2 ⁇ 10, and d1 and d2 adopt the same unit.
  • the number of particles of the first polymer having a maximum length between 10 ⁇ m and 30 ⁇ m is 10 to 30.
  • the first polymer includes a homopolymer formed from any one of the following monomers or a copolymer formed from at least two selected from the following monomers: vinylidene fluoride, hexafluoro Propylene, ethylene, propylene, vinyl chloride or propylene chloride.
  • the first polymer has a softening point of 90°C to 150°C.
  • the first polymer has a Dv50 of 3 ⁇ m to 16 ⁇ m.
  • the orthographic projection area of the first coating on the first surface accounts for 5% to 60% of the area of the first surface.
  • the coating area density W1 of the first coating layer is 0.4g/m 2 to 2g/m 2 .
  • the second coating includes a second polymer, wherein the second polymer has a Dv50 of 0.2 ⁇ m to 8 ⁇ m.
  • the second polymer includes a homopolymer formed from any one of the following monomers or a copolymer formed from at least two selected from the following monomers: ethyl acrylate, butyl acrylate ester, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile or butadiene.
  • the second coating layer has a coating area density W2 of 0.1 g/m 2 to 1 g/m 2 .
  • the bonding strength between the first coating and the positive electrode is 4 N/m to 20 N/m, or the bonding strength between the second coating and the negative electrode is 5 N/m. to 20N/m.
  • the bonding strength between the first coating and the negative electrode is 3N/m to 15N/m, and the bonding strength between the second coating and the cathode is 5N/m. to 20N/m.
  • the number of winding layers of the positive electrode and the negative electrode is N, where N ⁇ 4.
  • the first coating is disposed on the curved portion.
  • the first coating and/or the second coating include inorganic particles, and the inorganic particles account for 40% to 90% of the total weight of the coating in the first coating or the second coating. %.
  • the separator further includes a heat-resistant layer, and the heat-resistant layer may be disposed between the substrate and the first coating or between the substrate and the second coating.
  • the heat-resistant layer includes inorganic particles.
  • the present invention provides an electrochemical device including the secondary battery according to any of the preceding embodiments.
  • the present invention provides an electronic device including the secondary battery according to any of the foregoing embodiments.
  • Figure 1 is a schematic structural diagram of a battery according to some embodiments of the present application.
  • a term may refer to a variation of less than or equal to ⁇ 10% of the stated numerical value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • the difference between two values is less than or equal to ⁇ 10% of the mean value of said values (for example, less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%), then the two values can be considered to be "substantially" the same.
  • a list of items connected by the term “one of,” “one of,” “one of,” or other similar terms may mean any of the listed items.
  • the phrase “one of A and B” means only A or only B.
  • the phrase “one of A, B, and C” means only A; only B; or only C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • a list of items connected by the term "at least one of,” “at least one of,” “at least one of,” or other similar terms may mean that the listed items any combination of.
  • the phrase “at least one of A and B” means only A; only B; or A and B.
  • the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • the present application provides a secondary battery, which includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.
  • the positive electrode, the separator, and the negative electrode are sequentially stacked and wound to form a flat and curved portion.
  • the separator includes a base material, the base material has a first surface and a second surface opposite to the first surface, the first surface is provided with a first coating, and the third surface is provided with a first coating layer.
  • a coating includes a first polymer, and a second coating is provided on the second surface, wherein at the curved portion, the distance between adjacent negative electrodes and positive electrodes is d1, and at the straight portion, The distance between adjacent negative electrodes and positive electrodes is d2, where 1 ⁇ d1/d2 ⁇ 10, and d1 and d2 adopt the same unit.
  • the straight part in the winding structure may be, for example, the substantially parallel upper or lower part in FIG. 1
  • the curved part may be, for example, the part connecting the upper and lower straight parts in FIG. 1 (FIG. 1 only shows the left part and the right part omitted).
  • “upper”, “lower”, “left” and “right” are the relative positions of various parts of the battery in Figure 1, which will have different orientations depending on the battery placement or observation angle.
  • d1/d2 may be about 1.05, about 1.5, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or a range between any two of the foregoing values.
  • the research of this application found that by disposing a separator between the positive electrode and the negative electrode, wherein the separator is designed to include a base material and a first coating layer and a second coating layer respectively located on two opposite surfaces of the base material.
  • a coating includes a first polymer, and wherein the distance d1 between adjacent positive and negative electrodes in the curved portion of the battery and the distance d2 between adjacent positive and negative electrodes in the straight portion of the battery satisfy 1 ⁇ d1/d2 ⁇ 10 ( See Figure 1), which can provide space to alleviate the expansion of the negative electrode during the battery cycle, thereby avoiding local loss of electrolyte caused by extrusion of the electrolyte, and preventing the battery gap from being too large and causing insufficient electrolyte to fill the gap.
  • the local lack of electrolyte can ensure that the thickness of the main part of the battery (i.e., the straight part) does not increase significantly, and can also ensure the hardness of the battery, thereby improving the adhesion between the separator and the positive and negative electrodes, and ultimately improving the battery's performance. Rate performance, cycle performance, reduction in battery volume energy density loss, etc.
  • the number of particles of the first polymer having a maximum length between 10 ⁇ m and 30 ⁇ m is 10 to 30. In some embodiments, the number of particles of the first polymer under the aforementioned conditions is about 10, about 15, about 20, about 25, about 30, or a range between any two of the aforementioned values. This application study found that by controlling the number of first polymers within this range, a better thickness of the battery bending portion can be obtained. The greater the number, the greater the corresponding d1.
  • the first polymer includes a homopolymer formed from any one of the following monomers or a copolymer formed from at least two selected from the following monomers: vinylidene fluoride, hexafluoro Propylene, ethylene, propylene, vinyl chloride or propylene chloride.
  • the first polymer is polyvinylidene fluoride.
  • the first polymer is a copolymer of polyvinylidene fluoride and hexafluoropropylene or vinyl chloride, for example, a copolymer of 95 wt% polyvinylidene fluoride and 5 wt% hexafluoropropylene or 5 wt% vinyl chloride.
  • Homopolymers formed by any one of the aforementioned monomers or copolymers formed by at least two of them can realize the technical solution of the present application and obtain ideal battery performance.
  • PVDF polyvinylidene fluoride
  • the battery has low hardness and is easily deformed during assembly, and the winding structure is easily misaligned, causing safety risks.
  • the hardness is low.
  • the disordered expansion of the negative electrode will cause the interface between the positive and negative electrodes to be uneven, causing local lithium precipitation, thus affecting the battery performance.
  • the interface gap is very small, which easily hinders the transmission of electrolyte.
  • the battery body and corners are prone to insufficient electrolyte. This leads to insufficient lithium insertion and even lithium precipitation.
  • the first polymer has a softening point of 90°C to 150°C. In some embodiments, the first polymer has a softening point of about 95°C, about 100°C, about 105°C, about 110°C, about 115°C, about 120°C, about 125°C, about 130°C, about 135°C ° C, about 140 ° C, about 145 ° C, or a range between any two of the aforementioned values. If the softening point of the first polymer is too small, the separator will easily become blocked, thereby affecting the transmission of lithium ions and ultimately affecting the electrical performance of the battery.
  • the softening point of the first polymer If the softening point of the first polymer is too high, it will The lowering of the adhesion between the separator and the pole pieces causes the active material to fall off during cycling, ultimately affecting the electrical performance of the battery.
  • ideal electrical properties can be obtained.
  • the first polymer has a Dv50 of 3 ⁇ m to 16 ⁇ m. In some embodiments, the first polymer has a Dv50 of about 4 ⁇ m, about 5 ⁇ m, about 6 ⁇ m, about 7 ⁇ m, about 8 ⁇ m, about 9 ⁇ m, about 10 ⁇ m, about 11 ⁇ m, about 12 ⁇ m, about 13 ⁇ m, about 14 ⁇ m, about 15 ⁇ m. Or the range between any two values mentioned above.
  • the larger the Dv50 of the first polymer the easier it is to prepare a desired gap (ie, the aforementioned d1) at the curved portion of the battery. However, an excessively large Dv50 will also reduce the volumetric energy density of the battery.
  • the loss of volumetric energy density can be reduced while leaving space for expansion of the negative electrode.
  • the first coating further includes a first auxiliary binder, and the mass ratio of the first polymer to the first auxiliary binder is 2.5 to 18. In some embodiments, the mass ratio of the first polymer to the first auxiliary binder may be 3, 5, 7, 9, 11, 13, 15, 17 or a range between any two of the aforementioned values.
  • the mass ratio of the first polymer to the first auxiliary binder when the mass ratio of the first polymer to the first auxiliary binder is too low (for example, less than 2.5), the content of the first polymer decreases, so that the granular third
  • the gap reduction caused by a polymer affects the transmission of electrolyte between the first coating interface and the adhesive force between the first coating and the electrode piece; when the first polymer and When the mass ratio of the first auxiliary binder is too high (for example, higher than 18), the cohesion of the first coating is low, and the bonding performance of the first polymer will change with the cohesion of the first coating. To lower and to fall.
  • the mass ratio of the first polymer to the first auxiliary binder within the above range, excellent adhesion between the first coating layer and the electrode pole piece can be achieved.
  • This application has no special restrictions on the first auxiliary binder, as long as it meets the requirements of this application.
  • it can include polymethyl methacrylate, polyacrylonitrile, ethyl acrylate, butyl acrylate, ethyl methacrylate, benzene At least one of ethylene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile or butadiene.
  • the mass percentage of the first polymer is 85% to 95%, and the mass percentage of the first auxiliary binder is 5 % to 15%.
  • the first coating further includes a first wetting agent.
  • a first wetting agent there is no special limitation on the first wetting agent in this application, as long as it meets the requirements of this application, for example, it can be polyoxyethylene ether. Based on the total mass of the first coating, the mass percentage of the first wetting agent is 0.1%-1%.
  • the orthographic projection area of the first coating on the first surface accounts for 5% to 60% of the area of the first surface. In some embodiments, the proportion is about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, or The range between any two values mentioned above.
  • the coating area density W1 of the first coating layer is 0.4g/m 2 to 2g/m 2 . In some embodiments, the coating area density W1 of the first coating is about 0.5g/m 2 , about 0.6g/m 2 , about 0.7g/m 2 , about 0.8g/m 2 , about 0.9g /m 2 , about 1.0g/m 2 , about 1.1g/m 2 , about 1.2g/m 2 , about 1.3g/m 2 , about 1.4g/m 2 , about 1.5g/m 2 , about 1.6g/ m 2 , about 1.7g/m 2 , about 1.8g/m 2 , about 1.9g/m 2 or a range between any two of the aforementioned values.
  • the smaller the coating surface density W1 of the first coating layer the smaller the thickness of the bent portion of the battery.
  • the second coating includes a second polymer.
  • the second polymer has a Dv50 of 0.2 ⁇ m to 8 ⁇ m. In some embodiments, the second polymer has a Dv50 of about 0.5 ⁇ m, about 1.0 ⁇ m, about 1.5 ⁇ m, about 2.0 ⁇ m, about 2.5 ⁇ m, about 3.0 ⁇ m, about 3.5 ⁇ m, about 4.0 ⁇ m, about 4.5 ⁇ m. , about 5.0 ⁇ m, about 5.5 ⁇ m, about 6.0 ⁇ m, about 6.5 ⁇ m, about 7.0 ⁇ m or a range between any two of the aforementioned values.
  • the second polymer includes a homopolymer formed from any one of the following monomers or a copolymer formed from at least two selected from the following monomers: ethyl acrylate, butyl acrylate ester, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile or butadiene.
  • the second polymer is a copolymer of styrene, acrylonitrile, isobutyl acrylate, and/or ethyl methacrylate. In some embodiments, the second polymer consists of 80% styrene, 5% butadiene, 5% isobutyl acrylate, and 10% acrylonitrile. In some embodiments, the second polymer consists of 80% styrene, 10% isobutyl acrylate, and 10% acrylonitrile. In some embodiments, the second polymer consists of 80% styrene, 10% ethyl methacrylate, and 10% acrylonitrile.
  • the second coating further includes a second auxiliary binder.
  • the mass ratio of the second polymer to the second auxiliary binder is 2 to 20.
  • the mass ratio of the second polymer to the second auxiliary binder may be 2, 4, 6, 8, 10, 14, 16 or a range between any two of the aforementioned values.
  • the mass ratio of the second polymer to the second auxiliary binder is too low (for example, less than 2), the content of the second polymer decreases, affecting the second coating
  • the bonding force between the second polymer and the second auxiliary binder is too high (for example, higher than 20), the cohesion of the second coating is low, and the The adhesion properties of the second coating are reduced.
  • the mass percentage of the second polymer is 75% to 92.5%, and the mass percentage of the second auxiliary binder is 7.5% to 25%.
  • the second auxiliary binder can include polymethacrylate, sodium carboxymethylcellulose or dimethylsiloxane. of at least one.
  • the second coating further includes a second wetting agent.
  • This application has no special restrictions on the second wetting agent, as long as it meets the requirements of this application, for example, it can be organosiloxane. Based on the total mass of the second coating, the mass percentage of the second wetting agent is 0.1%-1%.
  • the second coating layer has a coating area density W2 of 0.1 g/m 2 to 1 g/m 2 .
  • the coating area density W2 of the second coating is about 0.2g/m 2 , about 0.3g/m 2 , about 0.4g/m 2 , about 0.5g/m 2 , about 0.6g /m 2 , about 0.7g/m 2 , about 0.8g/m 2 , about 0.9g/m 2 or a range between any two of the aforementioned values.
  • adding inorganic particles to the separator can further improve the strength and heat resistance of the separator.
  • the first coating and/or the second coating include inorganic particles, and the inorganic particles account for 40% to 90% of the total weight of the coating in the first coating or the second coating. %.
  • the separator further includes a heat-resistant layer, and the heat-resistant layer may be disposed between the substrate and the first coating or between the substrate and the second coating.
  • the heat-resistant layer includes inorganic particles.
  • the heat-resistant layer includes inorganic particles, a binder, a dispersant and a wetting agent in a mass ratio of (87-98.5):(1-10):(0.5-2):(0-1) agent.
  • the binder and wetting agent have the same definitions as the first auxiliary binder and the first wetting agent in the first coating.
  • the dispersant can be polyacrylic acid.
  • the inorganic particles include boehmite, magnesium hydroxide, alumina, titanium dioxide, At least one of silicon oxide, zirconium dioxide, tin dioxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride or aluminum nitride.
  • the particle size Dv50 of the inorganic particles is 0.5 ⁇ m to 35 ⁇ m.
  • the particle size of the inorganic particles should not be too large or too small.
  • the particle size of the inorganic particles is too large (for example, greater than 35 ⁇ m), it is difficult to achieve its thin coating design, which affects the energy density of the lithium-ion battery; when the particle size of the inorganic particles is too large
  • the particle size is small (for example, less than 0.5 ⁇ m)
  • the accumulation pores of inorganic particles are reduced, affecting ion transmission and thus affecting the dynamic performance of lithium-ion batteries.
  • the bonding strength between the first coating layer and the positive electrode is 4 N/m to 20 N/m. In some embodiments, the bonding strength between the first coating and the cathode is about 5N/m, about 6N/m, about 7N/m, about 8N/m, about 9N/m, about 10N /m, about 11N/m, about 12N/m, about 13N/m, about 14N/m, about 15N/m, about 16N/m, about 17N/m, about 18N/m, about 19N/m or any of the above The range between two values.
  • the bonding strength between the second coating layer and the negative electrode is 5 N/m to 20 N/m. In some embodiments, the bonding strength between the second coating and the negative electrode is about 6N/m, about 7N/m, about 8N/m, about 9N/m, about 10N/m, about 11N /m, about 12N/m, about 13N/m, about 14N/m, about 15N/m, about 16N/m, about 17N/m, about 18N/m, about 19N/m or between any two of the aforementioned values scope.
  • the bonding strength between the first coating layer and the negative electrode is 3 N/m to 15 N/m. In some embodiments, the bonding strength between the first coating layer and the negative electrode is about 4N/m, about 5N/m, about 6N/m, about 7N/m, about 8N/m, about 9N/m. m, about 10N/m, about 11N/m, about 12N/m, about 13N/m, about 14N/m or a range between any two of the aforementioned values.
  • the bonding strength between the second coating layer and the positive electrode is 5 N/m to 20 N/m. In some embodiments, the bonding strength between the second coating and the positive electrode is about 6N/m, about 7N/m, about 8N/m, about 9N/m, about 10N/m, about 11N /m, about 12N/m, about 13N/m, about 14N/m, about 15N/m, about 16N/m, about 17N/m, about 18N/m, about 19N/m or between any two of the aforementioned values scope.
  • the number of winding layers of the positive electrode and the negative electrode is N, where N ⁇ 4. In some embodiments, 6 ⁇ N ⁇ 35. In some embodiments, 8 ⁇ N ⁇ 30. In some embodiments, 10 ⁇ N ⁇ 25. In some embodiments, N is about 5, about 10, about 15, about 20, about 25, about 30, about 35, or a range between any two of the foregoing values.
  • the first coating is disposed on the curved portion.
  • the preparation method of the secondary battery of the present application is described in detail below, taking a lithium ion battery as an example.
  • the separator includes a substrate, a first coating disposed on a first surface of the substrate, and a second coating disposed on a second surface opposite to the first surface.
  • the base material is a non-woven fabric, film or composite film with a porous structure, and the material of the base material is at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • polypropylene porous membrane, polyethylene porous membrane, polypropylene non-woven fabric, polyethylene non-woven fabric or polypropylene-polyethylene-polypropylene porous composite membrane can be used.
  • the first coating layer and the second coating layer are respectively any one of the first coating layer and the second coating layer described in the previous embodiments.
  • Preparation of separator (1) Preparation of inorganic coating: Disperse inorganic particles, binder, dispersant, and wetting agent in the solvent system, stir thoroughly, and then apply to one or two of the separator substrates. On the surface, after drying, a separator with an inorganic coating located on one or both surfaces of the substrate (referred to as “inorganic coating separator” or “heat-resistant layer”) is obtained.
  • Preparation of the first coating Disperse the selected first polymer, first wetting agent, and first auxiliary binder in the solvent system.
  • inorganic particles can also be added, and stir and mix thoroughly. After uniformity, apply it on the first surface of the separator base material or any surface of the inorganic coating separator in step 1, and dry it to obtain a separator or separator with the first coating layer located on the first surface of the base material. A separator having the first coating on either surface of the inorganic coated separator in step 1 is obtained.
  • Preparation of the second coating Disperse the selected second polymer, second wetting agent, and second auxiliary binder in the solvent system.
  • inorganic particles can also be added, and stir and mix thoroughly. After uniformity, it is coated on the second surface of the separator obtained in step (2), and dried to obtain a final separator.
  • the final separator has: a first coating layer located on the first surface of the base material and a first coating layer located on the base material.
  • a second coating on the second surface of the substrate or having an inorganic coating on the first surface of the substrate, a first coating on the inorganic coating and an inorganic coating on the second surface of the substrate , a second coating located on the inorganic coating; or having an inorganic coating located on the first surface of the substrate, a first coating located on the inorganic coating and a second coating located on the second surface of the substrate a second coating; or having a first coating located on the first surface of the substrate, an inorganic coating located on the second surface of the substrate, and a second coating located on the inorganic coating.
  • Preparation of the negative electrode Disperse the negative active material, binder, dispersant and conductive material in a solvent system according to a certain mass ratio, stir thoroughly and mix evenly, then apply it on the negative electrode current collector, dry and cold press to obtain negative electrode.
  • binders include, but are not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyfluoro Ethylene, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene Rubber, epoxy or nylon.
  • the negative active material includes conductive material.
  • the conductive material includes, but is not limited to: natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver, or polyphenylene derivative.
  • the negative electrode current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate covered with conductive metal.
  • the solvent may include, but is not limited to: N-methylpyrrolidone.
  • Preparation of the positive electrode Disperse the positive electrode material, binder, dispersant and conductive material in a solvent system according to a certain mass ratio, stir thoroughly and mix evenly, then apply it on the positive electrode current collector, dry and cold press to obtain the positive electrode. .
  • the positive current collector may be, but is not limited to, aluminum foil or nickel foil.
  • the cathode material includes a material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as a “cathode material capable of absorbing/releasing lithium Li”).
  • cathode materials capable of absorbing/releasing lithium (Li) may include lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, phosphoric acid One or more of lithium iron, lithium titanate and lithium-containing manganese-based materials.
  • the chemical formula of lithium cobalt oxide can be Li x Co a M1 b O 2-c , where M1 is selected from nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr), silicon (Si) and their combinations, the values of x, a, b and c are within the following ranges: 0.8 ⁇ x ⁇ 1.2, 0.8 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.2, -0.1 ⁇ c ⁇ 0.2;
  • the chemical formula of lithium nickel cobalt manganate or lithium nickel cobalt aluminate can be Li y Ni d M2 e O 2-f , where M2 is selected from cobalt (Co), manganese (Mn), magnesium (Mg ), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn) ), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr), silicon (Si) and their combinations, the values of y, d, e and f are respectively within the following range: 0.8 ⁇ y ⁇ 1.2, 0.3 ⁇ d ⁇ 0.98, 0.02 ⁇ e ⁇ 0.7, -0.1 ⁇ f ⁇ 0.2;
  • the chemical formula of lithium manganate is Li z Mn 2-g M3 g O 4-h , where M3 represents a group selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), Boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca),
  • M3 represents a group selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), Boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca)
  • the z, g and h values are respectively in the following ranges: 0.8 ⁇ z ⁇ 1.2, 0 ⁇ g ⁇ 1.0 and -0.2 ⁇ h ⁇ 0.2.
  • a conductive material is used to improve the electrical conductivity of the active material by providing a conductive path to the active material.
  • the conductive material may include at least one of the following: acetylene black, Ketjen black, natural graphite, carbon black, carbon fiber, metal powder or metal fiber (such as copper, nickel, aluminum or silver), but the conductive material Examples are not limited to this.
  • the amount of conductive material can be appropriately adjusted. Based on 100 parts by weight of the cathode active material, the conductive material and the binder, the amount of the conductive material ranges from 1 part by weight to 30 parts by weight.
  • examples of the solvent include, but are not limited to, N-methylpyrrolidone, acetone, or water. In some embodiments, the amount of solvent can be adjusted appropriately.
  • the binder can assist in bonding between the active material and the conductive material, or assist in bonding between the active material and the current collector.
  • binders include, but are not limited to, polyvinylidene fluoride, polyvinylidene chloride, carboxymethylcellulose, polyvinyl acetate, polyvinylpyrrolidone, polypropylene, polyethylene, and various polymers. Based on 100 parts by weight of the active material, conductive material and binder, the amount of the binder ranges from 1 part by weight to 30 parts by weight.
  • the current collector has a thickness in the range of 3 microns to 20 microns, although the disclosure is not limited thereto.
  • the current collector is electrically conductive and does not cause adverse chemical changes in the manufactured battery.
  • Examples of the current collector include copper, stainless steel, aluminum, nickel, titanium, or alloys (eg, homo-nickel alloys), but the disclosure is not limited thereto.
  • fine irregularities eg, surface roughness
  • the current collector can be used in various forms, and examples thereof include films, sheets, foils, meshes, porous structures, foams, or similar materials, but the disclosure is not limited thereto.
  • the electrolyte includes an organic solvent, a lithium salt, and additives.
  • the organic solvent includes ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate At least one of ester or ethyl propionate.
  • the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt.
  • lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide LiN(CF3SO2)2(LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2)( LiFSI), at least one of lithium bisoxalatoborate LiB(C2O4)2(LiBOB) or lithium difluoroxalatoborate LiBF2(C2O4)(LiDFOB).
  • the lithium salt content is 5%-30% based on the quality of the electrolyte. In some embodiments, the content of the lithium salt is 6%-25% based on the quality of the electrolyte. In some embodiments, the content of the lithium salt is 8%-20% based on the quality of the electrolyte. In some embodiments, the content of the lithium salt is 6%-18% based on the quality of the electrolyte.
  • the additives include fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, vinyl sulfate, adiponitrile, succinonitrile, glutaronitrile , at least one of 1,3,6-hexanetrinitrile, 1,2,6-hexanetrinitrile, succinic anhydride, lithium difluorophosphate, and lithium tetrafluoroborate.
  • Preparation of the battery Stack the positive electrode, separator, and negative electrode in order so that the separator is between the positive and negative electrodes for isolation, and wind the N layer to obtain a bare cell.
  • the bare battery core obtained by winding is placed in the outer packaging, electrolyte is injected and packaged, and the complete battery core is obtained through processes such as formation, degassing and trimming.
  • the number of winding layers is defined as follows: Taking the curved part on either side (or the straight part on either side) as the criterion, each superimposed layer of the positive electrode, separator and negative electrode is marked as one layer, and the total number of superimposed layers is and is the number of winding layers of the battery.
  • the present application also provides an electrochemical device, which includes the secondary battery according to the foregoing content.
  • the secondary battery is a lithium secondary battery, such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.
  • the present application provides an electronic device including the secondary battery according to the foregoing content.
  • the electronic devices include, but are not limited to: notebook computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted Stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles , bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, etc.
  • Separator (1): According to the mass ratio of 93.1%:5.0%:1.5%:0.4%, boehmite, polymethyl methacrylate, polyacrylic acid, and polyoxyethylene ether are dispersed in the solvent system (water), After being thoroughly stirred, the separator is coated on the first surface of the separator base material and dried to obtain a separator with an inorganic coating on the first surface of the base film of the base material (referred to as "inorganic coating separator" or "resistant”). Thermosphere").
  • the inorganic particles are coated on the first surface of the base film of the substrate here, it should be understood that the inorganic particles can also be coated on another surface of the base film of the substrate, or on both sides of the base film of the substrate at the same time.
  • the surface, or both surfaces of the substrate base film, are not coated with inorganic particles.
  • step (2) Mix the selected first polymer (polyvinylidene fluoride, 100%), first auxiliary binder (polyacrylonitrile) and first wetting agent (polyoxyethylene ether) at a mass ratio of 89.5%, Disperse in water at a ratio of 10% and 0.5%, stir thoroughly and mix evenly, then coat on the first surface of the inorganic coating separator obtained in step (1) (i.e., coat the first polymer on top of the inorganic coating) ), and after drying, a separator having the first coating layer located on the first surface of the inorganic coating separator is obtained.
  • first polymer polyvinylidene fluoride, 100%
  • first auxiliary binder polyacrylonitrile
  • first wetting agent polyoxyethylene ether
  • the selected second polymer a copolymer formed by polymerization of 80% styrene, 10% isobutyl acrylate, and 10% acrylonitrile
  • the second auxiliary binder polymethacrylate
  • the second wetting agent organosiloxane
  • the second wetting agent is dispersed in the water at a mass ratio of 79.5%, 20% and 0.5%. After being thoroughly stirred and mixed evenly, the second wetting agent (organosiloxane) is applied to the second surface of the inorganic coating separator obtained in step (2). After drying, the separator required in this embodiment is obtained.
  • the coverage of the first coating (that is, the area ratio of the orthogonal projection area of the first coating on the first surface to the area of the first surface) is 40%,
  • the softening point of the first polymer is 125°C,
  • the Dv50 of the first polymer is 12 ⁇ m, and the areal density W1 of the first polymer is 1 g/m 2 .
  • the number of particles of the first polymer having a length between 10 ⁇ m and 30 ⁇ m is 25.
  • the Dv50 of the second polymer is 0.7 ⁇ m
  • the areal density W2 of the second polymer is 0.2 g/m 2 .
  • Positive electrode Mix the positive active material lithium cobalt oxide, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in the N-methylpyrrolidone solvent system in a weight ratio of 97:2:1, and mix them evenly. Coat it on the positive electrode current collector Al foil, dry it and cold press it to obtain the positive electrode.
  • PVDF polyvinylidene fluoride
  • Negative electrode Combine the active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener carbon methylcellulose sodium (CMC) in a deionized state at a mass ratio of approximately 95:2:2:1. After thoroughly stirring and mixing in the water solvent system, it is coated on a Cu foil, dried, and cold pressed to obtain a negative electrode.
  • SBR binder styrene-butadiene rubber
  • CMC thickener carbon methylcellulose sodium
  • Electrolyte In an argon atmosphere glove box with a water content of ⁇ 10 ppm, mix ethylene carbonate (abbreviated as EC), diethyl carbonate (abbreviated as DEC), and propylene carbonate (abbreviated as PC) according to 2:6: Mix evenly with a weight ratio of 2, then dissolve the fully dried lithium salt LiPF6 in the above solvent, the content of LiPF6 is 1mol/L, add 1.5% 1,3-propane sultone, 3% fluoroethylene carbonate, 2% adiponitrile. The content of each substance is based on the total weight of the electrolyte.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • Preparation of the battery Stack the positive electrode, separator, and negative electrode in order, so that the separator is between the positive and negative electrodes for isolation, roll it, place it in the outer package, inject the prepared electrolyte and package it, and then form it. Hot pressing, degassing, trimming and other processes are used to obtain the battery. Among them, the number of winding layers is 20. Wherein, in the curved part of the rolled structure, the distance between adjacent negative electrodes and positive electrodes is d1, and in the straight part of the rolled structure, the distance between adjacent negative electrodes and positive electrodes is d2, where d1/d2 is 2 and d1 and d2 are in the same units.
  • d1/d2 can be realized by, for example, coating or hot pressing technology.
  • the coating weight is relatively large, d1 will be larger. After the battery is hot pressed, d1 remains basically unchanged and d2 decreases significantly.
  • different d1 and d2 can be obtained, thereby controlling the size of d1/d2.
  • the size of d1/d2 can also be controlled through non-uniform coating.
  • the first coating is arranged to be located primarily in the bend.
  • Table 1 below specifically shows the differences in battery parameters in Examples 1 to 45 and Comparative Examples 1 to 3. Except for Comparative Example 3, which does not have the first/second auxiliary adhesive and the first/second wetting agent because there is no coating, the other examples and comparative examples have the first/second auxiliary adhesive and the first/second wetting agent.
  • the type and content of the second wetting agent are the same as the parameters in the above-mentioned Example 1, and will not be described again in the table.
  • the following tables only show different parameter settings of each embodiment and comparative example.
  • the only difference between Example 45 and Example 4 is that Example 43 does not contain an inorganic coating.
  • the number of particles here is the number of particles of the first polymer with a maximum length between 10 ⁇ m and 30 ⁇ m in a 250 ⁇ m ⁇ 200 ⁇ m area on the surface of the first coating.
  • Example 45 The difference between Example 45 and Example 1 is that the base material of the separator in Example 45 does not have a heat-resistant layer formed of inorganic particles, and its first coating layer and second coating layer are located on the third layer of the base material of the separator. on the first surface and on the second surface.
  • the difference between Examples 1 to 45 and Comparative Examples 1 to 3 is: d1/d2, the number of winding layers, in the 250 ⁇ m ⁇ 200 ⁇ m area on the surface of the first coating, the maximum length is 10 ⁇ m
  • the number of particles of the first polymer between 30 ⁇ m and 30 ⁇ m, the coverage of the first coating, the type and content of the first polymer, the first polymer softening point, the first polymer Dv50, the first polymer surface Area density, second polymer type and content, second polymer Dv50, second polymer area density, presence or absence of coating, etc.
  • CT computed tomography
  • 1 is the positive electrode diaphragm (positive electrode active material layer)
  • 2 is the positive electrode current collector
  • 3 is the separator
  • 4 is the negative electrode diaphragm (negative electrode active material layer)
  • 5 is the negative electrode current collector.
  • the positive electrode current collector 2 has positive electrode diaphragms (positive electrode active material layers) 3 on both upper and lower surfaces
  • the negative electrode current collector 5 has negative electrode diaphragms (negative electrode active material layers) 4 on both upper and lower surfaces.
  • Cut the isolation film coated with the first coating into a 10mm ⁇ 10mm sample then place the sample under the SEM for observation at 500x magnification, and select any 5 250 ⁇ m ⁇ 200 ⁇ m areas in the field of view to observe, area, and record Select the number of particles with a maximum length of the first polymer particles between 10 ⁇ m and 30 ⁇ m in the selected area, and then average it, which is the number of particles with a maximum length of the first polymer particles between 10 ⁇ m and 30 ⁇ m in the unit area of the first coating. Number of particles.
  • Use the image segmentation algorithm to identify the first coating and perform fitting calculations to obtain its coverage area S. Coverage S/(250 ⁇ 200)*100%. Take the average coverage of 5 positions to obtain the coverage of the first coating. Rate.
  • Adopt a universal differential scanning calorimeter (DSC) method take 5 mg of the first polymer sample prepared in each example and comparative example, heat it to 150°C at a heating rate of 5°C/min, and collect the DSC curve. The DSC curve determines the softening point, or softening temperature, of the first polymer.
  • the same test method is used for the Dv50 of inorganic particles and the second polymer.
  • the width of the glass plate should be at least 100% greater than the width of the cell, and the width of the glass plate should be at least 10% greater than the length of the battery.
  • Table 2 below shows various properties of Examples 1 to 45 and Comparative Examples 1 to 3.
  • the bonding force of Comparative Example 3 in Table 2 above refers to the bonding force between the first surface of the separator and the positive electrode and the second surface of the separator and the negative electrode respectively. of adhesion.
  • Example 1-45 satisfies the relationship formula 1 ⁇ d1/d2 ⁇ 10, wherein the first surface of the separator of Example 1-44 has a heat-resistant layer and a first coating layer located on the heat-resistant layer, And the second surface of the separator has a heat-resistant layer and a second coating located on the heat-resistant layer.
  • Example 1-45 and Comparative Example 3 are equivalent, but the battery hardness of Example 1-45 is significantly greater than that of the battery in Comparative Example 3, and the too low battery hardness in Comparative Example 3 causes the battery to It is easy to deform during assembly and the winding structure is easily misaligned, causing safety risks; in addition, the hardness is low.
  • the disordered expansion of the negative electrode will cause the interface between the positive and negative electrodes to be uneven, causing local decomposition. Lithium, thereby affecting battery performance.
  • a separator between the positive electrode and the negative electrode, wherein the separator is designed to include a base material and a first coating layer and a second coating layer respectively located on two opposite surfaces of the base material, wherein the first coating layer Including the first polymer, and wherein the distance d1 between adjacent positive and negative electrodes in the curved part of the battery and the distance d2 between adjacent positive and negative electrodes in the straight part of the battery satisfy 1 ⁇ d1/d2 ⁇ 10, space can be provided This can alleviate the expansion of the negative electrode during the cycle, prevent the electrolyte from being extruded and discharged, causing local loss of electrolyte, and prevent the gap from being too large, resulting in insufficient electrolyte filling the gap, resulting in local loss of electrolyte, and ensuring the main body of the battery.
  • the thickness of the straight part does not increase significantly, and it can also ensure the hardness of the battery and improve the bonding force between the separator and the positive and negative electrodes, thereby improving the battery's rate performance, cycle performance, and reducing the battery volume energy density. losses etc.
  • Example 4 Compared with Example 45 without heat-resistant coating, various properties of Example 4, especially the electrochemical performance, are further improved. This is mainly because the interface between the substrate surface and the polymer coating is relatively dense, which is not conducive to the transmission of lithium ions, and the inorganic particles in the heat-resistant coating can loosen the interface structure. For example, the inorganic particles can introduce some voids. , making the lithium ion transmission smoother, reducing diffusion resistance, etc., thereby further improving the electrical performance of the electrochemical device.
  • the number of winding layers of the battery is N, where N ⁇ 4.
  • the increase in the number of winding layers results in increased extrusion of the inner layers of the battery bend.
  • the greater the number of winding layers the greater the compression of the inner layer of the battery's curved part, and the more likely it is that local loss of electrolyte will occur.
  • space for electrolyte transmission and storage can be provided in the curved part, and better electrical performance can be obtained for batteries with different numbers of winding layers.
  • the length is between 10 ⁇ m and 30 ⁇ m.
  • the number of particles of the first polymer is 10 to 30. This application study found that by controlling the amount of the first polymer within this range, a better thickness of the battery bending portion can be obtained. The greater the number, the larger the corresponding d1.
  • the orthogonal projected area of the first coating on the first surface accounts for 50% of the first surface.
  • the area ratio is 5% to 60%.
  • the first polymer includes a homopolymer formed from any one of the following monomers or Copolymer formed from at least two monomers selected from the group consisting of vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride or propylene chloride.
  • the disordered expansion of the negative electrode will cause the interface between the positive and negative electrodes to be uneven, causing local lithium precipitation, thus affecting the battery performance.
  • the interface gap is very small, which easily hinders the transmission of electrolyte, and electrolyte is prone to appear in both the curved and straight parts of the battery. Insufficient, leading to insufficient lithium insertion or even lithium precipitation.
  • the softening point of the first polymer is 90°C to 150°C.
  • the study of this application found that the softening point of the first polymer is too small, which will easily cause the separator to be blocked, thus affecting the transmission of lithium ions and ultimately affecting the electrical performance of the battery. If it is too high, the bonding force between the separator and the pole piece will be reduced, resulting in active material falling off during the cycle, and ultimately affecting the electrical performance of the battery.
  • ideal electrical properties can be obtained.
  • the Dv50 of the first polymer is 3 ⁇ m to 16 ⁇ m.
  • This application study found that the larger the Dv50 of the first polymer, the easier it is to prepare the desired gap (i.e., the aforementioned d1) at the curved part of the battery.
  • an excessively large Dv50 will also reduce the volumetric energy density of the battery. .
  • the loss of volumetric energy density can be reduced while leaving space for expansion of the negative electrode.
  • the coating surface density W1 of the first coating is 0.4g/m2 to 2g/m2 2 .
  • This application study found that the smaller the coating area density W1 of the first coating layer, the smaller the thickness of the curved portion of the battery.
  • the second polymer includes a homopolymer formed from any one of the following monomers or Copolymer formed from at least two monomers selected from the group consisting of: ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methyl Acrylic acid, maleic acid, acrylonitrile or butadiene. Any second polymer within the aforementioned range can obtain a strong bonding force between the separator and the negative electrode.
  • the second polymer has a Dv50 of 0.2 ⁇ m to 8 ⁇ m.
  • the second polymer has a coating area density W2 of 0.1 g/m 2 to 1 g/m 2 .
  • this application provides a simple and easy method suitable for industrial production to prepare secondary batteries with high rate performance, cycle performance and hardness.
  • references throughout this specification to “some embodiments,” “partial embodiments,” “one embodiment,” “another example,” “example,” “specific example,” or “partial example” mean the following: At least one embodiment or example in this application includes a specific feature, structure, material or characteristic described in the embodiment or example. Accordingly, phrases such as “in some embodiments,” “in an embodiment,” “in one embodiment,” “in another example,” “in one example,” etc. may appear in various places throughout this specification. "in”, “in a particular example” or “for example” do not necessarily refer to the same embodiment or example in this application. Furthermore, the specific features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

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Abstract

本申请涉及一种二次电池，其包含正极、负极和设置于所述正极和所述负极之间的隔膜，所述正极、所述隔膜和所述负极依次层叠卷绕形成含有弯曲部和平直部的卷绕结构，所述隔膜包括基材、所述基材具有第一表面和与所述第一表面相对的第二表面，所述基材的第一表面上设置有第一涂层，所述基材的第二表面上设置有第二涂层，其中，在所述卷绕结构的弯曲部，相邻的负极和正极之间的距离为d1，在所述卷绕结构的平直部，相邻的负极和正极之间的距离为d2，其中1＜d1/d2＜10，且其中d1和d2采用相同的单位。

Description

一种二次电池及包含该电池的装置 技术领域
本申请涉及储能领域，具体涉及一种二次电池及包含该电池的装置。
背景技术
随着电子类的产品如笔记本电脑、手机、掌上游戏机和平板电脑等的普及，人们对电化学装置(例如，电池)的要求也越来越严格。在众多电池中，锂离子电池具有能量密度大、工作电压高、自放电率低、体积小、重量轻等特点，广泛应用于电能储存、便携式电子设备和电动汽车等各个领域。
发明内容
随着锂离子电池在消费终端等领域应用的迅速发展，人们对锂离子电池的充放电循环性能和能量密度也有了更高的要求。然而，在低温条件下，锂离子电池的实际充放电性能远小于设计值，制约了锂离子电池的进一步应用。
当前，采用现有电池技术制备的大多数锂离子电池，其负极在循环过程中不断膨胀，使得正极和负极之间的空间不断被挤压，电解液传输空间越来越小，并最终造成了电解液传输障碍。尤其是在弯曲部，由于应力集中在此处，弯曲部的电解液传输阻碍最严重。尤其在低温循环时，弯曲部容易出现电解液补给不及时，从而造成电解液断桥，导致弯曲部出现嵌锂不足和析锂，从而影响电池的性能。
为改善上述缺陷，本领域通常的做法是在电池初始阶段，增加正负极之间的间隙，为负极的膨胀预留空间，以减缓电解液传输障碍。但是这样做的弊端是，电池弯曲部和电池平直部的间隙均增加，导致电池的厚度增加，从而造成电池的体积能量密度的损失。
为解决上述问题以及本领域存在的一些其它问题，一方面，本发明提供了一种二次电池，其包含正极、负极和设置于所述正极和所述负极之间的隔膜，所述正极、所述隔膜和所述负极依次层叠卷绕形成含有弯曲部和平直部的卷绕结构，所述隔膜包括基材，所述基材具有第一表面和与 所述第一表面相对的第二表面，所述第一表面上设置有第一涂层，所述第一涂层包括第一聚合物，所述第二表面上设置有第二涂层，其中，在所述弯曲部，相邻的负极和正极之间的距离为d1，在所述平直部，相邻的负极和正极之间的距离为d2，其中1＜d1/d2＜10，且其中d1和d2采用相同的单位。
在一些实施例中，在所述第一涂层表面的250μm×200μm区域内，最大长度处于10μm至30μm之间的所述第一聚合物的颗粒数量为10个至30个。
在一些实施例中，所述第一聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：偏氟乙烯、六氟丙烯、乙烯、丙烯、氯乙烯或氯丙烯。
在一些实施例中，所述第一聚合物的软化点为90℃至150℃。
在一些实施例中，所述第一聚合物的Dv50为3μm至16μm。
在一些实施例中，所述第一涂层在所述第一表面上的正投影面积占所述第一表面的面积比例为5％至60％。
在一些实施例中，所述第一涂层的涂布面密度W1为0.4g/m 2至2g/m 2。
在一些实施例中，所述第二涂层包括第二聚合物，其中所述第二聚合物的Dv50为0.2μm至8μm。
在一些实施例中，所述第二聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：丙烯酸乙酯、丙烯酸丁酯、甲基丙烯酸乙酯、苯乙烯、氯苯乙烯、氟苯乙烯、甲基苯乙烯、丙烯酸、甲基丙烯酸、马来酸、丙烯腈或丁二烯。
在一些实施例中，所述第二涂层的涂布面密度W2为0.1g/m 2至1g/m 2。
在一些实施例中，所述第一涂层与所述正极之间的粘接强度4N/m至20N/m，或所述第二涂层与所述负极之间的粘接强度5N/m至20N/m。
在一些实施例中，所述第一涂层与所述负极之间的粘接强度3N/m至15N/m，且所述第二涂层与所述正极之间的粘接强度5N/m至20N/m。
在一些实施例中，所述正极和所述负极的卷绕层数为N，其中N≥4。
在一些实施例中，其中所述第一涂层设置于所述弯曲部。
在一些实施例中，所述第一涂层和/或所述第二涂层包括无机颗粒，所述无机颗粒在第一涂层或者第二涂层中占涂层总重量的40％～90％。在另一些实施例中，所述隔膜还包括耐热层，耐热层可以设置在基材和第一涂层之间或基材和第二涂层之间。耐热层包括无机颗粒。
另一方面，本发明提供了一种电化学装置，其包括根据前述任一实施例所述的二次电池。
又一方面，本发明提供了一种电子装置，其包括根据前述任一实施例所述的二次电池。
附图说明
图1是根据本申请的一些实施例的电池结构示意图。
具体实施方式
下文中，对本申请进行详细说明。应当理解，在说明书和所附权利要求中使用的术语不应被解释为限于一般和词典的含义，而是在发明人被允许适当定义术语以进行最佳解释的原则的基础上基于与本申请的技术方面相对应的含义和概念来解释。因此，说明书中所述的实施方案中所示的描述仅仅是用于说明的目的的具体实例，而不旨在显示本申请的所有技术方面，并且应当理解，在提交本申请时可以对其完成多种可选等价体和变体。
如本文中所使用，术语“大致”、“大体上”、“实质”及“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。举例来说，如果两个数值之间的差值小于或等于所述值的平均值的±10％(例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％)，那么可认为所述两个数值“大体上”相同。
在具体实施方式及权利要求书中，由术语“中的一者”、“中的一个”、“中的一种”或其他相似术语所连接的项目的列表可意味着所列项目中的任一者。例如，如果列出项目A及B，那么短语“A及B中的一者”意味着仅A或仅B。在另一实例中，如果列出项目A、B及C，那么短语“A、 B及C中的一者”意味着仅A；仅B；或仅C。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
一、二次电池
本申请提供一种二次电池，其包含正极、负极和设置于所述正极和所述负极之间的隔膜，所述正极、所述隔膜和所述负极依次层叠卷绕形成含有弯曲部和平直部的卷绕结构，所述隔膜包括基材、所述基材具有第一表面和与所述第一表面相对的第二表面，所述第一表面上设置有第一涂层，所述第一涂层包括第一聚合物，所述第二表面上设置有第二涂层，其中，在所述弯曲部，相邻的负极和正极之间的距离为d1，在所述平直部，相邻的负极和正极之间的距离为d2，其中1＜d1/d2＜10，且其中d1和d2采用相同的单位。其中卷绕结构中的平直部可以例如是图1中的基本上平行的上方或下方部分，而弯曲部可以例如是图1中连接上方和下方两个平直部的部分(图1仅展示了左边部分，省略了右边部分)。其中，“上”、“下”、“左”和“右”是图1中电池各部分的相对位置，会随着电池摆放位置或观察视角不同而具有不同方位。
在一些实施例中，d1/d2可为约1.05、约1.5、约2、约3、约4、约5、约6、约7、约8、约9或前述任意两数值之间的范围。
本申请研究发现，通过在正极和负极之间设置一隔膜，其中隔膜经设计以包括基材和分别位于基材的相对的两个表面上的第一涂层和第二涂层，所述第一涂层包括第一聚合物，且其中电池弯曲部的相邻正负极之间的距离d1与电池平直部的相邻正负极之间的距离d2满足1＜d1/d2＜10 (参见附图1)，可以提供空间以缓解电池循环过程中的负极膨胀，从而避免电解液受挤压排出造成的电解液局部缺失，可以避免电池间隙过大导致电解液没有足够的量填充间隙，造成电解液局部缺失，可以保证电池的主体部分(即，平直部)的厚度不显著增加，还可以保证电池的硬度从而改善隔膜与正负极之间的粘结力，并最终提高电池的倍率性能、循环性能、减小电池体积能量密度的损失等。
在一些实施例中，在所述第一涂层表面的250μm×200μm区域内，最大长度处于10μm至30μm之间的所述第一聚合物的颗粒数量为10个至30个。在一些实施例中，前述条件下的第一聚合物的颗粒数量为约10、约15、约20、约25、约30或前述任意两数值之间的范围。本申请研究发现，通过控制第一聚合物的数量在该范围内，可以获得较佳的电池弯曲部厚度，数量越多，相应的d1越大。
在一些实施例中，所述第一聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：偏氟乙烯、六氟丙烯、乙烯、丙烯、氯乙烯或氯丙烯。在一些实施例中，所述第一聚合物是聚偏氟乙烯。在一些实施例中，所述第一聚合物是聚偏氟乙烯与六氟丙烯或氯乙烯形成的共聚物，例如95wt％聚偏氟乙烯与5wt％六氟丙烯或5wt％氯乙烯形成的共聚物。前述单体中任意一种形成的均聚物或至少两种形成的共聚物均可以实现本申请的技术方案，获得理想的电池性能。然而，经本申请进一步研究发现，一方面，常规的水系聚偏氟乙烯(PVDF)作为第一聚合物形成隔膜的第一涂层时，虽然其大粒径可以为负极膨胀预留间隙，但是，由于材料软化点高，导致界面粘接力低，电池的能量密度损失较大。而且电池硬度低，在组装时容易变形、卷绕结构容易错位，引起安全风险。另外硬度低，在电池的充放电过程中，由于负极的无序膨胀会导致正负极之间的界面不平整，使局部出现析锂，从而影响电池性能。另一方面，非水系PVDF作为第一聚合物形成隔膜的第一涂层时，在被热压之后，界面间隙很小，易阻碍电解液的传输，电池主体和拐角均易出现电解液不足，导致嵌锂不足，甚至析锂。而在PVDF中加入六氟丙烯、乙烯、丙烯、氯乙烯或氯丙烯中的至少一者作为第一涂层时，既可以为负极膨胀提供理想的空隙，又可以保证隔膜与正负极之间的粘结力。
在一些实施例中，所述第一聚合物的软化点为90℃至150℃。在一些实施例中，所述第一聚合物的软化点为约95℃、约100℃、约105℃、约110℃、约115℃、约120℃、约125℃、约130℃、约135℃、约140℃、约145℃或前述任意两数值之间的范围。所述第一聚合物软化点太小，会使 得隔膜容易出现堵孔的现象，从而影响锂离子的传输，并最终影响电池的电性能，而所述第一聚合物软化点太高，则会降低隔膜与极片的粘结力低，从而在循环过程中出现活性材料的脱落，并最终影响电池的电性能。通过将所述第一聚合物软化点控制在前述范围内，可以获得理想的电性能。
在一些实施例中，所述第一聚合物的Dv50为3μm至16μm。在一些实施例中，所述第一聚合物的Dv50为约4μm、约5μm、约6μm、约7μm、约8μm、约9μm、约10μm、约11μm、约12μm、约13μm、约14μm、约15μm或前述任意两数值之间的范围。所述第一聚合物的Dv50越大，则越容易在电池的弯曲部制备想要的间隙(即，前述d1)，但是，过大的Dv50也会降低电池的体积能量密度。通过将第一聚合物的Dv50控制在上述范围，则可以在为负极膨胀预留空间的同时减小体积能量密度的损失。
在一些实施例中，所述第一涂层还包括第一辅助粘结剂，所述第一聚合物与所述第一辅助粘结剂质量比为2.5至18。在一些实施例中，所述第一聚合物与所述第一辅助粘结剂质量比可以是3、5、7、9、11、13、15、17或前述任意两数值之间的范围。不限于任何理论，当所述第一聚合物与所述第一辅助粘结剂质量比过低时(例如低于2.5)，所述第一聚合物的含量下降，使得颗粒状的所述第一聚合物带来的间隙减少，影响电解液在所述第一涂层界面间的传输，同时影响所述第一涂层与电极极片间的粘结力；当所述第一聚合物与所述第一辅助粘结剂质量比过高时(例如高于18)，所述第一涂层内聚力较低，所述第一聚合物的粘结性能会随所述第一涂层内聚力的降低而下降。通过控制所述第一聚合物与所述第一辅助粘结剂质量比在上述范围内，能够使所述第一涂层与电极极片间具有优良的粘结力。
本申请对第一辅助粘结剂没有特别限制，只要满足本申请要求即可，例如可以包括聚甲基丙烯酸甲酯、聚丙烯腈、丙烯酸乙酯、丙烯酸丁酯、甲基丙烯酸乙酯、苯乙烯、氯苯乙烯、氟苯乙烯、甲基苯乙烯、丙烯酸、甲基丙烯酸、马来酸、丙烯腈或丁二烯中的至少一种。
在一些实施例中，基于所述第一涂层的总质量，所述第一聚合物的质量百分含量为85％至95％，所述第一辅助粘结剂的质量百分含量为5％至15％。通过控制所述第一聚合物和所述第一辅助粘结剂的含量在上述范围内，能够得到粘接性能优异的第一聚合物，使第一涂层与正极之间具有较高的粘结力，从而提高锂离子电池在低温下的性能。
在一些实施例中，所述第一涂层还包括第一润湿剂。本申请对第一润湿剂没有特别限制，只要满足本申请要求即可，例如可以为聚氧乙烯醚。基于所述第一涂层的总质量，所述第一润湿剂的质量百分含量为0.1％-1％。
在一些实施例中，所述第一涂层在所述第一表面上的正投影面积占所述第一表面的面积比例为5％至60％。在一些实施例中，所述比例为约10％、约15％、约20％、约25％、约30％、约35％、约40％、约45％、约50％、约55％或前述任意两数值之间的范围。
在一些实施例中，所述第一涂层的涂布面密度W1为0.4g/m 2至2g/m 2。在一些实施例中，所述第一涂层的涂布面密度W1为约0.5g/m 2、约0.6g/m 2、约0.7g/m 2、约0.8g/m 2、约0.9g/m 2、约1.0g/m 2、约1.1g/m 2、约1.2g/m 2、约1.3g/m 2、约1.4g/m 2、约1.5g/m 2、约1.6g/m 2、约1.7g/m 2、约1.8g/m 2、约1.9g/m 2或前述任意两数值之间的范围。所述第一涂层的涂布面密度W1越小，电池的弯曲部厚度越小。通过将所述第一涂层的涂布面密度W1控制在上述范围内，可以实现更好的电性能。
在一些实施例中，所述第二涂层包括第二聚合物。
在一些实施例中，所述第二聚合物的Dv50为0.2μm至8μm。在一些实施例中，所述第二聚合物的Dv50为约0.5μm、约1.0μm、约1.5μm、约2.0μm、约2.5μm、约3.0μm、约3.5μm、约4.0μm、约4.5μm、约5.0μm、约5.5μm、约6.0μm、约6.5μm、约7.0μm或前述任意两数值之间的范围。
在一些实施例中，所述第二聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：丙烯酸乙酯、丙烯酸丁酯、甲基丙烯酸乙酯、苯乙烯、氯苯乙烯、氟苯乙烯、甲基苯乙烯、丙烯酸、甲基丙烯酸、马来酸、丙烯腈或丁二烯。
在一些实施例中，所述第二聚合物由苯乙烯、丙烯腈、丙烯酸异丁酯和/或甲基丙烯酸乙酯形成的共聚物。在一些实施例中，所述第二聚合物由80％苯乙烯，5％丁二烯，5％丙烯酸异丁酯以及10％丙烯腈组成。在一些实施例中，所述第二聚合物由80％苯乙烯，10％丙烯酸异丁酯以及10％丙烯腈组成。在一些实施例中，所述第二聚合物由80％苯乙烯，10％甲基丙烯酸乙酯以及10％丙烯腈组成。
在一些实施例中，所述第二涂层还包括第二辅助粘结剂。所述第二聚合物与所述第二辅助粘 结剂质量比为2至20。在一些实施例中，所述第二聚合物与所述第二辅助粘结剂质量比可以是2、4、6、8、10、14、16或前述任意两数值之间的范围。不限于任何理论，当所述第二聚合物与所述第二辅助粘结剂质量比过低时(例如低于2)，所述第二聚合物的含量下降，影响所述第二涂层与电极极片间的粘结力；当所述第二聚合物与所述第二辅助粘结剂质量比过高时(例如高于20)，所述第二涂层内聚力较低，所述第二涂层粘结性能下降。通过控制所述第二聚合物与第二辅助粘结剂质量比在上述范围内，能够使所述第二涂层与电极极片间具有优良的粘结力。
在一些实施例中，基于第二涂层的总质量，第二聚合物的质量百分含量为75％至92.5％，第二辅助粘结剂的质量百分含量为7.5％至25％。通过控制第二聚合物和第二辅助粘结剂的含量在上述范围内，能够得到粘接性能优异的第二涂层，使第二涂层与负极之间具有较高的粘结力，从而提高锂离子电池在低温下的性能。
本申请对第二辅助粘结剂没有特别限制，只要满足本申请要求即可，例如第二辅助粘结剂可以包括聚甲基丙烯酸酯、羧甲基纤维素钠或二甲基硅氧烷中的至少一种。
在一些实施例中，所述第二涂层还包括第二润湿剂。本申请对第二润湿剂没有特别限制，只要满足本申请要求即可，例如可以为有机硅氧烷。基于所述第二涂层的总质量，所述第二润湿剂的质量百分含量为0.1％-1％。
在一些实施例中，所述第二涂层的涂布面密度W2为0.1g/m 2至1g/m 2。在一些实施例中，所述第二涂层的涂布面密度W2为约0.2g/m 2、约0.3g/m 2、约0.4g/m 2、约0.5g/m 2、约0.6g/m 2、约0.7g/m 2、约0.8g/m 2、约0.9g/m 2或前述任意两数值之间的范围。
申请人发现隔膜中添加无机颗粒能够进一步提高隔膜的强度和耐热性能。
在一些实施例中，所述第一涂层和/或所述第二涂层包括无机颗粒，所述无机颗粒在第一涂层或者第二涂层中占涂层总重量的40％～90％。
在另一些实施例中，所述隔膜还包括耐热层，耐热层可以设置在基材和第一涂层之间或基材和第二涂层之间。耐热层包括无机颗粒。通过在基材和第一涂层之间设置耐热层，能够进一步提高隔膜的强度和耐热性能。本申请对耐热层的厚度没有特别限制，例如可以为0.6μm至40μm，只要使得耐热层满足本申请要求即可。
在另一些实施例中，耐热层包括质量比为(87-98.5)∶(1-10)∶(0.5-2)∶(0-1)的无机颗粒、 粘结剂、分散剂以及润湿剂。所述粘结剂和润湿剂与第一涂层中的第一辅助粘结剂和第一润湿剂的定义相同。本申请对所述分散剂没有特别限制，只要满足本申请要求即可，例如分散剂可以为聚丙烯酸。
本申请对耐热层、第一涂层和第二涂层中的无机颗粒没有特别限制，只要能达到本申请目的即可，无机颗粒包括勃姆石、氢氧化镁、氧化铝、二氧化钛、二氧化硅、二氧化锆、二氧化锡、氧化镁、氧化锌、硫酸钡、氮化硼或氮化铝中的至少一种。
在一些实施例中，所述无机颗粒粒径Dv50为0.5μm至35μm。无机颗粒的粒径不宜过大或过小，当无机颗粒的粒径过大时(例如大于35μm)，难以实现其薄涂布设计，影响锂离子电池的能量密度；当无机颗粒的粒径过小时(例如小于0.5μm)，导致无机颗粒堆积孔隙减小，影响离子传输，从而影响锂离子电池的动力学性能。通过控制无机颗粒的Dv50在上述范围内，能够使隔膜具有较高的能量密度和优良的动力学性能。
在一些实施例中，所述第一涂层与所述正极之间的粘接强度为4N/m至20N/m。在一些实施例中，所述第一涂层与所述正极之间的粘接强度为约5N/m、约6N/m、约7N/m、约8N/m、约9N/m、约10N/m、约11N/m、约12N/m、约13N/m、约14N/m、约15N/m、约16N/m、约17N/m、约18N/m、约19N/m或前述任意两数值之间的范围。
在一些实施例中，所述第二涂层与所述负极之间的粘接强度为5N/m至20N/m。在一些实施例中，所述第二涂层与所述负极之间的粘接强度为约6N/m、约7N/m、约8N/m、约9N/m、约10N/m、约11N/m、约12N/m、约13N/m、约14N/m、约15N/m、约16N/m、约17N/m、约18N/m、约19N/m或前述任意两数值之间的范围。
在一些实施例中，所述第一涂层与所述负极之间的粘接强度为3N/m至15N/m。在一些实施例中，所述第一涂层与所述负极之间的粘接强度约4N/m、约5N/m、约6N/m、约7N/m、约8N/m、约9N/m、约10N/m、约11N/m、约12N/m、约13N/m、约14N/m或前述任意两数值之间的范围。
在一些实施例中，所述第二涂层与所述正极之间的粘接强度为5N/m至20N/m。在一些实施例中，所述第二涂层与所述正极之间的粘接强度为约6N/m、约7N/m、约8N/m、约9N/m、约10N/m、约11N/m、约12N/m、约13N/m、约14N/m、约15N/m、约16N/m、约17N/m、约18N/m、约19N/m或前述任意两数值之间的范围。
在一些实施例中，所述正极和所述负极的卷绕层数为N，其中N≥4。在一些实施例中，6≤N≤35。在一些实施例中，8≤N≤30。在一些实施例中，10≤N≤25。在一些实施例中，N为约5、约10、约15、约20、约25、约30、约35或前述任意两数值之间的范围。
在一些实施例中，其中所述第一涂层设置于所述弯曲部。
二、一种制备前述二次电池的方法
如下以锂离子电池为例详细描述了本申请的二次电池的制备方法。
隔膜：隔膜包括基材、设置在基材的第一表面上的第一涂层以及设置在与所述第一表面相对的第二表面上的第二涂层。基材为具有多孔结构的无纺布、膜或复合膜，基材的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。第一涂层和第二涂层则分别为根据前述实施例所述的第一涂层和第二涂层中的任意一种。
隔膜的制备：(1)无机涂层的制备：将无机颗粒、粘结剂、分散剂、润湿剂分散于溶剂体系中，充分搅拌均与后，涂敷于隔膜基材的一个或者两个表面上，经过烘干，得到具有位于基材的一个或者两个表面上的无机涂层的隔膜(简称“无机涂层隔膜”或“耐热层”)。
(2)第一涂层制备：将所选取的第一聚合物、第一润湿剂、第一辅助粘结剂分散于溶剂体系中，一些实施例中，还可以加入无机颗粒，充分搅拌混合均匀后，涂覆于隔膜基材的第一表面上或者步骤1中的无机涂层隔膜的任一表面上，经过烘干，得到具有位于基材第一表面上的第一涂层的隔膜或得到具有位于步骤1中的无机涂层隔膜的任一表面上的第一涂层的隔膜。
(3)第二涂层制备：将所选取的第二聚合物、第二润湿剂、第二辅助粘结剂分散于溶剂体系中，一些实施例中，还可以加入无机颗粒，充分搅拌混合均匀后，涂覆于步骤(2)中获得的隔膜的第二表面上，经过烘干，得到最终隔膜，所述最终隔膜：具有位于基材的第一表面上的第一涂层和位于基材的第二表面的第二涂层；或具有位于基材的第一表面上的无机涂层、位于所述无机涂层上的第一涂层和位于基材的第二表面的无机涂层、位于所述无机涂层上的第二涂层；或具有位于基材的第一表面上的无机涂层、位于所述无机涂层上的第一涂层和位于基材的第二表面的第二涂层；或具有位于基材的第一表面上第一涂层和位于基材的第二表面的无机涂层、位于所述无机涂层上的第二涂层。
负极的制备：将负极活性物质、粘结剂、分散剂和导电材料按一定的质量比分散于溶剂体系中充分搅拌混合均匀后，涂覆于负极集流体上，经过烘干、冷压，得到负极。
在一些实施例中，粘合剂包括，但不限于：聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙。
在一些实施例中，负极活性物质包括导电材料。在一些实施例中，导电材料包括，但不限于：天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、金属粉、金属纤维、铜、镍、铝、银或聚亚苯基衍生物。
在一些实施例中，负极集流体包括，但不限于：铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或覆有导电金属的聚合物基底。
在一些实施例中，溶剂可以包括，但不限于：N-甲基吡咯烷酮。
正极的制备：将正极材料、粘结剂、分散剂和导电材料按一定的质量比分散于溶剂体系中充分搅拌混合均匀后，涂覆于正极集流体上，经过烘干、冷压，得到正极。
在本申请的一些实施例中，所述正极集流体可以为，但不限于，铝箔或镍箔。
在一些实施例中，正极材料包括能够吸收和释放锂(Li)的材料(下文中，有时称为“能够吸收/释放锂Li的正极材料”)。能够吸收/释放锂(Li)的正极材料的实例可以包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和含锂锰基材料中的一种或多种。
在上述正极材料中，钴酸锂的化学式可以为Li xCo aM1 bO 2-c，其中，M1选自由镍(Ni)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、钇(Y)、镧(La)、锆(Zr)、硅(Si)及其组合组成的群组，x、a、b和c值分别在以下范围内：0.8≤x≤1.2、0.8≤a≤1、0≤b≤0.2、-0.1≤c≤0.2；
在上述正极材料中，镍钴锰酸锂或镍钴铝酸锂的化学式可以为Li yNi dM2 eO 2-f，其中，M2选自由钴(Co)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、 铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、锆(Zr)、硅(Si)及其组合组成的群组，y、d、e和f值分别在以下范围内：0.8≤y≤1.2、0.3≤d≤0.98、0.02≤e≤0.7、-0.1≤f≤0.2；
在上述正极材料中，锰酸锂的化学式为Li zMn 2-gM3 gO 4-h，其中M3表示选自由钴(Co)、镍(Ni)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)及其组合组成的群组，z、g和h值分别在以下范围内：0.8≤z≤1.2、0≤g＜1.0和-0.2≤h≤0.2。
在一些实施例中，导电材料以通过向活性物质提供导电路径来改善所述活性物质的导电性。所述导电材料可以包括如下中的至少一种：乙炔黑、科琴黑、天然石墨、炭黑、碳纤维、金属粉末或金属纤维(例如铜、镍、铝或银)，但所述导电材料的示例并不限于此。在一些实施例中，可适宜的调节导电材料的量。基于100重量份的正极活性物质，导电材料和粘结剂，所述导电材料的量的范围为1重量份至30重量份。
在一些实施例中，所述溶剂的示例包括但不限于N-甲基吡咯烷酮，丙酮或水。在一些实施例中，可适当的调节溶剂的量。
在一些实施例中，所述粘结剂可以帮助所述活性物质和所述导电材料之间的粘结，或者帮助所述活性物质和所述集流体之间的粘结。所述粘结剂的示例包括但不限于聚偏氟乙烯、聚偏氯乙烯、羧甲基纤维素、聚乙酸乙烯酯、聚乙烯基吡咯烷酮、聚丙烯、聚乙烯和各种聚合物。基于100重量份的活性物质、导电材料和粘结剂，所述粘结剂的量的范围为1重量份至30重量份。
在一些实施例中，所述集流体具有3微米至20微米范围内的厚度，但本公开内容不限于此。所述集流体是导电的，且不在所制造的电池中引起不利的化学变化。所述集流体的实施例包括铜、不锈钢、铝、镍、钛或合金(例如同-镍合金)，但不公开内容不限于此。在一些实施例中，所述集流体的表面上可包括细小的不规则物(例如，表面粗糙度)以增强所述集流体的表面对活性物质的粘合。在一些实施例中，集流体可以多种形式使用，其实施例包括膜、片、箔、网、多孔结构体、泡沫体或无妨物，但本公开内容不限于此。
电解液：在一些实施例中，所述电解液包括有机溶剂、锂盐和添加剂。在一些实施例中， 有机溶剂包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯或丙酸乙酯中的至少一种。
在一些实施例中，锂盐包括有机锂盐或无机锂盐中的至少一种。在一些实施例中，锂盐包括六氟磷酸锂(LiPF6)、双三氟甲烷磺酰亚胺锂LiN(CF3SO2)2(LiTFSI)、双(氟磺酰)亚胺锂Li(N(SO2F)2)(LiFSI)、双草酸硼酸锂LiB(C2O4)2(LiBOB)或二氟草酸硼酸锂LiBF2(C2O4)(LiDFOB)中的至少一种。
在一些实施例中，基于所述电解液的质量，所述锂盐含量为5％-30％。在一些实施例中，基于所述电解液的质量，所述锂盐的含量为6％-25％。在一些实施例中，基于所述电解液的质量，所述锂盐的含量为8％-20％。在一些实施例中，基于所述电解液的质量，所述锂盐的含量为6％-18％。
在一些实施例中，添加剂包含氟代碳酸乙烯酯，碳酸亚乙烯酯，乙烯基碳酸亚乙酯，1，3-丙烷磺内酯，硫酸乙烯酯，己二腈，丁二腈，戊二腈，1，3，6-己烷三腈，1，2，6-己烷三腈，琥珀酸酐，二氟磷酸锂，四氟硼酸锂中的至少一者。
电池的制备：将正极、隔膜、负极按顺序叠好，使隔膜处于正负极中间起到隔离的作用，并卷绕N层得到裸电芯。将经卷绕所得裸电芯置于外包装中，注入电解液并封装，经过化成、脱气、切边等工艺流程获得完整电芯。其中，卷绕层数定义如下：以任意一侧的弯曲部(或者任意一侧的平直部)为准，每出现一次正极、隔膜和负极的叠加层就标记为一层，全部叠加层的和就是电池的卷绕层数。
三、电化学装置
本申请还提供了一种电化学装置，其包括根据前述内容所述的二次电池。在一些实施例中，所述二次电池为是锂二次电池，例如，锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
四、电子装置
本申请提供了一种电子装置，其包含根据前述内容所述的二次电池。
根据本申请的一些实施例，所述电子装置包括，但不限于：笔记本电脑、笔输入型计算机、 移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池等。
五、具体的实施例
下面结合实施例，对本申请做进一步详细的描述。然而，应理解，以下实施例仅是示例，本申请的实施例方式不限于此。
实施例1至45和对比例1至3
实施例1
隔膜：(1)：依据质量比为93.1％∶5.0％∶1.5％∶0.4％，将勃姆石、聚甲基丙烯酸甲酯、聚丙烯酸、聚氧乙烯醚分散于溶剂体系(水)中，充分搅拌均后，涂敷于隔膜基材的第一表面上，经过烘干，得到具有位于基材的基膜第一表面上的无机涂层的隔膜(简称“无机涂层隔膜”或“耐热层”)。虽然此处将无机颗粒涂覆在基材的基膜第一表面上，应理解，无机颗粒也可以涂覆在基材基膜的另一个表面，或同时涂覆在基材基膜的两个表面，或者基材基膜的两个表面上均未涂覆无机颗粒。
(2)将所选取的第一聚合物(聚偏氟乙烯，100％)、第一辅助粘结剂(聚丙烯腈)和第一润湿剂(聚氧乙烯醚)按照质量比89.5％、10％和0.5％的比例分散于水中，充分搅拌混合均匀后，涂覆于步骤(1)得到的无机涂层隔膜的第一表面上(即，将第一聚合物涂覆在无机涂层上方)，经过烘干，得到具有位于无机涂层隔膜的第一表面上的第一涂层的隔膜。
(3)将所选取的第二聚合物(80％苯乙烯，10％丙烯酸异丁酯，10％丙烯腈聚合形成的共聚物)、第二辅助粘结剂(聚甲基丙烯酸酯)和第二润湿剂(有机硅氧烷)按照质量比79.5％、20％和0.5％的比例分散于水中充分搅拌混合均匀后，涂覆于步骤(2)中获得的无机涂层隔膜的第二表面上，经过烘干，得到本实施例所需隔膜。
其中，在上述制备隔膜的过程中，第一涂层覆盖率(即，所述第一涂层在所述第一表面上的正投影面积占所述第一表面的面积比例)为40％，第一聚合物的软化点为125℃，第一聚合物的Dv50为12μm，第一聚合物的面密度W1为1g/m 2，在所述第一涂层的表面的250μm×200μm区域 内，长度处于10μm至30μm之间的所述第一聚合物的颗粒数量为25个。其中，第二聚合物的Dv50为0.7μm，第二聚合物的面密度W2为0.2g/m 2。
正极：将正极活性材料钴酸锂、与导电剂乙炔黑以及粘结剂聚偏二氟乙烯(PVDF)按重量比97∶2∶1在N-甲基吡咯烷酮溶剂体系中充分搅拌混合均匀后，涂覆于正极集流体Al箔上，烘干、冷压，得到正极。
负极：将活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂碳甲基纤维素钠(CMC)按照质量比约为95∶2∶2∶1在去离子水溶剂体系中充分搅拌混合均匀后，涂覆于Cu箔上烘干、冷压，得到负极。
电解液：在含水量＜10ppm的氩气气氛手套箱中，将碳酸乙烯酯(简写为EC)、碳酸二乙酯(简写为DEC)、碳酸丙烯酯(简写为PC)、按照2∶6∶2的重量比混合均匀，再将充分干燥的锂盐LiPF6溶解于上述溶剂，LiPF6的含量为1mol/L，加入1.5％的1，3-丙烷磺内酯、3％的氟代碳酸乙烯酯、2％的己二腈。其中各物质含量是以电解液的总重量计。
电池的制备：将正极、隔膜、负极按顺序叠好，使隔膜处于正负极中间起到隔离的作用，并卷绕、置于外包装中，注入配好的电解液并封装，经过化成，热压，脱气，切边等工艺得到电池。其中，卷绕层数为20。其中，在所述卷绕结构的弯曲部，相邻的负极和正极之间的距离为d1，在所述卷绕结构的平直部，相邻的负极和正极之间的距离为d2，其中d1/d2为2且其中d1和d2采用相同的单位。其中，d1/d2可以通过，例如，涂布或热压技术来实现。当涂布的重量比较大时，d1会较大。电池经过热压后，d1基本不变，d2显著减小。通过不同的涂布重量和热压条件，可以得到不同的d1和d2，从而控制d1/d2的大小。另外，也可以通过非均匀涂布来控制d1/d2的大小。例如，第一涂层经布置以主要位于弯曲部。
如下表1具体示出了实施例1至45和对比例1至3中的电池参数的差异。除了对比例3因为没有涂层而相应地不具有第一/二辅助粘结剂和第一/二润湿剂外，其它实施例和对比例的第一/二辅助粘结剂和第一/二润湿剂的种类和含量与上述实施例1中的参数相同，表格中不再赘述。如下表格仅展示各实施例和对比例的不同参数设置。实施例45与实施例4的区别仅在于实施例43不含有无机涂层。
表1
Figure PCTCN2022084668-appb-000001
Figure PCTCN2022084668-appb-000002
Figure PCTCN2022084668-appb-000003
Figure PCTCN2022084668-appb-000004
Figure PCTCN2022084668-appb-000005
Figure PCTCN2022084668-appb-000006
Figure PCTCN2022084668-appb-000007
Figure PCTCN2022084668-appb-000008
Figure PCTCN2022084668-appb-000009
[1]：此处颗粒数量为，在所述第一涂层的表面的250μm×200μm区域内，最大长度处于10μm至30μm之间的所述第一聚合物的颗粒数量。
[2]：实施例45与实施例1的区别在于实施例45的隔膜的基材上不具有无机颗粒形成的耐热层，其第一涂层和第二涂层位于隔膜的基材的第一表面和第二表面上。
由上述表1可知，实施例1至45和对比例1至3的区别在于：d1/d2，卷绕层数，在所述第一涂层的表面的250μm×200μm区域内，最大长度处于10μm至30μm之间的所述第一聚合物的颗粒数量，第一涂层的覆盖率，第一聚合物的种类和含量、第一聚合物软化点、第一聚合物Dv50、第一聚合物面面密度、第二聚合物种类和含量、第二聚合物Dv50、第二聚合物面密度、涂层的有无等方面。
除上述差异外，实施例1至45与对比例1至3中的负极、电解液、隔膜等并没有差异。
测试方法
(1)d1、d2的测试方法：
采用电子计算机断层扫描仪器(CT)，放大到300％的倍率，分别扫描电池的弯曲部和平直部，得到横截面图像，取10个点测量弯曲部相邻两层正极集流体之间的最短距离取平均值为D1(此处的“相邻”并非指物理上彼此接触，而是指在所测量的这两个正极集流体之间不存在另一正极集流体，很显然，这两个正极集流体之间还会有隔膜以及负极集流体)，则d1＝D1/2，取10个点测量平直部处上述相邻两层正极集流体之间的最短距离取平均值为D2，则d2＝D2/2，弯曲部选取的相邻两层正极集流体和平直部选取的相邻两层正极集流体是相连接对应的，即，如图1所示的那样，用来测试弯曲部的两层正极集流体和用来测试平直部的两层正极集流体是相同的两层正极集流体。
具体来讲，参见附图1：1为正极膜片(正极活性物质层)，2为正极集流体，3为隔膜，4为负极膜片(负极活性物质层)，5为负极集流体。正极集流体2的上下两个表面上均具有正极膜片(正极活性物质层)3，负极集流体5的上下两个表面上均具有负极膜片(负极活性物质层)4。取10个点测量弯曲部的相邻的两个正极集流体之间的距离取平均值为D1以及取10个点测量平直部的相邻的两个正极集流体之间的距离取平均值为D2，并计算得到d1＝D1/2和d2＝D2/2。
(2)第一聚合物的颗粒数量
将涂有第一涂层的隔离膜裁切为10mm×10mm样品，然后将样品放置在SEM下以500倍放大倍率观察，并在视野中选取任意5个250μm×200μm区域内观察，区域，记录所选取区域中第一聚合物颗粒最大长度处于10μm至30μm之间的颗粒数量，然后取平均值，即为第一涂层单位面积区域内第一聚合物颗粒最大长度处于10μm至30μm之间的颗粒数量。
(3)第一涂层的覆盖率
将涂有第一涂层的隔离膜裁切为10mm×10mm样品，然后将样品放置在SEM下以500倍放大倍率观察，并在视野中选取任意5个250μm×200μm区域。使用图像分割算法将第一涂层标识并拟合计算，得到其覆盖面积S，覆盖率＝S/(250×200)*100％，取5个位置的平均覆盖率得到第一涂层的覆盖率。
(4)软化点
采用通用型差示扫描量热仪(DSC)法：分别取5mg各实施例和对比例制备的第一聚合 物样品，以5℃/min的升温速率升温至150℃，采集DSC曲线，由所得DSC曲线确定第一聚合物的软化点，也即软化温度。
(5)颗粒Dv50
将第一聚合物分散在去离子水中，搅拌均匀。取浆料通过马尔文粒度测试仪进行颗粒度测量：将分散好的样品加入到马尔文粒度测试仪内，开始测试。测试结束可分别得到第一聚合物的颗粒度数据。无机颗粒以及第二聚合物的Dv50采用同样的测试方法。
(6)面密度
使用电子称测试涂层面密度，精度0.0001g。取涂布前的隔膜基材，裁切成10000mm 2，5片，称重取平均值m得到基材重量。取涂布第一涂层后的隔膜，裁切成10000mm 2，5片，称重取平均值M得到涂布第一涂层后的隔膜的重量，则第一涂层的面密度＝M-m，通过单位转换可将单位变成g/m 2。第二涂层面密度采用相同的测试方法。
(7)粘结力
采用180力剥离测试标准测试隔膜与正负极干压粘结力，将隔膜和正负极裁切成54.2mm×72.5mm样品，将隔膜与正极/负极复合，使用热压机热压，在温度为85度、压力为1Mpa的条件下维持85秒，将复合好的样品裁切成15mm×54.2mm小条，按照180°剥离测试标准测试粘结力。分别测试得到第一涂层与负极的粘结力、第一涂层与负极的粘结力、第二涂层与正极的粘结力、第二涂层与负极的粘结力。
(7)电池宽度
采用影像投影仪测试电池的宽度，将卷绕好的电池置于两片透明玻璃板之间，电池长度方向平行于玻璃板宽度方向，电池宽度方向平行于玻璃板的长度方向，玻璃板的长度大于电芯宽度至少100％，玻璃板宽度大于电池长度至少10％。在玻璃板长度方向且不覆盖电池的地方，使用两个30kg的夹子加紧电池，然后将电池平放于影像投影仪的测量桌面上，使用影像投影仪测量出电芯宽度，沿长度方向测试5个位置的宽度，取其平均值得到电池宽度
(8)电池硬度
采用三点弯曲法测试电池硬度：在25：下进行操作，将电池完全放电至3.0V，极耳做绝缘保 护。将万能试验机(Instron-3365)的硬度测试夹具下支撑杆的间距调整到电池宽度的2/3，电池平放在下夹具上，宽度方向与支撑杆垂直。调整夹具的上压头与宽度方向垂直，并处于电池的正中央位置，以5mm/min的速度往下压，上压头刚开始接触电池时，记录电池形变位移，当负载力从最大开始变小时，停止测试，取最大的抗形变的力作为电池的最大硬度。下支撑杆为圆弧形，直径10mm；上压头为圆弧形，直径10mm。
(9)电池倍率放电性能测试方法
-20℃条件下0.5C放电性能：电池25℃环境下静置5分钟，1.5C的充电电流下进行恒流充电，直到电池电压为4.45V，4.45V恒压充电到充电电流为0.05C，静置5分钟后，在0.5C的放电电流下进行恒流放电，直到电池电压为3V，记录首次循环的放电容量C1；重复以上充电流程，将电池充满电；然后将电池置于-20℃环境下，静置60分钟，在0.5C的放电电流下进行恒流放电，直到电池电压为3V，记录放电容量C2，则-20℃ 0.5C的放电性能＝C2/C1*100％。
25℃条件下不同倍率放电性能：电池常温下静置5分钟，1.5C的充电电流下进行恒流充电，直到电池电压为4.45V，4.45V恒压充电到充电电流为0.05C，静置5分钟后，在0.2C的放电电流下进行恒流放电，直到电池电压为3V，记录首次循环的放电容量D1；重复以上充电流程，将电池充满电，在xC的放电电流下进行恒流放电，直到电池电压为3V，记录此时的放电容量Dx，则不同倍率的放电性能＝Dx/D1*100％，其中x＝2、5。
12放条件下循环500次容量保持率：取被测电池在12℃测试温度下，静置30分钟，以2C的电流将电池恒流充电至4.45V，再以4.45V的恒压充电至0.05C；静置5分钟，再以1C的电流恒流放电至3.0V，静置5分钟。重复上述充放电流程500次，记录每一次循环后放电容量。通过下式计算电池第500次循环后容量保持率：第500次循环后容量保持率＝(第500次循环后放电容量/首次循环的放电容量)x100％
如下表2示出了实施例1至45和对比例1至3的各项性能。
表2
Figure PCTCN2022084668-appb-000010
Figure PCTCN2022084668-appb-000011
Figure PCTCN2022084668-appb-000012
Figure PCTCN2022084668-appb-000013
Figure PCTCN2022084668-appb-000014
注：对比例3的隔膜没有第一涂层和第二涂层，因此，上述表2中对比例3的粘结力分别指隔膜第一表面与正极的粘结力以及隔膜第二表面与负极的粘结力。
结果讨论
1.探讨无机涂层(即耐热层)、第一涂层和第二涂层的有无以及d1/d2对电池性能的影响
参考上述表1可知，实施例1-45满足关系式1＜d1/d2＜10，其中实施例1-44的隔膜的第一表面具有耐热层和位于耐热层上的第一涂层，且其隔膜的第二表面具有耐热层和位于耐热层上的第二涂层，实施例45的隔膜的第一表面和第二表面分别具有第一涂层和第二涂层，而对比例1与实施例1-44的区别在于其d1/d2＝1，对比例2与实施例1-44的区别在于其d1/d2＝11，对比例3与实施例1-45的区别在于其隔膜没有任何涂层。
参考上述表2可知，实施例1-45以及对比例1和2的电池的硬度相当(规格要求大于120N)，但是实施例1-45的电池的放电性能以及低温循环性能均优于对比例1和对比例2中的电池的放电性能以及低温循环性能，这主要是因为：对比例1中的d1/d2过低，电池弯曲部间隙过小，循环过程中负极膨胀时，电解液受挤压排出造成电解液局部缺失，循环性能恶化，而对比例2中的d1/d2过大，导致电池的弯曲部间隙过大，当电解液消耗后，易造成电解液局部缺失，循环性能恶化。
实施例1-45和对比例3的电池放电性能以及低温性能相当，但是实施例1-45的电池硬度显著大于对比例3中电池的硬度，而对比例3中过低的电池硬度则导致电池在组装时容易变形、卷绕结构容易错位，引起安全风险；另外硬度低，在电池的充放电过程中，由于负极的无序膨胀会导致正负极之间的界面不平整，使局部出现析锂，从而影响电池的性能。
很显然，通过在正极和负极之间设置一隔膜，其中隔膜经设计以包括基材和分别位于基材的相对的两个表面上的第一涂层和第二涂层，其中第一涂层包括第一聚合物，且其中电池弯曲部的相邻正负极之间的距离d1与电池平直部的相邻正负极之间的距离d2满足1＜d1/d2＜10，可以提供 空间以缓解循环过程中的负极的膨胀，避免电解液受挤压排出造成电解液局部缺失，可以避免间隙过大导致电解液没有足够的量填充间隙，造成电解液局部缺失，可以保证电池的主体部分(即，平直部)的厚度不显著增加，还可以保证电池的硬度从而改善隔膜与正负极之间的粘结力，从而提高电池的倍率性能、循环性能、减小电池体积能量密度的损失等。
本申请进一步研究发现，相比于不具有耐热涂层的实施例45，实施例4的各项性能，尤其是电化学性能，进一步得到改善。这主要是因为，基材表面与聚合物涂层的界面处相对比较致密，不利于锂离子的传输，而耐热涂层中的无机颗粒可以松散该界面结构，例如，无机颗粒可以引入一些空隙，使得锂离子传输更加通畅，降低扩散阻力，等，从而进一步改善电化学装置的电性能。
2.探讨卷绕层数
参考表1和表2可知，尤其是实施例11-13，在本申请的一些实施例中，电池的卷绕层数为N，其中N≥4。卷绕层数的增加导致电池弯曲部的内层受到的挤压增加。卷绕层数越多，电池弯曲部的内层受到的挤压越大，越容易出现电解液局部缺失。使用本隔膜后，可以在弯曲部提供电解液传输和存储的空间，对于不同卷绕层数的电池，均可以获得较佳的电性能。
3.探讨第一聚合物的个数
参考表1和表2可知，尤其是实施例4和14-17，在本申请的一些实施例中，在所述第一涂层的表面的250μm×200μm区域内，长度处于10μm至30μm之间的所述第一聚合物的颗粒数量为10个至30个。本申请研究发现，通过控制第一聚合物的数量在该范围内，可以获得较佳的电池弯曲部厚度数量越多，相应的d1越大。
4.探讨第一聚合物的覆盖率
参考表1和表2，尤其是实施例4和18-22，在本申请的一些实施例中，所述第一涂层在所述第一表面上的正投影面积占所述第一表面的面积比例为5％至60％。本申请研究发现，第一涂层的覆盖率过低会使得隔膜和极片的粘结力过低，从而导致电池硬度过低；而第一涂层的覆盖率过高则易造成隔膜堵孔，影响锂离子的传输，并最终影响电池的电性能。通过将所述第一涂层的覆盖率控制在前述范围内，可以获得较佳的电池硬度，且同时保持较好的电性能。
5.探讨第一聚合物的种类
参考表1和表2，尤其是实施例4与27-28，可知，在本申请的一些实施例中，所述第一聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：偏氟乙烯、六氟丙烯、乙烯、丙烯、氯乙烯或氯丙烯。
应当理解，前述单体中任意一种形成的均聚物或至少两种形成的共聚物均可以实现本申请的技术方案，获得理想的电池性能。然而，经进一步研究发现，一方面，常规的水系聚偏氟乙烯(PVDF)作为第一聚合物形成隔膜的第一涂层时，虽然其大粒径可以为负极膨胀预留间隙，但是，由于材料软化点高，导致界面粘接力低，电池的能量密度损失较大(相比于非水系PVDF减少约2％)；而且电池硬度低，在组装时容易变形、卷绕结构容易错位，引起安全风险；另外硬度低，在电池的充放电过程中，由于负极的无序膨胀会导致正负极之间的界面不平整，使局部出现析锂，从而影响电池性能。另一方面，非水系PVDF作为第一聚合物形成隔膜的第一涂层时，在被热压之后，界面间隙很小，易阻碍电解液的传输，电池弯曲部和平直部均易出现电解液不足，导致嵌锂不足，甚至析锂。而在PVDF中加入六氟丙烯、乙烯、丙烯、氯乙烯或氯丙烯中的至少一者来形成第一涂层时，既可以为负极膨胀提供理想的空隙，又可以保证隔膜与正负极之间的粘结力。
6.探讨第一聚合物的软化点
参考表1和表2，尤其是实施例4与25-28，可知，在本申请的一些实施例中，所述第一聚合物的软化点为90℃至150℃。本申请研究发现，所述第一聚合物软化点太小，会使得隔膜容易出现堵孔的现象，从而影响锂离子的传输，并最终影响电池的电性能，而所述第一聚合物软化点太高，则会降低隔膜与极片的粘结力低，从而在循环过程中出现活性材料的脱落，并最终影响电池的电性能。通过将所述第一聚合物软化点控制在前述范围内，可以获得理想的电性能。
7.探讨第一聚合物的Dv50
参考表1和表2，尤其是实施例4和29-31，可知，在本申请的一些实施例中，所述第一聚合物的Dv50为3μm至16μm。本申请研究发现，所述第一聚合物的Dv50越大，则越容易在电池的弯曲部制备想要的间隙(即，前述d1)，但是，过大的Dv50也会降低电池的体积能量密度。通过将第一聚合物的Dv50控制在上述范围，则可以在为负极膨胀预留空间的同时减小体积能量密度的损失。
8.探讨所述第一涂层的涂布面密度
参考表1和表2，尤其是实施例4和32-34，可知，在本申请的一些实施例中，所述第一涂层的涂布面密度W1为0.4g/m 2至2g/m 2。本申请研究发现，所述第一涂层的涂布面密度W1越小，电池的弯曲部厚度越小。通过将所述第一涂层的涂布面密度W1控制在上述范围内，可以实现更好的电性能。
9.探讨第二聚合物的种类、Dv50以及第二涂层涂布面密度
参考表1和表2，尤其是实施例4和35-36，可知，在本申请的一些实施例中，所述第二聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：丙烯酸乙酯、丙烯酸丁酯、甲基丙烯酸乙酯、苯乙烯、氯苯乙烯、氟苯乙烯、甲基苯乙烯、丙烯酸、甲基丙烯酸、马来酸、丙烯腈或丁二烯。前述范围内的任意一种第二聚合物均可以获得隔膜与负极之间的较强的粘结力。参考表1和表2，尤其是实施例4和37-41，在一些实施例中，所述第二聚合物的Dv50为0.2μm至8μm。参考表1和表2，尤其是实施例4和42-44，在一些实施例中，所述第二聚合物的涂布面密度W2为0.1g/m 2至1g/m 2。
如上是本申请所列举的实施例。然而，由于申请人不能穷举所有的实施例，凡是基于本申请的教导而做出的其它等价的实施例均属于本申请的保护范畴。综上，本申请提供了一种简单易行、且适用于工业化生产的方法来制备具有较高的倍率性能、循环性能以及硬度的二次电池。
整个说明书中对“一些实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例“，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (16)

  1. 一种二次电池，其包含正极、负极和设置于所述正极和所述负极之间的隔膜，所述正极、所述隔膜和所述负极依次层叠卷绕形成含有弯曲部和平直部的卷绕结构，所述隔膜包括基材，所述基材具有第一表面和与所述第一表面相对的第二表面，所述第一表面上设置有第一涂层，所述第一涂层包括第一聚合物，所述第二表面上设置有第二涂层，其中，
    在所述弯曲部，相邻的负极和正极之间的距离为d1，在所述平直部，相邻的负极和正极之间的距离为d2，其中1＜d1/d2＜10。
  2. 根据权利要求1所述的二次电池，其中，在所述第一涂层的表面的250μm×200μm区域内，最大长度处于10μm至30μm之间的所述第一聚合物的颗粒数量为10个至30个。
  3. 根据权利要求1所述的二次电池，其中，所述第一聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：偏氟乙烯、六氟丙烯、乙烯、丙烯、氯乙烯或氯丙烯。
  4. 根据权利要求1所述的二次电池，其中，所述第一聚合物的软化点为90℃至150℃。
  5. 根据权利要求1所述的二次电池，其中，所述第一聚合物的Dv50为3μm至16μm。
  6. 根据权利要求1所述的二次电池，其中，所述第一涂层在所述第一表面上的正投影面积占所述第一表面的面积比例为5％至60％。
  7. 根据权利要求1所述的二次电池，其中，所述第一涂层的涂布面密度W1为0.4g/m 2至2g/m 2。
  8. 根据权利要求1所述的二次电池，其中，所述第二涂层包括第二聚合物，其中所述第二聚合物的Dv50为0.2μm至8μm。
  9. 根据权利要求8所述的二次电池，其中，所述第二聚合物包括由以下单体中的任意一种形成的均聚物或由选自以下单体中的至少两种形成的共聚物：丙烯酸乙酯、丙烯酸丁酯、甲基丙烯酸乙酯、苯乙烯、氯苯乙烯、氟苯乙烯、甲基苯乙烯、丙烯酸、甲基丙烯酸、马来酸、丙烯腈或丁二烯。
  10. 根据权利要求1所述的二次电池，其中，所述第二涂层的涂布面密度W2为0.1g/m 2至1g/m 2。
  11. 根据权利要求1所述的二次电池，其中，所述第一涂层与所述正极之间的粘接强度4N/m至20N/m，或所述第二涂层与所述负极之间的粘接强度5N/m至20N/m。
  12. 根据权利要求1所述的二次电池，其中，所述第一涂层与所述负极之间的粘接强度3N/m至15N/m，且所述第二涂层与所述正极之间的粘接强度5N/m至20N/m。
  13. 根据权利要求1所述的二次电池，其中所述正极和所述负极的卷绕层数为N，其中N≥4。
  14. 根据权利要求1所述的二次电池，其中所述第一涂层设置于所述弯曲部。
  15. 一种电化学装置，其包括根据权利要求1-14所述的二次电池。
  16. 一种电子装置，其包括根据权利要求1-14所述的二次电池。
PCT/CN2022/084668 2022-03-31 2022-03-31 一种二次电池及包含该电池的装置 WO2023184443A1 (zh)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006107742A (ja) * 2004-09-30 2006-04-20 Sanyo Electric Co Ltd 非水電解質二次電池とその製造方法
CN1808759A (zh) * 2004-11-12 2006-07-26 三洋电机株式会社 具有扁平螺旋电极体的二次电池的制造方法
JP2016181409A (ja) * 2015-03-24 2016-10-13 株式会社Ｇｓユアサ 蓄電素子
CN107785620A (zh) * 2016-08-26 2018-03-09 丰田自动车株式会社 锂离子二次电池和电池组
CN209217029U (zh) * 2018-12-29 2019-08-06 宁德时代新能源科技股份有限公司 二次电池以及电池模组
CN114144932A (zh) * 2021-03-31 2022-03-04 宁德新能源科技有限公司 一种隔离膜及包含所述隔离膜的电化学装置和电子装置
CN114175384A (zh) * 2021-03-31 2022-03-11 宁德新能源科技有限公司 隔离膜及包含该隔离膜的电化学装置和电子装置

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006107742A (ja) * 2004-09-30 2006-04-20 Sanyo Electric Co Ltd 非水電解質二次電池とその製造方法
CN1808759A (zh) * 2004-11-12 2006-07-26 三洋电机株式会社 具有扁平螺旋电极体的二次电池的制造方法
JP2016181409A (ja) * 2015-03-24 2016-10-13 株式会社Ｇｓユアサ 蓄電素子
CN107785620A (zh) * 2016-08-26 2018-03-09 丰田自动车株式会社 锂离子二次电池和电池组
CN209217029U (zh) * 2018-12-29 2019-08-06 宁德时代新能源科技股份有限公司 二次电池以及电池模组
CN114144932A (zh) * 2021-03-31 2022-03-04 宁德新能源科技有限公司 一种隔离膜及包含所述隔离膜的电化学装置和电子装置
CN114175384A (zh) * 2021-03-31 2022-03-11 宁德新能源科技有限公司 隔离膜及包含该隔离膜的电化学装置和电子装置

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