[go: up one dir, main page]
More Web Proxy on the site http://driver.im/

WO2024119286A1 - 聚合物、隔离膜及其相关的二次电池和用电装置 - Google Patents

聚合物、隔离膜及其相关的二次电池和用电装置 Download PDF

Info

Publication number
WO2024119286A1
WO2024119286A1 PCT/CN2022/136425 CN2022136425W WO2024119286A1 WO 2024119286 A1 WO2024119286 A1 WO 2024119286A1 CN 2022136425 W CN2022136425 W CN 2022136425W WO 2024119286 A1 WO2024119286 A1 WO 2024119286A1
Authority
WO
WIPO (PCT)
Prior art keywords
structural unit
group
polymer
unsubstituted
substituted
Prior art date
Application number
PCT/CN2022/136425
Other languages
English (en)
French (fr)
Inventor
李雷
陈美煌
郑义
魏满想
徐�明
孙成栋
Original Assignee
宁德时代新能源科技股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to PCT/CN2022/136425 priority Critical patent/WO2024119286A1/zh
Publication of WO2024119286A1 publication Critical patent/WO2024119286A1/zh

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes

Definitions

  • the present application relates to the field of batteries, and in particular to a polymer, an isolation membrane and related secondary batteries and electrical devices.
  • Secondary batteries have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a polymer, a separator and related secondary batteries and electrical devices.
  • the first aspect of the present application provides a polymer, which comprises a first structural unit, a second structural unit and a third structural unit; the first structural unit comprises a structural unit represented by formula (I):
  • R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group; R2 includes one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, and a substituted or unsubstituted C1-C20 hydroxyalkyl group; alternatively, R2 includes one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, and a C1-C12 hydroxyalkyl group;
  • the second structural unit includes a structural unit represented by formula (II):
  • R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group;
  • the third structural unit includes a structural unit represented by formula (III):
  • R4 to R11 each independently include a substituted or unsubstituted C1-C10 alkyl group, one or more of the structural units shown in formula (III-1), and at least one of R4 to R11 includes the structural unit shown in formula (III-1),
  • R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group; R 13 includes a substituted or unsubstituted C1-C10 alkyl group; alternatively, R 13 includes a substituted or unsubstituted C3-C10 alkyl group.
  • the first structural unit in the present application can adjust the glass transition temperature of the polymer due to the flexible monomer segment in the molecular segment, improve the toughness and peel strength of the polymer, and help to play a good bonding role.
  • the second structural unit can produce excellent swelling resistance and high bonding, and help to improve the ion conductivity of the secondary battery.
  • the polymer is applied to the separator, the polymer is in contact with the electrolyte, and the polymer is not easy to swell, and it has good swelling resistance.
  • the third structural unit can give the polymer advantages in heat resistance and mechanical properties, and can ensure the stability of the polymer during the long-term cycle charge and discharge process of the secondary battery, effectively isolate the positive and negative pole pieces, thereby ensuring the safety performance of the secondary battery.
  • the first structural unit and the third structural unit can cooperate to play a synergistic role, improve the bonding performance and heat resistance of the polymer; the first structural unit and the second structural unit can cooperate to play a synergistic role, can improve the stability and swelling resistance of the polymer, etc.
  • the three structural units in the polymer cooperate with each other and can jointly improve the bonding, stability, swelling resistance and thermal stability of the polymer.
  • R1 includes a hydrogen atom or a methyl group
  • R2 includes a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a n-octyl group, an isooctyl group, a 2-ethylhexyl group, a dodecyl group, or an isobornyl group.
  • R 3 includes a hydrogen atom or a methyl group.
  • R4 to R11 each independently include a structural unit as shown in formula (III-1); optionally, R12 includes a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group or a n-pentyl group; and/or R13 includes a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a n-octyl group, an isooctyl group or a 2-ethylhexyl group.
  • one of R 4 to R 11 includes a structural unit as shown in formula (III-1); optionally, R 12 includes a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group or a n-pentyl group; and/or R 13 includes a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a n-octyl group, an isooctyl group or a 2-ethylhexyl group.
  • the molar content of the first structural unit is recorded as A%, 60 ⁇ A ⁇ 100; optionally, 60 ⁇ A ⁇ 80.
  • the molar content of the first structural unit is within the above range, its proportion in the polymer is relatively large, which can improve the flexibility of the polymer, thereby significantly improving the adhesion of the polymer; when the polymer is applied to the isolation membrane, it can improve the bonding force between the polymer and the substrate of the isolation membrane.
  • the molar content of the second structural unit is recorded as B%, 0 ⁇ B ⁇ 20; optionally, 5 ⁇ B ⁇ 20.
  • the stability of the polymer can be significantly improved.
  • the molar content of the third structural unit is recorded as C%, 0 ⁇ C ⁇ 20; optionally, 5 ⁇ C ⁇ 20.
  • the heat resistance of the polymer can be guaranteed, and its proportion is relatively small, which is conducive to increasing the proportion of the first structural unit and the second structural unit, and improving the overall adhesion, stability and anti-swelling properties of the polymer.
  • the molar content of the first structural unit is recorded as A%
  • the molar content of the second structural unit is recorded as B%
  • the molar content of the third structural unit is recorded as C%
  • the polymer satisfies one or more of conditions (1) to (3): (1) 3 ⁇ A/B ⁇ 16; (2) 3 ⁇ A/C ⁇ 16; (3)
  • A:B:C is (12 to 16): (1 to 4): (1 to 4).
  • the number average molecular weight of the polymer is 20000 to 80000, and can be 30000 to 50000.
  • the number average molecular weight of the polymer is within the above range, it is conducive to forming polymer particles with a smaller particle size.
  • it can achieve a light and thin coating of the coating in the separator, reduce the overall thickness of the separator, and thus facilitate the improvement of the energy density of the secondary battery; and the particle size of the polymer particles formed by the polymer will not be too small, which can reduce the risk of polymer particles blocking the substrate in the separator, and can improve the overall air permeability and other properties of the separator.
  • the polymer is in a granular form, and the polymer further satisfies one or more of conditions (I) to (III): (I) the morphology of the polymer includes spherical and/or quasi-spherical shapes; (II) the volume distribution particle size Dv50 of the polymer satisfies: 0.1 ⁇ m ⁇ Dv50 ⁇ 2.0 ⁇ m; optionally, 0.5 ⁇ m ⁇ Dv50 ⁇ 1.2 ⁇ m; (III) the specific surface area of the polymer is denoted as S, and its unit is m 2 /g, 5.0 ⁇ S ⁇ 12.0; optionally, 6.0 ⁇ S ⁇ 10.0.
  • the adhesion, stability, anti-swelling and heat resistance of the polymer can be further improved.
  • the second aspect of the present application provides a method for preparing a polymer, the method being used to prepare the polymer as described in any embodiment of the first aspect of the present application, the method comprising: providing a first monomer, a second monomer and a third monomer; mixing the first monomer, the second monomer and the third monomer, and subjecting the first monomer, the second monomer and the third monomer to polymerization reaction under the action of an initiator to generate a polymer, wherein the first monomer comprises a compound represented by formula (IV),
  • R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group; R2 includes one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, and a substituted or unsubstituted C1-C20 hydroxyalkyl group; alternatively, R2 includes one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, and a C1-C12 hydroxyalkyl group;
  • the second monomer includes a compound represented by formula (V),
  • R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group;
  • the third monomer includes a compound represented by formula (VI),
  • R 30 to R 37 each independently include a substituted or unsubstituted C1-C10 alkyl group, one or more of the structural units shown in formula (VI-1), and at least one of R 30 to R 37 includes the structural unit shown in formula (VI-1),
  • R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group;
  • R 13 includes a substituted or unsubstituted C1-C10 alkyl group; alternatively, R 13 includes a substituted or unsubstituted C3-C10 alkyl group.
  • the step of mixing the first monomer, the second monomer and the third monomer and causing a polymerization reaction to generate a polymer under the action of an initiator includes: adding the first monomer, the second monomer and the third monomer to a solvent and an emulsifier and mixing them to form a mixed system; adding the initiator to the mixed system, causing a polymerization reaction to generate the polymer under the action of the initiator.
  • the first monomer includes one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate.
  • the second monomer includes acrylonitrile and/or methacrylonitrile.
  • the third monomer includes one or more of methacryloxypropyl cage polysilsesquioxane, methacryloxypropyl heptaisobutyl polysilsesquioxane, methacryloxypropyl heptaoctyl polysilsesquioxane, acryloxypropyl cage polysilsesquioxane, acryloxypropyl heptaisobutyl polysilsesquioxane and methacryloxypropyl heptaoctyl polysilsesquioxane.
  • the third aspect of the present application also provides an isolation membrane, comprising a substrate and a coating arranged on at least one surface of the substrate, wherein the coating comprises a polymer as described in any embodiment of the first aspect of the present application or a polymer prepared by the method as described in any embodiment of the second aspect of the present application.
  • the mass percentage of the polymer is m%, m ⁇ 70; optionally, 80 ⁇ m ⁇ 95.
  • the mass percentage of the polymer is within the above range, the overall adhesion, stability, anti-swelling and heat resistance of the isolation membrane can be further improved.
  • the isolation film satisfies one or more of the following conditions (A) to (G):
  • the longitudinal heat shrinkage rate of the isolation film at 150°C for 1 hour is ⁇ 1 ⁇ 5.0%, optionally 0.5% ⁇ 1 ⁇ 3%;
  • the transverse heat shrinkage rate of the isolation film at 150°C for 1 hour is ⁇ 2 ⁇ 5.0%, optionally 0.5% ⁇ 2 ⁇ 2%;
  • the longitudinal tensile strength of the isolation membrane is R m1 ⁇ 3000 kg/cm 2 , optionally 3500 kg/cm 2 ⁇ R m1 ⁇ 4500 kg/cm 2 ;
  • the transverse tensile strength of the isolation film is R m2 ⁇ 3000 kg/cm 2 , optionally 3500 kg/cm 2 ⁇ R m2 ⁇ 4500 kg/cm 2 ;
  • the air permeability of the isolation membrane is MAP ⁇ 250s/100mL, optionally 120s/100mL ⁇ MAP ⁇ 180s/100mL;
  • the wetted length of the isolation film is L ⁇ 30 mm, optionally, 30 mm ⁇ L ⁇ 80 mm;
  • the wetting speed of the isolation film is u ⁇ 3 mm/s, optionally, 3 mm/s ⁇ u ⁇ 10 mm/s.
  • the third aspect of the present application further provides a secondary battery, comprising the isolation membrane of any embodiment of the second aspect of the present application.
  • the fourth aspect of the present application also provides an electrical device, comprising the secondary battery described in the third aspect of the present application.
  • FIG. 1 is a schematic diagram of an embodiment of a secondary battery of the present application.
  • FIG. 2 is an exploded schematic diagram of an embodiment of the secondary battery of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of a battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of a battery pack of the present application.
  • FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present application as a power source.
  • range disclosed in the present application is defined in the form of a lower limit and an 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 special range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range 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).
  • the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of the present application.
  • alkyl encompasses straight and branched alkyl groups.
  • the alkyl group may be a C1 to C50 alkyl group, a C1 to C40 alkyl group, a C1 to C30 alkyl group, a C1 to C20 alkyl group, a C1 to C12 alkyl group, a C1 to C10 alkyl group, a C1 to C6 alkyl group, a C1 to C5 alkyl group, a C1 to C3 alkyl group.
  • the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, etc.
  • the alkyl group may be optionally substituted.
  • cycloalkyl refers to a ring structure formed by more than or equal to three carbon atoms.
  • cycloalkyl can be C3 to C50 cycloalkyl, C3 to C40 cycloalkyl, C3 to C30 cycloalkyl, C3 to C20 cycloalkyl, C3 to C12 cycloalkyl, C3 to C10 cycloalkyl, C3 to C6 cycloalkyl, C3 to C4 cycloalkyl.
  • cycloalkyl includes cyclopropyl, cycloisopropyl, cyclobutyl, cycloisobutyl, tert-butyl ring, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl etc.
  • cycloalkyl can be optionally substituted.
  • hydroxyalkyl is that a hydrogen atom in an alkyl group is replaced by a hydroxyl group.
  • a hydroxyalkyl group can be a C1 to C50 hydroxyalkyl group, a C1 to C40 hydroxyalkyl group, a C1 to C30 hydroxyalkyl group, a C1 to C20 hydroxyalkyl group, a C1 to C12 hydroxyalkyl group, a C1 to C10 hydroxyalkyl group, a C1 to C6 hydroxyalkyl group, a C1 to C5 hydroxyalkyl group, a C1 to C3 hydroxyalkyl group.
  • an alkyl group includes a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxyisopropyl group, a hydroxybutyl group, a hydroxyisobutyl group, a hydroxytert-butyl group, a hydroxypentyl group, a hydroxyhexyl group, a hydroxyheptyl group, a hydroxyoctyl group, etc.
  • an alkyl group can be optionally substituted.
  • hydrogen refers to 1H (protium, H), 2H (deuterium, D) or 3H (tritium, T). In various embodiments, “hydrogen” may be 1H (protium, H).
  • C1 to C8 alkyl discloses C1, C2, C3, C4, C5, C6, C7, C8, C1 to C8, C1 to C7, C1 to C6, C1 to C5, C1 to C4, C1 to C3, C1 to C2, C2 to C8, C2 to C7, C2 to C6, C2 to C5, C2 to C4, C2 to C3, C3 to C8, C3 to C7, C3 to C6, C3 to C5, C3 to C4, C4 to C8, C4 to C7, C4 to C6, C4 to C5, C5 to C8, C5 to C7, C5 to C6, C6 to C8, C6 to C7 and C7 to C8 alkyl.
  • the substituent group may be a halogen atom or a heteroatom.
  • halogen atom means a fluorine atom, a chlorine atom, a bromine atom or the like.
  • heteroatom refers to a nitrogen atom, a sulfur atom, a phosphate atom, and the like.
  • a secondary battery typically includes an electrode assembly and an electrolyte.
  • the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet. Its main function is to prevent the positive electrode sheet and the negative electrode sheet from short-circuiting, while allowing active ions to pass freely to form a loop.
  • the separator is an important component of the secondary battery, and the safety performance of the secondary battery can be improved by improving the performance of the separator.
  • the isolation film in the related art has poor adhesion, and the isolation film has poor adhesion to the positive and negative pole pieces.
  • a coating containing a polymer is applied to the substrate to improve its adhesion; however, the polymer coating still has the problem of high-temperature shrinkage.
  • the secondary battery will release heat during the long-term cycle charge and discharge process, and the heat causes the temperature inside the secondary battery to rise.
  • the isolation film has poor heat resistance and a high shrinkage rate at high temperatures, so that the isolation film as a whole cannot play a good insulating role for the positive and negative pole pieces, thereby deteriorating the safety performance of the secondary battery.
  • the isolation film also needs to have good swelling resistance under the infiltration of the electrolyte.
  • the isolation film of the related art is difficult to take into account adhesion, heat resistance and swelling resistance.
  • the coating includes a polymer, and the polymer is formed by polymerizing monomers with multiple functions, thereby improving the performance of the isolation membrane.
  • the technical solution of the present application is described in detail below.
  • the present application provides a polymer, which includes a first structural unit, a second structural unit, and a third structural unit.
  • the first structural unit comprises a structural unit represented by formula (I),
  • R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group;
  • R2 includes one or more of substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C1-C20 hydroxyalkyl; alternatively, R2 includes one or more of C1-C12 alkyl, C3-C12 cycloalkyl, C1-C12 hydroxyalkyl.
  • the second structural unit comprises a structural unit represented by formula (II),
  • R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.
  • the third structural unit includes a structural unit represented by formula (III),
  • R4 to R11 each independently include a substituted or unsubstituted C1-C10 alkyl group, one or more of the structural units shown in formula (III-1), and at least one of R4 to R11 includes the structural unit shown in formula (III-1),
  • R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group; R 13 includes a substituted or unsubstituted C1-C10 alkyl group; alternatively, R 13 includes a substituted or unsubstituted C3-C10 alkyl group.
  • the polymer of the present application includes a first structural unit, a second structural unit and a third structural unit, and has good adhesion, stability, anti-swelling and heat resistance, etc.
  • the first structural unit can be formed by opening the carbon-carbon double bond of an acrylic ester monomer during the polymerization process.
  • the flexible monomer segment in the molecular chain segment can adjust the glass transition temperature of the polymer, improve the toughness and peel strength of the polymer, and help to exert a good bonding effect.
  • the second structural unit can be formed by opening the carbon-carbon double bond of acrylonitrile monomers during the polymerization process.
  • the second structural unit can produce excellent anti-swelling and high adhesion, and help improve the ion conductivity of the secondary battery.
  • the polymer is used in the separator, the polymer is in contact with the electrolyte, and the polymer is not easy to swell, and it has good anti-swelling properties.
  • the third structural unit is formed by opening the carbon-carbon double bond of the substituted or unsubstituted acryloxy group of polysilsesquioxane during the polymerization process.
  • Polysilsesquioxane can be considered as a material containing an organic-inorganic hybrid core-shell structure, with an internal inorganic framework as the core, that is, a skeleton structure composed of Si-O-Si or Si-O bonds; its shell is composed of an organic substituent (C1-C5 alkyl), the organic substituent is wrapped outside the skeleton structure, and the organic substituent is connected to the Si element of the skeleton structure.
  • the core structure of polysilsesquioxane can give the polymer advantages in heat resistance and mechanical properties, and its shrinkage is poor. It can ensure the stability of the polymer during the long-term cycle charge and discharge of the secondary battery, effectively isolate the positive and negative pole pieces, thereby ensuring the safety performance of the secondary battery; and because the particle size of polysilsesquioxane is small and the specific surface area is large, in terms of physical scale, it is similar to most polymer segments, so that the atoms on the surface of polysilsesquioxane have high reactivity, and the polymer modified by polysilsesquioxane has good heat resistance, flame retardancy and oxidation resistance.
  • the synergistic effect between the structural units cannot be ignored.
  • the first structural unit and the third structural unit can play a synergistic role in improving the bonding performance and heat resistance of the polymer; the first structural unit and the second structural unit can play a synergistic role in improving the stability and anti-swelling property of the polymer.
  • the molar content of the first structural unit is recorded as A%, 60 ⁇ A ⁇ 100.
  • the molar content of the first structural unit is within the above range, its proportion in the polymer is relatively large, which can improve the flexibility of the polymer, thereby significantly improving the adhesion of the polymer; when the polymer is applied to an isolation membrane, it can improve the bonding strength between the polymer and the substrate of the isolation membrane.
  • 60 ⁇ A ⁇ 80 the molar content of the first structural unit can be 60%, 65%, 70%, 75%, 80% or a range consisting of any two of the above values.
  • the molar content of the second structural unit is recorded as B%, 0 ⁇ B ⁇ 20.
  • the stability of the polymer can be significantly improved.
  • the molar content of the second structural unit can be 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20% or a range consisting of any two of the above values.
  • the molar content of the third structural unit is recorded as C%, 0 ⁇ C ⁇ 20.
  • the heat resistance of the polymer can be guaranteed, and its proportion is relatively small, which is beneficial to increase the proportion of the first structural unit and the second structural unit, and improve the overall adhesion, stability and anti-swelling properties of the polymer.
  • 5 ⁇ C ⁇ 20 the molar content of the third structural unit can be 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20% or a range consisting of any two of the above values.
  • the polymer includes a first structural unit, which gives the polymer good adhesion and flexibility; however, since the polymer will inevitably come into contact with the electrolyte when applied to the isolation membrane, the swelling effect of the electrolyte will reduce the adhesion of the polymer to a certain extent; and the polymer also includes a second structural unit, and the cyano group in the second structural unit can play a synergistic role with the first structural unit to jointly improve the anti-swelling and adhesion properties of the polymer; especially when the present application further satisfies 3 ⁇ A/B ⁇ 16, the first structural unit can more fully play a synergistic role with the second structural unit to improve the adhesion, stability and anti-swelling properties of the polymer.
  • A/B can be 3, 4, 5, 8, 10, 12, 15, 16 or a range consisting of any two of the above values.
  • the polymer includes a first structural unit, which gives the polymer good adhesion, but its own heat resistance is relatively poor.
  • the polymer also includes a third structural unit, and the inorganic structure of polysilsesquioxane in the third structural unit can synergize with the first structural unit to improve the overall heat resistance and adhesion of the polymer; especially when the present application further satisfies 3 ⁇ A/C ⁇ 16, the first structural unit can more fully synergize with the third structural unit to improve the adhesion and heat resistance of the polymer.
  • A/C can be 3, 4, 5, 8, 10, 12, 15, 16 or a range consisting of any two of the above values.
  • A:B:C is (12 to 16):(1 to 4):(1 to 4).
  • the three structural units in the polymer cooperate with each other to jointly improve the adhesion, stability, anti-swelling and thermal stability of the polymer.
  • A:B:C can be 12:4:4, 13:4:3, 14:4:2, 15:4:1, 16:3:1, 13:3:4 or 15:1:4.
  • the first structural unit includes a variety of chemical structures, and the specific chemical structure of the first structural unit is described below.
  • R 1 includes a hydrogen atom or a methyl group.
  • R 2 comprises methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-octyl, isooctyl, 2-ethylhexyl, dodecyl, or isobornyl.
  • the first structural unit includes one or more of the structures represented by formula (I-1) to the structures represented by formula (I-8):
  • the second structural unit includes a variety of chemical structures, and the specific chemical structure of the second structural unit is described below.
  • R 3 includes a hydrogen atom or a methyl group.
  • the second structural unit includes one or more of the structures represented by formula (II-1) to the structures represented by formula (II-4):
  • the third structural unit includes a variety of chemical structures, and the specific chemical structure of the third structural unit is described below.
  • R4 to R11 each independently include a structural unit as shown in formula (III-1); optionally, R12 includes a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group or a n-pentyl group; and/or R13 includes a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a n-octyl group, an isooctyl group or a 2-ethylhexyl group.
  • one of R 4 to R 11 includes a structural unit as shown in formula (III-1); optionally, R 12 includes a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group or a n-pentyl group; and/or R 13 includes a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a n-octyl group, an isooctyl group or a 2-ethylhexyl group.
  • the types of groups in the polymer can be determined by infrared spectroscopy.
  • the infrared spectrum of the material can be tested to determine the characteristic peaks it contains, thereby determining the type of the modified group.
  • the material can be subjected to infrared spectroscopy analysis using instruments and methods known in the art, such as an infrared spectrometer (such as the IS10 Fourier transform infrared spectrometer from Nicolet, USA), and tested in accordance with GB/T 6040-2019 General Rules for Infrared Spectroscopy Analysis Methods.
  • the polymer has a characteristic peak in the range of 1750 cm -1 to 1735 cm -1 in its infrared spectrum, which indicates the presence of an ester group.
  • the polymer has a characteristic peak at 2260 cm -1 to 2220 cm -1 in its infrared spectrum, which indicates the presence of a cyano group.
  • the polymer has a characteristic peak at 1100 cm -1 to 1120 cm -1 in its infrared spectrum, which indicates the presence of a Si-O-Si skeleton of silsesquioxane.
  • the inventors found in further research that when the specific parameters of the polymer are within a specific range, the adhesion and stability of the polymer can be significantly improved.
  • the number average molecular weight of the polymer is 20,000 to 80,000, and can be optionally 30,000 to 50,000.
  • the number average molecular weight of the polymer can be 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, or a range consisting of any two of the above values.
  • the number average molecular weight of the polymer is within the above range, it is conducive to the formation of polymer particles with a smaller particle size.
  • the isolation membrane When applied to an isolation membrane, it can achieve a thin coating of the coating in the isolation membrane, reduce the overall thickness of the isolation membrane, and thus facilitate the improvement of the energy density of the secondary battery; and the particle size of the polymer particles formed by the polymer will not be too small, which can reduce the risk of polymer particles clogging the substrate in the isolation membrane and improve the overall air permeability and other properties of the isolation membrane.
  • the number average molecular weight of the polymer can be tested by gel permeation chromatography (GPC). Specifically, the GPC1515 instrument of Waters Company of the United States is used for the test. The sample is dissolved in tetrahydrofuran, the dissolution time is more than 12 hours, the concentration of the sample is 4 mg/ml, the sample is filtered, the test temperature is 25°C, and the test flow rate is 1 ml/min for testing.
  • GPC gel permeation chromatography
  • the inventors have found in further studies that when the polymer is in a granular form, the adhesion, stability, anti-swelling and heat resistance of the polymer can be further improved when at least one of the following conditions is met.
  • the morphology of the polymer includes spherical and/or quasi-spherical shapes.
  • the polymer is in a granular form.
  • the spherical and/or quasi-spherical granules can ensure good overlap between particles, and there are gaps between the particles, which is conducive to building a stable spatial network structure, thereby improving the ion transport characteristics and external force extrusion resistance of the separator.
  • the gaps between the spherical and/or quasi-spherical particles are large, which can slow down the effect of the coating on the air permeability of the substrate, further improve the overall air permeability and ion conductivity of the separator, and improve the dynamic performance of the secondary battery.
  • the larger porosity between the spherical and/or quasi-spherical particles is conducive to improving the wettability of the separator to the electrolyte and the liquid retention rate and liquid retention rate of the separator, further improving the dynamic performance of the secondary battery; and the larger porosity can have a weight reduction effect, which is conducive to improving the energy density per unit weight of the secondary battery; and it can reduce the amount of polymer in the coating, which is conducive to reducing the cost of the secondary battery.
  • the morphology of the polymer can be observed by a scanning electron microscope (SEM), for example, a JSM-5610LV scanning electron microscope produced by FEI Company of the United States is used to observe the morphology structure after vacuum gold spraying on the sample.
  • SEM scanning electron microscope
  • the volume distribution particle size Dv50 of the polymer satisfies: 0.1 ⁇ m ⁇ Dv50 ⁇ 2.0 ⁇ m; optionally, 0.5 ⁇ m ⁇ Dv50 ⁇ 1.2 ⁇ m.
  • the particle size of the polymer is relatively small, which is conducive to the uniform dispersion of the polymer when the polymer is applied to the isolation membrane, and the performance of the film layer formed by it is more uniform.
  • the volume distribution particle size Dv50 of the polymer can be 0.1 ⁇ m, 0.2 ⁇ m, 0.5 ⁇ m, 0.8 ⁇ m, 1.0 ⁇ m, 1.2 ⁇ m, 1.5 ⁇ m, 2.0 ⁇ m or a range consisting of any two of the above values.
  • the volume distribution particle size Dv50 of a polymer is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured with reference to GB/T 19077-2016 particle size distribution laser diffraction method and using a laser particle size analyzer (e.g., Master Size 3000).
  • a laser particle size analyzer e.g., Master Size 3000
  • the specific surface area of the polymer is denoted as S, and its unit is m 2 /g, 5.0 ⁇ S ⁇ 12.0; alternatively, 6.0 ⁇ S ⁇ 10.0.
  • S the specific surface area of the polymer
  • the specific surface area of the polymer is relatively large, which is conducive to good overlap between particles, making it easier to form a pore structure between polymer particles, which is conducive to the migration of active ions.
  • the specific surface area of the polymer can be 5.0m 2 /g, 5.5m 2 /g, 6.0m 2 /g, 7.0m 2 /g, 8.0m 2 / g, 9.0m 2 /g, 10.0m 2 /g, 11.0m 2 / g, 12.0m 2 /g or a range consisting of any two of the above values.
  • the specific surface area of a polymer is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured by nitrogen adsorption specific surface area analysis test method according to GB/T 19587-2017 and calculated by BET (Brunauer Emmett Teller) method. Alternatively, the nitrogen adsorption specific surface area analysis test can be performed by Tri-Star 3020 specific surface area pore size analysis tester from Micromeritics, USA.
  • the present application provides a method for preparing a polymer, which can be used to prepare the polymer of any embodiment of the first aspect of the present application.
  • the method comprises:
  • Step S100 providing a first monomer, a second monomer and a third monomer
  • Step S200 mixing the first monomer, the second monomer and the third monomer, and causing a polymerization reaction under the action of an initiator to generate a polymer.
  • the first monomer, the second monomer and the third monomer are mixed and copolymerized, and the formed polymer is a copolymer of the three monomers.
  • the first monomer includes a compound represented by formula (IV),
  • R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R1 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group;
  • R2 includes one or more of substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C1-C20 hydroxyalkyl; alternatively, R2 includes one or more of C1-C12 alkyl, C3-C12 cycloalkyl, C1-C12 hydroxyalkyl.
  • the first monomer is an acrylic acid ester compound, and when it is polymerized, the carbon-carbon double bond opens to form a first structural unit.
  • the first monomer includes one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate.
  • the second monomer includes a compound represented by formula (V),
  • R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 3 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.
  • the second monomer is an acrylonitrile compound, and when it is polymerized, the carbon-carbon double bond opens to form a second structural unit.
  • the second monomer includes acrylonitrile and/or methacrylonitrile.
  • the third monomer includes a compound represented by formula (VI),
  • R 30 to R 37 each independently include a substituted or unsubstituted C1-C10 alkyl group, one or more of the structural units represented by formula (VI-1), and at least one of R 30 to R 37 is the structural unit represented by formula (VI-1),
  • R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group; alternatively, R 12 includes one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group;
  • R 13 includes a substituted or unsubstituted C1-C10 alkyl group; alternatively, R 13 includes a substituted or unsubstituted C3-C10 alkyl group.
  • the third monomer includes one or more of methacryloxypropyl cage polysilsesquioxane, methacryloxypropyl heptaisobutyl polysilsesquioxane, methacryloxypropyl heptaoctyl polysilsesquioxane, acryloxypropyl cage polysilsesquioxane, acryloxypropyl heptaisobutyl polysilsesquioxane and methacryloxypropyl heptaoctyl polysilsesquioxane.
  • step S200 specifically includes:
  • Step S210 adding a first monomer, a second monomer and a third monomer into a solvent and an emulsifier and mixing them to form a mixed system;
  • Step S220 adding an initiator to the mixed system, and causing a polymerization reaction under the action of the initiator to generate a polymer.
  • the present application can copolymerize multiple monomers by emulsion polymerization, and the polymerization method is simpler.
  • the present application can also adopt other polymerization methods, such as solution polymerization, suspension polymerization, etc.
  • the process parameters used in the polymerization process can be selected from the commonly used parameters in the field, which will not be repeated here.
  • the emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkyl diphenyl oxide disulfonate, and ammonium ethoxylated alkylphenol sulfate.
  • the ratio of the mass percentage of the emulsifier to the mass percentage of the first monomer, the second monomer and the third monomer is 0.1% to 5%, that is, the amount of the emulsifier is 0.1% to 5% of the total mass of the three monomers.
  • the mass percentage of the emulsifier is within the above range, the first monomer, the second monomer and the third monomer can be emulsified and dispersed in the solvent to form a relatively uniform system.
  • the initiator includes potassium persulfate and/or ammonium persulfate.
  • the ratio of the mass percentage of the initiator to the mass percentage of the second monomer, the second monomer and the third monomer is 0.15% to 1%, that is, the amount of the initiator is 0.1% to 5% of the total mass of the three monomers.
  • the mass percentage of the initiator is within the above range, sufficient polymerization can be ensured.
  • the solvent may include water such as deionized water.
  • the method includes:
  • prepolymer deionized water, emulsifier, first polymerizable monomer, second polymerizable monomer and third polymerizable monomer are mixed and stirred uniformly to obtain prepolymer;
  • Preparation of polymer Add emulsifier and deionized water into a container and stir and emulsify for 30 to 60 minutes.
  • a uniform and stable emulsion is obtained; then the prepolymer and initiator solution prepared in the step are slowly added dropwise (the initiator potassium persulfate and/or ammonium persulfate is dissolved in deionized water to form a solution), after the addition is completed, the temperature is raised to 90°C to 110°C and kept warm for reaction for 0.5h, cooled to 40°C, the pH is adjusted to 7 to 8 with ammonia water, filtered, discharged, and the polymer is obtained through a drying process.
  • the present application proposes an isolation membrane.
  • the isolation membrane includes a substrate and a coating disposed on at least one surface of the substrate, wherein the coating includes a polymer as described in any embodiment of the first aspect of the present application or a polymer prepared by the method described in any embodiment of the second aspect of the present application. Since the polymer has excellent adhesion, stability, swelling resistance and heat resistance, when it is applied to the coating of the isolation membrane, the adhesion, stability, swelling resistance and heat resistance of the isolation membrane as a whole can be significantly improved.
  • the mass percentage of the polymer is m%, and m ⁇ 70;
  • the mass percentage of the polymer is within the above range, the adhesion, stability, anti-swelling and heat resistance of the isolation film as a whole can be further improved.
  • the mass percentage of the polymer m% can be 70%, 80%, 85%, 86%, 88%, 90%, 92%, 95%, 98%, 99% or a range consisting of any two of the above values.
  • the present application has no particular restrictions on the material of the substrate, and any known substrate with good chemical stability and mechanical stability can be selected, such as at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the substrate can be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer can be the same or different.
  • the coating layer may further include a filler.
  • the filler may include at least one of inorganic particles and organic particles.
  • the decomposition temperature of the filler may be above 200° C., so that the filler has the characteristics of good thermal stability and being difficult to decompose, thereby further improving the heat resistance of the isolation film.
  • the inorganic particles have the characteristics of high thermal stability and not easy to decompose.
  • the inorganic particles include at least one of inorganic particles with a dielectric constant of 5 or more, inorganic particles with ion conductivity but not storing ions, and inorganic particles capable of electrochemical reactions.
  • the inorganic particles having a dielectric constant of 5 or more include at least one of boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite , hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti) O3 (abbreviated as PZT), Pb1 - mLamZr1 - nTinO3 (abbreviated as PLZT, 0 ⁇ m ⁇ 1, 0 ⁇ n ⁇ 1), Pb
  • each inorganic particle can be modified by chemical modification and/or physical modification.
  • the chemical modification includes coupling agent modification (for example, using silane coupling agent, titanate coupling agent, etc.), surfactant modification, polymer grafting modification, etc.
  • the physical modification can be mechanical force dispersion, ultrasonic dispersion, high energy treatment, etc.
  • the modification treatment can reduce the agglomeration of inorganic particles, thereby enabling them to form a more stable and uniform spatial network structure with nanocellulose; in addition, by selecting coupling agents, surfactants or polymer-modified inorganic particles with specific functional groups, it is also helpful to improve the coating's wetting properties for the electrolyte and improve the bonding strength between the coating and the substrate.
  • the inorganic particles having ion conductivity but not storing ions include Li3PO4 , lithium titanium phosphate Lix1Tiy1 ( PO4 ) 3 , lithium aluminum titanium phosphate Lix2Aly2Tiz1 ( PO4 ) 3 , (LiAlTiP) x3Oy3 type glass , lithium lanthanum titanate Lix4Lay4TiO3 , lithium germanium thiophosphate Lix5Gey5Pz2Sw , lithium nitride Lix6Ny6 , SiS2 type glass Lix7Siy7Sz3 and P2S5 type glass Lix8Py8S At least one of z4 , 0 ⁇ x1 ⁇ 2, 0 ⁇ y1 ⁇ 3, 0 ⁇ x2 ⁇ 2, 0 ⁇ y2 ⁇ 1, 0 ⁇ z1 ⁇ 3, 0 ⁇ x3 ⁇ 4, 0 ⁇ y3 ⁇ 13, 0 ⁇ x4 ⁇ 2, 0 ⁇ y4 ⁇ 3, 0 ⁇ x5 ⁇ 4,
  • the inorganic particles capable of undergoing electrochemical reaction include at least one of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials and lithium-titanium compounds.
  • Organic particles have good thermal stability and are not easy to decompose, which can improve the heat resistance of the isolation membrane; at the same time, when the internal temperature of the secondary battery reaches the melting point of the organic particles due to overcharge abuse, heat abuse, etc., the organic particles can also melt and be sucked into the micropores of the substrate due to capillary action to play a role in closing the pores and breaking the circuit, which is beneficial to ensure that the secondary battery has high safety performance.
  • the organic particles include but are not limited to polyethylene particles, polypropylene particles, polystyrene particles, melamine resin particles, phenolic resin particles, polyester particles (such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, polyaryletherketone particles, and copolymers of butyl acrylate and ethyl methacrylate (such as cross-linked polymers of butyl acrylate and ethyl methacrylate).
  • polyester particles such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate
  • polyimide particles such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate
  • polyimide particles such as polyethylene terephthalate
  • the glass transition temperature of the organic particles may be above 130°C.
  • the organic particles include but are not limited to at least one of melamine formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, and polyaryletherketone particles.
  • the coating further comprises a binder.
  • a binder comprises at least one of an aqueous solution type acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, sodium acrylate monomers or a copolymer with other comonomers), polyvinyl alcohol, isobutylene-maleic anhydride copolymer, and polyacrylamide.
  • the content of the binder in the coating is less than 30%, based on the mass of the coating.
  • the isolation film may further include an adhesive layer, which is disposed on at least a portion of the surface of the coating and includes a binder.
  • the adhesive layer can not only prevent the coating from falling off and improve the safety performance of the secondary battery, but also improve the interface between the isolation film and the electrode and enhance the cycle performance of the secondary battery.
  • the binder includes at least one of an acrylate monomer homopolymer or copolymer, an acrylic acid monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer.
  • the comonomer includes but is not limited to at least one of an acrylate monomer, an acrylic acid monomer, an olefin monomer, a halogen-containing olefin monomer, a fluoroether monomer, and the like.
  • the binder includes a vinylidene fluoride based polymer, such as a homopolymer of vinylidene fluoride monomer (VDF) and/or a copolymer of vinylidene fluoride monomer and other comonomers.
  • VDF vinylidene fluoride monomer
  • the other comonomers may be at least one of an olefin monomer, a fluorine-containing olefin monomer, a chlorine-containing olefin monomer, an acrylate monomer, an acrylic monomer, and a fluoroether monomer.
  • the other comonomers may include trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), 1,2-vinylidene fluoride, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro (alkyl vinyl) ether (e.g., perfluoro (methyl vinyl) ether PMVE, perfluoro (ethyl vinyl) ether PEVE, perfluoro (propyl vinyl) ether PPVE), perfluoro (1,3-dioxole) and perfluoro (2,2-dimethyl-1,3-dioxole) (PDD).
  • VF3 trifluoroethylene
  • CTFE chlorotrifluoroethylene
  • TFE tetrafluoroethylene
  • HFP hexafluoropropylene
  • perfluoro (alkyl vinyl) ether e.g., perfluoro (methyl vinyl) ether PMVE, perfluoro
  • the longitudinal heat shrinkage rate ⁇ 1 of the isolation film at 150° C. for 1 hour is ⁇ 5.0%, optionally, 0.5% ⁇ 1 ⁇ 3%.
  • the transverse heat shrinkage rate ⁇ 2 of the isolation film at 150° C. for 1 hour is ⁇ 5.0%, optionally, 0.5% ⁇ 2 ⁇ 2%.
  • the isolation film of the present application has low thermal shrinkage in both the transverse and longitudinal directions at a high temperature of 150° C., thereby further improving the safety performance of the secondary battery.
  • the longitudinal tensile strength of the separator is R m1 ⁇ 3000 kg/cm 2 , optionally, 3500 kg/cm 2 ⁇ R m1 ⁇ 4500 kg/cm 2 .
  • the transverse tensile strength of the separator is R m2 ⁇ 3000 kg/cm 2 , optionally, 3500 kg/cm 2 ⁇ R m2 ⁇ 4500 kg/cm 2 .
  • the isolation membrane of the present application has high tensile strength in both the transverse and longitudinal directions, so that when the secondary battery expands, the isolation membrane is less likely to be damaged, thereby further improving the safety performance of the secondary battery.
  • the air permeability of the isolation membrane is MAP ⁇ 250s/100mL, and optionally, 120s/100mL ⁇ MAP ⁇ 180s/100mL.
  • the isolation membrane of the present application has good air permeability, thereby improving ion transmission properties.
  • the wetted length L of the isolation film is ⁇ 30 mm, optionally, 30 mm ⁇ L ⁇ 80 mm.
  • the wetting speed of the isolation film u ⁇ 3 mm/s, optionally, 3 mm/s ⁇ u ⁇ 10 mm/s.
  • the separator of the present application has good electrolyte infiltration characteristics, thereby being able to improve ion transport characteristics and secondary battery capacity.
  • the heat shrinkage, tensile strength and air permeability of the isolation film have well-known meanings in the art and can be measured by methods known in the art. For example, they can all be tested with reference to standard GB/T 36363-2018.
  • the wetting length and wetting speed of the isolation membrane have well-known meanings in the art and can be measured by methods known in the art.
  • An exemplary test method is as follows: cut the isolation membrane into samples with a width of 5 mm and a length of 100 mm, fix the two ends of the sample and place it horizontally; take 0.5 mg of electrolyte and drop it in the center of the sample. After reaching the specified time (1 min in this application), take a picture and measure the length of the electrolyte diffusion, thereby obtaining the wetting length and wetting speed of the isolation membrane.
  • multiple (for example, 5 to 10) samples can be taken for testing, and the test results are obtained by calculating the average value.
  • the electrolyte can be prepared as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20 to obtain an organic solvent, and the fully dried LiPF 6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the coating parameters (such as surface density, thickness, etc.) of the above-mentioned isolation film are the coating parameters of one side of the substrate.
  • the coating parameters on either side satisfy the present application and are considered to fall within the protection scope of the present application.
  • the present application further provides a method for preparing an isolation membrane, which can be used to prepare the isolation membrane of any embodiment of the third aspect of the present application.
  • the method comprises:
  • Step S10 providing a substrate
  • Step S20 preparing a coating slurry: mixing a polymer in a solvent according to a predetermined mass to prepare the coating slurry;
  • Step S30 coating: coating the coating slurry on at least one surface of the substrate to form a coating and drying to obtain an isolation film, wherein the isolation film includes a substrate and a coating disposed on at least one surface of the substrate.
  • the polymer in step S20 can be the polymer of any embodiment of the first aspect of the present application, or a polymer prepared by the method described in any embodiment of the second aspect of the present application.
  • the solvent in step S20, may be water, such as deionized water.
  • the coating slurry may further include other components, for example, a dispersant, a wetting agent, a binder, etc.
  • the solid content of the coating slurry in step S20, can be controlled between 28% and 45%, for example, between 30% and 38%.
  • the film surface problem of the coating layer can be effectively reduced and the probability of uneven coating can be reduced, thereby further improving the energy density and safety performance of the secondary battery.
  • the coating is performed using a coating machine.
  • the present application has no particular restrictions on the type of coating machine, for example, a commercially available coating machine can be used.
  • the coating machine includes a gravure roller; the gravure roller is used to transfer the coating slurry to the substrate.
  • the coating method may be transfer coating, spin spray coating, dip coating, etc.
  • the method further comprises the following steps:
  • Step S40 secondary coating: coating a slurry containing a binder on at least a portion of the surface of the coating layer, and forming an adhesive layer after drying.
  • the coating method is rotary spraying.
  • the preparation method of the isolation film of the present application obtains the coating layer by one-time coating, which greatly simplifies the production process of the isolation film.
  • Some parameters such as raw materials and their contents used in the preparation method of the isolation membrane of the present application can refer to the isolation membrane of the first aspect of the implementation method of the present application, and will not be repeated here.
  • the present application also provides a secondary battery.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • secondary batteries include electrode assemblies and electrolytes.
  • the electrode assemblies include positive electrode sheets, negative electrode sheets, and separators.
  • the separators are arranged between the positive electrode sheets and the negative electrode sheets, and mainly play the role of preventing the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.
  • the present application has no particular limitation on the type of secondary battery.
  • the secondary battery may be a lithium ion battery, a sodium ion battery, etc.
  • the secondary battery may be a lithium ion secondary battery.
  • the secondary battery described in the present application includes the isolation membrane of the third aspect of the present application or the isolation membrane prepared by the method of the fourth aspect of the embodiment of the present application, and the isolation membrane is spaced between the positive electrode plate and the negative electrode plate.
  • at least one side of the isolation membrane close to the negative electrode plate has the coating of the present application.
  • the side of the isolation membrane close to the positive electrode plate has the coating of the present application, and the side of the isolation membrane close to the negative electrode plate also has the coating of the present application; thus, the secondary battery of the present application can improve its own safety performance.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including 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 active material may include but is not limited to at least one of a lithium-containing transition metal oxide, a lithium-containing phosphate and their respective modified compounds.
  • the lithium transition metal oxide may include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their respective modified compounds.
  • lithium-containing phosphate may include but are not limited to at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and their respective modified compounds.
  • the positive electrode active material for the lithium ion battery may include at least one of a lithium transition metal oxide and a modified compound thereof of the general formula Li a Ni b Co c M d O e A f . 0.8 ⁇ a ⁇ 1.2, 0.5 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 1 ⁇ e ⁇ 2, 0 ⁇ f ⁇ 1, M includes at least one of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes at least one of N, F, S and Cl.
  • a positive electrode active material for a lithium ion battery may include at least one of LiCoO2 , LiNiO2 , LiMnO2 , LiMn2O4 , LiNi1/ 3Co1 / 3Mn1 / 3O2 (NCM333 ) , LiNi0.5Co0.2Mn0.3O2 ( NCM523 ) , LiNi0.6Co0.2Mn0.2O2 ( NCM622 ) , LiNi0.8Co0.1Mn0.1O2 (NCM811), LiNi0.85Co0.15Al0.05O2 , LiFePO4 , and LiMnPO4 .
  • the positive electrode active material may include but is not limited to at least one of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.
  • the positive electrode active material for a sodium ion battery may include at least one of NaFeO2 , NaCoO2 , NaCrO2 , NaMnO2 , NaNiO2 , NaNi1/2Ti1/ 2O2 , NaNi1/2Mn1/ 2O2 , Na2/3Fe1 / 3Mn2 / 3O2 , NaNi1 / 3Co1 / 3Mn1 / 3O2 , NaFePO4 , NaMnPO4 , NaCoPO4 , Prussian blue-based materials, and materials of the general formula XpM'q ( PO4 ) rOxY3 -x .
  • X includes at least one of H + , Li + , Na + , K + and NH4 + , M' is a transition metal cation, optionally at least one of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halogen anion, optionally at least one of F, Cl and Br.
  • the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and/or surface coating the positive electrode active material.
  • the positive electrode film layer may further include a positive electrode conductive agent.
  • a positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the mass percentage of the positive electrode conductive agent is ⁇ 5%.
  • the positive electrode film layer may also optionally include a positive electrode binder.
  • the positive electrode 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 acrylic resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them uniformly.
  • the solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.
  • 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 and including 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 active material may be a negative electrode active material for a secondary battery known in the art.
  • the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.
  • the tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.
  • the negative electrode film layer may further include a negative electrode conductive agent.
  • a negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the mass percentage of the negative electrode conductive agent is ⁇ 5%.
  • the negative electrode film layer may also optionally include a negative electrode binder.
  • the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • aqueous acrylic resin e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include other additives.
  • other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.
  • CMC sodium carboxymethyl cellulose
  • PTC thermistor materials etc.
  • the mass percentage of the other additives is ⁇ 2%.
  • 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 material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode plate described in the present application also includes a conductive primer layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.
  • the negative electrode plate described in the present application also includes a protective layer covering the surface of the negative electrode film layer.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.
  • the electrolyte salt may include but is not limited to at least one of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium
  • the electrolyte salt may include but is not limited to at least one of sodium hexafluorophosphate (NaPF 6 ), sodium tetrafluoroborate (NaBF 4 ), sodium perchlorate (NaClO 4 ), sodium hexafluoroarsenate (NaAsF 6 ), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO 2 F 2 ), sodium difluorobis(oxalatophosphate) (NaDFOP) and sodium tetrafluorooxalatophosphate (NaPF 6 ), sodium tetrafluoroxalatophosphate
  • the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl s
  • the electrolyte may further include additives, for example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature power performance, etc.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature power performance, etc.
  • the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process and/or a lamination process.
  • the secondary battery may include an outer package, which may be used to package 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, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • 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 is used to cover the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film may form an electrode assembly 52 through a winding process and/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 may be one or more, which can be adjusted according to demand.
  • the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and/or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and a secondary battery is obtained through vacuum packaging, standing, forming, shaping and other processes.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the battery module can contain multiple secondary batteries, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG3 is a schematic diagram of a battery module 4 as an example.
  • a plurality of secondary batteries 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 secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are schematic diagrams of a battery pack 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, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 may be arranged in the battery box in any manner.
  • the sixth aspect of the implementation mode of the present application provides an electric device, which includes at least one of the secondary battery, battery module or battery pack of the present application.
  • the secondary battery, battery module or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device.
  • the electric device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • the electrical device may select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • Fig. 6 is a schematic diagram of an electric device as an example.
  • 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 electric device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the electric device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • the polymer was prepared by a method similar to that of Example A, except that at least one of the raw material composition and content was adjusted.
  • PE substrate thickness of 7 ⁇ m, porosity of 40%, ion conductivity of 1.20mS/cm.
  • Preparation of coating slurry The polymer prepared in Example A and the binder aqueous solution type polyacrylic acid are mixed uniformly in a proper amount of solvent deionized water at a mass ratio of 90:10 to obtain coating slurry.
  • the prepared coating slurry was coated on both surfaces of the PE substrate using a coating machine, and a separator was obtained through drying and slitting steps.
  • the coating on one side of the PE substrate had an area density of 0.9 g/m 2 and a thickness of 0.45 ⁇ m.
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) were mixed uniformly in a proper amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry; the positive electrode slurry was coated on the positive electrode current collector aluminum foil, and the positive electrode sheet was obtained through drying, cold pressing, slitting, cutting and other processes.
  • the surface density of the positive electrode sheet is 0.207mg/mm 2 , and the compaction density is 3.5g/cm 3 .
  • the negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) were mixed evenly in a proper amount of solvent deionized water according to a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry; the negative electrode slurry was coated on the negative electrode current collector copper foil, and the negative electrode sheet was obtained through drying, cold pressing, striping and cutting processes.
  • the surface density of the negative electrode sheet is 0.126mg/ mm2
  • the compaction density is 1.7g/ cm3 .
  • Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 30:70 to obtain an organic solvent, and fully dried LiPF 6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a secondary battery is obtained.
  • the secondary battery was prepared by a method similar to that of Example 1, except that the preparation parameters of the isolation membrane were different. The specific parameters are shown in Table 3.
  • the secondary battery was prepared by a method similar to that of Example 1, except that the coating slurry was prepared by the following method: the polymer prepared in Example A, filler alumina (average particle size Dv50 is 300 nm), and binder aqueous solution type polyacrylic acid were mixed in a proper amount of solvent deionized water in a mass ratio of 80:15:5 to obtain a coating slurry with a solid content of 35 wt%.
  • the positive electrode sheet of the battery was overlapped with the separator, and placed on a hot press.
  • the parameters of the hot press were set as follows: temperature of 25°C, pressure of 10t, and time of 30s.
  • the separator/positive electrode sheet samples were pressed to obtain bonded separator/positive electrode sheet samples.
  • the separator/electrode sheet samples were cut into rectangular strips of 150 ⁇ 20mm.
  • the positive electrode sheet side of the rectangular strip was pasted on the steel plate with double-sided tape, and the separator and the positive electrode sheet were separated by 2cm in the length direction at one end of the rectangular strip to obtain the test sample.
  • Sample preparation The isolation film prepared above was punched into samples with a width of 50 mm and a length of 100 mm using a punching machine. Five parallel samples were placed on A4 paper, and then the A4 paper with the samples was placed on corrugated paper with a thickness of 1 mm to 5 mm.
  • Sample test Set the temperature of the blast oven to 150°C. After the temperature reaches the set temperature and stabilizes for 30 minutes, put the A4 paper placed on the corrugated paper into the blast oven and start timing. After the set time (1 hour in this application) is reached, measure the length and width of the isolation film, and mark the values as a and b respectively.
  • the polymer of Comparative Example 1 includes a first structural unit and a second structural unit.
  • the isolation membrane adopts the polymer its bonding performance is good, but the hot box failure temperature of the secondary battery is low, and thermal runaway is prone to occur;
  • the polymer of Comparative Example 2 includes a first structural unit and a third structural unit.
  • the isolation membrane adopts the polymer its heat resistance is improved to a certain extent, but the bonding performance of the isolation membrane is relatively poor.
  • the polymers of Examples 1 to 16 include a first structural unit, a second structural unit, and a third structural unit, which can improve the heat resistance, adhesion, and anti-swelling properties of the polymer. Adjusting the molar content of the three structural units can regulate the properties of the polymer to a certain extent, especially when 3 ⁇ A/B ⁇ 16, 3 ⁇ A/C ⁇ 16, and/or A:B:C is (12 to 16):(1 to 4):(1 to 4), the performance of the polymer can be further improved.
  • the polymers have good heat resistance, and when their content is relatively high, the heat resistance of the isolation membrane is better.
  • Inorganic particles such as aluminum oxide can also be used as heat-resistant auxiliary materials to further improve the heat resistance of the isolation membrane.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

本申请提供了一种聚合物、隔离膜及其相关的二次电池和用电装置。所述聚合物包括第一结构单元、第二结构单元和第三结构单元；第一结构单元包括式(I)所示的结构单元，式(I)中，R1包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；R2包括取代或未取代的C1-C20烷基、取代或未取代的C3-C20环烷基、取代或未取代的C1-C20羟烷基中的一种或多种；第二结构单元包括式(II)所示的结构单元，式(II)中，R3包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；第三结构单元包括式(III)所示的结构单元。聚合物中的三种结构单元之间可以相互协同，共同改善聚合物的粘结性、稳定性、抗溶胀性和热稳定性。

Description

聚合物、隔离膜及其相关的二次电池和用电装置 技术领域
本申请涉及电池领域，具体涉及一种聚合物、隔离膜及其相关的二次电池和用电装置。
背景技术
二次电池具有容量高、寿命长等特性，因此广泛应用于电子设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。
随着电池应用范围越来越广泛，对二次电池安全性能的要求也逐渐严苛。如何不断的提高二次电池的安全性能，仍然是本领域技术人员亟待解决的问题。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种聚合物、隔离膜及其相关的二次电池和用电装置。
本申请的第一方面提供了一种聚合物，所述聚合物包括第一结构单元、第二结构单元和第三结构单元；第一结构单元包括式(I)所示的结构单元：
Figure PCTCN2022136425-appb-000001
式(I)中，R 1包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 1包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；R 2包括取代或未取代的C1-C20烷基、取代或未取代的C3-C20环烷基、取代或未取代的C1-C20羟烷基中的一种或多种；可选地，R 2包括C1-C12烷基、C3-C12环烷基、C1-C12羟烷基中的一种或多种；
第二结构单元包括式(II)所示的结构单元：
Figure PCTCN2022136425-appb-000002
式(II)中，R 3包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 3包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
第三结构单元包括式(III)所示的结构单元：
Figure PCTCN2022136425-appb-000003
式(III)中，R 4至R 11各自独立地包括取代或未取代的C1-C10烷基、如式(III-1)所示的结构单元中的一种或多种，且R 4至R 11中至少一者包括式(III-1)所示的结构单元，
Figure PCTCN2022136425-appb-000004
式(III-1)中，R 12包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 12包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；R 13包括取代或未取代的C1-C10烷基；可选地，R 13包括取代或未取代的C3-C10烷基。
由此，本申请中第一结构单元由于分子链段中的柔性单体链段能够调节聚合物的玻璃转变温度，改善聚合物的韧性和剥离强度，有助于发挥良好的粘结作用。第二结构单元能够产生优异的抗溶胀性和高粘结性，且有助于提高二次电池的离子导通率。在聚合物应用于隔离膜时，聚合物与电解液相接触，聚合物不易发生溶胀，其具有较好的抗溶胀性。第三结构单元可以赋予聚合物在耐热和机械性能方面的优势，能够在二次电池长期循环充放电过程中，保证聚合物的稳定性，有效隔绝正负极极片，从而保证二次电池的安全性能。第一结构单元和第三结构单元配合能够发挥协同作用，提高聚合物的粘结性能和耐热性能；第一结构单元和第二结构单元配合能够发挥协同作用，能够改善聚合物的稳定性和抗溶胀性等。聚合物中的三种结构单元之间相互协同，能够共同改善聚合物的粘结性、稳定性、抗溶胀性和热稳定性。
在一些实施方式中，R 1包括氢原子或甲基；和/或R 2包括甲基、乙基、正丙基、 异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基、2-乙基己基、十二烷基或异冰片基。
在一些实施方式中，R 3包括氢原子或甲基。
在一些实施方式中，R 4至R 11各自独立地包括如式(III-1)所示的结构单元；可选地，R 12包括氢原子、甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基或正戊基；和/或R 13包括正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基或2-乙基己基。
在一些实施方式中，R 4至R 11中其中一者包括如式(III-1)所示的结构单元；可选地，R 12包括氢原子、甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基或正戊基；和/或R 13包括正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基或2-乙基己基。
在一些实施方式中，基于第一结构单元、第二结构单元和第三结构单元的总摩尔量计，第一结构单元的摩尔含量记为A％，60≤A＜100；可选地，60≤A≤80。第一结构单元的摩尔含量在上述范围时，其在聚合物中的占比相对较大，能够改善聚合物的柔性，从而使得聚合物的粘结性得到显著提高；在聚合物应用于隔离膜时，能够提高聚合物和隔离膜的基材的结合力。
在一些实施方式中，基于第一结构单元、第二结构单元和第三结构单元的总摩尔量计，第二结构单元的摩尔含量记为B％，0＜B≤20；可选地，5≤B≤20。第二结构单元的摩尔含量在上述范围时，能够显著改善聚合物的稳定性。
在一些实施方式中，基于第一结构单元、第二结构单元和第三结构单元的总摩尔量计，第三结构单元的摩尔含量记为C％，0＜C≤20；可选地，5≤C≤20。第三结构单元的摩尔含量在上述范围时，能够保证聚合物的耐热性，且其占比相对较小，有利于提高第一结构单元和第二结构单元的占比，提高聚合物整体的粘结性、稳定性和抗溶胀性等性能。
在一些实施方式中，基于第一结构单元、第二结构单元和第三结构单元的总摩尔量计，第一结构单元的摩尔含量记为A％，第二结构单元的摩尔含量记为B％，第三结构单元的摩尔含量记为C％；聚合物满足条件(1)至条件(3)中的一个或多个：(1)3≤A/B≤16；(2)3≤A/C≤16；(3)A：B：C为(12至16)：(1至4)：(1至4)。第一结构单元、第二结构单元和第三结构单元的摩尔含量满足上述比值时，三种结构单元之间相互协同，进一步改善聚合物的粘结性、稳定性、抗溶胀性和热稳定性。
在一些实施方式中，聚合物的数均分子量为20000至80000，可选为30000至50000。在聚合物的数均分子量在上述范围时，有利于形成粒径较小的聚合物颗粒，在应用于隔离膜时，能够实现隔离膜中涂层的轻薄涂布，减小隔离膜的整体厚度，从而便于二次电池的能量密度的提升；并且聚合物所形成的聚合物颗粒的粒径不会过小，能够减少聚合物颗粒堵塞隔离膜中基材的风险，能够改善隔离膜整体的透气度等性能。在一些实施方式中，聚合物为颗粒状，聚合物还满足条件(Ⅰ)至条件(III)中的一个或多个：(Ⅰ)聚合物的形貌包括球形和/或类球形；(II)聚合物的体积分布粒径Dv50 满足：0.1μm≤Dv50≤2.0μm；可选地，0.5μm≤Dv50≤1.2μm；(III)聚合物的比表面积记为S，其单位为m 2/g，5.0≤S≤12.0；可选地，6.0≤S≤10.0。聚合物为颗粒状时，满足上述条件中的至少一个时，能够更进一步改善聚合物的粘结性、稳定性、抗溶胀性和耐热性。
本申请第二方面提供了一种制备聚合物的方法，所述方法用于制备如本申请第一方面任一实施方式所述的聚合物，所述方法包括：提供第一单体、第二单体和第三单体；将所述第一单体、所述第二单体和所述第三单体混合，并在引发剂的作用下发生聚合反应生成聚合物，其中，所述第一单体包括式(IV)所示的化合物，
Figure PCTCN2022136425-appb-000005
式(IV)中，R 1包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 1包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；R 2包括取代或未取代的C1-C20烷基、取代或未取代的C3-C20环烷基、取代或未取代的C1-C20羟烷基中的一种或多种；可选地，R 2包括C1-C12烷基、C3-C12环烷基、C1-C12羟烷基中的一种或多种；
所述第二单体包括式(V)所示的化合物，
Figure PCTCN2022136425-appb-000006
式(V)中，R 3包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 3包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
所示第三单体包括式(VI)所示的化合物，
Figure PCTCN2022136425-appb-000007
式(VI)中，R 30至R 37各自独立地包括取代或未取代的C1-C10烷基、如式(VI-1)所示的结构单元中的一种或多种，且R 30至R 37中至少一者包括式(VI-1)所示的结构单元，
Figure PCTCN2022136425-appb-000008
式(VI-1)中，R 12包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 12包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
R 13包括取代或未取代的C1-C10烷基；可选地，R 13包括取代或未取代的C3-C10烷基。
在一些实施方式中，所述将所述第一单体、所述第二单体和所述第三单体混合，并在引发剂的作用下发生聚合反应生成聚合物的步骤，包括：于溶剂和乳化剂中加入所述第一单体、所述第二单体和所述第三单体并混合形成混合体系；于所述混合体系中加入所述引发剂，在所述引发剂的作用下发生聚合反应生成所述聚合物。
在一些实施方式中，所述第一单体包括丙烯酸甲酯、丙烯酸乙酯、丙烯酸正丙酯、丙烯酸异丙酯、丙烯酸正丁酯、丙烯酸异丁酯、丙烯酸仲丁酯、丙烯酸叔丁酯、丙烯酸正戊酯、丙烯酸正辛酯、丙烯酸异辛酯、丙烯酸-2-乙基己酯、丙烯酸环己酯、丙烯酸月桂酯、丙烯酸-2-羟基乙酯、丙烯酸-2-羟基丙酯、甲基丙烯酸甲酯、甲基丙烯酸乙酯、甲基丙烯酸正丁酯、甲基丙烯酸-2-乙基己酯、甲基丙烯酸异冰片酯、甲基丙烯酸月桂酯、甲基丙烯酸-2-羟基乙酯和甲基丙烯酸-2-羟基丙酯的一种或多种。
在一些实施方式中，所述第二单体包括丙烯腈和/或甲基丙烯腈。
在一些实施方式中，所述第三单体包括甲基丙烯酰氧丙基笼型聚倍半硅氧烷、甲基丙烯酰氧丙基七异丁基聚倍半硅氧烷、甲基丙烯酰氧丙基七辛基聚倍半硅氧烷、丙烯酰氧丙基笼型聚倍半硅氧烷、丙烯酰氧丙基七异丁基聚倍半硅氧烷和甲基丙烯酰氧丙基七辛基聚倍半硅氧烷中的一种或多种。
本申请第三方面还提供了一种隔离膜，包括基材和设置在所述基材至少一个表面上的涂层，所述涂层包括如本申请第一方面任一实施方式所述的聚合物或如本申请第二方面任一实施方式所述的方法制备得到的聚合物。
在一些实施方式中，基于所述涂层的质量计，所述聚合物的质量百分含量为m％，m≥70；可选地，80≤m≤95。聚合物的质量百分含量在上述范围时，可以更进一步改善隔离膜整体的粘结性、稳定性、抗溶胀性和耐热性等。
在一些实施方式中，所述隔离膜满足如下条件(A)至(G)中的一个或多个：
(A)所述隔离膜在150℃、1h下的纵向热收缩率η 1≤5.0％，可选地0.5％≤η 1≤3％；
(B)所述隔离膜在150℃、1h下的横向热收缩率η 2≤5.0％，可选地0.5％≤η2≤2％；
(C)所述隔离膜的纵向拉伸强度R m1≥3000kg/cm 2，可选地3500kg/cm 2≤R m1≤4500kg/cm 2；
(D)所述隔离膜的横向拉伸强度R m2≥3000kg/cm 2，可选地3500kg/cm 2≤R m2≤4500kg/cm 2；
(E)所述隔离膜的透气度MAP≤250s/100mL，可选地120s/100mL≤MAP≤180s/100mL；
(F)所述隔离膜的润湿长度L≥30mm，可选地，30mm≤L≤80mm；
(G)所述隔离膜的润湿速度u≥3mm/s，可选地，3mm/s≤u≤10mm/s。
本申请第三方面还提供了一种二次电池，包括本申请第二方面任一实施方式的隔离膜。
本申请第四方面还提供了一种用电装置，包括本申请第三方面所述的二次电池。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的二次电池的一实施方式的示意图。
图2是图1的二次电池的实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
附图未必按照实际的比例绘制。
附图标记说明如下：
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、盖板；
6、用电装置。
具体实施方式
以下，详细说明具体公开了本申请的聚合物、隔离膜及其相关的二次电池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)。
在本申请中，术语“多个”、“多种”等是指两个或两种以上。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。
除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测试方法进行测定，例如，可以按照本申请的实施例中给出的测试方法进行测定。
术语“烷基”涵盖直链和支链烷基。例如，烷基可为C1至C50烷基、C1至C40烷基、C1至C30烷基、C1至C20烷基、C1至C12烷基、C1至C10烷基、C1至C6烷基、C1至C5烷基、C1至C3烷基。在一些实施例中，烷基包括甲基、乙基、丙基、异丙基、丁基、异丁基、叔丁基、戊基、己基、庚基、辛基等。另外，烷基可以是任选地被取代的。
术语“环烷基”是指大于或等于三个的碳原子构成环状结构。例如，环状烷基可为C3至C50环烷基、C3至C40环烷基、C3至C30环烷基、C3至C20环烷基、C3至C12环烷基、C3至C10环烷基、C3至C6环烷基、C3至C4环烷基。在一些实施例中，环状烷基包括环丙基、环异丙基、环丁基、环异丁基、环叔丁基、环戊基、环己基、环庚基、环辛基等。另外，环状烷基可以是任选地被取代的。
术语“羟烷基”为烷基中的一个氢原子被羟基取代。例如，羟烷基可为C1至C50羟烷基、C1至C40羟烷基、C1至C30羟烷基、C1至C20羟烷基、C1至C12羟烷基、C1至C10羟烷基、C1至C6羟烷基、C1至C5羟烷基、C1至C3羟烷基。在一些实施例中，烷基包括羟甲基、羟乙基、羟丙基、羟异丙基、羟丁基、羟异丁基、羟叔丁基、羟戊基、羟己基、羟庚基、羟辛基等。另外，烷基可以是任选地被取代的。
术语“氢”是指1H(氕，H)、2H(氘，D)或3H(氚，T)。在各实施例中，“氢”可以是1H(氕，H)。
在本说明书的各处，化合物的取代基以组或范围公开。明确地预期这种描述包括这些组和范围的成员的每一个单独的子组合。例如，明确地预期术语“C1至C8烷基”单独地公开C1、C2、C3、C4、C5、C6、C7、C8、C1至C8、C1至C7、C1至C6、C1至C5、C1至C4、C1至C3、C1至C2、C2至C8、C2至C7、C2至C6、C2至C5、C2至C4、C2至C3、C3至C8、C3至C7、C3至C6、C3至C5、C3至C4、C4至C8、C4至C7、C4至C6、C4至C5、C5至C8、C5至C7、C5至C6、C6至C8、C6至C7和C7至C8烷基。
作为其它实例，明确地预期范围为5至40的整数单独地公开5、6、7、8、9、10、11、12、13、14、15、16、17、18、19、20、21、22、23、24、25、26、27、28、29、30、31、32、33、34、35、36、37、38、39和40；明确地预期范围为1至20的整数单独地公开1、2、3、4、5、6、7、8、9、10、11、12、13、14、15、16、17、18、19和20。据此，可明确地预期其它组或范围。
当上述基团经取代时，取代基团可以是卤素原子或杂原子。
术语“卤素原子”是指氟原子、氯原子、溴原子等。
术语“杂原子”是指氮原子、硫原子、磷酸子等。
通常情况下，二次电池包括电极组件和电解液，电极组件包括正极极片、负极极片和隔离膜，隔离膜设置在正极极片和负极极片之间，主要起到防止正极极片和负极极片短路的作用，同时可以使活性离子自由通过形成回路。
随着二次电池的应用及推广，人们对二次电池的性能(例如安全性能)要求越来越高。隔离膜是二次电池的重要组成部分，可以通过改善隔离膜的性能提升二次电池的安全性能。
发明人发现，相关技术中的隔离膜的粘结性较差，隔离膜与正负极极片粘结效果差，通常在基材上涂覆含有聚合物的涂层，以提升其粘结性；但是聚合物涂层仍存在高温收缩的问题，具体地，二次电池在长期循环充放电过程中，会释放热量，热量导致二次电池内的温度升高，而隔离膜由于耐热性能较差，在高温下收缩率较高，使得隔离膜整体无法对正负极极片起到良好的隔绝作用，从而恶化二次电池的安全性能。此外，隔离膜还需要满足在电解液的浸润下具有良好的抗溶胀性，这是因为隔离膜如果容易溶胀，隔离膜的体积增大较大，可能会对正负极极片造成挤压，对正负极极片造成不利影响。由此可见，相关技术的隔离膜难以兼顾粘结性、耐热性能和抗溶胀性。
为了解决上述问题，发明人从改进隔离膜的涂层性能的角度出发，涂层包括聚 合物，通过具有多种功能的单体聚合形成所述聚合物，从而改善隔离膜的性能，接下来对本申请的技术方案进行详细说明。
聚合物
第一方面，本申请提出了一种聚合物，所述聚合物包括第一结构单元、第二结构单元和第三结构单元。
所述第一结构单元包括式(I)所示的结构单元，
Figure PCTCN2022136425-appb-000009
式(I)中，R 1包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 1包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
R 2包括取代或未取代的C1-C20烷基、取代或未取代的C3-C20环烷基、取代或未取代的C1-C20羟烷基中的一种或多种；可选地，R 2包括C1-C12烷基、C3-C12环烷基、C1-C12羟烷基中的一种或多种。
所述第二结构单元包括式(II)所示的结构单元，
Figure PCTCN2022136425-appb-000010
式(II)中，R 3包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 3包括氢原子、取代或未取代的C1-C3烷基中的一种或多种。
第三结构单元包括式(III)所示的结构单元，
Figure PCTCN2022136425-appb-000011
式(III)中，R 4至R 11各自独立地包括取代或未取代的C1-C10烷基、如式(III-1)所示的结构单元中的一种或多种，且R 4至R 11中至少一者包括式(III-1)所示的结构单元，
Figure PCTCN2022136425-appb-000012
式(III-1)中，R 12包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 12包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；R 13包括取代或未取代的C1-C10烷基；可选地，R 13包括取代或未取代的C3-C10烷基。
本申请的聚合物包括第一结构单元、第二结构单元和第三结构单元，其具有良好的粘结性、稳定性、抗溶胀性和耐热性等。
尽管机理尚不十分明确，本申请的发明人推测可能的原因包括如下几点：
第一结构单元可由丙烯酸酯类单体在聚合过程中打开碳碳双键所形成，由于分子链段中的柔性单体链段能够调节聚合物的玻璃转变温度，改善聚合物的韧性和剥离强度，有助于发挥良好的粘结作用。
第二结构单元可由丙烯腈类单体在聚合过程中打开碳碳双键所形成，第二结构单元能够产生优异的抗溶胀性和高粘结性，且有助于提高二次电池的离子导通率。在聚合物应用于隔离膜时，聚合物与电解液相接触，聚合物不易发生溶胀，其具有较好的抗溶胀性。
第三结构单元由含有取代或未取代的丙烯酰氧基烷基聚倍半硅氧烷在聚合过程中打开取代或未取代的丙烯酰氧基的碳碳双键所形成，聚倍半硅氧烷可以认为是一种包含有机-无机杂化的核壳结构的材料，其内部无机框架作为内核，即Si-O-Si或Si-O键构成的骨架结构；其外壳由有机取代基(C1-C5烷基)组成，有机取代基包裹在骨架结构外，有机取代基与骨架结构的Si元素连接。聚倍半硅氧烷的内核结构可以赋予聚合物在耐热和机械性能方面的优势，其收缩性较差，能够在二次电池长期循环充放电过程中，保证聚合物的稳定性，有效隔绝正负极极片，从而保证二次电池的安全性能；并且由于聚倍半硅氧烷的粒径较小，比表面积较大，在物理尺度上，其和大多聚合物链段相近，使得聚倍半硅氧烷表面上的原子具有较高的反应活性，经聚倍半硅氧烷改性的聚合物具有较好的耐热性、阻燃性和抗氧化性等性能。
上述分析虽然是基于各个结构单元进行的，但是也不能忽略各个结构单元之间的协同作用。具体地，第一结构单元和第三结构单元配合能够发挥协同作用，提高聚合物的粘结性能和耐热性能；第一结构单元和第二结构单元配合能够发挥协同作用，能够改善聚合物的稳定性和抗溶胀性等。
在一些实施例中，基于第一结构单元、第二结构单元和第三结构单元的总摩尔量计，第一结构单元的摩尔含量记为A％，60≤A＜100。第一结构单元的摩尔含量在上述范围时，其在聚合物中的占比相对较大，能够改善聚合物的柔性，从而使得聚合物的粘结性得到显著提高；在聚合物应用于隔离膜时，能够提高聚合物和隔离膜的基材的结合力。可选地，60≤A≤80。示例性地，第一结构单元的摩尔含量可以为60％、65％、70％、75％、80％或是上述任意两个数值组成的范围。
在一些实施例中，基于第一结构单元、第二结构单元和第三结构单元的总摩尔量计，第二结构单元的摩尔含量记为B％，0＜B≤20。第二结构单元的摩尔含量在上述范围时，能够显著改善聚合物的稳定性。可选地，5≤B≤20。示例性地，第二结构单元的摩尔含量可以为2％、5％、8％、10％、12％、15％、18％、20％或是上述任意两个数值组成的范围。
在一些实施例中，基于第一结构单元、第二结构单元和第三结构单元的总摩尔量计，第三结构单元的摩尔含量记为C％，0＜C≤20。第三结构单元的摩尔含量在上述范围时，能够保证聚合物的耐热性，且其占比相对较小，有利于提高第一结构单元和第二结构单元的占比，提高聚合物整体的粘结性、稳定性和抗溶胀性等性能。可选地，5≤C≤20。示例性地，第三结构单元的摩尔含量可以为2％、5％、8％、10％、12％、15％、18％、20％或是上述任意两个数值组成的范围。
聚合物包括第一结构单元，第一结构单元赋予聚合物良好的粘结性和柔韧性；但是由于聚合物应用于隔离膜时会不可避免地与电解液接触，电解液的溶胀作用会在一定程度上降低聚合物的粘结性；而聚合物还包括第二结构单元，第二结构单元中的氰基可以与第一结构单元发挥协同作用，共同改善聚合物的抗溶胀性和粘结性能；尤其是本申请进一步满足3≤A/B≤16时，第一结构单元能够和第二结构单元之间能够更充分发挥协同作用，改善聚合物的粘结性和稳定性以及抗溶胀性。示例性地，A/B可以为3、4、5、8、10、12、15、16或是上述任意两个数值组成的范围。
聚合物包括第一结构单元，第一结构单元赋予聚合物良好的粘结性，但是其自身的耐热性能相对较差，在聚合物应用于隔离膜时，随着二次电池充放电时间的增长，二次电池内的温度升高，可能会造成第一结构单元的破坏；而聚合物还包括第三结构单元，第三结构单元中的聚倍半硅氧烷的无机结构，能够和第一结构单元协同作用，改善聚合物整体的耐热性能和粘结性能；尤其是本申请进一步满足3≤A/C≤16时，第一结构单元能够和第三结构单元之间能够更充分发挥协同作用，改善聚合物的粘结性能和耐热性能。示例性地，A/C可以为3、4、5、8、10、12、15、16或是上述任意两个数值组成的范围。
在一些实施例中，A：B：C为(12至16)：(1至4)：(1至4)。第一结构单元、第二结构单元和第三结构单元的摩尔含量满足上述比值时，聚合物中三种结构单元之间相互协同，共同改善聚合物的粘结性、稳定性、抗溶胀性和热稳定性。示例性地，A：B：C可以为12:4:4、13:4:3、14:4:2、15:4:1、16:3:1、13:3:4或15:1:4。第一结构单元包括多种化学结构，接下来对第一结构单元的具体化学结构进行说明。
在一些实施例中，R 1包括氢原子或甲基。
在一些实施例中，R 2包括甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基、2-乙基己基、十二烷基或异冰片基。
示例性地，第一结构单元包括式(I-1)所示结构至式(I-8)所示结构中的一个或多个：
Figure PCTCN2022136425-appb-000013
第二结构单元包括多种化学结构，接下来对第二结构单元的具体化学结构进行说明。
在一些实施例中，R 3包括氢原子或甲基。
示例性地，第二结构单元包括式(II-1)所示结构至式(II-4)所示结构中的一个或多个：
Figure PCTCN2022136425-appb-000014
第三结构单元包括多种化学结构，接下来对第三结构单元的具体化学结构进行 说明。
在一些实施方式中，R 4至R 11各自独立地包括如式(III-1)所示的结构单元；可选地，R 12包括氢原子、甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基或正戊基；和/或R 13包括正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基或2-乙基己基。
在一些实施方式中，R 4至R 11中其中一者包括如式(III-1)所示的结构单元；可选地，R 12包括氢原子、甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基或正戊基；和/或R 13包括正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基或2-乙基己基。
聚合物中的基团种类可以采用红外光谱法进行测定。例如，可以测试材料的红外光谱，确定其包含的特征峰，从而确定改性基团的种类。具体地，可以用本领域公知的仪器及方法对材料进行红外光谱分析，例如采用红外光谱仪(如美国尼高力(nicolet)公司的IS10型傅里叶变换红外光谱仪)，依据GB/T 6040-2019红外光谱分析方法通则进行测试。
在一些实施例中，所述聚合物的红外谱图中具有1750cm -1至1735cm -1的特征峰，其表示存在酯基。
在一些实施例中，所述聚合物的红外谱图中具有2260cm -1至2220cm -1的特征峰，其表示存在氰基。
在一些实施例中，所述聚合物的红外谱图中具有1100m -1至1120cm -1的特征峰，其表示存在倍半硅氧烷的Si-O-Si骨架。
发明人在进一步研究中发现，聚合物的特定参数在特定范围时，可以显著改善聚合物的粘结性和稳定性等。
在一些实施例中，聚合物的数均分子量为20000至80000，可选为30000至50000。示例性地，聚合物的数均分子量可以为20000、25000、30000、35000、40000、45000、50000、55000、60000、65000、70000、75000、80000或是上述任意两个数值组成的范围。在聚合物的数均分子量在上述范围时，有利于形成粒径较小的聚合物颗粒，在应用于隔离膜时，能够实现隔离膜中涂层的轻薄涂布，减小隔离膜的整体厚度，从而便于二次电池的能量密度的提升；并且聚合物所形成的聚合物颗粒的粒径不会过小，能够减少聚合物颗粒堵塞隔离膜中基材的风险，能够改善隔离膜整体的透气度等性能。
聚合物的数均分子量可以通过凝胶渗透色谱法(GPC)测试。具体地，使用美国Waters公司的GPC1515仪器进行测式，将样品溶于四氢呋喃中，溶解时间12h以上，样品的浓度为4mg/ml，过滤制样，测试温度为25℃，测试流速为1ml/min进行测试。
发明人在进一步研究中发现，聚合物为颗粒状时，在满足以下条件中的至少一个时，能够更进一步改善聚合物的粘结性、稳定性、抗溶胀性和耐热性。
在一些实施例中，聚合物的形貌包括球形和/或类球形。在聚合物应用于隔离膜时，聚合物呈现颗粒状，球形和/或类球形颗粒状能够保证颗粒和颗粒之间的良好搭 接，且颗粒之间存在空隙，有利于构建稳定的空间网络结构，由此能够提升隔离膜的离子传输特性和耐外力挤压能力。并且球形和/或类球形颗粒之间的空隙较大，能够减缓涂层对基材透气度的影响，进一步改善隔离膜整体的透气度和离子导通率，提升二次电池的动力学性能。再者，球形和/或类球形颗粒之间较大的孔隙率有利于提升隔离膜对电解液的润湿性以及隔离膜的持液率和保液率，进一步提升二次电池的动力学性能；而且较大的孔隙率能够起到减重效果，有利于提升二次电池单位重量的能量密度；并且能够减少涂层中聚合物的用量，有利于降低二次电池的成本。
聚合物的形貌可以通过扫描电子显微镜SEM进行观察，例如采用美国FEI公司JSM-5610LV型扫描电镜，对样品进行真空喷金后，观察形貌结构。
在一些实施例中，聚合物的体积分布粒径Dv50满足：0.1μm≤Dv50≤2.0μm；可选地，0.5μm≤Dv50≤1.2μm。聚合物的颗粒粒径相对较小，在聚合物应用于隔离膜时，有利于聚合物的均匀分散，其所构成的膜层性能更均匀。示例性地，聚合物的体积分布粒径Dv50可以为0.1μm、0.2μm、0.5μm、0.8μm、1.0μm、1.2μm、1.5μm、2.0μm或是上述任意两个数值组成的范围。
聚合物的体积分布粒径Dv50为本领域公知的含义，可采用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如Master Size 3000)进行测试。
在一些实施例中，聚合物的比表面积记为S，其单位为m 2/g，5.0≤S≤12.0；可选地，6.0≤S≤10.0。聚合物的比表面积在上述范围时，聚合物的比表面积相对较大，有利于颗粒之间的良好搭接，使得聚合物颗粒之间更容易形成孔隙结构，有利于活性离子的迁移。示例性地，聚合物的比表面积可以为5.0m 2/g、5.5m 2/g、6.0m 2/g、7.0m 2/g、8.0m 2/g、9.0m 2/g、10.0m 2/g、11.0m 2/g、12.0m 2/g或是上述任意两个数值组成的范围。
聚合物的比表面积为本领域公知的含义，可采用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(BrunauerEmmett Teller)法计算得出。可选地，氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪进行。
制备聚合物的方法
第二方面，本申请提供了一种制备聚合物的方法。所述方法能够用于制备本申请第一方面任一实施例的聚合物。
所述方法包括：
步骤S100，提供第一单体、第二单体和第三单体；
步骤S200，将第一单体、第二单体和第三单体混合，并在引发剂的作用下发生聚合反应生成聚合物。
本申请将第一单体、第二单体和第三单体混合后进行共聚，所形成的聚合物为三种单体的共聚物。
所述第一单体包括式(IV)所示的化合物，
Figure PCTCN2022136425-appb-000015
式(IV)中，R 1包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 1包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
R 2包括取代或未取代的C1-C20烷基、取代或未取代的C3-C20环烷基、取代或未取代的C1-C20羟烷基中的一种或多种；可选地，R 2包括C1-C12烷基、C3-C12环烷基、C1-C12羟烷基中的一种或多种。
所述第一单体为丙烯酸酯类化合物，在其进行聚合时，碳碳双键打开形成第一结构单元。
示例性地，第一单体包括丙烯酸甲酯、丙烯酸乙酯、丙烯酸正丙酯、丙烯酸异丙酯、丙烯酸正丁酯、丙烯酸异丁酯、丙烯酸仲丁酯、丙烯酸叔丁酯、丙烯酸正戊酯、丙烯酸正辛酯、丙烯酸异辛酯、丙烯酸-2-乙基己酯、丙烯酸环己酯、丙烯酸月桂酯、丙烯酸-2-羟基乙酯、丙烯酸-2-羟基丙酯、甲基丙烯酸甲酯、甲基丙烯酸乙酯、甲基丙烯酸正丁酯、甲基丙烯酸-2-乙基己酯、甲基丙烯酸异冰片酯、甲基丙烯酸月桂酯、甲基丙烯酸-2-羟基乙酯和甲基丙烯酸-2-羟基丙酯的一种或多种。
所述第二单体包括式(V)所示的化合物，
Figure PCTCN2022136425-appb-000016
式(V)中，R 3包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 3包括氢原子、取代或未取代的C1-C3烷基中的一种或多种。
所述第二单体为丙烯腈类化合物，在其进行聚合时，碳碳双键打开形成第二结构单元。
示例性地，第二单体包括丙烯腈和/或甲基丙烯腈。
所示第三单体包括式(VI)所示的化合物，
Figure PCTCN2022136425-appb-000017
式(VI)中，R 30至R 37各自独立地包括取代或未取代的C1-C10烷基、如式(VI-1)所示的结构单元中的一种或多种，且R 30至R 37中至少一者为式(VI-1)所示的结构单元，
Figure PCTCN2022136425-appb-000018
式(VI-1)中，R 12包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 12包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
R 13包括取代或未取代的C1-C10烷基；可选地，R 13包括取代或未取代的C3-C10烷基。
示例性地，第三单体包括甲基丙烯酰氧丙基笼型聚倍半硅氧烷、甲基丙烯酰氧丙基七异丁基聚倍半硅氧烷、甲基丙烯酰氧丙基七辛基聚倍半硅氧烷、丙烯酰氧丙基笼型聚倍半硅氧烷、丙烯酰氧丙基七异丁基聚倍半硅氧烷和甲基丙烯酰氧丙基七辛基聚倍半硅氧烷中的一种或多种。
在一些实施例中，步骤S200具体包括：
步骤S210，于溶剂和乳化剂中加入第一单体、第二单体和第三单体并混合形成混合体系；
步骤S220，于混合体系中加入引发剂，在引发剂的作用下发生聚合反应生成聚合物。
本申请可以通过乳液聚合的方式进行多种单体的共聚，聚合方法更为简便。当然，本申请还可以采用其它聚合手段，例如溶液聚合、悬浮聚合等，聚合过程所采用的工艺参数可以选择本领域常用参数，在此不再赘述。
在一些实施例中，乳化剂包括十二烷基硫酸钠、十二烷基苯磺酸钠、烷基二苯基氧化物二磺酸盐、乙氧基化烷基酚硫酸铵中的一种或多种。
在一些实施例中，基于混合体系的总质量计，乳化剂的质量百分含量与所述第一单体、第二单体和第三单体的质量百分含量的比值为0.1％至5％，即乳化剂的用量为三种单体总质量的0.1％至5％。乳化剂的质量百分含量在上述范围时，可以将第一单体、第二单体和第三单体乳化分散于溶剂中，形成较为均一的体系。
在一些实施例中，引发剂包括过硫酸钾和/或过硫酸铵。
在一些实施例中，基于混合体系的总质量计，引发剂的质量百分含量与所述第二单体、第二单体和第三单体的质量百分含量的比值为0.15％至1％，即引发剂的用量为三种单体总质量的0.1％至5％。引发剂的质量百分含量在上述范围时，可以保证充分聚合。
在一些实施例中，溶剂可以包括水例如去离子水。
作为一具体实施例，所述方法包括：
预聚体的制备：将去离子水、乳化剂、第一聚合单体、第二聚合单体和第三聚合单体共混搅拌均匀后，得到预聚体；
聚合物的制备：在容器中加入乳化剂、去离子水，搅拌乳化30min至60min，
得到均匀稳定的乳液；然后分别缓慢滴加上步制备的预聚体及引发剂溶液(将引发剂过硫酸钾和/或过硫酸铵溶于去离子水中形成溶液)，待滴加完毕后升温到90℃至110℃并保温反应0.5h，冷却到40℃，用氨水调节pH至7至8后，过滤，出料，经干燥工艺制得聚合物。
隔离膜
第三方面，本申请提出了一种隔离膜。
所述隔离膜包括基材和设置在所述基材至少一个表面上的涂层，所述涂层包括如本申请第一方面任一实施例所述的聚合物或如本申请第二方面任一实施例所述的方法制备得到的聚合物。由于聚合物具有优异的粘结性、稳定性、抗溶胀性和耐热性等，在其应用于隔离膜的涂层时，可以显著改善隔离膜整体的粘结性、稳定性、抗溶胀性和耐热性等。
在一些实施例中，基于涂层的质量计，聚合物的质量百分含量为m％，m≥70；
可选地，80≤m≤95。聚合物的质量百分含量在上述范围时，可以更进一步改善隔离膜整体的粘结性、稳定性、抗溶胀性和耐热性等。聚合物的质量百分含量m％可以为70％、80％、85％、86％、88％、90％、92％、95％、98％、99％或是上述任意两个数值组成的范围。
本申请对所述基材的材质没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的基材，例如玻璃纤维、无纺布、聚乙烯、聚丙烯和聚偏二氟乙烯中的至少一种。所述基材可以是单层薄膜，也可以是多层复合薄膜。所述基材为多层复合薄膜时，各层的材料可以相同，也可以不同。
在一些实施例中，涂层还可以包括填料。进一步地，填料可包括无机颗粒和有机颗粒中的至少一种。
在一些实施例中，所述填料的分解温度可在200℃以上，由此填料可具有热稳定性好且不易分解的特性，进而可以进一步提升隔离膜的耐热性。
无机颗粒具有热稳定性高且不易分解的特性。在一些实施例中，可选地，所述无机颗粒包括具有5以上介电常数的无机颗粒、具有离子传导性但不储存离子的无机颗粒和能够发生电化学反应的无机颗粒中的至少一种。
可选地，所述具有5以上介电常数的无机颗粒包括勃姆石、氧化铝、氧化锌、氧化硅、氧化钛、氧化锆、氧化钡、氧化钙、氧化镁、氧化镍、氧化锡、氧化铈、氧化钇、氧化铪、氢氧化铝、氢氧化镁、碳化硅、碳化硼、氮化铝、氮化硅、氮化硼、氟化镁、氟化钙、氟化钡、硫酸钡、硅酸镁铝、硅酸镁锂、硅酸镁钠、膨润土、水辉石、钛酸锆、钛酸钡、Pb(Zr,Ti)O 3(简写为PZT)、Pb 1-mLa mZr 1-nTi nO 3(简写为PLZT，0＜m＜1，0＜n＜1)、Pb(Mg 3Nb 2/3)O 3-PbTiO 3(简写为PMN-PT)、及其各自的改性无机颗粒中的至少一种。可选地，各无机颗粒的改性方式可为化学改性和/或物理改性。 所述化学改性方式包括偶联剂改性(例如采用硅烷偶联剂、钛酸酯偶联剂等)、表面活性剂改性、聚合物接枝改性等。所述物理改性方式可为机械力分散、超声分散、高能处理等。通过改性处理能够减少无机颗粒的团聚，由此能使其与纳米纤维素搭建形成更稳定和均一的空间网络结构；此外，通过选择具有特定官能团的偶联剂、表面活性材料或聚合物改性无机颗粒，还有助于提升涂层对电解液的浸润特性，提升涂层与基材之间的粘结强度。
可选地，所述具有离子传导性但不储存离子的无机颗粒包括Li 3PO 4、磷酸钛锂Li x1Ti y1(PO 4) 3、磷酸钛铝锂Li x2Al y2Ti z1(PO 4) 3、(LiAlTiP) x3O y3型玻璃、钛酸镧锂Li x4La y4TiO 3、硫代磷酸锗锂Li x5Ge y5P z2S w、氮化锂Li x6N y6、SiS 2型玻璃Li x7Si y7S z3和P 2S 5型玻璃Li x8P y8S z4中的至少一种，0＜x1＜2，0＜y1＜3，0＜x2＜2，0＜y2＜1，0＜z1＜3，0＜x3＜4，0＜y3＜13，0＜x4＜2，0＜y4＜3，0＜x5＜4，0＜y5＜1，0＜z2＜1，0＜w＜5，0＜x6＜4，0＜y6＜2，0＜x7＜3，0＜y7＜2，0＜z3＜4，0＜x8＜3，0＜y8＜3，0＜z4＜7。由此能够进一步提升隔离膜的离子传输特性。
可选地，所述能够发生电化学反应的无机颗粒包括含锂过渡金属氧化物、含锂磷酸盐、碳基材料、硅基材料、锡基材料和锂钛化合物中的至少一种。
有机颗粒具有热稳定性好且不易分解的特性，由此可以提升隔离膜的耐热性；同时，当二次电池因为过充滥用、热滥用等使其内部温度达到有机颗粒的熔点时，有机颗粒还可以融化，并因毛细作用而被吸入基材的微孔中起到闭孔和断路的作用，从而有利于保证二次电池具有高安全性能。
在一些实施例中，所述有机颗粒包括但不限于聚乙烯颗粒、聚丙烯颗粒、聚苯乙烯颗粒、三聚氰胺树脂颗粒、酚醛树脂颗粒、聚酯颗粒(例如聚对苯二甲酸乙二酯、聚萘二甲酸乙二酯、聚对苯二甲酸丁二酯)、聚酰亚胺颗粒、聚酰胺酰亚胺颗粒、聚芳酰胺颗粒、聚苯硫醚颗粒、聚砜颗粒、聚醚砜颗粒、聚醚醚酮颗粒、聚芳醚酮颗粒、丙烯酸丁酯与甲基丙烯酸乙酯的共聚物(例如丙烯酸丁酯与甲基丙烯酸乙酯的交联聚合物)中的至少一种。
在一些实施例中，可选地，所述有机颗粒的玻璃化转变温度可以在130℃以上。由此当二次电池内部温度达到130℃时，有机颗粒不会由玻璃态转变为粘流态，由此能够确保隔离膜不剧烈收缩。更可选地，所述有机颗粒包括但不限于三聚氰胺甲醛树脂颗粒、酚醛树脂颗粒、聚酯颗粒、聚酰亚胺颗粒、聚酰胺酰亚胺颗粒、聚芳酰胺颗粒、聚苯硫醚颗粒、聚砜颗粒、聚醚砜颗粒、聚醚醚酮颗粒和聚芳醚酮颗粒中的至少一种。
在一些实施例中，所述涂层还包括粘结剂。本申请对粘结剂的种类没有特别的限制，可以选用任意公知的具有良好粘结性的材料。作为示例，所述粘结剂包括水溶液型丙烯酸类树脂(例如，丙烯酸、甲基丙烯酸、丙烯酸钠单体均聚物或与其他共聚单体共聚物)、聚乙烯醇、异丁烯-马来酸酐共聚物和聚丙烯酰胺中的至少一种。
可选地，所述涂层中的所述粘结剂的含量为＜30％，基于涂层的质量计。
在一些实施例中，所述隔离膜还可以包括粘接层，所述粘接层设置在所述涂层 的至少一部分表面上，所述粘接层包括粘结剂。粘接层不仅能够防止涂层脱落，提高二次电池的安全性能，而且能够改善隔离膜与电极的界面，提升二次电池的循环性能。
可选地，所述粘结剂包括丙烯酸酯类单体均聚物或共聚物、丙烯酸类单体均聚物或共聚物、含氟烯烃单体均聚物或共聚物中的至少一种。所述共聚单体包括但不限于丙烯酸酯类单体、丙烯酸类单体、烯烃单体、含卤素烯烃单体、氟醚类单体等中的至少一种。
可选地，所述粘结剂包括偏二氟乙烯基聚合物，例如偏二氟乙烯单体(VDF)的均聚物和/或偏二氟乙烯单体与其他共聚单体的共聚物。所述其他共聚单体可为烯烃单体、含氟烯烃单体、含氯烯烃单体、丙烯酸酯类单体、丙烯酸类单体、氟醚类单体中的至少一种。可选地，所述其他共聚单体可包括三氟乙烯(VF3)、三氟氯乙烯(CTFE)、1,2-二氟乙烯、四氟乙烯(TFE)、六氟丙烯(HFP)、全氟(烷基乙烯基)醚(例如全氟(甲基乙烯基)醚PMVE、全氟(乙基乙烯基)醚PEVE、全氟(丙基乙烯基)醚PPVE)、全氟(1,3-间二氧杂环戊烯)和全氟(2,2-二甲基-1,3-间二氧杂环戊烯)(PDD)中的至少一种。
在一些实施例中，隔离膜在150℃、1h下的纵向热收缩率η 1≤5.0％，可选地，0.5％≤η 1≤3％。
在一些实施例中，隔离膜在150℃、1h下的横向热收缩率η 2≤5.0％，可选地，0.5％≤η2≤2％。
本申请的隔离膜在150℃的高温下，横向和纵向两个方向均具有低热收缩率，由此能够进一步提升二次电池的安全性能。
在一些实施例中，隔离膜的纵向拉伸强度R m1≥3000kg/cm 2，可选地，3500kg/cm 2≤R m1≤4500kg/cm 2。
在一些实施例中，隔离膜的横向拉伸强度R m2≥3000kg/cm 2，可选地，3500kg/cm 2≤R m2≤4500kg/cm 2。
本申请的隔离膜在横向和纵向两个方向均具有高拉伸强度，由此在二次电池膨胀时，隔离膜出现破损的概率较小，从而能够进一步提升二次电池的安全性能。
在一些实施例中，隔离膜的透气度MAP≤250s/100mL，可选地，120s/100mL≤MAP≤180s/100mL。本申请的隔离膜具有良好的透气度，由此能够提升离子传输特性。
在一些实施例中，隔离膜的润湿长度L≥30mm，可选地，30mm≤L≤80mm。
在一些实施例中，隔离膜的润湿速度u≥3mm/s，可选地，3mm/s≤u≤10mm/s。
本申请的隔离膜具有良好的电解液浸润特性，由此能够提升离子传输特性和二次电池容量发挥。
隔离膜的热收缩率、拉伸强度和透气度均具有本领域公知的含义，可以采用本领域已知的方法进行测量。例如，均可参照标准GB/T 36363-2018进行测试。
隔离膜的润湿长度、润湿速度均具有本领域公知的含义，可以采用本领域已知的方法进行测量。示例性测试方法如下：将隔离膜裁切成宽度为5mm、长度为100mm 的样品，将样品两端固定后水平放置；取0.5mg电解液滴在样品中央，达到规定时间(本申请为1min)后，拍照并测量电解液扩散的长度，由此得到隔离膜的润湿长度和润湿速度。为了保证测试结果的准确性，可取多个(例如5至10个)样品进行测试，并且测试结果通过计算平均值得到。电解液可以按照如下方法配制：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)按照质量比30:50:20进行混合得到有机溶剂，将充分干燥的LiPF 6溶解于上述有机溶剂中配制成浓度为1mol/L的电解液。
需要说明的是，上述隔离膜的涂层参数(例如面密度、厚度等)均为基材单侧的涂层参数。当涂层设置在基材的两侧时，其中任意一侧的涂层参数满足本申请，即认为落入本申请的保护范围内。
制备隔离膜的方法
第四方面，本申请还提供了一种制备隔离膜的方法。所述方法可以用于制备本申请第三方面任一实施例的隔离膜。
所述方法包括：
步骤S10，提供基材；
步骤S20，制备涂覆浆料：将聚合物按照预定质量在溶剂中混合，配制成所述涂覆浆料；
步骤S30，涂布：将所述涂覆浆料涂布于所述基材的至少一个表面上，形成涂层并干燥，获得隔离膜，其中，所述隔离膜包括基材和设置在所述基材的至少一个表面上的涂层。
步骤S20中的聚合物可以采用本申请第一方面任一实施例的聚合物，或是本申请第二方面任一实施例所述的方法制备得到的聚合物。
在一些实施例中，在步骤S20中，所述溶剂可以为水，例如去离子水。
在一些实施例中，在步骤S20中，所述涂覆浆料还可以包括其他组分，例如，还可以包括分散剂、润湿剂、粘结剂等。
在一些实施例中，在步骤S20中，所述涂覆浆料的固含量可以控制在28％至45％之间，例如，可以在30％至38％之间。当涂覆浆料的固含量在上述范围内时，可以有效减少涂层的膜面问题以及降低涂布不均匀出现的概率，从而进一步改善二次电池的能量密度和安全性能。
在一些实施例中，在步骤S30中，所述涂布采用涂布机。本申请对涂布机的型号没有特殊限制，例如可以采用市购涂布机。所述涂布机包括凹版辊；所述凹版辊用于将涂覆浆料转移到基材上。
在一些实施例中，在步骤S30中，所述涂布方式可以采用转移涂布、旋转喷涂、浸涂等。
在一些实施例中，所述方法还包括以下步骤：
步骤S40，二次涂布：将包含粘结剂的浆料涂布在所述涂层的至少一部分表面上，干燥后形成粘接层。可选地，所述涂布方式采用旋转喷涂。
本申请的隔离膜的制备方法通过一次涂布制得涂层，大大简化了隔离膜的生产工艺流程。
本申请的隔离膜的制备方法中使用的一些原料及其含量等参数可以参考本申请实施方式第一方面的隔离膜，此处不再赘述。
如果没有特别的说明，在本申请的隔离膜的制备方法中所使用的各原料均可以通过市购获得。
二次电池
第五方面，本申请还提供了一种二次电池。
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，二次电池包括电极组件和电解液，所述电极组件包括正极极片、负极极片和隔离膜，所述隔离膜设置在所述正极极片和所述负极极片之间，主要起到防止正极和负极短路的作用，同时可以使活性离子通过。
本申请对二次电池种类没有特别的限制，例如，所述二次电池可以为锂离子电池、钠离子电池等，特别地，所述二次电池可以为锂离子二次电池。
本申请所述的二次电池包括本申请第三方面的隔离膜或通过本申请实施方式第四方面的方法制备的隔离膜，所述隔离膜间隔于所述正极极片和所述负极极片之间。可选地，至少所述隔离膜靠近所述负极极片的一侧具有本申请的涂层。进一步地。隔离膜靠近正极极片的一侧具有本申请的涂层，隔离膜靠近负极极片的一侧也具有本申请的涂层；由此，本申请的二次电池能够改善其自身的安全性能。
[正极极片]
在一些实施例中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面且包括正极活性材料的正极膜层。例如，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层设置在所述正极集流体的两个相对表面中的任意一者或两者上。
当本申请的二次电池为锂离子电池时，所述正极活性材料可包括但不限于含锂过渡金属氧化物、含锂磷酸盐及其各自的改性化合物中的至少一种。所述锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、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、锂镍钴铝氧化物及其各自的改性化合物中的至少一种。所述含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、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及其各自的改性化合物中的至少一种。
在一些实施例中，为了进一步提高二次电池的能量密度，用于锂离子电池的正极活性材料可以包括通式为Li aNi bCo cM dO eA f的锂过渡金属氧化物及其改性化合物中的至少一种。0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M包括Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti和B中的至少一种，A包括N、F、S和Cl中的至少一种。
作为示例，用于锂离子电池的正极活性材料可包括LiCoO 2、LiNiO 2、LiMnO 2、 LiMn 2O 4、LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、LiNi 0.85Co 0.15Al 0.05O 2、LiFePO 4、LiMnPO 4中的至少一种。
当本申请的二次电池为钠离子电池时，所述正极活性材料可包括但不限于含钠过渡金属氧化物、聚阴离子材料(如磷酸盐、氟磷酸盐、焦磷酸盐、硫酸盐等)、普鲁士蓝类材料中的至少一种。
作为示例，用于钠离子电池的正极活性材料可包括NaFeO 2、NaCoO 2、NaCrO 2、NaMnO 2、NaNiO 2、NaNi 1/2Ti 1/2O 2、NaNi 1/2Mn 1/2O 2、Na 2/3Fe 1/3Mn 2/3O 2、NaNi 1/3Co 1/3Mn 1/3O 2、NaFePO 4、NaMnPO 4、NaCoPO 4、普鲁士蓝类材料、通式为X pM’ q(PO 4) rO xY 3-x的材料中的至少一种。在通式X pM’ q(PO 4) rO xY 3-x中，0＜p≤4，0＜q≤2，1≤r≤3，0≤x≤2，X包括H +、Li +、Na +、K +和NH 4 +中的至少一种，M’为过渡金属阳离子，可选地为V、Ti、Mn、Fe、Co、Ni、Cu和Zn中的至少一种，Y为卤素阴离子，可选地为F、Cl和Br中的至少一种。
在本申请中，上述各正极活性材料的改性化合物可以是对所述正极活性材料进行掺杂改性和/或表面包覆改性。
在一些实施例中，所述正极膜层还可选地包括正极导电剂。本申请对所述正极导电剂的种类没有特别的限制，作为示例，所述正极导电剂包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的至少一种。在一些实施例中，基于所述正极膜层的总质量，所述正极导电剂的质量百分含量为≤5％。
在一些实施例中，所述正极膜层还可选地包括正极粘结剂。本申请对所述正极粘结剂的种类没有特别的限制，作为示例，所述正极粘结剂可包括聚偏二氟乙烯(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-六氟丙烯共聚物和含氟丙烯酸酯类树脂中的至少一种。在一些实施例中，基于所述正极膜层的总质量，所述正极粘结剂的质量百分含量为≤5％。
在一些实施例中，所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铝、铝合金、镍、镍合金、钛、钛合金、银和银合金中的至少一种。作为示例，所述高分子材料基层可包括聚丙烯(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)和聚乙烯(PE)中的至少一种。
所述正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至 少一个表面且包括负极活性材料的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
所述负极活性材料可采用本领域公知的用于二次电池的负极活性材料。作为示例，所述负极活性材料可包括但不限于天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂中的至少一种。所述硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物和硅合金材料中的至少一种。所述锡基材料可包括单质锡、锡氧化物和锡合金材料中的至少一种。
在一些实施例中，所述负极膜层还可选地包括负极导电剂。本申请对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的至少一种。在一些实施例中，基于所述负极膜层的总质量，所述负极导电剂的质量百分含量为≤5％。
在一些实施例中，所述负极膜层还可选地包括负极粘结剂。本申请对所述负极粘结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的至少一种。在一些实施例中，基于所述负极膜层的总质量，所述负极粘结剂的质量百分含量为≤5％。
在一些实施例中，所述负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC)、PTC热敏电阻材料等。在一些实施例中，基于所述负极膜层的总质量，所述其他助剂的质量百分含量为≤2％。
在一些实施例中，所述负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铜、铜合金、镍、镍合金、钛、钛合金、银和银合金中的至少一种。作为示例，所述高分子材料基层可包括聚丙烯(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)和聚乙烯(PE)中的至少一种。
所述负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
所述负极极片并不排除除了所述负极膜层之外的其他附加功能层。例如在某些实施例中，本申请所述的负极极片还包括夹在所述负极集流体和所述负极膜层之间、设置在所述负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施例中，本申请所述的负极极片还包括覆盖在所述负极膜层表面的保护层。
[电解液]
在二次电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱 出，电解液在正极极片和负极极片之间起到传导活性离子的作用。本申请对电解液的种类没有特别的限制，可根据实际需求进行选择。
所述电解液包括电解质盐和溶剂。所述电解质盐和所述溶剂的种类不受具体的限制，可根据实际需求进行选择。
当本申请的二次电池为锂离子电池时，作为示例，所述电解质盐可包括但不限于六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)和四氟草酸磷酸锂(LiTFOP)中的至少一种。
当本申请的二次电池为钠离子电池时，作为示例，所述电解质盐可包括但不限于六氟磷酸钠(NaPF 6)、四氟硼酸钠(NaBF 4)、高氯酸钠(NaClO 4)、六氟砷酸钠(NaAsF 6)、双氟磺酰亚胺钠(NaFSI)、双三氟甲磺酰亚胺钠(NaTFSI)、三氟甲磺酸钠(NaTFS)、二氟草酸硼酸钠(NaDFOB)、二草酸硼酸钠(NaBOB)、二氟磷酸钠(NaPO 2F 2)、二氟二草酸磷酸钠(NaDFOP)和四氟草酸磷酸钠(NaTFOP)中的至少一种。
作为示例，所述溶剂可包括但不限于碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸乙烯酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)和二乙砜(ESE)中的至少一种。
在一些实施例中，所述电解液中还可选地包括添加剂。例如，所述添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，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、改善电池高温性能的添加剂、改善电池低温功率性能的添加剂等。
在一些实施例中，所述正极极片、所述隔离膜和所述负极极片可通过卷绕工艺和/或叠片工艺制成电极组件。
在一些实施例中，所述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液。
在一些实施例中，所述二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。所述二次电池的外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)和聚丁二酸丁二醇酯(PBS)中的至少一种。
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。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图2所示，外包装可包括壳体51和盖板53。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用于盖设所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺和/或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。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，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺和/或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在本申请的一些实施例中，根据本申请的二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，在电池模块4中，多个二次电池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二次电池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，多个二次电池5容纳于该容纳空间。
在一些实施例中，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根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，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用于盖设下箱体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。
用电装置
本申请实施方式第六方面提供一种用电装置，所述用电装置包括本申请的二次电池、电池模块或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(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。
所述用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置的示意图。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高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
聚合物的制备
实施例A
预聚体制备
向5L三口瓶中分别1400g的去离子水和7g十二烷基硫酸钠，于1500r/min的转速下搅拌乳化30min，得到均匀稳定的乳液，然后再依次加入645.68g丙烯酸甲酯、79.59g丙烯腈和663.50g甲基丙烯酰氧丙基笼型聚倍半硅氧烷(丙烯酸甲酯、丙烯腈和甲基丙烯酰氧丙基笼型聚倍半硅氧烷的摩尔含量比值为15:3:2)，继续于1500r/min的转速下搅拌30min，得到均匀的预聚体。
聚合物制备
在干燥的三口瓶中，加入3g乳化剂和1000g去离子水，高速搅拌乳化30min，得到均匀稳定的乳液；然后利用蠕动泵分别缓慢滴加上个步骤制备的预聚体及引发剂溶液(将引发剂3g过硫酸钾溶于30g去离子水中形成溶液)，待滴加完毕后升温到90℃并保温反应0.5h，冷却到40℃，用氨水调节pH至7～8后，过滤，出料，经干燥工艺制得聚合物。
实施例B至实施例E
采用与实施例A相似的方法制备聚合物，与实施例A不同的是，调整了原料成分和含量等中的至少一者。
聚合物制备的相关参数如表1和表2所示。
实施例1
隔离膜的制备
提供PE基材：厚度为7μm，孔隙率为40％，离子导通率为1.20mS/cm。
配制涂覆浆料：将上述实施例A制备的聚合物、粘结剂水溶液型聚丙烯酸按照质量比90:10在适量的溶剂去离子水中混合均匀，得到涂覆浆料。
涂布：将所配制的涂覆浆料用涂布机涂布在PE基材的2个表面上，通过干燥、分切工序，得到隔离膜。位于PE基材单侧的涂层的面密度为0.9g/m 2、厚度为0.45μm。
正极极片的制备
将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、导电剂炭黑(Super P)、粘结剂聚偏二氟乙烯(PVDF)按照质量比96.2:2.7:1.1在适量的溶剂N-甲基吡咯烷酮(NMP)中混合均匀，得到正极浆料；将正极浆料涂布于正极集流体铝箔上，通过烘干、冷压、分条、裁切等工序，得到正极极片。正极极片的面密度为0.207mg/mm 2，压实密度为3.5g/cm 3。
负极极片的制备
将负极活性材料人造石墨、导电剂炭黑(Super P)、粘结剂丁苯橡胶(SBR)和羧甲基纤维素钠(CMC)按照质量比96.4:0.7:1.8:1.1在适量的溶剂去离子水中混合均匀，得到负极浆料；将负极浆料涂布于负极集流体铜箔上，通过烘干、冷压、分条、裁切工序，得到负极极片。负极极片的面密度为0.126mg/mm 2，压实密度为1.7g/cm 3。
电解液的制备
将碳酸乙烯酯(EC)和碳酸甲乙酯(EMC)按照质量比30:70进行混合得到有机溶剂，将充分干燥的LiPF 6溶解于上述有机溶剂中配制成浓度为1mol/L的电解液。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件置于外包装中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
对比例、实施例2至实施例15
二次电池采用与实施例1类似的方法制备，不同之处在于隔离膜的制备参数不同，具体参数详见表3。
实施例16
二次电池采用与实施例1类似的方法制备，不同之处在于涂覆浆料的制备方法，具体为：将上述实施例A制备的聚合物、填料氧化铝(平均粒径Dv50为300nm)、粘结剂水溶液型聚丙烯酸按照质量比80：15：5，在适量的溶剂去离子水中混合均匀，得到固含量为35wt％的涂覆浆料。
测试部分
1.隔离膜与正极极片粘结力测试
将电池正极极片与隔离膜重叠在一起，置于热压机上，设定热压机参数为：温度为25℃，压力为10t，时间为30s，施压制得粘结的隔离膜/正极片样品；将隔离膜/极片样品裁切成150×20mm的矩形样条。通过双面胶将上述矩形样条的正极片一面粘贴在钢板上，在矩形样条的一端将隔离膜与正极片沿长度方向分开2cm的长度，制得测试试样。
将钢板保持水平并用万能试验机(协强仪器制造(上海)有限公司，型号CTM2100)下方夹具固定，将如上所述的隔离膜的剥离端部用万能试验机的上方夹具固定，并连接拉力机。设置测试条件为拉伸速率20mm/min，水平拉动10cm。待拉力稳定后，记录拉力值，通过拉力值与样品宽度的比值，得到隔离膜与极片粘结力。
2.隔离膜的热收缩率测试
样品制备：将上述制备的隔离膜用冲压机冲切成宽度为50mm、长度为100mm的样品，取5个平行样品放置在A4纸上，再将装有样品的A4纸放置在厚度为1mm至5mm的瓦楞纸上。
样品测试：将鼓风式烘箱温度设置为150℃，待温度达到设定温度并稳定30 min后，将放置在瓦楞纸上面的A4纸放入鼓风式烘箱，开始计时，到达设定时间(本申请为1h)后，测量隔离膜的长度和宽度，数值分别标记为a和b。
热收缩率计算：纵向(MD)热收缩率＝[(100-a)/100]×100％，横向(TD)热收缩率＝[(50-b)/50]×100％，取5个平行样品的平均值作为测试结果。
3.二次电池的热箱测试
在25℃下，将二次电池以1C恒流充电至4.2V，继续恒压充电至电流为≤0.05C，静置5min；然后在DHG-9070A DHG系列高温烘箱中带夹具测试各二次电池，以5℃/min的速率从室温升至80±2℃，保持30min；之后再以5℃/min升温速度升温，每升温5℃，保温30min，直至二次电池失效。升温过程中监控二次电池表面温度变化，当温度开始急剧上升时对应的烘箱温度即为二次电池的热箱失效温度。二次电池的热箱失效温度越高，表明二次电池的热安全性能越好。
表1
Figure PCTCN2022136425-appb-000019
表2
Figure PCTCN2022136425-appb-000020
Figure PCTCN2022136425-appb-000021
表3
Figure PCTCN2022136425-appb-000022
由表1至表3可知，对比例1的聚合物包括第一结构单元和第二结构单元，隔离膜采用所述聚合物时，其粘结性能较好，但是二次电池的热箱失效温度较低，容易发生热失控；对比例2的聚合物包括第一结构单元和第三结构单元，隔离膜采用所述聚合物时，其耐热性能具有一定提升，但是隔离膜的粘结性能相对较差。
而实施例1至实施例16的聚合物包括第一结构单元、第二结构单元和第三结构单元，能够兼顾改善聚合物的耐热性能、粘结性能和抗溶胀性能。调整三个结构单元的摩尔含量可以在一定程度上调控聚合物的性能，尤其是3≤A/B≤16、3≤A/C≤16和/或A：B：C为(12至16)：(1至4)：(1至4)时，聚合物的性能能够得到进一步的提升。实施例15至17，聚合物具有良好的耐热性能，在其含量相对较高时，隔离膜的耐热性能较好。无机颗粒例如氧化铝也可以作为耐热辅料，进一步提升隔离膜的耐热性能。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存 在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (16)

  1. 一种聚合物，包括第一结构单元、第二结构单元和第三结构单元；
    所述第一结构单元包括式(I)所示的结构单元：
    Figure PCTCN2022136425-appb-100001
    式(I)中，R 1包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 1包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
    R 2包括取代或未取代的C1-C20烷基、取代或未取代的C3-C20环烷基、取代或未取代的C1-C20羟烷基中的一种或多种；可选地，R 2包括C1-C12烷基、C3-C12环烷基、C1-C12羟烷基中的一种或多种；
    所述第二结构单元包括式(II)所示的结构单元：
    Figure PCTCN2022136425-appb-100002
    式(II)中，R 3包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 3包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
    所述第三结构单元包括式(III)所示的结构单元：
    Figure PCTCN2022136425-appb-100003
    式(III)中，R 4至R 11各自独立地包括取代或未取代的C1-C10烷基、如式(III-1)所示的结构单元中的一种或多种，且R 4至R 11中至少一者包括式(III-1)所示的结构单元，
    Figure PCTCN2022136425-appb-100004
    式(III-1)中，R 12包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 12包括氢原子、或者取代或未取代的C1-C3烷基；
    R 13包括取代或未取代的C1-C10烷基；可选地，R 13包括取代或未取代的C3-C10烷基。
  2. 根据权利要求1所述的聚合物，其中，R 1包括氢原子或甲基；和/或
    R 2包括甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基、2-乙基己基、十二烷基或异冰片基。
  3. 根据权利要求1或2所述的聚合物，其中，R 3包括氢原子或甲基。
  4. 根据权利要求1至3中任一项所述的聚合物，其中，
    所述R 4至R 11各自独立地包括如式(III-1)所示的结构单元；可选地，R 12包括氢原子、甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基或正戊基；和/或R 13包括正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基或2-乙基己基；或
    所述R 4至R 11中其中一者包括如式(III-1)所示的结构单元；可选地，R 12包括氢原子、甲基、乙基、正丙基、异丙基、正丁基、仲丁基、叔丁基或正戊基；和/或R 13包括正丙基、异丙基、正丁基、仲丁基、叔丁基、正戊基、正辛基、异辛基或2-乙基己基。
  5. 根据权利要求1至4中任一项所述的聚合物，其中，
    基于所述第一结构单元、所述第二结构单元和所述第三结构单元的总摩尔量计，所述第一结构单元的摩尔含量记为A％，60≤A＜100；可选地，60≤A≤80；和/或
    基于所述第一结构单元、所述第二结构单元和所述第三结构单元的总摩尔量计，所述第二结构单元的摩尔含量记为B％，0＜B≤20；可选地，5≤B≤20；和/或
    基于所述第一结构单元、所述第二结构单元和所述第三结构单元的总摩尔量计，所述第三结构单元的摩尔含量记为C％，0＜C≤20；可选地，5≤C≤20。
  6. 根据权利要求1至5中任一项所述的聚合物，其中，基于所述第一结构单元、所述第二结构单元和所述第三结构单元的总摩尔量计，所述第一结构单元的摩尔含量记为A％，所述第二结构单元的摩尔含量记为B％，所述第三结构单元的摩尔含量记为C％；所述聚合物满足条件(1)至条件(3)中的一个或多个：
    (1)3≤A/B≤16；
    (2)3≤A/C≤16；
    (3)A：B：C为(12至16)：(1至4)：(1至4)。
  7. 根据权利要求1至6中任一项所述的聚合物，其中，
    所述聚合物的数均分子量为20000至80000，可选为30000至50000。
  8. 根据权利要求1至7中任一项所述的聚合物，其中，所述聚合物为颗粒状，所述聚合物还满足条件(Ⅰ)至条件(III)中的一个或多个：
    (Ⅰ)所述聚合物的形貌包括球形和/或类球形；
    (II)所述聚合物的体积分布粒径Dv50满足：0.1μm≤Dv50≤2.0μm；可选地，0.5μm≤Dv50≤1.2μm；
    (III)所述聚合物的比表面积记为S，其单位为m 2/g，5.0≤S≤12.0；可选地，6.0≤S≤10.0。
  9. 一种制备聚合物的方法，包括：
    提供第一单体、第二单体和第三单体；
    将所述第一单体、所述第二单体和所述第三单体混合，并在引发剂的作用下发生聚合反应生成聚合物，
    其中，所述第一单体包括式(IV)所示的化合物，
    Figure PCTCN2022136425-appb-100005
    式(IV)中，R 1包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 1包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
    R 2包括取代或未取代的C1-C20烷基、取代或未取代的C3-C20环烷基、取代或未取代的C1-C20羟烷基中的一种或多种；可选地，R 2包括C1-C12烷基、C3-C12环烷基、C1-C12羟烷基中的一种或多种；
    所述第二单体包括式(V)所示的化合物，
    Figure PCTCN2022136425-appb-100006
    式(V)中，R 3包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 3包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
    所述第三单体包括式(VI)所示的化合物，
    Figure PCTCN2022136425-appb-100007
    式(VI)中，R 30至R 37各自独立地包括取代或未取代的C1-C10烷基、如式(VI-1)所示的结构单元中的一种或多种，且R 30至R 37中至少一者包括式(VI-1)所示的结构单元，
    Figure PCTCN2022136425-appb-100008
    式(VI-1)中，R 12包括氢原子、取代或未取代的C1-C5烷基中的一种或多种；可选地，R 12包括氢原子、取代或未取代的C1-C3烷基中的一种或多种；
    R 13包括取代或未取代的C1-C10烷基；可选地，R 13包括取代或未取代的C3-C10烷基。
  10. 根据权利要求9所述的方法，其中，将所述第一单体、所述第二单体和所述第三单体混合，并在引发剂的作用下发生聚合反应生成聚合物的步骤，包括：
    于溶剂和乳化剂中加入所述第一单体、所述第二单体和所述第三单体并混合形成混合体系；
    于所述混合体系中加入所述引发剂，在所述引发剂的作用下发生聚合反应生成所述聚合物。
  11. 根据权利要求9或10所述的方法，其中，
    所述第一单体包括丙烯酸甲酯、丙烯酸乙酯、丙烯酸正丙酯、丙烯酸异丙酯、丙烯酸正丁酯、丙烯酸异丁酯、丙烯酸仲丁酯、丙烯酸叔丁酯、丙烯酸正戊酯、丙烯酸正辛酯、丙烯酸异辛酯、丙烯酸-2-乙基己酯、丙烯酸环己酯、丙烯酸月桂酯、丙烯酸-2-羟基乙酯、丙烯酸-2-羟基丙酯、甲基丙烯酸甲酯、甲基丙烯酸乙酯、甲基丙烯酸正丁酯、甲基丙烯酸-2-乙基己酯、甲基丙烯酸异冰片酯、甲基丙烯酸月桂酯、甲基丙烯酸-2-羟基乙酯和甲基丙烯酸-2-羟基丙酯的一种或多种；和/或，
    所述第二单体包括丙烯腈和/或甲基丙烯腈；和/或
    所述第三单体包括甲基丙烯酰氧丙基笼型聚倍半硅氧烷、甲基丙烯酰氧丙基七异丁基聚倍半硅氧烷、甲基丙烯酰氧丙基七辛基聚倍半硅氧烷、丙烯酰氧丙基笼型聚倍半硅氧烷、丙烯酰氧丙基七异丁基聚倍半硅氧烷和甲基丙烯酰氧丙基七辛基聚倍半硅氧烷中的一种或多种。
  12. 一种隔离膜，包括基材和设置在所述基材至少一个表面上的涂层，所述涂层包括如权利要求1至8中任一项所述的聚合物或如权利要求9至11中任一项所述的方法制备得到的聚合物。
  13. 根据权利要求12所述的隔离膜，其中，基于所述涂层的质量计，所述聚合物的质量百分含量为m％，m≥70；可选地，80≤m≤95。
  14. 根据权利要求12或13所述的隔离膜，其中，所述隔离膜满足如下条件(A)至(G)中的一个或多个：
    (A)所述隔离膜在150℃、1h下的纵向热收缩率η 1≤5.0％，可选地，0.5％≤η 1≤3％；
    (B)所述隔离膜在150℃、1h下的横向热收缩率η 2≤5.0％，可选地，0.5％≤η2≤2％；
    (C)所述隔离膜的纵向拉伸强度R m1≥3000kg/cm 2，可选地，3500kg/cm 2≤R m1≤4500kg/cm 2；
    (D)所述隔离膜的横向拉伸强度R m2≥3000kg/cm 2，可选地，3500kg/cm 2≤R m2≤4500kg/cm 2；
    (E)所述隔离膜的透气度MAP≤250s/100mL，可选地，120s/100mL≤MAP≤180s/100mL；
    (F)所述隔离膜的润湿长度L≥30mm，可选地，30mm≤L≤80mm；
    (G)所述隔离膜的润湿速度u≥3mm/s，可选地，3mm/s≤u≤10mm/s。
  15. 一种二次电池，包括如权利要求12至14中任一项所述的隔离膜。
  16. 一种用电装置，包括如权利要求15所述的二次电池。
PCT/CN2022/136425 2022-12-05 2022-12-05 聚合物、隔离膜及其相关的二次电池和用电装置 WO2024119286A1 (zh)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/136425 WO2024119286A1 (zh) 2022-12-05 2022-12-05 聚合物、隔离膜及其相关的二次电池和用电装置

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/136425 WO2024119286A1 (zh) 2022-12-05 2022-12-05 聚合物、隔离膜及其相关的二次电池和用电装置

Publications (1)

Publication Number Publication Date
WO2024119286A1 true WO2024119286A1 (zh) 2024-06-13

Family

ID=91378408

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2022/136425 WO2024119286A1 (zh) 2022-12-05 2022-12-05 聚合物、隔离膜及其相关的二次电池和用电装置

Country Status (1)

Country Link
WO (1) WO2024119286A1 (zh)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130330590A1 (en) * 2011-02-25 2013-12-12 Zeon Corporation Porous membrane for secondary battery, slurry for secondary battery porous membrane and secondary battery
KR20150056122A (ko) * 2013-11-14 2015-05-26 주식회사 포스코 리튬 이차 전지용 고분자 전해질, 이의 제조 방법, 및 이를 포함하는 리튬 이차 전지
JP2016031868A (ja) * 2014-07-29 2016-03-07 富士フイルム株式会社 全固体二次電池、電池用電極シート、電池用電極シートの製造方法、固体電解質組成物、固体電解質組成物の製造方法、および全固体二次電池の製造方法
CN107384261A (zh) * 2017-07-21 2017-11-24 中国乐凯集团有限公司 一种锂离子电池隔膜耐热层用水性粘合剂、制备方法及其应用
CN108493387A (zh) * 2018-04-23 2018-09-04 东莞市魔方新能源科技有限公司 电池隔膜涂层用粘接剂及其制备方法
CN111704702A (zh) * 2020-06-24 2020-09-25 南方科技大学 一种聚丙烯腈前驱体纺丝液及其制备方法和应用
CN111718446A (zh) * 2019-03-18 2020-09-29 陆筱棣 一种制备聚合物微球的方法及得到的聚合物微球与应用

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130330590A1 (en) * 2011-02-25 2013-12-12 Zeon Corporation Porous membrane for secondary battery, slurry for secondary battery porous membrane and secondary battery
KR20150056122A (ko) * 2013-11-14 2015-05-26 주식회사 포스코 리튬 이차 전지용 고분자 전해질, 이의 제조 방법, 및 이를 포함하는 리튬 이차 전지
JP2016031868A (ja) * 2014-07-29 2016-03-07 富士フイルム株式会社 全固体二次電池、電池用電極シート、電池用電極シートの製造方法、固体電解質組成物、固体電解質組成物の製造方法、および全固体二次電池の製造方法
CN107384261A (zh) * 2017-07-21 2017-11-24 中国乐凯集团有限公司 一种锂离子电池隔膜耐热层用水性粘合剂、制备方法及其应用
CN108493387A (zh) * 2018-04-23 2018-09-04 东莞市魔方新能源科技有限公司 电池隔膜涂层用粘接剂及其制备方法
CN111718446A (zh) * 2019-03-18 2020-09-29 陆筱棣 一种制备聚合物微球的方法及得到的聚合物微球与应用
CN111704702A (zh) * 2020-06-24 2020-09-25 南方科技大学 一种聚丙烯腈前驱体纺丝液及其制备方法和应用

Similar Documents

Publication Publication Date Title
CN110754009B (zh) 锂二次电池
CN110785886B (zh) 锂二次电池
KR102246767B1 (ko) 리튬이차전지용 세퍼레이터, 이를 채용한 리튬이차전지 및 그 제조방법
WO2022141508A1 (zh) 一种电化学装置和电子装置
US20210167393A1 (en) Lithium ion secondary battery
JP7495528B2 (ja) リチウム二次電池用セパレータ及びそれを備えたリチウム二次電池
CN110419137B (zh) 电极组件和包括其的锂电池
WO2024174080A1 (zh) 隔离膜、其制备方法及其相关的二次电池和用电装置
WO2022205165A1 (zh) 一种隔离膜及包含所述隔离膜的电化学装置和电子装置
WO2024174093A1 (zh) 隔离膜、其制备方法及其相关的二次电池和用电装置
CN106531938A (zh) 非水电解液二次电池
WO2022110226A1 (zh) 一种隔离膜、其制备方法及其相关的二次电池、电池模块、电池包和装置
WO2024119286A1 (zh) 聚合物、隔离膜及其相关的二次电池和用电装置
WO2023245840A1 (zh) 隔离膜、其制备方法及其相关的二次电池和用电装置
WO2023060534A1 (zh) 一种二次电池
WO2024119287A1 (zh) 隔离膜、其制备方法及其相关的二次电池和用电装置
CN116157945A (zh) 一种二次电池及包含该电池的装置
WO2024119290A1 (zh) 隔离膜及其制备方法、二次电池和用电装置
WO2024119288A1 (zh) 隔离膜及其制备方法、二次电池和用电装置
WO2024119289A1 (zh) 隔离膜及其制备方法、二次电池和用电装置
CN115803960A (zh) 一种隔离膜、含有它的二次电池及其相关的电池模块、电池包和装置
WO2024212052A1 (zh) 隔离膜及其相关的二次电池和用电装置
WO2024065161A1 (zh) 粘结剂组合物和包含其的隔离膜
JP5979299B1 (ja) 積層多孔質フィルム、蓄電デバイス用セパレータおよび蓄電デバイス
WO2024108520A1 (zh) 二次电池和用电装置

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22967454

Country of ref document: EP

Kind code of ref document: A1