Isolating membrane, battery monomer, battery and electric device

Abstract

The invention discloses an isolating membrane, a battery monomer, a battery and an electric device. The isolating membrane comprises a base membrane and a coating arranged on at least one side of the base membrane, and the coating comprises a covalent organic framework material; the covalent organic framework material includes a chelating group for chelating transition metal ions. The isolating membrane can hinder formation of dendritic crystals, so that the reliability of the battery monomer is further improved; the cycle performance, the dynamic performance and the service life of the battery monomer can be improved; the invention also provides a battery monomer, a battery and an electric device with the above advantages.

Description

Technical Field

[0001] This application belongs to the technical field of energy storage devices, and particularly relates to a separator, a battery cell, a battery, and an electrical device. Background Art

[0002] In recent years, electrical devices represented by lithium batteries have been widely used and promoted in various industries such as various electronic products and new energy vehicles. At the same time, people have put forward higher requirements for the cycle performance, charge and discharge performance, and reliability of batteries.

[0003] A separator is usually provided in a battery. The separator is a thin film with pores, which is used to isolate the positive electrode plate and the negative electrode plate to prevent short circuit between the positive electrode plate and the negative electrode plate inside the battery. At the same time, the separator can allow active ions such as lithium ions to pass through. The separator has the function of holding the electrolyte. Therefore, the role of the separator in battery performance is very crucial and still needs to be improved. Summary of the Invention

[0004] The purpose of this application is to provide a separator, a battery cell, a battery, and an electrical device. The separator can hinder the formation of dendrites, further improve the reliability of the battery cell; can also improve the cycle performance, kinetic performance, and service life of the battery cell; this application also provides a battery and an electrical device including the above battery cell.

[0005] In a first aspect, an embodiment of this application provides a separator. The separator includes a base film and a coating disposed on at least one side of the base film. Among them, the coating includes a covalent organic framework material; the covalent organic framework material includes a chelating group for chelating transition metal ions.

[0006] According to the embodiment of this application, the covalent organic framework material exists in the coating of the separator. By the type and pore size of the covalent organic framework material, the insertion rate of the electrolyte solvent can be controlled, which is beneficial to the transmission rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery. According to the embodiment of this application, a certain amount of chelating groups in the covalent organic framework material can form complexes with transition metal ions, such as transition metal ions such as nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, thereby reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating group can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating group hinders the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit of the separator, and improving the reliability of the battery.

[0007] In any embodiment of the present application, based on the total mass of the coating, the coating comprises 0.01% to 1% of the covalent organic framework material, optionally 0.05% to 0.6%.

[0008] According to the embodiments of the present application, controlling the content of the covalent organic framework material in the coating within a suitable range can enable the coating to have a suitable content of chelating groups, which is beneficial to the rapid transmission of active ions in the battery including the separator membrane, form complexes with a certain amount of transition metal ions, reduce the adverse effects of transition metal ions on the stability of electrolyte components and the damage to the SEI film, prevent the precipitation of transition metal ions to form dendrites, improve the stability of the SEI film, and thus improve the cycling performance of the battery; it also improves the reliability of the battery.

[0009] In any embodiment of the present application, the chelating groups include one or more of cyano groups and amino groups.

[0010] According to the embodiments of the present application, the chelating groups of the above types can form complexes with transition metal ions, reduce the concentration of transition metal ions in the electrolyte, and thus reduce the adverse effects of transition metal ions on the stability of electrolyte components; the chelating groups can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycling performance of the battery; the chelating groups prevent the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reduce the probability of internal short circuit of the separator membrane, and improve the reliability of the battery.

[0011] According to the embodiments of the present application, the covalent organic framework material used is formed by the reaction of a first monomer with symmetry and a second monomer with symmetry, which is beneficial to the uniformity of pores and the formation of a stable spatial conformation. The insertion rate of the electrolyte solvent can be controlled by the type and pore size of the covalent organic framework material, which is beneficial to the transmission rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery.

[0012] In any embodiment of the present application, the covalent organic framework material includes a first covalent organic framework material obtained by the reaction of a first monomer and a second monomer. The first monomer includes at least one of formulas (1) to (5); the second monomer includes at least one of formulas (6) to (7); the first covalent organic framework material is obtained by the reaction of the amino group contained in the first monomer with any one of the aldehyde group or ketone group contained in the second monomer;

[0013]

[0014]

[0015] Among them, in formula (4), M includes one or more of copper element and nickel element;

[0016] In the formula (5), R8, R9, R10, R11, R12, and R13 each independently include any one of a substituted or unsubstituted C1-C8 alkyl group, H, a substituted or unsubstituted amide group, a C1-C8 alkoxy group, a substituted or unsubstituted phenoxy group, and an alkylsulfonyl group. The substituents in the substituted C1-C8 alkyl group each independently include any one of a halogen atom and a cyano group; the substituents of the substituted amide group and the substituted phenoxy group each independently include an amino group; at least two of R8, R9, R10, R11, R12, and R13 have an amino group and the formula (5) is a monomer with bifunctional, trifunctional, or tetrafunctional symmetry;

[0017] In the formula (6), R14, R15, R16, R17, R18, and R19 each independently include any one of a C1-C8 alkyl group, an amino group, H, a hydroxyl group, an alkoxy group, a phenoxy group, an aldehyde group, and a ketone group. At least two of R14, R15, R16, R17, R18, and R19 have an aldehyde group or a ketone group, and the formula (6) is a monomer with bifunctional, trifunctional, or tetrafunctional symmetry; Optionally, in the formula (6), R14 and R15 are connected to form a furan-dione and R17 and R18 are connected to form a furan-dione.

[0018] According to an embodiment of the present application, the first monomer reacts with the second monomer to form a covalent organic framework material with regular pores, which can control the insertion rate of the electrolyte solvent, is beneficial to the transport rate of ions (such as lithium ions) in the battery, and thus is beneficial to the fast charge and discharge performance of the battery.

[0019] According to an embodiment of the present application, the covalent organic framework material composed of the above monomers is a highly ordered, three-dimensional organic material with relatively uniform pore sizes, and it has a good glass transition temperature. It exists in the coating of the separator membrane. The insertion rate of the electrolyte solvent can be controlled by the type and pore size of the covalent organic framework material, which affects the transport rate of ions (such as lithium ions) in the battery, and thus affects the charge and discharge performance of the battery. The chelating group can form complexes with transition metal ions, such as transition metal ions like nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, thereby reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating group can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating group hinders the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator membrane, and improving the reliability of the battery.

[0020] In any embodiment of the present application, the covalent organic framework material includes at least one of a first covalent organic framework material obtained by reacting a first monomer having trifunctionality with a second monomer having difunctionality or tetrafunctionality, and a first covalent organic framework material obtained by reacting a first monomer having difunctionality or tetrafunctionality with a second monomer having trifunctionality.

[0021] According to the embodiments of the present application, the reaction form of the functional group matching between the first monomer and the second monomer is conducive to forming a covalent organic framework material with regular pores, can control the insertion rate of the electrolyte solvent, is conducive to the transport rate of active ions (such as lithium ions) in the battery, and thus is conducive to the fast charge and discharge performance of the battery.

[0022] In any embodiment of the present application, the first monomer includes at least one of formula (1), formula (2), formula (3), formula (5-I), formula (5-II), formula (5-III), formula (5-IV), formula (5-V), formula (VI):

[0023]

[0024]

[0025] According to the embodiments of the present application, the reaction between the first monomer of the above type and the second monomer is conducive to forming a covalent organic framework material with regular pores, can control the insertion rate of the electrolyte solvent, is conducive to the transport rate of ions (such as lithium ions) in the battery, and thus is conducive to the fast charge and discharge performance of the battery.

[0026] In any embodiment of the present application, the second monomer includes at least one of formula (7), formula (6-I), formula (6-II), formula (6-III), formula (6-IV):

[0027]

[0028] According to the embodiments of the present application, the reaction between the first monomer and the second monomer of the above type is conducive to forming a covalent organic framework material with regular pores, can control the insertion rate of the electrolyte solvent, is conducive to the transport rate of ions (such as lithium ions) in the battery, and thus is conducive to the fast charge and discharge performance of the battery.

[0029] In any embodiment of the present application, the covalent organic framework material includes a second covalent organic framework material obtained by reacting a third monomer represented by formula (8) with a fourth monomer represented by formula (9):

[0030]

[0031] According to the embodiments of the present application, the third monomer and the fourth monomer react to form a second covalent organic framework material with regular pores, which can control the insertion rate of the electrolyte solvent, facilitate the transport rate of ions (such as lithium ions) in the battery, and thus facilitate the fast charge and discharge performance of the battery. According to the embodiments of the present application, the covalent organic framework material composed of the above monomers is a highly ordered, three-dimensional organic material with relatively uniform pore sizes and good glass transition temperature. It is present in the coating of the separator. By varying the type and pore size of the covalent organic framework material, the insertion rate of the electrolyte solvent can be controlled, affecting the transport rate of ions (such as lithium ions) in the battery, and thus affecting the charge and discharge performance of the battery. The chelating group can form complexes with transition metal ions, such as nickel ions, cobalt ions, manganese ions and other transition metal ions, reducing the concentration of transition metal ions in the electrolyte, and thus reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating group can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating group hinders the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator, and improving the reliability of the battery.

[0032] In any embodiment of the present application, the coating comprises a polymer obtained by reacting a fifth monomer represented by any one of formulas (10) to (12) and a sixth monomer represented by formula (13), and the polymer is obtained by reacting the amino group contained in the fifth monomer with any one of the aldehyde group or ketone group contained in the sixth monomer;

[0033]

[0034] wherein, R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 each independently comprises any one of a substituted or unsubstituted C1-C8 alkyl group, an amino group, a C1-C8 alkoxy group, a substituted or unsubstituted amide group, a substituted or unsubstituted phenoxy group, and an alkylsulfonyl group; the substituents in the substituted C1-C8 alkyl group each independently comprise any one of a halogen atom and a cyano group; the substituents of the substituted amide group and the substituted phenoxy group each independently comprise an amino group;

[0035] R20, R21, R22, R23, R24, and R25 each independently include any one of C1-C8 alkyl, amino, H, hydroxyl, alkoxy, phenoxy, aldehyde group, and ketone group, and at least two of R20, R21, R22, R23, R24, and R25 have an aldehyde group or a ketone group; optionally, R20 and R21 are connected to form furan-dione or R23 and R24 are connected to form furan-dione.

[0036] According to an embodiment of the present application, a small amount of this polymer is included in the coating, and this polymer can be obtained by modifying a covalent organic framework material, in which groups such as alkoxy, phenoxy, and amino are introduced, which can make the coating have a certain effect of chelating metal ions and can also promote the passage of active ions such as lithium ions through the separator membrane.

[0037] In any embodiment of the present application, the covalent organic framework material includes a first group for promoting the transport of active ions; optionally, the first group includes one or more of alkoxy and phenoxy containing C1-C8; it can be alkoxy, -OCH 3 .

[0038] According to an embodiment of the present application, the first groups such as alkoxy and phenoxy have a certain active ion affinity and can form stable coordination compounds with active ions such as lithium ions, thereby forming active ion transport channels, such as lithium ion channels. These channels can help active ions transport faster in the electrolyte and improve the fast charge and discharge performance of the battery.

[0039] In any embodiment of the present application, in the covalent organic framework material per unit mass, the molar ratio of the chelating group to the first group is 1:(10-100).

[0040] According to an embodiment of the present application, the covalent organic framework material has a chelating group and a first group; controlling the molar ratio of the chelating group to the first group within the above range, the chelating group can chelate transition metal ions, and the first group can form an active ion transport channel. The chelating group is beneficial to adsorbing transition metal ions and promoting the transport of active ions, which affects the selectivity of the separator membrane; further, when the molar ratio of the chelating group to the first group is within the above range, on the basis of taking into account the complexation of transition metal ions, it effectively promotes the transport of active ions, which is convenient for improving the service life of the battery and the fast charge and discharge performance of the battery.

[0041] In any embodiment of the present application, the weight average molecular weight of the covalent organic framework material is 5×10 2 ~80×10 4 , and it can be 6×10 2 ~75×10 4 .

[0042] According to the embodiments of the present application, when the weight-average molecular weight of the covalent organic framework material is within the above range, it can have more structural units, provide more molecular crosslinking points, thereby increasing the bonding strength with other components in the separator coating; it can control the insertion rate of the electrolyte solvent, which is beneficial to the transport rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery.

[0043] In any embodiment of the present application, the glass transition temperature of the covalent organic framework material is -50°C to -10°C, and can be optionally -35°C to -25°C.

[0044] According to the embodiments of the present application, when the glass transition temperature of the covalent organic framework material is within the above range, it is beneficial to the ionic conductivity of the separator and beneficial to the thermal stability of the separator.

[0045] In any embodiment of the present application, the covalent organic framework material includes micropores; optionally, the average pore diameter of the micropores is 0.5 nm to 5 nm, and can be optionally 0.8 nm to 1.5 nm.

[0046] According to the embodiments of the present application, by selecting covalent organic framework materials formed from different monomers, which have micropores with different pore diameters, controlling the average pore diameter of the micropores within the above range is beneficial to controlling the speed of active ions passing through the separator, beneficial to complexing transition metal ions, improving the charge and discharge rate of the battery and improving the reliability of the battery.

[0047] In any embodiment of the present application, the covalent organic framework material is granular, and the average particle size Dv50 of the covalent organic framework material is 0.01 μm to 1 μm; optionally, 0.05 μm to 0.1 μm.

[0048] According to the embodiments of the present application, by selecting covalent organic framework material particles with different particle sizes and controlling their average particle size within the above range, it is beneficial to controlling the speed of active ions passing through the separator, beneficial to complexing transition metal ions, improving the charge and discharge rate of the battery and improving the reliability of the battery.

[0049] In any embodiment of the present application, the total pore volume of the covalent organic framework material is 0.8 cm 3 / g to 1.5 cm 3 / g.

[0050] According to the embodiments of the present application, by selecting covalent organic framework materials formed from different monomers, which have different total pore volumes, controlling the total pore volume within the above range is beneficial to controlling the speed of active ions passing through the separator, beneficial to complexing transition metal ions, improving the charge and discharge rate of the battery and improving the reliability of the battery.

[0051] Second aspect, an embodiment of the present application provides a battery cell, including the separator of the first aspect. The battery cell of the embodiment of the present application has improved reliability, cycle performance, kinetic performance, and service life.

[0052] In any implementation manner of the present application, the battery cell includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive electrode active material film layer, and the negative electrode plate includes a negative electrode active material film layer. At least one of the positive electrode active material film layer and the negative electrode active material film layer includes a covalent organic framework material.

[0053] According to the embodiment of the present application, the covalent organic framework material exists in at least one of the positive electrode active material film layer and the negative electrode active material film layer. By the type and pore size of the covalent organic framework material, the insertion rate of the electrolyte solvent can be controlled, which is beneficial to the transmission rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery. According to the embodiment of the present application, a certain amount of chelating groups in the covalent organic framework material can form complexes with transition metal ions, such as transition metal ions like nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, and thus reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating groups hinder the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator, and improving the reliability of the battery.

[0054] Third aspect, an embodiment of the present application provides a battery, including the battery cell of the second aspect. The battery of the embodiment of the present application includes the battery provided by the embodiment of the present application, and thus has at least the same advantages as the battery cell.

[0055] Fourth aspect, an embodiment of the present application provides an electrical device, including the battery of the third aspect.

[0056] The electrical device of the embodiment of the present application includes the battery provided by the embodiment of the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0058] Figure 1 A schematic structural diagram of the separator of the embodiment of the present application is shown.

[0059] Figure 2 A schematic diagram of an implementation manner of the battery cell of the present application is shown.

[0060] Figure 3 shows the present application Figure 2 exploded view.

[0061] Figure 4 shows a schematic diagram of an embodiment of the battery module of the present application.

[0062] Figure 5 shows a schematic diagram of an embodiment of the battery pack of the present application.

[0063] Figure 6 shows the present application Figure 5 exploded view.

[0064] Figure 7 shows a schematic diagram of an embodiment of a device in which a battery cell of the present application is used as a power source.

[0065] The drawings of the present application are not necessarily drawn to scale. Detailed embodiments

[0066] In order to make the inventive purpose, technical solution and beneficial technical effects of the present application clearer, the present application will be described in detail below in combination with specific embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application and not for limiting the present application.

[0067] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, although not explicitly recited, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be used as its own lower or upper limit and combined with any other point or single value or combined with other lower or upper limits to form a range not explicitly recited.

[0068] In the description herein, it should be noted that unless otherwise specified, "above" and "below" include the recited number, and "one or several" means two or more for "several".

[0069] The above inventive content of the present application does not intend to describe every disclosed embodiment or every implementation manner of the present application. The following description more specifically illustrates exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. In each instance, the listings are only representative groups and should not be construed as exhaustive.

[0070] In the present application, "substituted" means that a hydrogen atom in the described group is replaced by a substituent.

[0071] In the present application, "substituted or unsubstituted" means that the described group may be substituted or may not be substituted. When the described group is substituted, it should be understood that it is optionally substituted by a group acceptable in the art, including but not limited to: cyano, halogen atom, C1-10 alkyl, C1-10 alkoxy, or a combination of the above groups, etc.

[0072] In the present application, "alkyl" refers to a saturated hydrocarbon group, which is a hydrocarbon group formed by removing one H from an alkane molecule. The symbol "Cn" before alkyl represents the number of carbon atoms in the alkyl, which can be an integer from 1 to 8. The number of carbon atoms in the alkyl can be from 1 to 8, from 1 to 7, from 1 to 6, or from 1 to 4. The alkyl can be a straight-chain alkyl or a branched-chain alkyl. For example, "C1-8 straight-chain alkyl" refers to a straight-chain alkyl containing 1 to 8 carbon atoms, and each occurrence can independently be C1 straight-chain alkyl, C2 straight-chain alkyl, C3 straight-chain alkyl, C4 straight-chain alkyl, C5 straight-chain alkyl, C6 straight-chain alkyl, C7 straight-chain alkyl, or C8 straight-chain alkyl. "C1-8 branched-chain alkyl" refers to a branched-chain alkyl containing 1 to 8 carbon atoms, and each occurrence can independently be C1 branched-chain alkyl, C2 branched-chain alkyl, C3 branched-chain alkyl, C4 branched-chain alkyl, C5 branched-chain alkyl, C6 branched-chain alkyl, C7 branched-chain alkyl, or C8 branched-chain alkyl.

[0073] The term "alkoxy" refers to a group having -O-alkyl, that is, it contains the alkyl as defined above and an oxygen atom, and the alkyl is connected to the parent nucleus structure via this oxygen atom. For example, "C1-C6 alkoxy" refers to an alkoxy in which the alkyl part contains 1 to 6 carbon atoms, and each occurrence can independently be C1 alkoxy, C2 alkoxy, C3 alkoxy, C4 alkoxy, C5 alkoxy, or C6 alkoxy. As defined above, the alkyl part of the alkoxy can also be a branched-chain alkyl or a straight-chain alkyl. Suitable examples include but are not limited to: methoxy (-O-CH 3 or -OMe), ethoxy (-O-CH 2 CH 3 or -OEt) and tert-butoxy (-O-C(CH 3 ) 3 or -OtBu).

[0074] The term "phenoxy" refers to a group having -O-phenyl, that is, it contains the alkyl as defined above and an oxygen atom, and the alkyl is connected to the parent nucleus structure via this oxygen atom. For example, "C6-C18 phenoxy" refers to a phenoxy in which the alkyl part contains 6 to 18 carbon atoms, and each occurrence can independently be C6 phenoxy, C7 phenoxy, C 8 phenoxy, C 9 phenoxy, C 10 phenoxy or C 11Phenoxy group and the like. Suitable examples include but are not limited to: phenoxy group, methylphenoxy group (-O-phenyl-CH 3 ), ethylphenoxy group (-O-phenyl-CH 2 CH 3 ), and tert-butylphenoxy group (-O-phenyl-

[0075] The term "amino group" refers to any one of -NH 2 , –NH-, that is, the generalized amino group.

[0076] Battery cells have attracted much attention due to their high energy, long cycle life, good safety performance and other characteristics. Battery cells represented by lithium-ion batteries have been widely used in all aspects of daily life, such as cameras, laptop computers, and electric vehicles.

[0077] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. Improving the service life, cycle performance and reliability of battery cells has always been the pursuit in the industry.

[0078] For example, in order to improve the energy density of the battery core, the nickel content in the positive electrode plate is generally relatively high. However, as the nickel content increases, during the charge and discharge process of the battery cell, the Li / Ni mixing and the H2-H3 phase transformation in the positive electrode active material are relatively serious, which affects the cycle performance and storage life of the battery.

[0079] It has been found through research that the valence states of transition metal elements in the nickel-cobalt-manganese ternary material change during the charge and discharge cycle, and phase transformation occurs, which will affect the cycle performance and storage life of the battery. Generally, doping some specific elements in the positive electrode active material can change the energy band structure of the positive electrode active material and solve the above problems.

[0080] However, the transition metal elements in the positive electrode active material will gradually be released during the long-term charge and discharge process and deposited on the negative electrode. The release of transition metal elements will reduce the cycle performance of the positive electrode active material during the charge and discharge process, and the deposition of transition metal elements will damage the SEI film on the surface of the negative electrode and affect the composition of the electrolyte in the battery. Transition metal elements will also form dendrites during the charge and discharge process of the battery, thereby reducing the cycle performance and charge and discharge performance of the battery and reducing the reliability of the battery.

[0081] In view of this, the technical solution of the embodiment of the present application provides a separator that can at least reduce the deposition of metal elements, especially transition metal elements, on the negative electrode plate during the charge and discharge process of the battery, thereby reducing its adverse impact on the cycle performance of the battery and improving the reliability and service life of the battery.

[0082] Separator

[0083] In a first aspect, an embodiment of the present application provides a separator, which includes a base film and a coating disposed on at least one side of the base film. The coating includes a covalent organic framework material.

[0084] Covalent Organic Frameworks (COFs) are organic materials with a highly ordered three-dimensional structure and relatively uniform pore sizes. Their main characteristic is that they are constructed from organic units connected by covalent bonds, forming a spatial network structure through covalent bonds. Present in the coating of the separator, the insertion rate of the electrolyte solvent can be controlled by the type and pore size of the covalent organic framework material, which is beneficial to the transport rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery. In some alternative embodiments, the covalent organic framework material includes chelating groups for chelating transition metal ions.

[0085] According to the embodiments of the present application, a certain amount of chelating groups in the covalent organic framework material can form complexes with transition metal ions, such as transition metal ions like nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, thereby reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating groups can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating groups hinder the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator, and improving the reliability of the battery.

[0086] Whether the coating contains a covalent organic framework material can be detected by sampling the coating and separating the polymer from the coating.

[0087] As an example, Step 1: Weigh a certain amount of the coating and record it as M1. Then disperse the coating in an acetone solvent, with the mass ratio of the coating to acetone being 1:10. Ultrasonic the mixed solution containing the coating for 20 - 40 minutes, with the ultrasonic frequency being 20 - 40 HZ, which can be 25 HZ. Then repeat the cleaning and filtration process 3 times (to remove the binder polyacrylate CCS) for the coating. After drying, obtain the coating with the binder polyacrylate CCS peeled off, denoted as M2.

[0088] Step 2: Peel off the coating of the binder polyacrylate in Step 1, and then put the coating into a mixed solution of water and ethanol with a volume ratio of water:ethanol of 1:1 and a mass ratio of the coating to the mixed solution of 1:10. Ultrasonic the mixed solution containing the coating for 20 - 40 min at an ultrasonic frequency of 20 - 40 HZ, which can be 25 HZ, then wash and filter, collect the coating after peeling off the polymer, dry it, and weigh the collected particles after peeling off the polymer and record it as M3. Then continue to put the collected particles of the peeled-off polymer into the mixed solution of water and ethanol, continue to ultrasonic for 20 - 40 min, then wash, filter and separate, continue to collect the particles after peeling off the polymer, dry it, and weigh the collected particles and record it as M4. When the mass change between M4 and M3 is < 0.05%, it indicates that the polymer is peeled off completely. Then adopt mass spectrometry: By ionizing polymer molecules and measuring their mass, the molecular weight of polymer molecules can be determined or whether the polymer molecules contain covalent organic framework materials can be determined. It can also be analyzed and determined by nuclear magnetic resonance method or infrared spectroscopy method.

[0089] In some alternative embodiments, based on the total mass of the coating, the coating comprises 0.01% - 1% of the covalent organic framework material, optionally 0.05% - 0.6%.

[0090] The coating comprises any value or the range composed thereof of 0.01%, 0.03%, 0.05%, 0.07%, 0.09%, 0.11%, 0.13%, 0.15%, 0.17%, 0.19%, 0.21%, 0.23%, 0.25%, 0.27%, 0.29%, 0.31%, 0.33%, 0.35%, 0.37%, 0.39%, 0.41%, 0.43%, 0.45%, 0.47%, 0.49%, 0.51%, 0.53%, 0.55%, 0.57%, 0.59%, 0.61%, 0.63%, 0.65%, 0.67%, 0.69%, 0.71%, 0.73%, 0.75%, 0.77%, 0.79%, 0.81%, 0.83%, 0.85%, 0.87%, 0.89%, 0.91%, 0.93%, 0.95%, 0.97%, 0.99%, 1% of the covalent organic framework material.

[0091] The mass content of the covalent organic framework material in the coating can be detected by sampling the coating and separating the polymer. As an example, Step 1: Take a certain amount of the coating and weigh its mass as M1. Then disperse the coating into an acetone solvent with a coating-to-acetone mass ratio of 1:10. Ultrasonic the mixed solution containing the coating for 20 - 40 min at an ultrasonic frequency of 20 - 40 HZ, which can be 25 HZ. Then repeat the cleaning and filtration 3 times (to remove the binder polyacrylate CCS) for the coating. After drying, obtain the coating with the binder polyacrylate CCS peeled off, denoted as M2. Step 2: Take the coating with the binder polyacrylate CCS peeled off in Step 1, and then put the coating into a mixed solution of water and ethanol with a volume ratio of water:ethanol of 1:1 and a coating-to-mixed solution mass ratio of 1:10. Ultrasonic the mixed solution containing the coating for 20 - 40 min at an ultrasonic frequency of 20 - 40 HZ, which can be 25 HZ. Then clean and filter, collect the coating after peeling off the polymer, and after drying, weigh the collected particles after peeling off the polymer as M3. Then continue to put the collected particles after peeling off the polymer into the mixed solution of water and ethanol, continue to ultrasonic for 20 - 40 min, then clean and filter for separation, continue to collect the particles after peeling off the polymer, and after drying, weigh the collected particles as M4. When the mass change between M4 and M3 is < 0.05%, it indicates that the polymer is peeled off cleanly. Then, using mass spectrometry: By ionizing the polymer molecules and measuring their mass, the content m of the covalent organic framework material in the separated polymer can be determined as m = M4 - M2. The calculation method for the mass content of the covalent organic framework material is (M4 - M2) / M1×100%.

[0092] In some alternative embodiments, the chelating group includes one or more of cyano and amino groups.

[0093] According to the embodiments of the present application, cyano can be generally understood as a carbon-nitrogen triple bond. In some embodiments, a carbon-nitrogen double bond also has the effect of the chelating group of the present application, and the carbon-nitrogen double bond (C=N) can be included in the chelating group, belonging to the general cyano. Amino can be generally understood as -NH 2 , any one of -NH-.

[0094] According to the embodiments of the present application, chelating groups of the above types can form complexes with transition metal ions, reduce the concentration of transition metal ions in the electrolyte, thereby reducing the adverse effects of transition metal ions on the stability of electrolyte components; the chelating group can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating group hinders the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reduces the probability of internal short circuit in the separator membrane, and improves the reliability of the battery.

[0095] In some alternative embodiments, the covalent organic framework material comprises a first covalent organic framework material formed by the reaction of a first monomer having symmetry and a second monomer having symmetry.

[0096] According to the embodiments of the present application, the covalent organic framework material used is formed by the reaction of a first monomer having symmetry and a second monomer having symmetry, which is beneficial to the uniformity of pores and the formation of a stable spatial conformation. The insertion rate of the electrolyte solvent can be controlled by the type and pore size of the covalent organic framework material, which is beneficial to the transport rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery.

[0097] In some alternative embodiments, the weight-average molecular weight of the covalent organic framework material is 5×10 2 ~80×10 4 , and may be optionally 6×10 2 ~75×10 4 .

[0098] The weight-average molecular weight of the covalent organic framework material may include but is not limited to 5×10 2 , 6×10 2 , 7×10 2 , 8×10 2 , 9×10 2 , 10×10 3 , 5×10×10 3 , 6×10×10 3 , 10×10 4 , 20×10 4 , 30×10 4 , 40×10 4 , 50×10 4 , 51×10 4 , 53×10 4 , 55×10 4 , 57×10 4 , 59×10 4 , 60×10 4 , 61×10 4 , 63×10 4 , 65×10 4 ,

[0099] 67×10 4 , 69×10 4 , 70×10 4 , 71×10 4 , 73×10 4 , 75×10 4 , 77×10 4 , 79×10 4 , 80×104 Any value within or the range composed thereof.

[0100] According to the embodiments of the present application, when the weight-average molecular weight of the covalent organic framework material is within the above range, it can have more structural units, can provide more molecular crosslinking points, thereby increasing the bonding strength with other components in the separator coating; it can control the insertion rate of the electrolyte solvent, which is beneficial to the transport rate of ions (such as lithium ions) in the battery, and thus is beneficial to the fast charge and discharge performance of the battery.

[0101] The weight-average molecular weight of the covalent organic framework material has the meaning well-known in the art and can be tested by the instruments and methods known in the art. As an example, the weight-average molecular weight of the polymer in the present application can be determined with reference to the gel permeation chromatography method of Standard GB / T21863-2008. Specifically, in the present application, an ultra-high performance polymer chromatograph: ACQUITY APC (detector: ACQUITY refractive index detector) can be used and the following test steps are carried out:

[0102] (1) Power on and warm up: Install the chromatographic column and pipeline, turn on the console, test power supply, etc. in sequence, and open the test software Empower; (2) Parameter setting, injection volume: 0 μL to 50 μL (determined according to the sample concentration); pump flow rate: 0.2 mL / min; mobile phase: NMP solution of 30 mol / L LiBr; sealing cleaning solution: isopropanol; pre-column: PL gel 10um MiniMIX-B Guard (size: 50 mm×4.6 mm×2); analytical column: PL gel 10um MiniMIX-B (size: 250 mm×4.6 mm); standard product: polystyrene set; running time: 30 min; detector: ACQUITY refractive index (RI) detector; column oven temperature: 90 °C; detector temperature: 55 °C; (3) Sample test: a. Preparation of standard sample and test sample: Weigh 0.002 g to 0.004 g of standard sample / test sample respectively and add 2 mL of mobile phase liquid to prepare a mixed standard of 0.1% to 0.5%, and place it in the refrigerator for >8 h; b. Standard solution / sample test: Edit the group of samples to be tested, select the established sample group method, click the run queue after the baseline is stable, and start testing the samples; (4) Data processing: According to the relationship between the retention time and the molecular weight, use the chemical workstation to establish a calibration curve, integrate and quantify the sample spectrum, and the chemical workstation automatically generates the result of the weight-average molecular weight.

[0103] In some alternative embodiments, the glass transition temperature of the covalent organic framework material is -50 °C to -10 °C, and can be optionally -35 °C to -25 °C.

[0104] According to the embodiments of the present application, the glass transition temperature of the covalent organic framework material within the above range is beneficial to the ionic conductivity of the separator membrane and the thermal stability of the separator membrane.

[0105] The glass transition temperature Tg of the covalent organic framework material has the meaning well-known in the art and can be measured by the instruments and methods well-known in the art. For example, it can be measured by differential scanning calorimetry (DSC) according to the standard ISO 11357-2-2013.

[0106] In some alternative embodiments, the covalent organic framework material includes a first covalent organic framework material obtained by the reaction of a first monomer and a second monomer. The first monomer includes at least one of formulas (1) to (5); the second monomer includes at least one of formulas (6) to (7); the first covalent organic framework material is obtained by the reaction of the amino group contained in the first monomer with any one of the aldehyde group or ketone group contained in the second monomer;

[0107]

[0108]

[0109] Among them, in formula (4), M includes one or several of copper element and nickel element;

[0110] In formula (5), R8, R9, R10, R11, R12, and R13 each independently include any one of a substituted or unsubstituted C1-C8 alkyl group, H, a substituted or unsubstituted amide group, a C1-C8 alkoxy group, a substituted or unsubstituted phenoxy group, and an alkylsulfonyl group. The substituents in the substituted C1-C8 alkyl group each independently include any one of a halogen atom and a cyano group; the substituents of the substituted amide group and the substituted phenoxy group each independently include an amino group; at least two of R8, R9, R10, R11, R12, and R13 have an amino group and formula (5) is a symmetric monomer with difunctionality, trifunctionality, or tetrafunctionality;

[0111] In formula (6), R14, R15, R16, R17, R18, and R19 each independently include a C1-C8 alkyl group, an amino group, H, a hydroxyl group, an alkoxy group, a phenoxy group, an aldehyde group, or a ketone group. At least two of R14, R15, R16, R17, R18, and R19 have an aldehyde group or a ketone group, and formula (6) is a symmetric monomer with difunctionality, trifunctionality, or tetrafunctionality; Optionally, in formula (6), R14 and R15 are connected to form a furan-dione and R17 and R18 are connected to form a furan-dione.

[0112] According to the embodiments of the present application, the first monomer reacts with the second monomer to form a covalent organic framework material with regular pores, which can control the insertion rate of the electrolyte solvent, facilitate the transport rate of ions (such as lithium ions) in the battery, and thus facilitate the fast charge and discharge performance of the battery.

[0113] According to the embodiments of the present application, the covalent organic framework material composed of the above monomers is a highly ordered, three-dimensional organic material with relatively uniform pore sizes and good glass transition temperature. It is present in the coating of the separator. The insertion rate of the electrolyte solvent can be controlled by the type and pore size of the covalent organic framework material, affecting the transport rate of ions (such as lithium ions) in the battery, and thus affecting the charge and discharge performance of the battery. The chelating group can form complexes with transition metal ions, such as transition metal ions like nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, thereby reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating group can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating group hinders the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator, and improving the reliability of the battery.

[0114] In some alternative embodiments, the covalent organic framework material includes at least one of a first covalent organic framework material obtained by reacting a first monomer with trifunctionality and a second monomer with difunctionality or tetrafunctionality, and a first covalent organic framework material obtained by reacting a first monomer with difunctionality or tetrafunctionality and a second monomer with trifunctionality.

[0115] According to the embodiments of the present application, the reaction form of the functional group combination of the first monomer and the second monomer is conducive to forming a covalent organic framework material with regular pores, which can control the insertion rate of the electrolyte solvent, facilitate the transport rate of ions (such as lithium ions) in the battery, and thus facilitate the fast charge and discharge performance of the battery.

[0116] In some alternative embodiments, the first monomer includes at least one of formula (1), formula (2), formula (3), formula (5-I), formula (5-II), formula (5-III), formula (5-IV), formula (5-V), and formula (VI):

[0117]

[0118]

[0119]

[0120] According to the embodiments of the present application, the reaction of the first monomer of the above type with the second monomer is beneficial to the formation of a covalent organic framework material with regular pores, which can control the insertion rate of the electrolyte solvent and is beneficial to the transport rate of ions (such as lithium ions) in the battery, thereby being beneficial to the fast charge and discharge performance of the battery.

[0121] In some alternative embodiments, the second monomer includes at least one of formula (7), formula (6-I), formula (6-II), formula (6-III), and formula (6-IV):

[0122]

[0123] According to the embodiments of the present application, the reaction of the first monomer with the second monomer of the above type is beneficial to the formation of a covalent organic framework material with regular pores, which can control the insertion rate of the electrolyte solvent and is beneficial to the transport rate of ions (such as lithium ions) in the battery, thereby being beneficial to the fast charge and discharge performance of the battery.

[0124] In some alternative embodiments, the covalent organic framework material includes a second covalent organic framework material obtained by the reaction of a third monomer represented by formula (8) and a fourth monomer represented by formula (9):

[0125]

[0126] According to the embodiments of the present application, the reaction of the third monomer and the fourth monomer forms a second covalent organic framework material with regular pores, which can control the insertion rate of the electrolyte solvent and is beneficial to the transport rate of ions (such as lithium ions) in the battery, thereby being beneficial to the fast charge and discharge performance of the battery. According to the embodiments of the present application, the covalent organic framework material composed of the above monomers is a highly ordered, three-dimensional organic material with relatively uniform pore sizes, and it has a good glass transition temperature. It exists in the coating of the separator membrane. The insertion rate of the electrolyte solvent can be controlled by the type and pore size of the covalent organic framework material, affecting the transport rate of ions (such as lithium ions) in the battery, thereby affecting the charge and discharge performance of the battery. The chelating group can form complexes with transition metal ions, such as transition metal ions like nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, thereby reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating group can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating group hinders the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator membrane, and improving the reliability of the battery.

[0127] In some alternative embodiments, the coating comprises a polymer obtained by reacting a fifth monomer represented by any one of formulas (10) to (12) and a sixth monomer represented by formula (6), and the polymer is formed by reacting the amino group contained in the fifth monomer with any one of the aldehyde group or ketone group contained in the sixth monomer;

[0128]

[0129] wherein, R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 each independently comprises any one of a substituted or unsubstituted C1-C8 alkyl group, an amino group, a C1-C8 alkoxy group, a substituted or unsubstituted amide group, a substituted or unsubstituted phenoxy group, and an alkylsulfonyl group; the substituents in the substituted C1-C8 alkyl group each independently comprise any one of a halogen atom and a cyano group; the substituents of the substituted amide group and the substituted phenoxy group comprise an amino group;

[0130] R20, R21, R22, R23, R24, R25 each independently comprise any one of a C1-C8 alkyl group, an amino group, H, a hydroxyl group, an alkoxy group, a phenoxy group, an aldehyde group, and a ketone group, and at least two of R20, R21, R22, R23, R24, R25 have an aldehyde group or a ketone group; optionally, R20 and R21 are connected to form a furan-dione or R23 and R24 are connected to form a furan-dione.

[0131] According to the present embodiment, the coating comprises a polymer formed by the above types of monomers, and the content of this polymer is relatively small. This polymer can be obtained by modifying a covalent organic framework material, in which groups such as alkoxy groups, phenoxy groups, and amino groups are introduced, which can endow the coating with a certain ability to chelate metal ions and can also promote the passage of active ions such as lithium ions through the separator membrane.

[0132] In some alternative embodiments, the covalent organic framework material comprises a first group for promoting the transport of active ions; optionally, the first group comprises one or more of a C1-C8 alkoxy group and a phenoxy group; it can be a phenoxy group, -OCH 3 .

[0133] According to the embodiments of the present application, the first groups such as alkoxy groups and phenoxy groups have a certain affinity for active ions and can form stable coordination compounds with active ions such as lithium ions, thereby forming active ion transport channels, such as lithium ion channels. These channels can help active ions transport faster in the electrolyte and improve the fast charge and discharge performance of the battery.

[0134] In some alternative embodiments, in the covalent organic framework material per unit mass, the molar ratio of the chelating group to the first group is 1:(10 to 100).

[0135] Optionally, the molar ratio of the chelating group to the first group can be any value among 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95, 1:100 or the range composed of them.

[0136] According to the embodiments of the present application, the covalent organic framework material has a chelating group and a first group; by controlling the molar ratio of the chelating group to the first group within the above range, the chelating group can chelate transition metal ions, and the first group can form an active ion transport channel. The chelating group is beneficial to adsorbing transition metal ions and promoting the transport of active ions, which affects the selectivity of the separator; further, when the molar ratio of the chelating group to the first group is within the above range, on the basis of taking into account the complexation of transition metal ions, it effectively promotes the transport of active ions, facilitating the improvement of the battery life and the rapid charge and discharge performance of the battery.

[0137] The chelating group and the first group can be detected by detection methods well-known in the art, such as mass spectrometry or infrared spectroscopy.

[0138] In some alternative embodiments, the covalent organic framework material includes micropores; optionally, the average pore diameter of the micropores is 0.5 nm to 5 nm, and can be 0.8 nm to 1.5 nm.

[0139] The average pore diameter of the micropores can be 0.5 nm, 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 3.5 nm, 4.0 nm, 4.5 nm, 5.0 nm.

[0140] According to the embodiments of the present application, by selecting covalent organic framework materials formed by different monomers, micropores with different pore diameters are obtained. By controlling the average pore diameter of the micropores within the above range, it is beneficial to control the speed of active ions passing through the separator, beneficial to complexing transition metal ions, and improving the charge and discharge rate of the battery and the reliability of the battery.

[0141] As an example, an automatic specific surface area and micropore size analyzer of PMI Instruments in the United States can be used for measurement by the gas adsorption method. Specifically, an appropriate amount of the separator sample (about 100 mg) can be taken. The sample is placed in a sample tube, and its mass is recorded as m1 mg. The sample tube is installed on a degassing station, and the sample is heated and vacuum degassed to remove the gas adsorbed on the surface of the separator. Subsequently, after the sample is cooled to room temperature, helium gas is backfilled to atmospheric pressure. The mass of the sample tube is weighed and recorded as m2 mg, and (m2 - m1) is the weight of the sample after degassing. Referring to the test standard GB / T 19587-2017, the sample tube is placed in a liquid nitrogen environment. After the sample tube is evacuated, helium gas is introduced into the sample tube and then evacuated, and the adsorption amount, adsorption-desorption isotherm, and BET surface area A of the sample at each partial pressure point are measured. Based on the adsorption-desorption isotherm, the capillary radius rk corresponding to the capillary condensation occurring at the abscissa P / P0 is obtained through the Kelvin formula. Under this P / P0 condition, all pores smaller than the rk value are filled with the adsorbate of capillary condensation. Therefore, the adsorption volume Vr corresponding to this relative pressure P / P0 on the adsorption isotherm is the total volume of all pores with a radius less than or equal to this rk. A curve of Vr - rk is plotted, which is the integral distribution curve of pore volume versus pore radius. On the integral distribution curve, the volume ΔVr of the increase in adsorption amount when the pore radius increases by Δr is obtained by the graphical method, and ΔVr / Δr is calculated. A plot of ΔVr / Δr versus rk is the differential distribution curve of pore radius. The pore size value corresponding to the maximum point on the abscissa of the differential distribution curve is the maximum pore size of the separator. Using the multi-molecular layer adsorption theory (BET theory), the average pore size of the separator can be calculated through the formula d = 4V / A, where d represents the average pore size, V represents the total pore volume (the volume of the adsorbed gas converted into liquid), and A represents the BET surface area of the sample. [WZ1] National standard GB / T 19587-2017 Determination of specific surface area of solid materials by gas adsorption BET method.

[0142] In some alternative embodiments, the covalent organic framework material is granular, and the average particle size Dv50 of the covalent organic framework material is 0.01 μm to 1 μm; optionally, 0.05 μm to 0.1 μm.

[0143] According to the embodiments of the present application, when preparing the separator, covalent organic framework material particles with appropriate particle sizes can be added to the coating, and controlling their average particle sizes within the above range is beneficial to the uniformity of the distribution of the covalent organic framework material, so as to control the speed of active ions passing through the separator, facilitate the complexation of transition metal ions, improve the charge and discharge rate of the battery, and improve the reliability of the battery.

[0144] The average particle size Dv50 of the particles has the meaning well known in the art, which represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by the instruments and methods well known in the art. For example, it can be conveniently measured by referring to GB / T19077-2016 Laser Diffraction Method for Particle Size Distribution and using a laser particle size analyzer, such as the Mastersizer 2000E type laser particle size analyzer of Malvern Instruments Limited, UK.

[0145] In some alternative embodiments, the total pore volume of the covalent organic framework material is 0.8 cm 3 / g to 1.5 cm 3 / g.

[0146] According to the embodiments of the present application, the covalent organic framework materials formed by selecting different monomers have different total pore volumes. Controlling the total pore volume within the above range is beneficial to controlling the speed of active ions passing through the separator membrane, beneficial to complexing transition metal ions, improving the charge and discharge rate of the battery and improving the reliability of the battery.

[0147] According to the embodiments of the present application, the total pore volume of the covalent organic framework material can be measured by the gas adsorption method using a fully automatic specific surface area and micropore size analyzer of PMI Instruments, USA, and obtained through the above calculation.

[0148] In some alternative embodiments, the ratio of the thickness of the coating to the thickness of the separator membrane is (0.01 - 0.35):1, and can be optionally (0.05 - 0.25):1.

[0149] Optionally, the ratio of the thickness of the coating to the thickness of the separator membrane can be any value in 0.01:1, 0.03:1, 0.05:1, 0.07:1, 0.09:1, 0.11:1, 0.13:1, 0.15:1, 0.17:1, 0.19:1, 0.21:1, 0.23:1, 0.25:1, 0.27:1, 0.29:1, 0.31:1, 0.33:1, 0.35:1 or the range composed of them.

[0150] According to the embodiments of the present application, controlling the ratio of the thickness of the coating to the thickness of the separator membrane within a suitable range can make the separator membrane have a suitable content of covalent organic framework material and a suitable amount of chelating groups. The covalent organic framework material has pores with a suitable distribution rate and the separator membrane has a suitable thickness, which is beneficial to the rapid transmission of active ions in the battery containing the separator membrane. And the chelating groups can form complexes with a certain amount of transition metal ions, reducing the adverse effects of transition metal ions on the stability of the electrolyte components and the damage to the SEI film, hindering the precipitation of transition metal ions to form dendrites, improving the stability of the SEI film and thus improving the cycle performance of the battery; avoiding the formation of dendrites is beneficial to improving the reliability of the battery.

[0151] In addition, the coating in the separator with the above thickness ratio provides sufficient bonding effect and "thermal shutdown" protection effect.

[0152] The thickness of the coating and the separator can be sampled and detected under an electron microscope, and the detection can be carried out by using equipment and methods well-known in the art. For example, the cross-section of the separator along the thickness direction can be scanned by a scanning electron microscope (SEM) to measure the thickness of the coating, the thickness of the base film, and the thickness of the separator, etc. The average thickness of the coating and the average thickness of the separator are respectively determined as their thicknesses, and their ratio is obtained by calculation.

[0153] In some alternative embodiments, the thickness of the separator is 3 μm to 20 μm, and can be selected as 5 μm to 15 μm.

[0154] The thickness of the separator can be any value among 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or the range composed of them.

[0155] According to the embodiments of the present application, controlling the thickness of the separator within a suitable range can enable the separator to have a suitable content of covalent organic framework materials and chelating groups, which is beneficial to the rapid transport of active ions in the battery containing the separator, form complexes with a certain amount of transition metal ions, reduce the adverse effects of transition metal ions on the stability of electrolyte components and the damage to the SEI film, prevent the precipitation of transition metal ions to form dendrites, improve the stability of the SEI film, thereby improving the cycle performance of the battery; and also improve the reliability of the battery.

[0156] In some alternative embodiments, the thickness of the coating is 0.03 μm to 7 μm, and can be selected as 0.08 μm to 2.5 μm.

[0157] The thickness of the coating can be any value among 0.03 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm or the range composed of them.

[0158] According to the embodiments of the present application, controlling the thickness of the coating within a suitable range can enable the coating to have a suitable content of covalent organic framework materials and chelating groups, which is beneficial to the rapid transmission of active ions in the battery containing the separator membrane, form complexes with a certain amount of transition metal ions, reduce the adverse effects of transition metal ions on the stability of electrolyte components and the damage to the SEI film, prevent the precipitation of transition metal ions to form dendrites, improve the stability of the SEI film, and thus improve the cycling performance of the battery; it also improves the reliability of the battery.

[0159] The thicknesses of the base film, separator membrane, and coating all have the meanings well-known in the art and can be measured using instruments and methods known in the art. An exemplary method for testing the thickness of the separator membrane is as follows: Take a sample with a length of 500 mm and a width of 100 mm; evenly take 5 points on the sample (for example, take one point every 100 mm along the length direction of the sample), and use a ten-thousandth thickness gauge to measure the thickness of the separator membrane at these 5 different positions, and take the average value as the thickness of the separator membrane. The length direction of the sample is parallel to the TD direction of the separator membrane. The thickness of the base film can be measured with reference to the above method. If a coating is provided on one side of the separator membrane, subtract the thickness of the base film from the thickness of the separator membrane, and the result is the thickness of the coating. If the two opposite sides of the separator membrane are respectively provided with the coating to be measured and the coating on the opposite side of the coating to be measured, subtract the sum of the thicknesses of the base film and the coating on the opposite side from the thickness of the separator membrane, and the result is the thickness of the coating to be measured.

[0160] Figure 1 A separator membrane is shown as an example. The separator membrane includes a base film 10 and a coating 20 laminated on either surface of the base film 10. As Figure 1 shown, the base film 10 is a microporous porous thin film. The coating 20 is a microporous porous film layer containing heat-resistant particles. Figure 1 The separator membrane described is only exemplary. For example, in other examples, the separator membrane may include a base film 10 and coatings 20 laminated on two surfaces of the base film 10 opposite to each other in the thickness direction.

[0161] In some embodiments, the coating weight is 1.82 g / m 2 ~2.1 g / m 2 .

[0162] According to the embodiments of the present application, when the coating weight is within the above range, it is beneficial for the battery to effectively inhibit the further expansion of the short-circuit point area caused by the heat melting of the separator membrane when the separator membrane is punctured and short-circuited under abnormal conditions, and further reduces the risk of thermal runaway or short-circuit failure of the battery.

[0163] The grammage of the coating is a meaning well-known in the art and can be measured by instruments and methods well-known in the art. For example, take a single-sided coated separator film (if it is a double-sided coated electrode sheet, the coating on one side can be wiped off first), punch it into small round pieces with an area of S1, weigh it, and record it as M1. Then wipe off the coating of the above-mentioned weighed separator film, weigh the weight of the base film, and record it as M0. The grammage of one side of the coating = (the weight M1 of the separator film - the weight M0 of the current collector) / S1.

[0164] The present application does not impose obvious restrictions on the types of inorganic particles in the coating, and any inorganic particles that can achieve the purpose of the present application can be used. The above-mentioned types of inorganic particles can achieve the purpose of the present application.

[0165] The coating includes inorganic particles. On the one hand, it can improve the strength of the separator film, and thus can further enhance the ability of the separator film to resist being pierced by foreign particles. Especially when the separator film is pierced and short-circuited under abnormal conditions of the battery, it can effectively inhibit the further expansion of the short-circuit point area caused by the melting of the separator film by the heat generated by the short circuit, and further reduce the risk of thermal runaway or short-circuit failure of the battery. In some alternative embodiments, the coating includes inorganic particles. Optionally, the inorganic particles include one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride.

[0166] In some alternative embodiments, based on the total mass of the coating, the coating includes inorganic particles with a mass content of 98.5% to 99.49%. The coating containing the above mass content of inorganic particles is beneficial for the separator film to play a "thermal shutdown" role in the battery and reduce the probability of battery short circuit.

[0167] In some alternative embodiments, the coating includes a binder. Optionally, the binder includes one or more of polyvinylidene fluoride and polyacrylate.

[0168] The present application does not impose obvious restrictions on the types of binders in the coating, and any binder that can achieve the purpose of the present application can be used. The above-mentioned types of binders can achieve the purpose of the present application. The binder can bond the inorganic particles to the base film and obtain a high peel strength between the coating and the base film. As an example of the binder used for promoting the layer, it may also include one or several of polybutadiene-styrene copolymer, polyacrylonitrile-acrylic acid copolymer, polytetrafluoroethylene, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene copolymer.

[0169] In some alternative embodiments, based on the total mass of the coating, the coating comprises a binder with a mass content of 0.05% to 0.5%. The coating containing inorganic particles with the above mass content is beneficial to improving the stability of the separator coating and reducing the risk of being punctured.

[0170] This application does not impose obvious restrictions on the type of the base film, and any base film that can achieve the purpose of this application can be used. The base film of the above type can achieve the purpose of this application. In some alternative embodiments, the base film comprises one or more of polyolefin, polyester, polyacetal, polyamide, polycarbonate, polyacrylate, polyimide, polyether ether ketone, polybenzimidazole, polyethersulfone, polyphenylene ether, and polyphenylene sulfide. Optionally, it comprises one or more of polyethylene homopolymer or copolymer, polypropylene homopolymer or copolymer, cycloolefin copolymer, polyethylene naphthalate polyethylene terephthalate, poly(p-phenylene terephthalamide), and polybutylene terephthalate. For example, the base film obtained with a polyethylene-based polymer as the main polymer component can have good strength and toughness, so that the separator can have a high ability to resist puncture by foreign particles, thereby improving the reliability of the battery.

[0171] In some embodiments, the porosity of the base film is 20% to 80%, optionally 20% to 50%, and further optionally 35% to 45%. When the porosity of the base film is within an appropriate range, it helps the separator to have an appropriate electrolyte retention amount, thereby enabling the electrochemical device to take into account both high cycle performance and energy density.

[0172] In some embodiments, the air permeability value of the base film is 30 s / 100 cc to 300 s / 100 cc, optionally 50 s / 100 cc to 250 s / 100 cc, and further optionally 80 s / 100 cc to 200 s / 100 cc. When the air permeability value of the base film is within an appropriate range, it is convenient for ions to pass through the separator, thus helping the battery to have high capacity performance and cycle performance.

[0173] In some embodiments, the separator satisfies: the thermal shrinkage rate in the MD direction (l M0 -l M ) / l M0 ×100% ≤ 5%, optionally, (l M0 -l M ) / l M0 ×100% ≤ 5%, ≤ 4%, ≤ 3%, or ≤ 2.5%. l M represents the MD direction length l M0 of a specimen with an MD direction length of 100 mm and a TD direction length l T0 of 100 mm after being held at 130 °C for 1 h, in mm.

[0174] In some embodiments, the isolation film satisfies: the heat shrinkage rate in the TD direction (l T0 -l T ) / l T0 ×100%≤5%, optionally, (l T0 -l T ) / l T0 ×100%≤5%,≤4%,≤3%,or≤2.5%. T The length l of the separator in the MD direction is M0 100mm and TD length l T0 It is the TD length in mm of a 100 mm sample after being kept at 130°C for 1 hour.

[0175] The isolation film is cut into MD direction length l M0 100mm and TD length l T0 The sample is 100mm in diameter, the MD direction of the sample is parallel to the MD direction of the isolation film, and the TD direction of the sample is parallel to the TD direction of the isolation film; the sample is placed in a 130℃ oven and heated for 1h; the length of the sample in the MD direction after heating is l M Or TD direction length l T , and calculate the thermal shrinkage in MD or TD direction. The test can refer to the national standard GB / T 36363-2018.

[0176] The separator has a smaller shrinkage rate under heat conditions and thus has higher heat resistance, which helps to further improve the reliability of the battery.

[0177] In some embodiments, the isolation membrane is formed with a cross-sectional area of ​​0.5 mm 2 After being pierced by a needle and kept at 150°C for 10 minutes, the hole expansion rate of the pinhole is ≤8%, optionally ≤7%, ≤6%, ≤5%, ≤4.5%, ≤4%, ≤3%, or ≤2.5%. The hole expansion rate is (S 1 -S 0 ) / S 0 ×100%,S 0 represents the initial area of ​​the pinhole, S 1 It represents the pinhole area after being kept at 150°C for 10 minutes. The cross-sectional area of ​​the pin is, for example, circular. 0 and S 1 The test can be conducted using instruments and methods known in the art. For example, a microscope. As an example, the GP-300C-13.3-inch display-0.5x objective lens of Kunshan Gaopin Precision Instrument Co., Ltd. can be used to magnify the hole through the instrument and mark the hole area with the area marking module provided by the system. After the isolation membrane is pierced by a needle, the pinhole expansion rate under heating conditions is small, and its heat resistance is high. In particular, a smaller rupture area can reduce the risk of thermal runaway of the battery.

[0178] The separator membrane can be selected from any one or more of the separator membranes of the present application. In some embodiments, the separator membrane described in the present application and other separator membranes known in the art can be selected and used in combination in the battery. The battery includes the separator membrane of the present application, and thus can have the same or similar beneficial effects.

[0179] [Preparation method of separator membrane]

[0180] The embodiment of the present application provides a preparation method of a separator membrane, and the method includes:

[0181] Providing a covalent organic framework material, the covalent organic framework material includes a chelating group for chelating transition metal ions;

[0182] Forming a coating on at least one surface of the base film with a slurry containing the covalent organic framework material to obtain the separator membrane of the first aspect.

[0183] According to the embodiment of the present application, adding a covalent organic framework material to the coating of the separator membrane can control the insertion rate of the electrolyte solvent through the type and pore size of the covalent organic framework material, which is beneficial to the transport rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery. According to the embodiment of the present application, a certain amount of chelating groups in the covalent organic framework material can form complexes with transition metal ions, such as transition metal ions such as nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, thereby reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating groups can reduce the damage of transition metal ions to the SEI film, improve the stability of the SEI film, and thus improve the cycle performance of the battery; the chelating groups hinder the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator membrane, and improving the reliability of the battery.

[0184] The coating can be formed by coating a slurry containing the covalent organic framework material on at least one surface of the base film and drying. The covalent organic framework material can be selected from those described herein.

[0185] The solvent of the slurry can be one or more of aqueous solvents (such as deionized water, etc.) and organic solvents (such as N-methylpyrrolidone NMP, dimethylacetamide DMAC, acetone, etc.). The slurry can also contain a binder. The binder can be selected from those described herein. The coating method of the slurry can be any one or more of gravure coating (such as microgravure coating), dip coating, knife coating, wire bar coating, spraying, electrospinning.

[0186] Battery cell

[0187] In the second aspect, the embodiment of the present application provides a battery cell, including the separator membrane of the first aspect.

[0188] The battery cell includes any one or several separator films of the present application. Therefore, the battery cell can have high safety performance.

[0189] The battery cell of the present application can be any battery cell that can occur using a separator film that can be conceived by those skilled in the art. For example, the battery cell can be a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor, etc. In particular, the battery cell of the present application is a secondary battery. Examples of the battery cell include but are not limited to lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, etc.

[0190] In some alternative embodiments, the battery cell includes a positive electrode plate and a negative electrode plate, and a separator film interposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode active material film layer, the negative electrode plate includes a negative electrode active material film layer, and at least one of the positive electrode active material film layer and the negative electrode active material film layer includes a covalent organic framework material.

[0191] According to the embodiments of the present application, the covalent organic framework material exists in at least one of the positive electrode active material film layer and the negative electrode active material film layer. By the type and pore size of the covalent organic framework material, the insertion rate of the electrolyte solvent can be controlled, which is beneficial to the transmission rate of ions (such as lithium ions) in the battery, and thus beneficial to the fast charge and discharge performance of the battery. According to the embodiments of the present application, a certain amount of chelating groups in the covalent organic framework material can form complexes with transition metal ions, such as transition metal ions such as nickel ions, cobalt ions, and manganese ions, reducing the concentration of transition metal ions in the electrolyte, and thus reducing the adverse effects of transition metal ions on the stability of the electrolyte components; the chelating groups hinder the precipitation of transition metal ions to form dendrites by reducing the concentration of transition metal ions in the electrolyte, reducing the probability of internal short circuit in the separator film, and improving the reliability of the battery.

[0192] [Positive electrode plate]

[0193] In some alternative embodiments, the battery includes a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0194] The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be the positive electrode active material known in the art for battery cells.

[0195] In some alternative embodiments, the positive electrode active material includes a positive electrode active material doped with a doping element.

[0196] In some embodiments, the positive electrode active material contains a doping element including at least one of aluminum, zirconium, boron, magnesium, zinc, calcium, and titanium, which can enable the positive electrode active material to have a high energy density while maintaining better structural stability during charge and discharge, thereby improving the cycle performance and kinetic performance of the battery cell. The above chelating group can form a complex with the above metal ions, reduce the adverse effect of the metal ions on the stability of the electrolyte components, and improve the reliability of the battery.

[0197] In some alternative embodiments, the positive electrode active material includes a lithium transition metal oxide or a modified compound thereof having a structural formula of Li a Ni b Co c Mn f M d O e where 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, and M includes one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B.

[0198] In some alternative embodiments, the positive electrode active material can be a layered transition metal oxide. In some alternative embodiments, the positive electrode active material can be a doped ternary positive electrode nickel cobalt manganese material. When the positive electrode active material is of the above types, using the positive electrode active material doped with a doping element can effectively improve the energy band structure of the positive electrode active material, thereby improving the cycle stability of the battery cell including it.

[0199] As an example, the positive electrode active material can include LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.80Co 0.15 Al 0.05 O 2 、 LiFePO 4 and LiMnPO 4 one or more of them.

[0200] The modified compounds of the above positive electrode active materials can be doping modification and / or surface coating modification of the positive electrode active materials.

[0201] In some alternative embodiments, the mass percentage content W3 of the doping element in the positive electrode active material is 0.005% to 0.5%, optionally 0.005% to 0.45%. Controlling the mass percentage content W4 of the doping element in the positive electrode active material within the above range can effectively reduce or avoid the phenomena of Li / Ni mixing and H2-H3 phase transition occurring in the positive electrode active material during the charge and discharge process of the battery cell, and improve the cycle life, storage life, and power performance of the battery cell. When the mass percentage content W4 of the doping element in the positive electrode active material is lower than 0.005%, the structure of the positive electrode active material cannot be improved, or the improvement effect is small; when the mass percentage content W4 of the doping element in the positive electrode active material is higher than 0.5%, the energy density of the battery cell may be reduced.

[0202] In some alternative embodiments, the ratio of b to (b + c + f) is 0.8 - 0.98:1; optionally 0.82 - 0.96:1. When the ratio of the molar amount of nickel element to the sum of the molar amounts of nickel element, cobalt element, and manganese element is within the above range, the positive electrode material can have good cycle performance, high specific capacity, high safety, and low cost, and can also improve the specific capacity of the positive electrode active material.

[0203] In some alternative embodiments, the ratio of c to (b + c + f) is 0.01 - 0.2:1; optionally 0.015 - 0.15:1. When the ratio of the molar amount of cobalt element to the sum of the molar amounts of nickel element, cobalt element, and manganese element is within the above range, the positive electrode material can have good cycle performance, high specific capacity, high safety, and low cost, and can also improve the cycle performance of the positive electrode active material.

[0204] In some alternative embodiments, the ratio of f to (b + c + f) is 0.1 - 0.2:1; optionally 0.15 - 0.2:1. Herein, (b + c + f) represents the sum of b, c, and f. When the ratio of the molar amount of manganese element to the sum of the molar amounts of nickel element, cobalt element, and manganese element is within the above range, the positive electrode material can have good cycle performance, high specific capacity, high safety, and low cost, and can also improve the cycle performance of the positive electrode active material.

[0205] In some alternative embodiments, the areal density of the positive electrode active material layer is 3.0 g / cm 3 or more. When the areal density of the positive electrode active material layer is within the above range, according to the conventional content of the positive electrode active material in the positive electrode active material layer is generally 92% to 98.5%, indicating that there is more positive electrode active material therein, which can improve the cycle performance of the battery cell.

[0206] The areal density of the positive electrode active material layer has the meaning well-known in the art and can be measured by the instruments and methods well-known in the art. For example, take a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the positive electrode active material layer on one side can be wiped off first), and punch it into small round pieces with an area of S 1 , weigh it, and record it as M 1 . Then wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode sheet, weigh the weight of the positive electrode current collector, and record it as M 0 . The areal density of the positive electrode active material layer = (the weight M of the positive electrode sheet 1 – the weight M of the positive electrode current collector 0 ) / S 1 .

[0207] For example, when the battery cell is a lithium-ion battery cell or a lithium metal battery cell, the positive electrode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides may include one or more 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. Examples of lithium-containing phosphates with an olivine structure may include one or more 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 manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds. The present application is not limited to these materials, and other conventionally well-known materials that can be used as positive electrode active materials can also be used.

[0208] In some alternative embodiments, the positive electrode active material layer may further optionally include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0209] In some alternative embodiments, the positive electrode active material layer may further optionally include a positive electrode binder. The present application does not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0210] In some alternative embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the 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. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0211] The positive electrode active material layer is generally formed by coating a positive electrode paste on a positive electrode current collector and then drying and cold pressing. The positive electrode paste is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0212] [Negative electrode tab]

[0213] In some alternative embodiments, the battery cell further includes a negative electrode tab, and the negative electrode tab includes a negative electrode active material layer; the negative electrode active material layer includes graphite. The negative electrode active material layer of the battery cell includes a battery, which can effectively store active lithium and is beneficial to the cycle performance of the battery cell.

[0214] The specific composition and structure of the negative electrode tab, etc., may be selected according to the type of the battery cell, and the embodiments of the present application do not limit this.

[0215] For example, when the battery cell is a lithium-ion battery cell, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0216] The negative electrode active material is a material capable of extracting and inserting active ions (such as lithium ions, etc.). The negative electrode active material can be a material well-known in the art. As an example, the negative electrode active material includes, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials can include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloy materials. The tin-based materials can include one or more of elemental tin, tin oxides, and tin alloy materials. The present application is not limited to these materials, and other conventionally well-known materials that can be used as negative electrode active materials can also be used.

[0217] In some alternative embodiments, the negative electrode active material layer further includes silicon element. As a negative electrode active material, silicon element has advantages such as high capacity (4200 mA·h / g) and low lithium deintercalation voltage. Adding silicon element to the negative electrode active material layer helps to improve the storage performance of the negative electrode sheet for active lithium and reduce the lithium deintercalation voltage of the negative electrode.

[0218] In some alternative embodiments, based on the total mass of the negative electrode active material layer, the negative electrode active material layer contains less than or equal to 8% of silicon element. When the mass content of silicon element in the negative electrode active material layer is within the above range, it is beneficial to control the volume expansion rate of the negative electrode active material layer and improve the performance of the battery cell on the basis of improving the capacity of the negative electrode sheet and reducing the lithium deintercalation voltage.

[0219] In some alternative embodiments, the tap density of the negative electrode active material layer is 1.3 - 1.7 g / cm 3 . When the tap density of the negative electrode active material layer is within the above range, it is beneficial to control the risk of current collector extension caused by the volume change of the active material during charge and discharge of the battery cell; and the risk of fracture of the positive electrode sheet caused by the extension of the negative electrode sheet, thereby improving the problems of wrinkles of the negative electrode sheet and battery deformation.

[0220] In addition, when the negative electrode active material layer contains a certain amount of silicon element, it is particularly important to control the tap density of the negative electrode active material layer, which is beneficial to improving or avoiding the problems of wrinkles of the negative electrode sheet and battery deformation.

[0221] The tap density of the negative electrode active material layer has the meaning well-known in the art and can be measured by instruments and methods well-known in the art. For example, take a single-sided coated and cold-pressed negative electrode sheet, measure the thickness of the negative electrode active material layer, and then refer to the test method for measuring the areal density of the positive electrode active material layer to obtain the areal density of the negative electrode active material layer. The tap density of the negative electrode active material layer = the areal density of the negative electrode sheet / the thickness of the negative electrode sheet.

[0222] In some alternative embodiments, when the positive electrode active material is a doped ternary nickel-cobalt-manganese positive electrode material and the negative electrode active material includes graphite, the electromotive force difference of the battery cell ≥ 4.2V. The electromotive force difference of the battery cell ≥ 4.2V is beneficial to the improvement of the battery energy density.

[0223] In some alternative embodiments, the negative electrode active material layer may also optionally include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0224] In some alternative embodiments, the negative electrode active material layer may also optionally include a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. As an example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0225] In some alternative embodiments, the negative electrode active material layer may also optionally include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0226] In some alternative embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, 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. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0227] The negative electrode active material layer is usually formed by coating a negative electrode slurry on the negative electrode current collector and then 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 additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0228] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in some alternative embodiments, the negative electrode tab of the present application may further include a conductive bottom coating (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector; in some alternative embodiments, the negative electrode tab of the present application may further include a protective layer covering the surface of the negative electrode active material layer.

[0229] When the battery cell is a lithium metal battery cell, the negative electrode tab may not include a negative electrode active material capable of deintercalating and intercalating active ions. For example, in some alternative embodiments, the negative electrode tab may include a lithium sheet or a lithium alloy sheet; in other embodiments, the negative electrode tab includes a reticular or foamed three-dimensional skeleton layer, such as, for example, foamed copper (or copper alloy), foamed nickel (or nickel alloy), copper (or copper alloy) mesh, nickel (or nickel alloy) mesh, etc.

[0230] [Method for preparing a battery cell]

[0231] The method for preparing a battery cell may include the step of assembling a negative electrode tab, a positive electrode tab, and an electrolyte to form a battery cell. In some alternative embodiments, the positive electrode tab, the separator, and the negative electrode tab may be wound or laminated in sequence, with the separator positioned between the positive electrode tab and the negative electrode tab to serve as an isolation function, resulting in an electrode assembly (i.e., an electrode core); the electrode assembly is placed in an outer package, electrolyte is injected, and it is sealed to obtain a battery cell. In some alternative embodiments, through processes such as vacuum packaging, standing, formation, and shaping, a battery cell is obtained.

[0232] In some alternative embodiments, the preparation of the battery cell may further include the step of preparing the positive electrode tab. As an example, the positive electrode active material, the conductive agent, and the binder may be dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode tab is obtained.

[0233] In some alternative embodiments, the preparation of the battery cell may further include the step of preparing the negative electrode tab. As an example, the negative electrode active material, the binder, and optionally a thickening agent and a conductive agent are dispersed in a solvent, which may be deionized water, to form a uniform negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode tab is obtained.

[0234] The positive electrode tab, the negative electrode tab, and the separator can be made into an electrode assembly through a lamination process or a winding process, with the separator positioned between the positive electrode tab and the negative electrode tab to serve as an isolation function; the electrode assembly is placed in an outer package, electrolyte is injected, and it is sealed to obtain a battery. The separator in the electrode assembly includes at least one or several separators as described in the present application.

[0235] The outer packaging of the battery is used to encapsulate the electrode assembly and the electrolyte. In some embodiments, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as one or several of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0236] This application places no particular restrictions on the shape of the battery, which can be cylindrical, square, or any other arbitrary shape. As Figure 2 is a battery cell 5 with a square structure as an example.

[0237] In some embodiments, referring to Figure 3 , the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. 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 battery cell 5 can be one or several, which can be adjusted according to requirements.

[0238] The battery

[0239] In a third aspect, an embodiment of this application provides a battery, including the battery cell of the second aspect.

[0240] In some alternative embodiments, the battery cells can be assembled into a battery module. The number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0241] Figure 4 is a battery module 4 as an example. Referring to Figure 4 , in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Further, the multiple battery cells 5 can be fixed by fasteners.

[0242] Optionally, the battery module 4 can further include a housing with a receiving space, and multiple battery cells 5 are accommodated in the receiving space.

[0243] In some alternative embodiments, the above battery module can also be assembled into a battery, and the number of battery modules contained in the battery can be adjusted according to the application and capacity of the battery.

[0244] Figure 5 is a battery 1 as an example. Referring to Figure 5 and Figure 6, in the battery 1, a battery box and a plurality of battery modules 4 disposed in the battery box may be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0245] In some embodiments of the present application, battery cells according to the present application can be assembled into battery modules. The number of battery cells included in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0246] Optionally, the battery module may further include a housing having an accommodation space, and a plurality of battery cells are accommodated in the accommodation space.

[0247] In some alternative embodiments, the above battery modules can be further assembled into a battery pack. The number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0248] Electric device

[0249] In a fourth aspect, an embodiment of the present application provides an electrical device including the battery of the third aspect. The electrical device of the present application includes the battery cell of the first aspect of the present application, and thus has at least the advantages of the application of the battery cell.

[0250] The battery cell or the battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical 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, a satellite, an energy storage system, etc.

[0251] Figure 7 is a schematic diagram of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high energy density requirements of the electrical device, a battery pack or a battery module can be used.

[0252] Another example of the electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and a battery cell can be used as the power source.

[0253] Embodiment

[0254] The following examples describe more specifically the content disclosed in the present application. These examples are for illustrative purposes only, as various modifications and variations within the scope of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0255] Preparation Example 1-1

[0256] Preparation of the separator membrane:

[0257] Base film: A PE film containing polyethylene, sourced from Shanghai Enjie Co., Ltd., with a thickness of 9 μm.

[0258] Preparation of the coating: First, prepare a covalent organic framework material:

[0259] First, add the first monomer to a flask of the solvent N,N-dimethylformamide to dissolve it and prepare a 1 mol / L solution of the first monomer; then add the second monomer to a flask of the solvent N,N-dimethylformamide to dissolve it and prepare a 1 mol / L solution of the second monomer; add them to a microchannel reactor according to a reaction molar ratio of the first monomer: the second monomer of 3:2, with a reaction temperature of 65 °C and a reaction time of 2 h. The covalent organic framework material COF-1 is prepared, and the average pore diameter of the micropores of the covalent organic framework material is 2.3 nm; among them, the structures of the first monomer and the second monomer are shown as follows. After detection, the weight-average molecular weight of the covalent organic framework material is 11073. The prepared covalent organic framework material is composed of several structural blocks connected together, and the structure of one structural block is as follows. The virtual bonds in the structural block represent chemical connection points, which can generally connect to another structural block of the covalent organic framework material, and the structural blocks are connected to each other to form the covalent organic framework material. The relationship between the structural blocks in the following other preparation examples and the covalent organic framework material is the same as that in this preparation example.

[0260]

[0261] Then, add 98.95 parts by weight of alumina particles, 1 part by weight of a polyacrylate binder, and 0.05 part by mass of the covalent organic framework material of Example 1 to deionized water, mix evenly to form a slurry; then, using a microgravure coating method, apply the slurry on one side and uniformly coat it on any surface in the self-thickness direction of the base film; after drying in an oven, a coating is obtained. The thickness of the coating is 2 μm.

[0262] Preparation Examples 1-1a to 1-1c

[0263] The difference between this preparation example and Preparation Example 1-1 is that the content of the covalent organic framework material in the coating is different, and the total amount of the polyacrylate binder and the covalent organic framework material remains unchanged, as shown in Table 1 specifically.

[0264] Preparation Example 1-1d

[0265] The difference between this preparation example and Preparation Example 1-1 is that the separator membrane uses a PP-based membrane, sourced from Shanghai Enjie Co., Ltd., and the thickness of the base membrane is 9 μm. As shown in Table 1 specifically.

[0266] Preparation Example 1-2

[0267] The difference between this preparation example and Preparation Example 1-1 is that the type of the covalent organic framework material is different. A commercially available covalent organic framework material sourced from Shanghai Kaishu Chemical Technology Co., Ltd. is selected. After testing, the weight-average molecular weight of the covalent organic framework material is 6952. The monomers used in the preparation and their structural blocks are as follows.

[0268]

[0269] Preparation Example 1-3

[0270] The difference between this preparation example and Preparation Example 1-1 is that the type of the covalent organic framework material is different. A commercially available covalent organic framework material sourced from Shanghai Kaishu Chemical Technology Co., Ltd. is selected. After testing, the weight-average molecular weight of the covalent organic framework material is 5356. The monomers used in the preparation and their structural blocks are as follows.

[0271]

[0272] Preparation Example 1-4

[0273] The difference between this preparation example and Preparation Example 1-1 is that the covalent organic framework material prepared is different:

[0274] A commercially available covalent organic framework material sourced from Shanghai Kaishu Chemical Technology Co., Ltd. is selected. After testing, the weight-average molecular weight of the covalent organic framework material is 6452. The monomers used in the preparation and their structural blocks are as follows.

[0275]

[0276] Preparation Example 1-5

[0277] The difference between this preparation example and Preparation Example 1-1 is that the type of the covalent organic framework material is different: A commercially available covalent organic framework material sourced from Shanghai Kaishu Chemical Technology Co., Ltd. is selected. After testing, the weight-average molecular weight of the covalent organic framework material is 7271. The monomers used in the preparation and their structural blocks are as follows. Among them, the R group is a methoxy group. Among them, M is a copper ion. The covalent organic framework material in this example has a small amount of unreacted amino groups at the end.

[0278]

[0279] Preparation Examples 1-6

[0280] The difference between this preparation example and Preparation Examples 1-1 is as follows: the type of covalent organic framework material is different. A commercially available covalent organic framework material from Shanghai Kaishu Chemical Technology Co., Ltd. was selected. After testing, the weight-average molecular weight of the covalent organic framework material was 5664. The monomers and their structural blocks used in the preparation are as follows. The covalent organic framework material in this example has a small amount of unreacted amino groups at its ends.

[0281]

[0282] Example 1-1

[0283] Preparation of lithium battery:

[0284] (1) Preparation of the positive electrode sheet: The positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 , conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were made into a positive electrode slurry in N-methylpyrrolidone (NMP). The solid content in the positive electrode slurry was 50 wt%, and the mass ratio of LiNi 0.5 Co 0.2 Mn 0.3 O 2 , Super P, and PVDF was 9:0.7:0.3. The positive electrode slurry was coated on the current collector aluminum foil, dried at 85°C, then cold-pressed, and then trimmed, sliced, and slit. After that, it was dried under vacuum at 85°C for 4 h to make the positive electrode sheet.

[0285] (2) Preparation of the electrolyte:

[0286] In a glove box filled with argon (water content < 10 ppm, oxygen content < 1 ppm), ethylene carbonate and ethyl methyl carbonate were added to a beaker in a mass ratio of 1:1 and stirred and mixed. Subsequently, LiPF6 and LiFSI were slowly added so that their mass fractions in the electrolyte were 4% respectively. After the lithium salts were completely dissolved, vinylene sulfate (DTD) and 1,3-propane sultone were added to the above electrolyte and mixed evenly. The mass fractions of vinylene sulfate (DTD) and 1,3-propane sultone were 0.5% to obtain the electrolyte.

[0287] (3) Preparation of the negative electrode sheet:

[0288] Graphite, which serves as the negative electrode active material, is mixed evenly with conductive agent Super P, thickening agent CMC, and binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. The solid content in the negative electrode slurry is 30 wt%, and the mass ratio of graphite, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 80:15:3:2. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C, and then after cold pressing, edge trimming, slicing, and slitting, it is dried in a vacuum at 120°C for 12 h to prepare a negative electrode sheet.

[0289] (4) Separator: The separator prepared in the above-mentioned embodiment is used. The thicknesses of the base film and the coating in the separator are shown in Table 1. The content of the covalent organic framework material in the coating is shown in Table 1.

[0290] (5) Preparation of lithium-ion battery:

[0291] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed in the middle of the positive and negative electrode sheets to isolate the positive and negative electrodes, and then wound to obtain a bare battery cell. The electrode tabs are welded, the bare battery cell is placed in the outer package, and the above-prepared electrolyte is injected into the dried battery cell, followed by encapsulation, static settling, formation, shaping, capacity testing, etc., to complete the preparation of the lithium-ion battery (the thickness of the soft-pack lithium-ion battery is 4.0 mm, the width is 60 mm, and the length is 140 mm).

[0292] Examples 1-2 to 1-4

[0293] The preparation method is similar to that of Example 1, except that: the content of the covalent organic framework material in the separator is adjusted to control the relevant parameters of the separator; see Table 1 for details.

[0294] Examples 2-1 to 2-2

[0295] The preparation method is similar to that of Example 1, except that: the ratio of the thickness of the coating to the separator is different; see Table 1 for details.

[0296] Examples 3-1 to 3-5

[0297] The preparation method is similar to that of Example 1, except that: different covalent organic framework materials are used in the separator to control the relevant parameters of the separator; see Table 1 for details.

[0298] Example 4

[0299] The preparation method is similar to that of Example 2-1, except that: the separator is different. The base film in the separator is a PP base film sourced from Shanghai Enjie Co., Ltd., and the separator is Example 1-1d. See Table 1 for details.

[0300] Comparative Example 1

[0301] The preparation method is similar to that of Example 1, except that: no covalent organic framework material is added. The preparation of the coating includes: adding 98.95 parts by weight of alumina particles and 1.05 parts by weight of polyacrylate binder into deionized water, mixing evenly to form a slurry; then adopting a microgravure coating method to evenly coat the slurry on any surface in the self-thickness direction of the PE base film; after drying in an oven, a coating is obtained. The thickness of the coating is 2 μm.

[0302] Test section

[0303] (1) Detection of the cycle capacity retention rate of the lithium-ion battery:

[0304] The ambient temperature is adjusted to 25 °C, and the first charge and discharge are carried out. The battery is charged to 4.2 V at a charging current of 1C, and then charged at a constant voltage until the charging rate reaches 0.05C, and then left standing for 10 min. Then, a constant current discharge is carried out at 1C until the discharge cut-off voltage of 3.0 V. This is one charge-discharge cycle. Record the discharge capacity as C0. Carry out 300 cycles according to the above charge-discharge process. The discharge capacity at the 300th cycle is C1. The cycle capacity retention rate of the battery = C1 / C0 * 100%.

[0305] (2) Test of the charge and discharge efficiency (rate performance) of the lithium-ion battery:

[0306] Connect the battery to a tester and place it in a stable environment at 25 °C. Use a blue power tester to test the battery performance. The test conditions are as follows: Under the environment of 25 °C, the test method for the discharge capacity retention rate at a discharge rate of 2C is as follows:

[0307] Perform constant current charging on the secondary battery at a charging rate of 0.5C until the voltage of the secondary battery reaches 4.2 V; perform constant voltage charging on the secondary battery at a charging voltage of 4.2 V until the charging rate reaches 0.025C; perform constant current discharge on the secondary battery at a discharge rate of 0.5C until the voltage of the secondary battery reaches 3.0 V; repeat the above process 3 times, and take the average discharge capacity of the secondary battery as the actual discharge capacity of the secondary battery (the discharge capacity at a discharge rate of 0.5C);

[0308] Perform constant current charging on the secondary battery at a charging rate of 0.5C until the voltage of the secondary battery reaches 4.2 V; perform constant voltage charging on the secondary battery at a charging voltage of 4.2 until the charging rate reaches 0.025C; perform constant current discharge on the secondary battery at a discharge rate of 2C until the voltage of the secondary battery reaches 3.0 V; repeat the above process 3 times, and take the average discharge capacity as the actual discharge capacity of the secondary battery at a discharge rate of 2C;

[0309] The discharge rate performance at a discharge rate of 2C = the actual discharge capacity at a discharge rate of 2C / the actual discharge capacity of the secondary battery at a discharge rate of 0.5C.

[0310] (3) Test method for the battery K value: The battery K value refers to the voltage drop of the battery per unit time, usually with the unit of mV / d, and is an index used to measure the self-discharge rate of lithium batteries. The method for measuring the K value is as follows: Measure OCV1 at time t1 and measure OCV2 at time t2. K = (OCV1 - OCV2) / (t2 - t1). The time of t2 - t1 is 14 days.

[0311] (4) Detection method for the initial Coulomb efficiency:

[0312] Use a brand-new battery that has not experienced a complete charge-discharge cycle. Charge it at 0.33C to 4.2V at a constant voltage until the current is 0.05C at 25°C, record the charge capacity, let it stand for 30 minutes, discharge it at 0.33C to 3.0V and measure the discharge capacity during this period, and let it stand for 30 minutes; calculate the Coulomb efficiency by calculating the ratio of the discharge capacity to the charge capacity.

[0313]

[0314] According to Table 1, it can be seen that the separator membrane prepared in the embodiment of the present application has good cycle stability for the battery, as well as excellent initial Coulomb efficiency and charge-discharge performance. The battery prepared in the embodiment, compared with Comparative Example 1, may be that the inclusion of covalent organic framework materials and chelating groups therein improves the cycle stability of the battery, as well as excellent initial Coulomb efficiency and charge-discharge performance.

[0315] The covalent organic framework material contained in Separator Membrane Preparation Example 1-1, compared with Separator Membrane Preparation Examples 1-2 to 1-6, contains phenoxy groups in Separator Membrane Preparation Example 1-1. When it is applied to the battery, it has the effect of promoting the transport of active ions, thereby improving the initial Coulomb efficiency and charge-discharge performance of the battery.

[0316] The battery prepared in Example 5 has relatively lower cycle stability compared with other examples. The reason may be that different types of base membranes are used in the separator membrane preparation examples, which affect the performance of the battery.

[0317] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A separator membrane, characterized in that, the separator membrane comprises a base film and a coating disposed on at least one side of the base film, wherein the coating comprises a covalent organic framework material; the covalent organic framework material comprises a chelating group for chelating transition metal ions.

2. The separator membrane according to claim 1, characterized in that, the separator membrane satisfies at least one of the following conditions: 1) Based on the total mass of the coating, the coating comprises 0.01% to 1% of the covalent organic framework material, optionally 0.05% to 0.6%; 2) The chelating group comprises one or more of cyano group and amino group.

3. The separator membrane according to claim 1 or 2, characterized in that, the covalent organic framework material comprises a first covalent organic framework material obtained by reacting a first monomer and a second monomer, the first monomer comprises at least one of formula (1) to formula (5); the second monomer comprises at least one of formula (6) to formula (7); the first covalent organic framework material is obtained by reacting the amino group contained in the first monomer with any one of the aldehyde group or ketone group contained in the second monomer; wherein, in formula (4), M comprises one or more of copper element and nickel element; in formula (5), R8, R9, R10, R11, R12, R13 each independently comprise any one of substituted or unsubstituted C1-C8 alkyl, H, substituted or unsubstituted amide group, C1-C8 alkoxy group, substituted or unsubstituted phenoxy group, alkylsulfonyl group, and the substituents in the substituted C1-C8 alkyl each independently comprise any one of halogen atom and cyano group; the substituents in the substituted amide group and the substituted phenoxy group each independently comprise amino group; at least two of R8, R9, R10, R11, R12, R13 have amino groups and formula (5) is a symmetric monomer with difunctionality, trifunctionality, or tetrafunctionality; in formula (6), R14, R15, R16, R17, R18, R19 each independently comprise any one of C1-C8 alkyl, amino group, H, hydroxyl group, alkoxy group, phenoxy group, aldehyde group, and ketone group, at least two of R14, R15, R16, R17, R18, R19 have aldehyde group or ketone group, and formula (6) is a symmetric monomer with difunctionality, trifunctionality, or tetrafunctionality; optionally, in formula (6), R14 and R15 are connected to form furan-dione and R17 and R18 are connected to form furan-dione.

4. The separator membrane according to claim 3, characterized in that, the covalent organic framework material comprises at least one of a first covalent organic framework material obtained by reacting a trifunctional first monomer with a difunctional or tetrafunctional second monomer and a first covalent organic framework material obtained by reacting a difunctional or tetrafunctional first monomer with a trifunctional second monomer.

5. The separator membrane according to claim 3 or 4, characterized in that, The first monomer includes at least one of formula (1), formula (2), formula (3), formula (5-I), formula (5-II), formula (5-III), formula (5-IV), formula (5-V), formula (5-VI):

6. The separator according to any one of claims 3-5, characterized in that the second monomer includes at least one of formula (7), formula (6-I), formula (6-II), formula (6-III), formula (6-IV):

7. The separator according to any one of claims 1-6, characterized in that the covalent organic framework material is obtained by reacting a third monomer represented by formula (8) with a fourth monomer represented by formula (9) to obtain a second covalent organic framework material:

8. The separator according to any one of claims 1-7, characterized in that the coating includes a polymer obtained by reacting a fifth monomer represented by any one of formulas (10) to (12) and a sixth monomer represented by formula (13), and the polymer is obtained by reacting an amino group contained in the fifth monomer with any one of an aldehyde group or a ketone group contained in the sixth monomer; Among them, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 each independently includes any one of a substituted or unsubstituted C1-C8 alkyl group, an amino group, a C1-C8 alkoxy group, a substituted or unsubstituted amide group, a substituted or unsubstituted phenoxy group, and an alkylsulfonyl group; the substituents in the substituted C1-C8 alkyl group each independently include any one of a halogen atom and a cyano group; the substituents in the substituted amide group and the substituted phenoxy group each independently include an amino group; R20, R21, R22, R23, R24, R25 each independently include any one of C1-C8 alkyl, amino, H, hydroxyl, alkoxy, phenoxy, aldehyde group, ketone group, and at least two of R20, R21, R22, R23, R24, R25 have an aldehyde group or a ketone group; optionally, R20 and R21 are connected to form furan-dione or R23 and R24 are connected to form furan-dione.

9. The separator according to any one of claims 1-8, characterized in that The covalent organic framework material includes a first group for promoting the transport of active ions; optionally, the first group includes one or more of alkoxy groups containing C1-C8 and phenoxy groups; it may be phenoxy group, -OCH 3 .

10. The separator according to claim 9, characterized in that in the covalent organic framework material, the molar ratio of the chelating group to the first group is 1:(10-100).

11. The separator according to any one of claims 1-10, characterized in that the glass transition temperature of the covalent organic framework material is -50°C to -10°C, optionally -35°C to -25°C; and / or, The weight-average molecular weight of the covalent organic framework material is 5×10 2 ~80×10 4 , and can be optionally 6×10 2 ~75×10 4 .

12. The separator according to any one of claims 1-11, characterized in that the covalent organic framework material satisfies at least one of the following conditions: 1) The covalent organic framework material includes micropores; optionally, the average pore diameter of the micropores is 0.5 nm to 5 nm, optionally 0.8 nm to 1.5 nm; 2) The covalent organic framework material is granular, and the average particle size Dv50 of the covalent organic framework material is 0.01 μm to 1 μm; optionally, 0.05 μm to 0.1 μm; 3) The total pore volume of the covalent organic framework material is 0.8 cm 3 / g to 1.5 cm 3 / g.

13. A battery monomer, characterized in that it includes the separator according to any one of claims 1-12.

14. The battery monomer according to claim 13, characterized in that the battery monomer includes a positive electrode plate and a negative electrode plate, the positive electrode plate includes a positive electrode active material film layer, the negative electrode plate includes a negative electrode active material film layer, and at least one of the positive electrode active material film layer and the negative electrode active material film layer includes the covalent organic framework material.

15. A battery, characterized in that, it includes the battery cell described in claim 13 or 14.

16. An electrical device, characterized in that, it includes the battery described in claim 15.

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