Isolation film, battery, and electric device

Abstract

The present application relates to a separator film, a battery and an electric device, the separator film comprising a substrate and a functional layer provided on at least one side of the substrate, the substrate comprising a polymer film and an organic structure connected to the surface of the polymer film, the organic structure comprising a chelating group; the functional layer comprising a positive charge group.

Description

Technical Field

[0001] This application relates to a separator, a battery, and an electrical device. Background Technology

[0002] Batteries, with their high capacity and long lifespan, are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Due to the significant advancements in battery technology, higher performance requirements have been placed on them. To improve battery performance, the separator within the battery is typically optimized and improved.

[0003] However, when separators are currently used in batteries, the reliability and cycle performance of the batteries are still relatively poor. Summary of the Invention

[0004] This application provides a separator, a battery, and an electrical device, and the reliability and cycle performance of the battery described in this application can be improved.

[0005] In a first aspect, embodiments of this application provide an isolation membrane, the isolation membrane comprising a substrate and a functional layer disposed on at least one side of the substrate, the substrate comprising a polymer film and an organic structure attached to the surface of the polymer film, the organic structure comprising chelating groups; the functional layer comprising positively charged groups.

[0006] Therefore, the separator in this embodiment includes a substrate and a functional layer disposed on at least one side of the substrate. The substrate includes a polymer film and an organic structure attached to the surface of the polymer film, the organic structure including chelating groups; the functional layer includes positively charged groups. When the separator is applied to a battery cell, the functional layer has a positive charge, which can generate a strong electrostatic repulsion force on transition metal ions, making it more likely that the transition metal ions will be trapped by the functional layer on the side of the functional layer facing the positive electrode. The chelating groups contained in the substrate can combine with the transition metal ions through coordination to form chelates, stabilizing the transition metal ions in the chelates, further reducing the risk of transition metal ions migrating to the negative electrode, and mitigating the risk of transition metal ions precipitating on the surface of the negative electrode and forming metal dendrites, thereby improving the reliability of the battery cell. This also reduces the self-discharge rate of the battery cell and improves the cycle performance of the battery cell.

[0007] In some embodiments, the functional layer includes a porous structure with an average pore size in the nanometer range; optionally, the average pore size of the porous structure is between 1.0 nm and 3.0 nm. When the average pore size of the porous structure is within the above range, it is beneficial to further improve the retention effect of the functional layer on transition metal ions.

[0008] In some embodiments, the thickness of the functional layer is 10 nm to 50 nm. The introduction of the functional layer can not only improve the retention capacity of transition metal ions, but also improve the mechanical properties of the separator and enhance its structural strength to a certain extent.

[0009] In some embodiments, the positively charged groups include at least one of imide groups, amide groups, and imine groups; optionally, the functional layer containing the imide groups includes at least one of polyimide and polyetherimide; the functional layer containing the amide groups includes at least one of polyamide, polyetheramide, polyacrylamide, polyarylsulfone amide, and polyarylsulfone amide; the functional layer containing the imine groups includes at least one of polyethyleneimine and polymethpropyleneimide. The functional layers made of the above materials are beneficial for improving the overall thermal stability of the separator and its wettability in the electrolyte.

[0010] In some embodiments, the organic structure is disposed on the surface of the polymer film; or the organic structure is grafted onto the surface of the polymer film. The organic structure and the polymer film have strong bonding ability, and the connection stability between the organic structure and the polymer film is higher.

[0011] In some embodiments, the organic structure comprises 2% to 10% by mass, based on the total mass of the substrate. A mass percentage of organic structure within this range imparts excellent chelating ability to the substrate.

[0012] In some embodiments, the chelating group may include at least one of a carboxyl group and an imino group; optionally, the organic structure containing the carboxyl group includes at least one of ammonium acrylate, 2-methyl-2-ammonium acrylate, methacrylic acid, butenoic acid, 3-methylbutenoic acid, 4-methyl-3-pentenoic acid, and (E)-4-(4-methylpiperazin-1-yl)2-butenoic acid; optionally, the organic structure containing the imino group includes at least one of iminodiacetic acid, diethyl iminodiacetic acid, iminotriacetic acid, 3,3'-iminodipropionic acid, disodium iminodiacetic acid, and 3-[(aminoiminomethyl)thio]propionic acid.

[0013] The coordination between the aforementioned groups and transition metal ions is stronger, which is beneficial for stabilizing the transition metal ions in the separator.

[0014] In some embodiments, the weight-average molecular weight of the organic structure is less than or equal to 1000 Da; it may be selected from 100 Da to 900 Da. The relatively low weight-average molecular weight of the organic structure is beneficial to improving the success rate of grafting the organic structure onto the polymer film, and the connection stability between the organic structure and the polymer film is higher.

[0015] In some embodiments, the thickness of the substrate is less than or equal to 16 μm, and can be selected from 5 μm to 14 μm. The functional layer of the embodiments of this application is beneficial to improving the overall mechanical properties of the separator, thereby allowing the use of a thinner substrate, which helps to improve the energy density of the battery cell.

[0016] In some embodiments, the polymer membrane comprises at least one of a polyolefin-based polymer and an ionomer fiber; optionally, the polyolefin-based polymer comprises at least one of polyethylene, polypropylene, and polyvinylidene fluoride. Alternatively, the ionomer comprises at least one of polycyclohexylimine, polyethyleneamine, polyphosphononitrile, and polyoxymethylene. The above types of polymers have a higher success rate when grafted onto organic structures.

[0017] Secondly, embodiments of this application also propose a battery, wherein the battery cell includes a separator as described in any embodiment of the first aspect of this application.

[0018] Thirdly, embodiments of this application also propose an electrical device including a battery as described in any embodiment of the second aspect of this application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of one embodiment of the battery cell of this application.

[0021] Figure 2 yes Figure 1 An exploded view of the implementation method of the battery cell.

[0022] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0023] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0024] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0025] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses the battery cell of this application as a power source.

[0026] The accompanying drawings may not be drawn to scale.

[0027] The annotations in the attached figures are explained as follows:

[0028] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module;

[0029] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0030] 53. Cover plate;

[0031] 6. Electrical appliances. Detailed Implementation

[0032] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the separator, battery cell, battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0033] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] A battery cell includes a positive electrode, a negative electrode, a separator, and an electrolyte. The separator is located between the positive and negative electrodes to separate them. The positive electrode includes a positive active material, which is the donor of active ions such as sodium ions and lithium ions. The negative electrode is the acceptor of active ions. The electrolyte provides a migration path for active ions between the positive and negative electrodes. During the production and charging of battery cells, transition metal ions in the positive electrode active material can dissolve in the electrolyte. On the one hand, the dissolution of transition metal ions may cause structural collapse of the positive electrode active material, reducing the structural stability of the positive electrode sheet. On the other hand, transition metal ions migrate to the surface of the negative electrode sheet via the electrolyte, which may damage the SEI film on the surface of the negative electrode sheet, increasing the risk of side reactions due to direct contact between the negative electrode sheet and the electrolyte, and reducing the cycle stability of the battery cell. Furthermore, transition metal ions may precipitate on the surface of the negative electrode sheet to form metal dendrites. The growth of metal dendrites may pierce the separator of the battery cell, causing direct contact between the positive and negative electrode sheets and triggering a short circuit, which reduces the reliability of the battery cell, increases the self-discharge rate of the battery cell, and deteriorates the cycle performance of the battery cell.

[0038] In view of the above problems, this application proposes a separator membrane, which includes a substrate and a functional layer disposed on at least one side of the substrate. The substrate includes a polymer film and an organic structure attached to the surface of the polymer film, the organic structure including chelating groups; the functional layer includes positively charged groups. When the separator membrane is applied to a battery cell, the functional layer has a positive charge, which can generate a strong electrostatic repulsion force on transition metal ions, making it more likely that the transition metal ions will be trapped by the functional layer on the side of the functional layer facing the positive electrode. The chelating groups contained in the substrate can combine with the transition metal ions through coordination to form chelates, stabilizing the transition metal ions in the chelates, further reducing the risk of transition metal ions migrating to the negative electrode, and mitigating the risk of transition metal ions precipitating on the surface of the negative electrode and forming metal dendrites, thereby improving the reliability of the battery cell. This also reduces the self-discharge rate of the battery cell and improves the cycle performance of the battery cell. The technical solution of this application will be described in detail below.

[0039] Separating membrane

[0040] In a first aspect, embodiments of this application provide a separating membrane, the separating membrane comprising a substrate and a functional layer disposed on at least one side of the substrate, the substrate comprising a polymer membrane and an organic structure attached to the surface of the polymer membrane, the organic structure comprising chelating groups; the functional layer comprising positively charged groups.

[0041] The substrate includes two surfaces that are opposite each other along the thickness direction of the separator film. The functional layer can be disposed on either of the two surfaces or on both surfaces.

[0042] The separator includes a substrate and a functional layer. The functional layer is disposed on one of the two surfaces of the substrate. In this case, when the separator is applied to a battery cell, the substrate of the separator can be disposed closer to the positive electrode plate relative to the functional layer, that is, the functional layer is located on the side of the substrate away from the positive electrode plate; or the functional layer of the separator can be disposed closer to the positive electrode plate relative to the substrate, that is, the substrate is located on the side of the functional layer away from the positive electrode plate.

[0043] First, taking the substrate located on the side of the functional layer facing away from the positive electrode as an example, during the charging process of a single battery cell, active ions such as lithium ions and sodium ions in the positive electrode are released from the positive electrode active material and migrate towards the negative electrode. Transition metal ions such as nickel ions, cobalt ions, and manganese ions in the positive electrode may also dissolve from the positive electrode active material into the electrolyte and migrate towards the negative electrode. When the active ions and transition metal ions move to the separator between the positive and negative electrodes, since the functional layer of the separator has a positive charge, and the active ions and transition metal ions also have a positive charge, the active ions and transition metal ions are subjected to electrostatic repulsion. The valence state of the active ions is usually low, such as +1, so the electrostatic repulsion force they experience is relatively small, that is, the effect of electrostatic repulsion on the active ions is relatively small. Despite the weak electrostatic discharge, active ions can still migrate from the functional layer to the negative electrode. Because transition metal ions typically have a higher valence state (e.g., +2) and are subject to greater electrostatic repulsion, they are more likely to be trapped by the functional layer on the side facing the positive electrode. Even with this trapping effect, some transition metal ions may still migrate towards the negative electrode. In this case, the chelating groups contained in the substrate can combine with transition metal ions through coordination to form chelates, stabilizing the transition metal ions within the chelates. This further reduces the risk of transition metal ions migrating to the negative electrode and mitigates the risk of transition metal ions precipitating on the surface of the negative electrode to form metal dendrites, thus improving the reliability of the battery cell. This also reduces the self-discharge rate of the battery cell, improving its cycle performance.

[0044] Secondly, taking the functional layer located on the side of the substrate away from the positive electrode as an example, during the charging process of a battery cell, when active ions and transition metal ions move to the separator between the positive and negative electrodes, the chelating groups contained in the separator substrate can combine with the transition metal ions through coordination to form chelates, stabilizing the transition metal ions in the chelates and reducing the risk of the transition metal ions moving further toward the negative electrode. Even if some transition metal ions are not fixed by the substrate in time, the functional layer will further retain the transition metal ions between the functional layer and the substrate through repulsion, thereby further promoting the formation of chelates between the substrate and the transition metal ions, reducing the risk of transition metal ions migrating to the negative electrode, and mitigating the risk of transition metal ions precipitating on the surface of the negative electrode and forming metal dendrites, thus improving the reliability of the battery cell. This also reduces the self-discharge rate of the battery cell and improves the cycle performance of the battery cell.

[0045] Of course, if the separator includes a substrate and a functional layer, with the functional layer disposed on both surfaces of the substrate, the separator's retention and stabilization effects on transition metal ions can be further enhanced, thereby further mitigating the risk of transition metal ions precipitating on the surface of the negative electrode and forming metal dendrites, and improving the reliability of the battery cell. This also reduces the self-discharge rate of the battery cell and improves its cycle performance.

[0046] Positively charged groups exhibit a strong charge repulsion effect on high-valence transition metal ions, mitigating their migration across the separator to the negative electrode and the subsequent formation of metal dendrites that pierce the separator and cause self-discharge. When chelating groups are simultaneously introduced onto the separator, they effectively immobilize and adsorb the transition metal ions repelled by the positively charged groups. Because the repulsion of the positively charged groups reduces the migration rate of the transition metal ions, a longer reaction time is allowed for the chelating groups to immobilize and adsorb them, thus significantly enhancing their ability to do so. Therefore, the combined action of positively charged groups and chelating groups on transition metal ions demonstrates a strong synergistic effect, significantly improving the adsorption and removal capacity of these ions.

[0047] In some embodiments, the functional layer includes a porous structure with an average pore size in the nanometer range, for example, less than 10 nm. The porous structure of the functional layer facilitates the smooth migration of active ions between the positive and negative electrode plates. Compared to active ions, transition metal ions typically have larger ionic radii, making them more easily trapped by the nanometer-sized pores on the side of the functional layer closer to the positive electrode plate, thereby improving the trapping effect of the functional layer.

[0048] Optionally, the average pore size of the porous structure can be from 1.0 nm to 3.0 nm. When the average pore size of the porous structure is within the above range, it is beneficial to further improve the retention effect of the functional layer on transition metal ions.

[0049] For example, the average pore size of the porous structure can be 1.0 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2.0 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm, 2.7 nm, 2.8 nm, 2.9 nm, 3.0 nm, or any range of two of the above values.

[0050] In the embodiments of this application, the average pore size of the functional layer has a meaning known in the art and can be measured using equipment and methods known in the art. For example, a 1 mm by 1 mm area in the isolation membrane can be taken as a sample and observed by scanning electron microscopy (SEM) to count its pore size; or the average pore size can be calculated by taking multiple samples and calculating the average pore size.

[0051] In some embodiments, the thickness of the functional layer is 10 nm to 50 nm. The introduction of the functional layer can not only improve the retention capacity of transition metal ions, but also improve the mechanical properties of the separator and enhance its structural strength to a certain extent.

[0052] For example, the thickness of the functional layer can be 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm, 45nm, 46nm, 47nm, 48nm, 49nm, 50nm, or any range of two of the above values.

[0053] In some embodiments, the positively charged groups include at least one of imide groups, amide groups, and imine groups. The functional layer of the above-described material is beneficial for improving the overall thermal stability of the separator and its wettability in the electrolyte.

[0054] For example, the functional layer containing the imide group includes at least one of polyimide (PI) and polyetherimide (PE).

[0055] For example, the functional layer containing the amide group includes at least one of polyamide (PA), polyetheramide, polyacrylamide, polyarylether sulfonamide, and polyarylether sulfone amide.

[0056] For example, the functional layer containing the imine group includes at least one of polyethyleneimine (PEI) and polymethyl methacrylate (PMI).

[0057] In some embodiments, the thickness of the substrate may be less than or equal to 16 μm, and may be selected from 5 μm to 14 μm. The functional layer of the embodiments of this application is beneficial to improving the overall mechanical properties of the separator, thereby allowing for the use of a thinner substrate, which helps to improve the energy density of the battery cell. Exemplarily, the thickness of the substrate may be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 12 μm, 15 μm, 16 μm, or any combination of two of the above values.

[0058] In some embodiments, the porosity of the substrate is greater than or equal to 25%. When the porosity of the substrate is within the above range, the air permeability of the substrate can be ensured to facilitate the migration of active ions, and due to the relatively small porosity, the mechanical properties of the substrate can also be guaranteed, providing good support for the functional layer.

[0059] In some embodiments, the polymer film may include at least one polyolefin-based polymer (e.g., at least one of polyethylene, polypropylene, and polyvinylidene fluoride) and an ionomer. Exemplarily, the ionomer includes at least one of polycyclohexylimine, polyethyleneamine, polyphosphononitrile, and polyoxymethylene.

[0060] Optionally, the polymer film may include a polyolefin-based polymer, which has a higher success rate in grafting with organic structures. The substrate may be a single-layer film or a multilayer composite film. When the substrate is a multilayer composite film, the materials of each layer may be the same or different. The substrate formed by the above polymers exhibits good chemical and mechanical stability.

[0061] The substrate includes a polymer membrane and an organic structure attached to the surface of the polymer membrane. Attachment can refer to the organic structure being disposed as an independent organic compound on the surface of the polymer membrane, such as coating the surface of the polymer membrane with an organic structure to form a coating. Alternatively, attachment can refer to the grafting of an organic structure onto the polymer membrane. In this case, the organic structure can refer to a functional group (e.g., a functional group obtained by losing hydrogen atoms from an organic compound). That is, the organic structure is grafted onto the side chains of the polymer membrane, thereby modifying the polymer membrane and endowing it with the function of an organic structure. Optionally, the substrate includes a polymer membrane and an organic structure grafted onto the surface of the polymer membrane. This attachment method results in higher connection stability between the organic structure and the polymer membrane. Furthermore, the chelating groups in the organic structure can chelate transition metal ions through coordination, binding the transition metal ions both intermolecularly and intramolecularly. This enhances the coordination between the chelating groups and the transition metal ions, making it less likely for the transition metal ions to detach, thus effectively reducing the number of transition metal ions migrating to the negative electrode.

[0062] In the aforementioned polymer film, the side chains of the polymer are modified by grafting with organic structures. These organic structures include chelating groups with chelating properties, and the introduction of these organic structures imparts chelating ability to the substrate surface. In some embodiments, the mass percentage of the organic structure, based on the total mass of the substrate, is 2% to 10%. A mass percentage of the organic structure within this range imparts excellent chelating ability to the substrate.

[0063] For example, the mass percentage of the organic structure can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range of any two of the above values.

[0064] In some embodiments, the chelating group may include at least one of a carboxyl group and an imino group, which has a stronger coordination effect with the transition metal ion and is beneficial for stabilizing the transition metal ion in the separator.

[0065] It should be noted that an organic structure may consist only of chelating groups; an organic structure may also include other groups in addition to chelating groups, that is, an organic structure is composed of chelating groups and other groups. For example, an organic structure is a group formed by grafting an organic compound onto a polymer film. For example, during the grafting process, the organic compound may lose hydrogen atoms to form an organic structure.

[0066] Optionally, the organic structure containing the carboxyl group includes at least one of ammonium acrylate, 2-methyl-2-ammonium acrylate, methacrylic acid, butenoic acid, 3-methylbutenoic acid, 4-methyl-3-pentenoic acid, and (E)-4-(4-methylpiperazin-1-yl)2-butenoic acid.

[0067] Optionally, the organic structure containing an imino group includes at least one of iminodiacetic acid, diethyl iminodiacetic acid, iminotriacetic acid, 3,3'-iminodipropionic acid, disodium iminodiacetic acid, and 3-[(aminoiminomethyl)thio]propionic acid.

[0068] In some embodiments, the organic structure may also include active ions such as lithium ions and sodium ions. These active ions can bind to chelating groups through coordination. When the separator is applied to a lithium-ion battery cell, lithium ions can be released from the organic structure, which is beneficial for replenishing the battery system with active lithium ions. When the separator is applied to a sodium-ion battery cell, sodium ions can be released from the organic structure, which is beneficial for replenishing the battery system with active sodium ions.

[0069] In some embodiments, the molar ratio of the active ion to the chelating group is 0.01 to 1:1.

[0070] In the embodiments of this application, the types of functional groups in the substrate can be determined using infrared spectroscopy. For example, the infrared spectrum of the material can be tested to determine its characteristic peaks, thereby identifying the types of modified functional groups. Specifically, the material can be subjected to infrared spectral analysis using instruments and methods known in the art, such as an infrared spectrometer (e.g., a Nicolet IS10 Fourier transform infrared spectrometer) and tested according to the General Rules for Infrared Spectroscopic Analysis in GB / T 6040-2019.

[0071] In some embodiments, the infrared spectrum of the substrate has a value of 1708.4 cm⁻¹. -1 The characteristic peak indicates the presence of a carboxyl group.

[0072] In some embodiments, the infrared spectrum of the substrate has a 1400 cm⁻¹ area. -1 Up to 1450cm -1 The characteristic peak indicates the presence of imino groups.

[0073] In some embodiments, the weight-average molecular weight of the organic structure is less than or equal to 1000 Da; it can be selected from 100 Da to 900 Da. The relatively small weight-average molecular weight of the organic structure is beneficial to improving the success rate of grafting the organic structure onto the polymer film, and the connection stability between the organic structure and the polymer film is higher.

[0074] For example, the weight-average molecular weight of the organic compound can be 100 Da, 110 Da, 120 Da, 130 Da, 140 Da, 150 Da, 160 Da, 170 Da, 180 Da, 190 Da, 200 Da, 210 Da, 220 Da, 230 Da, 240 Da, 250 Da, 260 Da, 270 Da, 280 Da, 290 Da, 300 Da, 310 Da, 320 Da, 340 Da, 350 Da, 360 Da, 370 Da, 380 Da, or 390 Da. a. 400Da, 410Da, 450Da, 460Da, 480Da, 500Da, 520Da, 550Da, 560Da, 580Da, 600Da, 620Da, 650Da, 680Da, 700Da, 720Da, 750Da, 780Da, 800Da, 820Da, 850Da, 880Da, 890Da, 900Da, 920Da, 950Da, 960Da, 980Da, 1000Da, or a range consisting of any two of the above values.

[0075] In this application, the weight-average molecular weight of organic structures has a meaning known in the art and can be tested using equipment or methods known in the art. Specifically, the weight-average molecular weight of organic compounds can be tested by gel permeation chromatography (GPC). Specifically, a GPC1515 instrument from Waters Corporation, USA, was used for the determination. The sample was dissolved in tetrahydrofuran for more than 12 hours, the sample concentration was 4 mg / ml, the sample was filtered, the test temperature was 25°C, and the test flow rate was 1 ml / min.

[0076] In some embodiments, the separator may also include a heat-resistant coating, which may include inorganic particles.

[0077] For example, the separator includes a substrate and a functional layer, the functional layer being disposed on one of the two surfaces of the substrate, and the heat-resistant coating being located between the substrate and the functional layer, or on the side of the functional layer away from the substrate, or on the side of the substrate away from the functional layer.

[0078] For example, the separator includes a substrate and a functional layer, the functional layer being disposed on both surfaces of the substrate, and the heat-resistant coating being located between the substrate and the functional layer, or on the side of the functional layer facing away from the substrate.

[0079] In some embodiments, the mass percentage of inorganic particles in the heat-resistant coating is less than or equal to 30%. Exemplarily, the mass percentage of inorganic particles in the heat-resistant coating is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, or a range of any two of the above values.

[0080] Inorganic particles may include at least one of the following: inorganic particles having a dielectric constant of 5 or higher, inorganic particles having the ability to transport active ions, and inorganic particles capable of undergoing electrochemical oxidation and reduction.

[0081] In some embodiments, inorganic particles having a dielectric constant of 5 or higher may include boehmite (γ-AlOOH), alumina (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), and silicon oxides (SiO2). x (0<x≤2), Tin dioxide (SnO2), Titanium oxide (TiO2), Calcium oxide (CaO), Zinc oxide (ZnO), Zirconia (ZrO2), Yttrium oxide (Y2O3), Nickel oxide (NiO), Hafnium dioxide (HfO2), Cerium oxide (CeO2), Zirconium titanate (ZrTiO3), Barium titanate (BaTiO3), Magnesium fluoride (MgF2), Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Tin O3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1) and Pb (Mg3Nb) 2 / 3 At least one of O3-PbTiO3 (abbreviated as PMN-PT).

[0082] In some embodiments, the inorganic particles capable of transporting active ions may include lithium phosphate (Li3PO4) and lithium titanium phosphate (Li... x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium titanium aluminum phosphate (Li x Al y Ti z (PO4)3, 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y Glass-like materials (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 type glass (Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5 type glass (Li x P y S z At least one of the following: 0 < x < 3, 0 < y < 3, 0 < z < 7.

[0083] In some embodiments, the inorganic particles capable of undergoing electrochemical oxidation and reduction may include at least one of lithium-containing transition metal oxides, lithium-containing phosphates with an olivine structure, carbon-based materials, silicon-based materials, tin-based materials, and lithium-titanium compounds.

[0084] In some embodiments, the heat-resistant coating may further include an adhesive. As an example, the adhesive may include at least one of an aqueous acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, sodium acrylate monomer, or a copolymer with other comonomers), polyvinyl alcohol (PVA), isobutylene-maleic anhydride copolymer, and polyacrylamide.

[0085] In some embodiments, the thickness of the heat-resistant coating can be from 0.1 μm to 4 μm, optionally from 0.5 μm to 3 μm. This helps to improve the energy density of the battery cell. In this application, the thickness of the heat-resistant coating refers to the thickness of the heat-resistant coating located on one side of the substrate. Exemplarily, the thickness of the heat-resistant coating can be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or any range of two of the above values.

[0086] It should be noted that the functional layer parameters and heat-resistant coating parameters (e.g., thickness) of the aforementioned separator are all parameters of the functional layer and heat-resistant coating on one side of the substrate. When the functional layer parameters are disposed on both sides of the substrate, if the functional layer parameters on either side meet the requirements of this application, it is considered to fall within the protection scope of this application. Similarly, when the heat-resistant coating parameters are disposed on both sides of the substrate, if the heat-resistant coating parameters on either side meet the requirements of this application, it is considered to fall within the protection scope of this application.

[0087] Methods for preparing isolation membranes

[0088] Secondly, embodiments of this application provide a method for preparing a separating membrane, the method comprising:

[0089] Step S100: Provide a polymer film;

[0090] Step S200: An organic structure is disposed on the surface of a polymer film and the organic structure is attached to the surface of the polymer film to form a substrate. The organic structure includes chelating groups.

[0091] Step S300: A functional layer containing positively charged groups is disposed on at least one side of the polymer film.

[0092] In some embodiments, in step S100, the organic structure is attached to the polymer film surface by grafting. Specifically, the organic structure can be grafted to the polymer film surface by means of ultraviolet light grafting, initiator initiation, etc. Optionally, ultraviolet light grafting is used, which is more convenient to operate and has a higher grafting success rate.

[0093] In some embodiments, after step S200, the method may further include treating the substrate obtained in step S200 with an aqueous lithium hydroxide solution, and then washing the substrate with deionized water to a pH of about 7.0, so that the substrate contains lithium ions. This can be understood as at least some chelating groups coordinating with lithium ions to form a lithium-based chelate compound-modified substrate. During charging and discharging, lithium ions can replenish lithium in the system, which is beneficial to improving the capacity of the battery cell.

[0094] In some embodiments, in step S300, an interfacial polymerization method can be used to form a functional layer on the polymer film. Specifically, a solution containing polymeric monomers is placed on the surface of the polymer film (the surface is a surface modified with organic structures) to initiate the polymerization of the polymeric monomers to form a functional layer; or the functional layer can also be formed by coating a polymer solution onto the polymer film and then drying it.

[0095] battery cell

[0096] Thirdly, embodiments of this application provide a battery cell including a separator. The separator may include the separator of any embodiment of the first aspect of this application or a separator prepared by the method of any embodiment of the second aspect of this application. The separator serves to isolate the positive electrode and the negative electrode. By employing the above-mentioned separator, the reliability, self-discharge performance, and cycle performance of the battery cell can be improved.

[0097] [Positive electrode plate]

[0098] In some implementations, the battery cell also includes a positive electrode.

[0099] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0100] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0101] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0102] In some embodiments, the positive electrode active material may be a positive electrode active material known in the art for use in battery cells. As an example, the positive electrode active material may include at least one of the following materials: layered positive electrode active materials (e.g., ternary, lithium nickel oxide / sodium, lithium cobalt oxide / sodium, lithium manganese oxide / sodium, lithium-rich / sodium layered and rock salt phase layered materials, etc.), olivine-type phosphate active materials, spinel-structured positive electrode active materials (e.g., spinel lithium manganese oxide, spinel lithium nickel manganese oxide, lithium-rich spinel lithium manganese oxide, and lithium nickel manganese oxide, etc.).

[0103] For example, the general formula of the layered structure positive electrode active material is Li x A y Ni a Co b Mn c M (1 -abc)Y z Wherein, 0≤x≤2.1, 0≤y≤2.1, and 0.9≤x+y≤2.1; 0≤a≤1, 0≤b≤1, 0≤c≤1, and 0.1≤a+b+c≤1; 1.8≤z≤3.5; A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; Y includes one or more of O and F. Specifically, layered positive electrode active materials may include lithium cobalt oxide (LCO), lithium nickel oxide (LNO), and lithium manganese oxide (LMO), etc.

[0104] Optionally, the layered structure positive electrode active material is a ternary material, such as 0 < a ≤ 1, 0 < b ≤ 1, 0 < c ≤ 1. For example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) and LiNi 0.5 Co 0.2 Mn 0.3 One or more of O2 (NCM523).

[0105] For example, the general formula of olivine-type phosphate active substances is Li x A y Me a M b P 1-c X c Y zWherein, 0≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F. Specifically, olivine-type phosphate active substances include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0106] For example, the general formula of a spinel-structured positive electrode active material is Li x A y Mn a M 2-a Y z Wherein, 0≤x≤2, 0≤y≤1, and 0.9≤x+y≤2; 0.5≤a≤2; 3≤z≤5; A includes one or more of Na, K, and Mg; M includes one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; Y includes one or more of O and F. Specifically, the positive electrode active materials with spinel structure include LiMn2O4 and LiNi. 0.5 Mn 1.5 O4, LiCr 0.3 Mn 1.7 O4, Li 1.1 Al 0.1 Mn 1.9 O4, Li2Mn2O4 and Li 1.5 One or more of Mn2O4.

[0107] During the charging and discharging process, active ions such as Li undergo insertion / extraction and consumption, resulting in varying molar Li content in the battery cell at different discharge states. In the embodiments of this application regarding the positive electrode active material, the molar Li content refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar Li content may change when the positive electrode active material is applied to the battery system.

[0108] In the embodiments of this application, the molar content of oxygen (O) in the positive electrode active materials is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of oxygen (O) to change. In reality, the molar content of oxygen (O) will fluctuate.

[0109] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0110] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0112] [Negative electrode plate]

[0113] In some implementations, the battery cell also includes a negative electrode.

[0114] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0115] The negative electrode active material may be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy materials.

[0116] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage content of the negative electrode conductive agent is ≤5 wt%.

[0117] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose particular limitations on the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne 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). In some embodiments, the mass percentage of the negative electrode binder is ≤5 wt% based on the total weight of the negative electrode film layer.

[0118] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other additives is ≤2 wt% based on the total weight of the negative electrode film.

[0119] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0120] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0121] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet described in this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet described in this application further includes a protective layer covering the surface of the negative electrode film layer.

[0122] Electrolyte

[0123] In some implementations, the battery cell may also include an electrolyte.

[0124] During the charging and discharging process of a single battery cell, active ions repeatedly insert and extract between the positive and negative electrode plates, while the electrolyte acts as a conductor for these active ions. The embodiments of this application do not impose any particular restrictions on the type of electrolyte; it can be selected according to actual needs.

[0125] The electrolyte comprises an electrolyte salt and a solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual needs.

[0126] When the battery cell in the embodiments of this application is a lithium-ion battery, as an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0127] When the battery cell in the embodiments of this application is a sodium-ion battery, as an example, the electrolyte salt may include, but is not limited to, at least one of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0128] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0129] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0130] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process and / or a stacking process.

[0131] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0132] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a soft package, such as a pouch. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0133] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The example shown is a square-structured battery cell 5.

[0134] In some implementations, such as Figure 2As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process and / or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted according to requirements.

[0135] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0136] In some embodiments of this application, the battery cells according to this application 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.

[0137] Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0138] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0139] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0140] Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0141] The battery in the embodiments of this application may include one or more battery cells. When the battery includes multiple battery cells, the battery may include a battery module or a battery pack.

[0142] Electrical appliances

[0143] A fourth aspect of this application provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0144] The electrical device can be configured to use individual battery cells, battery modules, or battery packs according to its usage requirements.

[0145] Figure 6 This is a schematic diagram of an example electrical device 6. This electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 6, a battery pack or battery module can be used.

[0146] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0147] Example

[0148] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0149] Preparation of Lithium-ion Batteries in Examples and Comparative Cases

[0150] 1. Preparation of positive electrode sheet

[0151] Aluminum foil with a thickness of 12μm was used as the positive electrode current collector.

[0152] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.4:1.1 in an appropriate amount of solvent N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode sheet is obtained.

[0153] 2. Preparation of negative electrode sheet

[0154] A copper foil with a thickness of 8μm was used as the negative electrode current collector.

[0155] Artificial graphite (anode active material), styrene-butadiene rubber (SBR) (binder), sodium carboxymethyl cellulose (CMC-Na) (thickener), and carbon black (Super P) (conductive agent) are mixed thoroughly in an appropriate amount of deionized water at a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the surface of copper foil (anode current collector), and after drying and cold pressing, a negative electrode sheet is obtained.

[0156] 3. Separating membrane

[0157] (1) Disperse the organic compound in NMP solvent, spray the organic compound solution evenly on the surface of the polyolefin PE base film (7μm) by spraying, and then graft the organic structure in the organic compound onto the PE surface by ultraviolet light grafting to obtain the organic structure modified polyolefin base film, thus obtaining the substrate.

[0158] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0159] (3) A functional monomer is sprayed onto the modified surface (i.e. the surface with the organic structure) of a lithium-based organic structure-modified polyolefin-based film. After reaction, a functional layer is generated on the surface of the polyolefin-based film, thereby obtaining a separation film composed of a functional layer and a substrate.

[0160] 4. Preparation of electrolyte

[0161] In an environment with a water content of less than 10 ppm, the organic solvents ethylene carbonate (EC) and diethyl carbonate (DMC) are mixed at a volume ratio of 1:1 to obtain the electrolyte solvent. Then, the lithium salt is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0162] 5. Preparation of battery cells

[0163] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrode assembly is then wound up. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0164] Example 1

[0165] The lithium-ion battery is prepared using the above steps, wherein the preparation step of the separator includes:

[0166] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0167] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0168] (3) Spray the first functional monomer m-phenylenediamine MPD (10%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0169] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), is sprayed onto the surface of the polyolefin-based film. After 20 seconds of reaction, a functional layer is formed on the surface of the film, thereby obtaining a separation film composed of the functional layer and the substrate.

[0170] The methacrylic acid grafting rate was 8.5% according to the test. The grafting rate G = (m1-m0) / m0, where m1 is the mass of the PE film after light grafting and m0 is the mass of the blank PE film (ungrafted).

[0171] Comparative Example 1

[0172] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that a polyethylene (PE) membrane (12 μm) was used as the separator.

[0173] Comparative Example 2

[0174] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the preparation steps of the separator included:

[0175] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of the PE film (12μm) by spraying. Then, graft methacrylic acid groups by ultraviolet light grafting for 60s to obtain the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE substrate film is fixed at 30cm.

[0176] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based polypropylene film modified with methacrylic acid groups.

[0177] Comparative Example 3

[0178] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the preparation steps of the separator included:

[0179] m-phenylenediamine MPD (10%) was sprayed onto the surface of a polypropylene membrane (12 μm), and excess aqueous monomer was removed after 30 s.

[0180] A 5% hexane solution of pyromellitic methyl chloride (TMC) was sprayed onto the surface of the polyolefin-based film, and the reaction was carried out for 20 seconds. A functional layer was formed on the surface of the film, thereby obtaining a separation film composed of a functional layer and a substrate.

[0181] Example 2

[0182] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the average pore size and thickness of the functional layer in the separator were adjusted.

[0183] Example 2-1

[0184] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0185] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0186] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0187] (3) Spray the first functional monomer m-phenylenediamine MPD (9%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0188] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After a reaction time of 22 seconds, a functional layer was formed on the surface of the film, thus obtaining a separation membrane composed of the functional layer and the substrate.

[0189] Example 2-2

[0190] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0191] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0192] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0193] (3) Spray the first functional monomer m-phenylenediamine MPD (9%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0194] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After reacting for 25 seconds, a functional layer was formed on the surface of the film, thus obtaining a separation membrane composed of the functional layer and the substrate.

[0195] Example 2-3

[0196] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0197] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0198] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0199] (3) Spray the first functional monomer m-phenylenediamine MPD (11%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0200] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After a reaction time of 22 seconds, a functional layer was formed on the surface of the film, thus obtaining a separation membrane composed of the functional layer and the substrate.

[0201] Examples 2-4

[0202] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0203] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0204] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0205] (3) Spray the first functional monomer m-phenylenediamine MPD (12%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0206] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After reacting for 25 seconds, a functional layer was formed on the surface of the film, thus obtaining a separation membrane composed of the functional layer and the substrate.

[0207] Examples 2-5

[0208] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0209] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0210] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0211] (3) Spray the first functional monomer m-phenylenediamine MPD (13%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0212] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After reacting for 25 seconds, a functional layer was formed on the surface of the film, thus obtaining a separation membrane composed of the functional layer and the substrate.

[0213] Examples 2-6

[0214] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0215] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0216] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0217] (3) Spray the first functional monomer m-phenylenediamine MPD (13%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0218] A 6% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After reacting for 30 seconds, a functional layer was formed on the surface of the film, thus obtaining a separation membrane composed of the functional layer and the substrate.

[0219] Examples 2-7

[0220] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0221] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0222] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0223] (3) Spray the first functional monomer m-phenylenediamine MPD (14%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0224] A 6% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After a reaction of 38 s, a functional layer was formed on the surface of the film, thus obtaining a separator composed of the functional layer and the substrate.

[0225] Examples 2-8

[0226] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0227] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0228] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0229] (3) Spray the first functional monomer m-phenylenediamine MPD (15%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0230] A 7% hexane solution of the second functional monomer, trimesoyl chloride (TMC), was sprayed onto the polyolefin-based film. After a reaction of 46 s, a functional layer was formed on the surface of the film, thus obtaining a separation membrane composed of the functional layer and the substrate.

[0231] Examples 2-9

[0232] A lithium-ion battery was prepared using a method similar to that in Example 1. The difference was that the preparation method of the separator was adjusted. The preparation process of the separator is as follows:

[0233] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a polyolefin PE film (7μm) by spraying. Then, graft the organic structure of the organic compound onto the PE surface by ultraviolet light grafting for 60s to obtain a polyolefin film modified with organic structure, thus obtaining the substrate. The photoinitiator in the grafting process is benzophenone, the light source is a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE film is fixed at 30cm.

[0234] (2) The substrate obtained in step (1) was treated with 2 wt% lithium hydroxide aqueous solution and then washed with deionized water until neutral to obtain a lithium-based organic structure modified polyolefin film.

[0235] (3) Spray the first functional monomer m-phenylenediamine MPD (17%) onto the modified surface (i.e. the surface with organic structure) of the lithium-based organic structure-modified polyolefin film, and remove the excess aqueous monomer after 30s.

[0236] A hexane solution (8%) of the second functional monomer pyromellitic methyl chloride (TMC) was sprayed onto the surface of the polyolefin-based film and reacted for 55 seconds. A functional layer was formed on the surface of the film, thereby obtaining a separation membrane composed of a functional layer and a substrate.

[0237] Examples 3-1 and 3-2

[0238] Lithium-ion batteries were prepared using a method similar to that of Example 1. The difference from Example 1 is that the types of functional layers in the substrate of the separator were adjusted in Examples 3-1 and 3-2.

[0239] Examples 4-1 to 4-4

[0240] Lithium-ion batteries were prepared using a method similar to that of Example 1. The difference from Example 1 is that the mass percentage of organic structures in the substrate of the separator was adjusted in Examples 4-1 to 4-4.

[0241] Examples 5-1 and 5-2

[0242] Lithium-ion batteries were prepared using a method similar to that of Example 1. The difference from Example 1 is that the types of organic structures in the substrate of the separator were adjusted in Examples 5-1 and 5-2.

[0243] Example 6

[0244] The lithium-ion battery was prepared using a method similar to that in Example 1. The difference from Example 1 was that the type of organic structure in the substrate of the separator was adjusted. (1) 10g of methacrylic acid was weighed and dispersed in 200g of NMP solvent. The methacrylic acid solution was sprayed evenly onto the surface of the polyolefin PE base film (7μm) by spraying. Then, the organic structure in the organic compound was grafted onto the PE surface by ultraviolet light grafting. The grafting time was 60s, and the polyolefin base film modified with organic structure was obtained, thus obtaining the substrate. The photoinitiator in the grafting process was benzophenone, the light source was a 500W high-pressure mercury lamp, and the distance between the ultraviolet lamp and the surface of the PE base film was fixed at 30cm.

[0245] (2) Spray the first functional monomer m-phenylenediamine MPD (10%) onto the modified surface (i.e. the surface with organic structure) of the polyolefin-based film modified with organic structure, and remove the excess aqueous monomer after 30s.

[0246] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), is sprayed onto the surface of the polyolefin-based film. After 20 seconds of reaction, a functional layer is formed on the surface of the film, thereby obtaining a separation film composed of the functional layer and the substrate.

[0247] Example 7

[0248] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference was that the arrangement of the organic structures in the substrate of the separator was adjusted (the organic structures were directly coated onto the surface of the substrate).

[0249] (1) Weigh 10g of methacrylic acid and disperse it in 200g of NMP solvent. Spray the methacrylic acid solution evenly onto the surface of a PE film (7μm) by spraying and dry to obtain the substrate.

[0250] (2) Spray the first functional monomer m-phenylenediamine MPD (10%) onto the modified surface (i.e. the surface with organic structure) of the polyolefin-based film modified with organic structure, and remove the excess aqueous monomer after 30s.

[0251] A 5% hexane solution of the second functional monomer, trimesoyl chloride (TMC), is sprayed onto the surface of the polyolefin-based film. After 20 seconds of reaction, a functional layer is formed on the surface of the film, thereby obtaining a separation film composed of the functional layer and the substrate.

[0252] The relevant parameters for the embodiments and comparative examples are shown in Table 1.

[0253] Test section

[0254] 1. Cycle performance testing of lithium-ion batteries

[0255] A lithium-ion battery is charged at 25°C with a constant current of 2C to 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C, and then discharged at a constant current of 1C to 2.8V. This constitutes one charge-discharge cycle. Using the initial discharge capacity as 100%, calculate the capacity retention rate after 500 cycles. Capacity retention rate (%) after 500 cycles = (Discharge capacity of the 500th cycle / Initial discharge capacity) × 100%.

[0256] 2. K-value test

[0257] The K value can be used to describe the self-discharge rate of a battery cell. It can be calculated by dividing the open-circuit voltage difference between two tests by the time interval Δt between the two voltage tests. The formula is: K = (OCV2 - OCV1) / Δt. That is, K can represent the voltage drop per unit time. Generally speaking, the larger the K value, the faster or larger the open-circuit voltage drops, and there may be a micro-short circuit in the battery cell.

[0258] Test Results

[0259] The test results are shown in Table 1.

[0260] Table 1

[0261]

[0262]

[0263] In Table 1, the K value represents the K value obtained from the test when the time interval is 14 days.

[0264] As shown in Table 1, compared with Comparative Example 1, Comparative Example 2 has chelating groups on the substrate. The chelating groups can chelate transition metal ions, but there is a risk of desorption of transition metal ions. Comparative Example 3 has a functional layer on the outside of the substrate. The functional layer can retain transition metal ions to a certain extent, but the retention effect is relatively weak.

[0265] The functional layer in this embodiment has a positive charge, which can generate a strong electrostatic repulsion force on transition metal ions. The transition metal ions are more likely to be trapped by the functional layer on the side of the functional layer facing the positive electrode. The chelating groups contained in the substrate can combine with the transition metal ions through coordination to form chelates, stabilizing the transition metal ions in the chelates, further reducing the risk of transition metal ions migrating to the negative electrode, and mitigating the risk of transition metal ions precipitating on the surface of the negative electrode and forming metal dendrites, thereby improving the reliability of the battery cell. This also reduces the self-discharge rate of the battery cell and improves the cycle performance of the battery cell.

[0266] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A separating membrane, comprising: A substrate comprising a polymer film and an organic structure attached to the surface of the polymer film, said organic structure comprising chelating groups; and A functional layer disposed on at least one side of a substrate, the functional layer comprising positively charged groups; The positively charged group includes at least one of an imide group, an amide group, and an imine group; The organic structure is grafted onto the surface of the polymer film, and the organic structure has a mass percentage content of 2% to 10% based on the total mass of the substrate.

2. The separator according to claim 1, wherein, The functional layer includes a porous structure with an average pore size in the nanometer range.

3. The isolation membrane according to claim 2, wherein the average pore size of the porous structure is 1.0 nm to 3.0 nm.

4. The separator according to claim 1 or 2, wherein, The thickness of the functional layer is 10 nm to 50 nm.

5. The separator according to any one of claims 1 to 3, wherein the functional layer containing the imide group comprises at least one of polyimide and polyetherimide; The functional layer containing the amide group includes at least one of polyamide, polyetheramide, polyacrylamide, polyarylene sulfone amide, and polyarylene sulfone amide; The functional layer containing the imine group includes at least one of polyethyleneimine and polymethpropyleneimine.

6. The separator according to any one of claims 1 to 3, wherein, The chelating group includes at least one of carboxyl and imino groups.

7. The separator according to claim 6, wherein the organic structure containing the carboxyl group comprises at least one selected from ammonium acrylate, 2-methyl-2-ammonium acrylate, methacrylic acid, butenoic acid, 3-methylbutenoic acid, 4-methyl-3-pentenoic acid, and (E)-4-(4-methylpiperazin-1-yl)2-butenoic acid.

8. The separator according to claim 6, wherein the organic structure containing imino groups comprises at least one of iminodiacetic acid, diethyl iminodiacetic acid, iminotriacetic acid, 3,3'-iminodipropionic acid, disodium iminodiacetic acid, and 3-[(aminoiminomethyl)thio]propionic acid.

9. The separator according to any one of claims 1 to 3, wherein, The weight-average molecular weight of the organic structure is less than or equal to 1000 Da.

10. The separator according to any one of claims 1 to 3, wherein, The weight-average molecular weight of the organic structure is less than or equal to 100 Da to 900 Da.

11. The separator according to any one of claims 1 to 3, wherein, The thickness of the substrate is less than or equal to 16 μm.

12. The separator according to any one of claims 1 to 3, wherein the thickness of the substrate is less than or equal to 5 μm to 14 μm.

13. The separator according to any one of claims 1 to 3, wherein, The polymer membrane includes at least one of polyolefins and ionic polymers.

14. The separator according to claim 13, wherein, The polyolefin polymer includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

15. The separator membrane according to claim 13, wherein, The ionic polymer includes at least one of poly(ethylene imine), polyvinylamine, polyphosphononitrile, and polyoxymethylene.

16. A battery comprising a separator as claimed in any one of claims 1 to 15.

17. An electrical device comprising the battery as claimed in claim 16.

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