Battery monomer, battery and electric device

Abstract

The invention provides a battery monomer, a battery and a power utilization device, the battery monomer comprises a positive pole piece, a negative pole piece and an isolating membrane, the isolating membrane is arranged between the positive pole piece and the negative pole piece, the isolating membrane comprises an isolating body and a polymer layer arranged on at least one surface of the isolating body, the polymer layer comprises an aldehyde ketone polymer, preparing the aldehyde ketone polymer into a sheet-shaped structural body; the sheet-shaped structural body is subjected to a dynamic frequency scanning test at (Tm + 20) DEG C to obtain an elastic modulus G '-energy consumption modulus G' curve, the slope of the elastic modulus G '-energy consumption modulus G' curve is K, K is larger than or equal to 0.8 and smaller than infinity, and Tm DEG C represents the melting temperature of the aldehyde ketone polymer.

Description

[0001] This application is a divisional application based on the invention with application number 202380060957.2, application date April 17, 2023, applicant CATL, entitled "Separation membrane, battery cell, battery and power supply device". Technical Field

[0002] This application relates to the field of batteries, specifically to a battery cell, a battery, and an electrical device. Background Technology

[0003] Battery cells have characteristics such as high capacity and long lifespan, and are therefore 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, etc.

[0004] As batteries are used in a wider range of applications, the requirements for the performance of individual battery cells are becoming increasingly stringent. However, the current storage performance of individual battery cells is relatively poor and still needs further improvement. Summary of the Invention

[0005] The embodiments of this application were made in view of the above-mentioned problems, and the purpose of this application is to provide a battery cell, a battery, and an electrical device.

[0006] The first aspect of this application provides a battery cell, which includes a positive electrode, a negative electrode, and a separator. The separator is disposed between the positive and negative electrode and includes a separator body and a polymer layer disposed on at least one surface of the separator body. The polymer layer includes an aldehyde-ketone polymer, wherein the aldehyde-ketone polymer is formed into a sheet-like structure; the sheet-like structure is in (T m The elastic modulus G' - energy dissipation modulus G” curve was obtained by dynamic frequency scanning test at +20℃. The slope of the elastic modulus G' - energy dissipation modulus G” curve is K, 0.8≤K<∞, T m °C indicates the melting temperature of the aldehyde-ketone polymer.

[0007] Therefore, when the polymer of the present application satisfies the above-mentioned range, it can reduce the molecular chain entanglement state, which is beneficial to the diffusion of electrolyte between molecular chains; and the polymer still maintains a certain molecular chain entanglement state, which can lock the electrolyte inside the polymer and reduce the risk of polymer dissolving in electrolyte, thereby improving the stability of polymer performance; the polymer and electrolyte can form a three-dimensional interconnected interface between the separator and the electrode, which has a network structure, which is beneficial to increase the diffusion rate of active ions such as lithium ions from the electrolyte phase to the electrode, and increase the conductivity of the separator, reduce concentration polarization, so that active ions can be quickly embedded into the electrode and uniformly deposited, thereby improving the storage performance of the battery cell.

[0008] In some implementations, 0.8 ≤ K ≤ 100; alternatively, 0.8 ≤ K ≤ 10; further alternatively, 0.8 ≤ K ≤ 1.

[0009] In some embodiments, the aldehyde-ketone polymer is added to a first solvent at 70°C to form an aldehyde-ketone polymer system; the aldehyde-ketone polymer system is allowed to stand at 70°C for 8 hours, and then allowed to stand at 25°C for ≥24 hours. The aldehyde-ketone polymer system is then filtered through a 200-mesh filter to obtain the remaining first substance. The mass of the aldehyde-ketone polymer is q (in grams); the mass of the first substance is m (in grams); the aldehyde-ketone polymer and the first substance satisfy: 5 ≤ m / q ≤ 1000, optionally, 5 ≤ m / q ≤ 20; further optionally, 5 ≤ m / q ≤ 12. This embodiment of the application, by increasing the temperature, can achieve the expansion of polymer molecular chains within the safe operating temperature range of the battery cell, promoting mutual attraction and physical bonding between the polymer molecular chains and the electrolyte. At room temperature, the activity of the aldehyde-ketone polymer molecular chain segments decreases, remaining attached to the surface of the insulating body and locking the electrolyte in the polymer's spatial environment, forming a gel or gel-like state. This can improve the transport rate of active ions such as lithium ions and enhance storage performance.

[0010] In some embodiments, the glass transition temperature (Tg) of the aldehyde-ketone polymer is given by -100 ≤ Tg ≤ 55 °C; alternatively, -100 ≤ Tg ≤ 50 °C; further alternatively, -80 ≤ Tg ≤ 30 °C; and even more alternatively, 0 ≤ Tg ≤ 30 °C. The relatively low glass transition temperature of the polymer results in better segmental flexibility of the molecular chains, making it easier for adjacent molecular chains to open.

[0011] In some embodiments, the aldehyde-ketone polymer comprises the structural unit shown in formula (I). Formula (I); In formula (I), R1 includes a single bond, a substituted or unsubstituted C1-C6 methylene group; R2 includes a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group; optionally, R1 includes a single bond, a substituted or unsubstituted C1-C4 methylene group; and R2 includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0012] In some embodiments, the aldehyde-ketone polymer includes at least one of the structural units shown in formula (I-1) to formula (I-6). Formula (I-1), Formula (I-2), Formula (I-3), Formula (I-4), Formula (I-5), Formula (I-6).

[0013] In some embodiments, the aldehyde-ketone polymer comprises the structural unit shown in formula (II). Formula (II); In formula (II), R3 to R6 each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s each independently select an integer from 0 to 5, and at least one of r and s is selected from a positive integer.

[0014] Optionally, R3 to R6 each independently include a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C2 hydroxyalkyl group, or a substituted or unsubstituted C1-C2 alkoxy group.

[0015] In some embodiments, the aldehyde-ketone polymer includes at least one of the structural units shown in formula (II-1) to formula (II-4). Formula (II-1) Formula (II-2) Formula (II-3) Equation (II-4).

[0016] In some implementations, n is selected from a positive integer from 500 to 15000.

[0017] In some embodiments, the molecular weight of the aldehyde-ketone polymer is 1.2 × 10⁻⁶. 5 g / mol to 1.0 × 10 6 g / mol.

[0018] When the molecular weight of aldehyde-ketone polymers is within the above range, the molecular chains of the aldehyde-ketone polymers can be stretched in the electrolyte, but they are not easily completely dissolved and dispersed by the electrolyte. This is beneficial for controlling the uniform distribution and dispersion of the aldehyde-ketone polymer molecular chains in the electrolyte. Furthermore, it can further improve the flexibility between the molecular chains of aldehyde-ketone polymers. The interaction forces between the molecular chains are relatively weak, which is conducive to solvent molecules in the electrolyte opening the molecular chains and entering between the molecular chains and being wrapped by the molecular chains. This facilitates the entry of active ions into the active substance through the solvent, enabling the smooth and rapid migration of active ions.

[0019] In some embodiments, the isolation body includes a substrate, and a polymer layer is disposed on at least one surface of the substrate.

[0020] In some embodiments, the insulating body includes a substrate and a heat-resistant coating, the heat-resistant coating being disposed on at least one surface of the substrate, and a polymer layer being disposed on the surface of the heat-resistant coating facing away from the substrate.

[0021] In some embodiments, the polymer layer also includes heat-resistant particles. The synergistic effect of the heat-resistant particles and the aldehyde-ketone polymer can further enhance the overall heat resistance and ion transport performance of the separator.

[0022] In some embodiments, the mass percentage of the aldehyde-ketone polymer to the mass percentage of the heat-resistant particles, based on the total mass of the polymer layer, is (0.2 to 5):1; optionally, it is (0.5 to 2):1. When the contents of the heat-resistant particles and the aldehyde-ketone polymer are within the above range, the overall heat resistance and ion transport performance of the separator can be further improved.

[0023] In some embodiments, the coating basis weight of the polymer layer can be 0.5 mg / 1540.25 mm. 2 Up to 5mg / 1540.25mm 2 When the basis weight of the polymer layer is within the above range, the overall heat resistance and ion transport performance of the separator can be further improved.

[0024] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes at least one of lithium phosphate compound, lithium transition metal oxide, sodium phosphate compound and sodium transition metal oxide.

[0025] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The negative active material layer includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0026] Secondly, this application proposes a battery comprising a battery cell as described in any embodiment of the first aspect of this application.

[0027] Thirdly, this application proposes an electrical device including a battery as described in any embodiment of the second aspect of this application. Attached Figure Description

[0028] 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.

[0029] Figure 1This is a schematic diagram of one embodiment of the battery cell of this application.

[0030] Figure 2 yes Figure 1 An exploded view of the implementation method of the battery cell.

[0031] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0032] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0033] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0034] 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.

[0035] The accompanying drawings may not be drawn to scale.

[0036] The annotations in the attached figures are explained as follows: 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical appliances. Detailed Implementation

[0037] The following detailed description 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 actually 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0038] 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.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0042] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0044] The term "alkyl" encompasses both straight-chain and branched alkyl groups. For example, an alkyl group can be C1-C5, C1-C4, C1-C3, or C1-C2 alkyl. In some embodiments, the alkyl group includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, etc. Additionally, the alkyl group may optionally be substituted. When substituted, the substituent includes a fluorine atom.

[0045] The term "alkoxy group" refers to a group in which an alkyl group is bonded to an oxygen atom by a single bond. For example, an alkoxy group can be a C1-C5 alkoxy group, a C1-C3 alkoxy group, or a C1-C2 alkoxy group. In some embodiments, an alkoxy group may include a methoxy group, an ethoxy group, or a propoxy group. Additionally, an alkoxy group may optionally be substituted.

[0046] The term "halogen atom" refers to fluorine atoms, chlorine atoms, bromine atoms, etc.

[0047] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

[0048] A single 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 isolate them. There is a solid-liquid interface between the electrodes and the electrolyte, where side reactions may occur, degrading the performance of the battery cell. Taking the positive electrode as an example, the positive active material contained in the positive electrode has a solid-liquid interface with the electrolyte. At this interface, the positive active material may react with the electrolyte, degrading the storage performance of the battery cell. Furthermore, these side reactions may produce byproducts that are detrimental to the battery cell's cycling performance, thus further worsening its storage capacity.

[0049] In view of the above problems, this application proposes a separator from the perspective of interface construction. The separator includes a separator body and a polymer layer disposed on at least one surface of the separator body. The polymer molecular chains in the polymer layer have segmental flexibility. When the separator is applied to a battery cell, the polymer layer comes into contact with the electrolyte phase, the polymer molecular chains unfold and open, and the electrolyte can diffuse between the molecular chains, forming a three-dimensional interconnected interface between the separator and the electrode. This interface has a network structure, which is beneficial to improving the diffusion rate of active ions, such as lithium ions, from the electrolyte phase to the electrode, and improving the conductivity of the separator, reducing concentration polarization, so that active ions can be quickly embedded into the electrode and uniformly deposited, thereby improving the storage performance of the battery cell.

[0050] Separating membrane In a first aspect, embodiments of this application propose an isolation membrane, the isolation membrane comprising an isolation body and a polymer layer disposed on at least one surface of the isolation body, the polymer layer comprising an aldehyde-ketone polymer, wherein the aldehyde-ketone polymer is formed into a sheet-like structure; the sheet-like structure is in (T m The elastic modulus G' - energy dissipation modulus G” curve was obtained by dynamic frequency scanning test at +20℃. The slope of the elastic modulus G' - energy dissipation modulus G” curve is K, 0.8≤K<∞, T m °C indicates the melting temperature of the aldehyde-ketone polymer.

[0051] Specifically, the preparation process of the sheet-like structure is as follows: The polymer is vacuum dried at 80°C for 12 hours. The dried polymer is then hot-pressed into thin sheets using a flat vulcanizing machine. The hot-pressing temperature is set to (Tm+20)°C, the calendering thickness is 1-2 minutes, the calendering time is 2 minutes, and the pressure is 8 MPa. After calendering for 2 minutes, the sample is removed and placed on another vulcanizing machine of the same model for cold pressing at a pressure of 10 MPa. Polymer discs (sheet-like structures) of a fixed size can be obtained using a circular mold with a diameter of 25 mm. For example, the sheet-like structure can be a disc with a thickness of 1-2 mm and a diameter of 25 mm; alternatively, it can be prepared according to the sample standard required by the testing equipment.

[0052] According to the conclusions of classical linear viscoelasticity, for polymers, the elastic modulus G' - energy dissipation modulus G" curve exhibits frequency dependence in the terminal region (the range approaching the maximum angular velocity), and the longest chain of the polymer plays a role in the viscoelastic behavior.

[0053] The specific steps of the dynamic frequency scanning test are as follows: A TA-AR2000EX rotational rheometer (TA Instruments, USA) is used for the dynamic frequency scanning test. The parallel plate diameter is 25mm and the thickness is 0.9mm. To ensure the test is conducted within the linear springback region, the strain is 2% during the dynamic frequency scanning test, the test temperature is Tm+20℃, and the frequency scanning range is 500rad / s≤w. 2 ≤0.05rad / s, so as to obtain data in the lowest possible frequency range.

[0054] Dynamic frequency scanning tests can characterize the degree of molecular chain entanglement during solid-state melting (molten state). Compared to linear or short-branched structures, long-branched, network, and low-crosslinked structures exhibit high entanglement and deviate from linear end-effector behavior, resulting in solid-state polymer behavior. When the polymer of this application meets the above-mentioned range, it can further reduce the molecular chain entanglement state, which is beneficial for electrolyte diffusion between molecular chains. Furthermore, the polymer still maintains a certain degree of molecular chain entanglement, which can lock the electrolyte inside the polymer and reduce the risk of polymer dissolving in the electrolyte, thus improving the stability of polymer performance. The polymer and electrolyte can form a three-dimensional interconnected interface between the separator and the electrode. This interface has a network structure, which is beneficial for increasing the diffusion rate of active ions, such as lithium ions, from the electrolyte phase to the electrode, improving the conductivity of the separator, reducing concentration polarization, and allowing active ions to quickly embed into the electrode and deposit uniformly, thereby improving the storage performance of the battery cell.

[0055] In some implementations, 0.8 ≤ K ≤ 100; alternatively, 0.8 ≤ K ≤ 10.

[0056] For example, K can be 0.8, 1, 1.01, 1.1, 1.2, 1.5, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000 or a range of any two of the above values.

[0057] In some embodiments, the glass transition temperature of the aldehyde-ketone polymer is Tg, which is in °C, and -100 ≤ Tg ≤ 50; alternatively, -80 ≤ Tg ≤ 30.

[0058] The glass transition temperature (TVT) is the temperature at which polymer chains transition from frozen to mobile. TVT significantly affects the flexibility of polymer molecular chains; a lower TVT generally results in better flexibility at room temperature, while a higher TVT leads to poorer flexibility. TVT can be measured using differential scanning calorimetry (DSC). Specifically, the testing procedure involves taking a 0.5g to 0.8g sample, placing it in a crucible, and subjecting it to heating and cooling at a nitrogen atmosphere. The temperature is increased at a rate of 10℃ / min from an initial temperature 20℃ lower than the intrinsic Tg to a cutoff temperature 20℃ higher than the intrinsic Tm. The actual Tg and Tm of the material are determined based on the endothermic and exothermic peaks or transition points during this process.

[0059] The glass transition temperature of polymers is relatively low, the molecular chain segments are more flexible, and adjacent molecular chains are more easily broken. For example, the glass transition temperature of aldehyde-ketone polymers can be -100℃, -90℃, -80℃, -60℃, -30℃, 0℃, 30℃, 50℃, or any combination of two of the above values.

[0060] In some embodiments, the aldehyde-ketone polymer comprises the structural unit shown in formula (I). Formula (I); In formula (I), R1 includes a single bond, a substituted or unsubstituted C1-C6 methylene group; R2 includes a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group; Optionally, R1 includes a single bond, or a substituted or unsubstituted C1-C4 methylene group.

[0061] Optionally, R1 includes a single bond, or a substituted or unsubstituted C1-C2 methylene group.

[0062] Optionally, R2 includes a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group.

[0063] In the embodiments of this application, a single bond indicates that the group does not exist, and the atoms on both sides of the group are connected by a single bond. For example, R1 is a single bond, indicating that the carbon atoms on both sides of R1 are connected by a single bond.

[0064] For example, the aldehyde-ketone polymer includes at least one of the structural units shown in formula (I-1) to formula (I-6). Formula (I-1), Formula (I-2), Formula (I-3), Formula (I-4), Formula (I-5), Formula (I-6).

[0065] For example, the aldehyde-ketone polymer comprises the structural unit shown in formula (II), Formula (II); In formula (II), R3 to R6 each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s each independently select an integer from 0 to 5, and at least one of r and s is selected from a positive integer.

[0066] Optionally, R3 to R6 each independently include a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C2 hydroxyalkyl group, or a substituted or unsubstituted C1-C2 alkoxy group.

[0067] In some embodiments, the aldehyde-ketone polymer includes at least one of the structural units shown in formula (II-1) to formula (II-4). Formula (II-1) Formula (II-2) Formula (II-3) Equation (II-4).

[0068] The aforementioned aldehyde-ketone polymers have a low degree of molecular chain entanglement, which is beneficial to improving the flexibility of the molecular chains. The molecular chains can fully extend in the electrolyte, thereby further improving the interfacial properties.

[0069] The polymers described above are merely examples of structural groups in the main molecular chains. In the embodiments of this application, the polymers may also be obtained by copolymerizing the above structural groups with a small amount of other types of structural groups (such as olefin structural units, ester monomers, nitrile monomers, amide monomers, etc.).

[0070] The functional groups of the polymer in this application can be detected by infrared spectrophotometry (IR). Specifically, the polymer is tested using a Thermo Nicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR), and then tested according to standard GB / T6040-2002. The test range is 600~4000 cm⁻¹ using the ATR method. -1 Repeatability: ±2cm -1 Resolution: better than 4cm -1 ; Transmission depth 0.2~0.6μm.

[0071] The structure of the polymer in this application can be determined by nuclear magnetic resonance (NMR). Specifically, 1H NMR and 13CN MR are performed on a Varian MercuryPlus-400 NMR spectrometer at a test temperature of 20°C, with TMS as an internal standard, CDCl3 as a solvent, and a proton resonance frequency of 400 MHz.

[0072] The polymer monomer types described in this application (especially suitable for monomers that constitute a small proportion of the polymer) can be analyzed using pyrolysis-gas chromatography-mass spectrometry (GC-MS). The specific testing steps are as follows: Accurately weigh 0.5 mg of sample into a sample cup, fix it to the injection rod, and then insert it into the pyrolyzer installed near the GC (gas chromatograph) injection port. After the pyrolyzer reaches the set temperature, press the injection button. The sample cup will fall rapidly into the core of the pyrolysis furnace through free fall. In an inert N2 atmosphere, the volatile components will instantly vaporize and be carried into the gas chromatography column by the carrier gas for separation. Finally, the components will be detected by flame ionization detector (FID) or mass spectrometer (MS) to obtain a gas chromatogram or total ion chromatogram.

[0073] When the above groups are substituted, the substituents may include one or more of the following: nitrile (-CN), nitro, sulfonic acid, sulfonyl, carboxyl, amide, ester, and halogen atoms such as chlorine, fluorine, and bromine. These substituents are high-pressure resistant and are more conducive to stabilizing the polymer structure.

[0074] In some implementations, n is selected from a positive integer from 500 to 15000.

[0075] Optionally, n is selected from a positive integer between 500 and 10000.

[0076] In some embodiments, the polymer has a molecular weight of 1.2 × 10⁻⁶. 5 g / mol to 1.0 × 10 6 g / mol.

[0077] When the molecular weight of the aldehyde-ketone polymer is within the aforementioned range, the polymer chains can be stretched out in the electrolyte, but are not easily completely dissolved and dispersed. This is beneficial for controlling the uniform distribution and dispersion of the polymer chains in the electrolyte. Furthermore, it can improve the flexibility between the polymer chains, resulting in relatively weaker intermolecular forces. This facilitates solvent molecules in the electrolyte to open the chains and enter between them, becoming encapsulated by the chains. This, in turn, allows active ions to pass through the solvent and enter the active substance, enabling their smooth and rapid migration. For example, the molecular weight of the aldehyde-ketone polymer can be 1.2 × 10⁻⁶. 5 g / mol, 2×10 5 g / mol, 5×10 5 g / mol, 8×10 5g / mol, 1×10 6 g / mol or a range consisting of any two of the above values.

[0078] The molecular weight of the polymer has a well-known meaning in the art and can be determined using commonly used equipment and methods in the art. Gel permeation chromatography (GPC) can be used for testing. The specific test steps are as follows: take an appropriate amount of the sample to be tested (the sample concentration should be 8%-12% opacity), add 20 ml of deionized water, and simultaneously incubate for 5 min (53 kHz / 120 W) to ensure that the sample is completely dispersed. Then, the sample is measured according to the standard GB / T19077-2016 / ISO13320:2009.

[0079] Alternatively, a multi-angle laser scattering (MALLS) instrument can be used for testing. Specifically, an instrument combining a GPC with a Dawn Heleos II multi-angle laser light scattering device, an Optilab T-rEX refractive index (RI) detector, and a ViscoStar II viscometer (Wyatt Technology Corporation, USA) is employed. Tests are conducted at 30°C using tetrahydrofuran as the mobile phase at a flow rate of 1.0 ml / min. SEC-SAMLL data are processed using the commercial software ASTRA6 to obtain molecular weight parameters.

[0080] The polymer in the embodiments of this application can further improve the cycle performance and storage performance of the battery cell when it meets one or more of the following conditions.

[0081] In some embodiments, the aldehyde-ketone polymer is added to a first solvent at 70°C to form an aldehyde-ketone polymer system. After standing at 70°C for 8 hours and then at 25°C for ≥24 hours, the aldehyde-ketone polymer system undergoes two stages of standing treatment. Part of the aldehyde-ketone polymer system swells and adsorbs, transforming into a gel state. The aldehyde-ketone polymer system is then filtered through a 200-mesh filter, leaving the first substance. The mass of the aldehyde-ketone polymer is q (g); the mass of the first substance is m (g); the aldehyde-ketone polymer and the first substance satisfy: 5 ≤ m / q ≤ 1000; optionally, 10 ≤ m / q ≤ 1000; further optionally, 10 ≤ m / q ≤ 50. Exemplarily, m / q can be 5, 10, 20, 25, 28, 30, 32, 35, 40, 50, 80, 100, 200, 500, 1000, or a range of any two of the above values.

[0082] For example, based on the mass of the polymer system, the ratio of the mass content of the polymer to the mass content of the first solvent ranges from 1:100 to 1:10, for example 3:50.

[0083] For example, the first solvent is the same as or similar to the solvent of the electrolyte, and the first solvent may include at least one of carbonate solvents and ether solvents. For example, carbonate solvents include cyclic carbonate solvents and / or linear carbonate solvents.

[0084] Examples of cyclic carbonate solvents include one or more of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinyl ethylene carbonate VEC, and dioctyl carbonate CC.

[0085] As examples of linear carbonate solvents, linear carbonate solvents include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), diphenyl carbonate (DPC), methyl allyl carbonate (MAC), and polycarbonate (VA).

[0086] Examples of ether solvents include one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran (2me-thf), 1,3-dioxolane (DOL), dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), and diethylene glycol dimethyl ether (DG).

[0087] Optionally, the first solvent may also contain lithium salts and electrolyte additives, such as lithium hexafluorophosphate, vinylene carbonate (VC), and fluorovinylene carbonate (FEC).

[0088] In this application, m / q is also referred to as precipitation value, which characterizes the ability of polymers and electrolytes to transform into a gel-like state.

[0089] The first substance mainly includes gel-state substances formed by polymers and a first solvent. In this type of gel-state substance, the molecular structure of the polymer remains basically unchanged.

[0090] In some embodiments, the first substance is dried at 80°C for 12 hours to remove the first solvent from the first substance, and then detected by infrared spectrophotometry (IR) or nuclear magnetic resonance (NMR). After drying, the main component of the first substance is the polymer mentioned above.

[0091] The embodiments of this application, by increasing the temperature, can achieve the expansion of polymer molecular chains within the safe operating temperature range of the battery cell, promoting the mutual attraction and physical bonding between the polymer molecular chains and the electrolyte. At room temperature, the activity of aldehyde-ketone polymer molecular chain segments decreases, remaining attached to the surface of the insulating body and locking the electrolyte in the polymer's spatial environment, forming a gel or gel-like state. This can improve the transport rate of active ions such as lithium ions, and enhance cycle performance and storage performance.

[0092] In this embodiment, the separator film includes a separator body and a polymer layer. The polymer layer is disposed on at least one surface of the separator body, meaning that the polymer layer can be disposed on one or both surfaces of the separator body. Since the separator body has various structural forms, the polymer layer correspondingly has various placement forms. Aldehyde-ketone polymers can be dispersed in a solvent to form a polymer mixture system, which is then coated onto the separator body using coating processes such as atomization spraying or gravure coating.

[0093] In some embodiments, the isolation body includes a substrate, and a polymer layer is disposed on at least one surface of the substrate.

[0094] In other embodiments, the insulating body includes a substrate and a heat-resistant coating, the heat-resistant coating being disposed on at least one surface of the substrate, and a polymer layer being disposed on the surface of the heat-resistant coating opposite to the substrate. It is understood that the heat-resistant coating may be disposed on one or both surfaces of the substrate.

[0095] The embodiments of this application do not impose particular limitations on the material of the substrate. Any known substrate with good chemical and mechanical stability can be selected. For example, the substrate may include at least one of porous polyolefin-based resin membranes (e.g., polyethylene, polypropylene, polyvinylidene fluoride), porous glass fiber, and porous nonwoven fabric. The substrate can be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer can be the same or different.

[0096] In some embodiments, the porosity of the substrate is greater than or equal to 25%; optionally, it is between 25% and 50%. When the porosity of the substrate is within the above range, the air permeability of the substrate can be improved, which is conducive to the migration of active ions. Furthermore, due to the relatively small porosity, the mechanical properties of the substrate can also be improved, and it provides good support for the polymer layer.

[0097] 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 12 μm. 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 range of two of the above values.

[0098] The heat-resistant coating may include heat-resistant particles. In some embodiments, the heat-resistant particles include at least one of inorganic and organic particles. By incorporating heat-resistant particles, the heat resistance of the separator can be improved.

[0099] In some embodiments, the mass percentage of inorganic particles in the heat-resistant coating is ≤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.

[0100] 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.

[0101] 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 Ti n 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).

[0102] 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 w0 < 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.

[0103] 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.

[0104] In some embodiments, the heat-resistant coating may also include other organic particles, such as at least one of polystyrene, polyethylene, polyimide, melamine resin, phenolic resin, polypropylene, polyester (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyphenylene sulfide, polyarylamide, polyamide-imide, polyimide, copolymers of butyl acrylate and ethyl methacrylate, and mixtures thereof.

[0105] In some embodiments, the heat-resistant coating may also include an adhesive. As an example, the adhesive may include at least one of aqueous acrylic resins (e.g., homopolymers of acrylic acid, methacrylic acid, sodium acrylate monomers, or copolymers with other comonomers), polyvinyl alcohol (PVA), isobutylene-maleic anhydride copolymers, and polyacrylamide.

[0106] In some embodiments, the thickness of the heat-resistant coating can be ≤4μm. This helps to improve the energy density of the battery cell. In the embodiments of 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 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, or any range of two of the above values.

[0107] In some embodiments, the polymer layer may further include heat-resistant particles. The synergistic effect of the heat-resistant particles and the aldehyde-ketone polymer can further improve the overall heat resistance and ion transport performance of the separator. The aldehyde-ketone polymer and the heat-resistant particles can be dispersed in a solvent to form a polymer mixture system, which is then coated onto the separator body using coating processes such as atomization spraying or gravure coating.

[0108] In some embodiments, the mass percentage of the aldehyde-ketone polymer to the mass percentage of the heat-resistant particles, based on the total mass of the polymer layer, is (0.2 to 5.0):1; optionally, it is (0.5 to 2.0):1. When the contents of the heat-resistant particles and the aldehyde-ketone polymer are within the above range, the overall heat resistance and ion transport performance of the separator can be further improved. For example, the ratio of the mass percentage of the aldehyde-ketone polymer to the mass percentage of the heat-resistant particles can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.8:1, 1.0:1, 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.5:1, 2.8:1, 3.0:1, 3.2:1, 3.5:1, 3.8:1, 4.0:1, 4.2:1, 4.5:1, 4.8:1, 5.0:1, or any range of two of the above values.

[0109] In some embodiments, the coating basis weight of the polymer layer can be 0.5 mg / 1540.25 mm. 2 Up to 5mg / 1540.25mm 2 When the basis weight of the polymer layer is within the above range, the overall heat resistance and ion transport performance of the separator can be further improved.

[0110] Optionally, the coating basis weight of the polymer layer can be 0.5 mg / 1540.25 mm. 2 Up to 3.5mg / 1540.25mm 2 .

[0111] For example, the coating basis weight of the polymer layer can be 0.5 mg / 1540.25 mm. 2 0.6mg / 1540.25mm 2 0.8mg / 1540.25mm 2 1.0mg / 1540.25mm 2 1.2mg / 1540.25mm 2 1.5mg / 1540.25mm 2 1.8mg / 1540.25mm 2 2.0mg / 1540.25mm 2 2.5mg / 1540.25mm 2 3mg / 1540.25mm 2 3.5mg / 1540.25mm 2 4mg / 1540.25mm 2 4.5mg / 1540.25mm 2 5mg / 1540.25mm 2Or a range consisting of any two of the above values.

[0112] In the embodiments of this application, the coating weight of the polymer layer refers to the weight on one side. For example, if both sides of the substrate are provided with polymer layers, then this refers to the coating weight of the polymer layer on one side of the substrate.

[0113] Coating basis weight is a term known in the art and can be tested using equipment and methods known in the art, by cutting the same master roll substrate and release film into 1540.25 mm pieces. 2 Weigh 10 small discs of the separator film and calculate the coating weight of the polymer in the separator film.

[0114] battery cell In a second aspect, embodiments of this application provide a battery cell, which includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is disposed between the positive electrode and the negative electrode, and the separator includes the separator as described in any embodiment of the first aspect of this application.

[0115] [Positive electrode plate] The positive electrode includes a positive current collector and a layer of positive active material disposed on at least one surface of the positive current collector.

[0116] As an example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0117] The positive electrode active material layer includes a positive electrode active material, which 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: lithium phosphate compound, lithium transition metal oxide, sodium phosphate compound, and sodium transition metal oxide.

[0118] For example, the general formula of olivine-type phosphate active substances (containing lithium phosphate compounds) 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.

[0119] For example, lithium transition metal oxides (layered materials such as ternary, lithium nickel oxide / sodium, lithium cobalt oxide / sodium, lithium manganese oxide / sodium, lithium-rich layered and rock salt phase layered materials, etc.). The general formula for layered cathode active materials is: Li x A y Ni a Co b Mn c M (1-a-b-c) 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. Optionally, y=0. Specifically, the layered structure positive electrode active material may include lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 One or more of O2 (NCM811) and NCA.

[0120] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include aluminum foil or aluminum alloy foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of the metal material include one or more combinations selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer substrate may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0121] In some embodiments, the positive electrode active material layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more combinations selected from superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is less than 5% based on the total mass of the positive electrode active material layer.

[0122] In some embodiments, the positive electrode active material layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include one or more combinations selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the positive electrode binder is less than 5% based on the total mass of the positive electrode active material layer. The positive electrode binder has a higher crystallinity than the aldehyde-ketone polymer of this application. The positive electrode binder has a higher melting temperature than the aldehyde-ketone polymer of this application.

[0123] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this. Of course, the preparation of the positive electrode sheet is not limited to the above methods; the preparation methods described earlier can also be used.

[0124] [Negative electrode plate] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector and including a negative active material.

[0125] For example, the negative electrode current collector has two surfaces opposite each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0126] 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. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0127] In some embodiments, the negative electrode active material 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, the mass percentage of the negative electrode conductive agent is ≤5% based on the total mass of the negative electrode active material layer.

[0128] In some embodiments, the negative electrode active material layer may optionally include a negative electrode binder. This application does not impose any particular limitation 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% based on the total mass of the negative electrode active material layer.

[0129] In some embodiments, the negative electrode active material layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc. In some embodiments, the mass percentage of other additives is ≤2% based on the total mass of the negative electrode active material layer.

[0130] 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).

[0131] The negative electrode active material 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 usually formed by dispersing the 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. Of course, the preparation of the negative electrode sheet is not limited to the above methods; the preparation methods described earlier can also be used.

[0132] The negative electrode sheet does not exclude additional functional layers besides the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode active material layer.

[0133] Electrolyte 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. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to actual needs.

[0134] Electrolytes consist of electrolyte salts and solvents. The types of electrolyte salts and solvents are not specifically limited and can be selected according to actual needs.

[0135] When the battery cell 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 bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0136] When the battery cell 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).

[0137] 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 ethylene 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), diethyl sulfone (ESE), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2me-thf), 1,3-dioxolane (DOL), dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), and diethylene glycol dimethyl ether (DG).

[0138] 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.

[0139] In some implementations, the positive electrode, separator, and negative electrode can be fabricated into an electrode assembly using a winding process and / or a stacking process.

[0140] 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.

[0141] In some embodiments, the outer packaging of the battery cell can be a rigid 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 flexible package, such as a pouch. The material of the flexible package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0142] In some implementations, the positive electrode, separator, and negative electrode can be fabricated into an electrode assembly using a winding or stacking process.

[0143] 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.

[0144] In some embodiments, such as Figure 1 and Figure 2 As 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 forming 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 through a winding process 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 a single battery cell 5 may be one or more, and can be adjusted according to requirements.

[0145] 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 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.

[0146] 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.

[0147] 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.

[0148] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0149] 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.

[0150] Both battery module 4 and battery pack can be used as specific examples of batteries in the embodiments of this application.

[0151] 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.

[0152] Electrical appliances Thirdly, this application provides an electrical device, which includes at least one of the battery cell, battery module, and battery pack described in this application. The battery cell, battery module, and battery pack can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0153] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements. Figure 6 This is a schematic diagram of an example electrical device. The 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, a battery pack 1 or a battery module can be used. Another example electrical device could be a mobile phone, tablet, laptop, etc. These devices typically require a slim and lightweight design, and can use individual battery cells as their power source.

[0154] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0155] Example 1: Preparation of Lithium-ion Batteries (1) Preparation of the positive electrode sheet: Aluminum foil with a thickness of 12μm was used as the positive electrode current collector.

[0156] LiNi, the positive electrode active material 0.6 Co 0.2 Mn 0.2 O2 (NCM622), conductive carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The mass ratio of NCM622, conductive carbon black, and PVDF in the positive electrode slurry is 97.5:1.4:1.1. The positive electrode slurry is coated onto a current collector aluminum foil and vacuum dried at 100°C, followed by cold pressing. Then, it is trimmed, cut into sheets, slit, and dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet.

[0157] (2) Preparation of negative electrode sheet: A copper foil with a thickness of 8μm was used as the negative electrode current collector.

[0158] Artificial graphite (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed evenly in a weight ratio of 97.4:2:0.5:2.6 and then added to deionized water to prepare a negative electrode slurry. The negative electrode slurry was coated onto a copper foil current collector and dried at 85°C. Then, it was cold-pressed, trimmed, cut into sheets, and slit. Finally, it was dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet.

[0159] (3) Preparation of electrolyte: In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate EC and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 3:7 to obtain an electrolyte solvent. Subsequently, lithium salt LiPF6 was mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0160] (4) Preparation of the separating membrane An 8μm polyethylene film (PE) was used as the substrate.

[0161] 15g of aldehyde-ketone polymer was dispersed in 100mL of dimethyl carbonate (DMC) solvent to form a mixture. The mixture was then atomized and sprayed onto both surfaces of a polyethylene film to form polymer layers. Water was used as the atomizing solvent, and the mass content of the mixture was 1%.

[0162] (5) Preparation of lithium-ion batteries: 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.

[0163] Comparative Example 1 A lithium-ion battery was prepared using a method similar to that of Example 1, except that the separator in Comparative Example 1 was a 7 μm polyethylene film (PE).

[0164] Comparative Example 2 Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the aldehyde-ketone polymer of the separator in Comparative Example 2 was replaced with a different material.

[0165] Example 2-1 Lithium-ion batteries were prepared using a method similar to that of Example 1. The difference from Example 1 is that the aldehyde-ketone polymer of the separator in Example 2-1 was changed.

[0166] Examples 3-1 to 3-5 Lithium-ion batteries were prepared using a method similar to that of Example 1. The difference from Example 1 is that the thickness of the polymer layer of the separator was adjusted in Examples 3-1 to 3-5.

[0167] Example 4-1 A lithium-ion battery was prepared using a method similar to that of Example 1. The difference between Example 4-1 and Example 4-1 is that the placement of the polymer layer in the separator was adjusted. Specifically, the preparation steps of the separator included: A 7μm polyethylene film (PE) was used as the substrate for the release liner; Silicon oxide particles and aqueous binder-type polyacrylic acid are mixed evenly in an appropriate amount of deionized water at a mass ratio of 20:80 to obtain a coating slurry.

[0168] The prepared coating slurry is applied to two surfaces of the PE substrate using a coating machine to form a heat-resistant coating.

[0169] 15g of aldehyde-ketone polymer was dispersed in 100mL of dimethyl carbonate (DMC) solvent to form a mixture. The mixture was then atomized and sprayed onto the surface of a heat-resistant coating to form a polymer layer, thereby obtaining a release film. Water was used as the atomizing solvent, and the mass content of the mixture was 1%.

[0170] Examples 4-2 to 4-6 Lithium-ion batteries were prepared using a method similar to that of Example 1. The difference from Example 1 is that the composition of the polymer layer of the separator was adjusted in Examples 4-2 to 4-6. Specifically, the preparation steps of the separator included: A 7μm polyethylene film (PE) was used as the substrate for the release liner; A mixture of silicon oxide particles and 15g of aldehyde-ketone polymer was dispersed in 100mL of dimethyl carbonate (DMC) solvent to form a mixed system. This mixed system was then atomized and sprayed onto the surface of a heat-resistant coating to form a polymer layer, thereby obtaining a release film. Specifically, in Example 4-2, the mass ratio of silicon oxide particles to aldehyde-ketone polymer was 1.5:1; in Example 4-3, the mass ratio was 0.5:1; in Example 4-4, the mass ratio was 2:1; in Example 4-5, the mass ratio was 0.2:1; and in Example 4-5, the mass ratio was 0.5:1.

[0171] The data for the examples and comparative examples are shown in Table 1.

[0172] Test section 1. Lithium-ion battery capacity retention test The lithium-ion batteries prepared in the examples and comparative examples were charged at a constant current of 1 / 3C to 4.25V at room temperature, then charged at a constant voltage of 4.25V to a current of 0.05C, left to rest for 5 minutes, and then discharged at 1 / 3C to 2.8V. The resulting capacity was recorded as the initial capacity C0. The batteries were then adjusted to 97% SOC and stored at 60°C. The above steps were repeated for the same battery, and the discharge capacity Cn of the battery was recorded every 30 days. The battery capacity retention rate after 30 days was calculated as Pn = Cn / C0 * 100%. A dot plot of battery capacity retention rate versus storage days was obtained with the values ​​of points P1, P2...P5 as the ordinate and the corresponding storage time as the abscissa. The battery capacity retention rate data in the table are the data measured after 150 days of storage under the above test conditions, i.e., the value of P5.

[0173] 2. Lithium-ion battery DC impedance test The lithium-ion batteries prepared in the examples and comparative examples were charged at 25°C with a constant current of 1 / 3C to 4.25V, then charged with a constant voltage of 4.25V to a current of 0.05C. After resting for 5 minutes, the voltage V1 was recorded. Then, the batteries were discharged at 1 / 3C for 30 seconds, and the voltage V2 was recorded. The internal resistance DCR1 of the battery after the first cycle was obtained by calculating (V2-V1) / 1 / 3C. The battery was then charged at room temperature with a constant current of 1 / 3C to 4.25V, then charged with a constant voltage of 4.25V to a current of 0.05C, rested for 5 minutes, and then discharged at 1 / 3C to 2.8V. The resulting capacity was recorded as the initial capacity C0. The battery was then adjusted to 97% SOC and stored at 60°C. Repeat the above steps for the same battery every 30D, and record the internal resistance DCRn of the battery for the nth time (n=1, 2, 3...5). Plot the values ​​of the five points DCR1, DCR2, DCR3...DCR5 on the vertical axis and the corresponding number of cycles on the horizontal axis to obtain a curve of the storage days of the battery discharge DCIR.

[0174] The battery internal resistance increase rate in the table is calculated as (DCRn - DCR1) / DCR1 * 100%. The data in the table were obtained after 150 days of storage under the above test conditions.

[0175] Test Results The test results are shown in Table 1.

[0176] Table 1 In Table 1, 70% formaldehyde refers to the total molar amount of formaldehyde and polyvinyl alcohol, with a formaldehyde molar percentage of 70%.

[0177] As shown in Table 1, compared to Comparative Example 1, the addition of the aldehyde-ketone polymer of this application to the separator in the embodiments of this application improves the cycle performance and storage performance of the lithium-ion battery. Compared to Comparative Example 2, the embodiments of this application, when satisfying 0.8≤K<∞, especially 0.8≤K≤100; optionally, when 0.8≤K≤10, have a more loose molecular chain arrangement, smaller intermolecular forces, and easier opening of adjacent molecular chains. Chain segment movement is achieved through intermolecular rotation, forming a highly flexible molecular chain structure, which can more significantly improve the cycle performance and storage performance of the lithium-ion battery.

[0178] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator comprises: Isolate the main body; A polymer layer comprising an aldehyde-ketone polymer is disposed on at least one surface of the insulating body. in, The aldehyde-ketone polymer is formed into a sheet-like structure; the sheet-like structure is in (T m The elastic modulus G' - energy dissipation modulus G” curve was obtained by dynamic frequency scanning test at +20℃. The slope of the elastic modulus G' - energy dissipation modulus G” curve is K, 0.8≤K<∞, T m °C represents the melting temperature of the aldehyde-ketone polymer.

2. The battery cell according to claim 1, wherein, 0.8≤K≤100; optionally, 0.8≤K≤10; further optionally, 0.8≤K≤1.

3. The battery cell according to claim 1 or 2, wherein, The aldehyde-ketone polymer is added to a first solvent at 70°C to form an aldehyde-ketone polymer system. The aldehyde-ketone polymer system was allowed to stand at 70°C for 8 hours, and then at 25°C for ≥24 hours. After filtration through a 200-mesh filter, the remaining substance was the first component. Wherein, the mass of the aldehyde-ketone polymer is q, and its unit is g; the mass of the first substance is m, and its unit is g; the aldehyde-ketone polymer and the first substance satisfy: 5≤m / q≤1000, optionally, 5≤m / q≤20; further optionally, 5≤m / q≤12.

4. The battery cell according to any one of claims 1 to 3, wherein, The glass transition temperature of the aldehyde-ketone polymer is Tg, in °C, where -100≤Tg≤55; optionally, -100≤Tg≤50; further optionally, -80≤Tg≤30; and further optionally, 0≤Tg≤30.

5. The battery cell according to any one of claims 1 to 4, wherein, The aldehyde-ketone polymer comprises the structural unit shown in formula (I). Equation (I); In formula (I), R1 includes a single bond, a substituted or unsubstituted C1-C6 methylene group; R2 includes a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group; Optionally, R1 includes a single bond, a substituted or unsubstituted C1-C2 methylene group; Optionally, R2 includes a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group.

6. The battery cell according to claim 5, wherein, The aldehyde-ketone polymer includes at least one of the structural units shown in formula (I-1) to formula (I-6). Equation (I-1), Equation (I-2), Equation (I-3), Equation (I-4), Equation (I-5), Equation (I-6).

7. The battery cell according to any one of claims 1 to 6, wherein, The aldehyde-ketone polymer comprises the structural unit shown in formula (II). Formula (II); In formula (II), R3 to R6 each independently includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s each independently select an integer from 0 to 5, and at least one of r and s is selected from a positive integer; Optionally, R3 to R6 each independently include a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C2 hydroxyalkyl group, or a substituted or unsubstituted C1-C2 alkoxy group.

8. The battery cell according to claim 7, wherein, The aldehyde-ketone polymer comprises at least one of the structural units shown in formula (II-1) to formula (II-4). Formula (II-1) Formula (II-2) Formula (II-3) Equation (II-4).

9. The battery cell according to any one of claims 5 to 8, wherein, n is a positive integer selected from 500 to 15000; and / or The molecular weight of the aldehyde-ketone polymer is 1.2 × 10⁻⁶. 5 g / mol to 1.0 × 10 6 g / mol.

10. The battery cell according to any one of claims 1 to 9, wherein, The insulating body includes a substrate, and the polymer layer is disposed on at least one surface of the substrate.

11. The battery cell according to any one of claims 1 to 9, wherein, The insulating body includes a substrate and a heat-resistant coating. The heat-resistant coating is disposed on at least one surface of the substrate, and the polymer layer is disposed on the surface of the heat-resistant coating opposite to the substrate.

12. The battery cell according to any one of claims 1 to 11, wherein, The polymer layer also includes heat-resistant particles; Optionally, based on the total mass of the polymer layer, the mass percentage of the aldehyde-ketone polymer to the mass percentage of the heat-resistant particles is (0.2 to 5):1; optionally, it is (0.5 to 2):

1.

13. The battery cell according to any one of claims 1 to 12, wherein, The polymer layer has a coating basis weight of 0.5 mg / 1540.25 mm. 2 Up to 5mg / 1540.25mm 2 .

14. The battery cell according to any one of claims 1 to 13, wherein, The positive electrode 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 includes at least one of lithium phosphate compound, lithium transition metal oxide, sodium phosphate compound, and sodium transition metal oxide.

15. The battery cell according to any one of claims 1 to 14, wherein, The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The negative active material layer includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

16. A battery comprising a battery cell according to any one of claims 1 to 15.

17. An electrical device comprising the battery according to claim 16.

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