Polymers, electrode sheets and related battery cells, batteries and power consumption devices

Abstract

The present application provides a polymer, an electrode sheet, and related battery cells, batteries, and power consumption devices. The polymer includes an aldehyde-ketone polymer, and the aldehyde-ketone polymer is formed into a sheet-like structure. A dynamic frequency scan test is performed on the sheet-like structure at (Tm+20)°C to obtain a G'-G" curve, where the slope of the G'-G" curve is K, where 0.8≦K<∞, and Tm°C represents the melting temperature of the aldehyde-ketone polymer. The present application improves the cycle performance and storage performance of battery cells.

Description

[Technical Field]

[0001] This application relates to the field of batteries, and more particularly to polymers, electrode sheets and their associated battery cells, batteries and power consuming devices. [Background technology]

[0002] Due to their characteristics such as high capacity and long life, battery cells are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools.

[0003] As the range of battery applications becomes wider, the requirements for battery cell performance become more stringent. To improve the safety performance of battery cells, the performance of electrode sheets in battery cells is typically optimized and improved. However, currently, poor interfacial properties of active materials in electrode sheets result in poor cycle performance and storage performance when used in battery cells. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and aims to provide a polymer, an electrode sheet, and related battery cells, batteries, and power consuming devices.

[0005] A first aspect of the present application provides a polymer applicable to a battery cell, the polymer including an aldehyde-ketone polymer, the aldehyde-ketone polymer being formed into a sheet-like structure, and the sheet-like structure being subjected to a dynamic frequency scan test at (Tm+20)°C to obtain a G'-G" curve of elastic modulus, the G'-G" curve having a slope of K, 0.8≦K<∞, and Tm°C representing the melting temperature of the aldehyde-ketone polymer.

[0006] When the polymer of the present application satisfies the above range, the entanglement of molecular chains can be further reduced, which is advantageous for the development of the molecular chains of the solvent molecules in the electrolyte; the polymer still maintains a certain entanglement of molecular chains, allowing the solvent molecules to be in-situ locked inside the polymer, reducing the risk of the polymer dissolving in the electrolyte and improving the stability of the polymer's performance; and the polymer forms a protective layer on the surface of the active material, which is advantageous for improving the solid-liquid interface properties, reducing side reactions between the active material and the electrolyte, and improving the cycle performance and storage performance of the battery cell.

[0007] In some embodiments, 0.8≦K≦100, and optionally 0.8≦K≦10.

[0008] In some embodiments, the aldehyde-ketone polymer has a glass transition temperature, Tg, in ° C., where -100≦Tg≦50, and optionally, -80≦Tg≦30. The lower the glass transition temperature of the polymer, the greater the segmental flexibility of the molecular chains, allowing adjacent molecular chains to open more easily.

[0009] In some embodiments, the aldehyde-ketone polymer comprises a structural unit represented by formula (I). JPEG2025531274000002.jpg33161

[0010] In formula (I), R1 comprises a single bond or a substituted or unsubstituted C1-C6 methylene group, R2 comprises a hydrogen atom or a substituted or unsubstituted C1-C6 alkyl group, and optionally, R1 comprises a single bond or a substituted or unsubstituted C1-C2 methylene group, and R2 comprises a hydrogen atom or a substituted or unsubstituted C1-C3 alkyl group.

[0011] In some embodiments, the aldehyde-ketone polymer comprises at least one structural unit represented by formula (I-1) through formula (I-6). JPEG2025531274000003.jpg121150

[0012] In some embodiments, the aldehyde-ketone polymer comprises a structural unit represented by formula (II). JPEG2025531274000004.jpg25161

[0013] In formula (II), R3 to R6 each independently comprise a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1 to C3 alkyl group, a substituted or unsubstituted C1 to C3 hydroxyalkyl group, or a substituted or unsubstituted C1 to C3 alkoxy group; r and s each independently represent an integer selected from 0 to 5, and at least one of r and s is selected from positive integers; and optionally, R3 to R6 each independently comprise a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1 to C3 alkyl group, a substituted or unsubstituted C1 to C2 hydroxyalkyl group, or a substituted or unsubstituted C1 to C2 alkoxy group.

[0014] In some embodiments, the aldehyde-ketone polymer comprises at least one of structural units represented by formula (II-1) through formula (II-4). JPEG2025531274000005.jpg73161

[0015] In some embodiments, n is a positive integer selected from 500 to 15,000, and / or the molecular weight of the aldehyde-ketone polymer is 1.2×10 5 g / mol ~ 1.0 × 10 6g / mol. When the molecular weight of the polymer is in the above range, it can ensure that the polymer has a certain solubility in the electrolyte, and is unlikely to be completely dissolved or dispersed by the electrolyte, which is advantageous for adjusting the distribution and dispersion of the polymer on the surface of the active material, and it can further improve the flexibility between the molecular chains of the polymer, and the interaction force between the molecular chains is relatively weak, which is advantageous for the solvent molecules in the electrolyte to open the molecular chains, enter between the molecular chains, and be enveloped by the molecular chains, which is advantageous for the active ions to enter the active material through the solvent, thereby realizing the smooth and rapid movement of the active ions.

[0016] A second aspect of the present application provides a positive electrode sheet, the positive electrode sheet including a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, the positive electrode active material layer including a positive electrode active material and a polymer, and the polymer including the polymer according to any one of the embodiments of the first aspect of the present application.

[0017] A third aspect of the present application provides a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, the negative electrode active material layer including a negative electrode active material and a polymer, and the polymer including the polymer according to any one of the embodiments of the first aspect of the present application.

[0018] A fourth aspect of the present application provides a battery cell, the battery cell including a positive electrode sheet and a negative electrode sheet, the positive electrode sheet including the positive electrode sheet according to any one of the embodiments of the second aspect of the present application, and / or the negative electrode sheet including the negative electrode sheet according to any one of the embodiments of the third aspect of the present application.

[0019] A fifth aspect of the present application provides a battery including the battery cell according to the fourth aspect of the present application.

[0020] A sixth aspect of the present application provides a power consuming device including a battery according to the fifth aspect of the present application. [Brief explanation of the drawings]

[0021] In order to more clearly explain the technical solutions of the embodiments of the present application, the following will briefly describe the drawings that need to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on the drawings without exerting creative efforts.

[0022] [Figure 1] 1 is a schematic diagram of an embodiment of a battery cell of the present application. [Figure 2] FIG. 2 is an exploded schematic view of an embodiment of the battery cell of FIG. 1. [Figure 3] 1 is a schematic diagram of an embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of an embodiment of a battery pack of the present application. [Figure 5] 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of one embodiment of a power consuming device that includes a battery cell of the present application as a power source.

[0023] The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, detailed descriptions will be given of embodiments specifically disclosing the polymer, electrode sheet, and related battery cells, batteries, and power consumption devices of the present application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0025] "Ranges" disclosed herein are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of that particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 and maximum range values ​​of 3, 4, and 5 are recited, then ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. Unless otherwise specified, the numerical range "a to b" herein is a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is an abbreviation for combinations of these numerical values. Furthermore, notation that a parameter is an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions. Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0027] Unless otherwise specified, all steps in this application may be performed in order or randomly, but are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, when it is stated that the method may further 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 may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0028] Unless otherwise specified, the terms "comprise" and "include" used in this application mean open-ended and may also be closed-ended. For example, the terms "comprise" and "include" can mean "comprise" or "include" other components not listed, or "comprise" or "include" only the listed components.

[0029] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0030] As used herein, the terms "plurality" and "plurality" refer to two or more.

[0031] The term "alkyl" includes straight-chain and branched-chain alkyls. For example, an alkyl group can be a C1-C5 alkyl group, a C1-C4 alkyl group, a C1-C3 alkyl group, or a C1-C2 alkyl group. In some embodiments, alkyl includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and the like. Additionally, alkyl groups can be optionally substituted. When substituted, the substituents include fluorine atoms.

[0032] The term "alkoxy group" refers to a group in which an alkyl group and an oxygen atom are linked by a single bond. For example, the alkoxy group may be a C1-C5 alkoxy group, a C1-C3 alkoxy group, or a C1-C2 alkoxy group. In some embodiments, the alkoxy group may include a methoxy group, an ethoxy group, or a propoxy group. The alkoxy group may also be optionally substituted.

[0033] The term "hydroxyalkyl group" refers to a group in which a hydroxy group and an alkyl group are linked by a single bond. For example, the hydroxyalkyl group may be a C1-C8 hydroxyalkyl group, a C1-C5 hydroxyalkyl group, a C1-C3 hydroxyalkyl group, or a C1-C2 hydroxyalkyl group. In some embodiments, the hydroxyalkyl group may include hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, etc. Additionally, the hydroxyalkyl group may be optionally substituted.

[0034] The term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom, and the like.

[0035] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In each embodiment, "hydrogen" may be 1H (protium, H).

[0036] A battery cell includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. A solid-liquid interface exists between the electrode sheet and the electrolyte, and side reactions may occur at this interface, potentially degrading the performance of the battery cell. Taking a positive electrode sheet as an example, a solid-liquid interface exists between the positive electrode active material contained in the positive electrode sheet and the electrolyte. Side reactions may occur at this interface between the positive electrode active material and the electrolyte, causing a loss of the positive electrode active material and thus reducing the cycle performance of the battery cell. Furthermore, the side reactions may produce products that are detrimental to the cycle performance of the battery cell, thereby deteriorating the storage performance of the battery cell.

[0037] Therefore, embodiments of the present application provide a polymer that, when applied to a positive electrode sheet and / or a negative electrode sheet, can form an in-situ gel on the surface of a solid-phase active material, i.e., form a stable solid-liquid interface on the surface of the active material, thereby reducing the risk of side reactions occurring at the solid-liquid interface and improving the cycle performance and storage performance of the battery cell.

[0038] polymer

[0039] According to a first aspect, the present application provides a polymer for use in a battery cell, the polymer comprising an aldehyde-ketone polymer, the aldehyde-ketone polymer being formed into a sheet-like structure, and the sheet-like structure being subjected to a dynamic frequency scan test at (Tm+20)°C to obtain a G'-G" curve of elastic modulus, the G'-G" curve having a slope of K, where 0.8≦K<∞, and Tm°C represents the melting temperature of the aldehyde-ketone polymer.

[0040] Specifically, the process for producing the sheet-like structure is as follows: the polymer is vacuum-dried at 80°C for 12 hours. The dried polymer is hot-pressed into a sheet using a press vulcanizer, with the hot-press temperature set to (Tm+20)°C, the rolled thickness set to 1-2 mm, the rolled time set to 2 minutes, and the pressure set to 8 MPa. After 2 minutes of rolling, the sample is removed and placed in another vulcanizer of the same model for cold pressing at a cold press pressure of 10 MPa. A circular mold with a diameter of 25 mm is used to obtain a polymer wafer (sheet-like structure) of a certain size. For example, the sheet-like structure may be a wafer with a thickness of 1-2 mm and a diameter of 25 mm, and may be manufactured according to the sample standard required for the testing device.

[0041] According to the classical linear viscoelasticity conclusion, for polymers, especially linear polymers, the elastic modulus G'-loss modulus G" relationship in the terminal region of the elastic modulus G'-loss modulus G" curve (the range close to the maximum value of the angular velocity) satisfies frequency dependence, and the longest chain of the polymer affects the viscoelastic behavior.

[0042] The specific steps of the dynamic frequency scan test were performed using a TA-AR2000EX rotational rheometer (TA Instruments, USA). The parallel plates had a diameter of 25 mm and a thickness of 0.9 mm. To ensure that the test was conducted in the linear elastic region, the strain during the dynamic frequency scan test was 2%, the test temperature was Tm + 20°C, and the frequency scan range was 500 rad / s or less. 2 By keeping the frequency below 0.05 rad / s, data in the lowest possible frequency range can be obtained.

[0043] Dynamic frequency sweep tests can reveal the degree of molecular chain entanglement in solid-phase melting (molten state). Compared to linear or short-chain branched structures, long-chain branched structures, network structures, and low-crosslinked structures have a higher degree of entanglement, exhibiting behavior that deviates from the chain ends, and the polymer exhibits solid-phase behavior. When the polymer of the present application satisfies the above range, the molecular chain entanglement can be further reduced, favoring the interchain expansion of solvent molecules in the electrolyte. Furthermore, the polymer still maintains a certain molecular chain entanglement state, allowing solvent molecules to be in situ locked inside the polymer, reducing the risk of the polymer dissolving in the electrolyte and improving the performance stability of the polymer. Furthermore, the polymer is advantageous for forming a protective layer on the surface of the active material, improving solid-liquid interfacial properties, reducing side reactions between the active material and the electrolyte, and improving the cycle performance and storage performance of the battery cell.

[0044] In some embodiments, 0.8≦K≦100, and optionally 0.8≦K≦10.

[0045] Illustratively, K may be 0.8, 0.9, 1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the foregoing values.

[0046] In some embodiments, the aldehyde-ketone polymer has a glass transition temperature, Tg, in ° C., where -100≦Tg≦50, and optionally, -80≦Tg≦30.

[0047] The glass transition temperature (Tg) is the temperature at which a polymer segment transitions from freezing to motion. This temperature has a certain effect on the flexibility of the polymer molecular chains. The lower the Tg, the better the flexibility of the polymer molecular chains at room temperature. The higher the Tg, the worse the flexibility of the molecular chains at room temperature. The Tg can be tested using differential scanning calorimetry (DSC). Specifically, the test involves taking a 0.5g-0.8g sample, placing it in a crucible, and heating the sample under a nitrogen atmosphere at a heating rate of 10°C / min from an initial temperature 20°C below the intrinsic Tg to a cutoff temperature 20°C above the intrinsic Tm. The actual Tg and Tm of the material are determined based on the endothermic and heat-releasing peaks or transition points of the material during this process.

[0048] The polymer has a relatively low glass transition temperature, which allows the molecular chain segments to have better flexibility and allows adjacent molecular chains to open more easily. For example, the glass transition temperature of the aldehyde-ketone polymer may be −100° C., −90° C., −80° C., −60° C., −30° C., 0° C., 30° C., 50° C., or a range consisting of any two of the above values.

[0049] In some embodiments, the aldehyde-ketone polymer comprises a structural unit represented by formula (I). JPEG2025531274000006.jpg33161

[0050] In formula (I), R1 includes a single bond or a substituted or unsubstituted C1 to C6 methylene group, and R2 includes a hydrogen atom or a substituted or unsubstituted C1 to C6 alkyl group.

[0051] Optionally, R1 comprises a single bond, a substituted or unsubstituted C1-C2 methylene group.

[0052] Optionally, R2 comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0053] In the embodiments of the present application, a single bond represents that the group is absent and the atoms on both sides of the group are connected by a single bond, for example, R1 is a single bond and the carbon atoms on both sides of R1 are connected by a single bond.

[0054] Illustratively, the aldehyde-ketone polymer includes at least one of the structural units represented by formula (I-1) to formula (I-6). JPEG2025531274000007.jpg110161

[0055] Illustratively, the aldehyde-ketone polymer comprises a structural unit represented by formula (II): JPEG2025531274000008.jpg25161

[0056] In formula (II), R3 to R6 each independently comprise a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1 to C3 alkyl group, a substituted or unsubstituted C1 to C3 hydroxyalkyl group, or a substituted or unsubstituted C1 to C3 alkoxy group; r and s each independently represent an integer selected from 0 to 5, and at least one of r and s is selected from positive integers; and optionally, R3 to R6 each independently comprise a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1 to C3 alkyl group, a substituted or unsubstituted C1 to C2 hydroxyalkyl group, or a substituted or unsubstituted C1 to C2 alkoxy group.

[0057] In some embodiments, the aldehyde-ketone polymer comprises at least one of structural units represented by formula (II-1) through formula (II-4). JPEG2025531274000009.jpg73161

[0058] The aldehyde-ketone polymer has a low degree of entanglement of molecular chains, which is advantageous in improving the flexibility of the molecular chains, and the molecular chains can be sufficiently spread in the electrolyte, thereby further improving the interfacial properties of the active material.

[0059] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with other types of structural groups (e.g., olefin-based structural units, enol-based structural units, acrylonitrile-based structural units, etc.).

[0060] The groups of the polymer of the present application can be detected by infrared spectroscopy (IR). Specifically, the polymer is tested using a ThermoNicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrophotometer (FTIR-ATR), and then tested according to standard GB / T 6040-2002. The test range is ATR method 600-4000 cm. -1 and the overlap is ±2cm -1 The resolution is better than 4 cm and the penetration depth is 0.2-0.6 μm.

[0061] The structure of the polymer of the present application can be determined by nuclear magnetic resonance (NMR) analysis, specifically, 1H NMR and 13C NMR were performed on a Varian Mercury Plus-400 nuclear magnetic resonance spectrometer at a test temperature of 20°C, TMS as the internal standard, CDCl3 as the solvent, and a proton resonance frequency of 400 MHz.

[0062] The type of polymer monomer used in this application (especially applicable to monomers that account for a small proportion in the polymer) can be determined by pyrolysis / gas chromatography / mass spectrometry. The specific test steps are as follows: 0.5 mg of sample is accurately weighed and placed in a sample cup, which is then attached to a sample injection rod and placed in a cracker installed near the GC (gas chromatograph) injection port. After the temperature of the cracker reaches the set temperature, the injection button is pressed and the sample cup quickly falls into the core of the cracking furnace through a free-falling body. In the inert gas N2 atmosphere, the volatile components are instantly gasified and enter the gas chromatograph column from the carrier gas for separation. Finally, the flame ionization detector FID or mass spectrometer MS is used for detection, and a gas chromatograph or total ion chromatogram is obtained.

[0063] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonyl group, a carboxyl group, an ester group, a chlorine atom, a fluorine atom, and a bromine atom. The above substituents are high-pressure-resistant and are advantageous in stabilizing the polymer structure.

[0064] In some embodiments, n is selected from positive integers between 500 and 15,000.

[0065] Optionally, n is selected from the positive integers between 500 and 10,000.

[0066] In some embodiments, the molecular weight of the polymer is 1.2×10 5 g / mol ~ 1.0 × 10 6 g / mol.

[0067] When the molecular weight of the polymer is within the above range, it is possible to ensure that the polymer exhibits a certain solubility in the electrolyte, and it is difficult for the polymer to be completely dissolved and dispersed by the electrolyte, which is advantageous for adjusting the distribution and dispersion of the polymer on the surface of the active material. In addition, it is possible to further improve the flexibility between the molecular chains of the polymer, and the interaction between the molecular chains is relatively weak, which is advantageous for the solvent molecules in the electrolyte to open the molecular chains, enter between the molecular chains, and be enveloped by the molecular chains, which is advantageous for the active ions to enter the active material through the solvent and realize smooth and rapid migration of the active ions. For example, the molecular weight of the polymer is 1.2×10 5 g / mol, 2 × 10 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1×10 6 g / mol, 1.0 × 10 6 It may be g / mol or a range consisting of any two of the above values.

[0068] The molecular weight of a polymer is a known term in the art and can be measured using commonly used instruments and methods in the art. Gel permeation chromatography (GPC) can be used. The specific test steps are to take an appropriate amount of target test sample (ensure that the sample concentration is 8%-12% opacity), add 20ml of deionized water, and apply ultrasonic waves for 5 minutes (53KHz / 120W) to ensure the sample is completely dispersed, and then measure the sample according to GB / T19077-2016 / ISO13320:2009 standard.

[0069] Alternatively, the test was performed using a multi-angle laser light scattering (MALLS) system, specifically, a GPC system using a DawnHeleos II multi-angle laser light scattering instrument, an OptilabT-rEX refractive index (RI) detector, and a ViscoStar II viscometer (Wyatt Technology Corporation, USA). The test was performed at 30°C with tetrahydrofuran as the mobile phase at a flow rate of 1.0 ml / min, and the molecular weight parameters were obtained by processing the SEC-SAMLL data using the commercial software ASTRA6.

[0070] Further investigation has revealed that the cycle performance and storage performance of the battery cell can be further improved by making the polymer further satisfy one or more of the following conditions:

[0071] In some embodiments, the polymer is added to a first solvent at 45° C. to form a polymer system, which undergoes two stages of standing at 45° C. for 8 hours and at 25° C. for 24 hours or more, resulting in in-situ conversion of a portion of the polymer system into a gel-state substance. The polymer system is then filtered through a 200-mesh filter to leave a first substance. The mass of the polymer is n (g), the mass of the first substance is m (g), and the ratios of the polymer and the first substance satisfy 5≦m / n≦1000, optionally 10≦m / n≦1000, and optionally 10≦m / n≦50. Exemplarily, m / n may be 5, 10, 20, 25, 28, 30, 32, 35, 40, 50, 80, 100, 200, 500, 1000, or a range consisting of any two of the foregoing values.

[0072] Illustratively, the ratio of the mass content of the polymer to the mass content of the first solvent, relative to the mass of the polymer system, ranges from 1:100 to 1:10, for example 3:50.

[0073] Illustratively, the first solvent may be the same as or similar to the solvent of the electrolyte, and the first solvent may include a carbonate-based solvent, for example, a cyclic carbonate solvent and / or a linear carbonate solvent.

[0074] Examples of the cyclic carbonate solvent include at least one of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC.

[0075] Examples of the chain carbonate solvent include at least one of dimethyl carbonate DMC, diethyl carbonate DEC, ethyl methyl carbonate EMC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate VA.

[0076] Optionally, the first solvent may contain both a lithium salt and an electrolyte additive, such as lithium hexafluorophosphate, vinylene carbonate (VC), or fluorovinylene carbonate (FEC).

[0077] In this application, m / n is also referred to as the sedimentation value, and represents the ability of a polymer and solvent to convert into a gel-state material.

[0078] The first substance includes a gel-state substance mainly composed of a polymer and a first solvent, and in such a gel-state substance, the molecular structure of the polymer remains almost unchanged.

[0079] In some embodiments, the first material is dried at 80°C for 12 hours to remove the first solvent in the first material, and then infrared spectroscopy (IR) or nuclear magnetic resonance (NMR) testing is performed, and the main component of the first material after drying is the aforementioned polymer.

[0080] In this invention, by increasing the temperature, the polymer molecular chains can be expanded within the safe operating temperature range of the battery cell, promoting mutual attraction and physical bonding between the polymer molecular chains and the solvent. At room temperature, the polymer molecules have reduced segment activity, allowing them to adhere to the active material surface while simultaneously locking the electrolyte in the space and environment where the polymer is located, forming an in-situ gel-like state. This protects the active material interface and maintains normal lithium ion transport, thereby establishing interfacial protection, reducing surface side reactions, and improving cycle performance and storage performance.

[0081] Positive electrode sheet

[0082] In a second aspect, the present application provides a cathode sheet including a cathode current collector and a cathode active material layer provided on the cathode current collector, the cathode active material layer including a cathode active material and a polymer, and the polymer including the polymer described in any one of the embodiments of the first aspect of the present application.

[0083] As an example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode active material layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0084] The electrode sheet can be formed by applying the slurry to a current collector, drying it, and cold pressing it. Alternatively, the electrode sheet can be derived from a battery cell. The battery cell can be disassembled, and the electrode sheet soaked in the electrolyte can be removed from the battery cell. The electrode sheet soaked in the electrolyte can be vacuum-dried at 100°C for 12 hours to obtain the electrode sheet, which can then be used for testing the electrode sheet, such as its absorption rate.

[0085] The polymer can be synthesized by emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization, etc. Alternatively, the polymer can be derived from a battery cell. The battery cell is disassembled, and the electrode sheet soaked in the battery cell electrolyte is removed. The active material of the resulting electrode sheet is peeled from the current collector by external force to form a powder sample. This powder is then added to DMC and stirred at 80°C and 500 rpm for 8 hours. After stirring is complete, the mixture is allowed to stand at room temperature for 10 minutes. The supernatant is removed at 80°C and dried for 12 hours to obtain the polymer. The resulting polymer may contain a small amount of lithium salt, but this has little effect on infrared and sedimentation value tests. To ensure the accuracy of the polymer, the lithium salt can be separated by further washing with DMC at room temperature.

[0086] In some embodiments, the positive electrode active material layer satisfies the following conditions:

[0087] JPEG2025531274000010.jpg14161

[0088] JPEG2025531274000011.jpg16161

[0089] v / λ>1.00 Equation (3)

[0090] In formulas (1) to (3),

[0091] λ represents the porosity of the positive electrode active material layer,

[0092] P1 represents the actual compressed density of the positive electrode active material layer, and its unit is g / cm 3 and

[0093] P2 represents the true compressed density of the positive electrode active material, and its unit is g / cm 3 and

[0094] v represents the liquid absorption rate of the positive electrode active material layer, and its unit is mg / s.

[0095] d represents the diameter of a capillary in a capillary test of the positive electrode active material layer, and its unit is mm;

[0096] h represents the liquid level in the capillary tube, and its unit is mm;

[0097] ρ indicates the density of the electrolyte in the capillary test, and its unit is g / cm 3 and

[0098] t indicates the time it takes for the electrolyte to be absorbed in the capillary, and its unit is s.

[0099] In this application, the actual compressed density P1 refers to the ratio of the mass to the thickness of the positive electrode active material layer per unit area of ​​the electrode sheet. The actual compressed density is determined by the force applied by the roll to press the electrode sheet after coating, and is expressed in units of g / cm. 3 The specific test steps are as follows: take an electrode sheet with a certain area S, weigh the mass M of its positive electrode active material layer, and take the thickness D of the positive electrode active material layer; the actual compressed density is M / (S×D).

[0100] In this application, the true compressed density P2 refers to the density of the positive electrode active material itself in the positive electrode active material layer, specifically, the mass of the unit "actual volume of the solid material (not including open pores, closed pores, and inter-particle voids)" in a dense state. The true volume V is obtained by testing, and the true compressed density is calculated based on P=m / V. This test can be performed in accordance with GB / T24586-2009. Specifically, the test steps are as follows:

[0101] 1) Pretreatment: Place a clean, dry sample cup on the balance, reset it, add the powder sample to the sample cup, occupying approximately half of the volume of the sample cup, and record the mass of the sample.

[0102] 2) Place the sample cup containing the sample into the true density tester, seal the test system, introduce helium gas according to the process, detect the gas pressure in the sample chamber and the expansion chamber, and then calculate the true volume based on Boyle's law (PV=nRT) to calculate the true compressed density.

[0103] Here, the volume of the sample cup is 3.5 cm 3 and the analysis gas is helium gas.

[0104] Equation (1) makes it possible to calculate the porosity λ of the active material layer from the actual compressed density and the true compressed density.

[0105] in particular, JPEG2025531274000012.jpg1176.

[0106] where V1 represents the volume of the positive electrode active material layer having a mass m, and its unit is cm 3 is.

[0107] V2 represents the volume of the active particles in the positive electrode active material layer with mass m, and its unit is cm 3 is.

[0108] m represents the mass of the positive electrode active material layer, and its unit is g.

[0109] Equation (2) can represent the rate at which a certain point on the electrode sheet almost completely absorbs the liquid (e.g., electrolyte) in the capillary within a unit time. In this application, a certain point on the electrode sheet refers to a region of the electrode sheet having a certain area, which corresponds to the cross-sectional area of ​​the capillary.

[0110] In the present application, a method for detecting the liquid absorption rate of an electrode sheet includes the following steps.

[0111] A predetermined amount of electrolyte is drawn up using a capillary tube.

[0112] The capillary tube is brought into contact with the electrode sheet, and the target measurement electrode sheet absorbs the electrolyte in the capillary tube by capillary action.

[0113] After a predetermined time t has passed, the liquid level h of the absorbed electrolyte in the capillary is recorded, and the amount of absorbed electrolyte is calculated based on the liquid level h, diameter d, and density ρ of the electrolyte in the capillary. The liquid absorption rate v of the electrode sheet is quantitatively calculated based on the ratio of the absorbed amount to the predetermined time t.

[0114] Illustratively, the value of d is between 0.2 and 1, for example, 0.2, and the value of h is between 3 and 5, for example, 3.

[0115] The capillary tube has a capillary channel that can directly absorb the electrolyte by capillary action, without the need for an external driving means to provide absorbing power. In this way, when absorbing the electrolyte by capillary action, the amount absorbed can be more accurately controlled. Meanwhile, the electrode sheet absorbs the electrolyte by its own capillary action. When the capillary tube contacts the target electrode sheet, the electrode sheet absorbs the electrolyte from the capillary, and when the electrode sheet is released from the contact, the electrolyte in the capillary does not flow out. Therefore, the amount of electrolyte absorbed by the electrode sheet can be accurately measured based on the amount of electrolyte absorbed in the capillary, which further improves the accuracy of the test results and enables the quantitative calculation of the absorption rate of the electrode sheet.

[0116] In this application, tests are conducted using a standard electrolyte as a test sample. For the specific formulation of the electrolyte, reference can be made to the electrolyte formulation in the examples.

[0117] Equation (3) shows the liquid absorption rate of the electrode sheet at the porosity λ and can represent the liquid absorption rate of the electrode sheet.

[0118] The polymer of this application is introduced into the manufacturing process of the active material layer, forms a uniform high wetting point inside the active material layer, and uniformly improves the wetting performance of the active material layer, thereby improving the liquid absorption rate of the entire active material layer and improving the cycle performance of the battery cell using the electrode sheet.

[0119] Optionally, 1.00 < v / λ < 50.00.

[0120] In some embodiments, 1.00 < v / λ < 4.00. Optionally, 1.20 ≤ v / λ ≤ 3.80. Further optionally, 1.4 ≤ v / λ ≤ 3.6. Exemplarily, v / λ may be 1.20, 1.40, 1.80, 2.00, 2.50, 3.00, 3.50, 3.60, 3.80, 3.90 or a range consisting of any two of the above numerical values.

[0121] In some embodiments, with respect to the mass of the positive electrode active material layer, the mass percentage of the polymer is A%, and 0.1 ≤ A ≤ 1.5.

[0122] When the mass percentage of the polymer is within the above range, the interfacial properties of the positive electrode active material layer can be significantly improved. Exemplarily, the mass percentage of the polymer may be 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5% or a range consisting of any two of the above numerical values.

[0123] The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material for battery cells known in the art. For example, the positive electrode active material may include at least one of a layered positive electrode active material (e.g., a ternary material, a lithium / sodium nickelate, a lithium / sodium cobaltate, a lithium / sodium manganate, a lithium-rich / sodium-rich layered material, and a rock salt phase layered material), an olivine-type phosphate active material, and a spinel-type positive electrode active material (e.g., a spinel lithium manganate, a spinel lithium nickel manganate, a lithium-rich spinel lithium manganate, and a lithium nickel manganate).

[0124] 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-a-b-c) Y z where 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 is one or more elements selected from Na, K, and Mg; M is one or more elements selected from 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; and Y is one or more elements selected from O and F. Optionally, y=0. Specifically, the layered positive electrode active material may be lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), or 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 O2 (NCM523) may be included.

[0125] For example, the general formula of the olivine-type phosphate active material is Li x A y Me a M b P 1-c X c Y z where 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 is one or more elements selected from Na, K, and Mg, Me is one or more elements selected from Mn, Fe, Co, and Ni, M is one or more elements selected from 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 is one or more elements selected from S, Si, Cl, B, C, and N, and Y is one or more elements selected from O and F. Specifically, the olivine-type phosphate active material includes at least eleven or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0126] For example, the general formula of the positive electrode active material with a spinel structure is Li x A y Mn a M 2-a Y z where 0≦x≦2, 0≦y≦1, and 0.9≦x+y≦2. 0.5≦a≦2. 3≦z≦5. A is one or more elements selected from Na, K, and Mg; M is one or more elements selected from 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; and Y is one or more elements selected from O and F. Specifically, the positive electrode active material having a spinel structure is LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiCr 0.3 Mn 1.7 O4, Li 1.1 Al 0.1Mn 1.9 O4, Li2Mn2O4 and Li 1.5 It contains one or more of Mn2O4.

[0127] In some embodiments, the positive electrode current collector may be a metal foil piece or a composite current collector. Examples of the metal foil piece include aluminum foil and aluminum alloy foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include one or more combinations selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymeric material base layer may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0128] In some embodiments, the positive electrode active material layer optionally further includes a positive electrode conductive agent. The type of positive electrode conductive agent is not particularly limited herein, and examples of the positive electrode conductive agent include one or a combination of two or more 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 5% or less of the total mass of the positive electrode active material layer.

[0129] In some embodiments, the positive electrode active material layer optionally further includes a positive electrode binder. The type of positive electrode binder is not particularly limited in the present application. For example, the positive electrode binder may include one or a combination of one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. In some embodiments, the mass percentage of the positive electrode binder is 5% or less with respect to the total mass of the positive electrode active material layer. The crystallinity of the positive electrode binder is higher than that of the aldehyde-ketone polymer of the present application. The melting temperature of the positive electrode binder is higher than that of the aldehyde-ketone polymer of the present application.

[0130] The positive electrode active material layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0131] Negative electrode sheet

[0132] In a third aspect, the present application provides a negative electrode sheet including a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, the negative electrode active material layer including a negative electrode active material and a polymer including the polymer described in any one of the examples of the first aspect of the present application.

[0133] As an example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0134] In some embodiments, the negative electrode active material layer satisfies the following formula: v / λ>1.00 Equation (4)

[0135] In formula (4),

[0136] λ represents the porosity of the negative electrode active material layer,

[0137] v represents the liquid absorption rate of the negative electrode active material layer, and its unit is mg / s.

[0138] The detection methods of λ and v are the same as those described for the positive electrode active material layer, and the description is omitted here.

[0139] In some embodiments, 3.00 < v / λ < 50.00, and optionally, 3.40 ≤ v / λ ≤ 30.00. Exemplarily, v / λ may be 3.20, 3.40, 3.50, 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, 7.00, 8.00, 9.00, 9.50, 10.00, 10.50, 11.00, 12.00, 13.00, 14.00 or a range consisting of any two of the above numerical values.

[0140] In some embodiments, with respect to the mass of the negative electrode active material layer, the mass percentage of the polymer is B%, and 0.2 ≤ B ≤ 5.0.

[0141] When the mass percentage of the polymer is within the above range, the interfacial properties of the negative electrode active material layer can be significantly improved. Exemplarily, the mass percentage of the polymer may be 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% or a range consisting of any two of the above numerical values.

[0142] In some embodiments, the negative electrode current collector may be a metal foil piece or a composite current collector. For example, copper foil may be used as the metal foil piece. The composite current collector may include a polymeric substrate and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0143] In some embodiments, the negative electrode active material may be a known battery negative electrode active material. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be at least one selected from silicon elemental, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from tin elemental, tin-oxygen compounds, and tin alloys. The present application is not limited to these materials, and other conventional materials usable as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination.

[0144] In some embodiments, the negative electrode active material layer optionally further comprises a negative electrode binder, which may be at least one selected from styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0145] In some embodiments, the negative electrode active material layer optionally further includes a conductive agent, which may be at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0146] In some embodiments, the negative electrode active material layer may optionally further include other auxiliary agents such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0147] In some embodiments, the negative electrode sheet can be obtained by dispersing the components for producing the negative electrode sheet, such as the negative electrode active material, the polymer, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, applying the negative electrode slurry to a negative electrode current collector, and then performing processes such as drying and cold pressing to obtain the negative electrode sheet.

[0148] Battery cell

[0149] In a fourth aspect, the present application provides a battery cell including a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, the battery cell being a lithium ion battery.

[0150] In some embodiments, the positive electrode sheet may be a positive electrode sheet according to any one of the second aspects of the present application, thereby improving the cycle performance and storage performance of the battery cell. The negative electrode sheet may be a conventional negative electrode sheet.

[0151] In some other embodiments, the negative electrode sheet may be a negative electrode sheet according to any one of the third aspects of the present application, thereby improving the cycle performance and storage performance of the battery cell. The positive electrode sheet may be a normal positive electrode sheet.

[0152] In yet another embodiment, the positive electrode sheet may be a positive electrode sheet according to any one of the embodiments of the second aspect of the present application, and the negative electrode sheet may be a negative electrode sheet according to any one of the embodiments of the third aspect of the present application, thereby improving the cycle performance and storage performance of the battery cell.

[0153] [Electrolytes]

[0154] The battery cell further includes an electrolyte that serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not specifically limit the type of electrolyte, and it can be selected as needed. The electrolyte may be, for example, liquid, gel, or all-solid.

[0155] In some embodiments, the electrolyte is an electrolytic solution, which includes an electrolyte salt and a solvent.

[0156] By way of example, the lithium salt may include one or more of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium difluorosulfonylimide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxaloborate (LiDFOB), lithium disoxaloborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorodisoxalophosphate (LiDFOP), and lithium tetrafluorooxalophosphate (LiTFOP).

[0157] By way of example, the organic solvent may comprise one or a combination of more selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), 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).

[0158] In some embodiments, the electrolyte solution optionally further includes an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve certain performance of the battery, such as an additive that improves the overcharge performance of the battery or an additive that improves the high-temperature or low-temperature performance of the battery.

[0159] [Separator]

[0160] In some embodiments, the battery cell further includes a separator. In the present application, the type of separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0161] In some embodiments, the separator may be made of one or a combination of materials selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0162] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be wound or laminated to form an electrode assembly.

[0163] In the present application, the shape of the battery cell is not particularly limited, and may be cylindrical, rectangular, or any other shape. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0164] In some embodiments, as shown in FIGS. 1 and 2 , the exterior may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a housing cavity. The case 51 has an opening communicating with the housing cavity, and the cover plate 53 covers the opening to close the housing cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is sealed in the housing cavity. The electrode assembly 52 is impregnated with an electrolyte. The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted as needed.

[0165] Methods for manufacturing the battery cell of the present application are well known. In some embodiments, a battery cell can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly by a winding process or a lamination process, and the electrode assembly can be placed in a housing. After drying, the electrode assembly can be infused with an electrolyte, and the battery cell can be obtained through processes such as vacuum sealing, standing, chemical conversion, and shaping.

[0166] In some embodiments of the present application, the battery cells of the present application may be assembled into a battery module, and the number of battery cells included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0167] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, the plurality of battery cells 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of battery cells 5 may be fixed by fasteners.

[0168] Optionally, the battery module 4 may further include a housing having an accommodation space in which the plurality of battery cells 5 are accommodated.

[0169] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0170] Both the battery module 4 and the battery pack can be specific examples of the battery of the present application.

[0171] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery case includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0172] power consumption equipment

[0173] According to a fifth aspect, the present application provides a power consuming device including at least one of the battery cell, battery module, and battery pack of the present application. The battery cell, battery module, and battery pack may use the power source of the power consuming device or may use the energy storage means of the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc.

[0174] A power consuming device can be selected from a battery cell, a battery module, or a battery pack depending on its usage needs. FIG. 6 is a schematic diagram of an example power consuming device. The power consuming device 6 may be an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like. To meet the requirements for high output and high energy density of the power consuming device, a battery pack 1 or a battery module may be adopted. Other examples of power consuming devices include mobile phones, tablet computers, and laptops. The power consuming device is usually required to be thin, and a battery cell may be adopted as a power source.

[0175] Example

[0176] The following examples of the present application are described. The examples described below are illustrative and are intended to explain the present application only and should not be construed as limiting the present application. Although specific techniques or conditions are not specified in the examples, they are carried out according to techniques or conditions described in literature in this field or according to product specifications. The reagents or equipment used are not specified by manufacturer and are all ordinary products available from commercial sources.

[0177] Example 1

[0178] (1) Manufacturing of positive electrode sheets

[0179] As the positive electrode current collector, an aluminum foil having a thickness of 12 μm is used.

[0180] A positive electrode slurry is prepared using an aldehyde-ketone polymer, a positive electrode active material (LiFePO4), a conductive agent (carbon black), and a binder (e.g., polyvinylidene fluoride and N-methylpyrrolidone (NMP)). The mass ratio of the aldehyde-ketone polymer, LiFePO4, conductive carbon black, PVDF, and N-methylpyrrolidone (NMP) in the positive electrode slurry is 0.5:96.8:2:0.7:29. The positive electrode slurry is applied to an aluminum foil current collector, dried at 85°C, cold-pressed, trimmed, cut, and stripped, and then dried in a vacuum at 85°C for 4 hours to produce a positive electrode sheet.

[0181] (2) Manufacturing of negative electrode sheets

[0182] A copper foil with a thickness of 8 μm is used as the negative electrode current collector.

[0183] The negative electrode slurry is prepared by uniformly mixing aldehyde-ketone polymer, artificial graphite as the negative electrode active material, carbon black as the conductive agent, styrene butadiene rubber (SBR) as the binder, sodium hydroxymethylcellulose (CMC) as the thickener, and deionized water in a weight ratio of 2.5:94:0.5:2:1:100. The negative electrode slurry is applied to a copper foil current collector and dried at 85°C. After that, it is cold pressed, trimmed, cut, and stripped, and then dried in a vacuum at 120°C for 12 hours to produce a negative electrode sheet.

[0184] (3) Electrolyte production

[0185] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 3:7 to obtain an electrolyte solvent, and then the resulting solvent is mixed with lithium salt LiPF6 to produce an electrolyte with a lithium salt concentration of 1 mol / L.

[0186] (4) Lithium-ion battery manufacturing

[0187] A 16 μm polyethylene film (PE) is used as the separator. The positive electrode sheet, separator, and negative electrode sheet are stacked in this order, with the separator positioned between the positive and negative electrode sheets to provide isolation, and then rolled up to obtain an electrode assembly. The electrode assembly is placed in an outer case, dried, and then an electrolyte is injected. After vacuum sealing, standing, chemical conversion, shaping, and other processes, a lithium-ion battery is obtained.

[0188] Comparative Example 1

[0189] A lithium ion battery was manufactured using a method similar to that of Example 1, except that no aldehyde-ketone polymer was added to the positive electrode sheet of Comparative Example 1, and no aldehyde-ketone polymer was added to the negative electrode sheet of Comparative Example 1.

[0190] Comparative Example 2

[0191] A lithium ion battery was manufactured in a manner similar to that of Example 1, except that the positive and negative electrode sheets of Comparative Example 2 were made of aldehyde-ketone polymer.

[0192] Examples 2 and 3

[0193] Lithium ion batteries were manufactured in a manner similar to that of Example 1, except that the positive and negative electrode sheets of Examples 2 and 3 were made of aldehyde-ketone polymer.

[0194] Example 4

[0195] A lithium ion battery was fabricated in a manner similar to that of Example 1, except that an aldehyde-ketone polymer was added to the positive electrode sheet of Example 4, and no aldehyde-ketone polymer was added to the negative electrode sheet of Example 4.

[0196] Example 5

[0197] A lithium ion battery was fabricated in a manner similar to that of Example 1, except that an aldehyde-ketone polymer was added to the negative electrode sheet of Example 5, but no aldehyde-ketone polymer was added to the positive electrode sheet of Example 5.

[0198] The data for the examples and comparative examples are shown in Table 1.

[0199] Testing section

[0200] 1. Lithium-ion battery capacity retention rate test

[0201] The lithium-ion batteries fabricated 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 0.05C at 4.25V, left for 5 minutes, and then discharged at 1 / 3C to 2.8V. The resulting capacity was designated 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 batteries, recording the discharge capacity, Cn, every 30 days. The battery capacity retention, Pn, is calculated as Cn / C0 × 100% every 30 days. A dot graph of battery capacity retention versus storage days was obtained by plotting the five points, P1, P2, ..., P5, on the ordinate and the corresponding storage time on the abscissa. The battery capacity retention data in Table 1 is the data obtained after 150 days of storage under the above test conditions, i.e., the value for P5.

[0202] 2. DC impedance test of lithium-ion batteries

[0203] The lithium-ion batteries prepared in the examples and comparative examples were charged at a constant current of 1 / 3 C to 4.25 V at 25°C, then charged at a constant voltage of 0.05 C at 4.25 V, and then left for 5 minutes. The voltage V1 was recorded. The batteries were then discharged at 1 / 3 C for 30 seconds, and the voltage V2 was recorded. This was calculated as (V2 - V1) / 1 / 3 C, giving the battery's internal resistance DCR1 after the first cycle. The batteries were then charged at a constant current of 1 / 3 C to 4.25 V at room temperature, then charged at a constant voltage of 0.05 C at 4.25 V, then left for 5 minutes. The resulting capacity was recorded as the initial capacity C0. The batteries were then adjusted to 97% state of charge (SOC) and stored at 60°C. The above steps are repeated for the same battery every 30 days, and the internal resistance DCRn (n=1, 2, 3, ..., 5) of the battery at the nth time is recorded. The five point values ​​DCR1, DCR2, DCR3, ..., DCR5 are plotted on the vertical axis, and the corresponding number of cycles is plotted on the horizontal axis, to obtain a graph showing the number of days the battery discharge DCIR is stored.

[0204] In Table 1, the increase rate of the internal resistance of the battery = (DCRn-DCR1) / DCR1 x 100%, and the data in Table 1 is data obtained after the test was performed under the above test conditions after storing for 150 days.

[0205] In Table 1, the increase rate of the internal resistance of the battery = (DCRn-DCR1) / DCR1 x 100%, and the data in Table 1 is data obtained after the test was performed under the above test conditions after storing for 150 days.

[0206] Test results

[0207] JPEG2025531274000013.jpg89163

[0208] In Table 1, 100% formaldehyde means that the mass percentage of formaldehyde relative to the total mass of Monomer 1 and Monomer 2 is 100%.

[0209] 30% polyvinyl alcohol means that the mass percentage of polyvinyl alcohol is 30% relative to the total mass of cell 1 and cell 2.

[0210] As can be seen from Table 1, compared to Comparative Example 1, the Examples of the present application, in which the polymer of the present application was added to the positive electrode sheet and / or negative electrode sheet, exhibited improved cycle performance and storage performance of the lithium-ion battery. Compared to Comparative Example 2, the Examples of the present application, in which 0.8≦K<∞ was satisfied, particularly 0.8≦K≦100, and further 0.8≦K≦10, tended to have sparse molecular chain arrangements, weak interchain forces, and easily opened adjacent molecular chains, allowing segmental motion through intramolecular rotation, forming a molecular chain structure with high flexibility, resulting in more significant improvements in cycle performance and storage performance of the lithium-ion battery.

[0211] While the present application has been described above with reference to preferred embodiments, various modifications may be made thereto without departing from the spirit of the present application, and equivalent components may be substituted. In particular, the technical features described in each embodiment may be combined in any manner as long as there is no structural contradiction. The present application is not limited to the specific embodiments disclosed herein, but includes all technical means falling within the scope of the claims. [Explanation of symbols]

[0212] 1 battery pack 2 Upper housing 3 Lower housing 4 Battery Module 5 battery cells 51 cases 52 Electrode Assembly 53 Lid plate 6 Power consumption equipment

Claims

1. A polymer applied to a battery cell, comprising an aldehyde-ketone polymer, The aldehyde-ketone polymer is formed into a sheet-like structure, and a G'-G" curve of the sheet-like structure is obtained by a dynamic frequency scanning test at (Tm+20)°C, the slope of the G'-G" curve is K, and 0.8≦K<∞, and Tm°C represents the melting temperature of the aldehyde-ketone polymer. A polymer characterized by:

2. 0.8≦K≦100, optionally 0.8≦K≦10; The polymer of claim 1.

3. the glass transition temperature of the aldehyde-ketone polymer is Tg, in ° C., -100≦Tg≦50, optionally -80≦Tg≦30; The polymer according to claim 1 or 2.

4. The aldehyde-ketone polymer comprises a structural unit represented by formula (I): In formula (I), R 1 includes a single bond, a substituted or unsubstituted C1 to C6 methylene group, and R 2 contains a hydrogen atom or a substituted or unsubstituted C1 to C6 alkyl group, Optionally, R 1 contains a single bond, a substituted or unsubstituted C1-C2 methylene group, Optionally, R 2 includes a hydrogen atom or a substituted or unsubstituted C1-C3 alkyl group; The polymer of any one of claims 1 to 3.

5. The aldehyde-ketone polymer contains at least one structural unit represented by formula (I-1) to formula (I-6): The polymer of claim 4.

6. The aldehyde-ketone polymer comprises a structural unit represented by formula (II): In formula (II), R 3 ~R 6 each independently comprises a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1 to C3 alkyl group, a substituted or unsubstituted C1 to C3 hydroxyalkyl group, or a substituted or unsubstituted C1 to C3 alkoxy group, r and s each independently represent an integer selected from 0 to 5, and at least one of r and s is selected from a positive integer; Optionally, R 3 ~R 6 each independently contains a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1 to C3 alkyl group, a substituted or unsubstituted C1 to C2 hydroxyalkyl group, or a substituted or unsubstituted C1 to C2 alkoxy group, The polymer of any one of claims 1 to 5.

7. The aldehyde-ketone polymer contains at least one structural unit represented by formula (II-1) to formula (II-4): The polymer of claim 6.

8. n is a positive integer between 500 and 15,000, and / or The molecular weight of the aldehyde-ketone polymer is 1.2×10 5 g / mol~1.0×10 6 g / mol, The polymer of any one of claims 4 to 7.

9. A positive electrode sheet, a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material and a polymer, The polymer comprises a polymer according to any one of claims 1 to 8. A positive electrode sheet characterized by:

10. A negative electrode sheet, a negative electrode current collector; and a negative electrode active material layer provided on the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material and a polymer, The polymer comprises a polymer according to any one of claims 1 to 8. A negative electrode sheet characterized by:

11. A battery cell including a positive electrode sheet and a negative electrode sheet, The positive electrode sheet includes the positive electrode sheet according to claim 9 , and / or The negative electrode sheet includes the negative electrode sheet according to claim 10. A battery cell characterized by:

12. A battery comprising the battery cell of claim 11.

13. 13. A power consuming device comprising the battery of claim 12.

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