Lithium secondary batteries and power consuming devices

Abstract

This application provides an ester-based polymer, a polar plate, and related battery cells, batteries, and power consumption devices. The ester-based polymer is added to a first solvent at 45°C to form an ester-based polymer system. The ester-based polymer system is allowed to stand at 45°C for 8 hours, and then allowed to stand at 25°C for ≥ 24 hours. The ester-based polymer system is then filtered through a 200-mesh filter to leave a first substance, where the mass of the ester-based polymer is n (g), the mass of the first substance is m (g), and the ratio of the ester-based polymer and the first substance satisfies 5 ≤ ​​m / n ≤ 1000. When the ester-based polymer is used in a battery cell, it can improve the cycle performance of the battery cell.

Description

[Technical Field]

[0001] This application relates to the field of batteries, and more particularly to ester-based polymers, plates and related 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 power-consuming devices such as mobile phones, laptops, battery-powered vehicles, electric cars, electric airplanes, electric steamships, electric toy cars, electric toy steamships, electric toy airplanes, and power tools.

[0003] As the range of battery applications becomes wider, the requirements for battery cell performance are becoming increasingly stringent. To improve the safety performance of battery cells, the performance of the electrodes in the battery cells is generally optimized and improved. However, the active material in current electrodes has relatively poor electrolyte storage capacity, and when used in battery cells, the cycle performance of the battery cells is relatively poor. Summary of the Invention

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

[0005] A first aspect of the present application provides an ester-based polymer for use in a battery cell, comprising adding the ester-based polymer to a first solvent at 45°C to form an ester-based polymer system, allowing the ester-based polymer system to stand at 45°C for 8 hours and then at 25°C for ≥24 hours, and then filtering the ester-based polymer system through a 200-mesh filter to leave a first substance, wherein the mass of the ester-based polymer is n (g), the mass of the first substance is m (g), and the ratio of the ester-based polymer and the first substance satisfies 5≦m / n≦1000. When the ester-based polymer satisfies the above condition, the cycle performance and storage performance of the battery cell can be further improved.

[0006] As a result, the ester-based polymer of the present application can achieve molecular chain extension within the relatively high safe operating temperature range of the secondary battery, and can promote the mutual attraction and physical bonding between the ester-based polymer molecular chain and the solvent in the electrolyte, which is advantageous for the bonding between the ester-based polymer molecular chain and the solvent, thereby storing the electrolyte in the active material layer. The ester-based polymer may not be mobile within the relatively low safe operating temperature range of the secondary battery, and the ester-based polymer adheres to the active material surface to maintain a state in which the electrolyte is retained in the spatial environment where the ester-based polymer is located, which can improve the storage capacity of the active material layer and provide relatively good infiltration performance of the electrolyte into the active material layer, thereby improving the cycle performance of the secondary battery using the ester-based polymer.

[0007] In some embodiments, 10≦m / n≦1000, and more preferably, 10≦m / n≦50. When the ester-based polymer satisfies the above conditions, the cycle performance of the battery cell can be further improved.

[0008] In some embodiments, the first solvent comprises a cyclic carbonate solvent and / or a linear carbonate solvent; Optionally, the cyclic carbonate solvent comprises one or more of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC; Optionally, the linear carbonate solvent comprises one or more of dimethyl carbonate DMC, diethyl carbonate DEC, ethyl methyl carbonate EMC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate VA.

[0009] In some embodiments, the ester-based polymer is fabricated as a sheet-like structure, and the sheet-like structure comprises (T m+20°C, a dynamic frequency scanning test was carried out to obtain the elastic modulus G'-loss elastic modulus G" curve, and the slope of the elastic modulus G'-loss elastic modulus G" curve was K, and <K<∞であり、T m ° C. represents the melting temperature of the ester polymer.

[0010] Therefore, when the ester-based polymer of the present application satisfies the above range, it can further reduce the entanglement of molecular chains, which is favorable for the diffusion of solvent molecules between molecular chains in the electrolyte, and the ester-based polymer still maintains a certain entanglement of molecular chains, which can retain the solvent molecules in situ inside the polymer, reducing the risk of the ester-based polymer dissolving in the electrolyte and improving the stability of the ester-based polymer performance. It is also favorable for the ester-based polymer to form a protective layer on the surface of the active material and improve the solid-liquid interface performance, reducing side reactions between the active material and the electrolyte and improving the cycle performance of the battery cell.

[0011] In some embodiments, the glass transition temperature of the ester-based polymer is Tg, expressed in °C, in the range of -100 < Tg < 50, and optionally in the range of -80 < Tg < 30. The relatively low glass transition temperature of the ester-based polymer allows the chain segments of the molecular chain to have better flexibility, allowing adjacent molecular chains to open more easily and form an in-situ gel, thereby enhancing the infiltration of the electrolyte into the active material layer and thereby improving the cycling performance of the battery cell.

[0012] In some embodiments, the ester-based polymer comprises a structural unit according to formula (I): [ka] In formula (I), R1, R2 and R3 each independently comprise a hydrogen atom or a substituted or unsubstituted C1 to C8 alkyl group, R4 comprises a substituted or unsubstituted C1 to C8 alkyl group or a substituted or unsubstituted C1 to C8 hydroxyalkyl group, and optionally R1 comprises a hydrogen atom or a substituted or unsubstituted methyl group, R2 and R3 each independently comprise a hydrogen atom, R4 comprises a substituted or unsubstituted C1 to C6 alkyl group or a substituted or unsubstituted C1 to C6 hydroxyalkyl group, and R4 comprises a substituted or unsubstituted C1 to C4 alkyl group or a substituted or unsubstituted C1 to C4 hydroxyalkyl group.

[0013] In some embodiments, the ester-based polymer comprises a structural unit represented by formula (I-1) to a structural unit represented by formula (I-15): [ka] [ka] It includes at least one of the following.

[0014] In some embodiments, the ester-based polymer comprises a structural unit shown in formula (II): [ka] In formula (II), R5 comprises a substituted or unsubstituted C2 to C6 methylene group, and alternatively, R5 comprises a substituted or unsubstituted C2 to C4 methylene group.

[0015] In some embodiments, the ester-based polymer comprises a structural unit represented by formula (II-1) to a structural unit represented by formula (II-5): [ka] It includes at least one of the following.

[0016] In some embodiments, n is a positive integer selected from 800 to 20,000, and / or the molecular weight of the ester-based polymer is 1.2×10 5 g / mol ~ 1.0 × 10 6 g / 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 not easily completely dissolved and dispersed by the electrolyte, which is favorable for adjusting the distribution and dispersion of the polymer on the surface of the active material, and 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 favorable for the solvent molecules in the electrolyte to open the molecular chains, enter between the molecular chains, and be wrapped by the molecular chains, which is favorable for the active ions to enter the active material through the solvent, and realize the smooth and fast movement of the active ions.

[0017] A second aspect of the present application provides a positive electrode plate, the positive electrode plate including a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, the positive electrode film layer including a positive electrode active material and an ester-based polymer, and the ester-based polymer including the ester-based polymer described in any one of the embodiments of the first aspect of the present application.

[0018] A third aspect of the present application provides a negative electrode plate, the negative electrode plate including a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector, the negative electrode film layer including a negative electrode active material and an ester-based polymer, and the ester-based polymer including the ester-based polymer described in any one of the embodiments of the first aspect of the present application.

[0019] A fourth aspect of the present application provides a battery cell including a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises the positive electrode plate according to any one of the embodiments of the second aspect of the present application, and / or the negative electrode plate comprises the negative electrode plate according to any one of the embodiments of the third aspect of the present application.

[0020] A fifth aspect of the present application provides a battery, the battery including the battery cell according to the fourth aspect of the present application.

[0021] A sixth aspect of the present application provides a power consuming device, the power consuming device comprising a battery according to the fifth aspect of the present application. [Brief explanation of the drawings]

[0022] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application. It is obvious that the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without exerting any creative efforts. [Figure 1] 1 is a schematic diagram of one 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 one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] FIG. 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.The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments specifically disclosing the ester-based polymer, electrode plate, and related battery cell, battery, and power consumption device of the present application will be described in detail. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of structures that are actually the same may be omitted. This is to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Note that the 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.

[0024] The "ranges" disclosed in this application 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, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and any combination is possible; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also possible. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all possible. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents that the present specification has already listed all real numbers between "0-5," and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] 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.

[0026] Unless otherwise stated, all steps in this application may be performed in order or randomly, preferably in order. For example, a method including steps (a) and (b) 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, a method that may further include step (c) means that step (c) may be added to the method in any order, e.g., 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.

[0027] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open-ended or closed-ended. For example, "comprise" and "comprises" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included.

[0028] 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, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0029] As used in this application, the terms "plurality" and "plurality" refer to two or more.

[0030] The term "alkyl group" covers straight-chain and branched-chain alkyl groups. For example, the alkyl group may 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, the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and the like. The alkyl group may also be optionally substituted. When substituted, the substituent may include a fluorine atom.

[0031] The term "alkoxy group" refers to a group in which an alkyl group and an oxygen atom are connected 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. Additionally, the alkoxy group may be optionally substituted.

[0032] The term "halogen atom" refers to fluorine atom, chlorine atom, bromine atom, and the like.

[0033] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In some embodiments, "hydrogen" may be 1H (protium, H).

[0034] A secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, and the electrolyte permeates the positive electrode plate and the negative electrode plate, thereby realizing smooth movement of active ions between the positive electrode plate and the negative electrode plate.

[0035] An electrode plate (e.g., a positive electrode plate and / or a negative electrode plate) includes a current collector and an active material layer disposed on at least one surface of the current collector. The active material layer has a pore structure, and the electrolyte diffuses from the surface of the active material into the active material layer through this pore structure, thereby allowing the active material layer to be infiltrated with the electrolyte and allowing active ions to smoothly migrate from the positive electrode plate to the negative electrode plate.

[0036] In related art, the active material layer often exhibits relatively poor electrolyte affinity, resulting in relatively poor electrolyte infiltration into the active material layer, and therefore relatively poor electrolyte storage capacity of the active material layer. During the use, transportation, or assembly of a secondary battery as a module, the secondary battery may be subjected to external pressure, which may cause the electrolyte in the active material layer to be pressed out of the active material layer, making it gradually difficult for the electrolyte to be sucked back, resulting in a decrease in secondary battery capacity and a deterioration in the cycle performance of the secondary battery.

[0037] In view of the above problems, the embodiment of the present application improves the electrolyte storage capacity of the electrode plate by adding an ester-based polymer to the electrode plate, thereby improving the affinity between the electrode plate and the electrolyte and improving the infiltration performance of the electrolyte into the electrode plate, thereby improving the cycle performance of a secondary battery that employs the ester-based polymer.

[0038] Ester-based polymer According to a first aspect, the present application proposes an ester-based polymer for use in a battery cell. The ester-based polymer is added to a first solvent at 45°C to form an ester-based polymer system. The ester-based polymer system is then allowed to stand at 45°C for 8 hours and then at 25°C for ≥24 hours. After undergoing two-stage settling treatment, the ester-based polymer system is partially transformed into a gel-state substance in situ. The ester-based polymer system is then filtered through a 200-mesh filter to leave a first substance. After filtering the ester-based polymer system through the 200-mesh filter, the fluid phase solvent is filtered, and the residue, i.e., the first substance, is retained. The mass of the ester-based polymer is n (g), and the mass of the first substance is m (g), and the ratio of the ester-based polymer and the first substance satisfies 5≦m / n≦1000, optionally 10≦m / n≦1000, and more optionally 10≦m / n≦50. Illustratively, 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 above values.

[0039] Exemplarily, based on the mass of the ester-based polymer system, the ratio range of the mass content of the ester-based polymer to the mass content of the first solvent is 1:100 to 1:10, for example, 3:50.

[0040] For example, the first solvent and the solvent of the electrolyte may be the same or similar, and the first solvent may include a carbonate-based solvent, such as a cyclic carbonate solvent and / or a chain carbonate solvent.

[0041] Examples of cyclic carbonate solvents include one or more of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC.

[0042] Examples of the linear carbonate solvent 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.

[0043] Alternatively, the first solvent may simultaneously contain a lithium salt and an electrolyte additive, such as lithium hexafluorophosphate, vinylene carbonate (VC), fluorovinylene carbonate (FEC), and the like.

[0044] In this application, m / n is also referred to as the sedimentation value, which characterizes the ability of an ester-based polymer and solvent to transform into a gel-state material.

[0045] The first substance includes a gel-state substance formed mainly from the ester-based polymer and the first solvent, and in such a gel-state substance, the molecular structure of the ester-based polymer hardly changes.

[0046] In some embodiments, the first substance is dried at 80°C for 12 hours to remove the first solvent in the first substance, and detection by infrared spectrophotometry (IR) or nuclear magnetic resonance (NMR) test is performed. The main component of the first substance after drying is the aforementioned ester-based polymer.

[0047] The ester-based polymer can realize the stretching of the molecular chain within a relatively high safe operating temperature range of the secondary battery, and can promote the mutual attraction and physical bonding between the ester-based polymer molecular chain and the solvent in the electrolyte. It is advantageous for the bonding between the ester-based polymer molecular chain and the solvent, thereby storing the electrolyte in the active material layer. The ester-based polymer may not have mobility within a relatively low safe operating temperature range of the secondary battery. The ester-based polymer adheres to the surface of the active material and maintains the state of holding the electrolyte in the spatial environment where the ester-based polymer is located, which can improve the liquid storage capacity of the active material layer, and the infiltration performance of the electrolyte into the active material layer is relatively good, thereby improving the cycle performance of the secondary battery employing the aforementioned ester-based polymer.

[0048] This application can realize the stretching of the ester-based polymer molecular chain within the safe operating temperature range of the battery cell by raising the temperature, and can promote the mutual attraction and physical bonding between the ester-based polymer molecular chain and the solvent. At room temperature, the activity of the ester-based polymer molecular chain segments decreases, adheres to the surface of the active material, and maintains the electrolyte in the spatial environment where the ester-based polymer is located, forming a state similar to an in-situ gel, improving the liquid storage capacity of the active material, and improving the cycle performance.

[0049] In some embodiments, the ester-based polymer is fabricated as a sheet-like structure. The sheet-like structure undergoes a dynamic frequency scanning test at (Tm + 20)°C to obtain a storage modulus G'-loss modulus G" curve. The slope of the storage modulus G'-loss modulus G" curve is K, where 1 < K < ∞, 1 < K ≤ 100, and optionally, 1 < K ≤ 10. Tm°C represents the melting temperature of the ester-based polymer.

[0050] Illustratively, K may be 1.01, 1.1, 1.2, 1.5, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the foregoing values.

[0051] 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 flat-plate vulcanizer, with the hot-press temperature set to (Tm+20)°C, the rolled thickness set to 1-2 mm, the press delay set to 2 min, and the pressure set to 8 MPa. After 2 min of rolling, the sample is removed and placed on 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 fixed-size polymer wafer (sheet-like structure). For example, the sheet-like structure may be a wafer with a thickness of 1-2 mm and a diameter of 25 mm. Samples may be prepared according to the sample specifications required for the test equipment.

[0052] According to the classical chain viscoelasticity conclusion, for polymers, especially chain polymers, the elastic modulus G'-loss modulus G" curve in the terminal region (the range approaching the maximum angular velocity) conforms to a frequency dependence, and the longest chain of the polymer influences the viscoelastic behavior.

[0053] The specific steps of the dynamic frequency scan test are as follows: a TA-AR2000EX rotational rheometer (TA Instruments, USA) is used to perform the dynamic frequency scan test. The parallel plates have a diameter of 25 mm and a thickness of 0.9 mm. To ensure that the test is in the linear bullet region, the strain during the dynamic frequency scan test is 2%, the test temperature is Tm + 20°C, and the frequency scan range of the test is 500 rad / s or less. 2 ≦0.05 rad / s, and to obtain data in the lowest frequency range possible.

[0054] Dynamic frequency sweep tests can characterize the degree of molecular chain entanglement in solid-state melting (molten state). Compared with linear or short-branched structures, long-branched, network, and low-crosslinked structures have a higher degree of entanglement and exhibit behavior that deviates from linear end-points, resulting in a polymer exhibiting solid-state behavior. When the polymer of the present application satisfies the above range, the molecular chain entanglement can be further reduced, favoring the diffusion of solvent molecules between the molecular chains in the electrolyte, while the polymer still maintains a certain molecular chain entanglement, allowing the solvent molecules to be retained in situ within the polymer and reducing the risk of the polymer dissolving in the electrolyte. This can improve the performance stability of the ester-based polymer, and is also beneficial for the polymer to form a protective layer on the surface of the active material, improving solid-liquid interfacial performance, reducing side reactions between the active material and the electrolyte, and improving the cycle performance and storage performance of the battery cell.

[0055] In some embodiments, the glass transition temperature of the ester-based polymer is Tg, in degrees Celsius, and is −100≦Tg≦50, and optionally −80≦Tg≦30.

[0056] The glass transition temperature is the transition temperature at which the chain segments of an ester polymer transition from freezing to movement. The glass transition temperature has a certain effect on the flexibility of the ester polymer molecular chain. The lower the glass transition temperature, the better the flexibility of the ester polymer molecular chain at room temperature. The higher the glass transition temperature, the worse the flexibility of the molecular chain at room temperature. The glass transition temperature can be measured by differential scanning calorimetry (DSC). Specifically, the test steps are as follows: take a sample of 0.5g-0.8g, place the sample in a crucible, and heat the sample in a nitrogen gas atmosphere. The temperature is increased at a rate of 10°C / min from an initial temperature 20°C lower than the intrinsic Tg of the material to a cutoff temperature 20°C higher than the intrinsic Tm of the material. The actual glass transition temperature (Tg) and melting temperature (Tm) of the material are determined according to the endothermic peak or transition point of the material during the process.

[0057] The glass transition temperature of the ester-based polymer is relatively low, the chain segments of the molecular chain are more flexible, and adjacent molecular chains are more likely to open. For example, the glass transition temperature of the ester-based 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.

[0058] In some embodiments, the ester-based polymer comprises a structural unit according to formula (I): [ka] In formula (I), R1, R2, and R3 each independently represent a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R4 represents a substituted or unsubstituted C1-C8 alkyl group or a substituted or unsubstituted C1-C8 hydroxyalkyl group; Optionally, R1 comprises a hydrogen atom or a substituted or unsubstituted methyl group; Alternatively, R2 and R3 each independently comprise a hydrogen atom; Alternatively, R4 comprises a substituted or unsubstituted C1-C6 alkyl group or a substituted or unsubstituted C1-C6 hydroxyalkyl group; Optionally, R4 comprises a substituted or unsubstituted C1 to C4 alkyl group, or a substituted or unsubstituted C1 to C4 hydroxyalkyl group.

[0059] For example, the ester-based polymer may include structural units represented by formula (I-1) to structural units represented by formula (I-15): [ka] [ka] It includes at least one of the following.

[0060] In some embodiments, the ester-based polymer comprises a structural unit shown in formula (II): [ka] In formula (II), R5 comprises a substituted or unsubstituted C2 to C6 methylene group, and alternatively, R5 comprises a substituted or unsubstituted C2 to C4 methylene group.

[0061] In some embodiments, the ester-based polymer comprises a structural unit represented by formula (II-1) to a structural unit represented by formula (II-5): [ka] It includes at least one of the following.

[0062] The degree of entanglement of the ester polymer molecular chains is relatively low, which is advantageous for improving the flexibility of the molecular chains, and the molecular chains can be sufficiently extended in the electrolyte, thereby further improving the interfacial performance of the active material.

[0063] The above polymers are merely examples of structural groups in the main molecular chain, and in embodiments of the present application, the polymers may be obtained by copolymerizing the above structural groups with other types of structural groups (e.g., olefin-based structural units, acrylonitrile-based structural units, etc.).

[0064] The groups of the polymer of the present application can be detected by infrared spectrophotometry (IR). Specifically, the polymer is tested using a ThermoNicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR) and is tested in accordance with the standard GB / T6040-2002. The test range is ATR 600-4000 cm -1 , Reproducibility: ±2cm -1 , Resolution: 4cm -1 It has a better penetration depth of 0.2-0.6 μm.

[0065] The structure of the polymers of the present application can be tested by nuclear magnetic resonance NMR, specifically, 1H NMR and 13C NMR were performed on a Varian MercuryPlus-400 nuclear magnetic resonance instrument, with a test temperature of 20°C, TMS as the internal standard, CDCl3 as the solvent, and a proton resonance frequency of 400 MHz.

[0066] The polymer monomer type of this application (especially applicable to monomers with a relatively small proportion in the polymer) can be carried out by decomposition-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, and then attached to a sample injection rod, and then placed in a cracker installed near the GC (gas chromatography) sample injection port. After the temperature of the cracker reaches the set temperature, the sample injection button is pressed, and the sample cup falls rapidly into the core of the decomposition furnace by free fall. In the inert gas N2 atmosphere, the volatile components are instantly gasified and carried by the carrier gas into the gas chromatography column for separation, and finally detected by a flame ionization detector FID or a mass spectrometer MS, thereby obtaining a gas chromatograph or total ion current graph.

[0067] When the above groups are substituted, the substituents may include one or more of a nitrile group, 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 substituents, which are further advantageous in stabilizing the structure of the polymer.

[0068] In some embodiments, n is a positive integer selected from the range of 800 to 20,000.

[0069] Optionally, n is a positive integer selected from 1,000 to 15,000.

[0070] In some embodiments, the molecular weight of the polymer is 1.2×10 5 g / mol ~ 1.0 × 10 6 g / mol.

[0071] When the molecular weight of the polymer is within the above range, it can ensure that the polymer exhibits a certain solubility in the electrolyte, and is not easily 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, and can further improve the flexibility between the molecular chains of the polymer, and the 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 wrapped by the molecular chains, thereby advantageous for the active ions to enter the active material through the solvent, and realize the smooth and fast movement 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, 1.5 × 10 6 It may be g / mol or a range consisting of any two of the above values.

[0072] The molecular weight of ester polymers is a known term in the art and can be measured by using instruments and methods commonly used in the art. It can be tested by using gel permeation chromatography (GPC). The specific test steps are as follows: take an appropriate amount of sample to be measured (sample concentration should ensure 8%-12% light blocking), add 20ml of deionized water, and wait for more than 5 minutes (53KHz / 120W) to ensure the sample is completely dispersed, then measure the sample according to GB / T19077-2016 / ISO13320:2009 standard.

[0073] Alternatively, a multi-angle laser scattering analyzer (MALLS) was used for the test, specifically, a GPC with a DawnHeleos II multi-angle laser light scattering device, an OptilabT-rEX refractive index (RI) detector, and a ViscoStar II viscometer (Wyatt Technology Corporation, USA). The test was conducted at 30°C using tetrahydrofuran as the flow phase at a flow rate of 1.0 ml / min. The commercial software ASTRA6 was used to process the SEC-SAMLL data and obtain molecular weight parameters.

[0074] positive electrode plate According to a second aspect, the present application proposes a positive electrode plate, the positive electrode plate including a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, the positive electrode film layer including a positive electrode active material and an ester-based polymer, and the ester-based polymer including the ester-based polymer described in any one of the embodiments of the first aspect of the present application.

[0075] For example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0076] The electrode plate may be prepared by applying the slurry to a current collector, drying it, and cold pressing it. Alternatively, the electrode plate may be derived from a battery cell, and may be prepared by disassembling the battery cell, removing the electrode plate that is immersed in the electrolyte from the battery cell, and subjecting the electrode plate to vacuum drying at 100°C for 12 hours to obtain the electrode plate, which can be used for electrode plate tests such as liquid absorption rate.

[0077] Ester-based polymers can be synthesized using methods such as emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization. Alternatively, ester-based polymers can be derived from battery cells. The battery cells are disassembled, and the electrodes immersed in the electrolyte are removed. The active material from the electrodes is peeled from the current collectors by external force to form a powder sample. This powder is then added to dimethyl carbonate (DMC) and stirred at 500 rpm for 8 hours at 80°C. After stirring, the sample is allowed to stand at room temperature for 10 minutes. The supernatant is then dried at 80°C for 12 hours to obtain the ester-based polymer. The resulting ester-based polymer may contain a small amount of lithium salt, but this has little effect on infrared and sedimentation tests. To ensure the accuracy of the ester-based polymer, the lithium salt can be separated by further washing with DMC at room temperature.

[0078] In some embodiments, the positive electrode active material layer satisfies the following:

number

[0079] In the present application, the actual compaction density P1 is the ratio of the mass of the positive electrode active material layer per unit area of ​​the electrode plate to the thickness. The actual compaction density is determined by the force applied by the roller after coating the electrode plate, and is expressed in units of g / cm. 3 The specific test steps are to take an electrode plate with a certain area S, measure the mass M of its positive electrode active material layer, and measure the thickness D of the positive electrode active material layer, and the actual compaction density = M / (S × D).

[0080] In this application, the true packed density P2 refers to the density of the positive electrode active material itself in the positive electrode active material layer, and specifically refers to the mass of the unit "actual volume of the solid material (excluding open pores, closed pores, and inter-particle voids)" in a dense state. It is obtained by testing the true volume V, and then calculating the true packed density based on P=m / V. This can be tested with reference to GB / T24586-2009. Specifically, the test steps are as follows:

[0081] 1) Pretreatment: Take a clean and dry sample cup and place it on the balance, clear it, add the powder sample to the sample cup, occupying about 1 / 2 of the volume of the sample cup, and record the sample mass; 2) Place the sample cup containing the sample in the true density tester, seal the test system, pass helium gas through it according to the procedure, detect the gas pressure in the sample chamber and the expansion chamber, and then calculate the true compacted density by calculating the true volume based on Bohr's law (PV=nRT).

[0082] Here, the volume of the sample cup is 3.5 cm 3 , analysis gas: helium gas.

[0083] Equation (1) can calculate the porosity λ of the active material layer based on the actual compaction density and the true compaction density.

[0084] in particular,

number

[0085] Here, V1 represents the volume of the positive electrode active material layer per mass m, and its unit is cm 3 and V2 represents the volume occupied by the active particles in the positive electrode active material layer in mass m, and its unit is cm 3 and m represents the mass of the positive electrode active material layer, and its unit is g.

[0086] Equation (2) can characterize the rate at which a point on a plate nearly completely absorbs the liquid (e.g., electrolyte) in the capillary per unit time. In this application, a point on a plate refers to a region of the plate having a certain area, which corresponds to the cross-sectional area of ​​the capillary.

[0087] In this application, the method for detecting the liquid absorption rate of the electrode plate is as follows: Aspirating a predetermined amount of electrolyte using a capillary tube; Bringing the capillary tube into contact with the electrode plate, the electrode plate to be measured absorbs the electrolyte in the capillary tube by capillary action; and a step of recording the liquid level h at which the electrolyte in the capillary is absorbed after a predetermined time t has elapsed, calculating the amount of electrolyte absorbed based on the liquid level h, diameter d, and density ρ of the electrolyte in the capillary, and quantitatively calculating the liquid absorption rate v of the electrode plate based on the ratio of the absorbed amount to the predetermined time t.

[0088] Illustratively, the d value is between 0.2 and 1, for example, the value is 0.2, and the h value is between 3 and 5, for example, the value is 3.

[0089] The capillary has a capillary channel, whereby the capillary does not need to be provided with a liquid suction power by an external driving unit and can directly suck the electrolyte by capillary action. Thus, when sucking the electrolyte by capillary action, the suction amount can be more accurately controlled. On the other hand, since the electrode plate absorbs the electrolyte by its own capillary action, only when the capillary contacts the electrode plate to be measured, the electrode plate sucks the electrolyte out of the capillary. When separating from the contact, the electrolyte in the capillary does not flow out, so that the amount of the electrolyte absorbed in the capillary accurately reflects that the electrode plate has absorbed the corresponding volume of the electrolyte, further improving the test result accuracy and realizing the quantitative calculation of the absorption rate of the electrode plate for absorbing the electrolyte.

[0090] In this application, a standard electrolyte is used as a test sample for testing, and the specific formulation of the electrolyte may refer to the formulation of the electrolyte in the examples.

[0091] Equation (3) represents the liquid suction rate of the electrode plate at the porosity λ and may be used to characterize the liquid suction speed of the electrode plate.

[0092] By introducing the ester-based polymer of this application in the manufacturing process of the active material layer, a uniform high wetting point is formed inside the active material layer, and by uniformly enhancing the wetting performance of the active material layer, the liquid suction speed of the whole active material layer is increased, thereby improving the cycle performance of the battery cell adopting the electrode plate.

[0093] Optionally, 1.00 < v / λ < 50.00.

[0094] In some embodiments, 1.00 < v / λ < 4.00, optionally, 1.20 ≤ v / λ ≤ 3.80, and 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.

[0095] In some embodiments, the mass content of the ester-based polymer is A %, based on the mass of the positive electrode active material layer, where 0.1≦A≦1.5.

[0096] When the mass content of the ester-based polymer is within the above range, the interfacial performance of the positive electrode active material layer can be significantly improved. For example, the mass content of the ester-based 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 values.

[0097] The positive electrode film layer includes a positive electrode active material, which may be a positive electrode active material known in the art and used in battery cells. 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 / sodium-rich layered material, and a rock salt 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).

[0098] For example, the general formula of the layered positive electrode active material is Li x A y Ni a Co b Mn c M (1-a-b-c) Y zwhere 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, and 1.8≦z≦3.5; A is one or more selected from Na, K, and Mg; M is one or more 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 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.

[0099] 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 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 is one or more selected from Na, K, and Mg; Me is one or more selected from Mn, Fe, Co, and Ni; M is one or more 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 selected from S, Si, Cl, B, C, and N; and Y is one or more selected from O and F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0100] For example, the general formula of the positive electrode active material having 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 selected from Na, K, and Mg, M is one or more 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 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 0.1 Mn 1.9 O4, Li2Mn2O4 and Li 1.5 Mn2O4.

[0101] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. Examples of the metal foil sheet include aluminum foil or aluminum alloy foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include one or more combinations selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymer base layer may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0102] In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. The present application is not particularly limited to the type of positive electrode conductive agent, and examples of the positive electrode conductive agent include 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 content of the positive electrode conductive agent is 5% or less, based on the total mass of the positive electrode film layer.

[0103] In some embodiments, the positive electrode membrane layer optionally further includes a positive electrode adhesive. The present application is not particularly limited to the type of positive electrode adhesive, and for example, the positive electrode adhesive may include one or more combinations selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass content of the positive electrode adhesive is 5% or less based on the total mass of the positive electrode membrane layer.

[0104] The positive electrode film layer is generally obtained by applying a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a selective conductive agent, a selective adhesive, and any other components in a solvent and uniformly stirring them. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0105] Negative electrode plate According to a third aspect, the present application proposes a negative electrode plate, which includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector. The negative electrode film layer includes a negative electrode active material and an ester-based polymer, and the ester-based polymer includes the ester-based polymer described in any one of the examples of the first aspect of the present application.

[0106] As an example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0107] In some embodiments, the negative electrode active material layer satisfies the formula v / λ > 1.00 (Formula 4). In Formula (4), λ represents the porosity of the negative electrode active material layer. v represents the liquid absorption rate of the negative electrode active material layer, and its unit is mg / s.

[0108] The detection methods of λ and v are the same as those of the positive electrode active material layer, and will not be described further here.

[0109] 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.

[0110] In some embodiments, the mass content of the ester-based polymer is B %, based on the mass of the negative electrode active material layer, where 0.2≦B≦5.0.

[0111] When the mass content of the ester-based polymer is within the above range, the interfacial performance of the negative electrode active material layer can be significantly improved. For example, the mass content of the ester-based 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 values.

[0112] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, the metal foil sheet may be copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base. 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 polymer base (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0113] In some embodiments, the negative electrode active material may be a battery negative electrode active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicone-based material, a tin-based material, and lithium titanate. The silicone-based material may be at least one selected from the group consisting of a silicone element, a silicone oxide, a silicone carbon composite, a silicone nitrogen composite, and a silicone alloy. The tin-based material may be at least one selected from the group consisting of a tin element, a tin oxide, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials usable as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination.

[0114] In some embodiments, the negative electrode membrane layer further optionally includes a negative electrode adhesive, 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).

[0115] In some embodiments, the negative electrode film layer further optionally 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.

[0116] In some embodiments, the negative electrode membrane layer optionally further comprises other additives, such as a thickener (eg, carboxymethylcellulose sodium (CMC-Na)).

[0117] In some embodiments, the negative electrode plate can be manufactured in the following manner: Components for manufacturing the negative electrode plate, such as the negative electrode active material, the ester polymer, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then coated onto a negative electrode current collector, and the negative electrode plate is obtained after processes such as drying and cold pressing.

[0118] Battery cell According to a fourth aspect, the present application provides a battery cell, the battery cell including a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate, and the battery cell may be a lithium ion battery or the like.

[0119] In some embodiments, the positive electrode plate may be the positive electrode plate of any one of the embodiments of the second aspect of the present application, thereby improving the cycle performance of the battery cell, and the negative electrode plate may be a conventional negative electrode plate.

[0120] In some other embodiments, the negative electrode plate may be the negative electrode plate according to any one of the embodiments of the third aspect of the present application, thereby improving the cycle performance of the battery cell, and the positive electrode plate may be a conventional positive electrode plate.

[0121] In some further embodiments, the positive electrode plate may employ the positive electrode plate according to any one of the embodiments of the second aspect of the present application, and the negative electrode plate may employ the negative electrode plate according to any one of the embodiments of the third aspect of the present application, thereby improving the cycle performance of the battery cell.

[0122] [Electrolyte] The battery cell further includes an electrolyte, which serves to conduct ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, and the electrolyte may be selected as needed. For example, the electrolyte may be liquid, gel, or all-solid.

[0123] In some embodiments, the electrolyte is an electrolytic solution, which includes an electrolyte salt and a solvent.

[0124] By way of example, the lithium salt may include one or more combinations selected from lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0125] By way of example, the organic solvent may comprise one or more combinations 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), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0126] In some embodiments, the electrolyte solution may further optionally contain additives, such as an additive for forming a negative electrode film or a positive electrode film, and may further include additives that can improve some battery performance, such as an additive for improving the overcharge performance of the battery or an additive for improving the high-temperature or low-temperature performance of the battery.

[0127] [Separator] In some embodiments, the battery cell further includes a separator. The present application does not particularly limit the type of separator, and any known porous separator with good chemical and mechanical stability may be selected.

[0128] In some embodiments, the separator may be made of one or more of 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.

[0129] In some embodiments, the positive electrode plate, separator, and negative electrode plate can be fabricated into an electrode assembly by a winding process or a stacking process.

[0130] The present application does not particularly limit the shape of the battery cell, which may be cylindrical, rectangular, or any other shape. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0131] In some embodiments, as shown in FIGS. 1 and 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted as needed.

[0132] The manufacturing method of the battery cell of the present application is well known. In some embodiments, a battery cell may be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate may be formed into an electrode assembly by a winding process or a stacking process, the electrode assembly may be placed in an outer package, dried, and then the electrolyte may be injected. The battery cell may be obtained through processes such as vacuum packaging, standing, chemical conversion, and shaping.

[0133] In some embodiments of the present application, the battery cells according to 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.

[0134] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, a 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.

[0135] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of battery cells 5 are accommodated in this accommodating space.

[0136] In some embodiments, the battery modules may be further 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.

[0137] Both the battery module 4 and the battery pack may be specific examples of the battery of the present application.

[0138] 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 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 and is used to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0139] power consumption equipment According to a fifth aspect, the present application provides a power consuming device, the 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 be used as a power source for the power consuming device or as an energy storage unit for 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.), an electric train, a ship, a satellite, an energy storage system, etc.

[0140] A power consuming device may select 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 a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density, the power consuming device may employ a battery pack 1 or a battery module. Another example power consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. The power consuming device generally requires a thin design and may employ a battery cell as a power source.

[0141] Example The following describes the examples of this application. The examples described below are illustrative and are intended to help interpret this application, but should not be understood as limitations on this application. If specific techniques or conditions are not specified in the examples, they are carried out according to techniques or conditions described in literature in the field or according to the product instructions. The reagents or equipment used do not indicate the manufacturers, and are all conventional products that are commercially available.

[0142] Example 1 (1) Manufacturing of positive electrode plates: A 12 μm thick aluminum foil was used as the positive electrode current collector.

[0143] A positive electrode slurry was prepared using an ester polymer, a positive electrode active material (LiFePO4), a conductive agent (carbon black), and an adhesive (e.g., polyvinylidene fluoride and N-methylpyrrolidone (NMP)). The mass ratio of the ester polymer, LiFePO4, conductive agent (carbon black), PVDF, and N-methylpyrrolidone (NMP) in the positive electrode slurry was 0.5:96.8:2:0.7:29. The positive electrode slurry was applied to an aluminum foil current collector, dried at 85°C, cold-pressed, trimmed, cut, and slit, and then dried in a vacuum at 85°C for 4 hours to prepare a positive electrode plate.

[0144] (2) Manufacturing of negative electrode plates: A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0145] The negative electrode slurry was prepared by uniformly mixing an ester polymer, artificial graphite as the negative electrode active material, carbon black as the conductive agent, styrene butadiene rubber (SBR) as the adhesive, sodium carboxymethyl cellulose (CMC-Na) as the thickener, and deionized water in a weight ratio of 2.5:94:0.5:2:1:100. The negative electrode slurry was applied to a copper foil current collector, dried at 85°C, and then cold-pressed, trimmed, cut, and slit. The negative electrode plate was then dried in a vacuum at 120°C for 12 hours.

[0146] (3) Electrolyte production In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain an electrolyte solvent, which was then mixed with lithium salt LiPF6 to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0147] (4) Lithium-ion battery manufacturing: A 16 μm polyethylene film (PE) was used as a separator. The positive electrode plate, separator, and negative electrode plate were stacked in this order, with the separator positioned between the positive and negative electrodes to provide isolation, and then wound up to obtain an electrode assembly. The electrode assembly was placed in an outer case, dried, and then an electrolyte was injected. After vacuum packaging, standing, chemical formation, and shaping, a lithium-ion battery was obtained.

[0148] Comparative Example 1 A lithium ion battery was manufactured using a method similar to that of Example 1, but the difference from Example 1 is that no ester-based polymer was added to the positive electrode plate of Comparative Example 1, and no ester-based polymer was added to the negative electrode plate of Comparative Example 1.

[0149] Comparative Example 2 A lithium ion battery was manufactured using a method similar to that of Example 1, but the difference from Example 1 is that the positive electrode plate and the negative electrode plate of Comparative Example 2 were made of ester-based polymer materials.

[0150] Examples 2 to 4 The lithium ion batteries were manufactured using a method similar to that of Example 1, but the difference from Example 1 is that the positive electrode plate and the negative electrode plate of Examples 2 to 4 were made of ester-based polymer materials.

[0151] Example 5 A lithium ion battery was manufactured using a method similar to that of Example 1, but the difference from Example 1 is that an ester-based polymer was added to the positive electrode plate of Example 5, and an ester-based polymer was not added to the negative electrode plate of Example 5.

[0152] Examples 6 to 9 The lithium ion batteries were manufactured using a method similar to that of Example 1, but the difference from Example 1 is that the content of the ester-based polymer in the positive electrode plate of Examples 6 to 9 was adjusted.

[0153] Examples 10 to 12 The lithium ion batteries were manufactured using a method similar to that of Example 1, but the difference from Example 1 is that the content of the ester-based polymer in the negative electrode plate of Examples 10 to 12 was adjusted.

[0154] The data for the examples and comparative examples are shown in Table 1.

[0155] Test part 1. Lithium-ion battery capacity retention rate test The lithium-ion batteries prepared in the examples and comparative examples were charged to 4.25V at room temperature using a 1.2C step charge, then further charged to a constant voltage of 4.25V at a current of 0.05C, allowed to stand for 5 minutes, and then discharged to 2.8V at a current of 0.33C. The resulting capacity was designated as the initial capacity C0, and the clamping force of the lithium-ion battery was set to 10,000 N. The same battery was subjected to the above steps, and the discharge capacity Cn after the nth cycle was recorded. The battery capacity retention after each cycle was calculated as Pn = Cn / C0 * 100%. The values ​​of the 200 points P1, P2...P200 were used as the ordinate and the corresponding cycle number as the abscissa, to obtain a curve of the battery capacity retention vs. cycle number for the ester-based polymers of the examples and comparative examples.

[0156] In this test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 200th cycle corresponds to n=200. For example, the capacity retention data of the battery corresponding to Example 1 in Table 1 is the data measured after 200 cycles under the above test conditions, i.e., the P200 value. The test process for Comparative Example 1 and the other Examples is the same as above.

[0157] 2. DC impedance test for lithium-ion batteries The lithium-ion batteries prepared in the Examples and Comparative Examples were charged to 4.25 V at 25°C using a 1.2 C step charge, then further charged at a constant voltage of 4.25 V to a current of 0.05 C and 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 same battery was then subjected to the same procedure, and the battery's internal resistance (DCRn) after the nth cycle (n = 1, 2, 3 ... 200) was simultaneously recorded. The values ​​of the 200 points (DCR1, DCR2, DCR3 ... DCR200) ​​were plotted on the ordinate, with the corresponding cycle number plotted on the abscissa, to plot the battery discharge DCIR versus cycle number for the ester-based polymers of the Examples and Comparative Examples.

[0158] In this test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 200th cycle corresponds to n=200. For example, in Table 1, the battery internal resistance increase rate of Example 1 = (DCRn-DCR1) / DCR1*100%, and the test process of Comparative Example 1 and other Examples is the same as above. The data in Table 1 is data measured after 200 cycles under the above test conditions.

[0159] Test Results

[0160] [Table 1]

[0161] In Table 1, 100% methyl methacrylate refers to the mass content of methyl methacrylate being 100% based on the total mass of Monomer 1, Monomer 2 and Monomer 3. 85% vinyl acetate refers to a vinyl acetate content of 85% by mass based on the total mass of Monomer 1, Monomer 2, and Monomer 3, and 15% ethylene refers to an ethylene content of 15% by mass based on the total mass of Monomer 1, Monomer 2, and Monomer 3.

[0162] As can be seen from Table 1, the examples of the present application, which added the ester-based polymer of the present application to the positive and / or negative electrodes, improved the cycle performance of lithium-ion batteries compared to Comparative Example 1. Compared to Comparative Example 2, the examples of the present application, when 5≦m / n≦1000, especially 10≦m / n≦50, tended to have looser molecular chain arrangements, with weaker interchain forces and easier opening of adjacent molecular chains, allowing for chain segment motion through intermolecular rotation and forming a more flexible molecular chain structure, resulting in a more significant improvement in the cycle performance of lithium-ion batteries.

[0163] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and equivalents may be substituted for the components therein without departing from the scope of the present application. In particular, the technical features recited in each embodiment may be combined in any manner unless there is a structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims. [Explanation of symbols]

[0164] The symbols are explained as follows: 1, battery pack, 2, upper housing, 3, lower housing, 4, battery module, 5, battery cell, 51, case, 52, electrode assembly, 53, cover plate, 6, power consumption equipment.

Claims

1. An ester-based polymer for use in a battery cell, adding the ester-based polymer to a first solvent at 45°C to form an ester-based polymer system; The ester-based polymer system is allowed to stand at 45°C for 8 hours, and then allowed to stand at 25°C for ≥ 24 hours. After that, the ester-based polymer system is filtered through a 200 mesh filter to leave a first substance; Here, the mass of the ester-based polymer is n and its unit is g, the mass of the first substance is m and its unit is g, and the ester-based polymer and the first substance satisfy 5≦m / n≦1000.

2. 2. The ester-based polymer of claim 1, wherein 10≦m / n≦1000, and further optionally, 10≦m / n≦50.

3. the first solvent contains a cyclic carbonate solvent and / or a chain carbonate solvent, Optionally, the cyclic carbonate solvent comprises one or more of ethylene carbonate EC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC; Optionally, the linear carbonate solvent comprises one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), diphenyl carbonate (DPC), methyl allyl carbonate (MAC) and polycarbonate (VA). The ester-based polymer of claim 1 or 2.

4. The ester-based polymer is prepared as a sheet-like structure, and the sheet-like structure is ｍ A dynamic frequency scan test was carried out at 20°C (+20°C) to obtain a curve of elastic modulus G'-loss modulus G"; the slope of the curve of elastic modulus G'-loss modulus G" is K, where 1<K<∞; and T ｍ 4. The ester-based polymer of claim 1, wherein °C represents the melting temperature of the ester-based polymer.

5. The ester-based polymer according to any one of claims 1 to 4, wherein the glass transition temperature of the ester-based polymer is Tg, and the unit is ° C., and −100≦Tg≦50, and optionally −80≦Tg≦30.

6. The ester-based polymer contains a structural unit represented by formula (I): 【Chemical 1】 In formula (I), R １ , R ２ and R ３ each independently represents a hydrogen atom or a substituted or unsubstituted C1 to C8 alkyl group, R ４ comprises a substituted or unsubstituted C1 to C8 alkyl group or a substituted or unsubstituted C1 to C8 hydroxyalkyl group, Selectively, R １ contains a hydrogen atom or a substituted or unsubstituted methyl group, R ２ and R ３ each independently contains a hydrogen atom, R ４ includes a substituted or unsubstituted C1 to C6 alkyl group or a substituted or unsubstituted C1 to C6 hydroxyalkyl group, Selectively, R ４ The ester-based polymer according to any one of claims 1 to 5, wherein R2 is a substituted or unsubstituted C1 to C4 alkyl group, or a substituted or unsubstituted C1 to C4 hydroxyalkyl group.

7. The ester-based polymer comprises a structural unit represented by formula (I-1) to a structural unit represented by formula (I-15): 【Chemistry 2】 【Chemistry 3】 The ester-based polymer according to claim 6, comprising at least one of:

8. The ester-based polymer contains a structural unit represented by formula (II): 【Chemistry 4】 In formula (II), R ５ contains a substituted or unsubstituted C2 to C6 methylene group, Optionally, R ５ The ester-based polymer according to any one of claims 1 to 7, wherein R2 is a substituted or unsubstituted C2 to C4 methylene group.

9. The ester-based polymer comprises a structural unit represented by formula (II-1) to a structural unit represented by formula (II-5): 【Chemistry 5】 The ester-based polymer according to claim 8, comprising at least one of:

10. n is a positive integer selected from 800 to 20,000, and / or The molecular weight of the ester polymer is 1.2×10 ５ g / mol~1.0×10 ６ The ester-based polymer according to any one of claims 6 to 9, wherein the molecular weight is 1000 or more, and the molecular weight is 1000 or more.

11. 11. A positive electrode plate comprising: a positive electrode current collector; and a positive electrode film layer disposed on the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material and an ester-based polymer, the ester-based polymer comprising the ester-based polymer according to claim 1.

12. 11. A negative electrode plate comprising: a negative electrode current collector; and a negative electrode film layer disposed on the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material and an ester-based polymer, the ester-based polymer comprising the ester-based polymer according to claim 1.

13. A battery cell including a positive electrode plate and a negative electrode plate, The positive electrode plate comprises the positive electrode plate according to claim 11; and / or A battery cell, wherein the negative electrode plate comprises the negative electrode plate of claim 12.

14. A battery comprising the battery cell of claim 13.

15. 15. A power consuming device comprising the battery of claim 14.

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