Electrode sheet and related battery cells, batteries and power consumption devices

Abstract

The present application provides an electrode sheet and related battery cells, batteries, and power consumption devices. The electrode sheet includes a current collector and an active material layer provided on at least one surface of the current collector. The active material layer includes an active material and a polymer, and the active material layer satisfies the following formulas (1) to (3). The polymer, as a constituent part of the active material layer, forms uniform high-wet points within the active material layer, uniformly improving the wetting performance of the active material layer and increasing the liquid absorption rate of the entire active material layer, thereby improving the cycle performance of the battery cell. [Equation 1] TIFF2025526518000079.tif19134 [Number 2] TIFF2025526518000080.tif18134 [Number 3] TIFF2025526518000081.tif16134 Figure 1

Description

[Technical Field]

[0001] This application relates to the field of batteries, and in particular to electrode sheets and 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 scooters, 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 expands, the requirements for battery cell performance are also becoming increasingly stringent. To improve the safety performance of battery cells, it is common to optimize the performance of electrode sheets in battery cells. However, the active materials in current electrode sheets have poor liquid absorption properties, which results in poor cycle 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 its object is to provide an electrode sheet and related battery cells, batteries, and power consuming devices.

[0005] A first aspect of the present application provides an electrode sheet, the electrode sheet including a current collector and an active material layer provided on at least one surface of the current collector, The active material layer contains an active material and a polymer, and the active material layer satisfies the following formulas (1) to (3):

number

number

number

[0006] Thus, the polymer of the present application is introduced into the manufacturing process of the active material layer, thereby forming a uniform high wettability point inside the active material layer, uniformly improving the wettability performance of the active material layer, improving the liquid absorption rate of the entire active material layer, and improving the cycle performance of the battery cell using the electrode sheet.

[0007] In some embodiments, the active material includes a positive electrode active material, and the active material layer satisfies 1.00 < v / λ < 4.00, optionally 1.20 ≤ v / λ ≤ 3.80.

[0008] In some embodiments, the active material includes a positive electrode active material, and based on the mass of the active material layer, the mass percentage of the polymer is A%, and 0.1 ≤ A ≤ 1.5. When the mass percentage of the polymer is within the above range, the liquid absorption capacity of the positive electrode active material layer can be significantly improved.

[0009] In some embodiments, the active material includes a negative electrode active material, and the active material layer satisfies 3.00 < v / λ < 50.00, optionally 3.40 ≤ v / λ ≤ 30.00.

[0010] In some embodiments, the active material includes a negative electrode active material, and the mass percentage of the polymer is B%, based on the mass of the active material layer, and 0.2≦B≦5.0 When the mass percentage of the polymer is in this range, the liquid absorption capacity of the negative electrode active material layer can be significantly improved.

[0011] In some embodiments, the polymer has a crystallinity of X, as measured by differential scanning calorimetry. C %, and 0 <X C ≦30, the melting temperature of the polymer is Tm, and its unit is °C, and 0 <Tm≦140である。

[0012] As a result, in the present application, the polymer has good affinity with the electrolyte solution in the battery cell, so that the solvent in the electrolyte solution quickly diffuses between the molecular chains of the polymer, is enveloped by the molecular chains, and forms an in-situ gel on the surface of the active material. This improves the infiltration performance of the electrolyte solution into the active material layer, increases the liquid absorption rate of the entire active material layer, and improves the cycle performance of a battery cell using the electrode sheet.

[0013] In some embodiments, the polymer has a glass transition temperature, Tg, in °C, in the range of -150≦Tg≦60. The polymer has a relatively low glass transition temperature, which allows the molecular chain segments to have better flexibility, adjacent molecular chains to open more easily, and allows for more in-situ gel formation, thereby improving the infiltration of the electrolyte into the active material layer and improving the cycling performance of the battery cell.

[0014] In some embodiments, the polymer comprises at least one of structural units represented by formula (I) through (III). [ka] [ka] [ka]

[0015] In formula (I) and formula (II), R1, R2, R3, and R4 each independently comprise a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and at least one of R1, R2, R3, and R4 comprises a fluorine atom, and when substituted, the substituent comprises a fluorine atom; in formula (III), R5 comprises a single bond or a substituted or unsubstituted C1-C3 alkyl group, and when substituted, the substituent comprises a fluorine atom; p is a positive integer of 1 to 3; and n is a positive integer of 1,000 to 30,000.

[0016] As a result, the polymer of the present application has a linear structure or a short-chain branched structure, and the degree of entanglement of these structural types is low, which is advantageous for improving the flexibility of the molecular chain, allowing the molecular chain to fully unfold in the electrolyte, and further improving the infiltration performance of the electrolyte into the active material.

[0017] In some embodiments, R1, R2, R3, and R4 each independently comprise a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C2 alkyl group, or a substituted or unsubstituted C1-C2 alkoxy group; more preferably, R1, R2, R3, and R4 each independently comprise a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group.

[0018] In some embodiments, the polymer comprises at least one of structural units represented by formula (I-1) through (I-11). [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0019] In some embodiments, the polymer comprises at least one of structural units represented by formula (II-1) to structural units represented by formula (II-5). [ka] [ka] [ka] [ka] [ka]

[0020] In some embodiments, the polymer comprises at least one of structural units represented by formula (III-1) to structural units represented by formula (III-3). [ka] [ka] [ka]

[0021] In some embodiments, n is a positive integer between 5,000 and 20,000.

[0022] In some embodiments, the molecular weight of the polymer is 2×10 5 g / mol ~ 1.5 × 10 6 g / mol. When the molecular weight of the polymer is within this range, it is possible to ensure that the polymer exhibits a certain solubility in the electrolyte and is not easily completely dissolved or dispersed in the electrolyte, which is advantageous for adjusting the distribution and dispersion of the polymer on the surface of the active material, and the electrolyte can uniformly infiltrate the active material layer, thereby improving the absorption rate of the entire active material layer and improving the cycle performance of a battery cell using the electrode sheet. It is also possible to further improve the flexibility of the polymer molecular chains, and the interaction between the molecular chains is relatively weak, which is advantageous for solvent molecules in the electrolyte to open the molecular chains and enter between them to be enveloped by them, which is advantageous for active ions to enter the active material through the solvent and realize smooth and rapid movement of the active ions, thereby improving the dynamic performance of the battery cell.

[0023] A second aspect of the present application provides a battery cell including the electrode sheet according to any of the embodiments of the first aspect of the present application.

[0024] A third aspect of the present application provides a battery including the battery cell according to the second aspect of the present application.

[0025] A fourth aspect of the present application provides a power consuming device including a battery cell according to the third aspect of the present application. [Brief explanation of the drawings]

[0026] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required 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 obtain other drawings based on the drawings without any creative efforts. [Figure 1] FIG. 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. [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] 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. [Explanation of symbols]

[0027] 1 battery pack 2 Upper box 3 Lower box 4 Battery Module 5 battery cells 51 cases 52 Electrode Assembly 53 Cover plate 6 Power consumption equipment DETAILED DESCRIPTION OF THE INVENTION

[0028] 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 detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially identical configurations may be omitted. This is done 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.

[0029] The "ranges" disclosed in this application are defined in the form of lower and upper limits. 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 that particular range. Such defined ranges may be inclusive or exclusive of the endpoints, 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. In this application, unless otherwise specified, a numerical range "a to b" is represented by the abbreviation 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 included herein, and "0 to 5" is an abbreviation for combinations of these numerical values. Furthermore, expressing a parameter as 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.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all steps in this application may be performed in order or randomly, but are preferably performed in order. For example, when a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when a method is described as further including 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.

[0032] 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.

[0033] 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 conditions are met for "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).

[0034] In this application, the terms "plurality" and "plural types" mean two or more than two.

[0035] The term "alkyl group" encompasses straight-chain and branched 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.

[0036] 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. In addition, the alkoxy group may be optionally substituted.

[0037] The term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom, and the like.

[0038] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In each embodiment, "hydrogen" may be 1H (protium, H).

[0039] The battery cell includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive and negative electrode sheets. The electrode assembly has a gap-pore structure, and the electrolyte infiltrates into the electrode assembly. The driving force for infiltration is mainly capillary force, which is a spontaneous infiltration process. The current collector barrier in the electrode sheet allows the electrolyte to infiltrate from the end face of the electrode assembly through the separator into the electrode assembly. The gaps between the layers of the electrode assembly act as a current guide, and the separator acts as a current divider. The steps in which the electrolyte solution permeates the interior of the electrode assembly include: (1) the electrolyte solution is transported between the electrode sheet and the separator by capillary force; (2) the electrolyte solution preferentially permeates into the pores of the separator (the permeation rate of the electrolyte solution in the separator is much faster than that in the active material layer of the electrode sheet); and (3) the electrolyte solution diffuses through the separator to the surfaces of the positive and negative electrode sheets on both sides and permeates into the pores of the active material layer.

[0040] The inventors discovered that a polymer is used as an adhesive in the active material layer to adhere the active material to the surface of the current collector, and that the polymer must be immersed in the electrolyte for a long period of time. Therefore, to ensure the polymer's performance, a polymer with a high degree of crystallinity is typically used to maintain good adhesion and support for the active material layer. However, electrode sheets using such polymers have poor affinity with the electrolyte, resulting in poor wetting of the electrode sheet and a slower diffusion rate of the electrolyte from the surface of the active material layer into the interior of the active material layer. This results in poor liquid absorption by the active material, which in turn deteriorates the cycle performance of the battery cell.

[0041] Therefore, in order to improve the liquid absorption rate of the active material layer, the inventors hope to improve the cycle performance of the battery cell by improving the material in the active material layer, for example, the polymer, to increase the liquid absorption rate. Electrode sheet

[0042] According to a first aspect, there is provided an electrode sheet including a current collector and an active material layer provided on at least one surface of the current collector, the active material layer including an active material and a polymer. The electrode sheet may be a positive electrode sheet and / or a negative electrode sheet, and accordingly, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer.

[0043] The electrode sheet may be obtained by applying the slurry to a current collector, drying the slurry, and cold-pressing the slurry. Alternatively, the electrode sheet may be derived from a battery cell, and the battery cell may be disassembled, and the electrode sheet soaked in the electrolyte may be removed from the battery cell and vacuum-dried at 100°C for 12 hours to obtain the electrode sheet, which may then be used for electrode sheet tests such as liquid absorption rate.

[0044] The polymer can be synthesized by emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization, etc. Alternatively, if the polymer is derived from a battery cell, the battery cell can be disassembled, and the electrode sheet soaked in the electrolyte removed. The active material of the resulting electrode sheet is peeled from the current collector by external force to form a powder sample, which is then added to dimethyl carbonate (DMC) and stirred at 500 rpm for 8 hours at 80°C. After stirring, the mixture is left to stand at room temperature for 10 minutes. The supernatant is then removed and dried at 80°C for 12 hours to obtain the polymer. The resulting polymer may contain a small amount of lithium salt, but this does not generally affect infrared testing or precipitation value testing. To ensure the accuracy of the polymer, the lithium salt can be separated by further washing at room temperature with DMC.

[0045] The active material layer satisfies the following formulas (1) to (3).

number

number

number

[0046] In the present application, the actual compressed density P1 is the ratio of the mass to the thickness of the active material layer per unit area of the electrode sheet, and is determined by the force with which the electrode sheet is roll-pressed after being coated, and its unit is g / cm. 3 The specific test steps are to take an electrode sheet with a certain area S, weigh the mass M of its active material layer, and measure the thickness D of the active material layer, and the actual compressed density is M / (S×D).

[0047] In the present application, the true compressed density P2 refers to the density of the active material itself in the active material layer. For example, if the active material is a negative electrode active material, such as graphite, the density of graphite is 2.25 g / cm 3 and the true compressed density of the active material is 2.25 g / cm 3 is.

[0048] Taking a positive electrode active material as an example, this specifically means taking a mass of a certain "actual volume of the solid material (not including open pores, closed pores, and interparticle pores)" in a compacted state, obtaining the true volume V through testing, and then determining the true compressed density based on P = m / V, which can be tested in accordance with GB / T24586-2009. Specifically, the test steps are as follows:

[0049] 1) Pretreatment: Place a clean, dry sample cup on the balance, clear it, and add the powder sample to the sample cup, occupying approximately half of the sample cup volume. Record the mass of the sample.

[0050] 2) Place the sample cup containing the sample in the true density tester, seal the test system, and use the program to infuse helium gas into the test cup, detect the gas pressure in the sample chamber and the expansion chamber, and then calculate the true volume based on Bohr's law (PV=nRT) to calculate the true compressed density.

[0051] Here, the volume of the sample cup is 3.5 cm 3 ,Analysis gas: helium gas.

[0052] In formula (1), the porosity λ of the active material layer can be calculated from the actual compressed density and the true compressed density.

[0053] in particular,

number

[0054] Here, V1 represents the volume of the active material layer per mass m, and its unit is cm 3 and V2 represents the volume occupied by the active material particles in the active material layer at mass m, and its unit is cm 3 is.

[0055] m represents the mass of the active material layer, and its unit is g.

[0056] Equation (2) can express 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, the certain point on the electrode sheet is a region of the electrode sheet having a certain area, which corresponds to the cross-sectional area of the capillary.

[0057] In the present application, the method for detecting the liquid absorption rate of the electrode sheet includes: Adsorbing a predetermined amount of electrolyte with the capillary; The capillary is brought into contact with the electrode sheet, and the test electrode sheet absorbs the electrolyte in the capillary by capillary action. After a predetermined time t has elapsed, the height h of the electrolyte absorbed in the capillary is recorded, the amount of the electrolyte absorbed is calculated based on the height h of the electrolyte level and diameter d of the capillary and the density ρ of the electrolyte, and the liquid absorption rate v of the electrode sheet is quantitatively calculated based on the ratio of the amount of the electrolyte absorbed to the predetermined time length t.

[0058] 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.

[0059] The capillaries have capillary channels that allow them to directly adsorb the electrolyte by capillary action without requiring an external drive unit to provide suction. In this way, the amount of electrolyte adsorbed can be more accurately controlled when adsorbing by capillary action. Meanwhile, the electrode sheet absorbs the electrolyte by its own capillary action. When the capillaries are in contact with the electrode sheet to be tested, the electrode sheet draws out the electrolyte from the capillaries, and when they are not in contact, the electrolyte in the capillaries does not flow out. This allows the amount of electrolyte absorbed by the capillaries to accurately indicate that the electrode sheet has absorbed a corresponding volume of electrolyte, further improving the accuracy of the test results and enabling quantitative calculation of the absorption rate of the electrode sheet.

[0060] Equation (3) represents the liquid absorption rate of an electrode sheet at a porosity λ and can be used to represent the liquid absorption rate of an electrode sheet.

[0061] When the polymer of the present application is introduced into the active material layer during the manufacturing process, it forms uniform high infiltration points inside the active material layer, uniformly improves the infiltration performance of the active material layer, increases the liquid absorption rate of the entire active material layer, and improves the cycle performance of a battery cell using the electrode sheet.

[0062] Selectable, 1.00 <v / λ<50.00である。

[0063] In some embodiments, the polymer has a crystallinity as measured by differential scanning calorimetry of X C %, and 0 <X C ≦30, the melting temperature of the polymer is Tm, in °C, and 0 <Tm≦140である。

[0064] Crystallization refers to the process in which atoms, ions, or molecules in a material are arranged in a certain spatial order to form an order. The conformation of a polymer in a crystal is determined by two factors: intramolecular and intermolecular forces, and the intermolecular forces affect the stacking density between molecular chains. Crystallinity X C The percentage represents the degree of crystallization in the material and can be measured by differential scanning calorimetry (DSC). Specifically, the test involves taking 0.5 g to 0.8 g of a sample, placing the sample in a carrier crucible, and heating the sample under a nitrogen gas atmosphere at a heating rate of 10°C / min from an initial temperature 20°C lower than the material's inherent Tg to a process off temperature 20°C higher than the material's inherent Tm. The actual glass transition temperature (Tg) and melting temperature (Tm) of the material are determined based on the endothermic and exothermic peak values or transition points of the material during the process.

[0065] While fluoropolymers commonly used in conventional secondary batteries have relatively high crystallinity and melting temperatures, the polymers have good liquid-phase electrolyte resistance, effectively providing long-term adhesion or anti-repulsion effects for active materials during battery use. The polymers (fluoropolymers) used in this application have relatively low crystallinity and melting temperatures, resulting in sparse molecular chain arrangements, small inter-molecular forces, and flexible segments, allowing adjacent molecular chains to open easily.

[0066] Because the polymer has good affinity with the electrolyte in the battery cell, the solvent in the electrolyte quickly diffuses between the molecular chains of the polymer and is enveloped by the molecular chains, forming an in-situ gel on the surface of the active material. This improves the infiltration performance of the electrolyte into the active material layer, increases the liquid absorption rate of the entire active material layer, and improves the cycle performance of the battery cell using the electrode sheet.

[0067] Illustratively, the polymer has a crystallinity X measured by differential scanning calorimetry. C The % may be 5%, 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of the above values.

[0068] Illustratively, the melting temperature of the polymer may be 10°C, 20°C, 50°C, 70°C, 90°C, 100°C, 120°C, 140°C, or a range consisting of any two of the foregoing values.

[0069] In some embodiments, the glass transition temperature of the polymer is Tg, in °C, where -150 < Tg < 60.

[0070] The glass transition temperature (Tg) is the temperature at which a polymer segment transitions from frozen to mobile. The Tg has a certain effect on the flexibility of the polymer molecular chain. The lower the Tg, the better the flexibility of the polymer molecular chain at room temperature. The higher the Tg, the worse the flexibility of the molecular chain at room temperature. The Tg can be measured by differential scanning calorimetry (DSC). The lower the Tg of a polymer, the more flexible the molecular chain segments are, and the easier it is for adjacent molecular chains to open, leading to more in-situ gel formation. This improves the infiltration of the electrolyte into the active material layer and the cycle performance of the battery cell. For example, the Tg of a fluoropolymer may be −150°C, −140°C, −120°C, −100°C, −80°C, −60°C, −30°C, 0°C, 30°C, 60°C, or a range consisting of any two of the above values.

[0071] In some embodiments, the polymer comprises at least one of structural units represented by formula (I) through (III). [ka] [ka] [ka]

[0072] In formula (I) and formula (II), R1, R2, R3 and R4 each independently contain a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and at least one of R1, R2, R3 and R4 contains a fluorine atom, and when substituted, the substituent contains a fluorine atom.

[0073] In formula (III), R5 comprises a single bond, a substituted or unsubstituted C1-C3 alkyl group, and when substituted, the substituent comprises a fluorine atom.

[0074] p is a positive integer from 1 to 3.

[0075] n is a positive integer between 1,000 and 30,000.

[0076] In some embodiments, R1, R2, R3, and R4 each independently comprise a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C2 alkyl group, or a substituted or unsubstituted C1-C2 alkoxy group, and at least one of R1, R2, R3, and R4 comprises a fluorine atom.

[0077] In some embodiments, R1, R2, R3, and R4 each independently comprise a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group.

[0078] In some embodiments, the polymer comprises at least one of structural units represented by formula (I-1) through (I-11). [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0079] Optionally, the polymer comprises at least two of the structural units represented by formula (I-1) to (I-11).

[0080] In some embodiments, the polymer comprises at least one of structural units represented by formula (II-1) to structural units represented by formula (II-5). [ka] [ka] [ka] [ka] [ka]

[0081] In some embodiments, the polymer comprises at least one of structural units represented by formula (III-1) to structural units represented by formula (III-3). [ka] [ka] [ka]

[0082] Exemplarily, the polymer includes one or more of polyperfluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroethylenepropene copolymer FEP, perfluoroalkoxy polymer PFA, perfluoropolyether PFPE, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE, and perfluoro(1-butenyl vinyl ether) polymer (abbreviated as CYTOP).

[0083] Optionally, the polymer comprises one or more of polyperfluoroethylene PTFE, polyvinylidene fluoride PVDF, perfluoroethylene propene copolymer FEP, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE.

[0084] The polymer may be derived from one or more of the following monomers: fluorocycloethane, fluoroethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropene, trifluoropropene, tetrafluoropropene, and pentafluoropropene. Alternatively, the polymer may be derived from at least two of the following monomers: fluorocycloethane, fluoroethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropene, trifluoropropene, tetrafluoropropene, and pentafluoropropene.

[0085] The monomers used in the above polymers are all short-chain monomers, which are advantageous for forming a straight-chain linear structure or a short-chain branched structure through polymerization. This type of structure has a low degree of entanglement, which improves the flexibility of the molecular chains and allows the molecular chains to fully unfold in the electrolyte, thereby further improving the infiltration performance of the electrolyte into the active material and improving the interfacial performance of the active material.

[0086] The groups of the polymer of the present application can be detected by infrared spectroscopy IR, specifically, the polymer is tested by Thermo Nicolet Nexus 670 attenuated total reflection infrared Fourier transform infrared spectrometer (FTIR-ATR), and then the test is performed in accordance with the standard GB / T6040-2002, the test range is ATR method 600-4000 cm -1 , Reproducibility: ±2cm -1 , resolution: 4cm -1 Higher penetration depth: 0.2-0.6 μm.

[0087] The structure of the polymer of the present application can be determined by nuclear magnetic resonance NMR, specifically, by H NMR and C NMR using a Varian Mercury Plus-400 nuclear magnetic resonance instrument, the measurement temperature is 20°C, TMS is the internal standard, CDCl3 is the solvent, and the proton resonance frequency is 400 MHz.

[0088] In some embodiments, n is a positive integer between 5,000 and 20,000.

[0089] In some embodiments, the molecular weight of the polymer is 2×10 5 g / mol ~ 1.5 × 10 6 g / mol.

[0090] When the molecular weight of the polymer is within the above range, the polymer exhibits a certain solubility in the electrolyte and is unlikely to be completely dissolved or dispersed in the electrolyte, which is advantageous for adjusting the distribution and dispersion of the polymer on the surface of the active material. The electrolyte can uniformly infiltrate the active material layer, thereby improving the absorption rate of the entire active material layer and improving the cycle performance of a battery cell using the electrode sheet. Furthermore, the flexibility of the polymer molecular chains can be further improved, 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. This is advantageous for the active ions to enter the active material via the solvent, thereby realizing smooth and rapid migration of the active ions. For example, the molecular weight of the polymer is 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.

[0091] The molecular weight of a polymer is a known value in the art and can be measured using equipment and methods commonly used in the art, such as gel permeation chromatography (GPC). The specific test steps are to take an appropriate amount of sample to be measured (ensure that the sample concentration is 8%-12% and the light shielding degree is 8%), add 20 ml of deionized water, and simultaneously apply ultrasonic waves (53 KHz / 120 W) outside for 5 minutes to completely disperse the sample, and then measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0092] Alternatively, the test was performed using a multi-angle laser light scattering (MALLS) analyzer, specifically, a GPC combined with a DawnHeleos II multi-angle laser light scattering analyzer, an Optilab T-rEX refractive index (RI) detector, and a Visco Star II viscometer (Wyatt Technology Corporation, USA). The test was performed at 30°C using tetrahydrofuran as the mobile phase at a flow rate of 1.0 ml / min. The SEC-SAMLL data was processed using the commercially available software ASTRA6 to obtain molecular weight parameters.

[0093] Through further research, the inventors have discovered that the cycling performance of the battery cell can be further improved if the polymer further satisfies one or more of the following conditions:

[0094] In some embodiments, the polymer is added to a first solvent at a first temperature to form a polymer system, the polymer system is allowed to stand at the first temperature for 8 hours and then at a second temperature for 24 hours or more, and after undergoing a two-stage standing process, a portion or all of the polymer system is converted in-situ into a gel-state substance, and the polymer system is then filtered through a 200-mesh filter, leaving a first substance, and the first temperature is higher than the second temperature, wherein the mass of the polymer is n in grams, the mass of the first substance is m in grams, and the ratio of the polymer and the first substance satisfies 5≦m / n≦1000, optionally 10≦m / n≦1000, and 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 foregoing values.

[0095] Illustratively, based on the weight of the polymer system, the ratio of the weight content of the polymer to the weight content of the first solvent ranges from 1:100 to 1:10, for example, 3:50.

[0096] For example, the first solvent may be the same as or similar to the solvent of the electrolyte, and may include a carbonate-based solvent, such as a cyclic carbonate solvent and / or a linear carbonate solvent.

[0097] 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.

[0098] Examples of linear carbonate solvents include one or more of dimethyl carbonate DMC, diethyl carbonate DEC, ethyl methyl carbonate EMC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate VA.

[0099] Optionally, the first solvent may simultaneously contain a lithium salt and an electrolyte additive, such as lithium hexafluorophosphate, vinylene carbonate (VC), fluoroethylene carbonate (FEC), and the like.

[0100] In this application, m / n is also referred to as the sedimentation value, which represents the ability of the polymer and solvent to be converted into a gel-state material.

[0101] The first substance includes a gel-state substance formed mainly by a polymer and a first solvent, and in such a gel-state substance, the molecular structure of the polymer hardly changes.

[0102] 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 detected by infrared spectroscopy (IR) or tested by nuclear magnetic resonance (NMR), and the main component of the first material after drying is the aforementioned polymer.

[0103] In this application, the glass transition temperature of the polymer ≤ the first temperature ≤ the melting temperature of the polymer, and the first temperature is the normal operating temperature of the battery cell.

[0104] The first temperature is greater than the second temperature, and the first temperature and the second temperature may be set as the safe operating temperature range of the battery cell. Exemplarily, the first temperature may be 60°C to 80°C, for example 70°C, and the second temperature may be -30°C to 30°C, for example 25°C. That is, the first temperature is the high operating temperature of the battery cell, and the second temperature approximates normal temperature or low temperature.

[0105] In this application, by increasing the temperature, the expansion of the polymer molecular chains can be realized within the safe operating temperature range of the battery cell, promoting the mutual attraction and physical bonding between the polymer molecular chains and the solvent, and improving the liquid absorption capacity. At normal temperature, the activity of the polymer molecular segments decreases and is retained to adhere to the surface of the active material, locking the electrolyte in a certain spatial environment of the polymer to form a state similar to an in-situ gel, improving the liquid locking ability, and improving the cycle performance. Positive electrode sheet

[0106] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material and a polymer. In this application, the polymer includes the aforementioned polymer.

[0107] For example, the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode active material layer is provided on one or both of the two surfaces of the positive electrode current collector.

[0108] 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.

[0109] In some embodiments, the weight percentage of the polymer is A %, based on the weight of the positive electrode active material layer, where 0.1≦A≦1.5.

[0110] When the mass percentage of the polymer is in the above range, the liquid absorption capacity of the positive electrode active material layer can be significantly improved. For example, the mass percentage A% 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 values.

[0111] 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 known in the art for use 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-rich / sodium 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).

[0112] 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 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 It may also contain one or more of O2 (NCM523).

[0113] 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 types selected from Na, K, and Mg; Me is one or more types selected from Mn, Fe, Co, and Ni; M is one or more types 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 types selected from S, Si, Cl, B, C, and N; and Y is one or more types selected from O and F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0114] 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 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 0.1 Mn 1.9 O4, Li2Mn2O4 and Li 1.5 Mn2O4.

[0115] 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 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, and 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).

[0116] In some embodiments, the positive electrode active material layer may optionally further include a positive electrode conductive agent. The type of positive electrode conductive agent in the present application is not particularly limited. For example, the positive electrode conductive agent may include one or a combination of materials selected from the group consisting of superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, Ketjen black, carbon particles, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is 5% or less, based on the total mass of the positive electrode active material layer.

[0117] In some embodiments, the positive electrode active material layer may optionally further include a positive electrode binder. In the present application, the type of positive electrode binder is not particularly limited. For example, the positive electrode binder may include one or a combination of polyvinylidene fluoride (PVDF). In some embodiments, the mass percentage of the positive electrode binder is 5% or less, based on the total mass of the positive electrode active material layer. The crystallinity of the positive electrode binder is higher than that of the aforementioned polymers in the present application. The melting temperature of the positive electrode binder is higher than that of the aforementioned polymers in the present application.

[0118] The positive electrode active material layer is usually formed by applying a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, the polymer, an optionally selectable conductive agent, an optionally selectable positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. Negative electrode sheet

[0119] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material and a polymer. In the present application, the polymer includes the aforementioned polymer.

[0120] For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0121] 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.

[0122] In some embodiments, based on the mass of the negative electrode active material layer, the mass percentage of the polymer is B%, where 0.2 ≤ B ≤ 5.0. When the mass percentage of the polymer is within the above range, the liquid absorption capacity of the negative electrode active material layer can be significantly improved. Exemplarily, the mass percentage B% 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.

[0123] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, copper foil may be used as the metal foil sheet. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material 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 material substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0124] 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, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be at least one selected from elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxycompounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials used as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination.

[0125] In some embodiments, the negative electrode active material layer may further include a negative electrode binder, if necessary. The negative electrode binder 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). The crystallinity of the negative electrode binder is higher than that of the aforementioned polymers of the present application. The melting temperature of the negative electrode binder is higher than that of the aforementioned polymers of the present application.

[0126] In some embodiments, the negative electrode active material layer may further include a conductive agent, if necessary, which may be at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the negative electrode active material layer may further contain other auxiliary agents, such as a thickener (for example, sodium carboxymethylcellulose (CMC-Na)), as needed.

[0128] In some embodiments, the components for producing the negative electrode sheet, such as the negative electrode active material, the polymer, the conductive agent, the negative electrode binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied to a negative electrode current collector, and the negative electrode sheet is obtained after steps such as drying and cold pressing. This allows the negative electrode sheet to be produced. Battery cell

[0129] According to a second 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 may be a lithium-ion battery or the like.

[0130] In some embodiments, the positive electrode sheet may be an electrode sheet according to any one of the first aspects of the present application, thereby improving the cycle performance of the battery cell, and the negative electrode sheet may be a conventional electrode sheet.

[0131] In some embodiments, the negative electrode sheet may be an electrode sheet according to any one of the first aspects of the present application, thereby improving the cycle performance of the battery cell, and the positive electrode sheet may be a conventional electrode sheet.

[0132] In some embodiments, the positive electrode sheet may be an electrode sheet according to any one of the embodiments of the first aspect of the present application, and the negative electrode sheet may be an electrode sheet according to any one of the embodiments of the first aspect of the present application, thereby improving the cycle performance of the battery cell. [Electrolyte]

[0133] The battery cell further includes an electrolyte, which serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte in the present application is not particularly limited and can be selected according to needs. The electrolyte may be, for example, liquid, gel, or all-solid.

[0134] In some embodiments, the electrolyte uses an electrolytic solution, which includes an electrolyte salt and a solvent.

[0135] Exemplarily, the lithium salt may include one or a combination of more selected from lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorodisalophosphate (LiDFOP), and lithium tetrafluorooxalophosphate (LiTFOP).

[0136] Exemplary organic solvents may include one or 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).

[0137] In some embodiments, the electrolyte solution may further contain additives as needed. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that improves certain battery performance, 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. [Separator]

[0138] In some embodiments, the battery cell further includes a separator. The type of separator in the present application is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0139] 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.

[0140] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be formed into an electrode assembly by a winding or lamination process.

[0141] The shape of the battery cell of the present application 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.

[0142] 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 includes a bottom plate and a side plate connected to the bottom plate, and a storage chamber is formed by the bottom plate and the side plate. The case 51 has an opening communicating with the storage chamber, and the cover plate 53 covers the opening to close the storage chamber. 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 storage chamber. 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 types and may be adjusted according to needs.

[0143] The method for manufacturing the battery cell of the present application is 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 wound or stacked to form an electrode assembly, which can then be placed in a housing and dried. The electrode assembly can then be infused with an electrolyte, and the battery cell can be obtained through processes such as vacuum sealing, standing, chemical conversion, and shaping.

[0144] In some embodiments of the present application, the battery cells of the present application can 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.

[0145] 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.

[0146] Optionally, the battery module 4 further includes a housing having an accommodating space, and the plurality of battery cells 5 are accommodated in the accommodating space.

[0147] 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 depending on the application and capacity of the battery pack.

[0148] 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 box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0149] Both the battery module and the battery pack can be examples of the battery of the present application. power consumption equipment

[0150] According to a third 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 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.), a train, a ship, a satellite, an energy storage system, etc.

[0151] A power consuming device can be configured as a battery cell, a battery module, or a battery pack depending on its needs. FIG. 6 is a schematic diagram of an exemplary power consuming device. The power consuming device 6 may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the power consuming device, a battery pack 1 or a battery module may be adopted. Another exemplary power consuming device may be a mobile phone, a tablet computer, a laptop, etc. Such a power consuming device is usually required to be thin, and may adopt a battery cell as its power source. Example

[0152] The following examples of the present application are described. The examples described below are illustrative and are intended only to interpret the present application and should not be understood as limitations on the present application. Unless specific techniques or conditions are specified in the examples, the techniques, conditions, or product instructions described in the literature in this field are used. Unless the manufacturer is specified, the reagents or equipment used are all commercially available, ordinary products. Example 1 (1) Manufacturing of positive electrode sheets

[0153] As the positive electrode current collector, an aluminum foil having a thickness of 12 μm was used.

[0154] A positive electrode slurry was prepared using fluoropolymer, LiFePO4, a positive electrode active material, carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) as binders. The mass ratio of fluoropolymer, LiFePO4, conductive 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, edge-cut, cut, and divided into stripes, and then dried in a vacuum at 85°C for 4 hours to prepare a positive electrode sheet. (2) Manufacturing of negative electrode sheets

[0155] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0156] A fluoropolymer, 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 were uniformly mixed in a weight ratio of 2.5:94:0.5:2:1:100 to prepare a negative electrode slurry. The negative electrode slurry was applied to a copper foil current collector and dried at 85°C. After that, the foil was cold pressed, edge-cut, cut, and divided into stripes. The negative electrode sheet was then dried in a vacuum at 120°C for 12 hours to prepare a negative electrode sheet. (3) Electrolyte production

[0157] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain an electrolyte solvent, which was then mixed with lithium salt LiPF6 to obtain an electrolyte with a lithium salt concentration of 1 mol / L. (4) Lithium-ion battery manufacturing

[0158] A 16 μm polyethylene film (PE) was used as the separator. The positive electrode sheet, separator, and negative electrode sheet were stacked in this order, and the separator was placed between the positive electrode sheet and the negative electrode sheet to serve as an insulator. The stack was then wound to obtain an electrode assembly. The electrode assembly was placed in an outer can, dried, and then an electrolyte was injected. After vacuum sealing, standing, chemical conversion, and shaping, a lithium-ion battery was obtained. Comparative Example 1

[0159] A lithium ion battery was manufactured in a manner similar to that of Example 1. Unlike Example 1, polyvinylidene fluoride (PVDF, crystallinity 48%, melting point 164°C) was added as a binder to the positive electrode sheet of Comparative Example 1, and no other fluoropolymer was added. Styrene butadiene rubber was added as a binder to the negative electrode sheet of Comparative Example 1, and no fluoropolymer was added. Comparative Example 2

[0160] A lithium ion battery was manufactured in a similar manner to Example 1, but unlike Example 1, the positive electrode sheet and negative electrode sheet of Comparative Example 2 were made of fluoropolymer materials. Examples 2 to 4

[0161] Lithium ion batteries were produced in a similar manner to Example 1, but unlike Example 1, the positive electrode sheets and negative electrode sheets of Examples 2 to 4 were made of fluoropolymer materials. Examples 5 to 7

[0162] Lithium ion batteries were produced in a similar manner to Example 1, but unlike Example 1, the content of fluoropolymer in the positive electrode sheets of Examples 5 to 7 was adjusted. Examples 8 to 10

[0163] Lithium ion batteries were produced in a similar manner to Example 1, but unlike Example 1, the content of fluoropolymer in the negative electrode sheets of Examples 8 to 10 was adjusted.

[0164] The data for the examples and comparative examples are shown in Table 1. Test part 1. Lithium-ion battery capacity retention test

[0165] The lithium-ion batteries manufactured in the examples and comparative examples were charged at a constant current of 1C to 4.25V at room temperature, then further charged at a constant voltage of 4.25V until the current reached 0.05C, left for 5 minutes, and then discharged at 1C to 2.8V, with the resulting capacity designated as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity Cn of the battery after n cycles was recorded at the same time. The capacity retention rate of the battery after each cycle was calculated as Pn = Cn / C0 * 100%, and a spot diagram of the battery's capacity retention rate versus cycle number was obtained by using the 1200 point values P1, P2...P1200 as the ordinate and the corresponding cycle number as the abscissa.

[0166] In this test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 1200th cycle corresponds to n=1200. For example, the capacity retention data of the battery corresponding to Example 1 in Table 1 is data measured after 1200 cycles under the above test conditions, i.e., the P1200 value. The test process for Comparative Example 1 and other Examples is the same as above.

[0167] 2. Lithium-ion battery DC impedance test

[0168] The lithium-ion batteries prepared in the examples and comparative examples were charged at a constant current of 1 / 3C to 4.25V at 25°C, then further charged at a constant voltage of 4.25V until the current reached 0.05C. After 5 minutes of storage, the voltage V1 was recorded. The batteries were then discharged at 1 / 3C for 30 seconds, and the voltage V2 was recorded. This voltage was calculated as (V2 - V1) / 1 / 3C, giving the battery's internal resistance (DCR1) after the first cycle. The same battery was then subjected to the same procedure, recording its internal resistance (DCRn) after the nth cycle (n = 1, 2, 3, ... 1200). A graph of the discharge DCIR vs. cycle number for the batteries corresponding to the polymers used in the examples and comparative examples was plotted using the 1200-point values (DCR1, DCR2, DCR3, ... DCR1200) as the ordinate and the corresponding cycle number as the abscissa.

[0169] In this test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 1200th cycle corresponds to n=1200. For example, in Table 1, the internal resistance increase rate of the battery 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 1200 cycles under the above test conditions. Test Results

[0170] [Table 1]

[0171] In Table 1, VDF stands for vinylidene fluoride, HFP stands for hexafluoropropylene, TFE stands for tetrafluoroethylene, 90% VDF means that the molar percentage of VDF is 90% of the total molar amount of VDF and HFP, and 10% FEP means that the molar percentage of FEP is 10%.

[0172] As can be seen from Table 1, compared to Comparative Example 1, in the Examples of the present application, the fluoropolymer of the present application is added to the positive electrode sheet and / or negative electrode sheet, and the fluoropolymer forms uniform high infiltration points inside the active material layer, uniformly improving the infiltration performance of the active material layer and increasing the liquid absorption rate of the entire active material layer, thereby improving the cycle performance of a battery cell using the electrode sheet.

[0173] Compared with Comparative Example 2, the Examples of the present application can more significantly improve the cycle performance of lithium ion batteries when v / λ>1 is satisfied.

[0174] Although the present application has been described above with reference to preferred embodiments, various modifications may be made without departing from the scope of the present application, and some of the components may be replaced with equivalents. In particular, as long as there is no structural contradiction, the technical features described in each embodiment may be arbitrarily combined. The present application is not limited to the specific embodiments disclosed above, but includes all technical solutions falling within the scope of the claims.

Claims

1. a current collector and an active material layer provided on at least one surface of the current collector, The active material layer contains an active material and a polymer, and the active material layer satisfies the following formulas (1) to (3): [Equation 1] [Equation 2] [Equation 3] In formulas (1) to (3), λ represents the porosity of the active material layer, P １ indicates the actual compressed density of the active material layer, and its unit is g / cm ３ and P ２ indicates the true compressed density of the active material, and its unit is g / cm ３ and v represents the liquid absorption rate of the active material layer, and its unit is mg / s, d represents the diameter of the capillary in a capillary test of the active material layer, and its unit is mm; h represents the height of the liquid surface in the capillary, and its unit is mm; ρ indicates the density of the electrolyte in the capillary test, and its unit is g / cm ３ and t represents the time it takes for the electrolyte to be absorbed in the capillary, and its unit is s; Electrode sheet.

2. The electrode sheet according to claim 1 , wherein the active material comprises a positive electrode active material, and the active material layer satisfies 1.00<v / λ<4.00, and optionally 1.20≦v / λ≦3.

80.

3. 3. The electrode sheet according to claim 1, wherein the active material comprises a positive electrode active material, and the mass percentage of the polymer is A%, based on the mass of the active material layer, and 0.1≦A≦1.

5.

4. 2. The electrode sheet according to claim 1, wherein the active material comprises a negative electrode active material, and the active material layer satisfies 3.00<v / λ<50.00, and optionally 3.40≦v / λ≦30.

00.

5. 5. The electrode sheet according to claim 1, wherein the active material comprises a negative electrode active material, and the mass percentage of the polymer is B%, based on the mass of the active material layer, and 0.2≦B≦5.

0.

6. The polymer has a crystallinity of X, as measured by differential scanning calorimetry. Ｃ %, and 0<X Ｃ ≦30, The melting temperature of the polymer is Tm, and its unit is ° C., and 0 < Tm ≦ 140; The electrode sheet according to claim 1 .

7. The electrode sheet according to any one of claims 1 to 6, wherein the glass transition temperature of the polymer is Tg, expressed in °C, and -150≦Tg≦60.

8. The polymer comprises at least one structural unit selected from the structural units represented by formula (I) to the structural units represented by formula (III), 【Chemical 1】 【Chemistry 2】 【Chemistry 3】 In formula (I) and formula (II), R １ , R ２ , R ３ and R ４ each independently contains a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1 to C3 alkyl group, or a substituted or unsubstituted C1 to C3 alkoxy group, and R １ , R ２ , R ３ and R ４ at least one of contains a fluorine atom, and when substituted, the substituent contains a fluorine atom; Selectable, R １ , R ２ , R ３ and R ４ each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a substituted or unsubstituted C1-C2 alkyl group, or a substituted or unsubstituted C1-C2 alkoxy group, and more selectively, R １ , R ２ , R ３ and R ４ each independently contains a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group, In formula (III), R ５ comprises a single bond, a substituted or unsubstituted C1-C3 alkyl group, and if substituted, the substituent comprises a fluorine atom; and p is a positive integer from 1 to 3; The electrode sheet according to any one of claims 1 to 7, wherein n is a positive integer of 1,000 to 30,000.

9. The electrode sheet according to any one of claims 1 to 8, wherein the polymer contains at least one structural unit represented by formula (I-1) to formula (I-11). 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 【Chemistry 7】 【Chemistry 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 【Chemistry 14】

10. The electrode sheet according to any one of claims 1 to 9, wherein the polymer further contains at least one structural unit represented by formula (II-1) to formula (II-5): 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 【Chemistry 18】 【Chemistry 19】

11. The electrode sheet according to any one of claims 1 to 10, wherein the polymer further contains at least one structural unit represented by formula (III-1) to formula (III-3). 【Chemistry 20】 【Chemical 21】 【Chemical 22】

12. n is a positive integer between 5,000 and 20,000, and / or The molecular weight of the polymer is 2×10 ５ g / mol~1.5×10 ６ The electrode sheet according to claim 8 , wherein the surface area of the electrode sheet is 100 μm or less.

13. A battery cell comprising the electrode sheet according to any one of claims 1 to 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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