Battery cell and preparation method therefor, battery device and electric device

Abstract

A battery cell and a preparation method therefor. The height of the battery cell is 120 mm or more. The battery cell comprises an electrode sheet and an electrolyte. The electrode sheet extends in a first direction, and the length thereof in the first direction is greater than that in a second direction, the second direction being perpendicular to the first direction and being the same as the height direction of the battery cell. The electrode sheet comprises a current collector and an electrode film layer which is arranged on at least one side of the current collector in a third direction and comprises an active material, the third direction being perpendicular to the first direction and the second direction. The electrode film layer has a middle region and two side regions, the middle region and the two side regions being arranged in the second direction. In the third direction, in the middle region, a functional layer is provided on the side of the electrode film layer away from the current collector; the length of the functional layer in the second direction is the same as the length of the middle region, and the functional layer contains ether and / or anhydride.

Description

Battery cells, their manufacturing methods, battery devices, and electrical devices

[0001] Cross-reference to related applications

[0002] This disclosure is based on and claims priority to Chinese Patent Application No. 202510366507.7, filed on March 26, 2025, entitled "Battery Cell, Method for Preparation Thereof, Battery Device and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of battery technology, and in particular to a battery cell, a method for preparing the battery cell, a battery device, and an electrical device. Background Technology

[0004] In recent years, with the increasingly wide range of applications for battery cells, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, aerospace, and many other fields. With the rapid development of batteries, higher requirements have been placed on battery cycle performance, especially for taller battery cells.

[0005] Therefore, how to improve the cycle performance of high-density battery cells has become an urgent technical problem to be solved. Summary of the Invention

[0006] This disclosure is made in view of the above-mentioned problems, and its object is to provide a high-strength battery cell, a method for preparing the same, a battery device, and an electrical device, wherein the battery cell of this disclosure has excellent cycle performance.

[0007] To achieve the above objectives, the first aspect of this disclosure provides a battery cell with a height of 120 mm or more. The battery cell includes an electrode and an electrolyte, as shown in FIG1. ​​The electrode extends along a first direction (the length direction of the electrode), and its length in the first direction is greater than its length in a second direction (the width direction of the electrode). The second direction is perpendicular to the first direction and is the same as the height direction of the battery cell. The electrode includes a current collector 521 and an electrode film layer comprising active material disposed on at least one side of the current collector along a third direction. The third direction (the stacking direction of the current collector and the electrode film layer) is perpendicular to the first and second directions. The electrode film layer has a middle region and two side regions, which are arranged along the second direction. Taking the position at half the length of the electrode film layer in the second direction as the midpoint, and taking a line passing through the midpoint and perpendicular to the second direction as the central axis, the middle region is a region formed by extending from the central axis along the second direction to both ends of the electrode film layer. Along the third direction, in the middle region, a functional layer is provided on the side of the electrode film layer away from the current collector. The length of the functional layer in the second direction is the same as the length of the middle region in the second direction, and the functional layer contains ether and / or acid anhydride. This battery cell can achieve uniform wetting of electrolyte in the height direction of the electrode, and can form a uniform high-quality SEI film / CEI film in the height direction, thereby improving the cycle performance of the battery cell.

[0008] In some embodiments, when the length from the midpoint to one end of the electrode film in the second direction is defined as L, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 80%L from the center to both ends and greater than or equal to the distance formed by extending 10%L from the center to both ends. By providing a functional layer of the above-mentioned length in the middle region of the electrode film, the wetting consistency of the electrolyte in the height direction of the battery cell can be improved, thereby improving the cycle performance of the battery cell.

[0009] In some embodiments, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 66%L from the center to both ends and greater than or equal to the distance formed by extending 20%L from the center to both ends. This is beneficial for further improving the uniformity of electrolyte wetting in the height direction of the battery cell, thereby further improving the cycle performance of the battery cell.

[0010] In some embodiments, the functional layer is continuous or discontinuous in the first direction. In some embodiments, the length of the functional layer in the first direction is 30% to 100% of the length of the electrode. This is beneficial for further improving the wetting uniformity of the electrode.

[0011] In some embodiments, the functional layer includes fluoroethers and / or acid anhydrides. This reduces the surface tension of the electrolyte in the middle region of the electrode film, thereby improving the electrolyte wetting ability in the middle region and thus benefiting the cycle performance of the battery cell.

[0012] In some embodiments, the fluoroether comprises a compound of formula (1), R1-O-R2 of formula (1), wherein R1 is selected from C1 to C2. 10 Fluorinated alkyl groups or C2-C 10 fluoroalkenyl; R2 is selected from C1 to C2. 10 Alkyl groups, C2-C 10 alkenyl, C1-C 10 Fluorinated alkyl groups or C2-C 10 The fluorinated alkenyl group; the acid anhydride includes one or more of inorganic acid anhydrides and unsubstituted or fluorinated organic acid anhydrides having 2 to 4 carbon atoms. In some embodiments, the functional layer includes one or more of dimethyl ether, ethyl fluoroethyl ether, perfluoropropyl vinyl ether, perfluoroethyl ether, perfluorodiisopropyl ether, acetic anhydride, trifluoroacetic anhydride, maleic anhydride, sulfuric anhydride, and phosphoric anhydride. The above ethers and / or acid anhydrides have strong electron-withdrawing groups, which can reduce surface tension and improve wettability.

[0013] In some implementations, the height of the battery cell is 215mm-260mm.

[0014] In some embodiments, the electrode includes a positive electrode and a negative electrode. The negative electrode includes a current collector and a negative electrode film layer, and a functional layer is provided on the side of the negative electrode film layer away from the current collector. By providing a functional layer in the middle region of the negative electrode film layer, the wetting ability of the middle region of the negative electrode can be improved, which is beneficial to forming a SEI film with high uniformity in the height direction, thereby improving the cycle performance of the battery cell.

[0015] In some embodiments, the electrolyte comprises an electrolyte salt, and the concentration difference between the electrolyte salt in the two side regions and the concentration in the middle region of the negative electrode film is 0 mol / L to 0.2 mol / L. In some embodiments, the concentration difference between the electrolyte salt in the two side regions and the concentration in the middle region of the negative electrode film is 0 mol / L to 0.12 mol / L. The small difference in electrolyte salt concentration between the two side regions and the middle region indicates good uniformity of electrolyte wetting in the height direction in the battery cell of this disclosure, which is beneficial for forming a uniform SEI film / CEI film.

[0016] In some implementations, the functional layer accounts for 0.01% to 2% of the mass of the electrode film layer. This allows for both improved cycle performance and rate performance of the battery cell.

[0017] In some implementations, the thickness of the third-side upward functional layer is between 0.02 μm and 2 μm. This is beneficial in two ways: firstly, it enhances the wetting ability of the intermediate region by utilizing the functional layer; secondly, it helps to balance the rate performance of the individual cells.

[0018] The second aspect of this disclosure provides a method for preparing a battery cell with a height of 120 mm or more, comprising the following steps:

[0019] Electrode preparation steps: An active material is coated onto a current collector to form an electrode film, resulting in an electrode. The electrode extends along a first direction, with its length in the first direction greater than its length in the second direction. The second direction is perpendicular to the first direction and parallel to the height direction of the battery cell. In the second direction, the electrode film has a central region and two side regions, arranged along the second direction. The midpoint of the electrode film in the second direction is taken as half its length, and a line passing through this midpoint and perpendicular to the second direction is taken as the central axis. The central region is formed by extending from the central axis along the second direction towards both ends of the electrode film.

[0020] Coating step: A slurry containing ether and / or acid anhydride is coated in the middle area of ​​the electrode film to form a functional layer.

[0021] A functional layer is formed by setting a central region and two side regions in the second direction of the electrode (i.e., the height direction of the battery cell), and coating the central region with the aforementioned slurry. This functional layer can reduce the surface tension of the electrolyte, thereby improving the wetting effect of the electrolyte on the central region of the electrode film layer, and further improving the wetting consistency of the electrolyte in the height direction of the battery cell. This results in the formation of a uniform, high-quality SEI / CEI film in the height direction, which is beneficial to improving the cycle performance of the battery cell.

[0022] In some embodiments, when the length from one end of the electrode film to the center in the second direction is defined as L, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 80%L from the center to both ends and greater than or equal to the distance formed by extending 10%L from the center to both ends.

[0023] In some implementations, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 66%L from the center to both ends and greater than or equal to the distance formed by extending 20%L from the center to both ends.

[0024] In some implementations, the thickness of the functional layer is from 0.02 μm to 2 μm.

[0025] In some embodiments, the functional layer includes fluoroethers and / or acid anhydrides.

[0026] In some embodiments, the slurry also contains a solvent, which includes one or more of carbonates, sulfates, sulfites, sulfonates, and phosphates.

[0027] A third aspect of this disclosure provides a battery device that includes the battery of the first aspect of this disclosure, or includes a battery prepared according to the preparation method provided in the second aspect of this disclosure.

[0028] A fourth aspect of this disclosure provides an electrical device, including the battery device of the third aspect of this disclosure. Attached Figure Description

[0029] Figure 1 is a schematic diagram of the internal structure of a battery cell according to an embodiment of the present disclosure.

[0030] Figure 2 is a cross-sectional view of the battery cell in Figure 1 in the second direction.

[0031] Figure 3 is a schematic diagram of a battery cell according to one embodiment of the present disclosure.

[0032] Figure 4 is an exploded view of a battery cell according to an embodiment of the present disclosure shown in Figure 3.

[0033] Figure 5 is a schematic diagram of a battery module according to one embodiment of the present disclosure.

[0034] Figure 6 is a schematic diagram of a battery pack according to one embodiment of the present disclosure.

[0035] Figure 7 is an exploded view of a battery pack according to an embodiment of the present disclosure, as shown in Figure 6.

[0036] Figure 8 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present disclosure.

[0037] Explanation of reference numerals in the attached drawings: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 521 Current collector; 522 Electrode film layer; 523 Functional layer; 524 Midpoint; 525 Central axis; 53 Top cover assembly. Detailed Implementation

[0038] The following detailed description, with appropriate reference to the accompanying drawings, discloses the battery cell, method for manufacturing the battery cell, battery device, and power-consuming device of this disclosure. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0039] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0042] Unless otherwise specified, the terminology used in this disclosure has the common meaning as commonly understood by those skilled in the art.

[0043] Unless otherwise specified, the values ​​of the parameters mentioned in this disclosure can be determined using various test methods commonly used in the art, for example, according to the test methods given in this disclosure.

[0044] In this disclosure, the battery cell is a secondary battery, which can be reactivated by charging after discharge to continue its use. The battery cell can be a lithium-ion battery, a sodium-ion battery, or a sodium-lithium-ion battery; this disclosure is not limited to these. The battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator is positioned between the positive and negative electrodes, primarily preventing short circuits between the positive and negative electrodes while allowing ions to pass through.

[0045] Currently, in relatively tall battery cells, after the initial electrolyte injection, the electrolyte wettes from the periphery towards the center. Due to the chromatographic effect of electrolyte creep, the concentration of electrolyte salts and additives in the electrolyte gradually decreases from the edges to the center, resulting in the quality of the initial anode film (SEI film) in the center of the battery cell being inferior to that in other areas. Therefore, there is an urgent need for a method to improve the electrolyte wetting ability of local areas of the electrode.

[0046] To address the aforementioned issues, some reports have indicated that adding electrolyte wetting agents to the electrolyte of individual battery cells can reduce the surface tension of the electrolyte and thus improve its wetting ability. However, this method only improves the overall wettability of the electrolyte to the electrode and still cannot improve the uniformity of electrolyte wetting along the height of the electrode. In particular, for taller battery cells, the central part of the cell is still difficult to wet with electrolyte, resulting in uneven electrolyte distribution along the height of the cell. This leads to inconsistent film composition during the formation stage, causing problems such as lithium plating during cycling and affecting the battery's cycle performance.

[0047] Based on this, this disclosure proposes a battery cell, its preparation method, a battery device, and an electrical device. The battery cell of this disclosure has good electrolyte wetting uniformity in the height direction and excellent cycle performance. The following provides a more detailed description of this disclosure and optional embodiments.

[0048] battery cell

[0049] The first aspect of this disclosure provides a battery cell with a height of 120 mm or more. The battery cell includes an electrode and an electrolyte, as shown in FIG1. ​​The electrode extends along a first direction (the length direction of the electrode), and its length in the first direction is greater than its length in a second direction (the width direction of the electrode). The second direction is perpendicular to the first direction and is the same as the height direction of the battery cell. The electrode includes a current collector 521 and an electrode film layer 522 disposed on at least one side of the current collector along a third direction and including an active material. The third direction (the stacking direction of the current collector and the electrode film layer) is perpendicular to the first and second directions. The electrode film layer has a middle region and two side regions, which are arranged along the second direction. The midpoint 524 is located at half the length of the electrode film layer in the second direction. A line passing through the midpoint 524 and perpendicular to the second direction is taken as the central axis 525. The middle region is a region formed by extending from the central axis 525 along the second direction to both ends of the electrode film layer. Along the third direction, in the intermediate region, a functional layer 523 is provided on the side of the electrode film layer away from the current collector. The length of the functional layer 523 in the second direction is the same as the length of the intermediate region in the second direction, and the functional layer 523 contains ether and / or acid anhydride.

[0050] In this disclosure, for battery cells with a height of 120 mm or more, a functional layer is provided in the middle region of the electrode film layer along a second direction (i.e., the height direction of the battery cell). The functional layer includes ethers and / or anhydrides. Because ether bonds and anhydride bonds have strong electronic attraction and small intermolecular interaction forces, they can reduce surface tension and reduce the contact angle between the electrolyte and the electrode film layer, thereby improving the wetting ability of the electrolyte in the middle region of the electrode film layer and improving the wetting consistency of the electrolyte in the height direction of the battery cell. This can form a uniform, high-quality SEI film / CEI film in the height direction, which is beneficial to improving the cycle performance of the battery cell.

[0051] In the battery cells disclosed herein, the ethers and / or anhydrides in the functional layers can be determined using infrared spectroscopy. Specifically, infrared spectroscopy analysis of the material can be performed using instruments and methods known in the art to detect the ether bonds and anhydride bonds in the functional layers. For example, an infrared spectrometer (such as the Nicolet IS10 Fourier transform infrared spectrometer) can be used, and the test can be performed according to the general rules of infrared spectroscopy analysis method in GB / T 6040-2019.

[0052] In this disclosure, the height of a single battery cell can be measured using a micrometer or a height gauge. Exemplarily, the height of the battery in this disclosure can be a value within a range of 120mm, 150mm, 180mm, 200mm, 215mm, 220mm, 240mm, 260mm, or any combination thereof. Optionally, the height of a single battery cell is between 215mm and 260mm.

[0053] In some embodiments, as shown in FIG2, when the length from one end of the electrode film layer to the center in the second direction is defined as L, the length of the functional layer 523 in the second direction is less than or equal to the distance formed by extending 80%L from the center to both ends and greater than or equal to the distance formed by extending 10%L from the center to both ends. By providing a functional layer of the above-mentioned length in the middle region of the electrode film layer, the electrolyte wetting ability in the middle region can be improved, thereby improving the wetting consistency of the electrolyte in the height direction of the battery cell, which is beneficial to improving the cycle performance of the battery cell. For example, the length of the functional layer in the second direction is a value between the distances formed by extending 80%L, 75%L, 70%L, 75%L, 66%L, 60%L, 55%L, 50%L, 45%L, 40%L, 35%L, 30%L, 25%L, 20%L, 15%L, and 10%L from the center to both ends, or any range of two of these. Optionally, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 66%L from the center to both ends and greater than or equal to the distance formed by extending 20%L from the center to both ends.

[0054] In some embodiments, the functional layer is continuous or discontinuous in the first direction. The length of the functional layer in the first direction is less than or equal to the length of the electrode film layer in the first direction. Exemplarily, the length of the functional layer in the first direction is the same as the length of the electrode film layer in the first direction, or is a value between 30% and 100% of the length of the electrode film layer in the first direction, for example, a value between 100%, 95%, 90%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 33%, 30%, or any combination thereof. Preferably, in the first direction, the length of the functional layer is 33% to 100% of the length of the electrode.

[0055] In some embodiments, the functional layer includes fluorinated ethers and / or acid anhydrides. In this disclosure, fluorinated ethers refer to fluorinated ether compounds whose molecular structure contains an ether bond (-O-) and a fluorine atom. The fluorine atom in the fluorinated ether and the -O=COC=O- structure in the acid anhydride both exhibit strong electron attraction. Placing the functional layer containing fluorinated ethers and / or acid anhydrides in the middle region of the electrode film can reduce the surface tension of the electrolyte in the middle region of the electrode film, decrease the contact angle between the electrolyte and the electrode film, thereby improving the electrolyte wetting ability in the middle region. This is beneficial for improving the consistency of electrolyte wetting along the height direction of the battery cell, thus improving the cycle performance of the battery cell.

[0056] In some embodiments, the fluoroether comprises a compound represented by formula (1).

[0057] R1-O-R2 Equation (1)

[0058] In the formula, R1 is selected from C1 to C2. 10 Fluorinated alkyl groups or C2-C 10 fluoroalkenyl; R2 is selected from C1 to C2. 10 Alkyl groups, C2-C 10 alkenyl, C1-C 10 Fluorinated alkyl groups or C2-C 10 Fluoroalkenyl groups.

[0059] Acid anhydrides include one or more of inorganic acid anhydrides and organic acid anhydrides that are unsubstituted or fluorinated and have 2 to 4 carbon atoms.

[0060] In some implementations, R1 and R2 are each independently C1 to C2. 10 Perfluorinated substituted alkyl groups.

[0061] In some embodiments, the ethers include perfluoroethyl ether, dimethyl ether, ethylfluoroethyl ether, perfluoropropyl vinyl ether, and perfluorodiisopropyl ether. The anhydrides include, for example, one or more of acetic anhydride, trifluoroacetic anhydride, maleic anhydride, sulfuric anhydride, and phosphoric anhydride. These compounds can reduce the surface tension of the electrolyte in the middle region of the electrode film, which is beneficial to improving the wetting consistency of the electrolyte in the height direction of the battery cell, thereby improving the cycle performance of the battery cell.

[0062] In some embodiments, the height of the battery cell is 215mm-260mm. When the height of the battery cell is within this range, the wettability of the battery cell in the height direction is significantly improved, and the cycle performance of the battery cell is significantly improved. Exemplarily, the height of the battery cell is a value between 215mm, 220mm, 230mm, 239mm, 250mm, 260mm, or any combination thereof.

[0063] In some embodiments, the electrode includes a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector and containing a positive active material. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector and containing a negative active material. A functional layer is provided in the middle region of the negative electrode film layer, on the side away from the negative current collector. By providing a functional layer in the middle region of the negative electrode film layer, the wetting ability of the middle region of the negative electrode can be improved, thereby improving the wetting consistency of the electrolyte in the height direction of the negative electrode and facilitating the formation of a highly uniform SEI film in the height direction, thus improving the cycle performance of the battery cell.

[0064] In some embodiments, the electrolyte comprises an electrolyte salt, and the concentration difference between the electrolyte salt in the two side regions and the electrolyte salt concentration in the middle region in the electrode film layer is 0 mol / L to 0.2 mol / L. The wettability of the middle region of the battery cell disclosed herein is improved, and the increased electrolyte salt concentration in the middle region reduces the concentration difference between the electrolyte salt in the two side regions and the middle region. This indicates that the electrolyte exhibits good wetting consistency in the height direction in the battery cell disclosed herein, which is beneficial for forming a uniform SEI film / CEI film, thereby improving the cycle performance of the battery cell. For example, the difference between the concentration of the electrolyte salt in the intermediate region and the concentration of the electrolyte salt in the two side regions is a value within a range of 0 mol / L, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.10 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.17 mol / L, 0.18 mol / L, 0.19 mol / L, 0.2 mol / L, or any two of these. Preferably, the difference between the concentration of the electrolyte salt in the intermediate region and the concentration of the electrolyte salt in the two side regions is from 0 mol / L to 0.12 mol / L.

[0065] In this disclosure, the concentration of electrolyte salts in the middle and lateral regions of the electrode film can be measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0066] In some embodiments, the functional layer accounts for 0.01% to 2% of the mass of the electrode film layer. This functional layer enhances the wetting ability of the intermediate region and improves the electrolyte wetting uniformity of the battery cell in the height direction, thereby benefiting the cycle performance of the battery cell while also balancing the rate performance of the battery cell. For example, the mass percentage of the functional layer relative to the mass of the electrode is a value between 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any combination thereof.

[0067] In some embodiments, the thickness of the third-party upward functional layer is between 0.02 μm and 2 μm. This is beneficial in two ways: firstly, it enhances the wetting ability of the central region; secondly, it helps to maintain the rate performance of the individual battery cells. For example, the thickness of the functional layer is a value within a range of 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.10 μm, 0.12 μm, 0.14 μm, 0.16 μm, 0.18 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, or any combination thereof.

[0068] The second aspect of this disclosure provides a method for preparing a battery cell, characterized in that the height of the battery cell is 120 mm or more, comprising the following steps:

[0069] Electrode preparation steps: An active material is coated onto a current collector to form an electrode film, resulting in an electrode. The electrode extends along a first direction, with its length in the first direction greater than its length in the second direction. The second direction is perpendicular to the first direction and parallel to the height direction of the battery cell. In the second direction, the electrode film has a central region and two side regions, arranged along the second direction. The midpoint of the electrode film in the second direction is taken as half its length, and a line passing through this midpoint and perpendicular to the second direction is taken as the central axis. The central region is formed by extending from the central axis along the second direction towards both ends of the electrode film.

[0070] Coating step: A slurry containing ether and / or acid anhydride is coated in the middle area of ​​the electrode film to form a functional layer.

[0071] By setting a middle region and two side regions in the second direction of the electrode (i.e., the height direction of the battery cell), and coating the middle region with the above-mentioned slurry, a functional layer is formed. This functional layer can reduce the surface tension of the electrolyte, thereby improving the wetting effect of the electrolyte on the middle region of the electrode film layer, and further improving the wetting consistency of the electrolyte in the height direction of the battery cell, forming a uniform and high-quality SEI film / CEI film in the height direction, which is beneficial to improving the cycle performance of the battery cell.

[0072] In some embodiments, when the length from one end of the electrode film to the center in the second direction is defined as L, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 80%L from the center to both ends and greater than or equal to the distance formed by extending 10%L from the center to both ends.

[0073] In some implementations, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 66%L from the center to both ends and greater than or equal to the distance formed by extending 20%L from the center to both ends.

[0074] In some implementations, the thickness of the functional layer is from 0.02 μm to 2 μm.

[0075] In some embodiments, the slurry also contains a solvent, which, exemplarily, includes one or more of carbonates, sulfates, sulfites, sulfonates, and phosphates. For example, the solvent may include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), dimethyl sulfate, diethyl sulfate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, 4-isopropylphenyl diphenyl phosphate, diphenyl octyl phosphate, trioctyl phosphate, and dodecyl phosphate, etc. The components of the battery cell of this disclosure are described in detail below.

[0076] Negative electrode sheet

[0077] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0078] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0079] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0080] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this disclosure is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0081] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of 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).

[0082] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0084] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0085] Positive electrode sheet

[0086] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes the positive electrode material disclosed herein, or the positive electrode material prepared according to the preparation method of the present disclosure.

[0087] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector. In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0088] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this disclosure is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.1 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0089] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0090] In the examples of positive electrode active materials in this disclosure, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0091] In some embodiments, when the battery cell is a sodium-ion battery, the positive electrode active material may be a known positive electrode active material for sodium-ion batteries. As an example, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc.

[0092] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0093] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0094] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0095] electrolytes

[0096] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This disclosure does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid or gel-like.

[0097] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0098] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0099] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0100] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0101] Separating membrane

[0102] In some embodiments, the battery cell also includes a separator. This disclosure does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0103] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0104] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0105] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0106] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0107] This disclosure does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 shows a square battery cell 5 as an example.

[0108] In some embodiments, referring to FIG4, the outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0109] Battery device

[0110] In addition, a third aspect of this disclosure provides a battery device that includes the battery cell of this disclosure.

[0111] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0112] Figure 5 shows a battery module 4 as an example. Referring to Figure 5, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0113] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0114] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0115] Figures 6 and 7 illustrate a battery pack 1 as an example. Referring to Figures 6 and 7, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0116] Electrical appliances

[0117] Furthermore, a fourth aspect of this disclosure provides an electrical device, which includes the battery device provided in this disclosure. The battery device can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0118] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0119] Figure 8 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0120] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0121] Example

[0122] The following describes embodiments of this disclosure. The embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0123] Example 1

[0124] Preparation of battery cells

[0125] Preparation of the positive electrode: Lithium iron phosphate (LFP) active material, acetylene black (ACH) conductive agent, and PVDF binder are mixed in a weight ratio of 94:4:2. N-methylpyrrolidone (NMP) solvent is added, and the mixture is thoroughly stirred to obtain a uniform positive electrode slurry. This slurry is then coated onto both sides of the positive electrode current collector aluminum foil. The coating weight of the positive electrode slurry is 0.224 g / 1540.25 mm. 2 (Based on weight excluding solvent), after drying and cold pressing, a positive electrode sheet is obtained.

[0126] Preparation of negative electrode sheet:

[0127] Artificial graphite (specific capacity 340 mAh / g), acetylene black (conductive agent), and SBR+CMC (binder) were mixed in a weight ratio of 95:1.5:3.1:0.4. Deionized water was added as a solvent, and the mixture was stirred thoroughly to obtain a negative electrode slurry. The negative electrode slurry was then coated onto both sides of the copper foil used as the negative electrode current collector, with a coating weight of 0.136 g / 1540.25 mm. 2 (Based on weight excluding solvent), after drying and cold pressing, a negative electrode film layer is formed on both sides of the current collector (the length in the first direction is 13403 mm; the length in the second direction is 227 mm), thus obtaining the negative electrode sheet.

[0128] Take 100 mL of perfluorodiisopropyl ether, 100 mL of acetic anhydride and 800 mL of ethylene carbonate (EC) solvent and mix them evenly to obtain a mixture.

[0129] The above-mentioned mixture is sprayed onto the middle region of the negative electrode film layers on both sides of the obtained negative electrode sheet to form a functional layer. The length of the functional layer in the first direction is the same as the length of the negative electrode film layer in the first direction. The length of the functional layer in the second direction is the distance formed by extending 66%L (where L is the length from one end of the negative electrode film layer to the center in the second direction) from the center of the negative electrode film layer to both sides (i.e., 150 mm). The length of the functional layer on one side of the negative electrode film layer in the third direction (i.e., the thickness of the functional layer) is 20 nm. The mass percentage of the functional layer relative to the mass of the negative electrode film layer is 0.015%.

[0130] Electrolyte preparation:

[0131] In an argon atmosphere glove box with a water content of <10ppm, EC, PC, and DMC were mixed in a weight ratio of 1:1:1. Then, LiPF6, VC, DTD, and PS were added to the mixed organic solvent and stirred until homogeneous to obtain an electrolyte. The concentration of LiPF6 was 1 mol / L, and the mass percentages of VC, DTD, and PS were 3%, 1%, and 1%, respectively.

[0132] Preparation of the separating membrane:

[0133] Polyethylene porous membrane is used as the separation membrane.

[0134] Assembly of individual battery cells:

[0135] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting cells are then wound to obtain a bare cell. The bare cell is placed in a casing with a height of 239 mm, the electrolyte is injected, and the casing is then encapsulated for formation to obtain a single battery cell with a height of 239 mm.

[0136] Parameter testing

[0137] Contact angle test:

[0138] The negative electrode sheet was left to stand at room temperature (25°C) for 1 hour. Electrolyte (the liquid used for contact angle testing) was then dropped onto the functional layer, and the contact angle was measured using a contact angle measuring instrument.

[0139] Electrolyte salt concentration determination:

[0140] The battery cell is disassembled to obtain the negative electrode. The central region is then cut away from the two side regions along the height direction (the second direction). The electrode is centrifuged to obtain the electrolyte. Ion chromatography is used, utilizing the principle of ion exchange, where different ions have different partition coefficients between the stationary and mobile phases, thus achieving separation. The separated electrolyte salt ions are detected using a conductivity detector, and the ion concentration in the electrolyte salt is determined by comparing the peak area or peak height with a standard solution. This leads to the calculation of the electrolyte salt concentration, and ultimately, the difference in electrolyte concentration between the two side regions and the central region.

[0141] Battery cell performance testing

[0142] Cyclic performance test:

[0143] At 25℃, the battery cell is first charged at a constant current of 1C (i.e., the current value at which the theoretical capacity is completely discharged within 1 hour) to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, the battery is discharged at a constant current of 1C to a voltage of 2.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The lithium-ion rechargeable battery is subjected to multiple charge-discharge cycles using the above method until the discharge capacity of the lithium-ion rechargeable battery decays to 90%, and the number of cycles is recorded.

[0144] Example 2-11

[0145] Battery cells were prepared using the same method as in Example 1, except that the type of ether and / or anhydride or the height of the battery cell was adjusted as shown in Table 1.

[0146] Comparative Example 1

[0147] Battery cells were prepared using the same method as in Example 1, except that in Comparative Example 1, after obtaining the negative electrode sheet, ethylene carbonate solvent was sprayed onto the middle region of the negative electrode sheet, without using ether and acid anhydride.

[0148] Comparative Example 2

[0149] Battery cells were prepared using the same method as in Example 1, except that in Comparative Example 2, after obtaining the negative electrode sheet, the mixture from Example 1 was sprayed onto the entire surface of the negative electrode film to form a functional layer on the entire surface of the film.

[0150] Table 1

[0151] The same test methods as in Example 1 were used to test Examples 1 to 11 and Comparative Examples 1 and 2. The results are shown in Table 2 below.

[0152] Table 2

[0153] The results show that setting a functional layer containing ether and / or anhydride in the middle region of the electrode film can reduce the contact angle between the electrolyte and the electrode film, improve the electrolyte wetting ability in the middle region, improve the electrolyte wetting consistency between the middle region and the two sides (i.e., in the height direction of the battery cell), and thus improve the cycle performance of the battery cell.

[0154] Examples 12-17

[0155] Battery cells were prepared using the same method as in Example 1, except that the dimensions of the functional layers were adjusted as shown in Table 3.

[0156] Table 3

[0157] Examples 12-17 were tested using the same testing method as Example 1, and the results are shown in Table 4 below.

[0158] Table 4

[0159] The results show that by setting the above-mentioned functional layer in the corresponding area of ​​the electrode film layer of this disclosure, the contact angle between the electrolyte and the electrode film layer can be reduced, the electrolyte wetting consistency in the height direction of the battery cell can be improved, and thus the cycle performance of the battery cell can be improved.

[0160] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A battery cell, The height of the battery cell is 120mm or more. The battery cell includes electrodes and an electrolyte. The electrode extends along a first direction, the length of which is greater than the length of a second direction. The second direction is perpendicular to the first direction and coincides with the height direction of the battery cell. The electrode includes a current collector and an electrode film layer comprising active material disposed on at least one side of the current collector along a third direction, the third direction being perpendicular to both the first and second directions. The electrode film layer has a central region and two side regions, which are arranged along the second direction. The midpoint is defined as the location halfway along the length of the electrode film in the second direction. A line perpendicular to the second direction and passing through the midpoint is taken as the central axis. The intermediate region is formed by extending from the central axis along the second direction towards both ends of the electrode film. Along the third direction, in the intermediate region, on the side of the electrode film layer away from the current collector, a functional layer is provided, the length of the functional layer in the second direction is the same as the length of the intermediate region in the second direction, and the functional layer contains ether and / or acid anhydride.

2. The battery cell according to claim 1, wherein, When the length from the midpoint to one end of the electrode film in the second direction is defined as L, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 80%L from the center to both ends and greater than or equal to the distance formed by extending 10%L from the center to both ends.

3. The battery cell according to claim 2, characterized in that, The length of the functional layer in the second direction is less than or equal to the distance formed by extending 66%L from the center to both ends and greater than or equal to the distance formed by extending 20%L from the center to both ends.

4. The battery cell according to any one of claims 1 to 3, wherein, In the first direction, the functional layer exists continuously or intermittently.

5. The battery cell according to any one of claims 1 to 4, wherein, In the first direction, the length of the functional layer is 30% to 100% of the length of the electrode.

6. The battery cell according to any one of claims 1 to 5, wherein, The functional layer includes fluoroethers and / or acid anhydrides.

7. The battery cell according to claim 6, wherein, The fluoroether includes compounds represented by formula (1). R1-O-R2 Equation (1) In the formula, R1 is selected from C1 to C2. 10 Fluorinated alkyl groups or C2-C 10 The fluorinated alkenyl group, R2 is selected from C1 to C2. 10 Alkyl groups, C2-C 10 alkenyl, C1-C 10 Fluorinated alkyl groups or C2-C 10 Fluoroalkenyl groups; The acid anhydrides include one or more of inorganic acid anhydrides and organic acid anhydrides having 2 to 4 carbon atoms that are unsubstituted or fluorinated.

8. The battery cell according to claim 1, wherein, The functional layer includes one or more of dimethyl ether, ethyl fluoroethyl ether, perfluoropropyl vinyl ether, perfluoroethyl ether, perfluorodiisopropyl ether, acetic anhydride, trifluoroacetic anhydride, maleic anhydride, sulfuric anhydride, and phosphoric anhydride.

9. The battery cell according to any one of claims 1 to 8, wherein, The height of the battery cell is 215mm-260mm.

10. The battery cell according to any one of claims 1 to 9, wherein, The electrode includes a positive electrode and a negative electrode. The negative electrode includes a current collector and a negative electrode film layer. The functional layer is provided on the side of the negative electrode film layer away from the current collector.

11. The battery cell according to claim 10, wherein, The electrolyte includes an electrolyte salt, and in the negative electrode film layer, the concentration difference of the electrolyte salt in the two side regions and the concentration of the electrolyte salt in the middle region is 0 mol / L to 0.2 mol / L.

12. The battery cell according to claim 11, wherein, In the electrode film layer, the difference between the concentration of the electrolyte salt in the two side regions and the concentration of the electrolyte salt in the middle region is 0 mol / L to 0.12 mol / L.

13. The secondary battery according to any one of claims 1 to 12, wherein, The mass percentage of the functional layer relative to the mass of the electrode film is 0.01% to 2%.

14. The secondary battery according to any one of claims 1 to 13, wherein, In the third direction, the thickness of the functional layer is 0.02 μm to 2 μm.

15. A method for preparing a battery cell, wherein the height of the battery cell is 120 mm or more, comprising the following steps: Electrode preparation steps: An active material is coated onto a current collector to form an electrode film, resulting in an electrode. The electrode extends along a first direction, with its length in the first direction greater than its length in a second direction. The second direction is perpendicular to the first direction and aligns with the height direction of the battery cell. The electrode film has a central region and two side regions, arranged along the second direction. The midpoint is located at half the length of the electrode film in the second direction. A line passing through this midpoint and perpendicular to the second direction is taken as the central axis. The central region is formed by extending from the central axis along the second direction towards both ends of the electrode film. Coating step: A slurry containing ether and / or acid anhydride is coated in the middle region of the electrode film to form a functional layer.

16. The preparation method according to claim 15, wherein, When the length from the midpoint to one end of the electrode film in the second direction is defined as L, the length of the functional layer in the second direction is less than or equal to the distance formed by extending 80%L from the center to both ends and greater than or equal to the distance formed by extending 10%L from the center to both ends.

17. The preparation method according to claim 15 or 16, wherein, The length of the functional layer in the second direction is less than or equal to the distance formed by extending 66%L from the center to both ends and greater than or equal to the distance formed by extending 20%L from the center to both ends.

18. The preparation method according to any one of claims 15 to 17, wherein, The thickness of the functional layer is from 0.02 μm to 2 μm.

19. The preparation method according to any one of claims 15 to 18, wherein, The slurry includes fluoroethers and / or acid anhydrides.

20. The preparation method according to any one of claims 15 to 19, wherein, The slurry also contains a solvent, which includes one or more of carbonates, sulfates, sulfites, sulfonates, and phosphates.

21. A battery device comprising a battery cell according to any one of claims 1 to 14, or comprising a battery cell prepared by the preparation method according to any one of claims 15 to 20.

22. An electrical device comprising the battery device of claim 21.

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