Battery monomer, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a negative pole piece, the negative pole piece comprises a negative pole current collector and a negative pole film layer located on at least one side of the negative pole current collector, the negative pole film layer comprises a pressing aid, the pressing aid is of a sheet structure, the maximum sheet diameter of the pressing aid in the direction perpendicular to the thickness direction is L1, the thickness of the pressing aid is L2, and L1 / L2 is larger than or equal to 2. The battery monomer provided by the invention has improved cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery cell, a battery device, and an electrical device. Background Technology

[0002] Battery cells are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric car toys, electric toy ships, electric toy airplanes, and power tools.

[0003] In the development of battery cells, improving the cycle performance of battery cells is one of the urgent problems to be solved. Summary of the Invention

[0004] This application provides a battery cell, a battery device, and an electrical device that can improve the cycle performance of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, the battery cell including a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer located on at least one side of the negative current collector, the negative electrode film layer including a pressure booster, the pressure booster having a sheet-like structure, the maximum sheet diameter of the pressure booster being L1, the thickness of the pressure booster being L2, and L1 / L2≥2.

[0006] In this application, a pressure-boosting agent with a sheet-like structure is added to the negative electrode film layer, and the ratio of the maximum sheet diameter to its thickness is limited to be greater than or equal to 2. When the pressure-boosting agent with this structural feature is added to the positive electrode film layer, the sheet-like structured pressure-boosting agent will slip under the rolling pressure during the rolling process, thereby reducing the residual stress of the negative electrode sheet after rolling, and thus reducing the thickness rebound of the negative electrode sheet, giving the negative electrode sheet higher dimensional stability, thereby improving the cycle performance of the battery cell.

[0007] In some embodiments, 10 ≤ L1 / L2 ≤ 1000.

[0008] In some embodiments, the minimum diameter of the pressure-boosting agent is L3, where 1 ≤ L1 / L3 ≤ 10.

[0009] In some embodiments, 1μm≤L1≤500μm; optionally, 5μm≤L1≤100μm.

[0010] In some embodiments, 0.1 μm ≤ L3 ≤ 50 μm; alternatively, 1 μm ≤ L3 ≤ 20 μm.

[0011] In some embodiments, 1nm ≤ L2 ≤ 500nm; alternatively, 10nm ≤ L2 ≤ 100nm.

[0012] In some embodiments, the pressure-boosting agent comprises one or more of layered zirconium phosphate, layered carbon material, and layered silicate. The layered carbon material has a graphite microcrystalline structure, wherein the radial dimension of the graphite microcrystalline is La, the axial dimension is Lc, and La / Lc≥10.

[0013] In some embodiments, 10 ≤ La / Lc ≤ 100.

[0014] In some embodiments, the layered carbon material includes one or more of flake graphite, expanded graphite, and graphene.

[0015] In some embodiments, the mass content of the pressure booster in the negative electrode film layer is 0.5% to 5%.

[0016] In some embodiments, the compaction density of the negative electrode sheet is 1.0 g / cm³. 3 Up to 2.2 g / cm 3 .

[0017] In some embodiments, the single-sided coating surface density of the negative electrode film is 0.1 g / 1540.25 mm. 2 Up to 0.3g / 1540.25mm 2 .

[0018] In some embodiments, the thickness rebound rate of the negative electrode sheet after cold pressing and standing for 72 hours is less than or equal to 10%.

[0019] Secondly, embodiments of this application provide a battery device, including a single battery cell from the first aspect of this application.

[0020] Thirdly, embodiments of this application provide an electrical device, including the battery device of the second aspect of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0022] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0023] Figure 2 An exploded schematic diagram of a battery device provided in some embodiments of this application.

[0024] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0025] The accompanying drawings are not necessarily drawn to scale.

[0026] The reference numerals in the attached drawings are explained as follows: 1. Vehicle; 2. Battery unit; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Reception space; 6. Battery module; 7. Battery cell. Detailed Implementation

[0027] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of 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 for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0028] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0030] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0031] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0033] In this application, the terms "multiple" or "various" refer to two or more kinds of things.

[0034] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0035] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0036] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0037] The battery device mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0038] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. When there are multiple battery cells, they are connected in series, parallel, or mixed connections through a busbar.

[0039] In some embodiments, the battery device may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0040] In some embodiments, the battery device may be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0041] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0042] In some embodiments, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0043] The technical solutions described in the embodiments of this application are applicable to battery devices and electrical devices that use battery devices.

[0044] Battery devices can be used as the power source for electrical devices or as energy storage units for electrical devices. Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, tablets, laptops, etc.), vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0045] Electrical devices can choose the type of battery device according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0046] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0047] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0048] like Figure 1 As shown, a battery device 2 is installed inside the vehicle 1. The battery device 2 can be located at the bottom, front, or rear of the vehicle 1. The battery device 2 can be used to power the vehicle 1; for example, the battery device 2 can serve as the operating power source for the vehicle 1.

[0049] The vehicle 1 may also include a controller 3 and a motor 4. The controller 3 is used to control the battery device 2 to supply power to the motor 4, for example, for the power needs of the vehicle 1 during starting, navigation and driving.

[0050] In some embodiments, the battery device 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0051] Figure 2 This is a schematic diagram of a battery explosion provided for some embodiments of this application. For example... Figure 2 As shown, the battery device 2 includes a housing 5 and battery cells (not shown), with the battery cells housed within the housing 5.

[0052] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0053] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0054] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0055] In battery device 2, there can be one or more battery cells. If there are multiple battery cells, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells are connected in both series and parallel configurations. Multiple battery cells can be directly connected in series, in parallel, or in a mixed configuration, and then the whole assembly of multiple battery cells is housed in housing 5. Alternatively, multiple battery cells can first be connected in series, in parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, in parallel, or in a mixed configuration to form a whole assembly, which is then housed in housing 5.

[0056] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0057] like Figure 3As shown, in some embodiments, there are multiple battery cells 7, which are first connected in series, parallel, or mixed to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or mixed to form a whole and housed in a casing.

[0058] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0059] The battery cells mentioned in the embodiments of this application may include lithium-ion battery cells or sodium-ion battery cells.

[0060] The battery cell includes an electrode assembly. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited to this.

[0061] Electrode assemblies generally include a positive electrode, a negative electrode, and a separator.

[0062] [Negative electrode plate]

[0063] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a pressure booster, which has a sheet-like structure. The maximum sheet diameter of the pressure booster is L1, and the thickness of the pressure booster is L2, where L1 / L2≥2.

[0064] In the preparation of the negative electrode sheet, after the negative electrode slurry containing the negative electrode active material is coated on the surface of the negative electrode current collector, a negative electrode film layer needs to be formed on the surface of the negative electrode current collector through operations such as rolling. During the rolling process, due to the large rolling pressure, the negative electrode sheet undergoes a certain degree of deformation. After the rolling pressure is removed, the electrode sheet exhibits a thickness springback phenomenon, which reduces the compaction density of the negative electrode film layer. At the same time, this springback phenomenon can cause errors in the thickness of the negative electrode sheet, affecting the subsequent assembly of battery cells. Furthermore, changes in the thickness of the negative electrode sheet during battery cell cycling can lead to a decrease in the cycle performance of the battery.

[0065] In this embodiment, a pressure-enhancing agent with a sheet-like structure is added to the negative electrode film layer, and the ratio of the maximum sheet diameter to its thickness is defined as greater than or equal to 2. When this pressure-enhancing agent with this structural feature is added to the positive electrode film layer, the sheet-like structure slips under the rolling pressure during the rolling process, thereby reducing residual stress on the negative electrode sheet after rolling and reducing thickness rebound, resulting in higher dimensional stability and improved cycle performance of the battery cell. Furthermore, during the negative electrode sheet preparation process, the same rolling pressure can achieve a higher compaction density in the negative electrode film layer, or a higher compaction density can be achieved with only a lower rolling pressure. Lower rolling pressure reduces compression damage to the negative electrode active material, resulting in higher capacity and improved first-time efficiency of the battery cell.

[0066] In some embodiments, the maximum diameter L1 of the pressure booster and the thickness L2 of the pressure booster can satisfy 10 ≤ L1 / L2 ≤ 1000. Exemplarily, the value of L1 / L2 can be 2, 5, 8, 10, 20, 30, 50, 80, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or any range of the above values; optionally, 20 ≤ L1 / L2 ≤ 800.

[0067] The ratio of the maximum sheet diameter to the thickness of the pressure-enhancing agent is further limited to the above-mentioned range. The pressure-enhancing agent has a better sheet-like structure, which can further reduce the thickness rebound during the rolling process of the negative electrode sheet and improve the cycle performance of the battery cell. At the same time, with the ratio of the maximum sheet diameter to the thickness of the pressure-enhancing agent within the above-mentioned range, the pressure-enhancing agent has high structural strength, which can reduce the breakage damage of the pressure-enhancing agent itself during the rolling process.

[0068] In some embodiments, the minimum diameter of the pressure-boosting agent is L3, where 0.1 ≤ L1 / L3 ≤ 1. Exemplarily, the value of L1 / L3 can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or a range of any of the above values. Optionally, 0.3 ≤ L1 / L3 ≤ 0.8.

[0069] While maintaining the aforementioned ratio between the maximum and minimum sheet diameters of the booster, limiting the ratio of the maximum to minimum sheet diameters within the specified range allows the booster to possess a better sheet-like structure. This enables it to slide under rolling pressure during the negative electrode preparation process, reducing the thickness rebound of the negative electrode film. Furthermore, by limiting the ratio of the maximum to minimum sheet diameters within the specified range, the booster can exhibit higher mechanical strength, further reducing structural damage such as breakage during rolling. This improves the dimensional stability of the negative electrode and consequently enhances the cycle performance of the battery cell.

[0070] In this application, the maximum and minimum sheet diameters and thickness of the booster are dimensional parameters for a single booster material, referring to data measured based on the same booster particle / sheet. The maximum and minimum sheet diameters can be the maximum and minimum dimensions of the booster on a plane perpendicular to its thickness. The maximum and minimum sheet diameters can be measured using methods and instruments known in the art; for example, scanning electron microscopy (SEM) images can be used to measure the booster dimensions. Specifically, a portion of the negative electrode film layer can be peeled off from the negative electrode sheet to expose its interior. An SEM image of the negative electrode film surface can then be obtained, and the actual dimensions of the booster can be measured within the SEM image. The maximum sheet diameter can be the maximum distance between the booster edge points in the SEM image, and the minimum sheet diameter can be the minimum distance between the booster edge points in the SEM image. Similarly, the booster thickness can be measured using an SEM image of the cross-section of the negative electrode film layer.

[0071] In some embodiments, the maximum tablet diameter of the pressure booster can be from 1 μm to 500 μm. Exemplarily, the maximum tablet diameter of the pressure booster can be 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, or any range of the above values. Optionally, the maximum tablet diameter of the pressure booster can be from 5 μm to 100 μm.

[0072] In some embodiments, the minimum tablet diameter of the pressure booster can be from 0.1 μm to 50 μm. Exemplarily, the minimum tablet diameter of the pressure booster can be 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1.0 μm, 1.5 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any range of the above values. Exemplarily, the minimum tablet diameter of the pressure booster can be from 1 μm to 20 μm.

[0073] In some embodiments, the thickness of the pressure booster can be from 1 nm to 500 nm. For example, the thickness of the pressure booster can be 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any range of the above values. Optionally, the thickness of the pressure booster can be from 10 nm to 100 nm.

[0074] In this embodiment, the specific size of the pressure booster is limited to the above-mentioned range. It has a size close to that of the negative electrode active material, which can be better dispersed in the negative electrode film layer, thereby improving the dispersion uniformity of each component in the negative electrode film layer. On the other hand, the pressure booster with a specific size within the above-mentioned range can have high mechanical strength, which can reduce the damage to the pressure booster structure during the rolling process of the negative electrode sheet. This can further improve the dimensional stability of the negative electrode sheet and improve the cycle performance of the battery cell.

[0075] In some embodiments, the pressure-boosting agent may include one or more of layered zirconium phosphate, layered carbon materials, and layered silicates.

[0076] Alternatively, layered silicates may include one or more of montmorillonite, kaolinite, palygorskite, and mica.

[0077] In some embodiments, the layered carbon material may have a graphite microcrystal structure, wherein the radial dimension of the graphite microcrystal in the layered carbon material is La, the axial dimension is Lc, and La / Lc≥10.

[0078] In this application, the radial dimension La of the graphite microcrystal refers to the average width of the graphite microcrystal along the a-axis direction, and the axial dimension Lc refers to the average height of the graphite microcrystals stacked along the c-axis direction. Graphite microcrystals are a structure formed by stacking graphite wafers, each composed of carbon atoms. These graphite wafers are bonded together by van der Waals forces to form a layered structure. Using carbon materials with a graphite microcrystal structure as a pressure enhancer has two advantages: firstly, it exhibits good compatibility and conductivity with the negative electrode active material, which helps reduce the internal resistance of the battery cell and improve its initial efficiency; secondly, when the aforementioned carbon material is used as a pressure enhancer, relative slippage can occur between the graphite wafers in the graphite microcrystal structure under rolling pressure, thereby further reducing the residual stress of the negative electrode sheet after rolling, reducing the thickness rebound of the negative electrode sheet, and further improving the cycle performance of the battery cell.

[0079] In some embodiments, the radial and axial dimensions of the graphite crystallites can satisfy 10 ≤ La / Lc ≤ 100. Exemplarily, the value of La / Lc can be 10, 12, 15, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or any range of the above values.

[0080] In some embodiments, the layered structure may include one or more of flake graphite, graphene, and expanded graphite.

[0081] The aforementioned type of pressure enhancer, under the size conditions specified in this application, can have a good sheet-like structure. When applied to the negative electrode film layer, it can effectively reduce the thickness rebound of the negative electrode sheet after rolling, improve the dimensional stability of the negative electrode sheet, and thus improve the cycle performance of the battery cell.

[0082] In some embodiments, the mass content of the voltage booster in the negative electrode film layer can be from 0.5% to 5%. Exemplarily, the mass content of the voltage booster in the negative electrode film layer can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.8%, 4.0%, 4.2%, 4.5%, 4.8%, 5.0%, or any range of the above values.

[0083] By limiting the amount of pressure-boosting agent added to the negative electrode film layer within the above range, it is beneficial to further reduce the thickness rebound of the negative electrode sheet after rolling, improve the dimensional stability of the negative electrode sheet, and thus improve the cycle performance of the battery cell.

[0084] In some embodiments, the compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 Up to 2.2 g / cm 3 For example, the compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 , or a range consisting of any of the above values.

[0085] In this application, compaction density refers to the ratio of the coating surface density of the positive electrode film to the thickness of the positive electrode film. The compaction density of the negative electrode sheet can be calculated and measured as follows: Compaction density = Coating surface density / (Thickness of negative electrode sheet after rolling - Thickness of current collector). By adding a pressure-enhancing agent to the negative electrode film, the negative electrode sheet can achieve a higher compaction density under lower rolling pressure, which is beneficial to improving the capacity of the battery cell.

[0086] In some embodiments, the surface density of the coating on one side of the negative electrode film can be 0.1 g / 1540.25 mm. 2 Up to 0.3g / 1540.25mm 2 For example, the surface density of the coating on one side of the negative electrode film can be 0.1 g / 1540.25 mm. 2 0.2g / 1540.25mm 2 0.3g / 1540.25mm 2 , or a range consisting of any of the above values.

[0087] In some embodiments, the thickness rebound rate of the negative electrode sheet after cold pressing and standing for 72 hours can be less than or equal to 10%, and optionally, the thickness rebound rate of the negative electrode sheet after cold pressing and standing for 72 hours can be less than or equal to 6%.

[0088] In this application, the thickness rebound rate of the negative electrode sheet refers to the change between the initial thickness of the negative electrode sheet after rolling and the thickness after standing for a certain period of time. It can be measured as follows: The initial thickness of the negative electrode sheet after rolling is measured using a micrometer and recorded as h1. The negative electrode sheet is then left to stand at room temperature for 72 hours, and the thickness is measured again and recorded as h2. The thickness rebound rate (%) of the negative electrode sheet is calculated as (h2-h1) / h1*100%. By adding a certain amount of pressure-enhancing agent to the negative electrode film layer, the negative electrode sheet can have a lower thickness rebound rate, resulting in higher dimensional stability and thus improving the cycle performance of the battery cell.

[0089] In some embodiments, the negative electrode film layer may further include a negative electrode active material.

[0090] As an example, the negative electrode active material may include one or more of the following: artificial graphite, natural graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, and silicon-carbon composites.

[0091] Silicon-based composite materials can be prepared by methods known in the art. For example, they can be prepared by vapor deposition using graphite and silicon materials as raw materials.

[0092] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0095] 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. The negative electrode current collector can be made of materials such as metal foil, carbon-coated metal foil, or porous metal plate, and copper foil is an option.

[0096] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, aluminum foil, and aluminum alloy foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one side of the polymeric material substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymeric material substrates include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0097] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet may also include a conductive undercoat layer sandwiched between the negative electrode current collector and the negative electrode film layer and located on the surface of the negative electrode current collector, which may be composed of a conductive agent and a binder; in some embodiments, the negative electrode sheet may also include a protective layer covering the surface of the negative electrode film layer.

[0098] The negative electrode sheet can be prepared as follows: The negative electrode active material, negative electrode binder, negative electrode conductive agent, and optional other additives are dispersed in a solvent and stirred evenly to form a negative electrode slurry; the negative electrode slurry is coated onto a negative electrode current collector, and after drying, rolling, and other processes, a negative electrode sheet is formed. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0099] [Positive electrode plate]

[0100] In some embodiments, 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 and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0101] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium, thereby obtaining a negative electrode-free lithium metal battery cell.

[0102] As examples, positive electrode active materials may include, but are not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composites, and their respective modified compounds.

[0103] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e D f One or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0104] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining battery cells that balance high capacity and high reliability.

[0105] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0106] In some embodiments, the positive electrode active material includes a material capable of both sodium extraction and insertion. This results in a sodium-free negative electrode battery cell. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including, but not limited to, P2-type, O3-type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0107] In some embodiments, as an example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0108] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0109] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0111] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a first layer of polymeric material and a layer of metallic material formed on at least one surface of the first layer of polymeric material. As an example, the metallic material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the first layer of polymeric material may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0112] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0113] [Electrolytes]

[0114] A single battery cell includes an electrolyte.

[0115] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0116] In some embodiments, the electrolyte includes anion, which may include bis(fluorosulfonyl)imide anion (FSI). - ), bis(trifluoromethanesulfonyl)imide anion (TFSI) - ), dioxaborate anion (BOB) - ), difluorooxalate borate anion (DFOB) - ), difluorodioxanol phosphate anion (DFOP) - ), tetrafluorooxalate phosphate anion (TFOP) - ), difluorophosphate anion (PO2F2) - ), hexafluorophosphate anion (PF6) - ), tetrafluoroborate anion (BF4) - ), hexafluoroarsenate anion (AsF6) - ), trifluoromethanesulfonate anion (CF3SO3) - One or more of the following.

[0117] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0118] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or higher, optionally 0.7 mol / L or higher, and further optionally 4 mol / L or lower, optionally 2.5 mol / L or lower, or 1.7 mol / L or lower. When the concentration of the electrolyte salt is within the above range, the electrolyte can have a suitable ionic conductivity.

[0119] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, and nitriles. Esters may include, but are not limited to, one or more of carbonates, phosphate esters, carboxylic esters, sulfate esters, and sulfonates. Carbonates may include cyclic carbonates and / or chain carbonates; optionally, carbonates may include both cyclic and chain carbonates. Chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0120] As an example, organic solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyl One or more of the following: decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecylfluorohexyl methyl ether, 5-trifluoromethyl dodecylfluorohexyl ethyl ether, 5-trifluoromethyl dodecylfluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecylfluorooctyl methyl ether, 7-trifluoromethyl hexadecylfluorooctyl ethyl ether, and 7-trifluoromethyl hexadecylfluorooctyl propyl ether.

[0121] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0122] Methods for preparing battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer package, dried, and then injected with the electrolyte. After vacuum sealing, settling, and formation processes, a battery cell is obtained. Multiple battery cells can be further connected in series, parallel, or a combination thereof to form a battery module. Multiple battery modules can also be connected in series, parallel, or a combination thereof to form a battery pack. In some embodiments, multiple battery cells can also be directly assembled into a battery pack.

[0123] [Isolation Component]

[0124] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0125] In some embodiments, the isolation chamber includes an isolation membrane. This application does not impose any particular limitation on the type of isolation membrane; any known porous membrane with good chemical and mechanical stability can be selected.

[0126] In some embodiments, the material of the separator may include at least one 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, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation. The separator may be a single component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating may also be applied to the surface of the separator.

[0127] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0128] Example

[0129] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0130] Test section

[0131] 1. Resilience of negative electrode sheet thickness

[0132] After the negative electrode sheet is rolled, its initial thickness is measured using a micrometer and recorded as h1. After the negative electrode sheet is left to stand for 72 hours, its thickness is measured again and recorded as h2. The thickness is then calculated using the following method:

[0133] Thickness resilience (%) = (h2-h1) / h1*100%.

[0134] 2. First-time effect

[0135] After electrolyte injection, the battery cells are charged at a constant current of 0.1C to the upper limit cutoff voltage of 3.65V, and then charged at a constant voltage to the current cutoff of 0.05C. The charging capacity is recorded as C0. After standing for 1 hour, the cells are discharged at a constant current of 0.1C to the discharge cutoff voltage of 2.0V. The discharge capacity is recorded as D0. The initial efficiency (%) is calculated as follows: D0 / C0*100%.

[0136] 2. Cycle performance of individual battery cells

[0137] At 45℃, the battery cell is charged at a constant current of 0.5C to the upper limit cutoff voltage of 3.65V, then charged at a constant voltage to the current cutoff of 0.05C, left to stand for 30 minutes, and then discharged at a constant current of 1C to the discharge cutoff voltage of 2.0V. The discharge capacity is recorded as D1. The above charging and discharging operation is repeated until the capacity retention rate of the battery cell drops below 80%, and the number of cycles is recorded as n. Wherein, the capacity retention rate (%) = Dn / D1*100%, and Dn is the discharge capacity of the battery cell in the nth cycle.

[0138] Example 1

[0139] Negative electrode sheet

[0140] The negative electrode active material graphite, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC), conductive agent Super P, and pressure booster flake graphite are added to deionized water at a mass ratio of 95.3:1:1:0.7:2 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then evenly coated onto the negative electrode current collector copper foil. After drying, rolling, slitting, and laser die-cutting, the negative electrode sheet is obtained.

[0141] Positive electrode sheet

[0142] Lithium iron phosphate (LiFePO4), a positive electrode active material, polyvinylidene fluoride (PVDF), a binder, and SuperP, a conductive agent, are added to the solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:1.5:1.5 and mixed evenly to form a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained by drying, cold pressing, slitting, and laser die-cutting.

[0143] Separating membrane

[0144] A polyethylene film with a thickness of 7μm was selected.

[0145] electrolyte

[0146] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of 4:2:4 to obtain an organic solvent. The electrolyte salt lithium hexafluorophosphate (LiPF6) and the additive ethylene carbonate were added. The amount of ethylene carbonate added was 2 wt%, and the concentration of the electrolyte salt was 1.0 mol / L.

[0147] battery cell

[0148] The positive electrode, separator, and negative electrode are stacked in sequence to form an electrode assembly. The electrode assembly tabs are welded to the top cover to form a whole and then placed in an aluminum shell. Finally, the battery cell is made through processes such as top cover welding, electrolyte injection, and formation.

[0149] Examples 2 to 10

[0150] The difference from Example 1 is that the specifications of the pressure booster are different, as detailed in Table 1.

[0151] Comparative Examples 1 to 2

[0152] The difference from Example 1 is that the specifications of the pressure booster are different, as detailed in Table 1.

[0153] Table 1

[0154]

[0155]

[0156] Examples 11 to 14

[0157] The difference from Example 1 is that the content of the voltage booster in the negative electrode film layer and the preparation parameters of the positive electrode film layer are different, as detailed in Table 2.

[0158] Table 2

[0159]

[0160] Comparative Example 3

[0161] The difference from Example 1 is that no voltage booster is added to the negative electrode film layer; otherwise, they are the same as in Example 1.

[0162] The battery cell performance test results for each embodiment and comparative example are shown in Table 3 below.

[0163] Table 3

[0164]

[0165]

[0166] Based on the embodiments and the data in Table 3, it can be seen that by adding a pressure-enhancing agent with a specific size structure to the negative electrode film layer, the thickness rebound of the negative electrode sheet after cold pressing can be effectively reduced, and a high compaction density can be achieved under a lower rolling pressure, which can effectively improve the cycle performance of the battery cell.

[0167] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, The device includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a pressure booster, which has a sheet-like structure. The maximum sheet diameter of the pressure booster is L1, and the thickness of the pressure booster is L2, where L1 / L2≥2.

2. The battery cell according to claim 1, characterized in that, 10≤L1 / L2≤1000.

3. The battery cell according to claim 1 or 2, characterized in that, The minimum diameter of the pressure-boosting agent is L3, where 1 ≤ L1 / L3 ≤ 10.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The pressure-boosting agent satisfies at least one of the following conditions: (1) 1μm≤L1≤500μm; (2) 0.1μm≤L3≤50μm; (3) 1nm≤L2≤500nm.

5. The battery cell according to claim 4, characterized in that, The pressure-boosting agent satisfies at least one of the following conditions: (1) 5μm≤L1≤100μm; (2) 1μm≤L3≤20μm; (3) 10nm≤L2≤100nm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The pressure-boosting agent includes one or more of layered zirconium phosphate, layered carbon materials, and layered silicates.

7. The battery cell according to claim 6, characterized in that, The layered carbon material has a graphite microcrystalline structure, wherein the radial dimension of the graphite microcrystalline is La, the axial dimension is Lc, and La / Lc≥10.

8. The battery cell according to claim 7, characterized in that, 10≤La / Lc≤100.

9. The battery cell according to any one of claims 6 to 8, characterized in that, The layered carbon material includes one or more of flake graphite, expanded graphite, and graphene.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The mass content of the pressure-boosting agent in the negative electrode film layer is 0.5% to 5%.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The compaction density of the negative electrode sheet is 1.0 g / cm³. 3 Up to 2.2 g / cm 3 .

12. The battery cell according to any one of claims 1 to 11, characterized in that, The single-sided coating surface density of the negative electrode film is 0.1 g / 1540.25 mm. 2 Up to 0.3g / 1540.25mm 2 .

13. The battery cell according to any one of claims 1 to 12, characterized in that, The thickness rebound rate of the negative electrode sheet after cold pressing and standing for 72 hours is less than or equal to 10%.

14. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1 to 13.

15. An electrical appliance, characterized in that, Includes the battery device as described in claim 14.

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