Battery cell, lithium ion battery, and electric device

Abstract

A battery cell, a lithium ion battery, and an electric device. The battery cell comprises a wound electrode assembly, and the wound electrode assembly has bent areas. The wound electrode assembly comprises a negative electrode sheet and a positive electrode sheet, the negative electrode sheet comprises a plurality of first bent portions located in the bent areas, and the positive electrode sheet comprises a plurality of second bent portions located in the bent areas; the distance L1 between the concave surface of a second bent portion and the convex surface of an adjacent first bent portion located on the inner side of the second bent portion is greater than or equal to the distance L2 between the convex surface of the second bent portion and the concave surface of an adjacent first bent portion located on the outer side of the second bent portion, 17 μm≤L1≤34 μm, 14 μm≤L2≤34 μm, and L1≥L2; the equivalent charge rate c of the battery cell from 10% SOC to 80% SOC satisfies: 3C≤c≤8C. The battery cell can enable fast-charging lithium ion batteries to have good cycle performance and safety performance.

Description

Battery cells, lithium-ion batteries and electrical devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application 202410505641.6, filed on April 25, 2024, entitled “Battery cell, lithium-ion battery and power device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of batteries, and more specifically, to a battery cell, a lithium-ion battery, and an electrical device. Background Technology

[0004] In recent years, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace, thus achieving great development.

[0005] Fast-charging lithium-ion batteries are a key area of ​​development in the lithium-ion battery industry. While focusing on their electrical performance, people also demand excellent safety and performance. Lithium plating is one of the main reasons affecting battery cycle performance and safety. Lithium plating can lead to rapid battery cycle drops and easily form lithium dendrites. These dendrites may puncture the separator, causing a short circuit and creating a safety hazard. The causes and consequences of lithium plating in fast-charging lithium-ion batteries are more complex than in ordinary lithium-ion batteries. Therefore, how to improve the negative lithium plating phenomenon is a technical problem that urgently needs to be solved.

[0006] Summary of the Invention

[0007] This application addresses the aforementioned technical problems and aims to provide a battery cell, a lithium-ion battery, and an electrical device. The battery cell employs a wound electrode assembly and is a fast-charging lithium-ion battery cell. The bending area of ​​the wound electrode assembly has a special design that effectively improves the lithium plating problem in the bending area, thereby enhancing the cycle performance and safety performance of the fast-charging lithium-ion battery.

[0008] In a first aspect, a battery cell is provided, the battery cell including a wound electrode assembly having a bending region, the wound electrode assembly including a negative electrode sheet and a positive electrode sheet, the negative electrode sheet including a plurality of first bending portions located in the bending region, the positive electrode sheet including a plurality of second bending portions located in the bending region; wherein, the distance between the convex surface of the first bending portion and the concave surface of the adjacent second bending portion located outside it is L1, the distance between the concave surface of the first bending portion and the convex surface of the adjacent second bending portion located inside it is L2, 17μm≤L1≤34μm, 14μm≤L2≤34μm, and L1≥L2; the equivalent charging rate c of the battery cell from 10% SOC to 80% SOC satisfies: 3C≤c≤8C.

[0009] In the embodiments of this application, the battery cell is a fast-charging lithium-ion battery cell. In this fast-charging lithium-ion battery, by controlling L1 and L2 within a suitable range, the positive and negative electrode sheets located in the bending region can have good wettability without adversely affecting lithium-ion kinetics or the energy density of the lithium-ion battery. Furthermore, the embodiments of this application also control L1 ≥ L2, so that there is a relatively large distance between the convex surface of the bent portion of the negative electrode sheet and the concave surface of the adjacent positive electrode sheet. This distance can alleviate the compression of the concave surface of the positive electrode sheet against the convex surface of the negative electrode sheet during lithium-ion battery cycling. Therefore, the embodiments of this application can improve the problem of lithium plating in the corner region of the electrode assembly and improve the cycle performance and safety performance of the fast-charging lithium-ion battery.

[0010] In one possible implementation, the thickness H of the wound electrode assembly satisfies: 5mm ≤ H ≤ 35mm.

[0011] In one possible implementation, 5mm≤H≤17mm, 17μm≤L1≤24μm, 14μm≤L2≤23μm; or when 17mm<H≤35mm, 24μm<L1≤34μm, 23μm<L2≤34μm.

[0012] In the embodiments of this application, L1 and L2 can be set within a suitable range in combination with the thickness of the wound electrode assembly, so that H and L1, L2 in the fast-charging lithium-ion battery can be matched with each other, thereby improving the lithium plating problem of the fast-charging lithium-ion battery.

[0013] In one possible implementation, the wound electrode assembly includes: an isolation member disposed between the negative electrode and the positive electrode, the isolation member including a plurality of first isolation member bending portions and second isolation member bending portions arranged sequentially from the inside to the outside in the bending area; wherein, the first isolation member bending portion is disposed between the convex surface of the first bending portion and the concave surface of the adjacent second bending portion located on its outer side, and the second isolation member bending portion is disposed between the concave surface of the first bending portion and the convex surface of the adjacent first bending portion located on its inner side.

[0014] In one possible implementation, at least one surface of the first insulating member bend is provided with a first coating, and at least one surface of the second insulating member bend is provided with a second coating.

[0015] In one possible implementation, the first coating comprises a first coating material, and the second coating comprises a second coating material; the average volumetric particle size Dv501 of the first coating material is greater than or equal to the average volumetric particle size Dv502 of the second coating material.

[0016] In the embodiments of this application, by controlling the average volume particle size of the coating material on the surfaces of the first and second spacer bends to satisfy: Dv501≥Dv502, L1≥L2 can also be made.

[0017] In one possible implementation, 10μm≤Dv501≤15μm; 8μm≤Dv502≤15μm.

[0018] In the embodiments of this application, by controlling the average volume particle size of the coating material within a suitable range, it is possible to improve lithium deposition in the bending zone while reducing the adverse effects on lithium-ion kinetics.

[0019] In one possible implementation, the first coating material includes at least one of polyvinylidene fluoride, polyimide, polyurethane, polyvinyl alcohol, polyvinyl ether, and polyacrylic acid; the second coating material includes at least one of polyvinylidene fluoride, polyimide, polyurethane, polyvinyl alcohol, polyvinyl ether, and polyacrylic acid.

[0020] In one possible implementation, the areal density ρ1 of the first coating satisfies: 0.3 × 10⁻⁶ -3 mg / mm 2 ≤ρ1≤0.8×10 -3 mg / mm 2 .

[0021] In one possible implementation, the areal density ρ2 of the second coating satisfies: 0.3 × 10⁻⁶ -3 mg / mm 2 ≤ρ2≤1.0×10-3 mg / mm 2 .

[0022] In one possible implementation, the negative electrode sheet includes a negative electrode active material, wherein the average volumetric particle size Dv503 of the negative electrode active material satisfies: 6μm≤Dv503≤12μm.

[0023] In one possible implementation, the battery cell includes an electrolyte, wherein the ionic conductivity σ of the electrolyte at 20°C to 30°C satisfies: 8mS / cm≤σ≤19mS / cm.

[0024] In one possible implementation, the battery cell (300) can provide a charging rate of 3C when 8mS / cm≤σ≤13mS / cm and 8μm≤Dv503≤12μm.

[0025] In one possible implementation, the battery cell (300) is able to provide a charging rate of 4C when 10mS / cm≤σ≤15mS / cm and 7μm≤Dv503≤12μm.

[0026] In one possible implementation, the battery cell (300) is able to provide a charging rate of 5C when 11mS / cm≤σ≤17mS / cm and 6.5μm≤Dv503≤12μm.

[0027] In one possible implementation, the battery cell (300) can provide a charging rate of 8C when 13mS / cm≤σ≤19mS / cm and 6μm≤Dv503≤12μm.

[0028] In a second aspect, a lithium-ion battery is provided, the lithium-ion battery comprising the battery cell described in the second aspect.

[0029] Thirdly, an electrical device is provided, the electrical device comprising the lithium-ion battery described in the third aspect. Attached Figure Description

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0031] Figure 1 is a schematic diagram of a wound electrode assembly according to this application.

[0032] Figure 2 is a schematic diagram of another type of wound electrode assembly of this application.

[0033] Figure 3 is a partial schematic diagram of a wound electrode assembly according to this application.

[0034] Figure 4 is a partially enlarged schematic diagram of Figure 3.

[0035] Figure 5 is a schematic diagram of a battery cell according to this application.

[0036] Figure 6 is a schematic diagram of a battery module according to this application.

[0037] Figure 7 is a schematic diagram of a lithium-ion battery according to this application.

[0038] Figure 8 is another schematic diagram of a lithium-ion battery according to this application. Detailed Implementation

[0039] The following detailed description of embodiments of the lithium-ion battery and power-consuming device of this application is provided with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually 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 the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0040] 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.

[0041] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] Unless otherwise specified, in this application, the phrase "A and / or B" means "A, B, or both A and B". More specifically, the condition "A and / or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] 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.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] The embodiments of this application will be described next.

[0046] In recent years, rechargeable batteries have seen significant development due to their high energy density and long lifespan, finding widespread application in power tools, electronic products, electric vehicles, aerospace, and other fields. Typically, a rechargeable battery consists of 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 these active ions between the electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through, ensuring the normal electrochemical reaction of the rechargeable battery.

[0047] Taking lithium-ion batteries as an example, lithium-ion batteries are a typical type of rechargeable battery. Because they rely on the chemical reaction of lithium ions intercalating and deintercalating between the positive and negative electrodes for charging and discharging, lithium-ion batteries are also known as rocking chair batteries. During the charging process of a lithium-ion battery, lithium ions are extracted from the positive electrode active material, move to the negative electrode through the conduction of the electrolyte, and intercalate into the negative electrode active material; while during the discharging process, lithium ions are extracted from the negative electrode active material, move to the positive electrode through the conduction of the electrolyte, and intercalate into the positive electrode active material.

[0048] It should be understood that the “lithium intercalation” or “intercalation” process described in this application refers to the process in which lithium ions are intercalated into the positive electrode active material or the negative electrode active material due to an electrochemical reaction, while the “de-lithium extraction”, “de-lithium extraction”, or “de-intercalation” process described in this application refers to the process in which lithium ions are extracted from the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0049] In this application, a battery refers to a physical module comprising one or more battery cells to provide electrical energy. For example, the battery mentioned in this application may include a battery module or a battery pack. A battery generally includes a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells. A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode, a negative electrode, and a separator. A wound electrode assembly is a common structure in lithium-ion batteries, which is formed by separating continuous, elongated positive and negative electrode sheets with a separator, and then winding them together to create an electrode assembly with a wound structure.

[0050] Fast-charging lithium-ion batteries are a type of lithium-ion battery with fast-charging (FC) capability, meaning they can be charged to full or near-full charge in a relatively short time. Different regions have different industry standards for the specific definition of fast charging. Generally, charging a battery to 80% of its full capacity in 0.5 to 2 hours is considered fast charging; furthermore, charging in less than 10 minutes is considered extreme fast charging (XFC). As the application of fast-charging lithium-ion batteries becomes more widespread and the usage scenarios more diverse, new requirements are being placed on their cycle performance and energy density, and good safety performance is also required.

[0051] During the cycling process of lithium-ion batteries, lithium plating on the negative electrode can lead to battery capacity decay and a sharp drop in cycle life. In severe cases, lithium dendrites can form, which may puncture the separator, causing a short circuit and potentially leading to safety issues. The factors contributing to lithium plating during lithium-ion battery cycling are diverse and complex. Essentially, lithium ions that have been extracted from the positive electrode active material cannot be successfully inserted into the negative electrode active material, thus depositing on the surface of the negative electrode.

[0052] During the cycling process of lithium-ion batteries, the electrode assembly undergoes volume expansion. For wound electrode assemblies, as the volume expands, the bending area is subjected to tensile force from the straight area, leading to electrolyte extrusion in the bending area and causing lithium plating on the negative electrode. For fast-charging lithium-ion batteries, the fast-charging process involves a large number of lithium ions rapidly embedding into the negative electrode, resulting in even faster electrode expansion and a more severe lithium plating problem. Furthermore, if the spacing between the positive and negative electrode sheets is too large, the electrolyte cannot completely fill the gaps; conversely, if the spacing is too small, the electrolyte cannot adequately wet the electrodes, hindering lithium-ion transport and causing lithium plating on the negative electrode. The spacing between the positive and negative electrode sheets also directly affects the thickness and width of the electrode assembly, thus impacting the energy density of fast-charging lithium-ion batteries.

[0053] For the portion of the negative electrode located in the bending region, it has both a convex and a concave surface. When designing electrode assemblies, considering energy density and lithium plating, the distance between the positive and negative electrodes is typically designed to be small. This means the distance between the convex surface and the adjacent positive electrode, and the distance between the concave surface and another adjacent positive electrode, are also relatively small. When the electrode assembly expands, due to the aforementioned tensile force, the distance between the convex surface and the adjacent positive electrode, and the distance between the concave surface and another adjacent positive electrode, are further compressed, causing electrolyte to be squeezed out and lithium-ion kinetics to decrease. Furthermore, the convex surface of the negative electrode experiences greater tensile force than the concave surface, making the electrolyte squeezing out more severe. Therefore, insufficient wetting on the convex surface of the negative electrode intensifies concentration polarization, resulting in a much higher probability of lithium plating compared to the concave surface. Generally, once lithium plating occurs in the bending region of the negative electrode, it usually occurs on the convex surface.

[0054] In view of this, this application provides a battery cell, a lithium-ion battery, and a power supply device. The charging rate c of the battery cell satisfies: 3C ≤ c ≤ 8C. Furthermore, in the wound electrode assembly of the battery cell, the distance between the negative electrode and the positive electrode in the bending region is controlled within a suitable range, and the distance between the convex surface of the negative electrode and the positive electrode is set to be greater than or equal to the distance between the concave surface of the negative electrode and the positive electrode. This improves the wettability of the electrode assembly in the fast-charging lithium-ion battery, alleviates the compression of the positive and negative electrodes by the rapid expansion of the electrode assembly during fast charging, thereby reducing the tendency for lithium deposition on the negative electrode in the bending region and improving the cycle performance and safety performance of the lithium-ion battery.

[0055] [Battery cell]

[0056] As mentioned earlier, a battery cell consists of an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The following section will provide a detailed introduction to the battery cell and its various components.

[0057] First, a battery cell is provided, whose equivalent charging rate *c* from 10% SOC to 80% SOC satisfies: 3C ≤ *c* ≤ 8C. If the battery cell is placed on a charging station, the time it takes to charge from 0% SOC to 100% SOC can be directly recorded. For example, if the time is around 20 minutes (with an error of no more than 1 minute), it is generally considered a 3C fast-charging battery. If the time is around 15 minutes (with an error of no more than 1 minute), it is generally considered a 4C fast-charging battery. Another example: if the time is around 12 minutes (with an error of no more than 1 minute), it is generally considered a 5C fast-charging battery. Yet another example: if the time is around 10 minutes (with an error of no more than 1 minute), it is generally considered a 6C fast-charging battery.

[0058] The aforementioned charging rate is the equivalent charging rate of a lithium-ion battery during the process of charging from 10% SOC to 80% SOC at 25℃ to 35℃. During the charging process from 10% SOC to 80% SOC, the lithium-ion battery may undergo a transition from constant current charging to constant voltage charging; therefore, the charging rate is not constant. For example, if a lithium-ion battery is started charging at 25℃ and charged from 10% SOC to 80% SOC in 10 minutes... The charging process is as follows: initially at 5C from 10% SOC to 45% SOC, then at 4.6C from 45% SOC to 50% SOC, 4.3C from 50% SOC to 55% SOC, 3.9C from 55% SOC to 60% SOC, 3.6C from 60% SOC to 65% SOC, 3.3C from 65% SOC to 70% SOC, 3.1C from 70% SOC to 75% SOC, and 2.9C from 75% SOC to 80% SOC, after which charging is complete. The charging time for a lithium-ion battery from 0% SOC to 100% SOC at 1C is 60 minutes. Therefore, given that the lithium-ion battery was charged from 10% SOC to 80% SOC in 10.5 minutes, the equivalent charging rate of this process can be calculated as: [(80% SOC - 10% SOC) / (100% SOC - 0% SOC)] × [(1C × 60min) / 10min] = 4C.

[0059] The aforementioned battery cell includes a wound electrode assembly. Figure 1 is a schematic structural diagram of a wound electrode assembly 1 according to an embodiment of this application.

[0060] As shown in Figure 1, the wound electrode assembly 1 has a bending region A. The electrode assembly 1 includes a negative electrode 11 and a positive electrode 12. The negative electrode 11 includes a plurality of first bending portions 11a located in the bending region A, and the positive electrode 12 includes a plurality of second bending portions 12a located in the bending region. The plurality of first bending portions 11a and the plurality of second bending portions 12a are arranged sequentially from the inside to the outside. The distance between the convex surface of the first bending portion 11a and the concave surface of the adjacent second bending portion 12a located on its outer side is L1, and the distance between the concave surface of the first bending portion 11a and the convex surface of the adjacent second bending portion 12a located on its inner side is L2. 17μm≤L1≤34μm, 14μm≤L2≤34μm, and L1≥L2.

[0061] Specifically, L1 can be 17μm, 18μm, 19μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, or 34μm, or a value within the range obtained by any combination of the above two values. L2 can be 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, or 34μm, or a value within the range obtained by any combination of the above two values.

[0062] In the fabrication process of the wound electrode assembly 1, a continuous elongated positive electrode sheet 12 (represented by a solid black line in the figure) and a negative electrode sheet 11 (represented by a short black dashed line in the figure) are typically separated by a spacer 13 (represented by a solid gray line in the figure). The assembly is then wound along the winding axes x and y to obtain the wound electrode assembly 1 with a wound structure. To avoid short circuits between the positive and negative electrodes within the wound structure, two or more spacers 13 are typically used. Figure 1 shows the winding axes x and y as straight lines perpendicular to the plane of the paper. Figure 1 illustrates the electrode assembly 1 obtained by winding the assembly clockwise around the winding axes x and y. In other embodiments, the assembly can also be wound counterclockwise around the winding axes x and y to obtain the electrode assembly 1.

[0063] In a specific example, when winding the aforementioned components, a spacer 13, a negative electrode 11, another spacer 13, and a positive electrode 12 stacked in sequence are wound along the winding axis. Thus, in the wound structure electrode assembly, the spacer 13, the negative electrode 11, the other spacer 13, and the positive electrode 12 are arranged in a cyclic manner from the inside to the outside.

[0064] Referring again to Figure 1, in another specific example, the wound electrode assembly 1 has both a bending region A and a straight region B, with the two ends of the bending region A connected to the two straight regions B respectively. In the straight region B, the portions of the negative electrode 11, the positive electrode 12, and the separator 13 located within the straight region B are basically straight; in the bending region A, the portions of the negative electrode 11, the positive electrode 12, and the separator 13 located within the bending region A are all bent. Exemplarily, the negative electrode 11, the positive electrode 12, and the separator 13 located within the bending region A are at least partially arc-shaped or elliptical arc-shaped. The straight region B can be a straight region B formed between the two winding axes x and y during the winding process, where the aforementioned assembly is wound around the two winding axes x and y respectively; or it can be a straight region B formed after being wound around the winding axis x or the winding axis y into a cylindrical electrode assembly and then processed through hot pressing or other processes.

[0065] Besides the winding structure shown in Figure 1, the wound electrode assembly 1 can also be a cylindrical electrode assembly as shown in Figure 2. In this case, any range along the circumference of the wound electrode assembly 1 can be defined as the bending region A. Figure 2 shows the case where the negative electrode 11, the positive electrode 12, and the two insulating pieces 13 are wound clockwise around a winding axis x to form a cylindrical electrode assembly. In other embodiments, the aforementioned assembly can also be wound counterclockwise around the winding axis x to form the electrode assembly 1.

[0066] Based on this, it should be understood that "from the inside out" as used in this application refers to the radial direction of the wound electrode assembly from the position close to the winding axis to the position far away from the winding axis.

[0067] Both the negative electrode 11 and the positive electrode 12 have a certain thickness. As shown in Figure 1, after being wound, of the two surfaces in the thickness direction of the negative electrode 11, the surface closer to and facing the winding axis x or y is the concave surface of the negative electrode 11, and the other surface farther from and away from the winding axis x or y is the convex surface of the negative electrode 11. Similarly, of the two surfaces in the thickness direction of the positive electrode 12, the surface closer to and facing the winding axis x or y is the concave surface of the positive electrode 12, and the other surface farther from and away from the winding axis x or y is the convex surface of the positive electrode 12.

[0068] For the first bending portion 11a and the second bending portion 12a, the surface that is closer to the winding axis x or y and faces the winding axis x or y is the concave surface of the first bending portion 11a and the concave surface of the second bending portion 12a, and the surface that is farther from the winding axis x or y and away from the winding axis x or y is the convex surface of the first bending portion 11a and the convex surface of the second bending portion 12a.

[0069] The distance L1 between the convex surface of the first bend 11a and the concave surface of the second bend 12a, and the distance L2 between the concave surface of the first bend 11a and the convex surface of the second bend 12a, directly affect the cycle performance and safety performance of lithium-ion batteries. During the cycle of a single cell in a fast-charging lithium-ion battery, the rapid expansion of the wound electrode assembly causes the bend area A to be subjected to circumferential tensile force from the straight area B and pressure from the positive electrode sheet in a short period of time. This results in severe electrolyte extrusion in the bend area A, deterioration of lithium-ion kinetics, and impact on the fast-charging performance of the fast-charging lithium-ion battery. For the negative electrode sheet 11, its convex surface experiences greater tensile force than its concave surface, and the convex surface of the negative electrode sheet 11 suffers from more severe electrolyte extrusion than the concave surface, leading to insufficient electrolyte wetting on the convex surface of the negative electrode sheet 11 and a higher risk of lithium plating. If L1 and L2 are too small, it will be detrimental to the wetting of the negative electrode 11 and the positive electrode 12 by the electrolyte, and it will not be able to meet the rapid expansion requirements of the wound electrode assembly 1 during fast charging. If L1 and L2 are too large, the electrolyte will not be able to fill the gap between the negative electrode 11 and the positive electrode 12 and will have an adverse effect on the energy density of the lithium-ion battery. Both of these conditions will cause lithium deposition on the negative electrode 11.

[0070] In this embodiment, the distance L1 between the convex surface of the negative electrode 11 and the concave surface of its adjacent outer positive electrode 12, and the distance L2 between the concave surface of the negative electrode 11 and the convex surface of its adjacent inner positive electrode 12 are controlled within a suitable range. This range allows the electrode to have good wettability in the bending area and store sufficient electrolyte. Furthermore, it allows the negative electrode 11 of the fast-charging lithium-ion battery to have sufficient expansion space during fast charging. Therefore, it can improve the problem of lithium deposition in the bending area A of the negative electrode of the battery cell in the fast-charging lithium-ion battery, and improve the cycle performance and safety performance of the fast-charging lithium-ion battery. On the other hand, during fast charging, the wound electrode assembly 1 expands rapidly. In the bending area A, the adjacent positive electrode 12 located outside the negative electrode 11 will exert radial pressure on the negative electrode 11. With L1 and L2 controlled within a suitable range, by controlling L1≥L2, the positive electrode 12 located on the outside of the negative electrode 11 can be made relatively far from the convex surface of the adjacent negative electrode 11, thereby alleviating the compression of the positive electrode 12 on the convex surface of the negative electrode 11 during the expansion of the electrode assembly 1, and thus improving the situation where the electrolyte is squeezed out by the compression of the negative electrode 11.

[0071] Therefore, the battery cell provided in this embodiment can reduce the problem of lithium plating on the negative electrode of fast-charging lithium-ion batteries, and in particular, can effectively reduce the risk of lithium plating on the convex surface of the first bending portion 11a, thereby improving the cycle performance and safety performance of fast-charging lithium-ion batteries.

[0072] In one embodiment, referring to Figure 1, the thickness H of the wound electrode assembly 1 satisfies: 5mm ≤ H ≤ 35mm.

[0073] Specifically, H can be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, 31mm, 32mm, 33mm, 34mm, 35mm, or a value within the range obtained by any combination of the above two values.

[0074] Considering that the wound electrode assembly 1 expands rapidly during fast charging, the problem of compression between the electrodes is more severe than that of ordinary lithium-ion batteries. Therefore, the values ​​of L1 and L2 can be considered comprehensively based on the thickness of the wound electrode assembly 1. For example, the thicker the wound electrode assembly 1, the greater the expansion space required for the positive and negative electrodes, especially the negative electrode, and the larger the values ​​of L1 and L2 will be.

[0075] In one embodiment, 5mm≤H≤17mm, 17μm≤L1≤24μm, and 14μm≤L2≤23μm. In another embodiment, when 17mm<H≤35mm, 24μm<L1≤34μm and 23μm<L2≤34μm.

[0076] In this embodiment, by matching the value ranges of H and L1, L2, the probability of lithium plating on the negative electrode of the fast-charging lithium-ion battery can be effectively reduced, thereby improving the cycle performance of the fast-charging lithium-ion battery.

[0077] In one embodiment, referring to FIG1, the wound electrode assembly 1 includes a separator 13 disposed between the negative electrode 11 and the positive electrode 12. The separator 13 includes a plurality of first separator bending portions 131 and second separator bending portions 132 arranged sequentially from the inside to the outside in the bending region A. The first separator bending portions 131 are disposed between the convex surface of the first bending portion 11a and the concave surface of the adjacent second bending portion 12a located outside it, and the second separator bending portions 132 are disposed between the concave surface of the first bending portion 11a and the convex surface of the adjacent second bending portion 12a located inside it. Based on this, the physical meaning of L1 can be interpreted as the sum of the gap between the convex surface of the first bending portion 11a and the concave surface of the first separator bending portion 131, the thickness of the first separator bending portion 131, and the gap between the convex surface of the first separator bending portion 131 and the second bending portion 12a. The physical meaning of L2 can be interpreted as the gap between the concave surface of the second bend 12a and the convex surface of the second spacer bend 132, the thickness of the second spacer bend 132, and the sum of the gap between the concave surface of the first bend 11a and the convex surface of the second spacer bend 132.

[0078] As mentioned earlier, in order to avoid short circuits between the positive and negative electrodes inside the wound structure, two or more insulating elements 13 are usually used. After the elongated insulating elements 13 are wound, they are alternately arranged in the bending area A of the wound electrode assembly 1, thereby forming a first insulating element bending portion 131 and a second insulating element bending portion 132 arranged sequentially from the inside to the outside.

[0079] Figure 3 is a partial schematic diagram of a wound electrode assembly according to an embodiment of this application. Figure 4 is a partial enlarged schematic diagram of a wound electrode assembly according to an embodiment of this application.

[0080] In one embodiment, as shown in Figures 3 and 4, at least one side of the surface of the first isolation member bending portion 131 is provided with a first coating 1311, and at least one side of the surface of the second isolation member bending portion 132 is provided with a second coating 1321.

[0081] Specifically, the spacer 13 includes a substrate and a coating disposed on its surface in the thickness direction. Of the two surfaces of the spacer 13 in the thickness direction, only one surface may be coated, or both surfaces may be coated. The coating disposed on the surface of the spacer 13 can be integral, that is, the surface of the elongated spacer 13 is coated, and after winding, the portions of the spacer 13 located in the straight region B and the bending region A are coated. The coating disposed on the surface of the spacer 13 can also be intermittent, that is, the surface of the elongated spacer 13 is coated at intervals, and after winding, the portions of the spacer 13 located in the bending region A are coated, while the portions located in the straight region B are not coated.

[0082] Preferably, both surfaces of the separator 13 in the thickness direction are coated. On the one hand, considering that during processing, coating only one side may cause the surface tension on both sides of the separator 13 to differ, resulting in automatic winding and increasing processing difficulty. On the other hand, to achieve an effect similar to double-sided coating, the thickness of the coating on one side needs to be increased. In an overall coating scheme, this would further increase the thickness of the flat region B, which is detrimental to the volumetric energy density of the lithium-ion battery. Coating both sides solves the above problems and improves the lithium deposition problem of the negative electrode 11 in the bending region A.

[0083] In one embodiment, the thickness h1 of the first coating 1311 is greater than or equal to the thickness h2 of the second coating 1321.

[0084] In this embodiment, by controlling the thickness of the first coating 1311 and the second coating 1321 to satisfy h1≥h2, the distance between the first bent portion 11a and the adjacent second bent portion 12a can be effectively controlled, so that L1≥L2. This improves the problem of electrolyte being squeezed out during the expansion of the wound electrode assembly 1 on the convex surface of the first bent portion 11a, improves the wettability of the convex surface of the first bent portion 11a, suppresses lithium deposition in the bending area A, and helps improve the cycle performance and safety performance of the fast-charging lithium-ion battery.

[0085] In one embodiment, 10μm≤h1≤20μm; 8μm≤h2≤20μm.

[0086] Specifically, h1 can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, or 20μm, or a value within the range obtained by any combination of the above two values. h2 can be 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, or 20μm, or a value within the range obtained by any combination of the above two values.

[0087] If the coating thickness is too small, its effect on improving electrolyte extrusion is limited; if the coating thickness is too large, the distance between the negative electrode 11 and the positive electrode 12 in the corner region A becomes too large, resulting in an excessively long lithium-ion transport path, which is detrimental to lithium-ion kinetics. This prevents lithium from being intercalated on the negative electrode 11, leading to purple spots, and also negatively impacts fast-charging performance. Therefore, in this embodiment, by controlling the thicknesses of the first and second coatings within appropriate ranges, it is possible to alleviate lithium deposition at the first bend 11a while reducing the adverse effects on lithium-ion kinetics.

[0088] In one embodiment, the first coating 1311 includes a first coating material, and the second coating 1321 includes a second coating material; the average volumetric particle size Dv501 of the first coating material is greater than or equal to the average volumetric particle size Dv502 of the second coating material.

[0089] In this embodiment, by controlling the average volumetric particle size of the first and second coating materials to satisfy Dv501≥Dv502, the distance between the first bent portion 11a and the adjacent second bent portion 12a can be effectively controlled, ensuring L1≥L2. This improves the problem of electrolyte being squeezed out during the expansion of the wound electrode assembly 1 on the convex surface of the first bent portion 11a, enhances the wettability of the convex surface of the first bent portion 11a, suppresses lithium deposition in the bending region A, and helps improve the cycle performance and safety performance of the fast-charging lithium-ion battery. The principle of control may be that for coating materials with a larger average volumetric particle size, the coating surface density is usually relatively small and the coating thickness is relatively large during the coating process; while for coating materials with a smaller average volumetric particle size, the coating surface density is usually relatively large and the coating thickness is relatively small during the coating process. Therefore, by controlling the average volumetric particle size of the coating materials, the distance between the first bent portion 11a and the adjacent second bent portion 12a can be controlled.

[0090] In one embodiment, 10μm≤Dv501≤15μm; 8μm≤Dv502≤15μm.

[0091] Specifically, Dv501 can be 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm, or a value within the range obtained by any combination of the above two values. Dv502 can be 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm, or a value within the range obtained by any combination of the above two values.

[0092] If the average volumetric particle size of the coating material is too small and the coating thickness is too thin, its effect on improving electrolyte extrusion is limited. If the average volumetric particle size of the coating material is too large and the coating thickness is too large, the spacing between the negative electrode 11 and the positive electrode 12 in the corner region A will be too large, resulting in an excessively long lithium-ion transport path, which is detrimental to lithium-ion kinetics. This prevents lithium from being intercalated on the negative electrode 11 to form purple spots and also hinders fast-charging performance. Therefore, in this embodiment, by controlling the average volumetric particle size of the first coating material and the second coating material to be within appropriate ranges, it is possible to alleviate lithium deposition at the first bend 11a while reducing the adverse effects on lithium-ion kinetics.

[0093] In one embodiment, the first coating material includes at least one of polyvinylidene fluoride (PVDF), polyimide (PI), polyurethane (PU), polyvinyl alcohol (PVA), polyvinyl ether (PEO), polyacrylic acid (PAA), and polycarbosilane (PCS); the second coating material includes at least one of PVDF, PI, PU, ​​PVA, PEO, PAA, and PCS.

[0094] It should be understood that the first coating material and the second coating material can be the same or different.

[0095] In one specific embodiment, both the first and second coating materials are PCS, and the surface of the separator 13 has an integral coating. In this case, during the hot-pressing process of the wound electrode assembly to form the flat region B, the PCS on the separator 13 will partially melt in the hot-pressed portion, which can bond the separator 13 to its adjacent negative electrode 11 and positive electrode 12, improving the tightness of the wound electrode assembly 1 and reducing the risk of battery performance degradation due to loosening of the wound electrode assembly during battery cycling. In the portion not hot-pressed, the PCS on the separator 13 will remain stable, that is, it will remain stably on the surface of the separator 13 in the bending region A in the form of a coating, so that there is a certain distance between the negative electrode 11 and the positive electrode 12 in the bending region A, thereby improving the wettability of the negative electrode 11 in the bending region A.

[0096] In one embodiment, the areal density ρ1 of the first coating satisfies: 0.3 × 10⁻⁶ -3 mg / mm 2 ≤ρ1≤0.8×10 -3 mg / mm 2 .

[0097] Specifically, ρ1 can be 0.3 × 10 -3 mg / mm 2 0.4×10 -3 mg / mm 2 0.5×10 -3 mg / mm 2 0.6×10 -3 mg / mm 2 0.7×10 -3 mg / mm 2 0.8×10 -3 mg / mm 2 , or its value is within the range obtained by combining any two of the above values.

[0098] In one embodiment, the areal density ρ2 of the second coating satisfies: 0.3 × 10⁻⁶ -3 mg / mm 2 ≤ρ2≤1.0×10 -3 mg / mm 2 .

[0099] Specifically, ρ2 can be 0.3 × 10 -3 mg / mm 2 0.4×10 -3 mg / mm 2 0.5×10 -3 mg / mm 20.6×10 -3 mg / mm 2 0.7×10 -3 mg / mm 2 0.8×10 -3 mg / mm 2 0.9×10 -3 mg / mm 2 1.0×10 -3 mg / mm 2 , or its value is within the range obtained by combining any two of the above values.

[0100] By adjusting the coating density of the first and second coatings, the coating thickness can be indirectly controlled, thereby achieving L1≥L2. Furthermore, when the separator has an integral coating, the volume of the wound electrode assembly can be controlled by adjusting the coating density, thus helping to improve the volumetric energy density of fast-charging lithium-ion batteries.

[0101] Next, we will further introduce the positive electrode, negative electrode, and insulating components in the electrode assembly.

[0102] [Negative electrode plate]

[0103] A negative electrode typically 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 includes a negative electrode active material.

[0104] 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.

[0105] In one embodiment, 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 polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In one embodiment, 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 application 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.

[0107] In one embodiment, the average volumetric particle size Dv503 of the negative electrode active material satisfies: 6μm≤Dv503≤12μm.

[0108] Specifically, Dv503 can be 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, or a value within the range obtained by any combination of the above two values.

[0109] In one embodiment, the negative electrode film layer further includes an adhesive. The adhesive 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).

[0110] In one embodiment, the negative electrode film layer further includes 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.

[0111] In one embodiment, the negative electrode film layer also includes other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0112] In one embodiment, the negative electrode sheet can be prepared by forming a negative electrode slurry using the components described above. For example, the negative electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form the negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained.

[0113] [Positive electrode plate]

[0114] 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 including a positive electrode active material.

[0115] 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.

[0116] In one embodiment, 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0117] In one embodiment, the positive electrode active material may be a known positive electrode active material for 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 application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries 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 NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), 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-containing 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 iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. During the charging and discharging process, Li undergoes insertion / extraction and consumption, resulting in different molar contents of Li in the positive electrode active material when the battery is discharged to different states. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the positive electrode active material is applied to the battery system. In the examples of positive electrode active materials in this application, the molar content of O is only an ideal value; lattice oxygen release causes changes in the molar content of O, and the actual molar content of O will fluctuate.

[0118] In one embodiment, the positive electrode film layer further includes 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.

[0119] In one embodiment, the positive electrode film layer further includes 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.

[0120] In one embodiment, the positive electrode sheet can be prepared by forming a positive electrode slurry from the components described above. For example, a first positive electrode active material and / or a second positive electrode active material, a conductive agent, a binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained.

[0121] [Isolation Component]

[0122] This application does not impose any particular restrictions on the type of separator. For example, any known porous membrane with good chemical and mechanical stability can be selected.

[0123] In one embodiment, 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.

[0124] [Electrolyte]

[0125] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements. The electrolyte includes electrolyte salts and solvents.

[0126] In one embodiment, 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.

[0127] In one embodiment, 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.

[0128] In one embodiment, the electrolyte may also include additives, which 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 or low-temperature performance, etc.

[0129] In one embodiment, the ionic conductivity σ of the electrolyte at 20℃~30℃ satisfies: 8mS / cm≤σ≤19mS / cm.

[0130] Specifically, σ can be 8 mS / cm, 9 mS / cm, 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, 18 mS / cm, 19 mS / cm, or its value can be within the range obtained by any combination of the above two values.

[0131] The above provides a detailed introduction to the internal structure of a single fast-charging lithium-ion battery cell. The following section will introduce other structural aspects of the battery cell.

[0132] In one embodiment, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0133] In one embodiment, 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.

[0134] This application 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 5 shows a square battery cell 400 as an example.

[0135] Fast-charging lithium-ion battery cells (400) typically require electrolytes with high ionic conductivity, as the ionic conductivity of the electrolyte affects the lithium-ion transport rate between the positive and negative electrodes. Higher ionic conductivity results in better fast-charging performance for the battery cell (400). Furthermore, the average volumetric particle size (Dv503) of the negative electrode active material influences the ion transport channels within the negative electrode active material layer, thus affecting the fast-charging capability of the battery cell (400). Smaller Dv503 in the negative electrode active material is more conducive to shortening the lithium-ion transport particle size, and thus to providing a higher charging rate.

[0136] Based on this, by adjusting the negative electrode active material Dv503 and combining it with electrolytes of different lithium-ion conductivity, commercially available, unused battery cells 400 can provide charging rates of 3C to 8C.

[0137] For example, under the conditions of 8mS / cm≤σ≤13mS / cm and 8μm≤Dv503≤12μm, the 400-cell battery can provide a charging rate of 3C.

[0138] For example, under the conditions of 10mS / cm≤σ≤15mS / cm and 7μm≤Dv503≤12μm, a single cell of battery 400 can provide a charging rate of 4C.

[0139] For example, under the conditions of 11mS / cm≤σ≤17mS / cm and 6.5μm≤Dv503≤12μm, a single cell of battery 400 can provide a charging rate of 5C.

[0140] For example, under the conditions of 13mS / cm≤σ≤19mS / cm and 6μm≤Dv503≤12μm, the 300-cell battery can provide a charging rate of 8C.

[0141] Figure 6 shows a battery module 500 as an example. Referring to Figure 6, in the battery module 500, multiple battery cells 400 can be arranged sequentially along the length of the battery module 500. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 400 can be fixed in place by fasteners.

[0142] Alternatively, in one embodiment, the battery module 500 may further include a housing with a receiving space in which a plurality of battery cells 400 are received.

[0143] Optionally, in one embodiment, the battery module 500 can also be assembled into a lithium-ion battery. The number of battery modules 500 contained in the lithium-ion battery can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery.

[0144] Figures 7 and 8 illustrate a lithium-ion battery 600 as an example. Referring to Figures 7 and 8, the lithium-ion battery 600 may include a battery case and multiple battery modules 500 disposed within the battery case. The battery case includes an upper housing 601 and a lower housing 602, the upper housing 601 covering the lower housing 602 to form a closed space for accommodating the battery modules 500. The multiple battery modules 500 can be arranged in any manner within the battery case.

[0145] It should be understood that in some embodiments, the lithium-ion battery 600 described above is also referred to as a lithium-ion battery pack. The individual battery cells 400 can be first assembled into a battery module 500, and the lithium-ion battery 600 is composed of the battery module 500. Alternatively, the lithium-ion battery 600 can be directly assembled from the individual battery cells 400, omitting the intermediate form of the battery module 500.

[0146] In addition, this application also provides an electrical device that includes the lithium-ion battery 600 in the foregoing embodiments.

[0147] In another embodiment, the electrical device includes at least one of the battery cell 400, battery module 500, or lithium-ion battery 600 provided in this application. The battery cell 400, battery module 500, or lithium-ion battery 600 can be used as the power source of the electrical device or as the 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.

[0148] As an electrical device, you can choose a single battery cell (400), a battery module (500), or a lithium-ion battery (600) depending on your usage requirements.

[0149] This is an example of an electrical device. The 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 lithium-ion battery 600 or a battery module 500 can be used as the power source.

[0150] 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 400mAh battery for power.

[0151] 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.

[0152] [Examples 1-7 and Comparative Examples 1-4]

[0153] Example 1

[0154] (1) Preparation of negative electrode sheet

[0155] Artificial graphite (negative electrode active material), acetylene black (conductive agent), sodium carboxymethyl cellulose (thickener), and styrene-butadiene rubber (binder) were dissolved in deionized water at a mass ratio of 96:1:1:2 and mixed thoroughly to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil (negative electrode current collector). After drying, rolling, and slitting, negative electrode sheets were obtained. The coating weight of the negative electrode film on the negative electrode sheet was 0.119 mg / mm². 2 The compaction density of the negative electrode sheet is 1.65 g / cm³. 3 .

[0156] (2) Preparation of positive electrode sheet

[0157] Lithium iron phosphate (CFP), acetylene black (conductive agent), and polyvinylidene fluoride (PVDF) (binder) were dissolved in N-methylpyrrolidone (N-methylpyrrolidone) at a mass ratio of 97:1:2 and mixed thoroughly to obtain a CFP slurry. The CFP slurry was then uniformly coated onto an aluminum foil current collector. After drying, rolling, and slitting, the CFP electrode sheets were obtained. The coating weight of the negative electrode film on the negative electrode sheet was 0.26 mg / mm². 2 The compaction density of the positive electrode sheet is 2.55 g / cm³. 3 .

[0158] (3) Preparation of electrolyte

[0159] Ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. A certain mass of lithium hexafluorophosphate was slowly added, and the mixture was stirred thoroughly until it was completely dissolved. The concentration of lithium hexafluorophosphate in the electrolyte was 1 mol / L. After the solution returned to room temperature, 2 wt% of vinylene carbonate and 1 wt% of fluoroethylene carbonate were added, and the mixture was thoroughly mixed to obtain the electrolyte.

[0160] (4) Preparation of the isolation component

[0161] Two long, thin polyethylene (PE) films are used as separators. Both surfaces of the first and second separators are coated with a polyvinylidene fluoride (PVDF) coating. The average volumetric particle size (Dv501) of the coating material on the surface of the first separator is 10 μm, and the coating surface density (ρ1) is 0.6 × 10⁻⁶. -3 mg / mm 2 The average volumetric particle size Dv502 of the coating material on the surface of the second separator is 8 μm, and the coating surface density ρ2 is 0.4 × 10⁻⁶. -3 mg / mm 2 .

[0162] (5) Preparation of battery cells

[0163] The negative electrode 11, the first separator, the negative electrode 12, and the second separator are stacked and wound in sequence to obtain a wound electrode assembly 1; the wound electrode assembly is placed in an aluminum shell, dried, and then injected with electrolyte. After processes such as encapsulation, settling, formation, aging, and secondary encapsulation, a battery cell 400 is obtained.

[0164] Therefore, in the electrode assembly 1 of the battery cell 400 of Example 1, L1 = 23 μm, L2 = 19 μm, and H = 16.3 mm. A rate test was performed on the battery cell 400, and the equivalent charge rate of the battery cell 400 from 10% SOC to 80% SOC at 35°C was measured to be 4C.

[0165] Example 2

[0166] Compared with Example 1, in the electrode assembly 1 of Example 2, Dv501 = 13 μm, Dv502 = 10 μm, L1 = 30 μm, L2 = 23 μm, and H = 16.3 mm.

[0167] Example 3

[0168] Compared with Example 1, in the electrode assembly 1 of Example 3, Dv501 = 15 μm, Dv502 = 12 μm, L1 = 35 μm, L2 = 28 μm, and H = 16.2 mm.

[0169] Example 4

[0170] Compared with Example 1, in the electrode assembly 1 of Example 4, Dv501 = 13 μm, Dv502 = 13 μm, L1 = 30 μm, L2 = 30 μm, and H = 16.3 mm.

[0171] Example 5

[0172] Compared with Example 1, in electrode assembly 1 of Example 5, ρ1 = 0.8 × 10 -3 mg / mm 2 ρ2=1.0×10 -3 mg / mm 2 , L1=25μm, L2=23μm, H=16.2mm.

[0173] Example 6

[0174] Compared with Example 1, in Example 6, the coating material on the surface of the first and second isolation membranes is polyimide, with L1 = 23 μm, L2 = 19 μm, and H = 16.2 mm.

[0175] Example 7

[0176] Compared with Example 1, in Example 7, the coating material of the first separator is PVDF, the coating material of the second separator is polyimide, L1 = 23 μm, L2 = 19 μm, and H = 16.2 mm.

[0177] Comparative Example 1

[0178] Compared with Example 1, in the electrode assembly 1 of Comparative Example 1, Dv501 = 8 μm, Dv502 = 10 μm, L1 = 19 μm, L2 = 23 μm, and H = 16.4 mm.

[0179] Comparative Example 2

[0180] Compared with Example 1, in the electrode assembly 1 of Comparative Example 2, Dv501 = 10 μm, Dv502 = 15 μm, L1 = 13 μm, L2 = 19 μm, and H = 37.4 mm.

[0181] Comparative Example 3

[0182] Compared with Example 1, in the electrode assembly 1 of Comparative Example 3, Dv501 = 5 μm, Dv502 = 8 μm, L1 = 12 μm, L2 = 19 μm, and H = 16.3 mm.

[0183] Comparative Example 4

[0184] Compared with Example 1, in the electrode assembly 1 of Comparative Example 4, Dv501 = 20 μm, Dv502 = 15 μm, L1 = 47 μm, L2 = 35 μm, and H = 16.3 mm.

[0185] Product parameters of Examples 1-7 and Comparative Examples 1-4.

[0186] Table 1: Product and performance parameters of Examples 1-7 and Comparative Examples 1-4

[0187] In Table 1, “Material 1” represents the type of the first coating material, “Material 2” represents the type of the second coating material, “Dv501” represents the average volumetric particle size of the first coating material, “Dv502” represents the average volumetric particle size of the second coating material, “ρ1” represents the coating surface density of the first coating material, “ρ2” represents the coating surface density of the second coating material, “L1” represents the distance between the concave surface of the second bent portion 12a in the electrode assembly and the convex surface of the adjacent first bent portion 11a located inside it, “L2” represents the distance between the convex surface of the second bent portion 12a and the concave surface of the adjacent first bent portion 11a located outside it, and “H” represents the thickness of the wound electrode assembly 1.

[0188] Battery performance tests were conducted on Examples 1-7 and Comparative Examples 1-4, and the measured performance data are detailed in Table 2.

[0189] Table 2: Product parameters of Examples 1-7 and Comparative Examples 1-4

[0190] In Table 2, "Cycle Performance" represents the number of cycles of the battery cell 400 in the cycle test. The specific test method is described later. "Lithium Deposition on the Convex Surface of the First Bending Section" represents the lithium deposition on the convex surface of the negative electrode 11 in the bending region A of the electrode assembly 1 after the battery cell 400 has undergone 1000 cycles. "Inner Ring 1-Fold" refers to the first bending section 11a closest to the winding axis x or y among the multiple first bending sections 11a of the wound electrode assembly 1; "Inner Ring 2-Fold" refers to the second first bending section 11a from the inside out, starting from the first bending section 11a closest to the winding axis x or y, and so on. "Outer Ring Concave Surface" refers to the concave surface of one or more first bending sections 11a furthest from the winding axis x or y among the multiple first bending sections 11a of the wound electrode assembly 1.

[0191] Analysis and comparison of Examples 1-7 and Comparative Examples 1-4 show that, after long-cycle testing, the fast-charging lithium-ion batteries of Examples 1-7 exhibited fewer first bends 11a with lithium plating; while Comparative Examples 1-3 showed a greater number of first bends 11a with lithium plating, and lithium plating occurred not only in bend area A but also in straight area B. Comparative Example 4, although not exhibiting lithium plating, showed purple spots. Furthermore, the cycle performance of Examples 1-7 was significantly better than that of Comparative Examples 1-4. This demonstrates that by controlling L1 and L2 within appropriate ranges, and ensuring that L1 ≥ L2, the problem of lithium plating in the corner areas of the electrode components of fast-charging lithium-ion batteries can be effectively improved, thereby enhancing the cycle performance of the fast-charging lithium-ion batteries.

[0192] Comparative analysis of data from Examples 1-4 shows that adjusting the Dv50 of the coating material can effectively control L1 and L2. It can be seen that as the Dv50 of the coating material increases, L1 and L2 also increase, the number of first bends 11a where lithium plating occurs gradually decreases, and safety performance improves accordingly. On the other hand, compared to Example 1, the cycle performance of Examples 2-4 is further improved, but the cycle performance of Examples 3-4 is inferior to that of Example 2. This is because the further increase of L1 and L2 affects lithium-ion kinetics. This indicates that by controlling Dv501 and Dv502 within a suitable range, L1 and L2 can be controlled within a suitable range, thereby improving the problem of lithium plating in the bend region A of the wound electrode assembly 1 and improving the cycle performance of the lithium-ion battery. Data from Comparative Example 4 shows that excessively large Dv501 and Dv502 lead to excessively large L1 and L2. In this case, although lithium plating does not occur in the first bend 11a, the cycle performance of the battery deteriorates. A possible reason is that if L1 and L2 are too large, the electrolyte will not be able to completely fill the bending region A, leading to difficulties in lithium-ion transport, the formation of purple spots, and a deterioration in cycle performance. Therefore, this indicates that by controlling Dv501 and Dv502 within a suitable range, L1 and L2 can be regulated within a suitable range, thereby improving lithium deposition in the bending region A and further enhancing the cycle performance of fast-charging lithium-ion batteries.

[0193] As can be seen from the data in Examples 1 and 5, while adjusting Dv501 and Dv502, controlling ρ1 and ρ2 within a suitable range can also indirectly keep L1 and L2 within a suitable range, thereby improving the lithium deposition situation in the bending region A and further enhancing the cycle performance of the lithium-ion battery.

[0194] Examples 6-7 demonstrate the use of different coating materials to achieve the same L1 and L2 as in Example 1. The lithium-ion batteries of Examples 6-7 also exhibit good safety and cycle performance.

[0195] Comparative Examples 1 and 3 both demonstrate the case where L1 is less than L2, with Comparative Example 1 showing better performance. In Comparative Example 1, both L1 and L2 are within the appropriate range described above, while in Comparative Example 3, L1 is not within this range. This again illustrates the crucial role of controlling L1 and L2 within appropriate ranges in improving the cycle performance of fast-charging lithium-ion batteries. Comparative Example 2 shows a case where the electrode assembly thickness H is large, but L1 and L2 are small. It can be seen that Comparative Example 2 also exhibits a relatively severe lithium plating problem. This proves that if the range of H cannot be matched with the range of L1 and L2, a large electrode assembly thickness but small L1 and L2 will not be compatible with the expansion of the negative electrode 11 during cycling. Therefore, it demonstrates the effect of comprehensively considering the ranges of H, L1, and L2 on improving lithium plating and cycle performance of fast-charging lithium-ion batteries.

[0196] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0197] 1. Cyclic performance testing methods

[0198] The battery cell 400 of the fast-charging lithium-ion battery is placed at 35°C and charged from 0% SOC to 40% SOC at a constant current of 5C; then charged from 40% SOC to 45% SOC at a constant current of 4.6C; then charged from 45% SOC to 50% SOC at a constant current of 4.3C; then charged from 50% SOC to 55% SOC at a constant current of 4C; then charged from 55% SOC to 60% SOC at a constant current of 3.7C; then charged from 60% SOC to 65% SOC at a constant current of 3.4C; and then charged from 65% SOC to 60% SOC at a constant current of 3.1C. Charge to 70% SOC; then charge at a constant current of 2.9C from 70% SOC to 75% SOC; then charge at a constant current of 2.7C from 75% SOC to 80% SOC; then charge at a constant current of 1.8C from 80% SOC to 85% SOC; then charge at a constant current of 1.1C from 85% SOC to 90% SOC; then charge at a constant current of 0.6C from 90% SOC to 95% SOC; finally charge at a constant current of 0.3C from 95% SOC to 100% SOC; let stand for 60 minutes, then discharge at a constant current of 0.33C to 2.0V. This charge-discharge cycle is counted. Record the number of cycles when the capacity of a single 400 cell decreases to 80% SOH (i.e., 80% of the rated capacity).

[0199] 2. Test methods for lithium plating

[0200] Following the above charging and discharging cycle, repeat 1000 times, fully charge the battery cell to 400, then disassemble it to check the lithium plating status or whether purple spots have formed on the negative electrode plate 11 in corner area A.

[0201] 3. Test methods for H, L1, and L2

[0202] The battery cell 400 was discharged at 25°C with a constant current of 0.33C to the cutoff voltage of the battery cell, and then a CT test was performed. The CT test started from the innermost circle of the corner area A. On a certain radial direction of the winding axis in the bending area A, the distance between the convex surface of the negative electrode 11 and the concave surface of the positive electrode 12 was marked as L1, the distance between the concave surface of the negative electrode 11 and the convex surface of the positive electrode 12 was marked as L2, and the thickness of the electrodes in all straight areas B was marked as H.

[0203] 4. Test method for average volumetric particle size (Dv50)

[0204] After disassembling the battery cell 400, take the separator located in the bending area A. Then, soak and clean the separator with DMC solvent, repeat the cleaning more than 3 times, and dry it in a vacuum oven at 45°C for more than 24 hours until the separator is completely dry.

[0205] The dried separator was placed under a scanning electron microscope (SEM). Using software such as Nano Measurer, the size, length, and pore size of the particles in the SEM images were statistically analyzed to obtain the Dv50 of the separator coating material in the SEM. To improve measurement accuracy, N SEM images (N≥5) of the same sample were obtained, and the corresponding Dv50 data were analyzed. The N Dv50 values ​​were then averaged to obtain the Dv50 of the sample.

[0206] 5. Testing method for charging rate

[0207] The battery cell 400 of the fast-charging lithium-ion battery was placed at 35°C and discharged to 2.0V at a constant current of 0.33C, allowed to stand for 1 minute, then discharged to 2.0V at a constant current of 0.1C, and allowed to stand for 30 minutes. It was then charged from 0% SOC to 40% SOC at a constant current of 5C; then charged from 40% SOC to 45% SOC at a constant current of 4.6C; then charged from 45% SOC to 50% SOC at a constant current of 4.3C; then charged from 50% SOC to 55% SOC at a constant current of 4C; then charged from 55% SOC to 60% SOC at a constant current of 3.7C; and then charged at 3.4C... Charge from 0% SOC to 100% SOC using a constant current of C: 1.1C from 60% SOC to 65% SOC; then charge from 65% SOC to 70% SOC using a constant current of C: 3.1C; then charge from 70% SOC to 75% SOC using a constant current of C: 2.9C; then charge from 75% SOC to 80% SOC using a constant current of C: 2.7C; then charge from 80% SOC to 85% SOC using a constant current of C: 1.8C; then charge from 85% SOC to 90% SOC using a constant current of C: 1.1C; then charge from 90% SOC to 95% SOC using a constant current of C: 0.6C; finally charge from 95% SOC to 100% SOC using a constant current of C: 0.3C. Record the charging time t from 0% SOC to 100% SOC. The equivalent charging rate of a single 400 battery cell from 10% SOC to 80% SOC is c = [(80% SOC - 10% SOC) / (100% SOC - 0% SOC)] × [(1C × 60min) / t min].

[0208] 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 single battery cell (400), characterized in that, The battery cell (400) includes a wound electrode assembly (1) having a bending region (A), and the wound electrode assembly (1) includes: The negative electrode (11) and the positive electrode (12) include a plurality of first bends (11a) located in the bending region (A) and the positive electrode (12) include a plurality of second bends (12a) located in the bending region (A). The distance between the convex surface of the first bent portion (11a) and the concave surface of the adjacent second bent portion (12a) located on its outer side is L1, and the distance between the concave surface of the first bent portion (11a) and the convex surface of the adjacent second bent portion (12a) located on its inner side is L2. 17μm≤L1≤34μm, 14μm≤L2≤34μm, and L1≥L2.

2. The battery cell (400) according to claim 1, characterized in that, The battery cell includes an electrolyte, and the ionic conductivity σ of the electrolyte at 20℃~30℃ satisfies: 8mS / cm≤σ≤19mS / cm; The equivalent charging rate c of the battery cell (400) from 10% SOC to 80% SOC satisfies: 3C≤c≤8C.

3. The battery cell (400) according to claim 1 or 2, characterized in that, The thickness H of the wound electrode assembly (1) satisfies: 5mm≤H≤35mm.

4. The battery cell (400) according to claim 3, characterized in that, 5mm≤H≤17mm, 17μm≤L1≤24μm, 14μm≤L2≤23μm; or when 17mm<H≤35mm, 24μm<L1≤34μm, 23μm<L2≤34μm.

5. The battery cell (400) according to any one of claims 1-4, characterized in that, The wound electrode assembly (1) includes: An isolation member (13) is disposed between the negative electrode plate (11) and the positive electrode plate (12). The isolation member (13) includes a plurality of first isolation member bending portions (131) and second isolation member bending portions (132) arranged sequentially from the inside to the outside in the bending area (A). The first isolation member bend (131) is disposed between the convex surface of the first bend (11a) and the concave surface of the adjacent second bend (12a) located outside it, and the second isolation member bend (132) is disposed between the concave surface of the first bend (11a) and the convex surface of the adjacent second bend (12a) located outside it.

6. The battery cell (400) according to claim 5, characterized in that, The first isolation member bend (131) has a first coating (1311) on at least one side of its surface, and the second isolation member bend (132) has a second coating (1321) on at least one side of its surface.

7. The battery cell (400) according to claim 6, characterized in that, The first coating (1311) includes a first coating material, and the second coating (1321) includes a second coating material; The average volumetric particle size Dv501 of the first coating material is greater than or equal to the average volumetric particle size Dv502 of the second coating material.

8. The battery cell (400) according to claim 6, characterized in that, 10μm≤Dv501≤15μm; 8μm≤Dv502≤15μm.

9. The battery cell (400) according to any one of claims 7-8, characterized in that, The first coating material includes at least one of polyvinylidene fluoride, polyimide, polyurethane, polyvinyl alcohol, polyvinyl ether, polyacrylic acid, and polycarbosilane; the second coating material includes at least one of polyvinylidene fluoride, polyimide, polyurethane, polyvinyl alcohol, polyvinyl ether, polyacrylic acid, and polycarbosilane.

10. The battery cell (400) according to any one of claims 6-8, characterized in that, The areal density ρ1 of the first coating (1311) satisfies: 0.3 × 10⁻⁶ -3 mg / mm 2 ≤ρ1≤0.8×10 -3 mg / mm 2 .

11. The battery cell (400) according to any one of claims 6-8, characterized in that, The coating density ρ2 of the second coating (1321) satisfies: 0.3 × 10⁻⁶ -3 mg / mm 2 ≤ρ2≤1.0×10 -3 mg / mm 2 .

12. The battery cell (400) according to any one of claims 1-11, characterized in that, The negative electrode sheet includes a negative electrode active material, and the average volumetric particle size Dv503 of the negative electrode active material satisfies: 6μm≤Dv503≤12μm.

13. The battery cell (400) according to any one of claims 2-12, characterized in that, The battery cell (400) can provide a charging rate of 3C when the conditions are 8mS / cm≤σ≤13mS / cm and 8μm≤Dv503≤12μm.

14. The battery cell (400) according to any one of claims 2-12, characterized in that, With 10mS / cm≤σ≤15mS / cm and 7μm≤Dv503≤12μm, the battery cell (400) can provide a charging rate of 4C.

15. The battery cell (400) according to any one of claims 2-12, characterized in that, With 11mS / cm≤σ≤17mS / cm and 6.5μm≤Dv503≤12μm, the battery cell (400) can provide a charging rate of 5C.

16. The battery cell (400) according to any one of claims 2-12, characterized in that, With 13mS / cm≤σ≤19mS / cm and 6μm≤Dv503≤12μm, the battery cell (400) can provide a charging rate of 8C.

17. A lithium-ion battery (600), characterized in that, The lithium-ion battery (600) comprises the battery cell (400) according to any one of claims 1-16.

18. An electrical appliance, characterized in that, The electrical device includes the lithium-ion battery (600) as described in claim 17.

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