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

Abstract

Provided in the present application are a battery cell, a manufacturing method therefor, a battery device and an electric device. The battery cell comprises an electrode assembly, and the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator located between the positive electrode sheet and the negative electrode sheet; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer; the negative electrode film layer is arranged on at least one side of the negative electrode current collector; the negative electrode film layer comprises a negative electrode active material and a conductive agent; the negative electrode active material comprises a carbon-based material and a silicon-based material; the conductive agent comprises a sheet-shaped carbon-based conductive agent; and the negative electrode film layer is single-layered or multi-layered, and the mass content of the silicon element in the negative electrode film layer having the sheet-shaped carbon-based conductive agent and the silicon-based material is 30-80%. The conductivity of a silicon-containing negative electrode and the stability during cycling are improved.

Description

Battery cells, their manufacturing methods, battery devices and electrical devices Cross-references to related applications This application claims ownership of the patent filed on November 4, 2024, entitled "Battery Cell, Its Manufacturer". The priority of Chinese patent application 202411561728.1, entitled "Power supply, battery device and power consumption device", the entire contents of which are incorporated herein by reference. Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a method for manufacturing the same, a battery device, and an electrical device. Background Technology

[0002] In recent years, high-energy-density lithium-ion batteries have been widely used in the electric vehicle industry. Silicon, with its high specific capacity, has become a widely used high-capacity anode material. However, silicon materials, as anodes in lithium batteries, still face problems such as poor cycle performance and large volume expansion. The theoretical specific capacity of pure silicon anodes can reach as high as 4200 mAh / g (45℃).

[0003] However, silicon itself has some problems: ① poor conductivity results in low electrochemical activity; ② high-silicon anode sheets may experience particle breakage and active material detachment from the conductive network during repeated cyclic expansion, leading to deactivation of the active material. These problems result in insufficient cycle life of the battery cells, failing to meet commercialization requirements. Summary of the Invention

[0004] This application provides a battery cell, a method for manufacturing the same, a battery device, and an electrical device to improve the conductivity and cycle stability of a silicon-containing anode.

[0005] The first aspect of this application provides a battery cell including an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode. The negative electrode includes a negative current collector and a negative electrode film. The negative electrode film is disposed on at least one side of the negative current collector. The negative electrode film includes a negative active material and a conductive agent. The negative active material includes a carbon-based material and a silicon-based material. The conductive agent includes a sheet-like carbon-based conductive agent. The negative electrode film is a single layer or multiple layers. The mass content of silicon in the negative electrode film having the sheet-like carbon-based conductive agent and the silicon-based material is 30%-80%.

[0006] The sheet-like carbon-based conductive agent of this application is not prone to agglomeration and can be uniformly covered on the surface of silicon-based materials, forming a good conductive network and buffer structure. Theoretically, compared with particulate conductive agents, the sheet-like carbon-based conductive agent can form surface contact with silicon-based material particles, significantly improving the interfacial electronic conduction of low-conductivity silicon-based materials and increasing the activity of the negative electrode. Moreover, the sheet-like carbon-based conductive agent has a certain degree of flexibility, which can buffer the expansion and contraction of silicon-based materials during cycling to a certain extent, ensuring good electrical contact between the sheet-like carbon-based conductive agent and silicon-based material particles throughout the entire life cycle, thus improving cycle life. At the same time, the chance of direct contact between silicon-based materials coated by the sheet-like carbon-based conductive agent is greatly reduced, controlling hard collisions between silicon-based material particles during cyclic expansion and contraction, thereby delaying the breakage and pulverization caused by the extrusion between silicon-based material particles, further improving cycle life. Experiments have shown that when the mass content of silicon element in the silicon-based film layer is less than 30%, the carbon-based material fully encapsulates the silicon-based material, greatly reducing the aggregation between silicon-based material particles. Therefore, the addition of the sheet-like carbon-based conductive agent cannot play the role of improving conductivity and the aforementioned buffering effect. When the mass content of silicon element in the film containing silicon-based material is above 30%, the sheet-like carbon-based conductive agent has a significant effect on improving conductivity and buffering effect.

[0007] In any embodiment of the first aspect, the average diameter of the sheet-like carbon-based conductive agent is 0.5 μm-10 μm, optionally 0.6 μm-7 μm. This can further improve the conductivity of the sheet-like carbon-based conductive agent.

[0008] In any embodiment of the first aspect, the average thickness of the sheet-like carbon-based conductive agent is 0.1 μm-5 μm, optionally 0.2 μm-2 μm; optionally, the ratio of the average thickness to the average diameter of the sheet-like carbon-based conductive agent is 1 / 30-1 / 3. This better utilizes the buffering effect of the sheet-like carbon-based conductive agent, reduces particle breakage, lowers the loss of active lithium, and further improves cycle life.

[0009] In any embodiment of the first aspect, the powder resistivity of the sheet-like carbon-based conductive agent at a pressure of 12 MPa is 1 mΩ·cm to 15 mΩ·cm.

[0010] In any embodiment of the first aspect, the sheet-like carbon-based conductive agent includes any one or more of sheet-like graphite and sheet-like graphene.

[0011] In any embodiment of the first aspect, in the cross-sectional region along the thickness direction of the negative electrode sheet in which the negative electrode film layer has a silicon-based material, the area ratio of the sheet-like carbon-based conductive agent to the area of ​​the silicon-based material is 4%-20%. This achieves a more complete encapsulation of the silicon-based material by the sheet-like carbon-based conductive agent.

[0012] In any embodiment of the first aspect, the conductive agent further includes dot-like conductive agents and / or linear conductive agents. Optionally, the dot-like conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, or carbon dots; optionally, the linear conductive agent includes carbon nanotubes and / or carbon nanofibers. The dot-like and linear conductive agents are interspersed in the small pores between the silicon-based materials, forming a richer conductive network in conjunction with the sheet-like carbon-based conductive agent, further improving conductivity.

[0013] In any embodiment of the first aspect, the carbon-based material includes any one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0014] In any embodiment of the first aspect, the silicon-based material includes one or more of elemental silicon, silicon oxides, silicon-carbon composites, and silicon alloys.

[0015] In any embodiment of the first aspect, the mass content of silicon in the negative electrode film is 30%-55%. This utilizes the addition of silicon to increase the specific capacity of the negative electrode film and improve the energy density of the battery cell.

[0016] In any embodiment of the first aspect, the negative electrode film is multilayered, and at least a portion of the sheet-like carbon-based conductive agent and silicon-based material are disposed in the same negative electrode film.

[0017] In any embodiment of the first aspect, the negative electrode film layer includes: a first negative electrode film layer disposed on one side of the negative electrode current collector; and a second negative electrode film layer disposed on the side of the first negative electrode film layer away from the negative electrode current collector, wherein the first negative electrode film layer and the second negative electrode film layer are each independently provided with a silicon-based material.

[0018] Silicon exhibits high expansion properties, while carbon-based materials are relatively soft. If silicon is directly distributed within carbon-based materials, its expansion during continuous charge-discharge cycles will compress the carbon-based materials, leading to a deterioration in lithium intercalation kinetics and capacity loss. However, by layering carbon-based and silicon-based materials in a multilayer coating manner, with flexible adjustments to the ratio of the two materials in different film layers, the direct contact area between the silicon and carbon-based materials can be effectively controlled, improving the cycle life of the carbon-rich film. Simultaneously, a stable conductive network can be constructed within the silicon-rich film using sheet-like carbon-based conductive agents. For example, under the guidance of this application, those skilled in the art can incorporate more sheet-like carbon-based conductive agents in film layers with higher silicon content, thereby more effectively preventing the silicon-based material from detaching from the conductive network during cycling and improving the stable cycling of the silicon-rich film.

[0019] In any embodiment of the first aspect, the first negative electrode film layer and the second negative electrode film layer each independently include a binder. The mass content of silicon-based material in the first negative electrode film layer is greater than the mass content of silicon-based material in the second negative electrode film layer. Optionally, the mass content of binder in the first negative electrode film layer is greater than or equal to the mass content of binder in the second negative electrode film layer, and / or the mass content of binder in the first negative electrode film layer is 5%-10%. When the silicon-based material is mainly distributed in the lower first negative electrode film layer, due to the high specific capacity of the silicon-based material, the binder content in the first negative electrode film layer is allowed to increase while maintaining high energy density. The increased binder content can significantly improve the adhesion of the negative electrode film layer to the negative electrode current collector, reducing the risk of cyclic delamination.

[0020] In any embodiment of the first aspect, the mass content of silicon-based material in the second negative electrode film is greater than that in the first negative electrode film, and the thickness ratio of the first negative electrode film to the second negative electrode film is (1:4)-(4:1), optionally (6:5)-(1:1). When the silicon-based material is mainly distributed in the surface of the second film, due to the harder silicon-based material particles, it is less likely to be compacted under the same pressure compared to the first negative electrode film rich in carbon-based material. This allows for the formation of a larger porosity in the upper layer, resulting in a structure with high porosity in the upper layer and low porosity in the lower layer in the thickness direction of the negative electrode film. This is beneficial for the diffusion and migration of active ions. Without sacrificing energy density, the kinetic performance of the battery cell can still be improved by controlling the above thickness ratio.

[0021] The second aspect of this application provides a method for manufacturing any of the battery cells provided in the first aspect above. The method includes a process for manufacturing a negative electrode sheet, the process of which includes:

[0022] A negative electrode slurry is formed by mixing a negative electrode active material, a conductive agent and a solvent. The negative electrode active material includes carbon-based materials and silicon-based materials, and the conductive agent includes sheet-like carbon-based conductive agents.

[0023] After the negative electrode slurry is placed on the negative electrode current collector, it is pressed and dried to obtain the negative electrode sheet.

[0024] When a flake-shaped carbon-based conductive agent is used as the conductive agent for the negative electrode, the negative electrode slurry containing the flake-shaped carbon-based conductive agent has high stability and is not easy to gel, thus providing a longer working time for the processing of the negative electrode sheet.

[0025] In any embodiment of the second aspect, the viscosity of the negative electrode slurry with a solid content of 30% to 40% is 8000 mPa·s to 12000 mPa·s at 25°C and 60 rpm.

[0026] In any embodiment of the second aspect, before forming the negative electrode slurry, the manufacturing process further includes coating the surface of the silicon-based material with a sheet-like carbon-based conductive agent, optionally by spray drying.

[0027] A third aspect of this application provides a battery device comprising a plurality of battery cells, wherein the battery cells include any of the battery cells provided in the first aspect described above.

[0028] The fourth aspect of this application provides an electrical device, including any of the battery cells provided in the first aspect or any of the battery devices provided in the third aspect, wherein the battery cells or battery devices are used to store or provide electrical energy. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced 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.

[0030] Figure 1 is a SEM image of the ion-polished cross-section of the negative electrode sheet of Embodiment 1 of this application.

[0031] Figure 2 is a SEM image of the ion-polished cross-section of the negative electrode sheet of Comparative Example 1 of this application.

[0032] Figure 3 is an SEM image of the ion-polished cross-section of the negative electrode sheet of Embodiment 16 of this application.

[0033] Figure 4 is a schematic diagram of a battery cell according to one embodiment of this application.

[0034] Figure 5 is an exploded view of a battery cell according to an embodiment of this application, as shown in Figure 4.

[0035] Figure 6 is a schematic diagram of a battery module according to an embodiment of this application.

[0036] Figure 7 is a schematic diagram of a battery pack according to one embodiment of this application.

[0037] Figure 8 is an exploded view of a battery pack according to an embodiment of this application, as shown in Figure 7.

[0038] Figure 9 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0039] The accompanying drawings are not drawn to scale.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Casing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0042] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0043] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, its manufacturing method, battery assembly, and battery module of the 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 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.

[0044] 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.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0047] 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.

[0048] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0049] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0050] [Battery cell]

[0051] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0052] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0053] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0054] To improve the conductivity of silicon, adding carbon nanotubes or more conductive carbon black to the negative electrode slurry can enhance the negative electrode capacity and improve the cycle performance of the battery cell.

[0055] However, adding carbon nanotubes or more conductive carbon black deteriorates the stability of the anode slurry. This is mainly because both conductive carbon black and carbon nanotubes are nanomaterials, making dispersion difficult. Furthermore, the slurry easily gels during settling, causing processing difficulties. Additionally, the nano-conductive particles maintain point-to-point contact with the silicon active material, resulting in insufficient electron conduction. During the cyclic expansion and contraction of silicon, the conductive particles may lose contact with the silicon, causing the silicon to detach from the conductive network and become deactivated.

[0056] To improve the conductivity and cycle stability of silicon-containing negative electrodes, a first embodiment of this application provides a battery cell. The battery cell includes an electrode assembly, which includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode. The negative electrode includes a negative current collector and a negative electrode film. The negative electrode film is disposed on at least one side of the negative current collector and includes a negative electrode active material and a conductive agent. The negative electrode active material includes a carbon-based material and a silicon-based material, and the conductive agent includes a sheet-like carbon-based conductive agent. The negative electrode film is a single layer or multiple layers, and the mass content of silicon in the negative electrode film having sheet-like carbon-based conductive agent and silicon-based material is 30%-80%.

[0057] The sheet-like carbon-based conductive agent of this application is not prone to agglomeration and can be uniformly covered on the surface of silicon-based materials, forming a good conductive network and buffer structure. Theoretically, compared with particulate conductive agents, the sheet-like carbon-based conductive agent can form surface contact with silicon-based material particles, significantly improving the interfacial electronic conduction of low-conductivity silicon-based materials and increasing the activity of the negative electrode. Moreover, the sheet-like carbon-based conductive agent has a certain degree of flexibility, which can buffer the expansion and contraction of silicon-based materials during cycling to a certain extent, ensuring good electrical contact between the sheet-like carbon-based conductive agent and silicon-based material particles throughout the entire life cycle, thus improving cycle life. At the same time, the chance of direct contact between silicon-based materials coated by the sheet-like carbon-based conductive agent is greatly reduced, controlling hard collisions between silicon-based material particles during cyclic expansion and contraction, thereby delaying the breakage and pulverization caused by the extrusion between silicon-based material particles, further improving cycle life. Experiments have shown that when the mass content of silicon element in the silicon-based film layer is less than 30%, the carbon-based material fully encapsulates the silicon-based material, greatly reducing the aggregation between silicon-based material particles. Therefore, the addition of the sheet-like carbon-based conductive agent cannot play the role of improving conductivity and the aforementioned buffering effect. When the mass content of silicon element in the film containing silicon-based material is above 30%, the sheet-like carbon-based conductive agent has a significant effect on improving conductivity and buffering effect.

[0058] When the negative electrode film layer is multilayered, silicon-based materials can be disposed in one or more of them. When silicon-based materials and carbon-based materials are mixed and disposed in one of the layers, the amount of sheet-like carbon-based conductive agent added is determined according to the content of silicon-based materials.

[0059] Of course, when the negative electrode film is multilayered, the above limitation does not mean that the sheet-like carbon-based conductive agent can only be disposed in the film layer with silicon-based material. It can also be disposed in the film layer without silicon-based material. It's just that the advantages of the sheet-like carbon-based conductive agent mentioned above cannot be utilized, but it can still perform basic conductivity. In some embodiments, the negative electrode film is multilayered, and at least part of the sheet-like carbon-based conductive agent and silicon-based material are disposed in the same negative electrode film layer.

[0060] To further improve the conductivity of the sheet-like carbon-based conductive agent, in some embodiments, the average diameter of the sheet-like carbon-based conductive agent is 0.5μm-10μm, and can be selected as 0.6μm-7μm.

[0061] The sheet-like carbon-based conductive agent with this average diameter can more fully coat the silicon-based material, forming a more stable conductive network, further reducing material loss caused by the destruction of the conductive network, and improving the performance of the electrode.

[0062] The average diameter can be measured using SEM (Semiconductor Electron Microscopy). A negative electrode sheet is subjected to SEM testing to measure the diameter of the sheet-like carbon-based conductive agent within the field of view. When the cross-sectional shape of the sheet-like carbon-based conductive agent in the field of view is a regular circle, the diameter of the sheet-like carbon-based conductive agent is the diameter of that circle; when the cross-sectional shape of the sheet-like carbon-based conductive agent is an irregular circle, the diameter of the sheet-like carbon-based conductive agent is the equivalent diameter of a regular circle with the same area as the irregular circle.

[0063] To better leverage the buffering effect of the sheet-like carbon-based conductive agent, in some embodiments, the average thickness of the sheet-like carbon-based conductive agent is 0.1 μm-5 μm, optionally 0.2 μm-2 μm.

[0064] Within this thickness range, the sheet-like carbon-based conductive agent can act as a buffer, preventing direct compression between silicon-based active materials, reducing particle breakage, decreasing active lithium loss, and further improving cycle life.

[0065] Thickness can also be measured using SEM images. The negative electrode sheet is ion-polished and then subjected to SEM under backscattering conditions to measure the thickness of the sheet-like carbon-based conductive agent in the field of view. When the thickness of a sheet-like carbon-based conductive agent is not uniform, the thickness is the average thickness of that sheet-like carbon-based conductive agent (for example, 10 points are randomly selected along the length of the sheet-like carbon-based conductive agent, the thickness at these 10 points is measured, and the average value is taken).

[0066] Due to stress, if the thickness of the sheet-like carbon-based conductive agent is too large, it will affect its adhesion to silicon-based material particles. In order to make full use of the above-mentioned conductive and buffering effects, in some embodiments, the ratio of the average thickness to the average diameter of the sheet-like carbon-based conductive agent is 1 / 30-1 / 3, and can be selected as 1 / 5-1 / 3.

[0067] In some embodiments, in order to improve the conductivity of the flake-shaped carbon-based conductive agent, the powder resistivity of the flake-shaped carbon-based conductive agent at a pressure of 12 MPa is selected to be 1 mΩ·cm-15 mΩ·cm, and can be selected to be 3 mΩ·cm-7 mΩ·cm.

[0068] The powder resistivity was mainly tested using the four-probe method. A certain mass of flake-shaped carbon-based conductive agent was weighed, the depth of the feeding chamber was adjusted, the flake-shaped carbon-based conductive agent was added into the feeding chamber, and a pressure of 12 MPa was applied. Data was collected manually, and the powder resistivity test results were recorded.

[0069] In some embodiments, the above-mentioned sheet-like carbon-based conductive agent includes any one or more of sheet-like graphite and sheet-like graphene.

[0070] It should be noted that the sheet graphite and sheet graphene described in the above embodiments refer to graphite and graphene whose sheet structure can be seen from SEM.

[0071] The sheet-like carbon-based conductive agent of this application is mainly added to address the expansion and poor conductivity issues of silicon-based materials. To more effectively solve these problems, in some embodiments, in the cross-sectional region along the thickness direction of the negative electrode sheet where the negative electrode film layer with silicon-based material is located, the area ratio of the sheet-like carbon-based conductive agent to the area of ​​the silicon-based material is 4%-20%. This achieves a more thorough encapsulation of the silicon-based material by the sheet-like carbon-based conductive agent.

[0072] The area ratio of the sheet-like carbon-based conductive agent to the silicon-based material can be measured using SEM images and ImageJ software. The negative electrode sheet was ion-polished and then subjected to SEM testing under backscattering conditions. ImageJ software was used to distinguish the sheet-like carbon-based conductive agent and the silicon-based material, and the cross-sectional area was calculated to obtain the area ratio of the sheet-like carbon-based conductive agent to the silicon-based material.

[0073] In some embodiments, to synergistically improve conductivity with the aforementioned sheet-like carbon-based conductive agent, the conductive agent further includes dot-like and / or linear conductive agents. Optionally, the dot-like conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, or carbon dots; optionally, the linear conductive agent includes carbon nanotubes and / or carbon nanofibers. The dot-like and linear conductive agents are interspersed in the small pores between the silicon-based materials, forming a richer conductive network in conjunction with the sheet-like carbon-based conductive agent, further improving conductivity.

[0074] The carbon-based material used in the negative electrode active material of this application may be selected from conventional carbon-based materials used in negative electrode active materials. In some embodiments, the carbon-based material includes any one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0075] The silicon-based material used in the negative electrode active material of this application can be selected from conventional silicon-based materials used in negative electrode active materials. In some embodiments, the silicon-based material includes one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys. Optionally, the silicon-based material is a silicon-carbon composite. This silicon-carbon composite typically uses porous carbon as a substrate. Compared to elemental silicon, silicon oxide, and other silicon-based active materials, under the same capacity design, the silicon-carbon composite exhibits lower volume change rebound in a fully charged state and a longer cycle life.

[0076] In some embodiments, the silicon content in the negative electrode film is 30%-55% by mass. This is to increase the specific capacity of the negative electrode film and improve the energy density of the battery cell by adding silicon.

[0077] The method for testing the silicon content is as follows: The silicon content in the negative electrode film is tested by alkaline fusion-inductively coupled plasma atomic emission spectrometry. The negative electrode sheet is taken, and the powder of the negative electrode film is collected through a scraping process. After grinding, mixing with KOH crystals, high-temperature melting, hot water dissolution, volume adjustment, and dilution, the powder is then tested using an ICP-OES instrument.

[0078] When the negative electrode film is multilayered, the area ratio of the aforementioned sheet-like carbon-based conductive agent to the silicon-based material, which is 4%-20%, refers to the area ratio of the two in a cross-sectional region of the negative electrode film layer that simultaneously contains both silicon-based material and sheet-like conductive agent. Of course, when the negative electrode film is single-layered, the aforementioned area ratio of the aforementioned sheet-like carbon-based conductive agent to the silicon-based material, which is 4%-20%, refers to the area ratio of the two in any cross-sectional region of the entire negative electrode film layer.

[0079] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on one side of the negative electrode current collector, and the second negative electrode film layer is disposed on the side of the first negative electrode film layer away from the negative electrode current collector. The first negative electrode film layer and the second negative electrode film layer are each independently disposed with silicon-based material.

[0080] Silicon exhibits high expansion properties, while carbon-based materials are relatively soft. If silicon is directly distributed within carbon-based materials, its expansion during continuous charge-discharge cycles will compress the carbon-based materials, leading to a deterioration in lithium intercalation kinetics and capacity loss. However, by layering carbon-based and silicon-based materials in a multilayer coating manner, with flexible adjustments to the ratio of the two materials in different film layers, the direct contact area between the silicon and carbon-based materials can be effectively controlled, improving the cycle life of the carbon-rich film. Simultaneously, a stable conductive network can be constructed within the silicon-rich film using sheet-like carbon-based conductive agents. For example, under the guidance of this application, those skilled in the art can incorporate more sheet-like carbon-based conductive agents in film layers with higher silicon content, thereby more effectively preventing the silicon-based material from detaching from the conductive network during cycling and improving the stable cycling of the silicon-rich film.

[0081] In some examples, the mass content of silicon-based material in the first negative electrode film is greater than that in the second negative electrode film. The area ratio of the sheet-like carbon-based conductive agent to the silicon-based material in the cross-sectional region of the first negative electrode film is a1, and the area ratio of the sheet-like carbon-based conductive agent to the silicon-based material in the cross-sectional region of the second negative electrode film is a2, where a1 > a2. Alternatively, in some examples, the mass content of silicon-based material in the first negative electrode film is less than that in the second negative electrode film. The area ratio of the sheet-like carbon-based conductive agent to the silicon-based material in the cross-sectional region of the first negative electrode film is a1, and the area ratio of the sheet-like carbon-based conductive agent to the silicon-based material in the cross-sectional region of the second negative electrode film is a2, where a1 < a2.

[0082] In some embodiments, the first negative electrode film layer and the second negative electrode film layer each independently include a binder, the mass content of silicon-based material in the first negative electrode film layer is greater than the mass content of the second negative electrode film layer, optionally the mass content of the binder in the first negative electrode film layer is greater than or equal to the mass content of the binder in the second negative electrode film layer, and / or the mass content of the binder in the first negative electrode film layer is 5%-10%.

[0083] When silicon-based materials are mainly distributed in the lower first negative electrode film layer, due to the high specific capacity of silicon-based materials, the binder content of the first negative electrode film layer can be increased while maintaining high energy density. The increase in binder content can significantly improve the adhesion of the negative electrode film layer to the negative electrode current collector and reduce the risk of cyclic delamination.

[0084] As an example, 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).

[0085] In the above embodiments, the first negative electrode film layer can be a film layer that uses only silicon-based materials as negative electrode active materials, and the second negative electrode film layer can be a film layer that uses only carbon-based materials as negative electrode materials.

[0086] In some embodiments, the mass content of silicon-based material in the second negative electrode film is greater than that in the first negative electrode film, and the thickness ratio of the first negative electrode film to the second negative electrode film is (1:4)-(4:1), optionally (6:5)-(1:1). When the silicon-based material is mainly distributed in the surface of the second film, due to the harder silicon-based material particles, it is less likely to be compacted under the same pressure compared to the first negative electrode film rich in carbon-based material. This allows for the formation of a larger porosity in the upper layer, resulting in a structure in the thickness direction where the upper layer has high porosity and the lower layer has low porosity. This is beneficial for the diffusion and migration of active ions. Without sacrificing energy density, the kinetic performance of the battery cell can still be improved by controlling the above thickness ratio.

[0087] In the above embodiments, the second negative electrode film layer can be a film layer that uses only silicon-based materials as negative electrode active materials, and the first negative electrode film layer can be a film layer that uses only carbon-based materials as negative electrode materials.

[0088] The second embodiment of this application provides a method for manufacturing any of the battery cells provided in the first embodiment above. The manufacturing method includes a process for manufacturing a negative electrode sheet. The manufacturing process includes: mixing a negative electrode active material, a conductive agent and a solvent to form a negative electrode slurry, wherein the negative electrode active material includes a carbon-based material and a silicon-based material, and the conductive agent includes a sheet-like carbon-based conductive agent; and then pressing and drying the negative electrode slurry onto a negative electrode current collector to obtain a negative electrode sheet.

[0089] When a flake-shaped carbon-based conductive agent is used as the conductive agent for the negative electrode, the negative electrode slurry containing the flake-shaped carbon-based conductive agent has high stability and is not easy to gel, thus providing a longer working time for the processing of the negative electrode sheet.

[0090] Of course, if the negative electrode film layer of the prepared negative electrode sheet is multi-layered, the corresponding negative electrode slurry can be prepared according to the film layer layout requirements, and then layered coating can be performed. The specific operation of layered coating is based on the conventional layered coating operation method, and will not be described in detail in this application.

[0091] In some embodiments, the viscosity of the negative electrode slurry with a solid content of 30% to 40% is 8000 mPa·s to 12000 mPa·s at 25°C and 60 rpm.

[0092] In order to form a more uniform coating of silicon-based material by the sheet-like carbon-based conductive agent, in some embodiments, the manufacturing process includes coating the surface of the silicon-based material with the sheet-like carbon-based conductive agent before forming the negative electrode slurry. Optionally, the sheet-like carbon-based conductive agent is coated on the surface of the silicon-based material by spray drying.

[0093] In some embodiments, the mass of the silicon-based material accounts for 65%-90% of the total mass of the silicon-based material, carbon-based material, and conductive agent. In some embodiments, the mass of the sheet-like carbon-based conductive agent accounts for 3%-10% of the total mass of the silicon-based material, carbon-based material, and conductive agent.

[0094] As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0095] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0096] [Positive electrode plate]

[0097] A positive electrode typically 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.

[0098] 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.

[0099] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer 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.).

[0100] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, when the secondary battery is a lithium-ion secondary battery, 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 battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0101] When the secondary battery is a sodium-ion secondary battery, as an example, the positive electrode active material of the sodium-ion secondary battery may include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0102] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0103] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0104] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0105] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0106] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni), and Na3(VO4) y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0107] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0108] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0109] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0111] [Electrolytes]

[0112] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0113] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0114] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0115] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0116] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0117] In some embodiments, the gel electrolyte comprises a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0118] In some embodiments, the solid electrolyte includes polymer solid electrolyte, inorganic solid electrolyte, and composite solid electrolyte.

[0119] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0120] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0121] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0122] [Isolation Component]

[0123] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0124] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0125] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. 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. The separator can be a single component located between the positive and negative electrodes, or it can 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 can also be applied to the surface of the separator.

[0126] 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 isolate the positive and negative electrodes. In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0127] [Electrode Assembly]

[0128] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0129] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0130] In some implementations, the electrode assembly is a stacked structure.

[0131] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0132] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0133] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0134] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0135] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0136] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0137] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0138] [shell]

[0139] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0140] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0141] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0142] For example, Figure 4 shows a square-structured battery cell 5 as an example.

[0143] In some embodiments, referring to FIG5, the outer packaging may include a housing 51 and an end cap 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the end cap 53 can be closed by covering the opening to seal the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator membrane can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0144] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0145] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0146] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0147] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0148] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0149] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0150] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0151] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0152] [Battery Device]

[0153] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0154] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0155] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0156] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0157] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0158] Figure 6 shows a battery module 4 as an example. Referring to Figure 6, in the battery module 4, multiple secondary battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary battery cells 5 can be fixed in place using fasteners.

[0159] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0160] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0161] Figures 7 and 8 show a battery pack 1 as an example. Referring to Figures 7 and 8, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0162] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0163] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0164] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0165] 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.

[0166] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0167] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for 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.

[0168] As the electrical device, a single secondary battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0169] Figure 9 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0170] [Example]

[0171] 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.

[0172] Example 1

[0173] The manufacturing process of negative electrode sheets

[0174] Silicon-carbon composite particles (silicon content of 50%), sheet graphite conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) are dispersed in deionized water at a mass ratio of 80:10:4:1:5 and stirred into a homogenous slurry. The slurry is then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0175] Positive electrode sheet

[0176] LiNi, a positive electrode active material, is a lithium nickel cobalt manganese oxide (LiNi). 0.9 Co 0.05 Mn 0.05 O2, polyvinylidene fluoride (PVDF) binder, and conductive carbon black (Super P) conductive agent are mixed uniformly in N-methylpyrrolidone (NMP) solvent at a mass ratio of 96%:2%:2% to prepare a positive electrode slurry. The positive electrode slurry is coated onto the surface of aluminum foil and dried, followed by cold pressing to obtain the positive electrode sheet.

[0177] Separating membrane

[0178] Polyethylene film (PE diaphragm) is used as the separation membrane.

[0179] electrolyte

[0180] Ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. The fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0181] Assembly:

[0182] The positive electrode, separator, and negative electrode are wound or stacked in sequence to obtain an electrode assembly. The electrode assembly is placed in a packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion secondary battery is obtained.

[0183] Testing of sheet-like graphite conductive materials:

[0184] Average diameter test: The negative electrode sheet was subjected to SEM testing to measure the diameter of the flake-shaped graphite conductive agent in the field of view. When the cross-sectional shape of the flake-shaped carbon-based conductive agent in the field of view is a regular circle, the diameter of the flake-shaped graphite conductive agent is the diameter of that circle; when the cross-sectional shape of the flake-shaped graphite conductive agent is an irregular circle, the diameter of the flake-shaped graphite conductive agent is the equivalent diameter of a regular circle with the same area as the irregular circle. The SEM image of the ion-polished cross-section of the negative electrode sheet of Example 1 is recorded in Figure 1.

[0185] Thickness test: The negative electrode sheet was ion polished and then subjected to SEM under backscattering conditions to measure the thickness of the sheet graphite conductive agent in the field of view. When the thickness of a sheet graphite conductive agent is not uniform, the thickness is the average thickness of the sheet graphite conductive agent (for example, 10 points are randomly selected along the length of the sheet carbon-based conductive agent, the thickness at these 10 points is measured, and the average value is taken).

[0186] Powder resistivity testing: The test is mainly conducted using the four-probe method. A certain mass of flake graphite conductive agent is weighed, the depth of the feeding chamber is adjusted, the flake graphite conductive agent is added into the feeding chamber, and a pressure of 12 MPa is applied. Data is collected manually, and the powder resistivity test results are recorded.

[0187] Viscosity test: The viscosity of the slurry was tested at 25°C and 60 rpm.

[0188] Area ratio test of flake graphite conductive agent to silicon-based material: The negative electrode sheet was ion polished and SEM was performed under backscattering conditions. ImageJ software was used to distinguish the flake graphite conductive agent and silicon-based material and calculate the cross-sectional area to obtain the area ratio of the flake graphite conductive agent to the silicon-based material (the area ratio is shown in the table).

[0189] The method for testing the silicon content: The silicon content in the negative electrode film layer containing both sheet-like carbon-based conductive agent and silicon-based material is tested using alkaline fusion-inductively coupled plasma atomic emission spectrometry (ICP-OES). The negative electrode sheet is taken, and the powder of the negative electrode film layer is collected through a scraping process. After grinding, mixing with KOH crystals, high-temperature melting, hot water dissolution, volume adjustment, and dilution, the silicon content is analyzed using an ICP-OES device. The test results are basically consistent with the theoretical calculation results, at approximately 40%.

[0190] Negative electrode resistance test: Cut the rolled negative electrode into 5cm×10cm pieces and place them between the two electrodes of the film resistance meter. Set the pressure (25MPa) and holding time (25s) through the control software and start the test. The corresponding film resistance value is automatically read and the average resistance of 10 random points is taken as the electrode film resistance.

[0191] Cyclic performance test: At 25°C, the secondary batteries prepared in each embodiment and comparative example were charged at a constant current rate of 0.33C to the charging cutoff voltage of 4.25V, then charged at a constant voltage rate to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.5C to the discharge cutoff voltage of 2.5V, allowed to stand for 5 minutes. This constitutes one charge-discharge cycle. The capacity of the first discharge process is recorded as C1. The batteries were then subjected to cyclic charge-discharge tests in this manner until the capacity of the nth discharge process reached 0.8C1, at which point the cycle was terminated, and the number of cycles at this point was recorded as the cycle life of the battery at 25°C.

[0192] The test results are recorded in Table 1.

[0193] Examples 2 to 8 use sheet-like graphite conductive materials 2 to 8 to replace the sheet-like graphite conductive material 1 in Example 1, and the rest are the same as in Example 1.

[0194] Example 9

[0195] Multilayer graphene was used to replace the sheet-like graphite conductive material 1 in Example 1, while the rest remained the same as in Example 1. Tests were conducted using the methods described above, and the results are recorded in Table 1.

[0196] Comparative Example 1

[0197] Based on Example 1, the silicon-carbon composite particles (silicon content 50% by mass), graphite, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 80:10:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1. The ion-polished cross-section SEM image of the negative electrode sheet of Comparative Example 1 is recorded in Figure 2.

[0198] The above testing method was used for the test, and the test results are recorded in Table 1.

[0199] Table 1

[0200] A comparison of the data in Table 1 shows that the use of flake graphite conductive agent in the embodiment reduced the resistance of the negative electrode sheet and significantly improved the cycle performance of the battery cell.

[0201] The average diameter and thickness of the flake graphite conductive agents in Examples 1 to 5 gradually increased, meaning the particle size gradually increased. With the increase in particle size, the resistivity of the flake graphite conductive agent gradually increased, as did the resistance of the negative electrode sheet. This indicates that controlling the aforementioned dimensional characteristics of the flake carbon-based conductive agent is beneficial for adjusting the powder resistivity and thus selecting a flake conductive agent with better conductivity. Simultaneously, with the increase in particle size, the viscosity of the negative electrode slurry gradually decreased, indicating that its stability in the negative electrode slurry increased with increasing particle size. Furthermore, a comparison of the data from each example reveals that when the thickness of the flake graphite conductive agent is too large and the aspect ratio is too small (Example 6) or the aspect ratio is too large (Example 8), it affects the improvement of the cycle performance of the battery cell.

[0202] The following examines the effect of flake graphite conductive agent 1 on improving the cycle life and negative electrode resistance of battery cells with different silicon contents.

[0203] Example 10

[0204] Based on Example 1, the silicon-carbon composite particles (silicon content 50% by mass), graphite, sheet conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 80:5:5:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0205] Example 11

[0206] Based on Example 1, the following steps were performed: silicon, graphite, sheet conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 80:5:5:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The rest of the process was the same as in Example 1.

[0207] Example 12

[0208] Based on Example 1, the following steps were performed: silicon, sheet-like conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 80:10:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0209] Example 13

[0210] Based on Example 1, the silicon-carbon composite particles (silicon content 50% by mass), graphite, sheet conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 60:20:10:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0211] Example 14

[0212] Based on Example 1, the silicon-carbon composite particles (silicon content 50% by mass), graphite, sheet conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 60:25:5:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0213] Comparative Example 2

[0214] Based on Example 1, the silicon-carbon composite particles (silicon content 50% by mass), graphite, molybdenum disulfide agglomerated particles (prepared according to the preparation method of Example 1 in patent application CN117374221A), Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 80:5:5:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0215] Comparative Example 3

[0216] Based on Example 1, the silicon-carbon composite particles (silicon content 50% by mass), graphite, sheet conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 35:50:5:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0217] Comparative Example 4

[0218] Based on Example 1, the silicon-carbon composite particles (silicon content 50% by mass), graphite, sheet conductive material 1, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 35:45:10:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0219] Comparative Example 5

[0220] Based on Example 1, the silicon-carbon composite particles (silicon content of 50%), graphite, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 35:55:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0221] Comparative Example 6

[0222] Based on Example 1, the following steps were performed: elemental silicon, graphite, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 80:10:4:1:5 and stirred until homogenized. The mixture was then coated onto the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0223] Comparative Example 7

[0224] Based on Example 1, the silicon-carbon composite particles (silicon content of 50%), graphite, Super P carbon black, dispersant (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 60:30:4:1:5 and stirred into a homogenous slurry. This slurry was then coated onto the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain the negative electrode sheet. The rest was the same as in Example 1.

[0225] The test results are recorded in Table 2.

[0226] Table 2

[0227] The data comparison in Table 2 shows that when the silicon content in the negative electrode film of Comparative Examples 3 to 5 is less than 30%, the addition of flake-shaped carbon-based conductive agents can reduce the slurry viscosity, but it does not improve the cycle performance of the battery cells. When the silicon content in the negative electrode film is above 30%, the flake-shaped carbon-based conductive agents can reduce the slurry viscosity, reduce the negative electrode resistance, and improve the cycle performance of the battery cells.

[0228] In the following embodiments, the negative electrode sheet of the battery cell has a double negative electrode film layer, and the rest of the structure is the same as in Example 1. The following only describes the preparation process of the negative electrode sheet.

[0229] Example 15

[0230] Negative electrode graphite layer slurry: Active material graphite, conductive agent Super P carbon black, dispersant sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 80:14:1:5 to form a uniform negative electrode slurry A.

[0231] Silicon layer slurry: Silicon-carbon composite particles (silicon content of 50% by mass), sheet graphite conductive material 1, Super P carbon black, dispersant sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 80:10:4:1:5 to form a uniform negative electrode slurry B.

[0232] Coating: Negative electrode paste A and negative electrode paste B are sequentially coated onto the current collector copper foil using LOM coating. The coating weight of negative electrode paste A is 3 mg / cm³. 2 The coating weight of negative electrode slurry B is 3.2 mg / cm³. 2 After drying and cold pressing, a negative electrode sheet is obtained. The thickness of the lower negative electrode film layer formed by negative electrode slurry A is 28 μm, and the thickness of the lower negative electrode film layer formed by negative electrode slurry B is 25 μm.

[0233] Example 16

[0234] Negative electrode paste A and negative electrode paste B were sequentially coated onto the current collector copper foil using a LOM coating method. The coating weight of negative electrode paste A was 4.0 mg / cm³. 2 The coating density of negative electrode slurry B is 3.2 mg / cm³. 2 After drying and cold pressing, a negative electrode sheet is obtained. The thickness of the lower negative electrode film layer formed by negative electrode slurry A is 30 μm, and the thickness of the lower negative electrode film layer formed by negative electrode slurry B is 25 μm. The SEM image of the ion-polished cross-section of the negative electrode sheet of Example 16 is recorded in Figure 3.

[0235] Example 17

[0236] Negative electrode paste A and negative electrode paste B were sequentially coated onto the current collector copper foil using a LOM (Laminated Object Manufacturing) coating method. The coating density of negative electrode paste A was 4.0 mg / cm³. 2 The coating weight of negative electrode slurry B is 3.8 mg / cm³. 2 After drying and cold pressing, a negative electrode sheet is obtained. The thickness of the lower negative electrode film layer formed by negative electrode slurry A is 30 μm, and the thickness of the lower negative electrode film layer formed by negative electrode slurry B is 30 μm.

[0237] Example 18

[0238] Negative electrode paste B and negative electrode paste A were sequentially coated onto the current collector copper foil using a LOM coating method. After drying and cold pressing, the negative electrode sheet was obtained. The coating weight of negative electrode paste B was 3.8 mg / cm³. 2 The coating density of negative electrode slurry A is 4.0 mg / cm³. 2 After drying and cold pressing, a negative electrode sheet is obtained, with a thickness of 30 μm corresponding to the lower negative electrode film layer formed by negative electrode slurry B and the thickness of the lower negative electrode film layer formed by negative electrode slurry A.

[0239] Example 19

[0240] Silicon layer slurry: Silicon-carbon composite particles (silicon content of 50% by mass), sheet graphite conductive material 1, Super P carbon black, dispersant sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 75:10:4:1:10 to form a uniform negative electrode slurry C.

[0241] Negative electrode paste C and negative electrode paste A were sequentially coated onto the current collector copper foil using a LOM coating method. After drying and cold pressing, the negative electrode sheet was obtained. The coating weight of negative electrode paste C was 3.8 mg / cm³. 2 The coating weight of negative electrode slurry A is 4.0 mg / cm³. 2 After drying and cold pressing, a negative electrode sheet is obtained, with a thickness of 30 μm corresponding to the lower negative electrode film layer formed by negative electrode slurry C and the thickness of the lower negative electrode film layer formed by negative electrode slurry A.

[0242] Comparative Example 8

[0243] Silicon layer slurry: Silicon-carbon composite particles (silicon content of 50% by mass), graphite, Super P carbon black, dispersant sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 80:10:4:1:5 to form a uniform negative electrode slurry D.

[0244] Negative electrode paste A and negative electrode paste D were sequentially coated onto the current collector copper foil using LOM coating. After drying and cold pressing, the negative electrode sheet was obtained. The coating weight of negative electrode paste A was 3.8 mg / cm³. 2 The coating density of negative electrode slurry D is 3.2 mg / cm³. 2 After drying and cold pressing, the negative electrode sheet is obtained. The thickness of the lower negative electrode film layer formed corresponding to negative electrode slurry A is 28 μm, and the thickness of the lower negative electrode film layer formed corresponding to negative electrode slurry D is 25 μm.

[0245] Comparative Example 9

[0246] Negative electrode paste D and negative electrode paste A were sequentially coated onto the current collector copper foil using a LOM coating method. After drying and cold pressing, the negative electrode sheet was obtained. The coating weight of negative electrode paste D was 3.2 mg / cm³. 2 The coating weight of negative electrode slurry A is 3.8 mg / cm³. 2 After drying and cold pressing, a negative electrode sheet is obtained. The thickness of the lower negative electrode film layer formed by the negative electrode slurry D is 25 μm, and the thickness of the lower negative electrode film layer formed by the negative electrode slurry A is 28 μm.

[0247] The negative electrode resistance and cycle life of the battery cells were tested using the above test methods, and the results are recorded in Table 3.

[0248] In addition, the energy density and kinetic performance of Examples 15 to 19 were tested. First, the weight of the secondary battery was weighed and recorded as M0 using a balance. Then, at 25°C, the secondary batteries prepared in each example and comparative example were charged at a constant current rate of 0.33C to the charging cutoff voltage of 4.25V, then charged at a constant voltage to a current of 0.05C, and allowed to stand for 5 minutes. Then, they were discharged at a constant current rate of 0.33C to a discharge cutoff voltage of 2.5V, and allowed to stand for 5 minutes. The energy of the first discharge process was recorded as E0, and the discharge capacity as C0. Then, the batteries were charged at a constant current rate of 0.33C to the cutoff voltage of 4.25V, then charged at a constant voltage to a current of 0.05C, and allowed to stand for 5 minutes. Then, they were discharged at a constant current rate of 2C to the cutoff voltage of 2.5V, and allowed to stand for 5 minutes. The discharge capacity of this discharge process was recorded as C1. The energy density of the battery cell was E0 / M0, and the rate performance was C1 / C0. The test results are recorded in Table 3.

[0249] Table 3

[0250] Based on the data comparison between Example 15 and Comparative Example 8 in Table 3, and the data comparison between Example 16, Example 17 and Comparative Example 9, it can be seen that when the negative electrode sheet has a double negative electrode film layer, adding flake graphite conductive agent to the corresponding film layer containing silicon-carbon composite particles can also reduce the resistance of the negative electrode sheet and improve the cycle performance of the battery cell.

[0251] Furthermore, a comparison of the data from Examples 15 to 17 shows that distributing the thickness of the upper film layer containing silicon-carbon composite particles to the thickness of the lower film layer without silicon-carbon composite particles can improve the dynamic performance of the battery cell without reducing the energy density.

[0252] A comparison of Examples 18 and 19 shows that when a film containing silicon-carbon composite particles is placed in the lower layer, due to the high specific capacity advantage of silicon, even though more binder is used in the lower film layer of Example 19, the energy density of the battery cells in the two examples is basically the same. However, the cycle performance of Example 19 is better than that of Example 18.

[0253] 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, comprising an electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, the negative electrode including a negative current collector and a negative electrode film, the negative electrode film being disposed on at least one side of the negative current collector, the negative electrode film including a negative electrode active material and a conductive agent, the negative electrode active material including a carbon-based material and a silicon-based material, the conductive agent including a sheet-like carbon-based conductive agent, the negative electrode film being a single layer or multiple layers, and the silicon content in the negative electrode film having the sheet-like carbon-based conductive agent and the silicon-based material being 30%-80% by mass.

2. The battery cell according to claim 1, wherein, The average diameter of the sheet-like carbon-based conductive agent is 0.5μm-10μm, and can be selected as 0.6μm-7μm.

3. The battery cell according to claim 1 or 2, wherein, The average thickness of the sheet-like carbon-based conductive agent is 0.1 μm-5 μm, optionally 0.2 μm-2 μm; optionally, the ratio of the average thickness to the average diameter of the sheet-like carbon-based conductive agent is 1 / 30-1 / 3.

4. The battery cell according to any one of claims 1 to 3, wherein, The powder resistivity of the flake-shaped carbon-based conductive agent at a pressure of 12 MPa is 1 mΩ·cm-15 mΩ·cm.

5. The battery cell according to any one of claims 1 to 4, wherein, The sheet-like carbon-based conductive agent includes any one or more of sheet-like graphite and sheet-like graphene.

6. The battery cell according to any one of claims 1 to 5, wherein, In the cross-sectional region along the thickness direction of the negative electrode sheet in which the silicon-based material is present, the area of ​​the sheet-like carbon-based conductive agent is in the ratio of 4% to 20% of the area of ​​the silicon-based material.

7. The battery cell according to any one of claims 1 to 6, wherein, The conductive agent further includes dot-shaped conductive agents and / or linear conductive agents. Optionally, the dotted conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, or carbon dots; Optionally, the linear conductive agent includes carbon nanotubes and / or carbon nanofibers.

8. The battery cell according to any one of claims 1 to 7, wherein, The carbon-based material includes any one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

9. The battery cell according to any one of claims 1 to 8, wherein, The silicon-based material includes one or more of elemental silicon, silicon oxides, silicon-carbon composites, and silicon alloys.

10. The battery cell according to any one of claims 1 to 9, wherein, The silicon content in the negative electrode film is 30%-55% by mass.

11. The battery cell according to claim 10, wherein, The negative electrode film is multilayered, and at least a portion of the sheet-like carbon-based conductive agent and the silicon-based material are disposed in the same negative electrode film.

12. The battery cell according to claim 11, wherein, The negative electrode film layer includes: The first negative electrode film layer is disposed on one side of the negative electrode current collector; The second negative electrode film layer is disposed on the side of the first negative electrode film layer away from the negative electrode current collector. The silicon-based material is independently disposed in both the first negative electrode film layer and the second negative electrode film layer.

13. The battery cell according to claim 12, wherein, The first negative electrode film layer and the second negative electrode film layer each independently include a binder. The mass content of the silicon-based material in the first negative electrode film layer is greater than that in the second negative electrode film layer. Optionally, the mass content of the binder in the first negative electrode film layer is greater than or equal to the mass content of the binder in the second negative electrode film layer, and / or the mass content of the binder in the first negative electrode film layer is 5%-10%.

14. The battery cell according to claim 12, wherein, The mass content of the silicon-based material in the second negative electrode film is greater than that in the first negative electrode film. The thickness ratio of the first negative electrode film to the second negative electrode film is (1:4)-(4:1), and can be selected as (6:5)-(1:1).

15. A method for manufacturing a battery cell according to any one of claims 1 to 14, the method comprising a process for manufacturing a negative electrode sheet, the process comprising: A negative electrode slurry is formed by mixing a negative electrode active material, a conductive agent, and a solvent. The negative electrode active material includes carbon-based materials and silicon-based materials, and the conductive agent includes a sheet-like carbon-based conductive agent. The negative electrode slurry is placed on the negative electrode current collector and then pressed and dried to obtain the negative electrode sheet.

16. The manufacturing method according to claim 15, wherein, The viscosity of the negative electrode slurry with a solid content of 30% to 40% is 8000 mPa·s to 12000 mPa·s at 25°C and 60 rpm.

17. The manufacturing method according to claim 15 or 16, wherein, Before forming the negative electrode slurry, the manufacturing process also includes coating the surface of the silicon-based material with the sheet-like carbon-based conductive agent, optionally by spray drying.

18. A battery device comprising a plurality of battery cells, wherein, The battery cell includes any one of claims 1 to 14.

19. An electrical device comprising a battery cell according to any one of claims 1 to 14 or a battery device according to claim 18, wherein the battery cell or the battery device is used to store or provide electrical energy.

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