Battery cell, method for manufacturing the same, battery device, energy storage device, power consumption device

Abstract

The application discloses a battery monomer, a preparation method thereof, a battery device, an energy storage device and a power utilization device. A negative electrode current collector of a negative electrode sheet of the battery monomer is provided with a through hole, and at least one negative electrode active layer extends into the through hole while being laminated on at least one surface of the negative electrode current collector. The through hole of the battery monomer can construct an electrolyte infiltration channel in an electrode assembly, so that the electrolyte can directly and rapidly infiltrate into the interior of the electrode assembly through the first through hole, the electrolyte infiltration path is shortened, the stress in the interior of the electrode assembly in the battery monomer, especially the stress in the inner ring, can be reduced, and the electrolyte infiltration efficiency of the electrode assembly in the battery monomer is effectively improved. The battery device, the energy storage device and the power utilization device contain the battery monomer.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a battery cell and its preparation method, a battery device, an energy storage device, and an electrical device. Background Technology

[0002] To improve battery energy density, current industry practices commonly employ methods such as increasing electrode area and enlarging cell size. Increasing electrode area means more active material can be arranged within a limited space, thus increasing battery capacity. Conversely, increasing cell size helps reduce the number of connecting components and casing material in the battery pack, further improving overall energy density.

[0003] However, these methods also bring new problems. For example, increasing the electrode areal density and the size of the battery cell can lead to a decrease in electrolyte wetting effect, especially in cylindrical batteries. The electrolyte is the medium for ion transport inside the battery, and its wetting effect directly affects the battery's capacity and cycle performance. If the electrolyte cannot fully wet the active materials on the electrode surface and inside, it will lead to a loss of battery capacity and a decrease in cycle performance. Summary of the Invention

[0004] In view of the above problems, this application provides a battery cell and a battery device, energy storage device, and power consumption device containing the battery cell, so as to solve the technical problems of capacity loss and cycle performance degradation caused by unsatisfactory electrolyte wettability in existing battery cells.

[0005] In a first aspect, embodiments of this application provide a single battery cell. The battery cell of this application includes a negative electrode sheet, which includes a negative electrode current collector. The negative electrode current collector has two opposing surfaces, and a negative electrode active material layer is stacked on at least one of the surfaces. The negative electrode current collector has multiple first through-holes penetrating the two surfaces, and at least one of the negative electrode active material layers extends into the first through-hole.

[0006] In this embodiment, the battery cell utilizes a first through-hole formed in the negative electrode current collector within the negative electrode sheet. This creates an electrolyte wetting channel within the electrode assembly, allowing the electrolyte to rapidly penetrate the assembly directly through these through-holes. This shortens the wetting path and effectively improves the electrolyte wetting efficiency. Simultaneously, the presence of the first through-hole increases the overall porosity of the negative electrode sheet, providing a buffer space for volume expansion during charging and discharging. This reduces internal stress, particularly in the inner ring, further facilitating electrolyte wetting and enhancing the structural stability of the electrode assembly. Therefore, the electrolyte wetting efficiency of the battery cell in this embodiment is significantly improved, effectively enhancing the battery cell's capacity utilization and cycle performance.

[0007] In some embodiments, a first negative electrode active material layer is disposed on one surface of the negative electrode current collector, and a second negative electrode active material layer is disposed on the other surface; wherein, the first negative electrode active material layer extends into the first through hole, and the first through hole extends into the second negative electrode active material layer.

[0008] In this embodiment, the first through hole extends into and penetrates the second negative electrode active material layer.

[0009] Extending the first through hole into the second negative electrode active material layer can further reduce the stress in the inner ring of the electrode assembly and accelerate the rate at which the electrolyte penetrates into the electrode assembly.

[0010] In this embodiment, the first negative electrode active material layer extends into the first through-hole and at least partially fills the first through-hole in the second negative electrode active material layer. Thus, the first negative electrode active material layer extending into and filling the first through-hole is in direct contact with the second negative electrode active material layer. The first and second negative electrode active material layers are connected as a single unit through multiple first through-holes, making the negative electrode active material layer extending into and filling the multiple first through-holes a medium for electrolyte wetting and migration. This can further improve the electrolyte wetting rate and the efficiency of electrolyte migration into the electrode assembly, especially the inner ring of cylindrical electrode assemblies, thereby improving the capacity utilization and cycle performance of the battery cell. Simultaneously, increasing the proportion of negative electrode active material in the negative electrode sheet can increase the capacity of the negative electrode sheet, thereby increasing the energy density of the battery cell.

[0011] In some embodiments, the first through hole includes at least one of the following (1) to (4):

[0012] (1) In the unit area of ​​the surface of the negative electrode current collector, the total cross-sectional area of ​​the first through hole accounts for 0.1% to 25% along the direction parallel to the surface;

[0013] (2) Along the length direction of the negative electrode current collector, the distance between two adjacent first through holes is 1mm to 100mm;

[0014] (3) Along the width direction of the negative electrode current collector, the distance between two adjacent first through holes is 1mm to 20mm;

[0015] (4) Along the surface direction parallel to the negative electrode current collector, the cross-sectional area of ​​a single first through hole is 0.2 mm. 2 ~3.2mm 2 .

[0016] Distributing the first through holes at the aforementioned spacing on the surface of the negative electrode current collector and controlling the cross-sectional area of ​​each first through hole within the aforementioned range can further increase the number of channels for electrolyte to wet the electrode assembly, adjust the overall porosity of the negative electrode sheet, and provide buffer space for the volume expansion of the electrode assembly during charging and discharging, thereby alleviating the stress inside the electrode assembly, especially the stress in the inner ring, thus improving the efficiency of electrolyte wetting into the electrode assembly, and further enhancing the capacity utilization and cycle performance of the battery cell.

[0017] In some embodiments, the negative electrode active material in the negative electrode active material layer includes a silicon-based material, and the silicon-based material accounts for 1% to 50% of the total mass of the negative electrode active material; and in the unit area of ​​the surface of the negative electrode current collector, the total cross-sectional area of ​​the first through hole accounts for 0.1% to 10% along the direction parallel to the surface.

[0018] In this embodiment, the silicon-based material accounts for 1% to 10% of the total mass of the negative electrode active material, and the total cross-sectional area of ​​the first through hole accounts for 0.1% to 2%.

[0019] In this embodiment, the silicon-based material accounts for 10% to 25% of the total mass of the negative electrode active material, and the total cross-sectional area of ​​the first through hole accounts for 2% to 5%.

[0020] In this embodiment, the silicon-based material accounts for 25% to 50% of the total mass of the negative electrode active material, and the total cross-sectional area of ​​the first through hole accounts for 5% to 10%.

[0021] Adding silicon-based materials within this range to the negative electrode active material can effectively improve the specific capacity of the battery cell compared to traditional carbon-based materials, thereby increasing the energy density of the battery cell. Simultaneously, controlling the distribution of the first through-hole on the surface of the negative electrode current collector within the aforementioned range allows the negative electrode sheet to have an appropriate total porosity, providing a suitable buffer space for the volume expansion of the silicon-based material during charging and discharging. This effectively alleviates the stress generated inside the electrode assembly, especially the inner ring, during charging and discharging, while also improving the electrolyte wetting path. By improving the electrolyte wetting efficiency inside the electrode assembly, especially the inner ring, the structural stability of the electrode assembly can be enhanced, thereby improving the battery cell's capacity utilization, energy density, and cycle performance.

[0022] In the embodiments, the silicon-based material includes one of elemental silicon, silicon-carbon composite materials, silicon-oxygen composite materials, and silicon-based alloy materials. These silicon-based materials have high specific capacity.

[0023] In this embodiment, the negative electrode active material further includes a carbon-based material, which is mixed and distributed with the silicon-based material in the negative electrode active material layer, and the carbon-based material accounts for 1% to 50% of the total mass of the negative electrode active material. Using a mixture of carbon-based and silicon-based materials as the negative electrode active material can effectively alleviate the volume expansion of the battery assembly during charging and discharging, thereby reducing the internal stress of the electrode assembly and improving the electrolyte wetting efficiency of the electrode assembly, while improving the specific capacity of the negative electrode sheet.

[0024] In the example, the carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fiber. These carbon-based materials possess relatively high specific capacity, good conductivity, and interfacial stability with the electrolyte.

[0025] In some embodiments, the negative electrode active material layer is provided with a porous structure, and the porosity of the negative electrode active material layer is 10% to 40%.

[0026] In some embodiments, the negative electrode active material layer is provided with a porous structure, and the pore size of the negative electrode active material layer is 0.2μm to 2μm.

[0027] By controlling the porosity and pore size of the negative electrode active material layer within the aforementioned range, it is possible to further improve the wettability of the electrolyte into the electrode assembly, and increase the electrolyte wetting rate inside the electrode assembly, especially the inner ring, in conjunction with the first through hole opened by the negative electrode current collector mentioned above.

[0028] In some embodiments, the dry basis weight of the negative electrode active material layer on one surface of the negative electrode sheet is 1.4–1.8 g / 1540.25 mm. 2By controlling the coating amount of the negative electrode active material layer on one side within a certain range, the specific capacity of the negative electrode sheet can be appropriately increased while effectively improving the electrolyte wetting efficiency inside the electrode assembly.

[0029] In some embodiments, the positive current collector in the positive electrode sheet has two opposing surfaces, and the positive current collector has multiple second through holes penetrating the two surfaces. A positive active material layer is stacked on at least one of the surfaces of the positive current collector. By also having through holes in the positive current collector of the positive electrode sheet, the second through holes in the positive electrode sheet and the first through holes in the negative electrode sheet form a through-hole system, further improving the electrolyte wetting channels in the electrode assembly and enhancing the efficiency of reducing internal stress in the electrode assembly, thereby further improving the electrolyte wetting efficiency and structural stability of the electrode assembly.

[0030] In this embodiment, the positive electrode active material layer extends into the second through-hole. The positive electrode active material layer extending into the second through-hole can act as an electrolyte wetting medium, increasing the rate at which the electrolyte rapidly wets into the electrode assembly through the portion of the positive electrode active material layer filling the second through-hole, thereby increasing the proportion of positive electrode active material in the positive electrode sheet.

[0031] In this embodiment, a first positive electrode active material layer is disposed on one surface, and a second positive electrode active material layer is disposed on the other surface; wherein, the first positive electrode active material layer extends into the second through hole, and the second through hole extends into the second positive electrode active material layer.

[0032] In this embodiment, the second through hole extends into and penetrates the second positive electrode active material layer.

[0033] Extending the second through hole into the second positive electrode active material layer can further reduce the stress in the inner ring of the electrode assembly and accelerate the rate at which the electrolyte wets into the electrode assembly.

[0034] In this embodiment, the first positive electrode active material layer extends into the second through-hole and at least partially fills the second through-hole in the second intermediate electrode active material layer. Thus, the first positive electrode active material layer extending into and filling the second through-hole is in direct contact with the second positive electrode active material layer, and the first and second positive electrode active material layers are connected as a single unit through multiple second through-holes. Because the positive electrode active material layer extends into the second through-hole and connects the two positive electrode active material layers, the wettability of the electrolyte to the positive electrode sheet is improved, as is the uniformity of electrolyte wetting between the two positive electrode active material layers. Simultaneously, the proportion of positive electrode active material in the positive electrode sheet can be increased, thereby increasing the capacity of the positive electrode sheet and thus improving the energy density of the battery cell.

[0035] In the embodiment, the second through hole includes at least one of the following (1) to (4):

[0036] (1) Along the length direction of the positive current collector, the spacing between two adjacent second through holes is 1mm to 100mm;

[0037] (2) Along the width direction of the positive current collector, the spacing between two adjacent second through holes is 1mm to 20mm;

[0038] (3) Along the surface direction parallel to the positive current collector, the cross-sectional area of ​​a single second through hole is 0.2 mm. 2 ~3.2mm 2 ;

[0039] (4) In the unit area of ​​the surface of the positive current collector, the total cross-sectional area of ​​the second through hole along the direction parallel to the surface of the positive current collector accounts for 1% to 15%.

[0040] By controlling the distribution and unit area ratio of the second through-hole on the surface of the positive electrode current collector, as well as the through-hole size, within the aforementioned range, the through-hole system formed by the second through-hole in the positive electrode sheet and the first through-hole in the negative electrode sheet can be optimized. This enhances the electrolyte wetting effect on the electrode assembly, improves the wetting efficiency of the electrolyte into the electrode assembly, especially the inner ring, and further improves the structural stability of the electrode assembly, thereby further improving the capacity utilization and cycle performance of the battery cell.

[0041] In this embodiment, the porosity of the positive electrode active material layer is 15% to 20%. Controlling the porosity of the positive electrode active material layer within this range, in conjunction with the aforementioned negative electrode sheet, can further improve the wetting rate of the electrolyte into the electrode assembly, especially the inner ring.

[0042] In some embodiments, the electrolyte contained in the battery cell includes at least one of the following (1) to (3):

[0043] (1) The electrolyte comprises additives of the following components in weight percentage:

[0044] Ethylene carbonate: 40wt%~70wt%;

[0045] Ethyl methyl carbonate: 20wt%~50wt%;

[0046] Fluorinated ethylene carbonate: 5wt%~15wt%;

[0047] (2) The conductivity of the electrolyte is 9mS / cm≤σ≤15mS / cm, or 5mS / cm≤σ<9mS / cm;

[0048] (3) The actual density of the electrolyte is 1.01 g / cm³. 3 ~1.38g / cm 3 .

[0049] The electrolyte described above can effectively wet cells with good wettability, and also has high conductivity and ion transport performance, as well as high thermal and chemical stability, further improving the capacity utilization and cycle performance of battery cells.

[0050] In some embodiments, the battery cell includes a cylindrical battery cell. Because the current collector of the negative electrode or further positive electrode in the cylindrical battery cell contains through-holes, it can effectively alleviate the stress inside the electrode assembly, especially in the inner ring, and improve the wettability of the electrolyte to the inside of the electrode assembly, especially the inner ring, thereby improving the capacity utilization and cycle performance of the cylindrical battery cell.

[0051] Secondly, embodiments of this application provide a method for preparing a single battery cell. The method for preparing a single battery cell according to embodiments of this application includes the following steps:

[0052] The negative electrode, separator, and positive electrode are assembled into an electrode assembly;

[0053] The electrode assembly is encapsulated within the cavity of the outer packaging to form a single battery cell;

[0054] The negative electrode sheet includes a negative electrode current collector, which has two surfaces arranged opposite to each other. A negative electrode active material layer is stacked on at least one of the surfaces. The negative electrode current collector has a plurality of first through holes penetrating the two surfaces, and the negative electrode active material layer extends into the first through holes.

[0055] In some embodiments, the method for preparing the negative electrode includes the following steps:

[0056] A negative electrode current collector is provided, and a first through hole is formed on the negative electrode current collector, such that the first through hole penetrates two oppositely disposed surfaces of the negative electrode current collector;

[0057] The negative electrode slurry is subjected to a film-forming treatment on at least one surface of the negative electrode current collector to form a negative electrode active material layer, and at least one of the negative electrode active material layers extends into the first through hole to prepare a negative electrode sheet.

[0058] This method can effectively create a first through hole in the negative electrode current collector, and allow the negative electrode active material layer to extend and fill the first through hole.

[0059] In some embodiments, the method for preparing the negative electrode includes the following steps:

[0060] A negative electrode current collector is provided, and a negative electrode slurry is subjected to a film-forming treatment on one surface of the negative electrode current collector to form a first negative electrode active material layer;

[0061] Along the direction from the other surface of the negative electrode current collector to the first negative electrode active material layer, the first through hole is opened on the other surface of the negative electrode current collector, such that the first through hole at least penetrates the negative electrode current collector;

[0062] Another portion of negative electrode slurry is subjected to a film-forming treatment on the other surface of the negative electrode current collector to form a second negative electrode active material layer, and the second negative electrode active material layer extends into the first through hole to prepare the negative electrode sheet.

[0063] This method can effectively open the first through hole on the negative electrode current collector and allow the negative electrode active material layer to extend and fill the first through hole, while controlling the extension of the first through hole into the negative electrode active material layer.

[0064] In this embodiment, the negative electrode slurry includes a pore-forming agent, and the pore-forming agent in the negative electrode slurry has a mass content of 0.5% to 2%. This range of pore-forming agent content can adjust the porosity of the negative electrode active material layer.

[0065] In this embodiment, the negative electrode slurry contains negative electrode active materials including carbon-based materials and silicon-based materials, and the compaction density of the mixture of the carbon-based materials and the silicon-based materials is 1.4–1.6 g / cm³. 3 ; and / or, the silicon-based material accounts for 1% to 50% of the total mass of the carbon-based material and the silicon-based material.

[0066] By controlling the compaction density of the mixture of carbon-based and silicon-based materials within this range and controlling the silicon-based material content within this range, the specific capacity of the negative electrode sheet can be effectively improved, and the volume expansion rate of the negative electrode active material layer during charging and discharging can be alleviated, thereby relieving the stress inside the electrode assembly.

[0067] In some embodiments, the method for preparing the positive electrode includes the following steps:

[0068] A positive current collector is provided, and a second through hole is formed in the positive current collector, such that the second through hole penetrates two oppositely disposed surfaces of the positive current collector;

[0069] The positive electrode slurry is subjected to a film-forming treatment on at least one surface of the positive electrode current collector to form a positive electrode active material layer, and at least one of the positive electrode active material layers extends into the second through hole to prepare a positive electrode sheet.

[0070] This method can effectively create a second through hole on the positive electrode current collector, and allow the positive electrode active material layer to extend and fill the second through hole.

[0071] In some embodiments, the method for preparing the positive electrode includes the following steps:

[0072] A positive electrode current collector is provided, and a positive electrode slurry is film-formed on one surface of the positive electrode current collector to form a first positive electrode active material layer;

[0073] A second through hole is formed on the other surface of the positive electrode current collector along the direction from the first positive electrode active material layer, such that the second through hole at least penetrates the positive electrode current collector;

[0074] Another portion of the positive electrode slurry is subjected to a film-forming treatment on the other surface of the positive electrode current collector to form a second positive electrode active material layer, and the second positive electrode active material layer extends into the second through hole to prepare the positive electrode sheet.

[0075] This method can effectively open a second through hole on the positive electrode current collector and allow the positive electrode active material layer to extend and fill the second through hole, while controlling the extension of the second through hole into the positive electrode active material layer.

[0076] Thirdly, embodiments of this application provide a battery device. The battery device of this application includes the battery cell described in the above-described embodiments or a battery cell prepared by the method described in the above-described embodiments. The battery device of this application has good cycle life and improved energy density.

[0077] Fourthly, embodiments of this application provide an energy storage device. The energy storage device of this application includes a single battery cell or a battery assembly as described in the previous application, wherein the single battery cell or the battery assembly is used to store or provide electrical energy. The energy storage device of this application can safely and sustainably perform energy storage operations.

[0078] Fifthly, embodiments of this application provide an electrical device. This electrical device includes a battery cell, a battery assembly, or an energy storage device, wherein the battery cell or battery assembly is used to store or provide electrical energy. The electrical device of this application can operate safely and for a long time.

[0079] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0080] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0081] Figure 1 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0082] Figure 2 This is a schematic diagram of the structure of the negative electrode sheet in a battery cell according to an embodiment of this application; wherein, Figure A is a schematic diagram of one structure of the negative electrode sheet, and Figure B is a schematic diagram of another structure of the negative electrode sheet;

[0083] Figure 3 for Figure 2 A schematic diagram of the negative electrode current collector contained in the negative electrode sheet;

[0084] Figure 4 This is a schematic diagram of one embodiment of the battery module of this application;

[0085] Figure 5 This is an exploded view of the battery pack in the embodiment of the application.

[0086] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses a battery as a power source, as described in the present application.

[0087] The reference numerals in the detailed embodiments are as follows:

[0088] 10-Battery cell, 11-Casing, 12-Top cover, 13-Bottom cover, 14-Electrode assembly, 140-Negative electrode sheet, 141-Negative current collector, 1411-First through hole, 142-Negative active material layer, 1421-First negative active material layer, 1422-Second negative active material layer.

[0089] 20-Battery Module;

[0090] 30 - Battery pack, 31 - Upper casing, 32 - Lower casing. Detailed Implementation

[0091] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0092] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0093] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0094] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0095] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0096] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0097] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0098] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0099] With the rapid development of electric vehicles, energy storage systems, and other fields, higher requirements are being placed on the energy density of batteries. Currently, the industry generally adopts methods such as increasing the areal density of electrode sheets and increasing the size of battery cells (such as 4680 cylindrical cells) to improve battery energy density.

[0100] Increasing the areal density of the electrodes means that more active material can be arranged within a limited space, thereby effectively increasing the battery capacity. This method optimizes electrode design, increasing the content of active material per unit area, thus improving the battery's energy density without changing its volume. Simultaneously, increasing the size of individual battery cells is also an effective means of improving battery energy density. By increasing the size of individual battery cells, the connecting components and casing material in the battery module or battery pack can be reduced, thereby further reducing the weight and volume of the battery module or battery pack and improving the overall energy density.

[0101] However, these methods all have some problems in practical applications. First, increasing the electrode surface density and the size of the battery cell leads to a decrease in the electrolyte wetting effect of the electrode assembly within the battery cell. The electrolyte is the key medium for ion transfer in the battery cell, and its wetting effect directly affects the performance and lifespan of the battery cell. Especially inside the electrode assembly within the battery cell, due to structural limitations and poor electrolyte flow, electrolyte wetting is even more difficult. Second, existing battery cells generally use wound electrode assemblies. This wound structure makes the inner ring of the electrode assembly more prone to insufficient electrolyte wetting. The wound structure reduces the contact area between the active material and the electrolyte in the inner ring of the electrode assembly, while also increasing the expansion pressure in the inner ring, further reducing electrolyte wetting. In addition, to improve battery capacity, high specific capacity electrode materials, such as silicon-based materials, are generally used. These high specific capacity electrode materials undergo significant volume expansion during charge and discharge, thereby increasing the expansion pressure of the electrode assembly, especially the inner ring of the wound structure electrode assembly. This expansion pressure not only affects the mechanical stability of the electrode assembly, but also further reduces the electrolyte wettability of the electrode assembly, especially the inner ring of the wound structure electrode assembly.

[0102] Actual testing revealed that when a cylindrical battery cell reached 50% SOH (State of Health), the stress on the outer ring of the electrode assembly ranged from 0 to 2 MPa, while the stress in the middle reached 3 to 6 MPa, and the stress on the inner ring was as high as 7 to 9 MPa. This high stress state severely affected the electrolyte wettability of the wound electrode assembly, especially the inner ring, thus impacting the performance and lifespan of the battery cell.

[0103] Although some methods for improving electrolyte wetting of battery electrode components have emerged in the prior art, such as creating pores in the active material layer of the electrode to improve electrolyte wettability, the effects of these methods are not ideal. In particular, for the inner ring of the electrode component, due to the complex structure and stress concentration, electrolyte wettability remains difficult to improve effectively.

[0104] To effectively improve the electrolyte wettability of electrode components in a single battery cell, particularly the inner ring of a wound electrode component, this application provides a battery cell that improves the electrode by creating through-holes in the current collector. An active material layer is stacked on the surface of the current collector with these through-holes, extending into the holes. Because the current collector has through-holes, the electrolyte can directly wet and diffuse into the electrode component after passing through the active material layer. This effectively shortens the electrolyte's wetting path and increases the overall porosity of the electrode, providing a buffer space for volume expansion and reducing internal stress. This allows the electrolyte to wet into the electrode component more quickly, effectively improving the wetting efficiency. Thus, this effectively improves the battery cell's capacity utilization and cycle performance.

[0105] [Battery cell]

[0106] In a first aspect, embodiments of this application provide a battery cell. The battery cell of this application includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer; wherein the negative electrode current collector has two opposing surfaces, and the negative electrode current collector has a plurality of through holes penetrating its two surfaces; the negative electrode active material layer is stacked on at least one surface of the negative electrode current collector, and at least one negative electrode active material layer extends into the through holes of the negative electrode current collector.

[0107] This application's embodiments of the battery cell include a battery outer packaging, an electrode assembly encapsulated within the battery outer packaging, and an electrolyte soaking the electrode assembly. The outer packaging refers to the component used to encapsulate the electrode assembly; the electrode assembly typically includes a positive electrode, a negative electrode, and a separator separating the positive and negative electrode. A through-hole in the negative electrode current collector refers to a hole structure extending from one surface of the negative electrode current collector to another. In this application's embodiment description, the through-hole in the negative electrode current collector is uniformly defined as a first through-hole. Multiple through-holes can be understood as the negative electrode current collector having two or more through-holes. At least one negative electrode active material layer extends into the first through hole of the negative electrode current collector. This can be understood as follows: when a negative electrode active material layer is stacked on one surface of the negative electrode sheet, the negative electrode active material layer covers the first through hole and protrudes into the first through hole along the channel of the first through hole; when negative electrode active material layers are stacked on both surfaces of the negative electrode sheet, one negative electrode active material layer covers the first through hole and protrudes into the first through hole along the channel of the first through hole, or two negative electrode active material layers cover the first through hole and protrude into the first through hole along the channel of the first through hole.

[0108] In this embodiment of the battery cell, a first through-hole is formed in the negative electrode current collector contained in the negative electrode sheet. Firstly, the electrolyte can directly and rapidly wet the interior of the electrode assembly through these first through-holes, thereby significantly shortening the electrolyte wetting path and effectively improving the electrolyte wetting efficiency of the electrode assembly. At least one negative electrode active material layer extends into the first through-hole of the negative electrode current collector. The negative electrode active material layer filling the first through-hole can accelerate the guidance of the electrolyte through the first through-hole into the interior of the electrode assembly.

[0109] Secondly, the presence of the first through-hole increases the overall porosity of the negative electrode. This provides the electrolyte with richer and more efficient wetting channels, accelerating the electrolyte wetting rate.

[0110] Meanwhile, the first through hole also provides a buffer space for the volume expansion of the electrode assembly during charging and discharging, thereby reducing the stress inside the electrode assembly, especially the stress in the inner ring. This also facilitates the wetting of the electrolyte into the electrode assembly, especially the inner ring, and improves the structural stability of the electrode assembly.

[0111] Therefore, the electrolyte wetting efficiency of the battery cells in this embodiment of the application is significantly improved, thereby effectively improving the capacity utilization and cycle performance of the battery cells.

[0112] Outer packaging of individual battery cells:

[0113] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc.; of course, it can also be a soft package. The shape of the outer packaging can be cylindrical, square, or any other arbitrary shape. This outer packaging shape gives the battery cell its shape; therefore, the shape of the battery cell can be cylindrical, square, or any other arbitrary shape corresponding to the shape of the outer packaging. In the exemplary example, the battery cell can be as follows: Figure 1 The shown is a cylindrical battery cell 10.

[0114] In some embodiments, such as Figure 1 As shown, the outer packaging of the battery cell 10 may include a cylindrical shell 11, a top cover 12, and a bottom cover 13. The top cover 12 and the bottom cover 13 respectively cover the two ends of the shell 11 and together with the shell 11 form an accommodating space. The cylindrical electrode assembly 14 is encapsulated within the accommodating space.

[0115] Electrode assembly of a single battery cell:

[0116] In the battery cell of this application embodiment, the electrode assembly typically includes a positive electrode, a negative electrode, and a separator, and the separator is stacked between the positive electrode and the negative electrode to play an isolation role, separating the positive electrode and the negative electrode.

[0117] In some embodiments, the electrode assembly included in the battery cell of this application has a wound structure. In an exemplary example, the electrode assembly is as follows: Figure 1 The cylindrical wound structure shown in the electrode assembly 14 corresponds to a cylindrical battery cell. In the example, the electrode assembly can be a 4680 cylindrical electrode assembly or an 18650 cylindrical electrode assembly, and the corresponding battery cell can be a 4680 cylindrical battery cell or an 18650 cylindrical battery cell. Of course, the electrode assembly can also be a prismatic battery electrode assembly or a stacked electrode assembly, and both prismatic battery electrode assemblies and stacked electrode assemblies are within the scope of the embodiments disclosed in this application.

[0118] Negative electrode in the electrode assembly:

[0119] In some embodiments, the negative electrode structure included in the electrode assembly can be as follows: Figure 2As shown, the negative electrode sheet 140 includes a negative electrode current collector 141 and two negative electrode active material layers 142. The negative electrode current collector 141 has two opposing surfaces and a plurality of first through holes 1411 extending through the two opposing surfaces. A first negative electrode active material layer 1421 in the negative electrode active material layer 142 is stacked on one surface of the negative electrode current collector 141, and a second negative electrode active material layer 1422 in the negative electrode active material layer 142 is stacked on the other surface of the negative electrode current collector 141. In this case, the first negative electrode active material layer 1421 extends into the first through hole 1411, and the first through hole 1411 extends into the second negative electrode active material layer 1422. Alternatively, the second negative electrode active material layer 1422 can extend into the first through hole 1411, and the first through hole 1411 can extend into the first negative electrode active material layer 1421.

[0120] In the embodiment, the extension of the first negative electrode active material layer 1421 into the first through hole 1411 can be understood as the first negative electrode active material layer 1421 being as follows: Figure 2 The first through-hole 1411 shown in Figure A is partially filled with the negative electrode current collector 141. Of course, the entire first through-hole 1411 of the negative electrode current collector 141 can also be filled.

[0121] In this embodiment, the extension of the first through-hole 1411 into the second negative electrode active material layer 1422 can be understood as follows: Figure 2 As shown in Figure A, the first through-hole 1411 extends into the second negative electrode active material layer 1422 and penetrates the entire second negative electrode active material layer 1422. At this time, the second negative electrode active material layer 1422 also has through-holes, and these through-holes correspond one-to-one with the first through-holes 1411 in the negative electrode current collector 141. Alternatively, the first through-hole 1411 may extend into the second negative electrode active material layer 1422 but not penetrate the entire second negative electrode active material layer 1422.

[0122] like Figure 2 As shown, the first through-hole 1411 of the negative electrode current collector 141 extends into or further penetrates the second negative electrode active material layer 1422 therein. This effectively lengthens the channel of the first through-hole 1411, further accelerating the rate at which the electrolyte wets into the electrode assembly; it also increases the buffer space provided for the volume expansion of the electrode assembly during charging and discharging, further reducing the stress inside the electrode assembly, especially the stress in the inner ring. Therefore, extending the first through-hole 1411 into the second negative electrode active material layer 1422 can further reduce the stress in the inner ring of the electrode assembly and accelerate the rate at which the electrolyte wets into the electrode assembly.

[0123] In the embodiments, based on Figure 2The structure of the negative electrode 140 shown in Figure A is as follows: Figure 2 As shown in Figure B, the first negative electrode active material layer 1421 extends into the first through-hole 1411 of the negative electrode current collector 141, and at least partially fills the first through-hole 1411 in the second negative electrode active material layer 1422. At this time, the first negative electrode active material layer 1421 extending into and filling the first through-hole 1411 is in direct contact with the second negative electrode active material layer 1422, and the first negative electrode active material layer 1421 and the second negative electrode active material layer 1422 are connected as one unit through multiple first through-holes 1411. Thus, the negative electrode active material layers extending into and filling the multiple first through-holes 1411 constitute the medium for electrolyte wetting and migration, thereby further improving the electrolyte wetting rate and the efficiency of electrolyte migration into the electrode assembly, especially the inner ring of the cylindrical electrode assembly, thereby improving the capacity utilization and cycle performance of the battery cell. Meanwhile, since the negative electrode active material layer 142 extends to the first through hole 1411 and the two negative electrode active material layers 142 are connected, the proportion of negative electrode active material in the negative electrode sheet 140 is increased, which can improve the capacity of the negative electrode sheet and thus improve the energy density of the battery cell.

[0124] In some embodiments, the distribution of the first through holes in the negative electrode sheet on the surface of the negative electrode current collector can be along the length direction of the negative electrode current collector, and the spacing between two adjacent first through holes is 1mm to 100mm, optionally 1mm to 50mm. In exemplary examples, it can be a typical but non-limiting spacing such as 1mm, 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, or any range between two spacing values.

[0125] In some embodiments, the spacing between two adjacent first through holes along the width direction of the negative electrode current collector can be 1mm to 20mm, optionally 1mm to 10mm. In exemplary examples, it can be a typical but non-limiting spacing such as 1mm, 3mm, 5mm, 7mm, 10mm, 11mm, 13mm, 15mm, 17mm, 20mm, or any range between two spacing values.

[0126] Wherein, along the length direction of the negative electrode current collector can be as follows: Figure 3 As shown, along the x-axis direction of the negative electrode current collector 141, the distance between two adjacent first through holes 1411 is 'a', therefore, 'a' can be 1mm to 100mm; along the width direction of the negative electrode current collector, it can be as follows... Figure 2As shown in the y-axis direction, the distance between two adjacent first through holes 1411 along the y-axis is b, which can be 1mm to 20mm. This distance between adjacent first through holes can be recorded using a charge-coupled device (CCD camera), or detected using an electron microscope. Distributing the first through holes 1411 at the aforementioned distance on the surface of the negative electrode current collector 141 further increases the number of channels for electrolyte to penetrate the electrode assembly, adjusts the overall porosity of the negative electrode sheet, and provides buffer space to reduce volume expansion during charging and discharging, alleviating internal stress, especially in the inner ring. This improves the efficiency of electrolyte penetration into the electrode assembly, thereby further enhancing the capacity utilization and cycle performance of the battery cell.

[0127] In some embodiments, along the surface direction parallel to the negative electrode current collector, the cross-sectional area of ​​a single first through-hole in the above embodiments is 0.2 mm. 2 ~3.2mm 2 The optional thickness is 0.45mm. 2 ~1.23mm 2 In the example, it can be 0.2mm 2 0.5mm 2 0.8mm 2 1mm 2 1.5mm 2 2mm 2 2.5mm 2 3.0mm 2 3.2mm 2 The cross-sectional area can be a typical but not limiting area or a range between any two area values. This cross-sectional area can be calculated using images collected by a charge-coupled device (CCD camera) or detected using an electron microscope. Alternatively, it can be directly controlled and adjusted using a single first through-hole. In this embodiment, the diameter of the single first through-hole can be controlled to be 0.5 mm to 2 mm, optionally 0.75 mm to 1.25 mm. Controlling the cross-sectional area or diameter of the single first through-hole within this range can further adjust the overall porosity of the negative electrode and improve the electrolyte wetting rate into the electrode assembly. Furthermore, the shape of the first through-hole can be a circular through-hole, or other shapes such as elliptical, square, or irregular shapes.

[0128] In some embodiments, the total cross-sectional area of ​​the first through-hole per unit area on the surface of the negative electrode current collector, along the direction parallel to the surface of the negative electrode current collector, accounts for 0.1% to 25%, optionally 5% to 20%. In exemplary examples, it can be a typical but non-limiting area such as 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, or any range between two area values. The total cross-sectional area percentage of the first through-hole can be calculated using images collected by the aforementioned charge-coupled device (CCD camera). Controlling the distribution of the first through-hole on the unit surface of the negative electrode current collector within the above range can optimize the electrolyte wetting path of the electrode assembly and the total porosity of the negative electrode sheet, providing a suitable buffer space for the volume expansion of the silicon-based material during charging and discharging of the battery cell. This effectively alleviates the stress generated inside the electrode assembly, especially the inner ring, during charging and discharging, improving the electrolyte wetting efficiency and structural stability of the electrode assembly, especially the inner ring. Simultaneously, it can also increase the content of the negative electrode active material layer in the negative electrode sheet, thereby increasing the specific capacity of the negative electrode sheet.

[0129] In some embodiments, the negative electrode current collector may include, but is not limited to, a metal or composite current collector. In embodiments where the negative electrode current collector is a metallic material, it may include copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, silver alloys, etc.

[0130] In the embodiments, when the negative electrode current collector is a composite current collector, the composite current collector may include a composite material of polymer materials and metals. The polymer materials in the composite material may include, but are not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The metals in the composite material may include, but are not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may be obtained by mixing polymer materials and metals, or it may be coated onto at least one side of the polymer material by electroplating, coating, or other methods.

[0131] In addition, the thickness of the negative electrode current collector in the above embodiments can be a conventional thickness.

[0132] In the embodiments described above, the negative electrode active material contained in the negative electrode active material layer of the negative electrode sheet can be a conventional negative electrode active material suitable for lithium-ion batteries, sodium-ion batteries, or other types of batteries. As in the embodiments, the negative electrode active material in the negative electrode active material layer can be, but is not limited to, a mixture or composite material formed from any one or more of carbon-based materials, silicon-based materials, alloy materials, and titanium-based materials. In the exemplary examples, carbon-based materials include, but are not limited to, one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers; silicon-based materials can include, but are not limited to, elemental silicon, silicon-carbon composite materials, silicon-oxygen composite materials, and silicon-based alloy materials.

[0133] In some embodiments, the negative electrode active material in the negative electrode active material layer of the negative electrode sheet includes silicon-based material, and the silicon-based material accounts for 1% to 50% of the total mass of the negative electrode active material; in a unit area of ​​the negative electrode current collector surface (specifically, the surface on which the negative electrode active material layer is stacked), the total cross-sectional area of ​​the first through-hole mentioned above accounts for 0.1% to 10% along the direction parallel to the surface of the negative electrode current collector. The content of the silicon-based material can be quantitatively detected using methods such as mass spectrometry or nuclear magnetic resonance (NMR). The percentage of the total cross-sectional area of ​​the first through-hole can be calculated using images collected by the aforementioned charge-coupled device (CCD camera). Adding this range of silicon-based material to the negative electrode active material can effectively improve the specific capacity of the battery cell compared to traditional carbon-based materials, thereby increasing the energy density of the battery cell. Simultaneously controlling the distribution of the first through-holes on the surface of the negative electrode current collector within the aforementioned range of 0.1% to 10% allows the negative electrode sheet to possess an appropriate total porosity, working together with the negative electrode active material layer. This provides a suitable buffer space for the volume expansion of the silicon-based material during charging and discharging, effectively alleviating the stress generated inside the electrode assembly, especially the inner ring, during charging and discharging. It also improves the electrolyte wetting path, enhancing the structural stability of the electrode assembly and increasing its electrolyte retention capacity. Therefore, controlling the proportion of the total cross-sectional area of ​​all first through-holes per unit area on the surface of the negative electrode current collector and the proportion of silicon-based material in the negative electrode active material within the aforementioned ranges effectively improves the specific capacity of the negative electrode sheet and the electrolyte wetting rate inside the electrode assembly, especially the inner ring, and enhances the structural stability of the electrode assembly. This, in turn, improves the capacity utilization, energy density, and cycle performance of the battery cell.

[0134] In some embodiments, the negative electrode active material contained in the negative electrode active material layer of the negative electrode sheet includes a silicon-based material, and when the silicon-based material accounts for 1% to 10% of the total mass of the negative electrode active material, the total cross-sectional area of ​​the first through hole mentioned above accounts for 0.1% to 2% of the unit area of ​​the negative electrode current collector surface (specifically, the surface on which the negative electrode active material layer is stacked).

[0135] In some embodiments, the negative electrode active material contained in the negative electrode active material layer of the negative electrode sheet includes a silicon-based material, and when the silicon-based material accounts for 10% to 25% of the total mass of the negative electrode active material, the total cross-sectional area of ​​the first through hole mentioned above accounts for 2% to 5% of the unit area of ​​the negative electrode current collector surface (specifically, the surface on which the negative electrode active material layer is stacked).

[0136] In some embodiments, the negative electrode active material contained in the negative electrode active material layer of the negative electrode sheet includes a silicon-based material, and when the silicon-based material accounts for 25% to 50% of the total mass of the negative electrode active material, the total cross-sectional area of ​​the first through hole mentioned above accounts for 5% to 10% of the unit area of ​​the surface of the negative electrode current collector (specifically, the surface on which the negative electrode active material layer is stacked).

[0137] By further controlling the proportion of the total cross-sectional area of ​​all first through holes per unit area on the surface of the negative electrode current collector and the proportion of silicon-based material in the negative electrode active material within the aforementioned ranges, the specific capacity of the negative electrode sheet and the electrolyte wetting rate and structural stability of the electrode assembly can be further improved, thereby further maximizing the capacity of the battery cell and improving the energy density and cycle performance of the battery cell.

[0138] In some embodiments, when the negative electrode active material contained in the negative electrode active material layer of the negative electrode sheet includes the aforementioned silicon-based material, the negative electrode active material also includes a carbon-based material. In this case, the carbon-based material and the silicon-based material are mixed and distributed in the negative electrode active material layer, and the carbon-based material accounts for 1% to 50% of the total mass of the negative electrode active material. In exemplary examples, when the negative electrode active material is a mixture of carbon-based and silicon-based materials, the proportion of carbon-based material is as follows: when the silicon-based material accounts for 1%, the carbon-based material accounts for 99%; when the silicon-based material accounts for 5%, the carbon-based material accounts for 95%; when the silicon-based material accounts for 10%, the carbon-based material accounts for 90%; when the silicon-based material accounts for 20%, the carbon-based material accounts for 80%; when the silicon-based material accounts for 30%, the carbon-based material accounts for 70%; when the silicon-based material accounts for 40%, the carbon-based material accounts for 60%; and when the silicon-based material accounts for 50%, the carbon-based material accounts for 50%. Using a mixture of carbon-based and silicon-based materials as the negative electrode active material, compared to using only carbon-based materials, not only improves the specific capacity of the negative electrode but also effectively mitigates volume expansion during charging and discharging, thereby reducing internal stress within the electrode assembly and improving electrolyte wetting efficiency. Furthermore, it enhances the conductivity of the negative electrode and the stability of the electrolyte interface, ultimately improving the capacity utilization and cycle performance of the individual battery cells.

[0139] In this embodiment, the silicon-based material includes silicon, and the carbon-based material includes graphite. Graphite possesses relatively high specific capacity, good conductivity, and interfacial stability with the electrolyte, while silicon has a high specific capacity. Therefore, the negative electrode active material comprises a mixture of silicon and graphite, which can effectively improve the energy density and cycle performance of the battery cell.

[0140] In some embodiments, the negative electrode active material layer in the negative electrode sheet of the above embodiments is further provided with a porous structure, and the porosity of the negative electrode active material layer is 10% to 40%, optionally 20% to 30%. In the exemplary examples, it can be a typical but non-limiting porosity such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any range between two porosity values.

[0141] In the embodiments, when the negative electrode active material layer in the negative electrode sheet of the above embodiments is further provided with a porous structure, the pore size of the porous structure in the negative electrode active material layer is 0.2μm to 2μm, optionally 0.5μm to 1μm. In the exemplary example, it can be a typical but non-limiting pore size such as 0.2μm, 0.5μm, 0.8μm, 1.0μm, 1.3μm, 1.5μm, 1.8μm, 2.0μm, or a range between any two pore size values.

[0142] By creating a porous structure within the negative electrode active material layer and controlling the porosity and pore size within this range, the first through-hole in the negative electrode current collector described above can be used to further improve the wettability of the electrolyte into the electrode assembly, thereby increasing the electrolyte wetting rate inside the electrode assembly, especially in the inner ring. The porosity and pore size of the negative electrode active material layer can be detected using methods such as gas adsorption or scanning electron microscopy.

[0143] In some embodiments, the mass content of the negative electrode active material in the negative electrode active material layer of the above embodiments can be 85% to 98%, and can be selected as 95% to 98%. In exemplary examples, it can be a typical but non-limiting content such as 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any range between two content values.

[0144] In addition, the negative electrode active material layer may also include at least one of a conductive agent and a binder. The conductive agent is used to collect current between the negative electrode active materials and between the active materials and the current collector, improving electronic conductivity. Simultaneously, the conductive agent can also promote the wetting of the negative electrode sheet by the electrolyte. The binder can improve the bonding strength between the substances in the negative electrode active material layer and between the negative electrode active material layer and the current collector, thereby improving the structural stability and mechanical properties of the negative electrode sheet, such as peel strength.

[0145] In the embodiments, the mass content of the conductive agent in the negative electrode active material layer can be 0.5% to 10%. In exemplary examples, it can be a typical but non-limiting content such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two content values. Other contents can also be set as needed. In exemplary examples, the conductive agent includes one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.

[0146] In the embodiments, the mass content of the binder in the negative electrode active material layer can be 0.5% to 10%. In the exemplary examples, it can be a typical but non-limiting content such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two content values. Other contents can also be set as needed. In the exemplary examples, the binder includes, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0147] In some embodiments, the dry basis weight of the negative electrode active material layer on one surface of the negative electrode sheet, i.e., on a single surface of the negative electrode sheet, is 1.4–1.8 g / 1540.25 mm. 2 By controlling the coating amount of the negative electrode active material layer on one side within a certain range, the specific capacity of the negative electrode sheet can be appropriately increased while effectively improving the electrolyte wetting efficiency inside the electrode assembly.

[0148] Positive electrode in the electrode assembly:

[0149] In the embodiments described above, the positive electrode sheet included in the electrode assembly of the battery cell can be a positive electrode sheet of a lithium-ion battery cell, a sodium-ion battery cell, or other types of batteries. In the embodiments of this application, the positive electrode sheet included in the electrode assembly comprises a positive current collector and a positive active material layer; wherein, the positive current collector has two surfaces disposed opposite to each other, and the positive active material layer is stacked on at least one surface of the positive current collector.

[0150] In some embodiments, the positive current collector of the positive electrode sheet has multiple through holes penetrating both surfaces. These through holes refer to a hole structure where one surface of the positive current collector penetrates the other surface. In this case, the structure of the positive current collector is similar to... Figure 3The structure of the negative electrode current collector is similar. In the specification of the embodiments of this application, the through holes opened in the positive electrode current collector are uniformly defined as second through holes to distinguish them from the first through holes contained in the negative electrode current collector mentioned above. The multiple through holes opened in the positive electrode current collector, which are also the second through holes, can be understood to mean that the number of through holes opened in the positive electrode current collector is two or more. By also creating through holes (specifically, second through holes) in the positive current collector of the positive electrode, after the positive electrode and the negative electrode are assembled into an electrode assembly, the second through hole in the positive electrode and the first through hole in the negative electrode form a through hole system, further enriching the electrolyte wetting channels in the electrode assembly. This allows the electrolyte to directly and rapidly wet into the interior of the electrode assembly, especially the interior of the cylindrical wound electrode assembly, thereby further shortening the electrolyte wetting path and improving the electrolyte wetting efficiency of the electrode assembly. At the same time, the first and second through holes can provide buffer space for the volume expansion of the electrode assembly during charging and discharging, further relieving the stress inside the electrode assembly, especially the inner ring, and further improving the wetting of the electrolyte into the interior of the electrode assembly, especially the inner ring. It can also further improve the structural stability of the electrode assembly. In this way, the positive electrode with the second through hole and the negative electrode with the first through hole can enhance the electrolyte wetting effect on the electrode assembly, improve the wetting efficiency of the electrolyte into the electrode assembly, especially the inner ring, and further improve the structural stability of the electrode assembly, thereby further improving the capacity utilization and cycle performance of the battery cell.

[0151] Furthermore, in the positive electrode sheet containing the aforementioned second through-hole, the positive electrode active material layer can extend into the second through-hole on the positive electrode current collector, or it can choose not to extend into the second through-hole. Relatively speaking, it is more ideal for one or two layers of positive electrode active material to extend into the second through-hole on the positive electrode current collector. In this way, the positive electrode active material layer extending into the second through-hole can act as an electrolyte wetting medium, increasing the rate at which the electrolyte rapidly wets into the electrode assembly through the portion of the positive electrode active material layer filled in the second through-hole. At the same time, it can increase the proportion of positive electrode active material in the positive electrode sheet, thereby increasing the specific capacity of the positive electrode sheet.

[0152] In this embodiment, in the positive electrode sheet containing the aforementioned second through-hole, positive electrode active material layers are stacked on both surfaces of the positive electrode current collector. One positive electrode active material layer is defined as the first positive electrode active material layer, and the other positive electrode active material layer is defined as the second positive electrode active material layer. The first positive electrode active material layer extends into the second through-hole, and the second through-hole extends into the second positive electrode active material layer. Alternatively, the second positive electrode active material layer can extend into the second through-hole, and the second through-hole can also extend into the second positive electrode active material layer.

[0153] In this embodiment, the extension of the first positive electrode active material layer into the second through-hole can be understood as the first positive electrode active material layer partially filling the second through-hole of the positive electrode current collector. At this time, the structure of the positive electrode sheet is similar to... Figure 2 The negative electrode structure shown in Figure A is also possible. Alternatively, it could be a second through-hole filled with the positive current collector.

[0154] In this embodiment, the extension of the second through-hole into the second positive electrode active material layer can be understood as the second through-hole extending into and penetrating the entire second positive electrode active material layer. In this case, the second positive electrode active material layer also has through-holes, and these through-holes correspond one-to-one with the second through-holes opened in the positive electrode current collector. Of course, it is also possible that the second through-hole extends into the second positive electrode active material layer but does not penetrate the entire second positive electrode active material layer.

[0155] The second through-hole in the positive electrode current collector extends into or further penetrates the second positive electrode active material layer. This effectively lengthens the channel of the second through-hole, further accelerating the rate of electrolyte wetting into the electrode assembly; it also increases the buffer space provided for the volume expansion of the electrode assembly during charging and discharging, further reducing the stress inside the electrode assembly, especially in the inner ring. Therefore, extending the second through-hole into the second positive electrode active material layer can further reduce the stress in the inner ring of the electrode assembly and accelerate the rate of electrolyte wetting into the electrode assembly.

[0156] In this embodiment, based on the structure of the positive electrode sheet described above, the first positive electrode active material layer extends into the second through-hole opened in the positive electrode current collector, and at least partially fills the second through-hole extending into the second positive electrode active material layer. At this time, the structure of the positive electrode sheet is similar to... Figure 2 The negative electrode structure is shown in Figure B. The first positive electrode active material layer, extending and filling the second through-hole, is in direct contact with the second positive electrode active material layer. The first and second positive electrode active material layers are connected as one unit through multiple second through-holes. This extension of the positive electrode active material layer into the second through-hole and the connection between the two layers improves the wettability of the electrolyte to the positive electrode and the uniformity of electrolyte wetting between the two positive electrode active material layers. It also increases the proportion of positive electrode active material in the positive electrode, thereby increasing the capacity of the positive electrode and ultimately improving the energy density of the battery cell.

[0157] In the embodiments, in the positive electrode sheet containing the above-mentioned second through hole, the distribution of the second through hole on the surface of the positive electrode current collector can be along the length direction of the positive electrode current collector, and the spacing between two adjacent second through holes can be 1mm to 100mm, optionally 1mm to 50mm. In the exemplary example, it can be a typical but non-limiting spacing such as 1mm, 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, or any range between two spacing values.

[0158] In the embodiments, in the positive electrode sheet containing the above-mentioned second through hole, along the width direction of the positive electrode current collector, the spacing between two adjacent second through holes can be 1mm to 20mm, optionally 1mm to 10mm. In the exemplary example, it can be a typical but non-limiting spacing such as 1mm, 3mm, 5mm, 7mm, 10mm, 11mm, 13mm, 15mm, 17mm, 20mm, or any range between two spacing values.

[0159] The structure of the positive current collector in the positive electrode at this point is similar to the structure of the negative current collector in the negative electrode described above. Therefore, along the length of the positive current collector, it can be as follows: Figure 3 As shown in the x-axis direction, the spacing between two adjacent second through holes along this x-axis direction is 1mm to 100mm; the width direction of the positive electrode current collector can also be as shown in the figure. Figure 3 As shown in the y-axis direction, the spacing between two adjacent second through holes along this direction is 1mm to 20mm. This spacing can be recorded using a charge-coupled device (CCD camera) or detected using an electron microscope. Distributing the second through holes at the aforementioned spacing on the surface of the positive electrode current collector improves the through-hole system formed by the second through holes in the positive electrode and the first through holes in the negative electrode, thereby enhancing the electrolyte wetting effect on the electrode assembly in the battery cell of this embodiment. This improves the wetting efficiency of the electrolyte into the electrode assembly, especially the inner ring, and further enhances the structural stability of the electrode assembly, thus further improving the capacity utilization and cycle performance of the battery cell.

[0160] In the embodiments, in the positive electrode sheet containing the aforementioned second through-hole, along the surface direction parallel to the positive electrode current collector, the cross-sectional area of ​​a single second through-hole in each of the above embodiments is 0.2 mm. 2 ~3.2mm 2 The optional thickness is 0.45mm. 2 ~1.23mm 2 In the example, it can be 0.2mm 2 0.5mm 2 0.8mm 2 1mm 2 1.5mm 2 2mm2 2.5mm 2 3.0mm 2 3.2mm 2 The area can be a typical but not limiting area or a range between any two area values. The cross-sectional area of ​​the second through-hole can be calculated by collecting images using a charge-coupled device (CCD camera) or detected by an electron microscope. Alternatively, a single second through-hole can be used for control and adjustment. In this embodiment, the diameter of a single second through-hole can be controlled to be 0.5 mm to 2 mm, optionally 0.75 mm to 1.25 mm. Controlling the cross-sectional area or diameter of a single second through-hole within this range can further adjust the overall porosity of the positive electrode and, together with the negative electrode, enhance the rate of electrolyte wetting into the electrode assembly. Furthermore, the shape of the second through-hole can be circular, or other shapes such as elliptical, square, or irregular. It can be the same as or different from the shape of the first through-hole.

[0161] In some embodiments, the total cross-sectional area of ​​the second through-hole per unit area on the surface of the positive electrode current collector, along the direction parallel to the surface of the positive electrode current collector, accounts for 0.1% to 15%, optionally 1% to 10%. In exemplary examples, it can be a typical but non-limiting area such as 0.1%, 1%, 3%, 5%, 7%, 10%, 12%, 15%, or any range between two area values. The total cross-sectional area percentage of the second through-hole can be calculated using images collected by the aforementioned charge-coupled device (CCD camera). Controlling the distribution of the second through-hole on the unit surface of the positive electrode current collector within the above range can further adjust the overall porosity of the positive electrode sheet and, together with the aforementioned negative electrode sheet, enhance the efficiency of improving the electrolyte wetting rate into the electrode assembly.

[0162] In some embodiments, the porosity of the positive electrode active material layer in the positive electrode sheet described above can be 15% to 20%, optionally 17% to 20%. In exemplary cases, it can be typical but not limiting porosities such as 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%, or any range between two porosity values. Controlling the porosity of the positive electrode active material layer within this range, in conjunction with the aforementioned negative electrode sheet, can further improve the electrolyte wetting rate into the electrode assembly, especially the inner ring. When the positive electrode current collector in the positive electrode sheet has the aforementioned second through-hole, this range of porosity in the positive electrode active material layer can also, in conjunction with the second through-hole in the positive electrode current collector, further improve the electrolyte wettability and structural stability of the positive electrode sheet. Therefore, the positive electrode sheet with this range of porosity, together with the negative electrode sheet, can improve the electrolyte wetting efficiency and structural stability within the electrode assembly.

[0163] In some embodiments, the positive current collector contained in the positive electrode sheet in the above embodiments may include, but is not limited to, metal current collectors, carbon current collectors, conductive resin current collectors, and composite current collectors of metal and resin, and more specifically, aluminum, copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, etc. In the embodiments, the current collector may also be a dense film layer or a porous film layer. In the embodiments, the current collector may be, but is not limited to, aluminum foil or porous aluminum foil.

[0164] In some embodiments, the mass content of the positive electrode active material in the positive electrode active material layer of the above-mentioned positive electrode sheet can be 90% to 98%, optionally 92% to 96%. In exemplary examples, it can be typical but non-limiting contents such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%, or any range between two contents. Positive electrode active material within this content range can effectively improve the energy density of the positive electrode sheet.

[0165] In the embodiments, the positive electrode active material may include a sodium-ion positive electrode active material or a lithium-ion positive electrode active material. When the positive electrode active material contains sodium ion, the battery cell in this embodiment may be a sodium battery cell; when the positive electrode active material contains lithium ion, the battery cell in this embodiment may be a lithium battery cell.

[0166] In the example, the sodium-ion positive electrode active material may include one or more of the following: sodium layered oxides, polyanionic compounds, and Prussian blue compounds. For example, layered oxides may include Na... x MO2, where M = one or more of Fe, Mn, Ni, Co, Cr, Sc, Ti, V, Cr, Cu, and Zn, and 0.4 ≤ x ≤ 1, for example, NaFe. 0.33 Mn 0.33 Ni 0.33 O2, NaFe 0.5 Ni 0.5 O2, Na 0.6 MnO2, Na 0.44 MnO2, Na 0.65 Mn 0.75 Ni 0.25 O2, NaNi 0.5 Mn 0.5 O2, Na 0.78 Ni 0.23 Mn 0.69 O2, NaVO2, NaFeO2, Na 0.7CoO2, etc. Polyanionic compounds can include one or more of phosphate, pyrophosphate, sulfate type, and anion-doped type, such as olivine-type NaFePO4, Na2FeP2O7, NaFePO4F, Na3V2(PO4)3, and NaFeSO4. 0.61 Fe[Fe(CN)6] 0.94 BR-FeHCF, Na 1.48 Ni[Fe(CN)6] 0.89 NaNi 0.05 Mn 0.95 One or more of [Fe(CN)6].

[0167] In the example, the lithium-ion cathode active material may include, but is not limited to, at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, ternary materials, etc.

[0168] The aforementioned types of sodium-ion or lithium-ion cathode active materials have high specific capacity, or further, high structural stability and good cycle performance.

[0169] In the embodiments, the positive electrode active material layer contained in the above-mentioned positive electrode sheet generally includes components such as binders and conductive agents in addition to the positive electrode active material components mentioned above. The binder can enhance the mechanical properties between the positive electrode active material layer itself and the current collector. The conductive agent can effectively improve the conductivity of the positive electrode, such as reducing the resistance of the positive electrode.

[0170] In the embodiments, the mass content of the binder contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%, and in exemplary examples, it can be a typical but non-limiting content such as 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, or any range between two content values.

[0171] In the embodiments, the adhesive may include one or more of oil-soluble adhesives, water-soluble adhesives, and emulsion adhesives. In the exemplary embodiments, the oil-soluble adhesive may include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, and polyacrylonitrile; in the exemplary embodiments, the water-soluble adhesive may include one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, and cyclodextrin; in the exemplary embodiments, the emulsion adhesive may include one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0172] The content of this range and the types of binders mentioned above can effectively enhance the mechanical properties of the positive electrode active material layer and the bonding strength between it and the current collector, thereby effectively improving the cycle performance of the positive electrode.

[0173] In the embodiments, the mass content of the conductive agent contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%. In exemplary examples, it can be a typical but non-limiting content such as 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, or a range between any two content values. In the embodiments, the conductive agent may include one or more of acetylene black (SP), conductive carbon black (super-P), Ketjen black, graphene, etc. This range of content and the above-mentioned types of conductive agents can effectively improve the conductivity of the positive electrode active material layer.

[0174] The diaphragm in the electrode assembly:

[0175] In the embodiments of this application, the separator contained in the battery cell is disposed between the positive electrode and the negative electrode, as described above, separating the positive electrode and the negative electrode. The separator can be any known porous structure separator with electrochemical and mechanical stability. In the embodiments, the separator includes at least one single-layer or multi-layer film of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0176] Electrolyte:

[0177] In this embodiment, the electrolyte contained in the battery cell is encapsulated in an outer package and wets the aforementioned electrode assembly. For example, it can wet the interior of the electrode assembly through the first through hole opened in the negative current collector of the negative electrode sheet in the aforementioned electrode assembly. When the positive current collector of the positive electrode sheet is opened in the second through hole, the electrolyte can also wet the interior of the electrode assembly through the through hole system formed by the first and second through holes. This effectively shortens the path for the electrolyte to wet the interior of the electrode assembly, especially the inner ring, so that the electrolyte can effectively wet the interior of the electrode assembly, especially the cylindrical wound electrode assembly, thereby improving the electrolyte wetting efficiency of the electrode assembly.

[0178] In some embodiments, the electrolyte contained in the battery cell of this application includes, in addition to the electrolyte, additives comprising the following components in weight percentage:

[0179] Ethylene carbonate (EC): 40wt%–70wt%;

[0180] Ethyl methyl carbonate (EMC): 20wt%~50wt%;

[0181] Fluorinated ethylene carbonate (FEC): 5 wt% to 15 wt%.

[0182] In the example, the content of EC can be a typical but non-limiting content such as 40wt%, 50wt%, 60wt%, 70wt%, or any range between two content values; the content of EMC can be a typical but non-limiting content such as 20wt%, 30wt%, 40wt%, 50wt%, or any range between two content values; and the content of FEC can be a typical but non-limiting content such as 5%, 8%, 10%, 13%, 15%, or any range between two content values.

[0183] The conductivity of the electrolyte can be increased by increasing the EMC content or decreasing the EC content, and vice versa. In the example, the electrolyte conductivity (σ) is 9 mS / cm ≤ σ ≤ 15 mS / cm, which can be selected as 9 mS / cm ≤ σ ≤ 13 mS / cm (high conductivity electrolyte), or the electrolyte conductivity (σ) is greater than 5 mS / cm ≤ σ < 9 mS / cm (ordinary electrolyte). In the example, the actual density of the electrolyte is 1.01 g / cm³. 3 ~1.38g / cm 3 .

[0184] In addition, the electrolyte contained in the above electrolyte can be the electrolyte commonly used in ion battery electrolytes.

[0185] Electrolytes containing these components and their content and true density have good wettability to the electrode assembly described above, effectively penetrating the interior of the electrode assembly. They also have high ion transport performance, as well as high thermal and chemical stability. Based on the electrode assembly described above, they can further improve the capacity utilization and cycle performance of the battery cells.

[0186] [Preparation methods for battery cells]

[0187] Secondly, this application also provides a method for preparing the battery cell described in the above-described embodiments. The method for preparing the battery cell in this application includes the following steps:

[0188] S10: Assemble the negative electrode, separator and positive electrode into an electrode assembly;

[0189] S20: The electrode assembly is encapsulated in the cavity of the outer packaging to form a battery cell.

[0190] Step S10:

[0191] In step S10, the positive electrode, negative electrode, and separator are all the positive electrode, negative electrode, and separator contained in the battery cell of the above-described embodiment. Therefore, the negative electrode current collector contained in the negative electrode has two surfaces arranged opposite to each other, and a negative electrode active material layer is stacked on at least one surface. The negative electrode current collector has a plurality of first through holes penetrating the two surfaces, and the negative electrode active material layer extends into the first through holes.

[0192] In the battery cell assembled by the battery cell preparation method of the present application embodiment, the negative electrode current collector contained in the negative electrode sheet has a first through hole. The first through hole can form a channel for the electrolyte to wet into the electrode assembly, effectively shortening the electrolyte wetting path into the electrode assembly. Moreover, it can provide buffer space for the volume expansion of the electrode assembly, reduce the stress inside the electrode assembly, and thus improve the overall wetting efficiency of the electrode assembly.

[0193] In some embodiments, the negative electrode sheet can be prepared according to a preparation method including the following steps:

[0194] S11: Provide a negative electrode current collector, and provide a first through hole in the negative electrode current collector so that the first through hole penetrates two oppositely arranged surfaces of the negative electrode current collector;

[0195] S12: The negative electrode slurry is subjected to a film-forming treatment on at least one surface of the negative electrode current collector to form a negative electrode active material layer, and at least one negative electrode active material layer extends into the first through hole to prepare a negative electrode sheet.

[0196] In some embodiments, the negative electrode sheet can also be prepared according to a preparation method including the following steps:

[0197] S13: Provide a negative electrode current collector, and perform a film-forming treatment on one surface of the negative electrode slurry to form a first negative electrode active material layer;

[0198] S14: Along the direction from the other surface of the negative electrode current collector to the first negative electrode active material layer, a first through hole is opened on the other surface of the negative electrode current collector, such that the first through hole at least penetrates the negative electrode current collector;

[0199] S15: Another portion of negative electrode slurry is applied to the other surface of the negative electrode current collector to form a second negative electrode active material layer, and the second negative electrode active material layer extends into the first through hole to prepare a negative electrode sheet.

[0200] The above-mentioned method for preparing the negative electrode sheet can effectively open the first through hole on the negative electrode current collector, and allow the negative electrode active material layer to extend and fill the first through hole.

[0201] In steps S11 and S14, as some embodiments of this application, the method for forming the first through hole on the negative electrode current collector can employ laser drilling. Using laser drilling can effectively improve the size of the first through hole and the accuracy of its distribution on the surface of the negative electrode current collector, and can also reduce burr generation, thereby improving the quality and safety performance of the negative electrode sheet. Of course, other mechanical methods can also be used to form the first through hole. Furthermore, by first forming a first negative electrode active material layer on one surface of the negative electrode current collector according to steps S13 to S15, then performing the first through-hole opening process, and then forming a second negative electrode active material layer on the other surface of the negative electrode current collector, on the one hand, the first through-hole is at least partially filled with negative electrode active material layer material, effectively preventing the negative electrode sheet from containing through-holes that penetrate the entire negative electrode sheet, thereby improving the structural stability of the negative electrode sheet during cycling and mitigating the collapse of the negative electrode active material layer around the first through-hole contained in the negative electrode sheet; on the other hand, the capacity of the negative electrode sheet is increased by at least partially filling the first through-hole with negative electrode active material layer material; finally, compared with forming negative electrode active material layers on both surfaces of the negative electrode current collector first and then opening through-holes, energy consumption can be saved and the cost of the negative electrode sheet can be reduced.

[0202] Furthermore, the first through-hole opened in step S14 can at least penetrate the negative electrode current collector, or it can extend into the first negative electrode active material layer in step S13, or further penetrate the first negative electrode active material layer. When it penetrates the first negative electrode active material layer, the negative electrode sheet structure prepared in step S15 can be as follows: Figure 2 The negative electrode structure shown is as follows.

[0203] In steps S12, S13, and S15, the method for forming a film of the negative electrode slurry on the surface of the negative electrode current collector can be performed using conventional film-forming methods. During the film-forming process, the negative electrode slurry has a certain fluidity. In steps S12 and S15, the negative electrode slurry flows into the first through-hole, or a certain external force is applied to the negative electrode slurry to increase the filling rate, filling amount, and filling depth of the negative electrode slurry into the first through-hole. At the same time, the extension of the first through-hole into the negative electrode active material layer can be controlled.

[0204] In some embodiments, the negative electrode slurry in steps S12, S13, and S15 contains a mixture of carbon-based and silicon-based materials as the negative electrode active material. In these embodiments, the compaction density of the carbon-based and silicon-based material mixture is 1.4–1.6 g / cm³. 3In the embodiments, silicon-based materials account for 1% to 50% of the total mass of carbon-based and silicon-based materials, optionally at proportions of 1% to 10%, 10% to 25%, and 25% to 50%. Controlling the compaction density of the carbon-based and silicon-based material mixture within this range and / or controlling the silicon-based material content within this range effectively improves the specific capacity of the negative electrode and alleviates the volume expansion rate of the negative electrode active material layer during charging and discharging. This, combined with the first through-hole opened in the negative electrode current collector, effectively alleviates the volume expansion of the electrode assembly during charging and discharging and relieves the internal stress of the electrode assembly, thereby improving the overall wetting efficiency of the electrode assembly.

[0205] In some embodiments, a pore-forming agent is also added to the negative electrode slurry in step S12. By adding a pore-forming agent to the negative electrode slurry, a porous structure can be formed in the negative electrode active material layer during or after the film-forming process, after the pore-forming agent is removed. This porous structure, together with the first through-hole in the negative electrode current collector, improves the electrolyte wetting path of the electrode assembly. Simultaneously, this porous structure, together with the first through-hole, provides buffer space for the volume expansion of the negative electrode active material layer, reducing the volume expansion of the electrode assembly, lowering the internal stress of the electrode assembly, and improving the overall wetting efficiency of the electrode assembly.

[0206] In the embodiments, when a pore-forming agent is added to the negative electrode slurry, the mass content of the pore-forming agent in the negative electrode slurry can be 0.5% to 2%, optionally 0.7% to 1.4%. In exemplary cases, it can be typical but non-limiting contents such as 0.5%, 0.7%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.8%, and 2%, or any range between two such contents. This range of added pore-forming agent can control the porosity of the negative electrode active material layer within the porosity range of the negative electrode active material layer contained in the negative electrode sheet of the battery cell in the embodiments of the above application.

[0207] In the example, the pore-forming agent can be a soluble salt, such as, but not limited to, chloride salts and nitrates. The chloride salt can include, but is not limited to, at least one of sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl), and magnesium chloride (MgCl); the nitrate salt can include sodium nitrate (NaNO3), potassium nitrate (KNO3), and magnesium nitrate (Mg(NO3)2). These soluble salts can be dissolved and removed by placing the prepared negative electrode sheet in an aqueous solution, thereby forming a porous structure in the negative electrode active material layer. Of course, the pore-forming agent can also be a thermally decomposable compound, such as, but not limited to, NH4C2O4.

[0208] In some embodiments, the positive electrode sheet is prepared according to a preparation method including the following steps:

[0209] S16: Provides a positive current collector, and a second through hole is provided on the positive current collector, so that the second through hole penetrates two oppositely arranged surfaces of the positive current collector;

[0210] S17: The positive electrode slurry is subjected to a film-forming treatment on at least one surface of the positive electrode current collector to form a positive electrode active material layer, and at least one positive electrode active material layer extends into the second through hole to prepare a positive electrode sheet.

[0211] In some embodiments, the positive electrode sheet can also be prepared according to a preparation method including the following steps:

[0212] S18: Provides a positive electrode current collector, and performs a film-forming treatment on one surface of the positive electrode slurry to form a first positive electrode active material layer;

[0213] S19: Along the direction from the other surface of the positive electrode current collector to the first positive electrode active material layer, a second through hole is opened on the other surface of the positive electrode current collector, such that the second through hole at least penetrates the positive electrode current collector;

[0214] S110: Another portion of positive electrode slurry is film-formed on the other surface of the positive electrode current collector to form a second positive electrode active material layer, and the second positive electrode active material layer extends into the second through hole to prepare a positive electrode sheet.

[0215] This method can effectively create a second through hole on the positive electrode current collector, and allow the positive electrode active material layer to extend and fill the second through hole.

[0216] In steps S16 and S19, in the embodiment, the method of opening a second through hole on the positive current collector can refer to the method of opening a first through hole on the negative current collector in step S11, such as, but not limited to, using laser drilling.

[0217] In steps S17, S18, and S110, the method for forming a film of the positive electrode slurry on the surface of the positive electrode current collector can be performed using conventional film formation methods. During the film formation process, the positive electrode slurry has a certain fluidity. In steps S17 and S110, the positive electrode slurry flows into the second through-hole, or a certain external force is applied to the negative electrode slurry to increase the filling rate, filling amount, and filling depth of the positive electrode slurry into the second through-hole. At the same time, the extension of the second through-hole into the positive electrode active material layer can be controlled.

[0218] In addition, the positive electrode slurry can be prepared in accordance with conventional positive electrode slurry formulations.

[0219] [Battery Device]

[0220] Thirdly, embodiments of this application also provide a battery device. The battery device of this application includes the battery cell described in the above-described embodiments or the battery cell prepared by the method described in the above-described embodiments. Because the battery device includes the battery cell described in the above-described embodiments, the battery device of this application has a good cycle life and improved energy density.

[0221] 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.

[0222] In some embodiments, the battery device of this application may include any one of a battery cell, a battery module, or a battery pack.

[0223] When the battery device in this application embodiment includes a battery module, the battery module includes the battery cells described in the above application embodiment. The battery module may contain multiple of the above-described battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0224] In some embodiments, Figure 4 This is a schematic diagram of battery module 20 as an example. (See diagram for example.) Figure 4 As shown, in the battery module 20, multiple battery cells 10 can be arranged sequentially along the length of the battery module 20. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 10 can be fixed in place using fasteners.

[0225] Optionally, the battery module 20 may also include a housing with a receiving space in which multiple battery cells 10 are received.

[0226] When the battery in this application embodiment includes a battery pack, the battery pack refers to the assembly of battery cells from the above-described application embodiments, that is, it may contain multiple battery cells from the above-described application embodiments, and multiple battery cells are assembled into a battery module. The specific number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0227] In some embodiments, Figure 5 This is a schematic diagram of a battery pack 30 as an example. The battery pack 30 may include a battery compartment and multiple battery modules 20 disposed within the battery compartment. The battery compartment includes an upper compartment 31 and a lower compartment 32. The upper compartment 31 covers the lower compartment 32, forming a closed space for accommodating the battery modules 20. The multiple battery modules 20 can be arranged in any manner within the battery compartment.

[0228] [Energy Storage Device]

[0229] Fourthly, embodiments of this application provide an energy storage device. The energy storage device of this application includes a single battery cell or a battery device as described in the previous application embodiments, wherein the single battery cell or the battery device is used to store or provide electrical energy. Based on the use of the single battery cell or battery device of this application embodiment, the energy storage device of this application embodiment can safely and sustainably perform energy storage operations.

[0230] This application provides an energy storage device including one or more battery clusters to increase the voltage and capacity of the energy storage device. The battery cluster may include multiple battery devices, which are connected in series via a busbar to increase the voltage of the energy storage device. When the energy storage device includes multiple battery clusters, the multiple battery clusters are connected in parallel to increase the capacity of the energy storage device.

[0231] Energy storage devices can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems. Energy storage devices can store electrical energy as needed and output it when appropriate. For example, an energy storage device can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours. The energy storage system provided in this application embodiment can be any power system that requires energy storage devices.

[0232] In some embodiments, the energy storage device is an energy storage container or an energy storage cabinet.

[0233] In some embodiments, the energy storage device may include a cabinet and one or more battery clusters housed within the cabinet.

[0234] In some embodiments, the energy storage device may include modules such as a thermal management module, a main control module, a central control module, a power distribution module, and a fire protection module.

[0235] As an example, the thermal management module may include a liquid cooling unit that supplies coolant to each battery device via piping to regulate the temperature of the individual battery cells.

[0236] As an example, the main control module can serve as the battery management unit for the battery cluster, used to monitor and manage the battery cluster. The main control module can monitor information such as the current, voltage, power, or temperature of the battery cluster. For instance, it can control the charging and discharging current and voltage of the battery cluster. The main control module includes modules such as an auxiliary battery management unit (SBMU) and a fusion switch.

[0237] As an example, the central control module can serve as the battery management unit for an energy storage device, used to monitor and manage the device. The central control module can monitor information such as the energy storage device's current, voltage, power, state of charge, or temperature. For instance, it can control the charging and discharging current and voltage of the energy storage device. As an example, the central control module includes modules such as an Insulation Monitoring Module (IMM), a Master Battery Management Unit (MBMU), an Ethernet (ETH) module, and a fiber optic conversion module.

[0238] As an example, the fire protection module includes a control panel, detectors, alarm devices, etc., used to detect, alarm, or extinguish fires in the energy storage system.

[0239] As an example, a power distribution module can be used to distribute power to modules in an energy storage device that require electricity.

[0240] [Electrical appliances]

[0241] Fifthly, embodiments of this application also provide an electrical device. The electrical device of this application includes a power supply unit or an energy storage unit, and may also include other auxiliary or necessary components. The power supply unit or energy storage unit contains a battery cell, a battery device, and an energy storage device as described in the above-described application embodiments. The battery cell or battery device is used to store or provide electrical energy.

[0242] Based on the battery cells, battery devices, or energy storage devices used in the embodiments of this application, the electrical devices of the embodiments of this application can operate safely and for a long time.

[0243] Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, portable devices, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric vehicles, electric toys, power tools, etc.), electric trains, ships, satellites and spacecraft, energy storage systems, etc. The type of electrical device can be selected from individual battery cells, battery modules, or battery packs according to its usage requirements.

[0244] Figure 6 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0245] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0246] [Example]

[0247] 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.

[0248] 1. Example of a single battery cell:

[0249] Example 1:

[0250] This embodiment 1 provides a lithium-ion battery cell, each lithium-ion battery cell including an outer packaging, an electrode assembly encapsulated within the cavity of the outer packaging, and an electrolyte wetting the electrode assembly. The electrode assembly includes a positive electrode, a separator, a phase change heat absorption layer, and a negative electrode, and the positive electrode, separator, phase change heat absorption layer, and negative electrode are sequentially stacked from the positive electrode to the negative electrode. The negative electrode includes a negative current collector with two opposing surfaces and a negative active material layer stacked on both surfaces of the negative current collector; the negative current collector has through holes (defined as first through holes), and the negative active material in the sequential layers of the negative electrode includes a mixture of graphite and elemental silicon. Specifically, the pore density of the through holes in the negative current collector, the cross-sectional area of ​​a single through hole, and the mass content of elemental silicon in the negative active material are shown in Table 1 below.

[0251] The preparation method of a lithium-ion battery cell includes the following steps:

[0252] S1. Preparation of the negative electrode:

[0253] S11. The negative electrode active material (a mixture of graphite and silicon), conductive carbon black, dispersant, and surfactant are mixed in an appropriate amount of water at a mass ratio of 98.1:0.5:1.1:0.3. At the same time, 1% of the slurry mass of NaCl soluble salt additive is added and stirred thoroughly to form a uniform upper negative electrode slurry. The solid content of the negative electrode slurry is 0.5 kg / kg (mass of solid matter / mass of slurry containing solvent).

[0254] The negative electrode active material (a mixture of graphite and silicon), conductive carbon black, dispersant, surfactant, and polyvinylidene fluoride (PVDF) binder were mixed in an appropriate amount of water at a mass ratio of 96.3:0.5:1.1:0.3:1.8. Simultaneously, 1% NaCl soluble salt additive (by mass of the slurry) was added and thoroughly stirred to form a uniform lower layer of negative electrode slurry. The solid content of the negative electrode slurry was 0.5 kg / kg (mass of solids / mass of slurry containing solvent).

[0255] S12. The lower negative electrode slurry prepared in step S11 is first coated onto one surface of a 6μm copper foil, and then the upper negative electrode slurry is coated onto the surface of the lower negative electrode slurry film. After drying, a laser is used to create a layer penetrating the copper foil and the negative electrode active material on the surface of the copper foil. Then, the lower negative electrode slurry is coated onto the other surface of the copper foil in the same way, followed by the upper negative electrode slurry. After drying again, the negative electrode sheet is obtained after cold pressing and slitting. The coating weight of the negative electrode slurry on the copper foil surface is 0.145g / 1540.25mm. 2 The compacted density of the negative electrode sheet after drying is 3.6 g / cm³. 3 ;

[0256] S2. Preparation of the positive electrode:

[0257] Ternary nickel-cobalt-manganese material (with nickel accounting for 92 wt%), conductive carbon black, polyvinylidene fluoride (PVDF) binder, and surfactant were thoroughly mixed in an appropriate amount of N-methylpyrrolidone solvent at a mass ratio of 98.04:0.8:0.9:0.26 to form a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of a 13 μm positive electrode current collector aluminum foil. After drying, cold pressing, and slitting, the positive electrode sheet was obtained. The solid content of the positive electrode slurry was 0.77 kg / kg (mass of solid matter / mass of slurry containing solvent), and the coating weight of the positive electrode slurry on the copper foil surface was 0.272 g / 1540.25 mm. 2 The compacted density of the positive electrode sheet after drying is 3.6 g / cm³. 3 ;

[0258] S3. Assembly of individual battery cells:

[0259] The negative electrode sheet prepared in step S1 and the positive electrode sheet prepared in step S2 are assembled with the separator into a cylindrical electrode assembly with a wound structure, then placed in an outer packaging, dried and injected with electrolyte. After vacuum sealing, standing, formation and shaping processes, lithium-ion cylindrical battery cells are obtained respectively.

[0260] The diaphragm is made of polyethylene (PE) substrate and contains ceramic coating (water-based boehmite slurry coating, CCS) coating and polymer coating (PCS) coating.

[0261] The lithium salt in the electrolyte is lithium hexafluorophosphate (LiPF6), and the solvent includes ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a 5:5 mass ratio.

[0262] Examples 2 to 13:

[0263] Examples 2 to 13 and Comparative Example 1 each provide a lithium-ion battery cell. The structure of each lithium-ion battery cell is the same as that of the battery cell in Example 1. The difference between the lithium-ion battery cell in Example 1 and the lithium-ion battery cell in Example 2 to 9 is that the negative electrode is different. The negative electrode contained in the lithium-ion battery cells of each example is shown in Table 1 below.

[0264] In particular, the positive electrode sheet contained in the lithium-ion battery cell in Examples 10 to 13 is different from that in Example 1. Specifically, the positive electrode sheet contained in the lithium-ion battery cell in Examples 10 to 13 has a second through hole on the aluminum foil positive electrode current collector. The pore density and cross-sectional area of ​​the second through hole are shown in Table 1 for Examples 10 to 13.

[0265] Comparative Example 1:

[0266] Comparative Example 1 provides a lithium-ion battery cell that differs from the lithium-ion battery cell in Example 1 in that the copper foil current collector of the negative electrode in the lithium-ion battery cell in Comparative Example 1 does not have a first through hole.

[0267] 2. Performance testing of positive and negative electrode plates:

[0268] 2.1 Method for detecting the percentage of the total cross-sectional area of ​​the copper foil with the first through-hole in the negative electrode and the aluminum foil with the second through-hole in the positive electrode (denoted as the through-hole distribution density):

[0269] CCD camera calculation method: Record the ratio of the through-hole area to the unit area of ​​the electrode sheet;

[0270] Distribution density (%) of the first and second through holes = Cross-sectional area of ​​the through holes (obtained by CCD camera) / Unit area of ​​the current collector on one side.

[0271] 2.2 Method for detecting the porosity of the negative electrode active material layer in the negative electrode sheet:

[0272] The porosity of the negative electrode active material layer was detected using an AccuPycⅡ1340 characterization instrument with nitrogen or helium (purity ≥99.995%) as the medium gas, in accordance with the standard method of GB / T 24586-2009.

[0273] Porosity = Sample pore volume V1 / Total sample volume V2; where V1 is obtained using an AccuPycⅡ1340 instrument (based on Bohr's law PV = nRT), and V2 is the total external volume of the electrode (generally, small circular pieces are cut, and the cylindrical volume formula is used for calculation).

[0274] The performance test results of the positive and negative electrodes in each embodiment are shown in Table 1 below:

[0275] Table 1

[0276]

[0277] 3. Electrochemical performance testing of individual ion battery cells in each embodiment:

[0278] The ion battery cells provided in Examples 1 to 13 and Comparative Example 1 were subjected to the relevant electrochemical performance tests listed in Table 2 below, using the methods described below. The results are shown in Table 2. Table 2 lists the relevant performance testing methods for the ion battery cells.

[0279] Energy density detection method: First, obtain the discharge capacity and voltage plateau using a charge-discharge machine; then, obtain the total volume of the cylindrical cell casing according to the design, and the ratio is the volumetric energy density.

[0280] Volumetric energy density = voltage plateau × cell discharge capacity / (3.14 × diameter of cylinder base × diameter of cylinder base × height of cylinder shell).

[0281] Methods for testing cycle count and capacity retention:

[0282] Capacity calibration at 25℃: 1 / 3C charging rate, full charge; 1 / 3C discharging rate, full discharge; repeat three times, and record the discharge capacity of the third discharge as the rated discharge capacity Cn.

[0283] Cycling at 25℃: 0.33Cn charge and discharge, charge and discharge range from 0-100% SOC, voltage range from 2.5-4.25V; rest at 25℃ for 30min, then charge at 0.33Cn with constant current and constant voltage to 4.25V; after resting for 30min, discharge at 0.33Cn with constant current to 2.5V; after resting for 30min, repeat the above charge and discharge process, and record the capacity retention rate after 500 cycles.

[0284] Fast charging capability; time to charge from 10% to 80% under 4C conditions.

[0285] Table 2

[0286] Example Energy density (Wh / L) Capacity retention rate (%) Fast charging capability (min) Example 1 730 92.2 21 Example 2 735 94.0 20 Example 3 737 94.5 19 Example 4 740 93 18 Example 5 728 92.6 22 Example 6 722 90.8 23 Example 7 725 91.8 21 Example 8 750 91.6 20 Example 9 760 91.2 19 Example 10 740 94.4 18 Example 11 745 95.0 18 Example 12 748 95.2 18 Example 13 752 94.4 18 Comparative Example 1 720 90.2 25

[0287] As can be seen from the data in Table 2, comparing Examples 1 to 6, it can be seen that as the density of the first through-hole distribution in the negative electrode gradually increases, the energy density of the lithium-ion battery shows a gradual increasing trend. This is because the higher the density of the first through-hole distribution in the negative electrode, the more capacity space is provided for the negative electrode active material layer material, thereby increasing the energy density of the lithium-ion battery.

[0288] Comparing Examples 1 to 6, it can be seen that as the density of the first through-hole distribution in the negative electrode gradually increases, the capacity retention and fast-charging capability of the lithium-ion battery show an increasing trend, as seen in Examples 3 to 6. However, as the density of the first through-hole distribution in the negative electrode continues to increase, the capacity retention and fast-charging capability of the lithium-ion battery show a decreasing trend. For example, the capacity retention and fast-charging capability of the lithium-ion battery in Example 2 are lower than those in Example 3, and the capacity retention and fast-charging capability of the lithium-ion battery in Example 1 are lower than those in Example 2. This is because as the density of the first through-hole distribution in the negative electrode continues to increase, the risk of collapse of the negative electrode active material layer during charging and discharging increases, which may lead to a small portion of the negative electrode active material detaching from the substrate. This results in the capacity retention and fast-charging capability of the lithium-ion batteries in Examples 1 and 2 being lower than those in Example 3. Therefore, a total cross-sectional area ratio of 5% to 20% for the first through-hole can relatively improve the electrolyte wettability of the electrode components in the lithium-ion battery, thereby improving the cycle performance and fast-charging capability of the lithium-ion battery.

[0289] Comparing Examples 7 to 9, it can be seen that adjusting the negative electrode active material in the negative electrode active material layer according to the appropriate distribution density of the first through-hole can adjust the energy density of the lithium-ion battery, specifically by adjusting the content of silicon-based material.

[0290] Comparing Examples 10 to 12 with Example 5, it can be seen that by further providing a second through-hole on the positive electrode, in addition to the first through-hole on the negative electrode, the energy density, cycle performance, and fast-charging capability of the lithium-ion battery can be further improved. For example, the lithium-ion batteries in Examples 10 to 12 exhibit superior energy density, cycle performance, and fast-charging capability compared to those in Example 5.

[0291] Further comparison of Examples 10 to 12 shows that as the density of the second through-hole distribution in the positive electrode gradually increases within a certain range, the energy density of the lithium-ion battery shows an increasing trend, while the capacity retention initially increases and then decreases. For example, the capacity retention rate of the lithium-ion battery in Example 13 is lower than that in Example 12; however, the impact on fast charging capability is not significant.

[0292] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A single battery cell, characterized in that: The device includes a negative electrode sheet, which includes a negative electrode current collector. The negative electrode current collector has two surfaces disposed opposite to each other. A negative electrode active material layer is stacked on at least one of the surfaces. The negative electrode current collector has a plurality of first through holes penetrating the two surfaces, and at least one of the negative electrode active material layers extends into the first through hole.

2. The battery cell as described in claim 1, characterized in that: A first negative electrode active material layer is disposed on one surface of the negative electrode current collector, and a second negative electrode active material layer is disposed on the other surface; wherein, the first negative electrode active material layer extends into the first through hole, and the first through hole extends into the second negative electrode active material layer.

3. The battery cell as described in claim 2, characterized in that: The first through hole extends into and penetrates the second negative electrode active material layer.

4. The battery cell as described in claim 2 or 3, characterized in that: The first negative electrode active material layer extends into the first through hole and at least partially fills the first through hole extending into the second negative electrode active material layer.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The first through hole includes at least one of the following (1) to (4): (1) In the unit area of ​​the surface of the negative electrode current collector, the total cross-sectional area of ​​the first through hole accounts for 0.1% to 25% along the direction parallel to the surface; (2) Along the length direction of the negative electrode current collector, the distance between two adjacent first through holes is 1mm to 100mm; (3) Along the width direction of the negative electrode current collector, the distance between two adjacent first through holes is 1mm to 20mm; (4) Along the surface direction parallel to the negative electrode current collector, the cross-sectional area of ​​a single first through hole is 0.2 mm. 2 ~3.2mm 2 .

6. The battery cell according to any one of claims 1 to 5, characterized in that: The negative electrode active material in the negative electrode active material layer includes silicon-based material, and the silicon-based material accounts for 1% to 50% of the total mass of the negative electrode active material; and in the unit area of ​​the surface of the negative electrode current collector, the total cross-sectional area of ​​the first through hole accounts for 0.1% to 10% along the direction parallel to the surface.

7. The battery cell as described in claim 6, characterized in that: The silicon-based material accounts for 1% to 10% of the total mass of the negative electrode active material, and the total cross-sectional area of ​​the first through hole accounts for 0.1% to 2%.

8. The battery cell as described in claim 6, characterized in that: The silicon-based material accounts for 10% to 25% of the total mass of the negative electrode active material, and the total cross-sectional area of ​​the first through hole accounts for 2% to 5%.

9. The battery cell as described in claim 6, characterized in that: The silicon-based material accounts for 25% to 50% of the total mass of the negative electrode active material, and the total cross-sectional area of ​​the first through hole accounts for 5% to 10%.

10. The battery cell according to any one of claims 6 to 9, characterized in that: The silicon-based material includes one of elemental silicon, silicon-carbon composite materials, silicon-oxygen composite materials, and silicon-based alloy materials; and / or The negative electrode active material further includes a carbon-based material, which is mixed and distributed with the silicon-based material in the negative electrode active material layer, and the carbon-based material accounts for 1% to 50% of the total mass of the negative electrode active material.

11. The battery cell as described in claim 10, characterized in that: The carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fiber.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The negative electrode active material layer has a porous structure, and the porosity of the negative electrode active material layer is 10% to 40%; or / and The negative electrode active material layer is provided with a porous structure, and the pore size of the negative electrode active material layer is 0.2 μm to 2 μm; or / and The dry basis weight of the negative electrode active material layer on one surface of the negative electrode sheet is 1.4–1.8 g / 1540.25 mm. 2 .

13. The battery cell according to any one of claims 1 to 12, characterized in that: The positive electrode current collector contained in the positive electrode sheet of the battery cell has two surfaces arranged opposite to each other. The positive electrode current collector has a plurality of second through holes penetrating the two surfaces. A positive electrode active material layer is stacked on at least one of the surfaces of the positive electrode current collector.

14. The battery cell as described in claim 13, characterized in that: The positive electrode active material layer extends into the second through-hole; or / and A first positive electrode active material layer is disposed on one surface of the positive electrode current collector, and a second positive electrode active material layer is disposed on the other surface; wherein, the first positive electrode active material layer extends into the second through hole, and the second through hole extends into the second positive electrode active material layer.

15. The battery cell as described in claim 14, characterized in that: The second through-hole extends into and penetrates the second positive electrode active material layer; and / or The first positive electrode active material layer extends into the second through hole and at least partially fills the second through hole in the second intermediate electrode active material layer.

16. The battery cell according to any one of claims 13 to 15, characterized in that: The second through hole includes at least one of the following (1) to (4): (1) Along the length direction of the positive current collector, the spacing between two adjacent second through holes is 1mm to 100mm; (2) Along the width direction of the positive current collector, the spacing between two adjacent second through holes is 1mm to 20mm; (3) Along the surface direction parallel to the positive current collector, the cross-sectional area of ​​a single second through hole is 0.2 mm. 2 ~3.2mm 2 ; (4) In the unit area of ​​the surface of the positive current collector, the total cross-sectional area of ​​the second through hole along the direction parallel to the surface of the positive current collector accounts for 1% to 15%.

17. The battery cell according to any one of claims 13 to 16, characterized in that: The porosity of the positive electrode active material layer is 15% to 20%.

18. The battery cell according to any one of claims 1 to 17, characterized in that: The electrolyte contained in the battery cell includes at least one of the following (1) to (3): (1) The electrolyte comprises additives of the following components in weight percentage: Ethylene carbonate: 40wt%~70wt%; Ethyl methyl carbonate: 20wt%~50wt%; Fluorinated ethylene carbonate: 5wt%~15wt%; (2) The conductivity of the electrolyte is 9mS / cm≤σ≤15mS / cm, or 5mS / cm≤σ<9mS / cm; (3) The actual density of the electrolyte is 1.01 g / cm³. 3 ~1.38g / cm 3 .

19. The battery cell according to any one of claims 1 to 18, characterized in that: The battery cell includes cylindrical battery cells.

20. A method for preparing a single battery cell, characterized in that, Includes the following steps: The negative electrode, separator, and positive electrode are assembled into an electrode assembly; The electrode assembly is encapsulated within the cavity of the outer packaging to form a single battery cell; The negative electrode sheet includes a negative electrode current collector, which has two surfaces arranged opposite to each other. A negative electrode active material layer is stacked on at least one of the surfaces. The negative electrode current collector has a plurality of first through holes penetrating the two surfaces, and the negative electrode active material layer extends into the first through holes.

21. The preparation method according to claim 20, characterized in that, The method for preparing the negative electrode sheet includes the following steps: A negative electrode current collector is provided, and a first through hole is formed on the negative electrode current collector, such that the first through hole penetrates two oppositely disposed surfaces of the negative electrode current collector; The negative electrode slurry is subjected to a film-forming treatment on at least one surface of the negative electrode current collector to form a negative electrode active material layer, and at least one of the negative electrode active material layers extends into the first through hole to prepare the negative electrode sheet.

22. The preparation method according to claim 20, characterized in that, The method for preparing the negative electrode sheet includes the following steps: A negative electrode current collector is provided, and a negative electrode slurry is subjected to a film-forming treatment on one surface of the negative electrode current collector to form a first negative electrode active material layer; Along the direction from the other surface of the negative electrode current collector to the first negative electrode active material layer, the first through hole is opened on the other surface of the negative electrode current collector, such that the first through hole at least penetrates the negative electrode current collector; Another portion of negative electrode slurry is subjected to a film-forming treatment on the other surface of the negative electrode current collector to form a second negative electrode active material layer, and the second negative electrode active material layer extends into the first through hole to prepare the negative electrode sheet.

23. The preparation method according to claim 21 or 22, characterized in that: The negative electrode slurry includes a pore-forming agent, the pore-forming agent having a mass content of 0.5% to 2% in the negative electrode slurry; and / or The negative electrode slurry contains negative electrode active materials including carbon-based materials and silicon-based materials, and the compaction density of the mixture of the carbon-based materials and the silicon-based materials is 1.4 to 1.6 g / cm³. 3 ; and / or, the silicon-based material accounts for 1% to 50% of the total mass of the carbon-based material and the silicon-based material.

24. The preparation method according to any one of claims 20 to 23, characterized in that: The method for preparing the positive electrode sheet includes the following steps: A positive current collector is provided, and a second through hole is formed in the positive current collector, such that the second through hole penetrates two oppositely disposed surfaces of the positive current collector; The positive electrode slurry is subjected to a film-forming treatment on at least one surface of the positive electrode current collector to form a positive electrode active material layer, and at least one of the positive electrode active material layers extends into the second through hole to prepare a positive electrode sheet.

25. The preparation method according to any one of claims 20 to 23, characterized in that, The method for preparing the positive electrode sheet includes the following steps: A positive electrode current collector is provided, and a positive electrode slurry is film-formed on one surface of the positive electrode current collector to form a first positive electrode active material layer; A second through hole is formed on the other surface of the positive electrode current collector along the direction from the first positive electrode active material layer, such that the second through hole at least penetrates the positive electrode current collector; Another portion of the positive electrode slurry is subjected to a film-forming treatment on the other surface of the positive electrode current collector to form a second positive electrode active material layer, and the second positive electrode active material layer extends into the second through hole to prepare the positive electrode sheet.

26. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1 to 19 or the battery cell prepared by the preparation method described in any one of claims 20 to 25.

27. An energy storage device, characterized in that, Includes a battery cell as described in any one of claims 1 to 19 or a battery device as described in claim 26, wherein the battery cell or the battery device is used to store or provide electrical energy.

28. An electrical appliance, characterized in that, It includes a battery cell according to any one of claims 1 to 19, a battery device according to claim 26, or an energy storage device according to claim 27, wherein the battery cell or the battery device is used to store or provide electrical energy.

Images