Battery monomer, battery device and electric equipment

Abstract

The invention relates to a battery monomer, a battery device and electric equipment, and provides a battery monomer with relatively high safety performance. The battery monomer comprises a negative pole piece, the negative pole film layer is arranged on at least one side surface of the positive pole current collector, the negative pole film layer comprises a silicon-based material, at least one first groove which is sunken in the direction close to the negative pole current collector is formed in the side surface, away from the negative pole current collector, of the negative pole film layer, and the first groove extends in the first direction; the first direction is perpendicular to the thickness direction of the negative pole piece.

Description

Technical Field

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

[0002] With increasing environmental pollution, the new energy industry is attracting more and more attention. Within the new energy industry, battery technology is a crucial factor in its development.

[0003] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, safety, and reliability. The design of the negative electrode in a battery cell has a crucial impact on the cell's performance; therefore, providing a battery cell with high safety performance is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell with higher safety performance.

[0005] To achieve the above objectives, this application provides a battery cell, a battery device, and an electrical appliance.

[0006] In a first aspect, a battery cell is provided, comprising: a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer, the negative electrode film layer being disposed on at least one side surface of the negative current collector, the negative electrode film layer comprising a silicon-based material, and the side surface of the negative electrode film layer away from the negative current collector being provided with at least one first groove recessed in a direction close to the negative current collector, the first groove extending along a first direction, the first direction being perpendicular to the thickness direction of the negative electrode sheet.

[0007] In this embodiment, the negative electrode film layer of the negative electrode sheet includes a silicon-based material. Therefore, a first groove is provided on the surface of the negative electrode film layer away from the negative electrode current collector. The first groove can provide a certain expansion space for the silicon expansion in the negative electrode film layer, reduce the overall expansion force of the negative electrode sheet, reduce the risk of the negative electrode sheet breaking due to expansion, and improve the safety performance of the battery cell.

[0008] In one possible implementation, the negative electrode film layer includes: a first coating layer comprising a first negative electrode active material, the first negative electrode active material comprising a carbon material; a second coating layer comprising a second negative electrode active material, the second negative electrode active material comprising a silicon-based material; and a third coating layer comprising a third negative electrode active material, the third negative electrode active material comprising a carbon material, wherein at least one first groove is provided on the surface of the third coating layer on the side away from the negative electrode current collector; wherein, in a second direction, the first coating layer, the second coating layer, and the third coating layer are sequentially stacked in a direction away from the negative electrode current collector, the second direction being the thickness direction of the negative electrode sheet.

[0009] In this embodiment, the negative electrode film of the negative electrode sheet is configured with a three-layer structure. Specifically, the first coating near the negative electrode current collector and the third coating away from the negative electrode current collector respectively comprise carbon materials, and the middle second coating comprises silicon-based materials. By configuring the negative electrode film layer with the above-mentioned three-layer structure, the problem of negative electrode film layer peeling and cracking caused by silicon expansion in the negative electrode film layer during battery charging and discharging is improved. At the same time, the direct contact between the silicon-based material and the electrolyte at the interface is reduced, and the side reactions between the silicon-based material and the electrolyte are reduced, thereby improving the cycle performance and safety performance of the battery. In addition, the setting of the first groove can also increase the contact area between the surface of the third coating layer and the electrolyte, thereby reducing the solid-phase transport of lithium ions, improving ionic conductivity, improving the rate performance of the battery, and the groove can accommodate and store a certain amount of electrolyte, thereby improving the electrolyte wettability of the negative electrode sheet and extending the battery's service life.

[0010] In one possible implementation, the second negative electrode active material comprises a silicon-based material and a carbon material, wherein, based on the total mass of the second coating, the mass percentage P1 of the silicon-based material satisfies: 10% ≤ P1 ≤ 80%.

[0011] Setting the content of silicon-based material in the second coating within the above-mentioned range can effectively improve the specific capacity of the battery.

[0012] In one possible implementation, the first negative electrode active material further includes a silicon-based material, wherein the mass percentage P2 of the silicon-based material, based on the total mass of the first coating, satisfies: P2 ≤ 10%.

[0013] The negative electrode active material of the first coating includes silicon-based materials, which can improve the specific energy of the battery. At the same time, setting the content of silicon-based materials in the first coating within the above-mentioned range can reduce the possibility of the first coating debonding from the negative electrode current collector due to the expansion of silicon-based materials.

[0014] In a possible implementation, the third negative electrode active material further includes a silicon-based material. Based on the total mass of the third coating, the mass percentage P3 of the silicon-based material satisfies: P3 ≤ 10%.

[0015] The negative electrode active material of the third coating includes a silicon-based material, which can improve the specific energy of the battery. At the same time, setting the content of the silicon-based material in the third coating within the above range can reduce the possibility of side reactions occurring due to the direct contact between the silicon-based material in the third coating and the electrolyte.

[0016] In a possible implementation, in the second direction, the ratio A of the size of the first groove to the size of the third coating satisfies: 0 < A ≤ 1.

[0017] In a possible implementation, the size L of the first groove in the third direction satisfies: 0 < L < 60 mm, and the third direction is perpendicular to the first direction and the second direction.

[0018] In the embodiments of the present application, setting the size L of the first groove in the third direction within the above range can not only provide sufficient expansion space for the negative electrode sheet but also ensure the overall structural integrity of the third coating and reduce the possibility of the third coating peeling off.

[0019] In a possible implementation, a plurality of the first grooves arranged along the third direction are provided on the surface of the third coating away from the negative electrode current collector. Among the plurality of the first grooves, the distance D between two adjacent first grooves satisfies: 0 < D < 60 mm.

[0020] In the embodiments of the present application, setting the distance between two adjacent first grooves within the above range can not only effectively improve the expansion force of the negative electrode sheet but also prevent the distance between two adjacent first grooves from being too small, resulting in the connection of adjacent first grooves when the negative electrode sheet expands and affecting the overall structural stability of the third coating.

[0021] In a possible implementation, the negative electrode sheet is wound along the winding direction to form a wound structure. The wound structure includes a flat area and bending areas provided on both sides of the flat area. At least one of the first grooves is provided on the surface of the third coating in the bending areas away from the negative electrode current collector.

[0022] In the embodiments of the present application, when the negative electrode sheet is wound into a wound structure, at least one of the first grooves is provided on the surface of the third coating in the bending areas away from the negative electrode current collector, so that the wound structure has a certain expansion space in the bending areas, reduces the expansion force in the bending areas, and reduces the risk of the negative electrode sheet breaking due to stress concentration in the bending areas.

[0023] In one possible implementation, the surface of the first coating away from the negative electrode current collector is provided with at least one second groove recessed in the direction close to the negative electrode current collector.

[0024] On the one hand, the second groove can provide more space for the expansion of silicon in the negative electrode film, reducing the overall expansion force of the negative electrode sheet and lowering the risk of the negative electrode sheet breaking due to expansion. On the other hand, the second groove can also increase the contact area between the inside of the negative electrode sheet and the electrolyte, thereby reducing the solid-phase transport of lithium ions, improving ionic conductivity, and improving the rate performance of the battery. In addition, the second groove can hold and store a certain amount of electrolyte, further improving the electrolyte wettability of the negative electrode sheet and extending the battery's lifespan.

[0025] In one possible implementation, in the second direction, the ratio B of the size of the second groove to the size of the first coating satisfies: 0 <B<1。

[0026] In this embodiment, the second groove is configured as a non-penetrating groove in the thickness direction of the negative electrode sheet, thereby avoiding the exposure of the surface of the negative electrode current collector at the second groove and reducing the risk of the negative electrode film layer falling off due to the reduced contact area between the negative electrode film layer and the negative electrode current collector.

[0027] In one possible implementation, the negative electrode sheet is wound along the winding direction to form a winding structure, the winding structure including a straight region and bending regions disposed on both sides of the straight region, and at least one second groove is provided on the side surface of the first coating of the bending region away from the negative electrode current collector.

[0028] In one possible implementation, the battery cell further includes a solid electrolyte that fills the first groove and / or the second groove.

[0029] In this embodiment, filling the first groove with solid electrolyte can reduce the possibility of direct contact between the silicon-based material of the second coating and the liquid electrolyte, thereby reducing the occurrence of side reactions. On the other hand, solid electrolyte has lithium-ion conductivity. Filling the first groove and / or the second groove with solid electrolyte can provide more ion transport paths when the liquid electrolyte is insufficient in the later stages of cycling, avoiding battery capacity decay caused by the "break-bridge" of lithium-ion pathways due to insufficient electrolyte, and improving charge / discharge rate performance and cycle life.

[0030] In one possible implementation, the solid electrolyte includes at least one of oxide electrolytes, sulfide electrolytes, and polymer electrolytes.

[0031] In one possible implementation, the oxide electrolyte includes at least one of lithium garnet oxide, tin oxide, and bismuth oxide; the sulfide electrolyte includes at least one of lithium sulfide and sodium sulfide; the polymer electrolyte includes a polymer and a lithium salt, wherein the polymer includes at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate, and the lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiBF4, LiClO4, and LiAlCl4.

[0032] In one possible implementation, the silicon-based material includes at least one of elemental silicon, silicon-carbon composites, silicon oxides, silicon-nitrogen composites, and silicon alloys.

[0033] In one possible implementation, the carbon material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microspheres.

[0034] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

[0035] Thirdly, an electrical device is provided, comprising a battery cell in the first aspect and any possible implementation thereof, or a battery device in the second aspect, wherein the battery cell or the battery device is used to store or provide electrical energy.

[0036] In one possible implementation, the electrical equipment includes vehicles, ships, or spacecraft. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application;

[0039] Figure 2 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application;

[0040] Figure 3 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application;

[0041] Figure 4 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application;

[0042] Figure 5This is a schematic diagram of a battery cell according to an embodiment of this application;

[0043] Figure 6 This is a schematic diagram of a battery device according to an embodiment of this application;

[0044] Figure 7 This is a schematic diagram of a vehicle according to an embodiment of this application. Detailed Implementation

[0045] Embodiments of the battery cell, battery device, and electrical appliance of this application have been described in detail with appropriate reference to the accompanying drawings; however, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application 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 description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0047] In this application, the reference to "embodiment" means that a specific 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 mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0048] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0049] 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, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0050] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0051] In this application, "multiple" refers to two or more (including two), and similarly, "multiple groups" refers to two or more (including two), and "multiple pieces" refers to two or more (including two).

[0052] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0054] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0055] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0056] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0057] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0058] In some embodiments, the battery cell in this application can be a metal battery. Specifically, the metal battery may include lithium metal secondary batteries, sodium metal batteries, or magnesium metal batteries, etc. This application does not limit this.

[0059] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During the charging and discharging process, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through.

[0060] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0061] In some embodiments, the positive electrode can be a positive electrode sheet, which can include a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0062] In some embodiments, the negative electrode may be a negative electrode sheet, which may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0063] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0064] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0065] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride, and ceramic.

[0066] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0067] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel-like, or solid.

[0068] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0069] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc. The housing includes a shell and end caps.

[0070] The battery mentioned in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0071] In some embodiments, the battery device may be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0072] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0073] In some embodiments, the battery device may be located within an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0074] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, charge / discharge rate, safety, and reliability. The negative electrode, as a crucial component of the battery cell, is a significant factor influencing its performance. For example, the negative electrode active material is a key factor affecting the specific energy of the battery cell, and the specific energy of the battery cell is closely related to the specific capacity of the negative electrode active material. Generally, the higher the specific capacity of the negative electrode active material, the better it is for improving the specific energy of the battery cell. Silicon-based materials, due to their high theoretical specific capacity, can achieve the goal of increasing the specific energy of the battery cell when used as negative electrode active materials. However, silicon-based materials undergo significant volume expansion during charging, and the resulting large expansion stress can damage the structure of the silicon-based material. This structural damage not only disrupts the electrical contact between silicon materials but may also cause the negative electrode film to detach from the negative electrode current collector, hindering the ion extraction and insertion processes. Furthermore, the irreversibility of ion extraction and insertion processes increases, reducing the initial charge / discharge efficiency of the battery cell and affecting its cycle performance and safety.

[0075] In view of this, this application provides a battery cell. The battery cell includes a negative electrode sheet, the negative electrode film layer of which is composed of a silicon-based material, and a first groove is provided on the surface of the negative electrode film layer on the side away from the negative electrode current collector. The first groove can provide a certain expansion space for the silicon expansion in the negative electrode film layer, reduce the overall expansion force of the negative electrode sheet, reduce the risk of the negative electrode sheet breaking due to expansion, and improve the safety performance of the battery cell.

[0076] The various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0077] [Battery cell]

[0078] This application provides a battery cell including a negative electrode sheet.

[0079] Figure 1 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application. For example, as shown... Figure 1 As shown, the negative electrode 1 includes a negative current collector 10 and a negative electrode film layer 11 disposed on at least one side surface of the negative current collector 10, the negative electrode film layer 11 comprising a silicon-based material.

[0080] The negative electrode current collector 10 has two opposing surfaces along its thickness direction. The negative electrode film layer 11 can be disposed on one surface of the negative electrode current collector 10 or on both surfaces. As an example, such as... Figure 1 As shown, the negative electrode film layer 11 is disposed on both sides of the negative electrode current collector 10.

[0081] like Figure 1 As shown, at least one first groove 1131 is provided on the surface of the negative electrode film layer 11 away from the negative electrode current collector 10, recessed in a direction close to the negative electrode current collector 10. The first groove 1131 extends in a first direction, which is perpendicular to the thickness direction of the negative electrode sheet 1. For example, the first direction is as follows: Figure 1 The x-direction is shown, and the second direction is as follows: Figure 1 The y-direction is shown below. For ease of description, the first direction will be referred to as the x-direction and the second direction as the y-direction. Figure 1 The example is illustrated by having four first grooves 1131 on the side of the negative electrode film layer 11 away from the negative electrode current collector 10, which does not constitute a limitation on the number of first grooves 1131 in the embodiments of this application.

[0082] In this embodiment, the negative electrode film 11 of the negative electrode sheet 1 includes a silicon-based material. Therefore, a first groove 1131 is provided on the surface of the negative electrode film 11 away from the negative electrode current collector 10. The first groove 1131 can provide a certain expansion space for the silicon expansion in the negative electrode film 11, reduce the overall expansion force of the negative electrode sheet 1, reduce the risk of the negative electrode sheet 1 breaking due to expansion, and improve the safety performance of the battery cell.

[0083] In some embodiments, such as Figure 2 As shown, the negative electrode film layer 11 includes a first coating layer 111, a second coating layer 112, and a third coating layer 113. In a second direction, the first coating layer 111, the second coating layer 112, and the third coating layer 113 are sequentially stacked along a direction away from the negative electrode current collector 10. In this embodiment, the second direction refers to the thickness direction of the negative electrode sheet 1.

[0084] Specifically, the first coating 111 includes a first negative electrode active material, which includes a carbon material; the second coating 112 includes a second negative electrode active material, which includes a silicon-based material; and the third coating 113 includes a third negative electrode active material, which includes a carbon material.

[0085] like Figure 2 As shown, at least one first groove 1131 is provided on the side surface of the third coating 113 away from the negative electrode current collector 10. Figure 2 The example is illustrated by having four first grooves 1131 on the side of the third coating 113 away from the negative electrode current collector 10, which does not constitute a limitation on the number of first grooves 1131 in the embodiments of this application.

[0086] In this embodiment, the negative electrode film 11 of the negative electrode sheet 1 includes three coatings: a first coating 111 close to the negative electrode current collector 10, a third coating 113 away from the negative electrode current collector 10, and a second coating 112 located between the first coating 111 and the third coating 113. The negative electrode active materials of the first coating 111 and the third coating 113 are respectively carbon materials, and the negative electrode active material of the second coating 112 is a silicon-based material. By setting the negative electrode film 11 to the above-mentioned three-layer structure, the problem of detachment and cracking of the negative electrode film 11 caused by silicon expansion in the negative electrode film 11 during the charging and discharging process of the battery is improved. At the same time, the direct contact between the silicon-based material and the electrolyte at the interface is reduced, and the side reactions between the silicon-based material and the electrolyte are reduced, thereby improving the cycle performance and safety performance of the battery. Meanwhile, the first groove 1131 can also increase the contact area between the surface of the third coating 113 and the electrolyte, thereby reducing the solid-phase transport of lithium ions, increasing ionic conductivity, and improving the rate performance of the battery. In addition, the groove can hold and store a certain amount of electrolyte, thereby improving the electrolyte wettability of the negative electrode 1 and extending the battery's service life.

[0087] In some embodiments, the second negative electrode active material includes silicon-based material and carbon material, wherein, based on the total mass of the second coating 112, the mass percentage P1 of the silicon-based material satisfies: 10% ≤ P1 ≤ 80%.

[0088] For example, P1 can be 10%, 20%, 30%, 40%, 45%, 50%, 65%, 70%, 75%, 80%, or a value within the range obtained by any combination of the above two values.

[0089] Setting the content of silicon-based material in the second coating 112 within the above-mentioned range can effectively improve the specific capacity of the battery.

[0090] In some embodiments, the first negative electrode active material further includes a silicon-based material, and the mass percentage P2 of the silicon-based material, based on the total mass of the first coating 111, satisfies: P2≤10%.

[0091] For example, P2 can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a value within the range obtained by any combination of the above two values.

[0092] The negative electrode active material of the first coating 111 includes silicon-based materials, which can improve the specific energy of the battery. At the same time, setting the content of silicon-based materials in the first coating 111 within the above-mentioned range can reduce the possibility of the first coating 111 debonding from the negative electrode current collector 10 due to the expansion of the silicon-based materials.

[0093] In some embodiments, the third negative electrode active material further includes a silicon-based material. Based on the total mass of the third coating 113, the mass percentage P3 of the silicon-based material satisfies: P2 ≤ 10%.

[0094] Exemplarily, P3 can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or its value is within the range obtained by combining any two of the above values.

[0095] The negative electrode active material of the third coating 113 includes a silicon-based material, which can improve the specific energy of the battery. At the same time, setting the content of the silicon-based material in the third coating 113 within the above range can reduce the possibility of side reactions occurring due to the direct contact between the silicon-based material in the third coating 113 and the electrolyte.

[0096] In some embodiments, as Figure 3 shown, in the y direction, the size of the first groove 1131 is H1, and the size of the third coating 113 is T1. The ratio A of H1 to T1 satisfies: 0 < A ≤ 1.

[0097] Exemplarily, A can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or its value is within the range obtained by combining any two of the above values.

[0098] In some embodiments, the size L of the first groove 1131 in the third direction satisfies: 0 < L < 60 mm. The third direction is perpendicular to the y direction and the x direction. For example, as Figures 1 to 3 shown in the z direction. For the convenience of description below, the third direction is described as the z direction.

[0099] Exemplarily, L can be 4 mm, 10 mm, 20 mm, 30, 40, 50, 55 mm, or its value is within the range obtained by combining any two of the above values.

[0100] In some embodiments, the size L of the first groove 1131 in the third direction satisfies: 0 < L < 0.5W, where W is the size of the battery cell in the z direction. Exemplarily, W can be 120 mm.

[0101] In the embodiments of the present application, setting the size L of the first groove 1131 in the z direction within the above range can not only provide sufficient expansion space for the negative electrode plate 1 but also ensure the overall structure of the third coating 113 and reduce the possibility of the third coating 113 falling off.

[0102] Exemplarily, the value of L can be determined according to the formula L = (1 - a)*W / n; where a represents the ratio of the expansion force of the battery cell provided with the first groove 1131 to the expansion force of the battery cell not provided with the first groove 1131, W represents the dimension of the battery cell in the z direction, and n represents the number of the first grooves 1131.

[0103] Specifically, during the preparation process of the negative electrode plate 1, a specific value of a can be preset, that is, the improvement degree of the expansion force of the battery cell after the first groove 1131 is provided relative to the expansion force of the battery cell not provided with the first groove 1131 is preset in advance, and then according to the simulation calculation, when the dimension of the battery cell in the z direction and the number of the first grooves 1131 are determined, the value of L is determined.

[0104] In some embodiments, a plurality of first grooves 1131 arranged along the z direction are provided on the surface of the third coating 113 away from the negative electrode current collector 10. Among the plurality of first grooves 1131, the distance D between two adjacent first grooves 1131 satisfies: 0 < D < 60 mm.

[0105] Exemplarily, D can be 6 mm, 9.3 mm, 20 mm, 30 mm, 40 mm, 50 mm, 55 mm, or its value is within the range obtained by combining any two of the above values.

[0106] In some embodiments, the distance D between two adjacent first grooves 1131 satisfies: 0 < D < 0.5W, where W is the dimension of the battery cell in the z direction. Exemplarily, W can be 120 mm.

[0107] It should be noted that in the embodiments of the present application, the distance between two adjacent first grooves 1131 refers to the distance between the two side walls of two adjacent first grooves 1131 that are close to each other in the z direction. For example, as Figure 3 shown.

[0108] In the embodiments of the present application, setting the distance between two adjacent first grooves 1131 within the above range can not only effectively improve the expansion force of the negative electrode plate 1, but also avoid the distance between two first grooves 1131 being too small, resulting in the connection of adjacent first grooves 1131 when the negative electrode plate 1 expands, affecting the overall structural stability of the third coating 113.

[0109] For example, the value of D can be determined according to the formula D = a * W / n. That is, during the preparation of the negative electrode 1, the spacing between adjacent first grooves 1131 is determined according to the size of the battery cell in the z direction, the ratio of the expansion force of the battery cell with the first groove 1131 to the expansion force of the battery cell without the first groove 1131, and the number of first grooves 1131, so that the spacing between adjacent first grooves 1131 is set within a suitable range.

[0110] In some embodiments, the negative electrode sheet 1 is wound along the winding direction to form a winding structure. The winding structure includes a straight region and a bending region disposed on both sides of the straight region. At least one first groove 1131 is disposed on the side surface of the negative electrode film layer 11 away from the negative electrode current collector 10 in the bending region.

[0111] In some embodiments, the negative electrode sheet 1 is wound along the winding direction to form a winding structure. The winding structure includes a straight region and a bending region disposed on both sides of the straight region. At least one first groove 1131 is provided on the side surface of the third coating 113 of the bending region away from the negative electrode current collector 10.

[0112] In this embodiment, when the negative electrode sheet 1 is wound into a wound structure, at least one first groove 1131 is provided on the side surface of the third coating 113 corresponding to the bending area away from the negative electrode current collector 10, so that the wound structure has a certain expansion space in the bending area, reducing the expansion force in the bending area and reducing the risk of the negative electrode sheet 1 breaking due to stress concentration in the bending area.

[0113] In some embodiments, such as Figure 4 As shown, the surface of the first coating 111 away from the negative electrode current collector 10 is provided with at least one second groove 1111 recessed in the direction close to the negative electrode current collector 10.

[0114] On the one hand, the second groove 1111 can provide a certain expansion space for the silicon expansion in the negative electrode film layer 11, reduce the overall expansion force of the negative electrode sheet 1, and reduce the risk of the negative electrode sheet 1 breaking due to expansion. On the other hand, the second groove 1111 can also increase the contact area between the inside of the negative electrode sheet 1 and the electrolyte, thereby reducing the solid phase transport of lithium ions, improving ionic conductivity, and improving the rate performance of the battery. In addition, the second groove 1111 can accommodate and store a certain amount of electrolyte, further improving the electrolyte wettability of the negative electrode sheet 1 and extending the battery's service life.

[0115] In some embodiments, the second groove 1111 extends along the x-direction.

[0116] In some embodiments, the second groove 1111 extends along the y direction.

[0117] In this embodiment of the application, the first groove 1131 and the second groove 1111 may extend in the same direction or in different directions.

[0118] For example, the first groove 1131 extends along the x-direction, and a plurality of first grooves 1131 are arranged along the z-direction; the second groove 1111 extends along the x-direction, and a plurality of second grooves 1111 are arranged along the z-direction.

[0119] For example, the first groove 1131 extends along the x-direction, and a plurality of first grooves 1131 are arranged along the z-direction; the second groove 1111 extends along the z-direction, and a plurality of second grooves 1111 are arranged along the x-direction.

[0120] In some embodiments, such as Figure 4 As shown, in the y-direction, the size of the second groove 1111 is H2, and the size of the first coating 111 is T2. The ratio B of H2 to T2 satisfies: 0 <B<1。

[0121] For example, B can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or a value within the range obtained by any combination of the above two values.

[0122] In this embodiment of the application, in the thickness direction of the negative electrode sheet 1, the second groove 1111 is set as a groove that does not penetrate the first coating 111, thereby avoiding the exposure of the surface of the negative electrode current collector 10 at the second groove 1111 and reducing the risk of corrosion of the negative electrode current collector 10.

[0123] In some embodiments, at least one second groove 1111 is provided on the side surface of the first coating 111 of the bending region away from the negative electrode current collector 10.

[0124] It should be noted that when at least one second groove 1111 is provided on the side surface of the first coating 111 away from the negative electrode current collector 10, since the side surface of the first coating 111 away from the negative electrode current collector 10 also needs to be coated with a second negative electrode active material to form a second coating, there is a possibility that the second groove 1111 may be partially filled.

[0125] In some embodiments, during the preparation of the negative electrode sheet, a foaming agent can be filled into the second groove, which decomposes and disappears at high temperature. For example, when the negative electrode sheet is heated and dried in an oven, the foaming agent will decompose and disappear, and there will be no foaming agent in the second groove of the dried negative electrode sheet. At this time, the first coating, the second coating and the third coating have been basically formed, which can reduce the possibility that the second groove 1111 is filled by the second negative electrode active material.

[0126] In some embodiments, the first groove and / or the second groove can be formed by laser cleaning.

[0127] In some embodiments, the battery cell further includes a solid electrolyte, which fills a first groove 1131 and / or a second groove 1111.

[0128] In this embodiment, filling the first groove 1131 with a solid electrolyte can reduce the possibility of direct contact between the silicon-based material of the second coating 112 and the electrolyte, thereby reducing the occurrence of side reactions. On the other hand, the solid electrolyte has high lithium-ion conductivity and can quickly conduct lithium ions. Filling the first groove 1131 and / or the second groove 1111 with a solid electrolyte can improve the specific energy of the battery.

[0129] In some embodiments, the solid electrolyte includes at least one of oxide electrolytes, sulfide electrolytes, and polymer electrolytes.

[0130] For example, oxide electrolytes include at least one of lithium garnet oxide, tin oxide, and bismuth oxide.

[0131] For example, sulfide electrolytes include at least one of lithium sulfide and sodium sulfide.

[0132] For example, the polymer electrolyte includes a polymer and a lithium salt. For instance, the polymer may include at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. As another example, the lithium salt may include at least one of LiPF6, LiFSI, LiTFSI, LiBF4, LiClO4, and LiAlCl4.

[0133] In some embodiments, the silicon-based material includes at least one of elemental silicon, silicon-carbon composite, silicon oxide, silicon-nitrogen composite, and silicon alloy.

[0134] In some embodiments, the carbon material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microspheres.

[0135] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. The battery cell can be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a magnesium-ion battery, etc.

[0136] Figure 5 This is a schematic diagram of a battery cell according to an embodiment of this application. For example, such as... Figure 5 As shown, the battery cell 3 is a square battery cell. The battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33 disposed in the housing 31.

[0137] The electrode assembly 33 can be made from a positive electrode, a negative electrode, and a separator through a winding process or a stacking process.

[0138] End cap assembly 32 includes electrode terminals 322, such as Figure 5 As shown, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0139] The battery cell 3 also includes a current collector 34, which is used to connect the tab 332 and the electrode terminal 322 of the electrode assembly 33. For example, in the case of a negative electrode in this embodiment, one current collector 34 is used to connect the tab and the negative electrode terminal of the negative electrode, and another current collector 34 is used to connect the tab and the positive electrode terminal of the positive electrode.

[0140] In some embodiments, the battery cell 3 includes an electrode assembly 33, which includes an electrode assembly body 331 and a tab 332 extending from the electrode assembly body 331.

[0141] In some embodiments, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0142] [Positive electrode plate]

[0143] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0144] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0145] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0146] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0147] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0148] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0149] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0150] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0151] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0152] [Negative electrode plate]

[0153] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0154] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0155] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0156] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0157] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0158] [Electrolytes]

[0159] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0160] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0161] Electrolyte salts may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0162] Solvents may include one or more of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0163] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and performance additives that can improve certain battery performance, such as performance additives that improve battery overcharge performance, battery high temperature or low temperature performance, etc.

[0164] [Isolation Component]

[0165] The separator is used to isolate the positive electrode and the negative electrode. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0166] The material of the separator can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film; there are no particular restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different; there are no particular restrictions.

[0167] Positive electrode, negative electrode and separator can be made into electrode assembly by winding process or stacking process.

[0168] [Battery Device]

[0169] This application provides a battery device, including the battery cell described in the above embodiments. The battery cell can be a battery cell after formation and aging processes. Figure 6 This is a schematic diagram of the structure of a battery device according to an embodiment of this application. Figure 6 As shown, the battery device 5 may include multiple battery cells 3 to meet different power usage requirements. The shape of the battery cell 3 in this embodiment can be set according to actual application. For example, the battery cell 3 may be as follows: Figure 5 The cuboid shown can also be different. Figure 5 The embodiments shown are cylindrical or other shapes, but are not limited to these.

[0170] It should be understood that, such as Figure 6 As shown, the battery device 5 in this embodiment may further include a housing 51, which can be used to accommodate multiple battery cells 3. The housing 51 in this embodiment has a hollow interior, and the multiple battery cells 3 are accommodated within the housing 51. The housing 51 may include two parts, referred to herein as a first housing portion 511 and a second housing portion 512, which are fastened together. The shapes of the first housing portion 511 and the second housing portion 512 can be determined according to the shape of the components housed inside, for example, according to the shape of the combination of the multiple battery cells 3 housed inside. At least one of the first housing portion 511 and the second housing portion 512 has an opening. For example, as... Figure 7 As shown, the first housing portion 511 and the second housing portion 512 can both be hollow cuboids with one open side. The openings of the first housing portion 511 and the second housing portion 512 are opposite to each other, and the first housing portion 511 and the second housing portion 512 are interlocked to form a housing 51 with a closed cavity, which can be used to accommodate multiple battery cells 3. The multiple battery cells 3 are connected in parallel, series, or mixed and placed inside the housing 51 formed by the interlocking of the first housing portion 511 and the second housing portion 512.

[0171] For example, unlike Figure 6As shown, either the first housing portion 511 or the second housing portion 512 may have only one hollow cuboid with an opening, while the other is plate-shaped to cover the opening. Taking the second housing portion 512 as a hollow cuboid with one opening, and the first housing portion 511 as a plate-shaped example, then the first housing portion 511 covers the opening of the second housing portion 512 to form a housing 51 with a closed chamber, which can be used to accommodate multiple battery cells 3.

[0172] The battery cells 3 can be directly assembled into the battery device 5, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into the battery device 5.

[0173] [Electrical Equipment]

[0174] This application provides an electrical device including the battery device described in the above embodiments.

[0175] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices.

[0176] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0177] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0178] For example, such as Figure 7The diagram shown is a structural schematic of a vehicle 7 according to one embodiment of this application. The vehicle 7 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. The vehicle 7 can have a motor 4, a controller 6, and a battery device 5 installed inside. The controller 6 controls the battery device 5 to supply power to the motor 4. For example, the battery device 5 can be installed at the bottom, front, or rear of the vehicle 7. The battery device 5 can be used to power the vehicle 7; for example, it can serve as the operating power source for the vehicle 7's electrical system, such as meeting the power requirements for starting, navigation, and operation. In another embodiment of this application, the battery device 5 can not only serve as the operating power source for the vehicle 7 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to the vehicle 7.

[0179] 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.

[0180] [Examples and Comparative Examples]

[0181] 1. Preparation of negative electrode sheet

[0182] Negative electrode plate 1:

[0183] 290.7g of negative electrode active material (a mixture of silicon-carbon composite material and artificial graphite in a mass ratio of 4:6), 4.2g of binder polystyrene-butadiene rubber, 3.45g of dispersant sodium carboxymethyl cellulose, and 1.65g of conductive agent conductive carbon black were mixed, and an appropriate amount of deionized water was added to obtain a negative electrode slurry with a solid content of 55%. The above negative electrode slurry was coated on copper foil, and after drying, a negative electrode film layer was formed. Laser milling was performed on the surface of the negative electrode film layer away from the copper foil to form a first groove. The ratio A of the height of the first groove to the thickness of the negative electrode film layer was 0.33, and the dimension L of the first groove in the third direction was 4mm. Finally, after cold pressing and slitting, negative electrode sheet 1 was obtained.

[0184] Negative electrode plate 2:

[0185] First negative electrode slurry: 96.9g of artificial graphite (first negative electrode active material), 1.4g of polystyrene-butadiene rubber (binder), 1.15g of sodium carboxymethyl cellulose (dispersant), and 0.55g of conductive carbon black (conductive agent) are mixed and then an appropriate amount of deionized water is added to obtain a first negative electrode slurry with a solid content of 55%.

[0186] Second negative electrode slurry: 96.9g of the second negative electrode active material (a mixture of silicon-carbon composite material and artificial graphite in a mass ratio of 8:2), 1.4g of binder polystyrene-butadiene rubber, 1.15g of dispersant sodium carboxymethyl cellulose, and 0.55g of conductive agent conductive carbon black were mixed and then an appropriate amount of deionized water was added to obtain a second negative electrode slurry with a solid content of 55%.

[0187] Third negative electrode slurry: Mix 96.9g of artificial graphite (third negative electrode active material), 1.4g of polystyrene-butadiene rubber (binder), 1.15g of sodium carboxymethyl cellulose (dispersant), and 0.55g of conductive carbon black (conductive agent), and add an appropriate amount of deionized water to obtain a third negative electrode slurry with a solid content of 55%.

[0188] First, a first negative electrode slurry is coated onto copper foil and dried to form a first coating. Then, a second negative electrode slurry is coated onto the first coating and dried to form a second coating. Finally, a third negative electrode slurry is coated onto the second coating and dried to form a third coating. The coated negative electrode sheet is then subjected to a 1.6 g / cm³ application. 3 The compaction density is achieved by rolling, and then laser milling is performed on the surface of the third coating away from the copper foil to form the first groove. The ratio A of the height of the first groove to the thickness of the third coating is 1, and the dimension L of the first groove in the third direction is 4mm. Finally, after slitting, the negative electrode sheet 2 is obtained.

[0189] Negative electrode 3: The preparation of negative electrode 3 is similar to that of negative electrode 2. The difference is that the second negative electrode active material in negative electrode 3 is a silicon-carbon composite material and artificial graphite with a mass ratio of 2:8.

[0190] Negative electrode 4: The preparation of negative electrode 4 is similar to that of negative electrode 2, except that the second negative electrode active material in negative electrode 4 is a silicon-carbon composite material and artificial graphite with a mass ratio of 1:9.

[0191] Negative electrode 5: The preparation of negative electrode 5 is similar to that of negative electrode 3. The difference is that the first negative electrode active material in negative electrode 5 is a silicon-carbon composite material and artificial graphite with a mass ratio of 5:95, and the third negative electrode active material is a silicon-carbon composite material and artificial graphite with a mass ratio of 5:95.

[0192] Negative electrode 6: The preparation of negative electrode 6 is similar to that of negative electrode 3, except that the ratio A of the height of the first groove to the thickness of the third coating in negative electrode 6 is 0.5.

[0193] Negative electrode 7: The preparation of negative electrode 7 is similar to that of negative electrode 6, except that the first groove in negative electrode 7 is filled with solid electrolyte lithium aluminum titanium phosphate.

[0194] Negative electrode sheet 8: 290.7g of negative electrode active material (silicon-carbon composite material and artificial graphite mixed in a mass ratio of 4:6), 4.2g of binder polystyrene-butadiene rubber, 3.45g of dispersant sodium carboxymethyl cellulose, and 1.65g of conductive agent conductive carbon black are mixed and an appropriate amount of deionized water is added to obtain a negative electrode slurry with a solid content of 55%. The above negative electrode slurry is coated on copper foil, and then dried, cold-pressed, and slit to obtain negative electrode sheet 8.

[0195] Negative electrode 9: The preparation of negative electrode 9 is similar to that of negative electrode 3, except that negative electrode 9 does not have a first groove.

[0196] [Example 1]

[0197] (1) Negative electrode plate

[0198] The negative electrode sheet is the negative electrode sheet 1 prepared as described above.

[0199] (2) Preparation of positive electrode sheet

[0200] 98.1g of positive electrode active material LiNi8CoMnO2, 0.8g of conductive agent conductive carbon black, and 1.1g of binder polyvinylidene fluoride (PVDF) were dry-mixed. Then, an appropriate amount of solvent N-methylpyrrolidone (NMP) was added to the mixture to adjust the viscosity to 6000 Pa·s. The mixture was stirred at 500 rpm / min for 3 hours to obtain a positive electrode slurry. The positive electrode slurry was coated on aluminum foil, and then dried, cold-pressed, and slit to obtain a positive electrode sheet.

[0201] (3) Separation membrane: A polyethylene membrane with a thickness of 7μm is used as the base membrane, and the two sides of the base membrane are coated with a 1.5μm Al2O3 ceramic coating.

[0202] (4) Preparation of electrolyte: Ethyl carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) are mixed in a volume ratio of 2:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L.

[0203] (5) Preparation of lithium-ion battery: The above positive electrode sheet, separator and negative electrode sheet are stacked and wound in sequence to obtain electrode assembly; the electrode assembly is placed in outer packaging, the electrolyte prepared above is added, and after encapsulation, standing, formation and aging processes, a battery cell is obtained. The size of the battery cell is 120mm*70mm*40mm, which is Example 1.

[0204] The battery cells of Examples 2-7 and Comparative Examples 1-2 are prepared using methods similar to those of the battery cell of Example 1, except that different negative electrode plates are used (negative electrode plates 1-7 are used in Examples 1-7, and negative electrode plates 8-9 are used in Comparative Examples 1-2), as detailed in Table 1. Performance parameters of Examples 1-7 and Comparative Examples 1-2 are shown in Tables 2 and 3.

[0205] Table 1 Product parameters of Examples 1-7 and Comparative Examples 1-2

[0206]

[0207] In Table 1, P2 represents the mass percentage of silicon-based material based on the total mass of the first coating; P1 represents the mass percentage of silicon-based material based on the total mass of the second coating; P3 represents the mass percentage of silicon-based material based on the total mass of the third coating; and A represents the ratio of the size (height) of the first groove to the size (thickness) of the third coating in the second direction.

[0208] Table 2 Performance parameters of Example 1 and Comparative Example 1

[0209]

[0210] As shown in the results of Example 1 and Comparative Example 1, by setting a first groove on the surface of the negative electrode film away from the copper foil, the expansion force of the battery is significantly reduced, which is beneficial to improving the safety performance of the battery. At the same time, the capacity retention rate is improved and the cycle performance is also improved.

[0211] Table 3 Performance parameters of Examples 2-7 and Comparative Example 2

[0212]

[0213] As shown in the results of Example 3 and Comparative Example 2, by setting the first groove on the third coating of the negative electrode film, the expansion force and DCR of the battery are significantly reduced, while the capacity retention rate is improved and the cycle performance is significantly improved.

[0214] Based on the results of Example 5 and Comparative Examples 2 and 3, when silicon-carbon composite materials are doped into the first and third coatings of the negative electrode film, the overall silicon content of the negative electrode film increases, thus improving the volumetric energy density of the battery. At the same time, the expansion force of the battery also increases. However, since the third coating in Example 5 has a first groove, the expansion force and DCR of the battery are still lower than those of the battery in Comparative Example 2, respectively. Moreover, compared with Comparative Example 2, the capacity retention rate and cycle performance of the battery in Example 5 are significantly improved.

[0215] As shown in the results of Examples 6 and 7, filling the first groove with a solid electrolyte slightly increases the expansion force of the battery, but reduces the DCR of the battery. The capacity retention rate and cycle performance are improved, which is beneficial to improving the overall performance of the battery.

[0216] Compared to Examples 3-7 and Comparative Example 2, Example 2 has a higher silicon content in the negative electrode film, resulting in a greater expansion force of the battery. However, it can be seen that due to the presence of a first groove in the third coating layer in Example 2, the battery's capacity retention rate and cycle performance are slightly worse than those of Comparative Example 2. Nevertheless, the volumetric energy density of the battery in Example 2 is significantly improved compared to Comparative Example 2. Therefore, Example 2 has better overall performance than Comparative Example 2.

[0217] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0218] 1. Expansion force test

[0219] Special steel plate clamps are installed on both sides of the battery, and pressure sensors are mounted on the clamps. At the beginning of the test, an initial preload of 1000N is applied to the clamps to secure the battery cells. During the battery charge-discharge cycle test, the pressure sensors record the battery pressure at the clamps in real time. This value is recorded as the battery expansion force, and the change in expansion force during the battery cycle can be recorded accordingly.

[0220] 2. 2C Rate Capacity Retention Test

[0221] At 25°C, the battery was charged to 4.20V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 5.0V, and allowed to stand for 10 minutes. It was then discharged to 2.50V with a current of 0.33C and allowed to stand for 10 minutes. The resulting capacity was recorded as the initial capacity C0. Then, the battery was charged under the same conditions and discharged at 2C. The resulting capacity was recorded as C. n The capacity retention rate Qn for each battery rate discharge is calculated using the following formula: Qn=(Cn / C0)×100%.

[0222] 3. Initial DC Resistance (DCR) Test

[0223] At 25℃, the battery was charged to 4.20V with a current of 0.33C, and then charged to 0.05C with a constant voltage of 5.0V. The battery was then left to stand for 10 minutes. The battery was then discharged with a constant current of 0.33C for 60 minutes to adjust the battery to 50% SOC. The battery voltage at this time was recorded as U1. The battery was then discharged with a constant current of 4C for 10 seconds. The instantaneous voltage U2 at 10 seconds of discharge was recorded. The initial DCR of the battery was represented by the discharge DCR at 50% SOC. The initial DCR of the battery was calculated as (U1-U2) / 4C, where C is the nominal capacity of the battery.

[0224] 4. Cyclic capacity retention test

[0225] At 25℃, the battery is charged to 4.20V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 4.20V, left to stand for 10 minutes, and then discharged to 2.50V with a current of 0.33C, left to stand for 10 minutes. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated, and the discharge capacity Cn of the battery after the nth cycle is recorded. The battery capacity retention rate (%) after n cycles is calculated as (Cn / C0) × 100%.

[0226] For example, the capacity retention rate (%) of a lithium-ion battery after 500 cycles at 25°C = (discharge capacity of the 500th cycle / discharge capacity of the first cycle) × 100%.

[0227] 5. Energy density testing

[0228] At 25℃, discharge to the lower limit voltage in the form of constant current discharge (0.33C rate), let stand for 30 minutes, then charge to the upper limit cutoff voltage in the form of constant current and constant voltage charging (constant current 0.33C, constant voltage charging to 0.05C), let stand for 30 minutes, and measure the discharge energy E (in Wh). Repeat 3 times and take the average value of the discharge energy E of the 3 times as E0. Divide it by the volume V of the hard-shell battery cell, and the volumetric energy density (in Wh / L) is E0 / V.

[0229] 6. Confirmation of silicon-based material content

[0230] The silicon content in the negative electrode was tested using inductively coupled plasma mass spectrometry (ICP) in accordance with the national standard GB / T 14849.4-2014: First, the film on the negative electrode was scraped to remove powder, and then digested with hydrofluoric acid using the plate digestion method. Then, the elemental content was determined by inductively coupled plasma atomic emission spectrometry.

[0231] 7. Determining the dimensions

[0232] By observing the negative electrode sheet using a scanning electron microscope, the thickness of each coating layer of the negative electrode film, as well as the height and spacing of the grooves, can be observed.

[0233] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, Comprising: A negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer, the negative electrode film layer is disposed on at least one side surface of the negative electrode current collector, the negative electrode film layer includes a silicon-based material, and at least one first groove recessed in a direction close to the negative electrode current collector is provided on a side surface of the negative electrode film layer far from the negative electrode current collector, the first groove extends in a first direction, and the first direction is perpendicular to the thickness direction of the negative electrode plate.

2. The battery cell according to claim 1, characterized in that, The negative electrode film layer includes: A first coating layer, the first coating layer includes a first negative electrode active material, and the first negative electrode active material includes a carbon material; A second coating layer, the second coating layer includes a second negative electrode active material, and the second negative electrode active material includes a silicon-based material; A third coating layer, the third coating layer includes a third negative electrode active material, and the third negative electrode active material includes a carbon material. At least one of the first grooves is provided on a side surface of the third coating layer far from the negative electrode current collector; Wherein, in a second direction, the first coating layer, the second coating layer, and the third coating layer are sequentially stacked in a direction away from the negative electrode current collector, and the second direction is the thickness direction of the negative electrode plate.

3. The battery cell according to claim 2, characterized in that, The second negative electrode active material includes a silicon-based material and a carbon material. Wherein, based on the total mass of the second coating layer, the mass percentage content P1 of the silicon-based material satisfies: 10% ≤ P1 ≤ 80%.

4. The battery cell according to claim 2 or 3, characterized in that, The first negative electrode active material further includes a silicon-based material. Based on the total mass of the first coating layer, the mass percentage content P2 of the silicon-based material satisfies: P2 ≤ 10%.

5. The battery cell according to any one of claims 2 to 4, characterized in that, The third negative electrode active material further includes a silicon-based material. Based on the total mass of the third coating layer, the mass percentage content P3 of the silicon-based material satisfies: P3 ≤ 10%.

6. The battery cell according to any one of claims 2 to 5, characterized in that, In the second direction, the ratio A of the size of the first groove to the size of the third coating layer satisfies: 0 < A ≤ 1.

7. The battery cell according to any one of claims 2 to 6, characterized in that, The size L of the first groove in a third direction satisfies: 0 < L < 60 mm, and the third direction is perpendicular to the first direction and the second direction.

8. The battery cell according to claim 7, characterized in that, At least one of the first grooves arranged in the third direction is provided on a side surface of the third coating layer far from the negative electrode current collector. Among the plurality of first grooves, the distance D between two adjacent first grooves satisfies: 0 < D < 60 mm.

9. The battery cell according to any one of claims 2 to 8, characterized in that, The negative electrode plate is wound along a winding direction to form a winding structure. The winding structure includes a flat area and bending areas provided on both sides of the flat area. At least one of the first grooves is provided on a side surface of the negative electrode film layer in the bending area far from the negative electrode current collector.

10. The battery cell according to any one of claims 2 to 9, characterized in that, At least one second groove recessed in a direction close to the negative electrode current collector is provided on a side surface of the first coating layer far from the negative electrode current collector.

11. The battery cell according to claim 10, characterized in that, In the second direction, the ratio B of the size of the second groove to the size of the first coating layer satisfies: 0 < B < 1.

12. The battery cell according to claim 10 or 11, characterized in that, The negative electrode plate is wound along a winding direction to form a winding structure. The winding structure includes a flat area and bending areas provided on both sides of the flat area. At least one of the second grooves is provided on a side surface of the first coating layer in the bending area far from the negative electrode current collector.

13. The battery cell according to any one of claims 10 to 12, characterized in that, The battery cell also includes a solid electrolyte, which fills the first groove and / or the second groove.

14. The battery cell according to claim 13, characterized in that, The solid electrolyte includes at least one of oxide electrolytes, sulfide electrolytes, and polymer electrolytes.

15. The battery cell according to claim 14, characterized in that, The oxide electrolyte includes at least one of lithium garnet oxide, tin oxide, and bismuth oxide; The sulfide electrolyte includes at least one of lithium sulfide and sodium sulfide; The polymer electrolyte comprises a polymer and a lithium salt. The polymer comprises at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. The lithium salt comprises at least one of LiPF6, LiFSI, LiTFSI, LiBF4, LiClO4, and LiAlCl4.

16. The battery cell according to any one of claims 2 to 15, characterized in that, The carbon material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microspheres.

17. The battery cell according to any one of claims 1 to 16, characterized in that, The silicon-based material includes at least one of elemental silicon, silicon-carbon composite, silicon oxide, silicon-nitrogen composite, and silicon alloy.

18. A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1-17.

19. An electrical appliance, characterized in that, include: A plurality of battery cells according to any one of claims 1-17, or a battery device according to claim 18, wherein the battery cells or the battery device are used to store or provide electrical energy.

20. The electrical equipment according to claim 19, characterized in that, The electrical equipment includes vehicles, ships, or spacecraft.

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