WO2024020775A1 - Electrode assembly, battery cell, battery and electric device - Google Patents

Abstract

Provided in the embodiments of the present application are an electrode assembly, a battery cell, a battery and an electric device. The electrode assembly is of a wound structure and comprises a first electrode plate, which comprises a first current collector and a first active material layer coated on a surface of the first current collector, and has multiple first straight regions and multiple first corner regions alternately arranged in a winding direction of the first electrode plate, wherein from the start end of winding of the first electrode plate, the first active material layers in the first N first corner regions are each provided with a first recess that is located on an inner side of the first corner region, where N≥1. The battery cell composed of the electrode assembly has high safety.

Description

Electrode components, battery cells, batteries and electrical equipment Technical field

The present application relates to the field of battery technology, and in particular to an electrode assembly, a battery cell, a battery and electrical equipment.

Background technique

Energy conservation and emission reduction are the key to the sustainable development of the automobile industry. Electric vehicles have become an important part of the sustainable development of the automobile industry due to their advantages in energy conservation and environmental protection. For electric vehicles, battery technology is an important factor related to their development.

In the development of battery technology, in addition to improving the energy density of batteries, battery safety is also an issue that cannot be ignored. Therefore, how to improve the safety of batteries is an urgent technical problem that needs to be solved in battery technology.

Contents of the invention

The purpose of this application is to provide an electrode assembly, a battery cell, a battery and electrical equipment. The battery cell composed of the electrode assembly has high safety.

This application is realized through the following technical solutions:

In a first aspect, the present application provides an electrode assembly. The electrode assembly has a wound structure. The electrode assembly includes a first pole piece. The first pole piece includes a first current collector and a coating on the The first active material layer on the first current collector surface, the first pole piece has a plurality of first straight areas and a plurality of first corner areas, the first straight areas and the first corner areas are along The winding directions of the first pole pieces are alternately arranged; wherein, starting from the winding starting end of the first pole pieces, the first active material layers in the first N first corner areas are provided with first Groove, the first groove is located inside the first corner area, N≥1.

According to the electrode assembly according to the embodiment of the present application, the first active material layer in the first N first corner areas from the winding starting end of the first pole piece is provided with first grooves, and the first groove is located in the first corner area. to reduce the risk of the first active material layer in the first corner area cracking, falling off, or even the first current collector breaking, thereby improving the safety of the battery cell composed of the electrode assembly.

According to some embodiments of the present application, N=2.

In the above solution, the first active material layers in the first two first corner areas are provided with first grooves, that is, the two first corner areas of the innermost first active material layer are both provided with first grooves, Make the folding radius of the innermost ring smaller, reduce or even eliminate the stress and obstacles in the first corner area of the inner ring of the first pole piece, and effectively reduce cracking, powder loss, and cracking of the first active material layer in the first corner area of the innermost ring. Even the risk of the first current collector breaking, as well as reducing the risk of shed active material particles puncturing the isolation membrane.

According to some embodiments of the present application, the first groove extends along the width direction of the pole piece.

In the above solution, since the width direction of the first pole piece is parallel to the extension direction of the winding axis of the electrode assembly, the first groove extends along the width direction of the first pole piece, which can effectively alleviate the stress concentration in the first corner area.

According to some embodiments of the present application, the first groove is at least partially located in the middle of the first corner area along the winding direction of the first pole piece.

In the above solution, the middle part of the first corner area is the stress concentration area during the first pole piece being pressed, and the first groove is at least partially located in the middle part of the first corner area, which can effectively reduce the first active material in the first corner area. There is a risk of layer cracking, powder loss, or even the first current collector breaking.

According to some embodiments of the present application, the depth of the first groove is H1, and the thickness of the first active material layer inside the first current collector is H2, satisfying 80%≤H1/H2≤100%.

In the above solution, the depth of the first groove and the thickness of the first active material layer inside the first current collector satisfy the above relationship, so that the first active material layers on both sides of the width direction of the first groove do not interfere. If the depth of the first groove is too small, the first active material layers on both sides of the width direction of the first groove will easily interfere, causing the first active material layers on both sides to be in contact and squeezed, which will easily cause the first active material layer to collapse. fall off.

According to some embodiments of the present application, 85%≤H1/H2≤95%.

In the above solution, when 85% ≤ H1/H2 ≤ 95% compared to 80% ≤ H1/H2 ≤ 100%, the first active material layer on both sides of the width direction of the first groove is less likely to interfere, and There is a first active material layer with a certain capacity in the first groove, so that the battery cell composed of the electrode assembly has a higher energy density.

According to some embodiments of the present application, the width of the first groove is L1, and the thickness of the first active material layer inside the first current collector is H2, satisfying 1.5≤L1/H2≤2.5.

In the above solution, the width of the first groove and the thickness of the first active material layer inside the first current collector satisfy the above relationship, which facilitates reducing the stress in the first corner area and reducing the stress of the first active material layer in the first corner area. There is a risk of cracking, powder loss, or even breakage of the first current collector. At the same time, the battery cell composed of the electrode assembly has a large energy density. If the width of the first groove is too small, the first active material layers on both sides of the width direction of the first groove will easily interfere, causing the first active material layers on both sides to be in contact and extruded, which will easily cause the first active material layer to collapse. fall off. If the width of the first groove is too large, the capacity of the first active material layer in the first corner area is less, which affects the energy density of the battery cell composed of the electrode assembly.

According to some embodiments of the present application, 1.8≤L1/H2≤2.2.

In the above solution, compared to 1.5≤L1/H2≤2.5, when 1.8≤L1/H2≤2.2, it can not only reduce the stress in the first corner area, but also make the battery cell composed of the electrode assembly have a higher Large energy density.

According to some embodiments of the present application, the cross section of the first groove is V-shaped, semi-circular, semi-elliptical or trapezoidal.

In the above solution, the cross section of the first groove has the above shape, which is convenient for reducing the stress in the first corner area and also facilitates processing and manufacturing. When the cross section of the first groove is V-shaped, after the electrode assembly is rolled and extruded, the distance between the two opposite groove walls of the first groove is reduced or even the two groove walls are close together, which can reduce the Risk of lithium precipitation. When the cross section of the first groove is semicircular, semielliptical or trapezoidal, after the electrode assembly is wound and extruded, the first groove is extruded and deformed, but the first groove is not closed, and the first groove is extruded and deformed. The groove can accommodate electrolyte, so that the battery cell composed of the electrode assembly can store more electrolyte.

According to some embodiments of the present application, the first groove penetrates the first active material layer along the width direction of the first pole piece.

In the above solution, the first groove penetrates the first active material layer along the width direction of the first pole piece, which facilitates processing and effectively reduces cracking, powder loss, and even breakage of the first current collector in the first active material layer in the first corner area. risks of.

According to some embodiments of the present application, the electrode assembly further includes a second pole piece, the second pole piece has an opposite polarity to the first pole piece, the second pole piece includes a second current collector and a coating On the second active material layer on the surface of the second current collector, the second pole piece has a plurality of second straight areas and a plurality of second corner areas, and the second straight areas and the second corner areas Zones are alternately arranged along the winding direction of the second pole piece; starting from the winding starting end of the second pole piece, the second active material layers of the first M second corner zones are provided with a third Two grooves, the second groove is located inside the second corner area, M≥1.

In the above solution, the second active material layer in the first M second corner areas of the winding starting end of the second pole piece is provided with second grooves, and the second groove is located inside the second corner area to reduce the The risk of the second active material layer in the second corner area cracking, falling off, or even the first current collector breaking, and reducing the risk of falling active material particles penetrating the isolation film, improves the safety of the battery cell composed of the electrode assembly. .

According to some embodiments of the present application, M=2.

In the above solution, the second active material layers in the first two second corner areas are provided with second grooves, that is, the two second corner areas of the innermost second active material layer are both provided with second grooves, Make the folding radius of the innermost ring smaller, reduce or even eliminate the stress and obstacles in the second corner area of the inner ring of the second pole piece, and effectively reduce the cracking, powder loss, and Even the risk of the second current collector breaking, as well as reducing the risk of shed active material particles puncturing the isolation membrane.

According to some embodiments of the present application, the second groove extends along the width direction of the second pole piece.

In the above solution, since the width direction of the second pole piece is parallel to the extension direction of the winding axis of the electrode assembly, the second groove extends along the width direction of the second pole piece, which can effectively alleviate the stress concentration in the second corner area.

According to some embodiments of the present application, the second groove is at least partially located in the middle of the second corner area along the winding direction of the second pole piece.

In the above solution, the middle part of the second corner area is the stress concentration area during the pressure of the second pole piece, and the second groove is at least partially located in the middle part of the second corner area, which can effectively reduce the second active material in the second corner area. There is a risk of layer cracking, powder loss, or even the second current collector breaking.

According to some embodiments of the present application, the depth of the second groove is H3, and the thickness of the second active material layer inside the second current collector is H4, satisfying 80%≤H3/H4≤100%.

In the above solution, the depth of the second groove and the thickness of the second active material layer inside the second current collector satisfy the above relationship, so that the second active material layer on both sides of the width direction of the second groove does not interfere. If the depth of the second groove is too small, the second active material layers on both sides of the width direction of the second groove will easily interfere, causing the second active material layers on both sides to be in contact and extruded, which will easily cause the second active material layer to collapse. fall off.

According to some embodiments of the present application, 85%≤H3/H4≤95%.

In the above solution, when 85% ≤ H3/H4 ≤ 95% compared to 80% ≤ H3/H4 ≤ 100%, the second active material layer on both sides of the width direction of the second groove is less likely to interfere, and There is a second active material layer with a certain capacity at the second groove, so that the battery cell composed of the electrode assembly has a higher energy density.

According to some embodiments of the present application, the width of the second groove is L2, and the thickness of the second active material layer inside the second current collector is H4, satisfying 1.5≤L2/H4≤2.5.

In the above solution, the width of the second groove and the thickness of the second active material layer inside the second current collector satisfy the above relationship, which facilitates reducing the stress in the second corner area and reducing the stress of the second active material layer in the second corner area. There is a risk of cracking, powder loss, or even the second current collector breaking. At the same time, the battery cell composed of the electrode assembly has a large energy density. If the width of the second groove is too small, the second active material layers on both sides of the width direction of the second groove will easily interfere, causing the second active material layers on both sides to be in contact and extruded, which will easily cause the second active material layer to collapse. fall off. If the width of the second groove is too large, the capacity of the second active material layer in the second corner area is less, which affects the energy density of the battery cell composed of the electrode assembly.

According to some embodiments of the present application, 1.8≤L2/H4≤2.2.

In the above solution, compared to 1.5≤L2/H4≤2.5, when 1.8≤L2/H4≤2.2, it can not only reduce the stress in the second corner area, but also make the battery cell composed of the electrode assembly have a higher Large energy density.

According to some embodiments of the present application, the cross section of the second groove is V-shaped, semi-circular, semi-elliptical or trapezoidal.

In the above solution, the cross section of the second groove has the above shape, which is convenient for reducing the stress in the second corner area and also facilitates processing and manufacturing. When the cross section of the second groove is V-shaped, after the electrode assembly is rolled and extruded, the distance between the two opposite groove walls of the second groove is reduced or even the two groove walls are close together, which can reduce the Risk of lithium precipitation. When the cross-section of the second groove is semicircular, semi-elliptical or trapezoidal, after the electrode assembly is wound and extruded, the second groove is extruded and deformed, but the second groove is not closed. The groove can accommodate electrolyte, so that the battery cell composed of the electrode assembly can store more electrolyte.

According to some embodiments of the present application, the second groove penetrates the second active material layer along the width direction of the second pole piece.

In the above solution, the second groove runs through the second active material layer along the width direction of the second pole piece, which facilitates processing and effectively reduces cracking, powder loss, and even breakage of the second current collector in the second active material layer in the second corner area. risks of.

In a second aspect, the present application provides a battery cell, including the electrode assembly provided by any of the above solutions.

In a third aspect, the present application provides a battery, including a box and a plurality of battery cells provided in any of the above solutions, and a plurality of the battery cells are arranged in the box.

In a fourth aspect, the present application provides an electrical device, including the battery provided in any of the above solutions, where the battery is used to provide electrical energy.

The above description is only an overview of the technical solutions of the present application. In order to have a clearer understanding of the technical means of the present application, they can be implemented according to the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and understandable. , the specific implementation methods of the present application are specifically listed below.

Description of drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. Those of ordinary skill in the art can also obtain other drawings based on the drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of a vehicle provided by some embodiments of the present application;

Figure 2 is an exploded view of a battery provided by some embodiments of the present application;

Figure 3 is an exploded view of a battery cell provided by some embodiments of the present application;

Figure 4 is a schematic structural diagram of an electrode assembly provided by some embodiments of the present application;

Figure 5 is a top view of the first pole piece in an expanded state provided by some embodiments of the present application;

Figure 6 is a schematic structural diagram of the first pole piece in an expanded state provided by some embodiments of the present application;

Figure 7 is an enlarged view of part A of Figure 4;

Figure 8 is a top view of the second pole piece in an expanded state provided by some embodiments of the present application;

Figure 9 is a schematic structural diagram of the second pole piece in an expanded state provided by some embodiments of the present application;

Figure 10 is a partial enlarged view of B in Figure 4;

In the drawings, the drawings are not drawn to actual scale.

Marking description: 100-battery; 10-box; 11-first sub-box; 12-second sub-box; 20-battery cell; 21-cover; 22-casing; 23-electrode assembly; 230 -pole tab; 231-first pole piece; 2311-first current collector; 2312-first active material layer; 2313-first straight area; 2314-first corner area; 2315-first groove; 232- The second pole piece; 2321-the second current collector; 2322-the second active material layer; 2323-the second straight area; 2324-the second corner area; 2325-the second groove; 233-isolation film; 24-electrode Terminal; 200-controller; 300-motor; 1000-vehicle.

Detailed ways

The embodiments of the present application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the technical field belonging to this application; the terms used herein are for the purpose of describing specific embodiments only and are not intended to be used in Limitation of this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

In the description of the embodiments of this application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying the relative importance or implicitly indicating the quantity or specificity of the indicated technical features. Sequence or priority relationship.

Reference herein to "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearances of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art understand, both explicitly and implicitly, that the embodiments described herein may be combined with other embodiments.

In the description of the embodiments of this application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to means two or more pieces (including two pieces), unless otherwise clearly and specifically limited.

In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "width", "thickness", "upper" and "lower" is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the implementation of the present application. Examples and simplified descriptions are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be construed as limiting the embodiments of the present application.

In the description of the embodiments of this application, unless otherwise clearly stated and limited, technical terms such as "installation", "connection", "connection" and "fixing" should be understood in a broad sense. For example, it can be a fixed connection or a removable connection. It can be disassembled and connected, or integrated; it can also be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two elements or an interaction between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

In this application, the battery mentioned refers to a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack.

The battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode plate, a negative electrode plate and a separator. Battery cells mainly rely on the movement of metal ions between the positive and negative electrodes to work. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode current collector. The current collector without the positive electrode active material layer is used as a positive electrode tab. Taking lithium-ion batteries as an example, the material of the positive electrode current collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganate, etc. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector. The current collector without the negative electrode active material layer is used as a negative electrode tab. The material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon. In order to ensure that large currents can pass through without melting, the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together. The material of the isolation film can be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene), etc.

In order to make the lithium-ion battery cell smaller in size and have higher energy density, the negative electrode plate, positive electrode plate and separator in the electrode assembly of the lithium-ion battery cell can be rolled or folded and then compacted. The electrode assembly includes a straight area and corner areas located at both ends of the straight area. The straight area refers to the area with a parallel structure in the electrode assembly, that is, the negative electrode piece, the positive electrode piece and the isolation unit in the straight area. The surface of the membrane is all flat. The corner area refers to the area with a bent structure in the electrode assembly, that is, the negative electrode tab, positive electrode tab, and isolation film are all bent in the corner area, that is, each layer of the negative electrode tab, The surfaces of the positive electrode piece and the separator are both curved surfaces.

The development of battery technology must consider multiple design factors at the same time, such as energy density, discharge capacity, charge and discharge rate and other performance parameters. In addition, battery safety also needs to be considered.

The safety of the battery is mainly caused by internal short circuits, such as lithium deposition, shedding of the active material layer, etc., resulting in contact between the positive and negative electrodes. The inventor found through research that the rolled electrode assembly has low safety. The rolled electrode assembly needs to be compacted after the winding is completed. During the extrusion process, the electrode assembly self-polarizes due to stress concentration. The active material layers in the first N (N≥1) corner areas from the starting end of the sheet are prone to risks such as cracking, powder falling off (active material layer falling off), and even current collector breakage. Among them, cracking of the active material layer can easily lead to Insufficient space for lithium insertion, thereby increasing the probability of lithium precipitation; the fallen active material layer is usually granular, and the granular active material can easily pierce the isolation film; the current collector fracture can easily scratch the isolation film, making these risks easy to cause the positive electrode piece Short circuit with the negative electrode plate, which reduces the safety of the battery cell.

In view of this, in order to solve the problem of reduced safety of battery cells caused by short circuit between the positive electrode piece and the negative electrode piece, the inventor designed an electrode assembly after in-depth research, which is installed in the corner area of the electrode piece close to the winding axis. Grooves reduce the risk of cracking of the active material layer, powder loss, and even breakage of the current collector, and improve the safety of the battery cells composed of the electrode assembly.

The battery cells disclosed in the embodiments of the present application can be used in, but are not limited to, vehicles, ships, aircraft, and other electrical equipment. The power supply system of the electrical equipment can be composed of battery cells, batteries, etc. disclosed in this application.

Embodiments of the present application provide an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, a mobile phone, a tablet computer, a laptop, an electric toy, an electric tool, an electric bicycle, an electric motorcycle, an electric car, a ship, Spacecraft and more. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, spaceships, etc.

For the convenience of explanation in the following embodiments, an electrical device according to an embodiment of the present application is a vehicle.

Please refer to Figure 1 , which is a schematic structural diagram of a vehicle provided by some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. The battery 100 is disposed inside the vehicle 1000 , and the battery 100 may be disposed at the bottom, head, or tail of the vehicle 1000 . The battery 100 can be used to power the vehicle 1000 . For example, the battery 100 can be used as an operating power source for the vehicle 1000 and for the circuit system of the vehicle 1000 , such as for the starting, navigation and operating power requirements of the vehicle 1000 .

The vehicle 1000 may also include a controller 200 and a motor 300 . The controller 200 is used to control the battery 100 to provide power to the motor 300 , for example, for starting, navigating and driving the vehicle 1000 .

In some embodiments of the present application, the battery 100 can not only be used as an operating power source for the vehicle 1000 , but also can be used as a driving power source for the vehicle 1000 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000 .

Please refer to Figure 2, which is an exploded view of a battery provided by some embodiments of the present application. The battery 100 includes a case 10 and battery cells 20 , and the battery cells 20 are accommodated in the case 10 . Among them, the box 10 is used to provide an accommodation space for the battery cells 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first sub-box 11 and a second sub-box 12. The first sub-box 11 and the second sub-box 12 cover each other. The first sub-box 11 and the second sub-box 12 are The two sub-boxes 12 jointly define an accommodation space for accommodating the battery cells 20 . The second sub-box 12 can be a hollow structure with one end open, and the first sub-box 11 can be a plate-like structure. The first sub-box 11 is covered with the open side of the second sub-box 12 so that the first sub-box 11 can have a plate-like structure. The box 11 and the second sub-box 12 jointly define an accommodation space; the first sub-box 11 and the second sub-box 12 can also be hollow structures with one side open, and the open side of the first sub-box 11 It is closed on the open side of the second sub-box 12 .

In the battery 100, there may be a plurality of battery cells 20, and the plurality of battery cells 20 may be connected in series, in parallel, or in mixed connection. Mixed connection means that the plurality of battery cells 20 are connected in series and in parallel. The plurality of battery cells 20 can be directly connected in series or in parallel or mixed together, and then the whole composed of the plurality of battery cells 20 can be accommodated in the box 10 ; of course, the battery 100 can also be a plurality of battery cells 20 First, the battery modules are connected in series, parallel, or mixed to form a battery module, and then multiple battery modules are connected in series, parallel, or mixed to form a whole, and are accommodated in the box 10 . The battery 100 may also include other structures. For example, the battery 100 may further include a bus component for realizing electrical connections between multiple battery cells 20 .

The battery cell 20 may be a secondary battery or a primary battery; the battery cell 20 may also be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited thereto.

Please refer to Figure 3, which is an exploded view of a battery cell provided by some embodiments of the present application. As shown in FIG. 3 , the battery cell 20 includes a cover 21 , a case 22 , an electrode assembly 23 and other functional components. The housing 22 has an opening, and the cover 21 closes the opening to isolate the internal environment of the battery cell 20 from the external environment.

The cover 21 refers to a component that covers the opening of the case 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the cover 21 can be adapted to the shape of the housing 22 to fit the housing 22 . Optionally, the cover 21 can be made of a material with a certain hardness and strength (such as aluminum alloy). In this way, the cover 21 is less likely to deform when subjected to extrusion and collision, so that the battery cell 20 can have higher durability. Structural strength and safety performance can also be improved. Functional components such as electrode terminals 24 may be provided on the cover 21 . The electrode terminal 24 may be used to electrically connect with the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20 . The cover body 21 can also be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which are not particularly limited in the embodiments of the present application. In some embodiments, an insulating structure may be provided inside the cover 21 , and the insulating structure may be used to isolate the electrical connection components in the housing 22 from the cover 21 to reduce the risk of short circuit. For example, the insulating structure may be plastic, rubber, etc.

The housing 22 is a component used to cooperate with the cover 21 to form an internal environment of the battery cell 20 , wherein the formed internal environment can be used to accommodate the electrode assembly 23 , electrolyte, and other components. The housing 22 and the cover 21 may be independent components. An opening may be provided on the housing 22 and the cover 21 covers the opening at the opening to form an internal environment of the battery cell 20 . The housing 22 can be of various shapes and sizes, such as rectangular parallelepiped, cylinder, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23 . The housing 22 may be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which are not particularly limited in the embodiments of the present application.

The electrode assembly 23 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 23 may be contained within the housing 22 . The electrode assembly 23 is mainly formed by winding or stacking a positive electrode piece and a negative electrode piece, and is usually provided with an isolation film between the positive electrode piece and the negative electrode piece. The isolation film is used to separate the positive electrode piece and the negative electrode piece. Avoid internal short circuit between positive and negative electrode pieces. The portions of the positive electrode piece and the negative electrode piece that contain active material constitute the main body of the battery assembly, and the portions of the positive electrode piece and the negative electrode piece that do not contain active material constitute the tabs 230 respectively. The positive electrode tab and the negative electrode tab can be located together at one end of the main body or respectively located at both ends of the main body. During the charging and discharging process of the battery, the positive active material and the negative active material react with the electrolyte, and the tabs 230 are connected to the electrode terminals 24 to form a current loop.

According to some embodiments of the present application, with reference to Figures 4 to 7, Figure 4 is a schematic structural diagram of an electrode assembly provided by some embodiments of the present application, and Figure 5 is a top view of the first pole piece in an unfolded state provided by some embodiments of the present application. FIG. 6 is a schematic structural diagram of the first pole piece in an unfolded state provided by some embodiments of the present application, and FIG. 7 is a partial enlarged view of A in FIG. 4 . This application provides an electrode assembly 23. The electrode assembly 23 has a wound structure. The electrode assembly 23 includes a first pole piece 231. The first pole piece 231 includes a first current collector 2311 and is coated on the surface of the first current collector 2311. The first active material layer 2312, the first pole piece 231 has a plurality of first straight areas 2313 and a plurality of first corner areas 2314, the first straight areas 2313 and the first corner areas 2314 are along the first pole piece 231 The winding directions of 2315 is located inside the first corner area 2314, N≥1.

In the figure, the direction indicated by letter J is the winding direction of the electrode assembly 23 , that is, the winding direction of the first pole piece 231 .

The first pole piece 231 is a pole piece constituting the electrode assembly 23. The first pole piece 231 may be a negative pole piece, or the first pole piece 231 may also be a positive pole piece.

The first active material layer 2312 is coated on the surface of the first current collector 2311. It may be that the first active material layer 2312 is coated on one side of the first current collector 2311 in the thickness direction, or it may be the first active material layer. 2312 is coated on the two opposite surfaces of the first current collector 2311 in the thickness direction. Optionally, the first active material layer 2312 is coated on two opposite surfaces of the first current collector 2311 in the thickness direction.

The first straight region 2313 refers to the region where the first pole piece 231 has a parallel structure, that is, the surfaces of the first pole piece 231 in the first straight region 2313 are all flat. The first corner area 2314 refers to the area where the first pole piece 231 has a bent structure, that is, the first pole piece 231 in the first corner area 2314 is bent, and the surface of the first pole piece 231 in the first corner area 2314 is uniform. is a surface.

Starting from the winding starting end D1 of the first pole piece 231 , the first N first corner areas 2314 are N first corner areas 2314 close to the winding axis of the electrode assembly 23 .

Along the thickness direction of the first current collector 2311, the projection of the first groove 2315 on the first current collector 2311 may be in the shape of a strip, a circle, or a polygon such as a triangle or a pentagon. The first groove 2315 is a groove of the first active material layer 2312 provided in the first N first corner areas 2314, and the first groove 2315 is located inside the first corner area 2314, that is, the first groove 2315 is located in the The side of the first corner area 2314 close to the winding axis.

The first groove 2315 extends along the width direction X1 of the first pole piece 231 , and the width direction X1 of the first pole piece 231 is perpendicular to the winding direction of the first pole piece 231 .

When N=1, the first groove 2315 is disposed in the first corner area 2314 of the first pole piece 231 from the winding start end, that is, the first groove 2315 is disposed closest to the electrode assembly 23 The first corner area 2314 of the winding axis.

According to the electrode assembly 23 of the embodiment of the present application, the first active material layer 2312 of the first N first corner areas 2314 from the winding starting end D1 of the first pole piece 231 is provided with a first groove 2315. The groove 2315 is located inside the first corner area 2314. The location of the first groove 2315 is the stress concentration area of the first corner area 2314. After the electrode assembly 23 is wound and compacted, the stress concentration of the first corner area 2314 can be reduced. The risk of an active material layer 2312 cracking, powder falling off, or even the first current collector 2311 breaking, thus reducing the risk of lithium precipitation, reducing the risk of active material particles puncturing the isolation film 233 (see Figure 4), and reducing the risk of the first current collector 2311 breaking. The risk of the current collector 2311 scratching the isolation film 233 improves the safety of the battery cell 20 composed of the electrode assembly 23 .

According to some embodiments of the present application, N=2.

Starting from the winding starting end D1 of the first pole piece 231, the first active material layer 2312 in the first two first corner areas 2314 is provided with first grooves 2315, that is, the first grooves 2315 in the innermost ring of the first active material layer 2312. The two first corner areas 2314 are both provided with first grooves 2315 to reduce the folding radius of the innermost ring, reduce or even eliminate the stress and obstacles in the first corner area 2314 of the inner ring of the first pole piece 231, and effectively reduce the innermost ring area. This reduces the risk of the first active material layer 2312 in the first corner area 2314 of the circle cracking, falling off powder, or even the first current collector 2311 breaking, and reducing the risk of the falling active material particles penetrating the isolation film 233 .

According to some embodiments of the present application, the first groove 2315 extends along the width direction X1 of the first pole piece 231 .

In the figure, the direction indicated by the letter X1 is the width direction of the first pole piece 231 , and the width direction X1 of the first pole piece 231 is parallel to the extending direction of the winding axis of the electrode assembly 23 .

Since the width direction X1 of the first pole piece 231 is parallel to the extension direction of the winding axis of the electrode assembly 23, the first groove 2315 extends along the width direction X1 of the first pole piece 231, which can effectively alleviate the stress concentration in the first corner area 2314. .

According to some embodiments of the present application, along the winding direction of the first pole piece 231, the first active material layer 2312 of the first corner region 2314 may be provided with a plurality of first grooves 2315, and the plurality of first grooves 2315 are provided along the winding direction of the first pole piece 231. The pole pieces 231 are arranged at intervals in the winding direction.

According to some embodiments of the present application, along the winding direction of the first pole piece 231, the first groove 2315 is at least partially located in the middle of the first corner area 2314.

The middle part of the first corner area 2314 may be the center line of the first corner area 2314 , and the distance from this part to the front and rear ends of the first corner area 2314 along the winding direction of the first pole piece 231 is equal. For example, when the first corner area 2314 is unfolded, the middle part of the first corner area 2314 is the center line of the first pole piece 231 in the length direction.

The fact that the first groove 2315 is at least partially located in the middle of the first corner area 2314 means that the area where the first groove 2315 is located covers the center line of the first corner area 2314. Along the winding direction of the first pole piece 231, the first groove 2315 is located in the center of the first corner area 2314. The distance between the two ends of the groove 2315 and the corresponding two ends of the first corner area 2314 may be equal or unequal.

The middle part of the first corner area 2314 may be the stress concentration area when the first pole piece 231 is pressed. The first groove 2315 is at least partially located in the middle part of the first corner area 2314, which can effectively reduce the first activity of the first corner area 2314. There is a risk of the material layer 2312 cracking, powder falling off, or even the first current collector 2311 breaking.

According to some embodiments of the present application, as shown in Figure 6, the depth of the first groove 2315 is H1, and the thickness of the first active material layer 2312 inside the first current collector 2311 is H2, which satisfies 80%≤H1/H2≤ 100%.

In the figure, the direction indicated by letter Z1 is the thickness direction of the first pole piece 231 .

Alternatively, H1/H2 can be 80%, 85%, 90%, 95% or 100%, etc.

The first groove 2315 extends from the surface of the first active material layer 2312 in the first corner region 2314 away from the first current collector 2311 toward the first current collector 2311 . The depth of the first groove 2315 refers to the size of the first groove 2315 in the thickness direction Z1 of the first pole piece 231 . The length of the first groove 2315 refers to the size of the first groove 2315 in the width direction X1 of the first pole piece 231 .

In the above solution, the depth H1 of the first groove 2315 and the thickness H2 of the first active material layer 2312 inside the first current collector 2311 satisfy the above relationship, so that the first active material on both sides of the first groove 2315 in the width direction Layer 2312 does not interfere. If the depth of the first groove 2315 is too small, the first active material layers 2312 on both sides of the first groove 2315 in the width direction are likely to interfere, causing the first active material layers 2312 on both sides to be in contact and extruded, easily causing the first The active material layer 2312 is peeled off.

According to some embodiments of the present application, 85%≤H1/H2≤95%.

Alternatively, H1/H2 can be 85%, 88%, 90%, 92% or 95%, etc.

Relative to 80%≤H1/H2≤100%, when 85%≤H1/H2≤95%, the first active material layer 2312 on both sides of the width direction of the first groove 2315 is less likely to interfere, and the first groove 2315 is less susceptible to interference. The groove 2315 has a first active material layer 2312 with a certain capacity, so that the battery cell composed of the electrode assembly 23 has a higher energy density.

According to some embodiments of the present application, as shown in FIG. 7 , the width of the first groove 2315 is L1, and the thickness of the first active material layer 2312 inside the first current collector 2311 is H2, which satisfies 1.5≤L1/H2≤2.5. .

Alternatively, L1/H2 can be 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4 or 2.5, etc.

The width of the first groove 2315 refers to the size of the first groove 2315 in the winding direction of the first pole piece 231 . That is, when the first pole piece 231 is unfolded, the size of the first groove 2315 in the winding direction (longitudinal direction) of the first pole piece 231 is the width of the first groove 2315 .

In the above solution, the width L1 of the first groove 2315 and the thickness H2 of the first active material layer 2312 inside the first current collector 2311 satisfy the above relationship, which facilitates reducing the stress in the first corner area 2314 and reducing the stress in the first corner area. 2314, the first active material layer 2312 has the risk of cracking, powder falling off, or even the first current collector 2311 breaking. At the same time, the battery cell 20 composed of the electrode assembly 23 has a greater energy density. If the width of the first groove 2315 is too small, the first active material layers 2312 on both sides of the width direction of the first groove 2315 are likely to interfere, causing the first active material layers 2312 on both sides to be in contact and extruded, easily causing the first The active material layer 2312 is peeled off. If the width of the first groove 2315 is too large, the capacity of the first active material layer 2312 in the first corner area 2314 will be less, which will affect the energy density of the battery cell 20 composed of the electrode assembly 23 .

According to some embodiments of the present application, 1.8≤L1/H2≤2.2.

Compared with 1.5≤L1/H2≤2.5, when 1.8≤L1/H2≤2.2, it can not only reduce the stress in the first corner area 2314, but also make the battery cell 20 composed of the electrode assembly 23 have a larger Energy Density.

According to some embodiments of the present application, as shown in FIGS. 6 and 7 , the cross section of the first groove 2315 is V-shaped, semi-circular, semi-elliptical or trapezoidal.

The cross section of the first groove 2315 refers to the cross section taken from a plane perpendicular to the width direction X1 of the first pole piece 231 when the first pole piece 231 is unfolded.

In the above solution, the cross section of the first groove 2315 has the above shape, which is convenient for reducing the stress in the first corner area 2314 and also facilitates processing and manufacturing. When the cross section of the first groove 2315 is V-shaped, after the electrode assembly 23 is rolled and extruded, the distance between the two opposite groove walls of the first groove 2315 is reduced or even the two groove walls are close to each other. , can reduce the risk of lithium precipitation. When the cross section of the first groove 2315 is semicircular, semielliptical or trapezoidal, after the electrode assembly 23 is wound and extruded, the first groove 2315 is extruded and deformed, but the first groove 2315 is not When closed, the first groove 2315 can accommodate the electrolyte, so that the battery cell 20 composed of the electrode assembly 23 can store more electrolyte.

When the cross section of the first groove 2315 is V-shaped, the angle between the two opposite groove walls of the first groove 2315 is α, which satisfies 20°≤α<180°. Alternatively, α=20 °, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, etc.

Optionally, 40°≤α≤50°.

Alternatively, α=45°.

According to some embodiments of the present application, as shown in FIG. 5 , the first groove 2315 penetrates the first active material layer 2312 along the width direction X1 of the first pole piece 231 .

The first groove 2315 extends from one end to the other end of the first active material layer 2312 along the width direction X1 of the first pole piece 231 . The first groove 2315 has the largest size in the width direction X1 of the first pole piece 231 .

In the above solution, the first groove 2315 penetrates the first active material layer 2312 along the width direction X1 of the first pole piece 231, which facilitates processing and effectively reduces cracking, powder loss, and There is even a risk of the first current collector 2311 breaking.

In some embodiments, in the same first corner area 2314, multiple first grooves 2315 can be provided, and the plurality of first grooves 2315 are spaced apart along the width direction X1 of the first pole piece 231, so as to reduce the A corner area 2314 stress.

Please refer to Figure 4, and further refer to Figures 8 to 10. Figure 8 is a top view of the second pole piece in the unfolded state provided by some embodiments of the present application, and Figure 9 is a view of the second pole piece in the unfolded state provided by some embodiments of the present application. Structural diagram, Figure 10 is a partial enlarged view of B in Figure 4. According to some embodiments of the present application, the electrode assembly 23 further includes a second pole piece 232 with an opposite polarity to the first pole piece 231. The second pole piece 232 includes a second current collector 2321 and a second current collector 2321 coated on the second pole piece 232. The second active material layer 2322 on the surface of the second current collector 2321 and the second pole piece 232 have a plurality of second straight areas 2323 and a plurality of second corner areas 2324. The second straight areas 2323 and the second corner areas 2324 are along The winding directions of the second pole pieces 232 are alternately arranged; starting from the winding starting end D2 of the second pole piece 232, the second active material layers 2322 of the first M second corner areas 2324 are provided with second grooves 2325. The two grooves 2325 are located inside the second corner area 2324, M≥1.

The second pole piece 232 is a pole piece with the opposite polarity of the first pole piece 231. For example, the first pole piece 231 can be a negative pole piece, and the second pole piece 232 can be a positive pole piece; or, the first pole piece 231 can be is a positive pole piece, and the second pole piece 232 can be a negative pole piece.

The second active material layer 2322 is coated on the surface of the second current collector 2321. The second active material layer 2322 may be coated on one side of the second current collector 2321 in the thickness direction, or it may be a second active material layer. 2322 is coated on the two opposite surfaces of the second current collector 2321 in the thickness direction. Optionally, the second active material layer 2322 is coated on two opposite surfaces of the second current collector 2321 in the thickness direction.

The second straight region 2323 refers to a region where the second pole piece 232 has a parallel structure, that is, the surfaces of the second pole piece 232 in the second straight region 2323 are all planar. The second corner area 2324 refers to an area where the second pole piece 232 has a bent structure, that is, the second pole piece 232 in the second corner area 2324 is bent, and the surface of the second pole piece 232 in the second corner area 2324 is uniform. is a surface.

Starting from the winding starting end D2 of the second pole piece 232 , the first M second corner areas 2324 are M second corner areas 2324 close to the winding axis of the electrode assembly 23 .

The second groove 2325 is a groove of the second active material layer 2322 provided in the first M second corner areas 2324, and the second groove 2325 is located inside the second corner area 2324, that is, the second groove 2325 is located inside the second corner area 2324. The side of the second corner area 2324 close to the winding axis.

The second groove 2325 extends along the width direction X2 of the second pole piece 232 , and the width direction X2 of the second pole piece 232 is perpendicular to the winding direction of the second pole piece 232 .

When M=1, the second groove 2325 is disposed in the first second corner area 2324 of the second pole piece 232 from the winding start end, that is, the second groove 2325 is disposed closest to the electrode assembly 23 The second corner area 2324 of the winding axis.

The second active material layers 2322 of the first M second corner areas 2324 from the winding starting end D2 of the second pole piece 232 are provided with second grooves 2325, and the second grooves 2325 are located inside the second corner areas 2324. , the position of the second groove 2325 is the stress concentration area of the second corner area 2324. After the electrode assembly 23 is wound and compacted, it can reduce cracking, powder loss, and Even the risk of the second current collector 2321 breaking, thus reducing the risk of lithium precipitation, reducing the risk of active material particles puncturing the isolation film 233 (see Figure 4), and reducing the risk of the second current collector 2321 scratching the isolation film 233. risk, thereby improving the safety of the battery cell 20 composed of the electrode assembly 23 .

According to some embodiments of the present application, M=2.

Starting from the winding starting end D2 of the second pole piece 232, the second active material layer 2322 of the first two second corner areas 2324 is provided with second grooves 2325, that is, the second groove 2322 of the innermost ring of the second active material layer 2322. The two second corner areas 2324 are both provided with second grooves 2325 to reduce the folding radius of the innermost ring, reduce or even eliminate the stress and obstacles in the second corner area 2324 of the inner ring of the second pole piece 232, and effectively reduce the innermost ring area. The risk of the second active material layer 2322 in the second corner area 2324 of the circle cracking, powder falling off, or even the second current collector 2321 breaking, and the risk of falling off active material particles penetrating the isolation film 233 are reduced.

According to some embodiments of the present application, the second groove 2325 extends along the width direction X2 of the second pole piece 232 .

In the figure, the direction indicated by letter X2 is the width direction of the second pole piece 232 , and the width direction X2 of the second pole piece 232 is parallel to the extension direction of the winding axis of the electrode assembly 23 .

Since the width direction X2 of the second pole piece 232 is parallel to the extension direction of the winding axis of the electrode assembly 23, the second groove 2325 extends along the width direction X2 of the second pole piece 232, which can effectively alleviate the stress concentration in the second corner area 2324. .

According to some embodiments of the present application, along the winding direction of the second pole piece 232, the second active material layer 2322 of the second corner region 2324 may be provided with a plurality of second grooves 2325, and the plurality of second grooves 2325 are provided along the winding direction of the second pole piece 232. The diode pieces 232 are arranged at intervals in the winding direction.

According to some embodiments of the present application, along the winding direction of the second pole piece 232, the second groove 2325 is at least partially located in the middle of the second corner region 2324.

The middle part of the second corner area 2324 may be the center line of the second corner area 2314, and the distance from this part to the front and rear ends of the second corner area 2324 along the winding direction of the second pole piece 232 is equal. For example, when the second corner area 2324 is unfolded, the middle part of the second corner area 2324 is the centerline of the second pole piece 232 in the length direction.

The second groove 2325 is at least partially located in the middle of the second corner area 2324. This means that the area where the second groove 2325 is located covers the center line of the second corner area 2324. Along the winding direction of the second pole piece 232, the second groove 2325 is located at least partially in the middle of the second corner area 2324. The distance between the two ends of the groove 2325 and the corresponding two ends of the second corner area 2324 may be equal or unequal.

The middle part of the second corner area 2324 may be the stress concentration area during the pressing process of the second pole piece 232. The second groove 2325 is at least partially located in the middle part of the second corner area 2324, which can effectively reduce the second activity of the second corner area 2324. There is a risk of the material layer 2322 cracking, powder falling off, or even the second current collector 2321 breaking.

According to some embodiments of the present application, as shown in Figure 9, the depth of the second groove 2325 is H3, and the thickness of the second active material layer 2322 inside the second current collector 2321 is H4, which satisfies 80%≤H3/H4≤ 100%.

In the figure, the direction indicated by letter Z2 is the thickness direction of the second pole piece 232 .

Alternatively, H3/H4 can be 80%, 85%, 90%, 95% or 100%, etc.

The second groove 2325 extends from the surface of the second active material layer 2322 in the second corner region 2324 away from the second current collector 2321 toward the second current collector 2321 . The depth of the second groove 2325 refers to the size of the second groove 2325 in the thickness direction Z2 of the second pole piece 232 . The length of the second groove 2325 refers to the size of the second groove 2325 in the width direction X2 of the second pole piece 232 .

In the above solution, the depth H3 of the second groove 2325 and the thickness H4 of the second active material layer 2322 inside the second current collector 2321 satisfy the above relationship, so that the second active material on both sides of the width direction of the second groove 2325 Layer 2322 does not interfere. If the depth of the second groove 2325 is too small, the second active material layers 2322 on both sides of the second groove 2325 in the width direction are likely to interfere, causing the second active material layers 2322 on both sides to be in contact and extruded, which may easily cause a second The active material layer 2322 is peeled off.

According to some embodiments of the present application, 85%≤H3/H4≤95%.

Alternatively, H3/H4 can be 85%, 88%, 90%, 92% or 95%, etc.

Compared with 80%≤H3/H4≤100%, when 85%≤H3/H4≤95%, the second active material layer 2322 on both sides of the width direction of the second groove 2325 is less likely to interfere, and the second groove 2325 is less likely to interfere. The groove 2325 has a second active material layer 2322 with a certain capacity, so that the battery cell 20 composed of the electrode assembly 23 has a higher energy density.

According to some embodiments of the present application, as shown in FIG. 10 , the width of the second groove 2325 is L2, and the thickness of the second active material layer 2322 inside the second current collector 2321 is H4, which satisfies 1.5≤L2/H4≤2.5. .

Alternatively, L2/H4 can be 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4 or 2.5, etc.

The width of the second groove 2325 refers to the size of the second groove 2325 in the winding direction of the second pole piece 232 . That is, when the second pole piece 232 is unfolded, the size of the second groove 2325 in the winding direction (longitudinal direction) of the second pole piece 232 is the width of the second groove 2325 .

In the above solution, the width L2 of the second groove 2325 and the thickness H4 of the second active material layer 2322 inside the second current collector 2321 satisfy the above relationship, which facilitates reducing the stress in the second corner area 2324 and reducing the stress in the second corner area. The second active material layer 2322 of 2324 has the risk of cracking, powder falling off, or even the second current collector 2321 breaking. At the same time, the battery cell 20 composed of the electrode assembly 23 has a greater energy density. If the width of the second groove 2325 is too small, the second active material layers 2322 on both sides of the second groove 2325 in the width direction are likely to interfere, causing the second active material layers 2322 on both sides to be in contact and extruded, which may easily cause a second The active material layer 2322 is peeled off. If the width of the second groove 2325 is too large, the capacity of the second active material layer 2322 in the second corner area 2324 will be less, which will affect the energy density of the battery cell 20 composed of the electrode assembly 23 .

According to some embodiments of the present application, 1.8≤L2/H4≤2.2.

Compared with 1.5≤L2/H4≤2.5, when 1.8≤L2/H4≤2.2, the stress in the second corner area 2324 can be reduced, and the battery cell 20 composed of the electrode assembly 23 can also have a larger Energy Density.

According to some embodiments of the present application, as shown in FIGS. 9 and 10 , the cross section of the second groove 2325 is V-shaped, semi-circular, semi-elliptical or trapezoidal.

The cross section of the second groove 2325 refers to the cross section taken from a plane perpendicular to the width direction X2 of the second pole piece 232 when the second pole piece 232 is unfolded.

In the above solution, the cross section of the second groove 2325 has the above shape, which is convenient for reducing the stress in the second corner area 2324 and also facilitates processing and manufacturing. When the cross section of the second groove 2325 is V-shaped, after the electrode assembly 23 is rolled and extruded, the distance between the two opposite groove walls of the second groove 2325 is reduced or even the two groove walls are close to each other. , can reduce the risk of lithium precipitation. When the cross section of the second groove 2325 is semicircular, semielliptical or trapezoidal, after the electrode assembly 23 is wound and extruded, the second groove 2325 is extruded and deformed, but the second groove 2325 is not When closed, the second groove 2325 can accommodate the electrolyte, so that the battery cell 20 composed of the electrode assembly 23 can store more electrolyte.

When the cross section of the second groove 2325 is V-shaped, the angle between the two opposite groove walls of the second groove 2325 is β, satisfying 20°≤β<180°, optionally, β=20 °, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, etc.

Optionally, 40°≤β≤50°.

Alternatively, β=45°.

According to some embodiments of the present application, as shown in FIG. 8 , the second groove 2325 penetrates the second active material layer 2322 along the width direction X2 of the second pole piece 232 .

The second groove 2325 extends from one end to the other end of the second active material layer 2322 along the width direction X2 of the second pole piece 232 . The second groove 2325 has the largest size in the width direction X2 of the second pole piece 232 .

In the above solution, the second groove 2325 penetrates the second active material layer 2322 along the width direction X2 of the second pole piece 232, which facilitates processing and effectively reduces cracking, powder loss, and There is even a risk of the second current collector 2321 breaking.

In some embodiments, in the same second corner area 2324, multiple second grooves 2325 can be provided, and the plurality of second grooves 2325 are spaced apart along the width direction X2 of the second pole piece 232, so as to reduce the The stress in the second corner area 2324.

According to some embodiments of the present application, the electrode assembly 23 further includes an isolation film 233 disposed between the first pole piece 231 and the second pole piece 232 for insulating the first pole piece 231 and the second pole piece 233 . 232. The isolation film 233 can allow metal ions to pass through to facilitate the transmission of electrical energy.

It should be pointed out that in the above embodiment, when the first pole piece 231 is a negative pole piece and the second pole piece 232 is a positive pole piece, the first pole piece 231 is located inside the second pole piece 232, and the second groove is The number, position, depth and width of 2325 and the first grooves 2315 may or may not be equal. The first grooves 2315 and the second grooves 2325 must be arranged in such a way that the electrode assembly 23 satisfies the CB (Cell Balance) value of less than 1. Among them, the CB value refers to the ratio of the capacity of the negative active material per unit area to the capacity of the positive active material per unit area.

According to some embodiments of the present application, the present application also provides a battery cell 20. The battery cell 20 includes the electrode assembly 23 provided in any of the above embodiments.

According to some embodiments of the present application, the present application also provides a battery 100. The battery 100 includes a case 10 and a plurality of battery cells 20 provided in any of the above embodiments. The plurality of battery cells 20 are arranged in the case 10. Inside.

According to some embodiments of the present application, the present application also provides an electrical device. The electrical device includes the battery 100 provided in any of the above embodiments, and the battery 100 is used to provide electric energy.

The electrical equipment may be any of the above-mentioned devices or systems using the battery 100 .

According to some embodiments of the present application, referring to FIGS. 4 to 10 , the present application provides an electrode assembly 23 . The electrode assembly 23 includes a first pole piece 231 , a second pole piece 232 , and an electrode assembly disposed between the first pole piece 231 and the second pole piece 232 . In the isolation film 233 between the two pole pieces 232, the first pole piece 231 is a negative pole piece, and the second pole piece 232 is a positive pole piece. The first pole piece 231 includes a first current collector 2311 and a first active material layer 2312 coated on the surface of the first current collector 2311. The first pole piece 231 has a plurality of first straight areas 2313 and a plurality of first corner areas 2314, and the first straight areas 2313 and the first corner areas 2314 are alternately arranged along the winding direction of the first pole piece 231; wherein , starting from the winding starting end D1 of the first pole piece 231, the first active material layer 2312 of the first two first corner areas 2314 is provided with first grooves 2315, and the first grooves 2315 are located in the first corner areas 2314. The first groove 2315 extends inside and along the width direction X1 of the first pole piece 231 and penetrates the first active material layer 2312 along the width direction X1 of the first pole piece 231 . The second pole piece 232 includes a second current collector 2321 and a second active material layer 2322 coated on the surface of the second current collector 2321. The second pole piece 232 has a plurality of second straight areas 2323 and a plurality of second corner areas 2324. The second straight areas 2323 and the second corner areas 2324 are alternately arranged along the winding direction of the second pole piece 232; since Starting from the winding starting end D2 of the second pole piece 232, the second active material layer 2322 of the first two second corner areas 2324 is provided with second grooves 2325. The second grooves 2325 are located inside the second corner areas 2324 and Extending along the width direction X2 of the second pole piece 232 , the second groove 2325 penetrates the second active material layer 2322 along the width direction X2 of the second pole piece 232 .

According to the electrode assembly 23 of the embodiment of the present application, the first active material layer 2312 of the two first corner areas 2314 of the innermost ring of the first pole piece 231 is provided with a first groove 2315, and the first groove 2315 is located at the first corner area 2314 of the first pole piece 231. Inside a corner area 2314, at the same time, the second active material layer 2322 of the two innermost corners of the second pole piece 232 is provided with a second groove 2325, and the second groove 2325 is located at the second corner. The inside of the area 2324 can reduce the risk of the first active material layer 2312 in the first corner area 2314 cracking, falling off, or even the first current collector 2311 breaking, and reducing the risk of the first active material layer 2312 in the second corner area 2324 cracking, falling off. There is no risk of powder or even the first current collector 2311 breaking, thereby improving the safety of the battery cell composed of the electrode assembly 23 .

Specific examples will be used for further description below.

Example 1

Taking a lithium-ion battery cell as an example, the positive active material layer is lithium iron phosphate, the coating weight on one side is 358 mg/1540.25mm ² , and the thickness on one side is 120 μm; the negative active material layer is artificial graphite, and the coating weight on one side is 245mg/1540.25mm ² , single-sided thickness 67μm. Use a V-shaped scraper to make grooves in the two corners of the innermost ring before winding the positive electrode piece and the negative electrode piece respectively, and clean up the dust. The V-shaped grooves in the two corner areas of the innermost ring of the positive electrode plate have a width of 240 μm and a depth of 110 μm; the V-shaped grooves in the two corner areas of the innermost ring of the negative electrode plate have a width of 134 μm and a depth of 60 μm. The positive electrode piece and the negative electrode piece in the inner corner area of the electrode assembly obtained by rolling and pressing have no active material layer cracking, powder falling off, base material exposure, base material cracking, falling active material particles piercing the isolation film, etc. question.

Example 2

Taking a lithium-ion battery cell as an example, the positive active material layer is lithium nickel cobalt manganate 811 ternary system, the coating weight on one side is 404mg/1540.25mm ² , and the thickness on one side is 76μm; the negative active material layer is artificial graphite. The coating weight on one side is 261mg/1540.25mm ² , and the thickness on one side after cold pressing is 102μm. Use an arc-shaped scraper to groove the positive and negative electrode pieces in the two corner areas of the innermost ring before winding them, and clean up the dust. The width of the arc-shaped grooves in the two corner areas of the innermost ring of the positive electrode plate is 152 μm and the depth is 70 μm; the width of the arc-shaped grooves in the two corner areas of the innermost ring of the negative electrode plate is 204 μm and the depth is 60 μm. The positive and negative electrode plates in the inner corner area of the electrode assembly obtained by rolling and pressing have no problems such as active material cracking, powder falling off, base material exposure, base material cracking, and falling active material particles piercing the isolation film. .

While the present application has been described with reference to preferred embodiments, various modifications may be made and equivalents may be substituted for components thereof without departing from the scope of the application. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any way. The application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims (23)

1. An electrode assembly. The electrode assembly has a wound structure. The electrode assembly includes a first pole piece. The first pole piece includes a first current collector and a first current collector coated on the surface of the first current collector. Active material layer, the first pole piece has a plurality of first straight areas and a plurality of first corner areas, the first straight areas and the first corner areas follow the roll of the first pole piece Arranged alternately around directions;

   Wherein, starting from the winding starting end of the first pole piece, the first active material layers in the first N first corner areas are provided with first grooves, and the first grooves are located in the first Inside a corner area, N≥1.
2. The electrode assembly of claim 1, wherein N=2.
3. The electrode assembly according to claim 1 or 2, wherein the first groove extends along the width direction of the first pole piece.
4. The electrode assembly according to any one of claims 1 to 3, wherein the first groove is at least partially located in the middle of the first corner region along the winding direction of the first pole piece.
5. The electrode assembly according to any one of claims 1 to 4, wherein the depth of the first groove is H1, and the thickness of the first active material layer inside the first current collector is H2, satisfying 80%≤H1/H2≤100%.
6. The electrode assembly according to claim 5, wherein 85%≤H1/H2≤95%.
7. The electrode assembly according to any one of claims 1 to 6, wherein the width of the first groove is L1, and the thickness of the first active material layer inside the first current collector is H2, satisfying 1.5≤L1/H2≤2.5.
8. The electrode assembly according to claim 7, wherein 1.8≤L1/H2≤2.2.
9. The electrode assembly according to any one of claims 1 to 8, wherein the cross section of the first groove is V-shaped, semi-circular, semi-elliptical or trapezoidal.
10. The electrode assembly according to any one of claims 1 to 9, wherein the first groove penetrates the first active material layer along the width direction of the first pole piece.
11. The electrode assembly according to any one of claims 1 to 10, wherein the electrode assembly further includes a second pole piece, the second pole piece has an opposite polarity to the first pole piece, and the second pole piece has a polarity opposite to that of the first pole piece. The pole piece includes a second current collector and a second active material layer coated on the surface of the second current collector. The second pole piece has a plurality of second straight areas and a plurality of second corner areas. Two straight areas and the second corner area are alternately arranged along the winding direction of the second pole piece;

    Starting from the winding starting end of the second pole piece, the second active material layers in the first M second corner areas are provided with second grooves, and the second grooves are located at the second corners. Inside the area, M≥1.
12. The electrode assembly of claim 11, wherein M=2.
13. The electrode assembly according to claim 11 or 12, wherein the second groove extends along the width direction of the second pole piece.
14. The electrode assembly according to any one of claims 11 to 13, wherein the second groove is at least partially located in the middle of the second corner region along the winding direction of the second pole piece.
15. The electrode assembly according to any one of claims 11 to 14, wherein the depth of the second groove is H3, and the thickness of the second active material layer inside the second current collector is H4, satisfying 80%≤H3/H4≤100%.
16. The electrode assembly according to claim 15, wherein 85%≤H3/H4≤95%.
17. The electrode assembly according to any one of claims 11 to 16, wherein the width of the second groove is L2, and the thickness of the second active material layer inside the second current collector is H4, satisfying 1.5≤L2/H4≤2.5.
18. The electrode assembly according to claim 17, wherein 1.8≤L2/H4≤2.2.
19. The electrode assembly according to any one of claims 11 to 18, wherein the cross section of the second groove is V-shaped, semi-circular, semi-elliptical or trapezoidal.
20. The electrode assembly according to any one of claims 11 to 19, wherein the second groove penetrates the second active material layer along the width direction of the second pole piece.
21. A battery cell including the electrode assembly according to any one of claims 1-20.
22. A battery includes a box and a plurality of battery cells according to claim 21, and a plurality of the battery cells are arranged in the box.
23. An electrical device includes the battery according to claim 22, wherein the battery is used to provide electrical energy.

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