Battery monomer, battery device and electric equipment

Abstract

The utility model relates to the technical field of batteries, provides a battery monomer, a battery device and electric equipment, and can reduce or avoid the problem of pole piece cracking. The battery monomer comprises a shell and an electrode assembly, the electrode assembly is arranged in the shell and comprises pole pieces and diaphragms, the pole pieces and the diaphragms are wound to form a multi-layer structure, and the pole pieces and the diaphragms are alternately stacked; the diaphragm comprises a plurality of diaphragm layers along the thickness direction of the pole piece; the electrode assembly comprises a plane area and a corner area, and the porosity of the diaphragm layer in the corner area is smaller than that of the diaphragm layer in the plane area; in the corner area, the plurality of diaphragm layers comprise a first diaphragm layer and a second diaphragm layer, the first diaphragm layer is closer to the winding center of the electrode assembly than the second diaphragm layer, and the porosity of at least one part of the first diaphragm layer is smaller than that of the corresponding area of the second diaphragm layer.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, battery device and electrical equipment. Background Technology

[0002] Currently, most battery cells are manufactured using a wound electrode assembly method. During the charging and discharging process, the battery cell expands, and with each charge-discharge cycle, stress gradually accumulates within the cell, which may lead to electrode breakage, affecting the battery's stability and lifespan. Utility Model Content

[0003] This application provides a battery cell, a battery device, and an electrical appliance that can reduce or avoid the problem of electrode cracking.

[0004] This application provides a battery cell, including a housing and an electrode assembly, wherein the electrode assembly is disposed within the housing and includes an electrode sheet and a separator, the electrode sheet and the separator being wound to form a multilayer structure, and the electrode sheet and the separator being alternately stacked; along the thickness direction of the electrode sheet, the separator includes multiple separator layers; the electrode assembly includes a planar region and a corner region, the porosity of the separator layer in the corner region is less than the porosity of the separator layer in the planar region; in the corner region, the multiple separator layers include a first separator layer and a second separator layer, the first separator layer being closer to the winding center of the electrode assembly than the second separator layer, and the porosity of at least a portion of the first separator layer being less than the porosity of the corresponding region of the second separator layer.

[0005] The battery cell, electrode, and separator winding provided in this application have a multi-layered separator structure along the thickness direction of the electrode, with each layer being a separator layer. Among the multiple separator layers in the corner region of the electrode assembly, there is at least a first separator layer and a second separator layer. The first separator layer is closer to the winding center of the electrode assembly than the second separator layer, and at least a portion of the porosity of the first separator layer is less than the porosity of the corresponding region of the second separator layer. That is, it includes at least two separator layers, with the porosity of the separator layer closer to the winding center being less than that of the separator layer farther from the winding center. Thus, since the porosity of the inner ring is smaller than that of the outer ring, the lithium insertion amount of the negative electrode near the inner ring can be effectively reduced, thereby reducing electrode rebound and mitigating the impact of electrode expansion force deterioration in the later stages of battery cell charge-discharge cycles. This reduces the deformation and cracking risk of the outer ring electrode, while simultaneously reducing the compressive stress of the inner ring electrode, further reducing the cracking risk of the inner ring electrode. Therefore, the problem of electrode cracking can be reduced or avoided.

[0006] In some embodiments of this application, the diaphragm includes a variable gap layer group along the thickness direction of the electrode sheet, the variable gap layer group includes at least two diaphragm layers, and the porosity of the diaphragm layers in the variable gap layer group gradually increases; in the first diaphragm layer and the second diaphragm layer, at least the second diaphragm layer belongs to the variable gap layer group.

[0007] Here, in the diaphragm, the diaphragm layers with varying porosity can be set in specific layers. Therefore, a variable porosity layer group is set, which includes at least two diaphragm layers, and the porosity of the diaphragm layers in the variable porosity layer group gradually increases. In this way, by setting the porosity variation in specific layers or specific locations, the porosity can be easily controlled and adjusted to meet different technical requirements and reduce or avoid the problem of electrode cracking.

[0008] In some embodiments of this application, along the thickness direction of the electrode sheet, the separator further includes a basic layer group, which includes at least two separator layers. The basic layer group is closer to the winding center of the electrode assembly than the variable gap layer group, and the porosity of the separator layers in the basic layer group is equal. The first separator layer belongs to the basic layer group or the variable gap layer group, and the second separator layer belongs to the variable gap layer group.

[0009] Here, within the diaphragm, there can also be combinations that do not exhibit porosity changes, namely, basic layer groups. These basic layer groups consist of at least two diaphragm layers, and the porosity of the diaphragm layers within the basic layer group is equal, meaning no porosity change occurs. This facilitates overall layout and setup, making porosity adjustment more convenient. Furthermore, it reduces process steps involving porosity changes, improves production efficiency, and lowers production costs.

[0010] In some embodiments of this application, the basic layer group is closer to the winding center of the electrode assembly than the variable gap layer group, and the porosity of the diaphragm layer in the basic layer group is less than the porosity of any diaphragm layer in the variable gap layer group.

[0011] Here, the basic layer group is closer to the inside than the variable gap layer group. Therefore, the porosity of the membrane layer in the basic layer group is less than that of the membrane layer in the variable gap layer group, so that the membrane of the entire electrode assembly always maintains that the porosity of the inner part is less than that of the outer part.

[0012] In some embodiments of this application, the number of layers in the variable gap layer group accounts for between one-quarter and one-half of the total number of layers in the diaphragm.

[0013] Here, a range of the number of layers in the variable porosity layer group is given, which can be between one-quarter and one-half of the total number of layers. This allows for a greater number of layers with varying porosity in the diaphragm of the electrode assembly, thereby enhancing the effect of reducing electrode cracking.

[0014] In some embodiments of this application, along the circumference of the electrode assembly, the variable gap layer group covers the central axis region of the corner region.

[0015] Here, the stress of the electrode assembly is relatively large in the central axis region of the corner area. Therefore, in order to avoid the electrode sheet cracking in this area, the variable gap layer group covers the central axis region of the corner area.

[0016] In some embodiments of this application, along the circumference of the electrode assembly, the variable gap layer group covers the central axis region of the corner region in a fan shape, and the area of ​​the variable gap layer group is greater than or equal to one-quarter of the area of ​​the entire corner region.

[0017] Here, the areas of high electrode stress in the corner region of the electrode assembly are roughly fan-shaped. Therefore, the corresponding variable gap layer group covers the central axis region of the corner region in a fan shape, further enhancing the ability to prevent electrode cracking.

[0018] In some embodiments of this application, the variable gap layer completely covers the corner area along the circumference of the electrode assembly.

[0019] Here, the variable porosity layer completely covers the corner area, and the porosity variation in the entire corner area has been optimized, making the electrode in the entire corner area more resistant to cracking.

[0020] In some embodiments of this application, in the corner region, the difference in porosity between the membrane layer with the largest porosity and the membrane layer with the smallest porosity is greater than or equal to 15%.

[0021] Here, a maximum range of porosity differences is set to further prevent electrode cracking.

[0022] In some embodiments of this application, the diaphragm includes a base membrane, a first adhesive layer, and a second adhesive layer, the first adhesive layer and the second adhesive layer being coated on two opposite surfaces of the base membrane; in the first diaphragm layer, the porosity of at least one of the base membrane, the first adhesive layer and the second adhesive layer is less than the porosity of the corresponding base membrane, the first adhesive layer and the second adhesive layer in the second diaphragm layer.

[0023] Here, porosity can be controlled by altering the porosity of any one or more of the base membrane, the first adhesive layer, and the second adhesive layer in the diaphragm. This allows for more diverse methods of porosity adjustment and control, adapting to different design requirements.

[0024] A second aspect of this application provides a battery device, including a housing and a battery cell of the first aspect, wherein the battery cell of the first aspect is disposed in the housing.

[0025] The battery device provided in this application, since it includes the battery cell of the first aspect, has the same technical effect, namely, it can reduce or avoid the problem of electrode cracking.

[0026] A third aspect of this application provides an electrical device, including a battery device for providing electrical energy (a second aspect).

[0027] The battery device provided in this application, since it includes the battery device of the second aspect, has the same technical effect, namely, it can reduce or avoid the problem of electrode cracking. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a vehicle as the electrical equipment in an embodiment of this application;

[0031] Figure 2 This is a schematic diagram of the battery device according to an embodiment of this application;

[0032] Figure 3 This is an exploded structural diagram of a battery cell according to an embodiment of this application;

[0033] Figure 4 This is one of the structural schematic diagrams of the electrode assembly of a battery cell according to an embodiment of this application;

[0034] Figure 5 This is a second schematic diagram of the electrode assembly of a battery cell according to an embodiment of this application;

[0035] Figure 6 This is a porosity variation diagram of trends a, b, and c of the separator of the battery cell in an embodiment of this application.

[0036] Figure 7 This is a diagram showing the porosity changes of the separator in the battery cell according to an embodiment of this application, based on trends d, e, and f.

[0037] Figure 8 This is a porosity variation diagram of trends g, h, and j of the separator of a battery cell in an embodiment of this application.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1000-Electrical equipment; 100-Battery unit; 200-Controller; 300-Motor; 110-Casing; 111-First casing section; 112-Second casing section; 120-Battery cell; 1-Shell; 2-Electrode assembly; 21-Electrode sheet; 22-Separator; 221-Separator layer; 222-Variable gap layer group; 223-Basic layer group. Detailed Implementation

[0040] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0043] In the description of the embodiments of this application, technical terms such as "first," "second," and "third" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0044] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0045] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects are in an "or" relationship.

[0046] In the description of the embodiments of this application, the technical terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed, operated or used in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0047] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0048] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical term "contact" should be interpreted broadly, and can be direct contact, contact through an intermediate medium layer, contact between two contacting parties with substantially no interaction force, or contact between two contacting parties with interaction force.

[0049] The following is a detailed description of this application.

[0050] In the related technology, during the cyclic charging and discharging process of the battery cell 120 and electrode assembly 2, the electrode 21 expands and rebounds significantly, which increases the expansion force of the cell. In addition, the interlayer compressive stress of the electrode 21 is large, resulting in a large tensile deformation of the electrode 21. At the same time, the electrode 21 is affected by the extrusion friction and local tensile deformation force, which makes the electrode 21 prone to cracking and affects the service life of the battery cell 120.

[0051] This application discloses a battery cell 120, a battery device 100, and an electrical device 1000, which can reduce or avoid the problem of electrode 21 cracking.

[0052] Electrical equipment 1000 can include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, vehicles, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0053] The battery device 100 disclosed in this application embodiment can be used in electrical equipment 1000 that uses batteries as power sources, or as energy storage devices, wherein energy storage devices include energy storage containers, energy storage cabinets, etc.

[0054] In the following embodiments, for ease of explanation, an example of an electrical device according to an embodiment of this application is a vehicle.

[0055] Figure 1 The diagram illustrates the structure of a vehicle as provided in some embodiments of this application. The vehicle 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 vehicles, etc. Figure 1 As shown, a battery device 100 is installed inside the vehicle. The battery device 100 can be located at the bottom, front, or rear of the vehicle. The battery device 100 can be used to power the vehicle; for example, the battery device 100 can serve as the vehicle's operating power source. The vehicle may also include a controller 200 and a motor 300. The controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle during starting, navigation, and driving.

[0056] In some embodiments of this application, the battery device 100 can not only serve as the operating power source for the vehicle, but also as the driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0057] Figure 2 This is an exploded view of a battery device 100 provided in some embodiments of this application. The battery device 100 mentioned in the embodiments of this application may also include one or more battery cell 120 assemblies (not shown in the figure, please refer to the combination of multiple battery cells 120) for providing voltage and capacity. The battery cell 120 assembly may include multiple battery cells 120, which are connected in series, parallel, or mixed connection through a busbar.

[0058] In some embodiments, the battery cell assembly 120 is typically formed by arranging multiple battery cells 120.

[0059] As an example, the battery cell 120 assembly can be a battery module, which is composed of multiple battery cells 120 arranged and fixed to form an independent module.

[0060] As an example, a battery module can be formed by bundling multiple battery cells 120 together with cable ties.

[0061] In some embodiments, such as Figure 2 As shown, the battery device 100 can be a battery pack, which includes a housing 110 and one or more battery cells 120 assemblies, the battery cells 120 assemblies being housed within a cavity.

[0062] As an example, the battery cell 120 assembly can be a battery module, and the battery cell 120 assembly can be housed in the cavity by fixing the battery module in the cavity.

[0063] As an example, the battery cell 120 assembly can also be housed in the cavity by directly fixing multiple battery cells 120 to the cavity.

[0064] As an example, such as Figure 2 As shown, the housing 110 may include a first housing part 110 and a second housing part 110. The first housing part 110 and the second housing part 110 are fastened together to form a closed space, or cavity, inside the housing 110 to house the battery cell 120 assembly. Here, "closed" refers to covering or closing, which can be sealed or unsealed. The first housing part 110 may be a top cover or a bottom plate.

[0065] In some embodiments, the housing 110 may be part of the vehicle's chassis structure. For example, a portion of the housing 110 may be at least a portion of the vehicle's floor, or a portion of the housing 110 may be at least a portion of the vehicle's crossbeams and longitudinal beams.

[0066] In this embodiment of the application, the battery cell 120 can be a secondary battery. A secondary battery refers to a battery cell 120 that can be used again after being discharged by recharging to activate the active materials.

[0067] The battery cell 120 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.

[0068] Additionally, by way of example, the battery cell 120 can be a cylindrical battery cell 120, a prismatic battery cell 120, a pouch battery cell 120, or a battery cell 120 of other shapes. The prismatic battery cell 120 includes a prismatic battery cell 120, a blade-shaped battery cell 120, and a multi-prismatic battery cell 120. For example, the multi-prismatic battery cell 120 is a hexagonal prismatic battery cell 120. There are no particular limitations in the embodiments of this application.

[0069] Reference Figure 3In some embodiments, the housing includes an end cap and a housing 1. The housing 1 has an opening, and the end cap closes the opening to form a sealed space for accommodating the electrode assembly 2 and substances such as electrolytes. The housing 1 may have one or more openings. One or more end caps may also be provided.

[0070] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through an adapter. The electrode terminal can be provided on the end cap or on the housing 1.

[0071] In some embodiments, a pressure relief mechanism is provided on the housing. The pressure relief mechanism is used to release the internal pressure of the battery cell 120.

[0072] A battery cell 120 typically includes an electrode assembly 2. The electrode assembly 2 includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell 120, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator is positioned between the positive and negative electrodes to prevent short circuits while allowing active ions to pass through.

[0073] In some embodiments, the electrode assembly 2 further includes an isolator disposed between the positive and negative electrodes.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] In some embodiments, the battery cell 120 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, or solid.

[0078] In some embodiments, the electrode assembly 2 is a wound structure. The positive electrode 21 and the negative electrode 21 are wound into a wound structure.

[0079] As an example, multiple positive electrode plates 21 and multiple negative electrode plates 21 can be set, and multiple positive electrode plates 21 and multiple negative electrode plates 21 can be stacked alternately.

[0080] As an example, multiple positive electrode plates 21 can be provided, and negative electrode plates 21 can be folded to form multiple stacked folded segments, with a positive electrode plate 21 sandwiched between adjacent folded segments.

[0081] As an example, both the positive electrode 21 and the negative electrode 21 are folded to form multiple stacked folded segments.

[0082] As an example, multiple separators can be provided, each disposed between any adjacent positive electrode 21 or negative electrode 21.

[0083] As an example, the separator can be continuously arranged, and can be arranged between any adjacent positive electrode 21 or negative electrode 21 by folding or rolling.

[0084] In some embodiments, the electrode assembly 2 may be flat.

[0085] In some embodiments, the electrode assembly 2 is provided with tabs that can conduct current from the electrode assembly 2. The tabs include a positive tab and a negative tab.

[0086] Reference Figure 3 This application provides a battery cell 120, including a housing 1 and an electrode assembly 2, wherein the electrode assembly 2 is disposed within the housing 1, as shown in the figure. Figure 4 and Figure 5 The electrode assembly 2 includes an electrode 21 and a separator 22. The electrode 21 and the separator are wound to form a multilayer structure, and the electrode 21 and the separator are alternately stacked. Along the thickness direction of the electrode 21, the separator includes a plurality of separator layers 221. The electrode assembly 2 includes a planar region and a corner region. The porosity of the separator layer 221 in the corner region is less than the porosity of the separator layer 221 in the planar region. In the corner region, the plurality of separator layers 221 include a first separator layer 221 and a second separator layer 221. The first separator layer 221 is closer to the winding center of the electrode assembly 2 than the second separator layer 221. The porosity of at least a portion of the first separator layer 221 is less than the porosity of the corresponding region of the second separator layer 221.

[0087] The electrode 21 and the diaphragm are wound together to form a multi-layer structure, which means that the electrode 21 and the diaphragm are wound together. In other words, the electrode assembly 2 can be a wound structure.

[0088] The electrode assembly 2 exhibits a multi-layered structure, meaning that the electrode 21 and the diaphragm are stacked and alternate.

[0089] A planar region refers to the area in the electrode assembly 2 where the electrode sheet 21 is flat or has very little bending and is nearly flat. In the prismatic battery, the wound electrode assembly 2 is shaped into an elliptical structure. In this elliptical structure, except for the flat parts of the two arcs, the electrode sheet 21 is basically flat and has no bending, which is a planar region.

[0090] The corner region refers to the area in the electrode assembly 2 where the electrode sheet 21 has a larger bending amount. After the wound electrode assembly 2 is wound, it needs to be shaped and installed into the housing 1. For example, in a prismatic battery, the wound electrode assembly 2 will be shaped into an elliptical structure, in which the electrode sheet 21 with a larger bending amount in the two arc parts of the ellipse is the corner region.

[0091] It should be noted that after the electrode 21 is wound, it first forms a cylinder with a circular cross-section. Then, through stretching, shaping, and other processes, it forms a cylinder with an approximately elliptical cross-section. This cross-section can be understood as a rectangle with a semi-circular fan-shaped structure on each of its opposite sides. That is, the rectangular part is a planar area, and the fan-shaped part is a corner area.

[0092] The electrode assembly 2 of the battery cell 120 in this embodiment can be a wound structure. In the wound electrode assembly 2, refer to... Figure 4 and Figure 5 The corner area has a greater degree of curvature, especially the inner electrode 21 in the corner area, which is prone to cracking when the electrode 21 is subjected to pressure. Therefore, the embodiments of this application can optimize the porosity distribution of the separator in the corner area, thereby more effectively reducing the rebound, tensile deformation and interlayer compressive stress of the electrode 21, and thus effectively reducing the risk of cracking of the electrode 21 in the corner area.

[0093] Along the thickness direction of the electrode 21, the separator comprises multiple separator layers 221. This means that the separator has a multi-layered structure along the thickness direction of the electrode 21, with each layer being a separator layer 221. Each separator layer 221 can be understood as a segment that completes one turn around the center of the electrode assembly 2. In a scheme where the electrode 21 and the separator are continuously wound using a continuous sheet structure, the definition of each turn can be either the outermost or innermost turn. For example, starting from the outermost end of the separator, one turn around the center of the electrode assembly 2 constitutes the outermost separator layer 221, and then sequentially moving inwards, each turn around the center of the electrode assembly 2 constitutes a separator layer 221.

[0094] The multiple membrane layers 221, including a first membrane layer 221 and a second membrane layer 221, means that at least two of the multiple membrane layers 221 can satisfy the following structural requirements. For ease of description, these two membrane layers 221 can be defined as the first membrane layer 221 and the second membrane layer 221. It should be noted that the first membrane layer 221 and the second membrane layer 221 may be any two membrane layers 221 that satisfy the structural requirements among the multiple membrane layers 221, and do not specifically refer to two membrane layers 221 with fixed positions among the multiple membrane layers 221.

[0095] The winding center of electrode assembly 2 refers to the innermost center of electrode sheet 21 during winding. Electrode sheet 21 is wound around this center to form the basic structure of electrode assembly 2. It should be noted that in the battery cell 120 of this application embodiment, the winding center of the corner region in electrode assembly 2 is the geometric center of the corner region, that is, the center of the semi-circular sector.

[0096] The fact that the first diaphragm layer 221 is closer to the winding center of the electrode assembly 2 than the second diaphragm layer 221 means that the positions of the first diaphragm layer 221 and the second diaphragm layer 221 are different relative to the winding center, and the first diaphragm layer 221 is relatively closer to the inner ring, while the second diaphragm layer 221 is relatively closer to the outer ring.

[0097] Porosity refers to the percentage of pore volume in a material to the total volume of the material in its natural state. In other words, components with low porosity are relatively denser, while those with high porosity are relatively less dense.

[0098] At least a portion of the first membrane layer 221 means that the first membrane layer 221 may have a porosity that is less than the porosity of the corresponding region of the second membrane layer 221, or a portion of the first membrane layer 221 may have a porosity that is less than the porosity of the corresponding region of the second membrane layer 221.

[0099] The region corresponding to the second membrane layer 221 refers to the area along the radial direction of the electrode assembly 2 where the porosity of the second membrane layer 221 corresponds radially to the portion of the first membrane layer 221 where the porosity changes. In other words, along the radial direction of the electrode assembly 2, at least a portion of the first membrane layer 221 has a porosity that is smaller than the porosity of the corresponding radial portion of the second membrane layer 221.

[0100] The battery cell 120, electrode 21, and separator winding provided in this application have a multi-layered structure along the thickness direction of the electrode 21, with each layer being a separator layer 221. Among the multiple separator layers 221 in the corner region of the electrode assembly 2, there is at least a first separator layer 221 and a second separator layer 221. The first separator layer 221 is closer to the winding center of the electrode assembly 2 than the second separator layer 221, and the porosity of at least a portion of the first separator layer 221 is less than the porosity of the corresponding region of the second separator layer 221. In other words, at least two separator layers 221 are included, with the porosity of the separator layer 221 closer to the winding center being less than the porosity of the separator layer 221 farther from the winding center. In this way, since the porosity of the inner ring is smaller than that of the outer ring, the amount of lithium intercalated in the negative electrode 21 near the inner ring can be effectively reduced, thereby reducing the rebound of the electrode 21. This mitigates the impact of the deterioration of the expansion force of the electrode 21 in the later stages of the battery cell's 120 charge-discharge cycle, reduces the deformation and cracking risk of the outer ring electrode 21, and simultaneously reduces the compressive stress of the inner ring electrode 21, further reducing the risk of cracking. Therefore, the problem of electrode 21 cracking can be reduced or avoided.

[0101] It should be noted that in the battery cell 120 of this application embodiment, the separator layer 221 with low porosity effectively reduces the channels for lithium ions. This slows down the extraction and insertion of lithium ions during the charging and discharging process of the battery cell 120, resulting in less expansion of the electrode 21 and less stress, making it less prone to cracking. Simultaneously, the reduced expansion of the separator layer 221 with low porosity also reduces its impact on the expansion of the outer electrode 21, further reducing the stress on the outer electrode 21. Therefore, the outer electrode 21 is also less prone to cracking. In summary, by setting the porosity of the inner layer to be lower than that of the outer layer, the amount of lithium inserted into the negative electrode 21 can be effectively reduced, the rebound of the electrode 21 can be reduced, and the interlayer compressive stress can be decreased, thereby reducing the risk of cracking of the electrode 21.

[0102] Furthermore, in the battery cell 120 of this application embodiment, the porosity of at least a portion of the first separator layer 221 is less than the porosity of the corresponding region of the second separator layer 221. This can be improved based on related technologies. The improvement direction can be to increase the porosity of the second separator layer 221, that is, the separator layer 221 relatively to the outer ring; or it can be to decrease the porosity of the first separator layer 221, that is, the separator layer 221 relatively to the inner ring; of course, it can also be adjusted in both directions. Among them, the embodiment of reducing the porosity of the first separator layer 221, that is, the separator layer 221 relatively to the inner ring, is easy to implement, has the least impact on the battery cell 120, and has better electrochemical performance.

[0103] Here, because the corner area of ​​the electrode assembly 2 is subjected to greater stress than the planar area, the porosity of the membrane layer 221 in the corner area is less than that in the planar area, making the electrode 21 in the corner area less prone to cracking.

[0104] In the battery cell 120 of this application embodiment, the porosity of the separator is optimized so that the porosity of at least one separator layer 221 relative to the inner ring is less than the porosity of the separator layer 221 relative to the outer ring. The specific porosity setting and pattern can be implemented in various ways. For example, there may be porosity variations between adjacent separator layers 221; or porosity variations every two or more separator layers 221; or the first two cases may alternate or occur randomly. Furthermore, the region, location, and size of the porosity optimization can also be set as needed. Some possible implementation methods are illustrated below.

[0105] In some embodiments of this application, the diaphragm includes a variable gap layer group 222 extending outward along the thickness direction of the electrode 21. The variable gap layer group 222 includes at least two diaphragm layers 221, and the porosity of the diaphragm layers 221 in the variable gap layer group 222 gradually increases. In the first diaphragm layer and the second diaphragm layer, at least the second diaphragm layer belongs to the variable gap layer group 222.

[0106] The membrane includes a variable porosity layer group 222, which includes at least two membrane layers 221. For ease of description, at least two membrane layers 221 with optimized porosity are named a variable porosity layer group 222. The variable porosity layer group 222 may include two or more membrane layers 221.

[0107] The gradual increase in porosity of the membrane layer 221 in the variable gap layer group 222 means that the porosity of the membrane layer 221 in the variable gap layer group 222 can increase layer by layer or every few layers. In other words, the porosity of the membrane layer 221 in the variable gap layer group 222 generally shows a gradual increasing trend, and conforms to the rule that the porosity of the inner membrane layer 221 is less than that of the outer membrane layer 221.

[0108] In the first diaphragm layer and the second diaphragm layer, at least the second diaphragm layer belongs to the variable gap layer group 222. This means that in the above scheme, the multiple diaphragm layers 221 include the first diaphragm layer 221 and the second diaphragm layer 221. When the variable gap layer group 222 is provided, the second diaphragm layer must belong to the variable gap layer group 222. The first diaphragm layer may or may not belong to the variable gap layer group 222.

[0109] In this embodiment, the membrane layer 221 with varying porosity in the diaphragm can be set in specific layers. Based on this, a variable porosity layer group 222 is provided, which includes at least two membrane layers 221, and the porosity of the membrane layers 221 in the variable porosity layer group 222 gradually increases. In this way, by setting the porosity variation in specific layers or specific locations, the porosity can be easily controlled and adjusted to meet different technical requirements, and the problem of electrode 21 cracking can be reduced or avoided.

[0110] In some embodiments of this application, the porosity growth pattern of the membrane layer 221 in the variable gap layer group 222 along the radial outward direction of the electrode assembly 2 includes at least one of linear growth, exponential growth, logarithmic growth, and stepwise growth.

[0111] Where y is the porosity value, x is the number of concentric circles (1 for the innermost circle and N for the outermost circle), c is the initial porosity of the innermost circle, K can range from 0.004 to 0.007, a can range from 0.01006122 to 0.01012245, b can range from -0.00012245 to -0.00006122, and k can range from 0.05 to 0.09.

[0112] Linear growth refers to the growth of values ​​at a fixed slope, which is represented by a sloping straight line.

[0113] Exponential growth refers to the growth of values ​​that increase with curvature, which approaches infinity or zero, and its behavior is parabolic.

[0114] Logarithmic growth is characterized by the growth of values ​​that increase with curvature approaching zero, exhibiting a parabolic pattern.

[0115] Step-growth refers to a process where the values ​​increase at intervals within a certain range, and the curve in the chart is represented by a matrix of dots or line segments at different heights.

[0116] Here, the porosity of the membrane layer 221 can be increased in various ways, for example, linear growth, exponential growth, logarithmic growth, step growth, etc. These growth methods can be selected and set according to actual needs.

[0117] To better understand the porosity growth pattern of the membrane layer 221 in the variable porosity layer, some possible embodiments are shown with reference to the figures. Figure 6 The graph shows the porosity changes for trends a, b, and c; refer to... Figure 7 The graph shows the porosity changes for trends d, e, and f; refer to... Figure 8 , which shows the porosity changes for trends g, h, and j. Figure 6The functional formulas for the porosity changes of trends a, b, and c are as follows:

[0118] Trend a:

[0119] Trend b:

[0120] Trend c:

[0121] in This represents the porosity value. The number of concentric circles (ranging from 1 to N, where 1 is the innermost circle and N is the outermost circle). The initial porosity of the innermost circle (this porosity can be 20%~35%). The value range can be 0.004 to 0.007. The value range can be 0.01006122~0.01012245. The value range can be -0.00012245 to -0.00006122. The value can range from 0.05 to 0.09.

[0122] In some embodiments of this application, in the corner region, the difference in porosity between the membrane layer 221 with the largest porosity and the membrane layer 221 with the smallest porosity is greater than or equal to 15%.

[0123] Here, the maximum range of porosity difference is set to further prevent the electrode 21 from cracking.

[0124] In some embodiments of this application, along the thickness direction of the electrode 21, the separator further includes a basic layer group 223, which includes at least two separator layers 221. The basic layer group 223 is closer to the winding center of the electrode assembly 2 than the variable gap layer group 222. The porosities of the separator layers 221 in the basic layer group 223 are equal. The first separator layer belongs to the basic layer group 223 or the variable gap layer group 222, and the second separator layer belongs to the variable gap layer group 222.

[0125] The diaphragm also includes a basic layer group 223, which includes at least two diaphragm layers 221. This means that among the multiple diaphragm layers 221 of the diaphragm, at least two consecutive diaphragm layers 221 have equal porosity. These combinations can be defined as the basic layer group 223.

[0126] The fact that the porosity of the membrane layer 221 in the basic layer group 223 is equal means that the porosity of the membrane layer 221 does not change.

[0127] The first diaphragm layer belongs to the basic layer group 223 or the variable gap layer group 222. The second diaphragm layer belongs to the variable gap layer group 222. This means that in the above scheme, the multiple diaphragm layers 221 include the first diaphragm layer 221 and the second diaphragm layer 221. When the basic layer group 223 and the variable gap layer group 222 are provided, the second diaphragm layer must belong to the variable gap layer group 222. The first diaphragm layer belongs to the basic layer group 223 or it can belong to the variable gap layer group 222.

[0128] Here, within the diaphragm, there can also be combinations that do not exhibit porosity changes, namely, a basic layer group 223. This basic layer group 223 includes at least two diaphragm layers 221, and the porosity of the diaphragm layers 221 in the basic layer group 223 is equal, meaning there is no porosity change. This facilitates the overall layout and setup, making porosity adjustment more convenient. Moreover, it reduces the process flow involving porosity changes, improves production efficiency, and lowers production costs.

[0129] In the battery cell 120 of this application embodiment, there may be both a variable gap layer group 222 and a basic layer group 223. Provided that the basic layer group 223 is closer to the winding center of the electrode assembly 2 than the variable gap layer group 222, the specific number of layers and the level of the variable gap layer group 222 and the basic layer group 223 can be set as needed.

[0130] In some embodiments of this application, the basic layer group 223 is closer to the winding center of the electrode assembly 2 than the variable gap layer group 222, and the porosity of the membrane layer 221 in the basic layer group 223 is less than the porosity of any membrane layer 221 in the variable gap layer group 222.

[0131] The porosity of the membrane layer 221 in the basic layer group 223 is less than the porosity of any membrane layer 221 in the variable gap layer group 222. This means that the porosity of all membrane layers 221 in the basic layer group 223 will be less than the porosity of the smallest membrane layer 221 in the variable gap layer group 222. This allows for flexible configuration of specific porosity optimization schemes, ensuring that the porosity of the membrane layers 221 in the relatively inner layer group 223 is always less than the porosity of the membrane layers 221 in the relatively outer layer group 222.

[0132] Here, the basic layer group 223 is closer to the inside than the variable gap layer group 222. Therefore, the porosity of the membrane layer 221 in the basic layer group 223 is less than the porosity of the membrane layer 221 in the variable gap layer group, so that the membrane of the entire electrode assembly 2 always maintains that the porosity of the inner part is less than the porosity of the outer part.

[0133] In some embodiments of this application, the number of layers in the variable gap layer group 222 accounts for between one-quarter and one-half of the total number of layers in the diaphragm.

[0134] Here, the range of the number of layers in the variable porosity layer group 222 is given, which can be between one-quarter and one-half of the total number of layers. In this way, the porosity variation of the diaphragm in the electrode assembly 2 has a large number of varying layers, thereby enhancing the effect of reducing the cracking of the electrode sheet 21.

[0135] It should be noted that "between one-quarter and one-half" refers to values ​​including one-quarter, one-half, and values ​​between one-quarter and one-half, such as one-third. That is, in some embodiments, the number of layers in the variable gap layer group 222 accounts for one-third of the total number of layers in the membrane.

[0136] Reference Figure 4 and Figure 5 In some embodiments of this application, the porosity of multiple membrane layers 221 in the planar region of the electrode assembly 2 is consistent, and the porosity of the membrane layer 221 in the planar region is greater than that of the membrane layer 221 in the corner region.

[0137] In the embodiment of this application, which includes a basic layer group 223 and a variable gap layer group 222, the porosity of the membrane layer 221 in the planar region is greater than that of the membrane layer 221 in the basic layer group 223. That is, the porosity of the membrane layer 221 in the basic layer group 223 is not gradually varied, and can be smaller than that of the membrane layer 221 in the planar region. In this way, the overall porosity of the corner region is smaller than that of the planar region, and the electrode 21 in the corner region is less prone to cracking.

[0138] In some embodiments of this application, the porosity of the membrane layer 221 in the planar region is 40% to 55%, and the porosity of the membrane layer 221 in the basic layer group 223 is 20% to 35%.

[0139] For the wound-type battery module of the square-shell battery cell 120 with high silicon system, the porosity setting range of this embodiment can be applied.

[0140] Here, some embodiments are given of the porosity range of the membrane layer 221 in the planar region and the porosity range of the membrane layer 221 in the base layer, which makes the electrode 21 less prone to cracking.

[0141] The porosity of the multiple membrane layers 221 in the variable gap layer group 222 is optimized, which can effectively prevent the electrode 21 from cracking. Based on this, in order to target areas of the electrode 21 that are prone to cracking, such as corner areas, the variable gap layer group 222 is set in the corner areas. The variable gap layer group 222 can be set in a part of the corner area or in the entire corner area.

[0142] Reference Figure 4 and Figure 5In some embodiments of this application, along the circumference of the electrode assembly 2, the variable gap layer group 222 covers the central axis region of the corner region.

[0143] The central region of the corner area refers to the middle position of the corner area along the circumference of the electrode assembly 2, that is, the central region of the corner area that is relatively far from both sides.

[0144] Since the stress of the electrode assembly 2 is relatively large in the central axis region of the corner area, in order to prevent the electrode sheet 21 in this area from cracking, the variable gap layer group 222 covers the central axis region of the corner area.

[0145] The variable gap layer group 222 covers the central axis region of the corner area. It can be that the variable gap layer group 222 only covers the central axis region of the corner area, or the variable gap layer group 222 covers the entire corner area.

[0146] Based on this, refer to Figure 4 In some embodiments of this application, along the circumference of the electrode assembly 2, the variable gap layer group 222 covers the central axis region of the corner region in a fan shape, and the area of ​​the variable gap layer group 222 is greater than or equal to one-quarter of the area of ​​the entire corner region.

[0147] Here, the areas of high stress in the electrode 21 within the corner region of the electrode assembly 2 are roughly fan-shaped. Therefore, correspondingly, the variable gap layer group 222 covers the central axis region of the corner region in a fan shape, further enhancing the ability to prevent the electrode 21 from cracking.

[0148] Reference Figure 5 In some other embodiments of this application, the variable gap layer group 222 completely covers the corner area along the circumference of the electrode assembly 2.

[0149] Here, the variable porosity layer group 222 completely covers the corner area, and the porosity change of the entire corner area has been optimized, making the electrode 21 in the entire corner area more resistant to cracking.

[0150] In the embodiments of the battery cell 120 of this application, the porosity change of the separator layer 221 can be achieved by process means, and the porosity change of the separator layer 221 can be controlled by different structural regions inside it.

[0151] In some embodiments of this application, the diaphragm includes a base membrane, a first adhesive layer, and a second adhesive layer, the first adhesive layer and the second adhesive layer being coated on two opposite surfaces of the base membrane; in the first diaphragm layer 221, the porosity of at least one of the base membrane, the first adhesive layer and the second adhesive layer is less than the porosity of the corresponding base membrane, the first adhesive layer and the second adhesive layer in the second diaphragm layer 221.

[0152] Here, porosity can be controlled by altering the porosity of any one or more of the base membrane, the first adhesive layer, and the second adhesive layer in the diaphragm. This allows for more diverse methods of porosity adjustment and control, adapting to different design requirements.

[0153] The porosity of the base film can be controlled through the film formation process. For example, the porosity difference of the base film in different layers and different locations can be achieved by intermittent dry stretching. For example, after the melt extrusion of materials such as PP, PE, PVDF, and PTFE, the initial stretching rate is 10-100 mm / min at a stretching temperature of 120-160℃. Starting from the inner ring, the unidirectional / bidirectional stretching ratio of the base film in the corner area and the planar area is controlled at intervals. The stretching ratio of the base film in the planar area is 3-5 times, and the stretching ratio of the inner and middle ring base films in the corner area is 1-3 times. Starting from the outer ring base film in the corner area, every N rings (N is 1-3), the stretching ratio is decreased by a certain value of 0.01-0.2 times, so that the porosity of the base film in the outer corner area increases by 0.1%-2% ring by ring.

[0154] Porosity control of the first and / or second adhesive layers can be achieved through a coating process. For example, different specific gravities of PCS and PCCS layers can be applied intermittently to the base film surface to achieve differences in porosity in different rings and locations of the diaphragm 22. For instance, the initial weight of the PCS and PCCS coating on the planar diaphragm 22 is 0.3–0.5 mg / 1540.25 mm², the thickness is 1–2 μm, and the air permeability is 100–150 s / cc. The initial weight of the PCS and PCCS coating on the inner and middle rings of the corner diaphragm 22 is 0.55–0.85 mg / 1540.25 mm², the thickness is 3–5 μm, and the air permeability is 150–300 s / cc, with a thickness ratio of 1.5–3 times to the planar adhesive layer thickness and an air permeability ratio of 1.3–2 times. In the corner region, the outer ring of the diaphragm 22 layer is applied every N rings (N is 1...). ~3) A certain weight value of 0.01~0.1mg / 1540.25mm2 is added in each ring to achieve a thickness of 0.01um~1um for the 22 layers of diaphragm in the outer corner area.

[0155] This application also provides a battery device 100, including a housing 110 and a battery cell 120 as described in the above embodiment, wherein the battery cell 120 is disposed inside the housing 110.

[0156] The battery device 100 provided in this application has the same technical effect as the battery cell 120 in the above embodiment, and can reduce or avoid the problem of electrode 21 cracking.

[0157] This application also provides an electrical device 1000, including a battery device 100 of the above embodiments for providing electrical energy.

[0158] The battery device 100 provided in this application, since it includes the battery device 100 of the above embodiment, has the same technical effect and can reduce or avoid the problem of electrode 21 cracking.

[0159] The above are merely specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery cell, characterized in that, include: case; An electrode assembly, disposed within the housing, includes an electrode sheet and a diaphragm, wherein the electrode sheet and the diaphragm are wound to form a multi-layered structure, and the electrode sheet and the diaphragm are alternately stacked; Along the thickness direction of the electrode sheet, the separator comprises multiple separator layers; The electrode assembly includes a planar region and a corner region, wherein the porosity of the membrane layer in the corner region is less than the porosity of the membrane layer in the planar region; In the corner region, the plurality of membrane layers include a first membrane layer and a second membrane layer, wherein the first membrane layer is closer to the winding center of the electrode assembly than the second membrane layer, and at least a portion of the porosity of the first membrane layer is less than the porosity of the corresponding region of the second membrane layer.

2. The battery cell according to claim 1, characterized in that, Along the thickness direction of the electrode sheet outward, the diaphragm includes a variable gap layer group, the variable gap layer group includes at least two diaphragm layers, and the porosity of the diaphragm layers in the variable gap layer group gradually increases; Of the first diaphragm layer and the second diaphragm layer, at least the second diaphragm layer belongs to the variable gap layer group.

3. The battery cell according to claim 2, characterized in that, Along the thickness direction of the electrode sheet, the separator further includes a basic layer group, the basic layer group including at least two separator layers, the basic layer group being closer to the winding center of the electrode assembly than the variable gap layer group, and the porosity of the separator layers in the basic layer group being equal. The first membrane layer belongs to the basic layer group or the variable gap layer group, and the second membrane layer belongs to the variable gap layer group.

4. The battery cell according to claim 3, characterized in that, The basic layer group is closer to the winding center of the electrode assembly than the variable gap layer group, and the porosity of the diaphragm layer in the basic layer group is less than the porosity of any one of the diaphragm layers in the variable gap layer group.

5. The battery cell according to claim 3, characterized in that, The number of layers in the variable gap layer group accounts for between one-quarter and one-half of the total number of layers in the diaphragm.

6. The battery cell according to claim 2, characterized in that, Along the circumferential direction of the electrode assembly, the variable gap layer group covers the central axis region of the corner region.

7. The battery cell according to claim 6, characterized in that, Along the circumference of the electrode assembly, the variable gap layer group covers the central axis region of the corner region in a fan shape, and the area of ​​the variable gap layer group is greater than or equal to one-quarter of the area of ​​the entire corner region.

8. The battery cell according to claim 6, characterized in that, Along the circumference of the electrode assembly, the variable gap layer completely covers the corner region.

9. The battery cell according to claim 1, characterized in that, Within the corner region, the difference in porosity between the membrane layer with the largest porosity and the membrane layer with the smallest porosity is greater than or equal to 15%.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The diaphragm includes a base membrane, a first adhesive layer, and a second adhesive layer, wherein the first adhesive layer and the second adhesive layer are coated on two opposite surfaces of the base membrane; In the first membrane layer, the porosity of at least one of the base membrane, the first adhesive layer, and the second adhesive layer is less than the porosity of the corresponding base membrane, the first adhesive layer, and the second adhesive layer in the second membrane layer.

11. A battery device, characterized in that, include: Box; The battery cell according to any one of claims 1 to 10 is disposed in the housing.

12. An electrical appliance, characterized in that, include: The battery device of claim 11 for providing electrical energy.

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