Electrode assembly, battery cell, battery, and electrical device

Abstract

The present application provides an electrode assembly, a battery cell, a battery, and an electrical device. The electrode assembly comprises electrode sheets, and the electrode sheets are wound in a winding direction; the electrode assembly has two first planes opposite to each other in a first direction, two second planes opposite to each other in a second direction, and arc-shaped surfaces, each arc-shaped surface is connected to two adjacent first plane and second plane, and the winding direction, the first direction and the second direction intersect in pairs; surfaces, where two ends of one arc-shaped surface are connected to a center line, and the corresponding arc-shaped surface define a bending area; each electrode sheet comprises a current collector and an active material layer, and the active material layer is coated on the current collector; the current collector in at least the bending area comprises an elastic layer and a conductive layer, the conductive layer is arranged on at least one side of the elastic layer in the thickness direction, and the active material layer is coated on the side of the conductive layer facing away from the elastic layer.

Description

Electrode assembly, battery cell, battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202420136152.3, filed on January 19, 2024, entitled “Electrode assembly, battery cell, battery and electrical device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an electrode assembly, a battery cell, a battery, and an electrical device. Background Art

[0004] Batteries are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes and power tools, etc.

[0005] In the development of battery cell technology, in addition to improving the performance of battery cells, the reliability of battery cells is also an issue that needs to be considered. Therefore, how to improve the reliability of battery cells is an issue that needs to be continuously improved in battery cell technology.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide an electrode assembly, a battery cell, a battery, and an electrical device, which can improve the reliability of the battery cell.

[0008] In the first aspect, the present application provides an electrode assembly including a pole piece, which is wound along a winding direction; the electrode assembly has two first planes opposite to each other along a first direction, two second planes opposite to each other along a second direction, and an arcuate surface, the arcuate surface connects the two adjacent first planes and second planes, and the winding direction, the first direction, and the second direction intersect with each other; the arcuate surface has a center line, and the connecting surfaces of the two ends of the arcuate surface and the center line and the arcuate surface form a bending area, the pole piece includes a current collector and an active material layer, and the active material layer is coated on the current collector; at least the current collector in the bending area includes an elastic layer and a conductive layer, the conductive layer is provided on at least one side of the elastic layer along the thickness direction, and the active material layer is coated on the side of the conductive layer facing away from the elastic layer.

[0009] The electrode assembly provided in the embodiment of the present application is configured such that the electrode assembly includes a first plane relative to each other along a first direction and a second plane relative to each other along a second direction. When the electrode assembly is applied to a battery cell, this is beneficial for increasing the capacity of the battery cell, thereby increasing the energy density of the battery cell. The current collector provided in the bending zone includes an elastic layer and a conductive layer. The high ductility and high elasticity of the elastic layer can be utilized to buffer the bending force and stress concentration borne by the pole pieces in the bending zone, thereby reducing the gap between the pole pieces of the electrode assembly. This helps reduce the risk of lithium deposition in the pole pieces in the bending zone during use of the electrode assembly, and reduces the risk of the pole pieces rupturing due to bending. Thus, when the electrode assembly is applied to a battery cell, this helps improve the reliability of the battery cell.

[0010] In some embodiments, the current collector of each electrode sheet at any location along the winding direction of the electrode sheet includes an elastic layer and a conductive layer. This helps improve the overall elasticity of the current collector of the electrode assembly and reduces stress concentration in the current collector. Furthermore, during the preparation of the electrode assembly, the electrode sheets each include an elastic layer and a conductive layer, allowing for an integrated electrode sheet molding arrangement, facilitating the manufacture of the electrode assembly.

[0011] In some embodiments, the conductive layer is disposed on both sides of the elastic layer along the thickness direction, which is beneficial for increasing the capacity of the electrode assembly and the flow capacity of the current collector.

[0012] In some embodiments, the elastic layer is made of polyethylene terephthalate or polypropylene, which helps to further reduce the gap between the pole pieces in the bending area, thereby reducing the risk of lithium deposition in the pole pieces in the bending area and further reducing the risk of pole pieces breaking in the bending area.

[0013] In some embodiments, the conductive layer is made of copper or aluminum, which is beneficial for improving the conductivity of the conductive layer and the current carrying capacity of the electrode tab of the electrode assembly.

[0014] In some embodiments, the thickness h of the conductive layer satisfies: 0.5 μm ≤ h ≤ 1.5 μm. This is beneficial for improving the conductivity of the current collector of the electrode assembly and, when the electrode assembly is used in a battery cell, also for improving the energy density of the battery cell.

[0015] In some embodiments, the elastic modulus E of the elastic layer satisfies: 5000 MPa≤E≤9000 MPa. This is beneficial for improving the stress concentration buffering effect of the elastic layer on the current collector while simplifying the preparation process of the current collector.

[0016] In some embodiments, the elongation at break of the elastic layer satisfies: 30%≤e≤80%, which helps to further reduce the risk of the current collector in the bend area breaking and the risk of stress concentration in the current collector in the bend area.

[0017] In some embodiments, the two first planes are parallel to each other, the two second planes are parallel to each other, and the plane on which the first planes lie and the plane on which the second planes lie are perpendicular to each other. When the electrode assembly is applied to a battery cell, it is beneficial to further improve the utilization of the internal space of the battery cell, thereby increasing the energy density of the battery cell.

[0018] In some embodiments, a tangent plane at one end of the curved surface connected to the first plane is tangent to the corresponding first plane; and / or a tangent plane at one end of the curved surface connected to the second plane is tangent to the corresponding second plane. This helps reduce the risk of distortion of the first plane or the second plane during the electrode assembly molding process, thereby reducing the risk of lithium deposition during use due to shape distortion of the electrode assembly.

[0019] In a second aspect, a battery cell provided according to an embodiment of the present application includes a housing and an electrode assembly provided by any of the above embodiments, wherein the housing has a receiving cavity, and the electrode assembly is received in the receiving cavity.

[0020] The battery cell provided in the embodiment of the present application is conducive to improving the energy density of the battery cell, reducing the risk of lithium plating in the battery cell, and reducing the risk of the battery cell electrode rupture during use, which is conducive to improving the reliability of the battery cell.

[0021] In a third aspect, an embodiment of the present application provides a battery, comprising the battery cell provided in the above embodiment.

[0022] The battery provided in the embodiment of the present application has the same technical effects as the battery cells provided in the above embodiments, and thus will not be described in detail here.

[0023] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising the battery provided in the above embodiment, and the battery is used to provide electrical energy.

[0024] The electrical device provided in the embodiment of the present application has the same technical effects as the battery provided in the above embodiment, and thus will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0026] FIG1 is a schematic structural diagram of a vehicle provided in an embodiment of the present application;

[0027] FIG2 is a schematic structural diagram of a battery provided in an embodiment of the present application;

[0028] FIG3 is a schematic structural diagram of a battery module in a battery provided in an embodiment of the present application;

[0029] FIG4 is a schematic diagram of an exploded structure of a battery cell provided in an embodiment of the present application;

[0030] FIG5 is a front view of an electrode assembly provided in an embodiment of the present application;

[0031] FIG6 is a cross-sectional view of an electrode piece of an electrode assembly provided in an embodiment of the present application;

[0032] FIG7 is a cross-sectional view of an electrode piece of another electrode assembly provided in an embodiment of the present application.

[0033] In the accompanying drawings, the drawings are not necessarily drawn to scale.

[0034] Marking Description:

[0035] 1. Vehicle; 1a. Motor; 1b. Controller;

[0036] 10. Battery; 11. First housing; 12. Second housing;

[0037] 20. Battery module;

[0038] 30. Battery cell; 31. Housing; 31a. Accommodation cavity; 311. Housing; 312. End cap; 32. Electrode assembly; 32a. Bend region; 321. Electrode body; 321a. First plane; 321b. Second plane; 321c. Arc-shaped surface; 321d. Centerline; 321e. Connection surface; 322. Tab;

[0039] 40, pole piece; 41, current collector; 411, elastic layer; 412, conductive layer; 42, active material layer;

[0040] M, winding direction; X, first direction; Y, second direction; Z, thickness direction. DETAILED DESCRIPTION

[0041] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0042] In the description of this application, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly perpendicular, but is within the allowable error range. "Parallel" is not strictly parallel, but is within the allowable error range.

[0043] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0044] It should also be noted that, in the description of this application, unless otherwise specified or limited, the terms "installed," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0045] The term "plurality" used in this application refers to two or more (including two).

[0046] In this application, battery cells may include lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium-lithium-ion battery cells, sodium-ion battery cells, or magnesium-ion battery cells, and the embodiments of this application are not limited thereto. Battery cells may be cylindrical, flat, rectangular, or in other shapes, and the embodiments of this application are not limited thereto.

[0047] The battery mentioned in the embodiments of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in hybrid through a busbar.

[0048] In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0049] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are housed in the case.

[0050] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0051] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0052] A battery cell typically includes an electrode assembly. This assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of a battery cell, active ions (such as lithium ions) are inserted and removed between the positive and negative electrodes. The separator, located between the positive and negative electrodes, prevents short circuits while allowing the active ions to pass through.

[0053] In some embodiments, the positive electrode may be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0054] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0055] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium with a silver surface treatment may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0056] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, this application is not limited to these materials; other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used singly or in combination of two or more.

[0057] In some embodiments, the positive electrode may be a carbon foam or a metal foam. The metal foam may be nickel foam, copper foam, aluminum foam, or an alloy foam, among others. When the metal foam is used as the positive electrode, the surface of the metal foam may or may not be provided with a positive electrode active material. For example, a lithium source material, potassium metal, or sodium metal may be filled and / or deposited within the metal foam, where the lithium source material is lithium metal and / or a lithium-rich material.

[0058] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0059] As an example, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, silver-surface-treated stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0060] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0061] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0062] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0063] In some embodiments, the negative electrode may be made of carbon foam or metal foam. The metal foam may be nickel foam, copper foam, aluminum foam, or alloy foam. When the metal foam is used as the negative electrode sheet, the surface of the metal foam may or may not be provided with a negative electrode active material.

[0064] As an example, the negative electrode current collector may be filled with or / and deposited with a lithium source material, potassium metal, or sodium metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0065] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0066] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode and the negative electrode. The present application does not particularly limit the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0067] As an example, the main material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0068] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on needs. The electrolyte can be liquid, gel, or solid.

[0069] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into the wound structure.

[0070] In some embodiments, the electrode assembly is a laminate structure.

[0071] Multiple positive electrode sheets and multiple negative electrode sheets can be provided respectively, and multiple positive electrode sheets and multiple negative electrode sheets can be alternately stacked.

[0072] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet may be folded to form a plurality of stacked folded segments, with a positive electrode sheet being sandwiched between adjacent folded segments.

[0073] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of stacked folded segments.

[0074] As an example, a plurality of separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0075] As an example, the separator may be provided continuously, and may be provided between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0076] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0077] In some embodiments, the electrode assembly is provided with tabs that can conduct current from the electrode assembly. The tabs include a positive tab and a negative tab.

[0078] The battery cell also includes a housing, which has a housing formed inside for accommodating the electrode assembly. The housing can protect the electrode assembly from the outside to prevent external foreign matter from affecting the charging or discharging of the electrode assembly.

[0079] The more space the electrode assembly occupies in the shell, the more conducive it is to improving the energy density of the battery. For this reason, it is necessary to set the shape of the electrode assembly to match the shape of the shell as much as possible. In the related art, in the preparation of the electrode assembly, after the electrode assembly is wound and formed, after being shaped in one direction to form two first planes opposite to the electrode assembly, the electrode assembly is also shaped along another intersecting direction to form two other opposite second planes of the electrode assembly, and the first plane and the second plane intersect and are respectively straight. However, the electrode assembly formed in this way will form a bending zone in the area where the first plane and the second plane intersect, and the gap between the pole pieces in the bending zone will be larger, and the pole pieces in the bending zone will be subjected to greater bending stress, which can easily cause lithium deposition and fracture of the pole pieces in the bending zone. In this way, when the electrode assembly is used in a battery cell, the reliability performance of the battery cell is seriously affected.

[0080] In view of this, an embodiment of the present application provides a technical solution, which provides a current collector for the electrode in the bending zone including an elastic layer and a conductive layer. When the electrode in the bending zone is bent, the bending stress of the electrode is relieved by the elastic deformation of the elastic layer, and the elastic layer in the bending zone is easy to deform, which is beneficial to reducing the gap between the electrode pieces. In this way, it is beneficial to reduce the problem of stress concentration in the electrode in the bending zone, and is beneficial to the gap between the electrode pieces in the bending zone, and further helps to increase the risk of electrode breakage and lithium plating in the bending zone. In the scenario where the electrode assembly is used in the battery, it is beneficial to improve the reliability performance of the battery cell.

[0081] The technical solutions described in the embodiments of the present application are applicable to electrode assemblies, battery cells including electrode components, batteries including battery cells, and electrical devices using batteries.

[0082] Electrical devices may include vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. Vehicles may include fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles may include pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0083] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device.

[0084] As shown in FIG1 , a battery 10 is provided inside a vehicle 1. The battery 10 may be provided at the bottom, head, or tail of the vehicle 1. The battery 10 may be used to power the vehicle 1, for example, the battery 10 may serve as an operating power source for the vehicle 1.

[0085] The vehicle 1 may further include a controller 1b and a motor 1a. The controller 1b is used to control the battery 10 to supply power to the motor 1a, for example, to meet the power requirements of the vehicle 1 during starting, navigation, and driving.

[0086] In some embodiments of the present application, the battery 10 can not only serve as the operating power source of the vehicle 1, but also serve as the driving power source of the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0087] 2 , the battery 10 includes battery cells (not shown in FIG2 ) and may further include a case for accommodating the battery cells.

[0088] The box body is used to accommodate battery cells, and the box body can be of various structural forms. In some embodiments, the box body can include a first box body portion 11 and a second box body portion 12. The first box body portion 11 and the second box body portion 12 cover each other. The first box body portion 11 and the second box body portion 12 jointly define a storage space for accommodating battery cells. The second box body portion 12 can be a hollow structure with one end open, and the first box body portion 11 is a plate-shaped structure. The first box body portion 11 covers the open side of the second box body portion 12 to form a box body with a storage space; the first box body portion 11 and the second box body portion 12 can also both be hollow structures with one side open. The open side of the first box body portion 11 covers the open side of the second box body portion 12 to form a box body with a storage space. Of course, the first box body portion 11 and the second box body portion 12 can be of various shapes, such as cylinders, cuboids, etc.

[0089] In order to improve the sealing performance after the first box body 11 and the second box body 12 are connected, a sealing member such as a sealant or a sealing ring may be provided between the first box body 11 and the second box body 12 .

[0090] Assuming that the first box body portion 11 covers the second box body portion 12 , the first box body portion 11 can also be referred to as an upper box cover, and the second box body portion 12 can also be referred to as a lower box body.

[0091] In the battery 10, there can be one or more battery cells. If there are multiple battery cells, they can be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections. Multiple battery cells can be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery module 20 is housed in a housing. Alternatively, multiple battery cells can be first connected in series, in parallel, or in a hybrid connection to form a battery module 20. Multiple battery modules 20 are then connected in series, in parallel, or in a hybrid connection to form a single unit, which is then housed in a housing.

[0092] As shown in FIG3 , in some embodiments, a battery module 20 includes multiple battery cells 30. Multiple battery cells 30 are first connected in series, parallel, or in series to form a battery module 20. Multiple battery modules 20 are then connected in series, parallel, or in series to form a single unit and housed in a housing.

[0093] In some embodiments, the multiple battery cells 30 in the battery module 20 may be electrically connected via a busbar 50 to achieve parallel connection, series connection, or mixed connection of the multiple battery cells 30 in the battery module 20 .

[0094] The battery 10 may also not have a box body, but include multiple battery cells connected in series or in parallel. After the multiple battery cells are connected in series or in parallel, they are fixed by structures such as steel belts or binding straps. Then, multiple batteries 10 are connected in series or in parallel to form a new energy storage unit.

[0095] In some embodiments, the multiple battery cells in the battery 10 may be electrically connected via the busbar 50 to achieve parallel connection, series connection, or hybrid connection of the multiple battery cells in the battery 10 .

[0096] As shown in Figures 4 to 7, the electrode assembly 32 provided according to the embodiment of the present application includes a pole piece 40, which is wound along a winding direction M. The electrode assembly 32 has two first planes 321a opposite each other along a first direction X, two second planes 321b opposite each other along a second direction Y, and an arcuate surface 321c. The arcuate surface 321c connects the two adjacent first planes 321a and second planes 321b, and the winding direction M, the first direction X, and the second direction Y intersect. The arcuate surface 321c has a centerline 321d. The connecting surfaces 321e at both ends of the arcuate surface 321c and the centerline 321d, as well as the arcuate surface 321c, form a bending region 32a. The pole piece 40 includes a current collector 41 and an active material layer 42. The active material layer 42 is coated on the current collector 41. The current collector 41 of at least the bending region 32 a includes an elastic layer 411 and a conductive layer 412 . The conductive layer 412 is disposed on at least one side of the elastic layer 411 along the thickness direction Z. The active material layer 42 is coated on the side of the conductive layer 412 facing away from the elastic layer 411 .

[0097] The electrode assembly 32 includes a positive electrode sheet, a negative electrode sheet and an isolating member, and the isolating member is arranged between the positive electrode sheet and the negative electrode sheet. The electrode sheet 40 provided in the embodiment of the present application can be used as the positive electrode sheet of the electrode assembly 32, or, it can also be used as the negative electrode sheet of the electrode assembly 32, or, the positive electrode sheet and the negative electrode sheet of the electrode assembly 32 can be provided to include the electrode sheet 40 provided in the embodiment of the present application, except that the materials of the current collector 41 of the positive electrode sheet and the negative electrode clip or the specific materials of the active material layer 42 are not the same.

[0098] The electrode assembly 32 includes two first planes 321a that are opposite to each other along a first direction X, and two second planes 321b that are opposite to each other along a second direction Y. The first planes 321a and the second planes 321b are respectively straight. The first direction X and the second direction Y intersect, and optionally, the first direction X and the second direction Y can be perpendicular to each other.

[0099] It should be noted that the first plane 321a and the second plane 321b mentioned here are straight, and the first plane 321a and the second plane 321b are not necessarily absolutely flat. Instead, within the allowable error range, the first plane 321a and the second plane 321b have a certain flatness error range and surface roughness range.

[0100] The electrode sheet 40 is wound along a winding direction M, and the positive electrode sheet, negative electrode sheet, and separator of the electrode assembly 32 can be first formed into a cylindrical electrode assembly through a winding process. Since the electrode assembly 32 includes a first flat surface 321a and a second flat surface 321b, during the preparation of the electrode assembly 32, after the positive electrode sheet, separator, and negative electrode sheet are wound together to form a cylindrical electrode assembly, the cylindrical electrode assembly can be subjected to a molding and shaping process using two pressing plates to form two first flat surfaces 321a that are opposite to each other along the first direction X and two second flat surfaces 321b that are opposite to each other along the second direction Y, thereby forming the finished electrode assembly 32.

[0101] The arcuate surface 321c has a centerline 321d, and the arcuate surface 321c can be in an arc shape or an elliptical shape. The two ends of the arcuate surface 321c, the connecting surfaces 321e of the centerline 321d, and the arcuate surface 321c enclose a bending region 32a. The pole piece 40 in the bending region 32a is all in a coiled shape, while the pole piece 40 in the area opposite the first plane 321a and the second plane 321b, excluding the arcuate region, can be straight.

[0102] By setting the electrode assembly 32 to include a first plane 321a opposite along the first direction X and a second plane 321b opposite along the second direction Y, when the electrode assembly 32 is applied to the battery cell 30, it is beneficial to increase the gap between the electrode assembly 32 and the outer shell 31 of the battery cell 30, and thus it is beneficial to fully utilize the space within the outer shell 31 to increase the capacity of the battery cell 30, and thus increase the energy density of the battery cell 30.

[0103] Since the arcuate surface 321 c connects the first plane 321 a and the second plane 321 b , one electrode assembly 32 may have four arcuate surfaces 321 c and four bending regions 32 a spaced apart from each other.

[0104] The electrode 40 includes a current collector 41 and an active material layer 42. At least the current collector 41 in the bending area 32a includes an elastic layer 411 and a conductive layer 412. The current collector 41 in the bending area 32a can be set to include an elastic layer 411 and a conductive layer 412, while the current collector 41 of the electrode 40 outside the bending area 32a of the electrode assembly 32 can only include the conductive layer 412; or, the current collector 41 of the electrode 40 in any area can also be set to include both a conductive layer 412 and an elastic layer 411, which can be selected according to actual needs.

[0105] The current collector 41 in the bend region 32a includes an elastic layer 411 and a conductive layer 412. The elastic layer 411 may be made of a polymer material. Compared to the conductive layer 412, the elastic layer 411 has excellent elasticity and ductility. During the shaping process of the electrode assembly 32, the deformation of the elastic layer 411 can buffer the bending force and stress concentration experienced by the electrode pieces 40 in the bend region 32a. This helps reduce the gap between the electrode pieces 40 in the bend region 32a and helps reduce the risk of the electrode pieces 40 in the bend region 32a rupturing due to bending. Furthermore, the elastic layer 411 has a low hardness and is not easily pierced through the separators between the electrode pieces 40 of the electrode assembly 32, which helps improve the safety margin of the electrode assembly 32.

[0106] Therefore, the electrode assembly 32 provided in the embodiment of the present application, by providing the electrode assembly 32 including first planes 321a opposite each other along the first direction X and second planes 321b opposite each other along the second direction Y, is advantageously used to increase the capacity of the battery cell 30, thereby increasing the energy density of the battery cell 30. Furthermore, the current collector 41 provided in the bending region 32a includes an elastic layer 411 and a conductive layer 412. The high ductility and high elasticity of the elastic layer 411 can be utilized to buffer the bending force and stress concentration experienced by the electrode pieces 40 in the bending region 32a, thereby advantageously reducing the gaps between the electrode pieces 40 of the electrode assembly 32. This, during use of the electrode assembly 32, is advantageously used to reduce the risk of lithium deposition in the electrode pieces 40 in the bending region 32a, as well as the risk of the electrode pieces 40 rupturing due to bending. Thus, when the electrode assembly 32 is used in the battery cell 30, it is advantageously used to improve the reliability of the battery cell 30.

[0107] In some embodiments, along the winding direction M of the pole piece 40 , the current collector 41 of the pole piece 40 at any location includes an elastic layer 411 and a conductive layer 412 .

[0108] In this way, along the winding direction M of the electrode piece 40, the current collector 41 includes an elastic layer 411 and a conductive layer 412, which is beneficial to improving the overall elasticity of the current collector 41 of the electrode assembly 32 and reducing the stress concentration phenomenon of the current collector 41. In addition, during the preparation process of the electrode assembly 32, the electrode piece 40 includes an elastic layer 411 and a conductive layer 412, and the electrode piece 40 can be set to be an integrally formed setting, which facilitates the manufacture of the electrode assembly 32.

[0109] As shown in FIG. 7 , in some embodiments, the conductive layer 412 is disposed on both sides of the elastic layer 411 along the thickness direction Z.

[0110] Since the active material layer 42 is coated on the conductive layer 412, by arranging the conductive layer 412 on both sides of the elastic layer 411 along the thickness direction Z, the active material layer 42 can be coated on both sides of the current collector 41 along the thickness direction Z. This is beneficial to improving the capacity of the electrode assembly 32 and improving the flow capacity of the current collector 41.

[0111] In some embodiments, the material of the elastic layer 411 includes polyethylene terephthalate (PET) or polypropylene (PP).

[0112] Both PET and PP have good elasticity and ductility, and have good mechanical properties and bending resistance. Therefore, setting the material of the elastic layer 411 includes PET or PP, which is beneficial to further reduce the gap between the pole pieces 40 in the bending area 32a, so as to reduce the risk of lithium deposition in the pole pieces 40 in the bending area 32a, and is beneficial to further reduce the risk of rupture of the pole pieces 40 in the bending area 32a.

[0113] In some embodiments, the material of the conductive layer 412 includes copper or aluminum.

[0114] The portion of one end of the conductive layer 412 that is not coated with the active material layer 42 can be used to form the tab 322 of the electrode assembly 32. Both copper and aluminum have good electrical conductivity and low resistance. Therefore, setting the material of the conductive layer 412 to include copper or aluminum is beneficial to improving the electrical conductivity of the conductive layer 412 and improving the current flow capacity of the tab 322 of the electrode assembly 32.

[0115] As shown in FIG. 6 and FIG. 7 , in some embodiments, the thickness h of the conductive layer 412 satisfies: 0.5 μm≤h≤1.5 μm.

[0116] Optionally, h may be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm, etc.

[0117] It can be understood that the thicker the conductive layer 412 is, the more conducive it is to improving the conductivity of the current collector 41 , and the thinner the conductive layer 412 is, the more conducive it is to reducing the volume and weight of the electrode assembly 32 .

[0118] After long-term research and numerous experiments, the inventors found that setting 0.5 μm≤h≤1.5 μm is beneficial to improving the conductivity of the current collector 41 of the electrode assembly 32 while also improving the energy density of the battery cell 30 when the electrode assembly 32 is applied to the battery cell 30.

[0119] In some embodiments, the elastic modulus E of the elastic layer 411 satisfies: 5000 MPa≤E≤9000 MPa.

[0120] Optionally, the elastic modulus E of the elastic layer 411 may be 5000 MPa, 5500 MPa, 6000 MPa, 6500 MPa, 7000 MPa, 7500 MPa, 8000 MPa, 8500 MPa or 9000 MPa, etc.

[0121] It is understandable that a lower elastic modulus of the elastic layer 411 is beneficial to reducing stress concentration of the current collector 41 , while a higher elastic modulus of the elastic layer 411 is beneficial to improving the structural stability of the elastic layer 411 and facilitating the preparation and molding of the elastic layer 411 .

[0122] After long-term research and numerous experiments, the inventors found that setting 5000 MPa≤E≤9000 MPa is beneficial to improving the role of the elastic layer 411 in buffering the stress concentration of the current collector 41 while also simplifying the preparation process of the current collector 41 .

[0123] In some embodiments, the elongation at break e of the elastic layer 411 satisfies: 30%≤e≤80%.

[0124] Optionally, the elongation at break e of the elastic layer 411 may be 30%, 40%, 50%, 60%, 70% or 80%, etc.

[0125] After long-term research and a large number of experiments, the inventors found that setting 30%≤e≤80% is beneficial to further reduce the risk of fracture of the collector 41 in the bending area 32a, and is beneficial to further reduce the risk of stress concentration in the collector 41 in the bending area 32a.

[0126] As shown in FIG5 , in some embodiments, the two first planes 321 a are parallel to each other, the two second planes 321 b are parallel to each other, and the plane where the first planes 321 a are located and the plane where the second planes 321 b are located are perpendicular to each other.

[0127] When the electrode assembly 32 formed in this way is applied to the battery cell 30 , it is beneficial to further improve the utilization rate of the internal space of the battery cell 30 , thereby increasing the energy density of the battery cell 30 .

[0128] As shown in Figure 5, in some embodiments, the tangent surface of one end of the arc surface 321c connected to the first plane 321a is tangent to the corresponding first plane 321a; and / or, the tangent surface of one end of the arc surface 321c connected to the second plane 321b is tangent to the corresponding second plane 321b.

[0129] In this way, during the forming process of the electrode assembly 32, the risk of deformation of the first plane 321a or the second plane 321b is reduced, which in turn helps reduce the risk of lithium deposition during use of the electrode assembly 32 due to shape deformation.

[0130] As shown in FIG4 , a battery cell 30 provided according to an embodiment of the present application includes a housing 31 and an electrode assembly 32 provided in any of the above embodiments. The housing 31 has a receiving cavity 31 a , and the electrode assembly 32 is received in the receiving cavity 31 a .

[0131] The battery cell 30 provided in the embodiment of the present application is beneficial to improving the energy density of the battery cell 30, reducing the risk of lithium plating in the battery cell 30, and reducing the risk of the electrode 40 of the battery cell 30 rupturing during use, which is beneficial to improving the reliability of the battery cell 30.

[0132] The battery 10 provided according to the embodiment of the present application includes the battery cell 30 provided in the embodiment. The battery 10 provided in the embodiment of the present application has the same technical effects as the battery cell 30 provided in the above embodiment, and will not be repeated here.

[0133] The electrical device provided according to an embodiment of the present application includes the battery 10 provided in the above embodiment, and the battery 10 is used to provide electrical energy.

[0134] The electrical device provided in the embodiment of the present application has the same technical effects as the battery 10 provided in the embodiment of the present application, and thus will not be described in detail here.

[0135] As shown in Figures 4 to 7, in some embodiments, the electrode assembly 32 provided in the embodiments of the present application includes a pole piece 40, which is wound along a winding direction M. The battery cell 30 has two first planes 321a opposite each other along a first direction X, two second planes 321b opposite each other along a second direction Y, and an arcuate surface 321c. The arcuate surface 321c connects the two adjacent first planes 321a and second planes 321b. The winding direction M, the first direction X, and the second direction Y are perpendicular to each other. The two first planes 321a are parallel to each other, the two second planes 321b are parallel to each other, and the planes on which the first planes 321a and the planes on which the second planes 321b are located are perpendicular to each other. The tangent plane of the end of the arcuate surface 321c connected to the first plane 321a is tangent to the corresponding first plane 321a, and the tangent plane of the end of the arcuate surface 321c connected to the second plane 321b is tangent to the corresponding second plane 321b. The arcuate surface 321c has a centerline 321d. The connecting surfaces 321e at both ends of the arcuate surface 321c and the centerline 321d, as well as the arcuate surface 321c, form a bending region 32a. The pole piece 40 includes a current collector 41 and an active material layer 42, and the active material layer 42 is coated on the current collector 41. The current collector 41 in the bending region 32a includes an elastic layer 411 and a conductive layer 412. The conductive layer 412 is provided on both sides of the elastic layer 411 along the thickness direction Z, and the active material layer 42 is coated on the side of the conductive layer 412 facing away from the elastic layer 411. The material of the elastic layer 411 includes polyethylene terephthalate or polypropylene, and the material of the conductive layer 412 includes copper or aluminum. The thickness h of the conductive layer 412 satisfies the following requirements: 0.5 μm ≤ h ≤ 1.5 μm. The elastic modulus E of the elastic layer 411 satisfies: 5000 MPa≤E≤9000 MPa, and the elongation at break e of the elastic layer 411 satisfies: 30%≤e≤80%.

[0136] The electrode assembly 32 provided in the embodiment of the present application, when applied to a battery cell 30, is advantageously used to increase the capacity of the battery cell 30, thereby increasing the energy density of the battery cell 30. It is also advantageously used to reduce the gaps between the pole pieces 40 of the electrode assembly 32, thereby reducing the risk of lithium deposition in the pole pieces 40 in the bending region 32a during use of the electrode assembly 32, and reducing the risk of the pole pieces 40 rupturing due to bending. Thus, when the electrode assembly 32 is applied to a battery cell 30, it is advantageously used to improve the reliability of the battery cell 30.

[0137] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions within the scope of the claims.

Claims

1. An electrode assembly, the electrode assembly comprising: A pole piece, the pole piece being wound along a winding direction; The electrode assembly has two first planes opposite to each other in a first direction, two second planes opposite to each other in a second direction, and an arc surface, the arc surface connecting two adjacent ones of the first planes and the second planes, the winding direction, the first direction, and the second direction intersecting pairwise; The arc surface has a center line, a connection surface between two ends of the arc surface and the center line, and the arc surface enclose a bending region, the pole piece includes a current collector and an active material layer, and the active material layer is coated on the current collector; At least the current collector in the bending region includes an elastic layer and a conductive layer, the conductive layer is disposed on at least one side of the elastic layer in the thickness direction, and the active material layer is coated on a side of the conductive layer facing away from the elastic layer.

2. The electrode assembly according to claim 1, wherein, Along the winding direction of the pole piece, the current collector of the pole piece at any position includes the elastic layer and the conductive layer.

3. The electrode assembly according to claim 1, wherein, The conductive layer is disposed on both sides of the elastic layer in the thickness direction.

4. The electrode assembly according to claim 1, wherein, The material of the elastic layer includes polyethylene terephthalate or polypropylene.

5. The electrode assembly according to claim 1, wherein, The material of the conductive layer includes copper or aluminum.

6. The electrode assembly according to claim 1, wherein, The thickness h of the conductive layer satisfies: 0.5 μm ≤ h ≤ 1.5 μm.

7. The electrode assembly according to any one of claims 1-6, wherein, The elastic modulus E of the elastic layer satisfies: 5000 MPa ≤ E ≤ 9000 MPa.

8. The electrode assembly according to any one of claims 1-6, wherein, The fracture elongation e of the elastic layer satisfies: 30% ≤ e ≤ 80%.

9. The electrode assembly according to any one of claims 1-8, wherein, The two first planes are parallel to each other, the two second planes are parallel to each other, and the plane where the first plane is located and the plane where the second plane is located are perpendicular to each other.

10. The electrode assembly according to any one of claims 1-8, wherein, A tangent plane at an end of the arc surface connected to the first plane is tangent to the corresponding first plane; And / or, a tangent plane at an end of the arc surface connected to the second plane is tangent to the corresponding second plane.

11. A battery cell, comprising: A housing having a receiving cavity; The electrode assembly according to any one of claims 1 to 10, the electrode assembly being received in the receiving cavity.

12. A battery, comprising the battery cell according to claim 11.

13. An electrical device, comprising the battery according to claim 12, the battery being used to provide electrical energy.

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