Electrode assembly, battery cell, battery and electric device

Abstract

The utility model provides an electrode assembly, a battery monomer, a battery and a power utilization device. The electrode assembly comprises a pole piece, and the pole piece is wound in the winding direction; the electrode assembly is provided with two first planes opposite in the first direction, two second planes opposite in the second direction and an arc-shaped surface, the arc-shaped surface is connected with the two adjacent first planes and second planes, and the winding direction, the first direction and the second direction intersect in pairs; the connecting surfaces of the two ends of the arc-shaped surface and the center line and the arc-shaped surface define a bending area, the pole piece comprises a current collector and an active material layer, and the active material layer is coated on the current collector; the current collector of 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 along the thickness direction, and the active material layer is coated on one side of the conductive layer back to the elastic layer. The electrode assembly provided by the utility model is beneficial to reducing the risk of lithium precipitation of the pole piece in the bending area, reducing the risk of breakage of the pole piece due to bending, and improving the reliability of the battery monomer.

Description

Technical Field

[0001] 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

[0002] Batteries are widely used in electronic devices, such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes and power tools, etc.

[0003] 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 of continuous improvement in battery cell technology. Utility Model Content

[0004] 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.

[0005] 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 the second plane, and the winding direction, the first direction, and the second direction intersect each other; the arcuate surface has a center line, and the connecting surfaces at both ends of the arcuate surface and the center line and the arcuate surface enclose 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 arranged 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.

[0006] The electrode assembly provided in the embodiment of the present application is provided with a first plane opposite to each other along a first direction and a second plane opposite to each other along a second direction. When the electrode assembly is applied to a battery cell, it is beneficial to improve the capacity of the battery cell, thereby improving the energy density of the battery cell. The current collector in the bending zone is provided with an elastic layer and a conductive layer. The high ductility and high elasticity of the elastic layer can be used to buffer the bending force and stress concentration borne by the pole piece in the bending zone, which is beneficial to reduce the gap between the pole pieces of the electrode assembly, so as to reduce the risk of lithium deposition in the pole piece in the bending zone during the use of the electrode assembly, and reduce the risk of the pole piece being broken due to bending. In this way, when the electrode assembly is applied to a battery cell, it is beneficial to improve the reliability of the battery cell.

[0007] In some embodiments, along the winding direction of the pole piece, the current collector of any pole piece includes an elastic layer and a conductive layer. This is beneficial to improving the overall elasticity of the current collector of the electrode assembly and reducing the phenomenon of stress concentration of the current collector. In addition, during the preparation of the electrode assembly, the pole piece includes an elastic layer and a conductive layer, and the pole piece can be integrally formed to facilitate the manufacture of the electrode assembly.

[0008] In some embodiments, the conductive layer is disposed on both sides of the elastic layer in the thickness direction, which is beneficial to improving the capacity of the electrode assembly and the flow capacity of the current collector.

[0009] In some embodiments, the material of the elastic layer includes polyethylene terephthalate or polypropylene, which is beneficial to further reduce the gap between the pole pieces in the bending area, thereby reducing the risk of lithium deposition on the pole pieces in the bending area, and is beneficial to further reduce the risk of rupture of the pole pieces in the bending area.

[0010] In some embodiments, the material of the conductive layer includes copper or aluminum. Providing the conductive layer with copper or aluminum is beneficial to improving the conductive performance of the conductive layer and improving the current carrying capacity of the electrode tab of the electrode assembly.

[0011] In some embodiments, the thickness h of the conductive layer satisfies: 0.5 μm≤h≤1.5 μm. This is beneficial to improving the conductivity of the current collector of the electrode assembly and, when the electrode assembly is applied to a battery cell, also to improving the energy density of the battery cell.

[0012] In some embodiments, the elastic modulus E of the elastic layer satisfies: 5000MPa≤E≤9000MPa. In this way, it is beneficial to improve the stress concentration effect of the elastic layer on the current collector and simplify the preparation process of the current collector.

[0013] In some embodiments, the elongation at break of the elastic layer satisfies: 30%≤e≤80%. This is beneficial to further reduce the risk of the current collector in the bending area breaking and the risk of stress concentration in the current collector in the bending area.

[0014] In some embodiments, the two first planes are parallel to each other, the two second planes are parallel to each other, and the plane where the first planes are located and the plane where the second planes are located are perpendicular to each other. In this way, when the electrode assembly formed is applied to a battery cell, it is beneficial to further improve the utilization rate of the internal space of the battery cell, thereby improving the energy density of the battery cell.

[0015] In some embodiments, the tangent plane of one end of the arc surface connected to the first plane is tangent to the corresponding first plane; and / or the tangent plane of one end of the arc surface connected to the second plane is tangent to the corresponding second plane. In this way, during the forming process of the electrode assembly, the risk of distortion of the first plane or the second plane is reduced, thereby reducing the risk of lithium deposition during use of the electrode assembly due to shape distortion.

[0016] 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.

[0017] 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 rupture of the battery cell pole piece during use, which is conducive to improving the reliability of the battery cell.

[0018] In a third aspect, an embodiment of the present application provides a battery, comprising the battery cell provided in the above embodiment.

[0019] The battery provided in the embodiment of the present application has the same technical effect as the battery cell provided in the above embodiment, which will not be described in detail here.

[0020] 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.

[0021] The electric device provided in the embodiment of the present application has the same technical effect as the battery provided in the above embodiment, and thus will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0023] Figure 1 is a schematic structural diagram of a vehicle provided in an embodiment of the present application;

[0024] Figure 2 is a schematic diagram of the structure of a battery provided in an embodiment of the present application;

[0025] Figure 3 is a schematic diagram of the structure of a battery module in a battery provided in an embodiment of the present application;

[0026] Figure 4is a schematic diagram of an exploded structure of a battery cell provided in an embodiment of the present application;

[0027] Figure 5 is a front view of an electrode assembly provided in an embodiment of the present application;

[0028] Figure 6 is a cross-sectional view of an electrode piece of an electrode assembly provided in an embodiment of the present application;

[0029] Figure 7 It is a cross-sectional view of a pole piece of another electrode assembly provided in an embodiment of the present application.

[0030] In the drawings, the drawings are not necessarily drawn to scale.

[0031] Marking Description:

[0032] 1. Vehicle; 1a. Motor; 1b. Controller;

[0033] 10. Battery; 11. First box body; 12. Second box body;

[0034] 20. Battery module;

[0035] 30. Battery cell; 31. Shell; 31a. Accommodation cavity; 311. Shell; 312. End cap; 32. Electrode assembly; 32a. Bending area; 321. Electrode body; 321a. First plane; 321b. Second plane; 321c. Arc surface; 321d. Center line; 321e. Connection surface; 322. Tab;

[0036] 40, pole piece; 41, current collector; 411, elastic layer; 412, conductive layer; 42, active material layer;

[0037] M, winding direction; X, first direction; Y, second direction; Z, thickness direction. DETAILED DESCRIPTION

[0038] The following detailed description and drawings of the embodiments of the present application are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0039] In the description of the present application, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating the orientation or positional relationship, are only for the convenience of describing the present 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 and operated in a specific orientation, and therefore cannot be understood as a limitation on the present 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 vertical, but is within the allowable error range. "Parallel" is not strictly parallel, but is within the allowable error range.

[0040] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0041] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0042] The term "plurality" used in the present application refers to two or more (including two).

[0043] In the present application, the battery cell may include a lithium-ion secondary battery cell, a lithium-ion primary battery cell, a lithium-sulfur battery cell, a sodium-lithium-ion battery cell, a sodium-ion battery cell or a magnesium-ion battery cell, etc., and the embodiments of the present application do not limit this. The battery cell may be cylindrical, flat, rectangular or other shapes, etc., and the embodiments of the present application do not limit this.

[0044] 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 mixed connection through a busbar component.

[0045] 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.

[0046] 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 accommodated in the case.

[0047] 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.

[0048] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0049] A battery cell generally includes an electrode assembly. The electrode 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 embedded and removed between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0050] In some embodiments, the positive electrode may be a positive electrode sheet, and the positive electrode sheet 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.

[0051] 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 disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0052] 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 silver surface treatment may be used. The composite current collector may include a polymer material base 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.).

[0053] 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 their respective modified compounds. However, the present application is not limited to these materials, and 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 alone or in combination of two or more.

[0054] In some embodiments, the positive electrode may be foamed carbon or foamed metal. The foamed metal may be foamed nickel, foamed copper, foamed aluminum or foamed alloy. When the foamed metal is used as the positive electrode, the positive electrode active material may not be provided on the surface of the foamed metal, but of course, the positive electrode active material may also be provided. As an example, lithium source material, potassium metal or sodium metal may also be filled or / and deposited in the foamed metal, and the lithium source material is lithium metal and / or lithium-rich material.

[0055] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0056] 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, etc. may be used. The composite current collector may include a polymer material base 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.).

[0057] 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.

[0058] 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 disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0059] As an example, the negative electrode active material may adopt the negative electrode active material for battery cells known in the art. 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, lithium titanate, etc.

[0060] In some embodiments, the negative electrode may be foamed carbon or foamed metal. The foamed metal may be foamed nickel, foamed copper, foamed aluminum or foamed alloy, etc. When the foamed metal is used as the negative electrode sheet, the surface of the foamed metal may not be provided with a negative electrode active material, but of course, a negative electrode active material may also be provided.

[0061] As an example, a lithium source material, potassium metal or sodium metal may be filled or / and deposited in the negative electrode current collector, and the lithium source material is lithium metal and / or lithium-rich material.

[0062] 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.

[0063] In some embodiments, the electrode assembly further includes a separator, which is disposed between the positive electrode and the negative electrode. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0064] 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.

[0065] In some embodiments, the battery cell further includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. The electrolyte can be liquid, gel or solid.

[0066] 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.

[0067] In some embodiments, the electrode assembly is a laminate structure.

[0068] A plurality of positive electrode sheets and a plurality of negative electrode sheets can be provided respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets can be alternately stacked.

[0069] 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.

[0070] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of folded sections that are stacked.

[0071] 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.

[0072] As an example, the separator may be disposed continuously, and disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0073] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0074] In some embodiments, the electrode assembly is provided with tabs, which can lead current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0075] The battery cell further includes a housing, and a housing is formed inside the housing to accommodate 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.

[0076] 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 in another intersecting direction to form two other opposite second planes of the electrode assembly, 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, 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 is easy to 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.

[0077] In view of this, an embodiment of the present application provides a technical solution, which includes an elastic layer and a conductive layer by setting a current collector of the pole piece in the bending zone. When the pole piece in the bending zone is bent, the bending stress of the pole piece 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 pole pieces. In this way, it is beneficial to reduce the problem of stress concentration in the pole pieces in the bending zone, and is beneficial to the gap between the pole pieces in the bending zone, and further helps to increase the risk of pole piece fracture and lithium plating in the bending zone. In the scenario where the electrode assembly is applied in the battery, it is beneficial to improve the reliability performance of the battery cell.

[0078] The technical solutions described in the embodiments of the present application are applicable to an electrode assembly, a battery cell including an electrode assembly, a battery including a battery cell, and an electrical device using the battery.

[0079] The electrical device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The vehicle may be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, and the like; the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, and the like; the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the like; the electric tool may include a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and an electric tool for railways, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator, and an electric planer, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0080] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle as an example.

[0081] like Figure 1As shown, a battery 10 is provided inside the 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 be used as an operating power source for the vehicle 1.

[0082] 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.

[0083] In some embodiments of the present application, the battery 10 can not only serve as an operating power source for the vehicle 1, but also serve as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0084] See also Figure 2 As shown, the battery 10 includes a battery cell ( Figure 2 (not shown). The battery 10 may further include a case for accommodating the battery cells.

[0085] The box body is used to accommodate battery cells, and the box body can be in various structural forms. In some embodiments, the box body may 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 may be a hollow structure with one end open, the first box body portion 11 is a plate-like structure, and 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 may also 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 may be in various shapes, such as a cylinder, a cuboid, etc.

[0086] 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, a sealing ring, etc., may be further provided between the first box body 11 and the second box body 12 .

[0087] 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.

[0088] In the battery 10, there can be one or more battery cells. If there are more than one battery cell, the battery cells can be connected in series, in parallel, or in a mixed connection. Mixed connection means that the battery cells are connected in series and in parallel. The battery cells can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the battery cells can be accommodated in the box. Alternatively, the battery cells can be first connected in series, in parallel, or in a mixed connection to form a battery module 20. The battery modules 20 are then connected in series, in parallel, or in a mixed connection to form a whole, and then accommodated in the box.

[0089] like Figure 3 As shown, in some embodiments, in the battery module 20, there are multiple battery cells 30. The multiple battery cells 30 are first connected in series, in parallel, or in mixed series to form the battery module 20. The multiple battery modules 20 are then connected in series, in parallel, or in mixed series to form a whole, and are accommodated in the box.

[0090] 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 .

[0091] The battery 10 may also not have a casing, 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.

[0092] In some embodiments, multiple battery cells in the battery 10 may be electrically connected via a busbar 50 to achieve parallel connection, series connection, or mixed connection of the multiple battery cells in the battery 10 .

[0093] like Figures 4 to 7 As shown, 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 to each other along a first direction X, two second planes 321b opposite to each other along a second direction Y, and an arc surface 321c, the arc surface 321c connects 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 arc surface 321c has a center line 321d, and the connecting surfaces 321e at both ends of the arc surface 321c and the center line 321d and the arc surface 321c enclose a bending area 32a, and 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 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 .

[0094] The electrode assembly 32 includes a positive electrode sheet, a negative electrode sheet and an isolating member, wherein the isolating member is disposed 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 exactly the same.

[0095] The electrode assembly 32 includes two first planes 321a opposite to each other along a first direction X and two second planes 321b opposite to each other along a second direction Y. The first plane 321a and the second plane 321b are respectively straight. The first direction X and the second direction Y intersect, and optionally, the first direction X can be perpendicular to the second direction Y.

[0096] 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, but within the allowable error range, the first plane 321a and the second plane 321b have a certain flatness error range and surface roughness range.

[0097] The pole piece 40 is wound along the winding direction M, and the positive pole piece, the negative pole piece and the 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 plane 321a and a second plane 321b, in the preparation process of the electrode assembly 32, after the positive pole piece, the separator and the negative pole piece are wound together to form a cylindrical electrode assembly, the cylindrical electrode assembly can be subjected to a molding and shaping process by two pressing plates to form two first planes 321a opposite to each other along the first direction X and two second planes 321b opposite to each other along the second direction Y, thereby forming a finished electrode assembly 32.

[0098] The arc surface 321c has a center line 321d, and the arc surface 321c can be in an arc shape or an ellipse, etc. The two ends of the arc surface 321c and the connecting surface 321e of the center line 321d and the arc surface 321c enclose a bending area 32a, and the pole pieces 40 in the bending area 32a are all in a winding shape, and the pole pieces 40 in the area opposite to the first plane 321a and the second plane 321b except the arc area can be straight.

[0099] By setting the electrode assembly 32 to include a first plane 321a opposite to each other along the first direction X and a second plane 321b opposite to each other 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 further facilitate to make full use of the space in the outer shell 31 to increase the capacity of the battery cell 30, and further improve the energy density of the battery cell 30.

[0100] Since the arc surface 321c connects the first plane 321a and the second plane 321b, one electrode assembly 32 may have four arc surfaces 321c and four bending regions 32a disposed at intervals.

[0101] The pole piece 40 includes a current collector 41 and an active material layer 42, and at least the current collector 41 in the bending zone 32a includes an elastic layer 411 and a conductive layer 412. The current collector 41 in the bending zone 32a can be arranged to include an elastic layer 411 and a conductive layer 412, and the current collector 41 of the pole piece 40 outside the bending zone 32a of the electrode assembly 32 can only include the conductive layer 412; or, the current collector 41 of the pole piece 40 in any area can also be arranged to include both a conductive layer 412 and an elastic layer 411, which can be selected according to actual needs.

[0102] The current collector 41 of the bending area 32a includes an elastic layer 411 and a conductive layer 412. The elastic layer 411 may include a polymer material. Compared with the conductive layer 412, the elastic layer 411 has good elasticity and ductility. In the process of shaping the electrode assembly 32, the bending force and stress concentration borne by the pole piece 40 of the bending area 32a can be buffered by the deformation of the elastic layer 411, which is conducive to reducing the gap between the pole pieces 40 of the bending area 32a, and is conducive to reducing the risk of the pole piece 40 of the bending area 32a being broken due to bending. In addition, the elastic layer 411 has a low hardness and is not easy to pierce the isolation piece between the pole pieces 40 of the electrode assembly 32, which is conducive to improving the safety margin of the electrode assembly 32.

[0103] Therefore, the electrode assembly 32 provided in the embodiment of the present application is provided with the first plane 321a opposite to each other along the first direction X and the second plane 321b opposite to each other along the second direction Y. When the electrode assembly 32 is applied to the battery cell 30, it is beneficial to improve the capacity of the battery cell 30, and further improve the energy density of the battery cell 30. The current collector 41 provided in the bending area 32a includes an elastic layer 411 and a conductive layer 412. The high ductility and high elasticity of the elastic layer 411 can be used to buffer the bending force and stress concentration borne by the pole piece 40 in the bending area 32a, which is beneficial to reduce the gap between the pole pieces 40 of the electrode assembly 32, so as to reduce the risk of lithium deposition in the pole piece 40 in the bending area 32a during the use of the electrode assembly 32, and reduce the risk of the pole piece 40 being broken due to bending. In this way, when the electrode assembly 32 is applied to the battery cell 30, it is beneficial to improve the reliability of the battery cell 30.

[0104] 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 .

[0105] In this way, along the winding direction M of the pole 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 pole piece 40 includes an elastic layer 411 and a conductive layer 412, and the pole piece 40 can be set to be an integrally formed setting, which is convenient for the manufacture of the electrode assembly 32.

[0106] like Figure 7 As shown, in some embodiments, the conductive layer 412 is disposed on both sides of the elastic layer 411 along the thickness direction Z.

[0107] 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 current flow capacity of the current collector 41.

[0108] In some embodiments, the material of the elastic layer 411 includes polyethylene terephthalate (PET) or polypropylene (PP).

[0109] Both PET and PP have good elasticity and ductility, and have good mechanical properties and bending resistance. Therefore, 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.

[0110] In some embodiments, the material of the conductive layer 412 includes copper or aluminum.

[0111] 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 pole ear 322 of the electrode assembly 32. Copper and aluminum both have good electrical conductivity and low resistance. Therefore, setting the conductive layer 412 to include copper or aluminum is beneficial to improving the electrical conductivity of the conductive layer 412 and to improving the current carrying capacity of the pole ear 322 of the electrode assembly 32.

[0112] like Figure 6 and Figure 7 As shown, in some embodiments, the thickness h of the conductive layer 412 satisfies: 0.5 μm≤h≤1.5 μm.

[0113] 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.

[0114] It can be understood that the thicker the conductive layer 412 is, the more beneficial it is to improve the conductivity of the current collector 41 , and the thinner the conductive layer 412 is, the more beneficial it is to reduce the volume of the electrode assembly 32 and reduce the weight of the electrode assembly 32 .

[0115] After long-term research and a large number of experiments, the inventors found that setting 0.5μm≤h≤1.5μm is beneficial to improving the conductivity of the collector 41 of the electrode assembly 32, and when the electrode assembly 32 is applied to the battery cell 30, it is also beneficial to improving the energy density of the battery cell 30.

[0116] In some embodiments, the elastic modulus E of the elastic layer 411 satisfies: 5000 MPa≤E≤9000 MPa.

[0117] 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.

[0118] 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 .

[0119] After long-term research and a large number of experiments, the inventors found that setting 5000MPa≤E≤9000MPa 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 .

[0120] In some embodiments, the elongation at break of the elastic layer 411 satisfies: 30%≤e≤80%.

[0121] Optionally, the elongation at break e of the elastic layer 411 may be 30%, 40%, 50%, 60%, 70% or 80%, etc.

[0122] 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.

[0123] like Figure 5 As shown, in some embodiments, the two first planes 321a are parallel to each other, the two second planes 321b are parallel to each other, and the plane where the first planes 321a are located and the plane where the second planes 321b are located are perpendicular to each other.

[0124] 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 improving the energy density of the battery cell 30 .

[0125] like Figure 5 As shown, 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.

[0126] 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 to reduce the risk of lithium deposition during use of the electrode assembly 32 due to shape deformation.

[0127] like Figure 4As shown, the battery cell 30 provided according to the 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.

[0128] The battery cell 30 provided in the embodiment of the present application is conducive to improving the energy density of the battery cell 30, and is conducive to reducing the risk of lithium plating of the battery cell 30, and reducing the risk of the pole piece 40 of the battery cell 30 rupturing during use, which is conducive to improving the reliability performance of the battery cell 30.

[0129] 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 effect as the battery cell 30 provided in the above embodiment, which will not be described in detail here.

[0130] The electrical device provided according to the embodiment of the present application includes the battery 10 provided in the above embodiment, and the battery 10 is used to provide electrical energy.

[0131] The electric device provided in the embodiment of the present application has the same technical effect as the battery 10 provided in the embodiment of the present application, and thus will not be described in detail here.

[0132] like Figures 4 to 7As shown, in some embodiments, the electrode assembly 32 provided in the embodiment of the present application includes a pole piece 40, and the pole piece 40 is wound along the winding direction M. The battery cell 30 has two first planes 321a opposite to each other along the first direction X, two second planes 321b opposite to each other along the second direction Y, and an arc surface 321c. The arc surface 321c connects 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 plane where the first plane 321a is located and the plane where the second plane 321b is located are perpendicular to each other. The tangent of the end of the arc surface 321c connected to the first plane 321a is tangent to the corresponding first plane 321a, and the tangent of the end of the arc surface 321c connected to the second plane 321b is tangent to the corresponding second plane 321b. The arc surface 321c has a center line 321d, and the connecting surfaces 321e at both ends of the arc surface 321c and the center line 321d and the arc surface 321c enclose a bending area 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 of the bending area 32a includes an elastic layer 411 and a conductive layer 412, and the conductive layer 412 is arranged 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: 0.5μm≤h≤1.5μm. 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%.

[0133] The electrode assembly 32 provided in the embodiment of the present application is beneficial to improving the capacity of the battery cell 30, and further improving the energy density of the battery cell 30, when the electrode assembly 32 is applied to the battery cell 30. It is also beneficial to reduce the gap between the pole pieces 40 of the electrode assembly 32, so as to reduce the risk of lithium deposition in the pole piece 40 of the bending area 32a during the use of the electrode assembly 32, and reduce the risk of the pole piece 40 being broken due to bending. In this way, when the electrode assembly 32 is applied to the battery cell 30, it is beneficial to improve the reliability of the battery cell 30.

[0134] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An electrode assembly, characterized in that: The electrode assembly comprises: A pole piece, wherein the pole piece is wound along a winding direction; The electrode assembly comprises two first planes opposite to each other in a first direction, two second planes opposite to each other in a second direction, and an arcuate surface, wherein the arcuate surface connects two adjacent first planes and the second plane, and the winding direction, the first direction, and the second direction intersect each other; the arcuate surface comprises a center line, and the connecting surfaces of the two ends of the arcuate surface and the center line and the arcuate surface enclose a bending area, and the electrode sheet comprises 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 zone includes an elastic layer and a conductive layer, the conductive layer is arranged 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.

2. The electrode assembly according to claim 1, characterized in that: Along the winding direction of the pole piece, the current collector of the pole piece at any location includes the elastic layer and the conductive layer.

3. The electrode assembly according to claim 1, characterized in that: The conductive layer is arranged on both sides of the elastic layer along the thickness direction.

4. The electrode assembly according to claim 1, characterized in that: The elastic layer is made of polyethylene terephthalate or polypropylene.

5. The electrode assembly according to claim 1, characterized in that: The material of the conductive layer includes copper or aluminum.

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

7. The electrode assembly according to claim 1, characterized in that: The elastic modulus E of the elastic layer satisfies: 5000MPa≤E≤9000MPa.

8. The electrode assembly according to claim 1, characterized in that: The elongation at break e of the elastic layer satisfies: 30%≤e≤80%.

9. The electrode assembly according to claim 1, characterized in that: The two first planes are parallel to each other, the two second planes are parallel to each other, and the plane where the first planes are located and the plane where the second planes are located are perpendicular to each other.

10. The electrode assembly according to claim 1, characterized in that: A tangent plane at one end of the arc surface connected to the first plane is tangent to the corresponding first plane; and / or a tangent plane at one end of the arc surface connected to the second plane is tangent to the corresponding second plane.

11. A battery cell, characterized in that: include: A housing having a receiving cavity; The electrode assembly according to any one of claims 1 to 10, wherein the electrode assembly is accommodated in the accommodating cavity.

12. A battery, characterized in that: Comprising the battery cell as claimed in claim 11.

13. An electrical device, characterized in that: Comprising the battery of claim 12, the battery being used to provide electrical energy.

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