Electrode assembly, preparation method therefor, battery cell, battery, electrical device and energy storage device

Abstract

Disclosed in the present disclosure are an electrode assembly, a preparation method therefor, a battery cell, a battery, an electrical device and an energy storage device. The electrode assembly comprises: a jellyroll structure, the jellyroll structure being formed by rolling up a laminate comprising a positive electrode sheet and a negative electrode sheet, a separator being interposed between the positive electrode sheet and the negative electrode sheet, the jellyroll structure comprising bending zones, the positive electrode sheet comprising at least one positive electrode bending part located in the bending zones, the negative electrode sheet comprising at least one negative electrode bending part located in the bending zones, and in the rolling axis direction of the jellyroll structure, two ends of the separator exceeding the positive electrode bending part and the negative electrode bending part; and a protective layer attached to the surface of the positive electrode bending part and / or the surface of the negative electrode bending part, at least one end of the protective layer exceeding the separator in the rolling axis direction of the jellyroll structure.

Description

Electrode assembly and preparation method thereof, battery cell, battery, power device, energy storage device Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular to an electrode assembly and a preparation method thereof, a battery cell, a battery, an electrical device, and an energy storage device. Background Art

[0002] New energy batteries are being used more and more widely in life and industry. For example, new energy vehicles equipped with batteries have been widely used. In addition, batteries are also being increasingly used in energy storage fields.

[0003] In new energy vehicles equipped with batteries, these batteries can provide full or partial power. In the energy storage sector, batteries can be installed in energy storage boxes or directly at the user's side. In the development of battery technology, in addition to improving the performance of battery cells, thermal runaway is also a significant concern. Therefore, reducing the risk of thermal runaway in battery cells is a pressing technical challenge in battery technology.

[0004] Summary of the Invention

[0005] To solve the above technical problems, the present disclosure provides an electrode assembly and a preparation method thereof, a battery cell, a battery, an electrical device, and an energy storage device, which can reduce the risk of thermal runaway of the battery.

[0006] The present disclosure is achieved through the following technical solutions.

[0007] A first aspect of the present disclosure provides an electrode assembly, comprising: a winding structure formed by winding a stack including a positive electrode sheet and a negative electrode sheet, an isolating member sandwiched between the positive electrode sheet and the negative electrode sheet, the winding structure including a bending area, the positive electrode sheet including at least one positive electrode bending portion located in the bending area, the negative electrode sheet including at least one negative electrode bending portion located in the bending area, and along the winding axis direction of the winding structure, both ends of the isolating member extend beyond the positive electrode bending portion and the negative electrode bending portion; and a protective layer attached to the surface of the positive electrode bending portion and / or the surface of the negative electrode bending portion, and along the winding axis direction of the winding structure, at least one end of the protective layer extends beyond the isolating member.

[0008] By attaching a protective layer to the positive and negative bending parts, the risk of breakage and active material shedding when the positive and negative bending parts are bent can be reduced, thereby reducing the risk of thermal runaway of the electrode assembly, battery cells and even the entire battery; the protective layer extends beyond the isolation piece, so that the adhesive tape can completely cover the positive and negative electrode sheets and reliably protect them, and the attachment position of the protective layer can be visually inspected through the exposed part during the battery manufacturing process, so that the accuracy of the attachment position can be confirmed in time.

[0009] In some embodiments, the protective layer is attached to the surface of the positive electrode bend and / or the surface of the negative electrode bend by adhesive bonding or electrostatic adsorption. Adhesive bonding provides a more secure attachment, while electrostatic adsorption reduces the possibility of damaging the electrode during attachment.

[0010] In some embodiments, along the stacking direction of the wound structure, each of the positive electrode bends includes a first concave surface and a first convex surface located on opposite sides, and the protective layer includes a first protective layer and a second protective layer attached to the first concave surface and the first convex surface, respectively. By attaching the protective layer to both the first concave surface and the first convex surface on both the front and back sides of the positive electrode bend, the risk of fracture of the positive electrode bend is further reduced, and the risk of the positive electrode active material layer on both surfaces of the positive electrode bend being detached is reduced, thereby reducing the risks of short circuits, thermal runaway, and the like.

[0011] In some embodiments, along the stacking direction of the winding structure, each of the negative electrode bends includes a second concave surface and a second convex surface located on opposite sides, and the protective layer includes a third protective layer and a fourth protective layer attached to the second concave surface and the second convex surface respectively.

[0012] By attaching a protective layer to the second concave surface and the second convex surface on both sides of the positive and negative electrode bend, the risk of short circuit and thermal runaway caused by the breakage of the negative electrode bend is further reduced, and the risk of the negative electrode active material layer on both surfaces of the negative electrode bend is reduced, thereby reducing the impact on the battery capacity and cycle life.

[0013] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, and the protective layer covers the positive electrode active material layer at the positive electrode bending portion in the positive electrode sheet; and / or, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, and the protective layer covers the negative electrode active material layer at the negative electrode bending portion in the negative electrode sheet.

[0014] By covering the positive electrode active material layer at the positive electrode bend and / or the negative electrode active material layer at the negative electrode bend with the protective layer, the positive electrode active material layer and the negative electrode active material layer can be fully protected, reducing the risk of the positive electrode active material layer and the negative electrode active material layer falling off.

[0015] In some embodiments, at the positive electrode bend portion, along the winding axis direction, the first edge of the protective layer located at the positive electrode bend portion exceeds the positive electrode active material layer but does not exceed the separator, and the second edge of the protective layer located at the positive electrode bend portion exceeds the separator, wherein the first edge is located at one end of the protective layer along the winding axis direction, and the second edge is located at the other end of the protective layer along the winding axis direction; and / or, at the negative electrode bend portion, along the winding axis direction, the third edge of the protective layer located at the negative electrode bend portion exceeds the negative electrode active material layer but does not exceed the separator, and the fourth edge of the protective layer located at the negative electrode bend portion exceeds the separator, wherein the third edge is located at one end of the protective layer along the winding axis direction, and the fourth edge is located at the other end of the protective layer along the winding axis direction.

[0016] Since the protective layer covers the positive and negative active material layers with only one edge extending beyond the separator, it can be visually observed that the protective layer is located at the adhesive position of the positive electrode bend. Compared with the case where both edges extend beyond the separator, the risk of the separator sticking to the roller and causing itself to tear can be reduced.

[0017] In some embodiments, the positive electrode current collector is provided with a positive electrode tab on one side of the winding axis, and the first edge of the protective layer is located on the same side as the positive electrode tab along the winding axis; and / or the negative electrode current collector is provided with a negative electrode tab on one side of the winding axis, and the third edge of the protective layer is located on the same side as the negative electrode tab along the winding axis. By ensuring that the edge of the protective layer on the same side of the tab does not extend beyond the separator, the risk of false alarms from detection equipment on the side of the tab can be avoided.

[0018] In some embodiments, along the winding axis direction, the length of the protective layer exceeding the positive electrode bending portion is 4mm to 6mm; and / or, along the winding axis direction, the length of the protective layer exceeding the negative electrode bending portion is 4mm to 6mm.

[0019] By making the protective layer exceed the specified length of the positive and negative electrode bending parts, the part of the protective layer extending outside can be easily visually observed, thereby making it easy to confirm the position of the protective layer and also facilitating the determination of the attachment position of the protective layer on the positive and negative electrode sheets.

[0020] In some embodiments, along the winding axis direction, the length of the protective layer exceeding the isolation member is 1 mm to 4 mm.

[0021] By controlling the length of the protective layer extending beyond the spacer to between 1 mm and 4 mm, it is possible to visually check the pasting position of the protective layer and reduce the risk of the protective layer sticking to the roller and causing tearing.

[0022] In some embodiments, along the winding axis direction, at at least one end, one of the first protective layer and the second protective layer exceeds the other.

[0023] In some embodiments, the first protective layer includes a first end and a second end located at both ends along the winding direction of the winding structure, and the second protective layer includes a third end and a fourth end located at both ends along the winding direction, the third end and the first end are on the same side of the winding direction and are staggered along the winding direction, and / or the fourth end and the second end are on the same side of the winding direction and are staggered along the winding direction.

[0024] By staggering the two ends of the same side of the first protective layer and the second protective layer, the step height of the ends of the stacked protective layers can be reduced compared to non-staggered conditions. Therefore, during the extrusion molding process of the winding structure, a buffer can be formed for the extrusion of the isolation member, reducing the risk of wrinkling of the isolation member, thereby reducing the possibility of the pores of the isolation member being blocked due to wrinkles.

[0025] In some embodiments, the offset length between the third end and the first end along the winding direction is greater than zero and less than or equal to 2 mm; and / or the offset length between the fourth end and the second end along the winding direction is greater than zero and less than or equal to 2 mm.

[0026] By controlling the staggered length between the ends of the first protective layer and the second protective layer on the same side of the winding direction to be greater than zero and less than or equal to 2 mm, the risk of wrinkling of the separator and the risk of tearing due to roller sticking can be reduced.

[0027] In some embodiments, the third protective layer includes a fifth end and a sixth end in the winding direction of the winding structure, the fourth protective layer includes a seventh end and an eighth end in the winding direction, the seventh end and the fifth end are on the same side of the winding direction and are staggered along the winding direction, and / or the eighth end and the sixth end are on the same side of the winding direction and are staggered along the winding direction.

[0028] By staggering the two ends of the third and fourth protective layers on the same side, the step height of the ends of the stacked protective layers can be reduced compared to non-staggered conditions. Therefore, during the extrusion molding process of the winding structure, a buffer can be formed for the extrusion of the isolation member, reducing the risk of wrinkling of the isolation member, thereby reducing the possibility of the pores of the isolation member being blocked due to wrinkles.

[0029] In some embodiments, the staggered length between the seventh end and the fifth end along the winding direction is greater than zero and less than or equal to 2 mm; and / or the staggered length between the eighth end and the sixth end along the winding direction is greater than zero and less than or equal to 2 mm.

[0030] By controlling the staggered length of the third protective layer and the fourth protective layer at both ends on the same side along the winding direction to be greater than zero and less than or equal to 2 mm, the risk of wrinkling of the separator and the risk of tearing due to roller sticking can be reduced.

[0031] In some embodiments, the winding structure includes a straight area connected to the bending area, and the protective layer extends from at least one end of the winding structure in the winding direction to the junction between the straight area and the bending area or extends to the straight area beyond the junction along the winding direction.

[0032] Therefore, the protective layer located at the positive electrode bend can cover the positive electrode active material layer in the winding direction, and the positive electrode active material layer is fully protected; the protective layer located at the negative electrode bend can cover the negative electrode active material layer in the winding direction, and the negative electrode active material layer is fully protected.

[0033] In some embodiments, the positive electrode sheet includes a plurality of positive electrode bending portions located in the bending zone and arranged along the stacking direction of the winding structure, and the protective layer is attached to at least the positive electrode bending portion located innermost along the stacking direction; and / or, the negative electrode sheet includes a plurality of negative electrode bending portions located in the bending zone and arranged along the stacking direction of the winding structure, and the protective layer is attached to at least the negative electrode bending portion located innermost along the stacking direction.

[0034] Because the innermost positive and negative electrode bends in the stacking direction are subject to greater tensile forces, they are more likely to break or cause active material to fall off. Therefore, the protective layer is attached to at least the innermost positive and negative electrode bends to protect them, helping to reduce the risk of short circuits and thermal runaway in the entire battery.

[0035] In some embodiments, the protective layer is made of polyethylene terephthalate, polypropylene, polyethylene, polyimide or non-woven fabric.

[0036] In some embodiments, at least one of the second protective layers at the first convex surface has pores for ion permeation; or, both the first protective layer at the first concave surface and the second protective layer at the first convex surface include a blocking portion for blocking ions.

[0037] The first protective layer located on the first concave surface and the second protective layer located on the first convex surface have pores for ion permeation, which can protect the positive electrode bend from fracture and the risk of the respective active materials falling off. At the same time, it can also reduce the impact of the protective layer attached to the positive electrode bend on the release of the positive electrode active material from the positive electrode active material layer at the positive electrode bend. The ion blocking portion on the first protective layer can block a portion of the lithium ions provided by the positive electrode active material layer, thereby reducing the phenomenon of lithium plating.

[0038] In some embodiments, the third protective layer located on the second concave surface and the fourth protective layer located on the second convex surface both have pores for ion permeation.

[0039] Since the third protective layer at the second concave surface of the negative electrode bend and the fourth protective layer at the second convex surface both have pores for ion penetration, they can protect the negative electrode bend and reduce lithium plating.

[0040] In some embodiments, the protective layer having pores for ion permeation has an air permeability of 220±70 sec / 100 cc.

[0041] In some embodiments, the pores have a pore size of 100 nm to 400 nm.

[0042] A second aspect of the present disclosure provides a battery cell, comprising: a housing and at least one electrode assembly provided by the first aspect of the present disclosure, wherein the electrode assembly is accommodated in the housing.

[0043] A third aspect of the present disclosure provides a battery, comprising: a box body and at least one battery cell provided by the second aspect of the present disclosure, wherein the battery cell is accommodated in the box body.

[0044] A fourth aspect of the present disclosure provides an electrical device, which includes at least one battery cell provided by the second aspect of the present disclosure or the battery provided by the third aspect of the present disclosure for providing electrical energy.

[0045] A fifth aspect of the present disclosure provides an energy storage device, comprising the battery provided in the third aspect of the present disclosure, wherein the battery is capable of storing electrical energy and providing electrical energy.

[0046] The sixth aspect of the present disclosure provides a method for preparing an electrode assembly, comprising: providing a positive electrode sheet, a negative electrode sheet and an isolating member; attaching a protective layer to the positive electrode sheet and / or the negative electrode sheet; stacking and winding the positive electrode sheet, the negative electrode sheet and the isolating member to form a winding structure, wherein, in the winding structure, an isolating member is sandwiched between the positive electrode sheet and the negative electrode sheet, the winding structure includes a bending area, the positive electrode sheet includes at least one positive bending portion located in the bending area, the negative electrode sheet includes at least one negative bending portion located in the bending area, along the winding axis direction of the winding structure, two ends of the isolating member extend beyond the positive bending portion and the negative bending portion, the protective layer is pasted on the surface of the positive bending portion and / or the surface of the negative bending portion, and along the winding axis direction of the winding structure, at least one end of the protective layer extends beyond the isolating member. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present disclosure. The same reference numerals are used throughout the drawings to denote the same components. In the drawings:

[0048] FIG1 is a schematic structural diagram of a vehicle provided by some embodiments of the present disclosure;

[0049] FIG2 is a perspective exploded schematic diagram of a battery provided by some embodiments of the present disclosure;

[0050] FIG3 is a perspective schematic diagram of a battery module provided by some embodiments of the present disclosure;

[0051] FIG4 is a perspective exploded schematic diagram of a battery cell provided by some embodiments of the present disclosure;

[0052] FIG5 is a perspective schematic diagram of an electrode assembly provided in some embodiments of the present disclosure;

[0053] FIG6 is a cross-sectional schematic diagram of an electrode assembly provided in some embodiments of the present disclosure;

[0054] FIG7 is a partially enlarged schematic diagram of FIG6;

[0055] FIG8 is a schematic cross-sectional view of position zz in FIG7;

[0056] FIG9 is a schematic structural diagram of a positive electrode sheet of an electrode assembly provided by some embodiments of the present disclosure unfolded along a winding direction;

[0057] FIG10 is a schematic structural diagram of a negative electrode sheet of an electrode assembly provided by some embodiments of the present disclosure unfolded along a winding direction;

[0058] FIG11 is a cross-sectional schematic diagram of an electrode assembly provided in some other embodiments of the present disclosure;

[0059] FIG12 is a partially enlarged schematic diagram of FIG11;

[0060] FIG13 is a schematic structural diagram of a positive electrode sheet of an electrode assembly provided by other embodiments of the present disclosure unfolded along a winding direction;

[0061] FIG14 is a schematic structural diagram of a negative electrode sheet of an electrode assembly provided by other embodiments of the present disclosure unfolded along a winding direction;

[0062] FIG15 is a flow chart of a method for preparing an electrode assembly according to some embodiments of the present disclosure.

[0063] Description of Reference Numerals

[0064] 1,000 vehicles;

[0065] 100 batteries, 200 controllers, 300 motors;

[0066] 110 housing, 120 first housing portion, 130 second housing portion, 140 battery module, 150 accommodation space, 160 battery cell;

[0067] 10 electrode assembly, 20 housing, 21 shell, 22 end cover, 30 positive electrode terminal, 40 negative electrode terminal, 50 pressure relief mechanism;

[0068] 11 positive electrode sheet, 111 positive electrode bent portion, 112 positive electrode current collector, 112a positive electrode current collecting portion, 112b positive electrode convex portion (positive electrode tab), 113 positive electrode active material layer, 111a first concave surface, 111b first convex surface;

[0069] 12 negative electrode sheet, 121 negative electrode bend, 122 negative electrode current collector, 122a negative electrode current collecting portion, 122b negative electrode convex portion (positive electrode tab), 123 negative electrode active material layer, 124 insulating layer, 121a second concave surface, 121b second convex surface;

[0070] 13. Isolation piece;

[0071] 14 protective layer, 141 first protective layer, 142 second protective layer, 143 third protective layer, 144 fourth protective layer, 141a first end, 141b second end, 142a third end, 142b fourth end, 143a fifth end, 143b sixth end, 144a seventh end, 144b eighth end, 14a first edge, 14b second edge, 14c third edge, 14d fourth edge;

[0072] A bending area, B straight area, C winding direction, K winding axis direction, E stacking direction, length d1, length d2. DETAILED DESCRIPTION

[0073] The following embodiments of the technical solution of the present disclosure are described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present disclosure and are therefore only examples and are not intended to limit the scope of protection of the present disclosure.

[0074] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure; the terms "including" and "having" and any variations thereof in the specification and claims of the present disclosure and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0075] In the description of the embodiments of the present disclosure, technical terms such as "first," "second," "third," "fourth," "fifth," "sixth," "seventh," and "eighth" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present disclosure, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0076] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present disclosure. 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 herein may be combined with other embodiments.

[0077] In the description of the embodiments of the present disclosure, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0078] In the description of the embodiments of the present disclosure, the orientations or positional relationships indicated by technical terms such as "length", "width", "thickness", "inside", "outside", "stacking direction", and "winding axis direction" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed, operated or used in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present disclosure.

[0079] In the description of the embodiments of the present disclosure, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal connectivity between two components or interaction between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present disclosure based on specific circumstances.

[0080] In the description of the embodiments of the present disclosure, unless otherwise clearly specified and limited, the technical term "contact" should be understood in a broad sense, and can be direct contact, contact through an intermediate medium layer, contact with essentially no interaction force between the two contacting parties, or contact with interaction force between the two contacting parties.

[0081] Hereinafter, the present disclosure will be described in detail.

[0082] Currently, new energy batteries are increasingly being used in everyday life and industry. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in aerospace and other fields. As the application areas of new energy batteries continue to expand, market demand is also growing.

[0083] During the preparation of wound bare cells, the wound electrode assembly needs to be extruded and shaped to eliminate wrinkles and internal air in the separator, reduce the risk of short circuits, and improve surface flatness for easier insertion into the shell. When the electrode assembly is squeezed, the active material on the pole piece at the bend due to winding may fall off, and there may even be a risk of the pole piece breaking at the bend. The shedding of active material on the pole piece is called powdering. Pole piece breakage or the shedding of active material on the pole piece can lead to thermal runaway problems in the battery. Pole piece breakage can easily puncture the separator, which may cause a short circuit between the adjacent positive and negative pole pieces, leading to thermal runaway problems and causing battery explosion and fire. The shedding of active material on the pole piece not only affects the battery capacity, but may also lead to lithium precipitation.

[0084] During the charging process of lithium-ion batteries or battery cells, when the number of lithium insertion sites in the negative active material layer of the negative electrode plate is less than the number of lithium ions that can be provided by the positive active material layer of the adjacent positive electrode plate, lithium plating is likely to occur. Lithium plating not only reduces the performance of lithium-ion batteries and significantly shortens the cycle life, but also limits the fast charging capacity of lithium-ion batteries. In addition, when lithium plating occurs in lithium-ion batteries, the precipitated lithium metal is very active and can react with the electrolyte at a lower temperature, causing the starting temperature of the battery's self-heating to decrease and the self-heating rate to increase, posing a risk of thermal runaway. Furthermore, when lithium plating is severe, the released lithium ions can form lithium dendrites on the surface of the negative electrode plate, and the lithium dendrites can easily pierce the separator, causing a short circuit between the adjacent positive and negative electrode plates, posing a risk of thermal runaway.

[0085] The wound electrode assembly (bare cell) is prone to lithium deposition in its bending area. The main reason for this lithium deposition is that the positive and negative pole pieces located in the bending area need to be bent, and the negative pole piece on the inner side of the positive pole piece is prone to insufficient lithium insertion space, which may cause the negative active material layer of the negative pole piece to have less lithium insertion sites than the positive active material layer of the adjacent positive pole piece, thereby causing lithium deposition. In addition, when the electrode assembly is squeezed and deformed, the surfaces of the positive and negative pole pieces in the bending area will be subjected to a large tensile force, especially the innermost positive pole piece and the innermost negative pole piece are subjected to a greater tensile force, which may easily cause the respective active material layers on the positive and negative pole pieces to fall off, affecting the battery capacity, and may even cause the positive and negative pole pieces in the bending area to break, leading to the risk of thermal runaway of the battery.

[0086] By attaching a protective layer (such as glue) to the positive and negative pole pieces in the bending area, the risk of cracking of the pole pieces and shedding of active materials can be reduced. However, the inventors found that even if glue is applied to the positive and negative pole pieces in the bending area, there may still be battery safety issues. To this end, the inventors tried to analyze the reasons and believed that the possible reasons are: since the pole pieces are wound after the glue is applied, the glue is wrapped in the winding structure, and it is impossible to determine whether the position of the glue is exactly in the bending area. If the position of the glue is not in the bending area, the risk of powder loss and fracture in the bending area still exists. Therefore, if the position of the glue cannot be accurately judged, there is still a risk of short circuit and thermal runaway caused by powder loss and pole piece fracture.

[0087] In view of this, an embodiment of the present disclosure provides an electrode assembly, comprising: a winding structure, the winding structure is formed by winding a stack including a positive electrode sheet and a negative electrode sheet, an isolating member is sandwiched between the positive electrode sheet and the negative electrode sheet, the winding structure includes a bending area, the positive electrode sheet includes at least one positive electrode bending portion located in the bending area, the negative electrode sheet includes at least one negative electrode bending portion located in the bending area, along the winding axis direction of the winding structure, both ends of the isolating member extend beyond the positive electrode bending portion and the negative electrode bending portion; and a protective layer attached to the surface of the positive electrode bending portion and / or the surface of the negative electrode bending portion, along the winding axis direction of the winding structure, at least one end of the protective layer extends beyond the isolating member.

[0088] By attaching the protective layer to the surface of the positive electrode bending portion and / or the surface of the negative electrode bending portion, the risk of fracture of the positive electrode sheet and / or the negative electrode sheet and shedding of the active material in the bending area can be reduced, thereby reducing the risk of thermal runaway of the electrode assembly, the battery cell and even the entire battery; and, by extending the protective layer beyond the isolation member, the protective layer can completely cover the positive and negative electrode sheets and reliably protect them, and the pasting position of the protective layer can be visually detected during the battery manufacturing process (for example, during the winding process), so that the pasting position can be accurately judged.

[0089] The electrode assembly of the embodiment of the present disclosure is applicable to battery cells and batteries.

[0090] The battery of the embodiment of the present disclosure can be used in, but is not limited to, energy storage power supply systems, vehicles, ships, aircraft and other electrical devices.

[0091] The batteries of the embodiments of the present disclosure can also be grouped together to form a battery pack. The battery pack can also be used in, but is not limited to, energy storage power supply systems, vehicles, ships, aircraft, and other electrical devices.

[0092] The embodiments of the present disclosure provide an electrical device including the above-mentioned battery or battery pack for providing electrical energy. The electrical device may be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, etc. 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, etc. The spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0093] The embodiments of the present disclosure further provide an energy storage device including the above-mentioned battery or battery pack. The energy storage device may be, but is not limited to, an energy storage box, an energy storage container, etc.

[0094] In the following embodiments, for the convenience of description, the electric device of one embodiment of the present disclosure is taken as an example of a vehicle 1000. The following description is made with reference to the accompanying drawings.

[0095] FIG1 is a schematic structural diagram of a vehicle 1000 provided in some embodiments of the present disclosure. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. As shown in FIG1 , a battery 100 is provided inside the vehicle 1000. The battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000. For example, the battery 100 may serve as an operating power source for the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and operating power requirements of the vehicle 1000 during driving.

[0096] In some embodiments of the present disclosure, the battery 100 can serve not only as an operating power source for the vehicle 1000 , but also as a driving power source for the vehicle 1000 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000 .

[0097] FIG2 is a perspective exploded view of a battery according to some embodiments of the present disclosure. As shown in FIG2 , the battery 100 includes a housing 110 and battery cells (not shown in FIG2 ). The battery cells are housed in the housing 110 .

[0098] The housing 110 is used to accommodate battery cells and can have various structures. In some embodiments, the housing 110 can include a first housing portion 120 and a second housing portion 130. The first housing portion 120 and the second housing portion 130 overlap each other, and the first housing portion 120 and the second housing portion 130 together define a storage space 150 for accommodating battery cells. The second housing portion 130 can be a hollow structure with one end open. The first housing portion 120 is a plate-like structure. The first housing portion 120 overlaps the open side of the second housing portion 130 to form the housing 110 with the storage space 150. The first housing portion 120 and the second housing portion 130 can also be hollow structures with one end open. The open side of the first housing portion 120 overlaps the open side of the second housing portion 130 to form the housing 110 with the storage space 150. Of course, the first box portion 120 and the second box portion 130 can be in various shapes, such as a cylinder, a cuboid, etc.

[0099] In order to improve the sealing performance after the first box body 120 and the second box body 130 are connected, a sealing member, such as a sealant or a sealing ring, may be provided between the first box body 120 and the second box body 130 .

[0100] Assuming that the first box portion 120 covers the top of the second box portion 130 , the first box portion 120 can also be referred to as an upper box cover, and the second box portion 130 can also be referred to as a lower box.

[0101] In the battery 100, 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 cell system can be housed within the housing 110. Alternatively, multiple battery cells can be first connected in series, in parallel, or in a hybrid connection to form a battery module 140, and then multiple battery modules 140 can be connected in series, in parallel, or in a hybrid connection to form a single system system, which can then be housed within the housing 110.

[0102] Figure 3 is a perspective schematic diagram of a battery module provided by some embodiments of the present disclosure. As shown in Figure 3, in some embodiments, multiple battery cells 160 are provided. Multiple battery cells 160 are first connected in series, parallel, or in series to form a battery module 140. Multiple battery modules 140 are then connected in series, parallel, or in series to form a single unit and housed within a housing.

[0103] The multiple battery cells 160 in the battery module 140 can be electrically connected via a busbar component to achieve parallel connection, series connection, or mixed connection of the multiple battery cells 160 in the battery module 140 .

[0104] Figure 4 is an exploded perspective view of a battery cell according to some embodiments of the present disclosure; Figure 5 is a perspective view of an electrode assembly according to some embodiments of the present disclosure. As shown in Figures 4 and 5 , a battery cell 160 according to embodiments of the present disclosure includes an electrode assembly 10 and a housing 20, with the electrode assembly 10 housed within the housing 20.

[0105] The battery cell 160 may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0106] The battery cell 160 can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel metal hydride battery, a nickel cadmium battery, a lead storage battery, etc., which is not limited in the embodiments of the present disclosure.

[0107] The electrode assembly 10 includes a positive electrode sheet, a negative electrode sheet, and a separator. During the charge and discharge process of the battery cell 160, active ions (such as lithium ions) are inserted and removed between the positive and negative electrode sheets. The separator is placed between the positive and negative electrode sheets to prevent short circuits between the positive and negative electrode sheets while allowing the active ions to pass through.

[0108] 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.

[0109] In some embodiments, the housing 20 can also be used to accommodate an electrolyte, such as an electrolyte solution. The housing 20 can have various structural forms. The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), or an aluminum-plastic film.

[0110] In some embodiments, the housing 20 may include a shell 21 and an end cap 22, wherein the shell 21 is a hollow structure with an opening on one side, and the end cap 22 covers the opening of the shell 21 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 10 and the electrolyte.

[0111] The housing 21 can have various shapes, such as a cube or a rectangular parallelepiped. The shape of the housing 21 can be determined based on the specific shape of the electrode assembly 10. The end cap 22 can have various structures, such as a plate-like structure or a hollow structure with one end open. For example, in FIG4 , the housing 21 has a rectangular parallelepiped structure, and the end cap 22 has a plate-like structure, which covers the opening at the top of the housing 21.

[0112] In some embodiments, the battery cell 160 may further include a positive electrode terminal 30, a negative electrode terminal 40, and a pressure relief mechanism 50, all of which are mounted on the end cap 22. The positive electrode terminal 30 and the negative electrode terminal 40 are both used to electrically connect to the electrode assembly 10 to output the electrical energy generated by the electrode assembly 10. The pressure relief mechanism 50 is used to relieve the pressure inside the battery cell 160 when the internal pressure or temperature of the battery cell 160 reaches a predetermined value.

[0113] Exemplarily, the pressure relief mechanism 50 is located between the positive electrode terminal 30 and the negative electrode terminal 40 . The pressure relief mechanism 50 may be a component such as an explosion-proof valve, an explosion-proof disk, an air valve, a pressure relief valve, or a safety valve.

[0114] In other embodiments, the housing 20 may also have other structures. For example, the housing 20 includes a shell 21 and two end caps 22. The shell 21 is a hollow structure with two opposing openings. One end cap 22 covers one opening of the shell 21 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 10 and the electrolyte. In this structure, the positive electrode terminal 30 and the negative electrode terminal 40 can be installed on the same end cap 22 or on different end caps 22. The pressure relief mechanism 50 can be installed on one end cap 22 or on both end caps 22.

[0115] It should be noted that, in the battery cell 160, there may be one or more electrode assemblies 10 housed in the housing 20. For example, in FIG4 , there are two electrode assemblies 10.

[0116] Figure 5 is a perspective schematic diagram of an electrode assembly provided in some embodiments of the present disclosure. Figure 6 is a cross-sectional schematic diagram of an electrode assembly provided in some embodiments of the present disclosure. Figure 7 is a partially enlarged schematic diagram of Figure 6. Figure 8 is a cross-sectional schematic diagram of position zz in Figure 7. Figure 9 is a structural schematic diagram of the positive electrode sheet of the electrode assembly provided in some embodiments of the present disclosure, unfolded along the winding direction. Figure 10 is a structural schematic diagram of the negative electrode sheet of the electrode assembly provided in some embodiments of the present disclosure, unfolded along the winding direction.

[0117] As shown in Figures 5 to 10, the electrode assembly 10 of the embodiment of the present disclosure includes a wound structure and a protective layer. The wound structure is formed by winding a stack of a positive electrode sheet 11 and a negative electrode sheet 12, with a separator 13 sandwiched between the positive electrode sheet 11 and the negative electrode sheet 12. The wound structure includes a bending area A. The positive electrode sheet 11 includes at least one positive electrode bending portion 111 located in the bending area A, and the negative electrode sheet 12 includes at least one negative electrode bending portion 121 located in the bending area A. Along the winding axis K of the wound structure, both ends of the separator 13 extend beyond the positive electrode bending portion 111 and the negative electrode bending portion 121. The protective layer 14 is attached to the surface of the positive electrode bending portion 111 and / or the surface of the negative electrode bending portion 112. Along the winding axis K of the wound structure, at least one end of the protective layer 14 extends beyond the separator 13.

[0118] As shown in Figure 9, the positive electrode sheet 11 includes a positive current collector 112 and a positive active material layer 113. The positive active material layer 113 is coated on the surface of the positive current collector 112. The positive current collector 112 includes a positive current collecting portion 112a and a positive protrusion 112b protruding from the positive current collecting portion 112a. The positive current collecting portion 112a is coated with the positive active material layer 113. At least a portion of the positive protrusion 112b is not coated with the positive active material layer 113. The positive protrusion 112b serves as the positive electrode tab. In the following description, the positive protrusion 112b may be the positive electrode tab 112b. Taking a lithium-ion battery as an example, the material of the positive current collector 112 can be aluminum (aluminum foil), and the positive active material layer 113 includes a positive active material. The positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0119] As shown in Figure 10, the negative electrode sheet 12 includes a negative electrode current collector 122 and a negative electrode active material layer 123. The negative electrode active material layer 123 is coated on the surface of the negative electrode current collector 122. The negative electrode current collector 122 includes a negative electrode current collecting portion 122a and a negative electrode protrusion 122b protruding from the negative electrode current collecting portion 122a. The negative electrode current collecting portion 122a is coated with the negative electrode active material layer 123, while at least a portion of the negative electrode protrusion 122b is not coated with the negative electrode active material layer 123. The negative electrode protrusion 122b serves as the negative electrode tab. In the following description, the negative electrode protrusion 122b may be the negative electrode tab 122b. Taking a lithium-ion battery as an example, the negative electrode current collector 122 may be made of copper (copper foil), and the negative electrode active material layer 123 includes a negative electrode active material, which may be carbon (e.g., graphite carbon) or silicon.

[0120] In order to ensure that a large current can pass without melting, the number of positive electrode tabs 112b is multiple and they are stacked together, and the number of negative electrode tabs 122b is multiple and they are stacked together.

[0121] As shown in Figures 5-8, the positive electrode sheet 11 and the negative electrode sheet 12 are stacked together to form a laminate. The laminate is wound more than two times around a winding axis K to form a wound structure. The winding axis K extends perpendicular to the winding direction C of the wound structure and the stacking direction E (see Figure 8).

[0122] A separator 13 is interposed between each adjacent positive electrode sheet 11 and negative electrode sheet 12. The separator 13 is used to isolate the positive electrode sheet 11 from the negative electrode sheet 12 to reduce the risk of a short circuit between the positive electrode sheet 11 and the negative electrode sheet 12. For example, the separator 13 may be made of PP (polypropylene) or PE (polyethylene).

[0123] The positive electrode sheet 11, the negative electrode sheet 12, and the separator 13 can all be strip-shaped structures. In the disclosed embodiment, the positive electrode sheet 11, the separator 13, the negative electrode sheet 12, and the separator 13 can be stacked in sequence, and then wound around the winding axis K from the inside outward for more than two turns to form a wound structure. In Figure 6, the wound structure is wound in a clockwise direction. Of course, the winding direction can also be counterclockwise.

[0124] The winding structure includes a bending zone A, which is an area on the positive electrode sheet 11 and the negative electrode sheet 12 where the bending structure is located, and is an example of a bending zone. In the bending zone A, the positive bending portion 111 and the negative bending portion 121 are alternately distributed along the stacking direction E of the winding structure, that is, in the bending zone A, the positive bending portion 111, the negative bending portion 121, the positive bending portion 111, the negative bending portion 121... are arranged in sequence from the inside to the outside, wherein the inside is closer to the winding axis K than the outside, and the stacking direction E is the layer thickness direction of the winding structure. For example, the innermost positive bending portion 111 is located outside the innermost negative bending portion 121. For example, the shape of the positive bending portion 111 and the negative bending portion 121 can be substantially arc-shaped.

[0125] As shown in Figures 8 to 10, along the winding axis direction K of the winding structure, the two ends of the separator 13 exceed the positive electrode bend portion 111 and the negative electrode bend portion 121. That is, along the winding axis direction K, the two ends of the separator 13 respectively exceed the two ends of the positive electrode bend portion 111, and, along the winding axis direction K, the two ends of the separator 13 respectively exceed the two ends of the negative electrode bend portion 121. In other words, along the winding axis K direction, the edges of the positive electrode bend portion 111 and the edges of the negative electrode bend portion 121 do not exceed the ends of the separator 13 and have a certain amount of indentation. As a result, the separator 13 can completely cover the positive electrode bend portion 111 and the negative electrode bend portion 121, effectively reducing the risk of short circuit between the positive electrode sheet 11 and the negative electrode sheet 12.

[0126] The protective layer 14 is attached to the surface of the positive electrode bend 111 and / or the surface of the negative electrode bend 112. As shown in FIG6 , the protective layer 14 may be attached to the surface of the positive electrode bend 111 of the positive electrode bend 111 and the negative electrode bend 121; or, as shown in FIG11 , the protective layer 14 may be attached to the surface of both the positive electrode bend 111 and the negative electrode bend 121. Alternatively, as shown in FIG11 , the protective layer 14 may be attached to the surface of both the positive electrode bend 111 and the negative electrode bend 121. The surface of the positive electrode bend 111 may be the surface of the positive active material layer 113 at the positive electrode bend 111 of the positive electrode tab 11. The surface of the negative electrode bend 121 may be the surface of the negative active material layer 123 at the negative electrode bend 121 of the negative electrode tab 12.

[0127] In some embodiments, the protective layer 14 is attached to the surface of the positive electrode bend 111 and / or the surface of the negative electrode bend 121 by adhesion or electrostatic adsorption. The protective layer 14 is attached to the surface of the positive electrode bend 111 and / or the surface of the negative electrode bend 121 by adhesion. The protective layer 14 may have an adhesive layer, and thus be attached to the surface of the positive electrode bend 111 and / or the surface of the negative electrode bend 121 by the adhesive layer. Alternatively, the protective layer 14 is attached to the surface of the positive electrode bend 111 and / or the surface of the negative electrode bend 121 by an adhesive. The adhesive may be a colloid or an adhesive layer coated on the surface of the positive electrode bend 111 and / or the surface of the negative electrode bend 121.

[0128] Along the winding axis direction K of the winding structure, at least one end of the protective layer 14 extends beyond the isolating member 13 . Alternatively, one end of the protective layer 14 extends beyond the isolating member 13 , and the other end of the protective layer 14 may or may not extend beyond the isolating member 13 .

[0129] The protective layer 14 may extend beyond the separator 13 when, along the winding axis K of the winding structure, the end of the protective layer 14 extends out of the edge of the separator 13 on the same side as the end of the protective layer 14. The protective layer 14 may not extend beyond the separator 13 when, along the winding axis K of the winding structure, the end of the protective layer 14 is retracted from the edge of the separator 13 on the same side as the end of the protective layer 14. The retracted position may be between the edge of the pole piece and the same side of the separator 13, or may be substantially flush with the edge of the pole piece.

[0130] The positive electrode bend 111 and the negative electrode bend 121 generate stress concentration during the bending process and may cause the risk of fracture and shedding of active materials on their respective surfaces, thereby posing a risk of thermal runaway of the battery. The disclosed embodiment attaches a protective layer 14 to the positive electrode bend 111 and the negative electrode bend 121, thereby reducing the risk of fracture and shedding of active materials when the positive electrode bend 111 and the negative electrode bend 121 are bent, thereby reducing the risk of thermal runaway of the electrode assembly, the battery cell and even the battery as a whole. The protective layer 14 extends beyond the separator 13, which enables the protective layer to completely cover the positive and negative electrode sheets and reliably protect them, and the attachment position of the protective layer 14 can be visually observed during the battery manufacturing process (for example, during the winding process), and the accuracy of the attachment position can be confirmed in a timely manner.

[0131] In some embodiments, the material of the protective layer 14 can be polyethylene terephthalate, polypropylene, polyethylene, polyimide, or non-woven fabric. In some embodiments, as shown in FIG9 , at the positive electrode bend 111 , along the winding axis K, the first edge 14 a of the protective layer 14 located at the positive electrode bend 111 extends beyond the positive electrode active material layer 113 but does not extend beyond the separator 13 , and the second edge 14 b of the protective layer 14 located at the positive electrode bend 111 extends beyond the separator 13 , wherein the first edge 14 a is located at one end of the protective layer 14 along the winding axis K, and the second edge 14 b is located at the other end of the protective layer 14 along the winding axis K.

[0132] The first edge 14a of the protective layer 14 located at the positive electrode bend 111 extends beyond the positive electrode active material layer 113 but does not extend beyond the separator 13. The first edge 14a may be located between the edge of the positive electrode active material layer 113 and the edge of the separator 13 on the same side along the winding axis direction K. For example, as shown in FIG13 , only a portion of the positive electrode current collecting portion 112a is coated with the positive electrode active material layer 113, and the area of ​​the positive electrode current collecting portion 112a not coated with the positive electrode active material layer 112a is coated with an insulating layer 114. The insulating layer 114 is located on a side of the positive electrode active material layer 113 near the positive electrode protrusion 112b (positive electrode tab), and between the edge of the positive electrode active material layer 113 and the edge of the separator 13 on the same side. The first edge 14a may be located within the insulating layer 114.

[0133] When the protective layer 14 is adhered to the surface of the positive electrode bending portion 111 through its own adhesive layer, the surface of the protective layer 14 extending beyond the separator 13 is sticky, and there is a possibility of sticking to the roller during the winding process, resulting in the risk of the protective layer 14 being torn.

[0134] In the embodiment of the present disclosure, along the winding axis direction K, the first edge 14a of the protective layer 14 located at the positive electrode bend 111 extends beyond the positive electrode active material layer 113 but does not extend beyond the isolation member 13, and the second edge 14b of the protective layer 14 located at the positive electrode bend 111 extends beyond the isolation member 13. Thus, while the protective layer 14 covers the positive electrode active material layer 113, only one edge extends beyond the isolation member 13. It can be visually observed that the protective layer 14 is located at the pasting position of the positive electrode bend 111. Compared with both edges extending beyond the isolation member 13, the risk of the isolation member 13 sticking to the roller and causing itself to tear can be reduced.

[0135] In some embodiments, as shown in Figure 10, at the negative electrode bend 121, along the winding axis direction k, the third edge 14c of the protective layer 14 located at the negative electrode bend 121 exceeds the negative electrode active material layer 123 but does not exceed the isolation member 13, and the fourth edge 14d of the protective layer 14 located at the negative electrode bend exceeds the isolation member, wherein the third edge 14c is located at one end of the protective layer 14 along the winding axis direction k, and the fourth edge 14d is located at the other end of the protective layer 14 along the winding axis direction K.

[0136] The third edge 14c of the protective layer 14 located at the negative electrode bend 121 extends beyond the negative electrode active material layer 123 but does not extend beyond the separator 13. This may be so that, along the winding axis direction K, the third edge 14c is located between the edge of the negative electrode active material layer 123 and the edge of the separator 13 on the same side. For example, as shown in FIG14 , only a portion of the negative electrode current collecting portion 122a is coated with the negative electrode active material layer 123, while the region of the negative electrode current collecting portion 122a not coated with the negative electrode active material layer 123 is coated with the insulating layer 124. The insulating layer 124 is located on the side of the negative electrode active material layer 123 near the negative electrode protrusion 122b (negative electrode tab) and between the edge of the negative electrode active material layer 123 and the edge of the separator 13 on the same side. The third edge 14c may be located within the insulating layer 124.

[0137] In the embodiment of the present disclosure, along the winding axis K direction, the third edge 14c of the protective layer 14 located at the negative electrode bend 121 extends beyond the negative electrode active material layer 123 but does not extend beyond the separator 13, and the fourth edge 14d of the protective layer 14 located at the negative electrode bend 121 extends beyond the separator 13. Thus, while the protective layer 14 covers the negative electrode active material layer 123, only one edge extends beyond the separator 13. It can be visually observed that the protective layer 14 is located at the pasting position of the negative electrode bend 121. Compared with both edges extending beyond the separator 13, the risk of the separator 13 sticking to the roller and causing itself to tear can be reduced.

[0138] In some embodiments, the length d1 of the protective layer 14 extending beyond the separator 13 along the winding axis direction K is 1 mm to 4 mm. This can be achieved by extending the protective layer 14 beyond the separator 13 by 1 mm to 4 mm at the positive electrode bend 111 or by extending the protective layer 14 beyond the separator 13 by 1 mm to 4 mm at the negative electrode bend 121.

[0139] The length d1 can be 1 mm, 2 mm, 3 mm, or 4 mm.

[0140] If the length d1 of the protective layer 14 extending beyond the separator 13 is too small, visual inspection is difficult. If the length d1 of the protective layer 14 extending beyond the separator 13 is too large, the risk of the protective layer 14 sticking to the roller and tearing during the winding process increases. Therefore, in the disclosed embodiments, the length d1 of the protective layer 14 extending beyond the separator 13 is controlled to between 1 mm and 4 mm. This not only facilitates visual inspection of the attachment position of the protective layer 14, but also reduces the risk of the protective layer 14 sticking to the roller and tearing.

[0141] In some embodiments, along the winding axis direction K, the protective layer 14 at the positive electrode bend 111 extends beyond the positive electrode bend 111 by a length d2 of 4 mm to 6 mm. Furthermore, along the winding axis direction K, the protective layer 14 at the negative electrode bend 121 extends beyond the negative electrode bend 121 by a length d2 of 4 mm to 6 mm.

[0142] The length d2 includes the length of the spacer 13 extending beyond the edge of the pole piece and the length of the protection layer 14 extending beyond the spacer 13 .

[0143] During the preparation of the electrode assembly, the protective layer 14 can be attached to the electrode first, and then the winding is performed. In the wound structure formed after winding, the edge of the electrode is smoother than the edge of the separator, making it easier to measure the excess dimension of the protective layer 14. Furthermore, after the protective layer 14 is attached to the electrode and before winding, it is also convenient to measure the excess dimension of the protective layer 14 beyond the electrode. Therefore, the excess length of the protective layer 14 beyond the separator 13 can be controlled by controlling the length of the protective layer 14 beyond the positive electrode bend 111 and / or the negative electrode bend 121, thereby improving the attachment accuracy of the protective layer 14.

[0144] In some embodiments, a positive electrode tab 112 b is provided on one side of the positive electrode current collector 112 a along the winding axis direction K, and a first edge 14 a of the protective layer 14 is located on the same side as the positive electrode tab 112 b along the winding axis direction K. That is, the first edge 14 a located on the same side as the positive electrode tab 112 b does not extend beyond the separator 13 .

[0145] In some embodiments, a negative electrode tab 122 b is provided on one side of the negative electrode current collector 122 a along the winding axis direction K, and the third edge 14 c of the protective layer 14 is located on the same side as the negative electrode tab 122 b along the winding axis direction K. That is, the third edge 14 a located on the same side as the negative electrode tab 122 b does not extend beyond the separator 13 .

[0146] During the winding process, a detection device is usually provided on the side of the tab (positive tab 112b, negative tab 122b). For example, the detection device can be a sensor for detecting the tab, which can be used to determine whether the tab is bent. If it is bent, it is considered unqualified. If the edge of the protective layer 14 (first edge 14a, third edge 14c) on the same side of the tab exceeds the separator 13, when the exceeding portion of the protective layer 14 passes through the sensor, it may cause the sensor to falsely report that the qualified positive tab is unqualified. Therefore, in the embodiment of the present disclosure, the risk of false reports from the detection equipment on the side of the tab can be avoided by ensuring that the edge of the protective layer 14 on the same side of the tab does not exceed the separator 13.

[0147] In some embodiments, as shown in FIG8 and FIG11 , the protective layer 14 may cover the positive electrode active material layer 113 on one side (the first concave surface 111a or the first convex surface 111b) or on both sides (the first concave surface 111a and the first convex surface 111b) of the positive electrode bend 111 of the positive electrode tab 11. Furthermore, the protective layer 14 may also cover the negative electrode active material layer 123 on one side (the second concave surface 121a or the second convex surface 121b) or on both sides (the second concave surface 121a and the second convex surface 121b) of the negative electrode bend 121 of the negative electrode tab 12.

[0148] Figure 11 is a cross-sectional schematic diagram of an electrode assembly provided in some other embodiments of the present disclosure. Figure 12 is a partially enlarged schematic diagram of Figure 11.

[0149] As shown in Figures 11 and 12, in some embodiments, along the stacking direction E of the winding structure, each positive electrode bending portion 111 includes a first concave surface 111a and a first convex surface 111b located on opposite sides, and the protective layer 14 includes a first protective layer 141 and a second protective layer 142 attached to the first concave surface 111a and the first convex surface 111b, respectively.

[0150] The stacking direction E of the wound structure can be the thickness direction of the positive electrode bend 111. Multiple positive electrode bends 111 can be arranged along the stacking direction E. Each positive electrode bend 111 includes a first concave surface 111a and a first convex surface 111b located on opposite sides. The first concave surface 111a is the inwardly concave side of the arc of the positive electrode bend 111, while the first convex surface 111b is the outwardly convex side of the arc of the positive electrode bend 111. The first concave surface 111a is closer to the winding axis than the first convex surface 111b.

[0151] During the bending process of the positive electrode bend 111, there is a risk of the active material layer falling off on both the front and back surfaces of the positive electrode bend 111, which may affect the battery capacity and may also cause the risk of thermal runaway of the battery. The disclosed embodiment further reduces the risk of the positive electrode bend 111 breaking by attaching a protective layer 14 to both the first concave surface 111a and the first convex surface 111b on both the front and back sides of the positive electrode bend 111. It can also reduce the risk of the positive electrode active material layer falling off on both surfaces of the positive electrode bend 111, thereby reducing the adverse effects on the battery capacity and the risk of thermal runaway of the battery.

[0152] In some embodiments, a first protective layer 141 and a second protective layer 142 may be attached to the first concave surface 111a and the first convex surface 111b of each positive electrode bending portion 111, respectively. In this way, multiple positive electrode bending portions 111 can be fully protected.

[0153] Because the innermost positive electrode bend 111 in the stacking direction E is subjected to greater tensile force than other positive electrode bends 111, it is more likely to break or cause the positive electrode active material layer to fall off. To address this, in some embodiments, a first protective layer 141 and a second protective layer 142 can be attached to the first concave surface 111a and the first convex surface 111b of the innermost positive electrode bend 111 in the stacking direction E, respectively. In this way, the innermost positive electrode bend 111 is effectively protected.

[0154] In some embodiments, as shown in FIG8 , along the winding axis direction K, at least one end of the first protective layer 141 and the second protective layer 142 extends beyond the other. That is, along the winding axis direction K, the ends of the first protective layer 141 and the second protective layer 142 on the same side are offset from each other (displaced from each other).

[0155] For example, along the winding axis direction K, one end of the first protective layer 141 on the same side exceeds one end of the second protective layer 142; or, along the winding axis direction K, one end of the second protective layer 142 on the same side exceeds one end of the first protective layer 141; or, along the winding axis direction K, both ends of the first protective layer 141 respectively exceed both ends of the second protective layer 142 on the same side; or, along the winding axis direction K, both ends of the second protective layer 142 respectively exceed both ends of the first protective layer 141 on the same side.

[0156] The overhanging dimension of one of the first protective layer 141 and the second protective layer 142 over the other may be 0-4 mm, for example, 0 mm, 1 mm, 2 mm, 3 mm, or 4 mm.

[0157] In some embodiments, along the stacking direction E of the winding structure, each negative electrode bend 121 includes a second concave surface 121a and a second convex surface 121b on opposite sides, and the protective layer 14 includes a third protective layer 143 and a fourth protective layer 144 attached to the second concave surface 121a and the second convex surface 121b respectively.

[0158] Multiple negative electrode bends 121 may be arranged along the stacking direction E. These multiple negative electrode bends 121 are alternately distributed with the multiple positive electrode bends 111 along the stacking direction E. Each negative electrode bend 121 includes a second concave surface 121a and a second convex surface 121b located on opposite sides. The second concave surface 121a is the inwardly concave side of the arc of the negative electrode bend 121, while the second convex surface 121b is the outwardly convex side of the arc of the negative electrode bend 121. The second concave surface 121a is closer to the winding axis than the second convex surface 121b.

[0159] During the bending process of the negative electrode bend 121, there is a risk of the active material layer falling off on both the front and back surfaces of the negative electrode bend 121, which may affect the battery capacity and may also cause the risk of thermal runaway of the battery. The disclosed embodiment further reduces the risk of the negative electrode bend 121 breaking by attaching a protective layer 14 to both the second concave surface 121a and the second convex surface 121b on both the front and back sides of the negative electrode bend 121. It can also reduce the risk of the negative electrode active material layer falling off on both surfaces of the negative electrode bend 121, thereby reducing the adverse effects on the battery capacity and the risk of thermal runaway of the battery.

[0160] In some embodiments, a third protective layer 143 and a fourth protective layer 144 may be attached to the second concave surface 121a and the second convex surface 121b of each negative electrode bend 121, respectively. In this way, multiple negative electrode bends 121 can be fully protected.

[0161] Since the innermost negative electrode bent portion 121 in the stacking direction E is subjected to a greater tensile force than other negative electrode bent portions 121 , it is more likely to be broken or the positive electrode active material layer to fall off.

[0162] In some embodiments, a third protective layer 143 and a fourth protective layer 144 may be attached to the second concave surface 121a and the second convex surface 121b of the innermost negative electrode bend 121 in the stacking direction E. In this way, the innermost negative electrode bend 121 is effectively protected.

[0163] In some embodiments, as shown in Figures 11 and 12, the first protective layer 141 includes a first end 141a and a second end 141b along the winding direction C of the winding structure, and the second protective layer 142 includes a third end 142a and a fourth end 142b in the winding direction C, the third end 142a and the first end 141a are located on the same side along the winding direction C and are staggered along the winding direction C, and / or the fourth end 142b and the second end 141b are located on the same side along the winding direction C and are staggered along the winding direction C.

[0164] The third end 142a and the first end 141a are offset along the winding direction C, meaning that the third end 142a and the first end 141a are not located at the same position along the winding direction C. For example, as shown in FIG12 , the third end 142a extends beyond the first end 141a along the winding direction C; in other words, the first end 141a extends counterclockwise relative to the third end 142a. Of course, the first end 141a may also extend beyond the third end 142a.

[0165] The fourth end 142b is offset from the second end 141b along the winding direction C, meaning that the fourth end 142b and the second end 141b are not located at the same position along the winding direction C. For example, as shown in FIG12 , the fourth end 142b extends beyond the second end 141b along the winding direction C; in other words, the fourth end 142b extends clockwise relative to the second end 141b. Of course, the second end 141b may also extend beyond the fourth end 142b.

[0166] The first protective layer 141 and the second protective layer 142 may be staggered at one end on the same side of the winding direction C; or, as shown in FIG12 , the first protective layer 141 and the second protective layer 142 may be staggered at both ends on the same side of the winding direction C. For example, the third end 142a is staggered with the first end 141a, while the fourth end 142b is not staggered with the second end 141b; or the fourth end 142b is staggered with the second end 141b, while the third end 142a is not staggered with the first end 141a; or the third end 142a is staggered with the first end 141a, while the fourth end 142b is staggered with the second end 141b.

[0167] Since the first protective layer 141 and the second protective layer 142 have a certain thickness, along the winding direction C, the end of the first protective layer 141 and the end of the second protective layer 142 respectively form a step with the surface of the positive electrode sheet 11. During the extrusion molding process of the winding structure, the greater the difference in the height of the step, the more obvious the extrusion of the separator 13, which can easily cause the separator 13 to wrinkle, thereby blocking the pores in the separator 13 and even posing a risk of breaking the separator. In the embodiment of the present disclosure, by staggering the ends of the first protective layer 141 and the second protective layer 142 on the same side, the step height at the end of each protective layer after stacking can be reduced compared to non-staggered. Therefore, during the extrusion molding process of the winding structure, it can form a buffer for the extrusion of the separator 13, reduce the risk of the separator 13 wrinkling, and thus reduce the blocking of the pores of the separator 13 caused by wrinkling.

[0168] In some embodiments, the third protective layer 143 includes a fifth end 143a and a sixth end 143b in the winding direction C of the winding structure, and the fourth protective layer 144 includes a seventh end 144a and an eighth end 144b in the winding direction C, the seventh end 144a and the fifth end 143a are located on the same side of the winding direction C and are staggered along the winding direction C, and / or the eighth end 144b and the sixth end 143b are on the same side of the winding direction C and are staggered along the winding direction C.

[0169] The third protective layer 143 and the fourth protective layer 144 may have ends on the same side along the winding direction C that are staggered, or the third protective layer 143 and the fourth protective layer 144 may have ends on both sides along the winding direction C that are staggered. For example, the seventh end 144a and the fifth end 143a are staggered, while the eighth end 144b and the sixth end 143b are not staggered; or the eighth end 144b and the sixth end 143b are staggered, while the seventh end 144a and the fifth end 143a are not staggered; or the seventh end 144a and the fifth end 143a are staggered, while the eighth end 144b and the sixth end 143b are staggered.

[0170] In the embodiment of the present disclosure, by staggering the two ends of the third protective layer 141 and the fourth protective layer 142 on the same side, the step height of the ends of the stacked protective layers can be reduced compared to non-staggered conditions. Therefore, during the extrusion molding process of the winding structure, a buffer can be formed for the extrusion of the isolation member 13, reducing the risk of wrinkling of the isolation member 13, thereby reducing the possibility of the pores of the isolation member 13 being blocked due to wrinkles.

[0171] In some embodiments, the offset length between the third end 142a and the first end 141a along the winding direction C is greater than zero and less than or equal to 2 mm; and / or the offset length between the fourth end 142b and the second end 141b along the winding direction C is greater than zero and less than or equal to 2 mm.

[0172] Exemplarily, the staggered length may be 0.5 mm, 1 mm, 1.5 mm, 1.8 mm, or 2 mm.

[0173] In some embodiments, the offset length between the seventh end 144a and the fifth end 143a along the winding direction C is greater than zero and less than or equal to 2 mm; and / or the offset length between the eighth end 144b and the sixth end 143b along the winding direction C is greater than zero and less than or equal to 2 mm.

[0174] Exemplarily, the staggered length may be 0.5 mm, 1 mm, 1.5 mm, 1.8 mm, or 2 mm.

[0175] Taking the staggered ends of the first protective layer 141 and the second protective layer 142 on the same side of the winding direction C as an example, if the length of the staggered ends of the first protective layer 141 and the second protective layer 142 on the same side of the winding direction C is too small, there is a risk of squeezing the separator 13 and causing wrinkles. If the length of the staggered ends of the first protective layer 141 and the second protective layer 142 on the same side of the winding direction C is too large, there is a large staggered distance between the portion of the first protective layer 141 that extends beyond the separator 13 and the portion of the second protective layer 142 that extends beyond the separator 13, resulting in a large surface area of ​​exposed glue on the portions of the first protective layer 141 and the second protective layer 142 that extend beyond the separator 13. During the winding process, it is easy to stick to the roller and cause the risk of tearing. Therefore, the length of the staggered ends of the first protective layer 141 and the second protective layer 142 on the same side of the winding direction C is controlled to be greater than zero and less than or equal to 2 mm, which can reduce both the risk of wrinkles on the separator 13 and the risk of tearing due to sticking to the roller.

[0176] In some embodiments, as shown in Figures 6 and 7, the winding structure includes a straight area B connected to the bending area A, and the protective layer 14 extends at least one end in the winding direction C of the winding structure to the junction between the straight area B and the bending area A or extends along the winding direction C beyond the junction to the straight area B.

[0177] Only one end of the protective layer 14 in the winding direction C of the wound structure extends to the boundary between the straight region B and the bent region A, or extends beyond the boundary along the winding direction C to the straight region B. Alternatively, both ends of the protective layer 14 in the winding direction C of the wound structure extend to the boundary between the straight region B and the bent region A, or extend beyond the boundary along the winding direction C to the straight region B. Thus, the protective layer 14 located at the positive electrode bent portion 111 can cover the positive electrode active material layer 113 in the winding direction C, fully protecting the positive electrode active material layer 113. The protective layer 14 located at the negative electrode bent portion 121 can cover the negative electrode active material layer 123 in the winding direction C, fully protecting the negative electrode active material layer 123.

[0178] In some embodiments, at least one of the first protective layer 141 located on the first concave surface 11 a and the second protective layer 142 located on the first convex surface 111 b has pores for ion permeation.

[0179] Pores for ion permeation may be present only in at least a portion of the first protective layer 141 located on the first concave surface 11a of the positive electrode bend 111. Alternatively, pores may be present only in at least a portion of the second protective layer 142 located on the first convex surface 111b of the positive electrode bend 111. Alternatively, pores may be present in both at least a portion of the first protective layer 141 located on the first concave surface 11a and at least a portion of the second protective layer 142 located on the first convex surface 111b of the positive electrode bend 111.

[0180] The ions may be active ions in the active material. For example, when the battery is a lithium ion battery, the active ions are lithium ions; when the battery is a sodium ion battery, the active ions may be sodium ions; when the battery is a magnesium ion battery, the active ions may be magnesium ions. Of course, the ions may also be other possible active ions present in the active material.

[0181] The protective layer has pores for ion permeation, thereby reducing or preventing the loss of battery capacity.

[0182] The first protective layer 141 located at the first concave surface 11a and the second protective layer 142 located at the first convex surface 111b have pores for ion penetration, which can protect the positive electrode bending portion 111 from the risk of breakage and the respective active materials falling off, and at the same time reduce the impact of the protective layer attached to the positive electrode bending portion 111 on the release of positive active materials in the positive electrode active material layer 113 at the positive electrode bending portion 111.

[0183] In some embodiments, the first protection layer 141 located on the first concave surface 11 a and the second protection layer 142 located on the first convex surface 111 b both include a blocking portion for blocking ions.

[0184] Because the number of lithium ions provided by the negative active material layer of the negative bent portion 121 is less than that provided by the positive active material layer of the adjacent positive bent portion 111, lithium plating may occur. In the disclosed embodiment, the ion blocking portion on the first protective layer 141 can block a portion of the lithium ions provided by the positive active material layer, thereby reducing lithium plating.

[0185] In some embodiments, the third protection layer 143 located on the second concave surface 121 a and the fourth protection layer 144 located on the second convex surface 121 b both have pores for ion permeation.

[0186] Because the number of lithium ions that can be inserted into the negative active material layer of the negative electrode bend 121 is less than that of the positive active material layer of the adjacent positive electrode bend 111, in other words, the number of lithium ions that can be inserted into the positive active material layer of the positive electrode bend 111 is greater than the number of lithium ions that can be inserted into the negative active material layer of the negative electrode bend 121, if the negative active material layer on the negative electrode bend 121 is blocked, it is more likely to result in insufficient lithium insertion sites in the negative active material layer, which is more likely to cause lithium deposition. Therefore, the third protective layer 143 on the second concave surface 121a of the negative electrode bend 121 and the fourth protective layer 144 on the second convex surface 121b of the negative electrode bend 121 both have pores for ion transmission. This protects the negative electrode bend 121 while also reducing lithium deposition.

[0187] The air permeability of the protective layer having pores for ion permeation is 220±70 sec / 100 cc (sec is seconds, cc is cubic centimeters). The air permeability can be measured, for example, according to the standard document GB / T36363-2018, that is, the time required for 100 ml of air to pass through a 6.45 cm² spacer under a pressure of 1.21 kPa applied by the test instrument in a test temperature, humidity, and normal pressure environment. The applied pressure of 1.21 kPa is a constant pressure, and the area of ​​6.45 cm² passed through is a fixed area.

[0188] The minimum size of the pores in the protective layer for ion permeation may range from 100 nm to 400 nm. For example, the minimum size of the pores may range from 100 nm, 120 nm, 150 nm, 200 nm, 210 nm, 220 nm, 250 nm, 270 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, and 400 nm. The minimum size of the pores may be measured using a scanning electron microscope.

[0189] The embodiment of the present disclosure further provides a battery cell 160 , comprising: a housing 20 and at least one of the electrode assemblies 10 mentioned above, wherein the electrode assembly 10 is accommodated in the housing 20 .

[0190] The embodiment of the present disclosure further provides a battery 100 , comprising: a housing 110 and at least one of the battery cells 160 mentioned above, wherein the battery cell 160 is housed in the housing 110 .

[0191] The embodiment of the present disclosure further provides an electrical device, which includes at least one of the above-mentioned battery cells 160 or batteries 100 for providing electrical energy.

[0192] An embodiment of the present disclosure further provides an energy storage device, comprising the battery mentioned above, which is capable of storing electrical energy and providing electrical energy.

[0193] The present disclosure also provides a method for preparing an electrode assembly, as shown in FIG15 , comprising:

[0194] Step S1: providing a positive electrode sheet, a negative electrode sheet and a separator;

[0195] Step S2: attaching a protective layer to the positive electrode sheet and / or the negative electrode sheet;

[0196] Step S3: The positive electrode sheets, the negative electrode sheets and the separator are stacked and wound to form a winding structure, wherein, in the winding structure, an separator is sandwiched between the positive electrode sheets and the negative electrode sheets, the winding structure includes a bending area, the positive electrode sheet includes at least one positive bending portion located in the bending area, the negative electrode sheet includes at least one negative bending portion located in the bending area, along the winding axis direction of the winding structure, both ends of the separator extend beyond the positive bending portion and the negative bending portion, a protective layer is adhered to the surface of the positive bending portion and / or the surface of the negative bending portion, and along the winding axis direction of the winding structure, at least one end of the protective layer extends beyond the separator.

[0197] In the embodiment of the present disclosure, a protective layer may be attached to the positive electrode sheet and / or the negative electrode sheet before the winding process is performed. Attaching the protective layer to the positive electrode sheet and / or the negative electrode sheet may be performed during the electrode sheet die-cutting process, and then the winding process is performed. Attaching the protective layer to the positive electrode sheet and / or the negative electrode sheet may also be performed while winding. For example, a pasting module may be integrated into the winding device, and the protective layer may be pasted to the positive electrode sheet and / or the negative electrode sheet during the winding process of the winding device.

[0198] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present disclosure, and they should all be included in the scope of the claims and description of the present disclosure. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present disclosure is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims. Industrial Applicability

[0199] The present disclosure provides an electrode assembly and preparation method thereof, a battery cell, a battery, an electrical device, and an energy storage device that reduce the risk of thermal runaway. By attaching a protective layer to the positive and negative electrode bends, the risk of fracture and active material shedding during bending of the positive and negative electrode bends can be reduced, thereby reducing the risk of thermal runaway of the electrode assembly, the battery cell, and even the entire battery. The protective layer extends beyond the separator, allowing the adhesive tape to completely cover the positive and negative electrode sheets and reliably protect them. Furthermore, during the battery manufacturing process, the attachment position of the protective layer can be visually inspected through the exposed portion, allowing the accuracy of the attachment position to be promptly confirmed.

Claims

1. An electrode assembly, comprising: a winding structure formed by winding a laminate including a positive electrode tab and a negative electrode tab, with a separator interposed between the positive electrode tab and the negative electrode tab, the winding structure including a bending region, the positive electrode tab including at least one positive bending portion located in the bending region, the negative electrode tab including at least one negative bending portion located in the bending region, and along the winding axis direction of the winding structure, both ends of the separator extending beyond the positive bending portion and the negative bending portion; and a protective layer attached to the surface of the positive bending portion and / or the surface of the negative bending portion, and along the winding axis direction of the winding structure, at least one end of the protective layer extending beyond the separator.

2. The electrode assembly according to claim 1, wherein the protective layer is attached to the surface of the positive bending portion and / or the surface of the negative bending portion by means of adhesion or electrostatic adsorption.

3. The electrode assembly according to claim 1 or 2, wherein along the stacking direction of the winding structure, each positive bending portion includes a first concave surface and a first convex surface located on opposite sides, and the protective layer includes a first protective layer and a second protective layer respectively attached to the first concave surface and the first convex surface.

4. The electrode assembly according to any one of claims 1 to 3, wherein along the stacking direction of the winding structure, each negative bending portion includes a second concave surface and a second convex surface located on opposite sides, and the protective layer includes a third protective layer and a fourth protective layer respectively attached to the second concave surface and the second convex surface.

5. The electrode assembly according to any one of claims 1 to 4, wherein the positive electrode tab includes a positive current collector and a positive active material layer provided on the surface of the positive current collector, and the protective layer covers the positive active material layer at the positive bending portion in the positive electrode tab; and / or, the negative electrode tab includes a negative current collector and a negative active material layer provided on the surface of the negative current collector, and the protective layer covers the negative active material layer at the negative bending portion in the negative electrode tab.

6. The electrode assembly according to claim 5, wherein at the positive bending portion, along the winding axis direction, a first edge of the protective layer located at the positive bending portion extends beyond the positive active material layer but does not extend beyond the separator, and a second edge of the protective layer located at the positive bending portion extends beyond the separator, where the first edge is located at one end of the protective layer along the winding axis direction, and the second edge is located at the other end of the protective layer along the winding axis direction; and / or, at the negative bending portion, along the winding axis direction, the The third edge extends beyond the negative electrode active material layer but does not extend beyond the separator, and the fourth edge of the protective layer located at the negative electrode bending portion extends beyond the separator, wherein the third edge is located at one end of the protective layer along the winding axis direction, and the fourth edge is located at the other end of the protective layer along the winding axis direction.

7. The electrode assembly according to claim 6, wherein, on the positive electrode current collector, a positive electrode tab is provided on one side in the winding axis direction, and the first edge of the protective layer is on the same side as the positive electrode tab along the winding axis direction; and / or, on the negative electrode current collector, a negative electrode tab is provided on one side in the winding axis direction, and the third edge of the protective layer is on the same side as the negative electrode tab along the winding axis direction.

8. The electrode assembly according to any one of claims 1 to 7, wherein, along the winding axis direction, the length by which the protective layer extends beyond the positive electrode bending portion is 4 mm to 6 mm; and / or, along the winding axis direction, the length by which the protective layer extends beyond the negative electrode bending portion is 4 mm to 6 mm.

9. The electrode assembly according to any one of claims 1 to 8, wherein, along the winding axis direction, the length by which the protective layer extends beyond the separator is 1 mm to 4 mm.

10. The electrode assembly according to claim 3, wherein, along the winding axis direction, at at least one end, one of the first protective layer and the second protective layer extends beyond the other.

11. The electrode assembly according to claim 3, wherein, the first protective layer includes a first end and a second end located at both ends along the winding direction of the winding structure, the second protective layer includes a third end and a fourth end located at both ends along the winding direction, the third end and the first end are on the same side in the winding direction and are offset from each other along the winding direction, and / or the fourth end and the second end are on the same side in the winding direction and are offset from each other along the winding direction.

12. The electrode assembly according to claim 11, wherein, the offset length between the third end and the first end along the winding direction is greater than zero and less than or equal to 2 mm; and / or, the offset length between the fourth end and the second end along the winding direction is greater than zero and less than or equal to 2 mm.

13. The electrode assembly according to claim 4, wherein, the third protective layer includes a fifth end and a sixth end located at both ends along the winding direction of the winding structure, the fourth protective layer includes a seventh end and an eighth end located at both ends along the winding direction, the seventh end and the fifth end are on the same side in the winding direction and are offset from each other along the winding direction, and / or the eighth end and the sixth end are on the same side in the winding direction and are offset from each other along the winding direction.

14. The electrode assembly according to claim 13, wherein, the offset length between the seventh end and the fifth end along the winding direction is greater than zero and less than or equal to 2 mm; and / or, The offset length between the eighth end and the sixth end along the winding direction is greater than zero and less than or equal to 2 mm.

15. The electrode assembly according to any one of claims 1 to 14, wherein, the winding structure includes a straight region connected to the bending region, at least one end of the protective layer in the winding direction of the winding structure extends to the junction between the straight region and the bending region or extends beyond the junction along the winding direction to the straight region.

16. The electrode assembly according to any one of claims 1 to 15, wherein, the positive electrode tab includes a plurality of the positive electrode bending portions arranged along the stacking direction of the winding structure in the bending region, and the protective layer is at least adhered to the positive electrode bending portion located innermost along the stacking direction; and / or, the negative electrode tab includes a plurality of the negative electrode bending portions arranged along the stacking direction of the winding structure in the bending region, and the protective layer is at least adhered to the negative electrode bending portion located innermost along the stacking direction.

17. The electrode assembly according to any one of claims 1 to 16, wherein, the material of the protective layer is polyethylene terephthalate, polypropylene, polyethylene, polyimide or non-woven fabric.

18. The electrode assembly according to claim 3, wherein, at least one of the first protective layer located at the first concave surface and the second protective layer located at the first convex surface has pores for ion permeation; or, both the first protective layer located at the first concave surface and the second protective layer located at the first convex surface include blocking portions for blocking ions.

19. The electrode assembly according to claim 4, wherein, both the third protective layer located at the second concave surface and the fourth protective layer located at the second convex surface have pores for ion permeation.

20. The electrode assembly according to claim 18 or 19, wherein, the air permeability of the protective layer having pores for ion permeation is 220 ± 70 sec / 100 cc.

21. The electrode assembly according to claim 18 or 19, wherein, the pores of the pores are 100 nm to 400 nm.

22. A battery cell, wherein, comprises: a housing and at least one electrode assembly according to any one of claims 1 - 21, and the electrode assembly is accommodated in the housing.

23. A battery, wherein, comprises: a box body and at least one battery cell according to claim 22, and the battery cell is received in the box body.

24. An electrical device, wherein, the electrical device includes at least one battery cell according to claim 22 or a battery according to claim 23 for providing electrical energy.

25. An energy storage device, wherein, comprises a battery according to claim 23, and the battery can store electrical energy and can provide electrical energy.

26. A method for preparing an electrode assembly, wherein, comprises: providing a positive electrode tab, a negative electrode tab and a separator; attaching a protective layer to the positive electrode tab and / or the negative electrode tab; The positive electrode sheet, the negative electrode sheet, and the separator are stacked and wound to form a wound structure. Among them, In the wound structure, a separator is sandwiched between the positive electrode sheet and the negative electrode sheet. The wound structure includes a bending area. The positive electrode sheet includes at least one positive electrode bending portion located in the bending area, and the negative electrode sheet includes at least one negative electrode bending portion located in the bending area. Along the winding axis direction of the wound structure, both ends of the separator extend beyond the positive electrode bending portion and the negative electrode bending portion. The protective layer is pasted on the surface of the positive electrode bending portion and / or the surface of the negative electrode bending portion. Along the winding axis direction of the wound structure, at least one end of the protective layer extends beyond the separator.

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