Electrode assembly and preparation method therefor, battery cell, battery, and electric device

Abstract

The present invention belongs to the technical field of batteries. Disclosed are an electrode assembly, a battery cell, a battery and an electric device. The electrode assembly comprises a wound structure and protective layers, wherein the wound structure is formed by winding in a winding direction a stack which comprises a positive electrode sheet and a negative electrode sheet, with a separator sandwiched between the positive electrode sheet and the negative electrode sheet, each of the positive electrode sheet and the negative electrode sheet comprising several bent parts; and both the inner side and outer side of at least one bent part have the protective layers attached thereto, the protective layers on the inner side and outer side of the same bent part being staggered at least at one end in the winding direction.

Description

Electrode assembly and preparation method, battery cell, battery, and electrical 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, and an electrical 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] Battery capacity is a key performance metric for measuring battery performance, and increasing it has long been a research and development topic in the industry. Furthermore, batteries often carry the risk of thermal runaway and fire, so reducing these risks 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, a battery cell, a battery, and an electrical device having high battery cell capacity and low thermal runaway risk.

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

[0007] A first aspect of the present disclosure provides an electrode assembly, comprising:

[0008] A wound structure, wherein the wound structure is formed by winding a stack including a positive electrode sheet and a negative electrode sheet along a winding direction, a separator is sandwiched between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet and the negative electrode sheet each include a plurality of bent portions;

[0009] a protective layer, the protective layer being attached to both inner and outer sides of at least one of the bent portions;

[0010] Wherein, the protective layers on the inner and outer sides of the same bent portion are staggered at at least one end along the winding direction.

[0011] The ends of one or both ends of the protective layer attached to the inner and outer sides of the bent part along the winding direction are staggered in the winding direction. On the one hand, the thickness difference at the edge of the protective layer can be greatly reduced, so that the thickness difference transitions smoothly, thereby reducing the stress concentration at the edge of the protective layer, and thus reducing the risk of closed cells due to excessive force on the isolation member, reducing the problem of lithium plating, and thus increasing the capacity of the battery cell; on the other hand, it reduces the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and thus reducing the risk of thermal runaway and fire.

[0012] In some embodiments, the protective layers on the inner and outer sides of the same bent portion are staggered at both ends along the winding direction.

[0013] The end portions at both ends are staggered. On the one hand, the thickness difference at both ends of the bent portion of the attached protective layer is smoothly transitioned, which can reduce the stress concentration at the two edges, thereby better reducing the risk of the separator being closed due to excessive force, reducing the problem of lithium plating, and thus increasing the capacity of the battery cell. On the other hand, it reduces the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and thus reducing the risk of thermal runaway and fire.

[0014] In some embodiments, both ends of the protective layer on the inner side of the same bent portion along the winding direction respectively extend beyond the corresponding two ends of the protective layer on the outer side; or

[0015] Both ends of the outer side of the protective layer of the same bent portion along the winding direction respectively extend beyond the corresponding two ends of the inner side of the protective layer; or

[0016] One end portion of the inner side of the protective layer of the same bending portion along the winding direction exceeds the corresponding end portion of the outer side of the protective layer, and the other end portion of the inner side of the protective layer along the winding direction is exceeded by the corresponding other end portion of the outer side of the protective layer.

[0017] The above three distribution situations of the protective layers on the inner and outer sides of the same bending part all achieve the staggered ends of the protective layer. On the one hand, the thickness difference is smoothly transitioned, thereby reducing the stress concentration at the two edges of the protective layer, thereby reducing the risk of closed holes due to excessive force on the separator, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell. On the other hand, the risk of indentation or cracking of the electrode is reduced, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0018] In some embodiments, along the winding axis direction of the wound structure, at least one end of at least one of the protective layers exceeds the active material of the bent portion.

[0019] In this way, the area of ​​the active material in the bent part covered by the protective layer can be increased, thereby better reducing the risk of cracking of the pole piece or falling off of the active material, which not only increases the capacity of the battery cell but also reduces the risk of thermal runaway and fire.

[0020] In some embodiments, one end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a first set size in the winding direction, and the other end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a second set size in the winding direction, wherein the first set size is equal to the second set size, or the first set size is not equal to the second set size.

[0021] The first set size may be equal to or different from the second set size. By setting the staggered sizes at both ends, on the one hand, the thickness difference is smoothly transitioned, thereby reducing the stress concentration at the two edges of the protective layer, reducing the risk of closed pores due to excessive force on the separator, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell. On the other hand, the risk of indentation or cracking of the electrode is reduced, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0022] In some embodiments, one end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a first set size in the winding direction, and the first set size does not exceed 2 mm, and / or, the other end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a second set size in the winding direction, and the second set size does not exceed 2 mm.

[0023] Limiting the offset to no more than 2mm prevents excessive offset, thereby increasing the overlap area between the inner and outer protective layers. This not only reduces stress concentration but also effectively mitigates the risk of cracking and active material shedding. Furthermore, if the protective layer extends beyond the bend along the winding axis, exposing the offset between the inner and outer protective layers to the adhesive surface, limiting the offset to no more than 2mm can reduce the risk of the exposed adhesive surface sticking to the roller during winding.

[0024] In some embodiments, one end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a first set size in the winding direction, and the first set size does not exceed 1.5 mm, and / or, the other end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a second set size in the winding direction, and the second set size does not exceed 1.5 mm.

[0025] Limiting the offset to no more than 1.5mm prevents excessive offset, thereby increasing the overlap between the inner and outer protective layers. This not only reduces stress concentration but also effectively mitigates the risk of cracking and active material loss. Furthermore, if the protective layer extends beyond the bend along the winding axis, exposing the offset between the inner and outer protective layers to the adhesive surface, limiting the offset to no more than 1.5mm can reduce the risk of excessive adhesive surface sticking to the roller during winding.

[0026] In some embodiments, one end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a first set size in the winding direction, and the first set size does not exceed 1 mm, and / or, the other end portion of the protective layer on the inner and outer sides of the same bending portion along the winding direction is staggered by a second set size in the winding direction, and the second set size does not exceed 1 mm.

[0027] Limiting the offset to no more than 1mm prevents excessive offset, thereby increasing the overlap area between the inner and outer protective layers. This not only reduces stress concentration but also effectively reduces the risk of cracking and active material shedding. Furthermore, if the protective layer 84 extends beyond the bend along the winding axis, causing the offset between the inner and outer protective layers to expose the bonding surface, limiting the offset to no more than 1mm reduces the risk of the exposed bonding surface sticking to the roller during winding.

[0028] In some embodiments, the positive electrode sheet and the negative electrode sheet both include several straight portions, the several bent portions and the several straight portions of the positive electrode sheet are alternately arranged one by one along the winding direction, and the several bent portions and the several straight portions of the negative electrode sheet are alternately arranged one by one along the winding direction, at least one of the protective layers is attached to the side of the bent portion at one end along the winding direction, and the other end extends to the side of the straight portion adjacent to the bent portion, or, at least one of the protective layers has both ends along the winding direction attached to the side of the bent portion, or, at least one of the protective layers has the middle portion along the winding direction attached to the side of the bent portion, and both ends extend to the sides of the two straight portions adjacent to the bent portion.

[0029] As mentioned above, for flat electrode assemblies, the above three conditions of the protective layer can reduce the risk of cracking of the electrode and shedding of the active material, which not only increases the capacity of the battery cell but also reduces the risk of thermal runaway and fire.

[0030] In some embodiments, the protective layer includes a main layer made of a polymer material.

[0031] The main layer made of polymer materials is easy to obtain and has good toughness and strength, which can effectively reduce the risk of cracking of the pole piece or shedding of the active material.

[0032] In some embodiments, the polymer material is at least one of polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoropropylene-vinylidene fluoride copolymer, trifluorochloropropylene-vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, and non-woven fabric.

[0033] The above materials are easy to obtain and have good toughness and strength, which can reduce the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and further reducing the risk of thermal runaway and fire.

[0034] In some embodiments, the protective layer further includes an adhesive layer, and the main layer is bonded to the side surface of the bent portion through the adhesive layer.

[0035] The main layer is bonded to the side of the bent portion via the adhesive layer, thereby achieving adhesion of the protective layer to the bent portion. This bonding method ensures that the main layer is firmly attached to the bent portion, and the bonding operation is simple and quick.

[0036] In some embodiments, the material of the adhesive layer is at least any one of acrylic acid-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic acid copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic acid grafted polyethylene, maleic anhydride grafted polyethylene, acrylic acid grafted polypropylene, maleic anhydride grafted polypropylene, polyvinylidene fluoride, carboxymethyl cellulose, polyimide, polyetherimide, polyethylene terephthalate, styrene-isoprene-styrene copolymer rubber, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, and styrene-isoprene-styrene copolymer.

[0037] The above material is easy to obtain and has good viscosity, and can firmly adhere the main body layer to the bent portion.

[0038] In some embodiments, the protective layer includes an ion-permeable portion and / or an ion-blocking portion.

[0039] Both the ion-permeable portion and the ion-blocking portion can provide support to the electrode, reducing the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and further reducing the risk of thermal runaway and fire.

[0040] In some embodiments, the protective layers on the inner and outer sides of the bent portion of the positive electrode sheet respectively include the ion-permeable portion, or the protective layers on the inner and outer sides of the bent portion of the positive electrode sheet respectively include the ion-blocking portion, or the protective layer on the inner side of the bent portion of the positive electrode sheet includes the ion-blocking portion, and the protective layer on the outer side includes the ion-permeable portion;

[0041] The protective layers on the inner and outer sides of the negative electrode sheet respectively include the ion-permeable portions.

[0042] In this way, this embodiment not only increases the capacity of the battery cells, but also reduces the risk of thermal runaway and fire.

[0043] In some embodiments, the air permeability of the ion-permeable portion is 220±70 sec / 100 cc.

[0044] By setting the air permeability of the ion-permeable portion, the speed at which active ions pass through the ion-permeable portion can be controlled within a suitable speed range. In this way, the battery cell capacity can be increased without causing lithium deposition due to excessive speed.

[0045] In some embodiments, the maximum size of the pores of the ion-permeable portion is in the range of 100 nm to 400 nm.

[0046] The pores are used for the passage of active ions. The diameter of the pores is limited to the range of 100nm to 400nm, which allows the active ions to pass freely and improves the capacity of the battery cell.

[0047] In some embodiments, the positive electrode plate includes a positive electrode current collector, the positive electrode current collector is made of aluminum, and the protective layer is attached to both the inner and outer sides of the bent portion of the positive electrode plate.

[0048] Attaching protective layers on both the inner and outer sides of the bent part of the positive electrode sheet can effectively reduce the risk of cracking of the aluminum positive electrode collector and detachment of the active material.

[0049] In some embodiments, the protective layer is attached to both inner and outer sides of the two bent portions of the innermost circle of the positive electrode plate.

[0050] The innermost bent portion of the positive electrode plate is the most bent and most susceptible to cracking. Therefore, attaching protective layers to both inner and outer sides of the two innermost bent portions can effectively reduce the risk of cracking of the positive electrode plate and separation of the active material.

[0051] A second aspect of the present disclosure provides a battery cell comprising: a shell, a cover plate, and at least one of the above-mentioned electrode assemblies, wherein the shell has a receiving cavity and an opening, the electrode assembly is received in the receiving cavity, and the cover plate is sealed in the opening of the shell.

[0052] The battery cells provided by the embodiments of the present disclosure not only increase the battery cell capacity, but also reduce the risks of thermal runaway and fire.

[0053] A third aspect of the present disclosure provides a battery, comprising: a box; and at least one of the above-mentioned battery cells, wherein the battery cell is accommodated in the box.

[0054] The battery provided by the embodiments of the present disclosure not only increases the battery capacity but also reduces the risk of thermal runaway and fire.

[0055] A fourth aspect of the present disclosure provides an electrical device, comprising the above-mentioned battery cell or the above-mentioned battery for providing electrical energy.

[0056] The power-consuming device provided by the embodiments of the present disclosure not only increases the battery capacity but also reduces the risk of thermal runaway and fire.

[0057] A fifth aspect of the present disclosure provides a method for preparing an electrode assembly, comprising:

[0058] Provide positive electrode sheets, negative electrode sheets and separators;

[0059] Attaching a protective layer to the positive electrode sheet and / or the negative electrode sheet;

[0060] The positive electrode sheet, the negative electrode sheet 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 sheet and the negative electrode sheet, and the positive electrode sheet and the negative electrode sheet each include a plurality of bent portions, and the protective layer is attached to both inner and outer sides of at least one of the bent portions, and the protective layers on the inner and outer sides of the same bent portion are staggered along at least one end of the winding direction.

[0061] Effects of the invention:

[0062] The present disclosure provides an electrode assembly, a battery cell, a battery, an electrical device, and a method for preparing the electrode assembly with high battery cell capacity and low thermal runaway risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments 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 accompanying drawings to represent the same components.

[0064] In the attached figure:

[0065] FIG1 is a schematic structural diagram of a vehicle provided by some embodiments of the present disclosure;

[0066] FIG2 is a perspective exploded schematic diagram of a battery provided by some embodiments of the present disclosure;

[0067] FIG3 is a schematic structural diagram of the battery module shown in FIG2 ;

[0068] FIG4 is a perspective exploded schematic diagram of a battery cell provided by some embodiments of the present disclosure;

[0069] FIG5 is a schematic structural diagram of a cross section of an electrode assembly provided by some embodiments of the present disclosure along a direction perpendicular to the winding axis;

[0070] FIG6 is a schematic structural diagram of a positive electrode sheet with a protective layer attached to an electrode assembly in a flat state according to some embodiments of the present disclosure;

[0071] FIG7 is a cross-sectional view of the section AA in FIG6 ;

[0072] FIG8 is a schematic structural diagram of a flattened negative electrode sheet with a protective layer attached to an electrode assembly provided by some embodiments of the present disclosure;

[0073] FIG9 is a cross-sectional view at BB in FIG8 ;

[0074] FIG10 is a schematic structural diagram of a positive electrode sheet or a negative electrode sheet with a protective layer attached thereto in a flat state according to some embodiments of the present disclosure;

[0075] FIG11 is a partial structural schematic diagram of a cross section of an electrode assembly provided in some embodiments of the present disclosure, perpendicular to the winding axis;

[0076] FIG12 is a partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis provided in some other embodiments of the present disclosure;

[0077] FIG13 is a partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis direction provided in still other embodiments of the present disclosure;

[0078] FIG14 is a flow chart of a method for preparing an electrode assembly according to some embodiments of the present disclosure.

[0079] Description of Reference Numerals

[0080] 1 vehicle; 2 battery; 3 controller; 4 motor; 5 housing; 51 first housing portion; 52 second housing portion; 53 storage space; 6 battery module; 7 battery cell;

[0081] 8 electrode assembly; 81 positive electrode sheet; 811 positive electrode current collector; 8111 positive electrode current collecting portion; 8112 positive electrode protrusion; 812 positive electrode active material layer; 813 insulating layer; 82 negative electrode sheet; 821 negative electrode current collector; 8211 negative electrode current collecting portion; 8212 negative electrode protrusion; 822 negative electrode active material layer; 83 separator; 84 protective layer;

[0082] 9 outer shell; 91 main body shell; 92 end cover; 10 positive electrode terminal; 11 pressure relief mechanism; 12 negative electrode terminal. DETAILED DESCRIPTION

[0083] 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.

[0084] 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.

[0085] In the description of the embodiments of the present disclosure, technical terms such as "first," "second," and "third" are used solely to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly specify the quantity, specific order, or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present disclosure, "plurality" means more than two, unless otherwise specifically defined.

[0086] 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.

[0087] 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.

[0088] In the description of the embodiments of the present disclosure, the orientations or positional relationships indicated by technical terms such as "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", and "circumferential" 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 should not be understood as limiting the embodiments of the present disclosure.

[0089] 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.

[0090] 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.

[0091] Hereinafter, the present disclosure will be described in detail.

[0092] 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 a variety of fields such as aerospace. As the application of power batteries continues to expand, market demand is also growing.

[0093] Battery capacity is a key performance metric for measuring battery performance. It represents the amount of electricity a battery can release under certain conditions (discharge rate, temperature, and cut-off voltage). Improving battery capacity has long been a research and development topic in the industry. Furthermore, batteries often carry the risk of thermal runaway and fire. Therefore, mitigating these risks is a pressing technical challenge in battery technology.

[0094] The battery mentioned in the embodiments of the present disclosure may include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed connection through a busbar. For example, the battery mentioned in the present disclosure may include a battery module or a battery pack. The battery generally includes a box for encapsulating one or more battery cells. The box can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells. The battery can also be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0095] In the present disclosure, battery cells may include lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium-lithium-ion battery cells, sodium-ion battery cells, or magnesium-ion battery cells, and the embodiments of the present disclosure are not limited to this. Battery cells may be cylindrical, flat, rectangular, or other shapes, and the embodiments of the present disclosure are not limited to this. Battery cells are generally divided into three types based on the packaging method: cylindrical battery cells, prismatic battery cells, and soft-pack battery cells, and the embodiments of the present disclosure are not limited to this.

[0096] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. A battery cell primarily operates by the movement of metal ions between the positive and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector. The positive current collector includes a positive current collector portion and a positive protrusion protruding from the positive current collector portion. The positive current collector portion is coated with the positive active material layer. At least a portion of the positive protrusion portion is not coated with the positive active material layer. The positive protrusion portion serves as a positive electrode tab. Taking a lithium-ion battery cell as an example, the material of the positive current collector can be aluminum, and the positive active material layer includes a positive active material. The positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, among others. The negative electrode sheet includes a negative current collector and a negative active material layer, which is coated on the surface of the current collector. The negative current collector includes a negative current collecting portion and a negative protrusion protruding from the current collecting portion. The negative current collecting portion is coated with the negative active material layer, while at least a portion of the negative protrusion is uncoated with the negative active material layer. The negative protrusion serves as the negative electrode tab. The negative current collector can be made of copper, and the negative active material layer includes a negative active material, which can be carbon or silicon, for example. To ensure that high currents can pass without melting, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together. The separator is a separator. The present disclosure does not specifically limit the type of separator; any known porous separator with good chemical and mechanical stability can be used. As an example, the primary material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. Furthermore, the electrode assembly can be a wound or laminated structure, but the present disclosure is not limited to this.

[0097] When a lithium-ion battery cell is charging, lithium ions are released from the positive electrode active material layer and embedded in the negative electrode active material layer. However, some abnormal situations may occur. For example, the negative electrode active material layer has insufficient space for lithium embedding, the resistance of lithium ions embedding in the negative electrode active material layer is too great, or the lithium ions are released from the positive electrode active material layer too quickly. The released lithium ions cannot be embedded in the negative electrode active material layer of the negative electrode plate in equal amounts. The lithium ions that cannot be embedded in the negative electrode plate can only obtain electrons on the surface of the negative electrode plate, thereby forming metallic lithium. This is the lithium plating phenomenon. Lithium plating not only reduces the performance of lithium-ion battery cells and significantly shortens the cycle life, but also limits the fast charging capacity of lithium-ion battery cells. In addition, when lithium plating occurs in lithium-ion battery cells, the released lithium metal is very active and can react with the electrolyte at a lower temperature, causing the starting temperature of the battery cell's self-heating to decrease and the self-heating rate to increase, seriously endangering the safety of the battery cell. Furthermore, when lithium plating is severe, the released lithium ions can form lithium crystals on the surface of the negative electrode, and the lithium crystals can easily puncture the separator, causing the risk of short circuit between the adjacent positive and negative electrodes.

[0098] At present, some electrode assemblies have protective layers adhered to the inner and outer sides of the bent portions of the positive and negative electrode sheets to prevent cracking or active material shedding at the bent portion of the sheet during pre-pressing and hot pressing, thereby increasing the capacity of the battery cell. However, the inventors of the present disclosure have noted that the overlapping of the protective layers adhered to the inner and outer sides results in a significant thickness difference between the edges of the protective layers and the portion not adhered to the protective layers. This results in the protective layers being subjected to significant concentrated stress when compressed, causing the corresponding separators at the edges to be subjected to excessive force and resulting in closed pores, leading to lithium deposition. Furthermore, the corresponding electrode sheets at the stress concentration points will have indentations. After long-term cycling of the battery cell, the expansion force is relatively large, and with continued force, there is a risk of cracking of the electrode sheets, which will form burrs after cracking. The burrs have the risk of puncturing the separators, leading to abnormal self-discharge and even the risk of thermal runaway and fire.

[0099] After research, the inventors of the present disclosure found that staggering the edges of the protective layers adhered to the inner and outer sides of the bent portion can, on the one hand, greatly reduce the thickness difference at the edges of the protective layers, thereby reducing the stress concentration at the edges of the protective layers, thereby reducing the risk of the separator being subjected to excessive force and causing closed pores, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell. On the other hand, it reduces the risk of indentation or cracking of the pole piece, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0100] Based on such a design concept, the inventors of the present disclosure designed an electrode assembly, which includes a winding structure and a protective layer. The winding structure is formed by winding a stack including a positive electrode sheet and a negative electrode sheet along a winding direction, and an insulating member is sandwiched between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet and the negative electrode sheet both include several bent parts; protective layers are attached to the inner and outer sides of at least one bent part; wherein, the protective layers on the inner and outer sides of the same bent part are staggered at at least one end along the winding direction.

[0101] The edges of the protective layers attached to the inner and outer sides of the bent part are staggered in the winding direction, which can greatly reduce the thickness difference at the edge of the protective layer. On the one hand, it makes the thickness difference transition smoothly, thereby reducing the stress concentration at the edge of the protective layer, thereby reducing the risk of closed cells due to excessive force on the separator, reducing the problem of lithium plating, and thereby increasing the battery capacity. On the other hand, it reduces the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0102] The technical solutions described in the embodiments of the present disclosure are applicable to batteries and electrical devices using batteries. Electrical devices may be vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. Vehicles may be fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles may be pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present disclosure do not impose any special restrictions on the above-mentioned electrical devices.

[0103] The present disclosure provides an electrical device. In the following embodiments, for ease of description, the electrical device of one embodiment of the present disclosure is described as a vehicle 1. The following description is made with reference to the accompanying drawings.

[0104] Figure 1 is a schematic structural diagram of a vehicle 1 provided in some embodiments of the present disclosure. The vehicle 1 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 Figure 1 , a battery 2 is provided inside the vehicle 1. The battery 2 may be provided at the bottom, head or tail of the vehicle 1. The battery 2 may be used to power the vehicle 1. For example, the battery 2 may serve as an operating power source for the vehicle 1. The vehicle 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery 2 to power the motor 4, for example, for starting, navigating and operating power requirements of the vehicle 1 during driving.

[0105] In some embodiments of the present disclosure, the battery 2 can serve not only as an operating power source for the vehicle 1 , but also as a driving power source for the vehicle 1 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1 .

[0106] Figure 2 is a perspective exploded schematic diagram of a battery 2 provided in some embodiments of the present disclosure. Figure 3 is a structural schematic diagram of the battery module shown in Figure 2. Figure 4 is a perspective exploded schematic diagram of a battery cell provided in some embodiments of the present disclosure.

[0107] As shown in FIG. 2 and FIG. 3 , the battery 2 includes a housing 5 and at least one battery cell 7 . The at least one battery cell 7 is accommodated in the housing 5 .

[0108] The housing 5 is used to accommodate the battery cells 7 and can have various structures. In some embodiments, the housing 5 can include a first housing portion 51 and a second housing portion 52. The first housing portion 51 and the second housing portion 52 overlap each other and together define a storage space 53 for accommodating the battery cells 7. The second housing portion 52 can be a hollow structure with one end open. The first housing portion 51 is a plate-like structure, and the first housing portion 51 overlaps the open side of the second housing portion 52 to form the housing 5 with the storage space 53. The first housing portion 51 and the second housing portion 52 can also both be hollow structures with one end open, and the open side of the first housing portion 51 overlaps the open side of the second housing portion 52 to form the housing 5 with the storage space 53. Of course, the first housing portion 51 and the second housing portion 52 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0109] In order to improve the sealing performance after the first box body 51 and the second box body 52 are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body 51 and the second box body 52 .

[0110] Assuming that the first box portion 51 covers the top of the second box portion 52 , the first box portion 51 can also be referred to as an upper box cover, and the second box portion 52 can also be referred to as a lower box.

[0111] In the battery 2, there may be multiple battery cells 7, which may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 7 may be placed in the storage space 53 formed by the first casing 51 and the second casing 52. Of course, the battery 2 may also be configured such that multiple battery cells 7 are first connected in series, in parallel, or in a hybrid connection to form a battery module 6, which is then connected in series, in parallel, or in a hybrid connection to form a single unit, which is then stored in the storage space 53 formed by the first casing 51 and the second casing 52. The battery 2 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 7.

[0112] In the embodiment of the present disclosure, the battery 2 may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0113] In the embodiment of the present disclosure, the battery cell 7 may be a secondary battery. A secondary battery refers to a battery cell 7 that can be continuously used by activating active materials by charging after the battery cell 7 is discharged.

[0114] The battery cell 7 can be a lithium-ion battery cell, a sodium-ion battery cell, a sodium-lithium-ion battery cell, a lithium metal battery cell, a sodium metal battery cell, a lithium-sulfur battery cell, a magnesium-ion battery cell, a nickel-hydrogen battery cell, a nickel-cadmium battery cell, a lead-acid battery cell, etc., and the embodiments of the present disclosure are not limited to this.

[0115] As shown in Figure 4, a battery cell 7 includes a housing 9 and at least one electrode assembly 8. The housing 9 is used to encapsulate the electrode assembly 8 and other components such as the electrolyte. The housing 9 can be made of steel, aluminum, plastic (e.g., polypropylene), composite metal (e.g., copper-aluminum composite), or aluminum-plastic film.

[0116] In some embodiments, the housing 9 includes an end cap 92 and a main body 91. The main body 91 has a cavity and an opening, and the electrode assembly 8 and electrolyte and other substances are accommodated in the cavity. The cover 92 seals the opening of the housing 91 to form a sealed space for accommodating the electrode assembly 8 and electrolyte and other substances. The main body 91 may have one or more openings. One or more end caps 92 may also be provided.

[0117] The main body shell 91 can be of various shapes, such as a cylinder, a rectangular parallelepiped, etc. The shape of the main body shell 91 can be determined according to the specific shape of the electrode assembly 8. For example, if the electrode assembly 8 is a cylindrical structure, a cylindrical shell can be selected; if the electrode assembly 8 is a rectangular parallelepiped structure, a rectangular parallelepiped shell can be selected. Of course, the end cover 92 can also be of various structures, such as a plate-like structure, a hollow structure with one end open, etc. For example, in Figure 4, the main body shell 91 is a rectangular parallelepiped structure, the end cover 92 is a plate-like structure, and the end cover 92 covers the opening at the top of the main body shell 91.

[0118] In some embodiments, the battery cell 7 may further include a positive electrode terminal 10, a negative electrode terminal 12, and a pressure relief mechanism 11, all of which are mounted on the end cap 92. The positive electrode terminal 10 and the negative electrode terminal 12 are both used to electrically connect to the electrode assembly 8 to output the electrical energy generated by the electrode assembly 8. The pressure relief mechanism 11 is used to relieve the pressure inside the battery cell 7 when the internal pressure or temperature of the battery cell 7 reaches a predetermined value.

[0119] Illustratively, the pressure relief mechanism 11 is located between the positive electrode terminal 10 and the negative electrode terminal 12 . The pressure relief mechanism 11 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.

[0120] Of course, in other embodiments, the housing 9 may have other structures. For example, the housing 9 includes a main body 91 and two end caps 92. The main body 91 is a hollow structure with two opposing openings. An end cap 92 covers one opening of the main body 91 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 8 and the electrolyte. In this structure, the positive electrode terminal 10 and the negative electrode terminal 12 can be mounted on the same end cap 92 or on different end caps 92. The pressure relief mechanism 11 can be mounted on one end cap 92 or on both end caps 92.

[0121] It should be noted that, in the battery cell 7, there may be one or more electrode assemblies 8 housed in the housing 9. For example, in FIG4 , there are two electrode assemblies 8.

[0122] Hereinafter, some embodiments of the present disclosure will be described in detail with reference to FIG. 5 to FIG. 13 .

[0123] Figure 5 is a schematic structural diagram of a cross section of an electrode assembly provided in some embodiments of the present disclosure along a direction perpendicular to the winding axis; Figure 6 is a schematic structural diagram of a positive electrode sheet with a protective layer attached to an electrode assembly provided in some embodiments of the present disclosure in a flat state; Figure 7 is a cross-sectional view at AA in Figure 6; Figure 8 is a schematic structural diagram of a negative electrode sheet with a protective layer attached to an electrode assembly provided in some embodiments of the present disclosure in a flat state; Figure 9 is a cross-sectional view at BB in Figure 8; Figure 10 is a schematic structural diagram of a positive electrode sheet or a negative electrode sheet with a protective layer attached to an electrode assembly provided in some embodiments of the present disclosure in a flat state; Figure 11 is a schematic structural diagram of a partial cross section of an electrode assembly provided in some embodiments of the present disclosure perpendicular to the winding axis; Figure 12 is a schematic structural diagram of a partial cross section of an electrode assembly provided in some other embodiments of the present disclosure perpendicular to the winding axis; Figure 13 is a schematic structural diagram of a partial cross section of an electrode assembly provided in some further embodiments of the present disclosure perpendicular to the winding axis.

[0124] As shown in Figure 5, the electrode assembly 8 provided in the embodiment of the present disclosure includes a winding structure and a protective layer 84. The winding structure is formed by winding a stack including a positive electrode sheet 81 and a negative electrode sheet 82 along a winding direction C, and an isolation member 83 is sandwiched between the positive electrode sheet 81 and the negative electrode sheet 82. The positive electrode sheet 81 and the negative electrode sheet 83 each include a plurality of bent portions; a protective layer 84 is attached to both the inner and outer sides of at least one bent portion; wherein, the protective layers 84 on the inner and outer sides of the same bent portion are staggered at at least one end along the winding direction C.

[0125] The winding direction C is the direction in which the positive electrode tab 81 and the negative electrode tab 82 are wound from the center to the periphery. In FIG5 , the winding direction C is the clockwise direction.

[0126] As shown in Figures 6 and 7, the positive electrode sheet 81 includes a positive current collector 811 and a positive active material layer 812. The positive active material layer 812 is coated on the surface of the positive current collector 811. The positive current collector 8111 includes a positive current collecting portion 8111 and a positive protrusion 8112 protruding from the positive current collecting portion 8111. The positive current collecting portion 8111 is coated with the positive active material layer 812. At least a portion of the positive protrusion 8112 is not coated with the positive active material layer 812, and the positive protrusion 8112 serves as the positive electrode tab. Taking a lithium-ion battery cell as an example, the material of the positive current collector 811 can be aluminum, and the positive active material layer 812 includes a positive active material. The positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0127] In some embodiments, only a portion of the positive electrode current collecting portion 8111 is coated with the positive electrode active material layer 812. The portion of the positive electrode current collecting portion 8111 not coated with the positive electrode active material layer 812 is coated with an insulating layer 813. The insulating layer 813 is located on the side of the positive electrode active material layer 812 that is close to the positive electrode tab. For example, the base of the positive electrode tab close to the positive electrode current collecting portion 8111 is also coated with the insulating layer 812.

[0128] As shown in Figures 8 and 9, the negative electrode sheet 82 includes a negative current collector 821 and a negative active material layer 822. The negative active material layer 822 is coated on the surface of the negative current collector 821. The negative current collector 821 includes a negative current collecting portion 8211 and a negative protrusion 8212 protruding from the negative current collecting portion. The negative current collecting portion 8211 is coated with the negative active material layer 822. At least a portion of the negative protrusion 8212 is not coated with the negative active material layer 822. The negative protrusion 8212 serves as the negative electrode tab. The negative current collector 821 can be made of copper, and the negative active material layer 822 includes a negative active material, which can be carbon, silicon, or the like.

[0129] Separator 83 is used to separate positive electrode sheet 81 from negative electrode sheet 82 to reduce the risk of short circuit between them. Separator 83 has a large number of micropores that allow the free passage of active ions and has good permeability to lithium ions. Therefore, separator 83 does not substantially block the passage of lithium ions. For example, separator 83 can be made of PP (polypropylene) or PE (polyethylene).

[0130] The positive electrode sheet 81, the negative electrode sheet 82, and the separator 83 are all strip-shaped structures. In the embodiment of the present disclosure, the negative electrode sheet 82, a separator 83, the positive electrode sheet 81, and another separator 83 can be stacked in sequence to form a laminate, and then the laminate is wound more than two times to form a wound structure.

[0131] The protective layer 84 is a sheet-like structure attached to the bent portion of the positive electrode sheet 81 and / or the negative electrode sheet 82. It has a certain degree of toughness and strength. When the electrode sheet is compressed and deformed, the protective layer 84 interacts with the electrode sheet to which it is attached, which helps to increase the strength of the electrode sheet, thereby reducing the risk of cracking of the electrode sheet or shedding of the active material. Before the negative electrode sheet 82, the separator 83 and the positive electrode sheet 81 are stacked, the protective layer 84 is used to find the portion of the positive electrode sheet 81 and the negative electrode sheet 82 that is about to bend through dimensional calculation, and the protective layer 84 is attached to the portion that is about to bend. Therefore, during the process of stacking and winding the negative electrode sheet 82, the separator 83 and the positive electrode sheet 81 into the electrode assembly 8, the protective layer 84 protects the bent portion of the positive electrode sheet 81 and the negative electrode sheet 82, thereby reducing the risk of cracking of the electrode sheet or shedding of the active material.

[0132] The electrode assembly 8 may be in various shapes. For example, the electrode assembly 8 may be a flat body, a prism (such as a triangular prism, a quadrangular prism, or a hexagonal prism), or other shapes.

[0133] The bent portion is a portion of the positive electrode tab 81 and the negative electrode tab 82 that is in a bent shape.

[0134] In some embodiments, the electrode assembly 10 is in the form of a prism, and the bent portions are the corner portions of the positive electrode sheet 81 and the negative electrode sheet 82 .

[0135] In some embodiments, as shown in FIG5 , the electrode assembly 10 is a flat body, and the bent portion is the arc-shaped portion of the positive electrode sheet 81 and the negative electrode sheet 82. In FIG5 , the positive electrode sheet 81 and the negative electrode sheet 82 are bent at the left side of the left dotted line and the right side of the right dotted line.

[0136] In some embodiments, attaching means adhering or coating or spraying.

[0137] The ends of the protective layer 84 attached to the inner and outer sides of the bent portion at one or both ends along the winding direction C are staggered in the winding direction C, which can greatly reduce the thickness difference at the edge of the protective layer 81. On the one hand, it makes the thickness difference transition smoothly, thereby reducing the stress concentration at the edge of the protective layer 84, thereby reducing the risk of the isolation member 83 being closed due to excessive force, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell. On the other hand, it reduces the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0138] In some embodiments, the protective layers 84 on the inner and outer sides of the same bending portion are staggered at one end along the winding direction C, and aligned at the other end.

[0139] By misaligning one end and aligning the other end, the stress concentration on one edge can be reduced to a certain extent, thereby reducing the risk of the separator 83 being blocked due to excessive force, reducing the problem of lithium plating, and thus increasing the capacity of the battery cell.

[0140] In some embodiments, the protective layers 84 on the inner and outer sides of the same bending portion are staggered at both ends along the winding direction C.

[0141] The end portions at both ends are staggered so that the thickness difference at both ends of the bent portion of the attached protective layer 84 transitions smoothly, which can reduce the stress concentration at the two edges, thereby reducing the risk of the isolation member 83 being closed due to excessive force, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell.

[0142] In some embodiments, as shown in Figure 12, the end portions of the inner side protective layer 84 of the same bending portion along the winding direction respectively exceed the corresponding end portions of the outer side protective layer; or, as shown in Figure 13, the end portions of the outer side protective layer of the same bending portion along the winding direction respectively exceed the corresponding end portions of the inner side protective layer; or, as shown in Figure 11, one end portion of the inner side protective layer of the same bending portion along the winding direction exceeds the corresponding one end portion of the outer side protective layer, and the other end portion of the inner side protective layer along the winding direction is exceeded by the corresponding other end portion of the outer side protective layer.

[0143] In the above, the three distribution situations of the protective layer 84 on the inner and outer sides of the same bending part all achieve the dislocation of the two ends of the protective layer 84. On the one hand, the thickness difference is smoothly transitioned, thereby reducing the stress concentration at the two edges of the protective layer 84, thereby reducing the risk of the isolation member 83 being closed due to excessive force, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell. On the other hand, the risk of indentation or cracking of the electrode is reduced, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0144] In some embodiments, along the winding axis direction L of the wound structure, at least one end of at least one protective layer 84 extends beyond the active material of the bent portion.

[0145] The active material includes a positive electrode active material coated on the positive electrode current collector 811 to form a positive electrode active material layer 812, and a negative electrode active material coated on the negative electrode current collector 821 to form a negative electrode active material layer 822. The protective layer 84 attached to the positive electrode sheet 81 has at least one end extending beyond the positive electrode sheet 81 along the winding axis L; the protective layer 84 attached to the negative electrode sheet 82 has at least one end extending beyond the negative electrode sheet 82 along the winding axis L.

[0146] In this way, the area of ​​the active material in the bent portion covered by the protective layer 84 can be increased, thereby better reducing the risk of cracking of the electrode sheet or shedding of the active material and improving the capacity of the battery cell.

[0147] For example, as shown in FIG6 and FIG8 , along the winding axis direction L of the winding structure, both ends of at least one protective layer 84 extend beyond the active material of the bent portion.

[0148] In this way, the area of ​​the bent portion covered by the protective layer 84 is further increased, thereby better reducing the risk of cracking of the electrode or shedding of the active material, increasing the capacity of the battery cell, and reducing the risk of thermal runaway and fire.

[0149] In some embodiments, along the winding axis direction L of the winding structure, a dimension of at least one end of at least one protective layer 84 extending beyond the active material of the bent portion is in a range of 1 mm to 3 mm.

[0150] For example, along the winding axis L of the winding structure, at least one end of at least one protective layer 84 extends beyond the active material of the bent portion by 1 mm, 2 mm, or 3 mm. Of course, other values ​​are also possible and are not specifically limited here.

[0151] Exemplarily, as shown in FIG6 , along the winding axis direction L of the winding structure, one end of at least one protective layer 84 of the positive electrode sheet 81 exceeds the bent portion, and the other end extends to the insulating layer 813 without exceeding the bent portion.

[0152] In some embodiments, as shown in FIG. 6 and FIG. 8 , along the winding axis direction L of the winding structure, at least one end of at least one protective layer 84 extends beyond the bent portion.

[0153] In Figure 6 , the portion of the positive electrode tab 81 located in region P1 is a bent portion, and the portion located in region P2 is a straight portion. Correspondingly, in Figure 8 , the portion of the negative electrode tab 82 located in region P1 is a bent portion, and the portion located in region P2 is a straight portion.

[0154] It is understood that the bent portion of the positive electrode tab 81 includes part of the positive electrode active material layer 812 and part of the insulating layer 813. The fact that the protective layer 84 of the positive electrode tab 81 extends beyond the bent portion means that the protective layer 84 extends beyond the edge of the insulating layer 813 away from the positive electrode active material layer 812. The fact that the protective layer 84 of the negative electrode tab 82 extends beyond the bent portion means that the protective layer 84 extends beyond the edge of the negative electrode active material layer 822.

[0155] In this way, the edge of the protective layer 84 extending beyond one end of the bent portion is not attached to the bent portion, and the edge will not leave an indentation on the bent portion, thereby reducing the risk of abnormal self-discharge and further reducing the risk of thermal runaway and fire.

[0156] Illustratively, along the winding axis direction L of the winding structure, both end portions of at least one protective layer 84 of the positive electrode sheet 81 extend beyond the bent portion.

[0157] Exemplarily, as shown in FIG8 , along the winding axis direction L of the winding structure, both ends of at least one protective layer 84 of the negative electrode sheet 82 extend beyond the bent portion.

[0158] In this way, the edges of the protective layer 84 extending beyond the two ends of the bent portion are not attached to the bent portion, and the edges will not leave indentations on the bent portion, thereby reducing the risk of abnormal self-discharge and further reducing the risk of thermal runaway and fire.

[0159] In some embodiments, as shown in Figure 10, the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a first set dimension d1 at one end along the winding direction C, and the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a second set dimension d2 at the other end along the winding direction C, wherein the first set dimension d1 is equal to the second set dimension d2, or the first set dimension d1 is not equal to the second set dimension d2.

[0160] The first set dimension d1 may be equal to the second set dimension d2, or may not be equal to the second set dimension d2. By setting the staggered dimensions at both ends, the thickness difference is smoothly transitioned, thereby reducing the stress concentration at the two edges of the protective layer 84, thereby reducing the risk of the separator 83 being closed due to excessive force, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell. Moreover, the risk of indentation or cracking of the electrode is reduced, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0161] In some embodiments, the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a first set dimension d1 at one end along the winding direction C, and the first set dimension d1 does not exceed 2 mm, and / or, the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a second set dimension d2 at the other end along the winding direction C, and the second set dimension d2 does not exceed 2 mm.

[0162] Limiting the offset to no more than 2mm prevents excessive offset, thereby increasing the overlap area of ​​the inner and outer protective layers 84. This not only reduces stress concentration but also effectively reduces cracking and active material shedding. Furthermore, if the protective layer 84 extends beyond the bend in the winding axis direction L, causing the offset between the inner and outer protective layers 84 to expose the adhesive surface, limiting the offset to no more than 2mm can reduce the risk of excessive exposed adhesive surface sticking to the roller during winding.

[0163] In some embodiments, the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a first set dimension d1 at one end along the winding direction C, and the first set dimension d1 does not exceed 1.5 mm, and / or, the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a second set dimension d2 at the other end along the winding direction C, and the second set dimension d2 does not exceed 1.5 mm.

[0164] Limiting the offset to no more than 1.5mm prevents excessive offset, thereby increasing the overlap area between the inner and outer protective layers 84. This not only reduces stress concentration but also effectively reduces cracking and active material shedding. Furthermore, if the protective layer 84 extends beyond the bend in the winding axis direction L, causing the offset between the inner and outer protective layers 84 to expose the adhesive surface, limiting the offset to no more than 1.5mm can reduce the risk of excessive exposed adhesive surface sticking to the roller during winding.

[0165] In some embodiments, the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a first set dimension d1 at one end along the winding direction C, and the first set dimension d1 does not exceed 1 mm, and / or, the protective layers 84 on the inner and outer sides of the same bending portion are staggered by a second set dimension d2 at the other end along the winding direction C, and the second set dimension d2 does not exceed 1 mm.

[0166] Limiting the offset to no more than 1mm prevents excessive offset, thereby increasing the overlap area between the inner and outer protective layers 84. This not only reduces stress concentration but also effectively reduces cracking and active material shedding. Furthermore, if the protective layer 84 extends beyond the bend in the winding axis direction L, causing the offset between the inner and outer protective layers 84 to expose the adhesive surface, limiting the offset to no more than 1mm can reduce the risk of excessive exposed adhesive surface sticking to the roller during winding.

[0167] In some embodiments, as shown in Figures 5 and 11 to 13, the positive electrode sheet 81 and the negative electrode sheet 82 each include a plurality of straight portions, the plurality of bent portions and the plurality of straight portions of the positive electrode sheet 81 are alternately arranged along the winding direction C, and the plurality of bent portions and the plurality of straight portions of the negative electrode sheet 82 are alternately arranged along the winding direction C, at least one protective layer 84 is attached to the side of the bent portion at one end along the winding direction C, and the other end extends to the side of the straight portion adjacent to the bent portion, or, both ends of at least one protective layer 84 along the winding direction C are attached to the side of the bent portion, or, the middle part of at least one protective layer 84 along the winding direction C is attached to the side of the bent portion, and both ends extend to the sides of the two straight portions adjacent to the bent portion.

[0168] Referring to Figure 5 , the electrode assembly 8 is a flat body, and the protective layer 84 can be formed in three situations depending on its distribution position. First, referring to Figure 11 , the protective layers 84 on both sides of the inner and outer sides are attached to the side of the bent portion at one end along the winding direction C, and the other end extends to the side of the straight portion adjacent to the bent portion. Second, referring to Figure 12 , both ends of the outer protective layer 84 along the winding direction C are attached to the side of the bent portion. Third, referring to Figure 12 , the inner protective layer 84 is attached to the side of the bent portion along the middle part of the winding direction C, and both ends extend to the side of the two straight portions adjacent to the bent portion.

[0169] As described above, for the flat electrode assembly 8, the above three conditions of the protective layer 84 can reduce the risk of cracking of the electrode piece and shedding of the active material, thereby increasing the capacity of the battery cell and reducing the risk of thermal runaway and fire.

[0170] In some embodiments, the protective layer 84 includes a main layer made of a polymer material.

[0171] The main layer made of polymer materials is easy to obtain and has good toughness and strength, which can effectively reduce the risk of cracking of the pole piece or shedding of the active material.

[0172] In some embodiments, the polymer material is a combination of any one or more of polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoropropylene-vinylidene fluoride copolymer, trifluorochloropropylene-vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, and non-woven fabric.

[0173] The above materials are easy to obtain and have good toughness and strength, which can reduce the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and further reducing the risk of thermal runaway and fire.

[0174] In some embodiments, the protective layer 84 further includes an adhesive layer, and the main layer is bonded to the side surface of the bent portion through the adhesive layer.

[0175] The main body layer is bonded to the side of the bent portion through the adhesive layer, thereby achieving bonding of the protective layer 84 to the bent portion. The bonding method ensures that the main body layer is firmly attached to the bent portion and the bonding operation is simple and quick.

[0176] In some embodiments, the material of the adhesive layer is acrylic acid-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic acid copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic acid grafted polyethylene, maleic anhydride grafted polyethylene, acrylic acid grafted polypropylene, maleic anhydride grafted polypropylene, polyvinylidene fluoride, carboxymethyl cellulose, polyimide, polyetherimide, polyethylene terephthalate, styrene-isoprene-styrene copolymer rubber, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, styrene-isoprene-styrene copolymer, or any one or a combination of more thereof.

[0177] The above material is easy to obtain and has good viscosity, and can firmly adhere the main body layer to the bent portion.

[0178] In some embodiments, the protective layer 84 includes an ion-permeable portion and / or an ion-blocking portion.

[0179] The ion-permeable portion has a structure with a large number of through pores and can ensure the free passage of active ions. The ion-permeable portion has good permeability to lithium ions. The material of the ion-permeable portion is any one or a combination of polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoropropylene-vinylidene fluoride copolymer, trifluorochloropropylene-vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride or its copolymer, polyarylate, fiber, nylon, and non-woven fabric.

[0180] The ion-blocking portion has no pores or extremely small pores, preventing active ions from passing through. The ion-blocking portion is made of any one or a combination of polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoropropylene-vinylidene fluoride copolymer, trifluorochloropropylene-vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride or its copolymers, polyarylate, fiber, nylon, and non-woven fabric.

[0181] Both the ion-permeable portion and the ion-blocking portion can provide support to the electrode, reducing the risk of indentation or cracking of the electrode, thereby reducing the risk of abnormal self-discharge, and further reducing the risk of thermal runaway and fire.

[0182] In some embodiments, the air permeability of the ion-permeable portion is 220±70 sec / 100 cc, where sec stands for seconds and cc stands for cubic centimeters.

[0183] Air permeability can be measured using the air permeability test method described in GB / T36363-2018. Specifically, in the test temperature, humidity, and normal pressure environment, the test instrument applies a pressure of 1.21kPa, and the area through which 100ml of air passes is 6.45cm 2 The time required for the isolation part. The applied pressure of 1.21kPa is a constant pressure, and the 6.45cm 2 The area is fixed. It is generally believed that the higher the air permeability, the slower the active ions pass through the ion-permeable part, and the lower the air permeability, the faster the active ions pass through the ion-permeable part.

[0184] The air permeability of the ion-permeable portion is set to 220±70sec / 100cc, which can control the speed of active ions passing through the ion-permeable portion within a suitable speed range. In this way, the battery cell capacity can be increased without causing lithium deposition due to excessive speed.

[0185] For example, the air permeability of the ion-permeable portion can be any one of 160sec / 100cc, 180sec / 100cc, 200sec / 100cc, 230sec / 100cc, 250sec / 100cc, and 280sec / 100cc. Of course, the air permeability of the ion-permeable portion can also be other values, which will not be repeated here.

[0186] In some embodiments, the minimum size of the pores of the ion-permeable portion is in the range of 100 nm to 400 nm.

[0187] The size of the pores in the ion-permeable portion can be measured using a scanning electron microscope.

[0188] The pores are used for active ions such as sodium ions and lithium ions to pass through. The diameter of the pores is limited to a range of 100 nm to 400 nm, allowing the active ions to pass freely, thereby increasing the capacity of the battery cell 7.

[0189] In some embodiments, the protective layers 84 on the inner and outer sides of the bent portion of the positive electrode sheet 81 respectively include ion-permeable portions; the protective layers 84 on the inner and outer sides of the negative electrode sheet 82 respectively include ion-permeable portions.

[0190] In this way, active ions between the positive electrode sheet 81 and the negative electrode sheet 82 can freely pass through the ion-permeable portion, fully utilizing the capacity of the battery cell 7 , thereby increasing the capacity of the battery cell 7 .

[0191] In some embodiments, the protective layers 84 on the inner and outer sides of the bent portion of the positive electrode plate 81 respectively include ion blocking portions; the protective layers 84 on the inner and outer sides of the negative electrode plate 82 respectively include ion permeable portions.

[0192] In some embodiments, the protective layer 84 on the inner side of the bent portion of the positive electrode plate 81 includes an ion blocking portion, and the protective layer 84 on the outer side includes an ion permeable portion; the protective layers 84 on both the inner and outer sides of the negative electrode plate 82 respectively include ion permeable portions.

[0193] The positive electrode sheet 81 and the negative electrode sheet 82 need to be bent. The negative electrode sheet 82 on the inside of the positive electrode sheet 81 is prone to insufficient lithium insertion space, which may cause the number of lithium insertion sites of the negative electrode active material layer 822 of the negative electrode sheet 82 to be less than the number of lithium ions that can be provided by the positive electrode active material layer 812 of the adjacent positive electrode sheet 81 on its outside, thereby causing lithium precipitation. Therefore, an ion blocking portion is attached to the inside of the positive electrode sheet 81 to block at least part of the ions provided by the positive electrode active material layer 812, so that the blocked ions cannot be embedded in the negative electrode active material layer 822 with fewer lithium insertion sites, thereby reducing the occurrence of lithium precipitation. In addition, the ion-permeable portion on the outside of the bent portion of the positive electrode sheet 81 can complete the normal deintercalation and shuttling of ions, fully utilizing the capacity of the battery cell 7, thereby increasing the capacity of the battery cell 7 on the basis of reducing the risk of thermal runaway of the battery cell 7. Similarly, the ion-permeable portions on the inner and outer sides of the negative electrode plate 82 can complete the normal deintercalation and shuttling of ions, fully utilizing the capacity of the battery cell 7, thereby increasing the capacity of the battery cell 7 while reducing the risk of thermal runaway of the battery cell 7.

[0194] In some embodiments, the positive electrode plate 81 includes a positive electrode current collector 811 . The positive electrode current collector 811 is made of aluminum. A protective layer 84 is attached to both the inner and outer sides of the bent portion of the positive electrode plate 81 .

[0195] The protective layer 84 is attached to both the inner and outer sides of the bent portion of the positive electrode sheet 81, which can effectively reduce the risk of cracking of the aluminum positive electrode collector and separation of the active material.

[0196] In some embodiments, a protective layer 84 is attached to both inner and outer sides of the two bent portions of the innermost circle of the positive electrode sheet 81 .

[0197] The innermost bent portion of the positive electrode sheet 81 is the most bent and most susceptible to cracking. Therefore, attaching a protective layer 84 to both inner and outer sides of the two innermost bent portions can effectively reduce the risk of cracking of the positive electrode sheet 81 and separation of the active material.

[0198] In some embodiments, a protective layer 84 is attached to both inner and outer sides of the two bent portions of the second circle of the positive electrode sheet 81 from the inside to the outside.

[0199] In some embodiments, a protective layer 84 is attached to both inner and outer sides of the two bent portions of the third circle of the positive electrode sheet 81 from the inside out.

[0200] The second and third bends are more prone to cracking due to their large bends. Therefore, protective layers 84 are applied to both the inner and outer sides of the second and third bends to minimize the risk of cracking of the positive electrode sheet 81 and the loss of active material. Of course, protective layers 84 can also be applied to the fourth, fifth, and sixth bends, though this is not a specific limitation.

[0201] The disclosed embodiment of the present application also provides a method for preparing an electrode assembly, as shown in FIG14 , comprising:

[0202] Step S1: providing a positive electrode sheet, a negative electrode sheet and a separator;

[0203] Step S2: attaching a protective layer to the positive electrode sheet and / or the negative electrode sheet;

[0204] Step S3: stacking and winding the positive electrode sheet, the negative electrode sheet and the separator to form a winding structure, wherein in the winding structure, an separator is sandwiched between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet and the negative electrode sheet each include a plurality of bent portions, and protective layers are attached to both inner and outer sides of at least one bent portion, and the protective layers on both inner and outer sides of the same bent portion are staggered at at least one end along the winding direction.

[0205] 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.

[0206] 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

[0207] The present disclosure provides an electrode assembly, a battery cell, a battery, an electrical device, and a method for preparing the electrode assembly with high battery cell capacity and low thermal runaway risk.

Claims

1. An electrode assembly, comprising: a winding structure formed by winding a laminate including a positive electrode tab and a negative electrode tab along a winding direction, with a separator sandwiched between the positive electrode tab and the negative electrode tab, and both the positive electrode tab and the negative electrode tab include a plurality of bent portions; a protective layer, with the protective layer attached to both the inner and outer sides of at least one of the bent portions; wherein, at least one end of the protective layers on the inner and outer sides of the same bent portion is misaligned along the winding direction.

2. The electrode assembly according to claim 1, wherein, both ends of the protective layers on the inner and outer sides of the same bent portion are respectively misaligned along the winding direction.

3. The electrode assembly according to claim 1 or 2, wherein, the protective layer on the inner side of the same bent portion respectively extends beyond the corresponding two ends of the protective layer on the outer side along the two ends of the winding direction; or the protective layer on the outer side of the same bent portion respectively extends beyond the corresponding two ends of the protective layer on the inner side along the two ends of the winding direction; or the protective layer on the inner side of the same bent portion extends beyond the corresponding one end of the protective layer on the outer side along one end of the winding direction, and the protective layer on the inner side is exceeded by the corresponding other end of the protective layer on the outer side along the other end of the winding direction.

4. The electrode assembly according to any one of claims 1 to 3, wherein, along the winding axis direction of the winding structure, at least one end of at least one of the protective layers extends beyond the active material of the bent portion.

5. The electrode assembly according to any one of claims 1 to 4, wherein, one end of the protective layers on the inner and outer sides of the same bent portion is staggered by a first set size along the winding direction, and the other end of the protective layers on the inner and outer sides of the same bent portion is staggered by a second set size along the winding direction, wherein, the first set size is equal to the second set size, or, the first set size is not equal to the second set size.

6. The electrode assembly according to any one of claims 1 to 5, wherein, one end of the protective layers on the inner and outer sides of the same bent portion is staggered by a first set size along the winding direction, and the first set size does not exceed 2 mm, and / or, the other end of the protective layers on the inner and outer sides of the same bent portion is staggered by a second set size along the winding direction, and the second set size does not exceed 2 mm.

7. The electrode assembly according to any one of claims 1 to 6, wherein, one end of the protective layers on the inner and outer sides of the same bent portion is staggered by a first set size along the winding direction, and the first set size does not exceed 1.5 mm, and / or, On the inner and outer sides of the same bending portion, the other end portions of the protective layers along the winding direction are staggered from each other in the winding direction by a second set size, and the second set size does not exceed 1.5 mm.

8. The electrode assembly according to any one of claims 1 to 7, wherein, on the inner and outer sides of the same bending portion, one end portion of the protective layers along the winding direction is staggered from each other in the winding direction by a first set size, and the first set size does not exceed 1 mm, and / or, on the inner and outer sides of the same bending portion, the other end portions of the protective layers along the winding direction are staggered from each other in the winding direction by a second set size, and the second set size does not exceed 1 mm.

9. The electrode assembly according to any one of claims 1 to 8, wherein, the positive electrode tab and the negative electrode tab both include a plurality of flat portions, and the plurality of bending portions and the plurality of flat portions of the positive electrode tab are alternately arranged one by one along the winding direction, and the plurality of bending portions and the plurality of flat portions of the negative electrode tab are alternately arranged one by one along the winding direction, at least one of the protective layers is attached to the side surface of the bending portion at one end along the winding direction, and the other end extends to the side surface of the flat portion adjacent to the bending portion, or at least one of the protective layers is attached to the side surface of the bending portion at both ends along the winding direction, or at least one of the protective layers is attached to the side surface of the bending portion at the middle portion along the winding direction, and both ends extend to the side surfaces of the two flat portions adjacent to the bending portion respectively.

10. The electrode assembly according to any one of claims 1 to 9, wherein, the protective layer includes a main body layer made of a polymer material.

11. The electrode assembly according to claim 10, wherein, the polymer material is at least any one of polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoropropylene-vinylidene fluoride copolymer, trifluorochloropropylene-vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, non-woven fabric.

12. The electrode assembly according to claim 10 or 11, wherein, the protective layer further includes an adhesive layer, and the main body layer is adhered to the side surface of the bending portion through the adhesive layer.

13. The electrode assembly according to claim 12, wherein, The material of the adhesive layer is at least any one of acrylic-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic acid copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic acid grafted polyethylene, maleic anhydride grafted polyethylene, acrylic acid grafted polypropylene, maleic anhydride grafted polypropylene, polyvinylidene fluoride, carboxymethyl cellulose, polyimide, polyetherimide, polyethylene terephthalate, styrene-isoprene-styrene copolymer rubber, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone oxygen type resin, polyurethane, styrene-isoprene-styrene copolymer.

14. The electrode assembly according to any one of claims 1 to 13, wherein, the protective layer includes an ion-permeable part and / or an ion-blocking part.

15. The electrode assembly according to claim 14, wherein, the protective layers on the inner and outer sides of the bent part of the positive electrode tab respectively include the ion-permeable part, or the protective layers on the inner and outer sides of the bent part of the positive electrode tab respectively include the ion-blocking part, or the protective layer on the inner side of the bent part of the positive electrode tab includes the ion-blocking part, and the protective layer on the outer side includes the ion-permeable part; the protective layers on the inner and outer sides of the negative electrode tab respectively include the ion-permeable part.

16. The electrode assembly according to claim 14 or 15, wherein, the air permeability of the ion-permeable part is 220 ± 70 sec / 100cc.

17. The electrode assembly according to claim 14 or 15, wherein, the minimum size of the pores of the ion-permeable part is in the range of 100 nm to 400 nm.

18. The electrode assembly according to any one of claims 1 to 17, wherein, the positive electrode tab includes a positive current collector, the material of the positive current collector is aluminum, and the protective layers are attached to both the inner and outer sides of the bent part of the positive electrode tab.

19. The electrode assembly according to any one of claims 1 to 18, wherein, the protective layers are attached to both the inner and outer sides of the two bent parts of the innermost circle of the positive electrode tab.

20. A battery cell, wherein, it includes: a housing, a cover plate and at least one electrode assembly according to any one of claims 1 to 19, wherein, the housing has a receiving cavity and an opening, and the electrode assembly is received in the receiving cavity; the cover plate closes the opening of the housing.

21. A battery, wherein, it includes: a box body; at least one battery cell according to claim 20, and the battery cell is housed in the box body.

22. An electrical device, wherein, the electrical device includes the battery cell according to claim 20 for providing electrical energy or the battery according to claim 21.

23. A method for preparing an electrode assembly, including: 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 interposed between the positive electrode sheet and the negative electrode sheet. Both the positive electrode sheet and the negative electrode sheet include a plurality of bent portions, and the protective layers are attached to both the inner and outer sides of at least one of the bent portions. The ends of the protective layers on the inner and outer sides of the same bent portion are offset at at least one end along the winding direction.

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