Electrode assembly, battery cell, battery and electric device

Abstract

The utility model discloses an electrode assembly, a battery monomer, a battery and a power utilization device, and belongs to the technical field of batteries. The electrode assembly comprises a winding structure and a protective layer, the winding structure is formed by winding a laminated body comprising a positive pole piece and a negative pole piece along the winding direction, a separator is clamped between the positive pole piece and the negative pole piece, and each of the positive pole piece and the negative pole piece comprises a plurality of bent parts; protective layers are attached to the inner side and the outer side of at least one bent part; wherein the protective layers on the inner side and the outer side of the same bent part are staggered along at least one end part of the winding direction. According to the electrode assembly, the battery monomer, the battery and the electric device provided by the embodiment of the invention, the capacity of the battery monomer can be improved, and the risks of thermal runaway and fire are reduced.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to electrode assemblies, battery cells, batteries and electrical devices. 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 areas such as energy storage.

[0003] Battery capacity is one of the important performance indicators to measure battery performance, and the improvement of battery capacity has always been one of the research and development topics in the industry. In addition, batteries usually have the risk of thermal runaway and fire, so how to reduce the risk of thermal runaway and fire is also a technical problem that needs to be solved in battery technology. Utility Model Content

[0004] In order to solve the above technical problems, the present application provides an electrode assembly, a battery cell, a battery and an electrical device with high battery cell capacity and low thermal runaway risk.

[0005] This application is implemented through the following technical solutions.

[0006] A first aspect of the present application provides an electrode assembly, comprising:

[0007] A winding structure, wherein the winding 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;

[0008] A protective layer, the protective layer being attached to both inner and outer sides of at least one of the bent portions;

[0009] Wherein, at least one end portion of the protective layers on the inner and outer sides of the same bending portion along the winding direction is staggered.

[0010] 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, thereby reducing the risk of closed cells due to excessive force on the isolation piece, reducing the problem of lithium deposition, 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.

[0011] In some embodiments, the protective layers on the inner and outer sides of the same bending portion are staggered at both ends along the winding direction.

[0012] Both ends are designed to be staggered. On the one hand, the thickness difference at both ends of the bent part of the attached protective layer is smoothly transitioned, which can reduce the stress concentration at the two edges, thereby better reducing the risk of closed cells due to excessive force on the isolation piece, reducing the problem of lithium precipitation, and thus 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 then reducing the risk of thermal runaway and fire.

[0013] In some embodiments, both end portions of the protective layer on the inner side of the same bent portion along the winding direction respectively exceed the corresponding end portions of the protective layer on the outer side; or

[0014] The two end portions of the outer side of the protective layer of the same bent portion along the winding direction respectively exceed the corresponding two end portions of the inner side of the protective layer; or

[0015] One end of the inner side of the same bending portion along the winding direction exceeds the corresponding end of the outer side of the protective layer, and the other end of the inner side of the protective layer along the winding direction is exceeded by the corresponding other end of the outer side of the protective layer.

[0016] The above three distribution conditions of the protective layers on the inner and outer sides of the same bending part all achieve the misalignment of the two 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 caused by excessive force on the isolation part, reducing the problem of lithium precipitation, and thereby increasing the capacity of the battery cell. On the other hand, the risk of indentation or cracking of the pole piece is reduced, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0017] In some embodiments, along the winding axis direction of the winding structure, at least one end of at least one of the protective layers exceeds the active material of the bent portion.

[0018] 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 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.

[0019] 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 dimension 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 dimension in the winding direction, wherein the first set dimension is equal to the second set dimension, or the first set dimension is not equal to the second set dimension.

[0020] 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 isolation member, reducing the problem of lithium precipitation, and thus increasing the capacity of the battery cell. On the other hand, the risk of indentation or cracking of the pole piece is reduced, thereby reducing the risk of abnormal self-discharge, and thus reducing the risk of thermal runaway and fire.

[0021] 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 dimension in the winding direction, and the first set dimension 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 dimension in the winding direction, and the second set dimension does not exceed 2 mm.

[0022] The offset size is limited to no more than 2mm, so that the offset size is not too large, so that the overlapping area of ​​the inner and outer protective layers is larger, and on the basis of reducing the degree of stress concentration, the effect of reducing the risk of cracking and active material shedding is better played. In addition, in the case where the protective layer exceeds the bending part in the winding axis direction and the offset part of the inner and outer protective layers leaks out of the bonding surface, the offset size is limited to no more than 2mm, which can reduce the occurrence of adhesion to the roller during winding due to the leaking bonding surface being too large.

[0023] 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 dimension in the winding direction, and the first set dimension 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 dimension in the winding direction, and the second set dimension does not exceed 1.5 mm.

[0024] The offset size is limited to no more than 1.5mm, so that the offset size is not too large, so that the overlapping area of ​​the inner and outer protective layers is larger, and on the basis of reducing the degree of stress concentration, the effect of reducing the risk of cracking and active material shedding is better played. In addition, in the case where the protective layer exceeds the bending part in the winding axis direction and the offset part of the inner and outer protective layers leaks out of the bonding surface, the offset size is limited to no more than 1.5mm, which can reduce the occurrence of adhesion to the roller during winding due to the leaking bonding surface being too large.

[0025] 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 dimension in the winding direction, and the first set dimension 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 dimension in the winding direction, and the second set dimension does not exceed 1 mm.

[0026] The offset size is limited to no more than 1mm, so that the offset size is not too large, so that the overlapping area of ​​the inner and outer protective layers is larger, and on the basis of reducing the stress concentration, the effect of reducing the risk of cracking and active material shedding is better played. In addition, in the case where the protective layer 84 exceeds the bending part in the winding axis direction and the offset part of the inner and outer protective layers leaks out of the bonding surface, the offset size is limited to no more than 1mm, which can reduce the occurrence of adhesion to the roller during winding due to the leaking bonding surface being too large.

[0027] In some embodiments, the positive electrode sheet and the negative electrode sheet each include a plurality of straight portions, the plurality of bent portions and the plurality of straight portions of the positive electrode sheet are alternately arranged along the winding direction, the plurality of bent portions and the plurality of straight portions of the negative electrode sheet are alternately arranged along the winding direction, at least one end of the protective layer along the winding direction is attached to the side of the bent portion, 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 along the winding direction are attached to the side of the bent portion, or, the middle portion of at least one protective layer along the winding direction is attached to the side of the bent portion, and both ends extend to the sides of two straight portions adjacent to the bent portion, respectively.

[0028] As mentioned above, for flat electrode assemblies, the above three conditions of the protective layer can reduce the risk of cracking of the pole piece 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.

[0029] In some embodiments, the protective layer includes a main layer made of a polymer material.

[0030] The main layer made of polymer material 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.

[0031] In some embodiments, the polymer material is 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, and non-woven fabric.

[0032] The above materials are easy to obtain and have good toughness and strength, which can reduce the risk of indentation or cracking of the pole piece, thereby reducing the risk of abnormal self-discharge, and further reducing the risk of thermal runaway and fire.

[0033] 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.

[0034] The main body layer is bonded to the side of the bent portion through the adhesive layer, so that the protective layer is bonded to the bent portion. The bonding method makes the main body layer firmly attached to the bent portion, and the bonding operation is simple and quick.

[0035] In some embodiments, the material of the adhesive layer is 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.

[0036] The above material is easy to obtain and has good adhesion, and can firmly adhere the main body layer to the bent part.

[0037] In some embodiments, the protective layer includes an ion-permeable portion and / or an ion-blocking portion.

[0038] Both the ion-permeable portion and the ion-blocking portion can provide a certain degree of support for the electrode, thereby 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.

[0039] 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;

[0040] The protective layers on both inner and outer sides of the negative electrode plate respectively include the ion-permeable portions.

[0041] In this way, this embodiment not only increases the capacity of the battery cells, but also reduces the risk of thermal runaway and fire.

[0042] In some embodiments, the air permeability of the ion-permeable portion comprises 220±70 sec / 100 cc.

[0043] By setting the air permeability of the ion-permeable portion, the speed of active ions passing through the ion-permeable portion can be controlled within a suitable speed range, thereby increasing the battery cell capacity without causing lithium deposition due to a too fast speed.

[0044] In some embodiments, the maximum size of the pores of the ion-permeable portion is in the range of 100 nm to 400 nm.

[0045] 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.

[0046] 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 inner and outer sides of the bent portion of the positive electrode plate.

[0047] Attaching protective layers to both the inner and outer sides of the bent portion of the positive electrode sheet can effectively reduce the risk of cracking of the aluminum positive electrode collector and detachment of the active material.

[0048] 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.

[0049] The innermost bent portion of the positive electrode sheet has the largest bending degree and is most susceptible to cracking. Therefore, attaching protective layers to both the inner and outer sides of the two innermost bent portions can effectively reduce the risk of cracking of the positive electrode sheet and separation of the active material.

[0050] The second aspect of the present application 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, and the electrode assembly is received in the receiving cavity; the cover plate closes the opening of the shell.

[0051] The battery cells provided in the embodiments of the present application not only increase the battery cell capacity, but also reduce the risk of thermal runaway and fire.

[0052] A third aspect of the present application provides a battery, comprising: a box body; and at least one of the above-mentioned battery cells, wherein the battery cell is accommodated in the box body.

[0053] The battery provided in the embodiments of the present application not only improves the battery capacity, but also reduces the risk of thermal runaway and fire.

[0054] A fourth aspect of the present application provides an electrical device, which includes the above-mentioned battery cell or the above-mentioned battery for providing electrical energy.

[0055] The power-consuming device provided in the embodiment of the present application not only increases the battery capacity, but also reduces the risk of thermal runaway and fire.

[0056] Utility Model Effect

[0057] The present application provides an electrode assembly, a battery cell, a battery and an electrical device with high battery cell capacity and low thermal runaway risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limitations of the present application. In addition, the same reference numerals are used to represent the same components throughout the drawings.

[0059] In the attached picture:

[0060] Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of the present application;

[0061] Figure 2 A three-dimensional exploded schematic diagram of a battery provided in some embodiments of the present application;

[0062] Figure 3 for Figure 2 A schematic diagram of the structure of the battery module shown;

[0063] Figure 4 A three-dimensional exploded schematic diagram of a battery cell provided in some embodiments of the present application;

[0064] Figure 5 A schematic structural diagram of a cross section of an electrode assembly provided in some embodiments of the present application along a direction perpendicular to the winding axis;

[0065] Figure 6A schematic structural diagram of a positive electrode sheet with a protective layer attached to an electrode assembly provided in some embodiments of the present application in a flat state;

[0066] Figure 7 for Figure 6 Sectional view at AA in the middle;

[0067] Figure 8 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 application in a flat state;

[0068] Fig. 9 for Figure 8 Sectional view at the middle BB;

[0069] Fig.10 A schematic diagram of the structure of a positive electrode sheet or a negative electrode sheet with a protective layer attached in a flat state provided in some embodiments of the present application;

[0070] Fig.11 A partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis direction provided in some embodiments of the present application;

[0071] Fig.12 A partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis direction provided in some other embodiments of the present application;

[0072] Fig.13 A partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis direction provided in some further embodiments of the present application.

[0073] Description of Reference Numerals

[0074] 1 vehicle; 2 battery; 3 controller; 4 motor; 5 housing; 51 first housing portion; 52 second housing portion; 53 accommodating space; 6 battery module; 7 battery cell; 8 electrode assembly; 81 positive electrode plate; 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 plate; 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; 9 outer shell; 91 main body shell; 92 end cover; 10 positive electrode terminal; 11 pressure relief mechanism; 12 negative electrode terminal. DETAILED DESCRIPTION

[0075] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0077] In the description of the embodiments of the present application, the technical terms "first", "second", "third", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0078] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0079] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0080] In the description of the embodiments of the present application, the orientation or position relationship 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 orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed, operated or used in a specific orientation. Therefore, they should not be understood as limitations on the embodiments of the present application.

[0081] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0082] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, the technical term "contact" should be understood in a broad sense, and may be direct contact or contact through an intermediate medium layer. It may be contact with essentially no interaction force between the two contacting parties, or it may be contact with interaction force between the two contacting parties.

[0083] Below, this application is described in detail.

[0084] At present, new energy batteries are increasingly used in life and industry. New energy batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.

[0085] Battery capacity is one of the important performance indicators to measure battery performance. It indicates the amount of electricity discharged by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.). Improving battery capacity has always been one of the research and development topics in the industry. In addition, batteries usually have the risk of thermal runaway and fire. Therefore, how to reduce the risk of thermal runaway and fire is also a technical problem that needs to be solved in battery technology.

[0086] The battery mentioned in the embodiments of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in mixed connection through a busbar. For example, the battery mentioned in the present application may include a battery module or a battery pack, etc. 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. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0087] In the present application, battery cells may include lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium-lithium-ion battery cells, sodium-ion battery cells or magnesium-ion battery cells, etc., and the embodiments of the present application do not limit this. Battery cells may be cylindrical, flat, rectangular or other shapes, etc., and the embodiments of the present application do not limit this. Battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells and soft-pack battery cells, and the embodiments of the present application do not limit this.

[0088] 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 mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. 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 and a positive convex portion protruding from the positive current collector. The positive current collector is coated with the positive active material layer. At least part of the positive convex portion is not coated with the positive active material layer. The positive convex portion serves as a positive electrode ear. 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, etc. The negative electrode sheet includes a negative current collector and a negative active material layer, and the negative active material layer is coated on the surface of the negative current collector; the negative current collector includes a negative current collector and a negative convex portion protruding from the negative current collector, the negative current collector is coated with a negative active material layer, at least part of the negative convex portion is not coated with the negative active material layer, and the negative convex portion serves as a negative electrode tab. The material of the negative current collector may be copper, and the negative active material layer includes a negative active material, and the negative active material may be carbon or silicon, etc. In order to ensure that a large current passes without melting, the number of positive pole tabs is multiple and stacked together, and the number of negative pole tabs is multiple and stacked together. The separator is a separator. The present application has no particular restrictions on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected. As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. In addition, the electrode assembly may be a winding structure or a laminated structure, and the embodiments of the present application are not limited thereto.

[0089] 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 lithium embedding space, the resistance of lithium ions embedding in the negative electrode active material layer is too large, 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 precipitation phenomenon. Lithium precipitation 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 precipitation occurs in lithium-ion battery cells, the precipitated lithium metal is very active and can react with the electrolyte at a lower temperature, causing the starting temperature of self-heat generation in the battery cell to decrease and the self-heat generation rate to increase, seriously endangering the safety of the battery cell. Furthermore, when lithium precipitation is severe, the released lithium ions can form lithium crystals on the surface of the negative electrode plate, and the lithium crystals can easily puncture the isolation piece, causing the risk of short circuit between the adjacent positive and negative electrode plates.

[0090] At present, protective layers are adhered to the inner and outer sides of the bent parts of the positive and negative pole pieces of some electrode assemblies to prevent the bending parts of the pole pieces from cracking or the active material from falling off during pre-pressing and hot pressing, thereby increasing the capacity of the battery cell. However, the inventors of the present application noticed that the protective layers adhered to the inner and outer sides are superimposed, so that the thickness difference between the edge of the protective layer and the part without the protective layer is large, resulting in a large concentrated stress at the edge of the protective layer when under pressure, so that the corresponding isolation piece at the edge is too stressed and closed, resulting in the problem of lithium precipitation, and the pole piece corresponding to the stress concentration point will have an indentation. After the battery cell is cycled for a long time, the expansion force is relatively large, and the pole piece is continuously stressed, and there is a risk of cracking. After cracking, burrs will be formed, and there is a risk of puncturing the isolation piece, resulting in abnormal self-discharge, and even the risk of thermal runaway and fire.

[0091] The inventors of the present application have discovered through research 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 closed cells due to excessive force on the isolation member, reducing the problem of lithium deposition, and thereby increasing the capacity of the battery cell. On the other hand, it can reduce 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.

[0092] Based on such a design concept, the inventor of the present application 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 each include a plurality of bent portions; a protective layer is attached to both inner and outer sides of at least one bent portion; wherein 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.

[0093] 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 isolation piece, reducing the problem of lithium deposition, 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.

[0094] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical devices using batteries. Electrical devices may be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and electric tools, etc. Vehicles may be fuel vehicles, gas vehicles, or new energy vehicles, and 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 application do not impose any special restrictions on the above-mentioned electrical devices.

[0095] The embodiment of the present application provides an electric device. In the following embodiments, for the convenience of description, the electric device of one embodiment of the present application is taken as a vehicle 1 as an example for description. The following is a description with reference to the accompanying drawings.

[0096] Figure 1 The schematic diagram of the structure of the vehicle 1 provided in some embodiments of the present application. The vehicle 1 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended range vehicle. Figure 1As shown, a battery 2 is disposed inside the vehicle 1, and the battery 2 can be disposed at the bottom, head, or tail of the vehicle 1. The battery 2 can be used to power the vehicle 1, for example, the battery 2 can be used as an operating power source for the vehicle 1. The vehicle 1 can also include a controller 3 and a motor 4, and 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.

[0097] In some embodiments of the present application, the battery 2 can be used 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.

[0098] Figure 2 A schematic three-dimensional exploded view of a battery 2 provided in some embodiments of the present application. Figure 3 for Figure 2 Schematic diagram of the structure of the battery module shown. Figure 4 A schematic three-dimensional exploded view of a battery cell provided for some embodiments of the present application.

[0099] like Figure 2 and Figure 3 As shown, the battery 2 includes a box body 5 and at least one battery cell 7 , and the at least one battery cell 7 is accommodated in the box body 5 .

[0100] The box body 5 is used to accommodate the battery cell 7, and the box body 5 can be a variety of structures. In some embodiments, the box body 5 can include a first box body portion 51 and a second box body portion 52, the first box body portion 51 and the second box body portion 52 cover each other, and the first box body portion 51 and the second box body portion 52 jointly define a storage space 53 for accommodating the battery cell 7. The second box body portion 52 can be a hollow structure with one end open, the first box body portion 51 is a plate-like structure, and the first box body portion 51 covers the open side of the second box body portion 52 to form a box body 5 with a storage space 53; the first box body portion 51 and the second box body portion 52 can also be a hollow structure with one side open, and the open side of the first box body portion 51 covers the open side of the second box body portion 52 to form a box body 5 with a storage space 53. Of course, the first box body portion 51 and the second box body portion 52 can be a variety of shapes, such as a cylinder, a cuboid, etc.

[0101] 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 .

[0102] Assuming that the first box body portion 51 covers the top of the second box body portion 52 , the first box body portion 51 can also be referred to as an upper box cover, and the second box body portion 52 can also be referred to as a lower box body.

[0103] In the battery 2, there can be multiple battery cells 7, and the multiple battery cells 7 can be connected in series, in parallel, or in mixed connection. Mixed connection means that the multiple battery cells 7 are both connected in series and in parallel. The multiple battery cells 7 can be directly connected in series, in parallel, or in mixed connection, and then the whole formed by the multiple battery cells 7 is placed in the accommodation space 53 formed by the first box body 51 and the second box body 52; of course, the battery 2 can also be in the form of multiple battery cells 7 connected in series, in parallel, or in mixed connection to form a battery module 6, and the multiple battery modules 6 are then connected in series, in parallel, or in mixed connection to form a whole, and are accommodated in the accommodation space 53 formed by the first box body 51 and the second box body 52. ​​The battery 2 can also include other structures, for example, the battery 2 can also include a converging component for realizing electrical connection between the multiple battery cells 7.

[0104] In the embodiment of the present application, the battery 2 may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0105] In the embodiment of the present application, 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.

[0106] 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., which is not limited in the embodiment of the present application.

[0107] like Figure 4 As shown, the battery cell 7 includes a housing 9 and at least one electrode assembly 8, and the housing 9 is used to encapsulate the electrode assembly 8 and components such as electrolyte. The housing 9 can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell) or an aluminum-plastic film.

[0108] In some embodiments, the housing 9 includes an end cap 92 and a main housing 91, the main housing 91 having a receiving cavity and an opening, the electrode assembly 8 and electrolyte and other substances are received in the receiving cavity; the cover plate 92 is sealed at the opening of the housing 91 to form a closed space for receiving the electrode assembly 8 and electrolyte and other substances. The main housing 91 may be provided with one or more openings. One or more end caps 92 may also be provided.

[0109] The main body shell 91 can be in various shapes, such as a cylinder, a cuboid, 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 cuboid structure, a cuboid shell can be selected. Of course, the end cap 92 can also be in various structures, such as a plate-like structure, a hollow structure with one end open, etc. For example, in Figure 4 In the embodiment, 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 .

[0110] 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, and the positive electrode terminal 10, the negative electrode terminal 12 and the pressure relief mechanism 11 are all mounted on the end cover 92. The positive electrode terminal 10 and the negative electrode terminal 12 are both used to be electrically connected to the electrode assembly 8 to output the electrical energy generated by the electrode assembly 8. The pressure relief mechanism 11 is used to release the pressure inside the battery cell 7 when the internal pressure or temperature of the battery cell 7 reaches a predetermined value.

[0111] Exemplarily, the pressure relief mechanism 11 is located between the positive electrode terminal 10 and the negative electrode terminal 12 , and 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.

[0112] Of course, in other embodiments, the housing 9 may also be other structures, for example, the housing 9 includes a main body shell 91 and two end covers 92, the main body shell 91 is a hollow structure with two opposite openings, and one end cover 92 is correspondingly covered at one opening of the main body shell 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 may be installed on the same end cover 92 or on different end covers 92; the pressure relief mechanism 11 may be installed on one end cover 92 or on both end covers 92.

[0113] It should be noted that, in the battery cell 7, the number of electrode assemblies 8 contained in the housing 9 may be one or more. Figure 4 In the embodiment, there are two electrode assemblies 8.

[0114] Below, refer to Figures 5 to 13 Some embodiments of the present application are described in detail.

[0115] Figure 5 A schematic structural diagram of a cross section of an electrode assembly provided in some embodiments of the present application along a direction perpendicular to the winding axis; Figure 6 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 application in a flat state; Figure 7 for Figure 6 Sectional view at AA in the middle; Figure 8 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 application in a flat state; Fig. 9 for Figure 8 Sectional view at the middle BB; Fig.10 A schematic diagram of the structure of a positive electrode sheet or a negative electrode sheet with a protective layer attached in a flat state provided in some embodiments of the present application; Fig.11 A partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis direction provided in some embodiments of the present application; Fig.12 A partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis direction provided in some other embodiments of the present application; Fig.13 A partial structural schematic diagram of a cross section of an electrode assembly perpendicular to the winding axis direction provided in some further embodiments of the present application.

[0116] like Figure 5 As shown, the electrode assembly 8 provided in the embodiment of the present application 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, an isolation member 83 is sandwiched between the positive electrode sheet 81 and the negative electrode sheet 82, and 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 inner and outer sides of at least one bent portion; wherein, the protective layers 84 on both inner and outer sides of the same bent portion are staggered at at least one end along the winding direction C.

[0117] The winding direction C is the direction in which the positive electrode sheet 81 and the negative electrode sheet 82 are wound from the center to the periphery. Figure 5 , the winding direction C is clockwise.

[0118] like Figure 6 and Figure 7 As shown, the positive electrode sheet 81 includes a positive current collector 811 and a positive active material layer 812, and the positive active material layer 812 is coated on the surface of the positive current collector 811; the positive current collector 811 includes a positive current collector 8111 and a positive convex portion 8112 protruding from the positive current collector 8111, the positive current collector 8111 is coated with the positive active material layer 812, at least part of the positive convex portion 8112 is not coated with the positive active material layer 812, and the positive convex portion 8112 serves as a 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, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganate, etc.

[0119] In some embodiments, only a portion of the positive electrode current collector 8111 is coated with the positive electrode active material layer 812, and the portion of the positive electrode current collector 8111 that is not coated with the positive electrode active material layer 812 is coated with an insulating layer 813, and the insulating layer 813 is located on a side of the positive electrode active material layer 812 that is close to the positive electrode tab. Exemplarily, the root of the positive electrode tab that is close to the positive electrode current collector 8111 is also coated with the insulating layer 812.

[0120] like Figure 8and Fig. 9 As shown, the negative electrode sheet 82 includes a negative current collector 821 and a negative active material layer 822, and 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 collector 8211 and a negative convex portion 8212 protruding from the negative current collector, the negative current collector 8211 is coated with the negative active material layer 822, at least part of the negative convex portion 8212 is not coated with the negative active material layer 822, and the negative convex portion 8212 serves as a negative electrode tab. The material of the negative current collector 821 can be copper, and the negative active material layer 822 includes a negative active material, and the negative active material can be carbon or silicon, etc.

[0121] The separator 83 is used to isolate the positive electrode sheet 81 from the negative electrode sheet 82 to reduce the risk of short circuit between the positive electrode sheet 81 and the negative electrode sheet 82. The separator 83 has a large number of through micropores, which can ensure the free passage of active ions and has good permeability to lithium ions. Therefore, the separator 83 basically cannot block the passage of lithium ions. Exemplarily, the material of the separator 83 can be PP (polypropylene) or PE (polyethylene).

[0122] 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 application, 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 stack, and then the stack is wound more than two times to form a winding structure.

[0123] The protective layer 84 is a sheet structure attached to the bent portion of the positive electrode sheet 81 and / or the negative electrode sheet 82, which has a certain toughness and strength. When the electrode sheet is compressed and deformed, the protective layer 84 interacts with the electrode sheet attached thereto, which is conducive to increasing the strength of the electrode sheet, thereby reducing the risk of cracking of the electrode sheet or shedding of active materials. Before the negative electrode sheet 82, the separator 83 and the positive electrode sheet 81 are stacked, the protective layer 84 finds the part of the positive electrode sheet 81 and the negative electrode sheet 82 that is about to be bent through size calculation, and attaches the protective layer 84 to the part that is about to be bent, so that in 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 part 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 active materials.

[0124] 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.

[0125] The bent portion is a portion of the positive electrode tab 81 and the negative electrode tab 82 that is in a bent shape.

[0126] 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 .

[0127] In some embodiments, Figure 5 As shown, 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. Figure 5 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.

[0128] In some embodiments, attaching means adhering or coating or spraying.

[0129] The ends of one or both ends of the protective layer 84 attached to the inner and outer sides of the bent portion 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 deposition, 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.

[0130] 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.

[0131] 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 isolation member 83 being subjected to excessive force and causing closed holes, reducing the problem of lithium deposition, and thus increasing the capacity of the battery cell.

[0132] 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.

[0133] 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 is smoothly transitioned, which can reduce the stress concentration at the two edges, thereby reducing the risk of the isolation member 83 being too stressed and causing closed cells, reducing the problem of lithium plating, and thereby increasing the capacity of the battery cell.

[0134] In some embodiments, Fig.12 As shown, the two end portions of the inner side protective layer 84 of the same bent portion along the winding direction respectively exceed the corresponding two end portions of the outer side protective layer; or, as shown Fig.13 As shown, the two end portions of the outer protective layer of the same bent portion along the winding direction respectively exceed the corresponding two end portions of the inner protective layer; or Fig.11As shown, one end of the inner protective layer of the same bending portion along the winding direction exceeds the corresponding one end of the outer protective layer, and the other end of the inner protective layer along the winding direction is exceeded by the corresponding other end of the outer protective layer.

[0135] In the above, the three distribution conditions of the protective layer 84 on the inner and outer sides of the same bending part all realize the misalignment 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 too stressed and causing closed holes, reducing the problem of lithium precipitation, and thereby increasing the capacity of the battery cell. On the other hand, the risk of indentation or cracking of the pole piece is reduced, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0136] In some embodiments, along the winding axis direction 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.

[0137] The active material includes a positive active material coated on the positive current collector 811 to form a positive active material layer 812, and a negative active material coated on the negative current collector 821 to form a negative active material layer 822. The protective layer 84 attached to the positive electrode sheet 81 has at least one end along the winding axis direction L that exceeds the positive active material of the positive electrode sheet 81; the protective layer 84 attached to the negative electrode sheet 82 has at least one end along the winding axis direction L that exceeds the negative active material of the negative electrode sheet 82.

[0138] 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 pole piece or shedding of the active material and improving the capacity of the battery cell.

[0139] For example, Figure 6 and Figure 8 As shown, 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.

[0140] 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 pole piece or shedding of the active material, increasing the capacity of the battery cell, and reducing the risk of thermal runaway and fire.

[0141] In some embodiments, along the winding axis direction L of the winding structure, the size of at least one end of at least one protective layer 84 that exceeds the active material of the bent portion is in the range of 1 mm to 3 mm.

[0142] For example, along the winding axis direction 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.

[0143] For example, Figure 6 As shown, 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.

[0144] In some embodiments, Figure 6 and Figure 8 As shown, along the winding axis direction L of the winding structure, at least one end of at least one protective layer 84 exceeds the bent portion.

[0145] Figure 6 In the embodiment, the portion of the positive electrode sheet 81 located in the region P1 is a bent portion, and the portion located in the region P2 is a straight portion. Figure 8 In the figure, the portion of the negative electrode sheet 82 located in the region P1 is a bent portion, and the portion located in the region P2 is a straight portion.

[0146] It can be understood that the bent portion of the positive electrode sheet 81 includes part of the positive electrode active material layer 812 and part of the insulating layer 813. The protective layer 84 of the positive electrode sheet 81 exceeds the bent portion, which means that the protective layer 84 exceeds the edge of the insulating layer 813 away from the positive electrode active material layer 812. The protective layer 84 of the negative electrode sheet 82 exceeds the bent portion, which means that the protective layer 84 exceeds the edge of the negative electrode active material layer 822.

[0147] 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.

[0148] Exemplarily, 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.

[0149] For example, Figure 8 As shown, 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 exceed the bent portion.

[0150] 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.

[0151] In some embodiments, Fig.10As shown, one end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a first set dimension d1 in the winding direction C, and the other end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a second set dimension d2 in 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.

[0152] 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 can be 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 too stressed and causing closed cells, reducing the problem of lithium deposition, and thereby increasing the capacity of the battery cell. In addition, the risk of indentation or cracking of the pole piece is reduced, thereby reducing the risk of abnormal self-discharge, and thereby reducing the risk of thermal runaway and fire.

[0153] In some embodiments, one end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a first set dimension d1 in the winding direction C, and the first set dimension d1 does not exceed 2 mm, and / or, the other end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a second set dimension d2 in the winding direction C, and the second set dimension d2 does not exceed 2 mm.

[0154] The offset size is limited to no more than 2 mm, so that the offset size is not too large, so that the overlapping area of ​​the inner and outer protective layers 84 is larger, and on the basis of reducing the stress concentration, the effect of reducing cracking and active material shedding is better played. In addition, in the case where the protective layer 84 exceeds the bending part in the winding axis direction L, so that the offset part of the inner and outer protective layers 84 leaks out of the bonding surface, the offset size is limited to no more than 2 mm, which can reduce the occurrence of adhesion to the roller during winding due to the leaking bonding surface being too large.

[0155] In some embodiments, one end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a first set dimension d1 in the winding direction C, and the first set dimension d1 does not exceed 1.5 mm, and / or, the other end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a second set dimension d2 in the winding direction C, and the second set dimension d2 does not exceed 1.5 mm.

[0156] The offset size is limited to no more than 1.5 mm, so that the offset size is not too large, so that the overlapping area of ​​the inner and outer protective layers 84 is larger, and on the basis of reducing the stress concentration, the effect of reducing cracking and active material shedding is better played. In addition, in the case where the protective layer 84 exceeds the bending part in the winding axis direction L, so that the offset part of the inner and outer protective layers 84 leaks out of the bonding surface, the offset size is limited to no more than 1.5 mm, which can reduce the occurrence of adhesion to the roller during winding due to the leaking bonding surface being too large.

[0157] In some embodiments, one end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a first set dimension d1 in the winding direction C, and the first set dimension d1 does not exceed 1 mm, and / or, the other end portion of the protective layer 84 on the inner and outer sides of the same bending portion along the winding direction C is staggered by a second set dimension d2 in the winding direction C, and the second set dimension d2 does not exceed 1 mm.

[0158] The offset size is limited to no more than 1 mm, so that the offset size is not too large, so that the overlapping area of ​​the inner and outer protective layers 84 is larger, and on the basis of reducing the stress concentration, the effect of reducing cracking and active material shedding is better played. In addition, in the case where the protective layer 84 exceeds the bending part in the winding axis direction L, so that the offset part of the inner and outer protective layers 84 leaks out of the bonding surface, the offset size is limited to no more than 1 mm, which can reduce the occurrence of adhesion to the roller during winding due to the leaking bonding surface being too large.

[0159] In some embodiments, Figure 5 , Figures 11 to 13 As shown, 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, 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, at least one protective layer 84 is attached to the side of the bent portion at both ends along the winding direction C, or, at least one protective layer 84 is attached to the side of the bent portion at the middle portion along the winding direction C, and the two ends extend to the sides of two straight portions adjacent to the bent portion, respectively.

[0160] See also Figure 5 The electrode assembly 8 is a flat body, and the protective layer 84 can be formed in three situations according to different distribution positions. Fig.11The protective layers 84 on both 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. Fig.12 The outer protective layer 84 is attached to the side of the bent portion at both ends along the winding direction C. Fig.12 The inner protective layer 84 is attached to the side of the bent portion in the middle portion along the winding direction C, and both ends extend to the side of the two straight portions adjacent to the bent portion.

[0161] As mentioned above, for the flat electrode assembly 8, the above three conditions of the protective layer 84 can reduce the risk of cracking of the pole piece 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.

[0162] In some embodiments, the protection layer 84 includes a main layer made of a polymer material.

[0163] The main layer made of polymer material 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.

[0164] In some embodiments, the polymer material is any one or more combinations 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.

[0165] The above materials are easy to obtain and have good toughness and strength, which can reduce the risk of indentation or cracking of the pole piece, thereby reducing the risk of abnormal self-discharge, and further reducing the risk of thermal runaway and fire.

[0166] 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.

[0167] The main body layer is bonded to the side of the bent portion through the adhesive layer, so that the protective layer 84 is bonded to the bent portion. The bonding method makes the main body layer firmly attached to the bent portion, and the bonding operation is simple and quick.

[0168] 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, any one or a combination of more of them.

[0169] The above material is easy to obtain and has good adhesion, and can firmly adhere the main body layer to the bent part.

[0170] In some embodiments, the protective layer 84 includes an ion-permeable portion and / or an ion-blocking portion.

[0171] The ion-permeable portion is a structure having a large number of through pores and capable of ensuring 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.

[0172] The ion blocking part is a structure without pores or with extremely small pores, which does not allow active ions to pass through. The material of the ion blocking part is any one or a combination of multiple 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.

[0173] Both the ion-permeable portion and the ion-blocking portion can provide a certain degree of support for the electrode, thereby 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.

[0174] In some embodiments, the air permeability of the ion-permeable portion comprises 220±70 sec / 100 cc, wherein sec stands for seconds and cc stands for cubic centimeters.

[0175] The 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 1.21 kPa, and the area through which 100 ml of air passes is 6.45 cm 2 The time required to separate the parts. The applied pressure of 1.21 kPa is a constant pressure, and the 6.45 cm 2 The area is a fixed area. 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.

[0176] 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 precipitation due to too fast a speed.

[0177] Exemplarily, 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 are not described here one by one.

[0178] In some embodiments, the minimum size of the pores of the ion-permeable portion is in the range of 100 nm to 400 nm.

[0179] The size of the pores of the ion-permeable portion can be measured by a scanning electron microscope (SEM).

[0180] The pores are used for active ions such as sodium ions and lithium ions to pass through, and 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 .

[0181] In some embodiments, the protective layers 84 on the inner and outer sides of the bent portion of the positive electrode sheet 81 include ion-permeable portions respectively; the protective layers 84 on the inner and outer sides of the negative electrode sheet 82 include ion-permeable portions respectively.

[0182] 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 .

[0183] In some embodiments, the protective layers 84 on the inner and outer sides of the bent portion of the positive electrode sheet 81 include ion blocking portions, respectively; and the protective layers 84 on the inner and outer sides of the negative electrode sheet 82 include ion permeable portions, respectively.

[0184] 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 inner and outer sides of the negative electrode plate 82 include ion permeable portions respectively.

[0185] The positive electrode sheet 81 and the negative electrode sheet 82 need to be bent. The negative electrode sheet 82 on the inner side 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 positive electrode sheet 81 adjacent to the outer side, thereby causing lithium precipitation. Therefore, an ion blocking portion is attached to the inner side 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 outer side of the bent portion of the positive electrode sheet 81 can complete the normal deintercalation and shuttling of ions, give full play to the capacity of the battery cell 7, and thus increase 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 insertion and removal 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.

[0186] 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, and a protective layer 84 is attached to both the inner and outer sides of the bent portion of the positive electrode plate 81 .

[0187] 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.

[0188] In some embodiments, a protective layer 84 is attached to both inner and outer sides of the two innermost bent portions of the positive electrode sheet 81 .

[0189] The innermost bent portion of the positive electrode sheet 81 is the most bent and most susceptible to cracking. Therefore, a protective layer 84 is attached to both inner and outer sides of the two innermost bent portions to effectively reduce the risk of cracking of the positive electrode sheet 81 and separation of the active material.

[0190] 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.

[0191] 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 to the outside.

[0192] The bending degree of the second and third bends is relatively large and is more prone to cracking. Therefore, the protective layer 84 is attached to both the inner and outer sides of the two bends of the second and third bends, which can well reduce the risk of cracking of the positive electrode sheet 81 and separation of the active material. Of course, the protective layer 84 can also be attached to the bends of the fourth, fifth and sixth bends, which is not specifically limited here.

[0193] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application is 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 replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. 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 application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An electrode assembly, characterized in that: include: A winding structure, wherein the winding 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; A protective layer, the protective layer being attached to both inner and outer sides of at least one of the bent portions; Wherein, at least one end portion of the protective layers on the inner and outer sides of the same bending portion along the winding direction is staggered.

2. The electrode assembly according to claim 1, characterized in that: The end portions of the protective layers on the inner and outer sides of the same bending portion along the winding direction are staggered respectively.

3. The electrode assembly according to claim 1, characterized in that: The two end portions of the protective layer on the inner side of the same bent portion along the winding direction respectively exceed the corresponding two end portions of the protective layer on the outer side; or The two end portions of the outer side of the protective layer of the same bent portion along the winding direction respectively exceed the corresponding two end portions of the inner side of the protective layer; or One end of the inner side of the same bending portion along the winding direction exceeds the corresponding end of the outer side of the protective layer, and the other end of the inner side of the protective layer along the winding direction is exceeded by the corresponding other end of the outer side of the protective layer.

4. The electrode assembly according to claim 1, characterized in that: Along the winding axis direction of the winding structure, at least one end of at least one of the protective layers exceeds the active material of the bent portion.

5. The electrode assembly according to any one of claims 1 to 4, characterized in that: One end portion of the protective layer on both 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 both sides of the same bending portion along the winding direction is staggered by a second set size in the winding direction. 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 4, characterized in that: One end portion of the protective layer on both sides of 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 portions of the protective layers on the inner and outer sides of the same bending portion along the winding direction are staggered by a second set dimension in the winding direction, and the second set dimension does not exceed 2 mm.

7. The electrode assembly according to any one of claims 1 to 4, characterized in that: One end portion of the protective layer on both 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 portions of the protective layers on the inner and outer sides of the same bending portion along the winding direction are staggered by a second set dimension in the winding direction, and the second set dimension does not exceed 1.5 mm.

8. The electrode assembly according to any one of claims 1 to 4, characterized in that: One end portion of the protective layer on both 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 portions of the protective layers on the inner and outer sides of the same bending portion along the winding direction are staggered by a second set dimension in the winding direction, and the second set dimension does not exceed 1 mm.

9. The electrode assembly according to any one of claims 1 to 8, characterized in that: The positive electrode sheet and the negative electrode sheet each include a plurality of straight portions, the plurality of bent portions and the plurality of straight portions of the positive electrode sheet are alternately arranged one by one along the winding direction, and the plurality of bent portions and the plurality of straight portions of the negative electrode sheet are alternately arranged one by one along the winding direction, At least one of the protective layers has one end in the winding direction attached to the side of the bent portion, and the other end extending to the side of the straight portion adjacent to the bent portion, or Both ends of at least one of the protective layers along the winding direction are attached to the side surfaces of the bent portion, or At least one of the protective layers is attached to the side surface of the bent portion at its middle portion along the winding direction, and both ends thereof extend to the side surfaces of the two straight portions adjacent to the bent portion, respectively.

10. The electrode assembly according to any one of claims 1 to 9, characterized in that: The protective layer comprises a main body layer made of a polymer material.

11. The electrode assembly according to claim 10, characterized in that: The polymer material is 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, and non-woven fabric.

12. The electrode assembly according to claim 10 or 11, characterized in that: The protective layer further comprises an adhesive layer, and the main body layer is bonded to the side surface of the bent portion through the adhesive layer.

13. The electrode assembly according to claim 12, characterized in that: The material of the adhesive layer is 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.

14. The electrode assembly according to any one of claims 1 to 13, characterized in that: The protective layer includes an ion-permeable portion and / or an ion-blocking portion.

15. The electrode assembly according to claim 14, characterized in that: The protective layers on both 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; The protective layers on both inner and outer sides of the negative electrode sheet respectively include the ion-permeable portions.

16. The electrode assembly according to claim 14 or 15, characterized in that: The air permeability of the ion-permeable portion includes 220±70sec / 100cc.

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

18. The electrode assembly according to any one of claims 1 to 17, characterized in that: 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 part of the positive electrode plate.

19. The electrode assembly according to any one of claims 1 to 18, characterized in that: The protective layer is attached to both inner and outer sides of the two bent parts of the innermost circle of the positive electrode plate.

20. A battery cell, characterized in that: include: A housing, a cover plate and at least one electrode assembly according to any one of claims 1 to 19, wherein: The shell 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, characterized in that: include: Box; At least one battery cell as claimed in claim 20, wherein the battery cell is accommodated in the box.

22. An electrical device, characterized in that: The electrical device comprises the battery cell according to claim 20 or the battery according to claim 21 for providing electrical energy.

Images