Electrode assembly and battery

Abstract

The invention belongs to the technical field of batteries, and discloses an electrode assembly and a battery, the electrode assembly is formed by winding a first pole piece, a diaphragm and a second pole piece, and the diaphragm is located between the first pole piece and the second pole piece; the electrode assembly further comprises a transition structure, the transition structure is arranged at the tail end of the second pole piece, the tail end of the first pole piece exceeds the end, away from the tail end of the second pole piece, of the transition structure, and the transition structure is used for providing a deformation space for deformation of the first pole piece in the thickness direction. According to the electrode assembly and the battery provided by the invention, the risk of foil breakage is reduced, and the electrode assembly and the battery have relatively high safety and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrode assembly and a battery. Background Art

[0002] Cylindrical batteries are widely used in electric vehicles, aircraft and other fields due to their high energy density and high safety.

[0003] In the prior art, the electrode assembly of a cylindrical battery is formed by stacking a positive electrode sheet, a separator, and a negative electrode sheet in sequence and then winding them together. In addition, in order to make full use of the material on the positive electrode sheet, the tail end of the negative electrode sheet must extend beyond the length of one end of the tail end of the negative electrode sheet so that the tail end of the negative electrode sheet can cover the tail end of the positive electrode sheet. The negative electrode sheet will expand during use, especially when the active material of the negative electrode sheet includes silicon, the expansion degree is even greater. Since the positive electrode sheet has a certain thickness, the negative electrode sheet will be squeezed by the tail end of the positive electrode sheet during expansion, which can easily cause the negative electrode sheet foil to break, thus posing a safety risk. In some solutions, a colloid can be pasted on the outermost circle of the negative electrode sheet. The setting of the colloid can prevent the outermost circle of the negative electrode sheet from breaking the foil. However, there is still a risk of breaking the foil in the 2nd to 5th circles of the negative electrode sheet from the outside to the inside.

[0004] Therefore, there is an urgent need for an electrode assembly and a battery that reduces the risk of foil breakage. Summary of the Invention

[0005] The first object of the present invention is to provide an electrode assembly to solve the technical problem in the prior art that the electrode foil is prone to breakage.

[0006] A second object of the present invention is to provide a battery with higher safety and reliability.

[0007] As conceived above, the technical solution adopted by the present invention is:

[0008] An electrode assembly, wherein the electrode assembly is formed by winding a first electrode sheet, a separator, and a second electrode sheet, wherein the separator is located between the first electrode sheet and the second electrode sheet;

[0009] The electrode assembly also includes a transition structure, which is arranged at the tail end of the second pole piece. The tail end of the first pole piece extends beyond the end of the transition structure away from the tail end of the second pole piece. The transition structure is used to provide deformation space for the deformation of the first pole piece in its thickness direction.

[0010] In one embodiment, the transition structure is formed by extending from the tail end of the second pole piece, and the thickness of the transition structure is less than the thickness of the second pole piece.

[0011] In one embodiment, the second pole piece is a double-sided coating structure, and the transition structure is a single-sided coating structure.

[0012] In one embodiment, the second pole piece and the transition structure are both double-sided coating structures, and the thickness of the transition structure gradually decreases along the extension direction away from the tail end of the second pole piece.

[0013] In one embodiment, the transition structure includes a first current collector and a first coating, and both sides of the first current collector have the first coating; along the extension direction away from the tail end of the second pole piece, the thickness of at least one of the first coatings gradually decreases.

[0014] In one embodiment, the thickness of the first coating layer is reduced by a range of 4 um / mm to 9 um / mm.

[0015] In one embodiment, the transition structure includes a second current collector and a first elastic coating, the second current collector and the third current collector of the second pole piece are an integrated structure, and at least one surface of the second current collector is provided with the first elastic coating;

[0016] Alternatively, the tail end of the diaphragm extends beyond the tail end of the second pole piece, and the transition structure includes a second elastic coating provided on the surface of the diaphragm facing away from the first pole piece, and the thickness of the second elastic coating is less than or equal to the thickness of the second pole piece.

[0017] In one embodiment, the surface of the second elastic coating facing away from the tail end of the second pole piece is flush with the end surface of the tail end of the first pole piece.

[0018] In one embodiment, in the length direction of the first pole piece, the dimension of the transition structure is L, wherein 20 mm ≤ L ≤ 40 mm; and / or,

[0019] In the length direction of the first pole piece, the size of the transition structure is L; the distance between the transition structure and the end face of the tail end of the first pole piece is D, and the ratio of L to D ranges from 1 to 4.

[0020] A battery comprises the electrode assembly as described above.

[0021] Beneficial effects of the present invention:

[0022] The electrode assembly provided by the present invention is provided with a transition structure at the tail end of the second pole piece, and the tail end of the first pole piece extends beyond the end of the transition structure away from the tail end of the second pole piece. Since the transition structure has a certain thickness, the tangential force on the first pole piece caused by the sudden change in the thickness of the tail end of the second pole piece can be reduced, thereby reducing the risk of foil breaking in the outermost circle of the first pole piece. Since the transition structure can provide deformation space for the deformation of the first pole piece in its thickness direction, the extrusion force applied by the tail end of the second pole piece to the outermost circle of the first pole piece and multiple circles of the electrode assembly from the outside to the inside is reduced, thereby reducing the risk of foil breaking in the outermost circle of the first pole piece and multiple circles of the electrode assembly from the outside to the inside, and can effectively improve the foil breaking problem of the electrode assembly, thereby improving the safety and reliability of the electrode assembly and the battery using the electrode assembly.

[0023] The battery provided by the present invention has high safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in describing the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without any creative work.

[0025] Figure 1 is a schematic structural diagram of an electrode assembly provided by an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of a partial structure of an electrode assembly provided by an embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of the partial structure of the first electrode assembly provided by an embodiment of the present invention;

[0028] Figure 4 is a schematic diagram of a partial structure of a second electrode assembly provided by an embodiment of the present invention;

[0029] Figure 5 is a partial structural diagram of a third electrode assembly provided by an embodiment of the present invention;

[0030] Figure 6 is a schematic diagram of a partial structure of a fourth electrode assembly provided by an embodiment of the present invention;

[0031] Figure 7 is a partial structural diagram of a fifth electrode assembly provided by an embodiment of the present invention;

[0032] Figure 8It is a schematic diagram of the partial structure of the sixth electrode assembly provided in an embodiment of the present invention.

[0033] In the picture:

[0034] 100, first pole piece; 200, diaphragm; 300, second pole piece; 310, third current collector; 320, pole piece coating; 400, transition structure; 410, first current collector; 420, first coating; 430, second current collector; 440, first elastic coating; 450, second elastic coating. DETAILED DESCRIPTION

[0035] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved more clearly, the technical solutions of the present invention are further described below with reference to the accompanying drawings and through specific embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the drawings only show portions relevant to the present invention, not all of them.

[0036] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0037] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0038] In the present invention, unless otherwise clearly stipulated and limited, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. Moreover, the first feature being "above", "above" and "above" the second feature includes the first feature being directly above and diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature. In the description of this embodiment, unless otherwise specified, "multiple" specifically refers to two or more.

[0039] In the description of this embodiment, terms such as "center," "longitudinal," "transverse," "length," "width," "thickness," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate description and simplify operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be understood as limiting the present invention. In addition, the terms "first" and "second" are used only to distinguish in the description and have no special meaning.

[0040] It should be noted that when an element is referred to as being “fixed to” or “disposed on” another element, it may be directly on the other element or there may be an element located in the middle.

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0042] This embodiment provides an electrode assembly that can reduce the risk of foil breakage and has a longer service life.

[0043] For example, Figures 1 to 8 As shown, the electrode assembly is formed by winding a first electrode sheet 100, a separator 200, and a second electrode sheet 300, wherein the separator 200 is located between the first electrode sheet 100 and the second electrode sheet 300. One of the first electrode sheet 100 and the second electrode sheet 300 is a positive electrode sheet, and the other is a negative electrode sheet. For example, in this embodiment, the first electrode sheet 100 is a negative electrode sheet, and the second electrode sheet 300 is a positive electrode sheet.

[0044] Optionally, the positive electrode sheet may generally include a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is directly or indirectly coated on the positive electrode current collector, the positive electrode current collector not coated with the positive electrode active material layer protrudes from the positive electrode current collector coated with the positive electrode active material layer, the positive electrode current collector not coated with the positive electrode active material layer serves as a positive electrode tab, and multiple positive electrode tabs are stacked together and electrically connected to the positive electrode column. The positive electrode current collector is usually a metal foil, such as aluminum foil. For example, the multiple positive electrode tabs stacked together can be directly welded to the positive electrode column to form an electrical connection; or, the battery cell assembly may further include a positive electrode adapter sheet, the multiple positive electrode tabs stacked together are welded to one end of the positive electrode adapter sheet, and the other end of the positive electrode adapter sheet is welded to the positive electrode column to form an electrical connection between the positive electrode tab sheet and the positive electrode column.

[0045] The negative electrode sheet can generally include a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is directly or indirectly coated on the negative electrode current collector. The negative electrode current collector not coated with the negative electrode active material layer protrudes from the negative electrode current collector coated with the negative electrode active material layer. The negative electrode current collector not coated with the negative electrode active material layer serves as a negative electrode tab. Multiple negative electrode tabs are stacked together and electrically connected to the negative electrode post. The negative electrode current collector is usually a metal foil, such as copper foil or aluminum foil. For example, the multiple stacked negative electrode tabs can be directly welded to the negative electrode post to form an electrical connection; alternatively, the battery cell assembly can further include a negative electrode adapter sheet. The multiple stacked negative electrode tab sheets are welded to one end of the negative electrode adapter sheet, and the other end of the negative electrode adapter sheet is welded to the negative electrode post to form an electrical connection between the negative electrode tab sheet and the negative electrode post. The material of the separator is not limited, for example, it can be polypropylene or polyethylene.

[0046] The diaphragm 200 has the functions of electronic insulation and ion conduction. In this embodiment, there is no particular limitation on the type of diaphragm 200, and any known porous structure diaphragm with good chemical and mechanical stability can be selected. As an example, the main material of the diaphragm can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The diaphragm can be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0047] It should be noted that both the first pole piece 100 and the second pole piece 300 have a head end and a tail end. The head end of the first pole piece 100 refers to the end located at the winding center of the electrode assembly, that is, the starting end of the first pole piece 100 along the winding direction, and the tail end of the first pole piece 100 refers to the end located at the outermost circle of the battery cell pole piece, that is, the end of the first pole piece 100 along the winding direction; the head end of the second pole piece 300 refers to the end located at the winding center of the electrode assembly, that is, the starting end of the second pole piece 300 along the winding direction, and the tail end of the second pole piece 300 refers to the end located at the outermost circle of the battery cell pole piece, that is, the end of the second pole piece 300 along the winding direction.

[0048] For example, Figure 3 As shown, the electrode assembly further includes a transition structure 400. The transition structure 400 is disposed at the tail end of the second pole piece 300, and the tail end of the first pole piece 100 extends beyond the end of the transition structure 400 away from the tail end of the second pole piece 300. That is, the first pole piece 100 extends beyond the tail end of the second pole piece 300 and beyond the transition structure 400. In other words, the orthographic projection of the transition structure 400 on the first pole piece 100 is located within the first pole piece 100 and does not extend beyond the first pole piece 100. The transition structure 400 is used to provide deformation space for the first pole piece 100 to deform in its thickness direction.

[0049] The electrode assembly provided in this embodiment is provided with a transition structure 400 at the tail end of the second pole piece 300, and the tail end of the first pole piece 100 extends beyond the transition structure 400 and is away from one end of the tail end of the second pole piece 300. Since the transition structure 400 has a certain thickness, the tangential force on the first pole piece 100 caused by the sudden change in the thickness of the tail end of the second pole piece 300 can be reduced, thereby reducing the risk of foil breaking at the outermost circle of the first pole piece 100. Since the transition structure 400 can provide deformation space for the deformation of the first pole piece 100 in its thickness direction, the extrusion force applied by the tail end of the second pole piece 300 to the outermost circle of the first pole piece 100 and multiple circles of the electrode assembly from the outside to the inside is reduced, thereby reducing the risk of foil breaking at the outermost circle of the first pole piece 100 and multiple circles of the electrode assembly from the outside to the inside, which can effectively improve the foil breaking problem of the electrode assembly and improve the safety and reliability of the electrode assembly and the battery using the electrode assembly.

[0050] Optionally, the transition structure 400 may be an independent structure relative to the first pole piece 100, the diaphragm 200, and the second pole piece 300, that is, the material of the transition structure 400 is different from that of the first pole piece 100, the diaphragm 200, and the second pole piece 300. Alternatively, the transition structure 400 may be formed by extending from the tail end of the second pole piece 300, that is, the material of the transition structure 400 is at least partially the same as that of the second pole piece 300, which is not limited in this embodiment.

[0051] The following describes in detail the specific structure of the transition structure 400 formed by extending from the tail end of the second pole piece 300. Of course, in other embodiments, the transition structure 400 can also be provided on the tail end of the second pole piece 300 by direct connection, indirect connection, or contact arrangement, which is not limited in this embodiment.

[0052] For example, Figures 3 to 5 As shown, the transition structure 400 is formed by extending from the tail end of the second pole piece 300, and the thickness of the transition structure 400 is less than that of the second pole piece 300. Thus, on the one hand, the transition structure 400 can be formed by thinning the second pole piece 300, which facilitates the processing and manufacturing of the transition structure 400; on the other hand, the material of the transition structure 400 is partially the same as that of the second pole piece 300, so that the electrode assembly does not introduce new materials due to the provision of the transition structure 400, thereby ensuring the safety of the electrode assembly.

[0053] It should be noted that the transition structure 400 is formed by extending from the tail end of the second pole piece 300, which means that the transition structure 400 also includes a current collector and an active material coating. The current collector of the transition structure 400 and the current collector of the second pole piece 300 are integrally formed as a one-piece structure, and the active material coating of the transition structure 400 and the active material coating of the second pole piece 300 are integrally formed as a one-piece structure.

[0054] There are many ways to realize that the thickness of the transition structure 400 is smaller than the thickness of the second pole piece 300 .

[0055] In some optional embodiments, such as Figure 3 As shown, the second pole piece 300 has a double-sided coating structure, and the transition structure 400 has a single-sided coating structure. For ease of understanding, the coating of the second pole piece 300 is referred to as the pole piece coating 320. Since the transition structure 400 lacks a coating layer, the thickness of the transition structure 400 is less than that of the second pole piece 300. By setting the transition structure 400 as a single-sided coating structure, on the one hand, when the first pole piece 100 is deformed, the thickness of the tail end of the second pole piece 300 does not suddenly drop to zero, so the tangential force on the first pole piece 100 is reduced, reducing the risk of foil breakage. On the other hand, since there is a gap on one side of the transition structure 400 in the thickness direction, the transition structure 400 can also deform when the first pole piece 100 in contact with it deforms. Therefore, it does not come into hard contact with the first pole piece 100, and does not cause the first pole piece 100 to break or crack due to extrusion. Moreover, when the first pole piece 100 is deformed to a certain extent, it will be supported by the transition structure 400, so that the transition structure 400 can not only provide expansion space for the expansion of the first pole piece 100, but also support the first pole piece 100, thereby reducing the problems of foil breakage, cracking, etc. of the first pole piece 100, thereby ensuring the safety and reliability of the electrode assembly.

[0056] It should be noted that a double-sided coating structure refers to a current collector with an active material coating on both sides, while a single-sided coating structure refers to a current collector with an active material coating on only one side. When the transition structure 400 has a single-sided coating structure, the active material coating of the transition structure 400 can be oriented toward the winding center of the electrode assembly or toward the outermost first electrode sheet 100, although this embodiment does not limit this.

[0057] In some other optional embodiments, such as Figure 4As shown, both the second pole piece 300 and the transition structure 400 are double-sided coating structures, that is, both sides of the current collector of the second pole piece 300 and the transition structure 400 are coated with active material. In addition, the thickness of the transition structure 400 gradually decreases along the extension direction away from the tail end of the second pole piece 300. Since the deformation law of the portion of the first pole piece 100 extending beyond the second pole piece 300 is that the deformation amplitude becomes larger and larger along the extension direction away from the tail end of the second pole piece 300, by setting the transition structure 400 as a structure with a gradual thickness change, the thickness of the transition structure 400 becomes smaller and smaller along the extension direction away from the tail end of the second pole piece 300, so that the shape of the transition structure 400 can match the deformation amplitude of the first pole piece 100, thereby better supporting the first pole piece 100 and reducing the risk of cracking of the first pole piece 100.

[0058] It should be noted that the extension direction away from the tail end of the second pole piece 300 can be understood as the direction in which the end of the transition structure 400 connected to the tail end of the second pole piece 300 points away from the end of the second pole piece 300 .

[0059] In some optional embodiments, please continue to see Figure 4 The transition structure 400 includes a first current collector 410 and a first coating 420. The first coating 420 can be the active material coating mentioned above or other materials, which is not limited in this embodiment. Both sides of the first current collector 410 have a first coating 420. Along the extension direction away from the tail end of the second pole piece 300, the thickness of at least one first coating 420 gradually decreases. Figure 4 The structure in which the thickness of the two first coatings 420 gradually decreases along the extension direction away from the tail end of the second pole piece 300 is shown. Figure 5 The figure shows a structure in which the thickness of one of the first coatings 420 gradually decreases along the extension direction away from the tail end of the second pole piece 300. Figure 4 or Figure 5 The structures shown can achieve the effect of reducing the risk of foil breakage of the first pole piece 100.

[0060] Optionally, the thickness of at least one first coating layer 420 gradually decreases along the extension direction away from the tail end of the second pole piece 300, and the range of the reduction in thickness of the first coating layer 420 is 4 μm / mm-9 μm / mm. In this way, the reduction in thickness of the first coating layer 420 can satisfy the requirements of providing expansion space for the first pole piece 100 and effectively supporting the first pole piece 100, further reducing the risk of foil breakage of the first pole piece 100.

[0061] For example, the thickness of the first coating 420 is reduced by 4 um / mm, 5 um / mm, 6 um / mm, 7 um / mm, 8 um / mm, 9 um / mm, etc.

[0062] Hereinafter, this embodiment will describe in detail the specific structure of the transition structure 400 when it is an independent structure.

[0063] In one embodiment, Figure 6 As shown, the transition structure 400 includes a second current collector 430 and a first elastic coating 440. The second current collector 430 and the third current collector 310 of the second pole piece 300 are an integral structure. The first elastic coating 440 is capable of elastic deformation. For example, the material of the first elastic coating 440 can be an elastic material. By providing the first elastic coating 440, when the first pole piece 100 is deformed, the first elastic coating 440 is squeezed, causing the first elastic coating 440 to elastically deform. In this way, it can provide expansion space for the expansion of the first pole piece 100 and can also elastically support the first pole piece 100, thereby reducing the risk of damaging the first pole piece 100 and having higher reliability. By providing the second current collector 430 of the transition structure 400 as an integral structure integrally formed with the third current collector 310 of the second pole piece 300, full use is made of the second pole piece 300, the preparation of the second current collector 430 is facilitated, and the structural complexity of the transition structure 400 is reduced.

[0064] In some optional embodiments, at least one surface of the second current collector 430 is provided with a first elastic coating 440, that is, one surface of the second current collector 430 may be provided with the first elastic coating 440, or both surfaces of the second current collector 430 may be provided with the second elastic coating 450, which is not limited in this embodiment. Figure 6 The structure in which the first elastic coating layer 440 is provided on both surfaces of the second current collector 430 is shown.

[0065] Illustratively, the material of the first elastic coating layer may be elastic materials such as rubber and silicone, which is not limited in this embodiment.

[0066] In other embodiments, the transition structure 400 may not include the second current collector 430, for example, Figure 7As shown, the tail end of the diaphragm 200 extends beyond the tail end of the second pole piece 300, that is, the diaphragm 200 has a portion located between the first pole piece 100 and the second pole piece 300, and also has a portion located on one side of the first pole piece 100 and extending beyond the second pole piece 300. At this time, the transition structure 400 includes a second elastic coating 450 provided on the surface of the diaphragm 200 facing away from the first pole piece 100. In this way, the second elastic coating 450 of the transition structure 400 can be fixedly connected to the tail end of the second pole piece 300 and / or the diaphragm 200 without the need to use the extended current collector for connection, thereby reducing the material used for the current collector and thus reducing the cost of the electrode assembly. In addition, the fixing method of the transition structure 400 is relatively simple and easy to operate. Optionally, the second elastic coating 450 in this embodiment can be fixedly connected to the diaphragm 200 to facilitate the assembly of the transition structure 400 in the electrode assembly.

[0067] In one embodiment, Figure 7 As shown, the thickness of the second elastic coating 450 can be less than the thickness of the second pole piece 300. This configuration allows the second elastic coating 450 to not only provide deformation space for the deformation of the first pole piece 100 due to its own elasticity, but also facilitates the gap on one side thereof to further elastically deform, thereby providing a larger deformation space for the deformation of the first pole piece 100, thereby reducing the risk of damaging the first pole piece 100 and having higher reliability.

[0068] In other embodiments, Figure 8 As shown, the thickness of the second elastic coating 450 can also be equal to the thickness of the second pole piece 300. Because the second elastic coating 450 can undergo elastic deformation, the second elastic coating 450 does not apply a tangential force to the first pole piece 100, thereby preventing the problem of foil breakage of the first pole piece 100. In this embodiment, the material of the second elastic coating 450 can be an elastic material such as rubber or silicone, which is not limited in this embodiment.

[0069] In one embodiment, Figure 8 As shown, the surface of the second elastic coating 450 facing away from the tail end of the second pole piece 300 is flush with the end face of the tail end of the first pole piece 100. That is, the surface of the second elastic coating 450 facing away from the tail end of the second pole piece 300 is coplanar with the end face of the tail end of the first pole piece 100. This arrangement can better support the first pole piece 100, reducing the risk of the first pole piece 100 being bent too much and breaking due to lack of support, thereby improving safety and reliability.

[0070] Alternatively, as Figure 3As shown, in the length direction of the first pole piece 100, the size of the transition structure 400 is L, where 20mm≤L≤40mm. It should be noted that the size of the transition structure 400 in the length direction of the first pole piece 100 is L, which can also be understood as the length of the transition structure 400 in its extension direction is L. By controlling the size of the transition structure 400 in the length direction of the first pole piece 100 to be within the above-mentioned range, the tail end of the first pole piece 100 can be effectively supported, and expansion space can be provided for the tail end of the outermost circle of the first pole piece 100 and multiple circles of the electrode assembly from the outside to the inside, thereby reducing the risk of the first pole piece 100 breaking the foil due to large tangential force, and improving the safety and reliability of the electrode assembly.

[0071] The dimension L of the transition structure 400 along the length of the first pole piece 100 cannot be too large. If it is too large, the support effect and anti-foil breakage effect of the first pole piece 100 will not be significantly improved, and the energy density of the electrode assembly will be reduced. The dimension L of the transition structure 400 along the length of the first pole piece 100 cannot be too small. If it is too small, there will still be the problem of excessive tangential force applied to the first pole piece 100, resulting in a higher risk of foil breakage of the first pole piece 100.

[0072] For example, the value of L is 20mm, 22mm, 25mm, 28mm, 30mm, 32mm, 35mm, 38mm, 40mm, etc.

[0073] In some optional embodiments, when the transition structure 400 does not include a component made of elastic material, in order to prevent the transition structure 400 from damaging the outermost first pole piece 100, the transition structure 400 is usually not flush with the end surface of the first pole piece 100. Figure 3 In the length direction of the first pole piece 100, the dimension of the transition structure 400 is L; the distance between the transition structure 400 and the end surface of the first pole piece 100 is D, where the ratio of L to D ranges from 1 to 4. This ensures that the transition structure 400 has a larger dimension in the length direction of the first pole piece 100, while preventing the end surface of the transition structure 400 facing away from the end of the second pole piece 300 from being flush with the end surface of the first pole piece 100. Consequently, the transition structure 400 will not damage the first pole piece 100, thereby preventing the first pole piece 100 from breaking.

[0074] This embodiment further provides a battery, comprising the above-mentioned electrode assembly. The battery provided by this embodiment has high safety and reliability.

[0075] Optionally, the battery can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel metal hydride battery, a nickel cadmium battery, a lead storage battery, etc., which is not limited in this embodiment.

[0076] In order to extend the effect of the battery provided by this embodiment, this embodiment provides 5 embodiments and 1 comparative example for illustration.

[0077] Example 1

[0078] Example 1 provides a battery. Specifically, to achieve higher energy density, the main active material of the positive electrode sheet is a ternary material, which is mixed with a binder, a conductive agent, and a solvent. Among them, the ternary material accounts for 98%. The slurry obtained after mixing is evenly coated on the current collector of the positive electrode sheet, wherein the thickness of the current collector of the positive electrode sheet is 12um. The double-sided coating weight is 50mg / cm 2 It should be noted that, along the length direction of the positive electrode sheet, a single-sided coating area is provided in the tail region of the positive electrode sheet with a length of about 30 mm to form a transition structure 400, that is, the transition structure 400 at this time is a part of the positive electrode sheet. At this time, the transition structure 400 in Example 1 has a size of 30 mm in the length direction of the positive electrode sheet, and the transition structure 400 is Figure 3 The structure shown in Figure 1. The total thickness of the positive electrode sheet after rolling is 157 μm. Finally, it is cut into positive electrode sheets of the required width.

[0079] To improve the overall energy density of the battery, the main active material of the negative electrode is a mixture of graphite and silicon-based materials, of which silicon-based materials account for 20%. Mixed with a binder, a conductive agent, and a solvent, the main active material accounts for 96%. The mixed slurry is evenly coated on the current collector of the negative electrode, where the thickness of the current collector of the negative electrode is 6um. The double-sided coating weight is 22mg / cm 2 The total thickness of the electrode sheet after rolling is 146 μm. Finally, it is cut into negative electrode sheets of the required width.

[0080] The positive and negative electrode sheets are wound into a cylindrical electrode assembly using a 10 μm thick separator 200. The distance (D) between the transition structure 400 and the end face of the negative electrode sheet is 15 mm. The electrode assembly diameter is set to 46 mm. Finally, the corresponding assembly steps are completed to complete the battery.

[0081] It should be noted that the positive electrode sheet of Example 1 is the second electrode sheet 300 , and the negative electrode sheet is the first electrode sheet 100 .

[0082] The battery in Example 1 was then cycled at 25°C, with a 0.5C charge / 1C discharge cycle and a voltage range of 2.5V-4.2V. After 200, 400, and 600 cycles, the battery was disassembled to observe the condition of the electrode sheets at the end of the electrode assembly. The test data is shown in Table 1.

[0083] Example 2

[0084] The difference between Example 2 and Example 1 is that the tail end of the positive electrode sheet is coated with a gradient, thereby obtaining Figure 4 The transition structure 400 shown is a portion of the positive electrode sheet. The transition structure 400 is 30 mm long along the length of the positive electrode sheet. The thickness of the first coating 420 of the transition structure 400 decreases gradually along the direction away from the rear end of the second electrode sheet 300, with the reduction rate being 5 μm / mm. The end of the transition structure 400, facing away from the rear end of the second electrode sheet 300, comprises a 12 μm thick foil region.

[0085] The other structures of the battery provided in Example 2 (such as the separator, the negative electrode plate, the assembly of the battery, etc.) are exactly the same as the corresponding structures in Example 1 and will not be repeated here.

[0086] The battery in Example 2 was then cycled at 25°C, with a 0.5C charge / 1C discharge cycle and a voltage range of 2.5V-4.2V. After 200, 400, and 600 cycles, the battery was disassembled to observe the condition of the electrode sheets at the end of the electrode assembly. The test data is shown in Table 1.

[0087] Example 3

[0088] The difference between Example 3 and Example 2 is that different coating process parameters are used on both sides of the tail end of the positive electrode sheet, thereby obtaining the following Figure 5 The transition structure 400 shown, that is, the transition structure 400 at this time is part of the positive electrode sheet. Among them, the length of the transition structure 400 in the longitudinal direction of the positive electrode sheet is 30mm. The first coating 420 on one side of the first current collector 410 of the transition structure 400 is a uniform thickness structure, that is, it is coated in a uniform and continuous coating manner. The first coating 420 on the other side of the first current collector 410 of the transition structure 400 is coated in a gradient manner, so that the thickness of the first coating 420 gradually decreases along the extension direction away from the tail end of the positive electrode sheet, and the reduction amplitude is 5um / mm. The thickness of the end of the transition structure 400 facing away from the tail end of the positive electrode sheet is 84um, specifically including the first coating 420 and the first current collector 410.

[0089] The other structures of the battery provided in Example 3 (such as the separator, the negative electrode plate, the assembly of the battery, etc.) are exactly the same as the corresponding structures in Example 1 or Example 2, and will not be repeated here.

[0090] The battery in Example 3 was then cycled at 25°C, with a 0.5C charge / 1C discharge cycle and a voltage range of 2.5V-4.2V. After 200, 400, and 600 cycles, the battery was disassembled to observe the condition of the electrode sheets at the end of the electrode assembly. The test data is shown in Table 1.

[0091] Example 4

[0092] The difference between Example 4 and Example 1 is that the transition structure uses elastic material instead of the active material of the positive electrode. Figure 6 As shown, the thickness of the transition structure 400 is equal to the thickness of the positive electrode sheet. Furthermore, a 30 mm empty foil area is reserved for the current collector at the end of the positive electrode sheet. The first elastic coating 440 of the transition structure 400 is coated on this empty foil area to obtain the transition structure 400. The thickness of the first elastic coating 440 on one side of the transition structure 400 is 72 μm.

[0093] The other structures of the battery provided in Example 4 (such as the separator, the negative electrode plate, the assembly of the battery, etc.) are exactly the same as the corresponding structures in Example 1 and will not be repeated here.

[0094] The battery in Example 4 was then cycled at 25°C, with a 0.5C charge / 1C discharge cycle and a voltage range of 2.5V-4.2V. After 200, 400, and 600 cycles, the battery was disassembled to observe the condition of the electrode sheets at the end of the electrode assembly. The test data is shown in Table 1.

[0095] Example 5

[0096] The difference between the battery provided in Example 5 and Example 1 is that the structures of the positive electrode sheet and the diaphragm are different. Specifically, Example 1 provides a battery. Specifically, in order to achieve higher energy density, the main active material of the positive electrode sheet adopts a ternary material, which is mixed with a binder, a conductive agent and a solvent. Among them, the proportion of ternary materials is 98%. The slurry obtained after mixing is evenly coated on the current collector of the positive electrode sheet, wherein the thickness of the current collector of the positive electrode sheet is 12um. The double-sided coating weight is 50mg / cm 2 The total thickness of the electrode after rolling is 157um.

[0097] The diaphragm in Example 5 is different from that in Example 1. Specifically, Figure 7As shown, the tail end of the diaphragm 200 is designed with a second elastic coating 450, which forms a transition structure 400. The second elastic coating 450 faces the positive electrode sheet. Along the length of the diaphragm 200, the coating length of the second elastic coating 450 is 15mm. The coating thickness is equal to half the thickness of the positive electrode sheet and is designed to be 78um. After winding, the second elastic coating 450 on the diaphragm 200 is sandwiched between the positive electrode sheet and the negative electrode sheet, thereby playing a supporting role. Among them, the thickness of the portion of the diaphragm 200 not provided with the second elastic coating 450 is 10um.

[0098] The other structures of the battery provided in Example 5 (such as the negative electrode plate, battery assembly, etc.) are exactly the same as the corresponding structures in Example 1 and will not be repeated here.

[0099] The battery in Example 5 was then cycled at 25°C, with a 0.5C charge / 1C discharge cycle and a voltage range of 2.5V-4.2V. After 200, 400, and 600 cycles, the battery was disassembled to observe the condition of the electrode sheets at the end of the electrode assembly. The test data is shown in Table 1.

[0100] Comparative Example

[0101] The positive electrode plate of the battery provided in the comparative example is exactly the same as the positive electrode plate in Example 5, that is, no special design is performed, and the negative electrode plate, diaphragm, assembly method and battery testing method in the comparative example are the same as those in Example 1, and will not be repeated here.

[0102] Table 1

[0103]

[0104] The battery cells of Examples 1-5 and the comparative example were disassembled after cycling, and the electrode conditions are shown in Table 1.

[0105] The disassembly results show that, compared to the comparative example, in Example 1, the thickness difference between the positive and negative electrode sheets was reduced from 157 μm to 72 μm and 84 μm, respectively, due to the single-sided coating of the tail end of the positive electrode sheet, forming a transition structure 400. No abnormal electrode sheet cracking was observed after 600 cycles. The phrase "no abnormal electrode sheet" in Table 1 refers to the absence of cracking, foil breakage, or coining.

[0106] In Example 2, since the tail end coating of the positive electrode sheet adopts a gradient thickness design to form a transition structure 400, there is no obvious thickness mutation between the negative electrode sheet and the positive electrode sheet, so no obvious abnormality is found after 600 cycles.

[0107] In Example 3, the tail coating of the positive electrode sheet adopts a single-sided gradient thickness design to form a transition structure 400. The thickness difference between the negative electrode sheet and the positive electrode sheet is 84 μm, and there is no cracking abnormality in the electrode sheet after 600 cycles.

[0108] The transition structure 400 in Examples 4 and 5 includes an elastic coating, which provides support and compensates for the thickness difference between the positive and negative electrode sheets. During cycling, the negative electrode sheet expands, but since there is no significant thickness difference, there are no noticeable abnormalities in the sheet after 600 cycles.

[0109] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. An electrode assembly, characterized in that The electrode assembly is formed by winding a first pole piece (100), a diaphragm (200) and a second pole piece (300), wherein the diaphragm (200) is located between the first pole piece (100) and the second pole piece (300); The electrode assembly further comprises a transition structure (400), wherein the transition structure (400) is arranged at the tail end of the second pole piece (300), the tail end of the first pole piece (100) extends beyond the transition structure (400) and is away from one end of the tail end of the second pole piece (300), and the transition structure (400) is used to provide deformation space for deformation of the first pole piece (100) in its thickness direction.

2. The electrode assembly according to claim 1, wherein The transition structure (400) is formed by extending the tail end of the second pole piece (300), and the thickness of the transition structure (400) is less than the thickness of the second pole piece (300).

3. The electrode assembly according to claim 2, characterized in that The second pole piece (300) is a double-sided coating structure, and the transition structure (400) is a single-sided coating structure.

4. The electrode assembly according to claim 2, wherein: The second pole piece (300) and the transition structure (400) are both double-sided coating structures, and the thickness of the transition structure (400) gradually decreases along an extension direction away from the tail end of the second pole piece (300).

5. The electrode assembly according to claim 4, characterized in that The transition structure (400) comprises a first current collector (410) and a first coating (420), wherein both sides of the first current collector (410) are provided with the first coating (420); and along an extension direction away from the tail end of the second pole piece (300), the thickness of at least one of the first coatings (420) gradually decreases.

6. The electrode assembly according to claim 5, characterized in that The range of the reduction in thickness of the first coating layer (420) is 4um / mm-9um / mm.

7. The electrode assembly according to claim 1, wherein: The transition structure (400) comprises a second current collector (430) and a first elastic coating (440); the second current collector (430) and the third current collector (310) of the second pole piece (300) are an integrated structure; at least one surface of the second current collector (430) is provided with the first elastic coating (440); Alternatively, the tail end of the diaphragm (200) extends beyond the tail end of the second pole piece (300), and the transition structure (400) includes a second elastic coating (450) provided on a surface of the diaphragm (200) facing away from the first pole piece (100), and a thickness of the second elastic coating (450) is less than or equal to a thickness of the second pole piece (300).

8. The electrode assembly according to claim 7, characterized in that The surface of the second elastic coating (450) facing away from the tail end of the second pole piece (300) is flush with the end surface of the tail end of the first pole piece (100).

9. The electrode assembly according to any one of claims 1 to 8, characterized in that: In the length direction of the first pole piece (100), the size of the transition structure (400) is L, wherein 20 mm ≤ L ≤ 40 mm; and / or, In the length direction of the first pole piece (100), the size of the transition structure (400) is L; the distance between the transition structure (400) and the end face of the tail end of the first pole piece (100) is D, and the ratio of L to D ranges from 1 to 4.

10. A battery, characterized in that Comprising the electrode assembly according to any one of claims 1 to 9.

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