An electrode assembly and a battery

Abstract

This invention provides an electrode assembly and a battery, relating to the field of electrode assembly technology. The electrode assembly is a wound structure formed by stacking positive and negative electrode sheets and winding them along a winding direction. The electrode assembly includes a straight region and a corner region, with the corner region located at both ends of the straight region. The positive electrode sheet includes a positive electrode starting segment located in the straight region, and the negative electrode sheet includes a negative electrode starting segment extending beyond the positive electrode starting segment in the opposite direction of the winding direction. The negative electrode starting segment extends through the corner region and terminates in the straight region. The projection of the positive electrode starting segment along a direction perpendicular to the straight region at least partially coincides with the projection of the negative electrode starting segment along a direction perpendicular to the straight region. The free end of the negative electrode starting segment shifts to form an approximately triangular shape with the negative electrode sheet, providing support for the corner region and reducing the collapse of the electrode assembly. This can further reduce the slippage of the negative electrode sheet and improve the problem of lithium plating in the corner region.

Description

Technical Field

[0001] This utility model relates to the field of electrode assembly technology, specifically to an electrode assembly and a battery. Background Technology

[0002] With the development of new energy technologies, batteries are being used more and more widely. Among them, wound cells are widely used because of their advantages such as mature technology, stable structure, and reliable performance.

[0003] A wound battery cell typically includes a flat area and corner areas at both ends of the flat area. During the cell production process, the electrode sheets of a wound battery cell are prone to slippage before hot pressing, which can increase the gap between the positive and negative electrode sheets in the corner area, making lithium plating more likely. This can lead to a decrease in battery energy density or even battery failure, affecting battery safety. Utility Model Content

[0004] In view of the problems existing in the prior art, the present invention provides an electrode assembly and a battery to improve the problem that the existing wound cell electrode sheets are prone to slippage, which leads to an increase in the gap between the positive and negative electrode sheets in the corner area.

[0005] To achieve the above and other related objectives, the first aspect of this utility model provides an electrode assembly. The electrode assembly is a wound structure formed by stacking a positive electrode sheet and a negative electrode sheet and then winding them along a winding direction. The electrode assembly includes a straight region and a corner region, with the corner region located at both ends of the straight region. The positive electrode sheet includes a positive electrode starting segment located in the straight region, and the negative electrode sheet includes a negative electrode starting segment extending beyond the positive electrode starting segment in the opposite direction of the winding direction. The negative electrode starting segment extends through the corner region and terminates in the straight region. The projection of the positive electrode starting segment along a direction perpendicular to the straight region at least partially coincides with the projection of the negative electrode starting segment along a direction perpendicular to the straight region.

[0006] In an exemplary embodiment of this application, the negative electrode starting segment includes a first segment close to the positive electrode starting segment, a second segment located in the corner region, and a third segment away from the positive electrode starting segment, wherein the first segment, the second segment, and the third segment are connected sequentially; the length of the third segment is greater than or equal to one-third of the length of the straight region in which the third segment is located, and less than or equal to one-half of the length of the straight region in which the third segment is located.

[0007] In an exemplary embodiment of this application, the free end of the negative electrode starting segment is disposed near one end of the flat region, and the free end of the positive electrode starting segment is disposed near the other end of the flat region; wherein, the length of the positive electrode starting segment exceeds one-half the length of the flat region.

[0008] In an exemplary embodiment of this application, the winding tail end of the positive electrode and the winding tail end of the negative electrode both terminate at the corner region.

[0009] In an exemplary embodiment of this application, the winding tail end of the positive electrode and the winding tail end of the negative electrode terminate in the same corner region; the winding tail end of the negative electrode is located outside the winding tail end of the positive electrode.

[0010] In an exemplary embodiment of this application, the electrode assembly includes adhesive tape, which is attached to the corner area where the winding tail ends of the positive electrode and the winding tail ends of the negative electrode are located, and extends bidirectionally to the straight area along the winding direction.

[0011] In an exemplary embodiment of this application, the negative electrode starting segment extends inward from the free end of the positive electrode starting segment and passes through the two corner areas.

[0012] In an exemplary embodiment of this application, the corner area that the positive electrode sheet passes through for the first time along the winding direction is the first corner area, and the other corner area is the second corner area; the distance from the free end of the negative electrode starting segment to the first corner area is 2 to 503 mm; the distance from the free end of the positive electrode starting segment to the second corner area is 7 to 505 mm.

[0013] In an exemplary embodiment of this application, the length of the overlapping area of ​​the projection of the positive electrode starting segment along the direction perpendicular to the straight region and the projection of the negative electrode starting segment along the direction perpendicular to the straight region along the first direction is 2 to 500 mm.

[0014] A second aspect of this application provides a battery comprising at least two electrode assemblies as described in any one of the above-mentioned methods.

[0015] In combination with existing technologies, the beneficial effects of this utility model are as follows:

[0016] The negative electrode of this application includes a negative electrode starting segment extending in the opposite direction of the positive electrode starting segment along the winding direction. The first corner region that the positive electrode passes through along the winding direction is called the first corner region, and the other corner region is called the second corner region. The negative electrode starting segment is at least partially located in the second corner region. The negative electrode starting segment forms a support in the second corner region, thereby reducing the displacement of the negative electrode at the first corner region. This improves the situation where the gap between the negative electrode and the positive electrode is too large at the first corner region due to the displacement of the negative electrode, effectively improving the lithium plating situation in the first corner region, improving the quality of the electrode assembly, and improving the battery quality.

[0017] The negative electrode starting section terminates in a flat region. The free end of the negative electrode starting section shifts to form an approximate triangle with the negative electrode sheet, improving stability and providing support for the corner region, thus reducing the collapse of the electrode assembly. At the same time, the triangle can further reduce the slippage of the negative electrode sheet, avoiding excessive gap between the negative and positive electrode sheets at the first corner region, and improving the lithium plating problem in the first corner region.

[0018] The projection of the positive electrode starting segment along the direction perpendicular to the flat region at least partially coincides with the projection of the negative electrode starting segment along the same direction perpendicular to the flat region. The support structure formed by the negative electrode starting segment presses the negative electrode sheet against the positive electrode starting segment, thereby stabilizing the gap between the positive electrode starting segment and the negative electrode sheet, increasing the frictional force on the positive electrode starting segment, and reducing slippage of the positive electrode starting segment. The positive electrode starting segment supports the outermost positive and negative electrode sheets, maintaining the stability of the inner structure of the winding structure, reducing the possibility of collapse on the inner side of the winding structure, and improving the quality of the electrode assembly. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of an exemplary electrode assembly of the present invention;

[0021] Figure 2 This is a schematic diagram of another exemplary electrode assembly of the present invention;

[0022] Figure 3 This is a schematic diagram of another exemplary electrode assembly of the present invention;

[0023] Figure 4 This is a schematic diagram of an exemplary battery according to the present invention.

[0024] Component designation explanation:

[0025] 100. Positive electrode plate; 110. Positive electrode starting segment;

[0026] 200. Negative electrode plate; 210. Negative electrode starting section;

[0027] 300, flat area;

[0028] 400. Corner area; 410. First corner area; 420. Second corner area;

[0029] 500. Diaphragm;

[0030] 600. Adhesive tape. Detailed Implementation

[0031] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. It should also be understood that the terminology used in the embodiments of this utility model is for describing specific implementation schemes and not for limiting the scope of protection of this utility model. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0032] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in this invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, equipment, and materials similar to or equivalent to those in the embodiments of this invention.

[0033] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of implementation of this utility model. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of implementation of this utility model.

[0034] A battery consists of electrode components and an electrolyte. The electrode components are composed of a positive electrode, a negative electrode, and a separator. The battery primarily functions by the movement of metal ions between the positive and negative electrode components. The positive electrode 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, and the uncoated positive current collector protrudes beyond the coated one, serving as the positive electrode tab. Taking a lithium-ion battery as an example, the positive current collector can be made of aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode includes a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative current collector, and the uncoated negative current collector protrudes beyond the coated one, serving as the negative electrode tab. The negative electrode current collector can be made of copper, and the negative electrode active material can be carbon or silicon, etc. To ensure that a large current can pass through without melting, there are multiple positive electrode tabs stacked together, and there are multiple negative electrode tabs stacked together. The separator can be made of PP (polypropylene) or PE (polyethylene), etc.

[0035] In lithium-ion batteries, during charging, lithium ions are extracted from the positive electrode and inserted into the negative electrode; during discharging, lithium ions are extracted from the negative electrode and inserted into the positive electrode. During charging, some abnormal situations may occur that lead to lithium plating. These abnormalities include insufficient lithium insertion space in the negative electrode, excessive resistance to lithium ion migration, and lithium ions detaching too quickly from the positive electrode but not being able to insert an equal amount into the negative electrode. Lithium ions that cannot be inserted into the negative electrode can only gain electrons on the surface of the negative electrode, thus forming elemental lithium, a phenomenon known as lithium plating.

[0036] Winded battery cells include a flat region and corner regions at both ends of the flat region. In the existing production process of wound battery cells, the inner electrode sheets are prone to displacement before hot pressing, which increases the gap between the positive and negative electrode sheets in the corner region. This makes lithium plating more likely to occur during charging, which can lead to a decrease in battery energy density or even battery failure, affecting battery safety.

[0037] Please see Figures 1 to 4In view of this, this application provides an electrode assembly and a battery. The electrode assembly is a wound structure formed by stacking a positive electrode 100 and a negative electrode 200 and winding them along a winding direction. The electrode assembly includes a straight region 300 and a corner region 400. The corner region 400 is located at both ends of the straight region 300 and at both ends of the straight region 300 in a first direction. The positive electrode 100 includes a positive electrode starting segment 110 located in the straight region 300, and the negative electrode 200 includes a negative electrode starting segment 210 extending beyond the positive electrode starting segment 110 in the opposite direction of the winding direction. The negative electrode starting segment 210 extends through the corner region 400 and terminates in the straight region 300. The projection of the positive electrode starting segment 110 along a direction perpendicular to the straight region 300 at least partially overlaps with the projection of the negative electrode starting segment 210 along a direction perpendicular to the straight region 300.

[0038] The negative electrode 200 of this application includes a negative electrode starting section 210 extending in the opposite direction of the positive electrode starting section 110 of the positive electrode 100 along the winding direction. The corner region 400 that the positive electrode 100 first passes through along the winding direction is a first corner region 410, and another corner region is a second corner region 420. The negative electrode starting section 210 is at least partially located in the second corner region 420. The negative electrode starting section 210 forms a support in the second corner region 420, thereby making it less likely for the negative electrode 200 at the first corner region 410 to slide into the second corner region 420. This reduces the displacement of the negative electrode 200 at the first corner region 410, improves the situation where the gap between the negative electrode 200 and the positive electrode 100 at the first corner region 410 is too large due to the displacement of the negative electrode 200, and effectively improves the lithium plating situation in the first corner region 410, improves the quality of the electrode assembly, and improves the battery quality.

[0039] The negative electrode starting section 210 terminates at the flat region 300. When the electrode assembly collapses internally, the first free end of the negative electrode starting section 210 shifts to form an approximate triangle with the negative electrode sheet 200, improving stability and providing support for the corner region 400, thus reducing the collapse of the electrode assembly. Simultaneously, the triangle can further reduce the slippage of the negative electrode sheet 200, preventing excessive gaps between the negative electrode sheet 200 and the positive electrode sheet 100 at the first corner region 410, and improving the lithium plating problem in the first corner region 410.

[0040] The projection of the positive electrode starting segment 110 along the direction perpendicular to the straight region 300 at least partially overlaps with the projection of the negative electrode starting segment 210 along the same direction perpendicular to the straight region 300. The support structure formed by the negative electrode starting segment 210 presses the negative electrode sheet 200 against the positive electrode starting segment 110, thereby stabilizing the gap between the positive electrode starting segment 110 and the negative electrode sheet 200, increasing the frictional force on the positive electrode starting segment 110, and reducing the slippage of the positive electrode starting segment 110. The positive electrode starting segment 110 provides support for the outermost positive electrode sheet 100 and negative electrode sheet 200, maintaining the stability of the inner structure of the winding structure, reducing the possibility of collapse on the inner side of the winding structure, and improving the quality of the electrode assembly.

[0041] Please see Figure 1 In one embodiment, the negative electrode starting segment 210 includes a first segment close to the positive electrode starting segment 110, a second segment located in the corner region 400, and a third segment away from the positive electrode starting segment 110. The first segment, the second segment, and the third segment are connected sequentially in the opposite direction of the winding direction. The length of the third segment is greater than or equal to one-third of the length of the straight region 300 in which the third segment is located, and less than or equal to one-half the length of the straight region 300 in which the third segment is located.

[0042] During battery cycling, the middle section expands significantly. By using a third segment whose length is less than or equal to half the length of the flat region 300, the middle area of ​​the winding structure can be avoided, thus mitigating expansion stress, reducing electrode assembly deformation, maintaining electrode assembly performance, and improving electrode assembly quality. Conversely, if the length of the third segment is greater than or equal to one-third the length of the flat region 300, the free end of the negative electrode starting segment 210 can be shifted to form an approximately triangular structure with the negative electrode sheet 200. This provides support for the second corner region 420, reduces slippage of the negative electrode sheet 200 at the first corner region 410, and improves the problem of excessive gap between the negative electrode sheet 200 and the positive electrode sheet 100 at the first corner region 410.

[0043] Please see Figure 2 In one embodiment, the free end of the negative electrode starting segment 210 is positioned near the flat region 300, which can effectively increase the buffer zone in the middle of the electrode assembly, avoid expansion during battery cycling, alleviate expansion pressure, reduce the deformation of the electrode assembly, and maintain the performance of the electrode assembly.

[0044] The free end of the positive electrode starting segment 110 is positioned near the other end of the flat region 300. The positive electrode starting segment 110 extends from the first corner region 410 along the flat region 300 towards the second corner region 420. Positioning the free end of the positive electrode starting segment 110 near the second corner region 420 effectively increases the overlap area between the positive electrode starting segment 110 and the negative electrode plate 200, increasing the active region area and improving the energy density of the electrode assembly. The large overlap area between the positive electrode starting segment 110 and the negative electrode plate 200 effectively fills the flat region 300, reducing deformation of the flat region 300, improving the flatness of the flat region 300, and thus ensuring the flatness of the electrode assembly.

[0045] The length of the positive electrode starting section 110 exceeds half the length of the flat region 300, which can increase the contact area between the positive electrode starting section 110 and the inner negative electrode plate 200, avoid the gap area between the negative electrode starting section 210 and the outer negative electrode plate 200 being too large, increase the support for the flat region 300, thereby improving the flatness of the flat region 300, reducing the deformation of the electrode assembly, and improving the flatness of the electrode assembly.

[0046] Please see Figure 1 In one embodiment, the winding ends of the positive electrode 100 and the negative electrode 200 both terminate at the corner region 400, which can ensure the flatness of the straight region 300, thereby making the electrode assembly flatter, making it easier to encapsulate the electrode assembly, effectively improving the space utilization of the battery, and increasing the energy density of the battery.

[0047] Please see Figure 1 In one embodiment, the winding tail end of the positive electrode 100 and the winding tail end of the negative electrode 200 are terminated at the same corner area 400, which reduces the amount of negative electrode 200 used and waste, increases the overlap area of ​​the positive electrode 100 and the negative electrode 200, that is, increases the active area and improves the energy density of the electrode assembly.

[0048] The winding tail end of the negative electrode 200 is located outside the winding tail end of the positive electrode 100. The negative electrode 200 wrapping the positive electrode 100 can prevent electrode misalignment and deformation, enhance the stability of the winding process, suppress thermal runaway, reduce short circuit risk, and improve yield and product quality.

[0049] Please see Figure 3 In one embodiment, the electrode assembly includes adhesive tape 600. Adhesive tape 600 is applied to the corner area 400 where the winding ends of the positive electrode 100 and the negative electrode 200 are located. Adhesive tape 600 bonds and fixes the winding end of the negative electrode 200, thereby preventing the outer ring of the negative electrode 200 from warping or shifting, which could lead to excessive gaps with adjacent positive electrode 100s. This improves the problem of lithium plating on the outer ring of the electrode assembly and enhances the quality of the electrode assembly.

[0050] The adhesive tape 600 extends bidirectionally along the winding direction to the flat region 300. This extension effectively improves the confinement of the outer ring of the negative electrode 200, thereby reducing slippage or warping of the outer ring and mitigating lithium plating. The thickness of the adhesive tape 600 is significantly less than that of the positive electrode 100 or the negative electrode 200. Therefore, the extension of the adhesive tape 600 to the flat region 300 has little or no impact on the flatness of the flat region 300, and thus has minimal impact on the energy density of the electrode assembly.

[0051] In one embodiment, the negative electrode starting segment 210 extends inward from the free end of the positive electrode starting segment 110 and passes through two corner regions 400, thereby further ensuring that the negative electrode starting segment 210 supports the inner side of the electrode assembly and improving the problem of lithium plating in the electrode assembly.

[0052] In one embodiment, the electrode assembly includes a diaphragm 500, which is electronically insulating to prevent electronic short circuits and ionically conductive to selectively allow ions to pass through, thereby maintaining the electrochemical reaction.

[0053] In one embodiment, no tabs are provided on the first layer of negative electrode sheet 200 near the winding center side. The negative electrode sheet 200 on the winding center side is smaller in size. Not providing tabs facilitates processing and winding, and facilitates the welding of tabs, thereby improving processing convenience.

[0054] In one embodiment, the distance from the free end of the negative electrode starting segment 210 to the first corner area 410 is 2 to 503 mm. The distance can be any value between 2 and 503 mm, such as 2 mm, 10 mm, 200 mm, 400 mm, 503 mm, etc., to ensure that the negative electrode starting segment 210 provides support for the corner area 400.

[0055] The distance from the free end of the positive electrode starting section 110 to the second corner region 420 is 7 to 505 mm. The distance can be any value between 7 and 505 mm, such as 7 mm, 10 mm, 100 mm, 300 mm, 505 mm, etc., to ensure the energy density of the battery assembly and reduce the slippage of the positive electrode starting section 110.

[0056] In one embodiment, the length of the overlapping area along the first direction of the projection of the positive electrode starting segment 110 along the direction perpendicular to the straight region 300 and the projection of the negative electrode starting segment 210 along the direction perpendicular to the straight region 300 is 2 to 500 mm. The length can be any value between 2 and 500 mm, such as 2 mm, 10 mm, 100 mm, 300 mm, 500 mm, etc. This ensures that after the free end of the negative electrode starting segment 210 is displaced, it indirectly presses against the positive electrode starting segment 110, improving the stability of the internal structure of the electrode assembly and preventing internal structural collapse.

[0057] Please see Figure 4 In one embodiment of the battery, the battery includes at least two electrode assemblies of any one of the above-mentioned types. The battery has a casing to protect the electrode assemblies. The casing can be square or the like, and this application does not impose any particular limitation on it. The casing material can be nickel-plated steel, aluminum, or the like, and this application does not impose any limitation on it.

[0058] The battery of this application includes at least two of the electrode components described above, which can effectively guarantee the energy density of the battery.

[0059] In this application, the positive electrode 100 passes through a first corner region 400 along the winding direction, which is a first corner region 410. Another corner region 400 is a second corner region 420. The negative electrode starting segment 210 is at least partially located in the second corner region 420. The negative electrode starting segment 210 forms a support in the second corner region 420, thereby making it less likely for the negative electrode 200 at the first corner region 410 to slide into the second corner region 420. This reduces the displacement of the negative electrode 200 at the first corner region 410, improves the situation where the gap between the negative electrode 200 and the positive electrode 100 at the first corner region 410 is too large due to the displacement of the negative electrode 200, and effectively improves the lithium plating situation in the first corner region 410, thereby improving the battery quality.

[0060] The negative electrode starting section 210 terminates at the flat region 300. When the electrode assembly collapses internally, the free end of the negative electrode starting section 210 shifts to form an approximate triangle with the negative electrode sheet 200, improving stability and providing support for the corner region 400, thus reducing the collapse of the electrode assembly. Simultaneously, the triangle can further reduce the slippage of the negative electrode sheet 200, preventing excessive gaps between the negative electrode sheet 200 and the positive electrode sheet 100 at the first corner region 410, and improving the lithium plating problem in the first corner region 410.

[0061] The projection of the positive electrode starting segment 110 along the direction perpendicular to the flat region 300 at least partially overlaps with the projection of the negative electrode starting segment 210 along the same direction perpendicular to the flat region 300. The support structure formed by the negative electrode starting segment 210 presses the negative electrode sheet 200 against the positive electrode starting segment 110, thereby stabilizing the gap between the positive electrode starting segment 110 and the negative electrode sheet 200, increasing the frictional force on the positive electrode starting segment 110, and reducing the slippage of the positive electrode starting segment 110. The positive electrode starting segment 110 provides support for the outermost positive electrode sheet 100 and negative electrode sheet 200, maintaining the stability of the inner structure of the winding structure, reducing the possibility of collapse of the inner side of the winding structure, and improving the battery quality.

[0062] The technical solutions described in the embodiments of this application are applicable to electrical devices that use batteries.

[0063] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special restrictions on the above-mentioned electrical equipment.

[0064] The electrode assembly and corresponding battery of this application have an approximately triangular shape formed by the free end of the negative electrode starting section 210 and the negative electrode sheet 200, which improves stability and provides support for the corner region 400, reducing the collapse of the electrode assembly. Simultaneously, the triangle further reduces the slippage of the negative electrode sheet 200, avoiding excessive gaps between the negative electrode sheet 200 and the positive electrode sheet 100 at the first corner region 410, thus improving the lithium plating problem in the first corner region 410. The starting section of the positive electrode starting section 110 supports the outermost positive electrode sheet 100 and negative electrode sheet 200, maintaining the stability of the inner structure of the winding structure, reducing the possibility of collapse within the winding structure, and improving battery quality. Therefore, this utility model effectively overcomes some practical problems in the prior art, thus having high utilization value and practical significance.

[0065] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. An electrode assembly, wherein the electrode assembly is a wound structure formed by stacking a positive electrode (100) and a negative electrode (200) and then winding them along a winding direction, characterized in that, include: Straight area (300); The corner area (400) is located at both ends of the straight area (300) in a first direction; The positive electrode (100) includes a positive electrode starting segment (110) located in the flat region (300), and the negative electrode (200) includes a negative electrode starting segment (210) extending beyond the positive electrode starting segment (110) in the opposite direction of the winding direction. The negative electrode starting segment (210) extends through the corner region (400) and terminates in the flat region (300). The projection of the positive electrode starting segment (110) along the direction perpendicular to the straight region (300) at least partially overlaps with the projection of the negative electrode starting segment (210) along the direction perpendicular to the straight region (300).

2. The electrode assembly according to claim 1, characterized in that, The negative electrode starting segment (210) includes a first segment close to the positive electrode starting segment (110), a second segment located in the corner area (400), and a third segment away from the positive electrode starting segment (110), wherein the first segment, the second segment, and the third segment are connected in sequence; The length of the third segment is greater than or equal to one-third of the length of the straight section (300) in which the third segment is located, and less than or equal to one-half of the length of the straight section (300) in which the third segment is located.

3. The electrode assembly according to claim 1, characterized in that, The free end of the negative electrode starting segment (210) is located near one end of the flat region (300), and the free end of the positive electrode starting segment (110) is located near the other end of the flat region (300). The length of the positive electrode starting segment (110) exceeds half the length of the straight region (300).

4. The electrode assembly according to claim 1, characterized in that, The winding ends of the positive electrode (100) and the winding ends of the negative electrode (200) both terminate at the corner region (400).

5. The electrode assembly according to claim 4, characterized in that, The winding tail end of the positive electrode (100) and the winding tail end of the negative electrode (200) terminate at the same corner area (400); The winding end of the negative electrode (200) is located outside the winding end of the positive electrode (100).

6. The electrode assembly according to claim 4, characterized in that, include: Adhesive tape (600) is applied to the corner area (400) where the winding ends of the positive electrode (100) and the negative electrode (200) are located, and extends bidirectionally in both directions along the winding direction to the straight area (300).

7. The electrode assembly according to claim 1, characterized in that, The negative electrode starting segment (210) extends inward from the free end of the positive electrode starting segment (110) and passes through the two corner areas (400).

8. The electrode assembly according to claim 1, characterized in that, The first corner region (400) that the positive electrode (100) passes through along the winding direction is the first corner region (410), and the other corner region (400) is the second corner region (420). The distance from the free end of the negative electrode starting section (210) to the first corner area (410) is 2 to 503 mm; The distance from the free end of the positive electrode starting section (110) to the second corner region (420) is 7-505 mm.

9. The electrode assembly according to claim 1, characterized in that, The length of the overlapping area of ​​the projection of the positive electrode starting segment (110) along the direction perpendicular to the straight region (300) and the projection of the negative electrode starting segment (210) along the direction perpendicular to the straight region (300) along the first direction is 2 to 500 mm.

10. A battery, characterized in that, It includes at least two electrode assemblies as described in any one of claims 1 to 9.

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