Electrode assembly and battery

Abstract

The utility model belongs to the technical field of batteries, and discloses an electrode assembly and a battery, the electrode assembly comprises a diaphragm and a plurality of pole pieces; the plurality of pole pieces are arranged on the same side of the diaphragm at intervals along the winding direction; along the winding direction, the plurality of pole pieces comprise a starting end pole piece, a plurality of first pole piece groups and a plurality of second pole piece groups, the first pole piece groups and the second pole piece groups are alternately arranged, each first pole piece group comprises two first pole pieces, and each second pole piece group comprises two second pole pieces; the polarities of the starting end pole piece, the second pole piece and the first pole piece are opposite; along the thickness direction of the electrode assembly, the starting end of the diaphragm is wound to one side, far away from the diaphragm, of the starting end pole piece, and the polarities of the two adjacent pole pieces are opposite. According to the electrode assembly and the battery provided by the utility model, the condition that the pole pieces are exposed can be avoided, and the production efficiency is relatively high.

Description

Technical Field

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

[0002] A laminated battery is a type of battery that is made by stacking multiple positive and negative electrodes through a diaphragm. Laminated batteries have high energy density, safety, and longer life, and are widely used in electric vehicles, drones, smart homes, and other fields. Compared with wound batteries, laminated batteries have a higher internal space utilization rate for the same size of shell, so the energy density and capacity density of laminated batteries are higher than those of wound batteries.

[0003] In the prior art, laminated batteries are usually arranged in a manner of one layer of electrode and one layer of diaphragm. There is no diaphragm covering the two sides of the electrode, which poses a risk of electrode leakage, affecting the quality of the laminated batteries. In addition, the diaphragm is usually provided in rolls, which requires a cutting device to cut the diaphragm, resulting in low production efficiency of the laminated batteries.

[0004] Therefore, an electrode assembly and a battery are urgently needed to solve the above problems. Utility Model Content

[0005] The utility model aims to provide an electrode assembly and a battery, which can avoid leakage of pole pieces and have high production efficiency.

[0006] As conceived above, the technical solution adopted by the utility model is:

[0007] An electrode assembly, the electrode assembly comprising a diaphragm and a plurality of electrode sheets;

[0008] The plurality of pole pieces are arranged at intervals on the same side of the diaphragm along the winding direction; along the winding direction, the plurality of pole pieces include a starting pole piece and a plurality of first pole piece groups and a plurality of second pole piece groups arranged alternately, the first pole piece group includes two first pole pieces, and the second pole piece group includes two second pole pieces; the polarity of the starting pole piece and the second pole piece is opposite to that of the first pole piece;

[0009] Along the thickness direction of the electrode assembly, the starting end of the diaphragm is wound to a side of the starting end electrode sheet away from the diaphragm, and the polarities of two adjacent electrode sheets are opposite.

[0010] Optionally, the electrode assembly further includes an end pole sheet, wherein the end pole sheet has a polarity opposite to that of a last pole sheet group of the first pole sheet group and the second pole sheet group alternately arranged along the winding direction.

[0011] Optionally, the starting end pole piece is a negative pole piece, and / or the ending pole piece is a negative pole piece.

[0012] Optionally, the diaphragm includes a first straight portion, multiple bent portions and multiple second straight portions, the bent portions and the second straight portions are alternately arranged in sequence along the winding direction, the first straight portion is connected to the first bent portion in the winding direction, and each pole piece is fixed on the second straight portion.

[0013] Optionally, both ends of the pole piece in the winding direction extend to the bending portion, and there is a gap between two adjacent pole pieces in the winding direction.

[0014] Optionally, the electrode assembly further includes an adhesive layer, and the electrode sheet is adhered to the second straight portion through the adhesive layer.

[0015] Optionally, the thickness of the bonding layer is 10 μm-20 μm.

[0016] Optionally, the width of the diaphragm is greater than the maximum of the width of the first pole piece and the width of the second pole piece; the length of the first straight portion is greater than the maximum of the length of the first pole piece and the length of the second pole piece;

[0017] Preferably, the width of the diaphragm is 2 mm to 6 mm greater than the maximum of the width of the first pole piece and the width of the second pole piece;

[0018] Preferably, the length of the first straight portion is 2 mm to 6 mm greater than the maximum length of the first pole piece and the second pole piece.

[0019] Optionally, the length of the positive electrode sheets in the plurality of electrode sheets is c1, and the width is c2, and the length of the negative electrode sheets in the plurality of electrode sheets is d1, and the width is d2, d1>c1, d2>c2;

[0020] Preferably, the length of the negative electrode sheet is 2 mm-6 mm greater than the length of the positive electrode sheet, and the width of the negative electrode sheet is 2 mm-6 mm greater than the width of the positive electrode sheet.

[0021] Another object of the utility model is to provide a battery with higher reliability and production efficiency.

[0022] As conceived above, the technical solution adopted by the utility model is:

[0023] A battery comprises the electrode assembly described above.

[0024] The electrode assembly and battery provided by the utility model have at least the following beneficial effects:

[0025] Multiple pole pieces are arranged on the same side of the diaphragm, and along the winding direction, the multiple pole pieces include a starting end pole piece and multiple first pole piece groups and multiple second pole piece groups that are alternately arranged. The polarities of the starting end pole piece, the first pole piece of the first pole piece group, and the second pole piece of the second pole piece group are opposite. In the finished product after winding, along the thickness direction of the electrode assembly, the starting end of the diaphragm is wound to the side of the starting end pole piece away from the diaphragm, and the polarities of two adjacent pole pieces are opposite. By arranging the pole pieces on the same side of the diaphragm, it is convenient to form an electrode assembly by winding the pole pieces. Combining the characteristics of wound batteries and stacked batteries, both sides of the pole pieces can be coated with the diaphragm, reducing the risk of leakage of the pole pieces, improving the quality of the electrode assembly, and the diaphragm does not need to be cut in advance, thereby improving the production efficiency of the electrode assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of the pole piece provided by the embodiment of the utility model being arranged on the diaphragm Figure 1 ;

[0027] Figure 2 This is a schematic diagram of the structure of the pole piece provided by the embodiment of the utility model being arranged on the diaphragm Figure 2 ;

[0028] Figure 3 This is a schematic diagram of the structure of the pole piece provided by the embodiment of the utility model being arranged on the diaphragm Figure 3 ;

[0029] Figure 4 It is a schematic diagram of the structure of the diaphragm, pole piece and bonding layer provided by the embodiment of the utility model;

[0030] Figure 5 It is a cross-sectional view of an electrode assembly provided in an embodiment of the utility model.

[0031] In the figure:

[0032] 100, diaphragm; 110, first straight portion; 120, bent portion; 130, second straight portion; 201, positive electrode sheet; 202, negative electrode sheet; 210, starting end sheet; 220, first electrode sheet group; 221, first electrode sheet; 230, second electrode sheet group; 231, second electrode sheet; 240, end electrode sheet; 300, bonding layer; X, winding direction. DETAILED DESCRIPTION

[0033] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and through specific implementation methods. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all of them.

[0034] 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, further definition and explanation thereof is not required in subsequent drawings.

[0035] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the present utility model, 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 obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. In the description of this embodiment, unless otherwise specified, "multiple" specifically refers to two or more.

[0037] In the description of this embodiment, the terms "upper", "lower", "right", etc., are based on the directions or positions shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0038] This embodiment provides an electrode assembly that can avoid leakage of electrode pieces and has high production efficiency.

[0039] like Figures 1 to 5As shown, the electrode assembly includes a diaphragm 100 and a plurality of pole pieces. The plurality of pole pieces are arranged at intervals on the same side of the diaphragm 100 along the winding direction X, so as to facilitate the placement or fixing of the pole pieces on the diaphragm 100. It should be noted that Figure 1 , Figure 2 and Figure 3 This is a schematic diagram of the electrode assembly before winding. Figure 4 is a schematic diagram of a partial structure of an electrode assembly, Figure 5 This is a schematic diagram of the finished product after the electrode assembly is wound. Figure 5 As shown, a plurality of pole pieces of the electrode assembly are arranged in sequence along the thickness direction, and a diaphragm 100 is provided between two adjacent pole pieces in the thickness direction.

[0040] See also Figure 1 , along the winding direction X, the plurality of pole pieces include a starting pole piece 210 and a plurality of first pole piece groups 220 and a plurality of second pole piece groups 230 that are alternately arranged. Each first pole piece group 220 includes two first pole pieces 221, and each second pole piece group 230 includes two second pole pieces 231; the polarity of the starting pole piece 210 and the second pole piece 231 is opposite to that of the first pole piece 221, that is, the polarity of the starting pole piece 210 is the same as that of the second pole piece 231, and the polarity of the starting pole piece 210 is opposite to that of the first pole piece 221. For example, when the starting pole piece 210 and the second pole piece 231 are both positive pole pieces, the first pole piece 221 is a negative pole piece.

[0041] It should be noted that each first pole piece group 220 includes two first pole pieces 221, and each second pole piece group 230 includes two second pole pieces 231. The first pole piece group 220 and the second pole piece group 230 are alternately arranged along the winding direction X, so that when winding, they can be directly wound one by one along the winding direction, that is, the flipping direction of each pole piece when winding is the same as the flipping direction of the starting end pole piece 210, which reduces the difficulty of winding and does not cause two pole pieces with the same polarity to be adjacent in the thickness direction of the electrode assembly.

[0042] In this embodiment, along the thickness direction of the electrode assembly, the starting end of the diaphragm 100 is wound to the side of the starting end electrode sheet 210 away from the diaphragm 100, so as to separate the starting end electrode sheet 210 and the first electrode sheet 221 adjacent to the starting end electrode sheet 210 through the starting end of the diaphragm 100. Since the electrode sheets are all arranged on the same side of the diaphragm 100, there is only one layer of diaphragm 100 between the winding starting end electrode sheet 210 and the first electrode sheet 221 adjacent to it, and there is only one layer of diaphragm 100 between any two adjacent electrode sheets in the thickness direction of the electrode assembly. Compared with the situation in the prior art where there are multiple layers of diaphragms 100 between two electrode sheets, the thickness of the electrode assembly can be smaller, the waste of the diaphragm 100 is reduced, and the difficulty of lithium ion transmission is reduced. In addition, by directly winding the starting end of the diaphragm 100 to the side of the starting end electrode sheet 210 away from the diaphragm 100, the integrity of the diaphragm 100 is fully utilized, and there is no need to set an independent diaphragm on the starting end electrode sheet 210.

[0043] It should be noted that the polarities of two adjacent pole pieces in the thickness direction of the electrode assembly are opposite to each other to ensure the performance of the electrode assembly.

[0044] When preparing the electrode assembly provided in this embodiment, the diaphragm 100 is first unfolded, and then the pole pieces are arranged one by one on the diaphragm 100, and the plurality of pole pieces are located on the same side of the diaphragm 100, and no pole piece is arranged at the starting end of the diaphragm 100. Afterwards, the starting end of the diaphragm 100 is pulled onto the starting end pole piece 210 and covers the starting end pole piece 210. Subsequently, the diaphragm 100 and the pole piece are wound along the winding direction X, so that the pole pieces are not in direct contact with each other, but are provided with the diaphragm 100, thereby ensuring the function of the formed electrode assembly.

[0045] The electrode assembly provided in this embodiment has multiple pole pieces arranged on the same side of the diaphragm 100, and along the winding direction X, the multiple pole pieces include a starting end pole piece 210 and multiple first pole piece groups 220 and multiple second pole piece groups 230 arranged alternately, the starting end pole piece 210, the first pole piece 221 of the first pole piece group 220 and the second pole piece 231 of the second pole piece group 230 have opposite polarities, and in the finished product after winding, along the thickness direction of the electrode assembly, the starting end of the diaphragm 100 is wound to the side of the starting end pole piece 210 away from the diaphragm 100, and the polarities of two adjacent pole pieces are opposite, by arranging the pole pieces on the same side of the diaphragm 100, it is convenient to form an electrode assembly by winding the pole pieces, combining the characteristics of the wound battery and the laminated battery, the two sides of the pole piece can be coated by the diaphragm 100, reducing the risk of leakage of the pole piece, improving the quality of the electrode assembly, and the diaphragm 100 does not need to be cut in advance, thereby improving the production efficiency of the electrode assembly.

[0046] Moreover, compared with the current laminated batteries, the idea provided in this embodiment is to realize the design of laminated batteries through winding. In terms of production process, the degree of automation of the winding process and the supporting equipment are in a mature stage, and the current electrode assembly manufacturing mostly adopts a winding production process, so that the electrode assembly provided in this embodiment does not require additional design of production equipment, thereby reducing production costs.

[0047] In addition, compared with the wound laminated battery design that has been proposed, most of the current technical solutions are to set pole pieces on the front and back sides of the diaphragm, or directly insert an independent unit similar to "positive pole piece-diaphragm-negative pole piece" between the diaphragm layers to achieve the effect from winding to stacking. In this embodiment, multiple pole pieces are placed on the same side of the diaphragm 100 and directly wound, which is clearer and the process flow is simpler.

[0048] Alternatively, if Figure 2 As shown, the electrode assembly further includes an end pole piece 240. The end pole piece 240 has a polarity opposite to that of the last pole piece group of the first pole piece group 220 and the second pole piece group 230 alternately arranged along the winding direction X, that is, the polarity of the end pole piece 240 is opposite to that of the pole piece group closest to it in the winding direction X, so as to ensure the normal function of the electrode assembly formed by winding.

[0049] For example, there is one or two end pole pieces 240, which is not limited in this embodiment. When there are two end pole pieces 240, the polarities of the two end pole pieces 240 are the same.

[0050] Preferably, the end pole piece 240 is a negative pole piece 202, that is, the polarity of the pole piece group closest to the end pole piece 240 along the winding direction X is a positive pole. Since the capacity of the battery is positively correlated with the utilization rate of the positive pole piece 201, the negative graphite exists as a carrier of lithium ions, and the outermost pole pieces of the electrode assembly in its thickness direction are all negative pole pieces 202, that is, both sides of each positive pole piece 201 have negative pole pieces 202. It can be seen that the outermost layers are all negative pole pieces 202, which can ensure that the coating of each positive pole piece 201 can be utilized, and the positive pole piece 201 is fully utilized, the utilization rate of the positive pole piece 201 is improved, and the capacity of the battery using the electrode assembly is improved. If the outermost layer is a positive pole piece 201, the coating on the positive pole piece 201 on the side not coated with the negative pole piece 202 will be wasted, resulting in a loss in battery capacity.

[0051] In the present embodiment, the starting end electrode sheet 210 (i.e., the electrode sheet of the innermost circle) is the positive electrode sheet 201 or the negative electrode sheet 202. In some optional embodiments, the starting end electrode sheet 210 is the negative electrode sheet 202. Since the length and width of the portion of the diaphragm 100 where the electrode sheet is set need to be much larger than the positive electrode sheet 201 (usually 4mm-10mm larger), if the innermost circle electrode sheet is set as the positive electrode sheet 201, then the diaphragm 100 covering the innermost circle positive electrode sheet 201 will have excess length and width, which may cause the diaphragm 100 to wrinkle and fold, thereby causing a short circuit between the positive and negative electrodes. However, when the starting end electrode sheet 210 is set as the negative electrode sheet 202, the diaphragm 100 will not have much excess length and width, thereby reducing the probability of the diaphragm 100 wrinkling and folding, thereby reducing the probability of a short circuit between the positive and negative electrodes, and ensuring the quality of the electrode assembly.

[0052] Optionally, combine Figure 2 and Figure 5 The diaphragm 100 includes a first straight portion 110, a plurality of bent portions 120 and a plurality of second straight portions 130. The bent portions 120 and the second straight portions 130 are alternately arranged in sequence along the winding direction X. The first straight portion 110 is connected to the first bent portion 120 in the winding direction X. Each pole piece is fixed on the second straight portion 130. The bent portion 120 is used for bending during winding, and the bent portion 120 can cover both sides of the pole piece to reduce the risk of leakage of the pole piece.

[0053] In some optional embodiments, such as Figure 1 As shown, along the winding direction X, the lengths of the multiple bends 120 gradually increase to meet the thickness of the positive electrode sheet 201 and the negative electrode sheet 202 and the thickness of the separator 100 at the corner, thereby meeting the winding requirements. The length direction of the bend 120 is the winding direction X.

[0054] It should be noted that if Figure 1 As shown, the length of the first bending portion 120 in the winding direction X is D1, the length of the second bending portion 120 in the winding direction X is D2, and so on, the length of the seventh bending portion 120 in the winding direction X is D7, and the values ​​of D1 to D7 gradually increase.

[0055] In this embodiment, each pole piece is fixed on the second straight portion 130, so that the pole piece does not move during the winding process, thereby preventing the probability of the pole piece being misaligned and ensuring the quality of the finished electrode assembly. It should be noted that the plurality of pole pieces correspond to the plurality of second straight portions 130 one by one, and each pole piece is fixed on the second straight portion 130 corresponding thereto.

[0056] Optionally, the pole piece preferably covers the second straight portion 130 , so that the utilization rates of the pole piece and the diaphragm 100 can reach the maximum.

[0057] In some optional embodiments, both ends of each pole piece in the winding direction X can extend to the bent portion 120, so that the pole piece can have a larger area, improve the utilization rate of the pole piece, and also improve the utilization rate of the diaphragm, thereby increasing the capacity of the electrode assembly. It should be noted that both ends of the pole piece in the winding direction X extend to two adjacent bent portions 120.

[0058] It should also be noted that there is a gap between two adjacent pole pieces in the winding direction X, that is, the pole piece cannot completely cover the bent portion 120. On the one hand, it can prevent the positive and negative electrodes from short-circuiting; on the other hand, the bent portion 120 cannot be pressed during hot pressing during the manufacturing process, which causes the gap between the pole pieces located at the bent portion 120 to be larger than the gap between the pole pieces located at the second straight portion 130, resulting in difficulty in lithium ion transmission and easy lithium precipitation. Therefore, the pole piece cannot completely cover the bent portion 120.

[0059] Optionally, the pole piece can be fixed on the second straight portion 130 by bonding. Figure 4 As shown, the electrode assembly further includes a bonding layer 300, and the electrode piece 200 is adhered to the second straight portion 130 through the bonding layer 300 to ensure the position of the electrode piece on the second straight portion 130. For example, the material of the bonding layer 300 can be polyvinylidene fluoride or other materials, which is not limited in this embodiment.

[0060] In this embodiment, the thickness of the adhesive layer 300 is 10 μm-20 μm. If the adhesive layer 300 is too thick, the thickness of the electrode assembly will be too large, thereby affecting the energy density of the battery. If the adhesive layer 300 is too thin, it will affect the bonding effect between the electrode sheet and the second straight portion 130. For example, the thickness of the adhesive layer 300 is 10 μm, 12 μm, 15 μm, 18 μm, and 20 μm.

[0061] Optionally, the width of the diaphragm 100 is greater than the maximum width of the first electrode piece 221 and the second electrode piece 231, so that the diaphragm 100 can completely cover the first electrode piece 221 and the second electrode piece 231 in its width direction to avoid short circuit between the positive and negative electrodes.

[0062] Preferably, the width of the diaphragm 100 is 2 mm to 6 mm larger than the maximum of the width of the first electrode sheet 221 and the width of the second electrode sheet 231. If the value is too different, it will cause waste of the diaphragm 100, the positive electrode sheet 201 and the negative electrode sheet 202. If the value is too small, the diaphragm 100 cannot completely cover the positive electrode sheet 201 or the negative electrode sheet 202 in its width direction, which will cause a short circuit inside the electrode assembly. For example, the width of the diaphragm 100 is 2 mm, 3 mm, 5 mm, or 6 mm larger than the maximum of the width of the first electrode sheet 221 and the width of the second electrode sheet 231.

[0063] Optionally, the length of the first straight portion 110 is greater than the maximum length of the first pole piece 221 and the second pole piece 231, so that the first straight portion 110 can completely cover the first pole piece 221 and the second pole piece 231 in its length direction to avoid short circuit between the positive and negative poles.

[0064] Preferably, the length of the first straight portion 110 is 2 mm to 6 mm greater than the maximum of the length of the first pole piece 221 and the length of the second pole piece 231. If the difference is too large, it will cause waste of the diaphragm 100, the positive pole piece 201 and the negative pole piece 202. If the difference is too small, the first straight portion 110 will not be able to completely cover the positive pole piece 201 or the negative pole piece 202 in its length direction, which will cause a short circuit inside the electrode assembly. For example, the length of the first straight portion 110 is 2 mm, 3 mm, 5 mm, or 6 mm greater than the maximum of the length of the first pole piece 221 and the length of the second pole piece 231.

[0065] Optionally, the length of the positive electrode sheet 201 in the plurality of electrode sheets is c1, and the width is c2, and the length of the negative electrode sheet 202 in the plurality of electrode sheets is d1, and the width is d2, d1>c1, d2>c2, that is, the length of the negative electrode sheet 202 is greater than the length of the positive electrode sheet 201, and the width of the negative electrode sheet 202 is greater than the width of the positive electrode sheet 201. Since the capacity of the battery is related to the utilization rate of the positive electrode sheet 201, the graphite of the negative electrode sheet 202 exists as a carrier of lithium ions. Therefore, the negative electrode sheet 202 is larger than the positive electrode sheet 201 to ensure that all lithium ions of the positive electrode sheet 201 can be embedded in the graphite of the negative electrode sheet 202, avoiding waste of the coating on the positive electrode sheet 201.

[0066] It should be noted that the thickness of the positive electrode sheet 201 is the same as the thickness of the negative electrode sheet 202 .

[0067] Preferably, the length of the negative electrode plate 202 is 2 mm-6 mm greater than the length of the positive electrode plate 201 , and the width of the negative electrode plate 202 is 2 mm-6 mm greater than the width of the positive electrode plate 201 .

[0068] This embodiment also provides a battery, including the above-mentioned electrode assembly. The battery provided by this embodiment has high reliability and production efficiency.

[0069] Optionally, the battery in this embodiment can be a laminated battery, which has high energy density, high safety and longer life, and is widely used in electric vehicles, drones, smart homes and other fields.

[0070] Note that the above are only preferred embodiments of the present invention and the technical principles used. 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 is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and 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 comprises a diaphragm (100) and a plurality of electrode sheets; The plurality of pole pieces are arranged at intervals on the same side of the diaphragm (100) along the winding direction (X); along the winding direction (X), the plurality of pole pieces include a starting end pole piece (210) and a plurality of first pole piece groups (220) and a plurality of second pole piece groups (230) arranged alternately, the first pole piece group (220) includes two first pole pieces (221), and the second pole piece group (230) includes two second pole pieces (231); the polarities of the starting end pole piece (210) and the second pole piece (231) are opposite to those of the first pole piece (221); Along the thickness direction of the electrode assembly, the starting end of the diaphragm (100) is wound to a side of the starting end electrode sheet (210) away from the diaphragm (100), and the polarities of two adjacent electrode sheets are opposite.

2. The electrode assembly according to claim 1, characterized in that: The electrode assembly further comprises an end pole piece (240), wherein the end pole piece (240) has a polarity opposite to that of the last pole piece group of the first pole piece group (220) and the second pole piece group (230) alternately arranged along the winding direction (X).

3. The electrode assembly according to claim 2, characterized in that: The starting end pole piece (210) is a negative pole piece (202), and / or the ending pole piece (240) is a negative pole piece (202).

4. The electrode assembly according to any one of claims 1 to 3, characterized in that: The diaphragm (100) comprises a first straight portion (110), a plurality of bent portions (120) and a plurality of second straight portions (130), wherein the bent portions (120) and the second straight portions (130) are alternately arranged in sequence along the winding direction (X), the first straight portion (110) is connected to the first bent portion (120) in the winding direction (X), and each pole piece is fixed on the second straight portion (130).

5. The electrode assembly according to claim 4, characterized in that: Both ends of the pole piece in the winding direction (X) extend to the bending portion (120), and a gap exists between two adjacent pole pieces in the winding direction (X).

6. The electrode assembly according to claim 4, characterized in that: The electrode assembly further comprises an adhesive layer (300), and the electrode sheet (200) is adhered to the second straight portion (130) via the adhesive layer (300).

7. The electrode assembly according to claim 6, characterized in that: The thickness of the bonding layer (300) is 10 μm-20 μm.

8. The electrode assembly according to claim 4, characterized in that: The width of the diaphragm (100) is greater than the maximum of the width of the first pole piece (221) and the width of the second pole piece (231); the length of the first straight portion (110) is greater than the maximum of the length of the first pole piece (221) and the length of the second pole piece (231).

9. The electrode assembly according to claim 8, characterized in that: The width of the diaphragm (100) is 2 mm to 6 mm greater than the largest of the width of the first pole piece (221) and the width of the second pole piece (231); And / or, the length of the first straight portion (110) is 2 mm to 6 mm greater than the maximum of the length of the first pole piece (221) and the length of the second pole piece (231).

10. The electrode assembly according to any one of claims 1 to 3, characterized in that: The length of the positive electrode sheet (201) among the plurality of electrode sheets is c1, and the width is c2; the length of the negative electrode sheet (202) among the plurality of electrode sheets is d1, and the width is d2, d1>c1, d2>c2.

11. The electrode assembly according to claim 10, characterized in that: The length of the negative electrode plate (202) is 2 mm to 6 mm greater than the length of the positive electrode plate (201), and the width of the negative electrode plate (202) is 2 mm to 6 mm greater than the width of the positive electrode plate (201).

12. A battery, characterized in that The electrode assembly comprises the electrode assembly according to any one of claims 1 to 11.

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