Wound electrode assembly, battery cell, battery and electrical equipment

Abstract

The embodiments of the present application provide a wound electrode assembly, a battery cell, a battery, an electrical device, a method for manufacturing an electrode assembly, and a manufacturing device thereof, and relate to the field of battery technology. The electrode assembly includes a positive electrode sheet and a negative electrode sheet; the positive electrode sheet includes a first positive electrode winding end portion and a positive electrode winding middle section; the negative electrode sheet includes a first portion and a second portion; the active material layer of the negative electrode sheet extends beyond the active material layer of the positive electrode sheet, and the difference between the maximum width of the negative electrode active material layer of the first portion and the minimum width of the positive electrode active material layer at the first positive electrode winding end portion is greater than the difference between the maximum width of the negative electrode active material layer of the second portion and the minimum width of the positive electrode active material layer at the positive electrode winding middle section. The electrode assembly can reduce the risk of lithium plating caused by the size of the portion of the negative electrode active material layer of the negative electrode sheet that extends beyond the positive electrode active material layer of the positive electrode sheet along the winding axis not meeting the design requirements.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a wound electrode assembly, a battery cell, a battery, an electrical device, a method for manufacturing an electrode assembly, and a manufacturing device thereof. Background Art

[0002] Lithium-ion batteries have become the mainstream product of secondary batteries due to their outstanding advantages such as high energy density and good cycle performance, and are widely used in portable appliances, power vehicles, mobile phones, spacecraft and other fields.

[0003] Graphite or silicon is commonly used as anode materials for batteries. Since their lithium insertion potential is close to that of metallic lithium, lithium deposition is prone to occur under certain conditions, which seriously affects the cycle performance of lithium-ion batteries. In severe cases, lithium deposition may form lithium dendrites, causing safety problems such as internal short circuits in the battery. Summary of the Invention

[0004] The embodiments of the present application provide a wound electrode assembly, a battery cell, a battery, an electrical device, a method for manufacturing an electrode assembly, and a manufacturing device thereof, so as to improve the problem of lithium plating in batteries.

[0005] In a first aspect, an embodiment of the present application provides a wound electrode assembly comprising a positive electrode sheet and a negative electrode sheet; the positive electrode sheet comprises a first positive electrode winding end portion and a positive electrode winding middle section that are interconnected; the negative electrode sheet comprises a first part and a second part that are interconnected, the first part being arranged opposite to the first positive electrode winding end portion, and the second part being arranged opposite to the positive electrode winding middle section; along the winding axis direction of the wound electrode assembly, the negative electrode active material layer of the negative electrode sheet exceeds the positive electrode active material layer of the positive electrode sheet, the maximum width of the negative electrode active material layer of the first part is H1, the minimum width of the positive electrode active material layer of the first positive electrode winding end portion is L1, the maximum width of the negative electrode active material layer of the second part is H2, and the minimum width of the positive electrode active material layer of the positive electrode winding middle section is L2, H1-L1>H2-L2.

[0006] In the above technical solution, by setting the width difference between the maximum width of the negative electrode active material layer of the first part and the minimum width of the positive electrode active material layer at the end of the first positive electrode winding to be greater than the width difference between the maximum width of the negative electrode active material layer of the second part and the minimum width of the positive electrode active material layer in the middle section of the positive electrode winding, that is, the maximum width difference between the positive electrode active material layer at the end of the first positive electrode winding and the negative electrode active material layer of the first part is greater than the maximum width difference between the negative electrode active material layer of the second part and the positive electrode active material layer in the middle section of the positive electrode winding, the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet that exceeds the positive electrode active material layer of the positive electrode sheet along the winding axis direction not meeting the design requirements is reduced.

[0007] In some embodiments of the first aspect of the present application, H1>H2.

[0008] In the above technical solution, since the first part is arranged opposite to the end portion of the first positive electrode winding, and the second part is arranged opposite to the middle section of the positive electrode winding, the maximum width of the negative electrode active material layer of the first part is greater than the maximum width of the negative electrode active material layer of the second part, which is equivalent to the negative electrode active material layer of the first part having an increased width relative to the negative electrode active material layer of the second part. While ensuring the energy density, it can reduce the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet that exceeds the positive electrode active material layer of the positive electrode sheet along the winding axis direction not meeting the design requirements.

[0009] In some embodiments of the first aspect of the present application, the minimum width of the negative electrode active material layer of the first portion is H3, where H3≥H2.

[0010] In the above technical solution, the minimum width of the negative electrode active material layer of the first part is not less than the maximum width of the negative electrode active material layer of the second part, so as to avoid the negative electrode active material layer of the first part exceeding the positive electrode active material layer at the end of the first positive electrode winding along the winding axis, which does not meet the design requirements and causes lithium deposition.

[0011] In some embodiments of the first aspect of the present application, 0.3 mm ≤ H1 - H2 ≤ 3 mm.

[0012] In the above technical solution, if the width of the negative active material layer of the first part is too large along the axial direction of winding, it may exceed the width of the diaphragm, and may also interfere with the top cover assembly, increasing the risk of short circuit. If the width of the negative active material layer of the first part is not enough, the size of the part of the negative active material layer of the negative electrode sheet that exceeds the positive active material layer of the positive electrode sheet along the winding axis cannot meet the design requirements. Therefore, 0.3mm≤H1-H2≤3mm can not only ensure the safety of the wound electrode assembly, but also reduce the risk of lithium plating caused by the size of the part of the negative active material layer of the negative electrode sheet that exceeds the positive active material layer of the positive electrode sheet along the winding axis not meeting the design requirements.

[0013] In some embodiments of the first aspect of the present application, along the winding axis direction, at least a portion of one end of the negative electrode active material layer of the first part exceeds the corresponding end of the negative electrode active material layer of the second part, and the other end of the negative electrode active material layer of the first part is flush with the other end of the negative electrode active material layer of the second part.

[0014] In the above technical solution, along the winding axis direction, at least part of one end of the negative electrode active material layer of the first part exceeds the corresponding end of the negative electrode active material layer of the second part, and the other end of the negative electrode active material layer of the first part is flush with the other end of the negative electrode active material layer of the second part. In this way, the negative electrode active material layer of the first part is widened from one side of the winding axis direction relative to the negative electrode active material layer of the second part, which makes the negative electrode sheet forming method simple and reduces the processing difficulty.

[0015] In some embodiments of the first aspect of the present application, the negative electrode sheet further includes a negative electrode ear, which is located at one end of the negative electrode sheet along the winding axis, and the end of the negative electrode active material layer of the first part close to the negative electrode ear at least partially exceeds the corresponding end of the negative electrode active material layer of the second part.

[0016] In the above technical solution, along the winding axis direction, the end of the negative electrode active material layer of the first part close to the negative electrode ear at least partially exceeds the corresponding end of the negative electrode active material layer of the second part. In this way, in the process of die-cutting to form the negative electrode ear, a negative electrode sheet with a width difference between the negative electrode active material layer of the first part and the negative electrode active material layer of the second part can be formed. That is, the negative electrode sheet with a width difference between the negative electrode active material layer of the first part and the negative electrode active material layer of the second part can be formed by utilizing the original forming process of the negative electrode sheet.

[0017] In some embodiments of the first aspect of the present application, the negative electrode sheet further includes a negative electrode ear, which is located at one end of the negative electrode sheet along the winding axis, and an end of the first part close to the negative electrode ear extends beyond the corresponding end of the second part, and the other end of the first part is flush with the other end of the second part.

[0018] In the above technical solution, along the winding axis direction, one end of the first part close to the negative electrode ear exceeds the corresponding end of the second part, and the other end of the first part is flush with the other end of the second part. In the process of die-cutting to form the negative electrode ear, a negative electrode sheet with a width difference between the first part and the second part can be formed, that is, the negative electrode sheet with a width difference between the first part and the second part can be formed by utilizing the original forming process of the negative electrode sheet.

[0019] In some embodiments of the first aspect of the present application, along the winding direction, the first portion has a connecting surface connected to the second portion; there are multiple negative electrode ears, and one of the multiple negative electrode ears protrudes from the first portion along the winding axis direction and has a first side surface close to the second portion, and the first side surface is coplanar with the connecting surface.

[0020] In the above technical solution, the connection surface of the first part is coplanar with one side surface of the negative electrode ear, so the connection surface is not located between the two negative electrode ears, which can avoid the diaphragm being punctured due to the width difference between the first part and the second part during the winding process and after the winding is completed, resulting in the connection position between the first part and the second part being tilted up.

[0021] In some embodiments of the first aspect of the present application, a negative electrode active material layer is provided on the negative electrode ear protruding from the first part along the winding axis direction, and the negative electrode active material layer on the negative electrode ear protruding from the first part is connected to the negative electrode active material layer of the first part.

[0022] In the above technical solution, the negative electrode active material layer on the negative electrode ear protruding from the first part is connected to the negative electrode active material layer of the first part, which is equivalent to further increasing the width of the negative electrode active material layer at some positions of the first part. This can further reduce the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet exceeding the positive electrode active material layer of the positive electrode sheet in the direction of the winding axis, which does not meet the design requirements.

[0023] In some embodiments of the first aspect of the present application, the wound electrode assembly includes a straight area and two bending areas, the two bending areas are respectively connected to the two ends of the straight area; the first part passes through the straight area at least twice.

[0024] In the above technical solution, after passing through the straight zone twice, the possibility of relative offset between the first positive electrode winding end and the first part is small, so the first part passes through the straight zone at least twice, which can minimize the risk of lithium plating caused by the relative offset between the first positive electrode winding end and the first part, resulting in the size of the part of the negative electrode active material layer of the negative electrode sheet exceeding the positive electrode active material layer of the positive electrode sheet in the winding axis direction not meeting the design requirements.

[0025] In some embodiments of the first aspect of the present application, the positive electrode sheet also includes a second positive electrode winding end, and the first positive electrode winding end and the second positive electrode winding end are respectively connected to the two ends of the positive electrode winding middle section; the negative electrode sheet also includes a third part, and the first part and the third part are respectively connected to the two ends of the second part, and the third part and the second positive electrode winding end are arranged opposite to each other; the maximum width of the negative electrode active material layer of the third part is H4, and the minimum width of the positive electrode active material layer of the second positive electrode winding end is L3, H4-L3>H2-L2.

[0026] In the above technical solution, the positive electrode sheet further includes a second positive electrode winding end, and the negative electrode sheet further includes a third portion, with the second positive electrode winding end and the third portion being arranged opposite each other. The maximum width difference between the positive electrode active material layer at the first positive electrode winding end and the negative electrode active material layer at the first portion is greater than the maximum width difference between the negative electrode active material layer at the second portion and the positive electrode active material layer at the middle section of the positive electrode winding. The maximum width difference between the positive electrode active material layer at the second positive electrode winding end and the negative electrode active material layer at the third portion is greater than the maximum width difference between the negative electrode active material layer at the second portion and the positive electrode active material layer at the middle section of the positive electrode winding. This can reduce the risk of lithium deposition caused by the size of the portion of the negative electrode active material layer of the negative electrode sheet that extends beyond the positive electrode active material layer of the positive electrode sheet in the direction of the winding axis not meeting design requirements.

[0027] In some embodiments of the first aspect of the present application, H4>H2.

[0028] In the above technical solution, since the third part is arranged opposite to the second positive electrode winding end portion, and the second part is arranged opposite to the positive electrode winding middle section, the maximum width of the negative electrode active material layer of the third part is greater than the maximum width of the negative electrode active material layer of the second part, which is equivalent to the negative electrode active material layer of the third part having an increased width relative to the negative electrode active material layer of the second part. This can reduce the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet exceeding the positive electrode active material layer of the positive electrode sheet in the winding axis direction not meeting the design requirements while ensuring the energy density.

[0029] In some embodiments of the first aspect of the present application, the minimum width of the negative electrode active material layer in the third portion is H5, where H5≥H2.

[0030] In the above technical solution, the minimum width of the negative electrode active material layer of the third part is not less than the maximum width of the negative electrode active material layer of the second part, thereby reducing the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet exceeding the positive electrode active material layer of the positive electrode sheet in the winding axis direction not meeting the design requirements.

[0031] In some embodiments of the first aspect of the present application, the maximum width of the positive electrode active material layer at the end of the first positive electrode winding is L4, the maximum width of the positive electrode active material layer at the middle section of the positive electrode winding is L5, L4 <L5。

[0032] In the above technical solution, the maximum width of the positive electrode active material layer at the end of the first positive electrode winding is smaller than the maximum width of the positive electrode active material layer in the middle section of the positive electrode winding, so that the maximum width difference between the positive electrode active material layer at the end of the first positive electrode winding and the negative electrode active material layer in the first part is greater than the maximum width difference between the negative electrode active material layer in the second part and the positive electrode active material layer in the middle section of the positive electrode winding. By changing the width of the first positive electrode winding end of the positive electrode sheet, the possibility of lithium deposition caused by the size of the part of the negative electrode active material layer of the negative electrode sheet exceeding the positive electrode active material layer of the positive electrode sheet in the winding axis direction not meeting the design requirements is reduced.

[0033] In some embodiments of the first aspect of the present application, along the winding axis direction, one end of the positive electrode active material layer in the middle section of the positive electrode winding at least partially extends beyond the corresponding end of the positive electrode active material layer at the end portion of the first positive electrode winding, and the other end of the positive electrode active material layer in the middle section of the positive electrode winding is flush with the other end of the positive electrode active material layer at the end portion of the first positive electrode winding.

[0034] In the above technical solution, along the winding axis direction, one end of the positive electrode active material layer in the middle section of the positive electrode winding at least partially exceeds the corresponding end of the positive electrode active material layer at the first positive electrode winding end, and the other end of the positive electrode active material layer in the middle section of the positive electrode winding is flush with the other end of the positive electrode active material layer at the first positive electrode winding end. In this way, the positive electrode active material layer at the first positive electrode winding end is widened from one side of the winding axis direction relative to the positive electrode active material layer in the middle section of the positive electrode winding, which makes the positive electrode sheet forming method simple and reduces the processing difficulty.

[0035] In some embodiments of the first aspect of the present application, the positive electrode sheet further includes a positive electrode ear. Along the winding axis, the positive electrode ear is located at one end of the positive electrode sheet, and the end of the positive electrode active material layer in the middle section of the positive electrode winding close to the positive electrode ear at least partially exceeds the end corresponding to the positive electrode active material layer at the end portion of the first positive electrode winding.

[0036] In the above technical solution, the end of the positive electrode active material layer in the middle section of the positive electrode winding close to the positive electrode ear at least partially exceeds the corresponding end of the positive electrode active material layer at the first positive electrode winding end. In this way, in the process of die-cutting to form the positive electrode ear, a positive electrode sheet with a width difference between the positive electrode active material layer at the first positive electrode winding end and the positive electrode active material layer in the middle section of the positive electrode winding can be formed. That is, the positive electrode sheet with a width difference between the positive electrode active material layer at the first positive electrode winding end and the positive electrode active material layer in the middle section of the positive electrode winding can be formed by utilizing the original forming process of the positive electrode sheet.

[0037] In a second aspect, an embodiment of the present application provides a battery cell, comprising a wound electrode assembly provided according to any embodiment of the first aspect.

[0038] In the above technical solution, the battery cell includes the wound electrode assembly provided by any embodiment of the first aspect. The battery cell is less likely to cause lithium deposition because the size of the part of the negative electrode active material layer of the negative electrode sheet that exceeds the positive electrode active material layer of the positive electrode sheet along the winding axis direction does not meet the design requirements.

[0039] In a third aspect, an embodiment of the present application provides a battery, comprising the battery cell provided in the embodiment of the second aspect.

[0040] In the above technical solution, the battery includes the battery cell provided by the second embodiment, and the possibility of lithium deposition is small because the size of the part of the negative active material layer of the negative electrode sheet that exceeds the positive active material layer of the positive electrode sheet along the winding axis does not meet the design requirements.

[0041] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising a battery cell provided according to an embodiment of the second aspect.

[0042] In the above technical solution, the electrical equipment includes the battery cell provided by the second aspect embodiment. The battery cell of the electrical equipment is less likely to cause lithium deposition because the size of the part of the negative electrode active material layer of the negative electrode sheet that exceeds the positive electrode active material layer of the positive electrode sheet along the winding axis direction does not meet the design requirements.

[0043] In a fifth aspect, an embodiment of the present application provides a method for manufacturing a wound electrode assembly, comprising: providing a positive electrode sheet, the positive electrode sheet comprising: a first positive electrode winding end portion and a positive electrode winding middle section connected to each other; providing a negative electrode sheet, the negative electrode sheet comprising: a first part and a second part connected to each other; winding the positive electrode sheet and the negative electrode sheet to form the wound electrode assembly, so that the first part is arranged opposite to the first positive electrode winding end portion, and the second part is arranged opposite to the positive electrode winding middle section; wherein, along the winding axis direction of the wound electrode assembly, the negative electrode active material layer of the negative electrode sheet exceeds the positive electrode active material layer of the positive electrode sheet, the maximum width of the negative electrode active material layer of the first part is H1, the minimum width of the positive electrode active material layer of the first positive electrode winding end portion is L1, the maximum width of the negative electrode active material layer of the second part is H2, and the minimum width of the positive electrode active material layer of the positive electrode winding middle section is L2, and H1-L1>H2-L2.

[0044] In the above technical solution, the width difference between the maximum width of the negative electrode active material layer of the first part of the provided negative electrode sheet and the minimum width of the positive electrode active material layer at the first positive electrode winding end of the provided positive electrode sheet is greater than the width difference between the maximum width of the negative electrode active material layer of the second part of the negative electrode sheet and the minimum width of the positive electrode active material layer in the middle section of the positive electrode winding of the positive electrode sheet. This can reduce the risk of lithium plating caused by the relative offset of the first part and the first positive electrode winding end caused by winding technology, winding equipment, etc., which causes the size of the part of the negative electrode active material layer of the negative electrode sheet that exceeds the positive electrode active material layer of the positive electrode sheet along the winding axis direction to not meet the design requirements.

[0045] In a sixth aspect, an embodiment of the present application provides a manufacturing device for a wound electrode assembly, comprising a first providing device, a second providing device and an assembling device, wherein the first providing device is configured to provide a positive electrode sheet, wherein the positive electrode sheet comprises a first positive electrode winding end portion and a positive electrode winding middle section connected to each other; the second providing device is configured to provide a negative electrode sheet, wherein the negative electrode sheet comprises a first part and a second part connected to each other; the assembling device is configured to wind the positive electrode sheet and the negative electrode sheet so that the first part is arranged opposite to the first positive electrode winding end portion, and the second part is arranged opposite to the positive electrode winding middle section; wherein, along the winding axis direction of the wound electrode assembly, the negative electrode active material layer of the negative electrode sheet exceeds the positive electrode active material layer of the positive electrode sheet, the maximum width of the negative electrode active material layer of the first part is H1, the minimum width of the positive electrode active material layer of the first positive electrode winding end portion is L1, the maximum width of the negative electrode active material layer of the second part is H2, and the minimum width of the positive electrode active material layer of the positive electrode winding middle section is L2, and H1-L1>H2-L2.

[0046] In the above technical solution, the positive and negative electrode sheets provided by the first providing device and the second providing device can reduce the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet that exceeds the positive electrode active material layer of the positive electrode sheet along the winding axis direction not meeting the design requirements during the process of winding to form a wound electrode assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0048] Figure 1 A schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0049] Figure 2An exploded view of a battery provided in accordance with some embodiments of the present application;

[0050] Figure 3 An exploded view of a battery cell provided in some embodiments of the present application;

[0051] Figure 4 A schematic structural diagram of a wound electrode assembly provided in some embodiments of the present application;

[0052] Figure 5 for Figure 4 P0-P0 sectional view;

[0053] Figure 6 A schematic structural diagram of an electrode assembly in which the first positive electrode winding end portion is a positive electrode winding tail section provided in some embodiments of the present application;

[0054] Figure 7 A schematic diagram of the structure of an electrode assembly in which the maximum width position of the negative electrode active material layer in the first portion and the minimum width position of the positive electrode active material layer at the first positive electrode winding end are staggered, according to some embodiments of the present application;

[0055] Figure 8 A schematic diagram of the structure of an electrode assembly corresponding to the position of the maximum width of the negative electrode active material layer in the first portion and the position of the minimum width of the positive electrode active material layer at the end of the first positive electrode winding according to some embodiments of the present application;

[0056] Figure 9 A schematic diagram of the structure of the negative electrode sheet provided in some embodiments of the present application;

[0057] Figure 10 A schematic diagram of the structure of a negative electrode sheet in which one end of the first portion extends beyond the second portion, provided in some embodiments of the present application;

[0058] Figure 11 A schematic diagram of die-cutting to form a negative electrode sheet in the prior art;

[0059] Figure 12 A schematic structural diagram of a negative electrode sheet in which one end of the first portion extends beyond the second portion provided in other embodiments of the present application;

[0060] Figure 13 A schematic structural diagram of a first portion of negative electrode sheets with non-uniform widths provided in some embodiments of the present application;

[0061] Figure 14 A schematic structural diagram of a first portion of negative electrode sheets with non-uniform widths provided in some other embodiments of the present application;

[0062] Figure 15 Schematic diagram of the structure of the negative electrode sheet provided in some embodiments of the present application;

[0063] Figure 16 Schematic diagram of the structure of the negative electrode sheet provided in other embodiments of the present application;

[0064] Figure 17 A schematic diagram of the structure of a negative electrode sheet provided in some further embodiments of the present application;

[0065] Figure 18 A schematic diagram of the structure of a negative electrode sheet with an inclined connection surface provided in some embodiments of the present application;

[0066] Figure 19 A schematic structural diagram of a negative electrode sheet in which the first side surface and the connection surface are not coplanar, provided in some embodiments of the present application;

[0067] Figure 20 A schematic diagram of the structure of a negative electrode sheet in which the negative electrode active material layer of the negative electrode tab and the negative electrode active material layer of the negative electrode body are connected, provided in some embodiments of the present application;

[0068] Figure 21 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application;

[0069] Figure 22 for Figure 19 A cross-sectional view taken along the P1-P1 direction;

[0070] Figure 23 Schematic diagram of the structure of electrode assemblies provided in other embodiments of the present application;

[0071] Figure 24 For some cases Figure 21 A cross-sectional view taken along the P2-P2 direction;

[0072] Figure 25 For other cases Figure 21 A cross-sectional view taken along the P2-P2 direction;

[0073] Figure 26 A schematic structural diagram of an electrode assembly with a first extension portion provided in some embodiments of the present application;

[0074] Figure 27 A schematic structural diagram of an electrode assembly with a first extension portion provided in some other embodiments of the present application;

[0075] Figure 28 A schematic structural diagram of an electrode assembly provided in some other embodiments of the present application;

[0076] Figure 29 A schematic structural diagram of a negative electrode sheet having a first portion, a second portion, and a third portion provided in some embodiments of the present application;

[0077] Figure 30 for Figure 28P3-P3 sectional view;

[0078] Figure 31 A schematic structural diagram of a wound electrode assembly provided in some further embodiments of the present application;

[0079] Figure 32 for Figure 29 P4-P4 sectional view;

[0080] Figure 33 A schematic structural diagram of an electrode assembly provided in some further embodiments of the present application;

[0081] Figure 34 For some cases Figure 31 A cross-sectional view taken along the P5-P5 direction;

[0082] Figure 35 For in other cases Figure 31 A cross-sectional view taken along the P5-P5 direction;

[0083] Figure 36 A schematic structural diagram of an electrode assembly with a second extension portion provided in some embodiments of the present application;

[0084] Figure 37 A schematic diagram of the structure of the positive electrode sheet provided in some embodiments of the present application;

[0085] Figure 38 Schematic diagram of the structure of the positive electrode sheet provided in other embodiments of the present application;

[0086] Figure 39 A schematic structural diagram of a positive electrode sheet provided in some further embodiments of the present application;

[0087] Figure 40 A flowchart of a method for manufacturing an electrode assembly is provided for some embodiments of the present application;

[0088] Figure 41 A schematic block diagram of the structure of the electrode assembly manufacturing equipment provided in some embodiments of the present application.

[0089] In the drawings, the drawings are not drawn to scale.

[0090] Marking instructions: 1000-vehicle; 100-battery; 10-case; 11-first case portion; 12-second case portion; 20-battery cell; 21-housing; 22-end cap assembly; 23-electrode assembly; 231-positive electrode sheet; 2311-positive electrode ear; 2312-positive electrode body; 23121-first positive electrode winding end; 23121a-positive electrode active material layer at the first positive electrode winding end; 23122-positive electrode winding middle section; 23122a-positive electrode active material layer at the positive electrode winding middle section; 23121b-starting end of the positive electrode winding starting section; 23121c-positive electrode winding End of the starting section; 23121d-end of the positive electrode winding end section; 23121e-starting end of the positive electrode winding end section; 23121f-positive electrode current collector at the first positive electrode winding end; 23123-second positive electrode winding end; 23123a-positive electrode active material layer at the second positive electrode winding end; 23123b-positive electrode current collector at the second positive electrode winding end; 23124-insulating layer; 23124a-insulating layer at the first positive electrode winding end; 23124b-insulating layer at the positive electrode winding middle section; 23124c-insulating layer at the second positive electrode winding end; 232-negative electrode sheet; 232 1-Negative electrode ear; 2321a-First side; 2321b-Negative electrode active material layer of the negative electrode ear; 2321c-Second side; 2322-Negative electrode body; 23221-First portion; 23221a-Negative electrode active material layer of the first portion; 23221b-Negative electrode current collector of the first portion; 23221c-Connecting surface; 23221d-Starting end of the first portion; 23221e-End of the first portion; 23222-Second portion; 23222a-Negative electrode active material layer of the second portion; 23222b-Negative electrode current collector of the second portion; 23223-Third portion; 23223a-the negative electrode active material layer of the third part; 23223b-the starting end of the third part; 23223c-the end of the third part; 23223d-the bonding surface; 23223e-the negative electrode current collector of the third part; 23224-the first extension portion; 23225-the second extension portion; 233-the diaphragm; 200-the controller; 300-the motor; A-the winding direction; B-the winding axis direction; C-the width direction; I-the straight area; II-the bending area; 400-the manufacturing equipment of the electrode assembly; 410-the first providing device; 420-the second providing device; 430-the assembling device. DETAILED DESCRIPTION

[0091] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0092] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0093] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0094] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "attached" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0095] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0096] The term "plurality" used in this application refers to two or more (including two).

[0097] In this application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application do not limit this. Battery cells may be cylindrical, flat, rectangular, or other shapes, etc., and the embodiments of this application do not limit this. Battery cells are generally divided into three types based on the packaging method: cylindrical battery cells, prismatic battery cells, and soft-pack battery cells, and the embodiments of this application do not limit this.

[0098] The battery referred to in the embodiments of this application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in this application may include a battery module or a battery pack. Batteries generally include a housing that encloses one or more battery cells. The housing prevents foreign matter from affecting the charging or discharging of the battery cells.

[0099] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. A battery cell primarily operates by the movement of metal ions between the positive and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive active material layer, which is coated on the surface of the positive current collector. Taking lithium-ion batteries 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, among others. The negative electrode sheet includes a negative current collector and a negative active material layer, which is coated on the surface of the negative current collector. The negative current collector can be made of copper, and the negative active material can be carbon or silicon, among others. To ensure that high currents can pass without fusing, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together. The separator can be made of materials such as PP (polypropylene) or PE (polyethylene). Furthermore, in this application, the electrode assembly is a wound structure.

[0100] The development of battery technology requires simultaneous consideration of multiple design factors, including performance parameters such as energy density, cycle life, discharge capacity, and charge / discharge rate. Furthermore, battery safety must be considered. Lithium plating is one of the primary factors affecting a battery's electrical and safety performance. Once it occurs, lithium plating not only degrades battery performance but also, as the amount of plating accumulates, dendrites form. These dendrites can potentially pierce the separator, causing a short circuit within the battery and posing a safety hazard. There are many reasons for lithium plating.

[0101] The inventors discovered that lithium deposition occurs at the start and end of winding of the electrode assembly. Analysis revealed that one of the main reasons for lithium deposition is that the size of the portion of the negative electrode active material layer of the negative electrode sheet that extends beyond the positive electrode active material layer of the positive electrode sheet along the winding axis does not meet design requirements. Further research revealed that the reasons for this failure are as follows:

[0102] For the head of the electrode assembly (the starting end of the electrode assembly winding), due to inaccurate feeding position, the wound electrode assembly formed by winding is pulled out from the winding needle, structural errors in the winding device, or the head of the positive electrode sheet and the head of the negative electrode sheet are not restrained, it is easy to cause the head of the positive electrode sheet and the head of the negative electrode sheet to be relatively offset, resulting in the size of the part of the negative electrode sheet that exceeds the positive electrode sheet along the winding axis direction not meeting the design requirements.

[0103] At the tail of the electrode assembly (the end of the winding of the electrode assembly), the negative electrode sheet will be cut at the end of the winding. After cutting, the tail of the negative electrode sheet has no tension. Therefore, the tail of the negative electrode sheet is prone to offset relative to the tail of the positive electrode sheet at the end of the winding. In addition, after the winding is completed, the electrode assembly needs to be transferred for hot pressing. During transportation, the tail of the positive electrode sheet and the tail of the negative electrode sheet are easily offset relative to each other, resulting in the size of the portion of the negative electrode sheet that extends beyond the positive electrode sheet along the winding axis not meeting the design requirements.

[0104] In view of this, an embodiment of the present application provides a technical solution, which reduces the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet that exceeds the positive electrode active material layer of the positive electrode sheet along the winding axis direction not meeting the design requirements by making the maximum width difference between the negative electrode active material layer of the negative electrode sheet at the head or tail position and the positive electrode active material layer of the positive electrode sheet greater than the maximum width difference between the negative electrode active material layer in the middle section and the positive electrode active material layer of the positive electrode sheet.

[0105] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical devices using batteries.

[0106] Electrical equipment can be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and electric tools, etc. Vehicles can be fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0107] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle 1000 as an example.

[0108] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head, or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 can also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0109] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0110] like Figure 2As shown, battery 100 includes a housing 10 and battery cells 20. The battery cells 20 are housed within the housing 10, which provides a space for the battery cells 20. The housing 10 includes a first housing portion 11 and a second housing portion 12, which together define a space for accommodating the battery cells 20. In battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, the multiple battery cells 20 can be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to a combination of series and parallel connections within the multiple battery cells 20. Multiple battery cells 20 can be directly connected in series, in parallel, or in a hybrid configuration, and then the entire battery cell 20 is housed within the housing 10. Alternatively, multiple battery cells 20 can be first connected in series, in parallel, or in a hybrid configuration to form a battery module, which is then connected in series, in parallel, or in a hybrid configuration to form a single unit housed within the housing 10. The battery cells 20 can be cylindrical, flat, or have other shapes.

[0111] In some embodiments, the battery 100 may further include a busbar component (not shown in the figure), and the multiple battery cells 20 may be electrically connected via the busbar component to achieve series connection, parallel connection, or mixed connection of the multiple battery cells 20 .

[0112] Please refer to Figure 3 , Figure 3 Shown is an exploded view of a battery cell 20 provided in some embodiments of the present application. The battery cell 20 includes a shell 21, an end cover assembly 22 and an electrode assembly 23. The shell 21 has an opening, the electrode assembly 23 is accommodated in the shell 21, and the end cover assembly 22 is used to seal the opening. The shell 21 can be in various shapes, such as cylindrical, flat, etc. The shape of the shell 21 can be determined according to the specific shape of the electrode assembly 23. For example, if the electrode assembly 23 is a cylindrical structure, the shell 21 can be a cylindrical structure; if the electrode assembly 23 is a flat structure, the shell 21 can be a rectangular parallelepiped structure. The material of the shell 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not impose any special restrictions on this.

[0113] The number of electrode assemblies 23 of the battery cell 20 may be one or more. Figure 3 The battery cell 20 is shown as an example, wherein the housing 21 is a rectangular parallelepiped and the two electrode assemblies 23 are flat. Figure 3 In the embodiment, two electrode assemblies 23 are arranged side by side.

[0114] Please refer to Figure 4 、 Figure 5 , Figure 4 A schematic structural diagram of a wound electrode assembly 23 is provided for some embodiments of the present application. Figure 5 for Figure 4The electrode assembly 23 includes a positive electrode sheet 231, a negative electrode sheet 232, and a separator 233. The positive electrode sheet 231, the negative electrode sheet 232, and the separator 233 are stacked and wound along a winding direction A to form the electrode assembly 23. The separator 233 is used to separate the positive electrode sheet 231 from the negative electrode sheet 232 to prevent internal short circuits in the battery 100 or the battery cell 20.

[0115] The positive electrode sheet 231 includes a positive electrode ear 2311 and a positive electrode body 2312. The positive electrode body 2312 of the positive electrode sheet 231 includes a first positive electrode winding end 23121 and a positive electrode winding middle section 23122 connected to each other. The positive electrode ear 2311 protrudes from the positive electrode body 2312 along the winding axis direction B; the negative electrode sheet 232 includes a negative electrode body 2322 and a negative electrode ear 2321. The negative electrode body 2322 of the negative electrode sheet 232 includes a first part 23221 and a second part 23222 connected to each other. The negative electrode ear 2321 protrudes from the negative electrode body 2322 along the winding axis direction B. Along the thickness direction of the positive electrode sheet 231, the positive electrode tab 2311 may or may not protrude from the positive electrode body 2312. For example, if the positive electrode tab 2311 is welded to one end of the positive electrode body 2312 along the winding axis direction B, the positive electrode tab 2311 may protrude from the positive electrode body 2312 along the thickness direction; if the positive electrode tab 2311 is formed by a die-cut positive electrode current collector, the positive electrode tab 2311 may not protrude from the positive electrode body 2312. Along the thickness direction of the negative electrode sheet 232, the negative electrode tab 2321 may or may not protrude from the negative electrode body 2322. For example, if the negative electrode tab 2321 is welded to one end of the negative electrode body 2322 along the winding axis direction B, the negative electrode tab 2321 may protrude from the negative electrode body 2322 along the thickness direction. If the negative electrode tab 2321 is formed by die-cutting the negative electrode current collector, the negative electrode tab 2321 may not protrude from the negative electrode body 2322. When the electrode assembly is wound, the thickness direction of the positive electrode sheet 231 is perpendicular to the winding axis direction B of the electrode assembly 23, and the thickness direction of the negative electrode sheet 232 is perpendicular to the winding axis direction B of the electrode assembly 23.

[0116] The first part 23221 is arranged opposite to the first positive electrode winding end 23121, and the second part 23222 is arranged opposite to the positive electrode winding middle section 23122; along the winding axis direction B of the wound electrode assembly 23, the negative electrode active material layer of the negative electrode sheet 232 exceeds the positive electrode active material layer of the positive electrode sheet 231, the maximum width of the negative electrode active material layer 23221a of the first part is H1, the minimum width of the positive electrode active material layer 23121a at the first positive electrode winding end is L1, the maximum width of the negative electrode active material layer 23222a of the second part is H2, and the minimum width of the positive electrode active material layer 23122a in the positive electrode winding middle section is L2, H1-L1>H2-L2.

[0117] By setting the width difference between the maximum width of the negative electrode active material layer 23221a of the first part and the minimum width of the positive electrode active material layer 23121a at the end of the first positive electrode winding to be greater than the width difference between the maximum width of the negative electrode active material layer 23222a of the second part and the minimum width of the positive electrode active material layer 23122a in the middle section of the positive electrode winding, that is, the maximum width difference between the positive electrode active material layer 23121a at the end of the first positive electrode winding and the negative electrode active material layer 23221a of the first part is greater than the maximum width difference between the negative electrode active material layer 23222a of the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding, the risk of lithium plating caused by the size of the part of the negative electrode active material layer of the negative electrode sheet 232 that exceeds the positive electrode active material layer of the positive electrode sheet 231 along the winding axis direction B not meeting the design requirements is reduced.

[0118] It should be noted that the width of the positive active material layer of the positive electrode sheet 231 and the width of the negative active material layer of the negative electrode sheet 232 both refer to the dimensions along the winding axis B of the wound electrode assembly 23. Specifically, the maximum width of the negative active material layer 23221a in the first portion refers to the maximum dimension of the negative active material layer 23221a in the first portion along the winding axis B; the minimum width of the positive active material layer 23121a at the end of the first positive electrode winding refers to the minimum dimension of the positive active material layer 23121a at the end of the first positive electrode winding refers to the minimum dimension of the positive active material layer 23121a at the end of the first positive electrode winding refers to the minimum dimension of the positive active material layer 23121a at the end of the first positive electrode winding refers to the maximum dimension of the negative active material layer 23222a in the second portion along the winding axis B; and the minimum width of the positive active material layer 23122a in the middle section of the positive electrode winding refers to the minimum dimension of the positive active material layer 23122a in the middle section of the positive electrode winding refers to the minimum dimension of the positive active material layer 23122a in the middle section of the positive electrode winding refers to the minimum dimension of the positive active material layer 23122a in the middle section of the positive electrode winding refers to the minimum dimension of the positive active material layer 23122a in the middle section of the positive electrode winding refers to the minimum dimension of the positive active material layer 23122a in the middle section of the positive electrode winding refers to the minimum dimension of the positive active material layer 23122a in the middle section of the positive electrode winding

[0119] The maximum width difference refers to the difference between the maximum width and the minimum width. The maximum width difference between the positive electrode active material layer 23121a at the end of the first positive electrode winding and the negative electrode active material layer 23221a in the first part is H1-L1; the maximum width difference between the negative electrode active material layer 23222a in the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding is H2-L2.

[0120] In some embodiments, see Figure 4 、 Figure 5The first positive electrode winding end portion 23121 is the starting section of the positive electrode winding. The first positive electrode winding end portion 23121 is the positive electrode body 2312 that is wound for a distance along the winding direction A of the wound electrode assembly 23 starting from the starting end 23121b of the positive electrode winding starting section. The positive electrode winding middle section 23122 is the positive electrode body 2312 that is connected to the end of the first positive electrode winding end portion 23121 (the end 23121c of the positive electrode winding starting section) and is wound for a distance along the winding direction A of the wound electrode assembly 23.

[0121] The portion with a larger line width shown in the diagram of this application is the portion where the width of the negative electrode active material layer of the negative electrode sheet 232 is increased, and does not mean that the thickness of the portion with a larger line width of the negative electrode sheet 232 is larger than the thickness of the portion with a smaller line width of the negative electrode sheet 232. When the electrode assembly is in a wound state, the thickness direction of the negative electrode sheet 232 is perpendicular to the winding axis direction B of the electrode assembly 23.

[0122] The first part 23221 is arranged opposite to the first positive electrode winding end 23121, that is, the first part 23221 is arranged opposite to the starting section of the positive electrode winding, which is further explained as follows: the starting end 23221d of the first part corresponds to the starting end 23121b of the starting section of the positive electrode winding, and the end 23221e of the first part corresponds to the end 23121c of the starting section of the positive electrode winding.

[0123] When the first positive electrode winding end 23121 is the positive electrode winding starting section, the positive electrode active material layer at the positive electrode winding starting end and the negative electrode active material layer 23221a of the first part satisfy: H1-L1>H2-L2, which can reduce the possibility that the positive electrode winding starting section and the first part 23221 are relatively offset due to inaccurate feeding position, the wound electrode assembly formed by winding is pulled out from the winding needle, structural errors of the winding device, or the positive electrode winding starting section and the first part 23221 are not bound, thereby causing the size of the part of the negative electrode sheet 232 that exceeds the positive electrode sheet 231 along the winding axis direction B to not meet the design requirements.

[0124] In some embodiments, as Figure 6 As shown, the first positive electrode winding end portion 23121 is the positive electrode winding tail section, and the first positive electrode winding end portion 23121 is the positive electrode body 2312 that is wound for a distance starting from the end 23121d of the positive electrode winding tail section and wound in the opposite direction of the winding direction A of the wound electrode assembly 23, and the positive electrode winding middle section 23122 is the positive electrode body 2312 that is connected to the starting end of the first positive electrode winding end portion 23121 (the starting end 23121e of the positive electrode winding tail section) and wound in the opposite direction of the winding direction A of the wound electrode assembly 23.

[0125] The first portion 23221 is disposed opposite the first positive electrode winding end 23121, that is, the first portion 23221 is disposed opposite the positive electrode winding end section. Specifically, the end 23221e of the first portion corresponds to the end 23121d of the positive electrode winding end section, and the starting end 23221d of the first portion corresponds to the starting end 23121e of the positive electrode winding end section. The positive electrode active material layer of the positive electrode winding end section and the negative electrode active material layer 23221a of the first portion satisfy the following relationship: H1-L1>H2-L2. This reduces the possibility that the first portion 23221 may shift relative to the positive electrode winding end section during transportation due to a lack of tension in the first portion 23221 after the negative electrode sheet 232 is cut at the end of winding, or due to the need to transfer the electrode assembly 23 to hot pressing after winding is completed. This could result in the negative electrode sheet 232 extending beyond the positive electrode sheet 231 along the winding axis B, potentially failing to meet design requirements.

[0126] Along the winding direction A, each position on the positive electrode active material layer 23121a at the first positive electrode winding end has a corresponding position on the negative electrode active material layer 23221a in the first portion. In some embodiments, the position of the maximum width of the negative electrode active material layer 23221a in the first portion and the position of the minimum width of the positive electrode active material layer 23121a at the first positive electrode winding end are staggered. For example, Figure 7 In the figure, M1 is the position with the largest width of the negative electrode active material layer 23221a in the first portion, and N1 is the position with the smallest width of the positive electrode active material layer 23121a at the first positive electrode winding end. M1 and N1 are offset in the winding direction A. Figure 7 In FIG. 2 , the dotted lines other than the dotted line representing the diaphragm 233 are only used to clarify the relative positional relationship between M1 and N1.

[0127] In some embodiments, the maximum width position of the first portion of the negative electrode active material layer 23221a corresponds to the minimum width position of the first positive electrode winding end portion 23121. For example, Figure 8 In the figure, M2 is the position of the negative electrode active material layer 23221a in the first portion having the largest width, and N2 is the position of the positive electrode active material layer 23121a at the first positive electrode winding end portion having the smallest width. M2 and N2 correspond to each other. Figure 8 In FIG. 2 , the dotted lines other than the dotted line representing the diaphragm 233 are only used to clarify the relative positional relationship between M2 and N2.

[0128] In order to achieve a maximum width difference between the positive electrode active material layer 23121a at the end of the first positive electrode winding and the negative electrode active material layer 23221a in the first part, which is greater than the maximum width difference between the negative electrode active material layer 23222a in the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding, the negative electrode sheet 232, the positive electrode sheet 231, or both the positive electrode sheet 231 and the negative electrode sheet 232 can be improved.

[0129] In some embodiments, the structure of the negative electrode sheet 232 is improved to achieve a maximum width difference between the positive electrode active material layer 23121a at the end of the first positive electrode winding and the negative electrode active material layer 23221a in the first part, which is greater than the maximum width difference between the negative electrode active material layer 23222a in the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding.

[0130] In some embodiments, please refer to Figure 9 , Figure 9 Schematic diagram of the structure of the negative electrode sheet 232 provided in some embodiments of the present application. Along the winding axis direction B (consistent with the width direction C shown in the figure), there is a width difference between the negative electrode active material layer 23221a of the first portion and the negative electrode active material layer 23222a of the second portion, H1>H2. This is equivalent to the negative electrode active material layer 23221a of the first portion being wider than the negative electrode active material layer 23222a of the second portion. While ensuring energy density, this can reduce the risk of lithium deposition caused by the size of the portion of the negative electrode active material layer of the negative electrode sheet 232 that extends beyond the positive electrode active material layer of the positive electrode sheet 231 along the winding axis direction B not meeting design requirements.

[0131] In some embodiments, the minimum width of the first portion of the negative electrode active material layer 23221a is H3, where H3 ≥ H2. If the maximum width of the first portion of the negative electrode active material layer 23221a is greater than the maximum width of the second portion of the negative electrode active material layer 23222a, and the minimum width of the first portion of the negative electrode active material layer 23221a is not less than the maximum width of the second portion of the negative electrode active material layer 23222a, the possibility of lithium deposition caused by relative offset between the first positive electrode winding end portion 23121 and the first portion 23221, resulting in the negative electrode active material layer 23221a of the first portion extending beyond the positive electrode winding end portion along the winding axis direction B, not meeting design requirements, can be reduced.

[0132] When the width of the first portion 23221 is too large, it may exceed the width of the diaphragm 233 and may collide with the end cap assembly 22 (such as Figure 3If the width of the first portion 23221 is too small, it can easily be affected by the tolerances of the winding equipment and fail to cover the first positive electrode winding end 23121. In some embodiments, 0.3 mm ≤ H1-H2 ≤ 3 mm. This ensures the safe use of the wound electrode assembly 23 and allows the first portion 23221 of the negative electrode sheet 232 to cover the first positive electrode winding end 23121, reducing the possibility that the negative electrode active material layer of the negative electrode sheet 232 may extend beyond the positive electrode active material layer of the positive electrode sheet 231 along the winding axis B, failing to meet design requirements. In some embodiments, 0.3 mm ≤ H1-H2 ≤ 1.5 mm.

[0133] In some embodiments, please refer to Figure 9 The negative electrode active material layer 23221a in the first portion has a uniform width structure, and thus the widths of the negative electrode active material layer 23221a in the first portion are the same, H1 = H3.

[0134] In some embodiments, as Figure 9 As shown, along the winding axis direction B (which is consistent with the width direction C shown in the figure), both ends of the first portion of the negative electrode active material layer 23221 a extend beyond both ends of the second portion of the negative electrode active material layer 23222 a . Figure 9 The dotted line is only used to distinguish the first portion 23221 from the second portion 23222 and does not affect the structure of the negative electrode sheet 232 .

[0135] In some embodiments, as Figure 10 As shown, along the winding axis direction B (consistent with the width direction C shown in the figure), one end of the negative electrode active material layer 23221a of the first part exceeds the corresponding end of the negative electrode active material layer 23222a of the second part, and the other end of the negative electrode active material layer 23221a of the first part is flush with the other end of the negative electrode active material layer 23222a of the second part. Figure 10 The dotted line is only used to distinguish the first portion 23221 from the second portion 23222 and does not affect the structure of the negative electrode sheet 232 .

[0136] One end of the negative electrode active material layer 23221a of the first part extends beyond the corresponding end of the negative electrode active material layer 23222a of the second part, which means that the end of the negative electrode active material layer 23221a of the first part extends beyond the end of the negative electrode active material layer 23222a of the second part along the winding axis direction B and is closest to it.

[0137] In some embodiments, please refer to Figure 10Along the winding axis direction B (which is consistent with the width direction C shown in the figure), the negative electrode tab 2321 is located at one end of the negative electrode sheet 232. The end of the first portion of the negative electrode active material layer 23221a closest to the negative electrode tab 2321 extends beyond the corresponding end of the second portion of the negative electrode active material layer 23222a. The other end of the first portion of the negative electrode active material layer 23221a is flush with the other end of the second portion of the negative electrode active material layer 23222a. "Flush" means that the other end of the first portion of the negative electrode active material layer 23221a and the other end of the second portion of the negative electrode active material layer 23222a are located in the same plane. Along the winding axis direction B, the end of the first portion of the negative electrode active material layer 23221a closest to the negative electrode tab 2321 extends entirely beyond the corresponding end of the second portion of the negative electrode active material layer 23222a. The other end of the first portion of the negative electrode active material layer 23221a is flush with the other end of the second portion of the negative electrode active material layer 23222a.

[0138] The negative electrode sheet 232 is generally formed in the following manner: Figure 11 As shown, a negative electrode active material layer with uniform width is coated on the negative electrode current collector, and then the negative electrode ears 2321 are formed by die-cutting on both sides of the negative electrode current collector in the width direction C. Then, two negative electrode sheets 232 with negative electrode ears 2321 on one side are formed by cutting from the middle position in the width direction C, that is, Figure 11 Two negative electrode sheets 232 are formed by die-cutting in the direction of the dotted line. The end of the first portion of the negative electrode active material layer 23221a near the negative electrode tab 2321 extends beyond the corresponding end of the second portion of the negative electrode active material layer 23222a. During the die-cutting process to form the negative electrode tab 2321, a negative electrode sheet 232 having a width difference between the first portion of the negative electrode active material layer 23221a and the second portion of the negative electrode active material layer 23222a can be formed. In other words, a negative electrode sheet having a width difference between the first portion of the negative electrode active material layer 23221a and the second portion of the negative electrode active material layer 23222a can be formed using the existing molding process for the negative electrode sheet 232.

[0139] It should be noted that, after winding to form an electrode assembly, the width direction C of the negative electrode current collector is consistent with the winding axis direction B of the electrode assembly.

[0140] In some embodiments, as Figure 12 As shown, along the winding axis direction B (consistent with the width direction C shown in the figure), one end of the negative electrode active material layer 23221a of the first part away from the negative electrode ear 2321 may at least partially exceed the corresponding end of the negative electrode active material layer 23222a of the second part, and the other end of the negative electrode active material layer 23221a of the first part is flush with the other end of the negative electrode active material layer 23222a of the second part. Figure 12The dotted line is only used to distinguish the first portion 23221 from the second portion 23222 and does not affect the structure of the negative electrode sheet 232 .

[0141] In some embodiments, the first portion of the negative electrode active material layer 23221a has a variable width structure, and thus the width of the first portion of the negative electrode active material layer 23221a is not uniform. The first portion of the negative electrode active material layer 23221a has a variable width structure and has various structural forms.

[0142] Please refer to Figure 13 The width of the negative electrode active material layer 23221a of the first part gradually increases in the direction away from the second part 23222, and the width of any position of the negative electrode active material layer 23221a of the first part is greater than the maximum width of the negative electrode active material layer 23222a of the second part. Figure 13 The dotted line is only used to distinguish the first portion 23221 from the second portion 23222 and does not affect the structure of the negative electrode sheet 232 .

[0143] like Figure 14 As shown, the width of the first portion of the negative electrode active material layer 23221a is smaller than the width of the other portions of the first portion of the negative electrode active material layer 23221a. Figure 14 In the embodiment, the width of the negative electrode active material layer on both sides of the negative electrode tab 2321 protruding from the first portion 23221 is greater than the width of the negative electrode active material layer at the connection between the first portion 23221 and the negative electrode tab 2321. When H3 = H2, the end of the negative electrode active material layer 23221a of the first portion near the negative electrode tab 2321 partially protrudes beyond the negative electrode active material layer 23222a of the second portion. When H3 > H2, the end of the negative electrode active material layer 23221a of the first portion near the negative electrode tab 2321 completely protrudes beyond the negative electrode active material layer 23222a of the second portion. Figure 14 The dotted line is only used to distinguish the first portion 23221 from the second portion 23222 and does not affect the structure of the negative electrode sheet 232 .

[0144] As long as the maximum width of the negative electrode active material layer 23221a in the first portion is greater than the maximum width of the negative electrode active material layer 23222a in the second portion, and the minimum width of the negative electrode active material layer 23221a in the first portion is not less than the maximum width of the negative electrode active material layer 23222a in the second portion, the possibility of lithium plating can be reduced. Therefore, along the winding axis direction B, the width of the negative electrode current collector 23221b in the first portion and the width of the negative electrode current collector 23222b in the second portion can be the same or different.

[0145] In some embodiments, as Figure 15As shown, along the winding axis direction B (consistent with the width direction C shown in the figure), the width of the negative electrode current collector 23221b of the first part is consistent with that of the negative electrode current collector 23222b of the second part, one end of the negative electrode active material layer 23221a of the first part close to the negative electrode ear 2321 is flush with the corresponding end of the negative electrode current collector 23221b of the first part, and the other end of the negative electrode active material layer 23221a of the first part is flush with the corresponding end of the negative electrode current collector 23221b of the first part. one end of the negative electrode current collector 23222b of the second part close to the negative electrode ear 2321 extends beyond the corresponding end of the negative electrode active material layer 23222a of the second part, and the other end of the negative electrode current collector 23222b of the second part is flush with the corresponding end of the negative electrode active material layer 23222a of the second part; one end of the negative electrode active material layer 23221a of the first part close to the negative electrode ear 2321 extends beyond the corresponding end of the negative electrode active material layer 23222a of the second part.

[0146] In some embodiments, as Figure 16 As shown, along the winding axis direction B (consistent with the width direction C in the figure), one end of the negative electrode current collector 23221b of the first part away from the negative electrode ear 2321 exceeds the corresponding end of the negative electrode active material layer 23221a of the first part, and the other end of the negative electrode current collector 23221b of the first part is flush with the other end of the negative electrode active material layer 23221a of the first part; one end of the negative electrode current collector 23222b of the second part away from the negative electrode ear 2321 exceeds the corresponding end of the negative electrode active material layer 23222a of the second part, and the other end of the negative electrode current collector 23222b of the second part is flush with the other end of the negative electrode active material layer 23221a of the first part. The corresponding ends of the negative electrode active material layers 23222a of the two parts are flush; the end of the negative electrode current collector 23221b of the first part away from the negative electrode ear 2321 is flush with the end of the negative electrode current collector 23222b of the second part away from the negative electrode ear 2321; the end of the negative electrode active material layer 23221a of the first part away from the negative electrode ear 2321 is flush with the corresponding end of the negative electrode active material layer 23222a of the second part, and the end of the negative electrode active material layer 23221a of the first part close to the negative electrode ear 2321 exceeds the corresponding end of the negative electrode active material layer 23222a of the second part.

[0147] In some embodiments, as Figure 17As shown, along the winding axis direction B (consistent with the width direction C in the figure), one end of the first portion 23221 close to the negative electrode ear 2321 extends beyond the corresponding end of the second portion 23222, and the other end of the first portion 23221 is flush with the other end of the second portion 23222. It can be understood that one end of the negative electrode current collector 23221b of the first portion close to the negative electrode ear 2321 extends beyond the corresponding end of the negative electrode current collector 23222b of the second portion, and the other end of the negative electrode current collector 23221b of the first portion is flush with the other end of the negative electrode current collector 23222b of the second portion; one end of the negative electrode active material layer 23221a of the first portion close to the negative electrode ear 2321 extends beyond the corresponding end of the negative electrode active material layer 23222a of the second portion, and the other end of the negative electrode active material layer 23221a of the first portion is flush with the other end of the negative electrode active material layer 23222a of the second portion; One end of the negative electrode current collector 23221b close to the negative electrode ear 2321 is flush with one end of the negative electrode active material layer 23221a of the first part close to the negative electrode ear 2321, and the other end of the negative electrode current collector 23221b of the first part is flush with the other end of the negative electrode active material layer 23221a of the first part; one end of the negative electrode current collector 23222b of the second part close to the negative electrode ear 2321 is flush with one end of the negative electrode active material layer 23222a of the second part close to the negative electrode ear 2321, and the other end of the negative electrode current collector 23222b of the second part is flush with the other end of the negative electrode active material layer 23222a of the second part. This type of negative electrode sheet 232 is not only convenient for coating the negative electrode active material layer, but also can form a negative electrode sheet 232 with a width difference between the first part 23221 and the second part 23222 during the process of die-cutting to form the negative electrode ear 2321. That is, the negative electrode sheet 232 with a width difference between the first part 23221 and the second part 23222 can be formed by utilizing the original molding process of the negative electrode sheet 232.

[0148] In some embodiments, see Figure 17 Along the winding direction A, the first portion 23221 has a connecting surface 23221c connected to the second portion 23222. There are multiple negative electrode tabs 2321, one of which protrudes from the first portion 23221 along the winding axis direction B and has a first side surface 2321a adjacent to the second portion 23222. The first side surface 2321a is coplanar with the connecting surface 23221c. The connecting surface 23221c connecting the first portion 23221 and the second portion 23222 is coplanar with one side surface of the negative electrode tab 2321. This prevents the connecting surface 23221c from warping due to lack of restraint during and after winding, thereby puncturing the separator 233.

[0149] In some embodiments, see Figure 17, along the winding axis direction B (consistent with the width direction C in the figure), the extension direction of the first side surface 2321a is consistent with the winding axis direction B, and the connecting surface 23221c is a plane parallel to the first side surface 2321a, that is, the extension direction of the connecting surface 23221c is consistent with the winding axis direction B.

[0150] In some embodiments, as Figure 18 As shown, the first side surface 2321a is an inclined surface that gradually tilts toward the second portion 23222 from top to bottom in the figure, and the connecting surface 23221c is also an inclined surface. Along the winding axis direction B, the connecting surface 23221c gradually tilts toward the second portion 23222 starting from the end close to the negative electrode ear 2321.

[0151] In some embodiments, as Figure 19 As shown, the connecting surface 23221 c may also be located between two adjacent negative electrode tabs 2321 and not be coplanar with the side surface of any negative electrode tab 2321 .

[0152] In some embodiments, the number of the negative electrode tab 2321 may be one, and the first side surface 2321 a of the negative electrode tab 2321 may be coplanar or non-coplanar with the connecting surface 23221 c .

[0153] In some embodiments, as Figure 20 As shown, along the winding axis direction B (consistent with the width direction C shown in the figure), a negative electrode active material layer is provided on the negative electrode tab 2321 protruding from the first portion 23221, and the negative electrode active material layer 2321b of the negative electrode tab protruding from the first portion 23221 is connected to the negative electrode active material layer 23221a of the first portion. The negative electrode active material layer on the negative electrode tab 2321 also serves to cover the positive electrode sheet 231, which is equivalent to further increasing the width of the negative electrode active material layer at a portion of the first portion 23221. This can further reduce the risk of lithium deposition caused by the negative electrode active material layer of the negative electrode sheet 232 extending beyond the positive electrode active material layer of the positive electrode sheet 231 in the winding axis direction B not meeting design requirements.

[0154] In some embodiments, please refer to Figure 21The wound electrode assembly 23 includes a straight region I and two bent regions II, each connected to the ends of the straight region I. The first portion 23221 passes through the straight region I at least twice. In practice, after passing through the straight region I twice, the winding length of the first portion 23221 is close to one turn. When entering the next turn of winding, it has a certain restraining effect on the starting end 23121b of the positive electrode winding start segment and the starting end of the negative electrode sheet 232. The possibility of relative offset between the first positive electrode winding end 23121 and the first portion 23221 is low. Therefore, the first portion 23221 passes through the straight region I at least twice. This can minimize the possibility of lithium deposition caused by the relative offset between the first positive electrode winding end 23121 and the first portion 23221, resulting in the positive electrode active material layer 23121a of the first positive electrode winding end extending beyond the negative electrode active material layer 23221a of the first portion along the winding axis direction B not meeting design requirements.

[0155] The positive electrode collector of the positive electrode sheet 231 is coated with a positive electrode active material layer on both the inner and outer sides. The widths of the positive electrode active material layers on the inner and outer sides of the positive electrode collector of the positive electrode sheet 231 can be the same or different. The negative electrode collector of the negative electrode sheet 232 is coated with a negative electrode active material layer on both the inner and outer sides. The widths of the negative electrode active material layers on the inner and outer sides of the negative electrode collector of the negative electrode sheet 232 can be the same or different.

[0156] In some embodiments, the width of the negative electrode active material layer 23221a of the first part and the width of the positive electrode active material layer 23121a of the first positive electrode winding end can be compared only by the width comparison of the negative electrode active material layer of the first part 23221 facing the first positive electrode winding end 23121 and the positive electrode active material layer of the first positive electrode winding end 23121 facing the first part 23221. Then, only the width of the negative electrode active material layer of the first part 23221 facing the first positive electrode winding end 23121 can be increased to satisfy H1-L1>H2-L2.

[0157] It should be noted that the inner and outer sides of the positive current collector of the positive electrode sheet 231 and the negative current collector of the negative electrode sheet 232 are relative to the winding axis. The side of the positive current collector of the positive electrode sheet 231 close to the winding axis is the inner side of the positive current collector of the positive electrode sheet 231, and the side of the positive electrode sheet 231 away from the winding axis is the outer side of the positive current collector of the positive electrode sheet 231. The side of the negative current collector of the negative electrode sheet 232 close to the winding axis is the inner side of the negative current collector of the negative electrode sheet 232, and the side of the negative current collector of the negative electrode sheet 232 away from the winding axis is the outer side of the negative current collector of the negative electrode sheet 232.

[0158] In some embodiments, as Figure 21 、 Figure 22As shown, the first part 23221 passes through the straight area I twice, and the first positive electrode winding end 23121 passes through the straight area I twice. The negative electrode active material layer on the outside of the negative electrode collector 23221b of the first part of the two straight areas I faces the positive electrode active material on the inside of the positive electrode collector 23121f of the first positive electrode winding end. The negative electrode active material layer on the outside of the negative electrode collector 23221b of the first part of the two straight areas I can only be widened to satisfy: H1-L1>H2-L2.

[0159] In some embodiments, as Figure 23 、 Figure 24 As shown, the first part 23221 passes through the straight area I three times, which are the first straight area, the second straight area and the third straight area in the order of passing (first → last). If the first positive electrode winding end 23121 passes through the straight area I twice, the negative electrode active material layer on the inner side of the negative electrode current collector 23221b of the first part of the third straight area faces the positive electrode active material layer on the outer side of the positive electrode current collector 23121f of the first positive electrode winding end located in the first straight area, and the positive electrode active material layer on the outer side of the positive electrode current collector 23121f of the first positive electrode winding end located in the first straight area is located between the first straight area and the second straight area. The negative electrode active material layer on the outside of the negative electrode collector 23221b in the first part of the straight area faces the positive electrode active material layer on the inside of the positive electrode collector 23121f at the first positive electrode winding end. Then, along the winding axis direction B, only the negative electrode active material layer on the outside of the negative electrode collector 23221b located in the first part of the second straight area and the negative electrode active material layer on the inside of the negative electrode collector 23221b located in the first part of the third straight area can be widened to satisfy H1-L1>H2-L2.

[0160] like Figure 25 As shown, if the first positive electrode winding end 23121 passes through the straight area I three times, the negative electrode active material layers on the inner and outer sides of the negative electrode current collector 23221b located in the first part of the third straight area respectively face the positive electrode active material layer on the outer side of the positive electrode current collector 23121f located at the first positive electrode winding end of the first straight area and the positive electrode active material layer on the inner side of the positive electrode current collector 23121f located at the first positive electrode winding end of the third straight area, and the negative electrode current collector 23221b located in the first part of the first straight area and the second straight area respectively face the positive electrode active material layer on the outer side of the positive electrode current collector 23121f located at the first positive electrode winding end of the first straight area. The negative electrode active material layer on the outside of 3221b faces the positive electrode active material layer on the inside of the positive electrode collector 23121f located at the first positive electrode winding end of the first flat area and the second flat area. Then, along the winding axis direction, only the negative electrode active material layer on the outside of the negative electrode collector 23221b located in the first part of the first flat area and the second flat area, and the negative electrode active material layers on the inside and outside of the negative electrode collector 23221b located in the first part of the third flat area can be widened to satisfy H1-L1>H2-L2.

[0161] In some embodiments, the wound electrode assembly 23 is a cylindrical electrode assembly 23 , and the first portion 23221 is wound at least once.

[0162] like Figure 26 As shown, in order to ensure that the negative electrode sheet 232 can completely cover the positive electrode sheet 231 in the winding direction A, the negative electrode body 2322 also includes a first extension portion 23224. Along the winding direction A, the first extension portion 23224 is connected to the end of the first part 23221 away from the second part 23222, and the first extension portion 23224 exceeds the starting end of the first positive electrode winding end 23121 (the starting end 23121b of the positive electrode winding starting section) in the opposite direction of the winding direction A. Among them, the width of the negative electrode active material layer of the first extension portion 23224 along the winding axis direction B may be increased or not increased relative to the negative electrode active material layer 23222a of the second part. The negative electrode active material layer of the first extension portion 23224 increases in width relative to the negative electrode active material layer 23222a of the second part (please refer to Figure 23 ).like Figure 26 As shown, the negative electrode active material layer of the first extension portion 23224 does not have a larger width than the negative electrode active material layer 23222a of the second portion.

[0163] In some embodiments, as Figure 27 As shown, the negative electrode tab 2321 protrudes from the first extension portion 23224. Thus, along the winding direction A, the negative electrode active material layers on both sides of the negative electrode tab 2321 of the first extension portion 23224 have a greater width relative to the negative electrode active material layers 23222a of the second portion. In some embodiments, along the winding direction A, only one side of the negative electrode active material layers on both sides of the negative electrode tab 2321 of the first extension portion 23224 has a greater width relative to the negative electrode active material layers 23222a of the second portion.

[0164] In some embodiments, as Figure 28 As shown, the positive electrode body 2312 of the positive electrode sheet 231 further includes a second positive electrode winding end 23123 , and the first positive electrode winding end 23121 and the second positive electrode winding end 23123 are respectively connected to two ends of the positive electrode winding middle section 23122 .

[0165] The negative electrode body 2322 of the negative electrode sheet 232 also includes a third part 23223, the first part 23221 and the third part 23223 are respectively connected to the two ends of the second part 23222, and the third part 23223 and the second positive electrode winding end 23123 are arranged opposite to each other; the maximum width of the negative electrode active material layer 23223a of the third part is H4, and the minimum width of the positive electrode active material layer 23123a of the second positive electrode winding end is L3, H4-L3>H2-L2.

[0166] In some embodiments, the first positive electrode winding end portion 23121 is the positive electrode winding starting segment, and the second positive electrode winding end portion 23123 is the positive electrode winding ending segment. The first positive electrode winding end portion 23121 is the positive electrode body 2312 wound along the winding direction A of the wound electrode assembly 23 for a distance, starting from the starting end 23121b of the positive electrode winding starting segment. The positive electrode winding middle segment 23122 is the positive electrode body 2312 wound along the winding direction A of the wound electrode assembly 23 for a distance, connected to the end of the first positive electrode winding end portion 23121 (the end 23121c of the positive electrode winding starting segment). The second positive electrode winding end portion 23123 is a positive electrode body 2312 that is wound for a distance starting from the end 23121d of the positive electrode winding tail section (the end of the second positive electrode winding end portion 23123) in the opposite direction of the winding direction A of the wound electrode assembly 23, and the positive electrode winding middle section 23122 is a positive electrode body 2312 that is connected to the starting end of the second positive electrode winding end portion 23123 (the starting end 23121e of the positive electrode winding tail section) and is wound for a distance in the opposite direction of the winding direction A of the wound electrode assembly 23.

[0167] The third part 23223 and the second positive electrode winding end 23123 are arranged opposite to each other, that is, the third part 23223 is arranged opposite to the positive electrode winding tail section, which is further explained as follows: the starting end 23223b of the third part corresponds to the starting end of the second positive electrode winding end 23123 (the starting end 23121e of the positive electrode winding tail section), and the end 23223c of the third part corresponds to the end of the second positive electrode winding end 23123 (the end 23121d of the positive electrode winding tail section).

[0168] The maximum width difference between the positive electrode active material layer 23121a at the end of the first positive electrode winding and the negative electrode active material layer 23221a in the first part is greater than the maximum width difference between the negative electrode active material layer 23222a in the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding. The maximum width difference between the positive electrode active material layer 23123a at the end of the second positive electrode winding and the negative electrode active material layer 23223a in the third part is greater than the maximum width difference between the negative electrode active material layer 23222a in the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding, thereby reducing the risk of lithium plating caused by the relative offset between the head of the positive electrode sheet 231 and the head of the negative electrode sheet 232, and the tail of the positive electrode sheet 231 and the tail of the negative electrode sheet 232, so that the size of the part of the negative electrode active material layer of the negative electrode sheet 232 that exceeds the positive electrode active material layer of the positive electrode sheet 231 along the winding axis direction does not meet the design requirements.

[0169] In some embodiments, as Figure 28 、 Figure 29As shown, H4>H2. Because the third portion 23223 is disposed opposite the second positive electrode winding end portion 23123, and the second portion 23222 is disposed opposite the positive electrode winding middle section 23122, the maximum width of the negative electrode active material layer 23223a of the third portion is greater than the maximum width of the negative electrode active material layer 23222a of the second portion. This is equivalent to the negative electrode active material layer 23223a of the third portion having a greater width than the negative electrode active material layer 23222a of the second portion. This can reduce the risk of lithium deposition caused by the size of the portion of the negative electrode active material layer of the negative electrode sheet 232 that extends beyond the positive electrode active material layer of the positive electrode sheet 231 in the winding axis direction B not meeting design requirements, while ensuring energy density.

[0170] In some embodiments, the minimum width of the third portion of the negative electrode active material layer 23223a is H5, where H5 ≥ H2. The minimum width of the third portion of the negative electrode active material layer 23223a is no less than the maximum width of the second portion of the negative electrode active material layer 23222a, thereby reducing the risk of lithium deposition caused by the portion of the third portion of the negative electrode active material layer 23223a extending beyond the positive electrode active material layer 23123a at the end of the second positive electrode winding in the winding axis direction B not meeting design requirements.

[0171] The structure of the third part 23223 can refer to the structure of the first part 23221, the structural relationship between the third part 23223 and the second part 23222 can refer to the structural relationship between the first part 23221 and the second part 23222, the structure of the second positive electrode winding end 23123 can refer to the first positive electrode winding end 23121, the relative relationship between the second positive electrode winding end 23123 and the third part 23223 can refer to the relative relationship between the first positive electrode winding end 23121 and the first part 23221, and will not be repeated here.

[0172] Please continue to see Figure 29 Along the winding axis direction B (which corresponds to the width direction C in the figure), the negative electrode tab 2321 is located at one end of the negative electrode sheet 232. The end of the third portion of the negative electrode active material layer 23223a closest to the negative electrode tab 2321 extends beyond the corresponding end of the second portion of the negative electrode active material layer 23222a. The other end of the third portion of the negative electrode active material layer 23223a is flush with the other end of the second portion of the negative electrode active material layer 23222a. Along the winding axis direction B, the end of the third portion of the negative electrode active material layer 23223a closest to the negative electrode tab 2321 extends entirely beyond the corresponding end of the second portion of the negative electrode active material layer 23222a. The other end of the third portion of the negative electrode active material layer 23223a is flush with the other end of the second portion of the negative electrode active material layer 23222a.

[0173] One end of the third portion 23223 near the negative electrode ear 2321 extends beyond the corresponding end of the second portion 23222, and the other end of the third portion 23223 is flush with the other end of the second portion 23222. It can be understood that one end of the negative electrode current collector 23223e of the third portion near the negative electrode ear 2321 extends beyond the corresponding end of the negative electrode current collector 23222b of the second portion, and the other end of the negative electrode current collector 23223e of the third portion is flush with the other end of the negative electrode current collector 23222b of the second portion; one end of the negative electrode active material layer 23223a of the third portion near the negative electrode ear 2321 extends beyond the corresponding end of the negative electrode active material layer 23222a of the second portion, and the other end of the negative electrode active material layer 23223a of the third portion is flush with the other end of the negative electrode active material layer 23222a of the second portion; One end of the negative electrode collector 23223e close to the negative electrode ear 2321 is flush with one end of the negative electrode active material layer 23223a of the third part close to the negative electrode ear 2321, and the other end of the negative electrode collector 23223e of the third part is flush with the other end of the negative electrode active material layer 23221a of the first part; one end of the negative electrode collector 23222b of the second part close to the negative electrode ear 2321 is flush with one end of the negative electrode active material layer 23222a of the second part close to the negative electrode ear 2321, and the other end of the negative electrode collector 23222b of the second part is flush with the other end of the negative electrode active material layer 23222a of the second part. This type of negative electrode sheet 232 is not only convenient for coating the negative electrode active material layer, but also can form a negative electrode sheet 232 with a width difference between the third part 23223 and the second part 23222 during the process of die-cutting to form the negative electrode ear 2321, that is, the negative electrode sheet 232 with a width difference between the third part 23223 and the second part 23222 can be formed by utilizing the original molding process of the negative electrode sheet 232.

[0174] The third portion 23223 has a bonding surface 23223d connected to the second portion 23222. There are multiple negative electrode tabs 2321, one of which protrudes from the third portion 23223 along the winding axis direction B and has a second side surface 2321c proximal to the second portion 23222. The second side surface 2321c is coplanar with the bonding surface 23223d. The bonding surface 23223d is coplanar with a side surface of the negative electrode tab 2321 to prevent the bonding surface 23223d from tilting due to lack of restraint during and after winding, thereby puncturing the separator 233.

[0175] The third portion 23223 passes through the flat region I at least once. In some embodiments, as Figure 28 、 Figure 30As shown, the third part 23223 passes through a straight area I once, the second positive electrode winding end 23123 passes through a straight area I once, and the negative electrode active material layer on the inner side of the negative electrode collector 23223e of the third part faces the positive electrode active material layer on the outer side of the positive electrode collector 23123b of the second positive electrode winding end. Then, only the negative electrode active material layer on the inner side of the negative electrode collector 23223e of the third part can be widened to satisfy H4-L3>H2-L2.

[0176] In some embodiments, the outer diameter of the winding needle used to form the electrode assembly 23 is relatively small, and the number of times the third portion passes through the straight region I can be appropriately increased.

[0177] In some embodiments, as Figure 31 、 Figure 32 As shown, the third part 23223 passes through the straight area I twice, then the negative electrode active material layer on the inner side of the negative electrode collector 23223e of the third part located in the two straight areas I faces the positive electrode active material layer on the outer side of the positive electrode collector 23123b at the second positive electrode winding end, then only the negative electrode active material layer on the inner side of the negative electrode collector 23223e of the third part located in the two straight areas I can be widened to satisfy H4-L3>H2-L2.

[0178] In some embodiments, as Figure 33 、 34 As shown, along the winding direction A, the third part 23223 passes through the three straight areas I, and the second positive electrode winding end 23123 passes through the three straight areas I. In the order of passing (first → last), they are the first straight area, the second straight area and the third straight area respectively. The negative electrode active material layers on the inner and outer sides of the negative electrode collector 23223e of the third part of the first straight area face the positive electrode active material layer on the outer side of the positive electrode collector 23123b of the second positive electrode winding end in the first straight area and the positive electrode active material layer on the inner side of the positive electrode collector 23123b of the second positive electrode winding end in the third straight area. The negative electrode active material layer located on the inner side of the negative electrode collector 23222b located in the second part of the second flat area and the third flat area faces the positive electrode active material layer located on the outer side of the positive electrode collector 23123b located at the second positive electrode winding end of the second flat area and the third straight area. Then, along the winding axis direction B, only the negative electrode active material layers on the inner and outer sides of the negative electrode collector 23223e located in the third part of the first flat area and the negative electrode active material layer on the inner side of the negative electrode collector 23222b located in the second part of the second flat area and the third straight area can be widened to satisfy H4-L3>H2-L2.

[0179] like Figure 35As shown, if the third part 23223 passes through the straight zone I three times and the second positive electrode winding end 23123 passes through the straight zone I twice, the positive electrode active material layers on the inner and outer sides of the positive electrode collector 23123b of the second positive electrode winding end located in the second straight zone respectively face the negative electrode active material layer on the outer side of the negative electrode collector 23223e located in the third part of the first straight zone and the negative electrode active material layer on the inner side of the negative electrode collector 23223e located in the third part of the third straight zone, and the positive electrode active material layer on the outer side of the positive electrode collector 23123b of the second positive electrode winding end located in the first straight zone faces the negative electrode active material layer on the inner side of the negative electrode collector 23223e located in the third part of the second straight zone. Then, along the winding axis direction B, only the negative electrode active material layer on the outside of the negative electrode collector 23223e located in the third part of the first straight area and the negative electrode active material layer on the inside of the negative electrode collector 23223e located in the third part of the second straight area and the third straight area can be widened to satisfy H4-L3>H2-L2.

[0180] To ensure that the negative electrode sheet 232 completely covers the positive electrode sheet 231 in the winding direction A, the negative electrode body 2322 further includes a second extension portion 23225. Along the winding direction A, the second extension portion 23225 is connected to the end of the third portion 23223 away from the second portion 23222. The second extension portion 23225 extends beyond the end of the second positive electrode winding end portion 23123 along the winding direction A. The width of the second extension portion 23225 may or may not be greater than that of the second portion 23222. Figure 33 In the embodiment, the second extension portion 23225 has a greater width than the second portion 23222. Figure 36 In the embodiment, the width of the negative electrode active material layer in the second extension portion 23225 is not increased relative to that of the negative electrode active material layer 23222a in the second portion.

[0181] In some embodiments, the third portion 23223 may also be wound at least once. For example, when the wound electrode assembly 23 is a cylindrical structure, the third portion 23223 may be wound at least once.

[0182] In some embodiments, the structure of the positive electrode sheet 231 is improved to achieve a maximum width difference between the positive electrode active material layer 23121a at the end of the first positive electrode winding and the negative electrode active material layer 23221a in the first part, which is greater than the maximum width difference between the negative electrode active material layer 23222a in the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding.

[0183] In some embodiments, as Figure 37As shown, along the winding axis direction B (which is consistent with the width direction C), the maximum width of the positive electrode active material layer 23121a at the first positive electrode winding end is L4, and the maximum width of the positive electrode active material layer 23122a in the middle section of the positive electrode winding is L5. Since L4 < L5, it is also possible to make the maximum width difference between the first positive electrode winding end 23121 and the first part 23221 greater than the maximum width difference between the negative electrode active material layer 23222a of the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding. By changing the width of the first positive electrode winding end 23121 of the positive electrode sheet 231, the size of the part where the negative electrode active material layer of the negative electrode sheet 232 exceeds the positive electrode active material layer of the positive electrode sheet 231 in the winding axis direction B due to the relative offset between the positive electrode sheet 231 and the negative electrode sheet 232 can be reduced so that it does not meet the design requirements.

[0184] In some embodiments, please continue to refer to Figure 37 , the maximum width of the positive electrode active material layer 23123a at the second positive electrode winding end is L6, and the maximum width of the positive electrode active material layer 23122a in the middle section of the positive electrode winding is L5. Since L6 < L5, the maximum width difference between the positive electrode active material layer 23121a at the first positive electrode winding end and the negative electrode active material layer 23221a of the first part is greater than the maximum width difference between the negative electrode active material layer 23222a of the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding. The maximum width difference between the positive electrode active material layer 23123a at the second positive electrode winding end and the negative electrode active material layer 23223a of the third part is greater than the maximum width difference between the negative electrode active material layer 23222a of the second part and the positive electrode active material layer 23122a in the middle section of the positive electrode winding. The size of the part where the negative electrode active material layer of the negative electrode sheet 232 exceeds the positive electrode active material layer of the positive electrode sheet 231 in the winding axis direction B due to the relative offset of the head and tail of the negative electrode sheet 232 during the winding process can be reduced so that it does not meet the design requirements.

[0185] The maximum width difference between the positive electrode active material layer 23123a at the second positive electrode winding end and the negative electrode active material layer 23223a of the third part refers to H4 - L3.

[0186] In some embodiments, the positive electrode active material layer 23121a at the first positive electrode winding end can be a constant-width structure, then L1 = L4. Or the positive electrode active material layer 23121a at the first positive electrode winding end can be a variable-width structure, then L1 < L4.

[0187] In some embodiments, the positive electrode active material layer 23122a in the middle section of the positive electrode winding can be a constant-width structure, then L2 = L5. Or the positive electrode active material layer 23122a in the middle section of the positive electrode winding can be a variable-width structure, then L2 < L5.

[0188] In some embodiments, the positive electrode active material layer 23123a at the second positive electrode winding end may be a uniform width structure, then L6 = L3. Alternatively, the positive electrode active material layer 23123a at the second positive electrode winding end may be a variable width structure, then L3 <L6。

[0189] In some embodiments, along the winding axis direction B, one end of the positive electrode active material layer 23122a in the middle section of the positive electrode winding at least partially extends beyond the corresponding end of the positive electrode active material layer 23121a at the first positive electrode winding end, while the other end of the positive electrode active material layer 23122a in the middle section of the positive electrode winding is flush with the other end of the positive electrode active material layer 23121a at the first positive electrode winding end. This reduces the width of the first positive electrode winding end 23121 relative to the positive electrode winding middle section 23122 on the side along the winding axis direction B, simplifying the molding of the positive electrode sheet 231 and reducing processing difficulty.

[0190] In some embodiments, along the winding axis direction B, the positive electrode tab 2311 is located at one end of the positive electrode sheet 231, and the end of the positive electrode active material layer 23122a in the middle section of the positive electrode winding, which is closer to the positive electrode tab 2311, extends beyond the corresponding end of the positive electrode active material layer 23121a at the first positive electrode winding end. The end of the positive electrode active material layer 23122a in the middle section of the positive electrode winding, which is closer to the positive electrode tab 2311, extends beyond the corresponding end of the positive electrode active material layer 23123a at the second positive electrode winding end. This allows the positive electrode sheet 231 to be formed in which both the positive electrode active material layer 23121a at the first positive electrode winding end and the positive electrode active material layer 23123a at the second positive electrode winding end have a width difference with the positive electrode active material layer 23122a in the middle section of the positive electrode winding during die-cutting of the positive electrode tab 2311 or during installation of the insulating layer 23124, thereby reducing processing difficulty.

[0191] Generally, the positive electrode sheet 231 further includes an insulating layer 23124, which is used to separate the burrs at one end of the positive electrode body 2312 along the winding axis direction B from the negative electrode body 2322 ( Figure 18) to reduce the risk of short circuits. Along the winding axis direction B, the insulating layer 23124 is provided between the positive electrode tab 2311 and the positive electrode active material layer on the positive electrode body 2312. The insulating layer 23124 is applied to the positive electrode current collector of the positive electrode body 2312. The greater the width occupied by the insulating layer 23124, the smaller the width of the positive electrode active material layer that can be applied at the corresponding position. Conversely, the smaller the width occupied by the insulating layer 23124, the larger the width of the positive electrode active material layer that can be applied at the corresponding position. Therefore, the minimum width of the insulating layer 23124a at the end of the first positive electrode winding is greater than the maximum width of the insulating layer 23124b in the middle section of the positive electrode winding. The minimum width of the insulating layer 23124c at the end of the second positive electrode winding is greater than the maximum width of the insulating layer 23124b in the middle section of the positive electrode winding.

[0192] Insulating layer 23124 includes an inorganic filler and a binder. The inorganic filler includes one or more of boehmite, aluminum oxide, magnesium oxide, titanium dioxide, zirconium oxide, silicon dioxide, silicon carbide, boron carbide, calcium carbonate, aluminum silicate, calcium silicate, potassium titanate, and barium sulfate. The binder includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, polyacrylate, polyacrylic acid-acrylate, polyacrylonitrile-acrylic acid, and polyacrylonitrile-acrylate.

[0193] In some embodiments, along the winding axis direction B, the widths of the positive electrode active material layer 23123a at the first positive electrode winding end 23121, the positive electrode winding middle section 23122 and the second positive electrode winding end are consistent, and the insulating layer 23124 is applied on the side of the positive electrode active material layer 23123a at the first positive electrode winding end 23121, the positive electrode winding middle section 23122 and the second positive electrode winding end close to the positive electrode ear 2311, and the insulating layer 23124 is applied on the positive electrode active material layer so that the insulating layer 23124 overlaps with the positive electrode active material layer, and the positive electrode active material layer not covered by the insulating layer 23124 is the effective active material layer of the positive electrode body 2312. The maximum width of the insulating layer 23124a at the first positive electrode winding end and the maximum width of the insulating layer 23124c at the second positive electrode winding end are both greater than the maximum width of the insulating layer 23124b in the middle section of the positive electrode winding. In this way, the maximum width of the effective active material layer of the first positive electrode winding end 23121 and the maximum width of the effective active material layer of the second positive electrode winding end 23123 are both smaller than the maximum width of the effective positive electrode active material layer in the middle section 23122 of the positive electrode winding.

[0194] In some embodiments, as Figure 38As shown, along the winding axis direction B (which is consistent with the width direction C), the end of the positive electrode active material layer 23122a in the middle section of the positive electrode winding, which is away from the positive electrode tab 2311, may extend beyond the corresponding end of the positive electrode active material layer 23121a at the first positive electrode winding end. The end of the positive electrode active material layer 23122a in the middle section of the positive electrode winding, which is away from the positive electrode tab 2311, may extend beyond the corresponding end of the positive electrode active material layer 23123a at the second positive electrode winding end.

[0195] In some embodiments, as Figure 39 As shown, along the winding axis direction B (which is consistent with the width direction C), both ends of the positive electrode active material layer 23122a in the middle section of the positive electrode winding may extend beyond the corresponding ends of the positive electrode active material layer 23121a at the first positive electrode winding end. Both ends of the positive electrode active material layer 23122a in the middle section of the positive electrode winding may extend beyond the corresponding ends of the positive electrode active material layer 23123a at the second positive electrode winding end.

[0196] In some embodiments, the structures of the positive electrode sheet 231 and the negative electrode sheet 232 are modified to meet the requirements of H1-L1 > H2-L2 and H4-L3 > H2-L2. While increasing the width of the negative electrode active material layer 23221a in the first portion, the width of the positive electrode active material layer 23121a at the end of the first positive electrode winding is reduced. While increasing the width of the negative electrode active material layer 23223a in the third portion, the width of the positive electrode active material layer 23123a at the end of the second positive electrode winding is reduced.

[0197] In some embodiments, the negative electrode active material layer 23223a of the third part is not widened relative to the negative electrode active material layer 23222a of the second part. By increasing the size of the negative electrode active material layer 23221a of the first part in the winding axis direction B and reducing the size of the positive electrode active material layer 23123a at the second positive electrode winding end in the winding axis direction B, the following conditions are satisfied: H1-L1>H2-L2, H4-L3>H2-L2.

[0198] In some embodiments, the negative electrode active material layer 23221a of the first part is not widened relative to the negative electrode active material layer 23222a of the second part. The size of the positive electrode active material layer 23121a at the first positive electrode winding end in the winding axis direction B can be reduced and the size of the negative electrode active material layer 23223a of the third part in the winding axis direction B can be increased, thereby satisfying: H1-L1>H2-L2, H4-L3>H2-L2.

[0199] The present application also provides a method for manufacturing a wound electrode assembly 23, such as Figure 40 As shown, the manufacturing method of the wound electrode assembly 23 includes:

[0200] S100: Providing a positive electrode sheet 231, the positive electrode sheet 231 comprising a first positive electrode winding end portion 23121 and a positive electrode winding middle section 23122 connected to each other;

[0201] S200: providing a negative electrode sheet 232, wherein the negative electrode sheet 232 includes a first portion 23221 and a second portion 23222 connected to each other;

[0202] S300: Winding the positive electrode sheet 231 and the negative electrode sheet 232 to form a wound electrode assembly 23, so that the first portion 23221 is arranged opposite to the first positive electrode winding end portion 23121, and the second portion 23222 is arranged opposite to the positive electrode winding middle section 23122; wherein, along the winding axis direction B of the wound electrode assembly 23, the negative electrode active material layer of the negative electrode sheet 232 exceeds the positive electrode active material layer of the positive electrode sheet 231, the maximum width of the negative electrode active material layer 23221a of the first portion is H1, the minimum width of the positive electrode active material layer 23121a at the first positive electrode winding end portion is L1, the maximum width of the negative electrode active material layer 23222a of the second portion is H2, and the minimum width of the positive electrode active material layer 23122a in the positive electrode winding middle section is L2, H1-L1>H2-L2.

[0203] The present application does not limit the order in which the steps of the method for manufacturing the wound electrode assembly 23 are executed, as long as the electrode assembly 23 can be manufactured.

[0204] The present application also provides a manufacturing device 400 for a wound electrode assembly. Figure 41As shown, the manufacturing equipment 400 of the wound electrode assembly includes a first providing device 410, a second providing device 420 and an assembling device 430, the first providing device 410 is configured to provide a positive electrode sheet 231, the positive electrode sheet 231 includes a first positive electrode winding end portion 23121 and a positive electrode winding middle section 23122 connected to each other; the second providing device 420 is configured to provide a negative electrode sheet 232, the negative electrode sheet 232 includes a first portion 23221 and a second portion 23222 connected to each other; the assembling device 430 is configured to wind the positive electrode sheet 231 and the negative electrode sheet 232 so that the first portion 23221 is connected to the first positive electrode winding end portion 23121. 121 are arranged relative to each other, and the second part 23222 is arranged relative to the positive electrode winding middle section 23122; wherein, along the winding axis direction B of the wound electrode assembly 23, the negative electrode active material layer of the negative electrode sheet 232 exceeds the positive electrode active material layer of the positive electrode sheet 231, the maximum width of the negative electrode active material layer 23221a of the first part is H1, the minimum width of the positive electrode active material layer 23121a at the first positive electrode winding end is L1, the maximum width of the negative electrode active material layer 23222a of the second part is H2, and the minimum width of the positive electrode active material layer 23122a in the positive electrode winding middle section is L2, H1-L1>H2-L2.

[0205] The positive electrode sheet 231 and the negative electrode sheet 232 provided by the first providing device 410 and the second providing device 420 can compensate for the relative offset of the positive electrode sheet 231 and the negative electrode sheet 232 at the head or tail caused by the structural tolerance and winding error of the assembly device 430 during the process of winding to form the wound electrode assembly 23, so that the negative electrode active material layer of the negative electrode sheet 232 exceeds the positive electrode active material layer of the positive electrode sheet 231.

[0206] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A wound electrode assembly, wherein: include: A positive electrode sheet, comprising a first positive electrode winding end portion and a positive electrode winding middle section connected to each other; as well as A negative electrode sheet comprising a first portion and a second portion connected to each other, wherein the first portion is disposed opposite to an end portion of the first positive electrode winding, and the second portion is disposed opposite to a middle section of the positive electrode winding; Along the winding axis of the wound electrode assembly, the negative electrode active material layer of the negative electrode sheet extends beyond the positive electrode active material layer of the positive electrode sheet. The maximum width of the negative electrode active material layer in the first portion is H1, the minimum width of the positive electrode active material layer at the end of the first positive electrode winding is L1, the maximum width of the negative electrode active material layer in the second portion is H2, and the minimum width of the positive electrode active material layer in the middle section of the positive electrode winding is L2, where H1-L1>H2-L2. The positive electrode sheet also includes a second positive electrode winding end portion, the first positive electrode winding end portion and the second positive electrode winding end portion are respectively connected to the two ends of the positive electrode winding middle section, the first positive electrode winding end portion is the positive electrode winding starting section, and the second positive electrode winding end portion is the positive electrode winding ending section. The minimum width of the negative electrode active material layer of the first part is H3, wherein H1>H2, H3≥H2.

2. The wound electrode assembly according to claim 1, wherein 0.3mm≤H1-H2≤3mm.

3. The wound electrode assembly according to claim 1, wherein: Along the winding axis direction, at least part of one end of the negative electrode active material layer of the first part exceeds the corresponding end of the negative electrode active material layer of the second part, and the other end of the negative electrode active material layer of the first part is flush with the other end of the negative electrode active material layer of the second part.

4. The wound electrode assembly according to claim 3, wherein: The negative electrode sheet also includes a negative electrode ear. Along the winding axis, the negative electrode ear is located at one end of the negative electrode sheet, and the end of the negative electrode active material layer of the first part close to the negative electrode ear at least partially exceeds the corresponding end of the negative electrode active material layer of the second part.

5. The wound electrode assembly according to any one of claims 1 to 4, wherein: The negative electrode sheet also includes a negative electrode ear. Along the winding axis, the negative electrode ear is located at one end of the negative electrode sheet. An end of the first part close to the negative electrode ear extends beyond a corresponding end of the second part, and the other end of the first part is flush with the other end of the second part.

6. The wound electrode assembly according to claim 5, wherein: Along the winding direction of the wound electrode assembly, the first portion has a connection surface connected to the second portion; There are a plurality of negative electrode tabs, one of which protrudes from the first portion along the winding axis and has a first side surface close to the second portion, and the first side surface is coplanar with the connecting surface.

7. The wound electrode assembly according to claim 5, wherein: Along the winding axis direction, a negative electrode active material layer is provided on the negative electrode tab protruding from the first portion, and the negative electrode active material layer on the negative electrode tab protruding from the first portion is connected to the negative electrode active material layer of the first portion.

8. The wound electrode assembly according to any one of claims 1 to 7, wherein: The wound electrode assembly includes a straight area and two bent areas, wherein the two bent areas are respectively connected to two ends of the straight area; The first portion passes through the flat region at least twice.

9. The wound electrode assembly according to any one of claims 1 to 8, wherein: The negative electrode sheet further includes a third portion, wherein the first portion and the third portion are respectively connected to two ends of the second portion, and the third portion and the second positive electrode winding end portion are arranged opposite to each other; The maximum width of the negative electrode active material layer in the third portion is H4, the minimum width of the positive electrode active material layer at the second positive electrode winding end portion is L3, and H4-L3>H2-L2.

10. The wound electrode assembly according to claim 9, wherein: The minimum width of the negative electrode active material layer in the third portion is H5, wherein H4>H2, and H5≥H2.

11. The wound electrode assembly according to any one of claims 1 to 10, wherein: The maximum width of the positive electrode active material layer at the end of the first positive electrode winding is L4, and the maximum width of the positive electrode active material layer at the middle section of the positive electrode winding is L5, L4 <L5。 12. The wound electrode assembly according to claim 11, wherein: Along the winding axis direction, one end of the positive electrode active material layer in the middle section of the positive electrode winding at least partially exceeds the corresponding end of the positive electrode active material layer at the end portion of the first positive electrode winding, and the other end of the positive electrode active material layer in the middle section of the positive electrode winding is flush with the other end of the positive electrode active material layer at the end portion of the first positive electrode winding.

13. The wound electrode assembly according to claim 12, wherein: The positive electrode sheet also includes a positive electrode ear. Along the winding axis direction, the positive electrode ear is located at one end of the positive electrode sheet, and the end of the positive electrode active material layer in the middle section of the positive electrode winding close to the positive electrode ear at least partially extends beyond the end corresponding to the positive electrode active material layer at the end of the first positive electrode winding.

14. A battery cell, wherein: Comprising a wound electrode assembly according to any one of claims 1 to 13.

15. A battery, wherein: The battery cell according to claim 14 is included.

16. An electrical device, wherein: The battery cell according to claim 14 is included.

17. A method for manufacturing a wound electrode assembly, wherein: include: A positive electrode sheet is provided, the positive electrode sheet comprising: a first positive electrode winding end portion and a positive electrode winding middle section connected to each other; A negative electrode sheet is provided, the negative electrode sheet comprising: a first portion and a second portion connected to each other; Winding the positive electrode sheet and the negative electrode sheet to form the wound electrode assembly, so that the first portion is disposed opposite to the end of the first positive electrode winding, and the second portion is disposed opposite to the middle section of the positive electrode winding; Wherein, along the winding axis direction of the wound electrode assembly, the negative electrode active material layer of the negative electrode sheet exceeds the positive electrode active material layer of the positive electrode sheet, the maximum width of the negative electrode active material layer in the first portion is H1, the minimum width of the positive electrode active material layer at the end of the first positive electrode winding is L1, the maximum width of the negative electrode active material layer in the second portion is H2, and the minimum width of the positive electrode active material layer in the middle section of the positive electrode winding is L2, and H1-L1>H2-L2; The positive electrode sheet also includes a second positive electrode winding end portion, the first positive electrode winding end portion and the second positive electrode winding end portion are respectively connected to the two ends of the positive electrode winding middle section, the first positive electrode winding end portion is the positive electrode winding starting section, and the second positive electrode winding end portion is the positive electrode winding ending section. The minimum width of the negative electrode active material layer of the first part is H3, wherein H1>H2, H3≥H2.

18. A device for manufacturing a wound electrode assembly, wherein: include: A first providing device is configured to provide a positive electrode sheet, wherein the positive electrode sheet includes a first positive electrode winding end portion and a positive electrode winding middle section connected to each other; a second providing device configured to provide a negative electrode sheet, wherein the negative electrode sheet includes a first portion and a second portion connected to each other; an assembly device configured to wind the positive electrode sheet and the negative electrode sheet so that the first portion is disposed opposite to an end portion of the first positive electrode winding and the second portion is disposed opposite to a middle section of the positive electrode winding; Wherein, along the winding axis direction of the wound electrode assembly, the negative electrode active material layer of the negative electrode sheet exceeds the positive electrode active material layer of the positive electrode sheet, the maximum width of the negative electrode active material layer in the first portion is H1, the minimum width of the positive electrode active material layer at the end of the first positive electrode winding is L1, the maximum width of the negative electrode active material layer in the second portion is H2, and the minimum width of the positive electrode active material layer in the middle section of the positive electrode winding is L2, and H1-L1>H2-L2; The positive electrode sheet also includes a second positive electrode winding end portion, the first positive electrode winding end portion and the second positive electrode winding end portion are respectively connected to the two ends of the positive electrode winding middle section, the first positive electrode winding end portion is the positive electrode winding starting section, and the second positive electrode winding end portion is the positive electrode winding ending section. The minimum width of the negative electrode active material layer of the first part is H3, wherein H1>H2, H3≥H2.

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