Wound electrode body and battery

Abstract

The embodiment of the utility model provides a winding type electrode body and a battery. The wound electrode body comprises a positive plate, a negative plate and a diaphragm which are arranged in a laminated and wound manner. The positive plate is provided with a straight section positioned in the flat part of the wound electrode body and an arc section positioned in the bent part of the wound electrode body, and the positive plate comprises a positive current collector and a positive active layer arranged on the positive current collector. The positive active layer is provided with at least one groove part I, the at least one groove part I is at least partially positioned on the arc section of the positive plate, and the average thickness of the positive active layer on the arc section of the positive plate is smaller than the average thickness of the positive active layer on the straight section of the positive plate. The negative plate is provided with a straight section positioned in the flat part and an arc section positioned in the bent part, the negative plate comprises a negative current collector and a negative active layer arranged on the negative current collector, the negative active layer is provided with at least one groove part II, and the at least one groove part II is at least partially positioned in the arc section of the negative plate.

Description

Technical Field

[0001] This utility model relates to the field of batteries, and in particular, to a wound electrode body and a battery. Background Technology

[0002] A lithium-ion battery cell consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, lithium ions repeatedly insert and extract between the two electrodes: during charging, lithium ions extract from the positive electrode, pass through the electrolyte, and insert into the negative electrode, leaving the negative electrode in a lithium-rich state; the reverse occurs during discharging.

[0003] Some lithium-ion batteries, such as pouch cells, have flat, wound electrode bodies (also known as cores). Along the width direction, the flat electrode body includes two opposing curved portions and a flat portion located between them.

[0004] As the number of battery charge-discharge cycles increases, lithium plating occurs at the curved portion of the flat electrode. Utility Model Content

[0005] In view of this, the present invention provides a wound electrode body and a battery having the same, to solve the problem of lithium plating at the curved portion of a flat electrode body.

[0006] On one hand, this utility model provides a wound electrode body, which includes a positive electrode sheet, a negative electrode sheet, and a separator stacked and wound together. The positive electrode sheet has a straight section in a flat portion of the wound electrode body and an arcuate section in a curved portion of the wound electrode body. The positive electrode sheet includes a positive current collector and a positive active layer disposed thereon. The positive active layer has at least one groove portion one, which is at least partially located in the arcuate section of the positive electrode sheet. The thickness of the positive active layer in the arcuate section of the positive electrode sheet where the groove portion one is disposed is less than its thickness in the straight portion of the positive electrode sheet. The negative electrode sheet has a straight section in the flat portion and an arcuate section in the curved portion. The negative electrode sheet includes a negative current collector and a negative active layer disposed thereon. The negative active layer has at least one groove portion two.

[0007] Alternatively or supplementally, the first groove may include a plurality of grooves, the length direction of which is perpendicular to the length direction of the positive electrode sheet; and / or, the first groove may include a plurality of grooves, the length direction of which is parallel to the length direction of the positive electrode sheet.

[0008] Alternatively or supplementarily, the first groove portion includes, in sequence, a first groove to an Nth groove along the length direction of the positive electrode sheet. The first groove includes a first sidewall and a second sidewall that are opposite each other along the length direction of the positive electrode sheet. The first sidewall of the first groove and the second sidewall of the Nth groove are both sloped. The groove extends through the positive electrode active layer along the width direction of the positive electrode sheet.

[0009] Alternatively or supplementarily, the first sidewall of the first tank forms an angle α1 with the positive current collector, and the second sidewall of the Nth tank forms an angle α2 with the positive current collector, with the values ​​of angle α1 and angle α2 ranging from 35° to 80°.

[0010] Alternatively or supplementally, the wound electrode body has a thickness H, and the groove portion has a dimension W in the length direction of the positive electrode sheet, wherein the thickness H and the dimension W satisfy: 3.14*H / 2-2mm≤W≤3.14*H / 2+2mm.

[0011] Alternatively or supplementally, the surface of the groove includes a rough surface.

[0012] Alternatively or supplementally, the roughened surface is 2*2mm. 2 The height difference between the highest and lowest points within the range ranges from 1 μm to 10 μm.

[0013] Alternatively or supplementarily, the groove section one includes a plurality of grooves one, each groove one having a width S1 and a depth T1, and adjacent grooves one having a spacing D1. The width S1 ranges from 0.05 mm to 2 mm, the depth T1 ranges from 1 μm to 35 μm, and the spacing D1 ranges from 0.5 mm to 10 mm.

[0014] Alternatively or supplementally, at least one groove portion two is located at least partially in the arcuate segment of the negative electrode sheet, the groove portion two comprising a plurality of groove portions two having a length direction parallel to the length direction of the negative electrode sheet; and / or, at least one groove portion two extends along the winding direction of the wound electrode body and terminates in the arcuate segment or straight segment.

[0015] Alternatively or supplementarily, the first groove has a dimension W along the length of the positive electrode plate, and the second groove has a length L1. The dimension W and the length L1 satisfy: W ≤ L1 ≤ W + 10 mm.

[0016] Alternatively or supplementally, at least one groove extends along the winding direction of the wound electrode body through the arc segment and located in the straight segment.

[0017] Alternatively or supplementarily, along the length direction of the negative electrode sheet, the distance between the two ends of at least one groove portion two is L3, and the negative electrode active layer has a length L2, wherein the lengths L3 and L2 satisfy: L2-10mm≤L3≤L2.

[0018] Alternatively or supplementarily, the second groove portion includes a plurality of groove segments arranged along the length direction of the negative electrode sheet. Here: the plurality of groove segments are connected end to end; or, the plurality of groove segments are staggered along the width direction of the negative electrode sheet; or, the plurality of groove segments are spaced apart along the length direction of the negative electrode sheet, with adjacent groove segments having a spacing D2, the value of the spacing D2 ranging from 0.2 mm to 10 mm.

[0019] Alternatively or supplementally, along the winding direction of the wound electrode body, the end of each slot segment is located in the straight section of the negative electrode sheet.

[0020] Alternatively or supplementally, the second groove includes a plurality of second grooves, the length direction of which is perpendicular to the length direction of the negative electrode sheet.

[0021] Alternatively or supplementarily, the groove of the second groove has a width S2, the groove of the second groove has a depth T2, the adjacent grooves of two adjacent grooves of the second groove have a spacing D3, the lowest point of the groove of the second groove has a spacing D4 with the negative current collector, the width S2 ranges from 50μm to 250μm, the depth T2 ranges from 3μm to 35μm, the spacing D3 ranges from 0.5mm to 5mm, and the spacing D4 ranges from 3μm to 70μm.

[0022] Alternatively or supplementarily, the positive current collector has a thickness H and a tensile strength P, wherein the ratio of the values ​​of thickness H and tensile strength P satisfies: 5 < P / H < 12.

[0023] Secondly, this application provides a lithium-ion secondary battery, including the aforementioned wound electrode body.

[0024] According to the spiral-wound electrode body and lithium-ion secondary battery provided in this embodiment of the invention, the positive electrode active layer is provided with a plurality of grooves arranged at intervals, and the plurality of grooves are at least partially located in the arc segment of the positive electrode sheet. Therefore, the average thickness of the positive electrode active layer in the arc segment of the positive electrode sheet is less than its average thickness in the straight segment of the positive electrode sheet. This is equivalent to thinning the positive electrode active layer in the arc segment of the positive electrode sheet. In this way, the positive electrode active material in the arc segment is reduced, thereby increasing the capacity margin of the opposite negative electrode super-positive electrode in the curved part of the spiral-wound electrode body (i.e., N / P ratio: negative electrode capacity per unit area / positive electrode capacity per unit area) in the same stage and under the same conditions, thus effectively solving the lithium plating problem caused by insufficient N / P ratio in the curved part of the spiral-wound electrode body. In addition, the plurality of grooves arranged at intervals in the positive electrode active layer can also facilitate the storage of electrolyte, further improving the problems of lithium plating and black spots caused by the lack of electrolyte due to the difficulty in storing electrolyte in the curved part of the spiral-wound electrode body and the resulting ion migration obstruction.

[0025] Furthermore, the second groove on the negative electrode active layer can increase the electrolyte storage capacity, thereby improving the lithium-ion transport rate and reducing side reactions and lithium plating problems caused by electrolyte deficiency. Then, when the second groove is combined with the first groove on the positive electrode plate where the arc segment is perpendicular to the length direction of the positive electrode plate, the electrolyte in that area can be further locked in to prevent it from being squeezed out of the arc, further increasing the electrolyte content in that area and improving the lithium plating problem. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of lithium-ion migration when the positive electrode active layer at the arc portion is located outside the negative electrode active layer.

[0027] Figure 2 This is a schematic diagram of lithium-ion migration when the positive electrode active layer at the arc portion is located inside the negative electrode active layer.

[0028] Figure 3 This is a schematic diagram of a positive electrode sheet according to one embodiment of the present invention.

[0029] Figure 4 for Figure 3 A top view of the neutral cathode plate.

[0030] Figure 5 This is a schematic diagram of the structure of the long groove on the positive electrode sheet according to an embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram of a positive electrode sheet according to another embodiment of the present invention.

[0032] Figure 7 This is a schematic diagram of a negative electrode sheet according to an embodiment of the present invention.

[0033] Figure 8 for Figure 7 A cross-sectional view of the negative electrode along CC.

[0034] Figure 9 This is a schematic diagram of a negative electrode sheet according to an embodiment of the present invention.

[0035] Figure 10 This is a schematic diagram of a negative electrode sheet according to another embodiment of the present invention.

[0036] Figure 11 This is a schematic diagram of a negative electrode sheet according to another embodiment of the present invention.

[0037] Figure 12 This is a schematic diagram of a negative electrode sheet according to another embodiment of the present invention.

[0038] Figure 13 This is a three-dimensional schematic diagram of a wound electrode body according to an embodiment of the present invention.

[0039] Figure 14 for Figure 13 A cross-sectional view along DD of the medium-wound electrode body.

[0040] Figure 15 This is a schematic diagram of a battery according to an embodiment of the present invention.

[0041] Figure 16This is a schematic diagram of a lithium-ion secondary battery according to another embodiment of the present invention.

[0042] Figure label:

[0043] 1000, Lithium-ion secondary battery;

[0044] 100. Winded electrode body; 101a. First curved portion; 101b. Second curved portion; 102. Flat portion;

[0045] 10. Positive electrode sheet; 11. Positive electrode active layer; 111. Trench 1 / Trench 1; 111a. First trench 1; 111n. Nth trench 1; 1111. First sidewall; 1112. Second sidewall; 12. Positive electrode current collector; 13. Straight section of positive electrode sheet; 14. Arc section of positive electrode sheet;

[0046] 20. Negative electrode sheet; 21. Negative electrode active layer; 211. Second groove section; 22. Negative electrode current collector; 212. Narrow groove section; 23. Straight section of negative electrode sheet; 24. Arc section of negative electrode sheet;

[0047] 200. Shell;

[0048] 30. Diaphragm. Detailed Implementation

[0049] With the rapid development of lithium-ion battery technology, higher demands are being placed on the energy density, fast charging capability, and charge / discharge rate of lithium-ion batteries. Fast-charging lithium batteries are also a development trend in consumer lithium-ion batteries. However, the development of fast-charging technology has also brought about safety issues related to lithium-ion batteries.

[0050] For example, in batteries including flat, wound electrodes, the inventors discovered that under rapid charging conditions, lithium plating at the bends of the wound electrodes can easily cause black spots, leading to a decrease in the cycle performance of the lithium battery and swelling and failure at the bends of the cell, which greatly reduces the lifespan of the lithium battery.

[0051] The wound electrode body includes a positive electrode sheet, a negative electrode sheet, and a separator arranged in layers. The positive and negative electrode sheets are wound together with the separator to form a wound electrode body having a flat section and a curved section. In conventional wound electrode bodies, the thickness of the positive active layer is the same in both the flat and curved sections of the positive electrode sheet. The inventors discovered that the main reason for the black spots of lithium deposition in the curved section of the wound electrode body is that the curved section has a certain curvature, resulting in a relatively small NP ratio between the negative and positive electrodes.

[0052] Specifically, refer to Figure 1 and Figure 2 In the curved section, when the negative electrode B is located on the outer arc and the positive electrode A is located on the inner arc (e.g.) Figure 2As shown in the diagram, during charging, lithium ions released from the positive electrode active layer migrate to the negative electrode B in a divergent manner. At this point, the lithium ions are dispersed on the surface of the negative electrode B. In this case, the NP ratio between the negative and positive electrodes is relatively large, making lithium deposition less likely. However, when the negative electrode B is located on the inner arc and the positive electrode A is located on the outer arc (as shown in the diagram),... Figure 1 As shown in the diagram, during charging, lithium ions released from the positive electrode migrate to the negative electrode B in an aggregated state. At this point, the lithium ions accumulate on the surface of the negative electrode B. In this situation, the relative NP ratio between the negative and positive electrodes is small, making lithium deposition more likely. Therefore, lithium deposition and black spots occur at the bend.

[0053] To address the aforementioned problems, this utility model embodiment provides a wound electrode body 100 and a battery 1000. Below, in conjunction with… Figures 3 to 16 The wound electrode body 100 and the battery 1000 of the present invention will be described in the following embodiments.

[0054] For ease of explanation, this embodiment of the utility model refers to the "width direction," "thickness direction," and "length direction" of the electrode body 100. The width direction of the wound electrode body 100 refers to the direction from one bend to another, indicated by arrow U in the figure; the length direction of the wound electrode body 100 refers to the direction parallel to the winding axis E, indicated by arrow R in the figure; the thickness direction of the wound electrode body 100 refers to the direction perpendicular to both the width and length directions, indicated by arrow V in the figure.

[0055] In addition, this article will also mention the length, width, and thickness directions of each electrode. The length direction of the electrode refers to the direction from the starting end of the winding to the ending end, indicated by arrow X in the diagram; the width direction of the electrode is perpendicular to the length direction, that is, from one edge of the electrode to the other edge, indicated by arrow Y in the diagram; the thickness direction of the electrode is perpendicular to both the length and width directions, indicated by arrow Z in the diagram. After the electrode is wound, its length direction is the winding direction.

[0056] Exemplary wound electrode body

[0057] See 3 to Figure 14 The wound electrode body 100 may include a positive electrode 10, a negative electrode 20, and a separator 30 arranged in layers. The positive electrode 10 and the negative electrode 20 are wound together with the separator 30 to form a wound electrode body 100 having a flat portion 102 and two curved portions 101a and 101b. The two curved portions 101a and 101b are distributed along the width direction at opposite ends of the flat portion 102. The two curved portions 101a and 101b are collectively referred to as curved portion 101.

[0058] The positive electrode 10 includes a positive current collector 12 and a positive active layer 11 disposed thereon, wherein the two positive active layers 11 may be located on opposite sides of the positive current collector 12 in the thickness direction. The negative electrode 20 may include a negative current collector 22 and a negative active layer 21 disposed thereon, wherein the two negative active layers 21 may be located on opposite sides of the negative current collector 22 in the thickness direction.

[0059] By way of example only, the positive electrode current collector 12 can be a strip-shaped metal foil. The positive electrode current collector has a thickness H and a tensile strength P, where the thickness H and tensile strength P satisfy: 5 < P / H < 12, to ensure that the positive electrode current collector 12 has suitable strength and tensile strength, thereby ensuring overall performance. The positive electrode active layer 11 can contain a positive electrode active material capable of reversibly absorbing and releasing charge carriers. In addition, it can further include conductive materials, binders, and various additives. By way of example only, the metal foil mentioned here can be aluminum foil, the positive electrode active material can be a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide, the conductive material can be a carbon-based material such as acetylene black, and the binder can be polyvinylidene fluoride, etc.

[0060] By way of example only, the negative electrode current collector 22 can be a strip of metal foil, and its active material layer can contain a negative electrode active material capable of reversibly absorbing and releasing charge carriers, a binder, a dispersant, and various additives. By way of example only, the metal foil mentioned here can be copper foil, the negative electrode active material can be a carbon-based material such as graphite, the binder can be a rubber such as styrene-butadiene rubber, and the dispersant can be a cellulose such as carboxymethyl cellulose.

[0061] The separator 30 is a component that insulates the positive electrode 10 and the negative electrode 20. As some examples, the separator 30 can be a porous strip made of resin composed of polyolefin resins such as polyethylene and polypropylene. Of course, other materials can also be used to construct the separator 30.

[0062] Along its length, the positive electrode 10 includes multiple straight segments 13 and multiple arc segments 14, which are arranged alternately. After winding, the arc segments 14 of the positive electrode 10 are located in the curved portion 101 of the wound electrode body 100, and the straight segments 13 of the positive electrode 10 are located in the flat portion 102 of the wound electrode body 100. Correspondingly, along its length, the negative electrode 20 includes multiple straight segments 23 and multiple arc segments 24, which are arranged alternately. After winding, the arc segments 24 of the negative electrode 20 are located in the curved portion 101 of the wound electrode body 100, and the straight segments 23 of the negative electrode 10 are located in the flat portion 102 of the wound electrode body 100.

[0063] like Figures 3 to 6As shown, the positive electrode active layer 11 may have at least one groove 111, for example, a plurality of grooves 111 arranged at intervals, i.e., the first groove 111 to the Nth groove 111. The plurality of grooves 111 may be at least partially located in the arc segment of the positive electrode sheet 10, so that the thickness of the positive electrode active layer 11 in the arc segment of the positive electrode sheet 10 is less than its thickness in the straight segment 13 of the positive electrode sheet 10. Reference Figures 7 to 12 The negative electrode active layer 21 may have at least one groove 211, such as a plurality of grooves 211 arranged at intervals.

[0064] This is equivalent to thinning the positive electrode active layer 11 of the arc-shaped section of the positive electrode 10. Reducing the amount of positive electrode active material in the arc-shaped section of the positive electrode 10 increases the N / P ratio of the curved portion of the wound electrode body 100, thus solving the lithium plating problem caused by insufficient N / P ratio in the curved portion of the wound electrode body 100. Furthermore, the multiple grooves 111 spaced apart in the positive electrode active layer 11 facilitate electrolyte storage, further improving the problems of lithium plating and black spots caused by hindered ion migration due to electrolyte deficiency in the curved portion of the wound electrode body 100, which makes it difficult to store electrolyte.

[0065] Furthermore, the second groove 211 provided on the negative electrode active layer 21 can increase the electrolyte storage capacity, thereby increasing the lithium ion transport rate and reducing side reactions and lithium plating problems caused by electrolyte deficiency. When the second groove 211 is combined with the first groove 111 provided on the positive electrode plate with the arc segment perpendicular to the length direction of the positive electrode plate, the electrolyte in this area can be further locked in to prevent it from being squeezed out of the arc, further increasing the electrolyte content in this area and improving the lithium plating problem.

[0066] It should be noted that the positive electrode 10 has multiple arc segments 14. Within each arc segment 14, multiple grooves 111 can be provided. That is, within each arc segment 14, a first groove 111a to an Nth arc segment 111n can be provided. When describing the multiple grooves 111 in this document, it refers to any one of the multiple arc segments 14.

[0067] refer to Figures 3 to 5 In some embodiments, the length direction of each groove 111 may be perpendicular to the length direction (X direction) of the positive electrode 10.

[0068] Continue to refer to Figures 3 to 5 The plurality of grooves 111 along the length of the positive electrode 10 may include a first groove 111a to an Nth groove 111n arranged sequentially. Each groove 111 may include a first sidewall 1111 and a second sidewall 1112 opposite to each other along the length of the positive electrode 10. The bottom of each groove 111 may be relatively flat.

[0069] Continue to refer to Figures 3 to 5 The first sidewall 1111 of the first groove 111a and the second sidewall 1112 of the Nth groove 111n can both be sloped. In this way, the groove walls of the multiple grooves 111 can transition to the surface of other parts of the positive electrode active layer 11 more smoothly, avoiding the vertical groove walls from squeezing the diaphragm 30 and causing the diaphragm 30 to rupture and resulting in a short circuit between the positive and negative electrodes.

[0070] Furthermore, such as Figure 5 As shown, the first sidewall 1111 of the first groove 111a can form an angle α1 with the positive current collector 12, and the second sidewall 1112 of the Nth groove 111n can form an angle α2 with the positive current collector 12. The angles α1 and α2 are greater than 0° and less than 90°. Alternatively, they can be 10°, 20°, 35°, 40°, 50°, 60°, 70°, or 85°.

[0071] The first sidewall 1113 of the first groove 111a and the second sidewall 1114 of the Nth groove 111n are set as slopes, and the values ​​of the angles α1 and α2 between them and the positive current collector 12 are set to the above range. This can avoid the problem of short circuit between the positive and negative electrodes caused by the groove wall squeezing the diaphragm 30 and causing the diaphragm 30 to break. At the same time, it can also avoid the risk of excessive loss of positive active material and excessive loss of energy density.

[0072] It is understood that the second sidewall 1112 of the first groove 111a, the first sidewall 1111 of the Nth groove 111n, and the first and second sidewalls 1111 and 1112 of the other grooves 111 between them can be vertical (i.e., perpendicular to the thickness direction of the positive electrode current collector 12) or sloping, preferably sloping, to facilitate the storage of electrolyte.

[0073] In some embodiments, reference 3 to Figure 5 and Figure 14 As shown, the wound electrode body 100 can have a thickness H, and the number of slots 111 can be N. Here, the thickness H and the number N can satisfy: (3.14*H / 2+2mm) / 5≤N≤(3.14*H / 2+2mm) / 2, where N can be an integer, that is, the slots 111 are located at least in the arc segment 14 of the positive electrode 10.

[0074] In this way, ensuring that the groove 111 is located at least in the arc segment 14 of the positive electrode 10 can improve the N / P ratio of the curved part of the wound electrode body 100, solve the lithium plating problem caused by insufficient N / P ratio in the curved part, and at the same time avoid excessive loss of positive electrode active material, resulting in excessive energy density loss.

[0075] In other alternative embodiments, such as Figure 6As shown, the length direction of groove 111 can be parallel to the length direction of the positive electrode 10.

[0076] In some embodiments, such as Figures 3 to 6 and Figure 14 As shown, the wound electrode body 100 has a thickness H, and the groove portion 111 has a dimension (i.e., width) W in the length direction of the positive electrode sheet 10. When the length direction of the groove portion 111 is perpendicular to the length direction of the positive electrode sheet 10, W is the total width of the plurality of groove portions 111 (i.e., the distance between the first sidewall 1111 of the first groove portion 111a and the second sidewall 1112 of the Nth groove portion 111n). When the length direction of the groove portion 111 is parallel to the length direction of the positive electrode sheet 10, W is the length of one groove portion 111.

[0077] The thickness H of the wound electrode body 100 and the width W of the groove portion 111 along the length of the positive electrode sheet 10 can satisfy: 3.14*H / 2 - 2mm ≤ W ≤ 3.14*H / 2 + 2mm. This ensures that when performing a surface scan to form a long groove to thin the arc-shaped active material, the entire arc segment can be covered. If the width is less than the left-hand value, the surface scan width will not be able to cover the entire arc segment, and lithium deposition at the bend will occur. If the width is greater than the left-hand value, the surface scan width will be too large, resulting in excessive loss of positive electrode active material and excessive energy density loss.

[0078] In some embodiments, such as Figure 5 As shown, the surface of tank 111 (including the bottom and sidewalls) can be an uneven, rough surface to increase the porosity of the area, which is more conducive to electrolyte storage.

[0079] Furthermore, the rough surface is 2*2mm 2 Within a range of 2mm × 2mm, the height difference between the highest and lowest points ranges from 1μm to 10μm. Furthermore, the bottom surface of groove 111 is within a 2*2mm... 2 That is, within a 2mm × 2mm range, the height difference between the highest and lowest points ranges from 1μm to 10μm, optionally 2μm, 4μm, 6μm, or 8μm, etc., and the sidewall is 0.2*0.2mm. 2 Within a range of 0.2mm × 0.2mm, the height difference between the highest and lowest points ranges from 1μm to 10μm, optionally 2μm, 4μm, 6μm, or 8μm. A value less than 3μm is detrimental to further electrolyte storage and may lead to lithium plating risk in later stages of cycling. A value greater than 10μm indicates that higher protrusions may puncture the separator, causing a short circuit risk in the battery.

[0080] Furthermore, such as Figure 5As shown, each groove 111 can have a width S1, each groove 111 can have a depth T1, and adjacent grooves 111 can have a spacing D1. The width S1 ranges from 0.05 mm to 2 mm, and optionally, is 0.08 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, and 1.8 mm. The depth T1 ranges from 1 μm to 35 μm, and optionally, is 3 μm, 8 μm, 12 μm, 15 μm, 18 μm, 22 μm, 25 μm, 28 μm, and 31 μm. The spacing D1 ranges from 0.5 mm to 10 mm, and optionally, is 1.0 mm, 1.5 mm, 1.8 mm, 2.1 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, or 4.5 mm, to ensure an improved N / P ratio at the bend and prevent lithium deposition at this location, while also considering energy density. Meanwhile, controlling the depth T1 within this range ensures that the distance from the bottom of the long trench to the positive current collector 12 is 2μm to 5μm, optionally 3μm or 4μm, thereby preventing damage to the positive current collector 12 during the manufacture of the long trench and preventing strip breakage during production. Here, S1 refers to the width of each trench.

[0081] As mentioned above, the multiple slots 211 are at least partially located in the arc segment 24 of the negative electrode 20.

[0082] refer to Figures 8 to 11 In some embodiments, the length direction of each groove 211 is parallel to the length direction of the negative electrode 20, that is, parallel to the winding direction of the arc segment.

[0083] This effectively prevents the electrolyte in that area from being squeezed out of the arc segment, further increasing the electrolyte content in that area to improve the lithium plating problem. Furthermore, when combined with the case where the groove portion 111 is provided perpendicular to the length direction of the positive electrode 10 on the arc segment, it further prevents the electrolyte in that area from being squeezed out of the arc, further increasing the electrolyte content in that area and improving the lithium plating problem.

[0084] In some embodiments, reference Figure 9 and Figure 12 Along the winding direction of the wound electrode body 100, at least one groove 211 may end at either the arc segment 24 or the straight segment 23 of the negative electrode 20. That is, the groove 211 only covers the arc segment of the negative electrode 20 and does not cover the straight segment of the negative electrode 20.

[0085] In some embodiments, reference Figures 4 to 6 , Figure 9 and Figure 12At least one groove 111 has a dimension W along the length of the positive electrode 10, and at least one groove 211 has a length L1. The dimension W and the length L1 satisfy: W ≤ L1 ≤ W + 10 mm.

[0086] For example, when the length direction of the groove in each second groove 211 is parallel to the length direction of the negative electrode 20, L1 is the length of one groove; when the length direction of the groove in each second groove 211 is perpendicular to the length direction of the negative electrode 20, L1 is the length of multiple grooves. The meaning of W here has already been mentioned in the description of the positive electrode 10 above, and will not be repeated here.

[0087] refer to Figures 3 to 9 and Figures 12 to 14 In this way, after winding, the orthogonal projection of the first groove 111 on the negative electrode sheet 20 will fall within multiple second grooves 211, ensuring that the second grooves 211 wrap around the first groove 111, which can better receive lithium ions from the positive electrode, improve the negative electrode reaction kinetics in the interface region between the two, and allow the negative electrode to have better reaction kinetics in the interface region so as to receive lithium ions and improve the lithium plating problem.

[0088] In other alternative embodiments, such as Figure 10 and Figure 11 As shown, multiple grooves 211 can extend through the arc segment 24 and the straight segment 23 of the negative electrode 20. That is, the multiple grooves 211 cover both the arc segment 24 and the straight segment 23 of the negative electrode 20.

[0089] Furthermore, each groove portion 211 may include a plurality of narrow groove segments 212 arranged along the length direction of the negative electrode 20.

[0090] For example, in some examples, multiple slot segments 212 can be connected end to end.

[0091] For example, in other examples, multiple slot segments 212 may be staggered along the width direction of the negative electrode 20.

[0092] For example, in other examples, multiple slot segments are arranged at intervals along the length of the negative electrode 20.

[0093] When multiple slot segments are arranged at intervals along the length of the negative electrode 20, two adjacent slot segments have a spacing D2, the value of which ranges from 0.2mm to 10mm, and optionally is 0.5mm, 1mm, 1.5mm, 2.0mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 6mm, 7mm, 8mm or 9mm, etc.

[0094] Of course, it can also be a combination of these settings, such as multiple slot segments ending at each other and staggered along the width and / or length direction of the negative electrode 20, or multiple slot segments spaced apart along the length direction of the negative electrode 20 and staggered along the width and / or length direction of the negative electrode 20.

[0095] Furthermore, along the winding direction of the wound electrode body, the end of each slot segment 212 is located in the straight segment 23 of the negative electrode sheet 20 to avoid the connection position between two slot segments falling into the arc, which helps to further reduce the risk of lithium plating.

[0096] In some embodiments, reference Figure 10 and Figure 11 Along the length of the negative electrode sheet, the distance between the two ends of at least one second groove can be L3, and the negative electrode active layer 21 can have a length L2. The lengths L1 and L2 can satisfy: L2 - 10 mm ≤ L3 ≤ L2. For example, when multiple second grooves 211 are discontinuously arranged along the length of the negative electrode sheet 20 (e.g.... Figure 11 As shown), L3 is the distance between the left end of the leftmost slot segment 212 and the right end of the rightmost slot segment 212. When the slot section 211 is continuously arranged along the length direction (as shown), L3 represents the distance between the left end of the leftmost slot segment 212 and the right end of the rightmost slot segment 212. Figure 10 As shown in the diagram, L1 is the distance between the left and right ends of the second groove. This avoids the problem of the negative electrode 20 exceeding the paste coverage when the groove is set, which could damage the foil and cause it to break.

[0097] In some other alternative embodiments, such as Figure 12 As shown, the length direction of the groove of the second groove 211 can be perpendicular to the length direction of the negative electrode 20, that is, perpendicular to the winding direction of the arc segment.

[0098] The perpendicularity and parallelism mentioned in this article are not absolute perpendicularity or parallelism; appropriate errors, such as ±10%, should be included.

[0099] In this way, when this arrangement is combined with the case where the groove 111 on the arc segment of the positive electrode 10 is parallel to the groove 111 set in the length direction of the positive electrode 10, the electrolyte in this area can be effectively locked in to prevent it from being squeezed out of the arc, thereby further increasing the electrolyte content in this area to improve the lithium plating problem.

[0100] In some embodiments, reference Figures 7 to 12Each groove in section 211 can have a V-shaped cross-sectional shape, meaning the V-shaped opening can face upwards. The V-shaped sidewall increases the surface area of ​​the negative electrode for receiving lithium ions, allowing it to receive lithium ions from the positive electrode more quickly. This further facilitates electrolyte storage, enabling faster reception of lithium ions from the positive electrode, improving lithium ion transport speed, and thus enhancing the kinetic performance of the negative electrode's arc segment. It allows for the rapid reception of large quantities of lithium ions from the positive electrode, preventing their accumulation on the negative electrode surface and thus avoiding lithium plating.

[0101] Furthermore, such as Figure 8 As shown, the groove of the second groove 211 has a width S2, a depth T2, a spacing D3 between two adjacent grooves of the second groove 211, and a spacing D4 between the lowest point of the groove of the second groove 211 and the negative electrode current collector 22. The width S2 can range from 50μm to 250μm, optionally 70μm, 100μm, 130μm, 160μm, 190μm or 220μm, etc. The depth T2 can range from 3μm to 35μm, optionally 5μm or 7μm. The spacing D3 can range from 0.5 mm to 5 mm, optionally 0.8 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.5 mm, 3.5 mm, or 4.5 mm. The spacing D4 can range from 3 μm to 70 μm, optionally 5 μm, 7 μm, 9 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, or 60 μm. This increases the electrolyte storage capacity while maintaining the N / P ratio. Simultaneously, controlling the depth T2 within this range ensures that the distance between the bottom of the slot and the negative electrode current collector 22 is not less than 3 μm to 10 μm, preventing damage to the negative electrode current collector 22 during slot fabrication and thus avoiding breakage.

[0102] It should be noted that the wound electrode body of this utility model can be implemented by one or more combinations of the above embodiments, or by variations thereof.

[0103] Exemplary lithium-ion secondary battery

[0104] On the other hand, such as Figure 15 and 16 As shown, this embodiment of the present invention also provides a lithium-ion secondary battery 1000. The lithium-ion secondary battery 1000 includes the above-described wound electrode body 100.

[0105] refer to Figure 15 and 16The lithium-ion secondary battery 1000 may include a wound electrode body 100 and a housing 200. The housing 200 may have a receiving cavity, which may house one or more wound electrode bodies 100.

[0106] like Figure 15 As shown, in some embodiments, the casing 200 may be square. That is, the lithium-ion secondary battery 1000 may be a square lithium-ion secondary battery 1000. The material of the casing 200 may be the same as conventionally used materials and is not particularly limited. For example, the casing 200 may be made of metal, specifically aluminum (alloy) or iron (alloy).

[0107] like Figure 16 As shown, in some embodiments, the casing 200 is flat and made of a relatively soft material, such as aluminum-plastic film. That is, in this embodiment, the lithium-ion secondary battery 1000 can be a pouch lithium-ion secondary battery 1000.

[0108] It is foreseeable that in other examples of the present invention, the battery 1000 may also be implemented as a type other than the square lithium-ion secondary battery 1000 and the pouch lithium-ion secondary battery 1000.

[0109] It should be noted that the other aspects of the lithium-ion secondary battery 1000 can be the same as the conventional battery 1000. For the sake of simplicity, the present invention will not elaborate on these aspects.

[0110] The lithium-ion secondary battery 1000 provided according to the embodiments of this utility model has the same effects as the wound electrode body 100 described above, as detailed above, and will not be repeated here.

[0111] It should be noted that, in this invention, "battery" refers to an energy storage device capable of repeated charging and discharging, which can be interpreted as the concept of a "secondary battery." In the embodiments of this utility model, the concept of "secondary battery" may include lithium-ion secondary batteries, etc.

[0112] It should be understood that the term "comprising" and its variations used in the embodiments of this utility model are open-ended, meaning "including but not limited to". The term "according to" means "at least in part according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least another embodiment". The term "a plurality of" means "more than one", which implies covering two, three or more cases.

[0113] It should be understood that although terms such as "first" or "Nth" may be used in embodiments of the present invention to describe various elements, such as the first long slot and the Nth long slot, these elements are not defined by these terms, which are only used to distinguish one element from another.

[0114] The protection scope of this utility model embodiment is not limited to the above embodiments. Any variations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in this utility model embodiment should be included within the protection scope of this utility model embodiment. Therefore, the protection scope of this utility model embodiment should be determined by the protection scope of the claims.

[0115] The technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the present utility model embodiments.

[0116] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Unless otherwise specified, the processing procedures and techniques involved are conventional technical methods.

[0117] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the present invention.

[0118] It should be noted that α1, α2, roughness, groove size, and the size of concave and convex parts can be controlled by processing parameters, such as laser forming parameters.

[0119] Example 1-1

[0120] Lithium cobalt oxide, polyvinylidene fluoride, and acetylene black, the positive electrode active materials, were mixed in a mass ratio of 97.2:1.3:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred until a homogeneous and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto a 10 μm thick positive electrode current collector 11 (aluminum foil). The coated aluminum foil was dried, rolled, and slit to obtain a positive electrode sheet 10. A groove 111 was formed on the positive electrode active layer 11 of the positive electrode sheet 10 using a laser (see...). Figure 6 The width W of groove 111 is 5.53 mm, the width S1 of groove 111 is 1.02 mm, the depth T1 is 18.6 μm, the spacing D1 between adjacent grooves is 4.89 mm, and the bottom roughness of groove 111 is 2*2 mm. 2 The height difference between the highest and lowest points within the range is 4.5 μm, and the sidewall roughness is 0.2*0.2 mm. 2The height difference between the highest and lowest points within the range is 4.5 μm. The angle α1 between the first sidewall 1113 of the first groove 111a and the positive current collector 12 is 35.1°. The angle α2 between the second sidewall 1114 of the Nth groove 111n and the positive current collector 12 is 35.1°.

[0121] The negative electrode active material (a combination of artificial graphite and silicon carbon, with a mass ratio of artificial graphite to silicon carbon of 7:3), single-walled carbon nanotubes, conductive carbon black, and styrene-butadiene rubber are mixed in a mass ratio of 95.9:0.1:1:3. Deionized water is added, and the mixture is stirred until a homogeneous and fluid negative electrode slurry is formed. This negative electrode slurry is uniformly coated onto a 6 μm thick negative electrode current collector 21 (copper foil). The coated copper foil is dried, rolled, and slit to obtain a negative electrode sheet 20. A second groove 211 is laser-formed on the negative electrode active layer 21. The width S2 of the groove 211 is 50.1 μm, the depth T2 is 3.2 μm, and the distance D4 between the bottom of the groove 211 and the negative electrode current collector 22 is 11.8 μm. The distance D3 between adjacent grooves in the second groove 211 is 0.51 mm, and the length L1 of the second groove 211 is 5.67 mm. The thickness of the negative electrode active layer 21 is 15.0 μm.

[0122] The prepared positive electrode 10, separator 30, and negative electrode 20 are stacked and wound to form a wound electrode body 100. Then, through encapsulation, baking, electrolyte injection, formation, secondary sealing, sorting, and OCV, a lithium-ion secondary battery 1000 is obtained. Here, the thickness H of the wound electrode body is 4.76 mm.

[0123] It should be noted that the other forming processes and materials involved in the positive electrode 10 and negative electrode 20 are conventional techniques in this field and will not be described in detail here.

[0124] Examples 1-2

[0125] The difference from Example 1-1 is that W is 7.56 mm, α1 is 54.9°, α2 is 54.9°, L1 is 12.61 mm, S2 is 150.0 μm, T2 is 19.8 μm, D3 is 2.53 mm, D4 is 5.2 μm, and the thickness of the negative electrode active layer 21 is 25 μm.

[0126] Examples 1-3

[0127] The difference from Example 1-1 is that W is 9.39 mm, α1 is 79.6°, α2 is 79.6°, L1 is 19.33 mm, S2 is 249.0 μm, T2 is 34.9 μm, D3 is 4.97 mm, D4 is 3.1 μm, and the thickness of the negative electrode active layer 21 is 38 μm.

[0128] Examples 1-4

[0129] The difference from Embodiment 1-1 is that the arrangement of the groove 111 is as follows: Figure 4 The length direction of the groove 111 is perpendicular to the length direction of the electrode.

[0130] Examples 1-5

[0131] The difference from Embodiments 1-2 is that the arrangement of the groove 111 is as follows: Figure 4 The length direction of the groove 111 is perpendicular to the length direction of the electrode.

[0132] Examples 1-6

[0133] The difference from embodiments 1-3 is that the arrangement of the groove 111 is as follows: Figure 4 The length direction of the groove 111 is perpendicular to the length direction of the electrode.

[0134] Examples 1-7

[0135] The difference from Embodiment 1-1 is that the arrangement of the second groove 211 is as follows: Figure 10 and Figure 11 That is, the two grooves are simultaneously set on the arc section and the straight section of the negative electrode sheet, with D2 being 0.35mm, and the lengths of the negative electrode active layer being L2 being 1853.0mm and L3 being 1849.8mm.

[0136] Examples 1-8

[0137] The difference from Embodiments 1-2 is that the arrangement of the groove 211 is as follows: Figure 10 and Figure 11 D2 is 5.13 mm, and the lengths of the negative electrode active layer are L2 1853.0 mm and L3 1848.3 mm.

[0138] Examples 1-9

[0139] The difference from embodiments 1-3 is that the arrangement of the second groove 211 is as follows: Figure 10 and Figure 11 D2 is 9.97 mm, and the lengths of the negative electrode active layer are L2 1853.0 mm and L3 1851.9 mm.

[0140] Example 2-1

[0141] The difference from Examples 1-2 is that W is 3.31 mm.

[0142] Example 2-2

[0143] The difference from Examples 1-2 is that W is 13.91 mm.

[0144] Example 3-1

[0145] The difference from Examples 1-2 is that α1 and α2 are 3.5°.

[0146] Example 3-2

[0147] The difference from Examples 1-2 is that α1 and α2 are 88.6°.

[0148] Example 4-1

[0149] The difference from Examples 1-2 is that the roughness of the bottom surface and sidewall of the groove 211 is 0.7 μm.

[0150] Example 4-2

[0151] The difference from Examples 1-2 is that the roughness of the bottom surface and sidewall of the groove 211 is 1.2 μm.

[0152] Example 4-3

[0153] The difference from Examples 1-2 is that the roughness of the bottom surface and sidewall of the groove 211 is 9.8 μm.

[0154] Example 4-4

[0155] The difference from Examples 1-2 is that the roughness of the bottom surface and sidewall of the groove 211 is 12.1 μm.

[0156] Example 5-1

[0157] The difference from Examples 1-2 is that D1 is 0.32 mm.

[0158] Example 5-2

[0159] The difference from Examples 1-2 is that D1 is 0.54 mm.

[0160] Example 5-3

[0161] The difference from Examples 1-2 is that D1 is 9.86 mm.

[0162] Example 5-4

[0163] The difference from Examples 1-2 is that D1 is 11.05 mm.

[0164] Example 6-1

[0165] The difference from Examples 1-2 is that T1 is 0.70 mm.

[0166] Example 6-2

[0167] The difference from Examples 1-2 is that T1 is 1.30 mm.

[0168] Example 6-3

[0169] The difference from Examples 1-2 is that T1 is 34.70 mm.

[0170] Example 6-4

[0171] The difference from Examples 1-2 is that T1 is 38.20 mm.

[0172] Example 7-1

[0173] The difference from Examples 1-2 is that S1 is 0.43 mm.

[0174] Example 7-2

[0175] The difference from Examples 1-2 is that S1 is 0.59 mm.

[0176] Example 7-3

[0177] The difference from Examples 1-2 is that S1 is 1.95 mm.

[0178] Example 7-4

[0179] The difference from Examples 1-2 is that S1 is 2.69 mm.

[0180] Example 8-1

[0181] The difference from Examples 1-2 is that L1 is 5.31 mm.

[0182] Example 8-2

[0183] The difference from Examples 1-2 is that L1 is 7.62 mm.

[0184] Example 8-3

[0185] The difference from Examples 1-2 is that L1 is 17.49 mm.

[0186] Example 8-4

[0187] The difference from Examples 1-2 is that L1 is 24.31 mm.

[0188] Comparative Example 1

[0189] The difference from Embodiments 1-2 is that the groove 111 is not provided.

[0190] Comparative Example 2

[0191] The difference from Embodiments 1-2 is that the groove 211 is not provided.

[0192] The batteries of the embodiments and comparative examples were tested according to the following test methods.

[0193] Lithium plating test conditions and evaluation criteria: Using a charge-discharge device, the batteries prepared in the above examples and comparative examples were charged and discharged 800 times at a constant temperature of 25℃±3℃ and a 2C rate. After 800 charge-discharge cycles, the batteries were disassembled and the plating was observed. Plating and black spots covering more than 70% of the arc area were defined as very severe plating; plating and black spots covering 50% to 70% of the arc area were defined as severe plating; plating and black spots covering 30% to 50% of the arc area were defined as lithium plating; plating and black spots covering less than 30% of the arc area were defined as slight plating; and 0% was defined as no plating.

[0194] Test conditions and evaluation criteria for separator rupture: The battery is charged and discharged 100 times at a 2C rate under constant temperature conditions of 25℃±3℃. After 100 charge and discharge cycles, the separator is disassembled and the rupture condition is observed. If the separator is ruptured, a burn point will appear on the negative electrode. The larger the burn point area, the more serious the rupture. Generally, a burn point with an outer circle diameter between 0.01mm and 0.1mm is defined as a slight rupture, 0.1mm to 0.3mm is defined as a rupture, and a burn point larger than 0.3mm is defined as a severe rupture.

[0195] Test conditions and evaluation criteria for electrode breakage: The battery is charged and discharged 800 times at a 2C rate under constant temperature conditions of 25℃±3℃. After being fully charged 800 times, the negative electrode is disassembled and the breakage of the negative electrode is observed. No cracks in the negative electrode indicate that it has not broken.

[0196] Table 1 shows the test results for each embodiment and comparative example.

[0197] Table 1 Test Results

[0198]

[0199]

[0200] The test results above show that setting a groove one in the positive electrode active layer and a groove two in the negative electrode active layer can reduce and avoid lithium plating at the bend.

Claims

1. A wound electrode body, characterized in that, The device includes a positive electrode, a negative electrode, and a separator, which are stacked and wound together. The positive electrode has a straight section in a flat portion of the wound electrode and an arcuate section in a curved portion of the wound electrode. The positive electrode includes a positive current collector and a positive active layer disposed thereon. The positive active layer has at least one groove, which is at least partially located in the arcuate section of the positive electrode. The thickness of the positive active layer in the arcuate section of the positive electrode where the groove is located is less than its thickness in the straight portion of the positive electrode. The negative electrode has a straight section in the flat portion and an arcuate section in the curved portion. The negative electrode includes a negative current collector and a negative active layer disposed thereon. The negative active layer has at least one groove.

2. The wound electrode body according to claim 1, characterized in that, The groove portion one includes a plurality of grooves one, the length direction of which is perpendicular to the length direction of the positive electrode sheet; and / or The groove portion one includes multiple grooves one, and the length direction of the groove one is parallel to the length direction of the positive electrode sheet.

3. The wound electrode body according to claim 2, characterized in that, The groove portion one includes, sequentially, a first groove one to a Nth groove one along the length direction of the positive electrode sheet. Each groove one includes a first sidewall and a second sidewall that are opposite each other along the length direction of the positive electrode sheet. The first sidewall of the first groove one and the second sidewall of the Nth groove one are both sloped. The groove one extends through the positive electrode active layer along the width direction of the positive electrode sheet.

4. The wound electrode body according to claim 3, characterized in that, The first sidewall of the first slot forms an angle α1 with the positive current collector, and the second sidewall of the Nth slot forms an angle α2 with the positive current collector. The values ​​of the included angles α1 and α2 range from 35° to 80°.

5. The wound electrode body according to claim 1, characterized in that, The wound electrode body has a thickness H, and the groove has a dimension W in the length direction of the positive electrode sheet. The thickness H and the dimension W satisfy: 3.14×H / 2-2 mm≤W≤3.14×H / 2+2 mm.

6. The wound electrode body according to any one of claims 1 to 5, characterized in that, The surface of the groove includes a rough surface.

7. The wound electrode body according to claim 6, characterized in that, The rough surface is 2×2 mm 2 The height difference between the highest and lowest points within the range ranges from 1 μm to 10 μm.

8. The wound electrode body according to any one of claims 1 to 5, characterized in that, The groove section includes a plurality of grooves, each groove having a width S1 and a depth T1. Adjacent grooves have a spacing D1. The width S1 ranges from 0.05 mm to 2 mm, the depth T1 ranges from 1 μm to 35 μm, and the spacing D1 ranges from 0.5 mm to 10 mm.

9. The wound electrode body according to claim 1, characterized in that, The at least one groove portion two is located at least partially in the arc segment of the negative electrode sheet, the groove portion two includes a plurality of groove portions two, the length direction of the groove portions two is parallel to the length direction of the negative electrode sheet; and / or, the at least one groove portion two extends along the winding direction of the wound electrode body and ends in the arc segment or the straight segment.

10. The wound electrode body according to claim 1, characterized in that, The first groove has a dimension W along the length of the positive electrode sheet, and the second groove has a length L1. The dimension W and the length L1 satisfy: W≤L1≤W+10mm.

11. The wound electrode body according to claim 9, characterized in that, The at least one groove extends along the winding direction of the wound electrode body through the arc segment and located in the straight segment.

12. The wound electrode body according to claim 11, characterized in that, Along the length direction of the negative electrode sheet, the distance between the two ends of the at least one groove portion two is L3, the negative electrode active layer has a length L2, and the length L3 and the length L2 satisfy: L2-10 mm≤L3≤L2.

13. The wound electrode body according to claim 11, characterized in that, The second groove portion includes multiple narrow groove segments arranged along the length direction of the negative electrode sheet, wherein: The plurality of slot segments connect end to end; or... The plurality of slot segments are staggered along the width direction of the negative electrode sheet; or, The plurality of slot segments are arranged at intervals along the length of the negative electrode sheet, and two adjacent slot segments have a spacing D2, the value of which ranges from 0.2 mm to 10 mm.

14. The wound electrode body according to claim 13, characterized in that, Along the winding direction of the wound electrode body, the end of each slot segment is located in the straight section of the negative electrode sheet.

15. The wound electrode body according to claim 1, characterized in that, The length direction of the groove in the second groove is perpendicular to the length direction of the negative electrode sheet.

16. The wound electrode body according to claim 1, characterized in that, The second groove has a width S2, a depth T2, a distance D3 between two adjacent grooves, and a distance D4 between the lowest point of the groove and the negative current collector. The width S2 ranges from 50 μm to 250 μm, the depth T2 ranges from 3 μm to 35 μm, the distance D3 ranges from 0.5 mm to 5 mm, and the distance D4 ranges from 3 μm to 70 μm.

17. The wound electrode body according to claim 1, characterized in that, The positive current collector has a thickness H and a tensile strength P, wherein the ratio of the thickness H to the tensile strength P satisfies: 5 < P / H < 12.

18. A lithium-ion secondary battery, characterized in that, Includes a wound electrode body according to any one of claims 1 to 17.

Images