Pole piece and battery

Abstract

The invention relates to the technical field of batteries, and discloses a pole piece and a battery, the pole piece comprises a pole piece body, the pole piece body comprises a current collector and an active layer arranged on at least one side surface of the current collector, and the pole piece body comprises a current collector empty foil area not coated with the active layer; the tab comprises a tab connecting area connected with the current collector empty foil area and a tab extending area extending out of the edge of the current collector empty foil area, the tab connecting area is provided with a first surface and a second surface which are oppositely arranged in the thickness direction of the pole piece, the first surface is arranged towards the current collector empty foil area, and the second surface is arranged away from the current collector empty foil area; the first surface comprises a first area, and the roughness of the first area is greater than that of the second surface; and the first adhesive layer is bonded between the tab connecting region and the current collector empty foil region. The mechanical occlusion effect of the first area improves the connection reliability of the tab and the current collector, the roughness of the second surface is small, the risk of short circuit of the positive electrode and the negative electrode is reduced, and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to electrodes and batteries. Background Technology

[0002] Electrodes are a crucial component of batteries, typically consisting of an electrode body and tabs. The electrode body includes a current collector and an active material coated on its surface, while the tabs are connected to the current collector. However, the connection between the tabs and current collectors in existing technologies is unreliable. During long-term charge-discharge cycles or when subjected to drops or vibrations, the tabs can easily shift or even detach due to expansion, contraction, or vibration, leading to cell failure and severely impacting battery reliability. Summary of the Invention

[0003] In view of this, the present invention provides an electrode and a battery to solve the problem of poor reliability of the connection between the electrode tab and the current collector.

[0004] In a first aspect, the present invention provides an electrode sheet, comprising: an electrode sheet body, including a current collector and an active layer disposed on at least one side surface of the current collector, the electrode sheet body including a current collector empty foil region not coated with the active layer; an electrode tab, including an electrode tab connection region connected to the current collector empty foil region and an electrode tab extension region extending out of the edge of the current collector empty foil region, the electrode tab connection region having a first surface and a second surface disposed opposite to each other along the electrode sheet thickness direction, the first surface being disposed facing the current collector empty foil region, the second surface being disposed away from the current collector empty foil region, the first surface including a first region, the roughness of the first region being greater than the roughness of the second surface; and a first adhesive layer, the first adhesive layer being bonded between the electrode tab connection region and the current collector empty foil region.

[0005] In one optional embodiment, the active layer has a tab groove, and the current collector hollow foil area is located in the tab groove; the tab groove extends along the Y direction of the electrode body, and the tab extends along the Y direction; Along the X direction, the distance between the edge of the first region and the edge of the tab connection region is W, where 0.5mm≤W≤2 mm; And / or, along the Y direction, the tab connection area has a first side and a second side disposed opposite to each other, the first side being flush with one edge of the electrode body along the Y direction, and along the Y direction, the distance between the edge of the first area near the first side and the first side is H, where 0≤H≤5 mm; And / or, along the Y direction, the distance between the edge of the first region near the second side and the second side is D, where 0≤D≤5 mm.

[0006] In one alternative implementation, the arithmetic mean deviation of the surface roughness of the first region is R. am The maximum height of the outline is R. zm Where 1.5 μm≤R am ≤20 μm, 5 μm≤R zm ≤30 μm; And / or, the arithmetic mean deviation of the surface roughness of the second surface is R. ab The maximum height of the outline is R. zb Where 0.05 μm≤R ab ≤0.5 μm, 0.05 μm≤R zb ≤3 μm; And / or, the first surface further includes a second region, the roughness of the first region being greater than the roughness of the second region.

[0007] In one optional embodiment, the projected area of ​​the first region on the current collector foil region is S. m The area of ​​the overlapping region between the tab connection area and the current collector hollow foil area is S. t , of which S m With S t The relationship between them is: 0.1 ≤ S m / S t ≤0.9; And / or, 25 mm 2 ≤S m ≤216 mm 2 50 mm 2 ≤S t ≤250 mm 2 .

[0008] In one optional embodiment, the projected area of ​​the first adhesive layer on the current collector hollow foil region is S. j , of which S j With S m The relationship between them is: 0.2 ≤ S j / S m ≤1.45, 10 mm 2 ≤S j ≤312 mm 2 ; And / or, the coverage area of ​​the first adhesive layer on the first region is S. jm , of which S jm With S m The relationship between them is: S jm / S m ≥0.3, 10 mm 2 ≤S jm ≤48 mm2 ; And / or, the swelling degree of the first adhesive layer in the electrolyte is less than 7%.

[0009] In one optional embodiment, the first region includes a plurality of protrusions and a plurality of recesses, at least a portion of the protrusions contacting the current collector foil region, and the recesses being located between two adjacent protrusions, with at least a portion of the first adhesive layer embedded in the recesses. And / or, the first adhesive layer is a conductive adhesive layer, the first adhesive layer comprising at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin or styrene-butadiene rubber; the first adhesive layer further comprises a conductive agent, the conductive agent comprising at least one of gold, silver, copper, nickel, iron, aluminum, tin, lead, zinc, graphene, carbon black, carbon nanotubes, and graphite.

[0010] In one optional embodiment, a recess is provided in the region where the current collector air foil region is connected to the tab connection region, and the recess is recessed toward a first surface away from the tab connection region; And / or, the recess includes blind holes that do not penetrate the current collector empty foil area along the electrode thickness direction and through holes that penetrate the current collector empty foil area, the number of through holes is N1, and the total number of recesses is N0, wherein N1 / N0≤0.1.

[0011] Secondly, the present invention also provides a battery comprising the aforementioned electrode, wherein the current collector is selected from at least one of a metal current collector or a composite current collector.

[0012] In one optional embodiment, the current collector is a composite current collector, comprising a substrate layer and a conductive layer stacked together. The conductive layers are disposed on both sides of the substrate layer in the thickness direction. Each side of the conductive layer has a current collector empty foil area without the active layer coated on it, so as to form tab grooves on both sides of the electrode sheet. Each tab groove is provided with one tab. The electrode sheet is wound to form a wound electrode assembly. The distance between two tabs on the electrode sheet of the same polarity along the width direction of the wound electrode assembly is d, where d ≥ 1.5 mm. The electrode sheet is at least one of a positive electrode sheet or a negative electrode sheet.

[0013] In one optional embodiment, the battery further includes: a casing; an electrode assembly disposed in the casing, the electrode assembly including the electrode plates; and an electrolyte comprising a solvent, the solvent including a fluorocarboxylic acid ester, the fluorocarboxylic acid ester including ethyl difluoroacetate, wherein the ethyl difluoroacetate has a mass percentage content of 10% to 65% based on the total mass of the electrolyte.

[0014] The technical solution of this application has the following beneficial effects: This application provides an electrode sheet, comprising an electrode sheet body, a tab, and a first adhesive layer. A first region with a larger roughness is formed on the first surface of the tab facing the current collector foil area; that is, the roughness of the surface of the tab facing the current collector foil area is greater than the roughness of the surface of the tab away from the current collector foil area. When the tab is connected to the current collector foil area, in addition to the first adhesive layer bonding the tab to the current collector, the larger roughness of the first region allows for mechanical meshing between the first adhesive layer and the current collector foil area, increasing the connection strength between the tab and the current collector foil area. This improves the connection reliability between the tab and the electrode sheet, significantly suppressing the problem of tab displacement or even detachment during battery cycling or drops, improving battery cycle performance, and enhancing battery reliability. Furthermore, the smaller roughness of the second surface of the tab away from the current collector prevents the tab from scratching the adhesive paper or separator it contacts, reducing the risk of the tab puncturing the adhesive paper or separator and causing a short circuit between the positive and negative electrodes, further improving battery safety.

[0015] Additional aspects and advantages of the embodiments of this application will be described and shown in part in the following description, or illustrated by practice of the embodiments of this application. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a electrode according to an embodiment of the present invention; Figure 2 for Figure 1 A cross-sectional view along the AA direction; Figure 3 This is a schematic diagram of the structure of an electrode sheet according to an embodiment of the present invention; Figure 4 This is a schematic diagram of another electrode structure according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of a pole group according to an embodiment of the present invention; Figure 6 for Figure 5 A magnified view of part B in the diagram; Figure 7 This is a cross-sectional view of a current collector according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 10. Electrode body; 101. Current collector empty foil area; 11. Current collector; 111. Positive current collector; 112. Negative current collector; 1101. Substrate layer; 1102. Conductive layer; 12. Active layer; 121. Positive active layer; 122. Negative active layer; 13. Tab groove; 14. Tab protective adhesive; 15. Receiving groove; 16. Insulating protective adhesive; 20. Tab; 201. Tab connection area; 2011. First side; 2012. Second side; 202. Tab extension area; 21. First surface; 211. First region; 212. Second region; 22. Second surface; 30. First adhesive layer; 40. Seal; 50. Diaphragm. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Electrodes are an important component of batteries. An electrode typically consists of an electrode body and tabs. The electrode body includes a current collector and an active material coated on its surface. The tabs are connected to the current collector. Current technologies have poor reliability in the connection between the tabs and the current collector. During long-term cycling or when the battery experiences abnormalities such as drops or vibrations, the tabs are prone to displacement or even detachment, leading to cell failure and severely impacting the battery's electrical performance and reliability.

[0021] The following is combined Figures 1 to 7 The following describes embodiments of the present invention.

[0022] According to an embodiment of the present invention, an electrode is provided, comprising: an electrode body 10, an electrode tab 20, and a first adhesive layer 30. The electrode body 10 includes a current collector 11 and an active layer 12 disposed on at least one side surface of the current collector 11. The electrode body 10 includes a current collector empty foil region 101 uncoated with the active layer 12. The electrode tab 20 includes an electrode tab connecting region 201 connected to the current collector empty foil region 101 and an electrode tab extending region 202 extending from the edge of the current collector empty foil region 101. The electrode tab connecting region 201 has a first surface 21 and a second surface 22 disposed opposite to each other along the electrode thickness direction. The first surface 21 is disposed facing the current collector empty foil region 101, and the second surface 22 is disposed away from the current collector empty foil region 101. The first surface 21 includes a first region 211, and the roughness of the first region 211 is greater than the roughness of the second surface 22. The first adhesive layer 30 is bonded between the electrode tab connecting region 201 and the current collector empty foil region 101.

[0023] In this embodiment, the electrode sheet has a first region 211 with a larger roughness on the first surface 21 of the tab 20 facing the current collector foil area 101. That is, the roughness of the surface of the tab 20 facing the current collector foil area 101 is greater than the roughness of the surface of the tab 20 away from the current collector foil area 101. This ensures that when the tab 20 is connected to the current collector foil area 101, along the thickness direction of the electrode sheet, the orthographic projection of the first adhesive layer on the electrode sheet body and the orthographic projection of the first region on the electrode sheet body at least partially overlap. This allows the first adhesive layer 30 to bond the tab 20 to the current collector foil area 101. Because the first region 211 has a larger roughness, it can bond with both the first adhesive layer and the current collector foil area. The mechanical meshing between the foil areas 101 increases the connection strength between the tab 20 and the current collector empty foil area 101, improving the connection reliability between the tab 20 and the current collector empty foil area 101. This greatly suppresses the problem of the tab 20 shifting or even falling off during battery cycling or drops, thereby improving the battery's cycle performance and reliability. Furthermore, the roughness of the second surface 22 of the tab 20 facing away from the current collector 11 is small, which can prevent the tab 20 from scratching the adhesive paper or separator it contacts. This helps reduce the risk of the tab 20 puncturing the adhesive paper or separator and causing a short circuit between the positive and negative electrodes, further improving battery safety and cycle life.

[0024] It should be noted that the tab 20 is electrically connected to the current collector 11. The first region 211 is a roughened region formed by roughening treatment, which increases the roughness of the region. The roughening methods of the first region 211 include, but are not limited to, laser scanning, chemical etching, needle roller extrusion and other methods.

[0025] In one embodiment, such as Figure 3 and Figure 6 As shown, the active layer 12 has a tab groove 13, and the current collector empty foil area 101 is located in the tab groove 13.

[0026] Specifically, the electrode is wound along its length to form an electrode group, and the electrode lug 13 is located in the region 1 / 5 to 4 / 5 of the electrode length from the starting point of the winding along the X direction.

[0027] It should be noted that the electrode has mutually perpendicular X and Y directions, with the X direction being the length direction of the electrode. For example, the X direction... Figure 3 The direction indicated by the middle arrow "X" is the Y-direction, which represents the width direction of the electrode. The Y-direction is as follows: Figure 3 The direction indicated by the middle arrow "Y" is such that the XY plane is perpendicular to the thickness direction of the electrode sheet. Specifically, the tab groove 13 is disposed on one side of the electrode sheet body along the Y direction, the tab groove 13 extends along the Y direction of the electrode sheet body 10, and the tab 20 extends along the Y direction so that the tab 20 can extend out of the winding core.

[0028] In one embodiment, further combination Figure 3 As shown, along the X direction, the distance between the edge of the first region 211 and the edge of the tab connection region 201 is W, where 0.5 mm ≤ W ≤ 2 mm. It should be noted that along the X direction, the first region 211 has two oppositely arranged sides, and the tab connection region 201 has two oppositely arranged tab sides. W is the distance between any side of the first region 211 along the X direction and the tab side adjacent to that side. The first region 211 is formed through a roughening process. If W is less than 0.5 mm, the distance between the edge of the first region 211 and the edge of the tab connection region 201 is too small. The edge of the first region 211 is prone to increasing the amount of metal debris generated when subjected to pressure, leading to excessively rapid battery self-discharge and affecting the battery's cycle performance. Furthermore, excessive roughening may cause local thinning of the tab 20, or even micro-cracks, becoming weak points in the mechanical strength of the tab 20 and reducing the battery's reliability. If W is greater than 2 mm... If the distance between the edge of the first region 211 and the edge of the tab connection region 201 is too large, the area of ​​the first region 211 on the tab 20 will be too small, resulting in insufficient contact area between the first region 211 and the current collector empty foil region 101. This will cause the battery resistance to increase or the connection strength between the tab 20 and the current collector empty foil region 101 to decrease, affecting the cycle performance of the battery. Therefore, by limiting W to a value within the range of 0.5 mm to 2 mm, it is possible to avoid the edge of the first region 211 being too close to the edge of the tab connection region 201, which would cause metal debris to easily be generated at the edge of the first region 211 when it is under pressure, thereby reducing the self-discharge of the battery and ensuring that the battery has good cycle performance. At the same time, it is possible to ensure that the first region 211 has sufficient area on the tab 20, so that the tab 20 can fully contact the current collector empty foil region 101 through the first region 211, thereby reducing the internal resistance of the battery and enhancing the connection strength between the tab 20 and the current collector empty foil region 101. Furthermore, it is possible to avoid excessive roughening of the tab 20, thereby ensuring the mechanical strength of the tab 20 and ensuring that the battery has high reliability in use.

[0029] Optionally, the value of W is any one of 0.5 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, or a value between any two of these values.

[0030] In one embodiment, along the Y direction, the tab connection area 201 has a first side 2011 and a second side 2012 disposed opposite to each other. The first side 2011 is flush with one side edge of the electrode body 10 along the Y direction. Along the Y direction, the distance between the edge of the first area 211 near the first side 2011 and the first side 2011 is H, where 0≤H≤5 mm. It should be noted that the first side 2011 is the boundary line between the tab connection area 201 and the tab extension area 202, and is flush with one edge of the electrode body 10 along the Y direction. Therefore, H is the distance between the edge of the first region 211 near the first side 2011 and the edge of the adjacent electrode. If H is less than 0, meaning the first region 211 extends beyond the tab connection area 201, the first region 211 will be exposed beyond the electrode edge, potentially piercing the separator and causing a short circuit due to contact with the electrode or tab of the other polarity, severely affecting battery safety. To further ensure battery safety, it is preferable that H is greater than 0, meaning there is a certain distance between the edge of the first region 211 near the first side 2011 and the first side 2011, to prevent damage to the first side 2011 of the tab connection area 201 due to the larger roughness of the first region when the battery is under pressure, thus affecting current transmission. If H is greater than 5... If H is within the range of 0 to 5 mm, the distance between the edge of the first region 211 near the first side 2011 and the first side 2011 is too large, and the area of ​​the first region 211 is too small. This results in insufficient contact area between the first region 211 and the current collector empty foil region 101, causing an increase in battery resistance or a decrease in the connection strength between the tab 20 and the current collector empty foil region 101. Therefore, by limiting H to a value within the range of 0 to 5 mm, it is possible to ensure that the first region 211 does not exceed the range of the tab connection region 201, thereby preventing the first region 211 from puncturing the separator and improving battery safety. At the same time, it is possible to ensure that the first region 211 has sufficient area so that the tab 20 can make full contact with the current collector empty foil region 101 through the first region 211, reducing the battery internal resistance and enhancing the connection strength between the tab 20 and the current collector empty foil region 101, thereby improving the battery cycle performance.

[0031] Optionally, the value of H is any one of 0 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, or a value between any two of these values.

[0032] In one embodiment, along the Y direction, the distance between the edge of the first region 211 near the second side 2012 and the second side 2012 is D, where 0≤D≤5 mm. It should be noted that the first region 211 is located on the tab 20, while the second side 2012 is a side edge of the tab 20 along the Y direction. Therefore, D will not be less than 0. When the edge of the first region 211 near the second side 2012 is flush with the second side 2012, D equals 0. To further ensure the safety of battery use, it is preferable that D is greater than 0, that is, there is a certain distance between the edge of the first region 211 near the second side 2012 and the second side 2012. This is because when the battery is under pressure, stress concentration will occur at the edge of the tab connection area 201. If the edge of the first region 211 near the second side 2012 coincides with the second side 2012 of the tab connection area 201, under the same pressure, the stress concentration will aggravate the damage caused by the rougher first region 211 to the current collector foil area 101, affecting current transmission and reducing battery cycle performance. If D is greater than 5... If the distance between the edge of the first region 211 near the second side 2012 and the second side 2012 is too large, the size of the first region 211 along the Y direction will be too small, resulting in an insufficient contact area between the first region 211 and the current collector empty foil region 101. This will cause an increase in battery resistance or a decrease in the connection strength between the tab 20 and the current collector empty foil region 101. Therefore, by limiting D to a value within the range of 0 to 5 mm, it is possible to ensure that the first region 211 has a sufficient area, allowing the tab 20 to make full contact with the current collector empty foil region 101 through the first region 211, thereby reducing the battery's internal resistance and enhancing the connection strength between the tab 20 and the current collector empty foil region 101, thus improving the battery's reliability.

[0033] Optionally, the value of D is any one of 0 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, or a value between any two of these values.

[0034] Additionally, in other embodiments, such as Figure 4 As shown, the current collector empty foil region 101 is located at the starting end of the winding of the electrode sheet. The current collector empty foil region 101 is the area at the starting end of the winding of the electrode sheet where the active layer 12 is not coated. The tab 20 is connected to the current collector empty foil region 101.

[0035] In one embodiment, the arithmetic mean deviation of the surface roughness of the first region 211 is R. am The maximum height of the outline is R. zm Where 1.5 μm≤R am ≤20 μm, 5 μm≤R zm ≤30 μm. It should be noted that R...am R is the arithmetic mean difference of the surface roughness of zone 211 in the first region, where is the mean; zm The extreme value of surface roughness in the first region 211; by simultaneously defining R am and R zm The value of R is used to represent the surface roughness of the first region 211. am Less than 1.5 μm or R zm If the surface roughness is less than 5 μm, the surface roughness of the first region 211 is too small, and the improvement in the connection strength between the tab 20 and the current collector empty foil region 101 is not significant; if R am Greater than 20 μm or R zm If the surface roughness of the first region 211 is greater than 30 μm, it will cause negative compression damage to the current collector empty foil region 101 when the tab 20 is connected to the current collector empty foil region 101. Furthermore, if the back side of the current collector empty foil region 101 (i.e., the side of the current collector 11 away from the tab 20 along the electrode thickness direction) is coated with an active layer 12, the first region 211 with excessive roughness will also compress the active layer 12, causing the active layer 12 on the back side of the tab groove to crack or fall off, which will lead to the inability of lithium ions in this area to be properly inserted and extracted, increasing internal resistance and reducing battery capacity and cycle life.

[0036] Therefore, by limiting R am Values ​​are taken in the range of 1.5 μm to 20 μm, and R zm The value is selected in the range of 5 μm to 30 μm, so that the first region 211 has a reasonable surface roughness. This can effectively improve the connection strength between the tab 20 and the current collector empty foil region 101, and also avoid the first region 211 from causing excessive compression damage to the current collector empty foil region 101 and the active layer 12 on the back of the current collector empty foil region 101. This ensures that lithium ions can be normally inserted and extracted on the active layer 12, avoids the increase of battery internal resistance, and helps to maintain the battery with high capacity and cycle life.

[0037] Optionally, R am The value is any one of 1.5 μm, 2 μm, 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, or a value between any two of these values; R zm The value is any one of 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, or a value between any two of these values.

[0038] In one embodiment, the arithmetic mean deviation of the surface roughness of the second surface 22 is R. ab The maximum height of the outline is R.zb Where 0.05 μm≤R ab ≤0.5 μm, 0.05 μm≤R zb ≤3 μm. It should be noted that the second surface 22 is the tab connection area 201 along the electrode thickness direction (e.g., ...). Figure 2 The surface of the second surface 22 (in the direction of the "Z" indicated by the middle arrow) facing away from the current collector 11 can also have a second adhesive tape. The second adhesive tape is insulating adhesive tape, used to fix the tab 20, further ensuring the connection stability between the tab connection area 201 and the current collector empty foil area 101. The second surface 22 is relatively smooth with low surface roughness. If R ab If the deviation is greater than 0.5 μm, the arithmetic mean deviation of the surface roughness of the second surface 22 is too large. If R zb If the surface roughness is greater than 3 μm, the maximum height of the surface roughness profile of the second surface 22 will be too large. Both excessive heights will lead to excessive surface roughness of the second surface 22, making it easy for the second surface 22 to puncture the second adhesive tape, causing the second adhesive tape to fail and affecting the connection stability between the tab connection area 201 and the current collector empty foil area 101. Furthermore, if R... ab Greater than 0.5 μm, R zb When the surface roughness is greater than 3 μm, the surface roughness of the second surface is too large, which also poses a risk of puncturing the separator, affecting the integrity of the separator, reducing ion transport efficiency, and reducing battery cycle performance. In reality, the surface roughness cannot be reduced to zero. ab Less than 0.05 μm or R zb If the surface roughness is less than 0.05 μm, the surface roughness of the second surface 22 is too small, and its bonding force with the second adhesive paper or separator is weak, which can easily lead to the second adhesive paper falling off or poor adhesion to the separator. This will also reduce the cycle performance of the battery. On the other hand, if the surface roughness of the second surface 22 is too small, the processing difficulty is too high, the cost is too high, and it does not meet the actual needs.

[0039] Therefore, by limiting R ab Values ​​are taken in the range of 0.05 μm to 0.5 μm, and R zb The value is selected in the range of 0.05 μm to 3 μm, so that the second surface 22 has a reasonable surface roughness. This can prevent the second adhesive paper or separator attached to the second surface 22 from being punctured, thereby ensuring the connection stability between the tab connection area 201 and the current collector empty foil area 101, ensuring the reliability and cycle performance of the battery. It can also avoid excessively high roughness requirements, which would lead to excessive processing difficulty and help reduce production costs.

[0040] Optionally, R abThe value is any one of 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, or a value between any two of these values; R zb The value is any one of 0.05 μm, 0.08 μm, 0.1 μm, 0.12 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.25 μm, 0.28 μm, 3 μm, or a value between any two values.

[0041] In one embodiment, the first surface 21 further includes a second region 212, wherein the roughness of the first region 211 is greater than the roughness of the second region 212. It should be noted that the first region 211 is a roughened region on the first surface 21, and the unroughened region on the first surface 21 is the second region 212. Further combining... Figures 2 to 3 As can be seen, the second region 212 is the area near the edge of the tab connection area 201. By setting the roughness of the first region 211 to be greater than that of the second region 212, on the one hand, the connection strength between the first region 211 and the current collector empty foil area 101 is guaranteed, and on the other hand, the roughness of the second region 212 is too large, which would cause large stress on the current collector when the tab 20 is bonded to the current collector empty foil area 101. This avoids tearing or micro-cracks in the current collector corresponding to the edge of the tab during the charging and discharging process due to volume expansion or drop vibration of the battery, thereby improving the reliability of the battery.

[0042] In one embodiment, the arithmetic mean deviation of the surface roughness of the second region 212 is R. as The arithmetic mean deviation of the surface roughness of the current collector empty foil region 101 is R. af , where 3≤R am / R af ≤100, 0.2≤R as / R af ≤6, 0.1 μm≤R as ≤0.6 μm, 0.1 μm≤R af ≤0.5 μm.

[0043] It should be noted that the first surface 21 of the tab 20 is bonded to the current collector foil area 101 through the first adhesive layer 30. am / R af R is the ratio of the arithmetic mean deviation of the surface roughness of the first region 211 to the arithmetic mean deviation of the surface roughness of the current collector empty foil region 101. am / R afIf the surface roughness is less than 3, then the surface roughness of the first region 211 is too small relative to the surface roughness of the current collector empty foil region 101, and the improvement in the connection strength between the tab 20 and the current collector empty foil region 101 is not significant; if R am / R af If the surface roughness is greater than 100, the surface roughness of the first region 211 is too large relative to the surface roughness of the current collector empty foil region 101. The first region 211 is prone to causing compression damage to the current collector empty foil region 101 and the active layer 12 on the back of the current collector empty foil region 101, resulting in cracks in the current collector empty foil region 101 during use, as well as cracking or peeling off of the active layer 12, leading to an increase in the battery's internal resistance and affecting its reliability. as / R af R is the ratio of the arithmetic mean deviation of the surface roughness of the second region 212 to the arithmetic mean deviation of the surface roughness of the current collector empty foil region 101. as / R af If the surface roughness is less than 0.2, then the surface roughness of the second region 212 is too small compared to the surface roughness of the current collector empty foil region 101, and the second region 212 is too smooth, which is not conducive to the bonding stability of the first adhesive layer 30; if R as / R af If the surface roughness is greater than 6, then the surface roughness of the second region 212 is too large relative to the surface roughness of the current collector empty foil region 101. This can easily cause the tab 20 to generate a large stress on the current collector 11 when it is connected to the current collector empty foil region 101. As a result, the current collector corresponding to the edge of the tab may tear or develop micro-cracks when the battery expands in volume or is dropped and vibrated during charging and discharging. This will increase the resistance of the battery and affect its reliability.

[0044] At the same time, if R as If the surface roughness is less than 0.1 μm, the surface roughness of the second region 212 is too small, which is detrimental to the bonding stability of the first adhesive layer 30 on the second region 212; if R as If the surface roughness of the second region 212 is greater than 0.6 μm, then the surface roughness of the second region 212 is too large. When the tab 20 is connected to the current collector foil region 101, the second region 212 will also generate significant stress on the current collector 11. Consequently, during battery charging and discharging, due to volume expansion or drop vibration, tearing or micro-cracks may occur on the current collector 11 at the position corresponding to the tab edge, leading to increased battery resistance. Similarly, if R... af If the surface roughness is less than 0.1 μm, the surface roughness of the current collector empty foil region 101 is too small, which is not conducive to the bonding stability of the first adhesive layer 30 on the current collector empty foil region 101; if R af If the surface roughness is greater than 0.5 μm, the surface roughness of the current collector empty foil region 101 is too large, which reduces the local thickness of the current collector 11, making it a weak point in the mechanical strength of the current collector 11 and reducing the reliability of the battery.

[0045] Therefore, by limiting R am / R af Values ​​range from 3 to 100, R as / R af It takes values ​​in the range of 0.2 to 6, and R as Values ​​were taken in the range of 0.1 μm to 0.6 μm, R af By taking values ​​within the range of 0.1 μm to 0.5 μm, the connection stability of the contact area between the first adhesive layer 30 and the tab 20 and the current collector empty foil area 101 is ensured, while controlling the roughness of the second area 212 at the edge of the tab to not be too large. This avoids generating large stress on the current collector 11 when the tab 20 and the current collector empty foil area 101 are bonded, thereby preventing tearing or micro-cracks in the current collector area corresponding to the tab edge during battery charging and discharging due to volume expansion or battery drop vibration, avoiding increased battery resistance, and improving battery cycle performance and reliability.

[0046] It should be noted that the surface roughness test method is as follows: Disassemble the battery, peel the tab 20 off the current collector 11, and then use an ultrasonic cleaner to remove foreign matter or adhesive layer from the surface. Then, use a Mitutoyo roughness tester (such as SJ-310) to test the roughness of the first area 211 and other areas respectively. During the test, place the tab 20 flat on the test table and fix one end. Place the probe of the roughness tester above the area to be tested, and then click "Start Test" to read the data (arithmetic mean deviation R of the surface roughness of the area to be tested). a Maximum outline height R z ).

[0047] In one embodiment, the projected area of ​​the first region 211 on the current collector empty foil region 101 is S. m The area of ​​the overlapping region between the tab connection region 201 and the current collector empty foil region 101 is S. t , of which S m With S t The relationship between them is: 0.1 ≤ S m / S t ≤0.9. It should be noted that the projected area of ​​the first region 211 on the current collector empty foil region 101 refers to the projected area of ​​the first region 211 projected orthographically onto the current collector empty foil region 101 along the electrode thickness direction; S m / S t That is, the area ratio of the first region 211 on the electrode connection region 201, if S m / S t If the value is less than 0.1, the area of ​​the first region 211 is too small, which can easily lead to insufficient connection reliability between the tab 20 and the current collector empty foil region 101, and will also deteriorate the current transmission capability between the tab connection region 201 and the current collector empty foil region 101, reducing the battery cycle performance; if Sm / S t If the value is greater than 0.9, the area of ​​the first region 211 is too large, and the edge of the first region 211 is too close to the edge of the tab. During the bonding process between the tab 20 and the current collector foil area 101, the first region 211 is prone to generating metal fragments when subjected to pressure, which can lead to excessively rapid self-discharge of the battery or even cause an internal short circuit in the battery, resulting in fire and explosion. At the same time, if the first region 211 is too large, excessive roughening treatment may cause local thinning of the tab 20 or the current collector 11, or even micro-cracks, which become weak points in the mechanical strength of the tab.

[0048] Therefore, by limiting S m / S t The value is selected within the range of 0.1 to 0.9, so that the first region 211 has a reasonable area ratio on the tab connection region 201. This can effectively improve the connection strength between the tab 20 and the current collector empty foil region 101, ensuring the connection reliability between the tab 20 and the current collector empty foil region 101. It can also prevent the generation of too much metal debris during the connection process between the tab 20 and the current collector empty foil region 101, thereby avoiding the problem of excessive self-discharge of the battery or even internal short circuit of the battery, which may lead to fire and explosion. In addition, it can avoid excessive roughening of the tab 20, thereby ensuring the mechanical strength of the tab 20 and ensuring that the battery has high reliability in use.

[0049] Optionally, S m / S t The value is any one of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or a value between any two values.

[0050] In one embodiment, 25 mm 2 ≤S m ≤216 mm 2 50 mm 2 ≤S t ≤250 mm 2 If S m Less than 25 mm 2 If the first region 211's projected area on the current collector empty foil region 101 is too small, the connection reliability between the tab 20 and the current collector empty foil region 101 is insufficient; if S m Greater than 216 mm 2 If the projected area of ​​the first region 211 on the current collector foil region 101 is too large, and the edge of the first region 211 is too close to the edge of the electrode tab, the first region 211 is prone to generating metal fragments when subjected to pressure, leading to excessively rapid battery self-discharge or even causing an internal short circuit, resulting in fire and explosion. Furthermore, it weakens the mechanical strength of the electrode tab 20, reducing its reliability. If S t Less than 50 mm 2If the area of ​​the overlapping region between the tab connection region 201 and the current collector empty foil region 101 is too small, the flow area between the tab 20 and the current collector 11 will be insufficient, resulting in an increase in the internal resistance between the tab 20 and the current collector 11, which will affect the electrical performance of the battery; if S t Greater than 250 mm 2 If the area of ​​the overlap between the tab connection area 201 and the current collector empty foil area 101 is too large, it will occupy too much space on the current collector 11. Correspondingly, if the area of ​​the current collector empty foil area 101 is too large, the area of ​​the active layer 12 will be reduced, resulting in a decrease in battery capacity.

[0051] Therefore, by limiting S m At 25 mm 2 Up to 216 mm 2 Takes values ​​within the range, and S t At 50 mm 2 Up to 250 mm 2 Taking values ​​within the specified range can effectively improve the connection strength between the tab 20 and the current collector empty foil area 101, ensuring the connection reliability between the tab 20 and the current collector empty foil area 101. It can also prevent the tab 20 from generating metal fragments when subjected to pressure, thus avoiding the problem of excessively rapid battery self-discharge or even internal short circuits that could lead to fire and explosion. It can also ensure the mechanical strength of the tab 20, ensuring battery reliability. At the same time, it can also ensure that there is sufficient flow area between the tab 20 and the current collector 11, reducing the battery's internal resistance, improving battery cycle performance, and ensuring that the battery has a high capacity.

[0052] Optionally, S m The value is 25 mm 2 50 mm 2 75 mm 2 100 mm 2 125 mm 2 150 mm 2 175 mm 2 200mm 2 216 mm 2 Any value in S or the value between any two values; t The value is 50 mm 2 75 mm 2 100 mm 2 125mm 2 150 mm 2 175 mm 2 200 mm 2 225 mm 2 250 mm 2 It can be any value in the range or the value between any two values.

[0053] In one embodiment, the projected area of ​​the first adhesive layer 30 on the current collector empty foil region 101 is Sj, where S j With S m The relationship between them is: 0.2 ≤ S j / S m ≤1.45, 10 mm 2 ≤S j ≤312 mm 2 It should be noted that the tab 20 is electrically connected to the current collector 11 through the first adhesive layer 30. If S j / S m Less than 0.2, or S j Less than 10 mm 2 If the area of ​​the first adhesive layer 30 is too small, it can easily lead to insufficient bonding area between the first region 211 and the current collector empty foil region 101, resulting in excessively high connection resistance and low connection strength between the tab 20 and the current collector 11; if S j / S m Greater than 1.45, or S j Greater than 312 mm 2 If the area of ​​the first adhesive layer 30 is too large, it will occupy too much space, reducing the battery energy density. Therefore, by limiting S... j / S m It takes values ​​between 0.2 and 1.45, and S j At 10 mm 2 Up to 312 mm 2 The values ​​are selected within the range so that the first adhesive layer 30 has a reasonable area. This ensures that there is sufficient bonding area between the first region 211 and the current collector empty foil region 101, thereby ensuring that there is a small connection resistance and a high connection strength between the tab 20 and the current collector empty foil region 101, improving the battery's electrical performance and reliability. At the same time, it avoids the first adhesive layer 30 occupying too much space, which is beneficial to improving the battery's energy density.

[0054] Optionally, S j / S m The value is any one of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.45, or a value between any two values; S j The value is 10 mm 2 50 mm 2 100 mm 2 150 mm 2 200 mm 2 250 mm 2 300 mm 2312 mm 2 It can be any value in the range or the value between any two values.

[0055] Preferably, S j With S m The range of values ​​for the ratio between them is: 0.8 ≤ S m / S j ≤1.2.

[0056] In one embodiment, the coverage area of ​​the first adhesive layer 30 on the first region 211 is S. jm , of which S jm With S m The relationship between them is: S jm / S m ≥0.3, 10 mm 2 ≤S jm ≤48 mm 2 It should be noted that the tab 20 is electrically connected to the current collector 11 through the first adhesive layer 30. jm This refers to the area covered by the first adhesive layer 30 on the first region 211 after the tab 20 is peeled off from the current collector 11; S jm / S m The upper limit is 1, meaning that the first zone 211 is completely covered by the first adhesive layer 30. If S jm / S m Less than 0.3, or S jm Less than 10 mm 2 If the coverage area of ​​the first adhesive layer 30 on the first region 211 is too small, the electrical connection between the tab 20 and the current collector 11 is insufficient, the resistance is high, and the charge / discharge performance and cycle performance of the battery are poor. Therefore, by limiting S jm / S m A value of not less than 0.3 ensures sufficient electrical connection between the tab 20 and the current collector 11, which helps reduce battery resistance and improve battery charging and discharging performance.

[0057] It should be noted that the projected area of ​​the first region 211 on the current collector empty foil region 101 is S. m The first adhesive layer 30 covers an area of ​​S on the first region 211. jm The test method is as follows: Cut out the tab groove area (including the tab) of the electrode sheet, remove the insulating protective adhesive layer on the surface of the tab, take a double-sided tape larger than the size of the tab groove and stick it flat on the test table, then stick the side of the cut electrode sheet away from the tab onto the double-sided tape, and then slowly peel off the tab along a path perpendicular to the table. Measure the size of the first region 211 and the size of the adhesive layer attached to the surface of the first region 211 under a 2.5D microscope.

[0058] In one embodiment, the swelling degree of the first adhesive layer 30 in the electrolyte is less than 7%. By limiting the swelling degree of the first adhesive layer 30 in the electrolyte to less than 7%, the bonding reliability between the tab 20 and the current collector foil region 101 can be ensured, thereby ensuring that the internal resistance of the battery and the bonding strength of the tab are not significantly affected, and improving the reliability of battery use. It should be noted that the electrolyte composition is not limited here. Currently, the mainstream LiPF6 system tested shows the greatest swelling of the colloid, while other individual systems show lower swelling.

[0059] The method for testing the swelling degree of the first adhesive layer 30 in the electrolyte is as follows: Disassemble the battery, and then cut off the tab and the current collector connected to it along the edge of the tab groove on the electrode sheet. If there is an active coating on the back of the tab groove, the cut-off part needs to be cleaned in an ultrasonic cleaning tank until no active coating is attached to the current collector. Then clean the sample with DMC solvent. Finally, bake the sample in a vacuum oven at 80°C for 2 hours, cool it to room temperature in a dry environment, weigh it and record the weight M1. Then, completely immerse the dried sample in the electrolyte (1 M LiPF6 dissolved in EC / EMC / DMC (1:1:1 vol.)) and seal it. Store it at 60°C for 7 days. After storage, quickly remove the sample with tweezers, gently and quickly wipe off the residual electrolyte on its surface with lint-free paper, and then immediately weigh it on a balance to measure its current weight M2. The swelling degree is calculated as [(M2-M1) / M1]×100%.

[0060] In one embodiment, the first region 211 includes a plurality of protrusions and a plurality of recesses. At least some of the protrusions are in contact with the current collector empty foil region 101, and there is a recess between two adjacent protrusions. At least a portion of the first adhesive layer 30 is embedded in the recess. It should be noted that after the first region 211 is roughened, it forms a structure in which a plurality of protrusions and a plurality of recesses are distributed alternately. The embedding of at least a portion of the first adhesive layer 30 in the recess can increase the contact area between the first adhesive layer 30 and the tab 20 and form an interlocking structure, thereby improving the bonding strength between the tab 20 and the current collector empty foil region 101, and thus improving the drop resistance of the battery. This effectively prevents the tab 20 from separating from the current collector 11 during battery use. In one embodiment, a plurality of protrusions in the first region 211 can pass through the first adhesive layer 30 and directly contact the current collector empty foil region.

[0061] In one embodiment, the protrusion height of the protrusion is 5 μm to 30 μm; the recess depth of the recess is 5 μm to 50 μm, ensuring the bonding strength between the tab 20 and the current collector empty foil area 101.

[0062] In one embodiment, the first adhesive layer 30 is a conductive adhesive layer, comprising at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin, or styrene-butadiene rubber; the first adhesive layer 30 also includes a conductive agent, comprising at least one of gold, silver, copper, nickel, iron, aluminum, tin, lead, zinc, graphene, carbon black, carbon nanotubes, and graphite. By setting the first adhesive layer 30 as a conductive adhesive layer, the tab 20 and the current collector 11 are electrically connected through the first adhesive layer 30. Metal materials such as gold, silver, copper, nickel, iron, aluminum, tin, lead, and zinc, as well as carbon materials such as graphene, carbon black, carbon nanotubes, and graphite, are all conductive materials with good conductivity, ensuring that the first adhesive layer 30 has good conductivity, which helps to reduce the internal resistance between the tab 20 and the current collector 11 and improve the charge and discharge performance of the battery.

[0063] In one embodiment, the thickness of the first adhesive layer 30 is 2 μm to 40 μm, preferably 6 μm to 20 μm.

[0064] In one embodiment, a recess is provided in the region where the current collector empty foil region 101 is connected to the electrode connection region 201, and the recess is recessed toward the first surface 21 away from the electrode connection region 201. The recess is provided on the side of the current collector empty foil region 101 facing the electrode connection region 201, and the recess is formed by a portion of the surface of the current collector empty foil region 101 recessed along the electrode thickness direction toward the direction away from the electrode connection region 201. By providing a recess in the region where the current collector empty foil region 101 is connected to the electrode connection region 201, the first adhesive layer 30 can be filled in the recess, thereby improving the connection stability of the electrode 20, the first adhesive layer 30, and the current collector 11, and improving the connection reliability between the electrode 20 and the current collector 11.

[0065] In one embodiment, the dimensions of the recess along the X direction and / or the Y-square range from 5 μm to 100 μm; the recess depth ranges from 1 μm to 35 μm. It should be noted that the dimensions of the recess along the X direction and / or the Y-square refer to the opening width of the recess. If the opening width of the recess is less than 5 μm or the recess depth is less than 1 μm, the recess is too small, which will weaken the effect on improving the connection strength between the tab 20 and the current collector empty foil region 101. If the opening width of the recess is greater than 100 μm or the recess depth is greater than 35 μm, the recess size is too large, which will severely compress the active layer on the back of the current collector, affecting the charge and discharge performance of the active layer in that area. Therefore, by limiting the width of the recess to a range of 5 μm to 100 μm and the depth of the recess to a range of 1 μm to 35 μm, it is possible to ensure that the recess can effectively enhance the connection strength between the tab 20 and the current collector empty foil area 101, thereby improving the connection reliability between the tab 20 and the current collector empty foil area 101. At the same time, it is possible to avoid excessive compression of the active layer on the back of the current collector by the recess, thereby avoiding cracking or peeling of the active layer and ensuring the charging and discharging performance of the battery.

[0066] Optionally, the dimensions of the recess along the X direction and / or the Y square are any value of 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or a value between any two of these values; the recess depth is any value of 1 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or a value between any two of these values.

[0067] Preferably, the recess is a circular pit. It is understood that, as an alternative embodiment, the opening shape of the recess can also be elliptical, triangular, quadrilateral, or other polygonal.

[0068] In one embodiment, the recess includes blind holes that do not penetrate the current collector empty foil area 101 along the electrode thickness direction and through holes that penetrate the current collector empty foil area 101. The number of through holes is N1, and the total number of recesses is N0, where N1 / N0 ≤ 0.1. It should be noted that by providing through holes, the bonding strength between the first adhesive layer 30 and the current collector empty foil area 101 can be further increased. If no through holes are provided or the number of blind holes is too large, the bonding effect between the first adhesive layer 30 and the tab 20 will be weakened, affecting the conductivity between the tab 20 and the current collector 11. If N1 / N0 is greater than 0.1, the proportion of the number of through holes in the total number of recesses will be too large, which will lead to a decrease in the strength of the current collector 11 and a decrease in the current collection conductivity of the current collector at the tab position. Therefore, by setting the recesses to include blind holes and through holes, and the ratio of the number of through holes to the total number of recesses is not greater than 0.1, the bonding strength between the first adhesive layer 30 and the current collector empty foil area 101 can be improved, and excessive damage to the strength of the current collector 11 can be avoided. This ensures the bonding strength and conductivity between the tab 20 and the current collector empty foil area 101, reduces the battery internal resistance, and improves the reliability of the battery.

[0069] It should be noted that the methods for setting recesses, through holes or blind holes in the current collector empty foil area 101 of the electrode include, but are not limited to, any one or a combination of several of the following: mechanical molding, laser processing, photolithography, chemical etching, stamping, etc.

[0070] Among them, mechanical molding involves using rollers with raised surfaces to mold the foil, forming recesses, blind holes, and through holes on the surface of the current collector; laser processing involves using laser drilling equipment to ablate the empty foil area 101 of the current collector to form blind holes or micro-hole structures; photolithography and chemical etching involve using photoresist masks, exposure, development, and chemical etching to form regularly or irregularly distributed recesses or micro-holes on the surface of the current collector; and stamping involves using a die to directly punch through holes into the foil, forming regularly or irregular recesses or holes. Optionally, the electrode can be a positive electrode or a negative electrode. The tab connected to the positive electrode is a positive tab. The positive electrode includes a positive current collector 111 and a positive active layer 121 disposed on at least one side surface of the positive current collector 111. The tab connected to the negative electrode is a negative tab. The negative electrode includes a negative current collector 112 and a negative active layer 122 disposed on at least one side surface of the negative current collector 112.

[0071] Optionally, the positive electrode active layer 121 includes a positive electrode active material. In some embodiments, the positive electrode active material includes a layered lithium composite oxide with the general chemical formula Li(1+x)NiyCozM(1-yz)O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; and M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0072] In some other embodiments, the positive electrode active material includes aluminum-doped lithium cobalt oxide.

[0073] The negative electrode active layer 122 includes a silicon-based negative electrode material, which includes at least one of silicon-carbon material or silicon-oxygen material, and the sphericity of the silicon-based material is 0.85-0.98.

[0074] According to an embodiment of the present invention, in another aspect, a battery is also provided, the battery including the aforementioned electrode, and the current collector 11 being selected from at least one of a metal current collector or a composite current collector. It should be noted that the metal current collector is a single conductive metal layer, and the metal current collector can be connected to a tab 20 on one side of its thickness direction; the composite current collector includes a substrate layer 1101 and conductive layers 1102 disposed on both sides of the substrate layer 1101 in the thickness direction. The substrate layer 1101 is a non-conductive material such as PET or PP, and the conductive layers 1102 are metal conductive layers. Each of the two conductive layers 1102 is connected to a tab 20 to achieve overall conductivity of the composite current collector.

[0075] In one embodiment, the current collector 11 is a composite current collector, comprising a substrate layer 1101 and a conductive layer 1102 stacked together. The conductive layers 1102 are disposed on both sides of the substrate layer 1101 in the thickness direction. Each side of the conductive layers 1102 has a current collector empty foil area 101 without the active layer 12 coated thereon, forming tab grooves 13 on both sides of the electrode sheet. Each tab groove 13 contains a tab 20, which is electrically connected to the composite current collector through a first adhesive layer 30. After the electrode sheet is wound, a wound electrode assembly is formed. The distance between two tabs 20 on the same polarity electrode sheet along the width direction of the wound electrode assembly is d, where d ≥ 1.5 mm. The electrode sheet is at least one of a positive electrode sheet or a negative electrode sheet. Specifically, the thickness direction of the substrate layer 1101 is the same as the thickness direction of the electrode sheet. Figure 7 The direction indicated by the middle arrow is the "Z" direction; the width direction refers to... Figure 5The middle arrow indicates the "width direction". By setting the conductive layers 1102 on both sides of the composite current collector to be connected to a tab 20 respectively, the active layers 12 on both sides of the current collector 11 are electrically connected to the tab 20, which improves the overcurrent capacity between the tab 20 and the composite current collector, reduces resistance, and improves the battery's charge and discharge capacity. At the same time, the distance between the two tabs 20 on the same electrode in the wound electrode assembly along the width direction of the wound electrode assembly is limited to not less than 1.5 mm, which ensures that the two tabs 20 will not overlap in their thickness direction, thereby avoiding battery thickness and improving battery energy density.

[0076] In one embodiment, the battery further includes: a casing, an electrode assembly, and an electrolyte. The electrode assembly is disposed in the casing and includes the electrode sheets described above; the electrolyte includes a solvent, which includes a fluorocarboxylic acid ester, and the fluorocarboxylic acid ester includes ethyl difluoroacetate. The ethyl difluoroacetate content is 10% to 65% by mass based on the total mass of the electrolyte. It should be noted that ethyl difluoroacetate (DFEA) includes at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluoroacetate, preferably 2,2-difluoroethyl acetate.

[0077] The presence of the first region 211 increases the surface area of ​​the tab, forming a micro-region that can accommodate the electrolyte, creating an "interfacial electrolyte enrichment region." Excessive electrolyte enrichment accelerates the swelling and aging of the first adhesive layer 30. When the mass percentage of DFEA is greater than 10%, the hydrogen bonding interaction between DFEAs is enhanced, increasing viscosity. This reduces the penetration of solvent molecules from the electrolyte into the first adhesive layer 30 through the gap between the tab and the first adhesive layer 30 during cycling, thereby slowing down the swelling and aging of the first adhesive layer 30 and improving battery cycle performance. If the mass percentage of ethyl difluoroacetate is less than 10%, the effect is insignificant. If the mass percentage of ethyl difluoroacetate is greater than 65%, the excessive content leads to excessive electrolyte viscosity. Increased viscosity results in negative effects such as decreased ionic conductivity and poor wettability, thus deteriorating battery cycle performance.

[0078] Therefore, by limiting the mass percentage of ethyl difluoroacetate in the electrolyte to between 10% and 65%, the electrolyte has a reasonable viscosity, which can slow down the swelling and aging of the first adhesive layer 30, and also ensure the ionic conductivity and wetting performance of the electrolyte, thereby improving the battery cycle performance.

[0079] Optionally, the mass percentage of ethyl difluoroacetate is any one of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or 65%, or a value between any two of these values.

[0080] In one embodiment, a seal 40 is connected to the tab 20. The seal 40 is located in a portion of the tab extension area 202 near the tab connection area 201 and covers the surface of the tab 20. The seal 40 is generally composed of a single layer or three layers of PP or modified PP. The material of the seal 40 is the same as the PP layer of the inner wall of the aluminum-plastic film of the casing. The seal 40 tightly wraps the tab metal strip and is then heat-sealed with the aluminum-plastic film of the casing to ensure sealing and form a sealed battery casing space.

[0081] In one embodiment, the electrode assembly includes a positive electrode, a negative electrode, and a separator 50. The separator 50 is disposed between the positive electrode and the negative electrode to prevent the positive / negative electrodes from directly contacting each other and causing a short circuit.

[0082] Further integration Figure 6 As shown, a tab groove 13 is formed on the negative electrode active layer 122 of the negative electrode sheet, and the negative electrode tab is located in the tab groove 13. A tab protective adhesive 14 is provided on the side of the tab 20 away from the negative electrode current collector 112. The tab protective adhesive 14 can prevent the tab 20 from directly contacting the separator 50, thereby preventing the tab 20 from damaging the separator 50. A receiving groove 15 corresponding to the tab groove 13 on the negative electrode sheet is formed on the positive electrode active layer 121 of the positive electrode sheet. The groove depth of the receiving groove 15 is smaller than that of the positive electrode active layer 122. The thickness of 21 is such that the total thickness of the negative electrode tab plus the tab protective adhesive 14 may be greater than the depth of the tab groove 13, protruding from the surface of the negative electrode sheet. The receiving groove 15 provides clearance space for the negative electrode tab and / or the tab protective adhesive 14 on the negative electrode tab, avoiding an increase in the core thickness, thereby reducing the core volume and improving the battery energy density. The receiving groove 15 is provided with insulating protective adhesive 16, which is used to further ensure the insulation between the positive and negative electrodes and improve the battery safety.

[0083] The battery of this application will be described in detail below through specific embodiments. The specific differences of the batteries are shown in Tables 1 and 2.

[0084] Example 1 The battery fabrication in this embodiment includes the following steps: (1) Positive electrode plate: Positive electrode active material: Lithium cobalt oxide (doped with Mg and Al, median particle size of 17 μm) 97.2 parts by weight; Positive electrode conductive agent: Super P and carbon nanotubes (where Super P: carbon nanotube mass ratio = 1:1) total 1.5 parts by weight; Positive electrode binder: polyvinylidene fluoride (PVDF520) 1.3 parts by weight; The positive electrode active material, positive electrode binder, and positive electrode conductive agent are mixed in N-methylpyrrolidone (NMP) solvent and continuously stirred under the action of a stirrer to form a uniform positive electrode slurry. Subsequently, the positive electrode slurry is coated on both sides of the positive electrode current collector (composite current collector), and electrode tab grooves to accommodate the positive electrode tabs are reserved on the active layer on both sides of the positive electrode current collector. It is then placed in a vacuum oven at 120°C and dried for 5 hours. After rolling and slitting, the desired positive electrode sheet is obtained. The electrode sheet is processed with a recess in the area where the current collector foil area and the electrode tab connection area are connected. The recess includes blind holes and through holes. The ratio of the number of through holes N1 to the total number of recesses N0 is 0.05. Positive tab: The required metal strip for the positive tab is cut, and the surface of the tab connection area facing the positive current collector is roughened by laser scanning to form the first region. The arithmetic mean deviation R of the surface roughness of the first region is... am 10 μm, maximum profile height R zm The arithmetic mean deviation R of the surface roughness of the second surface of the tab on the side opposite to the positive current collector is 22 μm. ab 0.25 μm, maximum profile height R zb The thickness is 2.5 μm; the edge distance W along the X direction between the edge of the first region and the edge of the electrode connection region is 1.5 mm; the distance H along the Y direction between the edge of the first region 211 near the first side 2011 and the first side 2011 is 2.5 mm; the distance D along the Y direction between the edge of the first region 211 near the second side 2012 and the second side 2012 is 2.5 mm; the projected area S of the first region on the current collector empty foil region is... m 90 mm 2 The area S of the overlapping region between the tab connection region and the current collector empty foil region t 180 mm 2 S m / S t It is 0.5; The electrode connection area of ​​the positive electrode tab is placed in the electrode tab groove, and the positive electrode tab is bonded to the positive current collector through the first adhesive layer. The projected area S of the first adhesive layer on the empty foil area of ​​the current collector is... j 120 mm 2 S j / S m The coverage area S of the first adhesive layer on the first region is 1.33. jm 36 mm 2 S jm / S m It is 0.4.

[0085] (2) Negative electrode plate: Negative electrode active material: 80.5 parts by weight of graphite, 16 parts by weight of silicon carbide, totaling 96.5 parts by weight; Negative electrode conductive agent: 1.5 parts by weight of carbon nanotubes; Negative electrode binder: 1 part by weight of sodium carboxymethyl cellulose (CMC) and 1 part by weight of styrene-butadiene rubber (SBR); The negative electrode active material and negative electrode binder are mixed in an aqueous solvent and continuously stirred under the action of a stirrer to form a uniform and fluid negative electrode slurry. Subsequently, the slurry is coated on both sides of the negative electrode current collector (composite current collector), and electrode tab grooves to accommodate negative electrode tabs are reserved on the active layer on both sides of the negative electrode current collector. It is then placed in a vacuum oven at 120°C and dried for 5 hours. After rolling and slitting, the desired negative electrode sheet is obtained. The electrode sheet is processed with a recess in the area where the current collector foil area and the electrode tab connection area are connected. The recess includes blind holes and through holes. The ratio of the number of through holes N1 to the total number of recesses N0 is 0.05. Negative tab: The metal strip required for the negative tab is cut, and the surface of the tab connection area facing the negative current collector is roughened by laser scanning to form the first region. The arithmetic mean deviation R of the surface roughness of the first region is... am 10 μm, maximum profile height R zm The arithmetic mean deviation R of the surface roughness of the second surface of the tab on the side opposite to the positive current collector is 22 μm. ab 0.25 μm, maximum profile height R zb The thickness is 2.5 μm; the edge distance W along the X direction between the edge of the first region and the edge of the electrode connection region is 1.5 mm; the distance H along the Y direction between the edge of the first region 211 near the first side 2011 and the first side 2011 is 2.5 mm; the distance D along the Y direction between the edge of the first region 211 near the second side 2012 and the second side 2012 is 2.5 mm; the projected area S of the first region on the current collector empty foil region is... m 90 mm 2 The area S of the overlapping region between the tab connection region and the current collector empty foil region t 180 mm 2 S m / S t It is 0.5; The tab connection area of ​​the negative electrode is placed in the tab groove, and the negative electrode tab is bonded to the negative current collector through the first adhesive layer. The projected area S of the first adhesive layer on the empty foil area of ​​the current collector is... j 120 mm 2 S j / S m The coverage area S of the first adhesive layer on the first region is 1.33. jm 36 mm 2S jm / S m It is 0.4.

[0086] (3) Electrolyte: In an argon glove box with a water content of <0.1ppm and an oxygen content of <0.1ppm, propylene carbonate (PC), 2,2-difluoroethyl acetate (DFEA), and propyl propionate (PP) were mixed evenly, and then fluoroethylene carbonate (FEC), vinylene carbonate (VC), nitrile additives 1,3,6-hexanetrionitrile (HTCN), 1,3-propanesulfonyl lactone (PS), lithium bis(trifluoromethanesulfonylimide) (LITFSI), lithium hexafluorophosphate (LiPF6), and lithium difluorophosphate (LiPO2F2) were added to form a homogeneous solution. After passing the physical property test, the electrolyte was obtained. The electrolyte comprises, by mass, 5% PC, 35% 2,2-difluoroethyl acetate, 20% PP, 15% FEC, 0.2% VC, 3% HTCN, 3% PS, 7% LITFSI, 11% LiPF6, and 0.8% LiPO2F2.

[0087] (4) Diaphragm: A functional layer is formed by coating one side of a 5μm polyethylene substrate with a mixture of Al2O3 and polyvinylidene fluoride, and coating the other side with a polyvinylidene fluoride adhesive layer. The functional layer is formed by coating the substrate with both the Al2O3 layer and the polyvinylidene fluoride adhesive layer. The functional layer is adjacent to the positive electrode and has a thickness of 0.8μm.

[0088] (5) Preparation of lithium-ion batteries: After the positive electrode sheet of step (1), the separator of step (4), and the negative electrode sheet of step (2) are prepared by winding, the battery cell is fixed by adhesive tape. Then the bare battery cell is placed in an aluminum-plastic film shell, and the electrolyte of step (3) is injected into the dried bare battery cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, the required lithium-ion battery is obtained. The distance d between the two tabs on the same polarity electrode sheet along the width direction of the wound electrode group is 2 mm.

[0089] The data for Examples 2 to 41 are shown in Table 1.

[0090] In Example 39, based on the total mass of the electrolyte, the following components accounted for the following mass percentages: PC 5%, 2,2-difluoroethyl acetate 65%, propyl propionate (PP) 3%, FEC 8%, VC 0.2%, 1,3,6-hexanetrionitrile (HTCN) 3%, PS 3%, LITFSI 1%, LiPF6 11%, and LiPO2F2 0.8%.

[0091] In Example 40, based on the total mass of the electrolyte, the following components were present: PC (5%), 2,2-difluoroethyl acetate (8%), propyl propionate (PP) (47%), FEC (15%), VC (0.2%), 1,3,6-hexanetrionitrile (HTCN) (3%), PS (3%), LITFSI (7%), LiPF6 (11%), and LiPO2F2 (0.8%).

[0092] In Example 41, based on the total mass of the electrolyte, the mass percentages of PC were 2%, 2,2-difluoroethyl acetate was 68%, propyl propionate (PP) was 3%, FEC was 8%, VC was 0.2%, nitrile additive 1,3,6-hexanetrionitrile (HTCN) was 3%, PS was 3%, LITFSI was 1%, LiPF6 was 11%, and LiPO2F2 was 0.8%.

[0093] Comparative Example 1 In Comparative Example 1, the tab does not have a first region, the roughness of the first surface and the second surface of the tab are equal, and other parameters are set as in Example 1.

[0094] Comparative Example 2 Comparative Example 2 was carried out in accordance with Example 1, except that the arithmetic mean deviation R of the surface roughness of the first region was... am 0.2 μm, maximum profile height R zm It is 1.5 μm, R am R zm Too small, R am <R ab And R zm <R zb This is not within the scope of this application.

[0095] Comparative Example 3 Comparative Example 3 was carried out in accordance with Example 1, except that the arithmetic mean deviation R of the surface roughness of the second surface was...ab 12 μm, maximum profile height R zb 20 μm, R ab R zb Too large, R am <R ab And R zm <R zb This is not within the scope of this application.

[0096] Comparative Example 4 Comparative Example 4 was carried out in accordance with Example 1, except that the arithmetic mean deviation R of the surface roughness of the first region was... am 0.2 μm, maximum profile height R zm 5 μm, R am Too small, R am <R ab But R zm >R zb This is not within the scope of this application.

[0097] Comparative Example 5 Comparative Example 5 was carried out in accordance with Example 1, except that the arithmetic mean deviation R of the surface roughness of the first region was... am The arithmetic mean deviation R of the surface roughness of the second surface is 1.5 μm. ab It is 1.7 μm, R ab Too large, R am <R ab But R zm >R zb This is not within the scope of this application.

[0098] Table 1

[0099] Table 2

[0100] The relevant performance of the batteries in the above embodiments and comparative examples was tested, and the test results are recorded in Table 3. The test methods are as follows: 1. Drop Test Method Fully charge the battery as required, test the initial voltage, internal resistance, and thickness within 1 hour before the drop, and then drop the device after installation. Place the fully charged battery-equipped device at a designated height and drop it freely onto a cement floor covered with PVC material, repeating the process 5 times, once on each side and once on each corner, for a total of 38 drops. After completing the 5 drops, let the battery stand at room temperature for 24 hours, and then test the voltage and internal resistance. Cycle 1: Height 3 feet, 6 sides (once per side, 6 times in total); Cycle 2: Height 3 feet, 6 faces and 4 corners (1 time for each face and 1 time for each corner, 10 times in total); Cycle 3: Height 3 feet, 6 sides (once per side, 6 times in total); Cycle 4: Height 4 feet, 6 faces and 4 corners (1 time for each face and 10 times for a total); Cycle 5: Height 5 feet, 6 sides (once per side, 6 times in total).

[0101] Judgment criteria: No leakage, voltage drop < 0.01V, internal resistance increase < 30mΩ; Measure the battery voltage and internal resistance before the drop using a voltage and internal resistance tester. Specifically, after the drop test, let the battery stand for 24 hours, and then measure the battery voltage and internal resistance after the drop using a voltage and internal resistance tester. The voltage drop is equal to the battery voltage before the drop test minus the battery voltage after the drop test, and the internal resistance increase is equal to the battery internal resistance after the drop test minus the battery internal resistance before the drop test.

[0102] 2. Loop Testing Method Place the battery on the fixture of the charge-discharge cycle tester and charge it at a constant current of 2.5C to 4.2V at 25℃. Then charge it at a constant current and constant voltage of 1.6C to 4.4V and cut off at 0.05C. Let it stand for 10 minutes. Then discharge it at 0.7C to 3.0V. Repeat this cycle 800 times. Measure the discharge capacity of the battery when it is fully charged on the 800th cycle as C1 and the discharge capacity of the battery when it is fully charged on the first cycle as C0. C1 / C0 is the capacity retention rate after 800 cycles.

[0103] Table 3

[0104] As can be seen from Tables 1 and 3, compared with Comparative Examples 1 to 5, the drop test pass rate and cycle capacity retention rate of the batteries in Examples 1 to 41 are improved to varying degrees. This indicates that by setting a roughened first region on the tab, with the roughness of the first region being greater than that of the second surface, and by adjusting the relevant parameters of the tab within a reasonable range, the connection strength between the tab and the current collector can be increased, suppressing the problem of tab displacement or even detachment during battery cycling or dropping, and improving the cycle life of the battery.

[0105] In contrast, the battery in Comparative Example 1 does not have a first zone on the tab, and the roughness of the first and second surfaces of the tab is equal. The battery drop test pass rate is only 8 / 20, and the cycle capacity retention rate is 84.1%. Compared with Example 1, the drop test pass rate and cycle capacity retention rate of Comparative Example 1 are significantly lower, indicating that the connection strength between the tab without a first zone and the current collector is significantly reduced, the connection reliability is too poor, and the battery performance is too poor.

[0106] For the battery in Comparative Example 2, although a first region is provided on the electrode tab, the arithmetic mean deviation R of the surface roughness of the first region is... am Maximum outline height R zm The surface roughness of the first region is too small, resulting in a battery drop test pass rate of 10 / 20 and a cycle capacity retention rate of 86.7%, which are significantly lower than those of Example 1. This indicates that when the roughness of the first region is too small, it does not significantly improve the connection strength between the tab and the current collector. For the battery of Comparative Example 3, the arithmetic mean deviation R of the surface roughness of the second surface is... ab Maximum outline height R zb Both were too rough, resulting in a battery drop test pass rate of 10 / 20 and a cycle capacity retention rate of 84.8%, a significant decrease compared to Example 1. This indicates that excessive roughness of the second surface also affects the connection stability between the tab and the current collector, as well as the battery's cycle life. Both Comparative Example 2 and Comparative Example 3 batteries exhibited the problem of the second surface roughness being greater than that of the first region, i.e., R... am <R ab And R zm <R zb In this situation, it is not conducive to improving the connection stability between the tab and the current collector, and the battery cycle life is poor.

[0107] For the battery in Comparative Example 4, the arithmetic mean deviation R of the surface roughness in the first region is... am Too small, although it satisfies R zm >R zb But R am <R ab It does not meet the R requirements defined in this application. am >R ab And R zm >R zb The battery drop test pass rate was 11 / 20 and the cycle capacity retention rate was 86.8%, which were also lower than those of Example 1; for the battery of Comparative Example 5, the arithmetic mean deviation R of the surface roughness of the second surface was... ab Too large, making R am <R ab It does not meet the R requirements defined in this application. am >R ab And R zm >R zb The battery drop test pass rate was 13 / 20 and the cycle capacity retention rate was 84.5%, which is lower than that of Example 1. It is evident that when the arithmetic mean deviation of the surface roughness of the first region is less than the arithmetic mean deviation of the surface roughness of the second surface, it is detrimental to improving the connection stability between the tab and the current collector, and the battery cycle life is poor.

[0108] Unless otherwise stated, the values ​​of all parameters mentioned in this application can be determined using testing methods commonly used in the art. Unless otherwise stated, the test temperature for all parameters is 25°C.

[0109] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electrode sheet, characterized in that, include: The electrode body (10) includes a current collector (11) and an active layer (12) disposed on at least one side surface of the current collector (11). The electrode body (10) includes a current collector empty foil area (101) that is not coated with the active layer (12). The tab (20) includes a tab connection area (201) connected to the current collector empty foil area (101) and a tab extension area (202) extending out of the edge of the current collector empty foil area (101). The tab connection area (201) has a first surface (21) and a second surface (22) disposed opposite to each other along the thickness direction of the electrode sheet. The first surface (21) is disposed facing the current collector empty foil area (101), and the second surface (22) is disposed away from the current collector empty foil area (101). The first surface (21) includes a first region (211), and the roughness of the first region (211) is greater than the roughness of the second surface (22). A first adhesive layer (30) is bonded between the tab connection area (201) and the current collector hollow foil area (101).

2. The electrode sheet according to claim 1, characterized in that, The active layer (12) has a tab groove (13) and the current collector hollow foil area (101) is located in the tab groove (13); The tab groove (13) extends along the Y direction of the electrode body (10), and the tab (20) extends along the Y direction; Along the X direction, the distance between the edge of the first region (211) and the edge of the tab connection region (201) is W, where 0.5 mm ≤ W ≤ 2 mm; And / or, along the Y direction, the tab connection area (201) has a first side (2011) and a second side (2012) disposed opposite to each other, the first side (2011) being flush with one edge of the electrode body (10) along the Y direction, and along the Y direction, the distance between the edge of the first area (211) near the first side (2011) and the first side (2011) is H, where 0≤H≤5 mm; And / or, along the Y direction, the distance between the edge of the first region (211) near the second side (2012) and the second side (2012) is D, where 0≤D≤5 mm.

3. The electrode sheet according to claim 1, characterized in that, The arithmetic mean deviation of the surface roughness of the first region (211) is R. am The maximum height of the outline is R. zm Where 1.5 μm≤R am ≤20 μm, 5 μm≤R zm ≤30 μm; And / or, the arithmetic mean deviation of the surface roughness of the second surface (22) is R ab The maximum height of the outline is R. zb Where 0.05 μm≤R ab ≤0.5 μm, 0.05 μm≤R zb ≤3 μm; And / or, the first surface (21) further includes a second region (212), the roughness of the first region (211) being greater than the roughness of the second region (212).

4. The electrode sheet according to claim 1, characterized in that, The projected area of ​​the first region (211) on the current collector empty foil region (101) is S. m The area of ​​the overlapping region between the tab connection region (201) and the current collector hollow foil region (101) is S. t , of which S m With S t The relationship between them is: 0.1 ≤ S m / S t ≤0.9; and / or, 25 mm 2 ≤S m ≤216 mm 2 , 50 mm 2 ≤S t ≤250 mm 2 .

5. The electrode sheet according to claim 4, characterized in that, The projected area of ​​the first adhesive layer (30) on the current collector hollow foil area (101) is S. j , of which S j With S m The relationship between them is: 0.2 ≤ S j / S m ≤1.45, 10 mm 2 ≤S j ≤312 mm 2 ; And / or, the coverage area of ​​the first adhesive layer (30) on the first region (211) is S. jm , of which S jm With S m The relationship between them is: S jm / S m ≥0.3, 10 mm 2 ≤S jm ≤48 mm 2 ; And / or, the swelling degree of the first adhesive layer (30) in the electrolyte is less than 7%.

6. The electrode sheet according to claim 1, characterized in that, The first region (211) includes a plurality of protrusions and a plurality of recesses, at least a portion of the protrusions are in contact with the current collector foil region (101), and there is a recess between two adjacent protrusions, at least a portion of the first adhesive layer (30) is embedded in the recess; And / or, the first adhesive layer (30) is a conductive adhesive layer, the first adhesive layer (30) includes at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin or styrene-butadiene rubber; the first adhesive layer (30) also includes a conductive agent, the conductive agent including at least one of gold, silver, copper, nickel, iron, aluminum, tin, lead, zinc, graphene, carbon black, carbon nanotubes, and graphite.

7. The electrode sheet according to any one of claims 1 to 6, characterized in that, A recess is provided in the area where the current collector air foil area (101) is connected to the electrode connection area (201), and the recess is recessed toward the first surface (21) away from the electrode connection area (201); And / or, the recess includes blind holes that do not penetrate the current collector empty foil area (101) along the electrode thickness direction and through holes that penetrate the current collector empty foil area (101), the number of through holes is N1, and the total number of recesses is N0, wherein N1 / N0≤0.

1.

8. A battery, characterized in that, The battery includes the electrode sheet according to any one of claims 1 to 7, and the current collector (11) is selected from at least one of metal current collectors or composite current collectors.

9. The battery according to claim 8, characterized in that, The current collector (11) is a composite current collector, which includes a substrate layer (1101) and a conductive layer (1102) stacked together. The conductive layer (1102) is disposed on both sides of the substrate layer (1101) in the thickness direction. Each side of the conductive layer (1102) is provided with a current collector empty foil area (101) that is not coated with the active layer (12) so as to form a tab groove (13) on both sides of the electrode sheet. Each tab groove (13) is provided with a tab (20). The electrode sheet is wound to form a wound electrode group. The distance between two electrode tabs (20) on the electrode sheet of the same polarity along the width direction of the wound electrode group is d, where d≥1.5 mm. The electrode is at least one of a positive electrode or a negative electrode.

10. The battery according to claim 8, characterized in that, The battery also includes: shell; An electrode assembly is disposed in the housing, the electrode assembly including the electrode sheet; The electrolyte includes a solvent, the solvent including a fluorocarboxylic acid ester, the fluorocarboxylic acid ester including ethyl difluoroacetate, wherein the ethyl difluoroacetate has a mass percentage content of 10% to 65% based on the total mass of the electrolyte.

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