Battery cell

Abstract

The invention discloses a battery cell, and relates to the technical field of batteries. The battery cell comprises a first pole piece, a diaphragm and a second pole piece opposite to the first pole piece in polarity; the diaphragms are attached to the two sides of the first pole piece in the thickness direction and stacked with the first pole piece, each diaphragm comprises an extension part exceeding the first pole piece in the first direction of the first pole piece, the extension parts on the two sides of the first pole piece are bonded with each other, and the first pole piece and the diaphragms are both of a continuous structure; the first pole piece comprises a plurality of bent sections and a plurality of stacked first stacking sections, and the bent sections are connected with the adjacent first stacking sections; the first pole piece comprises a plurality of thinned areas, and the thickness of the thinned areas is smaller than that of other areas of the first pole piece. By arranging the first pole piece and the diaphragm into a continuous structure, the first pole piece can be prevented from being cut, so that the condition that an active substance falls onto the diaphragm to damage the diaphragm during cutting, so that the positive pole piece is in contact with the negative pole piece to form an internal short circuit is avoided, and the self-discharge rate of the battery cell is protected from being influenced.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and more particularly, to an electrode core. Background Art

[0002] With the wide application of lithium-ion batteries, higher requirements are put forward for their performance, which gradually promotes the development of lithium-ion batteries towards high energy density and high rate. Stacked electrode cores are widely used in the fields of fast charging and high energy density batteries due to their advantages such as small internal resistance, high energy density, and long cycle life.

[0003] When the thickness of the electrode core is fixed, the thinner the thickness of the foil material, the corresponding active material content can be increased. Therefore, using high-strength thin foil material can effectively improve the energy density of the electrode core. However, when cutting the electrode sheet, the active material at the edge of the electrode sheet is likely to fall off. After the active material falls onto the separator and is hot-pressed, it will cause the separator to break, resulting in the direct contact between the positive and negative electrodes of the electrode core, which is likely to form an internal short circuit, thereby increasing the voltage attenuation, and ultimately leading to an increase in the K value of the electrode core and poor performance. The K value of the electrode core is a key index to measure the self-discharge rate of the electrode core. It usually represents the proportion of the capacity lost by the self-discharge of the electrode core per unit time to the initial capacity, and is generally calculated as the percentage of the self-discharge capacity loss per day. An increase in the K value of the electrode core will affect the self-discharge rate of the electrode core.

[0004] In summary, how to provide an electrode core that can avoid affecting the self-discharge rate of the electrode core due to cutting the electrode sheet is an urgent problem to be solved by those skilled in the art at present. Summary of the Invention

[0005] In view of this, the purpose of the present application is to provide an electrode core. By setting the first electrode sheet and the separator as a continuous integral structure, cutting the first electrode sheet can be avoided, thereby avoiding the situation where the active material falls onto the separator during cutting and damages the separator, resulting in the contact between the positive electrode sheet and the negative electrode sheet to form an internal short circuit, and protecting the self-discharge rate of the electrode core from being affected.

[0006] In order to achieve the above purpose, the present application provides the following technical solutions:

[0007] An electrode core includes a first electrode sheet, a separator, and a second electrode sheet having a polarity opposite to that of the first electrode sheet;

[0008] The separator is attached to both sides of the first electrode sheet in the thickness direction and is stacked with the first electrode sheet. The separator includes an extension portion that extends beyond the first electrode sheet along a first direction of the first electrode sheet, and the extension portions on both sides of the first electrode sheet are bonded to each other; the first electrode sheet and the separator are of a continuous structure;

[0009] The first pole piece includes a plurality of bent segments and a plurality of first stacked segments stacked on top of each other, and the bent segments connect adjacent first stacked segments; the first pole piece includes a thinned area formed on the bent segments, and the thickness of the thinned area is less than the thickness of other areas of the first pole piece; the second pole piece includes a plurality of second stacked segments, and the second stacked segments are located between two adjacent first stacked segments; along the length direction of the first pole piece, the size of the thinned area is greater than or equal to the size of the bent segments, and both ends of the thinned area extend beyond the bent segments.

[0010] Optionally, the first pole piece is a negative electrode piece and the second pole piece is a positive electrode piece.

[0011] Optionally, the thickness of the positive electrode piece is H 1 , and the maximum distance between the end of the positive electrode piece and the inner side of the bent segment is a first distance H 2 , and the covering distance of the part of the thinned area on the first stacked segment is a second distance H 3 , the second distance H 3 is less than or equal to the first distance H 2 and the difference from the thickness H 1 of the positive electrode piece minus 1 mm;

[0012] And / or, the length of the thinned area is greater than or equal to the length of a semi-circular arc with the thickness H 1 of the positive electrode piece as the diameter, and the length of the thinned area is less than or equal to the sum of the length of a semi-circular arc with the thickness H 1 of the positive electrode piece as the diameter and twice the second distance H 3 .

[0013] Optionally, the first pole piece is a positive electrode piece, the second pole piece is a negative electrode piece, the first pole piece includes a first current collector and a tab extending outward from the first current collector; an insulating area is provided between adjacent tabs, and insulating layers are provided on both sides in the thickness direction of the part of the first pole piece located in the insulating area, and the thickness of the insulating area is greater than or equal to the thickness of the thinned area; along the length direction of the first pole piece, the insulating area covers at least part of the thinned area.

[0014] Optionally, the insulating area covers all of the bent segments and part of the first stacked segments connected to the bent segments.

[0015] Optionally, the thickness of the negative electrode piece is H 4 , the maximum distance between the end of the negative electrode piece and the inner side of the bent segment is a third distance H 5 , the covering distance of the insulating area on the first stacked segment is a fourth distance H 6 , the third distance H 5Greater than or equal to 0 and less than or equal to 1 mm, the fourth distance H 6 Greater than or equal to the third distance H 5 The sum with 0.1 mm and less than or equal to the third distance H 5 The sum with 1 mm;

[0016] And / or, the length of the insulating region is greater than or equal to the semi-circular arc length with the thickness H of the negative electrode sheet as the diameter, and the length of the thinning region is less than or equal to the semi-circular arc length with the thickness H of the negative electrode sheet as the diameter and twice the fourth distance H 4 4 The sum. 6

[0017] Optionally, a concavo-convex region is provided on one side in the thickness direction of the first electrode sheet, and a plurality of concave portions are provided in the concavo-convex region.

[0018] Optionally, there is a first gap T between the edge of the concavo-convex region and one end of the first electrode sheet where the tab is provided, 1 and there is a second gap T between the edge of the concavo-convex region and one end in the length direction of the second electrode sheet; the distance between adjacent concave portions in the first direction in the concavo-convex region is greater than the second gap T 2 2 and / or the distance between adjacent concave portions in the second direction in the concavo-convex region is greater than the first gap T 1

[0019] Optionally, in the second direction, the concavo-convex region at least partially covers one end of the first electrode sheet where the tab is provided; the ceramic region for connecting with the first electrode sheet in the tab is provided with the concave portion, and the depression depth of the concave portion in the tab is less than the depression depth of the concave portion in the first electrode sheet.

[0020] Optionally, the depth of the concave portion is less than the thickness of the first electrode sheet, and the side of the first electrode sheet facing away from the concave portion is a plane.

[0021] The present application provides an electric core, which includes a first electrode sheet, a separator, and a second electrode sheet with a polarity opposite to that of the first electrode sheet; the separator is attached to both sides in the thickness direction of the first electrode sheet and is stacked with the first electrode sheet. The separator includes an extension portion extending beyond the first electrode sheet along the first direction of the first electrode sheet, and the extension portions on both sides of the first electrode sheet are bonded to each other; the first electrode sheet and the separator are both continuous structures; the first electrode sheet includes a plurality of bending segments and a plurality of first stacked segments stacked on top of each other, and the bending segments connect adjacent first stacked segments; the first electrode sheet includes a thinning region formed on the bending segments, and the thickness of the thinning region is less than the thickness of other regions of the first electrode sheet; the second electrode sheet includes a plurality of second stacked segments, and the second stacked segments are located between two adjacent first stacked segments. ​​​​

[0022] In the battery cell provided by the present application, both the first electrode sheet and the separator are continuous structures, which avoids cutting the first electrode sheet, thereby preventing the active material from falling onto the separator during cutting and damaging the separator, resulting in the contact between the positive electrode sheet and the negative electrode sheet to form an internal short circuit. This can effectively protect the K value and self-discharge rate of the battery cell from being affected. Additionally, in the present application, there is a thinning area covering all the bent sections and part of the first stacked section connected to the bent section. This facilitates bending of the bent section of the first electrode sheet and can effectively increase the curvature of the bent section, preventing the active material in the bent section from falling onto the separator and also avoiding wrinkles or bubbles in the separator. It can also prevent the internal resistance of the battery cell from increasing and prevent black spots from appearing inside the battery cell after cycling. Furthermore, the thinning area also covers part of the first stacked section connected to the bent section. The width of the thinning area is greater than the width of the bent section. The thinning area can clean both the bent section and the first stacked section through laser or a scraper, preventing the active material on the first electrode sheet at the bent section from falling onto the separator during lamination and avoiding affecting the K value of the battery cell. Moreover, along the length direction, the size of the thinning area is greater than or equal to the size of the bent section, and both ends of the thinning area extend beyond the bent section, effectively preventing the phenomenon that when the junction between the thinning area and the non-thinning area is located in the arc area, during the charge and discharge process, the extrusion stress received by the junction area in the arc area is relatively large, causing the active particles at the junction to fall off and resulting in a short circuit. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0024] Figure 1 Schematic diagram of the composite state structure of the first electrode sheet and the separator provided by the present application;

[0025] Figure 2 Schematic diagram of the structure when the first electrode sheet is the negative electrode sheet;

[0026] Figure 3 For Figure 2 Schematic diagram of the structure of the battery cell composed of the first electrode sheet in the folded state;

[0027] Figure 4 Schematic diagram of the structure when the first electrode sheet is the positive electrode sheet;

[0028] Figure 5 For Figure 4 Schematic diagram of the structure of the battery cell composed of the first electrode sheet in the folded state;

[0029] Figure 6Schematic diagram of the structure with concave and convex regions provided in the first electrode sheet;

[0030] Figure 7 is Figure 6 Schematic cross-sectional view of the concave and convex regions in;

[0031] Figure 8 Schematic diagram of the structure with strip-shaped concave portions provided in the negative electrode sheet;

[0032] Figure 9 is Figure 8 Schematic cross-sectional view of the concave and convex regions in.

[0033] Figures 1-9 In:

[0034] 1 is the first electrode sheet, 11 is the thinned area, 12 is the first stacked segment, 13 is the bent segment 13, 2 is the positive electrode sheet, 21 is the insulating area, 3 is the negative electrode sheet, 4 is the separator, 5 is the tab, 6 is the concave and convex region, and 61 is the concave portion. Specific implementation manners

[0035] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0036] The core of the present application is to provide a battery cell. By setting the first electrode sheet and the separator as a continuous integral structure, cutting of the first electrode sheet can be avoided, thereby avoiding the situation where active substances fall onto the separator during cutting and damage the separator, causing the positive electrode sheet and the negative electrode sheet to contact and form an internal short circuit, and protecting the self-discharge rate of the battery cell from being affected.

[0037] Embodiment 1

[0038] This specific embodiment discloses a battery cell. As Figure 1 shown, the battery cell includes a first electrode sheet 1, a separator 4, and a second electrode sheet having a polarity opposite to that of the first electrode sheet 1; the separator 4 is attached to both sides of the first electrode sheet 1 in the thickness direction and is stacked with the first electrode sheet 1. The separator 4 includes an extension portion that extends beyond the first electrode sheet 1 along the first direction of the first electrode sheet 1, and the extension portions on both sides of the first electrode sheet 1 are adhesively bonded to each other; the first electrode sheet 1 and the separator 4 are both continuous integral structures; the first electrode sheet 1 includes a plurality of bent segments 13 and a plurality of first stacked segments 12 stacked on top of each other, and the bent segments 13 connect adjacent first stacked segments 12; the first electrode sheet 1 includes a thinned area 11 formed on the bent segments 13, and the thickness of the thinned area 11 is less than the thickness of other areas of the first electrode sheet 1; the second electrode sheet includes a plurality of second stacked segments, and the second stacked segments are located between two adjacent first stacked segments 12.

[0039] Specifically, the thinning area 11 can cover the entire bent section 13 and a part of the first stacked section 12 connected to the bent section 13.

[0040] Specifically, as Figure 1 shown, the first direction can be Figure 1 the length direction from left to right at the angle shown in

[0041] In the battery cell provided in this specific embodiment, the first electrode sheet 1 and the separator 4 are both continuous integral structures, which avoids cutting the first electrode sheet 1, thereby avoiding the active material falling onto the separator 4 during cutting and damaging the separator 4, resulting in the positive electrode sheet 2 contacting the negative electrode sheet 3 to form an internal short circuit. This can effectively protect the K value and self-discharge rate of the battery cell from being affected. In addition, in this application, there is a thinning area 11 that covers the entire bent section 13 and a part of the first stacked section 12 connected to the bent section 13, which facilitates bending at the bent section 13 of the first electrode sheet 1, and can effectively increase the curvature of the bent section 13, avoiding the active material of the bent section 13 from falling onto the separator 4 and also avoiding wrinkles or bubbles on the separator 4; it can also avoid an increase in the internal resistance of the battery cell and prevent black spots from appearing inside the battery cell after cycling.

[0042] In addition, the thinning area 11 also covers a part of the first stacked section 12 connected to the bent section 13. As Figure 2 shown, the widths of the two thinning areas 11 are S 1 and S 2 , and the widths of adjacent two bent sections are L 1 and L 2 . The width of the thinning area 11 is greater than the width of the bent section. The thinning area 11 can clean both the bent section and the first stacked section 12 through laser or a scraper, that is, it satisfies S 1 > L 1 , S 2 > L 2 . The width of the thinning area 11 is greater than the width of the bent section. The thinning area 11 can clean both the bent section 13 and the first stacked section 12 through laser or a scraper, which can prevent the active material on the first electrode sheet 1 at the bent section 13 from falling onto the separator 4 during lamination, avoiding affecting the K value of the battery cell.

[0043] The battery cell further includes a second electrode sheet, the second electrode sheet has a polarity opposite to that of the first electrode sheet 1, and the second electrode sheet includes a plurality of second stacked sections. When the battery cell is in a stacked state, the second stacked sections are located between two adjacent first stacked sections 12.

[0044] The second pole piece is wrapped by the bent section 13 of the first pole piece 1. When the first pole piece 1 is the negative pole piece 3, there is no risk of poor coverage at both ends of the positive pole piece 2, and no special control is required, which can significantly improve the process efficiency; moreover, both ends in the width direction of the positive pole piece 2 are protected by the arc, and are not easily damaged by the outside.

[0045] As Figure 3 shown, the position of the thinning area 11 facing the second pole piece in the thinning area 11 can be set as the thinnest area, and the thickness of the thinning area 11 of the first lamination section gradually increases from the thinnest area to both ends. The thickness of the thinnest area of the thinning area 11 is W 1 , this setting of the thinning area 11 with the thickness gradually increasing from the middle to both ends can make the bent section 13 bend better, maximize the bending radius of the bent section 13, and avoid the diaphragm 4 from wrinkling when bending.

[0046] In the actual setting process, along the length direction of the first pole piece 1, the size of the thinning area 11 is greater than or equal to the size of the bent section 13 to completely cover the bent section 13; it can effectively prevent that when the junction of the thinning area and the non-thinning area is located in the arc area, during the charge and discharge process, the extrusion stress received by the junction area in the arc area is relatively large, so that the active particles at the junction fall off, resulting in a short circuit phenomenon; of course, it can also be that along the length direction of the first pole piece 1, the size of the thinning area 11 is greater than the size of the bent section 13, and both ends of the thinning area 11 extend beyond the bent section 13 to cover part of the first lamination section 12.

[0047] Embodiment 2

[0048] As Figure 2 、 Figure 3 shown, the first pole piece 1 is the negative pole piece 3, and the second pole piece is the positive pole piece 2; the thickness of the positive pole piece 2 is H 1 , the maximum distance between the end of the positive pole piece 2 and the inner side of the bent section 13 is the first distance H 2 , the covering distance of the thinning area 11 in the first lamination section 12 is the second distance H 3 , the second distance H 3 is less than or equal to the difference between the first distance H 2 and the thickness H 1 of the positive pole piece 2 minus 1 mm; , this can avoid the pole piece powder falling off at the bent section 13 while the negative pole piece 3 can cover the positive pole piece 2. , a certain distance H 2 is reserved at the edge of the side of the positive pole piece 2 from the inner side of the bent section 13, which can avoid the lateral burrs of the positive pole piece 2 from piercing the diaphragm 4 and causing a short circuit of the battery cell, and at the same time can retain more energy density of the battery cell. In this specific embodiment, the thickness H 1 of the positive pole piece 2 ranges from 30 μm to 150 μm; the first distance H2 ranges from 0.1 mm to 2 mm; the second distance H 3 ranges from 0 mm to 0.97 mm.

[0049] In addition, the length of the thinning area 11 can be made greater than or equal to the length of the semi-circular arc with the thickness H 1 of the positive electrode sheet 2 as the diameter, and the length of the thinning area 11 is less than or equal to the length of the semi-circular arc with the thickness H 1 of the positive electrode sheet 2 as the diameter plus twice the second distance H 3 ; specifically, the length of the thinning area 11 is S 1 ; . It effectively ensures that the width of the thinning area 11 is greater than the width of the bending section 13, avoiding the active material on the first electrode sheet 1 at the bending section 13 from falling onto the separator 4 during lamination, thereby affecting the K value of the battery cell, and more energy density of the battery cell can be retained.

[0050] Embodiment 3

[0051] Combined with Figure 4 , Figure 5 as shown, the first electrode sheet 1 is the positive electrode sheet 2, the second electrode sheet is the negative electrode sheet 3, the first electrode sheet 1 includes a first current collector and a tab 5 extending outward from the first current collector; an insulating area 21 is provided between adjacent tabs 5, and insulating layers are provided on both sides in the thickness direction of the part of the first electrode sheet 1 located in the insulating area 21. The insulating area 21 can be realized by coating ceramics, sticking adhesive paper or other methods on the surface of the positive electrode sheet 2. Among them, the adjacent two insulating areas 21 are respectively on one side and the other side of the first electrode sheet 1. By providing the insulating area 21, it is possible to avoid the active material on the positive electrode sheet 2 at the bending section 13 from falling onto the separator 4 during lamination, avoiding affecting the K value of the battery cell, and at the same time, it can also ensure that the negative electrode sheet 3 can cover the positive electrode sheet 2, avoiding lithium plating of the battery cell.

[0052] To ensure the insulation performance, the thickness of the insulating area 21 is greater than or equal to the thickness of the thinning area 11.

[0053] Furthermore, for Figure 4 the first electrode sheet 1, during actual processing, the thinning area 11 can be formed between the two tabs 5 first and then the insulation treatment can be carried out, which can more effectively avoid the active material on the electrode sheet from falling onto the separator 4 during lamination and avoid affecting the K value of the battery cell.

[0054] As Figure 4 shown, the insulating area 21 covers all of the bending section 13 and part of the first lamination section 12 connected to the bending section 13. The widths of the adjacent two insulating areas 21 are respectively S 3 and S 4 , and the widths of the adjacent two bending sections 13 are respectively L 3 and L4 Among them, the width of the insulating region 21 is greater than the width of the bent section 13, that is, it satisfies S 3 > L 3 , S 4 > L 4 , and at the same time, the insulating region 21 needs to reach the first stacked section 12 of the positive electrode sheet 2. This can avoid the active material on the electrode sheet at the bent section 13 from falling onto the separator 4 while the negative electrode sheet 3 can cover the positive electrode sheet 2, avoiding lithium plating in the battery cell.

[0055] As Figure 5 shown, the thickness of the negative electrode sheet 3 is H 4 , and the maximum distance between the end of the negative electrode sheet 3 and the inner side of the bent section 13 is the third distance H 5 , , minimizing the energy loss of the battery cell due to insulation, and at the same time ensuring that the negative electrode sheet 3 covers the positive electrode sheet 2, avoiding lithium plating in the battery cell.

[0056] The covering distance of the insulating region 21 on the first stacked section 12 is the fourth distance H6. The third distance H5 is greater than or equal to 0 and less than or equal to 1 mm. The fourth distance H6 is greater than or equal to the sum of the third distance H5 and 0.1 mm and less than or equal to the sum of the third distance H5 and 1 mm. ; Under the condition of minimizing the energy density loss of the battery cell, the negative electrode sheet 3 can cover the positive electrode.

[0057] In this specific embodiment, the thickness H 4 of the negative electrode sheet 3 ranges from 30 μm to 150 μm; the third distance H 5 ranges from 0 mm to 1 mm; the fourth distance H 6 ranges from 0.1 mm to 1.1 mm.

[0058] The length of the insulating region 21 is S 3 , and the length of the insulating region 21 is greater than or equal to the length of a semi-circular arc with the thickness H 4 of the negative electrode sheet 3 as the diameter, and the length of the thinned region 11 is less than or equal to the sum of the length of a semi-circular arc with the thickness H 4 of the negative electrode sheet 3 as the diameter and twice the fourth distance H 6 ; ; It can ensure that the width of the insulating region 21 is greater than the width of the bent section 13, avoiding the active material on the electrode sheet at the bent section 13 from falling onto the separator 4 during lamination, and at the same time ensuring that the negative electrode sheet 3 can cover the positive electrode sheet 2, avoiding lithium plating in the battery cell.

[0059] Example 4

[0060] An uneven region 6 can be provided on one side in the thickness direction of the first electrode sheet 1, and a plurality of concave portions 61 are provided in the uneven region 6.

[0061] As Figure 6 shown, there is a first gap T between the edge of the concavo-convex area 6 and one end of the first pole piece 1 where the tab 5 is provided 1 , and there is a second gap T between the edge of the concavo-convex area 6 and one end in the length direction of the second pole piece 2 ; the spacing L 1 , L 2 between adjacent concave portions 61 in the first direction in the concavo-convex area 6 is greater than the second gap T 2 , and the spacing W 1 , W 2 between adjacent concave portions 61 in the second direction in the concavo-convex area 6 is greater than the first gap T 1 . This ensures that there are more concave portions 61 in the first stacked section 12 and the bent section 13 on the first pole piece 1, which can prevent the paste on the pole piece from falling off at the bent section 13 during lamination, and can also prevent air bubbles from appearing between the diaphragm 4 and the pole piece during lamination.

[0062] As Figure 6 shown, the first spacing dimensions between adjacent concave portions 61 in the first direction are different. Specifically, the first spacing dimension can be I 1 or I 2 ; and the range of the ratio of different first spacing dimensions is from 0.6 to 1.4 . The second spacing dimensions between adjacent concave portions 61 in the second direction are different. The second spacing can be W 1 or W 2 ; and the range of the ratio of different second spacing dimensions is from 0.6 to 1.4 .

[0063] In this specific embodiment, the spacings between adjacent concave portions 61 in the first direction and the second direction are not limited to be the same. During the actual processing, there is no need to ensure that the spacings between adjacent concave portions 61 are the same, which can effectively improve the die-cutting efficiency and quality.

[0064] During actual processing, as Figure 7 shown, the thickness of the position on the first pole piece 1 where no concave portion 61 is provided is H 1 , the depth of the concave portion 61 is h 2 , the thickness of the position on the first pole piece 1 where the concave portion 61 is provided is h 1 , and the spacing between the centers of two adjacent concave portions 61 is L 1 . It can be made such that the depth of the concave portion 61 is less than the thickness H of the position on the first pole piece 1 where no concave portion 61 is provided 1 , and the side of the first pole piece 1 facing away from the concave portion 61 is a plane.

[0065] When the side of the first pole piece 1 facing away from the concave portion 61 is a plane, the thickness of the position on the first pole piece 1 where no concave portion 61 is provided is H 1The thickness h of the position in the first electrode tab 1 where the recess 61 is provided 1 and the depth h of the recess 61 2 The sum; when one side of the first electrode tab 1 facing away from the recess 61 is convex, the thickness of the position in the first electrode tab 1 where the recess 61 is not provided is H 1 is less than the thickness h of the position in the first electrode tab 1 where the recess 61 is provided 1 and the depth h of the recess 61 2 The sum.

[0066] Furthermore, it can be made such that ; to ensure that the recess 61 of the first electrode tab 1 has sufficient depth, the wettability of the electrolyte can be increased, thereby increasing the cycle life of the battery. At the same time, the consistency of the overall adhesion force of the stepped battery can be improved, and the lithium-ion transmission paths tend to be consistent, meeting the uniform distribution of lithium ions on the negative electrode tab 3 during the charge and discharge process and preventing lithium deposition during the cycle.

[0067] In addition, in the second direction, the concave-convex area 6 at least partially covers one end of the first electrode tab 1 where the tab 5 is provided; the ceramic area of the tab 5 for connecting with the first electrode tab 1 is provided with a recess 61, and the recess depth of the recess 61 in the tab 5 is less than the recess depth of the recess 61 in the first electrode tab 1.

[0068] The setting of the ceramic area is mainly used to prevent the aluminum foil in the tab 5 from directly contacting the graphite in the electrode tab, and at the same time, the ceramic area can also play a role in avoiding burrs.

[0069] As Figure 8 shown, the first electrode tab 1 can be the negative electrode tab 3, and the recess 61 is a strip-shaped recess 61 provided on the negative electrode tab 3; the distance between the edge of the strip-shaped recess 61 in the second direction and the edge of the negative electrode tab 3 is T 3 , and the distance between the edge of the concave-convex area 6 in the first direction and the edge of the negative electrode tab 3 is T 4 , the distance between two adjacent strip-shaped recesses 61 is L 3 or L 4 , the distance between two adjacent strip-shaped recesses 61 is L 3 or L 4 are both greater than the distance T between the edge of the concave-convex area 6 in the first direction and the edge of the negative electrode tab 3 4 . To ensure that the first layer stack segment 12 of the electrode tab and the bend have more recesses 61, the recesses 61 are provided in the bend segment 13, reducing the thickness of the bend segment 13, which can avoid the paste on the electrode tab from falling powder at the bend segment 13, and can also avoid the appearance of air bubbles between the diaphragm 4 and the electrode tab during lamination. In addition, the distance between adjacent depressions in the first direction can be equal or unequal, that is , to ensure the die-cutting efficiency and quality.

[0070] As shown in FIG. 9, the thickness of the negative electrode sheet 3 is H 4 , the thickness of the concave portion 61 on the negative electrode sheet 3 is h 4 , the depth of the concave portion 61 is h 3 . Among them, H 4 ≤h 4 +h 3 , 0≤ <1, 0≤ <1. Ensure that the concave portion 61 of the electrode sheet has sufficient depth, thereby reducing the thickness of the bent section 13, which can avoid the paste shedding on the electrode sheet at the arc during lamination, and can also prevent air bubbles from appearing between the separator 4 and the electrode sheet during lamination.

[0071] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. Any combination of all the embodiments provided in this application falls within the protection scope of this invention, and will not be elaborated here.

[0072] The above has introduced the battery cell provided in this application in detail. Specific examples are used herein to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the method and its core idea of this application. It should be noted that for those of ordinary skill in the art, without departing from the principle of this application, several improvements and modifications can still be made to this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A battery cell, characterized in that: It comprises a first pole piece (1), a diaphragm (4) and a second pole piece having a polarity opposite to that of the first pole piece (1); The diaphragm (4) is attached to both sides of the first pole piece (1) in a thickness direction and is stacked with the first pole piece (1); the diaphragm (4) comprises an extension portion extending beyond the first pole piece (1) along a first direction of the first pole piece (1); the extension portions on both sides of the first pole piece (1) are bonded to each other; the first pole piece (1) and the diaphragm (4) are a continuous structure; The first pole piece (1) comprises a plurality of bent sections (13) and a plurality of first stacked sections (12), wherein the bent sections (13) connect adjacent first stacked sections (12); the first pole piece (1) comprises a thinned area (11) formed on the bent sections (13), wherein the thickness of the thinned area (11) is less than the thickness of other areas of the first pole piece (1); the second pole piece comprises a plurality of second stacked sections, wherein the second stacked sections are located between two adjacent first stacked sections (12); along the length direction of the first pole piece (1), the size of the thinned area (11) is greater than or equal to the size of the bent sections (13), and both ends of the thinned area (11) extend beyond the bent sections (13).

2. The battery cell according to claim 1, characterized in that: The thickness of the positive electrode sheet (2) is H1, the maximum distance between the end of the positive electrode sheet (2) and the inner side of the bent section (13) is a first distance H2, the covering distance of the thinned area (11) in the first stacking section (12) is a second distance H3, and the second distance H3 is less than or equal to the difference between the first distance H2 and the thickness H1 of the positive electrode sheet (2) minus 1 mm; And / or, the length of the thinned area (11) is greater than or equal to the length of a semicircular arc with the thickness H1 of the positive electrode sheet (2) as the diameter, and the length of the thinned area (11) is less than or equal to the sum of the length of a semicircular arc with the thickness H1 of the positive electrode sheet (2) as the diameter and twice the second distance H3.

3. The battery cell according to claim 1, characterized in that: The first pole piece (1) is a positive pole piece (2), the second pole piece is a negative pole piece (3), the first pole piece (1) comprises a first current collector and a pole ear (5) extending outward from the first current collector; an insulating region (21) is provided between two adjacent pole ears (5), an insulating layer is provided on both sides of a portion of the first pole piece (1) located in the insulating region (21) in a thickness direction, the thickness of the insulating region (21) is greater than or equal to the thickness of the thinned region (11); along the length direction of the first pole piece (1), the insulating region (21) at least covers a portion of the thinned region (11).

4. The battery cell according to claim 3, characterized in that: The insulating region (21) covers the bending section (13) and a portion of the first stacked section (12) connected to the bending section (13).

5. The battery cell according to claim 3, characterized in that: The thickness of the negative electrode sheet (3) is H4, the maximum distance between the end of the negative electrode sheet (3) and the inner side of the bent section (13) is a third distance H5, the covering distance of the insulating area (21) in the first stacking section (12) is a fourth distance H6, the third distance H5 is greater than or equal to 0 and less than or equal to 1 mm, and the fourth distance H6 is greater than or equal to the sum of the third distance H5 and 0.1 mm and less than or equal to the sum of the third distance H5 and 1 mm; And / or, the length of the insulating area (21) is greater than or equal to the length of a semicircular arc with the thickness H4 of the negative electrode sheet (3) as the diameter, and the length of the thinned area (11) is less than or equal to the sum of the length of a semicircular arc with the thickness H4 of the negative electrode sheet (3) as the diameter and twice the fourth distance H6.

6. The battery cell according to any one of claims 1 to 5, characterized in that: A concave-convex area (6) is provided on one side of the first pole piece (1) in the thickness direction, and the concave-convex area (6) is provided with a plurality of concave portions (61).

7. The battery cell according to claim 6, characterized in that: A first gap T1 is formed between the edge of the concavo-convex region (6) and one end of the first pole piece (1) on which the pole ear (5) is provided, and a second gap T2 is formed between the edge of the concavo-convex region (6) and one end of the second pole piece in the length direction; a spacing between adjacent recesses (61) in the concavo-convex region (6) in the first direction is greater than the second gap T2, and / or a spacing between adjacent recesses (61) in the concavo-convex region (6) in the second direction is greater than the first gap T1.

8. The battery cell according to claim 6, characterized in that: In the second direction, the concave-convex area (6) at least partially covers one end of the first pole piece (1) provided with a pole lug (5); the ceramic area of ​​the pole lug (5) is provided with the concave portion (61), and the depression depth of the concave portion (61) in the pole lug (5) is smaller than the depression depth of the concave portion (61) in the first pole piece (1).

9. The battery cell according to claim 6, characterized in that: The depth of the recess (61) is less than the thickness of the first pole piece (1), and a side of the first pole piece (1) facing away from the recess (61) is a plane.

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