Method for improving pole piece cracks caused by positive pole lug marks

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a method for improving pole piece cracks caused by positive pole lug marks, which comprises the following steps: 1) obtaining a pole piece with a coating area and an empty foil area which are mutually spaced; 2) performing chamfering treatment on four right angles at the bottom of the rectangular tab to obtain a tab with a fillet at the bottom; (3) welding the bottom, with the fillet, of the tab in the empty foil area of the pole piece through welding equipment; (4) rolling the pole piece welded with the pole lug; (5) the cylindrical roll core is arranged in the steel shell; the right angle of the positive pole lug is designed into the round corner, so that indentations left on the pole piece by the pole lug can be reduced; the round corner design can reduce stress concentration, so that the pressure is dispersed more uniformly, and cracks of the pole piece are reduced; the edge of the tab is sharpened, that is, the thickness of the edge is reduced, so that the pressure dispersion effect can be further enhanced; the sharpened edge can better bear the pressure on the pole piece, and cracks of the pole piece are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of lithium-ion batteries, and in particular to a method for improving cracks in a pole piece caused by a positive pole ear mark. Background Art

[0002] In the manufacturing process of cylindrical lithium-ion batteries, as the energy density of the battery becomes higher and higher, the use of silicon-based negative electrode materials is becoming more and more common; at the same time, in order to take into account high-rate application scenarios such as power tools, the structure of the winding core adopts a centrally placed positive electrode tab and a negative electrode bipolar tab structure, thereby reducing the internal resistance of the battery cell and improving the battery rate performance.

[0003] However, since the silicon negative electrode expands and contracts during the charging and discharging process, this will cause stress to the internal structure of the battery, causing the positive electrode tab to leave indentations on the electrode. In severe cases, these indentations may cause the electrode to break, thereby affecting the performance and life of the battery. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the cracks in the pole piece caused by the positive pole ear mark, aiming to solve the problem in the prior art that the positive pole ear leaves an indentation on the pole piece and the pole piece breaks due to the indentation.

[0005] The present invention is implemented in this way. The method for improving the cracks of the positive electrode tab caused by the positive electrode tab includes the following steps:

[0006] 1) Applying the active slurry on the current collector and drying it to obtain a pole piece with a coating area and an empty foil area spaced apart from each other;

[0007] 2) Chamfering the four right angles at the bottom of the rectangular pole ear to obtain a pole ear with two rounded corners at the bottom; the length of the pole ear is 50-60 mm, the width is 3-6 mm, the rounded corners are in the width direction of the rectangular pole ear, and the angles of the two rounded corners are both 10° to 35°;

[0008] 3) Welding the bottom of the pole ear with rounded corners in the empty foil area of ​​the pole piece by welding equipment;

[0009] 4) rolling up the pole piece welded with the pole lug to form a cylindrical winding core;

[0010] 5) Place the cylindrical winding core into the steel shell.

[0011] Furthermore, in the step 1), the empty foil area is arranged between two adjacent coating areas.

[0012] Furthermore, in the step 1), the length of the empty foil area is smaller than the length of the coating area, and the thickness of the coating area is greater than the thickness of the empty foil area.

[0013] Furthermore, in the step 3), the bottom of the tab with rounded corners is welded to the empty foil area by ultrasonic welding.

[0014] Furthermore, in the step 2), the thickness of the four right-angled edges of the outer periphery of the pole ear is thinned by the chamfering treatment to form the two rounded corners, and the thickness of the outer periphery of the pole ear is thinned by the chamfering treatment to form a pole ear with a stepped structure with a slope, and the angle between the plane where the slope is located and the plane where the step is located is 2° to 5°; the step has two steps; the edge of the pole ear after thinning has a curvature, which can reduce the sharpness of its edge.

[0015] Furthermore, in the step 3), the tab is welded on the empty foil area to form a welding surface, the area of ​​the welding surface is smaller than the area of ​​the empty foil area, and there is a gap between the welding surface and the edge of the empty foil area.

[0016] Furthermore, in the step 4), the bottom of the tab and the bottom of the winding core are spaced apart from each other.

[0017] Furthermore, in the step 4), the top of the tab is exposed outside the winding core.

[0018] Furthermore, an annular ring is protruding outward on the outer periphery of the pole lug, and the annular ring is arranged circumferentially along the outer periphery of the pole lug, the annular ring is located above the bottom of the pole lug, the annular ring is exposed outside the winding core, and the bottom of the annular ring abuts against the top of the winding core;

[0019] The bottom of the annular ring has an inwardly recessed upper groove, which is arranged circumferentially along the bottom of the annular ring. The top edge of the empty foil area is inserted in the upper groove, and the inner side wall of the upper groove abuts against the top edge of the empty foil area.

[0020] Furthermore, a plurality of flanges are provided on the outer circumference of the pole lug, and the plurality of flanges are stacked in sequence along the circumferential and axial directions of the outer circumference of the pole lug, and the plurality of flanges are stacked in sequence from the top of the annular ring to the top of the pole lug, and are gradually reduced from bottom to top to form a step ring.

[0021] Compared with the prior art, the method for improving the cracks in the pole piece caused by the positive electrode ear mark provided by the present invention can reduce the indentation left by the ear on the pole piece by designing the right angle of the positive electrode ear as a rounded corner; the rounded corner design can reduce stress concentration, so that the pressure is more evenly dispersed, and the occurrence of pole piece cracks is reduced; by sharpening the edge of the ear, that is, thinning the edge thickness, the pressure dispersion effect can be further enhanced; the sharpened edge can better withstand the pressure on the pole piece and avoid the occurrence of cracks in the pole piece; the use of positive electrode ears with rounded corners and sharpened edges can effectively avoid the problem of pole piece cracks caused by the positive electrode ear mark, thereby improving the performance and life of cylindrical lithium-ion batteries; and solves the problem that the positive electrode ear leaves an indentation on the pole piece and the pole piece breaks due to the indentation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the working process of the method for improving the cracks of the electrode piece caused by the positive electrode ear print provided by the present invention;

[0023] Figure 2 It is a schematic diagram of the structural arrangement of the pole piece and the pole ear provided by the present invention;

[0024] Figure 3 is a schematic diagram of the side view structure of the pole ear provided by the present invention;

[0025] Figure 4 It is a schematic diagram of the structural arrangement of the pole piece and the welding surface provided by the present invention;

[0026] Figure 5 It is a schematic diagram of the front view structure of the pole ear and the winding core provided by the present invention.

[0027] In the figure: pole piece 10, pole ear 20, winding core 30, coating area 11, empty foil area 12, welding surface 13, fillet 21, annular ring 22, upper groove 23, flange 24. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] The implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0030] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0031] Reference Figure 1-5 The figure shows a preferred embodiment of the present invention.

[0032] The method for improving the cracks of the positive electrode caused by the ear print of the positive electrode comprises the following steps:

[0033] 1) Applying the active slurry on the current collector and drying it to obtain a pole piece 10 having a coating area 11 and a hollow foil area 12 spaced apart from each other;

[0034] 2) The four right angles at the bottom of the rectangular pole ear 20 are chamfered to obtain a pole ear 20 with two rounded corners 21 at the bottom; the pole ear 20 has a length of 50 to 60 mm and a width of 3 to 6 mm. The rounded corners 21 are in the width direction of the rectangular pole ear 20, and the angles of the two rounded corners 21 are both 10° to 35°;

[0035] 3) Welding the bottom of the pole ear 20 with the fillet 21 to the empty foil area 12 of the pole piece 10 by welding equipment;

[0036] 4) Rolling up the pole piece 10 welded with the pole lug 20 to form a cylindrical winding core 30;

[0037] 5) Place the cylindrical winding core 30 into the steel shell.

[0038] The above-mentioned method for improving the cracks in the pole piece caused by the positive electrode ear mark can reduce the indentation left by the ear 20 on the pole piece 10 by designing the right angle of the positive electrode ear 20 as a rounded corner 21; the rounded corner 21 design can reduce stress concentration, so that the pressure is more evenly dispersed, and the occurrence of cracks in the pole piece 10 is reduced; the pressure dispersion effect can be further enhanced by sharpening the edge of the ear 20, that is, thinning the edge thickness; the sharpened edge can better withstand the pressure on the pole piece 10, avoiding the occurrence of cracks in the pole piece 10; the positive electrode ear 20 with a rounded corner 21 design and a sharpened edge can effectively avoid the problem of cracks in the pole piece 10 caused by the ear 20 mark on the positive electrode 10, thereby improving the performance and life of the cylindrical lithium-ion battery; and solves the problem that the positive electrode ear 20 leaves an indentation on the pole piece 10, and the pole piece 10 breaks due to the indentation.

[0039] In this embodiment, in step 1), the empty foil area 12 is disposed between two adjacent coating areas 11. In this way, the pole tab 20 can be welded to the pole piece 10 through the empty foil area 12, and the pole piece 10 can wrap and roll the pole tab 20 through the two adjacent coating areas 11.

[0040] In this embodiment, in step 1), the length of the empty foil area 12 is smaller than the length of the coating area 11, and the empty foil area 12 is used as a blank for welding the pole ear 20 on the pole piece 10; the thickness of the coating area 11 is greater than the thickness of the empty foil area 12, because the coating area 11 is filled with powder, so the coating area 11 is thicker than the empty foil area 12.

[0041] In this embodiment, in step 3), the bottom of the tab 20 with the fillet 21 is welded to the empty foil area 12 by ultrasonic welding. This facilitates increasing the stability of the welding process.

[0042] In this embodiment, in step 2), the thickness of the four right-angled edges of the outer periphery of the pole ear 20 is thinned by chamfering to form two rounded corners 21, and the thickness of the outer periphery of the pole ear 20 is thinned by chamfering to form a pole ear 20 with a stepped structure with a slope, and the angle between the plane where the slope is located and the plane where the step is located is 2° to 5°; the step has two steps; the edge of the thinned pole ear 20 has a curvature, which can reduce the sharpness of its edge.

[0043] That is, the edge is designed as a stepped structure with a slope, so that the shear force generated after extrusion is further dispersed and transferred, thereby avoiding cracks in the pole piece 10 caused by extrusion;

[0044] The edge thickness of the pole ear 20 is thinned to increase the contact area between the pole ear 20 and the pole piece 10 , so that the pressure can be better dispersed on the pole piece 10 , the pressure concentration on the pole piece 10 is reduced, and the occurrence of cracks in the pole piece 10 is further avoided.

[0045] In step 3), the tab 20 is welded on the empty foil area 12 to form a welding surface 13, the area of ​​the welding surface 13 is smaller than the area of ​​the empty foil area 12, and there is a gap between the welding surface 13 and the edge of the empty foil area 12. In this way, the tab 20 can be prevented from being unstable due to insufficient welding surface 13.

[0046] In step 4), a gap is arranged between the bottom of the pole tab 20 and the bottom of the winding core 30 to facilitate subsequent processing.

[0047] In this embodiment, in step 4), the top of the pole tab 20 is exposed outside the winding core 30. In this way, it is convenient for the subsequent winding core 30 to be welded to the top cover through the pole tab 20.

[0048] In this embodiment, an annular ring 22 is protruded outward on the outer periphery of the pole ear 20, and the annular ring 22 is arranged circumferentially along the outer periphery of the pole ear 20. The annular ring 22 is located above the bottom of the pole ear 20, and the annular ring 22 is exposed outside the winding core 30, and the bottom of the annular ring 22 abuts against the top of the winding core 30.

[0049] The bottom of the annular ring 22 has an inwardly recessed upper groove 23 , which is arranged circumferentially along the bottom of the annular ring 22 , the top edge of the empty foil area 12 is inserted into the upper groove 23 , and the inner side wall of the upper groove 23 abuts against the top edge of the empty foil area 12 .

[0050] The pole ear 20 can be clamped on the outer side of the pole piece 10 through the annular ring 22, which is used to limit the position of the pole ear 20 on the pole piece 10, increase the stability of the pole ear 20 welded on the pole piece 10, and also limit the retention of the top of the pole ear 20 exposed during the winding process of the pole piece 10;

[0051] The annular ring 22 is clamped on the top edge of the empty foil area 12 by the upper groove 23 , so that the tab 20 can be positioned on the empty foil area 12 through the upper groove 23 , which is convenient for subsequent welding positioning work.

[0052] In this embodiment, a plurality of flanges 24 are provided on the outer periphery of the pole lug 20, and the plurality of flanges 24 are stacked sequentially along the circumferential and axial directions of the outer periphery of the pole lug 20, and the plurality of flanges 24 are stacked sequentially along the direction from the top of the annular ring 22 to the top of the pole lug 20, and are gradually reduced from bottom to top to form a step ring.

[0053] The step ring formed by the multiple flanges 24 of the pole ear 20 can increase the welding surface 13, and the welding points are evenly distributed, which can improve the current flow capacity and ensure the uniformity of the flow conduction, providing conditions for achieving fast charging.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the cracks in the positive electrode tabs that result in the cracks in the electrode, characterized in that: The following steps are involved: 1) Applying the active slurry on the current collector and drying it to obtain a pole piece with a coating area and an empty foil area spaced apart from each other; 2) Chamfering the four right angles at the bottom of the rectangular pole ear to obtain a pole ear with two rounded corners at the bottom; the length of the pole ear is 50-60 mm, the width is 3-6 mm, the rounded corners are in the width direction of the rectangular pole ear, and the angles of the two rounded corners are both 10° to 35°; 3) Welding the bottom of the pole ear with rounded corners in the empty foil area of ​​the pole piece by welding equipment; 4) rolling up the pole piece welded with the pole lug to form a cylindrical winding core; 5) Place the cylindrical winding core into the steel shell.

2. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to claim 1, characterized in that: In the step 1), the empty foil area is arranged between two adjacent coating areas.

3. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to claim 2, characterized in that: In the step 1), the length of the empty foil area is shorter than the length of the coating area, and the thickness of the coating area is greater than the thickness of the empty foil area.

4. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to claim 3, characterized in that: In the step 3), the bottom of the tab with rounded corners is welded to the empty foil area by ultrasonic welding.

5. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to claim 4, characterized in that: In the step 2), the thickness of the four right-angled edges of the outer periphery of the pole lug is thinned by the chamfering treatment to form the two rounded corners, and the thickness of the outer periphery of the pole lug is thinned by the chamfering treatment to form a pole lug with a stepped structure with a slope, and the angle between the plane where the slope is located and the plane where the step is located is 2° to 5°; the step has two steps; the edge of the pole lug after thinning has a curvature, which can reduce the sharpness of its edge.

6. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to claim 5, characterized in that: In the step 3), the tab is welded on the empty foil area to form a welding surface, the area of ​​the welding surface is smaller than the area of ​​the empty foil area, and there is a gap between the welding surface and the edge of the empty foil area.

7. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to any one of claims 1 to 6, characterized in that: In the step 4), the bottom of the tab is spaced apart from the bottom of the winding core.

8. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to claim 7, characterized in that: In the step 4), the top of the tab is exposed outside the winding core.

9. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark as claimed in claim 8, characterized in that: An annular ring is protruding outward on the outer periphery of the pole ear, and the annular ring is arranged circumferentially along the outer periphery of the pole ear. The annular ring is located above the bottom of the pole ear, and the annular ring is exposed outside the winding core, and the bottom of the annular ring abuts against the top of the winding core; The bottom of the annular ring has an inwardly recessed upper groove, which is arranged circumferentially along the bottom of the annular ring. The top edge of the empty foil area is inserted in the upper groove, and the inner side wall of the upper groove abuts against the top edge of the empty foil area.

10. The method for improving the cracks in the electrode piece caused by the positive electrode ear mark according to claim 9, characterized in that: A plurality of flanges are arranged on the outer circumference of the pole lug, and the plurality of flanges are stacked in sequence along the circumferential and axial directions of the outer circumference of the pole lug, and the plurality of flanges are stacked in sequence along the direction from the top of the annular ring to the top of the pole lug, and are gradually reduced from bottom to top to form a step ring.

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