Tab protective tape structure, battery cell, lithium-ion battery and electronic equipment

Abstract

The present invention discloses a tab protection tape structure, a battery cell, a lithium-ion battery, and an electronic device, and belongs to the technical field of lithium-ion batteries. The main technical solution of the tab protection tape structure is: a pole piece; a tab, wherein the tab is connected to the pole piece; and adhesive tape, wherein the adhesive tape includes a cutting straight edge, a cutting angle, and a cutting portion, wherein the adhesive tape completely covers the portion where the tab and the pole piece overlap, and both cutting portions are completely attached to the active coating of the pole piece, and the cutting angle is located outside the edge of the pole piece. The tab protection tape structure of the present invention has a smaller area of ​​the pole piece active coating covered by it, which ensures the effectiveness of the active coating, thereby effectively improving the energy density of the battery cell, effectively reducing the phenomenon of lithium plating at the tab position, and further reducing the phenomenon of lithium plating at the tab position due to the tip effect of the adhesive tape during the cycle of the battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a tab protection tape structure, a battery cell, a lithium-ion battery and an electronic device. Background Art

[0002] With the rapid development of mobile and portable electronic devices, demands for faster charging speeds in soft-pack lithium-ion batteries are increasing. Generally, methods for accelerating charging speeds in soft-pack lithium-ion batteries include using high-rate negative electrode materials and optimizing cell structure. The currently mainstream cell design—the central tab placement—effectively accelerates battery charging speeds.

[0003] The center-tab structure welds the cathode and anode tabs near the center of the electrode sheets. The positive and negative electrode sheets and separator are then wound together to form a bare cell. In this center-tab structure, a layer of tab protective adhesive is applied to the tab welding locations to prevent ultrasonic welding of the tabs from puncturing the separator and causing a short circuit.

[0004] Reference Figure 1 The current method used in the industry is to use a cutter to cut the tape into squares of appropriate size and affix them to the welding position of the tab when winding the tab protective tape. To ensure that the tab welding position is completely covered, the tape also needs to cover part of the graphite on the electrode. Taking the anode of the battery cell as an example, during the later cycle of the battery cell, this part of the covered graphite cannot effectively accommodate the lithium ions released from the cathode, which will cause lithium ions to precipitate at the edge of the tape, resulting in lithium deposition at the tab. At the same time, because the tab protective tape is rectangular, the tip effect is more likely to occur at the sharp corners of the tape, resulting in more serious lithium deposition at the sharp corners of the tape.

[0005] In view of this, it is necessary to improve the structure of the existing tab protection tape. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a tab protective tape structure, a battery cell, a lithium-ion battery and an electronic device, which can effectively reduce the phenomenon of lithium plating at the tab.

[0007] The present invention discloses a tab protection tape structure, comprising: a pole piece; a tab, wherein the tab is connected to the pole piece; and tape, wherein the tape comprises a cutting straight edge, a cutting sharp corner, and a cutting portion, wherein the tape completely covers the overlapping portion between the tab and the pole piece, wherein both cutting portions are completely adhered to the active coating of the pole piece, and the cutting sharp corner is located outside the edge of the pole piece.

[0008] Preferably, the cutting portion is a cutting fillet.

[0009] Preferably, the cutting portion is a cutting chamfer.

[0010] Preferably, the pole piece includes a current collector and an active coating, and the active coating is coated on the current collector.

[0011] Preferably, the current collector is a long strip of metal sheet, a hollow area is provided on the current collector, and the active coating is coated on all surfaces of the current collector outside the hollow area.

[0012] Preferably, the tab is welded to the area of ​​the pole piece where the active coating is provided, the position where the tab is welded to the pole piece forms a welding area, and the adhesive tape completely covers the welding area.

[0013] Preferably, the pole tab is welded at a middle position in the length direction of the pole piece.

[0014] The present invention also discloses a battery cell comprising any one of the above-mentioned tab protection tape structures.

[0015] The present invention also discloses a lithium ion battery comprising the above-mentioned battery cell.

[0016] The present invention also discloses an electronic device comprising the lithium ion battery.

[0017] The beneficial effects of this application are:

[0018] The area of ​​the tape with a cutting part can be made smaller. Therefore, after the tape is affixed to the tab, the area of ​​the active coating covered is smaller, ensuring the effectiveness of the active coating, thereby effectively improving the energy density of the battery cell and effectively reducing the phenomenon of lithium deposition at the tab. At the same time, after the tape is provided with a cutting part, it can also reduce the lithium deposition phenomenon at the tab due to the tip effect of the tape during the cycle of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0020] Figure 1 This is a schematic diagram of the structure of the tab protection tape in the prior art;

[0021] Figure 2 This is a schematic structural diagram of Example 1 of the present invention;

[0022] Figure 3 This is a schematic structural diagram of Example 2 of the present invention;

[0023] Figure 4 This is a comparison chart of the cyclic expansion rates of the existing protective tape and the tape of the present invention at 25°C;

[0024] Figure 5 This is a comparison chart of the cycle retention rates of the existing protective tape and the tape of the present invention at 25°C;

[0025] Figure 6 This is a comparison chart of the cyclic expansion rates of the existing protective tape and the tape of the present invention at 45°C;

[0026] Figure 7 The figure is a comparison chart of the cycle retention rate of the existing protective tape and the tape of the present invention at 45°C.

[0027] Explanation of the reference numerals: 1. Pole piece; 11. Current collector; 111. Empty surface area; 12. Active coating; 2. Pole ear; 21. Welding area; 3. Adhesive tape; 31. Cutting straight edge; 32. Cutting sharp corner; 33. Cutting portion; 331. Cutting rounded corner; 332. Cutting chamfer. DETAILED DESCRIPTION

[0028] The following diagrams illustrate various embodiments of the present invention. For clarity, many practical details are included in the following description. However, it should be understood that these practical details are not intended to limit the present invention. In other words, in some embodiments of the present invention, these practical details are not essential. Furthermore, to simplify the drawings, some commonly used structures and components are depicted in a simplified schematic manner.

[0029] It should be noted that all directional indications such as up, down, left, right, front, back, etc. in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0030] In addition, in the present invention, descriptions such as "first" and "second" are only used for descriptive purposes and do not specifically refer to the order or sequence, nor are they used to limit the present invention. They are only used to distinguish between parts or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings:

[0032] Reference Figure 2 and Figure 3 , is a tab protection tape structure disclosed in the present invention, comprising a pole piece 1, a tab 2 and a tape 3, wherein the pole piece 1 comprises a current collector 11 and an active coating 12 coated on the current collector 11. In this embodiment, the current collector 11 is made of copper foil, and the material of the active coating 12 is graphite. The current collector 11 is a long strip structure, and an empty surface area 111 is provided at one end of the current collector 11. The active coating 12 is coated on all surfaces of the current collector 11 outside the empty surface area 111.

[0033] Reference Figure 2 and Figure 3 The pole tab 2 is a long metal sheet, one end of which is welded to the portion of the current collector 11 covered with the active coating 12. In this embodiment, the end of the pole tab 2 is welded to the middle position in the length direction of the pole piece 1, and the portion where the pole tab 2 is welded to the pole piece 1 forms a welding area 21; the adhesive tape 3 is a sheet-like structure, and the adhesive tape 3 has four opposite cutting straight edges 31, wherein two opposite cutting straight edges 31 form a cutting corner 32 with one cutting straight edge 31 between them, and a cutting portion 33 is formed with the other cutting straight edge 31 between them, and the cutting portion 33 is a transition structure connected between the two cutting straight edges 31.

[0034] Reference Figure 2 and Figure 3 The adhesive tape 3 is affixed to the position where the tab 2 and the pole piece 1 are welded, and the adhesive tape 3 covers the entire welding area 21. The straight cutting edge 31 of the adhesive tape 3, which is adjacent to the two cutting corners 32, is located outside the edge of the pole piece 1 and is parallel to the edge of the pole piece 1, so that the two cutting corners 32 are both located outside the pole piece 1, and the two cutting portions 33 of the adhesive tape 3 are completely affixed to the active coating 12 of the pole piece 1. Due to the provision of the cutting portion 33, the area of ​​the adhesive tape 3 can be made smaller, so the area of ​​the active coating 12 covered by the adhesive tape 3 is smaller, which can effectively improve the energy density of the battery cell. At the same time, after the adhesive tape 3 is provided with the cutting portion 33, the lithium plating phenomenon caused by the tip effect of the adhesive tape 3 at the tab 2 during the cycle of the battery cell can be reduced.

[0035] Example 1

[0036] In this embodiment, the cutting portion 33 is a cutting fillet 331 , and the cutting fillet 331 is an arc-shaped transition structure connecting two adjacent cutting straight edges 31 .

[0037] Example 2

[0038] In this embodiment, the cutting portion 33 is a cutting chamfer 332 , and the cutting chamfer 332 is a straight edge transition structure connecting two adjacent cutting straight edges 31 .

[0039] Two types of battery cells were made using the square adhesive tape 3 in the prior art and the adhesive tape 3 with rounded corners 331. The two types of battery cells were cycle tested at 25°C and 45°C, respectively, using the same charge and discharge rates (0.5C CC+CV to 4.45V, 0.2C DC to 3.0V).

[0040] Reference Figure 4 and Figure 6 In terms of cyclic expansion, at 25°C, neither type of tape 3 showed any expansion failure. However, the expansion rate of the rectangular conventional tape 3 was consistently greater than that of the tape 3 with rounded corners 331, by approximately 0.5%. At 45°C, the rectangular conventional tape 3 showed a thickness change rate of ≥10% after 400 cycles, indicating failure, while the tape 3 with rounded corners 331 did not fail. (Judgment criteria: 1. At 25°C, the thickness expansion rate of the full charge to the initial half-charge state after 800 cycles is ≤10%. 2. At 45°C, the thickness expansion rate of the full charge to the initial half-charge state is ≤10% for 400 cycles and ≤12% for 500 cycles.)

[0041] Reference Figure 5 and Figure 7 In terms of cycle retention, at 25°C, both types of adhesive tape 3 met the test requirements, but the adhesive tape 3 with rounded corners 331 performed better than the square adhesive tape 3. (Judgment criteria: 1. At 25°C, the cycle retention rate of the initial half-charge state after 800 cycles of full charge is ≥ 80%. 2. At 45°C, the cycle retention rate of the initial half-charge state after 500 cycles of full charge is ≥ 80%).

[0042] Disassembly of the interfaces of the two battery cells revealed that the rectangular conventional tape 3-cell had severe lithium deposition at two anode tabs, which was the main cause of thickness expansion failure. The tape 3-cell with rounded corners 331 had slight lithium deposition at two anode tabs.

[0043] A comparative test was conducted using the square adhesive tape 3 in the prior art and the adhesive tape 3 with the cut chamfer 332 . The test results were similar to those in the above case.

[0044] The present invention further discloses a battery cell comprising any one of the above-mentioned lithium-ion battery protective adhesive tape 3 structures; a lithium-ion battery comprising the above-mentioned battery cell; and an electronic device comprising the above-mentioned lithium-ion battery.

[0045] To sum up, the area of ​​the adhesive tape 3 with the cutting portion 33 can be made smaller. Therefore, after the adhesive tape 3 is affixed to the pole tab 2, the area of ​​the active coating 12 covered by it is smaller, ensuring the effectiveness of the active coating 12, thereby effectively improving the energy density of the battery cell and effectively reducing the phenomenon of lithium deposition at the pole tab 2. At the same time, after the adhesive tape 3 is provided with the cutting portion 33, the lithium deposition phenomenon at the pole tab 2 due to the tip effect of the adhesive tape 3 during the cycle of the battery cell can be reduced.

[0046] The above is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. A tab protection tape structure, characterized in that: include: Pole piece (1); A pole lug (2), the pole lug (2) being connected to the pole piece (1); Adhesive tape (3), the adhesive tape (3) comprising a cutting straight edge (31), a cutting sharp corner (32) and a cutting portion (33), the adhesive tape (3) completely covering the portion where the pole lug (2) and the pole piece (1) overlap, the two cutting portions (33) completely affixed to the active coating (12) of the pole piece (1), and the cutting sharp corner (32) being located outside the edge of the pole piece (1); The cutting portion (33) is a cutting fillet (331) or a cutting chamfer (332), wherein the cutting fillet (331) is an arc-shaped transition structure connected between two adjacent cutting straight edges (31), and the cutting chamfer (332) is a straight edge transition structure connected between two adjacent cutting straight edges (31).

2. The tab protection tape structure according to claim 1, characterized in that: The pole piece (1) comprises a current collector (11) and an active coating (12), wherein the active coating (12) is coated on the current collector (11).

3. The tab protection tape structure according to claim 2, characterized in that: The current collector (11) is a long strip of metal sheet. A hollow area (111) is provided on the current collector (11). The active coating (12) is coated on all surfaces of the current collector (11) outside the hollow area (111).

4. The tab protection tape structure according to claim 3, characterized in that: The pole tab (2) is welded to the area of ​​the pole piece (1) where the active coating (12) is provided, and the position where the pole tab (2) and the pole piece (1) are welded forms a welding area (21), and the adhesive tape (3) completely covers the welding area (21).

5. The tab protection tape structure according to claim 4, characterized in that: The pole tab (2) is welded at a middle position in the length direction of the pole piece (1).

6. A battery cell, characterized in that: The invention comprises the tab protection tape structure as described in any one of claims 1 to 5.

7. A lithium-ion battery, characterized in that: Including the battery cell according to claim 6.

8. An electronic device, characterized in that: Including the lithium ion battery according to claim 7.

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