Multilayer current collector tab structure

Abstract

The invention discloses a multi-layer current collector tab structure, and relates to the technical field of multi-layer current collectors. The multi-layer current collector tab structure comprises a multi-layer current collector and a tab, wherein the multi-layer current collector comprises a macromolecular base film layer and a metal layer; the metal layers are arranged on the upper surface and the lower surface of the macromolecular base film layer; a penetrating slit is formed in the multi-layer current collector in the thickness direction, and one side of the tab penetrates through the slit and is electrically connected with the metal layer. According to the multi-layer current collector tab structure described by the invention, one tab is adopted, is electrically connected with the metal layers of the multi-layer current collector at the same time, and is annularly sleeved on the multi-layer current collector, so that on one hand, the use amount of tab materials is reduced, and the welding strength and mechanical strength between the multi-layer current collector and the tab are improved; and the risk that the polymer base film and the metal layer are stripped after being used for a long time is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-layer current collector tabs, and in particular to a multi-layer current collector tab structure. Background Art

[0002] The multilayer current collector has a "sandwich" structure, with the inner layer being a polymer layer (such as PET, PP or PI) and the two sides being metal conductive layers (such as Al or Cu). Since the multilayer current collector is not conductive in the thickness direction, it is impossible to directly form a tab. The current tab welding of the multilayer current collector is to weld two pieces of pure metal foil to the metal layers on both sides of the multilayer current collector by ultrasonic roll welding.

[0003] The existing tab structure has the following disadvantages: 1. Each layer of current collector is matched with at least two metal foils, and the tab is heavy, which is not conducive to improving the battery energy density and increases material costs; 2. Because the metal layer on the current collector is very thin, the welding reliability between the metal foil and the metal layer is poor.

[0004] Therefore, we propose a multi-layer current collector tab structure. Summary of the Invention

[0005] The object of the present invention is to provide a multi-layer current collector tab structure to solve the problems raised in the prior art.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a multi-layer current collector tab structure, comprising a multi-layer current collector and a tab, wherein the multi-layer current collector comprises a polymer base film layer and a metal layer; the metal layer is arranged on the upper surface and the lower surface of the polymer base film layer.

[0007] Furthermore, the multi-layer current collector is provided with a through slit in the thickness direction, and one side of the tab is electrically connected to the metal layer through the slit.

[0008] Furthermore, the tab is U-shaped; one side of the tab passes through the slit and protrudes from the slit as a short side, and the side of the tab away from the slit is a long side;

[0009] The length of the long side is greater than the short side.

[0010] Furthermore, the end of the short side, the long side and the metal layer are overlapped and ultrasonically welded to form a weld mark in area A.

[0011] Furthermore, the portion of the short side that does not overlap with the metal layer is welded to the long side, so that the tab is looped in a "9" shape on the slit of the multi-layer current collector.

[0012] Furthermore, an active material layer is provided on the side of the metal layer away from the polymer base film layer.

[0013] Furthermore, the tab is offset toward the active material layer, and the bottom of the U-shaped region of the tab overlaps with the metal layer in the direction in which the slit extends away from the tab. Ultrasonic welding is performed on the overlapping portion to form a weld mark in zone B.

[0014] Furthermore, during ultrasonic welding, solder is added.

[0015] Furthermore, the solder is one or more of tin-based solder, tin-bismuth alloy solder, tin-zinc alloy solder and tin-indium alloy solder.

[0016] Furthermore, the material of the polymer base film layer is one of PET (polyethylene terephthalate), PI (polyimide), PP (polypropylene) and PE (polyethylene).

[0017] Furthermore, the coverage of the active material layer does not exceed the extending direction of the slit close to the tab.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. A multi-layer current collector tab structure described in the present application uses a tab that is electrically connected to the metal layer of the multi-layer current collector at the same time and is looped over the multi-layer current collector. On the one hand, this reduces the amount of tab material used and improves the welding strength and mechanical strength between the multi-layer current collector and the tab, making it less likely to fall off during battery use. On the other hand, traditional multi-layer current collectors immersed in the electrolyte for too long will cause the polymer base film and the metal layer to peel off. In the tab structure of this scheme, the long side and the short side of the tab are welded to each other at the edge of the multi-layer current collector, and this weld mark and the weld mark between the tab and the metal layer of the multi-layer current collector are connected, which is equivalent to forming a lock edge structure at the edge of the multi-layer current collector, reducing the risk of peeling between the polymer base film and the metal layer after long-term use.

[0020] 2. The multi-layer current collector tab structure described in this application has a low-melting-point solder added during welding, which has good current-carrying capacity when the battery is in normal use. However, when the ambient temperature is too high or the current increases abnormally, the local temperature is too high, and these solders will melt and drive the multi-layer current collector locked in the tab to melt, cutting off the current from the tab connection and reducing the risk of further thermal runaway.

[0021] 3. A multi-layer current collector tab structure described in the present application, the B zone weld mark in the above technical solution welds the U-shaped area of the tab together, and welds it to the metal layer of the multi-layer current collector at the same time, on the one hand, improves the welding strength between the tab and the multi-layer current collector, and at the same time expands the welding area to improve the flow capacity; on the other hand, the multi-layer current collectors on both sides of the slit are welded to the tab, reducing the fatigue of the slit during long-term use and causing the multi-layer current collector to tear, thereby improving the structural reliability.

[0022] 4. In the multi-layer current collector tab structure described in this application, the weld marks in area A and the weld marks in area B can be welded at one time, thereby improving welding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the planar structure of the multi-layer current collector tab obtained in Example 1 of the present invention;

[0024] Figure 2 2 is a cross-sectional view of the multi-layer current collector tab structure obtained in Example 1 of the present invention;

[0025] Figure 3 2 is a cross-sectional view of the multi-layer current collector tab structure obtained in Example 2 of the present invention;

[0026] Figure 4 Schematic diagram of the planar structure of the multi-layer current collector tab obtained in Example 2 of the present invention;

[0027] Figure 5 This is a planar schematic diagram of the A-area weld mark and the B-area weld mark of the multi-layer current collector tab structure obtained in Example 3 of the present invention, which are welded together at one time.

[0028] In the figure, 1. Multi-layer current collector, 2. Tab, 3. Polymer base film layer, 4. Metal layer, 5. Active material layer, 6. Short side, 7. Long side, 8. Slit. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] In the following specific embodiments,

[0031] Tin-bismuth alloy solder, 500 mesh;

[0032] The polymer base film layer is a PET base film with a thickness of 6 μm;

[0033] Example 1: A multi-layer current collector tab structure, such as Figure 1 and Figure 2 As shown, it includes a multilayer current collector 1 and a tab 2; the multilayer current collector 1 includes a polymer base film layer 3 and a metal layer 4; the metal layer 4 is provided on the upper surface and the lower surface of the polymer base film layer 3; an active material layer 5 is provided on the side of the metal layer 4 away from the polymer base film layer 3;

[0034] The multilayer current collector 1 is provided with a through slit 8 in the thickness direction. One side of the tab 2 is electrically connected to the metal layer 4 through the slit 8. The coverage of the active material layer 5 does not exceed the direction in which the slit 8 extends close to the tab 2.

[0035] One side of the tab 2 passes through the slit 8 and slightly protrudes from the slit 8 as a short side 6, and the side of the tab 2 away from the slit 8 is a long side 7, forming a "U" shape with one side longer and the other side shorter;

[0036] like Figure 3 and Figure 4 As shown, the end of the short side 6, the long side 7 and the metal layer 4 overlap and are ultrasonically welded to form a weld mark in area A; the portion of the short side 6 that does not overlap with the metal layer 4 is welded to the long side 7, so that the tab 2 is looped in a "9" shape on the slit 8 of the multi-layer current collector 1;

[0037] The tab 2 is offset toward the active material layer 5, and the bottom of the "U"-shaped area of the tab 2 overlaps with the metal layer 4 in the direction in which the slit 8 extends away from the tab 2. Ultrasonic welding is performed on the overlapping portion to form a weld mark in area B. During ultrasonic welding, tin-bismuth alloy solder is added.

[0038] Example 2: A multi-layer current collector tab structure, such as Figure 1 and Figure 2 As shown, it includes a multilayer current collector 1 and a tab 2; the multilayer current collector 1 includes a polymer base film layer 3 and a metal layer 4; the metal layer 4 is provided on the upper surface and the lower surface of the polymer base film layer 3; an active material layer 5 is provided on the side of the metal layer 4 away from the polymer base film layer 3;

[0039] The multilayer current collector 1 is provided with a through slit 8 in the thickness direction. One side of the tab 2 is electrically connected to the metal layer 4 through the slit 8. The coverage of the active material layer 5 does not exceed the direction in which the slit 8 extends close to the tab 2.

[0040] One side of the tab 2 passes through the slit 8 and slightly protrudes from the slit 8 as a short side 6, and the side of the tab 2 away from the slit 8 is a long side 7, forming a "U" shape with one side longer and the other side shorter;

[0041] like Figure 5 As shown, the end of the short side 6, the long side 7 and the metal layer 4 overlap in three layers, and the portion of the short side 6 that does not overlap with the metal layer 4 is welded to the long side 7, so that the tab 2 is looped in a "9" shape on the slit 8 of the multi-layer current collector 1; the tab 2 is offset toward the active material layer 5, and the bottom of the "U"-shaped area of the tab 2 overlaps with the metal layer 4 in the direction in which the slit 8 extends away from the tab 2;

[0042] Ultrasonic welding is simultaneously performed on the end of the short side 6, the overlapping portion of the long side 7 and the metal layer 4, and the overlapping portion of the metal layer 4 in the bottom of the "U"-shaped area of the tab 2 and the slit 8 away from the extension direction of the tab 2 to form a single welding mark; tin-bismuth alloy solder is added during ultrasonic welding.

[0043] Example 3: A multi-layer current collector tab structure, such as Figure 1 and Figure 2 As shown, it includes a multilayer current collector 1 and a tab 2; the multilayer current collector 1 includes a polymer base film layer 3 and a metal layer 4; the metal layer 4 is provided on the upper surface and the lower surface of the polymer base film layer 3; an active material layer 5 is provided on the side of the metal layer 4 away from the polymer base film layer 3;

[0044] The multilayer current collector 1 is provided with a through slit 8 in the thickness direction. One side of the tab 2 is electrically connected to the metal layer 4 through the slit 8. The coverage of the active material layer 5 does not exceed the direction in which the slit 8 extends close to the tab 2.

[0045] One side of the tab 2 passes through the slit 8 and slightly protrudes from the slit 8 as a short side 6, and the side of the tab 2 away from the slit 8 is a long side 7, forming a "U" shape with one side longer and the other side shorter;

[0046] The end of the short side 6, the long side 7 and the metal layer 4 are overlapped and ultrasonically welded to form a weld mark; the part of the short side 6 that does not overlap with the metal layer 4 is welded together with the long side 7, so that the tab 2 presents a "9"-shaped ring on the slit 8 of the multi-layer current collector 1; during ultrasonic welding, tin-bismuth alloy solder is added.

[0047] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A multi-layer current collector tab structure, characterized in that: The multilayer current collector (1) comprises a multilayer current collector (1) and a tab (2); the multilayer current collector (1) comprises a polymer base film layer (3) and a metal layer (4); the metal layer (4) is arranged on the upper surface and the lower surface of the polymer base film layer (3); The multilayer current collector (1) is provided with a through slit (8) in the thickness direction, and one side of the tab (2) is electrically connected to the metal layer (4) through the slit (8).

2. The multi-layer current collector tab structure according to claim 1, characterized in that: The pole lug (2) is U-shaped; one side of the pole lug (2) passes through the slit (8) and protrudes from the slit (8) as a short side (6), and the side of the pole lug (2) away from the slit (8) serves as a long side (7); The length of the long side (7) is greater than the short side (6).

3. The multi-layer current collector tab structure according to claim 2, characterized in that: The end of the short side (6), the long side (7) and the metal layer (4) are overlapped and ultrasonically welded to form a weld mark in area A.

4. The multi-layer current collector tab structure according to claim 2, characterized in that: The portion of the short side (6) that does not overlap with the metal layer (4) is welded to the long side (7), so that the tab (2) is looped in a "9" shape on the slit (8) of the multilayer current collector (1).

5. The multi-layer current collector tab structure according to claim 1, characterized in that: An active material layer (5) is provided on the side of the metal layer (4) facing away from the polymer base film layer (3).

6. The multi-layer current collector tab structure according to claim 5, characterized in that: The pole tab (2) is offset toward the active material layer (5), and the bottom of the "U"-shaped region of the pole tab (2) and the metal layer (4) in the direction in which the slit (8) extends away from the pole tab (2) overlap, and ultrasonic welding is performed on the overlapping portion to form a weld mark in zone B.

7. The multi-layer current collector tab structure according to claim 5, characterized in that: During ultrasonic welding, brazing filler metal is added.

8. The multi-layer current collector tab structure according to claim 7, characterized in that: The solder is one or more of tin-based solder, tin-bismuth alloy solder, tin-zinc alloy solder and tin-indium alloy solder.

9. The multi-layer current collector tab structure according to claim 5, characterized in that: The coverage of the active material layer (5) does not exceed the extending direction of the slit (8) close to the tab (2).

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