A composite current collector tab welding method

Abstract

The present invention discloses a composite current collector pole ear welding structure and a welding method thereof, aiming to solve the problem of inability to conduct electricity due to the inability of the middle pole piece to conduct electricity during the welding of the existing composite current collector. The specific steps of the invention are: S1: connecting mutually displaced pole ears on adjacent pole pieces respectively; S2: installing a plurality of connecting pieces on a connecting body respectively; S3: a gripping device moves the connecting body together with the connecting piece to the top of the pole piece, and the connecting piece is inserted between the adjacent pole piece pole ears respectively, so that the pole piece pole ears and the connecting piece are superimposed on each other; S4: a first welding mechanism is arranged along the superposition direction of the pole piece pole ear and the connecting piece, a filling body is arranged on the connecting piece, and the first welding mechanism preheats and extrude-welds the pole piece pole ear; S5: ultrasonically welding the connecting piece to the pole piece pole ear through a second welding mechanism.

Description

Technical Field

[0001] The invention relates to the technical field of lithium batteries, and more specifically to a composite current collector tab welding method. Background Art

[0002] The composite current collector has better flexibility and mechanical strength, and the pole piece is not easy to break during rolling and use; high ductility, when the lithium-ion battery is subjected to external physical impact, especially when it is impacted by sharp objects or heavy objects, the metal layers on both sides of the composite current collector will break, and the middle polymer layer can wrap the fracture surface of the metal layers on both sides from the fracture with its own ductility, to prevent the fracture surface from piercing the diaphragm and contacting other places to cause short circuit, which solves the problem that lithium-ion batteries are prone to internal short circuits after being subjected to external physical impact, and then cause thermal runaway and other safety issues. Polymer film as a substrate material has a lower mass density, which can reduce the overall mass of the battery and increase the battery energy density. However, because the middle polymer layer is insulating, the middle pole piece cannot be connected and conductive during conventional welding. In this regard, the Chinese invention patent application with publication number CN111435727A discloses a "battery pole piece and battery cell", which is achieved by increasing the length or width of the pole ear during die cutting, and covering the previous pole ear with the next pole ear; the Chinese invention patent application with publication number CN111900413A discloses "a method for welding the pole ear of a composite current collector of a lithium battery". The two metal pole ears clamp the composite current collector pole ear for pre-welding → stack the conventional pole ears → finally weld the multi-layer pole ears to improve the conductive effect. The methods of the above two patents can solve the problem of inability to connect and conduct electricity during the welding process of the composite current collector, but the operation process is relatively complicated, and the equipment and equipment need to be upgraded, and the personnel need professional training. The complexity of the process will also damage the consistency of the battery. Summary of the invention

[0003] The present invention overcomes the drawback of existing composite current collector welding that the composite current collector cannot be connected and conductive due to the inability of the middle pole piece to be connected and conductive, and provides a composite current collector pole ear welding method, which can make the metal layers on both sides of the pole piece connected and conductive, thereby making the composite current collector connected and conductive.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A composite current collector tab welding method, comprising the following specific steps:

[0006] S1: Connect mutually offset pole ears on adjacent pole pieces respectively;

[0007] S2: installing a plurality of connecting sheets on the connecting body to form a connecting member;

[0008] S3: The grasping device moves the connecting piece to the top of the pole piece, and the connecting piece is respectively inserted between the pole ears of the adjacent pole pieces, so that the pole ears and the connecting piece are superimposed on each other;

[0009] S4: a first welding mechanism is arranged along the superposition direction of the pole piece and the pole ear and the connecting piece, a filling body is arranged on the connecting piece, and the first welding mechanism preheats and performs extrusion welding on the pole piece and the pole ear;

[0010] S5: ultrasonically welding the connecting piece to the pole piece and the pole ear through a second welding mechanism.

[0011] Preferably, the connecting member includes a first welding portion, a second welding portion and a third welding portion.

[0012] Preferably, the connecting pieces are staggered along the diagonal direction on the inner wall of the connector, and two adjacent connecting pieces are arranged at an equal distance.

[0013] Preferably, the first welding portion comprises a first soldering groove and a filling body, wherein the first soldering groove is arranged in the wall of the connector, and the filling body is arranged in the first soldering groove, and the filling body is a solder material.

[0014] Preferably, the first soldering groove is composed of a rectangular groove and an extension groove extending from the side wall of the rectangular groove. A full filling body is provided in the rectangular groove, and a part of the filling body is provided in the extension groove, so that a part of the gap is left on the side of the extension groove away from the rectangular groove, and the depth of the rectangular groove is greater than the depth of the extension groove. When the filling body is heated and liquefied, through the extrusion of the first welding mechanism, part of the filling body flows into the reserved gap and contacts the upper and lower walls of the composite current collector pole piece and the pole ear, so as to realize the soldering connection of the contact surface, thereby improving the welding strength; the reserved gap can prevent the filling body from being filled too much, so that it flows out under the extrusion, thereby increasing the welding thickness.

[0015] Preferably, the second welding portion comprises a second soldering groove and a filling body. The second soldering groove is arranged in an "L"-shaped structure and is arranged in a wall body at the connection between the connecting piece and the connecting body.

[0016] Preferably, the third welding portion is arranged at the junction of the connecting piece and the pole ear of the composite current collector to be welded, and ultrasonic welding is performed by the second welding mechanism.

[0017] Preferably, the first welding mechanism includes a preheating device and an extrusion mechanism. The preheating device first makes the composite current collector pole piece ear and the connecting piece together with the connecting body fit and overlap to form a superimposed structure. The superimposed structure is provided with two trapezoidal surfaces with a trapezoidal structure. The preheating device is then used to preheat the superimposed structure so that the filling body is heated and liquefied. The superimposed structure is then extruded along the superimposed direction by the extrusion mechanism so that the filling body in the first soldering groove and the second soldering groove is fully in contact with the contact surface of the composite current collector pole piece ear, thereby realizing multi-point welding of the contact surface.

[0018] Preferably, the extrusion mechanism includes brackets arranged on both sides of the superimposed structure, slide grooves are arranged in the wall bodies of the two brackets on opposite sides, a pressure plate mechanism is arranged in the slide groove, and a piston cylinder for driving the pressure plate mechanism, the pressure plate mechanism includes a plurality of extrusion plates, the length of the extrusion plates is adapted to the trapezoidal surface of the superimposed structure, the length of the extrusion plates on the positive trapezoidal surface of the superimposed structure is shortened layer by layer, and the length of the extrusion plates on the reverse trapezoidal surface (back facing) of the superimposed structure is increased layer by layer, a connecting structure is provided between two adjacent extrusion plates, the connecting structure includes a connecting rod sleeve, a connecting rod slidably arranged in the connecting rod sleeve, a telescopic spring is connected between the connecting rod sleeve and the end face of the connecting rod, the connecting rod sleeve is fixedly connected to a relatively shorter extrusion plate, the connecting rod is fixedly connected to a relatively upper extrusion plate, both ends of the extrusion plate are respectively slidably arranged in the slide grooves on both sides, and limit blocks are installed at the ends of the slide grooves, and the limit blocks are used to prevent the end extrusion plates from sliding out. When the extrusion mechanism is started, the piston cylinder drives the piston rod to drive the upper and lower extrusion plates to slowly move toward the middle side. At this time, the upper and lower extrusion plates squeeze the superimposed structure along the slide groove. At the same time, the inner extrusion plate is squeezed layer by layer along the slide groove under the action of the telescopic spring, so that the inner superimposed structure can be evenly and stably extruded, thereby achieving uniform welding.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) the metal layers on both sides of the composite current collector are connected and conductive through the connector structure; (2) multi-point uniform welding of the first welding part and the second welding part on the inner side of the connector can be achieved through the preheating device and the extrusion mechanism in the first welding mechanism, thereby effectively improving the connection strength and conductivity between the composite current collector and the connector. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic structural diagram of embodiment 1 of the present invention;

[0021] Figure 2 yes Figure 1 Sectional view at "AA" in the figure;

[0022] Figure 3 It is a schematic structural diagram of the connecting piece of the present invention;

[0023] Figure 4 is a partial schematic diagram of a connecting piece of the present invention;

[0024] Figure 5 It is a structural schematic diagram of the combination of the extrusion mechanism and the superposition structure of the present invention;

[0025] In the figure: the pole ear 1; the first welding part 101; the second welding part 102; the third welding part 103; the superimposed structure 104; the connecting piece 2; the connecting body 3; the connecting piece 4; the first soldering groove 5; the filling body 6; the rectangular groove 7; the extension groove 8; the gap 9; the second soldering groove 10; the bracket 11; the slide groove 12; the piston cylinder 13; the extrusion plate 14; the connecting rod sleeve 15; the connecting rod 16; the slide rod groove 17; the telescopic spring 18; the limit block 19. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings:

[0027] Embodiment 1:

[0028] A composite current collector tab welding method (see attached Figure 1-5 ), the specific steps are:

[0029] S1: Connect mutually offset pole ears 1 to adjacent pole pieces respectively;

[0030] S2: several connecting sheets 2 are respectively installed on the connecting body 3 to form a connecting piece 4; the connecting piece is provided with a first welding portion 101, a second welding portion 102 and a third welding portion 103; the connecting sheets 2 are staggered along the diagonal direction on the inner wall of the connecting body 3, and the two adjacent connecting sheets are arranged at an equal distance; the first welding portion includes a first soldering groove 5 and a filling body 6, the first soldering groove 5 is arranged in the wall of the connecting piece 4, and the filling body 6 is arranged in the first soldering groove 5; the filling body 6 is a solder material;

[0031] S3: The grabbing device moves the connecting piece 4 to the top of the pole piece. The grabbing device adopts a conventional computer-controlled manipulator unit to grab the operation. The connecting pieces 2 are respectively inserted between the adjacent pole piece tabs 1, so that the pole piece tabs 1 and the connecting pieces 2 are interlaced and overlapped with each other.

[0032] S4: a first welding mechanism is arranged along the superposition direction of the pole piece and the pole ear 1 and the connecting piece 2, a filling body 6 is arranged on the connecting piece 2, and the first welding mechanism preheats and performs extrusion welding on the pole piece and the pole ear;

[0033] S5: ultrasonically welding the connecting sheet to the pole piece and the pole tab 2 through a second welding mechanism.

[0034] The first soldering groove 5 is composed of a rectangular groove 7 and an extension groove 8 extending along the side wall of the rectangular groove. A full filling body 6 is provided in the rectangular groove 7, and a part of the filling body 6 is provided in the extension groove 8, so that a part of the gap 9 is left on the side of the extension groove 8 away from the rectangular groove 7. The depth of the rectangular groove 7 is greater than the depth of the extension groove 8. When the filling body 6 is heated and liquefied, through the extrusion of the first welding mechanism, part of the filling body 6 flows into the reserved gap 9 and contacts the upper and lower walls of the composite current collector pole piece and the pole ear 1, so as to realize the solder connection of the contact surface, thereby improving the welding strength; the reserved gap 9 can prevent the solder from being filled too much, so that it flows out under the extrusion, thereby increasing the welding thickness; the second welding part includes a second soldering groove 10 and a filling body, and the second soldering groove 10 is set in an "L"-shaped structure and is set in the wall body at the connection between the connecting piece 2 and the connecting body 3.

[0035] Welding is a two-step operation:

[0036] See attached Figure 1 To Attachment Figure 5 The first step, namely step S4, is to weld and fix the composite current collector pole piece and pole ear by a first welding mechanism.

[0037] The first welding mechanism includes a preheating device and an extrusion mechanism. The preheating device adopts electromagnetic induction heating to first make the composite current collector pole piece and the connecting piece fit and overlap, and then form a superimposed structure 104. The superimposed structure is provided with two trapezoidal surfaces with a trapezoidal structure. Then, the preheating device performs electromagnetic induction heating around it to make the solder liquefy due to the heat. Then, the superimposed structure is extruded along the superimposed direction by the extrusion mechanism, so that the solder in the first soldering groove 5 and the second soldering groove 10 is fully in contact with the contact surface of the composite current collector pole piece and the ear 1, thereby realizing multi-point welding of the contact surface.

[0038] The extrusion mechanism 200 includes a bracket 11 arranged on both sides of the stacked structure, a slide groove 12 is arranged in the wall body of the two brackets on the opposite side, a pressure plate mechanism is arranged in the slide groove 12, and a piston cylinder 13 for driving the pressure plate mechanism, the pressure plate mechanism includes a plurality of extrusion plates 14, the length of the extrusion plates 14 is adapted to the trapezoidal surface of the stacked structure, the length of the extrusion plates on the positive trapezoidal surface of the stacked structure is shortened layer by layer, the length of the extrusion plates on the reverse trapezoidal surface (backward) of the stacked structure is increased layer by layer, and a connecting structure is provided between two adjacent extrusion plates The connection structure includes a connecting rod sleeve 15 and a connecting rod 16. A sliding rod groove 17 is provided in the connecting rod sleeve 15. The connecting rod 16 is slidably arranged in the sliding rod groove 17. A telescopic spring 18 is connected between the end faces of the connecting rod sleeve 15 and the connecting rod 16. The connecting rod sleeve 15 is fixedly connected to a relatively shorter extrusion plate 14. The connecting rod 16 is fixedly connected to a relatively upper extrusion plate 14. The two ends of the extrusion plate 14 are respectively slidably arranged in the two side slide grooves 12. The end of the slide groove 12 is installed with a limit block 19. The limit block 19 is used to prevent the end extrusion plate 14 from sliding out. When the extrusion mechanism is started, the piston cylinder drives the piston rod to drive the upper and lower extrusion plates to slowly move toward the middle side. At this time, the upper and lower extrusion plates squeeze the superimposed structure along the slide groove. At the same time, the inner extrusion plate is squeezed layer by layer along the slide groove under the action of the telescopic spring, so that the inner superimposed structure can be evenly and stably extruded, thereby achieving uniform welding.

[0039] The second step, namely step S5:

[0040] The third welding portion is ultrasonically welded by the second welding mechanism.

[0041] The third welding part is arranged at the junction of the connecting piece and the pole ear of the composite current collector to be welded, and the second welding mechanism adopts the existing ultrasonic welding equipment, which belongs to the existing technology.

[0042] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A composite current collector tab welding method, characterized in that: The specific steps are: S1: Connect mutually offset pole ears on adjacent pole pieces respectively; S2: installing a plurality of connecting sheets on the connecting body to form a connecting member; S3: The grasping device moves the connecting piece to the top of the pole piece, and the connecting piece is respectively inserted between the pole ears of the adjacent pole pieces, so that the pole ears and the connecting piece are superimposed on each other; After the pole piece and the pole ear are matched and superimposed with the connecting piece, a superimposed structure is formed, and two trapezoidal surfaces in a trapezoidal structure are provided on the superimposed structure. The length of the extruded plate of the positive trapezoidal surface on the superimposed structure is shortened layer by layer, and the length of the extruded plate of the reverse trapezoidal surface on the superimposed structure is increased layer by layer. When the upper and lower extrusion plates extrudes the stacked structure along the slide grooves in the brackets on both sides of the stacked structure, the inner extrusion plate is extruded layer by layer along the slide grooves under the action of the telescopic springs between the upper and lower extrusion plates; S4: a first welding mechanism is arranged along the superposition direction of the pole piece and the pole ear and the connecting piece, a filling body is arranged on the connecting piece, and the first welding mechanism preheats and performs extrusion welding on the pole piece and the pole ear; S5: ultrasonically welding the connecting piece to the pole piece and the pole ear through a second welding mechanism.

2. A composite current collector tab welding method according to claim 1, characterized in that: The connecting piece is provided with a first welding portion, a second welding portion and a third welding portion.

3. A composite current collector tab welding method according to claim 1, characterized in that: The connecting pieces are staggeredly arranged along the diagonal direction on the inner wall of the connecting body, and the distance between two adjacent connecting pieces is equal.

4. A composite current collector tab welding method according to claim 2 or 3, characterized in that: The first welding portion includes a first soldering groove and a filling body. The first soldering groove is arranged in the wall body of the connecting member, and the filling body is arranged in the first soldering groove.

5. A composite current collector tab welding method according to claim 4, characterized in that: The first soldering groove is composed of a rectangular groove and an extended groove extending along the side wall of the rectangular groove.

6. A composite current collector tab welding method according to claim 2 or 3, characterized in that: The second welding portion includes a second soldering groove and a filling body. The second soldering groove is arranged in an "L"-shaped structure and is arranged in a wall body at the connection between the connecting piece and the connecting body.

7. A composite current collector tab welding method according to claim 6, characterized in that: The third welding portion is arranged at the junction of the connecting piece and the pole ear of the composite current collector to be welded, and ultrasonic welding is performed by the second welding mechanism.

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