CN111769289A - A kind of welding method of flexible current collector - Google Patents

Abstract

The invention discloses a welding method for a flexible current collector, comprising the following steps: S1. A pole piece 1 is obtained by attaching a conductive foil to one side of a flexible current collector and welding, and a welding spot 1 is formed on the pole piece 1; S2, A plurality of pole pieces 1 are stacked together, and the pole piece 2 is obtained by welding again at the position of the solder joint 1, and then the pole piece 2 is welded to the tab outside the battery. The invention avoids the insufficient flow capacity caused by direct welding of the multi-layer composite current collector, and also avoids the problems of waste of foil, excessive thickness of the tab and deformation of the winding core caused by the double-layer foil wrapping welding.

Description

A kind of welding method of flexible current collector

technical field

The invention relates to the technical field of foil welding, in particular to a welding method of a flexible current collector.

Background technique

The application of flexible current collectors in lithium-ion batteries is becoming more and more extensive with the improvement of energy density. The flexible current collector generally includes a support layer and a conductive layer connected to both sides of the support layer. Since the outside of the flexible current collector is a metal layer with good electrical and thermal conductivity, and the inner layer is an organic molecular insulating layer, the welding of the current collector and the internal resistance after welding affect a series of performances of the battery.

The welding of flexible current collectors generally adopts ultrasonic welding, and the conductive foil is welded to the flexible current collector on the tab side for use. The current collector method, but this welding method is more wasteful and will cause the tab area to be thicker, especially for the subsequent cell welding and assembly of the large-capacity core, which brings a certain degree of difficulty, which is easy to lead to false welding of the tabs. , and to a certain extent increases the weight of the battery.

However, the welding of one side of the flexible current collector and the conductive foil is directly used. Since the two sides of the flexible current collector are not connected, the conduction on both sides cannot be achieved. .

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background technology, the present invention proposes a method for detecting metal magnetic impurities in a positive electrode material. The present invention avoids the insufficient flow capacity caused by direct welding of multilayer composite current collectors, and also avoids double-layer foil packs. Foil waste due to welding, excessive tab thickness and core deformation.

The welding method of a flexible current collector proposed by the present invention includes the following steps:

S1. Attach and weld the conductive foil to one side of the flexible current collector to obtain a pole piece 1, and a solder joint 1 is formed on the pole piece 1;

S2. Stack a plurality of pole pieces 1 together, and weld the pole pieces 2 again at the positions of the solder joints 1, and then weld the pole pieces 2 with the tabs outside the battery.

Preferably, in S2, the flexible current collector in the pole piece 2 is arranged adjacent to the conductive foil.

Preferably, in S1, the shape of the solder joint 1 is a continuous strip or spaced dots.

Preferably, in S2, the welding method is ultrasonic welding, the welding pressure is greater than 30 PSI, and the welding tooth depth is less than 3 mm.

Preferably, in S1, the flexible current collector includes: a support layer and a conductive plating layer, wherein the conductive plating layer is attached to the surface of the support layer.

Preferably, the thickness of the support layer is 0.1-20 μm.

Preferably, the thickness of the conductive plating layer is 0.1-10 μm.

Preferably, in S1, the material of the conductive foil includes at least one of copper, aluminum, silver, and nickel.

Preferably, in S1, the welding method is spot welding or seam welding.

Beneficial effects:

In the present invention, the conductive foil is first welded with one side of the flexible current collector to form a welding small unit, that is, the pole piece 1, and then a plurality of small cells are compounded together, and the welding is continued on the original welding point of the pole piece 1 by pressure compounding. The pole piece 2 in which the flexible current collector and the conductive foil are arranged adjacently is obtained; when the pole piece 2 is welded, by using a suitable welding method and adjusting the appropriate welding pressure and welding tooth depth, the cracking of the solder joint 1 caused by the secondary welding can be avoided. It has little effect on the welding strength of the pole piece 1; it can also realize the compounding of multiple welding units, realize double-sided conduction, and avoid excessive internal resistance on both sides; this welding method avoids direct welding of multi-layer composite assemblies. The insufficient flow capacity caused by the fluid also avoids the waste of foil, excessive thickness of the tabs and deformation of the winding core caused by double-layer foil wrap welding.

Detailed ways

Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments.

Example 1

A welding method for a flexible current collector, comprising the following steps:

S1. Paste the flexible current collector (12 μm thick, 10 mm long, 22 mm wide) and aluminum foil (12 μm thick, 15 mm long, 22 mm wide) and ultrasonically spot-weld to obtain a pole piece 1, and a solder joint 1 is formed on the pole piece 1, wherein, The shape of the solder joint 1 is the spaced dot shape;

S2. Take a plurality of pole pieces 1 and cut them into the same size, then stack them together, and ultrasonically spot weld the pole piece 2 at the position of the solder joint 1, and then ultrasonically weld the pole piece 2 to the aluminum tab outside the battery. Among them, the flexible current collector in the pole piece 2 is arranged adjacent to the aluminum foil, the welding pressure is 40PSI, and the welding tooth depth is 1.5mm.

Example 2

A welding method for a flexible current collector, comprising the following steps:

S1. Paste the flexible current collector (10 μm thick, 15 mm wide) and aluminum foil (12 μm thick, 20 mm wide) and seam welding to obtain a pole piece 1, and a solder joint 1 is formed on the pole piece 1, wherein the shape of the solder joint 1 is continuous strip;

S2. Take a plurality of pole pieces 1 and cut them into the same size, then stack them together, and ultrasonically spot weld the pole piece 2 at the position of the solder joint 1, and then ultrasonically weld the pole piece 2 to the aluminum tab outside the battery. Among them, the flexible current collector in the pole piece 2 is arranged adjacent to the aluminum foil, the welding pressure is 45PSI, and the welding tooth depth is 1.3mm.

Example 3

A welding method for a flexible current collector, comprising the following steps:

S1. Paste the flexible silver-plated composite current collector (10 μm thick, 15 mm wide) and aluminum foil (12 μm thick, 20 mm wide) and seam welding to obtain a pole piece 1, and a solder joint 1 is formed on the pole piece 1. The shape is a continuous strip;

S2. Take a plurality of pole pieces 1 and cut them into 20mm wide, then stack them together, and ultrasonically spot weld the pole pieces 2 at the position of the solder joint 1, and then ultrasonically weld the pole pieces 2 to the aluminum tabs outside the battery. Among them, the flexible current collector in the pole piece 2 is arranged adjacent to the aluminum foil, the welding pressure is 40PSI, and the welding tooth depth is 1.5mm.

Example 4

A welding method for a flexible current collector, comprising the following steps:

S1. Paste the flexible current collector (6.5μm thick, 18mm wide) and copper foil (6μm thick, 22mm wide) and seam welding to obtain a pole piece 1, and a solder joint 1 is formed on the pole piece 1. Among them, the shape of the solder joint 1 is a continuous strip;

S2. Take a plurality of pole pieces 1 and cut them into 20mm wide, then stack them together, and ultrasonically spot weld the pole pieces 2 at the position of the solder joint 1, and then ultrasonically weld the pole pieces 2 to the copper tabs outside the battery. Among them, the flexible current collector in the pole piece 2 is arranged adjacent to the copper foil, the welding pressure is 35PSI, and the welding tooth depth is 1mm.

Comparative ratio

A welding method for a flexible current collector, comprising the steps of:

S1. Put the copper foil 1 (6μm thick, 22mm wide), the flexible current collector (6.5μm thick, 15mm wide), and the copper foil 2 (6μm thick, 22mm wide) on top of each other in order, and then roll-weld to get the pole piece 1; take the pole piece Sheet 1 is cut to 20mm, and then ultrasonically welded to the external copper tabs.

The resistances of the pole pieces after welding of Examples 1-4 and Comparative Examples were tested, and the results are shown in the following table.

resistance Example 1 Example 2 Example 3 Example 4 Comparative ratio R1(mΩ) 18 16 15 6 8 R2(mΩ) 20 18 16 14 15

Remarks: The measured data is measured by the Japanese BT3554 portable internal resistance meter, and the obtained data is the average value.

From the results in the above table, it can be seen that the difference in internal resistance between Example 4 and the comparative example is not large, but Example 4 saves half of the welding foil material. While reducing the amount of welding foil material, the present invention can Keep the internal resistance from increasing.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (9)

1. a welding method of flexible current collector, is characterized in that, comprises the steps: S1. Attach and weld the conductive foil to one side of the flexible current collector to obtain a pole piece 1, and a solder joint 1 is formed on the pole piece 1; S2. Stack a plurality of pole pieces 1 together, and weld the pole pieces 2 again at the positions of the solder joints 1, and then weld the pole pieces 2 with the tabs outside the battery. 2 . The welding method of the flexible current collector according to claim 1 , wherein in S2 , the flexible current collector and the conductive foil are arranged adjacent to each other in the pole piece 2 . 3 . 3 . The welding method of the flexible current collector according to claim 1 or 2 , wherein, in S1 , the shape of the welding point 1 is a continuous strip shape or a spaced point shape. 4 . 4 . The welding method of the flexible current collector according to claim 1 , wherein in S2 , the welding method is ultrasonic welding, the welding pressure is greater than 30 PSI, and the welding tooth depth is less than 3 mm. 5 . 5 . The welding method of the flexible current collector according to claim 1 , wherein in S1 , the flexible current collector comprises: a support layer and a conductive plating layer, wherein the conductive plating layer is attached to the surface of the support layer. 6 . 6 . The welding method of the flexible current collector according to claim 5 , wherein the thickness of the support layer is 0.1-20 μm. 7 . 7 . The welding method of the flexible current collector according to claim 5 , wherein the thickness of the conductive plating layer is 0.1-10 μm. 8 . 8 . The method for welding a flexible current collector according to claim 1 , wherein, in S1 , the material of the conductive foil includes at least one of copper, aluminum, silver, and nickel. 9 . 9 . The welding method of the flexible current collector according to claim 1 , wherein, in S1 , the welding method is spot welding or seam welding. 10 .