Convex spot welding method for negative collector plate of large cylindrical lithium battery

Abstract

The invention discloses a convex spot welding method for a negative collector plate of a large cylindrical lithium battery. The convex spot welding method comprises a resistance welding needle, a battery cell, the collector plate, a steel shell, a resistance welding lower electrode, a circular convex point structure and an elliptical convex point structure, the current collecting plates are divided into a positive current collecting plate and a negative current collecting plate, and the negative current collecting plate comprises a negative current collecting plate with a convex point design, a negative current collecting plate with a round convex point design and a negative current collecting plate with an elliptical convex point design. The welding area of the negative electrode collector plate is designed to be of a convex point type structure, the pseudo soldering rate of the bottom of a resistance welding spot is reduced, the welding area of the bottom of the spot is increased, the internal resistance of the battery is reduced, the purpose of low charging and discharging temperature rise is achieved, the safety performance is improved, and high-rate charging and discharging can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of negative current collecting discs of lithium batteries, and in particular to a convex spot welding method for negative current collecting discs of large cylindrical lithium batteries. Background Art

[0002] In the existing cylindrical steel shell lithium battery with full-ear structure, the negative electrode collector disc and the shell bottom are connected by a resistance welding point. The negative electrode collector disc and the shell bottom are fixed by only one welding point. The welding area is small, the current capacity is low, and it is easy to have cold welding, which leads to increased internal resistance and excessive temperature rise, affecting the safety performance of the battery. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a bump welding method for the negative current collector of a large cylindrical lithium battery. The bottom welding point of the center point of the negative current collector is designed to be in the form of a bump. The bump structure can be a circular bump, an elliptical bump, or other bump forms. The bump welding can weld multiple welds at the same time in one welding cycle. The production efficiency is high and there is no influence of shunt. The welding strength is high and the welding area is large. It improves the abnormality of the bottom point cold welding and the small area causing the internal resistance to increase and the charging and discharging temperature to rise.

[0004] The present invention proposes a method for spot welding of negative current collectors of large cylindrical lithium batteries, comprising a resistance welding needle, a battery cell, a current collector, a steel shell, a resistance welding lower electrode, a circular bump structure, and an elliptical bump structure; The current collecting disc is divided into a positive current collecting disc and a negative current collecting disc, and the negative current collecting disc includes a negative current collecting disc with a convex dot design, a negative current collecting disc with a round dot convex dot design, and a negative current collecting disc with an elliptical convex dot design; The steel shell is made of SPCC; The negative current collecting plate is circular; The welding place between the negative current collecting plate and the battery cell is formed with two grooves, which fits the battery cell more closely without gaps, thus preventing abnormal fire from occurring during welding; The negative current collecting plate is provided with two oval notches and two circular notches to facilitate the infiltration of electrolyte during filling and achieve the effect of weight reduction; The negative electrode current collector is made of T2 material, and the center bottom welding point is in the form of a convex point, which can be a circular convex point or an elliptical convex point; The material of the resistance welding needle is alumina copper, and the material of the resistance welding lower electrode is copper; The bump welding method can weld multiple welding points simultaneously in one welding cycle, with high production efficiency and no shunting effect, high welding strength and large welding area. The current density of the bump welding is concentrated at the bump, and the high current density allows welding with a smaller current, and can reliably form multiple smaller weld nuggets. The bump welding bumps are accurately positioned and uniform in size, the welding strength of each point is uniform, and the welding quality is reliable. The welding method further comprises the following steps: S1: The negative terminal of the battery cell is welded to the negative electrode collector plate with a dot convex design or the negative electrode collector plate with an elliptical convex design, and the positive terminal of the battery cell is welded to the positive electrode collector plate. The positive terminal is covered with an insulating sheet and high-temperature tape and then placed in the steel shell; S2: After entering the steel shell, the circular convex structure or elliptical convex structure of the negative electrode current collector is tightly fitted with the bottom of the steel shell; S3: After entering the steel shell, the battery cell is inserted into the resistance welding needle. Under the influence of the electrode pressure, pre-pressing time, welding time, welding current and holding time of the resistance welding machine, the negative electrode current collector with a convex design is crushed and melted together with the shell bottom to form multiple small molten cores, thus achieving the purpose of welding; S4: Carry out subsequent battery production processes.

[0005] The beneficial effects of the present invention are as follows: the negative electrode current collecting plate welding area is designed as a structure with a convex point form, which reduces the cold weld rate of the resistance welding point, increases the welding strength and welding area of ​​the bottom point, thereby reducing the internal resistance of the battery to achieve the purpose of low charging and discharging temperature rise, improve safety performance, and enable high-rate charging and discharging. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 This is an enlarged view of structure A of the present invention; Figure 3 This is a schematic structural diagram of the negative electrode current collecting disk with a dot-convex design in the present invention; Figure 4 Schematic diagram of the structure of the circular convex point structure in the present invention; Figure 5 A schematic diagram of the structure of the negative electrode current collecting disk with an elliptical convex point design in the present invention; Figure 6 Schematic diagram of the structure of the elliptical convex point structure in the present invention.

[0007] In the figure: 1. Resistance welding needle; 2. Battery cell; 3. Negative electrode current collector with bump design; 4. Steel shell; 5. Resistance welding lower electrode; 6. Negative electrode current collector with round dot bump design; 7. Round bump structure; 8. Negative electrode current collector with elliptical bump design; 9. Elliptical bump structure. DETAILED DESCRIPTION

[0008] The present invention will be further explained below with reference to specific embodiments. Example

[0009] refer to Figure 1-6 In this embodiment, a method for spot welding a negative current collector of a large cylindrical lithium battery is proposed, comprising a resistance welding needle 1, a battery cell 2, a current collector, a steel shell 4, a resistance welding lower electrode 5, a circular bump structure 7, and an elliptical bump structure 9; The current collecting disc is divided into a positive current collecting disc and a negative current collecting disc, and the negative current collecting disc includes a negative current collecting disc 3 with a convex dot design, a negative current collecting disc 6 with a dot convex dot design, and a negative current collecting disc 8 with an elliptical convex dot design; The steel shell 4 is made of SPCC; The negative current collecting plate is circular; The welding place between the negative collector plate and the battery cell 2 is formed with two grooves, which fits the battery cell 2 more closely without gaps, thus preventing the abnormality of explosion during welding; The negative current collecting plate is provided with two oval notches and two circular notches to facilitate the infiltration of electrolyte during filling and achieve the effect of weight reduction; The negative electrode current collector is made of T2 material, and the center bottom welding point is in the form of a convex point, which can be a circular convex point or an elliptical convex point; The material of the resistance welding needle 1 is alumina copper, and the material of the resistance welding lower electrode 5 is copper; The bump welding method can weld multiple welding points simultaneously in one welding cycle, with high production efficiency and no shunting effect, high welding strength and large welding area. The current density of the bump welding is concentrated at the bump, and the high current density allows welding with a smaller current, and can reliably form multiple smaller weld nuggets. The bump welding bumps are accurately positioned and uniform in size, the welding strength of each point is uniform, and the welding quality is reliable. The welding method further comprises the following steps: S1: The negative terminal of the battery cell 2 is welded to the negative electrode collector plate 6 with a dot-shaped convex design or the negative electrode collector plate 8 with an elliptical convex design, and the positive terminal of the battery cell 2 is welded to the positive electrode collector plate. The positive terminal is covered with an insulating sheet and high-temperature tape and then placed in the steel shell 4; S2: After entering the steel shell 4, the circular convex structure 7 or the elliptical convex structure 9 of the negative electrode current collecting plate is tightly fitted with the bottom of the steel shell 4; S3: After entering the steel shell 4, the battery cell 2 is passed through the resistance welding needle 1. Under the influence of the electrode pressure, pre-pressing time, welding time, welding current and holding time of the resistance welding machine, the negative electrode current collecting plate 3 with a convex design is crushed and melted together with the shell bottom to form multiple small molten cores, thereby achieving the purpose of welding; S4: Carry out subsequent battery production processes.

[0010] It can be seen from the above-mentioned large cylindrical current collecting plate and convex spot welding method that the welding point at the bottom of the center point of the negative current collecting plate is designed to be in the form of a convex spot. The convex spot structure can be a circular convex spot, an elliptical convex spot or other convex spot forms. Bump spot welding can weld multiple welding points at the same time in one welding cycle, with high production efficiency and no shunt effect. The welding strength is high and the welding area is large, which improves the abnormality of low solder joints at the bottom point and the small area causing large internal resistance and increased charging and discharging temperature.

[0011] In this embodiment, the steel shell material is SPCC nickel-plated, the shell bottom thickness is 0.7mm, the negative current collecting disc material is T2, the outer diameter is φ38.5mm, the raw material thickness is 0.3mm, the bump height is 0.1mm, the number of circular bump structures 7 is 33, the number of elliptical bump structures 9 is 11, the diameter of the center welding is φ5mm, and after the battery core 2 is welded to the positive and negative current collecting discs, an insulating sheet is wrapped with high-temperature tape, and then inserted into the steel shell 4. The resistance welding needle 1 is inserted, and the negative current collecting disc and the shell bottom are welded by resistance bump welding. Multiple small molten cores are formed at the bumps to improve the welding strength and welding area.

[0012] In this embodiment, the negative electrode current collecting plate welding area is designed to have a convex structure, which reduces the cold weld rate of the resistance welding point, increases the welding strength and welding area of ​​the bottom point, thereby reducing the internal resistance of the battery to achieve the purpose of low charging and discharging temperature rise, improve safety performance, and enable high-rate charging and discharging.

[0013] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for spot welding of negative collector plates of large cylindrical lithium batteries, characterized in that: It comprises a resistance welding needle (1), a battery cell (2), a current collecting plate, a steel shell (4), a resistance welding lower electrode (5), a circular convex point structure (7) and an elliptical convex point structure (9); The current collecting disc is divided into a positive current collecting disc and a negative current collecting disc, and the negative current collecting disc includes a negative current collecting disc (3) with a convex point design, a negative current collecting disc (6) with a round dot convex point design, and a negative current collecting disc (8) with an elliptical convex point design; The steel shell (4) is made of SPCC; The negative current collecting plate is circular; The welding point between the negative current collecting plate and the battery cell (2) is formed by two grooves; The negative current collecting plate is provided with two elliptical notches and two circular notches; The negative electrode current collector is made of T2 material, and the central bottom welding point is in the form of a convex point; The material of the resistance welding needle (1) is aluminum oxide copper, and the material of the resistance welding lower electrode (5) is copper; The welding method also The following steps are involved: S1: The negative terminal of the battery cell (2) is welded to the negative current collector (6) with a convex point design, the positive terminal of the battery cell (2) is welded to the positive current collector, and the positive terminal is covered with an insulating sheet and wrapped with high-temperature tape and then placed in a steel shell (4); S2: After entering the steel shell (4), the circular convex structure (7) of the negative electrode current collector is tightly fitted with the bottom of the steel shell (4); S3: After entering the steel shell (4), the battery cell (2) is inserted into the resistance welding needle (1), and the negative electrode current collector (3) with a convex point design is crushed and melted together with the shell bottom under the action of the electrode pressure, pre-pressing time, welding time, welding current and holding time of the resistance welding machine, forming multiple small molten cores, thereby achieving the purpose of welding; S4: Carry out the subsequent production process of the battery.

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