Cylindrical battery and welding and pulling force detection method thereof

Abstract

The invention discloses a cylindrical battery and a welding and pulling force detection method thereof.The battery comprises a shell, a roll core and a current collecting disc, an anti-explosion valve is arranged in the center of the bottom of the shell of the battery, a laser welding platform is arranged between the anti-explosion valve and the shell, the current collecting disc is round, a liquid guide hole is formed in the middle of the current collecting disc, and the roll core is arranged in the shell. The liquid guide hole plays a role in electrolyte infiltration in the roll core and also plays a role in gas conduction during explosion pressure testing of the anti-explosion valve, the laser welding platform is sunken like the interior of the shell, the sunken depth is 0.1-0.5 mm, the anti-explosion valve is round and concentric with the bottom of the shell, and the diameter of the anti-explosion valve is 1 / 4-3 / 4 of the diameter of the bottom of the shell. The explosion-proof valve is arranged at the bottom of the battery shell, the explosion-proof valve plays a role in protecting the safety of the battery and also serves as a channel for welding tension detection, the shell and the collector plate are not required to be damaged by cutting, the penetration welding strength can be tested, the strength of a penetration welding wire can be tested in the whole section, and local pseudo soldering can be effectively detected.

Description

Technical Field

[0001] This invention relates to the field of new energy battery technology, and in particular to a cylindrical battery and its welding and tensile testing methods. Background Technology

[0002] The welding of the cylindrical battery casing to the current collector is a critical process in battery manufacturing, directly affecting the battery's electrical performance. Traditional processes mostly use resistance welding, ultrasonic welding, or laser welding to spot weld the current collector to the steel casing at the center. This results in a small welding area and hinders PACK welding. To further increase the welding area and avoid the PACK welding zone, laser penetration welding at the casing edge is gradually being adopted. However, because the current collector lacks an extension shank, conventional tensile testing methods require cutting the casing and can only test the strength of the weld at the cut location, not the overall weld strength. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a cylindrical battery and its welding and tensile testing method. An explosion-proof valve is designed in the center of the battery shell, and the bottom edge of the shell is connected to the current collector by laser penetration welding. The explosion-proof pressure is tested by pressure testing, and then the tensile force of the penetration weld is tested by squeezing through the explosion-proof port.

[0004] The present invention proposes a cylindrical battery, comprising a casing, a winding core, and a current collector. An explosion-proof valve is provided at the bottom center of the battery casing, and a laser welding platform is provided between the explosion-proof valve and the casing.

[0005] Preferably, the collector plate is circular with a liquid guiding hole in the middle. In addition to wetting the electrolyte inside the core, the liquid guiding hole also serves to conduct gas during the explosion-proof valve burst pressure test.

[0006] Preferably, the laser welding platform is recessed inside the shell, with a recess depth of 0.1~0.5mm.

[0007] Preferably, the explosion-proof valve is circular and concentric with the bottom of the housing, and the diameter of the explosion-proof valve is 1 / 4 to 3 / 4 of the diameter of the bottom of the housing.

[0008] This invention also relates to a welding and tensile testing method for cylindrical batteries, comprising the following steps: S1: After the core tabs and current collectors are welded together, they are inserted into the housing, and then the current collectors and the housing are welded together using a laser welding machine; S2: The explosion-proof valve is damaged by pressurizing the inside of the battery; S3: Then, use a tensile test to squeeze the manifold with the pressure bar; S4: Test the welding strength of the manifold.

[0009] Preferably, the tensile test extrusion bar is equipped with an indenter, which is circular and has a diameter between the central liquid guide hole of the manifold and the explosion-proof valve.

[0010] Preferably, the edge of the pressure head is rounded with a radius of 0.5~2mm to prevent pressure concentration at the edge of the pressure head, which could lead to damage to the manifold during the extrusion test.

[0011] The beneficial effects of this invention are: 1. The bottom of the battery casing of the present invention is provided with an explosion-proof valve. In addition to protecting the safety of the battery, the explosion-proof valve also serves as a channel for welding tensile testing. 2. The penetration weld strength can be tested without cutting or damaging the shell and manifold. 3. It can test the strength of the through weld line in the whole section and effectively detect local cold welds. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the collector disk proposed in this invention; Figure 2 This is a schematic diagram of the battery casing proposed in this invention; Figure 3 This is a schematic diagram of the casing of the explosion-proof valve proposed in this invention after it ruptures; Figure 4 This is a schematic diagram of the penetration welding tensile test proposed in this invention; Figure 5 This is a schematic diagram of the cross-sectional view of the penetration welding tensile test proposed in this invention. Detailed Implementation

[0013] The present invention will be further explained below with reference to specific embodiments.

[0014] refer to Figure 1-5 This embodiment proposes a cylindrical battery, including a casing, a winding core, and a current collector. An explosion-proof valve is provided at the bottom center of the battery casing, and a laser welding platform is provided between the explosion-proof valve and the casing.

[0015] In this embodiment, the collecting plate is circular with a liquid guiding hole in the middle. In addition to wetting the electrolyte inside the core, the liquid guiding hole also serves to conduct gas during the explosion-proof valve burst pressure test. The laser welding platform is recessed inside the shell with a depth of 0.1~0.5mm. The explosion-proof valve is circular and concentric with the bottom of the shell, and the diameter of the explosion-proof valve is 1 / 4~3 / 4 of the diameter of the bottom of the shell.

[0016] This invention also proposes a welding and tensile testing method for cylindrical batteries, comprising the following steps: S1: After the core tabs and current collectors are welded together, they are inserted into the housing, and then the current collectors and the housing are welded together using a laser welding machine; S2: The explosion-proof valve is damaged by pressurizing the inside of the battery; S3: Then, use a tensile test to squeeze the manifold with the pressure bar; S4: Test the welding strength of the manifold.

[0017] The tensile test extrusion bar is equipped with an indenter, which is circular. The diameter of the indenter is between the central liquid guide hole of the manifold and the explosion-proof valve. The edge of the indenter is rounded with a radius of 0.5~2mm to prevent pressure concentration at the edge of the indenter, which could cause damage to the manifold during the extrusion test. Example

[0018] Taking the 32140 steel-cased cylindrical battery as an example, the positive and negative electrode plates and the separator are wound to form a core, which is then welded to the current collector and then laser-through welded to the steel casing. After baking, liquid injection, sealing and capacity testing, the battery is formed.

[0019] The compression test process is as follows: After the manifold is welded to the steel shell, the opening of the steel shell is sealed with a sealing plug. Air is vented into the steel shell and pressurized until the explosion-proof valve on the steel shell ruptures. The ruptured explosion-proof valve and the sealing plug are removed. The pressure test extrusion rod is then used to press down uniformly from the manifold at the opening of the explosion-proof valve on the steel shell until the extrusion pressure suddenly drops. The maximum pressure value is recorded as the welding tensile force.

[0020] To confirm the reliability of the tensile testing scheme, batteries with different degrees of poor soldering were simulated by blocking or reducing the energy of the solder wire trajectory.

[0021] The experimental results are as follows:

[0022] As can be seen from Examples 1-6, when the area of ​​the poor weld penetration of the casing reaches 10-20%, the internal resistance of the battery does not change significantly, but the welding pull has decreased by 16-33%, which can effectively detect batteries with local poor weld penetration.

[0023] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cylindrical battery, comprising a casing, a winding core, and a current collector, characterized in that, An explosion-proof valve is located at the bottom center of the battery casing, and a laser welding platform is provided between the explosion-proof valve and the casing.

2. A cylindrical battery according to claim 1, characterized in that, The manifold is circular with a liquid guide hole in the middle.

3. A cylindrical battery according to claim 1, characterized in that, The laser welding platform is recessed inside the shell, with a depth of 0.1~0.5mm.

4. A cylindrical battery according to claim 1, characterized in that, The explosion-proof valve is circular and concentric with the bottom of the housing. The diameter of the explosion-proof valve is 1 / 4 to 3 / 4 of the diameter of the bottom of the housing.

5. A method for welding and tensile testing of a cylindrical battery, characterized in that, Includes the following steps: S1: After the core tabs and current collectors are welded together, they are inserted into the housing, and then the current collectors and the housing are welded together using a laser welding machine; S2: The explosion-proof valve is damaged by pressurizing the inside of the battery; S3: Then, use a tensile test to squeeze the manifold with the pressure bar; S4: Test the welding strength of the manifold.

6. The welding and tensile testing method for a cylindrical battery according to claim 5, characterized in that, The tensile test extrusion bar is equipped with an indenter, which is circular and has a diameter between the central liquid guide hole of the manifold and the explosion-proof valve.

7. The welding and tensile testing method for a cylindrical battery according to claim 6, characterized in that, The edge of the pressure head is rounded with a radius of 0.5~2mm to prevent pressure concentration at the edge of the pressure head, which could cause damage to the manifold during the extrusion test.

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