A sodium-ion cylindrical battery resistance welding process method

Abstract

The application provides a sodium ion cylindrical battery resistance welding process method, and the first stage is that an aluminum-nickel composite strip tab is heated to between the melting point of aluminum and the melting point of nickel by using a resistance welding device with a set low current, at this time, the aluminum layer starts to melt, and the resistance welding device is pressed to squeeze the molten aluminum liquid out from between the nickel layer of the tab and the nickel-plated layer of the steel shell, at this time, the two nickel layers are directly contacted, and the aluminum liquid is solidified after being squeezed around the tab; the second stage is that the nickel layer of the aluminum-nickel composite strip tab is heated to melt by using the resistance welding device with a set high current, so that the nickel layer of the tab is fused with the surface of the nickel-plated layer of the nickel-plated steel shell. The abnormal problems such as virtual welding, aluminum liquid splashing and sparking of the resistance welding between the negative tab of the cylindrical battery and the bottom of the nickel-plated steel shell can be effectively improved by the segmented resistance welding method, and the product yield is improved. The welding firmness between the aluminum-nickel composite strip tab and the nickel-plated steel shell is improved by the improved welding process, and the safety of the battery is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of cylindrical battery welding technology, and in particular to a resistance welding process for sodium-ion cylindrical batteries. Background Technology

[0002] In the production of cylindrical batteries, the negative electrode sheet is connected to the nickel-plated steel shell via two tabs at both ends. These tabs are made of aluminum-nickel composite strips, rolled from both aluminum and nickel. The aluminum layer at one end of the aluminum-nickel composite strip is ultrasonically welded to the aluminum foil of the electrode current collector, while the nickel layer at the other end is resistance welded to the bottom of the steel shell, thus connecting the internal electrodes to the external circuitry. Resistance welding utilizes the resistance heat generated by the current passing through the workpiece and the contact area as a heat source to locally heat the workpiece while applying pressure for welding. During resistance welding, the welding materials need to be heated to a liquid state above their melting point to achieve fusion. Due to the significant difference in melting points between aluminum and nickel (aluminum melting point 660℃, nickel melting point 1453℃), the temperature at which the nickel layer melts is much higher than the melting point of aluminum, causing the aluminum to absorb heat and melt into a liquid state. Because the welding process is simultaneously under pressure, the compressed molten aluminum can splash and spark. The heat absorbed by melting aluminum can cause the temperature in the welding zone to drop, preventing the nickel layer from fusing properly and resulting in a poor weld. After cooling, metal particles may form, leading to short circuits in the battery cell or even safety issues. Summary of the Invention

[0003] To address the aforementioned problems, this invention aims to propose a resistance welding process for sodium-ion cylindrical batteries. The process involves segmented resistance welding between the aluminum-nickel composite strip tab and the nickel-plated steel shell. First, the aluminum in the aluminum-nickel composite strip tab is welded, and the molten aluminum is squeezed around the tab and solidified. Then, the nickel is welded, directly fusing the nickel layer with the nickel-plated steel shell. This improves the welding quality between the aluminum-nickel composite strip tab and the nickel-plated steel shell, preventing problems such as aluminum splashing caused by direct high-pressure, high-temperature welding and the aluminum absorbing heat, which can lead to incomplete nickel layer welding.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0005] A resistance welding process for sodium-ion cylindrical batteries, wherein the aluminum-nickel composite strip tabs are joined to a nickel-plated steel shell using segmented resistance welding, specifically including the following steps:

[0006] First stage: Using a resistance welding device, the aluminum-nickel composite strip tab is heated to between the melting points of aluminum and nickel using a low current. At this time, the aluminum layer begins to melt, and the resistance welding device applies pressure to squeeze the molten aluminum liquid out from between the nickel layer of the tab and the nickel-plated layer of the steel shell. At this time, the two nickel sheets are in direct contact, while the molten aluminum liquid is squeezed to the area around the tab and then solidifies.

[0007] The second stage: The resistance welding device heats the nickel layer of the aluminum-nickel composite strip tab to melt using a set high current, so that the nickel layer of the tab fuses with the nickel plating surface of the nickel-plated steel shell.

[0008] Furthermore, the welding parameters of the resistance welding device in the first stage are as follows: adjustable welding pressure of 30-70N, low current of 1.2-1.8KA, and time of 4-8ms.

[0009] Furthermore, the welding parameters of the resistance welding device in the second stage are as follows: adjustable welding pressure range of 30-70N, high current of 2.0-3.0KA, and time of 3-10ms.

[0010] Furthermore, the welding parameters of the resistance welding device in the first stage are as follows: welding pressure of 52N, low current of 1.55KA, and time of 6ms.

[0011] Furthermore, the welding parameters of the resistance welding device in the second stage are as follows: welding pressure of 52N, high current of 2.5KA, and time of 3.2ms.

[0012] Furthermore, when the aluminum-nickel composite strip tab is welded to the nickel-plated steel shell, the aluminum layer of the aluminum-nickel composite strip tab is close to the nickel layer of the nickel-plated steel shell.

[0013] Beneficial effects: This invention can effectively improve the abnormal problems such as poor welding, aluminum splashing, and arcing in the resistance welding between the negative electrode tab of the cylindrical battery and the bottom of the nickel-plated steel shell through segmented resistance welding, thereby improving the product yield. This invention improves the welding strength between the aluminum-nickel composite strip tab and the nickel-plated steel shell through the improved welding process, which is conducive to improving the stability and consistency of the product's electrical performance and greatly improves the safety of battery use. Attached Figure Description

[0014] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0015] Figure 1 This is a flowchart of the resistance welding process for sodium-ion cylindrical batteries according to an embodiment of the present invention;

[0016] Figure 2 This is a current and time distribution diagram during the resistance welding process of the sodium-ion cylindrical battery resistance welding method described in this embodiment of the invention;

[0017] Figure 3 This is a schematic diagram of the structure of the aluminum-nickel composite strip tab before welding to the nickel-plated steel shell according to an embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram of the aluminum-nickel composite strip tab and nickel-plated steel shell structure after being welded using the sodium-ion cylindrical battery resistance welding process described in this embodiment of the invention. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] During resistance welding of aluminum-nickel composite strips, the melting points of aluminum and nickel differ significantly (aluminum melting point 660℃, nickel melting point 1453℃). When the nickel layer melts, the temperature is much higher than that of aluminum. Simultaneously, the welding process is under pressure, and the compressed molten aluminum can splash, spark, and cause abnormalities such as incomplete welds. Furthermore, upon cooling, metal particles are generated, potentially leading to short circuits in the battery cell and even safety issues.

[0022] Example 1

[0023] Based on the above-mentioned defects and shortcomings of the existing technology, see [link to relevant documentation]. Figure 1-4 This embodiment describes a resistance welding process for a sodium-ion cylindrical battery. The aluminum-nickel composite strip tabs are joined to a nickel-plated steel shell using segmented resistance welding. The specific steps include:

[0024] First stage: Using a resistance welding device, the aluminum-nickel composite strip tab is heated to between the melting points of aluminum and nickel using a low current. At this time, the aluminum layer begins to melt, and the resistance welding device applies pressure to squeeze the molten aluminum liquid out from between the nickel layer of the tab and the nickel-plated layer of the steel shell. At this time, the two nickel sheets are in direct contact, while the molten aluminum liquid is squeezed to the area around the tab and then solidifies.

[0025] The second stage: The resistance welding device heats the nickel layer of the aluminum-nickel composite strip tab to melt using a set high current, so that the nickel layer of the tab fuses with the nickel plating surface of the nickel-plated steel shell.

[0026] It should be noted that since the aluminum has been extruded to the periphery of the electrode tab, it is no longer subjected to the pressure applied by the resistance welding device. Even if the aluminum is melted back into molten aluminum, there will be no problem of molten aluminum splashing. In addition, since the aluminum layer is expelled to the periphery, it will not affect the thermal fusion of the nickel layer, thus avoiding the problem of poor soldering.

[0027] In this embodiment of segmented resistance welding, the current of the first segment is relatively low, and the heat generated is small. This allows the aluminum to be melted without melting the nickel, thereby extruding the molten aluminum and enabling the second segment to achieve the purpose of directly fusing the nickel layer of the tab to the nickel layer of the nickel-plated steel shell.

[0028] In a specific example, the welding parameters of the resistance welding device in the first stage are as follows: adjustable welding pressure of 30-70N, low current of 1.2-1.8KA, and time of 4-8ms.

[0029] In a specific example, the welding parameters of the resistance welding device in the second stage are as follows: adjustable welding pressure of 30-70N, high current of 2.0-3.0KA, and time of 3-10ms.

[0030] It should be noted that the welding parameter ranges for the two stages mentioned above were determined through preliminary verification in this embodiment.

[0031] In this embodiment, the two welding processes are performed with different currents, welding pressures, and welding times. In the second stage of welding, it is necessary to determine whether there is any arcing. After the welding is completed, the tensile strength is tested to confirm that there is no incomplete weld.

[0032] In a specific example, the welding parameters of the resistance welding device in the first stage are: welding pressure of 52N, low current of 1.55KA, and time of 6ms.

[0033] In a specific example, the welding parameters of the resistance welding device in the second stage are: welding pressure of 52N, high current of 2.5KA, and time of 3.2ms.

[0034] When the first welding parameter is 52N 1.55KA 6ms and the second welding parameter is 52N 2.5KA 3.2ms, the resistance welding process of aluminum-nickel composite strip can be completed without arcing or incomplete welding. The current and time distribution during the welding process is as follows: Figure 1 As shown.

[0035] In a specific example, when the aluminum-nickel composite strip tab is welded to the nickel-plated steel shell, the aluminum layer of the aluminum-nickel composite strip tab is close to the nickel layer of the nickel-plated steel shell.

[0036] It should be noted that the aluminum layer of the aluminum-nickel composite strip tab is close to the nickel layer of the nickel-plated steel shell. When welding, the molten aluminum is located between the nickel layer of the aluminum-nickel composite strip tab and the nickel layer of the nickel-plated steel shell. At this time, applying pressure through the resistance welding device can reduce the probability of the extruded molten aluminum splashing due to pressure and can better extrude the molten aluminum to the area around the tab.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A resistance welding process for sodium-ion cylindrical batteries, characterized in that, The aluminum-nickel composite strip tabs are connected to the nickel-plated steel shell using segmented resistance welding, specifically including the following process: When the aluminum-nickel composite strip tab is welded to the nickel-plated steel shell, the aluminum layer of the aluminum-nickel composite strip tab is close to the nickel layer of the nickel-plated steel shell. In the first stage, a resistance welding device is used to heat the aluminum-nickel composite strip tab to between the melting point of aluminum and the melting point of nickel at a low current. At this time, the aluminum layer begins to melt, and at the same time, the resistance welding device applies pressure to squeeze the molten aluminum liquid out from between the nickel layer of the tab and the nickel-plated layer of the steel shell. At this time, the two nickel sheets are in direct contact, and the molten aluminum liquid is squeezed to the vicinity of the tab and then solidifies. The welding parameters of the resistance welding device in the first stage are as follows: the welding pressure is adjustable from 30 to 70 N, the low current is 1.2 to 1.8 kA, and the time is 4 to 8 ms. The second stage: The resistance welding device heats the nickel layer of the aluminum-nickel composite strip tab to melt with a set high current, so that the nickel layer of the tab is fused with the nickel plating surface of the nickel-plated steel shell. The welding parameters of the resistance welding device in the second stage are as follows: the welding pressure is adjustable from 30 to 70 N, the high current is 2.0 to 3.0 kA, and the time is 3 to 10 ms.

2. The resistance welding process for sodium-ion cylindrical batteries according to claim 1, characterized in that, The welding parameters of the resistance welding device in the first stage are: welding pressure of 52N, low current of 1.55KA, and time of 6ms.

3. The resistance welding process for sodium-ion cylindrical batteries according to claim 1, characterized in that, The welding parameters of the resistance welding device in the second stage are as follows: welding pressure of 52N, high current of 2.5KA, and time of 3.2ms.

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