Arc welding device for secondary battery and welding method using the same

Abstract

An arc welding device for a secondary battery according to one embodiment of the present application includes: an upper fixing portion in which a plurality of welding electrode units connected to one pole of a welding power source are provided; and a lower fixing portion provided to face the upper fixing portion across a welding object and connected to the other pole of the welding power source, wherein the upper fixing portion includes a first facing surface facing the welding object and concavely formed toward the welding object, and the lower fixing portion has a second facing surface facing the first facing surface and convexly formed corresponding to a concave shape of the first facing surface.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0022437, filed on February 19, 2021, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

[0003] This disclosure relates to an arc welding apparatus for secondary batteries and a welding method using the arc welding apparatus, and more specifically, to a welding apparatus and method for applying arc welding when welding electrode contacts and electrode leads of secondary batteries. Background Technology

[0004] Recently, due to the depletion of fossil fuels, rising energy prices, and increased concern about environmental pollution, the demand for eco-friendly alternative energy sources has become an indispensable factor in future life. Therefore, ongoing research into various power generation technologies such as nuclear, solar, wind, and tidal power, and the development of energy storage devices for more efficient utilization of energy generated in these ways, have attracted attention.

[0005] In particular, with technological advancements and the increasing demand for mobile devices, the demand for batteries as an energy source has increased rapidly. As a result, a great deal of research has been conducted on batteries that can meet various needs.

[0006] Typically, there is a high demand for lithium secondary batteries, such as lithium-ion batteries and lithium-ion polymer batteries, which have advantages such as high energy density, high discharge voltage, and high output stability.

[0007] Secondary batteries can also be classified according to the structure of the electrode assembly in which positive electrodes, negative electrodes, and a separator inserted between the positive and negative electrodes are stacked. Generally, examples include jelly roll type electrode assemblies, which have a structure in which elongated positive and negative electrodes are wound with a separator inserted between them, and stacked type electrode assemblies, in which multiple positive and negative electrodes cut into units of predetermined size are sequentially stacked with a separator inserted between them. Recently, to address the problems of jelly roll type and stacked type electrode assemblies, a stacked / folded type electrode assembly, a hybrid type of jelly roll and stacked type, has been developed. This stacked / folded type electrode assembly has a structure in which unit cells with predetermined units of positive and negative electrodes are stacked with a separator inserted between them, located on a separator membrane, and sequentially wound.

[0008] Furthermore, based on the shape of the casing, secondary batteries can be classified into cylindrical secondary batteries with electrode assemblies built into cylindrical casings, prismatic secondary batteries with electrode assemblies built into prismatic casings, and pouch-type secondary batteries with electrode assemblies built into pouch-type casings of laminated sheets.

[0009] In the case of widely used pouch-type secondary batteries, an electrode assembly in which the positive electrode, negative electrode, and a separator disposed between them are stacked is housed within a pouch-type casing. Here, multiple electrode tabs connected to each electrode are soldered to electrode leads and electrically connected to external components via exposed electrode leads.

[0010] When electrode contacts are joined to electrode leads, welding methods are typically used, specifically ultrasonic welding and laser welding. However, in the case of ultrasonic welding, fine metallic foreign matter can be generated due to friction with the oxide film during the welding process, and short-circuit defects can occur when this foreign matter adheres to the secondary battery. Furthermore, even in the case of laser welding, which has recently become widely used to avoid the disadvantages of ultrasonic welding, there is a problem of short-circuit failures due to spatter generated during welding, and as this spatter accumulates, frequent changes of fixtures or nozzles are required. Summary of the Invention

[0011] Technical issues

[0012] The purpose of this invention is to provide an arc welding apparatus for secondary batteries that can improve welding reliability while reducing welding costs and preventing spatter when welding electrode contacts and electrode leads of secondary batteries, as well as a welding method using the arc welding apparatus.

[0013] The problems to be solved by the present invention are not limited to those described above, and those skilled in the art will clearly understand from this specification and the accompanying drawings any problems not mentioned.

[0014] Technical solution

[0015] An arc welding apparatus for a secondary battery according to an exemplary embodiment of the present invention includes: an upper fixing part having a plurality of welding electrode units disposed therein and connected to one pole of a welding power source; and a lower fixing part having the lower fixing part facing the upper fixing part across an object to be welded and connected to another pole of the welding power source; wherein the upper fixing part includes a first facing surface that faces the object to be welded and is recessed toward the object to be welded, and the lower fixing part has a second facing surface that faces the first facing surface and is protruded in relation to the recessed shape of the first facing surface.

[0016] An electric arc can be generated between the plurality of welding electrode units and the lower fixing part by supplying the welding power source.

[0017] The first surface may include multiple arc holes corresponding to multiple welding electrode units.

[0018] The arc welding apparatus may further include: a first nozzle unit, which supplies inert gas into the interior of the upper fixed part.

[0019] A plurality of gas supply holes may be formed in the second facing surface of the lower fixing part, and the arc welding device may further include a second nozzle unit that supplies inert gas into the interior of the lower fixing part.

[0020] The objects to be welded can be the electrode contacts and electrode leads of the secondary battery.

[0021] The upper fixing part may include one or more materials selected from copper, copper-based alloys, ceramics and quartz.

[0022] The plurality of welding electrode units may include a plurality of tungsten electrodes.

[0023] As a welding method using the above-described arc welding apparatus for secondary batteries, another exemplary embodiment of the welding method according to the present invention includes: preparing an electrode assembly including a plurality of electrode tabs protruding to the outside; disposing the electrode tabs and electrode leads between the upper fixing portion and the lower fixing portion; attaching a first facing surface and a second facing surface to each other with respect to the electrode tabs and the electrode leads; and generating an arc between the welding electrode unit and the lower fixing portion to perform gas shielded tungsten arc welding (GTAW).

[0024] In performing GTAW, the base current supplied to the plurality of welding electrode units can range from 2A to 4A, and the peak current can range from 4A to 10A.

[0025] GTAW can be performed as pulse welding at frequencies of 2000Hz or higher.

[0026] Beneficial effects

[0027] According to an exemplary embodiment, an arc welding apparatus for secondary batteries is provided, which can improve welding reliability while reducing welding costs and generating spatter when welding electrode contacts and electrode leads of secondary batteries, and a welding method using the arc welding apparatus is also provided.

[0028] The effects of the present invention are not limited to those described above, and those skilled in the art will clearly understand from this specification and the accompanying drawings any effects not mentioned. Attached Figure Description

[0029] Figure 1a and Figure 1b This is a diagram illustrating a schematic structure of an arc welding apparatus for secondary batteries according to an exemplary embodiment of the present invention.

[0030] Figure 2 It is shown Figure 1a and Figure 1b An enlarged view of the structure of the lower fixing part. Detailed Implementation

[0031] Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings to enable those skilled in the art to practice them. The invention can be implemented in various different ways and is not limited to the examples described herein.

[0032] To describe the invention more clearly, parts irrelevant to the description may be omitted, and the same or similar parts may be indicated by the same reference numerals throughout the application.

[0033] Furthermore, for ease of illustration, the dimensions and thicknesses of each component shown in the accompanying drawings may be arbitrarily depicted; therefore, the invention is not necessarily limited to the exemplary embodiments shown in the drawings. In the drawings, for clarity, the thicknesses of individual layers, regions, etc., may be exaggerated. In the drawings, for ease of illustration, the thicknesses of some layers and regions may be exaggerated.

[0034] Furthermore, unless explicitly stated otherwise, the word “including” and variations such as “containing” or “comprising” will be understood to imply inclusion of the stated element but not exclusion of any other element.

[0035] Throughout the application, when referring to "in a plan view," it means viewing the target element from above, and when referring to "in a cross-sectional view," it means viewing the target element as a vertically cut section from the side.

[0036] In the following text, reference will be made to Figure 1a and Figure 1b as well as Figure 2 A welding apparatus for a secondary battery and a welding method using the welding apparatus are described according to an exemplary embodiment of the present invention.

[0037] Figure 1a and Figure 1b This is a diagram illustrating a schematic structure of an arc welding apparatus for secondary batteries according to an exemplary embodiment of the present invention. Figure 2 It is shown Figure 1a and Figure 1b An enlarged view of the structure of the lower fixing part.

[0038] Reference Figure 1a and Figure 1b as well as Figure 2 According to an exemplary embodiment of the present invention, the arc welding apparatus 100 for a secondary battery is a welding apparatus 100 for combining a plurality of electrode contacts 10 connected to the electrodes of an electrode assembly with electrode leads 20, and includes an upper fixing portion 120 and a lower fixing portion 130 provided with the electrode contacts 10 and electrode leads 20 inserted between them.

[0039] In particular, the arc welding apparatus 100 for secondary batteries is an apparatus for arc welding, not a structure used in related technologies for ultrasonic welding or laser welding to join electrode contacts 10 and electrode leads 20. Generally, arc welding, also known as gas-shielded tungsten arc welding, is a welding method that melts and joins substrates using the heat of an electric arc generated by a tungsten electrode. Here, because an inert gas such as Ar or He is used as the shielding gas, arc welding is also called tungsten inert gas (TIG) welding.

[0040] An arc welding apparatus 100 for a secondary battery according to an exemplary embodiment of the present invention allows the arc welding method to be applied to a welding method for joining electrode tabs 10 to electrode leads 20, in order to prevent the generation of spatter and foreign matter and damage to the battery.

[0041] The upper fixing portion 120 includes a plurality of welding electrode units 200 therein, each connected to one pole of a welding power source (not shown). The welding electrode units 200 may be tungsten electrodes and may be disposed inside the upper fixing portion 120 such that their ends communicate with the outside through arc holes 122 formed in the first facing surface 121 of the upper fixing portion 120. Power can be supplied through the welding electrode units 200 to generate an electric arc AR. The tungsten electrodes constituting the welding electrode units 200 may include zirconium oxide-based or lanthanum-based tungsten, but are not particularly limited thereto.

[0042] The first facing surface 121 faces the object to be welded, i.e., the electrode lead 20 and the electrode tab 10 are recessed and can be formed below the upper fixing portion 120. The first facing surface 121 can be in close contact with the second facing surface 131 of the lower fixing portion 130, which will be described below, to reliably fix the electrode lead 20 and the electrode tab 10 to be welded during welding and to minimize the gap between them.

[0043] Furthermore, the upper fixing portion 120 may be formed in the shape of a chamber in which the welding electrode unit 200 is disposed, and the upper fixing portion 120 may also include a first nozzle portion 123 for supplying inert gas IG to its upper portion. The inert gas IG is supplied through the first nozzle portion 123 and passes through the interior of the upper fixing portion 120 to serve as a shielding gas during welding through the aforementioned arc hole 122. As a shielding gas, a single gas or a mixture of gases selected from Ar, He, N2, etc., may be used, but there are no particular limitations. When the inert gas IG is supplied to the welding portion through the upper fixing portion 120 during welding, the welding portion is prevented from contacting oxygen. In an exemplary embodiment of the present invention, this structure can be simply provided by the upper fixing portion 120.

[0044] The upper fixing part 120 may include one or more materials selected from copper, copper-based alloys, ceramics, and quartz. Therefore, even if the heat generated by the arc increases during arc welding, it can be cooled quickly, thus enabling repeated work, and due to the heat resistance of the material, it can be suitably used for arc welding.

[0045] A lower fixing part 130, connected to the other pole of the welding power source and separated from the object to be welded, is provided below the upper fixing part 120. The lower fixing part 130 includes a second facing surface 131, which faces the first facing surface 121 and is formed in a protruding manner corresponding to the concave shape of the first facing surface 121. On the second facing surface 131, the electrode contacts 10 and electrode leads 20 to be welded are provided. The arrangement direction of the electrode contacts 10 and electrode leads 20 is not particularly limited. That is, as... Figure 1a As shown, the electrode tabs 10 and electrode leads 20 can be arranged such that their protruding shapes correspond to each other in the length direction, or as... Figure 1b As shown, the electrode tabs 10 and electrode leads 20 can be arranged in the width direction. Furthermore, even if the shape of each of the electrode tabs 10 and electrode leads 20 is bent to correspond to the shape of the contact surfaces of the upper fixing part 120 and the lower fixing part 130 during the welding process, additional shaping can be performed through subsequent pressing processes to achieve an appropriate shape, so that such bending does not affect the welding quality or performance of the final product.

[0046] The electrode contacts 10 and electrode leads 20 to be welded can be disposed on the second facing surface 131. The first facing surface 121 of the upper fixing part 120 can be in close contact with the second facing surface 131 to perform arc welding. Therefore, the gap between the electrode contacts 10 and electrode leads 20 can be minimized, and the electrode contacts 10 and electrode leads 20 can be stably supported during welding. Thus, arc welding can be easily applied to the electrode contacts 10 and electrode leads 20.

[0047] In addition, such as Figure 2As shown, a plurality of gas supply holes 132 may be further formed on the second facing surface 131. Furthermore, a second nozzle portion 133 communicating internally with the lower fixing portion 130 may be provided to supply inert gas. Inert gas can be supplied through the gas supply holes 132 to further improve adhesion between the objects to be welded and to prevent them from contacting oxygen during welding.

[0048] The lower fixing portion 130 may comprise copper or a copper-based alloy with good thermal conductivity. Therefore, rapid cooling can be achieved, but the invention is not limited thereto.

[0049] As described above, when using the welding apparatus 100 for secondary batteries according to an exemplary embodiment of the present invention, arc welding that does not cause spatter can be applied to the combination of the electrode contacts 10 and the electrode leads 20 of the secondary battery. As a result, the welding apparatus can be simplified without the need to add additional devices for removing spatter (such as suction devices), and secondary batteries can be manufactured without causing short-circuit defects due to spatter. Furthermore, the welding electrode unit is included in the upper fixing part, which itself can be used as a fixing fixture together with the lower fixing part, and the inert gas IG can also be easily supplied through the upper fixing part. Therefore, the cost of constructing the corresponding facilities can be lower, thereby reducing the overall equipment investment cost and suppressing the occurrence of defects, thus significantly improving process efficiency.

[0050] In another exemplary embodiment of the present invention, a welding method using the welding apparatus for secondary batteries described above is provided.

[0051] That is, in the electrode assembly in which the positive electrode, the negative electrode, and the diaphragm disposed between the positive and negative electrodes are stacked, a plurality of electrode contacts and electrode leads that are connected to the corresponding electrodes and protrude outward are aligned and disposed on the upper fixing part 120 and the lower fixing part 130. Then, the first facing surface 121 of the upper fixing part 120 and the second facing surface 131 of the lower fixing part 130 are in close contact through the electrode contacts 10 and the electrode leads 20.

[0052] At this time, as described above, since the first facing surface 121 has a concave shape and the second facing surface 131 has a corresponding convex shape, the adhesion between the electrode lead 20 and the electrode tab 10 disposed between them can be improved, and the electrode lead 20 and the electrode tab 10 can be fixed more stably.

[0053] Subsequently, power is supplied to generate an electric arc AR between the welding electrode unit 200 and the lower fixing part 130, and welding (i.e., gas shielded tungsten arc welding) is performed by the generated electric arc AR. That is, with the upper fixing part 120 in close contact with the electrode lead 20 and the electrode tab 10, the welding electrode unit 200 is close to the object to be welded, and in this state, power is supplied to generate an electric arc AR, so that the substrate can be melted and welding is performed.

[0054] At this time, the supplied power may have a base current in the range of 2A to 4A, and a peak current in the range of 4A to 10A. If the current value is less than this range, welding may not be sufficiently performed, and if the current value is greater, damage to the electrode leads 20 and electrode contacts 10 may occur. In particular, in an exemplary embodiment of the invention, by supplying a relatively small base current while simultaneously supplying a large peak current, sufficient welding can be performed without damaging the electrode leads 20 and electrode contacts 10.

[0055] Furthermore, GTAW can perform pulse welding at frequencies of 2000 Hz or higher. Therefore, welding can be performed without damaging the electrode leads 20 and electrode contacts 10.

[0056] As described above, according to an exemplary embodiment of the present invention, arc welding can be applied to the welding process of combining electrode tabs 10 with electrode leads 20 during the manufacturing of secondary batteries, so that welding with high reliability can be performed even with simple facilities without causing spatter, thereby reducing the defect rate during manufacturing and reducing process costs.

[0057] Although the invention has been described in conjunction with exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0058] [Reference Marker Explanation]

[0059] 100: Arc welding equipment for secondary batteries

[0060] 200: Welding electrode unit

[0061] 120: Upper fixing part

[0062] 130: Lower fixed part

[0063] 121: First face on the surface

[0064] 131: Second face on surface

[0065] 10: Electrode contacts

[0066] 20: Electrode leads.

Claims

1. An arc welding apparatus for secondary batteries, the arc welding apparatus comprising: The upper fixing part is provided with a plurality of welding electrode units connected to one pole of the welding power source; as well as The lower fixing part is configured to face the upper fixing part across the object to be welded, and is connected to the other pole of the welding power source; The upper fixing part includes a first facing surface that faces the object to be welded and has a recessed shape formed recessed towards the object to be welded. The lower fixing part has a second facing surface, which faces the first facing surface and has a protruding shape that is formed in a protruding manner corresponding to the recessed shape of the first facing surface. The first facing surface can be in close contact with the second facing surface.

2. The arc welding apparatus according to claim 1, wherein: An electric arc is generated between the plurality of welding electrode units and the lower fixing part by supplying the welding power source.

3. The arc welding apparatus according to claim 1, wherein: The first surface includes a plurality of arc holes corresponding to a plurality of welding electrode units.

4. The arc welding apparatus according to claim 1, further comprising: The first nozzle unit supplies inert gas into the interior of the upper fixed part.

5. The arc welding apparatus according to claim 1, wherein: A plurality of gas supply holes are formed in the second facing surface of the lower fixing part. The arc welding apparatus further includes a second nozzle unit, which supplies inert gas into the interior of the lower fixed part.

6. The arc welding apparatus according to claim 1, wherein: The objects to be welded are the electrode contacts and electrode leads of the secondary battery.

7. The arc welding apparatus according to claim 1, wherein: The upper fixing part includes one or more materials selected from copper, copper-based alloys, ceramics and quartz.

8. The arc welding apparatus according to claim 1, wherein: The plurality of welding electrode units include a plurality of tungsten electrodes.

9. A welding method using an arc welding apparatus for secondary batteries according to any one of claims 1 to 8, the welding method comprising: Prepare an electrode assembly, the electrode assembly including a plurality of electrode tabs protruding to the outside; The electrode contacts and electrode leads are disposed between the upper fixing part and the lower fixing part; The first and second facing surfaces are attached to each other with the electrode contacts and the electrode leads in between; as well as An electric arc is generated between the welding electrode unit and the lower fixing part to perform gas-shielded tungsten inert gas welding.

10. The welding method according to claim 9, wherein: In performing gas-shielded tungsten inert gas welding, the base current supplied to the plurality of welding electrode units ranges from 2A to 4A, and the peak current ranges from 4A to 10A.

11. The welding method according to claim 10, wherein: Gas-shielded tungsten inert gas welding is performed as pulse welding with a frequency of 2000 Hz or higher.

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