Ultrasonic cleaning device and ultrasonic cleaning method

Abstract

An ultrasonic cleaning device according to one embodiment of the present invention comprises: a cleaning housing part including a cleaning solution for immersing a welding assist jig that assists in welding joints included in a battery cell; and an ultrasonic generating part that applies ultrasonic waves to the cleaning solution to vibrate the cleaning solution in a spherical wave pattern, wherein metal foreign matter attached to the welding assist jig is removed by the cleaning solution.

Description

Technology Field

[0001] The present invention relates to an ultrasonic cleaning device and an ultrasonic cleaning method, and more specifically, to an ultrasonic cleaning device and an ultrasonic cleaning method for cleaning a welding assist jig that assists in forming a welded part included in a battery cell through ultrasound. Background Technology

[0002] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. In particular, secondary batteries are attracting significant interest as an energy source not only for mobile devices such as mobile phones, digital cameras, laptops, and wearable devices, but also for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles.

[0003] These secondary batteries are classified according to the shape of the battery case into cylindrical and prismatic batteries, in which the electrode assembly is embedded in a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is embedded in a pouch-type case made of an aluminum laminate sheet. Here, the electrode assembly embedded in the battery case is a power generation element capable of charging and discharging, consisting of a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode. It is classified into a jelly-roll type, which is wound with a separator interposed between long sheet-type positive and negative electrodes coated with active material, and a stack type, in which a plurality of positive and negative electrodes are sequentially stacked with a separator interposed between them.

[0004] Among these, pouch-type batteries, in particular those with a structure in which a stacked or stacked / folded electrode assembly is embedded in a pouch-type battery case made of aluminum laminate sheets, are seeing a gradual increase in usage due to reasons such as low manufacturing costs, small weight, and easy deformation.

[0005] FIG. 1 is a top view of a battery cell. FIG. 2 is a cross-sectional view taken along the a-a' axis in FIG. 1. Referring to FIG. 1 and FIG. 2, the battery cell (10) includes a battery case (30) in which an electrode assembly (20) is mounted in a storage portion (31R, 32R) and a sealing portion (31S, 32S) is formed with a structure in which the outer periphery is sealed by heat fusion. The battery case (30) may include an upper case (31) and a lower case (32), and the upper sealing portion (31S) of the upper case (31) and the lower sealing portion (32S) of the lower case (32) are heat-fused to each other so that the battery case (30) is sealed. The battery cell (10) includes an electrode lead (40) that protrudes outwardly from the battery case (30) via sealing portions (31S, 32S), and a lead film (50) is positioned between the upper and lower portions of the electrode lead (40) and the sealing portions (31S, 32S).

[0006] In the battery cell (10), the electrode lead (40) is electrically connected to a plurality of electrode tabs (25) included in the electrode assembly (20). Here, the electrode lead (40) and the plurality of electrode tabs (25) may be welded together by forming a weld joint at a location where they come into contact with each other. During the welding process between the electrode tabs (25) and the electrode lead (40), welding auxiliary parts are arranged to bring the electrode tabs (25) and the electrode lead (40) closer together, thereby increasing the reliability of the weld joint between the electrode tabs (25) and the electrode lead (40).

[0007] However, metal foreign matter, such as weld beads, may adhere to the welding auxiliary parts during the aforementioned welding process, and this metal foreign matter may detach into the battery cells during subsequent production, causing problems such as quality degradation. In this case, the welding auxiliary parts can be replaced periodically, or the metal foreign matter attached to them can be physically removed by methods such as cutting; however, there is a problem in that productivity is reduced due to the time required for such replacement or removal.

[0008] Accordingly, there is a growing need to develop an ultrasonic cleaning device capable of rapidly and effectively removing metallic foreign matter generated on welding auxiliary parts during the welding process between the electrode tab and the electrode lead. The problem to be solved

[0009] The problem to be solved by the present invention is to provide an ultrasonic cleaning device and an ultrasonic cleaning method for cleaning a welding assist jig that assists in forming a welded part included in a battery cell through ultrasound.

[0010] The problems that the present invention aims to solve are not limited to those described above, and problems not mentioned will be clearly understood by those skilled in the art from this specification and the attached drawings. means of solving the problem

[0011] An ultrasonic cleaning device according to one embodiment of the present invention comprises: a cleaning housing part including a cleaning solution for immersing a welding assist jig that assists in welding joints included in a battery cell; and an ultrasonic generating part that applies ultrasonic waves to the cleaning solution to vibrate the cleaning solution in a spherical wave pattern, wherein metal foreign matter attached to the welding assist jig is removed by the cleaning solution.

[0012] The above ultrasonic generating unit generates ultrasonic waves having a frequency of 10 kHz or more to 50 kHz or less, and can vibrate the cleaning solution under ultrasonic frequency fluctuations of 100 Hz / ms or more to 2000 Hz / ms or less.

[0013] The above-mentioned welded joint is formed between a plurality of electrode tabs and electrode leads of an electrode assembly included in the battery cell, and the above-mentioned welding assist jig can bring the plurality of electrode tabs and the electrode leads into close contact.

[0014] The above welding auxiliary jig may be made of SKH51 (High speed tool steels), SKD11 (cold alloy tool steel), SUS420 (martensite stainless steel), SUS430 (ferritic phosphorus stainless steel), or SUS304 (austenitic stainless steel).

[0015] The electrode tab is an anode tab made of aluminum (Al), the cleaning solution is a solution for removing aluminum from the welding assist jig, and the metal foreign matter may contain residues of aluminum (Al).

[0016] The above cleaning solution may be an aqueous solution containing at least one of potassium hydroxide and sodium hydroxide.

[0017] The above ultrasonic generator can vibrate the cleaning solution for a time of 1 minute or more to 5 minutes or less at a temperature of 50 degrees or more to 75 degrees or less.

[0018] The above electrode tab is a negative electrode tab made of copper (Cu), the above cleaning solution is a solution for removing copper from the above welding assist jig, and the above metallic foreign matter may contain residue of copper (Cu).

[0019] The above cleaning solution may be an aqueous solution containing 5% or more by weight and less than 10% by weight of nitric acid.

[0020] The above ultrasonic generator can vibrate the cleaning solution for a time of 10 minutes or more to 40 minutes or less at a temperature of 50 degrees or more to 70 degrees or less.

[0021] An ultrasonic cleaning method according to another embodiment of the present invention comprises: an immersion step of immersing a welding assisting jig that assists a welding joint included in a battery cell into a cleaning housing; and a foreign matter removal step in which an ultrasonic generator applies ultrasonic waves to the cleaning liquid to vibrate the cleaning liquid in a spherical wave pattern, wherein in the foreign matter removal step, metal foreign matter attached to the welding assisting jig can be removed by the cleaning liquid, the welding joint is formed between a plurality of electrode tabs and electrode leads of an electrode assembly included in the battery cell, and the welding assisting jig can bring the electrode tabs and the electrode leads into close contact.

[0022] In the above foreign matter removal step, the ultrasonic generator generates ultrasonic waves having a frequency of 10 kHz or more to 50 kHz, and can vibrate the cleaning solution under an ultrasonic frequency variation of 100 Hz / ms or more to 2000 Hz / ms or less.

[0023] An ultrasonic cleaning method further comprising a rinsing and drying step for rinsing and drying the welding auxiliary jig removed from the cleaning housing after the above foreign matter removal step.

[0024] The electrode tab is an anode tab made of aluminum (Al), and the cleaning solution is an aqueous solution containing at least one of potassium hydroxide and sodium hydroxide, and in the foreign matter removal step, the ultrasonic generator can vibrate the cleaning solution for a time of 1 minute or more to 5 minutes or less at a temperature of 50 degrees or more to 75 degrees or less.

[0025] The electrode tab is a cathode tab made of copper (Cu), and the cleaning solution is an aqueous solution containing 5% by weight or more to less than 10% by weight of nitric acid, and in the foreign matter removal step, the ultrasonic generator can vibrate the cleaning solution for a time of 10 minutes or more to 40 minutes or less at a temperature of 50 degrees or more to 70 degrees or less. Effects of the invention

[0026] The ultrasonic cleaning device and ultrasonic cleaning method according to an embodiment of the present invention can effectively remove metallic foreign matter from a welding assist jig generated during the welding process by using ultrasound to a welding assist jig that assists in forming a weld included in a battery cell.

[0027] The effects of the present invention are not limited to the effects described above, and unmentioned effects will be clearly understood by those skilled in the art from this specification and the accompanying drawings. Brief explanation of the drawing

[0028] Figure 1 is a top view of a battery cell. Figure 2 is a cross-sectional view taken along the a-a' axis in Figure 1. FIG. 3 is a drawing showing an ultrasonic cleaning device according to the present embodiment. FIGS. 4 and FIGS. 5 are drawings showing a welding auxiliary jig to be cleaned of the ultrasonic cleaning device of FIG. 3. Figure 6 is a drawing showing the state of the welding auxiliary jig of Figure 5 before metal foreign matter is cleaned by the ultrasonic cleaning device of Figure 3. Specific details for implementing the invention

[0029] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0030] To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0031] Furthermore, throughout the specification, when a part is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0032] FIG. 3 is a drawing showing an ultrasonic cleaning device according to the present embodiment.

[0033] Referring to FIGS. 2 and 3, an ultrasonic cleaning device (1000) according to one embodiment of the present invention comprises: a cleaning housing part (1100) including a cleaning liquid (1300) for immersing a welding assist jig (100) that assists in welding joints included in a battery cell (10); and an ultrasonic generating part (1200) that applies ultrasonic waves to the cleaning liquid (1300) to vibrate the cleaning liquid (1300) in a spherical wave pattern.

[0034] The cleaning housing portion (1100) may be a case member with an open top. Although not shown in FIG. 3, the top of the cleaning housing portion (1100) may be covered by a separate member. The cleaning housing portion (1100) may have a size that can accommodate a welding assist jig (100).

[0035] The cleaning housing portion (1100) can accommodate a cleaning solution (1300). The amount of cleaning solution (1300) accommodated in the cleaning housing portion (1100) may be sufficient to immerse the entire welding assist jig (100).

[0036] The ultrasonic generator (1200) is located at the bottom of the cleaning housing (1100) and can generate ultrasonic waves that vibrate the cleaning liquid (1300) contained within the cleaning housing (1100) in a spherical wave pattern. However, the location of the ultrasonic generator (1200) is not limited to this, and any location capable of applying ultrasonic waves to the cleaning liquid (1300) contained within the cleaning housing (1100) may be applied to this embodiment. At this time, the spherical wave pattern can be achieved by generating ultrasonic waves while continuously varying the ultrasonic frequency.

[0037] The ultrasonic generating unit (1200) may generate a mechanical signal by vibrating a plurality of vibrators contained within the ultrasonic generating unit (1200). As this mechanical signal is transmitted to the medium of the cleaning liquid (1300), the sound pressure of the cleaning liquid (1300) changes, and a cavitation phenomenon may occur. Here, the cavitation phenomenon of the cleaning liquid (1300) can weaken the surface tension of the foreign matter surface, and the turbulence generated by cavitation can continuously supply clean cleaning liquid to the foreign matter surface, which can be effective for peeling and removing foreign matter.

[0038] The ultrasonic generating unit (1200) can generate ultrasonic waves having a frequency of 10 kHz or more and 50 kHz or less. For example, the ultrasonic generating unit (1200) can generate ultrasonic waves having a frequency of 25 kHz to 40 kHz. More preferably, the ultrasonic generating unit (1200) can generate ultrasonic waves having a frequency of 25 kHz.

[0039] Accordingly, in the ultrasonic cleaning device (1000) according to the present embodiment, the ultrasonic generating unit (1200) generates ultrasonic waves having a frequency of 25 kHz to 40 kHz in the cleaning liquid, thereby effectively removing foreign matter having a size of 2 µm or more to 50 µm or less, which is a metal foreign matter generated during a general battery cell welding process.

[0040] The ultrasonic generating unit (1200) can vibrate the cleaning solution (1300) under ultrasonic frequency fluctuations of 100 Hz / ms or more to 2000 Hz / ms or less. Here, vibration may mean a sweep that continuously varies the oscillation frequency of the ultrasonic waves at a predetermined speed.

[0041] Accordingly, in the ultrasonic cleaning device (1000) according to the present embodiment, the ultrasonic generating unit (1200) can cause the cleaning liquid (1300) to vibrate in a spherical wave pattern by the variation of the ultrasonic frequency, and the welding assist jig (100) can be uniformly cleaned through the cleaning liquid (1300) vibrating in a spherical wave pattern. In particular, as the cleaning liquid (1300) contained in the cleaning housing unit (1100) vibrates in a spherical wave pattern, the sound pressure uniformity can be improved, and effective cleaning can be performed even at a location separated from the center of the cleaning housing unit (1100) to the periphery.

[0042] In contrast, if the ultrasonic generator (1200) vibrates the cleaning liquid (1300) without frequency variation or under frequency variation of less than 100 Hz / ms, a standing wave problem may occur in part of the cleaning liquid (1300), and the cleaning of the welding assist jig (100) may be poor or the welding assist jig (100) may be damaged. In addition, if the ultrasonic generator (1200) vibrates the cleaning liquid (1300) under frequency variation of more than 2000 Hz / ms, various types of frequencies may be generated, and the cleaning power applied by the cleaning liquid (1300) to the welding assist jig (100) may be reduced.

[0043] FIGS. 4 and FIGS. 5 are drawings showing a welding auxiliary jig, which is the object to be cleaned by the ultrasonic cleaning device of FIG. 3. FIGS. 6 is a drawing showing the state of the welding auxiliary jig of FIG. 5 before metal foreign matter is cleaned by the ultrasonic cleaning device of FIG. 3.

[0044] Referring to FIGS. 4 and 5, the welding assist jig (100) may include a main body (110) and a central part (120) located on the center plane of the main body (110). The central part (120) may have an insertion part (130) formed therein, into which a portion requiring welding between components included in a battery cell can be inserted. The central part (120) may have a shape protruding from the main body (110) as shown in FIGS. 4 and 5, but this is an exemplary shape, and various other shapes may also be included in this embodiment.

[0045] For example, the welding assist jig (100) may be made of SKH51 (High speed tool steels), SKD11 (cold alloy tool steel), SUS420 (martensite stainless steel), SUS430 (ferritic-phosphorus stainless steel), or SUS304 (austenitic stainless steel). However, it is not limited thereto, and any material that does not melt during welding and can stably support the area requiring welding may be included in this embodiment.

[0046] More specifically, the welded joint may be formed between a plurality of electrode tabs (25) and electrode leads (40) of an electrode assembly (20) included in a battery cell (10), and a welding assist jig (100) may bring the plurality of electrode tabs (25) and electrode leads (40) into close contact. That is, with the plurality of electrode tabs (25) and electrode leads (40) inserted into the insertion part (130) of the welding assist jig (100), the welding assist jig (100) may bring the electrode tabs (25) and electrode leads (40) into close contact with each other.

[0047] Referring to FIG. 6, in a welding assist jig (100), metal foreign matter (135), such as a weld bead generated during the welding process, may be attached to the inside and surroundings of the insertion part (130). The ultrasonic cleaning device (1000) according to the present embodiment can remove the metal foreign matter (135) attached to the welding assist jig (100) through a cleaning solution (1300).

[0048] Referring to FIG. 2, the electrode tab (25) may be an anode tab made of aluminum (Al) or a cathode tab made of copper (Cu). Here, the metal foreign material (135) may be a residue containing aluminum (Al) or copper (Cu).

[0049] In the ultrasonic cleaning device (1000) according to the present embodiment, the cleaning solution (1300) can be set differently depending on the type of electrode tab (25) that is in close contact with the welding assist jig (100).

[0050] In the case where the electrode tab (25) is an anode tab made of aluminum (Al), the cleaning solution (1300) may be a solution for removing aluminum from the welding aid jig (100). More specifically, the cleaning solution (1300) may be a strongly alkaline solution for dissolving aluminum attached to the welding aid jig (100). In particular, when the electrode tab (25) is made of aluminum, the entire amount can be removed in a short time because it can be dissolved by the cleaning solution (1300).

[0051] For example, the cleaning solution (1300) may be an aqueous solution containing at least one of potassium hydroxide and sodium hydroxide. Here, the cleaning solution (1300) may be an aqueous solution containing 5% by weight or more to 10% by weight or less of potassium hydroxide and / or sodium hydroxide. Additionally, the cleaning solution (1300) may be an aqueous solution containing 0.1% by weight or more to 5% by weight or less of potassium hydroxide and 0.1% by weight or more to 5% by weight or less of sodium hydroxide. Here, potassium hydroxide reacts with aluminum according to reaction formula 1 and sodium hydroxide reacts with aluminum according to reaction formula 2, respectively, to remove aluminum attached to the welding assist jig (100).

[0052] KOH + Al + H2O → KAlO2 + 1.5H2 (Reaction Equation 1)

[0053] NaOH + Al + H2O → NaAlO2 + 1.5H2 (Reaction Equation 2)

[0054] As another example, the cleaning solution (1300) may be an aqueous solution containing a nonionic and / or anionic surfactant in addition to potassium hydroxide and sodium hydroxide. Here, the cleaning solution (1300) may be an aqueous solution containing a nonionic and / or anionic surfactant in an amount of 0.1% by weight or more to 10% by weight or less. Additionally, the cleaning solution (1300) may be an aqueous solution containing a nonionic surfactant in an amount of 0.1% by weight or more to 5% by weight or less and an anionic surfactant in an amount of 0.1% by weight or more to 5% by weight or less.

[0055] At this time, the ultrasonic generating unit (1200) can vibrate the cleaning solution (1300) for a period of time from 1 minute to 5 minutes at a temperature of 50 degrees or more to 75 degrees or less.

[0056] However, if the cleaning time by the ultrasonic cleaning device (1000) exceeds 5 minutes, the welding assist jig (100) may be damaged by the cleaning solution (1300) containing a strong alkaline solution. Conversely, if the cleaning time by the ultrasonic cleaning device (1000) is less than 1 minute, the reaction between the aluminum attached to the welding assist jig (100) and the cleaning solution (1300) may not occur sufficiently.

[0057] In addition, if ultrasonic waves are generated at a temperature exceeding 75 degrees Celsius in the ultrasonic generating unit (1200), the reactivity of the cleaning solution (1300) increases, which may cause problems such as damage to the welding assist jig (100) or a reverse reaction. Furthermore, in this case, there is a problem that the temperature of the cleaning solution (1300) becomes excessively high, causing it to vaporize and increase in concentration in a short period of time, so that it is classified as a hazardous substance and cannot be used in actual industrial fields.

[0058] Conversely, if the ultrasonic waves are generated at a temperature of less than 50 degrees Celsius in the ultrasonic generating unit (1200), the reaction between the aluminum attached to the welding assist jig (100) and the cleaning liquid (1300) may not occur sufficiently or the reaction speed may be excessively low.

[0059] Accordingly, in the ultrasonic cleaning device (1000) according to the present embodiment, when a welding assist jig (100) is in close contact with a plurality of anode tabs and electrode leads (40) made of aluminum, the ultrasonic cleaning device (1000) according to the present embodiment can effectively remove metal foreign matter (135) attached to the welding assist jig (100).

[0060] Additionally, if the electrode tab (25) is a negative tab made of copper (Cu), the cleaning solution (1300) may be a solution for removing copper from the welding aid jig (100). More specifically, the cleaning solution (1300) may be a solution for reducing copper attached to the welding aid jig (100) to copper nitrate.

[0061] For example, the cleaning solution (1300) may be an aqueous solution containing nitric acid. Here, for example, the cleaning solution (1300) may be an aqueous solution containing 5% by weight or more and less than 10% by weight of nitric acid. In particular, since a concentration of pure nitric acid of 10% by weight or more can be classified as a hazardous substance, the cleaning solution (1300) may contain less than 10% by weight of nitric acid. Here, the nitric acid can react with copper according to reaction formula 3 and / or reaction formula 4, respectively, to remove copper attached to the welding aid jig (100).

[0062] 2Cu + 10HNO3→ 2Cu(NO3)2+ 4H2O + 5NO2 (Scheme 3)

[0063] 3Cu + 8HNO3→ 3Cu(NO3)2+ 4H2O + 2NO (Scheme 4)

[0064] As another example, the cleaning solution (1300) may be an aqueous solution containing phosphoric acid in addition to nitric acid. Here, the cleaning solution (1300) may be an aqueous solution containing 5% by weight or more to 10% by weight or less of phosphoric acid.

[0065] As another example, the cleaning solution (1300) may be an aqueous solution containing a surfactant in addition to nitric acid. Here, the cleaning solution (1300) may be an aqueous solution containing 0.1% by weight or more to 5% by weight or less of a nonionic and / or anionic surfactant.

[0066] At this time, the ultrasonic generating unit (1200) can vibrate the cleaning solution (1300) for a period of time from 10 minutes to 40 minutes at a temperature of 50 degrees or more to 70 degrees or less.

[0067] In particular, when the electrode tab (25) is made of copper, some of the copper nitrate obtained by the reaction between the copper attached to the welding aid jig (100) and the cleaning solution (1300) may settle at the bottom of the cleaning housing part (1100). That is, when the electrode tab (25) is made of copper, a relatively longer time may be required compared to when the electrode tab (25) is made of aluminum.

[0068] However, if the cleaning time by the ultrasonic cleaning device (1000) exceeds 40 minutes, the welding assist jig (100) may be damaged by the cleaning solution (1300) containing an acidic solution. Conversely, if the cleaning time by the ultrasonic cleaning device (1000) is less than 10 minutes, the reaction between the copper attached to the welding assist jig (100) and the cleaning solution (1300) may not occur sufficiently.

[0069] In addition, if ultrasonic waves are generated at a temperature of more than 70 degrees Celsius from the ultrasonic generating unit (1200), the reactivity of the cleaning solution (1300) increases, and damage to the welding assist jig (100) may occur. Conversely, if ultrasonic waves are generated at a temperature of less than 50 degrees Celsius from the ultrasonic generating unit (1200), the reaction between the copper attached to the welding assist jig (100) and the cleaning solution (1300) may not occur sufficiently.

[0070] If the electrode tab (25) is made of copper, the degree of damage to the welding aid jig (100) due to the acidity of the cleaning solution (1300) can be minimized by considering additional processes or devices. For example, after some of the copper attached to the welding aid jig (100) is cleaned in an ultrasonic cleaning device (1000), the remaining copper attached to the welding aid jig (100) can be effectively removed by additionally undergoing a high-temperature ultrasonic rinsing process using water.

[0071] Accordingly, in the ultrasonic cleaning device (1000) according to the present embodiment, when a welding assist jig (100) brings into close contact with a plurality of cathode tabs made of copper and electrode leads (40), the ultrasonic cleaning device (1000) according to the present embodiment can effectively remove metal foreign matter (135) attached to the welding assist jig (100).

[0073] Hereinafter, an ultrasonic cleaning method according to another embodiment of the present invention will be described.

[0074] Referring to FIGS. 2 and 3, an ultrasonic cleaning method according to another embodiment of the present invention comprises: an immersion step of immersing a welding assist jig (100) that assists in welding a battery cell (10) into a cleaning housing part (1100); and a foreign matter removal step in which an ultrasonic generator (1200) applies ultrasonic waves to a cleaning liquid (1300) to vibrate the cleaning liquid (1300) in a spherical wave pattern, wherein in the foreign matter removal step, metal foreign matter attached to the welding assist jig (100) can be removed by the cleaning liquid (1300), and the welding joint is formed between a plurality of electrode tabs (25) and electrode leads (40) of an electrode assembly (20) included in the battery cell (10), and the welding assist jig (100) can bring the electrode tabs (25) and electrode leads (40) into close contact.

[0075] In the above foreign matter removal step, the ultrasonic generating unit (1200) generates ultrasonic waves having a frequency of 10 kHz or more to 50 kHz or less, and can vibrate the cleaning liquid (1300) under ultrasonic frequency fluctuations of 100 Hz / ms or more to 2000 Hz / ms or less.

[0076] After the above foreign matter removal step, a rinsing and drying step may be further included for rinsing and drying the welding assist jig (100) removed from the cleaning housing part (1100). Here, the rinsing and drying step may be a step of high-temperature ultrasonic cleaning using water and then drying.

[0077] The electrode tab (25) is an anode tab made of aluminum (Al), and the cleaning solution (1300) is an aqueous solution containing at least one of potassium hydroxide and sodium hydroxide, and in the foreign matter removal step, the ultrasonic generating unit (1200) can vibrate the cleaning solution (1300) for a time of 1 minute or more to 5 minutes or less at a temperature of 65 degrees or more to 75 degrees or less.

[0078] The electrode tab (25) is a negative electrode tab made of copper (Cu), and the cleaning solution (1300) is a solution made of an aqueous solution containing 5% by weight or more to less than 10% by weight of nitric acid, and in the foreign matter removal step, the ultrasonic generating unit (1200) can vibrate the cleaning solution (1300) for a time of 10 minutes or more to 20 minutes or less at a temperature of 50 degrees or more to 60 degrees or less.

[0079] Accordingly, the ultrasonic cleaning method according to the present embodiment can effectively remove metal foreign matter (135) attached to the welding assist jig (100).

[0081] The content of the present invention is explained below through more specific embodiments, but the following embodiments are intended to illustrate the invention and the scope of the invention is not limited thereto.

[0083] <Example 1>

[0084] An electrode assembly in which a cathode, an anode, and a separator interposed between the cathode and the anode are sequentially laminated was manufactured through a general lamination process. Here, the cathode is made of graphite, the anode is made of nickel-cobalt-manganese (NCM), and the separator is made of polyethylene (PE). Here, the anode tab attached to the anode is aluminum, and the cathode tab attached to the cathode is copper (Cu).

[0085] The welding assist jig is a laser mask made of SKH51 (high-speed steel), and it brings multiple anode tabs and electrode leads included in the manufactured electrode assembly into close contact, welding the spaces between the multiple anode tabs and electrode leads to which the welding jig is in contact multiple times. After the welding process, aluminum residue contained in the anode tabs is attached to the welding assist jig.

[0087] <Example 2>

[0088] A welding assist jig can be manufactured in the same manner as Example 1, except that a plurality of cathode tabs and electrode leads included in the manufactured electrode assembly are in close contact, and copper residue included in the cathode tabs is attached to the welding assist jig after the welding process.

[0090] <Experimental Example 1_Result of Aluminum Foreign Matter Removal>

[0091] The welding auxiliary jig of Example 1 was immersed for 3 minutes at 70 degrees Celsius in an ultrasonic cleaning device that generates ultrasonic waves having a frequency of 25 kHz, uses an aqueous solution containing 4.5 wt% or less of potassium hydroxide, 4.5 wt% or less of sodium hydroxide, 5 wt% or less of a nonionic surfactant, and 5 wt% or less of anionic surfactant as the cleaning solution, and vibrates the cleaning solution under frequency fluctuations of 100 Hz / ms or more to 2000 Hz / ms or less, and the results are shown in Table 2.

[0092] Referring to Table 2, in the case of the welding assist jig of Example 1, in which a plurality of anode tabs and electrode leads are in close contact in the ultrasonic cleaning device according to the present embodiment, it can be seen that aluminum residue attached to the welding assist jig is effectively removed.

[0093] Cleaning solution composition Foreign matter removal result Before cleaning After cleaning 4.5 wt% or less of potassium hydroxide + 4.5 wt% or less of sodium hydroxide + 5 wt% or less of nonionic surfactant + 5 wt% or less of anionic surfactant Foreign matter No foreign matter

[0094] <Experimental Example 2_Result of Copper Foreign Matter Removal 1>

[0095] The welding auxiliary jig of Example 2 was immersed for 15 minutes at 55 degrees Celsius in an ultrasonic cleaning device that generates ultrasonic waves having a frequency of 25 kHz and vibrates an aqueous solution containing 9.50 wt% nitric acid under frequency fluctuations of 100 Hz / ms or more and 2000 Hz / ms or less. In addition, under the same conditions, the welding auxiliary jig was immersed in the cleaning solution for 30 minutes. The results are shown in Table 3.

[0096] Referring to Table 3, in the case of the welding assist jig of Example 2, in which a plurality of cathode tabs and electrode leads are in close contact in the ultrasonic cleaning device according to the present embodiment, it can be confirmed that when immersed for 15 minutes in an aqueous solution containing 9.50 wt% nitric acid, some of the copper residue attached to the welding assist jig is removed and there is no surface damage to the welding assist jig. In addition, when the welding assist jig of Example 2 is immersed for 30 minutes under the same conditions, it can be confirmed that all of the copper residue attached to the welding assist jig is removed.

[0097] Cleaning solution composition Foreign matter removal result Before cleaning After cleaning 9.50 wt% nitric acid (15 min) Foreign matter Partial removal of foreign matter, reaction with copper 9.50 wt% nitric acid (30 min) Foreign matter Complete removal of foreign matter

[0098] <Experimental Example 3_Result of Copper Foreign Matter Removal 2>

[0099] The welding assist jig of Example 2 was immersed for 15 minutes at 55 degrees Celsius in an ultrasonic cleaning device that generates ultrasonic waves having a frequency of 25 kHz, and uses 1) an aqueous solution containing 10 wt% ammonium, 2) an aqueous solution containing 5 wt% iron chloride, and 3) an aqueous solution containing 3 wt% iron chloride as cleaning solutions, and vibrates each cleaning solution under frequency fluctuations of 100 Hz / ms or more to 2000 Hz / ms or less, and the results are shown in Table 4.

[0100] Referring to Table 4, in the case of the welding assist jig of Example 2, in which a plurality of cathode tabs and electrode leads are in close contact in the ultrasonic cleaning device according to the present embodiment, it can be seen that copper residue attached to the welding assist jig is not removed in the aqueous solution containing 10 wt% ammonium and the aqueous solution containing 3 wt% iron chloride. In addition, in the case of the aqueous solution containing 5 wt% iron chloride, although the reaction with copper is active, it can be seen that damage occurs to the surface of the welding assist jig.

[0101] Cleaning solution composition Foreign matter removal result Before cleaning After cleaning 10 wt% ammonium Foreign matter Contains foreign matter, no reaction with copper whatsoever 5 wt% iron chloride Foreign matter No foreign matter, surface damage 3 wt% iron chloride Foreign matter Foreign matter present, minimal reaction with copper, partial surface damage

[0102] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

Claim 1 An ultrasonic cleaning device comprising: a cleaning housing part including a cleaning solution for immersing a welding assist jig that assists in welding joints included in a battery cell; and an ultrasonic generator part that applies ultrasonic waves to the cleaning solution to vibrate the cleaning solution in a spherical wave pattern, wherein metal foreign matter attached to the welding assist jig is removed by the cleaning solution. Claim 2 An ultrasonic cleaning device according to claim 1, wherein the ultrasonic generating unit generates ultrasonic waves having a frequency of 10 kHz or more to 50 kHz or less, and vibrates the cleaning liquid under ultrasonic frequency fluctuations of 100 Hz / ms or more to 2000 Hz / ms or less. Claim 3 In claim 1, the weld joint is formed between a plurality of electrode tabs and electrode leads of an electrode assembly included in the battery cell, and the welding assist jig is an ultrasonic cleaning device that brings the plurality of electrode tabs and the electrode leads into close contact. Claim 4 In paragraph 3, the welding assist jig is an ultrasonic cleaning device made of SKH51 (High speed tool steels), SKD11 (cold alloy tool steel), SUS420 (martensite stainless steel), SUS430 (ferritic phosphorus stainless steel), or SUS304 (austenitic stainless steel). Claim 5 In paragraph 3, the electrode tab is an anode tab made of aluminum (Al), the cleaning solution is a solution for removing aluminum from the welding assist jig, and the metal foreign matter is an ultrasonic cleaning device containing residues of aluminum (Al). Claim 6 In paragraph 5, the ultrasonic cleaning device wherein the cleaning solution is an aqueous solution comprising at least one of potassium hydroxide and sodium hydroxide. Claim 7 In claim 6, the ultrasonic cleaning device wherein the ultrasonic generating part vibrates the cleaning solution for a time of 1 minute or more to 5 minutes or less at a temperature of 50 degrees or more to 75 degrees or less. Claim 8 In paragraph 3, the electrode tab is a cathode tab made of copper (Cu), the cleaning solution is a solution for removing copper from the welding assist jig, and the metal foreign matter is an ultrasonic cleaning device containing residues of copper (Cu). Claim 9 An ultrasonic cleaning device according to claim 8, wherein the cleaning solution is an aqueous solution containing 5% by weight or more and less than 10% by weight of nitric acid. Claim 10 In claim 9, the ultrasonic cleaning device wherein the ultrasonic generating part vibrates the cleaning solution for a time of 10 minutes or more to 40 minutes or less at a temperature of 50 degrees or more to 70 degrees or less. Claim 11 An ultrasonic cleaning method comprising: an immersion step of immersing a welding assist jig that assists a welding joint included in a battery cell into a cleaning liquid included in a cleaning housing; and a foreign matter removal step in which an ultrasonic generator applies ultrasonic waves to the cleaning liquid to vibrate the cleaning liquid in a spherical wave pattern, wherein in the foreign matter removal step, metal foreign matter attached to the welding assist jig is removed by the cleaning liquid, the welding joint is formed between a plurality of electrode tabs and electrode leads of an electrode assembly included in the battery cell, and the welding assist jig brings the electrode tabs and electrode leads into close contact. Claim 12 In claim 11, in the foreign matter removal step, the ultrasonic generating unit generates ultrasonic waves having a frequency of 10 kHz or more to 50 kHz or less, and the cleaning solution is vibrated under an ultrasonic frequency variation of 100 Hz / ms or more to 2000 Hz / ms or less. Claim 13 An ultrasonic cleaning method according to claim 11, further comprising a rinsing and drying step of rinsing and drying the welding auxiliary jig removed from the cleaning housing after the foreign matter removal step. Claim 14 In claim 13, the electrode tab is an anode tab made of aluminum (Al), the cleaning solution is an aqueous solution comprising at least one of potassium hydroxide and sodium hydroxide, and in the foreign matter removal step, the ultrasonic generating unit vibrates the cleaning solution for a time of 1 minute or more to 5 minutes or less at a temperature of 50 degrees or more to 75 degrees or less. Claim 15 In claim 13, the electrode tab is a cathode tab made of copper (Cu), the cleaning solution is an aqueous solution containing 5% by weight or more and less than 10% by weight of nitric acid, and in the foreign matter removal step, the ultrasonic generating unit vibrates the cleaning solution for a time of 10 minutes or more and 40 minutes or less at a temperature of 50 degrees or more and 70 degrees or less.

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