Method for bonding electrode tab and lead tab, secondary battery module manufactured thereby, and secondary battery pack and vehicle comprising secondary battery module

Abstract

The present invention relates to a method for bonding an electrode tab and a lead tab of a lithium secondary battery, and provides a method for bonding an electrode tab and a lead tab, comprising: performing preliminary welding of the electrode tab through non-contact welding; performing tab cutting; and performing main welding of the electrode tab and the lead tab through contact welding.

Description

A method for joining electrode tabs and lead tabs, a secondary battery module manufactured thereby, a secondary battery pack including said secondary battery module, and an automobile

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0152136 filed on October 31, 2024, and all contents disclosed in the literature of said Korean patent applications are incorporated herein as part of this specification.

[0003] The present invention relates to a method for joining an electrode tab and a lead tab, a secondary battery module manufactured thereby, a secondary battery pack including such a secondary battery module, and an automobile. Specifically, the invention relates to a method for joining an electrode tab and a lead tab of a secondary battery using lithium metal as a lead tab, a secondary battery module manufactured thereby, a secondary battery pack including such a secondary battery module, and an automobile.

[0004] As interest in energy storage technology continues to grow, research and development on electrochemical devices are gradually increasing as application fields expand to include mobile phones, tablets, laptops, and camcorders, as well as electric vehicles (EVs) and hybrid electric vehicles (HEVs).

[0005] Electrochemical devices are the field receiving the most attention in this regard, and among them, the development of lithium secondary batteries, such as rechargeable lithium-sulfur batteries, is becoming the focus of interest.

[0006] Furthermore, recently, research and development on new electrode and battery designs has been conducted to improve capacity density and specific energy in the development of such batteries.

[0007] During the manufacturing of such lithium secondary batteries, welding operations are performed to bind tabs between unit electrodes in order to obtain the output suitable for the application, and at this time, a process of joining the electrode tabs and lead tabs is carried out.

[0008] Figure 1 is a diagram showing the state in which an electrode tab and a lead tab are joined in a typical secondary battery, and Figure 2 is a plan view of a lead tab joined to an electrode tab in a typical secondary battery.

[0009] As shown in FIG. 1, a general secondary battery requires an electrode tab (positive tab or negative tab, 2) to electrically connect the positive plate and the negative plate constituting the electrode assembly (1) to an external device, and this electrode tab (2) is joined to a lead tab (positive lead tab or negative lead tab, 3) as shown in FIG. 2 by welding.

[0010] Additionally, the lead tab (3) includes a metal lead (3a) and a lead film (3b) locally located on one or both sides thereof as shown in FIG. 2, and the metal lead (3a) located on one side thereof is joined to overlap with the electrode tab.

[0011] Lithium-sulfur batteries, which are attracting attention as next-generation rechargeable batteries capable of replacing lithium-ion batteries, utilize only pure lithium metal (Li-metal) as the active material in the negative electrode. In one example, the negative electrode of a lithium-sulfur battery can be composed entirely of lithium.

[0012] In lithium-sulfur batteries, which have the characteristic of inducing a catholyte reaction from sulfur in the anode and lithium metal in the cathode, the biggest bottleneck during the life cycle is swelling of the anode and cathode.

[0013] In particular, during charging and discharging, lithium metal undergoes a significant increase in thickness due to the formation of pores and dendrites caused by the deposition and desorption reactions of lithium ions.

[0014] During this process, excess electrolytes enter the locally enlarged pores, ultimately leading to an electrolyte deficiency, which results in a rapid deterioration of lifespan characteristics.

[0015] Due to these causes, lithium metal anodes are easily damaged, and if they continue to deteriorate, even the anode tabs—which have relatively weaker physical properties compared to lithium-ion battery (LIB) anodes—are damaged, ultimately leading to a short circuit even with a minor impact.

[0016] In the case of sulfur batteries using lithium metal as the negative electrode, problems such as lithium tearing, spreading, and stretching caused by the low rigidity of lithium metal, as well as adhesion occurring during lithium contact, must be resolved.

[0017] FIG. 3 is a diagram illustrating a method of joining electrode tabs and lead tabs of a secondary battery according to the prior art.

[0018] The joining of the electrode tab (2) and lead tab (3) of a secondary battery according to the prior art proceeds in the order of ultrasonic welding (preliminary welding) → tab cutting → laser welding (main welding) as shown in FIG. 3.

[0019] Drawing symbol 1 indicates an electrode assembly, and drawing symbol 2a indicates a portion of the electrode tab (2) that has been ultrasonically welded.

[0020] In this way, in the conventional preliminary welding, ultrasonic welding of the electrode tab (2) is performed, and in the main welding, laser welding is performed by overlapping the electrode tab (2) and the lead tab (3).

[0021] 3a is the lead of the lead tab (3), 3b is the lead film, and 3c is a processed hole created by overlapping the lead (3a) with the ultrasonic welded part (2a) and then laser welding.

[0022] Figure 4 is a schematic diagram showing the process of lithium metal being damaged in Figure 3.

[0023] In the case of lithium metal, due to its low rigidity, there is a problem where pre-welding with ultrasonic welding causes it to spread very thinly, resulting in reduced rigidity and significant metal damage.

[0024] In addition, a problem arises where the tab width increases due to lithium metal spreading.

[0025] When laser welding is performed after ultrasonic welding, a processing hole (3c) is created in the weld, and the weld is weakened by this processing hole (3c), so the lithium metal is easily torn off.

[0026] Accordingly, the present invention provides a method for joining an electrode tab and a lead tab, wherein lithium adhesion does not occur and damage to the lithium metal can be minimized and spreading of the lithium metal does not occur when the lithium metal is joined to the electrode tab using a lithium metal as a lead tab.

[0027] The present invention also provides a secondary battery module manufactured by the bonding method, a secondary battery pack including the same, and an automobile.

[0028] The present invention relates to a method for joining an electrode tab and a lead tab of a lithium secondary battery, wherein

[0029] A method for joining an electrode tab and a lead tab is provided, comprising the steps of: pre-welding the electrode tab by non-contact welding to define a joint with the lead tab; performing tab cutting on the electrode tab; and joining the electrode tab and the lead tab by main welding by contact welding.

[0030] The lead tab comprises a lead formed of lithium metal and a lead film locally located on one or both sides of the lead, and a portion of the lead may be bonded to overlap with a portion of the electrode tab.

[0031] In the above preliminary welding step, a processing hole defining the joint of the electrode tab and the lead tab may be formed, and in the above main welding step, the electrode tab and the lead tab may be welded and joined at the joint, and the processing hole may be filled.

[0032] The above non-contact welding is preferably laser welding.

[0033] The laser welding described above is performed by a laser scanner head configured to irradiate a laser beam onto an electrode tab of an electrode assembly, and the laser beam irradiated from the laser scanner head can be incident perpendicularly on the electrode tab.

[0034] The above contact welding may be ultrasonic welding, and the ultrasonic welding may be performed through an ultrasonic welding machine that includes a horn and anvil in the portion where the lead and the electrode tab overlap.

[0035] The above ultrasonic welding can be performed by positioning the overlapping portion of the lead and the electrode tab on the flat surface of the anvil, and by pressing and vibrating the overlapping portion of the lead and the electrode tab with the horn, so that spot welding is performed at the point of contact between the overlapping portion of the lead and the electrode tab and the horn.

[0036] The bonding method described above can be applied during the manufacturing process of a lithium metal secondary battery or a lithium-sulfur secondary battery comprising a lithium metal anode.

[0037] Meanwhile, the present invention provides a secondary battery module comprising a plurality of secondary batteries manufactured by the aforementioned method of joining electrode tabs and lead tabs.

[0038] Such a secondary battery module may include a lithium metal secondary battery or a lithium-sulfur secondary battery including a negative electrode containing lithium metal as the secondary battery.

[0039] In addition, the present invention provides a secondary battery pack comprising the aforementioned secondary battery module and a pack case in which a plurality of said secondary battery modules are provided and stored.

[0040] In addition, the present invention provides an automobile comprising the aforementioned secondary battery pack.

[0041] According to the means for solving the aforementioned problem, the present invention has the following effects.

[0042] The present invention has the effect of preventing lithium adhesion and minimizing damage to the lithium metal by performing the preliminary welding of the electrode tab as a non-contact welding method, thereby avoiding direct contact with the lithium metal.

[0043] In addition, the present invention has the effect of preventing lithium metal spreading because the pre-welding of the electrode tab is performed using a non-contact laser welding method, thereby not applying pressure to the overlapping portion of the electrode tab and the lead tab.

[0044] In addition, the present invention performs preliminary laser welding followed by tap cutting, and then proceeds with the main welding using ultrasonic welding, a contact method. This eliminates the processing holes formed in the lithium metal during laser welding, thereby improving the electrical connection and ensuring better welding performance.

[0045] Figure 1 is a diagram showing the state in which the electrode tab and the lead tab are joined in a typical secondary battery.

[0046] Figure 2 is a plan view of a lead tab joined to an electrode tab in a typical secondary battery.

[0047] FIG. 3 is a diagram illustrating a method of joining electrode tabs and lead tabs of a secondary battery according to the prior art.

[0048] Figure 4 is a schematic diagram showing the process of lithium metal being damaged in Figure 3.

[0049] FIG. 5 is a diagram illustrating a method for joining an electrode tab and a lead tab of a secondary battery according to the present invention.

[0050] Figure 6 is a drawing showing the state in which a processed hole is formed in the lithium metal after laser welding of Figure 5.

[0051] Figure 7 is a drawing showing the front view of the lithium metal after ultrasonic welding of Figure 5.

[0052] Figure 8 is a drawing showing the rear side of Figure 7.

[0053] FIG. 9 is a schematic diagram showing the configuration of a secondary battery pack according to the present invention.

[0054] FIG. 10 is a schematic diagram showing a vehicle including the secondary battery pack of FIG. 9.

[0055] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Accordingly, in some embodiments, well-known process steps, well-known device structures, and well-known techniques are not specifically described to avoid the present invention being interpreted ambiguously. Throughout the specification, like reference numerals refer to like components.

[0056] In drawings, thicknesses may be enlarged to clearly represent multiple layers and regions. Throughout the specification, the same reference numerals are used for similar parts. When a part such as a layer, film, region, or plate is described as being "above" another part, this includes not only cases where it is "immediately above" another part, but also cases where there is another part in between. Conversely, when a part is described as being "immediately above" another part, it means that there is no other part in between. Furthermore, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only cases where it is "immediately below" another part, but also cases where there is another part in between. Conversely, when a part is described as being "immediately below" another part, it means that there is no other part in between.

[0057] FIG. 5 is a drawing for explaining a method of joining an electrode tab and a lead tab of a secondary battery according to the present invention.

[0058] Figure 6 is a drawing showing the state in which a processed hole is formed in the lithium metal after laser welding of Figure 5, Figure 7 is a drawing showing the front side of the lithium metal after ultrasonic welding of Figure 5, and Figure 8 is a drawing showing the rear side of Figure 7.

[0059] The secondary battery requires an electrode tab (20) to electrically connect the positive plate and the negative plate constituting the electrode assembly (10) to an external device, and this electrode tab (20) is joined to a lead tab (30) by welding. This secondary battery can be a lithium metal secondary battery or a lithium-sulfur secondary battery including a negative electrode containing lithium metal.

[0060] A plurality of electrode assemblies (10) constituting such a secondary battery can be stacked to form a secondary battery module.

[0061] In the method of joining the electrode tab (20) and lead tab (30) of a secondary battery according to the present invention, as shown in FIG. 5, the preliminary welding of the electrode tab (20) is performed by non-contact welding, e.g., laser welding, and the tab cutting of the electrode tab is performed, and the main welding of the electrode tab (20) and lead tab (30) can be performed by contact welding, e.g., ultrasonic welding.

[0062] The electrode tab (20) is, for example, a portion formed to extend a predetermined length from one side of a lithium metal electrode and is connected to the lead (32) of the lead tab (30) to provide a conductive path for charging and discharging a lithium secondary battery.

[0063] The electrode tab (20) may be formed by stacking multiple individual lithium metal electrode tabs.

[0064] The lead tab (30) includes a lead (32) formed of lithium metal and a lead film (34) locally located on one or both sides of the lead (32).

[0065] The lead film (34) can be made of a polymer resin film.

[0066] This lead film (34) can be located in the approximately middle area of ​​the lead (32).

[0067] The lead film (34) serves to seal the welded area as the polymer melts during the sealing of the aluminum pouch. By doing so, the lead film (34) can prevent leakage of the electrolyte.

[0068] Such lead film (34) may be a polyester film, a polyphenylene sulfide film, a polyamide film, a polyimide film, or a polyolefin resin film, preferably a polyolefin resin film, and more preferably a polypropylene (PP) film.

[0069] Meanwhile, the aforementioned non-contact welding, such as laser welding, has the advantage of a fast welding speed and a small weld point size by directing a laser beam onto a localized area.

[0070] Laser welding in the present invention is performed by a laser scanner head configured to irradiate a laser beam onto an electrode tab (20) of an electrode assembly (10), and the laser beam irradiated from the laser scanner head can be incident perpendicularly on the electrode tab (20).

[0071] When a laser beam from a laser scanner head is incident perpendicularly on an electrode tab (20), a plurality of electrode tabs are joined, and a processing hole (32a) of a predetermined shape can be created as shown in FIG. 6. This processing hole (32a) defines the part to be joined with the lead (32) in the main welding and can be formed at a position corresponding to the location where the main welding is to be performed.

[0072] However, such a processing hole (32a) causes the welded portion of the lithium metal lead (32) and the electrode tab (20) to weaken.

[0073] In the present invention, the laser-welded portion, for example, the area where the processing hole (32a) is formed, can be filled by performing contact welding, for example, ultrasonic welding, by attaching a lead (32) to the laser-welded portion, for example, the area where the processing hole (32a) is formed. As a result, there is an advantage in that the welded portion and joint of the lead (32) and the electrode tab (20) can be prevented from weakening.

[0074] Referring to FIG. 5, reference numeral 36 indicates a laser-welded portion and an ultrasonic welded portion on a portion where a lead (32) is attached.

[0075] The laser scanner head may include optical circuits such as fiber optics, glass-based planar light circuits and semiconductor-based planar light circuits, and free space optics including optical elements such as lenses, polarizers, and splitters.

[0076] As such, the present invention performs the preliminary welding of the electrode tab (20) by laser welding, thereby preventing direct contact with the lithium metal, so lithium adhesion does not occur and damage to the lithium metal can be minimized, and since pressure is not applied to the overlapping portion of the electrode tab (20) and the lead tab (30), spreading of the lithium metal does not occur.

[0077] As described above, laser welding is performed as a non-contact welding preliminary weld, and then tab cutting is performed on the electrode tab. This tab cutting can be performed, for example, by removing a portion of the end of the electrode tab where the preliminary weld was performed.

[0078] Afterwards, contact welding, for example, ultrasonic welding, can be performed as the main welding to join the lead (32) and the electrode tab (20).

[0079] This ultrasonic welding can be performed using an ultrasonic welder that includes a horn and anvil in the overlapping portion of the lead (32) and the electrode tab (20).

[0080] Such ultrasonic welding can be performed by positioning the overlapping portion of the lead (32) and the electrode tab (20) on the flat surface of the anvil, and by pressing and vibrating the overlapping portion of the lead (32) and the electrode tab (20) with the horn, so that spot welding is performed at the point of contact between the overlapping portion of the lead (32) and the electrode tab (20) and the horn.

[0081] Ultrasonic welding can be appropriately adjusted according to conditions such as the material, thickness, etc. of the electrode tab (20), the lead (32) of the lead tab (30), and the lead film (34) so ​​that the electrode tab (20) and the lead (32) are easily joined within a range where the electrode tab (20) is not damaged.

[0082] Ultrasonic welding can be performed at a frequency of 15 to 70 kHz.

[0083] As such, the present invention performs laser welding, which is a preliminary welding, followed by tap cutting, and then proceeds with ultrasonic welding, which is a contact method for the main welding. As shown in FIGS. 7 and 8, the processing hole (32a) formed in the lithium metal during laser welding disappears, thereby improving the electrical connection and making the welding more effective.

[0084] The machining hole (32a) in Fig. 7 shows that it was filled while performing ultrasonic welding.

[0085] The bonding method described above can be appropriately applied in the manufacturing process of a lithium metal secondary battery or a lithium-sulfur secondary battery comprising a lithium metal negative electrode. By doing so, damage to the electrode tab and / or lead made of lithium metal can be suppressed, and the degradation of the lifespan of the secondary battery can be effectively suppressed.

[0086] FIG. 9 is a schematic diagram showing the configuration of a secondary battery pack according to the present invention, and FIG. 10 is a schematic diagram showing an automobile including the secondary battery pack of FIG. 9.

[0087] The secondary battery pack (P) includes the aforementioned secondary battery module (M) and a pack case (C) in which a plurality of secondary battery modules (M) are provided and stored.

[0088] This secondary battery pack (P) can be provided in a vehicle (V) as a fuel source for the vehicle.

[0089] For example, the secondary battery pack (P) can be provided in the vehicle (V) in an electric vehicle, a hybrid vehicle, and other ways in which the secondary battery pack (P) can be used as a fuel source.

[0090] In addition, it goes without saying that the secondary battery pack (P) can be equipped in other devices, mechanisms, and facilities, such as an energy storage system that utilizes secondary batteries, in addition to the vehicle (V).

[0091] Thus, since the device, mechanism, and facility equipped with the secondary battery pack (P), such as the secondary battery pack (P) according to the present invention and the automobile (V), includes the aforementioned secondary battery module (M), it is possible to realize a secondary battery pack (P) having all the advantages of the aforementioned secondary battery module (M) and a device, mechanism, and facility such as an automobile equipped with such a secondary battery pack (P).

[0092] [Explanation of the symbol]

[0093] 10: Electrode assembly

[0094] 20: Electrode tab

[0095] 30: Lead tab

[0096] 32 : Lead

[0097] 32a : Machining hole

[0098] 34: Lead film

[0099] M : Secondary battery module

[0100] P : Secondary battery pack

[0101] C: Pack case

[0102] V : Car

Claims

A method for joining the electrode tab and lead tab of a lithium secondary battery, A step of pre-welding the electrode tab by non-contact welding to define the joint with the lead tab; A step of performing tab cutting for the electrode tab; and A method for joining electrode tabs and lead tabs, comprising the step of joining electrode tabs and lead tabs by contact welding. In claim 1, The lead tab comprises a lead formed of lithium metal and a lead film locally located on one or both sides of the lead. A method for joining an electrode tab and a lead tab, wherein a portion of the lead is joined so as to overlap with a portion of the electrode tab. In claim 1, A method for joining an electrode tab and a lead tab, wherein, in the above preliminary welding step, a processing hole defining the joint of the electrode tab and the lead tab is formed. In claim 3, A method for joining electrode tabs and lead tabs in which, in the above-mentioned main welding step, the electrode tabs and lead tabs are welded and joined at the joint, and the processing hole is filled. In claim 1, The above non-contact welding is a laser welding method for joining electrode tabs and lead tabs. In claim 5, The above laser welding is performed by a laser scanner head configured to irradiate a laser beam onto the electrode tab of an electrode assembly, and A method for joining an electrode tab and a lead tab, wherein a laser beam irradiated from the laser scanner head is incident perpendicularly on the electrode tab. In claim 1, The above contact welding is an ultrasonic welding method for joining electrode tabs and lead tabs. In claim 7, A method for joining an electrode tab and a lead tab, wherein the above ultrasonic welding is performed using an ultrasonic welding machine comprising a horn and an anvil in the portion where the lead and the electrode tab overlap. In claim 8, A method for joining an electrode tab and a lead tab, wherein the above ultrasonic welding is performed by positioning the overlapping portion of the lead and the electrode tab on the flat surface of the anvil, and while the horn presses and vibrates the overlapping portion of the lead and the electrode tab, spot welding is performed at the point of contact between the overlapping portion of the lead and the electrode tab and the horn. In claim 1, A method for joining electrode tabs and lead tabs applicable to a lithium metal secondary battery or a lithium-sulfur secondary battery including a lithium metal negative electrode. A secondary battery module comprising a plurality of secondary batteries manufactured by a method of joining an electrode tab and a lead tab according to any one of claims 1 to 10. In claim 11, The above secondary battery is a secondary battery module that is a lithium metal secondary battery or a lithium-sulfur secondary battery including a negative electrode containing lithium metal. A secondary battery pack comprising a secondary battery module according to claim 11 and a pack case in which a plurality of secondary battery modules are provided and stored. An automobile comprising a secondary battery pack according to claim 13.

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