Ultrasonic welding device and welding method

Abstract

The invention provides an ultrasonic welding device and a welding method, the ultrasonic welding device is used for welding tabs of a secondary battery, the ultrasonic welding device comprises a welding head and a tab collecting device, the tab collecting device is used for collecting the tabs, the thickness of a single-layer tab is d [mu] m, d is larger than or equal to 4 and smaller than or equal to 5.5, the welding head is provided with a welding face, and the welding face is used for abutting against the collected tabs. Every two adjacent edges of the welding surface are transited through a fillet, the welding surface comprises a welding tooth area and an edge area surrounding the welding tooth area, a plurality of protruding welding teeth are arranged on the welding surface, the welding teeth are located in the welding tooth area, in the direction from the center of the welding surface to the edges of the welding surface, the width of the edge area is W1mm, the radius of the fillet is R mm, and R is larger than or equal to 0.8 and smaller than or equal to 1.3. The value range of W1 / R is 0.8 to 1.2. According to the technical scheme, the tab tearing probability caused by ultrasonic welding can be reduced at least, and the quality of the secondary battery is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an ultrasonic welding apparatus and welding method. Background Technology

[0002] With the continuous development of new energy technologies, the application fields of secondary batteries are constantly expanding, and related technologies are also continuously advancing. Types of secondary batteries include nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, lithium-ion batteries, and polymer lithium-ion batteries. For secondary batteries, the thickness of the conventional electrode current collector is greater than or equal to 6μm. Currently, to achieve high energy density battery structure designs, thinner aluminum or copper foil materials are generally used for the current collectors of the positive and negative electrodes. Industry advancements involve ultrasonically welding the current collectors of the positive and negative electrodes to the adapter plates to achieve the basic framework structure for battery charging and discharging. However, existing ultrasonic welding equipment still needs further improvement to avoid the impact of welding on the quality of the secondary battery. Summary of the Invention

[0003] In view of the problems existing in the related technologies, the purpose of this invention is to provide an ultrasonic welding device and welding method, which can at least reduce the probability of electrode tearing caused by ultrasonic welding, so as to ensure the quality of secondary batteries.

[0004] To achieve the above objectives, the present invention provides an ultrasonic welding apparatus for welding tabs of secondary batteries. The ultrasonic welding apparatus includes a welding head and a tab gathering device. The tab gathering device is used to gather the tabs. The thickness of a single-layer tab is d μm, where 4 ≤ d ≤ 5.5. The welding head has a welding surface for abutting against the gathered tabs. Each pair of adjacent edges of the welding surface is transitioned by a rounded corner. The welding surface includes a welding tooth area and an edge area surrounding the welding tooth area. The welding surface is provided with multiple protruding welding teeth, each welding tooth being located within the welding tooth area. From the center of the welding surface to the edge of the welding surface, the width of the edge area is W1 mm. The radius of the rounded corner is R mm, satisfying: 0.8 ≤ R ≤ 1.3. The value range of W1 / R is 0.8-1.2.

[0005] In some embodiments, the welding teeth have a convex curved surface, and the welding teeth are arranged in an array of multiple rows and columns within the welding tooth area.

[0006] In some embodiments, the welding teeth are arranged in 3-4 rows in the welding tooth area, and the welding teeth are arranged in 7-11 columns in the welding tooth area.

[0007] In some embodiments, the ultrasonic welding apparatus further includes: a welding seat, disposed opposite to the welding head, for supporting the electrode tabs and an adapter piece for welding the electrode tabs.

[0008] In some embodiments, the tab gathering device includes: an adapter plate base for supporting the adapter plate together with the welding seat; and a protective cover disposed above the adapter plate base, wherein the protective cover and the adapter plate base together clamp the tab to gather the tab, wherein the adapter plate base has a positioning groove for fixing the adapter plate.

[0009] In some embodiments, the protective cover includes a first surface and a first side surface connected to the first surface. The first surface abuts against the tab, and the first side surface faces the electrode assembly having the tab. The first surface and the first side surface are connected by a rounded transition. The adapter plate includes a second surface and a second side surface connected to the second surface. The second surface faces the protective cover, and the second side surface faces the electrode assembly. The second surface and the second side surface are connected by a rounded transition.

[0010] The present invention also provides an ultrasonic welding method, which uses the above-mentioned ultrasonic welding device to weld electrode tabs. The welding method includes: stacking multiple electrode tabs; and using a welding head to perform ultrasonic welding on the stacked multiple electrode tabs.

[0011] In some embodiments, the welding amplitude of ultrasonic welding is greater than or equal to 80% and less than or equal to 90%.

[0012] In some embodiments, the welding energy of ultrasonic welding is greater than or equal to 280J and less than or equal to 320J.

[0013] In some embodiments, the welding pressure of ultrasonic welding is less than or equal to 770N and greater than or equal to 730N.

[0014] The beneficial technical effects of this invention include:

[0015] The technical solution of this application limits the radius R of the welding head to within the range of 0.8mm to 1.3mm, and designs the ratio W1 / R of the edge area width W1 mm ​​of the welding surface to the radius R of the corner to be 0.8-1.2. This can ensure welding quality while avoiding excessive space occupied by the edge area, thus saving space occupied by the external dimensions of the welding head and preventing interference with the tab convergence device. Furthermore, when the thickness of the single-layer tab is 4μm-5.5μm, the reasonable range of W1 / R for thin tabs balances the impact of ultrasonic welding on the tab surface and the effective welding area of ​​ultrasonic welding, and can reduce the probability of tab tearing caused by ultrasonic welding, especially avoiding damage to the surface tab, thus ensuring the quality of the secondary battery. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of a secondary battery in an embodiment of the present invention.

[0018] Figure 2 This is a cross-sectional structural diagram of a secondary battery with its casing removed, according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of an electrode assembly in an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of one state of welding between the electrode tab and the adapter piece in an embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of one structure of the electrode sheet in an embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram of a single tab and electrode sheet in an embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram of the welding process between the electrode tab and the adapter piece in an embodiment of the present invention.

[0024] Figure 8A and Figure 8B A planar schematic diagram of the welding surface of the welding head and a cross-sectional schematic diagram of the welding head are shown respectively in the embodiments of the present invention.

[0025] Figure 9A and Figure 9B A planar schematic diagram of the welding surface of a conventional welded joint and a cross-sectional schematic diagram of the welded joint are shown respectively.

[0026] Figure 10 A schematic diagram of the ultrasonic welding apparatus in an embodiment of the present invention is shown during the welding of the electrode tab and the adapter piece.

[0027] Figure 11 This is a flowchart of an ultrasonic welding method according to an embodiment of this application. Detailed Implementation

[0028] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.

[0029] Embodiments of this application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are indicated by similar reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative and diagrammatic in nature and are intended to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0030] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, these terms may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately.

[0031] In this specification, unless otherwise specified or limited, relative terms such as “central,” “longitudinal,” “lateral,” “front,” “rear,” “right,” “left,” “inner,” “outer,” “lower,” “higher,” “horizontal,” “vertical,” “above,” “below,” “above,” “below,” “top,” “bottom,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the directions described in the discussion or depicted in the accompanying drawings. These relative terms are used for descriptive convenience only and do not require that this application be constructed or operated in a particular orientation.

[0032] For ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0033] With the continuous development of new energy technologies, the application fields of rechargeable batteries are constantly expanding, and related technologies are also continuously advancing. Types of rechargeable batteries include nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, lithium-ion batteries, and polymer lithium-ion batteries. For rechargeable batteries, the thickness of the conventional electrode current collector is greater than or equal to 6μm. Currently, to achieve high energy density battery structure designs, thinner aluminum foil or copper foil materials are generally used for the current collectors of the positive and negative electrodes (especially based on the current 6μm thickness of copper foil, it can be thinned to 5.5μm, or even 4μm, which can reduce costs and improve energy density). The industry practice involves ultrasonically welding the current collectors of the positive and negative electrodes to the adapter plates to achieve the basic framework structure for lithium battery charging and discharging.

[0034] Ultrasonic welding of the current collector and adapter plate of the positive and negative electrodes involves pressing the current collector and adapter plate together with a welding head and welding seat while applying high-frequency vibration to achieve welding. To avoid tearing of the weld edge due to vibration of the welding head during welding, the chamfer radius of the welding head edge is usually >2mm, and the edge area without welding teeth also has a large width. This results in the welding head size usually being much larger than the weld size, which can easily interfere with the tab gathering tooling. At the same time, the large welding head design restricts the tab gathering position, and the tab must be tightly attached to the cell for gathering. If the gathering is too tight, the tab can easily tear, which is detrimental to the quality of the secondary battery. Based on the above technical problems, this application provides an ultrasonic welding device and welding method for welding tabs of secondary batteries.

[0035] The following combination Figures 1 to 6 The present invention relates to a secondary battery, which can be welded using the ultrasonic welding apparatus and welding method of the present invention. See also Figures 1 to 3 As shown, the secondary battery 1200 in this embodiment may include a housing 1210, a top cover 1220, and an electrode assembly 1230. The housing 1210 has an internal accommodating space, and one end of the housing 1210 has an opening. The electrode assembly 1230 can be accommodated within the internal accommodating space of the housing 1210. The top cover 1220 can close onto the opening of the housing 1210 and is fixedly connected to the housing 1210, so that the interior of the housing 1210 is relatively sealed. The electrode assembly 1230 is generally in two sets, and the two sets of electrode assemblies 1230 are stacked within the housing 1210. The stacking direction of the two sets of electrode assemblies 1230 is along the thickness direction of the secondary battery.

[0036] like Figure 3 As shown, the electrode assembly 1230 may include a first electrode 100a, a second electrode 100b, and a separator 200. The separator 200 is located between the first electrode 100a and the second electrode 100b to isolate the first electrode 100a and the second electrode 100b, preventing them from contacting and causing a short circuit. The first electrode 100a, the separator 200, and the second electrode 100b are simultaneously wound to form the wound electrode assembly 1230. In some other embodiments, the electrode assembly 1230 may also be formed in a stacked form.

[0037] Specifically, the first electrode 100a may include a first current collector and a first active material layer. The first active material layer is coated on a portion of the surface of the first current collector. In some embodiments, the first electrode 100a is a negative electrode, the first current collector is a negative current collector, and the first active material layer is a negative active material layer. The second electrode 100b may include a second current collector and a second active material layer. The second active material layer is coated on a portion of the surface of the second current collector. In some embodiments, the second electrode 100b is a positive electrode, the second current collector is a positive current collector, and the second active material layer is a positive active material layer.

[0038] Taking the 1200 secondary battery as an example of a lithium-ion battery, the positive electrode current collector can be made of aluminum. The positive electrode active material layer can include positive electrode active materials, such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. For high-nickel ternary lithium batteries, the positive electrode active material can be a ternary material composed of nickel, cobalt, and manganese. The negative electrode current collector can be made of copper. The negative electrode active material layer can include negative electrode active materials, such as carbon or silicon. The separator 200 can be made of materials such as PP (polypropylene) or PE (polyethylene).

[0039] Combination Figure 4 and Figure 5 As shown, the first electrode 100a may include a plurality of first tabs 120a, which are stacked in the thickness direction of the electrode assembly 1230 after the electrode assembly 1230 is wound. Similarly, the second electrode 100b includes a plurality of second tabs 120b, which are stacked in the thickness direction of the electrode assembly 1230 after the electrode assembly 1230 is wound. In some embodiments, the first tabs 120a are negative tabs, and the second tabs 120b are positive tabs.

[0040] A connector 1221 is provided on the side of the top cover 1220 facing the housing 1210. When the electrode assembly 1230 is placed inside the housing 1210, the first tab 120a and the second tab 120b are both located on the side of the electrode assembly 1230 facing the top cover 1220. When assembling the secondary battery, two sets of electrode assemblies 1230 can be placed on both sides of the connector 1221, and the first tab 120a and the second tab 120b of each set of electrode assemblies 1230 can be welded to the connector 1221 respectively (see [reference]). Figure 4As shown), welding can be performed using ultrasonic welding. Subsequently, after bending the two electrode assemblies 1230 relative to the adapter piece 1221, the electrode assemblies 1230 and the adapter piece 1221 are placed into the housing 1210 as a whole, thus completing the assembly of the secondary battery 1200. At this time, both the first tab 120a and the second tab 120b are in a bent state (see...). Figure 2 (As shown).

[0041] In some embodiments, reference Figure 5 In this embodiment, the first electrode 100a may include an electrode body 110 and a plurality of first tabs 120a, wherein the first tabs 120a are connected to one side of the electrode body 110 along a first direction D1. The plurality of first tabs 120a extend from the electrode body 110 along the first direction D1. The plurality of first tabs 120a are arranged at intervals D2 along a second direction so that after the first electrode 100a is wound, the plurality of first tabs 120a can be approximately aligned. Here, the first direction D1 is perpendicular to the second direction D2. After the electrode assembly is wound, the first direction D1 may correspond to the height direction of the secondary battery 1200 and the axial direction of the electrode assembly 1230. In specific applications, the first direction D1 can be understood as the height direction of the first tabs 120a, and the second direction D2 can be understood as the width direction of the first tabs 120a.

[0042] The electrode body 110 may include a first current collector 111 and a first active material layer 112 coated on opposite sides of the first current collector 111. The coating area of ​​the first active material layer 112 may completely cover a portion of the first current collector 111 of the electrode body 110, or it may partially cover a portion of the first current collector 111 of the electrode body 110. When the first active material layer 112 partially covers a portion of the first current collector 111 of the electrode body 110, the portion of the first current collector 111 near the first tab 120a is the area not coated with the first active material layer 112.

[0043] In this embodiment, the first tab 120a can be considered as a structure formed after the first current collector 111 is cut; that is, the first tab 120a and the electrode body 110 are an integral structure. At least a portion of the first tab 120a can be formed in the area of ​​the first current collector 111 not coated with the first active material layer 112. In this case, the thickness of the first current collector 111 is the same as the thickness of the first tab 120a; when the thickness of the first current collector 111 decreases, the thickness of the first tab 120a also decreases. Figure 5In the illustrated embodiment, the first active material layer 112 is coated on a portion of the first tab 120a. In other embodiments, the first tab 120a may not include the first active material layer 112. In other embodiments, the first tab 120a and the electrode body 110 may be cut separately and then fixed to the electrode body 110 by welding or other means.

[0044] According to some embodiments, a method for forming a secondary battery may include the following steps: stirring a slurry of an active material layer; coating the slurry onto a current collector (e.g., a first current collector 111) to form an active material layer (e.g., a first active material layer 112); rolling and cutting tabs (e.g., first tabs 120a); winding an electrode assembly 1230; pairing two sets of electrode assemblies 1230 and welding them to an adapter piece 1221; welding the adapter piece 1221 to an electrode post; after welding, inserting it into a housing 1210, wrapping it with an insulating film, and then welding the top cover 1220 to the housing 1210.

[0045] In addition, in some embodiments, the first electrode 120a is set as the negative electrode, and the thickness of a single layer of the first electrode 120a is dμm, where 4≤d≤5.5. That is to say, the thickness of the first electrode 120a in this embodiment is reduced compared to the thickness of the negative electrode in conventional technical solutions (e.g., 6μm), which is beneficial to improving energy density.

[0046] The first tab 120a and the second tab 120b of each electrode assembly 1230 are welded to the adapter piece 1221 to form a welded portion 125. It should be noted that when ultrasonic welding is used to weld the first tab 120a to the adapter piece 1221, multiple first tabs 120a are typically pre-welded together ultrasonically first, and then a layer of first tabs 120a near the adapter piece 1221 is welded to the adapter piece 1221 using laser welding. The laser welding area is located within the ultrasonic welding area, which prevents welding spatters caused by the large gaps between the first tabs 120a during laser welding. Therefore, when using both ultrasonic welding and laser welding, the welded portion 125 in this embodiment can be understood as the area where the first tabs 120a and the second tabs 120b are ultrasonically welded.

[0047] See Figure 7 As shown, during the ultrasonic welding of the first electrode 120a and the adapter piece 1221, the welding head 310 of the ultrasonic welding device abuts against the first electrode 120a and the adapter piece 1221, and high-frequency vibration is applied to achieve welding of the first electrode 120a and the adapter piece 1221. Figure 8A and Figure 8B A plan view of the welding surface 320 of the welding head 310 and a cross-sectional view of the welding head 310 are shown respectively. Combined with... Figure 8Aand Figure 8B As shown, the welding head 310 has a welding surface 320, which is used to abut against the first electrode tab 120a to weld the first electrode tab 120a to the adapter piece 1221 and form a welding portion 125. The welding surface 320 is provided with a plurality of protruding welding teeth 329, which can form corresponding welding recesses 129 in the welding portion 125 (see...). Figure 6 ).

[0048] The weld surface 320 is transitioned between each pair of adjacent edges 311 by a fillet 313. Such a weld surface 320 can be described as having a rounded rectangular shape. The weld surface 320 includes a weld tooth area 322 and an edge area 324 surrounding the weld tooth area 322. Each weld tooth 329 is located within the weld tooth area 322, meaning that no portion of the edge area 324 is provided with weld teeth 329. The edge area 324 has a width W1 mm ​​in the direction from the center of the weld surface 320 to its edge. The radius of the fillet 313 is R mm, where R satisfies: 0.8 ≤ R ≤ 1.3, that is, the radius R mm is in the range of 0.8 mm to 1.3 mm. Furthermore, the ratio of width W1 to radius R, W1 / R, ranges from 0.8 to 1.2, that is, 0.8 ≤ W1 / R ≤ 1.2.

[0049] For comparison, Figure 9A and Figure 9B A plan view of the welding surface of the conventional welding head 31 and a cross-sectional view of the welding head 31 are shown respectively. See also Figure 9A and Figure 9B As shown, the radius R2 mm of the fillet 33 on the outer edge of the welding head 31 is usually R2 mm ≥ 2 mm, and the width of the edge area is correspondingly larger. This results in the welding head 31 being much larger than the welding tooth area 32 where the welding tooth 39 is located. Such a welding head 31 is prone to interference with the tab gathering device. At the same time, the large design of the welding head 31 restricts the tab gathering position. The tab must be tightly attached to the cell for gathering. If the gathering is too tight, it can easily cause the tab to tear, which is detrimental to the quality of the secondary battery.

[0050] The technical solution of this application limits the radius R of the fillet 313 to the range of 0.8mm to 1.3mm. This limits R within an appropriate range to avoid excessively large weld head size and ensure electrode welding quality. It should be understood that if the radius R is greater than 1.3, the weld head size will be too large; if the radius R is less than 0.8, the fillet will be too small, potentially causing significant stress on the electrode during welding and affecting the welding quality. Furthermore, designing the ratio W1 / R of the width W1 to the radius R as 0.8-1.2 allows for matching an appropriate edge area width W1 based on the radius R, avoiding excessive space occupation by the edge area and thus saving space occupied by the weld head's overall dimensions.

[0051] In a preferred embodiment, W1 / R is approximately 1, meaning the width W1 mm ​​of the edge region 324 is substantially the same as the radius R mm of the fillet 313. In a preferred embodiment, the radius R of the fillet 313 is approximately 1, and the width W1 of the edge region is approximately 1. For comparison, see [link to relevant documentation]. Figure 9A and Figure 9B As shown, the radius R2 mm of the fillet 33 of the existing welding head 31 is usually 2 mm. The length L22 of the welding head 31 is equal to the length L21 mm + 4 mm of the welding tooth area 32, and the width W22 is equal to the width W21 mm + 4 mm of the welding tooth area 32.

[0052] In this invention, the radius R mm of the fillet 313 of the welding surface 320 is preferably designed to be 1 mm. Therefore, the length L mm of the welding head 310 is the length L2 mm + 2R mm of the welding tooth area 322, i.e., L mm = L2 mm + 2 mm; the width W is the width W of the welding tooth area 322 + 2R mm, i.e., W mm = W2 mm + 2 mm. Compared to, for example... Figure 9A and Figure 9B As shown in the conventional design, with the same size of the welding tooth area 322, the present invention greatly saves the space occupied by the external dimensions of the welding head 310.

[0053] This application also provides an ultrasonic welding apparatus. Figure 10 A schematic diagram of the ultrasonic welding apparatus during the welding of the electrode tab and the adapter plate is shown. Figures 8A-8B and Figure 10 As shown, the ultrasonic welding apparatus may include the aforementioned welding head 310 and welding seat 330. The welding head 310 and welding seat 330 are disposed opposite to each other, and the welding seat 330 is used to support the first electrode tab 120a and the adapter piece 1221 for welding the first electrode tab 120a. The aforementioned welding surface 320 of the welding head 310 abuts against the first electrode tab 120a, and the welding head 310 and the welding seat 330 together clamp the first electrode tab 120a and the adapter piece 1221 to weld the first electrode tab 120a and the adapter piece 1221.

[0054] The ultrasonic welding apparatus also includes an electrode gathering device 400, which gathers the first electrode 120a to keep it flat and stably stacked. The welding surface 320 of the welding head 310 abuts against the gathered first electrode 120a to ensure welding quality.

[0055] As described above, since the radius R mm of the fillet 313 of the welding surface 320 and the width W1 mm ​​of the edge region 324 satisfy 0.8≤R≤1.3 and 0.8≤W1 / R≤1.2, the edge region can be kept from occupying too much space while ensuring welding quality. This saves space occupied by the external dimensions of the welding head 310 and prevents interference with the tab convergence device 400. Furthermore, when the thickness of the single-layer first tab 120a is 4μm-5.5μm, the reasonable range of 0.8≤W1 / R≤1.2 for such a thin tab balances the impact of ultrasonic welding on the tab surface and the effective welding area of ​​ultrasonic welding. This reduces the probability of tab tearing caused by ultrasonic welding, especially avoiding damage to the surface tab and ensuring the quality of the secondary battery.

[0056] In some embodiments, the welding teeth 329 of the welding head 310 have a protruding curved surface. The welding teeth 329 may be spherical. The welding teeth 329 may have a circular planar shape. The welding teeth 329 are arranged in a multi-row and multi-column array within the welding tooth area 322. Through the design and array arrangement of the spherical welding teeth 329, while saving the external dimensions of the welding head, it is possible to ensure that energy is efficiently transferred to the welding surface 320 during the welding process, so that the first electrode tab 120a and the adapter piece 1221 can form a strong welding joint, and for thin electrode tabs with a thickness of 4μm-5.5μm, the electrode tab will not be damaged by reducing the radius R of the fillet 313.

[0057] In some preferred embodiments, the welding teeth 329 are arranged in 3-4 rows and 7-11 columns in the welding tooth area 322. Limiting the number of welding teeth 329 to 3-4 rows avoids welding too many or too few rows. If there are too many rows, the diameter of the welding teeth 329 will be too small, potentially causing excessive stress on the electrode tabs and making them prone to tearing; if there are too few rows, the diameter of the welding teeth 329 will be too large, and the vibration during ultrasonic welding will also cause the electrode tabs to tear easily, and the welding pull force cannot be guaranteed. Figure 8A In the example shown, the welding teeth 329 are arranged in 3 rows and 9 columns in the welding tooth area 322. Limiting the welding teeth 329 to an appropriate number of rows of 3 to 4 can reduce the probability of tab tearing when the tab thickness is thin (4μm-5.5μm) while ensuring welding pull strength.

[0058] Specifically, the tab retraction device 400 may include an adapter plate base 410 and a protective cover 420. The adapter plate base 410 can be used to support the adapter plate 1221 together with the welding seat 330. The protective cover 420 is disposed above the adapter plate base 410. The protective cover 420 and the adapter plate base 410 together clamp the first tab 120a to retract the first tab 120a. In the ultrasonic welding process, the tab retraction device 400 is designed to be implemented in conjunction with welding dynamics.

[0059] The adapter plate base 410 may have a positioning groove 411, which can be used to fix the adapter piece 1221. In the ultrasonic welding process, the adapter plate base 410 can be designed as an integrated tray with a pre-reserved positioning groove. The positioning groove 411 can be a contour groove of the adapter piece 1221, that is, the shape of the positioning groove 411 can match the shape of the adapter piece 1221 to accurately fix the position of the adapter piece 1221 and prevent the adapter piece 1221 from shifting due to the vibration of ultrasonic welding. Different groove depths can be used to arrange the positive / negative electrode adapter pieces so that the welding surface of the adapter piece maintains a zero-step state relative to the outer edge of the first electrode tab 120a adjacent to the adapter plate base 410, which facilitates the high-precision positioning of the electrode assembly 1230 and the adapter piece 1221.

[0060] The protective cover 420 includes a first surface 422 and a first side surface 424 connected to the first surface 422. The first surface 422 abuts against the first tab 120a. The first side surface 424 faces the electrode assembly 1230 having the first tab 120a, and the first surface 422 and the first side surface 422 are connected by a rounded corner 423. In a typical design, the first surface 422 and the first side surface 422 are connected at a right angle. The protective cover 420 has a rounded corner 423 transition structure on the outside, which allows the physical alignment of the first tab 120a to be completed during the pre-pressing stage. During the welding process, the elastic constraint lip of the cover edge generates a dynamic clamping effect under the action of ultrasound, which works in synergy with the radial vibration force of the welding head ball teeth: the ball tooth array is responsible for the local plasticizing flow of material, while the cover constraint lip continuously applies a circumferential closing force to prevent the tab from springing back. The lower edge of the protective cover 420 is rounded 423, which can ensure a smooth transition during the thin tab contraction process. For thin tabs (4μm-5.5μm) that are prone to tearing, it can further reduce the probability of tab tearing caused by stress concentration during the contraction process.

[0061] Furthermore, the adapter plate 410 may include a second surface 412 and a second side surface 414 connected to the second surface 412. The second surface 412 faces the protective cover 420, and the second side surface 414 faces the electrode assembly 1230. The second surface 412 and the second side surface 414 of the adapter plate 410 are connected by a rounded corner 413. The outer edge of the adapter plate 410 is provided with a rounded corner 413. When the first electrode tab 120a is clamped and bundled by the adapter plate 410 and the protective cover 420 plate, the rounded corner 413 can reduce the probability of the thin electrode tab being torn due to edge stress concentration during the bundling process. The rounded corner design of the protective cover 420 plate and the adapter plate 410 ensures a smooth transition of the electrode tab.

[0062] This application optimizes the design of the ultrasonic welding device, which can save welding head space while ensuring welding effect, allowing for greater operational space for electrode tab convergence, reducing electrode tab tearing caused by thin electrode tab convergence space, and greatly improving space utilization efficiency during the welding process of electrode tab and adapter plate.

[0063] This application also provides an ultrasonic welding method, which can use the above-mentioned ultrasonic welding device to weld the tabs of a secondary battery. Figure 11 This is a flowchart of an ultrasonic welding method according to an embodiment of this application. See also... Figure 11 As shown, welding method 500 may include step S502, which involves stacking multiple electrode tabs (e.g., multiple first electrode tabs 120a). Welding method 500 also includes step S504, which involves ultrasonically welding the stacked multiple electrode tabs using a welding head (e.g., welding head 310 of an ultrasonic welding device).

[0064] By employing the aforementioned ultrasonic welding device to weld the tabs of the secondary battery, the welding effect is ensured while saving space occupied by the welding head. This allows for greater operational space for tab retraction, preventing interference with the tab retraction device and significantly improving space utilization efficiency during the tab welding process. Furthermore, for thin tabs with a single-layer thickness of 4μm-5.5μm, a balance can be struck between the impact of ultrasonic welding on the tab surface and the effective welding area, while also reducing the probability of tab tearing caused by ultrasonic welding, thus guaranteeing the quality of the secondary battery.

[0065] In typical designs (e.g., for 6μm thick tabs), the welding amplitude is approximately 75%. In some embodiments of the invention, the ultrasonic welding amplitude is greater than or equal to 80% and less than or equal to 90%. By increasing the ultrasonic welding amplitude to a suitable range of greater than or equal to 80% and less than or equal to 90%, this application can maximize welding efficiency and produce a more compact weld (e.g., weld 125) while ensuring the weld head size satisfies 0.8 ≤ R ≤ 1.3 and 0.8 ≤ W1 / R ≤ 1.2.

[0066] In some embodiments, the welding energy of ultrasonic welding is greater than or equal to 280 J and less than or equal to 320 J. In typical designs (e.g., for 6 μm thick tabs), the welding energy is approximately 250 J. By increasing the welding energy to greater than or equal to 280 J and less than or equal to 320 J, this application maximizes the welding energy input while ensuring that the weld head size satisfies 0.8 ≤ R ≤ 1.3 and 0.8 ≤ W1 / R ≤ 1.2, resulting in a more compact weld (e.g., weld 125).

[0067] In some embodiments, the ultrasonic welding pressure is less than or equal to 770 N and greater than or equal to 730 N. In typical designs (e.g., for 6 μm thick tabs), the welding pressure is approximately 800 N. By reducing the welding pressure to less than or equal to 770 N and greater than 730 N, this application minimizes the pressure on the tabs during welding, while ensuring the weld head size meets 0.8 ≤ R ≤ 1.3 and 0.8 ≤ W1 / R ≤ 1.2, and is suitable for thin tabs (4 μm-5.5 μm), thus preventing cracking of the tabs at the weld edge.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An ultrasonic welding apparatus for welding the tabs of a secondary battery, characterized in that, It includes a welding head and an electrode tab gathering device, wherein the electrode tab gathering device is used to gather the electrode tabs, and the thickness of a single layer of the electrode tab is d μm, where 4 ≤ d ≤ 5.

5. The welding head has a welding surface for abutting against the tapered electrode tab. Each pair of adjacent edges of the welding surface is transitioned by a rounded corner, and the welding surface includes a weld tooth area and an edge area surrounding the weld tooth area. The welding surface is provided with multiple protruding welding teeth, each of which is located within the welding tooth area. From the center of the welding surface to the edge of the welding surface, the width of the edge area is W1 mm, and the radius of the fillet is R mm, satisfying: 0.8≤R≤1.3, and the value range of W1 / R is 0.8-1.

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2. The ultrasonic welding apparatus according to claim 1, characterized in that, The welding teeth have protruding curved surfaces, and the welding teeth are arranged in an array of multiple rows and columns within the welding tooth area; The welding surface is a rounded rectangle.

3. The ultrasonic welding apparatus according to claim 2, characterized in that, The welding teeth are arranged in 3-4 rows in the welding tooth area, and in 7-11 columns in the welding tooth area.

4. The ultrasonic welding apparatus according to claim 1, characterized in that, Also includes: A welding seat is disposed opposite to the welding head and is used to support the electrode tab and the adapter piece that matches the welding of the electrode tab.

5. The ultrasonic welding apparatus according to claim 4, characterized in that, The electrode retraction device includes: The adapter plate base is used to support the adapter plate together with the welding seat; A protective cover is disposed above the base plate of the adapter plate, wherein the protective cover and the base plate of the adapter plate together clamp the electrode tab to consolidate the electrode tab. The adapter plate base has a positioning groove for fixing the adapter plate.

6. The ultrasonic welding apparatus according to claim 5, characterized in that, The protective cover includes a first surface and a first side surface connected to the first surface. The first surface abuts against the electrode tab, and the first side surface faces the electrode assembly having the electrode tab. The first surface and the first side surface are connected by a rounded corner. The adapter plate includes a second surface and a second side surface connected to the second surface. The second surface faces the protective cover, and the second side surface faces the electrode assembly. The second surface and the second side surface are connected by a rounded corner transition.

7. An ultrasonic welding method, characterized in that, The electrode tabs are welded using the ultrasonic welding apparatus as described in any one of claims 1-6, wherein the ultrasonic welding method comprises: Multiple electrodes are stacked together; The welding head is used to perform ultrasonic welding on multiple stacked tabs.

8. The ultrasonic welding method according to claim 7, characterized in that, The ultrasonic welding amplitude is greater than or equal to 80% and less than or equal to 90%.

9. The ultrasonic welding method according to claim 7, characterized in that, The ultrasonic welding energy is greater than or equal to 280J and less than or equal to 320J.

10. The ultrasonic welding method according to claim 7, characterized in that, The ultrasonic welding pressure is less than or equal to 770N and greater than or equal to 730N.

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