Welding method and welding apparatus for secondary battery, and method and apparatus for monitoring secondary battery welding process

Abstract

The present invention relates to a welding method and welding apparatus for a secondary battery capable of irradiating laser light to the inner side of a lower can, and to a method and apparatus for monitoring a secondary battery welding process capable of confirming a welding state while performing welding. The welding apparatus according to the present invention includes a laser irradiation apparatus that welds an electrode joint to a lower can by irradiating laser light to a center hole of an electrode assembly, and a jig that protects the electrode assembly during laser irradiation. The monitoring apparatus according to the present invention includes a jig and a laser irradiation apparatus, wherein the laser irradiation apparatus includes a laser irradiation apparatus for welding, a laser irradiation apparatus for illumination, and an image sensor. The laser for welding and the laser for illumination are irradiated in a vertical direction from an upper side of the center hole.

Description

Technical Field

[0001] This invention relates to a welding method and welding apparatus for secondary batteries, and more specifically, to a welding method and welding apparatus for secondary batteries, wherein a laser beam is used to weld the electrode joints of an electrode assembly to a lower tank, wherein welding is performed by emitting the laser beam into the inside of the lower tank, and more specifically, emitting the laser beam causes defocusing, thereby preventing external deformation of the lower tank and increasing welding strength and welding efficiency; and a monitoring method and monitoring apparatus for the welding process of secondary batteries, which can inspect and monitor the welding status during welding. Background Technology

[0002] Push-button batteries, typically known as coin-type and stud-type batteries, have a thin stud or button shape and are widely used in various devices such as remote controls, watches, toys, and computer parts.

[0003] These button-type batteries were originally manufactured as non-rechargeable primary batteries, but with the recent development of miniaturized devices, they have also been widely manufactured as rechargeable and dischargeable secondary batteries.

[0004] Moreover, similar to cylindrical or pouch-shaped secondary batteries, button-type secondary batteries have a rechargeable and rechargeable structure, in which electrode components and electrolyte are embedded within the casing.

[0005] In particular, the button-type secondary battery differs from the cylindrical secondary battery in that it has a simpler structure and a very small can height, but it has a similar structure to the cylindrical secondary battery because the coiled electrode assembly is installed inside the can made of metal.

[0006] Meanwhile, the button-type secondary battery is manufactured by embedding electrode components in a can formed by connecting the upper and lower cans.

[0007] The electrode assembly is manufactured by winding a diaphragm, a negative electrode, and a positive electrode in a stacked state on a winding core. Therefore, it has a structure in which a central hole is formed at the center after the winding core is removed, and the electrode connectors are manufactured to protrude upwards and downwards, respectively. Typically, when the electrode connectors are located on the lower can, the upper electrode connector is the positive electrode connector, and the lower electrode connector is the negative electrode connector. That is, when the electrode assembly is embedded, the upper and lower cans are connected, sealed, and electrically insulated. Therefore, the upper can is connected to the positive electrode connector and serves as the positive electrode, and the lower can is connected to the negative electrode connector and serves as the negative electrode.

[0008] At the same time, such as Figure 1As shown, the electrode connector is welded to the lower can in the manufacturing process of the button-type secondary battery of the related technology. The welding of the negative electrode connector in the electrode connector 2a of the related technology is performed as follows: when the electrode assembly 2 is installed into the lower can 3 such that the electrode connector is positioned in the center hole 2b, the fixture 1 is in close contact with the inner bottom surface of the lower can 3 through the center hole 2b, and then the lower can 3 is inverted and irradiated with a laser beam from the outside.

[0009] However, in the aforementioned method of performing welding from the outside, the bonding occurs when the lower tank 3 is relatively larger than the negative electrode connector. Therefore, laser welding may be limited depending on the material properties and thickness of the lower tank 3, and its commercial value may be degraded because weld marks are left on the outer surface of the lower tank 3.

[0010] In addition, when performing welding, it is necessary to check and monitor whether the welding is performed properly. Summary of the Invention

[0011] Technical issues

[0012] Therefore, in order to solve the problems of the above-mentioned related technologies, the main objective of the present invention is to provide a welding method and welding equipment for secondary batteries, wherein a laser beam is emitted to the inside of the lower tank.

[0013] In addition, another objective is to provide a monitoring method and monitoring device for the welding process of secondary batteries, which can check the welding status after welding is completed or during welding.

[0014] Technical solutions

[0015] To achieve the above objectives, the present invention provides a welding apparatus and a welding method for welding electrode connectors (one of the positive electrode connector and the other of the negative electrode connector, particularly the negative electrode connector) to the bottom surface of a lower tank, as well as a monitoring method and a monitoring apparatus for a secondary battery welding process, which can monitor the welding process during welding.

[0016] The welding apparatus according to the invention is a welding apparatus for secondary batteries, wherein, when an electrode assembly having a central hole is placed on a lower tank, the electrode connector of the electrode assembly is welded to the inner bottom surface of the lower tank by the welding apparatus. The welding apparatus includes: a clamp comprising an insertion portion and a base portion, the insertion portion having a tubular shape and a diameter capable of entering the central hole of the electrode assembly, and the base portion having an enlarged diameter to form a disk shape at the end of the insertion portion; and a laser irradiation apparatus configured to emit a laser beam into the hole of the insertion portion, wherein welding is performed when the electrode assembly is placed on the lower tank such that the electrode connector is placed within the central hole, and the laser beam is emitted to the contact point between the inner bottom surface of the lower tank and the electrode connector after passing through the hole of the insertion portion of the clamp.

[0017] The lower can has a cylindrical shape with its lower side closed by an inner bottom surface and its top side open, and the diameter of the base portion is larger than the diameter of the lower can, such that when the insertion portion is inserted into the central hole of the electrode assembly installed in the lower can, the base portion is positioned above the lower can.

[0018] When the base portion is positioned above the lower tank in such a way that the electrode connector is in close contact with the inner bottom surface of the lower tank at the insertion portion of the clamp, the height (h) of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion is in the range of 0.25 mm to 1.5 mm.

[0019] More specifically, the height (h) of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion is in the range of 0.53 mm to 1.5 mm.

[0020] Furthermore, the height (h) and diameter (d) of the lower tank are determined such that the value obtained by dividing the height (h) by the diameter (d) is in the range of 0.35 to 0.6.

[0021] The hole formed along the longitudinal direction of the insertion portion has the following shape, wherein the diameter is largest on the side forming the base portion and gradually decreases in the direction away from the base portion.

[0022] The base portion has a shape that is relatively high at the edges and gradually decreases in the direction of the hole toward the center.

[0023] The base portion has grooves on its side surface, so that when the insertion portion enters the center hole, the upper end of the lower can is inserted into the groove.

[0024] The insertion portion has a length such that when the insertion portion enters the central hole, the electrode connector can make close contact with the inner bottom surface of the lower tank.

[0025] The clamp is made of metal, and the bottom surface of the base portion facing the electrode assembly and the surface of the insertion portion are coated with an insulating layer for insulating electricity.

[0026] Here, the insulating layer is made of a material with a lower thermal conductivity than the clamp.

[0027] At the same time, the laser beam is emitted in a defocused state. In the defocused state, the focal point is formed before the laser beam reaches the contact point between the inner bottom surface of the lower tank and the electrode connector.

[0028] Furthermore, the welding method according to the present invention is a welding method for a secondary battery, wherein when an electrode assembly having a central hole is placed on a lower tank, the electrode connector of the electrode assembly is welded to the inner bottom surface of the lower tank by a welding method, the welding method comprising: an electrode assembly placement step, wherein the electrode assembly placement step places the electrode assembly on the lower tank such that the electrode connector is placed in the central hole of the electrode assembly; a clamp placement step, wherein the clamp placement step places a clamp above the electrode assembly such that an insertion portion enters the central hole, the clamp placement comprising a base portion having a disk shape and an insertion portion extending vertically from the base portion and having a tubular shape; and a welding step, wherein the welding step emits a laser beam into a hole inside the insertion portion and welds the electrode connector to the inner bottom surface of the lower tank.

[0029] The laser beam emitted during the welding process is a pulsed laser beam with an IR wavelength.

[0030] During the fixture placement process, the end of the insertion portion ensures that the electrode connector is in close contact with the inner bottom surface of the lower tank.

[0031] When the base portion is positioned above the lower can such that the electrode connector is in close contact with the inner bottom surface of the lower can at the insertion portion of the fixture, the height (h) of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion is in the range of 0.25 mm to 1.5 mm, and more particularly, in the range of 0.53 mm to 1.5 mm, and the inner bottom surface of the lower can is welded together with the electrode connector during the welding process, thereby forming a welding area at one point.

[0032] The height (h) and diameter (d) of the lower tank are determined such that the value obtained by dividing the height (h) by the diameter (d) is in the range of 0.35 to 0.6.

[0033] During the welding process, the laser beam is emitted in a defocused state, in which the focal point is formed before the laser beam reaches the contact point between the inner bottom surface of the lower tank and the electrode joint.

[0034] Here, during the welding process, the focal point of the laser beam is formed between one-third and two-thirds of the way between the uppermost and lowermost ends of the insertion portion. Furthermore, in this case, the laser beam emitted during the welding process is one of a quasi-continuous wave laser, a pulsed laser, or a CW-modulated laser.

[0035] The monitoring device for welding processes according to the present invention is a monitoring device for welding processes of secondary batteries, wherein when an electrode assembly having a central hole is placed on a lower tank, the electrode connector of the electrode assembly is welded to the lower tank. The monitoring device includes: a clamp and a laser irradiation device. The clamp is provided with an insertion portion having a tubular shape and a diameter capable of entering the central hole of the electrode assembly. The laser irradiation device is configured to emit a laser beam into the hole of the insertion portion. The laser irradiation device includes: a welding laser irradiation device configured to emit a welding laser beam into the hole of the insertion portion via a focusing lens to weld the contact point between the electrode connector and the lower tank when the electrode assembly is placed inside the lower tank such that the electrode connector is placed in the central hole; an illumination laser irradiation device configured to emit an illumination laser beam into the hole of the insertion portion via a focusing lens; and an image sensor configured to receive the reflected illumination laser beam, wherein the welding laser beam and the illumination laser beam are emitted vertically from the top side of the central hole.

[0036] The welding laser beam is reflected from the first dichroic mirror and passes through the focusing lens, while the illumination laser beam is reflected from the second dichroic mirror and passes through the focusing lens.

[0037] Each of the first and second dichroic mirrors is configured such that a portion of the laser beam is reflected from it and another portion of the laser beam is transmitted through it, wherein the welding laser beam is reflected from the first dichroic mirror and emitted to the focusing lens, and the illumination laser beam is transmitted through the first dichroic mirror and emitted to the focusing lens.

[0038] The illumination laser beam reflected from the welding point is transmitted through the first dichroic mirror and then through the second dichroic mirror, and reaches the image sensor.

[0039] The welding laser irradiation apparatus includes: a welding laser oscillator configured to emit a welding laser beam; a first optical insulator configured such that the welding laser beam emitted from the welding laser oscillator is allowed to pass through it as it moves in a forward direction, but is blocked upon return; and a first collimator configured such that the welding laser beam, having passed through the first optical insulator, becomes parallel after passing through the first collimator.

[0040] The illumination laser irradiation device includes: an illumination laser oscillator configured to emit an illumination laser beam; a second optical insulator configured such that the illumination laser beam emitted from the illumination laser oscillator is allowed to pass through it as it moves in a forward direction, but is blocked upon return; and a second collimator configured such that the illumination laser beam that has passed through the second optical insulator becomes parallel after passing through the second collimator.

[0041] The illumination laser beam passes through the focusing lens and has a diameter smaller than the inner diameter of the hole in the insertion part.

[0042] The emission of the illumination laser beam stops when the welding laser beam is emitted, and the emission of the welding laser beam stops when the illumination laser beam is emitted.

[0043] The clamp is provided with a base portion, which has an enlarged diameter to form a disc shape at the end of the insertion portion.

[0044] The monitoring method for a welding process according to the present invention is a monitoring method for a secondary battery welding process, wherein when an electrode assembly having a central hole is placed on a lower tank, the electrode connector of the electrode assembly is welded to the lower tank. The monitoring method includes: an electrode assembly placement step, wherein the electrode assembly is placed on the lower tank such that the electrode connector is placed in the central hole of the electrode assembly; a clamp placement step, wherein the clamp placement step is to place a clamp, the clamp including a tubular insertion portion such that the insertion portion enters the central hole; a welding step, wherein the welding step emits a welding laser beam through a focusing lens into the hole of the insertion portion to weld the contact point between the electrode connector and the lower tank; and a sensing step, wherein the sensing step receives an illumination laser beam using an image sensor, the illumination laser beam being emitted through a focusing lens into the hole of the insertion portion and then reflected, wherein the welding laser beam and the illumination laser beam are emitted vertically from the top side of the central hole.

[0045] Another monitoring method for a secondary battery welding process provided in this invention is a monitoring method for a secondary battery welding process, wherein when an electrode assembly having a central hole is placed on a lower tank, the electrode connector of the electrode assembly is welded to the lower tank. The monitoring method includes: an electrode assembly placement process, which places the electrode assembly on the lower tank such that the electrode connector is placed in the central hole of the electrode assembly; a clamp placement process, which places a clamp including a tubular insertion portion such that the insertion portion enters the central hole; a welding process, which emits a laser beam through a focusing lens to the hole of the insertion portion to weld the contact point between the electrode connector and the lower tank; and a sensing process, which uses an image sensor to receive the laser beam reflected from the welding point, wherein during the sensing process, the laser beam is emitted to the hole of the insertion portion after its output adjustment, and the image sensor receives the reflected laser beam.

[0046] Beneficial effects

[0047] In the present invention with the above configuration, the electrode connector (negative connector) is welded by emitting a laser beam onto the inside of the lower tank. Therefore, no welding marks are left on the lower tank, thus enhancing commercial value.

[0048] The base portion of the fixture is positioned above the lower can, allowing for stable laser beam emission. Furthermore, it prevents foreign matter generated during welding from entering the electrode assembly and mitigates potential damage from heat generated by laser irradiation. Moreover, the movement of the insertion portion is adjusted when the base portion is positioned on the insertion portion. Therefore, welding can be performed stably. More specifically, in the fixture of this application, the base portion is formed to be larger than the diameter of the lower can, thus suppressing the effects of spatter. That is, spatter is likely to occur during welding due to the characteristics of laser welding. This spatter represents the melting and dispersion of metal particles from the lower can and electrode joint, which can penetrate into the electrode assembly. These metal particles can move inside the electrode assembly and may cause short circuits. The fixture of this application is provided to prevent the penetration of these metal particles. Because the base portion has a larger diameter than the lower can, the penetration of metal particles is effectively prevented.

[0049] In this invention, the inner diameter of the hole in the insertion portion can vary depending on the number of welding points, and therefore, the volume of the electrode assembly inside the lower tank can be maximized.

[0050] For example, when the weld point is at one location, and the inner diameter of the hole formed in the insertion portion is limited to the range of 0.25 mm to 1.5 mm, the volume of the electrode assembly can be increased to approximately 100% of the internal volume of the lower tank, thus improving charging and discharging capacity. On the other hand, when the weld point is at three locations, the inner diameter of the hole is limited to the range of 0.53 mm to 1.5 mm (due to the increased diameter of the central hole in the electrode assembly), and the volume of the electrode assembly is reduced. Therefore, the volume of the electrode assembly is reduced to 97% of the internal volume of the lower tank, but the weld strength is enhanced.

[0051] In the fixture provided by this invention, the hole formed along the longitudinal direction of the insertion portion has a shape in which the diameter is largest on the side forming the base portion and gradually decreases in the direction away from the base portion. Therefore, the range of the points to be welded can be precisely limited.

[0052] The base portion of the fixture has a shape that is relatively high at the edges and gradually decreases in the direction of the central hole. This allows the gas supplied during laser welding to be easily discharged.

[0053] Additionally, the base portion has grooves on its side surface, allowing the upper end of the lower can to insert into the bottom surface of the base portion when the clamp insertion part enters the central hole. Therefore, welding is performed stably while the clamp is fixed.

[0054] Furthermore, the bottom surface of the base portion and the surface of the insertion portion are coated with an insulating layer for electrical insulation. Therefore, the electrode assembly can be protected from the heat generated during laser beam emission.

[0055] Furthermore, in this invention, the laser beam is emitted in a defocused state, such that the focal point is formed within an internal hole formed in the insertion portion of the fixture, and therefore, the maximum inner diameter of the laser beam entering the fixture can be reduced. Thus, the diameter of the fixture (especially the insertion portion) can be reduced, but the volume of the electrode assembly can be increased (by reducing the inner diameter of the central hole of the electrode assembly). Therefore, the capacity of the secondary battery can be increased. Moreover, when the laser beam is emitted in a defocused state, spatter can be more effectively suppressed and minimized. That is, the area at the point where the laser beam reaches and the temperature of the point to be welded can be adjusted by defocusing. Therefore, spatter can be suppressed or minimized by adjusting the height of the focal point according to the welding conditions.

[0056] In this invention, when the laser beam is defocused, the focal point is formed between one-third and two-thirds of the way between the uppermost and lowermost ends of the insertion portion. Therefore, the diameter of the laser beam's cross-section can be minimized.

[0057] In this invention, when the electrode joint is welded, the illumination laser beam is emitted vertically, just like the welding laser beam. Therefore, the welding status can be inspected and monitored more clearly. That is, because the illumination laser beam is emitted vertically, no shadowed areas appear.

[0058] Furthermore, in this invention, the welding laser beam can be used as an illumination laser beam by adjusting the output of the welding laser irradiation device, without using a separate illumination laser irradiation device. Therefore, the welding equipment can be manufactured in a more compact size, and its structure can be simplified. Attached Figure Description

[0059] Figure 1 This is a cross-sectional view showing the state in which the electrode connector is welded to the lower tank by emitting a laser beam from the outside during the process of a button-type secondary battery assembly according to the related technology.

[0060] Figure 2 This is a cross-sectional view showing the state in which the electrode connector (the negative electrode connector among the electrode connectors) is welded to the lower tank by emitting a laser beam into the lower tank in the process of the button-type secondary battery assembly according to the first embodiment of the present invention.

[0061] Figure 3 It is a perspective view showing the disassembled state of the lower tank, electrode assembly, and fixture.

[0062] Figure 4 It is a perspective view showing the can of a cylindrical battery with a relatively high height and diameter, and the lower can of the button-type battery of the present invention, and illustrates the inner diameter of the hole formed in the fixture required during single-point welding and the inner diameter of the hole formed in the fixture required during multi-point welding.

[0063] Figure 5 This is an enlarged view showing the state of the laser beam being emitted to the electrode connector.

[0064] Figure 6 The figures illustrate several modified examples of the clamp according to the present invention.

[0065] Figure 7 This is a longitudinal cross-sectional view of a fixture using a modified example of the present invention.

[0066] Figure 8 This diagram illustrates the state in which the electrode connector (the negative electrode connector in the electrode connector) is welded to the lower tank and the state in which a focal point is formed by emitting a laser beam into the lower tank during the manufacturing process of a button-type secondary battery assembly according to a second embodiment of the present invention.

[0067] Figure 9 This is a diagram showing the disassembled state of the lower can, electrode assembly, and fixture in the button-type secondary battery assembly process according to the second embodiment.

[0068] Figure 10 This is a schematic illustration of the height z of the focal point of the laser beam relative to the height h of the electrode assembly.

[0069] Figure 11 This is a diagram illustrating a simplified configuration of a monitoring device for a secondary battery welding process according to a preferred embodiment of a third embodiment of the present invention.

[0070] Figure 12 The path that enables the reflection of the laser beam is represented by a dashed line and added to... Figure 11 The image of the image.

[0071] [Description of the symbol]

[0072] 2: Electrode assembly 3: Lower tank

[0073] 10: Fixture 11: Base section

[0074] 12: Insertion part 13: Hole

[0075] 20: Laser irradiation equipment; 30: Focusing lens

[0076] 40: Image sensor; 50: Welding laser irradiation device

[0077] 51: Welding laser oscillator 52: First collimator

[0078] 53: First dichroic mirror; 54: First optical insulator

[0079] 60: Illumination laser irradiation device; 61: Illumination laser oscillator

[0080] 62: Second collimator; 63: Second dichroic mirror

[0081] 64: Second optical insulator Detailed Implementation

[0082] In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings, enabling those skilled in the art to readily practice the invention. However, the present invention can be embodied in various different forms and is not limited to the embodiments described herein.

[0083] Parts irrelevant to the description will be omitted in order to clearly describe the invention, and the same or similar elements will be indicated by the same reference numerals throughout the specification.

[0084] Furthermore, the terms or words used in this specification and claims should not be construed as having a general meaning or dictionary-based meaning, but should be interpreted as meanings and concepts that are within the scope of the invention, based on the inventor's ability to correctly define the concepts of the terms in order to best describe and explain the principles of his or her invention.

[0085] This invention relates to a welding method and apparatus for secondary batteries, which improves the efficiency of the welding process by emitting a laser beam onto the inside of the lower tank 3 (the side where the electrode assembly is installed) without leaving welding marks on the outside of the lower tank. Furthermore, this invention relates to a method and apparatus for monitoring the welding status during the welding process of secondary batteries. Embodiments of the invention will be described in detail below with reference to the accompanying drawings.

[0086] First Implementation Method

[0087] In this embodiment, a welding method and welding equipment are provided, wherein welding is performed by emitting a laser beam onto the inside of the lower tank 3.

[0088] The welding method provided in this invention is as follows: when the electrode assembly 2 with a central hole 2b is placed on the lower tank 3, the electrode connector 2a (here, the electrode connector is a negative electrode connector) of the electrode assembly 2 is welded to the inner bottom surface of the lower tank 3. The welding method includes an electrode assembly placement process, a fixture placement process, and a welding process.

[0089] Figure 2 This is a cross-sectional view showing the state in which the electrode connector 2a is welded to the lower tank 3 by emitting a laser beam into the lower tank 3 during the button-type secondary battery assembly process according to the present invention, and Figure 3 This is a perspective view showing the disassembled state of the lower tank 3, electrode assembly 2, and clamp 10.

[0090] During the electrode assembly placement process, electrode assembly 2 is placed inside the lower tank 3. Electrode assembly 2 is manufactured by winding a diaphragm, negative electrode, diaphragm, and positive electrode onto a winding core in a stacked state as in the structure of related technologies, and thus has a structure with a central hole 2b formed at the center after the winding core is removed. Furthermore, the electrode connectors are manufactured to protrude upwards and downwards respectively (positive electrode connector on the upper side and negative electrode connector on the lower side).

[0091] Therefore, electrode assembly 2 is installed onto lower tank 3 such that the negative electrode connector located on the lower side contacts the inner bottom surface of lower tank 3. When electrode assembly 2 is placed on lower tank 3, electrode connector 2a, which serves as the negative electrode connector, is located within the central hole 2b of electrode assembly 2.

[0092] Then, with the electrode assembly 2 placed on the lower tank 3, the fixture placement process is performed. The fixture 10 provided in the embodiment includes a base portion 11 having a disc shape and an insertion portion 12 extending vertically from the center of the base portion 11 and having a pipe shape. A hole 13 formed along the longitudinal direction inside the insertion portion 12 has a vertical opening structure passing through the base portion 11 and the insertion portion 12.

[0093] The clamp 10 is positioned from the top to the bottom of the electrode assembly 2, and the insertion portion 12 enters the central hole 2b of the electrode assembly 2. The diameter of the base portion 11 of the clamp 10 is larger than the diameter of the lower can 3, and therefore rests above the upper end of the lower can 3. Here, the end of the insertion portion 12 ensures that the negative electrode connector is in close contact with the inner bottom surface of the lower can 3.

[0094] Furthermore, with the fixture 10 placed on the lower tank 3, a welding process is performed, wherein a laser beam is emitted through the hole 13 to the inside of the insertion portion 12 to weld the electrode connector to the inner bottom surface of the lower tank 3.

[0095] Here, the emitted laser beam can be a pulsed laser beam with an IR wavelength, and the IR wavelength can be from 1060 nm to 1080 nm, preferably 1070 nm (to have an IR wavelength of 1060 nm to 1080 nm). Figure 5 (The shape shown).

[0096] Figure 4 It shows a relatively high height and diameter (except for) Figure 4 The diagram shows a perspective view of the canister of a cylindrical battery (excluding the one on the right and the two on the left) and the lower canister 3 of the button-type battery of the present invention, and illustrates the inner diameter of the hole 13 formed in the fixture 10 during single-point welding and the inner diameter of the hole 13 formed in the fixture during multi-point welding.

[0097] Reference Figure 4 In this invention, the emitted laser beam is emitted such that the diameter of the laser beam on the cross-section is minimized at the focal point (converging at the focal point), and is emitted such that a focal point is formed at the electrode connector (negative electrode connector).

[0098] Therefore, the diameter of the laser beam in cross-section gradually increases in the direction away from the electrode junction. For example, when in Figure 4 When performing single-point welding, under the condition of emitting laser beams with the same standard, the cans of cylindrical batteries with a height of 65mm (18650 standard battery) and cylindrical batteries with a height of 70mm (21700 standard battery) require holes with inner diameters of 3.25mm and 3.5mm, respectively.

[0099] Here, the outer diameter of the 18650 standard battery can is 18 mm, and the outer diameter of the 21700 standard battery can is 21 mm. The hole through which the laser beam passes serves as the center hole of the electrode assembly (or the inner diameter of the hole formed in the fixture when inserted). Due to manufacturing limitations, the center hole must be manufactured in a cylindrical shape; therefore, the capacity of the electrode assembly is increased by reducing the diameter of the center hole to avoid limitations caused by laser interference. Thus, compared to the volume without a center hole, the volume of the 18650 and 21700 standard batteries is reduced by the volume of the center hole through which the laser beam passes, and therefore the maximum volume dimensions are limited to 96.7% and 97.2%, respectively.

[0100] On the other hand, when the lower canister 3 of the button-type battery of this application has a height h of 5 mm and a diameter d (outer diameter) of 11 mm, the inner diameter of the hole 13 through which the laser beam passes needs to be 0.25 mm to 1.5 mm. This means that the inner diameter of the insertion portion 21 of the clamp needs to be 0.25 mm to 1.5 mm.

[0101] In other words, compared to welding a tank with a large height, the inner diameter of the hole 13 required to reduce the height of the lower tank can be significantly reduced in this invention. Therefore, the inner diameter of the central hole 2b formed in the electrode assembly 2 can be reduced, and thus, the volume of the electrode assembly 2 can be increased to 98.1% to 99.9% of its volume compared to the volume without the central hole 2b.

[0102] The object of the present invention is to determine the inner diameter of the insertion portion 12 of the clamp such that the volume of the energy-generating portion can be increased to 98.1% to 99.9%, and therefore, the thickness of the insertion portion can be considered sufficiently thin.

[0103] Specifically, when multi-point welding is performed by moving the focus of the laser beam, the center hole of the electrode assembly must have a larger diameter. For example, when 18650 standard cells and 21700 standard cells undergo multi-point welding, the inner diameter of the hole must increase from 3.25 mm to 6.99 mm and from 3.5 mm to 7.53 mm, respectively. In this case, the volume is limited to 84.9% and 87.1% respectively compared to the volume without a center hole.

[0104] However, in the structure of this application, even when performing multi-point welding, the lower limit of the hole diameter increases from 0.25 mm to 0.53 mm. Even under these conditions, 98.1% to 99.7% of the volume can be ensured compared to the volume without forming a center hole.

[0105] This is because the outer rays of the laser beam are emitted in a curved path, such as... Figure 5As shown, this illustrates an amplified state where a laser beam is emitted onto the electrode connector. That is, for the transverse cross-section Wo of the laser beam emitted onto electrode connector 2a, the transverse cross-section W does not increase sharply to a specific height Z; instead, the transverse cross-section is formed to be larger above that specific height. Therefore, the diameter of the hole through which the emitted laser beam passes must be increased further according to the height of the can or lower can 3.

[0106] Therefore, in this invention, the size of the clamp 10 is limited to a certain range in order to prevent damage to the electrode assembly and the clamp and to prevent interference from the laser beam.

[0107] In other words, when the inner bottom surface of the lower tank 3 and the electrode connector 2a are welded such that the welding area between them is formed at a point during the welding process (when single-point welding is performed), when the base portion 11 is placed above the lower tank 3 and the insertion portion 12 of the clamp makes the electrode connector 2a in close contact with the inner bottom surface of the lower tank 3, the height h of the insertion portion is 5 mm or less, and the inner diameter of the hole 13 formed in the insertion portion is 0.25 mm to 1.5 mm.

[0108] Furthermore, when the inner bottom surface of the lower tank 3 and the electrode connector 2a are welded such that the welding area between them is formed at three points during the welding process (when multi-point welding is performed), when the base portion 11 is placed above the lower tank 3 and the insertion portion 12 of the clamp 10 makes the electrode connector 2a in close contact with the inner bottom surface of the lower tank 3, the height h of the insertion portion is 5 mm or less, and the inner diameter of the hole 13 formed in the insertion portion 12 is 0.53 mm to 1.5 mm.

[0109] [Table 1]

[0110] (When performing single-point welding on a lower tank with a diameter of 11mm and a height of 5mm)

[0111] Diameter of the inserted portion (mm) 0.25 0.50 0.75 1.00 1.25 1.50 2.0 Available volume (%) 99.9 99.7 99.5 99.1 98.7 98.1 96.7

[0112] [Table 2]

[0113] (When performing multi-point welding on a lower tank with a diameter of 11mm and a height of 5mm)

[0114] Diameter of the inserted portion (mm) 0.53 1.0 1.5 2.00 2.5 Available volume (%) 99.7 99.1 98.1 96.7 94.8

[0115] Referring to Tables 1 and 2 above, when performing single-point welding on a lower can with a diameter of 11 mm and a height of 5 mm according to the present invention, the minimum inner diameter of the hole 13 in the insertion portion 12 can be determined to be 0.25 mm. In this case, when it is less than 0.25 mm, there is interference between the laser beam and the fixture 10, and welding may be impossible. Therefore, when the diameter is 0.25 mm, the maximum usable volume for single-point welding can be obtained as 99.9%.

[0116] Furthermore, when performing multi-point welding, the minimum inner diameter of the hole 13 in the insertion portion 12 can be determined to be 0.53 mm. Even in this case, when it is less than 0.53 mm, there is interference between the laser beam and the fixture 10, and welding may be impossible. Therefore, when the diameter is 0.53 mm, the maximum usable volume of multi-point welding can be obtained as 99.7%.

[0117] Meanwhile, in order to meet the mass production standards that are the standard for significant differences in button-type secondary batteries, the minimum usable volume in the lower tank 3 needs to be 98% or higher.

[0118] Referring to Table 1 for single-point welding, when the inner diameter of hole 13 is 1.5 mm, the usable volume is 98.1%. However, when the inner diameter exceeds this, the usable volume decreases sharply to less than 98%, i.e., 96.7%. Therefore, in the welding method according to the invention, for single-point welding, the inner diameter of the hole formed in the insertion portion needs to be limited to the range of 0.25 mm to 1.5 mm.

[0119] Furthermore, even when referring to Table 2 for multi-point welding, the usable volume is 98.1% when the inner diameter of the hole is 1.5 mm, but when the inner diameter exceeds this, the usable volume decreases sharply to less than 98%, i.e., 96.7%. Therefore, in the welding method according to the present invention, for multi-point welding, the inner diameter of the hole formed in the insertion portion needs to be limited to the range of 0.53 mm to 1.5 mm.

[0120] Furthermore, in the lower tank provided in this invention, the height h and diameter d are determined such that the value obtained by dividing the height h by the diameter d (i.e., h / d) has a range from 0.35 to 0.6. For example, when the diameter is 11 mm and the height is 5 mm, the value is 0.45 and satisfies the above range. Within this ratio range, the most efficient battery can be implemented.

[0121] In addition, this embodiment also provides a welding device for secondary batteries, wherein when the electrode assembly 2 having a central hole 2b is placed on the lower tank 3, the electrode connector 2a of the electrode assembly 2 is welded to the inner bottom surface of the lower tank 3.

[0122] Referring to the accompanying drawings, the welding equipment of the present invention includes a fixture 10 and a laser irradiation device 20.

[0123] The clamp 10 is provided with an insertion portion 12 and a base portion 11. The insertion portion 12 is tubular and has a diameter that allows it to enter the central hole 2b of the electrode assembly 2. The base portion 11 has an enlarged diameter to form a disc shape at the end of the insertion portion 12. The diameter of the base portion 11 is larger than the diameter of the lower can 3, and the length of the insertion portion 12 is such that when the base portion 11 is positioned above the upper end of the lower can 3, the electrode connector 2a can press against the inner bottom surface of the lower can 3 within the central hole 2b of the electrode assembly 2. Furthermore, the hole 13 formed inside the insertion portion 12 is configured to open vertically when passing through the base portion 11.

[0124] Furthermore, the laser irradiation device 20 is configured to emit a laser beam toward the hole 13 of the insertion portion 12, and the laser beam is emitted such that a focal point is formed at the electrode connector 2a.

[0125] Therefore, with the electrode assembly 2 placed on the lower tank 3 such that the electrode connector 2a is placed in the center hole 2b, welding is performed when the laser beam is emitted after passing through the insertion portion 12 of the fixture 10 to the contact point between the inner bottom surface of the lower tank 3 and the electrode connector 2a.

[0126] Meanwhile, in this embodiment, the lower tank 3 has a cylindrical shape, its lower side is closed by the inner bottom surface, and its top side is open.

[0127] Furthermore, as described above, in order to suppress the volume loss of the electrode assembly 2 as much as possible, the clamp 10 according to the embodiment is formed such that when the base portion 11 is placed above the lower tank 3 and the insertion portion 12 of the clamp 10 makes the electrode connector 2a in close contact with the inner bottom surface of the lower tank 3, the height h of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion has a range from 0.25 mm to 1.5 mm.

[0128] Furthermore, when the base portion 11 is positioned above the lower tank 3 and the insertion portion 12 of the clamp 10 makes the electrode connector 2a in close contact with the inner bottom surface of the lower tank 3, the height h of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion has a range from 0.53 mm to 1.5 mm (in the case of forming multiple welding areas).

[0129] In addition, such as Figure 6 As shown, it illustrates several modified examples of the clamp 10 according to the invention. In addition to the general structure (a) in which the circular plate-shaped base portion 11 is connected to the upper end of the cylindrical insertion portion 12, the clamp 10 provided in the embodiment may have several additional structures.

[0130] That is, in the clamp 10, the hole 13 formed along the longitudinal direction of the insertion portion 12 has the following shape (b), the diameter of which is the largest on the side forming the base portion 11 and gradually decreases in the direction away from the base portion 11.

[0131] Furthermore, the base portion 11 may have the following shape (c), wherein it has a relatively high height at the edge portion and gradually decreases in the direction toward the central hole 13, that is, the shape of the wedge-shaped groove 14 is formed in the base portion 11.

[0132] Furthermore, the base portion 11 may have the following structure (d), wherein a groove 15 is formed on the side surface, such that when the insertion portion 12 enters the central hole 2b, the upper end of the lower can 3 is inserted into the groove 15.

[0133] The fixture with shape (b) can precisely limit the range of the welding point, the fixture with configuration (c) can facilitate the flow of gas supplied together during laser welding, and the fixture with configuration (d) can stably perform welding when fixed to the lower tank 3.

[0134] Figure 7 This is a longitudinal cross-sectional view of a fixture using a modified example of the present invention. In, as... Figure 7 In the fixture 10 shown, the bottom surface of the base portion 11 facing the electrode assembly 2 and the surface of the insertion portion 12 are coated with an insulating layer 16 for insulating electricity. The insulating layer 16 may be made of a material having a lower thermal conductivity than the fixture 10. Therefore, when heat is generated due to welding, the heat to be transferred to the electrode assembly is blocked, thereby preventing the deterioration of the electrode assembly.

[0135] In the first embodiment of the present invention with the above-described configuration, the electrode connector (negative connector) is welded by emitting a laser beam onto the inside of the lower tank. Therefore, no welding marks are left on the lower tank 3, thus enhancing commercial value.

[0136] The base portion 11 of the fixture 10 is positioned above the lower tank 3, thus allowing the laser beam to be emitted stably. Furthermore, it prevents foreign matter generated during welding from entering the electrode assembly 2 and protects against damage that may be caused by heat from laser irradiation.

[0137] In this invention, the inner diameter of the hole 13 in the insertion portion 12 can be varied according to the number of welding points, thus maximizing the volume of the electrode assembly 2 within the lower tank 3. For example, when the welding point is at a single location, and the inner diameter of the hole 13 formed in the insertion portion 12 is limited to between 0.25 mm and 1.5 mm, the volume of the electrode assembly 2 can be increased to approximately 100% of the internal volume of the lower tank 3, thereby improving charging and discharging capacity. On the other hand, when the welding point is at multiple locations, the inner diameter of the hole 13 is limited to a range from 0.53 mm to 1.5 mm (due to the increased diameter of the central hole of the electrode assembly), and the volume of the electrode assembly is reduced. Therefore, the volume of the electrode assembly is reduced to 97% of the internal volume of the lower tank, but the welding strength is enhanced.

[0138] In the clamp 10 provided in this invention, the hole formed along the longitudinal direction of the insertion portion 12 has a shape in which the diameter is largest on the side forming the base portion and gradually decreases in the direction away from the base portion. Therefore, the range of the points to be welded can be precisely limited.

[0139] Furthermore, the base portion of the fixture has a shape that is relatively high at the edges and gradually decreases in the direction of the central hole. Therefore, the gas supplied during laser welding can be easily discharged.

[0140] Additionally, the base portion has grooves on its side surface, allowing the upper end of the lower can to insert into the bottom surface of the base portion when the clamp insertion part enters the central hole. Therefore, welding is performed stably while the clamp is fixed.

[0141] Second Implementation Method

[0142] In this embodiment, a welding method and welding equipment are provided, wherein welding is performed by emitting a laser beam onto the inside of the lower tank 3, thereby causing defocusing.

[0143] The welding method provided in this embodiment is a welding method for secondary batteries, wherein when the electrode assembly 2 having a central hole 2b is placed on the lower tank 3, the electrode connector 2a of the electrode assembly 2 is welded to the inner bottom surface of the lower tank 3. As in the first embodiment, the welding method includes an electrode assembly placement step, a fixture placement step, and a welding step.

[0144] Figure 8 This diagram illustrates the state in which the electrode connector (the negative electrode connector among the electrode connectors) is welded to the lower can and the state in which a laser beam is emitted into the lower can during the button-type secondary battery assembly process according to the present invention, and the state in which a focal point is formed. Figure 9 This diagram shows the disassembled state of the lower tank, electrode assembly, and fixture. Figure 10 This is a schematic illustration of the height z of the focal point of the laser beam relative to the height h of the electrode assembly.

[0145] Referring to the accompanying drawings, the electrode assembly placement process and the fixture placement process are performed in the same manner as in the first embodiment.

[0146] In other words, the electrode assembly 2 is placed inside the lower tank 3 during the electrode assembly placement process, and the fixture placement process is performed while the electrode assembly 2 is placed on the lower tank 3.

[0147] The clamp 10 provided in the embodiment may also have the same or similar structure as the first embodiment. That is, a clamp 10 is provided that includes a base portion 11 having a disk shape and an insertion portion 12 extending vertically from the center of the base portion 11 and having a tubular shape. Here, the hole 13 formed in the insertion portion 12 along the longitudinal direction has a vertical opening structure that passes through the base portion 11 and the insertion portion 12, and the clamp 10 is positioned above the electrode assembly such that the insertion portion 12 enters the central hole 2b.

[0148] Furthermore, with the insertion portion 12 of the fixture 10 inserted into the central hole 2b, a welding process is performed, wherein a laser beam is emitted through the internal hole 13 of the insertion portion 12 to weld the electrode connector 2a to the inner bottom surface of the lower tank 3.

[0149] Here, the laser beam to be emitted can be one of a quasi-continuous wave laser, a pulsed laser, or a CW-modulated laser. In the quasi-continuous wave laser category, a continuous wave laser (in which an uninterrupted beam is continuously generated) or a pulsed laser (in which the light emission itself lasts only for a very short period of time) can be selected.

[0150] Quasi-continuous wave lasers can be used for welding between electrode connector 2a and lower tank 3 because of the flexibility in adjusting the output and laser wavelength. Furthermore, during the welding process, the inner bottom surface of lower tank 3 and electrode connector 2a can be individually welded to each other at multiple points.

[0151] Meanwhile, during the welding process provided in the embodiment, the laser beam is emitted in a defocused state, wherein a focal point is formed before the laser beam reaches the contact point between the inner bottom surface of the lower tank 3 and the electrode connector 2a.

[0152] In other words, the laser beam used for welding is emitted such that the diameter of the cross-section is largest at the emission point and smallest at the focal point (converging at the focal point). The laser beam converges at the focal point and then reaches the welding point, i.e., the electrode joint 2a is in a state of gradually increasing diameter. Therefore, the laser beam is emitted in a defocused state, so that the focal point is formed within the fixture before reaching the electrode joint.

[0153] The dictionary definition of defocus is the absence of a precise focal point, with '+' defocus indicating a focal point in front of the object and '-' defocus indicating a focal point behind the object. Therefore, the laser beam in this invention is emitted in a '+' defocused state, as... Figure 8 and Figure 9 As shown.

[0154] Here, the focal point of the laser beam is formed between one-third and two-thirds of the way between the uppermost and lowermost ends of the insertion portion 12. Preferably, the focal point is formed in the middle of the internal hole of the insertion portion 12. That is, when the height of the electrode assembly is h, and the height at which the focal point is formed is as follows... Figure 10 When z is shown, it is preferable that the focus is formed at a position, where h = 2z (here, as shown in the figure). Figure 10 As shown, the electrode assembly has a height h so as to contact or approach the bottom surface of the base portion, and the base portion is considered to be thin enough that its thickness is negligible.

[0155] Furthermore, z can be formed in the range of 1 / 3h ≤ z ≤ 2 / 3h.

[0156] For reference only. Figure 10 In the diagram, h and z represent the case where the height of the insertion portion 12 and the height of the electrode assembly 2 are assumed to be equal. However, when the height of the insertion portion 12 is greater than the height of the electrode assembly 2, the height z forming the focal point can be further increased according to the size of the insertion portion, but the height of the focal point shall not exceed the height of the electrode assembly.

[0157] As described above, since the laser beam is emitted in a '+' defocused state, the diameter of the laser beam entering the fixture 10 in its transverse cross-section may be smaller than the diameter when focusing is performed at the welding area. That is, when focusing is performed at the welding area, the inner diameter of the internal hole 13 of the insertion portion 12 is further increased to avoid interference. However, when the focus shifts upward by z due to '+' defocusing, the diameter of the laser beam in its cross-section at the point of entry into the insertion portion 12 decreases, and the inner diameter of the internal hole 13 of the insertion portion 12 can also be reduced. Therefore, the size of the fixture 10 can be reduced. Figure 9 As shown, the laser beam focused at the focal point is emitted in a wedge shape. Therefore, the diameter of the internal hole of the clamp insertion part needs to be increased to avoid interference, so that the focal point is formed at the electrode connector 2a. Due to this increase in the diameter of the internal hole, the size of the central hole 2b of the electrode assembly 2 must also be increased, which may limit the total capacity of the electrode assembly 2.

[0158] Therefore, the welding method according to the embodiment enables the welding of electrode assemblies with even smaller dimensions, and minimizes the size of the central hole 2b while increasing the capacity of the electrode assembly 2.

[0159] Meanwhile, the clamp 10 is made of metal material and has sufficient strength and thermal resistance, and the insertion portion 12 that enters the center hole 2b of the electrode assembly 2 can be manufactured to have a sufficiently small thickness.

[0160] In addition, this embodiment also provides a welding device for secondary batteries, wherein when the electrode assembly 2 having a central hole 2b is placed on the lower tank 3, the electrode connector 2a of the electrode assembly 2 is welded to the inner bottom surface of the lower tank 3.

[0161] Referring to the accompanying drawings, the welding equipment of the present invention includes a fixture 10 and a laser irradiation device 20.

[0162] The clamp 10 may be formed only by an insertion portion 12 having a tubular shape and a diameter capable of entering the central hole 2b of the electrode assembly 2, or it may include an insertion portion 12 having a tubular shape and a diameter capable of entering the central hole 2b of the electrode assembly 2, and a base portion 11 having an enlarged diameter to form a disk shape at the end of the insertion portion 12.

[0163] Furthermore, the laser irradiation device 20 is configured to emit a laser beam into the hole 13 of the insertion portion 12, and the laser beam is emitted such that a focal point is formed within the insertion portion 12 of the fixture 10 before reaching the welding point.

[0164] In other words, with the electrode assembly 2 placed on the lower tank 3 such that the electrode connector 2a is positioned within the central hole 2b, welding is performed when the laser beam, after passing through the internal hole 13 of the insertion portion 12, is emitted to the contact point between the inner bottom surface of the lower tank 3 and the electrode connector 2a. The laser irradiation device 20 emits the laser beam in a '+' defocused state, wherein a focal point is formed before the laser beam reaches the contact point between the inner bottom surface of the lower tank 3 and the electrode connector 2a.

[0165] Therefore, in order to create a '+' defocus, the laser irradiation device 20 can be coupled to a sliding device (not shown), which can rise and fall to adjust the position of the focal point. The sliding device can be configured not only to raise and lower the laser irradiation device 20 to adjust the position of the focal point, but also to slide the laser irradiation device in the left-right and front-back directions to form multiple welding points.

[0166] In the present invention with the above configuration, the negative electrode connector is welded by emitting a laser beam onto the inside of the lower tank 3. Therefore, no welding marks are left on the outer surface of the lower tank, thus improving commercial value.

[0167] Specifically, in this invention, the laser beam is emitted in a defocused state, such that a focal point is formed within the internal hole 13 formed in the insertion portion 12 of the clamp, and thus the maximum inner diameter of the laser beam entering the clamp can be reduced. Therefore, the diameter of the clamp (particularly the insertion portion 12) can be reduced, but the volume of the electrode assembly can be increased (by reducing the size of the central hole). Therefore, the capacity of the secondary battery can be increased.

[0168] Furthermore, the movement of the insertion part is adjusted when the base part is placed on the insertion part. Therefore, welding can be performed stably.

[0169] In this invention, when the laser beam is defocused, a focal point is formed between one-third and two-thirds of the way between the uppermost and lowermost points of the insertion portion (the base portion can be assumed to be sufficiently thin). Therefore, the diameter of the laser beam's cross-section can be minimized.

[0170] Third Implementation Method

[0171] In this embodiment, a monitoring device and a monitoring method for the secondary battery welding process are provided.

[0172] Figure 11 This is a diagram illustrating a simplified configuration of a monitoring device for a secondary battery welding process according to a preferred embodiment of the present invention, and Figure 12 The path that enables the reflection of the laser beam is represented by a dashed line and added to... Figure 11 The diagram. However, to prevent the lines in the attached diagram from overlapping, in Figure 11 and Figure 12 Electrode assembly 2 and fixture 10 are omitted, and only the lower tank 3 is shown.

[0173] Reference Figure 11 and Figure 12 The monitoring device of the present invention includes the clamp 10 and the laser irradiation device 20 described in the foregoing embodiments.

[0174] Here, the clamp 10 may have a structure from which the base portion 11 is removed, that is, it may only have an insertion portion 12, which has a tubular shape and a diameter that allows it to enter the central hole of the electrode assembly, or it may have both an insertion portion 12 and a base portion 11.

[0175] Furthermore, in this embodiment, the laser irradiation device 20 that emits a laser beam into the hole of the insertion portion includes a welding laser irradiation device 50, an illumination laser irradiation device 60, and an image sensor 40.

[0176] When welding and monitoring are performed by the monitoring equipment, the electrode assembly 2 is embedded in the lower tank 3, and the electrode connector 2a is configured to contact the inner bottom surface of the lower tank 3.

[0177] Therefore, the welding laser irradiation device 50 can emit a welding laser beam Y with the electrode assembly 2 placed inside the lower tank 3 such that the electrode connector 2a is placed in the central hole 2b.

[0178] The welding laser irradiation device 50 emits a welding laser beam Y into the central hole 2b (more precisely, into the hole of the fixture insertion part) via the focusing lens 30 to weld the contact point between the electrode joint 2a and the lower tank 3.

[0179] The welding laser irradiation device 50 includes: a welding laser oscillator 51 that emits a welding laser beam Y; a first optical insulator 54 configured such that the welding laser beam Y emitted from the welding laser oscillator 51 is allowed to pass through it as it moves in the forward direction, but is blocked when it returns; a first collimator 52 configured such that the welding laser beam Y that has passed through the first optical insulator 54 becomes parallel after passing through it; and a first dichroic mirror 53 configured such that the welding laser beam Y that has passed through the first collimator 52 is reflected from it to a focusing lens 30.

[0180] The welding laser oscillator 51 emits a welding laser beam Y with appropriate output, and the emitted welding laser beam Y is directed to a first optical insulator 54. The first optical insulator 54 is a Faraday isolator and is configured to transmit the laser beam in only one direction.

[0181] In other words, the first optical insulator 54 is configured such that the welding laser beam Y emitted from the welding laser oscillator 51 is allowed to pass through it as it moves in the forward direction, but is blocked (by part of the first dichroic mirror) upon return. The detailed internal structure of the Faraday isolator is well known in the art, and therefore its detailed description will be omitted here.

[0182] The welding laser beam Y, having passed through the first optical insulator 54, is emitted to the first collimator 52. The first collimator 52 parallelizes the welding laser beam Y by suppressing diffusion (in the radial direction) and focusing the beam, thereby keeping its diameter constant. That is, the laser beam has diffuse characteristics when emitted, but the first collimator 52 can provide this function through a combination of multiple optical lenses to suppress the diffusion of the welding laser beam Y.

[0183] The welding laser beam Y, which has passed through the first collimator 52, is emitted to the first dichroic mirror 53. The first dichroic mirror 53 can reflect part of the laser beam and allow another part to pass through it, depending on the characteristics of the laser beam, and is manufactured such that the welding laser beam Y with a relatively high output is completely reflected from it.

[0184] The welding laser beam Y, which has been reflected from the first dichroic mirror 53, is emitted toward the welding point and passes through the focusing lens 30 in the emission path, and is emitted in a converging state, so that a focal point is formed in the welding area where the electrode joint and the lower tank are in contact with each other.

[0185] Meanwhile, the illumination laser irradiation device 60, which emits an illumination laser beam L with a relatively lower output than the welding laser beam Y, is also configured to have a similar configuration to the welding laser irradiation device 50.

[0186] In other words, the illumination laser irradiation device 60 includes: an illumination laser oscillator 61 that emits an illumination laser beam L; a second optical insulator 64 configured such that the illumination laser beam L emitted from the illumination laser oscillator 61 is allowed to pass through it as it moves in the forward direction, but is blocked upon return; a second collimator 62 configured such that the illumination laser beam L that has passed through the second optical insulator 64 becomes parallel after passing through it; and a second dichroic mirror 63 configured such that the illumination laser beam L that has passed through the second collimator 62 is reflected from it to the focusing lens 30. A portion of the illumination laser beam L is reflected from it, and another portion is transmitted through it, such that the illumination laser beam L reflected from the welding area is transmitted through it.

[0187] If possible, the illumination laser oscillator 61 emits an illumination laser beam L with an output capable of providing a sufficient amount of light to the image sensor 40 without affecting the welding quality, and the emitted illumination laser beam L is emitted to the second optical insulator 64.

[0188] The second optical insulator 64 is a Faraday isolator similar to the first optical insulator 54, and is configured to transmit the illumination laser beam L in only one direction.

[0189] The illumination laser beam L, which has passed through the second optical insulator 64, is emitted to the second collimator 62. Similar to the first collimator 52, the second collimator 62 also parallelizes the illumination laser beam L by suppressing diffusion and focusing the beam, thereby keeping its diameter constant.

[0190] The illumination laser beam L, which has passed through the second collimator 62, is emitted to the second dichroic mirror 63. The second dichroic mirror 63 is configured to reflect a portion of the illumination laser beam L while allowing another portion to be transmitted through it.

[0191] The illumination laser beam L reflected from the second dichroic mirror 63 is emitted toward the welding point. Here, the first dichroic mirror 53 allows all or almost all of the illumination laser beam L to be transmitted through it. The illumination laser beam L, having passed through the first dichroic mirror 53, reaches the welding area after passing through the focusing lens 30. Here, the illumination laser beam L may have a diameter larger than the inner diameter of the central hole before reaching the focusing lens 30, but its diameter becomes smaller than the inner diameter of the hole in the jig insertion portion when passing through the focusing lens 30. Moreover, the diameter of the illumination laser beam L reflected from the welding area can return to its original size when passing through the focusing lens 30.

[0192] The illumination laser beam L, reflected from the welding area, is transmitted through the focusing lens 30, the first dichroic mirror 53, and the second dichroic mirror 63, and then reaches the image sensor 40. Here, the focusing lens 30, the first dichroic mirror 53, and the second dichroic mirror 63 can be tuned such that the amount of light transmitted to the image sensor 40 for the illumination laser beam L reflected from the welding area is greater than the amount of light reflected and lost. For example, the welding laser beam Y and the illumination laser beam L differ from each other in laser characteristics such as output and / or wavelength, and can therefore be tuned such that the transmittance and reflectance when the welding laser beam Y enters and leaves are different from the transmittance and reflectance when the illumination laser beam L enters and leaves.

[0193] In other words, the illumination laser beam L emitted from the illumination laser irradiation device 60 is transmitted through the first dichroic mirror 53 and the focusing lens 30 disposed in the welding laser irradiation device 50, and then reflected to the image sensor 40. Therefore, in the laser irradiation device 20 of the present invention, the welding laser beam Y and the illumination laser beam L can be emitted vertically from the top side of the central hole 2b (more precisely, the hole of the clamp insertion portion).

[0194] Therefore, in the device of the present invention, the first dichroic mirror 53 is configured to reflect all or most of the welding laser beam Y and allow all or most of the illumination laser beam L to be transmitted through it. The second dichroic mirror 63 is configured to reflect a portion of the illumination laser beam L and allow another portion to be transmitted through it, and thus, at least a portion of the illumination laser beam L reflected from the welding point can reach the image sensor 40.

[0195] Simultaneously, depending on the output or characteristics of the laser beams, the illumination laser beam L and the welding laser beam Y can be emitted at the same time. However, to avoid interference between the laser beams, the emission of the illumination laser beam L can be stopped when the welding laser beam Y is emitted, and the emission of the welding laser beam Y can be stopped when the illumination laser beam L is emitted.

[0196] More specifically, the illumination laser beam L and the welding laser beam Y can be emitted simultaneously. However, the welding laser beam Y is emitted continuously, and the emission of the welding laser beam Y can be stopped, while the illumination laser beam L is emitted within a specific time period to avoid interference.

[0197] In addition, this embodiment also provides a monitoring method for the secondary battery welding process.

[0198] The monitoring method according to the embodiment is a monitoring method for the welding process of secondary batteries, wherein when the electrode assembly 2 having a central hole 2b is placed on the lower tank 3, the electrode connector 2a of the electrode assembly 2 is welded to the inner bottom surface of the lower tank 3. The monitoring method includes an electrode assembly placement process, a fixture placement process, a welding process, and a sensing process.

[0199] During the electrode assembly placement process, electrode assembly 2 is placed inside the lower tank 3, such that electrode connector 2a is placed within the central hole 2b. That is, as... Figure 11 and Figure 12 As shown, electrode assembly 2 is placed inside lower tank 3, such that electrode assembly 2 is exposed upwards. Here, electrode connector 2a of electrode assembly 2 and the inner bottom surface of lower tank 3 are in contact with each other, and the point of contact between electrode connector 2a and lower tank 3 is exposed upwards in a central hole 2b formed at the center of electrode assembly 2.

[0200] As described above, when the electrode assembly 2 is set and placed on the lower tank 3, a clamp receiving process is performed, wherein a clamp including a tubular insertion portion is positioned such that the insertion portion enters the central hole, and then a welding process is performed.

[0201] During the welding process, the welding laser beam Y is emitted from above the hole of the insertion part into the hole of the insertion part via the focusing lens 30, and thus the contact point between the electrode connector 2a and the lower tank 3 is welded.

[0202] For the welding laser beam Y emitted during the welding process, it is desirable to focus it on or slightly above the welding point (+defocus state) via the focusing lens 30. However, during emission, the welding laser beam Y is emitted in a manner that does not damage the electrode assembly 2. Here, in order to protect the electrode assembly 2 from the influence of the welding laser beam Y, the clamp 10 may have a structure in which the base portion 11 is connected to the upper end of the insertion portion 12, as described above.

[0203] Furthermore, a sensing process is performed to check the weld status during or after welding. During the sensing process, an illumination laser beam L is emitted into a central hole 2b via a focusing lens 30. The image sensor 40 can receive the reflected illumination laser beam L and optically inspect the weld quality.

[0204] The image sensor 40 can calculate and process data about the received illumination laser beam L and provide information about the welded section as an image. The provided image is sent to a separate display device, or converted into a digital signal, and then sent to an operator or central computer that controls the entire production process.

[0205] Here, the illumination laser beam L emitted during the sensing process is emitted vertically from the upper side of the central hole 2b, just like the welding laser beam Y, so that the illumination laser beam L can inspect the welding points inside the electrode assembly 2.

[0206] Meanwhile, the monitoring method of the present invention can be performed solely by the welding laser irradiation device 50 without the illumination laser irradiation device 60. That is, when welding is performed after the electrode assembly 2 with the center hole 2b is placed on the lower tank 3, or after welding is completed, the welding laser beam Y can be used as the illumination laser beam L by reducing and converting its output to match the output of the illumination laser beam L.

[0207] In this case, it is not necessary to have a separate illumination laser irradiation device 60, and it is possible to monitor using only a welding laser irradiation device 50.

[0208] In the present invention with the above configuration, the welding of electrode joint 2a is performed inside the lower tank 3, thus improving the appearance quality. Furthermore, when welding electrode joint 2a is performed, the illumination laser beam L is emitted perpendicularly in the same manner as the welding laser beam Y, thus allowing for clearer inspection and monitoring of the welding status.

[0209] Furthermore, in this invention, the welding laser beam Y can be used as the illumination laser beam L by adjusting the output of the welding laser irradiation device 50, without using a separate illumination laser irradiation device 60. Therefore, the welding equipment can be manufactured in a more compact size, and its structure can be simplified.

[0210] Although the present invention has been described with reference to specific embodiments and accompanying drawings, the present invention is not limited thereto, and various changes and modifications can be made by those skilled in the art within the scope of the technical concept of the present invention and the equivalents of the appended claims.

[0211] Cross-references to related applications

[0212] This application claims priority to Korean Patent Application No. 10-2020-0116432, filed on September 10, 2020; Korean Patent Application No. 10-2020-0117213, filed on September 11, 2020; Korean Patent Application No. 10-2020-0117214, filed on September 11, 2020; and Korean Patent Application No. 10-2021-0119653, filed on September 8, 2021, the entire contents of which are incorporated herein by reference.

Claims

1. A welding device for secondary batteries, wherein, When an electrode assembly with a central hole is placed on the lower tank, the electrode connector of the electrode assembly is welded to the inner bottom surface of the lower tank using the welding equipment, the welding equipment comprising: A clamp comprising an insertion portion and a base portion, the insertion portion having a tubular shape and a diameter capable of entering the central hole of the electrode assembly, the base portion having an enlarged diameter to form a disk shape at an end of the insertion portion, the insertion portion extending vertically from the base portion; and A laser irradiation device configured to emit a laser beam into the hole of the insertion portion. Specifically, with the electrode assembly positioned on the lower tank such that the electrode connector is placed within the central hole, welding is performed when the laser beam, after passing through the hole inside the insertion portion of the fixture, is emitted to the contact point between the inner bottom surface of the lower tank and the electrode connector. The lower tank has a cylindrical shape with its lower side closed by the inner bottom surface and its top side open, and the diameter of the base portion is larger than the diameter of the lower tank.

2. The welding equipment according to claim 1, wherein, When the insertion portion is inserted into the center hole of the electrode assembly installed in the lower tank, the base portion is positioned above the lower tank.

3. The welding equipment according to claim 2, wherein, When the base portion is positioned above the lower can such that the electrode connector is in close contact with the inner bottom surface of the lower can at the insertion portion of the clamp, the height (h) of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion is in the range of 0.25 mm to 1.5 mm.

4. The welding equipment according to claim 2, wherein, When the base portion is positioned above the lower can such that the electrode connector is in close contact with the inner bottom surface of the lower can at the insertion portion of the clamp, the height (h) of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion is in the range of 0.53 mm to 1.5 mm.

5. The welding equipment according to claim 2, wherein, The height (h) and diameter (d) of the lower tank are determined such that the value obtained by dividing the height (h) by the diameter (d) is in the range of 0.35 to 0.

6.

6. The welding equipment according to claim 2, wherein, The hole formed along the longitudinal direction of the insertion portion has the following shape: the diameter is largest on the side forming the base portion and gradually decreases in the direction away from the base portion.

7. The welding equipment according to claim 2, wherein, The base portion has the following shape: the base portion has a relatively high height at the edge portion and gradually decreases in the direction of the hole towards the center.

8. The welding equipment according to claim 2, wherein, The base portion has a groove on its side surface, such that when the insertion portion enters the central hole, the upper end of the lower can is inserted into the groove.

9. The welding equipment according to claim 2, wherein, The insertion portion has a length that allows the electrode connector to make close contact with the inner bottom surface of the lower tank when the insertion portion enters the central hole.

10. The welding equipment according to claim 2, wherein, The clamp is made of metal.

11. The welding equipment according to claim 10, wherein, The bottom surface of the base portion facing the electrode assembly and the surface of the insertion portion are coated with an insulating layer for insulating electricity.

12. The welding equipment according to claim 11, wherein, The insulating layer is made of a material having a lower thermal conductivity than the clamp.

13. The welding equipment according to claim 1, wherein, The laser beam is emitted in a defocused state, in which a focal point is formed before the laser beam reaches the contact point between the inner bottom surface of the lower tank and the electrode connector.

14. A welding method for secondary batteries, wherein, When an electrode assembly with a central hole is placed on the lower tank, the electrode connector of the electrode assembly is welded to the inner bottom surface of the lower tank by the welding method, which includes the following steps: The electrode assembly placement process involves placing the electrode assembly on the lower tank such that the electrode connector is placed inside the central hole of the electrode assembly. The clamp placement process involves placing a clamp above the electrode assembly such that an insertion portion enters the central hole. The clamp includes a base portion and the insertion portion, which extends vertically from the base portion and has a tubular shape. The base portion has an enlarged diameter to form a disc shape at the end of the insertion portion. as well as The welding process involves emitting a laser beam into a hole inside the insertion portion and welding the electrode connector to the inner bottom surface of the lower tank. The lower tank has a cylindrical shape with its lower side closed by the inner bottom surface and its top side open, and the diameter of the base portion is larger than the diameter of the lower tank.

15. The welding method according to claim 14, wherein, The laser beam emitted during the welding process is a pulsed laser beam with an IR wavelength.

16. The welding method according to claim 14, wherein, During the fixture placement process, the end of the insertion portion brings the electrode connector into close contact with the inner bottom surface of the lower tank.

17. The welding method according to claim 14, wherein, When the base portion is positioned above the lower can such that the electrode connector is in close contact with the inner bottom surface of the lower can at the insertion portion of the clamp, the height (h) of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion is in the range of 0.25 mm to 1.5 mm. The inner bottom surface of the lower tank and the electrode connector are welded in the welding process, so that a welding area is formed at a point.

18. The welding method according to claim 14, wherein, When the base portion is positioned above the lower can such that the electrode connector is in close contact with the inner bottom surface of the lower can at the insertion portion of the clamp, the height (h) of the insertion portion is 5 mm or less, and the inner diameter of the hole formed in the insertion portion is in the range of 0.53 mm to 1.5 mm. The inner bottom surface of the lower tank and the electrode connector are welded in the welding process, thereby forming a welding area at multiple points.

19. The welding method according to claim 14, wherein, The height (h) and diameter (d) of the lower tank are determined such that the value obtained by dividing the height (h) by the diameter (d) is in the range of 0.35 to 0.

6.

20. The welding method according to claim 14, wherein, During the welding process, the laser beam is emitted in a defocused state, in which a focal point is formed before the laser beam reaches the contact point between the inner bottom surface of the lower tank and the electrode connector.

21. The welding method according to claim 20, wherein, During the welding process, the focal point of the laser beam is formed between one-third and two-thirds of the way within the uppermost and lowermost ends of the insertion portion.

22. The welding method according to claim 20, wherein, The laser beam emitted during the welding process is one of a quasi-continuous wave laser, a pulsed laser, and a CW modulated laser.

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