Secondary battery

Abstract

The present disclosure provides a secondary battery capable of improving welding quality. As an example, a secondary battery is disclosed, the secondary battery including: an electrode assembly; a current collector bonded to the electrode assembly; a case in which the electrode assembly is accommodated; a cover plate bonded to the case to seal the electrode assembly and the current collector; and a terminal plate connected to the current collector and exposed through the cover plate, wherein at least one of between the electrode assembly and the current collector and between the current collector and the terminal plate can be performed with double-beam and swing welding.

Description

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2021-0157780, filed on November 16, 2021, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a secondary battery that can improve welding quality. Background Technology

[0003] A secondary battery is an electrical energy storage system that converts electrical energy into chemical energy and stores the converted energy to provide high energy density. Unlike primary batteries, which cannot be recharged, secondary batteries are rechargeable and widely used in IT devices such as smartphones, cell phones, laptops, and tablet PCs. In recent years, electric vehicles have gained attention due to concerns about environmental pollution, and the trend of using high-capacity secondary batteries in electric vehicles is growing. Secondary batteries need to have high energy density, high output, and stability characteristics.

[0004] The information disclosed in this background section is only intended to enhance the understanding of the background art of the invention, and therefore may contain information that does not constitute prior art. Summary of the Invention

[0005] This disclosure provides a secondary battery that can improve welding quality.

[0006] The secondary battery according to this disclosure may include: an electrode assembly; a current collector coupled to the electrode assembly; a housing in which the electrode assembly is housed; a cover coupled to the housing to seal the electrode assembly and the current collector; and a terminal plate connected to the current collector and exposed through the cover plate, wherein at least one of the electrode assembly and the current collector and the current collector and the terminal plate may be subjected to dual-beam and oscillating welding.

[0007] Here, the dual beams used for welding may include a first region formed at the center and a second region formed around the first region.

[0008] In addition, the first region of the dual beams can have a circular shape, and the second region can have a ring shape.

[0009] Additionally, oscillating welding can be performed along the second region.

[0010] Additionally, oscillating welding can be performed along the edge of the dual beams, while simultaneously forming repeating arcs.

[0011] Additionally, oscillating welding can include beads with a repeating serrated shape.

[0012] In addition, in the serrated shape, the diameter difference between the outer serrated part (A) and the inner serrated part (B) can be greater than or equal to 5 μm.

[0013] In addition, dual-beam and oscillating welding can be performed on the connection between the housing and the cover plate.

[0014] In addition, at least one of the electrode assembly and the current collector, as well as the current collector and the terminal block, can be made of dissimilar metals to perform welding. Attached Figure Description

[0015] Figure 1 This is a perspective view showing a secondary battery according to an embodiment of the present disclosure.

[0016] Figure 2 This is a cross-sectional view showing a secondary battery according to an embodiment of the present disclosure.

[0017] Figure 3A and Figure 3B A laser beam used in a secondary battery according to an embodiment of the present disclosure is shown.

[0018] Figure 4 This is a photograph showing the welding area used in a secondary battery according to an embodiment of the present disclosure.

[0019] Figure 5A and Figure 5B This is an enlarged photograph showing the welding area used in a secondary battery according to an embodiment of the present disclosure.

[0020] Figure 6 It is a graph showing the absorption rate of the laser beam according to the material used. Detailed Implementation

[0021] Preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings.

[0022] Examples of this disclosure are provided to explain it more fully to those skilled in the art, and the following examples may be modified in various other forms. However, this disclosure may be embodied in many different forms and should not be construed as limited to the exemplary (or exemplary) embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will convey to those skilled in the art aspects and features of this disclosure.

[0023] Additionally, for the sake of brevity and clarity, the dimensions or thicknesses of various components are exaggerated in the accompanying drawings. The same reference numerals always refer to the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, it will be understood that when element A is referred to as being "connected to" element B, element A may be directly connected to element B, or there may be an intermediate element C between them, such that element A and element B are indirectly connected to each other.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising or including” and / or variations thereof are used in this specification, it indicates the presence of the stated features, quantities, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, quantities, steps, operations, elements, components, and / or groups thereof.

[0025] It will be understood that although the terms first, second, etc., may be used herein to describe various components, elements, regions, layers, and / or parts, these components, elements, regions, layers, and / or parts should not be limited by these terms. These terms are used only to distinguish one component, element, region, layer, and / or part from another component, element, region, layer, and / or part. Thus, for example, without departing from the teachings of this disclosure, the first component, first element, first region, first layer, and / or first part discussed below may be referred to as a second component, second element, second region, second layer, and / or second part.

[0026] For ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” and “above” may be used herein to describe the relationship between one element or feature as shown in the figures and another (other) element or feature. It will be understood that, in addition to the orientation depicted in the figures, spatial relative terms are intended to cover different orientations of the device in use or operation. For example, if an element or feature in the figures is flipped, an element described as “below” or “under” another element or feature would then be positioned “above” or “above” said other element or feature. Thus, the exemplary term “below” can encompass both above and below orientations.

[0027] Figure 1 This is a perspective view showing an exemplary secondary battery according to an embodiment of the present disclosure.

[0028] exist Figure 1 In the example shown, the secondary battery 100 may include an electrode assembly 110 (see...). Figure 2), first terminal 120, second terminal 130, housing 140 and cover assembly 150.

[0029] In some examples, the first terminal 120 and the second terminal 130 may penetrate the cover assembly 150 and be exposed upwards. In some examples, the first terminal 120 may include, or be referred to as, the negative terminal, and the second terminal 130 may include, or be referred to as, the positive terminal.

[0030] In some examples, the upper insulating member 162 may be positioned between the first terminal 120 and the cover assembly 150, and the connecting member 180 may be positioned between the second terminal 130 and the cover assembly 150. Therefore, the first terminal 120 and the cover assembly 150 can be electrically insulated from each other (i.e., separated). Alternatively, when the connecting member 180 is made of a conductive material, the second terminal 130 and the cover assembly 150 can be electrically connected to each other (i.e., joined), so the housing 140 can, for example, be filled with a positive (or negative) polarity.

[0031] In some examples, the housing 140 can be formed using a deep drawing process of a sheet metal or a bending and welding process of a sheet metal. Additionally, the housing 140 has space to accommodate the electrode assembly 110 and the cover assembly 150 to be placed, and can be in the form of a hexahedron. In some examples, the housing 140 may include a rectangular base 141 having long and short sides, long sides 142 and 143 that bend and extend from the long side of the base 141 toward the cover assembly 150, and short sides 144 and 145 that extend from the short side of the base 141 toward the cover assembly 150. In some examples, the housing 140 may include, or be referred to as, a housing, outer shell, or external material.

[0032] In some examples, the cover assembly 150 may include a cover plate 151, a plug 152, and a safety vent 153. This will be explained again below.

[0033] Figure 2 This is a cross-sectional view showing a secondary battery according to an embodiment of the present disclosure.

[0034] like Figure 2 As shown, the secondary battery 100 may include an electrode assembly 110 having a winding axis in a horizontal direction (i.e., a direction substantially parallel to the length direction of the cover assembly 150). In some examples, the electrode assembly may include both stacked and wound types.

[0035] The electrode assembly 110 can be formed by winding or stacking a stack of a first electrode plate 111, a diaphragm 113, and a second electrode plate 112, wherein the first electrode plate 111, the diaphragm 113, and the second electrode plate 112 are formed in a plate shape or a film shape. In some examples, the first electrode plate 111 can be used as a negative electrode, and the second electrode plate 112 can be used as a positive electrode. Of course, the reverse is also possible. In some examples, the first electrode plate 111 is formed by coating a first electrode active material (such as graphite or carbon) onto a first electrode current collector formed of a metal foil (such as copper, copper alloy, nickel, or nickel alloy), and may include a first electrode uncoated portion 111a as a region where the first electrode active material is not coated. In some examples, the second electrode plate 112 is formed by coating a second electrode active material (such as a transition metal oxide) onto a second electrode current collector formed of a metal foil (such as aluminum or aluminum alloy), and may include a second electrode uncoated portion 112a as a region where the second electrode active material is not coated. In some examples, a separator 113 is located between the first electrode plate 111 and the second electrode plate 112 to prevent short circuits and allow lithium ions to move, and may comprise a polyethylene, polypropylene, or a composite membrane of polyethylene and polypropylene. Alternatively, the separator 113 may comprise a functional membrane in which an inorganic material layer is coated onto a porous polymer membrane. Alternatively, the separator 113 may be replaced with an inorganic solid electrolyte (such as a sulfide electrolyte, oxide electrolyte, or phosphate electrolyte) that does not require an electrolyte in a liquid or gel state. A first terminal 120 electrically connected to the first electrode plate 111 and a second terminal 130 electrically connected to the second electrode plate 112 may be located at opposite ends of the electrode assembly 110. In some examples, the electrode assembly 110 may be housed together with the electrolyte in a housing 140. In some examples, the electrolyte may comprise a lithium salt (such as LiPF6) in an organic solvent (such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), or ethyl methyl carbonate (EMC)). Alternatively, the electrolyte may be in liquid or gel form. In some examples, when using inorganic solid electrolytes, the electrolyte solution can be omitted.

[0036] The first terminal 120 may be made of metal and may be electrically connected to the first electrode plate 111. In some examples, the first terminal 120 may include a first current collector 121, a first terminal post 122, and a first terminal plate 123.

[0037] In some examples, the first current collector 121 may contact a first electrode uncoated portion 111a protruding from one end of the electrode assembly 110. Essentially, the first current collector 121 may be welded to the first electrode uncoated portion 111a. In some examples, the first current collector 121 may be formed in an approximately "L" shape. In some examples, the first terminal post 122 may be integrally formed on the first current collector 121, or the first terminal post 122 may be separately provided for riveting and / or welding to the first current collector 121. In some examples, the first current collector 121 may be made of copper or a copper alloy. Additionally, as a method for welding the first current collector 121 to the first electrode uncoated portion 111a, laser welding with a dual beam and wobble structure can be used, which will be described later.

[0038] In some examples, the first terminal post 122 may project upward through a cover plate 151 (described later) and extend a predetermined length, and may be electrically connected from the lower part of the cover plate 151 to the first current collector 121. Additionally, in some examples, the first terminal post 122 may include a flange 122a extending along the length of the cover plate 151 to prevent the first terminal post 122 from falling out. The first terminal post 122 may be integrally formed with the first current collector 121, or may be riveted and / or welded after insertion into the first current collector 121. In some examples, the first terminal post 122 may be electrically insulated from the cover plate 151. In some examples, the first terminal post 122 may be made of copper, a copper alloy, aluminum, or an aluminum alloy. The first terminal plate 123 may include holes 123a to which the first terminal post 122 may be joined and riveted and / or welded. In some examples, the interface between the upwardly exposed first terminal post 122 and the first terminal plate 123 may be welded to each other. Alternatively, the method for welding the first terminal post 122 to the first terminal plate 123 can also be laser welding with a dual-beam and oscillating structure, which will be described later.

[0039] In some examples, a busbar (not shown) made of aluminum or aluminum alloy is welded to the first terminal plate 123, so that multiple secondary batteries can be connected in series or in parallel.

[0040] The second terminal 130 may also be made of metal and may be electrically connected to the second electrode plate 112. In some examples, the second terminal 130 may include a second current collector 131, a second terminal post 132, and a second terminal plate 133. The second current collector 131 may contact the uncoated portion 112a of the second electrode protruding from one end of the electrode assembly 110. Alternatively, as a method for welding the second current collector 131 to the uncoated portion 112a of the second electrode, laser welding with a dual-beam and oscillating structure may be used, which will be described later.

[0041] In some examples, the second terminal post 132 may be integrally formed on the second current collector 131, or the second terminal post 132 may be separately provided to be inserted into and attached to the second current collector 131. The second current collector 131 may be made of, for example, but not limited to, aluminum or aluminum alloy.

[0042] The second terminal post 132 may protrude upward and extend a predetermined length through the cover plate 151, which will be described later, and may be electrically connected from the lower portion of the cover plate 151 to the second current collector 131. The second terminal post 132 may protrude and extend a predetermined length to the upper portion of the cover plate 151, and may simultaneously include a flange 132a to prevent the second terminal post 132 from falling out from the lower portion of the cover plate 151. In the second terminal post 132, the area located below the flange 132a may be inserted into the second current collector 131 and then riveted and / or welded. In some examples, the second terminal post 132 may be made of aluminum or an aluminum alloy.

[0043] The second terminal plate 133 may include a hole 133a, and the second terminal post 132 may be coupled to the hole 133a. Additionally, the second terminal post 132 and the second terminal plate 133 may be riveted and / or welded to each other. Furthermore, the method for welding the second terminal post 132 to the second terminal plate 133 may be laser welding with a dual-beam and oscillating structure, which will be described later.

[0044] Additionally, multiple secondary batteries can be connected in series or in parallel by welding a busbar (not shown) made of aluminum or aluminum alloy to the second terminal plate 133. In some examples, the second terminal plate 133 can be electrically connected to the cover plate 151, so the cover plate 151 and the housing 140, which will be described below, have the same polarity as the second terminal 130 (e.g., the positive terminal).

[0045] The cover assembly 150 can be coupled to the housing 140. In some examples, the cover assembly 150 may include, or be referred to as, a cover plate 151. The cover plate 151 seals the space of the housing 140 and may be formed of the same material as the housing 140. In some examples, the cover plate 151 may be coupled to the housing 140 by laser welding. In some examples, since the cover plate 151 may have the same polarity as the second terminal 130 as described above, the cover plate 151 and the housing 140 may have the same polarity. In some examples, the cover plate 151 may include through-holes through which the first terminal post 122 and the second terminal post 132 respectively pass. In some examples, the cover plate 151 may also include an injection hole 151c and a vent hole 151d, with electrolyte injected into the injection hole 151c and a safety vent installed in the vent hole 151d. In some examples, a plug 152 may block the injection hole 151c to prevent leakage of electrolyte contained inside the housing 140. In some examples, the plug 152 can be laser-welded to the cover plate 151 after being attached to the injection port 151c. In some examples, the safety vent 153 blocks the vent port 151d, and when the internal pressure of the housing 140 exceeds a set pressure, the internal high-pressure gas can be released to the outside. In some examples, the safety vent 153 can be laser-welded to the cover plate 151 after being attached to the vent port 151d.

[0046] In some examples, the insulating sealing gasket 161 may be placed between the first terminal post 122 and the through hole of the cover plate 151. That is, the sealing gasket 161 may be formed inside the through hole of the cover plate 151, and the first terminal post 122 may protrude upward through the through hole of the sealing gasket 161.

[0047] In some examples, the upper insulating member 162 may be positioned between the first current collector 121 and the cover plate 151. In other examples, the upper insulating member 162 may be positioned between the first terminal plate 123 and the cover plate 151. Therefore, the first terminal 120 may be electrically insulated (separated) from the cover plate 151.

[0048] In some examples, an insulating sealing gasket 171 may be placed between the second terminal post 132 and the through-hole of the cover plate 151. That is, the sealing gasket 171 may be formed inside the through-hole of the cover plate 151, and the second terminal post 132 may protrude upward through the through-hole 171a of the sealing gasket 171. Additionally, in some examples, a connecting member 180 may be placed between the second terminal plate 133 and the cover plate 151. Therefore, the second terminal 130 may be electrically connected to the cover plate 151.

[0049] The welding method used in the secondary battery according to embodiments of the present disclosure will be described in more detail below.

[0050] Figure 3A and Figure 3B A laser beam used in a secondary battery according to an embodiment of the present disclosure is shown.

[0051] first, Figure 3A The dual-beam design can be initially applied to the welding structure of a secondary battery, for example, in the aforementioned welding between the first current collector 121 and the first uncoated electrode portion 111a, between the first terminal post 122 and the first terminal plate 123, between the second current collector 131 and the second uncoated electrode portion 112a, and between the second terminal post 132 and the second terminal plate 133. However, in addition to welding between current components, this welding structure can also be used in welding other components required for manufacturing a secondary battery according to embodiments of the present disclosure. For example, the welding structure of the present disclosure can also be applied to the welding between the housing 140 and the cover plate 151 in a secondary battery assembly.

[0052] at the same time, Figure 3A The dual-beam structure may include a first region having a central circular shape and a second region surrounding the first region in a ring shape. As shown, in the first region, the laser beam is concentrated to have a relatively high energy density, and in the second region, the laser beam is formed along the ring shape to have a lower energy density than in the first region. The dual beams move along the interface of the components to be welded or the welding surfaces in an overlapping state, thereby welding the components.

[0053] At the same time, such as Figure 3B As shown, after double-beam welding, welding using a wobbling technique can be performed a second time along the second region. In the wobbling technique, welding is performed while drawing an approximate arc, and additional welding can be performed along the second region.

[0054] Specifically, oscillating welding is a method for performing welding while simultaneously rotating a laser spot at high speed, and it has the advantage of reducing spatter formed by tiny keyholes. More specifically, oscillating welding can provide the desired welding effect while varying conditions such as the size of the laser spot, the oscillation diameter according to the circumferential speed, and the linear welding speed along a secondary region. Furthermore, in oscillating welding, the smaller the laser spot, the higher the power density that can be achieved. Therefore, oscillating welding can be used to weld various metals and can stably produce keyholes, thereby reducing spatter formation and minimizing the heat-affected zone (HAZ).

[0055] Thus, when a double-beam welding technique is applied for the first welding and an oscillation technique is applied for the second welding, the welding reliability of the components to be welded is increased, and in particular, the generation of metallic foreign matter such as spatter can be reduced. Therefore, the reliability and lifespan of secondary batteries manufactured using this welding technique can be improved.

[0056] The welding areas in the secondary battery according to embodiments of the present disclosure will be described in more detail below.

[0057] Figure 4 This is a photograph showing the welding area used in a secondary battery according to an embodiment of the present disclosure. Figure 5A and Figure 5B This is an enlarged photograph showing the welding area used in a secondary battery according to an embodiment of the present disclosure.

[0058] As shown, a portion of the welding area where dual-beam and oscillating techniques were applied is magnified, such as... Figure 5A and Figure 5B As shown in the image.

[0059] Specifically, refer to Figure 5B The serrated shape produced by the oscillating technique is shown in an enlarged view. Here, in the oscillating technique, due to the rotation of the laser beam's focal point, a wave (wave) bead with a serrated shape can be formed along the radius of rotation. Furthermore, in the serrated shape, the diameter difference between the outer serrated portion (A) and the inner serrated portion (B) can be greater than or equal to 5 μm. When the diameter difference is greater than or equal to 5 μm, the advantage is increased bonding strength in the welding area formed according to the oscillating technique.

[0060] The materials that can be used in secondary batteries according to embodiments of the present disclosure will be described in more detail below.

[0061] Figure 6 It is a graph showing the absorption rate of the laser beam according to the material used.

[0062] Reference Figure 4 and Figure 6 This allows us to confirm the relationship between the absorptivity of each metal material and the wavelength of the laser beam, and to consider the absorptivity when determining the material of the object to be welded and the wavelength of the laser beam to be used. For example, in the case of copper (Cu), the absorptivity is high at short wavelengths, but it tends to gradually decrease with increasing wavelength, and drops to about 5% in the infrared (IR) region.

[0063] Furthermore, in the case of aluminum (Al), there is almost no change in the short-wavelength band, but the absorptivity gradually increases in the visible light region, and after showing a maximum absorptivity, the absorptivity in red-visible light tends to decrease again. Additionally, it can be observed that the absorptivity decreases to approximately 5% in the infrared (IR) region.

[0064] As another example, in the case of iron (Fe), it can be seen that the absorption rate gradually decreases as the wavelength increases from infrared to visible light, and the absorption rate is 35% in the band of about 1 μm.

[0065] Therefore, in the secondary battery according to embodiments of this disclosure, welding between dissimilar metals can be applied, and a laser beam of appropriate wavelength can be selected according to the material of each component. For example, in the case of welding dissimilar metals such as copper (Cu) and aluminum (Al), which are typically used as negative and positive electrodes respectively, welding can be performed using laser beams of red visible light and surrounding wavelengths with similar absorption rates.

[0066] Furthermore, in the secondary battery according to embodiments of the present disclosure, the application of dual-beam and oscillation techniques along with the optimal absorption band improves the welding quality by reducing the generation of foreign matter while increasing the bonding force during the welding of various components.

[0067] As described above, the secondary battery according to this disclosure can improve welding quality by applying dual-beam and oscillation techniques together to reduce foreign matter generation while increasing bonding strength during welding of each construction.

[0068] While the foregoing embodiments are merely one example of implementing a secondary battery according to the present disclosure, they are not limited to this embodiment. However, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims.

Claims

1. A secondary battery comprising: an electrode assembly; a current collector bonded to the electrode assembly; a case in which the electrode assembly is accommodated; a cover plate bonded to the case to seal the electrode assembly and the current collector; and a terminal plate connected to the current collector and exposed through the cover plate, wherein at least one of between the electrode assembly and the current collector and between the current collector and the terminal plate is performed with double-beam welding and wobble welding, wherein a double-beam for welding includes a first area formed at a center and a second area formed around the first area, and wherein the wobble welding is performed only along the second area after the double-beam welding. The current collector, the terminal plate, and the terminal post constitute each of a first terminal and a second terminal of the secondary battery.

2. The secondary battery according to claim 1, further comprising a terminal post passing through the cover plate from the current collector to be connected to the terminal plate, wherein The first area of the double-beam has a circular shape, and the second area has an annular shape, and 3. The secondary battery according to claim 2, wherein wherein an energy density of the second area is less than that of the first area. The wobble welding is performed along the second area.

4. The secondary battery according to claim 2, wherein The wobble welding forms a repeated arc while being performed along an edge of the double-beam.

5. The secondary battery according to claim 1, wherein The wobble welding includes a wave bead having a repeated zigzag shape.

6. The secondary battery according to claim 1, wherein In the zigzag shape, a difference in diameter between an outer zigzag portion and an inner zigzag portion is greater than or equal to 5 µm.

7. The secondary battery according to claim 6, wherein The double-beam welding and the wobble welding are also performed on the bonding between the case and the cover plate.

8. The secondary battery according to claim 1, wherein At least one of the electrode assembly and the current collector and the current collector and the terminal plate is made of dissimilar metals to perform welding.

9. The secondary battery according to claim 1, wherein ​

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