Method for manufacturing secondary battery

Abstract

According to example embodiments, a method for manufacturing a secondary battery is provided. The method comprises the steps of: collapsing an embossed structure of an electrode tab; and welding the collapsed portion of the embossed structure of the electrode tab and a battery case.

Description

Method of manufacturing a secondary battery

[0001] The present invention relates to a method for manufacturing a secondary battery. More specifically, the present invention relates to a method for manufacturing a secondary battery having a cylindrical case. This application claims the benefit of Korean Application No. 10-2023-0176248, filed December 7, 2023, which is incorporated herein by reference in its entirety.

[0002] Unlike primary batteries, secondary batteries can be charged and discharged multiple times. They are widely used as a power source for various wireless devices, including handsets, laptops, and cordless vacuum cleaners. Recently, improved energy density and economies of scale have dramatically reduced the per-unit manufacturing cost of secondary batteries. Furthermore, as the range of battery electric vehicles (BEVs) has increased to match that of fuel-powered vehicles, the primary use of secondary batteries is shifting from mobile devices to mobility.

[0003] The manufacturing of secondary batteries includes electrode processes, including mixing, coating, roll pressing, slitting, and notching; an assembly process, which embeds the electrode assembly in a case; and an activation process, which electrically activates and stabilizes the battery cells. After the activation process, the battery cells can be stacked to form a cell stack. The cell stack can be mounted in a housing with a module frame, or directly in the housing without a module frame.

[0004] The technical idea of ​​the present invention is to provide a method for manufacturing a secondary battery with improved reliability.

[0005] According to exemplary embodiments of the present invention for solving the above-described problem, a method for manufacturing a secondary battery is provided. The method comprises the steps of: collapsing an embossed structure of an electrode tab; and welding a collapsed portion of the embossed structure of the electrode tab to a battery case.

[0006] The current carrying area between the battery case and the electrode tab increases due to the collapse of the embossed structure of the electrode tab.

[0007] The step of collapsing the embossed structure of the electrode tab includes applying a first voltage waveform to the electrode tab with a first electrode rod, and the step of welding the battery case includes applying a second voltage waveform different from the first voltage waveform to the electrode tab with the first electrode rod.

[0008] The first voltage waveform applied to the electrode tab softens the electrode tab.

[0009] The temperature of the electrode tab to which the first voltage waveform is applied is below the melting point.

[0010] The second voltage waveform applied to the electrode tab melts the electrode tab.

[0011] The temperature of the electrode tab to which the second voltage waveform is applied is higher than the melting point.

[0012] Each of the first voltage waveform and the second voltage waveform has a square waveform including a ramp section.

[0013] The first peak of the first voltage waveform is different from the second peak of the second voltage waveform.

[0014] The first peak of the first voltage waveform is smaller than the second peak of the second voltage waveform.

[0015] The duration of the first voltage waveform is different from the duration of the second voltage waveform.

[0016] The duration of the first voltage waveform is shorter than the duration of the second voltage waveform.

[0017] The step of collapsing the embossed structure of the electrode tab includes applying a first current waveform to the electrode tab with a first electrode rod, and the step of welding the battery case includes applying a second current waveform different from the first current waveform to the electrode tab with the first electrode rod.

[0018] The first peak of the first current waveform is smaller than the second peak of the second current waveform.

[0019] The first peak of the first current waveform is different from the second peak of the second current waveform.

[0020] The duration of the first current waveform is different from the duration of the second current waveform.

[0021] The duration of the first current waveform is shorter than the duration of the second current waveform.

[0022] A method for manufacturing a secondary battery according to exemplary embodiments of the present invention can secure a current-carrying area between an electrode tab and a battery case by collapsing an embossed structure of an electrode tab, thereby improving the stability and reliability of secondary battery manufacturing.

[0023] The effects that can be obtained from the exemplary embodiments of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly derived and understood by those skilled in the art to which the exemplary embodiments of the present disclosure pertain from the following description. In other words, unintended effects resulting from practicing the exemplary embodiments of the present disclosure can also be derived by those skilled in the art from the exemplary embodiments of the present disclosure.

[0024] FIG. 1 is a flowchart illustrating a method for manufacturing a secondary battery according to exemplary embodiments.

[0025] FIG. 2 is a flowchart illustrating a method for manufacturing a secondary battery according to exemplary embodiments.

[0026] Figures 3 to 5 are enlarged partial cross-sectional views of parts of Figure 2.

[0027] FIG. 6 is a graph for explaining a method for manufacturing a secondary battery according to exemplary embodiments.

[0028] FIGS. 7 and 8 are drawings for explaining the effect of a method for manufacturing a secondary battery according to exemplary embodiments.

[0029] Figure 9 is a graph for explaining a welding method according to other exemplary embodiments.

[0030] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0031] Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0032] In addition, when describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description is omitted.

[0033] Since the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art, the shapes and sizes of components in the drawings may be exaggerated, omitted, or schematically illustrated for clearer explanation. Accordingly, the sizes and proportions of each component do not fully reflect the actual sizes or proportions.

[0034]

[0035] (Example 1)

[0036] FIG. 1 is a flowchart illustrating a method for manufacturing a secondary battery according to exemplary embodiments.

[0037] FIG. 2 is a flowchart illustrating a method for manufacturing a secondary battery according to exemplary embodiments.

[0038] Figures 3 to 5 are enlarged partial cross-sectional views of a portion (POR) of Figure 2.

[0039] Fig. 6 is a graph for explaining a method for manufacturing a secondary battery according to exemplary embodiments. In Fig. 6, the horizontal axis represents time expressed in arbitrary units (arbitrary uint), and the vertical axis represents voltage expressed in arbitrary units.

[0040] Referring to FIGS. 1 to 3, at P110, the electrode tab (120) of the electrode assembly (110) and the battery case (130) can be aligned.

[0041] The electrode assembly (110) may include a positive electrode (111), a separator (112), and a negative electrode (113). The electrode assembly (110) may be of a jelly-roll type. The positive electrode (111) may include a positive electrode collector and a positive electrode active material. The negative electrode (113) may include a negative electrode collector and a negative electrode active material.

[0042] The thickness of the positive electrode current collector may range from about 3 μm to about 500 μm. The positive electrode current collector may not cause chemical changes in the secondary battery to be ultimately manufactured and may have high conductivity. The positive electrode current collector may include, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum. The positive electrode current collector may also include stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. The surface of the positive electrode current collector may include a micro-roughened structure to increase the adhesion of the active material. The positive electrode current collector may have a shape such as a film, a sheet, a foil, a net, a porous material, a foam, or a non-woven fabric.

[0043] The thickness of the negative electrode current collector may be in the range of about 3 μm to about 500 μm. The negative electrode current collector may not cause chemical changes in the secondary battery ultimately manufactured and may have high conductivity. The negative electrode current collector may include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, and an aluminum-cadmium alloy. The negative electrode current collector may also include stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The surface of the negative electrode current collector may include a micro-roughened structure to increase the adhesion of the active material. The negative electrode current collector may have a shape such as a film, a sheet, a foil, a net, a porous material, a foam, or a non-woven fabric.

[0044] A cathode active material is a material capable of causing an electrochemical reaction. The cathode active material may be a lithium transition metal oxide. Examples of the cathode active material include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2) substituted with one or more transition metals; lithium manganese oxide substituted with one or more transition metals; chemical formula LiNi 1-y M yLithium nickel oxide expressed as O2 (wherein, M is any one of Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn, and Ga, and 0.01≤y≤0.7); Li 1+z Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, Li 1+zN i 0.4 Mn 0.4 Co 0.2 Li like O2 1+z Ni b Mn c Co 1-(b+c+d) M d O (2-e) A e (wherein, -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2, 0≤e≤0.2, b+c+d<1, M is any one of Al, Mg, Cr, Ti, Si, and Y, and A is any one of F, P, and Cl) Lithium nickel cobalt manganese composite oxide; chemical formula Li 1+x M 1-y M' y PO 4-z X z (wherein, M is a transition metal, more specifically, one of Fe, Mn, Co, and Ni, M' is one of Al, Mg, and Ti, X is one of F, S, and N, -0.5≤x≤+0.5, 0≤y≤0.5, and 0≤z≤0.1) and may include an olivine-based lithium metal phosphate.

[0045] The negative active material may include carbon, such as non-graphitizable carbon, graphitic carbon, etc. The negative active material may include, for example, Li x Fe2O3(0≤x≤1), LixWO2(0≤x≤1), Sn x Me 1-x Me' y O z(wherein Me is any one of Mn, Fe, Pb and Ge, and Me' is any one of Al, B, P, Si, elements of group 1, 2 and 3 of the periodic table and halogens; 0 <x≤1이고; 1≤y≤3 이며; 1≤z≤8) 등의 금속 복합 산화물을 포함할 수 있다. 음극 활물질은, 예컨대, 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금을 포함할 수 있다. 음극 활물질은, 예컨대, SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 금속 산화물을 포함할 수 있다. 음극 활물질은, 예컨대, 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료 등을 포함할 수 있다.

[0046] The positive electrode (111) may include a holding portion, which is a portion to which a positive electrode active material is applied, and a non-conductive portion, where the positive electrode current collector is exposed because the positive electrode active material is not applied. The negative electrode (113) may include a holding portion, which is a portion to which a negative electrode active material is applied, and a non-conductive portion, where the negative electrode current collector is exposed because the positive electrode active material is not applied. A negative electrode tab (120) may be bonded to the non-conductive portion of the negative electrode (113). The negative electrode tab (120) may be fixed to the negative electrode (113) by, for example, a method such as ultrasonic welding.

[0047] An insulating plate (140) may be provided below the electrode assembly (110) to prevent a short circuit between the battery case (130) and the electrode assembly (110). In addition, an insulating plate (140) may be provided above the electrode assembly (110) to prevent a short circuit between the electrode assembly (110) and the cap assembly (not shown). The cap assembly may be coupled to the battery case (130), and the cap assembly may isolate the interior of the battery cell from the exterior together with the battery case (130).

[0048] The battery case (130) may include aluminum (Al), iron (Fe), or an alloy thereof. The battery case (130) may accommodate a cylindrical electrode assembly (110). The battery case may include a bottom plate (131) and a side surface (132). The upper portion of the side surface (132) may include an opening for inserting the electrode assembly (110). The opening of the side surface (132) may be closed by a cap assembly. As a non-limiting example, the side surface (132) may have a cylindrical shape. The side surface (132) may also have a square pillar shape.

[0049] In the alignment of the electrode tab (120) and the battery case (130), the electrode tab (120) and the battery case (130) can be pressed by first and second welding rods (W1, W2). The first welding rod (W1) can penetrate the core of the electrode assembly (110). The first welding rod (W1) can be in contact with the electrode tab (120). The second welding rod (W2) can be in contact with the bottom plate (131) of the battery case (130). The electrode tab (120) and the battery case (130) can be in contact with each other by the pressing of the first and second welding rods (W1, W2).

[0050]

[0051] Next, referring to FIGS. 1, 4, and 6, at P120, the embossed structure (EBS) of the electrode tab (120) can be collapsed. By collapsing the embossed structure (EBS) of the electrode tab (120), the current-carrying area between the bottom plate (131) of the battery case (130) and the electrode tab (120) can be increased.

[0052] Disintegrating the embossed structure (EBS) of the electrode tab may include applying a first voltage waveform (VF1) to the electrode tab (120) with the first electrode rod (W1). Applying the first voltage waveform (VF1) to the electrode tab (120) with the first electrode rod (W1) means adjusting the voltage difference between the first electrode rod (W1) and the second electrode rod (W2) such that the voltage difference between the first electrode rod (W1) and the second electrode rod (W2) follows the first voltage waveform (VF1).

[0053] By applying the first voltage waveform (VF1), a current may be induced sequentially through the first electrode rod (W1), the electrode tab (120), the battery case (130), and the second electrode rod (W2), and the temperature of the electrode tab (120) may increase due to the heat transfer effect of the current. The temperature of the electrode tab (120) to which the first voltage waveform (VF1) is applied may be lower than the melting point of the electrode tab (120). Accordingly, despite the application of the first voltage waveform (VF1), the electrode tab (120) may not melt. The electrode tab (120) may be softened by the application of the first voltage waveform (VF1), and accordingly, the embossed structure (EBS) of the electrode tab (120) may be collapsed.

[0054]

[0055] Next, referring to FIGS. 1, 5, and 6, at P130, the electrode tab (120) and the battery case (130) can be welded. Welding the electrode tab (120) and the battery case (130) can include applying a second voltage waveform (VF2) to the electrode tab (120) with a second electrode rod (W2). Applying the second voltage waveform (VF2) to the electrode tab (120) with the second electrode rod (W2) means adjusting the voltage difference between the first electrode rod (W1) and the second electrode rod (W2) so that the voltage difference between the first electrode rod (W1) and the second electrode rod (W2) follows the second voltage waveform (VF2).

[0056] By applying the second voltage waveform (VF2), a current may be induced sequentially through the first electrode rod (W1), the electrode tab (120), the battery case (130), and the second electrode rod (W2), and the temperature of the electrode tab (120) and the battery case (130) may increase due to the heat transfer effect of the current. The temperature of the electrode tab (120) to which the second voltage waveform (VF2) is applied may be higher than the melting point of the electrode tab (120). Alternatively, the temperature of the battery case (130) to which the second voltage waveform (VF2) is applied may be higher than the melting point of the battery case (130). Accordingly, by applying the first voltage waveform (VF1), either one of the electrode tab (120) and the battery case (130) may be melted.

[0057] In exemplary embodiments, by the collapse of the embossed structure (EBS) of P120, a sufficient current-carrying area can be secured between the electrode tab (120) and the battery case (130), and accordingly, the reliability of welding of the electrode tab (120) and the battery case can be improved.

[0058] According to exemplary embodiments, the first voltage waveform (VF1) and the second voltage waveform (VF2) may be square waveforms including a ramping section. However, the present invention is not limited thereto, and the first voltage waveform (VF1) and the second voltage waveform (VF2) may have various waveforms, such as a triangle waveform, a sawtooth waveform, a sine waveform, etc.

[0059] The first voltage waveform (VF1) may be different from the second voltage waveform (VF2). The peak of the first voltage waveform (VF1) may be different from the peak of the second voltage waveform (VF2). The peak of the first voltage waveform (VF1) may be smaller than the peak of the second voltage waveform (VF2). The duration of the first voltage waveform (VF1) may be different from the duration of the second voltage waveform (VF2). The duration of the first voltage waveform (VF1) may be shorter than the duration of the second voltage waveform (VF2).

[0060] According to exemplary embodiments, the first voltage waveform (VF1) and the second voltage waveform (VF2) may be different types of waveforms. For example, the first voltage waveform (VF1) may be a square waveform and the second voltage waveform (VF2) may be a triangular waveform. In another example, the first voltage waveform (VF1) may be a triangular waveform and the second voltage waveform (VF2) may be a square waveform. In another example, the first voltage waveform (VF1) may be a sawtooth waveform and the second voltage waveform (VF2) may be a square waveform.

[0061]

[0062] FIGS. 7 and 8 are drawings illustrating the effects of a method for manufacturing a secondary battery according to exemplary embodiments. More specifically, FIG. 7 illustrates a resulting bead of welding an electrode tab and a battery case according to a comparative example, and FIG. 8 illustrates a resulting bead of welding an electrode tab and a battery case according to an experimental example.

[0063] Referring to FIGS. 7 and 8, unlike the comparative example in which many splashes occurred, the beads according to the experimental example substantially do not contain any splashes. According to the experimental example, a relatively wide current-carrying area can be secured between the electrode tab (120, see FIG. 4) and the battery case (130, see FIG. 4) by the collapse of the embossed structure (EBS, see FIG. 4), thereby improving the stability and reliability of resistance welding.

[0064]

[0065] Fig. 9 is a graph for explaining a welding method according to other exemplary embodiments. In Fig. 9, the horizontal axis represents time expressed in arbitrary units (arbitrary uint), and the vertical axis represents current expressed in arbitrary units.

[0066] Referring to FIGS. 4, 5, and 9, a first current waveform (CF1) and a second current waveform (CF2) can be applied to a first welding rod (W1) and a second welding rod (W2). The first current waveform (CF1) and the second current waveform (CF2) can replace the first and second voltage waveforms (CF1, CF2) of FIG. 6.

[0067] According to exemplary embodiments, the first current waveform (CF1) and the second current waveform (CF2) may be square waveforms including a ramping section. However, the present invention is not limited thereto, and the first current waveform (CF1) and the second current waveform (CF2) may have various waveforms, such as a triangle waveform, a sawtooth waveform, or a sine waveform.

[0068] The first current waveform (CF1) may be different from the second current waveform (CF2). The peak of the first current waveform (CF1) may be different from the peak of the second current waveform (CF2). The peak of the first current waveform (CF1) may be smaller than the peak of the second current waveform (CF2). The duration of the first current waveform (CF1) may be different from the duration of the second current waveform (CF2). The duration of the first current waveform (CF1) may be shorter than the duration of the second current waveform (CF2).

[0069]

[0070] The present invention has been described in more detail through drawings and examples. However, the configurations described in the drawings or examples described in this specification are merely embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

Claims

1. A step of collapsing the embossed structure of the electrode tab; and A method for manufacturing a secondary battery, comprising the step of welding a collapsed portion of the embossed structure of the electrode tab and a battery case.

2. In paragraph 1, A method for manufacturing a secondary battery, characterized in that the current-carrying area between the battery case and the electrode tab increases by collapse of the embossed structure of the electrode tab.

3. In paragraph 1, The step of collapsing the embossed structure of the electrode tab comprises applying a first voltage waveform to the electrode tab with a first electrode rod, and A method for manufacturing a secondary battery, characterized in that the step of welding the battery case includes applying a second voltage waveform different from the first voltage waveform to the electrode tab with the first electrode rod.

4. In paragraph 3, A method for manufacturing a secondary battery, wherein the first voltage waveform applied to the electrode tab softens the electrode tab.

5. In paragraph 3, A method for manufacturing a secondary battery, characterized in that the temperature of the electrode tab to which the first voltage waveform is applied is below the melting point.

6. In paragraph 3, A method for manufacturing a secondary battery, wherein the second voltage waveform applied to the electrode tab melts the electrode tab.

7. In paragraph 3, A method for manufacturing a secondary battery, characterized in that the temperature of the electrode tab to which the second voltage waveform is applied is higher than the melting point.

8. In paragraph 3, A method for manufacturing a secondary battery, wherein each of the first voltage waveform and the second voltage waveform has a square waveform including a ramp section.

9. In paragraph 3, A method for manufacturing a secondary battery, characterized in that the first peak of the first voltage waveform is different from the second peak of the second voltage waveform.

10. In paragraph 3, A method for manufacturing a secondary battery, characterized in that the first peak of the first voltage waveform is smaller than the second peak of the second voltage waveform.

11. In paragraph 3, A method for manufacturing a secondary battery, characterized in that the length of the duration of the first voltage waveform is different from the length of the duration of the second voltage waveform.

12. In paragraph 3, A method for manufacturing a secondary battery, characterized in that the duration of the first voltage waveform is shorter than the duration of the second voltage waveform.

13. In paragraph 1, The step of collapsing the embossed structure of the electrode tab comprises applying a first current waveform to the electrode tab with a first electrode rod, and A method for manufacturing a secondary battery, characterized in that the step of welding the battery case includes applying a second current waveform different from the first current waveform to the electrode tab with the first electrode rod.

14. In paragraph 13, A method for manufacturing a secondary battery, characterized in that the first peak of the first current waveform is smaller than the second peak of the second current waveform.

15. In paragraph 13, A method for manufacturing a secondary battery, characterized in that the first peak of the first current waveform is different from the second peak of the second current waveform.

16. In paragraph 13, A method for manufacturing a secondary battery, characterized in that the length of the duration of the first current waveform is different from the length of the duration of the second current waveform.

17. In paragraph 13, A method for manufacturing a secondary battery, characterized in that the duration of the first current waveform is shorter than the duration of the second current waveform.

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