Method for manufacturing secondary batteries

Abstract

According to an exemplary embodiment, a method for manufacturing a secondary battery is provided. The method includes the steps of: destroying the embossed structure of an electrode tab; and welding the destroyed portion of the embossed structure of the electrode tab to a battery case.

Description

[Technical Field]

[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 interests of Korean application No. 10-2023-0176248, filed on 7 December 2023, which is herein by reference in whole. [Background technology]

[0002] Unlike primary batteries, rechargeable batteries can be charged and discharged multiple times. Rechargeable batteries are widely used as an energy source for a variety of wireless devices such as handsets, laptops, and wireless vacuum cleaners. In recent years, improvements in energy density and economies of scale have dramatically reduced the manufacturing cost per unit capacity of rechargeable batteries, and as the driving range of battery electric vehicles (BEVs) increases to levels comparable to those of fuel-powered vehicles, the main applications of rechargeable batteries are shifting from mobile devices to mobility.

[0003] The manufacturing of secondary batteries includes an electrode process, which includes mixing, coating, roll pressing, slitting, and notching; an assembly process, which involves housing the electrode assembly in a case; and an activation process, which involves electrically activating and stabilizing the battery cells. After the activation process, the battery cells can be stacked to form a cell stack. The cell stack may be mounted in a housing with a module frame, or it may be mounted directly in the housing without a module frame. [Overview of the project] [Problems that the invention aims to solve]

[0004] The technical concept of this invention aims to solve the problem of manufacturing a rechargeable battery with improved reliability. [Means for solving the problem]

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

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

[0007] The step of destroying 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 above-mentioned 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 above-mentioned second voltage waveform is applied is above its melting point.

[0012] Each of the above-mentioned first voltage waveform and second voltage waveform has a rectangular waveform that includes a ramp section.

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

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

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

[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 bar, 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 bar.

[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.

Advantages of the Invention

[0022] The method for manufacturing a secondary battery according to an exemplary embodiment of the present invention can ensure the current-carrying area between the electrode tab and the battery case by collapsing the embossed structure of the electrode tab, whereby the stability and reliability of secondary battery manufacturing can be improved.

[0023] The effects obtainable 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 having ordinary knowledge in the technical field to which the exemplary embodiments of the present disclosure belong from the following description. That is, unintended effects associated with implementing the exemplary embodiments of the present disclosure can also be derived by those having ordinary knowledge in the technical field from the exemplary embodiments of the present disclosure.

Brief Description of the Drawings

[0024] [Figure 1] This is a flowchart illustrating a method for manufacturing a secondary battery according to an exemplary embodiment. [Figure 2] This is a cross-sectional view illustrating a method for manufacturing a secondary battery according to an exemplary embodiment. [Figure 3] This is a partially cross-sectional view, enlarged from the area shown in Figure 2. [Figure 4] This is a partially cross-sectional view, enlarged from the area shown in Figure 2. [Figure 5] This is a partially cross-sectional view, enlarged from the area shown in Figure 2. [Figure 6] This graph illustrates a method for manufacturing a secondary battery according to an exemplary embodiment. [Figure 7] These drawings illustrate the effects of a method for manufacturing a secondary battery according to an exemplary embodiment. [Figure 8] These drawings illustrate the effects of a method for manufacturing a secondary battery according to an exemplary embodiment. [Figure 9] This graph illustrates a welding method according to another exemplary embodiment. [Modes for carrying out the invention]

[0025] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. As a premise, terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical spirit of the present invention, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their own invention.

[0026] Therefore, the embodiments described herein and the configurations shown in the drawings represent only one of the most preferred embodiments of the present invention and do not represent the entire technical concept of the present invention; there may be a variety of equivalents and modifications that can be substituted for them at the time of filing.

[0027] Furthermore, in describing the present invention, if it is determined that a specific description of a related known configuration or function may obscure the gist of the present invention, such detailed description will be omitted.

[0028] Since embodiments of the present invention are provided to more fully explain the invention to an ordinary person, the shapes and sizes of the components in the drawings may be exaggerated, omitted, or shown schematically for the sake of clarity. Accordingly, the sizes and proportions of each component do not fully reflect the actual sizes and proportions.

[0029] (First Embodiment) Figure 1 is a flowchart illustrating a method for manufacturing a secondary battery according to an exemplary embodiment.

[0030] Figure 2 is a cross-sectional view illustrating a method for manufacturing a secondary battery according to an exemplary embodiment.

[0031] Figures 3 to 5 are enlarged partial cross-sectional views of the POR portion in Figure 2.

[0032] Figure 6 is a graph illustrating a method for manufacturing a secondary battery according to an exemplary embodiment. In Figure 6, the horizontal axis represents time expressed in arbitrary units, and the vertical axis represents voltage expressed in arbitrary units.

[0033] Referring to Figures 1 to 3, at P110, the electrode tabs 120 of the electrode assembly 110 and the battery case 130 can be aligned.

[0034] The electrode assembly 110 may include a positive electrode 111, a separator membrane 112, and a negative electrode 113. The electrode assembly 110 may be of the jelly roll type. The positive electrode 111 may include a positive electrode current collector and a positive electrode active material. The negative electrode 113 may include a negative electrode current collector and a negative electrode active material.

[0035] The thickness of the positive electrode current collector can range from approximately 3 μm to approximately 500 μm. The positive electrode current collector may not induce chemical changes in the final manufactured secondary battery and may have high conductivity. The positive electrode current collector can 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, etc. The surface of the positive electrode current collector may include a micro-textured structure to enhance the adhesion of the active material. The positive electrode current collector can be in the form of a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0036] The thickness of the negative electrode current collector can range from approximately 3 μm to approximately 500 μm. The negative electrode current collector may not induce chemical changes in the final manufactured secondary battery and may have high conductivity. The negative electrode current collector can include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloys. 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-textured structure to enhance the adhesion of the active material. The negative electrode current collector can be in the form of a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0037] The positive electrode active material is a substance capable of undergoing electrochemical reactions. The positive electrode active material can be a lithium transition metal oxide. Examples of positive electrode active materials 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; and materials with the chemical formula LiNi 1-y M y Lithium nickel oxide represented by O2 (where M is one of Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn, and Ga, and 0.01 ≤ y ≤ 0.7); Li 1+z Ni1 / 3 Co 1 / 3 Mn 1 / 3 O2, Li 1+z Ni 0.4 Mn 0.4 Co 0.2 Li such as O2 1+z Ni b Mn c Co 1-(b+c+d) M d O (2-e) A e (where -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 represented by the chemical formula Li 1+x M 1-y M' y PO 4-z X z (where M is a transition metal, more specifically, any one of Fe, Mn, Co and Ni, M' is any one of Al, Mg and Ti, X is any one of F, S and N, -0.5 ≤ x ≤ +0.5, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.1) and can include olivine-type lithium metal phosphate represented by

[0038] The negative electrode active material can include carbon such as graphitizable carbon and graphite-based carbon. The negative electrode active material can be, for example, Li x Fe2O3 (0 ≤ x ≤ 1), Li x WO2 (0 ≤ x ≤ 1), Sn x Me 1-x ​​​​(Here, Me is any one of Mn, Fe, Pb, and Ge, Me' is any one of Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, and halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8), etc. Metal composite oxides can be included. The negative electrode active material can include, for example, lithium metal; lithium alloy; silicon-based alloy; tin-based alloy. The negative electrode active material can include, for example, metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5. The negative electrode active material can include, for example, conductive polymers such as polyacetylene; Li-Co-Ni-based materials, etc.

[0039] The positive electrode 111 can include a land portion where the positive electrode active material is applied and a non-land portion where the positive electrode current collector is exposed without the positive electrode active material being applied. The negative electrode 113 can include a land portion where the negative electrode active material is applied and a non-land portion where the negative electrode current collector is exposed without the negative electrode active material being applied. The negative electrode tab 120 can be coupled to the non-land portion of the negative electrode 113. The negative electrode tab 120 can be fixed to the negative electrode 113 by a method such as ultrasonic welding, for example.

[0040] Below the electrode assembly 110, an insulating plate 140 can be provided to prevent a short circuit between the battery case 130 and the electrode assembly 110. Also, on the electrode assembly 110, an insulating plate 140 can be provided to prevent a short circuit between the electrode assembly 110 and a cap assembly (not shown). The cap assembly can be coupled to the battery case 130, and the cap assembly can isolate the inside of the battery cell from the outside together with the battery case 130.

[0041] The battery case 130 may include aluminum (Al), iron (Fe), or an alloy thereof. The battery case 130 can accommodate a cylindrical electrode assembly 110. The battery case may include a bottom plate 131 and side panels 132. The upper part of the side panels 132 may include an opening for inserting the electrode assembly 110. The opening in the side panels 132 may be closed by a cap assembly. As a non-limiting example, the side panels 132 may have a cylindrical shape. The side panels 132 may have a rectangular prism shape.

[0042] In aligning the electrode tab 120 and the battery case 130, the electrode tab 120 and the battery case 130 can be pressurized by the first welding rod W1 and the second welding rod W2. The first welding rod W1 can penetrate the core of the electrode assembly 110. The first welding rod W1 can come into contact with the electrode tab 120. The second welding rod W2 can come into contact with the bottom plate 131 of the battery case 130. Due to the pressurization by the first welding rod W1 and the second welding rod W2, the electrode tab 120 and the battery case 130 can come into contact with each other.

[0043] Next, referring to Figures 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.

[0044] Breaking the embossed structure EBS of the electrode tab can include applying a first voltage waveform VF1 to the electrode tab 120 with the first electrode rod W1. Applying a 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 so that the voltage difference between the first electrode rod W1 and the second electrode rod W2 follows the first voltage waveform VF1.

[0045] By applying the first voltage waveform VF1, a current can be induced sequentially through the first electrode rod W1, electrode tab 120, battery case 130, and second electrode rod W2, and the heat transfer effect of this current can raise the temperature of the electrode tab 120. The temperature of the electrode tab 120 to which the first voltage waveform VF1 is applied may be below the melting point of the electrode tab 120. As a result, the electrode tab 120 may not melt despite the application of the first voltage waveform VF1. The electrode tab 120 can be softened by the application of the first voltage waveform VF1, thereby causing the embossed structure EBS of the electrode tab 120 to collapse.

[0046] Next, referring to Figures 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 may include applying a second voltage waveform VF2 to the electrode tab 120 with the second electrode rod W2. Applying a 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.

[0047] By applying the second voltage waveform VF2, a current can be induced sequentially through the first electrode rod W1, electrode tab 120, battery case 130, and second electrode rod W2, and the heat transfer effect of this current can cause the temperatures of the electrode tab 120 and battery case 130 to rise. The temperature of the electrode tab 120 to which the second voltage waveform VF2 is applied may be above 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 above the melting point of the battery case 130. As a result, by applying the first voltage waveform VF1, either the electrode tab 120 or the battery case 130 can be melted.

[0048] According to an exemplary embodiment, the collapse of the embossed structure EBS of P120 ensures a sufficient current-carrying area between the electrode tab 120 and the battery case 130, thereby improving the reliability of the welding between the electrode tab 120 and the battery case.

[0049] According to exemplary embodiments, the first voltage waveform VF1 and the second voltage waveform VF2 may be square waveforms including ramping sections. However, the first voltage waveform VF1 and the second voltage waveform VF2 may have a variety of waveforms, such as triangular waveforms, sawtooth waveforms, and sinusoidal waveforms.

[0050] The first voltage waveform VF1 may differ from the second voltage waveform VF2. The peak of the first voltage waveform VF1 may differ 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 differ 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.

[0051] According to exemplary embodiments, the first voltage waveform VF1 and the second voltage waveform VF2 may be of different types. For example, the first voltage waveform VF1 may be a square waveform and the second voltage waveform VF2 may be a triangular waveform. Another example is that the first voltage waveform VF1 may be a triangular waveform and the second voltage waveform VF2 may be a square waveform. Yet another example is that the first voltage waveform VF1 may be a sawtooth waveform and the second voltage waveform VF2 may be a square waveform.

[0052] Figures 7 and 8 are diagrams illustrating the effects of a method for manufacturing a secondary battery according to an exemplary embodiment. More specifically, Figure 7 shows the resulting beads from welding the electrode tab to the battery case in a comparative example, and Figure 8 shows the resulting beads from welding the electrode tab to the battery case in an experimental example.

[0053] Referring to Figures 7 and 8, unlike the comparative example in which a lot of splash occurred, the beads in the experimental example are substantially splash-free. According to the experimental example, the collapse of the embossed EBS structure (see Figure 4) allows for a relatively large current-carrying area between the electrode tab 120 (see Figure 4) and the battery case 130 (see Figure 4), thereby improving the stability and reliability of resistance welding.

[0054] Figure 9 is a graph illustrating a welding method according to another exemplary embodiment. In Figure 9, the horizontal axis represents time expressed in arbitrary units, and the vertical axis represents current expressed in arbitrary units.

[0055] Referring to Figures 4, 5, and 9, a first current waveform CF1 and a second current waveform CF2 can be applied to the first welding rod W1 and the second welding rod W2. The first current waveform CF1 and the second current waveform CF2 can be replaced with the first voltage waveform CF1 and the second voltage waveform CF2 in Figure 6.

[0056] According to exemplary embodiments, the first current waveform CF1 and the second current waveform CF2 may be square waveforms including ramping sections. However, the first current waveform CF1 and the second current waveform CF2 may have a variety of waveforms, such as triangular waveforms, sawtooth waveforms, and sinusoidal waveforms.

[0057] The first current waveform CF1 may differ from the second current waveform CF2. The peak of the first current waveform CF1 may differ 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 differ 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.

[0058] The present invention has been described in more detail above with reference to the drawings and embodiments. However, the configurations described in the drawings or embodiments described herein are merely one embodiment of the present invention and do not represent the entire technical concept of the present invention. Therefore, there may be a variety of equivalents and modifications that can be substituted for them at the time of filing.

Claims

1. Steps to break down the embossed structure of the electrode tab, A method for manufacturing a secondary battery, comprising the step of welding the collapsed portion of the embossed structure of the electrode tab to a battery case.

2. A method for manufacturing a secondary battery according to claim 1, wherein 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.

3. The step of destroying the embossed structure of the electrode tab includes applying a first voltage waveform to the electrode tab with a first electrode rod. A method for manufacturing a secondary battery according to claim 1, wherein 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. The method for manufacturing a secondary battery according to claim 3, wherein the first voltage waveform applied to the electrode tab softens the electrode tab.

5. A method for manufacturing a secondary battery according to claim 3, wherein the temperature of the electrode tab to which the first voltage waveform is applied is below the melting point.

6. The method for manufacturing a secondary battery according to claim 3, wherein the second voltage waveform applied to the electrode tab melts the electrode tab.

7. A method for manufacturing a secondary battery according to claim 3, wherein the temperature of the electrode tab to which the second voltage waveform is applied is above the melting point.

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

9. A method for manufacturing a secondary battery according to claim 3, wherein the first peak of the first voltage waveform is different from the second peak of the second voltage waveform.

10. A method for manufacturing a secondary battery according to claim 3, wherein the first peak of the first voltage waveform is smaller than the second peak of the second voltage waveform.

11. A method for manufacturing a secondary battery according to claim 3, wherein the duration of the first voltage waveform is different from the duration of the second voltage waveform.

12. A method for manufacturing a secondary battery according to claim 3, wherein the duration of the first voltage waveform is shorter than the duration of the second voltage waveform.

13. The step of destroying the embossed structure of the electrode tab includes applying a first current waveform to the electrode tab with a first electrode rod. A method for manufacturing a secondary battery according to any one of claims 1 to 12, wherein 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. A method for manufacturing a secondary battery according to claim 13, wherein the first peak of the first current waveform is smaller than the second peak of the second current waveform.

15. A method for manufacturing a secondary battery according to claim 13, wherein the first peak of the first current waveform is different from the second peak of the second current waveform.

16. A method for manufacturing a secondary battery according to claim 13, wherein the duration of the first current waveform is different from the duration of the second current waveform.

17. A method for manufacturing a secondary battery according to claim 13, wherein the duration of the first current waveform is shorter than the duration of the second current waveform.

Images