Stress relief method of pole piece, manufacturing method and manufacturing method of battery roll core

Abstract

The application discloses a stress relieving method of a pole piece, a manufacturing method of the pole piece, and a manufacturing method of a battery roll core. The stress relieving method of the pole piece comprises the following steps: providing a pretreated pole piece, wherein the pretreated pole piece comprises a tab welding area; connecting the tab welding area with a direct current device; and outputting a current through the tab welding area by the direct current device, and making the tab welding area reach and maintain a required temperature for stress relieving to relieve the stress of the tab welding area. The application can fully relieve the stress of the pole piece, so that the tab welding position or the area at the overhang of the negative pole piece will not easily break due to stress in the long cycle process of the battery after the pole piece is manufactured into the battery roll core, thereby improving the long cycle performance of the battery.

Description

Technical Field

[0001] This application relates to the field of secondary batteries, and in particular to a method for stress relief of electrode sheets, a method for manufacturing electrode sheets, and a method for manufacturing battery cores. Background Technology

[0002] In battery manufacturing technology, especially in lithium-ion battery processes, drying is a crucial step. This is because moisture in lithium-ion batteries can severely impact battery performance, such as reducing capacity and affecting safety. Therefore, after coating, the entire electrode assembly or the wound bare cell is typically vacuum-baked to remove moisture from the electrodes. Furthermore, this process can release stress in the electrodes, improving battery performance.

[0003] However, this method has limited effect on stress relief in the current collector, especially in areas of stress concentration (e.g., the tab welding area, the overhang area of ​​the negative electrode). In some manufacturing processes, stress in the current collector is relieved by heat transfer through heating the welding head during tab welding. This method is not only slow but also easily damages the anti-oxidation layer on the surface of the current collector. Furthermore, during long-cycle battery operation, the areas at the tab welding location or the overhang of the negative electrode are prone to fracture due to high stress, thereby increasing the resistance of the internal and external current circuits and even causing capacity decay, leading to battery failure. Summary of the Invention

[0004] The purpose of this application is to provide a method for stress relief of electrode sheets, a manufacturing method, and a method for manufacturing battery cores, which can fully eliminate the stress of electrode sheets, prevent the electrode sheets from cracking due to stress problems, and improve the long cycle performance of the battery.

[0005] To achieve the above objectives, this application provides a method for relieving electrode stress, comprising:

[0006] A pre-treated electrode sheet is provided, the pre-treated electrode sheet including an electrode tab welding area;

[0007] The tab welding area is connected to a DC power device, and the DC power device outputs current through the tab welding area to bring the tab welding area to and maintain the temperature required to relieve stress, thereby relieving the stress in the tab welding area.

[0008] Optionally, the pretreated electrode is a positive electrode and / or a negative electrode.

[0009] Optionally, the maximum output current of the DC power device is 100A.

[0010] Optionally, the voltage regulation range of the DC power device is 0 to 30V.

[0011] Optionally, the temperature range required to relieve stress is 50°C to 60°C.

[0012] Optionally, the DC power device outputs current to maintain the electrode welding area at the stress-relief temperature for a first duration.

[0013] To achieve the above objectives, this application also provides a method for manufacturing an electrode sheet, including the electrode sheet stress relief method described above;

[0014] The electrode manufacturing method further includes:

[0015] The tabs are welded onto the pretreated electrode while it still retains its thermal ductility after the pretreated electrode has been stress-relieved.

[0016] Optionally, after the pretreated electrode has been stress-relieved, the tab is welded onto the pretreated electrode within a second time period, the second time period being 1 to 3 seconds.

[0017] To achieve the above objectives, this application also provides a method for manufacturing a battery core for a secondary battery, comprising:

[0018] A pre-treated electrode sheet is provided, the pre-treated electrode sheet including an electrode tab welding area;

[0019] The electrode welding area is connected to a DC power device, and the DC power device outputs current through the electrode welding area to make the electrode welding area reach and maintain the temperature required to relieve stress in the electrode welding area.

[0020] The electrode tab is welded to the electrode tab welding area;

[0021] The material to be wound is wound into a bare core, wherein the material to be wound includes the pre-treated electrode sheet after welding the tabs.

[0022] Optionally, the core material to be wound includes a positive electrode sheet, a negative electrode sheet, and a separator. The pre-treated electrode sheet after welding the tabs is the positive electrode sheet and / or the negative electrode sheet, and the separator is used to separate the positive electrode sheet and the negative electrode sheet.

[0023] In this embodiment, the electrode stress relief method connects the tab welding area of ​​the pretreated electrode to a DC power device. The DC power device outputs current through the tab welding area, bringing it to and maintaining the required stress-relief temperature. This embodiment utilizes the thermal effect of the current to generate heat within the substrate of the pretreated electrode, effectively relieving stress. Furthermore, the conductivity of the substrate is higher than that of the surface anti-oxidation layer, so the thermal effect is concentrated in the substrate, preventing external heat transfer from damaging the surface anti-oxidation layer. This method effectively eliminates electrode stress, ensuring that after the electrode is manufactured into a battery core, the welding position of the tab or the overhang area of ​​the negative electrode will not easily break due to stress during long-cycle operation, thus improving the battery's long-cycle performance. Attached Figure Description

[0024] Figure 1 This is a flowchart of a stress relief method for an electrode sheet according to an embodiment of this application.

[0025] Figure 2 This is a schematic diagram showing the connection between the electrode welding area and the DC power device in an embodiment of this application.

[0026] Figure 3 This is a schematic diagram showing the output current of the DC device to the electrode in an embodiment of this application.

[0027] Figure 4 This is a flowchart illustrating the method for manufacturing the electrode sheet according to an embodiment of this application.

[0028] Figure 5 This is a schematic diagram of the tabs being welded to the electrode sheet according to an embodiment of this application.

[0029] Figure 6 This is a flowchart illustrating a method for manufacturing a battery core according to an embodiment of this application.

[0030] Figure 7 This is a schematic diagram of the bare core obtained after winding according to an embodiment of this application. Detailed Implementation

[0031] To illustrate the technical content, structural features, and effects of this application in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0032] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0033] Example 1

[0034] Please see Figures 1 to 3 This embodiment discloses a method for relieving electrode stress, including:

[0035] S11, a pre-treated electrode 1 is provided, the pre-treated electrode 1 including an electrode tab welding area 11.

[0036] Specifically, the pretreated electrode 1 is a positive electrode and / or a negative electrode.

[0037] Furthermore, the pretreated electrode 1 is manufactured from the current collector using an electrode manufacturing process, which includes:

[0038] (1) Slurry preparation: Mix the positive / negative electrode active materials, conductive agent, binder and appropriate amount of solvent evenly to form positive / negative electrode slurry.

[0039] Specifically, common positive electrode active materials include lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials (such as lithium nickel cobalt manganese oxide). Common negative electrode active materials include graphite, silicon-based materials, and lithium titanate. Conductive agents such as carbon black and graphene are used to improve the conductivity of the electrode, while binders such as polyvinylidene fluoride (PVDF) are used to bond the active materials to the current collector.

[0040] (2) Coating: The positive / negative electrode slurry is uniformly coated on the surface of the current collector.

[0041] The prepared positive / negative slurries are uniformly coated onto the current collector. The coating process requires control of the slurry thickness and uniformity to ensure the quality of the positive / negative electrodes.

[0042] Generally speaking, the substrate for the current collector used in the positive electrode is aluminum foil, while the substrate for the current collector used in the negative electrode is copper foil.

[0043] (3) Roll pressing: The coated current collector is subjected to roll pressing treatment.

[0044] Rolling enhances the adhesion between the active material and the foil, preventing the active material from peeling off during electrolyte immersion and battery use. Furthermore, ensuring a smooth and flat electrode surface prevents burrs on the coating surface from puncturing the separator and causing short circuits. Compacting the electrode coating material reduces the electrode volume, thereby increasing the battery's energy density.

[0045] Electrode rolling is divided into two methods: cold rolling and hot rolling. In terms of rolling procedures, it can be divided into single rolling and multiple rolling. Multiple rolling is relatively complex, but it can reduce electrode rebound, resulting in better electrode gloss and higher thickness consistency.

[0046] (4) Cutting: Cut the current collector after rolling according to the required size to obtain the electrode sheet.

[0047] (5) Baking: Baking the electrode sheets.

[0048] The main purpose of baking the electrode is to remove moisture and organic solvents from it, thereby improving its stability and electrochemical performance. Baking ensures that the active material in the electrode is fully dried, preventing performance degradation or safety issues caused by residual moisture during subsequent production and use.

[0049] Generally, the baking temperature of the positive electrode is slightly higher than that of the negative electrode. Depending on the materials and process requirements, the baking temperature is typically between 100-130℃. For example, some studies suggest that baking the positive electrode at 110-130℃ for 12 hours yields better results, while baking the negative electrode at 100-120℃ for 12 hours is preferable. However, the specific baking temperature needs to be adjusted based on the battery design and manufacturing process.

[0050] Typically, the baking process needs to be carried out in a vacuum environment or under the protection of an inert gas. The surface of the electrode to be baked must be clean and free of impurities, and it needs to be cooled to room temperature after baking before being taken out.

[0051] S12, connect the tab welding area 11 to the DC power device 2, and use the DC power device 2 to output current through the tab welding area 11 to make the tab welding area 11 reach and maintain the temperature required to relieve stress in order to relieve the stress in the tab welding area 11.

[0052] The electrode welding area 11 is connected to the DC power device 2 as follows: Figure 2 and Figure 3 As shown, where, Figure 3 The arrow points in the direction of the current.

[0053] Specifically, an anti-oxidation layer is formed on the surface of the pretreated electrode 1.

[0054] More specifically, the anti-oxidation layer is a chromium passivation layer or an aluminum passivation layer.

[0055] During the output current process, the thermal effect of the current is used to generate heat inside the pretreated electrode 1, thereby effectively eliminating stress. At this time, the conductivity of the substrate of the pretreated electrode 1 is higher than that of the surface anti-oxidation layer, so the thermal effect of the current will be concentrated on the substrate of the pretreated electrode 1, thus avoiding damage to the anti-oxidation layer on the surface of the pretreated electrode 1 by external heat transfer.

[0056] Specifically, the maximum output current of the DC power device 2 is 100A. Of course, this application does not limit the maximum output current of the DC power device 2.

[0057] Specifically, the voltage regulation range of the DC power device 2 is 0 to 30V. Of course, this application does not limit the voltage regulation range of the DC power device 2.

[0058] Specifically, the temperature range required to relieve stress is 50℃ to 60℃.

[0059] It is understandable that the temperature required to relieve stress is a range, not a specific value.

[0060] Specifically, the DC power supply 2 outputs current to maintain the electrode welding area 11 at the temperature required to relieve stress for a first duration, which needs to be set according to actual conditions. Alternatively, stress relief can be determined by observing or measuring the parameters of the electrode, in which case the energizing duration does not need to be set to a fixed duration.

[0061] Specifically, the DC power supply 2 includes a DC regulated power supply, a DC constant current source, and a high-power DC power supply, which can be selected according to needs.

[0062] In this embodiment, the electrode stress relief method connects the tab welding area 11 of the pretreated electrode 1 to a DC power device 2. The DC power device 2 outputs current through the tab welding area 11, bringing it to and maintaining the temperature required for stress relief, thus eliminating the stress in the tab welding area 11. This embodiment utilizes the thermal effect of the current to generate heat within the substrate of the pretreated electrode 1, effectively relieving stress. Furthermore, the conductivity of the substrate of the pretreated electrode 1 is higher than that of the surface anti-oxidation layer, so the thermal effect of the current is concentrated in the substrate, preventing external heat transfer from damaging the surface anti-oxidation layer. This method effectively eliminates electrode stress, ensuring that after the electrode is manufactured into a battery core, the welding position of the tab 3 or the area at the overhang of the negative electrode will not easily break due to stress during long-cycle operation, thereby improving the long-cycle performance of the battery.

[0063] Example 2

[0064] Please see Figure 4 and Figure 5 This embodiment discloses a method for manufacturing an electrode sheet, including:

[0065] S21, a pre-treated electrode 1 is provided, the pre-treated electrode 1 including an electrode tab welding area 11.

[0066] S22, connect the tab welding area 11 to the DC power device 2, and use the DC power device 2 to output current through the tab welding area 11 to make the tab welding area 11 reach and maintain the temperature required to relieve stress in order to relieve the stress in the tab welding area 11.

[0067] It should be understood that the specific implementation details of steps S21 and S22 are the same as those of steps S11 and S12 in Embodiment 1, and will not be repeated here.

[0068] S23, the tab 3 is welded onto the pretreated electrode 1 while it still retains thermal ductility characteristics after the pretreated electrode 1 has been stress-relieved.

[0069] Specifically, after the pretreated electrode 1 is stress-relieved, the tab 3 is welded onto the pretreated electrode 1 within a second time period, which is 1 to 3 seconds. Of course, the second time period is not limited to this.

[0070] Please see Figure 5 It is important to understand that after stress relief is achieved in the tab welding area 11, the tab 3 should be welded as quickly as possible to ensure that the electrode maintains better thermal expansion characteristics during the welding process. Furthermore, the tab welded to the positive electrode is the positive tab, and the tab welded to the negative electrode is the negative tab; the number of tabs 3 can be single or multiple.

[0071] Specifically, the tab welding area 11 is typically located at a specific position on the electrode sheet. The choice of this position depends on the battery design, the layout of the tabs 3, and the requirements of the welding process. Generally, the welding area needs to meet the following conditions:

[0072] (1) Easy to operate: The welding area should be easy to operate the welding equipment to ensure that the welding head can be accurately aligned and pressure applied during the welding process.

[0073] (2) Welding quality: The welding area should be able to produce good welding effect, that is, the welding point is firm and free from defects such as cracks and incomplete welding.

[0074] (3) Structural stability: The welded tab 3 and the electrode sheet should have good structural stability and be able to withstand various forces and stresses generated during battery use.

[0075] Specifically, the main welding methods that can be selected are ultrasonic welding and laser welding.

[0076] Example 3

[0077] Please see Figure 6 and Figure 7 This embodiment discloses a method for manufacturing a battery core for a secondary battery, comprising:

[0078] S31, a pre-treated electrode 1 is provided, the pre-treated electrode 1 including an electrode tab welding area 11.

[0079] S32, connect the tab welding area 11 to the DC power device 2, and use the DC power device 2 to output current through the tab welding area 11 to make the tab welding area 11 reach and maintain the temperature required to relieve stress in order to relieve the stress in the tab welding area 11.

[0080] It should be understood that the specific implementation details of steps S31 and S32 are the same as those of steps S21 and S22 in Embodiment 2 and steps S11 and S12 in Embodiment 1, and will not be repeated here.

[0081] S33, weld the tab 3 to the tab welding area 11.

[0082] It should be understood that the specific implementation details of step S33 are the same as those of step S23 in Embodiment 2, and will not be repeated here.

[0083] S34, wind the material to be wound into a bare core 4 (e.g. Figure 7 As shown), the material to be wound includes the pre-treated electrode sheet 1 after welding the electrode tab 3.

[0084] Specifically, the core material to be wound includes a positive electrode sheet, a negative electrode sheet, and a separator. The pre-treated electrode sheet 1 after welding the tab 3 is a positive electrode sheet and / or a negative electrode sheet, and the separator is used to separate the positive electrode sheet and the negative electrode sheet.

[0085] In the above-described battery core manufacturing process, the pre-treated electrode sheet 1 can be either a positive or negative electrode sheet. Before winding into a core, the positive electrode sheet, separator, and negative electrode sheet are placed in a specific order, such as separator-positive electrode-separator-negative electrode, and then wound using a winding machine. During the winding process, it is necessary to ensure the alignment and adhesion between the positive and negative electrode sheets and the separator (especially the separator end 5) to avoid misalignment, wrinkles, and uneven thickness at the separator end 5. Furthermore, after winding, a terminating tape 6 is used to fix the bare core 4 to ensure the integrity and stability of the battery structure, while providing reliable insulation protection to prevent internal short circuits.

[0086] After winding, the following processes can be used for further processing:

[0087] (1) Filling electrolyte: The electrolyte is filled into the bare core 4 by means of impregnation or coating to achieve ion transport between the positive and negative electrodes.

[0088] (2) Sealing and encapsulation: Seal the core and add sealant to the seal to ensure that the electrolyte does not leak. Then put the core into an aluminum-plastic composite film bag and perform heat sealing and other encapsulation treatments.

[0089] (3) Molding test: The finished core is inspected for appearance, electrical performance and safety performance to ensure that the core meets the design requirements and quality standards.

[0090] Specifically, the above method is applicable to the production of cores for secondary batteries such as cylindrical and pouch batteries.

[0091] In summary, in this embodiment, by connecting the tab welding area 11 of the pretreated electrode 1 to the DC power device 2, the output current is used to bring the tab welding area 11 to and maintain the temperature required for stress relief. The thermal effect of the current generates heat within the substrate of the pretreated electrode 1, thereby effectively relieving stress. Furthermore, the conductivity of the substrate of the pretreated electrode 1 is higher than that of the surface anti-oxidation layer, so the thermal effect of the current is concentrated in the substrate, preventing external heat transfer from damaging the surface anti-oxidation layer. After energizing, the tab 3 is welded to the tab welding area 11 within a second time period to ensure that the pretreated electrode 1 maintains superior thermal elongation characteristics during the welding process. Finally, the pretreated electrode 1 is wound to form a bare core 4. This application can effectively eliminate the stress in the core, preventing the welding position of the tab 3 or the area at the overhang of the negative electrode from easily breaking due to stress during long-cycle operation, thus improving the long-cycle performance of the battery.

[0092] The above-disclosed examples are merely preferred embodiments of this application, intended to facilitate understanding and implementation by those skilled in the art. They should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with the scope of this application are still within the scope of this application.

Claims

1. A method for manufacturing electrode sheets, characterized in that, include: A pre-treated electrode sheet is provided, the pre-treated electrode sheet including an electrode tab welding area; The electrode welding area is connected to a DC power device, and the DC power device outputs current through the electrode welding area to make the electrode welding area reach and maintain the temperature required to relieve stress, thereby relieving the stress in the electrode welding area. The temperature range required to relieve stress is 50℃~60℃; The conductivity of the substrate of the pretreated electrode is higher than that of the surface anti-oxidation layer of the pretreated electrode, and the current thermal effect is concentrated in the substrate. The tabs are welded onto the pretreated electrode while it still retains its thermal ductility after the pretreated electrode has been stress-relieved.

2. The electrode fabrication method as described in claim 1, characterized in that, The pretreated electrode is a positive electrode and / or a negative electrode.

3. The electrode fabrication method as described in claim 1, characterized in that, The maximum output current of the DC power device is 100A.

4. The electrode fabrication method as described in claim 1, characterized in that, The voltage adjustment range of the DC power device is 0~30V.

5. The electrode fabrication method as described in claim 1, characterized in that, The DC power device outputs current to maintain the electrode welding area at the stress relief temperature for a first duration.

6. The electrode fabrication method as described in claim 1, characterized in that, After the pretreated electrode sheet is stress-relieved, the electrode tab is welded onto the pretreated electrode sheet within a second time period, which is 1 to 3 seconds.

7. A method for manufacturing a battery core, used in a secondary battery, characterized in that, include: A pre-treated electrode sheet is provided, the pre-treated electrode sheet including an electrode tab welding area; The electrode welding area is connected to a DC power device, and the DC power device outputs current through the electrode welding area to make the electrode welding area reach and maintain the temperature required to relieve stress, thereby relieving the stress in the electrode welding area. The electrode tab is welded to the electrode tab welding area; The material to be wound is wound into a bare core, wherein the material to be wound includes the pre-treated electrode sheet after welding the electrode tabs; The temperature range required to relieve stress is 50℃~60℃; The conductivity of the substrate of the pretreated electrode is higher than that of the surface anti-oxidation layer of the pretreated electrode, and the current thermal effect is concentrated in the substrate. The tabs are welded onto the pretreated electrode while it still retains its thermal ductility after the pretreated electrode has been stress-relieved.

8. The method for manufacturing a battery core as described in claim 7, characterized in that, The material to be wound includes a positive electrode sheet, a negative electrode sheet, and a separator. The pre-treated electrode sheet after welding the tabs is the positive electrode sheet and / or the negative electrode sheet. The separator is used to separate the positive electrode sheet and the negative electrode sheet.

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