A method for repairing poor welding of battery sealing nails

Abstract

The present invention relates to the technical field of battery sealing nail welding, and in particular to a method for repairing poorly welded battery sealing nails, comprising the following steps: S1, laser removal of defective sealing nails, wherein the removal range at least covers the defective sealing nail welding track, the minimum requirement for sealing nail welding penetration is ≤ removal depth ≤ maximum requirement for sealing nail welding penetration, and the radius of the defective sealing nail is R1; S2, setting a new sealing nail within the removal range and laser welding it, wherein the radius of the new sealing nail is R2, and R2>R1. By utilizing the advantages of small focal diameter, high power density, small heat-affected zone and contactless welding of the welding beam, the defective sealing nail is removed and then the new sealing nail is welded, so that the cleaning depth and range of the removal process are controllable, and the penetration depth and width of the welding process are controllable, thereby improving the welding quality of the newly installed sealing nails and improving the yield rate of repair welding of defective battery cells. At the same time, the laser cleaning and welding range can be adjusted to achieve compatibility with repair welding of sealing nails of different diameters and expand the scope of adaptability.

Description

Technical Field

[0001] The present invention relates to the technical field of battery sealing nail welding, and in particular to a method for repairing defective welding of battery sealing nails. Background Art

[0002] The multi-step manufacturing process of existing lithium-ion batteries and battery packs requires the use of laser welding technology. For example, the fixation of structures such as the tabs, top covers, poles, explosion-proof valves, sealing pins, module side seals, and busbar galvanometers all involve laser welding processes. Among them, laser welding of sealing pins is an important link in the lithium battery production process and also a difficult link. As the final sealing link of lithium batteries, the quality of laser welding of sealing pins is directly related to the quality of the product. If the welding is poor, there will be a risk of leakage, and if it flows into the end product, there will be a safety risk of fire.

[0003] However, the sealing pins must first undergo a liquid injection process when welding. After the battery cell is injected and during transportation, the electrolyte will remain in the sink of the injection port, and electrolyte crystals will form after a period of standing. When the sealing pins are laser welded, it is easy to have explosion points or welding defects when encountering electrolyte crystals, resulting in a battery cell with poor sealing pin welding. The traditional defect treatment method of filling with aluminum wire, grinding with a file, and secondary welding along the original trajectory is difficult to operate, and the secondary welding is prone to form explosion points or welding defects again, the qualified rate of repair welding is low, and the penetration depth of the repaired battery cell is difficult to guarantee. At the same time, the traditional defect treatment method of milling off the welding seam with a milling cutter and re-welding a new sealing aluminum pin is not universal and needs to be customized, has high requirements for equipment positioning, and has the risk of electric shock.

[0004] Therefore, there is an urgent need for a technical solution to solve the technical problems of low yield rate of re-welding of battery cells due to poor welding of existing battery sealing nails and the risk of electric shock. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for repairing poorly welded battery sealing nails, in order to address the technical problems of low yield rate of repaired battery cells and risk of electric shock caused by poorly welded battery sealing nails.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for repairing poorly welded battery sealing pins comprises the following steps: S1, laser removal of defective sealing pins, wherein the removal range at least covers the welding track of the defective sealing pins, the minimum welding penetration requirement of the sealing pins is ≤ the removal depth ≤ the maximum welding penetration requirement of the sealing pins, and the radius of the defective sealing pins is R1; S2, setting a new sealing pin within the removal range and laser welding it, wherein the radius of the new sealing pins is R2, and R2>R1.

[0008] The present invention provides a method for repairing poorly welded battery sealing nails. By taking advantage of the advantages of small laser welding beam focus diameter, high power density, small heat-affected zone and contactless welding, the defective sealing nails are removed and then new sealing nails are welded. The cleaning depth and range of the removal process are controllable, and the penetration depth and penetration width of the welding process are controllable, thereby improving the welding quality of the newly installed sealing nails and the yield rate of repair welding of defective battery cells. At the same time, the laser cleaning and welding range can be adjusted according to the size of the sealing nails to achieve compatibility with repair welding of sealing nails of different diameters, thereby expanding the scope of application of the repair welding method.

[0009] As a preferred embodiment of the present invention, the process further includes a first-article confirmation step, which includes confirming the penetration depth and width of the newly installed sealing pins. If the first-article confirmation is qualified, the welding parameters of the repair welding machine are maintained, and the defective battery cells are repaired with sealing pins according to steps S1-S2. If the first-article confirmation is unqualified, the welding parameters of the repair welding machine are adjusted, and repair welding and first-article confirmation are repeated. Batch repair welding after first-article confirmation can ensure that the welding parameters better meet the sealing pin welding process requirements, thereby improving the repair welding yield rate of defective battery cells and improving repair welding efficiency.

[0010] As a preferred embodiment of the present invention, first-article confirmation is performed separately according to the work shifts in the production plan and / or divided into batches according to the cumulative number of defective batteries. Defective batteries in the same shift are produced under similar production conditions. After the first-article confirmation is qualified, the remaining defective batteries are repaired with the same or similar welding parameters, which is conducive to improving the efficiency of repair welding. If the number of defective batteries in the same shift is relatively small, repair welding is performed after the number of defective batteries accumulates to a certain level, thus reducing the number of first-article confirmations and lowering the cost of repair welding.

[0011] As a preferred embodiment of the present invention, the first-article confirmation includes the following steps: A. disassembling and removing the positive electrode top cover of the battery cell; B. cutting the top cover along the diameter direction of the sealing pin to form a first piece and a second piece, and the area of ​​the first piece is larger than that of the second piece; C. soaking the first piece in alkaline solution to expose the welding area; D. testing the penetration depth and width of the welding area under a microscope.

[0012] As a preferred embodiment of the present invention, the sealing pin welding penetration depth is required to be 0.3-0.9 mm, and the weld width is required to be 0.8-1.7 mm.

[0013] As a preferred embodiment of the present invention, the welding parameters of the repair welding machine include main machine power, defocusing amount, welding speed, and welding frequency. By adjusting these parameters, the removal depth, weld penetration, and weld width can be adjusted and coordinated, achieving precise manual control of the removal depth, weld penetration, and weld width.

[0014] As a preferred embodiment of the present invention, the process further includes detecting whether the repaired battery cell is leaking. If so, the process proceeds to step S1-S2 for re-re ...

[0015] As a preferred embodiment of the present invention, the detection comprises placing the repaired battery cell upside down in a vacuum chamber, maintaining the pressure at a vacuum level P for a time period of t, placing pH test paper under the inverted battery cell, and determining leakage by observing the color change of the pH test paper. The vacuum level P is 10-100 Pa, and the pressure is maintained for a time period of t of 10-60 minutes. The pH test paper allows for intuitive observation of battery cell leakage, and combined with the vacuuming operation, the detection is highly intuitive, convenient, quick, and accurate.

[0016] As a preferred solution of the present invention, in S1, the removal range is determined by CCD recognition of the peripheral edge line of the defective sealing pin weld, with high recognition accuracy.

[0017] As a preferred embodiment of the present invention, in S2, the laser welding includes covering the welding trajectory of the newly installed sealing pin with an annular beam, and the welding trajectory of the newly installed sealing pin is determined by CCD recognition. The annular beam cooperates with the circular structure of the sealing pin to improve the uniformity of the weld quality, thereby improving the overall welding quality.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0019] 1. By taking advantage of the small focal diameter, high power density, small heat-affected zone and contactless welding of laser welding beam, defective sealing nails can be removed and then new sealing nails can be welded. The cleaning depth and range of the removal process can be controlled, and the penetration depth and width of the welding process can be controlled, thereby improving the welding quality of the new sealing nails and the yield rate of defective battery core repair welding.

[0020] 2. The laser cleaning and welding range can be adjusted according to the size of the sealing pins to achieve compatibility with sealing pins of different diameters and expand the scope of application of the repair welding method;

[0021] 3. After the first batch of defective battery cells are confirmed, batch re-welding can ensure that the welding parameters better meet the requirements of the sealing nail welding process, thereby improving the repair welding yield of defective battery cells and improving the repair welding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of a method for repairing defective welding of battery sealing nails according to the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of setting up a new sealing nail;

[0024] Figure 3is a schematic diagram of the welding track and the annular beam in Example 1;

[0025] Figure 4 This is a flow chart of a method for repairing defective welding of a battery sealing nail according to Example 3;

[0026] Figure 5 It is a schematic diagram of the top cover structure during the first article confirmation process;

[0027] Figure 6 It is a structural diagram of the first block of the first article confirmation process.

[0028] icon:

[0029] 1-defective sealing nail, 2-newly installed sealing nail, 3-welding track, 4-annular beam, 5-top cover, 51-first piece, 52-second piece. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings.

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] Example 1

[0033] like Figure 1 As shown, a method for repairing poor welding of battery sealing nails specifically includes the steps S1-S2.

[0034] S1. Remove the defective sealing nail 1 by laser. The removal range at least covers the defective sealing nail welding track 3. The minimum requirement of the sealing nail welding penetration depth is ≤ the removal depth ≤ the maximum requirement of the sealing nail welding penetration depth. The radius of the defective sealing nail 1 is R1.

[0035] The removal range is determined by CCD identifying the outer edge line of the weld of the defective sealing nail 1.

[0036] Specifically, CCD recognition first identifies the center position of the defective battery cell filling hole and the radius R1 of the defective sealing pin 1, and transmits the coordinates of the center position to the repair welding machine through the PLC control system. The repair welding machine emits a circular light beam 4 along the coordinates of the center position according to the requirements of the sealing pin welding depth and width, covering the defective sealing pin 1 welding track 3, and removes the defective sealing pin by laser to form a removal range.

[0037] Specifically, such as Figure 3As shown, the welding track 3 is composed of several welding points. After the CCD identifies the center position of the injection hole, the outermost size of the removal range can be determined by combining any two points on the outermost edge of the welding track 3.

[0038] Among them, the radius of the annular light beam 4 can be adjusted by adjusting the main power and defocus of the repair welding machine to cover the welding track 3 of the defective sealing nail 1, and the removal depth can be adjusted by adjusting the laser main power, defocus, welding speed and welding frequency of the repair welding machine.

[0039] In this embodiment, the sealing pin welding penetration depth is required to be 0.3-0.9 mm, therefore, 0.3 mm ≤ removal depth ≤ 0.9 mm.

[0040] S2, set a new sealing nail 2 in the removal range and laser weld it. The radius of the new sealing nail 2 is R2. Figure 2 As shown, R2>R1.

[0041] In this embodiment, laser welding involves covering the welding trajectory 3 of the newly installed sealing pin 2 with an annular beam 4, which is identified by CCD recognition. The annular beam 4 cooperates with the circular structure of the sealing pin to improve the uniformity of the weld quality, thereby improving the overall welding quality.

[0042] Specifically, the CCD recognition first identifies and determines the center position of the newly installed sealing pin 2 and the radius R2 of the newly installed sealing pin 2, and transmits the coordinates of the center position to the repair welding machine through the PLC control system. The repair welding machine emits a circular light beam 4 along the coordinates of the center position according to the requirements of the welding depth and width of the sealing pin, covering the welding track 3 of the newly installed sealing pin 2 and laser welding.

[0043] Specifically, such as Figure 3 As shown, after the CCD identifies the center position of the injection hole, the outermost size of the annular beam 4 can be determined in combination with any two points on the outermost edge of the newly installed sealing nail 2. At the same time, the inner circle size of the annular beam 4 can be determined in combination with the inner circle size of the original welding track 3, so that the inner circle size of the annular beam 4 is smaller than the inner circle size of the original welding track 3.

[0044] A method for repairing poorly welded battery sealing nails in this embodiment uses the advantages of small laser welding beam focus diameter, high power density, small heat-affected zone and contactless welding to remove the defective sealing nail 1 and then weld a new sealing nail 2, so that the cleaning depth and range of the removal process are controllable, and the penetration depth and width of the welding process are controllable, thereby improving the welding quality of the newly installed sealing nail 2 and the yield rate of repair welding of defective battery cells. At the same time, the laser cleaning and welding range can be adjusted according to the size of the sealing nail to achieve compatibility with repair welding of sealing nails of different diameters, thereby expanding the scope of application of the repair welding method.

[0045] Example 2

[0046] like Figure 1 As shown, a method for repairing poorly welded battery sealing pins in this embodiment, based on Example 1, also includes a step of detecting whether the battery cell after repairing is leaking. If it is leaking, re-re-welding is performed according to steps S1-S2. If it is not leaking, the battery cell is turned down normally.

[0047] This embodiment provides a method for repairing a defective battery sealing pin weld. The method includes placing a repaired battery cell upside down in a vacuum chamber, maintaining the pressure at a vacuum level P for a time t, placing pH test paper under the inverted battery cell, and observing the color change of the pH test paper to determine whether there is leakage. The pH test paper can directly observe battery cell leakage, making the detection highly intuitive, convenient, quick, and accurate, thereby ensuring that the repaired battery cell meets the requirements of use.

[0048] Specifically, the pH test paper can be placed under the inverted battery cell and enter the vacuum box together with the inverted battery cell, so that after the battery cell is taken out of the vacuum box, the leakage situation can be obtained as soon as possible, and the occurrence of inaccurate detection caused by manual operation of the pH test paper and the detection time interval can be avoided, thereby improving the detection accuracy.

[0049] In this embodiment, the vacuum degree P is 10-100 Pa, and the pressure holding time t is 10-60 min.

[0050] Example 3

[0051] like Figure 4 As shown, a method for repairing poor welding of battery sealing nails in this embodiment, on the basis of Example 1, is used to repair the sealing nails for batches of defective battery cells, and the welding parameters of the repair welding machine are confirmed by the first piece confirmation method. The first piece confirmation includes the confirmation of the penetration depth and penetration width of the newly installed sealing nails. If the first piece confirmation is qualified, the welding parameters of the repair welding machine are maintained, and the defective battery cells are repaired with the sealing nails according to steps S1-S2. If it is unqualified, the welding parameters of the repair welding machine are adjusted, and the repair welding and first piece confirmation are performed again to obtain the welding parameters of the repair welding machine that better meet the requirements of the sealing nail welding process, thereby improving the repair welding yield of defective battery cells and improving the repair welding efficiency.

[0052] Specifically, the first piece of confirmation can be a sample of a defective battery cell that has been laser cleaned and then re-studded, or a fake battery cell with an empty aluminum shell but a welded top cover, such as Figure 4 As shown, this embodiment is described by taking a sample in which a defective battery cell is laser cleaned and then re-soldered as an example.

[0053] Preferably, the first piece confirmation is carried out separately according to the work shifts in the production plan, wherein the shifts include the day shift and the night shift set according to the production conditions. The defective battery cells of the same shift are produced under similar production conditions. The first piece confirmation of each shift is carried out based on the shift. After the first piece is confirmed to be qualified, the remaining defective battery cells are repaired with the same or similar welding parameters, which is conducive to ensuring the uniformity of welding parameters and improving the repair efficiency.

[0054] Preferably, when the number of defective cells produced in a single shift is small, the first piece confirmation is divided into batches according to the cumulative amount of defective cells, so as to improve the repair welding efficiency and reduce the repair welding cost by reducing the number of first piece confirmations.

[0055] Specifically, the timing of confirming the first batch of defective battery cells will be adjusted according to actual conditions.

[0056] Preferably, the first piece confirmation includes the following steps: A. disassembling and removing the positive electrode top cover 5 of the battery cell; B. cutting the top cover along the diameter direction of the newly installed sealing nail 2 to form a first block 51 and a second block 52, with the area of ​​the first block being larger than that of the second block; C. soaking the first block in alkaline solution to expose the welding area; D. performing a weld depth and weld width test on the welding area under a microscope.

[0057] Specifically, such as Figure 5 As shown, cut the positive electrode top cover 5 of the battery cell along the dotted line to obtain Figure 6 The cross-sectional view of the top cover 5 is shown. The weld area is corroded by immersing the weld area in a solution that does not react with the aluminum material of the top cover 5, such as a sodium hydroxide solution or a hydrofluoric acid solution. The weld area is then exposed, and the weld depth and weld width are then detected under a three-dimensional optical microscope.

[0058] In this embodiment, the sealing pin welding penetration depth is required to be 0.3-0.9 mm, and the weld width is required to be 0.8-1.7 mm.

[0059] In this embodiment, the welding parameters of the repair welding machine include main machine power, defocusing amount, welding speed, and welding frequency. By adjusting these parameters, the removal depth, weld penetration, and weld width can be adjusted and coordinated, achieving precise manual control of the removal depth, weld penetration, and weld width.

[0060] The present embodiment provides a method for repairing defective battery sealing pin welding. Based on the first embodiment, batch repair welding is performed on defective battery cells after the first piece is confirmed. This can ensure that the welding parameters of the repair welding process better meet the requirements of the sealing pin welding process, thereby improving the repair welding yield of defective battery cells and improving the repair welding efficiency.

[0061] Furthermore, the battery cells that have been repaired in batches are tested for leakage using the detection method in Example 2. If there is no leakage, the battery cells are put into use normally. If there is leakage, the battery cells are re-re-welded according to steps S1-S2 and then tested for leakage.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for repairing poor welding of battery sealing nails, characterized in that: The steps include: S1. Remove defective sealing nails with laser. The removal range must at least cover the welding track of the defective sealing nails. The removal range is determined by the CCD identifying the outer edge of the defective sealing nail weld. The minimum welding penetration depth of the sealing nail is ≤ the removal depth ≤ the maximum welding penetration depth of the sealing nail. The radius of the defective sealing nail is R1. S2. Install new sealing pins within the removal range and laser weld them. The radius of the new sealing pins is R2, where R2>R1. The first-article confirmation step is also included. The first-article confirmation includes the confirmation of the penetration depth and width of the newly installed sealing nails. If the first-article confirmation is qualified, the welding parameters of the repair welding machine are maintained, and the defective battery cells are repaired with sealing nails according to the steps S1-S2. If the first-article confirmation is unqualified, the welding parameters of the repair welding machine are adjusted, and the repair welding and first-article confirmation are completed again. First Article Confirmation includes the following steps: A. Disassemble and remove the positive cover of the battery cell; B. Cut the top cover along the diameter direction of the sealing nail to form a first piece and a second piece, with the first piece being larger in area than the second piece; C. Soak the first piece in lye to expose the welding area; D. Test the penetration depth and width of the welding area under a microscope.

2. A method for repairing poor welding of battery sealing nails according to claim 1, characterized in that: The first article confirmation is carried out separately according to the work shifts in the production plan and / or separately according to the batches divided by the cumulative number of defective batteries.

3. A method for repairing welding of battery sealing nails with poor welding according to claim 1, characterized in that: The welding depth of sealing nails is required to be 0.3-0.9mm, and the welding width is required to be 0.8-1.7mm.

4. A method for repairing welding defects of battery sealing nails according to claim 1, characterized in that: The welding parameters of the repair welding machine include host power, defocus amount, welding speed and welding frequency.

5. A method for repairing welding defects of battery sealing nails according to any one of claims 1 to 4, characterized in that: It also includes the step of detecting whether the battery cell after the repair welding is leaking. If it is leaking, re-solder it according to the steps of S1-S2. If it is not leaking, the battery cell is turned off normally.

6. A method for repairing welding defects of battery sealing nails according to claim 5, characterized in that: The detection includes placing the repaired battery cell upside down in a vacuum box, holding the pressure for a time t at a vacuum degree P, placing a pH test paper under the inverted battery cell, and judging whether there is leakage by observing the color change of the pH test paper. The vacuum degree P is 10-100Pa, and the pressure holding time t is 10-60min.

7. A method for repairing defective welding of battery sealing pins as claimed in claim 1, characterized in that: In S2, the laser welding includes covering the welding track of the newly installed sealing pin by means of an annular light beam, and the welding track of the newly installed sealing pin is determined by CCD recognition.

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