Short circuit detection method for accelerating defect diagnosis of battery cell after lamination

Abstract

The invention discloses a short-circuit detection method for accelerating cell defect diagnosis after lamination, and belongs to the technical field of novel lithium batteries. The short-circuit detection method for accelerating the defect diagnosis of the battery cell after lamination comprises the following steps: (1) after a single battery cell is laminated, carrying out first h i-pot test full detection to judge whether the battery cell is short-circuited or not; (2) testing a short-circuit cell, repairing and re-laminating; performing baking treatment on a qualified single battery cell under a vacuum pressure applying condition, and taking out the battery cell after the battery cell is cooled; (3) carrying out second h i-pot test full inspection on the single battery cell treated in the step (2), and judging whether the battery cell is short-circuited or not; and (4) repairing the short-circuited single battery cell, and completing short-circuit detection on the qualified single battery cell. According to the short-circuit detection method for high-temperature pressurization after lithium battery cell lamination, the battery cells with problems and defects can be accurately removed in advance, so that material scrapping in the subsequent process is reduced, and the consistency and safety performance of the finished battery cells are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel lithium batteries, and in particular relates to a short-circuit detection method for accelerating the diagnosis of battery cell defects after lamination. Background Art

[0002] In recent years, lithium-ion battery safety accidents have occurred frequently, and most of them occur in the form of thermal runaway. For lithium batteries, internal short circuits are often the root cause of thermal runaway, so battery quality issues have become a hot topic of concern in production and manufacturing. In the production and manufacturing process of lithium batteries, the generation of internal short circuits is generally related to factors such as dust, burrs, and impurities. Therefore, in the production and manufacturing process of lithium batteries, short circuit testing is required for each process, among which short circuit testing after stacking is the first short circuit detection process. If all problematic cells can be removed in time after stacking, cells with hidden short circuit points can be prevented from flowing to subsequent work sections. On the premise of improving product quality, for the process, it can reduce the difficulty of reworking short-circuited cells, reduce material waste in subsequent work sections, and improve the production qualification rate.

[0003] Conventional short-circuit detection after stacking typically involves short-circuiting a single cell using a voltage of approximately 100-200V and an internal resistance of 10-20MΩ. If the leakage current output by the cell exceeds the set value, a short circuit is detected. However, this detection method is inefficient and often fails to detect hidden short-circuit points, such as fine powder or tiny burrs that fail to penetrate the separator. These hidden short-circuit points are often detected after the battery is baked. After stacking, the cells undergo multiple layers of adhesive bonding, significantly improving the adhesion between the electrodes. After a vacuum bake at 90-100°C for 6-12 hours, the electrodes expand due to the heat, changing the physical and chemical properties of the separator. Fine dust and burrs trapped between the electrodes can easily pierce the separator due to the expansion and compression. Batteries that short-circuit after baking are basically impossible to repair. Therefore, in order to reduce the possibility of short-circuiting after baking, single cells with hidden short-circuit points must be removed and repaired after stacking during the battery production process to improve the production qualification rate and battery product quality. Summary of the Invention

[0004] The embodiment of the present invention provides a short-circuit detection method for accelerating the diagnosis of battery cell defects after lamination, aiming to solve the problem that the current short-circuit detection method cannot effectively eliminate battery cells with defects in advance, resulting in a high rate of material scrap in subsequent processes and low consistency of finished battery cells. The present invention divides the short-circuit detection method of the lithium battery cell through high-temperature pressurization after lamination into two steps. The second step is to bake the battery cell under high temperature and pressure in an oven for a period of time before short-circuit detection, and then perform a secondary short-circuit detection at room temperature. The battery cell with defects can be accurately eliminated in advance, thereby reducing material scrap in subsequent processes and improving the consistency and safety performance of the finished battery cell.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A short circuit detection method for accelerating battery cell defect diagnosis after lamination, comprising the following steps:

[0007] (1) After the single cell is stacked, the first hi-pot test is carried out to determine whether the cell has a short circuit based on the leakage current output during the cell test;

[0008] (2) If the single cell tested short-circuited in step (1) is repaired and re-stacked; if the single cell tested qualified in step (1), it is baked under vacuum pressure and taken out after the cell cools down;

[0009] (3) performing a second hi-pot test on the single cell processed in step (2), and determining whether the cell has a short circuit based on the leakage current output during the cell test;

[0010] (4) If the single cell tested short-circuited in step (3) is returned for repair, the single cell tested qualified in step (3) is stacked and then subjected to short-circuit detection to accelerate cell defect diagnosis. The qualified single cell enters the next process for assembly.

[0011] In step (1), the single cell stack is a single cell formed by stacking a positive electrode sheet, a separator and a negative electrode sheet.

[0012] In step (1), the test environment temperature of the first hi-pot test is 25±5°C.

[0013] In step (1), the voltage of the first hi-pot test is set to 200-300V, and the internal resistance is set to 20MΩ.

[0014] In step (1), the determination of whether the battery cell has a short circuit is made based on the leakage current output during the battery cell test, specifically by using a short circuit tester.

[0015] In step (2), the vacuum pressure condition is: applying a pressure of 5 to 50 kgf to the single battery cell in a vacuum environment of -95±5 KPa.

[0016] The pressure of 5 to 50 kgf is a gravitational pressure of 5 to 50 kgf applied by a heavy object to the battery cell.

[0017] In step (2), the baking temperature of the baking treatment is 90 to 130° C., and the baking time is 1 to 4 hours.

[0018] In step (2), the vacuum is preferably a vacuum environment provided in a vacuum oven.

[0019] In step (2), the cooling is to reduce the temperature to 25±5°C.

[0020] In step (3), the voltage of the second hi-pot test is set to 50-200V, and the internal resistance is set to 20MΩ.

[0021] In step (3), the determination of whether the battery cell has a short circuit is made based on the leakage current outputted during the battery cell test, specifically by using a short circuit tester.

[0022] The present invention sets two short-circuit detection processes after stacking positive electrode sheets, diaphragms and negative electrode sheets into single battery cells; the single battery cells after stacking and gluing are first subjected to a 200-300V high-voltage short-circuit test at room temperature, and the battery cells with obvious problem points are removed and repaired, and then the single battery cells are placed in a vacuum oven at 90-130°C and a certain pressure (5-50kgf) is applied to bake for 1-4 hours. After the battery cells are cooled to room temperature, the short-circuit test is performed on the baked battery cells again with a voltage of 50-200V, so that the battery cells with hidden short-circuit points are removed and repaired, thereby improving the quality of the single battery cells after stacking and reducing the scrapping of short-circuited batteries after subsequent assembly.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] The present invention simulates the overall state of the subsequent process (mainly the baking state) of a single battery cell after stacking, accelerates the diagnosis of short-circuited batteries with various problems, thereby improving the quality of the single battery cell after stacking and the efficiency of the overall process, reducing the scrapping of batteries in the subsequent process, improving the production qualification rate, and reducing the process cost.

[0025] The short-circuit detection method for accelerating the diagnosis of battery cell defects after lamination proposed in the present invention can more quickly and accurately eliminate problematic single cells. Single cells with hidden short-circuit points can be eliminated and repaired in advance before the single cells are assembled, thereby reducing the failure rate of short-circuit testing after baking, improving the quality of single cells flowing into the subsequent process, reducing the scrapping of batteries in the subsequent process, improving the production qualification rate and reducing the process cost.

[0026] The present invention uses a short-circuit detection method under high temperature and pressure after lithium battery cell stacking to accurately eliminate battery cells with problems and defects in advance, thereby reducing material scrap in subsequent processes and improving the consistency and safety performance of finished battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a short-circuit detection method for accelerating the diagnosis of battery cell defects after lamination according to the present invention;

[0028] Figure 2 This is a schematic diagram of the forces acting on the battery cell in the oven. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] At present, the current short-circuit detection method has the problem of being unable to effectively eliminate battery cells with defects in advance, resulting in a high rate of material scrap in subsequent processes and low consistency of finished battery cells. In order to solve the above technical problems, the present invention proposes a short-circuit detection method for accelerating the diagnosis of battery cell defects after lamination. The present invention is divided into two steps through the method of short-circuit detection by high-temperature pressurization after lithium battery cell lamination. The second step is to bake the battery cells under high temperature and pressure in an oven for a period of time before short-circuit detection, and then perform a secondary short-circuit detection at room temperature. The battery cells with defects can be accurately eliminated in advance to reduce material scrap in subsequent processes and improve the consistency and safety performance of the finished battery cells.

[0032] Example 1

[0033] like Figure 1 and Figure 2 As shown, a short circuit detection method for accelerating battery cell defect diagnosis after lamination includes the following steps:

[0034] (1) After the single cell is stacked, the first hi-pot test is carried out at 25±5℃. The voltage of the test is set to 200V and the internal resistance is set to 20MΩ. According to the leakage current output during the cell test, the short circuit tester is used to determine whether the cell has a short circuit.

[0035] (2) If the short-circuited cell tested in step (1) is repaired and re-stacked; the qualified cell tested in step (1) is placed in a vacuum oven at 90°C, a pressure of 20kgf is applied to it, and it is baked in a vacuum environment of -95Kpa for 4 hours. The cell is taken out after the temperature drops to 25±5°C;

[0036] (3) performing a second hi-pot test on the single cell processed in step (2), wherein the voltage of the test is set to 100 V and the internal resistance is set to 20 MΩ, and determining whether the cell has a short circuit by using a short circuit tester based on the leakage current output during the cell test;

[0037] (4) If the short-circuited cell is returned for repair after the test in step (3), the short-circuit test of the cell that has passed the test in step (3) is accelerated after the stacking of the cells. The cell that has passed the test enters the next process for assembly.

[0038] Example 2

[0039] A short circuit detection method for accelerating battery cell defect diagnosis after lamination, comprising the following steps:

[0040] (1) After the single cell is stacked, the first hi-pot test is carried out at 25±5℃. The voltage of the test is set to 250V and the internal resistance is set to 20MΩ. According to the leakage current output during the cell test, the short circuit tester is used to determine whether the cell has a short circuit.

[0041] (2) If the short-circuited cell is tested in step (1), it is repaired and re-stacked; the qualified single cell tested in step (1) is placed in a vacuum oven at 100°C, a pressure of 10kgf is applied to the single cell, and the cell is baked in a vacuum environment of -95Kpa for 2h, and the cell is taken out after the temperature drops to 25±5°C;

[0042] (3) performing a second hi-pot test on the single cell treated in step (2), with the voltage set to 50V and the internal resistance set to 20MΩ, and determining whether the cell has a short circuit by using a short circuit tester based on the leakage current output during the cell test;

[0043] (4) If the short-circuited cell is returned for repair after the test in step (3), the short-circuit test of the cell that has passed the test in step (3) is accelerated after the stacking of the cells. The cell that has passed the test enters the next process for assembly.

[0044] Example 3

[0045] A short circuit detection method for accelerating battery cell defect diagnosis after lamination, comprising the following steps:

[0046] (1) After the single cell is stacked, the first hi-pot test is carried out at 25±5℃. The voltage of the test is set to 200V and the internal resistance is set to 20MΩ. According to the leakage current output during the cell test, the short circuit tester is used to determine whether the cell has a short circuit.

[0047] (2) If the short-circuited cell is tested in step (1), it is repaired and re-stacked; the qualified single cell tested in step (1) is placed in a vacuum oven at 105°C, a pressure of 20kgf is applied to it, and it is baked in a vacuum environment of -95Kpa for 2h, and the cell is taken out after it cools to 25±5°C;

[0048] (3) performing a second hi-pot test on the single cell processed in step (2), wherein the voltage of the test is set to 50V and the internal resistance is set to 20MΩ, and determining whether the cell has a short circuit by a short circuit tester based on the leakage current output during the cell test;

[0049] (4) If the single cell tested short-circuited in step (3) is returned for repair, the single cell tested qualified in step (3) is stacked and then subjected to short-circuit detection to accelerate cell defect diagnosis. The qualified single cell enters the next process for assembly.

[0050] Compared with the original short-circuit detection method (i.e., a full hi-pot test in one go), the qualified rate of the cell manufacturing process of the assembled battery after short-circuit detection using the methods of Examples 1 to 3 of the present invention is increased to 100%.

[0051] 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 short circuit detection method for accelerating the diagnosis of battery cell defects after lamination, characterized by: The following steps are involved: (1) After the single cell is stacked, the first hi-pot test is carried out to determine whether the cell has a short circuit based on the leakage current output during the cell test; (2) If the single cell tested short-circuited in step (1) is repaired and re-stacked; if the single cell tested qualified in step (1), it is baked under vacuum pressure and taken out after the cell cools down; (3) performing a second hi-pot test on the single cell processed in step (2), and determining whether the cell has a short circuit based on the leakage current output during the cell test; (4) If a single cell that has been tested short-circuited in step (3) is returned for repair, the short-circuit detection for cell defect diagnosis is accelerated after the single cell that has passed the test in step (3) is stacked.

2. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (1), the single cell stack is a single cell formed by stacking a positive electrode sheet, a separator and a negative electrode sheet.

3. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (1), the test environment temperature of the first hi-pot test is 25±5°C.

4. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (1), the voltage of the first hi-pot test is set to 200-300V, and the internal resistance is set to 20MΩ.

5. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (2), the vacuum pressure condition is: applying a pressure of 5 to 50 kgf to the single battery cell in a vacuum environment of -95±5 KPa.

6. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 5, characterized in that: The pressure of 5 to 50 kgf is a gravitational pressure of 5 to 50 kgf applied by a heavy object to the battery cell.

7. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (2), the baking temperature of the baking treatment is 90 to 130° C., and the baking time is 1 to 4 hours.

8. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (2), the vacuum is a vacuum environment provided in a vacuum oven.

9. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (2), the cooling is to reduce the temperature to 25±5°C.

10. The short-circuit detection method for accelerating battery cell defect diagnosis after lamination according to claim 1, characterized in that: In step (3), the voltage of the second hi-pot test is set to 50-200V, and the internal resistance is set to 20MΩ.

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