Application method of a leakage detection method for soft-pack batteries and its detection method

Abstract

The present invention discloses an application method and a detection method for a leakage detection method of a soft-pack battery. To solve the problems of low efficiency and high equipment requirements of existing lithium-ion battery leakage detection equipment, the detection method includes the following steps: Q1: Place the soft-pack battery in a sealed space; Q2: Perform a vacuum pumping treatment on the sealed space to keep the soft-pack battery under a specific pumping air pressure for a specific evacuation time; Q3: Detect the thickness of the battery cell after the pressure holding is completed; Q4: Compare the thickness expansion value with the thickness expansion determination standard, and those with an expansion exceeding the standard value are unqualified products. The beneficial effects of the present invention are as follows: It can avoid misjudgment of normal batteries due to the precipitation of trace gases or solvent volatilization inside them, or damage due to irreversible residue of the precipitated gas dissolution; By adopting the steps S2-step S7 of an application method of a leakage detection method of a soft-pack battery, the best test parameters can be formulated for different products, and the product has strong practicability.

Description

Technical Field

[0001] The present invention relates to the field of pouch battery detection, and particularly to an application method and a detection method of a leakage detection method for pouch batteries. Background Art

[0002] Lithium-ion batteries are an organic electrolyte system and are extremely sensitive to water and air. The failure of their encapsulation will lead to abnormal battery performance, and in severe cases, it will also cause safety problems during use. To address this issue, battery manufacturers usually add leakage detection devices during the production process to identify defective products during production and prevent defective batteries from flowing out.

[0003] An "Automatic Detection Device for Micro-leakage of Pouch Lithium Batteries" disclosed in a Chinese patent document, with the publication number CN212059287U, includes a conveying mechanism for transporting materials. A positive pressure test component is provided between the conveying mechanisms. An inductor component for detecting the surface flatness is provided at the discharge end of the conveying mechanism and located at the positive pressure test component. The inductor component is electrically connected to an external control terminal. In the present invention, the battery is subjected to a positive pressure test in a closed mold cavity formed by a die. When the upper and lower dies are closed, the detection suction cups on the inner walls of the upper and lower dies are in close contact with the upper and lower surfaces of the battery respectively. Then, the closed cavity formed by the die is inflated through an air pipe with a certain set value. After the pressure is detected by the pressure valve and reaches the set value, it is kept under pressure for 36s. If there are leak holes on the battery surface or the seal edge fails and cracks, the high-pressure gas will enter the battery interior through the failure position, forming a pressure difference with the area covered by the suction cup, thereby causing the area covered by the suction cup or the entire battery surface to bulge. Its disadvantages are as follows: The packaging of pouch lithium batteries is soft, and the suction cups will leave imprints on the packaging surface, affecting product sales. At the same time, the current surface of the pouch battery is not absolutely flat, and it is difficult to ensure the effectiveness of the suction cup seal. Moreover, the gas source for the battery expansion is external inflation, and the effect is slow.

[0004] A patent (authorization publication number CN 209296241 U) discloses a core leakage detection device, which uses the method of vacuum pumping to accelerate the evaporation of the electrolyte and detects the leakage problem with a VOC detection device. Although this detection method can detect defective cores, its detection time is greater than 15s, and the negative pressure is -95Kpa. To ensure that the electrolyte evaporates and is detected by a highly sensitive detection device, the equipment efficiency is low. At the same time, the volatile gas needs to be fully dissipated when the next pack of cores comes in to ensure production continuity, and the equipment requirements are high and the technology is complex. Summary of the Invention

[0005] The present invention mainly aims to solve the problems of low efficiency and high equipment requirements of existing lithium-ion battery leakage detection equipment, and provides an application method and a detection method for a soft-pack battery leakage detection method. At the same time, this method can avoid misjudgment of normal batteries due to the precipitation of trace gases or the volatilization of solvents inside, or damage due to irreversible residue of the precipitated gas dissolution.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A soft-pack battery leakage detection method includes the following steps:

[0008] Q1: Place the soft-pack battery in a sealed space;

[0009] Q2: Perform a vacuum pumping treatment on the sealed space so that the soft-pack battery is pressurized at a specific pumping air pressure for a specific evacuation time;

[0010] Q3: Perform a thickness detection on the battery after the pressure holding is completed;

[0011] Q4: Compare the thickness expansion value with the thickness expansion determination standard, and those with an expansion exceeding the standard value are unqualified products.

[0012] Preferably, the thickness expansion determination standard is that the thickness change is less than 3 mm.

[0013] The thickness expansion change of 3 mm is the standard for judging whether a battery is qualified. Therefore, by setting the thickness expansion determination standard to be less than the set value, the accuracy of this method can be better improved.

[0014] Preferably, the thickness expansion determination standard is that the thickness change is less than 1 mm.

[0015] The thickness expansion change of 1 mm is the standard for judging whether a battery is excellent. Therefore, by setting the thickness expansion determination standard to be less than the set value, the accuracy of this method can be better improved. The thickness expansion change of 0.5 mm is the standard for judging whether a battery is high-end and can be used as the standard for subsequent battery evaluation.

[0016] To ensure the smooth implementation of the soft-pack battery leakage detection method, the present invention also includes an application method of the above soft-pack battery leakage detection method to determine the specific pumping air pressure and the specific evacuation time, including the following steps:

[0017] S1: Place the soft-pack battery in a sealed space;

[0018] S2: Set the pumping air pressure to be greater than or equal to the initial pumping air pressure, set the evacuation time, perform a vacuum pumping treatment on the sealed space, and perform a soft-pack battery expansion thickness detection, and confirm the gas residue amount in the battery after measurement;

[0019] S3: Change the evacuation time and repeat step S2;

[0020] S4: Analyze the changes in thickness expansion and gas residue with the increase of evacuation time, and take the time when the battery thickness and gas residue no longer change significantly as the test time for leak detection;

[0021] S5: Set the test time determined in step S3 as the evacuation time, set the evacuation pressure as the initial evacuation pressure, evacuate the enclosed space, and conduct thickness expansion detection, and confirm the gas residue in the battery after measurement;

[0022] S6: Change the evacuation pressure and repeat step S5;

[0023] S7: Analyze the changes in thickness expansion and gas residue with the increase of evacuation pressure, and take the pressure when the battery thickness and gas residue no longer change significantly as the evacuation pressure for leak detection.

[0024] In steps S2 and S5, vacuum is pumped in the enclosed space, so that the pouch battery placed therein expands in thickness due to the internal and external air pressure difference, and thus can be recognized and judged by the thickness detection device. The thickness detection method adopted by the thickness detection device is the laser ranging method. By using the vacuum pumping method, since there is no need to inflate strongly, and the thickness change of the battery is caused by the gas precipitation inside the battery, the battery expands quickly and the test is rapid.

[0025] The initial evacuation pressure in steps S2 and S5 is the lower limit of the evacuation pressure, that is, the air pressure value of the last vacuum pumping of the battery.

[0026] Through steps S2 - S7, the iterative verification method is used to avoid misjudgment of normal batteries due to the precipitation of trace gases or solvent volatilization inside them, or being damaged due to irreversible residue of the precipitated gas dissolution, and ensure the smooth application of this method in the formulation of detection conditions.

[0027] Under certain vacuum conditions, the precipitation of gas or volatilization of solvent inside the pouch battery will cause the battery to expand, so as to identify the leaking battery based on the change of the battery thickness. And the leaking battery contains more dissolved gas inside and requires a lower vacuum degree.

[0028] Preferably, step S3 includes the following steps:

[0029] S31: Gradually increase the evacuation test time by 1 - 5 seconds;

[0030] S32: Repeat step S2 until the thickness expansion of the pouch battery no longer changes significantly.

[0031] By gradually increasing the evacuation test time, analyze the relationship between thickness expansion and evacuation time until the battery thickness no longer changes significantly, and determine the test time for leak detection. This method can accurately determine the test time, and increasing it by 1 - 5 seconds each time can prevent over-evacuation caused by too long evacuation time, improving the accuracy of this method.

[0032] Preferably, the gradual increase in the evacuation test time in step S31 is 2 seconds.

[0033] Increasing the time by 2 seconds each time can more accurately determine the test time.

[0034] Preferably, step S6 includes the following steps:

[0035] S61: Gradually increase the evacuation pressure by 5 - 20 torr;

[0036] S62: Repeat step S5 until the thickness expansion of the soft-pack battery no longer changes significantly.

[0037] By gradually increasing the evacuation pressure, analyze the relationship between thickness expansion and evacuation pressure until the battery thickness no longer changes significantly, and determine the evacuation pressure for leak detection. This method can accurately determine the test time, and increasing it by 5 - 20 torr each time can prevent over-evacuation caused by too much increase in evacuation pressure, improving the accuracy of this method.

[0038] Preferably, the increased value of the gradually increased evacuation pressure is 10 torr.

[0039] Increasing the evacuation pressure by 10 torr each time can more accurately determine the evacuation pressure.

[0040] Preferably, the method for confirming the gas residue amount in the battery is the ultrasonic detection method.

[0041] The ultrasonic detection method can inspect the surface and internal quality of the inspected component without damaging the workpiece or the working state of the raw material, improving the accuracy of this method.

[0042] The standard for the ultrasonic detection method to identify gas residue is less than 10%, and more precisely it can be less than 5%. The most suitable standard can be used according to requirements.

[0043] The beneficial effects of the present invention are:

[0044] (1) This method can avoid misjudgment of normal batteries due to the precipitation of trace gases or solvent volatilization inside them, or being damaged due to irreversible residue of the precipitated gas dissolution.

[0045] (2) The vacuum pumping method is adopted. Since it does not require strong inflation, the thickness change of the battery caused by the gas evolution inside the battery is avoided, the battery expansion speed is fast, and the test is rapid.

[0046] (3) By adopting the steps S2 - S7 of the application method of a soft - package battery leakage detection method, the best test parameters can be formulated for different products, and the product has strong practicability.

[0047] (4) The evacuation pressure takes the lower limit of the evacuation pressure as the initial evacuation pressure, and the test conditions are gradually relaxed. The finally determined evacuation pressure can not only identify the leaking battery, but also will not damage the normal battery. The amount of gas evolved inside the battery is controllable, avoiding bubble residues and affecting the use of the battery. Description of the Drawings

[0048] Figure 1 It is a schematic flow chart of the detection method.

[0049] Figure 2 It is a schematic flow chart of the application method. Specific Embodiments

[0050] The following further describes the application method and the detection method of a soft - package battery leakage detection method of the present invention in combination with the drawings and specific embodiments.

[0051] Example 1:

[0052] A soft - package battery leakage detection method includes the following steps:

[0053] Q1: Put the soft - package battery into a closed space;

[0054] Q2: Perform vacuum pumping on the closed space to keep the soft - package battery under a specific evacuation pressure for a specific evacuation time;

[0055] Q3: Detect the thickness of the battery after the pressure - maintaining is completed;

[0056] Q4: Compare the thickness expansion value with the thickness expansion judgment standard. Those with expansion exceeding the standard value are unqualified products.

[0057] The thickness expansion judgment standard is that the thickness change is less than 3 mm.

[0058] The thickness expansion change of 3 mm is the standard for judging whether a battery is qualified. Therefore, taking the thickness change less than the set thickness expansion judgment standard can better improve the accuracy of this method.

[0059] The thickness expansion judgment standard is that the thickness change is less than 1 mm.

[0060] A thickness expansion change of 1 mm is the criterion for judging whether a battery is excellent. Therefore, by setting the thickness change to be less than the set thickness expansion judgment criterion, the accuracy of this method can be better improved. A thickness expansion change of 0.5 mm is the criterion for judging whether a battery is high-end and can be used as the criterion for subsequent battery evaluation.

[0061] As Figure 1 shown, an application method of a soft-pack battery leakage detection method includes the following steps:

[0062] S1: Place the soft-pack battery in a sealed space;

[0063] S2: Set the evacuation pressure to 150 torr and the evacuation time to 1 s. Evacuate the sealed space and detect the expansion thickness of the soft-pack battery, and confirm the gas residue amount in the battery core after measurement;

[0064] S3: Change the evacuation time to 2 s, 5 s, 10 s, 15 s in sequence, and repeat step S2;

[0065] S4: Analyze the changes of the thickness expansion and the gas residue amount with the increase of the evacuation time. Take the time of 5 s when the battery thickness and the gas residue amount no longer change significantly as the test time for leakage detection;

[0066] S5: Set the test time determined in S3 as the evacuation time, set the evacuation pressure as the initial evacuation pressure, evacuate the sealed space, and perform thickness expansion detection, and confirm the gas residue amount in the battery core after measurement;

[0067] S6: Change the evacuation pressure and repeat step S5;

[0068] S7: Analyze the changes of the thickness expansion and the gas residue amount with the increase of the evacuation pressure. Take the evacuation pressure of 35 torr when the battery thickness and the gas residue amount no longer change significantly as the evacuation pressure for leakage detection.

[0069] The experimental data of this application method are as follows:

[0070] Under the evacuation pressure of 150 torr, the thickness expansion (mm) of the verified battery core:

[0071] Under the evacuation pressure of 150 torr, the change of the gas residue amount in the verified battery core with time:

[0072] Under the evacuation time of 5 s, the thickness expansion (mm) of the verified battery core:

[0073] Under the evacuation time of 5 s, the change of the gas residue amount in the verified battery core with the evacuation pressure:

[0074] Finally, through this application method, the test conditions for leakage detection are determined as a detection time of 5 s and a pumping air pressure of 35 torr.

[0075] In steps S2 and S5, vacuum is pumped in a closed space, so that the pouch cell placed therein expands in thickness due to the internal and external air pressure difference, and thus is recognized and determined by the thickness detection device. The thickness detection method adopted by the thickness detection device is the laser ranging method. By using the vacuum pumping method, since there is no need to inflate strongly, the thickness of the battery changes due to the gas precipitation inside the battery, and the battery expands quickly and the test is rapid.

[0076] The initial pumping air pressure in steps S2 and S5 is the lower limit of the pumping air pressure, and the lower limit of the pumping air pressure is 20 torr, that is, the air pressure value of the last vacuum pumping of the battery.

[0077] Through steps S2 - S7, the iterative verification method is used to avoid misjudgment of normal batteries due to the precipitation of trace gases or solvent volatilization inside them, or damage due to irreversible residue of the precipitated gas dissolution, and ensure the successful application of this method in the formulation of detection conditions.

[0078] Under certain vacuum conditions, the gas precipitation or solvent volatilization inside the pouch cell will cause the battery to expand, so as to identify the leaking battery based on the change in the battery thickness. And the leaking battery dissolves more gas inside and has a lower vacuum requirement.

[0079] Step S3 includes the following steps:

[0080] S31: Gradually increase the evacuation test time by 1 - 5 s;

[0081] S32: Repeat step S2 until the thickness expansion of the pouch cell no longer changes significantly.

[0082] By gradually increasing the evacuation test time, analyze the relationship between the thickness expansion and the evacuation time until the battery thickness no longer changes significantly, and determine the test time for leakage detection. In this way, the test time can be accurately determined, and increasing by 1 - 5 s each time can prevent the occurrence of over-evacuation due to too long evacuation time and improve the accuracy of this method.

[0083] The evacuation test time is gradually increased by 2 s in step S31.

[0084] Increasing the time by 2 s each time can more accurately determine the test time.

[0085] Step S6 includes the following steps:

[0086] S61: Gradually increase the pumping air pressure by 5 - 20 torr;

[0087] S62: Repeat step S5 until there is no obvious change in the thickness expansion of the soft-pack battery.

[0088] By gradually increasing the evacuation pressure, analyze the relationship between the thickness expansion and the evacuation pressure until there is no obvious change in the battery thickness, and determine the evacuation pressure used for leak detection. This method can accurately determine the test time, and increasing by 5 - 20 torr each time can prevent the occurrence of over-evacuation caused by excessive increase in the evacuation pressure, improving the accuracy of this method.

[0089] The increment of gradually increasing the evacuation pressure is 10 torr.

[0090] Increasing the evacuation pressure by 10 torr each time can more accurately determine the evacuation pressure.

[0091] Confirm that the method for verifying the gas residue in the verification battery is the ultrasonic detection method.

[0092] The ultrasonic detection method can inspect the surface and internal quality of the inspected component without damaging the workpiece or the working state of the raw material, avoiding incorrect detection results caused by improper detection methods during the detection process, and improving the accuracy of this method.

[0093] The standard for the ultrasonic detection method to identify gas residue is less than 10%, and more precisely less than 5%. The most suitable standard can be used according to requirements.

[0094] It should be understood that this embodiment is only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. Application method of a leakage detection method for soft-pack batteries, characterized in that, it includes the following steps: S1: Place the soft-pack battery in a closed space; S2: Set the evacuation pressure to be greater than or equal to the initial evacuation pressure, set the evacuation time, evacuate the closed space, and perform thickness detection of the expansion of the soft-pack battery, and confirm the gas residue amount in the battery after measurement; S3: Change the evacuation time and repeat step S2; S4: Analyze the changes in thickness expansion and gas residue amount with the increase of evacuation time, and take the time when the battery thickness and gas residue amount no longer change significantly as the test time for leakage detection; S5: Set the test time determined in step S3 as the evacuation time, set the evacuation pressure as the initial evacuation pressure, evacuate the closed space, and perform thickness expansion detection, and confirm the gas residue amount in the battery after measurement; S6: Change the evacuation pressure and repeat step S5, step S6 includes the following steps: S61: Gradually increase the evacuation pressure by 5 - 20 torr; S62: Repeat step S5 until the thickness expansion of the soft-pack battery no longer changes significantly; S7: Analyze the changes in thickness expansion and gas residue amount with the increase of evacuation pressure, and take the pressure when the battery thickness and gas residue amount no longer change significantly as the evacuation pressure for leakage detection.

2. The application method of a leakage detection method for soft-pack batteries according to claim 1, characterized in that, step S3 includes the following steps: S31: Gradually increase the evacuation test time by 1 - 5 seconds; S32: Repeat step S2 until the thickness expansion of the soft-pack battery no longer changes significantly.

3. The application method of a leakage detection method for soft-pack batteries according to claim 2, characterized in that, the evacuation test time is gradually increased by 2 seconds in step S31.

4. The application method of a leakage detection method for soft-pack batteries according to claim 2, characterized in that, the increased value of the gradually increased evacuation pressure is 10 torr.

5. The application method of a leakage detection method for soft-pack batteries according to claim 1, characterized in that, the method for confirming the gas residue amount in the battery is the ultrasonic detection method.

6. A leakage detection method for soft-pack batteries, applicable to the application method of a leakage detection method for soft-pack batteries according to any one of claims 1 - 5, characterized in that, it includes the following steps: Q1: Place the soft-pack battery in a closed space; Q2: Evacuate the closed space, and keep the soft-pack battery under pressure for a specific evacuation time at a specific evacuation pressure; Q3: Perform thickness detection on the battery after pressure holding; Q4: Compare the thickness expansion value with the thickness expansion judgment standard, and those with expansion exceeding the standard value are unqualified products.

7. The leakage detection method for soft-pack batteries according to claim 6, characterized in that, the thickness expansion judgment standard is that the thickness change is less than 3 mm.

8. The leakage detection method for soft-pack batteries according to claim 7, characterized in that, the thickness expansion judgment standard is that the thickness change is less than 1 mm.

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