Leak detection device and leak detection method

Abstract

The present invention provides a leak detection device and a leak detection method, which relate to the technical field of battery aluminum-plastic film damage detection. It includes a cylinder body, a piston fixed inside the cylinder body, a suction cup fixed at the lower part of the piston, and a plug arranged at the upper part of the piston; the plug and the piston are both provided with an air passage connected as one, and the upper part of the air passage is provided with a connector for connecting a vacuum pumping device; an adsorption cavity that can expand and contract with the on and off of the vacuum state is formed between the lower part of the piston and the suction cup, and the adsorption cavity is connected to the air passage; the lower part of the cylinder body includes a resisting plane that can resist the battery cell to be detected at the lower part of the cylinder body when the adsorption cavity is in a contracted state, thereby resisting the upward movement of the battery cell. The present application adopts a direct detection method, has a simple structure, a simple detection method, a high detection accuracy, and will not cause missed detection or wrong detection. It can effectively avoid the problem of suction cup marks, and also greatly reduces the production and detection costs and improves the detection efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of battery aluminum-plastic film damage detection, in particular to a leakage detection device and a leakage detection method. Background Art

[0002] Lithium batteries are a type of battery that uses lithium metal or lithium alloy as positive / negative electrode materials and non-aqueous electrolyte solutions. Compared with ordinary batteries, lithium batteries are lower carbon and environmentally friendly, have a longer service life, and are lightweight, have high specific energy, and are well adaptable to both high and low temperatures. It is precisely because of these many advantages that lithium batteries have been increasingly widely used in life.

[0003] However, in the production of lithium batteries, there are usually damage, leakage and bulging of lithium batteries, which have a huge impact on their performance and safety. Therefore, finished lithium batteries are usually tested for damage and leakage during production.

[0004] In the prior art, a leak detection device is usually used to detect whether the battery is damaged. For example, the Chinese patent with application number 201810064866.7 discloses a "battery leak detection device and battery leak detection method", which includes a detection suction cup structure arranged in a sealed cavity, and the detection suction cup structure includes a suction cup body, a first adsorption cavity structure arranged at the adsorption end of the suction cup body, and a second adsorption cavity structure arranged at the adsorption end of the suction cup body and located in the first adsorption cavity structure. When leak detection is performed, the first adsorption cavity structure is in a vacuum state, the second adsorption cavity structure is in a vacuum state or a normal pressure state, and the sealed cavity is in a pressurized state. Since the first adsorption cavity structure is in a vacuum state, it detects the leakage problem of the block battery cell by adjusting the pressure states of the sealed cavity structure, the first sealed cavity structure, and the second sealed cavity structure.

[0005] The applicant has found that this type of battery leakage detection device has the following numerous drawbacks during actual use:

[0006] 1. Since there are two adsorption chambers, the two adsorption chambers are evacuated through two sets of vacuum pumping structures respectively, and the entire leak detection device is also arranged in the sealed chamber, that is, the pressure of the sealed chamber and the two adsorption chambers needs to be adjusted respectively, the operation is complicated, and the pressure state of the three chambers is not easy to adjust to a suitable state, and the success rate of detection is low;

[0007] 2. When the battery surface is damaged, the suction cup cannot pull open the aluminum-plastic film on the surface of the battery cell, so the air path cannot be opened between the damaged port and the suction cup lip, and a bulge cannot be formed at the suction cup, resulting in failure to detect damage. Therefore, there is an inaccurate detection, which is prone to false detection and missed detection;

[0008] 3. Due to the special structure including multiple sets of vacuum devices, multiple adsorption chambers, and piston outer cylinder and piston inner cylinder, during the test, the rubber suction cup is adsorbed upward, so that the lower surface of the piston directly contacts the surface of the aluminum-plastic film. Therefore, after the test, adsorption marks (i.e. suction cup marks) will be produced on the surface of the battery cell, causing the outer surface of the battery cell to deform, affecting the normal use of the battery cell, and even causing the battery cell to be scrapped in severe cases;

[0009] 4. Due to the unreasonable structure of the adsorption chamber, after the test is completed, even if the vacuum device is turned off, the inside of the adsorption chamber is in a complete vacuum state, so that the rubber adsorption part is completely tightly adsorbed together and cannot be opened, affecting the use;

[0010] 5. Because it includes multiple sets of vacuum devices, when testing softer cells, even if the cells are not damaged, the vacuum force may be too strong and bulge may form, causing normal cells to be misjudged as damaged.

[0011] 6. The structure is complex, including a piston inner cylinder, a piston outer cylinder, and multiple sets of vacuum devices, and the structure of the rubber adsorption part is also relatively complex. The manufacturing cost of the entire device is high, and it is inconvenient to use and maintain. Summary of the invention

[0012] In order to solve the problems in the prior art, the present invention provides a leak detection device and a leak detection method, which do not need to place a suction cup in a sealed cavity, can directly perform leak detection, have high detection accuracy, and will not cause false detection or missed detection; solve the problem of suction cup marks on normal battery cells; and have a simpler structure; greatly reduce production and detection costs.

[0013] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a leak detection device, which includes a cylinder body, a piston fixed inside the cylinder body, a suction cup fixed at the bottom of the piston, and a plug arranged at the top of the piston; the plug and the inside of the piston are both provided with an air passage which is connected as a whole, and the upper part of the air passage is provided with a connector for connecting a vacuum device; an adsorption cavity which can expand and contract with the on and off of the vacuum state is formed between the lower part of the piston and the suction cup, and the adsorption cavity is connected to the air passage; the lower part of the cylinder body includes a resisting plane which can resist the battery cell to be detected at the lower part of the cylinder body when the adsorption cavity is in a contracted state, thereby resisting the upward movement of the battery cell.

[0014] Preferably, a accommodating chamber is provided above the air passage inside the piston, the accommodating chamber is communicated with the air passage, an elastic element is provided in the accommodating chamber, the upper portion of the elastic element is fixed on the lower surface of the plug, and the lower portion of the elastic element abuts against the lower surface of the accommodating chamber.

[0015] Preferably, the elastic element is a compression spring, which is in a compressed state when the adsorption chamber contracts, and is in a natural state when the air passage is not vacuumed, and the lower surface of the suction cup is lower than the resisting plane of the lower part of the cylinder body.

[0016] Preferably, a connecting groove is provided on the lower outer surface of the piston, the suction cup is a hollow rubber body structure, and a connecting convex ring corresponding to the connecting groove is provided on the upper inner surface of the suction cup, and the suction cup is clamped on the outside of the piston through the connecting groove and the connecting convex ring.

[0017] According to a further preferred embodiment, the adsorption cavity at the bottom of the suction cup includes an outwardly expanding conical cavity and a columnar cavity connected to the conical cavity, the conical cavity is located at the bottom of the air channel and connected to the air channel, and the columnar cavity is located at the bottom of the conical cavity.

[0018] In a further preferred solution, a piston groove is transversely formed on the lower surface of the piston, and the piston groove is connected to the air channel and the conical cavity.

[0019] According to a further preferred solution, a suction cup inner boss is integrally formed inside the suction cup, the suction cup inner boss is located inside the conical cavity, and the interior of the suction cup inner boss forms the cylindrical cavity, and a suction cup groove is formed through the upper surface of the suction cup inner boss.

[0020] According to a further preferred embodiment, a wavy lip consistent with the shape of the conical cavity is integrally formed on the outer surface of the lower portion of the suction cup, and the outer periphery of the lower portion of the suction cup is an outwardly flared conical adsorption port, the inner side of the conical adsorption port is a horizontal adsorption end face, and a plurality of adsorption holes connected to the conical cavity are evenly arranged on the horizontal adsorption end face.

[0021] According to a further preferred embodiment, a step surface is integrally formed inside the cylinder body, the piston is fixed to the step surface of the cylinder body by a flange integrally formed with the piston, and a seal is provided between the piston and the cylinder body; the plug is fixed to the upper part of the cylinder body, and a seal is also provided between the plug and the cylinder body.

[0022] The present application also provides a leak detection method for the above leak detection device, which comprises the following steps:

[0023] S1. Place the suction cup lip at the bottom of the leak detection device against the upper surface of the battery cell to be tested;

[0024] S2, open the vacuum device connected to the cylinder of the leak detection device. Since the vacuum device is connected to the adsorption cavity in the suction cup, the adsorption cavity of the suction cup is in a negative pressure state. Since the outside of the suction cup is in a normal pressure or positive pressure state, under the negative pressure state, the lip of the lower part of the suction cup shrinks upward, so that the abutment plane of the lower part of the cylinder located at the periphery of the suction cup abuts against the aluminum-plastic film on the upper surface of the battery cell to be tested. The cylinder applies a downward force to the peripheral aluminum-plastic film, and the lip of the suction cup pulls the aluminum-plastic film upward because the adsorption cavity is in a negative pressure state, thereby releasing the gas channel inside the battery cell;

[0025] S3. At this time, if there is a leak in the battery cell to be tested, the external atmosphere enters the battery cell from the leak port. Since the periphery of the suction cup device is in a pressurized or normal pressure state, and the adsorption cavity is in a negative pressure state, a pressure difference is formed in the hollow part of the suction cup through the released gas channel, and the pressure difference causes the aluminum-plastic film to deform and bulge;

[0026] S4. Release the negative pressure in the adsorption chamber, remove the leak detection device, and observe the adsorbed surface of the battery cell. If a bulge appears at the position corresponding to the adsorption chamber, the battery cell is unqualified; if no bulge appears at the position corresponding to the adsorption chamber, the battery cell is qualified.

[0027] Compared with the prior art, the leak detection device and leak detection method of the present invention have the following beneficial effects:

[0028] 1. This application only sets up one adsorption chamber and adopts a set of vacuum pumping devices. When testing the battery, the vacuum degree is easier to control, the operation is more convenient, and the detection accuracy is higher;

[0029] 2. The present invention can directly detect leaks without placing the leak detection device in a pressurized sealed environment. That is, the present invention can directly detect leaks through the suction cup when the outer pressure is normal, which is more convenient to use and has lower costs. The structure of the entire detection suction cup device is simpler, and the manufacturing and detection costs are greatly reduced.

[0030] 3. The present application sets a cylinder body so that when the adsorption chamber is vacuumed for detection, the aluminum-plastic film at the bottom of the adsorption chamber is pulled upward, and a downward reverse force is applied to the outer aluminum-plastic film, thereby solving the problem that the air passage between the damaged opening and the suction cup lip cannot be opened during detection in the prior art, so that as long as damage occurs, it can be detected immediately, the detection accuracy is high, and there will be no false detection or missed detection;

[0031] 4. The suction cup of the present application is a hollow integrated structure with a simple structure, and the entire suction cup is fixed on the piston, which solves the problem in the prior art that suction cup marks are easily left on the surface of the battery cell after detection;

[0032] 5. The present application has a simple structure and the detection process is easy to control. When detecting a relatively soft battery cell, even if the battery cell is not damaged, it will not cause deformation or bulging, thus solving the technical problem in the prior art that a normal battery cell is misjudged as damaged.

[0033] 6. In order to avoid the inside of the rubber suction cup being completely tightly fitted together after the test is completed, the present application has a piston groove laterally opened on the lower surface of the piston, and the piston groove is connected to the adsorption cavity. After the test is completed, the adsorption surfaces inside the rubber suction cup can be easily opened under the action of the elastic element, thereby separating the test suction cup from the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the overall structure of a leak detection device of the present invention;

[0035] Figure 2 A bottom view of a leak detection device of the present invention;

[0036] Figure 3 This is a structural cross-sectional view of a leak detection device of the present invention;

[0037] Figure 4 A schematic diagram of the three-dimensional structure of a piston of a leak detection device of the present invention;

[0038] Figure 5 A schematic diagram of the three-dimensional structure of a suction cup of a leak detection device of the present invention;

[0039] Figure 6 A cross-sectional view of a suction cup of a leak detection device of the present invention;

[0040] Figure 7 A schematic diagram of the detection state of a leak detection method of a leak detection device of the present invention;

[0041] Figure 8 A leak detection principle diagram of a leak detection method of a leak detection device of the present invention;

[0042] Fig. 9 The present invention is attached Figure 8 A magnified view of part A in FIG.

[0043] The markings in the figure are:

[0044] 1-cylinder body; 2-plug; 3-piston; 31-flange; 32-connecting groove; 33-piston groove; 4-suction cup; 41-connecting convex ring; 42-wavy lip; 43-conical adsorption port; 44-horizontal adsorption end surface; 45-adsorption hole; 46-inner boss of the suction cup; 47-suction cup groove; 5-battery cell; 6-air channel; 7-connector; 8-adsorption cavity; 81-conical cavity; 82-cylindrical cavity; 9-accommodating cavity; 10-elastic element; 11-step surface; 12-resistance plane; 13-seal. DETAILED DESCRIPTION

[0045] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0046] Embodiment 1

[0047] Reference Figures 1 to 9 The present embodiment provides a leak detection device for leak detection of a block-shaped battery cell, which includes a hollow cylinder 1, a piston 3 fixed inside the cylinder 1, a suction cup 4 fixed to the lower part of the piston 3, and a plug 2 arranged on the upper part of the piston 3, that is, the plug 2, the piston 3, and the suction cup 4 are arranged inside the cylinder 1 from top to bottom.

[0048] The plug 2 and the cylinder body 1 are fixed by threaded connection, and can also be fixed by other means such as bolt fastening.

[0049] The plug 2 and the piston 3 are both provided with an air passage 6 which is connected as one. The air passage 6 is linear. A connector 7 for connecting a vacuum device is provided on the upper portion of the air passage 6. The connector 7 is fixed to the upper portion of the plug 2. By connecting a vacuum device to the connector 7, a negative pressure state is achieved in the air passage 6.

[0050] An adsorption chamber 8 that can expand and contract with the adjustment of pressure is formed between the lower part of the piston 3 and the suction cup 4 , and the adsorption chamber 8 is communicated with the air channel 6 .

[0051] An accommodating chamber 9 is provided above the air passage 6 inside the piston 3, and the accommodating chamber 9 is communicated with the air passage 6. An elastic element 10 is provided in the accommodating chamber 9, and the upper portion of the elastic element 10 is fixed on the lower surface of the plug 2, and the lower portion of the elastic element 10 is against the lower surface of the accommodating chamber 9.

[0052] The lower outer surface of the piston 3 is transversely provided with a connecting groove 32, the suction cup 4 is a hollow rubber body structure, and the upper inner surface of the suction cup 4 is transversely provided with a connecting convex ring 41 corresponding to the connecting groove 32, the connecting convex ring 41 is clamped in the connecting groove 32, and the connection between the suction cup 4 and the piston 3 is achieved through the connecting convex ring 41 and the connecting groove 32. In addition, in order to ensure the sealing of the adsorption chamber 8, a sealant is also applied on the connecting surface between the suction cup 4 and the piston 3.

[0053] The suction cup 4 is an integrally formed rubber suction cup, and the adsorption cavity 8 at the lower part of the suction cup 4 includes an outward-expanding conical cavity 81 and a cylindrical cavity 82 which are connected as one. The conical cavity 81 is located at the lower part of the air channel 6 and is connected to the air channel 6, and the cylindrical cavity 82 is located at the lower part of the conical cavity 81.

[0054] The outer surface of the lower part of the suction cup 4 is integrally formed with a wavy lip 42 that is consistent with the shape of the conical cavity 81. The outer periphery of the lower part of the suction cup 4 is an outward-expanding conical suction port 43. The inner side of the conical suction port 43 is a horizontal suction end surface 44. The horizontal suction end surface 44 is evenly provided with a plurality of suction holes 45 that are connected to the conical cavity 81.

[0055] The cylinder body 1 is a hollow structure inside, and the cylinder body can be a cylinder, a cuboid, a cube or other available structures. A step surface 11 is integrally formed inside the cylinder body 1, and the piston 3 is mounted on the step surface 11 of the cylinder body 1 through a flange 31 integrally formed with the piston 3. The piston 3 can move up and down relative to the cylinder body 1, and a moving space for the piston 3 is formed between the upper part of the piston 3 and the lower part of the plug 2. The moving space is connected to the accommodating chamber 9, that is, the piston 3 can move up and down in the space above the step surface 11 of the cylinder body 1 and below the plug 2. The up and down movement of the piston 3 can drive the suction cup 4 to move up and down.

[0056] In the present application, the cylinder 1 includes a resisting plane 12 which can resist the battery cell 5 to be detected at the lower part of the cylinder 1 when the adsorption chamber 8 is in a contracted state, thereby resisting the upward movement of the battery cell 5. The resisting plane 12 is a plane, which is the lower surface of the cylinder 1. When the adsorption chamber 8 is evacuated, the resisting plane 12 resists the upper surface of the battery cell to be detected. In order to prevent the lower part of the cylinder 1 from forming an indentation on the surface of the battery cell 5, the lower part of the cylinder 1 can be made of rubber material, that is, the resisting plane 12 is a rubber plane.

[0057] In this embodiment, the elastic element 10 is a compression spring. When the air passage 6 is not in a vacuum state, the compression spring is in a naturally compressed state. Under the elastic force of the compression spring itself, the piston 3 moves downward, and the flange 31 of the piston 3 abuts against the step surface 11 of the cylinder body 1. At this time, the conical adsorption port 43 at the bottom of the suction cup 4 is lower than the abutment plane 12 at the bottom of the cylinder body 1. When the air passage 6 is not in a vacuum state, the abutment plane 12 is higher than the bottom of the suction cup 4 and cannot abut against the upper surface of the battery cell 5. At this time, the bottom of the suction cup 4 abuts against the upper surface of the battery cell 5, and the abutment plane 12 is a distance away from the upper part of the upper surface of the battery cell 5. On the contrary, when a vacuum pump is connected to the connector 10, the adsorption chamber 8 is in a negative pressure state, the piston 3 moves upward, and the abutment plane 12 at the bottom of the cylinder body 1 can abut against the upper surface of the battery cell 5.

[0058] In the present application, a piston groove 33 is transversely provided on the lower surface of the piston 3, and the piston groove 33 is connected to the air channel 6 and the conical cavity 81. The provision of the piston groove 33 can effectively avoid the situation that after the detection is completed, even if the vacuum is not passed, the negative pressure in the adsorption cavity 8 cannot be released, and the inside of the adsorption cavity 8 is still adsorbed and adhered together, thus affecting the use. By providing the piston groove 33 at the lower part of the piston 4, the piston groove 33 will not be deformed when the vacuum is drawn. Therefore, after the vacuum is stopped, the air in the piston groove 33 can quickly release the negative pressure in the adsorption cavity 8, restore the shape of the adsorption cavity 8, and thus separate the lower part of the suction cup 4 from the surface of the battery cell 5.

[0059] In the present application, the suction cup 4 has an inner suction cup boss 46 integrally formed therein, the inner suction cup boss 46 is located inside the conical cavity 81 , and the inner suction cup boss 46 is located between the cylindrical cavity 82 and the conical cavity 81 , and the inner suction cup boss 46 forms the cylindrical cavity 82 .

[0060] In the present application, since the cavity between the piston 3 and the plug 2 is connected to the accommodating cavity and the air channel, in order to ensure the sealing performance of the adsorption cavity, a seal 13 is provided between the piston 3 and the cylinder body 1, and a seal 13 is also provided between the plug 2 and the cylinder body 1. The seal 13 can be an O-ring or other various sealing structures.

[0061] Embodiment 2

[0062] On the basis of the above-mentioned embodiment, in this embodiment, a suction cup groove 47 is formed through the upper surface of the suction cup inner boss 46 inside the suction cup 4. The suction cup groove 47 is used to replace the piston groove 33 in the first embodiment. The suction cup groove 46 has the same function as the piston groove 33, so that after the vacuum is stopped, the air in the suction cup groove 46 can quickly release the negative pressure in the adsorption cavity 8, restore the shape of the adsorption cavity 8, and thus separate the lower part of the suction cup 4 from the surface of the battery cell 5.

[0063] Embodiment 3

[0064] By adopting the above two embodiments in combination, a piston groove 33 is transversely opened on the lower surface of the piston 3, and a suction cup groove 47 is penetrated through the upper surface of the inner boss 46 of the suction cup, which can play a better role in quickly releasing the negative pressure in the adsorption cavity 8, which will not be repeated here.

[0065] In the above three embodiments, the arrangement of the piston and the suction cup can be flexibly selected and can also be individually adapted to other detection devices, and is suitable for a variety of occasions.

[0066] Embodiment 4

[0067] On the basis of the above three embodiments, this embodiment can also place the entire leakage detection device in a positive pressure environment, or perform pressurized detection on the battery cell.

[0068] The working principle of a leak detection device in this application is:

[0069] Place the leak detection device on the surface of the battery cell 5 to be tested (such as the attached Figure 7 As shown in the figure, a vacuum device is connected to the connector 7 to put the adsorption chamber 8 inside the leak detection device in a negative pressure state. Under the negative pressure, the conical adsorption port 43 and the horizontal adsorption end surface 44 of the suction cup 4 adsorb the aluminum-plastic film on the surface of the battery cell 5, and pull the aluminum-plastic film located at the lower part of the columnar cavity 82 upward, while the resisting plane 12 at the lower part of the cylinder body 1 presses the aluminum-plastic film located at the lower part downward. Under the action of the cylinder body 1 and the suction cup 4, the gas path inside the battery cell 5 is opened (as shown in the figure). Figure 8 and Fig. 9 As shown). Once the aluminum-plastic film of the battery cell 5 is damaged, the external atmosphere will enter the battery cell 5. Under the action of the negative pressure in the adsorption cavity 8 of the leak detection device, the atmosphere forms a pressure difference in the lower hollow part of the suction cup through the air path. The pressure difference causes the aluminum-plastic film at the lower part of the suction cup to deform and bulge, thereby determining that the battery cell is a damaged and unqualified battery cell; on the contrary, if there is no bulging phenomenon, it is a qualified battery cell.

[0070] Embodiment 4

[0071] The present application also relates to a leak detection method of the leak detection device as described above, which comprises the following steps:

[0072] S1. Place the suction cup lip at the bottom of the leak detection device against the upper surface of the battery cell to be tested;

[0073] S2, open the vacuum device connected to the cylinder of the leak detection device. Since the vacuum device is connected to the adsorption cavity in the suction cup, the adsorption cavity of the suction cup is in a negative pressure state. Since the outside of the suction cup is in a normal pressure or positive pressure state, under the negative pressure state, the lip of the lower part of the suction cup shrinks upward, so that the abutment plane of the lower part of the cylinder located at the periphery of the suction cup abuts against the aluminum-plastic film on the upper surface of the battery cell to be tested. The cylinder applies a downward force to the peripheral aluminum-plastic film, and the lip of the suction cup pulls the aluminum-plastic film upward because the adsorption cavity is in a negative pressure state, thereby releasing the gas channel inside the battery cell;

[0074] S3. At this time, if there is a leak in the battery cell to be tested, the external atmosphere enters the battery cell from the leak port. Since the periphery of the suction cup device is in a pressurized or normal pressure state, and the adsorption cavity is in a negative pressure state, a pressure difference is formed in the hollow part of the suction cup through the released gas channel, and the pressure difference causes the aluminum-plastic film to deform and bulge;

[0075] S4. Release the negative pressure in the adsorption chamber, remove the leak detection device, and observe the adsorbed surface of the battery cell. If a bulge appears at the position corresponding to the adsorption chamber, the battery cell is unqualified; if no bulge appears at the position corresponding to the adsorption chamber, the battery cell is qualified.

[0076] The present application uses a direct detection method and has a simple structure, a simple detection method, a high detection accuracy, and will not have missed detections or false detections. It can also effectively avoid the problem of suction cup marks that occur in detections in the prior art, and also greatly reduces production and detection costs and improves detection efficiency.

[0077] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A leak detection device, characterized in that: It includes a cylinder, a piston fixed inside the cylinder, a suction cup fixed at the bottom of the piston, and a plug provided at the top of the piston; the plug and the piston are both provided with an air passage connected as one, and the top of the air passage is provided with a connector for connecting a vacuum pump; an adsorption cavity that can expand and contract with the on and off of the vacuum state is formed between the bottom of the piston and the suction cup, and the adsorption cavity is connected to the air passage; the bottom of the cylinder includes a resisting surface that can resist the battery cell to be detected at the bottom of the cylinder when the adsorption cavity is in a contracted state, thereby forming a resisting surface for resisting the upward movement of the battery cell; Turn on the vacuum pumping device, which is connected to the adsorption cavity in the suction cup. The adsorption cavity of the suction cup is in a negative pressure state, and the outside of the suction cup is in a normal pressure or positive pressure state. Under the negative pressure state, the lip at the bottom of the suction cup shrinks upward, and the abutting plane at the bottom of the cylinder body located outside the suction cup abuts against the aluminum-plastic film on the upper surface of the battery cell to be tested. The cylinder body applies a downward force to the outer aluminum-plastic film, and the lip of the suction cup pulls the aluminum-plastic film upward to release the gas channel inside the battery cell.

2. A leak detection device according to claim 1, characterized in that: A accommodating chamber is provided above the air passage inside the piston, the accommodating chamber is communicated with the air passage, an elastic element is arranged in the accommodating chamber, the upper portion of the elastic element is fixed on the lower surface of the plug, and the lower portion of the elastic element abuts against the lower surface of the accommodating chamber.

3. A leak detection device according to claim 2, characterized in that: The elastic element is a compression spring, which is in a compressed state when the adsorption cavity contracts. When the air channel is not vacuumed, the compression spring is in a natural state, and the lower surface of the suction cup is lower than the supporting plane of the lower part of the cylinder body.

4. A leak detection device according to claim 3, characterized in that: The lower outer surface of the piston is provided with a connecting groove, the suction cup is a hollow rubber body structure, and the upper inner surface of the suction cup is provided with a connecting convex ring corresponding to the connecting groove, and the suction cup is clamped on the outside of the piston through the connecting groove and the connecting convex ring.

5. A leak detection device according to claim 4, characterized in that: The adsorption cavity at the bottom of the suction cup includes an outward-expanding conical cavity and a columnar cavity connected to the conical cavity. The conical cavity is located at the bottom of the air channel and is connected to the air channel. The columnar cavity is located at the bottom of the conical cavity.

6. A leak detection device according to claim 5, characterized in that: A piston groove is transversely formed on the lower surface of the piston, and the piston groove is connected with the air channel and the conical cavity.

7. A leak detection device according to claim 6, characterized in that: A suction cup inner boss is integrally formed inside the suction cup, the suction cup inner boss is located inside the conical cavity, and the interior of the suction cup inner boss forms the columnar cavity, and a suction cup groove is formed through the upper surface of the suction cup inner boss.

8. A leak detection device according to claim 7, characterized in that: The outer surface of the lower part of the suction cup is integrally formed with a wavy lip that is consistent with the shape of the conical cavity. The outer periphery of the lower part of the suction cup is an outward-expanding conical suction port. The inner side of the conical suction port is a horizontal suction end face. The horizontal suction end face is evenly provided with multiple suction holes that are connected to the conical cavity.

9. A leak detection device according to claim 8, characterized in that: The cylinder body has a step surface integrally formed inside, the piston is fixed to the step surface of the cylinder body via a flange integrally formed with the piston, and a seal is provided between the piston and the cylinder body; the plug is fixed to the upper part of the cylinder body, and a seal is also provided between the plug and the cylinder body.

10. A leak detection method for the leak detection device according to any one of claims 1 to 9, characterized in that: It includes the following steps: S1. Place the suction cup lip at the bottom of the leak detection device against the upper surface of the battery cell to be tested; S2, open the vacuum device connected to the cylinder of the leak detection device. Since the vacuum device is connected to the adsorption cavity in the suction cup, the adsorption cavity of the suction cup is in a negative pressure state. Since the outside of the suction cup is in a normal pressure or positive pressure state, under the negative pressure state, the lip of the lower part of the suction cup shrinks upward, so that the abutment plane of the lower part of the cylinder located at the periphery of the suction cup abuts against the aluminum-plastic film on the upper surface of the battery cell to be tested. The cylinder applies a downward force to the peripheral aluminum-plastic film, and the lip of the suction cup pulls the aluminum-plastic film upward because the adsorption cavity is in a negative pressure state, thereby releasing the gas channel inside the battery cell; S3. At this time, if there is a leak in the battery cell to be tested, the external atmosphere enters the battery cell from the leak port. Since the periphery of the suction cup device is in a pressurized or normal pressure state, and the adsorption cavity is in a negative pressure state, a pressure difference is formed in the hollow part of the suction cup through the released gas channel, and the pressure difference causes the aluminum-plastic film to deform and bulge; S4. Release the negative pressure in the adsorption chamber, remove the leak detection device, and observe the adsorbed surface of the battery cell. If a bulge appears at the position corresponding to the adsorption chamber, the battery cell is unqualified. If there is no bulging phenomenon at the position corresponding to the adsorption cavity, the battery cell is qualified.

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