Soft package battery gas detection device and detection method thereof

Abstract

The invention discloses a soft package battery gas detection device and a detection method thereof. The device comprises a window film packaging module arranged on a battery and a low-pressure adjustable mass spectrum detection module used for battery gas detection, the window film packaging module comprises a gas sampling window, a low-melting-point alloy layer, a modified polypropylene layer and an outer film layer which are formed in a composite film layer of the battery; the low-pressure adjustable mass spectrum detection module comprises a gas inlet end mounting unit, a preceding-stage low-pressure cabin unit, a high-vacuum cabin unit and a mass spectrum detection unit; and gas generated in the battery enters the mass spectrometry detection unit through the preceding-stage low-pressure cabin unit and the high-vacuum cabin unit for qualitative and quantitative analysis. By means of the arrangement, repeatable nondestructive detection of the gas in the soft package lithium battery, multiple in-situ detection in different periods and long-term state tracking are achieved, and an efficient and reliable technical means is provided for research and on-line safety monitoring of the evolution process of the gas in the lithium battery.

Description

Technical Field

[0001] This invention relates to the field of battery testing technology, specifically to a gas detection device for pouch batteries and its inspection method. Background Technology

[0002] Soft-pack lithium batteries are widely used in consumer electronics and new energy vehicles due to their high energy density, light weight, and excellent charge and discharge efficiency. However, side reactions during battery cycling can generate gas, causing the battery to swell and affecting performance and safety.

[0003] Currently, most commonly used battery gas detection methods are destructive, such as puncture sampling. These methods require damaging the battery structure, causing it to fail, making long-term, continuous, and repeated monitoring of the same battery impossible. Furthermore, the introduction of external gases can easily introduce measurement errors. Therefore, there is an urgent need for a gas analysis device that can repeatedly perform in-situ non-destructive testing while maintaining the integrity of the battery structure. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a gas detection device and inspection method for pouch batteries, which can achieve long-term, continuous, and repetitive real-time acquisition and mass spectrometry analysis of the internal gas of the battery without damaging the internal structure and usage status of the battery.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A gas detection device for a soft-pack battery includes a window film encapsulation module disposed on the battery and a low-pressure adjustable mass spectrometry detection module for detecting gas in the battery. The window film encapsulation module includes a gas sampling window formed on the composite film layer of the battery. The gas sampling window is filled with a low melting point alloy layer. The inner end of the low melting point alloy layer extends to the cell inside the battery and a modified polypropylene layer is provided between the cell and the cell. The outer end of the low melting point alloy layer extends to the opening of the gas sampling window and an outer film layer covering the composite film is provided. The low-pressure adjustable mass spectrometry detection module includes an air inlet mounting unit for fixing the battery, a pre-stage low-pressure chamber unit connected to the air inlet mounting unit, a high-vacuum chamber unit connected to the pre-stage low-pressure chamber unit, and a mass spectrometry detection unit connected to the high-vacuum chamber unit; the gas generated inside the battery enters the mass spectrometry detection unit via the pre-stage low-pressure chamber unit and the high-vacuum chamber unit for qualitative and quantitative analysis.

[0006] The aforementioned gas detection device for pouch batteries enables repeatable, non-destructive testing of the internal gases of pouch lithium batteries. Traditional testing methods typically require breaking the battery packaging to obtain internal gas samples, leading to battery failure and preventing subsequent testing. This device, by setting a controllable detection area on the battery packaging structure, along with a dedicated detection interface and window structure, allows gas sampling and analysis to be completed without destructive opening. After testing, the detection area can be resealed using a low-melting-point alloy, effectively restoring the battery's original sealing performance and functionality. This enables multiple in-situ tests and long-term state tracking of the battery at different cycles, providing an efficient and reliable technical means for studying the evolution of internal gases in lithium batteries and for online safety monitoring.

[0007] Furthermore, the composite film layer consists of a nylon layer, an aluminum film layer, and a polypropylene layer from the outside to the inside. The outer film layer covers the outside of the nylon layer, and the modified polypropylene layer is disposed inside the polypropylene layer and protrudes towards the battery cell. The modified polypropylene layer is thinner than the polypropylene layer.

[0008] Furthermore, the thickness of the modified polypropylene layer is 5–20 μm, and the outer film layer is a tearable plastic film.

[0009] Furthermore, the gas sampling window is a small hole formed on the composite membrane layer, and the radius of the small hole does not exceed 1 cm.

[0010] Furthermore, the melting point of the low-melting-point alloy layer is within the battery's extreme operating temperature range, not exceeding 60°C.

[0011] Furthermore, the air intake mounting unit includes an interface and a back plate that is sealed to the interface. The battery is clamped between the back plate and the interface and sealed by a gasket. The opening below the interface is connected to the pre-stage low-pressure chamber unit.

[0012] Furthermore, the pre-stage low-pressure chamber unit includes a pre-stage low-pressure chamber connected to the air inlet mounting unit. The pre-stage low-pressure chamber is equipped with a vacuum gauge to monitor the pressure inside the pre-stage low-pressure chamber. The pre-stage low-pressure chamber is equipped with a valve to open and close the connection between the pre-stage low-pressure chamber and the outside. The pre-stage low-pressure chamber maintains the air pressure at 0.5-0.01 bar through a pre-pump to collect the gas generated by the battery in a no-carrier gas manner. The pre-stage low-pressure chamber is equipped with at least two pre-pumps, one of which is in a normally open state, and the other starts and stops according to the pressure reading of the vacuum gauge.

[0013] Furthermore, the high vacuum chamber unit includes a high vacuum chamber, which is connected to the pre-stage low-pressure chamber unit via a carrier gas connection pipe, and the pressure inside the high vacuum chamber is maintained below 0.00005 bar by two high vacuum pumps; the high vacuum chamber is connected to the mass spectrometry detection unit via a detector connection pipe.

[0014] A method for inspecting a gas detection device for a soft-pack battery, the method comprising the following steps: Pre-processing is used to form a pouch cell with a gas sampling window; The low-melting-point alloy layer is melted during battery operation, opening the outer film layer; The encapsulated battery is fixed in the air intake mounting unit; The gas generated by the battery is collected through the differential pressure between the pre-stage low-pressure chamber unit and the high-vacuum chamber unit. The generated gas is introduced into the mass spectrometry detection unit for gas composition and content analysis; After completing the test, remove the battery, refill the low-melting-point alloy layer and cover the outer membrane layer, reseal the gas sampling window, and then place the battery in operation for a period of time before retesting.

[0015] Furthermore, the pretreatment includes: opening a small hole with a radius of 0.6 cm on the composite film layer of the battery, extending to the cell; setting a modified polypropylene layer at the inner end of the small hole; filling the small hole with a low melting point alloy layer up to the upper end face of the small hole; and covering the small hole with the outer film layer to obtain a soft-pack battery with a gas sampling window.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The gas detection device for soft-pack batteries, through the setting of the window film encapsulation module and the low-pressure adjustable mass spectrometry detection module, can realize repeatable and non-destructive detection of the gas inside the soft-pack lithium battery. The gas sampling and analysis can be completed without destructive opening during the detection process. After the detection is completed, the detection area can be resealed with a low-melting-point alloy, effectively restoring the original sealing performance and function of the battery; 2. The gas detection device for soft-pack batteries can also continuously monitor the changes in the gas inside the battery without affecting the structural integrity and electrochemical performance of the battery, thus ensuring the safety of lithium batteries. The system provides an efficient and reliable detection method for integrity assessment, life study, and failure mechanism analysis; 3. The window film encapsulation module can open a gas sampling window on the original soft-pack battery. By filling the gas sampling window with the low-melting-point alloy layer, the gas sampling window can be sealed under normal circumstances to maintain the integrity of the battery. When inspection is required, the low-melting-point alloy can be melted at a certain temperature to form a controllable gas sampling channel on the battery, realizing the non-destructive release of battery gas. This process does not affect the normal operation of the battery; 4. At both ends of the low-melting-point alloy layer are set The modified polypropylene layer and the outer film layer allow the low-melting-point alloy layer to be tightly and firmly bonded to the pores of the composite film layer at normal temperatures. The modified polypropylene layer prevents electrolyte leakage from the gas sampling window, while the outer film layer provides protection against contamination and damage. The outer film layer can be removed when testing is required and can also be reapplied later. 5. The window film encapsulation module can be reused multiple times. The sealed battery can still undergo normal charge-discharge cycles and gas sampling analysis without significant impact on its airtightness and electrochemical performance. This allows the same battery to be used in different cycles. Multiple in-situ detections and long-term status tracking within the battery provide a feasible means for studying the internal gas evolution process of lithium batteries and for online safety monitoring; 6. The gas inlet mounting unit can be used to fix the repackaged soft-pack battery, and the front-stage low-pressure chamber unit ensures that gas can spontaneously flow into the chamber from the gas sampling window opened by the battery through pressure control; the high-vacuum chamber unit is connected to the front-stage low-pressure chamber unit through a connecting pipe, and the gas is driven to spontaneously enter the high-vacuum chamber through the pressure difference; the mass spectrometry detection unit can be connected to the high-vacuum chamber unit through a pipeline to analyze the composition and content of the incoming gas. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the packaging process of a gas detection device for a soft-pack battery according to the present invention; Figure 2 This is a schematic diagram of the low-pressure adjustable mass spectrometry detection module of the present invention; Figure 3This is a schematic flowchart of the detection method of a gas detection device for a soft-pack battery according to the present invention; In the diagram: 1. Nylon layer; 2. Aluminum film layer; 3. Polypropylene layer; 4. Battery; 5. Battery cell; 6. Outer film layer; 7. Low melting point alloy layer; 8. Modified polypropylene layer; 9. Gas sampling window; 10. Backplate; 11. Interface (built-in sealing gasket); 12. Sealing connector; 13. Valve; 14. Foreboard pump; 15. Vacuum gauge; 16. Foreboard auxiliary pump; 17. First high vacuum pump; 18. Second high vacuum pump; 19. Foreboard low-pressure chamber; 20. High vacuum chamber; 21. Mass spectrometer detection unit. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be noted that the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] Example 1: A gas detection device for a soft-pack battery is provided, such as... Figure 1 and Figure 2 As shown, it includes a window film encapsulation module disposed on battery 4, and a low-pressure adjustable mass spectrometry detection module for battery gas detection. The window film encapsulation module includes a gas sampling window 9 formed on the composite film layer of the battery 4. The gas sampling window 9 is filled with a low melting point alloy layer 7. The inner end of the low melting point alloy layer 7 extends to the cell 5 inside the battery and a modified polypropylene layer 8 is provided between the cell 5 and the cell 5. The outer end of the low melting point alloy layer 7 extends to the opening of the gas sampling window 9 and an outer film layer 6 covering the composite film is provided. The low-pressure adjustable mass spectrometry detection module includes an air inlet mounting unit that fixes the battery 4, a pre-stage low-pressure chamber unit that is connected to the air inlet mounting unit, a high-vacuum chamber unit that is connected to the pre-stage low-pressure chamber unit, and a mass spectrometry detection unit that is connected to the high-vacuum chamber unit. The gas generated in the battery 4 enters the mass spectrometry detection unit through the pre-stage low-pressure chamber unit and the high-vacuum chamber unit for qualitative and quantitative analysis.

[0021] This pouch battery gas detection device, through the window film encapsulation module and the low-pressure adjustable mass spectrometry detection module, enables repeatable and non-destructive detection of gases inside pouch lithium batteries. The gas sampling and analysis can be completed without destructive opening during the detection process. After the detection is completed, the detection area can be resealed with a low-melting-point alloy, effectively restoring the battery's original sealing performance and functionality.

[0022] This soft-pack battery gas detection device can continuously monitor changes in the gas inside the battery without affecting the battery's structural integrity and electrochemical performance, providing an efficient and reliable detection method for lithium battery safety assessment, lifespan research, and failure mechanism analysis.

[0023] The window film encapsulation module can create a gas sampling window 9 on the original pouch battery. By filling the gas sampling window 9 with the low-melting-point alloy layer 7, the gas sampling window 9 can be sealed under normal circumstances to maintain the integrity of the battery. When inspection is required, the low-melting-point alloy can be melted at a certain temperature and poured out or sucked out to form a controllable gas sampling channel on the battery, realizing the non-destructive release of battery gas. This process does not affect the normal operation of the battery, so as to connect with the low-pressure adjustable mass spectrometry detection module to complete the qualitative and quantitative analysis of the gas.

[0024] The modified polypropylene layer 8 and the outer film layer 6 are provided at both ends of the low melting point alloy layer 7. On the one hand, this allows the low melting point alloy layer to be tightly and firmly bonded to the pores of the composite film layer. On the other hand, the modified polypropylene layer 8 can also prevent electrolyte leakage from the gas sampling window. The outer film layer 6 plays a protective role, preventing contamination and damage. The outer film layer 6 can be removed when testing is required, or it can be reapplied later.

[0025] This design allows the window film encapsulation module to be reused multiple times. Verification shows that the sealed battery can still undergo normal charge-discharge cycles and gas sampling analysis, and its airtightness and electrochemical performance are not significantly affected. This enables multiple in-situ tests and long-term status tracking of the same battery in different cycles, providing a feasible means for the study of the internal gas evolution process of lithium batteries and online safety monitoring.

[0026] The air inlet mounting unit can be used to fix the repackaged pouch battery. The pre-stage low-pressure chamber unit ensures that gas can spontaneously flow into the chamber from the gas sampling window opened by the battery through pressure control. The high-vacuum chamber unit is connected to the pre-stage low-pressure chamber unit through a connecting pipe, and the gas is driven to spontaneously enter the high-vacuum chamber through the pressure difference. The mass spectrometry detection unit (such as a mass spectrometer) is connected to the high-vacuum chamber unit through a pipeline to analyze the composition and content of the incoming gas.

[0027] Furthermore, the composite film layer consists of a nylon layer 1, an aluminum film layer 2, and a polypropylene layer 3 from the outside to the inside. The outer film layer 6 covers the outside of the nylon layer 1. The modified polypropylene layer 8 is disposed inside the polypropylene layer 3 and protrudes towards the battery cell. The modified polypropylene layer 8 is thinner than the polypropylene layer 3.

[0028] The nylon layer 1 is the outermost protective layer, providing mechanical strength, wear resistance, and scratch resistance, and resisting corrosion from the external environment. The middle layer is the aluminum film layer 2, which isolates moisture and air from the air, preventing electrolyte deterioration and leakage, and providing a certain rigidity for the battery, facilitating battery molding. The inner layer is the polypropylene layer 3, which can form a strong seal under heating and pressure, encapsulating the battery cell and resisting chemical corrosion from the internal electrolyte. Small holes are made on this composite film layer to form the gas sampling window 9. The modified polypropylene layer 8 protrudes slightly from the inner surface of the original aluminum film layer to enhance the adhesion and sealing with the battery cell.

[0029] Preferably, the modified polypropylene layer 8 has a thickness of 5 to 20 μm, which is relatively thin and does not negatively affect the original structure while meeting the encapsulation requirements; the outer film layer 6 is a tearable plastic film, which is easy to cover and remove.

[0030] Furthermore, the gas sampling window 9 is a small hole formed on the composite membrane layer, the radius of which does not exceed 1 cm, preferably around 0.6 cm. This small hole can meet the requirements for gas release.

[0031] Furthermore, the melting point of the low-melting-point alloy layer 7 is within the extreme operating temperature range of the battery, generally not exceeding 60°C, preferably 50-60°C. Its composition may include metallic bismuth (Bi), lead (Pb), tin (Sn), cadmium (Cd), etc., such as bismuth-based alloys, bismuth-tin alloys, etc. Under normal circumstances, it can remain solid and soften or melt with slight heating so that it can be removed.

[0032] After the battery under test has been working for a period of time, the outer film layer 6 on the surface of the gas sampling window 9 is removed, and the low melting point alloy layer 7 is melted by local heating at 50-60°C. Since the melting point of the low melting point alloy is within the extreme operating temperature range of the battery, the battery can still maintain normal operation at this time.

[0033] The thickness of the low-melting-point alloy layer 7 is comparable to that of the composite film layer, which can effectively seal the gas sampling window and also ensure a tight connection with the aluminum film layer.

[0034] Furthermore, the air intake mounting unit includes an interface 11 and a back plate 10 that is sealed to the interface 11. The battery 4 is clamped between the back plate 10 and the interface 11 and sealed by a sealing gasket. The opening below the interface 11 is connected to the pre-stage low-pressure chamber unit.

[0035] The backplate 10 can be connected and fixed to the interface 11 by multiple sealing screws. The interface 11 and the backplate 10 can be connected to form a housing structure that accommodates and clamps the battery 4. The backplate 10 can provide a certain rigid support to prevent battery deformation and ensure that the battery is subjected to uniform force and has a stable shape. The sealing gasket can ensure the airtightness of the mating surface between the battery and the interface. After the battery 4 is installed, its gas sampling window 9 faces downward. The lower part of the interface 11 is connected to the pre-stage low-pressure chamber. After the low melting point alloy layer 7 in the window area melts, it is exposed to the inner modified polypropylene layer 8. The small height difference between it and the composite film layer forms a gas channel, allowing the gas inside the battery to flow out spontaneously and enter the pre-stage low-pressure chamber below.

[0036] Furthermore, the pre-stage low-pressure chamber unit includes a pre-stage low-pressure chamber 19 connected to the air inlet mounting unit. The pre-stage low-pressure chamber 19 is equipped with a vacuum gauge 15 for monitoring the pressure inside the pre-stage low-pressure chamber 19. The pre-stage low-pressure chamber 19 is equipped with a valve 13 for opening and closing the communication between the pre-stage low-pressure chamber 19 and the outside. The pre-stage low-pressure chamber 19 maintains the air pressure at 0.5-0.01 bar through a pre-pump to collect the gas generated by the battery in a no-carrier gas manner. The pre-stage low-pressure chamber 19 is equipped with at least two pre-pumps, one of which is in a normally open state, and the other starts and stops according to the pressure reading of the vacuum gauge.

[0037] The air intake mounting unit is tightly connected to the pre-stage low-pressure chamber via the interface. The pre-stage low-pressure chamber includes two pre-stage pumps, namely pre-stage pump 14 and pre-stage auxiliary pump 16; pre-stage pump 14 is always on, while the pre-stage auxiliary pump 16 is activated or deactivated depending on the specific gas production situation of the battery.

[0038] Optionally, a vacuum gauge 15 is provided in the pre-stage low-pressure chamber 19 to monitor the pressure in the pre-stage low-pressure chamber. The pressure in the pre-stage low-pressure chamber 19 should be maintained at 0.5-0.01 bar to prevent excessively low pressure from causing battery swelling or abnormal performance. It also ensures that the pressure in the pre-stage chamber is slightly lower than atmospheric pressure, causing gas inside the battery to spontaneously flow into the pre-stage chamber. When the reading of the vacuum gauge 15 indicates that the gas pressure is slightly high, the pre-stage auxiliary pump 16 is turned on; when the reading of the vacuum gauge 15 indicates that the gas pressure is low, the pre-stage auxiliary pump 16 is turned off.

[0039] Furthermore, the high vacuum chamber unit includes a high vacuum chamber 20, which is connected to the pre-stage low-pressure chamber unit via a carrier gas connection pipe and is maintained at a pressure below 0.00005 bar by two high vacuum pumps; the high vacuum chamber 20 is connected to the mass spectrometry detection unit 21 via a detector connection pipe.

[0040] Both vacuum pumps (first high vacuum pump 17 and second high vacuum pump 18) are in a normally-on state, ensuring that the pressure in the high vacuum chamber 20 is maintained below 0.00005 bar. The pressure difference between the pre-stage low-pressure chamber 19 and the high vacuum chamber 20 causes the gas collected in the pre-stage low-pressure chamber 19 to spontaneously flow into the low-pressure chamber. After reaching a lower pressure, the gas flows into the mass spectrometry detection unit 21 through the detector connecting tube, realizing the qualitative and quantitative analysis of the gas produced by the battery.

[0041] Example 2: A method for inspecting a gas detection device for a soft-pack battery.

[0042] Taking the measurement of gas generation during the formation process of the battery under test 4 as an example, the detection steps of the in-situ gas detection device provided by the invention are explained, combined with Figures 1-3 As shown, the inspection method includes the following steps: (1) Pre-processing to form a pouch cell with a gas sampling window; Specifically, a small hole with a radius of 0.6 cm is made in the composite film layer of the battery, extending to the cell. A modified polypropylene layer 8 is placed inside the small hole, and a low melting point alloy layer 7 is filled into the small hole up to the upper surface of the small hole. The outer film layer 6 is then covered outside the small hole to obtain a soft-pack battery with a gas sampling window.

[0043] (2) When the battery is working, the low melting point alloy layer 7 is melted to open the outer film layer 6; Specifically, after the battery under test has been working for a period of time, the outer film layer 6 on the surface of the gas sampling window is removed, and the low melting point alloy layer 7 is melted by local heating at 50-60°C. Since the melting point of the low melting point alloy is within the extreme operating temperature range of the battery, the battery can still maintain normal operation at this time.

[0044] (3) Fix the packaged battery into the air inlet mounting unit; Specifically, the prepared battery under test is placed downwards between the back plate 10 and the interface 11, and the back plate 10 and the interface 11 are fixed with the sealing connector 12 to stably hold the battery, so that the gas sampling window 9 is exposed in the front low-pressure area.

[0045] (4) Collect the generated gas from the battery through the differential pressure between the pre-stage low-pressure chamber unit and the high-vacuum chamber unit; (5) The generated gas is introduced into the mass spectrometry detection unit for gas composition and content analysis; Specifically, the valve 13 is opened, and the switching status of the front auxiliary pump 16 is adjusted according to the reading of the vacuum gauge 15 in the front low-pressure chamber; under the action of pressure, the gas spontaneously flows from the battery to the front low-pressure chamber 19, the high vacuum chamber 20, and finally reaches the mass spectrometry detection unit 21.

[0046] (6) After the test is completed, close the valve 13 in the front low-pressure chamber, loosen the sealing connector 12 between the back plate and the interface, remove the battery, refill the low melting point alloy layer 7 and cover the outer membrane layer 6, and reseal the gas sampling window 9. The battery can continue to work normally. When there is a test requirement, the outer membrane layer of the gas sampling window area can be reopened, the low melting point alloy layer can be melted, and the above steps can be repeated to detect the internal gas.

[0047] In actual testing, continuous sampling of lithium battery gases at different discharge stages can be achieved through repeated sealing and measurement over a long period, with the battery operating continuously for at least one month. After mass spectrometry analysis, the obtained gases can identify major gaseous components such as H2, O2, CO, CO2, and C2H4, thereby monitoring the electrolyte decomposition and side reaction processes within the battery and enabling early warning of the battery's safety status.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gas detection device for a soft-pack battery, characterized in that, This includes a window film encapsulation module mounted on the battery, and a low-pressure adjustable mass spectrometry detection module for battery gas detection. The window film encapsulation module includes a gas sampling window formed on the composite film layer of the battery. The gas sampling window is filled with a low melting point alloy layer. The inner end of the low melting point alloy layer extends to the cell inside the battery and a modified polypropylene layer is provided between the cell and the cell. The outer end of the low melting point alloy layer extends to the opening of the gas sampling window and an outer film layer covering the composite film is provided. The low-pressure adjustable mass spectrometry detection module includes an air inlet mounting unit for fixing the battery, a pre-stage low-pressure chamber unit connected to the air inlet mounting unit, a high-vacuum chamber unit connected to the pre-stage low-pressure chamber unit, and a mass spectrometry detection unit connected to the high-vacuum chamber unit; the gas generated inside the battery enters the mass spectrometry detection unit via the pre-stage low-pressure chamber unit and the high-vacuum chamber unit for qualitative and quantitative analysis.

2. The gas detection device for soft-pack batteries according to claim 1, characterized in that, The composite film consists of a nylon layer, an aluminum film layer, and a polypropylene layer from the outside to the inside. The outer film layer covers the outside of the nylon layer, and the modified polypropylene layer is disposed inside the polypropylene layer and protrudes towards the battery cell. The modified polypropylene layer is thinner than the polypropylene layer.

3. The gas detection device for soft-pack batteries according to claim 1, characterized in that, The thickness of the modified polypropylene layer is 5–20 μm, and the outer film layer is a tearable plastic film.

4. The gas detection device for soft-pack batteries according to claim 1, characterized in that, The gas sampling window is a small hole formed on the composite membrane layer, and the radius of the small hole does not exceed 1 cm.

5. The gas detection device for soft-pack batteries according to claim 1, characterized in that, The melting point of the low-melting-point alloy layer is within the battery's extreme operating temperature range, not exceeding 60°C.

6. The gas detection device for soft-pack batteries according to claim 1, characterized in that, The air intake mounting unit includes an interface and a back plate that is sealed to the interface. The battery is clamped between the back plate and the interface and sealed by a gasket. The opening below the interface is connected to the pre-stage low-pressure chamber unit.

7. The gas detection device for a soft-pack battery according to claim 1, characterized in that, The pre-stage low-pressure chamber unit includes a pre-stage low-pressure chamber connected to the air inlet mounting unit. A vacuum gauge is installed inside the pre-stage low-pressure chamber to monitor the pressure within it. A valve is installed on the pre-stage low-pressure chamber to open and close the connection between the pre-stage low-pressure chamber and the outside environment. The pre-stage low-pressure chamber maintains a pressure of 0.5-0.01 bar via a pre-stage pump to collect the gas generated by the battery in a no-carrier gas manner. The pre-stage low-pressure chamber is equipped with at least two pre-stage pumps, one of which is in a normally open state, and the other starts and stops according to the pressure reading of the vacuum gauge.

8. The gas detection device for a soft-pack battery according to claim 1, characterized in that, The high vacuum chamber unit includes a high vacuum chamber, which is connected to the preceding low-pressure chamber unit via a carrier gas connection pipe, and the pressure inside the high vacuum chamber is maintained below 0.00005 bar by two high vacuum pumps. The high vacuum chamber is connected to the mass spectrometry detection unit via a detector connecting tube.

9. The inspection method of the gas detection device for pouch batteries according to any one of claims 1-8, characterized in that, The inspection method includes the following steps: Pre-processing is used to form a pouch cell with a gas sampling window; The low-melting-point alloy layer is melted during battery operation, opening the outer film layer; The encapsulated battery is fixed in the air intake mounting unit; The gas generated by the battery is collected through the differential pressure between the pre-stage low-pressure chamber unit and the high-vacuum chamber unit. The generated gas is introduced into the mass spectrometry detection unit for gas composition and content analysis; After completing the test, remove the battery, refill the low-melting-point alloy layer and cover the outer membrane layer, reseal the gas sampling window, and then place the battery in operation for a period of time before retesting.

10. The inspection method of the gas detection device for soft-pack batteries according to claim 9, characterized in that, The pretreatment includes: making a small hole with a radius of 0.6 cm on the composite film layer of the battery, extending to the cell; setting a modified polypropylene layer at the inner end of the small hole; filling the small hole with a low melting point alloy layer up to the upper end of the small hole; and covering the small hole with the outer film layer to obtain a soft-pack battery with a gas sampling window.

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