Device for collecting and measuring in-situ produced gas in exhaust process of square battery

Abstract

The utility model belongs to the technical field of lithium ion batteries, and particularly relates to a square battery exhaust process in-situ produced gas collecting and measuring device which comprises a buffer bottle, a charging and discharging tester, a vacuum pump and a gas collecting bottle. One end of the vacuum pump is connected with the buffer bottle, the other end of the vacuum pump is connected with the gas collection bottle, the gas collection bottle is provided with a temperature collector and a pressure gauge, and the charging and discharging tester is connected with the positive electrode and the negative electrode of a battery to be tested. The device is high in reliability, convenient to operate and low in cost, gas volume in-situ monitoring in the exhaust process of the square battery can be achieved, and meanwhile gas collection can be completed for component testing. The device solves the current situation of lack of research means in the exhaust process of the square battery, and can help engineers to improve the battery system and optimize the technological process.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium-ion batteries, and particularly relates to an in-situ gas production collection and measurement device during the exhaust process of a square battery. Background Art

[0002] With the continuous development of the new energy industry, lithium-ion battery technology is also undergoing continuous innovation. Research on battery systems and processes is crucial for improving energy density. Changes to battery systems and processes can also affect internal chemical reactions, leading to changes in the battery's SEI components. Battery research is still developing, and people still have higher expectations for improving the performance of lithium-ion batteries. Therefore, new methods are needed to study battery development and production processes.

[0003] The structure of a lithium-ion battery consists of four parts: the positive electrode, the negative electrode, the separator, and the electrolyte. The production of batteries includes processes such as homogenization, coating, rolling, shearing, winding, assembly, injection, exhaust, and formation. During the exhaust process, the electrolyte components will undergo a series of chemical reactions on the surface of the negative electrode, thereby forming a dense SEI film to protect the negative electrode, avoid the embedding of solvent macromolecules, and ensure the stability of the negative electrode material structure. During the exhaust process, a large amount of gas will be produced. Each gas can indicate that a certain side reaction has occurred on the surface of the negative electrode. At the same time, different gases also come from different electrolyte components. Therefore, the analysis of gas production during the exhaust formation process plays an important role in improving the battery system and process. By analyzing the gas composition and volume, the system formula and the exhaust process can be optimized, thereby producing an SEI film with a more stable mechanical structure, thereby improving battery performance.

[0004] The battery exhaust process is carried out using specialized exhaust equipment. The process involves placing the battery after liquid injection into the equipment fixture. The battery is then charged with a low current, and the gas generated inside the battery is discharged by negative pressure through the pipe connecting the equipment to the battery injection hole. A large amount of gas is generated during the exhaust process, and the gas volume can range from tens of milliliters to hundreds of liters due to different battery energy densities. Currently, there is little research on gas production during the exhaust process, mainly because the gas generated by the exhaust is directly discharged by the equipment to the gas treatment device for treatment, and then discharged into the atmosphere. During this process, the gas from the exhaust process cannot be collected. Currently, there is no systematic study of methods for in-situ gas production during the venting process of prismatic batteries. Some patents have proposed methods for analyzing in-situ gas production in batteries, but these methods have the following shortcomings: First, they cannot test prismatic batteries and lack adaptability. Prismatic batteries have high energy density and produce more gas, and most existing testing methods are designed for small-capacity batteries. Second, they cannot fully simulate the in-situ gas production of prismatic batteries and lack reliability. The electrochemical reaction during the venting process of prismatic batteries will cause a large amount of gas to be generated. A negative pressure environment is conducive to the discharge of gas generated by the electrochemical reaction and ensures full contact between the positive and negative electrodes and the diaphragm interface. Existing testing methods cannot achieve real-time gas discharge during the electrochemical reaction and real-time measurement of the gas volume during the venting process, which will lead to doubts about the reliability of the results. For example, a Chinese patent discloses a method and device for in-situ detection of gas production in soft-pack batteries. Publication number: CN115902648A. This patent is mainly used in the field of soft-pack batteries. The soft-pack battery is encapsulated in a sealed mold, the battery is charged and discharged, and the generated gas is transferred to a differential electrochemical mass spectrometer through a carrier gas to achieve gas composition testing. This method can realize gas volume testing of soft-pack batteries, but it is not suitable for square batteries and requires the use of a mass spectrometer, which is relatively expensive.

[0005] For example, a Chinese patent, publication number CN215065939U, discloses a battery gas production measurement device. This patent uses a water displacement method to measure battery volume expansion during charge and discharge, thereby measuring gas production and enabling in-situ gas production testing. However, for rigid-shell batteries like prismatic cells, volume expansion occurs only after gas production reaches a certain pressure, making this method unreliable. Utility Model Content

[0006] The purpose of the utility model is to provide an in-situ gas production collection and measurement device for a square battery exhaust process, so as to solve the problems existing in the prior art.

[0007] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: an in-situ gas production collection and measurement device for the exhaust process of a square battery, comprising a buffer bottle, a charge and discharge tester, a vacuum pump and a gas collecting bottle, one end of the buffer bottle being sealedly connected to the liquid injection hole of the battery to be tested through an air guide tube, one end of the vacuum pump being connected to the buffer bottle, and the other end of the vacuum pump being connected to the gas collecting bottle, a temperature collector and a pressure gauge being installed on the gas collecting bottle, and the charge and discharge tester being connected to the positive and negative poles of the battery to be tested.

[0008] Preferably, a first one-way valve is installed on the pipeline between the vacuum pump and the buffer bottle.

[0009] Preferably, a second one-way valve is installed on the pipeline between the vacuum pump and the gas collecting bottle.

[0010] Preferably, a first valve is installed on the pipeline between the vacuum pump and the gas collecting bottle.

[0011] Preferably, the gas collecting bottle is connected to an exhaust pipeline, and a second valve is installed on the exhaust pipeline.

[0012] Preferably, the liquid injection hole of the battery to be tested is connected to a conical flask, and the air guide tube is sealedly connected to the upper end of the conical flask.

[0013] Preferably, the air guide tube extends deep into the bottom of the buffer bottle.

[0014] Preferably, an air bag is connected to the end of the exhaust pipe.

[0015] Preferably, the flow rate of the vacuum pump is 0.05-4 L / min, and the positive exhaust pressure is 0.1-0.5 MPa.

[0016] Preferably, the gas collecting bottle is a thermally insulated bottle.

[0017] The beneficial effects of this utility model are as follows: this device, assembled from a few simple components, enables in-situ gas collection during the prismatic battery degassing process. Highly reliable, easy to operate, and low-cost, it enables in-situ monitoring of gas volume during the degassing process of prismatic batteries, while also collecting the gas for composition testing. This device addresses the current lack of research methods for the degassing process of prismatic batteries and can help engineers improve battery systems and optimize process flows. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a structural diagram of this embodiment;

[0019] Figure 2 This is a flow chart of this embodiment;

[0020] Figure 3This is a graph showing the pressure change trend over time in the gas collecting bottle during the exhaust process of the battery in this embodiment;

[0021] Figure 4 This is a graph showing the change trend of the gas volume in the gas collecting bottle over time calculated by the formula in this embodiment;

[0022] Explanation of the accompanying symbols: 1. Buffer bottle; 2. Charge and discharge tester; 3. Vacuum pump; 4. Gas collecting bottle; 5. Gas guide tube; 6. Battery to be tested; 7. Liquid injection hole; 8. Temperature collector; 9. Pressure gauge; 10. First one-way valve; 11. Second one-way valve; 12. First valve; 13. Exhaust pipe; 14. Second valve; 15. Conical flask. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0025] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixedly connected," and "fixed connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0026] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0027] like Figure 1 and Figure 2Figure 1 shows an in-situ gas collection and measurement device for a prismatic battery during degassing, comprising a buffer bottle 1, a charge-discharge tester 2, a vacuum pump 3, and a gas collection bottle 4. One end of the buffer bottle is sealed to a liquid injection hole 7 of a battery under test 6 via an air guide tube 5. The buffer bottle prevents trace amounts of electrolyte from entering the vacuum pump or gas collection bottle, potentially causing structural corrosion and extending the tooling's service life.

[0028] Furthermore, a conical flask 15 is connected to the injection hole of the battery to be tested, the air guide tube is sealed and connected to the upper end of the conical flask, and one end of the vacuum pump is connected to the buffer bottle. This embodiment uses a vacuum pump to give a negative pressure environment to the internal space of the battery, and the gas generated in the electrochemical reaction can be extracted to realize the exhaust process. At the same time, a simple conical flask structure is adopted, and a reflux operation is performed through the conical flask. After the gas discharge is completed, the electrolyte will flow back to the inside of the battery, realizing the reflux of the electrolyte during the exhaust process, avoiding the electrolyte from entering the gas collection pipeline and causing electrolyte loss, and is consistent with the negative pressure environment inside the battery during the exhaust process of the battery in production, and has high reliability.

[0029] In order to collect gas, the other end of the vacuum pump is connected to the gas collecting bottle, which is equipped with a temperature collector 8 and a pressure gauge 9. In this embodiment, the gas collecting bottle can be replaced. Gas collecting bottles of different volumes can be replaced according to the battery capacity. It can be adapted to the exhaust collection of large batteries. A pressure gauge and a temperature collector are installed therein. The gas volume is measured by monitoring the pressure and temperature in the gas collecting bottle. At the same time, the gas collecting bottle adopts a heat-insulating bottle, which needs to be kept warm and does not exchange heat with the external environment. Gas collecting bottles of different volumes are used according to the battery capacity and electrochemical system. The gas collecting bottle can be flexibly replaced. The gas collecting bottle requires a certain pressure-resistant design and is made of metal, preferably stainless steel 316.

[0030] The charge and discharge tester is connected to the positive and negative electrodes of the battery to be tested, and charging is performed according to the standard battery exhaust process.

[0031] In this embodiment, a first one-way valve 10 is installed on the pipeline between the vacuum pump and the buffer bottle, a second one-way valve 11 is installed on the pipeline between the vacuum pump and the gas collecting bottle, a first valve 12 is installed on the pipeline between the vacuum pump and the gas collecting bottle, an exhaust pipeline 13 is connected to the gas collecting bottle, and a second valve 14 is installed on the exhaust pipeline. The use of the one-way valve and the valve in combination can prevent gas backflow and cause deviation in the results.

[0032] In this embodiment, the flow rate of the vacuum pump is adjustable and is used to extract the gas from the battery. The interior of the battery is at negative pressure during this process. The flow rate of the vacuum pump is preferably 0.05-4 L / min, and the positive exhaust pressure of the vacuum pump is adjustable. The positive exhaust pressure is preferably 0.1-0.5 MPa.

[0033] The testing method of this embodiment is as follows:

[0034] Connect the air duct to the battery: connect the air duct input end to the liquid injection hole of the battery after injection, and ensure that the connection position is in close contact without leakage to ensure air tightness;

[0035] Discharge of internal air: Open the first valve 12 and the second valve 14, turn on the vacuum pump, and discharge the air in the conical flask 15, the air guide tube 5 and the buffer bottle 1 into the gas collecting bottle 4. The vacuum pump is equipped with an external pressure gauge. When the reading of the vacuum pump pressure gauge reaches the vacuum degree required by the process, close the first valve 12, then turn off the vacuum pump. When the pressure display in the gas collecting bottle is consistent with the atmospheric pressure, close the second valve 14 and record the value P1 of the pressure gauge and the value T1 of the temperature collector at this time.

[0036] Charging: Connect the positive and negative poles of the battery to the charge and discharge tester, and charge according to the standard battery exhaust process to ensure that it is the same as the battery process.

[0037] Exhaust: Turn on the vacuum pump, then open the first valve 12, and continuously extract the gas generated by charging and send it to the gas collecting bottle. During the process, record the value P2 of the pressure gauge and the value T2 of the temperature collector at any time. Adjust the parameters of the vacuum pump according to the vacuum degree set in the battery exhaust process to ensure that they are consistent with the battery exhaust process parameters. After the exhaust process is completed, close the first valve 12 first, and then turn off the vacuum pump.

[0038] Calculation of gas production volume: According to the ideal gas state equation, PV=nRT, where V is the volume inside the gas collecting bottle, which is a constant. Calculation of gas production volume: ΔV= [P2*T1 / (P1*T2)-1]*V.

[0039] Collecting gas: Put the air bag into the tail end of the second valve 14 to ensure good air tightness, open the second valve 14, and after the air bag is inflated, wrap the air bag and remove it to complete the gas collection.

[0040] The following is an example of using this device to detect in-situ gas production during the exhaust process of a square battery:

[0041] The battery model used is lithium iron phosphate square battery, the battery size is 71mm*173*mm*207mm, and the capacity is 280Ah. After the battery is filled with liquid, it is connected to the test fixture of this patent. According to the test process proposed in this patent, the in-situ gas monitoring of the exhaust process is carried out. The results are as follows Figure 3 and Figure 4As shown in the figure, the atmospheric pressure is 101 kPa, and the gas collection bottle has a capacity of 1 L. The pressure change curve is plotted based on the pressure gauge value, and the gas production volume is calculated using the gas production volume calculation formula, resulting in a gas production curve. The curve shows that the gas production rate is fastest in the first stage of the battery exhaust process, and the gas production rate decreases in the next two stages, with the final gas production volume for the entire process being 225 mL. This data can help R&D engineers adjust exhaust processes and product systems.

[0042] It should be pointed out that a number of improvements and modifications may be made without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An in-situ gas collection and measurement device for the exhaust process of a square battery, characterized by: It includes a buffer bottle, a charge and discharge tester, a vacuum pump and a gas collecting bottle. One end of the buffer bottle is sealed with the liquid injection hole of the battery to be tested through an air guide tube, one end of the vacuum pump is connected to the buffer bottle, and the other end of the vacuum pump is connected to the gas collecting bottle. A temperature collector and a pressure gauge are installed on the gas collecting bottle. The charge and discharge tester is connected to the positive and negative poles of the battery to be tested.

2. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1, characterized in that: A first one-way valve is installed on the pipeline between the vacuum pump and the buffer bottle.

3. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1, characterized in that: A second one-way valve is installed on the pipeline between the vacuum pump and the gas collecting bottle.

4. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1, characterized in that: A first valve is installed on the pipeline between the vacuum pump and the gas collecting bottle.

5. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1 is characterized in that: The gas collecting bottle is connected to an exhaust pipeline, and a second valve is installed on the exhaust pipeline.

6. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1, characterized in that: The liquid injection hole of the battery to be tested is connected to a conical flask, and the air guide tube is sealed and connected to the upper end of the conical flask.

7. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1, characterized in that: The air guide tube extends deep into the bottom of the buffer bottle.

8. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 5, characterized in that: The end of the exhaust pipe is connected to an air bag.

9. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1, characterized in that: The flow rate of the vacuum pump is 0.05-4 L / min, and the positive pressure exhaust pressure is 0.1-0.5 MPa.

10. The in-situ gas collection and measurement device for the exhaust process of a prismatic battery according to claim 1, characterized in that: The gas collecting bottle is a heat-insulating bottle.

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