Soft pack battery exhaust device and gas measuring device

Abstract

The utility model belongs to the field of battery testing, and specifically relates to a soft-pack battery exhaust device and a gas measuring device, including an exhaust needle, an air duct connected to the exhaust needle, and an exhaust device and an exhaust bag sequentially arranged on the air duct; a first valve is arranged between the needle and the exhaust device; a second valve is arranged on the air duct between the exhaust device and the air bag. The device is simple in equipment, convenient to connect and operate, easy to assemble, and low in cost. It overcomes the disadvantages of gas impurity pollution, and the test results of gas production components are accurate. Gas production can be observed in real time on-site, which is helpful for gas production mechanism analysis. The device can also be reused, has no requirements for the battery power state and gas production state, and is safe and reliable.

Description

Technical Field

[0001] The utility model belongs to the field of battery testing, and in particular relates to a soft-pack battery exhaust device and a gas measuring device. Background Art

[0002] With the development of society, people's demand for energy is increasing, and the requirements are getting higher and higher. Traditional energy can no longer meet people's requirements. In today's information explosion society, the key components of mobile electronic products, entertainment, computers and communication equipment are lithium-ion secondary batteries. Compared with metal lithium secondary batteries, the safety of lithium-ion batteries has been greatly improved, but there are still many hidden dangers. The safety of lithium-ion batteries has always been a hot topic. An important factor affecting safety is the generation of gas, especially the large amount of gas generated at high temperature will directly lead to battery explosion.

[0003] Among them, soft-pack lithium-ion batteries have the advantages of small size, light weight, high specific energy, and flexible design compared to metal-cased lithium-ion batteries. However, during the use of the battery, the bloating of the soft-pack battery will have a negative impact on the performance and pose a safety risk.

[0004] Lithium-ion soft-pack batteries may produce gas during formation, circulation, and storage, such as the formation of SEI (Solid Electrolyte Interface) film, decomposition of SEI film, high water content in the battery, lithium precipitation, internal short circuit, overcharge and over-discharge, etc. Gas comes from the complex reaction of various components in contact. Although it is difficult to accurately analyze the gas evolution mechanism, the gas production and gas composition of soft-pack batteries can be analyzed.

[0005] During the first charge and discharge process of the battery, a SEI film will form on the electrode surface. The formation of the negative electrode SEI film mainly comes from the reduction and decomposition of the solvent in the electrolyte. A large amount of gas will be generated during the decomposition of the electrolyte, which is an inevitable process. The presence of water in the impurities will cause the lithium salt to decompose and generate HF, which will cause the instability of the battery system and affect the battery's electrical performance and safety. Therefore, it is crucial to pay attention to the gas composition and gas production of the battery for battery safety analysis.

[0006] During the test of soft-pack battery gas, since the aluminum-plastic shell of the soft-pack battery does not have shrinkage, air may mix in from the pinhole during the process of taking gas directly with a needle tube, resulting in inaccurate measurement results; and the sealing is not good, the gas in the soft-pack battery cannot be evacuated, and the gas volume cannot be accurately measured. Using some gas measurement devices for testing is more complicated, has high requirements for tooling, and is not convenient to operate.

[0007] CN208270003U provides a device for measuring the gas production of lithium-ion soft-pack batteries, including a liquid tank, an overflow collection container and a suspension device. By measuring the difference in the volume of liquid overflowing from the liquid tank before and after formation, the gas production generated by the soft-pack battery to be tested in the formation process is measured. However, this scheme measures the gas production of the soft-pack battery under the pressure of the external medium liquid, and the pole piece will expand and contract during charging and discharging, so the drainage method will cause inaccurate measurement results, and the gas composition cannot be directly measured while measuring the gas volume.

[0008] CN101846597A samples the gas produced by nickel-hydrogen batteries, and includes a sampling needle and a gas collecting cylinder. The sampling needle is installed on the sampling port. The residual gas inside the gas sampler itself is not emptied thoroughly, and impurities are easily mixed in to affect the analysis results. The production is inconvenient. Due to the corrosiveness of the electrolyte, the device is not suitable for reuse after testing.

[0009] CN218035225U proposes a device for detecting gas production of soft-pack batteries, which is composed of a detection bottle, a gas collection tube, a vacuum bottle, and a pressure sensor. The device is complex and costly. In the device, the gas collection tube is inserted into the air bag reserved in the battery to collect and test the gas, but the air bag of the battery is generally made of aluminum plastic without shrinkage, and it cannot be guaranteed that the gas collection tube will not leak when inserted into the battery and will not introduce other gas impurities. Therefore, the patent does not solve the problem of airtightness. Utility Model Content

[0010] The purpose of the utility model is to overcome the defects in the prior art and provide a soft-pack battery exhaust device and a gas measuring device.

[0011] In order to achieve the above-mentioned purpose, the utility model adopts the following technical solutions:

[0012] A gas extraction device for a soft-pack battery, comprising a gas extraction needle, an air guide tube connected to the gas extraction needle, and a gas extraction device and a gas extraction bag sequentially arranged on the air guide tube;

[0013] A first valve is arranged between the needle and the air extraction device; a second valve is arranged on the air guide tube between the air extraction device and the air extraction bag.

[0014] The air extraction device is a piston cylinder; the piston cylinder comprises an outer cylinder, a piston arranged in the outer cylinder and a moving rod connected to the piston.

[0015] The outer cylinder is provided with scales. The moving rod is provided with a handle.

[0016] The volume of the outer cylinder is 1-20mL.

[0017] The air extraction needle penetrates into the soft-pack battery; and a sealant is provided at the contact point between the air extraction needle and the soft-pack battery.

[0018] The connection between the air guide tube, the air extraction device and the air extraction needle is provided with vaseline.

[0019] The air extraction bag is provided with a switch valve.

[0020] The air guide tube between the air extraction needle and the air extraction device is provided with a connecting needle head which is in communication with the air guide tube.

[0021] A third valve is arranged between the connecting needle and the gas extraction needle.

[0022] The utility model also includes a gas measuring device, comprising the soft-pack battery exhaust device and a gas measuring device connected to the connecting needle; the gas measuring device is a gas chromatograph.

[0023] Compared with the prior art, the beneficial effects of the utility model are:

[0024] The present application provides a soft-pack battery exhaust device and a gas measurement device, which are of great significance for improving the battery formation process, and enhancing the battery cycle performance and safety performance. The device is simple in equipment, convenient to connect and operate, easy to assemble, and low in cost. It overcomes the disadvantages of gas impurity pollution, and the test results of gas production components are accurate. The gas production can be observed in real time in situ, which is helpful for the analysis of the gas production mechanism. The device can also be reused, has no requirements for the battery power state and gas production state, and is safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The overall structural diagram of the soft-pack battery exhaust device when an air bag is left for the soft-pack battery of the utility model;

[0026] Figure 2 It is a schematic diagram of the overall structure of the soft-pack battery exhaust device when the soft-pack battery of the utility model has no air bag. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the best embodiment.

[0028] Figure 1-2 A gas extraction device for a soft-pack battery is shown, comprising a gas extraction needle 3, a gas guide tube 4 connected to the gas extraction needle, and a gas extraction device 6 and a gas extraction bag 7 sequentially arranged on the gas guide tube;

[0029] A first valve 5 is provided between the air extraction needle 3 and the air extraction device 6 ; a second valve 10 is provided on the air guide tube between the air extraction device 6 and the air extraction bag 7 .

[0030] The exhaust device 6 is a piston cylinder; the piston cylinder includes an outer cylinder, a piston disposed in the outer cylinder, and a moving rod connected to the piston, and the moving rod is provided with a handle. The outer cylinder is provided with a scale, and can be a syringe; according to the displacement of the gas of the soft-pack battery, the volume of the syringe can be 1-20mL, specifically 1mL, 5mL, 15mL, 20mL, etc.

[0031] The gas extraction needle 3 penetrates the soft-pack battery; the contact point between the gas extraction needle 3 and the soft-pack battery 1 is provided with a sealant 2, which is a high-temperature resistant silicone sealant in this application (a high-temperature working condition sealing adhesive made of organic silicone as the main body, defoaming agent, leveling agent, curing agent and other polymer materials). The sealant has the advantages of soft texture, good flexibility and good shrinkage, and can fit well with the aluminum-plastic shell of the soft-pack battery to make it more airtight. When extracting gas, the gas extraction needle penetrates the sealant and penetrates into the aluminum-plastic shell. By utilizing the advantages of silicone itself, it can shrink instantly, thus avoiding the disadvantages of leakage and mixing of gas impurities.

[0032] The connection between the air guide tube 4, the air extraction device 6 and the air extraction needle 3 is provided with vaseline. The air extraction bag 7 is provided with a switch valve 11.

[0033] A connecting needle 8 connected to the air duct is provided on the air duct 4 between the air extraction needle 3 and the air extraction device 6. A third valve 9 is provided between the connecting needle 8 and the air extraction needle 3. The present application also includes a gas measuring device, including the soft-pack battery air extraction device and a gas measuring device connected to the connecting needle; the gas measuring device is a gas chromatograph.

[0034] The implementation process of the utility model specifically includes the following steps:

[0035] 1) When the soft pack battery 1 has an air pocket, use the method as follows Figure 1 First, apply sealant 2 to the air bag of the soft-pack battery, and apply vaseline to the interface between the air guide tube 4, the air extraction device 6, and the air extraction needle 3 to ensure sealing.

[0036] 2) Empty the gas in the air bag and verify the air tightness; close the first valve 5 and the third valve 9, open the second valve 10, and use the vacuum device 6 to empty the gas in the air bag 7. When the piston in the vacuum device rebounds, it is considered that the gas in the air bag is emptied, in a negative pressure state, and the air tightness is good. After the gas in the air bag is emptied, close the second valve 10. At this moment, the first valve 5, the third valve 9 and the second valve 10 are all in a closed state.

[0037] 3) Gas measurement. Insert the gas extraction needle 3 into the aluminum plastic of the soft-pack battery through the sealant 2, open only the first valve 5, and use the vacuum device 6 to extract the gas. When measuring the volume, read the volume according to the scale of the outer cylinder. If the amount of gas is large and the gas cannot be evacuated at one time, close the first valve 5, open the second valve 10, inject the gas in the vacuum device 6 into the gas extraction bag 7 through the switch valve 11 of the gas extraction bag, and then close the second valve 10, repeat the above operation, record the outer cylinder reading, and calculate the cumulative gas volume.

[0038] When testing the gas composition, open the first valve 5, use the exhaust device 6 to extract the gas, insert the connecting needle 8 into the gas measuring device, i.e., the gas chromatograph, close the first valve 5, open the third valve 9, inject the gas in the exhaust device into the gas measuring instrument, and directly perform the test.

[0039] Similarly, when the soft pack battery has no air pocket, such as Figure 2 As shown, sealant is applied to the ear side, and the rest is the same as when there is an air bag.

[0040] The gas production and composition of the battery at different stages can be measured, including:

[0041] Stage 1: Measurement of gas volume and gas composition of the battery after pre-formation. The results are shown in Table 1.

[0042] Table 1 Measurement of gas volume and gas composition of the battery after pre-formation

[0043] Gas volume <![CDATA[H2]]> CO <![CDATA[CH4]]> <![CDATA[CO2]]> <![CDATA[C2H4]]> <![CDATA[C2H6]]> 6mL 72.66％ 4.996％ 1.73％ 0.48％ 19.16％ 0.98％

[0044] The SEI film will be formed when the battery is pre-charged for the first time. The SEI film is mainly formed by the reduction and decomposition of solvents such as ethylene carbonate (EC) and high-purity diethyl carbonate (DEC) in the electrolyte at the negative electrode to generate lithium alcohol oxide compounds. Therefore, gas is generated while the film is formed. During the first cycle of charge and discharge, H2 mainly comes from the decomposition of trace water in the battery, and CO and alkane gases mainly come from the reduction and decomposition of solvents.

[0045] Stage 2: Measurement of gas production and gas composition during battery cycle failure. The results are shown in Table 2.

[0046] Table 2 Measurement table of battery cycle failure gas production and gas composition

[0047] Gas volume <![CDATA[O2]]> CO <![CDATA[CH4]]> <![CDATA[C2H4]]> <![CDATA[C2H6]]> 57.5mL 1.54％ 1.76％ 88.47％ 1.11％ 8.08％

[0048] The battery decays quickly after 800 cycles and produces a lot of gas. Based on the gas production results, the cause of failure can be analyzed. From the composition of the gas production, there is no H2, CO2 and other gases, which can rule out the factor of poor battery sealing causing gas production; alkane gas is mainly produced by the decomposition of electrolyte, combined with the fact that there is basically no electrolyte in the battery after disassembly, indicating that it may be due to poor film formation, resulting in the subsequent continuous decomposition of the electrolyte and gas production.

[0049] Stage 3: Measurement of gas production and gas composition of high temperature storage batteries. The results are shown in Table 3.

[0050] Table 3 Measurement of gas production and gas composition of high temperature storage batteries

[0051] Gas volume <![CDATA[H2]]> CO <![CDATA[CH4]]> <![CDATA[CO2]]> <![CDATA[C2H6]]> 5.2mL 33.06％ 1.55％ 0.10％ 65.18％ 0.10％

[0052] When the battery is stored at high temperature, gas will be generated. According to the gas production results, CO2 is the main gas. This is because the SEI film decomposes during the high-temperature storage of the battery, producing more CO2. The decomposed SEI will regenerate and produce a small amount of alkane gas.

[0053] The results show that through the above three stages, the battery will produce different gases during the formation, cycle, and failure process. The gas composition and gas volume can be combined to analyze the gas production mechanism or determine whether the battery is abnormal. The process can also be improved and guided according to the gas composition and gas volume, ultimately improving the battery's electrical performance and safety performance.

[0054] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation methods and application scopes. The contents of this specification should not be understood as limiting the present invention.

Claims

1. A soft pack battery exhaust device, characterized in that: It comprises an air extraction needle, an air guide tube connected to the air extraction needle, and an air extraction device and an air extraction bag sequentially arranged on the air guide tube; A first valve is arranged between the air extraction needle and the air extraction device; a second valve is arranged on the air guide tube between the air extraction device and the air extraction bag.

2. The air extraction device for a soft-pack battery according to claim 1, characterized in that: The air extraction device is a piston cylinder; the piston cylinder comprises an outer cylinder, a piston arranged in the outer cylinder and a moving rod connected to the piston.

3. The air extraction device for soft-pack batteries according to claim 2, characterized in that: The outer cylinder is provided with scales; the moving rod is provided with a handle.

4. The air extraction device for a soft-pack battery according to claim 2, characterized in that: The volume of the outer cylinder is 1-20 ml.

5. The air extraction device for soft-pack batteries according to claim 1, characterized in that: The air extraction needle penetrates into the soft-pack battery; and a sealant is provided at the contact point between the air extraction needle and the soft-pack battery.

6. The air extraction device for a soft-pack battery according to claim 1, characterized in that: The connection between the air guide tube, the air extraction device and the air extraction needle is provided with vaseline.

7. The air extraction device for a soft-pack battery according to claim 1, characterized in that: The air extraction bag is provided with a switch valve.

8. The air extraction device for a soft-pack battery according to claim 1, characterized in that: The air guide tube between the air extraction needle and the air extraction device is provided with a connecting needle head which is in communication with the air guide tube.

9. The air extraction device for soft-pack batteries according to claim 8, characterized in that: A third valve is arranged between the connecting needle and the gas extraction needle.

10. A gas measuring device, characterized in that: It comprises the soft-pack battery exhaust device as described in claim 8 or 9 and a gas measuring device connected to the connecting needle; the gas measuring device is a gas chromatograph.

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