A device and method for in-situ detection of internal gas of thermal runaway of lithium battery

Abstract

The application discloses a kind of lithium battery thermal runaway internal gas in-situ detection device and method, belong to lithium battery detection technical field.The lithium battery thermal runaway internal gas in-situ detection device of the application includes detection instrument, the detection instrument is communicated with battery by gas outlet pipe and back gas pipe, the gas outlet pipe passes into detection instrument with the gas in battery, the back gas pipe is detected with the gas of detection instrument and is sent back into battery.The method of the application detects using the above device, avoids air interference in reaction process, can in the process without collecting lithium battery internal gas, the composition and concentration of internal gas and electrolyte steam in the process of lithium battery thermal runaway are monitored in real time in-situ, so that researchers have more clear understanding to the chemical reaction process and internal pressure evolution process in battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery testing technology, specifically to an in-situ detection device and method for internal gas in lithium battery thermal runaway. Background Technology

[0002] In recent years, lithium-ion batteries have been rapidly developed due to their advantages such as high specific energy, long lifespan, good cycle performance, and low environmental pollution, and have been widely used in important fields such as electric vehicles, energy storage power stations, and communication base stations.

[0003] However, with the widespread application of lithium batteries, various electric vehicle fires and energy storage power station fires have occurred frequently. When lithium batteries are subjected to electrical abuse, thermal abuse, and mechanical abuse, the internal electrode materials, separators, and electrolytes react with each other, generating a large amount of heat and leading to thermal runaway. During thermal runaway, lithium batteries produce certain gases, and the electrolyte also vaporizes upon heating, resulting in an increase in internal battery pressure. When the internal pressure exceeds the pressure withstand threshold of the battery casing, the casing will rupture, causing leakage, fire, or even explosion, thus affecting battery safety. Therefore, analyzing the gas generation process inside the battery, such as the gas composition and concentration, can provide a deeper understanding of its gas generation mechanism and internal pressure growth process, which is of great significance for battery thermal safety research.

[0004] Current methods for studying thermal runaway gas generation in lithium-ion batteries primarily involve placing the battery in a sealed container and inducing thermal runaway through thermal abuse, electrical abuse, and mechanical abuse, followed by detecting the gas composition. However, these methods do not utilize internal battery gas monitoring before the safety valve opens. Furthermore, the complex internal chemical reactions that occur continuously during the process from self-heating to safety valve opening lead to a complex internal gas generation process. During the collection of this internal gas, issues such as temperature cooling, poor sealing, and air interference make accurate real-time monitoring of the gas composition and concentration impossible. Moreover, existing methods cannot measure electrolyte vapor.

[0005] Chinese invention patent document, publication number: CN113009350A, publication date: June 22, 2021, discloses a method and a sampling device for analyzing the influence of internal battery gas on thermal runaway. The device includes a first connecting pipe, a vacuum pump, a second connecting pipe, and a gas collecting device connected sequentially to the battery. The vacuum pump extracts the internal gas of the battery under test, and the gas is collected by the gas collecting device. The gas is then passed into a gas chromatograph for quantitative analysis of the gas components. Table 1 shows the composition of the internal battery gas and the percentage of each gas obtained in the embodiment provided by this invention patent. Its shortcomings include: when using the vacuum pump to extract the internal gas of the battery through the first connecting pipe, it causes gas production and internal pressure loss during the battery's thermal runaway process, damaging the internal environment of the battery; and the device fails to measure the gas production in real time during the battery's thermal runaway process. Summary of the Invention

[0006] 1. The technical problem that the invention aims to solve

[0007] To overcome the shortcomings of the prior art, the present invention provides an in-situ detection device and method for internal gases in lithium battery thermal runaway, aiming to make up for the problems in the prior art such as the difficulty in online detection of gas components generated during thermal runaway of lithium battery, the difficulty in monitoring electrolyte vapor, and the interference from air.

[0008] 2. Technical Solution

[0009] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0010] This invention provides an in-situ detection device for internal gases in lithium batteries during thermal runaway. The device includes a detection instrument connected to the battery via an outlet pipe and a return pipe. The outlet pipe introduces gas from inside the battery into the detection instrument, while the return pipe returns the gas detected by the instrument back into the battery. This design eliminates interference from external air during the detection of gas generation inside the battery, while avoiding gas generation and internal pressure losses caused by gas collection. The circulation pipe allows the gas generated inside the battery to flow back into the battery, preventing gas collection from affecting the internal reaction process and minimizing the impact of gas composition detection on the internal chemical reaction.

[0011] As a further improvement of the present invention, the outlet pipe is wrapped with an outlet heat tracing pipe, and the return pipe is wrapped with a return heat tracing pipe. The temperature of the outlet heat tracing pipe and the return heat tracing pipe is the same. The temperatures of the outlet heat tracing pipe and the return heat tracing pipe are adjustable and are the same as the battery temperature. Wrapping the pipes with real-time adjustable temperature heat tracing pipes ensures that the pipe temperature is the same as the battery temperature, which can guarantee that the internal gas temperature of the battery is the same as the gas temperature of the pipe. Furthermore, it can prevent the electrolyte vapor from condensing during transmission when detecting electrolyte vapor inside the battery, thereby accurately measuring the composition of the electrolyte vapor.

[0012] As a further improvement of the present invention, the battery temperature is the surface temperature of the battery casing. Under adiabatic conditions, the temperature difference between the inside and outside of the battery is 1°C when thermal runaway does not occur. Therefore, the temperature of the gas inside the battery can be reflected by the surface temperature of the battery.

[0013] As a further improvement of the present invention, the vent pipe is connected to the battery via a one-way vent valve, which controls the gas to flow unidirectionally from inside the battery into the vent pipe. The one-way vent valve ensures that the gas does not flow back when exiting the battery, thereby guaranteeing the stability of the gas flow.

[0014] As a further improvement of the present invention, the return gas pipe is connected to the battery via a one-way return gas valve, which controls the gas to flow unidirectionally from the return gas pipe into the battery. The one-way return gas valve ensures that the gas does not flow back into the battery, thereby guaranteeing the stability of the detection gas flow.

[0015] As a further improvement of the present invention, a second small explosion-proof valve is provided at the connection between the vent pipe and the battery, which blocks the battery's vent hole. A first small explosion-proof valve is provided at the connection between the return pipe and the battery, which blocks the battery's return vent hole. By providing the first and second small explosion-proof valves, the battery's integrity can be maintained when gas detection is not performed, thus avoiding damage to the battery before detection and resulting in distorted detection results. Simultaneously, the first and second small explosion-proof valves are conveniently located for puncturing during experiments, eliminating the need to drill holes in the battery and facilitating the detection process.

[0016] As a further improvement of the present invention, a flow regulator and a flow pump are installed on the outlet pipe. By installing the flow regulator and flow pump, the airflow stability can be ensured, thus improving the detection results.

[0017] As a further improvement of the present invention, the outlet one-way valve is connected to the inside of the battery through an outlet connector, and the outlet connector is sealed to both the outlet one-way valve and the battery; the return one-way valve is connected to the inside of the battery through a return connector, and the return connector is sealed to both the return one-way valve and the battery. Sealing the outlet and return one-way valves to the battery through connectors ensures airtightness and avoids interference from external gases.

[0018] This invention also provides an in-situ detection method for internal gas in lithium battery thermal runaway, utilizing the aforementioned device for detection, the steps of which are as follows:

[0019] Step 1: Connect the outlet pipe and return pipe to the outlet port and return port respectively through a one-way valve and a connector, and wrap the heat tracing pipe around the outside of the outlet pipe and return pipe.

[0020] Step 2: Connect the outlet pipe and return pipe to the testing instrument to complete the device assembly;

[0021] Step 3: Puncture the first and second small explosion-proof valves on the battery to allow the battery to form a gas loop with the testing instrument through the pipe;

[0022] Step 4: Set the temperatures of the outlet and return heat tracing pipes, and wait for the temperatures to stabilize.

[0023] Step 5: Turn on the testing instrument and adjust the flow rate of the flow regulator and the power of the flow pump to stabilize the circulating airflow between the battery and the testing instrument.

[0024] Step Six: The battery is subjected to abuse methods such as heating and overcharging, and the gas is detected in real time using a testing instrument. The detection method of this invention utilizes a circulation pipeline, allowing the gas generated inside the battery to flow back into the battery, avoiding any impact on the internal reaction process due to gas collection, and minimizing the influence of gas composition detection on the internal chemical reaction of the battery.

[0025] 3. Beneficial effects

[0026] Compared with existing known technologies, the technical solution provided by this invention has the following significant advantages:

[0027] Traditional methods mostly involve collecting gas from inside the battery, resulting in gas production losses and internal pressure losses. This invention utilizes a circulation pipeline to allow gas generated inside the battery to flow back into the battery, avoiding any impact on the internal reaction process caused by gas collection and minimizing the influence of gas composition detection on the battery's internal chemical reactions.

[0028] Furthermore, the detection instrument uses a Raman spectrometer, which can monitor the gas composition and electrolyte vapor in real time. Using the device of this invention, in-situ concentration monitoring of gas generation from internal chemical reactions and electrolyte evaporation can be carried out, thereby enabling researchers to have a clearer understanding of the internal chemical reaction process and internal pressure evolution of the battery. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the in-situ detection device of the present invention;

[0030] Figure 2 for Figure 1 Enlarged view of the structure at point A in the middle;

[0031] Figure 3 This figure shows the changes in the peak concentrations of CO2, H2, and C2H4 over time during the thermal abuse of lithium batteries.

[0032] Explanation of the labels in the diagram:

[0033] 1. Battery; 11. Safety valve; 2. Gas outlet pipe; 21. Flow regulator; 22. Flow pump; 23. Gas outlet heat tracing pipe; 3. Gas return pipe; 31. Gas return heat tracing pipe; 4. Detection instrument; 51. Gas return check valve; 52. Gas return connector; 53. First small explosion-proof valve; 54. Gas outlet check valve; 55. Gas outlet connector; 56. Second small explosion-proof valve. Detailed Implementation

[0034] To make the above-mentioned objects, features, and advantages of the invention more apparent and understandable, specific embodiments of the invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0040] Example

[0041] Combination Figure 1 and Figure 2This embodiment discloses an in-situ detection device for internal gas in lithium battery thermal runaway, comprising a detection instrument 4. The detection instrument 4 is connected to the battery 1 via an outlet pipe 2 and a return pipe 3. The outlet pipe 2 introduces gas from the battery 1 into the detection instrument 4, and the return pipe 3 returns the gas detected by the detection instrument 4 back into the battery 1. The battery 1 and the detection instrument 4 are connected by these two unidirectional pipes to form a gas circuit. A flow regulator 21 and a flow pump 22 are installed on the outlet pipe 2. The flow regulator 21 and the flow pump 22 ensure stable airflow and improve detection results.

[0042] In this embodiment, an outlet heating pipe 23 is wrapped around the outlet pipe 2, and a return heating pipe 31 is wrapped around the return pipe 3. The temperature of the outlet heating pipe 23 and the return heating pipe 31 are the same. Since the outlet pipe 2 and the return pipe 3 are exposed to the outside, when the gas inside the battery 1 enters and exits the detection instrument 4 through the pipes, the outside air will carry away the heat of the gas inside the pipes, causing the gas to return to the battery 1 and affect the internal environment of the battery 1. To eliminate these effects, this embodiment uses a real-time adjustable temperature heating pipe to heat and insulate the outlet pipe 2 and the return pipe 3. The temperature of the heating pipe changes with the temperature of the battery 1, ensuring that the temperature of the gas inside the battery 1 remains the same as the internal temperature of the battery 1 after passing through the pipes. This reduces variables in the detection process and avoids the condensation of electrolyte vapor during transmission when detecting electrolyte vapor inside the battery 1, thereby accurately measuring the composition and concentration of electrolyte vapor and further ensuring the accuracy of the detection results. In this embodiment, the temperature of battery 1 is the surface temperature of battery 1 casing. Under adiabatic conditions, the temperature difference between the inside and outside of battery 1 is 1°C when thermal runaway does not occur. Therefore, the surface temperature of battery 1 can reflect the internal gas temperature of battery 1.

[0043] In this embodiment, the gas outlet pipe 2 is connected to the battery 1 via a gas outlet one-way valve 54, which controls the gas to flow unidirectionally from the battery 1 into the gas outlet pipe 2. The gas return pipe 3 is connected to the battery 1 via a gas return one-way valve 51, which controls the gas to flow unidirectionally from the gas return pipe 3 into the battery 1. Simultaneously, the gas outlet one-way valve 54 is connected to the inside of the battery 1 via a gas return connector 52, which is sealed to both the gas outlet one-way valve 54 and the battery 1. The gas return one-way valve 51 is also connected to the inside of the battery 1 via a gas outlet connector 55, which is sealed to both the gas outlet one-way valve 54 and the battery 1. This embodiment's use of gas outlet one-way valves 54 and gas return one-way valves 51 ensures that gas does not flow back into or out of the battery 1, thus guaranteeing the stability of the detected gas flow. Simultaneously, the outlet check valve 54 and the return check valve 51 are sealed to the battery 1 via connectors to ensure airtightness and prevent interference from external gases. In this embodiment, high-temperature metal sealant is used for sealing.

[0044] In this embodiment, a second small explosion-proof valve 56 is also provided at the connection between the vent pipe 2 and the battery 1, which blocks the vent hole of the battery 1. A first small explosion-proof valve 53 is provided at the connection between the return pipe 3 and the battery 1, which blocks the return vent hole of the battery 1. By providing the first small explosion-proof valve 53 and the second small explosion-proof valve 56, the integrity of the battery 1 can be maintained when gas detection is not performed, thereby avoiding damage to the battery 1 before detection and resulting in distorted detection results. At the same time, the first small explosion-proof valve 53 and the second small explosion-proof valve 56 are convenient to puncture during the experiment, without the need to make holes in the battery 1, which facilitates the detection. In this embodiment, the first small explosion-proof valve 53 and the second small explosion-proof valve 56 are located on both sides of the safety valve 11.

[0045] This embodiment also provides an in-situ detection method for internal gas in lithium battery thermal runaway, the steps of which are as follows:

[0046] Step 1: Connect the outlet pipe 2 and return pipe 3 to the outlet port and return port respectively through a one-way valve and a connector, and wrap the heat tracing pipe around the outside of the outlet pipe 2 and return pipe 3.

[0047] Step 2: Connect the exhaust pipe 2 and the return pipe 3 to the testing instrument 4 to complete the device assembly;

[0048] Step 3: Puncture the first small explosion-proof valve 53 and the second small explosion-proof valve 56 on battery 1, so that battery 1 forms a gas loop with the testing instrument 4 through the pipe;

[0049] Step 4: Set the temperatures of the outlet heat tracing pipe 23 and the return heat tracing pipe 31, and wait for the temperatures to stabilize.

[0050] Step 5: Turn on the testing instrument 4, adjust the flow rate of the flow regulator 21 and the power of the flow pump 22 to stabilize the circulating airflow between the battery 1 and the testing instrument 4.

[0051] Step 6: Expose battery 1 to abuse methods such as heating and overcharging, and use detection instrument 4 to detect the gas in real time.

[0052] See Figure 3 In this embodiment, the device can detect the changes in the peak concentration signals of CO2, H2, and C2H4 over time during the thermal abuse of the lithium battery when detecting the gas inside the battery 1. However, the patent documents described in the background art can only detect the quantitative results shown in Table 1, and cannot reflect the changes in the gas inside the battery 1 during thermal runaway.

[0053] Table 1. Gas Detection Results of Battery (Patent No. CN113009350A)

[0054]

[0055] Traditional methods mostly involve collecting gas inside battery 1, resulting in gas production loss and internal pressure loss. This embodiment utilizes a circulation pipeline to allow the gas generated inside battery 1 to flow back into battery 1, avoiding any impact on the internal reaction process of battery 1 due to gas collection, and minimizing the influence of gas composition detection on the internal chemical reaction of battery 1.

[0056] Furthermore, the detection instrument 4 employs a Raman spectrometer, which can monitor the gas composition and electrolyte vapor in real time. Using the device and method of this embodiment, in-situ concentration monitoring of gas generation from the internal chemical reaction and electrolyte evaporation process of battery 1 can be carried out, thereby enabling researchers to have a clearer understanding of the internal chemical reaction process and internal pressure evolution process of battery 1.

[0057] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A device for in-situ detection of internal gas in lithium battery thermal runaway, characterized in that, The device includes a detection instrument (4), which is directly connected to the battery (1) body through an outlet pipe (2) and a return pipe (3) to form a closed gas circuit. The outlet pipe (2) introduces the gas inside the battery (1) into the detection instrument (4) in real time, and the return pipe (3) returns all the gas detected by the detection instrument (4) back to the battery (1) to maintain the integrity of the internal pressure and chemical reaction environment of the battery.

2. The in-situ detection device for internal gas in lithium battery thermal runaway according to claim 1, characterized in that, The outlet pipe (2) is wrapped with an outlet heat tracing pipe (23), and the return pipe (3) is wrapped with a return heat tracing pipe (31). The temperature of the outlet heat tracing pipe (23) and the return heat tracing pipe (31) are the same. The temperature of the outlet heat tracing pipe (23) and the return heat tracing pipe (31) is adjustable and is the same as the temperature of the battery (1).

3. The in-situ detection device for internal gas in lithium battery thermal runaway according to claim 1, characterized in that, The gas outlet pipe (2) is connected to the battery (1) through a gas outlet one-way valve (54), and the gas outlet one-way valve (54) controls the gas to flow unidirectionally from the battery (1) to the gas outlet pipe (2).

4. The in-situ detection device for internal gas in lithium battery thermal runaway according to claim 3, characterized in that, The return gas pipe (3) is connected to the battery (1) through the return gas check valve (51), and the return gas check valve (51) controls the gas to flow unidirectionally from the return gas pipe (3) to the battery (1).

5. The in-situ detection device for internal gas in lithium battery thermal runaway according to claim 1, characterized in that, A second small explosion-proof valve (56) is provided at the connection between the vent pipe (2) and the battery (1), and the second small explosion-proof valve (56) blocks the vent of the battery (1).

6. The in-situ detection device for internal gas in lithium battery thermal runaway according to claim 1, characterized in that, A first small explosion-proof valve (53) is provided at the connection between the gas return pipe (3) and the battery (1), and the first small explosion-proof valve (53) blocks the gas return hole of the battery (1).

7. The in-situ detection device for internal gas in lithium battery thermal runaway according to claim 1, characterized in that, A flow regulator (21) and a flow pump (22) are installed on the air outlet pipe (2).

8. The in-situ detection device for internal gas in lithium battery thermal runaway according to claim 4, characterized in that, The exhaust check valve (54) is connected to the inside of the battery (1) through the exhaust connector (55), and the exhaust connector (55) is sealed to both the exhaust check valve (54) and the battery (1); the return check valve (51) is connected to the inside of the battery (1) through the return connector (52), and the return connector (52) is sealed to both the return check valve (51) and the battery (1).

9. A method for in-situ detection of internal gas in a lithium battery during thermal runaway, characterized in that, The detection is performed using the apparatus according to any one of claims 1-8, and the steps are as follows: Step 1: Connect the outlet pipe (2) and return pipe (3) to the outlet and return ports respectively through a one-way valve and a connector, and wrap the heat tracing pipe around the outlet pipe (2) and return pipe (3); Step 2: Connect the outlet pipe (2) and return pipe (3) to the testing instrument (4) to complete the device assembly; Step 3: Puncture the first small explosion-proof valve (53) and the second small explosion-proof valve (56) on the battery (1) so that the battery (1) forms a gas loop with the testing instrument (4) through the pipe; Step 4: Set the temperature of the outlet heat tracing pipe (23) and the return heat tracing pipe (31), and wait for the temperature to stabilize; Step 5: Turn on the testing instrument (4), adjust the flow rate of the flow regulator (21) and the power of the flow pump (22) to stabilize the circulating airflow between the battery (1) and the testing instrument (4); Step 6: Heat the battery (1) and overcharge it. Use the detection instrument (4) to detect the gas in real time.

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