CN116298975A - Early smoke characteristic test platform for thermal runaway of battery and measurement method thereof - Google Patents

Abstract

The invention belongs to the field of testing instruments, and particularly relates to a testing platform for early smoke characteristics of thermal runaway of a battery and a measuring method for early smoke characteristics. The test platform is used for measuring the corresponding early smoke characteristics of the battery to be tested in the thermal runaway state caused by different initiation conditions. The platform comprises: the device comprises a test container, an airflow organization system, a wind speed sensor, a sound pressure sensor, a gas pressure sensor, a runaway triggering mechanism, a flue gas online analysis component, a sampling device, an electrical measurement component and an upper computer. Wherein the test vessel comprises a combustion chamber and a flue. And the airflow organization system is used for introducing background gas into the test container, enabling the background gas to enter from the bottom of the combustion chamber, lifting upwards below the battery and finally discharging along the tail section of the flue. The flue gas online analysis assembly comprises a first thermocouple sensor, a gas analyzer and a VOC monitor. The invention solves the problems of high difficulty and high risk of early smoke characteristic research of thermal runaway of the battery.

Description

A test platform for early smoke characteristics of battery thermal runaway and its measurement method

technical field

The invention belongs to the field of testing instruments, and in particular relates to a test platform for early smoke characteristics of battery thermal runaway and a method for measuring early smoke characteristics of battery thermal runaway.

Background technique

The rapid progress of rechargeable battery technologies such as lithium batteries has enabled the development of the electronics industry and the new energy vehicle industry to enter the fast lane. Today, with the increasing awareness of environmental protection, new energy vehicles represented by electric vehicles are likely to directly replace fuel vehicles. In this trend, improving battery energy density and charging performance, as well as improving battery safety are becoming technical problems that technicians need to solve urgently.

However, the fire caused by battery thermal runaway seriously threatens the safety of electrical equipment, and safety has become an important factor restricting its development. Considering that the fire accidents caused by battery thermal runaway have the characteristics of rapid development, irreversibility and great harm, therefore, early detection of battery thermal runaway and reserving reaction time for battery safety protection or fire protection are important in the field of battery safety. an important research direction.

For a series of rechargeable batteries such as lithium batteries, after thermal runaway of the battery, gases such as hydrogen, methane, and carbon monoxide are generally released, and smoke particles are also produced when deflagration or open flame occurs. Therefore, if the smoke characteristics of the early stage of battery thermal runaway are analyzed, and corresponding detectors are designed based on this, the goal of timely monitoring the risk of thermal runaway of the battery should be achieved. In addition, considering the variety of rechargeable batteries and the many causes of thermal runaway, it is necessary to classify the early characteristics of different types of batteries under different conditions. In particular, after thermal runaway or even deflagration of batteries, there are obvious differences in smoke characteristics and combustion states in different periods, so it is also necessary to accurately classify feature information in different periods.

However, under the existing technical conditions, there is no special test platform for the thermal runaway research of batteries. Technicians usually use the existing combustion test equipment used in various industrial product performance tests to implement various tests, or build small test platforms independently to implement test experiments. This not only has high security risks, but also makes it difficult to obtain effective high-precision data. To sum up, the existing lithium battery thermal runaway experimental devices cannot meet the problem of effectively identifying the early smoke characteristics of lithium battery thermal runaway. Those skilled in the art urgently need a set of high safety and more comprehensive battery thermal runaway smoke test equipment platform to study the characteristics and laws of the early stage of battery thermal runaway.

Contents of the invention

In order to solve the problem of difficulty and high risk in the study of early smoke characteristics of battery thermal runaway, and the lack of special testing instruments; Measurement methods.

The present invention adopts following technical scheme to realize:

An early smoke characteristics test platform for battery thermal runaway, which is used to measure the corresponding early smoke characteristics of the battery to be tested in the state of thermal runaway caused by different triggering conditions. This type of early flue gas characteristic test platform includes: test container, air flow organization system, wind speed sensor, sound pressure sensor, air pressure sensor, runaway trigger mechanism, flue gas online analysis component, sampling device, electrical measurement component, and host computer.

Among them, the test container includes a combustion chamber and a flue. A battery fixture is arranged in the center of the combustion chamber; a gas inlet is arranged at the bottom of the combustion chamber, and an inverted funnel-shaped fume collection hood is arranged at the top, and the gas outlet at the top of the fume collection hood communicates with a horizontally placed flue. A steady flow pipe is arranged at the interface between the flue and the combustion chamber, and a plurality of through holes for equipment installation are arranged on the outer wall of the flue.

The air flow organization system is used to introduce the background gas into the test container, and form a gas convection environment where the background gas enters from the bottom of the combustion chamber, rises vertically under the battery fixture, and finally is discharged along the outlet of the final section of the flue.

The wind speed sensor is installed 10cm behind the steady flow pipe in the flue. The sound pressure sensor is installed in the combustion chamber and used to measure the noise information of the battery thermal runaway process. The air pressure sensor is installed in the combustion chamber and used to measure the status data of the ambient instantaneous air pressure during the battery thermal runaway process.

The runaway triggering mechanism is installed at the battery fixture. The runaway triggering mechanism includes acupuncture actuators, extrusion actuators and heating devices, which are used for acupuncture, extrusion and heating operations on the battery to be tested respectively.

The flue gas online analysis component includes a first thermocouple sensor, a gas analyzer, and a VOC monitor. Various instruments in the flue gas online analysis component are installed in each through hole on the outer wall of the flue, and the detection element is inserted into the flue. The first thermocouple sensor is located at the front end of the flue closest to the steady flow tube, and the gas analyzer and VOC monitor are located at the rear side relative to the first thermocouple sensor.

The sampling device includes a smoke particle sampling device and a flue gas sampling device; various instruments in the sampling device are installed in through holes on the outer wall of the flue, and are located near the end of the flue.

The electrical measurement components are mounted in the battery fixture. The electrical measurement component is electrically connected to the battery to be measured through the electrode sheet, and the electrical measurement component is used to simulate the charging, discharging and natural state of the battery to be tested, and to obtain the electrical parameters of the battery during the measurement process. In addition, electrical measurement components are used to simulate short-circuit faults in batteries.

The upper computer is electrically connected with the airflow organization system, wind speed sensor, sound pressure sensor, air pressure sensor, out-of-control trigger mechanism, online analysis mechanism, sampling device and electrical measurement components. The upper computer is the control center and data processing center of the entire test platform. The upper computer can issue control instructions to other instruments or actuators, or collect detection data from instruments and sensors, analyze and process various data, and finally obtain the battery Analytical report of early signs of thermal runaway. In the present invention, the host computer is used for:

1. Control the air flow organization system to generate a uniform convective background gas environment that meets the preset conditions in the combustion chamber, and ensure that the measured value of the wind speed sensor in the initial state is 0.2±0.02m/s.

2. The out-of-control triggering mechanism or the electrical measurement component triggers the thermal runaway of the battery to be tested according to the measurement task, and determines the triggering moment of the thermal runaway in combination with the sampling data of the sound pressure sensor.

3. Obtain real-time measurement data of the online monitoring component, the electrical measurement component and the air pressure sensor.

4. Obtain the test results of the samples collected by the sampling device in the offline device.

5. Comprehensively analyze the online measurement sample data and the test results of the sample offline analysis, and generate a complete analysis report of the early smoke characteristics of the battery thermal runaway.

As a further improvement of the present invention, the test container also includes at least one openable airtight door and at least one transparent observation window. The interior of the test container is provided with a fireproof layer.

In addition, a binocular camera with both infrared and full-color cameras is installed outside the observation window of the test container, and the binocular camera is used to record image data during the thermal runaway experiment.

As a further improvement of the present invention, the air flow organization system includes: a high-pressure gas cylinder, a valve body, a gas flow meter, a centrifugal fan, and a low-speed axial fan. High-pressure gas cylinders contain the required background gas. The valve body is used to control the valve opening of the high-pressure cylinder to discharge the background gas to the combustion chamber. The gas flowmeter is installed at the gas inlet of the combustion chamber and the flue outlet respectively to measure the gas flow passing through the two places; the centrifugal fan is installed at the end of the flue to discharge the gas in the combustion chamber from the test container. The low-speed axial flow fan is installed at the bottom of the combustion chamber facing the battery holder, and is used to generate vertical upward lift.

As a further improvement of the present invention, nitrogen is used as the background gas, or a mixed gas of nitrogen and oxygen mixed by a gas mixing valve at a material ratio of 8:2.

As a further improvement of the present invention, a second thermocouple sensor and a pressure gauge are also provided on the battery fixture, and the second thermocouple sensor is used to measure the surface temperature of the battery under test during thermal runaway. The pressure gauge is used to measure the expansion pressure of the battery under test during thermal runaway.

As a further improvement of the present invention, the battery fixture includes a mounting groove, and the electric heating tube in the heating device is installed inside the battery fixture close to the bottom wall of the mounting groove. The extrusion actuator is installed directly above the battery clamp and can rotate horizontally relative to the battery clamp. The extrusion actuator adopts a hydraulic mechanism that feeds downward; and after a steel needle is installed at the front end of the pressure head of the hydraulic mechanism, the required acupuncture actuator is formed.

As a further improvement of the present invention, the smoke particle sampling device adopts copper mesh carbon film. The acquired smoke particle samples were analyzed by TEM electron microscope to obtain the composition, structure information (such as shape and particle size) and concentration information of the particles contained in the smoke.

The flue gas sampling device includes a sampling pump, a sampling tube and a vacuum bag; the sampling pump draws sample gas from the flue through the sampling tube and stores it in the vacuum bag. The collected gas samples were analyzed by gas chromatography-mass spectrometry (GC-MS).

As a further improvement of the present invention, the early flue gas characteristic test platform also includes a safety system, which is used to spray perfluorohexanone or liquid nitrogen into the combustion chamber after the test, so as to achieve fire prevention and cooling.

The present invention also includes a method for measuring early flue gas characteristics of a battery thermal runaway, which is used to complete the early flue gas characteristic analysis of batteries in different thermal runaway states by using the aforementioned early flue gas characteristic test platform for battery thermal runaway; the measurement The method includes the following steps:

1. Debugging stage:

S1: Install the battery to be tested on the battery fixture in the combustion chamber, and seal the combustion chamber.

S2: Replace the gas inside the test container with the background gas, and form a stable and uniform gas convection environment, while controlling the gas flow rate in the flue.

S3: Use detection instruments or sensors to continuously monitor the environmental parameters in the combustion chamber and the flue, and monitor the electrical parameters of the battery.

Environmental parameters include: combustion chamber sound pressure, combustion chamber instantaneous pressure, flue gas temperature, flue wind speed, composition and concentration of flue gas.

2. Test phase

S4: According to the preset measurement task, one or more operations of heating, extrusion, acupuncture, and short circuit are used to cause thermal runaway of the battery to be tested.

S5: Combining the sound pressure measurement data in the combustion chamber and the execution time of heating, extrusion, acupuncture or short circuit operations to comprehensively judge the thermal runaway occurrence time of the battery under test.

S6: According to the precise response time of each detection instrument or sensor, the detection data is divided into a stage before thermal runaway and a stage after thermal runaway. And during the window period, the smoke particles and smoke in the flue are sampled through the sampling device; wherein, the window period refers to the period during which the early smoke generated by the thermal runaway of the battery flows through the sampling device.

S7: After obtaining the required test data, stop ventilating the combustion chamber, extinguish the fire and cool down the battery to be tested, until the risk of battery deflagration is eliminated.

S8: Perform offline detection on the smoke particles and smoke samples obtained by the sampling device.

S9: Combining the process data of the pre-thermal runaway stage and the post-thermal runaway stage obtained during the online detection process and the experimental data of the offline detection, the early smoke characteristics of the battery to be tested in the thermal runaway state are analyzed and obtained.

As a further aspect of the present invention, in step S3, a VOC monitor and a gas analyzer are used to cooperatively monitor the composition and concentration of the flue gas, and a first thermocouple sensor is used to monitor the temperature of the flue gas.

In step S6, the precise response time of the VOC monitor is:

In the above formula, t _VOC is the initial response time of the VOC monitor; s ₁ is the distance between the VOC monitor and the steady flow tube; f is the wind speed at 10 cm behind the steady flow tube in the thermal runaway state of the battery under test.

The exact response time of the gas analyzer is:

In the above formula, _tgas is the initial response time of the gas analyzer; _s2 is the distance between the gas analyzer and the steady flow tube; d is the diameter of the sampling tube in the gas analyzer, l is the gas analyzer’s The length of the sampling tube, Q is the flow value corresponding to the unit suction of the gas analyzer.

The exact response time of the first thermocouple sensor is:

In the above formula, t _T is the initial response time of the thermocouple; s ₃ is the distance between the first thermocouple sensor and the steady flow tube.

The technical scheme provided by the invention has the following beneficial effects:

The test platform for early flue gas characteristics of battery thermal runaway provided by the present invention integrates the measuring instruments required for the measurement of battery thermal runaway, and optimizes the structural design and control system of the test platform, which can be completed in a highly automated manner. Various complex operations and complicated data processing work during the battery thermal runaway experiment. Finally, the potential safety hazards in the experimental process are reduced, and the accuracy and effect of data collection of various indicators are improved. This type of test platform has powerful performance and can be applied to various types of batteries and test tasks under different thermal runaway conditions, so it has extremely high practical value.

The test platform designed by the present invention adopts a special air flow organization system, which can generate a uniform and single temperature air flow environment formed by the background gas inside the test container, which can drive the thermal runaway of the battery to generate smoke to the rear end. Monitoring the flow of the instrument can reduce the interference of ambient gas on the test experiment. And when the flue gas production flow is small, positive pressure air supply is used as the carrier gas mode to organize the air flow, which solves the influence of uneven flue gas flow on the measurement accuracy of the battery thermal runaway flue gas; thus it is very suitable for the battery thermal runaway Early smoke characteristics were studied.

Compared with the traditional test scheme, the test platform of the present invention can also effectively control the convection process of the airflow, thereby facilitating precise control of the response time of each detection instrument, and effectively avoiding the influence of uneven flow velocity of flue gas or staying in the combustion chamber on the test results. And ultimately significantly improve the detection accuracy and reliability of various data indicators.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is a structure and equipment installation layout diagram of an early smoke characteristics test platform for battery thermal runaway provided in Embodiment 1 of the present invention.

FIG. 2 is a block diagram of the module connection of the control system in the early smoke characteristic test platform for battery thermal runaway in Embodiment 1 of the present invention.

Figure 3 is a schematic structural diagram of the test container in the test platform for early smoke characteristics of battery thermal runaway.

Figure 4 is a structural design diagram of the flue in the early flue gas characteristic test platform for battery thermal runaway.

Figure 5 is a structural layout diagram of the airflow organization system in the test container in the early smoke characteristics test platform for battery thermal runaway.

FIG. 6 is a schematic diagram of the assembly of the cylindrical battery and its battery fixture to be tested in Example 1. FIG.

FIG. 7 is a flow chart of the steps of a method for measuring early smoke characteristics of a battery thermal runaway provided in Embodiment 2 of the present invention.

Labeled in the figure:

1. Test container; 10. Sealed door; 11. Battery fixture; 12. Flue duct; 13. Wind speed sensor; 14. Sound pressure sensor; 15. Air pressure sensor; ;19, electrical measurement components; 20, second thermocouple sensor; 21, pressure gauge; 22, air flow organization system; 100, host computer; 101, observation window; 110, smoke hood; Eyebolt; 171. First thermocouple sensor; 172. Gas analyzer; 173. VOC monitor; 181. Sampling pump; 182. Smoke particle sampling device; 201. Binocular camera; 221. High-pressure gas cylinder; 222. Valve Body; 223, gas flow meter; 224, low-speed axial fan; 225, centrifugal fan.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Example 1

This embodiment provides a test platform for early smoke characteristics of a battery thermal runaway, which is used to measure the corresponding early smoke characteristics of a battery under test in a state of thermal runaway caused by different triggering conditions. The test platform provided in this embodiment is an automated test platform operated under the supervision of an operator, and the operation control of the battery thermal runaway process is automatically executed by the test platform, or executed according to a plan under the remote control of the operator. The collection and analysis of test data is automatically completed by the platform. Operators only need to remotely issue test instructions according to the requirements of the operation manual. Specifically, the test platform supports testing battery thermal runaway trigger conditions, including battery being pierced by a sharp object, battery being squeezed by a blunt object, battery body overheating, battery short circuit, and battery thermal runaway faults caused by a combination of the above different triggering conditions.

As shown in Figure 1, the early flue gas characteristic test platform provided by this embodiment includes: test container 1, airflow organization system 22, wind speed sensor 13, sound pressure sensor 15, air pressure sensor, out of control triggering mechanism 16, flue gas online analysis Component 17, sampling device, electrical measurement component 19, and host computer 100. As shown in FIG. 2 , the upper computer 100 is electrically connected to the airflow organization system 22 , the wind speed sensor 13 , the sound pressure sensor 15 , the air pressure sensor, the runaway mechanism 16 , the online analysis mechanism, the sampling device and the electrical measurement component 19 . The host computer 100 is the control center and data processing center of the whole test platform. The host computer 100 can issue control instructions to other instruments or actuators, or collect detection data from instruments and sensors, analyze and process various data, and finally obtain an analysis report on the early characteristics of battery thermal runaway.

Specifically, as shown in FIG. 3 , the test vessel 1 includes a combustion chamber and a flue 12 . A battery fixture 11 is arranged in the center of the combustion chamber, and is connected to the inner wall of the combustion chamber in the test container 1 through a support rod. The battery clamp 11 is used to clamp the battery to be tested, and keep the battery in a state of electrical connection with the electrical measurement assembly 19 during the test. The structure of the battery fixture 11 can be designed according to the shape of the battery to be tested. For example, for a pouch battery or a square battery, it is suitable to be placed on the battery fixture 11 with a mounting slot, while improving the versatility of the test platform for different types of batteries. The battery holder 11 should adopt a replaceable design. The bottom of the combustion chamber is provided with a gas inlet, and the top is provided with an inverted funnel-shaped smoke collection hood 110 , and the gas outlet at the top of the smoke collection hood 110 communicates with a horizontally placed flue 12 . In addition, the test container 1 of this embodiment also includes at least one openable and closable airtight door 10 and at least one transparent observation window 101 . The function of the airtight door 10 is to facilitate the test personnel to carry out safety checks inside the combustion chamber when the test starts and ends, and to correctly install the battery to be tested on the battery fixture 11 . The observation window 101 is made of high-temperature-resistant explosion-proof glass, and the observation window 101 can allow testers to observe the whole process of the thermal runaway state of the battery inside the combustion chamber during the test. Of course, in order to support the testers to observe the scene in the combustion chamber, there should also be a lighting system in the combustion chamber. At the same time, in this embodiment, a fireproof layer is provided on the inner wall of the test container 1 and the surface of some special cables or equipment to prevent the deflagration of the battery to be tested from causing damage to related equipment.

Specifically, in the scheme provided in this embodiment, the required test container 1 is prepared by using a stainless steel plate with high temperature resistance and explosion resistance. In the experimental container 1, the size of the battery combustion chamber is designed according to the actual experimental space requirements. In this embodiment, it is suggested that the inner cavity is a square structure with a size of 1.8m×1.8m×1.8m. The suggested size of the observation window 101 is 0.4m×0.3m, and the suggested size of the airtight door 10 is 1m×1.5m. The suggested dimension of the upper section of the top smoke collecting hood 110 is 0.8m, and the suggested height is 0.9m.

In this embodiment, as shown in Figure 4, the smoke exhaust pipe adopts a square pipe, the recommended length provided in this embodiment is 3m, and the recommended cross-sectional size is 0.4m×0.4m. A steady flow pipe 120 is arranged at the interface between the flue 12 and the combustion chamber. The steady flow pipe 120 is a pipe body containing a uniform mesh-shaped passage inside, and the steady flow pipe 120 can pass through a series of mesh-shaped passages evenly arranged. The "turbulent flow" at the smoke collecting hood 110 is converted into a "steady flow" that is uniform and whose velocity direction is parallel to the extension direction of the smoke exhaust pipe. In this embodiment, a plurality of through holes for installing various detection instruments are evenly opened on the outer wall of the flue 12; when the through holes are not in use, the through holes can be sealed with eyebolts 121 .

The air flow organization system 22 provided in this embodiment is mainly used to introduce the background gas into the test container 1, and form a system so that the background gas enters from the bottom of the combustion chamber, and is lifted vertically under the battery holder 11, and finally along the flue. 12 The gas convection environment discharged from the outlet of the end section.

Specifically, as shown in FIG. 5 , the airflow organization system 22 includes: a high-pressure gas cylinder 221 , a valve body 222 , a gas flow meter 223 , a centrifugal fan 225 , and a low-speed axial fan 224 . The high-pressure gas cylinder 221 is filled with required background gas. The valve body 222 is used to control the valve opening of the high-pressure gas cylinder 221 to discharge the background gas to the combustion chamber. The gas flow meter 223 is respectively installed at the positions of the gas inlet of the combustion chamber and the outlet of the flue 12, and is used to measure the flow of gas flowing through the two places; the centrifugal fan 225 is installed at the end of the flue 12, and is used to transfer the gas in the combustion chamber from the test Drain from container 1. The low-speed axial flow fan 224 is installed at the position where the bottom of the combustion chamber faces the battery holder 11, and is used to generate a vertical upward lift.

During the test, the high-pressure gas cylinder 221 continuously releases background gas from the gas inlet at the bottom of the combustion chamber to the combustion chamber. The smoke generated by the thermal runaway state of the battery body in the middle is "wrapped" to the upper smoke collecting hood 110 . At the same time, the suction effect of the centrifugal fan 225 at the end of the flue 12 will make the internal pressure of the flue 12 lower than the pressure in the combustion chamber, which will cause the mixed smoke in the smoke collecting hood 110 to be continuously "sucked" through the steady flow pipe 120 into the flue 12, and finally discharged from the outlet at the end of the flue 12.

In this embodiment, the flow rate of the gas in the flue 12 can be effectively regulated through joint control of the opening of the valve body 222 , the centrifugal fan 225 and the low-speed axial fan 224 . Specifically, the test platform of this embodiment requires that the wind speed in the flue 12 be maintained at 0.2±0.02 m/s during the test. In order to monitor the flow rate of flue gas, the wind speed sensor 13 is installed in the flue 12 in this embodiment, specifically, the wind speed sensor 13 is installed in the flue 12 10 cm behind the steady flow pipe 120 .

In the air flow organizing system 22 of this embodiment, the two gas flow meters 223 are respectively used to measure the flow rate of the background gas introduced into the system and the flow rate of the gas discharged from the system. The gas flow statistics of the two should be roughly the same in the non-test state, and the flow difference in the test state is caused by the smoke generated by the combustion state of the battery body after thermal runaway.

The test platform of the present embodiment passes into the effect of the background gas in the combustion chamber during the test phase and mainly includes the following two points:

One is to "purify" the gas in the combustion chamber to avoid the original complex gas composition in the combustion chamber or the complex external gas that enters the combustion chamber from affecting the thermal runaway of the battery or the combustion process, while avoiding the original complex gas in the combustion chamber Composition interferes with the analysis of early smoke characteristics after combustion.

The second is to aim at the characteristics of the low smoke content in the early stage of battery thermal runaway, use the background gas as the carrier gas mode to organize the air flow, and ensure that the cost of the smoke can be fully "loaded" into the flue 12, so as to realize the control of the early smoke Accurate measurement of characteristics; avoid early smoke from "accumulating" in the combustion chamber and mixing with smoke from other periods, thereby affecting the reliability of the final test results.

In this embodiment, with regard to the above objectives, the background gas should be chosen to have a composition and density close to that of air, and a gas that does not produce obvious flame retardancy or combustion-supporting gains. At the same time, the background gas should be easy to distinguish and detect, and it should be easy to filter the signal in the later data analysis process. Under such conditions, pure nitrogen was selected as the background gas in this embodiment. In addition, in other embodiments, a mixed gas obtained by mixing nitrogen and oxygen at a substance ratio of 8:2 may also be selected as the background gas. When using mixed gas, the air flow organization system 22 should adopt double gas cylinders to hold nitrogen and oxygen respectively, and pass a gas mixing valve to mix the released gas in the two gas cylinders evenly and then pass in through the gas inlet and outlet at the bottom of the combustion chamber.

In the solution provided by this embodiment, the sound pressure sensor 15 is installed in the combustion chamber and used to measure the noise information of the thermal runaway process of the battery. The air pressure sensor is installed in the combustion chamber and used to measure the status data of the ambient instantaneous air pressure during the battery thermal runaway process. The runaway triggering mechanism 16 is installed at the battery fixture 11, and the runaway triggering mechanism 16 includes an acupuncture actuator, a squeezing actuator and a heating device, which are respectively used to perform acupuncture, squeezing and heating operations on the battery to be tested.

In the product structure design of the early flue gas characteristic test platform of this embodiment, the battery fixture 11 includes a mounting groove, and the electric heating tube in the heating device is installed inside the battery fixture 11 close to the bottom wall of the mounting groove, and is heated The tube can heat the installation groove in the battery fixture 11 to a preset temperature, thereby causing the battery under test to appear in a thermal runaway state due to an excessively high surface temperature. Both the extrusion actuator and the acupuncture actuator are actually implemented by a vertical hydraulic mechanism, which is installed directly above the battery clamp 11 . When the hydraulic mechanism feeds downward, the pressure head at the lower end will exert compressive stress on the battery to be tested in the installation groove. In addition, technicians can also realize the action point and extrusion of the compressive stress by replacing the pressure head with different properties or structures. Adjust the pressure mode. In addition, it is only necessary to install a steel needle at the front end of the pressure head of the hydraulic mechanism to form the required acupuncture actuator and conduct acupuncture tests on the battery.

At the same time, it needs to be specially explained: in order to avoid the hydraulic mechanism from interfering with the convection path of the smoke generated by the thermal runaway of the battery, in a more optimized solution, the machine platform of the hydraulic mechanism in this embodiment can be used along the relative battery fixture 11. The active connection mode that rotates in the horizontal direction. The hydraulic mechanism is rotated to be directly above the battery clamp 11 while performing a squeezing or needling action. After the acupuncture or extruding action is completed, the hydraulic mechanism is lifted upwards and rotated to a position directly above the battery clamp 11 .

The electrical measurement assembly 19 is installed in the battery holder 11 . The electrical measurement component 19 is electrically connected to the battery to be measured through the electrode sheet. The electrical measurement component 19 is used to simulate the charging, discharging and natural state of the battery to be tested, and to obtain the electrical parameters of the battery during the measurement process. In addition, the electrical measurement component 19 is also used to simulate a short-circuit fault of the battery.

In other more optimized technical solutions, a second thermocouple sensor 20 and a pressure gauge 21 may also be arranged on the battery holder 11, and the second thermocouple sensor 20 is used to measure the surface temperature of the battery under test during thermal runaway. The pressure gauge 21 is used to measure the expansion pressure of the battery under test during thermal runaway. The measurement data of the second thermocouple sensor 20 and the pressure gauge 21 are mainly the temperature and shape changes of the battery body. This characteristic data has the following different purposes: (1) The surface temperature and deformation of the battery body itself are important for the thermal runaway of the battery. One of the target observation parameters. (2) In the measurement process of the early smoke characteristics of the battery thermal runaway, the above two characteristics can also be used as one of the criteria for evaluating whether the battery thermal runaway occurs.

In the solution provided in this embodiment, the criteria for whether thermal runaway of the battery occurs under different triggering conditions are different. For example, for lithium batteries, since batteries generally have poor needle penetration resistance, as long as the battery pack to be tested is penetrated, there is a high probability that it will directly cause thermal runaway of the battery. The thermal runaway failure of the battery caused by extrusion or heating will be affected by the deformation of the compressive stress and the temperature rise of the surface temperature. Only when the deformation or temperature rise exceeds the preset limit will the thermal runaway phenomenon occur. At this time, it is necessary to combine the data of the sound pressure sensor 15 to make a comprehensive judgment on whether the thermal runaway of the battery occurs. Generally speaking, after the battery is thermally out of control, it will be accompanied by a violent chemical reaction and cause the battery to bulge or even explode. Therefore, as long as a short but more intense sound pressure signal is detected in this test, it can be determined that the battery is at the corresponding moment. Thermal runaway has occurred.

After the battery surface temperature and expansion pressure are further obtained in this embodiment, the sound pressure data, battery surface temperature and expansion pressure can be used together to more reliably analyze when the battery thermal runaway phenomenon occurs. This is of great significance for more accurately determining whether the collected smoke characteristics belong to the early characteristics of battery thermal runaway.

The flue gas online analysis component 17 in this embodiment includes a first thermocouple sensor 171 , a gas analyzer 172 , and a VOC monitor 173 . Various instruments in the flue gas online analysis component 17 are installed in each through hole on the outer wall of the flue 12 , and the detection elements are inserted into the flue 12 . The first thermocouple sensor 171 is located on the side of the front end of the flue 12 closest to the steady flow tube 120 , and the first thermocouple is mainly used to test the flue gas temperature in the flue 12 . The gas analyzer 172 and the VOC monitor 173 are located on the rear side of the first thermocouple sensor 171. The gas analyzer 172 and the VOC detector have different sensitivities to different gases, and also have different quantitative analysis capabilities. In this embodiment, after installing two online gas composition and concentration analysis instruments at the same time, the two can complement each other to jointly detect the complex gas composition and concentration generated during the thermal runaway process of the battery. Of course, for the gas components that are still unable to be effectively distinguished by the above two online analysis instruments in this embodiment, it is necessary to use a more powerful gas chromatography-mass spectrometer (GC-MS) to analyze the collected gas samples offline come out later.

The sampling device includes a smoke particle sampling device 182 and a smoke sampling device; the smoke particle sampling device 182 adopts a copper mesh carbon film. The acquired smoke particle samples were analyzed by TEM electron microscope to obtain the composition, structure information (such as shape and particle size) and concentration information of the particles contained in the smoke.

The flue gas sampling device includes a sampling pump 181, a sampling tube and a vacuum bag; the sampling pump 181 draws sample gas from the flue 12 through the sampling tube and stores it in the vacuum bag. The collected gas samples were analyzed by gas chromatography-mass spectrometry (GC-MS).

Various instruments in the sampling device are installed in through holes on the outer wall of the flue 12 and are located near the end of the flue 12 . The special design of the installation position of the sampling device is mainly considered to reduce the impact on the detection accuracy of each instrument in the flue gas online analysis component 17, so it is chosen to perform sampling after the aforementioned instruments have completed data collection, and enter and use the collected smoke or flue gas samples to obtain richer sample data.

During the execution of test tasks by the early flue gas characteristic testing platform of this embodiment, the functions of the upper computer 100 can be roughly divided into the following points:

1. Control the air flow organization system 22 to generate a uniform convective background gas environment in the combustion chamber that meets the preset conditions, and ensure that the measured value of the wind speed sensor 13 in the initial state is 0.2±0.02m/s.

2. The out-of-control trigger mechanism 16 or the electrical measurement component 19 triggers the thermal runaway of the battery under test according to the needs of the measurement task, and determines the triggering time of the thermal runaway in combination with the sampling data of the sound pressure sensor 15 .

3. Obtain the real-time measurement data of the online monitoring component, the electrical measurement component 19 and the air pressure sensor.

4. Obtain the test results of the samples collected by the sampling device in the offline device.

5. Comprehensively analyze the online measurement sample data and the test results of the sample offline analysis, and generate a complete analysis report of the early smoke characteristics of the battery thermal runaway.

In the solution provided by this embodiment, the early smoke characteristics test platform may also include a safety system, which is used to inject liquid perfluorohexanone or liquid nitrogen into the combustion chamber after the test, so as to achieve fire prevention and cooling. The function of the safety system is actually to suppress the thermal runaway state of the battery under test after the test is completed, reduce the further risk of deflagration or explosion of the battery, or minimize the hazards of the battery under test that has already undergone deflagration or explosion. In this embodiment, a large number of instruments and equipment are arranged in the combustion chamber, so perfluorohexanone and liquid nitrogen are selected as disaster prevention gases that can both lower the temperature and suppress combustion.

In addition, in the more optimized solution of this embodiment, a binocular camera 201 with infrared and full-color cameras can also be set outside the observation window 101 of the test container 1, and the binocular camera 201 can record the thermal runaway of the battery to be tested. Image data throughout the experiment. In order for researchers to further study the visual characteristics of different stages of battery thermal runaway.

The solution provided in this embodiment will be described in more detail below in combination with the actual operation method and operation process of the early smoke characteristics test platform for battery thermal runaway:

Assuming that the user needs to perform a thermal runaway test on a cylindrical 18650 battery under acupuncture conditions, the hatch of the combustion chamber can be opened first, and the battery can be directly fixed on a battery fixture 11 similar to a U-shaped lock as shown in Figure 6 ;then close the hatch. Next, the equipment will automatically replace the gas inside the test container 1 through the airflow organization system 22, and control the airflow velocity in the flue 12 to reach a preset index. During this process, the flue gas online analysis component 17 will start to work to determine the initial data of various monitoring indicators in the test environment when the battery does not experience thermal runaway. When the data is stable, the test platform will remind the operator to start acupuncture.

After the testers receive the prompt information, they issue acupuncture instructions to the test platform, and the test platform performs acupuncture on the battery through the out-of-control triggering mechanism 16. After the acupuncture action is completed, the out-of-control triggering mechanism 16 automatically resets. At the same time, the controller accurately determines the precise moment when the battery thermal runaway occurs according to the execution time of the out-of-control acupuncture actuator and the changes in the monitoring data of the sound pressure sensor 15 , the second thermocouple sensor 20 , or the pressure gauge 21 .

After the thermal runaway of the battery occurs, the flue gas generated by the violent chemical reaction enters the flue 12 from the combustion chamber under the "load" of the background gas, and the detection signals of the various measuring instruments installed in the flue 12 will change. All detection data will be output to the host computer 100 . When the flue gas generated in the early stage of battery thermal runaway reaches the installation location of the sampling state, the controller controls these sampling states to complete the sample collection in their respective window periods, and sends it to the rear professional instrument for off-line analysis after the test is completed.

After the test, the host computer 100 will determine the various data corresponding to the early stage of thermal runaway in the test signal according to the occurrence time of battery thermal runaway and the precise response time of different measuring instruments; Correct the collected early data of thermal runaway using the correlation signal below.

Example 2

This embodiment provides a method for measuring the early smoke characteristics of the thermal runaway of the battery. Characteristics. Specifically, as shown in Figure 7, the measurement method provided in this embodiment includes the following steps:

1. Debugging stage:

S1: Install the battery to be tested on the battery fixture in the combustion chamber, and seal the combustion chamber.

S2: Replace the gas inside the test container with the background gas, and form a stable and uniform gas convection environment, while controlling the gas flow rate in the flue.

S3: Use detection instruments or sensors to continuously monitor the environmental parameters in the combustion chamber and the flue, and monitor the electrical parameters of the battery.

In this step, a VOC monitor and a gas analyzer are used to jointly monitor the composition and concentration of the flue gas, and a first thermocouple sensor is used to monitor the temperature of the flue gas. The environmental parameters collected include: combustion chamber sound pressure, combustion chamber instantaneous pressure, flue gas temperature, flue gas velocity, composition and concentration of flue gas.

2. Test phase

S4: According to the preset measurement task, one or more operations of heating, extrusion, acupuncture, and short circuit are used to cause thermal runaway of the battery to be tested.

S5: Combining the sound pressure measurement data in the combustion chamber and the execution time of heating, extrusion, acupuncture or short circuit operations to comprehensively judge the thermal runaway occurrence time of the battery under test.

S6: According to the precise response time of each detection instrument or sensor, the detection data is divided into a stage before thermal runaway and a stage after thermal runaway.

And during the window period, the smoke particles and smoke in the flue are sampled through the sampling device; wherein, the window period refers to the period during which the early smoke generated by the thermal runaway of the battery flows through the sampling device.

Specifically, the precise response time of the VOC monitor in this step is:

In the above formula, t _VOC is the initial response time of the VOC monitor; s ₁ is the distance between the VOC monitor and the steady flow tube; f is the wind speed at 10 cm behind the steady flow tube in the thermal runaway state of the battery under test.

The exact response time of the gas analyzer is:

In the above formula, _tgas is the initial response time of the gas analyzer; _s2 is the distance between the gas analyzer and the steady flow tube; d is the diameter of the sampling tube in the gas analyzer, l is the gas analyzer’s The length of the sampling tube, Q is the flow value corresponding to the unit suction of the gas analyzer.

The exact response time of the first thermocouple sensor is:

In the above formula, t _T is the initial response time of the thermocouple; s ₃ is the distance between the first thermocouple sensor and the steady flow tube.

S7: After obtaining the required test data, stop ventilating the combustion chamber, extinguish the fire and cool down the battery to be tested, until the risk of battery deflagration is eliminated.

S8: Perform offline detection on the smoke particles and smoke samples obtained by the sampling device.

S9: Combining the process data of the pre-thermal runaway stage and the post-thermal runaway stage obtained during the online detection process and the experimental data of the offline detection, the early smoke characteristics of the battery to be tested in the thermal runaway state are analyzed and obtained.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (10)

1. The early smoke characteristic test platform for the thermal runaway of the battery is characterized by being used for measuring the corresponding early smoke characteristics of the battery to be tested in the thermal runaway state caused by different initiation conditions; the early stage flue gas characteristic test platform includes:

A test vessel comprising a combustion chamber and a flue; a battery clamp is arranged in the center of the combustion chamber; the bottom of the combustion chamber is provided with a gas inlet, the top of the combustion chamber is provided with a fume collecting hood in an inverted funnel shape, and a gas outlet at the top of the fume collecting hood is communicated with a horizontally placed flue; a steady flow pipe is arranged at the interface between the flue and the combustion chamber, and a plurality of through holes for equipment installation are arranged on the outer wall of the flue;

the airflow organization system is used for introducing background gas into the test container, forming a gas convection environment which enables the background gas to enter from the bottom of the combustion chamber, vertically lift up under the battery clamp and finally discharge along the outlet of the tail section of the flue;

the wind speed sensor is arranged at a position 10cm behind the steady flow pipe in the flue;

a sound pressure sensor installed in the combustion chamber and used for measuring noise information of the battery thermal runaway process;

a gas pressure sensor installed in the combustion chamber and used for measuring state data of an ambient instantaneous gas pressure during thermal runaway of the battery;

the runaway triggering mechanism is arranged at the battery clamp and comprises a needling actuator, an extrusion actuator and a heating device, wherein the needling actuator, the extrusion actuator and the heating device are respectively used for needling, extruding and heating the battery to be tested;

The flue gas online analysis assembly comprises a first thermocouple sensor, a gas analyzer and a VOC monitor; each instrument in the flue gas online analysis assembly is installed in each through hole on the outer wall of the flue, and a detection element is inserted into the flue; the first thermocouple sensor is positioned at one side of the front end of the flue, which is closest to the steady flow pipe, and the gas analyzer and the VOC monitor are positioned at one side, which is back to the first thermocouple sensor;

the sampling device comprises a smoke particle sampling device and a smoke sampling device; each instrument in the sampling device is arranged in a through hole on the outer wall of the flue and is positioned close to the tail end of the flue;

an electrical measurement assembly mounted in the battery clamp; the electrical measurement component is electrically connected with the battery to be measured through the electrode plate, and is used for simulating the charge, discharge and natural states of the battery to be measured and obtaining the electrical parameters of the battery in the measurement process; the electrical measurement assembly is also used for simulating short-circuit faults of the battery;

the upper computer is electrically connected with the airflow organization system, the wind speed sensor, the sound pressure sensor, the air pressure sensor, the runaway triggering mechanism, the online analysis mechanism, the sampling device and the electrical measurement assembly; the upper computer is used for respectively: 1. controlling an airflow organization system to generate a uniform convection background gas environment meeting preset conditions in a combustion chamber, and ensuring that the actual measurement value of a wind speed sensor is 0.2+/-0.02 m/s in an initial state; 2. controlling a runaway triggering mechanism or an electrical measurement assembly to trigger thermal runaway of the battery to be tested according to a test task, and determining the triggering time of the thermal runaway by combining sampling data of a sound pressure sensor; 3. acquiring real-time measurement data of an on-line monitoring assembly, an electrical measurement assembly and an air pressure sensor; 4. acquiring a sample detection result of a sample acquired by a sampling device in off-line equipment; 5. and comprehensively analyzing the sample data measured on line and the detection result of the sample off-line analysis, and generating a complete early smoke characteristic analysis report of the thermal runaway of the battery.

2. The early stage fume characterization test platform for thermal runaway of batteries of claim 1, wherein: the test container also comprises at least one openable sealing door and at least one transparent observation window; a fireproof layer is arranged in the test container;

or alternatively

And a binocular camera with an infrared camera and a full-color camera is arranged outside the observation window of the test container, and the binocular camera is used for recording image data in the thermal runaway test process.

3. The early stage fume characterization test platform for thermal runaway of batteries of claim 2, wherein: the airflow organizing system includes: the high-pressure gas cylinder, the valve body, the gas flowmeter, the centrifugal fan and the low-speed axial flow fan; the high-pressure gas cylinder is filled with the required background gas; the valve body is used for controlling the opening degree of a valve for discharging background gas from the high-pressure gas cylinder to the combustion chamber; the gas flowmeter is respectively arranged at the positions of the gas inlet and the flue outlet of the combustion chamber and is used for measuring the flow of the gas flowing through the two positions; the centrifugal fan is arranged at the tail end of the flue and is used for exhausting gas in the combustion chamber from the test container; the low-speed axial flow fan is arranged at the bottom of the combustion chamber and opposite to the battery clamp, and is used for generating vertical upward lifting force.

4. An early stage fume characterization test platform for thermal runaway of a battery according to claim 3 wherein: the background gas adopts nitrogen or mixed gas obtained by uniformly mixing nitrogen and oxygen through a gas mixing valve according to the mass ratio of 8:2.

5. The early stage fume characterization test platform for thermal runaway of batteries of claim 1, wherein: the battery clamp is also provided with a second thermocouple sensor and a pressure gauge, wherein the second thermocouple sensor is used for measuring the surface temperature of the battery to be measured in the thermal runaway process; the pressure gauge is used for measuring the expansion pressure of the battery to be measured in the thermal runaway process.

6. The early stage fume characterization test platform for thermal runaway of batteries of claim 1, wherein: the battery clamp comprises a mounting groove, and an electric heating pipe in the heating device is arranged in the battery clamp at a position close to the bottom wall of the mounting groove; the extrusion actuator is arranged right above the battery clamp and can rotate along the horizontal direction relative to the battery clamp; the extrusion actuator adopts a downward feeding hydraulic mechanism; and after the steel needle is arranged at the front end of the pressure head of the hydraulic mechanism, the required needling actuator is formed.

7. The early stage fume characterization test platform for thermal runaway of batteries of claim 1, wherein: in the sampling device, the smoke particle sampling device adopts a copper net ultrathin carbon film, and an obtained smoke particle sample is analyzed by adopting a TEM (transmission electron microscope) so as to obtain the components, the structural information and the concentration information of particles contained in the smoke;

the flue gas sampling device comprises a sampling pump, a sampling tube and a vacuum air bag; the sampling pump extracts sample gas from the flue through the sampling tube and stores the sample gas in the vacuum air bag; and the collected gas sample is subjected to sample analysis through a gas chromatograph-mass spectrometer.

8. The early stage fume characterization test platform for thermal runaway of batteries of claim 1, wherein: the early flue gas characteristic test platform also comprises a safety system, wherein the safety system is used for spraying perfluorinated hexanone or liquid nitrogen into the combustion chamber after the test is finished so as to realize fireproof cooling.

9. A measurement method for early smoke characteristics of thermal runaway of a battery is characterized by comprising the following steps: an early smoke characteristic test platform for thermal runaway of the battery according to any one of claims 1-8 is adopted to complete early smoke characteristic analysis of the battery in different thermal runaway states; the measuring method comprises the following steps:

1. Debugging:

s1: mounting a battery to be tested on a battery clamp in a combustion chamber, and sealing the combustion chamber;

s2: the gas in the test container is replaced by the background gas, a stable and uniform gas convection environment is formed, and meanwhile, the gas flow rate in the flue is controlled;

s3: continuously monitoring environmental parameters of the combustion chamber and various places in the flue by adopting a detection instrument or a sensor, and monitoring electric parameters of the battery;

the environmental parameters include: sound pressure of a combustion chamber, instantaneous air pressure of the combustion chamber, temperature of flue gas, wind speed of the flue, composition and concentration of the flue gas;

2. actual measurement stage

S4: one or more operations of heating, extrusion, needling and short circuit are adopted according to a preset measurement task to cause thermal runaway of the battery to be measured;

s5: comprehensively judging the occurrence time of thermal runaway of the battery to be tested by combining sound pressure measurement data in the combustion chamber and the execution time of heating, extrusion, needling or short-circuit operation;

s6: dividing detection data into a pre-thermal runaway stage and a post-thermal runaway stage according to the accurate response time of each detection instrument or sensor; sampling smoke particles and smoke in a flue through a sampling device in a window period;

Wherein the window period refers to a period when early smoke generated by thermal runaway of the battery flows through the sampling device;

s7: after the required test data are obtained, stopping ventilation to the combustion chamber, and extinguishing and cooling the battery to be tested until the explosion risk of the battery is eliminated;

s8: offline detecting the smoke particles and the smoke samples obtained by the sampling device;

s9: and analyzing and obtaining early smoke characteristics of the battery to be tested in the thermal runaway state by combining process data of a pre-thermal runaway stage and a post-thermal runaway stage obtained in an online detection process and experimental data of offline detection.

10. The method for measuring early smoke characteristics of thermal runaway of a battery according to claim 9, wherein: in step S3, the components and the concentration of the flue gas are monitored cooperatively by using a VOC monitor and a gas analyzer, and the temperature of the flue gas is monitored by using a first thermocouple sensor;

in step S6, the accurate response time of the VOC monitor is:

in the above, t _VOC Initial response time for the VOC monitor; s is(s) ₁ The distance between the VOC monitor and the steady flow pipe; f is the wind speed at 10cm behind the control stabilizing tube in the thermal runaway state of the battery to be detected;

the accurate response time of the gas analyzer is as follows:

In the above, t _gas An initial response time for the gas analyzer; s is(s) ₂ Is the distance between the gas analyzer and the steady flow tube; d is the pipe diameter of a sampling pipe in the gas analyzer, l is the length of the sampling pipe in the gas analyzer, and Q is the flow value corresponding to the unit suction of the gas analyzer;

the accurate response time of the first thermocouple sensor is:

in the above, t _T Initial response time for thermocouple; s is(s) ₃ For the distance between the first thermocouple sensor and the steady flow tube。

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