A method for detecting thermal runaway exhaust characteristics of a lithium ion battery

Abstract

The present application relates to the technical field of lithium ion battery thermal safety test, and discloses a kind of lithium ion battery thermal runaway exhaust characteristic detection method, the method relies on low back pressure buffer cavity assembly device, through hardware synchronous acquisition mass loss, exhaust temperature, exhaust rate multiple physical parameters, combined with buffer pressure stabilization, gravity sedimentation separation, whole cavity heat insulation, cross section matching low back pressure structure, reduce the disturbance of detection device to battery exhaust detection process, so that the detection state is closer to actual thermal runaway exhaust state, the present application realizes thermal runaway whole process multiple parameter synchronous accurate measurement, solves the problems that existing detection scheme turbulent flow interference is big, sensor is easy to block, temperature measurement is distorted, back pressure interferes with working condition, parameter acquisition is not synchronous, provides standardized detection basis for battery explosion-proof design and safety optimization.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery thermal safety testing technology, specifically to a method for detecting the thermal runaway exhaust characteristics of lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in new energy vehicles, large-scale energy storage power stations, and other scenarios. When a battery experiences thermal runaway, it instantly releases a high-temperature, high-pressure mixed gas, which carries electrolyte droplets and solid active particles at high speed. Dynamic parameters such as exhaust velocity, flow rate, temperature, and total exhaust mass are the core basis for battery explosion-proof structure design, thermal runaway early warning algorithms, and battery safety optimization. The industry urgently needs standardized testing methods that can reproduce the actual exhaust conditions of batteries and measure multiple parameters simultaneously.

[0003] Existing battery thermal runaway venting detection solutions, such as Chinese patent application CN114279891A, describe an in-situ method for measuring the gas generation rate during lithium-ion battery thermal runaway. The measuring device used directly connects a pitot tube to the battery's safety valve. When battery thermal runaway is triggered, the venting from the battery directly impacts the pitot tube. The instantaneous jet velocity at the battery safety valve is extremely high, creating severe turbulence. This causes violent fluctuations in the pitot tube's differential pressure signal, significantly increasing the error in venting rate calculation and resulting in poor flow velocity measurement accuracy.

[0004] Because of its direct-connection structure, the ejected gas contains particulate matter and electrolyte droplets, which can easily clog and contaminate the sensor. Solid particles and electrolyte droplets ejected during thermal runaway can directly adhere to and clog the Pitot tube pressure sensing orifice and the temperature measuring thermocouple, causing sensor failure in a single test and resulting in extremely high long-term testing and maintenance costs.

[0005] Furthermore, during the measurement process, significant heat loss led to inaccurate and low-quality temperature readings. The high-temperature exhaust gas rapidly dissipated heat into the outside as it flowed through the metal cavity, and without any targeted heat insulation, the collected gas temperature was far lower than the actual exhaust temperature of the battery, rendering the temperature data unreliable.

[0006] Therefore, existing detection methods are unable to accurately obtain the dynamic parameters of exhaust gas during the entire thermal runaway process of lithium-ion batteries, and suffer from technical problems such as low measurement accuracy, distortion of operating conditions, and poor versatility. Summary of the Invention

[0007] The purpose of this invention is to provide a method for detecting the exhaust characteristics of thermal runaway in lithium-ion batteries, so as to solve the problem that the existing detection scheme has large turbulence interference, which leads to inaccurate exhaust rate measurement accuracy.

[0008] This invention provides a method for detecting the thermal runaway exhaust characteristics of lithium-ion batteries. A detection device is used to achieve simultaneous and accurate detection of multiple parameters related to battery thermal runaway exhaust. The detection device includes an electronic scale and a buffer chamber assembly. The electronic scale is used to measure the mass change of the battery before and after thermal runaway. The buffer chamber assembly is used to reduce exhaust turbulence interference and includes a buffer tank and deposition tanks located on both sides of the buffer tank and connected to it. The bottom of the buffer tank has a drain port, and the top has an exhaust port with the same inner diameter as the drain port. The side walls of the buffer tank are provided with differential pressure measurement holes and temperature measurement holes. The detection method includes the following steps: S1. Establishing a leak-free, low-interference testing environment: The battery under test is encapsulated in an explosion-proof, heat-insulating, and sealed shell. The shell has a single discharge port equipped with a safety valve. A fixing clamp is used to secure the battery. The battery is placed on the weighing platform of an electronic scale. The buffer chamber assembly is mounted above the battery, and the drain port of the buffer chamber is sealed to the safety valve. An S-shaped anti-clogging Pitot tube for measuring differential pressure is inserted into the center of the buffer chamber through the differential pressure measuring hole, and the gap in the hole is sealed. Multiple temperature sensors are inserted into the bottom, middle, and top of the buffer chamber through temperature measuring holes, respectively, and the gaps in these holes are sealed. S2. Before the battery thermal runaway is triggered, collect steady-state baseline data from the S-type anti-blocking Pitot tube, multiple armored thermocouples, and a precision electronic scale to establish a detection benchmark. S3. Use a preset abuse triggering method to trigger battery thermal runaway; S4. Collect multi-physical quantity data of the entire thermal runaway process and calculate the average gas temperature, mass loss rate and battery thermal runaway exhaust rate in the buffer tank in real time. S5. Extract the maximum exhaust rate and its occurrence time from the exhaust rate time series, extract the highest gas temperature and its occurrence time from the temperature time series, and calculate the total mass loss and the maximum mass loss rate from the mass data. S6. Integrate all test data and parameters to complete the test of battery thermal runaway exhaust characteristics.

[0009] The beneficial effects of this solution are as follows: By combining a buffer chamber assembly structure with multi-sensor synchronous data acquisition, accurate synchronous detection of multiple parameters throughout the entire thermal runaway gas expulsion process of lithium-ion batteries can be achieved. The buffer chamber assembly effectively reduces gas turbulence and stabilizes the measurement signal; the matching design between the drainage port and the top gas port enables low back pressure detection conditions, avoiding additional flow resistance that inhibits battery gas expulsion, completely restoring the original gas expulsion behavior of the battery, and ensuring the authenticity and reliability of the detection parameters. Simultaneously, the synchronous acquisition of mass, temperature, and differential pressure data provides comprehensive and accurate data support for gas expulsion characteristic analysis, solving the problems of measurement distortion and deviation from the actual operating conditions in existing technologies.

[0010] Furthermore, in step S1, the specific steps for establishing the leakage and low-interference detection conditions include: S101. Place the precision electronic scale horizontally, lay a 10mm thick mica heat insulation board on the scale platform, with each edge of the mica heat insulation board extending at least 20mm beyond the bottom surface of the battery to be tested, place the battery to be tested in the center on the mica heat insulation board, and ensure that the safety valve on the top of the battery is vertically facing upward. S102. Fix the drain port to the battery safety valve and seal it with a 2mm thick flexible graphite gasket on the bottom of the buffer box. S103. Insert the S-type anti-clogging Pitot tube into the buffer box through the side wall hole, so that the pressure sensing end is located at the center of the buffer box cross section, and seal the hole gap with a high temperature resistant graphite gasket; insert multiple Class I K-type armored thermocouples into the corresponding temperature measuring holes respectively, and seal and fix them with ceramic glue. S104. Connect the communication lines of the electronic scale, the Pitot tube transmitter, and the thermocouple transmitter to the data acquisition module to complete the hardware communication matching.

[0011] Beneficial effects: The mica heat insulation plate blocks the transmission of high battery temperature to the electronic scale sensor, avoiding weighing errors caused by high temperature deformation; the flexible graphite gasket is resistant to high temperature and does not produce gas due to high temperature decomposition, which can compensate for the flatness error of the contact surface and eliminate the leakage of high temperature gas; the centrally placed Pitot tube can collect the average static pressure of the cavity, and the multi-point thermocouples can realize the full-range temperature collection; the unified access data acquisition module provides the hardware foundation for subsequent synchronous sampling, and comprehensively ensures the accuracy and sealing of the measurement from the perspective of working condition setup.

[0012] Furthermore, the outer wall of the buffer cavity assembly is fixed by a support frame. The overall height of the buffer cavity assembly is adjusted by adjusting the support frame, and the support frame bolts are tightened after adjustment.

[0013] Beneficial effects: The adjustable support frame can accommodate batteries of different heights and sizes, expanding the applicability of the device; the locking bolts can prevent vibration during testing from causing displacement and air leakage in the cavity, ensuring the stability of the testing conditions.

[0014] Furthermore, in step S2, the data acquisition module is set to a fixed sampling interval of 1 second, and synchronously acquires the electronic scale mass reading, Pitot tube static pressure difference, and temperature values ​​of each thermocouple 60 seconds in advance. The hardware synchronously latches the three acquisition signals, and the sampling time deviation is ≤1ms. The acquired steady-state data is used as the calibration baseline for parameter changes before and after thermal runaway.

[0015] Beneficial effects: The use of hardware synchronous latching technology ensures that the three data channels of quality, temperature and pressure correspond one-to-one at the same time, and the sampling time deviation is controlled within the millisecond level, avoiding parameter matching distortion caused by time-sharing acquisition, and greatly improving the accuracy of dynamic exhaust rate calculation; the early acquisition of baseline data can eliminate the measurement error caused by zero-point drift of the equipment, and provide a precise benchmark for subsequent dynamic parameter calculation.

[0016] Furthermore, the battery thermal runaway triggering methods in step S3 include: heating plate triggering mode: a 430W thin-film heating element is attached to the side of the battery for constant heating until the battery surface temperature rise rate reaches 3℃ / s; overcharge triggering mode: the battery is continuously charged with a constant current of 1C, without voltage upper limit, until the battery internal short circuit, the voltage returns to zero and the surface temperature rise rate reaches 3℃ / s; needle penetration triggering mode: a 5mm diameter tungsten steel needle is used to vertically penetrate the center of the side of the battery at a speed of 20mm / s, with a penetration depth of 50% of the battery thickness, forcing an internal short circuit to trigger thermal runaway; after the triggering is completed, personnel evacuate, and the equipment automatically and continuously collects data throughout the process.

[0017] Beneficial effects: It covers three mainstream abuse triggering modes: heating, overcharging, and needle penetration, and uses the temperature rise rate as the threshold for thermal runaway judgment to standardize the triggering method; the entire process is automated and personnel are evacuated to a safe area after triggering, taking into account both the comprehensiveness of the test scenario and the safety of operation.

[0018] Furthermore, the specific parameter calculation method for step S4 includes: S41. Calculate the real-time average exhaust temperature inside the buffer tank using real-time temperature data from multiple thermocouples. The specific calculation logic is as follows:

[0019] in, It refers to the temperature at various locations inside the buffer tank. Represents the tag number. The weight assigned to different position numbers. The number of data collected; S42. Differentiate the real-time mass data of the electronic scale to obtain the real-time mass loss rate. When the mass loss rate first exceeds 0.01 kg / s, mark the corresponding time as the start time of exhaust. ; S43. Based on the rated capacity C of the battery under test and the effective area A of the battery safety valve, call the pre-calibrated correction coefficient. ; S44. Calculate the battery mass loss rate. Battery mass loss rate It is obtained through the following formula:

[0020] in, Let t represent the mass of the battery device, t represent time, and the data sampling interval be 1 second. S45, Calculate real-time exhaust rate Its calculation logic is as follows:

[0021] in, For correction factor, The effective area of ​​the battery safety valve. This is the universal gas constant. Let be the exhaust temperature of the battery at time t. The exhaust static pressure at time t was measured using an S-type pitot tube. denoted as the average molar mass of the gas.

[0022] Beneficial effects: Multi-point weighted average temperature calculation can eliminate temperature measurement deviations caused by temperature stratification within the cavity. When a single thermocouple fails, the data at that point can be automatically discarded, ensuring the reliability of the temperature measurement process. The mass loss rate accurately determines the exhaust start time, providing a benchmark for parameter timing alignment. By introducing correction coefficients based on battery capacity and safety valve area, and combining parameters such as temperature, static pressure, and gas molar mass, the true exhaust rate is calculated, effectively correcting measurement deviations caused by cavity structure and flow field distribution, and significantly improving the accuracy of exhaust rate parameters.

[0023] Furthermore, step S5 also records the following characteristic parameters: the time difference between the exhaust start time and the trigger start time, the exhaust temperature at the exhaust start time, and the total duration of exhaust.

[0024] Beneficial effects: Extracting multi-dimensional exhaust characteristic parameters not only includes peak data of rate, temperature, and mass, but also supplements auxiliary features such as exhaust delay, onset temperature, and duration, comprehensively characterizing the entire process of battery thermal runaway exhaust, and providing richer data support for battery safety design.

[0025] In step S6, all test data and parameters are integrated, including: integrating mass loss rate-time, exhaust temperature-time, exhaust rate-time time series curves, and all characteristic parameters, and generating a standardized test report.

[0026] Beneficial effects: Automatically integrates timing curves and characteristic parameters and generates standardized reports, reducing errors from manual data processing and improving testing efficiency; the unified report format also ensures the comparability of test results for different batches and models of batteries.

[0027] Furthermore, the buffer chamber assembly is made of 2mm special stainless steel plate or Hastelloy, the buffer tank volume is 500mL, and the deposition tank depth is 15mm; the outer wall of the buffer chamber assembly is covered with a 5mm thick heat insulation layer, which is made of silica aerogel felt or aluminum silicate ceramic fiber felt; among them, the lithium iron phosphate battery test uses a stainless steel chamber, the ternary lithium battery test uses a Hastelloy chamber; the high-precision temperature measurement test uses silica aerogel felt, and the batch comparison test uses aluminum silicate ceramic fiber felt.

[0028] Beneficial effects: Based on the gas corrosion characteristics of lithium iron phosphate and ternary batteries, stainless steel / Hastelloy alloy chambers are matched to balance structural strength and corrosion resistance, extending the service life of the chambers; differentiating between high-precision R&D testing and batch comparative testing scenarios, aerogel / ceramic fiber thermal insulation felts are matched, allowing for flexible adjustment of hardware configuration according to testing needs, balancing equipment cost and measurement accuracy; the outer layer of the entire chamber is insulated to block the heat dissipation of high-temperature gas to the outside, stabilizing the internal temperature field of the chamber, making the collected temperature data closer to the actual exhaust temperature of the battery.

[0029] Furthermore, the correction coefficient The calibration process includes: 1) Select multiple groups of batteries from the same batch and measure the effective area of ​​the safety valve outlet; 2) Perform three complete thermal runaway tests on each battery group, and simultaneously record the original pitot tube exhaust rate and electronic scale mass time sequence data; 3) Integrate the mass loss rate to obtain the total exhaust mass, and convert it to standard exhaust volume; integrate the exhaust rates before and after correction, and solve for each group with the goal of optimal volume matching. The corresponding optimal correction coefficient ; 4) Based on multiple sets of sample data, the correction coefficient formula is fitted using the double log-least squares method, and the fitting correlation coefficient is selected. The results will be stored in the device configuration file, and the correction coefficients will be directly called up for subsequent tests of the same battery model. When the battery model or the buffer chamber assembly structure design is changed, this calibration process will be re-executed.

[0030] Beneficial effects: A standardized correction model based on battery capacity and safety valve area is established, and the fitting coefficients are calibrated using the least squares method. The calibration process is standardized and reproducible. Calibration parameters can be reused for batteries of the same model, supporting testing of multiple battery systems such as square energy storage and ternary / lithium iron phosphate batteries. Data from different battery models can be compared horizontally, greatly improving the universality of the testing scheme and the comparability of test results. Attached Figure Description

[0031] Figure 1 A schematic diagram of the detection state structure of the detection device in Example 1; Figure 2This is a schematic diagram of the exploded structure of the detection device in Example 1; Figure 3 This is a schematic diagram of the buffer cavity assembly structure in Example 1; Figure 4 This is a schematic diagram of the thermal runaway exhaust characteristic detection method in Example 2; Explanation of reference numerals in the attached diagram: 1-Electronic scale, 2-Hardware synchronous acquisition module, 3-Battery under test, 4-Buffer tank, 5-Differential pressure detection mounting hole, 6-Temperature detection mounting hole, 7-Support frame, 8-Host computer, 9-Pitto tube, 10-Sedimentation tank, 11-Exhaust port, 12-Bolt, 13-Fixing clamp, 14-Drainage port. Detailed Implementation

[0032] The following detailed description illustrates the specific implementation method: Example 1: Taking the thermal runaway gas emission detection of a 314Ah lithium iron phosphate square energy storage battery as an example, a square lithium iron phosphate energy storage battery with a rated voltage of 3.2V and a rated capacity of 314Ah is selected. The diameter of the top circular safety valve is 10mm, and the effective area of ​​the safety valve is A=78.5 square millimeters.

[0033] like Figure 1 and Figure 2 As shown, the lithium-ion battery thermal runaway exhaust characteristic detection device disclosed in this embodiment includes an electronic scale 1, a buffer box 4, and a data acquisition component; the electronic scale 1 is used to place the battery 3 under test and measure its weight change.

[0034] The buffer box 4 is mounted on the battery under test 3. A drain port 14 is opened at the bottom of the buffer box 4, which is matched with the safety valve of the battery under test 3. A sedimentation tank 10 is set on the bottom side of the buffer box 4. A differential pressure detection mounting hole 5 and a temperature detection mounting hole 6 are opened on the middle side wall of the buffer box 4. An exhaust port 11 with the same inner diameter as the drain port 14 is provided at the top of the buffer box 4 to realize the low back pressure detection condition, avoid additional flow resistance to suppress battery exhaust, and completely restore the original exhaust behavior of the battery.

[0035] The data acquisition components include a host computer 8, a differential pressure detection unit, a temperature detection unit, and the electronic scale 1. The differential pressure detection unit includes a Pitot tube 9, which passes through the differential pressure detection mounting hole 5 and extends into the center of the buffer box 4, where it is suspended.

[0036] The temperature measuring unit contains three temperature sensors. The measuring heads of the three temperature sensors pass through the temperature detection mounting hole 6 and extend into the bottom, middle and top of the buffer box respectively. The electronic scale 1, Pitot tube 9, and temperature sensor are connected to the hardware synchronous acquisition module 2 via an RS485 communication line. The hardware synchronous acquisition module 2 then transmits the data to the host computer 8 for synchronous acquisition, processing, and storage of the mass, pressure, and temperature parameters of the thermal runaway exhaust.

[0037] Electronic scale 1 is an industrial precision electronic scale with a capacity of 30kg and an accuracy of 0.1g; the platform is covered with a 10mm thick mica heat insulation board, and the four sides of the heat insulation board extend 25mm beyond the bottom of the battery to block high temperature conduction and protect the weighing sensor.

[0038] The buffer box 4 is equipped with height-adjustable support frames 7 on both sides, and the buffer box 4 is fixedly mounted above the battery 3 under test via the support frames 7. The support frames 7 are made of galvanized carbon steel, and a fixed base is provided at the bottom of the support frames 7. The height of the support frames 7 is adjusted by a screw, which can be adjusted up and down by 50mm to accommodate batteries of different heights.

[0039] A 2mm flexible graphite gasket is placed between the drain port 14 of the buffer box 4 and the battery safety valve to seal and prevent leakage.

[0040] Hardware synchronous acquisition module 2, with a fixed 1s sampling interval, synchronous latching deviation of pressure difference, temperature and mass change signals <1ms.

[0041] like Figure 4 As shown, the buffer tank 4 and the deposition tank 10 constitute the buffer chamber assembly. The entire buffer chamber assembly is machined from 2mm special stainless steel plate, forming a rectangular sealed cavity with uniform internal dimensions: length 250mm, width 100mm, and height 200mm. The internal volume of the buffer tank is 5000mL. Symmetrical 15mm deep deposition tanks are arranged on both sides of the tank. The outer wall is covered with 5mm thick silica aerogel insulation felt, with a thermal conductivity ≤0.02W / (m²) at room temperature. K); The inner diameter of the bottom drain port and the top exhaust port is uniformly 20mm to achieve low back pressure with equal cross-sectional area.

[0042] The symmetrical sedimentation tanks on both sides of the tank have the following internal dimensions: 250mm long, 30mm wide, and 15mm deep. The recessed tanks are designed to settle electrolyte droplets and solid particles.

[0043] The differential pressure measuring hole is located at a vertical height of 100mm (center of the cross section) in the cavity, and the temperature measuring holes are located at vertical heights of 30mm (bottom measuring point), 90mm (middle measuring point), and 170mm (top measuring point).

[0044] Pitot tube 9 is an S-type anti-clogging Pitot tube calibrated in the wind tunnel with a pressure range of 0~10kPa. During installation, it is inserted into the center of the cavity cross section of the buffer box 4 through the differential pressure detection mounting hole 5.

[0045] Three Class I K-type armored thermocouples are selected as the temperature sensors and are inserted into three temperature detection mounting holes 6 located on the side wall of the buffer box 4, respectively. After the three Class I K-type armored thermocouples are inserted into their corresponding temperature detection mounting holes, they are sealed with high-temperature resistant graphite gaskets and ceramic adhesive.

[0046] Example 2: like Figure 1 and Figure 4 As shown, the method for detecting the thermal runaway exhaust characteristics of the lithium iron phosphate square energy storage battery in Example 1 is as follows: Step S1: Set up a leak-free, low-interference testing environment: The battery under test is encapsulated in an explosion-proof, heat-insulating, and sealed shell. The explosion-proof, heat-insulating, and sealed shell has a single discharge port with a safety valve installed. Two steel plates are used to clamp the battery under test 3, and the two steel plates are fastened with bolts 12 to form a fixing clamp 13 for the battery under test 3. The fixed battery under test 3 is placed horizontally on the electronic scale 1. A mica heat insulation board is laid on the platform of the electronic scale 1, and the battery under test 3 is placed in the center on the mica heat insulation board, ensuring that the safety valve on the top of the battery is vertically upward.

[0047] The buffer chamber assembly is mounted above the battery 3 under test, and the drain port 14 of the buffer box 4 is connected to the safety valve. A flexible graphite gasket is laid on the bottom surface of the buffer box 4 to seal the connection gap. An S-shaped anti-clogging Pitot tube is inserted into the buffer box through the side wall hole, so that the pressure sensing end is located at the center of the buffer box cross-section. A high-temperature resistant graphite gasket is used to seal the hole gap. Three armored thermocouples are inserted into the bottom, middle and top of the buffer box through temperature measurement holes, respectively, and the gaps of the temperature measurement holes are sealed. The communication lines of the electronic scale, the Pitot tube transmitter, and the thermocouple transmitter are connected to the hardware synchronous acquisition module 2 to complete the hardware communication matching.

[0048] Step S2: Collect calibration baseline parameters. The data acquisition module is set to a sampling interval of 1 second. Before the battery thermal runaway is triggered, the electronic scale mass reading, the pitot tube static pressure difference, and the temperature values ​​of each thermocouple are collected synchronously 60 seconds in advance as calibration baseline parameters for parameter changes before and after the thermal runaway is triggered.

[0049] Step S3: Select one of the following three battery thermal runaway triggering methods to trigger thermal runaway of the battery in this embodiment.

[0050] Three triggering methods are included: heating plate triggering mode: constant heating is achieved by attaching a thin-film heating element to the side of the battery until the surface temperature rise rate reaches 3℃ / s; overcharge triggering mode: the battery is continuously charged with a constant current without voltage upper limit until an internal short circuit occurs, the voltage returns to zero, and the surface temperature rise rate reaches 3℃ / s; needle penetration triggering mode: a tungsten steel needle is inserted into the center of the battery side to force an internal short circuit and trigger thermal runaway. After triggering, personnel evacuate, heating / overcharging / needle penetration operations are stopped, and automatic data acquisition is initiated. This embodiment preferably uses the heating plate triggering mode.

[0051] Step S4: Collect multi-physical quantity data of the entire thermal runaway process, and calculate the average gas temperature, mass loss rate and battery thermal runaway exhaust rate in the buffer tank in real time.

[0052] The specific parameter calculation method for step S4 includes: S41. Calculate the real-time average exhaust temperature inside the buffer tank using real-time temperature data from multiple thermocouples. The specific calculation logic is as follows:

[0053] in, It refers to the temperature at various locations inside the buffer tank. Represents the tag number. The weight assigned to different position numbers. This represents the number of data collected.

[0054] In this embodiment, the weight of the temperature measuring point at the bottom of the buffer tank is... Weight of temperature measuring point in the middle of the buffer box Weight of temperature measuring point on top of buffer tank If a single thermocouple fails, or the reading is below 50℃ or above 1200℃, the data at that point will be automatically removed, and the remaining temperature values ​​will be recalculated by normalizing the weights.

[0055] For example, in this embodiment, the bottom temperature is collected. Central ,top ; but: .

[0056] S42. Differentiate the real-time mass data of the electronic scale to obtain the real-time mass loss rate. Only when three consecutive sampling points consistently exceed this threshold is it marked. ; S43. Based on the rated capacity C of the battery under test and the effective area A of the battery safety valve, call the pre-calibrated correction coefficient. ; S44. Calculate the battery mass loss rate. Battery mass loss rate It is obtained through the following formula:

[0057] in, Let t represent the mass of the battery device, t represent time, and the data sampling interval be 1 second. S45, Calculate real-time exhaust rate Its calculation logic is as follows:

[0058] in, For correction factor, The effective area of ​​the battery safety valve. This is the universal gas constant. Let be the exhaust temperature of the battery at time t. The exhaust static pressure at time t was measured using an S-type pitot tube. denoted as the average molar mass of the gas.

[0059] S5. Record the temporal changes of characteristic parameters, extract the maximum exhaust rate and its occurrence time from the exhaust rate time series, extract the highest gas temperature and its occurrence time from the temperature time series, calculate the total mass loss and the maximum mass loss rate from the mass data; the time difference between the exhaust start time and the trigger start time, the exhaust temperature at the exhaust start time, and the total duration of exhaust.

[0060] Exhaust completion determination: Exhaust is determined to be complete when the mass loss rate is ≤0.0005kg / s for 10 consecutive seconds, and the total exhaust time is recorded.

[0061] S6. Integrate all test data and parameters to form a test report, including: integrating mass loss rate-time, exhaust temperature-time, exhaust rate-time time series curves, and all characteristic parameters, and generating a standardized test report.

[0062] Example 3 For the correction coefficient in Implementation 2 Calibration process: 1) Three groups of 280Ah batteries from the same batch were selected, with the effective areas of the safety valves being respectively... , , Covering multiple groups Ratio operating conditions.

[0063] 2) Perform three complete thermal runaway tests on each battery group, and simultaneously record the original pitot tube exhaust rate and electronic scale mass time sequence data.

[0064] 3) Integrate the mass loss rate to obtain the total exhaust mass, and convert it to standard exhaust volume; integrate the exhaust rates before and after correction, and solve for each group with the goal of optimal volume matching. The corresponding optimal correction coefficient .

[0065] 4) Based on multiple sets of sample data, the formula for the correction coefficient is... The double log-least squares method was used for fitting, and the correlation coefficient was selected. The result is that ( , A linear line with coordinates ) Based on the fitted straight line, we obtain and Numerical values; further measurements will be taken. The value can be directly used to call the corresponding correction coefficient. When changing the battery model or the design of the buffer chamber assembly, re-execute this calibration procedure to calculate the correction factor. .

[0066] The following example illustrates this: After three repeated tests for each group, the average optimal correction coefficient is taken: .

[0067] Double logarithmic fitting: yields Calculate each group , .

[0068] Group 1: C / A: 280 / 50 = 5.6 ≈1.7228, , ≈-1.1239; Group 2: C / A: 280 / 78.5≈3.567 ≈1.2717, , ≈-1.5325; Group 3: C / A: 280 / 50 = 5.6 ≈1.7228, , ≈-1.9519; by Using the sample points, the least squares method is used for linear fitting, with , Perform linear regression to obtain the fitted line. Corresponding parameters: , ; correlation coefficient It meets the qualification requirements.

[0069] The formula for calculating the correction factor for this battery model is as follows: Substitute the samples for verification (second group of samples). ; , and the best measured The results are largely consistent, and the calibration model is valid. The corrected system, once calibrated, can be directly used for subsequent tests of the same battery model. When changing the battery model or the design of the buffer chamber assembly, this calibration procedure should be repeated.

[0070] Based on the corrected parameters, device structural parameters, and measured operating data, the core real-time exhaust rate calculation formula of this invention is fully substituted and calculated as follows: First, the calculation logic is as follows:

[0071] Correction factor obtained after calibration: Effective area of ​​battery safety valve: Universal gas constant: Average molar mass of the thermal runaway exhaust mixture: (Molar mass of gas produced during typical thermal runaway of lithium batteries, industry-standard value).

[0072] Selected measured data at the peak of thermal runaway exhaust: real-time mass loss rate Real-time average exhaust temperature Real-time exhaust static pressure (Standard atmospheric pressure test environment).

[0073] Calculate the ratio of operating parameters: Square root operation: Substitute the values ​​into the master formula to calculate the real-time exhaust rate. : .

[0074] Example 4: The silica aerogel insulation felt in Example 1 can be replaced with 5mm aluminosilicate ceramic fiber felt, which has a temperature resistance of 1260℃ and a thermal conductivity of ≤0.035W / (m²) at room temperature. K). Its advantages are that the cost is only 1 / 5 to 1 / 10 of that of aerogel, it is tear-resistant and durable, and there is no organic fume pollution at high temperatures; the disadvantages are that the heat dissipation is slightly greater for the same thickness, and the absolute temperature measurement accuracy is slightly reduced. This solution can be applied to the comparative testing of multiple battery models. The effectiveness of the comparison can be guaranteed by using the same heat insulation material, which balances the test cost and the comparability of data.

[0075] If the measured ternary lithium battery experiences thermal runaway, the stainless steel buffer chamber assembly in Example 1 needs to be replaced with a Hastelloy chamber. This is because the decomposition of the LiPF6 electrolyte during thermal runaway in a ternary lithium battery produces highly corrosive HF gas. Stainless steel chambers are prone to intergranular corrosion and pitting, contaminating the testing environment. Hastelloy, on the other hand, is resistant to fluorine and chlorine-containing corrosive gases, showing no corrosion during long-term testing. This significantly reduces downtime costs associated with chamber replacement and makes it suitable for long-term cycle testing of ternary lithium batteries.

[0076] The above are merely embodiments of the present invention. Common knowledge such as specific structures and characteristics known in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the technical field to which the invention pertains before the application date or priority date, are able to obtain all prior art in the field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can improve and implement the solution based on the inspiration given in this application and their own capabilities. Some typical known structures or methods should not become obstacles for those skilled in the art to implement this application.

[0077] It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this invention, and these should also be considered within the scope of protection of this invention. These modifications and improvements will not affect the effectiveness of the invention or the practicality of the patent. The scope of protection claimed in this application shall be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for detecting the thermal runaway exhaust characteristics of a lithium-ion battery, characterized in that, A detection device is used to achieve simultaneous and accurate detection of multiple parameters of battery thermal runaway exhaust. The detection device includes an electronic scale and a buffer chamber assembly. The electronic scale is used to measure the mass change of the tested battery before and after thermal runaway. The buffer chamber assembly is used to reduce exhaust turbulence interference and includes a buffer tank and deposition tanks located on both sides of the buffer tank and connected to the buffer tank. The bottom of the buffer tank has a drain port and the top has an exhaust port with the same inner diameter as the drain port. The side walls of the buffer tank are provided with differential pressure measurement holes and temperature measurement holes. The detection method includes the following steps: S1. Establishing a leak-free, low-interference testing environment: The battery under test is encapsulated in an explosion-proof, heat-insulating, and sealed shell. The shell has a single discharge port equipped with a safety valve. A fixing clamp is used to secure the battery. The battery is placed on the weighing platform of an electronic scale. The buffer chamber assembly is mounted above the battery, and the drain port of the buffer chamber is sealed to the safety valve. An S-shaped anti-clogging Pitot tube for measuring differential pressure is inserted into the center of the buffer chamber through the differential pressure measuring hole, and the gap in the hole is sealed. Multiple temperature sensors are inserted into the bottom, middle, and top of the buffer chamber through temperature measuring holes, respectively, and the gaps in these holes are sealed. S2. Before the battery thermal runaway is triggered, collect steady-state baseline data from the S-type anti-blocking Pitot tube, multiple armored thermocouples, and a precision electronic scale to establish a detection benchmark. S3. Battery thermal runaway is triggered by a preset abuse triggering method; S4. Collect multi-physical quantity data of the entire thermal runaway process and calculate the average gas temperature, mass loss rate and battery thermal runaway exhaust rate in the buffer tank in real time. S5. Extract the maximum exhaust rate and its occurrence time from the exhaust rate time series, extract the highest gas temperature and its occurrence time from the temperature time series, and calculate the total mass loss and the maximum mass loss rate from the mass data. S6. Integrate all test data and parameters to complete the test of battery thermal runaway exhaust characteristics.

2. The method for detecting thermal runaway exhaust characteristics of lithium-ion batteries according to claim 1, characterized in that, Step S1 specifically includes: S101. Place the precision electronic scale horizontally, lay a mica heat insulation board on the platform of the electronic scale, place the battery to be tested in the center on the mica heat insulation board, and ensure that the safety valve on the top of the battery is vertically upward. S102. Fix the drain port to the battery safety valve and seal it by laying a flexible graphite gasket on the bottom of the buffer box. S103. Insert the S-type anti-clogging Pitot tube into the buffer box through the side wall hole, so that the pressure sensing end is located at the center of the buffer box cross section, and seal the hole gap with a high temperature resistant graphite gasket; insert multiple thermocouples into the corresponding temperature measuring holes respectively and seal the gap between the thermocouples and the temperature measuring holes. S104. Connect the communication lines of the electronic scale, the Pitot tube transmitter, and the thermocouple transmitter to the data acquisition module to complete the hardware communication matching.

3. The method for detecting the thermal runaway exhaust characteristics of lithium-ion batteries according to claim 1, characterized in that: The outer wall of the buffer cavity assembly is fixed by a support frame. The overall height of the buffer cavity assembly is adjusted by adjusting the support frame, and the support frame bolts are tightened after adjustment.

4. The method for detecting thermal runaway exhaust characteristics of lithium-ion batteries according to claim 1, characterized in that: In step S2, the data acquisition module sets the sampling interval and synchronously acquires the electronic scale mass reading, the pitot tube static pressure difference, and the temperature values ​​of each thermocouple before the battery thermal runaway is triggered, as a calibration baseline for parameter changes after the thermal runaway is triggered.

5. The method for detecting the thermal runaway exhaust characteristics of a lithium-ion battery according to claim 1, characterized in that, The battery thermal runaway triggering methods in step S3 include: Heating plate triggering mode: The battery is heated constantly by a thin film heating element attached to the side of the battery until the battery surface temperature rise rate reaches 3℃ / s; Overcharge trigger mode: The battery is continuously charged with a constant current without voltage limit until the battery is internally short-circuited, the voltage returns to zero, and the surface temperature rise rate reaches 3℃ / s. Needle penetration trigger mode: A tungsten steel needle is inserted into the center of the side of the battery to force an internal short circuit and trigger thermal runaway. Once the trigger is completed, personnel evacuate, and the equipment automatically and continuously collects data throughout the process.

6. The method for detecting thermal runaway exhaust characteristics of lithium-ion batteries according to claim 1, characterized in that, The specific parameter calculation method for step S4 includes: S41. Calculate the real-time average exhaust temperature inside the buffer tank using real-time temperature data from multiple thermocouples. The specific calculation logic is as follows: in, It refers to the temperature at various locations inside the buffer tank. Represents the tag number. The weight assigned to different position numbers; S42. Differentiate the real-time mass data of the electronic scale to obtain the real-time mass loss rate. When the mass loss rate first exceeds 0.01 kg / s, mark the corresponding time as the start time of exhaust. ; S43. Based on the rated capacity C of the battery under test and the effective area A of the battery safety valve, call the pre-calibrated correction coefficient. ; S44. Calculate the battery mass loss rate. Battery mass loss rate It is obtained through the following formula: in, Let t represent the mass of the battery device, t represent time, and the data sampling interval be 1 second. S45, Calculate real-time exhaust rate Its calculation logic is as follows: in, For correction factor, The effective area of ​​the battery safety valve. This is the universal gas constant. Let be the exhaust temperature of the battery at time t. The exhaust static pressure at time t was measured using an S-type pitot tube. denoted as the average molar mass of the gas.

7. The method for detecting thermal runaway exhaust characteristics of lithium-ion batteries according to claim 1, characterized in that: Step S5 also records the following characteristic parameters: the time difference between the exhaust start time and the trigger start time, the exhaust temperature at the exhaust start time, and the total duration of exhaust.

8. The method for detecting thermal runaway exhaust characteristics of lithium-ion batteries according to claim 1, characterized in that: In step S6, all test data and parameters are integrated, including: integrating mass loss rate-time, exhaust temperature-time, exhaust rate-time time series curves, and all characteristic parameters, and generating a standardized test report.

9. The method for detecting the thermal runaway exhaust characteristics of a lithium-ion battery according to claim 2, characterized in that: The buffer box is made of special stainless steel plate or Hastelloy alloy; the outer wall of the buffer box is covered with a heat insulation layer, which is made of silica aerogel felt or aluminum silicate ceramic fiber felt; among them, the lithium iron phosphate battery test uses a stainless steel chamber, the ternary lithium battery test uses a Hastelloy alloy chamber; the high-precision temperature measurement test uses silica aerogel felt, and the batch comparison test uses aluminum silicate ceramic fiber felt.

10. The method for detecting the thermal runaway exhaust characteristics of a lithium-ion battery according to claim 6, characterized in that, The correction coefficient The calibration process includes: 1) Select multiple sets of batteries from the same batch, with the same rated capacity, but different effective areas of the safety valve; 2) Each group of batteries was tested at least three times to collect the original exhaust rate and real-time mass loss rate data simultaneously; 3) The standard total exhaust volume is converted by integrating the mass loss, and the inverse solution is used to obtain different... The optimal ratio The value and correction coefficient satisfy the formula ,in and These are the fitting coefficients for this battery model; 4) Based on multiple sets of sample data, the correction coefficient formula is fitted using the double log-least squares method, and the fitting correlation coefficient is selected. The results yielded the fitting coefficients. , The fitting coefficients are stored in the device configuration file and can be directly called for subsequent tests of the same battery model. When the battery model or the structure design of the buffer chamber assembly is changed, this calibration process is re-executed.

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