Heat insulation heating device and method based on laser absorption spectrum tomography

Abstract

The invention relates to an adiabatic thermal device and method based on laser absorption spectrum tomography, which are suitable for application scenes requiring high precision, high sensitivity, dynamic quick response and lithium battery thermal runaway gas production temperature data measurement. The invention designs a battery thermal runaway measuring device combining thermal insulation heat and tunable semiconductor laser absorption spectroscopy (TDLAS) tomography, and the thermal runaway of the lithium battery can be measured by accurately measuring and reconstructing data signals of a two-dimensional temperature field of gas produced by the thermal runaway of the lithium battery and combining the gas production pressure, the temperature of the lithium battery and current and voltage data. And high-precision and high-sensitivity dynamic measurement of the thermal runaway process of the lithium battery is realized. The method solves the problems that a traditional temperature measurement method cannot realize lithium battery thermal runaway gas production temperature space distribution measurement and gas temperature measurement dynamic response lags behind, and provides support for lithium battery thermal runaway mechanism research.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery safety detection, and in particular to an adiabatic thermal device and method based on laser absorption spectroscopy tomography. Background Art

[0002] Accurately measuring the gas temperature field during thermal runaway of lithium batteries is key to assessing their safety. Thermal runaway of lithium batteries is a complex multi-physics coupling process involving electrochemical reactions, heat conduction, gas generation, and flow. The spatiotemporal distribution of the gas temperature field directly reflects the severity of the thermal runaway and the energy release characteristics. Traditional detection methods have the following core issues:

[0003] 1. Traditional thermocouple temperature measurement has the problems of low spatial resolution and slow dynamic response, making it difficult to capture transient high-temperature gas distribution. In addition, as a contact temperature measurement element, the thermocouple needs to be inserted into the gas flow field, which easily interferes with the flow field distribution and affects the measurement of the gas production temperature field and the construction of the data model.

[0004] 2. Although a single calorimetric system, such as an adiabatic calorimeter, can accurately measure the temperature rise and heat release of the battery body, it cannot obtain the spatial temperature distribution of thermal runaway gas production. It is difficult to establish a full-chain energy transfer model of "internal heat accumulation in the battery - gas production injection - external flame spread", and it cannot be correlated with the gas production temperature field in real time, resulting in a lack of multi-dimensional data support for the analysis of thermal runaway mechanisms.

[0005] 3. Tunable semiconductor laser absorption spectroscopy technology TDLAS is based on the principle of laser absorption spectroscopy and can realize non-contact gas temperature measurement. However, in the scenario of thermal runaway temperature measurement of lithium batteries, TDLAS is often arranged in an array, requiring multiple pairs of TDLAS sensors to work together. The measurement instrument is relatively expensive, and it does not achieve deep coupling with the adiabatic acceleration calorimetry system in the time-space dimension. It is impossible to synchronously obtain the gas production temperature field and calorimetric parameters (such as pressure, strain, and gas composition), which limits the possibility of multi-physics field coupling analysis. Summary of the Invention

[0006] In response to the above problems, the present invention provides an adiabatic thermal measurement device and method based on laser absorption spectroscopy tomography, which solves the problems in the prior art of being unable to measure the spatial distribution of gas production temperature during thermal runaway of lithium batteries and the dynamic response lag of gas temperature measurement.

[0007] The present invention provides an adiabatic heating device based on laser absorption spectroscopy tomography, comprising:

[0008] Adiabatic calorimeter, used to perform adiabatic calorimetry testing on lithium batteries;

[0009] A rotating platform is installed at the bottom of the furnace of the adiabatic calorimeter and is used to support and drive the temperature sensor to move along the circumference of the furnace;

[0010] A TDLAS temperature sensor is mounted on the rotating platform and is used to measure the temperature of the gas generated during the thermal runaway of the lithium battery;

[0011] Among them, the upper part of the furnace body of the adiabatic calorimeter is made of light-transmitting, heat-insulating and high-temperature resistant material. The TDLAS temperature sensor includes a laser generator and a receiver. The laser emitted by the laser generator passes through the gas space in the furnace body, and the receiver receives the laser signal after being absorbed by the gas, which is used to measure the gas temperature based on the principle of laser absorption spectroscopy.

[0012] The present invention provides an adiabatic calorimetry method based on laser absorption spectroscopy tomography, using the above-mentioned device, and comprising the following steps:

[0013] Step 1. Place the lithium battery sample into the furnace of the adiabatic calorimeter;

[0014] Step 2. Start the rotating platform to make the TDLAS temperature sensor move in a circular motion around the furnace body, performing a tomographic scan of the gas inside the furnace;

[0015] Step 3. Measure the temperature of the gas generated during the thermal runaway of the lithium battery using a TDLAS temperature sensor, and obtain the absorption spectrum of the gas based on the principle of laser absorption spectroscopy;

[0016] Step 4. Reconstruct the two-dimensional temperature field using an image reconstruction algorithm based on the absorption spectrum to obtain a gas temperature distribution map across the entire measurement cross section.

[0017] Step 5. Synchronously measure the temperature, current, voltage of the lithium battery and the pressure changes in the furnace to achieve joint analysis of multi-dimensional parameters.

[0018] Beneficial effects of the present invention:

[0019] 1. Based on the single TDLAS temperature measurement technology, this invention constructs the key technology research and system of temperature field tomography and analysis, improves the millisecond-level dynamic response and millimeter-level spatial positioning capability of the temperature field during the thermal runaway gas production process of lithium batteries, optimizes the two-dimensional temperature distribution iterative approximation and dynamic visualization image model, and provides innovative theories and technologies for the precise measurement and analysis of temperature fields.

[0020] 2. This invention integrates the adiabatic calorimetry and TDLA gas production temperature measurement systems in physical space through design, enabling synchronous signal acquisition of the two systems in time and space, and providing an adaptive integrated solution for lithium battery thermal runaway gas production temperature monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For ease of explanation, the present invention is described in detail with reference to the following drawings.

[0022] Figure 1The figure shows the structure of the heat insulation device based on laser absorption spectroscopy tomography;

[0023] Figure 2 This is a flow chart of the temperature measurement and analysis method;

[0024] Figure 3 This is the gas temperature distribution diagram on the furnace cross section. DETAILED DESCRIPTION

[0025] The present invention provides an adiabatic calorimetry device and method based on laser absorption spectroscopy tomography. The method is described in detail below with reference to the accompanying drawings and examples.

[0026] like Figure 1 As shown, an embodiment of the present application provides an adiabatic calorimetry device for lithium batteries based on laser absorption spectroscopy tomography, which consists of an adiabatic calorimeter, a rotating platform and a TDLAS temperature sensor. After being clamped by a fixture 3, the TDLAS sensor is mounted on a rotatable turntable 5 and moves in a uniform circular motion around the furnace body. The TDLAS sensor consists of a laser generator 1 and a receiver 2. The generator emits a laser to pass through the gas space of the furnace body (i.e., the adiabatic combustion field 4). The receiver receives a portion of the light signal absorbed by the gas and records the incident light intensity and the received light intensity of the laser. The device is based on tunable semiconductor laser absorption spectroscopy (TDLAS) tomography temperature measurement technology to achieve high-precision spatial reconstruction of the two-dimensional temperature field of gas production during thermal runaway of lithium batteries, quantification of dynamic response characteristics, and coordinated measurement with calorimetric parameters.

[0027] In some embodiments, the upper furnace body (equipped with a furnace cover 6) of the adiabatic calorimeter in this device should be made of high-temperature resistant glass 7 with high light transmittance and excellent thermal insulation. The height of the high-temperature resistant glass in the upper furnace body should be 1 / 10H to 1 / 2H of the total furnace height H, and the height from the furnace bottom should be 1 / 2H to 9 / 10H. The device is equipped with a 360° rotating platform mounted at the bottom of the adiabatic calorimeter furnace. A high-precision servo motor controls the uniform rotation of the turntable, driving the TDLAS temperature sensor mounted on the turntable to rotate uniformly around the calorimetric furnace.

[0028] Furthermore, before the measurement begins, ensure that the signal generating and receiving probes are on the same diameter, use an infrared zero calibration device to calibrate the positions of the generator and receiver, and record data at more than 20 points per rotation during the rotation process.

[0029] When conducting adiabatic thermal testing of lithium-ion batteries for thermal runaway, the absorption spectrum of the gas molecules is obtained based on the interaction between the laser and the gas molecules generated by the thermal runaway of the lithium-ion battery and the gas molecules' selective absorption characteristics of laser light of a specific wavelength. Based on the Beer-Lambert law, the amount of laser light of a specific frequency absorbed by the gas molecules generated by the thermal runaway of the lithium-ion battery is only related to the temperature. The gas temperature can be inverted based on the gas molecule absorption spectrum measured by the TDLAS sensor to obtain the two-dimensional temperature distribution of the gas generated by the thermal runaway of the lithium-ion battery within the adiabatic furnace. The specific principle is shown in the following formula:

[0030]

[0031] in is the absorbance, dimensionless, indicating the degree of absorption of light by a substance. is the incident light intensity, is the transmitted light intensity. is the molar absorptivity, in units of It is a characteristic constant of a substance, reflecting the substance's ability to absorb light of a specific wavelength. It is related to the properties of the absorbing substance, the wavelength of the incident light, etc. is the molar concentration of the absorbing substance, in units of . is the absorption layer thickness (optical path), the unit is , refers to the distance light travels in an absorbing medium.

[0032] Based on the two-dimensional temperature field measured by the TDLAS sensor, the image reconstruction algorithm is used to obtain the gas temperature distribution map on the entire measurement section, completing high-precision and high-sensitivity dynamic measurement of the gas production temperature of lithium battery thermal runaway.

[0033] When conducting lithium battery thermal runaway tests on an adiabatic thermal device based on laser absorption spectral tomography, the lithium battery temperature, current and voltage, gas production temperature distribution, and gas production pressure are measured simultaneously to achieve multi-dimensional parameter joint analysis of the thermal runaway process.

[0034] In some embodiments, a two-dimensional temperature field image reconstruction algorithm based on laser absorption spectroscopy tomography is established, namely, an algebraic iterative reconstruction ART algorithm. The specific calculation process is as follows:

[0035] The incident light intensity and the transmitted light intensity satisfy the Beer-Lambert law:

[0036]

[0037] in is the total gas pressure, is the spectral absorption coefficient, Optical path is the spectral absorbance; is the mole fraction of the absorbing component is the line intensity, which is related to temperature Function is a linear function, satisfy , considering the combined effects of temperature and pressure under thermal runaway conditions of lithium batteries, the Voigt linear function is generally selected, which is a linear function formed by the convolution of the Gaussian function and the Lorentz function:

[0038]

[0039] Defining the integrated absorption rate for:

[0040]

[0041] Combining the algebraic iterative reconstruction ART algorithm with regularization constraints, an image optimization model is established, and the iterative approximation and dynamic visualization technology of two-dimensional temperature distribution is developed to achieve the mathematical and physical reconstruction of line integral to surface temperature field.

[0042] Going further, the algebraic iterative reconstruction ART algorithm is as follows:

[0043] First, the pixel values of the image Initialize and set all pixel values to an initial value or a reasonable estimate (superscript represents the 0th iteration), and then Iterations ( ), process each projection equation in turn. The projection equation ( ), calculate the difference between the current estimated projection value and the actual measured projection value:

[0044]

[0045] Then update the pixel value based on this difference:

[0046]

[0047] When the termination condition is met:

[0048]

[0049] That is, when the error between the projection estimate and the actual measurement value is less than a certain threshold, the algorithm is considered to have converged and the iteration is stopped. It is the pixel value of the reconstructed image.

[0050] in is the relaxation factor, , used to control the update step size of each iteration to adjust the convergence speed and stability of the algorithm, A set small positive number.

[0051] like Figure 2 As shown, the embodiment of the present application also provides an adiabatic calorimetry method based on laser absorption spectroscopy tomography, comprising the following steps:

[0052] Step 1. Place a typical lithium battery sample (e.g., NCM811 square lithium battery sample) into the cylindrical adiabatic calorimeter furnace.

[0053] Step 2. Laminating the high-sensitivity thermocouple array to the surface of the lithium battery cell;

[0054] Step 3. Close the pressure relief valve and the on-off gas valve of the furnace body to ensure that the entire device is airtight and thermally insulated;

[0055] Step 4. Perform infrared calibration between the TDLAS transmitter and receiver to confirm that the TDLAS sensor is working properly and determine the TDLAS sensor position signal;

[0056] Step 5. Set the parameter signals of the reducer and servo motor drive unit to enable the servo motor to drive the TDLAS sensor to rotate at a constant speed to perform tomographic scanning inside the furnace;

[0057] Step 6. Set the adiabatic calorimetry test parameters, start the heating assembly to heat the sample pool, use the temperature sensor to monitor the temperature in the sample pool in real time, and adjust the output power of the calorimeter heating assembly based on the comparison between the measured temperature and the set temperature;

[0058] Step 7. After detecting that the sample has begun to react, active heating is stopped and the output power of the calorimeter heating component is adjusted based on the temperature feedback measured by the temperature sensor, tracking the temperature changes in the sample cell in real time;

[0059] Step 8. Perform tomographic measurements using the TDLAS temperature measurement module to obtain the absorption spectrum of the gas molecules generated during the reaction to a laser of a specific frequency. A pressure sensor is used to monitor pressure changes within the furnace, while simultaneously recording voltage and current signals to achieve multi-dimensional signal acquisition.

[0060] Step 9. Perform two-dimensional image reconstruction on the tomography data to obtain a gas production temperature distribution image;

[0061] Step 10. After the test, perform pressure relief and rapid cooling.

[0062] The gas temperature distribution diagram on the furnace cross section obtained after reconstruction of the gas production temperature data obtained from the test is as follows: Figure 3As shown, high-precision measurement of the spatial distribution of gas production temperature of lithium batteries is achieved.

[0063] The foregoing description is merely one or more embodiments of this specification and is not intended to limit this specification. It will be apparent to those skilled in the art that various modifications and variations may be made to one or more embodiments of this specification. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of one or more embodiments of this specification are intended to be within the scope of the claims of this specification.

Claims

1. An adiabatic calorimeter based on laser absorption spectroscopy tomography, characterized in that: include: Adiabatic calorimeter, used to perform adiabatic calorimetry testing on lithium batteries; A rotating platform is installed at the bottom of the furnace of the adiabatic calorimeter and is used to support and drive the temperature sensor to move along the circumference of the furnace; A TDLAS temperature sensor is mounted on the rotating platform and is used to measure the temperature of the gas generated during the thermal runaway of the lithium battery; Among them, the upper part of the furnace body of the adiabatic calorimeter is made of light-transmitting, heat-insulating and high-temperature resistant material. The TDLAS temperature sensor includes a laser generator and a receiver. The laser emitted by the laser generator passes through the gas space in the furnace body, and the receiver receives the laser signal after being absorbed by the gas, which is used to measure the gas temperature based on the principle of laser absorption spectroscopy.

2. The adiabatic heating device based on laser absorption spectroscopy tomography according to claim 1, characterized in that: The rotating platform is driven by a high-precision servo motor and can achieve uniform rotation. The TDLAS temperature sensor records data at least 20 points per rotation during the rotation process.

3. The adiabatic heating device based on laser absorption spectroscopy tomography according to claim 1 or 2, characterized in that: It also includes an infrared zero calibration device for calibrating the positions of the laser generator and receiver of the TDLAS temperature sensor to ensure that they are on the same diameter.

4. The adiabatic heating device based on laser absorption spectroscopy tomography according to claim 3, characterized in that: The adiabatic calorimeter also includes a high-sensitivity thermocouple array for measuring the temperature of the surface of the lithium battery cell.

5. The adiabatic heating device based on laser absorption spectroscopy tomography according to claim 3, characterized in that: It also includes a data processing unit for receiving the gas temperature data measured by the TDLAS temperature sensor, and reconstructing the two-dimensional temperature field through an image reconstruction algorithm to obtain a gas temperature distribution map on the entire measurement section.

6. The adiabatic heating device based on laser absorption spectroscopy tomography according to claim 5, characterized in that: The image reconstruction algorithm is an algebraic iterative reconstruction ART algorithm, which is combined with regularization constraints to achieve mathematical and physical reconstruction of the surface temperature field from line integrals.

7. A method for adiabatic calorimetry based on laser absorption spectroscopy tomography, using the device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1. Place the lithium battery sample into the furnace of the adiabatic calorimeter; Step 2. Start the rotating platform to make the TDLAS temperature sensor move in a circular motion around the furnace body, performing a tomographic scan of the gas inside the furnace; Step 3. Measure the temperature of the gas generated during the thermal runaway of the lithium battery using a TDLAS temperature sensor, and obtain the absorption spectrum of the gas based on the principle of laser absorption spectroscopy; Step 4. Reconstruct the two-dimensional temperature field using an image reconstruction algorithm based on the absorption spectrum to obtain a gas temperature distribution map across the entire measurement cross section. Step 5. Synchronously measure the temperature, current, voltage of the lithium battery and the pressure changes in the furnace to achieve joint analysis of multi-dimensional parameters.

8. The adiabatic calorimetry method based on laser absorption spectroscopy tomography according to claim 7, characterized in that: In step 3, the TDLAS temperature sensor includes a laser generator and a receiver. The laser emitted by the laser generator passes through the gas space in the furnace body. The receiver receives the laser signal absorbed by the gas and calculates the gas temperature based on the Beer-Lambert law.

9. The adiabatic calorimetry method based on laser absorption spectroscopy tomography according to claim 7, characterized in that: Before step 1, the method further includes: using an infrared zero calibration device to calibrate the positions of the laser generator and receiver of the TDLAS temperature sensor to ensure that they are on the same diameter.

10. The adiabatic calorimetry method based on laser absorption spectroscopy tomography according to claim 7, characterized in that: In step 5, the method further includes measuring the surface temperature of the lithium battery cell by using a high-sensitivity thermocouple array.

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