CN111812529A - A test method for aging thermal runaway of lithium-ion batteries under time-varying cycle conditions - Google Patents

Abstract

The invention provides a method for testing the aging thermal runaway of lithium ion batteries under time-varying cycle conditions. The aging test of the battery is carried out in the time-varying cycle condition to analyze the evolution process of battery performance, and the adiabatic accelerated calorimetry of the test batteries in different aging stages is extracted. The thermal runaway test of the battery is carried out in the instrument to obtain the thermal runaway characteristic temperature of the battery in different aging stages. Based on the results of the thermal runaway test, the change law of the thermal runaway characteristics of the battery in the entire life cycle and the coupling relationship between thermal runaway and aging mechanism are studied. , and the effect of different aging conditions on the thermal runaway characteristics of the battery.

Description

A test method for aging thermal runaway of lithium-ion batteries under time-varying cycle conditions

technical field

The invention belongs to the technical field of new energy vehicle power batteries, in particular to a method for testing the aging and thermal runaway of lithium ion batteries under time-varying cycle conditions.

Background technique

Lithium-ion batteries have the advantages of high specific energy, high specific power, long life, no memory effect, and environmental protection. They are widely used in electric vehicles and have become the preferred type of electric vehicle power batteries.

In recent years, with the popularization of electric vehicles, spontaneous combustion accidents of electric vehicles continue to occur, mainly due to the thermal runaway of the battery system. During the use of the battery, along with the side reactions of the charging and discharging process, the internal components will gradually age, and there will be aging phenomena such as SEI film thickening, loss of active lithium ions, lithium precipitation, and current collector corrosion, which will affect the battery's performance. At the same time, these side reaction products also have a great influence on the thermal runaway of the battery. When a thermal runaway failure occurs in the battery system, a series of exothermic chain reactions will occur inside it, causing the battery temperature to rise. When these reactions are out of control, accidents such as smoke, fire and combustion will occur, resulting in personnel and property losses. Safety accidents caused by thermal runaway of battery systems have become one of the key factors restricting the development of electric vehicles.

Therefore, how to effectively prevent the occurrence of thermal runaway, as well as how to detect thermal runaway in advance and give an early warning, is extremely important and urgent. Researchers have carried out a lot of research work on thermal runaway and abuse of batteries, however, the reasons that cause thermal runaway to occur and cause the battery temperature to rise sharply are still unclear. In addition, at present, when conducting battery thermal runaway test research, almost all new batteries are used as the research object, and the research conclusions obtained in this way cannot practically correspond to the thermal runaway problem of lithium-ion batteries in actual operating conditions.

SUMMARY OF THE INVENTION

In order to overcome the problems existing in the prior art, the present invention is designed. process, and extract the test batteries of different aging stages to conduct the thermal runaway test of the battery in the Accelerating Rate Calorimetry (ARC) to obtain the thermal runaway characteristic temperature of the battery in different aging stages. Based on the thermal runaway test results, the research and analysis In the whole life cycle of the battery, the change rule of thermal runaway characteristics, the coupling relationship between thermal runaway and aging mechanism, and the influence of different aging conditions on the thermal runaway characteristics of batteries.

The object of the present invention is to provide a lithium-ion battery aging thermal runaway test method under a time-varying cycle condition, comprising the following steps:

S1. Select a set of lithium ion battery cells for testing, wherein the set of lithium ion battery cells for testing includes several lithium ion battery cells with the same type and material system;

S2. Perform an aging test on each test lithium-ion battery cell in the selected test lithium-ion battery cell set according to different preset test temperatures and/or different time-varying cycle conditions, and perform an aging test during the aging test process. The battery voltage, current and temperature data of the lithium-ion battery cells are collected in the process, and the capacity test is carried out at the same time. Aged Li-ion battery cells with different capacity fade ratios are included in the collection;

S3. Use the external characteristic analysis method to analyze the aging test data of the aging lithium-ion battery cell set, so as to quantitatively compare and analyze the attenuation mechanism of the aging lithium-ion battery cell set;

S4. Use an adiabatic acceleration calorimeter to perform a battery thermal runaway test on each aged lithium-ion battery cell in the aged lithium-ion battery cell set, and perform a battery thermal runaway test according to the battery cell temperature data and temperature rise rate of each aged lithium-ion battery cell The data obtains the thermal runaway characteristic temperature of the aging lithium-ion battery cell corresponding to different test temperatures and/or different capacity decay ratios;

S5. Based on the thermal runaway characteristic temperature of the aging lithium-ion battery cell at different test temperatures and/or different capacity decay ratios, the change rule of the thermal runaway characteristics in the whole life cycle of the lithium-ion battery is obtained, and the coupling relationship between the thermal runaway and the aging mechanism is analyzed, and The effects of aging of lithium-ion batteries on thermal runaway characteristics under different test temperatures and/or different time-varying cycle conditions were analyzed.

Preferably, the method for selecting a set of test lithium-ion battery cells in the step S1 is: measuring battery capacity, open-circuit voltage and/or internal resistance for the test lithium-ion battery cells, and screening out relative Lithium-ion battery cells for testing with high consistency constitute a collection of lithium-ion battery cells for testing.

Preferably, the step S2 includes:

S21, according to the selected time-varying cycle condition, discharge the lithium-ion battery cell for the test to 20% of the power;

S22, charging the discharged test lithium-ion battery to 100% power to form a complete cycle condition;

S23. Collect the battery voltage, current and temperature data of the lithium-ion battery cell during the complete cycle condition, and repeat the step S21 to the step S22 until the test lithium-ion battery cell completes 20 complete cycles. The capacity test is carried out again, and the aging test is divided into segments according to the capacity decay ratio;

S24. Repeat the step S21 to the step S23 for a plurality of test lithium-ion battery cells to obtain aged lithium-ion battery cells with different attenuation ratios.

Preferably, in the step S2, performing the aging test for each lithium-ion battery cell according to the preset different time-varying cycle conditions includes: adopting the power battery cycle life test of the pure electric passenger vehicle of the relevant national standard GB/T 31484 Aging test using energy-based battery main discharge condition and dynamic stress condition; or using New European Test Cycle (NEDC), US Federal Vehicle Test Standard Procedure (FTP75), World Light Vehicle Test Cycle (WLTC), Japanese Motor Vehicle Test Aging test of battery equivalent test condition converted from working condition (JC08) or Chinese working condition (CATC).

Preferably, the aging test for each lithium-ion battery cell according to the preset different time-varying cycle conditions in the step S2 is performed under a selected constant temperature condition, and the selected constant temperature condition is 0°C, 25°C or 45°C.

Preferably, the different lithium-ion battery capacity decay ratios preset in the step S2 include new battery, 5% decay, 10% decay, 15% decay and 20% decay, so that the battery aging process is divided into five stages.

Preferably, the external characteristic analysis method in step S3 includes: incremental capacity method, differential voltage method, differential thermovoltage method and/or electrochemical impedance spectroscopy.

Preferably, the step S4 includes the following steps:

S41. Set the adiabatic acceleration calorimeter to 25°C, and place an aged lithium-ion battery cell in the adiabatic acceleration calorimeter experimental environment at 25°C for at least 24 hours;

S42, heating the aging lithium-ion battery cell, and simultaneously detecting the temperature and heating rate of the aging lithium-ion battery cell;

S43, when it is detected that the heating rate of the aging lithium-ion battery cell exceeds 0.02 °C/min, it is determined that the aging lithium-ion battery cell has entered a self-heating state, and the adiabatic acceleration calorimeter is transferred to the adiabatic working mode;

S44, the aging lithium-ion battery cell is self-heated in the adiabatic working mode until thermal runaway occurs, and the test is ended and the thermal runaway characteristic temperature of the aging lithium-ion battery cell is recorded;

S45. Repeat steps S41 to S44 for all remaining aged lithium-ion battery cells to obtain the thermal runaway characteristic temperatures of the aged lithium-ion battery cells corresponding to different capacity decay ratios.

Preferably, the method of heating the aged lithium-ion battery cells in the step S42 is performed in a heating setting with a heating step of 5° C. and a temperature stabilization duration of 10 minutes for each step.

Preferably, the thermal runaway characteristic temperature in the step S45 includes: self-heating temperature, thermal runaway trigger temperature and thermal runaway maximum temperature; the self-heating temperature is when the heating rate of the aged lithium-ion battery cell reaches 0.02°C/min The temperature of the battery cell of the thermal runaway; the thermal runaway trigger temperature is the temperature of the battery cell when the heating rate of the aging lithium-ion battery cell reaches 1°C/s; the maximum temperature of the thermal runaway is the aging lithium-ion battery cell during the test process. maximum temperature reached.

The beneficial effects of adopting the above technical solutions are:

Using the aging thermal runaway test method for lithium ion batteries under the time-varying cycle condition of the present invention, the aging test and the thermal runaway test are carried out in the time-varying cycle condition, the discharge current or power of the battery in a single cycle changes dynamically with time, and the cycle There is charging that represents energy feedback, which can better simulate the actual working conditions of the battery in the actual vehicle; the thermal runaway test of the battery at different aging stages can be used to study the change law of the thermal runaway characteristics of the battery throughout the life cycle. It is possible to compare the difference of the thermal runaway variation law of the battery in the whole life cycle under different time-varying cycle conditions; the invention realizes the difference research on the thermal runaway characteristics of the same material system battery, different time-varying cycle conditions and different aging stages , it is also possible to study the difference of thermal runaway characteristics of batteries with different material systems under the same time-varying cycle conditions and the same aging stage; the invention links the aging mechanism of the battery under different time-varying cycle conditions with the thermal runaway characteristics. , the coupling relationship between the aging law and the change law of thermal runaway in the battery life cycle can be analyzed.

The above and other objects, advantages and features of the present invention will be more apparent to those skilled in the art from the following detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings.

Description of drawings

Hereinafter, some specific embodiments of the present invention will be described in detail by way of example and not limitation with reference to the accompanying drawings. The same reference numbers in the figures designate the same or similar parts or parts. It will be understood by those skilled in the art that the drawings are not necessarily to scale. Objects and features of the present invention will become more apparent in view of the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flowchart of a test method for aging thermal runaway of a lithium-ion battery under time-varying cycle conditions according to an embodiment of the present invention.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are not intended to limit the protection scope of the present invention.

Referring to FIG. 1 , the aging thermal runaway test method of a lithium-ion battery under the time-varying cycle condition of the present embodiment specifically includes the following steps:

S1. Select a set of test lithium-ion battery cells, including measuring battery capacity, open circuit voltage and/or internal resistance for the test lithium-ion battery cells, and screen out relatively high consistency, that is, the measurement value consistency is better The test lithium ion battery cells constitute a test lithium ion battery cell set; the test lithium ion battery cell set includes several lithium ion battery cells with the same type and material system. That is to say, before conducting the battery aging thermal runaway test under time-varying cycle conditions, firstly, by measuring the battery capacity, open circuit voltage and internal resistance and other parameters, the battery with high consistency is selected to increase the comparability and credibility of the test. This is because the aging thermal runaway test under different working conditions cannot be completed on the same lithium-ion battery cell.

S2, for each test lithium-ion battery cell in the selected test-use lithium-ion battery cell set according to preset different test temperatures and/or different time-varying cycle conditions, perform an aging test of each lithium-ion battery cell, During the aging test, the battery voltage, current and temperature data of the lithium-ion battery cells are collected, and the capacity test is carried out at the same time. This step is to carry out the aging test of the battery under the selected time-varying cycle condition, until the battery's available capacity decays to 80% of the initial available capacity, and stop the aging test, and after the battery has experienced a certain number of time-varying cycle conditions , carry out a capacity test test, and divide the aging test into sections according to the capacity decay ratio; further preferably, it may specifically include sub-steps: S21, according to the selected time-varying cycle condition, discharge the test lithium-ion battery cells to 20% Electricity, optional time-varying cycle conditions include main discharge conditions and dynamic stress conditions (DST conditions) aging of pure electric passenger vehicle energy batteries using the relevant national standard GB/T 31484 for power battery cycle life test Test, or use New European Test Cycle (NEDC), US Federal Vehicle Test Standard Procedure (FTP75), World Light Vehicle Test Cycle (WLTC), Japanese Motor Vehicle Test Condition (JC08) or China Condition (CATC) Condition conversion The aging test of the battery equivalent test condition, the aging test of the time-varying cycle condition is carried out under the selected constant temperature condition, and the selected constant temperature condition can be 0°C, 25°C and/or 45°C; S22, Charge the discharged lithium-ion battery for the test to 100% power to form a complete cycle condition; S23, collect the battery voltage, current and temperature data of the lithium-ion battery during the aging test, and repeat the sub-step S21 Complete 20 complete cycle conditions from S22 to the test lithium-ion battery cell. At this time, the lithium-ion battery cell has experienced a certain number of cycle conditions. After that, the capacity test is performed, and the aging test is divided according to the capacity decay ratio. Step S24. Repeat steps S21 to S23 for a plurality of test lithium-ion battery cells to obtain aged lithium-ion battery cells with different attenuation ratios. Attenuation of 10%, attenuation of 15% and attenuation of 20%, the battery aging process is divided into five stages; wherein the aging lithium-ion battery cell set includes aging lithium-ion battery cells with different capacity attenuation ratios. The new battery is a commercial battery that has undergone chemical formation before leaving the factory, can be used normally, and has only been screened for consistency. In the aging test of lithium-ion battery under time-varying cycle conditions, when the SOC of the battery drops to 20%, the discharge cycle is completed, and the battery starts to be charged. down to 0.05C to complete battery charging. After every 20 complete charge-discharge cycles of the battery (that is, the battery SOC drops to 20%), a test of basic parameters such as capacity, open circuit voltage, and internal resistance of the battery is carried out.

S3. Quantitatively compare and analyze the decay mechanism of the aging lithium-ion battery cell aggregate battery using an external characteristic analysis method, the external characteristic analysis method includes using an incremental capacity method, a differential voltage method, a differential thermovoltage method and/or electrochemical impedance. Spectroscopy was used to analyze the aging test data. That is to say, after the lithium-ion battery aggregate time-varying cycle condition aging test is completed, based on the battery external characteristic data obtained by the test, the incremental capacity method, differential voltage method, differential thermovoltage method, electrochemical impedance spectroscopy method and other methods are used. The quantitative analysis of the aging behavior of the battery in different aging stages is carried out, and the capacity loss mechanism (ie, the decay mechanism) of the lithium-ion battery under different temperature time-varying cycle conditions is speculated.

S4. Use an adiabatic acceleration calorimeter (Accelerating Rate Calorimetry—ARC) to conduct a battery thermal runaway test on each test lithium-ion battery cell in the aging lithium-ion battery cell set, and perform a battery thermal runaway test according to the battery cell of the aging lithium-ion battery cell. The temperature data and the heating rate data are used to obtain the thermal runaway characteristic temperature of the aging lithium-ion battery cell corresponding to different test temperatures and/or different capacity decay ratios. That is to say, the test batteries of different aging stages are extracted, and the thermal runaway test of the battery is carried out in the ARC to obtain the thermal runaway characteristic temperature of the battery in different aging stages. Preferably, it specifically includes the following steps: S41, setting the adiabatic acceleration calorimeter to 25°C, and placing an aged lithium-ion battery cell in the adiabatic acceleration calorimeter experimental environment at 25°C for at least 24 hours; S42 , Heating the aging lithium-ion battery cell with the heating setting of the heating step size of 5 °C and the temperature stabilization time of each step of 10 minutes, and simultaneously detecting the temperature and heating rate of the aging lithium-ion battery cell; S43, when the aging lithium ion battery cell is detected. When the heating rate of the ion battery cell exceeds 0.02°C/min, it is determined that the aging lithium ion battery cell has entered a self-heating state, and the adiabatic acceleration calorimeter is transferred to the adiabatic working mode; S44, the aging lithium ion battery cell is in the adiabatic working mode. From heating until thermal runaway occurs, end the test and record the characteristic temperature of thermal runaway of the aged lithium-ion battery cell; S45, repeat steps S41 to S44 for all remaining aged lithium-ion battery cells to obtain the discharge capacity corresponding to different lithium-ion battery cells The thermal runaway characteristic temperature of an aging lithium-ion battery cell with a decay ratio; preferably, the battery is in a fully charged state, and at the same time, the thermal runaway test is performed within 1 hour after the completion of charging. The characteristic temperature of thermal runaway includes the self-heating temperature, the trigger temperature of thermal runaway and the maximum temperature of thermal runaway; the self-heating temperature is the temperature of the battery cell when the heating rate of the aged lithium-ion battery cell reaches 0.02°C/min; so The thermal runaway trigger temperature is the battery cell temperature when the heating rate of the aging lithium-ion battery cell reaches 1°C/s; the thermal runaway maximum temperature is the highest temperature reached by the aging lithium-ion battery cell during the test. In order to record the temperature data of the battery, it is preferable to set a temperature sensor at the geometric center of the battery parallel to the large plane of the electrode plate and/or the part of the battery tab for a prismatic battery or a pouch battery. The center point of the height of the outer cylindrical surface; preferably, during the thermal runaway test, test data such as time, battery temperature, heating rate and pressure can also be recorded.

S5. Summarize the change rule of thermal runaway characteristics in the whole life cycle of lithium-ion batteries based on the characteristic temperature of thermal runaway of aging lithium-ion battery cells at different test temperatures and/or different capacity decay ratios, and analyze the coupling relationship between thermal runaway and aging mechanism, and analyze the coupling relationship between thermal runaway and aging mechanism. The effects of different test temperatures and/or different time-varying cycle conditions on the thermal runaway characteristics of lithium-ion batteries were analyzed.

Based on the above thermal runaway test data and aging mechanism analysis results of aging batteries with different ambient temperatures and different time-varying cycle conditions, the change law of thermal runaway characteristics of batteries in the entire life cycle is studied, and the effects of different aging conditions on the thermal runaway characteristics of batteries are studied. In addition, the coupling relationship between thermal runaway and aging mechanism is analyzed, and a thermal runaway model for the entire life cycle of aging lithium-ion batteries under time-varying cycling conditions is established. At the same time, it is also possible to study the differences in thermal runaway characteristics of batteries with different material systems under the same time-varying cycle conditions and the same aging stage, providing support for better prediction and protection of thermal runaway in the battery life cycle.

The technical solutions provided by the embodiments of the present invention have been introduced in detail above. The principles and implementations of the embodiments of the present invention are described in this paper by using specific examples. The descriptions of the above embodiments are only applicable to help understand the embodiments of the present invention. At the same time, those skilled in the art will have changes in the specific implementation and application scope according to the embodiments of the present invention. To sum up, the content of this specification should not be construed as a limitation of the present invention.

Claims (10)

1. A lithium-ion battery aging thermal runaway test method under a time-varying cycle operating condition is characterized in that comprising the following steps: S1. Select a set of lithium ion battery cells for testing, wherein the set of lithium ion battery cells for testing includes several lithium ion battery cells with the same type and material system; S2. Perform an aging test on each test lithium-ion battery cell in the selected test lithium-ion battery cell set according to different preset test temperatures and/or different time-varying cycle conditions, and perform an aging test during the aging test process. The battery voltage, current and temperature data of the lithium-ion battery cells are collected in the process, and the capacity test is carried out at the same time. Aged Li-ion battery cells with different capacity fade ratios are included in the collection; S3. Use the external characteristic analysis method to analyze the aging test data of the aging lithium-ion battery cell set, so as to quantitatively compare and analyze the attenuation mechanism of the aging lithium-ion battery cell set; S4. Use an adiabatic acceleration calorimeter to perform a battery thermal runaway test on each aged lithium-ion battery cell in the aged lithium-ion battery cell set, and perform a battery thermal runaway test according to the battery cell temperature data and temperature rise rate of each aged lithium-ion battery cell The data obtains the thermal runaway characteristic temperature of the aging lithium-ion battery cell corresponding to different test temperatures and/or different capacity decay ratios; S5. Based on the thermal runaway characteristic temperature of the aging lithium-ion battery cell at different test temperatures and/or different capacity decay ratios, the change rule of the thermal runaway characteristics in the whole life cycle of the lithium-ion battery is obtained, and the coupling relationship between the thermal runaway and the aging mechanism is analyzed, and The effects of aging of lithium-ion batteries on thermal runaway characteristics under different test temperatures and/or different time-varying cycle conditions were analyzed. 2. the lithium ion battery aging thermal runaway test method under a kind of time-varying cycle working condition according to claim 1, it is characterized in that in described step S1, the method that chooses test lithium ion battery cell set is: for test use The lithium-ion battery cells are measured for battery capacity, open circuit voltage and/or internal resistance, and according to the measurement results, relatively high-consistency test lithium-ion battery cells are selected to form a test lithium-ion battery cell set. 3. A lithium-ion battery aging thermal runaway test method under a time-varying cycle condition according to claim 1, wherein the step S2 comprises: S21, according to the selected time-varying cycle condition, discharge the lithium-ion battery cell for the test to 20% of the power; S22, charging the discharged test lithium-ion battery to 100% power to form a complete cycle condition; S23. Collect the battery voltage, current and temperature data of the lithium-ion battery during the complete cycle condition, and repeat the steps S21 to S22 until the test lithium-ion battery completes 20 complete cycles The capacity test is carried out again, and the aging test is divided into segments according to the capacity attenuation ratio; S24. Repeat the step S21 to the step S23 for a plurality of test lithium-ion battery cells to obtain aged lithium-ion battery cells with different attenuation ratios. 4. The method for testing the aging thermal runaway of a lithium ion battery under a time-varying cycle condition according to claim 1, wherein in the step S2, each lithium-ion battery is tested according to preset different time-varying cycle conditions. The aging test of the battery cell includes: using the power battery cycle life test related national standard GB/T 31484 for the aging test of the energy-type battery for pure electric passenger vehicles under the main discharge condition and dynamic stress condition; or using the new European test cycle (NEDC), U.S. Federal Vehicle Test Standard Procedure (FTP75), World Light Vehicle Test Cycle (WLTC), Japanese Motor Vehicle Test Condition (JC08), or Battery Equivalent Test Condition Converted from China Condition (CATC) Aging test. 5 . The aging thermal runaway test method of a lithium ion battery under a time-varying cycle condition according to claim 1 , wherein the step S2 is performed according to preset different time-varying cycle conditions for each test. 6 . The aging test of the lithium ion battery cell is carried out under a selected constant temperature condition, and the selected constant temperature condition is 0°C, 25°C or 45°C. 6. The method for testing the aging thermal runaway of lithium-ion batteries under a time-varying cycle condition according to claim 1, wherein the different capacity decay ratios described in the step S2 include new batteries, 5% decay, and 5% decay. 10%, 15% decay and 20% decay, thus dividing the battery aging process into five stages. 7 . The aging thermal runaway test method for lithium-ion batteries under a time-varying cycle condition according to claim 1 , wherein the external characteristic analysis method in step S3 comprises: incremental capacity method, differential voltage method, differential thermovoltage and/or electrochemical impedance spectroscopy. 8. The method for testing lithium-ion battery aging thermal runaway under a time-varying cycle condition according to claim 1, wherein the step S4 comprises the following steps: S41. Set the adiabatic acceleration calorimeter to 25°C, and place an aged lithium-ion battery cell in the adiabatic acceleration calorimeter experimental environment at 25°C for at least 24 hours; S42, heating the aging lithium-ion battery cell, and simultaneously detecting the temperature and heating rate of the aging lithium-ion battery cell; S43, when it is detected that the heating rate of the aging lithium-ion battery cell exceeds 0.02 °C/min, it is determined that the aging lithium-ion battery cell has entered a self-heating state, and the adiabatic acceleration calorimeter is transferred to the adiabatic working mode; S44, the aging lithium-ion battery cell is self-heated in the adiabatic working mode until thermal runaway occurs, and the test is ended and the thermal runaway characteristic temperature of the aging lithium-ion battery cell is recorded; S45. Repeat steps S41 to S44 for all remaining aged lithium-ion battery cells to obtain the thermal runaway characteristic temperatures of the aged lithium-ion battery cells corresponding to different capacity decay ratios. 9 . The aging thermal runaway test method of a lithium ion battery under a time-varying cycle condition according to claim 8 , wherein the method of heating the aging lithium ion battery cell described in the step S42 is to use The temperature rise setting was performed with a temperature rise step of 5°C and a temperature stabilization duration of 10 minutes per step. 10 . The aging thermal runaway test method of a lithium-ion battery under a time-varying cycle condition according to claim 8 , wherein the thermal runaway characteristic temperature in step S45 includes: self-heating temperature, thermal runaway triggering temperature and the maximum temperature of thermal runaway; the self-heating temperature is the temperature of the battery cell when the heating rate of the aging lithium-ion battery cell reaches 0.02°C/min; the thermal runaway trigger temperature is the heating rate of the aging lithium-ion battery cell reaching 1 The temperature of the battery cell at ℃/s; the maximum temperature of thermal runaway is the maximum temperature reached by the aged lithium-ion battery cell during the test.

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