A method for calculating heat generation during thermal runaway of lithium-ion batteries

Abstract

The present invention is applicable to the field of battery technology and provides a method for calculating the heat generation of a lithium-ion battery during thermal runaway, comprising the following steps: S1. Heating the lithium-ion battery to thermal runaway, testing and recording the temperature change over time of the heating surface or the non-heating surface directly opposite the heating surface, to obtain an experimental temperature change curve; S2. simulating and fitting the experimental temperature change curve to obtain the effective heating power and heat dissipation coefficient; S3. Constructing a battery thermal abuse model, simulating the temperature change curve inside the lithium-ion battery, and calculating the heat generation of the lithium-ion battery during thermal runaway based on the surface temperature change curve and the internal temperature change curve. The present invention calculates the heat generation of a lithium-ion battery during thermal runaway by combining conventional heating runaway experiments with simulation methods. This method does not require expensive equipment and can greatly reduce the number of experiments. At the same time, considering the internal temperature can more accurately assess the total heat generation of thermal runaway.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for calculating heat generation during thermal runaway of a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have attracted considerable attention due to their high voltage platform, low self-discharge, high specific energy, and environmental friendliness. With the advancement of high-nickel technology, specific energy density has been further improved, but this presents a significant threat to battery safety. Battery safety primarily depends on the temperature threshold at which thermal runaway occurs and the total heat generated. The runaway temperature threshold is the threshold for thermal runaway; exceeding this temperature results in uncontrollable runaway or explosion. Total heat generation determines the severity of any such explosion.

[0003] Total heat generation is a key factor to consider in battery cell and module design. It can determine whether the compactness of the design will cause a chain reaction of battery cell explosions. Therefore, when designing a module, it is necessary to accurately measure or evaluate the total heat generation of the single battery cell that could cause a runaway situation.

[0004] The total heat generated by a battery cell is difficult to collect during conventional testing. Currently, there's no method that can fully capture the energy released during a cell explosion. The total heat generated can only be assessed by the rise in surface temperature. Currently, this can only be done using the expensive Accelerating Rate Calorimetry (ARC) instrument, which has a long test cycle and high costs. This makes it more suitable for use in universities or for research involving a small number of samples. Furthermore, the ARC instrument can only measure surface temperature, which can result in a lower heat output. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calculating the heat generation of a lithium-ion battery during thermal runaway, aiming to solve the technical problems of high cost and low accuracy in the existing lithium-ion battery thermal runaway heat generation test.

[0006] The present invention is implemented as follows: a method for calculating the heat generation of a lithium-ion battery due to thermal runaway, comprising the following steps:

[0007] S1. Heating the lithium-ion battery until thermal runaway occurs, testing and recording the temperature change over time of the heating surface or the non-heating surface opposite to the heating surface, to obtain an experimental temperature change curve;

[0008] S2. obtaining the effective heating power and heat dissipation coefficient by simulation fitting the experimental temperature change curve;

[0009] S3. Construct a battery thermal abuse model, simulate and obtain a temperature change curve inside the lithium-ion battery, and calculate the thermal runaway heat generation of the lithium-ion battery based on the surface temperature change curve and the internal temperature change curve.

[0010] In one embodiment of the present invention, the thermal runaway heat generation of the lithium-ion battery is calculated according to the following formula:

[0011] Q=q×△t

[0012] q=cm△T / △t

[0013] Wherein, Q is the heat generated by thermal runaway, q is the heat generated by thermal runaway power, c is the specific heat capacity, m is the battery mass, ΔT is the difference between the maximum average temperature and the temperature at the starting point of thermal runaway, Δt is the thermal runaway time, and the maximum average temperature is the average temperature of the maximum surface temperature and the maximum internal temperature of the lithium-ion battery.

[0014] In one embodiment of the present invention, the experimental temperature change curve includes a heating curve segment, a thermal runaway curve segment, and a cooling curve segment, and step S2 includes the following contents:

[0015] Selecting one of the heating curve segment, the thermal runaway curve segment, and the cooling curve segment, and making the simulated temperature curve coincide with the experimental temperature curve through simulation fitting, thereby obtaining a heat dissipation coefficient;

[0016] The heating curve segment is selected, and the simulated temperature curve is made to coincide with the experimental temperature curve through simulation fitting, thereby obtaining the effective heating power.

[0017] In one embodiment of the present invention, during the simulation process of step S2, a method of iterating the heat dissipation coefficient and the effective heating power multiple times is adopted to make the simulation temperature curve coincide with the experimental temperature curve.

[0018] In one embodiment of the present invention, in step S3, during the simulation, the electrolyte parameters of the thermal abuse model are corrected by an iterative correction method, and the temperature change curve inside the lithium-ion battery is obtained by simulation using the corrected thermal abuse model.

[0019] In one embodiment of the present invention, the temperature test of the lithium-ion battery is selected as the central area of the heating surface or the non-heating surface; in the step S3, the temperature change curve inside the lithium-ion battery is selected as the geometric center area of the lithium-ion battery.

[0020] In one embodiment of the present invention, in step S1, when the temperature rise rate of the lithium-ion battery reaches 3°C / s, it is determined to be thermal runaway.

[0021] In one embodiment of the present invention, the lithium-ion battery is square, and the heating surface is a surface of the lithium-ion battery with a relatively large area.

[0022] In one embodiment of the present invention, a heating sheet is used to press against the heating surface to heat the lithium-ion battery, and a thermocouple is used to monitor the temperature.

[0023] In one embodiment of the present invention, the thermal runaway time is 30S to 35S.

[0024] A method for calculating the heat generation due to thermal runaway of a lithium-ion battery according to the present invention has the following beneficial effects: by combining conventional heating runaway experiments with simulation methods, firstly, temperature changes are obtained through experimental tests under conventional conditions, and then a simulation method is applied for fitting, with simulation parameters continuously adjusted to make the simulated temperature curve match the experimental temperature curve. The temperature changes and thermal runaway time inside the lithium-ion battery can be known from the simulation parameters, and then the thermal runaway heat generation of the lithium-ion battery is calculated based on the surface temperature change curve and the internal temperature change curve. This method does not require the use of expensive equipment, can greatly reduce the number of experiments, and can more accurately assess the total heat generation due to thermal runaway by taking into account the internal temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a flow chart of a method for calculating heat generation during thermal runaway of a lithium-ion battery provided by an embodiment of the present invention;

[0027] Figure 2 1 is a schematic diagram of heating a lithium-ion battery provided by an embodiment of the present invention;

[0028] Figure 3 1 is an experimental temperature change curve of the heating surface of the lithium-ion battery provided by an embodiment of the present invention;

[0029] Figure 4 is a simulation fitting result of the temperature change of the heating surface of the lithium-ion battery provided by an embodiment of the present invention;

[0030] Figure 5 This is a curve of temperature changes inside and on the surface of a lithium-ion battery simulated by a thermal abuse model provided by an embodiment of the present invention.

[0031] The reference numerals used in the above drawings are as follows:

[0032] 10-lithium-ion battery; 20-heating plate. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly or indirectly located on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The directions or positions indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are only for the convenience of description and cannot be understood as limitations on this technical solution. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0035] Lithium-ion batteries have large capacities and can explode violently. Currently, measuring the total heat generated by thermal runaway requires only large-scale ARC equipment, which is expensive, requires long test cycles, and results in low test temperatures. Furthermore, the equipment requires collaborative testing by multiple professionals, making it unsuitable for large-scale sample testing and evaluation during battery cell development. This invention provides a method combining conventional testing experiments with simulations. The conventional testing experiment only requires testing runaway surface temperature changes in a standard explosion-proof cabinet, eliminating the need for sophisticated and expensive equipment. This method is both cost-effective and highly efficient. Finally, simulation methods are used for comparative calculations.

[0036] The design concept of this invention is to use ordinary experiments combined with simulation methods to accurately evaluate the total heat generation of the battery during thermal runaway; use simulation methods to calculate the effective heating power and heat dissipation coefficient; the simulation can monitor the internal temperature of the battery and the thermal runaway time, and use the internal and external averaging method to calculate the temperature rise, thereby obtaining an accurate total heat generation during thermal runaway.

[0037] To illustrate the technical solutions of the present invention, the following detailed description is provided in conjunction with specific drawings and examples. The present method for calculating the heat generation due to thermal runaway in lithium-ion batteries can be applied to various lithium-ion batteries, particularly prismatic lithium-ion batteries. Of course, the design principles of the present invention are also applicable to cylindrical lithium-ion batteries. The following detailed description of the technical solutions of the present invention is primarily based on prismatic lithium-ion batteries as an example.

[0038] See also Figure 1 The method for calculating the heat generation of a lithium-ion battery due to thermal runaway provided by an embodiment of the present invention comprises the following steps:

[0039] S1. Heating the lithium-ion battery to thermal runaway, testing and recording the temperature change over time of the heating surface or the non-heating surface opposite to the heating surface, to obtain an experimental temperature change curve;

[0040] S2. Obtain effective heating power and heat dissipation coefficient by simulation fitting the experimental temperature change curve;

[0041] S3. Construct a battery thermal abuse model, simulate the temperature change curve inside the lithium-ion battery, and calculate the thermal runaway heat generation of the lithium-ion battery based on the surface temperature change curve and the internal temperature change curve.

[0042] It should be understood that the order of the serial numbers of the steps in this embodiment does not mean that they must be executed in this order. The execution order of each process should be based on the actual process and should not constitute any limitation on the implementation process of the embodiment of the present invention. Any other steps that do not affect the implementation of the technical solution of the present invention may be included between any two steps of the present invention.

[0043] In one embodiment, an experimental temperature change curve is obtained by testing and recording the temperature change of the heating surface over time, the effective heating power and heat dissipation coefficient are obtained by simulation fitting the experimental temperature change curve of the heating surface, and finally the thermal runaway heat generation of the lithium-ion battery is calculated through the surface temperature change curve of the heating surface and the internal temperature change curve of the lithium-ion battery.

[0044] In another embodiment, an experimental temperature change curve can also be obtained by testing and recording the temperature change of the non-heating surface over time, wherein the non-heating surface refers to the surface opposite to the heating surface, and then the effective heating power and heat dissipation coefficient are obtained by simulation fitting the experimental temperature change curve of the non-heating surface, and finally the thermal runaway heat generation of the lithium-ion battery is calculated through the surface temperature change curve of the non-heating surface and the internal temperature change curve of the lithium-ion battery.

[0045] In one embodiment, in the above step S3, after the temperature change curve inside the lithium-ion battery is obtained through simulation, the thermal runaway heat generation of the lithium-ion battery is calculated according to the following formula: Q = q × △t, q = cm△T / △t. Among them, Q is the thermal runaway heat generation, q is the thermal runaway heat generation power, c is the specific heat capacity, m is the battery mass, △T is the difference between the highest average temperature and the thermal runaway starting point temperature, △t is the thermal runaway time, and the highest average temperature is the average temperature of the highest surface temperature and the highest internal temperature of the lithium-ion battery. In this embodiment, the internal temperature and thermal runaway time of the lithium-ion battery can be monitored through simulation, and the average temperature of the surface and internal temperatures is used to calculate the total heat generation, which has a high accuracy rate. In specific applications, the specific heat capacity c and the battery mass m can be measured by experiments and will not be described in detail here.

[0046] In one embodiment, the experimental temperature change curve of the lithium-ion battery includes a heating curve segment, a thermal runaway curve segment, and a cooling curve segment. The above step S2 specifically includes the following steps:

[0047] Select one of the heating curve segment, thermal runaway curve segment, and cooling curve segment, and make the simulated temperature curve coincide with the experimental temperature curve through simulation fitting, so as to obtain the heat dissipation coefficient;

[0048] The heating curve segment is selected, and the simulated temperature curve is made to coincide with the experimental temperature curve through simulation fitting, thereby obtaining the effective heating power.

[0049] In this embodiment, the heat dissipation coefficient and the effective heating power are obtained for the purpose of subsequent simulation fitting of the actual experimental curve.

[0050] When obtaining the heat dissipation coefficient, any one of the heating curve segments, the thermal runaway curve segment, and the cooling curve segment can be selected for simulation fitting, as the heat dissipation coefficient applies to the entire heating, runaway, and cooling processes. However, when obtaining the effective heating power, the heating curve segment must be selected for simulation fitting, as the effective heating power applies only to the heating phase. Preferably, when obtaining both the heat dissipation coefficient and the effective heating power, the heating curve segment should be selected for simulation fitting simultaneously to simplify the process.

[0051] In specific applications, the cooling curve segment after thermal runaway is selected. Since the battery is in a natural convection experimental environment, the simulated temperature curve coincides with the experimental temperature curve, so the heat dissipation coefficient can be known. The heating curve segment before thermal runaway is selected, and a uniform surface heating power is applied in the simulation. The temperature rise curve is adjusted to be consistent with the experiment. The effective heating power can be obtained by combining the heating area. The curve results are as follows: Figure 4 shown.

[0052] In one embodiment, during the simulation process of step S2 above, the simulation temperature curve is made to coincide with the experimental temperature curve by adopting a method of iterating the heat dissipation coefficient and the effective heating power multiple times. Specifically, the initial value of the heat dissipation coefficient can adopt the air heat dissipation coefficient, while the initial value of the effective heating power adopts the actual heating power of the battery. Then, different simulation temperature curves are obtained by continuously adjusting the input values of the heat dissipation coefficient and the effective heating power until the obtained simulation temperature curve coincides with the experimental temperature curve. The values of the heat dissipation coefficient and the effective heating power at this time are the final required values, and the values are applied to subsequent simulations. During the iterative process, the reference factors include: the magnitude of the effective heating power affects the highest point of the temperature, and the heat dissipation coefficient affects the temperature climbing speed. Then, the values of the heat dissipation coefficient and the effective heating power are adjusted in the direction close to the experimental temperature curve, which can reduce the number of iterations and simplify the experimental steps.

[0053] In one embodiment, during the simulation in step S3, the electrolyte parameters of the thermal abuse model are modified through an iterative correction method, and the temperature change curve inside the lithium-ion battery is simulated using the modified thermal abuse model. In this embodiment, by iteratively correcting the electrolyte parameters, the simulated model can be made more consistent with reality, thereby calculating a more accurate thermal runaway heat generation.

[0054] In specific applications, the battery thermal abuse model is first constructed using lithium-ion battery experimental tests and literature parameters, in which the electrolyte parameters are iteratively corrected by simulation fitting; then the corrected thermal abuse model parameters are used to simulate the entire thermal runaway process of the lithium-ion battery, monitor the temperature changes inside and on the surface, and finally calculate the heat generated by thermal runaway. Among them, the above thermal abuse model includes SEI (solid electrolyte) decomposition thermal reaction, negative electrode material-electrolyte thermal reaction, positive electrode material-electrolyte thermal reaction, and electrolyte thermal reaction, and various thermal reactions include the following parameters: heat release, pre-exponential factor and activation energy. The specific parameters are shown in the following table:

[0055]

[0056]

[0057] Among them, the various parameters of SEI decomposition, negative electrode material-electrolyte and positive electrode material-electrolyte in the above table are all obtained from experimental tests, and the parameters of the electrolyte cannot be tested by DSC (Differential Scanning calorimeter), so they need to be adjusted by combining experimental and simulation results with calculations. Specifically, the initial values of the various parameters of the electrolyte (i.e., the parameter values in the table) are reference parameters, and then the corrected electrolyte parameters are obtained by iterative correction through simulation fitting. Among them, the basis for judging whether the iteration of the electrolyte parameters is completed is that the initial temperature and the maximum temperature of the thermal runaway are not higher than the experimental error of 5%. It should be pointed out that the specific thermal abuse model equation can adopt the existing equation, which will not be described in detail here.

[0058] In one embodiment, in step S1, the temperature test of the lithium-ion battery is performed at the center of the heated surface or the non-heated surface. Accordingly, in step S3, the temperature change curve inside the lithium-ion battery is selected to be the geometric center of the lithium-ion battery. In this embodiment, the temperature change curves of the center area of the surface and the geometric center of the battery are selected, which can better reflect the thermal runaway process of the lithium-ion battery. In specific applications, the center point of the surface and the geometric center of the battery are preferably selected.

[0059] In one embodiment, when the temperature rise rate of the lithium-ion battery reaches 3° C. / s, it is determined to be thermal runaway. That is, when the temperature rise rate of the lithium-ion battery reaches 3° C. / s, heating of the heating surface is stopped.

[0060] In one embodiment, the lithium-ion battery is square, and the heating surface is selected as the large surface of the lithium-ion battery, that is, the surface with a relatively large area of the lithium-ion battery, so as to facilitate heating and improve test efficiency.

[0061] In one embodiment, see Figure 2 The lithium-ion battery 10 is heated by placing the heating plate 20 in close contact with the heating surface, and a thermocouple is used for temperature monitoring to improve test efficiency and facilitate subsequent simulation. In a specific application, the heating plate 20 can be a ceramic heating plate or a silicone heating plate.

[0062] In one embodiment, the thermal runaway time obtained by thermal abuse model simulation is 30S to 35S, such as 30S, 33S or 35S. In addition, the heating surface is 6000mm 2 Up to 10000mm 2 , heating power is 200w-300w.

[0063] In a specific embodiment, the method for calculating the heat generation of a lithium-ion battery due to thermal runaway comprises the following steps:

[0064] The first step is conventional test experiment, using a heating surface of 6000mm 2 The ceramic heating plate is placed close to the large surface of the square battery and heated at a power of 300W. At the same time, a thermocouple is used to monitor the temperature change of the heating surface. When the temperature rise rate of the lithium-ion battery reaches 3℃ / S, the heating is stopped and the experimental temperature change curve of the heating surface is recorded. Figure 3 As shown in the figure, it can be seen that the starting temperature of thermal runaway is 237.4℃ and the maximum temperature of thermal runaway is 702.2℃.

[0065] The second step is to simulate and fit the experimental temperature change curve to obtain the effective heating power and heat dissipation coefficient. First, a 48Ah heating model is created, and the heating power and heat dissipation coefficient are continuously adjusted. The commercial software FLUENT is used for simulation to make the simulated temperature change curve of the monitoring heating surface closely coincide with the experimental temperature change curve, and the error is controlled within 5%; then, the cooling curve segment after thermal runaway is taken (i.e., the temperature drop segment). Since the battery is in a natural convection experimental environment, the simulated temperature change curve coincides or is parallel to the experimental temperature change curve. The heat dissipation coefficient can be known from the simulation settings; then the largest heating curve segment before thermal runaway is taken, and a uniform surface heating power is applied in the simulation. The temperature rise curve is adjusted to coincide with the experiment (the error is controlled within 5%). The effective heating power can be obtained by combining the heating area. The simulation fitting results of the temperature change of the heating surface are as follows: Figure 4 shown.

[0066] The third step is to calculate the runaway heat generation through model simulation. First, the battery thermal abuse model is constructed using experimental test and literature parameters. The electrolyte parameters are iteratively corrected by simulation fitting. Then, the corrected thermal abuse model parameters are used to simulate the entire thermal runaway process of the battery, monitor the temperature changes inside and on the surface, and use the average temperature of the surface temperature and the internal temperature, combined with the thermal runaway time, and then use the formula q = cm△T / △t, Q = q×△t to calculate the heat generation. The thermal abuse model simulates the internal and surface temperature change curves of the lithium-ion battery as shown in the figure. Figure 5 As shown in the figure, it can be seen that the maximum temperature inside the battery is higher than the maximum temperature on the surface.

[0067] In this specific embodiment, through the above three steps, conventional temperature measurement experiments can be used in combination with continuous iterations of simulation methods to obtain a 48Ah battery thermal runaway heat generation of 418,000J. Accurately knowing this value is important for thermal diffusion prediction and protection.

[0068] In summary, the embodiments of the present invention use conventional test experiments combined with simulation methods to simply and quickly obtain the total heat generation of a battery out of control, which is more suitable for enterprise testing and evaluation and plays an important role in module safety design. At the same time, it uses simulation fitting to obtain accuracy that cannot be matched by experiments. At the same time, it is applicable to enterprises, highly efficient and low-cost.

[0069] The above descriptions are merely optional embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for calculating the heat generation of a lithium-ion battery due to thermal runaway, characterized in that: The following steps are involved: S1. Heating the lithium-ion battery until thermal runaway occurs, testing and recording the temperature change over time of the heating surface or the non-heating surface opposite to the heating surface, to obtain an experimental temperature change curve; S2. obtaining the effective heating power and heat dissipation coefficient by simulation fitting the experimental temperature change curve; S3. Constructing a battery thermal abuse model, simulating a temperature change curve inside the lithium-ion battery, and calculating the thermal runaway heat generation of the lithium-ion battery based on the surface temperature change curve and the internal temperature change curve; The experimental temperature change curve includes a heating curve segment, a thermal runaway curve segment, and a cooling curve segment, and step S2 includes the following contents: Selecting one of the heating curve segment, the thermal runaway curve segment, and the cooling curve segment, and making the simulated temperature curve coincide with the experimental temperature curve through simulation fitting, thereby obtaining a heat dissipation coefficient; Select the heating curve segment, and make the simulated temperature curve coincide with the experimental temperature curve through simulation fitting, thereby obtaining the effective heating power; During the simulation process of step S2, a method of iterating the heat dissipation coefficient and the effective heating power multiple times is adopted to make the simulation temperature curve coincide with the experimental temperature curve.

2. The method for calculating heat generation due to thermal runaway of a lithium-ion battery according to claim 1, wherein: The thermal runaway heat generation of the lithium-ion battery is calculated according to the following formula: Q=q×△t q=cm△T / △t Wherein, Q is the heat generated by thermal runaway, q is the heat generated by thermal runaway power, c is the specific heat capacity, m is the battery mass, ΔT is the difference between the maximum average temperature and the temperature at the starting point of thermal runaway, Δt is the thermal runaway time, and the maximum average temperature is the average temperature of the maximum surface temperature and the maximum internal temperature of the lithium-ion battery.

3. The method for calculating the heat generation of a lithium-ion battery due to thermal runaway according to claim 1, wherein: In step S3, during the simulation, the electrolyte parameters of the thermal abuse model are corrected by an iterative correction method, and the temperature change curve inside the lithium-ion battery is obtained by simulation using the corrected thermal abuse model.

4. The method for calculating the heat generation of a lithium-ion battery due to thermal runaway according to any one of claims 1 to 3, wherein: In step S1, the temperature test of the lithium-ion battery is performed on the central area of the heating surface or the non-heating surface; in step S3, the temperature change curve inside the lithium-ion battery is selected as the geometric center area of the lithium-ion battery.

5. The method for calculating the heat generation of a lithium-ion battery due to thermal runaway according to any one of claims 1 to 3, wherein: In step S1, when the temperature rise rate of the lithium-ion battery reaches 3°C / s, it is determined to be thermal runaway.

6. The method for calculating heat generation due to thermal runaway of a lithium-ion battery according to any one of claims 1 to 3, wherein: The lithium-ion battery is square in shape, and the heating surface is a surface of the lithium-ion battery with a relatively large area.

7. The method for calculating the heat generation of a lithium-ion battery due to thermal runaway according to any one of claims 1 to 3, wherein: A heating sheet is placed close to the heating surface to heat the lithium-ion battery, and a thermocouple is used to monitor the temperature.

8. The method for calculating heat generation due to thermal runaway of a lithium-ion battery according to claim 2, wherein: The thermal runaway time is 30S to 35S.

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