A method for testing thermal runaway expansion characteristic parameters of battery cells

Abstract

The present invention discloses a method for testing the expansion characteristic parameters of a battery cell under thermal runaway. First, two side pressure components and a heating plate are set on a test platform. Then, the battery cell to be tested is placed on the heating plate and located between the two side pressure components. The heating plate is started until the battery cell to be tested has a thermal runaway phenomenon. The maximum expansion pressure F of the battery cell to be tested relative to the two side pressure components is collected. The maximum extrusion contact area S of the battery cell to be tested and the inner side surfaces of the two side pressure components are collected. The value of the set distance d between the two side pressure components is adjusted. The maximum expansion pressure F and the maximum extrusion contact area S corresponding to different set distances d are measured. Finally, a relationship curve between the set distance d and the maximum expansion pressure F and a relationship curve between the set distance d and the maximum extrusion contact area S are established according to multiple groups of test data. The present invention obtains the maximum expansion pressure and contact area for different constraint boundaries when the battery cell is under thermal runaway through testing, and provides key data for the thermal runaway diffusion analysis of the battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery testing, and in particular to a method for testing thermal runaway expansion characteristic parameters of a battery cell. Background Art

[0002] Lithium-ion batteries are widely used in automobiles, electronic products and energy storage fields because of their high specific capacity, good charge and discharge performance, and long cycle life, which are superior to other types of batteries. With the continuous development of various industries, the requirements for battery safety and reliability are getting higher and higher. In recent years, thermal runaway events of battery systems have occurred frequently, and thermal runaway has become one of the difficulties in the industry.

[0003] Thermal runaway diffusion between battery cells in a battery system is a key influencing factor that causes thermal runaway safety risks in the battery system. The thermal runaway diffusion process is mainly determined by the thermal runaway characteristics of the battery cell itself. The thermal runaway characteristics of the battery cell mainly include gas production characteristics (gas composition, gas production rate, valve opening pressure), heat generation characteristics (self-heating temperature, thermal runaway temperature, heat generation power), electrical characteristics (short-circuit internal resistance, short-circuit current, etc.), mechanical properties and expansion characteristics. However, the impact of the thermal runaway mechanical properties and expansion characteristics of the battery cell on the thermal runaway diffusion is rarely considered. The influence of the expansion characteristics of the battery cell on the diffusion process of thermal runaway of the battery cell is mainly manifested in: the mechanical properties of the battery cell change at different stages of thermal runaway (mainly affected by the temperature and changes in the internal materials of the battery cell, and the overall manifestation is the attenuation of strength and stiffness). As the thermal runaway of the battery cell spreads, due to the expansion characteristics of the thermal runaway of the battery cell, the side of the battery cell that has experienced thermal runaway will be squeezed and deformed, forming a local gap with the battery cell on the side where thermal runaway has not occurred, thereby affecting the heat transfer to the battery cell on the side where thermal runaway has not occurred, and ultimately affecting the diffusion process of the thermal runaway of the battery cell. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for testing the expansion characteristic parameters of a battery cell under thermal runaway conditions. The maximum expansion pressure and contact area for different constraint boundaries during thermal runaway of the battery cell are obtained through testing, thereby providing key data for thermal runaway diffusion analysis of the battery cell.

[0005] The technical solution of the present invention is:

[0006] A method for testing thermal runaway expansion characteristic parameters of a battery cell specifically comprises the following steps:

[0007] (1) Two side pressure assemblies and a heating plate are set on the test platform. The set distance between the two side pressure assemblies is d, and the value of d is greater than the thickness of the battery cell to be tested. The heating plate is located between the two side pressure assemblies;

[0008] (2) Place the battery cell to be tested on the heating plate with the same spacing between the two side pressure components;

[0009] (3) Start the heating plate to heat the battery cell to be tested until the battery cell to be tested undergoes thermal runaway expansion;

[0010] (4) Collect the maximum expansion pressure F of the battery cell to be tested relative to the two side pressure components, and collect the maximum extrusion contact area S of the battery cell to be tested and the inner side surfaces of the two side pressure components, and the two side pressure components respectively obtain the corresponding maximum expansion pressure F and maximum extrusion contact area S;

[0011] (5) Adjust the value of the set distance d between the two side pressure components, and then repeat steps (2)-(4) to measure the maximum expansion pressure F and the maximum extrusion contact area S corresponding to different set distances d, thereby obtaining multiple sets of test data. Finally, a relationship curve between the set distance d and the maximum expansion pressure F and a relationship curve between the set distance d and the maximum extrusion contact area S are established based on the multiple sets of test data. From the two relationship curves, the maximum expansion pressure F and the maximum extrusion contact area S corresponding to any set distance d within the range of the relationship curve can be obtained.

[0012] The two side pressure components are provided with contact identification layers on their opposite inner sides, and the maximum extrusion contact area S between the battery cell to be tested and the inner sides of the two side pressure components is collected through the contact identification layers on the two side pressure components.

[0013] The contact identification layer is a printing pad layer, and the groove area on the printing pad layer is the maximum extrusion contact area S between the battery cell to be tested and the inner side of the side pressure component.

[0014] A high temperature resistant insulation layer is arranged between the heating plate and the test platform.

[0015] A high temperature resistant heat conductive layer is arranged between the heating plate and the battery cell to be tested.

[0016] The two side pressure assemblies each include a vertically arranged fixed plate and a side plate, and a pressure sensor fixed between the fixed plate and the side plate. The fixed plate is fixed on the test platform. The side plates of the two pressure measuring assemblies are respectively located on both sides of the battery cell to be tested. The contact identification layer is arranged on the inner side surface of the side plate. When the battery cell to be tested undergoes thermal runaway expansion, the side plate generates sliding friction relative to the pressure measuring platform. The pressure sensors of the two side pressure assemblies collect the maximum expansion pressure F of the battery cell to be tested relative to the two side pressure assemblies.

[0017] A lubrication layer is added between the side plate and the pressure measuring platform or a pulley is added at the bottom end of the side plate, thereby reducing the sliding friction between the side plate and the pressure measuring platform.

[0018] When the battery cell to be tested experiences thermal runaway expansion, voltage data of the battery cell to be tested is collected and monitored in real time.

[0019] In the step (5), when establishing the relationship curve between the set distance d and the maximum expansion pressure F and the relationship curve between the set distance d and the maximum extrusion contact area S, each set distance d corresponds to two maximum expansion pressures F and two maximum extrusion contact areas S, the two maximum expansion pressures F are averaged as the maximum expansion pressure F corresponding to each set distance d, and the two maximum extrusion contact areas S are averaged as the maximum extrusion contact area S corresponding to each set distance d, and a relationship curve is established between different set distances d and the corresponding maximum expansion pressures F, and a relationship curve is established between different set distances d and the corresponding average values ​​of the maximum extrusion contact areas S.

[0020] The testing principle of the present invention:

[0021] When the battery cell is in thermal runaway, the main manifestation of the battery cell is the expansion of the battery cell. When a certain pressure is reached, the explosion-proof valve at the top of the battery cell opens to release the pressure. At this time, the two large surfaces of the battery cell expand outward. When there is no external force acting on the battery cell shell, the two large surfaces of the battery cell shell will expand to the 201 position (see Figure 1 ), when external force acts on the outer shell of the battery cell, the temperature of the battery cell is high, and the substances inside the battery cell are discharged to the outside of the battery cell through the explosion-proof valve, causing the internal pressure of the battery cell to decrease, making the strength and rigidity of the battery cell drop significantly, and the two large surfaces of the battery cell shell will retract to the position 202 (see Figure 1 ).

[0022] See the stacking method of battery modules for details. Figure 2 When a certain battery cell 401 experiences thermal runaway, its strength and rigidity drop significantly, and the temperature is relatively high at this time. Before the explosion-proof valve is opened, the thermal runaway battery cell 401 expands, exerting pressure on all the battery cells 402 on its left side. All the battery cells 402 on the left side shift to the left, and all the battery cells 403 on the right side of the thermal runaway battery cell 401 generally remain in the same position. At this time, the contact area between the thermal runaway battery cell 401 and the battery cell 403 on the right side changes. The size of the contact area is affected by the number of all battery cells 402 on the left side. The present invention is used to calibrate the maximum expansion pressure and extrusion contact area of ​​battery cells with different specifications in different constraint spaces, and the thermal runaway of the battery cells on different constraint boundaries, that is, to obtain the value of the extrusion contact area between the thermal runaway battery cell 401 and the battery cell 403 on the right side for preliminary test analysis.

[0023] Advantages of the present invention:

[0024] The present invention proposes two key characteristic data of thermal runaway of battery cells: the battery cell thermal runaway expansion pressure-expansion spacing relationship curve Fd and the extrusion contact area-expansion spacing relationship curve Sd. The data on these two relationship curves have a direct impact on the diffusion process of thermal runaway of the battery cell, and provide key data for the thermal runaway diffusion analysis of battery cells of different specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of a single battery cell experiencing thermal runaway.

[0026] Figure 2 It is a structural schematic diagram of thermal runaway of the battery module.

[0027] Figure 3 It is a structural schematic diagram of the present invention for testing the thermal runaway expansion characteristic parameters of a battery cell.

[0028] Figure 4 4 is a curve diagram showing the relationship between the set distance d and the maximum expansion pressure F in the embodiment of the present invention.

[0029] Figure 5 4 is a curve diagram showing the relationship between the set distance d and the maximum extrusion contact area S in an embodiment of the present invention.

[0030] Figure markings: 201 - expansion surface of the thermal runaway battery cell, 202 - shrinkage surface of the thermal runaway battery cell after thermal runaway, 401 - thermal runaway battery cell in the battery cell module, 402 - all battery cells on the left side of the thermal runaway battery cell in the battery cell module, 403 - all battery cells on the right side of the thermal runaway battery cell in the battery cell module, 1 - test platform, 2 - heating plate, 3 - battery cell to be tested, 4 - fixing plate, 5 - side plate, 6 - pressure sensor. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] See Figure 3 , a method for testing the thermal runaway expansion characteristic parameters of a battery cell, specifically comprising the following steps:

[0033] (1) A heating plate 2 is arranged on the test platform 1, and a high temperature resistant heat insulation layer is arranged between the heating plate 2 and the test platform 1;

[0034] (2) placing the battery cell 3 to be tested on the heating plate 2, with a high temperature resistant heat conductive layer provided between the heating plate 2 and the battery cell 3 to be tested;

[0035] (3) Assemble two side pressure assemblies respectively, each of which includes a vertically arranged fixing plate 4 and a side plate 5, and a pressure sensor 6 fixed between the fixing plate 4 and the side plate 5, and an ink layer is provided on the inner side of the side plate 5;

[0036] (4) Fix the fixing plates 4 of the two side pressure assemblies on the test platform 1, and the side plates 5 of the two pressure measuring assemblies are respectively located on both sides of the battery cell 3 to be tested. A lubricating layer is added between the two side plates 5 and the pressure measuring platform 1, or a pulley is added at the bottom of the side plate to reduce the sliding friction between the side plates 5 and the pressure measuring platform 1. The set distance between the two side plates 5 is d, and the value of d is greater than the thickness of the battery cell 3 to be tested. The distances between the battery cell 3 to be tested and the two side plates 5 are equal;

[0037] (5) Start the heating plate 2 to heat the battery cell 3 to be tested until the battery cell 3 to be tested undergoes thermal runaway expansion, at which time the side plate 5 generates sliding friction relative to the pressure measuring platform 1;

[0038] (6) The maximum expansion pressure F of the battery cell 3 to be tested relative to the two side plates 5 is collected through the pressure sensor 6, and the voltage data of the battery cell 3 to be tested is collected and monitored in real time. The maximum extrusion contact area S between the battery cell 3 to be tested and the inner side surfaces of the two side plates 5 is collected through the ink layer on the two side plates 5 (the groove area on the ink layer is the maximum extrusion contact area S between the battery cell to be tested and the inner side surfaces of the side plates 5). The two side pressure components obtain the corresponding maximum expansion pressure F and maximum extrusion contact area S respectively;

[0039] (5) Adjust the value of the set distance d between the two side plates 5, and then repeat steps (2) to (4) to measure the maximum expansion pressure F and the maximum extrusion contact area S corresponding to different set distances d, so as to obtain multiple sets of test data, each set distance d corresponds to two maximum expansion pressures F and two maximum extrusion contact areas S, the two maximum expansion pressures F corresponding to each set distance d are averaged as the maximum expansion pressure F corresponding to each set distance d, and the two maximum extrusion contact areas S corresponding to each set distance d are averaged as the maximum extrusion contact area S corresponding to each set distance d, and finally, a relationship curve between the set distance d and the maximum expansion pressure F is established according to the multiple sets of test data (see Figure 4 ), the relationship curve between the set distance d and the maximum extrusion contact area S (see Figure 5 ), the maximum expansion pressure F and the maximum extrusion contact area S corresponding to any set distance d within the range of the relationship curve can be obtained from the two relationship curves.

[0040] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for testing the thermal runaway expansion characteristic parameters of a battery cell, characterized in that: The specific steps include: (1) Two side pressure assemblies and a heating plate are set on the test platform. The set distance between the two side pressure assemblies is d, and the value of d is greater than the thickness of the battery cell to be tested. The heating plate is located between the two side pressure assemblies; (2) Place the battery cell to be tested on the heating plate with the same spacing between the two side pressure components; (3) Start the heating plate to heat the battery cell to be tested until the battery cell to be tested undergoes thermal runaway expansion; (4) Collect the maximum expansion pressure F of the battery cell to be tested relative to the two side pressure components, and collect the maximum extrusion contact area S of the battery cell to be tested and the inner side surfaces of the two side pressure components, and the two side pressure components respectively obtain the corresponding maximum expansion pressure F and maximum extrusion contact area S; (5) Adjust the value of the set distance d between the two side pressure components, and then repeat steps (2)-(4) to measure the maximum expansion pressure F and the maximum extrusion contact area S corresponding to different set distances d, thereby obtaining multiple sets of test data. Finally, a relationship curve between the set distance d and the maximum expansion pressure F and a relationship curve between the set distance d and the maximum extrusion contact area S are established based on the multiple sets of test data. From the two relationship curves, the maximum expansion pressure F and the maximum extrusion contact area S corresponding to any set distance d within the range of the relationship curve can be obtained.

2. The method for testing the thermal runaway expansion characteristic parameters of a battery cell according to claim 1, characterized in that: The two side pressure components are provided with contact identification layers on their opposite inner sides, and the maximum extrusion contact area S between the battery cell to be tested and the inner sides of the two side pressure components is collected through the contact identification layers on the two side pressure components.

3. A method for testing thermal runaway expansion characteristic parameters of a battery cell according to claim 2, characterized in that: The contact identification layer is a printing pad layer, and the groove area on the printing pad layer is the maximum extrusion contact area S between the battery cell to be tested and the inner side of the side pressure component.

4. The method for testing the thermal runaway expansion characteristic parameters of a battery cell according to claim 1, characterized in that: A high temperature resistant heat insulating layer is arranged between the heating plate and the test platform.

5. The method for testing the thermal runaway expansion characteristic parameters of a battery cell according to claim 1, characterized in that: A high temperature resistant heat conductive layer is arranged between the heating plate and the battery cell to be tested.

6. A method for testing thermal runaway expansion characteristic parameters of a battery cell according to claim 2, characterized in that: The two side pressure assemblies each include a vertically arranged fixed plate and a side plate, and a pressure sensor fixed between the fixed plate and the side plate. The fixed plate is fixed on the test platform. The side plates of the two pressure measuring assemblies are respectively located on both sides of the battery cell to be tested. The contact identification layer is arranged on the inner side surface of the side plate. When the battery cell to be tested undergoes thermal runaway expansion, the side plate generates sliding friction relative to the pressure measuring platform. The pressure sensors of the two side pressure assemblies collect the maximum expansion pressure F of the battery cell to be tested relative to the two side pressure assemblies.

7. A method for testing thermal runaway expansion characteristic parameters of a battery cell according to claim 6, characterized in that: A lubrication layer is added between the side plate and the pressure measuring platform or a pulley is added at the bottom end of the side plate, thereby reducing the sliding friction between the side plate and the pressure measuring platform.

8. The method for testing thermal runaway expansion characteristic parameters of a battery cell according to claim 1, characterized in that: When the battery cell to be tested experiences thermal runaway expansion, voltage data of the battery cell to be tested is collected and monitored in real time.

9. A method for testing thermal runaway expansion characteristic parameters of a battery cell according to claim 1, characterized in that: In the step (5), when establishing the relationship curve between the set distance d and the maximum expansion pressure F and the relationship curve between the set distance d and the maximum extrusion contact area S, each set distance d corresponds to two maximum expansion pressures F and two maximum extrusion contact areas S, the two maximum expansion pressures F are averaged as the maximum expansion pressure F corresponding to each set distance d, and the two maximum extrusion contact areas S are averaged as the maximum extrusion contact area S corresponding to each set distance d, and a relationship curve is established between different set distances d and the corresponding maximum expansion pressures F, and a relationship curve is established between different set distances d and the corresponding average values ​​of the maximum extrusion contact areas S.

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