Device and method for collecting and analyzing gas produced in different thermal runaway stages of lithium ion battery

Abstract

The invention discloses a device and a method for collecting and analyzing gas produced in different thermal runaway stages of a lithium ion battery, and relates to the technical field of thermal runaway of the lithium ion battery, a closed box body for accommodating the lithium ion battery is provided with a plurality of gas collection ports, and the plurality of gas collection ports are located at different positions of the closed box body; the gas collection control part is respectively connected with each gas collection port pipeline of the closed box body, and is used for determining the thermal runaway stage of the lithium ion battery based on the surface temperature and the tab voltage of the lithium ion battery acquired by the sensing part; controlling the gas collection control part to obtain mixed gas at different gas collection ports in different thermal runaway stages to obtain the mixed gas corresponding to the different thermal runaway stages, and subsequently analyzing the mixed gas corresponding to the different thermal runaway stages. Therefore, the gas generated at different thermal runaway stages of the lithium ion battery and at different positions of the closed space can be efficiently and accurately collected and analyzed.

Description

Technical Field

[0001] The present application relates to the technical field of thermal runaway of lithium-ion batteries, and in particular to a device and method for collecting and analyzing gas produced at different positions of lithium-ion batteries at different thermal runaway stages in a confined space. Background Art

[0002] With the widespread application of lithium-ion batteries in energy storage systems, electric vehicles and other fields, their safety issues have become increasingly prominent, especially safety accidents caused by thermal runaway. Since lithium-ion batteries contain a large amount of active substances and electrical energy, when affected by various abuse conditions, the temperature of lithium-ion batteries may exceed the normal operating range, which may lead to thermal runaway accidents. In recent years, fires, explosions and other accidents caused by thermal runaway of lithium-ion batteries are common, which is still a bottleneck restricting the widespread application of lithium-ion batteries.

[0003] When thermal runaway occurs, the hazards of lithium-ion batteries are divided into two categories: direct heat release and generated gas emissions. Direct heat release can cause thermal runaway to spread inside the battery pack, while generated gas emissions may increase the risk of fire and explosion. When the temperature inside the lithium-ion battery gradually rises, the internal chemical materials will undergo redox reactions to generate a variety of gases. The types and concentrations of these gases change with the stage of thermal runaway. When thermal runaway occurs, the high-temperature gases and particulate matter generated flow in a confined space. The types and concentrations of gases collected at different stages of thermal runaway and at different locations in a confined space can reflect the development of thermal runaway. However, current related studies are all qualitative and quantitative analysis of gas production after thermal runaway of lithium-ion batteries, and there is still a technical gap in how to efficiently and accurately collect and analyze the gases generated at different stages of thermal runaway and at different locations in a confined space. Summary of the invention

[0004] The purpose of this application is to provide a device and method for collecting and analyzing gas produced in different thermal runaway stages of lithium-ion batteries, which can efficiently and accurately collect and analyze the gases produced in different thermal runaway stages of lithium-ion batteries and at different locations in a confined space.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a device for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages, wherein the device for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages comprises:

[0007] A sealed box for accommodating a lithium-ion battery; the sealed box has a plurality of gas collection ports, the plurality of gas collection ports are located at different positions of the sealed box, and each gas collection port is a through hole connecting the inside and the outside of the sealed box;

[0008] The gas collection control component is respectively connected to each gas collection port pipeline of the closed box to obtain the mixed gas at the gas collection port;

[0009] A sensing component, mounted on the lithium-ion battery, for obtaining the surface temperature and the tab voltage of the lithium-ion battery;

[0010] The processing component is communicated with the sensing component and the gas collection control component respectively, and is used to determine the thermal runaway stage of the lithium-ion battery based on the surface temperature and the tab voltage obtained by the sensing component, and to control the gas collection control component to obtain mixed gases at different gas collection ports at different thermal runaway stages, and to analyze the mixed gases corresponding to different thermal runaway stages.

[0011] Optionally, the sealed box has five gas collection ports, which are respectively a first gas collection port located on the first side of the sealed box, a second gas collection port located on the second side of the sealed box, a third gas collection port located on the third side of the sealed box, a fourth gas collection port located on the fourth side of the sealed box, and a fifth gas collection port located on the top surface of the sealed box; wherein, the first side and the third side are arranged opposite to each other, and the second side and the fourth side are arranged opposite to each other.

[0012] Optionally, the first gas collection port is located at the geometric center of the first side of the sealed box, the second gas collection port is located at the geometric center of the second side of the sealed box, the third gas collection port is located at the geometric center of the third side of the sealed box, the fourth gas collection port is located at the geometric center of the fourth side of the sealed box, and the fifth gas collection port is located at the geometric center of the top surface of the sealed box.

[0013] Optionally, the gas collection control component includes multiple control switches and multiple air bags, and the gas collection port, the control switch and the air bag correspond one to one. The gas collection port is connected to the air inlet of the control switch through a connecting pipe, and the air outlet of the control switch is connected to the air bag through a connecting pipe.

[0014] Optionally, the gas collection control component includes: five control switches and five air bags, the five control switches are respectively a first control switch, a second control switch, a third control switch, a fourth control switch and a fifth control switch, and the five air bags are respectively a first air bag, a second air bag, a third air bag, a fourth air bag and a fifth air bag;

[0015] The first gas collection port is connected to the gas inlet of the first control switch through a connecting pipe, and the gas outlet of the first control switch is connected to the first air bag through a connecting pipe; when the first control switch is turned on, the mixed gas at the first gas collection port enters the first air bag;

[0016] The second gas collection port is connected to the gas inlet of the second control switch through a connecting pipe, and the gas outlet of the second control switch is connected to the second air bag through a connecting pipe; when the second control switch is turned on, the mixed gas at the second gas collection port enters the second air bag;

[0017] The third gas collection port is connected to the gas inlet of the third control switch through a connecting pipe, and the gas outlet of the third control switch is connected to the third air bag through a connecting pipe; when the third control switch is turned on, the mixed gas at the third gas collection port enters the third air bag;

[0018] The fourth gas collection port is connected to the gas inlet of the fourth control switch through a connecting pipe, and the gas outlet of the fourth control switch is connected to the fourth air bag through a connecting pipe; when the fourth control switch is turned on, the mixed gas at the fourth gas collection port enters the fourth air bag;

[0019] The fifth gas collection port is connected to the air inlet of the fifth control switch through a connecting pipe, and the air outlet of the fifth control switch is connected to the fifth air bag through a connecting pipe; when the fifth control switch is turned on, the mixed gas at the fifth gas collection port enters the fifth air bag.

[0020] Optionally, the thermal runaway stages of the lithium-ion battery include an early stage of thermal runaway, a middle stage of thermal runaway, and a late stage of thermal runaway;

[0021] The initial stage of thermal runaway is the moment when thermal runaway starts. When the surface temperature obtained by the sensing component reaches the first preset temperature, it is the initial stage of thermal runaway.

[0022] The middle stage of thermal runaway is when the time after the surface temperature acquired by the sensing component reaches the first preset temperature reaches the first preset time after the first preset time starts.

[0023] The late stage of thermal runaway is the second preset time after the end of thermal runaway. When the time after the pole ear voltage obtained by the sensing component reaches zero reaches the second preset time, it is the late stage of thermal runaway.

[0024] Optionally, the processing component is used to control the first control switch and the second control switch to open at the initial stage of thermal runaway, store the mixed gas at the first gas collection port in the first air bag, and store the mixed gas at the second gas collection port in the second air bag, to obtain the mixed gas corresponding to the initial stage of thermal runaway; control the third control switch and the fourth control switch to open in the middle stage of thermal runaway, store the mixed gas at the third gas collection port in the third air bag, and store the mixed gas at the fourth gas collection port in the fourth air bag, to obtain the mixed gas corresponding to the middle stage of thermal runaway; control the fifth control switch to open in the late stage of thermal runaway, store the mixed gas at the fifth gas collection port in the fifth air bag, and obtain the mixed gas corresponding to the late stage of thermal runaway.

[0025] Optionally, the processing component includes a gas chromatograph and a processor;

[0026] The gas chromatograph is used to analyze the mixed gas in the first gas bag, the mixed gas in the second gas bag, the mixed gas in the third gas bag, the mixed gas in the fourth gas bag, and the mixed gas in the fifth gas bag, respectively, to obtain the components and content of the mixed gas at the first gas collection port, the components and content of the mixed gas at the second gas collection port, the components and content of the mixed gas at the third gas collection port, the components and content of the mixed gas at the fourth gas collection port, and the components and content of the mixed gas at the fifth gas collection port;

[0027] The processor is communicatively connected to the gas chromatograph, and is used to analyze and obtain an empirical model of gas production characteristics corresponding to an early stage of thermal runaway based on the components and contents of the mixed gas at the first gas collection port and the components and contents of the mixed gas at the second gas collection port; to analyze and obtain an empirical model of gas production characteristics corresponding to a middle stage of thermal runaway based on the components and contents of the mixed gas at the third gas collection port and the components and contents of the mixed gas at the fourth gas collection port; and to analyze and obtain an empirical model of gas production characteristics corresponding to a late stage of thermal runaway based on the components and contents of the mixed gas at the fifth gas collection port; wherein the empirical model of gas production characteristics is the components and contents of the mixed gas at different positions in the closed box.

[0028] Optionally, the processor is further used to determine the explosion limits of the mixed gas at different positions of the closed box in different thermal runaway stages based on an empirical model of gas production characteristics corresponding to different thermal runaway stages.

[0029] In a second aspect, the present application provides a method for collecting and analyzing gas produced at different thermal runaway stages of a lithium-ion battery, using the device for collecting and analyzing gas produced at different thermal runaway stages of a lithium-ion battery as described above, the method for collecting and analyzing gas produced at different thermal runaway stages of a lithium-ion battery comprises:

[0030] Based on the surface temperature and the tab voltage of the lithium-ion battery obtained by the sensing component, determine the thermal runaway stage of the lithium-ion battery;

[0031] At different stages of thermal runaway, the gas collection control component is controlled to obtain mixed gases at different gas collection ports to obtain mixed gases corresponding to different stages of thermal runaway;

[0032] The mixed gases corresponding to different thermal runaway stages are analyzed to obtain empirical models of gas production characteristics corresponding to different thermal runaway stages;

[0033] Based on the empirical model of gas production characteristics corresponding to different thermal runaway stages, the explosion limits of mixed gases at different positions of the closed box in different thermal runaway stages are determined.

[0034] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0035] The present application provides a device and method for collecting and analyzing gas produced in different thermal runaway stages of lithium-ion batteries. A sealed box for accommodating lithium-ion batteries has multiple gas collection ports, which are located at different positions of the sealed box. A gas collection control component is respectively connected to each gas collection port pipeline of the sealed box to obtain mixed gas at the gas collection port. Based on the surface temperature and the tab voltage of the lithium-ion battery obtained by the sensing component, the thermal runaway stage of the lithium-ion battery is determined. In different thermal runaway stages, the gas collection control component is controlled to obtain mixed gas at different gas collection ports to obtain mixed gas corresponding to different thermal runaway stages, which can efficiently and accurately complete the collection of gas produced in different thermal runaway stages. The mixed gas corresponding to different thermal runaway stages is analyzed to obtain the gas production characteristic empirical model corresponding to different thermal runaway stages. Based on the gas production characteristic empirical model corresponding to different thermal runaway stages, the explosion limit of the mixed gas at different positions of the sealed box in different thermal runaway stages is determined, which can efficiently and accurately complete the analysis of gas produced in different thermal runaway stages. The present application can efficiently and accurately collect and analyze the gas produced in different thermal runaway stages and different positions of the sealed space of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 This is a schematic diagram of the changes in the battery surface temperature and the ambient temperature provided in Example 1 of the present application; wherein, Figure 1 (a) is the change of battery surface temperature; Figure 1 (b) in the figure is the change in ambient temperature.

[0038] Figure 2 This is a schematic diagram of the analysis of the components and contents of mixed gases at different thermal runaway stages provided in Example 1 of the present application; wherein, Figure 2 (a) is the composition and content of the mixed gas at the moment of thermal runaway; Figure 2 (b) shows the composition and content of the mixed gas 10s after thermal runaway.

[0039] Figure 3 A schematic diagram of a method flow chart of a method for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages provided in Example 2 of the present application.

[0040] Figure 4 A detailed flow chart of a method for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages provided in Example 2 of the present application. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0042] Example 1

[0043] This embodiment provides a device for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages. The device for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages includes:

[0044] The sealed box is used to accommodate lithium-ion batteries. The sealed box has multiple gas collection ports, which are located at different positions of the sealed box, and each gas collection port is a through hole connecting the inside and outside of the sealed box.

[0045] The gas collection control component is respectively connected to each gas collection port pipeline of the closed box body, and is used to obtain the mixed gas at the gas collection port.

[0046] The sensing component is installed on the lithium-ion battery and is used to obtain the surface temperature and tab voltage of the lithium-ion battery.

[0047] The processing component is communicated with the sensing component and the gas collection control component respectively, and is used to determine the thermal runaway stage of the lithium-ion battery based on the surface temperature and the tab voltage obtained by the sensing component, and to control the gas collection control component to obtain mixed gases at different gas collection ports at different thermal runaway stages, and to analyze the mixed gases corresponding to different thermal runaway stages.

[0048] In this embodiment, the lithium-ion battery to be tested is placed in a sealed box, and the lithium-ion battery is subsequently processed to cause thermal runaway of the lithium-ion battery, and the gas production of the lithium-ion battery at different thermal runaway stages and different positions is collected and analyzed.

[0049] In this embodiment, gas collection ports are arranged around the sealed box and on the top. Specifically, five gas collection ports are arranged at the geometric centers of the four sides and the top of the box.

[0050] Specifically, the sealed box has five gas collection ports, which are respectively a first gas collection port located on the first side of the sealed box, a second gas collection port located on the second side of the sealed box, a third gas collection port located on the third side of the sealed box, a fourth gas collection port located on the fourth side of the sealed box, and a fifth gas collection port located on the top surface of the sealed box. The first side and the third side are arranged opposite to each other, and the second side and the fourth side are arranged opposite to each other.

[0051] Each gas collection port is a through hole connecting the inside and outside of the sealed box, that is, the first gas collection port passes through the first side surface, the second gas collection port passes through the second side surface, the third gas collection port passes through the third side surface, the fourth gas collection port passes through the fourth side surface, and the fifth gas collection port passes through the top surface.

[0052] Preferably, the first gas collection port is located at the geometric center of the first side of the sealed box, the second gas collection port is located at the geometric center of the second side of the sealed box, the third gas collection port is located at the geometric center of the third side of the sealed box, the fourth gas collection port is located at the geometric center of the fourth side of the sealed box, and the fifth gas collection port is located at the geometric center of the top surface of the sealed box.

[0053] The five gas collection ports are all capable of transporting the mixed gas located at the gas collection ports inside the closed box to the outside of the closed box, thereby facilitating the completion of the mixed gas collection process at different positions of the closed box.

[0054] In this embodiment, the gas collection control component includes multiple control switches and multiple air bags. The gas collection port, the control switch and the air bag correspond one to one. The gas collection port is connected to the air inlet of the control switch through a connecting pipe, and the air outlet of the control switch is connected to the air bag through a connecting pipe.

[0055] Among them, the connecting pipe can be a hose, and the control switch includes a shell, a button located on the surface of the shell and a solenoid valve located inside the shell. When the solenoid valve is opened, it will not cause obstruction, and the mixed gas can enter the air bag from the gas collection port. When the solenoid valve is closed, it will cause obstruction, and the mixed gas cannot enter the air bag from the gas collection port.

[0056] The gas collection port and the air bag are respectively connected through connecting pipes, so that the mixed gas at the gas collection port can be stored in the air bag, and a control switch is arranged on each connecting pipe, so that each gas collection port is equipped with an independent switch control to control whether the mixed gas at each gas collection port inside the closed box can enter the air bag through the connecting pipe. When the solenoid valve is opened by controlling the processing component or by manually pressing a button, the mixed gas at the gas collection port can be stored in the air bag. When the solenoid valve is closed by controlling the processing component or by manually pressing a button, the mixed gas at the gas collection port cannot be stored in the air bag, thereby ensuring the independent and continuous operation of the gas collection ports at different positions when exhausting gas.

[0057] Specifically, the gas collection control component includes: five control switches and five air bags, the five control switches are respectively a first control switch, a second control switch, a third control switch, a fourth control switch and a fifth control switch, and the five air bags are respectively a first air bag, a second air bag, a third air bag, a fourth air bag and a fifth air bag.

[0058] The first gas collection port is connected to the air inlet of the first control switch through a connecting pipe, and the air outlet of the first control switch is connected to the first air bag through a connecting pipe. When the first control switch is turned on, the mixed gas at the first gas collection port enters the first air bag. When the first control switch is turned off, the mixed gas at the first gas collection port cannot enter the first air bag.

[0059] The second gas collection port is connected to the air inlet of the second control switch through a connecting pipe, and the air outlet of the second control switch is connected to the second air bag through a connecting pipe. When the second control switch is turned on, the mixed gas at the second gas collection port enters the second air bag. When the second control switch is turned off, the mixed gas at the second gas collection port cannot enter the second air bag.

[0060] The third gas collection port is connected to the air inlet of the third control switch through a connecting pipe, and the air outlet of the third control switch is connected to the third air bag through a connecting pipe. When the third control switch is turned on, the mixed gas at the third gas collection port enters the third air bag. When the third control switch is turned off, the mixed gas at the third gas collection port cannot enter the third air bag.

[0061] The fourth gas collection port is connected to the air inlet of the fourth control switch through a connecting pipe, and the air outlet of the fourth control switch is connected to the fourth air bag through a connecting pipe. When the fourth control switch is turned on, the mixed gas at the fourth gas collection port enters the fourth air bag. When the fourth control switch is closed, the mixed gas at the fourth gas collection port cannot enter the fourth air bag.

[0062] The fifth gas collection port is connected to the air inlet of the fifth control switch through a connecting pipe, and the air outlet of the fifth control switch is connected to the fifth air bag through a connecting pipe. When the fifth control switch is turned on, the mixed gas at the fifth gas collection port enters the fifth air bag. When the fifth control switch is turned off, the mixed gas at the fifth gas collection port cannot enter the fifth air bag.

[0063] The gas collection control component of this embodiment is equipped with an independent switch control to ensure independent and continuous operation of different gas collection ports during gas extraction at different stages of thermal runaway. The gas collection control component can freely control the start time and end time of gas collection, and determine the start time of different gas collection ports according to the surface temperature and the tab voltage of the lithium-ion battery. Since the amount and rate of gas production of lithium-ion batteries in different stages of thermal runaway are different, in order to ensure the subsequent qualitative and quantitative analysis of the mixed gas, this embodiment sets the gas collection volume control to about 300mL, that is, when the volume of the mixed gas in the air bag is 300mL, it is the end time of the gas collection port, and the volume of the air bag used in this embodiment is 300mL. After the collection is completed, the control switch is turned off in time to prevent the mixed gas from leaking in reverse, and at the same time prevent the subsequent gas production from entering the air bag through the connecting pipe due to the pressure difference, causing the mixed gas in the air bag to be contaminated. It should be noted that 300mL is only an example given in this embodiment, and other volumes of air bags can also be selected as needed, such as 500mL.

[0064] In this embodiment, the device for collecting and analyzing gas produced at different thermal runaway stages of the lithium-ion battery may also include: a heating component, which is installed on the lithium-ion battery and is used to cause thermal runaway of the lithium-ion battery. The heating component may be a heating plate, which is installed on one surface of the lithium-ion battery, and the heating plate is used to laterally heat the lithium-ion battery until thermal runaway occurs, and the surface temperature and the tab voltage of the lithium-ion battery are obtained through the sensing component, so as to monitor the thermal runaway process of the lithium-ion battery in real time.

[0065] In this embodiment, the sensing components include: a temperature sensor installed on the surface of the lithium-ion battery, used to obtain the surface temperature of the lithium-ion battery; a voltage sensor, connected to the tab of the lithium-ion battery, used to obtain the tab voltage of the lithium-ion battery; wherein the temperature sensor can be a thermocouple.

[0066] This embodiment can also monitor changes in ambient temperature, where the ambient temperature refers to the temperature inside the sealed box.

[0067] In this embodiment, the thermal runaway stage of the lithium-ion battery includes the initial stage of thermal runaway, the middle stage of thermal runaway and the late stage of thermal runaway. When the internal materials of the lithium-ion battery begin to react, the voltage of the pole ear of the lithium-ion battery will decrease slightly, and a small amount of gas can be observed on the surface of the lithium-ion battery. Among them, the initial stage of thermal runaway is the moment when the thermal runaway starts. When the surface temperature obtained by the sensing component reaches the first preset temperature, it means that the thermal runaway starts, and it is the initial stage of thermal runaway. The first preset temperature can be about 350°C; the middle stage of thermal runaway is after the first preset time of the start of thermal runaway. When the surface temperature obtained by the sensing component reaches the first preset temperature, it is the middle stage of thermal runaway. The first preset time can be 10s; the late stage of thermal runaway is after the second preset time of the end of thermal runaway. When the pole ear voltage obtained by the sensing component is zero, it means that the thermal runaway ends. At this time, the ambient temperature begins to drop. When the time after the pole ear voltage obtained by the sensing component reaches zero reaches the second preset time, it is the late stage of thermal runaway. The second preset time can be 30s or 1min. Based on the above-mentioned division methods of different thermal runaway stages, the processing component of this embodiment can determine the thermal runaway stage of the lithium-ion battery based on the surface temperature and the tab voltage obtained by the sensor component.

[0068] When the thermal runaway stage of the lithium-ion battery includes the early stage of thermal runaway, the middle stage of thermal runaway and the late stage of thermal runaway, the processing component is used to control the first control switch and the second control switch to open at the early stage of thermal runaway, store the mixed gas at the first gas collection port in the first gas bag, and store the mixed gas at the second gas collection port in the second gas bag, so as to obtain the mixed gas (i.e., gas production) corresponding to the early stage of thermal runaway; control the third control switch and the fourth control switch to open at the middle stage of thermal runaway, store the mixed gas at the third gas collection port in the third gas bag, and store the mixed gas at the fourth gas collection port in the fourth gas bag, so as to obtain the mixed gas corresponding to the middle stage of thermal runaway; control the fifth control switch to open at the late stage of thermal runaway, store the mixed gas at the fifth gas collection port in the fifth gas bag, and obtain the mixed gas corresponding to the late stage of thermal runaway. Based on this, the gas collection control component can be controlled to obtain the mixed gas at different gas collection ports at different stages of thermal runaway, obtain the mixed gas corresponding to different stages of thermal runaway, and complete the gas production collection process at different stages of thermal runaway.

[0069] In the process of storing the mixed gas at the gas collection port into the air bag, the following two points need to be noted: first, when the volume of the mixed gas in the air bag reaches 300 mL, the control switch corresponding to the air bag should be turned off in time; second, in the middle stage of thermal runaway, the gas production is relatively large, and attention should be paid to the volume of the air bag to avoid the air bag from bursting.

[0070] It should be noted that, in this embodiment, according to experimental requirements, control switches corresponding to other gas collection ports may be selected to be turned on at different stages of thermal runaway.

[0071] In this embodiment, the processing component includes a gas chromatograph and a processor.

[0072] This embodiment uses a gas chromatograph to analyze the mixed gas in the airbag to determine the components and contents of the mixed gas corresponding to different thermal runaway stages. The components are the types of each gas included in the mixed gas, the contents are the proportions of each gas included in the mixed gas, and the proportions are the ratios of the concentrations of each gas included in the mixed gas to the concentration of the mixed gas, so as to complete the gas composition analysis. Specifically, the gas chromatograph is used to analyze the mixed gas in the first airbag, the mixed gas in the second airbag, the mixed gas in the third airbag, the mixed gas in the fourth airbag, and the mixed gas in the fifth airbag, respectively, to obtain the components and contents of the mixed gas at the first gas collection port, the components and contents of the mixed gas at the second gas collection port, the components and contents of the mixed gas at the third gas collection port, the components and contents of the mixed gas at the fourth gas collection port, and the components and contents of the mixed gas at the fifth gas collection port.

[0073] The processor is connected to the gas chromatograph for analyzing the gas production characteristics empirical model corresponding to the initial stage of thermal runaway based on the components and contents of the mixed gas at the first gas collection port and the components and contents of the mixed gas at the second gas collection port; analyzing the gas production characteristics empirical model corresponding to the middle stage of thermal runaway based on the components and contents of the mixed gas at the third gas collection port and the components and contents of the mixed gas at the fourth gas collection port; analyzing the gas production characteristics empirical model corresponding to the late stage of thermal runaway based on the components and contents of the mixed gas at the fifth gas collection port. Based on this, the mixed gas corresponding to different stages of thermal runaway can be analyzed to obtain the gas production characteristics empirical model corresponding to different stages of thermal runaway, and the gas production characteristics empirical model is the components and contents of the mixed gas at different positions in the closed box.

[0074] The processor may be a device with computing functions, such as a computer.

[0075] It should be noted that the gas chromatograph used for directional and quantitative analysis of gas needs to complete the calibration of the battery thermal runaway gas standard curve before testing. The battery thermal runaway gas standard curve uses the concentration of the standard sample as the horizontal coordinate and the peak area as the vertical coordinate. By making a battery thermal runaway gas standard curve, the concentration of the sample can be accurately determined. During the calibration process, the standard gas and carrier gas need to be calibrated. The configuration of the standard gas can refer to the research results reported in the existing literature, and multi-point calibration and correction can be performed. The carrier gases mainly include nitrogen, argon, helium, etc. The directional calibration of the carrier gas is mainly to reduce calculation errors.

[0076] Based on the obtained time series distribution data of the components and contents of the mixed gas (i.e., the components and contents of the mixed gas corresponding to different thermal runaway stages), an empirical model of the gas production characteristics corresponding to different thermal runaway stages in the thermal runaway process of the lithium-ion battery is established. Specifically, the components and contents of the mixed gas corresponding to each thermal runaway stage are used as input, and the fluent software is used to establish an empirical model of the gas production characteristics corresponding to each thermal runaway stage. The empirical model of the gas production characteristics is the components and contents of the mixed gas at different positions in the closed box, and the gas production release law at different thermal runaway stages in the thermal runaway process is analyzed. The components and contents of the gas produced at different thermal runaway stages are different. At the same time, due to the gas flow inside the closed box, the components and contents of the gas produced collected at different positions of the closed box will be different. The gas production release law refers to the components and contents of the gas produced at different positions in the closed box at different thermal runaway stages. A database of gas production release laws in the early, middle and late stages of thermal runaway and around the battery is established, thereby completing data analysis and model construction.

[0077] In this embodiment, the processor is further used to determine the explosion limits of the mixed gas at different positions of the closed box in different thermal runaway stages based on the empirical model of gas production characteristics corresponding to different thermal runaway stages.

[0078] In this embodiment, according to the Richard Chateli formula, the explosion limit of the mixed gas corresponding to different thermal runaway stages is theoretically calculated, and the calculation formula is as follows:

[0079]

[0080] Where L is the explosion limit of the pyrolysis gas of the lithium-ion battery, that is, the explosion limit of the mixed gas; V1, V2, V3...V n is the content of each component in the mixed gas (i.e. each gas included in the mixed gas); L1, L2, L3...L n It is the explosion limit of each component in the mixed gas.

[0081] Based on the different thermal runaway stages, such as the early, middle and late stages of thermal runaway, and the differences in gas types and concentrations at different locations such as the four sides and top of the lithium-ion battery, the correlation between internal material reactions and gas production during thermal runaway can be analyzed from a mechanism level. This can help accident investigators determine the degree of gas combustion and explosion at different stages of thermal runaway of lithium-ion batteries and at different locations inside the box, thereby providing methodological support for identifying the cause of the accident.

[0082] This embodiment can complete the collection and component analysis of gas produced by lithium-ion batteries at different thermal runaway stages and different locations. The explosion limits of gas produced at different thermal runaway stages and different locations can be used to infer the causes in reverse deduction during accident investigations, and can thus be applied to the study of thermal runaway mechanisms of lithium-ion batteries and the tracing of accident causes.

[0083] Lithium-ion battery thermal runaway produces various types of gas, and the concentration and flammability of each gas are different. Especially for accidents of combustion and explosion caused by thermal runaway of lithium-ion batteries, it is very difficult to determine at which stage of thermal runaway and at which position around the battery the combustion and explosion occurred, as well as the main gas types and concentrations at this time. This embodiment fills the gaps in existing research on gas acquisition and component analysis at different stages and locations during the thermal runaway of lithium-ion batteries through refined gas collection and qualitative and quantitative analysis methods, which is conducive to a more in-depth study of the thermal runaway mechanism, can help improve the efficiency of lithium-ion battery accident investigation, and solve the problem of difficulty in lithium-ion battery accident investigation.

[0084] The following provides experiments on gas collection and component analysis at different thermal runaway stages and locations of lithium-ion batteries:

[0085] Use a heating plate to heat the lithium-ion battery laterally until it reaches thermal runaway. The surface temperature of the lithium-ion battery rises sharply at the moment of thermal runaway. As the high-temperature gas is ejected, the ambient temperature in the closed box rises sharply. Figure 1 As shown, Figure 1 In the description, the heating surface refers to the surface of the lithium-ion battery that is in contact with the heating plate, the non-heating surface refers to any surface of the lithium-ion battery that is not in contact with the heating plate, the heating surface positive electrode refers to the position point on the heating surface close to the positive electrode of the lithium-ion battery, the heating surface center refers to the central position point of the heating surface, the heating surface negative electrode refers to the position point on the heating surface close to the negative electrode of the lithium-ion battery, the non-heating surface positive electrode refers to the position point on the non-heating surface close to the positive electrode of the lithium-ion battery, the non-heating surface center refers to the central position point of the non-heating surface, the non-heating surface negative electrode refers to the position point on the non-heating surface close to the negative electrode of the lithium-ion battery, and the box Body 1 refers to the position point on the first side of the sealed box body close to the first gas collection port, box 2 refers to the position point on the second side of the sealed box body close to the second gas collection port, box 3 refers to the position point on the third side of the sealed box body close to the third gas collection port, box 4 refers to the position point on the fourth side of the sealed box body close to the fourth gas collection port, upper cover near 1 refers to the position point on the top surface of the sealed box body close to the first side, upper cover in the middle refers to the position point on the top surface of the sealed box body close to the fifth gas collection port, and upper cover near 3 refers to the position point on the top surface of the sealed box body close to the third side. Turn on the control switch at the moment of thermal runaway and 10s after thermal runaway to collect the mixed gas in the sealed box. The collected mixed gas is analyzed by gas chromatograph to obtain the components (i.e., gas types) and contents (i.e., the concentration ratios of each gas) of the mixed gas. The gas production analysis at different stages of thermal runaway is shown as follows. Figure 2As shown in the figure, the composition of the mixed gas at the moment of thermal runaway and 10s after thermal runaway is not much different, mainly including CO2, CO, H2, C2H4, CH4, etc. When the lithium-ion battery is immediately evacuated at the moment of thermal runaway, CO2 accounts for the highest proportion in the mixed gas, and H2 accounts for a lower proportion than CO2. In the mixed gas 10s after thermal runaway, the proportion of CO2 is significantly higher than that of other gases, reaching 45.6%, which is about 15% higher than the proportion of CO2 in the mixed gas at the moment of thermal runaway, but the CO content is about 10% lower than the proportion of CO in the mixed gas at the moment of thermal runaway. Since the gas composition and proportion of different thermal runaway stages change after the thermal runaway of the lithium-ion battery, the danger of each thermal runaway stage will also be different. In the future, in-depth research can be carried out on the gas production characteristics and dangers of different stages of thermal runaway.

[0086] Example 2

[0087] like Figure 3 and Figure 4 As shown, this embodiment provides a method for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages, and the device for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages described in Example 1 is used. The method for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages includes:

[0088] S1: Based on the surface temperature and tab voltage of the lithium-ion battery obtained by the sensing component, determine the thermal runaway stage of the lithium-ion battery.

[0089] S2: At different stages of thermal runaway, the gas collection control component is controlled to obtain mixed gases at different gas collection ports to obtain mixed gases corresponding to different stages of thermal runaway.

[0090] S3: Analyze the mixed gas corresponding to different thermal runaway stages to obtain an empirical model of gas production characteristics corresponding to different thermal runaway stages.

[0091] S4: Based on the empirical model of gas production characteristics corresponding to different thermal runaway stages, determine the explosion limits of the mixed gas at different positions of the closed box in different thermal runaway stages.

[0092] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages, characterized in that: The device for collecting and analyzing gas produced by the lithium-ion battery at different thermal runaway stages comprises: A sealed box for accommodating a lithium-ion battery; the sealed box has a plurality of gas collection ports, the plurality of gas collection ports are located at different positions of the sealed box, and each gas collection port is a through hole connecting the inside and the outside of the sealed box; The gas collection control component is respectively connected to each gas collection port pipeline of the closed box to obtain the mixed gas at the gas collection port; A sensing component, mounted on the lithium-ion battery, for obtaining the surface temperature and the tab voltage of the lithium-ion battery; The processing component is communicated with the sensing component and the gas collection control component respectively, and is used to determine the thermal runaway stage of the lithium-ion battery based on the surface temperature and the tab voltage obtained by the sensing component, and to control the gas collection control component to obtain mixed gases at different gas collection ports at different thermal runaway stages, and to analyze the mixed gases corresponding to different thermal runaway stages.

2. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 1, characterized in that: The sealed box has five gas collection ports, which are respectively a first gas collection port located on the first side of the sealed box, a second gas collection port located on the second side of the sealed box, a third gas collection port located on the third side of the sealed box, a fourth gas collection port located on the fourth side of the sealed box and a fifth gas collection port located on the top surface of the sealed box; wherein the first side and the third side are arranged opposite to each other, and the second side and the fourth side are arranged opposite to each other.

3. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 2, characterized in that: The first gas collection port is located at the geometric center of the first side of the sealed box, the second gas collection port is located at the geometric center of the second side of the sealed box, the third gas collection port is located at the geometric center of the third side of the sealed box, the fourth gas collection port is located at the geometric center of the fourth side of the sealed box, and the fifth gas collection port is located at the geometric center of the top surface of the sealed box.

4. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 2, characterized in that: The gas collection control component includes multiple control switches and multiple air bags. The gas collection port, the control switch and the air bag correspond one to one. The gas collection port is connected to the air inlet of the control switch through a connecting pipe, and the air outlet of the control switch is connected to the air bag through a connecting pipe.

5. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 4, characterized in that: The gas collection control component includes: five control switches and five air bags, the five control switches are respectively a first control switch, a second control switch, a third control switch, a fourth control switch and a fifth control switch, and the five air bags are respectively a first air bag, a second air bag, a third air bag, a fourth air bag and a fifth air bag; The first gas collection port is connected to the gas inlet of the first control switch through a connecting pipe, and the gas outlet of the first control switch is connected to the first air bag through a connecting pipe; when the first control switch is turned on, the mixed gas at the first gas collection port enters the first air bag; The second gas collection port is connected to the gas inlet of the second control switch through a connecting pipe, and the gas outlet of the second control switch is connected to the second air bag through a connecting pipe; when the second control switch is turned on, the mixed gas at the second gas collection port enters the second air bag; The third gas collection port is connected to the gas inlet of the third control switch through a connecting pipe, and the gas outlet of the third control switch is connected to the third air bag through a connecting pipe; when the third control switch is turned on, the mixed gas at the third gas collection port enters the third air bag; The fourth gas collection port is connected to the gas inlet of the fourth control switch through a connecting pipe, and the gas outlet of the fourth control switch is connected to the fourth air bag through a connecting pipe; when the fourth control switch is turned on, the mixed gas at the fourth gas collection port enters the fourth air bag; The fifth gas collection port is connected to the air inlet of the fifth control switch through a connecting pipe, and the air outlet of the fifth control switch is connected to the fifth air bag through a connecting pipe; when the fifth control switch is turned on, the mixed gas at the fifth gas collection port enters the fifth air bag.

6. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 5, characterized in that: The thermal runaway stages of lithium-ion batteries include the early stage of thermal runaway, the middle stage of thermal runaway and the late stage of thermal runaway; The initial stage of thermal runaway is the moment when thermal runaway starts. When the surface temperature obtained by the sensing component reaches the first preset temperature, it is the initial stage of thermal runaway. The middle stage of thermal runaway is when the time after the surface temperature acquired by the sensing component reaches the first preset temperature reaches the first preset time after the first preset time starts. The late stage of thermal runaway is the second preset time after the end of thermal runaway. When the time after the pole ear voltage obtained by the sensing component reaches zero reaches the second preset time, it is the late stage of thermal runaway.

7. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 6, characterized in that: The processing component is used to control the first control switch and the second control switch to open at the initial stage of thermal runaway, store the mixed gas at the first gas collection port in the first gas bag, and store the mixed gas at the second gas collection port in the second gas bag, so as to obtain the mixed gas corresponding to the initial stage of thermal runaway; In the middle stage of thermal runaway, the third control switch and the fourth control switch are controlled to be open, the mixed gas at the third gas collection port is stored in the third gas bag, and the mixed gas at the fourth gas collection port is stored in the fourth gas bag, so as to obtain the mixed gas corresponding to the middle stage of thermal runaway; In the late stage of thermal runaway, the fifth control switch is controlled to be opened, and the mixed gas at the fifth gas collection port is stored in the fifth gas bag to obtain the mixed gas corresponding to the late stage of thermal runaway.

8. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 7, characterized in that: The processing unit includes a gas chromatograph and a processor; The gas chromatograph is used to analyze the mixed gas in the first gas bag, the mixed gas in the second gas bag, the mixed gas in the third gas bag, the mixed gas in the fourth gas bag, and the mixed gas in the fifth gas bag, respectively, to obtain the components and content of the mixed gas at the first gas collection port, the components and content of the mixed gas at the second gas collection port, the components and content of the mixed gas at the third gas collection port, the components and content of the mixed gas at the fourth gas collection port, and the components and content of the mixed gas at the fifth gas collection port; a processor, communicatively connected to the gas chromatograph, for analyzing and obtaining an empirical model of gas production characteristics corresponding to an early stage of thermal runaway based on the components and contents of the mixed gas at the first gas collection port and the components and contents of the mixed gas at the second gas collection port; and for analyzing and obtaining an empirical model of gas production characteristics corresponding to an intermediate stage of thermal runaway based on the components and contents of the mixed gas at the third gas collection port and the components and contents of the mixed gas at the fourth gas collection port; Based on the components and content of the mixed gas at the fifth gas collection port, an empirical model of gas production characteristics corresponding to the late stage of thermal runaway is analyzed; wherein the empirical model of gas production characteristics is the components and content of the mixed gas at different positions in the closed box.

9. The device for collecting and analyzing gas produced by lithium-ion batteries at different thermal runaway stages according to claim 8, characterized in that: The processor is also used to determine the explosion limits of the mixed gas at different positions of the closed box in different thermal runaway stages based on the empirical model of gas production characteristics corresponding to different thermal runaway stages.

10. A method for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages, using the device for collecting and analyzing gas produced by a lithium-ion battery at different thermal runaway stages as claimed in any one of claims 1 to 9, characterized in that: The method for collecting and analyzing gas produced by the lithium-ion battery at different thermal runaway stages includes: Based on the surface temperature and the tab voltage of the lithium-ion battery obtained by the sensing component, determine the thermal runaway stage of the lithium-ion battery; At different stages of thermal runaway, the gas collection control component is controlled to obtain mixed gases at different gas collection ports to obtain mixed gases corresponding to different stages of thermal runaway; The mixed gases corresponding to different thermal runaway stages are analyzed to obtain empirical models of gas production characteristics corresponding to different thermal runaway stages; Based on the empirical model of gas production characteristics corresponding to different thermal runaway stages, the explosion limits of mixed gases at different positions of the closed box in different thermal runaway stages are determined.

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