A method and device for researching thermal runaway of a segmented charging triggered lithium ion battery

Abstract

The application provides a research method and device for triggering thermal runaway of a segmented charging lithium ion battery, and the device comprises a lithium ion battery, a simulated energy storage cabin, a battery detector, a thermocouple group, a temperature recorder, a visible light monitoring device, a gas detector group, a gas sampling device and a gas chromatograph. The method comprises the following steps: in a charging preparation stage, the battery is fixed in the cabin, and it is confirmed that all devices are in normal operation; in a first charging stage, the battery is charged with constant current, and a charging pause voltage is set; in a charging pause stage, when the battery voltage reaches the charging pause voltage, the charging is paused, and the battery does not occur thermal runaway; in a second charging stage, after the pause is over, the battery is charged with constant current until thermal runaway occurs. The segmented charging in the above scheme can simulate the complex working conditions in the actual application of the lithium ion battery, and research the voltage, temperature, deformation, gas production and smoke production characteristics of the battery in the whole process, thereby providing strong support for the research on the thermal runaway safety warning technology of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion safety research technology, specifically a research method and apparatus for triggering thermal runaway of lithium-ion batteries through segmented charging. Background Technology

[0002] In recent years, lithium-ion batteries have become one of the most important battery types in the field of electrochemical energy storage due to their advantages such as high energy density, long lifespan, and good stability. They are widely used in electric vehicles, energy storage power stations, and aerospace. However, frequent safety incidents involving lithium-ion batteries during use indicate that they pose serious safety hazards, especially during thermal runaway. Lithium-ion batteries have been used in electric vehicles for a longer period, and current research on thermal runaway in lithium-ion batteries is mostly based on the operating conditions of power batteries. However, the operating conditions of energy storage batteries, which are stored for extended periods, are vastly different from those of power batteries. The significant characteristics of energy storage environments are constant temperature and static storage. Energy storage batteries have a closed, prefabricated structure, eliminating direct heat sources and the thermal runaway triggering conditions such as collisions or punctures common in electric vehicles. Overcharging-triggered thermal runaway is the most common failure condition for energy storage batteries, making it necessary to conduct research on overcharging-triggered thermal runaway in lithium-ion batteries under energy storage conditions.

[0003] Invention CN113064079A discloses a testing device and method for overcharge performance of lithium-ion power battery packs. The testing device includes a test chamber, a lithium-ion battery under test, gas pipelines, and a gas collection box. During battery charging, this method uses a composite FBG sensor to accurately measure transient changes in pressure and temperature, and simultaneously measures the total amount of gas generated, providing strong technical support for the analysis and improvement of lithium-ion battery safety performance. Invention CN114996932A discloses a modeling method for an overcharge thermal runaway model of lithium-ion batteries. This method establishes an electrochemical quasi-two-dimensional model, a lumped heat model, and a lumped heat abuse model for lithium-ion batteries. These models are coupled, and the initial overcharge thermal runaway model is calibrated using voltage and temperature curves of the lithium-ion battery recorded during testing, resulting in a final overcharge thermal runaway model coupled with electrochemical-thermal-thermal abuse parameters. This invention can more accurately simulate the overcharge thermal runaway behavior of lithium-ion batteries and obtain the voltage and temperature change patterns during the overcharge thermal runaway process. The invention, with publication number CN114739618A, discloses a comprehensive experimental method for visualizing lithium battery thermal runaway under multi-factor coupled stimulation. Based on a comprehensive experimental device for visualizing lithium battery thermal runaway under multi-factor coupled stimulation, it includes a thermal runaway sealed experimental tank, a high-pressure gas distribution system, a lithium battery clamping device, an external stimulus application device, a heat application device, a multi-stage gas collection system, a data acquisition system, and a central control cabinet. This experimental method can be used to study the thermal runaway laws of lithium batteries under multi-factor coupled effects and can perform multi-stage, full-cycle dynamic risk analysis of the entire thermal runaway process.

[0004] Thermal abuse, electrical abuse, and mechanical abuse are external factors that can trigger thermal runaway in lithium-ion batteries. These external factors can cause internal short circuits, generating a large amount of heat and gas in a short period. When excessive heat accumulates inside the battery, causing the internal temperature to exceed the reaction critical value, a series of chemical reactions are triggered, leading to thermal runaway. Considering the application scenarios of energy storage batteries, overcharging (electrical abuse) is a major factor triggering thermal runaway in lithium-ion batteries during use. Currently, energy storage compartments are typically equipped with gas detectors, smoke detectors, temperature sensors, etc., working in conjunction with a battery management system (BMS) to manage the state of lithium-ion batteries. To improve the operational reliability of lithium-ion batteries in energy storage systems and reduce related safety accidents, it is necessary to study the characteristics of overcharging-triggered thermal runaway in lithium-ion batteries.

[0005] Current research methods for studying overcharging-triggered thermal runaway in lithium-ion batteries generally focus on continuous, uninterrupted overcharging. However, lithium-ion batteries operate under complex and variable conditions, and overcharging can be discontinuous. Examples include: 1) discontinuous charging caused by direct malfunction of the energy storage unit's charging device; 2) discontinuous charging caused by poor contact between the charging system and the battery, or between different batteries; and 3) discontinuous charging caused by misjudgments by the Battery Management System (BMS) due to differences in the State of Health (SOH) of individual cells within a lithium-ion battery module. Existing thermal runaway research methods do not adequately consider these discontinuous charging conditions. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to propose a research method and apparatus for triggering thermal runaway of lithium-ion batteries through segmented charging. By employing a segmented charging method to trigger thermal runaway of lithium-ion batteries, the invention simulates the discontinuous charging conditions in practical applications and studies the characteristics of lithium-ion battery thermal runaway, such as voltage, temperature, deformation, gas generation, and smoke generation, during this process. This provides strong support for the research of lithium-ion battery thermal runaway safety early warning technology.

[0007] A research device for triggering thermal runaway of lithium-ion batteries by segmented charging includes a simulated energy storage chamber, a battery detector, a thermocouple assembly, a temperature recorder, a visible light monitoring device, a gas detector assembly, a gas sampling device, and a gas chromatograph.

[0008] The simulated energy storage chamber is used to simulate the energy storage application environment of lithium-ion batteries.

[0009] The battery tester is connected to the lithium-ion battery and is used to charge and discharge the lithium-ion battery, as well as monitor the voltage and current during the charging and discharging process.

[0010] The thermocouple assembly is arranged on the surface of the lithium-ion battery and is used to measure the surface temperature of the battery during thermal runaway.

[0011] The temperature recorder is connected to a thermocouple assembly and is used to record the changes in the surface temperature of the battery during the thermal runaway of the lithium-ion battery.

[0012] The visible light monitoring equipment is used to capture images of the simulated energy storage compartment and record the deformation and gas and smoke production behavior during the thermal runaway of the lithium-ion battery.

[0013] The gas detector array is used to monitor the concentration of various thermal runaway characteristic gases in the simulated energy storage chamber in real time.

[0014] The gas sampling device is used to periodically extract a small amount of gas from the simulated energy storage chamber and introduce it into the gas chromatograph.

[0015] The gas chromatograph is used to accurately detect the components of the introduced gas and analyze the variation patterns of the concentrations of various characteristic gases.

[0016] Furthermore, the simulated energy storage chamber is welded from steel plates.

[0017] Furthermore, the thermocouple assembly includes four thermocouples, with the thermocouple contacts arranged on the surface of the lithium-ion battery, and the tail of the thermocouple connected to a temperature recorder.

[0018] Furthermore, of the four thermocouples, the first thermocouple contact is arranged near the positive terminal of the battery, the second thermocouple contact is arranged near the negative terminal of the battery, the third thermocouple contact is arranged on the front of the battery, and the fourth thermocouple contact is arranged on the side of the battery.

[0019] A method for studying segmented charging-triggered thermal runaway of lithium-ion batteries, using the aforementioned apparatus, includes the following steps:

[0020] Charging preparation: Fix the lithium-ion battery in the simulated energy storage chamber, connect the lithium-ion battery to the battery tester, arrange the thermocouple group on the surface of the lithium-ion battery, turn on the other equipment and confirm that it is working properly.

[0021] The first stage of charging involves constant current charging of the lithium-ion battery using a battery tester. During the charging process, the battery tester monitors the voltage changes of the battery. The charging pause voltage is set to Vt. When the battery voltage reaches Vt, the power is completely cut off, and the battery will not experience thermal runaway. A gas detector group, a gas sampling device, and a gas chromatograph work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber. Visible light monitoring equipment captures images and records the deformation and gas and smoke production behavior of the lithium-ion battery during overcharging.

[0022] Charging pause: When the lithium-ion battery voltage rises to Vt, charging pauses. During the pause, the battery will not experience thermal runaway, but gas will still be generated. A gas detector group, a gas sampling device, and a gas chromatograph work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber. Visible light monitoring equipment captures images and records the deformation and gas and smoke generation behavior of the lithium-ion battery during the charging pause.

[0023] The second stage of charging: After a period of pause, the lithium-ion battery continues to be charged at a constant current until thermal runaway occurs. During the charging process, the battery detector monitors the voltage changes of the battery, and the gas detector group, gas sampling device and gas chromatograph work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber. Visible light monitoring equipment captures images and records the deformation and gas and smoke production behavior of the lithium-ion battery during the charging pause.

[0024] Furthermore, the charging pause voltage Vt = 20V.

[0025] Furthermore, the second charging pause time is 30 minutes.

[0026] This invention proposes a research method and device for segmented charging triggering thermal runaway of lithium-ion batteries. It can analyze the battery voltage, temperature, deformation, gas generation and smoke generation characteristics of lithium-ion batteries triggered by segmented overcharging, providing strong support for the research of lithium-ion battery thermal runaway safety early warning technology. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of one embodiment of the research device for triggering thermal runaway of lithium-ion batteries by segmented charging according to the present invention;

[0028] Figure 2 This is a flowchart of one embodiment of the research method for triggering thermal runaway of lithium-ion batteries by segmented charging according to the present invention;

[0029] Figure 3 (a) is a battery voltage signal diagram during the first stage of charging in the process of segmented charging triggering thermal runaway of lithium-ion battery according to an embodiment of the present invention, and (b) is a battery voltage signal diagram during the second stage of charging.

[0030] Figure 4 This is a graph showing the change in characteristic gas concentration during the segmented charging process that triggers thermal runaway of a lithium-ion battery according to an embodiment of the present invention.

[0031] Figure 5 This is a schematic diagram of the arrangement of thermocouple temperature measuring points on the surface of the segmented battery according to an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The process of thermal runaway triggered by overcharging in lithium-ion batteries can be divided into four stages, as follows:

[0034] The first stage involves lithium delithiation at the positive electrode and lithium insertion at the negative electrode, causing the battery voltage to gradually increase. During this stage, the lithium insertion at the negative electrode reacts with the polymer binder in the electrode material, producing hydrogen gas. Due to the small amount of gas produced, the lithium battery does not deform.

[0035] Second stage: Severe delithiation of the positive electrode, formation of a large number of lithium dendrites on the negative electrode, significant increase in battery voltage, and battery begins to expand and deform.

[0036] Phase 3: As the battery temperature rises, the solid electrolyte interface (SEI) decomposes at high temperatures, producing ethylene and carbon dioxide. Lithium-ionized material at the negative electrode reacts with the battery electrolyte, generating hydrocarbon gases. Oxygen produced by the decomposition of the positive electrode material reacts with the electrolyte to produce carbon monoxide and carbon dioxide. During this phase, the battery safety valve opens, releasing the gases generated by the internal chemical reactions, resulting in a significant increase in the concentration of various gases within the energy storage chamber.

[0037] Fourth stage: The lithium battery separator melts, causing direct contact between the two battery terminals, triggering an internal short circuit. This generates a large amount of heat, promoting side reactions such as electrolyte decomposition, and producing dense smoke. Thermal runaway occurs when the battery temperature reaches 200-300℃.

[0038] During the entire process of thermal runaway triggered by overcharging in lithium-ion batteries, the battery voltage continuously increases until an internal short circuit occurs, at which point the voltage drops to zero. Selecting an appropriate charging pause voltage during overcharging can prevent thermal runaway after charging is paused. In the first stage of charging, a charging pause voltage is set; charging is paused when the battery voltage reaches this value, and then resumed after a certain period until the battery experiences a complete internal short circuit, leading to thermal runaway. This invention is primarily used to study the battery characteristics during the thermal runaway process of lithium-ion batteries triggered by segmented charging.

[0039] like Figure 1 As shown, this embodiment of the invention provides a research device for segmented charging-triggered thermal runaway of lithium-ion batteries, including a lithium-ion battery 1, a simulated energy storage chamber 2, a battery detector 3, a thermocouple group 4, a temperature recorder 5, a visible light monitoring device 6, a gas detector group 7, a gas sampling device 8, and a gas chromatograph 9.

[0040] The lithium-ion battery 1 is selected from lithium-ion batteries with good appearance and 100% state of charge.

[0041] The simulated energy storage chamber 2 is welded from steel plates and is designed to simulate the energy storage application environment of the lithium-ion battery 1. The simulated energy storage chamber 2 has explosion-proof characteristics and has channels for connecting with other equipment around its perimeter.

[0042] The battery tester 3 is used to charge and discharge the lithium-ion battery 1, and can monitor the voltage and current of the lithium-ion battery 1 during the charging and discharging process.

[0043] like Figure 5 As shown, the thermocouple group 4 includes four thermocouples (ad). These thermocouples measure the surface temperature of the battery during thermal runaway. Their contacts are arranged on the surface of the lithium-ion battery 1, and their tails are connected to the temperature recorder 5. The arrangement of temperature measurement points on the battery surface is shown in the reference diagram. Figure 5Thermocouple a is located near the positive terminal of the battery, thermocouple b is located near the negative terminal of the battery, thermocouple c is located on the front of the battery, and thermocouple d is located on the side of the battery.

[0044] The temperature recorder 5 is connected to the thermocouple group 4 and is used to record the change in surface temperature of the lithium-ion battery 1 during thermal runaway.

[0045] The visible light monitoring device 6 is used to capture images inside the simulated energy storage chamber 2 and record the deformation and gas and smoke production behavior of the lithium-ion battery 1 during thermal runaway.

[0046] The gas detector group 7 is used to monitor the concentration of various thermal runaway characteristic gases in the simulated energy storage chamber 2 in real time.

[0047] The gas sampling device 8 is used to periodically extract a small amount of gas from the simulated energy storage chamber 2 and introduce it into the gas chromatograph 9.

[0048] The gas chromatograph 9 is used to accurately detect the components of the introduced gas and analyze the variation patterns of the concentrations of various characteristic gases.

[0049] like Figure 2 As shown in the figure, this embodiment of the invention provides a method for studying the thermal runaway of lithium-ion batteries triggered by segmented charging, using the above-mentioned apparatus. The method includes the following steps:

[0050] Charging preparation: Fix the lithium-ion battery 1 in the simulated energy storage chamber 2, connect the lithium-ion battery 1 to the battery tester 3, arrange the thermocouple group 4 on the surface of the lithium-ion battery 1, turn on the other equipment and confirm that it is working properly.

[0051] First stage of charging: The lithium-ion battery 1 is charged at a constant current using a battery tester 3. During the charging process, the battery tester 3 monitors the voltage change of the battery. The charging pause voltage is set to Vt (in this embodiment, Vt = 20V). When the battery voltage reaches Vt, the power is completely cut off, and the battery will not experience thermal runaway. The gas detector group 7, the gas sampling device 8, and the gas chromatograph 9 work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber 2. The visible light monitoring device 6 captures images and records the deformation and gas and smoke production behavior of the lithium-ion battery 1 during overcharging.

[0052] Charging pause: Charging pauses when the voltage of lithium-ion battery 1 rises to Vt. During the pause, the battery will not experience thermal runaway, but gas will still be generated. Gas detector group 7, gas sampling device 8, and gas chromatograph 9 work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber 2. Visible light monitoring equipment 6 captures images and records the deformation and gas / smoke generation behavior of lithium-ion battery 1 during the charging pause. The battery voltage change during this stage is referenced... Figure 3 Reference for changes in the concentration of some characteristic gases Figure 4;

[0053] The second stage of charging: After a period of pause (e.g., 30 minutes), lithium-ion battery 1 continues constant current charging until thermal runaway occurs. During charging, battery detector 3 monitors the battery voltage changes. Gas detector group 7, gas sampling device 8, and gas chromatograph 9 work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber 2. Visible light monitoring equipment 6 captures images and records the deformation and gas / smoke production behavior of lithium-ion battery 1 during the charging pause. The battery voltage change in this stage is referenced... Figure 3 Reference for changes in the concentration of some characteristic gases Figure 4 .

[0054] This invention employs a segmented charging method to trigger thermal runaway in lithium-ion batteries, simulating discontinuous charging conditions encountered in real-world applications, such as: 1) discontinuous charging caused by a direct malfunction of the energy storage compartment's charging device; 2) discontinuous charging caused by poor contact between the charging system and the battery, or poor contact between different batteries; and 3) discontinuous charging caused by misjudgments in the battery management system due to varying health states of individual cells within the lithium battery module. This segmented charging method for triggering thermal runaway in lithium-ion batteries can be implemented in two or more segments.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A research method for triggering thermal runaway in lithium-ion batteries through segmented charging, characterized in that... The study was conducted using a device for triggering thermal runaway of lithium-ion batteries through segmented charging. The device includes a simulated energy storage chamber, a battery detector, a thermocouple assembly, a temperature recorder, a visible light monitoring device, a gas detector assembly, a gas sampling device, and a gas chromatograph. The simulated energy storage chamber is used to simulate the energy storage application environment of lithium-ion batteries. The battery tester is connected to the lithium-ion battery and is used to charge and discharge the lithium-ion battery, as well as monitor the voltage and current during the charging and discharging process. The thermocouple assembly is arranged on the surface of the lithium-ion battery and is used to measure the surface temperature of the battery during thermal runaway. The temperature recorder is connected to a thermocouple assembly and is used to record the changes in the surface temperature of the battery during the thermal runaway of the lithium-ion battery. The visible light monitoring equipment is used to capture images of the simulated energy storage compartment and record the deformation and gas and smoke production behavior during the thermal runaway of the lithium-ion battery. The gas detector array is used to monitor the concentration of various thermal runaway characteristic gases in the simulated energy storage chamber in real time. The gas sampling device is used to periodically extract a small amount of gas from the simulated energy storage chamber and introduce it into the gas chromatograph. The gas chromatograph is used to accurately detect the components of the introduced gas and analyze the concentration variation patterns of each characteristic gas; the method includes the following steps: Charging preparation: Fix the lithium-ion battery in the simulated energy storage chamber, connect the lithium-ion battery to the battery tester, arrange the thermocouple group on the surface of the lithium-ion battery, turn on the other equipment and confirm that it is working properly. The first stage of charging involves constant current charging of the lithium-ion battery using a battery tester. During the charging process, the battery tester monitors the voltage changes of the battery. The charging pause voltage is set to Vt. When the battery voltage reaches Vt, the power is completely cut off, and the battery will not experience thermal runaway. A gas detector group, a gas sampling device, and a gas chromatograph work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber. Visible light monitoring equipment captures images and records the deformation and gas and smoke production behavior of the lithium-ion battery during overcharging. Charging pause: When the lithium-ion battery voltage rises to Vt, charging is paused. During the pause, the battery will not experience thermal runaway, but gas will still be generated. The gas detector group, gas sampling device and gas chromatograph work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber. Visible light monitoring equipment captures images and records the deformation and gas and smoke generation behavior of the lithium-ion battery during the charging pause. The second stage of charging: After a period of pause, the lithium-ion battery continues to be charged at a constant current until thermal runaway occurs. During the charging process, the battery detector monitors the voltage changes of the battery, and the gas detector group, gas sampling device and gas chromatograph work together to monitor the concentration changes of various thermal runaway characteristic gases in the simulated energy storage chamber. Visible light monitoring equipment captures images and records the deformation and gas and smoke production behavior of the lithium-ion battery during the charging pause.

2. The research method for segmented charging triggering thermal runaway of lithium-ion batteries as described in claim 1, characterized in that: The charging pause voltage Vt = 20 V.

3. The research method for segmented charging-triggered thermal runaway of lithium-ion batteries as described in claim 1, characterized in that: The second charging pause time is 30 minutes.

4. The research method for segmented charging-triggered thermal runaway of lithium-ion batteries as described in claim 1, characterized in that: The simulated energy storage chamber is welded from steel plates.

5. The research method for segmented charging-triggered thermal runaway of lithium-ion batteries as described in claim 1, characterized in that: The thermocouple assembly includes four thermocouples, with the thermocouple contacts arranged on the surface of the lithium-ion battery and the tail of the thermocouple connected to a temperature recorder.

6. The research method for segmented charging-triggered thermal runaway of lithium-ion batteries as described in claim 5, characterized in that: Of the four thermocouples, the first thermocouple contact is located near the positive terminal of the battery, the second thermocouple contact is located near the negative terminal of the battery, the third thermocouple contact is located on the front of the battery, and the fourth thermocouple contact is located on the side of the battery.

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