A battery thermal runaway temperature monitoring method based on electrode process principle

Abstract

This invention discloses a battery thermal runaway temperature monitoring method based on the electrode process principle. A coin cell is assembled and left at room temperature overnight. After the voltage is confirmed to be normal, it is installed in a battery cabinet and subjected to normal charge-discharge cycles of 0.1C for 3-10 cycles. The battery is then installed in a temperature-adjustable forced-air drying oven, and the activated coin cells are connected to an electrochemical workstation. The temperature-adjustable forced-air drying oven is heated from 25°C to 65°C at equal temperature intervals. The electrochemical workstation is used to perform EIS or CV measurements on the coin cells at each temperature to obtain the charge transfer resistance R of the coin cells. ct Or peak current I p Alternatively, an image showing the relationship between the relative diffusion coefficient and the internal temperature of a coin cell can be generated. Compared with existing technologies, the method according to the present invention can monitor the internal operating temperature of the battery in real time online, eliminating the problems of internal and external temperature lag and deviation, and effectively and timely reflecting the internal temperature of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery thermal runaway monitoring technology, and in particular to a battery thermal runaway temperature monitoring method based on the principle of electrode processes. Background Technology

[0002] Regardless of the type of battery, preventing and suppressing battery thermal runaway has always been a crucial issue in battery thermal management. Typically, exposure to high temperatures, external impacts, punctures, overcharging and discharging, external short circuits, and internal electrochemical side reactions can cause a rapid rise in battery temperature within a short period, further developing into a thermal runaway event, manifesting externally as fire, gas emission, or explosion. This poses a significant threat to the overall safety of many battery systems. For multi-cell batteries, not every cell experiences an internal short circuit or chemical degradation simultaneously. However, under normal circumstances, even if only one cell experiences an abnormal temperature, it can damage the entire battery and its power supply equipment, potentially leading to battery accidents such as fires or explosions.

[0003] To achieve effective and safe battery management, it is crucial to prevent and suppress battery thermal runaway events in advance. Common methods for detecting thermal runaway include: 1. Placing a temperature probe or sensor next to the battery pack to monitor the battery surface temperature. 2. Detecting the time corresponding to the amount of gas emitted during thermal runaway, thereby inferring the timing of the event. 3. In-situ multimodal calorimetry can also be used to test for thermal runaway in sodium batteries. Studies have shown that thermal runaway events in sodium batteries mainly occur during processes such as sodium melting, short circuits, gas generation, electrode decomposition reactions, exothermic reactions, battery heat release, and liner melting.

[0004] These methods also have shortcomings in measuring thermal runaway: 1. The internal temperature of the battery is often higher than the surface temperature, so temperature probes or sensors cannot effectively, accurately, and promptly reflect the internal temperature. 2. Detecting gases during thermal runaway by damaging the battery structure and collecting them in a large laboratory, using a remotely operated ventilation system for gas extraction and cleaning, requires large and costly equipment, making it unsuitable for industrialization. Furthermore, this method cannot reflect the real-time gas content emitted by the battery, thus failing to provide a specific method for detecting thermal runaway. 3. Simulation results may not be accurate. All of these conventional detection methods cannot reflect the internal temperature of the battery in real time.

[0005] Furthermore, since external conditions are easier to detect, temperature changes inside the battery can be understood through external detection methods to prevent thermal runaway. However, changes in the chemical composition of the electrodes inside the battery, such as short circuits or degradation of certain ions, are difficult to detect and cannot be prevented in advance because their initial changes do not cause changes in surface temperature or alter the photovoltaic power generation capacity.

[0006] Therefore, to monitor the internal temperature of a battery in real time and dynamically, it is necessary to start with the battery itself. Real-time, dynamic, online monitoring of the battery's internal temperature during operation necessitates the development of a battery thermal runaway temperature monitoring method based on electrode process principles. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a battery thermal runaway temperature monitoring method based on the electrode process principle. This method can monitor the internal temperature of the battery in real time and ultimately display the internal temperature of the battery visually on an electronic screen, accurately reflecting the battery temperature without any lag.

[0008] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0009] A method for monitoring battery thermal runaway temperature based on electrode process principles includes the following steps:

[0010] S1. Assemble the button cell battery and leave it at room temperature overnight after assembly.

[0011] S2. Use a multimeter to measure the voltage of the button cell. If the voltage is normal, install it in a battery cabinet and charge and discharge it at 0.1C for 3-10 cycles to activate the button cell.

[0012] S3. After removing the activated button cell from the battery cabinet, install it in a temperature-adjustable forced-air drying oven, and connect the activated button cell to the electrochemical workstation.

[0013] S4. In an adjustable-temperature drying oven, increase the temperature from 25°C to 65°C at equal intervals. After each temperature increase, maintain the coin cells at the set temperature for at least 60 minutes to ensure the internal temperature of the cells remains within the set range. Use an electrochemical workstation to perform EIS and / or CV measurements on the coin cells at each temperature, and use a computer connected to the electrochemical workstation to obtain the charge transfer resistance R of the coin cells. ct or peak current I p The relationship between the relative diffusion coefficient and the internal temperature of the coin cell was analyzed. Based on these data and the relationship between temperature, a corresponding graph was generated on the computer and displayed on the computer screen.

[0014] Furthermore, in step S4, the temperature interval is 5-10℃.

[0015] Furthermore, in step S4, during the CV detection of the button cell, the scanning window is set to 1.5-4.5V; the scanning rate is 2mV / s.

[0016] Furthermore, in step S4, the frequency range for EIS detection of the button cell is 0.01-100000Hz.

[0017] Compared with existing technologies, the method according to the present invention can directly reflect the internal temperature of the battery, that is, it can monitor the internal operating temperature of the battery in real time online, without the problems of internal and external temperature lag and deviation. It can effectively and timely reflect the internal temperature of the battery. When the battery temperature is abnormal, the battery can be dealt with in a timely manner to avoid greater problems caused by thermal runaway. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the battery thermal runaway temperature monitoring method based on the electrode process principle of the present invention.

[0019] Figure 2 For the results of EIS testing and R of different batteries ct and R s The image shows how the temperature changes.

[0020] Figure 3 This is the CV plot at a scan rate of 2mV / s.

[0021] Figure 4 It is four peak-to-peak values ​​(I) p Fit curves and peak voltage (ΔV) versus temperature.

[0022] Figure 5 This is a graph showing the relationship between the relative diffusion coefficient and temperature. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0024] Unless otherwise specified, all materials and equipment used in the following embodiments are commercially available.

[0025] Example 1

[0026] (1) The NASICON type positive electrode material Na4MnAl(PO4)3 was prepared by sol-gel method. It was mixed with conductive carbon and polyvinylidene fluoride in a ratio of 7:2:1, coated, dried, cut into pieces, and finally assembled into CR-2032 type button cell. The button cell was placed at room temperature overnight.

[0027] (2) Measure the voltage of the button cell with a multimeter. If the voltage is around 2V, it is a normal battery, indicating that it was not damaged during the assembly process. If the voltage is around 2V, it means that the battery was damaged during the assembly process. Return to step (1) and reassemble the button cell. Install the normal button cell in the Blue Battery Test Cabinet and charge and discharge it normally at 0.1C for 10 cycles. The purpose is to activate the button cell.

[0028] (3) Install the button cell from step (2) in a temperature-adjustable blower drying oven, and connect the activated button cell to an electrochemical workstation.

[0029] (4) The temperature-adjustable drying oven was heated from 25°C to 65°C at 10°C intervals. After each temperature increase, the coin cells were kept at the set temperature for at least 60 minutes to ensure that the internal temperature of the cells was within the set range. The coin cells at each temperature were subjected to EIS testing using an electrochemical workstation. The frequency range of the EIS was set from 0.01 to 100,000 Hz. The solution resistance R of the coin cells at each temperature was obtained. s Charge transfer resistance R ct The data was imported into the Zview software installed on the computer and fitted to obtain the data shown in Table 1.

[0030] Table 1

[0031]

[0032]

[0033] The solution resistance R of the coin cell at each temperature s Charge transfer resistance R ct The data, along with the fitted data in Table 1, can be imported into the Origin software installed on the computer to obtain the following results: Figure 2 The R values ​​of the different batteries shown s R ct The image shows how the temperature changes and is displayed on a computer screen, allowing even non-professionals to see the real-time temperature inside the battery.

[0034] Depend on Figure 2 It can be seen that as the internal temperature of the coin cell increases, the impedance of the coin cell gradually decreases, corresponding to... Figure 2 The radius of the middle semicircle is gradually decreasing. Figure 2 The right figure shows the R of different batteries. s and R ct A graph showing how temperature changes. (R) s The longitudinal axis applicable to the left half-axis, R ct The longitudinal axis applicable to the right half-axis, R sIt decreases with increasing temperature, but the trend is close to a straight line, indicating that R s It is not sensitive to temperature, so we do not use R. s To monitor temperature changes. ct It is the charge transfer resistance at the electrode surface, that is, between the electrolyte and the electrode. It is very sensitive to temperature, and its changes are quite large. At room temperature, R ct The Ω decreased by 400-700 Ω. As temperature increases, the electrode processes in the electrolyte and on the electrode surface react more rapidly, and R... ct The dominant factor is thermal motion. Higher temperatures lead to faster molecular diffusion, increasing the electron transport rate and quantity at the electrode surface, corresponding to R... ct Reduced. When the button cell is in normal operation, R decreases under different temperature control conditions. ct There will be a change; we can then monitor the internal temperature of the battery based on the change in resistance, i.e., using R... ct As a monitoring factor for battery thermal sensing, it achieves real-time online monitoring of the internal temperature of the coin cell during normal operation. This is achieved by real-time detection of the R... ct Then according to Figure 2 This can determine if the temperature of the button cell is abnormal. Once R ct When the temperature drops below a certain value, the battery reaches the point of thermal runaway. Timely thermal management of the button cell ensures safe operation, preventing thermal runaway and potential explosions.

[0035] Example 2

[0036] (1) The NASICON type positive electrode material Na4MnAl(PO4)3 was prepared by sol-gel method. It was mixed with conductive carbon and polyvinylidene fluoride in a ratio of 7:2:1, coated, dried, cut into pieces, and finally assembled into CR-2032 type button cell. The button cell was placed at room temperature overnight.

[0037] (2) Measure the voltage of the button cell with a multimeter. If the voltage is around 2V, it is a normal battery, indicating that it was not damaged during the assembly process. If the voltage is around 2V, it means that the battery was damaged during the assembly process. Return to step (1) and reassemble the button cell. Install the normal button cell in the Blue Battery Test Cabinet and charge and discharge it normally at 0.1C for 10 cycles. The purpose is to activate the button cell.

[0038] (3) Install the button cell from step (2) in a temperature-adjustable blower drying oven, and connect the activated button cell to an electrochemical workstation.

[0039] (4) The temperature-adjustable forced-air drying oven is heated from 25°C to 65°C at 10°C intervals. After each temperature increase, the coin cell is kept at the set temperature for at least 60 minutes to ensure that the internal temperature of the battery is within the set temperature. A CV (chemical current) test is performed on the coin cell at each temperature using an electrochemical workstation. The CV scan window should be set to 1.5-4.5V. The CV scan rate is 2mV / s. The peak current I of the coin cell is obtained. p The relationship between the temperature and the internal temperature of the coin cell is shown in Table 2.

[0040] Table 2

[0041] 25℃ 35℃ 45℃ 55℃ 65℃ <![CDATA[I p1 ]]> 3.6388E-4 4.3148E-4 5.1502E-4 5.6923E-4 5.4588E-4 <![CDATA[I p2 ]]> 1.9317E-4 2.2862E-4 2.8246E-4 3.3705E-4 3.7523E-4 <![CDATA[I p3 ]]> -1.2674E-4 -1.6012E-4 -1.9168E-4 -2.0662E-4 -1.7632E-4 <![CDATA[I p4 ]]> -1.2762E-4 -1.6294E-4 -1.9182E-4 -2.1841E-4 -2.375E-4

[0042] Depend on Figure 3 It is known that the higher the internal temperature of a coin cell, the more intense the redox reaction, and the degree of reduction reaction increases inversely with temperature. Therefore, a functional relationship can be determined by observing the relationship between the redox reaction inside the electrode material and temperature during normal charging and discharging of the battery:

[0043]

[0044] In the formula: Ip is the peak current, I0, A1, and a1 are all constants, and t represents the temperature; using the data in Table 2, the above formula is used to obtain:

[0045] I p1 '=(5.99636E-4)-(8.16074E-4)exp(-t / 20.56594) R 2 =0.89737;

[0046] I p2 ’ =-0.00253+(0.00261)exp(t / 596.01617)R 2 =0.98964;

[0047] I p3 ’ =-1.93988E-4+(8.36842E-4)exp(t / 10.00011)R 2 =0.8209;

[0048] I p4 ’ =-3.50329E-4+(3.41296E-4)exp(t / 58.36074)R 2 =0.9998;

[0049] Where: R 2This represents the magnitude of the error; the closer it is to 1, the smaller the error.

[0050] The temperature change can be inferred from the magnitude of the peak current during the redox reaction. It can be observed that at the same scan rate, the oxidation peak shifts slightly to the left with increasing temperature, while the reduction peak shifts slightly to the right with increasing temperature. The Ig of the coin cell at each temperature... p1 ’ I p2 ’ I p3 ’ I p4 ’ Import them together into the Origin software installed on your computer to get results such as... Figure 4 The four peak values ​​shown (I) p The fitting curves of temperature variation and the relationship between peak voltage (ΔV) and temperature variation are displayed on the computer screen.

[0051] Figure 4 The left figure is a fitting curve of the peak values ​​of the four peaks at a scan rate of 2 mV / s versus temperature. As the internal temperature of the coin cell increases, the peak current of the oxidation peak increases, while the peak current of the reduction peak increases in the opposite direction. Furthermore, there are two peak currents that show a different trend from the overall trend between 55℃ and 65℃, indicating that the internal structure of the coin cell may have changed. It is possible that the CEI film has begun to decompose, causing a charge transfer process inside the cell. Figure 4 The right figure shows the peak voltage and its variation with temperature at a scan rate of 2 mV / s. The trend is approximately a straight line, indicating that the peak voltage is minimally affected by temperature. Therefore, using peak voltage to detect internal temperature changes in the battery is not a feasible method. However, the relationship between peak current and temperature can be used to monitor the peak current I of the coin cell in real time. p Then according to Figure 4 The image on the right can be used to determine if the temperature of the button cell is abnormal, thus enabling real-time online monitoring of the internal temperature of the button cell.

[0052] Example 3

[0053] (1) The NASICON type positive electrode material Na4MnAl(PO4)3 was prepared by sol-gel method. It was mixed with conductive carbon and polyvinylidene fluoride in a ratio of 7:2:1, coated, dried, cut into pieces, and finally assembled into CR-2032 type button cell. The button cell was placed at room temperature overnight.

[0054] (2) Measure the voltage of the button cell with a multimeter. If the voltage is around 2V, it is a normal battery, indicating that it was not damaged during the assembly process. If the voltage is around 2V, it means that the battery was damaged during the assembly process. Return to step (1) and reassemble the button cell. Install the normal button cell in the Blue Battery Test Cabinet and charge and discharge it normally at 0.1C for 10 cycles. The purpose is to activate the button cell.

[0055] (3) Install the button cell from step (2) in a temperature-adjustable blower drying oven, and connect the activated button cell to an electrochemical workstation.

[0056] (4) The temperature-adjustable drying oven is heated from 25°C to 65°C at 10°C intervals. After each temperature increase, the coin cell is kept at the set temperature for at least 60 minutes to ensure that the internal temperature of the cell is within the set temperature. The coin cell is subjected to CV testing at each temperature using an electrochemical workstation. The CV scanning window should be set to 1.5-4.5V. The CV scanning rate is 2mV / s. The diffusion coefficient D0 of the coin cell at each temperature is calculated according to the following formula:

[0057]

[0058] In the formula: D0 represents the diffusion coefficient, I p The peak current is represented by T, the temperature by CV (cosine waveguide), and n represents the change in ion valence state, taken as the absolute value. For NMAP, n = 1, v is the scan rate, and C0 is the peak current. B The electrolyte concentration is 1 mol / L.

[0059] With D 25 The relative diffusion coefficient of the coin cell at different temperatures and its internal temperature are shown in Table 3, with the standard value D0 (measured at 25℃ under normal conditions). The subscripts indicate temperature.

[0060] Table 3

[0061]

[0062]

[0063] Importing the data in Table 3 and the temperature data into the Origin software installed on your computer will yield the following results: Figure 5 The graph showing the relationship between the relative diffusion coefficient and temperature is displayed on the computer screen.

[0064] Depend on Figure 5It can be seen that the relative diffusion coefficient exhibits a very complex nonlinear relationship with the increase of the internal temperature of the coin cell; as the internal temperature of the coin cell increases, the ratio of the diffusion coefficient increases, showing an overall upward trend. However, in the 55℃-65℃ range, similar to the previous peak current results, the upward trend changes. Figure 5 The trends of mid-peaks 3 and 4 begin to decline, but as the scan speed increases, in Figure 5 The peak values ​​of all four peaks showed a decreasing trend. The diffusion coefficient is related to the charge transfer process, indicating that the internal structure of the battery may have changed at this point, possibly due to the decomposition of the CEI film, which triggered the charge transfer process within the battery. Therefore, by real-time monitoring of the relative diffusion coefficient of the coin cell, and then based on... Figure 5 This allows you to determine if the temperature of the button cell battery is abnormal.

[0065] As can be seen from Examples 1-3 above, the principle of the present invention is as follows: First, the relationship between temperature-sensitive electrochemical parameters is found by exploring them, and the charge transfer resistance (R) is obtained by EIS and CV tests respectively. ct Peak current (I) p The relationship between parameters such as potential difference (ΔV) and diffusion coefficient (D0) and temperature is investigated. Firstly, based on the fact that during charge transfer, the electrode process reactions in the electrolyte and on the electrode surface accelerate with increasing temperature, R... ct The dominant factor is thermal motion. Higher temperatures lead to faster molecular diffusion, increasing the electron transport rate and quantity at the electrode surface, corresponding to R... ct The value of R decreases. When the battery is operating normally, under different temperature control conditions... ct There will be a change; we can use the change in resistance to monitor the change in the internal temperature of the battery, that is, using R... ct As a monitoring factor for battery thermal sensing, it achieves real-time online monitoring of the battery's internal temperature during normal operation. Once R ctBelow a certain value, the battery temperature reaches the point of thermal runaway. Timely thermal management can then be implemented to ensure safe operation and prevent accidents such as thermal runaway and explosions. Secondly, real-time monitoring of the battery via CV testing is crucial, especially for electrode materials with multiphase or multi-electron reactions, whose temperature sensitivity serves as a key factor in real-time temperature monitoring. Temperature changes rapidly affect the redox reactions of electrode materials. Temperature influences peak current, and their changes are essentially linear. Higher temperatures intensify redox reactions, while the reduction reaction intensifies inversely with temperature. Therefore, a functional relationship can be established between the redox reactions within the electrode materials and temperature during normal charging and discharging. The magnitude of the peak current during redox reactions can then be used to infer temperature changes. A one-to-one functional relationship between peak current and temperature allows for real-time monitoring of the redox peak current during battery operation. The relationship between the maximum normal operating temperature (critical temperature) and the peak current threshold is also important. When the peak current reaches the maximum threshold, timely intervention can be implemented to prevent thermal runaway. The peak voltage changes approximately as a straight line with increasing temperature, indicating that the peak voltage is only slightly affected by temperature, making it impractical to use peak voltage to detect internal temperature changes in the battery. As temperature increases, the ratio of diffusion coefficients increases, showing a non-linear relationship with temperature, and generally exhibiting an upward trend.

[0066] By measuring the temperature sensitivity coefficient and charge transfer resistance (R) ct Peak current (I) p Both the relative diffusion coefficient and temperature exhibit the following characteristics: Figure 2 , Figure 4 , Figure 5 The correspondence shown allows for real-time online detection of the battery's internal temperature using changes in these parameters. This effectively and promptly reflects the battery's internal temperature, enabling timely intervention when abnormal temperatures occur and preventing thermal runaway events.

[0067] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A battery thermal runaway temperature monitoring method based on the principle of electrode processes, characterized in that, Includes the following steps: S1. Assemble the button cell battery and leave it at room temperature overnight after assembly. S2. Use a multimeter to measure the voltage of the button cell. If the voltage is normal, install it in a battery cabinet and charge and discharge it at 0.1C for 3-10 cycles to activate the button cell. S3. After removing the activated button cell from the battery cabinet, install it in a temperature-adjustable forced-air drying oven, and connect the activated button cell to the electrochemical workstation. S4. In an adjustable-temperature drying oven, increase the temperature from 25°C to 65°C at equal intervals. After each temperature increase, maintain the coin cells at the set temperature for at least 60 minutes to ensure the internal temperature of the cells remains within the set range. Use an electrochemical workstation to perform EIS and / or CV measurements on the coin cells at each temperature, and use a computer connected to the electrochemical workstation to obtain the charge transfer resistance R of the coin cells. ct or peak current I p The relationship between the relative diffusion coefficient and the internal temperature of the coin cell was analyzed. Based on these data and the relationship between temperature, a corresponding graph was generated on the computer and displayed on the computer screen.

2. The battery thermal runaway temperature monitoring method based on the principle of electrode process according to claim 1, characterized in that: In step S4, the temperature interval is 5-10℃.

3. The battery thermal runaway temperature monitoring method based on the principle of electrode processes according to claim 1, characterized in that: In step S4, the CV detection of the button cell is performed at a scanning rate of 2mV / s.

4. The battery thermal runaway temperature monitoring method based on the principle of electrode process according to claim 1, characterized in that: In step S4, the frequency range for EIS detection of the button cell is 0.01-100000Hz.

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