Sodium-ion battery thermal runaway detection method and system

Abstract

The invention discloses a thermal runaway detection method and system for a sodium ion battery. The detection method comprises the following steps: acquiring battery voltage and surface pressure of a battery shell; a voltage change curve and a pressure change curve are obtained, the voltage change curve is a curve that the battery voltage changes along with time, and the pressure change curve is a curve that the surface pressure changes along with time; and in combination with the battery voltage, the pressure change curve, the surface pressure and the change of the pressure change curve, multi-stage early warning signals are sent out. According to the method, multi-stage early warning detection with pressure as a core parameter is adopted, the severity of thermal runaway can be effectively identified, corresponding measures are taken according to different stage characteristics, the detection accuracy is improved, the thermal runaway detection reliability of the sodium ion battery is improved, and the use safety of the sodium ion battery is improved.

Description

Technical Field

[0001] The present invention belongs to the field of battery technology, and in particular relates to a method and system for detecting thermal runaway of a sodium ion battery. Background Art

[0002] Sodium-ion batteries can experience thermal runaway under extreme operating conditions, leading to a sharp increase in internal battery temperature and even fire, explosion, and other safety incidents. During overcharging, the battery voltage exceeds the designed range, causing electrolyte decomposition and diaphragm damage, which in turn triggers thermal runaway reactions. This can easily lead to a sharp increase in battery temperature, fire, or explosion during the overcharging process.

[0003] In related technologies, some detection methods have been used to study the thermal runaway of lithium-ion batteries. However, since sodium-ion batteries differ from lithium-ion batteries in electrochemical properties, thermal stability, material systems, etc., the existing detection methods are not fully applicable to sodium-ion batteries. When detecting the thermal runaway of sodium-ion batteries, the reliability is low, which reduces the safety of sodium-ion batteries. Summary of the Invention

[0004] The purpose of the present invention is to make the detection of thermal runaway of sodium ion batteries more reliable, so as to improve the safety of sodium ion use.

[0005] To achieve the above objectives, the present invention proposes a sodium-ion battery thermal runaway detection method, comprising: obtaining a battery voltage and a surface pressure of a battery housing; obtaining a voltage change curve and a pressure change curve, wherein the voltage change curve is a curve showing the battery voltage changing over time, and the pressure change curve is a curve showing the surface pressure changing over time; and issuing a multi-level warning signal based on the battery voltage, the voltage change curve, the surface pressure, and the pressure change curve.

[0006] In an optional embodiment, the sodium-ion battery thermal runaway detection method further includes: obtaining a battery temperature; if the battery temperature is greater than a first preset temperature value, establishing a pressure-temperature coupling model based on the battery temperature and the surface pressure to obtain a corrected pressure value; wherein the corrected pressure value replaces the surface pressure in the pressure change curve.

[0007] In an optional embodiment, the calculation formula of the corrected pressure value is as follows: Where, P is the corrected pressure value, P measure is the measured pressure value, a is the temperature influence coefficient obtained by experimental fitting, T is the current measured temperature; T0 is the reference temperature.

[0008] In an optional embodiment, in combination with the battery voltage, the voltage change curve, the surface pressure, and the pressure change curve, a multi-level warning signal is issued respectively, specifically including: if the voltage change curve shows that the battery voltage continues to rise and the surface pressure is greater than a first preset pressure, a first-level warning signal is issued; if the pressure change curve shows that the surface pressure decreases, a second-level warning signal is issued;

[0009] If the pressure change curve shows that the pressure rise rate is greater than the preset pressure rate, and the voltage change curve shows that the voltage rise rate is greater than the preset voltage rate, a third-level warning signal is issued; if the voltage change curve shows that the battery voltage drops and the surface pressure is greater than the second preset pressure, a fourth-level warning signal is issued.

[0010] In an optional embodiment, before the surface pressure exceeds the second preset pressure, if the surface pressure rises sharply, the fourth warning is issued, and the sharp rise means that the surface pressure rises to more than 150% within a preset time period.

[0011] In an optional embodiment, the sodium-ion battery thermal runaway detection method further includes: obtaining the battery temperature; when the battery temperature rises to greater than a second preset temperature value, issuing a third-level warning signal; and / or obtaining the gas concentration in the battery, the gas concentration including the carbon dioxide concentration, the hydrogen concentration and the carbon monoxide concentration; when the gas concentration exceeds the preset concentration value, issuing the third-level warning signal.

[0012] In an optional embodiment, the sodium-ion battery thermal runaway detection method further includes: obtaining the battery weight of the battery; if the battery weight is lower than a preset weight and the voltage rise rate is greater than a preset voltage rate, issuing the third-level warning signal; if the battery weight is lower than a preset weight and the battery voltage drops, issuing the fourth-level warning signal.

[0013] In an optional embodiment, the sodium-ion battery thermal runaway detection method further includes: obtaining an incremental capacitance curve and a differential voltage curve; if a local peak appears in the incremental capacitance curve and a local trough appears in the differential voltage curve within the same time period, issuing the secondary warning signal; wherein the incremental capacitance curve is obtained by differentiating the capacitance and the open-circuit voltage: The differential voltage curve is the inverse of the incremental capacitance curve, and the calculation expression is: Where OCV is the open circuit voltage; Q is the capacity; V is the voltage; ΔQ and ΔV are the changes in battery capacity and voltage, respectively.

[0014] The present invention also proposes a sodium ion battery thermal runaway detection system, comprising: a voltage detection module for acquiring battery voltage; a pressure collector attached to the surface of the sodium ion battery shell to acquire surface pressure; a data processing module; and a data collector communicatively connected to the voltage detection module, the pressure collector, and the data processing module, respectively; wherein the data collector sends the battery voltage and the surface pressure acquired in real time to the data processing module, the data processing module obtains a voltage change curve based on the battery voltage, and obtains a pressure change curve based on the surface pressure, the voltage change curve being a curve of the battery voltage changing with time, and the pressure change curve being a curve of the surface pressure changing with time; the data processing module issues a multi-level warning signal based on changes in the battery voltage, the pressure change curve, the surface pressure, and the pressure change curve.

[0015] In an optional embodiment, the sodium ion battery thermal runaway detection system further includes: a temperature sensor, suitable for detecting the battery temperature of the sodium ion battery, the temperature sensor being communicatively connected to the data collector to send the battery temperature to the data processing module, the data processing module judging the battery temperature, and if the battery temperature is greater than a first preset temperature value, establishing a pressure-temperature coupling model based on the battery temperature and the surface pressure to obtain a corrected pressure value; wherein the corrected pressure value replaces the surface pressure in the pressure change curve; and / or when the battery temperature rises to greater than a second preset temperature value, a third-level warning signal is issued; and / or a gas detector is provided in the sodium ion battery to obtain gas in the battery. body concentration, the gas concentration includes carbon dioxide concentration, hydrogen concentration and carbon monoxide concentration; the gas detector is communicatively connected to the data collector, so that the data processing module obtains the gas concentration and makes a judgment, and when the gas concentration exceeds a preset concentration value, the three-level warning signal is issued; and / or a weight detection module is suitable for obtaining the battery weight of the battery, the weight detection module is communicatively connected to the data collector, so that the data processing module obtains the battery weight and makes a judgment, if the battery weight is lower than the preset weight and the voltage rising rate is greater than the preset voltage rate, the three-level warning signal is issued; if the battery weight is lower than the preset weight and the battery voltage drops, the four-level warning signal is issued.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention adopts a multi-level early warning detection method with pressure as the core parameter, which can effectively identify the severity of thermal runaway, so as to take corresponding measures according to the characteristics of different stages, thereby improving the accuracy of detection, improving the reliability of thermal runaway detection of sodium ion batteries, and improving the safety of sodium ion batteries.

[0018] 2. By using pressure changes as the core parameter and combining multi-dimensional monitoring such as voltage, temperature, and gas concentration, the present invention can effectively capture subtle changes in the battery under overcharge conditions and promptly discover early signs of thermal runaway. This allows for effective detection and early warning of thermal runaway, achieving accurate thermal runaway predictions and providing users with ample time to take emergency measures to avoid accidents.

[0019] 3. This invention proposes a four-level early warning scheme. By carefully dividing the different stages of the battery overcharging process and based on the changing pattern of battery surface pressure, combined with multiple indicators such as voltage, temperature, and gas concentration, it can issue early warnings in a timely manner according to different abnormal situations, ensuring that a clear alarm is issued before the battery enters a dangerous state, improving the accuracy and reliability of detection, and effectively reducing the safety risks caused by thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a sodium ion battery thermal runaway detection method provided for the implementation of the present invention;

[0021] Figure 2 A flow chart of another sodium ion battery thermal runaway detection method provided for the implementation of the present invention;

[0022] Figure 3 A block diagram of a sodium ion battery thermal runaway detection system provided by an embodiment of the present invention;

[0023] Figure 4 A block diagram of another sodium-ion battery thermal runaway detection system provided in an embodiment of the present invention.

[0024] Description of reference numerals:

[0025] 110, voltage detection module; 120, pressure collector; 130, data collector; 140, data processing module; 150, temperature sensor; 160, gas detector; 170, weight detection module. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, according to an embodiment of the present invention, on the one hand, a method for detecting thermal runaway of a sodium ion battery is provided, comprising the following steps:

[0028] Step S101: obtaining the battery voltage and the surface pressure of the battery housing;

[0029] Step S103: obtaining a voltage change curve and a pressure change curve, wherein the voltage change curve is a curve showing the battery voltage changing with time, and the pressure change curve is a curve showing the surface pressure changing with time;

[0030] Step S105: Combining the battery voltage, voltage change curve, surface pressure and pressure change curve, a multi-level warning signal is issued.

[0031] In this embodiment, the change in battery voltage may reflect the electrochemical reaction inside the battery, while the change in the surface pressure of the battery shell may indicate the generation or expansion of gas inside the battery.

[0032] After collecting the battery voltage and surface pressure data, these data are further processed to generate voltage change curves and pressure change curves. The voltage change curve is a trend graph of the battery voltage over time, which can intuitively show the dynamic changes of the battery voltage in different time periods. For example, under normal circumstances, the battery voltage will gradually decrease with the discharge process, but if there is an abnormal voltage fluctuation or rapid drop, it may mean that there is a short circuit or other fault inside the battery. The pressure change curve is a trend graph of the surface pressure of the battery shell over time, which reflects the changes in the internal pressure of the battery. When thermal runaway occurs inside the battery, a large amount of gas may be generated, causing the pressure inside the battery shell to rise sharply. The pressure change curve can capture this abnormal pressure change in time.

[0033] By combining the comprehensive changes in battery voltage, voltage curve, surface pressure, and pressure curve, and by setting a series of warning thresholds and rules, a multi-level warning signal is issued based on the changes in different parameters, thus analyzing and determining the battery's condition. For example, if the voltage curve exhibits abnormal fluctuations and the pressure curve shows an upward trend, it can be determined that the battery is at risk of thermal runaway. Different levels of warning signals are issued based on the degree of risk, allowing appropriate measures to be taken. Low-level warning signals alert operators to the battery status and conduct further inspection and analysis; high-level warning signals indicate a high risk of thermal runaway and require immediate emergency measures, such as power off, activation of the cooling system, or emergency response. Through real-time monitoring and analysis of multiple parameters, potential thermal runaway risks can be detected in advance, allowing appropriate measures to be taken to ensure the safe operation of the battery system. This multi-parameter comprehensive analysis and multi-level warning method can effectively improve the accuracy and reliability of thermal runaway detection in sodium-ion batteries, providing a strong guarantee for safe battery operation.

[0034] Furthermore, the sodium ion battery thermal runaway detection method further includes the following steps:

[0035] Step S201: Obtain battery temperature.

[0036] Step S203: If the battery temperature is greater than a first preset temperature value, a pressure-temperature coupling model is established based on the battery temperature and the surface pressure to obtain a corrected pressure value.

[0037] In this case, the surface pressure in the pressure curve is replaced by the corrected pressure value.

[0038] The chemical reactions within the battery, the stability of the electrode materials, and the physical and chemical properties of the electrolyte are all closely related to temperature. Considering that in high-temperature environments, the output signal of the sensor measuring surface pressure will shift due to temperature changes, resulting in measurement errors.

[0039] If the battery temperature is detected to be greater than the set first preset temperature value, which is usually set based on the thermal stability of the battery material, the normal operating temperature range, and historical data experience, it indicates that the battery may be in a potentially unstable state. At this time, a more accurate analysis method is needed to evaluate the pressure changes of the battery. The measured pressure value is corrected using a temperature calibration algorithm to ensure the accuracy of the data. Based on the current battery temperature and surface pressure data, a pressure-temperature coupling model is established. Inside the battery, an increase in temperature may lead to an increase in the gas generation rate, causing a rapid increase in pressure; at the same time, the increase in pressure may further affect the heat transfer and chemical reaction rate inside the battery. Therefore, the coupling model can more accurately describe this complex interaction relationship.

[0040] After obtaining the corrected pressure value, it replaces the original surface pressure data in the pressure change curve. This corrected pressure value more accurately reflects the actual pressure changes within the battery, thereby improving the accuracy of subsequent warning judgments. By using the corrected pressure value, the pressure change curve can more clearly demonstrate the dynamic trend of pressure and temperature coupling, providing a more reliable basis for early warning of thermal runaway.

[0041] Specifically, the calculation formula for the corrected pressure value is as follows:

[0042]

[0043] Where, P is the corrected pressure value, P measure is the measured pressure value, a is the temperature influence coefficient obtained by experimental fitting, T is the current measured temperature; T0 is the reference temperature, which can be set to room temperature.

[0044] Under thermal runaway, the battery is in a high-temperature state. Due to the large-scale release of gas inside the battery, the pressure may increase exponentially. Therefore, an exponential regression model can be used:

[0045]

[0046] In addition, for more complex pressure-temperature coupling relationships, multiple regression or neural networks can be used for correction.

[0047] In this embodiment, there is a strong coupling relationship between pressure and temperature during the thermal runaway process. As the temperature rises, the gas inside the battery expands, increasing the pressure. At the same time, high temperature will cause the electrolyte to decompose, further exacerbating the pressure increase. Pressure and gas are also closely related during the thermal runaway process, mainly driven by the accumulation of gases produced by electrolyte decomposition and SEI film rupture. As the thermal runaway progresses, a large amount of gases such as CO2, CO, and H2 are generated, causing the internal pressure of the battery to rise rapidly. Therefore, pressure directly reflects processes such as internal gas expansion, thermal stress accumulation, and material deformation. Therefore, during the thermal runaway process, the pressure change is the most significant, and can be used to build a multi-level early warning system with pressure change as the core. Taking into account the different pressure change rates in different stages, a threshold value should be set for the pressure change rate in each stage to determine whether it is abnormal.

[0048] Furthermore, if Figure 2 As shown, based on step S105, in combination with the battery voltage, voltage change curve, surface pressure and pressure change curve, multi-level warning signals are issued respectively, which specifically includes the following steps:

[0049] Step S1051: If the voltage variation curve shows that the battery voltage continues to rise and the surface pressure is greater than the first preset pressure, a first-level warning signal is issued.

[0050] Step S1053: If the pressure change curve shows that the surface pressure has dropped, a secondary warning signal is issued.

[0051] Step S1055: If the pressure change curve shows that the pressure rising rate is greater than the preset pressure rate, and the voltage change curve shows that the voltage rising rate is greater than the preset voltage rate, a third-level warning signal is issued.

[0052] Step S1057: If the voltage change curve shows that the battery voltage drops and the surface pressure is greater than the second preset pressure, a fourth-level warning signal is issued.

[0053] Based on step S1051, during the initial stages of battery overcharging, the battery voltage slowly rises from the starting voltage. At this point, if the battery surface pressure significantly increases and, as charging continues, exceeds a first preset pressure, this indicates an abnormal increase in the battery's internal pressure. The battery voltage also continues to slowly rise until it exceeds its cutoff voltage. This indicates that, although the sodium-ion battery has not undergone significant changes during this stage, with no obvious morphological changes such as swelling, the abnormal increase in pressure and voltage indicates a potential risk of overcharging and the onset of overheating. Therefore, a Level 1 warning signal is issued, indicating a possible overcharge state, triggering subsequent further testing and protective measures.

[0054] Based on step S1053, in the voltage change curve, under normal circumstances, the internal pressure of the battery should remain relatively stable. If the surface pressure drops to a certain extent, the pressure drop may mean that there is gas leakage inside the battery, the sealing is damaged, or the internal chemical reaction has changed. This pressure drop may indicate that the integrity of the battery structure is threatened or that there are abnormal changes in the internal reaction. The voltage rises slowly at this stage, indicating that the battery may enter an unstable state. In this case, the position is determined and the secondary warning is triggered, issuing a secondary warning signal to remind the operator that there may be structural problems with the battery or abnormal internal reactions, and further inspection of the battery's sealing and internal state is required.

[0055] Based on step S1055, if the pressure change curve shows a pressure rise rate greater than a preset pressure rate (this rate is set based on the pressure change range during normal battery operation and is used to determine whether the pressure change is abnormal), and the voltage change curve shows a voltage rise rate greater than a preset voltage rate (this rate is set based on the voltage change range during normal battery charge and discharge), this indicates that a violent chemical reaction may have occurred within the battery. For example, high temperature conditions accelerate the decomposition and oxidation of the electrolyte, generating a large amount of gas, causing a sharp increase in surface pressure and an abnormal gas generation rate within the battery. Furthermore, a rapid voltage rise rate indicates an abnormally violent electrochemical reaction within the battery. These indicators indicate that the battery's thermal runaway has entered an intensified stage and requires immediate emergency measures. In this case, the risk of thermal runaway is extremely high. The system determines the location and issues a level 3 warning signal, alerting the operator that the battery is in a highly dangerous state and requires immediate emergency measures, such as shutting off the power, activating the cooling system, or implementing emergency procedures.

[0056] Based on step S1057, when the voltage change curve shows that the battery voltage has dropped, and the surface pressure is greater than the second preset pressure value, and the second preset pressure value is higher than the first preset pressure value, indicating that the internal pressure of the battery is at a more dangerous level, this may mean that a serious fault has occurred inside the battery. The voltage drop may be due to internal short circuits or electrolyte drying up, while the high pressure indicates that a large amount of gas may have been generated inside the battery, causing an abnormal increase in pressure. In this case, the battery may be on the verge of thermal runaway, and the system will issue a level 4 warning signal to alert the operator that the battery is in an extremely dangerous state and that emergency measures need to be taken immediately, such as isolating the battery, activating the fire extinguishing system, or conducting an emergency evacuation.

[0057] This invention's four-level early warning system, centered around pressure changes, utilizes pressure sensors to precisely identify characteristic points of pressure rise, fall, and sudden changes, enabling early and accurate prediction of thermal runaway. Compared to traditional monitoring methods based primarily on temperature or voltage, this system can identify phenomena such as internal battery gas expansion and material deformation earlier and more accurately, ensuring timely warning before thermal runaway occurs, significantly improving the safety and stability of sodium-ion batteries.

[0058] By setting up these multi-level warning signals, the sodium-ion battery thermal runaway detection method can provide real-time assessment and graded warning of the battery's safety status based on the dynamic changes in battery voltage, pressure curve, surface pressure, and pressure curve. This graded warning mechanism not only promptly identifies potential battery risks but also takes appropriate measures based on the degree of risk, effectively reducing the probability of thermal runaway accidents and ensuring the safe operation of the battery system.

[0059] Wherein, before the surface pressure exceeds the second preset pressure, if the surface pressure rises sharply, a fourth warning is issued, where a sharp rise means that the surface pressure rises to more than 150% within a preset time period.

[0060] A "sharp rise" means that the surface pressure rises by 150% or more within a preset time period. Specifically, the preset time period is set based on the normal operating characteristics and historical data of the battery, and usually ranges from a few seconds to a few minutes. For example, assuming the surface pressure of the battery during normal operation is 100kPa, if the surface pressure rises from 100kPa to 250kPa or higher within a preset time period, such as 10 seconds, the surface pressure is considered to have risen sharply.

[0061] If the battery surface pressure then rises sharply after the fluctuation—when the battery pressure suddenly rises by more than 50% within tens to one or two hundred seconds—it can be considered a sudden pressure surge. Eventually, reaching a peak pressure point indicates uncontrollable chemical reactions or physical changes within the battery, such as rapid decomposition of the electrolyte, excessive gas generation, or damage to the battery's internal structure. These changes can cause a rapid increase in internal pressure, increasing the risk of thermal runaway or explosion. At this point, if the battery voltage also drops sharply, especially within a short period of time, it can be considered the beginning of a voltage drop. Given the potential performance differences between sodium-ion batteries made of different materials, calibration and adjustment should be performed based on the specific battery system and experimental conditions in actual applications. This stage indicates a rupture or leak within the battery, leading to a rapid release of internal pressure and structural damage. The system will issue a Level 4 warning based on the signals of a sharp pressure rise and voltage drop, and initiate emergency response measures to prevent further damage.

[0062] Furthermore, the sodium ion battery thermal runaway detection method further includes the following steps:

[0063] Step S301: obtaining battery temperature;

[0064] Step S303: When the battery temperature rises to a value greater than a second preset temperature, a third-level warning signal is issued.

[0065] The second preset temperature value is usually set based on the thermal stability of the battery materials and the normal operating temperature range, and is used to determine whether the battery is at a high risk of thermal runaway. When the battery temperature rises above the second preset temperature value, the second preset temperature value is usually set based on the thermal stability of the battery materials and the normal operating temperature range, and is used to determine whether the battery is at a high risk of thermal runaway, indicating that a violent chemical reaction may have occurred inside the battery, resulting in rapid heat accumulation, which in turn triggers thermal runaway and requires immediate emergency measures.

[0066] The following steps may also be included:

[0067] Step S305: Obtaining gas concentrations in the battery, the gas concentrations including carbon dioxide concentration, hydrogen concentration, and carbon monoxide concentration;

[0068] Step S307: When the gas concentration exceeds a preset concentration value, a third-level warning signal is issued.

[0069] When the gas concentration inside the battery exceeds a preset value, the system will issue a three-level warning signal. The preset concentration value is set based on gas generation during normal battery operation and safety standards, and is used to determine whether the gas concentration is at an abnormal level. When the gas concentration exceeds the preset concentration value, it indicates that a violent chemical reaction may have occurred within the battery under high temperature conditions, accelerating the decomposition and oxidation of the electrolyte.

[0070] The electrolyte within a battery is typically composed of organic solvents and salts. When thermal runaway occurs, decomposition reactions occur. In particular, electrolytes containing carbonate solvents, such as dimethyl carbonate, produce large amounts of carbon dioxide when decomposed at high temperatures. Monitoring changes in carbon dioxide concentration can help detect overcharge or overheating in batteries and serve as an early warning signal for thermal runaway. Hydrogen and carbon dioxide are often released simultaneously. Elevated hydrogen concentrations may indicate electrolysis of water or other chemical reactions within the battery. Therefore, monitoring these two gases provides a more comprehensive understanding of the reaction processes within the battery, providing earlier and more accurate warnings of thermal runaway in sodium-ion batteries. The generation of carbon monoxide may indicate incomplete combustion or other redox reactions within the battery. When the concentrations of these gases exceed preset limits, it indicates that a serious chemical reaction may have occurred within the battery, leading to increased gas generation rates and, in turn, an increased risk of thermal runaway. Therefore, when gas concentrations reach dangerous levels, the system will issue a Level 3 warning signal.

[0071] Through the cooperation of the temperature sensor 150 and the gas sensor, it is possible to respond quickly when the gas and temperature reach a certain threshold, thereby preventing possible safety risks in advance.

[0072] In addition, to ensure the accuracy of the early warning system, the system also monitors the quality of the battery in real time. Quality loss is often a precursor to battery bulging, rupture, or internal damage. The battery's quality changes are detected in real time by an electronic balance. When the quality loss reaches the set threshold, the system will issue an abnormal warning, indicating that major damage may have occurred inside the battery. The quality loss at this time not only reflects the physical deformation of the battery, but may also be caused by gas generation or damage to the internal structure of the battery. The sodium ion battery thermal runaway detection method also includes the following steps:

[0073] Step S401: Obtain the battery weight of the battery.

[0074] Step S403: If the battery weight is lower than the preset weight and the voltage rising rate is higher than the preset voltage rate, a level 3 warning signal is issued.

[0075] Step S405: If the battery weight is lower than the preset weight and the battery voltage drops, a level 4 warning signal is issued.

[0076] Furthermore, based on the chemical characteristics of sodium-ion batteries during thermal runaway, real-time monitoring of sodium metal deposition during overcharge can be achieved by combining electrochemical signal analysis. This method enables timely detection of early signs of sodium deposition during normal battery operation and the implementation of appropriate safety measures. First, the battery's electrochemical behavior is monitored using incremental capacitance (IC) and differential voltage (DV) curves. When the battery enters an overcharge state and sodium metal deposition begins, characteristic changes occur in the IC and DV curves. Incremental capacitance analysis can identify the onset of sodium deposition by differentially analyzing the relationship between capacity and voltage during discharge. Typically, in the early stages of overcharge, the battery's voltage and capacity change relatively slowly. The DV curve maintains a narrow fluctuation range, a low slope, and no obvious local lows or peaks. The IC curve, under normal charge, exhibits a continuous, smooth curve without distinct local peaks. However, as sodium metal deposition occurs, local peaks appear in the capacitance curve, indicating the onset of deposition. Differential voltage analysis observes the changes in battery voltage during charging and finds that the voltage platform related to sodium deposition, especially the early stage of sodium metal deposition, will have a clear local minimum point in the DV curve. By monitoring these electrochemical signals in real time, the start time and extent of sodium deposition can be effectively predicted. Once signs of sodium deposition are detected, the system can automatically issue an early warning signal to remind the operator to take measures, such as stopping charging, slowing down the charging rate, etc. Therefore, the sodium-ion battery thermal runaway detection method also includes the following steps:

[0077] Step S501: Acquire an incremental capacitance curve and a differential voltage curve.

[0078] Step S503: If a local peak appears in the incremental capacitance curve and a local trough appears in the differential voltage curve within the same time period, a second-level warning signal is issued.

[0079] The incremental capacitance curve is obtained by differentiating the capacitance with respect to the open circuit voltage:

[0080]

[0081] The differential voltage curve is the inverse of the incremental capacitance curve, and the calculation expression is:

[0082]

[0083] Where OCV is the open circuit voltage; Q is the capacity; V is the voltage; ΔQ and ΔV are the changes in battery capacity and voltage, respectively.

[0084] The incremental capacity curve is obtained by measuring the slight change in the battery's capacitance during the charge and discharge process. It reflects the dynamic characteristics of the electrochemical reaction within the battery. The differential voltage curve is obtained by measuring the differential change in battery voltage over time or charge and discharge amount. It reflects the dynamic changes in battery voltage during the charge and discharge process.

[0085] A local peak in the incremental capacity curve indicates a sudden change in the electrochemical reaction rate inside the battery. A local trough in the differential voltage curve indicates an abnormal decrease in the differential change in the battery voltage, which can more accurately capture abnormal changes within the battery. The simultaneous occurrence of these two abnormalities indicates that a complex abnormal reaction may have occurred within the battery and requires high attention. When the internal pressure of the battery exceeds the limit, a sudden pressure drop occurs due to battery rupture. Because the battery ruptures, the strain no longer takes effect and the voltage drops to 0V. At the same time, the energy inside the battery gradually dissipates and the temperature begins to drop.

[0086] After these four stages, if the surface pressure suddenly drops and the battery voltage drops to zero, it indicates that the battery's internal pressure has exceeded its final limit and a sudden pressure drop has occurred due to a battery rupture. Because the strain no longer acts due to the battery rupture, the voltage drops to 0V. Simultaneously, the energy within the battery gradually dissipates and the temperature begins to drop, triggering a Level 5 warning signal.

[0087] The present invention uses pressure as the core variable, supplemented by voltage, temperature, gas concentration, including key parameters such as carbon dioxide, carbon monoxide and hydrogen, mass loss and electrochemical signals, to achieve all-round monitoring. Through real-time monitoring and data analysis, thermal runaway risks can be discovered in time at different stages and early warnings can be issued, significantly improving battery safety. By using pressure, temperature, gas concentration, voltage, mass, incremental capacitance and differential voltage curves in multiple dimensions to detect thermal runaway of sodium-ion batteries in an overcharged state, in order to overcome the problem of explosion and fire caused by untimely thermal runaway detection in the prior art, a four-level early warning system with pressure as the core parameter is used for detection, which can effectively identify the severity of thermal runaway, thereby taking corresponding measures according to the characteristics of different stages, thereby improving the accuracy of detection. The present application designs different detection processes according to different thermal runaway stages. Each test link is interdependent and indispensable, making the entire system more scientific and effective.

[0088] like Figure 3 and Figure 4As shown, the present invention also proposes a sodium ion battery thermal runaway detection system, comprising: a voltage detection module 110, which obtains battery voltage; a pressure collector 120, which is attached to the surface of the sodium ion battery shell to obtain surface pressure; a data processing module 140; and a data collector 130, which is communicatively connected to the voltage detection module 110, the pressure collector 120 and the data processing module 140 respectively; wherein the data collector 130 sends the battery voltage and surface pressure collected in real time to the data processing module 140, and the data processing module 140 obtains a voltage change curve based on the battery voltage and a pressure change curve based on the surface pressure. The voltage change curve is a curve of the battery voltage changing with time, and the pressure change curve is a curve of the surface pressure changing with time. The data processing module 140 sends a multi-level warning signal based on the changes in the battery voltage, the pressure change curve, the surface pressure and the pressure change curve.

[0089] In this embodiment, the high-precision pressure collector 120 is attached to the surface of the battery. When gas is generated and accumulated inside the battery,

[0090] As the pressure in the battery casing gradually increases, the pressure collector 120 accurately captures pressure rises, falls, and sudden changes, converting them into electrical signals that reflect the degree of gas expansion and pressure evolution within the battery. However, in high-temperature environments, the pressure collector 120 may experience thermal drift, meaning its output signal may shift due to temperature fluctuations, leading to measurement errors. The sensitivity of the pressure collector 120 may decrease at high temperatures, necessitating the use of a temperature calibration algorithm.

[0091] Continue to combine Figure 4As shown, the sodium ion battery thermal runaway detection method further includes: a temperature sensor 150, adapted to detect the sodium ion battery temperature, the temperature sensor 150 being communicatively connected to the data collector 130 to send the battery temperature to the data processing module 140, the data processing module 140 determining the battery temperature, and if the battery temperature is greater than a first preset temperature value, establishing a pressure-temperature coupling model based on the battery temperature and the surface pressure to obtain a corrected pressure value; wherein the corrected pressure value replaces the surface pressure in the pressure change curve; and / or when the battery temperature rises to greater than a second preset temperature value, issuing a third-level warning signal; and / or a gas detector 160, disposed in the sodium ion battery, to obtain the gas concentration in the battery, The gas concentration includes the concentration of carbon dioxide, hydrogen and carbon monoxide; the gas detector 160 is connected in communication with the data collector 130 so that the data processing module 140 can obtain the gas concentration and make a judgment, and when the gas concentration exceeds the preset concentration value, a third-level warning signal is issued; and / or the weight detection module 170 is suitable for obtaining the battery weight of the battery. The weight detection module 170 is connected in communication with the data collector 130 so that the data processing module 140 can obtain the battery weight and make a judgment. If the battery weight is lower than the preset weight and the voltage rise rate is greater than the preset voltage rate, a third-level warning signal is issued; if the battery weight is lower than the preset weight and the battery voltage drops, a fourth-level warning signal is issued.

[0092] In this embodiment, three temperature sensors 150 can be set, respectively located at the positive electrode, negative electrode, and near the center of the sodium ion battery. In order to prevent the battery liquid from corroding the temperature sensor 150, the housing of the temperature sensor 150 is encapsulated with corrosion-resistant materials to ensure long-term stable operation. In addition, during the thermal runaway of the sodium ion battery, the gas sensor uses an integrated fiber optic carbon dioxide sensor and an integrated fiber optic hydrogen sensor. Due to its excellent anti-electromagnetic interference ability, high temperature resistance, and high pressure resistance, the fiber optic sensor can still maintain stable performance when facing the high temperature and high pressure environment brought about by the thermal runaway of the sodium ion battery, thereby ensuring the reliability of the test results.

[0093] The present invention achieves comprehensive and systematic battery status monitoring by combining multiple monitoring devices, including a high-precision pressure collector 120, a temperature sensor 150, a gas sensor, and a voltage detection module 110, along with a data collector 130 and a data processing module 140. The high sensitivity and rapid response of the high-precision pressure collector 120 accurately capture minute changes in battery pressure during thermal runaway, ensuring real-time monitoring of these changes. To prevent corrosion of the sensor by battery fluid, the sensor housing is encapsulated in corrosion-resistant materials, ensuring long-term stable operation.

[0094] The present invention can be widely used in fields such as electric vehicles, grid energy storage, and consumer electronics, providing reliable protection for the safe application of sodium-ion batteries.

[0095] This invention proposes a four-stage early warning system, with pressure as the core parameter and incorporating voltage, temperature, and gas concentration. The system sets critical thresholds based on pressure changes at each warning stage. By monitoring the rise and fall rates and abnormal fluctuations in battery surface pressure in real time, it accurately captures key signals such as internal gas accumulation, shell expansion, and structural stress changes. This allows for timely detection of potential danger signals and ensures that the battery operates in normal working order.

[0096] The above embodiments are provided for illustrative purposes only and are not intended to limit the scope of implementation. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to provide an exhaustive list of all implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for detecting thermal runaway of a sodium ion battery, characterized in that: The sodium ion battery thermal runaway detection method comprises: Obtaining battery voltage and surface pressure of battery casing; Obtaining a voltage change curve and a pressure change curve, wherein the voltage change curve is a curve showing the battery voltage changing over time, and the pressure change curve is a curve showing the surface pressure changing over time; A multi-level warning signal is issued in combination with the battery voltage, the voltage change curve, the surface pressure and the pressure change curve.

2. The sodium ion battery thermal runaway detection method according to claim 1, wherein: Also includes: Get battery temperature; If the battery temperature is greater than a first preset temperature value, establishing a pressure-temperature coupling model based on the battery temperature and the surface pressure to obtain a corrected pressure value; The surface pressure in the pressure variation curve is replaced by the corrected pressure value.

3. The method for detecting thermal runaway of sodium ion batteries in high altitude areas according to claim 2, characterized in that: The calculation formula of the corrected pressure value is as follows: Where, P is the corrected pressure value, P measure is the measured pressure value, a is the temperature influence coefficient obtained by experimental fitting, T is the current measured temperature; T0 is the reference temperature.

4. The sodium ion battery thermal runaway detection method according to any one of claims 1 to 3, characterized in that: In combination with the battery voltage, the voltage change curve, the surface pressure, and the pressure change curve, a multi-level warning signal is issued, specifically including: If the voltage change curve shows that the battery voltage continues to rise and the surface pressure is greater than a first preset pressure, a first-level warning signal is issued; If the pressure variation curve shows that the surface pressure has dropped, a secondary warning signal is issued; If the pressure change curve shows that the pressure rising rate is greater than the preset pressure rate, and the voltage change curve shows that the voltage rising rate is greater than the preset voltage rate, a level 3 warning signal is issued; If the voltage variation curve shows that the battery voltage drops and the surface pressure is greater than a second preset pressure, a fourth-level warning signal is issued.

5. The sodium ion battery thermal runaway detection method according to claim 4, characterized in that: Before the surface pressure exceeds the second preset pressure, if the surface pressure rises sharply, the fourth-level warning signal is issued. The sharp rise means that the surface pressure rises to more than 150% within a preset time period.

6. The sodium ion battery thermal runaway detection method according to claim 4, characterized in that: Also includes: Get battery temperature; When the battery temperature rises to a value greater than a second preset temperature, a third-level warning signal is issued; and / or Obtaining gas concentrations within the battery, the gas concentrations including carbon dioxide concentration, hydrogen concentration, and carbon monoxide concentration; When the gas concentration exceeds a preset concentration value, the third-level warning signal is issued.

7. The sodium ion battery thermal runaway detection method according to claim 4, characterized in that: Also includes: obtaining a battery weight of the battery; If the battery weight is lower than the preset weight and the voltage rising rate is higher than the preset voltage rate, the third-level warning signal is issued; If the battery weight is lower than a preset weight and the battery voltage drops, the fourth-level warning signal is issued.

8. The sodium ion battery thermal runaway detection method according to any one of claims 1 to 3, characterized in that: Also includes: Obtain incremental capacitance curve and differential voltage curve; If, within the same time period, a local peak appears on the incremental capacitance curve and a local trough appears on the differential voltage curve, the secondary warning signal is issued; The incremental capacitance curve is obtained by differentiating the capacitance with the open circuit voltage: The differential voltage curve is the inverse of the incremental capacitance curve, and the calculation expression is: Where OCV is the open circuit voltage; Q is the capacity; V is the voltage; ΔQ and ΔV are the changes in battery capacity and voltage, respectively.

9. A sodium ion battery thermal runaway detection system, characterized in that: include: Voltage detection module, obtains battery voltage; A pressure collector is attached to the surface of the sodium ion battery shell to obtain surface pressure; Data processing module; A data collector, communicatively connected to the voltage detection module, the pressure collector, and the data processing module respectively; In which, the data collector sends the battery voltage and the surface pressure collected in real time to the data processing module, and the data processing module obtains a voltage change curve based on the battery voltage, and obtains a pressure change curve based on the surface pressure. The voltage change curve is a curve of the battery voltage changing with time, and the pressure change curve is a curve of the surface pressure changing with time; the data processing module combines the changes in the battery voltage, the pressure change curve, the surface pressure and the pressure change curve to issue a multi-level warning signal.

10. The sodium ion battery thermal runaway detection system according to claim 9, characterized in that: Also includes: a temperature sensor adapted to detect the temperature of the sodium ion battery, the temperature sensor being communicatively connected to the data collector to transmit the battery temperature to the data processing module, the data processing module determining the battery temperature; and if the battery temperature is greater than a first preset temperature value, establishing a pressure-temperature coupling model based on the battery temperature and the surface pressure to obtain a corrected pressure value; wherein the corrected pressure value replaces the surface pressure in the pressure change curve; and / or issuing a level 3 warning signal when the battery temperature rises to greater than a second preset temperature value; and / or A gas detector is provided in the sodium ion battery to obtain the gas concentration in the battery, wherein the gas concentration includes the carbon dioxide concentration, the hydrogen concentration and the carbon monoxide concentration; the gas detector is communicatively connected to the data acquisition device so that the data processing module obtains the gas concentration and makes a judgment, and when the gas concentration exceeds a preset concentration value, the three-level warning signal is issued; and / or A weight detection module is adapted to obtain the battery weight of the battery. The weight detection module is communicatively connected to the data collector so that the data processing module obtains the battery weight and makes a judgment. If the battery weight is lower than a preset weight and the voltage rise rate is higher than a preset voltage rate, the third-level warning signal is issued; if the battery weight is lower than a preset weight and the battery voltage drops, the fourth-level warning signal is issued.

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