Battery thermal runaway early warning method based on single-point thin film pressure sensor

Abstract

The application belongs to the field of battery state monitoring, and discloses a battery thermal runaway early warning method based on a single-point thin film pressure sensor. A single-point thin film pressure sensor is arranged between adjacent battery cells in a battery pack to sense the battery cell pressure signal in real time. The charging and discharging process of the battery pack is monitored through the battery cell pressure signal, and the cycle pressure peak value sequence and the valley value sequence of the last N charging and discharging cycle periods of each battery cell in the charging and discharging process are recorded adaptively, and the dynamic grading pressure early warning threshold of each battery cell is calculated based on the sequence. The battery cell abnormality is identified and the thermal runaway early warning is performed according to the dynamic grading pressure early warning threshold. The application effectively offsets the interference of factors such as the battery cell manufacturing tolerance, the sensor individual difference, the installation deviation and the battery cell expansion caused by the charging and discharging cycle through the dynamic grading threshold of each battery cell, so that the early warning result is more suitable for the actual state of the battery, and a reliable basis is provided for the thermal runaway early identification.

Description

Technical Field

[0001] This invention belongs to the field of battery state monitoring, and specifically relates to an early warning method for battery thermal runaway based on a single-point thin-film pressure sensor. Background Technology

[0002] Energy storage / power batteries are devices that convert electrical energy into chemical energy and store it. They are widely used in grid dispatching, home energy storage, and commercial applications to balance power supply and demand and improve grid stability. However, thermal runaway of energy storage / power batteries is a serious safety hazard that can lead to fire, explosion, or system damage. When a battery experiences thermal runaway, a large amount of heat accumulates inside within a short period, causing the active materials of the positive and negative electrodes and the electrolyte to decompose. This further triggers an uncontrollable self-accelerating reaction, causing the battery temperature to rise continuously and producing gas, which may ultimately lead to a fire or even an explosion. Therefore, effectively monitoring and preventing battery thermal runaway is crucial for improving battery safety and extending battery life.

[0003] In energy storage power stations, due to the large number and close arrangement of individual cells, if one cell experiences thermal runaway, the heat generated can be conducted to surrounding cells, causing the thermal runaway to spread and escalate the damage. Current battery management systems (BMS) primarily focus on the entire battery pack, with insufficient precision in monitoring individual cells, easily overlooking early signs of thermal runaway. Limited by sensor size, cost, and integration, comprehensive monitoring of the entire battery pack is difficult, reducing the accuracy of early warnings. Furthermore, current BMSs mainly rely on signals such as temperature at the battery tabs and the battery's voltage for monitoring, failing to detect pressure changes between cells within the battery pack in a timely manner. This results in insufficient accuracy and response speed in early warnings of thermal runaway risks, making it difficult to effectively prevent thermal runaway from occurring.

[0004] Flexible sensors, capable of conforming to both planar and curved surfaces, hold immense application potential in this scenario. Their ultra-thin size allows them to adhere to the battery surface, monitoring signals such as temperature and pressure between battery contact surfaces, enabling simple and efficient integration without altering the battery pack's structure. However, while integrating sensors onto the surface of each cell allows for precise monitoring of individual cells, achieving early warning and management of battery thermal runaway remains challenging.

[0005] Some existing methods use array-type pressure sensors to collect battery surface pressure and provide early warning of thermal runaway. However, the signal acquisition and processing speed of array-type sensors is relatively slow, which reduces the timeliness of battery status monitoring. In addition, the layout cost and acquisition circuit cost of array-type sensors are high, which will significantly increase the cost of battery pack applications and is not conducive to the promotion and application of the solution.

[0006] Therefore, using a single-point thin-film pressure sensor is relatively more advantageous. This sensor is sandwiched between battery cells to measure pressure at a single point for thermal runaway early warning. However, this method also has drawbacks: the collected pressure exhibits significant inconsistencies and time-varying characteristics. Inconsistencies arise from manufacturing tolerances of the battery cells themselves, individual differences in the thin-film pressure sensors, and positional deviations during sensor installation. Time-varying characteristics include the gradual expansion of the battery cells after multiple charge-discharge cycles and uneven pressure distribution on the cell surface during a single charge-discharge cycle. Due to the inconsistencies and time-varying nature of the collected pressure data, traditional early warning methods using fixed pressure thresholds result in numerous false alarms and missed alarms, rendering them unsuitable for thermal runaway early warning. Summary of the Invention

[0007] To address the aforementioned issues, this invention provides an early warning method for battery thermal runaway based on a single-point thin-film pressure sensor. By employing an adaptive thermal runaway warning algorithm based on a single-point thin-film pressure sensor, false alarms and missed alarms are significantly reduced, enabling earlier identification of battery thermal runaway risks, significantly improving the accuracy and timeliness of warnings, and enhancing the overall safety of the battery system.

[0008] Therefore, the technical solution of the present invention is: an early warning method for battery thermal runaway based on a single-point thin-film pressure sensor, comprising the following steps:

[0009] S1. A single-point thin-film pressure sensor is used between adjacent cells in the battery pack to sense the cell pressure signal in real time.

[0010] S2. Monitor the charging and discharging process of the battery pack by using cell pressure signals, and adaptively record the peak cycle pressure of each cell over the most recent N charge-discharge cycles during the charging and discharging process. Sequence and Valley Value The sequence, where t represents the current charge / discharge cycle period, ;

[0011] S3, Utilizing peak cyclic pressure Sequence and Valley Value The sequence is used to calculate the dynamic graded pressure warning threshold for each cell. ;

[0012] S4. During the charging and discharging process of the battery cell, based on the calculated dynamic graded pressure warning threshold, perform battery cell anomaly identification and early warning of thermal runaway.

[0013] Based on the above scheme and as a preferred embodiment of the above scheme: in step S3, the calculation method of taking the average or median value is adopted, using the peak value of the cyclic pressure. Sequence and Valley Value Sequence, calculate characteristic peak values ​​of cyclic pressure and pressure characteristic valley The characteristic peak value of the cyclic pressure was obtained. ;

[0014] Based on the characteristic peak value of cyclic pressure and the characteristic peak value of cyclic pressure Calculate dynamic graded early warning thresholds , where k is a positive integer representing different warning levels.

[0015] Based on the above scheme and as a preferred embodiment of the above scheme: the dynamic hierarchical early warning threshold The calculation formula is as follows:

[0016]

[0017] in, This is the tiered early warning coefficient, with a value greater than 0.1.

[0018] Based on the above scheme and as a preferred embodiment of the above scheme: In step S2, during the charging and discharging process of the battery pack, the charging end point and discharging end point of the cell are identified by pressure changes, and the pressure peak value and pressure trough value of each charging and discharging cycle are recorded in the most recent N charging and discharging cycles to form the cycle pressure peak value. Sequence and Valley Value sequence.

[0019] Based on the above scheme and as a preferred embodiment of the above scheme: In step S2, by combining the charge and discharge control behavior of the battery management system, the peak cycle pressure is searched and recorded when the battery pack is nearing completion of charging. Search and record the trough value of cycle pressure when the battery pack is nearing the end of its discharge phase. ;

[0020] Alternatively, search for the maximum value of the cell pressure signal within the current charge / discharge cycle. and minimum value , respectively, as the peak value of the cyclic pressure and cyclic pressure trough Meanwhile, during the cyclic charging and discharging process, at the current pressure Below this charge / discharge cycle or higher Under certain circumstances, the current charge / discharge cycle will be... or Save as or :

[0021] .

[0022] Based on the above scheme and as a preferred option: In step S4, during the charging and discharging process of the battery pack, the measured cell pressure signal is compared with the dynamic graded early warning threshold to realize graded early warning. Corresponding handling operations are carried out according to different early warning grades. If no early warning is generated, step S2 is repeated.

[0023] Based on the above scheme and as a preferred embodiment of the above scheme: in step S1, the pressure-sensitive area of ​​the single-point thin-film pressure sensor is close to the midpoint of the large surface of the battery cell, so as to collect the mechanical pressure change signal of the battery cell in real time during the charging and discharging process of the battery pack.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] By adaptively recording the pressure peak and valley sequences of the most recent N charge-discharge cycles, the dynamic grading threshold of each cell is obtained. This effectively offsets the interference from factors such as cell manufacturing tolerances, individual sensor differences, installation deviations, and cell expansion caused by charge-discharge cycles. It overcomes the large number of false alarms and missed alarms caused by pressure data fluctuations, making the early warning results more consistent with the actual state of the battery and providing a reliable basis for early identification of thermal runaway.

[0026] Single-point thin-film pressure sensors are significantly less expensive than array-type sensors, reducing the cost of sensor layout and acquisition circuitry, thus lowering the overall cost of battery pack applications and better meeting the needs of commercialization. Flexible, ultra-thin sensors can be directly attached between battery cells, easily integrated into existing battery packs, avoiding the additional costs and technical difficulties associated with structural modifications, and are suitable for various energy storage / power battery scenarios.

[0027] By independently monitoring each battery cell using a single-point sensor, abnormal individual cells can be accurately located, preventing chain reactions caused by undetected thermal runaway of a single cell. Differentiated actions can be taken based on the comparison of pressure signals with different threshold levels (such as low-level warning prompts for inspection, and high-level warnings triggering emergency power cut-off), achieving refined safety management of the battery system and reducing the overall risk of safety accidents such as fires and explosions.

[0028] 4. Real-time monitoring of pressure changes in individual cells can not only provide early warnings of thermal runaway, but also indirectly reflect the cell's charge / discharge status and health (such as the correlation between expansion and cycle life), providing data support for battery maintenance. Timely detection and intervention of early anomalies can prevent cells from aging faster due to prolonged exposure to risk, extend the overall lifespan of the battery pack, reduce replacement costs, and improve the economics of energy storage / power battery systems. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method of the present invention;

[0030] Figure 2 This is a diagram showing the positional relationship between the sensor and the battery cell;

[0031] Figure 3 Pressure and temperature data curves for normal battery cycling and early thermal runaway processes.

[0032] The following are labeled in the diagram: Cell 1, Sensor 2. Detailed Implementation

[0033] The battery thermal runaway early warning method based on a single-point thin-film pressure sensor described in this embodiment includes the following steps:

[0034] S1. A single-point thin-film pressure sensor 2 is attached between adjacent cells 1 of the battery pack. The pressure-sensitive area of ​​the sensor 2 is as close as possible to the midpoint of the large surface of the cell 1 (e.g., ...). Figure 2 As shown, sensor 2 can be extended from the top or the side to collect the mechanical pressure change signal of cell 1 in real time during the charging and discharging process of the battery pack.

[0035] S2. During the charging and discharging process of the battery pack, the charging and discharging endpoints of the cells are identified by pressure changes. The peak and trough pressure values ​​of each charging and discharging cycle are recorded in the most recent N charging and discharging cycles to form the cycle pressure peak value. Sequence and Valley Value The sequence, where t represents the current charge / discharge cycle period, .

[0036] Specifically, by combining the charge and discharge control behavior of the battery management system (BMS), the peak cycle pressure is searched and recorded when the battery pack is nearing completion of charging. During the near completion of battery pack discharge, the lowest cycle pressure value is searched and recorded. Alternatively, search for the maximum and minimum values ​​of the cell pressure signal within the current charge / discharge cycle. and , respectively as and To improve the reliability of extracting peak and trough values ​​of cyclic pressure, it is necessary to measure the current pressure during the cyclic charge-discharge process. Below this charge / discharge cycle or higher Under certain circumstances, the current charge / discharge cycle will be... or Save as or :

[0037]

[0038] S3, Utilizing peak cyclic pressure Sequence and Valley Value The sequence is used to calculate the dynamic graded pressure warning threshold for each cell. ;

[0039] The calculation method employs the average or median value, utilizing the aforementioned peak cyclic pressure. Sequence and Valley Value Sequence, calculate characteristic peak values ​​of cyclic pressure and pressure characteristic valley The characteristic peak value of the cyclic pressure was obtained. ;

[0040] Utilizing the characteristic peak value of cyclic pressure and characteristic peak value of cyclic pressure The dynamic hierarchical early warning threshold is obtained using the following formula. :

[0041]

[0042] in, This is the tiered early warning coefficient, with a value greater than 0.1.

[0043] The These are empirical parameters; their specific values ​​need to be determined comprehensively based on the actual application scenario, risk assessment results, and historical data. A higher warning level indicates a higher degree of potential risk, therefore the corresponding parameter... The larger the value, the more sensitive it is to capture risk signals and trigger early warning mechanisms in advance.

[0044] To ensure the scientific validity and applicability of parameter selection, preliminary thermal runaway experiments can be conducted. By simulating the thermal runaway process under different operating conditions and recording the characteristic data of key nodes, parameter values ​​with the highest correlation to actual risks can be selected. Simultaneously, when determining the final parameters, sufficient safety margins must be maintained. This margin must consider the differences between experimental data and actual scenarios, the fluctuation range of equipment operation, and the impact of unforeseen factors, thereby allowing ample time for risk response and minimizing losses caused by thermal runaway.

[0045] S4. During the charging and discharging process of the battery pack, the measured cell pressure signal is compared with the dynamic graded warning threshold to realize graded warning. According to the different warning levels, the handling operations such as suspending charging and discharging, degrading the use of cells, and emergency shutdown are carried out. If no warning is generated, step S2 is repeated.

[0046] Figure 3 The graph shows the pressure and temperature data curves for the normal cycle and early thermal runaway processes of the battery. As can be seen from the graph, the first periodic curve represents the normal cycle stage of the battery, and the second pressure surge stage represents the early thermal runaway process of the battery.

[0047] During the normal battery cycle phase, the sum is calculated by averaging over 3 cycles. The key data points in the curve are as follows:

[0048] Peak cyclic pressure In sequence:

[0049] =1360 kPa;

[0050] =1409 kPa;

[0051] =1421 kPa;

[0052] Then: characteristic peak value of cyclic pressure =[ + ] / 3 = 1397 kPa;

[0053] Circulating pressure trough In sequence:

[0054] =878 kPa;

[0055] =905 kPa;

[0056] =921 kPa;

[0057] Then: Pressure characteristic valley value =[ + + ] / 3 = 901 kPa;

[0058] Cyclic pressure characteristic peak value =496 kPa;

[0059] =1893kPa ( Value 1);

[0060] =2389kPa ( (Value 2)

[0061] =2885kPa ( (Value 3)

[0062] During the charging and discharging process of the battery pack, the measured cell pressure signal is compared with the dynamic graded early warning threshold. , , By comparison, a tiered early warning system is implemented, and actions such as suspending charging and discharging, downgrading battery cells, emergency shutdown, and audible and visual alarms are carried out according to different early warning levels.

[0063] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for early warning of battery thermal runaway based on a single-point thin-film pressure sensor, characterized in that: Includes the following steps: S1. A single-point thin-film pressure sensor is used between adjacent cells in the battery pack to sense the cell pressure signal in real time. S2. Monitor the charging and discharging process of the battery pack by using cell pressure signals, and adaptively record the peak cycle pressure of each cell over the most recent N charge-discharge cycles during the charging and discharging process. Sequence and Valley Value The sequence, where t represents the current charge / discharge cycle period, ; S3, Utilizing peak cyclic pressure Sequence and Valley Value The sequence is used to calculate the dynamic graded pressure warning threshold for each cell. The calculation method uses the mean or median value, and utilizes the peak value of the cyclic pressure. Sequence and Valley Value Sequence, calculate characteristic peak values ​​of cyclic pressure and pressure characteristic valley The characteristic peak value of the cyclic pressure was obtained. ; Based on the characteristic peak value of cyclic pressure and the characteristic peak value of cyclic pressure Calculate dynamic graded early warning thresholds , where k is a positive integer representing different warning levels; The dynamic hierarchical early warning threshold The calculation formula is as follows: in, This is the tiered early warning coefficient, with a value greater than 0.1; S4. During the charging and discharging process of the battery cell, based on the calculated dynamic graded pressure warning threshold, perform battery cell anomaly identification and early warning of thermal runaway.

2. The method for early warning of battery thermal runaway based on a single-point thin-film pressure sensor as described in claim 1, characterized in that: In step S2, during the charging and discharging process of the battery pack, the charging and discharging endpoints of the cells are identified by pressure changes. The pressure peak and pressure trough values ​​of each charging and discharging cycle are recorded in the most recent N charging and discharging cycles to form the cycle pressure peak value. Sequence and Valley Value sequence.

3. The method for early warning of battery thermal runaway based on a single-point thin-film pressure sensor as described in claim 2, characterized in that: In step S2, by combining the charge and discharge control behavior of the battery management system, the peak cycle pressure is searched and recorded when the battery pack is nearing completion of charging. Search and record the trough value of cycle pressure when the battery pack is nearing the end of its discharge phase. ; Alternatively, search for the maximum value of the cell pressure signal within the current charge / discharge cycle. and minimum value , respectively, as the peak value of the cyclic pressure and cyclic pressure trough Meanwhile, during the cyclic charging and discharging process, at the current pressure Below this charge / discharge cycle or higher Under certain circumstances, the current charge / discharge cycle will be... or Save as or : 。 4. The method for early warning of battery thermal runaway based on a single-point thin-film pressure sensor as described in claim 1, characterized in that: In step S4, during the charging and discharging process of the battery pack, the measured cell pressure signal is compared with the dynamic graded early warning threshold to realize graded early warning. Corresponding handling operations are carried out according to different early warning levels. If no early warning is generated, step S2 is repeated.

5. The method for early warning of battery thermal runaway based on a single-point thin-film pressure sensor as described in claim 1, characterized in that: In step S1, the pressure-sensitive area of ​​the single-point thin-film pressure sensor is close to the midpoint of the large surface of the battery cell, so as to collect the mechanical pressure change signal of the battery cell in real time during the charging and discharging process of the battery pack.

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