A cell gas swelling monitoring method, system, device, and medium

Abstract

The application discloses a kind of battery swelling monitoring method, system, equipment and medium, it is related to battery technical field.Therein, the method includes: according to the preset sampling period, the real-time acquisition target battery is under each sampling time The AC impedance value;According to the sampling time and the AC impedance value, determine the multiple impedance growth rates of the target battery at different sampling time;Based on the impedance growth rate and the AC impedance value, the swelling condition of the target battery is monitored.Therefore, by implementing the application to realize the timely and accurate monitoring of swelling according to the internal AC impedance value mutation caused by battery swelling, the problem of not timely and not high monitoring result accuracy caused by using sensor for internal resistance diagnosis in the prior art can be solved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a method, system, device, and medium for monitoring cell bulging. Background Technology

[0002] As batteries are stored or used for a long time, the stability of the internal interface and active materials of the battery cells will decrease. In particular, abnormal side reactions may occur inside the battery cells, which will generate gas, causing the battery cells to expand and become bloated.

[0003] Gas buildup in battery cells can severely impact their performance and even pose safety risks. Therefore, accurately diagnosing whether a battery cell is in a gas-filled state is a crucial technical means to ensure the safety and stable performance of the cells.

[0004] Currently, methods for diagnosing cell inflation involve monitoring changes in the cell's internal resistance using pressure sensors, ultrasonic scanning, and DC internal resistance detection to determine its inflation status. However, these physical sensor-based monitoring methods, such as pressure sensors and ultrasonic scanning, cannot provide real-time warnings and are susceptible to external interference, leading to large errors in internal resistance detection and thus hindering accurate inflation monitoring. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention discloses a method, system, device, and medium for monitoring battery cell gas expansion, which improves the accuracy of battery cell gas expansion monitoring.

[0006] To achieve the above objectives, in a first aspect, the present invention discloses a method for monitoring cell gas expansion, comprising:

[0007] The AC impedance value of the target cell at each sampling moment is obtained in real time according to the preset sampling period;

[0008] Based on the sampling time and the AC impedance value, determine multiple impedance growth rates of the target cell over time;

[0009] The gas expansion status of the target battery cell is monitored based on the impedance growth rate and the AC impedance value.

[0010] This invention discloses a method for monitoring battery cell gas expansion. By monitoring changes in the internal impedance of the battery cell in real time, the gas expansion state of the battery cell can be accurately monitored. Specifically, the AC impedance value of the target battery cell at each moment is acquired in real time according to a preset sampling period. This AC impedance value accurately reflects the electrochemical reaction process of the battery cell, and the gas expansion state of the battery cell is monitored based on this electrochemical reaction process. Furthermore, the impedance growth rate of the target battery cell at different sampling moments is determined based on the AC impedance values ​​corresponding to different sampling moments. This impedance growth rate eliminates the influence of different monitoring time intervals on impedance transformation, thereby improving the accuracy of gas expansion monitoring. Finally, based on the sudden change in AC impedance value caused by battery cell gas expansion, the impedance growth rate and the AC impedance value are used to achieve gas expansion diagnosis, realizing accurate online monitoring of battery cell gas expansion.

[0011] As a preferred example, the step of acquiring the AC impedance value of the target cell at each moment in real time according to a preset sampling period includes:

[0012] The target battery cell is electrochemically excited according to a preset sampling period and a preset low-to-medium frequency AC signal cycle to obtain the AC impedance value of the target battery cell at each sampling time.

[0013] The real part of the AC impedance of the target cell at the sampling time is obtained based on the AC impedance value.

[0014] In the above scheme, cell gas expansion typically leads to an increase in charge transfer resistance and a significant increase in solid diffusion impedance. Since charge transfer impedance and diffusion impedance are mainly reflected in low-to-medium frequency AC signals, to achieve accurate monitoring of gas expansion through impedance changes, a low-to-medium frequency AC signal is used to electrochemically excite the target cell, enhancing the impedance transformation and thus improving the accuracy of gas expansion monitoring. Specifically, the target cell is electrochemically excited cyclically according to a preset sampling period to monitor gas expansion at each moment. Because cell gas expansion significantly increases internal contact resistance and ion transport resistance, directly leading to a significant increase in real impedance, the real part of the AC impedance is extracted from the obtained impedance values ​​to directly reflect the gas expansion transformation, thereby improving the accuracy and efficiency of gas expansion monitoring.

[0015] As a preferred example, determining the multiple impedance growth rates of the target cell over time based on the sampling time and the AC impedance value includes:

[0016] For any sampling time:

[0017] The real part of the AC impedance corresponding to the sampling time is taken as the current real part of the AC impedance, and the real part of the AC impedance corresponding to each of the multiple historical sampling times preceding the sampling time is taken as the historical real part of the AC impedance.

[0018] Based on the current AC impedance real part value, the sampling time, multiple historical AC impedance real parts values, and multiple historical sampling times, a linear fit is performed between the impedance real part value and the sampling time to obtain the impedance growth rate corresponding to the sampling time.

[0019] In the above scheme, during the monitoring of cell gas expansion by using the real part of AC impedance, the sampling time is linearly fitted with the real part of impedance by obtaining the real part of AC impedance at the current time and multiple historical times before the current time. This eliminates the influence of different monitoring time intervals on the change of the real part of AC impedance, and then uses the fitted impedance growth rate to improve the accuracy of cell gas expansion monitoring.

[0020] As a preferred example, the monitoring of the gas expansion status of the target battery cell based on the impedance growth rate and the AC impedance value includes:

[0021] For any sampling time:

[0022] The impedance growth rate corresponding to the sampling time is taken as the current impedance growth rate, and the impedance growth rate corresponding to each of the multiple historical sampling times before the sampling time is taken as the historical impedance growth rate.

[0023] Obtain the current impedance growth rate and the average and standard deviation of multiple historical impedance growth rates, and obtain the sum of the average and standard deviation;

[0024] When the current impedance growth rate is greater than the sum of the values, the target cell is determined to be in a gas-filled state at the sampling time.

[0025] In the above scheme, after obtaining the current impedance growth rate at the current sampling time, the current impedance growth rate at the current time is compared and analyzed with the multiple impedance growth rates obtained at multiple sampling times. The accuracy of cell expansion monitoring is improved based on the analysis and comparison results. Specifically, the average value and standard deviation of the multiple impedance growth rates are used to compare and analyze the current impedance growth rate at the current time to identify possible sudden increases in the current impedance growth rate, thereby improving the accuracy of expansion monitoring.

[0026] As a preferred example, the step of acquiring the AC impedance value of the target cell at each sampling moment in real time according to a preset sampling period further includes:

[0027] Obtain the real-time state of charge of the target battery cell;

[0028] When the real-time state of charge is within a preset state of charge range, the AC impedance value of the target cell at each sampling moment is obtained according to a preset sampling period.

[0029] In the above scheme, when monitoring the gas expansion of the battery cell by acquiring the fluctuation change of the AC impedance of the battery cell, in order to reduce the influence of the state of charge on the AC impedance test, the AC impedance test is selected to be performed in a specific state of charge range, so as to reduce the test deviation and improve the accuracy of gas expansion monitoring.

[0030] As a preferred example, the step of acquiring the AC impedance value of the target cell at each sampling moment in real time according to a preset sampling period further includes:

[0031] When the real-time state of charge is within a preset state of charge range, the first AC impedance value of the target cell is obtained;

[0032] Obtain the initial AC impedance value of the new battery cell under low-to-medium frequency AC signals; wherein the new battery cell is of the same type as the target battery cell;

[0033] The initial AC impedance value is compared with the first AC impedance value to obtain the AC impedance value of the target cell at each sampling time based on the comparison result, the sampling time of the first AC impedance value and the preset sampling period.

[0034] In the above scheme, at the initial moment of monitoring cell inflation, the first AC impedance value of the cell before inflation is acquired for subsequent AC impedance value acquisition. However, if the cell is in an inflation state when acquiring the first AC impedance value, the acquired value will be abnormally large, leading to a delay in subsequent slope increase determination and thus preventing timely monitoring of the cell's inflation status. Therefore, the above scheme ensures the effectiveness of inflation monitoring by acquiring the first AC impedance value of the cell before inflation.

[0035] Secondly, the present invention discloses a cell gas monitoring system, including an impedance sampling module, an impedance monitoring module and a gas monitoring module.

[0036] The impedance sampling module is used to obtain the AC impedance value of the target cell at each sampling moment in real time according to the preset sampling period.

[0037] The impedance monitoring module is used to determine multiple impedance growth rates of the target cell over time based on the sampling time and the AC impedance value.

[0038] The gas expansion monitoring module is used to monitor the gas expansion status of the target battery cell based on the impedance growth rate and the AC impedance value.

[0039] This invention discloses a battery cell gas monitoring system that accurately monitors the gas state of the battery cell in real time by monitoring changes in the internal impedance value. Specifically, it acquires the AC impedance value of the target battery cell at each moment according to a preset sampling period, so as to accurately reflect the electrochemical reaction process of the battery cell, and then monitors the gas state of the battery cell based on the electrochemical reaction process. Furthermore, it determines the impedance growth rate of the target battery cell at different sampling moments based on the AC impedance values ​​corresponding to different sampling moments, so as to eliminate the influence of different monitoring time intervals on impedance transformation, thereby improving the accuracy of gas monitoring. Finally, based on the sudden change in AC impedance value caused by battery cell gas, it uses the impedance growth rate and the AC impedance value to achieve gas diagnosis, realizing accurate online monitoring of battery cell gas.

[0040] As a preferred example, the impedance sampling module includes an excitation unit and a resolution unit;

[0041] The excitation unit is used to perform electrochemical excitation on the target cell in a cycle according to a preset sampling period and a preset low-frequency AC signal, so as to obtain the AC impedance value of the target cell at each sampling time.

[0042] The analytical unit is used to obtain the real part of the AC impedance of the target cell at the sampling time based on the AC impedance value.

[0043] Thirdly, the present invention discloses a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements a cell inflation monitoring method as described in the first aspect.

[0044] Fourthly, the present invention discloses a computer-readable storage medium comprising: a stored computer program, wherein, when the computer program is executed, the device on which the computer-readable storage medium is located is controlled to perform a cell gas monitoring method as described in the first aspect. Attached Figure Description

[0045] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1This is a schematic flowchart of a cell gas expansion monitoring method provided in an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the structure of a battery cell gas monitoring system provided in an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram illustrating the calculation process of impedance growth rate provided in an embodiment of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0050] See Figure 1 To address the technical problem of the inability to monitor the gas expansion state of battery cells in a timely and accurate manner in existing technologies, an embodiment of the present invention provides a method for monitoring battery cell gas expansion. This method monitors gas expansion based on the impedance changes during the electrochemical reaction process within the battery cell, thereby improving the timeliness and accuracy of monitoring. Specifically, the method includes:

[0051] Step 101: Obtain the AC impedance value of the target cell at each sampling moment in real time according to the preset sampling period.

[0052] Step 102: Based on the sampling time and the AC impedance value, determine multiple impedance growth rates of the target cell at different sampling times.

[0053] Step 103: Monitor the gas expansion of the target cell based on the impedance growth rate and the AC impedance value.

[0054] In this embodiment, the sampling period is the time interval between any two adjacent sampling moments when sampling the AC impedance value of the battery cell. Periodic sampling of the AC impedance value through this sampling period avoids sampling errors, thereby ensuring the accuracy of battery cell expansion monitoring. The AC impedance value is a measurable response signal generated within the battery cell by an electrochemical process following the application of an AC signal of a specific frequency and amplitude. The AC impedance value can be obtained through various means such as electrochemical testing or a terminal. For example, in one embodiment, an electrochemical workstation performs EIS (electrochemical impedance spectroscopy) testing to obtain AC impedance values ​​within a certain frequency range. The frequency during the EIS testing process can be set autonomously, such as 10kHz-0.01Hz, and the frequency sampling points are generally sampled every 10 decimal points. In another embodiment, an AC impedance meter can be used to obtain the AC impedance value at a fixed frequency. This frequency can be set autonomously, such as 1Hz. When testing the AC impedance value through a terminal, the AC impedance testing can also be achieved through the collaboration of various functional devices, consistent with an AC impedance meter.

[0055] In this first embodiment, before collecting the AC impedance value of the target cell at each sampling time according to the preset sampling period, to avoid useless monitoring due to the cell being in a gas-filled state and to avoid the influence of the cell's own state on the AC impedance value, the following steps are first used to identify the cell's gas-filled state and eliminate its influence on the AC impedance value before collecting the AC impedance value of the target cell according to the preset sampling period, thereby improving the accuracy of gas-filled state monitoring. Specifically, the steps include:

[0056] Step S1: Obtain the real-time state of charge of the target cell; when the real-time state of charge is within a preset state of charge range, obtain the AC impedance value of the target cell at each sampling time according to a preset sampling period.

[0057] Step S2: When the real-time state of charge is within a preset state of charge range, obtain the first AC impedance value of the target cell; obtain the initial AC impedance value of the new cell under low-frequency AC signals; wherein the new cell is of the same type as the target cell; compare the initial AC impedance value with the first AC impedance value, and obtain the AC impedance value of the target cell at each sampling time according to the comparison result, the sampling time of the first AC impedance value and the preset sampling period.

[0058] Specifically, during the performance testing of battery cells at the factory, the AC impedance test results are affected by fluctuations in the cell's state of charge (SOC), and the degree of influence varies depending on the SOC range. To improve the accuracy of the acquired AC impedance values, a new battery cell of the same type as the target cell can be selected for AC impedance testing. The fluctuations in the measured AC impedance values ​​of the new cell in different SOC ranges are obtained, and the optimal SOC range for the target cell is determined based on the AC impedance test results. Preferably, after testing the new cell, if it is found that the AC impedance test results within the SOC range of 40% to 60% show smaller fluctuations and deviations with changes in SOC, the real-time SOC of the target cell is determined to be within this range. Then, the AC impedance value of the target cell at each sampling moment is obtained according to a preset sampling period. It should be noted that the SOC refers to the ratio of the remaining charge of the battery cell to its rated capacity, which can be obtained through a management system, such as a Battery Management System (BMS), installed inside the battery cell. In this embodiment, obtaining the state of charge is not an improvement of the present invention, and can be obtained by existing technology.

[0059] Secondly, when determining that the target cell's state of charge (SOC) is within a preset SOC range, it is necessary to identify whether the target cell has already experienced gas expansion to avoid unnecessary subsequent monitoring or affecting the monitoring results. To this end, when determining that gas expansion monitoring of the target cell is feasible, the target cell is first electrochemically excited using the same low-to-medium frequency AC signal to obtain a first AC impedance value at which gas expansion monitoring is deemed feasible. Then, the initial AC impedance value of a new cell of the same type as the target cell is retrieved under the same low-to-medium frequency AC signal. The comparison between the initial AC impedance value and the first AC impedance value determines that the target cell is in a non-expanded state at the time of gas expansion monitoring. It should be noted that when obtaining the initial AC impedance value of a new cell, since cells do not typically experience gas expansion in the short term under most terminal operating conditions, one or more short-interval data point monitoring sessions can be performed initially, and these can be used as the initial AC impedance value for the non-expanded state.

[0060] In this embodiment, when monitoring the gas expansion of the battery cell by acquiring the fluctuation changes in the AC impedance of the battery cell, in order to reduce the influence of the state of charge on the AC impedance test, the AC impedance test is performed within a specific state of charge range to reduce test deviation and thus improve the accuracy of gas expansion monitoring. Next, at the initial moment of monitoring the gas expansion of the battery cell, a first AC impedance value is acquired when the battery cell is not in a gas-filled state for subsequent AC impedance value acquisition. If the first impedance value is acquired when the battery cell is in a gas-filled state, the acquired first AC impedance value will be abnormally large, leading to a delay in the subsequent slope increase determination and thus preventing timely monitoring of the battery cell's gas expansion status. Therefore, the above solution ensures the effectiveness of gas expansion monitoring by acquiring the first AC impedance value when the battery cell is not in a gas-filled state.

[0061] In this first embodiment, when the target cell is in its optimal state of charge range and is determined not to be gas-filled, the AC impedance value of the target cell is acquired in real time at each moment according to a preset sampling period, so as to identify gas filling based on the change in the AC impedance value. To improve the accuracy of gas filling identification by ensuring the accuracy of AC impedance value acquisition, step 101 can sample the AC impedance value through the following steps:

[0062] Step 1011: Electrochemically excite the target cell according to the preset sampling period and the preset low-frequency AC signal cycle to obtain the AC impedance value of the target cell at each sampling time.

[0063] Step 1012: Obtain the real part of the AC impedance of the target cell at the sampling time based on the AC impedance value.

[0064] In this embodiment, when the battery cell swells, the internal electrode structure expands and deforms, disrupting the electrical contact between active material particles and between the active material and the current collector. Simultaneously, gas accumulation hinders electrolyte penetration, reducing the effective reaction area. This leads to a significant increase in the charge transfer impedance (Rct) and diffusion impedance of the battery cell. Since charge transfer impedance and diffusion impedance are primarily displayed through low- to mid-frequency AC signals, to accurately identify whether the battery cell has swelled, the monitoring results can be obtained by detecting a sudden increase in the AC impedance of the battery cell under low- to mid-frequency AC signals.

[0065] Specifically, in this embodiment, the optimal characteristic frequency range corresponding to the low-to-medium frequency AC signal can be obtained by performing AC impedance testing on a new battery cell of the same type as the target battery cell. For example, in one embodiment, taking a silicon-carbon battery cell (3V~4.53V, 5780mAh) as an example, the new battery cell is fully charged and stored at 70℃ to accelerate gas expansion. A group of five cells is stored at high temperature for a certain time interval, and then subjected to capacity calibration at room temperature, thickness testing, and AC impedance testing at 50% SOC. Taking the 1Hz AC impedance of one of the cells during storage as an example, the specific calculation process is as follows:

[0066]

[0067] As shown in the table above, the first set of data is in an uninflated state, and a judgment can be made only if n ≥ 2 data points (at least two sets of slope data). The calculations for the remaining cells are the same, and the overall test results are as follows:

[0068]

[0069]

[0070] As shown in the table above, when the AC impedance test frequency range is 0.5Hz to 2Hz, there are no false positives in the diagnosis of gas expansion. However, when the AC impedance test frequency is too low, premature identification is likely to occur, and when the frequency is too high, delayed identification is likely to occur, especially when the frequency is too high, the risk of false positives is greater. Similarly, if it is found during the test that the characteristic frequency range of 0.3Hz to 2Hz, preferably 1Hz, provides higher diagnostic accuracy for the characteristic frequency Zre within this range, then the characteristic frequency range of the low-frequency AC signal should be set to 0.3Hz to 2Hz, preferably 1Hz.

[0071] Meanwhile, since AC impedance is divided into imaginary impedance and real impedance, and the real impedance is mainly affected by changes in physical structure (such as contact and transmission path), while the imaginary impedance is more affected by electrochemical processes (such as electric double layer and diffusion), when gas occurs in the battery cell, it directly leads to an increase in contact resistance and ion transport resistance. These changes are significant in the real impedance, while changes in the imaginary impedance may be masked by other factors. Therefore, to improve the accuracy and efficiency of gas detection, gas can be identified by extracting the real part of the AC impedance.

[0072] Specifically, according to a preset sampling period, the real part of the AC impedance of the battery cell under low-to-medium frequency AC signals is acquired at regular intervals. For example, multiple real part values ​​of AC impedance, such as Zre1, Zre2, ..., Zren, are obtained sequentially according to the sampling times t1, t2, ..., tn. Zre1 is the real part of the AC impedance corresponding to time t1, Zre2 is the real part of the AC impedance corresponding to time t2, and so on, with Zren being the real part of the AC impedance corresponding to time tn. The sampling interval between any two sampling times can be consistent or inconsistent. Preferably, to facilitate capturing the inflation time point, a consistent sampling interval can be selected.

[0073] In this embodiment, this step is based on the fact that cell gas expansion typically leads to an increase in charge transfer resistance and a significant increase in solid diffusion impedance. Since charge transfer impedance and diffusion impedance are mainly reflected in low-to-medium frequency AC signals, to achieve accurate monitoring of gas expansion through impedance changes, a low-to-medium frequency AC signal is used to electrochemically excite the target cell, thereby enhancing the impedance transformation and improving the accuracy of gas expansion monitoring. Specifically, the target cell is electrochemically excited cyclically according to a preset sampling period to monitor gas expansion at each moment. Because cell gas expansion significantly increases internal contact resistance and ion transport resistance, directly leading to a significant increase in real impedance, the real part of the AC impedance is extracted from the obtained impedance values ​​to directly reflect the gas expansion transformation, thus improving the accuracy and efficiency of gas expansion monitoring.

[0074] In this first embodiment, after obtaining the AC impedance value of the target cell at each sampling time, in order to identify gas expansion by recognizing sudden increases in the AC impedance value, the growth rate of the AC impedance value at each sampling time can be obtained in real time based on the multiple obtained AC impedance values, thereby improving the timeliness of identification. Specifically, step 102 can obtain the impedance growth rate through the following steps. These steps include:

[0075] Step 1021: For any sampling time: take the real part of the AC impedance corresponding to the sampling time as the current real part of the AC impedance, and take the real part of the AC impedance corresponding to each of the multiple historical sampling times before the sampling time as the historical real part of the AC impedance.

[0076] Step 1022: Based on the current AC impedance real part value, the sampling time, multiple historical AC impedance real parts values ​​and multiple historical sampling times, perform linear fitting between the impedance real part value and the sampling time to obtain the impedance growth rate corresponding to the sampling time.

[0077] Specifically, in this embodiment, after obtaining a real part value of AC impedance at each sampling time, a data point (t, Zre) is constructed based on the sampling time and the real part value of AC impedance. Then, a linear fit is performed between the real part value of impedance and the sampling time based on the data point constructed at the current sampling time and all historically monitored data points. The linear slope corresponding to the cell at the current sampling time is the impedance growth rate.

[0078] Preferably, when the nth data point is detected at the current time, the impedance real part value and sampling time are linearly fitted from the 0th group (t0, Zre0) to the 1st group (t1, Zre1), a total of 2 groups of data points, to obtain the impedance growth rate k1; the impedance real part value and sampling time are linearly fitted from the 0th group (t0, Zre0), the 1st group (t1, Zre1) to the 2nd group (t2, Zre2), a total of 3 groups of data points, to obtain the impedance growth rate k2, and so on, from the 0th group (t0, Zre0) to the nth group (tn, Zren), a total of n+1 groups of data points, to obtain the impedance growth rate kn corresponding to the current time tn. Preferably, refer to Figure 3 If two data points, 0 and 1, are detected at the current moment, the impedance growth rate k1 is calculated based on these two data points. If three data points, 0, 1, and 2, are detected at the current moment, the impedance growth rate k2 is calculated. If four data points, 0, 1, 2, and 3, are detected at the current moment, the impedance growth rate k3 is calculated, and so on, resulting in impedance growth rates k4, k5, k6, and so on. In summary, based on the real part of the AC impedance at each sampling moment—that is, the multiple real parts of the AC impedance corresponding to multiple historical sampling moments prior to each sampling moment—multiple impedance growth rates k1, k2, ..., kn corresponding to the current moment are obtained. The method of calculating the impedance growth rate by linear fitting to determine the slope is mainly to eliminate the influence of different monitoring time intervals on impedance changes.

[0079] In this embodiment, during the process of monitoring cell gas expansion by means of the real part of AC impedance, the above steps involve obtaining the real part of AC impedance at the current time and multiple historical times before the current time, and performing linear fitting between the sampling time and the real part of impedance to eliminate the influence of different monitoring time intervals on the change of the real part of AC impedance. In turn, the fitted impedance growth rate is used to improve the accuracy of cell gas expansion monitoring.

[0080] In this first embodiment, after obtaining multiple impedance growth rates corresponding to the current sampling time, to improve the accuracy of gas identification, step 103 can be performed by the following steps to identify gas. These steps are:

[0081] Step 1031: For any sampling time, take the impedance growth rate corresponding to the sampling time as the current impedance growth rate and take the impedance growth rate corresponding to each of the multiple historical sampling times before the sampling time as the historical impedance growth rate.

[0082] Step 1032: Obtain the current impedance growth rate and the average and standard deviation of the multiple historical impedance growth rates, and obtain the sum of the average and the standard deviation.

[0083] Step 1033: When the current impedance growth rate is greater than the sum of the values, it is determined that the target cell is in a gas-filled state at the sampling time.

[0084] In this first embodiment, after obtaining multiple impedance growth rates, such as k1, k2, ..., kn, corresponding to the current sampling time tn, the average value Avg(k1, k2, ..., kn) and the standard deviation SD(k1, k2, ..., kn) of the multiple impedance growth rates are calculated. Then, the sum of the average value Avg(k1, k2, ..., kn) and the standard deviation SD(k1, k2, ..., kn) is obtained to identify the gas-filled state of the target cell based on the comparison result between the current impedance growth rate kn corresponding to the current sampling time tn and the sum.

[0085] Specifically, when the current impedance growth rate kn is greater than the sum of the sums, that is, when kn satisfies kn>Avg(k1,k2,……,kn)+SD(k1,k2,……,kn), the target cell is identified as being in a gas-filled state at the current sampling time tn; otherwise, it is in a non-gas-filled state.

[0086] In this embodiment, after obtaining the current impedance growth rate at the current sampling time, this step compares and analyzes the current impedance growth rate at the current time with the multiple impedance growth rates obtained at multiple sampling times to improve the accuracy of cell gas expansion monitoring based on the analysis and comparison results. Specifically, the average value and standard deviation of the multiple impedance growth rates are used to compare and analyze the current impedance growth rate at the current time to identify possible sudden increases in the current impedance growth rate, thereby improving the accuracy of gas expansion monitoring.

[0087] On the other hand, refer to Figure 2 This embodiment also discloses a cell gas monitoring system, including an impedance sampling module 201, an impedance monitoring module 202 and a gas monitoring module 203.

[0088] The impedance sampling module 201 is used to obtain the AC impedance value of the target cell at each sampling moment in real time according to the preset sampling period.

[0089] The impedance monitoring module 202 is used to determine multiple impedance growth rates of the target cell over time based on the sampling time and the AC impedance value.

[0090] The gas expansion monitoring module 203 is used to monitor the gas expansion of the target cell based on the impedance growth rate and the AC impedance value.

[0091] In this embodiment, the impedance sampling module 201 includes an excitation unit and a resolution unit.

[0092] The excitation unit is used to perform electrochemical excitation on the target cell in a cycle according to a preset sampling period and a preset low-frequency AC signal, so as to obtain the AC impedance value of the target cell at each sampling time.

[0093] The analytical unit is used to obtain the real part of the AC impedance of the target cell at the sampling time based on the AC impedance value.

[0094] In addition to the methods and systems described above, this embodiment also discloses a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a cell gas monitoring method as described in the method embodiment.

[0095] In addition to the methods, systems, and terminal devices described above, this embodiment also discloses a computer-readable storage medium, including: a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute a cell gas monitoring method as described in the method embodiment.

[0096] It should be noted that when the battery cell gas monitoring system, terminal equipment, and storage medium implement the battery cell gas monitoring method described in the method embodiment through hardware modules, additional hardware support may be required. For example, the impedance sampling module requires additional hardware support to generate AC excitation signals to test AC impedance. The hardware support includes, but is not limited to, charging management integrated circuits (programmable charging controllers, etc.), high-frequency power switching elements (MOSFET / GaN FETs, etc.), real-time monitoring sensors (high-precision current and voltage sensors, high-speed ADC / DACs, etc.), and pulse active discharge circuit design (load switch + resistor network—actively discharging during charging pauses through a controllable load resistor; bidirectional DC-DC converter—feeding battery cell energy back to the power supply or capacitor (supporting bidirectional energy flow paths, etc.). The AC excitation signals generated by this hardware include, but are not limited to, sinusoidal AC signals, DC pulse composite equivalent AC signals, etc.

[0097] This embodiment discloses a method, system, device, and medium for monitoring battery cell gas expansion. By monitoring changes in the internal impedance of the battery cell in real time, the gas expansion state of the battery cell can be accurately monitored. Specifically, the AC impedance value of the target battery cell at each moment is acquired in real time according to a preset sampling period. This AC impedance value accurately reflects the electrochemical reaction process of the battery cell, and the gas expansion state of the battery cell is monitored based on this electrochemical reaction process. Furthermore, the impedance growth rate of the target battery cell at different sampling moments is determined based on the AC impedance values ​​corresponding to different sampling moments. This impedance growth rate eliminates the influence of different monitoring time intervals on impedance transformation, thereby improving the accuracy of gas expansion monitoring. Finally, based on the sudden change in AC impedance value caused by battery cell gas expansion, the impedance growth rate and the AC impedance value are used to achieve gas expansion diagnosis. This not only enables non-destructive online monitoring of battery cell gas expansion and real-time early warning, but also requires short testing time and has high accuracy.

[0098] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for monitoring cell gas expansion, characterized in that, include: The AC impedance value of the target cell at each sampling moment is obtained in real time according to a preset sampling period; wherein, the target cell is electrochemically excited according to the preset sampling period and a preset low-frequency AC signal to obtain the AC impedance value of the target cell at each sampling moment; the real part of the AC impedance of the target cell at the sampling moment is obtained according to the AC impedance value. Based on the sampling time and the AC impedance value, multiple impedance growth rates of the target cell at different sampling times are determined; wherein, for any sampling time: the real part of the AC impedance corresponding to the sampling time is taken as the current real part of the AC impedance, and the real part of the AC impedance corresponding to each of the multiple historical sampling times preceding the sampling time is taken as the historical real part of the AC impedance; based on the current real part of the AC impedance, the sampling time, the multiple historical real parts of the AC impedance, and the multiple historical sampling times, a linear fit is performed between the real part of the impedance and the sampling time to obtain the impedance growth rate corresponding to the sampling time; The gas expansion status of the target battery cell is monitored based on the impedance growth rate and the AC impedance value.

2. The method for monitoring cell gas expansion according to claim 1, characterized in that, The monitoring of the gas expansion status of the target battery cell based on the impedance growth rate and the AC impedance value includes: For any sampling time: The impedance growth rate corresponding to the sampling time is taken as the current impedance growth rate, and the impedance growth rate corresponding to each of the multiple historical sampling times before the sampling time is taken as the historical impedance growth rate. Obtain the current impedance growth rate and the average and standard deviation of multiple historical impedance growth rates, and obtain the sum of the average and standard deviation; When the current impedance growth rate is greater than the sum of the values, the target cell is determined to be in a gas-filled state at the sampling time.

3. The method for monitoring cell gas expansion according to claim 1, characterized in that, The step of acquiring the AC impedance value of the target cell at each sampling moment in real time according to a preset sampling period also includes: Obtain the real-time state of charge of the target battery cell; When the real-time state of charge is within a preset state of charge range, the AC impedance value of the target cell at each sampling moment is obtained according to a preset sampling period.

4. The method for monitoring cell gas expansion according to claim 3, characterized in that, The step of acquiring the AC impedance value of the target cell at each sampling moment in real time according to a preset sampling period also includes: When the real-time state of charge is within a preset state of charge range, the first AC impedance value of the target cell is obtained; Obtain the initial AC impedance value of the new battery cell under low-to-medium frequency AC signals; wherein the new battery cell is of the same type as the target battery cell; The initial AC impedance value is compared with the first AC impedance value to obtain the AC impedance value of the target cell at each sampling time based on the comparison result, the sampling time of the first AC impedance value and the preset sampling period.

5. A cell inflation monitoring system, characterized in that, Includes an impedance sampling module, an impedance monitoring module, and a gas monitoring module; The impedance sampling module is used to obtain the AC impedance value of the target cell at each sampling moment in real time according to a preset sampling period; wherein, the impedance sampling module includes an excitation unit and a parsing unit; The excitation unit is used to perform electrochemical excitation on the target cell in a cycle according to a preset sampling period and a preset low-frequency AC signal, so as to obtain the AC impedance value of the target cell at each sampling time. The analytical unit is used to obtain the real part of the AC impedance of the target cell at the sampling time based on the AC impedance value; The impedance monitoring module is used to determine multiple impedance growth rates of the target cell over time based on the sampling time and the AC impedance value. Specifically, for any given sampling time: the real part of the AC impedance corresponding to that sampling time is used as the current real part of the AC impedance, and the real part of the AC impedance corresponding to each of the previous multiple historical sampling times is used as the historical real part of the AC impedance. A linear fit is performed between the current real part of the AC impedance, the sampling time, the multiple historical real parts of the AC impedance, and the multiple historical sampling times to obtain the impedance growth rate corresponding to that sampling time. The gas expansion monitoring module is used to monitor the gas expansion status of the target battery cell based on the impedance growth rate and the AC impedance value.

6. A terminal device, characterized in that, The device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements a cell gas monitoring method as described in any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, include: A stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform a cell gas monitoring method as described in any one of claims 1-4.

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