Sodium ion battery module fault diagnosis method

Abstract

According to the sodium-ion battery module fault diagnosis method provided by the invention, the voltage value, the temperature value and the current value of the sodium-ion battery module are collected, the range value, the average value, the absolute deviation, the average absolute deviation, the direct-current internal resistance, the direct-current reference internal resistance, the battery voltage regression coefficient and the average voltage regression coefficient are calculated, and three preset conditions are adopted to diagnose the fault of the sodium-ion battery module. And fault diagnosis is carried out successively, so that accurate diagnosis of the faults of the sodium-ion battery module is realized.

Description

Technical Field

[0001] This application relates to the field of battery fault diagnosis technology, specifically to a method for diagnosing faults in sodium-ion battery modules. Background Technology

[0002] When sodium-ion batteries malfunction, they can trigger potential battery system safety issues, such as internal short circuits, electrolyte decomposition, electrode material aging, increased internal resistance, thermal runaway, and reduced battery life and efficiency. Therefore, accurate diagnosis of sodium-ion battery malfunctions is a key technological focus in this field. Summary of the Invention

[0003] This application aims to achieve accurate diagnosis of faults in sodium-ion battery modules and provides a method for diagnosing faults in sodium-ion battery modules.

[0004] To achieve this objective, the following technical solution is adopted in this application: A method for diagnosing faults in sodium-ion battery modules is provided, including the following steps: S1, construct a battery data sequence within time T for each cell in the sodium-ion battery module, the sequence including the first... Each cell in time T Voltage value at time Temperature value Current value ; S2, utilizing each battery The battery data sequence constructed within the time series T is used to diagnose faults in each battery and mark sodium-ion batteries that meet the first preset conditions.

[0005] Preferably, step S2 specifically includes the following steps: S21, calculate the range, average, absolute deviation, and mean absolute deviation of the voltage and temperature data within the time series T. The calculation method is expressed by the following formulas (1)-(4): (1) (2) (3) (4) This indicates that the sodium-ion battery module is in The range value at time; Indicates voltage value or temperature value ; , They represent The maximum and minimum values ​​in the range; This indicates that the sodium-ion battery module is in The average value at time; This indicates the number of individual cells in a sodium-ion battery module. This indicates that the sodium-ion battery module is in The absolute deviation value at time; This indicates that the sodium-ion battery module is in The mean absolute deviation value at time; S22, determine whether the temperature range of the sodium-ion battery module is less than a preset threshold RTh, and whether the voltage range is greater than a preset threshold RVh. If so, proceed to step S23; If not, then terminate the execution of step S2; S23, calculate each cell of the sodium-ion battery module Each within the time series T absolute voltage deviation at time Average absolute value deviation of voltage The corresponding weighted averages , The calculation methods are expressed by the following formulas (5)-(6): (5) (6) This represents the last moment within the time series T, i.e., the number of moments within the time series T. S24, determine the result calculated in step S23. Is it greater than the preset threshold DTh, and is the result calculated in step S23? Is it less than the preset threshold MADTh, and does the duration exceed [a certain value]? , If so, then the first The battery fault flag array element Flag_lst is recorded as 1; If not, then the first The Flag_lst record for the battery is 0.

[0006] Preferably, RTh = 10℃, RVh = 0.4V, DTh = 0.04V, and MADTh = 0.02V.

[0007] Preferably, the sodium-ion battery module fault diagnosis method provided in this application further includes the following steps: S3, perform secondary fault diagnosis on the sodium-ion battery module that has been marked in step S2, and mark the sodium-ion batteries that meet the second preset conditions. The diagnosis method includes the following steps: S31, Obtain the DC reference internal resistance DCR1 of the sodium-ion battery module; S32, determine whether there is a current with a value of 0 in the sodium-ion battery module within a certain time sequence T, that is, the sodium-ion battery module is in an open circuit state. If so, proceed to step S33; If not, then terminate step S3; S33, calculate the pulse duration after the sodium-ion battery module enters the charging or discharging state from the open-circuit state, provided that the module has been continuously in the open-circuit state for at least one preceding time sequence T in the next time sequence T. The internal DC resistance DCR2; S34, determine that during the time sequence T, when the sodium-ion battery module transitions from an open-circuit state to a charging state or a discharging state, the first... Battery temperature value Is the range less than a preset threshold? _Th, and whether And whether And whether DCR2 is greater than or equal to the DC reference internal resistance DCR of the battery SOC obtained in step S31 across the full range from 0% to 100%. _Bol Or less than or equal to the DC reference internal resistance DCR of the battery SOC obtained in step S31, which spans the full range from 0% to 100%. _Eol , If so, then the first The battery fault flag array element Flag_2nd is 0; If not, then the first The battery fault flag array element Flag_2nd is recorded as 1; These represent the lower and upper temperature limits, respectively. These represent the lower and upper limits of the current, respectively.

[0008] Preferably, the DC reference internal resistance DCR1 includes, within a controllable temperature range [Tdown, Tup], the voltage drop across the sodium-ion battery module in its initial battery life state, at a pulse duration. The DC reference internal resistance DCR obtained from internal testing _BolAnd / or within a controllable temperature range [Tdown, Tup], for the sodium-ion battery module in a state of battery life termination, at pulse duration The DC reference internal resistance DCR obtained from internal testing _Eol .

[0009] Preferably, the DC reference internal resistance DCR1 and the DC internal resistance DCR2 are calculated using the following formula (7): (7) In formula (7), , They represent the first Battery within time T Voltage and current values ​​at any given time; Including DCR1 and / or DCR2.

[0010] Preferably, the sodium-ion battery module fault diagnosis method provided in this application further includes the following steps: S4, perform a third fault diagnosis on the sodium-ion battery module that has been marked in step S3, and mark the sodium-ion batteries that meet the third preset conditions. The diagnosis method includes the following steps: S41, for fixed length voltage value Perform weighted average filtering to obtain the filtered result. and to Linear regression analysis was performed to obtain the battery voltage regression coefficients. ; S42, calculate the correlation between each individual battery cell. average and to Regression analysis was performed to obtain the average voltage regression coefficient of the sodium-ion battery module. ; S43, judgment and Is it reversed? If so, then the first The battery fault flag array element Flag_3rd is recorded as 1; If not, then the first The battery fault flag array element Flag_3rd is 0.

[0011] Preferably, (8) Indicates the first The battery in the time series T The voltage value at a given moment.

[0012] Preferably, if Flag_1st, Flag_2nd, and Flag_3rd of the same battery are all 1, the battery is determined to be a faulty battery; otherwise, it is determined to be a non-faulty battery.

[0013] This application obtains the voltage value of a sodium-ion battery module. Temperature value Current value Calculate the range, average, absolute deviation, mean absolute deviation, DC internal resistance, DC reference internal resistance, and battery voltage regression coefficient. Average voltage regression coefficient By setting three conditions and performing fault diagnosis step by step, the system can accurately diagnose faults in sodium-ion battery modules. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a flowchart illustrating the implementation steps of a sodium-ion battery module fault diagnosis method provided in an embodiment of this application. Figure 2 It represents the voltage values ​​of each cell in the sodium-ion battery module at different times within time series T. The weighted average value corresponding to the absolute voltage deviation. and the weighted average value corresponding to the average absolute value deviation of the voltage of the sodium-ion battery module at different times within time series T. Example graph of curves changing over time; Figure 3 This is a schematic diagram illustrating the method for calculating the DC internal resistance (DCR) of a sodium-ion battery module. Figure 4 It represents the current value of each cell in the sodium-ion battery module at different times within time series T. Temperature value and voltage value Example graph of curves changing over time; Figure 5 These are the voltage values, voltage noise reduction values, and linear regression analysis values ​​of each cell in a sodium-ion battery module at different times within a fixed time period L. Example graph of curves changing over time. Detailed Implementation

[0016] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0017] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this patent. To better illustrate the embodiments of this application, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0018] In the accompanying drawings of the embodiments of this application, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0019] In the description of this application, unless otherwise expressly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0020] This application provides a method for diagnosing faults in sodium-ion battery modules. Based on data such as battery voltage, temperature, and current collected by the battery management system, and combined with the battery behavior characteristics under charging and discharging conditions, the method can diagnose faults in sodium-ion battery modules. The method is easy to implement and convenient for engineering applications.

[0021] This embodiment provides a method for diagnosing faults in sodium-ion battery modules, such as... Figure 1 As shown, the specific steps include: S1 collects voltage, temperature, and current data for each cell in the sodium-ion battery module; voltage is in volts, temperature is in degrees Celsius, and current is in amperes. Record the time sequence T (T is the time length, such as 1 minute, 10 minutes, etc.) within the sodium-ion battery module system. Each cell in time T Voltage value at time Temperature value Current value , constitute the first The battery data sequence of a single battery within time T; S2, utilizing each battery The battery data sequence built within time T is used to perform the first fault diagnosis for each battery and mark the sodium-ion batteries that meet the first preset conditions. Step S2 specifically includes the following steps: S21, calculate the range, average, absolute deviation, and mean absolute deviation of the voltage and temperature data within time series T. The calculation method is expressed by the following formulas (1)-(4): (1) (2) (3) (4) This indicates that the sodium-ion battery module is in The range value at time; Indicates voltage value or temperature value ; , They represent The maximum and minimum values ​​in the range; This indicates that the sodium-ion battery module is in The average value at time; This indicates the number of individual cells in a sodium-ion battery module. This indicates that the sodium-ion battery module is in The absolute deviation value at time; This indicates that the sodium-ion battery module is in The mean absolute deviation value at time; S22, determine whether the temperature range of the sodium-ion battery module is less than a preset threshold RTh, and whether the voltage range is greater than a preset threshold RVh. If so, proceed to step S23; If not, then terminate the execution of step S2; S23 calculates each cell in the sodium-ion battery module Each within the time series T absolute voltage deviation at time Average absolute value deviation of voltage The corresponding weighted averages , The calculation methods are expressed by the following formulas (5)-(6): (5) (6) Indicates the time sequence within T The last moment of the time series, i.e., the number of moments within the time series T; S24, determine the result calculated in step S23. Is it greater than the preset threshold DTh, and is the result calculated in step S23? Is it less than the preset threshold MADTh, and does the duration exceed [a certain value]? (e.g., 5 minutes) If so, then the first The battery fault flag array element Flag_lst is recorded as 1; If not, then the first The Flag_lst record for the battery is 0; It should be noted here that, with The duration of the comparison is Greater than the preset threshold DTh and The duration of MADTh being less than the preset threshold.

[0022] Taking a sodium-ion battery module with 5 individual cells as an example, the calculation is performed for each cell in the sodium-ion battery module at each time point within time series T. The values ​​and calculations for the sodium-ion battery pack at each time point within time series T. Examples of values ​​are shown in Table a below: Voltage values ​​of each cell in the sodium-ion battery module at different times within time series T The weighted average value corresponding to the absolute voltage deviation. and the weighted average value corresponding to the average absolute value deviation of the voltage of the sodium-ion battery module at different times within time series T. Please refer to the appendix for the curve showing the change over time. Figure 2 .

[0023] The sodium-ion battery module system starts at the first moment of time T, collects the battery voltage of each cell in the module, and then calculates the voltage using formulas (1)-(6). and See the example of the calculation results. Figure 2 .

[0024] In this embodiment, it is preferred to set RTh=10℃, RVh=0.4V, DTh=0.04V, and MADTh=0.02V. For the sodium-ion battery module, from time 121 to time 151 in the example in Table a above, the temperature range is less than RTh, and the voltage range is greater than RVh. In Table a above, At time 121, the voltage was 0.046V, and at time 151, it was 0.081V, both greater than DTh, and the sodium-ion battery module... At time 121, the voltage was 0.012V, and at time 151, it was 0.013V, both less than MADTh, with a duration exceeding [a certain value]. The time is 5 minutes. At this time, the fault flag array element Flag_1st of the second battery in the sodium-ion battery module is recorded as 1.

[0025] From time 121 to time 151, in the sodium-ion battery module , , , All are less than DTh, and sodium-ion battery modules Less than MADTh, duration exceeds The time limit is 5 minutes. The fault flag array element Flag_1st for the first, third, fourth, and fifth batteries in the sodium-ion battery module is recorded as 0.

[0026] Based on the above results, the battery fault flag array Flag_1st for the sodium-ion battery module in the example in Table a is [0, 1, 0, 0, 0]. A Flag_1st record of 1 indicates the presence of a fault, and a Flag_1st record of 0 indicates the absence of a fault.

[0027] like Figure 1 As shown, after completing the initial fault diagnosis of the sodium-ion battery module in step S2, the process continues to the following steps: S3, perform secondary fault diagnosis on the sodium-ion battery module that has been marked in step S2, and for sodium-ion batteries whose marked locations meet the second preset conditions, the diagnosis method specifically includes the following steps: S31, within a controllable temperature range [Tdown, Tup] (Tdown and Tup represent the lower and upper temperature limits, respectively), test the sodium-ion battery module under initial battery life conditions, at a pulse duration. Internal DC reference resistor DCR _Bol The test also examined the performance of the sodium-ion battery module at the end of its battery life, including the pulse duration. Internal DC reference resistor DCR _Eol , In this embodiment, the DC reference internal resistance DCR1 (including DCR)_Bol and / or DCR _Eol The DC reference internal resistance DCR1 is calculated using the following formula (7): (7) In formula (7), , They represent the first Battery within time T Voltage and current values ​​at any given time.

[0028] Including DCR1.

[0029] The following combination Figure 3 The method for calculating the DC internal resistance (DCR) of the sodium-ion battery module in this embodiment is explained below: Figure 3 In China, utilizing X1, X3 The DC internal resistance DCR is calculated by dividing the voltage difference between the two points by the current difference between the two points, i.e., the above formula (7).

[0030] S32, determine whether there is a current of 0 in the sodium-ion battery module within a certain time sequence T, that is, the sodium-ion battery module is in an open circuit state. If so, proceed to step S33; If not, then terminate step S3; S33, calculate the pulse duration after the sodium-ion battery module enters the charging or discharging state from the open-circuit state (the moment when the current is 0) within the next time sequence T, provided that the module has been continuously in the open-circuit state for at least one preceding time sequence T. The DC internal resistance DCR2 is calculated using the same formula (7) above.

[0031] In this embodiment, Including DCR2.

[0032] S34, determine when the sodium-ion battery module transitions from an open-circuit state to a charging state or a discharging state within the time sequence T, and the first [missing information] in the sodium-ion battery module. Battery temperature value Whether the range (calculated by formula (1)) is less than the preset threshold. _Th, and whether And whether ( (These represent the lower and upper limits of the current, respectively), and whether DCR2 is greater than or equal to the DC reference internal resistance DCR of the battery SOC (state of charge) obtained in step S31, which spans the full range from 0% to 100%. _BolOr less than or equal to the DC reference internal resistance DCR of the battery SOC obtained in step S31, which spans the full range from 0% to 100%. _Eol , If so, then the first The battery fault flag array element Flag_2nd is 0; If not, then the first The battery fault flag array element Flag_2nd is recorded as 1.

[0033] The following combination Figure 4 Tables b and c illustrate the method for marking Flag_2nd in the second fault diagnosis in this embodiment: Table b shows the DC reference internal resistance (DCR) of the sodium-ion battery module at different temperatures and under different SOC states. _Bol Statistical example table: Table b Table c shows the DC reference internal resistance (DCR) of the sodium-ion battery module at different temperatures and under different state of charge (SOC). _Eol Statistical example table: Table c Figure 4 In formula (7), the voltage value (retaining 3 decimal places) and current value (retaining 1 decimal place) of the sodium-ion battery module at the 125th moment are respectively used as the values ​​in formula (7). , The voltage and current values ​​at the 483rd moment are respectively used as the values ​​in formula (7). and , Set to [20℃, 30℃], Set to [50 amps, 100 amps]. (By...) Figure 4 As can be seen, the second preset condition expressed in step S34 above is met. At this time, the DC internal resistance DCR2 of the first to fifth cells in the sodium-ion battery module of the example is calculated, and the calculation results are expressed in Table d below: Table d Finally, based on the above results, the battery fault flag array Flag_2nd for the first to fifth cells in the sodium-ion battery module is marked as [0, 1, 0, 0, 0].

[0034] like Figure 1 As shown, after completing the second fault diagnosis of the sodium-ion battery module in step S3, the process proceeds to step: S4, perform a third fault diagnosis on the sodium-ion battery module that has been marked in step S3, and mark the sodium-ion batteries that meet the third preset conditions. The diagnosis method includes the following steps: S41, for fixed length voltage value A weighted average filtering process is performed to achieve noise reduction. The processing method is expressed by the following formula (8): (8) Indicates the first Battery in a fixed length The filtering results calculated during the period; Indicates the first The battery in the time series T The voltage value at that moment; And on Linear regression analysis was performed to obtain the battery voltage regression coefficients. ; S42, calculate the correlation between each individual battery cell. average ; (9) This indicates the number of individual cells in a sodium-ion battery module. And on Linear regression analysis was performed to obtain the average voltage regression coefficient of the sodium-ion battery module. ; The formula for calculating the regression coefficient is as follows: (10) in, For the r-th data point in the array that needs to be analyzed using linear regression, there are s data points in total. For the time intervals in the array, For all average value, For all average value.

[0035] If all time intervals are equal, the following formula shall be used: (11) in, , For the array containing the 1st and sth data points (a total of s data points) that need to be analyzed using linear regression, The time intervals are in the array.

[0036] S43, judgment and Is it reversed? If so, then the first The battery fault flag array element Flag_3rd is recorded as 1 (suspected fault); If not, then the first The battery fault flag array element Flag_3rd is recorded as 0 (battery is normal).

[0037] The following is in conjunction with the appendix Figure 5 Table e provides a detailed explanation of the marking method for Flag_3rd: Table e according to Figure 5 As shown in Table e above, from time 8760 to time 8820, the voltage noise reduction array of the sodium-ion battery module was obtained after noise reduction processing of the voltage acquisition data. By analyzing different moments Linear regression analysis yielded the sodium-ion battery modules listed in Table e above. Values. According to Table e above, the values ​​of the first, second, fourth, and fifth batteries... Value and All in the same direction (both positive numbers), while the third battery... Value and If the values ​​are reversed (one positive and one negative, or 0 and a negative number), then the battery fault flag array Flag_3rd of the sodium-ion battery module will be set to [0, 0, 1, 0, 0].

[0038] Finally, if Flag_1st, Flag_2nd, and Flag_3rd of the same battery are all 1, the battery is determined to be a faulty battery; otherwise, it is determined to be a non-faulty battery.

[0039] For example, a battery is considered faulty only when Flag_1st, Flag_2nd, and Flag_3rd are all 1. Based on the above, the battery fault flag array Flag_1st = [0, 1, 0, 0, 0], the battery fault flag array Flag_2nd = [0, 1, 0, 0, 0], the battery fault flag array Flag_3rd = [0, 0, 1, 0, 0], and finally the battery fault flag array Flag_4th = [0, 0, 0, 0, 0].

[0040] In summary, this application obtains the voltage value of the sodium-ion battery module. Temperature value Current value Calculate the range, average, absolute deviation, mean absolute deviation, DC internal resistance, DC reference internal resistance, and battery voltage regression coefficient. Average voltage regression coefficient By setting three conditions and performing fault diagnosis step by step, the system can accurately diagnose faults in sodium-ion battery modules.

[0041] It should be stated that the above-described specific embodiments are merely preferred embodiments and technical principles applied in this application. Those skilled in the art should understand that various modifications, equivalent substitutions, and variations can be made to this application. However, such variations, as long as they do not depart from the spirit of this application, should be within the scope of protection of this application. Furthermore, some terminology used in this application's specification and claims is not limiting but merely for ease of description.

Claims

1. A method for diagnosing faults in a sodium-ion battery module, characterized in that, Including the following steps: S1, construct a battery data sequence within time T for each cell in the sodium-ion battery module, the sequence including the first... Each cell in time T Voltage value at time Temperature value Current value ; S2, utilizing each battery The battery data sequence constructed within the time series T is used to diagnose faults in each battery and mark sodium-ion batteries that meet the first preset conditions.

2. The method for fault diagnosis of a sodium-ion battery module according to claim 1, characterized in that, Step S2 specifically includes the following steps: S21, calculate the range, average, absolute deviation, and mean absolute deviation of the voltage and temperature data within the time series T. The calculation method is expressed by the following formulas (1)-(4): （1） （2） （3） （4） This indicates that the sodium-ion battery module is in The range value at time; Indicates voltage value or temperature value ; , They represent The maximum and minimum values ​​in the range; This indicates that the sodium-ion battery module is in The average value at time; This indicates the number of individual cells in a sodium-ion battery module. This indicates that the sodium-ion battery module is in The absolute deviation value at time; This indicates that the sodium-ion battery module is in The mean absolute deviation value at time; S22, determine whether the temperature range of the sodium-ion battery module is less than a preset threshold RTh, and whether the voltage range is greater than a preset threshold RVh. If so, proceed to step S23; If not, then terminate the execution of step S2; S23, calculate the value of each cell in the sodium-ion battery module. Each within the time series T absolute voltage deviation at time Average absolute value deviation of voltage The corresponding weighted averages , The calculation methods are expressed by the following formulas (5)-(6): （5） （6） This represents the last moment within the time series T, i.e., the number of moments within the time series T. S24, determine the result calculated in step S23. Is it greater than the preset threshold DTh, and is the result calculated in step S23? Is it less than the preset threshold MADTh, and does the duration exceed [a certain value]? , If so, then the first The battery fault flag array element Flag_lst is recorded as 1; If not, then the first The Flag_lst record for the battery is 0.

3. The method for fault diagnosis of a sodium-ion battery module according to claim 2, characterized in that, RTh=10℃, RVh=0.4V, DTh=0.04V, MADTh=0.02V.

4. The method for fault diagnosis of a sodium-ion battery module according to claim 1, characterized in that, It also includes the following steps: S3, perform secondary fault diagnosis on the sodium-ion battery module that has been marked in step S2, and mark the sodium-ion batteries that meet the second preset conditions. The diagnosis method includes the following steps: S31, Obtain the DC reference internal resistance DCR1 of the sodium-ion battery module; S32, determine whether the sodium-ion battery module has a current with a value of 0 within a certain time sequence T; If so, proceed to step S33; If not, then terminate the execution of step S3; S33, calculate the pulse duration after the sodium-ion battery module enters the charging or discharging state from the open-circuit state, provided that the module has been continuously in an open-circuit state for at least one preceding time sequence T in the next time sequence T. The internal DC resistance DCR2; S34, determine that within the current time sequence T, when the sodium-ion battery module transitions from an open-circuit state to a charging state or a discharging state, the first... Battery voltage value Is the range less than a preset threshold? _Th, and whether And whether And whether DCR2 is greater than the DC reference internal resistance DCR obtained in step S31 across the entire range of battery SOC from 0% to 100%. _Bol Or less than the DC reference internal resistance DCR of the battery SOC obtained in step S31, which spans the full range from 0% to 100%. _Eol , If so, then the first The battery fault flag array element Flag_2nd is 0; If not, then the first The battery fault flag array element Flag_2nd is recorded as 1; These represent the lower and upper temperature limits, respectively. These represent the lower and upper limits of the current, respectively.

5. The method for fault diagnosis of a sodium-ion battery module according to claim 4, characterized in that, The DC reference internal resistance DCR1 includes, within a controllable temperature range [Tdown, Tup], the voltage drop across the sodium-ion battery module in its initial battery life state, during the pulse duration. DC reference internal resistance DCR obtained from internal testing _Bol And / or within a controllable temperature range [Tdown, Tup], for the sodium-ion battery module in a state of battery life termination, at pulse duration DC reference internal resistance DCR obtained from internal testing _Eol .

6. The method for fault diagnosis of a sodium-ion battery module according to claim 5, characterized in that, The DC reference internal resistance DCR1 and the DC internal resistance DCR2 are calculated using the following formula (7): （7） In formula (7), , They represent the first Battery within time T Voltage and current values ​​at any given time; Including DCR1 and / or DCR2.

7. The method for fault diagnosis of a sodium-ion battery module according to claim 4, characterized in that, It also includes the following steps: S4, perform a third fault diagnosis on the sodium-ion battery module that has been marked in step S3, and mark the sodium-ion batteries that meet the third preset conditions. The diagnosis method includes the following steps: S41, for fixed length voltage value Perform weighted average filtering to obtain the filtered result. and to Linear regression analysis was performed to obtain the battery voltage regression coefficients. ; S42, calculate the correlation between each individual battery cell. average and to Regression analysis was performed to obtain the average voltage regression coefficient of the sodium-ion battery module. ; S43, judgment and Is it reversed? If so, then the first The battery fault flag array element Flag_3rd is recorded as 1; If not, then the first The battery fault flag array element Flag_3rd is 0.

8. The method for fault diagnosis of a sodium-ion battery module according to claim 7, characterized in that, （8） Indicates the first The battery is in the time series T The voltage value at a given moment.

9. A method for diagnosing faults in a sodium-ion battery module according to claim 7, characterized in that, If Flag_1st, Flag_2nd, and Flag_3rd of the same battery are all 1, the battery is determined to be a faulty battery; otherwise, it is determined to be a non-faulty battery.

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