Systematic diagnosis method, device and equipment for battery cell voltage anomaly and medium

Abstract

The application discloses a kind of system diagnosis method, device, equipment and medium of battery voltage anomaly, method includes: obtaining abnormal battery to be diagnosed and selecting matching normal battery as control sample;External factors are investigated to abnormal battery;If there is no external anomaly, the performance of battery body of abnormal battery and normal battery is analyzed, and multidimensional electrical performance difference data is obtained;According to the data, whether the performance of battery body of abnormal battery is abnormal is judged;If abnormal, failure root verification is carried out.The application is detected by three progressive detection of external factor investigation, performance analysis and failure root verification, first exclude external interference, then quantify the difference of performance of battery body, finally locate the failure cause from the structure, morphology and composition level, realize the accurate, full-dimensional, traceable detection of battery voltage anomaly, solve the problem that detection dimension of prior art is single, and the identification ability of hidden fault is insufficient.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a systematic diagnostic method, apparatus, equipment, and medium for abnormal cell voltage. Background Technology

[0002] In energy storage systems and electric vehicles, lithium-ion battery modules consist of a large number of individual battery cells connected in series and parallel. In actual production and use, it is common to see a phenomenon called "low voltage anomaly" where the voltage of a particular individual battery cell is much lower than that of the other cells in the same group.

[0003] Current technologies handle such problems in a relatively simplistic way, typically only performing a simple open-circuit voltage retest or capacity test. If the retested voltage is still low, it is directly judged as a "cell failure" and the cell is scrapped; if the retest is normal, it is attributed to "sampling abnormality." The drawback of this approach is: Unable to accurately pinpoint the root cause of the anomaly: Existing solutions only cover basic electrical performance testing and cannot determine whether the low voltage is caused by external factors, reversible damage to the battery cell, or permanent defects in the battery cell, resulting in a single testing dimension.

[0004] For hidden faults such as micro-short circuits inside the cell after over-discharge and abnormally high DC internal resistance but normal AC internal resistance, conventional detection methods cannot effectively quantify and characterize them, which may easily lead to the reuse of cells with potential safety hazards or incorrect attribution. Summary of the Invention

[0005] The problem solved by this invention is to provide a systematic diagnostic method, apparatus, device, and medium for abnormal cell voltage.

[0006] In a first aspect, embodiments of the present invention provide a systematic diagnostic method for abnormal cell voltage, comprising: Obtain the abnormal battery cell to be diagnosed, and select a normal battery cell that matches the abnormal battery cell as a control sample; External factors were investigated for the abnormal battery cells to determine whether there were any false abnormalities caused by external factors. If there are no false anomalies caused by external factors, perform cell body performance analysis on the abnormal cell and the normal cell to obtain multi-dimensional electrical performance difference data between the abnormal cell and the normal cell. Based on the multi-dimensional electrical performance difference data, determine whether the physical performance of the abnormal battery cell is abnormal; If the abnormal battery cell has abnormal performance, the root cause of the failure of the abnormal battery cell shall be verified.

[0007] In a second aspect, embodiments of the present invention provide a systematic diagnostic device for abnormal cell voltage, used to implement the diagnostic method described in the first aspect, the diagnostic device comprising: An abnormal cell acquisition module is used to acquire abnormal cells to be diagnosed and select normal cells that match the abnormal cells as control samples. The external factor investigation module is used to investigate the abnormal battery cell for external factors in order to determine whether there are any external factors causing the abnormality. The cell body performance analysis module is used to perform cell body performance analysis on the abnormal cell and the normal cell if there are no external factors causing the abnormality, so as to obtain multi-dimensional electrical performance difference data of the abnormal cell relative to the normal cell. The performance anomaly detection module is used to determine whether the inherent performance of the abnormal battery cell is abnormal based on the multi-dimensional electrical performance difference data. The failure root cause verification module is used to perform failure root cause verification on the abnormal battery cell if the cell's inherent performance is abnormal. Thirdly, embodiments of the present invention provide a computer device, the device including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; When a processor executes a program stored in a memory, it implements the steps of the systematic diagnostic method for abnormal cell voltage as described in the first aspect.

[0008] Fourthly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the systematic diagnostic method for abnormal cell voltage as described in the first aspect.

[0009] Beneficial Effects: This invention provides a systematic diagnostic method, apparatus, device, and medium for abnormal battery cell voltage. The method includes: acquiring the abnormal battery cell to be diagnosed and selecting a normal battery cell matching the abnormal battery cell as a control sample; investigating external factors in the abnormal battery cell to determine if there are any false abnormalities caused by external factors; if there are no false abnormalities caused by external factors, performing battery cell performance analysis on the abnormal battery cell and the normal battery cell to obtain multi-dimensional electrical performance difference data between the abnormal battery cell and the normal battery cell; determining whether the physical performance of the abnormal battery cell is abnormal based on the multi-dimensional electrical performance difference data; and verifying the root cause of failure of the abnormal battery cell if the physical performance of the abnormal battery cell is abnormal.

[0010] By acquiring normal battery cells that match the abnormal cells as control samples, and sequentially performing a three-level progressive testing process—external factor investigation, cell performance analysis, and failure root cause verification—a comprehensive testing system is achieved, encompassing everything from external connection links to the cell itself, and from electrical performance to structural morphology and chemical composition. This system can accurately distinguish whether voltage anomalies originate from external factors, reversible cell damage, or permanent cell defects, effectively solving the problem of existing technologies having only a single testing dimension and being unable to accurately pinpoint the root cause of anomalies. By acquiring multi-dimensional electrical performance difference data between abnormal and normal cells, and further locating the root cause of failure at the structural, morphological, and compositional levels, the system can effectively quantify and accurately identify hidden faults such as internal micro-short circuits after over-discharge and abnormally high DC internal resistance while AC internal resistance remains normal. This avoids the reuse of cells with potential safety hazards or incorrect attribution, improving the accuracy and safety of cell voltage anomaly diagnosis. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 A flowchart of a systematic diagnostic method for abnormal cell voltage provided in an embodiment of the present invention; Figure 2 A sub-flowchart of a systematic diagnostic method for abnormal cell voltage provided in an embodiment of the present invention; Figure 3 A sub-flowchart of a systematic diagnostic method for abnormal cell voltage provided in an embodiment of the present invention; Figure 4 A sub-flowchart of a systematic diagnostic method for abnormal cell voltage provided in an embodiment of the present invention; Figure 5 This is a comparison chart of electrical testing and charge / discharge performance characteristics provided in an embodiment of the present invention. Figure 6 Self-discharge / holding voltage test provided in this embodiment of the invention - self-discharge voltage decay curve based on K-value model; Figure 7 A schematic block diagram of a systematic diagnostic device for abnormal cell voltage provided in an embodiment of the present invention; Figure 8 A schematic block diagram of a computer device provided for an embodiment of the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0015] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0016] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0017] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0018] Please see Figure 1This invention provides a systematic diagnostic method for abnormal cell voltage, enabling accurate, comprehensive, and traceable detection of such abnormalities. This method is applied to a cell diagnostic system, executed by detection software installed within the system. The system includes hardware modules such as charge / discharge testing equipment, internal resistance tester, temperature acquisition device, X-ray / CT detection equipment, microscope, and energy dispersive spectroscopy. Each hardware module establishes a communication connection with a host computer to transmit data. The systematic diagnostic method for abnormal cell voltage includes steps S1 to S5.

[0019] S1. Obtain the abnormal battery cell to be diagnosed, and select a normal battery cell that matches the abnormal battery cell as a control sample.

[0020] In this embodiment, the abnormal cell is a low-voltage abnormal cell whose single-cell voltage is much lower than that of other cells in the same group during the operation of the energy storage system or electric vehicle battery module. The normal cell is the cell used as a reference to eliminate the interference of batch differences and test environment fluctuations on the diagnostic results, and to ensure that the comparison of subsequent multi-dimensional electrical performance difference data is statistically significant. This solves the technical problems of high misjudgment rate and non-reproducible diagnostic results caused by the lack of a reference in the prior art.

[0021] In some embodiments, S1 includes: selecting cells with abnormal voltage from the battery module as abnormal cells to be diagnosed; selecting normal cells from the same batch of batteries as control samples according to a preset matching rule; and placing the abnormal cells and the normal cells in a standard test environment for preprocessing.

[0022] In this embodiment, the battery module is composed of a large number of individual battery cells connected in series and parallel. The battery management system collects the voltage data of each individual battery cell in real time. When the voltage value of a certain individual battery cell is lower than the voltage values ​​of other cells in the same group and deviates from the average voltage value within the cluster by a preset deviation threshold, the cell is marked as an abnormal cell and included in the sample pool for diagnosis. The battery management system is an electronic management system used to monitor the voltage, current, and temperature status of each cell in the battery module; the average voltage value within the cluster is the arithmetic mean of the voltages of all individual battery cells in the same battery module. In a specific embodiment, the preset deviation threshold can be set to deviate from the average voltage value within the cluster by more than 0.1V.

[0023] The preset matching rules include three constraints: same-batch matching, same-module matching, and voltage range matching. Same-batch matching requires that normal and abnormal cells originate from the same production batch to eliminate the impact of batch differences on electrochemical performance. Same-module matching requires that normal and abnormal cells originate from the same battery module or a module with the same series-parallel topology to eliminate the impact of differences in module assembly processes. Voltage range matching requires that the current voltage of the normal cell falls within the mean range of the cell voltage cluster in that module, for example, within the mean ± 3σ range, where σ is the standard deviation of the voltage within the cluster, to ensure that the control sample is in a healthy state. Normal cells selected through these three constraints can effectively eliminate interference from individual differences and environmental factors, improving the accuracy of subsequent diagnosis.

[0024] The standard testing environment is a laboratory environment with a room temperature of 25°C, standard atmospheric pressure, and constant humidity. Pretreatment includes placing abnormal and normal cells in the standard testing environment for a preset time to allow the internal electrochemical state of the cells to reach equilibrium, eliminate the influence of temperature fluctuations during transportation or storage on the cell voltage and internal resistance parameters, and ensure the stability and repeatability of subsequent test data. The preset time can be 4 to 24 hours, and the specific setting can be determined according to the cell capacity and storage conditions.

[0025] S2. Investigate the abnormal battery cell for external factors to determine whether there are any false abnormalities caused by external factors.

[0026] In this embodiment, external factors are investigated to determine if the abnormality is caused by external factors. Existing technologies handle low-voltage abnormalities in cells in a relatively simplistic manner, typically only performing a simple open-circuit voltage retest or capacity test before directly diagnosing the cell as faulty. This ignores false anomalies caused by interference from external connection links, sampling systems, and peripheral circuits, resulting in a large number of cells being incorrectly judged as scrapped, increasing unnecessary after-sales costs. This step employs a three-tiered progressive investigation: visual and connection inspection, open-circuit voltage retest, and charge-discharge reproduction test. This systematically eliminates interference factors not related to the cell itself, ensuring that subsequent testing targets the true performance state of the cell itself. This solves the technical problem of existing technologies having a single detection dimension and being unable to accurately locate the root cause of the abnormality.

[0027] See also some examples. Figure 2 The step of investigating external factors to determine whether the abnormal cell is caused by external factors includes the following sub-steps: S21. Obtain the detection data of the appearance and connection parts of the abnormal battery cell, and check whether there are physical defects in the external connection links of the abnormal battery cell based on the detection data.

[0028] In this embodiment, an external image data of the abnormal battery cell is acquired using a visual diagnostic device, and contact resistance data of the abnormal battery cell's terminals, solder joints, and connectors is acquired using a resistance measuring device. The visual diagnostic device can be a high-resolution industrial camera combined with a machine vision analysis system, and the resistance measuring device can be a micro-ohmmeter or a high-precision multimeter. External connection links include the connection nodes between the battery cell terminals and the module busbar, the sampling harness and connectors between the battery cell and the battery management system, and the physical contact interface between the battery cell casing and the external structure. The acquired external image data is compared with a preset standard image to determine whether there are physical abnormalities such as bulging, leakage, cracks, terminal oxidation, or connector loosening; the acquired contact resistance data is compared with a preset resistance threshold to determine whether there is poor contact or cold solder joint. If either the external image data or the contact resistance data exceeds the preset standard, it is determined that there is a false abnormality caused by external factors, the process terminates, and an external link fault prompt is output; if neither exceeds the preset standard, the process proceeds to step S22. The terminals are the metal conductors extending outward from the positive and negative poles of the battery cell, used to realize the electrical connection between the battery cell and the external circuit; the solder joint is the connection node formed between the terminal and the connector through the welding process; the battery management system interface is the physical interface and wiring harness for transmitting the battery cell voltage sampling signal to the battery management system.

[0029] S22. The open-circuit voltage of the abnormal cell is re-measured and compared with the voltage data collected by the battery management system to determine the authenticity of the voltage abnormality.

[0030] In this embodiment, the abnormal cell is first placed in a standard test environment until its voltage stabilizes. The placement time can be 30 minutes to 2 hours to eliminate the influence of internal polarization on voltage measurement. Then, a calibrated high-precision multimeter, such as a 6.5-digit digital multimeter, is used to directly measure the open-circuit voltage between the positive and negative terminals of the abnormal cell. The open-circuit voltage is the terminal voltage between the positive and negative terminals of the cell when there is no load and no current flowing through it, and is recorded as the first voltage value. At the same time, the cell voltage data collected and reported by the battery management system at the same moment is read through the communication interface and recorded as the second voltage value. The absolute deviation between the first voltage value and the second voltage value is calculated and compared with a preset sampling allowable deviation threshold. The preset sampling allowable deviation threshold can be 5mV to 20mV, specifically set according to the sampling accuracy level of the battery management system. If the absolute deviation is less than or equal to the preset sampling allowable deviation threshold, and both the first voltage value and the second voltage value show low voltage, then the voltage abnormality is confirmed to be a real low voltage of the battery cell, and the process proceeds to step S23; if the absolute deviation is greater than the preset sampling allowable deviation threshold, then the voltage abnormality is determined to be a false abnormality caused by a sampling link failure, such as poor contact of the sampling line, drift of the battery management system sampling chip, or communication interference, and the process terminates and outputs a sampling system fault prompt.

[0031] S23. Perform a charge-discharge reproduction test on the abnormal battery cell, compare the charge-discharge curve and capacity of the abnormal battery cell with those of the normal battery cell to eliminate false alarms and external circuit faults, and confirm that the root cause of the voltage abnormality is located in the battery cell itself.

[0032] In this embodiment, the charge / discharge testing equipment is a battery testing system with constant current and constant voltage output functions, capable of recording voltage, current, capacity, and temperature data in real time. The equipment performs the same standardized charge / discharge process on both abnormal and normal battery cells: first, the cell is pre-charged using a preset charging specification, such as 3.6V constant current and constant voltage charging with a cutoff current of 16A. After charging, the cell is left to rest for a first preset time, such as 30 minutes. Then, the cell is discharged using a preset discharging specification, such as 30A constant current discharge with a cutoff voltage of 2.5V. After discharging, the cell is left to rest for a second preset time, such as 30 minutes. During the charge / discharge process, the charging capacity, discharging capacity, voltage change over time (charging / discharging curve waveform), and cell surface temperature data are recorded in real time. The charging and discharging curves and capacity of the abnormal battery cell are compared with those of the normal battery cell. If the abnormal battery cell cannot complete charging or discharging, or if the deviation of its capacity from that of the normal battery cell is greater than the preset capacity decay threshold, such as if the capacity retention rate is less than 80%, the abnormal battery cell is determined to have serious irreversible damage. If the charging and discharging curve of the abnormal battery cell is similar to that of the normal battery cell and the capacity deviation is within the preset normal range, false alarms caused by system false alarms and external circuit faults are ruled out, and the root cause of the voltage abnormality is confirmed to be in the battery cell itself. At the same time, the charging and discharging reproduction process is used to activate the battery cell that may be in a passivated state due to over-discharge, so that it can be restored to a testable state, avoiding the misjudgment and scrapping of the battery cell that is undervoltage only due to over-discharge protection. Proceed to step S3.

[0033] S3. If there are no false anomalies caused by external factors, perform cell body performance analysis on the abnormal cell and the normal cell to obtain multi-dimensional electrical performance difference data between the abnormal cell and the normal cell.

[0034] In this embodiment, if no external factors cause abnormalities, the performance of both abnormal and normal battery cells is analyzed to obtain multi-dimensional electrical performance difference data between the abnormal and normal cells. After excluding external interference, existing technologies typically rely solely on single open-circuit voltage measurements or simple charge / discharge capacity tests, lacking a tiered verification system from electrical performance to chemical state. This results in insufficient ability to identify complex failure modes such as over-discharge, aging, internal micro-short circuits, and self-discharge anomalies. This step constructs a multi-dimensional electrical performance difference dataset through systematic testing across four dimensions: appearance comparison analysis, internal resistance testing, charge / discharge performance and temperature rise testing, and self-discharge and voltage holding tests. This dataset quantifies the performance deviation between abnormal and normal cells, accurately identifies the type of voltage anomaly, and thus solves the technical problems of existing technologies, such as single detection dimensions and weak ability to identify deep-seated hidden dangers.

[0035] In some embodiments, see also Figure 3 Step S3 includes: S31. Obtain the appearance image data of the abnormal battery cell and the normal battery cell, and compare and analyze the appearance image data to obtain appearance difference data.

[0036] In this embodiment, abnormal and normal battery cells are placed side-by-side under standard light source conditions. Visual diagnostic devices are used to collect appearance image data for both. Standard light source conditions refer to a uniform light source environment with a color temperature of 6500K and an illuminance of not less than 1000 lux to ensure accurate color reproduction. Image processing algorithms are used to perform pixel-level comparisons of the two sets of appearance image data, extracting areas of color deviation, contour deformation, and abnormal surface texture. Based on the appearance difference data, it is determined whether the abnormal battery cell exhibits bulging, leakage, tab discoloration, or casing deformation: bulging refers to localized expansion and deformation of the battery cell casing due to internal gas generation; leakage refers to electrolyte seepage from the sealed area of ​​the battery cell casing; tab discoloration refers to oxidation discoloration of the positive and negative tabs due to overcurrent or overheating; casing deformation refers to irregular deformation of the battery cell casing caused by internal pressure or external compression. If any of the above appearance differences exist, it indicates that the battery cell body has suffered physical damage or is a precursor to thermal runaway. This appearance difference data serves as prior reference information for subsequent electrical performance testing, helping to narrow down the scope of failure mechanism investigation.

[0037] S32. Perform internal resistance tests on the abnormal battery cell and the normal battery cell to obtain the AC internal resistance, charging DC internal resistance and discharging DC internal resistance of the abnormal battery cell.

[0038] In this embodiment, the internal resistance test includes AC internal resistance test and DC internal resistance test. The AC internal resistance reflects the sum of the ohmic internal resistance and polarization internal resistance of the cell under AC signal, while the DC internal resistance reflects the internal resistance characteristics of the cell under actual DC operating conditions. The combination of the two can distinguish different failure mechanisms.

[0039] In some embodiments, the internal resistance test of the abnormal cell and the normal cell includes: After discharging the abnormal battery cell at a constant current of rated current to the cutoff voltage and letting it stand for a preset time, an AC internal resistance test is performed on the abnormal battery cell.

[0040] In this embodiment, the abnormal battery cell is first subjected to constant current discharge at its rated current until the cell voltage drops to a preset cutoff voltage, such as 2.5V. Then, it is left to stand for a preset time, such as 30 minutes, to allow the internal electrochemical state of the cell to stabilize. Subsequently, an AC excitation signal with a frequency of 1kHz and a small amplitude is applied to the cell using an internal resistance tester, and the AC voltage response across the cell is measured. The AC internal resistance of the abnormal battery cell is then calculated based on Ohm's law.

[0041] The abnormal battery cell is subjected to short-time high-current charging DC internal resistance test and discharging DC internal resistance test. Voltage data are obtained when charging stops and discharging stops, and the charging DC internal resistance and discharging DC internal resistance are calculated.

[0042] In this embodiment, the DC internal resistance test for charging adopts a short-duration high-current pulse charging method: A constant current is applied to the abnormal cell using a preset high current specification, such as 600A, for a preset short duration, such as 10 seconds. The cell voltage U1 at the moment charging stops is recorded. The cell is then left to rest for a second preset duration, such as 2 hours, to allow the internal polarization of the cell to fully relax. The stable voltage U2 after resting is recorded. The DC internal resistance test for discharging adopts a short-duration high-current pulse discharging method: A constant current is applied to the abnormal cell using the same preset high current specification for the same preset short duration. The cell voltage U3 at the moment discharging stops is recorded. This short-duration high-current pulse test method can effectively simulate the current surge under actual cell operating conditions, while avoiding the significant increase in cell temperature caused by prolonged high current, which would affect the accuracy of internal resistance measurement. The DC internal resistance is calculated according to the following formulas: Charging DC internal resistance R1 = (U2 - U1) / I, Discharging DC internal resistance R2 = (U2 - U3) / I, where I is the current value of the preset high current specification.

[0043] The failure type of the abnormal battery cell is determined based on the relative relationship between the AC internal resistance, the DC internal resistance during charging, and the DC internal resistance during discharging.

[0044] In this embodiment, the deviations between the AC internal resistance, charging DC internal resistance, and discharging DC internal resistance of the abnormal battery cell and the corresponding internal resistance of the normal battery cell are calculated, and each deviation is compared with its corresponding preset threshold. If the deviation of the AC internal resistance is within the preset normal range and the deviation of the DC internal resistance during discharge is greater than the first preset threshold, it is determined that the interface impedance has increased due to over-discharge. Over-discharge means that the depth of discharge of the cell exceeds the safe discharge cutoff conditions specified by the manufacturer, resulting in abnormal thickening of the solid electrolyte interphase (SEI) film on the negative electrode surface or deposition of electrolyte decomposition products. The SEI film is a passivation film formed by the reduction and decomposition of the electrolyte on the negative electrode surface of a lithium-ion battery. It has the characteristics of ion conduction and electronic insulation. Over-discharge will destroy its stability. If the deviation of at least two of the AC internal resistance, charging DC internal resistance, and discharging DC internal resistance exceeds their respective preset thresholds, it is determined that the internal connection is loose or the active material has fallen off. Loose internal connection means that the welding or mechanical connection between the internal tab and the electrode plate of the battery cell has increased resistance. Falling off active material means that the active material particles in the electrode coating are peeled off from the current collector surface, resulting in a reduction in the effective reaction area and an increase in internal resistance. If the deviation of the charging DC internal resistance is within the preset normal range and the deviation of the discharging DC internal resistance is greater than the second preset threshold, it is judged that there is an asymmetric interface reaction barrier. An asymmetric interface reaction barrier means that the electrochemical reaction kinetics at the positive and negative electrode interfaces of the battery cell show significant differences during charging and discharging, which is usually caused by local passivation of the negative electrode surface or degradation of the positive electrode material structure.

[0045] S33. Perform charge / discharge performance and temperature rise tests on the abnormal battery cell and the normal battery cell to obtain the charge / discharge capacity, voltage plateau, temperature rise characteristics, energy efficiency ratio and static voltage rebound data of the abnormal battery cell.

[0046] In this embodiment, both the abnormal and normal battery cells are first discharged at a constant current to the cutoff voltage and left to stand for a preset time, such as 30 minutes, to unify their initial state. During the charging test, a temperature acquisition device is attached to the surface of the battery cell, and a preset charging specification is used, such as 3.6V constant current and constant voltage charging with a cutoff current of 16A. After charging, the cells are left to stand for a third preset time, such as 60 minutes, during which the surface temperature rise, full charge capacity, and voltage data at the beginning and end of the standing period are recorded. During the discharging test, a temperature acquisition device is also attached to the surface of the battery cell, and a constant current is used to discharge the cells to the cutoff voltage, such as 2.5V. After discharging, the cells are left to stand for a fourth preset time, such as 60 minutes, during which the surface temperature rise, discharge capacity, and voltage data at the beginning and end of the standing period are recorded.

[0047] After obtaining the above data, the energy efficiency ratio (EER) of the abnormal cell is calculated. The EER is the ratio of discharge energy to charging energy. Discharge energy is obtained by integrating the product of voltage and current during discharge over time, and charging energy is obtained by integrating the product of voltage and current during charging over time. If the deviation of the EER of the abnormal cell from that of the normal cell is greater than the preset EER threshold, it indicates irreversible energy loss within the cell, such as heat generated by side reactions or micro-short-circuit leakage current. Simultaneously, the voltage rebound curve during the resting period after discharge is monitored. Please refer to [link to relevant documentation]. Figure 5 , Figure 5 This is a comparison chart of electrical test and charge / discharge performance characteristics provided in this embodiment of the invention. The chart shows a comparison of the voltage and temperature curves of a normal cell and an abnormal cell during the charge / discharge process. The abnormal cell exhibits problems such as abnormal discharge voltage fluctuations, abnormal temperature rise, and low charge / discharge efficiency. Based on this, it can be preliminarily determined that there is a problem inside the abnormal cell. If the voltage rebound value of the abnormal cell (i.e., the difference between the stable voltage after resting and the voltage at the moment of discharge cutoff) deviates from that of the normal cell by more than a preset rebound threshold, it indicates that the cell has severe internal polarization or an internal micro-short circuit. This result can help verify the conclusion of the DC internal resistance test in step S32.

[0048] S34. Perform self-discharge and voltage holding tests on the abnormal battery cell and the normal battery cell to obtain the self-discharge rate of the abnormal battery cell.

[0049] In this embodiment, self-discharge and voltage holding tests are performed on abnormal and normal battery cells to obtain the self-discharge rate of the abnormal battery cells. The self-discharge and voltage holding tests are used to quantify the voltage decay rate of the battery cells in a static state, in order to screen for internal micro-short circuits and the risk of persistent side reactions.

[0050] In some embodiments, the self-discharge and voltage holding tests performed on the abnormal battery cell and the normal battery cell include: After discharging the abnormal battery cell to the cutoff voltage at a constant current with the rated current and letting it stand, charge it with constant current and constant voltage according to the preset charging specifications and let it stand for a preset voltage holding time.

[0051] In this embodiment, the abnormal battery cell is first discharged at a constant current of the rated current to the cutoff voltage and left to stand for a preset time, such as 30 minutes. Then, it is continuously charged at a preset charging specification, such as 3.6V / 157A constant current and constant voltage, for a preset time, such as 20 minutes, until the battery cell reaches a partial state of charge. A partial state of charge refers to a state of charge (SOC) range of 50% to 80%, within which the battery cell voltage is most sensitive to self-discharge. After charging is complete, the battery cell is placed in a standard test environment and left to maintain its voltage for a preset time, such as 92 hours. During this period, any charging or discharging operations and external circuit connections are prohibited to isolate external current paths and ensure that voltage decay is caused only by internal self-discharge within the battery cell.

[0052] The voltage data of the abnormal cell is recorded in segments during the voltage holding time, and the self-discharge rate is calculated based on the segmented voltage data.

[0053] In this embodiment, the self-discharge rate is the rate of voltage decay caused by internal side reactions or micro-short circuits in the cell under open-circuit resting conditions. Within a preset voltage holding time, cell voltage data is recorded in segments according to preset sampling times. For example, voltage values ​​V0, V1, and V2 are recorded at the 8th, 32nd, and 80th hours of resting, respectively. V0 is the initial voltage, taken as the voltage value at the first sampling time after the start of resting. The K-value self-discharge rate is calculated based on the segmented voltage data. The K-value is the voltage decay rate per unit time, calculated using the formulas: K1=(V0-V1) / t1, K2=(V0-V2) / t2, where t1 is the time interval between V0 and V1 (e.g., 24 hours), and t2 is the time interval between V0 and V2 (e.g., 72 hours). This segmented K-value calculation method, compared to simply comparing the total voltage drop over 72 hours, can reflect the self-discharge trend earlier and more linearly, effectively distinguishing between normal aging and abnormal micro-short circuits. Please refer to [link to relevant documentation]. Figure 6 , Figure 6 This is a self-discharge / voltage holding test based on a K-value model provided in this embodiment of the invention, showing the self-discharge voltage decay curve. The figure illustrates the voltage decay curves of normal and abnormal cells during the static voltage holding period. The voltage decay rate of the abnormal cell is significantly higher than that of the normal cell. By calculating the self-discharge trend segment by K1 and K2, this difference can be reflected earlier and more linearly.

[0054] The self-discharge rate of the abnormal battery cell is compared with that of the normal battery cell to determine whether there is a risk of abnormal self-discharge.

[0055] In this embodiment, the deviation between the K value of the abnormal cell and the K value of the normal cell is calculated. If the deviation is greater than the preset self-discharge threshold, such as if the K value deviation exceeds 50% of the normal cell's K value, the abnormal cell is determined to have an abnormal self-discharge risk, indicating that there may be micro-short circuits, electrolyte impurities, or electrode defects inside the cell. If the deviation is within the preset normal range, the self-discharge performance is determined to be normal.

[0056] If there is a risk of abnormal self-discharge, the abnormal voltage is determined by combining the initial incoming data and current test data of the abnormal cell to determine whether the voltage abnormality is due to over-discharge damage during use or a manufacturing defect in the incoming material.

[0057] In this embodiment, the initial incoming data of abnormal battery cells is obtained through a battery cell barcode traceability system. This initial data includes key performance parameters such as the initial capacity, initial internal resistance, and initial K-value of the battery cell at the time of manufacture. The initial incoming data is compared with the current test data: if the initial incoming data is within a preset acceptable range while the current test data is abnormal, it indicates that the battery cell performed normally at the time of manufacture, and the voltage abnormality is due to over-discharge damage during use. Over-discharge damage during use refers to performance degradation caused by excessive discharge, long-term storage, or improper use of the battery cell in the actual operation of the energy storage system or electric vehicle. If the initial incoming data deviates from the preset acceptable range, it indicates that the battery cell already had potential defects at the time of manufacture, and the voltage abnormality is due to manufacturing defects. Manufacturing defects refer to inherent defects caused by improper process control during the battery cell production process, such as electrode burrs, diaphragm damage, or foreign matter contamination. This traceability mechanism enables precise determination of responsibility for failure from electrical performance abnormalities, providing a basis for subsequent quality control and process improvement.

[0058] S4. Based on the multi-dimensional electrical performance difference data, determine whether the physical performance of the abnormal battery cell is abnormal.

[0059] In this embodiment, the performance of an abnormal battery cell is determined based on multi-dimensional electrical performance difference data. In existing technologies, battery cell performance assessment often relies on engineers' personal experience, lacking quantitative comprehensive evaluation standards, leading to highly subjective and unrepeatable results. This step establishes a multi-dimensional joint judgment model, quantitatively comparing the electrical performance difference data obtained in step S3 with preset thresholds and performing a comprehensive evaluation according to preset weighting rules. This transforms qualitative experience into quantitative judgment, solving the technical problems of inconsistent judgment standards and low repeatability in existing technologies.

[0060] Specifically, the multi-dimensional electrical performance difference data includes the appearance difference data obtained in step S31, the AC internal resistance deviation, the charging DC internal resistance deviation, the discharging DC internal resistance deviation obtained in step S32, the charge and discharge capacity deviation, the energy efficiency ratio deviation, the static voltage rebound deviation obtained in step S33, and the self-discharge rate deviation obtained in step S34.

[0061] The above-mentioned differences are compared with their respective preset thresholds: If bulging, leakage, tab discoloration, or shell deformation are found in the appearance differences, the main body performance is directly determined to be abnormal; If any of the AC internal resistance deviation, charging DC internal resistance deviation, or discharging DC internal resistance deviation exceeds its corresponding preset internal resistance threshold, the internal resistance index is determined to be abnormal; If the charge / discharge capacity deviation exceeds the preset capacity threshold, or the energy efficiency ratio deviation exceeds the preset energy efficiency ratio threshold, or the static voltage rebound deviation exceeds the preset rebound threshold, the charge / discharge performance index is determined to be abnormal; If the self-discharge rate deviation exceeds the preset self-discharge threshold, the self-discharge index is determined to be abnormal.

[0062] The abnormality of each indicator is comprehensively evaluated according to the preset weighting rules. The preset weighting rules are the judgment logic rules pre-set according to the impact of each dimension indicator on the safety performance and cycle life of the battery cell: if the appearance indicator is abnormal, or at least two of the internal resistance indicator, charge and discharge performance indicator, and self-discharge indicator are abnormal at the same time, the battery cell is judged to have abnormal performance, and step S5 is executed; if only one indicator is abnormal and the other indicators are all within the preset normal range, or all indicators are within the preset normal range, the battery cell is judged to have no substantial abnormality in performance, the judgment result of the battery cell being normal is output and the process is terminated.

[0063] S5. If the abnormal battery cell has abnormal performance, then the root cause of the failure of the abnormal battery cell shall be verified.

[0064] In this embodiment, if the inherent performance of the abnormal battery cell is abnormal, a root cause verification is performed on the abnormal battery cell. Existing technologies typically scrap the battery cell directly after determining its performance is abnormal, lacking the ability to deeply trace the root cause of failure. This makes it impossible to distinguish between manufacturing defects in incoming materials and over-discharge / aging damage during use, resulting in a lack of precise basis for quality control and the recurrence of similar problems. This step, based on electrical performance testing, follows a progressive principle of non-destructive testing before destructive testing, and structure before morphology before composition. Through three layers of verification—X-ray / CT non-destructive testing, disassembly microscopy, and elemental composition analysis—it locates the root cause of voltage abnormalities at the structural, morphological, and compositional levels, accurately distinguishing between manufacturing defects in incoming materials and over-discharge damage during use. This provides the final basis for subsequent quality traceability, process improvement, and responsibility determination, thereby solving the technical problems of untraceable root causes of failure and a lack of precise basis for quality control in existing technologies.

[0065] In some embodiments, see also Figure 4 The step of performing root cause verification on the abnormal battery cell includes: S51. Perform X-ray or CT non-destructive testing on the abnormal battery cell to obtain an image of the internal structure of the abnormal battery cell, and determine whether the abnormal battery cell has internal structural defects based on the image of the internal structure.

[0066] In this embodiment, the abnormal battery cell is placed at the inspection station of an X-ray diagnostic device or a CT diagnostic device. High-energy X-rays penetrate the battery cell casing, and the absorption differences of different materials to X-rays are used to obtain a two-dimensional projection image or a three-dimensional tomographic image of the battery cell's interior. An X-ray diagnostic device is a non-destructive testing device that uses the principle of X-ray fluoroscopy to image the internal structure of an object. A CT diagnostic device, or computed tomography device, obtains the three-dimensional structural information of the tested object through multi-angle X-ray projection reconstruction. The internal structural image is then processed using image enhancement and defect identification algorithms to determine whether the abnormal battery cell has internal structural defects. Internal structural defects include winding or stacking misalignment (interlayer displacement between the electrode sheet and the separator during the winding or stacking process), electrode wrinkles (wavy deformation of the electrode sheet surface caused by uneven tension or foreign object compression), foreign object inclusions (non-designed substances such as metal particles and dust mixed into the battery cell), and local deformation (structural deformation caused by mechanical or thermal stress within the battery cell). If the aforementioned internal structural defects exist, it indicates that the voltage abnormality is a manufacturing defect in the incoming material, and a diagnostic conclusion of manufacturing defect is output; if no internal structural defects exist, proceed to step S52 for further verification.

[0067] S52. Obtain microscopic image data of the electrodes and separators of the abnormal battery cell after disassembly, and analyze the microscopic image data to locate microscopic failure characteristics.

[0068] In this embodiment, the abnormal battery cell is disassembled in a dry environment (such as a drying room with a dew point temperature below -40°C). The disassembly process can be carried out using automated disassembly equipment or special disassembly tools. The casing is opened along the weld seam or a pre-set disassembly line, and the internal battery cell core or stacked core is removed. This avoids secondary damage to the electrode and separator during the disassembly process, and separates the positive electrode, negative electrode, and separator samples. The samples are then placed under an optical microscope and an electron microscope for microscopic morphology observation: An optical microscope is an instrument that uses visible light and an optical lens system to magnify and observe tiny objects. The magnification is usually 10x to 1000x, and it is suitable for observing the macroscopic morphology of the electrode surface and separator damage. An electron microscope is an instrument that uses a focused electron beam to scan the sample surface and images it by detecting secondary electrons or backscattered electron signals. The magnification can reach thousands to hundreds of thousands of times, and it is suitable for observing the microstructure of the electrode coating, particle morphology, and micro-short circuit traces. By comparing microscopic images of abnormal and normal battery cells, microscopic failure characteristics can be identified: If dendritic crystals, i.e., lithium plating, are present on the surface of the negative electrode, lithium ions are reduced and deposited on the negative electrode surface to form metallic lithium dendrites, usually caused by over-discharge or low-temperature high-current charging; or if there are ablation marks on the electrode surface, i.e., local high temperature causing coating carbonization or current collector melting, it indicates that the battery cell has undergone deep over-discharge; if the positive or negative electrode shows coating peeling, or the separator has puncture holes or tears, it indicates incoming material manufacturing defects or internal micro-short circuits. The separator is a porous polymer film located between the positive and negative electrodes, which has the function of ion conduction and electronic insulation, and is a key component to prevent internal short circuits in the battery.

[0069] S53. Obtain elemental composition data of the abnormal location of the abnormal cell, and analyze the elemental composition data to confirm the chemical root cause of the voltage abnormality.

[0070] In this embodiment, the target micro-region is selected from the micro-failure feature region (such as lithium plating region, ablation region, foreign particles or membrane puncture region) located in step S52, and elemental composition analysis is performed by energy dispersive X-ray spectroscopy (EDS). EDS is a micro-region composition analysis instrument used in conjunction with an electron microscope. It determines the types and relative contents of elements in the micro-region by detecting the characteristic X-rays emitted after the sample is excited by an electron beam. The elemental composition data of the abnormal location is compared with the elemental composition data of the corresponding location in the normal cell: if an abnormal metal element (such as copper, iron, or other elements in the current collector or casing material) is detected at the abnormal location and this element is not present in the normal cell, it indicates the presence of metal foreign matter contamination, which is a defect in incoming material manufacturing; if the content of characteristic elements of electrolyte decomposition products such as fluorine and phosphorus is significantly higher than that in the normal cell at the abnormal location, it indicates that the cell has undergone serious electrolyte side reactions during use, which is over-discharge damage during use; if lithium is enriched in elemental form at the abnormal location (combined with the morphological observation in step S52), it further confirms the presence of lithium plating. Combining the structural analysis in step S51, the morphological observation in step S52, and the compositional analysis results in step S53, the final diagnostic conclusion is output: if structural defects and manufacturing defects coexist, it is determined to be a defect in incoming material manufacturing; if over-discharge characteristics (lithium plating, ablation, electrolyte decomposition) are the main features and there are no structural manufacturing defects, it is determined to be deep over-discharge damage during use.

[0071] This invention also provides a systematic diagnostic device for abnormal cell voltage, which is used to perform any embodiment of the aforementioned systematic diagnostic method for abnormal cell voltage. Specifically, please refer to... Figure 7 , Figure 7 This is a schematic block diagram of a system diagnostic device for abnormal cell voltage provided in an embodiment of the present invention.

[0072] like Figure 7 As shown, the system diagnostic device 100 for abnormal cell voltage includes: Abnormal cell acquisition module 110 is used to acquire abnormal cells to be diagnosed and select normal cells that match the abnormal cells as control samples. The external factor investigation module 120 is used to investigate the abnormal battery cell for external factors in order to determine whether there are any external factors causing the abnormality. The cell performance analysis module 130 is used to perform cell performance analysis on the abnormal cell and the normal cell if there is no abnormality caused by external factors, so as to obtain multi-dimensional electrical performance difference data of the abnormal cell relative to the normal cell. The performance anomaly judgment module 140 is used to determine whether the physical performance of the abnormal battery cell is abnormal based on the multi-dimensional electrical performance difference data. The failure root cause verification module 150 is used to verify the failure root cause of the abnormal battery cell if the cell's performance is abnormal.

[0073] The aforementioned systematic diagnostic device for abnormal cell voltage can be implemented as a computer program, which can be used in, for example... Figure 8 It runs on the computer device shown.

[0074] Please see Figure 8 , Figure 8 This is a schematic block diagram of a computer device provided in an embodiment of the present invention.

[0075] The computer device 500 includes a processor 502, a memory, and a network interface 505 connected via a communication bus 501. The memory may include a storage medium 503 and internal memory 504.

[0076] The storage medium 503 may store an operating system 5031 and a computer program 5032. When the computer program 5032 is executed, it enables the processor 502 to perform a systematic diagnostic method for abnormal cell voltage. The storage medium 503 may be a volatile storage medium or a non-volatile storage medium.

[0077] The processor 502 provides computing and control capabilities to support the operation of the entire computer device 500.

[0078] The internal memory 504 provides an environment for the operation of the computer program 5032 in the storage medium 503. When the computer program 5032 is executed by the processor 502, the processor 502 can perform a systematic diagnostic method for abnormal cell voltage.

[0079] This network interface 505 is used for network communication, such as providing data transmission. Those skilled in the art will understand that... Figure 4 The structure shown is merely a block diagram of a portion of the structure related to the present invention and does not constitute a limitation on the computer device 500 to which the present invention is applied. The specific computer device 500 may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements.

[0080] The processor 502 is used to run the computer program 5032 stored in the memory to implement the corresponding function in the above-mentioned systematic diagnostic method for abnormal cell voltage.

[0081] Those skilled in the art will understand that Figure 8The embodiments of the computer device shown do not constitute a limitation on the specific configuration of the computer device. In other embodiments, the computer device may include more or fewer components than illustrated, or combine certain components, or have different component arrangements. For example, in some embodiments, the computer device may include only memory and a processor. In such embodiments, the structure and function of the memory and processor are different from those shown. Figure 8 The embodiments shown are consistent and will not be described again here.

[0082] It should be understood that, in this embodiment of the invention, the processor 502 may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0083] In another embodiment of the invention, a computer-readable storage medium is provided. This computer-readable storage medium may be volatile or non-volatile. The computer-readable storage medium stores a computer program, wherein when executed by a processor, the computer program implements the steps included in the above-described systematic diagnostic method for abnormal cell voltage.

[0084] Those skilled in the art will readily understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention.

[0085] In the embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Units with the same function may be grouped into one unit. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or units, or it may be an electrical, mechanical, or other form of connection.

[0086] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention, depending on actual needs.

[0087] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0088] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a computer-readable storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned computer-readable storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), magnetic disks, or optical disks.

[0089] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A systematic diagnostic method for abnormal cell voltage, characterized in that, include: Obtain the abnormal battery cell to be diagnosed, and select a normal battery cell that matches the abnormal battery cell as a control sample; External factors were investigated for the abnormal battery cells to determine whether there were any false abnormalities caused by external factors. If there are no false anomalies caused by external factors, perform cell body performance analysis on the abnormal cell and the normal cell to obtain multi-dimensional electrical performance difference data between the abnormal cell and the normal cell. Based on the multi-dimensional electrical performance difference data, determine whether the physical performance of the abnormal battery cell is abnormal; If the abnormal battery cell has abnormal performance, the root cause of the failure of the abnormal battery cell shall be verified.

2. The systematic diagnostic method for abnormal cell voltage according to claim 1, characterized in that, The external factor investigation of the abnormal battery cell includes: Obtain inspection data on the appearance and connection parts of the abnormal battery cell, and check whether there are physical defects in the external connection links of the abnormal battery cell based on the inspection data; The open-circuit voltage of the abnormal cell, which was re-measured, was compared with the voltage data collected by the battery management system to determine the authenticity of the voltage abnormality. The abnormal battery cell was subjected to a charge-discharge reproduction test. The charge-discharge curve and capacity of the abnormal battery cell were compared with those of the normal battery cell to rule out false alarms and external circuit faults, and to confirm that the root cause of the voltage abnormality was located in the battery cell itself.

3. The systematic diagnostic method for abnormal cell voltage according to claim 1, characterized in that, The process of performing cell-body performance analysis on the abnormal cell and the normal cell to obtain multi-dimensional electrical performance difference data between the abnormal cell and the normal cell includes: Obtain the appearance image data of the abnormal battery cell and the normal battery cell, and compare and analyze the appearance image data to obtain appearance difference data; The abnormal battery cell and the normal battery cell are subjected to internal resistance tests to obtain the AC internal resistance, charging DC internal resistance and discharging DC internal resistance of the abnormal battery cell. The abnormal battery cell and the normal battery cell are subjected to charge-discharge performance and temperature rise tests to obtain the charge-discharge capacity, voltage plateau, temperature rise characteristics, energy efficiency ratio and static voltage rebound data of the abnormal battery cell. The abnormal battery cell and the normal battery cell are subjected to self-discharge and voltage holding tests to obtain the self-discharge rate of the abnormal battery cell.

4. The systematic diagnostic method for abnormal cell voltage according to claim 3, characterized in that, The internal resistance test of the abnormal battery cell and the normal battery cell includes: After discharging the abnormal battery cell at a constant current of rated current to the cutoff voltage and letting it stand for a preset time, an AC internal resistance test is performed on the abnormal battery cell. The abnormal battery cell is subjected to short-time high-current charging DC internal resistance test and discharging DC internal resistance test. The voltage data at the time of charging stop and discharging stop are obtained respectively, and the charging DC internal resistance and discharging DC internal resistance are calculated. The failure type of the abnormal battery cell is determined based on the relative relationship between the AC internal resistance, the DC internal resistance during charging, and the DC internal resistance during discharging.

5. The systematic diagnostic method for abnormal cell voltage according to claim 4, characterized in that, The step of determining the failure type of the abnormal battery cell based on the relative relationship between the AC internal resistance, the charging DC internal resistance, and the discharging DC internal resistance includes: If the deviation of the AC internal resistance is within the preset normal range and the deviation of the DC internal resistance of the discharge is greater than the first preset threshold, it is determined that the interface impedance rise is caused by over-discharge. If the deviation of at least two of the AC internal resistance, the charging DC internal resistance and the discharging DC internal resistance is greater than their respective preset thresholds, it is determined that the internal connection is loose or the active material has fallen off. If the deviation of the charging DC internal resistance is within a preset normal range and the deviation of the discharging DC internal resistance is greater than a second preset threshold, it is determined that there is an asymmetrical interface reaction barrier.

6. The method according to claim 3, characterized in that, The self-discharge and voltage holding tests performed on the abnormal battery cell and the normal battery cell include: After discharging the abnormal battery cell to the cutoff voltage at the rated current and letting it stand, charge it with constant current and constant voltage according to the preset charging specifications and let it stand for the preset voltage holding time. The voltage data of the abnormal cell is recorded in segments during the voltage holding time, and the self-discharge rate is calculated based on the segmented voltage data. The self-discharge rate of the abnormal battery cell is compared with the self-discharge rate of the normal battery cell to determine whether there is a risk of abnormal self-discharge. If there is a risk of abnormal self-discharge, the abnormal voltage is determined by combining the initial incoming data and current test data of the abnormal cell to determine whether the voltage abnormality is due to over-discharge damage during use or a manufacturing defect in the incoming material.

7. The systematic diagnostic method for abnormal cell voltage according to claim 1, characterized in that, The failure root cause verification of the abnormal battery cell includes: The abnormal battery cell is subjected to X-ray or CT non-destructive testing to obtain an image of its internal structure, and the presence of internal structural defects in the abnormal battery cell is determined based on the image. Microscopic image data of the electrodes and separators of the abnormal battery cell after disassembly are obtained, and the microscopic image data is analyzed to locate microscopic failure characteristics. Obtain elemental composition data of the abnormal location of the abnormal cell, and analyze the elemental composition data to confirm the chemical root cause of the voltage abnormality.

8. A systematic diagnostic device for abnormal cell voltage, used to perform the diagnostic method according to any one of claims 1-7, characterized in that, The device includes: An abnormal cell acquisition module is used to acquire abnormal cells to be diagnosed and select normal cells that match the abnormal cells as control samples. The external factor investigation module is used to investigate the abnormal battery cell for external factors in order to determine whether there are any external factors causing the abnormality. The cell body performance analysis module is used to perform cell body performance analysis on the abnormal cell and the normal cell if there are no external factors causing the abnormality, so as to obtain multi-dimensional electrical performance difference data of the abnormal cell relative to the normal cell. The performance anomaly detection module is used to determine whether the inherent performance of the abnormal battery cell is abnormal based on the multi-dimensional electrical performance difference data. The failure root cause verification module is used to verify the failure root cause of the abnormal battery cell if the cell's performance is abnormal.

9. A computer device, characterized in that, The device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; When a processor executes a program stored in a memory, it implements the steps of the systematic diagnostic method for abnormal cell voltage as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the systematic diagnostic method for abnormal cell voltage as described in any one of claims 1-7.

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