Secondary battery aging detection method and secondary battery management system

Abstract

The invention provides a secondary battery aging detection method, a secondary battery management system, electronic equipment and a computer readable storage medium. The secondary battery aging detection method comprises the following steps: acquiring a second-order differential curve of a secondary battery to be detected; performing polynomial fitting on the second-order differential curve to obtain a polynomial equation; determining the characteristic peak position of the secondary battery to be detected according to the polynomial equation and the standard characteristic peak position; wherein the standard characteristic peak position is a characteristic peak position corresponding to a secondary battery of the same type as the secondary battery to be detected under an unaged condition; and determining the aging state of the to-be-tested secondary battery according to the characteristic peak position of the to-be-tested secondary battery. Through the above mode, the detection accuracy of the aging state of the secondary battery is improved.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and more specifically, to a secondary battery aging detection method, a secondary battery management system, an electronic device, and a computer-readable storage medium. Background Technology

[0002] The aging state of a secondary battery is a crucial indicator, and detecting it is a key technology in secondary battery management systems. Determining the aging state allows for better management of charge and discharge methods, thereby extending battery life and maximizing performance. Currently, the aging state is primarily determined by analyzing the differential discharge curve. However, actual battery use involves complex conditions such as low-temperature charging and discharging, and high-rate charging and discharging. These conditions introduce dynamic interference into the differential discharge curve, leading to low accuracy in aging state detection based solely on the differential discharge curve. Summary of the Invention

[0003] The purpose of this application is to provide a method for detecting the aging of secondary batteries, a secondary battery management system, an electronic device, and a computer-readable storage medium, so as to improve the accuracy of detecting the aging state of secondary batteries.

[0004] In a first aspect, this application provides a method for detecting the aging of a secondary battery, comprising: acquiring a second-order differential curve of the secondary battery under test; wherein the second-order differential curve characterizes the relationship between the second-order differential of the secondary battery under test and the discharge capacity of the secondary battery under test during actual operation, and the second-order differential of the secondary battery under test is the second-order differential of the discharge voltage of the secondary battery under test with respect to the discharge capacity of the secondary battery under test; performing polynomial fitting on the second-order differential curve to obtain a polynomial equation; determining the characteristic peak position of the secondary battery under test based on the polynomial equation and a standard characteristic peak position; wherein the standard characteristic peak position is the characteristic peak position corresponding to a secondary battery of the same type as the secondary battery under test in the unaged state; and determining the aging state of the secondary battery under test based on the characteristic peak position of the secondary battery under test.

[0005] In the above scheme, the second-order differential curve of the secondary battery under test is obtained. Since there is considerable interference in the second-order differential curve, a multinomial function is used to fit it. This function fitting method aims to eliminate interference signals as much as possible, resulting in a polynomial equation. Then, by analyzing the relationship between the polynomial equation and the standard characteristic peak position, the characteristic peak position of the secondary battery under test is determined. Based on the characteristic peak position, the aging state of the secondary battery under test is determined, thereby improving the accuracy of aging state detection.

[0006] In an optional implementation, the step of performing polynomial fitting on the second-order differential curve to obtain a polynomial equation includes: filtering the second-order differential curve to obtain a filtered second-order differential curve; and performing polynomial fitting on the filtered second-order differential curve to obtain the polynomial equation.

[0007] In the above scheme, considering the complex actual operating conditions of the secondary battery under test, there may still be a lot of interference in the second-order differential curve of the secondary battery. Therefore, the second-order differential curve is filtered to reduce the noise signal present in the second-order differential curve, so as to improve the accuracy of polynomial fitting. This allows for the fitting of a polynomial equation that is closer to the second-order differential curve. Subsequently, the aging state detection of the secondary battery is determined based on the polynomial equation, thereby improving the accuracy of the aging state detection of the secondary battery.

[0008] In an optional implementation, filtering the second-order differential curve includes: filtering the second-order differential curve through a filter to obtain a first curve; determining whether the number of peaks of the first curve in a preset interval is greater than a first threshold; if it is greater, adjusting the parameters of the filter, and filtering the second-order differential curve through the adjusted filter to obtain a second curve; wherein the second curve is the filtered second-order differential curve.

[0009] In an optional implementation, adjusting the parameters of the filter and filtering the second-order differential curve with the adjusted filter to obtain a second curve includes: determining whether the number of peaks in the curve obtained by filtering the second-order differential curve with the adjusted filter in the preset interval is greater than a first threshold; if it is greater, adjusting the parameters of the filter until the number of peaks in the curve obtained by filtering the second-order differential curve with the adjusted filter in the preset interval is less than or equal to the first threshold; and filtering the second-order differential curve with the adjusted filter to obtain the second curve.

[0010] In an optional implementation, determining the characteristic peak position of the secondary battery under test based on the polynomial equation and the standard characteristic peak position includes: determining the discharge capacity corresponding to the inflection point in the polynomial equation that is closest to the standard characteristic peak position; wherein the discharge capacity corresponding to the inflection point is the characteristic peak position of the secondary battery under test.

[0011] In an optional implementation, determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation includes: determining the second derivative of the polynomial equation; and taking the discharge capacity corresponding to the zero point closest to the standard characteristic peak in the second derivative as the discharge capacity corresponding to the inflection point.

[0012] In an optional implementation, determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation includes: determining the first derivative of the polynomial equation; and taking the discharge capacity corresponding to the peak closest to the standard characteristic peak in the first derivative as the discharge capacity corresponding to the inflection point.

[0013] In an optional implementation, determining the aging state of the secondary battery under test based on the characteristic peak position includes: determining a first depth of discharge based on the characteristic peak position; determining an offset based on the first depth of discharge and a standard depth of discharge; wherein the standard depth of discharge is the depth of discharge determined based on the standard characteristic peak position of a secondary battery of the same type as the secondary battery under test in the unaged state; and determining the aging state of the secondary battery under test based on the offset.

[0014] In the above scheme, the more severe the aging of the secondary battery, the lower the discharge capacity and the shallower the depth of discharge during the phase transition of the active materials in the cathode and anode of the secondary battery during operation. This process is manifested in the differential discharge curve as follows: the peak corresponding to the characteristic peak of the secondary battery under test is farther from the peak corresponding to the standard characteristic peak. Therefore, by analyzing the relationship between the characteristic peak of the secondary battery under test and the standard characteristic peak, the difference (i.e., the offset) between the first depth of discharge corresponding to the characteristic peak and the standard depth of discharge corresponding to the standard characteristic peak is determined, and then the aging state of the secondary battery is determined based on the offset.

[0015] Secondly, this application provides a secondary battery management system, the secondary battery management system comprising:

[0016] The acquisition module is used to acquire the second-order differential curve of the secondary battery under test; wherein, the second-order differential curve represents the relationship between the second-order differential of the secondary battery under test and the discharge capacity of the secondary battery under test during actual operation, and the second-order differential of the secondary battery under test is the second-order differential of the discharge voltage of the secondary battery under test with respect to the discharge capacity of the secondary battery under test.

[0017] The processing module is used to perform polynomial fitting on the second-order differential curve to obtain a polynomial equation; determine the characteristic peak position of the secondary battery under test based on the polynomial equation and the standard characteristic peak position; wherein, the standard characteristic peak position is the characteristic peak position corresponding to a secondary battery of the same type as the secondary battery under test in the unaged state; and determine the aging state of the secondary battery under test based on the characteristic peak position of the secondary battery under test.

[0018] In an optional implementation, the processing module is specifically used to filter the second-order differential curve to obtain a filtered second-order differential curve; and to perform polynomial fitting on the filtered second-order differential curve to obtain the polynomial equation.

[0019] In an optional implementation, the processing module is specifically used to filter the second-order differential curve using a filter to obtain a first curve; determine whether the number of peaks of the first curve in a preset interval is greater than a first threshold; if it is greater, adjust the parameters of the filter, and filter the second-order differential curve using the adjusted filter to obtain a second curve; wherein, the second curve is the filtered second-order differential curve.

[0020] In an optional implementation, the processing module is specifically used to determine whether the number of peaks in the curve obtained by filtering the second-order differential curve with the adjusted filter in the preset interval is greater than a first threshold; if it is greater, the parameters of the filter are adjusted until the number of peaks in the curve obtained by filtering the second-order differential curve with the adjusted filter in the preset interval is less than or equal to the first threshold; the second curve is obtained by filtering the second-order differential curve with the adjusted filter.

[0021] In an optional implementation, the processing module is specifically used to determine the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation; wherein the discharge capacity corresponding to the inflection point is the characteristic peak of the secondary battery under test.

[0022] In an optional implementation, the processing module is specifically used to determine the second derivative of the polynomial equation; and to take the discharge capacity corresponding to the zero point of the second derivative that is closest to the standard characteristic peak as the discharge capacity corresponding to the inflection point.

[0023] In an optional implementation, the processing module is specifically used to determine the first derivative of the polynomial equation; and to take the discharge capacity corresponding to the peak closest to the standard characteristic peak in the first derivative as the discharge capacity corresponding to the inflection point.

[0024] In an optional implementation, the processing module is specifically used to determine a first discharge depth based on the characteristic peak position; determine an offset based on the first discharge depth and a standard discharge depth; wherein the standard discharge depth is the discharge depth determined based on the standard characteristic peak position of a secondary battery of the same type as the secondary battery under test without aging; and determine the aging state of the secondary battery under test based on the offset.

[0025] Thirdly, this application provides an electronic device, including: a memory and a processor, wherein the memory stores computer program instructions, and the computer program instructions are read and executed by the processor to perform the method as described in any of the foregoing embodiments.

[0026] Fourthly, this application provides a computer-readable storage medium storing computer program instructions, which, when read and executed by a computer, perform the method described in any of the foregoing embodiments. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a differential discharge curve provided for an embodiment of this application;

[0029] Figure 2 A schematic diagram of a differential discharge curve determined based on the real-time discharge voltage of a secondary battery, provided as an embodiment of this application;

[0030] Figure 3 A flowchart of a secondary battery aging detection method provided in this application embodiment;

[0031] Figure 4 A structural block diagram of a secondary battery aging detection device provided in an embodiment of this application;

[0032] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0033] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0034] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, relational terms such as "first," "second," etc., in the description of this application are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one…" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0035] During the use of a secondary battery, the active materials in the cathode and anode undergo phase transitions. By analyzing the changes in the discharge capacity of the secondary battery during these phase transitions, the loss of active materials can be determined, thus assessing the battery's aging status. Currently, differential discharge curves of secondary batteries are primarily determined under offline laboratory conditions by subjecting them to low-rate constant current discharge. Figure 1 As shown, Figure 1 To obtain the differential discharge curves under laboratory conditions, the battery was fully charged and kept at a stable temperature, then discharged at a constant current of 0.1C. When the active materials in the cathode and anode of the secondary battery undergo a phase transition, it appears as a peak in the differential discharge curve. Figure 1 The position corresponding to the vertical line (the discharge capacity of the secondary battery corresponding to this peak is also called the characteristic peak position). Therefore, for a secondary battery undergoing constant current discharge, the aging status of the secondary battery can be determined by identifying the characteristic peak position in the differential discharge curve of the secondary battery.

[0036] To detect the aging state of secondary batteries, it is necessary to determine their differential discharge curve, which in turn requires determining the battery's voltage during operation. However, in actual operation, secondary batteries operate under complex conditions, such as discharging at high temperatures or high-rate discharge currents. Figure 2As shown, the real-time voltage signal collected during the use of the secondary battery is subject to interference from dynamic factors. This results in a large amount of noise in the differential discharge curve determined based on the real-time voltage signal collected during the use of the secondary battery. It is difficult to directly determine the characteristic peak position based on the differential discharge curve, which in turn leads to low accuracy in detecting the aging state of the secondary battery.

[0037] To improve the accuracy of aging state detection of secondary batteries, this application discloses a secondary battery aging detection method, a secondary battery management system, an electronic device, and a computer-readable storage medium.

[0038] The following section will introduce the secondary battery aging test method disclosed in this application.

[0039] Please see Figure 3 , Figure 3 This application provides a flowchart of a secondary battery aging test method, which includes:

[0040] Step 101: Obtain the second-order differential curve of the secondary battery under test.

[0041] In this embodiment, the second-order differential curve represents the relationship between the second-order derivative of the secondary battery under test and its discharge capacity during actual operation. The second-order derivative of the secondary battery under test is the second-order derivative of its discharge voltage with respect to its discharge capacity. The differential discharge curve of the secondary battery under test represents the relationship between its first-order derivative and its discharge capacity. The first-order derivative of the secondary battery under test is the first-order derivative of its discharge voltage with respect to its discharge capacity. Therefore, the second-order differential curve of the secondary battery under test is the first derivative of its differential discharge curve.

[0042] During the operation of the secondary battery under test in the terminal, the discharge voltage and discharge rate of the secondary battery under test can be acquired in real time through the BMS. The discharge capacity of the secondary battery under test can be determined based on the discharge rate using the Coulomb integration method. The Coulomb integration method is as follows: Among them I t Let Q be the discharge rate of the secondary battery under test at time t. t Let Q be the discharge capacity of the secondary battery under test at time t. t-Δt Let be the discharge capacity of the secondary battery under test at time t-Δt.

[0043] After determining the discharge voltage and discharge capacity of the secondary battery under test, calculate the second derivative of the discharge voltage with respect to the discharge capacitance. The second-order differential curve of the secondary battery under test is determined based on the second-order differential of the secondary battery under test and the discharge capacity of the secondary battery under test.

[0044] The discharge capacity of a secondary battery under test can also be expressed using State of Charge (SOC) and Depth of Discharge (DDC). The discharge capacity of a secondary battery is the amount of electricity it has consumed. The SOC represents the ratio of the remaining charge to the total capacity of the battery. The DDC represents the ratio of the discharge capacity to the total capacity of the battery. These three values ​​can be converted into each other. Therefore, the second-order differential curve of a secondary battery under test can take many forms.

[0045] For example, by using the second derivative of the discharge voltage with respect to the discharge capacity of the secondary battery under test as the x-axis and the discharge capacity of the secondary battery under test as the y-axis, a second-order differential curve of the secondary battery under test can be obtained. Similarly, by using the second derivative of the discharge voltage with respect to the discharge capacity of the secondary battery under test as the x-axis and the state of charge (SOC) of the secondary battery under test as the y-axis, a second-order differential curve of the secondary battery under test can be obtained. Furthermore, the parameters represented by the x-axis and y-axis of the second-order differential curve of the secondary battery under test can be interchanged; for example, by using the second derivative of the discharge voltage with respect to the discharge capacity of the secondary battery under test as the y-axis and the discharge capacity of the secondary battery under test as the x-axis, a second-order differential curve of the secondary battery under test can be obtained.

[0046] Step 102: Perform polynomial fitting on the second-order differential curve to obtain the polynomial equation.

[0047] In this embodiment of the application, as described above, since there are many interferences in the differential discharge curve of the secondary battery under test, directly determining the characteristic peak position by analyzing multiple peaks of the differential discharge curve would result in low accuracy. Therefore, obtaining the second-order differential curve of the secondary battery under test by taking the first derivative of the differential discharge curve can eliminate some of the interference.

[0048] In some practical applications, significant interference still exists in the second-order differential curve, affecting the determination of the characteristic peak positions of the secondary battery under test. Analysis of the differential discharge curve reveals that the characteristic peak position is a single peak within the differential discharge curve, and multiple peaks exist within the differential discharge curve. Correspondingly, according to mathematical properties, the second-order differential curve obtained by taking the first derivative of the differential discharge curve also contains multiple peaks. The shape of the second-order differential curve is similar to that of a higher-order polynomial function. Therefore, a higher-order polynomial function is used to fit the second-order differential curve. This function fitting method eliminates interference signals in the second-order differential curve, yielding a polynomial equation. The characteristic peak positions of the secondary battery under test are then determined by analyzing the polynomial equation.

[0049] Specifically, a second-order differential equation is fitted using a k-th degree polynomial to obtain a k-th degree polynomial equation. Here, k can be 3, 4, 5, etc., and this application does not limit the degree of the polynomial. The degree of the polynomial can be determined based on the actual fitting conditions. Various polynomial fitting methods can be used for polynomial fitting, such as least squares method, Lagrange multiplication table, Newton's multiplication table, minimizing maximum deviation method, and inverse matrix method, etc., and this application does not specifically limit these methods.

[0050] Furthermore, as an optional implementation, step 102 above may include:

[0051] Step A1: Filter the second-order differential curve to obtain the filtered second-order differential curve;

[0052] Step A2: Perform polynomial fitting on the filtered second-order differential curve to obtain the polynomial equation.

[0053] In this embodiment, considering the complex actual operating conditions of the secondary battery under test, there may be considerable interference in the second-order differential curve of the secondary battery under test. Therefore, in order to further improve the detection accuracy, the second-order differential curve is filtered to eliminate the noise signal present in the second-order differential curve, so as to accurately determine the peaks and troughs of the second-order differential curve that are closest to the standard characteristic peak.

[0054] Considering that a second-order differential curve contains multiple peaks and troughs, which represent characteristic information of the curve, a filtering method that does not lose or alter this characteristic information should be selected during the filtering process. This application does not limit the filtering method used; various filtering methods that do not lose or alter the characteristic information of the second-order differential curve can be used to filter it.

[0055] Further, step A1 above may include: filtering the second-order differential curve through a filter to obtain a first curve; determining whether the number of peaks of the first curve in a preset interval is greater than a first threshold; if it is greater, adjusting the parameters of the filter, and filtering the second-order differential curve through the adjusted filter to obtain a second curve; wherein the second curve is the filtered second-order differential curve.

[0056] In this embodiment of the application, in order to improve the filtering effect, the second-order differential curve is first filtered by a filter to obtain the first curve. Combined with... Figure 1 and Figure 2It is known that the noise signal in the discharge voltage of the secondary battery under test presents as multiple peaks and troughs in the differential discharge curve. The second-order differential curve is the first derivative of the differential discharge curve of the secondary battery under test; therefore, the noise signal in the discharge voltage of the secondary battery under test also presents as multiple peaks and troughs in the second-order differential curve. Since multiple peaks and troughs exist in the polynomial equation, the peaks and troughs introduced by the noise signal will affect the polynomial fitting result during polynomial fitting, leading to inaccurate fitting and consequently errors in the characteristic peak positions determined subsequently based on the polynomial equation. Therefore, a filter is set up to eliminate the peaks and troughs introduced by the noise signal in the second-order differential curve. By judging the number of peaks in the first curve within the preset interval, it can be determined whether the filtering effect meets expectations.

[0057] As explained above regarding the second-order differential curve, it represents the relationship between the second-order derivative of the secondary battery under test and its discharge capacity, which can be expressed as the State of Charge (SOC). The following explanation uses the SOC representation of discharge capacity as an example to illustrate the preset range.

[0058] As described above, as the secondary battery under test ages, its characteristic peaks gradually decrease in size, eventually appearing near the standard characteristic peak. The filter is used to remove noise signals near the characteristic peak of the secondary battery under test, allowing subsequent steps to determine the characteristic peak based on the filtered second-order differential curve. Therefore, the preset range can be the SOC range near the standard characteristic peak.

[0059] In some embodiments, the upper limit of the preset interval is the sum of the SOC corresponding to the standard feature peak and the first SOC threshold, and the lower limit of the preset interval is the difference between the SOC corresponding to the standard feature peak and the second SOC threshold. The first SOC threshold and the second SOC threshold can be the same or different.

[0060] For example, if the SOC corresponding to the standard feature peak is 30%, the first SOC threshold is 10%, and the second SOC threshold is 10%, then the preset range is 20%-40%. As another example, if the SOC corresponding to the standard feature peak is 30%, the first SOC threshold is 10%, and the second SOC threshold is 20%, then the preset range is 10%-40%.

[0061] If the number of peaks in the first curve within the preset interval is less than or equal to the first threshold, it indicates that the filter has removed most of the noise signal in the second-order differential curve, and the filtering effect is good. The first curve is then used as the filtered second-order differential curve. If the number of peaks in the first curve within the preset interval is greater than the first threshold, it indicates that there is still a significant amount of noise signal in the second-order differential curve, and the filtering effect is poor. The filter parameters are adjusted to improve the filtering effect. The adjusted filter is then used to filter the second-order differential curve to obtain the second curve. If the number of peaks in the second curve within the preset interval is less than or equal to the first threshold, the second curve is then used as the filtered second-order differential curve. If the number of peaks in the second curve within the preset interval is greater than the first threshold, the filter parameters are adjusted again to further improve the filtering effect until the number of peaks in the filtered second-order curve within the preset interval is less than or equal to the first threshold.

[0062] The first threshold is positively correlated with the size of the preset interval; the larger the preset interval, the larger the specific value of the first threshold. For example, if the preset interval is 20%-40%, the first threshold is 4; if the preset interval is 10%-40%, the first threshold is 6.

[0063] Furthermore, as an optional implementation, step A1 above may include: detecting outliers on the second-order differential curve to determine at least one outlier; preprocessing the outlier and filtering the preprocessed second-order differential curve to obtain a filtered second-order differential curve.

[0064] In this embodiment, since the discharge voltage of the secondary battery under test contains noise signals, outliers exist in the second-order differential curve. Outliers affect the filtering effect of the filter. Therefore, in order to improve the accuracy of determining the characteristic peak position, outlier detection is first performed on the second-order differential curve. After identifying the outliers, preprocessing is performed to obtain the preprocessed second-order differential curve, and then filtering is performed to obtain the filtered second-order differential curve.

[0065] There are several ways to preprocess outliers. In some embodiments, identified outliers are removed from the second-order differential curve, thereby reducing their impact on subsequent filtering.

[0066] In other embodiments, after identifying outliers, replacement points are determined based on several points before and after the outlier, and the outlier is replaced by the replacement point. The replacement point can be the mean, median, or other values ​​of the several points before and after the outlier.

[0067] This application may employ various outlier detection algorithms for outlier detection and various outlier replacement algorithms for outlier replacement; this application does not impose any limitations on these methods.

[0068] Step 103: Determine the characteristic peak position of the secondary battery under test based on the polynomial equation and the standard characteristic peak position.

[0069] In this embodiment, the standard characteristic peak position is the characteristic peak position corresponding to a secondary battery of the same type as the one under test in the unaged state, that is, the discharge capacity of the standard secondary battery when a phase transition occurs. The standard characteristic peak position is pre-stored in the BMS.

[0070] The standard characteristic peak position can be used to determine the differential discharge curve of a new secondary battery of the same type as the one being tested in a laboratory environment, and the differential discharge curve can be analyzed and determined.

[0071] For example, a new secondary battery of the same type as the one being tested is fully charged and then discharged at a 0.1C rate. The discharge voltage and discharge capacity during the discharge process are obtained. The first derivative of the discharge voltage with respect to the discharge capacitance is calculated. Based on the first derivative and the discharge capacity, the differential discharge curve of the new secondary battery is determined. The standard characteristic peak position can be determined by analyzing the differential discharge curve.

[0072] The second-order differential curve is the first derivative of the differential discharge curve. The characteristic peak of the secondary battery under test is the discharge capacity corresponding to a peak in the differential discharge curve. Analysis of the secondary battery's operating characteristics shows that as the battery ages, its characteristic peak gradually decreases, eventually appearing near the standard characteristic peak. Mathematically, the discharge capacity corresponding to the inflection point in the second-order differential curve is the characteristic peak. Considering that there may be multiple inflection points in the second-order differential curve, the discharge capacity corresponding to the inflection point closest to the standard characteristic peak is the characteristic peak.

[0073] Specifically, step 103 may include: determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation; wherein the discharge capacity corresponding to the inflection point is the characteristic peak of the secondary battery under test.

[0074] Through the aforementioned step 102, polynomial fitting is performed on the second-order differential curve to remove most of the interference signals in the second-order differential curve, resulting in a polynomial equation. Since the characteristic peak position of the secondary battery under test is the inflection point closest to the standard characteristic peak position in this polynomial equation, the inflection point in the polynomial equation is determined by analyzing the image of the polynomial equation or by differentiating the polynomial equation. The discharge capacity corresponding to the inflection point closest to the standard characteristic peak position is taken as the characteristic peak position of the secondary battery under test.

[0075] The following introduces two methods for determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in a polynomial equation.

[0076] In some implementations, determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation may include: determining the second derivative of the polynomial equation; and taking the discharge capacity corresponding to the zero point closest to the standard characteristic peak in the second derivative as the discharge capacity corresponding to the inflection point.

[0077] In this embodiment, according to mathematical relationships, the inflection point of an equation corresponds to a zero in the second derivative of that equation. Therefore, by calculating the second derivative of the polynomial equation, the zero closest to the standard characteristic peak is determined, and the discharge capacity corresponding to this zero is taken as the characteristic peak of the secondary battery under test.

[0078] In other implementations, determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation may include: determining the first derivative of the polynomial equation; and taking the discharge capacity corresponding to the peak closest to the standard characteristic peak in the first derivative as the discharge capacity corresponding to the inflection point.

[0079] In this embodiment, according to mathematical relationships, the inflection point of an equation corresponds to the peak in the first derivative of that equation. Therefore, by calculating the first derivative of the polynomial equation, the peak closest to the standard characteristic peak is determined, and the discharge capacity corresponding to this peak is taken as the characteristic peak of the secondary battery under test.

[0080] The two methods described above for determining the inflection point closest to the standard characteristic peak in a polynomial equation are merely examples provided in this application. This application does not limit the specific method for determining the inflection point closest to the standard characteristic peak in a polynomial equation. Alternatively, the inflection point of the polynomial equation can be determined by directly analyzing the image of the polynomial equation, and then the discharge capacity corresponding to the inflection point can be used as the characteristic peak of the secondary battery under test.

[0081] Step 104: Determine the aging state of the secondary battery under test based on the characteristic peak position of the secondary battery under test.

[0082] In this embodiment, analysis of the operating characteristics of the secondary battery reveals that the more severe the aging of the secondary battery, the lower its discharge capacity and the shallower its depth of discharge during the phase transition of the active materials in the cathode and anode. In the differential discharge curve, the peak corresponding to the characteristic peak of the secondary battery is farther from the peak corresponding to the standard characteristic peak. Therefore, the aging state of the secondary battery can be determined by analyzing the relationship between its characteristic peak and the standard characteristic peak.

[0083] In some embodiments, step 104 includes: determining a first discharge depth based on a characteristic peak position; determining an offset based on the first discharge depth and a standard discharge depth; wherein the standard discharge depth is the discharge depth determined based on a standard characteristic peak position of a secondary battery of the same type as the secondary battery under test without aging; and determining the aging status of the secondary battery under test based on the offset.

[0084] In this embodiment, the characteristic peak position represents a discharge capacity, and the discharge depth is the ratio of the discharge capacity to the total discharge capacity. This is expressed by the formula: DOD1 = Q1 / Q max The first discharge depth can be determined. Here, DOD1 is the first discharge depth, Q1 is the characteristic peak position, and Q... max This represents the total discharge capacity.

[0085] The standard depth of discharge can be determined by the formula: DOD0 = Q0 / Q max Determined. Where DOD0 is the standard depth of discharge, Q0 is the standard characteristic peak position, and Q... max This represents the total discharge capacity.

[0086] The offset is the difference between the first discharge depth and the standard discharge depth, which can be determined by the formula: ΔDOD = DOD1 - DOD0.

[0087] In some embodiments, the aging condition of the secondary battery under test can be represented by an offset. The larger the offset, the worse the aging condition of the secondary battery under test; conversely, the smaller the offset, the milder the aging condition of the secondary battery under test.

[0088] In other embodiments, the loss of active material in the secondary battery under test is determined based on the offset and loss coefficient. The greater the loss of active material, the worse the aging condition of the secondary battery under test.

[0089] In this embodiment, the loss of active material in the secondary battery under test can be calculated using the following formula:

[0090] Loss = ratio * ΔDOD

[0091] Where Loss represents the loss of active material, ΔDOD represents the offset, and ratio represents the loss coefficient. The loss coefficient is determined based on the composition of the secondary battery under test.

[0092] Based on the same inventive concept, this application also provides a secondary battery management system. Please refer to [link / reference]. Figure 4 , Figure 4 This application provides a structural block diagram of a secondary battery management system 200, which may include:

[0093] The acquisition module 201 is used to acquire the second-order differential curve of the secondary battery under test; wherein, the second-order differential curve represents the relationship between the second-order differential of the secondary battery under test and the discharge capacity of the secondary battery under test during actual operation, and the second-order differential of the secondary battery under test is the second-order differential of the discharge voltage of the secondary battery under test with respect to the discharge capacity of the secondary battery under test.

[0094] Processing module 202 is used to perform polynomial fitting on the second-order differential curve to obtain a polynomial equation; determine the characteristic peak position of the secondary battery under test based on the polynomial equation and the standard characteristic peak position; wherein, the standard characteristic peak position is the characteristic peak position corresponding to a secondary battery of the same type as the secondary battery under test in the unaged condition; and determine the aging state of the secondary battery under test based on the characteristic peak position of the secondary battery under test.

[0095] In an optional implementation, the processing module 202 is specifically used to filter the second-order differential curve to obtain a filtered second-order differential curve; and to perform polynomial fitting on the filtered second-order differential curve to obtain the polynomial equation.

[0096] In an optional implementation, the processing module 202 is specifically used to filter the second-order differential curve through a filter to obtain a first curve; determine whether the number of peaks of the first curve in a preset interval is greater than a first threshold; if it is greater, adjust the parameters of the filter, and filter the second-order differential curve through the adjusted filter to obtain a second curve; wherein, the second curve is the filtered second-order differential curve.

[0097] In an optional implementation, the processing module 202 is specifically used to determine whether the number of peaks in the curve obtained by filtering the second-order differential curve with the adjusted filter in the preset interval is greater than a first threshold; if it is greater, the parameters of the filter are adjusted until the number of peaks in the curve obtained by filtering the second-order differential curve with the adjusted filter in the preset interval is less than or equal to the first threshold; the second curve is obtained by filtering the second-order differential curve with the adjusted filter.

[0098] In an optional implementation, the processing module 202 is specifically used to determine the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation; wherein the discharge capacity corresponding to the inflection point is the characteristic peak of the secondary battery under test.

[0099] In an optional implementation, the processing module 202 is specifically used to determine the second derivative of the polynomial equation; and to take the discharge capacity corresponding to the zero point of the second derivative that is closest to the standard characteristic peak as the discharge capacity corresponding to the inflection point.

[0100] In an optional implementation, the processing module 202 is specifically used to determine the first derivative of the polynomial equation; and to take the discharge capacity corresponding to the peak closest to the standard characteristic peak in the first derivative as the discharge capacity corresponding to the inflection point.

[0101] In an optional implementation, the processing module 202 is specifically used to determine a first discharge depth based on the characteristic peak position; determine an offset based on the first discharge depth and a standard discharge depth; wherein the standard discharge depth is the discharge depth determined based on the standard characteristic peak position of a secondary battery of the same type as the secondary battery under test without aging; and determine the aging state of the secondary battery under test based on the offset.

[0102] This application also provides an electronic device in its embodiments. Please refer to [link / reference]. Figure 5 , Figure 5 This is a structural block diagram of an electronic device provided in an embodiment of this application. The electronic device 300 includes: at least one processor 301, at least one communication interface 302, at least one memory 303, and at least one bus 304. The bus 304 is used for direct communication between these components, the communication interface 302 is used for signaling or data communication with other node devices, and the memory 303 stores machine-readable instructions executable by the processor 301. When the electronic device 300 is running, the processor 301 communicates with the memory 303 via the bus 304. When the machine-readable instructions are invoked by the processor 301, the secondary battery aging detection method described above is executed.

[0103] Processor 301 can be an integrated circuit chip with signal processing capabilities. The processor 301 can be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor.

[0104] The memory 303 may include, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.

[0105] Understandable. Figure 5 The structure shown is for illustrative purposes only; the electronic device 300 may also include components that are more advanced than those shown. Figure 5 The more or fewer components shown, or having the same Figure 5 The different configurations shown. Figure 5 The components shown can be implemented using hardware, software, or a combination thereof.

[0106] Furthermore, this application also provides a computer-readable storage medium storing a computer program, which, when run by a computer, executes the secondary battery aging detection method as described in the above embodiments.

[0107] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0108] Furthermore, 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 this embodiment according to actual needs.

[0109] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0110] It should be noted that if the function is implemented as a software module 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 this application, in essence, or the part that contributes to the prior art, or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0111] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0112] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for detecting the aging of secondary batteries, characterized in that, include: Obtain the second-order differential curve of the secondary battery under test; wherein, the second-order differential curve characterizes the relationship between the second-order differential of the secondary battery under test and the discharge capacity of the secondary battery under test during actual operation, and the second-order differential of the secondary battery under test is the second-order differential of the discharge voltage of the secondary battery under test with respect to the discharge capacity of the secondary battery under test. Polynomial fitting is performed on the second-order differential curve to obtain the polynomial equation; The characteristic peak position of the secondary battery under test is determined according to the polynomial equation and the standard characteristic peak position; wherein, the standard characteristic peak position is the characteristic peak position corresponding to a secondary battery of the same type as the secondary battery under test under the condition of no aging; The aging state of the secondary battery under test is determined based on the characteristic peak position of the secondary battery under test.

2. The secondary battery aging detection method according to claim 1, characterized in that, The process of performing polynomial fitting on the second-order differential curve to obtain a polynomial equation includes: The second-order differential curve is filtered to obtain a filtered second-order differential curve; The filtered second-order differential curve is fitted with a polynomial to obtain the polynomial equation.

3. The secondary battery aging detection method according to claim 2, characterized in that, The filtering of the second-order differential curve includes: The second-order differential curve is filtered by a filter to obtain the first curve; Determine whether the number of peaks in the first curve within a preset interval is greater than a first threshold. If the value is greater than the value, the parameters of the filter are adjusted, and the second-order differential curve is filtered by the adjusted filter to obtain a second curve; wherein, the second curve is the filtered second-order differential curve.

4. The secondary battery aging detection method according to claim 3, characterized in that, The process of adjusting the parameters of the filter and filtering the second-order differential curve using the adjusted filter to obtain a second curve includes: Determine whether the number of peaks in the preset interval of the second-order differential curve after the adjusted filter is applied to the second-order differential curve is greater than a first threshold. If the value is greater than the first threshold, adjust the parameters of the filter until the number of peaks in the second-order differential curve obtained by filtering the second-order differential curve through the adjusted filter is less than or equal to the first threshold in the preset interval. The second curve is obtained by filtering the second-order differential curve using an adjusted filter.

5. The method for detecting the aging of secondary batteries according to any one of claims 1-4, characterized in that, Determining the characteristic peak position of the secondary battery under test based on the polynomial equation and the standard characteristic peak position includes: Determine the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation; wherein the discharge capacity corresponding to the inflection point is the characteristic peak of the secondary battery under test.

6. The secondary battery aging detection method according to claim 5, characterized in that, Determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation includes: Determine the second derivative of the polynomial equation; The discharge capacity corresponding to the zero point of the second derivative closest to the standard characteristic peak is taken as the discharge capacity corresponding to the inflection point.

7. The secondary battery aging detection method according to claim 5, characterized in that, Determining the discharge capacity corresponding to the inflection point closest to the standard characteristic peak in the polynomial equation includes: Determine the first derivative of the polynomial equation; The discharge capacity corresponding to the peak closest to the standard characteristic peak in the first derivative is taken as the discharge capacity corresponding to the inflection point.

8. The secondary battery aging detection method according to claim 1, characterized in that, The step of determining the aging state of the secondary battery under test based on the characteristic peak position of the secondary battery under test includes: The first discharge depth is determined based on the characteristic peak position; The offset is determined based on the first discharge depth and the standard discharge depth; wherein, the standard discharge depth is the discharge depth determined based on the standard characteristic peak position of a secondary battery of the same type as the secondary battery under test, without aging. The aging state of the secondary battery under test is determined based on the offset.

9. A secondary battery management system, characterized in that, The secondary battery management system includes: The acquisition module is used to acquire the second-order differential curve of the secondary battery under test; wherein, the second-order differential curve represents the relationship between the second-order differential of the secondary battery under test and the discharge capacity of the secondary battery under test during actual operation, and the second-order differential of the secondary battery under test is the second-order differential of the discharge voltage of the secondary battery under test with respect to the discharge capacity of the secondary battery under test. The processing module is used to perform polynomial fitting on the second-order differential curve to obtain a polynomial equation; determine the characteristic peak position of the secondary battery under test based on the polynomial equation and the standard characteristic peak position; wherein, the standard characteristic peak position is the characteristic peak position corresponding to a secondary battery of the same type as the secondary battery under test in the unaged state; and determine the aging state of the secondary battery under test based on the characteristic peak position of the secondary battery under test.

10. An electronic device, characterized in that, include: A memory and a processor, wherein the memory stores computer program instructions, which are read and executed by the processor to perform the method as described in any one of claims 1-8.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer program instructions, which, when read and executed by a computer, perform the method as described in any one of claims 1-8.

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