Battery retirement criteria and capacity drop-off definition method

Abstract

The application provides a battery retirement standard and capacity diving degree definition method, obtains a capacity degradation curve of a battery, calculates a tangent slope of a point on the degradation curve in a set SOH range, wherein the upper limit of the set SOH range is X%SOH, and the lower limit of the set SOH range is Y%SOH; when the tangent slope of a point on the capacity degradation curve is greater than a set slope threshold, the point is taken as a life end point, if the efficiency of each point on the capacity degradation curve is less than or equal to the set slope threshold, the degradation point corresponding to Y%SOH is taken as the life end point, and the tangent value of the capacity diving angle is taken as the capacity diving degree, so that safe, efficient and accurate use and aging evaluation of the battery are realized.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a battery retirement standard and a method for defining capacity drop-off. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Lithium-ion batteries are a primary tool for addressing energy conservation and emission reduction policies and are widely used in electric vehicles and energy storage systems. A key obstacle to the development of the battery industry is the safety and non-linearity of battery degradation. Therefore, it is necessary to accurately identify the point at which batteries should be retired and assess their aging status to ensure the safe, efficient, and reliable operation of battery systems. This allows users to determine whether batteries should be replaced, avoiding unexpected capacity loss or even accidents. Furthermore, a proper assessment enables manufacturers to decide whether to recycle batteries as scrap metal or reuse them in other applications.

[0004] The capacity decay of lithium-ion batteries exhibits strong nonlinearity and uncertainty. After prolonged charge-discharge cycles or storage, batteries typically show a trend towards faster capacity decay. Traditional "one-size-fits-all" methods for identifying the end of battery life, using 80% State of Health (SOH) as the standard, fail to consider the battery degradation rate, resulting in significant limitations. This method not only fails to fully utilize healthy batteries but also struggles to effectively guarantee the safety of unhealthy batteries. When a battery has a high SOH but a large degradation rate, retiring it at 80% SOH compromises its safety; conversely, when a battery has a low SOH but a small degradation rate, its utilization value is high, and retiring it at 80% SOH results in low capacity utilization. Furthermore, traditional SOH-based battery assessment also has drawbacks; batteries with equal SOH may have different aging characteristics and degradation rates, making it impossible to reasonably evaluate battery aging. Therefore, how to reasonably and individually identify battery retirement points and accurately evaluate battery aging based on new indicators has become a crucial means to overcome key technological bottlenecks in power battery health management and the rapid development of related industries.

[0005] Many scholars have conducted extensive research on battery retirement point identification and capacity "plummeting," but currently, 80% SOH is generally used as the battery life endpoint, i.e., the retirement point; at the same time, there is still a lack of accurate evaluation methods for battery aging and degradation. For example, Chinese invention patent CN111175653A uses constant power charging and discharging of batteries to obtain the relationship between median voltage and cycle number and calculates the slope to identify the "plummeting" point and evaluate battery aging. However, the median voltage is not easy to measure and is greatly affected by capacity and external environment. Chinese invention patent CN112327194B uses 80% SOH as the battery life endpoint, determines the degradation characteristic angle based on the curvature of the degradation curve, and compares it with the angle threshold to determine whether a "plummeting" has occurred, further evaluating the degree of battery degradation and aging state. Chinese invention patent CN112327167B discloses a method for capacity "plummeting" and battery safety assessment. Based on the slope value of the capacity retention rate, the ratio of the slope value to the slope benchmark value is calculated. Based on the ratio and the corresponding threshold range, it is determined whether the battery has experienced a "plummeting" and the battery aging state and safety risk level are given. However, the selection of the threshold range in this method has a certain degree of subjectivity. Chinese invention patent CN113777495A calculates the real-time feature area enclosed by the actual battery degradation curve and the linear reference curve. This area is compared with a multi-level capacity "dip" threshold to assess the battery's risk level and degradation status. Chinese invention patent CN113777494A discloses a method for identifying "dip points" and evaluating battery aging based on geometric features. It calculates the deviation between the capacity degradation point and the aging reference point, compares the maximum deviation with a threshold, determines whether the battery has experienced a "dip," and evaluates the degree of battery aging based on the drop point and the degree of deviation.

[0006] In summary, the inventors found that the traditional standard of 80% SOH for battery life retirement has significant limitations. It not only fails to make full use of healthy batteries, but also makes it difficult to effectively ensure the safety of unhealthy batteries. Traditional methods of evaluating the degree of battery degradation and aging status based on single SOH, capacity angle, or slope cannot accurately reflect the differences in battery aging. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a battery retirement standard and a method for defining capacity drop, establishing personalized battery retirement standards and defining capacity drop, thereby achieving safe, efficient, and accurate battery use and aging evaluation.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] The first aspect of this invention provides a standard method for battery retirement.

[0010] A standard method for battery retirement includes the following processes:

[0011] Obtain the battery capacity degradation curve and calculate the tangent slope at the point on the degradation curve within the set SOH range, where the upper limit of the set SOH range is X%SOH and the lower limit of the set SOH range is Y%SOH.

[0012] When the slope of the tangent line at a certain point on the capacity decay curve is greater than the set slope threshold, this point is taken as the end of the lifetime. If the efficiency at each point on the capacity decay curve is less than or equal to the set slope threshold, the decay point corresponding to Y%SOH is taken as the end of the lifetime.

[0013] As a further limitation of the first aspect of the present invention, X%SOH is 80%SOH and Y%SOH is 60%SOH.

[0014] As a further limitation of the first aspect of the invention, the battery degradation curve is a curve of SOH relative to the number of cycles.

[0015] A second aspect of the present invention provides a battery retirement standard system.

[0016] A battery retirement standard system, comprising:

[0017] The tangent slope calculation module is configured to: acquire the battery degradation curve and calculate the tangent slope at a point on the degradation curve within a set SOH range, wherein the upper limit of the set SOH range is X%SOH and the lower limit of the set SOH range is Y%SOH.

[0018] The lifespan end determination module is configured to: when the slope of the tangent line at a certain point on the decay curve is greater than a set slope threshold, this point is taken as the lifespan end point; if the efficiency at each point on the decay curve is less than or equal to the set slope threshold, the decay point corresponding to Y%SOH is taken as the lifespan end point.

[0019] A third aspect of the present invention provides a method for defining capacity drop degree.

[0020] A method for defining capacity divergence includes the following steps:

[0021] Any point K on the connection capacity decay curve i Together with the end point of life B, form line segment K. i B, wherein the end of life is obtained based on the battery retirement standard method described in the first aspect of the present invention;

[0022] K i Projecting a point onto the X-axis of the coordinate system yields the projection point M. i Connect K i M i This forms a capacity diving triangle ΔK i BM i , will ∠K i BM iDefined as the capacity dive angle, with the tangent of the capacity dive angle as the capacity dive degree, where the X-axis of the coordinate system represents the number of cycles, and the Y-axis of the coordinate system represents SOH.

[0023] In this invention, battery aging can be assessed based on the capacity drop.

[0024] As a further limitation of the third aspect of the present invention, the greater the capacity drop, the stronger the nonlinearity of the battery, the greater the convexity of the capacity degradation curve, the faster the battery ages, the worse the battery safety in the later stage of use, and the higher the capacity utilization rate.

[0025] As a further limitation of the third aspect of the present invention, the line connecting the capacity decay start point A and the lifetime end point B is used as the baseline for calculating the capacity drop.

[0026] A fourth aspect of the present invention provides a capacity divergence definition system.

[0027] A capacity divergence definition system, comprising:

[0028] The decay curve connection module is configured to connect any point K on the capacity decay curve. i Together with the end point of life B, form line segment K. i B, wherein the end of life is obtained based on the battery retirement standard method described in the first aspect of the present invention;

[0029] The diving degree calculation module is configured to: calculate K i Projecting a point onto the X-axis of the coordinate system yields the projection point M. i Connect K i M i This forms a capacity diving triangle ΔK i BM i , will ∠K i BM i Defined as the capacity dive angle, with the tangent of the capacity dive angle as the capacity dive degree, where the X-axis of the coordinate system represents the number of cycles, and the Y-axis of the coordinate system represents SOH.

[0030] The present invention may also include a battery aging assessment module, which is configured to assess battery aging based on capacity drop.

[0031] The fifth aspect of the present invention provides a computer-readable storage medium having a program stored thereon, characterized in that, when executed by a processor, the program implements the steps in the battery retirement standard method as described in the first aspect of the present invention; or, when executed by a processor, the program implements the steps in the capacity drop-off definition method as described in the third aspect of the present invention.

[0032] The sixth aspect of the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the battery retirement standard method as described in the first aspect of the present invention; or, the processor executes the program to implement the steps in the capacity drop-off definition method as described in the third aspect of the present invention.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. Based on the capacity decay curve and capacity decay slope, this invention proposes a novel method for defining battery retirement standards. It abandons the traditional "one-size-fits-all" definition that uses 80% SOH as the retirement point, and can more accurately and reasonably identify the battery retirement time, further improving battery utilization and ensuring battery safety.

[0035] 2. Based on the retirement point and capacity degradation curve, this invention proposes a new index for evaluating battery aging, namely TDR (Total Drop Rate). TDR can more accurately and effectively assess the aging status and aging differences of batteries. The calculation results are stable, robust, and not easily affected by external environmental interference, providing guidance for the assessment of the remaining value of batteries at the time of retirement and their tiered utilization.

[0036] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0037] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0038] Figure 1 This is a schematic diagram of the process for identifying the retirement point of a lithium-ion battery according to Embodiment 1 of the present invention;

[0039] Figure 2 This is a schematic diagram of the SOH curve of 124 batteries as a function of the number of cycles provided in Embodiment 1 of the present invention;

[0040] Figure 3 This is a schematic diagram of the slope of 124 batteries as a function of the number of cycles (up to 80% SOH) provided in Embodiment 1 of the present invention.

[0041] Figure 4 This is a schematic diagram of the slope of 124 batteries as a function of the number of cycles (up to 60% SOH) provided in Embodiment 1 of the present invention.

[0042] Figure 5This is a schematic diagram showing the maximum slope distribution of 124 batteries at 80% SOH, as provided in Embodiment 1 of the present invention.

[0043] Figure 6 This is a schematic diagram showing the maximum slope distribution of 124 batteries at 60% SOH, as provided in Embodiment 1 of the present invention.

[0044] Figure 7 This is a schematic diagram of the battery degradation curve and lifespan endpoint based on a slope threshold, provided in Embodiment 1 of the present invention.

[0045] Figure 8 This is a schematic diagram of a representative battery life degradation curve and a standardized life end point provided in Embodiment 1 of the present invention;

[0046] Figure 9 This is a schematic diagram illustrating the proportion of battery life extension or reduction provided in Embodiment 1 of the present invention;

[0047] Figure 10 This is a flowchart of the lithium-ion battery retirement point identification, TDR definition and aging evaluation process provided in Embodiment 3 of the present invention.

[0048] Figure 11 A schematic diagram of different battery degradation curves with the same initial capacity and lifespan provided in Embodiment 3 of the present invention;

[0049] Figure 12 A schematic diagram of different battery degradation curves with the same initial capacity and lifespan provided in Embodiment 3 of the present invention;

[0050] Figure 13 This is a schematic diagram illustrating the changing trends of different battery degradation rates provided in Embodiment 3 of the present invention;

[0051] Figure 14 This is a schematic diagram illustrating the trend of TDR (Total Displacement Rate) of 124 batteries provided in Embodiment 3 of the present invention. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0054] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0055] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0056] Example 1:

[0057] like Figure 1 As shown, Embodiment 1 of the present invention provides a standard method for battery retirement, which can be used to determine battery retirement. It comprehensively considers the battery's state of equilibrium (SOH) and degradation rate, and calculates the slope k of the tangent line at each point on the degradation curve. i Find a suitable slope threshold, and define the battery life endpoint B, i.e. the retirement point, based on this slope threshold and standardize it.

[0058] Specifically, this invention uses publicly available experimental data to verify the feasibility and effectiveness of the proposed method. Lithium iron phosphate (LFP) batteries were cycled in a temperature-controlled chamber. The rated capacity of the batteries was 1.1 Ah, and the nominal voltage was 3.3 V. The dataset contained 124 batteries. The state of harmonics (SOH) of all batteries as a function of the number of charge-discharge cycles is shown in the figure below. Figure 2 As shown, Figure 2 The red line in the image represents the traditional end of battery life as defined by 80% SOH. Figure 2 It is evident that traditional methods only consider State of Health (SOH) and do not take into account the slope of the degradation curve. When a battery has a high SOH but a large degradation slope, retiring it at 80% SOH would compromise battery safety; conversely, when a battery has a low SOH but a small degradation slope, retiring it at 80% SOH would result in the battery not being fully utilized.

[0059] To solve this problem, the slope of the tangent line at each point on the battery degradation curve between SOH = 80% and SOH = 60% was calculated, and the results are as follows. Figure 3 and Figure 4 As shown. By Figure 3 and Figure 4 It can be seen that the longer the battery life, the smaller the change in slope, and the smaller the maximum value of the slope. Furthermore, the distribution of the maximum slope value was calculated at 80% SOH and 60% SOH, respectively. Figure 5 and Figure 6 As shown.

[0060] Depend on Figure 3 , Figure 4 , Figure 5 and Figure 6 It is known that when the traditional definition of battery retirement point as 80% SOH is used, the maximum slope of most batteries is less than 1.6 (mAh / cycle), while a small number of batteries have a maximum slope greater than 2 (mAh / cycle). When SOH = 60%, the maximum slope of over 90% of batteries exceeds 1.6 (mAh / cycle), and for most batteries, the slope increase from 80% SOH to 60% SOH is relatively small, less than 50%. This indicates that the degradation of most batteries is relatively slow, while a small number of batteries degrade more rapidly. These faster-degrading batteries experience a larger decrease in SOH within a shorter number of cycles. If retired according to a uniform 80% standard, batteries with low degradation rates cannot be fully utilized, while the safety of batteries with high degradation rates cannot be guaranteed.

[0061] Therefore, 1.6 (mAh / cycle) is chosen as the slope threshold, and this slope threshold and SOH are used together as the battery life termination standard (understandably, the slope threshold can vary depending on the statistical data of different batches of batteries); if the slope is greater than this threshold, the degradation point corresponding to this threshold is the end of the life; if the slope has not reached this threshold by 60% SOH, the degradation point corresponding to 60% SOH is taken as the end of the life. A degradation curve is plotted, as shown below. Figure 6 As shown. Figure 6 The green marker represents the standardized end of service life, the red line is the traditional end of service life defined by SOH=80%, and the pink line is the end of service life defined by SOH=70%.

[0062] Understandably, the 80% SOH here is the current industry standard setting, while the 60% SOH is a setting based on statistical results for each batch of batteries. Those skilled in the art can set it according to the above statistical method, or change the 80% SOH here when the industry standard changes after the development of battery technology. This will not be elaborated here.

[0063] Depend on Figure 7 As can be seen, the proposed method no longer uses 80% SOH as the retirement point, but instead defines the retirement point individually based on the battery's aging characteristics and degradation trajectory. For batteries with a rapid and significant lifespan degradation, even with a high SOH, early retirement is necessary to ensure battery safety. Conversely, for batteries with a slower lifespan degradation rate and a longer cycle life, the later degradation is approximately linear. Even with a low SOH, the slow degradation rate allows for continued use for a period before retirement, improving battery capacity utilization. Therefore, the proposed standardized lifespan end identification method overcomes the bottleneck of traditionally using 80% SOH as the lifespan end point, enabling more rational battery utilization and ensuring battery safety.

[0064] according to Figure 7 Three batteries were selected for analysis, such as Figure 8 As shown. By Figure 8 It can be seen that the three batteries exhibit different degradation trends and rates. Battery 1 degrades rapidly with a high rate, followed by Battery 2, while Battery 3 degrades relatively slowly with low non-linearity. Battery 1 has a high State of Health (SOH) but a large degradation rate. If 80% SOH is used as the retirement standard, the battery may age rapidly in a short period, compromising safety. Therefore, it needs to be retired earlier, with the retirement point indicated by the green pentagram in the figure. Battery 3 has a relatively smaller slope at 80% SOH. If 80% SOH is used as the retirement standard, the capacity utilization rate is low. It can continue to be used until around 66% SOH to further improve the battery's capacity utilization rate. Battery 2's retirement point, defined by its slope, is close to the retirement point defined by 80% SOH, thus simultaneously satisfying both safety and capacity utilization.

[0065] Depend on Figure 7 , Figure 8 It can be seen that the life end point standardized according to the slope threshold will shorten or lengthen the battery capacity degradation curve, that is, the number of cycles corresponding to the new life end point may be earlier or later. Figure 9 The percentage increase or decrease in lifespan is given. Figure 9 It can be seen that the proposed method can extend the life of most batteries by about 10%; shorten the life of a small number of batteries by less than 12%, reaching the retirement point earlier; extend the life of individual batteries by 20%; and extend or shorten the life of a very few batteries by 30%-40%, ensuring the reasonable and safe use of batteries.

[0066] Example 2:

[0067] Embodiment 2 of the present invention provides a battery retirement standard system, which can be used for battery retirement determination, including:

[0068] The tangent slope calculation module is configured to: acquire the battery degradation curve and calculate the tangent slope at a point on the degradation curve within a set SOH range, wherein the upper limit of the set SOH range is X%SOH and the lower limit of the set SOH range is Y%SOH.

[0069] The lifespan end determination module is configured to: when the slope of the tangent line at a certain point on the decay curve is greater than a set slope threshold, this point is taken as the lifespan end point; if the efficiency at each point on the decay curve is less than or equal to the set slope threshold, the decay point corresponding to Y%SOH is taken as the lifespan end point.

[0070] The detailed features of each module of the system are the same as those of the battery retirement standard method provided in Example 1, and will not be repeated here.

[0071] Example 3:

[0072] like Figure 10As shown, Embodiment 3 of the present invention provides a method for defining capacity degradation, which can be used for battery aging assessment. The method for defining capacity degradation is as follows: Connect the starting point A and the ending point B of capacity degradation to form a linear aging baseline AB, and connect each point K on the capacity degradation curve. i Together with the end point of life B, form line segment K. i B, and K i Projecting the point onto the x-axis yields the projection point M. i Connect K i M i This forms a capacity diving triangle ΔK i BM i . ∠K i BM i Defined as the capacity diving angle β, the tangent of the capacity diving angle β is defined as the terminal diving rate (TDR), as shown in Equation (1). TDR reflects the degree of capacity degradation of the battery during a unit cycle, and also reflects the battery capacity diving mechanism and characteristics to a certain extent. The larger the TDR, the faster the battery capacity degradation and aging rate, and the stronger the nonlinearity.

[0073]

[0074] In the formula, TDR is the capacity dive angle, and β is the capacity dive angle.

[0075] Specifically, it includes the following steps:

[0076] S1: Perform three capacity tests on the lithium-ion battery, and use the average value of the three capacity tests as the rated capacity of the battery.

[0077] S2: Conduct cyclic charge-discharge experiments on the battery to obtain data such as battery capacity, number of cycles, current, voltage, and temperature for each charge-discharge cycle, and preprocess the data.

[0078] S3: When the usable capacity of the battery is lower than 60% of the rated capacity, stop the cyclic charge-discharge experiment and record the number of cycles at this time;

[0079] S4: Analyze the data, plot the capacity decay curve as a function of the number of cycles, and perform smoothing and noise reduction.

[0080] S5: Calculate the slope of the tangent line corresponding to each point on the capacity decay curve, and calculate the distribution of the maximum slope.

[0081] S6: Obtain the slope threshold based on the distribution, and standardize and identify the end-of-life (EOL) of the battery by using the relationship between the slope threshold and the capacity.

[0082] S7: Based on the newly defined end of life and the beginning of degradation, calculate the battery capacity drop rate (TDR) using equation (1), and accurately evaluate battery aging based on the TDR obtained in S1.

[0083] Taking batteries 41 and 42 in the dataset as examples, the two batteries have roughly the same initial capacity and the same end-of-life. The state of equilibrium (SOH) and cycle count are normalized to the range [0, 1]. Figure 11 As shown.

[0084] Depend on Figure 11 It is known that batteries with the same initial capacity and end of life may exhibit different capacity degradation trends. The traditional method of evaluating batteries using SOH has certain limitations. It cannot assess their aging differences, nor can it assess their remaining value when the batteries are retired, thus making it impossible to carry out reasonable tiered utilization.

[0085] To address this issue, a linear aging baseline AB is formed by connecting the capacity degradation start point A and the end point B, as shown below. Figure 9 As shown by the dashed line, and based on each point C on AB. i Calculate the tangent of ∠CBx; connect the actual capacity decay point K. i And the destination B, simultaneously passing through K i Draw a perpendicular line from the point to the x-axis to obtain the perpendicular segment K. i M i ,like Figure 12 As shown, the capacity degradation points of the two batteries are respectively and The perpendicular segments are respectively and The resulting capacity diving triangles are respectively and Get the capacity diving angle and From equation (1), we can see that the diving degrees are as follows:

[0086]

[0087]

[0088] Based on equations (2) and (3), plot the curve of TDR (Takedown Degree) as a function of the number of cycles, as shown below. Figure 13 As shown, Figure 13 The dashed line in the figure represents the drop in the linear aging reference line. Figure 13 It is known that for batteries with the same initial capacity and lifespan, the TDR (Total Displacement Ratio) may change differently with the number of cycles. The larger the TDR, the stronger the nonlinearity of the battery, that is, the greater the convexity of the capacity degradation curve, the worse the battery's safety in the later stages of use, but the relatively higher the capacity utilization rate.

[0089] Meanwhile, for the same battery, as the number of cycles increases, the TDR gradually increases, and the slope of the curve reaches its maximum at a certain point. At this point, the battery's rate of degradation changes the fastest, indicating that the battery has reached its lifespan inflection point and entered the final stage of degradation. After the inflection point, battery safety deteriorates, capacity degradation further intensifies, and the linearity of capacity degradation increases with the number of uses, reaching its strongest near the lifespan termination point B, at which point the TDR is at its maximum and tends to stabilize.

[0090] Furthermore, according to equations (2), (3), and Figure 13 Plot the water drop rate variation curves of 124 batteries, as shown below. Figure 14 As shown. By Figure 14 It can be seen that the more cycles a battery has, the longer its lifespan, the lower its degradation curve, and the slower its capacity degradation rate. However, the degradation rate will be greater in the later stages, and the capacity utilization rate will be higher.

[0091] Comprehensive analysis Figure 7 , Figure 12 and Figure 14 It can be seen that the drop angle β and the TDR (Total Drop Rate) of the battery also reflect the overall trend of battery degradation to some extent. The larger the drop angle β, the greater the drop in battery capacity, that is, the larger the TDR, the more capacity decays the battery during a unit cycle. The faster the battery ages, the stronger the non-linearity, and the worse the safety, but the higher the battery capacity utilization rate. At the same time, the point where the drop rate changes the fastest also corresponds to the capacity inflection point to some extent, indicating that the capacity decay rate and drop rate are the largest at this moment. After this, the battery enters the drop period, with the capacity decreasing rapidly and the safety deteriorating.

[0092] Example 4:

[0093] Embodiment 4 of the present invention provides a capacity divergence definition system, comprising:

[0094] The decay curve connection module is configured to connect any point K on the capacity decay curve. i Together with the end point of life B, form line segment K. i B, wherein the end of life is obtained based on the battery retirement standard method described in the first aspect of the present invention;

[0095] The diving degree calculation module is configured to: calculate K i Projecting a point onto the X-axis of the coordinate system yields the projection point M. i Connect K i M i This forms a capacity diving triangle ΔK i BM i , will ∠K i BM iDefined as the capacity dive angle, with the tangent of the capacity dive angle as the capacity dive degree, where the X-axis of the coordinate system represents the number of cycles, and the Y-axis of the coordinate system represents SOH.

[0096] In this embodiment, optionally, a battery aging assessment module may also be included, configured to assess battery aging based on capacity drop.

[0097] The detailed features of each module of the system are the same as the capacity drop degree definition method provided in Embodiment 3, and will not be repeated here.

[0098] Example 5:

[0099] Embodiment 5 of the present invention provides a computer-readable storage medium having a program stored thereon, characterized in that, when the program is executed by a processor, it implements the steps in the battery retirement standard method as described in Embodiment 1 of the present invention; or, when the program is executed by a processor, it implements the steps in the capacity drop-off degree definition method as described in Embodiment 3 of the present invention.

[0100] Example 6:

[0101] Embodiment 6 of the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the battery retirement standard method as described in Embodiment 1 of the present invention; or, when the processor executes the program, it implements the steps in the capacity drop-off degree definition method as described in Embodiment 3 of the present invention.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A standard method for battery retirement, characterized in that, Includes the following processes: Obtain the battery capacity degradation curve and calculate the tangent slope at the point on the degradation curve within the set SOH range, where the upper limit of the set SOH range is X%SOH and the lower limit of the set SOH range is Y%SOH. When the slope of the tangent line at a certain point on the capacity degradation curve is greater than the set slope threshold, this point is taken as the end of the lifespan. If the slope of the tangent line at each point on the capacity degradation curve is less than or equal to the set slope threshold, the degradation point corresponding to Y%SOH is taken as the end of the lifespan. The slope threshold is determined based on the statistical data of different batches of batteries. X%SOH is 80%SOH, Y%SOH is 60%SOH; calculate the distribution of the maximum slope under 80%SOH and 60%SOH, and obtain the slope threshold based on the distribution.

2. The battery retirement standard method as described in claim 1, characterized in that, The battery degradation curve is a curve of SOH relative to the number of cycles.

3. A battery retirement standard system, employing a battery retirement standard method as described in any one of claims 1-2, characterized in that, include: The tangent slope calculation module is configured to: acquire the battery degradation curve and calculate the tangent slope at a point on the degradation curve within a set SOH range, wherein the upper limit of the set SOH range is X%SOH and the lower limit of the set SOH range is Y%SOH. The lifespan end determination module is configured to: when the slope of the tangent line at a certain point on the decay curve is greater than the set slope threshold, this point is taken as the lifespan end; if the slope of the tangent line at each point on the decay curve is less than or equal to the set slope threshold, the decay point corresponding to Y%SOH is taken as the lifespan end.

4. A method for defining capacity divergence, characterized in that, Includes the following processes: Any point K on the connection capacity decay curve i Together with the end point of life B, form line segment K. i B, wherein the end of life is obtained based on the battery retirement standard method according to any one of claims 1-2; K i Point projection onto coordinate system X Projection point M of axis i Connect K i M i This forms a capacity diving triangle ΔK i BM i , will ∠K i BM i Defined as the capacity dive angle, with the tangent of the capacity dive angle as the capacity dive degree, where the coordinate system... X The number of cycles along the axis, with the Y-axis of the coordinate system defined as SOH; The capacity drop index reflects the degree of capacity degradation of a battery during a unit cycle, reflecting the mechanism and characteristics of battery capacity drop. The larger the capacity drop index, the faster the battery capacity degradation and aging, and the stronger the non-linearity. The greater the capacity drop, the stronger the non-linearity of the battery, the greater the convexity of the capacity degradation curve, the faster the battery ages, the worse the battery safety in the later stages of use, and the higher the capacity utilization rate. The line connecting the starting point of capacity decay A and the end point of life B is used as the baseline for calculating the capacity drop.

5. A capacity divergence definition system, employing the capacity divergence definition method as described in claim 4, characterized in that, include: The decay curve connection module is configured to connect any point K on the capacity decay curve. i Together with the end point of life B, form line segment K. i B, wherein the end of life is obtained based on the battery retirement standard method according to any one of claims 1-2; The diving degree calculation module is configured to: calculate K i Point projection onto coordinate system X Projection point M of axis i Connect K i M i This forms a capacity diving triangle ΔK i BM i , will ∠K i BM i Defined as the capacity dive angle, with the tangent of the capacity dive angle as the capacity dive degree, where the coordinate system... X The number of cycles along the axis, with the Y-axis of the coordinate system defined as SOH.

6. A computer-readable storage medium having a program stored thereon, characterized in that, When executed by a processor, the program implements the steps in the standard method for battery retirement as described in any one of claims 1-2; or, when executed by a processor, the program implements the steps in the method for defining capacity drop as described in claim 4.

7. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the battery retirement standard method as described in any one of claims 1-2; or, when the processor executes the program, it implements the steps in the capacity drop-off definition method as described in claim 4.

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