Battery cell life prediction method reflecting storage characteristics of positive electrode active material

Abstract

The method for predicting the life of a battery cell according to the present invention includes virtually dividing a capacity of a battery cell, which is a measurement object for life prediction, into two or more capacity portions, and measuring charge and discharge cycle data of each of the capacity portions; correcting the charge and discharge cycle data by reflecting storage degradation of a positive electrode active material; and predicting the life of the battery cell based on the corrected charge and discharge cycle data.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0105113, filed on August 21, 2020, the entire contents of which are incorporated herein by reference.

[0002] This invention relates to a method for predicting the lifetime of a single battery cell, reflecting the storage characteristics of the positive electrode active material. Specifically, this invention relates to a method for predicting the lifetime of a single battery cell that, in an accelerated lifetime assessment method based on interval division, considers the error generation caused by storage characteristics according to the type of positive electrode active material, thereby removing the influence of calendar degradation (storage degradation) caused by storage characteristics. This interval division accelerated lifetime assessment method rapidly predicts the battery lifetime by dividing the battery capacity into multiple capacity portions. Background Technology

[0003] With the widespread use of portable electronic devices such as laptops, cameras, and mobile phones, the importance of secondary batteries, which are primarily used as power sources for actuation, is increasing.

[0004] Typically, a secondary battery has the following structure: the electrode assembly and electrolyte are sealed together in an external material, and two electrode terminals with different polarities are exposed to the outside. The electrode portion comprises multiple individual cells, and each individual cell has a structure in which a porous separator is inserted between a negative electrode plate and a positive electrode plate. Active materials that participate in the electrochemical reaction are coated on the negative and positive electrode plates, and the secondary battery is charged or discharged according to the electrochemical reaction and evaporation of the active materials.

[0005] Furthermore, the importance of technologies for management systems used to efficiently utilize and manage secondary batteries is increasing. In particular, such management systems should be able to accurately predict the state of health (SOH) of the secondary battery in order to appropriately adjust the charging or discharging output and SOC (state of charge) usage strategy.

[0006] Typically, to predict the lifespan of a secondary battery, at least 4,000 charge / discharge cycles are required. Conventionally, under real-world operating conditions, lifespan tests are performed while charging the battery to its full capacity. If such a test is conducted, only 4 to 5 cycles of data can be obtained at a time. Therefore, obtaining approximately 4,000 charge / discharge cycles takes about 900 days.

[0007] Therefore, according to the traditional method described above, it takes about 30 months to obtain experimental data for predicting the lifespan of lithium secondary battery cells.

[0008] To address this issue, Korean Patent Publication No. 10-2019-0106763 discloses an N-division accelerated lifespan assessment method. This method predicts the lifespan of a battery cell by dividing it into multiple capacity portions, obtaining charge and discharge cycle data for each capacity portion, and summing the obtained data. While this disclosed technique significantly reduces the time spent on battery cell lifespan assessment, it does not reflect the storage characteristics based on the type of positive electrode active material.

[0009] also, Figure 1 (a) to Figure 1 (c) shows the capacity retention for each SOC, depending on the type of positive electrode active material. Referring to the figures, a battery cell with a relatively low nickel content positive electrode composition is shown... Figure 1 As shown in (a), high storage degradation is observed at high SOC, but as Figure 1 (b) and Figure 1 As shown in (c), the opposite storage degradation phenomenon is observed above 75% SOC. That is, high storage degradation is shown in a specific capacity range depending on the composition of the cathode.

[0010] However, since existing accelerated life assessment methods may show distorted results due to storage degradation in specific capacity ranges with high nickel content, it is necessary to develop a technique for predicting the life of a single cell that can remove the degree of degradation caused by storage degradation. Summary of the Invention

[0011] [Technical Issues]

[0012] The present invention is designed to solve the above problems, and the purpose of the present invention is to correct the distorted results caused by storage degradation when evaluating the lifetime of a battery cell including cathode material that has been severely degraded by storage degradation based on the conventional N-division accelerated lifetime assessment method.

[0013] [Technical Solution]

[0014] A method for predicting the lifespan of a battery cell according to an embodiment of the present invention includes: virtually dividing the capacity of the battery cell, which is the object of measurement for lifespan prediction, into two or more capacity portions, and measuring charge and discharge cycle data for each of the capacity portions; correcting the charge and discharge cycle data by reflecting the storage degradation of the positive electrode active material; and predicting the lifespan of the battery cell based on the corrected charge and discharge cycle data.

[0015] In an embodiment of the invention, the process of obtaining storage degradation during the correction of charge and discharge cycle data includes: preparing an actual number of battery cells equal to twice the total number of capacity portions; measuring the capacity based on storage time with each of the actual battery cells set to a predetermined voltage; and deriving the storage degradation for each of the capacity portions based on the data obtained by the measurement.

[0016] In an embodiment of the invention, the predetermined voltage is the voltage measured at the end of a rest period after charging and discharging to the upper and lower limits of the capacity for each capacity portion.

[0017] In an embodiment of the invention, measuring charge and discharge cycle data for each capacity portion includes: determining the number of portions into which the capacity of a battery cell to be measured will be virtually divided, and preparing as many battery cells as the number of portions as the number of portions; and measuring the charge and discharge cycle data of the battery cells corresponding to the respective capacity portions by repeatedly charging and discharging the battery cells, wherein during the determination of the number of portions and preparation of the battery cells, the capacity portion of the battery cell to be measured can be determined based on the output voltage to be matched with the divided portions.

[0018] In embodiments of the invention, during the determination of the number of portions and preparation of the battery cells, the capacity portions may overlap each other by a predetermined amount in adjacent ranges.

[0019] In embodiments of the present invention, during the measurement of charge and discharge cycle data, a battery cell corresponding to a corresponding capacity portion can be repeatedly charged and discharged to obtain charge and discharge cycle data of the battery cell.

[0020] In an embodiment of the present invention, a method for charging and discharging a single battery cell includes:

[0021] In an embodiment of the present invention, a first reference voltage is determined that matches the upper limit capacity of a corresponding capacity portion of a battery cell; a second reference voltage is determined that matches the lower limit capacity of a corresponding capacity portion of a battery cell; the output voltage of the battery cell is measured; the output voltage is compared with the first reference voltage and the second reference voltage; and based on the result of comparing the output voltage with the first reference voltage and the second reference voltage, it is determined whether to charge or discharge the battery cell.

[0022] In an embodiment of the present invention, during the determination of whether to charge or discharge a battery cell, if the output voltage of the battery cell is equal to or less than a first reference voltage, charging is performed, and if the output voltage of the battery cell exceeds the first reference voltage, charging is stopped and discharging is performed.

[0023] In an embodiment of the present invention, during the determination of whether to charge or discharge a battery cell, if the output voltage of the battery cell is equal to or greater than a second reference voltage, then discharge is performed, and if the output voltage of the battery cell is less than the second reference voltage, then discharge is stopped and charging is performed.

[0024] In embodiments of the present invention, during the prediction of the lifespan of a battery cell, the lifespan of the battery cell is predicted by using one of the following: a first scheme to predict the lifespan of the battery cell by simply adding up the charge and discharge cycle data reflecting storage degradation for the corresponding capacity portion; a second scheme to predict the lifespan of the battery cell by combining and summing the charge and discharge cycle data reflecting storage degradation for the corresponding capacity portion; and a third scheme to predict the lifespan of the battery cell by using the multiplicative probability of the charge and discharge cycle data reflecting storage degradation for the corresponding capacity portion.

[0025] [Beneficial Effects]

[0026] The method for predicting the lifespan of a single battery cell according to the present invention can reliably predict lifespan by eliminating capacity reduction due to storage degradation when predicting lifespan using accelerated life assessment methods.

[0027] Furthermore, according to the present invention, the lifespan of the entire battery cell can be quickly predicted by dividing the capacity of a single battery cell into multiple capacity portions and rapidly collecting the charge and discharge cycle data of the battery cells in the corresponding capacity portions. Attached Figure Description

[0028] Figure 1 (a) to Figure 1 (c) is a graph showing the storage voltage measurements for the corresponding SOC based on the positive electrode composition.

[0029] Figure 2 This is a flowchart of a battery cell lifetime prediction method according to an embodiment of the present invention.

[0030] Figure 3 This is a flowchart of a battery cell lifetime prediction method according to an embodiment of the present invention.

[0031] Figure 4 This is a flowchart illustrating the process of charging and discharging a battery cell within a predetermined capacity range according to an embodiment of the present invention.

[0032] Figure 5 The results of the charge / discharge cycles of the five capacity portions are shown after each of the battery cells being measured is divided into five capacity portions.

[0033] Figure 6 This is a schematic diagram of the battery cell life prediction method of the present invention.

[0034] Figure 7 This is a flowchart of the correction steps according to an embodiment of the present invention.

[0035] Figure 8 This is a graph illustrating the results of measuring capacity based on storage time after each battery cell is charged with a predetermined voltage according to an embodiment of the present invention to deduce the degree of storage degradation.

[0036] Figure 9 It is a graph that corrects for storage degradation by reflecting the capacity portion.

[0037] Figure 10 It is a graph of capacity retention based on the number of battery cycles predicted by the traditional 5-stage accelerated life assessment method.

[0038] Figure 11 It is a graph based on the capacity retention rate of the battery cycle number, which reflects the predicted storage degradation, according to an embodiment of the present invention. Detailed Implementation

[0039] The invention will be described in detail below with reference to the accompanying drawings. The terms and words used in this specification and claims should not be construed as limited to common or dictionary terms, and the inventors may appropriately define the concepts of the terms in order to best describe their invention. The terms and words should be interpreted as having meanings and concepts consistent with the technical spirit of the invention.

[0040] In this application, it should be understood that terms such as “comprising” or “having” are intended to indicate the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and they do not preclude the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, parts or combinations thereof.

[0041] In this invention, after the total capacity of the battery cell to be measured is virtually divided into multiple capacity portions, charge and discharge cycle data are obtained for each corresponding capacity portion. Based on the obtained charge and discharge cycle data for each corresponding capacity portion, the battery cell life is predicted according to the storage characteristics of the positive electrode active material to reflect storage degradation.

[0042] Figures 2 to 4 This is a flowchart of a method for predicting the lifespan of a single battery cell according to an embodiment of the present invention. (Reference) Figure 2The method for predicting the lifespan of a battery cell according to the present invention includes: virtually dividing the capacity of the battery cell, which is the measurement object for lifespan prediction, into two or more capacity portions, and measuring charge and discharge cycle data for each capacity portion (S100); correcting the charge and discharge cycle data by reflecting the storage degradation of the positive electrode active material (S200); and predicting the lifespan of the battery cell based on the corrected charge and discharge cycle data (S300).

[0043] refer to Figure 3 For each capacity segment, the measurement of charge and discharge cycle data (S100) includes: determining the number of segments into which the capacity of the battery cell to be measured will be virtually divided, and preparing as many battery cells as the number of segments as the measurement segment (S110); and measuring the charge and discharge cycle data of the battery cell corresponding to the corresponding capacity segment by repeatedly charging and discharging the battery cell (S120).

[0044] In the step of virtually dividing the capacity (S110), the total capacity of the battery cell to be measured is virtually divided into two or more capacity portions, and the battery cell to be used for measurement is prepared. Step (S110) may include a step (S111) of determining the number of capacity portions into which the total capacity of the battery cell will be divided.

[0045] The step of determining the number of capacity segments is to determine the number of capacity segments into which the total capacity of a battery cell will be virtually divided. For example, if the total capacity of a battery cell is between 1 and 100, and the total capacity of the battery cell is divided into 5 segments, then each capacity segment can have a capacity range of 20.

[0046] The step of virtually dividing the capacity (S110) includes preparing as many battery cells as there are capacity portions, each having the same specifications as the battery cell being measured (S112). When the capacity of the battery cell being measured is virtually divided into 5 capacity portions, charge and discharge cycle data should be collected simultaneously for each capacity portion during charging and discharging. Therefore, it is necessary to have 5 battery cells (first to fifth battery cells) with the same specifications as the battery cell being measured. In other words, in order to obtain charge and discharge cycle data for the entire capacity simultaneously for each divided capacity portion during charging and discharging, it is necessary to have as many battery cells as there are capacity portions.

[0047] In this paper, charge and discharge cycle data can be the capacity data of a single battery cell after each charge / discharge operation within a defined capacity segment.

[0048] A capacity retention rate, indicating the rate of capacity retention in the initial state after performing a charge / discharge cycle for each capacity segment, is obtained, and the battery life can be predicted based on the capacity retention rate. For example, assuming a reference capacity retention rate of 50% to be judged as being in a deteriorated state or needing replacement, if the capacity retention rate calculated after performing 4000 charge / discharge cycles is equal to or less than the reference capacity retention rate, the battery cell life can be predicted to be 4000 charge / discharge cycles.

[0049] In a specific example, during the steps of determining the number of capacity portions and preparing individual battery cells, the capacity portions may overlap each other by a predetermined amount in adjacent ranges.

[0050] The step of measuring charge and discharge cycle data (S120) is a step of measuring the charge and discharge cycle data of the battery cells corresponding to the corresponding capacity by repeatedly charging and discharging the battery cells, and the step of obtaining the charge and discharge cycle data while charging and discharging the battery cells prepared in the preparation step (S112).

[0051] In an embodiment of the invention, the capacity is divided into five capacity portions, and five battery cells (first to fifth battery cells) corresponding to the five capacity portions are prepared. The first battery cell is configured to perform charging / discharging within a capacity range of 81 to 100, and its capacity is measured during each charge / discharge cycle for the 81 to 100 capacity range while the first battery cell is being charged and discharged. The second battery cell is configured to perform charging / discharging within a capacity range of 61 to 80, and its capacity is measured during each charge / discharge cycle for the 61 to 80 capacity range while the second battery cell is being charged and discharged. The third battery cell is configured to perform charging / discharging within a capacity range of 41 to 60, and its capacity is measured during each charge / discharge cycle for the 41 to 60 capacity range while the third battery cell is being charged and discharged. The fourth battery cell is configured to perform charging / discharging within a capacity range of 21 to 40, and its capacity is measured during each charge / discharge cycle for the 21 to 40 capacity range while the fourth battery cell is being charged and discharged. The fifth battery cell is configured to perform charging / discharging within a capacity range of 1 to 20, and the capacity is measured during each charge / discharge cycle for the capacity range of 1 to 20 while the fifth battery cell is being charged and discharged.

[0052] In the measurement step (S120) of the present invention, the scheme for charging and discharging a battery cell includes: determining a first reference voltage that matches the upper limit capacity of a corresponding capacity portion of the battery cell; determining a second reference voltage that matches the lower limit capacity of a corresponding capacity portion of the battery cell; measuring the output voltage of the battery cell; comparing the output voltage with the first reference voltage and the second reference voltage; and determining whether to charge or discharge the battery cell based on the result of comparing the output voltage with the first reference voltage and the second reference voltage.

[0053] For example, in the case of the second battery cell, a first reference voltage matching the upper limit capacity 80 of the capacity range and a second reference voltage matching the lower limit capacity 60 can be set.

[0054] In a specific example, in the step of determining whether to charge or discharge a battery cell, as a result of the comparison step, if the output voltage of the battery cell being measured is equal to or less than a first reference voltage, charging is performed; and as a result of the comparison step, if the output voltage of the battery cell exceeds the first reference voltage, charging is stopped and discharging is performed.

[0055] Furthermore, in the step of determining whether to charge or discharge a battery cell, as a result of the comparison step, if the output voltage of the battery cell being measured is equal to or greater than the second reference voltage, then discharge is performed; and as a result of the comparison step, if the output voltage of the battery cell is less than the second reference voltage, then discharge is stopped and charging is performed.

[0056] In the following text, reference will be made to Figure 5 A charging / discharging method is described. Similarly, a method for measuring the capacity of a second battery cell in each charge / discharge cycle, wherein a first reference voltage and a second reference voltage are set, is performed as follows: The first reference voltage is compared with the output voltage of the second battery cell (S124), and if the output voltage of the second battery cell is equal to or less than the first reference voltage, charging is continuously performed (S123), and if the output voltage of the second battery cell exceeds the first reference voltage, charging is stopped and discharging is performed (S121). Furthermore, the second reference voltage is compared with the output voltage of the second battery cell (S122), and if the output voltage of the second battery cell is equal to or greater than the second reference voltage, discharging is continuously performed (S121), and if the output voltage of the second battery cell is less than the second reference voltage, discharging of the second battery cell is stopped and charging is performed. In this way, it is possible to measure the capacity of a secondary battery cell in each charge / discharge cycle while repeatedly charging / discharging within a capacity range of 61 to 80.

[0057] Furthermore, in the example above, the first to fifth battery cells are set to not overlap with each other by means of their virtually divided ranges, but the ranges can also be set to partially overlap with each other.

[0058] That is, the first battery cell can be set to have a capacity range of 76 to 100, the second battery cell can be set to have a capacity range of 56 to 80, the third battery cell can be set to have a capacity range of 36 to 60, the fourth battery cell can be set to have a capacity range of 16 to 40, and the fifth battery cell can be set to have a capacity range of 1 to 25. In this case, the method of setting the capacity range of the first to fifth battery cells and measuring the capacity of the corresponding charge / discharge cycle can be performed in the same way as the method of setting the capacity range of the first to fifth battery cells and the method of measuring the capacity of the corresponding charge / discharge cycle, provided that the virtual division ranges of the battery cells do not overlap.

[0059] Similarly, if the ranges are designed to partially overlap, the error can be reduced by covering the error in another range—an error caused by the degradation in a particular range (e.g., the range of SOC 60 to 40) being greater in terms of the degradation of the cell in the range than in other ranges, resulting from the reduction in the area of ​​use of the negative electrode.

[0060] Figure 5 The illustration shows the results of measuring charge and discharge cycle data for each capacity segment by arranging the first to fifth battery cells according to an embodiment of the invention, corresponding to five divided capacity segments. (Reference) Figure 5 The left figure shows the charging and discharging of the first to fifth battery cells according to the capacity portions of the battery cells being measured, and the five figures on the right show the capacity retention rates of the first to fifth battery cells.

[0061] refer to Figure 5 The graph on the right shows that the capacity retention rate differs for the corresponding capacity portion during repeated charge / discharge cycles. Similarly, since the capacity retention rate varies across the capacity range, predicting the entire lifespan of a battery cell based on the capacity of only a portion of the cell's capacity range across charge / discharge cycles can lead to significant errors. Therefore, according to the accelerated lifespan assessment method of the present invention, the capacity of a battery cell across its entire capacity range is measured by setting the corresponding capacity ranges of the first to fifth battery cells to include the entire capacity of the cell.

[0062] The correction step (S200) is performed by eliminating storage degradation of the positive electrode active material in the charge and discharge cycle data for the corresponding capacity portion.

[0063] like Figure 1 As shown, storage degradation occurs significantly within a specific range of State of Charge (SOC), depending on the nickel content in the cathode material. In the accelerated life assessment method of this invention, the entire capacity range from 0 to 100 is divided into n intervals, and the life of a battery cell is predicted based on charge and discharge cycle data obtained while repeatedly charging and discharging the battery cell for each capacity segment. Here, storage degradation can vary depending on the capacity segment, and the obtained charge and discharge cycle data reflects both storage degradation and cycle degradation. Therefore, it can be measured as a value lower than the actual capacity retention rate. Similarly, the importance of the life prediction method of this invention lies in predicting life by performing a correction that eliminates storage degradation, reflecting only cycle degradation.

[0064] Figure 6 This is a schematic diagram of the battery cell life prediction method of the present invention. (For reference only.) Figure 6 The concept of the correction steps of this invention is explained as follows. Figure 6 The downward-sloping dashed line indicates the capacity retention rate calculated based on cycles in the life prediction step (S200) of the present invention using the N-division accelerated life assessment method, and Figure 6 The downward-sloping solid line shows the result of correction by the correction step (S300) of the present invention.

[0065] The degradation of lithium-ion batteries can be divided into cycle degradation and storage degradation (calendar degradation). Cycle degradation refers to the degradation that occurs during the flow of charging or discharging current in a secondary battery, generating Joule heat, and due to the irreversible degradation of the electrolyte and active materials as working ions (lithium ions in the case of lithium-ion batteries) are inserted from the electrodes or discharged. In this paper, storage degradation (calendar degradation) refers to the degradation that occurs during the no-load state, which is the state when the secondary battery is not currently being charged or discharged, i.e., in the calendar state. The capacity of a secondary battery can decrease even in the no-load state due to the irreversible degradation of the electrolyte and active materials coated on the electrodes. This is referred to as storage degradation or calendar degradation as a term to distinguish it from cycle degradation.

[0066] In the N-division accelerated lifetime assessment method of the present invention, battery cells with n corresponding capacity portions are prepared, and charge and discharge cycle data are obtained while repeatedly charging / discharging. At this time, storage degradation occurs due to the rest period after charging / discharging. Specifically, the storage degradation state varies in some SOC ranges depending on the composition of the cathode material, but since the conventional N-division accelerated lifetime assessment method does not consider the capacity reduction caused by this storage degradation, errors occur. Therefore, in the present invention, by means of... Figure 6 The correction is performed to eliminate storage degradation.

[0067] Figure 7 A flowchart illustrating correction steps for storage degradation of the positive electrode active material according to an embodiment of the present invention is shown. (Reference) Figure 7 The process of obtaining storage degradation during the calibration of charge and discharge cycle data (S200) includes: preparing an actual battery cell as many as twice the total number of capacity portions; measuring the capacity based on storage time with each actual battery cell set to a predetermined voltage; and deriving the storage degradation for each capacity portion based on the data obtained by measurement.

[0068] refer to Figure 7 The correction step (S200) of the present invention includes: preparing an actual number of battery cells equal to twice the total number of capacity portions (S210); measuring the capacity based on storage time with each actual battery cell set to a predetermined voltage (S220); and deriving the storage degradation of each capacity portion based on the data obtained by the measurement (S230). In this document, the predetermined voltage is the voltage measured at the end of a rest period after charging and discharging to the upper and lower limits of the capacity of each capacity portion.

[0069] In one example, by dividing the total capacity into a total of 5 parts and obtaining charge and discharge cycle data for each of the 5 capacity parts, 10 actual battery cells (first actual battery cell to tenth actual battery cell) are prepared, corresponding to twice the 5 used to calculate storage degradation. Furthermore, after charging each of the first to tenth actual battery cells, the capacity is measured according to the storage time. In this document, the predetermined voltage refers to the voltage measured at the end of the rest period after charging and discharging to the upper and lower limits of each capacity part. Specifically, the 10 actual battery cells are divided into two groups according to the capacity range. Subsequently, one battery cell in each group, consisting of two battery cells, is charged to the upper limit capacity, and the capacity retention rate for each storage time is measured at the voltage state measured at the end of the rest period, while the other battery cell in each group is charged to the lower limit capacity, and the capacity retention rate for each storage time is measured at the voltage state measured at the end of the rest period.

[0070] In a specific example, the capacity of the battery cell being measured was divided into a total of five capacity portions. The upper limit voltage of the first capacity portion was then set to 3.67V, and the lower limit voltage was set to 3V. The upper limit voltage of the second capacity portion was set to 3.73V, and the lower limit voltage was set to 3.435V. The upper limit voltage of the third capacity portion was set to 3.815V, and the lower limit voltage was set to 3.536V. The upper limit voltage of the fourth capacity portion was set to 3.962V, and the lower limit voltage was set to 3.626V. The upper limit voltage of the fifth capacity portion was set to 4.1V, and the lower limit voltage was set to 3.754V. Subsequently, charge / discharge cycles were repeated to obtain a charge / discharge cycle. In this case, in the calibration step of the present invention, for each of the five capacity portions, it is possible to obtain the output voltage measured at the end of the rest period after charging to the upper limit voltage and the output voltage measured at the end of the rest period after discharging to the lower limit voltage, and to measure the capacity retention rate of 10 actual battery cells based on the storage time while maintaining 10 output voltages. Table 1 shows the output voltage values ​​according to the step of measuring capacity based on the above storage time.

[0071] [Table 1]

[0072]

[0073] also, Figure 8 This is a graph showing the capacity retention rate for each storage time, measured at the end of each rest period after charging and discharging for each capacity segment as shown in Table 1, under voltage conditions. (Reference) Figure 8 Storage degradation was higher in the voltage ranges of 3.8755V (SOC 76%), 3.9907V (SOC 90%), and 3.8378V (SOC 71%).

[0074] Able to show Figure 8 The graph of capacity retention for each storage time calculates storage degradation for each capacity segment and can be corrected by reflecting the calculated storage degradation in the charge and discharge cycle data of each of the n capacity segments. Figure 9 The illustration shows charge and discharge cycle data corrected for storage degradation for each of the n capacity portions. Similarly, according to the invention, because of the effect of accelerated storage degradation within a specific range based on the characteristics of the positive electrode active material, battery life can be predicted more accurately based on charge and discharge cycle data for each capacity portion.

[0075] Furthermore, in the life prediction step (S200), which will be described later, the entire life of a battery cell can be predicted based on the capacity measured in charge / discharge cycles over the entire capacity range of the first to fifth battery cells, as corrected as described above.

[0076] The lifetime prediction step (S200) of the present invention is a step of predicting the lifetime of a battery cell based on data corrected for storage degradation in charge and discharge cycle data measured for each of a plurality of battery cells set for each of the divided capacity portions.

[0077] In this invention, the lifespan of the battery cell being measured is predicted based on charge and discharge cycle data measured in the battery cell using three different methods according to the corresponding capacity portions.

[0078] First, the lifespan of a battery cell can be predicted by simply adding up the charge and discharge cycle data measured in multiple battery cells that are set to the corresponding capacity portions.

[0079] Secondly, the lifespan of a battery cell can be predicted by simply calculating the sum of charge and discharge cycle data measured in multiple battery cells that are set to the corresponding capacity portions.

[0080] Finally, the lifespan of a battery cell can be predicted by using the multiplicative probability of charge and discharge cycle data measured in multiple battery cells that are set to the corresponding capacity portions.

[0081] Figure 10 This is a graph showing the residual capacity of a battery after cumulative discharge, derived from a conventional N-segment accelerated life assessment method (specifically, the 5-segment accelerated life assessment method) for a battery using a high-nickel cathode material (NCM811). Figure 11 The diagram illustrates a correction based on an embodiment of the invention, reflecting storage degradation.

[0082] refer to Figure 10 According to the conventional N-division accelerated life assessment method, the battery was shown to have 74.9% to 77.3% of its residual capacity after 7300 cycles (cumulative discharge capacity is 1500 kWh). Furthermore, the actual measured value was predicted to have 87.1% of its residual capacity after 7300 cycles. That is, the conventional N-division accelerated life assessment method has an error range of 9.8% to 12.3% based on 7300 cycles.

[0083] refer to Figure 11According to the predictions of the present invention, the battery is shown to have 79.2% to 80.9% of its residual capacity after 7300 cycles. This represents an error of 6.2% to 7.9% compared to the 87.1% predicted residual capacity shown in the actual measurement graph. In this paper, since the effects of accelerated storage degradation within a specific capacity range have been eliminated, it is even closer to the predicted capacity of the actual measured value than the residual capacity predicted by the conventional N-division accelerated lifetime assessment method.

[0084] Similarly, the method for predicting the lifespan of a single cell according to the present invention can improve the problem of distorted results generated due to accelerated storage degradation in a specific capacity range when the conventional N-division accelerated life assessment method is applied to high-nickel cathode cell cells.

[0085] The above description merely illustrates the technical concept of the present invention, and those skilled in the art can make various modifications and variations without departing from the essential characteristics of the invention. Therefore, the accompanying drawings disclosed herein are not intended to limit the technical concept of the invention, but rather to describe it, and the scope of the technical concept of the invention is not limited by these drawings. The scope of protection of the present invention should be interpreted by the following claims, and all technical concepts within the scope of the following claims should be interpreted as being included within the scope of the present invention.

Claims

1. A method for predicting the lifespan of a single battery cell, the method comprising: The capacity of a single battery cell, which is the object of measurement for life prediction, is virtually divided into two or more capacity portions, and charge and discharge cycle data for each of the capacity portions are measured. The charge and discharge cycle data are corrected by reflecting the storage degradation of the positive electrode active material, wherein the correction is performed by exempting the storage degradation of the positive electrode active material from the charge and discharge cycle data for the corresponding capacity portion. The process of obtaining the storage degradation during the correction of the charge and discharge cycle data includes: Prepare an actual number of individual battery cells equal to twice the total number of the aforementioned capacity portions; The capacity is measured over storage time with each of the actual battery cells set to a predetermined voltage; and Storage degradation for each of the capacity portions is derived based on the data obtained through the measurements; and The lifespan of the battery cells is predicted based on the corrected charge and discharge cycle data.

2. The method according to claim 1, wherein, The predetermined voltage is the voltage measured at the end of the rest period after charging and discharging to the upper and lower capacity limits for each capacity segment.

3. The method according to claim 1, wherein, The measurements of charge and discharge cycle data for each capacity segment include: The number of portions into which the capacity of the battery cell to be measured will be virtually divided is determined, and an equal number of battery cells to be measured are prepared; and The charge and discharge cycle data of the battery cells, corresponding to the respective capacity portions, are measured by repeatedly charging and discharging the battery cells. During the process of determining the number of the portions and preparing the battery cells, the capacity portion of the battery cell to be measured is determined based on the output voltage to be matched with the divided portions.

4. The method according to claim 3, wherein, During the determination of the number of the portions and the preparation of the battery cells, the capacity portions overlap each other by a predetermined amount in adjacent ranges.

5. The method according to claim 3, wherein, During the measurement of the charge and discharge cycle data, the battery cells corresponding to the respective capacity portions are repeatedly charged and discharged to obtain the charge and discharge cycle data of the battery cells.

6. The method according to claim 5, wherein, The charging and discharging schemes for the battery cells include: Determine a first reference voltage that matches the upper limit capacity of the corresponding capacity portion of the battery cell; Determine a second reference voltage that matches the lower limit capacity of the corresponding capacity portion of the battery cell; Measure the output voltage of the battery cell; The output voltage is compared with the first reference voltage and the second reference voltage; and Whether to charge or discharge the battery cell is determined based on the result of comparing the output voltage with the first reference voltage and the second reference voltage.

7. The method according to claim 6, wherein, During the determination of whether to charge or discharge the battery cell, if the output voltage of the battery cell is equal to or less than the first reference voltage, charging is performed, and if the output voltage of the battery cell exceeds the first reference voltage, charging is stopped and discharging is performed.

8. The method according to claim 6, wherein, During the determination of whether to charge or discharge the battery cell, if the output voltage of the battery cell is equal to or greater than the second reference voltage, discharge is performed, and if the output voltage of the battery cell is less than the second reference voltage, discharge is stopped and charging is performed.

9. The method according to claim 1, wherein, During the prediction of the battery cell's lifespan, the battery cell's lifespan is predicted using one of the following methods: A first scheme predicts the lifespan of a single battery cell by simply adding up the charge and discharge cycle data for the corresponding capacity portion that reflect the storage degradation. A second approach is to predict the lifespan of a single battery cell by combining and summing charge and discharge cycle data that reflect the degradation of the storage for the corresponding capacity portion. as well as A third approach is to predict the lifespan of a single battery cell using the multiplicative probability of charge and discharge cycle data for the corresponding capacity portion, which reflects the degradation of the storage.

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