Determination system and determination method

Abstract

A determination system (100) comprises: a calculating unit (15) for calculating, from each set of time-series data including a DC current value and at least one value of a DC voltage value or an SOC of a secondary battery (210) during charging / discharging, which is at least one of charging and discharging of the secondary battery, spectrum information representing a spectrum in a two-axis coordinate system in which one axis represents a relaxation time and the other axis represents intensity; and a determining unit (16) which uses shape information relating to the shape of the spectrum calculated by the calculating unit (15) to determine a control condition of the secondary battery (210).

Description

Determination system and determination method

[0001] The present disclosure relates to a decision-making system and a decision-making method.

[0002] In recent years, efforts have been made to efficiently utilize energy by using secondary batteries such as lithium-ion batteries as onboard power sources for ships, aircraft, and vehicles (railroads, automobiles, etc.), as well as for storing electricity in smart houses and smart grids. However, the characteristics of secondary batteries can rapidly deteriorate if used improperly. For this reason, in order to continue using products equipped with secondary batteries for long periods of time, it is preferable to appropriately set the operating conditions (control conditions) of the secondary battery. In the following, rapid deterioration of the characteristics of a secondary battery is referred to as a "battery abnormality," and battery abnormality is distinguished from deterioration over time that occurs with normal use.

[0003] An example of a battery abnormality is lithium deposition, a degradation phenomenon that occurs when a secondary battery is continuously used under conditions such as low temperature and high current. In lithium deposition, metallic lithium is deposited on the electrodes of the secondary battery, resulting in a decrease in capacity and an increase in resistance of the secondary battery. Furthermore, if the lithium deposition phenomenon continues to progress, it may eventually cause an internal short circuit in the secondary battery.

[0004] In order to prevent battery abnormalities, studies are being conducted to analyze the internal state of a battery. For example, the abstract of Patent Document 1 states that "the analyzer includes a battery state analyzer that detects changes in the state of components of a battery based on changes in the peak of relaxation time in a predetermined frequency band."

[0005] International Publication No. 2017 / 179266

[0006] FIG. 17 is a schematic diagram illustrating the temperature and current thresholds at which battery abnormalities occur. In order to reduce the frequency of secondary battery replacements and repairs due to battery abnormalities, it is preferable to identify the conditions under which battery abnormalities occur and control the battery so as to avoid using the secondary battery under those conditions. For example, to suppress the occurrence of lithium deposition, it is sufficient to identify in advance the temperature and current thresholds at which lithium deposition occurs. Specifically, in FIG. 17 , a function f representing the thresholds is determined, for example, through experiments, simulations, etc. Then, by avoiding use in region S above the graph of function f, lithium deposition can be suppressed. In other words, it is preferable to control the temperature, current, etc. of the secondary battery so as to avoid region S.

[0007] There are two main methods known for identifying conditions under which secondary batteries may develop abnormalities. One involves using a secondary battery continuously for an extended period of time at a constant temperature and current value, causing it to deteriorate, and determining whether or not a battery abnormality occurs during this process. This method is called a cycle degradation test, and by conducting cycle degradation tests under multiple temperature and current conditions, it is possible to identify conditions under which battery abnormalities may occur. However, identifying conditions under which abnormalities may occur through cycle degradation tests requires a test period of several months to several years, making it difficult to use this method to quickly detect and address the risk of secondary battery abnormalities.

[0008] Another method is to measure the reaction current value (hereinafter referred to as the reaction mode) flowing through a secondary battery. When a secondary battery is used under conditions that could cause battery abnormalities, the number of reaction modes measured during the secondary battery's charge and discharge process changes. For example, in the case of lithium deposition reduction, in addition to the normal battery reaction mode of lithium ion insertion into the electrode, a reaction mode of lithium ion deposition on the electrode surface occurs inside the secondary battery. This increases the number of reaction modes compared to normal charge and discharge reactions. In other words, by focusing on the change in the number of reaction modes, it is possible to determine whether a battery abnormality will occur under the secondary battery's operating conditions. Since measuring the number of reaction modes can be completed in a test of just a few minutes, it has the advantage of being able to quickly determine the risk of abnormalities compared to cycle degradation tests.

[0009] As a technique for measuring the number of reaction modes, the AC impedance method described in paragraph 0064 of Patent Document 1 uses an AC current value. However, a high AC current cannot be applied to a secondary battery. On the other hand, battery abnormalities are particularly noticeable when a large current flows through a secondary battery. Therefore, the AC impedance method using AC current cannot properly evaluate battery abnormalities in a secondary battery, and it is not possible to properly determine control conditions that can suppress battery abnormalities.

[0010] The problem to be solved by the present disclosure is to provide a determination system and a determination method that can appropriately determine control conditions that can suppress battery abnormalities.

[0011] The determination system of the present disclosure includes a calculation unit that calculates spectral information representing a spectrum in a two-axis coordinate system, one axis representing relaxation time and the other axis representing intensity, from time-series data including at least one of a DC current value and a DC voltage value or an SOC of the secondary battery during charging or discharging, which is at least one of charging and discharging of the secondary battery, and a determination unit that determines control conditions for the secondary battery using shape information regarding the shape of the spectrum calculated by the calculation unit. Other solutions will be described later in the description of embodiments of the invention.

[0012] According to the present disclosure, it is possible to provide a determination system and a determination method that can appropriately determine control conditions that can suppress battery abnormalities.

[0013] 1 is a block diagram showing a determination system of the present disclosure. FIG. 1 is a map showing calculation results of a relaxation spectrum for each temperature and each current value. FIG. 2 is a map showing calculation results of a relaxation spectrum for each temperature and each voltage value in another embodiment. FIG. 3 is a map showing calculation results of a relaxation spectrum for each voltage value and each current value in another embodiment. FIG. 4 is a diagram showing an example of a relaxation spectrum. FIG. 5 is a block diagram showing a determination system according to another embodiment. FIG. 6 is a block diagram showing a determination system according to another embodiment. FIG. 7 is a block diagram showing a determination system according to another embodiment. FIG. 8 is a block diagram showing a hardware configuration of the determination system. FIG. 9 is a flowchart showing a determination method of the present disclosure. FIG. 10 is a map showing conditions for battery abnormality occurrence from relaxation spectra obtained by actually performing an evaluation test. FIG. 11 is a map showing a range in which battery abnormality occurs, obtained by actually performing an evaluation test. FIG. 12 is a photograph of the electrode surface of a secondary battery used under condition 1 (Example). FIG. 13 is a photograph of the electrode surface of a secondary battery used under condition 2 (Comparative Example). FIG. 14 is a verification result showing the difference in battery capacity between the secondary battery used under condition 1 (Example) and the secondary battery used under condition 2 (Comparative Example). FIG. 15 is a verification result showing the difference in internal resistance between the secondary battery used under condition 1 (Example) and the secondary battery used under condition 2 (Comparative Example). 5A and 5B are schematic diagrams illustrating thresholds of temperature and current values ​​at which a battery abnormality occurs.

[0014] Hereinafter, modes for carrying out the present disclosure (hereinafter referred to as "embodiments") will be described with reference to the drawings. In the following description of one embodiment, other embodiments applicable to the one embodiment will also be described as appropriate. The present disclosure is not limited to the one embodiment described below, and different embodiments can be combined with each other or modified as desired without significantly impairing the effects of the present disclosure. Furthermore, the same components will be given the same reference numerals, and duplicate descriptions will be omitted. Furthermore, components having the same functions will be given the same names. The contents shown are merely schematic, and for convenience of illustration, changes may be made from the actual configuration within the scope of not significantly impairing the effects of the present disclosure, and some components may be omitted or modified between drawings. Furthermore, the same embodiment does not necessarily have to include all of the configurations.

[0015] FIG. 1 is a block diagram showing a determination system 100 according to the present disclosure. Hereinafter, the determination system 100 and the secondary battery 210 are collectively referred to as a battery system 300. Therefore, the battery system 300 includes the determination system 100 and the secondary battery 210. The determination system 100 determines control conditions (charge / discharge conditions) for the secondary battery 210 that suppress the occurrence of a battery abnormality in the secondary battery 210. As described above, the battery abnormality is an abnormality that is different from deterioration over time associated with normal use, such as, but not limited to, lithium deposition on the electrode surface.

[0016] The secondary battery 210 is connected to a power supply 500 and a power consumption device 400 such as a motor or an inverter. The power supply 500 charges the secondary battery 210. The power consumption device 400 is driven by power generated by discharging the secondary battery 210. Therefore, at least one of the charging and discharging (preferably both, hereinafter collectively referred to as charging and discharging) is performed in accordance with the control conditions determined by the determination system 100.

[0017] The control conditions of the secondary battery 210 include, for example, at least one of a DC current value during charging / discharging, a DC voltage value during charging / discharging, and the temperature of the secondary battery 210. Hereinafter, unless otherwise specified, the DC current value, DC voltage value, and temperature of the secondary battery will be simply referred to as a current value, a voltage value, and a temperature, etc. The secondary battery 210 is, for example, a lithium-ion secondary battery, but may be other types of secondary batteries, such as a lead-acid battery or a nickel-cadmium battery.

[0018] The determination system 100 includes a measurement unit 11, a recording unit 12, an assignment unit 13, a classification unit 14, a calculation unit 15, a determination unit 16, and a control unit 17. These may all be configured integrally, or at least some of them may be configured separately. When these are all configured integrally, the determination system 100 can be called a determination device. On the other hand, when at least some of them are configured separately, for example, the part may be stored in a server (not shown) installed in a remote location via a network.

[0019] The measurement unit 11 measures time-series data of each value, including a DC current value and at least one of a DC voltage value and the SOC of the secondary battery 210, during charging or discharging of the secondary battery 210. That is, the time-series data includes time-series data of the DC current value and j-series data of at least one of a DC voltage value and the SOC of the secondary battery 210. The measurement is performed continuously or at predetermined time intervals (e.g., every minute) during use, including during charging or discharging of the secondary battery 210 and standby mode when no charging or discharging is performed. Because there is a correlation between the DC voltage value and the SOC, in the following example, the measurement unit 11 measures time-series data related to the DC voltage value. However, the measurement unit 11 may also measure time-series data of the SOC. In addition, in the example of the present disclosure, the time-series data further includes time-series data of the temperature of the secondary battery 210.

[0020] The measurement unit 11 extracts time series data from a collection of measured time series data (so-called "raw data") for a period (timing) during which a relaxation spectrum can be calculated. The relaxation spectrum is a continuous function of relaxation time and is a spectrum (charge / discharge spectrum) in a two-axis coordinate system with one axis (e.g., the horizontal axis) representing relaxation time and the other axis (e.g., the vertical axis) representing intensity (spectral intensity). For example, it is preferable to extract time series data for at least one period during constant-voltage charging, after charging, or after discharging. "After charging" may be after constant-voltage charging or after constant-current charging. "After discharging" may be after constant-voltage discharging or after constant-current discharging. It is also preferable that there are multiple time series data extracted from different periods.

[0021] When extracting time-series data during constant-voltage charging, the measurement unit 11 extracts time-series data on the voltage, current, and temperature of the secondary battery 210 from time t1 when constant-voltage charging starts to time t2 when constant-voltage charging ends. "Constant-voltage charging" is a charging method in which the secondary battery 210 is charged while being maintained at a constant voltage. Furthermore, the measurement unit 11 also extracts the voltage value before (preferably immediately before) the start of charging the secondary battery 210. There is no limit to the time from time t1 to time t2, but it is preferably 1 minute or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less.

[0022] When extracting time-series data after charging (after charging has finished) or after discharging (after discharging has finished), the measurement unit 11 extracts time-series data on the voltage value, current value, and temperature of the secondary battery 210 from the charging or discharging end time t3 to a predetermined time t4. Furthermore, the measurement unit 11 also acquires the current value immediately before the charging or discharging of the secondary battery 210 is finished. There is no limit to the time from time t3 to time t4, but it is preferably 1 minute or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less.

[0023] There is no limitation on the method by which the measurement unit 11 acquires measurement data (data including the above-mentioned time-series data, voltage values ​​before charging starts, current values ​​immediately before charging and discharging, etc.) from the secondary battery 210. For example, the measurement unit 11 can measure data (e.g., measurement data) related to the secondary battery 210 at a location different from the installation location of the secondary battery 210. As a result, when the secondary battery 210 is installed in, for example, a vehicle, a ship, an airplane, etc., measurement data, for example, of the secondary battery 210 can be centrally managed by, for example, a server (not shown) located in a remote location. This can improve convenience.

[0024] Specifically, for example, the measurement unit 11 may acquire measurement data from the secondary battery 210 via a communication circuit such as an electric circuit or a wired LAN, or may acquire measurement data from a secondary battery 210 placed in a remote location via a network such as a wireless LAN, or may acquire measurement data by a combination of these methods. Furthermore, in the process of acquiring measurement data from the secondary battery 210, the measurement unit 11 may acquire the measurement data via some other device. For example, the measurement unit 11 may acquire the measurement data from the secondary battery 210 via an external device (not shown) such as a charging / discharging device. Furthermore, the measurement unit 11 may store the measurement data acquired from the secondary battery 210 on a server (not shown), and then acquire the measurement data itself.

[0025] The recording unit 12 stores the measurement data of the secondary battery 210 extracted by the measuring unit 11 (data including the time series data, the voltage value before the start of charging, the current value immediately before charging / discharging, etc.). It is preferable that the measurement data be classified and stored according to the timing at which the data was extracted. For example, measurement data D extracted between time tA and time tB isＡＢ and measurement data D extracted between time tC and time tD. ＣＤ If there is measurement data D ＡＢ , D ＣＤ It is preferable that the data are not grouped together, but are linked to the period in which they were acquired (for example, from time tA to time tB, from time tC to time tD, etc.) and stored individually on the recording unit 12.

[0026] The assigning unit 13 assigns a label to each spectrum calculated from time-series data acquired between different times in accordance with a predetermined rule using at least two of a DC current value, a DC voltage value, and a temperature. By providing the assigning unit 13, a map (described later) including a plurality of relaxation spectra can be created from time-series data acquired based on various times and types (current value, voltage value, or temperature).

[0027] In the example of the present disclosure, the assigning unit 13 refers to the measurement data stored in the recording unit 12 and calculates representative values ​​(examples of headings) of the current value, voltage value, and temperature. The calculated representative values ​​are assigned to the calculated relaxation spectrum and the measurement data used to calculate the relaxation spectrum. As will be described in detail later, the relaxation spectrum is calculated based on time-series data measured over different time periods. The calculated relaxation spectrum is then associated with the representative values.

[0028] When a plurality of measurement data extracted at different time intervals are stored in the recording unit 12, the assigning unit 13 calculates a representative value for each measurement data. Specifically, for example, the measurement data D extracted between time tA and time tB is ＡＢ and measurement data D extracted between time tC and time tD. ＣＤ If there is a measurement data D ＡＢ , D ＣＤ A representative value is calculated for each period.

[0029] The method for calculating the representative value (the method for determining the heading) is not particularly limited as long as it can be calculated according to the same predetermined rules regardless of the type and period of time-series data. Two examples of the method for calculating the representative value are shown below.

[0030] <Method 1 for calculating representative values: Calculating representative values ​​from measurement data during constant-voltage charging> For example, the current value immediately after the start of constant-voltage charging can be used as the representative current value. The average voltage value during constant-voltage charging can be used as the representative voltage value. Furthermore, the average value of the measured temperature over time can be used as the representative temperature value.

[0031] <Method 2 for calculating representative values: Calculating representative values ​​from measurement data after charging or discharging> For example, the representative current value can be the current value immediately before the end of charging or discharging. The representative voltage value can be the voltage value immediately before the end of charging or discharging. Furthermore, the representative temperature value can be the average value of the recorded time-series temperature data.

[0032] The classification unit 14 classifies the relaxation spectra according to the assigned headings so that the relaxation spectra are associated with at least two conditions: a current value (a direct current value), a voltage value (a direct current voltage value), or a temperature. By providing the classification unit 14, a map (described later) including multiple relaxation spectra can be created from time-series data acquired based on various times and types. Specific contents of the map will be described later with reference to, for example, FIG. 2 .

[0033] Each of the conditions here includes a numerical range, and therefore, the relaxation spectrum is associated with one of a plurality of numerical ranges constituting each condition, for example, for at least two conditions among a range of current values, a range of voltage values, and a range of temperature.

[0034] In the example disclosed herein, the classification unit 14 classifies each measurement data stored in the recording unit 12 using the control conditions (usage conditions) expected when using the secondary battery 210 and the representative values ​​assigned by the assignment unit 13. The control conditions include the expected usage ranges of current values, voltage values, and temperature when, for example, charging and discharging the secondary battery 210. The control conditions can be determined in advance based on, for example, the intended use of the secondary battery 210.

[0035] As a specific classification method, for example, the classification unit 14 divides the control conditions of the secondary battery 210 into a finite number of sections.ｍｉｎ ~T ｍａｘ When it is expected to be used in ｍｉｎ <T ｍａｘ ), the classification unit 14 ｍｉｎ ~T １ , T １ ~T ２ , T ２ ~T ３ , ..., T Ｎ－１ ~T ｍａｘ where N is an integer equal to or greater than 1. Similarly, for the current value and voltage value of the secondary battery 210, the classification unit 14 divides the expected usage range into a finite number of sections in a similar manner. The usage conditions of the secondary battery 210 may be registered in advance in the calculation unit 15 (described later), or may be determined based on measurement data of the secondary battery 210 acquired by the measurement unit 11. When the determination is based on measurement data, for example, the minimum value of the measured time-series data set (raw data), for example, for temperature, may be set as T ｍｉｎ , the maximum value is T ｍａｘ can be set to.

[0036] Next, the classification unit 14 selects which of the above-mentioned categories the representative value assigned to the time-series data, etc. by the assignment unit 13 corresponds to. In this way, the time-series data, etc. stored in the recording unit 12 are classified into each category. If the recording unit 12 stores multiple pieces of time-series data, etc. extracted at different times as described above, classification is performed for each piece of time-series data, etc.

[0037] If, as a result of classification, multiple pieces of data measured at different time points are assigned to the same section, the classification unit 14 processes the time series data so that the number of pieces of time series data for each of the current value, voltage value, and temperature is determined to be one. As a result, one relaxation spectrum is associated with one numerical range. The numerical range here is a numerical range included in at least two conditions of the current value, voltage value, or temperature, as described above. For example, in the case of temperature, the temperature range is T ｍｉｎ ~T １ , T １ ~T ２ , T ２ ~T ３ , ..., TＮ－１ ~T ｍａｘ Either of the following.

[0038] As a processing method, for example, only the most recently acquired data can be used. Alternatively, the result of taking the average of all data assigned to the same category can be used. Specifically, for example, if there is multiple time-series data of current values, the time-series data of the average current value can be created by taking the average of all the time-series data of current values.

[0039] The calculation unit 15 calculates spectral information representing the relaxation spectrum (an example of a spectrum). The spectral information may be a graph representing the relaxation spectrum, a function representing the relaxation spectrum, or the shape of the relaxation spectrum. The shape may include at least one of the number of peaks included in the relaxation spectrum, the positions of the peaks, the areas of the peaks, the half-widths of the peaks, and the skewness of the peaks, for example. The spectral information may be text information (e.g., numerical values) or information other than text information (e.g., shape).

[0040] The calculation unit 15 calculates the relaxation spectrum from time series data for at least one of the periods during constant voltage charging, after charging, and after discharging. The relaxation spectrum can be calculated using these time series data. A specific calculation method is as follows, but the calculation method is not limited to the following example.

[0041] <Calculation Method 1: Calculating the Relaxation Spectrum from Measurement Data During Constant-Voltage Charging> In this case, the relaxation spectrum ρ(τ) can be calculated from the equation (1) using the measurement data.

[0042]

[0043] ρ(τ) represents the relaxation spectrum, ΔV represents the difference between the battery voltage value before (preferably immediately before) the start of charging and the voltage value during constant voltage charging, and I(t) represents the time series data of the current value during constant voltage charging. －１ (reciprocal of a cursive capital letter L) denotes the inverse Laplace transform of I(t) / ΔV.

[0044] <Calculation Method 2: Calculating the Relaxation Spectrum from Measurement Data After Charging or Discharging> In this case, the relaxation spectrum ρ(τ) can be calculated from the following equation (2) using the measurement data.

[0045] ρ(τ) denotes the relaxation spectrum, and I ０ indicates the time series data of the current value immediately before the end of charging or discharging, and V(t) indicates the time series data of the voltage value after charging or discharging. －１ (the reciprocal of the capital letter L in cursive) is V(t) / I ０ shows the inverse Laplace transform of

[0046] Figure 2 is a map showing the calculation results of the relaxation spectrum for each temperature and each current value. As an example, Figure 2 shows an example in which temperatures are divided into T1 to T2, T2 to T3, and T3 to T4 (each of which represents a numerical range), and current values ​​are divided into I1 to I2, I2 to I3, and I3 to I4 (each of which represents a numerical range). Furthermore, for the nine relaxation spectra shown in Figure 2, the horizontal axis represents relaxation time, and the vertical axis represents spectral intensity, although these are omitted for the sake of simplicity. The same applies to Figures 3, 4, 11, and 12, which will be described later.

[0047] As described above, the calculation unit 15 (FIG. 1) calculates a relaxation spectrum for each category using the time-series data, etc., classified by the classification unit 14 (FIG. 1) into each category of temperature and current value. Therefore, for example, as a result of the classification, the relaxation spectrum calculated using the time-series data, etc., classified into the categories of temperatures T1 to T2 and current values ​​I1 to I2 is classified (stored) into the categories of temperatures T1 to T2 and current values ​​I1 to I2. Then, by classifying each relaxation spectrum into each category using each time-series data, etc., a map (relaxation spectrum map) such as that shown in FIG. 2 is obtained.

[0048] The mitigation spectrum is associated with the temperature of the secondary battery 210, as shown in FIG. 2, for example. The current value and voltage value capable of suppressing the occurrence of a battery abnormality may differ depending on the temperature of the secondary battery 210. In other words, even if the current value and voltage value are the same, the likelihood of a battery abnormality occurring may differ depending on the temperature of the secondary battery 210. Therefore, by determining the control conditions taking the temperature of the secondary battery 210 into consideration, it is possible to more effectively suppress a battery abnormality in the secondary battery 210. Note that, for example, depending on the installation environment of the secondary battery 210, the temperature of the secondary battery 210 may be predictable to some extent. Furthermore, the secondary battery 210 may be used at temperatures or for applications where a battery abnormality is unlikely to occur in the first place. Therefore, in these cases, the temperature need not be taken into consideration.

[0049] Furthermore, the relaxation spectra classified into each category are preferably based on time-series data measured over different periods. Note that the period referred to here is a period whose starting point is reset each time the secondary battery 210 is replaced, repaired, or the like. In FIG. 2 , the relaxation spectrum 200 preferably includes, for example, a first relaxation spectrum 221 calculated from time-series data from a first time to a second time, and a second relaxation spectrum 222 calculated from time-series data from a third time to a fourth time. By including multiple relaxation spectra 200, it is possible to determine the control conditions under which a battery abnormality occurs based on changes in the shape of the relaxation spectrum, as will be described in detail later.

[0050] 3 is a map showing the calculation results of the relaxation spectrum for each temperature and each voltage value in another embodiment. In FIG. 3, as an example, the temperatures are divided into T1 to T2, T2 to T3, and T3 to T4 (each of which is a numerical range), and the voltages are divided into V1 to V2, V2 to V3, and V3 to V4 (each of which is a numerical range).

[0051] 3 , the first range R1 includes temperatures T1 to T4 and voltages V1 to V3. Meanwhile, the second range R2 includes temperatures T1 to T4 and voltages V3 to V4. The half width of the peak of the second relaxation spectrum 222 included in the second range R2 is larger than the half width of the peak of the first relaxation spectrum 221 included in the first range R1.

[0052] As described above, the time series data of the present disclosure relates to current values ​​( FIG. 2 ), voltage values, and temperature. Therefore, while FIG. 2 shows a map relating to two of these, current values ​​and temperature, the map is not limited to current values ​​and temperature, and may also be a map relating to voltage values ​​and temperature as shown in FIG. 3 . The map of FIG. 3 can be created in the same manner as the embodiment of FIG. 2 above, except that time series data relating to voltage values ​​is used instead of current values.

[0053] 4 is a map showing the calculation results of the relaxation spectrum for each voltage value and each current value in another embodiment. In FIG. 4, as an example, the voltage values ​​are divided into V1 to V2, V2 to V3, and V3 to V4 (each of which is a numerical range), and the temperatures are divided into T1 to T2, T2 to T3, and T3 to T4 (each of which is a numerical range).

[0054] 4 , the first range R1 includes voltage values ​​V1 to T3 and current values ​​I1 to I3. On the other hand, the second range R2 includes voltage values ​​V3 to V4 and current values ​​I1 to I4, and voltage values ​​V1 to V4 and current values ​​I3 to I4. The half-width of the peaks of the second relaxation spectrum 222 included in the voltage values ​​V3 to V4 and current values ​​I1 to I4 (second range R2) is larger than the half-width of the peaks of the first relaxation spectrum 221 included in the first range R1. Furthermore, the number of peaks of the second relaxation spectrum 222 included in the voltage values ​​V1 to V4 and current values ​​I3 to I4 (second range R2) is larger than the number of peaks of the first relaxation spectrum 221 included in the first range R1.

[0055] As described above, the time-series data of the present disclosure relates to current values, voltage values, and temperature ( FIG. 2 ). Therefore, the present disclosure is not limited to the examples of FIGS. 2 and 3 , and may also use a map relating to voltage values ​​and current values ​​as shown in FIG. 4 . The map of FIG. 4 can be created in the same manner as in the embodiment of FIG. 2 , except that time-series data relating to voltage values ​​is used instead of temperature.

[0056] In the example of the present disclosure, for example, three maps shown in FIGS. 2 to 4 can be constructed based on time-series data of current values, voltage values, and temperature. Using the three maps allows more accurate control conditions to be determined. In particular, different control conditions may be determined between maps due to the influence of measurement errors, etc. In this case, the control conditions may be, for example, the conditions that place the smallest load on the secondary battery 210 (for example, the lowest current value and voltage value in the case of current values ​​and voltage values) or control conditions that are common between the maps.

[0057] 1 , the determination unit 16 determines the control conditions for the secondary battery 210 by using the shape information on the shape of the relaxation spectrum calculated by the calculation unit 15. As described above, the determined control conditions are control conditions for the secondary battery 210 that can suppress the occurrence of a battery abnormality in the secondary battery 210, such as the current value, voltage value, and temperature during charging and discharging.

[0058] Fig. 5 is a diagram showing an example of a relaxation spectrum 200. The relaxation spectrum 200 shown in Fig. 5 has two peaks 201 and 202. The positions of the peaks 201 and 202 correspond to relaxation times τ1 and τ2. The areas of the peaks 201 and 202 are S1 and S2. The half-widths of the peaks 201 and 202 are W1 and W2. The skewnesses of the peaks 201 and 202 are K1 and K2.

[0059] The shape information used by the determination unit 16 preferably includes a quantifiable index. Specifically, for example, the shape information preferably includes at least one of the number of peaks 201 and 202 in the relaxation spectrum 200, the positions of the peaks 201 and 202, the areas of the peaks 201 and 202, the half-widths of the peaks 201 and 202, and the skewness of the peaks 201 and 202. Since these are all quantifiable indexes, the possibility of abnormal degradation occurring can be determined using objective indexes when determining a battery abnormality, as will be described in detail later.

[0060] The determination unit 16 (FIG. 1) will be further described with reference to FIG. 2 above. Focusing on the number of peaks in the nine relaxation spectra shown in FIG. 2 , the second range R2, which covers temperatures T1 to T3 and current values ​​I3 to I4, has three peaks, unlike the two peaks in the first range R1, which is the other range. That is, when viewed from the perspective of the first range R1 other than the second range R2, which covers temperatures T1 to T3 and current values ​​I3 to I4, the number of peaks increases from the first range R1 to the second range R2. The first range includes the ranges of temperatures T1 to T4 and current values ​​I1 to I3, and the ranges of temperatures T3 to T4 and current values ​​I3 to I4.

[0061] As described above, the shape information of the relaxation spectrum corresponds to the occurrence of a reaction mode inside the secondary battery 210. Therefore, a change in the shape of the relaxation spectrum (e.g., an increase in the number of peaks) suggests the occurrence of a transient reaction mode. Therefore, the determination unit 16 determines the control conditions based on, for example, a change in the shape from the first relaxation spectrum 221 classified into the first range R1 to the second relaxation spectrum 222. This makes it possible to determine the control conditions under which a battery abnormality occurs, and therefore to determine the control conditions capable of suppressing the occurrence of a battery abnormality.

[0062] As described above, the number of peaks 201 and 202, the positions of the peaks 201 and 202, the areas of the peaks 201 and 202, the half-widths of the peaks 201 and 202, and the skewness of the peaks 201 and 202 in the relaxation spectrum 200 are all quantifiable indices. Therefore, if the shape of the relaxation spectrum changes, the changes in these indices can be expressed as a numerical "amount of change."

[0063] The determination unit 16 then determines that a battery abnormality will occur in the secondary battery 210 when the shape of the relaxation spectrum changes such that an index such as the number of peaks changes in a positive direction. For example, if the index is the number of peaks, the number of peaks changes in a positive direction (+1) from 2 (first range R1) to 3 (second range R2) as described above. Therefore, the determination unit 16 determines that a battery abnormality will occur at a temperature and current value in the second range R. Furthermore, in the case of the peak positions, although not shown in the drawings, if the relaxation times indicating the positions of the corresponding peaks in the relaxation spectra of the first range R1 and the second range R2 change, for example, from τ1 to τ2 (τ1 < τ2), it can be said that the relaxation times have changed in a positive direction.

[0064] When the index is the area of ​​a peak, although not shown in the figures, if the area of ​​a corresponding peak in each relaxation spectrum of the first range R1 and the second range R2 changes, for example, from S1 to S2 (S1 < S2), it can be said that the area has changed in a positive direction. The area of ​​the peak can be calculated using any method. When the index is the half-width of a peak, although not shown in the figures, if the half-width of a corresponding peak in each relaxation spectrum of the first range R1 and the second range R2 changes, for example, from W1 to W2 (W1 < W2), it can be said that the half-width has changed in a positive direction. The half-width of a peak can be calculated using any method. When the index is the skewness of a peak, although not shown in the figures, it can be said that the skewness has changed in a positive direction if the skewness of a corresponding peak in each relaxation spectrum of the first range R1 and the second range R2 changes, for example, from K1 to K2 (K1 < K2). The skewness of a peak can be calculated using any method.

[0065] As shown in FIG. 12 (described later), even if the area, half-width, skewness, etc. change in a positive direction (i.e., increase), it may be determined that no potential abnormality occurs. Therefore, a threshold value for the amount of change may be determined in advance for each quantifiable index, and a battery abnormality may be determined when a change occurs that exceeds the threshold value. Such a threshold value may be determined, for example, through experiments, simulations, trial runs, etc. Furthermore, to improve the accuracy of the determination, multiple indexes may be used for the determination.

[0066] The determination unit 16 then determines the control conditions so as to exclude any changes that are determined to result in a battery abnormality in the secondary battery 210. Specifically, with reference to FIG. 2 , the determination unit 16 determines that a battery abnormality will occur in, for example, a second range R2 in the map shown in FIG. 2 where, for example, the number of peaks increases compared to the first range R1, i.e., the number of peaks changes in the performance direction. As a result, the determination unit 16 determines that the conditions under which a battery abnormality will occur in the secondary battery 210 are the temperature and current values ​​corresponding to the second range R2. In this way, the secondary battery 210 can be controlled while avoiding the occurrence of a battery abnormality.

[0067] Furthermore, the determination unit 16 determines, as the control conditions, a current value less than the abnormal current value, a voltage value less than the abnormal voltage value, and a temperature less than the abnormal temperature, which correspond to the mitigation spectrum at which it is determined that a battery abnormality will occur in the secondary battery 210. This makes it possible to suppress the occurrence of a battery abnormality.

[0068] The control unit 17 controls the charging and discharging of the secondary battery 210 in accordance with the determined control conditions for the secondary battery 210. This effectively suppresses battery abnormalities in the secondary battery 210. In the example of the present disclosure, the control unit 17 controls the charging and discharging of the secondary battery 210 so as to suppress the frequency of use of the secondary battery 210 within the battery abnormality occurrence conditions (second range R2 ( FIG. 2 )) set by the determination unit 16. The charging and discharging control is performed by controlling the current value, voltage value, and temperature. Note that the control unit 17 does not completely reject use in the second range R2 as long as use in the second range R2 can be suppressed compared to when the determination system 100 of the present disclosure is not used. Note that the temperature of the secondary battery 210 can be controlled using a cooling mechanism, such as an air-cooling device such as a fan or a liquid-cooling device.

[0069] The secondary battery 210 to which the present disclosure is applicable includes any form, such as a secondary battery cell, a secondary battery module, a secondary battery pack, or a secondary battery system. The secondary battery 210 may be installed in, for example, electric mobility such as a ship, an aircraft, or a vehicle (such as a battery-powered train or an electric vehicle), or may be installed in a stationary battery storage system, or the use of the secondary battery 210 may be changed during use. For example, the present disclosure may be applicable to a case where a secondary battery 210 used in an electric mobility is reused as a stationary battery storage system.

[0070] Furthermore, the present disclosure can be applied regardless of the deterioration state of the secondary battery 210. For example, the secondary battery 210 may be a new (undegraded) battery, or a battery that has been used for some purpose and is in a deteriorated state (e.g., used, second-hand). It may also be a secondary battery 210 that has deteriorated over time as a result of not being used for a long period of time.

[0071] Furthermore, in addition to the application of suppressing the occurrence of battery abnormalities in the secondary battery 210, the present disclosure can also be applied to control for extending the life of the secondary battery 210 during use, suppressing deterioration, and the like.

[0072] The present disclosure can also be used to determine what applications new and used secondary batteries 210 are suitable for. The method for this determination is described below.

[0073] First, the secondary battery 210 is connected to a charge / discharge device (not shown), and the secondary battery 210 is charged / discharged under preset control conditions of current, voltage, and temperature. The time-series data obtained at this time is used to calculate the relaxation spectrum by the above-described method. Then, the calculated relaxation spectrum is used to determine control conditions that include at least two of the current, voltage, and temperature values ​​that do not cause a battery abnormality.

[0074] Next, the current, voltage, and temperature at which the secondary battery 210 will be used are evaluated for the intended application. For example, in the case of an electric vehicle, the current and voltage values ​​of the secondary battery 210 used to run the vehicle are determined based on the motor and inverter performance, and the temperature of the secondary battery 210 is predicted from the Joule heat generated at that time. In this way, it is evaluated whether the current, voltage, and temperature determined from the expected application of the secondary battery 210 fall within the current, voltage, and conditions determined from the relaxation spectrum. This makes it possible to determine whether the secondary battery 210 is suitable for the expected application.

[0075] Furthermore, the determination of the control conditions by the determination system 100 may be performed at any timing. For example, the control conditions may be determined when a product equipped with the secondary battery 210 is shipped from a factory, when the product is undergoing maintenance, etc. Then, subsequent control can be performed in accordance with the determined control conditions.

[0076] Furthermore, for example, when the determination system 100 and the secondary battery 210 are constantly connected via a network, the determination system 100 located in a remote location may constantly monitor the state of the secondary battery 210 and determine the control conditions, for example, at predetermined intervals. Then, each time the control conditions are determined, subsequent control can be performed using the determined control conditions.

[0077] Fig. 6 is a block diagram showing a determination system 100 according to another embodiment. A secondary battery 210 to be controlled by the determination system 100 shown in Fig. 6 includes a plurality of unit secondary batteries 211 connected to each other. The unit secondary batteries 211 are, for example, battery cells, battery modules, battery packs, battery systems, etc., and are battery modules in the illustrated example. Note that, in the example of Fig. 6, a plurality of unit secondary batteries 211 are connected to one determination system 100, but one determination system 100 may be connected to each unit secondary battery 211.

[0078] Furthermore, in the determination system 100 shown in FIG. 6 , the control unit 17 ( FIG. 1 ) performs different control for each unit secondary battery 211. Therefore, the secondary batteries 210 may all be unit secondary batteries 211 (e.g., new batteries) having similar characteristics, but it is preferable that at least some of them include degraded unit secondary batteries 211 (an example of a secondary battery, e.g., used secondary batteries). Depending on the operation of the battery system 300, new unit secondary batteries 211 and degraded unit secondary batteries 211 may be used together. Even in such a case, by performing different control for each unit secondary battery 211, it is possible to suppress battery abnormalities in each unit secondary battery 211.

[0079] First, by the method described above with reference to Figures 1 to 5, control conditions for suppressing the occurrence of battery abnormalities are determined for each unit secondary battery 211. That is, in the determination system 100 shown in Figure 6, the calculation unit 15 calculates spectrum information for each unit secondary battery 211. The determination unit 16 determines control conditions for each unit secondary battery 211. The determined control conditions are recorded in the recording unit 12 for each unit secondary battery 211.

[0080] When multiple unit secondary batteries 211 are connected to each other, the degree of deterioration of each unit secondary battery 211 may vary due to charging and discharging of the entire secondary battery 210. As a result, the current value, voltage value, and temperature that do not cause a battery abnormality may differ for each unit secondary battery 211. Therefore, the determination unit 16 determines control conditions that suppress the occurrence of battery abnormalities for each unit secondary battery 211, and determines control conditions that do not cause battery abnormalities in all unit secondary batteries 211. This makes it possible to suppress the occurrence of battery abnormalities in each unit secondary battery 211.

[0081] As described above, the secondary battery 210 is connected to a power consuming device 400 ( FIG. 1 ), such as a motor or an inverter. The current, voltage, and temperature used by the power consuming device 400 are expected to some extent depending on the application of the power consuming device 400. Therefore, the determination unit 16 determines, for each unit secondary battery 211, whether the current, voltage, and temperature planned for use by the power consuming device 400 are within the ranges of the control conditions determined for each unit secondary battery 211. If the determination result indicates that at least one of the planned (planned) current, voltage, and temperature deviates from the determined control conditions, the determination unit 16 restricts the deviating current, voltage, and temperature to fall within the ranges of the determined control conditions. The restriction may be performed, for example, so that the planned supply current, voltage, and temperature for each unit secondary battery 211 are set to the upper limit of the range of the determined control conditions. Alternatively, the restriction may be performed so that the control conditions of all unit secondary batteries 211 are common to all of the control conditions. After the above determination and appropriate restriction are performed for each of the unit secondary batteries 211 , power is supplied from the secondary batteries 210 to the power consuming devices 400 .

[0082] Although the discharging of the power consuming device 400 has been described above, the same determination and appropriate restriction may be made in the case of charging from the power source 500 as well.

[0083] Fig. 7 is a block diagram showing a determination system 100 according to another embodiment. The secondary battery 210 to be controlled by the determination system 100 shown in Fig. 7 includes a plurality of unit secondary batteries 211 connected to each other, similar to Fig. 6 above.

[0084] The determination system 100 shown in Fig. 7 further includes an update unit 18 in addition to the components of the determination system 100 shown in Fig. 1. The update unit 18 determines the control conditions again for each unit secondary battery 211 by the determination unit 16 when at least one of the current value, the current value, or the temperature changes during charge / discharge control of the secondary battery 210 by the control unit 17, and updates the determined control conditions as the control conditions by the control unit 17. By including the update unit 18, it is possible to suppress battery abnormalities in the unit secondary batteries 211 even when the state of the unit secondary batteries 211 changes during actual operation.

[0085] The update unit 18 may, for example, constantly monitor at least one of the current value, the current value, and the temperature, or may monitor at predetermined intervals (for example, every minute).

[0086] FIG. 8 is a block diagram showing a determination system 100 according to another embodiment. The determination system 100 shown in FIG. 8 further includes an output unit 19 in addition to the components of the determination system 100 shown in FIG. 1 . The output unit 19 outputs the determination result by the determination system 100 to an external device 600. The output determination result may be, for example, the determined control condition, the map described with reference to FIG. 2 , or at least a portion of the relaxation spectra included in the map. The output determination result may also be information such as a graph or function obtained by converting the determination result by the determination system 100 (e.g., the determined control condition) into the form of a graph described with reference to FIG. 17 .

[0087] The external device 600 may be, for example, a display device (display, monitor, etc.), an external storage device such as an HDD, or an external linked device that is provided independently of the determination system 100 and operates in conjunction with the determination system 100.

[0088] 9 is a block diagram showing the hardware configuration of the determination system 100. The determination system 100 is configured to include, for example, a CPU (Central Processing Unit) 1001, a RAM (Random Access Memory) 1002, a ROM (Read Only Memory) 1003, an I / F (Interface) 1004, a bus 1005, etc. The CPU 1001, RAM 1002, ROM 1003, and I / F 1004 are connected, for example, via the bus 1005. The determination system 100 is realized by a predetermined control program (e.g., the determination method of the present disclosure) stored in the ROM 1003 being loaded into the RAM 1002 and executed by the CPU 1001. Signals and information are exchanged between the determination system 100 and various devices (e.g., servers), external networks, etc., in terms of hardware, via the I / F 1004.

[0089] 10 is a flowchart showing the determination method of the present disclosure. The determination method of the present disclosure can be executed, for example, by the determination system 100 shown in FIG. 1. Therefore, the matters described with respect to the determination system 100 can be similarly applied to the determination method of the present disclosure.

[0090] The determination method of the present disclosure includes a measuring step S11, a recording step S12, an assigning step S13, a classifying step S14, a calculating step S15, a determining step S16, and a controlling step S17.

[0091] The measurement unit 11 measures time-series data of each value including a DC current value and at least one of a DC voltage value and the SOC of the secondary battery 210 during charging or discharging, which is at least one of charging and discharging of the secondary battery 210. The measurement step S11 can be executed by, for example, the measurement unit 11 (FIG. 1). The recording step S12 is a step of saving the measurement data of the secondary battery 210 extracted in the measurement step S11 (data including the time-series data, the voltage value before the start of charging, the current value immediately before charging or discharging, etc.). The recording step S12 can be executed by, for example, the recording unit 12 (FIG. 1).

[0092] The assigning step S13 is a step of assigning a label to each spectrum calculated from time-series data acquired between different times according to a predetermined rule using at least two of a DC current value, a DC voltage value, and a temperature. The assigning step S13 can be performed, for example, by the assigning unit 13 (FIG. 1). The classification step S14 is a step of classifying the relaxation spectra to which the label has been assigned so that the spectrum is associated with at least two conditions of a current value (DC current value), a voltage value (DC voltage value), and a temperature. The classification step S14 can be performed, for example, by the classifying unit 14 (FIG. 1).

[0093] The calculation step S15 is a step of calculating spectral information representing the relaxation spectrum (an example of a spectrum). The calculation step S15 can be performed by, for example, the calculation unit 15 (FIG. 1). The determination step S16 is a step of determining a control condition for the secondary battery 210 using shape information relating to the shape of the relaxation spectrum calculated in the calculation step S15. The determination step S16 can be performed by, for example, the determination unit 16 (FIG. 1).

[0094] The control step S17 is a step of controlling the charging and discharging of the secondary battery 210 in accordance with the control conditions for the secondary battery 210 determined in the determination step S16. The control step S17 can be executed by, for example, the control unit 17 (FIG. 1).

[0095] The present disclosure will be described in more detail below with reference to examples.

[0096] An evaluation test was actually conducted on the identification of conditions for battery abnormality occurrence using the determination system 100 and the control of the secondary battery 210 using the determination system 100 .

[0097] For the verification, a cylindrical lithium ion secondary battery (an example of the secondary battery 210) with a battery capacity of 5 Ah was used. The positive electrode (electrode 50 described below) contained LiNiMnCoO ２The secondary battery 210 was constructed by applying a coating of ZnO to a metal current collector, and the negative electrode was constructed of carbon. The measurement data used to calculate the relaxation spectrum were time-series data of the current, voltage, and temperature values ​​during use of the secondary battery 210. Furthermore, multiple time-series data during constant-voltage charging were extracted, and representative values ​​of the current and temperature and the relaxation spectrum were calculated from the extracted time-series data.

[0098] The representative current values ​​were divided into the following categories: 0 A to 25 A, 25 A to 50 A, 50 A to 75 A, 75 A to 100 A, and 100 A to 125 A. The representative temperature values ​​were divided into the following categories: 0 to 10°C, 10°C to 25°C, 25°C to 35°C, and 35°C to 45°C. The representative values ​​were then classified according to these categories.

[0099] Next, the relaxation spectrum was calculated for each of the time-series data classified into each section. If each section contained multiple pieces of time-series data acquired at different times, the relaxation spectrum was calculated using the time-series data acquired at the most recent time. For example, if a section designated by a current value of 0 A to 25 A and a temperature of 0°C to 10°C contained two types of time-series data acquired from time tA to time tB and from time tC to time tD (where tB<tC), the relaxation spectrum was calculated using the time-series data acquired from time tC to time tD.

[0100] Fig. 11 is a map showing the conditions for battery abnormality occurrence determined from the relaxation spectrum obtained through an actual evaluation test. In the map shown in Fig. 11, the conditions for battery abnormality occurrence were identified by focusing on the shape information of the obtained relaxation spectrum. Here, the number of peaks was used as the shape information of the relaxation spectrum. This is because, as mentioned above, the shape information of the relaxation spectrum corresponds to the reaction mode inside the battery, and in particular, an increase in the number of peaks on the relaxation spectrum suggests the occurrence of an abnormal reaction mode inside the battery.

[0101] FIG. 12 is a map obtained by an actual evaluation test, excluding the range in which battery abnormalities occur. The shaded area represents the second range R2, and the unshaded area represents the first range R1. The relaxation spectrum in the second range R2 is present in the following sections: a temperature of 0°C to 10°C and a current value of 50 A to 125 A; a temperature of 10°C to 25°C and a current value of 75 A to 125 A; and a temperature of 25°C to 35°C and a current value of 100 A to 125 A. The relaxation spectrum in the first range R1 is present in the following sections: a temperature of 0°C to 10°C and a current value of 0 A to 50 A; a temperature of 10°C to 25°C and a current value of 0 A to 75 A; a temperature of 25°C to 35°C and a current value of 0 A to 100 A; and a temperature of 35°C to 45°C and a current value of 0 A to 125 A.

[0102] Comparing the relaxation spectrum in the shaded second range R2 with the relaxation spectrum in the unshaded first range R1, the shaded relaxation spectrum has two peaks, while the unshaded relaxation spectrum has one peak. Therefore, the shaded second range R2 of the relaxation spectrum suggests the occurrence of an abnormal reaction mode within the battery. Therefore, it is believed that the occurrence of battery abnormalities can be suppressed by controlling the current value and temperature of the secondary battery 210 so as to minimize use of the secondary battery 210 under the temperature and current value conditions corresponding to the shaded first range R1.

[0103] Furthermore, to verify the effects of the present disclosure, it was verified whether or not a battery abnormality occurs when the secondary battery is controlled to avoid use under the temperature and current value conditions corresponding to the shaded relaxation spectrum in Fig. 9 (Condition 1, Example) and when the secondary battery is controlled to continue to be used primarily under those temperature and current value conditions (Condition 2, Comparative Example). In the verification, the secondary battery 210 that had been used continuously for about four months under Conditions 1 and 2 was disassembled, and it was investigated whether or not an abnormality occurred on the electrodes of the secondary battery 210.

[0104] 13 is a photograph of the surface of electrode 50 of secondary battery 210 (FIG. 1) used under Condition 1 (Example). As shown in FIG. 13, the surface of electrode 50 had a uniform appearance, and no abnormalities were found on the surface of electrode 50.

[0105] 14 is a photograph of the surface of the electrode 50 of the secondary battery 210 ( FIG. 1 ) used under Condition 2 (Comparative Example). As shown in FIG. 14 , a band-shaped deposition region 51 where lithium deposition abnormality occurred was confirmed on the surface of the electrode 50. Therefore, it was confirmed that the determination system 100 of the present disclosure can suppress the occurrence of battery abnormalities.

[0106] As another comparative example, the AC impedance method described in Patent Document 1 was also performed. However, it was not possible to measure time-series data on the current and voltage values ​​of the secondary battery 210. The reason for this is that, to obtain the results shown in Figures 11 and 12, a large current of up to approximately 100 A was applied to the secondary battery 210, but the voltage value reached an overvoltage value when the AC current value was applied, making it impossible to measure. As such, the results shown in Figures 11 and 12 can only be obtained by using DC current and DC voltage values, demonstrating that the present disclosure is more significant than the invention described in Patent Document 1.

[0107] Next, as another evaluation, the effectiveness of the present disclosure as a control method for suppressing deterioration of the secondary battery 210 and enabling the secondary battery 210 to be used for a long life was verified. In the verification, the secondary batteries 210 were used under conditions 1 and 2 determined in Figures 11 and 12 above, and the deterioration states after use were compared. Specifically, after about four months of use, the extent to which the battery capacity and internal resistance of each secondary battery 210 had deteriorated from when it was new was measured.

[0108] FIG. 15 shows the results of a verification showing the difference in battery capacity between the secondary battery 210 used under condition 1 (Example) and the secondary battery 210 used under condition 2 (Comparative Example). In FIG. 15 and FIG. 16 (described later), relative values ​​are shown when the battery capacity and internal resistance of a new (undegraded) secondary battery 210 are set to 100%. In FIG. 15 and FIG. 16 (described later), the numerical values ​​written above the bar graphs are the numerical values ​​used as the basis for creating the bar graphs shown below the numerical values. In FIG. 15, the vertical axis represents the capacity retention rate (%).

[0109] 15 , under condition 1 (Example), the battery capacity only decreased slightly (95.6%) even after about four months of use. On the other hand, under condition 2 (Comparative Example), the battery capacity decreased significantly after about four months of use, and the battery capacity decreased to about 75% (75.1%) of the battery capacity of a new secondary battery 210. Thus, it was found that by performing the control under condition 1, it is possible to suppress the decrease in battery capacity due to deterioration of the secondary battery 210.

[0110] 16 shows the results of verification showing the difference in internal resistance between the secondary battery 210 used under condition 1 (Example) and the secondary battery 210 used under condition 2 (Comparative Example). In FIG. 16, the vertical axis represents the resistance maintenance rate (%).

[0111] 16 , under condition 1 (Example), the internal resistance only increased slightly (107.4%) even after about four months of use. On the other hand, under condition 2 (Comparative Example), the internal resistance increased significantly after about four months of use, reaching about 1.9 times (187.1%) the internal resistance of a brand new secondary battery 210. Thus, it was found that the increase in internal resistance due to deterioration of the secondary battery 210 can be suppressed by controlling under condition 1.

[0112] 15 and 16 , by using the determination system 100, it is possible to perform charging and discharging in a manner that avoids a significant decrease in battery capacity and a significant increase in internal resistance. As a result, the present disclosure is effective in suppressing deterioration of the secondary battery 210, and a longer lifespan of the secondary battery 210 can be achieved.

[0113] REFERENCE SIGNS LIST 100 Determination system 11 Measurement unit 12 Recording unit 13 Assignment unit 14 Classification unit 15 Calculation unit 16 Determination unit 17 Control unit 18 Update unit 200 Relaxation spectrum 201 Peak 202 Peak 210 Secondary battery 211 Unit secondary battery 300 Battery system S11 Measurement step S12 Recording step S13 Assignment step S14 Classification step S15 Calculation step S16 Determination step S17 Control step

Claims

1. A determination system comprising: a calculation unit that calculates spectral information representing a spectrum in a two-axis coordinate system, one axis representing relaxation time and the other axis representing intensity, from time series data of each value including at least one of a DC current value and a DC voltage value or an SOC of the secondary battery during at least one of charging and discharging of the secondary battery; and a determination unit that determines control conditions for the secondary battery using shape information regarding the shape of the spectrum calculated by the calculation unit.

2. The determination system of claim 1, wherein the shape information includes at least one of the number of peaks in the spectrum, the position of the peak, the area of ​​the peak, the half-width of the peak, or the skewness of the peak.

3. The determination system according to claim 1, characterized in that the calculation unit calculates the spectrum from the time series data during at least one of the periods during constant voltage charging, after charging, and after discharging.

4. The determination system according to claim 1, characterized in that the time series data includes time series data of the temperature of the secondary battery, and the spectrum is associated with the temperature of the secondary battery.

5. The determination system according to claim 1, further comprising: an assignment unit that assigns a heading to each spectrum calculated from time series data acquired between different times in accordance with a predetermined rule using at least two of a DC current value, a DC voltage value, or a temperature; and a classification unit that classifies the spectrum to which the heading has been assigned so that it is associated with at least two conditions of a DC current value, a DC voltage value, or a temperature in accordance with the assigned heading.

6. The determination system according to claim 5, wherein each of the conditions includes a plurality of numerical ranges, and one of the numerical ranges is associated with one of the spectra.

7. The determination system described in claim 5, characterized in that the spectrum includes a first relaxed spectrum calculated from time series data from a first time to a second time and a second relaxed spectrum calculated from time series data from a third time to a fourth time, and the determination unit determines the control condition based on a change in shape from the first relaxed spectrum to the second relaxed spectrum.

8. The determination system described in claim 7, characterized in that the shape information regarding the shape includes a quantifiable index, and the determination unit determines that a battery abnormality will occur in the secondary battery when the shape changes such that the index changes in a positive direction, and determines the control conditions so as to exclude changes determined to cause a battery abnormality in the secondary battery.

9. The determination system according to claim 7, characterized in that the determination unit determines as the control condition a DC current value less than an abnormal DC current value, a DC voltage value less than an abnormal DC voltage value, or a temperature value less than an abnormal temperature corresponding to a spectrum in which it is determined that a battery abnormality will occur in the secondary battery.

10. The determination system of claim 1, wherein the secondary battery includes a depleted secondary battery.

11. The determination system according to claim 1, wherein the secondary battery includes a plurality of unit secondary batteries connected to each other.

12. The determination system according to claim 11, characterized in that the calculation unit calculates the spectrum information for each of the unit secondary batteries, and the determination unit determines the control condition for each of the unit secondary batteries.

13. The determination system according to claim 11, further comprising: a control unit which controls charging and discharging of the secondary battery in accordance with the determined control conditions of the secondary battery; and an update unit which, when at least one of a direct current value, a direct current value or a temperature changes during the charge and discharge control of the secondary battery by the control unit, determines again the control conditions for each unit secondary battery by the determination unit, and updates the determined control conditions as the control conditions by the control unit.

14. The determination system according to claim 1, further comprising a measurement unit that measures data relating to the secondary battery at a location different from the location where the secondary battery is installed.

15. A determination method comprising: a calculation step of calculating spectral information representing a spectrum in a two-axis coordinate system, one axis representing relaxation time and the other axis representing intensity, from time-series data of each value including at least one of a DC current value and a DC voltage value or an SOC of the secondary battery during at least one of charging and discharging of the secondary battery; and a determination step of determining control conditions for the secondary battery using shape information relating to the shape of the spectrum calculated in the calculation step.

Images