Secondary battery state determination device and secondary battery diagnosis method

Abstract

Provided is a secondary battery state determination device with which it is possible to determine the battery interior state from a total of one measurement on a secondary battery. The present invention is characterized by being provided with: a database in which are recorded relaxation spectra measured with respect to a plurality of secondary batteries, and the names of positive-electrode and negative-electrode active materials used in electrodes of the secondary batteries; a measurement unit that measures time-series data of a secondary battery being diagnosed; a calculation unit that calculates, from the time-series data measured by the measurement unit, the relaxation spectrum of the secondary battery being diagnosed; a comparison unit that acquires, from the database, the relaxation spectrum of a secondary battery matching the names of active materials used in the secondary battery being diagnosed, and compares the acquired relaxation spectrum with the relaxation spectrum calculated by the calculation unit; and a determination unit that, on the basis of the result of the comparison performed by the comparison unit, determines whether an abnormality has occurred in the secondary battery being diagnosed.

Description

Secondary battery state determination device and secondary battery diagnosis method

[0001] The present invention relates to a configuration of a secondary battery state determination device and a secondary battery diagnosis method using the same, and in particular to a technique that is effective when applied to evaluating the residual value of a secondary battery.

[0002] Lithium-ion secondary batteries (hereafter referred to as secondary batteries) are expected to be applied to a wide range of products, from electric mobility applications such as electric vehicles to stationary power sources, and their demand is steadily expanding. It is generally known that the lifespan of a secondary battery is closely related to its operating conditions, and continued use of a secondary battery under high-load conditions leads to rapid deterioration of battery performance (hereafter referred to as abnormal deterioration). Therefore, to ensure stable use of a secondary battery until the end of its product lifespan, it is important to properly assess the state of deterioration of the secondary battery.

[0003] In recent years, there have also been efforts to reuse used batteries from electric vehicles that have reached the end of their lifespan as stationary power sources. From the perspective of product reliability and safety, there has been a demand for a method to determine the state of deterioration of used batteries and whether or not they have abnormally deteriorated at the time of secondary reuse.

[0004] Examples of battery abnormalities include current concentration and lithium deposition. Current concentration, the former, is a degradation phenomenon that occurs when a secondary battery is used with a large current. A large current flows locally inside the battery, causing rapid degradation of that area. Lithium deposition, the latter, is a degradation phenomenon that occurs when a secondary battery is used at low temperatures and high voltages. Lithium ions are deposited on the negative electrode during the charge and discharge process, causing a deterioration in the capacity and resistance of the secondary battery. Furthermore, it has been reported that if the lithium deposition phenomenon continues to progress, it may eventually cause an internal short circuit in the secondary battery.

[0005] Therefore, studies are being conducted to analyze the internal state of a battery in order to detect abnormalities within the battery. For example, the abstract of Patent Document 1 states that "the analysis device includes a battery state analysis unit 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."

[0006] International Publication No. 2017 / 179266

[0007] To implement the method of Patent Document 1, it is necessary to compare the peak change in relaxation time in a predetermined frequency band before (when undegraded) and after (when degraded) the capacity or resistance of a secondary battery has deteriorated. Therefore, the method of Patent Document 1 requires measurements at least twice, once when undegraded and once when degraded.

[0008] Generally, measuring the battery state requires a certain amount of time and effort, so it is preferable to measure the battery state as few times as possible. Furthermore, the method of Patent Document 1 requires measuring the secondary battery before it is degraded, so it cannot be applied to applications other than those in which the secondary battery is used continuously from its undegraded state to its degraded state. For example, in the case of a used battery, the method of Patent Document 1 cannot be applied because measuring the used battery does not allow the secondary battery characteristics to be obtained when it is undegraded.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a secondary battery state determination device and a secondary battery diagnosis method that are capable of determining the internal state of a secondary battery from a total of one measurement of the battery.

[0010] In order to solve the above problems, the present invention is characterized by comprising a database that records relaxation spectra measured for a plurality of secondary batteries and the names of the positive and negative electrode active materials used in the electrodes of those secondary batteries; a measurement unit that measures time series data of the secondary battery to be diagnosed; a calculation unit that calculates the relaxation spectrum of the secondary battery to be diagnosed from the time series data measured by the measurement unit; a comparison unit that obtains from the database a relaxation spectrum of a secondary battery that matches the name of the active material used in the secondary battery to be diagnosed and compares it with the relaxation spectrum calculated by the calculation unit; and a determination unit that determines whether or not an abnormality has occurred in the secondary battery to be diagnosed based on the comparison result by the comparison unit.

[0011] The present invention also provides a method for diagnosing a secondary battery, comprising: (a) measuring time-series data of a secondary battery to be diagnosed; (b) calculating a relaxation spectrum of the secondary battery to be diagnosed from the time-series data measured in step (a); (c) obtaining, from a database, a relaxation spectrum of a secondary battery that matches the name of an active material used in the secondary battery to be diagnosed; (d) comparing the relaxation spectrum obtained in step (c) with the relaxation spectrum calculated in step (b); and (e) determining whether or not an abnormality has occurred in the secondary battery to be diagnosed based on the comparison result in step (d).

[0012] According to the present invention, it is possible to realize a secondary battery state determination device and a secondary battery diagnosis method that are capable of determining the internal state of a secondary battery from a total of one measurement of the battery.

[0013] This allows for an appropriate evaluation of the residual value of the secondary battery.

[0014] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0015] FIG. 1 is a diagram showing a schematic configuration of a secondary battery state determination device according to a first embodiment of the present invention; FIG. 2 is a diagram showing an example of a peak position of a relaxation spectrum; FIG. 3 is a diagram showing an example of a comparison result of a relaxation spectrum according to the present invention (before applying formula (3)); FIG. 4 is a diagram showing an example of a comparison result of a relaxation spectrum according to the present invention (after applying formula (3)); FIG. 5 is a diagram showing an example of a comparison result of a relaxation spectrum according to a second embodiment of the present invention; FIG. 6 is a diagram showing an example of a comparison result of a relaxation spectrum according to a third embodiment of the present invention; FIG. 7 is a diagram showing an example of a comparison result of a relaxation spectrum according to a third embodiment of the present invention (battery abnormality present); FIG. 8 is a flowchart showing a method for diagnosing a secondary battery according to a first embodiment of the present invention;

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same components or components having similar functions are designated by the same reference numerals, and detailed description of overlapping parts will be omitted.

[0017] In the following, a spectrum in a two-axis coordinate system in which one axis represents relaxation time and the other axis represents spectral intensity will be referred to as a relaxation spectrum or relaxation time distribution.

[0018] A secondary battery state determination device and a secondary battery diagnosis method according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4 and 7. FIG.

[0019] 1 is a block diagram showing a secondary battery state determination device 100 of this embodiment. As shown in FIG. 1, the secondary battery state determination device 100 of this embodiment uses measurement data for a battery system 200 or a secondary battery 210.

[0020] Here, the battery system 200 is a system that includes at least one or more secondary batteries 210 and a control device (not shown) for the secondary batteries 210. In the following, an example will be described in which the state determination device 100 is connected to the secondary battery 210, but the method of the present invention is not limited to the following embodiment and can be modified as desired within the scope that does not significantly impair the effects of the present invention.

[0021] The secondary battery state determination device 100 mainly comprises an input unit 10, a measurement unit 11, a calculation unit 12, a recording unit 13, a comparison unit 14, a determination unit 15, and an output unit 16. These may all be configured integrally, or at least some of them may be configured separately.

[0022] The input unit 10 inputs the names of the active materials used in the positive and negative electrodes of the secondary battery 210. An "active material" is one of the materials that make up the electrodes of a secondary battery. The active material plays a role in promoting the charge / discharge reaction of the secondary battery by storing and releasing lithium ions during charge / discharge. Typical active materials include graphite, lithium manganese oxide, and Li(NiMnCo)O. ２ There are no particular limitations on the input method to the input unit 10 as long as the input method can identify the active material used in the secondary battery 210.

[0023] For example, the substance name or composition formula may be input, or an abbreviation commonly used as a proper noun (e.g., Li(NiMnCo)O ２In this case, "NMC" may be input, or a data string used for machine learning such as a descriptor may be input.

[0024] 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 an SOC (States Of Charge) of the secondary battery 210 during charging or discharging, which is at least one of charging and discharging, of the secondary battery 210. That is, the time-series data includes time-series data of a DC current value and time-series data of at least one of a DC voltage value and an SOC of the secondary battery 210. The measurement is performed constantly or at predetermined time intervals (for example, every minute) during charging or discharging of the secondary battery 210, during use, including standby when charging or discharging is not performed, etc.

[0025] 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 measure time-series data of the SOC. In this embodiment, the time-series data may further include time-series data of the temperature of the secondary battery 210.

[0026] The measurement unit 11 extracts time-series data for a period (timing) during which a relaxation spectrum can be calculated from a collection of measured time-series data (so-called "raw data"). The relaxation spectrum is a continuous function of relaxation time, and is a relaxation spectrum (relaxation time distribution) 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 spectral intensity. To calculate the relaxation spectrum, it is preferable to use time-series data for at least one of the periods during constant-voltage charging, after charging, and 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.

[0027] 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 120 minutes or less, and more preferably 10 minutes or more and 60 minutes or less.

[0028] 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 120 minutes or less, and more preferably 10 minutes or more and 60 minutes or less.

[0029] The calculation unit 12 calculates the relaxation spectrum from time-series data during 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.

[0030] <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.

[0031] ρ(τ) = L －１ (I(t) / ΔV)...Equation (1) 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 denotes the inverse Laplace transform for I(t) / ΔV.

[0032] <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 equation (2) using the measurement data.

[0033] ρ(τ) = L －１ (V(t) / I ０ ) ... Equation (2) ρ(τ) indicates 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 (is V(t) / I ０ shows the inverse Laplace transform of

[0034] The recording unit 13 records, in association with each other, the relaxation spectrum measured for the secondary battery 210 that is not experiencing a battery abnormality and the name of the active material used in the secondary battery 210. The secondary battery 210 for recording data in the recording unit 13 may be a secondary battery different from the secondary battery 210 included in the battery system 200.

[0035] Here, "battery abnormality" refers to a degradation event such as current concentration or lithium deposition. Furthermore, a "secondary battery without a battery abnormality" refers to a secondary battery whose battery performance, such as capacity or resistance, is equal to or greater than the performance values ​​specified in the product specifications (i.e., in an undegraded state). Furthermore, "recorded in association with each other" means that the relaxation spectrum of the secondary battery 210 recorded in the recording unit 13 can be acquired based on the name of the active material used in the secondary battery 210.

[0036] The recording unit 13 preferably records relaxation spectra and names of active materials measured for a plurality of secondary batteries 210. In the plurality of secondary batteries 210, it is preferable that at least one of the active materials used in the positive and negative electrodes is different. For example, a secondary battery using graphite and lithium manganese oxide in the negative and positive electrodes, respectively, or a secondary battery using graphite and Li(NiMnCo)O in the negative and positive electrodes, respectively, may be used. ２It is preferable that the relaxation spectrum of a secondary battery using NMC (hereinafter referred to as "NMC") is recorded in the recording unit 13. Furthermore, it is particularly preferable that the relaxation spectrum of a secondary battery (half cell) using lithium metal in either the positive electrode or the negative electrode is recorded in the recording unit 13.

[0037] The comparison unit 14 compares the shape information of the relaxation spectrum in the calculation unit 12 with that in the recording unit 13 to determine whether or not a battery abnormality has occurred. The procedure for comparing the relaxation spectrum in the calculation unit 12 with that in the recording unit 13 is described below.

[0038] Based on the name of the active material of the secondary battery 210 acquired from the input unit 10, the comparison unit 14 searches the recording unit 13 for data on a secondary battery using the same active material, and acquires the relaxation spectrum measured in that secondary battery. If data that exactly matches the name of the active material of the secondary battery 210 is not present in the recording unit 13, the following process is performed.

[0039] (1) When there is no data matching the combination of the positive electrode and negative electrode of the secondary battery 210, in this case, the relaxation spectra of a half cell matching the name of the active material of the positive electrode of the secondary battery 210 and a half cell matching the name of the active material of the negative electrode of the secondary battery 210 are obtained from the recording unit 13. For example, when the secondary battery 210 is composed of graphite and lithium manganese oxide, the relaxation spectra of the half cells for graphite and lithium manganese oxide, respectively, are obtained from the recording unit 13.

[0040] (2) When the positive electrode, the negative electrode, or both of the secondary battery 210 are composed of multiple active materials and data corresponding to that combination does not exist: In this case, the relaxation spectrum of the half cell corresponding to each active material is obtained from the recording unit 13. For example, when the negative electrode of the secondary battery 210 is composed of graphite and the positive electrode is composed of lithium manganese oxide and NMC, the relaxation spectra of the half cells for graphite, lithium manganese oxide, and NMC are obtained from the recording unit 13.

[0041] (3) When the elemental mixing ratio of the active material used in the secondary battery 210 is different In this case, the relaxation spectrum of a secondary battery having a different elemental mixing ratio is obtained from the recording unit 13. For example, when the positive electrode active material of the secondary battery 210 is NMC and the elemental mixing ratio of N (nickel), M (manganese), and C (cobalt) is 8:1:1, the relaxation spectrum when the elemental mixing ratio is 1:1:1 may be obtained from the recording unit 13 and used as a substitute for the relaxation spectrum when the elemental mixing ratio is 8:1:1.

[0042] Next, the comparison unit 14 compares the shape information of the relaxation spectrum A obtained from the recording unit 13 with the relaxation spectrum B of the secondary battery 210 calculated by the calculation unit 12. For example, it is preferable to compare the number of peaks in the relaxation spectrum, the intensity of each peak, the position of each peak, the area of ​​each peak, the half-width of each peak, the skewness of each peak, and further the intensity ratio and area ratio thereof. Specifically, it is effective to normalize the relaxation spectra A and B and the relaxation time using the following formula (3) and compare the difference in their shapes on a graph.

[0043] J(τ*)=ρ(τ*) / ∫dτ*ρ(τ*)...Equation (3) However, τ*=τ / τ_peak.

[0044] Here, ∫dτ* represents the integral for the relaxation time τ*, and τ* represents the relaxation time τ normalized by the position τ_peak of the peak having the maximum area in the relaxation spectrum.

[0045] Fig. 2 shows a schematic example of the peak position (τ_peak) of the relaxation spectrum. Fig. 3A and Fig. 3B show the application and comparison of the above formula (3) to relaxation spectra A and B. Fig. 3A shows the results before applying formula (3), and Fig. 3B shows the results after applying formula (3).

[0046] When multiple relaxation spectra of half cells are obtained from the recording unit 13, these multiple relaxation spectra are summed to obtain relaxation spectrum A. An effective method for summing the relaxation spectra of each half cell is, for example, to use the following formula (4) to multiply the relaxation spectrum and the relaxation time by a constant and sum them. As an example, the following shows an example of a summing method when relaxation spectra for positive and negative electrode half cells are obtained from the recording unit 13.

[0047] ρ(τ) = a1 × ρ_positive electrode (a2 × τ) + b1 × ρ_negative electrode (b2 × τ) Equation (4) where a1, a2, b1, and b2 are constants, and ρ_positive electrode (τ) and ρ_negative electrode (τ) represent the relaxation spectra for the positive and negative electrode half-cells, respectively.

[0048] ρ(τ) in the above formula (4) is set as relaxation spectrum A and compared with relaxation spectrum B calculated by the calculation unit 12. At this time, various constants in formula (4) are determined so that X defined in the following formula (5) is minimized.

[0049] X = ∫dτ|ρ(τ) - ρ'(τ)| Equation (5) Here, ρ' represents relaxation spectrum B, and the symbol |A| means taking the absolute value of A. After determining each constant in relaxation spectrum A through the above procedure, the comparison unit 14 compares the shape information of relaxation spectrum A and B.

[0050] The determining unit 15 determines whether or not a battery abnormality has occurred in the secondary battery 210 based on the comparison result of the relaxed spectrum in the comparing unit 14. A method for determining a battery abnormality will be described below.

[0051] Since the number of peaks in the relaxation spectrum corresponds to the number of reaction processes inside the battery, an increase in the number of peaks suggests that an unsteady reaction is occurring inside the battery. Therefore, if the number of peaks in relaxation spectrum B is greater than that of relaxation spectrum A, it is determined that a battery abnormality has occurred.

[0052] Even if the number of peaks in the relaxation spectrum increases, it is difficult to accurately determine the number of peaks if the peak positions are close to each other. However, since changes appear in the peak intensity, area, half-width, etc., it is possible to determine that a battery abnormality has occurred when the difference in the peak intensity, area, or half-width between relaxation spectra A and B exceeds a predetermined threshold.

[0053] By following the above procedure, the state determination device 100 can determine whether or not a battery abnormality has occurred from a single measurement of the secondary battery 210. Therefore, it is not necessary to measure the secondary battery when it is not yet deteriorated, as in Patent Document 1, and the state can be determined even for a battery whose battery characteristics have already deteriorated, such as a used battery.

[0054] FIG. 7 shows a typical method for diagnosing a secondary battery using the state determination device 100 of this embodiment.

[0055] When the state determination device 100 starts the process, first, in step S1, the measuring unit 11 measures time-series data of the secondary battery to be diagnosed.

[0056] Next, in step S2, the calculation unit 12 calculates the relaxation spectrum of the secondary battery to be diagnosed from the time-series data measured in step S1.

[0057] Next, in step S3, the comparison unit 14 obtains from the recording unit 13 (database) the relaxation spectrum of a secondary battery that matches the name of the active material used in the secondary battery to be diagnosed.

[0058] Subsequently, in step S4, the comparison unit 14 compares the relaxation spectrum acquired from the recording unit 13 (database) with the relaxation spectrum calculated in step S2.

[0059] Next, in step S5, the determining unit 15 determines whether or not an abnormality has occurred in the secondary battery being diagnosed, based on the comparison result in step S4.

[0060] Finally, in step S6, the determination result in step S5 is output to the output unit 16 (display unit) to notify the user, and the process ends.

[0061] The secondary battery 210 to which the present invention can be applied 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 electric mobility such as a ship, an aircraft, or a vehicle (a battery-powered train or an electric vehicle), or may be installed in a stationary battery system, and the use of the secondary battery 210 may be changed during use. For example, the present invention can be applied to a case where a secondary battery 210 used in an electric mobility is reused as a stationary battery system.

[0062] A degraded secondary battery 210 was prepared, and a verification was conducted to determine whether the presence or absence of a battery abnormality could be determined from a single measurement using the state determination device 100. During the verification, the relaxation spectrum of a secondary battery using graphite and lithium manganese oxide for the negative electrode and the positive electrode, respectively, and the relaxation spectrum of a secondary battery using graphite and NMC for the negative electrode and the positive electrode, respectively, were recorded in the recording unit 13. The capacities of these secondary batteries were 50 Ah and 7 Ah, respectively, which were similar to the rated capacities described in the product specifications, and therefore the relaxation spectrum recorded in the recording unit 13 corresponds to the relaxation spectrum when the battery was not degraded.

[0063] As Example 1, an 18650-type secondary battery (battery capacity 2 Ah) was prepared, using graphite and NMC for the negative and positive electrodes, respectively. This secondary battery is different from the two secondary batteries recorded in the recording unit 13. Specifically, the external shapes of the secondary batteries recorded in the recording unit 13 are both rectangular, whereas the secondary battery used in Example 1 is cylindrical. Furthermore, the battery capacity of the former is 7 Ah to 50 Ah, while that of the latter is approximately 2 Ah.

[0064] The aforementioned 18650-type secondary battery 210 was placed in a 0°C environment and fully charged and fully discharged 100 times at a current value of 2 A, thereby causing the secondary battery capacity to deteriorate by approximately 20%. The deteriorated secondary battery 210 was connected to the state determination device 100, and material information for the positive and negative electrodes was input to the input unit 10. Furthermore, the secondary battery 210 was subjected to constant-current charging at a current value of 4 A from 3.8 V to 3.9 V, and when the voltage reached 3.9 V, the charging was switched to constant-voltage charging. Thereafter, constant-voltage charging continued for approximately one hour, and time-series data of voltage and current values ​​during charging was acquired by the measuring unit 11.

[0065] 4 shows the comparison result in the comparison unit 14 between the relaxation spectrum B of the secondary battery 210 calculated by the calculation unit 12 and the relaxation spectrum A acquired from the recording unit 13. In the comparison, the peak intensities and relaxation times of the relaxation spectra A and B were normalized using equation (3). From FIG. 4, it can be seen that the number of peaks in the relaxation spectrum B is greater than that in the relaxation spectrum A.

[0066] Based on the above results, the determining unit 15 determines that a battery abnormality has occurred in the secondary battery 210 and outputs the determination result to the output unit 16 .

[0067] To verify the above-mentioned determination result, the secondary battery 210 was disassembled and analyzed to check for the presence or absence of a battery abnormality. As a result, the occurrence of lithium deposition in the negative electrode of the secondary battery 210 was confirmed, and it was confirmed that the determination result was correct.

[0068] Second Embodiment A secondary battery state determination device and a secondary battery diagnosis method according to a second embodiment of the present invention will be described with reference to FIG.

[0069] In Example 2, the secondary battery 210 of Example 1 was placed in an environment of 25° C. and repeatedly charged and discharged 1000 times. The other test conditions and measurement conditions were the same as those of Example 1.

[0070] The comparison result of the relaxation spectra A and B in the comparison unit 14 in Example 2 is shown in Fig. 5. As can be seen from Fig. 5, the relaxation spectra A and B are in good agreement, and the determination unit 15 determines that no abnormality has occurred in the battery, and outputs the determination result to the output unit 16.

[0071] To verify the above-mentioned determination results, the secondary battery 210 was disassembled and analyzed to check for any abnormalities in the battery. As a result, no traces of lithium deposition or current concentration were found in the secondary battery 210, and it was confirmed that the determination results were correct.

[0072] Third Embodiment A secondary battery state determination device and a secondary battery diagnosis method according to a third embodiment of the present invention will be described with reference to FIGS. 6A and 6B.

[0073] In Example 3, the relaxation spectrum recorded in the recording unit 13 was replaced with data measured using a different secondary battery. A pouch-type secondary battery with a battery capacity of 34 mAh was prepared as the different secondary battery. The positive and negative electrode materials were lithium manganese oxide and graphite, and NMC and graphite, respectively. Using the data from the recording unit 13, the presence or absence of a battery abnormality was determined under the same conditions as in Examples 1 and 2.

[0074] 6A and 6B show the comparison results of the relaxation spectra A and B in the comparison unit 14 in Example 3. In this example, both cases where there is a battery abnormality and cases where there is no battery abnormality were confirmed.

[0075] 6A , it can be seen that when a battery abnormality occurs, the number of peaks in relaxation spectrum B is greater than that in relaxation spectrum A. Based on this result, the determination unit 15 determines that a battery abnormality has occurred in the secondary battery 210, and outputs the determination result to the output unit 16.

[0076] On the other hand, when there is no battery abnormality, as shown in FIG. 6B, the relaxation spectra A and B match well, and the determination unit 15 determines that there is no battery abnormality and outputs the determination result to the output unit 16.

[0077] The comparison results of Figures 6A and 6B are in good agreement with the comparison results of Example 1 (Figure 4) and Example 2 (Figure 5), and it was confirmed that the occurrence or non-occurrence of a battery abnormality can also be correctly determined in the case of Example 3.

[0078] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0079] 10...input section, 11...measuring section, 12...calculating section, 13...recording section, 14...comparing section, 15...determining section, 16...output section, 100...(secondary battery) state determination device, 200...battery system, 210...secondary battery.

Claims

1. A state determination device for a secondary battery, comprising: a database that records relaxation spectra measured for a plurality of secondary batteries and the active material names of the positive and negative electrodes used in those secondary batteries; a measurement unit that measures time-series data of the secondary battery to be diagnosed; a calculation unit that calculates the relaxation spectrum of the secondary battery to be diagnosed from the time-series data measured by the measurement unit; a comparison unit that acquires from the database the relaxation spectrum of a secondary battery that matches the active material name used in the secondary battery to be diagnosed and compares it with the relaxation spectrum calculated by the calculation unit; and a determination unit that determines whether an abnormality has occurred in the secondary battery to be diagnosed based on the comparison result in the comparison unit.

2. The state determination device for a secondary battery according to claim 1, wherein the relaxation spectrum is a relaxation time distribution in a two-axis coordinate system with one axis being the relaxation time and the other axis being the spectrum intensity.

3. The state determination device for a secondary battery according to claim 1, wherein the comparison unit compares the shape information of the relaxation spectrum, and the shape information includes at least one of the number of peaks, the intensity of the peaks, the position of the peaks, the area of the peaks, the half-value width of the peaks, and the skewness of the peaks in the relaxation spectrum.

4. The state determination device for a secondary battery according to claim 3, wherein the comparison unit normalizes and compares the area and relaxation time of the relaxation spectrum when comparing the shape information.

5. The state determination device for a secondary battery according to claim 1, wherein the secondary battery to be diagnosed is a secondary battery that has deteriorated due to being used in an electric mobility application including an electric vehicle and a battery electric train.

6. The state determination device for a secondary battery according to claim 1, wherein the secondary battery to be diagnosed is a secondary battery that has deteriorated due to being used as a stationary power source.

7. The state determination device for a secondary battery according to claim 1, wherein the database records the relaxation spectrum of a secondary battery in which lithium metal is used in at least one of the positive and negative electrodes.

8. A state determination device for a secondary battery according to claim 1, wherein the measurement unit measures time-series data of each value including at least one of a DC current value during charge and discharge of the secondary battery to be diagnosed and a DC voltage value or an SOC (state of charge). A state determination device for a secondary battery, characterized by this.

9. A state determination device for a secondary battery according to claim 1, wherein the calculation unit calculates a relaxation spectrum of the secondary battery to be diagnosed from time-series data in at least one of the periods during constant voltage charging, after charging, and after discharging of the secondary battery to be diagnosed. A state determination device for a secondary battery, characterized by this.

10. A method for diagnosing a secondary battery, comprising: (a) a step of measuring time-series data of the secondary battery to be diagnosed; (b) a step of calculating a relaxation spectrum of the secondary battery to be diagnosed from the time-series data measured in step (a); (c) a step of obtaining from a database a relaxation spectrum of a secondary battery that matches the name of the active material used in the secondary battery to be diagnosed; (d) a step of comparing the relaxation spectrum obtained in step (c) with the relaxation spectrum calculated in step (b); and (e) a step of determining whether an abnormality has occurred in the secondary battery to be diagnosed based on the comparison result in step (d). A method for diagnosing a secondary battery, characterized by having these steps.

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