Electronic apparatus and analysis method

Abstract

To provide an electronic apparatus and an analysis method that can perform analysis of deterioration in various deterioration modes.SOLUTION: An electronic apparatus according to an aspect of the present technique comprises a measurement unit, a storage unit, a calculation unit, and an analysis unit. The measurement unit measures, during and after charging or discharging of a battery pack formed by including a plurality of electric cells, the voltage and current of the plurality of electric cells included in the battery pack. The storage unit stores a voltage value and a current value obtained through the measurement performed by the measurement unit. The calculation unit calculates, for each of the electric cells, two or more circuit constants of an equivalent circuit of the electric cell, by using the voltage value and the current value stored in the storage unit. The analysis unit performs multivariate analysis by using information on the distribution of the two or more circuit constants in the plurality of electric cells or information on the distribution of two or more circuit constants in a plurality of normal batteries.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present technology relates to an electronic device and an analysis method. [Background technology]

[0002] In recent years, the use of secondary batteries has expanded to larger-scale devices such as electric vehicles and energy storage systems. The larger the device, the greater the damage caused by a fire, so the importance of developing technology to improve safety is increasing. In addition, it is important to properly understand abnormal behavior and deterioration of secondary batteries during use.

[0003] In Patent Document 1, attention is focused on the internal resistance as a circuit constant used to determine the deterioration of a secondary battery. In Patent Document 1, coulomb counting is performed during CV charging in CCCV charging, and the internal resistance is calculated with high accuracy based on the charged electrical quantity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-152755 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 requires only one circuit constant, the internal resistance, and is insufficient as a method for determining the deterioration of a secondary battery, since it is unable to express the deterioration phenomenon of the secondary battery from multiple perspectives. Therefore, it is desirable to provide an electronic device and an analysis method that can handle multiple circuit constants and can analyze deterioration due to various deterioration modes. [Means for solving the problem]

[0006] An electronic device according to a first aspect of the present technology includes a measurement unit, a storage unit, a calculation unit, and an analysis unit. The measurement unit measures the voltage and current of a plurality of cells included in a battery pack during and after charging or discharging the battery pack including the plurality of cells. The storage unit stores the voltage and current values ​​obtained by the measurement by the measurement unit. The calculation unit calculates two or more circuit constants of an equivalent circuit of the cells for each cell using the voltage and current values ​​stored in the storage unit. The analysis unit performs multivariate analysis using distribution information of the two or more circuit constants in the plurality of cells or distribution information of the two or more circuit constants in a plurality of normal batteries.

[0007] An electronic device according to a second aspect of the present technology includes a measurement unit, a storage unit, a calculation unit, and an analysis unit. The measurement unit measures the voltage and current of the cell during and after charging or discharging the cell. The storage unit stores the voltage and current values ​​obtained by the measurement by the measurement unit. The calculation unit calculates two or more circuit constants of an equivalent circuit of the cell using the voltage and current values ​​stored in the storage unit. The analysis unit performs multivariate analysis using distribution information of the two or more circuit constants in a plurality of normal batteries.

[0008] The analysis method according to the third aspect of the present technology includes the following four steps. (A) A measuring step for measuring the voltage and current of a plurality of single cells included in a battery pack during and after charging or discharging the battery pack including a plurality of single cells. (B) a storage step of storing the voltage and current values ​​obtained in the measurement step (C) a calculation step of calculating two or more circuit constants of an equivalent circuit of the unit cell for each unit cell using the voltage value and the current value stored in the storage step. (D) a solution process for performing a multivariate analysis using distribution information of two or more circuit constants in a plurality of single cells or distribution information of two or more circuit constants in a plurality of normal batteries.

[0009] The analysis method according to the fourth aspect of the present technology includes the following four steps. (A) A measurement step for measuring the voltage and current of a cell during and after charging or discharging the cell. (B) a storage step of storing the voltage and current values ​​obtained in the measurement step (C) a calculation step of calculating two or more circuit constants of an equivalent circuit of a single battery using the voltage value and the current value stored in the storage step (D) A solution process for performing multivariate analysis using distribution information of two or more circuit constants in multiple normal batteries. Effect of the Invention

[0010] According to the electronic device relating to the first aspect of the present technology and the analysis method relating to the third aspect of the present technology, a multivariate analysis is performed using distribution information of two or more circuit constants in a plurality of single cells, or distribution information of two or more circuit constants in a plurality of normal batteries, so that it is possible to analyze the deterioration of a secondary battery due to various deterioration modes.

[0011] According to the electronic device relating to the second aspect of the present technology and the analysis method relating to the fourth aspect of the present technology, a multivariate analysis is performed using distribution information of two or more circuit constants in a plurality of normal batteries, making it possible to analyze the deterioration of a secondary battery due to various deterioration modes.

[0012] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram illustrating an example of a functional block of an analysis device according to an embodiment of the present technology. [Diagram 2] FIG. 2 is a diagram showing an equivalent circuit of a secondary battery that is the subject of analysis by the analysis apparatus of FIG. [Diagram 3] FIG. 2 is a diagram illustrating an example of an analysis procedure in the analysis device of FIG. [Figure 4] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Diagram 5] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 6] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 7] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 8] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 9] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 10] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 11] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 12] 2 is a diagram illustrating an example of an analysis result in the analysis device of FIG. 1. [Figure 13] FIG. 13 is a diagram illustrating a modified example of a functional block of an analysis device according to an embodiment of the present technology. [Figure 14] FIG. 13 is a diagram illustrating a modified example of a functional block of an analysis device according to an embodiment of the present technology. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present technology will be described in detail with reference to the drawings.

[0015] <1. Embodiment> [composition] A configuration of an analysis device 10 according to an embodiment of the present technology will be described. The analysis device 10 is a device that analyzes the deterioration state of a secondary battery. In this embodiment, a secondary battery to be analyzed by the analysis device 10 is an assembled battery 20. The assembled battery 20 is, for example, a lithium ion secondary battery. The assembled battery 20 is configured to include a plurality of single cells 21. Each single cell 21 may be a unit cell, or may be a battery block in which a plurality of unit cells are connected. In each single cell 21, a plurality of secondary batteries may be connected in series, or a plurality of secondary batteries may be connected in parallel.

[0016] The analysis device 10 includes, for example, a charge / discharge unit 11, a voltage measurement unit 12, a current measurement unit 13, a temporary storage unit 14, a circuit constant calculation unit 15, and a multivariate analysis unit 16, as shown in FIG.

[0017] The charging / discharging unit 11 is a device that charges and discharges the assembled battery 20 installed in the analysis device 10. The charging / discharging unit 11 is capable of, for example, CCCV charging as charging. The charging / discharging unit 11 has a charging circuit that includes, for example, a generator and a converter. This charging circuit controls the voltage for charging the assembled battery 20.

[0018] The voltage measurement unit 12 has a measurement circuit that measures the voltage of each cell 21 included in the assembled battery 20. Note that, although FIG. 1 illustrates a configuration in which wiring is connected to the positive and negative electrodes of each cell 21 and the voltage of each cell 21 is measured by measuring the voltage obtained through the wiring, the method of measuring the voltage of each cell 21 is not limited to this method. The voltage measurement unit 12 stores data (voltage value) on the voltage measured by the measurement circuit in the temporary storage unit 14. The voltage measurement unit 12 measures the voltage of each cell 21 during and after charging or discharging the assembled battery 20 (steps S102 and S106 in FIG. 3).

[0019] The current measurement unit 13 has a measurement circuit that measures the current of each cell 21 included in the battery pack 20. Although FIG. 1 illustrates a configuration in which wiring is connected to the positive and negative electrodes of the battery pack 20 and the current of each cell 21 is measured by measuring the current acquired through the wiring, the method of measuring the current of each cell 21 is not limited to this method. The current measurement unit 13 stores data (current value) on the current measured by the measurement circuit in the temporary storage unit 14. The current measurement unit 13 measures the current of each cell 21 (i.e., the current of the battery pack 20) ​​during and after charging or discharging the battery pack 20 (steps S102 and S106 in FIG. 3).

[0020] The temporary storage unit 14 includes, for example, a volatile memory or a non-volatile memory. The temporary storage unit 14 stores the voltage value of each cell 21 measured by the voltage measurement unit 12 and the current value of each cell 21 measured by the current measurement unit 13. The temporary storage unit 14 stores the voltage values ​​and current values ​​measured during and after charging or discharging the battery pack 20 (steps S103 and S107 in FIG. 3).

[0021] The circuit constant calculation unit 15 calculates two or more circuit constants of the equivalent circuit of each cell 21 using the voltage and current values ​​during and after charging or discharging for each cell 21 stored in the temporary memory unit 14 (step S109 in FIG. 3).

[0022] Fig. 2 shows an equivalent circuit of each unit cell 21. As shown in Fig. 2, each unit cell 21 is represented by an equivalent circuit consisting of six elements: inductance L, solution resistance Rs, charge transfer resistance Rct, Warburg impedance σ, constant phase element CPE related to electric double layer capacitance Cdl, and differential capacitance C'. The following eight circuit constants of these six elements are calculated by curve fitting.

[0023] (8 circuit constants) Inductance L ·Solution resistance Rs ·Charge transfer resistance Rct Warburg impedance σ Parameters p and T for describing the constant phase element CPE (hereafter referred to as CPE(p) and CPE(T) respectively) ·Differential capacity C' Electric double layer capacitance Cdl

[0024] The inductance L, solution resistance Rs, charge transfer resistance Rct, Warburg impedance σ, parameter CPE(p), parameter CPE(T) and differential capacitance C' can be obtained, for example, as the output of analysis software EIS manufactured by Hokuto Denko Co., Ltd. The electric double layer capacitance Cdl is calculated by the following formula described in "Electrochemical Impedance Method" by Masayuki Itagaki, Maruzen Publishing (p.84). Cdl = CPE(T) (1 / CPE(p)) Rct ((1-CPE(p)) / CPE(p))

[0025] The multivariate analysis unit 16 derives distribution information of two or more circuit constants in the plurality of unit cells 21, and performs multivariate analysis using the distribution information thus obtained (step S110 in FIG. 3). The multivariate analysis unit 16 uses, for example, the Mahalanobis-Taguchi method or the one-class support vector machine method as a method of multivariate analysis. The multivariate analysis using the Mahalanobis-Taguchi method will be described in detail below. The multivariate analysis unit 16 derives the degree of anomaly ai for each unit cell 21, for example, by performing the following multivariate analysis.

[0026] (Preparation of the sample lithium-ion battery) Thirteen commercially available lithium-ion batteries US18650FTC1 (rated capacity 1.05Ah) whose main positive electrode active material is lithium iron phosphate (LiFePO4, LFP) and whose main negative electrode active material is graphite were prepared. All of them were from the same manufacturing lot. Ten of them were first discharged at a constant current equivalent to a 0.2 hour rate (the rated capacity is 1.05Ah, and the current value It at the 1 hour rate is 1.05A, so the current value I at the 0.2 hour rate is 0.2I = 210mA) until the voltage fell below 2.0V, and then immediately charged with CCCV at a set current of 1.05A (=1It) and a set voltage of 3.6V (a two-step charge in which constant current charging at a set current value is performed until the set voltage is reached, and constant voltage charging is performed when the set voltage is reached), and this was stopped 2.5h after the start of charging. While maintaining the batteries in a fully charged state, each of the 10 lithium-ion batteries was placed in a thermostatic chamber set to one of 10 different temperatures: 45°C, 50°C, ..., 90°C, and left there for 25 days to deteriorate.

[0027] (AC impedance measurement) To measure the circuit constants of the battery, the charging state was adjusted first. The battery was placed in a thermostatic bath at 23°C and CCCV charging was performed with a set current of 1.05A (=1It) and a set voltage of 3.6V. This CCCV charging was stopped when the current value during constant voltage charging fell below 105mA (=0.1It). After that, the battery was left in an open state for 1h, and AC impedance measurement was performed. SP-240 manufactured by Bio-Logic was used for AC impedance measurement. Regarding the measurement conditions, first, the control was set to potentiostatic mode regulated by voltage, and the effective value of the amplitude was set to 5mV. In addition, the center voltage and the open circuit voltage were made to match so that no bias current would flow during the measurement. The frequency sweep range was from 10kHz to 1mHz, and a logarithmic sweep was performed with five measurement points per digit of frequency. In addition, measurements were performed twice for each frequency to reduce random noise. Of the 13 lithium-ion batteries prepared, the three lithium-ion batteries that had not undergone the above-mentioned deterioration process were subjected to AC impedance measurements four times, while the 10 lithium-ion batteries that had undergone the above-mentioned deterioration process were subjected to AC impedance measurements only once.

[0028] (Multivariate analysis) For three lithium-ion batteries that had not undergone the above-mentioned deterioration process, AC impedance measurements were performed four times for each battery. The obtained data (each set containing eight circuit constants) were defined as 12 vectors xi (where i is an integer from 1 to 12) as shown in the following formula (1).

number

[0029] Next, the average value vector μ of the 12 sets of data for each circuit constant and the variance-covariance matrix Σ were calculated using equations (2) and (3), respectively.

number

number

[0030] Next, 10 sets of data (each of which also contains 8 circuit constants) obtained from 10 lithium-ion batteries that had undergone the above-mentioned degradation process were defined as 10 additional vectors xi (where i is an integer between 13 and 22) as shown in equation (4). Then, the degree of anomaly ai was calculated for all 22 vectors according to equation (5).

number

number

[0031] For comparison, we also calculated the degree of abnormality using only one circuit constant instead of multiple variables (Figures 4 to 11). In addition, for all results, we calculated the thresholds for determining whether or not there was an abnormality from the 95th and 99th percentiles in the F distribution table.

[0032] In addition, the results of the degree of anomaly calculated using all eight circuit constants are shown in Figure 12. In both figures, "A" to "L" on the horizontal axis are data obtained from batteries that have not undergone the above-mentioned deterioration process, which corresponds to i = 1, 2, ..., 12 in formula (5). Also, "M" to "V" on the horizontal axis are data obtained from batteries that have undergone the above-mentioned deterioration process, which corresponds to i = 13, 14, ..., 22 in formula (5). Since "A" to "L" have not undergone the above-mentioned deterioration process, in the following discussion, these are considered to be data obtained from good batteries (normal batteries). On the other hand, "M" to "V" are data obtained from batteries stored at storage temperatures of 45°C, 50°C, ..., 90°C, respectively, and the closer they are to Z, the greater the degree of deterioration, and all of them are considered to be data obtained from defective batteries.

[0033] From Figures 4 and 5, no clear difference in the degree of abnormality was found between the "A" to "L" batteries, which were deemed to be good products, and the "M" to "V" batteries, which were deemed to be bad products. In other words, it was found that it is not possible to judge whether a product is good or bad using only the impedance L or the solution resistance Rs.

[0034] Figures 6, 7 and 10 show that there is a tendency for the defective batteries to have a higher degree of abnormality than the "A" to "L" batteries, which were deemed to be good products, and the "M" to "V" batteries, which were deemed to be defective products. However, there is no clear difference between the two, which means that it is difficult to judge whether a product is good or defective using only one of the parameters CPE(p), CPE(T) and differential capacity C'.

[0035] Figures 8 and 9 show a clear tendency that defective batteries have a higher degree of abnormality than "A" to "L" batteries, which were deemed to be good products, and "M" to "V" batteries, which were deemed to be defective products. In other words, it was suggested that charge transfer resistance Rct and Warburg impedance σ are capable of determining whether a product is good or defective even when only one circuit constant is used. On the other hand, regardless of which circuit constant is used, when the degree of deterioration is small, such as "M" and "N", the degree of abnormality falls below the 95% threshold, making it difficult to find a significant difference from good products, and therefore it was found that there is a slight problem in terms of sensitivity.

[0036] From Figure 11, a clear tendency was observed in which the defective batteries had higher abnormalities than the "A" to "L" batteries, which were deemed to be good products, and the "M" to "V" batteries, which were deemed to be defective products. Even "M" and "N" batteries had abnormalities that exceeded the 99% threshold, which means that the electric double layer capacitance Cdl can be used to determine whether a product is good or defective, even when only one circuit constant is used.

[0037] Figure 12 shows a clear tendency for the degree of abnormality to be higher for defective batteries, between "A" through "L" batteries considered to be good and "M" through "V" batteries considered to be defective. Comparing Figures 11 and 12, in Figure 11, even among "A" through "L" batteries considered to be good, some have an abnormality degree close to the 95% threshold. On the other hand, in Figure 12, the abnormality degrees for "A" through "L" are all very small, which means that by using all eight circuit constants using the Mahalanobis-Taguchi method, it is possible to judge whether a product is good or defective with higher sensitivity.

[0038] For the above reasons, the multivariate analysis unit 16 selects, in the multivariate analysis, two or more circuit constants in the plurality of single cells 21, including at least a circuit constant related to a physical phenomenon causing a transient response. Such circuit constants include at least the electric double layer capacitance Cdl or the charge transfer resistance Rct.

[0039] The two or more circuit constants in the plurality of unit cells 21 selected in the multivariate analysis include, for example, the electric double layer capacitance Cdl and at least one of the inductance L, the solution resistance Rs, the charge transfer resistance Rct, the Warburg impedance σ, the parameter CPE(p), the parameter CPE(T), and the differential capacitance C'. Also, the two or more circuit constants in the plurality of unit cells 21 selected in the multivariate analysis include, for example, the charge transfer resistance Rct and at least one of the inductance L, the solution resistance Rs, the Warburg impedance σ, the parameter CPE(p), the parameter CPE(T), and the differential capacitance C'.

[0040] [effect] Next, the effects of the analysis device 10 will be described.

[0041] In recent years, the use of secondary batteries has expanded to larger-scale devices such as electric vehicles and energy storage systems. The larger the device, the greater the damage caused by a fire, so the importance of developing technology to improve safety is increasing. In addition, it is important to properly understand abnormal behavior and deterioration of secondary batteries during use.

[0042] In Patent Document 1, the internal resistance is focused on as a circuit constant used to determine the deterioration of a secondary battery. In Patent Document 1, coulomb counting is performed during CV charging in CCCV charging, and the internal resistance is calculated with high accuracy based on the charged electric quantity. However, the method described in Patent Document 1 cannot express the transient response of a secondary battery, and therefore cannot analyze deterioration from multiple angles, and is insufficient as a method for determining deterioration of a secondary battery.

[0043] On the other hand, in this embodiment, a multivariate analysis is performed using distribution information of two or more circuit constants in a plurality of single cells 21, or distribution information of two or more circuit constants in a plurality of normal batteries, so that it is possible to perform a multifaceted analysis, including degradation modes caused by the transient response of the secondary battery.

[0044] In this embodiment, for example, as shown in Fig. 13, multivariate analysis unit 16 may perform multivariate analysis using distribution information stored in storage unit 17 instead of distribution information of two or more circuit constants in a plurality of single cells 21. The distribution information stored in storage unit 17 is distribution information of two or more circuit constants in a plurality of normal batteries.

[0045] In this case, the two or more circuit constants in the plurality of normal batteries selected in the multivariate analysis include, for example, the electric double layer capacitance Cdl and at least one of the inductance L, the solution resistance Rs, the charge transfer resistance Rct, the Warburg impedance σ, the parameter CPE(p), the parameter CPE(T), and the differential capacitance C'. Also, the two or more circuit constants in the plurality of normal batteries selected in the multivariate analysis include, for example, the charge transfer resistance Rct and at least one of the inductance L, the solution resistance Rs, the Warburg impedance σ, the parameter CPE(p), the parameter CPE(T), and the differential capacitance C'.

[0046] In this embodiment, the secondary battery to be analyzed by the analysis device 10 may be, for example, a single cell 30 as shown in FIG. 14. In this case, the single cell 30 may be a unit cell or a battery block in which a plurality of unit cells are connected. In the single cell 30, a plurality of secondary batteries may be connected in series, or a plurality of secondary batteries may be connected in parallel. In this case, the multivariate analysis unit 16 may perform multivariate analysis using distribution information stored in the storage unit 17 instead of distribution information of two or more circuit constants in a plurality of single cells 21 as shown in FIG. 14. The distribution information stored in the storage unit 17 is distribution information of two or more circuit constants in a plurality of normal batteries. [Explanation of symbols]

[0047] 10...analysis device, 11...charging / discharging section, 12...voltage measurement section, 13...current measurement section, 14...temporary memory section, 15...circuit constant calculation section, 16...multivariate analysis section, 17...memory section, 20...battery pack, 21...single cell, 30...single cell.

Claims

1. a measurement unit that measures a voltage and a current of a plurality of single cells included in a battery pack configured to include a plurality of single cells during and after charging or discharging the battery pack; a storage unit that stores the voltage value and the current value obtained by the measurement by the measurement unit; a calculation unit that calculates two or more circuit constants of an equivalent circuit of the battery cell for each battery cell by using the voltage value and the current value stored in the storage unit; an analysis unit that performs multivariate analysis using distribution information of the two or more circuit constants in the plurality of single cells or distribution information of the two or more circuit constants in a plurality of normal batteries; Equipped with electronic equipment.

2. A measurement unit that measures the voltage and current of the battery cell during and after charging or discharging the battery cell; a storage unit that stores the voltage value and the current value obtained by the measurement by the measurement unit; a calculation unit that calculates two or more circuit constants of an equivalent circuit of the battery cell using the voltage value and the current value stored in the storage unit; an analysis unit that performs multivariate analysis using distribution information of the two or more circuit constants in a plurality of normal batteries; Equipped with electronic equipment.

3. The multivariate analysis method is the Mahalanobis-Taguchi method.

3. The electronic device according to claim 1 or 2.

4. The multivariate analysis method is a one-class support vector machine method.

3. The electronic device according to claim 1 or 2.

5. The two or more circuit constants include an electric double layer capacitance. The electronic device according to claim 1 .

6. The two or more circuit constants include a charge transfer resistance. The electronic device according to claim 1 .

7. a measuring step of measuring a voltage and a current of a plurality of single cells included in a battery pack during and after charging or discharging the battery pack including the plurality of single cells; a storage step of storing the voltage value and the current value obtained in the measurement step; a calculation step of calculating, for each of the unit cells, two or more circuit constants of an equivalent circuit of the unit cells using the voltage value and the current value stored in the storage step; an analysis step of performing a multivariate analysis using distribution information of the two or more circuit constants in the plurality of single cells or distribution information of the two or more circuit constants in a plurality of normal batteries; Includes Analysis method.

8. measuring the voltage and current of the cell during and after charging or discharging the cell; a storage step of storing the voltage value and the current value obtained in the measurement step; a calculation step of calculating two or more circuit constants of an equivalent circuit of the battery cell using the voltage value and the current value stored in the storage step; A solution process of performing a multivariate analysis using distribution information of the two or more circuit constants in a plurality of normal batteries; Includes Analysis method.

9. The multivariate analysis method is the Mahalanobis-Taguchi method. The analysis method according to claim 7 or 8.

10. The multivariate analysis method is a one-class support vector machine method. The analysis method according to claim 7 or 8.

11. The two or more circuit constants include an electric double layer capacitance. The analysis method according to any one of claims 7 to 10.

12. The two or more circuit constants include a charge transfer resistance. The analysis method according to any one of claims 7 to 10.

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