WO2023106378A1

WO2023106378A1 - Electronic appliance and analysis method

Info

Publication number: WO2023106378A1
Application number: PCT/JP2022/045335
Authority: WO
Inventors: 昌幸板垣; 重輔志村
Original assignee: 学校法人東京理科大学; 株式会社村田製作所
Priority date: 2021-12-10
Filing date: 2022-12-08
Publication date: 2023-06-15

Abstract

An electronic appliance according to an embodiment of the present invention is provided with a measurement unit, a storage unit, a calculation unit, and an analysis unit. Both during and after charging or discharging of a battery pack configured to include a plurality of cells, the measurement unit measures the voltages and currents of the plurality of cells included in the battery pack. The storage unit stores the voltage values and current values obtained through the measurement by the measurement unit. The calculation unit calculates, for each of the cells, two or more circuit constants of an equivalent circuit of that cell by using the voltage values and current values stored in the storage unit. The analysis unit performs multivariate analysis by using distribution information concerning the two or more circuit constants of the plurality of cells or distribution information concerning the two or more circuit constants of a plurality of normally operating batteries.

Description

Electronics and analysis methods

This technology relates to electronic devices and analysis methods.

In recent years, the use of secondary batteries has expanded to larger-scale equipment such as electric vehicles and energy storage systems. The larger the scale, the greater the damage when it catches fire, so the importance of technological development to improve safety is increasing. In addition, it is important to appropriately understand abnormal behavior and deterioration of secondary batteries during use.

In Patent Document 1, attention is paid to internal resistance as a circuit constant used for determining deterioration of a secondary battery. In Patent Literature 1, coulomb counting is performed during CV charging in CCCV charging, and the internal resistance is calculated with high accuracy based on the amount of charged electricity.

JP 2004-152755 A

However, in the method described in Patent Document 1, the circuit constant required is only one internal resistance, and the deterioration phenomenon of the secondary battery cannot be expressed from various aspects. is insufficient. Therefore, it is desirable to provide an electronic device and an analysis method capable of handling a plurality of circuit constants and capable of analyzing deterioration due to various deterioration modes.

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 the plurality of single cells included in the assembled battery during and after charging or discharging of the assembled battery configured including the plurality of single cells. The storage unit stores voltage values and current values obtained by measurement by the measurement unit. The calculator calculates 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 unit. The analysis unit performs multivariate analysis using distribution information of two or more circuit constants in a plurality of cells or distribution information of two or more circuit constants in a plurality of normal batteries.

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 measuring unit measures the voltage and current of the single cell during and after the charging or discharging of the single cell. The storage unit stores voltage values and current values obtained by measurement by the measurement unit. The calculation unit calculates two or more circuit constants of the equivalent circuit of the cell using the voltage value and the current value stored in the storage unit. The analysis unit performs multivariate analysis using distribution information of two or more circuit constants in a plurality of normal batteries.

An analysis method according to a third aspect of the present technology includes the following four steps.
(A) A measurement step (B) of measuring the voltage and current of a plurality of single cells included in the assembled battery during and after charging or discharging the assembled battery configured to include a plurality of single cells. a storage step (C) of storing the voltage and current values obtained in the measurement step; using the voltage and current values stored in the storage step to store two or more circuit constants of the equivalent circuit of the unit cell for each unit cell; Calculation step of calculating (D) Solution step of performing multivariate analysis using distribution information of two or more circuit constants in a plurality of cells or distribution information of two or more circuit constants in a plurality of normal batteries

An analysis method according to a fourth aspect of the present technology includes the following four steps.
(A) A measurement step of measuring the voltage and current of the single cell during and after the charging or discharging of the single 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 the equivalent circuit of the unit cell using the voltage and current values stored in the storage step (D) Distribution information of the two or more circuit constants in a plurality of normal batteries A solution process that performs multivariate analysis using

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

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

It should be noted that the effects of the present technology are not necessarily limited to the effects described here, and may be any of a series of effects related to the present technology described below.

It is a figure showing the functional block example of the analysis device concerning one embodiment of this art. FIG. 2 is a diagram showing an equivalent circuit of a secondary battery that is the object of analysis of the analysis apparatus of FIG. 1; 3 is a diagram showing an example of an analysis procedure in the analysis device of FIG. 1; FIG. FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; FIG. 2 is a diagram showing an example of an analysis result in the analysis device of FIG. 1; It is a figure showing the example of a changed completely type of the functional block of the analysis device concerning one embodiment of this art. It is a figure showing the example of a changed completely type of the functional block of the analysis device concerning one embodiment of this art.

Hereinafter, the form for implementing the present technology will be described in detail with reference to the drawings.

<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 state of deterioration of a secondary battery. In the present embodiment, the secondary battery to be analyzed by the analysis device 10 is the assembled battery 20 . The assembled battery 20 is, for example, a lithium ion secondary battery. The assembled battery 20 includes a plurality of single cells 21 . Each unit cell 21 may be a unit cell, or may be a battery block in which a plurality of unit cells are connected. In each cell 21, a plurality of secondary batteries may be connected in series, or a plurality of secondary batteries may be connected in parallel.

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. .

The charging/discharging unit 11 is a device that discharges and charges the assembled battery 20 installed in the analysis device 10 . The charging/discharging unit 11 can perform, for example, CCCV charging as charging. The charging/discharging section 11 has a charging circuit including, for example, a generator and a converter. This charging circuit controls the voltage for charging the assembled battery 20 .

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 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 acquired through the wiring. However, 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 unit cell 21 during and after charging or discharging of the assembled battery 20 (steps S102 and S106 in FIG. 3).

The current measurement unit 13 has a measurement circuit that measures the current of each unit cell 21 included in the assembled battery 20 . Note that FIG. 1 illustrates a configuration in which wiring is connected to the positive electrode and the negative electrode of the assembled battery 20, and the current of each unit cell 21 is measured by measuring the current acquired through the wiring. , the method of measuring the current of each unit 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 unit cell 21 (that is, the current of the assembled battery 20) during and after charging or discharging the assembled battery 20 (steps S102 and S106 in FIG. 3).

The temporary storage unit 14 includes, for example, a volatile memory or a nonvolatile 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 voltage values and current values measured during and after charging or discharging of the assembled battery 20 (steps S103 and S107 in FIG. 3).

The circuit constant calculator 15 calculates the equivalent circuit of the unit cell 21 using the voltage value and current value during and after charging or discharging for each unit cell 21 stored in the temporary storage unit 14. Two or more circuit constants are calculated for each cell 21 (step S109 in FIG. 3).

FIG. 2 shows an equivalent circuit of each unit cell 21. FIG. Each single cell 21, as shown in FIG. 2, has an inductance L, a solution resistance Rs, a charge transfer resistance Rct, a Warburg impedance σ, a constant phase element CPE associated with an electric double layer capacitance Cdl, and a differential capacitance C′. It is represented by an equivalent circuit consisting of elements. The following eight circuit constants possessed by these six elements are calculated by curve fitting.

(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 (hereinafter referred to as CPE(p) and CPE(T), respectively)
・Differential capacitance C′
・Electric double layer capacitance Cdl

For inductance L, solution resistance Rs, charge transfer resistance Rct, Warburg impedance σ, parameter CPE (p), parameter CPE (T) and differential capacitance C′, for example, as the output of analysis software EIS manufactured by Hokuto Denko Co., Ltd. can get. 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))}

The multivariate analysis unit 16 derives distribution information of two or more circuit constants in the plurality of cells 21, and performs multivariate analysis using the obtained distribution information (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. Multivariate analysis using the Mahalanobis-Taguchi method will be described in detail below. The multivariate analysis unit 16 derives the degree of abnormality ai for each cell 21 by, for example, performing the following multivariate analysis.

(Adjustment of lithium ion battery as sample)
Thirteen commercially available lithium ion batteries US18650FTC1 (rated capacity: 1.05 Ah) containing lithium iron phosphate (LiFePO4, LFP) as the main positive electrode active material and graphite as the main negative electrode active material were prepared. These are all from the same production lot. For 10 of them, the current value equivalent to 0.2 hour rate until the voltage drops below 2.0 V (the rated capacity is 1.05 Ah and the current value It of 1 hour rate is 1.05 A, so 0 The current value I at the .2 hour rate is 0.2I = 210mA), followed by rapid CCCV charging at a set current of 1.05A (= 1It) and a set voltage of 3.6V (reaching the set voltage). Two-step charging was performed in which constant-current charging was performed at a set current value until reaching the set voltage, and constant-voltage charging was performed when the set voltage was reached. This was stopped 2.5 hours after the start of charging. These 10 lithium-ion batteries were placed in thermostatic baths set to 10 levels of temperature (45°C, 50°C, …, 90°C) while maintaining their fully charged state, and then placed 25 times each. Degraded by storage for days.

(Measurement of AC impedance)
Before measuring the circuit constants of the battery, the state of charge was adjusted. It was placed in a constant temperature bath at 23° C., and CCCV charging was performed with a set current of 1.05 A (=1 It) and a set voltage of 3.6 V. This CCCV charging stopped when the current value during constant voltage charging fell below 105 mA (=0.1 It). After that, the battery was left open for 1 hour, and the AC impedance was measured. Bio-Logic SP-240 was used for AC impedance measurement. As for the measurement conditions, first, control was set to a potentiostatic mode regulated by voltage, and the effective value of the amplitude was set to 5 mV. In addition, the center voltage and the open circuit voltage were matched so that no bias current would flow during measurement. The frequency sweep range was from 10 kHz to 1 mHz, and a logarithmic sweep was performed with five measurement points per one digit of frequency. The measurement was performed twice for each frequency to reduce random noise. Of the 13 lithium-ion batteries prepared, AC impedance was measured four times for each of the three lithium-ion batteries that had not undergone the above-described deterioration process, and the AC impedance was measured for the ten lithium-ion batteries that had undergone the above-mentioned deterioration process. Only one impedance measurement was performed.

(Multivariate analysis)
12 sets of data (each containing 8 circuit constants) obtained by measuring AC impedance four times for each of the three lithium-ion batteries that have not undergone the above-described deterioration process are expressed by the following equation: It is defined as 12 vectors xi (i is an integer from 1 to 12) as shown in (1).

Next, a vector μ of average values of 12 sets of data for each circuit constant and a variance-covariance matrix Σ were obtained by Equations (2) and (3), respectively.

Next, 10 sets of data obtained from 10 lithium-ion batteries that have undergone the above-described deterioration process (again, each containing 8 circuit constants) are divided into 10 sets as shown in equation (4). defined as an additional vector xi (where i is an integer from 13 to 22). Then, the degree of anomaly ai was calculated according to the equation (5) for all 22 vectors.

For comparison, the degree of anomaly was also calculated using only one circuit constant instead of multivariate (Figs. 4 to 11). Further, for all results, a threshold value for determining whether or not there is an abnormality was calculated from the 95% quantile and the 99% quantile in the F distribution table.

Also, FIG. 12 shows the result of the degree of anomaly calculated using all eight circuit constants. In each figure, "A" to "L" on the horizontal axis are data obtained from a battery that has not undergone the above-described deterioration process, i = 1, 2, ..., 12 in equation (5). corresponds to Also, "M" to "V" on the horizontal axis are data obtained from the battery that has undergone the above-described deterioration process, which correspond to i = 13, 14, ..., 22 in Equation (5), respectively. ing. Since "A" to "L" did not undergo the above-described deterioration process, in the discussion below, these data were considered to be data obtained from non-defective 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. data obtained from a battery of

From FIGS. 4 and 5, there is a clear difference in the degree of abnormality between the "A" to "L" batteries, which are regarded as non-defective products, and the "M" to "V" batteries, which are regarded as defective batteries. was not seen. In other words, it has been found that it is not possible to determine whether a product is good or bad using only one of the impedance L and the solution resistance Rs.

From FIGS. 6, 7, and 10, between the batteries “A” to “L” regarded as non-defective and the batteries “M” to “V” regarded as defective, tended to have a high degree of anomaly. However, it cannot be said that there is a clear difference between the two. proved difficult.

From FIGS. 8 and 9, it can be seen that between the batteries A to L, which are regarded as non-defective products, and the batteries M to V, which are regarded as defective batteries, there is a higher abnormality in the defective batteries. There was a clear trend towards increasing That is, it was suggested that even when only one circuit constant is used for each of the charge transfer resistance Rct and the Warburg impedance σ, it is possible to determine whether the product is good or bad. On the other hand, when using either circuit constant, when the degree of deterioration such as "M" or "N" is small, the degree of abnormality falls below the threshold of 95%, and it is difficult to find a significant difference from a non-defective product. , was found to have some problems in terms of sensitivity.

From FIG. 11, it is clear that the abnormalities of the defective products are higher between the batteries of "A" to "L", which are regarded as non-defective products, and the batteries of "M" to "V", which are regarded as defective products. There was a tendency to Even with "M" and "N", the degree of abnormality exceeds the 99% threshold. found out.

From FIG. 12, it is clear that the abnormalities of the defective products are higher between the batteries of "A" to "L", which are regarded as non-defective products, and the batteries of "M" to "V", which are regarded as defective products. There was a tendency to Comparing FIG. 11 and FIG. 12, in FIG. 11, even in “A” to “L”, which are regarded as non-defective products, there are some cases where the degree of abnormality is close to the 95% threshold. On the other hand, in FIG. 12, the anomaly degrees of "A" to "L" are all very small. It turned out that it is possible to judge

From the above, the multivariate analysis unit 16 includes at least a circuit constant related to the physical phenomenon that causes the transient response as the two or more circuit constants in the plurality of cells 21 to be selected in the multivariate analysis. . Such a circuit constant corresponds to at least the electric double layer capacitance Cdl or the charge transfer resistance Rct.

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

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

In Patent Document 1, attention is paid to internal resistance as a circuit constant used for determining deterioration of a secondary battery. In Patent Literature 1, coulomb counting is performed during CV charging in CCCV charging, and the internal resistance is calculated with high accuracy based on the amount of charged electricity. However, the method described in Patent Literature 1 cannot express the transient response of the secondary battery, so it is not possible to analyze the deterioration from various aspects, and is insufficient as a method for determining the deterioration of the secondary battery.

On the other hand, in the present embodiment, multivariate analysis is performed using distribution information of two or more circuit constants in a plurality of cells 21 or distribution information of two or more circuit constants in a plurality of normal batteries. Therefore, it is possible to perform a multifaceted analysis including deterioration modes caused by the transient response of the secondary battery.

In the present embodiment, the multivariate analysis unit 16, for example, as shown in FIG. Multivariate analysis may be performed using distribution information. The distribution information stored in the storage unit 17 is distribution information of two or more circuit constants in a plurality of normal batteries.

At this time, 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, the inductance L, the solution resistance Rs, the charge transfer resistance Rct, the Warburg impedance σ, At least one of parameter CPE(p), parameter CPE(T) and differential capacitance C' is applicable. In addition, the two or more circuit constants in a plurality of normal batteries selected in the multivariate analysis include, for example, charge transfer resistance Rct, inductance L, solution resistance Rs, Warburg impedance σ, parameter CPE (p), parameter At least one of CPE(T) and differential capacitance C' applies.

Note that in the present embodiment, the secondary battery to be analyzed by the analysis device 10 may be, for example, the cell 30 as shown in FIG. At this time, the unit cell 30 may be a unit cell, or may be a battery block in which a plurality of unit cells are connected. In the unit cell 30, a plurality of secondary batteries may be connected in series, or a plurality of secondary batteries may be connected in parallel. Also, at this time, the multivariate analysis unit 16, for example, as shown in FIG. Multivariate analysis may be performed using The distribution information stored in the storage unit 17 is distribution information of two or more circuit constants in a plurality of normal batteries.

Since the effects described in this specification are merely examples, the effects of the present technology are not limited to the effects described in this specification. Accordingly, other advantages may be obtained with respect to the present technology.

Claims

a measuring unit that measures the voltage and current of the plurality of single cells included in the assembled battery during and after charging or discharging of the assembled battery configured including the plurality of single cells;
a storage unit that stores the voltage value and the current value obtained by the measurement in the measurement unit;
a calculation unit that calculates 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 unit;
an analysis unit that performs multivariate analysis using the distribution information of the two or more circuit constants in the plurality of cells or the distribution information of the two or more circuit constants in the plurality of normal batteries. .
a measuring unit that measures the voltage and current of the unit cell during and after charging or discharging the unit cell;
a storage unit that stores the voltage value and the current value obtained by the measurement in the measurement unit;
a calculation unit that calculates two or more circuit constants of an equivalent circuit of the cell using the voltage value and the current value stored in the storage unit;
An electronic device, comprising: an analysis unit that performs multivariate analysis using distribution information of the two or more circuit constants in a plurality of normal batteries.
3. The electronic device according to claim 1, wherein the method of multivariate analysis is the Mahalanobis-Taguchi method.
The electronic device according to claim 1 or 2, wherein the multivariate analysis method is a one-class support vector machine method.
The electronic device according to any one of claims 1 to 4, wherein the two or more circuit constants include electric double layer capacitance.
The electronic device according to any one of claims 1 to 4, wherein the two or more circuit constants include charge transfer resistance.
a measuring step of measuring the voltage and current of the plurality of single cells included in the assembled battery during and after charging or discharging of the assembled battery configured including the plurality of single cells;
a storage step of storing the voltage value and the current value obtained in the measuring step;
a calculating step of calculating two or more circuit constants of an equivalent circuit of the unit cell using the voltage value and the current value stored in the storing step;
an analyzing step of performing multivariate analysis using the distribution information of the two or more circuit constants in the plurality of cells or the distribution information of the two or more circuit constants in the plurality of normal batteries.
a measuring step of measuring the voltage and current of the single cell during and after the charging or discharging of the single cell;
a storage step of storing the voltage value and the current value obtained in the measuring step;
a calculating step of calculating two or more circuit constants of an equivalent circuit of the cell using the voltage value and the current value stored in the storing step;
and a solution step of performing multivariate analysis using the distribution information of the two or more circuit constants in a plurality of normal batteries.
9. The analysis method according to claim 7, wherein the method of multivariate analysis is the Mahalanobis-Taguchi method.
9. The analysis method according to claim 7, wherein the multivariate analysis method is a one-class support vector machine method.
The analysis method according to any one of claims 7 to 10, wherein the two or more circuit constants include electric double layer capacitance.
The analysis method according to any one of claims 7 to 10, wherein the two or more circuit constants include charge transfer resistance.