JP2019061924A - Method and device for estimating ion concentration of secondary battery - Google Patents

Abstract

To solve the problem in which, in the conventional evaluation method, it is difficult to estimate ion concentration in an electrolyte of a secondary battery.SOLUTION: The ion concentration estimation method includes: referring to a Nyquist diagram (S2) generated using a plurality of negative electrode impedance values acquired from a secondary battery (S1) adjusted to have a predetermined charging rate; and referring to ion concentration estimation information prepared in advance and showing correspondence between the size of a spiral-shaped portion of the Nyquist diagram and redox ion concentration to calculate redox ion concentration corresponding to the size of the spiral-shaped portion (S3 to S5).SELECTED DRAWING: Figure 10

Description

  The present invention relates to an ion concentration estimation method and an ion concentration estimation apparatus for a secondary battery, for example, an ion concentration estimation method and an ion concentration for a secondary battery for estimating the concentration of redox ion eluted in the electrolyte of the secondary battery It relates to an estimation device.

  In a secondary battery using a hydrogen storage alloy containing cobalt, nickel or the like as an electrode, the metal in the alloy is eluted into the electrolyte by corrosion of the hydrogen storage alloy. Then, the metal eluted in the electrolytic solution is redeposited on the positive electrode and the negative electrode. Therefore, in a secondary battery using a hydrogen storage alloy as an electrode, the self-discharge rate is accelerated by the reprecipitation of metal. Thus, when the self-discharge speed is increased, the secondary battery can not exhibit sufficient characteristics, and the secondary battery ends its life. Therefore, Patent Document 1 discloses an example of a method of evaluating the degree of deterioration of a secondary battery due to the acceleration of the secondary discharge rate.

  The evaluation method of the battery described in Patent Document 1 is a method of evaluating a battery having a positive electrode, a negative electrode, and a reference electrode for measuring the potential of the positive electrode and the negative electrode. The response current flowing between the positive electrode and the negative electrode and the response voltage applied to the positive electrode and the negative electrode are measured when an input voltage of different frequency is applied between the positive electrode and the negative electrode, and the potential difference between the positive electrode and the reference electrode and the negative electrode The potential difference between the positive electrode and the reference electrode is calculated based on the response current and the potential difference between the positive electrode and the reference electrode, and the potential difference between the positive electrode and the reference electrode is calculated. And the impedance between the negative electrode and the reference electrode is calculated. Then, by using the battery evaluation method described in Patent Document 1, it is judged based on the calculated impedance of the deterioration of the electrode during charge and discharge.

JP, 2016-48213, A

  However, in the evaluation method described in Patent Document 1, although the impedance of the positive electrode and the negative electrode can be measured, it is possible to know the concentration of the redox substance ion in the electrolytic solution that causes the acceleration of the self-discharge rate. There is a problem that can not be done.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a new method for estimating the ion concentration of a redox substance in an electrolytic solution.

  One aspect of the method for estimating the ion concentration of a secondary battery according to the present invention is a charging rate regulator for adjusting the charging rate of the secondary battery, and providing the secondary battery with switching the frequency of the measurement signal at predetermined intervals. Ion concentration estimation having a negative electrode impedance measuring device for measuring the negative electrode impedance value of the secondary battery, and a computing unit for estimating the ion concentration of the redox material in the electrolyte solution of the secondary battery based on the negative electrode impedance value It is an ion concentration estimating method of a secondary battery which estimates ion concentration in electrolyte solution of a secondary battery using a device, and a plurality of the above-mentioned negative electrode impedances acquired from a secondary battery adjusted to become a predetermined charge rate Reference to the Nyquist diagram generated using values, and prepared in advance, the ion showing the correspondence between the size of the spiral-shaped portion of the Nyquist diagram and the redox ion concentration Referring to degrees estimation information to calculate the redox substance ion concentration corresponding to the size of the spiral-shaped portion.

  Further, one aspect of the ion concentration estimating device for a secondary battery of the present invention is an ion concentration estimating device for estimating the ion concentration of a redox substance in the electrolyte solution of a secondary battery, and the charging rate of the secondary battery The measurement signal is output to the secondary battery while switching the charging rate adjuster to be adjusted and the frequency of the measurement signal at predetermined frequency intervals, and the negative electrode impedance value of the negative electrode of the secondary battery is measured for each frequency of the measurement signal And an operation unit for estimating the ion concentration in the electrolyte of the secondary battery based on the Nyquist diagram generated using the plurality of measured negative electrode impedance values, The calculation unit refers to ion concentration estimation information indicating the correspondence between the size of the spiral-shaped portion of the Nyquist diagram and the concentration of the redox ion, and the acid corresponds to the size of the spiral-shaped portion. To calculate the reduction substance ion concentration.

  Further, one aspect of the method for estimating the ion concentration of a secondary battery according to the present invention is a charging rate regulator for adjusting the charging rate of the secondary battery, and the secondary battery is provided while switching the frequency of the measurement signal at predetermined intervals. A battery impedance measuring device for measuring a battery impedance value between the positive electrode and the negative electrode of the secondary battery, and estimating the ion concentration of the redox substance in the electrolytic solution of the secondary battery based on the battery impedance value. And calculating the ion concentration of the secondary battery using the ion concentration estimating device having the calculation unit, wherein the ion concentration of the secondary battery is estimated to be a predetermined charging rate. The Nyquist diagram generated using the plurality of battery impedance values obtained from the next battery is referred to, and is determined in advance on the Nyquist diagram in the transition frequency region of the Nyquist diagram. The difference between the real value component or the imaginary value component between the two battery impedance values is calculated as the real value change amount or the imaginary value change amount, respectively, prepared in advance, and the real value change amount or The redox concentration ion concentration corresponding to the real value variation or the imaginary value variation is calculated with reference to the ion concentration estimation information indicating the correspondence between the imaginary value variation and the redox ion concentration.

  Moreover, one aspect of the ion concentration estimation device for a secondary battery of the present invention is an ion concentration estimation device for estimating the ion concentration in an electrolyte solution of a secondary battery, and charging for adjusting the charging rate of the secondary battery The measurement signal is output to the secondary battery while switching the frequency of the measurement signal at a predetermined frequency interval, and the battery impedance value between the positive electrode and the negative electrode of the secondary battery is determined for each frequency of the measurement signal. A battery impedance measuring device to be measured, and an operation unit for estimating the ion concentration in the electrolyte solution of the secondary battery based on the Nyquist diagram generated using the plurality of measured battery impedance values. The calculation unit may be a difference between real value components or two imaginary value components between two predetermined battery impedance values on the Nyquist diagram in the transition frequency region of the Nyquist diagram. Is calculated as a real value change amount or an imaginary value change amount, respectively, and is prepared in advance, and reference is made to the ion concentration estimation information showing the correspondence between the real value change amount or the imaginary value change amount and the redox ion concentration. Then, the redox ion concentration corresponding to the real value change amount or the imaginary value change amount is calculated.

  In the ion concentration estimation method and the ion concentration estimation apparatus for a secondary battery according to the present invention, the impedance value of the measured electrode or battery is acquired, the difference between the measurement points of these impedance values is determined, and electrolysis is performed based on the difference value. The redox ion concentration in the solution can be estimated.

  According to the ion concentration estimation method and the ion concentration estimation device for a secondary battery of the present invention, it becomes possible to estimate the ion concentration in the electrolyte solution of the secondary battery.

It is a block diagram of the ion concentration estimating device of the rechargeable battery concerning Embodiment 1 which estimates ion concentration of a single battery cell. It is a block diagram of the ion concentration estimating device of the secondary battery concerning Embodiment 1 which estimates the ion concentration of an assembled battery. It is a schematic diagram explaining the oxidation-reduction reaction in a battery cell. It is a figure explaining the difference by the presence or absence of Co ion of the Nyquist diagram of negative electrode impedance. It is a figure explaining the difference by the presence or absence of Co ion of the Nyquist diagram of the negative electrode impedance of the vicinity of the part which a spiral shape generate | occur | produces. It is a graph which shows the change over the frequency of the real value change amount between negative electrode impedance values. It is a graph which shows the relationship between Co ion concentration and the minimum real value value variation. It is a graph which shows the relationship between Co ion concentration and the remaining life of a secondary battery. It is a figure explaining the difference by the temperature of the Nyquist diagram of negative electrode impedance. 5 is a flowchart illustrating the flow of the method for estimating ion concentration of a secondary battery according to the first embodiment. It is a block diagram of the ion concentration estimating device of the secondary battery concerning Embodiment 2 which estimates ion concentration of a single battery cell. It is a figure explaining a transition frequency domain. It is a graph explaining the relationship between a negative electrode impedance value and Co ion concentration. It is a figure explaining the difference by the presence or absence of Co ion of the Nyquist diagram of positive electrode impedance. It is a graph explaining the relationship between a positive electrode impedance value and Co ion concentration. It is a graph explaining the relationship between a battery impedance value and Co ion concentration. It is a graph explaining the relationship between a battery admittance value and Co ion concentration. FIG. 10 is a flowchart for explaining the flow of a method for estimating ion concentration of a secondary battery according to a second embodiment.

Embodiment 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description and drawings are omitted and simplified as appropriate for clarification of the explanation. In the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted as necessary.

  Further, the processing described below is realized by, for example, a program executed in an arithmetic device such as an ECU (Electronic Control Unit). This program can be stored and provided to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include tangible storage media of various types. Examples of non-transitory computer readable media are magnetic recording media (eg flexible disk, magnetic tape, hard disk drive), magneto-optical recording media (eg magneto-optical disk), CD-ROM (Read Only Memory) CD-R, CD -R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)) is included. Also, the programs may be supplied to the computer by various types of transitory computer readable media. Examples of temporary computer readable media include electrical signals, light signals, and electromagnetic waves. The temporary computer readable medium can provide the program to the computer via a wired communication path such as electric wire and optical fiber, or a wireless communication path.

  FIG. 1 shows a block diagram of the ion concentration estimation apparatus 1 according to the first embodiment. As shown in FIG. 1, the ion concentration estimation apparatus 1 according to the first embodiment includes an ion concentration calculation apparatus 10, a negative electrode impedance measuring device 31, and a negative electrode impedance measuring device 32.

  In the block diagram shown in FIG. 1, the battery cell 20 which is the measurement object of the ion concentration estimation apparatus 1 was shown. The battery cell 20 is a single battery cell, and has a positive electrode 21, a negative electrode 22, and a reference electrode 23. The battery cell 20 is a chargeable / dischargeable secondary battery. The battery cell 20 is, for example, a nickel hydrogen battery, a lithium ion battery, or the like. Details of the battery cell 20 will be described later.

  The negative electrode impedance measuring device 31 outputs an alternating current signal as a measurement signal, and switches the frequency of the alternating current signal, and the impedance between the reference electrode 23 of the battery cell 20 and the negative electrode 22 for each frequency (hereinafter referred to as negative electrode impedance) Measure The negative electrode impedance measuring device 31 is, for example, a frequency response analysis device that analyzes the frequency response of the electrode.

  Before measuring the negative electrode impedance of the battery cell 20, the SOC adjuster 33 adjusts the charging ratio (SOC: State Of Charge) of the battery cell 20 to a predetermined charging ratio.

  The ion concentration calculation device 10 is, for example, an arithmetic device such as a computer, and stores various kinds of interfaces, programs, and evaluation results for controlling the arithmetic unit that executes a program, the negative electrode impedance measuring device 31, the SOC adjuster 33, and the like. Storage device (not shown). The ion concentration calculation device 10 estimates the ion concentration of the redox substance in the electrolytic solution of the battery cell 20 based on the measurement value measured by the negative electrode impedance measurement device 31. The ion concentration calculation device 10 includes a measurement control unit 11, a measurement value acquisition unit 12, an operation unit 13, and a memory 14.

  The measurement control unit 11 controls the negative electrode impedance measuring device 31 and the SOC regulator 33 according to a predetermined procedure. For example, the measurement control unit 11 controls the timing at which the SOC adjuster 33 adjusts the charging rate of the battery cell 20, and the timing at which the negative electrode impedance measuring device 31 outputs a measurement signal to obtain an impedance value from the battery cell 20. .

  The measured value acquiring unit 12 takes in the negative electrode impedance value measured by the negative electrode impedance measuring device 31, and generates a Nyquist diagram using the taken-in negative electrode impedance value. Such a method of impedance measurement is also called electrochemical impedance method. And in the electrochemical impedance method, the frequency of the input signal is changed from low frequency to high frequency, and the change in the impedance value at that time is plotted on the complex plane to obtain the Nyquist diagram (Cole-Cole plot) to analyze the inside of the battery I do.

  The calculation unit 13 is, for example, a program execution unit that executes a program stored in a storage device such as the memory 14 or the like. The calculation unit 13 estimates the battery life based on the measured value. Specifically, the calculation unit 13 analyzes the Nyquist diagram generated by the measurement value acquisition unit 12 to estimate the ion concentration in the electrolytic solution of the battery cell 20. In the analysis process for the Nyquist diagram, the operation unit 13 evaluates the size (for example, the size of an ellipse) of the spiral shaped waveform portion appearing in the Nyquist diagram, and estimates the ion concentration from the size of this elliptical shape. Do. Specifically, in the first embodiment, two processes are performed. In the first process, the difference between real value components between two negative electrode impedance values on the Nyquist diagram is calculated as a real value change amount. In the following, in order to determine the size of the spiral shape appearing in the Nyquist diagram by one value, the difference between the real value components of two adjacent negative electrode impedance values on the Nyquist diagram is determined as a real value change amount. An example of calculating the smallest real value change amount, which is the smallest value among the real value change amounts, will be described as an example. The negative electrode impedance values used to calculate the real value change amount do not necessarily have to be adjacent to each other, as long as they are separated by a constant interval. In the second process, oxidation reduction corresponding to the size of the spiral-shaped portion is prepared with reference to the ion concentration estimation information which is prepared in advance and indicates the correspondence between the size of the spiral-shaped portion of the Nyquist diagram and the redox ion concentration. Calculate the substance ion concentration. Hereinafter, an example in which the minimum real value change amount is used as an index indicating the size of the spiral shape portion will be described. That is, using the information indicating the correspondence between the minimum real value change amount and the redox ion concentration as the ion concentration estimation information, the redox ion concentration (for example, Co ion concentration) corresponding to the minimum real value change is calculated Do.

  In addition, the calculation unit 13 calculates with reference to battery life estimation information (for example, the graph in FIG. 8) indicating the relationship between the redox ion concentration (for example, Co ion concentration) and the remaining life of the secondary battery. The remaining life corresponding to the concentration of Co ions is calculated.

  The memory 14 is, for example, a non-volatile memory such as a flash memory. The memory 14 stores ion concentration estimation information and battery life estimation information. In the first embodiment, a graph showing the relationship between the Co ion concentration of FIG. 7 and the minimum real value change amount is included as the ion concentration estimation information. Further, the battery life estimation information includes a graph showing the relationship between the Co ion concentration and the remaining life of the secondary battery. The ion concentration estimation information and the battery life estimation information are prepared in advance by measuring a battery sample for graph creation. Note that the ion concentration estimation information and the battery life estimation information are not limited to the graph information, and may be a table or a mathematical expression that indicates the correspondence between two values used for analysis.

  In FIG. 1, although the battery cell of a single cell was shown as lifetime prediction object, the cell of measurement object can also be made into the battery module and assembled battery which connected several single cell in series. Then, the block diagram of the ion concentration estimation apparatus 2 which makes a battery module lifetime prediction object is shown in FIG.

  FIG. 2 shows the battery module 40 to be measured. The battery module 40 is composed of a plurality of battery cells 20 connected in series. The battery module 40 has one positive electrode 41, one negative electrode 42, and a reference electrode 23 provided for each battery cell 20. And in the ion concentration estimation apparatus 2, it replaces with the negative electrode impedance measuring device 31, and has the negative electrode impedance measuring device 32. FIG. The negative electrode impedance measuring device 32 measures the negative electrode impedances of the plurality of battery cells 20, respectively, and synthesizes (for example, adds) the negative electrode impedances of the plurality of battery cells obtained by the measurement. Generate as a measurement value.

  Then, the ion concentration estimation method of the secondary battery in the ion concentration estimation apparatus 1 concerning Embodiment 1 is demonstrated in detail. Therefore, first, the redox reaction of the additive (conductive material) of the battery cell 20 will be described. The schematic diagram explaining the oxidation reduction reaction in a battery cell in FIG. 3 is shown.

The negative electrode of a nickel hydrogen battery is made of a hydrogen storage alloy, and cobalt in the alloy is temporarily dissolved in an electrolytic solution (for example, in an alkaline aqueous solution) to repeat cobalt ion (HCoO ₂ ⁻ ) when charge and discharge are repeated as shown in FIG. And then reprecipitated on the surfaces of the positive electrode and the negative electrode. Thus, the re-deposition of cobalt causes the acceleration of the self-discharge rate. It was found that the degree of this self-discharge rate was in phase with the concentration of cobalt ions (Co ions) in the electrolyte. Therefore, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, it is possible to estimate the Co ion concentration in the electrolyte and to determine the period (remaining life) up to the life of the secondary battery. .

  Subsequently, the relationship between the Co ion concentration and the negative electrode impedance will be described. Therefore, FIG. 4 is a diagram for explaining the difference due to the presence or absence of Co ions in the Nyquist diagram of negative electrode impedance. The Nyquist diagram shown in FIG. 4 plots the real value component of the impedance on the horizontal axis and the imaginary value component of the impedance on the vertical axis. The Nyquist diagram of the negative electrode impedance is formed by plotting measurement values on a graph for each frequency of the measurement signal. As shown in FIG. 4, the Nyquist diagram gradually changes according to the change of frequency. Specifically, the Nyquist diagram changes so as to include a portion to be a semicircular curve and a portion to be a linear shape.

  Then, in order to verify the change in negative electrode impedance due to Co ions, a battery in which Co ions are forcibly added to the secondary battery for verification is created, and the Nyquist diagram without Co ion addition shown in FIG. A Nyquist diagram with Co ion addition was created. FIG. 4 shows the Nyquist diagram without Co ion addition in the upper diagram, and the Nyquist diagram with Co ion addition in the lower diagram. As shown in FIG. 4, when Co ions are added, the frequency of the measurement signal changes significantly in the shape of the Nyquist diagram in the range of 10 mHz to 10 Hz. Specifically, when the concentration of Co ions in the electrolytic solution becomes high, a spiral waveform appears in the Nyquist diagram. This spiral shaped waveform is characterized by becoming larger as the Co ion concentration becomes higher. Therefore, in the ion concentration estimation apparatus 1 according to the first embodiment, the ion concentration and remaining life evaluation of the secondary battery are performed focusing on the relationship between the size of the spiral shape and the ion concentration.

  Subsequently, the difference due to the presence or absence of Co ions in the Nyquist diagram near the portion where the spiral shape occurs will be described. FIG. 5 is a diagram for explaining the difference in negative electrode impedance in the vicinity of the portion where the spiral shape occurs due to the presence or absence of Co ions in the Nyquist diagram. As shown in FIG. 5, when there is no Co ion in the solution, the Nyquist diagram of the negative electrode impedance monotonously decreases once and changes monotonically at a certain negative electrode impedance value. On the other hand, when Co ions are present in the solution, a Nyquist diagram shows a spiral-shaped portion. As described above, the Nyquist diagram of the battery cell 20 has a significantly different shape depending on the presence or absence of Co ions. Then, the higher the concentration of Co ions in the electrolytic solution, the larger the spiral elliptical part.

  In the method for estimating the ion concentration of a secondary battery according to the first embodiment, the difference between real value components between adjacent negative electrode impedance values on the Nyquist diagram shown in FIG. 6 is calculated as a real value change amount, and the real value is calculated. Find the minimum real value change that minimizes the change. If there is a spiral shape, the minimum real value change amount becomes a negative value, and the minimum real value change amount decreases as the elliptical portion of the spiral shape increases. FIG. 5 shows the variation corresponding to the measurement signal of 1 Hz and the magnitude of the variation corresponding to the measurement signal of 800 mHz among the difference of the real value components between the negative electrode impedance values. The interval of the negative electrode impedance value for calculating the real value change amount may be set such that the minimum real value change amount can represent the size of the ellipse in consideration of the size of the spiral shaped ellipse.

  Here, the difference between the real value change amount and the frequency of the measurement signal will be described. FIG. 6 is a graph showing the change with the frequency of the real value change amount between the negative electrode impedance values. As shown in FIG. 6, the amount of change between negative electrode impedance values increases or decreases with frequency. In addition, there is a difference in the minimum value of the change in real value when comparing the case where the Co ion is added and the case where the Co ion is not added. In the following description, the minimum value of the real value change amount of the negative electrode impedance value is referred to as the minimum real value change amount.

  Thus, the minimum real value change amount changes in value due to the difference in Co ion concentration. Therefore, FIG. 7 shows a graph showing the relationship between the Co ion concentration and the minimum real value change amount. As shown in FIG. 7, there is a fixed relationship between the minimum real value change and the Co ion concentration. Specifically, as the Co ion concentration increases, the minimum change in real number tends to decrease. In particular, when the Co ion concentration becomes equal to or higher than a certain concentration, the decrease in the value of the minimum real value change becomes remarkable. For example, in the example of FIG. 7, when the concentration of Co ions is 10 mM or more, the decrease in minimum real value change becomes remarkable. In the method for estimating the ion concentration of the secondary battery according to the first embodiment, the Co ion concentration is calculated with reference to the graph showing the relationship between the Co ion concentration and the minimum change in real number shown in FIG. Further, a graph showing the relationship between the Co ion concentration and the real value change amount is generated by evaluating the evaluation sample in advance.

  Subsequently, the relationship between the Co ion concentration and the remaining life of the secondary battery will be described. Therefore, a graph showing the relationship between the remaining life of the secondary battery and the Co ion concentration is shown in FIG. As shown in FIG. 8, it can be seen that there is a fixed relationship between the Co ion concentration and the remaining life of the secondary battery. Specifically, the remaining life of the secondary battery decreases as the Co ion concentration increases. By using the Co ion concentration estimated by the method for estimating the ion concentration of the secondary battery according to the first embodiment and the graph shown in FIG. 8, the non-defective product / defective product of the secondary battery considering the remaining life of the secondary battery A decision can be made. The graph showing the relationship between the remaining life of the secondary battery and the Co ion concentration shown in FIG. 8 is generated by evaluating the evaluation sample in advance.

  As described above, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, the negative electrode impedance value of the battery cell 20 is measured, the Nyquist diagram is generated using the negative electrode impedance value, and the negative electrode impedance value is The minimum value (minimum real value change amount) of the real value change amount of is calculated, the Co ion concentration corresponding to the minimum real value change amount is calculated, and the life of the secondary battery is estimated based on the calculated Co ion concentration. However, the negative electrode impedance value has temperature characteristics. Therefore, when measuring the negative electrode impedance value, it is preferable to keep the temperature of the secondary battery to be measured constant.

  Therefore, the temperature characteristics of the negative electrode impedance value of the secondary battery will be described. FIG. 9 shows a diagram for explaining the difference due to the temperature of the Nyquist diagram of the negative electrode impedance.

  In the example shown in FIG. 9, the Nyquist diagram when the secondary battery is at 45 ° C. is shown in the upper view, and the Nyquist diagram when the secondary battery is at 25 ° C. is shown in the lower diagram. As shown in FIG. 9, when the temperature of the secondary battery is 45 ° C., the size of the spiral shape of the Nyquist diagram is larger than when the temperature is 25 ° C. That is, when the secondary battery is at 45 ° C. than when the secondary battery is at 25 ° C., the real value change amount can be measured larger, and the minimum real value change amount can be determined accurately. In addition, the accuracy of the minimum real value change can be increased, and the accuracy of the life estimation can also be improved.

  Subsequently, an ion concentration estimation procedure using the ion concentration estimation apparatus 1 according to the first embodiment will be described. FIG. 10 shows a flowchart for explaining the flow of the method for estimating the ion concentration of the secondary battery according to the first embodiment.

  As shown in FIG. 10, in the method for estimating ion concentration of a secondary battery according to the first embodiment, a temperature adjustment process in which the temperature of the battery is set to a preset temperature is performed (step S0). The temperature control process is performed, for example, by steps such as placing the battery cells 20 in a constant temperature bath for a certain period of time and warming the battery cells 20 with a heater. Next, in the first embodiment, SOC adjustment processing is performed to adjust the charging rate of the battery cell 20 to a preset charging rate (step S1). In the SOC adjustment process, the measurement control unit 11 gives the SOC adjuster 33 a charge rate adjustment instruction.

  Next, in the method for estimating ion concentration of a secondary battery according to the first embodiment, the negative electrode impedance value is measured (step S2). In the measurement of the negative electrode impedance value, the measurement control unit 11 gives a measurement instruction to the negative electrode impedance measuring device 31. The negative electrode impedance measuring device 31 measures the negative electrode impedance value of the battery cell 20 while switching the frequency of the measurement signal according to the measurement instruction. The measurement result may be stored at one end in the negative electrode impedance measurement device 31 and may be read out collectively by the measurement value acquisition unit 12 or may be read out by each measurement. In step S2, the Nyquist diagram is generated using the negative electrode impedance value measured by the measurement value acquisition unit 12.

  Next, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, the computing unit 13 calculates a real value change amount between two adjacent negative electrode impedance values on the Nyquist diagram (step S3). Then, the calculation unit 13 calculates the minimum value of the real value change amount calculated in step S3 (step S4). The minimum value calculated in step S4 is the minimum real value change amount.

  Next, in the method for estimating ion concentration of a secondary battery according to the first embodiment, the Co ion concentration corresponding to the minimum real-number value change calculated in step S4 is calculated (step S5). Then, the calculated Co ion concentration is compared with a preset threshold (step S6). If the Co ion concentration is determined to be less than or equal to the threshold value in the comparison process of step S6, the calculation unit 13 determines that the battery cell 20 to be inspected is a non-defective product and ends the process (step S8). On the other hand, if it is determined in the comparison process of step S6 that the Co ion concentration is larger than the threshold value, operation unit 13 determines battery cell 20 to be inspected as a defective product and ends the process (step S7).

  Although the process of the non-defective item determination (steps S6 to S8) of the battery cell 20 is described in the flowchart shown in FIG. 10, the process can be ended by the process up to the process of estimating the Co ion concentration in step S5. is there.

  From the above description, in the ion concentration estimation method according to the first embodiment, the negative electrode impedance value is measured while switching the frequency of the measurement signal at a predetermined frequency interval, and a real value between two negative electrode impedance values on the Nyquist diagram. The smallest real value change amount which is the smallest of the component differences is calculated. Then, the Co ion concentration corresponding to the minimum real value change amount is estimated with reference to the ion concentration estimation information (for example, the graph shown in FIG. 7).

  Thereby, in the ion concentration estimation method according to the first embodiment, the Co ion concentration in the electrolyte solution of the battery cell 20 can be estimated. Further, since there is a relationship as shown in FIG. 8 between the Co ion concentration and the life of the battery cell 20, the Co ion concentration that can be judged as non-defective based on this relationship is determined, and the determined Co ion concentration By doing this, it is possible to perform non-defective product judgment in consideration of the life of the battery cell 20 based on the Co ion concentration calculated from the measured negative electrode impedance value.

  Further, the ion concentration estimating apparatus 1 (or the ion concentration estimating apparatus 2) for realizing the ion concentration estimating method according to the first embodiment can be realized using the calculation function of an ECU or the like mounted on an automobile or the like. . Further, the ion concentration estimation method according to the first embodiment can calculate the Co ion concentration without destroying the battery cell 20. Because of this, in the ion concentration estimation method according to the first embodiment, for example, for a secondary battery mounted on a hybrid vehicle or the like, non-defective product determination taking into consideration the life of the secondary battery while using the vehicle It can be carried out.

Embodiment 2
In Embodiment 2, another aspect of the ion concentration estimation method will be described. In the ion concentration estimation method according to the second embodiment, the ion concentration of the redox material in the electrolyte solution of the secondary battery is estimated based on the battery impedance value between the positive electrode and the negative electrode of the secondary battery in the transition frequency region. The inventors found that the correlation with the ion concentration of the redox substance in the electrolytic solution appears only in the transition frequency region of the battery impedance, and reached the present invention. FIG. 11 shows a block diagram of the ion concentration estimation apparatus 3 according to the second embodiment. In the description of the second embodiment, the same components as the components described in the first embodiment are assigned the same reference numerals as in the first embodiment and the description will be omitted.

  As shown in FIG. 11, the ion concentration estimation apparatus 3 concerning Embodiment 2 makes the battery cell 60 a measuring object. In the ion concentration estimation method according to the second embodiment, the battery cell 60 does not need a reference electrode in order to measure the battery impedance value between the positive electrode and the negative electrode. Therefore, in the example shown in FIG. 11, the battery cell 60 has only the positive electrode 21 and the negative electrode 22.

  The ion concentration estimation device 3 according to the second embodiment includes an ion concentration calculation device 50, a battery impedance measurement device 71, and an SOC adjuster 33.

  The battery impedance measuring instrument 71 outputs an AC signal as a measurement signal, and switches the frequency of the AC signal for each frequency while changing the frequency of the AC signal (hereinafter referred to as battery impedance) between the positive electrode 21 and the negative electrode 22. taking measurement. The battery impedance measuring device 71 is, for example, a frequency response analysis device that analyzes the frequency response of the electrode.

  Before measuring the negative electrode impedance of the battery cell 20, the SOC adjuster 33 adjusts the charging ratio (SOC: State Of Charge) of the battery cell 60 to a predetermined charging ratio.

  The ion concentration calculation device 50 is, for example, an arithmetic device such as a computer, and stores various kinds of interfaces, programs, and evaluation results for controlling the calculation unit that executes a program, the battery impedance measuring device 71, the SOC adjuster 33, and the like. Storage device (not shown). The ion concentration calculation device 50 estimates the ion concentration of the redox substance in the electrolytic solution of the battery cell 60 based on the measurement value measured by the battery impedance measuring device 71. The ion concentration calculation device 50 includes a measurement control unit 51, a measurement value acquisition unit 52, a calculation unit 53, and a memory 54.

  The measurement control unit 51 controls the battery impedance measuring device 71 and the SOC regulator 33 according to a predetermined procedure. For example, the measurement control unit 51 controls the timing at which the SOC adjuster 33 adjusts the charging rate of the battery cell 20, and the timing at which the battery impedance measuring device 71 outputs a measurement signal to obtain an impedance value from the battery cell 60. .

  The measured value acquiring unit 52 takes in the battery impedance value measured by the battery impedance measuring instrument 71, and generates a Nyquist diagram using the taken battery impedance value. The Nyquist diagram is a Nyquist diagram (Cole-Cole plot) in which changes in impedance values are plotted on a complex plane.

  The calculation unit 63 is, for example, a program execution unit that executes a program stored in a storage device such as the memory 64 or the like. The computing unit 63 estimates the battery life based on the measured value. Specifically, the calculation unit 53 analyzes the Nyquist diagram generated by the measurement value acquisition unit 52, and estimates the ion concentration in the electrolytic solution of the battery cell 60. In the analysis process on the Nyquist diagram, the arithmetic unit 53 performs two processes in the second embodiment. In the first process, the difference between real value components of adjacent battery impedance values determined in advance in the transition frequency region on the Nyquist diagram or the difference between imaginary value components is changed by a real value or an imaginary value, respectively. Calculated as the amount of change. In the second process, the correspondence between the real value change amount or the imaginary value change amount and the redox ion concentration is indicated, and the real value change amount or the imaginary value change amount is referred to with reference to the ion concentration estimation information prepared in advance. Calculate the redox ion concentration corresponding to

  The memory 54 is, for example, a non-volatile memory such as a flash memory. The memory 54 stores ion concentration estimation information. In the second embodiment, a graph indicating the relationship between the Co ion concentration and the imaginary value change amount shown in FIG. 16 or 17 is included as the ion concentration estimation information. The ion concentration estimation information is created in advance by measuring a battery sample for graph creation. The ion concentration estimation information is not limited to the graph information, and may be a table or a mathematical expression that indicates the correspondence between two values used for analysis.

  Also in the second embodiment, as in the first embodiment, the measurement target can be a battery module in which a plurality of battery cells 60 are connected in series.

  In the second embodiment, analysis is performed focusing on the impedance value in the transition frequency region on the Nyquist diagram. Therefore, this transition frequency region will be described. In the method for estimating the ion concentration of the secondary battery according to the second embodiment, attention is particularly focused on the change in the Nyquist diagram of the transition frequency region which occurs in the range of 10 mHz to 10 Hz.

  A diagram for explaining a transition frequency region to which attention is paid by the method for estimating ion concentration of a secondary battery according to the second embodiment is shown in FIG. FIG. 12 shows the transition frequency region of the Nyquist diagram for the negative electrode impedance where the transition frequency region becomes clearer. As shown in FIG. 12, in the Nyquist diagram, a region having a correlation with a circular arc spectrum generated due to the capacity component of battery cell 20 and a predetermined value or more, and a linear spectrum generated due to the diffusion component of battery cell 20 And a region having a correlation of not less than a predetermined value (for example, a correlation coefficient of not less than 0.99), and a region in which the correlation deviates by not less than a constant value from any of the arc spectrum and the linear spectrum. In the ion concentration estimation method of the secondary battery according to the first embodiment, the frequency of the negative electrode impedance value at which the correlation value with the linear spectrum approaches a predetermined value or more from the frequency of the negative electrode impedance value where the correlation value with the arc spectrum deviates by a predetermined value or more. Is defined as a transition frequency domain.

  Here, the relationship between the battery impedance value and the Co ion concentration will be described in detail. In the ion concentration estimation method according to the second embodiment, the ion concentration is estimated based on the difference between real value components between two adjacent predetermined points on the Nyquist diagram or the difference between imaginary value components. In the following, as an example, an example will be described in which the impedance values obtained by the measurement signals of 100 mHz and 80 mHz included in the transition frequency domain are to be evaluated.

  The battery impedance value is affected by the negative electrode impedance value and the positive electrode impedance value. Therefore, the respective characteristics of the negative electrode impedance value and the positive electrode impedance value will be described. The negative electrode impedance value is the same as the characteristics described in the first embodiment.

  FIG. 13 shows a graph for explaining the relationship between the negative electrode impedance value and the Co ion concentration. 13 shows a graph showing the relationship between the difference between the real value component of the applied frequency 100 mHz and the real value component of the applied frequency 80 mHz and the Co ion concentration in the upper figure, and the lower figure shows the imaginary value component of the applied frequency 100 mHz in the upper figure. And a graph showing the relationship between the Co ion concentration and the difference between the and the imaginary value component of the applied frequency of 80 mHz.

  As shown in FIG. 13, in the negative electrode impedance value, the change amount of the real value component is hard to be influenced by the change of the Co ion concentration, and the change amount of the imaginary value component is easily influenced by the change of the Co ion concentration. Furthermore, the amount of change in the imaginary value component tends to decrease as the Co ion concentration increases.

  Subsequently, the characteristics of the positive electrode impedance value will be described. FIG. 14 shows a diagram for explaining the difference between the presence and absence of Co ions in the Nyquist diagram of positive electrode impedance. In FIG. 14, the upper figure shows a Nyquist diagram of positive electrode impedance in the state without addition of Co ion, and the lower diagram shows a Nyquist diagram of positive electrode impedance when Co ion is added.

  As shown in FIG. 14, in the positive electrode impedance, a winding-like Nyquist diagram waveform like the negative electrode impedance does not appear. However, also in the Nyquist diagram of positive electrode impedance, the waveform is different depending on the presence or absence of addition of Co ions.

  Therefore, FIG. 15 shows a graph for explaining the relationship between the positive electrode impedance value and the Co ion concentration. 15 shows a graph showing the relationship between the difference between the real value component of the applied frequency 100 mHz and the real value component of the applied frequency 80 mHz and the Co ion concentration in the upper figure, and the lower figure shows the imaginary value component of the applied frequency 100 mHz in the upper figure. And a graph showing the relationship between the Co ion concentration and the difference between the and the imaginary value component of the applied frequency of 80 mHz.

  As shown in FIG. 15, in the positive electrode impedance value, the change amount of the imaginary value component is not easily influenced by the change of the Co ion concentration, and the change amount of the real value component is easily influenced by the change of the Co ion concentration. Furthermore, the amount of change in the real-valued component tends to increase as the Co ion concentration increases.

  Subsequently, the battery impedance value will be described. FIG. 16 shows a graph for explaining the relationship between the battery impedance value and the Co ion concentration. In FIG. 16, the upper diagram shows a graph of the real value change amount between the battery impedance values obtained by the measurement signals of 100 mHz and 80 mHz among the battery impedance values and the Co ion concentration, and the lower diagram shows the battery impedance values. The graph of the imaginary value change amount and Co ion concentration between the battery impedance values acquired by the measurement signal of 100 mHz and 80 mHz was shown.

  As shown in FIG. 16, when viewed as the amount of change between predetermined two points of the battery impedance value, there is a fixed relationship between the Co ion concentration and the real value change amount and the imaginary value change amount. I understand that there is. The ion concentration estimation method according to the second embodiment estimates the ion concentration based on the amount of change in impedance between the two points.

  It is also possible to estimate the Co ion concentration based on the battery admittance value by calculating the battery admittance value from the measured battery impedance value instead of the impedance. Therefore, FIG. 17 shows a graph for explaining the relationship between the battery admittance value and the Co ion concentration when the imaginary value component of the battery impedance value of FIG. 16 is converted to the admittance value. As shown in FIG. 17, when looking at the relationship between the battery admittance value and the Co ion concentration, it is possible to obtain a graph in which the measured value is expanded. Therefore, it is possible to estimate the Co ion concentration with higher accuracy by estimating the Co ion concentration based on the battery admittance value. The estimation of the Co ion concentration by the admittance value is also applicable to the ion concentration estimation method according to the first embodiment.

  Subsequently, an ion concentration estimation procedure using the ion concentration estimation apparatus 1 according to the first embodiment will be described. FIG. 18 shows a flowchart for explaining the flow of the method for estimating the ion concentration of the secondary battery according to the second embodiment.

  As shown in FIG. 18, in the method for estimating ion concentration of a secondary battery according to the second embodiment, a temperature adjustment process is performed in which the temperature of the battery is set to a preset temperature (step S10). The temperature control process is performed, for example, by steps such as placing the battery cell 60 in a constant temperature bath for a certain period of time, warming the battery cell 20 with a heater, or the like. Next, in the second embodiment, SOC adjustment processing is performed to adjust the charging rate of the battery cell 60 to a preset charging rate (step S11). In the SOC adjustment process, the measurement control unit 51 gives the SOC adjuster 33 a charge rate adjustment instruction.

  Next, in the method for estimating ion concentration of a secondary battery according to the second embodiment, the battery impedance value is measured (step S12). In the measurement of the battery impedance value, the measurement control unit 51 gives a measurement instruction to the battery impedance measuring device 71. The battery impedance measuring device 71 measures the battery impedance value of the battery cell 60 while switching the frequency of the measurement signal according to the measurement instruction. The measurement result may be stored at one end in the battery impedance measuring device 71, and may be read out collectively by the measurement value acquisition unit 52, or may be read out by the measurement value acquisition unit 52 for each measurement. In step S12, the measured value acquiring unit 52 generates a Nyquist diagram using the measured battery impedance value.

  Next, in the method for estimating the ion concentration of the secondary battery according to the second embodiment, between the two adjacent points in the transition frequency region of 10 Hz or less by the operation unit 53 (for example, battery impedance values corresponding to measurement signals of 100 mHz and 80 mHz) The real value change amount and the imaginary value change amount of L are calculated (step S13). Then, operation unit 53 calculates the Co ion concentration corresponding to the real value change amount calculated in step S13 with reference to the graph shown in FIG. 16 (step S14). Further, the calculation unit 53 calculates the Co ion concentration corresponding to the imaginary value change amount calculated in step S13 with reference to the graph shown in FIG. 16 (step S15).

  Next, in the method of estimating the ion concentration of the secondary battery according to the second embodiment, the Co ion concentration calculated in step S14 or step S15 is compared with a preset threshold (step S16). If the Co ion concentration is determined to be equal to or less than the threshold value in the comparison process of step S16, the calculation unit 53 determines that the battery cell 60 to be inspected is a non-defective product and ends the process (step S18). On the other hand, if it is determined in the comparison process of step S16 that the Co ion concentration is higher than the threshold value, operation unit 53 determines battery cell 60 to be inspected as a defective product and ends the process (step S17).

  When the battery impedance characteristic of the battery cell 60 is as shown in FIG. 16, in the determination process of step S16, the Co ion concentration derived from the relationship between the imaginary value change and the Co ion concentration is used. Is preferred. This is because the change with respect to the Co ion concentration is larger in the imaginary value change amount. This is because the estimation accuracy of the Co ion concentration is improved by using a component having a large change with respect to the Co ion concentration.

  From the above description, in the ion concentration estimation method according to the second embodiment, the battery impedance value is measured while switching the frequency of the measurement signal at a predetermined frequency interval, and the real value change amount between two adjacent points determined in advance and At least one of the imaginary value change amounts is calculated. Then, the Co ion concentration corresponding to the real value change amount or the imaginary value change amount is estimated with reference to the ion concentration estimation information (for example, the graph shown in FIG. 16).

  In the second embodiment, the Co ion concentration is estimated based on the battery impedance value measured between the positive electrode and the negative electrode of battery cell 60. Thus, in the second embodiment, the battery cell 60 does not need to be provided with the reference electrode.

  The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the scope of the present invention. In the above embodiment, the case where the oxidation-reduction substance is cobalt (Co) has been described by taking a nickel hydrogen battery as an example. However, the redox material is not limited to this, and the present invention is applicable as long as it is a substance that reacts on both the positive electrode and the negative electrode. For example, in the case of a lithium ion storage battery, iron (Fe) etc. are mentioned as a redox material.

DESCRIPTION OF SYMBOLS 1 ion concentration estimation apparatus 2 ion concentration estimation apparatus 3 ion concentration estimation apparatus 10 ion concentration calculation apparatus 11 measurement control part 12 measured value acquisition part 13 calculating part 14 memory 20 battery cell 21 positive electrode 22 negative electrode 23 reference electrode 31 negative electrode impedance measuring device 32 Negative electrode impedance measuring device 33 SOC regulator 40 Battery module 41 Positive electrode 42 Negative electrode 50 Ion concentration calculating device 51 Measurement control unit 52 Measured value acquiring unit 53 Operation unit 54 Memory 60 Battery cell 71 Battery impedance measuring device

Claims (16)

Charge rate regulator to adjust the charge rate of the secondary battery,
A negative electrode impedance measuring device for measuring the negative electrode impedance value of the secondary battery by switching to the secondary battery while switching the frequency of the measurement signal at predetermined intervals;
Calculating the ion concentration in the electrolyte of the secondary battery using an ion concentration estimating device having a calculation unit for estimating the ion concentration of the redox material in the electrolyte of the secondary battery based on the negative electrode impedance value It is a method of estimating the ion concentration of a secondary battery,
Referring to a Nyquist diagram generated using a plurality of the negative electrode impedance values acquired from the secondary battery adjusted to have a predetermined charging rate,
The redox ion concentration corresponding to the size of the spiral-shaped portion is referred to with reference to the ion concentration estimation information prepared in advance and showing the correspondence between the size of the spiral-shaped portion and the redox ion concentration in the Nyquist diagram. Method of estimating ion concentration of secondary battery to be calculated.   The method according to claim 1, wherein the size of the spiral-shaped portion is determined based on a difference between real value components of the two negative electrode impedance values on the Nyquist diagram. The size of the spiral-shaped portion is determined based on the smallest real value change amount in which the value is the smallest among the differences between real value components of the two negative electrode impedance values on the Nyquist diagram,
The method for estimating ion concentration of a secondary battery according to claim 1, wherein the ion concentration estimation information indicates the correspondence between the minimum real value change amount and the redox ion concentration. The size of the spiral-shaped portion is determined based on the smallest real value change amount in which the value is the smallest among the differences between the real value components of two adjacent negative electrode impedance values on the Nyquist diagram,
The method for estimating ion concentration of a secondary battery according to claim 1, wherein the ion concentration estimation information indicates the correspondence between the minimum real value change amount and the redox ion concentration.   The Nyquist diagram is generated by plotting the negative electrode admittance value calculated from the negative electrode impedance value, and the size of the spiral shaped portion of the Nyquist diagram is determined based on the negative electrode admittance value. The ion concentration estimation method of the secondary battery of any one of-.   The method for estimating the ion concentration of a secondary battery according to any one of claims 1 to 5, wherein a temperature adjustment process is performed to set the secondary battery to a predetermined temperature before acquiring the negative electrode impedance value.   The remaining life corresponding to the calculated redox ion concentration is calculated with reference to battery life information indicating the relationship between the redox ion concentration and the remaining life of the secondary battery. The ion concentration estimation method of the secondary battery of any one term. An ion concentration estimation device for estimating the ion concentration of a redox substance in the electrolyte solution of a secondary battery, comprising:
Charge rate regulator to adjust the charge rate of the secondary battery,
A negative electrode impedance measuring device that outputs a measurement signal to the secondary battery while switching the frequency of the measurement signal at a predetermined frequency interval, and measuring the negative electrode impedance value of the negative electrode of the secondary battery for each frequency of the measurement signal;
And a calculation unit for estimating the ion concentration in the electrolyte solution of the secondary battery based on the Nyquist diagram generated using the plurality of measured negative electrode impedance values,
The arithmetic unit is
The ion concentration for calculating the redox ion concentration corresponding to the size of the spiral-shaped portion by referring to the ion concentration estimation information showing the correspondence between the size of the spiral-shaped portion and the redox ion concentration in the Nyquist diagram Estimator.   The calculation unit calculates remaining life corresponding to the calculated redox ion concentration with reference to battery life information indicating the relationship between the redox ion concentration and the remaining life of the secondary battery. Item 9. An apparatus for estimating ion concentration of a secondary battery according to item 8. Charge rate regulator to adjust the charge rate of the secondary battery,
A battery impedance measuring device which applies the frequency of a measurement signal to the secondary battery while switching the frequency of the measurement signal at predetermined intervals, and measures a battery impedance value between the positive electrode and the negative electrode of the secondary battery;
And calculating a concentration of ions in the electrolyte of the secondary battery using an ion concentration estimation apparatus having a calculation unit for estimating the ion concentration of the redox material in the electrolyte of the secondary battery based on the battery impedance value. It is a method of estimating the ion concentration of a secondary battery,
Referring to a Nyquist diagram generated using a plurality of the battery impedance values acquired from the secondary battery adjusted to have a predetermined charging rate,
In the Nyquist diagram, the difference between real-valued components between predetermined two battery impedance values on the Nyquist diagram in the transition frequency region or the difference between imaginary-valued components is changed by a real-valued value, or , Calculated as an imaginary value change,
The oxidation corresponding to the real value change amount or the imaginary value change amount with reference to ion concentration estimation information prepared in advance and showing the correspondence between the real value change amount or the imaginary value change amount and the redox ion concentration. The ion concentration estimation method of the secondary battery which calculates a reducing substance ion concentration.   The transition frequency range is determined from the measurement frequency of the battery impedance value at which the correlation value between the Nyquist diagram and the arc spectrum generated due to the capacity component of the secondary battery deviates by a predetermined value or more. 9. The method according to claim 8, wherein the frequency range between the measurement frequency of the battery impedance value and the correlation value with the linear spectrum generated due to the diffusion component of the secondary battery approaches a predetermined value or more. .   10. The secondary battery according to claim 8, wherein the battery impedance value used to calculate the real value change amount or the imaginary value change amount is two adjacent battery impedance values on the Nyquist diagram. Ion concentration estimation method.   The Nyquist diagram is generated by plotting a battery admittance value calculated from the battery impedance value, and the real value change amount or the imaginary value change amount is calculated based on the battery admittance value. The ion concentration estimation method of the secondary battery of any one of 10 items.   14. The remaining life corresponding to the calculated redox ion concentration is calculated with reference to battery life information indicating the relationship between the redox ion concentration and the remaining life of the secondary battery. The ion concentration estimation method of the secondary battery of any one term. An ion concentration estimating device for estimating ion concentration in an electrolyte solution of a secondary battery, comprising:
A charging rate regulator for adjusting the charging rate of the secondary battery;
A battery impedance that outputs a measurement signal to the secondary battery while switching the frequency of the measurement signal at predetermined frequency intervals, and measures a battery impedance value between the positive electrode and the negative electrode of the secondary battery for each frequency of the measurement signal A measuring instrument,
And an operation unit for estimating the ion concentration in the electrolyte solution of the secondary battery based on the Nyquist diagram generated using the plurality of measured battery impedance values.
The arithmetic unit is
In the Nyquist diagram, the difference between real-valued components between predetermined two battery impedance values on the Nyquist diagram in the transition frequency region or the difference between imaginary-valued components is changed by a real-valued value, or , Calculated as an imaginary value change,
The oxidation corresponding to the real value change amount or the imaginary value change amount with reference to ion concentration estimation information prepared in advance and showing the correspondence between the real value change amount or the imaginary value change amount and the redox ion concentration. Ion concentration estimation device for secondary battery that calculates the concentration of reducing substance ions.   The calculation unit calculates remaining life corresponding to the calculated redox ion concentration with reference to battery life information indicating the relationship between the redox ion concentration and the remaining life of the secondary battery. The ion concentration estimation apparatus of the secondary battery of item 15.

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