Battery degradation determination method, battery degradation determination device, battery management system, battery-equipped device, and storage medium

Abstract

Embodiments of the present invention relate to and provide a method for determining battery degradation, a battery degradation determination device, a battery management system, a battery-mounted device, and a storage medium that can appropriately correct the effects caused by uneven lithium concentration in at least one of the positive electrode and the negative electrode and infer the internal state of the battery. An embodiment provides a method for determining degradation of a battery to be determined. The degradation determination method infers a correction coefficient for correcting the difference in the lithium concentration distribution in the target electrode when charging the battery with the first current and the lithium concentration distribution in the target electrode when charging the battery with the second current, which is larger than the first current, based on the potential difference of the target electrode when charging the battery with the first current and the potential difference of the target electrode when charging the battery with the second current, and the impedance of the target electrode when charging with the second current, for the target electrode that is at least one of the positive electrode and the negative electrode of the battery.

Description

Technical Field

[0001] Embodiments of the present invention relate to a method for determining battery degradation, a device for determining battery degradation, a battery management system, a battery-mounted device, and a storage medium. Background Art

[0002] In recent years, for batteries such as secondary batteries, the internal state of the battery has been estimated based on measurement data including measured values such as the battery's current and voltage, and battery degradation has been determined based on the estimated internal state. In such determinations, the internal state of the battery being determined is estimated using parameters such as the capacity of the positive electrode's active material, the capacity of the negative electrode's active material, and the impedance (internal resistance) of the battery as internal state parameters representing the battery's internal state. Based on these estimated internal state parameters, the degree and rate of battery degradation are determined.

[0003] In batteries such as secondary batteries, it is necessary to estimate the internal state of the battery while the battery is being rapidly charged at a high charge rate, thereby shortening the charging time. For example, by supplying current to the battery based on a current waveform formed by superimposing the high-charge rate charging current and alternating current, the battery's impedance can be measured at each of multiple frequencies. However, in lithium-ion secondary batteries, if they are rapidly charged at a high charge rate, the diffusion of lithium ions in at least one of the positive and negative electrodes becomes the rate limiting factor ("rate of charge" in Japanese). Therefore, if a secondary battery or other battery is rapidly charged, the lithium concentration in at least one of the positive and negative electrodes becomes uneven, and the lithium concentration distribution in at least one of the positive and negative electrodes becomes unstable. When determining battery degradation, even if the lithium concentration in at least one of the positive and negative electrodes is uneven due to rapid charging, it is necessary to be able to appropriately correct for the effects of the uneven lithium concentration and estimate the internal state of the battery. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a battery degradation determination method, a battery degradation determination device, a battery management system, a battery-mounted device, and a storage medium that can appropriately correct the influence caused by the uneven lithium concentration and infer the internal state of the battery even when the lithium concentration in at least one of the positive electrode and the negative electrode is uneven.

[0005] In an embodiment, a degradation determination method for determining the degradation of a battery to be determined is provided. In the degradation determination method, for an object electrode that is at least one of the positive electrode and the negative electrode of the battery, a correction coefficient is inferred based on the difference between the potential of the object electrode during charging of the battery with a first current and the potential of the object electrode during charging of the battery with a second current greater than the first current, and the impedance of the object electrode during charging with the second current. The correction coefficient corrects the difference between the lithium concentration distribution in the object electrode during charging with the first current and the lithium concentration distribution in the object electrode during charging with the second current.

[0006] According to the above configuration, it is possible to provide a battery degradation determination method, a battery degradation determination device, a battery management system, a battery-mounted device, and a storage medium that can appropriately correct the influence caused by the uneven lithium concentration in at least one of the positive electrode and the negative electrode and infer the internal state of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic diagram showing a battery management system according to a first embodiment.

[0008] Figure 2 is a schematic diagram showing an example of the current flowing through the battery in the measurement of the impedance of the battery according to the first embodiment.

[0009] Figure 3 is a schematic diagram showing an example of the frequency characteristics of the impedance of the battery according to the first embodiment and the frequency characteristics of the impedance of each of the positive electrode and the negative electrode of the battery.

[0010] Figure 4 is a schematic diagram for explaining an internal state parameter indicating the internal state of the battery.

[0011] Figure 5 is a schematic diagram for explaining the following process in the first embodiment: inferring a correction coefficient for correcting the difference between the lithium concentration distribution in the positive electrode during charging with the first current and the lithium concentration distribution in the positive electrode during charging with the second current, and a correction coefficient for correcting the difference between the lithium concentration distribution in the negative electrode during charging with the first current and the lithium concentration distribution in the negative electrode during charging with the second current.

[0012] Figure 6 is a flowchart showing the process during charging with the first current by the degradation determination device according to the first embodiment.

[0013] Figure 7It is a flowchart showing the processing during charging with a second current by the degradation determination device of the first embodiment.

[0014] Figure 8 It is a schematic diagram showing the calculation results of the capacity retention rate during charging relative to 1C for each of the three test specimens during inspection verification.

[0015] Explanation of reference numerals

[0016] 1 Management system, 2 Battery-mounted device, 3 Degradation determination device, 5 Battery, 6 Measurement circuit, 7 Battery management unit, 11 Transceiver unit, 12 Impedance measurement unit, 13 Internal state inference unit, 15 Correction factor calculation unit, 16 Data storage unit. Detailed implementation manner

[0017] Hereinafter, the embodiments will be described with reference to the drawings.

[0018] (First embodiment)

[0019] First, as an example of the embodiment, the first embodiment will be described. Figure 1 It is a schematic diagram showing the management system of the battery of the first embodiment. As Figure 1 shown, the management system 1 includes a battery-mounted device 2 and a degradation determination device 3. A battery 5, a measurement circuit 6, and a battery management unit (BMU: battery management unit) 7 are mounted in the battery-mounted device 2. Examples of the battery-mounted device 2 include large-scale energy storage devices for power systems, smartphones, vehicles, power supply devices for installation, robots, and drones. Examples of the vehicle that becomes the battery-mounted device 2 include railway vehicles, electric buses, electric vehicles, plug-in hybrid vehicles, and electric motorcycles.

[0020] The battery 5 is, for example, a secondary battery such as a lithium-ion secondary battery. The battery 5 may be formed of a single battery cell (single cell), or may be a battery module or a battery unit block formed by electrically connecting a plurality of single battery cells. When the battery 5 is formed of a plurality of single battery cells, in the battery 5, the plurality of single battery cells may be electrically connected in series, and the plurality of single battery cells may also be electrically connected in parallel. In addition, in the battery 5, both a series connection structure in which a plurality of single battery cells are connected in series and a parallel connection structure in which a plurality of single battery cells are connected in parallel may be formed. In addition, the battery 5 may be any of a battery string, a battery array, and a storage battery in which a plurality of battery modules are electrically connected.

[0021] In a state where the battery 5 is being charged or discharged, etc., the measurement circuit 6 detects and measures parameters related to the battery 5. In the measurement circuit 6, in one charging or discharging, etc. of the battery 5, the detection and measurement of the parameters are periodically performed at a prescribed timing. That is, the measurement circuit 6 measures the parameters related to the battery 5 at each of a plurality of measurement time points in one charging or discharging, etc. of the battery 5, and measures the parameters related to the battery 5 a plurality of times. Among the parameters related to the battery 5, there are included the current flowing through the battery 5, the voltage of the battery 5, the temperature of the battery 5, and the like. Therefore, the measurement circuit 6 includes a galvanometer for measuring current, a voltmeter for measuring voltage, a temperature sensor for measuring temperature, and the like.

[0022] The battery management unit 7 controls the charging and discharging of the battery 5, etc., constitutes a processing device (computer) for managing the battery 5, and includes a processor and a storage medium. The processor includes any one of a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a microcomputer, an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), and the like. In the storage medium, in addition to a main storage device such as a memory, an auxiliary storage device may also be included. Examples of the storage medium include a magnetic disk, an optical disk (CD-ROM, CD-R, DVD, etc.), an optical magnetic disk (MO, etc.), and a semiconductor memory. In the battery management unit 7, the processor and the storage medium may each be one or plural. In the battery management unit 7, the processor performs processing by executing a program stored in the storage medium, etc. Further, in the battery management unit 7, the program executed by the processor may also be stored in a computer (server) connected via a network such as the Internet, or a server in a cloud environment. In this case, the program is downloaded via the network by the processor.

[0023] The deterioration determination device 3 determines the deterioration of the battery 5 based on information related to the battery 5. Therefore, the battery 5 becomes the determination object for the determination of deterioration by the deterioration determination device 3. In the present embodiment, the deterioration determination device 3 is provided outside the battery-mounted device 2. The deterioration determination device 3 includes a transceiver unit 11, an impedance measurement unit 12, an internal state inference unit 13, a correction coefficient calculation unit 15, and a data storage unit 16. The deterioration determination device 3 is, for example, a server that can communicate with the battery management unit 7 via a network. In this case, the deterioration determination device 3 has a processor and a storage medium in the same way as the battery management unit 7. Further, the transceiver unit 11, the impedance measurement unit 12, the internal state inference unit 13, and the correction coefficient calculation unit 15 perform a part of the processing performed by the processor of the deterioration determination device 3, and the storage medium of the deterioration determination device 3 functions as the data storage unit 16.

[0024] Further, in one example, the deterioration determination device 3 may be a cloud server configured in a cloud environment. The infrastructure of the cloud environment is composed of virtual processors such as virtual CPUs and cloud memories. Therefore, when the deterioration determination device 3 is a cloud server, the transceiver unit 11, the impedance measurement unit 12, the internal state inference unit 13, and the correction coefficient calculation unit 15 perform a part of the processing performed by the virtual processor. Further, the cloud memory functions as the data storage unit 16.

[0025] Further, the data storage unit 16 may be provided in a computer different from the battery management unit 7 and the deterioration determination device 3. In this case, the deterioration determination device 3 is connected to the computer provided with the data storage unit 16 via a network. Further, the deterioration determination device 3 may be mounted on the battery-mounted device 2. In this case, the deterioration determination device 3 is composed of a processing device mounted on the battery-mounted device 2 or the like. Further, when the deterioration determination device 3 is mounted on the battery-mounted device 2, it may be that a processing device mounted on the battery-mounted device 2 or the like performs the processing of the deterioration determination device 3 described later, and also performs the processing of the battery management unit 7 such as control of charging and discharging of the battery 5. Hereinafter, the processing of the deterioration determination device 3 will be described.

[0026] The transceiver 11 communicates with processing devices other than the degradation determination device 3 via a network. The transceiver 11 receives measurement data from the battery management unit 7, for example, and the measurement data includes the measurement results of the measurement circuit 6 of the aforementioned parameters related to the battery 5. Based on the measurement results in the measurement circuit 6, etc., the measurement data is generated by the battery management unit 7, etc. The measurement data includes the measured values of the parameters related to the battery 5 at each measurement timing of multiple measurement timings (multiple measurements). In addition, the measurement data includes the time change (time history record) of the parameters related to the battery 5. Therefore, the measurement data includes the time change (time history record) of the current of the battery 5, the time change (time history record) of the voltage of the battery 5, and the time change (time history record) of the temperature of the battery 5. The transceiver 11 writes the received measurement data to the data storage unit 16.

[0027] At least one of the battery management unit 7 and the processor of the degradation determination device 3 may estimate at least one of the charge capacity and SOC (state of charge) of the battery 5 based on, for example, the measurement results of the measurement circuit 6 for the parameters related to the battery 5. Furthermore, the degradation determination device 3 may obtain, as data included in the aforementioned measurement data, an estimated value of either the charge capacity or the SOC of the battery 5, and a temporal change (time history) in the estimated value of either the charge capacity or the SOC of the battery 5. Furthermore, the measurement data may also include data described below, which indicates the relationship between the aforementioned measured parameters related to the battery 5 and the estimated charge capacity or SOC of the battery 5. In this case, for example, data indicating the relationship between the measured voltage of the battery 5 and the estimated charge capacity or SOC of the battery 5 is included in the measurement data.

[0028] The real-time charge capacity of the battery 5 can be calculated based on the charge capacity of the battery 5 at the start of charging or discharging, etc., and the time variation of the current of the battery 5. In this case, the current cumulative value of the current of the battery 5 since the start of charging or discharging is calculated based on the time variation of the current. The charge capacity of the battery 5 is then calculated based on the charge capacity of the battery 5 at the start of charging or discharging, etc., and the calculated current cumulative value.

[0029] In addition, the SOC of the battery 5 is specified based on, for example, the voltage of the battery 5. In the battery 5, a lower limit voltage V is specified for the voltage. min And the upper limit voltage V maxWhen determining the state of charge (SOC) of the battery 5 based on the voltage of the battery 5, the SOC of the battery 5 is determined based on the voltage change of the battery 5 when the concentration of lithium at the positive electrode, negative electrode, etc. is in a stable or quasi-stable state. In one example, based on the voltage change of the battery 5 under the specified charging conditions where the concentration of lithium at the positive electrode, negative electrode, etc. becomes stable or quasi-stable, the SOC of the battery 5 is determined. In this case, the state where the voltage of the battery 5 under the aforementioned specified charging conditions becomes the lower limit voltage V min is set as the state where the SOC is 0%, and the state where the voltage of the battery 5 under the specified charging conditions becomes the upper limit voltage V max is set as the state where the SOC is 100%.

[0030] Moreover, the charging capacity of the battery 5 from the state where the SOC is 0% to the state where the SOC is 100% becomes the battery capacity of the battery 5. The real-time SOC of the battery 5 is the ratio of the real-time charging amount of the battery 5 with respect to the battery capacity of the battery 5, with the charging amount in the state where the SOC is 0% as the reference (0). Therefore, the SOC of the battery 5 can be calculated based on the battery capacity and the charging amount of the battery 5. In another example, instead of the voltage change of the battery 5 under the specified charging conditions, the SOC of the battery 5 can be determined based on the voltage change of the battery 5 when the concentration of lithium at the positive electrode, negative electrode, etc. is in a stable state, that is, the change in the open circuit voltage (OCV) of the battery 5. After a certain period of time has passed since the charging or discharging has stopped, the concentration of lithium becomes stable. Therefore, by combining the open circuit voltage at this time with the SOC, the SOC is determined based on the open circuit voltage.

[0031] The impedance measurement unit 12 measures the impedance of the battery 5 to be determined based on the measurement data received by the transceiver unit 11, etc. In the measurement of the impedance of the battery 5 by the impedance measurement unit 12, the battery management unit 7, etc. overlaps the current variation component ΔI that periodically changes with a specified current variation amplitude (2×ΔI max ) with the reference current value I ref to form a current waveform current (I ref +ΔI) and supplies it to the battery 5. Therefore, in the measurement of the impedance of the battery 5, a current waveform current that periodically changes with a specified current variation amplitude (2×ΔI ref ) centered around the reference current value I max is supplied to the battery 5 as the charging current. Here, the reference current value I ref corresponds to the time average value of the current supplied to the battery 5, and the current variation amplitude (2×ΔI max ) corresponds to the peak-to-peak value of the current variation component ΔI whose current value periodically changes.

[0032] Figure 2 is a schematic diagram showing an example of the current flowing through the battery in the measurement of the impedance of the battery in the first embodiment. In Figure 2 , the horizontal axis represents time t and the vertical axis represents current I. In Figure 2 an example, a reference current value I ref has a current variation component ΔI(t) that periodically varies with a current variation amplitude (2×ΔI max ), and a current waveform (I ref +ΔI(t)) that periodically varies with the reference current value I ref as the center current value is supplied to the battery 5 as a charging current. The current (I ref +ΔI(t)) is the locus of the time variation of the charging current. In addition, the ratio of the reference current value I ref to the battery capacity of the battery 5 is defined as the charging rate of the battery 5. In addition, it is preferable that the current (I ref +ΔI(t)) is continuously supplied to the battery 5 from the start to the end of the charging of the battery 5. However, it is also possible to instantaneously stop the supply of current to the battery 5 or reduce the current supplied to the battery 5 to a current value smaller than the reference current value I ref during the period from the start to the end of the charging of the battery 5. In this case, the impedance of the battery 5 is not measured during the period when the supply of current to the battery is stopped or reduced. In addition, in Figure 2 an example, the current waveform is a sine wave (sin wave), but the current waveform can also be a current waveform other than a sine wave such as a triangular wave and a sawtooth wave.

[0033] For the measurement circuit 6, in a state where the aforementioned current (I ref +ΔI(t)) is supplied to the battery 5 and the battery 5 is supplied with current in a current waveform that periodically varies in current value, the current and voltage of the battery 5 are measured at a plurality of measurement timings. Then, the transceiver unit 11 of the deterioration determination device 3 receives the measurement results of the current and voltage of the battery 5 in the following state as the aforementioned measurement data, and the state is a state where the battery 5 is being charged with a charging current having a current waveform that periodically varies in current value. The measurement results of the current and voltage of the battery 5 in a state where the battery 5 is supplied with current in a current waveform that periodically varies in current value include the measured values of the current and voltage of the battery 5 at each of the plurality of measurement timings and the time variations (time histories) of the current and voltage of the battery 5, respectively.

[0034] The impedance measurement unit 12 calculates the frequency characteristics of the impedance of the battery 5 based on the measurement results received by the transceiver unit 11. Thus, by passing a current through the battery 5 with the aforementioned current waveform whose current value changes periodically, the frequency characteristics of the impedance of the battery 5 are measured. In one example, the impedance measurement unit 12 calculates the peak-to-peak value (variation amplitude) in the periodic change of the current of the battery 5 based on the time change of the current of the battery 5, and calculates the peak-to-peak value (variation amplitude) in the periodic change of the voltage of the battery 5 based on the time change of the voltage of the battery 5. Then, the impedance measurement unit 12 calculates the impedance of the battery 5 from the ratio of the peak-to-peak value of the voltage to the peak-to-peak value of the current. Then, the impedance of the battery 5 as described above is calculated using a plurality of current waveforms with different frequencies, thereby measuring the frequency characteristics of the impedance of the battery 5.

[0035] In addition, in another example, a current waveform with a reference frequency is passed through the battery, and the time changes of the current and voltage of the battery 5 are obtained as measurement data. Then, the impedance measurement unit 12 performs Fourier transform or the like on the time changes of the current and voltage of the battery 5 respectively, and calculates the frequency spectra of the current and voltage of the battery 5 respectively as the frequency characteristics of the current and voltage of the battery 5. In the calculated frequency spectra of the current and voltage of the battery 5 respectively, in addition to the component of the aforementioned reference frequency, components that are integer multiples of the reference frequency are also shown. Then, the impedance measurement unit 12 calculates the autocorrelation function of the time change of the current of the battery 5 and the cross-correlation function between the time change of the current of the battery 5 and the time change of the voltage of the battery 5 based on the frequency characteristics of the current and voltage of the battery 5 respectively. Then, the impedance measurement unit 12 calculates the frequency characteristics of the impedance of the battery 5 using the autocorrelation function and the cross-correlation function. The frequency characteristics of the impedance of the battery 5 are calculated, for example, by dividing the cross-correlation function by the autocorrelation function.

[0036] The impedance measurement unit 12 obtains, for example, a complex impedance curve (Cole-Cole curve) of the impedance as a measurement result of the frequency characteristics of the impedance of the battery 5. In the complex impedance curve, the impedance of the battery 5 is shown for each of a plurality of frequencies. Then, in the complex impedance curve, the real part and the imaginary part of the impedance of the battery 5 are shown for each of a plurality of frequencies. In addition, the method of measuring the frequency characteristics of the impedance of the battery by passing a current through the battery with a current waveform whose current value changes periodically, and the complex impedance curve and the like as the measurement result of the frequency characteristics of the impedance of the battery are shown in Reference 1 (Japanese Patent Laid-Open No. 2019-132655) and Reference 2 (International Publication No. 2017 / 047192). In the present embodiment, similarly to any of Reference 1 and Reference 2, the frequency characteristics of the impedance of the battery 5 can also be measured.

[0037] The impedance measurement unit 12 calculates the impedance of each of the positive electrode and the negative electrode of the battery 5 based on the measurement results of the impedance of the battery 5, such as the frequency characteristics of the impedance of the battery 5 including the battery 5. Here, the impedance of the battery 5 includes the impedance of each of the positive electrode and the negative electrode, the resistance of the separator, and the like. Moreover, in each of the positive electrode and the negative electrode, the impedance includes an ohmic resistance, a reaction resistance, a diffusion resistance, and the like. In each of the positive electrode and the negative electrode, the ohmic resistance includes the electrical resistance of the electrode (current collector and active material-containing layer), the reaction resistance includes the resistance to charge movement on the interface of the electrode, and the resistance based on the coating film formed on the surface of the electrode, and the diffusion resistance includes the resistance to the diffusion of ions such as lithium ions in the active material.

[0038] An equivalent circuit model for the positive electrode, the negative electrode, and the separator of the battery 5 is stored in the data storage unit 16. In the equivalent circuit model, the relationships between the ohmic resistance of the positive electrode, the reaction resistance of the positive electrode, the diffusion resistance of the positive electrode, the ohmic resistance of the negative electrode, the reaction resistance of the negative electrode, the diffusion resistance of the negative electrode, and the resistance of the separator, etc., and the frequency are shown. That is, in the equivalent circuit model, the frequency characteristics of the above-mentioned resistances are shown. In addition, the frequency characteristics of each of the above-mentioned resistances change corresponding to the temperature and the charge amount (SOC) of the battery 5. Therefore, in the equivalent circuit model, for the frequency characteristics of each resistance, they are set for each of a plurality of different temperatures and for each of a plurality of different charge amounts (SOC).

[0039] The impedance measurement unit 12 performs a fitting calculation using the measurement results of the frequency characteristics of the impedance of the battery 5 and the frequency characteristics of each resistance in the equivalent circuit model. At this time, the ohmic resistance of the positive electrode, the reaction resistance of the positive electrode, the diffusion resistance of the positive electrode, the ohmic resistance of the negative electrode, the reaction resistance of the negative electrode, the diffusion resistance of the negative electrode, and the resistance of the separator, etc., are used as variables for the fitting calculation to calculate the variables. Then, the impedance measurement unit 12 calculates the impedance of the positive electrode from the calculated ohmic resistance of the positive electrode, the reaction resistance of the positive electrode, and the diffusion resistance of the positive electrode through the fitting calculation. In addition, the impedance measurement unit 12 calculates the impedance of the negative electrode from the calculated ohmic resistance of the negative electrode, the reaction resistance of the negative electrode, and the diffusion resistance of the negative electrode through the fitting calculation. Thus, the impedance of each of the positive electrode and the negative electrode is measured.

[0040] In the present embodiment, as described above, the impedance measurement unit 12 calculates the impedance of each of the positive electrode and the negative electrode using the measurement result of the frequency characteristics of the impedance of the battery 5 and the equivalent circuit model. Therefore, in the present embodiment, for the impedance of each of the positive electrode and the negative electrode of the battery 5, the frequency characteristics are calculated and measured. That is, from the frequency characteristics of the impedance of the battery 5, the frequency characteristics of the impedance of the positive electrode and the frequency characteristics of the impedance of the negative electrode are separated. The impedance measurement unit 12 obtains, for example, the aforementioned complex impedance curve (Cole-Cole curve) of the impedance as the measurement result of the frequency characteristics of the impedance of each of the positive electrode and the negative electrode. The impedance measurement unit 12 writes the measurement result of the impedance of the battery 5 and the measurement results of the impedance of each of the positive electrode and the negative electrode into the data storage unit 16.

[0041] Figure 3 is a schematic diagram showing an example of the frequency characteristics of the impedance of the battery according to the first embodiment and the frequency characteristics of the impedance of each of the positive electrode and the negative electrode of the battery. In Figure 3 it, the frequency characteristics of the impedance are represented by a complex impedance curve. Further, in Figure 3 it, the horizontal axis represents the real component ZRe of the impedance, and the vertical axis represents the imaginary component ZIm of the impedance. Moreover, in Figure 3 it, the frequency characteristics Z of the impedance of the battery 5, the frequency characteristics Z c [[ID=-- --]] of the positive electrode of the battery 5 and the frequency characteristics Z a of the negative electrode of the battery 5 are shown. In Figure 3 an example of it, from the frequency characteristics Z of the impedance of the battery 5, the frequency characteristics Z c of the positive electrode and the frequency characteristics Z a of the negative electrode are separated.

[0042] In addition, the equivalent circuit models of the positive electrode, the negative electrode, and the separator of the battery 5 are shown in Reference 1 and Reference 2. The impedance measurement unit 12 can calculate the aforementioned respective resistances by performing fitting calculations using either the measurement result of the frequency characteristics of the impedance of the battery 5 or the equivalent circuit models shown in Reference 1 and Reference 2. In this case, the impedance of the positive electrode is also calculated using the ohmic resistance, reaction resistance, and diffusion resistance of the positive electrode calculated by the fitting calculation, and the impedance of the negative electrode is calculated using the ohmic resistance, reaction resistance, and diffusion resistance of the negative electrode calculated by the fitting calculation. Further, in Reference 1 and Reference 2, the portions corresponding to the ohmic resistance, reaction resistance, and diffusion resistance in the complex impedance curve are shown.

[0043] When passing the aforementioned current (I refIn a state where the battery 5 is being charged with (+ΔI(t)), for each of a plurality of mutually different state of charge (SOC) levels, the impedance measurement unit 12 generates the aforementioned complex impedance curve for the frequency characteristics of the impedance of the battery 5, and measures the impedance of the battery 5. Then, for each of the plurality of state of charge (SOC) levels for which the impedance of the battery 5 has been measured, the impedance measurement unit 12 generates the aforementioned complex impedance curve for the frequency characteristics of the impedance of each of the positive electrode and the negative electrode, and measures the impedance of each of the positive electrode and the negative electrode.

[0044] In addition, the impedance measurement unit 12 measures the impedance of the battery 5 and the impedance of each of the positive electrode and the negative electrode as described above, respectively, in a state where the battery 5 is being charged by supplying the first current and in a state where the battery 5 is being charged by supplying a second current that is greater than the first current. Here, when charging the battery 5 with the first current, the aforementioned reference current value is set to a first reference current value (first average current value) I1 ref , and a current waveform that periodically varies with the first reference current value I1 ref as the center current value is used to supply current to the battery 5. Thus, when charging with the first current, a current waveform in which the periodically varying current variation component ΔI is superimposed on the current of the first reference current value I1 ref , that is, a current (I1 ref +ΔI) is supplied to the battery 5. On the other hand, when charging the battery 5 with the second current, the aforementioned reference current value is set to a second reference current value (second average current value) I2 ref that is greater than the first reference current value I1 ref , and a current waveform that periodically varies with the second reference current value I2 ref as the center current value is used to supply current to the battery 5. Thus, when charging with the second current, a current waveform in which the periodically varying current variation component ΔI is superimposed on the current of the second reference current value I2 ref , that is, a current (I2 ref +ΔI) is supplied to the battery 5.

[0045] In addition, in one example, in the current waveform of the first current and the current waveform of the second current, the current variation amplitude (2×ΔI max ) of the current variation component ΔI is made to be the same or approximately the same size. Moreover, the current variation amplitude (2×ΔI max ) of the current waveform of each of the first current and the second current is smaller than the difference value between the first reference current value I1 ref and the second reference current value I2 ref . The first reference current value I1 of the first current refConverted to a charging rate of 0.5C or less, preferably 0.3C or less. Therefore, when charging with the first current, the battery 5 is charged at a low charging rate. On the other hand, the second reference current value I2 of the second current ref Converted to a charging rate of 1C or more, preferably 3C or more. Therefore, when charging with the second current, the battery 5 is rapidly charged at a high charging rate.

[0046] The impedance measurement unit 12 measures the impedance of the battery 5 and the impedance of each of the positive electrode and the negative electrode for each of a plurality of different states of charge (SOC) during charging with the first current and during charging with the second current. During charging with the first current at a low charging rate for the battery 5, the impedance measurement unit 12 performs measurement of the impedance of the battery 5 and measurement of the impedance of each of the positive electrode and the negative electrode at intervals of 3% to 5% in terms of SOC. On the other hand, during charging with the second current at a high charging rate for the battery 5, the impedance measurement unit 12 preferably performs measurement of the impedance of the battery 5 and measurement of the impedance of each of the positive electrode and the negative electrode at intervals of 10% to 20% in terms of SOC. In the measurement of the impedance during charging with the second current, by increasing the interval of the plurality of states of charge (SOC) for which the impedance is measured, the influence of noise on the measurement of the frequency characteristics of the impedance of the battery 5, such as a plurality of impedance curves, is suppressed.

[0047] The internal state inference unit 13 acquires the impedance of the battery 5 measured at each of a plurality of charge amounts during charging with the first current, and the impedance of each of the positive electrode and the negative electrode measured at each of the plurality of charge amounts during charging with the first current. The internal state inference unit 13 infers the internal state of the battery 5 based on the measurement results of the impedance of each of the positive electrode and the negative electrode at each of the plurality of charge amounts during charging with the first current. Here, during the charging of the battery 5 with the first current, the battery 5 is charged at a low charging rate as described above, so that lithium ions are appropriately and uniformly diffused in each of the positive electrode and the negative electrode. In addition, heat generation inside the battery 5 is suppressed, and the temperature distribution inside the battery 5 becomes uniform or substantially uniform. Therefore, during charging with the first current, in each of the positive electrode and the negative electrode, the concentration of lithium at each active material particle becomes uniform or substantially uniform, and the concentration of lithium in each of the positive electrode and the negative electrode becomes uniform or substantially uniform. Thus, during charging with the first current, the lithium concentration distribution in each of the positive electrode and the negative electrode becomes stable or quasi-stable. Here, the lithium concentration distribution is a parameter indicating the non-uniformity of the lithium concentration in the positive electrode or the negative electrode. For example, it is set as the difference between the lithium concentration at the interface of the active material in contact with the electrolyte surface in the positive electrode or the negative electrode and the lithium concentration at the center of the active material. The unit of the difference between the lithium concentration at the interface of the active material and the lithium concentration at the center of the active material is, for example, (mol / m 3 ).

[0048] The internal state inference unit 13 infers the internal state of the battery 5 by inferring the internal state parameters of the battery 5. Examples of the internal state parameters of the battery 5 include the capacity (reaction area) of the positive electrode corresponding to the capacity of the electrode active material and the capacity (reaction area) of the negative electrode corresponding to the capacity of the negative electrode active material. In addition, the internal state parameters include the initial discharge amount of the positive electrode and the initial charge amount of the negative electrode, and may also include the impedance (internal resistance) of the battery 5 described above and the impedance of each of the positive electrode and the negative electrode. In addition, the shift of the operation window (SOW: Shift of Operation Window), which is the offset between the initial discharge amount of the positive electrode and the initial charge amount of the negative electrode, is included in the internal state parameters of the battery 5. In addition, the internal state parameters include the lithium concentration of the positive electrode and the lithium concentration of the negative electrode, and include the potential range available for the positive electrode and the potential range available for the negative electrode.

[0049] Figure 4 is a schematic diagram for explaining the internal state parameters indicating the internal state of the battery. In Figure 4In this case, the charge amount is shown on the horizontal axis and the potential is shown on the vertical axis. Based on the potential changes of the positive electrode and the negative electrode in a state where the concentration distributions of lithium in the positive electrode and the negative electrode are stable or quasi-stable, internal state parameters such as the capacity of the positive electrode and the capacity of the negative electrode are specified. In one example, based on the potential changes of the positive electrode and the negative electrode under specified charging conditions where the concentration distributions of lithium in the positive electrode, the negative electrode, etc. become stable or quasi-stable, internal state parameters are specified. For example, based on the potential changes of the positive electrode and the negative electrode during charging of the battery 5 based on the aforementioned first current (the first reference current value I1 ref ), internal state parameters are specified. In Figure 4 , the potential changes of the positive electrode and the potential changes of the negative electrode in a state where the concentration distributions of lithium in the positive electrode and the negative electrode are stable or quasi-stable are shown.

[0050] As Figure 4 shown, in the battery 5, for the potential of the positive electrode under the aforementioned specified charging conditions, a lower limit potential V cmin and an upper limit potential Vc max are specified. The potential of the positive electrode becomes higher as the charge amount of the battery increases. In addition, in the positive electrode, the discharge amount in a state where the potential of the positive electrode is the lower limit potential V cmin becomes the initial discharge amount of the positive electrode, and the discharge amount in a state where the potential of the positive electrode is the upper limit potential Vc max becomes the upper limit discharge amount of the positive electrode. Moreover, the discharge amount of the positive electrode from the initial discharge amount to the upper limit discharge amount becomes the capacity w c of the positive electrode of the battery 5. In addition, in the battery 5, for the potential of the negative electrode under the aforementioned specified charging conditions, a lower limit potential V amin and an upper limit potential V amax are specified. The potential of the negative electrode becomes lower as the charge amount of the battery increases. In addition, in the negative electrode, the charge amount in a state where the potential of the negative electrode is the upper limit potential V amax becomes the initial charge amount of the negative electrode, and the charge amount in a state where the potential of the negative electrode is the lower limit potential V amin becomes the upper limit charge amount of the negative electrode. Moreover, the charge amount of the negative electrode from the initial charge amount to the upper limit charge amount becomes the capacity w a of the negative electrode of the battery 5.

[0051] In addition, in Figure 4 , the aforementioned SOW as an internal state parameter is shown, and the aforementioned battery capacity w eff as a battery characteristic of a battery is shown. As described above, the battery capacity w eff corresponds to the voltage of the battery 5 from the lower limit voltage V min to the upper limit voltage V max under specified charging conditions.The amount of charge up to that point. In addition, among the potentials of the positive electrode under the specified charging conditions, the range between the potential corresponding to the lower limit voltage V min and the potential corresponding to the upper limit voltage V max becomes the potential range ΔV c that can be utilized by the positive electrode. Moreover, among the potentials of the negative electrode under the specified charging conditions, the range between the potential corresponding to the lower limit voltage V min and the potential corresponding to the upper limit voltage V max becomes the potential range ΔV a that can be utilized by the negative electrode. In addition, the concentration of lithium in each of the positive electrode and the negative electrode changes corresponding to the charge amount (SOC) of the battery 5. Hereinafter, the concentration of lithium in the positive electrode at the charge amount Y is denoted as C c,Y , and the concentration of lithium in the negative electrode at the charge amount Y is denoted as C a,Y . Moreover, the fully charged state of the positive electrode, that is, the concentration of lithium in the positive electrode at the upper limit charge amount of the positive electrode, is denoted as C c,max , and the fully charged state of the negative electrode, that is, the concentration of lithium in the negative electrode at the upper limit charge amount of the negative electrode, is denoted as C a,max .

[0052] Here, in the battery 5, if the battery 5 deteriorates due to use, at least one of the capacity of the positive electrode and the capacity of the negative electrode decreases. In addition, if the battery 5 deteriorates, the concentration C c,Y of lithium in the positive electrode at the charge amount Y and the concentration C a,Y of lithium in the negative electrode at the charge amount Y change with respect to the start of use of the battery 5 and the like. In addition, if the battery 5 deteriorates, the initial charge amount of the negative electrode, the initial discharge amount of the positive electrode, the SOW, and the potential ranges that can be utilized by each of the positive electrode and the negative electrode also change with respect to the start of use and the like. Therefore, it is important to regularly and appropriately infer the internal state of the battery 5 during the use of the battery 5.

[0053] In addition, in another example, instead of the potential changes of the positive electrode and the negative electrode under the aforementioned specified charging conditions, based on the potential changes of the positive electrode and the negative electrode in a state where the lithium concentration distributions in the positive electrode and the negative electrode are stable, that is, the changes in the open circuit potentials (OCP: open circuit potential) of the positive electrode and the negative electrode, the aforementioned internal state parameters are specified. However, when charging with the first current and the like, in a state where the lithium concentration distributions in the positive electrode and the negative electrode are stable or quasi-stable, the potential change of the positive electrode is almost identical to the change in the open circuit potential of the positive electrode, and the potential change of the negative electrode is almost identical to the change in the open circuit potential of the negative electrode. In the following description, based on the potential changes of the positive electrode and the negative electrode during charging with the first current in a state where the lithium concentration distributions in the positive electrode and the negative electrode are stable or quasi-stable, the aforementioned internal state parameters are specified.

[0054] In addition, during charging of the battery 5, based on the Butler–Volmer equation, the current I flowing through the positive electrode is expressed in the form of Equation (1-A). c , and the current I flowing through the negative electrode is expressed in the form of Equation (1-B). a In Equation (1-A), the capacity w of the aforementioned positive electrode is shown c , the concentration C of lithium at the interface between the active material of the positive electrode and the electrolyte c,s , and the concentration C of lithium in the positive electrode in the fully charged state of the positive electrode c,max . In Equation (1-B), the capacity w of the aforementioned negative electrode is shown a , the concentration C of lithium at the interface between the active material of the negative electrode and the electrolyte a,s , and the concentration C of lithium in the negative electrode in the fully charged state of the negative electrode a,max . In addition, in Equation (1-A), η c represents the overvoltage with respect to the open-circuit potential of the positive electrode. In Equation (1-B), η a represents the overvoltage with respect to the open-circuit potential of the negative electrode. In addition, in Equation (1-A) and Equation (1-B), C e represents the concentration of the electrolyte, β represents the reaction multiplier, and k represents the constant based on the Butler–Volmer equation. Here, Equation (1-A) is the interfacial reaction between the surface of the active material of the positive electrode and the electrolyte. However, when the lithium concentration C c，s at the surface of the active material of the positive electrode (interface between the active material and the electrolyte) is regarded as the same or approximately the same stable or quasi-stable state as the average lithium concentration C c of the positive electrode, Equation (1-A) can be expressed as Equation (1-C). Similarly, Equation (1-B) is the interfacial reaction between the surface of the active material of the negative electrode and the electrolyte. However, when the lithium concentration C a，s at the surface of the active material of the negative electrode (interface between the active material and the electrolyte) is regarded as the same or approximately the same stable or quasi-stable state as the average lithium concentration C a of the negative electrode, Equation (1-B) can be expressed as Equation (1-D).

[0055] I c = kw c (C c，max -C c，s ) 0.5 (C c，s ) 0.5 (C e ) 0.5 {exp(βη c )-exp(-βη c )} (1-A)

[0056] I a = kw a (C a，max - C a，s ) 0.5 (C a，s ) 0.5 (C e ) 0.5 {exp(βη a ) - exp(-βη a )} (1 - B)

[0057] I c = kw c (C c，max - C c ) 0.5 (C c ) 0.5 (C e ) 0.5 {exp(βη c ) - exp(-βη c )} (1 - C)

[0058] I a = kw a (C a，max - C a ) 0.5 (C a ) 0.5 (C e ) 0.5 {exp(βη a ) - exp(-βη a )} (1 - D)

[0059] When the concentration distributions of lithium in the positive electrode and the negative electrode during charging of the battery 5 at the first current and the like are in a stable or quasi-stable state, the impedance R of the positive electrode at the charge amount Y c，Y can be expressed as in Equation (2 - A) using Equation (1 - C). Similarly, in the above-mentioned stable or quasi-stable state, the impedance R of the negative electrode at the charge amount Y a，Y can be expressed as in Equation (2 - B) using Equation (1 - D). From Equations (2 - A) and (2 - B), in each of the positive electrode and the negative electrode, the smaller the capacity (reaction area), the higher the impedance. In addition, in each of the positive electrode and the negative electrode, the lower the concentration of lithium, the higher the impedance.

[0060] R c，Y ≈ 1 / (kw c (C c，max - C c，Y ) 0.5 (C c，Y ) 0.5(C e ) 0.5 ) (2 - A)

[0061] R a，Y ≈1 / (kw a (C a，max -C a，Y ) 0.5 (C a，Y ) 0.5 (C e ) 0.5 ) (2 - B)

[0062] During the inference of the internal state of the battery 5, the internal state inference unit 13 uses the measurement result of the impedance R c 1 of the positive electrode during charging with the first current, and the impedance R c with respect to the capacity w c of the positive electrode shown in the aforementioned formula (2 - A) c and the relationship of the lithium concentration C c to perform a fitting calculation. That is, a fitting calculation is performed to match the calculation result of formula (2 - A) to the measurement result of the impedance R c 1 of the positive electrode. At this time, the capacity w c of the positive electrode and the lithium concentration C c are used as variables for the fitting calculation to calculate the variables. Thus, the capacity w c of the positive electrode and the lithium concentration C

[0063] are inferred as internal state parameters. a 1 of the negative electrode during charging with the first current, and the impedance R a with respect to the capacity w a of the negative electrode shown in the aforementioned formula (2 - B) a and the relationship of the lithium concentration C a to perform a fitting calculation. That is, a fitting calculation is performed to match the calculation result of formula (2 - B) to the measurement result of the impedance R a 1 of the negative electrode. At this time, the capacity w a of the negative electrode and the lithium concentration C a are used as variables for the fitting calculation to calculate the variables. Thus, the capacity w a of the negative electrode and the lithium concentration C

[0064] As described above, when the concentration distribution of lithium in the positive electrode during charging with the first current is in a stable or quasi-stable state, the concentration of lithium on the surface of the active material of the positive electrode becomes the same as or approximately the same as the average lithium concentration in the active material of the positive electrode. Therefore, by using the fitting calculation of Equation (2-A), the capacity w of the positive electrode is appropriately inferred c and the concentration C of lithium c . Moreover, when the concentration distribution of lithium in the negative electrode is in a stable or quasi-stable state, the concentration of lithium on the surface of the active material of the negative electrode becomes the same as or approximately the same as the average lithium concentration in the active material of the negative electrode. Therefore, by using the fitting calculation of Equation (2-B), the capacity w of the negative electrode is appropriately inferred a and the concentration C of lithium a .

[0065] The following data is stored in the data storage unit 16: The data uses at least the charge amount of the positive electrode and the concentration C of lithium ions c , and calculates the potential V of the positive electrode in the above-mentioned stable or quasi-stable state c . The aforementioned data for calculating the potential V of the positive electrode in the stable or quasi-stable state corresponds to data representing the relationship between the concentration C of lithium in the positive electrode and the potential V of the positive electrode in the stable or quasi-stable state during charging with the first current, etc. The internal state inference unit 13 uses at least the inferred concentration C of lithium in the positive electrode c , and the aforementioned data for calculating the potential V of the positive electrode in the stable or quasi-stable state, and calculates the potential V of the positive electrode during charging with the first current c with respect to the potential V of the positive electrode c . Thus, a potential curve representing the relationship between the potential V1 of the positive electrode during charging with the first current and the charge amount is inferred c . The internal state inference unit 13 uses at least the inferred concentration C of lithium in the positive electrode c , and the aforementioned data for calculating the potential V of the positive electrode in the stable or quasi-stable state, and calculates the potential V of the positive electrode during charging with the first current c 1. Thus, a potential curve representing the relationship between the potential V c 1 of the positive electrode during charging with the first current and the charge amount is inferred

[0066] In addition, the following data is stored in the data storage unit 16: The data uses at least the charge amount of the negative electrode and the concentration C of lithium ions a to calculate the potential V of the negative electrode in the above-mentioned stable or quasi-stable state a . The aforementioned data for calculating the potential V of the negative electrode in the stable or quasi-stable state corresponds to data representing the relationship between the concentration C of lithium in the negative electrode and the potential V of the negative electrode in the stable or quasi-stable state during charging with the first current, etc. The internal state inference unit 13 uses at least the inferred concentration C of lithium in the negative electrode a , and the aforementioned data for calculating the potential V of the negative electrode in the stable or quasi-stable state, and calculates the potential V of the negative electrode during charging with the first current a with respect to the potential V of the negative electrode a . The internal state inference unit 13 uses at least the inferred concentration C of lithium in the negative electrode a , and the aforementioned data for calculating the potential V of the negative electrode in the stable or quasi-stable state, and calculates the potential V of the negative electrode during charging with the first currenta Based on the aforementioned data, calculate the potential V of the negative electrode during charging with the first current. a 1. Thus, infer the potential V of the negative electrode during charging with the first current. a 1 with respect to the charge amount.

[0067] By inferring the potential curves of the positive electrode and the negative electrode respectively in a stable or quasi-stable state during charging with the first current as described above, the internal state inference unit 13 can use the inferred potential curves to infer the initial charge amount of the negative electrode, the initial discharge amount of the positive electrode, and the SOW as internal state parameters. In addition, the internal state inference unit 13 infers the battery capacity w of the battery 5 based on the internal state parameters inferred as described above and the change in the voltage of the battery 5 during charging with the first current, etc. eff . Moreover, the internal state inference unit 13 is based on the inferred battery capacity w. eff And the potential curve of the positive electrode during charging with the first current, etc., to infer the available potential range ΔV of the positive electrode. c As an internal state parameter. Similarly, the internal state inference unit 13 is based on the inferred battery capacity w. eff And the potential curve of the negative electrode during charging with the first current, etc., to infer the available potential range ΔV of the negative electrode. a As an internal state parameter. The internal state inference unit 13 writes the inference result of the internal state of the battery 5 inferred during charging with the first current into the data storage unit 16 and stores it in the data storage unit 16.

[0068] In addition, in the present embodiment, through the processing of the internal state inference unit 13 and the correction coefficient calculation unit 15, based on the impedances of the positive electrode and the negative electrode respectively during charging with the second current, the internal state of the battery 5 can be inferred. However, during charging of the battery 5 with the second current, the battery 5 is rapidly charged at a high charging rate as described above. Therefore, in at least one of the positive electrode and the negative electrode, the diffusion of lithium ions becomes the rate-limiting factor for charging. Therefore, during charging with the second current, in at least one of the positive electrode and the negative electrode, the concentration of lithium in each active material particle becomes uneven, and in at least one of the positive electrode and the negative electrode, a difference occurs between the concentration of lithium on the surface of the active material and the average lithium concentration inside the active material. For example, in rapid charging based on a high charging rate, in at least one of the positive electrode and the negative electrode, the concentration of lithium on the surface of the active material particle is higher than the concentration of lithium inside the active material particle.

[0069] Therefore, during charging with the second current, the lithium concentration distribution becomes unstable in at least one of the positive electrode and the negative electrode. That is, the lithium concentration distribution in each of the positive electrode and the negative electrode during charging with the second current is different from that during charging with the first current or the like, where the lithium concentration distribution in the positive electrode and the negative electrode is stable or quasi-stable. In addition, in a battery or the like using coarse-grained lithium titanate as the negative electrode active material, during charging at a high charging rate, there is a tendency for the lithium concentration distribution in at least the negative electrode to expand and become unstable. On the other hand, in a battery or the like using fine-grained lithium titanate as the negative electrode active material, during charging based on a high charging rate, there is a tendency for the lithium concentration distribution in at least the positive electrode to expand and become unstable.

[0070] When the lithium concentration in the positive electrode is in a non-uniform state, that is, when the lithium concentration distribution in the positive electrode is in an unstable state, Equation (1-A) is not equivalent to Equation (1-C). Therefore, through the aforementioned fitting calculation using Equation (2-A), the appropriate capacity w of the positive electrode cannot be calculated. c and the lithium concentration C c value. Therefore, when inferring the internal state of the battery 5 based on the impedance R c of the positive electrode in a state where the lithium concentration distribution in the positive electrode is unstable, it is necessary to correct the influence caused by the non-uniformity of the lithium concentration in the positive electrode (the influence caused by the diffusion of lithium ions in the positive electrode becoming the rate-limiting factor), and infer the average concentration information inside the active material from the concentration information at the interface between the active material and the electrolyte. That is, it is necessary to correct the unstable factors of the lithium concentration distribution in the positive electrode and infer the internal state.

[0071] Similarly, when the lithium concentration in the negative electrode is in a non-uniform state, that is, when the lithium concentration distribution in the negative electrode is in an unstable state, Equation (1-B) is not equivalent to Equation (1-D). Therefore, through the aforementioned fitting calculation using Equation (2-B), the appropriate capacity w of the negative electrode cannot be calculated. a and the lithium concentration C a . Therefore, when inferring the internal state of the battery 5 based on the impedance R a of the negative electrode in a state where the lithium concentration distribution in the negative electrode is unstable, it is necessary to correct the influence caused by the non-uniformity of the lithium concentration in the negative electrode (the influence caused by the diffusion of lithium ions in the negative electrode becoming the rate-limiting factor), and infer the average concentration information inside the active material from the concentration information at the interface between the active material and the electrolyte. That is, it is necessary to correct the unstable factors of the lithium concentration distribution in the negative electrode and infer the internal state.

[0072] In the present embodiment, the correction coefficient calculation unit 15 acquires the impedance of the battery 5 measured at each of a plurality of charge amounts during charging with the second current, and the impedance of each of the positive electrode and the negative electrode measured at each of the plurality of charge amounts during charging with the second current. Further, the correction coefficient calculation unit 15 acquires the relationship between the potentials of the positive electrode and the negative electrode with respect to the charge amount during charging with the first current, that is, the potential curves of the positive electrode and the negative electrode during charging with the first current as the inference result of the internal state inference unit 13. Further, the correction coefficient calculation unit 15 acquires the measurement result of the voltage V1 of the battery 5 during charging with the first current and the measurement result of the voltage V2 of the battery 5 during charging with the second current.

[0073] When correcting the influence caused by the uneven concentration of lithium in the positive electrode, the correction coefficient calculation unit 15 is based on the potential curve of the positive electrode during charging with the first current and the impedance R of the positive electrode during charging with the second current c 2 and the impedance R of the negative electrode a 2, to infer the potential curve of the positive electrode during charging with the second current. That is, the correction coefficient calculation unit 15 infers the potential of the positive electrode at each of the plurality of charge amounts (SOC) during charging with the second current. At this time, the impedance R is used c 2, R a 2, the voltages V1, V2, and the potential V of the positive electrode during charging with the first current c 1, and through Equation (3-A), calculate the potential V of the positive electrode during charging with the second current c 2. In the potential curve of the positive electrode during charging with the second current, it shows the relationship between the potential of the positive electrode during charging with the second current and the charge amount.

[0074] Further, when correcting the influence caused by the uneven concentration of lithium in the negative electrode, the correction coefficient calculation unit 15 is based on the potential curve of the negative electrode during charging with the first current and the impedance R of the positive electrode during charging with the second current c 2 and the impedance R of the negative electrode a 2, to infer the potential curve of the negative electrode during charging with the second current. That is, the correction coefficient calculation unit 15 infers the potential of the negative electrode at each of the plurality of charge amounts (SOC) during charging with the second current. At this time, the impedance R is used c 2, R a 2, the voltages V1, V2, and the potential V of the negative electrode during charging with the first current a 1, and through Equation (3-B), calculate the potential V of the negative electrode during charging with the second current a2. In the potential curve of the negative electrode during charging with the second current, the relationship between the potential of the negative electrode during charging with the second current and the charge amount is shown.

[0075] V c 2 = V c 1+(V2 - V1)×(R c 2 / (R c 2 + R a 2)) (3 - A)

[0076] V a 2 = V a 1-(V2 - V1)×(R a 2 / (R c 2 + R a 2)) (3 - B)

[0077] The correction coefficient calculation unit 15 is based on the difference between the potential of the positive electrode during charging with the first current (the aforementioned potential curve) and the potential of the positive electrode during charging with the second current (the aforementioned potential curve), and the impedance R c 2 of the positive electrode during charging with the second current, and corrects the difference between the lithium concentration distribution at the positive electrode (target electrode) during charging with the first current in a stable or quasi - stable state and the lithium concentration distribution at the positive electrode (target electrode) during charging with the second current in an unstable state. At this time, the correction coefficient calculation unit 15 infers the correction coefficient ΔC c , as a parameter for correcting the difference between the lithium concentration distribution in the positive electrode during charging with the first current and the lithium concentration distribution in the positive electrode during charging with the second current. The correction coefficient ΔC c is a parameter for correcting the influence caused by the uneven lithium concentration at the positive electrode (target electrode) during charging with the second current, that is, the influence caused by the diffusion of lithium ions in the positive electrode becoming the rate - limiting factor during charging with the second current.

[0078] In addition, the correction coefficient calculation unit 15 is based on the difference between the potential of the negative electrode during charging with the first current (the aforementioned potential curve) and the potential of the negative electrode during charging with the second current (the aforementioned potential curve), and the impedance R a 2 of the negative electrode during charging with the second current, and corrects the difference between the lithium concentration distribution at the negative electrode (target electrode) during charging with the first current in a stable or quasi - stable state and the lithium concentration distribution at the negative electrode (target electrode) during charging with the second current in an unstable state. At this time, the correction coefficient calculation unit 15 infers the correction coefficient ΔC a, as a parameter for correcting the difference in the lithium concentration distribution in the negative electrode during charging with the first current and the lithium concentration distribution in the negative electrode during charging with the second current. Correction coefficient ΔC a is a parameter for correcting the influence caused by the uneven lithium concentration at the negative electrode (target electrode) during charging with the second current, that is, the influence caused by the diffusion of lithium ions in the negative electrode becoming rate-limiting during charging with the second current. During charging with the second current, for the measured impedance R c 2, R a For each of the multiple amounts of charge, the correction coefficient ΔC c 、ΔC a is inferred.

[0079] Figure 5 is a schematic diagram for explaining the following process in the first embodiment: the process of inferring the correction coefficient for correcting the difference in the lithium concentration distribution in the positive electrode during charging with the first current and the lithium concentration distribution in the positive electrode during charging with the second current, and the correction coefficient for correcting the difference in the lithium concentration distribution in the negative electrode during charging with the first current and the lithium concentration distribution in the negative electrode during charging with the second current. In Figure 5 , the amount of charge is shown on the horizontal axis and the potential is shown on the vertical axis. In addition, in Figure 5 , the potential curves of the positive and negative electrodes during charging with the first current are represented by solid lines, and the potential curves of the positive and negative electrodes during charging with the second current are represented by dashed lines.

[0080] When inferring the correction coefficient ΔC c for the positive electrode, the correction coefficient calculation unit 15 calculates, for each of the multiple amounts of charge of the impedance R c 2 of the positive electrode measured during charging with the second current, the multiplication value obtained by multiplying the difference value (I2 - I1) between the second current and the first current by the impedance R c 2 of the positive electrode during charging with the second current (R c 2×(I2 - I1)). Then, the correction coefficient calculation unit 15 sets the calculated multiplication value (R c 2×(I2 - I1)) as the overvoltage of the positive electrode during charging with the second current relative to charging with the first current, and calculates the potential (second potential) V c 2' after removing the element of the aforementioned overvoltage from the potential (first potential) V c 2 of the positive electrode during charging with the second current. The potential V c 2' after removing the element of the aforementioned overvoltage from the positive electrode is calculated using Equation (4-A). In addition, in Figure 5During charging with the second current, the potential V of the positive electrode becomes the charge amount Y c,Y 2 (reference point γ2), and from the potential V c and Y2, the overvoltage factor (R c,Y 2×(I2 - I1)) is removed, resulting in the potential V c,Y 2’ (reference point γ2’).

[0081] In addition, when inferring the correction coefficient ΔC for the negative electrode a the correction coefficient calculation unit 15 calculates, for each of a plurality of charge amounts of the impedance R a 2 of the negative electrode measured during charging with the second current, the multiplication value obtained by multiplying the difference value (I2 - I1) between the second current and the first current by the impedance R a 2 of the negative electrode during charging with the second current (R a 2×(I2 - I1)). Then, the correction coefficient calculation unit 15 sets the calculated multiplication value (R a 2×(I2 - I1)) as the overvoltage of the negative electrode during charging with the second current relative to charging with the first current, and calculates the potential (second potential) V a 2 from which the above-mentioned overvoltage factor has been removed from the potential (first potential) V a 2 of the negative electrode during charging with the second current. The potential V a 2’ from which the above-mentioned overvoltage factor has been removed in the negative electrode is calculated using Equation (4 - B). Additionally, in Figure 5 during charging with the second current, the potential V of the negative electrode becomes the charge amount Y a，Y 2 (refer to reference point α2), and from the potential V a，Y 2, the above-mentioned overvoltage factor (R a，Y 2×(I2 - I1)) is removed, resulting in the potential V a，Y 2’ (reference point α2’).

[0082] V c 2′ = V c 2 - R c 2×(I2 - I1) (4 - A)

[0083] V a 2′ = V a 2 + R a 2×(I2 - I1) (4 - B)

[0084] Then, when inferring the correction coefficient ΔC for the positive electrode c the correction coefficient calculation unit 15 calculates, for the impedance R cFor each of a plurality of charged amounts of 2, in the potential curve of the positive electrode during charging at the first current, calculate the potential (third potential) Vc1 that becomes the same as the potential (first potential) V c for the same charged amount as that of the 2 charge. In Figure 5 one example, in the potential curve of the positive electrode during charging at the first current, at the potential V c， Y 1 (reference point γ1) becomes the same charged amount Y as that of the potential V c，Y 2. Then, the correction coefficient calculation unit 15 is based on the potential (second potential) V c 2' and the potential (third potential) V c 1 difference, and the data of the relationship between the lithium concentration C c of the positive electrode and the potential of the positive electrode during charging at the first current (stable or quasi-stable state), calculate the correction coefficient ΔC c for the positive electrode. The correction coefficient ΔC c for the positive electrode corresponds to the difference value between the lithium concentration of the positive electrode at the potential (second potential) V c 2' and the lithium concentration of the positive electrode at the potential (third potential) V c 1 during charging at the first current. In Figure 5 one example, the difference value between the lithium concentration of the positive electrode at point γ2' and the lithium concentration of the positive electrode at point γ1 becomes the correction coefficient ΔC c，Y for the positive electrode at the charged amount Y.

[0085] In addition, when inferring the correction coefficient ΔC a for the negative electrode, the correction coefficient calculation unit 15 measures the impedance R a of the negative electrode during charging at the second current for each of a plurality of charged amounts of 2, and in the potential curve of the negative electrode during charging at the first current, calculates the potential (third potential) V a 1 that becomes the same as the potential (first potential) V a 2 for the same charged amount. In Figure 5 one example, in the potential curve of the negative electrode during charging at the first current, at the potential V a， Y 1 (reference point α1) becomes the same charged amount Y as that of the potential V a，Y 2. Then, based on the potential (second potential) V a，Y 2' and the potential (third potential) V a 1 difference represented by the correction coefficient calculation unit 15, and the data of the relationship between the lithium concentration C a of the negative electrode and the potential of the negative electrode during charging at the first current (stable or quasi-stable state), calculate the correction coefficient ΔC for the negative electrodea For the correction coefficient ΔC of the negative electrode a It is equivalent to the potential (second potential) V during charging at the first current a The difference value between the lithium concentration in the negative electrode at 2' and the lithium concentration in the negative electrode at the potential (third potential) V a at 1. In Figure 5 In one example, the difference value between the lithium concentration in the negative electrode at point α2' and the lithium concentration in the negative electrode at point α1 becomes the correction coefficient ΔC for the negative electrode at the charge amount Y a,Y .

[0086] As described above, the correction coefficient calculation unit 15 measures the impedance R c 2, R a for each of the multiple charge amounts during charging at the second current, and infers the aforementioned correction coefficient ΔC c , ΔC a . Then, the correction coefficient calculation unit 15 writes the inference results for the correction coefficient ΔC c , ΔC a into the data storage unit 16, and stores the inferred correction coefficient ΔC c , ΔC a in the data storage unit 16

[0087] In the inference of the internal state of the battery 5 during charging at the second current, the internal state inference unit 13 obtains the impedance of each of the positive electrode and the negative electrode measured at each of the multiple charge amounts during charging at the second current, and the inference results of the correction coefficient calculation unit 15 for the aforementioned correction coefficient ΔC c , ΔC a . Then, the internal state inference unit 13 infers the internal state of the battery 5 based on the impedance of the positive electrode and the negative electrode during charging at the second current, and the inferred correction coefficient ΔC c , ΔCa. Even in the inference of the internal state of the battery 5 during charging at the second current, the internal state inference unit 13 infers the capacity w c of the positive electrode, the lithium concentration C c of the positive electrode, the capacity w a of the negative electrode, and the lithium concentration C a of the negative electrode as internal state parameters

[0088] Here, when the lithium concentration distribution in the positive electrode becomes unstable due to charging at the second current, in the aforementioned fitting calculation using Equation (2-A), the appropriate capacity w c of the positive electrode and the lithium concentration C cvalue. Therefore, in the inference of the internal state of the battery 5 during charging with the second current, Equation (5-A) and Equation (5-B) are used in place of Equation (2-A). Then, the internal state inference unit 13 uses the measurement result of the impedance R c 2 of the positive electrode during charging with the second current, the correction coefficient ΔC c for the concentration distribution of lithium in the positive electrode, the inference result, and the impedance R c with respect to the capacity w c of the positive electrode, the concentration C c of lithium, and the correction coefficient ΔC c of the positive electrode to perform a fitting calculation. That is, the calculated result obtained by substituting the inferred correction coefficient ΔC c into Equation (5-A) and Equation (5-B) is matched to the measurement result of the impedance R c 2 of the positive electrode to perform a fitting calculation. At this time, the capacity w c of the positive electrode and the concentration C c of lithium are used as variables for the fitting calculation to calculate the variables. Thus, the capacity w c of the positive electrode and the concentration C c of lithium are inferred as internal state parameters.

[0089] In addition, by substituting Equation (5-B) into Equation (5-A), it becomes as shown in Equation (5-C). Therefore, in the inference of the internal state of the battery 5 during charging with the second current, the internal state inference unit 13 uses the relationship represented by Equation (5-C) to perform a fitting calculation, thereby inferring the capacity w c of the positive electrode and the concentration C c of lithium. In addition, in Equation (5-A) and Equation (5-B), C’ c，Y is a provisional value before correction for the correction coefficient ΔC c，Y of the concentration of lithium in the positive electrode at the charge amount Y. The provisional value C’ c，Y corresponds to the concentration of lithium in the region with a higher lithium concentration in the positive electrode in an unstable state where the lithium concentration is uneven. For example, the provisional value C’ c，Y corresponds to the concentration of lithium on the surface of the active material in the positive electrode in an unstable state. In this case, the correction coefficient ΔC c corresponds to the difference between the concentration of lithium on the surface of the active material of the positive electrode in a stable or quasi-stable state and the concentration of lithium on the surface of the active material of the positive electrode in an unstable state. In addition, in the inference of the capacity w c of the positive electrode and the concentration C c of lithium calculated based on the fitting using the relationship represented by Equation (5-C), the concentration C e of the electrolyte is ignored.Effect of the distribution. Here, in a temperature environment capable of performing rapid charging based on a high charging rate, that is, in a temperature range from room temperature to high temperature, the order of magnitude of the lithium diffusion coefficient in the electrolyte is larger than that of the lithium diffusion coefficients of the active materials in the positive electrode and the negative electrode, respectively. Therefore, during rapid charging based on a high charging rate, the lithium concentration distribution in the active material of either the positive electrode or the negative electrode is in a dominant low position compared to the concentration distribution of the electrolyte, and the concentration of the electrolyte can be ignored.

[0090] R c，Y ≈1 / (kw c (c c，max -C′ c，Y ) 0.5 (C′ c，Y ) 0.5 ) (5-A)

[0091] C′ c，Y =C c，Y +ΔC c，Y (5-B)

[0092] R c，Y ≈1 / (kw c (C c，nax -(C c，Y +ΔC c，Y )) 0.5 (C c，Y +ΔC c，Y ) 0.5 ) (5-C)

[0093] In addition, when the lithium concentration distribution in the negative electrode during charging with the second current becomes unstable, in the aforementioned fitting calculation using Equation (2-B), the capacity w of the negative electrode cannot be calculated appropriately a and the lithium concentration C a . Therefore, in the inference of the internal state of the battery 5 during charging with the second current, Equations (6-A) and (6-B) are used instead of Equation (2-B). Then, the internal state inference unit 13 uses the measurement result of the impedance R a 2 of the negative electrode during charging with the second current, the inference result of the correction coefficient ΔC a for the lithium concentration distribution in the negative electrode, and the impedance R a represented by Equations (6-A) and (6-B) a with respect to the capacity w of the negative electrode a , the lithium concentration C a and the correction coefficient ΔC of the negative electrode a to perform a fitting calculation. That is, the calculated results obtained by substituting the inferred correction coefficient ΔCa The fitting calculation is performed based on the measurement result of 2. At this time, the capacity w of the negative electrode a and the concentration C of lithium a are used as variables for the fitting calculation to calculate the variables. Thus, the capacity w of the negative electrode is inferred a and the concentration C of lithium a are used as internal state parameters.

[0094] In addition, by substituting Equation (6-B) into Equation (6-A), it becomes as shown in Equation (6-C). Therefore, in the inference of the internal state of the battery 5 during charging with the second current, the internal state inference unit 13 performs a fitting calculation by using the relationship represented by Equation (6-C), thereby inferring the capacity w of the negative electrode a and the concentration C of lithium a . In addition, in Equation (6-A) and Equation (6-B), C’ a，Y is the provisional value before correction for the correction coefficient ΔC of the concentration of lithium in the negative electrode at the charge amount Y a，Y . The provisional value C’ a，Y corresponds to the concentration of lithium in the region with a higher concentration of lithium in the negative electrode in an unstable state where the concentration of lithium is uneven. For example, the provisional value C’ a，Y corresponds to the concentration of lithium on the surface of the active material in the negative electrode in an unstable state. In this case, the correction coefficient ΔC a corresponds to the difference between the concentration of lithium on the surface of the active material in the negative electrode in a stable or quasi-stable state and the concentration of lithium on the surface of the active material in the negative electrode in an unstable state. In addition, in the inference of the capacity w of the negative electrode a and the concentration C of lithium a calculated based on the fitting using the relationship represented by Equation (6-C), as described above, the influence of the distribution of the concentration Ce of the electrolyte is ignored.

[0095] R a，Y ≈1 / (kw a (C a，max -C′ a，Y ) 0.5 (C′ a，Y ) 0.5 ) (6-A)

[0096] C′ a，Y =C a，Y +ΔC a，Y (6-B)

[0097] R a，Y ≈1 / (kw a (C a，max -(C a，Y +ΔC a，Y ))0.5 (C a，Y +ΔC a，Y ) 0.5 ) (6 - C)

[0098] In this embodiment, even if the concentration distribution of lithium in the positive electrode becomes unstable due to charging with the second current or the like, the correction coefficient ΔC c corrects the difference between the concentration distribution of lithium in the positive electrode in a stable or quasi - stable state (for example, when charging with the first current) and the concentration distribution of lithium in the positive electrode in an unstable state (for example, when charging with the second current). Therefore, even when the concentration distribution of lithium in the positive electrode is in an unstable state, by performing the aforementioned fitting calculation using the correction coefficient ΔC c and the formula (5 - C), in the inference of the capacity w c of the positive electrode and the concentration C c of lithium, the influence caused by the unevenness of the concentration of lithium in the positive electrode is appropriately corrected, and the capacity w c and the concentration C c of lithium are appropriately inferred.

[0099] In addition, in this embodiment, even if the concentration distribution of lithium in the negative electrode becomes unstable due to charging with the second current or the like, the correction coefficient ΔC a corrects the difference between the concentration distribution of lithium in the negative electrode in a stable or quasi - stable state and the concentration distribution of lithium in the negative electrode in an unstable state. Therefore, even when the concentration distribution of lithium in the negative electrode is in an unstable state, by performing the aforementioned fitting calculation using the correction coefficient ΔC a and the formula (6 - C), in the inference of the capacity w a of the negative electrode and the concentration C a of lithium, the influence caused by the unevenness of the concentration of lithium in the negative electrode is appropriately corrected, and the capacity w a and the concentration C a of lithium are appropriately inferred.

[0100] If the capacity w c , w a and the concentration C c , C a of lithium are inferred as described above during charging with the second current, the internal state inference unit 13 infers the potential curve (potential change with respect to the charge amount) of the positive electrode in a stable or quasi - stable state and the potential V c of the negative electrode in a stable or quasi - stable state in the same manner as the inference during charging with the first current. aThe potential curve (potential change with respect to the charge amount). In addition, the internal state inference unit 13 can infer the initial charge amount of the negative electrode, the initial discharge amount of the positive electrode, and the SOW as internal state parameters in the same way as the inference during charging with the first current, and can infer the potential range ΔV that the positive electrode can utilize c and the potential range ΔV that the negative electrode can utilize a The internal state inference unit 13 writes the inference result of the internal state of the battery 5 inferred during charging with the second current into the data storage unit 16 and stores it in the data storage unit 16.

[0101] In addition, as described above, based on the potential V of the positive electrode during charging with the first current (in a stable or quasi-stable state) inferred during charging with the first current c of the potential change, the correction coefficient ΔC for the positive electrode is calculated c Then, as described above, based on the potential V of the negative electrode during charging with the first current (in a stable or quasi-stable state) inferred during charging with the first current a of the potential change, the correction coefficient ΔC for the negative electrode is calculated a Therefore, as the potential curve of the positive electrode used in the calculation of the correction coefficient ΔC c and the potential curve of the negative electrode used in the calculation of the correction coefficient ΔC a using the potential curve with a shorter elapsed time from the time of inference until now can more appropriately infer the respective correction coefficients.

[0102] In the present embodiment, during charging with the second current, if the impedances of the positive electrode and the negative electrode are measured as described above, the processor or the like of the deterioration determination device 3 obtains the elapsed time since the last (most recent) inference of the internal state of the battery 5 based on charging with the first current. Then, when the obtained elapsed time is within a specified time, the correction coefficient calculation unit 15 calculates at least one of the aforementioned correction coefficients ΔC c 、ΔC a and the internal state inference unit 13 infers the internal state of the battery 5 including the capacity w c 、w a and the lithium concentration C c 、C a as described above.

[0103] On the other hand, when the obtained elapsed time exceeds the specified time, for the processor or the like of the deterioration determination device 3, after measuring the impedances of the positive electrode and the negative electrode during charging with the second current, the aforementioned correction coefficients ΔC c 、ΔC a, and the charging with the second current is terminated. Then, for the processor or the like of the deterioration determination device 3, the battery 5 is charged with the first current. In the state where the charging is being performed with the first current, as described above, the impedance of each of the positive electrode and the negative electrode is measured, and the internal state of the battery 5 is inferred. Thereby, the inference result of the potential change of the positive electrode and the negative electrode during charging with the first current (in a stable or quasi-stable state) is updated. Then, in the inference of the internal state of the battery 5 based on the charging with the second current after the next time, the updated inference result is used as the potential change of the positive electrode and the negative electrode during charging with the first current, and the correction coefficient ΔC is calculated as described above. c , ΔC a .

[0104] Figure 6 is a flowchart showing the processing during charging with the first current by the deterioration determination device according to the first embodiment. Figure 6 The processing of is performed by the processor or the like of the deterioration determination device 3 in the state where the battery 5 is being charged with the first current. If the start Figure 6 of the processing, the processor or the like of the deterioration determination device 3 supplies the aforementioned first current to the battery 5 and charges the battery 5 (S60). Then, the processor or the like of the deterioration determination device 3 measures the voltage of the battery 5 during charging with the first current and the time change of the voltage, and obtains the measurement result of the voltage of the battery 5 (S61). Then, the impedance measurement unit 12 measures the impedance of each of the positive electrode and the negative electrode of the battery 5 during charging with the first current as described above (S62).

[0105] Then, the internal state inference unit 13 infers the respective capacities and lithium concentrations of the positive electrode and the negative electrode by using the aforementioned fitting calculation using the formula (2-A) and the fitting calculation using the formula (2-B) and the like (S63). Then, based on the inference results of the capacities and lithium concentrations of the positive electrode and the negative electrode respectively, the internal state inference unit 13 infers the potentials of the positive electrode and the negative electrode respectively during charging with the first current (in a stable or quasi-stable state) as described above (S64). Thereby, the potential change of the positive electrode and the negative electrode in a stable or quasi-stable state during charging with the first current or the like is inferred. Then, based on the inference results of the potential change of the positive electrode and the negative electrode and the like, the internal state inference unit 13 infers the internal state including the potential ranges that can be utilized by the positive electrode and the negative electrode respectively as described above (S65). Then, the processor or the like of the deterioration determination device 3 ends the charging of the battery 5 (S66) and stores the inference results of the internal state and the like (S67).

[0106] Figure 7 is a flowchart showing the processing during charging with the second current by the deterioration determination device according to the first embodiment. Figure 7The processing of Figure 7 is performed by a processor or the like of the deterioration determination device 3 in a state where the battery 5 is being charged with the second current. If the

[0107] processing of

[0108] is started, the processor or the like of the deterioration determination device 3 supplies the aforementioned second current to the battery 5 and charges the battery 5 (S70). Then, the processor or the like of the deterioration determination device 3 measures the voltage of the battery 5 and the time change of the voltage during charging with the first current, and obtains the measurement result of the voltage of the battery 5 (S71). Then, the impedance measurement unit 12 measures the impedance of each of the positive electrode and the negative electrode of the battery 5 during charging with the second current as described above (S72). c Then, the processor or the like of the deterioration determination device 3 obtains the elapsed time since the last (most recent) inference of the internal state of the battery 5 based on charging with the first current, and determines whether the obtained elapsed time is within a specified time (S73). When the aforementioned elapsed time exceeds the specified time (S73 - No), the processor or the like of the deterioration determination device 3 ends the charging of the battery 5 (S78), and saves the inference result including the measurement results of the impedance of the positive electrode and the negative electrode, etc. (S79). In this case, the processor or the like of the deterioration determination device 3 executes the processing during charging with the first current as described above, and updates the inference result of the potential (potential change) of the positive electrode and the negative electrode during charging with the first current (stable or quasi-stable state). a

[0109] On the other hand, when the aforementioned elapsed time is within the specified time (S73 - Yes), the correction coefficient calculation unit 15 infers the potential (potential change) of the positive electrode and the negative electrode during charging with the second current as described above based on the potential (potential change) of the positive electrode and the negative electrode during charging with the first current and the measurement results of the impedance of the positive electrode and the negative electrode during charging with the second current (S74). Then, the correction coefficient calculation unit 15 calculates the aforementioned correction coefficient for at least one of the positive electrode and the negative electrode based on the inference results of the potential of the positive electrode and the negative electrode during charging with the first current and during charging with the second current, etc. (S75). At this time, the correction coefficient calculation unit 15 calculates the correction coefficient ΔC for the positive electrode using the aforementioned formula (4 - A) etc., c and calculates the correction coefficient ΔC for the negative electrode using the aforementioned formula (4 - B) etc., a ​For the fitting calculation of the above formula (6-C) and the like, the capacities of the positive electrode and the negative electrode and the concentration of lithium are inferred for each of the positive electrode and the negative electrode (S76). Then, based on the inference results of the capacities and the lithium concentrations in the positive electrode and the negative electrode, the internal state inference unit 13 infers the potentials of the positive electrode and the negative electrode in the stable or quasi-stable state as described above, and infers the available potential ranges of the positive electrode and the negative electrode as described above (S77). Then, the processor of the degradation determination device 3 or the like ends the charging of the battery 5 (S78) and stores the inference results of the internal state and the like (S79).

[0110] As described above, in the present embodiment, during charging at a high charging rate such as during charging with the second current, the impedances of the positive electrode and the negative electrode are measured. Then, for the target electrode that is at least one of the positive electrode and the negative electrode, the processor of the degradation determination device 3 or the like infers a correction coefficient for correcting the difference between the lithium concentration distribution in the target electrode during charging with the first current (stable or quasi-stable state) and the lithium concentration distribution in the target electrode during charging with the second current (unstable state) based on the difference between the potential of the target electrode during charging with the first current and the potential of the target electrode during charging with the second current, and the impedance of the target electrode during charging with the second current. Therefore, even when the concentration of lithium in at least one of the positive electrode and the negative electrode is in a non-uniform state due to rapid charging of the battery 5 or the like, the influence caused by the non-uniformity of the lithium concentration can be appropriately corrected by the correction coefficient.

[0111] In addition, by calculating the above-described correction coefficient for each of the positive electrode and the negative electrode, even when the battery 5 is rapidly charged based on a high charging rate during charging with the second current or the like, the internal state of the battery 5 can be appropriately inferred by the above-described operations using the correction coefficient. Thus, even when the battery 5 is rapidly charged, the capacities and the lithium concentrations of the positive electrode and the negative electrode are appropriately inferred, and the internal state parameters of the battery 5 are appropriately inferred.

[0112] Even in a state where the battery 5 is rapidly charged, the internal state of the battery 5 can be appropriately inferred, so that the battery 5 can be used more safely. For example, even in a state where the battery 5 is rapidly charged, the capacity of the negative electrode can be appropriately inferred, so that the decrease in the capacity of the negative electrode can be appropriately predicted, and overcharging of the battery 5 caused by the decrease in the capacity of the negative electrode can be effectively prevented. In addition, even in a state where the battery 5 is rapidly charged, the capacity of the positive electrode can be appropriately inferred, so that the decrease in the capacity of the positive electrode can be appropriately predicted, and overdischarge of the battery 5 caused by the decrease in the capacity of the positive electrode can be effectively prevented. In addition, even in a state where the battery 5 is rapidly charged, the concentration of lithium in the positive electrode can be appropriately inferred, so that the increase in the concentration of lithium in the positive electrode can be appropriately predicted, and side reactions caused by the increase in the concentration of lithium in the positive electrode can be effectively suppressed. By effectively suppressing side reactions and the like, the acceleration of the deterioration of the battery 5 can be effectively prevented.

[0113] In addition, when charging at the second current, the aforementioned correction coefficient may be calculated only for one of the positive electrode and the negative electrode. That is, as long as the aforementioned correction coefficient is calculated for the target electrode which is at least one of the positive electrode and the negative electrode, in the charging of the rapid battery 5 based on the high charging rate such as when charging at the second current, the correction coefficient is used to infer the internal state of the battery 5 as described above.

[0114] (Inspection confirmation related to the embodiment)

[0115] In addition, the following inspection confirmations related to the embodiment were carried out. In the inspection confirmation, for each of the test specimens A, B, and C, the full charge capacity during charging at a charging rate of 1C was measured, and the full charge capacity during charging at each of a plurality of charging rates of 3C or more was measured. Then, based on the measurement results, for each of the test specimens A to C, the capacity retention rate during charging at each of the plurality of charging rates of 3C or more with respect to the capacity during charging at 1C was calculated.

[0116] Here, as the test specimen A, a battery cell having a positive electrode and a negative electrode was used. In the test specimen A, a lithium nickel cobalt manganese composite oxide was used as the positive electrode active material, and lithium titanate was used as the negative electrode active material. In addition, in the test specimen A, by thickening the active material-containing layer in each of the positive electrode and the negative electrode, the thickness of each of the positive electrode and the negative electrode was set to 40 μm to 50 μm. The test specimen B was formed only of the positive electrode of the battery cell of the test specimen A. In addition, in the test specimen B, the active material-containing layer of the positive electrode was thinned compared to the test specimen A, and the thickness of the positive electrode was set to 10 μm. The test specimen C was formed only of the negative electrode of the battery cell of the test specimen A. In addition, in the test specimen C, the active material-containing layer of the negative electrode was thinned compared to the test specimen A, and the thickness of the negative electrode was set to 10 μm.

[0117] Figure 8 It is a schematic diagram showing the calculation results of the capacity retention rate during charging relative to 1C for each of the three test specimens under inspection confirmation. In Figure 8 , the charging rate is represented by the C-rate on the horizontal axis, and the capacity retention rate relative to the capacity during charging at 1C is represented by a percentage on the vertical axis. In addition, in Figure 8 , the solid line represents the capacity retention rate of test specimen A of the battery cell, the triangular curve represents the capacity retention rate of test specimen B with only the positive electrode, and the circular curve represents the capacity retention rate of test specimen C with only the negative electrode.

[0118] As Figure 8 shown, in test specimen A, as the charging rate increases, the capacity retention rate decreases linearly. In addition, in test specimen A, which is a battery cell, the relationship between the capacity retention rate and the charging rate shows the same tendency as that of test specimen C with only the negative electrode. Then, in test specimen A and test specimen C, the thicknesses of the active material-containing layers of the negative electrodes are different from each other, but in test specimen A and test specimen C, the relationship between the capacity retention rate and the charging rate becomes the same tendency. From this, it is confirmed that: in a battery cell formed of the same active material as test specimen A, that is, in a battery cell using lithium titanate as the negative electrode active material, during charging based on a high charging rate, the influence caused by the uneven concentration of lithium in the negative electrode becomes large. That is, it is confirmed that: in a battery cell using lithium titanate as the negative electrode active material, during charging based on a high charging rate, the influence of the uneven lithium concentration distribution in the negative electrode active material becomes large.

[0119] In addition, in test specimen A, there is no tendency that the reduction rate of the capacity retention rate becomes larger as the charging rate increases, etc., and as the charging rate increases, the capacity retention rate decreases linearly. In addition, as described above, even for test specimens A and C with different thicknesses, the relationship between the capacity retention rate and the charging rate becomes the same tendency. Therefore, it is confirmed that: in a battery cell formed of the same active material as test specimen A, during charging at a high charging rate, the influence caused by the concentration distribution of the electrolyte in the battery is small.

[0120] In addition, in test specimen B with only the positive electrode, compared with each of test specimen A, which is a battery cell, and test specimen C with only the negative electrode, the reduction rate of the capacity retention rate as the charging rate increases is small. Therefore, it is confirmed that: in a battery cell formed of the same active material as test specimen A, during charging based on a high charging rate, the influence caused by the concentration distribution of lithium in the positive electrode is small.

[0121] From the above inspection confirmation, it can be seen that: in order to appropriately infer the internal state of a battery cell formed of the same active material as test specimen A, it is necessary to infer at least the aforementioned correction coefficient ΔC for the negative electrode.a Then, use the deduced correction coefficient ΔC a and perform fitting calculations using the aforementioned formula (6-C), that is, it is necessary to deduce the internal state of the battery cell.

[0122] In at least one of the aforementioned embodiments or examples, for an object electrode that is at least one of the positive electrode and the negative electrode of the battery, based on the potential difference between the object electrode during charging of the battery with a first current and the object electrode during charging of the battery with a second current greater than the first current, and the impedance of the object electrode during charging with the second current, deduce a correction coefficient for correcting the difference in the lithium concentration distribution in the object electrode during charging with the first current and the lithium concentration distribution in the object electrode during charging with the second current. Thereby, it is possible to provide a battery degradation determination method, a battery degradation determination device, a battery management system, a battery-equipped device, and a storage medium that can appropriately correct the influence caused by the uneven lithium concentration in at least one of the positive electrode and the negative electrode and can deduce the internal state of the battery.

[0123] In addition, the above embodiments can be summarized into the following technical solutions.

[0124] Technical solution 1

[0125] A degradation determination method for determining the degradation of a battery to be determined includes:[[]]

[0126] For an object electrode that is at least one of the positive electrode and the negative electrode of the battery, based on the potential difference between the object electrode during charging of the battery with a first current and the object electrode during charging of the battery with a second current greater than the first current, and the impedance of the object electrode during charging with the second current, deduce a correction coefficient that corrects the difference in the lithium concentration distribution in the object electrode during charging with the first current and the lithium concentration distribution in the object electrode during charging with the second current.

[0127] Technical solution 2

[0128] In the degradation determination method of technical solution 1,[[]]

[0129] In the deduction of the correction coefficient,[[]]

[0130] Calculate the multiplication value at a certain charge amount by multiplying the difference value between the second current and the first current by the impedance of the object electrode at the certain charge amount during charging with the second current.

[0131] The second potential is calculated by removing the element of the calculated multiplication value from the first potential, where the first potential is the potential of the object electrode at a certain charge amount during the charging with the second current.

[0132] The correction coefficient is calculated based on the difference between the second potential and the third potential, where the third potential is the potential of the object electrode at the same certain charge amount as the first potential during the charging with the first current.

[0133] Technical solution 3

[0134] In the degradation determination method of Technical solution 2,

[0135] When calculating the correction coefficient for the positive electrode of the battery as the object electrode, the second potential is calculated from the first potential by the following formula (A-1).

[0136] When calculating the correction coefficient for the negative electrode of the battery as the object electrode, the second potential is calculated from the first potential by the following formula (A-2).

[0137] V c 2′ = V c 2 - R c 2×(I2 - I1) (A-1)

[0138] V a 2′ = V a 2 + R a 2×(I2 - I1) (A-2) [[ID=�5]]

[0139] Here, V c 2 represents the first potential of the positive electrode; R c 2 represents the impedance of the positive electrode at a certain charge amount during the charging with the second current; V c 2’ represents the second potential of the positive electrode; V a 2 represents the first potential of the negative electrode; R a 2 represents the impedance of the negative electrode at a certain charge amount during the charging with the second current; V a 2’ represents the second potential of the negative electrode; I1 represents the first current; I2 represents the second current.

[0140] Technical solution 4

[0141] In any of the degradation determination methods of Technical solutions 1 to 3, it further includes:

[0142] Based on the impedance of the object electrode during the charging with the second current and the deduced correction coefficient, deduce the internal state of the battery.

[0143] Technical solution 5

[0144] In the degradation determination method of Technical solution 4,

[0145] In the deduction of the internal state of the battery,

[0146] When the correction coefficient is deduced for the positive electrode of the battery as the object electrode, use the impedance of the positive electrode during the charging with the second current, the correction coefficient for the positive electrode, and the following formula (B-1) to perform a fitting calculation, so as to calculate the capacity and the concentration of lithium for the positive electrode.

[0147] When the correction coefficient is deduced for the negative electrode of the battery as the object electrode, use the impedance of the negative electrode during the charging with the second current, the correction coefficient for the negative electrode, and the following formula (B-2) to perform a fitting calculation, so as to calculate the capacity and the concentration of lithium for the negative electrode.

[0148] R c ≈ 1 / (kw c (C c，max -(C c +ΔC c )) 0.5 (C c +ΔC c ) 0.5 ) (B-1)

[0149] R a ≈ 1 / (kw a (C a，max -(C a +ΔC a )) 0.5 (C a +ΔC a ) 0.5 ) (B-2)

[0150] Here, R c 2 represents the impedance of the positive electrode; w c represents the capacity of the positive electrode; C c represents the concentration of lithium in the positive electrode; C c，max represents the concentration of lithium in the positive electrode in the fully charged state of the positive electrode; ΔC c represents the correction coefficient for the positive electrode; R a2 represents the impedance of the negative electrode; w a represents the capacity of the negative electrode; C a represents the concentration of lithium in the negative electrode; C a，max represents the concentration of lithium in the negative electrode in the fully charged state of the negative electrode; ΔC a represents the correction coefficient for the negative electrode; K represents a constant based on the Butler - Volmer equation.

[0151] Technical solution 6

[0152] In any of the deterioration determination methods of Technical solutions 1 to 3, it further includes:

[0153] By using the fitting calculation of the impedance of the object electrode during the charging with the first current to infer the internal state of the battery, thereby inferring the potential curve representing the relationship between the potential of the object electrode and the charge amount during the charging with the first current,

[0154] Based on the potential curve of the object electrode during the charging with the first current and the impedance of the object electrode during the charging with the second current, infer the potential of the object electrode during the charging with the second current.

[0155] Technical solution 7

[0156] In any of the deterioration determination methods of Technical solutions 1 to 3, it further includes

[0157] During the charging with the first current, supply current to the battery through a current waveform that periodically changes with the first reference current value as the center current value,

[0158] During the charging with the second current, supply current to the battery through a current waveform that periodically changes with a second reference current value larger than the first reference current value as the center current value.

[0159] Technical solution 8

[0160] For a deterioration determination device that determines the deterioration of a battery to be determined, it includes:

[0161] A processor infers a correction coefficient based on the potential difference between the object electrode, which is at least one of the positive electrode and the negative electrode of the battery, during charging of the battery with a first current and during charging of the battery with a second current greater than the first current, and the impedance of the object electrode during charging with the second current. The correction coefficient corrects the difference in the lithium concentration distribution in the object electrode during charging with the first current and the lithium concentration distribution in the object electrode during charging with the second current.

[0162] Technical solution 9

[0163] A management system for the battery includes:

[0164] The degradation determination device of technical solution 8; and

[0165] The battery is subjected to a determination related to the degradation by the degradation determination device.

[0166] Technical solution 10

[0167] A battery-mounted device includes:

[0168] The degradation determination device of technical solution 8; and

[0169] The battery is subjected to a determination related to the degradation by the degradation determination device.

[0170] Technical solution 11

[0171] A storage medium storing a degradation determination program for determining the degradation of a battery to be determined, the degradation determination program causing a computer to execute,

[0172] For an object electrode that is at least one of the positive electrode and the negative electrode of the battery, based on the potential difference between the object electrode during charging of the battery with a first current and the object electrode during charging of the battery with a second current greater than the first current, and the impedance of the object electrode during charging with the second current, a correction coefficient is inferred. The correction coefficient corrects the difference in the lithium concentration distribution in the object electrode during charging with the first current and the lithium concentration distribution in the object electrode during charging with the second current.

[0173] The embodiments of the present invention have been described, but these embodiments are presented only as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. These embodiments, their variations, are included in the scope of the invention and the gist, and are equally included in the scope of the invention described in the claims and its equivalents.

Claims

1. A method for determining degradation, which determines the degradation of a battery as an object to be determined, comprising: For an object electrode that is at least one of the positive electrode and the negative electrode of the battery, based on the difference between the potential of the object electrode during charging of the battery with a first current and the potential of the object electrode during charging of the battery with a second current greater than the first current, and the impedance of the object electrode during the charging with the second current, an adjustment coefficient is inferred, and the adjustment coefficient corrects the difference between the lithium concentration distribution in the object electrode during the charging with the first current and the lithium concentration distribution in the object electrode during the charging with the second current.

2. The method for determining degradation according to claim 1, wherein, In the inference of the adjustment coefficient, By multiplying the difference value between the second current and the first current by the impedance of the object electrode at a certain charge amount during the charging with the second current, a multiplication value at the certain charge amount is calculated, By removing the element of the calculated multiplication value from the first potential, a second potential is calculated, and the first potential is the potential of the object electrode at the certain charge amount during the charging with the second current, Based on the difference between the second potential and the third potential, the adjustment coefficient is calculated, and the third potential is the potential of the object electrode at the same certain charge amount during the charging with the first current as the first potential.

3. The method for determining degradation according to claim 2, wherein, When calculating the adjustment coefficient for the positive electrode of the battery as the object electrode, the second potential is calculated from the first potential by the following formula (A-1), When calculating the adjustment coefficient for the negative electrode of the battery as the object electrode, the second potential is calculated from the first potential by the following formula (A-2), V c 2' = V c2 -R c 2×(I2 - I1) (A1) V a 2' = V a 2 + R a 2×(I2 - I1) (A - 2) Here, V c 2 represents the first potential of the positive electrode; R c 2 represents the impedance of the positive electrode at a certain charge amount during the charging with the second current; V c 2’ represents the second potential of the positive electrode; V a 2 represents the first potential of the negative electrode; R a 2 represents the impedance of the negative electrode at a certain charge amount during the charging with the second current; V a 2’ represents the second potential of the negative electrode; I1 represents the first current; I2 represents the second current.

4. The method for determining degradation according to any one of claims 1 to 3 further comprises: Based on the impedance of the object electrode during the charging with the second current and the inferred adjustment coefficient, the internal state of the battery is inferred.

5. The method for determining degradation according to claim 4, wherein, In the inference of the internal state of the battery, When the adjustment coefficient is inferred for the positive electrode of the battery as the object electrode, using the impedance of the positive electrode during the charging with the second current, the adjustment coefficient for the positive electrode, and the following formula (B-1), a fitting calculation is performed to calculate the capacity and the lithium concentration for the positive electrode, When the adjustment coefficient is inferred for the negative electrode of the battery as the object electrode, using the impedance of the negative electrode during the charging with the second current, the adjustment coefficient for the negative electrode, and the following formula (B-2), a fitting calculation is performed to calculate the capacity and the lithium concentration for the negative electrode, R c ≈1 / (kw c (C c,max -(C c +ΔC c )) 0.5 (C c +ΔC c ) 0.5 ) (B - 1) R a ≈1 / (kw a (C a,max -(C a +ΔC a )) 0.5 (C a +ΔC a ) 0.5 ) (B - 2) Here, R c represents the impedance of the positive electrode; w c represents the capacity of the positive electrode; C c represents the concentration of lithium in the positive electrode; C c,max represents the concentration of lithium in the positive electrode in the fully charged state of the positive electrode; ΔC c represents the correction factor for the positive electrode; R a represents the impedance of the negative electrode; w a represents the capacity of the negative electrode; C a represents the concentration of lithium in the negative electrode; C a,max represents the concentration of lithium in the negative electrode in the fully charged state of the negative electrode; ΔC a represents the correction factor for the negative electrode; K represents a constant based on the Butler–Volmer equation.

6. The deterioration determination method according to any one of claims 1 to 3 further includes: Inferring the internal state of the battery by performing fitting calculation on the impedance of the target electrode during the charging with the first current, thereby inferring a potential curve representing the relationship between the potential of the target electrode and the charge amount during the charging with the first current. Based on the potential curve of the target electrode during the charging with the first current and the impedance of the target electrode during the charging with the second current, inferring the potential of the target electrode during the charging with the second current.

7. The deterioration determination method according to any one of claims 1 to 3 further includes: During the charging with the first current, supplying current to the battery through a current waveform that periodically varies with a first reference current value as the center current value. During the charging with the second current, supplying current to the battery through a current waveform that periodically varies with a second reference current value larger than the first reference current value as the center current value.

8. A deterioration determination device for determining the deterioration of a battery to be determined includes: A processor that infers a correction coefficient for correcting the difference in the lithium concentration distribution in the target electrode during the charging with the first current and the lithium concentration distribution in the target electrode during the charging with the second current, based on the difference between the potential of the target electrode during the charging of the battery with the first current and the potential of the target electrode during the charging of the battery with a second current larger than the first current, and the impedance of the target electrode during the charging with the second current, for at least one of the positive electrode and the negative electrode of the battery as the target electrode.

9. A battery management system includes: The deterioration determination device according to claim 8; and The battery, for which a determination related to the deterioration is made by the deterioration determination device.

10. A battery-mounted device includes: The deterioration determination device according to claim 8; and The battery, for which a determination related to the deterioration is made by the deterioration determination device.

11. A storage medium stores a deterioration determination program for determining the deterioration of a battery to be determined, and the deterioration determination program causes a computer to execute: Inferring a correction coefficient for correcting the difference in the lithium concentration distribution in the target electrode during the charging with the first current and the lithium concentration distribution in the target electrode during the charging with the second current, based on the difference between the potential of the target electrode during the charging of the battery with the first current and the potential of the target electrode during the charging of the battery with a second current larger than the first current, and the impedance of the target electrode during the charging with the second current, for at least one of the positive electrode and the negative electrode of the battery as the target electrode.

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