WO2018181609A1 - Degradation estimating device, degradation estimating method, and computer program - Google Patents

Abstract

The objective of the present invention is to provide a degradation estimating device, a degradation estimating method and a computer program with which it is possible for degradation of an electricity storage element to be estimated accurately. A degradation estimating device (101) is provided with: an acquiring unit (21) which acquires time-series data of the state of charge (SOC) of an electricity storage element; and an estimating unit (22) which estimates the degradation of the electricity storage element on the basis of the magnitude of variation of the SOC in the time-series data acquired by the acquiring unit (21). An electricity storage element degradation estimating method comprises: acquiring time-series data of the SOC of an electricity storage element; and estimating the degradation of the electricity storage element on the basis of the magnitude of variation of the SOC in the acquired time-series data.

Description

Degradation estimation apparatus, degradation estimation method, and computer program

The present invention relates to a deterioration estimation device, a deterioration estimation method, and a computer program for estimating deterioration of a storage element.

Electrical storage elements that store electrical energy and can supply energy as a power source when necessary are used. The power storage element is applied to portable equipment, power supply devices, transportation equipment including automobiles and railways, industrial equipment including aviation, space, and construction. It is important to always know the storage capacity of the storage element so that the energy stored as much as necessary can be used when necessary. It is known that a power storage element is chemically degraded mainly depending on time and use frequency. Therefore, the energy which can be utilized decreases according to time and use frequency. In order to use as much energy as necessary when necessary, it is important to grasp the deterioration state of the power storage element. So far, a technique for estimating deterioration of a power storage element has been developed.

Japanese Patent Laid-Open No. 2011-220900 discloses a battery deterioration estimation method. A battery deterioration estimation method for estimating the level of capacity deterioration of a secondary battery is a method of estimating the amount of current flowing through the secondary battery or the elapsed time corresponding to each of a plurality of usage conditions affecting the capacity deterioration of the secondary battery. Is accumulated over a predetermined period. In the battery deterioration estimation method, the deterioration coefficient indicating the ratio of the deterioration rate of the secondary battery in the plurality of use conditions to the deterioration rate of the secondary battery in a single use condition is calculated according to the corresponding plurality of use conditions. A second procedure is calculated for each. In the battery deterioration estimation method, the deterioration coefficient calculated for each of a plurality of use conditions corresponding to the second procedure is calculated by using the current integrated value or elapsed time integrated for each of the plurality of use conditions in the first procedure. And a third procedure for converting into the current integrated value or the elapsed time in the single use condition. The battery deterioration estimation method is a fourth method for estimating the level of capacity deterioration of the secondary battery based on the integrated current value or elapsed time converted in the third procedure and the deterioration rate under the single use condition. The procedure is as follows.

JP 2011-220900 A

In the conventional method, there is a case where the estimation accuracy of deterioration of the power storage element is not sufficient.
In the conventional method, various usage conditions (charge / discharge pattern, charge / discharge rate, environmental temperature, etc.) of the storage element are predicted, and tests and calculations are performed under the respective predicted use conditions. Data on deterioration is stored in advance in a data table. After starting the use of the storage element, measure the actual use condition in real time, read the data associated with the predicted use condition close to the actual use condition from the data table, and estimate the deterioration of the storage element Yes. In order to improve the estimation accuracy of deterioration in the conventional method, it is necessary to store data for as many predicted use conditions as possible. Preparing such a large amount of data is complicated.
Even if data is prepared for many predicted usage conditions, the actual usage conditions may deviate from the predicted usage conditions. When such a divergence occurs, the estimation accuracy of deterioration decreases. Further, it has not been sufficiently realized to perform deterioration estimation / prediction by appropriately selecting data on many predicted usage conditions according to actual usage conditions. Under such circumstances, there is a need for a technique for accurately estimating the deterioration of the power storage element.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a deterioration estimation device, a deterioration estimation method, and a computer program capable of accurately estimating deterioration of a power storage element. .

A deterioration estimation apparatus according to one aspect of the present invention includes an acquisition unit that acquires time-series data of a state of charge (SOC) in a storage element, and the SOC of the SOC in the time-series data acquired by the acquisition unit. An estimation unit configured to estimate deterioration of the power storage element based on the magnitude (difference) of fluctuation.

Here, “the magnitude of variation in SOC in time series data” is the difference in SOC when Δt time has elapsed from the SOC at a certain time t.
The present inventor has devised a new capacity deterioration model in consideration of “dynamic” deterioration (deterioration due to energization) due to insertion / extraction of electric energy to / from the power storage element. The present inventor has found an algorithm related to deterioration estimation derived from the model. Specifically, the present inventor has found that the degree of deterioration due to energization of the power storage element varies depending on the magnitude (difference) of SOC variation in the time series data. That is, the present inventor has found that the deterioration of the power storage element depends on the magnitude (difference) of the SOC fluctuation in the time series data. In the conventional estimation method that does not consider the magnitude of the SOC variation in the time series data, for example, the degradation estimated value when the SOC varies in the range of ± 10% centering on the SOC 50%, and ± 30 centering on the SOC 50%. %, The deterioration estimated value when the SOC fluctuates is the same (see FIGS. 21A and 21B). In the conventional method, it is impossible to adapt to the usage pattern (charge / discharge pattern) of the power storage element, which varies from user to user, and the estimation accuracy of deterioration cannot be sufficiently improved. It can be expected that the estimation accuracy of the deterioration can be improved by estimating the deterioration of the storage element by the estimation unit based on the magnitude of the SOC fluctuation in the time series data.

In an example of a model and an algorithm, a person who takes in and out electric energy (lithium ions when the storage element is a lithium ion battery) enters and exits through a film on the electrode surface (SEI film when the storage element is a lithium ion battery). The total amount of lithium ions present in the coating was considered.
Furthermore, you may consider the lithium ion contained in the film which peeled from the electrode surface with charging / discharging.
The validity of the algorithm considering the ion distribution and / or behavior is supported by experimental data. The consideration will be described later.

Since it is possible to accurately estimate the deterioration based on the time-series data of the SOC without preparing the parameters used for estimating the deterioration for each SOC fluctuation pattern, the preparation for estimating the deterioration of the storage element is remarkably simplified. Can be Further, it is possible to accurately estimate the deterioration of the power storage element regardless of the usage pattern (SOC fluctuation pattern) of the power storage element, which varies from user to user.

The estimation unit may estimate the deterioration of the storage element based on the magnitude of the SOC fluctuation and the center of the SOC fluctuation in the time series data.

The present inventor has found that in addition to the magnitude of the fluctuation of the SOC, the center of fluctuation of the SOC (central SOC) is also related to the deterioration due to energization of the power storage element. Even if the SOC fluctuation range when the SOC is fluctuated between the charge side (positive side) and the discharge side (minus side) with respect to a certain SOC is different, if the center SOC is different, the amount of deterioration due to energization of the storage element is also reduced. It is different (see FIG. 21C). The deterioration phenomenon is a chemical change, and the chemical change depends on the surrounding environment of the main chemical species. Since the environment changes when the center SOC is different, it is considered that the amount of deterioration due to energization of the power storage element is also different. The main cause of the capacity deterioration of the storage element is considered to be a difference in capacity balance between the positive electrode and the negative electrode (difference in capacity where charge ions can reversibly enter and exit the electrode between the positive electrode and the negative electrode of the storage element). The deviation in capacity balance is said to be caused by the growth of a film on the negative electrode active material (an SEI film when the power storage element is a lithium ion battery). It is assumed that the center SOC is different, that is, the potential of the negative electrode active material is different, which affects the growth of the SEI film. With the configuration in which the deterioration of the power storage element is estimated based on the magnitude of the SOC fluctuation and the center of the SOC fluctuation, the deterioration of the power storage element can be accurately estimated regardless of the difference in the center of the SOC fluctuation.

The estimation unit calculates an energization deterioration value indicating deterioration due to energization of the power storage element based on a magnitude of fluctuation of the SOC, and indicates the calculated energization deterioration value and deterioration not caused by energization of the power storage element. You may estimate degradation of the said electrical storage element based on the sum with a non-energization degradation value.

The inventor of the present invention has focused on the fact that the deterioration further proceeds when a power storage element that deteriorates with time even when left as it is is energized. A configuration in which an energization deterioration value indicating deterioration further progressed by energization is calculated based on the magnitude of variation in SOC and the deterioration of the storage element is estimated based on the sum of the calculation result and the non-energization deterioration value. Degradation can be estimated more accurately. The present inventor not only “deteriorated” static electricity storage elements with deterioration with time (not due to energization, deterioration due to neglect) but also “dynamic” deterioration due to electric energy input / output (due to energization). A new capacity deterioration model was devised in consideration of (deterioration due to energization). We found an algorithm for degradation estimation derived from the model.

The estimation unit may estimate the deterioration of the power storage element based on a change in a state of a SEI (Solid Electrolyte Interface) film on a negative electrode of the power storage element based on a magnitude of fluctuation of the SOC.

The present inventor incorporated a change in the state of the SEI film on the negative electrode in accordance with the magnitude of the SOC variation in the estimation of the deterioration amount of the storage element. By performing the estimation in consideration of the physical phenomenon in the negative electrode, it is possible to further improve the estimation accuracy of the deterioration of the storage element.

The estimation unit may estimate the deterioration of the power storage element based on a mathematical model that takes into account the destruction and regeneration of the SEI film on the negative electrode of the power storage element.

The present inventor has devised a mathematical model that takes into account the destruction and regeneration of the SEI film on the negative electrode of the electricity storage element in order to estimate the deterioration of the electricity storage element due to energization. This mathematical model is considered to represent the physical phenomenon in the electrode more correctly than the conventional mathematical model.

The mathematical model also takes into account the deterioration of the storage element due to the SEI film peeled from the negative electrode of the storage element.

The present inventor incorporated deterioration due to the SEI coating peeled from the negative electrode into the mathematical model. This mathematical model is considered to represent the physical phenomenon in the electrode more correctly than the conventional mathematical model.

As described above, the main cause of the capacity deterioration of the power storage element is a shift in capacity balance. Conventionally, it has been known that the capacity of a power storage element deteriorates with time.
The present inventor has found that the deviation in capacity balance increases due to energization. Based on this new knowledge, the deterioration of the storage element is estimated by estimating the deviation in the capacity balance between the positive electrode and the negative electrode as described below.

A deterioration estimation device according to another aspect of the present invention includes an estimation unit that estimates the deterioration of the capacity of a power storage element, which is the amount of electricity that can be reversibly extracted from the power storage element, based on the number of charge / discharge cycles.

In this specification, “estimate based on the number of charge / discharge cycles” means the number of charge / discharge cycles themselves, a numerical value (for example, energization time) correlated with the number of charge / discharge cycles, or an alternative expression of the number of charge / discharge cycles. This includes a case where capacity deterioration of the power storage element is estimated based on (for example, percentage, square root).

The estimation of the capacity deterioration of the power storage element based on the number of charge / discharge cycles may be performed using a mathematical model. Alternatively, the estimation of the capacity deterioration of the power storage element based on the number of charge / discharge cycles described above is performed by performing tests or calculations under various predicted use conditions of the power storage element, thereby obtaining data on the capacity deterioration of the power storage element. By preliminarily storing the data in a data table and selecting data appropriately according to actual use conditions, the capacity deterioration of the storage element based on the number of charge / discharge cycles may be estimated.

By energization (with an increase in the number of charge / discharge cycles), for example, one of the positive electrode and the negative electrode is not completely charged, and the amount of electricity that can be reversibly taken out from the storage element is reduced. Adopt new knowledge that “capacity shift” will increase. Thereby, deterioration of an electrical storage element can be estimated more accurately than before.

The estimation unit indicates a deterioration in the capacity of the power storage element at a predetermined number of charge / discharge cycles, an energization deterioration value indicating deterioration due to energization of the power storage element at that time, and a non-reduction indicating non-energization of the power storage element. You may estimate by the sum with an electricity supply degradation value.

As described above, the present inventor has found that the deviation in capacity balance increases due to energization. Conventionally, it has been considered that the same amount of deviation in the capacity balance occurs over time regardless of whether the power storage element is energized or not. Based on new knowledge, if the deterioration of the capacity of the power storage element at a predetermined number of charge / discharge cycles is estimated by the sum of the current-carrying deterioration value and the non-energization deterioration value at that time, the deterioration of the power storage element is more accurate than before. Can be estimated.

The difference between the energization deterioration value and the non-energization deterioration value may be configured to increase as the number of charge / discharge cycles increases.

When estimating the capacity deterioration of the electricity storage element based on the number of charge / discharge cycles using a mathematical model or a data table, the difference between the energized deterioration value and the non-energized deterioration value increases as the number of charge / discharge cycles increases. By configuring the mathematical model or the data table so as to increase, it is possible to estimate the deterioration of the storage element with higher accuracy than in the past.

The estimation unit may estimate the energization deterioration value by a sum of a film deterioration value caused by the SEI film grown on the negative electrode of the power storage element and a peel deterioration value caused by the SEI film peeled from the negative electrode. Good.

The present inventor has devised a mathematical model that takes into account the destruction and regeneration of the SEI film on the negative electrode of the electricity storage element in order to estimate the deterioration of the electricity storage element due to energization. This mathematical model is considered to represent the physical phenomenon in the electrode more correctly than the conventional mathematical model. The estimation unit estimates the energization deterioration value by a sum of a film deterioration value caused by the SEI film grown on the negative electrode of the power storage element and a peel deterioration value caused by the SEI film peeled from the negative electrode. Therefore, it is possible to estimate the deterioration of the power storage element with higher accuracy than in the past.

The deterioration estimation device may further include an acquisition unit that acquires time-series data of SOC in the power storage element, and the estimation unit may estimate the energization deterioration value based on the time-series data of the SOC.

The estimation unit can estimate the deterioration of the electricity storage device more accurately than the conventional one by estimating the energization deterioration value based on the time-series data of the SOC.

According to another aspect of the present invention, there is provided a method for estimating deterioration of a power storage element, wherein time series data of SOC in the power storage element is acquired, and based on the magnitude of fluctuation of the SOC in the acquired time series data, Estimate degradation.

The deterioration estimation method according to another aspect of the present invention estimates the deterioration of the capacity of the electricity storage element, which is the amount of electricity that can be reversibly extracted from the electricity storage element, based on the number of charge / discharge cycles.

A computer program according to another aspect of the present invention acquires, in a computer, time series data of SOC in a power storage element, and the deterioration of the power storage element based on the magnitude of fluctuation of the SOC in the acquired time series data. The process which estimates is performed.

A computer program according to another aspect of the present invention causes a computer to execute a process of estimating deterioration of the capacity of a power storage element, which is an amount of electricity that can be reversibly extracted from the power storage element, based on the number of charge / discharge cycles.

The deterioration estimation device according to one aspect of the present invention may be mounted on a battery management unit (BMU) or a cell monitoring unit (CMU) that is a monitoring device. The deterioration estimation device may be a part of a power storage device in which such a monitoring device is incorporated. The degradation estimation device may be configured separately from the electrical storage element and the electrical storage device, and may be connected to the electrical storage device including the electrical storage element targeted for degradation estimation at the time of degradation estimation. The deterioration estimation device may remotely monitor the power storage element and the power storage device.

The deterioration estimation method according to another aspect of the present invention can be realized in various modes such as a recording medium on which a computer program for realizing this method is recorded.

Thus, according to the aspect of the present invention, it is possible to accurately estimate the deterioration of the power storage element.

It is a figure which shows the structure of a monitoring apparatus. It is a figure which shows the structure of a degradation estimation apparatus. It is a figure for demonstrating deterioration of the battery which a deterioration estimation apparatus estimates. It is a figure for demonstrating the SOC-P curve in a new battery. It is the figure which represented typically the movement of the carrier in a battery. It is a figure for demonstrating the shift | offset | difference of the capacity | capacitance balance in a battery. It is a figure for demonstrating the shift | offset | difference of the capacity | capacitance balance in a battery. It is a figure which shows an example of the change of the deterioration amount by the electricity supply of a battery with respect to the fluctuation range of SOC. It is a figure which shows an example of the change of the deterioration amount by electricity supply of the battery with respect to center SOC. It is a figure which shows an example of the arrangement | sequence which the estimation part in a degradation estimation apparatus uses. It is a flowchart which shows the operation | movement procedure at the time of a degradation estimation apparatus estimating degradation of a battery. It is a flowchart which shows the operation | movement procedure at the time of a deterioration estimation apparatus calculating an energization deterioration value based on time series data. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows an example of the error in the deterioration estimation of the battery by a deterioration estimation apparatus. It is a figure which shows the aspect of the fluctuation | variation of various SOC. It is a flowchart which shows the operation | movement procedure at the time of the deterioration estimation apparatus which concerns on 2nd Embodiment estimating deterioration of a battery.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated. Moreover, you may combine arbitrarily at least one part of embodiment described below.

[Configuration and basic operation]
FIG. 1 is a diagram illustrating a configuration of a monitoring device. The monitoring device 151 includes a current sensor 51, a voltage sensor 52, a temperature sensor 53, a history creation unit 54, a counter 55, a storage unit 56, a communication unit 57, and a deterioration estimation device 101.

Some of the constituent elements included in the monitoring device 151 may be arranged apart from other constituent elements. For example, the deterioration estimation device 101 may be disposed in a remote place and communicate with the communication unit 57. In addition, a server that is arranged in a remote place and connected to the network may function as the degradation estimation apparatus 101.

The monitoring device 151 monitors the deterioration of the storage element to be monitored (in this embodiment, a lithium ion secondary battery). The monitoring device 151 may monitor one battery cell, or may monitor a plurality of battery cells (assembled batteries) connected in series or in parallel. Monitoring device 151 may constitute a power storage device (battery pack) together with the assembled battery.

The storage element to be monitored is not limited to a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, and may be another electrochemical cell to which a hypothesis, an algorithm, and a mathematical model described later are applicable. Hereinafter, the storage element to be monitored is also simply referred to as a battery.

The counter 55 in the monitoring device 151 counts clock pulses generated by an oscillation circuit using a crystal resonator, and holds the counted value. This count value may indicate the current time.

The current sensor 51 measures the current charged in the battery and the current discharged from the battery, and outputs an analog signal Ai indicating the measurement result to the history creating unit 54.

The voltage sensor 52 measures the voltage between the positive electrode and the negative electrode in the battery, and outputs an analog signal Av indicating the measurement result to the history creating unit 54.

The temperature sensor 53 measures the temperature T at a predetermined part of the battery and outputs an analog signal At indicating the measurement result to the history creating unit 54.

The history creation unit 54 converts, for example, analog signals Ai, Av, and At received from the current sensor 51, the voltage sensor 52, and the temperature sensor 53, respectively, into digital signals Di, Dv, and Dt at every predetermined sampling time.

The history creation unit 54 stores the count value of the counter 55 at the sampling time and the digital signals Di, Dv, and Dt in the storage unit 56. The storage unit 56 accumulates the sampling time, current value, voltage value, and temperature T for each sampling time.

The communication unit 57 may communicate with other devices such as a main control device (main ECU (Electronic Control Unit)) in a vehicle, a personal computer, a server, a smartphone, and a battery maintenance terminal, for example.

For example, when the communication unit 57 receives an instruction for estimating the deterioration state of the battery from another device, the communication unit 57 outputs the received estimation command to the deterioration estimation device 101. The monitoring device 151 may not include each sensor.

FIG. 2 is a diagram illustrating a configuration of the deterioration estimation apparatus.

With reference to FIG. 2, degradation estimation apparatus 101 includes control unit 20, storage unit 23, and interface unit 24. The interface unit 24 includes, for example, a LAN interface and a USB interface, and communicates with other devices such as the monitoring device 151 by wire or wireless.
A signal line or a terminal heading from the degradation estimation apparatus 101 to the communication unit 57 may function as an output unit that outputs an estimation result or the like. The communication unit 57 may function as an output unit.
When different input data is input to the degradation estimation apparatus 101, different outputs are obtained from the output unit. When different SOC fluctuation ranges (and / or central SOC) are input to the deterioration estimation apparatus 101, the output unit may output different outputs (for example, voltage value, duty ratio).
A display unit (or a notification unit) for displaying the output result may be connected to the output unit. The output from the output unit may be displayed on the display unit (or notification unit) via the communication unit 57.

The storage unit 23 stores a deterioration estimation program 231 for executing a deterioration estimation process described later. The deterioration estimation program 231 is provided in a state stored in a computer-readable recording medium 60 such as a CD-ROM, DVD-ROM, or USB memory, for example, and is stored in the storage unit 23 by being installed in the deterioration estimation apparatus 101. Is done. Further, the deterioration estimation program 231 may be acquired from an external computer (not shown) connected to the communication network and stored in the storage unit 23.
The storage unit 23 also stores data and the like necessary for the deterioration estimation process.

The control unit 20 includes, for example, a CPU, a ROM, a RAM, and the like, and controls the operation of the deterioration estimation apparatus 101 by executing a computer program such as the deterioration estimation program 231 read from the storage unit 23. The control unit 20 functions as a processing unit that executes the deterioration estimation process by reading and executing the deterioration estimation program 231.
Specifically, the control unit 20 includes an acquisition unit 21 and an estimation unit 22.

The acquisition unit 21 in the deterioration estimation apparatus 101 acquires time-series data of SOC (State Of Charge) in the battery.

More specifically, when receiving the estimation command from the communication unit 57, the acquisition unit 21 stores each sampling time, and the current value, voltage value, and temperature T at each sampling time in the monitoring device 151 according to the received estimation command. Obtained from the unit 56 via the interface unit 24.
In this way, the acquisition unit 21 acquires data measured after the start of battery use from the storage unit 56.
The acquisition unit 21 may alternatively acquire data from the data file.

The acquisition unit 21 secures a storage area for storing data on sampling time, SOC, and temperature.
For example, the acquiring unit 21 secures an array Ats having elements of ts [1] to ts [Snum] for storing data on Snum sampling times.

Also, the acquisition unit 21 secures an array Asoc having elements of sc [1] to sc [Snum] for storing data about the SOC at the sampling times ts [1] to ts [Snum].

Also, the acquisition unit 21 secures an array Atmp having elements of tmp [1] to tmp [Snum] for storing data about the temperature T at the sampling times ts [1] to ts [Snum].

The acquisition unit 21 calculates, for example, the amount of electricity supplied to the battery by counting current values at each sampling time, and converts the calculated amount of electricity into a change amount of the SOC. The acquisition unit 21 calculates the SOC at each sampling time based on the conversion result. The acquisition unit 21 may correct the SOC using, for example, a measured value of the open circuit voltage.

The acquisition unit 21 stores the sampling time corresponding to each element of the array Ats so that the index N of the array Ats (N is an integer from 1 to Snum) is in time series order.

The acquisition unit 21 stores the SOC at the sampling times ts [1] to ts [Snum] in sc [1] to sc [Snum], respectively. Similarly, the acquisition unit 21 stores the temperatures T at the sampling times ts [1] to ts [Snum] in tmp [1] to tmp [Snum], respectively.
The acquisition unit 21 outputs the arrays Ats, Asoc, and Atmp to the estimation unit 22.

FIG. 3 is a diagram for explaining battery deterioration estimated by the deterioration estimating apparatus. In FIG. 3, the vertical axis shows the battery capacity as a percentage when the battery capacity is new, and the horizontal axis shows the number of cycles when the total number of cycles, which is the total number of charge and discharge, is used as a reference. Shown as a percentage. The horizontal axis can also be regarded as the elapsed time from the new state.
Referring to FIG. 3, capacity change Cvu3 is a change with respect to the number of cycles of capacity when a battery is charged / discharged (true cycle deterioration fading), and is a result obtained by an energization test. is there. The capacity change Cvn3 is a capacity change with time when the battery is not energized (calendar capacity fading), and is a result obtained based on a neglect test performed in advance.

Thus, when the battery is energized, the degree of deterioration is greater than when the battery is left unattended. The difference between the capacity indicated by the capacity change Cvu3 and the capacity indicated by the capacity change Cvn3 can be regarded as deterioration due to energization of the battery. In other words, the deterioration of the battery is a deterioration not caused by the energization of the battery plus the deterioration caused by the energization of the battery.

[Displacement of capacity balance]
FIG. 4 is a diagram for explaining an SOC-P curve (SOC-V curve) in a new battery. In FIG. 4, the vertical axis indicates the potential, and the horizontal axis indicates the SOC.
FIG. 4 shows a change Cvp4 of the potential of the single positive electrode with respect to the SOC and a change Cvn4 of the potential of the single negative electrode with respect to the SOC in a new battery. The difference between the potential of the single positive electrode and the potential of the single negative electrode is the voltage between the electrodes in the battery (battery voltage). The change Cvc4 is a change of the voltage between the electrodes with respect to the SOC.

FIG. 5 is a diagram schematically showing carrier movement in a lithium ion secondary battery. The positive electrode Pp formed of lithium metal oxide and the negative electrode Np formed of carbon are immersed in the electrolytic solution EL. The positive electrode Pp has a plurality of sites Sp that can accommodate lithium ions. The negative electrode Np has a plurality of sites Sn that can accommodate lithium ions.

Although different from the state shown in the figure, in the discharge state of the new battery, all lithium ions are accommodated in the site Sp in the positive electrode Pp. When the battery is charged, some of the lithium ions accommodated in the positive electrode Pp move to the negative electrode Np via the electrolytic solution and are accommodated in the site Sn.

As shown in FIG. 5, it is known that in a deteriorated battery, a SEI (Solid Electrolyte Interface) coating Ls is formed on the surface of the negative electrode. The SEI film Ls has a property of capturing lithium ions.
When lithium ions are trapped in the SEI film Ls, a site Sp that does not contain lithium ions is generated in a discharged state. Further, in the charged state, the number of lithium ions accommodated at the site Sn is reduced as compared with a new battery.

FIG. 6 is a diagram for explaining a shift in capacity balance in the battery. 6 is the same as FIG.
FIG. 6 shows a change Cvp6 of the potential of the single positive electrode with respect to the SOC, a change Cvn6 of the potential of the single negative electrode with respect to the SOC, and a change Cvc6 of the voltage between the electrodes with respect to the SOC in the deteriorated battery.

When lithium ions are trapped in the SEI film Ls (see FIG. 5), the change in the potential of the negative electrode alone with respect to the SOC shifts in a direction in which the negative electrode Np is not fully charged. Specifically, the change Cvn4 shown in FIG. 4 shifts to become the change Cvn6 shown in FIG.
When such a shift occurs, the amount of electricity that can be reversibly taken out from the battery decreases even when the capacities of the positive electrode Pp and the negative electrode Pn do not deteriorate. Accordingly, the battery capacity is reduced.
This phenomenon and the battery capacity reduced by the phenomenon are defined as “capacity balance deviation” in this specification.
Generally, the above phenomenon occurs due to the difference in the side reaction rate between the positive electrode Pp and the negative electrode Pn. As described above, when carbon is used for the negative electrode Pn, the above phenomenon occurs due to the SEI film Ls formed on the negative electrode Pn.

[New findings 1]
FIG. 7 is a diagram for explaining a shift in capacity balance in the battery. In FIG. 7, the vertical axis represents the deterioration amount, and the horizontal axis represents the square root of the cycle number. The horizontal axis can also be regarded as the square root of the elapsed time from the new state.

Referring to FIG. 7, Cvu7 is a change with respect to the square root of the cycle number of the measured value of the capacity balance deviation when the battery is charged / discharged. Cvn7 is a change in the estimated value of the deviation in capacity balance when the battery is not charged or discharged. That is, the former is a transition of capacity balance deviation when energized, and the latter is a transition of capacity balance deviation that occurs over time when non-energized. The latter can be obtained as follows. First, by performing a standing test on a plurality of batteries having different temperatures from the SOC, the amount of deterioration with time (non-energization deterioration value Qcnd described later) at each SOC and temperature is obtained. Further, the coefficient at each SOC and temperature is obtained by using the following formula (2) or formula (3). Next, the amount of deterioration over time in the minute time during the cycle test is obtained at predetermined time intervals from each SOC in the cycle test, the square root of the time spent in that SOC (for example, minute time), and the corresponding coefficient obtained in advance. . The amount of deterioration with time in the cycle test is calculated by accumulating the amount of deterioration with time.

In a lithium ion secondary battery, it is known that an SEI film grows on the negative electrode. As the amount of lithium ions trapped in the SEI film increases as the SEI film grows, the deviation in capacity balance increases.
In other words, as the SEI film grows, the balance between the amount of lithium ions inserted and removed at the negative electrode and the amount of lithium ions inserted and removed at the positive electrode are shifted.

It has been conventionally known that even when the battery is not energized, the SEI film grows and the battery deteriorates like the deterioration amount change Cvn7. That is, even when the battery is not energized, it has been known that the battery deteriorates due to a shift in capacity balance over time.
According to the experiment conducted by the present inventor, as shown by Cvu7 in FIG. 7, as the number of cycles increases, the capacity balance shifts when the battery is energized compared to when the battery is not energized. Increased. From this, the present inventor has found that the deviation of the capacity balance is further increased by energization. This is a new finding that cannot be predicted from previously known theories and laws. As the number of cycles increases, the capacity balance shift increases, so it is presumed that the amount of SEI coating produced on the negative electrode active material is increased by energization. SEI coating is caused by the decomposition reaction on the negative electrode active material, and the growth slows down as the film thickness increases, so it is reported that the generation amount of SEI coating, that is, the deviation in capacity balance, gradually saturates when no current is applied. Has been. As described above, since the negative electrode active material expands and contracts by energization, the SEI film is destroyed or peeled off from the active material, so that the growth of the SEI film continues to regenerate without slowing down. It can be considered that an excessive amount of SEI film is formed.

[New knowledge 2]
FIG. 8 is a diagram illustrating an example of a change in the deterioration amount due to the energization of the battery with respect to the SOC fluctuation range. In FIG. 8, the vertical axis indicates the difference between the deterioration amount when a predetermined amount of electricity is energized and the deterioration amount in the 3% SOC fluctuation range, and the horizontal axis indicates the SOC fluctuation range.
In FIG. 8, the amount of deterioration due to energization after charging / discharging a predetermined number of times so that the center SOC becomes 60% is plotted against the fluctuation range of the SOC.

As shown in FIG. 8, the present inventor has found that even when the center SOC is the same, the amount of deterioration due to energization changes when the variation range of the SOC is different. It has been found that deterioration due to energization increases in accordance with the magnitude of SOC variation.
The mechanism of this phenomenon is not yet fully understood. The present inventor partially destroyed the SEI film formed on the surface of the negative electrode due to significant expansion (charge) and contraction (discharge) of the negative electrode as the variation of the SOC was larger, As a result, it is considered that the amount of deterioration due to energization of the battery increases.

[New knowledge 3]
FIG. 9 is a diagram illustrating an example of a change in the deterioration amount due to the energization of the battery with respect to the center SOC. In FIG. 9, the vertical axis indicates the difference between the deterioration amount when a predetermined amount of electricity is energized and the deterioration amount at the central SOC of 10%, and the horizontal axis indicates the central SOC that is the center of the SOC fluctuation. Here, the center SOC is an example of the center of the SOC fluctuation in the time-series data of the SOC.

In FIG. 9, the amount of deterioration due to energization after charging and discharging is repeated a predetermined number of times so that the fluctuation range of the SOC becomes 20% is plotted with respect to the center SOC.
Here, an example is given and demonstrated about charging / discharging operation | movement. Repeating charging / discharging so that the center SOC is 10% and the fluctuation range of SOC is 20% is repeating charging / discharging so that the SOC reciprocates between 0% and 20%.

As shown in FIG. 9, the present inventor has found that even when the SOC fluctuation range is the same, the deterioration amount due to energization changes when the central SOC is different. It has been found that the progress of deterioration due to energization varies depending on the central SOC. When the center SOC is low (for example, when the center SOC is 10%), the amount of deterioration is small although the SOC fluctuation range is the same as when the center SOC is around 50%. When the center SOC is high (for example, when the center SOC is 70%), the amount of deterioration is small compared to when the center SOC is around 50%, although the SOC fluctuation range is the same.

[Concept for new mathematical model]
Based on the above-mentioned new findings 1 to 3, the present inventor has obtained the following idea regarding a new mathematical model for estimating deterioration due to energization of a storage element.
(A) Incorporate the destruction and regeneration of the SEI coating on the negative electrode into the mathematical model. In addition to the knowledge that the growth rate of the SEI film decreases as the SEI film is formed, a unique idea that the growth rate of the SEI film returns to the original position when the SEI film is destroyed is expressed by a mathematical model.
(B) The amount of deterioration due to energization of the power storage element is increased as the variation of the SOC is increased.
(C) The coefficient has SOC dependency (the coefficient value varies according to the central SOC and / or the SOC fluctuation range).
(D) In the mathematical model, deterioration due to energization of the power storage element due to the SEI film that is broken and peeled off from the negative electrode of the power storage element is also considered.
This mathematical model is based on the assumption that ions, which are responsible for taking in and out electrical energy, enter and exit through the electrode surface coating (SEI coating). More specifically, it is a deterioration estimation model that takes into account ions present in the film, and also takes into account ions contained in the film peeled off from the electrode surface during charge and discharge.

[Calculation process of non-energized deterioration value Qcnd]
Referring to FIG. 2 again, estimation unit 22 estimates the deterioration of the battery based on the magnitude of the SOC variation in the SOC time-series data acquired by acquisition unit 21.
The estimation unit 22 estimates the deterioration of the battery based on, for example, the sum of the energization deterioration value Qcur and the non-energization deterioration value Qcnd. Specifically, as shown in the following formula (1), the estimation unit 22 calculates the sum of the energization deterioration value Qcur and the non-energization deterioration value Qcnd as a deterioration value Qdeg indicating battery deterioration.

The estimation unit 22 may transmit estimation result information indicating the calculated degradation value Qdeg to another device via the communication unit 57 as a response to the estimation command.
The estimation unit 22 is configured to estimate the degradation value Qdeg, which is the sum of the energization degradation value Qcur and the non-energization degradation value Qcnd, as battery degradation, but is not limited thereto. The estimation unit 22 may be configured to estimate a value based on the sum, a percentage value of the deterioration value Qdeg with respect to a predetermined reference, a deterioration level according to the deterioration value Qdeg, or the like as battery deterioration. Qcur is composed of at least Qrgn and Qdst. Specifically, it includes a film deterioration value Qrgn caused by the SEI film grown on the negative electrode and a peeling deterioration value Qdst caused by the SEI film peeled from the negative electrode. Qrgn is a deterioration value due to the film newly formed on the electrode by peeling off the SEI film due to SOC fluctuation, and Qdst is a deterioration value due to the film peeled off due to SOC fluctuation.

The non-energized deterioration value Qcnd increases with time. For example, the increment dQcnd per minute time dt of the non-energized deterioration value Qcnd is calculated by the following equation (2).

Here, the coefficient kc is a function of the SOC and the temperature T. By transforming Equation (2), Equation (3) is obtained.

Here, t indicates elapsed time, and kcr = √ (2 × kc). Therefore, the non-energized deterioration value Qcnd increases according to the root rule. Increasing according to the route rule means that the increment per unit time of the non-energized deterioration value Qcnd gradually decreases with the passage of time. The estimation unit 22 calculates the non-energization deterioration value Qcnd using at least one of the equations (2) and (3).

[Calculation process of energization deterioration value Qcur]
The estimation unit 22 estimates the deterioration due to the energization of the battery based on, for example, the change in the state of the film in the battery electrode based on the magnitude of the SOC variation.
In the present embodiment, the estimation unit 22 estimates the deterioration due to the energization of the battery in consideration of the peeling deterioration value caused by the coating peeled from the battery electrode.
More specifically, the estimation unit 22 calculates the sum of the film deterioration value due to the electrode film in the battery and the peeling deterioration value as the energization deterioration value Qcur.

As shown in Formula (1), the estimation unit 22 calculates the sum of the film deterioration value Qrgn caused by the SEI film grown on the negative electrode in the lithium ion secondary battery and the peel deterioration value Qdst caused by the SEI film peeled from the negative electrode. Is calculated as an energization deterioration value Qcur.

The storage unit 23 holds a correspondence relationship between the SOC and a coefficient kr (see formula (4) described later), which is a deterioration coefficient indicating the degree of progress of deterioration due to energization of the battery. The storage unit 23 may hold a correspondence table Tblr indicating a correspondence relationship between the SOC, the temperature T, and the coefficient kr.

For example, the temporal change of the deterioration amount due to energization for each temperature T and for each SOC is measured by a prior test.
The coefficient kr is calculated based on the measurement result of the test. Specifically, it is desirable that the coefficient kr is obtained by optimization calculation in comparison with the measurement result together with the elements of the array for calculating the division deterioration value described later.

Further, the storage unit 23 holds a correspondence relationship between the SOC and the deterioration coefficient (the above-described coefficient kc) indicating the degree of progress of deterioration not due to the energization of the battery. The storage unit 23 may hold a correspondence table Tblc indicating a correspondence relationship between the SOC, the temperature T, and the coefficient kc.

The correspondence relationship between the SOC and temperature T and the coefficient kc is derived, for example, by performing a test similar to the calculation of the coefficient kr.

The estimation unit 22 increases the film degradation value Qrgn with the passage of time, for example. For example, the estimating unit 22 determines that the film deterioration value Qrgn increases according to the coefficient kr corresponding to the SOC so that the increase in the film deterioration value Qrgn decreases according to the magnitude of the film deterioration value Qrgn. Qrgn is calculated.

Specifically, the increment dQrgn per minute time dt of the film deterioration value Qrgn is calculated by the following equation (4).

By transforming equation (4), the following equation (5) is obtained.

Here, krr = √ (2 × kr). Therefore, the film deterioration value Qrgn increases according to the root rule. Increasing according to the root rule means that the increment per unit time of the film deterioration value Qrgn gradually decreases with the passage of time. The estimation unit 22 calculates the film deterioration value Qrgn using at least one of the equations (4) and (5).

FIG. 10 is a diagram illustrating an example of an array used by the estimation unit in the degradation estimation apparatus. In FIG. 10, the vertical axis is a virtual axis that indicates both the center SOC and the SOC fluctuation range. The left side of FIG. 10 represents a state before the peeling of the SEI film occurs, and the right side of FIG. 10 represents a state after the peeling of the SEI film occurs. FIG. 10 shows a situation in which a variation in SOC of more than 12% and less than 14% occurs with a certain SOC (an SOC value between qd [j + 2] and qd [j + 3]) as described later. For example, the estimation unit 22 calculates the film deterioration value Qrgn by the sum of a plurality of division deterioration values.

Specifically, the estimation unit 22 secures a storage area for storing each division deterioration value.
The estimation unit 22 reserves an array Aqd having elements qd [1] to qd [Dnum] for storing Dnum division degradation values.
Here, the number of elements Dnum of the array Aqd is, for example, a value obtained by dividing 100% by the interval INT. The interval INT is a value that can be arbitrarily set. In this example, the interval INT is 2. Therefore, in this example, Dnum is 50.

The estimation unit 22 increases, for example, each of the plurality of division deterioration values with the passage of time. For example, the estimation unit 22 performs the division so that the growth rate of the division degradation value qd [j] decreases with the growth of the division degradation value qd [j] (so that the growth rate of the division degradation value gradually decreases). A degradation value qd [j] is calculated. Here, the index j is an integer from 1 to Dnum.

Specifically, the estimation unit 22 uses the following equation (6) based on the equation (4) to increase the division degradation value qd [j] increment Δ at the sampling times ts [N−1] to ts [N]. (Sj [N]) is calculated.

Here, Δt is an interval between sampling times ts [N−1] to ts [N]. The coefficient kr (sc [N], tmp [N]) is a coefficient corresponding to sc [N] and the temperature tmp [N] at the sampling time ts [N], and can be calculated based on the correspondence table Tblr. Formula (6) is a method of consolidating (integrating) the past deterioration history (deterioration path) from the initial stage to N-1, and newly taking the time from N-1 to N as the next sampling timing based on the aggregation. Increment (change value) of Δ (Sj [N]) divided deterioration value qd [j], which is an increase in (Δt), is obtained according to the root rule. Further, the function f of the equation (6) is expressed by the following equation (7).

Further, by expressing the divided deterioration value qd [j] at the sampling time ts [N−1] by qd [j] [N−1], the equation (7) can be transformed into the following equation (8). It is.

The smaller the degradation value qd [j] at the sampling time ts [N−1], the smaller Δ (Sj [N]). In other words, Δ (Sj [N]) increases as the divided deterioration value qd [j] at the sampling time ts [N−1] increases.

The estimation unit 22 calculates the division deterioration value qd [j] at the sampling time ts [N] by adding Δ (Sj [N]) to qd [j] [N−1].

As shown in the array Aqd before the occurrence of peeling in FIG. 10, the values calculated by the estimating unit 22 until the peeling occurs are indicated by hatching in each of the divided deterioration values qd [1] to qd [Dnum].

The estimation unit 22 estimates the deterioration of the battery by performing the following processing. For example, when the fluctuation magnitude of the SOC satisfies the predetermined condition C1, the estimation unit 22 adds the number of division deterioration values corresponding to the fluctuation magnitude among the plurality of division deterioration values to the peeling deterioration value Qdst. At the same time, each of the division deterioration values used for adding the peeling deterioration value Qdst is set to a predetermined value smaller than the division deterioration value.

Specifically, the predetermined condition C1 is, for example, that the magnitude of the SOC fluctuation is larger than the interval INT. In the example shown in FIG. 10, the SOC variation of greater than 12% and less than or equal to 14% occurs, and the situation where the SEI film is peeled off is shown. In this case, since the magnitude of the variation of the SOC is larger than the interval INT, in other words, 2, the predetermined condition C1 is satisfied.

When the predetermined condition C1 is satisfied, the estimating unit 22 adds the sum of each of the divided deterioration values qd [j] to qd [j + 5] before the occurrence of peeling to the peeling deterioration value Qdst. Here, the index j is, for example, a value at which the SOC immediately before the change is greater than (j−1) × INT and the SOC is equal to or less than j × INT.

And the estimation part 22 sets each value of division | segmentation degradation value qd [j] -qd [j + 5] to zero, as shown to the arrangement | sequence Aqd after peeling generation | occurrence | production.

The estimation unit 22 is not limited to the configuration in which each of the divided deterioration values qd [j] to qd [j + 5] is set to zero, and may be a value smaller than each of the divided deterioration values qd [j] to qd [j + 5]. For example, it may be configured to set to a predetermined value other than zero.

[Flow of operation]
The monitoring apparatus 151 or the deterioration estimation apparatus 101 in the monitoring apparatus 151 includes a control unit 20, and the control unit 20 reads out a deterioration estimation program 231 including some or all of the steps of the flowchart shown below from the storage unit 23. Execute.

FIG. 11 is a flowchart that defines an operation procedure when the deterioration estimation device estimates the deterioration of the battery.

Referring to FIG. 11, a situation is assumed in which control unit 20 of degradation estimation apparatus 101 receives an estimation command from another apparatus.

First, the degradation estimation apparatus 101 acquires time-series data of the battery SOC and temperature T (step S102).

Next, the deterioration estimation device 101 calculates a non-energization deterioration value Qcnd of the battery based on the time series data of the SOC and the temperature T (step S104).

The deterioration estimation device 101 calculates a battery energization deterioration value Qcur based on the time-series data of the SOC and the temperature T (step S106).

Degradation estimation apparatus 101 calculates the sum of energization deterioration value Qcur and non-energization deterioration value Qcnd as deterioration value Qdeg indicating the deterioration of the battery, and estimates the deterioration of the battery based on the calculation result (step S108).

The order of steps S104 and S106 is not limited to the above, and the order may be changed.

FIG. 12 is a flowchart that defines an operation procedure when the deterioration estimation device calculates an energization deterioration value based on time-series data. FIG. 12 shows details of the operation in step S106 of FIG. In this example, unlike the case shown in FIG. 9, the sampling interval is assumed such that the fluctuation range of the SOC in the sampling interval is smaller than the interval INT.

First, the degradation estimation apparatus 101 initializes the index N to 1 (step S202).

Next, the deterioration estimation apparatus 101 initializes the SOC_old, the array Aqd, and the peeling deterioration value Qdst. Specifically, degradation estimation apparatus 101 sets SOC_old to sc [1]. In addition, the degradation estimation apparatus 101 initializes each element qd [1] to qd [Dnum] in the array Aqd and the peel degradation value Qdst to zero (step S204).

Degradation estimation apparatus 101 increments index N (step S206).

Degradation estimation apparatus 101 determines index jt corresponding to the magnitude of the SOC variation (step S210) when sc [N] is larger than the sum of SOC_old and interval INT (YES in step S208).

Degradation estimation apparatus 101 determines, for example, an index jt where SOC_old is greater than (jt-1) × INT and SOC_old is equal to or less than jt × INT.

The deterioration estimation device 101 adds the division deterioration value qd [jt] to the peeling deterioration value Qdst (step S212).

Degradation estimation apparatus 101 sets division degradation value qd [jt] to zero (step S214).

Degradation estimation apparatus 101 updates the value of SOC_old to the sum of SOC_old and interval INT (step S216).

On the other hand, when sc [N] is less than or equal to the sum of SOC_old and interval INT (NO in step S208), degradation estimating apparatus 101 compares sc [N] with a value obtained by subtracting interval INT from SOC_old (step S218). ).

Degradation estimation apparatus 101 updates the value of SOC_old to a value obtained by subtracting interval INT from SOC_old when sc [N] is equal to or less than the value obtained by subtracting interval INT from SOC_old (step S220).

Next, degradation estimation apparatus 101 updates SOC_old (steps S216 and S220), or when sc [N] is larger than the value obtained by subtracting interval INT from SOC_old (NO in step S218), equation (6) Is used to update the values of the respective elements qd [1] to qd [Dnum] of the array Aqd (step S222).

The degradation estimation apparatus 101 compares the index N with the number of elements Snum of the array Ats, and if the index N is different from the number of elements Snum (NO in step S224), the index N is incremented (step S226).

Next, degradation estimation apparatus 101 compares sc [N] with the sum of SOC_old and interval INT (step S208).

On the other hand, when the index N matches the number of elements Snum (YES in step S224), the deterioration estimation device 101 performs a calculation process of the energization deterioration value Qcur (step S228). Specifically, the degradation estimation apparatus 101 calculates the sum of the film degradation value Qrgn that is the sum of qd [1] to qd [Dnum] and the peeling degradation value Qdst as the energization degradation value Qcur.

As described above, in this flowchart, the sampling interval is assumed such that the fluctuation range of the SOC in the sampling interval is smaller than the interval INT. However, if the fluctuation range is equal to or larger than the interval INT, in step S210, By determining a plurality of indexes, it is possible to calculate the energization deterioration value Qcur.

[effect]
13 to 20 are diagrams showing an example of errors in battery deterioration estimation by the deterioration estimating apparatus. 13 to 20, the vertical axis indicates an error, and the horizontal axis indicates the number of cycles.

Here, the error is, for example, a value obtained by dividing the absolute value of the difference between the calculated value and the actual measurement value by the actual measurement value in percentage.

13 to 20 show an error change Cvi by the deterioration estimation apparatus according to the embodiment of the present invention and an error change Cvr by the comparative example. The calculated value according to the comparative example is calculated based on, for example, the integrated value of the absolute value of the current flowing into and out of the battery, which is the amount of energized electricity.

FIGS. 13 to 16 show the results when the fluctuation range of the SOC is fixed to 20% while the central SOC is changed.

More specifically, in FIG. 13, error changes Cvi and Cvr after repeated charging and discharging are plotted against the number of cycles so that the SOC variation is 0% to 20%.

FIG. 14 plots error changes Cvi and Cvr after repeated charging and discharging so that the SOC variation is 20% to 40% against the number of cycles.

FIG. 15 plots error changes Cvi and Cvr after repeated charging and discharging so that the SOC variation is 40% to 60% against the number of cycles.

FIG. 16 plots error changes Cvi and Cvr after repeated charging and discharging so that the SOC variation is 60% to 80% against the number of cycles.

As shown in FIGS. 13 to 16, in the comparative example, the error is suppressed when the SOC variation is 40% to 60% and 60% to 80%, but the SOC variation is 0% to 20%. In the case of 20% to 40%, the error increases as the number of cycles increases.

On the other hand, in the deterioration estimation apparatus according to the embodiment of the present invention, the error is suppressed regardless of the increase in the number of cycles regardless of the magnitude of the fluctuation of the SOC.

FIG. 17 to FIG. 20 show results when the center SOC is fixed at 60% and the fluctuation range of the SOC is changed.

More specifically, FIG. 17 plots error changes Cvi and Cvr after repeated charging and discharging so that the center SOC is 60% and the fluctuation range of the SOC is 1% against the number of cycles. Has been.

FIG. 18 plots error changes Cvi and Cvr after repeated charging and discharging so that the center SOC is 60% and the fluctuation range of SOC is 10% against the number of cycles.

FIG. 19 plots error changes Cvi and Cvr after repeated charging and discharging so that the center SOC is 60% and the fluctuation range of the SOC is 40% against the number of cycles.

FIG. 20 plots error changes Cvi and Cvr after repeated charging and discharging so that the center SOC is 60% and the fluctuation range of the SOC is 60% against the number of cycles.

As shown in FIGS. 17 to 20, in the comparative example, the error is suppressed when the SOC fluctuation ranges are 10% and 40%, but the error is suppressed when the SOC fluctuation ranges are 1% and 60%. large.

On the other hand, in degradation estimating apparatus 101 according to the embodiment of the present invention, the error is equal or suppressed in any SOC fluctuation range.

(Second Embodiment)
The degradation estimation apparatus 101 according to the second embodiment has the same configuration as the degradation estimation apparatus 101 according to the first embodiment except that the following points are different.

The history creation unit 54 of the degradation estimation apparatus 101 according to the second embodiment stores the count value of the counter 55 at the sampling time and the digital signals Di, Dv, and Dt in the storage unit 56. The storage unit 56 stores the sampling time, current value, voltage value, and temperature T at each sampling time, and stores the number of charge / discharge cycles. Each time charge / discharge is repeated, the number of charge / discharge cycles is updated.

Referring to FIG. 22, a situation is assumed in which control unit 20 of degradation estimation apparatus 101 receives an estimation command from another apparatus. Hereinafter, for example, a case where charge / discharge is repeated so that the SOC reciprocates between 40% and 80% will be described.

First, the degradation estimation apparatus 101 acquires the number of charge / discharge cycles (step S300).
Deterioration estimating apparatus 101 acquires time-series data of battery SOC and temperature T (step S302).

Next, the deterioration estimation device 101 calculates a non-energization deterioration value Qcnd of the battery based on the time series data of the SOC and the temperature T (step S304).

Degradation estimation apparatus 101 calculates a battery energization deterioration value Qcur based on time-series data of SOC and temperature T (step S306).

The degradation estimation device 101 calculates the sum of the energization degradation value Qcur and the non-energization degradation value Qcnd as a degradation value Qdeg indicating the degradation of the battery, and estimates the degradation of the battery (shift in capacity balance) based on the computation result (step) S308). The energization deterioration value Qcur and the non-energization deterioration value Qcnd are calculated such that the difference between the energization deterioration value Qcur and the non-energization deterioration value Qcnd increases as the number of charge / discharge cycles increases. For example, a cycle test is performed in advance, and at least one of the coefficient kc and the coefficient kr is changed according to the number of charge / discharge cycles.

The order of steps S300 and S302 and the order of steps S304 and S306 are not limited to the above, and the order may be changed.

FIGS. 13 to 20 also show an example of an error in battery deterioration estimation by the deterioration estimating apparatus 101 of the second embodiment. That is, FIG. 13 shows a change in error with respect to the number of cycles when charging / discharging is repeated so that the SOC reciprocates between 0% and 20%. FIG. 14 shows a change in error with respect to the number of cycles when charging / discharging is repeated so that the SOC reciprocates between 20% and 40%. FIG. 15 shows a change in error with respect to the number of cycles when charge and discharge are repeated so that the SOC reciprocates between 40% and 60%. FIG. 16 shows a change in error with respect to the number of cycles when charging / discharging is repeated so that the SOC reciprocates between 60% and 80%.

FIG. 17 shows an error change with respect to the number of cycles when the charge / discharge is repeated so that the SOC reciprocates between 59.5% and 60.5%. FIG. 18 shows a change in error with respect to the number of cycles when charge and discharge are repeated so that the SOC reciprocates between 55% and 65%. FIG. 19 shows a change in error with respect to the number of cycles when charging / discharging is repeated so that the SOC reciprocates between 40% and 80%. FIG. 20 shows a change in error with respect to the number of cycles when charge and discharge are repeated so that the SOC reciprocates between 30% and 90%.

From FIG. 13 to FIG. 20, it is possible to estimate the deterioration of the storage element with higher accuracy than before by adopting the new knowledge that the deviation of the capacity balance increases as the number of charge / discharge cycles increases. confirmed.

The internal state of the electricity storage device can be grasped by estimating the amount of decrease in the amount of electricity that can be reversibly extracted from the electricity storage device due to an increase in capacity balance deviation. Since the potential of the negative electrode at 100% SOC is also known, when the power storage element is a lithium ion secondary battery, the risk of deposition of metallic lithium on the negative electrode is also known. The SOH (State of Health) of the electricity storage element including the risk can be monitored. Since the SOC-OCV curve can be obtained based on the deviation of the capacity balance, it is also possible to determine how to control the storage element.

Although the deterioration estimation apparatus 101 according to the first embodiment and the second embodiment of the present invention is configured to be provided inside the monitoring apparatus 151, the present invention is not limited to this. The degradation estimation apparatus 101 may be provided outside the monitoring apparatus 151. In this case, the deterioration estimation apparatus 101 acquires SOC time-series data from the monitoring apparatus 151 via a bus such as a USB (Universal Serial Bus) cable.

The deterioration estimation apparatus 101 is configured to use SOC time-series data, but is not limited thereto. Degradation estimation apparatus 101 may use time-series data of an absolute value such as a charge amount, time-series data of a charge level, and the like, instead of time-series data of SOC. The SOC time-series data may be ΔSOC obtained by a current integration method or the like, or may be data obtained by adding / subtracting ΔSOC to the initial SOC value.

In the deterioration estimation apparatus 101, the estimation unit 22 is configured to calculate the deterioration value as the battery deterioration estimation, but the present invention is not limited to this. The estimation unit 22 may calculate a level indicating battery deterioration, battery life, battery replacement time, and the like.

In the deterioration estimation device 101, the estimation unit 22 is configured to calculate the energization deterioration value Qcur based on the SOC fluctuation magnitude, the SOC at each acquisition time point, and the temperature T at each acquisition time point, but is not limited thereto. Not what you want. The estimation unit 22 may estimate the deterioration of the battery based on the magnitude of the SOC fluctuation. For example, the estimation unit 22 may set the coefficient kr as a fixed value when the variation of the SOC is small and the variation of the temperature T is small.

The estimation unit 22 may be configured to estimate deterioration due to energization of the battery based on, for example, the magnitude of SOC variation. For example, the estimation unit 22 calculates the energization deterioration value Qcur using the coefficient kr as a fixed value.

The estimation unit 22 may be configured to estimate battery deterioration based on, for example, the magnitude of SOC fluctuation and the center of SOC fluctuation in time-series data, and the magnitude of SOC fluctuation. The battery deterioration may be estimated based on the SOC at each acquisition time point. For example, when the variation in temperature T is small, the estimation unit 22 can calculate the energization deterioration value Qcur and the non-energization deterioration value Qcnd using the coefficient kr and the coefficient kc as functions of the SOC.
In the deterioration estimation device 101, the estimation unit 22 is configured to estimate the deterioration of the storage element based on the sum of the energization deterioration value Qcur and the non-energization deterioration value Qcnd, but the present invention is not limited to this. The estimation unit 22 may be configured to estimate the deterioration of the storage element based on the energization deterioration value Qcur without using the non-energization deterioration value Qcnd. For example, when the elapsed time from the new battery state is short, the estimation unit 22 can accurately estimate the deterioration of the storage element based on the energization deterioration value Qcur.

In the deterioration estimation device 101, the estimation unit 22 is configured to calculate the energization deterioration value Qcur based on the peeling deterioration value Qdst, but is not limited thereto. The estimation unit 22 may calculate the energization deterioration value Qcur without using the peeling deterioration value Qdst.

The above embodiment is not restrictive. The scope of the present invention is intended to include all modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 20 Control part 21 Acquisition part 22 Estimation part 23 Storage part 231 Degradation estimation program 51 Current sensor 52 Voltage sensor 53 Temperature sensor 54 History creation part 55 Counter 56 Storage part 57 Communication part 60 Recording medium 101 Degradation estimation apparatus 151 Monitoring apparatus

Claims (15)

1. An acquisition unit for acquiring time-series data of SOC in the storage element;
   A degradation estimation device comprising: an estimation unit that estimates degradation of the power storage element based on a magnitude of fluctuation of the SOC in the time-series data acquired by the acquisition unit.
2. The deterioration estimation device according to claim 1, wherein the estimation unit estimates deterioration of the power storage element based on a magnitude of fluctuation of the SOC and a center of fluctuation of the SOC in the time series data.
3. The estimation unit calculates an energization deterioration value indicating deterioration due to energization of the power storage element based on a magnitude of fluctuation of the SOC, and indicates the calculated energization deterioration value and deterioration not caused by energization of the power storage element. The deterioration estimation device according to claim 1, wherein deterioration of the power storage element is estimated based on a sum with a non-energized deterioration value.
4. The said estimation part estimates deterioration of the said electrical storage element based on the change of the state of the SEI film in the negative electrode of the said electrical storage element based on the magnitude | size of the fluctuation | variation of the said SOC. The degradation estimation apparatus according to item 1.
5. The deterioration estimation device according to claim 4, wherein the estimation unit estimates the deterioration of the electricity storage element based on a mathematical model that takes into account the destruction and regeneration of the SEI film on the negative electrode of the electricity storage element.
6. The deterioration estimation device according to claim 5, wherein the mathematical model also takes into account the deterioration of the storage element due to the SEI film peeled from the negative electrode of the storage element.
7. Deterioration estimation apparatus comprising an estimation unit that estimates the deterioration of the capacity of a storage element, which is the amount of electricity that can be reversibly extracted from the storage element, based on the number of charge / discharge cycles.
8. The estimation unit indicates a deterioration in the capacity of the power storage element at a predetermined number of charge / discharge cycles, an energization deterioration value indicating deterioration due to energization of the power storage element at that time, and a non-reduction indicating non-energization of the power storage element. The deterioration estimation apparatus according to claim 7, wherein the deterioration estimation apparatus estimates the sum by an energization deterioration value.
9. The deterioration estimation device according to claim 8, wherein a difference between the energization deterioration value and the non-energization deterioration value is configured to increase as the number of charge / discharge cycles increases.
10. The estimation unit estimates the energization deterioration value by a sum of a film deterioration value caused by an SEI film grown on a negative electrode of the power storage element and a peel deterioration value caused by an SEI film peeled from the negative electrode. Item 10. The deterioration estimation device according to Item 8 or 9.
11. An acquisition unit for acquiring SOC time-series data in the power storage device;
    The deterioration estimation device according to any one of claims 8 to 10, wherein the estimation unit estimates the energization deterioration value based on time series data of the SOC.
12. A method for estimating deterioration of a storage element,
    Obtain time-series data of SOC in the electricity storage device,
    A degradation estimation method for estimating degradation of the power storage element based on a magnitude of fluctuation of the SOC in the acquired time series data.
13. A method for estimating deterioration of a storage element,
    A degradation estimation method for estimating degradation of a capacity of a storage element, which is an amount of electricity that can be reversibly extracted from the storage element, based on the number of charge / discharge cycles.
14. On the computer,
    Obtain time-series data of SOC in the electricity storage device,
    A computer program that executes processing for estimating deterioration of the power storage element based on the magnitude of fluctuation of the SOC in the acquired time-series data.
15. On the computer,
    A computer program that executes processing for estimating deterioration of a capacity of a power storage element, which is an amount of electricity that can be reversibly extracted from the power storage element, based on the number of charge / discharge cycles.

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