JP5673097B2 - Non-aqueous electrolyte secondary battery OCV characteristic estimation method, OCV characteristic estimation apparatus, and power storage system - Google Patents

Description

  The present invention relates to an OCV characteristic estimation method, an OCV characteristic estimation apparatus, an OCV characteristic estimation apparatus that estimates an OCV characteristic that is a characteristic of an open circuit voltage of a nonaqueous electrolyte secondary battery, and a power storage system that includes the nonaqueous electrolyte secondary battery and the OCV characteristic estimation apparatus. About.

  The shift from gasoline cars to electric cars has become important as a global environmental problem. For this reason, use of a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery as a power source for an electric vehicle has been studied.

  However, the secondary battery is relatively weak against overcharge and overdischarge, and battery performance deteriorates when overcharge or overdischarge occurs. For this reason, it is necessary to prevent overcharge or overdischarge by grasping the OCV characteristic which is the characteristic of the open circuit voltage of the secondary battery and controlling the current value and the amount of electricity supplied to the secondary battery. That is, in order to prevent a decrease in battery performance of the secondary battery, it is extremely important to accurately grasp the OCV characteristics.

  For this reason, the technique which grasps | ascertains the OCV characteristic of the said secondary battery conventionally is proposed (for example, refer patent document 1 and 2). In patent document 1, the characteristic which shows the relationship between a charging rate and an open circuit voltage is acquired from the value measured beforehand, and the OCV characteristic is grasped | ascertained. Further, in Patent Document 2, the OCV characteristic is grasped based on the discharge characteristic by an arithmetic expression using the discharge capacity, the discharge current, and the like.

JP 2001-231179 A JP 2009-031219 A

  However, the conventional technology has a problem that the OCV characteristics of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery cannot be accurately grasped in the long term.

  In other words, in the techniques disclosed in Patent Documents 1 and 2, the OCV characteristics are grasped on the assumption that the OCV characteristics do not change even when the secondary battery is used over time. However, the inventors of the present application have found that the OCV characteristics of the secondary battery change with use as a result of intensive studies and experiments. For this reason, in the said prior art, when the said secondary battery is used for a long term, there exists a problem that the OCV characteristic of the said secondary battery cannot be grasped | ascertained correctly.

  The present invention has been made to solve the above-described problem, and can provide a non-aqueous electrolyte secondary battery capable of accurately estimating the OCV characteristics of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery over a long period of time. It is an object of the present invention to provide an OCV characteristic estimation method, an OCV characteristic estimation device, and a power storage system.

  In order to achieve the above object, an OCV characteristic estimation method according to an aspect of the present invention is a method in which a computer estimates an OCV characteristic indicating a relationship between an energization amount of electricity and an open circuit voltage of a nonaqueous electrolyte secondary battery. A first positive electrode OCP characteristic indicating a relationship between a first electric quantity, which is an energized electric quantity at a predetermined first point of time, and a positive electrode open circuit potential of the nonaqueous electrolyte secondary battery, and an estimation method, An OCP characteristic acquisition step of acquiring a first negative electrode OCP characteristic indicating a relationship between the first electric quantity of the electrolyte secondary battery and a negative electrode open circuit potential; and the non-water from the first time point to a predetermined second time point An increase amount acquisition step of acquiring an increase amount of impedance which is an increase amount of AC impedance at a predetermined frequency in the electrolyte secondary battery, the acquired first positive electrode OCP characteristic, first negative electrode OCP characteristic, and impedance Using a dancing increase, and a estimation step of estimating an OCV characteristics at the second time point of the nonaqueous electrolyte secondary battery.

  According to this, the OCV characteristic at the second time point is estimated using the acquired first positive electrode OCP characteristic, first negative electrode OCP characteristic, and impedance increase amount. That is, the OCV characteristic at the first time point can be grasped from the first positive electrode OCP characteristic and the first negative electrode OCP characteristic, but by using the OCV characteristic and the impedance increase amount at the first time point, The OCV characteristic at the second time point after the elapse of a predetermined period from the time point can be estimated. For this reason, since the OCV characteristic according to the elapsed period can be estimated even if the period elapses, the OCV characteristic of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery is accurately estimated in the long term. Can do.

  Preferably, in the estimation step, a second electricity amount that is an energized electricity amount at the second time point of the nonaqueous electrolyte secondary battery and a value obtained by multiplying the impedance increase amount by a predetermined constant are added. A characteristic indicating a relationship between the second electric quantity and the positive open circuit potential obtained by substituting the value into the first electric quantity of the first positive electrode OCP characteristic is calculated as the second positive electrode OCP characteristic, and the non-aqueous A characteristic indicating the relationship between the second electric quantity and the negative open circuit potential obtained by substituting the second electric quantity of the electrolyte secondary battery for the first electric quantity of the first negative electrode OCP characteristic is a second negative electrode. Calculated as an OCP characteristic, and obtained by subtracting the negative open circuit potential for the second electric quantity in the second negative OCP characteristic from the positive open circuit potential for the second electric quantity in the calculated second positive OCP characteristic. Above The characteristics showing the relationship between the second electrical quantity and the open-circuit voltage and estimates the OCV characteristics at the second time point.

  According to this, the second positive electrode OCP characteristic is calculated from the first positive electrode OCP characteristic and the impedance increase amount, the second negative electrode OCP characteristic is calculated from the first negative electrode OCP characteristic, and the calculated second positive electrode OCP characteristic and the second positive electrode OCP characteristic are calculated. The OCV characteristic at the second time point is estimated from the negative electrode OCP characteristic. Here, as a result of diligent research and experiments, the inventors of the present application have moved the amount of energized electricity in the first positive electrode OCP characteristic by a value obtained by multiplying the amount of increase in impedance by a predetermined constant. It was found that the characteristics coincided with the accuracy. That is, the second positive electrode OCP characteristic can be calculated accurately and easily from the first positive electrode OCP characteristic and the amount of increase in impedance. For this reason, since the OCV characteristic at the second time point with high accuracy can be estimated easily, the OCV characteristic of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery can be easily estimated with high accuracy over the long term. be able to.

  Preferably, in the increase acquisition step, the AC impedance at the first time point is applied to the non-aqueous electrolyte secondary battery at the first time point by applying an AC voltage or an AC current having the predetermined frequency to the nonaqueous electrolyte secondary battery. The first impedance is measured, and at the second time point, the alternating current voltage or alternating current of the predetermined frequency is applied to the non-aqueous electrolyte secondary battery, and the second impedance is the AC impedance at the second time point. The impedance increase is obtained by measuring two impedances and subtracting the first impedance from the second impedance.

  According to this, the first impedance and the second impedance are measured, and the amount of increase in impedance is calculated and acquired from the first impedance and the second impedance. Thereby, since the amount of increase in impedance can be easily obtained, the OCV characteristic of a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery can be easily estimated with high accuracy in the long term.

  The present invention can be realized not only as an OCV characteristic estimation method for such a non-aqueous electrolyte secondary battery, but also as an OCV characteristic estimation apparatus including a processing unit that performs steps included in the OCV characteristic estimation method. Can be realized. The present invention can also be realized as an integrated circuit including a characteristic processing unit included in such an OCV characteristic estimation device.

  The present invention also provides a power storage system including a non-aqueous electrolyte secondary battery and an OCV characteristic estimation device that estimates an OCV characteristic indicating a relationship between an energized electricity amount of the non-aqueous electrolyte secondary battery and an open circuit voltage. Can be realized.

  The present invention can also be realized as a program that causes a computer to execute characteristic processing included in the OCV characteristic estimation method. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet.

  According to the present invention, the OCV characteristics of a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery can be accurately estimated over the long term.

It is an external view of an electrical storage system provided with the OCV characteristic estimation apparatus which concerns on embodiment of this invention. It is a block diagram which shows the functional structure of the OCV characteristic estimation apparatus which concerns on embodiment of this invention. It is a figure which shows an example of OCV characteristic estimation data which concerns on embodiment of this invention. It is a flowchart which shows an example of the process in which the OCV characteristic estimation apparatus which concerns on embodiment of this invention estimates the OCV characteristic of a secondary battery. It is a flowchart which shows an example of the process in which the OCP characteristic acquisition part which concerns on embodiment of this invention acquires a 1st positive electrode OCP characteristic and a 1st negative electrode OCP characteristic. It is a figure which shows the initial stage positive electrode OCP characteristic and the initial stage negative electrode OCP characteristic which the OCP characteristic acquisition part which concerns on embodiment of this invention acquires. It is a figure which shows the 1st positive electrode OCP characteristic and 1st negative electrode OCP characteristic which the OCP characteristic acquisition part which concerns on embodiment of this invention acquires. It is a flowchart which shows an example of the process in which the increase amount acquisition part which concerns on embodiment of this invention acquires an impedance increase amount. It is a flowchart which shows an example of the process which the estimation part which concerns on embodiment of this invention estimates OCV characteristic in a 2nd time. It is a figure explaining the mechanism in which a secondary battery charges / discharges. It is a figure explaining the mechanism in which a secondary battery deteriorates. It is a figure which shows the relationship between the alternating current impedance which concerns on embodiment of this invention, and a reversible capacity | capacitance. It is a figure which shows the OCV characteristic in the 2nd time point which the estimation part which concerns on embodiment of this invention estimates. It is a figure which shows the change of the OCV characteristic which the OCV characteristic estimation apparatus which concerns on embodiment of this invention estimates. It is a block diagram which shows the structure which implement | achieves the OCV characteristic estimation apparatus which concerns on embodiment of this invention with an integrated circuit.

  Hereinafter, an OCV characteristic estimation device according to an embodiment of the present invention and a power storage system including the OCV characteristic estimation device will be described with reference to the drawings.

  First, the configuration of the power storage system 10 will be described.

  FIG. 1 is an external view of a power storage system 10 including an OCV characteristic estimation device 100 according to an embodiment of the present invention.

  As shown in the figure, the power storage system 10 accommodates the OCV characteristic estimation device 100, a plurality (six in the figure) secondary batteries 200, and the OCV characteristic estimation device 100 and the plurality of secondary batteries 200. Case 300 is provided.

  The OCV characteristic estimation device 100 is a circuit board on which a circuit that is disposed above the plurality of secondary batteries 200 and estimates the OCV characteristics of the plurality of secondary batteries 200 is mounted. Specifically, the OCV characteristic estimation device 100 is connected to a plurality of secondary batteries 200, acquires information from the plurality of secondary batteries 200, and the energized electricity amount and the open circuit of the plurality of secondary batteries 200. An OCV characteristic indicating a relationship with the voltage is estimated. The detailed functional configuration of the OCV characteristic estimation apparatus 100 will be described later.

  Here, the OCV characteristic of the secondary battery 200 is a characteristic indicating the relationship between the energized electricity amount of the secondary battery 200 and the open circuit voltage (OCV). Further, the open circuit voltage is a potential difference of an open circuit potential (OCP) between the positive electrode and the negative electrode of the secondary battery 200, and the negative circuit open circuit potential is calculated from the positive circuit open circuit potential of the secondary battery 200. Subtracted value.

  Further, the positive open circuit potential and the negative open circuit potential are the time when a sufficient time has elapsed after the secondary battery 200 is electrically disconnected from the external circuit (no load is applied between the positive electrode and the negative electrode). The positive electrode potential and the negative electrode potential of the secondary battery 200 in FIG. That is, the open circuit voltage indicates a voltage between the positive electrode and the negative electrode of the secondary battery 200 when a sufficient time has passed without a current flowing through the secondary battery 200.

  Here, OCV characteristic estimation device 100 is arranged above a plurality of secondary batteries 200, but OCV characteristic estimation device 100 may be arranged anywhere.

  The secondary battery 200 is a non-aqueous electrolyte secondary battery having a positive electrode and a negative electrode, for example, a lithium ion secondary battery. That is, the secondary battery 200 is, for example, a secondary battery in which the positive electrode is a lithium transition metal oxide such as lithium cobalt oxide and the negative electrode is a carbon material. In FIG. 6, six rectangular secondary batteries 200 are arranged in series to form an assembled battery. In addition, the number of the secondary batteries 200 is not limited to six, and may be another plural number or one. Further, the shape of the secondary battery 200 is not particularly limited.

  Next, a detailed functional configuration of the OCV characteristic estimation apparatus 100 will be described.

  FIG. 2 is a block diagram showing a functional configuration of OCV characteristic estimation apparatus 100 according to the embodiment of the present invention.

  The OCV characteristic estimation apparatus 100 is an apparatus that estimates the OCV characteristic indicating the relationship between the energized electricity amount of the secondary battery 200 and the open circuit voltage. As shown in the figure, the OCV characteristic estimation device 100 includes an OCP characteristic acquisition unit 110, an increase amount acquisition unit 120, an estimation unit 130, and a storage unit 140.

  The OCP characteristic acquisition unit 110 includes a first positive electrode OCP characteristic indicating a relationship between a first electric quantity that is an energized electric quantity at a predetermined first time point of the secondary battery 200 and a positive electrode open circuit potential; A first negative electrode OCP characteristic indicating a relationship between the first electric quantity and the negative electrode open circuit potential is obtained.

  Specifically, the OCP characteristic acquisition unit 110 includes an initial positive OCP characteristic indicating the relationship between the amount of electricity supplied to the positive electrode in the initial state of the secondary battery 200 and the positive open circuit potential, and the initial state of the secondary battery 200. The initial negative electrode OCP characteristic indicating the relationship between the amount of electricity supplied to the negative electrode and the open circuit potential of the negative electrode is obtained by reading from the storage unit 140.

  The OCP characteristic acquisition unit 110 is obtained by substituting a value obtained by adding the relative positional deviation of the positive electrode at the first time to the first electric quantity of the secondary battery 200 into the initial electric quantity of the initial positive electrode OCP characteristic. The first positive electrode OCP characteristic is obtained by calculating the characteristic indicating the relationship between one electric quantity and the positive electrode open circuit potential as the first positive electrode OCP characteristic. The relative positional shift of the positive electrode is a relative shift amount (amount of decrease in chargeable / dischargeable capacity) of the energized electricity amount in the OCP characteristic of the positive electrode.

  In addition, the OCP characteristic acquisition unit 110 has a characteristic indicating the relationship between the first electric quantity and the negative open circuit potential obtained by substituting the first electric quantity of the secondary battery 200 into the initial electric quantity of the initial negative electrode OCP characteristic. The first negative electrode OCP characteristic is obtained by calculating as the first negative electrode OCP characteristic.

  The predetermined first time point is a time point serving as a reference for calculation for estimating the OCV characteristic. Here, the first time point may be any time point, for example, the factory shipment time of the secondary battery 200. The first time point may be expressed in any unit such as minutes, hours, days, and months.

  The increase amount acquisition unit 120 acquires an impedance increase amount that is an increase amount of AC impedance at a predetermined frequency in the secondary battery 200 from the first time point to the predetermined second time point.

  Specifically, the increase amount acquisition unit 120 is first stored in the storage unit 140 by applying an AC voltage or AC current having a predetermined frequency to the secondary battery 200 and measuring it at the first time point. The first impedance that is the AC impedance at the first time point is acquired.

  Further, the increase amount acquisition unit 120 measures the second impedance, which is the AC impedance at the second time point, by applying an AC voltage or an AC current having a predetermined frequency to the secondary battery 200 at the second time point. Then, the increase amount acquisition unit 120 acquires the impedance increase amount by subtracting the first impedance from the second impedance.

  Then, the increase amount acquisition unit 120 updates the impedance increase amount stored in the storage unit 140 by storing the acquired impedance increase amount in the storage unit 140. Further, the increase amount acquisition unit 120 stores the measured second impedance in the storage unit 140 and updates the first impedance to the second impedance.

  The predetermined second time point is a time point when a predetermined period has elapsed from the first time point when the use of the secondary battery 200 is continued, but the predetermined time period may be any period, There is no particular limitation. Further, the unit of the predetermined period is not particularly limited, and is, for example, a period such as a minute order, an hour order, a day order, or a month order. That is, the second time point may be expressed in any unit such as minutes, hours, days, months, and the like, similar to the first time point.

  The estimation unit 130 uses the first positive electrode OCP characteristic and the first negative electrode OCP characteristic acquired by the OCP characteristic acquisition unit 110 and the impedance increase amount acquired by the increase amount acquisition unit 120 to generate the second time point of the secondary battery 200. The OCV characteristic at is estimated.

  Specifically, the estimation unit 130 adds a value obtained by adding a second electricity amount, which is an energized electricity amount at the second time point of the secondary battery 200, and a value obtained by multiplying an impedance increase amount by a predetermined constant to the first positive electrode. A characteristic indicating the relationship between the second electric quantity and the positive open circuit potential obtained by substituting the first electric quantity of the OCP characteristic is calculated as the second positive OCP characteristic.

  In addition, the estimation unit 130 has a characteristic indicating a relationship between the second electric quantity and the negative open circuit potential obtained by substituting the second electric quantity of the secondary battery 200 into the first electric quantity of the first negative electrode OCP characteristic. Calculated as the second negative electrode OCP characteristic.

  Then, the estimating unit 130 obtains the first obtained by subtracting the negative open circuit potential for the second electric quantity in the calculated second negative OCP characteristic from the positive open circuit potential for the second electric quantity in the calculated second positive OCP characteristic. The characteristic indicating the relationship between the two electric quantities and the open circuit voltage is estimated as the OCV characteristic at the second time point.

  As described above, the increase amount acquisition unit 120 measures the impedance as the third time point and the fourth time point, and acquires the impedance increase amount, whereby the impedance and the impedance increase amount stored in the storage unit 140 are acquired. Will be updated repeatedly. Then, the estimation unit 130 estimates the latest OCV characteristic from the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the impedance increase amount stored in the storage unit 140.

  The storage unit 140 is a memory for storing information for estimating the OCV characteristic. Specifically, the storage unit 140 stores OCV characteristic estimation data 141 including information for estimating the OCV characteristic. Details of the OCV characteristic estimation data 141 will be described later.

  FIG. 3 is a diagram showing an example of the OCV characteristic estimation data 141 according to the embodiment of the present invention.

  The OCV characteristic estimation data 141 is a collection of data indicating the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, the amount of increase in impedance, and the impedance. That is, as shown in the figure, the OCV characteristic estimation data 141 is a data table including “initial positive OCP characteristic”, “initial negative OCP characteristic”, “impedance increase amount”, and “impedance”.

  Specifically, in the “initial positive electrode OCP characteristic”, a function P (q) indicating the relationship between the energized electricity amount of the secondary battery 200 and the positive electrode open circuit potential in the initial state is stored. Further, in the “initial negative electrode OCP characteristic”, a function N (q) indicating the relationship between the amount of electricity supplied to the secondary battery 200 and the negative open circuit potential in the initial state is stored.

  In addition, the “impedance increase amount” stores ΔR which is a value indicating the increase amount of the impedance. Further, the “impedance” stores an impedance R that is an AC impedance of the secondary battery 200.

  Here, in the OCV characteristic estimation data 141, the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the impedance in the initial state are written in advance. The OCP characteristic acquisition unit 110 may acquire data to be written in the OCV characteristic estimation data 141 from a user input or the like, and store the data in the OCV characteristic estimation data 141 by storing the data in the storage unit 140. Good.

  The increase amount acquisition unit 120 updates the impedance and the impedance increase amount of the OCV characteristic estimation data 141 by storing the measured impedance and the acquired impedance increase amount in the storage unit 140.

  Next, the process in which the OCV characteristic estimation apparatus 100 estimates the OCV characteristic of the secondary battery 200 will be described.

  FIG. 4 is a flowchart showing an example of processing in which the OCV characteristic estimation device 100 according to the embodiment of the present invention estimates the OCV characteristic of the secondary battery 200.

  As shown in the figure, first, the OCP characteristic acquisition unit 110 acquires the first positive electrode OCP characteristic and the first negative electrode OCP characteristic of the secondary battery 200 (S102).

  Specifically, the OCP characteristic acquisition unit 110 calculates the first positive electrode OCP characteristic and the first negative electrode OCP characteristic from the initial positive electrode OCP characteristic and the initial negative electrode OCP characteristic of the secondary battery 200 and the relative positional deviation of the positive electrode at the first time point. Get properties and. A detailed description of the process in which the OCP characteristic acquisition unit 110 acquires the first positive OCP characteristic and the first negative OCP characteristic will be described later.

  And the increase amount acquisition part 120 acquires the impedance increase amount (S104).

  Specifically, the increase amount acquisition unit 120 acquires the first impedance of the secondary battery 200, measures the second impedance, and acquires the impedance increase amount from the first impedance and the second impedance. Further, the increase amount acquisition unit 120 causes the storage unit 140 to store the acquired impedance increase amount and the measured second impedance.

  A detailed description of the process in which the increase amount acquisition unit 120 acquires the impedance increase amount will be described later.

  And the estimation part 130 estimates the OCV characteristic in the 2nd time of the secondary battery 200 (S106).

  Specifically, the estimation unit 130 calculates the second positive OCP characteristic and the first negative OCP characteristic and the first negative OCP characteristic acquired by the OCP characteristic acquisition unit 110 and the impedance increase acquired by the increase acquisition unit 120 and The second negative electrode OCP characteristic is calculated, and the OCV characteristic at the second time point is estimated.

  A detailed description of the process in which the estimation unit 130 estimates the OCV characteristic at the second time point will be described later.

  As described above, the increase amount acquisition unit 120 repeatedly measures the impedance and acquires the impedance increase amount, thereby repeatedly updating the impedance and the impedance increase amount stored in the storage unit 140. Then, the estimation unit 130 estimates the latest OCV characteristic from the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the impedance increase amount stored in the storage unit 140.

  Note that the initial positive electrode OCP characteristic and the initial negative electrode OCP characteristic are stored in the storage unit 140 without being updated.

  As described above, the process in which the OCV characteristic estimation device 100 estimates the OCV characteristic of the secondary battery 200 ends.

  Next, a process (S102 in FIG. 4) in which the OCP characteristic acquisition unit 110 acquires the first positive electrode OCP characteristic and the first negative electrode OCP characteristic will be described in detail.

  FIG. 5 is a flowchart illustrating an example of processing in which the OCP characteristic acquisition unit 110 according to the embodiment of the present invention acquires the first positive OCP characteristic and the first negative OCP characteristic.

  As shown in the figure, first, the OCP characteristic acquisition unit 110 acquires the initial positive electrode OCP characteristic and the initial negative electrode OCP characteristic of the secondary battery 200, and the relative positional deviation of the positive electrode at the first time point of the secondary battery 200. (S202).

  Here, the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the impedance in the initial state are measured in advance and stored in the storage unit 140 in advance, but the circuit configuration and program of the OCP characteristic acquisition unit 110 are previously stored. Can also be incorporated. Or it is good also as what can be input by the user.

  The initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the impedance in the initial state can be obtained by measuring one secondary battery 200 as follows.

  First, a lithium ion secondary battery in the initial state of the same type as the lithium ion secondary battery whose OCV characteristics are to be estimated is obtained. The initial state can be, for example, the state at the time of factory shipment of the lithium ion secondary battery (the first time point described above), and the lithium ion secondary battery in the initial state can be obtained by purchasing a commercially available battery. A battery is available.

  Then, the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the impedance in the initial state are obtained from the lithium ion secondary battery thus obtained by measurement. The method for measuring these data is not limited. For example, the obtained lithium ion secondary battery is disassembled, the positive electrode and the negative electrode are taken out, and used for the lithium ion secondary battery. It may be measured in an electrolytic solution equivalent to the electrolytic solution, or may be measured by inserting a reference electrode into the electrolytic solution portion of the obtained lithium ion secondary battery and performing charge / discharge.

  As a measurement procedure, first, the lithium ion secondary battery was put into a discharged state, the values of the positive electrode OCP and the negative electrode OCP at that time were recorded, and then the measurement was performed by inserting the reference electrode or the disassembled positive electrode and negative electrode It is preferable to perform measurements for each.

  And when obtaining and measuring a lithium ion secondary battery with the state at the first time point as the initial state in this way, there is no relative displacement at the first time point because the characteristics at the first time point are measured. Therefore, the OCP characteristic acquisition unit 110 may acquire the relative displacement of the positive electrode at the first time point of the secondary battery 200 as zero.

  The initial positive electrode OCP characteristic and the initial negative electrode OCP characteristic may be measured not at the first time point but at any time point during use of the lithium ion secondary battery. In this case, since the relative position shift at the first time point is not zero, the OCP characteristic acquisition unit 110 calculates the decrease in chargeable / dischargeable capacity from the measurement time point of the OCP characteristic to the first time point at the first time point. Calculated as relative displacement. In this case, not only the measurement by inserting the reference electrode into the lithium ion secondary battery, but also by disassembling the lithium ion secondary battery and taking out and measuring the positive electrode and the negative electrode, It becomes easy to obtain the initial negative electrode OCP characteristics and the relative positional deviation.

  Here, the initial positive electrode OCP characteristic and the initial negative electrode OCP characteristic acquired by the OCP characteristic acquisition unit 110 will be described.

  FIG. 6 is a diagram showing the initial positive electrode OCP characteristic and the initial negative electrode OCP characteristic acquired by the OCP characteristic acquisition unit 110 according to the embodiment of the present invention. That is, the figure is a graph showing the characteristics of the relationship between the amount of electricity supplied in the initial state of the secondary battery 200 and the open circuit potentials of the positive electrode and the negative electrode.

  As shown in the figure, P (q) indicates the initial positive electrode OCP characteristic that is the relationship between the energized electricity quantity q in the initial state of the secondary battery 200 and the positive open circuit potential, and the energized electricity quantity q is Charging progresses as the value increases, and the positive electrode potential generally changes in a noble direction. N (q) indicates an initial negative electrode OCP characteristic that is a relationship between an energization electricity amount q in the initial state of the secondary battery 200 and a negative electrode open circuit potential, and charging progresses as the energization electricity amount q increases. In general, however, the negative electrode potential changes in a base direction.

  Further, P (q) -N (q) (dotted line portion shown in the figure) obtained by subtracting the initial negative electrode OCP characteristic from the initial positive electrode OCP characteristic is an energization quantity q and an open circuit voltage in the initial state of the secondary battery 200. Shows the characteristics of the relationship. Further, Q1 in the figure indicates the chargeable / dischargeable capacity of the secondary battery 200 in the initial state.

  Returning to FIG. 5, next, the OCP characteristic acquisition unit 110 acquires the first positive electrode OCP characteristic and the first negative electrode OCP characteristic (S204).

  Here, in the method of obtaining and measuring the lithium ion secondary battery with the state at the first time point as the initial state as described above, since there is no relative positional shift at the first time point, the OCP characteristic acquisition unit 110 is The initial positive electrode OCP characteristic and the initial negative electrode OCP characteristic are acquired as a first positive electrode OCP characteristic and a first negative electrode OCP characteristic, respectively.

  In addition, when there is a relative position shift at the first time point, the OCP characteristic acquisition unit 110 sets the relative position at the first time point to the first electricity amount that is the energized electricity amount at the first time point of the secondary battery 200. By calculating, as the first positive electrode OCP characteristic, a characteristic indicating the relationship between the first electric quantity and the positive circuit open circuit potential obtained by substituting the value obtained by adding the deviation into the initial electric quantity of the initial positive electrode OCP characteristic. The positive OCP characteristic is acquired.

  That is, when the initial positive electrode OCP characteristic is P (q) and the relative positional deviation of the positive electrode at the first time point is Δq, the OCP characteristic acquisition unit 110 calculates the first positive electrode OCP characteristic as P (q + Δq).

  In addition, the OCP characteristic acquisition unit 110 has a characteristic indicating the relationship between the first electric quantity and the negative open circuit potential obtained by substituting the first electric quantity of the secondary battery 200 into the initial electric quantity of the initial negative electrode OCP characteristic. The first negative electrode OCP characteristic is obtained by calculating as the first negative electrode OCP characteristic.

  That is, the OCP characteristic acquisition unit 110 calculates the first negative electrode OCP characteristic as N (q).

  FIG. 7 is a diagram showing the first positive electrode OCP characteristic and the first negative electrode OCP characteristic acquired by the OCP characteristic acquisition unit 110 according to the embodiment of the present invention. That is, the figure is a graph showing the characteristics of the relationship between the amount of electricity supplied at the first time point of the secondary battery 200 and the open circuit potentials of the positive electrode and the negative electrode.

  As shown in the figure, P (q + Δq) indicates the first positive electrode OCP characteristic which is the relationship between the energization amount q and the positive electrode open circuit potential at the first time point of the secondary battery 200. N (q) represents a first negative electrode OCP characteristic that is a relationship between the amount of electricity q applied at the first time of the secondary battery 200 and the negative circuit open circuit potential.

  Further, P (q + Δq) −N (q) (dotted line portion shown in the figure) obtained by subtracting the first negative electrode OCP characteristic from the first positive electrode OCP characteristic is the amount of energized electricity q at the first time point of the secondary battery 200. The characteristic of the relationship with the open circuit voltage is shown.

  Moreover, Q3 of the figure has shown the chargeable / dischargeable capacity | capacitance in the 1st time of the secondary battery 200. That is, in the initial state, the Q1 portion has a chargeable / dischargeable capacity, but the use of the battery up to the first time point prevents the Q2 portion from being charged / discharged.

  Note that the graph of the first positive electrode OCP characteristic P (q + Δq) is shifted by Δq in the axial direction (the left-right direction shown in the figure) of the energized electricity q without changing the shape of the graph of the initial positive electrode OCP characteristic P (q). Shows a curved line.

  As described above, the process (S102 in FIG. 4) in which the OCP characteristic acquisition unit 110 acquires the first positive OCP characteristic and the first negative OCP characteristic ends.

  Next, the process in which the increase amount acquisition unit 120 acquires the impedance increase amount (S104 in FIG. 4) will be described in detail.

  FIG. 8 is a flowchart illustrating an example of a process in which the increase amount acquisition unit 120 according to the embodiment of the present invention acquires the impedance increase amount.

  As shown in the figure, first, the increase amount acquisition unit 120 acquires a first impedance that is an AC impedance at the first time point of the secondary battery 200 (S302). Specifically, the increase amount acquisition unit 120 acquires the first impedance of the secondary battery 200 written in the OCV characteristic estimation data 141 from the storage unit 140. That is, since the impedance measured by obtaining the lithium ion secondary battery with the state at the first time point as the initial state as described above is the first impedance, the increase amount acquisition unit 120 sets the impedance to the first impedance. Get as.

  When the first impedance is not written in the OCV characteristic estimation data 141, the increase amount acquisition unit 120 measures the first impedance of the secondary battery 200 at the first time point, and uses the measured first impedance. It may be written in the OCV characteristic estimation data 141. For example, the increase amount acquisition unit 120 measures the first impedance that is the AC impedance at the first time point by applying an AC voltage or an AC current having a predetermined frequency to the secondary battery 200 at the first time point. The predetermined frequency will be described later. Moreover, the process in which the increase amount acquisition part 120 measures a 1st impedance is not specifically limited, The increase amount acquisition part 120 may measure a 1st impedance by what kind of method.

  Next, the increase amount acquisition unit 120 measures a second impedance that is an AC impedance at the second time point of the secondary battery 200 (S306). In other words, the increase amount acquisition unit 120 measures the second impedance at the second time point after the predetermined period has elapsed after continuing to use the secondary battery 200 from the first time point.

  Specifically, the increase amount acquisition unit 120 applies the AC voltage or the AC current of a predetermined frequency to the secondary battery 200 at the second time point in the same manner as when measuring the first impedance at the second time point. Measure the second impedance, which is the AC impedance at. The process in which the increase amount acquisition unit 120 measures the second impedance is not particularly limited, and the increase amount acquisition unit 120 may measure the second impedance by any method.

  Then, the increase amount acquisition unit 120 calculates an impedance increase amount that is an increase amount of the AC impedance of the secondary battery 200 from the first time point to the second time point (S308). Specifically, the increase amount acquisition unit 120 calculates the amount of increase in impedance by subtracting the first impedance acquired from the measured second impedance.

  Then, the increase amount acquiring unit 120 stores the acquired impedance increase amount and the measured second impedance in the storage unit 140 (S310). Accordingly, the increase amount acquisition unit 120 updates the impedance increase amount stored in the storage unit 140 and updates the impedance by rewriting the impedance to the second impedance.

  As described above, the process in which the increase amount acquisition unit 120 acquires the impedance increase amount (S104 in FIG. 4) ends.

  Next, a process (S106 in FIG. 4) in which the estimation unit 130 estimates the OCV characteristic at the second time point will be described in detail.

  FIG. 9 is a flowchart illustrating an example of processing for estimating the OCV characteristic at the second time point by the estimation unit 130 according to the embodiment of the present invention.

  As shown in the figure, first, the estimation unit 130 acquires a relational expression between the amount of increase in impedance and the second positive electrode OCP characteristic (S401).

  Here, a relational expression between the amount of increase in impedance and the second positive electrode OCP characteristic used when the estimation unit 130 estimates the OCV characteristic will be described in detail below.

  First, the mechanism in which the secondary battery 200 is charged and discharged and deteriorates will be described.

  FIG. 10 is a diagram illustrating a mechanism in which the secondary battery 200 performs charging / discharging.

  As shown to (a) of the figure, the secondary battery 200 is equipped with the positive electrode p, the negative electrode n, and the separator between the positive electrode p and the negative electrode n. Here, the case where the secondary battery 200 is a lithium ion secondary battery will be described. That is, for example, the positive electrode p is a lithium transition metal oxide such as lithium cobalt oxide, and the negative electrode n is a carbon material. The positive electrode p contains a large amount of lithium ions x.

  And when the secondary battery 200 is charged, it changes from the state shown to (a) of the figure to the state shown to (b) of the figure. That is, the lithium ion x moves from the positive electrode p to the negative electrode n. By the movement of the lithium ions x, the amount of electricity for the moved capacity can be charged.

  Similarly, when the secondary battery 200 is discharged, a transition is made from the state shown in FIG. 5B to the state shown in FIG. That is, the lithium ion x moves from the negative electrode n to the positive electrode p. Due to the movement of the lithium ions x, it is possible to discharge an amount of electricity corresponding to the moved capacity.

  As described above, the lithium ion x reciprocates between the positive electrode p and the negative electrode n, whereby the secondary battery 200 can be charged and discharged. And when this charging / discharging is continued and repeated, secondary battery 200 deteriorates by side reactions other than charging / discharging reaction, and the reversible capacity which is the capacity | capacitance which can be charged / discharged of secondary battery 200 decreases.

  FIG. 11 is a diagram illustrating a mechanism in which the secondary battery 200 deteriorates.

  Specifically, (a) of the figure shows a state of lithium ions x in an initial state before the secondary battery 200 repeats charging and discharging, and (b) of the figure shows a secondary battery. It is a figure which shows the state of the lithium ion x when 200 repeats charging / discharging and deteriorates.

  That is, when the charge and discharge described with reference to FIG. 10 are repeated from the initial state shown in FIG. 10A, a lithium-containing coating X is formed on the negative electrode n as shown in FIG. ,grow up. Specifically, the lithium ion x contained in the positive electrode p is accumulated and grown on the negative electrode n by reciprocating between the positive electrode p and the negative electrode n, whereby the lithium-containing coating X is generated.

  Here, both the amount of decrease in the reversible capacity of the secondary battery 200 due to the generation of the lithium-containing coating X and the amount of increase in the internal resistance of the secondary battery 200 are both in the route of the charge / discharge period of the secondary battery 200. The so-called “root rule” is established.

  Since the growth rate of the lithium-containing coating X is proportional to the root of the charge / discharge period, the amount of increase in the thickness l of the lithium-containing coating X shown in FIG. Proportional to period root. For these reasons, the increase amount of the thickness l is proportional to the decrease amount of the reversible capacity of the secondary battery 200 and the increase amount of the internal resistance of the secondary battery 200.

  That is, when the thickness l increases and the number of lithium ions x that can reciprocate between the positive electrode p and the negative electrode n decreases, the reversible capacity of the secondary battery 200 decreases. Further, as the thickness l increases, the internal resistance of the secondary battery 200 increases.

  From the above, the reversible capacity Q of the secondary battery 200 due to the generation of the lithium-containing coating X is expressed by the following formula 1 using the thickness l of the lithium-containing coating X. In the following formula 1, M represents the lithium density in the lithium-containing coating X, and S represents a break when the lithium-containing coating X is cut along the YY line shown in FIG. The area is shown.

      Q = M × l × S (Formula 1)

Here, the internal resistance of the battery is composed of a plurality of types of resistances such as an electrolyte resistance, a charge transfer resistance, and a diffusion resistance in addition to the resistance corresponding to the lithium-containing coating X. The resistance component can change. By selecting a predetermined frequency other than the resistance corresponding to the lithium-containing coating X, when it is possible to eliminate the influence of the resistance component that changes the degree of deterioration of the battery, the internal resistance R _AC of the secondary battery 200 The negative electrode film resistance R _film indicating the resistance value of the lithium-containing film X and the other resistance R ₀ are represented by the following formula 2.

R _AC = R _film + R ₀ (Formula 2)

Here, R _AC is, for example, the AC impedance of the secondary battery 200 to be measured when applying a 1kHz AC voltage or current to the secondary battery 200. R ₀ is a constant.

Therefore, in order to measure the internal resistance R _AC in the above formula 2, it is necessary to select a predetermined frequency corresponding to the lithium-containing film X. For example, a frequency as low as 0.1 Hz is not preferable because it is strongly influenced by the diffusion resistance in the solid phase. Here, the predetermined frequency is preferably 10 Hz to 5 kHz, more preferably 500 Hz to 2 kHz, and more preferably 1 kHz. The predetermined frequency does not need to be measured while changing a specific frequency range, and can be a fixed value such as 1 kHz.

  By selecting a predetermined frequency in this way, the measured impedance can effectively exclude most of the charge transfer resistance component and diffusion resistance component that change depending on the degree of deterioration, and the lithium-containing Impedance composed of a component corresponding to the coating X and an electrolyte resistance component considered to hardly change can be measured. It should be noted that the above preferred frequency range is at room temperature.

Further, the negative electrode film resistance R _film is expressed by the following formula 3 using the resistivity ρ of the lithium-containing film X, the thickness l of the lithium-containing film X, and the cross-sectional area S of the lithium-containing film X.

R _film = ρ · l / S (Formula 3)

Then, a linear relational expression indicating the relationship between the _AC impedance _RAC and the reversible capacity Q of the secondary battery 200 as in the following Expression 4 is derived from the above Expressions 1 to 3. The following A and B are constants.

R _AC = A × Q + B (Formula 4)

  Further, the second positive electrode OCP characteristic is calculated as P (q + Δq + ΔQ) when the first positive electrode OCP characteristic is P (q + Δq) and the decrease capacity of the reversible capacity Q from the first time point to the second time point is ΔQ. .

For this reason, when the impedance increase amount, which is the increase amount of the _AC impedance RAC from the first time point to the second time point, is ΔR, the second positive electrode OCP characteristic P (q + Δq + ΔQ) is expressed by 5 is calculated.

      P (q + Δq + ΔQ) = P (q + Δq−ΔR / A) (Formula 5)

  As described above, the inventors of the present application derived the above formula 5 as a result of intensive studies.

Next, a method for calculating the constants A and B by an experiment is illustrated by an example. First, a plurality of 600 mAh-class lithium ion secondary batteries using a mixture of LiMn ₂ O ₄ and Li [Co _1/3 Ni _1/3 Mn _1/3 ] O ₂ for the positive electrode and graphite for the negative electrode are prepared. did. Then, using the lithium ion secondary battery, a float charge life test at 45 ° C. is performed, and a plurality of lithium ions are in various deterioration states and in a 100% charge state (a charge state equivalent to the float test). A secondary battery was prepared, and a value of 1 kHz AC impedance and a value of reversible capacity were measured.

  Then, the relationship between 1 kHz AC impedance and reversible capacity was examined. In addition, 1 kHz alternating current impedance is alternating current impedance when measuring with the alternating voltage or alternating current whose frequency is 1 kHz.

  FIG. 12 is a diagram showing the relationship between the AC impedance and the reversible capacity according to the embodiment of the present invention.

That is, the figure is a graph showing experimental results in the experiment described above. Specifically, the figure for the same kind of reversible capacity three different lithium ion secondary battery, perform the above experiments, the graph and the value of the measured 1kHz AC impedance R _AC value and the reversible capacity Q It is a thing.

The inventors have, from this graph, the 1kHz AC impedance R _AC and the reversible capacity Q, it was found that a proportional relationship shown in Equation 6 below. That is, the following Expression 6 indicates that the values of A and B in Expression 4 are A = −0.32 and B = 260.

R _AC = −0.32Q + 260 (Formula 6)

In addition, the inventors of the present application confirmed by experiments that the linear relational expression shown in the above equation 6 is substantially the same regardless of the test temperature in the normal temperature range (−20 ° C. to 60 ° C.). Therefore, the 1kHz AC impedance R _AC and the reversible capacity Q, regardless of the test temperature, the relationship of Equation 5 above is satisfied.

  For this reason, the second positive electrode OCP characteristic P (q + Δq + ΔQ) expressed by Equation 5 above is calculated as Equation 7 below.

      Second positive electrode OCP characteristic = P (q + Δq + ΔR / 0.32) (Formula 7)

Thus, using Equation 7 above, it is possible to calculate the second positive electrode OCP characteristics from 1kHz AC impedance R _AC impedance increment [Delta] R, it is not necessary to calculate the reduction capacity ΔQ reversible capacity Q. In addition, since the second positive electrode OCP characteristic can be calculated by measuring an AC impedance of 1 kHz, complicated measurement such as impedance measurement in a wide frequency region is unnecessary.

  The relational expression shown in Equation 7 above is a mathematical formula that can be applied to a lithium ion secondary battery with an experimental design. However, a lithium ion secondary battery with a different design or other types of lithium ions can be used. It is conceivable that this formula is different in the secondary battery. For this reason, it is applicable to various types of lithium ion secondary batteries by conducting the experiment for each type of lithium ion secondary battery and determining a mathematical expression corresponding to the above formula 7.

  From the above, the estimation unit 130 obtains Expression 7, which is a relational expression between the amount of increase in impedance and the second positive electrode OCP characteristic when the first positive electrode OCP characteristic is P (q + Δq).

  Here, the relational expression shown in Expression 7 above is predetermined by the user and stored in the storage unit 140. Note that the relational expression may not be stored in the storage unit 140, and the estimation unit 130 may be configured to perform the calculation of Expression 7 using a circuit configuration or a program.

  Returning to FIG. 9, the estimation unit 130 calculates the second positive electrode OCP characteristic (S402). That is, as shown in the above equation 7, the estimation unit 130 sets a predetermined constant (1 in equation 7) to the second electricity amount q that is the energized electricity amount at the second time point of the secondary battery 200 and the impedance increase amount ΔR. The characteristic indicating the relationship between the second electric quantity and the positive open circuit potential obtained by substituting the value obtained by multiplying the value multiplied by /0.32) for the first electric quantity q of the first positive electrode OCP characteristic is the first characteristic. Calculated as the two-positive electrode OCP characteristic.

  Specifically, when the first positive electrode OCP characteristic is P (q + Δq), the estimation unit 130 calculates the second positive electrode OCP characteristic as P (q + Δq−ΔR / A) = P (q + Δq + ΔR / 0.32). To do.

  Further, the estimating unit 130 calculates the second negative electrode OCP characteristic (S404). Specifically, the estimation unit 130 obtains the relationship between the second electric quantity and the negative open circuit potential obtained by substituting the second electric quantity of the secondary battery 200 into the first electric quantity of the first negative electrode OCP characteristic. The characteristic shown is calculated as the second negative electrode OCP characteristic.

  That is, when the first negative electrode OCP characteristic is N (q), the estimation unit 130 calculates the second negative electrode OCP characteristic as N (q).

  Then, the estimation unit 130 calculates the OCV characteristic at the second time point (S406). Specifically, the estimation unit 130 subtracts the negative open circuit potential for the second electric quantity in the calculated second negative OCP characteristic from the positive open circuit potential for the second electric quantity in the calculated second positive OCP characteristic. The characteristic indicating the relationship between the obtained second electric quantity and the open circuit voltage is calculated as the OCV characteristic at the second time point.

  That is, when the second positive electrode OCP characteristic is P (q + Δq + ΔR / 0.32) and the second negative electrode OCP characteristic is N (q), the estimation unit 130 sets the OCV characteristic at the second time point to P (q + Δq + ΔR / 0.32) -N (q). For this reason, the OCV characteristic at the second time point can be calculated by calculating the second positive electrode OCP characteristic without calculating the decrease capacity ΔQ.

  Here, since ΔR / 0.32 = −ΔR / A = ΔQ, for convenience of explanation, the OCV characteristic at the second time point estimated by the estimation unit 130 using ΔQ will be described below.

  FIG. 13 is a diagram illustrating OCV characteristics at the second time point estimated by the estimation unit 130 according to the embodiment of the present invention. That is, this figure is a graph showing the characteristics of the relationship between the amount of energized electricity at the second time point of the secondary battery 200 and the open circuit potentials of the positive electrode and the negative electrode and the open circuit voltage.

  As shown in the figure, P (q + Δq + ΔQ) represents the second positive electrode OCP characteristic that is the relationship between the amount of electricity q applied at the second time point of the secondary battery 200 and the positive electrode open circuit potential. N (q) indicates the second negative electrode OCP characteristic that is the relationship between the amount of electricity q applied at the second time point of the secondary battery 200 and the negative open circuit potential.

  Further, P (q + Δq + ΔQ) −N (q) (dotted line portion shown in the figure) obtained by subtracting the second negative electrode OCP characteristic from the second positive electrode OCP characteristic is the amount of energized electricity q at the second time point of the secondary battery 200. The characteristic of the relationship with the open circuit voltage is shown.

  Moreover, Q5 of the figure has shown the capacity | capacitance which can be charged / discharged in the 2nd time of the secondary battery 200. FIG. In other words, the Q3 portion has a chargeable / dischargeable capacity at the first time point, but the use of the battery from the first time point to the second time point makes it impossible to charge / discharge the ΔQ portion.

  The graph of the second positive electrode OCP characteristic P (q + Δq + ΔQ) does not change the shape of the graph of the first positive electrode OCP characteristic P (q + Δq). A deviated curve is shown. That is, the graph of the second positive electrode OCP characteristic P (q + Δq + ΔQ) does not change the shape of the graph of the initial positive electrode OCP characteristic P (q), and shifts by Δq + ΔQ in the axial direction (the left-right direction shown in the figure) of the energized electricity q. Shows a curved line.

  The graph of the second negative electrode OCP characteristic N (q) shows the same curve as the graph of the first negative electrode OCP characteristic N (q).

  That is, even if the secondary battery 200 is repeatedly charged and discharged, the single electrode is hardly deteriorated with respect to the positive electrode and the negative electrode. On the other hand, by repeatedly charging and discharging the secondary battery 200, the internal resistance of the secondary battery 200 is apparently increased. However, this apparent increase in internal resistance is due to the consumption of some of the dopant lithium ions due to the reaction of the lithium-containing film growing on the negative electrode, which results in a capacitive balance shift between the positive and negative electrodes. The present inventors have found that this is only the case. For this reason, the OCV characteristic of the secondary battery 200 changes as the charge / discharge profiles of the positive electrode and the negative electrode shift. Considering this, the OCV characteristic of the secondary battery 200 can be estimated from the battery state diagram at a certain point in time and the battery capacity decreased thereafter.

  As described above, the process of estimating the OCV characteristic at the second time by the estimation unit 130 (S106 in FIG. 4) ends.

  Next, a change in the OCV characteristic due to the use of the secondary battery 200 estimated by the OCV characteristic estimation apparatus 100 will be described.

  FIG. 14 is a diagram showing a change in the OCV characteristic estimated by the OCV characteristic estimation apparatus 100 according to the embodiment of the present invention. In the figure, the OCV characteristic graphs shown in FIGS. 6, 7 and 13 are enlarged.

  F0 (q) in the figure indicates the OCV characteristic in the initial state, F1 (q) indicates the OCV characteristic at the first time point, and F2 (q) indicates that the OCV characteristic estimating apparatus 100 The OCV characteristic at the estimated second time point is shown.

  In other words, as shown in the figure, when the secondary battery 200 is used and charging and discharging are repeated, in many cases, the position and shape of the OCV curve indicating the relationship between the energized electricity amount and the open circuit voltage change.

  The inventors of the present application purchased a commercially available lithium ion secondary battery and conducted a life cycle test of 2000 cycles at 45 ° C. As a result, 64 mohm was obtained as the value of the impedance increase amount ΔR. For this reason, the inventors of the present application calculated the OCV characteristic F2 (q) at the second time point with ΔR = 64 in F2 (q) = P (q + Δq + ΔR / 0.32) −N (q). As a result, the OCV measured value of the actual lithium ion secondary battery was in good agreement.

  As described above, according to the OCV characteristic estimation device 100 according to the embodiment of the present invention, using the acquired first positive electrode OCP characteristic, first negative electrode OCP characteristic, and impedance increase amount, the OCV at the second time point is obtained. Estimate the characteristics. That is, the OCV characteristic at the first time point can be grasped from the first positive electrode OCP characteristic and the first negative electrode OCP characteristic, but by using the OCV characteristic and the impedance increase amount at the first time point, The OCV characteristic at the second time point after the elapse of a predetermined period from the time point can be estimated. For this reason, since the OCV characteristic according to the elapsed period can be estimated even if the period elapses, the OCV characteristic of the secondary battery 200 can be accurately estimated in the long term.

  Further, the second positive electrode OCP characteristic is calculated from the first positive electrode OCP characteristic and the amount of increase in impedance, the second negative electrode OCP characteristic is calculated from the first negative electrode OCP characteristic, and the calculated second positive electrode OCP characteristic and second negative electrode OCP characteristic are calculated. From the above, the OCV characteristic at the second time point is estimated. Here, as a result of diligent research and experiments, the inventors of the present application have moved the amount of energized electricity in the first positive electrode OCP characteristic by a value obtained by multiplying the amount of increase in impedance by a predetermined constant. It was found that the characteristics coincided with the accuracy. That is, the second positive electrode OCP characteristic can be calculated accurately and easily from the first positive electrode OCP characteristic and the amount of increase in impedance. For this reason, since the OCV characteristic at the second time point with high accuracy can be easily estimated, the OCV characteristic of the secondary battery 200 can be easily estimated with high accuracy in the long term.

  Further, the first positive electrode OCP characteristic is obtained by calculating the first positive electrode OCP characteristic from the initial positive electrode OCP characteristic and the relative positional deviation of the positive electrode. For example, the first positive electrode OCP characteristic can be easily calculated by disassembling the secondary battery 200 at the first time point and measuring the relative positional deviation of the positive electrode. Thereby, the first positive electrode OCP characteristic can be easily acquired, and the OCV characteristic of the secondary battery 200 can be easily estimated with high accuracy in the long term.

  Moreover, it acquires by measuring a 1st impedance, etc., and by measuring a 2nd impedance, it calculates and acquires an impedance increase amount from the said 1st impedance and a 2nd impedance. Thereby, since the amount of increase in impedance can be easily obtained, the OCV characteristic of the secondary battery 200 can be easily estimated with high accuracy in the long term.

  The power storage system 10 and the OCV characteristic estimation device 100 according to the embodiment of the present invention have been described above, but the present invention is not limited to this embodiment.

  That is, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  For example, in the above embodiment, the OCP characteristic acquisition unit 110 calculates the first positive electrode OCP characteristic and the first negative electrode OCP characteristic from the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the relative positional deviation of the positive electrode at the first time point. Thus, the estimation unit 130 estimates the OCV characteristic at the second time point from the first positive electrode OCP characteristic and the first negative electrode OCP characteristic. However, the OCP characteristic acquisition unit 110 does not use the initial positive electrode OCP characteristic, the initial negative electrode OCP characteristic, and the relative positional deviation of the positive electrode at the first time point, and the first positive electrode OCP characteristic and the first negative electrode OCP characteristic can be input by a user or the like. May be obtained. That is, if the OCP characteristic acquisition unit 110 acquires the positive and negative OCP characteristics at a certain point, and the increase amount acquisition unit 120 can acquire the impedance increase amount from the time point until a predetermined period has elapsed, The estimation unit 130 can estimate the OCV characteristic when the predetermined period has elapsed.

  In addition, the present invention can be realized not only as the power storage system 10 or the OCV characteristic estimation apparatus 100 but also as an OCV characteristic estimation method using a characteristic processing unit included in the OCV characteristic estimation apparatus 100 as a step. Can be realized.

  Each processing unit included in the OCV characteristic estimation apparatus 100 according to the present invention may be realized as an LSI (Large Scale Integration) that is an integrated circuit. That is, as shown in FIG. 15, the present invention can be realized as an integrated circuit 150 including an OCP characteristic acquisition unit 110, an increase amount acquisition unit 120, and an estimation unit 130. FIG. 15 is a block diagram showing a configuration for realizing OCV characteristic estimation apparatus 100 according to the embodiment of the present invention with an integrated circuit.

  Each processing unit included in the integrated circuit 150 may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

  The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. There is a possibility of adaptation of biotechnology.

  The present invention can also be realized as a program that causes a computer to execute characteristic processing included in the OCV characteristic estimation method. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet.

  The present invention can be applied to an OCV characteristic estimation device for a nonaqueous electrolyte secondary battery that can accurately estimate the OCV characteristics of a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery over a long period of time.

DESCRIPTION OF SYMBOLS 10 Power storage system 100 OCV characteristic estimation apparatus 110 OCP characteristic acquisition part 120 Increase amount acquisition part 130 Estimation part 140 Storage part 141 OCV characteristic estimation data 150 Integrated circuit 200 Secondary battery 300 Storage case

Claims (6)

An OCV characteristic estimation method in which a computer estimates an OCV characteristic indicating a relationship between an energized electricity amount of an non-aqueous electrolyte secondary battery and an open circuit voltage,
A first positive electrode OCP characteristic indicating a relationship between a first electric quantity, which is an energized electric quantity at a predetermined first time point of the nonaqueous electrolyte secondary battery, and a positive electrode open circuit potential; and the non-aqueous electrolyte secondary battery An OCP characteristic acquisition step of acquiring a first negative electrode OCP characteristic indicating a relationship between the first electric quantity and the negative electrode open circuit potential;
An increase amount acquisition step of acquiring an impedance increase amount that is an increase amount of AC impedance at a predetermined frequency in the nonaqueous electrolyte secondary battery from the first time point to a predetermined second time point by impedance measurement ;
Estimating the OCV characteristic at the second time point of the non-aqueous electrolyte secondary battery using the acquired first positive electrode OCP characteristic, first negative electrode OCP characteristic, and impedance increase amount. OCV characteristic estimation method. The non-aqueous electrolyte secondary battery is a lithium ion secondary battery in which a positive electrode is made of a lithium transition metal oxide and a negative electrode is made of a carbon material,
In the estimation step,
The value of the first positive electrode OCP characteristic is a value obtained by adding a second electric quantity that is the energized electric quantity at the second time point of the nonaqueous electrolyte secondary battery and a value obtained by multiplying the impedance increase amount by a predetermined constant. A characteristic indicating the relationship between the second electric quantity and the positive open circuit potential obtained by substituting for the first electric quantity is calculated as a second positive OCP characteristic,
A characteristic showing a relationship between the second electric quantity and the negative open circuit potential obtained by substituting the second electric quantity of the non-aqueous electrolyte secondary battery into the first electric quantity of the first negative electrode OCP characteristic. Calculated as the second negative electrode OCP characteristic,
The second electric quantity obtained by subtracting the negative open circuit potential with respect to the second electric quantity in the second negative electrode OCP characteristic from the positive open circuit potential with respect to the second electric quantity in the calculated second positive electrode OCP characteristic; The OCV characteristic estimation method according to claim 1, wherein a characteristic indicating a relationship with an open circuit voltage is estimated as an OCV characteristic at the second time point. In the increase amount acquisition step,
In the first time point, by applying an AC voltage or an AC current of the predetermined frequency to the non-aqueous electrolyte secondary battery, a first impedance that is an AC impedance at the first time point is measured,
In the second time point, by applying an alternating voltage or alternating current of the predetermined frequency to the nonaqueous electrolyte secondary battery, a second impedance that is an AC impedance at the second time point is measured,
The OCV characteristic estimation method according to claim 1, wherein the amount of increase in impedance is acquired by subtracting the first impedance from the second impedance. An OCV characteristic estimation device for estimating an OCV characteristic indicating a relationship between an energization amount of electricity and an open circuit voltage of a nonaqueous electrolyte secondary battery,
A first positive electrode OCP characteristic indicating a relationship between a first electric quantity, which is an energized electric quantity at a predetermined first time point of the nonaqueous electrolyte secondary battery, and a positive electrode open circuit potential; and the non-aqueous electrolyte secondary battery An OCP characteristic acquisition unit for acquiring a first negative electrode OCP characteristic indicating a relationship between the first electric quantity and the negative electrode open circuit potential;
The impedance increase is an increase of the AC impedance at a predetermined frequency in the non-aqueous electrolyte secondary battery from the first time point to a predetermined second time point, the increase amount acquisition unit that acquires the impedance measurement,
An estimation unit that estimates the OCV characteristic of the nonaqueous electrolyte secondary battery at the second time point using the acquired first positive electrode OCP characteristic, the first negative electrode OCP characteristic, and the impedance increase amount. OCV characteristic estimation device. A non-aqueous electrolyte secondary battery;
A power storage system comprising: the OCV characteristic estimation device according to claim 4 that estimates an OCV characteristic indicating a relationship between an energized electricity amount of the nonaqueous electrolyte secondary battery and an open circuit voltage. An integrated circuit for estimating an OCV characteristic indicating a relationship between an energization amount of electricity and an open circuit voltage of a nonaqueous electrolyte secondary battery,
A first positive electrode OCP characteristic indicating a relationship between a first electric quantity, which is an energized electric quantity at a predetermined first time point of the nonaqueous electrolyte secondary battery, and a positive electrode open circuit potential; and the non-aqueous electrolyte secondary battery An OCP characteristic acquisition unit for acquiring a first negative electrode OCP characteristic indicating a relationship between the first electric quantity and the negative electrode open circuit potential;
The impedance increase is an increase of the AC impedance at a predetermined frequency in the non-aqueous electrolyte secondary battery from the first time point to a predetermined second time point, the increase amount acquisition unit that acquires the impedance measurement,
An estimation unit that estimates the OCV characteristic of the nonaqueous electrolyte secondary battery at the second time point using the acquired first positive electrode OCP characteristic, the first negative electrode OCP characteristic, and the impedance increase amount. Integrated circuit.

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