JP5673083B2 - 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 Using a decrease capacity acquisition step of acquiring a decrease capacity that is a decrease in chargeable / dischargeable capacity of the electrolyte secondary battery, and using the acquired first positive electrode OCP characteristic, first negative electrode OCP characteristic, and the decrease capacity The non-aqueous electrolyte secondary battery And a estimation step of estimating the OCV characteristics at the second time point.

  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 reduced capacity. 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 the first time point can be obtained by using the OCV characteristic and the reduced capacity at the first time point. From this, it is possible to estimate the OCV characteristic at the second time point after a predetermined period has elapsed. 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 value obtained by adding the reduced capacity to a second electric quantity that is an energized electric quantity at the second time point of the non-aqueous electrolyte secondary battery is the first positive electrode OCP characteristic. A characteristic indicating the relationship between the second electric quantity and the positive open circuit potential obtained by substituting the first electric quantity is calculated as a second positive OCP characteristic, and the second electric quantity of the non-aqueous electrolyte secondary battery is calculated. Calculated as the second negative electrode OCP characteristic, the characteristic indicating the relationship between the second electric quantity and the negative open circuit potential obtained by substituting the first negative electrode OCP characteristic into the first electric quantity. The second electric quantity and the open circuit voltage 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 double positive OCP characteristic, Show the relationship Sexual estimates that 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 reduced capacity, 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 negative electrode are calculated. The OCV characteristic at the second time point is estimated from the OCP characteristic. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the second positive electrode OCP characteristic coincides with the characteristic in which the amount of energized electricity in the first positive electrode OCP characteristic is shifted by the reduced capacity with high accuracy. . That is, the second positive electrode OCP characteristic can be calculated accurately and easily from the first positive electrode OCP characteristic and the reduced capacity. 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 reduced capacity acquisition step, a first reversible capacity that is a chargeable / dischargeable capacity at the first time point of the nonaqueous electrolyte secondary battery is measured, and the nonaqueous electrolyte secondary battery is The second reversible capacity, which is a chargeable / dischargeable capacity at the second time point, is measured, and the reduced capacity calculated by subtracting the second reversible capacity from the first reversible capacity is obtained.

  According to this, the first reversible capacity and the second reversible capacity are measured, and the reduced capacity is calculated and acquired from the first reversible capacity and the second reversible capacity. Thereby, since a reduced capacity can be easily acquired, the OCV characteristic of a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery can be easily estimated with high accuracy over a long period of time.

  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 reduction capacity acquisition part which concerns on embodiment of this invention acquires reduction capacity. 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 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, a reduced capacity 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.

  Then, the OCP characteristic acquisition unit 110 uses a value obtained by adding the relative displacement of the positive electrode at the first time point (a decrease amount of chargeable / dischargeable capacity) to the first electric quantity of the secondary battery 200. The first positive OCP characteristic is obtained by calculating the characteristic indicating the relationship between the first electric quantity and the positive open circuit potential obtained by substituting for the electric quantity as the first positive OCP characteristic.

  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 reduced capacity acquisition unit 120 acquires a reduced capacity that is a reduction amount of the chargeable / dischargeable capacity of the secondary battery 200 from the first time point to a predetermined second time point.

  Specifically, the reduced capacity acquisition unit 120 first acquires a first reversible capacity that is a chargeable / dischargeable capacity at the first time point of the secondary battery 200 stored in the storage unit 140 by measurement or the like. To do. Further, the reduced capacity acquisition unit 120 measures the second reversible capacity, which is a chargeable / dischargeable capacity at the second time point of the secondary battery 200, and is calculated by subtracting the second reversible capacity from the first reversible capacity. Get reduced capacity.

  And the reduction | decrease capacity acquisition part 120 is memorize | stored in the memory | storage part 140 by making the memory | storage part 140 memorize | store the acquired reduction | decrease capacity | capacitance as a relative position shift | offset | difference of the electricity supply amount in the OCP characteristic of a positive electrode in a 2nd time point. The relative positional deviation of the energized electricity amount in the OCP characteristic is updated. Further, the reduced capacity acquisition unit 120 stores the measured second reversible capacity in the storage unit 140 and updates the first reversible capacity to the second reversible capacity.

  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 reduced capacity acquired by the reduced capacity acquisition unit 120 at the second time point of the secondary battery 200. The OCV characteristic of is estimated.

  Specifically, the estimation unit 130 substitutes a value obtained by adding the reduced capacity to the second electric quantity that is the energized electric quantity at the second time point of the secondary battery 200 into the first electric quantity of the first positive electrode OCP characteristic. The characteristic indicating the relationship between the second electric quantity and the positive open circuit potential obtained in this way is calculated as the second positive electrode 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.

  In this way, the reduced capacity acquisition unit 120 measures the reversible capacity as in the third time point and the fourth time point, and acquires the reduced capacity, thereby energizing electricity in the OCP characteristic stored in the storage unit 140. The relative displacement of the quantity and the reversible capacity are repeatedly updated. 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 relative displacement of the energized electricity amount in the OCP characteristic 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 an initial positive electrode OCP characteristic, an initial negative electrode OCP characteristic, a relative positional shift, and a reversible capacity. 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”, “relative position shift”, and “reversible capacity”.

  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 the “relative position deviation”, Δq, which is a value indicating a relative deviation amount (decreasing capacity) of the energized electricity amount in the OCP characteristic of the positive electrode, is stored. Further, the “reversible capacity” stores a reversible capacity Q that is a chargeable / dischargeable capacity 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 reversible capacity 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 reduced capacity acquisition unit 120 updates the relative position shift and the reversible capacity of the OCV characteristic estimation data 141 by storing the measured reversible capacity and the acquired reduced capacity 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.

  Then, the reduced capacity acquisition unit 120 acquires the reduced capacity (S104).

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

  The detailed description of the process in which the reduced capacity acquisition unit 120 acquires the reduced capacity 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 determines the second positive OCP characteristic and the first negative electrode OCP characteristic acquired by the OCP characteristic acquisition unit 110 and the first negative electrode OCP characteristic and the decreased capacity acquired by the reduced capacity acquisition unit 120. The two negative electrode OCP characteristics are calculated, and the OCV characteristics at the second time point are 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 reduced capacity acquisition unit 120 repeatedly measures the reversible capacity and acquires the reduced capacity, so that the relative positional deviation of the energized electricity amount in the OCP characteristic stored in the storage unit 140 and the reversible capacity are obtained. 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 relative displacement of the energized electricity amount in the OCP characteristic 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 and negative OCP characteristics and the reversible capacity in the initial state are measured in advance and stored in the storage unit 140 in advance. It can also be built into the program. 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 reversible capacity 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 reversible capacity in the initial state are acquired 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 positional deviation at the first time point is not zero, the OCP characteristic acquisition unit 110 determines the amount of decrease in the reversible capacity from the measurement time point of the OCP characteristic to the first time point as the relative positional deviation at the first time point. Calculate as 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, the OCP characteristic acquisition unit 110 acquires the first positive OCP characteristic and the first negative 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 (S104 in FIG. 4) in which the reduced capacity acquisition unit 120 acquires the reduced capacity will be described in detail.

  FIG. 8 is a flowchart showing an example of processing in which the reduced capacity acquisition unit 120 according to the embodiment of the present invention acquires the reduced capacity.

  As shown in the figure, first, the reduced capacity acquisition unit 120 acquires a first reversible capacity, which is a chargeable / dischargeable capacity at the first time point of the secondary battery 200 (S302). Specifically, the reduced capacity acquisition unit 120 acquires the first reversible capacity of the secondary battery 200 written in the OCV characteristic estimation data 141 from the storage unit 140. That is, as described above, the reversible capacity measured by obtaining the lithium ion secondary battery with the state at the first time point as the initial state is the first reversible capacity. Obtained as the first reversible capacity. Specifically, the reduced capacity acquisition unit 120 acquires the capacity of Q3 shown in FIG.

  When the first reversible capacity is not written in the OCV characteristic estimation data 141, the reduced capacity acquisition unit 120 measures the first reversible capacity of the secondary battery 200 at the first time point and measures the first reversible capacity. The reversible capacity may be written in the OCV characteristic estimation data 141. For example, the reduced capacity acquisition unit 120 measures the first reversible capacity by discharging the lithium ion secondary battery that is the target of OCV characteristic estimation after full charge at the first time point. The process in which the reduced capacity acquisition unit 120 measures the first reversible capacity is not particularly limited, and the reduced capacity acquisition unit 120 may measure the first reversible capacity by any method.

  Next, the reduced capacity acquisition unit 120 measures a second reversible capacity, which is a chargeable / dischargeable capacity at the second time point of the secondary battery 200 (S306). That is, the reduced capacity acquisition unit 120 measures the second reversible capacity at the second time point after the predetermined period has elapsed by continuing to use the secondary battery 200 from the first time point. Note that the reduced capacity acquisition unit 120 measures the second reversible capacity by the same processing as that for measuring the first reversible capacity.

  Then, the reduced capacity acquisition unit 120 calculates a reduced capacity, which is a reduction amount of the chargeable / dischargeable capacity of the secondary battery 200 from the first time point to a predetermined second time point (S308). Specifically, the reduced capacity acquisition unit 120 calculates the reduced capacity by subtracting the second reversible capacity measured from the acquired first reversible capacity.

  Then, the reduced capacity acquisition unit 120 stores the acquired reduced capacity in the storage unit 140 as a relative positional shift of the energized electricity amount in the OCP characteristic of the positive electrode at the second time point, and stores the measured second reversible capacity in the storage unit. 140 (S310). Thereby, the reduced capacity acquisition unit 120 updates the relative position shift of the OCV characteristic estimation data 141 stored in the storage unit 140 and updates the reversible capacity by rewriting the reversible capacity to the second reversible capacity.

  As described above, the process in which the reduced capacity acquisition unit 120 acquires the reduced capacity (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 calculates the second positive electrode OCP characteristic (S402). Specifically, the estimation unit 130 substitutes a value obtained by adding the reduced capacity to the second electric quantity that is the energized electric quantity at the second time point of the secondary battery 200 into the first electric quantity of the first positive electrode OCP characteristic. The characteristic indicating the relationship between the second electric quantity and the positive open circuit potential obtained in this way is calculated as the second positive electrode OCP characteristic.

  That is, when the first positive electrode OCP characteristic is P (q + Δq) and the reduced capacity is Q4, the reduced capacity acquisition unit 120 calculates “Δq + Q4” as the relative displacement of the energized electricity amount in the OCP characteristic of the positive electrode at the second time point. Is stored in the OCV characteristic estimation data 141 of the storage unit 140. For this reason, the estimation unit 130 calculates the second positive electrode OCP characteristic as P (q + Δq + Q4).

  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 + Q4) 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 + Q4) −N (q). And calculate.

  FIG. 10 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, the figure is a graph showing the characteristics of the relationship between the amount of electricity supplied at the second time point of the secondary battery 200, the open circuit potential of the positive electrode and the negative electrode, and the open circuit voltage.

  As shown in the figure, P (q + Δq + Q4) represents the second positive electrode OCP characteristic which is the relationship between the energization amount q and the positive electrode open circuit potential at the second time point of the secondary battery 200. 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 + Q4) −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. That is, although the Q3 portion has a chargeable / dischargeable capacity at the first time point, the use of the battery from the first time point to the second time point indicates that the Q4 portion cannot be charged / discharged.

  Here, Q3 represents the first reversible capacity measured by the reduced capacity acquisition unit 120, Q5 represents the second reversible capacity measured by the reduced capacity acquisition unit 120, and Q4 represents the reduced capacity acquisition unit. 120 shows the reduced capacity acquired.

  Note that the graph of the second positive electrode OCP characteristic P (q + Δq + Q4) is Q4 in the axial direction (the left-right direction shown in the figure) of the energized electricity quantity q without changing 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 + Q4) does not change the shape of the graph of the initial positive electrode OCP characteristic P (q), and Δq + Q4 shifts 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. 11 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.

  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.

  In addition, as a result of purchasing a commercially available lithium ion secondary battery and conducting a life test of 2000 cycles at 45 ° C., the present inventors obtained 200 mAh as a reduced capacity. Therefore, the inventors of the present application calculated the OCV characteristic F2 (q) at the second time point with Q4 = 200 mAh in F2 (q) = P (q + Δq + Q4) −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 apparatus 100 according to the embodiment of the present invention, using the acquired first positive electrode OCP characteristic, first negative electrode OCP characteristic, and reduced capacity, the OCV characteristic at the second time point. Is estimated. 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 the first time point can be obtained by using the OCV characteristic and the reduced capacity at the first time point. From this, it is possible to estimate the OCV characteristic at the second time point after a predetermined period has elapsed. 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 reduced capacity, 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 OCP characteristic From the above, the OCV characteristic at the second time point is estimated. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the second positive electrode OCP characteristic coincides with the characteristic in which the amount of energized electricity in the first positive electrode OCP characteristic is shifted by the reduced capacity with high accuracy. . That is, the second positive electrode OCP characteristic can be calculated accurately and easily from the first positive electrode OCP characteristic and the reduced capacity. 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 reversible capacity | capacitance etc., and by measuring a 2nd reversible capacity | capacitance, a reduced capacity | capacitance is calculated and acquired from the said 1st reversible capacity | capacitance and a 2nd reversible capacity | capacitance. Thereby, since the reduced capacity 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 OCP characteristic and the negative OCP characteristic at a certain point, and the reduced capacity acquisition unit 120 can acquire the reduced capacity from that point to the time when a predetermined period has elapsed, it is estimated. The 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. 12, the present invention can be realized as an integrated circuit 150 including an OCP characteristic acquisition unit 110, a reduced capacity acquisition unit 120, and an estimation unit 130. FIG. 12 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 Decrease capacity 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;
A reduced capacity acquisition step of acquiring a reduced capacity , which is a reduced amount of chargeable / dischargeable capacity of the nonaqueous electrolyte secondary battery from the first time point to a predetermined second time point , by measuring the capacity ;
An estimation step for estimating an OCV characteristic at the second time point of the non-aqueous electrolyte secondary battery using the acquired first positive electrode OCP characteristic, the first negative electrode OCP characteristic, and the reduced capacity. 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 non-aqueous electrolyte secondary battery is obtained by substituting a value obtained by adding the reduced capacity to the second electric quantity that is the energized electric quantity at the second time point into the first electric quantity of the first positive electrode OCP characteristic. , Calculating the characteristic indicating the relationship between the second electric quantity and the positive open circuit potential as the 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 reduced capacity acquisition step, a first reversible capacity that is a chargeable / dischargeable capacity at the first time point of the non-aqueous electrolyte secondary battery is measured, and at the second time point of the non-aqueous electrolyte secondary battery. The OCV characteristic according to claim 1, wherein a second reversible capacity that is a chargeable / dischargeable capacity of the first reversible capacity is measured, and the reduced capacity calculated by subtracting the second reversible capacity from the first reversible capacity is acquired. Estimation method. 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;
A reduced capacity acquisition unit that acquires a reduced capacity , which is a reduced amount of chargeable / dischargeable capacity of the nonaqueous electrolyte secondary battery from the first time point to a predetermined second time point , by measuring the capacity ;
An OCV comprising: an estimation unit that estimates an 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 reduced capacity. 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;
A reduced capacity acquisition unit that acquires a reduced capacity , which is a reduced amount of chargeable / dischargeable capacity of the nonaqueous electrolyte secondary battery from the first time point to a predetermined second time point , by measuring the capacity ;
An integration unit that estimates an OCV characteristic at the second time point of the non-aqueous electrolyte secondary battery using the acquired first positive electrode OCP characteristic, the first negative electrode OCP characteristic, and the reduced capacity; circuit.

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