JP2018078023A - Controller of lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately control a lithium ion secondary battery in which a plurality of positive electrode active materials are included at predetermined rates.SOLUTION: In a controller of a lithium ion secondary battery herein proposed, a positive electrode of the lithium ion secondary battery targeted includes a plurality of positive electrode active materials at predetermined rates. The controller comprises: a storage unit C in which the relation between an SOC and a positive electrode potential in an initial state of the targeted lithium ion secondary battery is recorded for each positive electrode active material included in the positive electrode; and a calculating unit E in which a map showing a temperature-SOC-degradation degree relation has been previously prepared for each positive electrode active material included in the positive electrode. In the controller, a degradation degree is calculated for each positive electrode active material based on temperature and SOC records; and the degradation degrees calculated for the respective positive electrode active materials are each multiplied by the rate of the positive electrode active material. Then, the resultant products are added up, whereby a degradation degree K1 of the positive electrode is calculated.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a control device for a lithium ion secondary battery.

  In the present specification, the “lithium ion secondary battery” means a secondary battery that uses lithium ions as electrolyte ions, and is capable of being charged and discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes. Here, the “lithium ion secondary battery” as a control target of the control device may include an “assembled battery” in which a plurality of battery elements are connected. Further, the “lithium ion secondary battery” as the control target of the control device may include a secondary battery incorporated as a battery element of the “assembled battery”.

  As a method for controlling a lithium ion secondary battery, JP 2013-89424 A discloses a method for predicting battery deterioration. In the prediction method disclosed in the publication, a data table is prepared for predicting how much the battery deteriorates when staying at a certain temperature and SOC for a predetermined time. And actually, the deterioration degree of a battery is estimated based on the history about temperature and SOC.

JP2013-89424A

  Regarding a method for estimating the deterioration degree of a lithium ion secondary battery, the technique proposed in Japanese Patent Application Laid-Open No. 2013-89424 can temporarily estimate the deterioration degree of a lithium ion secondary battery. However, it is desirable that the difference between the deterioration level calculated as the estimated value and the actual deterioration level of the lithium ion secondary battery is small. It is also desirable to be able to accurately estimate the open circuit voltage that can change as the lithium ion secondary battery deteriorates. Here, we propose a new method that can accurately estimate the open circuit voltage and the degree of deterioration of a lithium ion secondary battery. Here, a case where a plurality of positive electrode active materials are included at a predetermined ratio will be particularly described.

The proposed control device for a lithium ion secondary battery includes a temperature sensor, an SOC detection unit, recording units A to D, and calculation units E to I.
Here, the temperature sensor is a sensor that detects the temperature of the target lithium ion secondary battery.
The SOC detection unit detects the SOC of the target lithium ion secondary battery.
The recording unit A records a temperature history based on the temperature detected by the temperature sensor.
The recording unit B records an SOC history based on the SOC detected by the SOC detection unit.
The recording unit C records the relationship between the SOC in the initial state of the target lithium ion secondary battery and the positive electrode potential.
The recording unit D records the relationship between the SOC and the negative electrode potential in the initial state of the target lithium ion secondary battery.
The calculation unit E calculates the deterioration degree K1 of the positive electrode of the target lithium ion secondary battery based on the temperature history and the SOC history.
The calculation unit F calculates the deterioration degree K2 of the negative electrode of the target lithium ion secondary battery based on the temperature history and the SOC history.
The calculation unit G calculates the lithium trap amount TLi of the target lithium ion secondary battery based on the temperature history and the SOC history.
The calculation unit H calculates the starting point SP of the positive electrode potential and the negative electrode potential of the target lithium ion secondary battery based on the temperature history and the SOC history.
The calculation unit I includes the relationship between the SOC recorded in the recording unit C and the positive electrode potential, the relationship between the SOC recorded in the recording unit D and the negative electrode potential, and the deterioration degree K1 of the positive electrode calculated by the calculation unit E. The target lithium ion secondary battery based on the deterioration degree K2 of the negative electrode calculated by the calculation unit F, the lithium trap amount TLi calculated by the calculation unit G, and the starting point SP calculated by the calculation unit H The open circuit voltage of is calculated.
Here, in the case where the positive electrode of the target lithium ion secondary battery includes a plurality of positive electrode active materials at a predetermined ratio, in the storage unit C, for each positive electrode active material included in the positive electrode, The relationship between the SOC in the initial state of the target lithium ion secondary battery and the positive electrode potential may be recorded.
In the calculation part E, it is good for the map which shows the relationship of temperature-SOC-degradation degree for every positive electrode active material contained in a positive electrode beforehand. Then, based on the temperature history and the SOC history, the deterioration degree is calculated for each positive electrode active material, and the deterioration degree calculated for each positive electrode active material is multiplied by the ratio of the positive electrode active material to be added. The degree K1 may be calculated.

  According to this control apparatus, the target is determined in consideration of the degree of deterioration K1 of the positive electrode, the degree of deterioration K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP (in other words, the starting point of the positive electrode and the negative electrode contracts respectively). The open circuit voltage after deterioration of the lithium ion secondary battery is calculated. For this reason, the open circuit voltage after deterioration can be accurately calculated. This control device can be embodied by a computer. For example, the processes of the SOC detection unit, the recording units A to D, and the calculation units E to I can be realized by a processor that moves according to a predetermined program. Moreover, the method of this control apparatus can be applied also to the method of estimating the deterioration degree of a lithium ion secondary battery.

FIG. 1 is a graph showing a typical example of the relationship between the charging current amount of the lithium ion secondary battery and the open circuit voltage (OCV). FIG. 2 is a graph showing a typical relationship between the positive electrode potential and the negative electrode potential with respect to the charging current amount of the lithium ion secondary battery in the initial state. FIG. 3 is a graph showing a typical relationship between the positive electrode potential and the negative electrode potential with respect to the charging current amount of the deteriorated lithium ion secondary battery. FIG. 4 is a block diagram schematically showing the control device 100. FIG. 5 is a diagram illustrating data tables M1A to M4A in a neglected state. FIG. 6 is a diagram illustrating data tables M1B to M4B in the energized state. FIG. 7 is a flowchart illustrating an example of a control flow of the control device 100. FIG. 8 is a diagram illustrating data tables M1A to M4A in a neglected state according to another embodiment. FIG. 9 is a diagram exemplifying data tables M1B to M4B of energized states in another form.

  Hereinafter, an embodiment of a control device for a lithium ion secondary battery proposed here will be described. The embodiments described herein are, of course, not intended to limit the present invention in particular.

<Deterioration of lithium ion secondary battery>
The deterioration of the lithium ion secondary battery in this specification means the capacity deterioration of the lithium ion secondary battery. The battery capacity of a lithium ion secondary battery tends to decrease from the initial state due to use. The degree of deterioration of the lithium ion secondary battery is expressed as a ratio of the current battery capacity to the battery capacity in the initial state. That is, the degree of deterioration of the lithium ion secondary battery is represented by the following formula (A), and is a ratio of the current battery capacity when the battery capacity in the initial state is 100, and may also be referred to as a capacity maintenance ratio. .

Degree of deterioration of lithium ion secondary battery = (current battery capacity) / (initial battery capacity) × 100 (%) (A)

  Regarding the lithium ion secondary battery, the “initial state” can be arbitrarily determined in a state after the lithium ion secondary battery is assembled. For example, a state in which a lithium ion secondary battery is assembled, a predetermined conditioning process has passed, and can be normally used as a lithium ion secondary battery may be referred to as an “initial state”. The initial state of the lithium ion secondary battery may be a state when the lithium ion secondary battery is shipped.

<Battery capacity of lithium ion secondary battery>
Regarding the battery capacity of the lithium ion secondary battery, here, an upper limit voltage and a lower limit voltage of the lithium ion secondary battery are set in advance based on the open circuit voltage. Then, the lithium ion secondary battery is charged to the upper limit voltage by CCCV charging, and then the lithium ion secondary battery is discharged to the lower limit voltage by CCCV discharge. At this time, for the lithium ion secondary battery in the initial state, the discharge capacity when discharged from the upper limit voltage to the lower limit voltage is defined as the battery capacity in the initial state of the lithium ion secondary battery.

  In this embodiment, the lower limit voltage of the lithium ion secondary battery is set to 3.0 V and the upper limit voltage is set to 4.1 V based on the open circuit voltage for the target lithium ion secondary battery. In this case, the state where the open circuit voltage is 3.0 V is SOC 0%, and the state where the open circuit voltage is 4.1 V is SOC 100% (fully charged state). The battery capacity corresponds to the discharge capacity when charging until the open circuit voltage reaches 4.1 V by CCCV charging and discharging until the open circuit voltage reaches 3.0 V by CCCV discharge. Here, “SOC” is an abbreviation for “State Of Charge” and indicates the state of charge of the battery. Here, “SOC” is determined by the charging rate with respect to the fully charged state. Hereinafter, the charging rate with respect to the fully charged state is referred to as “charging rate”.

<Deterioration tendency of lithium ion secondary batteries>
Below, the deterioration event of a lithium ion secondary battery is demonstrated based on the knowledge of this inventor.

  FIG. 1 is a graph showing a typical example of the relationship between the charging current amount of the lithium ion secondary battery and the open circuit voltage (OCV). FIG. 2 is a graph showing a typical relationship between the positive electrode potential and the negative electrode potential with respect to the charging current amount of the lithium ion secondary battery in the initial state. FIG. 3 is a graph showing a typical relationship between the positive electrode potential and the negative electrode potential with respect to the charging current amount of the deteriorated lithium ion secondary battery. In addition, FIG.1, FIG2 and FIG.3 shows a typical example typically, and does not show a exact measurement result.

  Here, the solid line S in FIG. 1 shows the relationship between the SOC and the open circuit voltage (OCV) in the initial state for the lithium ion secondary battery. A broken line S1 indicates a relationship between the deteriorated SOC and the open circuit voltage (OCV). The horizontal axis of FIG. 2 and FIG. 3 has shown the electric current amount of charge or discharge. A solid line P in FIG. 2 indicates the positive electrode potential with respect to the charging current amount in the initial state. A solid line Q indicates the negative electrode potential with respect to the charging current amount in the initial state. A solid line P1 in FIG. 3 indicates the positive electrode potential with respect to the charge current amount after deterioration. A solid line Q indicates the negative electrode potential with respect to the charge current amount after deterioration. In FIG. 1, the horizontal axis indicates the SOC of the lithium ion secondary battery, and the vertical axis indicates the open circuit voltage (OCV). Moreover, as shown by a broken line, the positive electrode and the negative electrode are deteriorated by use (the capacity of the single electrode is reduced), and as a result, the battery capacity of the lithium ion secondary battery is reduced.

  In this specification, the positive electrode potential in the initial state is appropriately referred to as “OCP +”. The negative electrode potential in the initial state is appropriately referred to as “OCP−”. The positive electrode potential and the negative electrode potential can be grasped by the potential difference from the reference electrode. For example, metallic lithium is used for the reference electrode. The relationship between the SOC and the positive electrode potential (OCP +) in the initial state is typically as shown by the solid line P in FIG. The solid line P is appropriately referred to as “SOC-OCP +”. The relationship between the SOC and the negative electrode potential (OCP−) is typically as shown by the solid line Q in FIG. The solid line Q is appropriately referred to as “SOC-OCP-”.

<Deterioration tendency of lithium ion secondary batteries>
Here, FIGS. 1, 2 and 3 show, for example, lithium transition metal composite oxide having a layer structure (for example, lithium nickel cobalt manganese composite oxide) as positive electrode active material particles, and graphite particles having a graphite structure. The tendency about the lithium ion secondary battery used as a negative electrode active material is shown.

  As shown by solid lines P and Q in FIG. 2, in the lithium ion secondary battery in the initial state, the positive electrode potential P gradually decreases with respect to the discharge current amount, and the negative electrode potential Q gradually increases. At the end of discharge, the positive electrode potential P rapidly decreases and the negative electrode potential Q also increases rapidly. Further, the positive electrode potential P gradually increases with respect to the charging current amount, and the negative electrode potential Q decreases stepwise.

  In FIG. 2, the difference {P (i) −Q (i)} between the positive electrode potential P (i) and the negative electrode potential Q (i) in the same state of charge (i) is the open circuit voltage S of the lithium ion secondary battery. It corresponds to (i). The positive electrode potential P and the negative electrode potential Q as shown in FIG. 2 can be obtained, for example, by a test for measuring the positive electrode potential and the negative electrode potential, respectively. Further, the positive electrode potential P and the negative electrode potential Q can be theoretically determined according to the specifications of the lithium ion secondary battery. For example, the positive electrode potential P can be theoretically obtained based on the amount of the positive electrode active material contained in the positive electrode and the material characteristics of the positive electrode active material. The negative electrode potential Q can be theoretically obtained based on the amount of the negative electrode active material contained in the negative electrode and the material characteristics of the negative electrode active material.

  Further, at the positive electrode, lithium ions are released from the start end Ps to the end end Pt where the charging current amount is low. The positive electrode initial capacity W + is determined according to the amount of lithium ions released from the starting end Ps to the terminal end Pt. In the negative electrode, lithium ions are absorbed from the start end Qs to the end end Qt. Then, the negative electrode initial capacity W− is determined according to the release amount of lithium ions absorbed from the start end Qs to the end end Qt.

  On the other hand, as shown in FIG. 3, in the deteriorated lithium ion secondary battery, the timing at which the positive electrode potential P1 decreases and the timing at which the negative electrode potential Q1 increases with respect to the discharge current amount are higher than those in the initial state. Tend to be faster. Further, the timing at which the positive electrode potential P1 rises with respect to the amount of charging current is earlier than the initial state, and the timing at which the negative electrode potential Q1 falls stepwise with respect to the amount of charging current is later than the initial state.

  In FIG. 3, a broken line Qt indicates a position corresponding to the end point of the negative potential Q in the initial state of FIG. A broken line Ps indicates a position corresponding to the starting end of the graph of the positive electrode potential P in the initial state of FIG. 2 with reference to the broken line Pt. A broken line Qs indicates a position corresponding to the starting end of the graph of the negative electrode potential Q in the initial state of FIG. 2 with reference to the broken line Pt. As shown in FIG. 3, the graph of the positive electrode potential P <b> 1 after deterioration is a graph contracted along the horizontal axis (charge current amount) more than the graph of the positive electrode potential P in the initial state. As a result, the deteriorated positive electrode capacity W1 + is smaller than the positive electrode initial capacity W + (see FIG. 2). Further, the graph of the negative electrode potential Q1 after deterioration is a graph that is contracted along the horizontal axis (charge current amount) more than the graph of the negative electrode potential Q in the initial state. As a result, the negative electrode capacity W1- after deterioration is smaller than the negative electrode initial capacity W- (see FIG. 2).

  About the tendency after said deterioration, in the positive electrode, it is thought that the cause is that the amount of positive electrode active material that can release or occlude lithium ions decreases. That is, as shown in FIG. 3, the amount of the positive electrode active material that can release or occlude lithium ions is reduced during charging or discharging within a predetermined open circuit voltage range of the lithium ion secondary battery. This phenomenon is referred to as “deterioration of the positive electrode”. Moreover, since the width | variety in which a positive electrode functions along the horizontal axis which shows charge current amount becomes short, it can also be called "positive electrode shrinkage".

  Further, in the negative electrode, it is considered that the cause is that the amount of the negative electrode active material that can release or occlude lithium ions decreases. That is, the amount of the negative electrode active material that can release or occlude lithium ions is reduced during charging or discharging within a predetermined open circuit voltage range for the lithium ion secondary battery. This phenomenon is called “deterioration of the negative electrode”. Moreover, since the width | variety in which a negative electrode functions is shortened along the horizontal axis which shows charge current amount, it can also be called "negative electrode shrinkage".

  In order to obtain the relationship between the positive electrode potential P1 after deterioration and the negative electrode potential Q1 after deterioration with higher accuracy, the inventor reduces how much the positive electrode potential P1 after deterioration and the negative electrode potential Q1 after deterioration shrink due to deterioration. I think it is necessary to know what point it is and what position it has shrunk from. Here, with respect to the graph of the positive electrode potential P and the negative electrode potential Q in the initial state, the starting point at which the graph of the deteriorated positive electrode potential P1 and negative electrode potential Q1 contracts is referred to as “starting point SP”. In the example illustrated here, the starting point SP is the same starting point SP for both the positive electrode and the negative electrode. However, the starting point SP may be different between the positive electrode and the negative electrode. When considering that the SP is different between the positive electrode and the negative electrode, when calculating the starting point SP, it is preferable to prepare different data tables for the positive electrode and the negative electrode and calculate different starting points SP.

  In a lithium ion secondary battery, lithium ions are released from the positive electrode during charging, the negative electrode absorbs lithium ions, and charges are stored in the negative electrode. At the time of discharging, lithium ions stored in the negative electrode are released, and the lithium ions return to the positive electrode. In such charging and discharging, lithium ions are taken into the film or partially deposited, so that lithium that contributes to the battery reaction decreases as the deterioration progresses. Here, the amount of decrease in lithium that contributes to the battery reaction is referred to as “lithium trap amount”.

  As shown in FIGS. 2 and 3, for example, a decrease in lithium contributing to the battery reaction causes a relative deviation between the positive electrode potential P1 and the negative electrode potential Q1 after deterioration. Further, the graphs of the positive electrode potential P1 and the negative electrode potential Q1 after deterioration are contracted with respect to the graphs of the positive electrode potential P and the negative electrode potential Q in the initial state, respectively. For this reason, for example, when the discharge side is observed, the timing at which the degraded positive electrode potential P1 drops and the timing at which the negative electrode potential Q1 rises deviate due to degradation.

  In the lithium ion secondary battery control method proposed here, the open circuit of the lithium ion secondary battery is based on the positive electrode deterioration degree K1, the negative electrode deterioration degree K2, the lithium trap amount TLi, and the starting point SP. The voltage and the degree of deterioration are estimated.

  The deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP are estimated based on the temperature environment and the SOC history for the target lithium ion secondary battery. According to the lithium ion secondary battery control method proposed here, the open circuit voltage and deterioration degree of the lithium ion secondary battery can be estimated more accurately, and the lithium ion secondary battery can be controlled more appropriately. Is possible.

  FIG. 4 is a block diagram schematically showing the control device 100. The control device 100 is a device that embodies the lithium ion secondary battery control method proposed here. The control device 100 includes an arithmetic device that performs an arithmetic operation according to a predetermined program and a storage device that stores electronic information. The arithmetic device may be referred to as a central processing unit (CPU). The storage device may be referred to as a memory or a hard disk. The control device 100 performs a predetermined calculation process according to a predetermined program, and electrically controls the lithium ion secondary battery 10 based on the calculation result. For vehicle applications, the control device 100 may be incorporated in an electronic control unit (ECU) mounted on the vehicle to control the engine, steering, brake, secondary battery, and the like.

  In the example shown in FIG. 4, an input device 32 (for example, a power source) and an output device 34 (for example, an output destination external device) are connected to the positive electrode terminal 12 and the negative electrode terminal 14 of the lithium ion secondary battery 10 to be controlled. Are connected in parallel. In addition, an ammeter 22 is connected in series to the lithium ion secondary battery 10, and a voltmeter 24 is connected in parallel. A temperature sensor 26 is attached to the lithium ion secondary battery 10.

<Control device 100>
Information related to the measured values is input to the control device 100 from the ammeter 22, the voltmeter 24, and the temperature sensor 26. And the open circuit voltage and deterioration degree of the lithium ion secondary battery 10 are estimated, and charge and discharge of the lithium ion secondary battery 10 are controlled. In the example illustrated in FIG. 4, the control device 100 controls the input device 32, the output device 34, the input switch 42, and the output switch 44. For example, the control device 100 can adjust the value of the current supplied to the lithium ion secondary battery 10 by controlling the input device 32 or the output device 34. Further, for example, by controlling the input switch 42 or the output switch 44, the energization to the lithium ion secondary battery 10 can be stopped.

  Here, the temperature sensor 26 is a sensor that detects the temperature of the target lithium ion secondary battery 10, and is attached to a predetermined position, for example, a side surface of the lithium ion secondary battery 10. The temperature sensor 26 has a required sensitivity, and it is only necessary to obtain an electrical signal corresponding to the temperature in the control device 100. The structure of the temperature sensor 26 is not particularly limited as long as it exhibits such a function.

  As shown in FIG. 4, the control device 100 includes an SOC detection unit 101, recording units A to D, and calculation units E to J.

<SOC detection unit 101>
The SOC detection unit 101 is a processing unit that detects the SOC of the target lithium ion secondary battery 10 in the control device 100. As a method for detecting the SOC of the target lithium ion secondary battery 10, specifically, various methods can be employed. An example is shown below. The method for detecting the SOC is not limited to the method exemplified here.

<Example of method for detecting SOC>
A method for detecting the SOC of the lithium ion secondary battery 10 will be described. In this embodiment, for the same type lithium ion secondary battery, data corresponding to the relationship between the open circuit voltage (OCV) and the SOC in the initial state is obtained by a test and stored in the control device 100 in advance.

  Data corresponding to the change amount of the positive electrode potential P with respect to the charge current amount of the lithium ion secondary battery 10 in the initial state is obtained by a test and stored in the control device 100 in advance. Further, data corresponding to the amount of change in the negative electrode potential Q with respect to the charging current amount of the lithium ion secondary battery 10 in the initial state is obtained by a test and stored in the control device 100 in advance.

  The SOC detection unit 101 stores in advance the relationship between the open circuit voltage (OCV) and the SOC for the lithium ion secondary battery 10 in the initial state. Then, the SOC detector 101 detects the SOC of the lithium ion secondary battery 10 in the initial state based on the relationship between the open circuit voltage (OCV) and the SOC stored in advance and the open circuit voltage (OCV). . The detected SOC is stored in the control device 100 as the charging rate SOCy immediately before the integration period. Thereafter, a change amount (ΔSOC) of the charging rate is calculated based on an integrated current amount (ΔI) obtained by integrating the charge current amount and the discharge current amount in a predetermined integration period.

The integrated current amount (ΔI) becomes + when the charging current amount is larger than the discharging current amount, and becomes − when the discharging current amount is larger than the charging current amount. As shown in the following formula (B), the change amount (ΔSOC) of the charging rate is obtained by dividing the integrated current amount (ΔI) by the battery capacity (Io).

ΔSOC = ΔI / Io (B)

In addition, the battery capacity (Io) of the target lithium ion secondary battery 10 tends to deteriorate with use. That is, the battery capacity of the lithium ion secondary battery 10 tends to gradually decrease with use from the initial state. In calculating the change rate ΔSOC of the charging rate, the integrated current amount (ΔI) is divided by the battery capacity (Io). At this time, more precisely, the battery capacity (Io) is the battery capacity immediately before the integration period, and the battery capacity Ix after deterioration calculated in the immediately previous integration period is used. The change amount ΔSOC may be calculated. In this case, the battery capacity (Io) stored in the control device 100 may be updated as needed to the battery capacity Ix after deterioration calculated in the previous integration period. Note that the method for calculating the battery capacity Ix after deterioration will be described later.

ΔSOC = ΔI / Ix (B1)

The charging rate SOCx after the integration period is calculated by the sum of the charging rate SOCy immediately before the integration period and the change rate ΔSOC of the charging rate, as in the following equation (C).

SOCx = SOCy + ΔSOC (C)

The charge rate SOCy immediately before the integration period stored in the control device 100 may be updated as needed to the charge rate SOCx calculated after the integration period.

  In the equation (C), SOCy is the charging rate immediately before the integration period of the integrated current amount when calculating the change amount ΔSOC of the charging rate. Here, the integrated current amount (ΔI) and the charging rate SOCx after the integration period are calculated for each integration period with a predetermined unit time as an integration period. The integration period can be set arbitrarily. For example, the integration period may be set to 15 seconds, 30 seconds, 1 minute, 5 minutes, or 10 minutes. In this embodiment, the integration period is set to 1 minute, and the battery capacity after deterioration and the charge rate SOCx after the integration period are calculated every minute. There are various other methods for detecting the charge rate SOCx after the integration period. For example, an appropriate method may be adopted in consideration of the characteristics of the active material.

<Recording part A>
The recording unit A is a processing unit that records a temperature history based on the temperature detected by the temperature sensor 26 in the control device 100. For example, the temperature information detected by the temperature sensor 26 may be recorded in time series.

<Recording part B>
The recording unit B is a processing unit that records an SOC history based on the SOC detected by the SOC detection unit 101 in the control device 100. For example, information on the SOC detected by the SOC detection unit 101 may be recorded in time series.

<Recording part C>
In the recording unit C, the relationship between the SOC of the target lithium ion secondary battery 10 and the positive electrode potential P is recorded. In this embodiment, the recording unit C records the relationship between the SOC in the initial state of the lithium ion secondary battery 10 and the positive electrode potential P shown in FIG.

<Recording part D>
In the recording unit D, the relationship between the SOC of the target lithium ion secondary battery 10 and the negative electrode potential Q is recorded. In this embodiment, the relationship between the SOC in the initial state of the lithium ion secondary battery 10 and the negative electrode potential Q shown in FIG.

<Calculation units E to H>
The calculation unit E is a processing unit that calculates the deterioration degree K1 of the positive electrode of the target lithium ion secondary battery 10 based on the temperature history and the SOC history in the control device 100.
The calculation unit F is a processing unit that calculates the deterioration degree K2 of the negative electrode of the target lithium ion secondary battery 10 based on the temperature history and the SOC history in the control device 100.
The calculation unit G is a processing unit that calculates the lithium trap amount TLi of the target lithium ion secondary battery 10 based on the temperature history and the SOC history in the control device 100.
The calculation unit H is a processing unit that calculates the starting point SP (contraction starting point) of the positive electrode potential and the negative electrode potential of the target lithium ion secondary battery 10 based on the temperature history and the SOC history in the control device 100.

  FIGS. 5 and 6 exemplify data tables M1 to M4 used for calculating the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP, respectively. Among these, FIG. 5 illustrates data tables M1A to M4A in the neglected state. FIG. 6 illustrates data tables M1B to M4B in the energized state.

<Data tables M1-M4>
In the data tables M1 to M4 used for calculation of the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, and the lithium trap amount TLi, as shown in FIGS. 5 and 6, the lithium ion secondary battery is left as it is. It is prepared according to the state (leaving state) and the state where the lithium ion secondary battery is energized (energized state). Note that the data tables M1 to M4 shown in FIGS. 5 and 6 are respectively created for convenience of explanation in order to help understanding of the control method proposed here. The data tables M1 to M4 shown in FIGS. 5 and 6 do not necessarily indicate specific data for an actual lithium ion secondary battery. For example, in FIG. 5 and FIG. 6, data is input with respect to four temperatures of −30 ° C., 0 ° C., 25 ° C., and 60 ° C. for the temperature in increments of 20% from 0% to 100% for the SOC. . Actually, it is preferable to use data tables that are further subdivided for SOC and temperature.

  Such a data table is created, for example, by preliminarily testing how much deterioration occurs when a lithium ion secondary battery of the same type as the target lithium ion secondary battery stays in the temperature and SOC state. Good.

  In the left state, for example, the lithium ion secondary battery is left for a number of days (for example, about 10 days) at which the deterioration of the lithium ion secondary battery can be sufficiently observed at a specific temperature and SOC. Based on this test, the data tables M1A to M4A in the neglected state include the positive electrode deterioration degree K1, the negative electrode deterioration degree K2, and the lithium trap when left at a specific temperature and SOC for one day. The amount TLi and the starting point SP are evaluated.

  Further, in the energized state, for example, it is determined in advance so that deterioration can be sufficiently observed in a control in which charging and discharging are repeated in a short cycle so that an average state of a specific SOC is obtained at a specific temperature. For about 24 hours. In the energized state data tables M1B to M4B, based on this test, the positive electrode deterioration degree K1, the negative electrode deterioration degree K2 when the battery is energized for a day at a specific temperature and SOC, and a lithium trap. The amount TLi and the starting point SP are evaluated.

  Here, with regard to the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode, the initial state is assumed to be 1, and the degree of progress of the deterioration (positive electrode shrinkage) and the degree of (negative electrode shrinkage) are evaluated. The lithium trap amount TLi is evaluated by a numerical value corresponding to the capacity (Ah) according to the lithium trap amount, with the initial state being zero.

  The data tables M1A and M2A in FIG. 5 record the degree of deterioration (K1 / day) of the positive electrode when left for 1 day and the degree of deterioration (K2 / day) of the negative electrode when left for 1 day, respectively. In the example of FIG. 5, the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode are each evaluated by a coefficient with an initial state of 1, and the closer to 1, the smaller the deterioration. In the example of FIG. 5, when left at a low temperature of −30 ° C., the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode are each 1, indicating that the deterioration is small. On the other hand, the deterioration increases as the temperature increases. In particular, the positive electrode shows a tendency that the influence of temperature is larger than that of the negative electrode.

  The data tables M1B and M2B in FIG. 6 record the degree of deterioration K1 of the positive electrode and the degree of deterioration K2 of the negative electrode when energized for one day, respectively. In the example of FIG. 6, the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode are each evaluated by a coefficient with an initial state of 1, and the closer to 1, the smaller the deterioration. In the example of FIG. 6, it is shown that the deterioration of the positive electrode and the negative electrode is larger as the SOC is close to 0% or 100%, respectively. It is also shown that the higher the temperature, the greater the deterioration of the positive electrode and the negative electrode.

  The data table M3A in FIG. 5 records the lithium trap amount TLi when left for one day. In the example of FIG. 5, the lithium trap amount TLi is evaluated by numerical values from 0 to 1, respectively, and 0 indicates that the lithium trap amount TLi hardly increases. Further, the closer to 0, the smaller the lithium trap amount TLi is. Further, the lithium trap amount TLi being − indicates that the trapped lithium is recovered. In other words, lithium that has stopped contributing to the battery reaction of the lithium ion secondary battery is recovered to a state that can contribute to the reaction. The-value indicates the amount of lithium recovered.

  According to the data table M3A of FIG. 5, when the lithium ion secondary battery is left untreated, the lithium trap amount TLi depends on the temperature. Here, it is shown that when left in a low temperature state of −30 ° C., the lithium trap amount TLi is 0, and the lithium trap amount TLi hardly changes. It is shown that when the temperature is 0 ° C. to 25 ° C., the lithium trap amount TLi is negative, the lithium trap amount TLi decreases, and the amount of lithium contributing to the battery reaction increases. Further, it is shown that when the temperature rises to about 60 ° C., the lithium trap amount TLi becomes positive and the lithium trap amount TLi increases.

  The data table M3B in FIG. 6 records the lithium trap amount TLi when the power is supplied for one day. The data table M3B of FIG. 6 shows that, for the same SOC, the lithium trap amount TLi increases as the temperature becomes higher than the low temperature state of −30 ° C., and the influence on the lithium trap amount TLi is greater. Further, when the SOC is 40% to 60%, the lithium trap amount TLi is small. It is shown that the lithium trap amount TLi increases as the SOC approaches 0% and as the SOC approaches 100%.

  The data table M4A in FIG. 5 records the starting point SP when left for 1 hour. The data table M4B in FIG. 6 records the starting point SP when energized for 1 hour. In the examples of FIGS. 5 and 6, the starting point SP is evaluated by a numerical value from 0 to 1, and indicates that the closer to 0, the smaller the starting point SP, and the closer to 1, the starting point SP. Is large.

  For example, if the positive electrode deterioration degree K1, the negative electrode deterioration degree K2, the lithium trap amount TLi, and the starting point SP tend to be different from each other according to the energization rate, a plurality of data are set according to the energization rate level. A table should be prepared. For example, although not shown, for the data tables M1B, M2B, M3B, and M4B in the energized state, a plurality of data tables may be prepared according to the current rate. Alternatively, when energized, a correction coefficient for correcting the data table may be prepared according to the current rate. By using a data table corresponding to the current rate or correcting the data table according to the current rate, the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP are obtained. It can be calculated with high accuracy.

  In the following, calculation examples of the positive electrode deterioration degree K1, the negative electrode deterioration degree K2, the lithium trap amount TLi, and the starting point SP will be exemplified in order.

<Calculation example of the deterioration degree K1 of the positive electrode>
When calculating the degree of deterioration K1 of the positive electrode, the control device 100 calculates the temperature history of the lithium ion secondary battery 10 recorded in the recording unit A and the SOC history of the lithium ion secondary battery 10 recorded in the recording unit B. Based on the above, the data tables M1A and M1B relating to the deterioration degree K1 of the positive electrode are referred to for each unit time. Here, when the lithium ion secondary battery 10 is left unattended in the unit time, the data table M1A is referred to. When the lithium ion secondary battery 10 is energized in the unit time, the data table M1B is referred to. This makes it possible to appropriately evaluate the deterioration degree K1 (t) of the positive electrode every unit time. Here, the deterioration degree K1 (t) of the positive electrode indicates a reference value in a certain unit time (t). The positive electrode deterioration degree K1 can be obtained by integrating the obtained positive electrode deterioration degrees K1 (t) for each unit time during the use period of the lithium ion secondary battery 10.

<Calculation example of the deterioration degree K2 of the negative electrode>
The control device 100 calculates the deterioration degree K2 of the negative electrode based on the temperature history of the lithium ion secondary battery 10 recorded in the recording unit A and the SOC history of the lithium ion secondary battery 10 recorded in the recording unit B. Based on this, the data tables M2A and M2B relating to the negative electrode deterioration degree K2 are referred to every unit time. Here, when the lithium ion secondary battery 10 is left unattended in the unit time, the data table M2A is referred to. When the lithium ion secondary battery 10 is energized in the unit time, the data table M2B is referred to. Thereby, the deterioration degree K2 (t) of the negative electrode can be appropriately evaluated every unit time. Here, the deterioration degree K2 (t) of the negative electrode indicates a reference value in a certain unit time (t). In the period of use of the lithium ion secondary battery 10, the deterioration degree K2 of the negative electrode is obtained by integrating the obtained deterioration degree K2 (t) of the negative electrode per unit time.

In this embodiment, as described above, the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode per day are recorded in the data table. The reference values of the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode here are evaluated by a coefficient with an initial state of 1. Further, in the temperature history of the recording unit A and the temperature history of the recording unit B, it is assumed that a history for each minute is recorded. The calculation formula in this case is as the following formulas (D) and (E).

K1 = Π (1-{(1-K1 (t)) / 1440}) (D)
K2 = Π (1-{(1-K2 (t)) / 1440}) (E)

  Here, since the reference values of the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode are evaluated by a coefficient having an initial state of 1, the portion (1-K1 (t)) is a unit time ( Here, it shows how much deterioration proceeds in 1 day). In (1-K1 (t)) / 1440, the reference value of the data table evaluates the degree of deterioration per day, whereas the temperature history of the recording unit A and the temperature history of the recording unit B are one each. Since it is recorded in the history of every minute, it is divided by 1440 minutes (60 minutes × 24) and evaluated as the degree of deterioration per minute. (1-{(1-K1 (t)) / 1440}) indicates the degree of deterioration in the unit time (here, 1 minute). Π is a symbol indicating that (1-{(1-K1 (t)) / 1440}) is integrated. Here, Π indicates the total power.

  That is, (1-{(1-K1 (t)) (t = 0 to x) is calculated for each unit time (1 minute) from 0 to a predetermined period (x). In this way, the positive electrode deterioration degree K1 in the period (t = 0 to x) is obtained.Here, the positive electrode deterioration degree K1 is described, but the negative electrode deterioration degree K2 is described. It should be noted that an appropriate integration method may be employed as a method of integrating the deterioration degree per unit time depending on the method of setting the deterioration degree and the nature of the active material of the lithium ion secondary battery. For example, here, Π means the sum of powers, but depending on how the degradation degree is set, Π may be integrated as a sum.

With the above calculation formula, the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode in a certain period can be estimated. The control apparatus 100 is good to memorize | store the initial deterioration degree (deterioration degree calculated by the last time) of the said period. And it is good to multiply the initial deterioration degree of the said period and the calculated deterioration degree of the said period. Here, the initial degree of deterioration of the positive electrode during the period (deterioration degree calculated up to the previous time) is LK1. The initial deterioration degree of the negative electrode during this period (deterioration degree calculated up to the previous time) is defined as LK2. In this case, the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode can be calculated by the following equations (D1) and (E1).

K1 = LK1 × Π (1-{(1-K1 (t)) / 1440}) (D1)
K2 = LK2 × Π (1-{(1-K2 (t)) / 1440}) (E1)

For example, the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode from the initial state can be calculated by continuously calculating from the initial state.

<Calculation unit E>
The calculating unit E calculates the deterioration degree K1 of the positive electrode of the target lithium ion secondary battery 10 based on the temperature history and the SOC history. In this case, the control device 100 may include a recording unit E1 that stores data tables M1A and M1B in which the relationship between the temperature, the SOC, and the degree of deterioration of the positive electrode per unit time is recorded in advance. The calculation unit E may calculate the positive electrode deterioration degree K1 based on the positive electrode deterioration amount per unit time obtained from the data tables M1A and M1B stored in the recording unit G1 and the temperature history and the SOC history.

<Calculation unit F>
The calculation unit F calculates the deterioration degree K2 of the negative electrode of the target lithium ion secondary battery based on the temperature history and the SOC history. In this case, the control device 100 may include a recording unit F1 that stores data tables M2A and M2B in which the relationship between the temperature, the SOC, and the degree of deterioration of the negative electrode per unit time is recorded in advance. The calculation unit F may calculate the deterioration degree K2 of the negative electrode based on the negative electrode deterioration amount per unit time obtained from the data tables M2A and M2B stored in the recording unit F1 and the temperature history and the SOC history.

<Calculation unit G>
The calculation unit G calculates the lithium trap amount TLi of the target lithium ion secondary battery 10 based on the temperature history and the SOC history. In this case, the control device 100 may include a recording unit G1 that stores data tables M3A and M3B in which the relationship among the temperature, the SOC, and the lithium trap amount per unit time is recorded in advance. The calculation unit G may calculate the lithium trap amount TLi based on the data tables M3A and M3B stored in the recording unit G1 and the lithium trap amount ΔTLi per unit time obtained from the temperature history and the SOC history.

<Calculation of lithium trap amount TLi>
The lithium trap amount TLi is calculated by the following equation (F).

TLi = Σ (TLi (t) / 1440) (F)

That is, in this embodiment, the lithium trap amount TLi per day is recorded in the data tables M3A and M3B as described above. The reference value of the lithium trap amount TLi here is evaluated by a numerical value from 0 to 1, where 0 is the initial state and 1 is the state of maximum degradation. Further, in the temperature history of the recording unit A and the temperature history of the recording unit B, it is assumed that a history for each minute is recorded. Here, TLi (t) is a reference value of the lithium trap amount TLi in a certain unit time (t). Σ indicates a sum of products. For example, when calculating the lithium trap amount TLi in the period from 0 to x, (TLi (t) / 1440) from t = 0 to x may be added.

Moreover, the control apparatus 100 is good to memorize | store the initial lithium trap amount LTLi of the said period. In this case, by adding the initial lithium trap amount LTLi in the period and the lithium trap amount calculated in the period, the lithium trap amount TLi in consideration of the initial lithium trap amount LTLi in the period can be calculated. it can.
In this case, for example, the lithium trap amount TLi from the initial state can be calculated by calculating the lithium trap amount TLi continuously from the initial state by the following formula (F1).

TLi = LTLi + Σ (TLi (t) / 1440) (F1)

<Calculation unit H>
The calculation unit H calculates the positive electrode potential and the negative electrode potential starting point SP of the target lithium ion secondary battery based on the temperature history and the SOC history. In this case, the control device 100 may include a recording unit H1 that stores data tables M4A and M4B in which the relationship between the temperature, the SOC, and the starting point SP per unit time is recorded in advance. In this embodiment, the starting point SP is the sum of values obtained by multiplying the value of each square in the data tables M4A and M4B by the time spent in the condition defined by each square (stay time). It is evaluated by the value divided by the total sum of staying time.

  In the example of FIG. 5, when the lithium ion secondary battery 10 is left for 5 hours in a state where the SOC is 100% and 25 ° C., and then left for 5 hours in a state where the SOC is 80% and 60 ° C., the SOC of the data table M4A is 100%. Multiply the square value (1.0) at 25 ° C. by time (5 h). Then, time (5h) is multiplied by the square value (0.9) in the state of SOC 80% and 60 ° C. Add the multiplied values and divide by the total time (10h). SP = (1.0 × 5h + 0.9 × 5h) /10h=0.95. Here, the starting point SP is a starting point when the positive electrode potential P and the negative electrode potential Q contract. At the positive electrode potential P, the position of 0.95 (95%) of the positive electrode initial capacity W + becomes a starting point when the positive electrode potential P contracts due to deterioration. In the negative electrode potential Q, the position of 0.95 (95%) of the negative electrode initial capacity W− becomes a starting point when the negative electrode potential Q contracts due to deterioration.

<Calculation unit I>
The calculation unit I calculates the relationship between the SOC recorded in the recording unit C and the positive electrode potential P, the relationship between the SOC recorded in the recording unit D and the negative electrode potential Q, the deterioration degree K1 of the positive electrode, and the deterioration degree of the negative electrode. Based on K2, the lithium trap amount TLi, and the starting point SP, the open circuit voltage of the target lithium ion secondary battery 10 is calculated.

  For example, in the control device 100, the deterioration of the lithium ion secondary battery 10 as shown in FIG. 3 is based on the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP. Map data from which the subsequent positive electrode potential P1 and negative electrode potential Q1 can be derived is preferably prepared in advance. The map data can be expressed as (P1, Q1) = (K1, K2, TLi, SP). The open circuit voltage of the lithium ion secondary battery 10 can be derived as a potential difference between the derived positive electrode potential P1 after deterioration and the negative electrode potential Q1.

<Calculation part J>
The calculation unit J calculates the deterioration degree X of the lithium ion secondary battery 10 based on the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, and the lithium trap amount TLi. Here, the control device 100 can derive the deterioration degree X of the lithium ion secondary battery 10 based on the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP. Data should be prepared in advance. The map data can be expressed as X = (K1, K2, TLi, SP). The process of calculating the deterioration degree X of the lithium ion secondary battery 10 is based on the map data {X = (K1) based on the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP. , K2, TLi, SP)}.

  Further, as another method of the calculation unit I and the calculation unit J, as shown in FIG. 3, it is derived based on the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP. A method of calculating the open circuit voltage and the deterioration degree X based on the positive electrode potential P1 and the negative electrode potential Q1 after the deterioration can also be adopted.

  For example, the post-degradation positive electrode capacity (W1 +) can be calculated by the product of the positive electrode initial capacity (W +) and the positive electrode deterioration degree (K1). Further, the deviation amount X1 (current amount) of the start end P1s of the positive electrode potential P1 after deterioration based on the start end Ps of the positive electrode potential P in the initial state is based on the positive electrode initial capacity (W +) and the deterioration degree K1 of the positive electrode ( 1−K1) and the starting point (SP) {X1 = (W +) × (1−K1) × SP}. As shown in FIG. 3, the deteriorated positive electrode potential P1 is obtained by the positive electrode capacity W1 + after deterioration and the shift amount X1 of the starting end P1s of the positive electrode potential P1 after deterioration.

  Further, the negative electrode capacity (W1-) after deterioration can be calculated by the product of the negative electrode initial capacity (W-) and the deterioration degree (K2) of the negative electrode. Further, the amount of deviation X2 (current amount) of the starting end Q1s of the negative electrode potential Q1 after deterioration based on the starting end Qs of the negative electrode potential Q in the initial state is based on the negative electrode initial capacity (W−) and the deterioration degree K2 of the negative electrode. [X2 = TLi + {(W−) × (), which is obtained by the sum of the product {(W−) × (1−K2) × SP} of (1−K2) and the starting point (SP)) and the lithium trap amount TLi. 1-K2) × SP}]. As shown in FIG. 3, the negative electrode potential Q1 after deterioration is obtained by the negative electrode capacity W1- after deterioration and the shift amount X2 of the starting end Q1s of the negative electrode potential Q1 after deterioration.

The open circuit voltage (OCV) after deterioration can be estimated as a potential difference between the positive electrode potential P1 and the negative electrode potential Q1 after deterioration. Further, the position at which OCV (P1-Q1) becomes a predetermined lower limit voltage (3.0 V in this embodiment), and the OCV (P1-Q1) has a predetermined upper limit voltage (4 in this embodiment). .1V) is specified. And the battery capacity between 3.0V-4.1V is calculated. The calculated battery capacity is defined as a deteriorated battery capacity Ix. Then, the deterioration degree X (capacity maintenance ratio) of the lithium ion secondary battery 10 may be calculated by dividing the deteriorated battery capacity Ix by the initial capacity Io based on the following equation (G).

X = Ix / Io (G)

  As described above, the calculation units I and J of the control device 100 calculate the positive electrode potential deviation amount X1 and the negative electrode potential based on the positive electrode deterioration degree K1, the negative electrode deterioration degree K2, the lithium trap amount TLi, and the starting point SP. A process of estimating the estimated deviation amount X2, the open circuit voltage of the lithium ion secondary battery 10, the battery capacity Ix after deterioration, and the like may be included.

  In addition, the control device 100 energizes the lithium ion secondary battery 10 when the positive electrode deterioration degree K1 exceeds a predetermined threshold value or when the negative electrode deterioration degree K2 exceeds a predetermined threshold value. You may suppress the electric current value to perform. When the deterioration degree K1 of the positive electrode exceeds a predetermined threshold value, or when the deterioration degree K2 of the negative electrode exceeds a predetermined threshold value, the positive electrode active material or the negative electrode active material is deteriorated. There is a possibility, and by suppressing the value of current flowing through the lithium ion secondary battery 10, it is possible to suppress the progress of capacity deterioration of the lithium ion secondary battery 10.

<Current suppression part K>
In this case, the control device 100 may include a current suppression unit K that performs the process. The current suppression unit K applies to the lithium ion secondary battery 10 when the deterioration degree K1 of the positive electrode exceeds a predetermined threshold value or when the deterioration degree K2 of the negative electrode exceeds a predetermined threshold value. The current value to be energized is suppressed. Here, the threshold value can be arbitrarily set in accordance with a situation in which energization to the lithium ion secondary battery 10 should be suppressed.

For example, the control device 100 may include a recording unit F2 and a calculation unit F3. Here, the recording unit F2 includes a data table M5 {J in which a relationship between the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, and a coefficient J that suppresses a current value flowing through the lithium ion secondary battery 10 is determined in advance. = (K1, K2)} may be stored. The calculation unit F3 calculates a current value for energizing the lithium ion secondary battery based on the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode. Here, the processing of the calculation unit F3 is a current value for energizing the lithium ion secondary battery 10 based on the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, and the data table M5 {J = (K1, K2)}. A coefficient J for suppressing the above is obtained. Then, as in the equation (H), in normal control, the current value Ax that is actually energized is obtained by multiplying the current value Ao that should be energized by the lithium ion secondary battery 10 by the coefficient J.

Ax = Ao × J (H)

Here, the coefficient J is a coefficient that suppresses a current value that is applied to the lithium ion secondary battery 10, and may be set to a numerical value of 0 to 1.

  Further, based on the lithium trap amount TLi, when the lithium trap amount TLi exceeds a predetermined threshold, energization to the lithium ion secondary battery may be stopped. When the lithium trap amount TLi exceeds a predetermined threshold value, it means that in the lithium ion secondary battery 10, lithium that does not contribute to the battery reaction has increased beyond a predetermined amount. . In this case, by stopping energization of the lithium ion secondary battery 10, the amount of lithium contributing to the battery reaction can be recovered, and the lithium trap amount TLi can be reduced.

<Stop control unit L>
In this case, the control device 100 may include a stop control unit L. The stop control unit L stops energization of the lithium ion secondary battery 10 when it is larger than a predetermined threshold based on the lithium trap amount TLi. Here, the threshold value can be arbitrarily set according to a situation where energization of the lithium ion secondary battery 10 should be stopped.

  As described above, the control device 100 uses the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, or the lithium trap amount TLi as in the processes F1 and F2 described above as a method of calculating the deterioration degree of the lithium ion secondary battery 10. A processing unit that embodies a process of calculating the deterioration degree of the lithium ion secondary battery based on the above may be provided.

  FIG. 7 is a flowchart illustrating an example of a control flow of the control device 100. The control flow shown in FIG. 7 is as follows. This control flow assumes an application in which the lithium ion secondary battery 10 is mounted on a vehicle. Start processing: Here, the control flow is started in the state of entering the steady running mode.

S100: A unipolar map is held for each of the positive electrode potential P and the negative electrode potential Q in the initial state.
S101: The voltage, current, and temperature of the lithium ion secondary battery to be controlled are detected. In the control device 100, the temperature history based on the temperature detected by the temperature sensor is recorded in the recording unit A. The history of the voltage value and the current value is also recorded in the control device 100 (see FIG. 4).
S102: The SOC of the lithium ion secondary battery to be controlled is detected. In the control device 100, the SOC history based on the SOC detected by the SOC detection unit 101 is recorded in the recording unit B (see FIG. 4).
S103: The deterioration degree K1 of the positive electrode is calculated. In the control device 100, the calculation unit E calculates the deterioration degree K1 of the positive electrode of the target lithium ion secondary battery 10 based on the temperature history and the SOC history (see FIG. 4).
S104: The deterioration degree K2 of the negative electrode is calculated. In the control device 100, the calculation unit F calculates the deterioration degree K2 of the negative electrode of the target lithium ion secondary battery 10 based on the temperature history and the SOC history (see FIG. 4).
S105: A lithium trap amount TLi is calculated. In the control device 100, the calculation unit G calculates the lithium trap amount TLi of the target lithium ion secondary battery 10 based on the temperature history and the SOC history (see FIG. 4).
S106: A shrinkage start point SP is calculated. In the control device 100, the calculation unit H calculates the starting point SP of the positive electrode potential and the negative electrode potential of the target lithium ion secondary battery based on the temperature history and the SOC history (see FIG. 4).
S107: Based on the deterioration degree K1 of the positive electrode, the deterioration degree K2, the lithium trap amount TLi, and the starting point SP of the negative electrode, the open circuit voltage (OCV) after deterioration of the target lithium ion secondary battery 10, and the deterioration degree X Is calculated. In the control device 100, the calculation units I and J calculate the lithium trap amount TLi of the target lithium ion secondary battery 10 based on the temperature history and the SOC history (see FIG. 4).
S108: The capacity deterioration of the target lithium ion secondary battery is determined based on the deterioration degree K1 of the positive electrode and the deterioration degree K2 of the negative electrode. In the flow shown in FIG. 7, the control device 100 determines whether or not the deterioration degree K1 of the positive electrode exceeds a predetermined threshold value Lk1 (K1> Lk1) (see FIG. 4). Further, it is determined whether or not the deterioration degree K2 of the negative electrode exceeds a predetermined threshold value Lk2 (K2> Lk2).
S208: Current suppression control (S206) is performed when one of the positive electrode deterioration degree K1 and the negative electrode deterioration degree K2 exceeds a threshold value (Lk1, Lk2). In the control device 100, the current suppression unit K suppresses energization to the target lithium ion secondary battery 10. For example, the control device 100 stores in advance a function equation represented by Ig = f (k1, k2) or a data table, and applies the target lithium ion secondary battery 10 according to the calculated current value Ig. The current value to be energized may be controlled.
S109: It is determined whether or not the lithium trap amount TLi exceeds a predetermined threshold (Lt) (TLi> Lt).
S209: Stop control is performed. When the lithium trap amount TLi exceeds a predetermined threshold value (Lt), energization to the target lithium ion secondary battery 10 is stopped. The control device 100 is processed by the stop control unit L. For example, the control device 100 stores in advance a functional expression represented by Th = f (TLi) or a data table, and energizes the target lithium ion secondary battery 10 according to the calculated time Th. It is good to be comprised so that the time to stop may be set.
S110: A normal energization process is performed. In the determination step S108, the control device 100 determines that neither the deterioration level K1 nor the deterioration level K2 exceeds the threshold value (Lk1, Lk2). In the determination step S109, the lithium trap amount TLi is set to a predetermined threshold value ( Lt) is not exceeded, a normal energization process for the target lithium ion secondary battery 10 is performed.

  It is desirable that this control is always executed in a state where the target lithium ion secondary battery 10 is used, and returns to the start process after the control is completed. It is repeatedly executed in a state where the target lithium ion secondary battery 10 is used. Although illustration is omitted, a determination processing unit in which a condition for ending the control is set is provided in the process of returning to the start process after the control is completed, and the control is configured to be terminated with a condition. Also good.

  By the way, the positive electrode of the target lithium ion secondary battery may contain a plurality of positive electrode active materials at a predetermined ratio. In this case, in order to increase the accuracy of the deterioration degree K1 of the positive electrode, a map (in this embodiment, a data table) showing the relationship of temperature-SOC-deterioration degree is prepared in advance for each positive electrode active material included in the positive electrode. Good. Then, the degree of deterioration calculated for each positive electrode active material is calculated, and the degree of deterioration K1 of the positive electrode is calculated by multiplying the degree of deterioration calculated for each positive electrode active material by the ratio of the positive electrode active material. Good.

  For example, when the active material A and the active material B are included in the positive electrode, the active material A and the active material B may have different properties with respect to deterioration. In this case, for each positive electrode active material included in the positive electrode, a map (in this embodiment, a data table) showing a relationship of temperature-SOC-deterioration degree may be prepared in advance. Hereinafter, a case where two types of positive electrode active materials A and B are used for the positive electrode, and the mixing ratio (weight ratio) of the positive electrode active materials A and B is 4: 1 will be exemplified.

  FIG. 8 and FIG. 9 illustrate data tables M1 to M4 used for calculation of the deterioration degree K1 of the positive electrode, the deterioration degree K2 of the negative electrode, the lithium trap amount TLi, and the starting point SP, respectively. Among these, FIG. 8 illustrates data tables M1A to M4A in the neglected state. FIG. 9 illustrates data tables M1B to M4B in the energized state.

  In this embodiment, the active material A and the active material B are included in the positive electrode. As a data table for calculating the deterioration degree K1 of the positive electrode, a data table corresponding to the active material A and a data table corresponding to the active material B are prepared. In FIG. 8, the data table M1A-A is a data table corresponding to the active material A, and the data table M1A-B is a data table corresponding to the active material B. In FIG. 9, the data table M1B-A is a data table corresponding to the active material A, and the data table M1B-B is a data table corresponding to the active material B.

  In the calculation of the deterioration degree K1 of the positive electrode, the deterioration degree is calculated for each positive electrode active material based on the temperature history and the SOC history, and the deterioration degree calculated for each positive electrode active material is multiplied by the ratio of the positive electrode active material and added. By doing so, the deterioration degree K1 of the positive electrode is calculated.

For example, in the calculation of the deterioration degree K1-A for the positive electrode active material A, the control device 100 (see FIG. 4) records the temperature history of the lithium ion secondary battery 10 recorded in the recording unit A and the recording unit B. Based on the SOC history of the lithium ion secondary battery 10, the data tables M1A-A and M1B-A relating to the deterioration degree K1-A of the positive electrode active material A are referred to for each unit time. In the calculation of the deterioration degree K1-B for the positive electrode active material B, the control device 100 (see FIG. 4) recorded the temperature history of the lithium ion secondary battery 10 recorded in the recording unit A and the recording unit B. Based on the SOC history of the lithium ion secondary battery 10, the data tables M1A-B and M1B-B regarding the deterioration degree K1-B of the positive electrode active material B are referred to for each unit time.
Thereby, the deterioration degree K1-A of the positive electrode active material A and the deterioration degree K1-B of the positive electrode active material B are calculated. The deterioration degree K1-A of the positive electrode active material A and the deterioration degree K1-B of the positive electrode active material B are calculated in accordance with the calculation of the deterioration degree K1 of the positive electrode using the data table M1A, respectively.

Further, the deterioration degree K1 of the positive electrode is calculated by multiplying the deterioration degree (K1-A) and (K1-B) calculated for each positive electrode active material by multiplying the positive electrode active material ratio (weight ratio). .
In this case, the deterioration degree K1 of the positive electrode is obtained by the following equation.
K1 = (K1-A) × 0.8 + (K1-B) × 0.2

In addition, the positive electrode potential P in the initial state includes the positive electrode potential P (A) of the positive electrode active material A in the initial state, the positive electrode potential P (B) of the positive electrode active material B in the initial state, and the positive electrode active materials A and B. Calculated by weight ratio.
That is, the positive electrode potential P in the initial state is obtained by the following equation.
P = P (A) × 0.8 + P (B) × 0.2
Further, the positive electrode potential P1 after deterioration is obtained by the following equation.
P1 = (K1-A) * P (A) * 0.8 + (K1-B) * P (B) * 0.2

  In the recording part C in which the relationship between the initial state SOC and the positive electrode potential of the target lithium ion secondary battery is recorded, the relationship P (A) between the initial state SOC and the positive electrode potential of the positive electrode active material A and the positive electrode active The relationship P (B) between the SOC of the substance B in the initial state and the positive electrode potential may be recorded.

  Thus, when two types of positive electrode active materials A and B are used for the positive electrode, the relationship of temperature-SOC-degradation degree is set for each of the positive electrode active materials A and B included in the positive electrode as described above. The map shown may be prepared in advance. In addition, the relationship between the initial state SOC and the positive electrode potential may be recorded for each of the positive electrode active materials A and B.

  Then, based on the temperature history and the SOC history, the deterioration degree is calculated for each of the positive electrode active materials A and B, and the deterioration degree calculated for each of the positive electrode active materials A and B is multiplied by the ratio of the positive electrode active materials A and B. The deterioration degree K1 of the positive electrode may be calculated by adding them. Further, for each of the positive electrode active materials A and B, the deteriorated positive electrode potential P1 is obtained by multiplying the relationship between the initial state SOC and the positive electrode potential by multiplying the deterioration degree by the ratio of the positive electrode active materials A and B. It should be done.

  The positive electrode deterioration degree K1 and the deteriorated positive electrode potential P1 calculated here are treated in the same manner as the positive electrode deterioration degree K1 and the deteriorated positive electrode potential P1 when a single active material is contained in the positive electrode. . For example, the deterioration degree K1 of the positive electrode and the positive electrode potential P1 after deterioration calculated here are various controls such as the current suppression control in the current suppression unit K and the stop control in the stop control unit L described above in the flowchart shown in FIG. Used for.

  Here, the case where two types of positive electrode active materials A and B are used for the positive electrode and the mixing ratio (weight ratio) of the positive electrode active materials A and B is 4: 1 is exemplified. However, the present invention is not limited to this. For example, when the positive electrode of the target lithium ion secondary battery includes a plurality of positive electrode active materials at a predetermined ratio, the target lithium ion secondary battery is included in each positive electrode active material included in the positive electrode. A map (in this embodiment, a data table) showing the relationship between the SOC and the positive electrode potential in the initial state of the secondary battery and the relationship between the temperature, the SOC, and the degree of deterioration may be prepared in advance. Accordingly, the present invention can be applied when a plurality of positive electrode active materials such as three types and four types are used for the positive electrode.

  Heretofore, various control methods and control devices for the lithium ion secondary battery proposed here have been described. The control method and control device for the lithium ion secondary battery proposed here are not limited to the above-described embodiment, and various modifications can be made unless otherwise specified.

The lithium ion secondary battery control method and control apparatus proposed here can be applied to control of various lithium ion secondary batteries.
Examples of the positive electrode active material of the lithium ion secondary battery to be controlled include a lithium transition metal composite oxide.
As the lithium transition metal composite oxide, for example, a cobalt-rich (cobalt) material as a transition metal, a nickel-rich (nickel) material as a transition metal, and nickel, cobalt, and manganese as transition metals (so-called three) Original materials), manganese spinel materials, so-called olivine materials, and the like.
Examples of the negative electrode active material of the lithium ion secondary battery to be controlled include carbon-based negative electrode materials such as amorphous natural graphite and graphite, and lithium titanate.

DESCRIPTION OF SYMBOLS 10 Lithium ion secondary battery 12 Positive electrode terminal 14 Negative electrode terminal 22 Ammeter 24 Voltmeter 26 Temperature sensor 32 Input device 34 Output device 42 Input switch 44 Output switch 100 Control device 101 Detection part A Recording part B Recording part C Recording part D Recording Part E Calculation part E1 Recording part F Calculation part F1 Recording part F2 Recording part F3 Calculation part G Calculation part G1 Recording part H Calculation part H1 Recording part I Calculation part J Calculation part K Current suppression part L Stop control part M1-M5 Data table

Claims (1)

A temperature sensor for detecting the temperature of the target lithium ion secondary battery;
An SOC detector for detecting the SOC of the target lithium ion secondary battery;
A recording unit A for recording a temperature history based on the temperature detected by the temperature sensor;
A recording unit B that records an SOC history based on the SOC detected by the SOC detection unit;
A recording unit C that records the relationship between the SOC and the positive electrode potential in the initial state of the target lithium ion secondary battery;
A recording unit D that records the relationship between the SOC and negative electrode potential in the initial state of the target lithium ion secondary battery;
A calculation unit E that calculates a deterioration degree K1 of the positive electrode of the target lithium ion secondary battery based on the temperature history and the SOC history;
A calculation unit F that calculates a deterioration degree K2 of the negative electrode of the target lithium ion secondary battery based on the temperature history and the SOC history;
A calculation unit G that calculates a lithium trap amount TLi of the target lithium ion secondary battery based on the temperature history and the SOC history;
Based on the temperature history and the SOC history, a calculation unit H that calculates the starting point SP of the positive electrode potential and the negative electrode potential of the target lithium ion secondary battery,
The relationship between the SOC recorded in the recording unit C and the positive electrode potential, the relationship between the SOC recorded in the recording unit D and the negative electrode potential, the degree of deterioration K1 of the positive electrode calculated by the calculation unit E, and Based on the deterioration degree K2 of the negative electrode calculated by the calculation unit F, the lithium trap amount TLi calculated by the calculation unit G, and the starting point SP calculated by the calculation unit H, the target lithium ion 2 A calculation unit I for calculating an open circuit voltage of the secondary battery,
The positive electrode of the target lithium ion secondary battery includes a plurality of positive electrode active materials at a predetermined ratio,
In the storage unit C,
For each positive electrode active material contained in the positive electrode, the relationship between the SOC and the positive electrode potential in the initial state of the target lithium ion secondary battery is recorded,
In the calculation unit E,
For each positive electrode active material included in the positive electrode, a map showing a relationship of temperature-SOC-degradation degree is prepared in advance,
Based on the temperature history and the SOC history, the degree of deterioration is calculated for each positive electrode active material, and the degree of deterioration calculated for each positive electrode active material is multiplied by the ratio of the positive electrode active material, and added. The degree of deterioration K1 of the positive electrode is calculated.
Control device for lithium ion secondary battery.

Images