JP6668914B2 - Battery control device - Google Patents

Description

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

  2. Description of the Related Art A power supply system is used in which power is supplied to a load by a chargeable / dischargeable secondary battery, and the chargeable / dischargeable secondary battery can be charged even during operation of the load as needed. Typically, a hybrid vehicle or an electric vehicle including a motor driven by a secondary battery as a driving force source is equipped with such a power supply system. In these power supply systems, the stored power of the secondary battery is used as the driving power of the motor as a driving power source, the generated power when the motor generates regenerative power, and the power generated by the rotation of the engine. This secondary battery is charged by the generated power or the like. In such a power supply system, it is required that the state estimating device for the secondary battery accurately output a state of charge (SOC) for a fully charged state.

  In particular, in the case of a hybrid vehicle, the charging rate is set to a fully charged state (100%) so that the secondary battery can receive regenerative power and can immediately supply power to the electric motor when requested. ), And control is required to be performed in the vicinity (50-60%) of the state where the battery is not charged at all (0%).

  In addition, if the secondary battery is overdischarged or overcharged, the battery may be deteriorated and its life may be shortened. Therefore, in the use form of the secondary battery in which charge and discharge are repeatedly performed with the intermediate SOC as a control target as described above, the charge amount of the secondary battery is sequentially grasped to limit excessive charge and discharge. From the viewpoint of charge / discharge control, it is highly necessary to accurately estimate the state of the secondary battery.

Therefore, of the plurality of parameters in the battery model formula, three parameters that change according to the state change of the secondary battery, namely, the positive electrode capacity retention ratio k ₁ , the negative electrode capacity retention ratio k _2, and the surface of the positive electrode active material explore the positive and negative electrodes discrepancy capacity Delta] Q _s is the amount of variation in the battery capacity due to the change from the initial state of the correspondence between the local charging of the surface of the local charging rate and the negative electrode active material at the same time, in the lithium ion secondary battery A technique for estimating a state change due to deterioration has been proposed. According to such a technique, for example, even when the electrode wear and the deposition of the reaction-related substance (for example, deposition of metallic lithium) occur simultaneously, the state of the secondary battery can be accurately estimated (for example, And Patent Document 1).

Japanese Patent No. 5537236

By the way, the deterioration of the lithium ion secondary battery mounted on the electric vehicle is predicted, and the maximum dischargeable power Wout and the maximum chargeable power Win are limited according to the predicted deterioration, and the lithium ion It has been studied to suppress deterioration of the secondary battery. For example, a time change of the positive electrode capacity retention rate k ₁ , the negative electrode capacity retention rate k ₂ , and the positive / negative electrode composition correspondence displacement capacity ΔQ _s with respect to the running time of the electric vehicle is predicted by a test, and the predicted positive electrode capacity retention rate k ₁ , negative electrode capacity maintenance rate k _2, the maximum dischargeable electric power Wout of the lithium ion secondary battery, the method to limit the maximum chargeable power Win has been studied on the basis of the positive and negative electrodes discrepancy capacity Delta] Q _s.

  However, the deterioration of the lithium ion secondary battery mounted on the electric vehicle may progress faster than expected depending on how the user runs. In this case, in the method as exemplified above, the limitation on the maximum dischargeable power Wout and the maximum chargeable power Win becomes insufficient, and the deterioration of the secondary battery may progress faster than expected.

  Therefore, an object of the present invention is to suppress the deterioration of the lithium ion secondary battery from progressing faster than predicted from the running history of the electric vehicle.

  The battery control device of the present invention has a positive electrode capacity retention ratio that is a ratio of the positive electrode capacity in the deteriorated state to the positive electrode capacity in the initial state, and a negative electrode capacity retention ratio that is a ratio of the negative electrode capacity in the deteriorated state to the negative electrode capacity in the initial state. Based on the positive and negative electrode composition correspondence shift capacity, which is the amount of change in battery capacity due to a change from the initial state of the correspondence between the local charge rate on the positive electrode active material surface and the local charge rate on the negative electrode active material surface. A battery control device that estimates deterioration of a lithium ion secondary battery mounted on an electric vehicle, and limits chargeable / dischargeable power of the lithium ion secondary battery according to the deterioration of the lithium ion secondary battery, A measuring unit for measuring an open-circuit voltage curve indicating a change in the open-circuit voltage with respect to a change in the battery capacity, and an estimated open-circuit voltage curve substantially matching the actual measured value of the open-circuit curve measured by the measuring unit. A deterioration parameter calculation unit that calculates the positive electrode capacity retention ratio, the negative electrode capacity retention ratio, and the positive / negative electrode composition correspondence displacement capacity, and a predicted positive electrode capacity retention ratio based on the running history of the electric vehicle, and a predicted negative electrode capacity retention ratio. A predicted deterioration parameter calculation unit for calculating a predicted positive / negative electrode composition correspondence displacement capacity, and the positive electrode capacity maintenance ratio calculated by the deterioration parameter calculation unit is less than the predicted positive electrode capacity maintenance ratio, or calculated by the deterioration parameter calculation unit. When the negative electrode capacity retention rate is less than the predicted negative electrode capacity retention rate, or when the positive / negative electrode composition corresponding displacement capacity calculated by the deterioration parameter calculation unit exceeds the predicted positive / negative electrode composition corresponding displacement capacity, the lithium ion secondary battery It is determined that the deterioration of the battery is progressing faster than expected, and the chargeable / dischargeable power of the lithium ion secondary battery is changed to the lithium ion secondary battery. Degradation of and having and a power limiting unit for limiting from rechargeable power when predictable.

  The present invention can suppress that the deterioration of the lithium ion secondary battery progresses earlier than predicted from the running history of the electric vehicle.

It is a conceptual diagram which shows the internal structure of a lithium ion secondary battery. FIG. 4 is a diagram illustrating a change characteristic of an open circuit voltage with respect to a local change in SOC of a lithium ion secondary battery. It is a figure which shows the change of the open-circuit potential of the positive electrode accompanying the decrease of the positive electrode capacity of a lithium ion secondary battery, and the change of the open-circuit potential of the negative electrode accompanying the decrease of the negative electrode capacity. FIG. 4 is a diagram illustrating a deviation in composition correspondence between a positive electrode and a negative electrode of a lithium ion secondary battery. FIG. 3 is a diagram illustrating a shift in composition correspondence due to deterioration of a lithium ion secondary battery. FIG. 4 is a diagram illustrating a change in open-circuit voltage (open-circuit voltage curve) with respect to a battery capacity of a lithium ion secondary battery. Positive electrode capacity maintenance rate k _1, negative electrode capacity maintenance rate k _2, is an illustration of a calculation method will to match the open-circuit voltage curve actually measured open-circuit voltage curve estimated by changing the positive and negative electrodes discrepancy capacity Delta] Q _s. 1 is a system diagram illustrating a configuration of an electric vehicle equipped with a battery control device according to an embodiment of the present invention. It is a functional block diagram of a battery control device of an embodiment of the present invention. 5 is a flowchart showing an operation of the battery control device of the present invention for acquiring a running history of the electric vehicle. 5 is a flowchart (1) illustrating an operation of the battery control device of the present invention. It is a flowchart (2) which shows operation | movement of the battery control apparatus of this invention. FIG. 2 is a system diagram illustrating a test apparatus for creating a map of predicted deterioration parameters. FIG. 14 is a functional block diagram of the test apparatus shown in FIG. 13. 14 is a flowchart showing the operation of the test device shown in FIG. 16 is a flowchart showing the details of a process for identifying a predicted positive electrode capacity retention ratio k _1e , a predicted negative electrode capacity retention ratio k _2e , and a predicted positive / negative electrode composition correspondence displacement capacity ΔQ _se of the flowchart of FIG. 15. 14 is a graph showing a time change of a current command value Ib ^* to a battery of the test apparatus shown in FIG. 13 and a timing of calculating a predicted deterioration parameter. FIG. 14 is an explanatory diagram showing detection of an open-circuit voltage curve (actually measured value) measured by the test apparatus shown in FIG. 13 and a specified open-circuit voltage curve (estimated value). FIG. 5 is an explanatory diagram of a voltage error ΔV. FIG. 14 is an explanatory diagram showing a change in an open-circuit voltage curve (estimated value) due to battery deterioration in the case of a running pattern A acquired by the test device shown in FIG. 13. FIG. 14 is an explanatory diagram showing a temporal change of a predicted deterioration parameter acquired by the test device shown in FIG. 13. FIG. 4 is an explanatory diagram showing a limitation of Wout / Win by the battery control device of the present embodiment.

<Lithium ion secondary battery and characteristic formula>
Before describing the battery control device 40 according to the embodiment of the present invention, a lithium ion secondary battery (battery 10) for which the battery control device 40 of the present embodiment estimates deterioration and a characteristic formula thereof will be briefly described.

As shown in FIG. 1, the lithium ion secondary battery includes a negative electrode, a separator containing an electrolytic solution, and a positive electrode. Each of the negative electrode and the positive electrode is composed of an aggregate of spherical active materials. During discharging of the lithium ion secondary battery, a chemical reaction is performed on the interface of the active material of the negative electrode to release lithium ions Li ⁺ and electrons e ⁻ . On the other hand, a chemical reaction for absorbing lithium ions Li ⁺ and electrons e ⁻ is performed on the interface of the active material of the positive electrode. At the time of charging the lithium ion secondary battery, a reaction opposite to the above-described reaction is performed.

  The negative electrode is provided with a negative electrode current collector that absorbs electrons, and the positive electrode is provided with a positive electrode current collector that emits electrons. The negative electrode current collector is formed of, for example, copper, and is connected to the negative electrode terminal. The positive electrode current collector is made of, for example, aluminum and is connected to the positive electrode terminal. Transfer of lithium ions between the positive electrode and the negative electrode via the separator allows charging and discharging of the lithium ion secondary battery.

  Here, the state of charge inside the lithium ion secondary battery differs depending on the lithium concentration distribution in each of the active materials of the positive electrode and the negative electrode.

  The output voltage of the lithium ion secondary battery is represented by the following equation (1).

ここで、ＯＣＶは、リチウムイオン二次電池の開放電圧、Ｒ_ａは、リチウムイオン二次電池の全体における抵抗、Ｉは、リチウムイオン二次電池に流れる電流である。抵抗Ｒ_ａは、負極および正極で電子の移動に対する純電気的な抵抗と、活物質界面での反応電流発生時に等価的に電気抵抗として作用する電荷移動抵抗とが含まれる。

Here, OCV is the open-circuit voltage of the lithium ion secondary battery, _Ra is the resistance of the entire lithium ion secondary battery, and I is the current flowing through the lithium ion secondary battery. The resistance _Ra includes a pure electric resistance against movement of electrons between the negative electrode and the positive electrode, and a charge transfer resistance equivalently acting as an electric resistance when a reaction current is generated at the active material interface.

theta ₁ is localized charging rate in the surface of the positive electrode active material (hereinafter, .SOC that SOC charging rate is approximately the State Of Charge.) is, theta ₂ is localized in the surface of the negative electrode active material SOC. The resistance _Ra has characteristics that change according to changes in θ ₁ , θ ₂ and the battery temperature. In other words, the resistance R _a is, theta _1, can be expressed as a function of theta ₂ and battery temperature.

The local SOCs θ ₁ and θ ₂ are represented by the following equation (2).

ここで、Ｃ_ｓｅ，ｉは、活物質（正極または負極）の界面におけるリチウム濃度（平均値）であり、Ｃ_{ｓ，ｉ，ｍａｘ}は、活物質（正極または負極）における限界リチウム濃度である。なお、添字ｉの１は正極、２は負極を示す。限界リチウム濃度とは、正極や負極におけるリチウム濃度の上限値である。正極、負極の局所的ＳＯＣθ_１、θ_２は、それぞれ、０と１（０％と１００％）の間で変化する。

Here, C _{se, i} is the lithium concentration (average value) at the interface of the active material (positive electrode or negative electrode), and C _{s, i, max} is the limit lithium concentration in the active material (positive electrode or negative electrode). In addition, 1 of a subscript i shows a positive electrode, 2 shows a negative electrode. The limit lithium concentration is the upper limit of the lithium concentration in the positive electrode or the negative electrode. The local SOCs θ ₁ and θ ₂ of the positive electrode and the negative electrode vary between 0 and 1 (0% and 100%), respectively.

The positive electrode open potential U ₁ has a characteristic that changes in accordance with local SOC θ ₁ on the surface of the positive electrode active material, and the negative electrode open potential U ₂ has a characteristic that changes in accordance with local SOC θ ₂ on the surface of the negative electrode active material. have. FIG. 2 shows the relationship between the local SOC θ _{1 and the} positive electrode open potential U ₁ when the lithium ion secondary battery is in the initial state, and the relationship between the local SOC θ ₂ and the negative electrode open potential U ₂ .

As shown in FIG. 2, open-circuit voltage OCV of the lithium ion secondary battery is expressed as a potential difference of the positive electrode open-circuit potential U ₁ and the negative electrode open-circuit potential U _2. The initial state refers to a state in which the lithium ion secondary battery has not deteriorated, for example, a state immediately after the manufacture of the lithium ion secondary battery.

As shown in FIG. 2, when the lithium ion secondary battery is in the initial state and is almost fully charged, that is, when the open voltage OCV of the lithium ion secondary battery is VH shown in FIG. to have been moved, the local SOC [theta] ₂ of the negative electrode θ _H2 (= 1) negative electrode open-circuit potential _{U 2} in the lowest, the positive electrode open-circuit potential _{U 1} local SOC [theta] ₁ of the positive electrode at θ _L1 (= 0) is most Is getting higher. Conversely, when the discharge is close to complete discharge, that is, when the open-circuit voltage OCV of the lithium ion secondary battery is VL shown in FIG. 2, all lithium has moved to the positive electrode, and the local SOC θ _{1 of the} positive electrode is θ _H1 (= 1) at the positive electrode open-circuit potential _{U 1} is the lowest, the negative electrode open-circuit potential with local SOC [theta] ₂ of the negative electrode θ _L2 (= 0) is the highest. Data indicating these characteristics (U ₁ , U ₂ ) can be stored in the memory 42 shown in FIG. 8 in advance as a map.

  The open-circuit voltage OCV of a lithium ion secondary battery has a characteristic of decreasing as the discharge proceeds. Further, in the deteriorated lithium ion secondary battery, the amount of voltage drop for the same discharge time is larger than in the initial state lithium ion secondary battery. This indicates that the deterioration of the lithium ion secondary battery causes a decrease in the full charge capacity and a change in the open-circuit voltage curve. In the present embodiment, the change of the open-circuit voltage curve due to the deterioration of the lithium ion secondary battery is modeled as two phenomena that are considered to occur inside the lithium ion secondary battery in the deteriorated state.

  The two phenomena are a decrease in single electrode capacity at the positive electrode and the negative electrode, and a corresponding shift in composition between the positive electrode and the negative electrode.

  The decrease in the single-electrode capacity indicates a decrease in the capacity of accepting lithium in each of the positive electrode and the negative electrode. The decrease in the capacity for accepting lithium means that the active material or the like that effectively functions for charge and discharge is reduced.

Figure 3 is a variation of the positive electrode open-circuit potential U ₁ due to a reduction in positive electrode capacity and the change of the negative electrode open-circuit potential U ₂ due to a reduction in the negative electrode capacity is schematically shown. 3, Q_L1 on the axis of the positive electrode capacity is a capacity corresponding to the local SOC θ _L1 (= 0) in FIG. 2 in the initial state of the lithium ion secondary battery. Q_H11 is a capacity corresponding to the local SOC θ _H1 (= 1) in FIG. 2 in the initial state of the lithium ion secondary battery. Q_L2 on the axis of the negative electrode capacity is a capacity corresponding to the local SOC θ _L2 (= 0) in FIG. 2 in the initial state of the lithium ion secondary battery, and Q_H21 is a capacity in the initial state of the lithium ion secondary battery. , The capacitance corresponding to the local SOC θ _H2 (= 1) in FIG.

When the capacity of accepting lithium in the positive electrode decreases, the capacity corresponding to the local SOC θ _H1 (= 1) changes from Q_H11 to Q_H12. Further, when the lithium receiving capacity of the negative electrode decreases, the capacity corresponding to the local SOC θ _H2 (= 1) changes from Q_H21 to Q_H22.

Here, even if the lithium ion secondary battery deteriorates, the relationship between the local SOC θ ₁ and the positive electrode open potential U ₁ (the relationship shown in FIG. 2) does not change. Therefore, the relationship between the positive electrode open-circuit potential U ₁ for local SOC [theta] _1, is converted into the relationship of the positive electrode open-circuit potential U ₁ for positive electrode capacity, as shown in FIG. 3, the positive electrode open-circuit potential U ₁ for the positive electrode capacity of the deteriorated state The curve showing the relationship is in a state in which the curve of the initial state is reduced by the amount of deterioration of the lithium ion secondary battery.

Similarly, the negative electrode open-circuit potential U ₂ relationship to the local SOC [theta] _2, is converted into anode relationship between the open voltage U ₂ for the negative electrode capacity, as shown in FIG. 3, the negative electrode open-circuit potential U ₂ for the negative electrode capacity of the deteriorated state The curve showing the relationship is in a state in which the curve of the initial state is reduced by the amount of deterioration of the lithium ion secondary battery.

FIG. 4 schematically shows the correspondence of the composition between the positive electrode and the negative electrode. The difference in the composition correspondence means that when charge / discharge is performed using a pair of a positive electrode and a negative electrode, the combination of the composition of the positive electrode (θ ₁ ) and the composition of the negative electrode (θ ₂ ) is changed to the initial state of the lithium ion secondary battery. This indicates that the position is shifted.

A curve showing the relationship between the positive SOC and the negative electrode open potential U ₁ , U ₂ with respect to the local SOC θ ₁ , θ ₂ of the positive electrode and the negative electrode is similar to the curve shown in FIG. Here, when deterioration of the lithium ion secondary battery, the axis of the anode composition theta ₂ is shifted in the direction the positive electrode composition theta ₁ is smaller by [Delta] [theta] _2. Accordingly, the curve showing the negative electrode relationship between the open voltage U ₂₂ for the negative electrode compositions theta ₂ of the axis of the deteriorated state, to the curve showing the relationship between the negative electrode open-circuit potential U ₂₁ for the negative electrode compositions theta ₂ of the axis of the initial state, [Delta] [theta] only ₂ minute shifts in the direction of the positive electrode composition theta ₁ is reduced.

The composition of the negative electrode corresponding to the positive electrode composition theta _1fix is a lithium ion secondary battery is "theta _{2Fix_ini"} when in the initial state, becomes "theta _2Fix" is after the lithium ion secondary battery is deteriorated.

In the present embodiment, the two deterioration phenomena described above are modeled by introducing three deterioration parameters into the battery model. The three degradation parameters, positive electrode capacity maintenance rate k _1, a negative electrode capacity maintenance rate k _2, and positive and negative electrodes discrepancy capacity Delta] Q _s. A method for modeling the two deterioration phenomena will be described below.

The positive electrode capacity maintenance rate k _1, means the ratio of the positive electrode capacity of the deteriorated state for the positive electrode capacity in the initial state. Here, it is assumed that the positive electrode capacity is reduced by an arbitrary amount from the capacity in the initial state after the lithium ion secondary battery is in a deteriorated state. At this time, positive electrode capacity maintenance rate k ₁ is represented by the following formula (3).

Here, Q _{1_ini} represents the positive electrode capacity when the lithium ion secondary battery is in the initial state (Q_H11 shown in FIG. 3), and ΔQ ₁ is the decrease amount of the positive electrode capacity when the lithium ion secondary battery is deteriorated. Is shown. Thus positive electrode capacity when the lithium ion secondary battery becomes deteriorated state (Q_H12 shown in FIG. 3) _{becomes (Q 1_ini -ΔQ 1).} Further, k1 decreases from ₁ in the initial state. Here, the positive electrode capacity _{Q1_ini} in the initial state can be obtained in advance from the theoretical capacity or the charged amount of the active material.

The negative electrode capacity maintenance rate k _2, means the ratio of the negative electrode capacity of the deteriorated state of the negative electrode capacity in the initial state. Here, it is assumed that the negative electrode capacity is reduced by an arbitrary amount from the capacity in the initial state after the lithium ion secondary battery is in a deteriorated state. At this time, the negative electrode capacity maintenance rate k ₂ is represented by the following formula (4).

Here, Q _{2_ini} represents the negative electrode capacity (Q_H21 shown in FIG. 3) when the lithium ion secondary battery is in the initial state, and ΔQ ₂ is the decrease amount of the negative electrode capacity when the lithium ion secondary battery is deteriorated. Is shown. Thus the negative electrode capacity when the lithium ion secondary battery becomes deteriorated state (Q_H22 shown in FIG. 3) _{becomes (Q 2_ini -ΔQ 2).} Also, _{k 2} is reduced from 1 in the initial state. Here, the negative electrode capacity _{Q2_ini} in the initial state can be obtained in advance from the theoretical capacity or the charged amount of the active material.

  FIG. 5 is a schematic diagram for explaining a difference in composition correspondence between the positive electrode and the negative electrode.

When the lithium ion secondary battery becomes deteriorated state, a negative electrode capacity when the negative electrode composition theta ₂ is _1, the _{(Q 2_ini -ΔQ 2).} The positive / negative electrode composition displacement capacity ΔQ _s is a capacity corresponding to the displacement Δθ ₂ of the negative electrode composition axis θ ₂ with respect to the positive electrode composition axis θ ₁ . Thereby, the relationship of the following equation (5) is established. In addition, the positive / negative electrode composition correspondence shift capacity ΔQ _s is a correspondence relationship between a local SOC θ ₁ which is a local charge rate on the surface of the positive electrode active material and a local SOC θ ₂ which is a local charge rate on the surface of the negative electrode active material. 5 shows the amount of change in battery capacity due to a change from the initial state.

  The following equation (6) is obtained from the equations (4) and (5).

When the lithium ion secondary battery is in the initial state, the positive electrode composition theta _{1Fix_ini} corresponds to the negative electrode composition _θ 2fix_ini. When the lithium ion secondary battery is in a deteriorated state, the positive electrode composition theta _1fix corresponds to the negative electrode composition _θ 2fix. In addition, the deviation of the composition correspondence is based on the positive electrode composition θ _1fix in the initial state. That is, the positive electrode composition θ _1fix and the positive electrode composition θ _{1fix_ini} have the same value.

In the case where the composition correspondence shift occurs between the positive electrode and the negative electrode due to the deterioration of the lithium ion secondary battery, the positive electrode composition θ _1fix and the negative electrode composition θ _2fix after the deterioration of the lithium ion secondary battery are _expressed by the following equation (7). , (8).

The meaning of equation (8) will be described. When lithium is released from the positive electrode by charging while the lithium ion secondary battery is in a deteriorated state, the positive electrode composition θ1 decreases from ₁ . When the positive electrode composition theta ₁ is reduced to theta _1fix from 1, the amount of lithium released from the positive electrode is represented by the following formula (9).

ここで、（１−θ_１ｆｉｘ）の値は、リチウムイオン二次電池の充電による正極組成θ_１の減少分を示し、（ｋ_１×Ｑ_{１＿ｉｎｉ}）の値は、リチウムイオン二次電池の劣化後における正極容量を示している。

Here, the value of (1−θ _1fix ) indicates a decrease in the positive electrode composition θ ₁ due to the charging of the lithium ion secondary battery, and the value of (k ₁ × Q _{1 — ini} ) indicates the value after the deterioration of the lithium ion secondary battery. Shows the positive electrode capacity at.

_Assuming that all the lithium released from the positive electrode is taken into the negative electrode, the negative electrode composition θ _2fix is represented by the following formula (10).

ここで、（ｋ_２×Ｑ_{２＿ｉｎｉ}）の値は、リチウムイオン二次電池の劣化後における負極容量を示している。

Here, the value of (k ₂ × Q _{2 — ini} ) indicates the capacity of the negative electrode after deterioration of the lithium ion secondary battery.

On the other hand, when there is a deviation (Δθ ₂ ) corresponding to the composition between the positive electrode and the negative electrode, the negative electrode composition θ _2fix after deterioration is represented by the following equation (11).

Composition corresponding shift amount [Delta] [theta] ₂ using Formula (6) can be expressed using positive and negative electrodes discrepancy capacity Delta] Q _s. Thus, the negative electrode composition θ _2fix after deterioration is expressed by the above equation (8).

As shown in FIG. 5, the open-circuit voltage OCV when the lithium ion secondary battery is in a deteriorated state is expressed as a potential difference of the positive electrode open-circuit potential U ₁₁ and the negative electrode open-circuit potential U ₂₂ in a degraded state. That is, when the three deterioration parameters, ie, the positive electrode capacity retention ratio k ₁ , the negative electrode capacity retention ratio k ₂ , and the positive / negative electrode composition correspondence shift capacity ΔQ _s are specified, the negative electrode open potential when the lithium ion secondary battery is in the degraded state. it can be identified U _22, as a potential difference of the negative electrode open-circuit potential _{U 22} and the positive electrode open-circuit potential _{U 11,} it is possible to calculate the open circuit voltage OCV.

That is, the positive electrode capacity Q _{1_Ini} the initial _state, since the negative electrode capacity Q _{2_Ini} can be obtained in advance from the theoretical capacity and charge of the active material, positive electrode capacity maintenance rate k ₁ is a three degradation _parameters, negative electrode capacity maintenance rate If k ₂ and the positive / negative electrode composition correspondence displacement capacity ΔQ _s can be specified, the negative electrode composition θ _2fix in the deteriorated state can be calculated using Expression (8). Further, the deviation amount Δθ ₂ corresponding to the composition can be calculated using the equation (6). Now, as shown in FIG. 5, may be a positive electrode composition theta ₁ the deteriorated state to identify the negative electrode composition axis theta ₂ 0 position and the negative electrode composition theta _2Fix the deteriorated state with respect to the position of 1. Then, from the positions of 0 and θ _2fix, the position where the negative electrode composition axis θ ₂ in the deteriorated state becomes 1 can be specified as shown in FIG.

Even deteriorated lithium ion secondary battery, the relationship of the positive electrode open-circuit potential U ₁ for local SOC [theta] ₁ of the positive electrode, the relationship between the negative electrode open-circuit potential U ₂ for the local SOC [theta] ₂ of the negative electrode (the relationship shown in FIG. 2) is not changed . Thus, if a particular 0 and 1 positions of the negative electrode composition axis theta ₂ of the deterioration state for 1 and 0 position of the positive electrode composition theta ₁ of the deterioration state, between 1 and 0 of the positive electrode composition theta ₁ a degraded 2 drawing a curve showing the relationship between the positive electrode open-circuit potential U ₁ for local SOC [theta] ₁ of the positive electrode shown in the negative electrode open for local SOC [theta] ₂ of the negative electrode shown in FIG. 2 between 1 and 0 of the positive electrode composition theta ₁ a degraded When a curve showing the relationship between potential U _2, each curve, the positive electrode open-circuit potential U ₁₂ deteriorated state shown in FIG. _5, a negative electrode open-circuit potential U _22. As described above, when the curves indicating the positive electrode open potential U ₁₂ and the negative electrode open potential U ₂₂ can be specified, the open circuit voltage OCV of the deteriorated lithium ion secondary battery can be calculated.

Positive electrode capacity maintenance rate k ₁ is a three degradation parameters as described _above, calculates the open-circuit voltage OCV of the lithium ion secondary battery of the deteriorated state negative electrode capacity maintenance rate k _2, to identify the positive and negative electrodes discrepancy capacity Delta] Q _s can do.

In the lithium ion secondary battery in the initial state, a positive electrode capacity maintenance rate k ₁ and negative electrode capacity maintenance rate k ₂ is 1, a positive-negative electrodes discrepancy capacity Delta] Q _s is 0, calculated (estimated by the foregoing description ) Is equal to a value (actually measured value) when the open circuit voltage OCV of the lithium ion secondary battery in the initial state (new) is measured.

  As shown in FIG. 6, the open circuit voltage OCV of the lithium ion secondary battery increases as the battery capacity (A × h) increases, that is, as the secondary battery is charged. Hereinafter, a change curve of the open-circuit voltage OCV with respect to the battery capacity (A × h) is referred to as an open-circuit voltage curve. The open-circuit voltage curve shifts from the initial state to the left side in the figure when deteriorated, as shown by the one-dot chain line and the broken line in FIG.

Calculated as described above, positive electrode capacity maintenance rate k ₁ is a three degradation _parameters, negative electrode capacity maintenance rate k _2, the open circuit voltage OCV of the lithium ion secondary battery deteriorated state from the positive and negative electrodes discrepancy capacity Delta] Q _s it is possible to, it is possible to calculate the positive electrode capacity maintenance rate k _1, negative electrode capacity maintenance rate k _2, the open-circuit voltage curve of the lithium ion secondary battery from the positive and negative electrodes discrepancy capacity Delta] Q _s.

Therefore, as shown in FIG. 7, positive electrode capacity maintenance rate k ₁ is a three degradation _parameters, negative electrode capacity maintenance rate k _2, and set to a value obtained by estimating a positive and negative electrodes discrepancy capacity Delta] Q _s, the open state of deterioration A voltage curve (estimated value) is calculated, and the positive electrode capacity retention rate k ₁ , the negative electrode capacity retention rate k ₂ , and the positive / negative electrode composition are set so that the open-circuit voltage curve (estimated value) substantially matches the open-circuit voltage curve (actually measured value). by performing focusing calculated by changing the corresponding capacity shift Delta] Q _s, positive electrode capacity maintenance rate k ₁ in a certain deteriorated _state, the negative electrode capacity maintenance rate k _2, to identify the positive and negative electrodes discrepancy capacity Delta] Q _s, a lithium ion secondary Battery capacity deterioration can be estimated.

<Configuration of battery control device>
Next, the configuration of the battery control device 40 of the present embodiment will be described. First, the battery control device 40 according to the embodiment of the present invention mounted on the electric vehicle 100 will be described with reference to FIG. The electric vehicle 100 includes a battery 10, an inverter 13 connected to the battery 10 via the positive electrode line 11 and the negative electrode line 12, a motor generator 14 which is a vehicle driving motor driven and controlled by the inverter 13, An ECU 60 that controls the operation of the motor generator 14 and a battery control device 40 that monitors the state of the battery 10 and outputs the SOC of the battery 10, the maximum chargeable power Win, the maximum dischargeable power Wout, and the like to the ECU 60 are provided. . The electric vehicle 100 further includes an external power supply connector 15 connected to the positive electrode line 11 and the negative electrode line 12 and capable of charging the battery 10 with an external power supply.

  The battery 10 is provided with a voltage sensor 31 for detecting a voltage value Vb and a temperature sensor 33 for detecting a temperature Tb. Further, a current sensor 32 for detecting a current value Ib of the battery 10 is attached to the positive electrode line 11. The detection signals of the voltage sensor 31, the current sensor 32, and the temperature sensor 33 are input to the battery control device 40.

  The battery 10 is a chargeable / dischargeable secondary battery such as a lithium ion secondary battery. Motor generator 14 receives electric power output from battery 10, drives electric vehicle 100, converts kinetic energy generated during braking of electric vehicle 100 into electric power, and charges battery 10. Therefore, while the electric vehicle 100 is running, the battery 10 repeatedly charges and discharges. The current value Ib from the battery 10 is such that the discharge current is positive (+) and the charging current is negative (-).

  The battery control device 40 includes a CPU 41 that internally performs information processing and calculations, a memory 42 that stores a control program, control data, and the like, and a sensor interface 43 to which the voltage sensor 31, the current sensor 32, and the temperature sensor 33 are connected. The computer includes a CPU 41, a memory 42, and a sensor interface 43, which are connected to each other by a data bus 44. The ECU 60 is also a computer including a CPU for performing information processing and calculation, and a memory for storing control programs, control data, and the like. The ECU 60 is a higher-level control device of the battery control device 40. The battery control device 40 and the ECU 60 are connected by a data bus 45, and are configured to exchange data with each other. Note that the data bus 44 of the battery control device 40 is also connected to the data bus 45.

The memory 42 includes a map for calculating a predicted positive electrode capacity maintenance rate k _1f , a predicted negative electrode capacity maintenance rate k _2f, and a predicted positive / negative electrode composition correspondence shift capacity ΔQ _sf from the traveling history of the electric vehicle 100. Control data and control programs are stored.

  Next, functional blocks of the battery control device 40 of the present embodiment will be described with reference to FIG. As shown in FIG. 9, the battery control device 40 of the present embodiment includes a predicted deterioration parameter calculation unit 51, a measurement unit 52, a deterioration parameter calculation unit 53, and a power limiting unit 54.

The predicted deterioration parameter calculation unit 51 calculates the electric vehicle 100 from the voltage value Vb of the battery 10 detected by the voltage sensor 31, the current value Ib detected by the current sensor 32, and the temperature Tb detected by the temperature sensor 33 shown in FIG. Is accumulated in the memory 42 as an integrated travel time of each travel pattern. (Steps S101 to S104 in FIG. 10). In addition, from the memory 42, an integrated travel time for each travel pattern up to a time t1 at which the deterioration of the battery 10 is estimated, a map of a predicted degradation parameter created based on a test using the test apparatus 200 described later, or a time. The change curve and the predicted positive electrode capacity retention rate k _1f , predicted negative electrode capacity retention rate k _2f , and predicted positive / negative electrode composition corresponding displacement capacity ΔQ _sf at time t1 are calculated and output to the power limiting unit 54 (FIG. 11). Step S212 to step S214 in FIG. 12).

  The measuring unit 52 calculates the battery 10 at time t1 based on the voltage value Vb of the battery 10 detected by the voltage sensor 31 shown in FIG. 8, the current value Ib detected by the current sensor 32, and the temperature Tb detected by the temperature sensor 33. The OCV (t1) and the OCV (t2) of the battery 10 at the time t2 are detected, and the charging / discharging current between the time t1 and the time t2 is integrated to obtain an open-circuit voltage curve which is a change characteristic of the OCV with respect to the battery capacity. (Actual measured value) is detected and stored in the memory 42 (Steps S201 to S205 in FIG. 11).

Degradation parameter calculation part 53, a candidate of the positive electrode capacity maintenance rate k ₁ set, and the candidate of the negative electrode capacity maintenance rate k _2, open-circuit voltage curve (estimated value with a candidate of the positive and negative electrodes discrepancy capacity Delta] Q _s ) is calculated, the positive electrode capacity maintenance rate k ₁ which coincides with the open-circuit voltage curve stored in the memory 42 (measured value), and negative electrode capacity maintenance rate k _2, until the specific positive and negative electrodes discrepancy capacity Delta] Q _s, the perform repeated calculations, stores the identified positive electrode capacity maintenance rate k ₁ and negative electrode capacity maintenance rate k ₂ positive and negative electrodes discrepancy capacity Delta] Q _s and the open-circuit voltage curve (estimated value) in the memory 42 (step S206 in FIG. 11 To S211).

The power limiting unit 54 calculates the predicted positive electrode capacity maintenance ratio k _1f , the predicted negative electrode capacity maintenance ratio k _2f , the predicted positive / negative electrode composition correspondence shift capacity ΔQ _sf calculated by the predicted deterioration parameter calculating unit 51, and the positive electrode calculated by the deterioration parameter calculating unit. comparing the capacity maintenance rate k ₁ and negative electrode capacity maintenance rate k ₂ positive and negative electrodes discrepancy capacity Delta] Q _s, positive electrode capacity maintenance rate k _{1 <predicted} positive electrode capacity maintenance rate k _1f or, negative electrode capacity maintenance rate k _{2 <prediction} If any one of the negative electrode capacity retention rate k _2f or the positive / negative electrode composition corresponding displacement capacity ΔQ _s > predicted positive / negative electrode composition corresponding displacement capacity ΔQ _sf is satisfied, the chargeable / dischargeable power of the battery 10 is limited, and not otherwise. In this case, a signal for releasing the limitation on the chargeable / dischargeable power of the battery 10 is output (steps S215 to S217 in FIG. 12).

  The signal output from the power limiting unit 54 is input to the ECU 60. The ECU 60 sets the maximum chargeable power Win and the maximum dischargeable power Wout based on the signal, and sets the set maximum chargeable power Win and maximum settable dischargeable power Wout. The electric vehicle 100 is driven by controlling the inverter 13 and the motor generator 14 so as not to exceed.

  The functional blocks of the battery control device 40 of the present embodiment as described above are software mainly composed of the CPU 41 and the memory 42 included in the battery control device 40 and the programs read from the memory 42 and executed by the CPU 41. Is achieved.

<Map creation of predicted deterioration parameters>
Next, a map of predicted deterioration parameters is created using the test apparatus 200 shown in FIG. 13, that is, a predicted positive electrode capacity maintenance rate k _1e , a predicted negative electrode capacity maintenance rate k _2f , and a predicted positive capacity maintenance rate in each traveling pattern of the electric vehicle 100. the creation of a temporal change curve of the negative electrode composition corresponding capacity shift Delta] Q _se be described.

  As shown in FIG. 13, a test apparatus 200 that performs a deterioration test of a battery 210 that is a lithium ion secondary battery connects a battery 210, a power supply 221, a load 220, and a connection between the battery 210 and the power supply 221 or the load 220. Switches 216 and 217 for switching and a controller 230 for adjusting the current value Ib of the battery 210 using the load 220 or the power supply 221 of the battery 210 are provided. A voltage sensor 231 for detecting a voltage value Vb of the battery 210 is attached in parallel with the battery 210, and a current sensor 232 for detecting a current value Ib of the battery 210 is connected to a positive line of the battery 210. Further, a temperature sensor 233 that detects the temperature Tb of the battery 210 is attached to the battery 210. The controller 230 is a computer including a CPU that internally performs signal processing and arithmetic processing, and a memory that stores control data, programs, and the like. The controller 230 is connected to a power supply 221, a load 220, and switches 216 and 217, and each device operates according to a command from the controller 230. Each signal of the voltage sensor 231, the current sensor 232, and the temperature sensor 233 is configured to be input to the controller 230. Note that, in FIG. 13, a chain line indicates a signal line.

  Next, functional blocks of the test apparatus 200 shown in FIG. 13 will be described with reference to FIG. As illustrated in FIG. 14, the test apparatus 200 includes a battery load fluctuation adjustment unit 251, a measurement unit 252, and a predicted deterioration parameter map generation unit 253.

  The battery load change adjusting unit 251 adjusts the load change of the battery 210 according to the running pattern of the electric vehicle 100 by using the power supply 221, the load 220, and the switches 216 and 217 (step S301 in FIG. 15). The current value Ib of the battery 210 is such that the discharge current is positive (+) and the charge current is negative (-).

Measuring unit 252, the predicted positive electrode capacity maintenance rate _{k 1e} shown in step S303 of FIG. 15, the predicted negative electrode capacity maintenance rate _{k 2e,} among specific processing of the predictive positive and negative electrodes discrepancy capacity Delta] Q _se, the voltage sensor 231 shown in FIG. 13 The OCV (tt1) of the battery 210 at time tt1 and the OCV of the battery 210 at time tt2 are calculated based on the voltage value Vb of the battery 210 detected at step (b), the current value Ib detected at the current sensor 232, and the temperature Tb detected at the temperature sensor 233. (Tt2), the charge / discharge current between time tt1 and time tt2 is integrated, and an open-circuit voltage curve (actually measured value) which is a change characteristic of the OCV with respect to the battery capacity is detected. (Steps S401 to S405 in FIG. 16).

The predicted deterioration parameter map generation unit 253 calculates a predicted positive electrode capacity retention rate k _1e , a predicted negative electrode capacity retention rate k _2e , and a predicted positive / negative electrode composition corresponding displacement capacity ΔQ based on the open-circuit voltage curve (actually measured value) detected and indicated by the measurement unit 252. _{The se} is specified (step S303 in FIG. 15 and steps S406 to S411 in FIG. 16), and the time change curves of the predicted positive electrode capacity retention rate k _1e , the predicted negative electrode capacity retention rate k _2e , and the predicted positive / negative electrode composition correspondence displacement capacity ΔQ _se. Is created (step S305 in FIG. 15).

<Mapping of test equipment operation and predicted deterioration parameters>
Next, an operation of the test apparatus 200 and creation of a map of predicted deterioration parameters will be described with reference to FIGS.

The degree of deterioration of battery 210 varies depending on the running pattern of electric vehicle 100. For example, in the case of a driving pattern B in which a driver who makes heavy use of sudden start and sudden braking travels in the city, the deterioration of the battery 10 progresses more than the basic driving pattern A in which a general driver drives in the city. On the other hand, the traveling pattern C in which a driver whose accelerator work and brake work is slower than a general driver travels in a city has a slower progression of deterioration than the case of the traveling pattern A. Further, in the driving pattern D of the general driver when the environmental temperature is low, and in the driving pattern E of the general driver when the environmental temperature is high, the deterioration of the battery 10 progresses faster than the driving pattern A at the normal temperature. . Therefore, for example, about 5 to 10 types of traveling patterns such as the traveling patterns AE described above are prepared. Then, a time change curve of the battery current value Ib in each traveling pattern is prepared as a curve of the battery current command value Ib ^* . In the following description, first, a test on the basic traveling pattern A will be described.

The battery load variation adjusting unit 251 of the controller 230 adjusts the power supply 221, the switches 216, 217, and the load 220 according to the change curve of the current command value Ib ^* corresponding to the traveling pattern A, and as shown in FIG. A load variation (fluctuation in current value Ib) according to a variation curve of current command value Ib ^* is applied to battery 210. Discharging corresponds to acceleration of the electric vehicle 100, and charging corresponds to braking (regeneration) of the electric vehicle 100.

As shown in step S302 in FIG. 15, the battery load variation adjustment unit 251 performs a predetermined time, for example, about 30 minutes to 1 hour, for a predetermined number of times, for example, 100, according to a change curve of the current command value Ib ^* corresponding to the traveling pattern A. When the load change is applied to the battery 210 only once, the load change to the battery 210 is stopped as shown in FIG. This puts battery 210 in a relaxed state. The condition for determining that battery 210 is relaxed is, for example, that the maximum concentration difference of the lithium ion concentration in the active material in the battery model is equal to or less than a predetermined concentration difference, and the absolute value of the battery current is a predetermined value. It is a condition that it is less than or equal to the value.

At time tt1 shown in FIG. 17 when the battery 210 is in the relaxed state, the measurement unit 252 and the predicted deterioration parameter map generation unit 253 of the controller 230 perform the predicted positive electrode capacity maintenance ratio k _1e and the predicted negative electrode capacity shown in step S303 of FIG. maintenance rate _{k 2e,} starts processing for specifying predictive positive and negative electrodes discrepancy capacity Delta] Q _se.

  As shown in step S401 of FIG. 16, the battery load fluctuation adjusting unit 251 sets the switches 216 and 217 to the intermediate position at time tt1 to open the battery 210. Then, measuring section 252 detects open circuit voltage OCV (tt1) of battery 210 by voltage sensor 231 at time tt1. Thereafter, the battery load fluctuation adjusting unit 251 starts charging the battery 210 as shown in FIG. 17 with the switches 216 and 217 as power sources.

As shown in step S402 in FIG. 16, the measurement unit 52 starts integrating the charging current to the battery 210 at time tt1. The current is integrated by multiplying the product of the current value Ib detected by the current sensor 232 and the period Δt at every period Δt (for example, 0.1 seconds) as in the following equation (12).

Integrated current value (A × h) = Σ (Ib × Δt) / 3600 (12)

  At time tt2 when charging of the battery 210 ends, the battery load fluctuation adjusting unit 251 sets the switches 216 and 217 to the intermediate positions to open the battery 210 again. Then, as shown in step S403 of FIG. 16, the measuring unit 252 detects the open voltage OCV (tt2) of the battery 210 by the voltage sensor 231 at the time tt2.

In addition, as shown in step S404 in FIG. 16, the measurement unit 252 ends the integration of the current at time tt2. As shown in FIG. 18 and the following equation (13), the capacity of the battery 210 at the time tt2 is Q (tt2) (A × h) obtained by adding the integrated current value to the battery capacity Q (tt1) at the time tt1. .

Q (tt2) = Q (tt1) + integrated current value (13)

  Then, as shown in step S405 in FIG. 16, the measuring unit 252 stores a predicted open-circuit voltage curve (actually measured value) as shown by a solid line in FIG. 18 in the memory.

As shown in step S406 of FIG. 16, the predicted deterioration parameter map generation unit 253 calculates the candidate value of the predicted positive electrode capacity retention ratio k _1e , the candidate value of the predicted negative electrode capacity retention ratio k _2e , and the predicted positive / negative electrode composition correspondence shift capacity. A candidate value for ΔQ _se is set. Approximately ten candidate values for each predicted deterioration parameter may be set.

As shown in step S407 of FIG. 16, the predicted deterioration parameter map generation unit 253 determines the candidate value of the predicted positive electrode capacity maintenance ratio k _{1e and} the candidate value of the predicted negative electrode capacity maintenance ratio k _2e and the predicted positive and negative electrode composition set in step S406. as described above with reference to FIG using candidate value of the corresponding displacement volume Delta] Q _se, as a potential difference of the negative electrode open-circuit potential U ₂₂ and the positive electrode open-circuit potential U ₁₁ of the battery 10, calculates the open-circuit voltage OCV, FIG An open-circuit voltage curve (estimated value) indicated by a broken line in FIG. 18 is calculated.

  The predicted deterioration parameter map generator 253 calculates the voltage error ΔV and the capacitance error ΔQ as shown in step S408 of FIG. The voltage error ΔV is calculated by comparing the open-circuit voltage curve (estimated value) and the open-circuit voltage curve (actually measured value) as shown in FIG. The voltage error ΔV may be a voltage error at a specific battery capacity, or may be an average value of the voltage errors between two open voltage curves. Further, the capacitance error ΔQ is determined by using the open-circuit voltage curve (estimated value) to determine the capacitance Q1 between the open-circuit voltage OCV (tt1) before charging (time tt1) and the open-circuit voltage OCV (tt2) after charging (time tt2). Is calculated. In addition, the charged capacity Q2 can be calculated from the integrated current value integrated in steps S402 and S404 in FIG. By calculating the difference between the capacitances Q1 and Q2, the absolute value (| Q1-Q2 |) of the capacitance error ΔQ can be obtained.

  After calculating the voltage error ΔV and the capacity error ΔQ, the predicted deterioration parameter map generation unit 253 proceeds to step S409 in FIG. 16 and calculates an evaluation function f (ΔV, ΔQ) for the voltage error ΔV and the capacity error ΔQ. As the evaluation function f (ΔV, ΔQ), for example, a value obtained by weighting and adding the voltage error ΔV and the capacitance error ΔQ can be used.

  As shown in step S410 of FIG. 16, the predicted deterioration parameter map generation unit 253 calculates the evaluation function f (ΔV, ΔQ) calculated from the currently set predicted deterioration parameter from the previously set predicted deterioration parameter. A minimum value determination process is performed to determine whether the value is smaller than an evaluation function f (ΔV, ΔQ). Here, if the current evaluation function f (ΔV, ΔQ) is smaller than the previous evaluation function f (ΔV, ΔQ), the current evaluation function f (ΔV, ΔQ) is stored in the memory. If the current evaluation function f (ΔV, ΔQ) is larger than the previous evaluation function f (ΔV, ΔQ), the previous evaluation function f (ΔV, ΔQ) remains stored in the memory.

Predicted deterioration parameter map generator 253 proceeds to step S411 of FIG. 16, is changed predicted positive electrode capacity maintenance rate k _1e, predicted negative electrode capacity maintenance rate k _2e, the predicted negative electrodes discrepancy capacity Delta] Q _se in all search range determine Taka not all of the search range in predictive positive electrode capacity maintenance rate k _1e, it predicted negative electrode capacity maintenance rate k _2e, if changing the predicted negative electrodes discrepancy capacity Delta] Q _se, the process proceeds to step S411. On the other hand, if it has not been changed in all search ranges, the process returns to step S406.

As described above, the predicted deterioration parameter map generation unit 253 performs the steps until the predicted positive electrode capacity maintenance rate k _1e , the predicted negative electrode capacity maintenance rate k _2e , and the predicted positive and negative electrode composition correspondence shift capacity ΔQ _se are changed over the entire search range. Steps S406 to S410 are repeatedly executed. Then, when all searches are completed, the process proceeds to step S411 in FIG. 16 to specify an evaluation function f (ΔV, ΔQ) that is a minimum value, and to predict a predicted open-circuit voltage curve (estimated value) from which this evaluation function (minimum value) is obtained. Value), and a predicted positive electrode capacity retention rate k _1e , a predicted negative electrode capacity retention rate k _2e , and a predicted positive / negative electrode composition correspondence shift capacity ΔQ _se that define a predicted open-circuit voltage curve (estimated value). The deterioration parameter and the predicted open-circuit voltage curve (estimated value) are stored in the memory.

By the series of operations described above, the predicted positive electrode capacity maintenance ratio k _1e and the predicted negative electrode that define the predicted open-circuit voltage curve (estimated value) of the battery 210 when the electric vehicle 100 has traveled the traveling pattern A for the predetermined time and the predetermined number of times. it is possible to identify the capacity maintenance rate k _2e, the predicted negative electrodes discrepancy capacity Delta] Q _se.

As shown in step S304 in FIG. 15, the predicted deterioration parameter map generation unit 253 of the test apparatus 200 determines in step S301 in FIG. 15 that the usage period of the battery 210 elapses, for example, a time corresponding to a period of about 10 years. To S303 are repeatedly executed. Then, as shown in FIG. 20, a plurality of predicted open-circuit voltage curves (estimated values) corresponding to the use period in the case of the traveling pattern A are accumulated in the memory of the test apparatus. For example, the solid line a in FIG. 20 is the curve in the initial state, the broken line b is the curve after one year use, the dotted line c is the curve after three years use, and the two-dot chain line d is the five years use. This is the latter curve, and the dashed-dotted line e is the curve for 10 years of use. Then, according to each curve, the predicted positive electrode capacity maintenance rate k _1e , the predicted negative electrode capacity maintenance rate k _2e , and the predicted positive / negative electrode composition corresponding displacement capacity ΔQ _se after running for 1, 3, 5, 10 years in the running pattern A are shown. Stored. In the initial state, the predicted positive electrode capacity retention rate k _1e and the predicted negative electrode capacity retention rate k _2e are 1, and the predicted positive / negative electrode composition correspondence shift capacity ΔQ _se is 0. As shown in FIG. 20, the full charge capacity of the battery 210 in the initial state is Q _A0 , and the full charge capacity of the battery 210 after traveling for 1, 3, 5, 10 years is Q _A1 , Q _A2 , respectively. Q _A3 and Q _A4 .

After performing steps S301 to S303 for the usage period of the battery 210 as shown in step S304, the predicted deterioration parameter map generation unit 253 proceeds to step S305. As described above, by repeatedly executing steps S301 to S303, the memory stores the initial state and the predicted positive electrode capacity retention rate k after running for 1, 3, 5, 10 years in running pattern A in the memory. _1e, the predicted negative electrode capacity maintenance rate _{k 2e,} is predicted positive and negative electrodes discrepancy capacity Delta] Q _se are stored. Based on these data, the predicted deterioration parameter map generator 253 maintains the predicted positive electrode capacity when traveling in the traveling pattern A, as shown by the solid lines f ₁ , f ₂ , and f ₃ in FIGS. rate _{k 1e,} predicted negative electrode capacity maintenance rate _{k 2e,} and generates the time change curve of the predicted negative electrodes discrepancy capacity Delta] Q _se.

Similarly, the predicted deterioration parameter map generation unit 253 also executes steps S301 to S303 for the running pattern B and the running pattern C for about the use period of the battery 210, proceeds to step S305, and returns to FIG. c) As shown by the dashed lines g ₁ , g ₂ , and g ₃ , the predicted positive electrode capacity retention rate k _1e , the predicted negative electrode capacity retention rate k _2e , and the predicted positive / negative electrode composition corresponding displacement capacity ΔQ when traveling in the traveling pattern B. A time change curve of “ _se” is generated, and as shown by the two-dot chain lines h ₁ , h ₂ , and h ₃ in FIG. 21, the predicted positive electrode capacity retention rate k _1e and the predicted negative electrode capacity retention rate k when the vehicle travels in the traveling pattern C. _2e , a time change curve of the predicted positive / negative electrode composition correspondence displacement capacity ΔQ _se is generated.

  Then, the predicted deterioration parameter map generation unit 253 generates a map (FIGS. 21A to 21C) of a group of time-change curves of the predicted deterioration parameters of each traveling pattern generated in this manner, and stores the map in the memory. .

<Battery control operation>
Next, the operation of the battery control device 40 will be described with reference to FIGS. The predicted deterioration parameter calculation unit 51 of the battery control device 40 repeatedly executes Steps S101 to S104 shown in FIG. 10 at a predetermined cycle, for example, every 0.1 second. As shown in step S101 of FIG. 10, the predicted deterioration parameter calculation unit 51 calculates the voltage value Vb of the battery 10 detected by the voltage sensor 31 shown in FIG. 8, the current value Ib detected by the current sensor 32, and the temperature sensor 33. And the detected temperature Tb. Then, as shown in step S102 of FIG. 10, when it is determined that one trip of the electric vehicle 100 has been completed, the process proceeds to step S103 of FIG. 10, and the traveling pattern of the electric vehicle 100 during the trip period is determined. The trip time as shown in step S104 of FIG. 10 is stored in the memory 42 in addition to the integrated travel time of the travel pattern. For example, when it is determined that the travel on the first trip corresponds to travel pattern A described above, the first trip time is added to the accumulated travel time of travel pattern A, and the travel on the second trip is performed first. When it is determined that the travel time corresponds to the travel pattern B described in (1), the second trip time is added to the integrated travel time of the travel pattern B. The accumulation of the accumulated running time starts immediately after the use of the battery 10 is started, for example, when the ignition switch is first turned on after the completion of the electric vehicle 100 equipped with the battery 10, and thereafter, The running history is accumulated continuously. Note that the end of one trip in step S102 is that the ignition switch is turned off after running for 30 minutes to 1 hour or more at a predetermined speed such as 40 km / hr or more after the ignition switch is turned on. May be a period until the start.

  When the time t1 at which the deterioration of the battery 10 is estimated shown in FIG. 11 is reached, the measuring unit 52 and the deterioration parameter calculating unit 53 start the operation of estimating the deterioration of the battery 10. It should be noted that whether the electric vehicle 100 has traveled a predetermined distance after the end of the previous deterioration estimation, or the predetermined time has elapsed, and the SOC of the battery 10 is low enough to obtain an open-circuit voltage curve by charging, This is executed when the SOC of the battery 10 is in a relaxed state when the SOC of the battery 10 is high enough to obtain an open-circuit voltage curve by discharging. The determination condition that the battery 10 is relaxed is, for example, that the maximum concentration difference of the lithium ion concentration in the active material in the battery model is equal to or less than a predetermined concentration difference, and the absolute value of the battery current is a predetermined value. It is a condition that it is less than or equal to the value. Specifically, when the battery 10 is charged by an external power supply from a state where the SOC of the battery 10 is low, or when the electric vehicle 100 is stopped, the deterioration estimation operation of the battery 10 is executed.

  Hereinafter, as an example, a case will be described in which an external power supply is connected to the external power supply connector 15 shown in FIG. 8 and the deterioration estimation operation of the battery 10 is performed when the battery 10 is charged by the external power supply.

As shown in step S201 in FIG. 11, the measuring unit 52 detects the open voltage OCV of the battery 10 by the voltage sensor 31 at time t1 when the external power supply is connected to the external power supply connector 15 and charging of the battery 10 by the external power supply is started. (T1) is detected. When the current value Ib is flowing, the voltage value Vb, the current value Ib, and the temperature Tb may be detected, and the open circuit voltage OCV (t1) of the battery 10 may be calculated by the following equation (14).

OCV = Vb + Ra × Ib (14)

In the equation (14), Ra is a DC internal resistance of the battery 10. Since the DC internal resistance Ra changes according to the temperature Tb of the battery 10, a map indicating the relationship between the temperature Tb and the DC internal resistance Ra is stored in the memory 42, and the DC internal resistance Ra is determined from the map based on the detected temperature Tb. May be obtained and calculated by equation (14). As shown in FIG. 18, at time t1, the capacity of the battery 10 is Q (t1) (A × h).

In addition, as shown in step S202 of FIG. 11, the measuring unit 52 starts integrating the charging current to the battery 10 at time t1. The current is integrated by multiplying the product of the current value Ib detected by the current sensor 32 and the period Δt at every period Δt (for example, 0.1 seconds) as in the following equation (15).

Integrated current value (A × h) = Σ (Ib × Δt) / 3600 (15)

  As shown in step S203 of FIG. 11, the measuring unit 52 detects the open voltage OCV (t2) of the battery 10 by the voltage sensor 31 at the time t2 when the charging of the battery 10 ends. When the current value Ib is flowing, as described above, the voltage value Vb, the current value Ib, and the temperature Tb are detected, and the open-circuit voltage OCV (t2) of the battery 10 is calculated by Expression (16). May be.

Further, as shown in step S204 of FIG. 11, the measurement unit 52 ends the integration of the current at time t2. As shown in FIG. 18, the capacity of the battery 10 at the time t2 is calculated by adding the integrated current value to the battery capacity Q (t1) at the time t1, as shown in Expression (16). It is.

Q (t2) = Q (t1) + Integrated current value (16)

  Then, as shown in step S205 in FIG. 11, the measuring unit 52 stores an open-circuit voltage curve (actually measured value) as shown by a solid line in FIG.

Degradation parameter calculation part 53, as shown in step S206 of FIG. 11, and a candidate value of the candidate value and the positive and negative electrodes discrepancy capacity Delta] Q _s of the candidate value of positive electrode capacity maintenance rate k ₁ and negative electrode capacity maintenance rate k ₂ Set. Each candidate value may be set to about ten.

Degradation parameter calculation part 53, as shown in step S207 of FIG. 11, the candidate value of positive electrode capacity maintenance rate k ₁ and the candidate value of the negative electrode capacity maintenance rate k ₂ set in step S206 and negative electrodes discrepancy capacity Delta] Q _s above using the the candidate value as described with reference to FIG. 5, an electric potential difference between the negative electrode open-circuit potential U ₂₂ and the positive electrode open-circuit potential U ₁₁ of the battery 10, calculates the open-circuit voltage OCV, by a broken line in FIG. 18 The open-circuit voltage curve (estimated value) shown is calculated.

  The deterioration parameter calculator 53 calculates the voltage error ΔV and the capacitance error ΔQ as shown in step S208 of FIG. The voltage error ΔV and the capacitance error ΔQ are the same as described above.

  After calculating the voltage error ΔV and the capacitance error ΔQ, the deterioration parameter calculation unit 53 proceeds to step S209 in FIG. 11, and performs the evaluation function for the voltage error ΔV and the capacitance error ΔQ in the same manner as described in step S409 in FIG. f (ΔV, ΔQ) is calculated. Then, the deterioration parameter calculation unit 53 determines that the evaluation function f (ΔV, ΔQ) calculated from the currently set deterioration parameter is smaller than the evaluation function f (ΔV, ΔQ) calculated from the previously set deterioration parameter. A minimum value determination process is performed to determine whether or not this is the case. If the current evaluation function f (ΔV, ΔQ) is smaller than the previous evaluation function f (ΔV, ΔQ), the current evaluation function f (ΔV, ΔQ) is stored in the memory 42. If the current evaluation function f (ΔV, ΔQ) is larger than the previous evaluation function f (ΔV, ΔQ), the previous evaluation function f (ΔV, ΔQ) remains stored in the memory 42.

Deterioration parameter calculation unit 53 proceeds to step S210 of FIG. 11, determines whether varied positive electrode capacity maintenance rate k _1, negative electrode capacity maintenance rate k _2, the positive and negative electrodes discrepancy capacity Delta] Q _s in all search range and, all the positive electrode capacity maintenance rate k ₁ in the search _range, the negative electrode capacity maintenance rate k _2, if by changing the positive and negative electrodes discrepancy capacity Delta] Q _s, the flow proceeds to step S211. On the other hand, if it has not been changed in all the search ranges, the process returns to step S206.

Thus, the deterioration parameter calculation unit 53, positive electrode capacity maintenance rate k _1, negative electrode capacity maintenance rate k _2, until it is changed in the entire search range positive and negative electrodes discrepancy capacity Delta] Q _s is, the step S210 from step S206 Execute repeatedly. When all the searches have been completed, the process proceeds to step S211 in FIG. 11, where the evaluation function f (ΔV, ΔQ) that becomes the minimum value is specified, and the open-circuit voltage curve from which this evaluation function (minimum value) is obtained is specified. together, positive electrode capacity maintenance rate k ₁ defining the open-circuit voltage curve (estimated _value), negative electrode capacity maintenance rate k _2, to identify the positive and negative electrodes discrepancy capacity Delta] Q _s, identified open circuit voltage curve (estimated value), the positive electrode capacity maintenance rate _{k 1,} negative electrode capacity maintenance rate _{k 2,} and stores the positive and negative electrodes discrepancy capacity Delta] Q _s in the memory 42.

As shown in step S212, the predicted deterioration parameter calculation unit 51 reads out the accumulated traveling time (traveling history) for each traveling pattern up to time t1 previously stored in the memory 42 and, as shown in step S213, FIG. (a) from the running pattern every shown in (c) predictive positive electrode capacity maintenance rate _{k 1e,} predicted negative electrode capacity maintenance rate _{k 2e,} reads the time variation curve of the predicted negative electrodes discrepancy capacity Delta] Q _se, step S214 of FIG. 12 As shown in (1), weighting is performed based on the integrated time of each running pattern, and a predicted positive electrode capacity maintenance rate k _1f , a predicted negative electrode capacity maintenance rate k _2f , and a predicted positive / negative electrode composition correspondence shift capacity ΔQ _sf at time t1 are calculated. .

As shown in step S215 of FIG. 12, the power limiting unit 54 determines the positive electrode capacity retention rate k ₁ , the negative electrode capacity retention rate k ₂ , the positive / negative electrode composition correspondence displacement capacity ΔQ _s at the time t1 calculated by the deterioration parameter calculation unit 53, And the predicted positive electrode capacity maintenance ratio k _1f , predicted negative electrode capacity maintenance ratio k _2f , and predicted positive / negative electrode composition correspondence shift capacity ΔQ _{sf at} time t1 calculated by the predicted deterioration parameter calculation unit 51. In the following description, the last subscripts 1 to 6 indicate that they correspond to time t1 and time t12 to t16 in FIG.

As shown in FIG. 22 (a), at time t1, since positive electrode capacity maintenance rate k ₁₁ the calculated degradation parameter calculation unit 53 is smaller than the predicted positive electrode capacity maintenance rate k _1f1 calculated predicted deterioration parameter calculation unit 51 ( k ₁₁ <k _1f1 ), and regardless of the other two parameters, the power limiting unit 54 determines YES in step S215 of FIG. 12, that is, the progress of the deterioration of the battery 10 is earlier than the prediction of the predicted deterioration parameter calculation unit 51. Then, the process proceeds to step S216 in FIG. 12, and as shown in FIG. 22B, the chargeable / dischargeable power of the battery 10 (the maximum chargeable power Win, the maximum dischargeable power Wout) is predicted and the deterioration of the battery 10 is predicted. It is limited by the chargeable / dischargeable power (maximum chargeable power Win, maximum dischargeable power Wout) as predicted by the deterioration parameter calculation unit 51. In FIG. 22B, the vertical axis represents the absolute values of the maximum chargeable power Win and the maximum dischargeable power Wout.

Meanwhile, at time t12 in FIG. 22 (a), conversely, the positive electrode capacity maintenance rate k ₁₂ the calculated degradation parameter calculation unit 53 is greater than the expected positive electrode capacity maintenance rate k _1f2 which calculated the predicted deterioration parameter calculation unit 51 If (k ₁₁ ≧ k _1f1 ) and the other two parameters satisfy the conditions of (k ₂₁ ≧ k _2f1 ) and (ΔQ _s1 ≦ ΔQ _sf1 ), NO in step S215 of FIG. It is determined that the progress of deterioration of the battery 10 is slower than the prediction of the predicted deterioration parameter calculating unit 51, and the process proceeds to step S217 in FIG. 12, and the limit of the chargeable / dischargeable power of the battery 10 is released as shown in FIG. The chargeable / dischargeable power (the maximum chargeable power Win, the maximum dischargeable power Wout) is returned to the case where the deterioration of the battery 10 is as predicted by the predicted deterioration parameter calculation unit 51. Hereinafter, the same operation as described above is performed from time t13 to time t16 in FIG.

  As described above, the battery control device 40 of the present embodiment reduces the chargeable / dischargeable power of the battery 10 when the deterioration of the battery 10 progresses earlier than predicted from the traveling history of the electric vehicle 100. Since the restriction is imposed, it is possible to suppress the battery 10 from being deteriorated earlier than expected from the running history of the electric vehicle 100.

In the above-described embodiment, greater than the expected positive electrode capacity maintenance rate k _1f2 of positive electrode capacity maintenance rate k ₁₂ the calculated degradation parameter calculation unit 53 calculates the predicted deterioration parameter calculation unit 51, (k ₁₁ ≧ k _1f1 ), If the other two parameters are also (k ₂₁ ≧ k _2f1 ) or (ΔQ _s1 ≦ ΔQ _sf1 ), it is determined that the progress of the deterioration of the battery 10 is slower than the prediction of the predicted deterioration parameter calculating unit 51, and the battery Release the restriction on the chargeable / dischargeable power of the battery 10 and return to the chargeable / dischargeable power (maximum chargeable power Win, maximum dischargeable power Wout) when the deterioration of the battery 10 is as predicted by the predicted deterioration parameter calculation unit 51. However, depending on the degree of progress of the deterioration, the battery 10 can be charged and discharged when the deterioration of the battery 10 is as predicted by the predicted deterioration parameter calculation unit 51. Force (maximum chargeable power Win, the maximum dischargeable electric power Wout) to set a large rechargeable power than, may be improved drivability.

  In the embodiment described above, the deterioration of the battery 10 is estimated when the battery 10 is charged by the external power supply. For example, the open-circuit voltage OCV is detected while the electric vehicle 100 is stopped, and the deterioration of the battery 10 is estimated. Can also be performed.

  It is difficult to obtain an open-circuit voltage curve (actually measured value) except during external charging. However, when the battery 10, which is a lithium ion secondary battery, is in a relaxed state, it is located on the open-circuit voltage curve (actually measured value). Several open circuit voltages OCV can be measured. Here, when a current flows through the battery 10 or immediately after the current is interrupted, an accurate open-circuit voltage OCV cannot be measured due to a difference in lithium concentration in the active material.

  On the other hand, if the time has elapsed since the power supply to the battery 10 was cut off, the battery is in a relaxed state, and an accurate open circuit voltage OCV can be measured in a state where there is no lithium concentration difference. The case where the battery 10 is in the relaxed state includes, for example, when the electric vehicle 100 is stopped. Therefore, while the electric vehicle 100 is stopped, the open circuit voltage OCV (actually measured value) when the battery 10 has a specific capacity can be obtained.

  If a specific open circuit voltage OCV (actual measurement value) at a specific capacity can be measured, the voltage error ΔV can be obtained by comparing the open circuit voltage OCV (actual measurement value) with an open circuit voltage curve (estimated value). Further, by measuring a plurality of open-circuit voltages OCV (actually measured values), the capacitance error ΔQ can be obtained as described above. Specifically, the capacity Q1 between two points of the open-circuit voltage OCV (actually measured value) is calculated using the open-circuit voltage curve (estimated value). If the integrated current value for obtaining the open-circuit voltage OCV (actually measured value) at two points is measured, the capacity Q2 can be calculated from the integrated current value. Then, if the difference (| Q1-Q2 |) between the capacitance Q1 and the capacitance Q2 is obtained, the absolute value of the capacitance error ΔQ can be obtained.

If the voltage error ΔV and the capacity error ΔQ can be calculated, the minimum value of the evaluation function f (ΔV, ΔQ) is determined in the same manner as described above, and the positive electrode capacity maintenance rate k ₁ and the negative electrode capacity maintenance rate k ₂ are determined. The evaluation function f (ΔV, ΔQ) that is the minimum value is specified by changing the entire search range. The open-circuit voltage curve from which the evaluation function (minimum value) is obtained is specified, and the positive electrode capacity retention ratio k ₁ and the negative electrode capacity retention ratio k ₂ that define the open-circuit voltage curve (estimated value) are specified and specified. The open-circuit voltage curve (estimated value), the positive electrode capacity maintenance ratio k ₁ , and the negative electrode capacity maintenance ratio k ₂ are stored in the memory 42.

10, 210 battery, 11 positive electrode line, 12 negative electrode line, 13 inverter, 14 motor generator, 15 external power connector, 31, 231 voltage sensor, 32, 232 current sensor, 33, 233 temperature sensor, 40 battery control device, 41 CPU , 42 memory, 43 sensor interface, 44, 45 data bus, 51 predicted deterioration parameter calculation unit, 52, 252 measurement unit, 53 deterioration parameter calculation unit, 54 power limiting unit, 60 ECU, 100 electric vehicle, 200 test device, 216 , 217 switch, 220 load, 221 power supply, 251 battery load fluctuation adjustment unit, 253 prediction deterioration parameter map generator, _{k 1} positive electrode capacity maintenance rate, _{k 2} negative electrode capacity maintenance rate, Delta] Q _s positive and negative electrodes discrepancy capacity, Delta] t cycle .

Claims (1)

A positive electrode capacity retention ratio which is a ratio of the deteriorated state positive electrode capacity to the initial state positive electrode capacity,
A negative electrode capacity retention ratio which is a ratio of the negative electrode capacity in the deteriorated state to the negative electrode capacity in the initial state;
Based on the positive / negative electrode composition correspondence shift capacity, which is the amount of change in the battery capacity due to the change from the initial state of the correspondence between the local charge rate on the positive electrode active material surface and the local charge rate on the negative electrode active material surface. A battery control device that estimates deterioration of a lithium ion secondary battery mounted on an electric vehicle, and limits chargeable / dischargeable power of the lithium ion secondary battery according to the deterioration of the lithium ion secondary battery,
A measuring unit that measures an open-circuit voltage curve indicating a change in open-circuit voltage with respect to a change in battery capacity;
Deterioration parameter calculation for calculating the positive electrode capacity retention ratio, the negative electrode capacity retention ratio, and the positive / negative electrode composition correspondence displacement capacity, which specifies an open circuit curve estimated value that substantially matches the open circuit curve measured value measured by the measurement unit. Department and
A predicted deterioration parameter calculation unit that calculates a predicted positive electrode capacity maintenance ratio, a predicted negative electrode capacity maintenance ratio, and a predicted positive and negative electrode composition corresponding displacement capacity from the traveling history of the electric vehicle,
The positive electrode capacity maintenance ratio calculated by the deterioration parameter calculation unit is less than the predicted positive electrode capacity maintenance ratio, or the negative electrode capacity maintenance ratio calculated by the deterioration parameter calculation unit is less than the predicted negative electrode capacity maintenance ratio, or the deterioration parameter When the positive / negative electrode composition corresponding shift capacity calculated by the calculation unit exceeds the predicted positive / negative electrode composition corresponding shift capacity, it is determined that the deterioration of the lithium ion secondary battery is progressing faster than expected, and the lithium ion A power limiting unit that limits the chargeable / dischargeable power of the secondary battery from the chargeable / dischargeable power when the deterioration of the lithium ion secondary battery is as predicted,
The battery control device which has.

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