JP6624458B2 - Battery control system - Google Patents

Description

  The present invention relates to a battery control system for a secondary battery.

  Secondary batteries, such as lithium ion secondary batteries, which are lightweight and provide high energy density, are preferably used as power sources for vehicles. In this type of secondary battery, charge and discharge are performed by transferring charge carriers (for example, lithium in the case of a lithium ion secondary battery) between a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material. Is That is, at the time of charging, the charge carriers are extracted from the positive electrode active material and released as ions into the electrolytic solution (electrolyte). During charging, the charge carriers enter the structure of the negative electrode active material provided on the negative electrode side, where electrons that have passed through an external circuit are obtained from the positive electrode active material and are occluded. As a conventional technique relating to battery control of a secondary battery of this type, Patent Literature 1 is cited.

JP 2011-222343 A

  Patent Literature 1 includes a correlation map between the internal resistance due to aging and the section discharge amount, and converts at least one of the actually acquired section discharge amount and the waste part resistance by converting the correlation map through the correlation map, thereby depositing lithium. A battery system for determining the degree of is described. In this publication, it is assumed that the amount of decrease in the amount of discharge in a battery is the sum of the amount of decrease due to aging and the amount of decrease due to lithium deposition. Based on the knowledge that the discharge is not performed, the extent of the decrease in the discharge amount due to only the aging degradation is estimated based on the value of the internal resistance, and the degree of lithium precipitation is determined by subtracting this from the overall decrease. However, according to the study of the present inventor, since the internal resistance value also increases depending on the degree of lithium precipitation, when the deterioration due to lithium precipitation exceeds a predetermined amount, the estimation accuracy of lithium precipitation deterioration deteriorates, and Judgment may occur. I want to know the degree of lithium precipitation deterioration with high accuracy.

The battery control system for a secondary battery proposed here is a battery control system for a secondary battery including an electrode active material capable of reversibly inserting and extracting charge carriers. The battery control system includes a temperature sensor that detects a temperature of the secondary battery, a current sensor that detects a current flowing into and out of the secondary battery, a voltage sensor that detects a voltage of the secondary battery, and the charge carrier. and a calculation unit for calculating a capacity deterioration rate [Delta] C _y due to precipitation of. The calculating unit measures a resistance increase rate ΔR _current of the secondary battery from a current value detected by the current sensor and a voltage value detected by the voltage sensor; and a battery detected by the temperature sensor. Estimating a resistance increase rate ΔR _x and a capacity deterioration rate ΔC _x after material deterioration due to material wear of the secondary battery based on temperature frequency distribution information including a temperature and an integration time held at each battery temperature; Comparing the measured resistance increase rate ΔR _current with the estimated resistance increase rate after material deterioration ΔR _x ; and if the compared resistance increase rate satisfies the relationship of ΔR _x ≧ ΔR _current , using the first map showing the correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate (ΔC x ₊ ΔC _y), the resistance increase ratio after the estimated material degradation [Delta] R _x and capacity degradation rate [Delta] C _x Al, calculating a capacity deterioration rate [Delta] C _y due to deposition of the charge carriers, wherein the compared resistance increase rate may satisfy the relationship ΔR x _{<ΔR current,} excessive precipitation of the charge carriers occurs decision and, from the first map to a map showing the correlation between resistance increase ratio after material degradation [Delta] R _x and the total capacity deterioration rate (ΔC x ₊ ΔC _y) using a second map which characteristic is different from the from the estimated resistance increase ratio after material degradation [Delta] R _x and capacity degradation rate [Delta] C _x, and is configured to perform a step of calculating a capacity deterioration rate [Delta] C _y due to deposition of the charge carriers. According to such a configuration, in consideration of the resistance increase due to precipitation of the charge carriers, the capacity deterioration rate [Delta] C _y due to precipitation of the charge carriers is calculated, calculation accuracy is improved.

It is a block diagram showing the composition of the power supply system controlled by the battery control device of the secondary battery concerning this embodiment. It is a graph which shows the relationship between aging days and a resistance increase rate. It is a graph which shows the relationship between aging days and a capacity maintenance rate. 5 is a graph showing a relationship between a battery temperature T and a deterioration rate β. 4 is a graph showing a battery temperature frequency distribution. Is a graph showing a correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate after material degradation (ΔC x ₊ ΔC _y). Is a graph showing a correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate after material degradation (ΔC x ₊ ΔC _y). Is a graph showing a correlation between the resistance increasing rate [Delta] R _x and the total capacity deterioration rate after material degradation (ΔC x ₊ ΔC _y). Is a flowchart illustrating an example of a capacity deterioration rate [Delta] C _y calculation processing routine.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, members and parts having the same function are described with the same reference numerals. The dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. In addition, matters other than those specifically mentioned in the present specification, which are necessary for carrying out the present invention (for example, the configuration and manufacturing method of a positive electrode and a negative electrode, general techniques related to the construction of secondary batteries and other batteries) ) Can be understood as a design matter of a person skilled in the art based on the prior art in the field.

  Although not intended to be particularly limited, a preferred embodiment according to the battery control system of the present invention will be described below mainly for the case of controlling a lithium ion secondary battery. In this specification, the term “lithium ion secondary battery” refers to a secondary battery that utilizes lithium ions (Li ions) as electrolyte ions and achieves charge / discharge by transfer of charge accompanying lithium ions between positive and negative electrodes. Say.

  FIG. 1 is a block diagram illustrating a configuration of a battery control system 1 controlled by a control device of a lithium ion secondary battery 10 according to the present embodiment. The control device of the lithium ion secondary battery 10 is suitably used for a vehicle (typically, an automobile, particularly an automobile having an electric motor such as a hybrid automobile, an electric automobile, or a fuel cell automobile).

  The battery control system 1 includes a lithium ion secondary battery 10, a load 20 connected thereto, a temperature sensor (not shown) for detecting the temperature of the secondary battery 10, and a current flowing into and out of the secondary battery 10. The configuration may include a current sensor (not shown) for detecting, a voltage sensor (not shown) for detecting the voltage of the secondary battery, and an electronic control unit (ECU) 30. The ECU 30 is configured to control the operation of the lithium ion secondary battery 10 connected to the load 20, and controls the drive of the load 20 based on predetermined information. The load 20 connected to the lithium ion secondary battery 10 may include a power consuming device (for example, a motor) that consumes the power stored in the battery 10. In addition, the load 20 may include a power supply (charger) that supplies power capable of charging the battery 10.

  The lithium ion secondary battery 10 includes a positive electrode and a negative electrode that face each other with a separator interposed therebetween, and an electrolyte containing lithium ions supplied between the positive and negative electrodes. The positive electrode and the negative electrode contain an electrode active material capable of inserting and extracting lithium ions as charge carriers. When the battery 10 is charged, lithium ions are released from the positive electrode active material, and the lithium ions are occluded in the negative electrode active material through the electrolyte. Conversely, when the battery 10 is discharged, lithium ions occluded in the negative electrode active material are released, and the lithium ions are occluded again in the positive electrode active material through the electrolyte. With the movement of lithium ions between the positive electrode active material and the negative electrode active material, electrons flow from the active material to external terminals. Thereby, discharge is performed to the load 20.

Here, it is known that a lithium ion secondary battery generally deteriorates with use. According to the knowledge of the present inventors, the main causes of the deterioration are considered to be material deterioration due to wear of the material of the secondary battery and deterioration due to deposition of lithium on the negative electrode inside the secondary battery. When deterioration occurs with use, as shown in FIG. 2, the resistance increase rate ΔR _current calculated from the current flowing through the secondary battery and the amount of voltage drop may increase as the number of days elapses. The resistance increase rate ΔR _current includes the resistance increase due to lithium deposition in addition to the resistance increase due to material degradation (resistance increase rate ΔR _x ). Further, as shown in FIG. 3, as the number of days elapses, the capacity maintenance rate may tend to decrease (the capacity deterioration rate tends to increase). The capacity deterioration rate includes the capacity deterioration due to lithium deposition (capacity deterioration rate ΔC _y ) in addition to the capacity deterioration due to material deterioration (capacity deterioration rate ΔC _x ). The inventor determines the degree of lithium deposition (capacity deterioration rate ΔC _y due to lithium deposition) from the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x of the secondary battery without dismantling the secondary battery. I'm considering doing that.

Here, according to the knowledge of the present inventor, the influence of lithium deposition on the resistance increase rate ΔR _current is different between the normal deterioration state in which lithium precipitation is small and the abnormal deterioration state in which lithium is excessively precipitated. Specifically, in a normal deterioration state in which lithium deposition is small, the resistance increase rate ΔR _current does not increase so much even when lithium is deposited, but in an abnormal deterioration state in which lithium is excessively deposited, the resistance increase rate ΔR _current is lithium. Shows an increasing tendency as the precipitates. On the other hand, since the deterioration due to the wear of the material depends on the thermal history, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x due to the material deterioration can be estimated by using the heat load and the deterioration rate given to the battery. Therefore, by comparing the resistance increase rate ΔR _x due to material deterioration estimated from the thermal history with the actually measured resistance increase rate ΔR _current , whether the state of the secondary battery is the normal deterioration state with little lithium precipitation Alternatively, it can be determined whether the battery is in an abnormally deteriorated state in which lithium is excessively precipitated. Then, by using an appropriate correlation map in accordance with the respective deterioration states, the degree of lithium deposition (the capacity deterioration rate due to lithium deposition) can be determined from the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _{x of the} secondary battery. ΔC _y ) can be determined.

From the above findings, in the battery control system 1 disclosed herein, the ECU 30 calculates the resistance increase rate ΔR _{current of the} secondary battery from the current value detected by the current sensor and the voltage value detected by the voltage sensor. _Is measured (ΔR _current measurement step). Further, based on temperature frequency distribution information including the battery temperature detected by the temperature sensor and the accumulated time held at each battery temperature, the resistance increase rate ΔR _x and the capacity deterioration rate after material deterioration due to material wear of the secondary battery are obtained. Estimate ΔC _x (ΔR _x and ΔC _x estimation step). Then, comparing the resistance increase rate [Delta] R _x of the material after deterioration was estimated to have measured the resistance increase rate [Delta] R _current (comparison step). Here, when the compared resistance increase rate satisfies the relationship of ΔR _x ≧ ΔR _current , the ECU 30 determines the first correlation indicating the correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ). using the map, from the estimated resistance increase ratio after material degradation [Delta] R _x and capacity degradation rate [Delta] C _x, and calculates the capacity deterioration rate [Delta] C _y due to deposition of lithium. On the other hand, if the compared resistance increase rate satisfies the relationship of ΔR _x <ΔR _current , the ECU 30 determines that excessive precipitation of lithium has occurred, and uses the second map having characteristics different from those of the first map. From the estimated resistance increase rate ΔR _x after the material deterioration and the capacity deterioration rate ΔC _x , a capacity deterioration rate ΔC _y due to lithium precipitation is calculated (ΔC _y calculation step). Then, it is determined whether or not the value of the calculated capacity deterioration rate ΔC _y exceeds the allowable amount of Li precipitation ΔC _limit . If the capacity deterioration rate ΔC _y exceeds the allowable amount ΔC _limit , the use of the battery is determined. Is stopped (judgment step).

  A typical configuration of the ECU 30 includes at least a ROM (Read Only Memory) storing a program for performing such control, a CPU (Central Processing Unit) capable of executing the program, and temporarily storing data. It includes a random access memory (RAM) and an input / output port (not shown). The above-described current sensor, voltage sensor, and temperature sensor are attached to the secondary battery 10. The ECU 30 receives output signals of the respective sensors via input ports. The ECU 30 acquires information on current values, voltage values, and battery temperatures that enter and exit the secondary battery 10 based on output signals from the sensors. The ECU 30 constitutes a calculation unit of the present embodiment.

<ΔR _current measurement step>
The [Delta] R _current measuring step, ECU 30 is a resistance increase rate [Delta] R _current of the secondary battery and a drop amount [Delta] V _x of the current I _x and the battery voltage flowing in the lithium ion secondary battery 10 during charging and discharging of the load 20 Measure.

<ΔR _x and ΔC _x estimation step>
In the ΔR _x and ΔC _x estimation steps, the ECU 30 determines the resistance increase rate ΔR _x and the capacity degradation after material deterioration in the secondary battery based on the temperature frequency distribution information including the battery temperature and the integration time held at each battery temperature. Estimate the rate ΔC _x . According to the knowledge of the present inventor, since the deterioration due to the wear of the material depends on the thermal history, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC due to the material deterioration can be obtained by using the heat load and the deterioration rate given to the battery. _x can be estimated. Specifically, as shown in the temperature-accelerated Arrhenius model in FIG. 4, the higher the battery temperature, the higher the deterioration rate β. By utilizing this correlation, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after material deterioration can be estimated from the temperature frequency distribution information and the deterioration rate β.

  In this embodiment, as shown in FIG. 4, data indicating the relationship between the battery temperature and the deterioration rate is stored in a ROM in the form of a map, and a predetermined battery temperature (for example, a temperature range) is referred to with reference to this map. ) Is determined. Such data can be obtained by preparing a plurality of secondary batteries, subjecting them to endurance tests under various temperature conditions, and changing the resistance increase rate and the capacity deterioration rate at regular time intervals.

In addition, by accumulating and integrating the integrated time held at each battery temperature and the deterioration rate at each battery temperature, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after material deterioration can be calculated. Here, the accumulated time held at each battery temperature can be obtained by integrating the degree of the secondary battery held at a predetermined battery temperature (for example, a temperature range) for each predetermined battery temperature. The increase in resistance and the deterioration in capacity due to material deterioration may occur even when the battery is not charged or discharged (even if not used). Therefore, the counting of the integrated time is preferably performed both when the battery is used (for example, when the vehicle is running) and when the battery is not used (for example, when the vehicle is stopped). The obtained temperature frequency distribution information may be stored in the ROM in the form of a map or a table as shown in FIG.

<Comparison step>
In the comparison step, the ECU 30 compares the resistance increase rate ΔR _current measured in the ΔR _current measurement step with the resistance increase rate ΔR _x after material deterioration estimated in the ΔR _x and ΔC _x estimation steps.

<ΔC _y calculation step>
In the ΔC _y calculation step, if the resistance increase rate compared in the comparison step satisfies the relationship ΔR _x ≧ ΔR _current , the ECU 30 determines that excessive precipitation of lithium has not occurred, and the estimated resistance increase after material deterioration. based on the rate [Delta] R _x and capacity degradation rate [Delta] C _x, and calculates the capacity deterioration rate [Delta] C _y due to deposition of lithium. Specifically, as shown in FIG. 6, data showing the correlation between the resistance increase rate ΔR _x after the material degradation and the total capacity degradation rate (ΔC _x + ΔC _y ) under the condition that the lithium is not excessively precipitated. Is obtained in advance by a preliminary experiment or the like, and stored in the ROM in the form of a first map (Line 1). Then, with reference to the first map, a total capacity deterioration rate (ΔC _x + ΔC _y ) corresponding to the estimated resistance increase rate ΔR _x after material deterioration is estimated, and the estimated total capacity deterioration rate (ΔC _x + ΔC _y). ) from by subtracting the capacity deterioration rate [Delta] C _x after material degradation, to calculate the capacity degradation rate [Delta] C _y due to deposition of lithium.

Further, the [Delta] C _y calculation step, ECU 30, when compared to the resistance increase rate in comparison step satisfies the relationship ΔR x _{<ΔR current,} determines that the excessive deposition of lithium occurs, the first map and the properties by using different second map on the basis of the estimated resistance increase ratio after material degradation [Delta] R _x and capacity degradation rate [Delta] C _x, and calculates the capacity deterioration rate [Delta] C _y due to deposition of lithium. Specifically, as shown in FIG. 7, data showing the correlation between the resistance increase rate ΔR _x after the material degradation and the total capacity degradation rate (ΔC _x + ΔC _y ) under the condition where excessive precipitation of lithium occurs. Is obtained in advance by a preliminary experiment or the like and stored in the ROM in the form of a second map (Line 2). In this embodiment, Line2 second map, the total capacity deterioration rate corresponding to the resistance increase rate [Delta] R _x after material degradation (ΔC _x + ΔC _y) is shifted to larger (i.e. the right side than the Line1 of the first map ) Is set as follows. Then, referring to the second map, a total capacity deterioration rate (ΔC _x + ΔC _y ) corresponding to the estimated resistance increase rate ΔR _x after the material deterioration is estimated, and the estimated total capacity deterioration rate (ΔC _x + ΔC _y). ) from by subtracting the capacity deterioration rate [Delta] C _x after material degradation, to calculate the capacity degradation rate [Delta] C _y due to deposition of lithium.

Here, even if excessive deposition of lithium occurs (that is, ΔR _x <ΔR _current ), an attempt is made to calculate the capacity deterioration rate ΔC _y caused by the deposition of lithium using the first map, as shown in FIG. since, as shown in, the capacity deterioration rate [Delta] C _y is calculated actually less than, the capacity deterioration rate [Delta] C _y despite exceeds Li precipitated tolerance [Delta] C _limit, it is determined that the still available batteries there is a possibility. In contrast, by calculating the [Delta] R _current and [Delta] R _x from the magnitude relationship selects the second map capacity degradation rate [Delta] C _y of appropriately determine the capacity deterioration rate [Delta] C _y exceeds the allowable amount [Delta] C _limit The use of the battery can be reliably stopped.

<Judgment step>
In the determination step, the ECU 30 determines whether the value of the capacity deterioration rate ΔC _y calculated in the ΔC _y calculation step exceeds the allowable amount of Li precipitation ΔC _limit , and determines whether the capacity deterioration rate ΔC _y exceeds the allowable amount ΔC _limit . If so, stop using the battery. On the other hand, when the capacity deterioration rate [Delta] C _y does not exceed the allowable amount [Delta] C _limit to continue using the battery.

The operation of the battery control system 1 configured as described above will be described. Figure 9 is a flow chart showing an example of the capacity deterioration rate [Delta] C _y calculation processing routine executed by the battery control system 1 of the ECU30 in the present embodiment. This routine is executed, for example, immediately after the secondary battery is mounted on the vehicle.

When capacity deterioration rate [Delta] C _y calculation process shown in FIG. 9 is executed, CPU of ECU30, first, the lithium ion secondary battery (cell) 10 of the control target, the current I _x and the battery voltage across the secondary battery and a drop amount [Delta] V _x to measure the resistance increase rate [Delta] R _current of the secondary battery (step S10). Also, temperature frequency distribution information including the battery temperature and the accumulated time held at each battery temperature is obtained, and the secondary battery is referred to by referring to data indicating the relationship between the battery temperature and the deterioration rate stored in the ROM. Then, the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after the material deterioration due to the abrasion of the material are estimated (step S20).

Next, in step S30, the ECU 30 compares the resistance increase rate ΔR _current measured in step S10 with the aged deterioration rate ΔR _x estimated in step S20. If the compared resistance increase rates satisfy the relationship of ΔR _x ≧ ΔR _current (Yes), it is determined that excessive precipitation of lithium has not occurred, and the process proceeds to step S40. In step S40, the ECU 30 estimates using the first map (Line1) indicating the correlation between the resistance increase rate ΔR _x after the material deterioration stored in the ROM and the total capacity deterioration rate (ΔC _x + ΔC _y ). From the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after the material deterioration, the capacity deterioration rate ΔC _y due to the precipitation of lithium is calculated. On the other hand, when the compared resistance increase rates do not satisfy the relationship of ΔR _x ≧ ΔR _current (No), it is determined that excessive precipitation of lithium has occurred, and the process proceeds to step S50. In step S50, the ECU 30 estimates using the second map (Line2) indicating the correlation between the resistance increase rate ΔR _x after the material deterioration stored in the ROM and the total capacity deterioration rate (ΔC _x + ΔC _y ). From the resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after the material deterioration, the capacity deterioration rate ΔC _y due to the precipitation of lithium is calculated.

At step S60, ECU 30 determines whether the capacity degradation rate [Delta] C _y due to deposition of lithium calculated above is greater than the deposition of Li tolerance [Delta] C _limit (i.e. ΔC _y> ΔC _limit). If the capacity deterioration rate [Delta] C _y exceeds the allowable amount ΔC _limit (Yes), the process proceeds to step S70, the stop using the battery. On the other hand, when the capacity deterioration rate [Delta] C _y does not exceed the allowable amount ΔC _limit (No), the process proceeds to step S80, and continues the use of the battery.

According to the above embodiment, in consideration of the resistance increase due to lithium precipitation is charge carriers, the capacity deterioration rate [Delta] C _y due to deposition of lithium is calculated, calculation accuracy is improved. Then, based on the calculated capacity degradation rate [Delta] C _y, it can be a use permission determination of the battery without erroneous determination.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1 Battery control system 10 Lithium ion secondary battery 20 Load 30 ECU

Claims (1)

A battery control system for a secondary battery including an electrode active material capable of reversibly occluding and releasing charge carriers,
A temperature sensor for detecting a temperature of the secondary battery,
A current sensor for detecting a current flowing into and out of the secondary battery,
A voltage sensor for detecting a voltage of the secondary battery,
A calculation unit for calculating a capacity deterioration rate ΔC _y due to the deposition of the charge carriers,
The calculation unit,
Measuring a resistance increase rate ΔR _current of the secondary battery from a current value detected by the current sensor and a voltage value detected by the voltage sensor;
Based on temperature frequency distribution information including the battery temperature detected by the temperature sensor and the integrated time held at each battery temperature, the resistance increase rate ΔR _x and the capacity deterioration rate after material deterioration due to material wear of the secondary battery Estimating ΔC _x ;
Comparing the measured resistance increase rate ΔR _current with the estimated resistance increase rate after material deterioration ΔR _x ;
When the compared resistance increase rate satisfies the relationship of ΔR _x ≧ ΔR _current , using a first map showing a correlation between the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ), Calculating a capacity deterioration rate ΔC _y due to the deposition of the charge carriers from the estimated resistance increase rate ΔR _x and the capacity deterioration rate ΔC _x after the material deterioration;
If the compared resistance increase rate satisfies the relationship of ΔR _x <ΔR _current , it is determined that excessive deposition of the charge carrier has occurred, and the resistance increase rate ΔR _x after material deterioration and the total capacity deterioration rate (ΔC _x + ΔC _y ) using a second map having different characteristics from the first map, based on the estimated resistance increase rate ΔR _x and the capacity degradation rate ΔC _x after the material deterioration. It is configured to perform the steps of calculating a capacity deterioration rate [Delta] C _y due to precipitation of the carrier, the battery control system.

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