JP2021069142A - Deterioration determination device of lithium ion battery - Google Patents

Abstract

To secure a longer usage time with a large charge/discharge current in addition to making it possible to accurately determine the deterioration.SOLUTION: A limit integrated current value as a limit value in which a lithium ion battery 2 does not cause permanent deterioration is set so as to increase as the temperature of the battery 2 increases and decrease as the actual charge/discharge current value increases (in a map shown in Fig. 5). A deterioration evaluation value N is calculated every predetermined unit time (for example, 10 seconds) on the basis of the average charge/discharge current value and the limit integrated current value obtained from the map. When the deterioration evaluation value N falls below a predetermined threshold value (for example, 0) (when reaching the limit integrated current value), the maximum charge/discharge current value of the battery 2 is limited to the minimum value (for example, 40A) or less.SELECTED DRAWING: Figure 5

Description

The present invention relates to a deterioration determination device for a lithium ion battery.

The lithium ion battery is provided with a positive electrode and a negative electrode, and uses an electrolytic solution obtained by dissolving a lithium salt in a solvent as a supporting electrolyte. Lithium-ion batteries are widely used, for example, as electric vehicles, hybrid vehicles, and storage batteries in factories and homes.

Lithium-ion batteries have better input / output performance when charged and discharged at a large current (used in a high rate cycle) than when charged and discharged at a low current. Therefore, when using a lithium-ion battery, it is desired to charge and discharge with a maximum current as much as possible. In particular, when a lithium ion battery is used for supplying power to a drive motor in an automobile with an engine, it is strongly desired to use it at a large current in order to improve fuel efficiency.

On the other hand, a lithium-ion battery is temporarily deteriorated with use (temporary increase in charge / discharge resistance value), but the temporary deterioration is restored by suspending without charging / discharging. Is. In addition, lithium-ion batteries deteriorate over time, but if they are discharged at a large current for a long time, permanent deterioration that does not recover even if charging and discharging are stopped occurs, which is called high-rate cycle deterioration. It will end up. Permanent deterioration should be avoided as much as possible because the degree of deterioration is larger than that of aging deterioration.

Patent Document 1 discloses a method for determining deterioration of a lithium ion battery based on a discharge time at a large current and a bias in ion concentration in order to prevent high rate cycle deterioration in the lithium ion battery. .. Patent Document 1 also discloses that the longer the discharge time at a large current is, the more easily the deterioration is, and the larger the bias of the ion concentration is, the more easily the deterioration is.

Conventionally, in order to prevent permanent deterioration, a threshold value called the limit integrated current value (limit integrated current amount) is set, and when the integrated value of the discharge current exceeds the threshold value, the discharge current of the lithium ion battery is set to a predetermined value or less. It is limited to a small current value. When setting the limit integrated current value, the limit integrated current value (threshold value) was set on the premise of room temperature (around 25 ° C.).

However, limiting the discharge current of a lithium-ion battery to a small current value is not preferable, for example, in an electric vehicle or a hybrid vehicle, because it leads to deterioration of acceleration and fuel consumption (electricity cost). is there.

It is conceivable to increase the capacity of the lithium-ion battery so that the limit integrated current value is not reached at an early stage. However, increasing the capacity of the lithium-ion battery not only significantly increases the cost, but also increases the weight of electric vehicles and hybrid vehicles, which deteriorates acceleration and fuel efficiency (electricity cost). It will end up.

JP-A-2009-123435

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to enable more accurate deterioration determination and to secure a longer usage time with a large charge / discharge current. The purpose of the present invention is to provide a battery deterioration determination device.

The present invention has been made based on the finding that the higher the temperature of the lithium ion battery, the larger the limit integrated current value, as a result of experimentally verifying the relationship between the temperature of the lithium ion battery and the limit integrated current value. It is a thing. That is, the threshold used for limiting the maximum charge / discharge current value of the lithium-ion battery is set so as to increase as the temperature of the lithium-ion battery increases, so that this threshold can be set accurately to obtain the lithium-ion battery. By improving the accuracy of deterioration determination, it is possible to secure a longer time until the maximum charge / discharge current value is limited.

Specifically, in the present invention, the following first solution method is adopted.

A lithium-ion battery having a positive electrode and a negative electrode and using an electrolytic solution obtained by dissolving a lithium salt in a solvent as a supporting electrolyte.
A charge / discharge control unit that controls the charge / discharge of the lithium ion battery, a deterioration determination unit that determines the deterioration of the lithium ion battery, an actual integrated current value calculation unit that calculates the charge / discharge current integrated value in a predetermined period, and the like. A threshold setting unit for setting a higher threshold for the integrated charge / discharge current value as the temperature of the lithium ion battery is higher, and a control device having the same are provided.
The deterioration determination unit determines that the lithium ion battery has deteriorated when the actual integrated current value is equal to or greater than the threshold value.
When the charge / discharge control unit determines that the lithium ion battery is deteriorated by the deterioration determination unit, the charge / discharge control unit limits the charge / discharge current of the lithium ion battery to a predetermined value or less, while the lithium ion battery deteriorates. When it is not determined to be, the charge / discharge current of the lithium ion battery is not limited to the predetermined value or less.
(Corresponding to claim 1).

According to the first solution method, the threshold value can be set accurately and the deterioration determination of the lithium ion battery can be accurately performed. This makes it possible to prevent or suppress a situation in which the maximum charge / discharge current value of the lithium ion battery is unnecessarily limited. In particular, if the capacity of the lithium ion battery is the same, it is possible to extend the period during which charging / discharging can be performed with a large current.

A preferred embodiment based on the first solution method is as follows.

The threshold value can be set so that the higher the temperature of the lithium ion battery, the larger the increase allowance (corresponding to claim 2). In this case, the threshold value can be set accurately in response to the characteristic that the higher the temperature of the lithium ion battery, the larger the increase allowance of the limit integrated current value.

The threshold value can be set lower as the charge / discharge current value of the lithium ion battery increases (corresponding to claim 3). In this case, the threshold value can be set accurately in response to the characteristic that the larger the charge / discharge current of the lithium ion battery, the smaller the limit integrated current value.

The control device may have a temperature rise control unit that controls the temperature rise to raise the temperature of the lithium ion battery when the temperature of the lithium ion battery is equal to or lower than a predetermined temperature. Corresponding to claim 4). In this case, by raising the temperature of the lithium ion battery to an appropriate temperature at which the limit integrated current value becomes sufficiently large, it is preferable to secure a longer usage time with a large charge / discharge current.

The control device can make the current limit of the lithium ion battery stepwise implemented when the actual integrated current value is less than the threshold value (corresponding to claim 5). This is preferable in preventing a situation in which the maximum charge / discharge current value of the lithium ion battery changes to a small current value at once. In particular, when a lithium-ion battery is used to supply power to a vehicle drive motor, the maximum driving force of the drive motor suddenly decreases, which prevents the vehicle driver from feeling uncomfortable. It will be preferable.

The control device may further include a threshold correction unit that increases the threshold value according to the pause time during which the lithium ion battery is paused (corresponding to claim 6). In this case, the threshold value can be set accurately in response to the recovery of the temporary deterioration of the lithium ion battery during the pause time.

In order to achieve the above object, the following second solution method is adopted in the present invention.

A lithium-ion battery having a positive electrode and a negative electrode and using an electrolytic solution obtained by dissolving a lithium salt in a solvent as a supporting electrolyte.
A control device having a charge / discharge control unit that controls charging / discharging of the lithium ion battery and a deterioration determination unit that determines deterioration of the lithium ion battery.
With
The control device stores a map in which the limit integrated current value is set so as to decrease as the charge / discharge current value of the lithium ion battery increases and increase as the temperature of the lithium ion battery increases. Have,
The control device has an average charge / discharge current value calculation unit that calculates an average charge / discharge current value of the lithium ion battery at predetermined unit times.
The control device collates the calculated average discharge current value and the temperature of the lithium ion battery with the map for each predetermined unit time, and determines the limit integrated current value for each predetermined unit time. It has an integrated current value determination unit and
The control device has a deterioration evaluation value calculation unit that calculates a deterioration evaluation value based on the average charge / discharge current value and the limit integrated current value for each predetermined unit time.
The deterioration determination unit determines that the lithium ion battery is deteriorated when the deterioration evaluation value calculated by the deterioration evaluation value calculation unit becomes equal to or less than a predetermined threshold value.
When the deterioration determination unit determines that the lithium ion battery has deteriorated, the charge / discharge control unit limits the maximum charge / discharge current of the lithium ion battery to a predetermined value or less, while the lithium ion battery deteriorates. When it is not determined that the lithium ion battery is in use, the maximum charge / discharge current of the lithium ion battery is not limited to the predetermined value or less.
(Corresponding to claim 7).

According to the second solution method described above, it is possible to obtain the same effect as that of claim 1 by using the deterioration evaluation value indicating the degree of approach to the limit integrated current value. In particular, the control takes into consideration the temperature of the lithium ion battery and the actual charge / discharge current at predetermined unit times, which is preferable in appropriately responding to changes in temperature and discharge current.

A preferred embodiment based on the second solution method is as follows.

When the deterioration determination unit does not determine that the lithium ion battery has deteriorated, the charge / discharge control unit steps the maximum charge / discharge current of the lithium ion battery as the deterioration evaluation value decreases. It can be controlled so as to be small or continuously variable (corresponding to claim 8). In this case, it is possible to obtain the same effect as that of claim 5.

According to the present invention, it is possible to make the deterioration determination more accurate and to secure a longer usage time with a large charge / discharge current.

The figure which shows the drive system example and the control system example of the vehicle to which this invention is applied. The figure which shows the setting example of the operating area of an engine and a motor. The figure which shows the structure of the lithium ion battery in a simplified manner. The figure which shows an example of aged deterioration and permanent deterioration of a lithium ion battery. The figure which shows the map for determining the limit integrated current value based on the temperature and the discharge current value of a lithium ion battery. The figure which shows the situation which the deterioration evaluation value changes according to the pause time which stopped charge / discharge. The flowchart which shows the control example of this invention. The flowchart which shows the continuation of FIG. The figure which shows the setting example of the maximum discharge current value according to the deterioration evaluation value. The figure which shows the 2nd Embodiment of this invention and corresponds to FIG. The figure which shows the comparative example with this invention and corresponds to FIG.

First, the drive system of the vehicle (automobile) V to which the present invention is applied will be described with reference to FIG. In the figure, 1 is an engine (internal combustion engine) and 2 is a motor. Reference numeral 3 denotes a driving wheel that is driven by the engine 1 and also by the motor 2 as appropriate. The engine 1 is, for example, a gasoline engine or a diesel engine. The motor 2 functions not only for driving the drive wheels 3 but also as a generator during deceleration.

In the figure, reference numeral 10 denotes a lithium ion battery (in the following description, it may be simply referred to as a "battery"). The motor 2 is driven by the power supplied from the battery 10, and the electric power generated by the motor 2 is charged to the battery 2. In the embodiment, the battery 2 has an output voltage of 48 V, a maximum discharge current value of 80 A, and a capacity of 0.38 KWh, but is not limited thereto.

The output of the engine 1 is sequentially transmitted to the left and right drive wheels 3 via the first clutch 4, the motor 2, the second clutch 5, the transmission (transmission) 6, and the differential gear 7. When the drive wheels 3 are driven by the engine 1, the first clutch 4 and the second clutch 5 are connected, respectively. When the drive wheels 3 are driven by the motor 2, power is supplied from the battery 10 to the motor 2.

FIG. 2 shows an example of setting the operating regions of the engine 1 and the motor 2. In the example of FIG. 2, the engine 1 is always operated (driven) when the vehicle V is traveling. Further, the motor 2 appropriately assists the driving of the engine 1.

The drive area of the drive wheel 3 by the motor 2 is as follows. First, the motor 2 is driven in the first region R1 where the operating efficiency of the engine 1 is low (for example, 1500 rpm or less) and the load is low (the accelerator opening is, for example, 20% or less). ..

Second, the motor 2 is operated in a high load region (accelerator opening degree is, for example, 80% opening degree or more). Third, in the regions R1 other than the regions R1 and R2, the drive wheels 3 are basically driven only by the engine 1, but the motor 2 is driven during acceleration.

When the vehicle V is decelerated, the second clutch 5 is engaged, but the first clutch 4 is disconnected (disengaged). Further, during deceleration, the motor 2 is driven from the drive wheel 3 side, so that the motor 2 functions as a generator and the generated electric power is charged to the battery 2 (regeneration). Both clutches 4 and 5 are disconnected when idle or when the vehicle is stopped.

Next, a structural example of the battery 2 will be described with reference to FIG.

The battery 2 shown in FIG. 3 includes a positive electrode, a negative electrode, and a separator that insulates the positive electrode and the negative electrode, and uses a non-aqueous electrolyte solution in which a main electrolyte and a sub-electrolyte are dissolved in a non-aqueous solvent as supporting electrolytes.

The positive electrode is formed by mixing a positive electrode active material and an auxiliary agent (a binder and a conductive auxiliary agent) and applying them to a current collector. Aluminum foil is mentioned as a preferable current collector.

Preferred positive electrode active materials include composite metal oxides with lithium containing one or more selected from the group consisting of cobalt, manganese and nickel, phosphoric acid-based lithium compounds, and silicic acid-based lithium compounds. In particular, it is preferable to use lithium phosphate. These positive electrode active materials can be used alone or in combination of two or more.

Preferred phosphoric acid-based lithium compounds include, for example, LiMPO4 (M = transition metal Fe, Co, Ni, Mn, etc.) and Li2MPO4F (M = transition metal Fe, Co, Ni, Mn, etc.) having an olivine crystal structure. Of these, lithium iron phosphate LiFePO4 is preferable. Examples of the silicate-based lithium compound include Li2MSiO4 (M = transition metal Fe, Co, Ni, Mn, etc.).

As the binder, polyvinylidene fluoride (PVdF) can be preferably adopted. As the conductive auxiliary agent, carbon black, acetylene black, carbon nanofiber (CNF) and the like can be adopted.

The negative electrode is formed by mixing a negative electrode active material and an auxiliary agent (a binder and a conductive auxiliary agent) and applying the negative electrode to a current collector. A copper foil is mentioned as a preferable current collector.

As the negative electrode active material, it is preferable to use a graphite-based carbon material, that is, artificial graphite or natural graphite. The graphitized carbon material preferably has a low degree of graphitization from the viewpoint of improving the storage and release capacity of Li ions. Artificial graphite and hard carbon having a low degree of graphitization are preferable as the negative electrode active material. Since natural graphite having high crystallinity deteriorates quickly, it is preferable to use it in combination with surface-treated natural graphite or artificial graphite.

As the binder, styrene-butadiene rubber (SBR), styrene-butadiene rubber in combination with carboxymethyl cellulose as a thickener (SBR-CMC), PVdF, an imide-based binder and the like can be preferably adopted. .. As the conductive auxiliary agent, carbon black, acetylene black, carbon nanofiber CNF and the like can be preferably adopted.

The separator is not particularly limited, but a monolayer or laminated microporous film of polyolefin such as polypropylene or polyethylene, a woven fabric, a non-woven fabric, or the like can be adopted.

The non-aqueous electrolyte solution is obtained by dissolving a lithium salt (supporting electrolyte) in a non-aqueous solvent, and an additive is added as needed.

The type of non-aqueous solvent is not particularly limited, and is a cyclic carbonate ester such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl. Examples thereof include chain carbonate esters such as carbonate (DMC) and cyclic carboxylic acid esters such as γ-butyrolactone (GBL) and γ-valerolactone (GVL). As the non-aqueous solvent, one type may be used alone, or two or more types may be used in combination.

Additives for the non-aqueous solvent include a wettability improving solvent and a SEI forming solvent for improving the wettability of the electrolytic solution with respect to the separator.

Examples of the wettability improving solvent include dibutyl carbonate (DBC), methylbutyl carbonate (MBC), ethylbutyl carbonate (EBC) and the like. The amount of the wettability improving solvent added is preferably about 3% by mass or more and 10% by mass or less of the non-aqueous solvent.

Examples of the SEI-forming solvent include vinylene carbonate (VC), methylvinylene carbonate (MVC), ethylvinylene carbonate (EVC), fluorovinylene carbonate (FVC), vinylethylene carbonate (VEC), ethynylethylene carbonate (EEC), and ethylenesulfite. (ES), fluoroethylene carbonate (FEC) and the like. These SEI-forming solvents can be used alone or in combination of two or more. The amount of the SEI-forming solvent added is preferably about 0.5% by mass or more and 5% by mass or less of the non-aqueous solvent.

Preferred lithium salts include LiPF6, LiPO2F2, LiBF4, LiN (SO2F) 2, LiN (SO2CF3) 2, LiN (SO2C2F5) 2 and the like. The lithium salt may be used alone or in combination of two or more.

The concentration of the lithium salt in the non-aqueous electrolytic solution may be, for example, 0.5 M or more and 2.0 M or less.

In this embodiment, LiPF6 is adopted as the main electrolyte, LiPO2F2 is adopted as the sub-electrolyte, and a mixed solvent of propylene carbonate (PC) and γ-butyrolactone (GBL) is used as the solvent (PC: GBL = 80: 20 (volume ratio). )) Is adopted.

The battery 2 is provided with a temperature controller 20 for adjusting the temperature thereof. The temperature controller 20 has a cooler 21 and a heater 22. The cooler 21 is operated when the temperature of the battery 10 reaches a predetermined temperature (for example, 50 ° C. C) to prevent the temperature of the battery 10 from exceeding the allowable upper limit temperature (60 ° C. in the embodiment). The cooler 21 is, for example, an air-cooled type using conditioned air, but the present invention is not limited to this, and an appropriate one can be adopted.

The heater 22 raises the temperature of the battery 10 so that the temperature of the battery 10 is, for example, about 45 ° C. when the temperature of the battery 10 is low, for example, about room temperature. As will be described later, this temperature rise increases the limit integrated current value. As the heater 22, for example, an electric heater can be used, but the heater 22 is not limited to this. For example, when the cooling water temperature of the engine 1 is higher than a predetermined temperature, this cooling water can be used for raising the temperature.

FIG. 4 shows the state of deterioration of the battery 10, and shows the resistance change (change in resistance increase) after 10 years with the magnitude of the charge / discharge current (effective current) of the battery 10 as a parameter. In the figure, the normal deterioration shown by the broken line is called aged deterioration, and the resistance value increases slowly even if the discharge current is large.

On the other hand, in FIG. Permanent deterioration shown by a solid line occurs when charging / discharging at a large current equal to or higher than a predetermined current value is continued for a long time, and is also called high-rate cycle deterioration. The resistance value of the battery 10 is temporarily increased when discharging is continued, but the resistance value is lowered (recovered) by suspending charging / discharging, but in the case of permanent deterioration, charging / discharging is suspended. However, the resistance value is not restored. Therefore, long-term charging / discharging with a large current that causes permanent deterioration should be avoided.

When the charge / discharge current value (effective current value) is smaller than a predetermined value (for example, about 40 A), permanent deterioration is unlikely to occur. Therefore, although the charge / discharge current value can be limited to a small current value equal to or less than the above-mentioned predetermined value, permanent deterioration can be surely prevented, but in this case, since a large current cannot be obtained, the capacity of the battery 10 is increased. It is necessary to make it unfavorable.

FIG. 5 shows the relationship between the temperature of the battery 10, the charge / discharge current value, and the limit integrated current value, and is experimentally obtained. The limit integrated current value does not cause permanent deterioration even if it is charged and discharged with a large current if it is used in the range below this.

As can be understood from FIG. 5, when charging / discharging is performed with a large current, the limit integrated current value increases as the temperature of the battery 10 increases. For example, when the charge / discharge current value is 80 A and the temperature of the battery 10 is around 45 ° C., the limit integrated current amount becomes extremely large, such as 1000 / Ah. On the other hand, when the charge / discharge current value is 80 A and the temperature of the battery 10 is around 25 ° C. near room temperature, the limit integrated current amount becomes extremely small, such as 230 / Ah. As described above, the limit integrated current value differs greatly depending on the temperature of the battery 10, and the higher the temperature of the battery 10, the larger the increase allowance of the limit integrated current value.

From the above, by maintaining the temperature of the battery 10 at a high temperature, it is possible to sufficiently lengthen the charge / discharge time at a large current without increasing the capacity of the battery 10.

The limit integrated current value serves as a threshold value for determining whether or not to limit the charge / discharge current value of the battery 10 to a predetermined small current value or less. That is, in order to prevent permanent deterioration when the actual integrated current value obtained by multiplying the actual charge / discharge current value of the battery 10 and the charge / discharge time becomes equal to or greater than the limit integrated current value, the battery 10 is used. The charge / discharge current value of is limited to a small current value (for example, 40 A) of a predetermined value or less. Further, when the actual integrated current value is less than the limit integrated current value, there is still a margin before permanent deterioration, and charging / discharging with a large current is permitted.

The limit integrated current value can be directly used as a threshold value for limiting the charge / discharge current value of the battery 10 to a small current value. However, in consideration of the change in the temperature of the battery 10, in the present embodiment, the deterioration evaluation value N (N ≦ 1.0) related to the limit integrated current value is used to evaluate the deterioration every predetermined unit time. The value N is updated (subtracted).

Specifically, the average charge / discharge current value of the battery 10 is calculated every short predetermined unit time (for example, 10 seconds), and the deterioration evaluation value N is calculated based on the ratio of the average discharge current value to the limit integrated current value. By subtracting, the limit integrated current value is reached when the deterioration evaluation value N becomes 0, so that the charge / discharge current value of the battery 10 is limited to a small current value equal to or less than a predetermined value.

When the battery 10 is sufficiently suspended, the initial value of the deterioration evaluation value N is set to 1. Further, the discharge current value is measured every predetermined sampling time (for example, 0.1 to 1 second), and becomes the average value of the measured charge / discharge current values every predetermined unit time (for example, 10 seconds). The average discharge current value I is calculated. Then, the deterioration evaluation value N is updated based on the following mathematical formula. In this formula, 10s (10 seconds) is the predetermined unit time, and 3600s (3600 seconds) corresponds to 1 hour (h).

In the above formula, for example, when the temperature of the battery 10 is about 45 ° C. and the discharge current value of the battery 10 is 80 A, the limit integrated current value is 1000 Ah, and the value on the right side in the formula is 0.0002222. .. That is, when the battery is charged and discharged at 80 A for 10 seconds, the deterioration evaluation value is updated as a value that is 0.0002222 smaller than the previous value. Since such a deterioration evaluation value is calculated every short predetermined unit time, it is calculated as a value that accurately corresponds to a change in the discharge current value of the battery 10 and a change in temperature (the limit of the battery 10). Accurately calculate the degree of deterioration toward the integrated current value).

The battery 10 is restored in the deterioration recovery direction by suspending charging / discharging. FIG. 6 shows the correspondence between the pause time during which charging / discharging is suspended and the recovery tendency of the deterioration evaluation value N. FIG. 6 is the result of the experiment. If the pause time is 11 hours or more from the time when the deterioration evaluation value is 0, the deterioration evaluation value N is restored to 1.0 (complete restoration).

In FIG. 6, it is assumed that the deterioration evaluation value N at the end of the previous running is the α point in the figure (deterioration evaluation value is 0.65). When running is started again (charging / discharging of the battery 10 is started) at β time, which is approximately 7 hours after α time, the initial value of the deterioration evaluation value N is 0.95 in comparison with the characteristics shown in FIG. Will be done.

As shown in FIG. 1, a controller U as a control device is provided for charge / discharge amount control based on the deterioration evaluation value N. The controller U is configured by using a microcomputer, and has a CPU, ROM, RAM memory (storage means), an input / output interface, and the like. The characteristics shown in FIGS. 5 and 6 and the above-mentioned mathematical formulas are stored in ROM in advance.

Signals from various switches or sensors S1 to S4 are input to the controller U. S1 is an ignition switch. S2 is a temperature sensor that detects the temperature of the battery 10. S3 is a voltage sensor that detects the voltage of the battery 10. S4 is a current sensor that detects the charge / discharge current value of the battery 10. The controller U controls the degree of deterioration of the battery, charges / discharges (particularly, the magnitude of the discharge current value), and controls the temperature controller 20 (temperature control of the battery 10). Further, the controller U acquires the detected current value by the current sensor S4 every predetermined sampling period (for example, 0.1 to 1 second), and obtains the average current every predetermined unit time (10 seconds in the embodiment) described above. Calculate the value I.

An example of control by the controller U will be described with reference to the flowcharts shown in FIGS. 7 and 8. The latest value of the deterioration evaluation value N is stored at the end of the running, and the stored deterioration evaluation value N is appropriately used for setting the initial value when the next running is started. Further, in the following description, Q indicates a step.

The control shown in FIGS. 7 and 8 is started from the time when the engine 1 is started (when the ignition switch S1 is turned on). First, in Q1, the deterioration evaluation value N stored in the previous run is read out. In Q2, it is determined whether or not a predetermined time (for example, 11 hours) or more has passed since the last run was completed. When the determination in Q2 is YES, the initial value of the deterioration evaluation value N is set to 1.0 in Q3.

If NO in the determination of Q2, in Q4, based on the deterioration evaluation value N read in Q1 and the charge / discharge suspension time of the battery 10 from the end of the previous run to the start of the current run. The initial value of the deterioration evaluation value N is set (using the characteristics of FIG. 6).

After Q3 or after Q4, the temperature of the battery 10 is detected in Q5 (temperature detection by the temperature sensor S2). In Q6, it is determined whether or not the detected temperature of the battery 10 is within a predetermined temperature range. This predetermined temperature range is a high temperature region, and is 45 ° C. ± 1 ° C. in the embodiment. If the determination in Q6 is NO, the temperature of the battery 10 is controlled to be within the predetermined temperature range in Q7 (control over the temperature controller 20).

When the determination in Q6 is YES, or after Q7, the process proceeds to Q11 in FIG. 8, respectively. In Q11, the charge / discharge current value (effective current) I of the battery 10 is detected (detection by the current sensor S4). The detection of the discharge current value I in Q11 is performed by another routine, and the charge / discharge current value I detected in Q11 is obtained for a predetermined unit time (for example, 10 seconds) as described above. It is the average charge / discharge current value.

In Q12, it is determined whether or not the charge / discharge current value I is larger than the threshold value. This threshold value is set to be as large as possible within the range of the current value at which permanent deterioration does not occur even when discharged for a long time (40 A in the embodiment). If the determination in Q12 is YES, in Q13, the average current value I acquired in Q11 and the temperature of the battery 10 detected in Q5 are compared with the map shown in FIG. To be acquired. After that, in Q14, the deterioration evaluation value N is updated based on the above-mentioned mathematical formula.

After Q14, or when the determination of Q12 is NO, the process shifts to Q15, respectively. In Q15, it is determined whether or not the deterioration evaluation value N is larger than 0. If YES in the determination of Q15, there is a margin until the limit integrated current value is reached. In this case, in Q16, the maximum charge / discharge current value at which the battery 10 may be discharged is the maximum. It is set to a value (80A in the embodiment). Further, when the determination in Q17 is NO, it means that the limit integrated current value has been reached, and the maximum charge / discharge current value of the battery 10 is set to the minimum value (40 A in the embodiment).

After Q16 or after Q17, it is determined in Q18 whether or not the ignition switch S1 is turned off. If the determination of Q18 is NO, the process returns to Q11. If YES in the determination of Q18, the latest deterioration evaluation value N is stored in Q19 in preparation for the next run (storage of the controller U in the RAM). The deterioration evaluation value N stored in Q19 will be used for setting the initial value of the deterioration evaluation value N in Q4 at the start of the next running.

In FIGS. 7 and 8 described above, Q4 corresponds to the control content of the threshold value correction unit. Q7 corresponds to the control content of the temperature rise control unit. Q11 corresponds to the control content of the average charge / discharge current value calculation unit (actual integrated current value calculation unit). Q13 corresponds to the control content of the limit integrated current value determination unit using the storage unit. Q14 corresponds to the control content of the threshold value setting unit (deterioration evaluation value calculation unit). Q13 corresponds to the control content using the storage unit. Q15 corresponds to the control content of the deterioration determination unit.

FIG. 9 shows a situation in which the deterioration evaluation value N is gradually reduced and a state in which the maximum charge / discharge current value (effective current) of the battery 10 changes when the controls of FIGS. 7 and 8 described above are performed. .. As shown in FIG. 9, the maximum discharge current value is a large current of 80 A until the deterioration evaluation value N becomes 0. After the deterioration evaluation value N becomes 0, the maximum charge / discharge current value of the battery 10 is limited to a small current value (minimum value) such as 40 A in order to prevent permanent deterioration.

Since the temperature of the battery 10 is maintained at a high temperature, the limit integrated current value is set to a large value, whereby the degree of decrease of the deterioration evaluation value N becomes slow. That is, the time during which a large current can be discharged can be sufficiently lengthened.

FIG. 11 shows a comparative example and corresponds to FIG. In this comparative example, when the limit integrated current value is set to a constant temperature of room temperature (about 25 ° C.), the situation where the deterioration evaluation value N changes and the maximum charge / discharge current value of the battery 10 according to the deterioration evaluation value N It indicates the setting. Since the temperature of the battery 10 is as low as about room temperature, the limit integrated current value is extremely small as compared with the case of FIG. 9, and therefore the degree of decrease in the deterioration evaluation value N is large. Therefore, compared to the case of FIG. 9, the time required to limit the maximum discharge current value to a small predetermined value (40A) is shorter.

Second Embodiment FIG. 10 shows a second embodiment of the present invention and corresponds to FIG. In the present embodiment, the maximum charge / discharge current value of the battery 10 is gradually reduced as the deterioration evaluation value N decreases. That is, the maximum charge / discharge current value is gradually reduced to 80A, 70A, 60A, and 50A as the deterioration evaluation value N decreases from 1. As a result, the period during which the discharge with a large current can be performed is set to be a longer period than in the case of FIG. When the deterioration evaluation value N becomes 0, the maximum discharge current value of the battery 10 is limited to the minimum value (40A).

In this second embodiment, the maximum charge / discharge current value of the battery 10 is gradually reduced from the maximum value (80A), so that the driver of the vehicle V is gradually reduced in the driving force by the motor 2. You will recognize that. As a result, the driver is less likely to feel a sense of discomfort about the decrease in the driving force due to the motor 2, and is also preferable in encouraging driving by making good use of the driving force assist using the motor 2. By the way, when the maximum discharge current value of the battery 10 is suddenly reduced from the maximum value (for example, 80A) to the minimum value (for example, 40A), the driving force of the motor 2 is suddenly reduced, so that the driver feels uncomfortable. It is easy to feel, and it will take time to get used to the corresponding driving.

Third Embodiment In the third embodiment, although not shown, the maximum charge / discharge current value of the battery 10 is continuously and variably reduced as the deterioration evaluation value N decreases. The continuously variable decrease of the maximum charge / discharge current value according to the decrease of the deterioration evaluation value N can be performed linearly or non-linearly. The non-linear decrease degree of the maximum charge / discharge current value can be increased as the deterioration evaluation value N is larger, or may be increased as the deterioration evaluation value N is smaller. it can.

Here, the limit integrated current value may be directly used as a threshold value for determining whether or not to limit the maximum charge / discharge current value of the battery 10 to a small current value. In this case, the limit integrated current value obtained from the characteristics shown in FIG. 5 may be set as corresponding to a short time within a predetermined period.

Although the embodiments have been described above, the present invention is not limited to the embodiments, and appropriate modifications can be made within the scope of the claims. For example, the vehicle V has an engine 1, but the drive wheels 3 may be driven only by the motor 2 (the engine 1 is used exclusively for power generation), and the vehicle V does not have the engine 1. You may. The battery 10 is not limited to being mounted on the vehicle V, but may be used as a storage battery in a home or a factory. Of course, an object of the present invention is not limited to what is specified, but also implicitly includes providing what is expressed as substantially preferable or advantageous.

The present invention is particularly suitable for vehicles having a motor powered by a lithium ion battery.

1: Engine 2: Motor 3: Drive wheel 10: Battery 20: Temperature controller 21: Heat exchanger (for cooling)
22: Heater (for temperature rise)
U: Controller (control device)
S1: Ignition switch S2: Temperature sensor S4: Current sensor

Claims (8)

A lithium-ion battery having a positive electrode and a negative electrode and using an electrolytic solution obtained by dissolving a lithium salt in a solvent as a supporting electrolyte.
A charge / discharge control unit that controls the charge / discharge of the lithium ion battery, a deterioration determination unit that determines the deterioration of the lithium ion battery, an actual integrated current value calculation unit that calculates the charge / discharge current integrated value in a predetermined period, and the like. A threshold setting unit for setting a higher threshold for the integrated charge / discharge current value as the temperature of the lithium ion battery is higher, and a control device having the same are provided.
The deterioration determination unit determines that the lithium ion battery has deteriorated when the actual integrated current value is equal to or greater than the threshold value.
When the charge / discharge control unit determines that the lithium ion battery is deteriorated by the deterioration determination unit, the charge / discharge control unit limits the charge / discharge current of the lithium ion battery to a predetermined value or less, while the lithium ion battery deteriorates. When it is not determined to be, the charge / discharge current of the lithium ion battery is not limited to the predetermined value or less.
A deterioration determination device for a lithium ion battery. In claim 1,
A device for determining deterioration of a lithium ion battery, wherein the threshold value is set so that the higher the temperature of the lithium ion battery, the larger the increase allowance. In claim 1 or 2,
A device for determining deterioration of a lithium ion battery, wherein the threshold value is set lower as the charge / discharge current value of the lithium ion battery increases. In any one of claims 1 to 3,
The control device is characterized by having a temperature rise control unit that controls a temperature rise to raise the temperature of the lithium ion battery when the temperature of the lithium ion battery is equal to or lower than a predetermined temperature. Battery deterioration judgment device. In any one of claims 1 to 4,
The control device is a deterioration determination device for a lithium ion battery, wherein when the actual integrated current value is less than the threshold value, the current limit of the lithium ion battery is stepwise implemented. In any one of claims 1 to 5,
The control device is a deterioration determination device for a lithium ion battery, further comprising a threshold value correction unit that increases the threshold value according to a pause time in which the lithium ion battery is suspended. A lithium-ion battery having a positive electrode and a negative electrode and using an electrolytic solution obtained by dissolving a lithium salt in a solvent as a supporting electrolyte.
A control device having a charge / discharge control unit that controls charging / discharging of the lithium ion battery and a deterioration determination unit that determines deterioration of the lithium ion battery.
With
The control device stores a map in which the limit integrated current value is set so as to decrease as the charge / discharge current value of the lithium ion battery increases and increase as the temperature of the lithium ion battery increases. Have,
The control device has an average charge / discharge current value calculation unit that calculates an average charge / discharge current value of the lithium ion battery at predetermined unit times.
The control device collates the calculated average discharge current value and the temperature of the lithium ion battery with the map for each predetermined unit time, and determines the limit integrated current value for each predetermined unit time. It has an integrated current value determination unit and
The control device has a deterioration evaluation value calculation unit that calculates a deterioration evaluation value based on the average charge / discharge current value and the limit integrated current value for each predetermined unit time.
The deterioration determination unit determines that the lithium ion battery is deteriorated when the deterioration evaluation value calculated by the deterioration evaluation value calculation unit becomes equal to or less than a predetermined threshold value.
When the deterioration determination unit determines that the lithium ion battery has deteriorated, the charge / discharge control unit limits the maximum charge / discharge current of the lithium ion battery to a predetermined value or less, while the lithium ion battery deteriorates. When it is not determined that the lithium ion battery is in use, the maximum charge / discharge current of the lithium ion battery is not limited to the predetermined value or less.
A deterioration determination device for a lithium ion battery. In claim 7,
When the deterioration determination unit does not determine that the lithium ion battery has deteriorated, the charge / discharge control unit steps the maximum charge / discharge current of the lithium ion battery as the deterioration evaluation value decreases. A deterioration determination device for a lithium ion battery, which is controlled so as to be small or continuously variable.

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