JP7352860B2 - Lithium-ion battery deterioration determination device - Google Patents

Description

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

A lithium ion battery includes a positive electrode and a negative electrode, and uses an electrolytic solution prepared by dissolving a lithium salt in a solvent as a supporting electrolyte. Lithium ion batteries are widely used, for example, in electric vehicles, hybrid vehicles, or as storage batteries in factories and homes.

Lithium-ion batteries have better input/output performance when charged and discharged with a large current (used in high-rate cycles) than when charged and discharged with a low current. Therefore, when using a lithium ion battery, it is desirable to charge and discharge with as large a current as possible. In particular, when a lithium ion battery is used to power 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, lithium-ion batteries temporarily deteriorate with use (temporary increase in charging/discharging resistance), but the temporary deterioration can be recovered by taking a break without charging or discharging. It is. In addition, lithium-ion batteries deteriorate over time, but if they are discharged at large currents for long periods of time, permanent deterioration, called high-rate cycle deterioration, that does not recover even if charging and discharging is stopped, can occur. It will end up being put away. Since permanent deterioration has a greater degree of deterioration than aging deterioration, it should be avoided as much as possible.

Patent Document 1 discloses a device that determines the deterioration of a lithium ion battery based on the discharging time at a large current and the bias in ion concentration in order to prevent high rate cycle deterioration in the lithium ion battery. . This Patent Document 1 also discloses that the longer the discharge time with a large current, the more likely it is to deteriorate, and the greater the deviation in ion concentration, the more likely it is to be deteriorated.

In order to prevent permanent deterioration, conventionally, a threshold value called a limit cumulative current value (limit cumulative current amount) is set, and when the cumulative value of discharge current exceeds the threshold value, the discharge current of the lithium ion battery is reduced to a value below a predetermined value. The current is limited to a small value. When setting the limit integrated current value, the limit integrated current value (threshold value) is set on the premise of normal temperature (around 25° C.).

However, limiting the discharge current of a lithium-ion battery to a small current value is undesirable in electric vehicles and hybrid vehicles, for example, because it leads to deterioration in acceleration and fuel consumption (electricity consumption). be.

In order to prevent the cumulative current value from reaching the limit value early, it is possible to increase the capacity of the lithium ion battery. However, increasing the capacity of lithium-ion batteries not only significantly increases costs, but also increases the weight of electric and hybrid vehicles, which worsens acceleration and fuel efficiency (electricity costs). It will end up being put away.

Japanese Patent Application Publication No. 2009-123435

The present invention was made in consideration of the above circumstances, and its purpose is to provide a lithium ion battery that can more accurately determine deterioration and ensure a longer usage time at large charge/discharge currents. An object of the present invention is to provide a battery deterioration determination device.

The present invention was made based on the finding that as a result of experimentally verifying the relationship between the temperature of a lithium ion battery and the limit integrated current value, the higher the temperature of the lithium ion battery, the larger the limit integrated current value. It is something. In other words, by setting the threshold value used to limit the maximum charge/discharge current value of a lithium-ion battery so that it increases as the temperature of the lithium-ion battery increases, this threshold value can be set accurately and the maximum charging/discharging current value of the lithium-ion battery can be This improves the accuracy of deterioration determination and makes it possible to secure a longer period of time until the maximum charge/discharge current value is limited.

Specifically, the present invention adopts the following first solution.

A lithium ion battery comprising a positive electrode and a negative electrode, and using an electrolytic solution prepared by dissolving a lithium salt in a solvent as a supporting electrolyte;
a charge/discharge control unit that controls charging and discharging of the lithium ion battery; a deterioration determination unit that determines deterioration of the lithium ion battery; an actual cumulative current value calculation unit that calculates a cumulative charging/discharging current value for a predetermined period; A control device comprising : a threshold value setting unit that sets a higher threshold value for the integrated charging/discharging current value as the temperature of the lithium ion battery increases;
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,
The charge/discharge control section includes:
When the deterioration determining unit determines that the lithium ion battery has deteriorated , the charging/discharging current of the lithium ion battery is limited to a preset first maximum charging/discharging current value or less;
When the lithium ion battery is not determined to be deteriorated and the actual integrated current value is less than or equal to a value smaller than the threshold value by a predetermined integrated current value, the charging/discharging current of the lithium ion battery is set to the first maximum charging current value . limiting to a second maximum charging/discharging current value that is larger than the discharging current value;
When the lithium ion battery is not determined to be deteriorated and the actual integrated current value is larger than the threshold value by a predetermined actual integrated current value, the charging/discharging current of the lithium ion battery is changed to The charging/discharging current value is limited to a third maximum charging/discharging current value that is larger than the first maximum charging/discharging current value and smaller than the second maximum charging/discharging current value.
(corresponding to claim 1).

According to the first solution method, the threshold value can be set with high precision, and the deterioration of the lithium ion battery can be determined with high precision. Thereby, it is possible to prevent or suppress a situation in which the maximum charging/discharging 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 lengthen the period during which charging and discharging can be performed with a large current.
Additionally, this is preferable in order to prevent the situation where the maximum charging/discharging current value (second maximum charging/discharging current value) of the lithium ion battery suddenly changes to a small current value (below the first maximum charging/discharging current value). . In particular, when a lithium-ion battery is used to power a vehicle's drive motor, the maximum driving force of the drive motor suddenly decreases, which can cause discomfort to the vehicle driver. It becomes desirable.

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

The threshold value may be set such that the higher the temperature of the lithium ion battery is, the larger the increase amount is (corresponding to claim 2). In this case, the threshold value can be set accurately in accordance with the characteristic that the higher the temperature of the lithium ion battery is, the larger the amount of increase in the limit integrated current value becomes.

The threshold value may be set lower as the charging/discharging current value of the lithium ion battery increases (corresponding to claim 3). In this case, the threshold value can be set accurately in accordance with the characteristic that the limit integrated current value becomes smaller as the charging/discharging current of the lithium ion battery increases.

The control device may include a temperature increase control section that performs temperature increase control to increase the temperature of the lithium ion battery when the temperature of the lithium ion battery is below a predetermined temperature. (corresponding to claim 4). In this case, it is preferable to raise the temperature of the lithium ion battery to an appropriate temperature at which the limit integrated current value becomes sufficiently large, in order to ensure a longer usage time with a large charging/discharging current.

The control device controls the third maximum charging/discharging current when the lithium ion battery is not determined to be deteriorated and the actual cumulative current value is larger than the threshold value by a predetermined actual cumulative current value. The current limitation of the lithium ion battery can be implemented in stages by using a plurality of different values as the value (corresponding to claim 5). This is preferable in order to prevent a situation where the maximum charging/discharging current value of the lithium ion battery suddenly changes to a small current value. In particular, when a lithium-ion battery is used to power a vehicle's drive motor, the maximum driving force of the drive motor suddenly decreases, which can cause discomfort to the vehicle driver. It becomes desirable.

In order to achieve the above object, the present invention adopts the following second solution.

A lithium ion battery comprising a positive electrode and a negative electrode, and using an electrolytic solution prepared by dissolving a lithium salt in a solvent as a supporting electrolyte;
a control device having a charge/discharge control unit that controls charging and discharging of the lithium ion battery; and a deterioration determination unit that determines deterioration of the lithium ion battery;
Equipped with
The control device includes a storage unit storing a map set such that the limit integrated current value becomes smaller as the charging/discharging current value of the lithium ion battery becomes larger and becomes larger as the temperature of the lithium ion battery becomes higher. has
The control device includes an average charging/discharging current value calculation unit that calculates an average charging/discharging current value of the lithium ion battery every predetermined unit time,
The control device compares the calculated average charge/discharge current value and the temperature of the lithium ion battery with the map for each predetermined unit time, and determines a limit cumulative current value for each predetermined unit time. It has a limit integrated current value determining section,
The control device includes 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 has deteriorated when the deterioration evaluation value calculated by the deterioration evaluation value calculation unit becomes equal to or less than a predetermined threshold;
The charge/discharge control section includes:
When the deterioration determining unit determines that the lithium ion battery has deteriorated, the maximum charging and discharging current of the lithium ion battery is limited to a preset first maximum charging and discharging current value, while
When the lithium ion battery is not determined to be deteriorated and the deterioration evaluation value is greater than the predetermined threshold value by a predetermined deterioration evaluation value, the maximum charging/discharging current of the lithium ion battery is set to the first Limiting to a second maximum charging/discharging current value that is larger than the maximum charging/discharging current value,
When the lithium ion battery is not determined to be deteriorated and the deterioration evaluation value is less than the predetermined threshold value by a predetermined deterioration evaluation value, the maximum charging/discharging current of the lithium ion battery is set to the first The charging/discharging current value is limited to a third maximum charging/discharging current value that is larger than the maximum charging/discharging current value and smaller than the second maximum charging/discharging current value.
(corresponding to claim 6).

According to the second solution method, the same effects as those according to claim 1 can be obtained 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 charging/discharging current for each predetermined unit time, which is preferable in order to appropriately respond to changes in temperature and discharge current.

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

The charge/discharge control section is configured to control the charge/discharge control section when the deterioration determination section does not determine that the lithium ion battery has deteriorated and the deterioration evaluation value is less than a value larger than the predetermined threshold by a predetermined deterioration evaluation value. 3. Using a plurality of different values as the maximum charging/discharging current value, the maximum charging/discharging current of the lithium ion battery is decreased in a stepwise or continuously variable manner as the deterioration evaluation value decreases. (corresponding to claim 7 ). In this case, the same effects as those corresponding to claim 5 can be obtained.
The control device may be set to correct the deterioration evaluation value depending on the rest time during which the lithium ion battery is rested (corresponding to claim 8). In this case, the threshold value can be set accurately in response to the temporary deterioration of the lithium ion battery being recovered during the rest period.

According to the present invention, it is possible to perform deterioration determination with higher accuracy and to secure a longer usage time with a large charging/discharging current.

1 is a diagram showing an example of a drive system, etc., and an example of a control system of a vehicle to which the present invention is applied. The figure which shows the example of a setting of the operating area of an engine and a motor. FIG. 1 is a diagram showing a simplified structure of a lithium ion battery. FIG. 3 is a diagram showing an example of aging deterioration and permanent deterioration of a lithium ion battery. The figure which shows the map for determining a limit integrated current value based on the temperature and discharge current value of a lithium ion battery. The figure which shows the situation where a deterioration evaluation value changes according to the pause time when charge/discharge was stopped. 5 is a flowchart showing a control example of the present invention. 8 is a flowchart showing a continuation of FIG. 7. The figure which shows the example of a setting of the maximum discharge current value according to a deterioration evaluation value. FIG. 9 is a diagram corresponding to FIG. 9, showing a second embodiment of the present invention. FIG. 9 is a diagram corresponding to FIG. 9, showing a comparative example with the present invention.

First, a drive system of a vehicle (automobile) V to which the present invention is applied will be explained based on FIG. In the figure, 1 is an engine (internal combustion engine) and 2 is a motor. Reference numeral 3 denotes a drive wheel which 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 to drive the drive wheels 3 but also as a generator during deceleration.

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

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

FIG. 2 shows an example of setting the operating ranges of the engine 1 and motor 2. In FIG. In the example of FIG. 2, the engine 1 is constantly operated (driven) when the vehicle V is running. Further, the motor 2 assists the driving of the engine 1 as appropriate.

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

Second, the motor 2 is operated in a high load region (eg, when the accelerator opening is 80% or more). Thirdly, in a region R3 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 decelerating, the second clutch 5 is connected, but the first clutch 4 is disconnected (disconnected). Furthermore, during deceleration, the motor 2 is driven from the drive wheel 3 side, so the motor 2 functions as a generator, and the generated electric power is charged to the battery 2 (regeneration). Note that both clutches 4 and 5 are disconnected when the vehicle is idling or when the vehicle is stopped.

Next, a structural example of the battery 2 will be described with reference to FIG. 3.

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 prepared by dissolving a main electrolyte and a sub-electrolyte in a non-aqueous solvent as a supporting electrolyte.

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 the mixture to a current collector. A preferred current collector is aluminum foil.

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, phosphate-based lithium compounds, and silicate-based lithium compounds. In particular, it is preferable to use phosphate-based lithium. These positive electrode active materials can be used alone or in combination of two or more.

Preferred phosphate-based lithium compounds include, for example, LiMPO4 (M=transition metal Fe, Co, Ni, Mn, etc.) having an olivine crystal structure, and Li2MPO4F (M=transition metal Fe, Co, Ni, Mn, etc.). Among them, lithium iron phosphate LiFePO4 is preferred. 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 used. As the conductive aid, carbon black, acetylene black, carbon nanofiber (CNF), etc. can be employed.

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 mixture to a current collector. A preferred current collector is copper foil.

As the negative electrode active material, it is preferable to use a graphite-based carbon material, that is, artificial graphite or natural graphite. The graphite-based carbon material preferably has a low degree of graphitization from the viewpoint of improving the ability to absorb and release Li ions. Artificial graphite and hard carbon, which have a low degree of graphitization, are preferable as negative electrode active materials. Since highly crystalline natural graphite alone 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), the styrene-butadiene rubber combined with carboxymethyl cellulose as a thickener (SBR-CMC), PVdF, or an imide binder can be preferably used. . As the conductive aid, carbon black, acetylene black, carbon nanofiber CNF, etc. can be preferably employed.

There are no particular limitations on the separator, but a single-layer or laminated microporous film, woven fabric, non-woven fabric, or the like of polyolefin such as polypropylene or polyethylene can be used.

The nonaqueous electrolyte is formed by dissolving a lithium salt (supporting electrolyte) in a nonaqueous solvent, and additives are added as necessary.

There are no particular restrictions on the type of nonaqueous solvent, and examples include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), and dimethyl. Examples include chain carbonate esters such as carbonate (DMC), and cyclic carboxylic acid esters such as γ-butyrolactone (GBL) and γ-valerolactone (GVL). The non-aqueous solvents may be used alone or in combination of two or more.

Examples of non-aqueous solvent additives include wettability improving solvents that improve the wettability of the electrolytic solution to the separator and SEI forming solvents.

Examples of the wettability improving solvent include dibutyl carbonate (DBC), methyl butyl carbonate (MBC), and ethyl butyl carbonate (EBC). The amount of the wettability improving solvent added is preferably about 3% by mass or more and 10% by mass or less of the nonaqueous solvent.

SEI forming solvents include vinylene carbonate (VC), methyl vinylene carbonate (MVC), ethyl vinylene carbonate (EVC), fluorovinylene carbonate (FVC), vinyl ethylene carbonate (VEC), ethynyl ethylene carbonate (EEC), and ethylene sulfite. (ES), fluoroethylene carbonate (FEC), etc. 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 nonaqueous solvent.

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

The concentration of the lithium salt in the nonaqueous electrolyte may be, for example, 0.5M or more and 2.0M or less.

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

The battery 2 is provided with a temperature controller 20 for adjusting its temperature. The temperature controller 20 includes a cooler 21 and a temperature riser 22. The cooler 21 is activated when the temperature of the battery 10 reaches a predetermined temperature (for example, 50 degrees Celsius), and prevents the temperature of the battery 10 from rising above the allowable upper limit temperature (60 degrees Celsius in the embodiment). The cooler 21 is, for example, an air-cooled type that uses conditioned air, but is not limited to this and can be of any suitable type.

The temperature riser 22 raises the temperature of the battery 10, for example, when the temperature of the battery 10 is low, such as room temperature, to a temperature around 45°C. This temperature increase increases the limit integrated current value, as will be described later. For example, an electric heater can be used as the temperature riser 22, but the present invention is not limited to this. For example, when the coolant temperature of the engine 1 is higher than a predetermined temperature, this coolant can be used to raise 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 using the magnitude of the charging/discharging current (effective current) of the battery 10 as a parameter. The normal deterioration shown by the broken line in the figure is called aging deterioration, and the resistance value increases slowly even if the discharge current is large.

On the other hand, in Fig. 4. Permanent deterioration shown by the solid line occurs when charging and discharging at a large current greater than a predetermined current value continues for a long time, and is also called high-rate cycle deterioration. When the battery 10 continues to discharge, its resistance value temporarily increases, but when charging and discharging are stopped, the resistance value decreases (recovers). However, in the case of permanent deterioration, charging and discharging are stopped. However, the resistance value will not be restored. Therefore, long-term charging and discharging at large currents that may cause permanent deterioration should be avoided.

When the charging/discharging current value (effective current value) is small, below a predetermined value (for example, about 40 A), permanent deterioration is unlikely to occur. Therefore, if the charging/discharging current value is limited to a small current value below the above-mentioned predetermined value, permanent deterioration can be reliably prevented, but in this case, since a large current cannot be obtained, the capacity of the battery 10 must be increased. This is not desirable.

FIG. 5 shows the relationship between the temperature of the battery 10, the charging/discharging current value, and the limit integrated current value, which was determined experimentally. The limit integrated current value is such that if the battery is used within the range below, permanent deterioration will not occur even if charging and discharging are performed at a large current.

As understood from FIG. 5, when charging and discharging with a large current is performed, the limit integrated current value increases as the temperature of the battery 10 increases. For example, when the charging/discharging 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 charging/discharging current value is 80 A and the temperature of the battery 10 is around 25° C. near normal temperature, the limit integrated current amount becomes extremely small, such as 230/Ah. As described above, the limit integrated current value greatly differs depending on the temperature of the battery 10, and the higher the temperature of the battery 10, the larger the amount of increase in 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 charging/discharging time with a large current without increasing the capacity of the battery 10.

The limit integrated current value becomes a threshold value for determining whether or not to limit the charging/discharging current value of the battery 10 to a predetermined small current value or less. That is, when the actual integrated current value obtained by multiplying the actual charging/discharging current value of the battery 10 by the charging/discharging time exceeds the limit integrated current value, in order to prevent permanent deterioration, the battery 10 The charging/discharging current value is limited to a small current value (for example, 40 A) below a predetermined value. Furthermore, when the actual integrated current value is less than the limit integrated current value, there is still some margin before permanent deterioration occurs, and charging and discharging at a large current is allowed.

The limit integrated current value can be directly used as a threshold value for determining whether or not to limit the charging/discharging current value of the battery 10 to a small current value. However, in consideration of the temperature of the battery 10 changing, in this embodiment, a deterioration evaluation value N (N≦1.0) related to the limit cumulative current value is used to perform a deterioration evaluation every predetermined unit time. The value N is updated (subtracted).

Specifically, the average charging/discharging 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 this average discharging current value to the limit cumulative current value. When the deterioration evaluation value N becomes 0, it means that the limit integrated current value has been reached, so the charging/discharging current value of the battery 10 is limited to a small current value below a predetermined value.

When the battery 10 is sufficiently rested, the initial value of the deterioration evaluation value N is set to 1. In addition, the discharge current value is measured at every predetermined sampling time (for example, 0.1 to 1 second), and the average value of the measured charging and discharging current values is obtained at 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 formula. In this formula, 10s (10 seconds) is the above-mentioned 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 80A, the limit integrated current value is 1000Ah, and the value on the right side of the formula is 0.0002222. . That is, when charging and discharging at 80A for 10 seconds, the deterioration evaluation value is updated as a value that is smaller than the previous value by 0.0002222. Calculation of such a deterioration evaluation value is performed every short predetermined unit time, so it is calculated as a value that accurately corresponds to changes in the discharge current value and temperature changes of the battery 10 (the limit of the battery 10 Accurately calculate the degree of deterioration toward the integrated current value).

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

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

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

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 charging/discharging current value of the battery 10. The controller U performs control for determining the degree of deterioration of the battery, control for charging and discharging (particularly the magnitude of the discharge current value), and control for the temperature regulator 20 (temperature control for the battery 10). In addition, the controller U acquires the current value detected by the current sensor S4 every predetermined sampling period (for example, 0.1 to 1 second), and calculates the average current value every predetermined unit time (10 seconds in the embodiment) as described above. Calculate the value I.

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

The control shown in FIGS. 7 and 8 is started from the time the engine 1 is started (the time the ignition switch S1 is turned on). First, in Q1, the deterioration evaluation value N stored during the previous run is read out. In Q2, it is determined whether a predetermined period of time (for example, 11 hours) or more has passed since the last run. When the determination in Q2 is YES, the initial value of the deterioration evaluation value N is set to 1.0 in Q3.

When the determination in Q2 is NO, in Q4, based on the deterioration evaluation value N read out in Q1 and the charging/discharging rest 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 shown in FIG. 6).

After Q3 or after Q4, the temperature of the battery 10 is detected in Q5 (temperature detection by temperature sensor S2). In Q6, it is determined whether the detected temperature of the battery 10 is within a predetermined temperature range. This predetermined temperature range is a high temperature range, and is set to 45°C±1°C in the embodiment. When the determination in Q6 is NO, in Q7 the temperature of the battery 10 is controlled to be within the predetermined temperature range (control on the temperature controller 20).

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

In Q12, it is determined whether the charging/discharging current value I is larger than a threshold value. This threshold value is set to a current value as large as possible within the range of current values that do not cause permanent deterioration even if discharged for a long time (40 A in the embodiment). When the determination in Q12 is YES, in Q13, the limit integrated current value is determined by comparing the average current value I obtained in Q11 and the temperature of the battery 10 detected in Q5 with the map shown in FIG. be obtained. After this, in Q14, the deterioration evaluation value N is updated based on the above-mentioned formula.

After Q14 or when the determination in Q12 is NO, the process moves to Q15. In Q15, it is determined whether the deterioration evaluation value N is greater than 0 or not. When the determination in Q15 is YES, there is a margin until the limit cumulative current value is reached, and in this case, in Q16, the maximum charging/discharging current value at which the battery 10 can be discharged 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 charging/discharging 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 in Q18 is NO, return to Q5 . When the determination in Q18 is YES, the latest deterioration evaluation value N is stored in preparation for the next run (stored in the RAM of the controller U) in Q19. The deterioration evaluation value N stored in Q19 will be used to set the initial value of the deterioration evaluation value N in Q4 at the start of the next run.

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

FIG. 9 shows how the deterioration evaluation value N gradually decreases and how the maximum charging/discharging current value (effective current) of the battery 10 changes when the control shown in FIGS. 7 and 8 described above is performed. . As shown in FIG. 9, the maximum discharge current value is a large current of 80A until the deterioration evaluation value N becomes 0. Further, after the deterioration evaluation value N reaches 0, the maximum charging/discharging current value of the battery 10 is limited to a small current value (minimum value) such as 40 A 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, thereby slowing down the degree of decrease in the deterioration evaluation value N. In other words, the time during which discharge can be performed with a large current can be made sufficiently long.

FIG. 11 shows a comparative example and corresponds to FIG. 9. In this comparative example, when the limit integrated current value is set to a constant temperature of room temperature (approximately 25 degrees Celsius), the situation where the deterioration evaluation value N changes and the maximum charging/discharging current value of the battery 10 according to the deterioration evaluation value N are explained. settings. Since the temperature of the battery 10 is low, about room temperature, the limit integrated current value becomes an extremely small value compared to the case of FIG. 9, and therefore the degree of decrease in the deterioration evaluation value N becomes large. Therefore, compared to the case of FIG. 9, the time required to limit the maximum discharge current value to a small predetermined value (40 A) becomes shorter.

Second Embodiment FIG. 10 shows a second embodiment of the present invention and corresponds to FIG. 9. In this embodiment, the maximum charging/discharging current value of the battery 10 is made smaller in stages as the deterioration evaluation value N decreases. That is, as the deterioration evaluation value N decreases from 1, the maximum charge/discharge current value is decreased stepwise to 80A, 70A, 60A, and 50A. As a result, the period during which discharge can be performed with a large current is made longer than in the case of FIG. Note that when the deterioration evaluation value N becomes 0, the maximum discharge current value of the battery 10 is limited to the minimum value (40 A).

In this second embodiment, the maximum charging/discharging current value of the battery 10 is gradually reduced from the maximum value (80A), so that the driver of the vehicle V can experience a gradual reduction in the driving force of the motor 2. You will realize that. As a result, the driver is less likely to feel discomfort due to the reduction in the driving force by the motor 2, and it is also preferable to encourage driving that makes good use of the driving force assistance using the motor 2. Incidentally, if the maximum discharge current value of the battery 10 is suddenly reduced from the maximum value (e.g. 80A) to the minimum value (e.g. 40A), the driving force of the motor 2 will be reduced all at once, so the driver may feel something strange. It's easy to feel, and it takes time to get used to driving accordingly.

Third Embodiment In a third embodiment, although not shown, the maximum charging/discharging current value of the battery 10 is continuously and variably decreased in accordance with a decrease in the deterioration evaluation value N. The continuously variable decrease in the maximum charge/discharge current value in response to the decrease in the deterioration evaluation value N can be performed linearly or nonlinearly. The degree of non-linear decrease in the maximum charge/discharge current value can be set so that the degree of decrease becomes larger as the deterioration evaluation value N becomes larger, or the degree of decrease becomes larger as the deterioration evaluation value N becomes smaller. can.

Here, the limit integrated current value may be directly used as a threshold value for determining whether or not to limit the maximum charging/discharging 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 one corresponding to a short period of time within a predetermined period.

Although the embodiments have been described above, the present invention is not limited to the embodiments, and can be modified as appropriate within the scope of the claims. For example, although the vehicle V has an engine 1, the drive wheels 3 may be driven only by the motor 2 (the engine 1 is used exclusively for power generation), or it may not have the engine 1. It's okay. The battery 10 is not limited to being installed in the vehicle V, but may be used as a storage battery at home or in a factory. Of course, the object of the invention is not limited to what is expressly stated, but is also implicitly included to provide any expressed substantial preference or advantage.

The present invention is particularly suitable for use in a vehicle having a motor that receives power from 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 increase)
U: Controller (control device)
S1: Ignition switch S2: Temperature sensor S4: Current sensor

Claims (8)

A lithium ion battery comprising a positive electrode and a negative electrode, and using an electrolytic solution prepared by dissolving a lithium salt in a solvent as a supporting electrolyte;
a charge/discharge control unit that controls charging and discharging of the lithium ion battery; a deterioration determination unit that determines deterioration of the lithium ion battery; an actual cumulative current value calculation unit that calculates a cumulative charging/discharging current value for a predetermined period; A control device comprising: a threshold value setting unit that sets a higher threshold value for the integrated charging/discharging current value as the temperature of the lithium ion battery increases;
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,
The charge/discharge control section includes:
When the deterioration determining unit determines that the lithium ion battery has deteriorated, the charging/discharging current of the lithium ion battery is limited to a preset first maximum charging/discharging current value or less;
When the lithium ion battery is not determined to be deteriorated and the actual integrated current value is less than or equal to a value smaller than the threshold value by a predetermined integrated current value, the charging/discharging current of the lithium ion battery is set to the first maximum charging current value. limiting to a second maximum charging/discharging current value that is larger than the discharging current value;
When the lithium ion battery is not determined to be deteriorated and the actual integrated current value is larger than the threshold value by a predetermined actual integrated current value, the charging/discharging current of the lithium ion battery is changed to The charging/discharging current value is limited to a third maximum charging/discharging current value that is larger than the first maximum charging/discharging current value and smaller than the second maximum charging/discharging current value.
A lithium ion battery deterioration determination device characterized by the following. In claim 1,
A device for determining deterioration of a lithium ion battery, wherein the threshold value is set such that the higher the temperature of the lithium ion battery, the larger the increase amount. In claim 1 or claim 2,
A device for determining deterioration of a lithium ion battery, wherein the threshold value is set lower as the charging/discharging current value of the lithium ion battery increases. In any one of claims 1 to 3,
The lithium ion battery is characterized in that the control device includes a temperature increase control unit that performs temperature increase control to increase the temperature of the lithium ion battery when the temperature of the lithium ion battery is below a predetermined temperature. Battery deterioration determination device. In any one of claims 1 to 4,
The control device controls the third maximum charging/discharging current when the lithium ion battery is not determined to be deteriorated and the actual cumulative current value is larger than the threshold value by a predetermined actual cumulative current value. A deterioration determination device for a lithium ion battery, characterized in that the current limitation of the lithium ion battery is carried out in stages using a plurality of different values. A lithium ion battery comprising a positive electrode and a negative electrode, and using an electrolytic solution prepared by dissolving a lithium salt in a solvent as a supporting electrolyte;
a control device having a charge/discharge control unit that controls charging and discharging of the lithium ion battery; and a deterioration determination unit that determines deterioration of the lithium ion battery;
Equipped with
The control device includes a storage unit storing a map set such that the limit integrated current value becomes smaller as the charging/discharging current value of the lithium ion battery becomes larger and becomes larger as the temperature of the lithium ion battery becomes higher. has
The control device includes an average charging/discharging current value calculation unit that calculates an average charging/discharging current value of the lithium ion battery every predetermined unit time,
The control device compares the calculated average charge/discharge current value and the temperature of the lithium ion battery with the map for each predetermined unit time, and determines a limit cumulative current value for each predetermined unit time. It has a limit integrated current value determining section,
The control device includes 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 has deteriorated when the deterioration evaluation value calculated by the deterioration evaluation value calculation unit becomes equal to or less than a predetermined threshold;
The charge/discharge control section includes:
When the deterioration determining unit determines that the lithium ion battery has deteriorated, the maximum charging and discharging current of the lithium ion battery is limited to a preset first maximum charging and discharging current value, while
When the lithium ion battery is not determined to be deteriorated and the deterioration evaluation value is greater than the predetermined threshold value by a predetermined deterioration evaluation value, the maximum charging/discharging current of the lithium ion battery is set to the first Limiting to a second maximum charging/discharging current value that is larger than the maximum charging/discharging current value,
When the lithium ion battery is not determined to be deteriorated and the deterioration evaluation value is less than the predetermined threshold value by a predetermined deterioration evaluation value, the maximum charging/discharging current of the lithium ion battery is set to the first The charging/discharging current value is limited to a third maximum charging/discharging current value that is larger than the maximum charging/discharging current value and smaller than the second maximum charging/discharging current value.
A lithium ion battery deterioration determination device characterized by the following. In claim 6,
The charge/discharge control section is configured to control the charge/discharge control section when the deterioration determination section does not determine that the lithium ion battery has deteriorated and the deterioration evaluation value is less than a value larger than the predetermined threshold by a predetermined deterioration evaluation value. 3. Using a plurality of different values as the maximum charging/discharging current value, the maximum charging/discharging current of the lithium ion battery is decreased in a stepwise or continuously variable manner as the deterioration evaluation value decreases. A deterioration determination device for a lithium ion battery, characterized in that the device controls the deterioration of a lithium ion battery. In claim 6,
A deterioration determination device for a lithium ion battery, wherein the control device is set to correct the deterioration evaluation value according to a rest time during which the lithium ion battery is rested.

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