JP2019050094A - Charge/discharge control device for secondary battery - Google Patents

Abstract

To suppress deterioration of a battery comprising an anode containing an Si-based material and a carbon material.SOLUTION: An ECU executes control processing includes the steps of: acquiring OCV and a current integration amount (S100); calculating full charge capacity (S102); discriminating whether the full charge capacity is equal to or less than a threshold A (S104); and, in a case where it is discriminated that the full charge capacity is equal to or less than the threshold A (YES in S104), changing a use range of a battery pack in a CS mode (S106).SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to charge / discharge control of a lithium ion secondary battery.

  As a negative electrode of a lithium ion secondary battery, it is known that, for example, a composite negative electrode of a Si-based material containing silicon or silicon oxide and a carbon material is used. For example, graphite (graphite) is used as the carbon material.

  For example, Japanese Patent Application Laid-Open No. 2017-050203 discloses a lithium ion secondary battery including a negative electrode including a Si-based material and graphite.

JP 2017-050203 A

  However, when a Si-based material and a carbon material are mixed and used as a negative electrode, the Si-based material is responsible for the battery reaction in a relatively low SOC region. On the other hand, when a Si-based material is used as a negative electrode material, the volume of the active material during charging / discharging is larger than that of the carbon material, so the active material is isolated from the active material cracking or conductive network. It is easy for mechanical deterioration to progress. Therefore, when charging / discharging of the battery is continued in a relatively low SOC region, deterioration of the battery may be promoted. The above-mentioned patent document 1 does not consider such a problem.

  The present disclosure has been made in order to solve the above-described problems, and an object of the present disclosure is to provide a secondary battery charge / discharge control device that suppresses deterioration of a secondary battery including a negative electrode including a Si-based material and a carbon material. Is to provide.

  A charge / discharge control device for a secondary battery according to an aspect of the present disclosure is a charge / discharge control device for a secondary battery that controls charge / discharge of a lithium ion secondary battery including a negative electrode including a Si-based material and a carbon material. . The charge / discharge control device includes a current detection unit that detects a charge / discharge current of the secondary battery, and a control unit that controls the charge / discharge current. The control unit has a long charge / discharge period in the first SOC region of the first SOC region having hysteresis due to charging / discharging in relation to the OCV with respect to the SOC of the secondary battery and the second SOC region having smaller hysteresis than the first SOC region. In such a case, the charge / discharge frequency in the first SOC region is reduced as compared with the case where the charge / discharge period is short.

  When the negative electrode includes a Si-based material, the battery is more likely to deteriorate as the charge / discharge period in the first SOC region becomes longer. For this reason, the deterioration of the battery can be moderated by decreasing the frequency of charge / discharge in the first SOC region as the charge / discharge period in the first SOC region becomes longer. As a result, the deterioration of the secondary battery life can be suppressed.

  A charge / discharge control device for a secondary battery according to another aspect of the present disclosure is a charge / discharge control device for a secondary battery that controls charge / discharge of a lithium ion secondary battery including a negative electrode including a Si-based material and a carbon material. is there. The charge / discharge control device includes a current detection unit that detects a charge / discharge current of the secondary battery, and a control unit that controls the charge / discharge current. The control unit has a long charge / discharge period in the first SOC region of the first SOC region having hysteresis due to charging / discharging in relation to the OCV with respect to the SOC of the secondary battery and the second SOC region having smaller hysteresis than the first SOC region. In some cases, the difference between the control upper limit value and the control lower limit value of the SOC in the first SOC region, the allowable value of the input power of the secondary battery, and the allowable output power of the secondary battery than in the case where the charge / discharge period is short. Decrease at least one of the magnitudes of the values.

  When the negative electrode includes a Si-based material, the battery is more likely to deteriorate as the charge / discharge period in the first SOC region becomes longer. Therefore, as the charging / discharging period in the first SOC region becomes longer, the difference between the control upper limit value and the control lower limit value of the SOC, the allowable value of the input power of the secondary battery, and the allowable value of the output power of the secondary battery By reducing at least one of these, the change in the SOC becomes gradual, and the progress of deterioration of the battery can be made gradual. As a result, the deterioration of the secondary battery life can be suppressed.

  According to the present disclosure, it is possible to provide a secondary battery charge / discharge control device that suppresses deterioration of a secondary battery including a negative electrode including a Si-based material and a carbon material.

1 is a block diagram schematically showing an overall configuration of a hybrid vehicle in an embodiment. It is a figure for demonstrating CD mode and CS mode. It is a figure which shows the relationship between SOC of an assembled battery, and OSV. It is a flowchart which shows the control processing performed by ECU. It is a timing chart which shows the time change of a full charge capacity. It is a figure for demonstrating the use range of SOC before and behind a change. It is a flowchart which shows the control processing performed by ECU in a modification. 12 is a timing chart showing changes in full charge capacity, ΔSOC, input power allowable value Win, and output power allowable value Wout in a modified example.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  In the following, the secondary battery charge / discharge control device according to the embodiment of the present disclosure will be described as an example of a configuration that is mounted on a hybrid vehicle, but any vehicle including a secondary battery described below may be used. In particular, it is not limited to those mounted on hybrid vehicles. The vehicle may be, for example, an electric vehicle equipped with only a driving motor as a driving source. Further, the use of the secondary battery is not limited to a vehicle, and may be a stationary one.

  FIG. 1 is a block diagram schematically showing an overall configuration of a hybrid vehicle 1 (hereinafter simply referred to as a vehicle 1) in the present embodiment. The vehicle 1 includes a motor generator (MG) 10, 12, an engine 14, a power split mechanism 16, a charging relay (hereinafter referred to as CHR) 18, a charging device 20, an inlet 22, and a drive. A wheel 28, a power control unit (PCU) 40, a system main relay (hereinafter referred to as SMR (System Main Relay)) 50, a battery pack 100, a voltage sensor 210, and a current sensor 220; And a temperature sensor 230 and an electronic control unit (ECU) 300.

  Each of MGs 10 and 12 is, for example, a three-phase AC rotating electric machine. MG 10 is connected to the crankshaft of engine 14 via power split mechanism 16. When starting the engine 14, the MG 10 rotates the crankshaft of the engine 14 using the electric power supplied from the assembled battery 100. The MG 10 can also generate power using the power of the engine 14. The AC power generated by the MG 10 is converted into DC power by the PCU 40 and supplied to the assembled battery 100. Further, the AC power generated by the MG 10 may be supplied to the MG 12.

  The MG 12 rotates the drive shaft using at least one of the power supplied from the assembled battery 100 and the power supplied from the MG 10. The MG 12 can also generate power by regenerative braking. The AC power generated by the MG 12 is converted into DC power by the PCU 40 and supplied to the assembled battery 100.

  1 shows a configuration in which two motor generators are provided, the number of motor generators is not limited to this, and a configuration in which one motor generator is provided may be employed.

  PCU 40 includes, for example, an inverter and a converter that operate based on a control signal from ECU 300, and is configured to be able to convert electric power between assembled battery 100 and MGs 10 and 12.

  For example, when the battery pack 100 is discharged, the converter boosts the voltage supplied from the battery pack 100 and supplies the boosted voltage to the inverter. The inverter converts the DC power supplied from the converter into AC power and supplies it to at least one of MGs 10 and 12.

  On the other hand, when charging the assembled battery 100, the inverter converts AC power generated by at least one of the MGs 10 and 12 into DC power and supplies it to the converter. The converter steps down the voltage supplied from the inverter to a predetermined charging voltage and supplies it to the assembled battery 100. PCU 40 stops charging and discharging by stopping the operation of the inverter and the converter based on a control signal from ECU 300. The PCU 40 may have a configuration in which a converter is omitted.

  The SMR 50 is electrically connected to a power line connecting the assembled battery 100 and the PCU 40. When SMR 50 is closed in accordance with a control signal from ECU 300, power can be exchanged between assembled battery 100 and PCU 40.

  The assembled battery 100 is a rechargeable DC power supply, and includes a lithium ion battery. The assembled battery 100 is configured by connecting a plurality (n pieces) of lithium ion batteries (single cells) 110 (hereinafter referred to as cells 110) in series. The assembled battery 100 can supply power to at least one of the MGs 10 and 12 via the PCU 40. The cell 110 is configured by laminating a positive electrode, a negative electrode, and a separator in a predetermined order. In the present embodiment, the negative electrode of cell 110 includes, for example, a Si-based material such as Si or SiO and a carbon material. In the following description, a case where graphite (graphite) is used as the carbon material will be described as an example.

  More specifically, the negative electrode includes a negative electrode current collector and a negative electrode mixture layer including a negative electrode active material provided on the surface of the negative electrode current collector. For the negative electrode current collector, for example, a copper (Cu) foil or the like is used. The negative electrode mixture layer is provided on both sides or one side of the negative electrode current collector. The negative electrode mixture layer can include a binder, a conductive material, and the like in addition to the negative electrode active material. The negative electrode active material is composed of a Si-based material and graphite. The Si-based material and graphite are mixed at a predetermined ratio and formed as a negative electrode mixture layer on the surface of the negative electrode current collector.

  The inlet 22 is configured to be able to connect a power cable plug 24 connected to an external power supply 26 outside the vehicle. The charging device 20 is, for example, an AC / DC converter, and is configured to convert the voltage of power supplied from the external power source 26 into a voltage suitable for charging the assembled battery 100. The CHR 18 is turned on in response to a control signal from the ECU 300 when the plug 24 is connected to the inlet 22. At this time, electric power can be supplied to the assembled battery 100 via the inlet 22 and the charging device 20. On the other hand, the CHR 18 is turned off in response to a control signal from the ECU 300 when the plug 24 is removed from the inlet 22 or when the assembled battery 100 is completely charged via the inlet 22 and the charging device 20.

  The voltage sensor 210 detects voltages Vb (1) to Vb (n) between the terminals of the plurality of cells 110. The current sensor 220 detects a current Ib input / output to / from the assembled battery 100. The temperature sensor 230 detects the temperatures Tb (1) to Tb (n) of each of the plurality of cells 110. In the following description, voltages Vb (1) to Vb (n) of each cell 110 may be described as voltage Vb, and temperatures Tb (1) to Tb (n) may be described as temperature Tb. Each sensor outputs the detection result to ECU 300.

  ECU 300 is a control device that includes a CPU (Central Processing Unit) 301, a memory (ROM (Read Only Memory) and RAM (Random Access Memory)) 302, and an input / output buffer (not shown). ECU 300 controls each device so that vehicle 1 is in a desired state based on information received from each sensor and information such as a map and a program stored in memory 302. ECU 300 monitors the voltage, current, and temperature of assembled battery 100 and controls charging / discharging of assembled battery 100 using charging device 20 or PCU 40.

  During operation of the vehicle 1 having the above-described configuration, the ECU 300 selects either the CD (Charge Depleting) mode or the CS (Charge Sustaining) mode, and controls the engine 14 and the PCU 40 according to the selected mode. To do. The CD mode is a control mode that consumes SOC (State Of Charge) of the assembled battery 100. The CS mode is a control mode that maintains the SOC of the battery pack 100 within a predetermined range.

  The ECU 300 selects the CD mode after the charging of the assembled battery 100 is completed by external charging, for example, until the SOC of the assembled battery 100 drops to the control center of the SOC in the CS mode, and the SOC is in the CS mode. After falling to the SOC control center, the CS mode is selected.

  FIG. 2 is a diagram for explaining the CD mode and the CS mode. In FIG. 2, the horizontal axis represents time, and the vertical axis represents an example of change in SOC. In the example shown in FIG. 2, a case where the assembled battery 100 is fully charged (SOC = MAX) by external charging, and after the external charging is completed, traveling is started at time t (0) is shown.

  In the CD mode, basically, power stored in the assembled battery 100 (mainly power charged by external charging) is consumed. During traveling in the CD mode, the engine 14 does not operate in order to maintain the SOC. Therefore, although the SOC may temporarily increase due to the regenerative power of the MG 12 being decelerated, as a result, the rate of discharge becomes larger than the charge, and the SOC gradually decreases as a whole.

  On the other hand, in the CS mode, the normal SOC is maintained within a predetermined range (ΔSOC) defined by the control upper limit SOC (2) and the control lower limit SOC (1) with SOC_a as the control center. As an example, when the SOC decreases to SOC_a that is the control center in the CS mode at time t (1), ECU 300 starts engine 14 and shifts the control mode from the CD mode to the CS mode. Thereafter, ECU 300 operates engine 14 intermittently so that the SOC is maintained within a predetermined range. Specifically, ECU 300 operates engine 14 when the SOC decreases to control lower limit SOC (1) within a predetermined range, and stops engine 14 when the SOC reaches control upper limit SOC (2) within a predetermined range. To maintain the SOC within a predetermined range. That is, in the CS mode, the engine 14 operates to maintain the SOC within a predetermined range. Further, ECU 300 promotes discharging of battery pack 100 when the SOC is higher than the control center, and outputs engine 14 so as to promote charging of battery pack 100 when the SOC is lower than the control center. To control.

  As described above, when the mode is shifted from the CD mode to the CS mode, charging / discharging is continued within the range of SOC (1) to SOC (2) in the SOC of the assembled battery 100.

  Incidentally, as described above, the negative electrode of the cell 110 constituting the assembled battery 100 includes Si-based material and graphite as negative electrode materials. Compared with graphite, Si-based materials have a large volume change due to charge / discharge, and have characteristics such as active material cracking and isolation of the active material from the conductive network, which facilitates mechanical deterioration. Further, in the relationship between the SOC and the OCV (Open Circuit Voltage) of a lithium ion battery including a negative electrode including Si-based material and graphite as negative electrode materials, noticeable hysteresis is generated in the low SOC region than in the high SOC region. There is a case.

  FIG. 3 is a diagram illustrating a relationship between SOC and OSV in a lithium ion battery including a negative electrode including a Si-based material and graphite. The vertical axis | shaft of FIG. 3 shows OCV. The horizontal axis in FIG. 3 indicates the SOC.

  A solid line LN1 in FIG. 3 shows a change in the OCV when the assembled battery 100 is charged from the fully discharged state. A broken line LN2 in FIG. 3 shows a change in OCV when the assembled battery 100 is discharged from the fully charged state.

  FIG. 3 shows that there is a predetermined amount or more of OCV difference with respect to the same SOC in the low SOC region except when the SOC is 0% when comparing the solid line LN1 and the broken line LN2. That is, in such an SOC region, the relationship between SOC and OCV changes according to how the battery is used for a predetermined period (past history: ΔSOC, current, temperature, etc.). In FIG. 3, for convenience of explanation, with SOC_th as a boundary, a region where the SOC is larger than the threshold value SOC_th is a small hysteresis region, and a region where the SOC is smaller than the threshold value SOC_th is a large hysteresis region. SOC_th is, for example, a threshold value for distinguishing between an SOC region in which the difference in OCV in the same SOC is less than or equal to a threshold value and an SOC region in which the difference in OCV in the same SOC is greater than the threshold value. Is set.

  The reason why the hysteresis in the low SOC region is larger than the hysteresis in the high SOC region is that the Si material mainly reacts in the battery reaction during charge / discharge in the low SOC region. Therefore, when charging / discharging continues in the large hysteresis region, the deterioration of the assembled battery 100 is more likely to proceed than when charging / discharging continues in the small hysteresis region. As described above, when the mode is changed from the CD mode to the CD mode, the SOC is continuously charged and discharged within a predetermined range of SOC (1) to SOC (2) in the large hysteresis region. The deterioration of the assembled battery 100 can easily proceed.

  Therefore, in the present embodiment, ECU 300 includes first SOC region (hysteresis large region) having hysteresis due to charging / discharging in relation to OCV with respect to SOC of battery pack 100, and second SOC region having smaller hysteresis than the first SOC region. In the case where the charge / discharge period in the first SOC region is long among (small hysteresis), the frequency of charge / discharge in the first SOC region is lower than that in the case where the charge / discharge period is short.

  In the present embodiment, ECU 300 determines that ΔSOC used in the CS mode and the control center are larger than the threshold when the full charge capacity of assembled battery 100 is smaller than the threshold. Also, the frequency of charging / discharging in the large hysteresis region is reduced by changing to the high SOC side.

  If it does in this way, since the frequency of charging / discharging in a large hysteresis area | region can be reduced, it can suppress that deterioration of the assembled battery 100 is accelerated | stimulated.

  Hereinafter, a control process executed by the ECU 300 will be described with reference to FIG. FIG. 4 is a flowchart showing a control process executed by ECU 300. The processing shown in this flowchart is called and executed from a main routine (not shown) at every predetermined control cycle. Each step included in these flowcharts is basically realized by software processing by the ECU 300, but a part or all of the steps may be realized by hardware (electric circuit) produced in the ECU 300.

  In step (hereinafter, “step” is described as “S”) 100, ECU 300 acquires the OCV and current integration amount of cell 110 in the small hysteresis region. ECU 300 acquires the OCV and the current integration amount for each of the plurality of cells 110.

  Specifically, ECU 300 considers, for example, the value obtained by multiplying voltage Vb detected by voltage sensor 210 by internal resistance Rb of battery pack 100 and current Ib, that is, OCV by taking into account the influence of overvoltage and polarization. Is calculated. ECU 300 may calculate, for example, the slope of the change in current Ib with respect to the change in voltage Vb per unit time of cell 110 as an internal resistance, or may estimate using other known techniques.

  Further, ECU 300 calculates a current integrated amount between predetermined OCVs when the calculated OCV is larger than the OCV threshold corresponding to SOC_th (that is, the hysteresis small region). Specifically, ECU 300 calculates, for example, the current integration amount from the time when the calculated OCV becomes the first OCV to the time when the calculated OCV becomes the second OCV (<first OCV). The ECU 300 calculates the current current integration amount by adding a value obtained by multiplying the current detected by the current sensor 220 and the time from the calculation time of the previous current integration amount to the previous current integration amount. For example, ECU 300 resets the current integrated amount to an initial value (for example, zero) when OCV becomes the first OCV, starts calculation of the current integrated amount, and calculates the current integrated amount when OCV becomes the second OCV. The calculation ends.

  In S102, ECU 300 calculates a full charge capacity. The ECU 300 calculates the full charge capacity using, for example, the SOC difference corresponding to the difference between the first OCV and the second OCV and the current integrated amount. ECU 300 is based on, for example, the relationship between the OCV and the SOC shown in FIG. 3, the SOC difference calculated using the difference between the first OCV and the second OCV, and the charge amount based on the current integrated amount (for example, The charge amount for SOC 100% is calculated from the ratio of the charge amount to the SOC difference, and the full charge capacity is calculated. Note that the method for calculating the full charge capacity is not limited to the method described above, and may be calculated using other known techniques. ECU 300 calculates the full charge capacity for each of the plurality of cells 110.

  In S104, ECU 300 determines whether or not the calculated full charge capacity is equal to or less than threshold value A. The threshold A is a threshold for determining whether the degree of deterioration of the cell 110 is greater than or equal to a predetermined degree (that is, whether the full charge capacity has decreased from the initial value to a rate corresponding to the predetermined degree of deterioration). Value. If it is determined that the calculated full charge capacity is equal to or less than threshold value A (YES in S104), the process proceeds to S106. If it is determined that the calculated full charge capacity is greater than threshold A (NO in S104), the process returns to S100. For example, ECU 100 determines that the calculated full charge capacity is equal to or less than threshold A when at least one full charge capacity of cells 110 is equal to or less than threshold A.

  In S106, ECU 300 changes the usage range (ΔSOC and control center) of cells 110 in the CS mode. In the present embodiment, ECU 300 uses SOC (3) in which control lower limit SOC (1) is increased by a predetermined amount and SOC (4) in which control upper limit SOC (2) is increased by a predetermined amount. At the same time, the control center SOC_c is increased by a predetermined amount. Note that the control lower limit value, the control upper limit value, and the increase amount of the control center will be described as being the same amount as an example in the present embodiment.

  The operation of ECU 300 based on the above structure and flowchart will be described with reference to FIGS. 5 and 6. FIG. 5 is a timing chart showing the change with time of the full charge capacity. The vertical axis in FIG. 5 indicates the full charge capacity, and the horizontal axis in FIG. 5 indicates the total usage time. Moreover, FIG. 6 is a figure for demonstrating the use range of SOC before and behind a change. The vertical axis in FIG. 6 indicates OCV, and the horizontal axis in FIG. 6 indicates SOC. A solid line LN1 in FIG. 6 shows a change in the OCV of any one of the plurality of cells 110 when the assembled battery 100 is charged from the fully discharged state in the same manner as the solid line LN1 in FIG. A broken line LN2 in FIG. 6 shows a change in the OCV of the cell 110 when the assembled battery 100 is discharged from the fully charged state, similarly to the broken line LN2 in FIG. Also in FIG. 6, it is assumed that a small hysteresis region and a large hysteresis region are set with SOC_th as a boundary, as in FIG.

  After the external charging of the assembled battery 100 is completed, as shown in FIG. 5, when the operation of the vehicle 1 is first started at time t (2), the OCV and current integrated amount of the cell 110 in the small hysteresis region. Is started (S100). Then, the full charge capacity is calculated using the obtained OCV of the cell 110 and the accumulated current amount (S102). When it is determined that the calculated full charge capacity is greater than threshold value A (NO in S104), control lower limit value SOC (1), control upper limit value SOC (2), and control center SOC_c are changed. Not.

  As shown in FIG. 5, the full charge capacity of the cell 110 decreases as the total usage time of the battery pack 100 increases. If it is determined at time t (3) that the calculated full charge capacity is equal to or less than threshold value A (YES in S104), a plurality of cells 110 in the case where CS mode is selected are selected. The use range is changed (S106). That is, the control lower limit SOC (1) is set to SOC (3) that is higher than SOC (1), and the control upper limit SOC (2) is SOC (2) higher than SOC (2). 4) and the control center is set to SOC_c ′, which is a value higher than SOC_c.

  When the usage range of the plurality of cells 110 is changed in this way, as shown in FIG. 6, both ΔSOC and the control center are changed to the hysteresis small region side after the usage range is changed, and a part of the usage range is changed. It will be included in the small hysteresis area. As a result, when the CS mode is selected, charging / discharging is continued within the changed range of ΔSOC, so that the frequency of charging / discharging within the large hysteresis region is reduced. .

  As described above, according to the control device for a secondary battery according to the present embodiment, when the negative electrode includes a Si-based material, for example, when the CS mode is selected, the lithium ion secondary in the large hysteresis region As the charge / discharge period of the battery (total time since the start of use of the battery) becomes longer, the deterioration of the battery can easily proceed. For this reason, the longer the charge / discharge period in the large hysteresis region, the slower the charge / discharge frequency in the large hysteresis region than in the case where the charge / discharge period is short, thereby making it possible to moderate the deterioration of the battery. As a result, the deterioration of the secondary battery life can be suppressed. Therefore, it is possible to provide a secondary battery charge / discharge control device that suppresses deterioration of a secondary battery including a negative electrode including a Si-based material and a carbon material.

Hereinafter, modifications will be described.
In the above-described embodiment, the assembled battery 100 has been described as an example in which a plurality of cells are connected in series, but is not particularly limited to such a configuration. The assembled battery 100 may be configured, for example, by connecting a plurality of cells in parallel, or by connecting a plurality of assembled batteries configured by connecting a plurality of cells in series. It may be configured.

  Furthermore, in the above-described embodiment, as an example of using a Si-based material as a representative material of a negative electrode having a large volume change (expansion / shrinkage) of the active material, other materials (for example, alloyed with lithium, for example, (Sn-based material, Ge-based material or Pb-based material) may be used. Here, a material having a large volume change can be considered as a material exhibiting a larger expansion / contraction than a volume change of about 10% such as graphite. Moreover, when the volume change of the positive electrode active material is large, the hysteresis derived from the positive electrode may be considered from the same viewpoint as the hysteresis when the Si-based material is used.

  Furthermore, in the above-described embodiment, the assembled battery 100 may be a lithium ion battery, and various lithium ion batteries can be used. The assembled battery 100 may be, for example, a lithium ion battery using a liquid electrolyte, a polymer lithium ion battery using a gel polymer as an electrolyte, or an all solid using a solid electrolyte. Lithium ion batteries may be used.

  Furthermore, in the above-described embodiment, the voltage sensor 210 and the temperature sensor 230 are provided for each of the plurality of cells 110 to detect the voltage and temperature. For example, a predetermined number of cells 110 are grouped into one group. The voltage and temperature may be detected at.

  Further, in the above-described embodiment, the ΔSOC after the change is described as changing to the small hysteresis region side while maintaining the size of the ΔSOC before the change, but for example, the ΔSOC set in the large hysteresis region is changed. It may be set to be smaller than the magnitude of ΔSOC before the change (the magnitude of ΔSOC before the full charge capacity becomes equal to or less than threshold A).

  Furthermore, in the above-described embodiment, there is no particular mention of the input / output allowable values Win and Wout of the battery pack 100 when the full charge capacity is equal to or less than the threshold value A. When the threshold value A is less than or equal to the threshold value A, the full charge capacity is a threshold value A that is at least one of the allowable input value Win of the assembled battery 100 and the allowable value Wout of the output power of the assembled battery 100. You may set so that it may become smaller than the size before becoming below.

  A control process executed by ECU 300 in a modification in which the magnitude of ΔSOC and the allowable value of input / output power are reduced when the full charge capacity is equal to or less than threshold value A will be described below with reference to FIG. FIG. 7 is a flowchart showing a control process executed by ECU 300 in the modified example. Note that the processing of S100, S102, and S104 in the flowchart shown in FIG. 7 is the same as the processing of S100, S102, and S104 in the flowchart shown in FIG. Therefore, detailed description thereof will not be repeated.

  If it is determined that the full charge capacity is equal to or less than threshold value A (YES in S104), ECU 300 sets ΔSOC used in the CS mode in S200. Specifically, while maintaining the control center, ECU 300 sets ΔSOC by adding a predetermined value to the control lower limit value at the time of calculation and subtracting the predetermined value from the control upper limit value at the time of calculation.

  In S202, ECU 300 sets the magnitude of allowable value Win of input power to assembled battery 100 used in the CS mode and the magnitude of allowable value Wout of output power from assembled battery 100. In the following description, for example, a case where the allowable value Wout of the output power is a positive value and the allowable value Win of the input power is a negative value will be described as an example. In this case, the ECU 300 reduces the magnitude of the allowable value Win of the input power by adding a predetermined value to the allowable value Win of the input power at the time of calculation. Similarly, ECU 300 reduces the size of allowable value Wout of output power by subtracting a predetermined value from allowable value Wout of output power at the time of calculation.

  Hereinafter, the operation of the ECU 300 in this modification will be described with reference to FIG. FIG. 8 is a timing chart showing changes in the full charge capacity, ΔSOC, allowable input power value Win, and allowable output power value Wout in the modified example. The vertical axis of each graph in FIG. 8 indicates the full charge capacity, ΔSOC, and power from the top. The horizontal axis of each graph in FIG. 8 indicates the total usage time.

  After the external charging of the assembled battery 100 is completed, as shown in FIG. 8, when the operation of the vehicle 1 is first started at time t (4), the OCV of the cell 110 and the current integrated amount are acquired. It starts (S100). Then, the full charge capacity is calculated using the obtained OCV of the cell 110 and the accumulated current amount (S102). If it is determined that the calculated full charge capacity is greater than threshold value A (NO in S104), ΔSOC, input power allowable value Win, and output power allowable value Wout are not changed.

  As shown in FIG. 8, the full charge capacity decreases as the total usage time of the battery pack 100 increases. If it is determined at time t (5) that the calculated full charge capacity is equal to or less than threshold value A (YES in S104), ΔSOC used in the CS mode is set (S200). ), The allowable value of the input power and the allowable value of the output power used in the CS mode are set (S202).

  That is, a predetermined value is added to the control lower limit SOC (1) at time t (5), and ΔSOC reduced by subtracting the predetermined value from the control upper limit SOC (2) at time t (5) is set. The Thus, when the initial value of ΔSOC is ΔSOC_a, a value smaller than the initial value ΔSOC_a is set as ΔSOC at time t (5).

  Similarly, a predetermined value is added to the allowable value Win_a of input power at time t (5), and the predetermined value is subtracted from the allowable value Wout_a of output power at time t (5). Thereby, the allowable value Win of the input power and the allowable value Wout of the output power are set to values smaller than the initial value.

  After time t (5), the process shown in the flowchart of FIG. 7 is repeatedly executed, so that ΔSOC, the allowable value of input power Win, and the allowable value of output power Wout are Decrease from the initial value.

  When the negative electrode includes a Si-based material, for example, when the CS mode is selected, the deterioration of the battery can easily progress as the charge / discharge period of the lithium ion secondary battery in the large hysteresis region increases. Therefore, as the charge / discharge period in the large hysteresis region becomes longer, ΔSOC, the allowable value of input power Win, and the allowable value of output power Wout are reduced, so that the change in SOC becomes gentle and the deterioration of the battery is reduced. Progress can be slow. As a result, the deterioration of the secondary battery life can be suppressed.

  In the above-described modification, it has been described that ΔSOC, the allowable value Win of the input power, and the allowable value Wout of the output power are reduced when the full charge capacity is equal to or less than the threshold value A. , ΔSOC, the magnitude of the allowable value Win of the input power, and the magnitude of the allowable value Wout of the output power may be reduced. Further, in the above-described modified example, when the full charge capacity is equal to or less than the threshold value A, ΔSOC, the allowable value of input power Win, and the allowable value of output power Wout are assumed to be small. However, while moving ΔSOC to the hysteresis small region side so that a part of ΔSOC overlaps the hysteresis small region, ΔSOC, the magnitude of the allowable value Win of the input power, and the size of the allowable value Wout of the output power You may make it make at least any one of these small.

In addition, you may implement combining the above-mentioned modification, all or one part.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present disclosure is shown not by the above description of the embodiments but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

  1 vehicle, 10, 12 motor generator, 14 engine, 16 power split mechanism, 18 CHR, 20 charging device, 22 inlet, 24 plug, 26 external power supply, 28 drive wheel, 40 PCU, 50 SMR, 100 assembled battery, 110 cell , 210 voltage sensor, 220 current sensor, 230 temperature sensor, 300 ECU, 301 CPU, 302 memory.

Claims (2)

A charge / discharge control device for a secondary battery that controls charge / discharge of a lithium ion secondary battery comprising a negative electrode comprising a Si-based material and a carbon material,
A current detector for detecting a charge / discharge current of the secondary battery;
A controller for controlling the charge / discharge current,
In the first SOC region, the control unit includes a first SOC region having hysteresis due to charging / discharging in relation to an OCV with respect to the SOC of the secondary battery, and a second SOC region having a smaller hysteresis than the first SOC region. The charging / discharging control apparatus of a secondary battery which reduces the frequency of charging / discharging in said 1st SOC area | region when the charging / discharging period is long compared with the case where the said charging / discharging period is short. A charge / discharge control device for a secondary battery that controls charge / discharge of a lithium ion secondary battery comprising a negative electrode comprising a Si-based material and a carbon material,
A current detector for detecting a charge / discharge current of the secondary battery;
A controller for controlling the charge / discharge current,
In the first SOC region, the control unit includes a first SOC region having hysteresis due to charging / discharging in relation to an OCV with respect to the SOC of the secondary battery, and a second SOC region having a smaller hysteresis than the first SOC region. When the charge / discharge period is long, the difference between the control upper limit value and the control lower limit value of the SOC in the first SOC region and the allowable value of the input power of the secondary battery are larger than when the charge / discharge period is short. And a secondary battery charge / discharge control device that reduces at least one of the allowable values of the output power of the secondary battery.

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