JP5401884B2 - Lithium secondary battery charge control method, charge control device, and vehicle - Google Patents

Description

  The present invention relates to a charge control method for a lithium secondary battery, a charge control device, and a vehicle equipped with the device.

  Lithium secondary batteries are used as driving power sources for automobiles and the like. When the lithium secondary battery is repeatedly charged and discharged, the materials of the positive electrode and the negative electrode deteriorate. For example, the metal in the positive electrode active material is eluted and the internal resistance is gradually increased. When a battery having an increased internal resistance is used under a high voltage, the deterioration of the battery is further promoted. As a result, a decrease in battery capacity is accelerated.

  The decrease in the battery capacity due to the increase in the internal resistance of the battery as described above is called natural deterioration, and is accepted in the lithium secondary battery as the battery life. On the other hand, it is desired and studied to improve the total discharge amount (discharge integrated amount) until the battery capacity is lowered to a value that cannot be used (battery life expires).

  The cause of the decrease in the battery capacity is considered other than natural degradation, and various techniques for reducing the cause have been proposed.

  For example, a method has been proposed in which a period after the completion of charging is measured and discharged so as to be a predetermined voltage or less depending on the period, thereby reducing characteristic deterioration during long-term storage (see Patent Document 1). .

Further, in order to extend the life of the battery, there is also known an apparatus that sets an end voltage at which discharge is terminated according to the discharge characteristics of the battery, and changes the setting of the end voltage according to the use state of the battery (Patent Document 2). reference).
Japanese Patent Laid-Open No. 2002-367681 JP 2005-269708 A

  However, in the above-described invention, although deterioration of the battery due to long-term storage can be reduced, there is a problem that the discharge capacity (accumulated discharge amount) after long-term storage decreases due to natural deterioration due to an increase in internal resistance.

  The present invention has been made in view of the above circumstances, and reduces a battery's natural deterioration due to an increase in internal resistance, and maximizes the battery's integrated discharge amount. The object is to provide a vehicle.

The method for controlling the charging of a lithium secondary battery according to the present invention includes a constant current-constant voltage charging cycle for charging a lithium secondary battery, in which charging current supply is stopped during constant current charging or immediately after constant current charging. Includes a measurement process for measuring the voltage drop. Then, a determination step for determining whether or not the voltage drop amount is equal to or greater than a threshold value, and a setting for setting the target value of the full charge voltage when charging the lithium secondary battery lower than the current value when the voltage drop amount is equal to or greater than the threshold value And a process. A plurality of target values are prepared, and in the setting step, a lower target value is set every time the voltage drop amount exceeds the threshold value. The threshold is prepared in a plurality of stages, and further includes a threshold setting step for setting a lower threshold every time the target value is set lower.
The method for controlling the charging of a lithium secondary battery according to the present invention includes a constant current-constant voltage charging cycle for charging a lithium secondary battery, in which charging current supply is stopped during constant current charging or immediately after constant current charging. Includes a measurement process for measuring the voltage drop. Then, a determination step for determining whether or not the voltage drop amount is equal to or greater than a threshold value, and a setting for setting the target value of the full charge voltage when charging the lithium secondary battery lower than the current value when the voltage drop amount is equal to or greater than the threshold value And a process. In the constant current-constant voltage charge cycle constant current charging, the measurement process, the determination process, and the setting process are performed such that the voltage of the lithium secondary battery is set to a reference voltage that is set lower than a new target value that can be set in the setting process. It is executed when it reaches.

In the constant current-constant voltage charging cycle for charging the lithium secondary battery, the charging control device for the lithium secondary battery of the present invention stops supplying the charging current during constant current charging or immediately after constant current charging. Includes a measuring instrument that measures the voltage drop. And the determination part which determines whether the voltage drop amount is more than a threshold value, and the setting which sets the target value of the full charge voltage at the time of charging a lithium secondary battery lower than the present condition when the voltage drop amount is more than the threshold value And a storage unit for storing the target value in a plurality of stages. The setting unit reads a lower target value from the storage unit and sets it as a new target value every time the voltage drop amount exceeds the threshold value. The storage unit stores the threshold value in a plurality of stages, and the setting unit sets a lower threshold value every time the target value is set lower.
In the constant current-constant voltage charging cycle for charging the lithium secondary battery, the charging control device for the lithium secondary battery of the present invention stops supplying the charging current during constant current charging or immediately after constant current charging. Includes a measuring instrument that measures the voltage drop. And the determination part which determines whether the voltage drop amount is more than a threshold value, and the setting which sets the target value of the full charge voltage at the time of charging a lithium secondary battery lower than the present condition when the voltage drop amount is more than the threshold value Part. In constant current charging of a constant current-constant voltage charging cycle, when the voltage of the lithium secondary battery reaches a reference voltage set lower than a new target value that can be set by the setting unit, the measuring instrument performs measurement. The determination unit executes the determination, and the setting unit executes the setting.

  According to the charge control method and the charge control device of the lithium secondary battery of the present invention, since the voltage drop amount ΔV is used as the value of the parameter that increases due to natural deterioration, the elution of the metal in the positive electrode active material, etc. Using a value that directly increases due to material deterioration, natural deterioration due to an increase in internal resistance can be reliably detected, and the target value of the full charge voltage can be set low in accordance with the natural deterioration. When the target value of the full charge voltage is reduced, charging under a high voltage is reduced, so that natural deterioration can be reduced, and as a result, a reduction in battery capacity can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a schematic configuration of a charge control device for a lithium secondary battery, and FIG. 2 is a diagram illustrating a voltage of a CC-CV charge / discharge cycle.

  A charge control device 20 is connected to the lithium secondary battery 10. The lithium secondary battery 10 may be any secondary battery as long as lithium ions in the electrolyte conduct electricity. For example, a bipolar electrode in which a positive electrode active material layer is formed on one surface of a current collector and a negative electrode active material layer is formed on the other surface is a bipolar electrode in which a battery element in which an electrolyte layer is sandwiched is sealed Type secondary battery. Alternatively, a battery in which a positive electrode in which a positive electrode active material layer is formed on both surfaces of a positive electrode current collector and a negative electrode in which a negative electrode active material layer is formed on both surfaces of the negative electrode current collector are stacked via an electrolyte layer. This is a stacked secondary battery in which elements are sealed.

  The battery 10 is charged and discharged through a CC-CV (constant current-constant voltage) charge / discharge cycle shown in FIG. During CC (constant current) charging, the voltage value is increased while the current value is fixed, and charging is performed until the battery 10 reaches the target value of the full charge voltage. During CV (constant voltage) charging, the current value is reduced while the voltage value is fixed at the full charge voltage, and charging is performed until the battery reaches a predetermined capacity.

The charging control device 20 is a device that controls charging / discharging of the battery 10, and includes a detector 21, a storage unit 22, and a control unit 23. The detector 21 is attached to the battery 10. In the CC-CV charging cycle shown in FIG. 2, the detector 21 measures a voltage drop amount (hereinafter referred to as ΔV) after a predetermined time has elapsed since the supply of current was stopped during CC charging or immediately after CC charging. Here, the predetermined time is, for example, about 10 ⁻³ seconds to 10 minutes after the supply of current is stopped. During this time, voltage variations due to resistance variations in the battery are equalized.

  As the natural degradation of the battery 10 progresses, the material of the positive electrode and the negative electrode deteriorates. For example, the metal in the positive electrode active material is eluted, the internal resistance gradually increases, and the voltage drop amount ΔV after a predetermined time increases. . Therefore, the voltage drop amount ΔV becomes a parameter value that increases due to the natural deterioration of the battery 10.

  The storage unit 22 stores Vm (V1, V2,...) As candidates for the target value V of the full charge voltage when charging the battery 10. Here, V1> V2> V3... Further, the storage unit 22 stores αm (α1, α2,...) As candidates for the threshold value α as a set with each target value V (V1, V2,...). Here, the values become smaller in the order of α1> α2. The threshold value α is a value serving as a reference when changing a target value V of a full charge voltage described later. In addition, the storage unit 22 stores a plurality of stages of Im (I1, I2,...) As current value candidates during CC charging as a set with the target value V of the full charge voltage.

  The control unit 23 is connected to the detector 21 and the storage unit 22, and is also directly connected to the battery 10. The control unit 23 controls charging / discharging of the battery 10. As will be described later, the control unit 23 functions as a determination unit that determines whether the voltage drop amount ΔV is higher than the threshold value α. The control unit 23 also functions as a setting unit that sets a target value of the full charge voltage when charging the battery 10 based on the voltage drop amount ΔV detected by the detector 21. Furthermore, it also functions as a current setting unit that sets a current value during CC charging.

  Further, as shown in FIG. 2, the control unit 23 recharges the battery 10 by the voltage drop amount ΔV. This is one cycle of CC-CV charging including this recharging.

  The operation of the control unit 23 will be described in detail.

  FIG. 3 is a flowchart showing a flow of operation of the control unit.

  First, the control unit 23 substitutes 1 as a variable m as an initial value (step S1), sets the target value of the full charge voltage to V = V1, the threshold value α to α = α1, and the CC charge current value I. Is set to I = I1 (step S2).

  The controller 23 starts CC charging at the current value I with the start of charging (step S3). The current value I is, for example, a current that is charged to a full charge voltage V in 1 hour (1C charging). Alternatively, it may be a current that charges to a full charge voltage V in 30 minutes (2C charge) or a current that charges to a full charge voltage V in 20 minutes (3C charge).

  The controller 23 determines whether or not the voltage has reached the set target value V in CC charging (step S4). When the target value V has not been reached (step S4: NO), CC charging is continued.

When the target value V is reached (step S4: YES), the control unit 23 stops supplying current to the battery 10 (step S5) and waits for a predetermined time. Here, the predetermined time is 10 ⁻³ seconds to 10 minutes, for example, 1 second. The controller 23 uses the detector 21 to measure the voltage drop amount ΔV after a predetermined time of the battery 10 (step S6).

  The control unit 23 starts CC charging again in order to charge the battery 10 by the voltage drop amount ΔV so as to bring the battery 10 to a fully charged voltage (step S7). The controller 23 determines whether or not the voltage has reached the set target value V (step S8). When the target value V has not been reached (step S8: NO), CC charging is continued.

  When the target value V is reached (step S8: YES), the control unit 23 starts CV charging (step S9). And the control part 23 determines whether the electric current value which flows into the battery 10 is constant (step S10). If the current value is not constant (step S10: NO), CV charging is continued. When the current value is constant (step S10: YES), the control unit 23 ends the CV charging. The control part 23 discharges the battery 10 until it becomes a predetermined voltage as needed (step S11).

  After discharging, the control unit 23 determines whether or not the voltage drop amount ΔV measured in step S6 is greater than or equal to the threshold value α (step S12). If the voltage drop amount ΔV is not equal to or greater than the threshold value α (step S12: NO), the process proceeds to step S15.

  When the voltage drop amount ΔV is equal to or greater than the threshold value α (step S12: YES), the control unit 23 increments the variable m by 1 (step S13). The control unit 23 calls Vm, αm, and the CC charging current value Im from the storage unit 22, and sets the target value V (= Vm) of the full charging voltage, the threshold value α (= αm), and the CC charging current value I (I = Im ) Is updated (step S14). The target value Vm updated here is a value lower than the previous target value Vm-1.

  The control unit 23 determines whether or not to proceed to the next charge / discharge cycle (step S15), and when it proceeds (step S15: YES), the processing from step S3 is repeated. If it does not proceed to the next charge / discharge cycle (step S15: NO), the system is terminated.

  According to the above lithium secondary battery charge control device, the following effects can be obtained.

  As the value of the voltage drop ΔV is used as the value of the parameter that rises due to natural degradation, the natural degradation is ensured by using the value that rises directly due to material degradation such as elution of metal in the positive electrode active material. It can be detected and the target value of the full charge voltage can be set low according to the natural deterioration. When the target value of the full charge voltage is reduced, charging under a high voltage is reduced, so that natural deterioration can be reduced, and as a result, a reduction in battery capacity can be reduced.

The control unit 23 evaluates the voltage drop amount ΔV after the discharge following the current constant current-constant voltage charging cycle is executed, and when the threshold value α is equal to or larger than the threshold value α, the target value of the full charge voltage is lowered. The target value V is updated. That is, the target value is not updated during the current constant current-constant voltage charging cycle. Therefore, even if the amount of voltage drop during the measurement process is large, recharging is performed accordingly. Therefore, the amount of voltage drop ΔV due to natural degradation that can be used effectively without wastefully discharging the charged power is When the threshold value α is exceeded, the target value of the full charge voltage V at the next charge is lowered. That is, since the potential in the deteriorated state is lowered, elution of the metal in the positive electrode active material layer in the next charge can be suppressed, and acceleration of natural deterioration can be prevented. As a result, the accumulated discharge amount of the battery 10 can be improved.

  FIG. 4 is a diagram showing an example of the accumulated discharge amount of the battery.

  Referring to FIG. 4, when the target value of the full charge voltage is fixed at 4.3 V (V1), the discharge amount decreases linearly, and the integrated discharge amount is the amount indicated by cross hatching in FIG. It becomes. When the target value of the full charge voltage is fixed at 4.2 V (V2), the discharge amount decreases linearly with a smaller slope than when the target value is 4.3 V. When the target value of the full charge voltage is fixed at 4.1 V (V3), the discharge amount decreases linearly with a smaller slope than when the target value is 4.2 V. The smaller the target value, the smaller the initial discharge amount.

  However, in the above embodiment, the target value is prepared in multiple stages such as V1 = 4.3V, V2 = 4.2V, V3 = 4.1V, etc., so the target value is 4. The integrated discharge amount of the present embodiment is obtained as a sum set of integrated discharge amounts when fixed at 3 V, 4.2 V, and 4.1 V, respectively. That is, in the example of FIG. 4, in addition to the cross hatched portion, the discharge amount integrated amount can be obtained in the hatched portion. Battery degradation can be reduced more effectively, and the amount of accumulated discharge of the battery can be improved. As shown in FIG. 4, the threshold value αm is obtained in advance by experiments or the like so that the target value Vm is switched in order.

  Further, a plurality of threshold values α are prepared, and the threshold value α is set lower as the target value V of the full charge voltage is set lower. Even with batteries having the same degree of deterioration, the voltage drop amount ΔV increases as the full charge voltage increases. Therefore, when the target value V of the full charge voltage is lowered, the threshold value α is also lowered and the degree of deterioration can be determined, so that an appropriate threshold value α can be set according to the full charge voltage. The progress of the natural deterioration of the battery can be effectively reduced step by step, and the accumulated discharge amount of the battery can be improved.

  According to the embodiment, even if the target value V is set low, the time until the voltage reaches the target value V is shortened unless the current value I is changed. There is a correlation between the full charge voltage, the charging speed, and the voltage drop amount ΔV. As the time to the target value V becomes shorter, the voltage drop amount ΔV increases as a reaction. If the voltage drop amount ΔV increases for a reason different from the deterioration of the battery material, the deterioration of the battery cannot be determined accurately. Therefore, the charging time (speed) can be made the same by decreasing the current value I every time the target value V is set low. In the above-described embodiment, for example, the current I is adjusted so that 1C charging is always performed. As a result, it is possible to determine only the deterioration of the battery material by determining that the correlation balance of the voltage drop amount ΔV is broken among the full charge voltage, the charging speed, and the voltage drop amount ΔV.

  In the embodiment described above, for example, 1C charging is performed uniformly during one CC-CV charging cycle, but the present invention is not limited to this. The current value I may be adjusted so as to achieve 1C charging by changing the charging speed immediately before the full charge voltage is reached. As a result, even if the target value V is different, it is possible to make a legitimate evaluation by making the amount of voltage drop that causes a reaction proportional to the degree of deterioration.

  In addition, the said embodiment is applicable not only to the regular charging / discharging cycle which repeats charging / discharging of constant current but to all the charging / discharging cycles which may occur by use of the battery 10, such as the case where it recharges without using up capacity.

(Second Embodiment)
In the second embodiment, the voltage drop amount ΔV is evaluated at a different timing from the first embodiment, and the target value V of the full charge voltage is set.

  In 2nd Embodiment, since the effect | action of the control part 23 differs from 1st Embodiment, this effect | action is demonstrated.

  FIG. 5 is a flowchart showing a flow of operation of the control unit of the second embodiment.

  First, as an initial value, the control unit 23 substitutes 1 as a variable m (step S21), sets the target value of the full charge voltage to V = V1, the threshold value α to α = α1, and the CC charging current value I. Is set to I = I1 (step S22).

  The controller 23 starts CC charging at the current value I with the start of charging (step S23). The current value I is, for example, a current that is charged to a full charge voltage V in 1 hour (1C charging). Alternatively, it may be a current that charges to a full charge voltage V in 30 minutes (2C charge) or a current that charges to a full charge voltage V in 20 minutes (3C charge).

  The controller 23 determines whether or not the voltage of the battery 10 has reached the reference voltage Vt during CC charging (step S24). Here, the reference voltage Vt is set lower than the target value V of the full charge voltage that can be set in the future. For example, when the target value V1 of the full charge voltage of the current CC-CV charge cycle is V1 = 4.3V and V2 = 4.2V which can be set in the future, the reference voltage Vt = 4.1V.

  When the reference voltage Vt has not been reached (step S24: NO), CC charging is continued.

When the reference voltage Vt is reached (step S24: YES), the control unit 23 stops supplying current to the battery 10 (step S25) and waits for a predetermined time. Here, the predetermined time is 10 ⁻³ seconds to 10 minutes, for example, 1 second. The control unit 23 uses the detector 21 to measure the voltage drop amount ΔV of the battery 10 for a predetermined time (step S26).

  The controller 23 determines whether or not the measured voltage drop amount ΔV is greater than or equal to the threshold value α (step S27). If the voltage drop amount ΔV is not equal to or greater than the threshold value α (step S27: NO), the process proceeds to step S30.

  When the voltage drop amount ΔV is greater than or equal to the threshold value α (step S27: YES), the control unit 23 increments the variable m by 1 (step S28). The control unit 23 calls Vm, αm, and the CC charging current value Im from the storage unit 22, and sets the target value V (= Vm) of the full charging voltage, the threshold value α (= αm), and the CC charging current value I (I = Im ) Is updated (step S29). The target value Vm updated here is a value lower than the previous target value Vm-1.

  The control unit 23 starts CC charging again in order to charge the battery 10 to the target value V of the fully charged voltage (step S30). The controller 23 determines whether or not the voltage has reached the set target value V (step S31). When the target value V has not been reached (step S31: NO), CC charging is continued.

  When the target value V is reached (step S31: YES), the control unit 23 starts CV charging (step S32). And the control part 23 determines whether the electric current value which flows into the battery 10 is constant (step S33). If the current value is not constant (step S33: NO), CV charging is continued. When the current value is constant (step S33: YES), the control unit 23 ends the CV charging. The control part 23 discharges the battery 10 until it becomes a predetermined voltage as needed (step S34).

  After discharging, the control unit 23 determines whether or not to proceed to the next charge / discharge cycle (step S35), and when proceeding (step S35: YES), the processing from step S3 is repeated. If it does not proceed to the next charge / discharge cycle (step S35: NO), the system is terminated.

  According to the above lithium secondary battery charge control device, the following effects can be obtained.

  Since the voltage drop amount ΔV is measured at the time of the reference voltage Vt set lower than the new target value V that can be set, a new target value V is set when the voltage drop amount ΔV is greater than or equal to the threshold value α. Even in this case, the current voltage of the battery 10 does not exceed the target value V. Therefore, even if charging is continued up to the target value after changing the target value V from the current charging, it is not necessary to discharge excessively and it does not take extra time for charging.

  Further, similarly to the first embodiment, since the target value of the full charge voltage can be set low in accordance with the natural deterioration, the promotion of the natural deterioration can be reduced, and the discharge amount integrated amount of the battery can be maximized.

(Third embodiment)
The third embodiment has a new process in addition to the first and second embodiments. Therefore, it demonstrates centering on the newly added process. In the third embodiment, the detector 21 also serves as a temperature detector that detects the temperature of the battery 10.

  FIG. 6 is a flowchart showing steps unique to the third embodiment.

  In the flowchart shown in FIG. 6, there are two blocks (A) and (B). In the block (A), the threshold value α is adjusted based on the temperature of the battery 10, and in the block (B), the threshold value α is adjusted based on the number N of charge / discharge cycles.

  After the process of step S5 in FIG. 3 or step S25 in FIG. 5, the control unit 23 proceeds to step S40 in FIG. The controller 23 detects the battery temperature T by the detector 21 (step S40). The control unit 23 determines whether or not the detected temperature T is equal to or higher than a predetermined temperature β (step S41).

  When the detected temperature T is not equal to or higher than the predetermined temperature β (step S41: NO), the process proceeds to step S50. When the detected temperature T is equal to or higher than the predetermined temperature β (step S41: YES), the threshold α is divided by γ (γ> 1) (step S42). Thereby, the threshold value α is set to a lower value.

  Then, the control part 23 calls the charging / discharging cycle frequency N so far from the memory | storage part 22 (step S50). The storage unit 22 counts each time charging is repeated and stores the number of times.

  The controller 23 selects the coefficient εn (εn> 1) based on the number N of charge / discharge cycles (step S51). Here, the selected coefficient εn is stored in the storage unit 22 as a set of a plurality of coefficients (ε1, ε2,...). Whenever the number of times the battery 10 is used increases, the control unit 23 considers that the deterioration has progressed and selects an appropriate coefficient. For example, the coefficient εn is larger as n is larger, such as ε1 <ε2 <ε3 <. The control unit 23 may select the coefficient εn with the number of times N = n.

  The control unit 23 divides the threshold value α by εn (step S52). Thereby, the threshold value α is set to a lower value.

  As described above, in the block (A) of the second embodiment, the temperature of the battery 10 is detected, and when the temperature is equal to or higher than the predetermined temperature β, the threshold value α is set lower again. This is due to the following reason. As the material of the battery deteriorates, the resistance in the battery increases. On the other hand, the higher the temperature, the lower the resistance in the battery. Therefore, when the temperature is high, the amount of voltage drop is reduced by the amount of resistance, and it seems that the actual deterioration is not deteriorated. Here, if the target value is set based on the amount of voltage drop that has become smaller due to the high temperature, the target value is set low only after natural degradation has progressed more than at low temperatures. Therefore, as in the above-described process, when the temperature is high, the threshold value α is set (corrected) to be lower, and the target value of the full charge voltage is lowered in accordance with the actual natural deterioration. As a result, the discharge integrated amount can be appropriately maximized based on natural degradation.

  In the above embodiment, the coefficient γ1 is prepared for the predetermined temperature β. However, a plurality of sets of the predetermined temperature β and the coefficient γ1 may be prepared step by step. The higher the temperature, the greater the division by a factor γ1. Further, when the temperature is equal to or higher than the predetermined temperature, not only the division by the coefficient γ1 but also the multiplication by the coefficient γ1 may be performed when the temperature returns to the predetermined temperature or lower. Thereby, the threshold value α can be determined following the temperature.

  The timing of temperature measurement of the battery 10 is not limited to the above embodiment. For example, the measurement may be performed at the stage of entering the CV charge, the maximum temperature during use of the battery 10 may be measured, the temperature when the battery 10 is discharged may be measured, or the voltage may be measured at an arbitrary voltage. . The timing at which the temperature is detected can be appropriately determined depending on the scale and structure of the battery.

  Further, in the block (B) of the above embodiment, since the progress of the natural degradation of the battery 10 is estimated based on the number N of charge / discharge cycles and the threshold value α is lowered, the natural degradation is not affected by the abnormal degradation. The threshold value α can be adjusted. As a result, natural deterioration and abnormal deterioration can be distinguished, and the accumulated discharge amount can be secured.

  In the above embodiment, the case where the coefficient εn is selected with the number N = n is described, but the present invention is not limited to this. For example, the value of n is such that n = 1 when the battery is used up to near the end voltage (charged state 25%), and n = 0.5 when recharged with the charged state remaining 50% or more. May be increased. As a result, the natural degradation can be estimated with high accuracy in consideration of the use situation. As a result, a larger amount of accumulated discharge can be secured.

  In 2nd Embodiment, although the case where (A) block and (B) block were included was demonstrated, it is not limited to this. Only one of them can be applied to the procedure shown in FIG. 3 or FIG.

  In the above embodiment, the threshold value α is corrected to be lower by dividing by the coefficient γ or dividing by the coefficient εn. However, the present invention is not limited to this, and the threshold value α may be corrected by subtracting a predetermined value.

(Fourth embodiment)
4th Embodiment is a vehicle carrying the charging control apparatus of the lithium secondary battery of 1st-3rd embodiment.

  FIG. 7 is a schematic diagram of a vehicle equipped with a charge control device.

  As shown in FIG. 7, a lithium secondary battery 10 is mounted on a vehicle 30 such as an automobile. If the vehicle is equipped with the charge control device 20 to control charging / discharging, the same effects as in the first and second embodiments can be obtained. Therefore, even after the vehicle is shipped, it can be continuously controlled so that the integrated discharge amount is maximized in accordance with the state of the vehicle. As a result, the time until replacement of the battery 10 can be prolonged, and the maintenance cost of the user can be reduced.

(First embodiment)
Next, Example 1 to which the charge control process of the first embodiment is applied will be described.

  First, the configuration of the battery 10 used in the first example is as follows.

<Battery 10>
A positive electrode active material was formed by mixing 85% by weight of nickel-based active material, 10% by weight of acetylene black as a conductive additive, and 5% by weight of PVdF as a binder. A positive electrode active material was applied to both surfaces of a positive electrode current collector made of an aluminum foil to form a positive electrode. Further, 90% by weight of hard carbon and 10% by weight of PVdF as a binder were mixed to constitute a negative electrode active material. A negative electrode active material was applied to both sides of a negative electrode current collector made of copper foil to form a negative electrode. The formed positive and negative electrodes are alternately laminated via separators, sandwiched between two laminate sheets, into which an electrolyte solution in which LiPF6 is dissolved as a lithium salt is poured, and a part of the current collector is drawn out And sealed. According to the above procedure, three same batteries were prepared and used as Comparative Example 1, Comparative Example 2, and Example 1, respectively.

<Measurement>
About each battery, 1 C discharge capacity and the stable CV electric current value were measured with the following method.

  For Comparative Example 1, charging / discharging was repeated 10 times with the target value of the full charge voltage being 4.3 V and the end voltage at which the discharge was terminated being 2.5 V.

  For Comparative Example 2, charging / discharging was repeated 10 times, with the target value of the full charge voltage being 4.2 V and the end voltage at which discharge was terminated being 2.5 V.

  About Example 1, charging / discharging was repeated 10 times, applying the charge control method of 1st Embodiment. Here, the first full charge voltage target value V1 is set to 4.3V, the next full charge voltage target value V2 is set to 4.2V, and the threshold α1 is set to 0.05V. Also in Example 1, the end voltage was set to 2.5V.

  In order to accelerate the deterioration of each battery, the battery was maintained in a 45 ° C. environment for 48 hours in a fully charged state, and a 1-C discharge was defined as one cycle later.

<Result>
The measurement results are as shown in FIGS.

  8 is a diagram showing the relationship between the number of discharges and the discharge capacity, FIG. 9 is a diagram showing the relationship between the number of discharges and the voltage drop amount ΔV, and FIG. 10 is a diagram showing the relationship between the number of discharges and the CV current value. In FIG. 8, the graph is shown on the upper side, and the measured value of the discharge capacity is shown on the lower side.

<Comparative Example 1>
The measurement results of Comparative Example 1 are shown as white circles in FIGS. 8 and 10.

  In Comparative Example 1, as shown in FIG. 8, the 1C discharge capacity decreased each time the number of times was increased. The degree of decrease was the largest compared to Comparative Example 2 and Example 1.

  The voltage drop ΔV of Comparative Example 1 continued to increase gradually as shown in FIG.

  As shown in FIG. 10, in Comparative Example 1, the CV current value increased each time the number of discharges was repeated. An increase in the CV current value means an increase in the amount of electric leakage. As a result, the total discharge amount of Comparative Example 1 was 1055 mAh.

<Comparative example 2>
The measurement results of Comparative Example 2 are shown as crosses in FIGS.

  In Comparative Example 2, since the target value of the full charge voltage is as low as 4.2 V, the 1C discharge capacity is initially small as shown in FIG. However, the decrease rate of the 1C discharge capacity was small.

  The voltage drop ΔV of Comparative Example 2 was generally smaller than that of Comparative Example 1 and gradually increased.

  As shown in FIG. 10, in Comparative Example 2, the CV current value increased each time the number of discharges was repeated. However, compared with Comparative Example 1, the CV current value was considerably small. The total discharge amount of Comparative Example 2 was 1047 mAh.

<Example 1>
The measurement results of Example 1 are shown as white diamond marks in FIGS.

  In Example 1, as shown in FIG. 8, the 1C discharge capacity was initially large as in Comparative Example 1. This is because the target value of the full charge voltage is common at 4.3V.

  As shown in FIG. 9, during the third charge / discharge, the voltage drop ΔV was 0.061 V, which exceeded 0.05 V (threshold α1). Therefore, the target value of the full charge voltage is changed from V1 to V2 by the charge control method of the first embodiment. That is, it was set to 4.2 V, which was the same as in Comparative Example 2. Since the voltage value decreased, the CV current value also decreased at the fourth time as shown in FIG. As a result, referring to FIG. 8, the reduction rate of the 1C discharge capacity in Example 1 was substantially equal to the reduction rate of the 1C discharge capacity in Comparative Example 2 after the fourth time.

  The total discharge amount of Example 1 was 1098 mAh.

<Discussion>
From the above, it can be seen that, as in Comparative Example 1, if the target value of the full charge voltage remains as high as 4.3 V, the voltage drop amount ΔV is large and the total discharge capacity is small. On the other hand, as in Comparative Example 2, when the target value of the full charge voltage is as low as 4.2 V from the beginning, the rate of decrease in the 1C discharge capacity is small. However, since the original 1C discharge capacity is small, it can be seen that the total discharge capacity is also small.

  Compared to these comparative examples 1 and 2, in Example 1, the target value of the full charge voltage is initially set to 4.3V, and when the voltage drop amount ΔV exceeds the threshold value 0.05V, the target value of the full charge voltage is set. The setting was changed to 4.2V. As is apparent from the graph of FIG. 8, the 1C discharge capacity decreases at the same rate as in Comparative Example 1 at first, but the 1C discharge capacity decreases at the same rate as in Comparative Example 2 after the fourth time. To do. That is, the variation of 1C discharge capacity is the same as that of Comparative Example 1 and Comparative Example 2. As a result, it was found that the total discharge capacity of Example 1 was the highest value of 1098 mAh.

(Second embodiment)
Next, Example 2 to which the charge control process of the second embodiment is applied will be described.

  First, the configuration of the battery 10 used in the second example is as follows.

<Battery 10>
A positive electrode active material was formed by mixing 85% by weight of nickel-based active material, 10% by weight of acetylene black as a conductive additive, and 5% by weight of PVdF as a binder. A positive electrode active material was applied to both surfaces of a positive electrode current collector made of an aluminum foil to form a positive electrode. Further, 90% by weight of hard carbon and 10% by weight of PVdF as a binder were mixed to constitute a negative electrode active material. A negative electrode active material was applied to both sides of a negative electrode current collector made of copper foil to form a negative electrode. The formed positive electrode and negative electrode were alternately laminated via separators, sandwiched between two laminate sheets, and an electrolyte solution in which LiPF6 was dissolved as a lithium salt was poured into the inside thereof and sealed. According to the above procedure, three same batteries were prepared and used as Comparative Example 3, Comparative Example 4, and Example 2, respectively.

<Measurement>
About each battery, 1 C discharge capacity and the stable CV electric current value were measured with the following method.

  For Comparative Example 3, charging / discharging was repeated 10 times with the target value of the full charge voltage being 4.3 V and the end voltage at which the discharge was terminated being 2.5 V.

  For Comparative Example 4, charging / discharging was repeated 10 times, with the target value of the full charge voltage being 4.2 V and the end voltage at which discharge was terminated being 2.5 V.

  About Example 2, charging / discharging was repeated 10 times, applying the charge control method of 2nd Embodiment. Here, the first full charge voltage target value V1 is 4.3V, the next full charge voltage target value V2 is 4.2V, and the threshold α1 is 0.04V, which is stored in the storage unit 22. In Example 2, when the voltage first reached 4.1 V during CC charging, the supply of current was stopped and the voltage drop ΔV was measured. Also in Example 2, the end voltage during discharge was set to 2.5V.

  In order to accelerate the deterioration of each battery, the battery was maintained in a 45 ° C. environment for 48 hours in a fully charged state, and a 1-C discharge was defined as one cycle later.

<Result>
The measurement results are as shown in FIGS.

  11 is a diagram showing the relationship between the number of discharges and the discharge capacity, FIG. 12 is a diagram showing the relationship between the number of discharges and the voltage drop amount ΔV, and FIG. 13 is a diagram showing the relationship between the number of discharges and the CV current value. In FIG. 11, a graph is shown on the upper side and a measured value of the discharge capacity is shown on the lower side.

<Comparative Example 3>
The measurement results of Comparative Example 3 are shown as black circles in FIGS. 11 and 13.

  In Comparative Example 3, as shown in FIG. 11, the 1C discharge capacity decreased each time the number was repeated. The degree of decrease was the largest compared to Comparative Example 4 and Example 2.

  The voltage drop ΔV of Comparative Example 3 continued to increase gradually as shown in FIG.

  As shown in FIG. 13, in Comparative Example 3, the CV current value increased each time the number of discharges was repeated. An increase in the CV current value means an increase in the amount of electric leakage. As a result, the total discharge amount of Comparative Example 3 was 1055 mAh.

<Comparative Example 4>
The measurement results of Comparative Example 4 are shown as US marks in FIGS. 11 and 13.

  In Comparative Example 4, since the target value of the full charge voltage is as low as 4.2 V, the 1C discharge capacity is initially small as shown in FIG. However, the decrease rate of the 1C discharge capacity was small.

  The voltage drop amount ΔV of Comparative Example 4 was generally smaller than that of Comparative Example 3 and gradually increased.

  As shown in FIG. 12, in Comparative Example 4, the CV current value increased each time the number of discharges was repeated. However, compared with Comparative Example 3, the CV current value was considerably small. The total discharge amount of Comparative Example 4 was 1047 mAh.

<Example 2>
The measurement results of Example 2 are shown as black diamond marks in FIGS. 11 and 13.

  In Example 2, as shown in FIG. 11, the 1C discharge capacity was initially large as in Comparative Example 3. This is because the target value of the full charge voltage is common at 4.3V.

  As shown in FIG. 12, during the third charge / discharge, the voltage drop ΔV was 0.041V, which exceeded 0.04V (threshold α1). Therefore, the target value of the full charge voltage is changed from V1 to V2 by the charge control method of the second embodiment. That is, it was set to 4.2 V, which was the same as in Comparative Example 2. At the time of charging after the third voltage drop, the new target value V2 was immediately adopted and charged. Since the voltage value decreased, the CV current value also stopped increasing from the third time as shown in FIG. As a result, referring to FIG. 11, the reduction rate of the 1C discharge capacity of Example 1 was substantially equal to the reduction rate of the 1C discharge capacity of Comparative Example 2 after the fourth time.

  The total discharge amount of Example 1 was 1098 mAh.

<Discussion>
From the above, it can be seen that the voltage drop amount ΔV is large and the total discharge capacity is small when the target value of the full charge voltage remains as high as 4.3 V as in Comparative Example 3. On the other hand, as in Comparative Example 4, when the target value of the full charge voltage is as low as 4.2 V from the beginning, the decrease rate of the 1C discharge capacity is small. However, since the original 1C discharge capacity is small, it can be seen that the total discharge capacity is also small.

  Compared with these Comparative Examples 3 and 4, in Example 2, when the target value of the full charge voltage is initially 4.3V, and the voltage drop amount ΔV exceeds the threshold value 0.04V, the target value of the full charge voltage is The setting was changed to 4.2V. As is apparent from the graph of FIG. 11, the 1C discharge capacity is reduced at the same rate as in Comparative Example 3 at first, but the 1C discharge capacity is reduced at the same rate as in Comparative Example 4 after the fourth time. To do. That is, the variation in 1C discharge capacity is the same as that of Comparative Example 3 and Comparative Example 4. As a result, it was found that the total discharge capacity of Example 1 was the highest value of 1098 mAh.

  Further, when compared with Example 1 of the first embodiment, even when the voltage drop ΔV is measured after CC charging is finished, the voltage drop ΔV is measured when the voltage is lower than the full charge voltage. Even so, it was found that the total discharge could be maximized.

(Reference Example 1)
Next, Reference Example 1 will be described.

  First, the configuration of the battery 10 used in Reference Example 1 is as follows.

<Battery 10>
A positive electrode active material was formed by mixing 85% by weight of nickel-based active material, 10% by weight of acetylene black as a conductive additive, and 5% by weight of PVdF as a binder. A positive electrode active material was applied to both surfaces of a positive electrode current collector made of an aluminum foil to form a positive electrode. Further, 90% by weight of hard carbon and 10% by weight of PVdF as a binder were mixed to constitute a negative electrode active material. A negative electrode active material was applied to both sides of a negative electrode current collector made of copper foil to form a negative electrode. The formed positive electrode and negative electrode were alternately laminated via separators, sandwiched between two laminate sheets, and an electrolyte solution in which LiPF6 was dissolved as a lithium salt was poured into the inside thereof and sealed.

<Measurement>
A plurality of the batteries were prepared, and the charge / discharge cycle was repeated 100 times, 200 times, and 300 times to obtain batteries of deterioration A, deterioration B, and deterioration C, respectively. Further, for each of the batteries of degradation A, degradation B, and degradation C, 1C is charged after charging 1C up to a full charge voltage of 4.3V, a full charge voltage of 4.2V, or a full charge voltage of 4.1V. The amount of voltage drop ΔV was measured.

<Result>
The measurement results are as shown in FIG.

  FIG. 14 is a diagram illustrating the relationship between the charging condition and the voltage drop amount.

  Referring to FIG. 14, the battery of deteriorated C that was repeatedly charged and discharged many times had the largest voltage drop ΔV at any full charge voltage. Among batteries with deterioration C, the voltage drop amount ΔV was the largest when the target value of the full charge voltage was 4.3 V, and the voltage drop amount ΔV was the smallest when the target value was 4.1 V.

<Discussion>
From the above, it is understood that the voltage drop amount ΔV increases as the charge / discharge cycle increases, and the voltage drop amount ΔV decreases as the target value of the full charge voltage decreases.

  Therefore, as in the above embodiment, every time the full charge voltage is lowered stepwise, it is necessary to lower the threshold value α in order to switch the full charge voltage stepwise in proportion to the deterioration of the battery. I understand.

(Reference Example 2)
Next, Reference Example 2 will be described.

  First, the configuration of the battery 10 used in Reference Example 2 is the same as that of the battery used in Reference Example 1.

<Measurement>
A plurality of the batteries were prepared, and the charge / discharge cycle was repeated 100 times, 200 times, and 300 times to obtain batteries of deterioration A, deterioration B, and deterioration C, respectively. Further, each of the batteries of deterioration A, deterioration B, and deterioration C was charged at 0.2 C, 1 C, and 3 C up to a full charge voltage of 4.3 V, and a voltage drop ΔV after 1 second was measured.

<Result>
The measurement results are as shown in FIG.

  FIG. 15 is a diagram illustrating the relationship between the charging condition and the voltage drop amount.

  Referring to FIG. 15, the battery of deteriorated C with many repeated charge / discharge cycles had the largest voltage drop ΔV in any of 0.2C, 1C, and 3C charging. Among the batteries with deteriorated C, those with 3C charge had the largest voltage drop amount ΔV.

<Discussion>
From the above, it was found that even in the same battery, the voltage drop amount ΔV varies greatly depending on which of 0.2C, 1C, and 3C charging is adopted. When the target value V of the full charge voltage is changed, if the magnitude of the charging current is not changed, the charging speed is different as 0.2C, 1C, 3C. Therefore, when the target value V of the full charge voltage is changed, it is necessary to change the charging current and make the charging speed (C) uniform. By aligning, it becomes possible to accurately determine the deterioration of the battery.

(Reference Example 3)
Next, Reference Example 3 will be described.

  First, the configuration of the battery 10 used in Reference Example 3 is the same as that of the battery used in Reference Example 1.

<Measurement>
A plurality of the above batteries were prepared, and charged and discharged in an environment of 25 ° C., 45 ° C., and 55 ° C., respectively, to obtain batteries with deteriorated 25 ° C., deteriorated 45 ° C., and deteriorated 55 ° C. With respect to each of the batteries having a deterioration of 25 ° C., a deterioration of 45 ° C., and a deterioration of 55 ° C., the battery was charged with 1 C to a full charge voltage of 4.3 V, 4.2 V, and 4.1 V, and a voltage drop ΔV after 1 second was measured.

<Result>
The measurement results are as shown in FIG.

  FIG. 16 is a diagram illustrating the relationship between the charging condition and the voltage drop amount.

  Referring to FIG. 16, the battery with the lowest environmental temperature and the degraded 25 ° C. had the largest voltage drop ΔV, and the battery with the degraded 55 ° C. had the smallest voltage drop ΔV. Among batteries with a degradation of 25 ° C., those charged to a fully charged voltage of 4.3 V had the largest voltage drop amount ΔV.

<Discussion>
From the above, it has been found that even with batteries having the same degree of deterioration, the voltage drop amount ΔV decreases when the environmental temperature is high. That is, when the environmental temperature is high, the voltage drop amount ΔV is small regardless of the deterioration. Therefore, it is effective to correct the threshold value α low when the temperature increases according to the temperature.

(Battery material)
The material of each part in the lithium secondary battery of the present invention may be a known material, and is not particularly limited. For reference, the material of the lithium ion secondary battery will be briefly described below.

[Current collector]
For example, a metal or a conductive polymer can be adopted as the current collector. Specifically, metal materials, such as aluminum, nickel, iron, stainless steel, titanium, copper, are mentioned, for example. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum and copper are preferable from the viewpoints of electron conductivity and battery operating potential.

[Positive electrode active material layer and negative electrode active material layer]
The positive electrode active material layer and the negative electrode active material layer contain an active material, and further contain other additives as necessary.

i The positive electrode active material layer includes a positive electrode active material. Examples of the positive electrode active material include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium—such as those obtained by replacing some of these transition metals with other elements. Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material. Of course, positive electrode active materials other than those described above may be used.

The negative electrode active material layer includes a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite, soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, and lithium-metal alloy materials. . In some cases, two or more negative electrode active materials may be used in combination. Preferably, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. Of course, negative electrode active materials other than those described above may be used.

  The average particle diameter of each active material contained in each active material layer is not particularly limited, but is preferably 1 to 20 μm and more preferably 1 to 5 μm from the viewpoint of increasing output. However, it goes without saying that a form outside this range may be adopted. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the active material particles. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

  Examples of the additive that can be contained in the positive electrode active material layer and the negative electrode active material layer include a binder, a conductive additive, an electrolyte salt (lithium salt), and an ion conductive polymer.

  Examples of the binder include polyvinylidene fluoride (PVdF) and a synthetic rubber binder.

  The conductive auxiliary agent is an additive that is blended to improve the conductivity of the positive electrode active material layer 12 or the negative electrode active material layer 15. Examples of the conductive assistant include carbon materials such as carbon black such as acetylene black, graphite, and vapor grown carbon fiber. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of the output characteristics of the battery.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers.

  The compounding ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer is not particularly limited. The mixing ratio can be adjusted by appropriately referring to known knowledge about the non-aqueous solvent secondary battery.

  The thickness of each active material layer is not particularly limited, and conventionally known knowledge about the battery can be appropriately referred to. For example, the thickness of each active material layer is about 2 to 100 μm.

[Electrolyte layer]
As the electrolyte constituting the electrolyte layer, a liquid electrolyte or a polymer electrolyte can be used.

  The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent that can be used as the plasticizer include carbonates such as ethylene carbonate (EC) and propylene carbonate (PC). Further, as the supporting salt (lithium salt), a compound that can be added to the active material layer of the electrode, such as LiBETI, can be similarly employed.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and an intrinsic polymer electrolyte containing no electrolytic solution.

  The gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer made of an ion conductive polymer. Examples of the ion conductive polymer used as the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such polyalkylene oxide polymers, electrolyte salts such as lithium salts can be well dissolved.

  In addition, when an electrolyte layer is comprised from a liquid electrolyte or a gel electrolyte, you may use a separator for an electrolyte layer. Specific examples of the separator include a microporous film made of polyolefin such as polyethylene or polypropylene.

  The intrinsic polymer electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the matrix polymer, and does not include an organic solvent that is a plasticizer. Therefore, when the electrolyte layer is composed of an intrinsic polymer electrolyte, there is no fear of liquid leakage from the battery, and the reliability of the battery can be improved.

  The matrix polymer of the gel electrolyte or the intrinsic polymer electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte using an appropriate polymerization initiator. A polymerization treatment may be performed.

It is a figure which shows schematic structure of the charge control apparatus of a lithium secondary battery. It is a figure which shows the voltage of a CC-CV charging / discharging cycle. It is a flowchart which shows the flow of an effect | action of a control part. It is a figure which shows the example of the discharge integrated amount of a battery. It is a flowchart which shows the process peculiar to 2nd Embodiment. It is a flowchart which shows the process peculiar to 3rd Embodiment. It is the schematic of the vehicle carrying a charge control apparatus. It is a figure which shows the relationship between the frequency | count of discharge and discharge capacity. It is a figure which shows the relationship between the frequency | count of discharge and voltage drop amount (DELTA) V. It is a figure which shows the relationship between the frequency | count of discharge and a CV electric current value. It is a figure which shows the relationship between the frequency | count of discharge and discharge capacity. It is a figure which shows the relationship between the frequency | count of discharge and voltage drop amount (DELTA) V. It is a figure which shows the relationship between the frequency | count of discharge and a CV electric current value. It is a figure which shows the relationship between charging conditions and the amount of voltage drops. It is a figure which shows the relationship between charging conditions and the amount of voltage drops. It is a figure which shows the relationship between charging conditions and the amount of voltage drops.

Explanation of symbols

10 Lithium secondary battery,
20 charge control device,
21 detectors,
22 storage unit,
23 control unit,
30 vehicles.

Claims (15)

In a constant current-constant voltage charging cycle for charging a lithium secondary battery, a measurement step of measuring the amount of voltage drop by stopping the supply of charging current during constant current charging or immediately after constant current charging;
A determination step of determining whether the voltage drop amount is greater than or equal to a threshold;
When the amount of voltage drop is equal to or greater than the threshold, a setting step of setting a target value of a full charge voltage when charging the lithium secondary battery lower than the current state;
Only including,
The target value is prepared in a plurality of stages,
In the setting step, each time the voltage drop exceeds the threshold, a lower target value is set,
The threshold is prepared in multiple stages,
The lithium secondary battery charge control method further comprising a threshold setting step of setting a lower threshold each time the target value is set lower .   2. The method for controlling charging of a lithium secondary battery according to claim 1, wherein the setting step is executed after the discharge following the constant current-constant voltage charging cycle is executed.   3. The charge control of a lithium secondary battery according to claim 2, wherein the measurement step is executed when the voltage of the lithium secondary battery reaches the target value in constant current charging of the constant current-constant voltage charging cycle. Method. In a constant current-constant voltage charging cycle for charging a lithium secondary battery, a measurement step of measuring the amount of voltage drop by stopping the supply of charging current during constant current charging or immediately after constant current charging;
A determination step of determining whether the voltage drop amount is greater than or equal to a threshold;
When the amount of voltage drop is equal to or greater than the threshold, a setting step of setting a target value of a full charge voltage when charging the lithium secondary battery lower than the current state;
Including
The measuring step, the determining step and the setting step, the constant current - in the constant current charging of constant voltage charging cycle, the set reference voltage lower than the new target value can be set in the setting step, the lithium is ruri lithium charging control method for a secondary battery performed when the voltage of the secondary battery has reached. A temperature detection step of detecting a temperature in the vicinity of the lithium secondary battery;
A first correction step of correcting the threshold value lower when the detected temperature is equal to or higher than a predetermined temperature;
The charge control method for a lithium secondary battery according to any one of claims 1 to 4 , further comprising: A frequency measurement step of measuring the number of constant current-constant voltage charging cycles;
A second correction step of correcting the threshold value lower as the number of measurements increases;
The charge control method for a lithium secondary battery according to any one of claims 1 to 5 , further comprising: The current value during constant current charging in the constant current-constant voltage charging cycle is prepared in multiple stages,
Wherein every time the target value is set lower, the charging control method for a lithium secondary battery according to any one of claims 1 to 6, further having a current value setting step of setting a lower current value. In a constant current-constant voltage charging cycle for charging a lithium secondary battery, a measuring instrument that stops the supply of charging current and measures the amount of voltage drop during constant current charging or immediately after constant current charging;
A determination unit for determining whether the voltage drop amount is equal to or greater than a threshold;
When the amount of voltage drop is equal to or greater than the threshold, a setting unit that sets a target value of a full charge voltage when charging the lithium secondary battery lower than the current state,
A storage unit for storing the target value in a plurality of stages,
The setting unit reads a lower target value from the storage unit every time the voltage drop amount exceeds the threshold value, and sets it as a new target value.
The storage unit stores the threshold value in a plurality of stages,
The setting unit is a lithium secondary battery charge control device that sets a lower threshold every time the target value is set lower . 9. The lithium secondary battery according to claim 8 , wherein the setting unit sets a new target value after the discharge following the constant current-constant voltage charging cycle is executed when the voltage drop amount is equal to or greater than a threshold value. Charge control device. The charging of the lithium secondary battery according to claim 9 , wherein the measuring device performs measurement when the voltage of the lithium secondary battery reaches the target value in constant current charging of the constant current-constant voltage charging cycle. Control device. In a constant current-constant voltage charging cycle for charging a lithium secondary battery, a measuring instrument that stops the supply of charging current and measures the amount of voltage drop during constant current charging or immediately after constant current charging;
A determination unit for determining whether the voltage drop amount is equal to or greater than a threshold;
When the voltage drop amount is equal to or greater than the threshold value, a setting unit that sets a target value of a full charge voltage when charging the lithium secondary battery lower than the current state, and
In the constant current charging of the constant current-constant voltage charging cycle, the measurement is performed when the voltage of the lithium secondary battery reaches a reference voltage set lower than a new target value that can be set by the setting unit. vessel performs measurements, the determination unit performs the determination, the setting unit charge controller for ruri lithium secondary battery to perform the setting. A temperature detector for detecting a temperature in the vicinity of the lithium secondary battery;
The charge control device for a lithium secondary battery according to any one of claims 8 to 11 , wherein the setting unit corrects the threshold value lower when the detected temperature is equal to or higher than a predetermined temperature. The setting unit, the constant current - measuring the number of times of the constant voltage charging cycle, the charging of the lithium secondary battery according to any one of claims 8-12 for correcting lower the threshold the more the number of measurements increases Control device. A current value storage unit for storing a plurality of levels of current values during constant current charging in the constant current-constant voltage charging cycle;
A current value setting unit that sets a lower current value each time the target value is set lower by the setting unit;
The charge control device for a lithium secondary battery according to any one of claims 8 to 13 , further comprising: A vehicle on which the charge control device for a lithium secondary battery according to any one of claims 8 to 14 is mounted.

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