Charging control device, power storage device, and charging control method

Abstract

This charging control device: changes the charging current value in a process of charging a power storage element; charges the power storage element so that the charging current value becomes minimum at the end of charging; calculates the charging electricity amount from a change point, where the charging current value has changed, to the end of charging; and changes a next charging condition when the calculated charging electricity amount is equal to or greater than a prescribed threshold value.

Description

Charging control device, power storage device, and charging control method

[0001] The present disclosure relates to a charge control device, a power storage device, and a charge control method.

[0002] CCCV charging is a known method for charging a storage element. CCCV charging is a method in which a storage element is charged with a constant current until its voltage reaches a CV voltage, and then the secondary battery is charged with a constant voltage. Patent Document 1 listed below describes that when switching from CC charging to CV charging, a period is provided between CC charging and CV charging in which charging is performed while the charging current is reduced, in order to accurately match the voltage of the storage element to the CV voltage.

[0003] Patent No. 5525862

[0004] In energy storage devices such as lithium-ion secondary batteries, for example, charging at low temperatures or with a large charging current can cause a decrease in the negative electrode potential during charging, leading to the deposition of metals such as lithium on the negative electrode. This phenomenon of metal deposition in energy storage devices is called electrodeposition. Repeated electrodeposition is known to rapidly deteriorate the capacity of the energy storage device.

[0005] The present disclosure was completed in light of the above circumstances, and aims to suppress rapid deterioration of the capacity of an energy storage element. As a result of detailed investigation into the charging characteristics of an energy storage element, the present inventors have discovered that rapid deterioration of the capacity of an energy storage element can be suppressed by focusing on the amount of charged electricity.

[0006] The charging control device disclosed herein is a charging control device that controls the charging of a storage element, changes the charging current value during the charging process of the storage element, charges the storage element so that the charging current value is minimized at the end of charging, calculates the amount of charged electricity from the point at which the charging current value changes to the end of charging, and changes the next charging conditions if the calculated amount of charged electricity is equal to or greater than a predetermined threshold.

[0007] According to the present disclosure, it is possible to suppress rapid deterioration of the capacity of the energy storage element.

[0008] 1 is a diagram showing the electrical configuration of a battery and a charging device according to an embodiment;

[0023] FIG. 1 is an exploded perspective view of a battery;

[0024] FIG. 2 is a diagram showing changes in charging current and cell voltage during CCCV charging;

[0025] FIG. 3 is a diagram showing changes in charging current and cell voltage during multi-stage constant current charging;

[0026] FIG. 4 is a diagram showing the correlation between the charged quantity of electricity and the negative electrode potential at a change point;

[0027] FIG. 5 is a flowchart showing a process in which a charge control device controls the charging of a storage element;

[0028] FIG. 6 is a diagram showing the charging characteristics of a storage element;

[0029] FIG. 7 is a diagram showing an OCP table for a positive electrode;

[0029] FIG. 8 is a diagram showing the correspondence between the CCP of the positive electrode and the OCP table for the positive electrode;

[0009] (Summary of this embodiment) [1] The charge control device of the present disclosure is a charge control device that controls the charging of a storage element, changes a charging current value during the charging process of the storage element, charges the storage element so that the charging current value is minimized at the end of charging, calculates the amount of charging electricity from the point at which the charging current value changes to the end of charging, and changes the next charging conditions if the calculated amount of charging electricity is equal to or greater than a predetermined threshold.

[0010] The inventors investigated the correlation between the deterioration state of the storage element and the amount of charged electricity from the change point of the charging current value to the end of charging, and found that the capacity of the storage element begins to deteriorate rapidly when the amount of charged electricity exceeds a predetermined threshold. Therefore, with the above configuration, when the amount of charged electricity is equal to or greater than a predetermined threshold, it is possible to determine that there is a sign of rapid capacity deterioration. Then, when a sign of rapid capacity deterioration is detected, the rapid capacity deterioration can be suppressed by changing the next charging conditions.

[0011] [2] In the above [1], it is preferable that the threshold value is a numerical value when the closed circuit potential of the negative electrode of the storage element at the change point is estimated to be a predetermined reference value.

[0012] With this configuration, it is possible to set a threshold value that increases the possibility of electrodeposition occurring at the change point, thereby preventing rapid deterioration of the capacity of the energy storage element due to repeated electrodeposition.

[0013] [3] The power storage device of the present disclosure includes a power storage element and the charge control device described in [1] or [2] above.

[0014] [4] The charging control method disclosed herein is a charging control method for controlling the charging of a storage element, which changes a charging current value during the charging process of the storage element, charges the storage element so that the charging current value is minimized at the end of charging, calculates the amount of charging electricity from the point at which the charging current value changes to the end of charging, and changes the next charging conditions if the calculated amount of charging electricity is equal to or greater than a predetermined threshold.

[0015] According to this charging control method, when the amount of charged electricity is equal to or greater than a predetermined threshold, it is determined that there is a sign of a sudden deterioration in the capacity of the storage element, and the next charging conditions can be changed, thereby suppressing a sudden deterioration in the capacity of the storage element.

[0016] <Embodiment> (Configuration of battery 50 and charging device 10) An embodiment of the present disclosure will be described with reference to Figs. 1 to 9. Fig. 1 is a block diagram showing the electrical configuration of a battery 50 and a charging device 10. The battery 50 includes a current interruption device 53, a battery pack 60 consisting of a plurality of battery cells 62, a current measurement resistor 54, a management device 100, and a temperature sensor 115. The battery 50 is an example of a power storage device of the present disclosure. The battery cells 62 are an example of power storage elements of the present disclosure. The battery cells 62 are, for example, lithium-ion secondary batteries.

[0017] The current interruption device 53, current measurement resistor 54, and battery pack 60 are connected in series via power lines 55P and 55N. The power line 55P connects the positive external terminal 51 to the positive electrode of the battery pack 60. The power line 55N connects the negative external terminal 52 to the negative electrode of the battery pack 60. The current interruption device 53 and current measurement resistor 54 are located on the positive electrode side of the battery pack 60 and are provided on the positive electrode side power line 55P.

[0018] The current interruption device 53 is configured by a contact switch (mechanical type) such as a relay or a semiconductor switch such as an FET. By opening the current interruption device 53, the current of the battery 50 can be interrupted.

[0019] The current measuring resistor 54 generates a voltage according to the current of the battery pack 60. Discharge and charge can be determined from the polarity (positive or negative) of the voltage across the current measuring resistor 54. The temperature sensor 115 is of a contact type or a non-contact type and measures the temperature of the battery pack 60.

[0020] The management device 100 is provided on the circuit board unit 65. The management device 100 includes a voltage detection circuit 110, a processing unit 120, and a power supply circuit 130. The voltage detection circuit 110 is connected to both ends of each battery cell 62 via a signal line, and measures the cell voltage of each battery cell 62 and the total voltage of the assembled battery 60. The total voltage of the assembled battery 60 is the sum of the voltages of the multiple battery cells 62 connected in series.

[0021] The processing unit 120 includes a CPU 121 having a calculation function and a memory 123 serving as a storage unit. The processing unit 120 monitors the current of the assembled battery 60, the voltage of each battery cell 62, and the total voltage and temperature of the assembled battery 60 from the outputs of the current measurement resistor 54, the voltage detection circuit 110, and the temperature sensor 115. The processing unit 120 has a function of controlling charging of the battery 50. The management device 100 is an example of a charging control device of the present disclosure.

[0022] The memory 123 is a non-volatile storage medium such as a flash memory, an EEPROM, etc. The memory 123 stores a monitoring program for monitoring the state of the battery pack 60 and data required for executing the monitoring program.

[0023] The memory 123 stores a charge control program for controlling the charging of the battery cells 62 and data required for executing the charge control program (such as a threshold value for the amount of charge electricity, which will be described later). The charge control program can be written to a recording medium such as a CD-ROM.

[0024] Charging device 10 includes current detection resistor 11, charging circuit 13, and CPU 15, and is connected to external terminals 51 and 52 of battery 50. CPU 15 controls the magnitude of the charging current via charging circuit 13. Current detection resistor 11 is provided to detect the charging current.

[0025] As shown in Figure 2, the battery 50 includes a housing 71. The housing 71 includes a main body 73 and a lid 74 made of synthetic resin material. The main body 73 is cylindrical and has a bottom. The main body 73 includes a bottom portion 75 and four side portions 76. The four side portions 76 form an upper opening 77 at the top end.

[0026] The housing 71 houses the battery pack 60 and the circuit board unit 65. The battery pack 60 has a plurality of battery cells 62. The battery cells 62 may be lithium-ion secondary battery cells. The circuit board unit 65 is disposed on top of the battery pack 60.

[0027] The lid 74 closes an upper opening 77 of the main body 73. An outer peripheral wall 78 is provided around the lid 74. The lid 74 has a protruding portion 79 that is generally T-shaped in plan view. The positive electrode external terminal 51 is fixed to one corner of the front of the lid 74, and the negative electrode external terminal 52 is fixed to the other corner.

[0028] 6, the management device 100 of this embodiment executes a charging process (S1), a calculation process (S2) for calculating the amount of charged electricity, which will be described later, and a determination process (S3) for determining whether the amount of charged electricity is equal to or greater than a predetermined threshold. If the amount of charged electricity is equal to or greater than the predetermined threshold, the management device 100 executes a condition change process (S5) for changing the next charging conditions for the battery cell 62.

[0029] (Charging Process) In the charging process, the charging device 10 charges the battery cells 62 under the command of the processing unit 120. The processing unit 120 changes the charging current value during the charging process of the battery cells 62. The processing unit 120 then gradually reduces the charging current value, and controls the charging of the battery cells 62 so that the charging current value is minimized at the end of charging. Furthermore, the charging of the battery cells 62 is controlled so that the voltage of the battery cells 62 reaches a predetermined upper limit voltage at the end of charging.

[0030] The charging process may be performed using CCCV charging, as shown in FIG. 3 . CCCV charging is a method of charging the battery cells 62 with a constant current IC until the voltage of the battery cells 62 reaches an upper limit voltage Vmax (CC charging), and then constant voltage charging the battery cells 62 at the upper limit voltage Vmax (CV charging). CCCV charging has a transition point where the charging current value changes discontinuously when CC charging switches to CV charging. After the transition point, the charging current is gradually reduced to maintain the upper limit voltage Vmax. It is known that electrodeposition is likely to occur in the battery cells 62 at the transition point because the voltage is high and the charging current is large.

[0031] The charging process may also be multi-stage constant current charging. Multi-stage constant current charging is a method of gradually reducing the charging current of CC charging in multiple stages. For example, the multi-stage constant current charging shown in FIG. 4 includes two-stage CC charging and CV charging performed after CC charging. In two-stage CC charging, charging is performed at a constant current IC1 until the battery cell voltage reaches a switching voltage Vstep that is lower than the upper limit voltage Vmax. Then, charging is performed at a smaller constant current IC2 until the battery cell voltage reaches the upper limit voltage Vmax. Note that the CC charging of the multi-stage constant current charging may be performed in three or more stages. In addition to the change point (second change point) at which CC charging switches to CV charging, multi-stage constant current charging also has a first change point at which the charging current changes discontinuously during CC charging. In other words, multi-stage constant current charging includes multiple change points.

[0032] (Calculation Process) In the calculation process, the processing unit 120 calculates the amount of charged electricity after the charging process. The amount of charged electricity is defined as the amount of electricity provided from the charging device 10 to the battery cell 62 from the change point to the end of charging in the charging process.

[0033] For example, as shown in Fig. 3, when the charging process is performed by CCCV charging, the charged amount of electricity is the amount of electricity provided to the battery cell 62 during a period T. In other words, the charged amount of electricity is the amount of electricity provided to the battery cell 62 during CV charging.

[0034] Furthermore, as shown in Figure 4, when the charging process is performed by multi-stage constant current charging, the charged amount of electricity is the amount of electricity provided to the battery cell 62 during period T1 or period T2. Because multi-stage constant current charging includes multiple change points, multiple charged amounts of electricity can be calculated. In such a case, any one of the charged amounts of electricity may be used in the subsequent process, or two or more may be used. When two or more charged amounts of electricity are used, the subsequent process will be performed for each charged amount of electricity.

[0035] For simplicity, the following description of each process will be given on the assumption that the charging process is performed by CCCV charging.

[0036] (Correlation between Charging Amount of Electricity and Rapid Capacity Degradation) The present inventors conducted a detailed investigation of the charging characteristics of the battery cell 62 and found that, compared with the battery cell 62 immediately after manufacture, the capacity of the battery cell 62 after its end of life is smaller and the charging amount of electricity is larger. The present inventors then plotted the charging amount of electricity against the number of charge / discharge cycles of the battery cell 62 and found that, as shown in the upper graph of FIG. 5 , the charging amount of electricity increases significantly after a certain number of cycles Nth. It was also confirmed that, after this number of cycles Nth, the capacity of the battery cell 62 significantly decreases. Furthermore, as will be described in detail later, it was suggested that the rapid capacity degradation after this number of cycles Nth is due to electrodeposition. Based on these experimental results, it is believed that it is possible to detect signs of rapid capacity degradation of the battery cell 62 by setting the charging amount of electricity at this number of cycles Nth as a threshold Qth in advance and monitoring the charging amount of electricity each time a charging process is completed.

[0037] (Determination Process) In the determination process, it is determined whether the charged quantity of electricity is equal to or greater than a predetermined threshold Qth. The threshold Qth is stored in advance in the memory 123, for example. The threshold Qth may be determined experimentally. As will be described later, the threshold Qth may also be determined from the relationship between the negative electrode potential at the change point and the charged quantity of electricity.

[0038] (Condition Change Process) If the charged quantity of electricity is equal to or greater than a predetermined threshold Qth (S3: YES), it is determined that there is a sign of rapid capacity degradation (S4). Then, the processing unit 120 executes a condition change process (S5) to change the next charging conditions to suppress the occurrence of electrodeposition during the next charging. In the condition change process, the charging conditions are changed to make electrodeposition even less likely to occur. Specifically, the charging current value and the upper limit voltage are reduced, for example.

[0039] If the charged quantity of electricity is less than the predetermined threshold Qth (S3: NO), it is determined that there is no sign of rapid capacity deterioration (S6). In this case, the next charging conditions are not changed. This completes the charging control process for the battery cell 62 in this embodiment.

[0040] Similarly to the above, the charge control method of this embodiment includes a charging step of changing the charge current value during the charging of the battery cell 62 and charging the battery cell 62 so that the charge current value is minimized at the end of charging, a calculation step of calculating the amount of charged electricity from the change point at which the charge current value changes until the end of charging, and a determination step of determining whether the calculated amount of charged electricity is equal to or greater than a predetermined threshold Qth. The charge control method of this embodiment further includes a condition change step of changing the next charging condition if the amount of charged electricity is equal to or greater than the predetermined threshold Qth in the determination step.

[0041] (Regarding the Negative Electrode Potential at the Transition Point) As described above, the negative electrode potential is particularly likely to decrease at the transition point, making electrodeposition more likely to occur. For example, if the battery cell 62 is a lithium-ion secondary battery, deposition of metallic lithium, i.e., electrodeposition, may occur if the negative electrode potential (specifically, the closed circuit potential) becomes 0 V or less relative to the potential of metallic lithium. Therefore, if the magnitude of the negative electrode potential at the transition point is a positive value close to 0 V, it can be determined that there is a sign of rapid capacity degradation of the battery cell 62.

[0042] Hereinafter, it will be explained that the charging quantity of electricity being equal to or greater than the threshold value Qth is essentially the same as the magnitude of the negative electrode potential at the change point being equal to or less than a predetermined reference value Eth close to 0 V. First, the correlation between the charging quantity of electricity and the negative electrode potential at the change point will be derived.

[0043] When the battery cell 62 is charged by CCCV charging, the charging characteristics shown in Fig. 7 are obtained. The upper graph in Fig. 7 shows the positive electrode potential during the charging process, more specifically the closed circuit potential (CCP) of the positive electrode. The middle graph in Fig. 7 shows the negative electrode potential during the charging process, more specifically the CCP of the negative electrode. The lower graph in Fig. 7 shows the cell voltage during the charging process, more specifically the closed circuit voltage (CCV).

[0044] Here, the CCP of the positive electrode and the CCP of the negative electrode refer to the potentials of the positive electrode and the negative electrode of the battery cell 62 when the battery cell 62 is electrically connected to an external circuit (charging circuit 13) and current is flowing (a load is applied between the positive electrode and the negative electrode). Also, the CCV is the cell voltage in the same state, and is the potential difference between the CCP of the positive electrode and the CCP of the negative electrode. In other words, if the CCV, CCP of the positive electrode, and CCP of the negative electrode are VC, ECP, and ECN, respectively, the following equation (1) holds:

[0045] VC=ECP-ECN (1)

[0046] 7 represents the amount of electricity provided to the battery cell 62 by the charging device 10 during charging. The amount of electricity at the end of charging is QE, and the amount of electricity at the change point (i.e., when switching from CC charging to CV charging) is QE-Q1. In other words, the charged amount of electricity is Q1.

[0047] 8 shows a positive electrode open circuit potential (OCP) table. The positive electrode OCP table is data showing the relationship between the positive electrode OCP and the capacity (in the same units as the quantity of electricity) of the battery cell 62, and is obtained in advance through experiments. Here, the positive electrode OCP is the potential of the positive electrode of the battery cell 62 when the battery cell 62 is electrically disconnected from the external circuit (i.e., no load is applied between the positive electrode and the negative electrode).

[0048] It is known that the CCP of the positive electrode is equal to the sum of the OCP of the positive electrode and the amount of positive electrode polarization. That is, when the OCP of the positive electrode and the amount of positive electrode polarization are defined as EOP and PP, respectively, the following formula (2) holds:

[0049] ECP=EOP+PP (2)

[0050] Here, the amount of positive electrode polarization is an amount mainly caused by polarization due to a charge transfer reaction, and can be measured, for example, in a bipolar cell using a positive electrode as the working electrode and lithium metal as the counter electrode. The amount of positive electrode polarization depends on the charging current and the temperature of the battery cell 62. When a charging current is flowing, the amount of positive electrode polarization takes a positive value. The larger the charging current, the larger the amount of positive electrode polarization tends to be. The lower the temperature of the battery cell 62, the larger the amount of positive electrode polarization tends to be. A table can also be prepared in advance for the amount of positive electrode polarization according to temperature and charging current value.

[0051] Next, the positive electrode OCP at the change point is derived from the positive electrode CCP graph shown in the upper part of Figure 7 and the positive electrode OCP table. Figure 9 is a graph that enlarges the CV charging region of the upper part of Figure 7, and the positive electrode CCP is shown by the solid line. At the end of charging, the quantity of electricity is QE, and the positive electrode CCP is E1. Also, at the change point, the quantity of electricity is QE-Q1, and the positive electrode CCP is E2.

[0052] The graph in Fig. 9 also has a positive electrode OCP table (dashed line) superimposed on it. Here, the positive electrode OCP table is a table for the capacity of the battery cell 62, as shown in Fig. 8 , and is not a table for the amount of electricity. Therefore, we approximate that the positive electrode OCP and the positive electrode CCP are equal at the end of charging, and convert the horizontal axis in Fig. 9 . Strictly speaking, as expressed in equation (2), the positive electrode CCP is the sum of the positive electrode OCP and the amount of positive electrode polarization. However, because the charging current is at a minimum at the end of charging, the amount of positive electrode polarization is considered to be sufficiently small compared to the positive electrode OCP.

[0053] As shown in FIG. 8, the capacitance at which the positive electrode OCP is E1, i.e., the positive electrode CCP value at the end of charge (see FIG. 9), is C1. Therefore, as shown in FIG. 9, the horizontal axis of the positive electrode OCP table is offset so that the capacitance C1 corresponds to the quantity of electricity QE. Then, the positive electrode OCP at the change point is the value when the capacitance is C1-Q1, which is E3 (see FIGS. 8 and 9). Here, if the positive electrode OCP table is considered as a function EOP relating to the quantity of electricity, the positive electrode OCP at the change point (i.e., E3) can be rewritten as EOP(QE-Q1) (see FIG. 9). Similarly, if the positive electrode CCP is considered as a function ECP relating to the quantity of electricity, the positive electrode CCP at the change point (i.e., E2) can be rewritten as ECP(QE-Q1).

[0054] Furthermore, when formula (1) is considered as a function related to the quantity of electricity, the following relational formula (3) is established by substituting QE-Q1 as the quantity of electricity.

[0055] VC (QE-Q1) = ECP (QE-Q1) - ECN (QE-Q1) (3)

[0056] In equation (3), ECN (QE-Q1) is the negative CCP at the change point. VC (QE-Q1) is the CCV at the change point, and therefore the upper limit voltage Vmax (see the lower graph in Figure 7). That is, the following equation (4) holds true:

[0057] VC(QE-Q1)=Vmax (4)

[0058] Furthermore, when equation (2) is considered as a function related to the quantity of electricity, the following relational equation (5) is established by substituting QE-Q1 as the quantity of electricity.

[0059] ECP (QE-Q1) = EOP (QE-Q1) + PP (QE-Q1) (5)

[0060] From the formulas (3), (4), and (5), the CCP of the negative electrode at the change point is expressed by the following formula (6).

[0061] ECN (QE-Q1) = EOP (QE-Q1) + PP (QE-Q1) - Vmax (6)

[0062] In equation (6), Vmax is a constant. PP(QE-Q1) is the amount of polarization of the positive electrode, which is greatly affected by temperature and charging current, but is not so greatly affected by the quantity of electricity. On the other hand, EOP(QE-Q1) is the OCP of the positive electrode at the change point. As shown in FIG. 9, the OCP of the positive electrode is highly dependent on the quantity of electricity. Specifically, the OCP of the positive electrode tends to increase as the quantity of electricity increases. Therefore, EOP(QE-Q1) is a term that is highly dependent on the quantity of electricity Q1 charged. Therefore, ECN(QE-Q1), i.e., the CCP of the negative electrode at the change point, can be regarded as a function of the quantity of electricity Q1 charged. Equation (6) represents the correlation between the quantity of electricity Q1 charged and the CCP of the negative electrode at the change point. Specifically, the CCP of the negative electrode at the change point tends to decrease as the quantity of electricity Q1 charged increases.

[0063] As described above, for example, by using the charging characteristics of the battery cell 62, the positive electrode OCP table, and the positive electrode polarization amount table, it is possible to determine the correlation between the charged electrical quantity and the negative electrode CCP at the change point.

[0064] The graph in the lower part of Figure 5 shows the CCP of the negative electrode at the change point, estimated from the charge quantity (shown in the upper graph of Figure 5) using Equation (6). The vertical axis of the graph in the lower part of Figure 5 is based on the potential of metallic lithium. That is, the unit of the vertical axis is V vs. Li / Li+.

[0065] The CCP of the negative electrode at the change point takes a reference value Eth, which is a value slightly greater than 0 V, at the cycle number Nth when the charge quantity of electricity rises, and then becomes negative and rapidly decreases after the cycle number Nth. This indicates that in the region after the cycle number Nth where the rate of increase in the charge quantity of electricity becomes large, electrodeposition occurs significantly, and the capacity of the battery cell 62 rapidly deteriorates. From this correspondence, it can be seen that by focusing on the charge quantity of electricity, it is possible to detect signs of rapid deterioration in the capacity of the battery cell 62.

[0066] Furthermore, by using equation (6), the threshold value Qth of the charge quantity of electricity can be appropriately set by appropriately setting the reference value Eth of the CCP of the negative electrode at the change point. To detect signs of rapid capacity degradation of the battery cell 62 using the charge control device (management device 100) or charge control method of this embodiment, it is preferable that the reference value Eth is slightly greater than the value at which electrodeposition begins to occur. For example, the reference value Eth can be set to a value slightly greater than 0 V, based on the potential of metallic lithium. At low temperatures, electrodeposition may not occur even if the CCP of the negative electrode at the change point falls below 0 V. This is due to the fact that the amount of negative electrode polarization increases as the temperature decreases. Therefore, a value below 0 V may be set as the reference value depending on the temperature. Therefore, it is preferable to set multiple reference values ​​Eth for each temperature.

[0067] When determining the threshold value Qth from the reference value Eth, Equation (6) may be optimized using a positive electrode OCP table and a positive electrode polarization amount table when the capacity has deteriorated. Furthermore, the threshold value Qth is a quantity that depends on the likelihood of electrodeposition, and therefore varies significantly depending on the temperature and the upper limit voltage. Therefore, it is preferable to set multiple threshold values ​​Qth for each temperature and each upper limit voltage.

[0068] According to this embodiment, signs of rapid deterioration in the capacity of the battery cell 62 can be easily detected based on the magnitude relationship between the charged electrical quantity and a predetermined threshold Qth, without having to measure or estimate the CCP of the negative electrode using a charge control device (management device 100) or a charging device 10.

[0069] Effects of the embodiment The charge control device (management device 100) of this embodiment controls the charging of the energy storage elements (battery cells 62). The charge control device changes the charging current value during the charging process of the energy storage elements, charges the energy storage elements so that the charging current value is minimized at the end of charging, calculates the amount of charged electricity from the point at which the charging current value changes until the end of charging, and changes the next charging conditions if the calculated amount of charged electricity is equal to or greater than a predetermined threshold value Qth.

[0070] According to the above configuration, when the charged quantity of electricity is equal to or greater than a predetermined threshold Qth, it can be determined that there is a sign of rapid capacity degradation. If a sign of rapid capacity degradation is detected, the rapid capacity degradation can be suppressed by changing the next charging conditions.

[0071] In this embodiment, the threshold value Qth is preferably a value when the closed circuit potential of the negative electrode of the storage element at the change point is estimated to be a predetermined reference value Eth.

[0072] With this configuration, it is possible to set the threshold value Qth such that the possibility of electrodeposition occurring at the change point is high, thereby preventing rapid deterioration of the capacity of the energy storage element due to repeated electrodeposition.

[0073] <Other Embodiments> The present disclosure is not limited to the embodiments described above and illustrated in the drawings, but is intended to include all modifications within the meaning and scope of the claims as defined by the claims. The technical scope of the present disclosure also includes, for example, the following embodiments.

[0074] In the embodiment, the battery cell 62 is shown as an example of the power storage element. The power storage element may be a capacitor. The battery cell is not limited to a lithium-ion secondary battery cell, but may be other secondary battery cells such as a lead-acid battery cell, a nickel-metal hydride battery cell, or a lithium-air battery cell. The power storage element is not limited to a case where a plurality of battery cells are connected in series or series-parallel, and may be a single cell.

[0075] The present technology can be applied to a charging control program for a power storage device. The charging control program for a power storage device is a program that causes a computer to execute a charging control method according to an embodiment. The present technology can also be applied to a recording medium on which the charging control program for a power storage device is recorded. The computer is, for example, the processing unit 120.

[0076] 10: Charging device 50: Battery (power storage device) 60: Assembled battery 62: Battery cell (power storage element) 100: Management device (charging control device) 120: Processing unit Eth: Reference value Qth: Threshold value

Claims

1. A charge control device that controls the charging of a storage element, changes a charging current value during the charging process of the storage element, charges the storage element so that the charging current value is minimized at the end of charging, calculates the amount of charged electricity from the point at which the charging current value changes to the end of charging, and changes the next charging conditions if the calculated amount of charged electricity is equal to or greater than a predetermined threshold.

2. The charge control device according to claim 1, wherein the threshold value is a value when the closed circuit potential of the negative electrode of the storage element at the change point is estimated to be a predetermined reference value.

3. A power storage device comprising: a power storage element; and the charge control device according to claim 1 or 2.

4. A charge control method for controlling the charging of a storage element, comprising: changing a charging current value during the charging process of the storage element; charging the storage element so that the charging current value is minimized at the end of charging; calculating the amount of charged electricity from the point at which the charging current value changes until the end of charging; and changing the next charging conditions if the calculated amount of charged electricity is equal to or greater than a predetermined threshold.

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