Charging method and charging system

Abstract

To enable the precipitation of lithium metal to be accurately suppressed in charging a lithium-ion battery.SOLUTION: A charging method includes: determining a first and a second threshold at which lithium metal precipitates to lithium-ion battery electrodes, with regard to the charge current of the lithium-ion battery (S11); and controlling the charge current of the lithium-ion battery using a difference between the first and the second thresholds and the second threshold (S12-S16). The first threshold indicates a current boundary value at which precipitation of the lithium metal becomes likely to occur when the charge current of the lithium-ion battery exceeds the first threshold. The second threshold represents a smaller value than the first threshold and indicates a current boundary value at which precipitation of the lithium metal becomes likely to occur when the charge current of the lithium-ion battery exceeds continuously the second threshold.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a charging method and a charging system. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2012-016263 (Patent Document 1) discloses a technique for setting a Li deposition start voltage (the voltage at which lithium metal deposition starts inside the cell) according to a first charging current or a first charging power of a cell, and switching the first charging current or first charging power to a smaller second charging current or second charging power when the terminal voltage of the cell reaches the Li deposition start voltage. The Li deposition start voltage is set lower as the first charging current or first charging power is higher. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-016263 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in the above Patent Document 1, the charging current is reduced after the cell terminal voltage reaches the Li precipitation starting voltage, so there is a possibility that lithium metal precipitation cannot be sufficiently suppressed. In particular, when the performance of the charger is low, the response of the charging current control by the charger to the change in the target charging current value is likely to be slow. In charging control using such a charger, the reduction in the charging current is delayed, making lithium metal precipitation more likely to occur.

[0005] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to make it easier to appropriately suppress the deposition of lithium metal during charging of a lithium-ion battery. [Means for solving the problem]

[0006] A charging method according to an embodiment of the present disclosure includes determining a first threshold and a second threshold for a charging current of the lithium ion battery at which lithium metal precipitates on an electrode of the lithium ion battery, and controlling the charging current of the lithium ion battery using a difference between the first and second thresholds and the second threshold. The first threshold indicates a current boundary value at which lithium metal precipitates easily when the charging current of the lithium ion battery exceeds the first threshold. The second threshold is a value smaller than the first threshold and indicates a current boundary value at which lithium metal precipitates easily when the charging current of the lithium ion battery continuously exceeds the second threshold. Effect of the Invention

[0007] According to the present disclosure, it becomes easier to appropriately suppress the deposition of lithium metal during charging of a lithium-ion battery. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a charging system according to an embodiment of the present disclosure. [Diagram 2] 4 is a flowchart illustrating a charging method according to an embodiment of the present disclosure. [Diagram 3] 3 is a time chart showing an example of operation according to the charging method shown in FIG. 2. [Figure 4] FIG. 2 is a diagram showing a modification of the charging system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present disclosure will now be described in detail with reference to the accompanying drawings, in which the same or corresponding parts are designated by the same reference characters and will not be described repeatedly.

[0010] FIG. 1 is a diagram illustrating a charging system according to an embodiment of the present disclosure. With reference to FIG. 1, the charging system according to this embodiment includes a vehicle 100 and an EVSE 300. The EVSE 300 receives power supply from a power system PG. EVSE stands for Electric Vehicle Supply Equipment. The power system PG is a power grid constructed by power transmission and distribution equipment. A plurality of power plants (not shown) are connected to the power system PG. The power system PG receives power supply from these power plants. In this embodiment, the power system PG supplies AC power.

[0011] The EVSE 300 incorporates a power supply circuit 310 and includes a charging cable 320. The power supply circuit 310 is electrically connected to the power system PG. The charging cable 320 has a connector 320a (plug) at its tip, and includes a communication line and a power line inside. A single electric wire may serve as both the communication line and the power line. The power supply circuit 310 converts the power supplied from the power system PG into power suitable for supplying power to the vehicle 100, and outputs the converted power to the charging cable 320. The EVSE 300 outputs AC power from the connector 320a.

[0012] The vehicle 100 includes an inlet 60 to which a connector 320a can be attached and detached. When the connector 320a of the charging cable 320 connected to the main body of the EVSE 300 is connected to the inlet 60 of the parked vehicle 100, the vehicle 100 is electrically connected to the power grid PG via the EVSE 300 (hereinafter also referred to as a "plugged-in state"). On the other hand, for example, while the vehicle 100 is traveling, the vehicle 100 is not electrically connected to either the EVSE 300 or the power grid PG (hereinafter also referred to as a "plugged-out state").

[0013] The vehicle 100 further includes a battery 11, a system main relay (SMR) 12, a motor generator (MG) 20, a power control unit (PCU) 22, and an electronic control unit (ECU) 150. The ECU 150 includes a processor 151, a random access memory (RAM) 152, and a storage device 153. The storage device 153 is configured to be able to save stored information. In addition to programs, the storage device 153 stores information used in the programs (e.g., maps, formulas, and various parameters). In this embodiment, the processor 151 executes the programs stored in the storage device 153, thereby executing various controls in the ECU 150 (e.g., charging control of the battery 11). However, these processes may be executed only by hardware (electronic circuits) without using software. The ECU 150 according to this embodiment corresponds to an example of a "control device" according to the present disclosure.

[0014] Vehicle 100 is configured to be capable of running using electric power stored in battery 11. Vehicle 100 is, for example, an electric vehicle (BEV) that does not have an engine (internal combustion engine). However, the vehicle 100 is not limited to this, and may be a PHEV (plug-in hybrid vehicle) that has an internal combustion engine, or another type of electric vehicle (xEV).

[0015] In this embodiment, the battery 11 is a battery pack. The battery pack is configured by electrically connecting a plurality of secondary batteries (generally also called "cells") to each other. Each cell that configures the battery pack is a lithium ion secondary battery.

[0016] The cell includes a positive electrode, a negative electrode, an electrolyte (e.g., nonaqueous electrolyte), and a separator. For example, a sheet-like positive electrode, a negative electrode, and a separator are stacked, and the resulting stack is wound to form a wound body in which the electrodes and the separators are arranged alternately. In such a wound body, a separator is interposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode collector (e.g., aluminum foil) and a positive electrode active material layer. Examples of the positive electrode active material include lithium ion-containing transition metal oxides (NCM-based, LFP, LMFP, etc.). In this embodiment, an NCM-based (nickel-cobalt-manganese ternary system) is used as the positive electrode active material. The negative electrode sheet includes a negative electrode collector (e.g., copper foil) and a negative electrode active material layer. Examples of the negative electrode active material include carbon-based materials, silicon-containing carbon-based materials, silicon, lithium titanate (LTO), and niobium titanium oxide (NTO). In this embodiment, a carbon-based material (e.g., graphite) is used as the negative electrode active material. The negative electrode is a carbon-based electrode. The active material layers of the positive electrode and the negative electrode are formed, for example, by coating a composite material containing the active material on the surface of a current collector. In this embodiment, the positive electrode and the negative electrode have a monopolar structure. However, the present invention is not limited to this, and the positive electrode and the negative electrode may have a bipolar structure.

[0017] The above-mentioned wound body (laminate) is sealed in a battery case together with an electrolyte. The positive electrode current collector is electrically connected to a positive electrode terminal. The negative electrode current collector is electrically connected to a negative electrode terminal. A battery 11 (cell pack) is formed by connecting a plurality of cells having such a configuration in series, for example, as shown in FIG. 1. However, the connection of the cells in the cell pack is not limited to series and may include parallel connection.

[0018] The battery 11 is provided with a BMS (Battery Management System) 11a that monitors the state of the battery 11. The BMS 11a includes various sensors that detect the state of the battery 11 (for example, voltage, current, and temperature) and a monitoring IC (integrated circuit) to which detection signals from the various sensors are input. In this embodiment, a voltage sensor and a temperature sensor are provided for each cell that constitutes the battery 11 (battery pack). However, this is not limited to the above, and each of the voltage sensor and the temperature sensor may be provided for each of a plurality of cells, or only one may be provided for one battery pack.

[0019] The monitoring IC generates a signal indicating the state of the battery 11 (hereinafter also referred to as a "BMS signal") using detection signals from the various sensors, and outputs the generated BMS signal to the ECU 150. Based on the BMS signal, the ECU 150 acquires, for example, the temperature, current, voltage, SOC (State Of Charge), and SOH (State of Health) of the battery 11. The monitoring IC may have a function of equalizing cell voltages.

[0020] Vehicle 100 further includes a charger 61 and a charging relay 62. Charger 61 and charging relay 62 are located between inlet 60 and battery 11. Each of charger 61 and charging relay 62 is controlled by ECU 150. In this embodiment, a charging line including inlet 60, charger 61, and charging relay 62 is connected between SMR 12 and PCU 22. However, this is not limited thereto, and a charging line may be connected between battery 11 and SMR 12.

[0021] The charger 61 charges the battery 11 using power input to the inlet 60 from outside the vehicle. The charger 61 includes a power conversion circuit (e.g., an inverter) and is configured to be able to adjust the charging current. The power conversion circuit performs DC (direct current) / AC (alternating current) conversion. The charging relay 62 switches between connection / disconnection of the electrical path from the inlet 60 to the battery 11. The vehicle 100 further includes a detector 61a that monitors the state of the charger 61. The detector 61a includes various sensors (e.g., a current sensor and a voltage sensor) that detect the state of the charger 61, and outputs the detection results to the ECU 150.

[0022] With the vehicle 100 in a plugged-in state, external charging (i.e., charging of the battery 11 with power from outside the vehicle) becomes possible. Power for external charging is supplied to the inlet 60, for example, from the power system PG through a charging cable 320 of the EVSE 300. The charger 61 converts the AC power received by the inlet 60 into DC power suitable for charging the battery 11, and outputs the DC power to the battery 11. When external charging is performed, the charging relay 62 is set to a closed state (connected state), and when external charging is not performed, the charging relay 62 is set to an open state (disconnected state).

[0023] The MG 20 is, for example, a three-phase AC motor generator. The MG 20 functions as a traction motor for the vehicle 100. The MG 20 is driven by the PCU 22 to rotate the drive wheels of the vehicle 100. The MG 20 also performs regenerative power generation and outputs the generated power to the battery 11. The vehicle 100 further includes a motor sensor 21 that monitors the state of the MG 20. The motor sensor 21 includes various sensors (for example, a current sensor, a voltage sensor, and a temperature sensor) that detect the state of the MG 20, and outputs the detection results to the ECU 150. The number of traction motors included in the vehicle 100 is arbitrary, and may be one, two, or three or more. The traction motors may be in-wheel motors.

[0024] The PCU 22 drives the MG 20 using power supplied from the battery 11. The SMR 12 switches between connection and disconnection of an electric path from the battery 11 to the PCU 22. The PCU 22 includes, for example, an inverter and a converter. The SMR 12 and the PCU 22 are each controlled by the ECU 150. The SMR 12 is in a closed state (connected state) when the vehicle 100 is traveling. The SMR 12 is also in a closed state when power is exchanged between the battery 11 and the inlet 60 (and thus, the outside of the vehicle).

[0025] Incidentally, a lithium-ion secondary battery discharges and charges through chemical reactions (battery reactions) at the interfaces between the negative and positive electrode active materials and the electrolyte. + ) and electrons (e - ) occurs at the interface of the positive electrode active material, while lithium ions (Li + ) and electrons (e - During discharge, the reverse battery reaction occurs: release / absorption. Lithium ions are exchanged between the positive and negative electrode sheets via the separator, allowing the lithium ion secondary battery to be charged and discharged.

[0026] During charging of a lithium ion secondary battery, the absorption and diffusion in the negative electrode may not keep up with the supply of lithium ions, and lithium metal may precipitate on the surface of the negative electrode. If the lithium metal precipitates excessively, the precipitated lithium metal may short-circuit the positive electrode and the negative electrode. For this reason, in charging control of a lithium ion secondary battery, it is desirable to suppress the precipitation of lithium metal (hereinafter also referred to as "Li precipitation") so that the lithium metal does not precipitate excessively on the electrode surface (particularly the negative electrode surface) of the lithium ion secondary battery. For example, Li precipitation can be suppressed by reducing the charging current. However, when the charging current is reduced, the charging time (the time until charging is completed) becomes longer. Therefore, in this embodiment, the charging current is controlled based on the current boundary value at which Li precipitation is likely to occur. According to such control, it is possible to suppress the charging time from being extended by reducing the charging current more than necessary.

[0027] Specifically, the ECU 150 controls the charging current using a first threshold and a second threshold by executing a series of processes shown in Fig. 2 described below. The first threshold indicates a current boundary value at which Li deposition is likely to occur when the charging current of the battery 11 exceeds the first threshold. The second threshold is a value smaller than the first threshold and indicates a current boundary value at which Li deposition is likely to occur when the charging current of the battery 11 continuously exceeds the second threshold. The ECU 150 may acquire the charging current of the battery 11 using at least one of the detection result by the current sensor of the BMS 11a and the detection result by the current sensor of the detector 61a.

[0028] Fig. 2 is a flowchart showing a charging method according to this embodiment. The process shown in this flowchart is executed by ECU 150. The process flow shown in Fig. 2 is started, for example, when a condition for starting external charging is satisfied for vehicle 100. The condition for starting external charging may be satisfied when vehicle 100 is in a plugged-in state. Furthermore, in vehicle 100 for which timer charging is reserved in ECU 150, the condition for starting external charging may be satisfied when the start time for timer charging arrives in the plugged-in state.

[0029] Referring to FIG. 2, in S11, ECU 150 determines a first threshold value and a second threshold value. The first threshold defines a range of charging current in which Li deposition may occur in the battery 11. That is, if the charging current of the battery 11 exceeds the first threshold even momentarily, the possibility of Li deposition occurring increases. Such a first threshold is likely to vary depending on the state of the battery 11. The ECU 150 variably sets the first threshold using, for example, a first map. The first map is, for example, experimentally obtained and stored in the storage device 153. The ECU 150 may set the first threshold based on the voltage and temperature of the battery 11. The first map outputs the first threshold when, for example, the voltage and temperature of the battery 11 are input. A representative value (for example, an average value, a median value, or a maximum value) of data obtained for each of a plurality of cells constituting the battery 11 (battery pack) may be used as the value (voltage and temperature) of the battery 11. Instead of the first map, a learned model obtained by machine learning using AI (artificial intelligence) may be adopted.

[0030] The second threshold defines a range of charging current in which Li deposition is always suppressed in the battery 11. That is, Li deposition does not occur during charging of the battery 11 unless the charging current of the battery 11 exceeds the second threshold. However, if the current load continues and the final charging current (saturated charging current) exceeds the second threshold, the possibility of Li deposition occurring increases. The second threshold varies little with changes in the state of the battery 11. For this reason, the second threshold may be a fixed value. For example, an experimentally determined fixed value (second threshold) may be stored in the storage device 153. Alternatively, the ECU 150 may variably set the second threshold using, for example, a second map. The ECU 150 may reduce the second threshold as the thickness of the SEI (Solid Electrolyte Interphase) coating of the negative electrode increases. The second map outputs the second threshold when, for example, the thickness of the SEI coating formed on the surface of the negative electrode is input. The second map may be determined, for example, experimentally and stored in the storage device 153.

[0031] In S12, the ECU 150 judges whether the difference between the first threshold and the second threshold is equal to or greater than a predetermined reference value (hereinafter, referred to as "Th"). The ECU 150 obtains the difference between the first threshold and the second threshold (hereinafter, referred to as "difference X") by subtracting the second threshold from the first threshold. If the difference X is smaller than Th (NO in S12), the ECU 150 determines a predetermined value (hereinafter, referred to as "Mx") as a charging margin in S13. Mx is a fixed value. In this case, the charging margin is determined uniformly. For example, Mx is set in consideration of the performance variation of the charger 61 so that the charging current during charging of the battery 11 does not exceed the second threshold even if the performance of the charger 61 is low. If the difference X is equal to or greater than Th (YES in S12), the ECU 150 determines a charging margin according to the difference X within a range smaller than Mx in S14. Specifically, ECU 150 variably sets the charging margin such that the larger the difference X, the smaller the charging margin.

[0032] The greater the difference (difference X) between the first threshold and the second threshold, the less likely lithium metal deposition tends to occur. When the difference X is smaller than Th, it is considered that lithium metal deposition is more likely to occur. For this reason, in S13, Mx is determined as the charge margin. On the other hand, when the difference X is larger than Th, it is considered that lithium metal deposition is less likely to occur. For this reason, in S14, the charge margin is made smaller than Mx, thereby increasing the charge current of the battery 11. Furthermore, in S14, the greater the difference X, the smaller the charge margin is made, thereby increasing the charge current as the lithium metal deposition becomes more unlikely.

[0033] After the charging margin is determined in S13 or S14, the ECU 150 determines a charging command value based on the determined charging margin and a second threshold in S15. The charging command value indicates a target charging current value. The ECU 150 determines the target charging current value such that the charging current of the battery 11 is lower than the second threshold by the charging margin. The ECU 150 obtains the target charging current value by subtracting the charging margin from the second threshold.

[0034] By setting the charging margin as described above, it becomes easier to more reliably suppress lithium metal deposition even when a low-performance charger is used to control charging of the lithium ion battery. Also, by determining the charging margin using the difference between the first threshold and the second threshold, it is possible to control charging of the lithium ion battery so that the charging current of the lithium ion battery does not exceed the second threshold, and to increase the charging current of the lithium ion battery when it is determined based on the difference that lithium metal deposition is unlikely to occur.

[0035] In the next S16, the ECU 150 transmits the charging command value determined in S15 to the charger 61. The charger 61 that has received the charging command value controls the charging current of the battery 11 so that the charging current of the battery 11 approaches the target charging current value indicated by the charging command value. In this way, external charging of the battery 11 is performed.

[0036] In the next S17, the ECU 150 determines whether or not a charging end condition is satisfied. The charging end condition is satisfied, for example, when the amount of stored power in the battery 11 reaches a target value. The target value may be set automatically by the ECU 150 or the EVSE 300, or may be set by a user. The amount of stored power may be expressed as SOC. The target value may be a value indicating a full charge. The charging end condition may be changed as appropriate. For example, the charging end condition may be satisfied when a predetermined time has elapsed since the start of external charging. The charging end condition may also be satisfied in response to an instruction from a user to stop charging.

[0037] When the charging end condition is not satisfied (NO in S17), the process returns to the first step (S11). This allows external charging to continue. On the other hand, when the charging end condition is satisfied (YES in S17), the process flow ends. This allows external charging to end.

[0038] FIG. 3 is a time chart showing an example of operation according to the charging method shown in FIG. 2. In FIG. 3, lines L1, L2, and L3 respectively indicate the transition of the first threshold, the second threshold, and the target charging current value (charging command value) in the charging method shown in FIG. 2. In the example shown in FIG. 3, the second threshold is constant. In the charging method shown in FIG. 2, the ECU 150 variably controls the charging current of the battery 11 from the start of charging the battery 11 until the difference X (=first threshold-second threshold) falls below Th. In the example shown in FIG. 3, the difference X falls below Th at timing t1. After the difference X falls below Th, the ECU 150 maintains the charging current of the battery 11 at the target charging current value (=second threshold-Mx) determined based on the second threshold.

[0039] In a lithium-ion battery, as shown in FIG. 3, the difference between the first threshold and the second threshold is large immediately after the start of charging, and the difference becomes smaller as time passes, and the difference tends to converge to a constant value. In the charging method shown in FIG. 2, the charging current of the lithium-ion battery is variably controlled during a period when the difference between the first threshold and the second threshold is large immediately after the start of charging the lithium-ion battery. Since lithium metal is not easily precipitated during such a period, the precipitation of lithium metal is suppressed even if the charging current of the lithium-ion battery does not sufficiently follow the target value as a result of variably controlling the charging current of the lithium-ion battery using a charger with low responsiveness. In addition, in the charging method shown in FIG. 2, during a period when the difference between the first threshold and the second threshold is small, the charging current of the lithium-ion battery is maintained at the target value determined based on the second threshold. Therefore, even with a charger with low responsiveness, it is easy to make the charging current of the lithium-ion battery follow (maintain) the target value.

[0040] As described above, the charging method according to this embodiment includes the processes shown in Fig. 2. This charging method includes determining a first threshold and a second threshold for the charging current of a lithium ion battery (battery 11) at which lithium metal precipitates on the electrodes of the lithium ion battery (S11), and controlling the charging current of the lithium ion battery using the difference between the first threshold and the second threshold and the second threshold (S12 to S16). ECU 150 (control device) executes the charging method for battery 11 (lithium ion battery).

[0041] The charging method according to this embodiment will be described below in comparison with a comparative example. As a first comparative example, it is possible to control the charging current of the lithium ion battery based on the first threshold value, regardless of the difference between the first threshold value and the second threshold value. However, in such a charging method, depending on the responsiveness of the charger, it may not be possible to make the charging current of the lithium ion battery follow the first threshold value, which changes from moment to moment. Also, as a second comparative example, it is possible to maintain the charging current of the lithium ion battery at a target charging current value (=second threshold value-Mx) determined based on the second threshold value, regardless of the difference between the first threshold value and the second threshold value, as shown by line L4 in FIG. 3. However, in such a charging method, the charging current of the lithium ion battery is always small, and the charging time (the time until charging is completed) is long.

[0042] In the charging method according to this embodiment, the charging current of the lithium ion battery is controlled using the second threshold. By controlling the charging current of the lithium ion battery so that it does not exceed the second threshold, it is easy to suppress the deposition of lithium metal. Since the variation of the second threshold over time is small, it is possible to make the charging current of the lithium ion battery follow the second threshold even with a charger with low responsiveness. In addition, in the lithium ion battery, the larger the difference between the first threshold and the second threshold, the less likely the deposition of lithium metal tends to occur. Therefore, in the charging method, in addition to the second threshold, this difference is also used to control the charging current of the lithium ion battery. According to this charging method, while performing charging control of the lithium ion battery so that the charging current of the lithium ion battery does not exceed the second threshold, when it is determined based on the difference that the deposition of lithium metal is unlikely to occur, the charging current of the lithium ion battery is increased, thereby making it possible to shorten the charging time. Even if the performance of the charger 61 mounted on the vehicle 100 is low, the ECU 150 can appropriately suppress the deposition of lithium metal when charging the battery 11. In addition, ECU 150 (control device) may be configured to select a charging method from options including the charging method shown in FIG. 2, the charging method according to the first comparative example, and the charging method according to the second comparative example, and to execute the selected charging method.

[0043] In the above embodiment, charging control of the lithium ion battery is performed using a charger 61 mounted on the vehicle 100. However, this is not limited to this, and charging control of the lithium ion battery may be performed using a charger mounted on the EVSE. Figure 4 is a diagram showing a modified example of the charging system shown in Figure 1.

[0044] Referring to FIG. 4, the EVSE 300A incorporates a charger 331, a detector 331a, and a control device 332. The charger 331 includes a power conversion circuit (e.g., an inverter) and is configured to be able to adjust a charging current. The detector 331a includes various sensors (e.g., a current sensor and a voltage sensor) that detect the state of the charger 331, and outputs the detection result to the control device 332. The connector 320a of the EVSE 300A is connected to the inlet 60A of the vehicle 100A, so that the vehicle 100A is in a plugged-in state. In the vehicle 100A in the plugged-in state, the ECU 150A executes external charging of the battery 11 while communicating with the control device 332 via the charging cable 320. During external charging, the charger 331 converts AC power supplied from the power system PG into DC power and outputs the DC power to the connector 320a. That is, the EVSE 300A outputs DC power. The DC power output from the EVSE 300A to the vehicle 100A is input to the inlet 60A and is used to charge the battery 11.

[0045] The ECU 150A performs external charging of the battery 11 by the charging method shown in Fig. 2. In S16, the ECU 150A transmits the charging command value determined in S15 to the control device 332. The control device 332 that receives the charging command value controls the charger 331 so that the charging current of the battery 11 approaches the target charging current value indicated by the charging command value. In this way, the external charging of the battery 11 is performed. The control device 332 may obtain the charging current by using the detection result by the current sensor of the detector 331a.

[0046] The process flow shown in Fig. 2 can be modified as appropriate. For example, the order of the processes may be changed or unnecessary steps may be omitted depending on the purpose. Furthermore, the content of any of the processes may be changed. For example, in the process flow shown in Fig. 2, when the difference X matches Th, the process proceeds to S14, but the process may be modified to proceed to S13.

[0047] The configuration of the vehicle is not limited to the above-described configuration (see FIG. 1). For example, the vehicle may be configured to be capable of being charged wirelessly. A vehicle that performs wireless charging may be considered to be in a state equivalent to the above-described "plugged-in state" when the alignment between the power transmission unit (e.g., a power transmission coil) on the power supply equipment side and the power receiving unit (e.g., a power receiving coil) on the vehicle side is completed.

[0048] The lithium ion battery may be mounted on a resource other than an automobile. The resource may be a moving body other than an automobile (railroad car, ship, airplane, drone, walking robot, robot cleaner, etc.). The resource may be an electric machine or appliance (lighting device, air conditioner, cooking appliance, television, refrigerator, washing machine, etc.). The lithium ion battery to be charged may be a stationary lithium ion battery used in a building (house, factory, etc.) or outdoors.

[0049] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0050] 11 battery, 11a BMS, 60,60A inlet, 61 charger, 61a detector, 100,100A vehicle, 150,150A ECU, 300,300A EVSE, 331 charger, 331a detector, 332 control unit.

Claims

1. determining a first threshold value and a second threshold value at which lithium metal precipitates on an electrode of the lithium ion battery with respect to a charging current of the lithium ion battery; Controlling a charging current of the lithium ion battery using a difference between the first threshold value and the second threshold value and the second threshold value; Including, the first threshold indicates a current boundary value at which precipitation of the lithium metal is likely to occur when a charging current of the lithium ion battery exceeds the first threshold, The charging method, wherein the second threshold is a value smaller than the first threshold and indicates a current boundary value at which precipitation of the lithium metal is likely to occur when the charging current of the lithium ion battery continuously exceeds the second threshold.

2. Controlling the charging current determining a charge margin using the difference between the first threshold and the second threshold; determining a target charging current value such that the charging current of the lithium ion battery is lower than the second threshold by the charging margin; Controlling the charging current of the lithium ion battery so as to approach the target charging current value; The charging method of claim 1 , comprising:

3. Controlling the charging current determining whether the difference between the first threshold and the second threshold is greater than a reference value; determining a predetermined value as the charging margin when the difference between the first threshold value and the second threshold value is smaller than the reference value; determining the charging margin so that the charging margin is smaller than the predetermined value when the difference between the first threshold value and the second threshold value is larger than the reference value, and the charging margin becomes smaller as the difference between the first threshold value and the second threshold value becomes larger; The charging method according to claim 2 , comprising:

4. Controlling the charging current comprises: variably controlling a charging current of the lithium ion battery from a start of charging of the lithium ion battery until the difference between the first threshold value and the second threshold value falls below a predetermined value; After the difference falls below the predetermined value, maintaining the charging current of the lithium ion battery at the target charging current value determined based on the second threshold value; The charging method of claim 1 , comprising:

5. A charging system comprising: a lithium ion battery; and a control device that executes the charging method according to any one of claims 1 to 4 with respect to the lithium ion battery.

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