Power storage device and control method

Abstract

To achieve a long drivable distance even when the electric vehicle is used over a long period of time, while ensuring safety.SOLUTION: In a control method for a power storage device 100 with a lithium metal battery, the device is controlled so that the lithium metal battery is charged at a rate of 0.2C or less, and discharged at a rate of 1.0C or more and 2.0C or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device and a control method. [Background technology]

[0002] In recent years, research and development has been conducted on secondary batteries that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. Patent Document 1 describes an invention related to charge and discharge management aimed at suppressing battery degradation when using secondary batteries in mobility. Utilizing high-density secondary batteries is effective in improving the driving range of mobility. Patent Document 2 discloses a method for controlling an electric vehicle that uses a secondary battery. Patent Document 2 also discloses a usable secondary battery, a high-density lithium metal battery that uses metallic lithium in the anode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-120237 [Patent Document 2] Japanese Patent Application Publication No. 2023-38288 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in secondary battery technology, ensuring safety and maintaining a long driving range even when an electric vehicle is used for a long period of time are issues. In lithium metal batteries (LMBs), an inactive lithium metal layer forms on the surface of metallic lithium used as the negative electrode during charging and discharging. The formation of this inactive lithium metal layer reduces battery capacity and deteriorates cycle characteristics. Furthermore, the formation of this inactive lithium metal layer in lithium metal batteries increases the thickness of the battery cell.

[0005] In order to solve the above-mentioned problems, the present application aims to ensure safety and maintain a long cruising range even when an electric vehicle is used for a long period of time by improving cycle characteristics, etc., thereby contributing to energy efficiency. [Means for solving the problem]

[0006] (1) A control method according to one embodiment of the present invention is a control method for controlling a power storage device including a lithium metal battery, in which the lithium metal battery is charged at a rate of 0.2 C or less and discharged at a rate of 1.0 C or more and 2.0 C or less.

[0007] (2) In one aspect of the present invention, the lithium metal battery may be charged after being discharged depending on the charging resistance.

[0008] (3) In one aspect of the present invention, the storage device may include a first battery that is a lithium metal battery and a second battery that is a secondary battery other than a lithium metal battery, and when discharging from the storage device, power may be supplied from the second battery to the first battery.

[0009] (4) In one aspect of the present invention, the second battery may supply power to the first battery at a rate of 0.2 C or less.

[0010] (5) In one aspect of the present invention, the storage device includes a first battery that is a lithium metal battery and a third battery that is a secondary battery other than a lithium metal battery, and when charging the storage device, the first battery may be charged at a rate of 0.2C or less and the third battery may be charged at a rate exceeding 0.2C.

[0011] (6) In one aspect of the present invention, the storage device includes a first battery that is a lithium metal battery, and a second battery and a third battery that are secondary batteries other than lithium metal batteries, the second battery having a higher capacity density than the third battery, and the third battery having a higher output density than the second battery, and when charging the storage device, the charge rate of the first battery is 0.2 C or less, the charge rate of the second battery is a rate exceeding 0.2 C, and the charge rate of the third battery is higher than the charge rate of the second battery, and when discharging from the storage device, power may be supplied from the first battery to the second battery.

[0012] (7) In one aspect of the present invention, the power storage device may be mounted on an electric vehicle and may supply regenerative charge to the third battery.

[0013] (8) A power storage device according to one aspect of the present invention includes a plurality of battery blocks including an LMB block made up of a plurality of lithium metal battery cells, and each battery block is configured to be detachable.

[0014] (9) In one aspect of the present invention, the LMB block may be provided in plurality.

[0015] (10) In one aspect of the present invention, a second battery block may be provided that is made up of secondary battery cells other than lithium metal. [Effects of the Invention]

[0016] According to the control method (1) above, the rate at which a layer of lithium inactive material forms on the negative electrode lithium metal during charging and discharging of a lithium metal battery can be reduced, ensuring safety and improving the cycle characteristics of the energy storage device.

[0017] According to the control method (2) above, lithium inactive material that tends to form in a dendrite shape on the negative electrode during charging is removed from the negative electrode by discharging before charging, thereby flattening the surface and suppressing the formation of locally thick lithium inactive material on the negative electrode during charging, thereby improving cycle characteristics.

[0018] According to the control methods (3) to (5) above, a lithium metal battery that exhibits high capacity but has a limited charge rate in order to suppress the formation of lithium inactive substances is charged at a charge rate that can suppress the growth of lithium inactive substances, and by adjusting the SOC of batteries other than the lithium metal battery that are charged at a high charge rate during charging to be low, the SOC of the entire storage device can be increased over the long term, improving the cycle characteristics as well as the charge time and charge frequency.

[0019] According to the control method (6) above, during charging, batteries that can be charged at a higher charge rate are charged preferentially, and the difference between the charge and discharge rates of lithium metal batteries that have a discrepancy between the charge and discharge rates that can be suitably used can be filled in. This improves the cycle characteristics and increases the SOC of the entire energy storage device, thereby improving the charging time and charging frequency.

[0020] According to the control method (7) above, by supplying regenerative charging to a battery with a high battery capacity, the SOC of the entire power storage device can be increased for a long period of time.

[0021] According to the storage devices (8) and (9) above, even if the cycle characteristics of a lithium metal battery among the multiple battery blocks deteriorate due to long-term use, a long cruising range can be maintained by replacing the battery.

[0022] According to the above-mentioned storage devices (10) and (11), the lithium metal battery has a charge rate and discharge rate for maintaining high cycle characteristics during charging and discharging, and the second battery can be charged and discharged at a rate higher than that of the lithium metal battery, thereby increasing the SOC of the entire storage device over a long period of time. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a block diagram showing a schematic configuration of an electric vehicle equipped with a power storage device according to an embodiment of the present invention. [Figure 2] 2 is a circuit diagram for explaining a control method for charging the power storage device of FIG. 1. FIG. [Figure 3] 2 is a circuit diagram for explaining a control method for discharging the power storage device of FIG. 1. FIG. [Figure 4] 2 is a block diagram illustrating a control method during discharge in the power storage device of FIG. 1. FIG. [Figure 5] 3 is a circuit diagram for illustrating a control method for charging the power storage device according to the modified example of FIG. 2. FIG. [Figure 6] 3 is a circuit diagram for explaining a control method for discharging the power storage device according to the modified example of FIG. 2. FIG. [Figure 7] 10 is a circuit diagram for illustrating a control method during charging of the power storage device according to another modified example of FIG. 2.

[0031] FIG. [Figure 8] 10 is a circuit diagram for illustrating a control method for discharging the power storage device according to another modified example of FIG. 2.

[0031] FIG. [Figure 9] 1 is a graph showing the capacity retention rates of recycled metal batteries under each charge-discharge condition in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] Fig. 1 is a block diagram showing the schematic configuration of an electric vehicle equipped with a power storage device according to one embodiment of the present invention. In Fig. 1, thick solid lines indicate mechanical connections, double dotted lines indicate power wiring, and thin solid lines indicate control signals. The 1MOT type electric vehicle shown in Fig. 1 includes a motor generator (MG) 11, a PDU (Power Drive Unit) 13, and a power storage device 100 according to one embodiment. Each of the components included in the electric vehicle will now be described.

[0026] The power storage device 100 is provided with battery blocks each including a lithium metal battery. In the example shown in Fig. 1, an electric vehicle equipped with the power storage device 100 including battery blocks B1 to B3 each including lithium metal battery cells will be described. In Fig. 1, the power storage device 100 is described as having three battery blocks, but the number is not limited as long as the power storage device has a plurality of battery blocks each including lithium metal battery cells. For example, the number of battery blocks provided in the power storage device may be four or more.

[0027] The motor generator 11 is driven by electric power supplied from the power storage device 100 and generates power for propelling the electric vehicle. The torque generated by the motor generator 11 is transmitted to the drive wheels W via a gearbox GB, which includes a variable speed stage or a fixed speed stage, and a differential gear D. The motor generator 11 also operates as a generator when the electric vehicle is decelerating, and outputs braking force for the electric vehicle. Regenerative power generated by operating the motor generator 11 as a generator is stored in the battery of the power storage device 100.

[0028] The PDU 13 converts DC voltage into AC voltage and supplies three-phase current to the motor generator 11. The PDU 13 also converts AC voltage, which is input during regenerative operation of the motor generator 11, into DC voltage.

[0029] 1, the power storage device 100 includes a plurality of battery blocks B1 to B3, a VCU (Voltage Control Unit) 101, voltage sensors 103p, 103e, and 103a, current sensors 105p, 105e, and 105a, a vehicle speed sensor 108, a switch unit 111, an ECU (Electronic Control Unit) 109, and an APS (Accelerator Position Sensor, not shown). Each of the battery blocks B1 to B3 is detachably mounted on the power storage device 100. Each of the battery blocks B1 to B3 has a plurality of battery cells.

[0030] The battery blocks B1 to B3 are, for example, battery blocks made up of multiple lithium metal battery cells. The lithium metal battery cells are batteries that use one or both of lithium metal and lithium alloys for the negative electrode. The lithium alloy can be an alloy of lithium, an element selected from the group consisting of magnesium, aluminum, and indium, and inevitable impurities, with a lithium content of 90% or more and less than 100%. The inevitable impurity content of the aluminum alloy is 0.05% by mass or less.

[0031] The battery blocks B1 to B3 are preferably electrically connected to one another, which allows the battery blocks B1 to B3 to supply power to one another during discharge, such as while the electric vehicle is running.

[0032] The VCU 101 boosts the output voltage of the battery blocks B1 to B3 while it remains DC. The VCU 101 also reduces the power generated by the motor generator 11 and converted to DC when the electric vehicle is decelerating. The VCU 101 also reduces the output voltage of the battery blocks B1 to B3 while it remains DC. The power reduced by the VCU 101 is used to charge the battery blocks B1 to B3, for example. The voltage level or current level of the DC power output by the VCU 101 is controlled by the ECU 109.

[0033] Voltage sensor 103a detects the voltage Va of battery block B1. A signal indicating the voltage Va detected by voltage sensor 103a is sent to ECU 109. Voltage sensor 103e detects the voltage Ve of battery block B2. A signal indicating the voltage Ve detected by voltage sensor 103e is sent to ECU 109. Voltage sensor 103p detects the voltage Vp of battery block B3. A signal indicating the voltage Vp detected by voltage sensor 103p is sent to ECU 109.

[0034] When each of the battery blocks B1 to B3 is in an open state, the voltages Va, Ve, and Vp are open circuit voltages (OCV), and there is a predetermined relationship between the voltage Va detected by voltage sensor 103a, the voltage Ve detected by voltage sensor 103e, and the voltage Vp detected by voltage sensor 103p, as well as between battery block B1, battery block B2, and battery block B3, and a map has been obtained in advance. Based on the map, the ECU 109 can derive the storage capacity SOC of each of the battery blocks B1 to B3 from the obtained voltages Va, Ve, and Vp.

[0035] Current sensor 105a detects input / output current Ia of battery block B1. A signal indicating the input / output current Ia detected by current sensor 105a is sent to ECU 109. Current sensor 105e detects input / output current Ie of battery block B2. A signal indicating the input / output current Ie detected by current sensor 105e is sent to ECU 109. Current sensor 105p detects input / output current Ip of battery block B3. A signal indicating the input / output current Ip detected by current sensor 105p is sent to ECU 109.

[0036] The vehicle speed sensor 108 detects the traveling speed (vehicle speed) VP of the electric vehicle. A signal indicating the vehicle speed VP detected by the vehicle speed sensor 108 is sent to the ECU 109.

[0037] The switch unit 111 has a contactor MCa that connects and disconnects the current path from the battery block B1 to the PDU 13 or the VCU 101, a contactor MCe that connects and disconnects the current path from the battery block B2 to the VCU 101, and a contactor MCp that connects and disconnects the current path from the battery block B3 to the VCU 101. Each of the contactors MCa, MCe, and MCp is opened or closed under the control of the ECU 109.

[0038] The ECU 109 controls the PDU 13 and the VCU 101, and controls the opening and closing of the switch unit 111. The ECU 109 also determines the running state of the electric vehicle based on the vehicle speed VP indicated by a signal obtained from the vehicle speed sensor 108. When it is determined that the electric vehicle is not running, the ECU 109 controls the PDU 13 to turn all of the switching elements of the PDU 13 off, and controls the VCU 101 to turn all of the switching elements of the VCU 101 off. By controlling in this manner, each becomes an open circuit state.

[0039] 2 is a circuit diagram for explaining a control method for charging the power storage device 100 of FIG. 1, and shows an extracted portion of the power storage device 100 including the ECU 109 and battery blocks B1 to B3. The power storage device 100 is provided with a plurality of battery blocks B1 to B3. The plurality of battery blocks B1 to B3 provided in the power storage device 100 are connected in parallel. The battery blocks B1 to B3 are LMB blocks made up of lithium metal battery cells 30.

[0040] For ease of explanation, arrows are used in Figure 2 to indicate the power supplied from the power source to each of the battery blocks B1 to B3. When connected to an external power source E, such as a power station, the ECU 109 controls charging so that the charge rate of the battery blocks B1 to B3 is 0.2 C or less. The charge rate is controlled, for example, by the ECU 109 calculating the current required for each block, issuing a command to the external power source E for the total current value, and then distributing the current input from the external power source E to each block according to the calculated value.

[0041] Furthermore, when charging, it is preferable to discharge the battery blocks B1 to B3 in advance. The discharge rate at this time is preferably 1.0 C or higher. By rapidly discharging the lithium metal battery before charging, lithium inactive materials that tend to form dendrite-like on the negative electrode during charging are removed from the negative electrode by discharging before charging, thereby flattening the surface and preventing the formation of locally thick lithium inactive materials on the negative electrode during charging. For rapid discharge, the number of battery blocks is selected and discharged under the constraint that the discharge rate per LMB block is 1.0 C or higher and 2.0 C or lower, by opening and closing contactors connected in series with the battery blocks B1 to B3, etc.

[0042] Discharging a lithium metal battery before charging is performed, for example, depending on the charging resistance of the lithium metal battery. When the charging resistance is high, the layer of deposited inactive lithium metal is thick, and it is thought that the lithium inactive material formed in a dendrite shape is more likely to cause a short circuit than when the charging resistance is low. Therefore, discharging before charging is preferable. Thus, during charging, it is preferable to measure the charging resistance as an identification step and identify whether or not to perform rapid discharge depending on the charging resistance of the lithium metal battery.

[0043] Furthermore, the ECU 109 checks the charge / discharge capacity C of each battery block by applying constant current control for a time Δt, and when it determines that the charge / discharge capacity C is below a predetermined value, it can display a signal on the meter panel or the like to request that the battery block be removed and a new battery block be installed. In this process, the charge / discharge capacity C can be calculated by ΔAh / ΔSOC. ΔAh is the product of the constant current Ic and the time Δt. ΔSOC is the difference between SOC(t+Δt) and SOC(t). SOC(t) is the SOC of the battery block immediately before charging / discharging by constant current control. SOC(t+Δt) is the SOC of the battery block immediately after charging / discharging by constant current control. In other words, the charge / discharge capacity C is expressed by the following formula. C=ΔAh / ΔSOC=[(Ic×Δt) / {SOC(t+Δt)-SOC(t)}

[0044] Fig. 3 is a circuit diagram for explaining a control method for charging the power storage device 100 of Fig. 1, and shows an extracted part of the power storage device 100 including the ECU 109 and battery blocks B1 to B3. Fig. 4 is a block diagram for explaining a control method for discharging the power storage device of Fig. 1.

[0045] During discharge, the ECU 109 first acquires the voltage Va of the battery block B1 detected by the voltage sensor 103a, the voltage Ve of the battery block B2 detected by the voltage sensor 103e, and the voltage Vp of the battery block B3 detected by the voltage sensor 103p (step S1).

[0046] Next, the accelerator opening is measured by the APS to calculate the output corresponding to the load (step S2).

[0047] Next, the current value flowing through each battery pack when the combination of battery packs to be used is adjusted is calculated from the voltage measured in step S1 and the output calculated in step S2 (step S3).

[0048] Next, based on the calculation results in step S3, the combination of the battery blocks B1 to B3 through which current flows and the current value are determined so that the current value of the battery blocks B1 to B3 of the lithium metal batteries is 0 or a discharge rate of 1.0 to 2.0 C (step S4).

[0049] Next, the switch unit 111 is controlled so that the contactors MCa, MCe, and Mcp are opened and closed in accordance with the combination of battery blocks through which the current is to flow determined in step S4, and a current output command is issued to each of the battery blocks B1 to B3 (step S5). The output current is voltage-controlled by the VCU 101 and then supplied to the motor generator 11 via the PDU 13.

[0050] FIG. 5 is a circuit diagram for explaining a control method for charging the energy storage device according to the modified example of FIG. 2, and FIG. 6 is a circuit diagram for explaining a control method for discharging the energy storage device according to the modified example of FIG. 2. Parts of the energy storage device are shown in FIGS. 5 and 6. The energy storage device, part of whose electrical circuit is shown in FIGS. 5 and 6, differs from the energy storage device 100 shown in FIGS. 1 to 3 in that it includes a battery block B4 consisting of battery cells 40 other than lithium metal batteries in addition to battery blocks B1 and B3 consisting of lithium metal battery cells. Other configurations can be similar. Furthermore, in the energy storage device shown in FIGS. 5 and 6, the SOC of each battery block B1, B2, and B4 can be derived, just like in the energy storage device 100.

[0051] The battery block B4 includes a plurality of storage cells, such as lithium-ion secondary batteries or nickel-metal hydride batteries whose negative electrodes are not made of lithium metal. In this embodiment, the battery block B4 is also referred to as a second battery or a third battery. Note that the battery block B4 is not limited to secondary batteries such as the lithium-ion batteries or nickel-metal hydride batteries described above. For example, a capacitor or condenser that has a small storage capacity but can charge and discharge a large amount of power in a short period of time may also be used. The battery block is also referred to as a battery module.

[0052] Lithium ion secondary batteries are classified into, for example, high-power lithium ion secondary batteries and high-capacity lithium ion secondary batteries. High-power lithium ion secondary batteries are lithium ion secondary batteries that have a high power density but not a very high capacity density. On the other hand, high-capacity lithium ion secondary batteries are lithium ion secondary batteries that have a high capacity density but not a very high power density.

[0053] High-power lithium-ion batteries and high-capacity lithium-ion batteries have different characteristics. High-power lithium-ion secondary batteries are lithium-ion secondary batteries that have a lower energy weight density but a higher output weight density than high-capacity lithium-ion batteries. High-capacity lithium-ion secondary batteries are lithium-ion secondary batteries that have a lower output weight density but a higher energy weight density than high-power lithium-ion secondary batteries. Thus, high-capacity lithium-ion secondary batteries are relatively superior in terms of energy weight density, and high-power lithium-ion secondary batteries are relatively superior in terms of output weight density. Note that energy weight density refers to the amount of power per unit weight (Wh / kg), and output weight density refers to the power per unit weight (W / kg). Examples of high-power lithium-ion secondary batteries include lithium-ion secondary batteries that use graphite, hard carbon, or lithium titanate (LTO: Lithium Titanium Oxide) for the negative electrode.

[0054] The control of the power storage device according to the modified example can also be performed in the same manner as the charging and discharging described above. Furthermore, the charge rate and discharge rate may be adjusted taking into consideration that battery block B4 has different characteristics from battery blocks B1 to B3. For example, lithium ion secondary batteries, particularly high-power lithium ion secondary batteries, do not show any deterioration in cycle characteristics even when charged at a charge rate exceeding 0.2 C.

[0055] As described above, the power storage device is provided with battery blocks having different characteristics, and therefore, the ECU 109 performs power distribution control using the VCU 101 so as to make the most of the characteristics of each of the battery blocks B1, B3, and B4.

[0056] For example, during charging, control is performed so that battery block B4 is charged preferentially. Specifically, battery blocks B1 and B3 are charged at 0.2 C or less, and battery block B4 is charged at a rate exceeding 0.2 C. It is more preferable to charge battery block B4 at a rate exceeding 1.0 C. By controlling power distribution in this way, it is possible to increase the storage capacity (SOC: State Of Charge) of the entire power storage device even in a short charging time.

[0057] In addition, it is preferable that the regenerative power generated by the motor generator 11 is input preferentially to battery block B4, and is input only to battery block B4, or that the input to battery blocks B1 and B3 is input at a rate of 0.2C or less, and the remaining power is input to battery block B4.

[0058] During discharge, ECU 109 controls VCU 101 so that the discharge of battery blocks B1 and B3 is at a discharge rate of 1.0C or more and 2.0C or less using a control method similar to that of the above embodiment, and so that the discharge of battery block B4 is at a higher discharge rate than battery blocks B1 and B3.

[0059] Furthermore, when battery block B4 is composed of lithium-ion secondary battery cells, battery blocks B1, B3, and B4 are electrically connected, and it is preferable that battery block B4 be controlled to supply power to one or both of battery blocks B1 and B3 at a rate of 0.2 C or less. The ECU can supply power from battery block B4 to one or both of battery blocks B1 and B3 via a boost circuit. Power supply from battery block B4 to battery blocks B1 and B3 is performed when the SOC of battery block B4 is equal to or greater than a predetermined value and the SOC of battery blocks B1 and B3 is equal to or less than 50%, and is not performed when these conditions are not met. The predetermined SOC value for battery block B4 can be, for example, 30% or greater, and is preferably 50%.

[0060] By supplying power from battery block B4 to battery blocks B1 and B3 made up of lithium metal battery cells 30 at a rate of 0.2 C or less in this way, the lithium metal battery cells can be charged within a range that minimizes deterioration of the cycle characteristics.

[0061] In addition, the SOC of battery block B4 can be reduced without changing the SOC of the entire energy storage device, allowing battery block B4 to be charged preferentially using external power at a charging station, etc., which enables more charging in a short period of time, thereby increasing the SOC of the entire energy storage device over the long term and improving cycle characteristics as well as charging time and frequency.A battery block made of lithium metal battery cells requires about five hours of charging at a charge rate of 0.2C or less, but by controlling it in this way, charging time can be shortened, ensuring high marketability.

[0062] Fig. 7 is a circuit diagram for explaining a control method for charging the power storage device according to another modified example of Fig. 2. Fig. 8 is a circuit diagram for explaining a control method for discharging the power storage device according to another modified example of Fig. 2. In the example shown in Figs. 7 and 8, battery block B4 is a battery block made up of high-power lithium-ion secondary battery cells 40, and battery block B5 is a battery block made up of high-capacity lithium-ion secondary battery cells 50. In this embodiment, either high-power or high-capacity lithium-ion batteries can be used as the second battery and the third battery, but it is preferable to use battery block B5 made up of high-capacity lithium-ion secondary battery cells 50 as the second battery, and battery block B4 made up of high-power lithium-ion secondary battery cells 40 as the third battery.

[0063] 7 and 8, it is also possible to charge and discharge using the same control method as in the above embodiment. Furthermore, power distribution control is performed using VCU 101 to make the most of the different characteristics of battery blocks B1, B3 and battery blocks B4, B5.

[0064] During charging, ECU 109 controls the supply of power to battery blocks B4 and B5 preferentially over battery blocks B1 and B3. ECU 109 controls the charging of battery blocks B1 and B3 so that the charging rate is 0.2C or less, and controls the charging of battery blocks B4 and B5 so that the charging rate exceeds 0.2C.

[0065] During discharge, the ECU 109 controls the VCU 101 so that the discharge rate of the battery blocks B1 and B3 is between 1.0 C and 2.0 C using the same control method as in the above embodiment, and so that the discharge rate of the battery blocks B4 and B5 is higher than that of the battery blocks B1 and B3. The ECU 109 also controls the VCU so that the discharge rate of the battery block B4 is higher than that of the battery block B5. The battery blocks B1, B3, B4, and B5 are electrically connected, and it is preferable to control the supply of power from the battery block B4 to one or both of the battery blocks B1 and B3 at a rate of 0.2 C or less. Similarly, it is preferable to control the supply of power from the battery block B5 to one or both of the battery blocks B1 and B3 at a rate of 0.2 C or less. It is also preferable to supply power from the battery block B5, which is composed of high-capacity lithium-ion secondary battery cells 50, to the battery block B4, which is composed of high-power lithium-ion secondary battery cells 40. The power supply from battery block B4 to battery blocks B1 and B3 is performed when the SOC of battery block B4 is equal to or greater than a predetermined value and the SOC of battery blocks B1 and B3 is equal to or less than 50%, and is not performed when these conditions are not met. This predetermined value can be, for example, 30%, and preferably 50%. Similarly, the power supply from battery block B5 to battery blocks B1 and B3 is performed when the SOC of battery block B5 is equal to or greater than a predetermined value, and is not performed when it is less than the predetermined value. This predetermined value can be, for example, 30%, and preferably 50%.

[0066] By supplying power between battery blocks within a specified rate range in this way, the SOC balance of the battery blocks within the storage device can be set to an optimal value, which leads to reduced charging frequency, shorter charging time, and longer life for lithium metal batteries.

[0067] In the energy storage device whose circuit diagrams are partially shown in Figures 7 and 8, the regenerative power is preferentially input to battery block B4, and is preferably input only to battery block B4, or only to battery blocks B4 and B5, or input to battery blocks B1 and B3 at a rate of 0.2 C or less, input to battery block B5 at a rate of 0.5 C or less, and the remaining power is input to battery block B4.

[0068] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various modifications and improvements can be made to the above embodiments. Such modifications and improvements can also be included in the technical scope of the present invention. [Example]

[0069] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0070] A lithium metal battery cell was fabricated using an electrolyte of fluorine-containing lithium salt and with a negative electrode made of lithium metal.

[0071] [Example 1] As Example 1, the electric capacity of the lithium metal battery was measured when the lithium metal battery cell was repeatedly charged and discharged in an environment of 25° C., with one cycle consisting of charging at a charge rate of 0.2 C and discharging at a discharge rate of 1.0 C. In addition, the capacity retention rate of the lithium metal battery was calculated every five cycles, assuming the electric capacity after one cycle to be 100%.

[0072] [Comparative Example 1] The capacity retention rate of the lithium metal battery was calculated every 5 cycles in the same manner as in Example 1, except that the charge rate was changed to 0.33C and the discharge rate was changed to 0.33C.

[0073] FIG. 9 is a graph showing the capacity retention rates of the recycled metal batteries under the respective charge-discharge conditions of Example 1 and Comparative Example 1.

[0074] As shown in Figure 9, it was confirmed that charging and discharging at a charge rate of 0.2 C or less and a discharge rate of 1.0 C to 2.0 C showed superior cycle characteristics compared to charging and discharging at a charge rate above 0.2 C and a discharge rate below 1.0 C. These results confirmed that a battery block made of lithium metal battery cells can be significantly extended in battery life and range by controlling the charge rate to 0.2 C or less and the discharge rate to 1.0 C to 2.0 C. [Explanation of symbols]

[0075] 11 Motor generator 30 lithium metal battery cells 40 Lithium-ion secondary battery cells 50 lithium-ion secondary battery cells 100 Electricity storage device 103p, 103e, 103a voltage sensor 105p, 105e, 105a current sensor 108 Vehicle speed sensor 111 Switch section B1~B5 Battery Blocks D Differential Gear E External power supply GB Gearbox MCa, MCe, MCp contactors

Claims

1. A control method for controlling a power storage device including a lithium metal battery, comprising: A control method for controlling a lithium metal battery to be charged at a rate of 0.2C or less and discharged at a rate of 1.0C or more and 2.0C or less.

2. 10. The method of claim 1, further comprising discharging and then charging the lithium metal battery in response to a charging resistance.

3. the power storage device includes a first battery that is a lithium metal battery and a second battery that is a secondary battery other than a lithium metal battery; The control method according to claim 1 , wherein power is supplied from the second battery to the first battery when the power storage device is being discharged.

4. The control method according to claim 3 , wherein the power supply from the second battery to the first battery is performed at a rate of 0.2 C or less.

5. the power storage device includes a first battery that is a lithium metal battery and a third battery that is a secondary battery other than a lithium metal battery; The control method according to claim 1 , wherein when the power storage device is charged, the first battery is charged at a rate of 0.2 C or less, and the third battery is charged at a rate exceeding 0.2 C.

6. the power storage device includes a first battery that is a lithium metal battery, and a second battery and a third battery that are secondary batteries other than lithium metal batteries; the second battery has a higher capacity density than the third battery; the third battery has a higher power density than the second battery; When the power storage device is being charged, the charge rate of the first battery is equal to or less than 0.2 C, the charge rate of the second battery is greater than 0.2 C, and the charge rate of the third battery is higher than the charge rate of the second battery; The control method according to claim 1 , wherein power is supplied from the second battery to the first battery when the power storage device is being discharged.

7. The control method according to claim 5 or 6, wherein the power storage device is mounted on an electric vehicle and supplies regenerative power to the third battery.

8. a plurality of battery blocks including an LMB block made up of a plurality of lithium metal battery cells; In the power storage device, each battery block is configured to be detachable.

9. The power storage device according to claim 8 , comprising a plurality of the LMB blocks.

10. 9. The power storage device of claim 8, further comprising a second battery block made of secondary battery cells other than lithium metal.

11. The power storage device according to claim 10 , wherein the LMB block and the second battery block are configured to be electrically connectable.

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