All-solid-state battery and control method for all-solid-state batteries

Abstract

This method for controlling an all-solid-state battery comprises: a step for discharging a battery cell while constraining the battery cell at a first constraint pressure when the temperature of the battery cell is higher than or equal to a first temperature T1 set in advance and lower than a second temperature T2 set in advance; and a step for reducing the constraint pressure of the battery cell to a second constraint pressure lower than the first constraint pressure when the temperature of the battery cell is higher than or equal to the second temperature T2.

Description

Technical Field

[0001] The present invention relates to an all-solid-state battery and a method for controlling an all-solid-state battery.

Background Art

[0002] There is known a battery configured to control its operation according to temperature.

[0003] For example, Patent Document 1 (JP2013-20891A) discloses an invention related to a restraint structure of a battery pack. In this invention, a control unit acquires temperature information of the battery pack, compares the detected measured temperature with a reference temperature stored in advance, and when the measured temperature is higher than the reference temperature, a command "lower the restraint pressure" is output from the control unit to a restraint pressure variable device, and based on this command, the restraint pressure of the restraint band is adjusted.

[0004] On the other hand, Patent Document 2 (JP2002-141112A) discloses a battery device characterized in that when a temperature sensor detects the temperature of the outer surface or the internal atmosphere of a battery housing means set in advance, the battery is discharged to a capacity below a predetermined ratio of a reference capacity.

Summary of the Invention

[0005] By the way, the present inventors have been studying all-solid-state batteries. An all-solid-state battery is a secondary battery using a solid electrolyte. Among all-solid-state batteries, in particular, an all-solid-state battery having a negative electrode containing metallic lithium has been studied. In such an all-solid-state battery, when the temperature becomes abnormally high, metallic lithium may melt. Metallic lithium has high reactivity. Therefore, it is desired to prevent leakage of molten metallic lithium even if the temperature becomes abnormally high.

[0006] Patent documents 1 and 2 do not contain any descriptions of all-solid-state batteries having a negative electrode containing metallic lithium. Therefore, the object of the present invention is to provide an all-solid-state battery and a control method thereof that can prevent metallic lithium from leaking to the outside even if the temperature becomes abnormally high. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a block diagram showing the schematic configuration of an all-solid-state battery according to the first embodiment. [Figure 2] Figure 2 is a flowchart showing a control method for an all-solid-state battery according to the first embodiment. [Figure 3] Figure 3 is a schematic block diagram showing an all-solid-state battery according to the second embodiment. [Figure 4] Figure 4 is a flowchart showing a control method for an all-solid-state battery according to the second embodiment. [Figure 5] Figure 5 schematically illustrates the control mechanisms of a solid-state battery, the relationship between the charge level and the temperature of the battery cells. [Figure 6] Figure 6 is a schematic diagram showing an example of a battery cell according to the second embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings.

[0009] 1: First Embodiment Figure 1 is a block diagram showing the schematic configuration of an all-solid-state battery 1 according to the first embodiment. The all-solid-state battery 1 according to this embodiment is, for example, a secondary battery mounted in a vehicle or the like.

[0010] As shown in Figure 1, the all-solid-state battery 1 comprises a battery cell 2, a temperature detection mechanism 3, a restraining mechanism 4, a discharge mechanism 5, and a control mechanism 6.

[0011] Battery cell 2 is the part that realizes the charge and discharge function. Although not shown in the diagram, battery cell 2 comprises a solid electrolyte, a positive electrode, and a negative electrode. The negative electrode contains lithium metal. In battery cell 2, during charging, lithium ions move from the positive electrode to the negative electrode via the solid electrolyte, and lithium metal is deposited on the negative electrode. On the other hand, during discharge, the lithium metal from the negative electrode moves to the positive electrode side as lithium ions and is absorbed into the positive electrode. In other words, lithium metal is lost from the negative electrode during discharge. Note that the battery cell 2 contained in the all-solid-state battery 1 may be a single cell or multiple cells.

[0012] The restraint mechanism 4 is configured to restrain (pressure) the battery cell 2. In order to obtain the desired battery characteristics in the all-solid-state battery 1, each electrode must be firmly bonded to the solid electrolyte. Therefore, the battery cell 2 is restrained by the restraint mechanism 4 so that each electrode is firmly bonded to the solid electrolyte. If multiple battery cells 2 are provided, multiple battery cells 2 are restrained by the restraint mechanism 4.

[0013] The restraint mechanism 4 is also provided for vibration resistance. In other words, the restraint mechanism 4 provides vibration resistance to the battery cell 2. For example, if the all-solid-state battery 1 is mounted on a vehicle, vibrations from the vehicle may be applied to the battery cell 2. Vibrations may cause the components contained in the battery cell 2 to disperse. If multiple battery cells 2 are provided, vibrations may cause the multiple battery cells 2 to disperse. In contrast, because the battery cell 2 is restrained by the restraint mechanism 4, even if vibrations are applied, dispersion of the constituent components is prevented.

[0014] The restraint mechanism 4 is configured to allow adjustment of the restraint pressure.

[0015] The specific configuration of the restraint mechanism 4 is not particularly limited. For example, the restraint mechanism 4 can be realized by a pair of end plates arranged to sandwich the battery cell 2 in the stacking direction, and an actuator configured to pressurize and restrain the battery cell 2 with the pair of end plates.

[0016] The discharge mechanism 5 is configured to discharge the battery cell 2. The discharge mechanism 5 can be implemented, for example, by a load circuit connected to the battery cell 2.

[0017] The temperature detection mechanism 3 is configured to detect the temperature of the battery cell 2 and generate temperature data. Specifically, the temperature detection mechanism 3 detects the temperature of the negative electrode of the battery cell 2. The temperature detection mechanism 3 may be configured to measure the temperature of the battery cell 2 directly or indirectly. For example, the temperature detection mechanism 3 may be configured to indirectly determine the temperature of the battery cell 2 by measuring the temperature at a location some distance away from the battery cell 2.

[0018] The control mechanism 6 acquires temperature data from the temperature detection mechanism 3 and controls the operation of the solid-state battery 1 based on the acquired temperature data. The control mechanism 6 is implemented by a computer, such as a microcomputer. Specifically, the control mechanism 6 includes a storage device such as memory that stores the control program and an arithmetic unit such as a CPU that executes the control program. In the control mechanism 6, the function is realized when the arithmetic unit executes the control program. Specifically, the control mechanism 6 is programmed to control the operation of the solid-state battery 1 so that molten metallic lithium does not leak even if the battery cell 2 overheats abnormally and becomes hot.

[0019] Figure 2 is a flowchart showing the control method of the all-solid-state battery 1 performed by the control mechanism 6. The control method of the all-solid-state battery 1 will be described in detail below with reference to Figure 2.

[0020] (Step S10) First, the control mechanism 6 detects the temperature of the battery cell 2. That is, the control mechanism 6 acquires temperature data from the temperature detection mechanism 3.

[0021] (Step S20) When temperature data is acquired, the control mechanism 6 compares the temperature of the battery cell 2 with a preset first temperature T1. The first temperature T1 is a temperature serving as a criterion for determining whether there is an abnormal temperature rise. The first temperature T1 is set, for example, within the range of 100 to 150 °C. The first temperature T1 may be, for example, a temperature at which the control mechanism 6 determines that there is an abnormal temperature rise and notifies the user of the abnormal temperature rise via a notification mechanism such as a lamp.

[0022] (Step S30) If the temperature of the battery cell 2 is less than the first temperature T1, it can be said that it is in a normal state. Therefore, the control mechanism 6 does not perform any special processing. That is, the all-solid-state battery 1 is operated by normal operation.

[0023] (Step S40) On the other hand, when the temperature of the battery cell 2 is equal to or higher than the first temperature T1, the control mechanism 6 further compares the temperature of the battery cell with a second temperature T2. The second temperature T2 is a temperature higher than the first temperature T1 and is set from the viewpoint of determining whether the lithium metal melts. The second temperature T2 is set to a value, for example, within the range of 150 to 210 °C, preferably 160 to 200 °C.

[0024] (Step S50) If, in step S40, the temperature of the battery cell 2 is less than the second temperature T2, the control mechanism 6 discharges the battery cell 2 by the discharge mechanism 5 while restraining the battery cell 2 with a first restraint pressure by the restraint mechanism 4.

[0025] The first restraint pressure may be of a magnitude such that the vibration resistance of the battery cell 2 is maintained. The first restraint pressure may be the same as the restraint pressure during normal operation (step S30), but may be different from that during normal operation as long as the vibration resistance is maintained. In any case, since a certain level of restraint pressure is maintained, the vibration resistance of the battery cell 2 is ensured.

[0026] On the other hand, by discharging the battery cell 2 in this step, the lithium metal present at the negative electrode moves to the positive electrode and is absorbed into the positive electrode. The lithium absorbed into the positive electrode does not normally melt. In other words, by performing a discharge, the amount of lithium metal that can melt is reduced before the temperature of the battery cell 2 reaches the melting point of lithium metal.

[0027] (Step S60) On the other hand, if the temperature of the battery cell 2 is above the second temperature T2 in step S40, the control mechanism 6 reduces the restraining pressure of the battery cell 2 by the restraining mechanism 4 to a second restraining pressure that is lower than the first restraining pressure. If the temperature of the battery cell 2 is above the second temperature T2, it is assumed that the lithium metal is melted. If the battery cell 2 is restrained with a strong force while the lithium metal is melted, the molten lithium metal is likely to leak out of the battery cell 2. In contrast, by reducing the restraining pressure in this step, even if the lithium metal is melted, it becomes less likely to leak out.

[0028] Furthermore, the second restraining pressure should be smaller than the restraining pressure in step S50 (first restraining pressure). Preferably, the second restraining pressure is substantially zero. That is, the control mechanism 6 controls the restraining mechanism 4 so that the restraining pressure of the battery cell 2 is released.

[0029] Furthermore, the discharge operation cannot be performed when the lithium metal is molten. Therefore, in step 60, the control mechanism 6 does not perform the discharge operation.

[0030] The first embodiment has been described above. In this embodiment, the description concerns a configuration in which normal operation (step S3) is performed when the temperature of the battery cell 2 is below the first temperature T1. However, even if the temperature of the battery cell 2 is below the first temperature T1, the input and output of the battery cell 2 may be restricted by the control mechanism 6 when it approaches the first temperature T1 to some extent.

[0031] The following summarizes some representative aspects of the relationship between the configuration and effects of this embodiment.

[0032] The all-solid-state battery 1 according to this embodiment includes a battery cell 2 having a negative electrode made of lithium metal, a restraining mechanism 4 that restrains the battery cell, a discharge mechanism 5 that discharges the battery cell 2, a temperature detection mechanism 3 that detects the temperature of the battery cell 2 and generates temperature data, and a control mechanism 6 that controls the operation of the restraining mechanism 4 and the discharge mechanism 5 based on the temperature data. The control mechanism 6 restrains the battery cell 2 with a first restraining pressure using the restraining mechanism 4 and discharges the battery cell 2 using the discharge mechanism 5 when the temperature of the battery cell 2 is above a preset first temperature T1 and below a preset second temperature T2. The control mechanism 6 is also configured to reduce the restraining pressure by the restraining mechanism 4 to a second restraining pressure lower than the first restraining pressure when the temperature of the battery cell 2 is above the second temperature T2.

[0033] Furthermore, the control method for the all-solid-state battery according to this embodiment is a control method for an all-solid-state battery 1 comprising a battery cell 2 having a negative electrode containing lithium metal, and configured such that the battery cell 2 is constrained. This control method comprises the steps of detecting the temperature of the battery cell 2 (step S10) and controlling the operation of the battery cell 2 based on the temperature of the battery cell 2 (steps S50, S60). The control steps (steps S50, S60) include, when the temperature of the battery cell 2 is above a preset first temperature T1 and below a preset second temperature T2, the step of discharging the battery cell 2 while constraining the battery cell 2 with a first constraining pressure (step S50), and when the temperature of the battery cell 2 is above the second temperature T2, the step of lowering the constraining pressure of the battery cell 2 to a second constraining pressure lower than the first constraining pressure (step S60).

[0034] According to the all-solid-state battery 1 and its control method described above, when the temperature of the battery cell 2 reaches a first temperature T1 or higher, the battery cell 2 discharges, thus reducing the amount of lithium metal that could leak during melting. Therefore, even if the temperature at which lithium metal melts is subsequently reached, leakage of lithium metal is prevented.

[0035] Furthermore, when the temperature of battery cell 2 is above the first temperature T1 and below the second temperature T2, the restraint state of battery cell 2 is maintained at the first restraint pressure. As a result, even if battery cell 2 becomes abnormally hot, vibration resistance is maintained until the lithium metal melts.

[0036] On the other hand, when the temperature of battery cell 2 exceeds the second temperature T2, the confinement pressure of battery cell 2 is reduced to the second confinement pressure. As a result, even if the lithium metal melts, it becomes difficult for the molten lithium metal to be pushed out, preventing leakage to the outside.

[0037] 2: Second Embodiment Next, a second embodiment will be described. Note that the same configuration as in the first embodiment can be adopted, and this will not be explained.

[0038] Figure 3 is a schematic block diagram showing an all-solid-state battery 1 according to the second embodiment. In this embodiment, a charge level detection mechanism 7 is added compared to the first embodiment.

[0039] The charge level detection mechanism 7 is configured to detect the charge level (e.g., State of Charge) of the battery cell 2. Note that "detecting the charge level" also includes detecting the charge level by "estimation." For example, the charge level detection mechanism 7 may detect the charge level by estimating the State of Charge of the battery cell 2 from voltage or other factors. The charge level detection mechanism 7 is configured to generate charge level data indicating the detected charge level and notify the control mechanism 6.

[0040] The control mechanism 6 controls the operation of the restraint mechanism 4 and the discharge mechanism 5 by referring to the temperature data obtained from the temperature detection mechanism 3 as well as the charge amount data obtained from the charge amount detection mechanism 7. The control method of the all-solid-state battery 1 realized by the control mechanism 6 is described in detail below.

[0041] Figure 4 is a flowchart illustrating the control method for the all-solid-state battery 1 according to this embodiment. Figure 5 is a schematic diagram showing the control content of the all-solid-state battery 1, the charge amount, and the relationship with the temperature of the battery cell 2. In this embodiment, steps S21 to S23 are added compared to the first embodiment.

[0042] (Steps S10-30) Steps S10 to S30 are the same as in the first embodiment. That is, in step S10, the control mechanism 6 detects the temperature of the battery cell 2 (step S10). The control mechanism 6 then compares the temperature of the battery cell 2 with a first temperature T1 (step S20). If the temperature of the battery cell 2 is less than the first temperature T1, the control mechanism 6 operates the all-solid-state battery 1 in normal operation (step S30).

[0043] (Steps S21-22) On the other hand, if the temperature of the battery cell 2 is above the first temperature T1, the charge level of the battery cell 2 is detected. That is, the control mechanism 6 acquires charge level data via the charge level detection mechanism 7 (step S21). The control mechanism 6 then compares the charge level of the battery cell 2 with a preset first charge level A (%) (step S22).

[0044] (Steps S40-60) The operation when the charge level of battery cell 2 is equal to or greater than the first charge level A is the same as in steps S40 to S60 of the first embodiment. That is, the control mechanism 6 compares the temperature of battery cell 2 with the second temperature T2 (step S40). If the temperature of battery cell 2 is less than the second temperature T2, the control mechanism 6 restrains battery cell 2 with the first restraining pressure using the restraining mechanism 4, and discharges battery cell 2 with the discharge mechanism 5 until it is less than the first charge level A (step S50). On the other hand, if the temperature of battery cell 2 is equal to or greater than the second temperature T2, the control mechanism 6 reduces the restraining pressure of battery cell 2 using the restraining mechanism 4 to the second restraining pressure. In addition, the discharge operation by the discharge mechanism 5 is not performed (step S60).

[0045] (Step S23) On the other hand, if the charge level of the battery cell 2 in step S22 is less than the first charge level A, the control mechanism 6 controls the restraint mechanism 4 to restrain the battery cell 2 with a third restraint pressure. The third restraint pressure is a pressure that maintains vibration resistance and is greater than the second restraint pressure. The third restraint pressure may be the same as or different from the first restraint pressure. In addition, the control mechanism 6 does not perform a discharge process.

[0046] The above describes the control method for the all-solid-state battery 1 according to the second embodiment. According to this embodiment, when the charge amount of the battery cell 2 exceeds the first charge amount A, the operation of the all-solid-state battery 1 is controlled in the same manner as in the first embodiment. This prevents leakage of molten lithium metal, as in the first embodiment.

[0047] On the other hand, if the charge level of battery cell 2 is low (i.e., less than the first charge level A), even if the temperature of battery cell 2 is above the first temperature T1, battery cell 2 cannot be discharged (step S23). Therefore, a certain amount of power is secured. For example, if the all-solid-state battery 1 is mounted on a vehicle, if a discharge process is performed when the temperature rises abnormally and the power of battery cell 2 is completely lost, it may not be possible to secure the power necessary for moving the vehicle to safety. In contrast, according to this embodiment, since a discharge process is not performed when the charge level is less than the first charge level A, a certain amount of power is secured for moving the vehicle to safety. Furthermore, if the charge level of battery cell 2 is low, the amount of lithium metal that can be melted will be small, so even if the temperature of battery cell 2 subsequently reaches the melting temperature of lithium metal, the possibility of lithium metal leakage will be reduced.

[0048] Furthermore, in this embodiment, if the charge level of the battery cell 2 is less than the first charge level A, the battery cell 2 is restrained with a restraining pressure (third restraining pressure) that ensures vibration resistance even when the second temperature T2 is exceeded. As previously described, if the charge level of the battery cell 2 is less than the first charge level A, it can be said that there is little lithium metal that can melt. Therefore, even if the battery cell 2 is restrained, the possibility of lithium metal leaking to the outside is low. Under conditions where the possibility of leakage is low, the battery cell 2 is restrained with the third restraining pressure, so vibration resistance is ensured.

[0049] Furthermore, the first charge level A is set to a value such that the amount of lithium metal contained in the negative electrode does not leak to the outside. This point will be explained in detail below.

[0050] Figure 6 is a schematic diagram showing an example of a battery cell 2 according to this embodiment. This battery cell 2 is housed in a film-like outer casing 8. A buffer space 9 is provided between the outer casing 8 and the battery cell 2. With this configuration, even if some lithium metal melts, the molten lithium metal is contained in the buffer space 9 and does not reach the outside of the outer casing 8.

[0051] As previously described, the amount of lithium metal that can be melted, that is, the amount of lithium metal contained in the negative electrode, changes depending on the charge and discharge state of the battery cell 2. Specifically, the amount of lithium metal contained in the negative electrode increases during charging and decreases during discharge. Therefore, the first charge amount A is set to a charge amount such that the amount of lithium metal contained in the negative electrode is within the buffer space 9. If the first charge amount A is set to such a value, when the temperature of the battery cell 2 rises abnormally (exceeding the first temperature T1), the charge amount of the battery cell 2 will be reduced so that the amount of lithium metal contained in the negative electrode is within the range that can be contained in the buffer space 9. Consequently, even if the temperature at which the lithium metal melts is reached afterward, the molten lithium metal can be contained in the buffer space 9, preventing leakage to the outside.

[0052] More preferably, the first charge amount A is set to the maximum value among the charge amounts such that the amount of lithium metal deposited on the negative electrode can be accommodated in the buffer space 9. If the first charge amount A is set to such a value, vibration resistance is maintained to the maximum extent possible as long as the amount of lithium metal on the negative electrode is contained within the buffer space 9. Furthermore, power can be used until the temperature at which the lithium metal melts (second temperature T2) is reached.

[0053] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Claims

1. A control method for an all-solid-state battery comprising a battery cell having a negative electrode containing lithium metal, wherein the battery cell is configured to be restrained, The steps include detecting the temperature of the battery cell, The system includes a step of controlling the operation of the all-solid-state battery based on the temperature of the battery cell, The aforementioned control step is, The steps include comparing the temperature of the battery cell with a preset first temperature T1, Based on the result of the step of comparing with the first temperature T1, if the temperature of the battery cell is equal to or greater than the first temperature T1, the step of comparing the temperature of the battery cell with a preset second temperature T2, Based on the result of the step of comparing with the second temperature T2, if the temperature of the battery cell is less than the second temperature T2, the step of discharging the battery cell while constraining it with a first constraining pressure, Based on the result of the step of comparing with the second temperature T2, if the temperature of the battery cell is equal to or greater than the second temperature T2, the restraining pressure of the battery cell is reduced to a second restraining pressure that is lower than the first restraining pressure, Equipped with, Control methods for all-solid-state batteries.

2. A control method according to claim 1, Furthermore, the system includes a step of determining that the battery cell is in an abnormally high-temperature state when the temperature exceeds the first temperature T1. Control method.

3. A control method according to claim 1 or 2, The second temperature T2 is a value within the range of 150 to 210°C. Control method.

4. A control method according to claim 1 or 2, Furthermore, the method includes a step of detecting the charge level of the battery cell, The control step further includes, if the charge amount of the battery cell is less than a preset first charge amount A, the step of restraining the battery cell with a third restraining pressure greater than the second restraining pressure without discharging the battery cell, even if the temperature of the battery cell is equal to or greater than the first temperature T1. Control method.

5. A control method according to claim 4, The aforementioned battery cell is configured such that lithium metal is deposited on the negative electrode during charging and lithium metal is lost from the negative electrode during discharge. The all-solid-state battery further has an outer casing that houses the battery cells, Inside the outer casing, there is a buffer space provided to contain the molten lithium metal in the event that the lithium metal melts. The first charge amount A is such that the amount of lithium metal deposited on the negative electrode is such that it can be accommodated in the buffer space. Control methods for all-solid-state batteries.

6. A control method according to claim 5, The first charge amount A is the maximum charge amount such that the amount of lithium metal deposited on the negative electrode is such that it can be accommodated in the buffer space. Control methods for all-solid-state batteries.

7. A control method according to claim 1 or 2, The step of discharging the battery cell includes activating a discharge mechanism to discharge the battery cell. Control methods for all-solid-state batteries.

8. The control method according to claim 7, The step of reducing the pressure to the second restraining pressure further includes stopping the discharge operation by the discharge mechanism. Control methods for all-solid-state batteries.

9. A battery cell having a negative electrode containing lithium metal, A restraining mechanism for restraining the battery cell, A discharge mechanism for discharging the aforementioned battery cell, A temperature detection mechanism that detects the temperature of the battery cell and generates temperature data, A control mechanism that controls the operation of the restraint mechanism and the discharge mechanism based on the temperature data, Equipped with, The control mechanism is The temperature of the battery cell is compared with a preset first temperature T1. Based on the comparison result between the temperature of the battery cell and the first temperature T1, if the temperature of the battery cell is equal to or greater than the first temperature T1, the temperature of the battery cell is compared with a preset second temperature T2. Based on the comparison result between the temperature of the battery cell and the second temperature T2, if the temperature of the battery cell is less than the second temperature T2, the battery cell is constrained by the constraining mechanism with a first constraining pressure, while the battery cell is discharged by the discharge mechanism. When the temperature of the battery cell is equal to or higher than the second temperature T2, the restraining pressure by the restraining mechanism is configured to be lowered to a second restraining pressure that is lower than the first restraining pressure. All-solid-state battery.

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