All-solid-state battery and method for controlling all-solid-state battery

Abstract

A method for controlling an all-solid-state battery includes: discharging a battery cell while constraining the battery cell with a first constraining pressure when the temperature of the battery cell is equal to or greater than a preset first temperature (T1) and less than a preset second temperature (T2); and reducing the restraining pressure of the battery cell to a second restraining pressure lower than the first restraining pressure when the temperature of the battery cell is equal to or higher than a second temperature (T2).

Description

Technical Field

[0001] The present invention relates to an all-solid-state battery and a control method for the all-solid-state battery. Background Art

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

[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 obtains temperature information of the battery pack, compares the detected actual temperature with a pre-stored reference temperature, and when the actual temperature is higher than the reference temperature, the control unit outputs a "lower restraint pressure" instruction to a restraint pressure variable device, and adjusts the restraint pressure of the restraint belt based on the instruction.

[0004] On the other hand, Patent Document 2 (JP2002-141112A) discloses a battery device characterized in that when a temperature sensor detects a preset temperature of the external surface or internal atmosphere of a battery storage unit, the battery is discharged to a capacity that is less than a specified ratio of a reference capacity. Summary of the invention

[0005] In addition, the present inventors have conducted research on all-solid-state batteries. All-solid-state batteries are secondary batteries that use solid electrolytes. Among all-solid-state batteries, research has been conducted on all-solid-state batteries having a negative electrode containing metallic lithium. In such all-solid-state batteries, there is a possibility that metallic lithium melts when the temperature reaches an abnormally high temperature. Metallic lithium is highly reactive. Therefore, it is desirable to prevent the leakage of molten metallic lithium even if the temperature reaches an abnormally high temperature.

[0006] There is no description of an all-solid-state battery having a negative electrode containing metallic lithium in Patent Documents 1 and 2. Therefore, an 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 abnormally rises to a high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a block diagram showing a schematic structure of an all-solid-state battery according to the first embodiment.

[0008] Figure 2 This is a flowchart showing a control method of the all-solid-state battery according to the first embodiment.

[0009] Figure 3 This is a schematic block diagram showing an all-solid-state battery according to a second embodiment.

[0010] Figure 4: is a flowchart showing a control method of the all-solid-state battery according to the second embodiment.

[0011] Figure 5 This is a diagram schematically showing the relationship between the control content, charge amount, and temperature of the battery cell of the all-solid-state battery.

[0012] Figure 6 This is a schematic diagram showing an example of a battery unit according to the second embodiment. DETAILED DESCRIPTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] 1: First Implementation

[0015] Figure 1 1 is a block diagram showing a schematic configuration of an all-solid-state battery 1 according to the first embodiment. The all-solid-state battery 1 according to the present embodiment is, for example, a secondary battery mounted on a vehicle or the like.

[0016] like Figure 1 As shown, the all-solid-state battery 1 includes a battery cell 2 , a temperature detection mechanism 3 , a restraint mechanism 4 , a discharge mechanism 5 , and a control mechanism 6 .

[0017] The battery cell 2 is a part that realizes the charging and discharging functions. Although not shown in the figure, the battery cell 2 has a solid electrolyte, a positive electrode and a negative electrode. The negative electrode contains lithium metal. In the battery cell 2, during charging, lithium ions move from the positive electrode to the negative electrode with the help of the solid electrolyte, and lithium metal is precipitated at the negative electrode. On the other hand, during discharge, the lithium metal at the negative electrode moves to the positive electrode side as lithium ions and is absorbed by the positive electrode. That is, during discharge, lithium metal is lost from the negative electrode. In addition, the battery cell 2 included in the all-solid-state battery 1 can be either single or multiple.

[0018] The restraint mechanism 4 is configured to restrain (pressurize) 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 restraint mechanism 4 is used to restrain the battery cell 2 so that each electrode is firmly bonded to the solid electrolyte. In the case where a plurality of battery cells 2 are provided, the restraint mechanism 4 is used to restrain the plurality of battery cells 2.

[0019] The restraint mechanism 4 is also provided for vibration resistance. That is, the restraint mechanism 4 is used to impart vibration resistance to the battery cell 2. For example, when the all-solid-state battery 1 is mounted on a vehicle, the vibration of the vehicle is sometimes applied to the battery cell 2. There is a possibility that the components included in the battery cell 2 are dispersed due to vibration. In the case where a plurality of battery cells 2 are provided, there is a possibility that the plurality of battery cells 2 are dispersed due to vibration. In contrast, by restraining the battery cell 2 with the restraint mechanism 4, dispersion of structural components is prevented even when vibration is applied.

[0020] The restraint mechanism 4 is configured to be able to adjust the restraint pressure.

[0021] The specific structure of the restraint mechanism 4 is not particularly limited. For example, the restraint mechanism 4 can be implemented by a pair of end plates configured to clamp the battery cell 2 in the stacking direction and an actuator configured to pressurize and restrain the battery cell 2 through the pair of end plates.

[0022] The discharge mechanism 5 is configured to discharge the battery cell 2. The discharge mechanism 5 can be realized by a load circuit connected to the battery cell 2, for example.

[0023] 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 directly measure the temperature of the battery cell 2 or to indirectly measure the temperature of the battery cell 2. 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 position slightly separated from the battery cell 2.

[0024] The control mechanism 6 obtains temperature data from the temperature detection mechanism 3, and controls the operation of the all-solid-state battery 1 based on the obtained temperature data. The control mechanism 6 is implemented by a computer such as a microcomputer, for example. That is, the control mechanism 6 includes a storage device such as a memory storing a control program, and a computing device such as a CPU executing the control program. In the control mechanism 6, the function is realized by executing the control program by the computing device. Specifically, the control mechanism 6 is programmed to control the operation of the all-solid-state battery 1 so that even if the battery cell 2 is abnormally heated and becomes high temperature, the molten metal lithium will not leak.

[0025] Figure 2 1 is a flowchart showing a control method of the all-solid-state battery 1 executed by the control mechanism 6. Figure 2 A control method of the all-solid-state battery 1 will be described in detail.

[0026] (Step S10)

[0027] First, the control means 6 detects the temperature of the battery cell 2 . That is, the control means 6 acquires temperature data from the temperature detection means 3 .

[0028] (Step S20)

[0029] When the control mechanism 6 acquires the temperature data, it compares the temperature of the battery cell 2 with the first temperature T1 set in advance. The first temperature T1 is a temperature that serves as a criterion for determining whether the battery cell is in an abnormal temperature rise state. The first temperature T1 is set, for example, within a range of 100° C. to 150° C. The first temperature T1 may be, for example, a temperature that causes the control mechanism 6 to determine that the battery cell is in an abnormal temperature rise state and to notify the user of the abnormal temperature rise state by means of a notification mechanism such as a lamp.

[0030] (Step S30)

[0031] When the temperature of the battery cell 2 is lower than the first temperature T1, it can be said that the battery cell 2 is in a normal state. Therefore, the control mechanism 6 does not perform any special processing. In other words, the all-solid-state battery 1 is operated by normal operation.

[0032] (Step S40)

[0033] On the other hand, when the temperature of the battery cell 2 is higher than the first temperature T1, the control mechanism 6 further compares the temperature of the battery cell with the 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 is melted. The second temperature T2 is set, for example, to a value within the range of 150°C to 210°C, preferably to a value within the range of 160°C to 200°C.

[0034] (Step S50)

[0035] When the temperature of the battery cell 2 is lower than the second temperature T2 in step S40 , the control unit 6 discharges the battery cell 2 by the discharge unit 5 while restraining the battery cell 2 with the first restraining pressure by the restraining unit 4 .

[0036] The first restraint pressure may be of a magnitude sufficient to maintain the vibration resistance of the battery cell 2. The first restraint pressure may be the same as the restraint pressure during normal operation (step S30), but may also be different from the restraint pressure during normal operation as long as the vibration resistance is maintained. In short, since a certain degree of restraint pressure is maintained, the vibration resistance of the battery cell 2 is ensured.

[0037] On the other hand, in this step, the lithium metal present in the negative electrode moves to the positive electrode side and is absorbed by the positive electrode by discharging the battery cell 2. The lithium absorbed by the positive electrode is usually not melted. That is, by discharging, the amount of meltable lithium metal is reduced before the temperature of the battery cell 2 reaches the melting temperature of the lithium metal.

[0038] (Step S60)

[0039] On the other hand, when the temperature of the battery cell 2 is above the second temperature T2 in step S40, the control mechanism 6 reduces the restraint pressure of the restraint mechanism 4 on the battery cell 2 to a second restraint pressure lower than the first restraint pressure. When the temperature of the battery cell 2 is above the second temperature T2, it is considered that the lithium metal is melting. If the battery cell 2 is restrained with a strong force in a state where the lithium metal is melting, the melted lithium metal is likely to leak to the outside of the battery cell 2. In contrast, by reducing the restraint pressure in this step, it is difficult for the lithium metal to leak to the outside even if it is melted.

[0040] The second restraint pressure only needs to be smaller than the restraint pressure (first restraint pressure) in step S50 . Preferably, the second restraint pressure is substantially zero. That is, the control mechanism 6 controls the restraint mechanism 4 to release the restraint pressure of the battery cell 2 .

[0041] In addition, the discharge operation cannot be performed when the lithium metal is in a molten state. Therefore, in step 60, the control means 6 does not perform the discharge operation.

[0042] The first embodiment is described above. In addition, in this embodiment, a method of performing normal operation (step S3) when the temperature of the battery cell 2 is below the first temperature T1 is described. 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 can be limited by the control mechanism 6 when the temperature of the battery cell 2 is close to the first temperature T1 to some extent.

[0043] Hereinafter, representative relationships between the structure and the effects of the present embodiment will be summarized.

[0044] The all-solid-state battery 1 according to the present embodiment includes: a battery cell 2 having a negative electrode having lithium metal; a restraining mechanism 4 restraining the battery cell; a discharging mechanism 5 discharging the battery cell 2; a temperature detecting mechanism 3 detecting the temperature of the battery cell 2 and generating temperature data; and a control mechanism 6 controlling the operation of the restraining mechanism 4 and the discharging mechanism 5 based on the temperature data. When the temperature of the battery cell 2 is higher than a preset first temperature T1 and lower than a preset second temperature T2, the control mechanism 6 restrains the battery cell 2 with a first restraining pressure through the restraining mechanism 4 and discharges the battery cell 2 through the discharging mechanism 5. In addition, when the temperature of the battery cell 2 is higher than the second temperature T2, the control mechanism 6 is configured to reduce the restraining pressure of the restraining mechanism 4 to a second restraining pressure lower than the first restraining pressure.

[0045] In addition, the control method of the all-solid-state battery involved in the present embodiment is a control method of the all-solid-state battery 1, and the all-solid-state battery 1 is configured to have a battery cell 2 and constrain the battery cell 2, and the battery cell 2 has a negative electrode containing lithium metal. The control method includes the following steps: 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 step (steps S50, S60) includes the following steps: when the temperature of the battery cell 2 is above a predetermined first temperature T1 and below a predetermined second temperature T2, the battery cell 2 is constrained with a first constraint pressure while discharging the battery cell 2 (step S50); and when the temperature of the battery cell 2 is above the second temperature T2, the constraint pressure of the battery cell 2 is reduced to a second constraint pressure lower than the first constraint pressure (step S60).

[0046] According to the above-mentioned all-solid-state battery 1 and control method thereof, when the temperature of the battery cell 2 becomes above the first temperature T1, the battery cell 2 is discharged, thereby reducing the amount of lithium metal that may leak when melting in advance. Thus, even if the lithium metal reaches the melting temperature later, the leakage of the lithium metal is prevented.

[0047] When the temperature of the battery cell 2 is higher than the first temperature T1 and lower than the second temperature T2, the restraint state of the battery cell 2 is maintained at the first restraint pressure. Thus, even when the battery cell 2 reaches abnormally high temperature, vibration resistance is maintained until the lithium metal melts.

[0048] On the other hand, when the temperature of the battery cell 2 exceeds the second temperature T2, the confinement pressure of the battery cell 2 decreases to the second confinement pressure. Thus, even if the lithium metal melts, the melted lithium metal is difficult to be squeezed out, thereby preventing leakage to the outside.

[0049] 2: Second Implementation

[0050] Next, the second embodiment will be described. In addition, descriptions of aspects that can adopt the same configuration as the first embodiment will be omitted.

[0051] Figure 3 1 is a schematic block diagram showing an all-solid-state battery 1 according to a second embodiment. In this embodiment, a charge amount detection mechanism 7 is added to the first embodiment.

[0052] The charge amount detection mechanism 7 is configured to detect the charge amount (e.g., SOC) of the battery cell 2. In addition, "detecting the charge amount" also includes detecting the charge amount by "estimating". For example, the charge amount detection mechanism 7 may detect the charge amount by estimating the SOC of the battery cell 2 based on the voltage, etc. The charge amount detection mechanism 7 is configured to generate charge amount data indicating the detected charge amount and notify the control mechanism 6 of the charge amount data.

[0053] The control mechanism 6 controls the operation of the restraint mechanism 4 and the discharge mechanism 5 by referring to the charge amount data obtained from the charge amount detection mechanism 7 in addition to the temperature data obtained from the temperature detection mechanism 3. Next, the control method of the all-solid-state battery 1 implemented by the control mechanism 6 will be described in detail.

[0054] Figure 4 : is a flowchart showing a control method of the all-solid-state battery 1 according to the present embodiment. Figure 5 It is a diagram schematically showing the relationship between the control content of the all-solid-state battery 1, the charge amount, and the temperature of the battery cell 2. In this embodiment, the processing of steps S21 to S23 is added to the first embodiment.

[0055] (Steps S10 to S30)

[0056] Steps S10 to S30 are the same as those in the first embodiment. That is, in step S10, the control mechanism 6 detects the temperature of the battery cell 2 (step S10). Then, the control mechanism 6 compares the temperature of the battery cell 2 with the first temperature T1 (step S20). When the temperature of the battery cell 2 is lower than the first temperature T1, the control mechanism 6 operates the all-solid-state battery 1 through normal operation (step S30).

[0057] (Steps S21 to S22)

[0058] On the other hand, when the temperature of the battery cell 2 is above the first temperature T1, the charge amount of the battery cell 2 is detected. That is, the control mechanism 6 obtains the charge amount data by means of the charge amount detection mechanism 7 (step S21). Then, the control mechanism 6 compares the charge amount of the battery cell 2 with the preset first charge amount A (%) (step S22).

[0059] (Steps S40 to S60)

[0060] The actions when the charge amount of the battery cell 2 is greater than the first charge amount A are the same as steps S40 to S60 in the first embodiment. That is, the control mechanism 6 compares the temperature of the battery cell 2 with the second temperature T2 (step S40). When the temperature of the battery cell 2 is less than the second temperature T2, the control mechanism 6 constrains the battery cell 2 with the first constraining pressure through the constraining mechanism 4, and discharges the battery cell 2 until it is less than the first charge amount A through the discharging mechanism 5 (step S50). On the other hand, when the temperature of the battery cell 2 is greater than the second temperature T2, the control mechanism 6 lowers the battery cell 2 constrained by the constraining mechanism 4 to the second constraining pressure. In addition, the discharging action of the discharging mechanism 5 is not performed (step S60).

[0061] (Step S23)

[0062] On the other hand, when the charge amount of the battery cell 2 is less than the first charge amount A in step S22, the control mechanism 6 controls the restraint mechanism 4 so that the battery cell 2 is restrained with the third restraint pressure. The third restraint pressure is a pressure to maintain the vibration resistance, and is a value 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 the discharge process.

[0063] The above is a control method of the all-solid-state battery 1 according to the second embodiment. According to the present 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. Thus, leakage of the molten lithium metal is prevented in the same manner as in the first embodiment.

[0064] On the other hand, when the charge amount of the battery cell 2 is small (i.e., less than the first charge amount A), even if the temperature of the battery cell 2 is above the first temperature T1, the battery cell 2 is not discharged (step S23). Thus, a certain degree of power is ensured. For example, when the all-solid-state battery 1 is mounted on a vehicle, if a discharge process is performed during abnormal temperature rise and the battery cell 2 completely loses power, it is sometimes impossible to ensure the power required for vehicle retreat, etc. In contrast, according to the present embodiment, since a discharge process is not performed when the charge amount is less than the first charge amount A, a certain degree of power is ensured for vehicle retreat, etc. In addition, when the charge amount of the battery cell 2 is small, the amount of lithium metal that can be melted is small, so even if the temperature of the battery cell 2 reaches the melting temperature of lithium metal later, the possibility of lithium metal leakage is small.

[0065] In addition, in the present embodiment, when the charge amount of the battery cell 2 is less than the first charge amount A, the battery cell 2 is constrained by a constraining pressure (third constraining pressure) that ensures vibration resistance even when the second temperature T2 is exceeded. As described above, it can be said that when the charge amount of the battery cell 2 is less than the first charge amount A, there is less lithium metal that can be melted. Therefore, even if the battery cell 2 is constrained, the possibility of lithium metal leaking to the outside is low. Since the battery cell 2 is constrained by the third constraining pressure under the condition that the possibility of leakage is low, vibration resistance is ensured.

[0066] The first charge amount 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 aspect will be described in detail below.

[0067] Figure 6 1 is a schematic diagram showing an example of a battery cell 2 according to the present embodiment. The battery cell 2 is housed in a film-shaped outer shell 8. A buffer space 9 is provided between the outer shell 8 and the battery cell 2 in the outer shell 8. According to such a structure, even if the lithium metal is slightly melted, the melted lithium metal is contained in the buffer space 9 and does not reach the outside of the outer shell 8.

[0068] Here, as already mentioned, the amount of meltable lithium metal, that is, the amount of lithium metal contained in the negative electrode, changes according to 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 the amount of lithium metal decreases during discharging. 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 an amount that can be accommodated in the buffer space 9. If the first charge amount A is set to such a value, when the battery cell 2 is abnormally heated (exceeding the first temperature T1), the charge amount of the battery cell 2 is reduced so that the amount of lithium metal contained in the negative electrode is within the range that can be accommodated in the buffer space 9. Therefore, even if the lithium metal reaches the melting temperature later, the molten lithium metal can be accommodated in the buffer space 9 and leakage to the outside can be prevented.

[0069] More preferably, the first charge amount A is set to a maximum value among the charge amounts such that the amount of lithium metal deposited at the negative electrode is the amount that 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 as long as the amount of lithium metal in the negative electrode is the amount accommodated in the buffer space 9. In addition, electricity can be used as long as the lithium metal reaches the melting temperature (second temperature T2).

[0070] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate a part of application examples of the present invention and are not intended to limit the technical scope of the present invention to the specific structures of the above embodiments.

Claims

1. A control method for an all-solid-state battery, wherein the all-solid-state battery is configured to include a battery cell and to constrain the battery cell, wherein the battery cell has a negative electrode containing lithium metal, and the control method The following steps are involved: detecting a temperature of the battery cell; as well as controlling the operation of the all-solid-state battery based on the temperature of the battery cell, The controlling step includes the following steps: When the temperature of the battery cell is greater than or equal to a preset first temperature T1 and less than a preset second temperature T2, discharging the battery cell while restraining the battery cell with a first restraining pressure; and When the temperature of the battery cell is equal to or higher than the second temperature T2, the restraint pressure of the battery cell is reduced to a second restraint pressure lower than the first restraint pressure.

2. The control method according to claim 1, in, The following steps are also included: When the temperature of the battery cell exceeds the first temperature T1, it is determined that the battery cell is in an abnormal temperature rise state.

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

4. The control method according to claim 1 or 2, in, The following steps are also included: detecting the charge level of the battery cell, The control step also includes the following steps: when the charge amount of the battery cell is less than a predetermined first charge amount A, even if the temperature of the battery cell is above the first temperature T1, there is no need to discharge the battery cell and the battery cell is constrained with a third constraint pressure greater than the second constraint pressure.

5. The control method according to claim 4, in, The 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 discharging. The all-solid-state battery also has an outer shell, which accommodates the battery cell. A buffer space is provided inside the outer shell, and the buffer space receives the molten lithium metal when the lithium metal is molten. The first charge amount A is a charge amount such that the amount of lithium metal deposited at the negative electrode can be accommodated in the buffer space.

6. The control method according to claim 5, in, The first charge amount A is the maximum value among the charge amounts such that the amount of lithium metal deposited at the negative electrode can be accommodated in the buffer space.

7. An all-solid-state battery having: a battery cell having a negative electrode comprising lithium metal; a restraining mechanism that restrains the battery unit; a discharge mechanism that discharges the battery cell; a temperature detection mechanism for detecting the temperature of the battery cell and generating temperature data; and a control mechanism that controls the actions of the restraining mechanism and the discharging mechanism based on the temperature data, in, The control mechanism is composed of: When the temperature of the battery cell is higher than a preset first temperature T1 and lower than a preset second temperature T2, the battery cell is constrained by the constraining mechanism with a first constraining pressure, and the battery cell is discharged by the discharging mechanism. When the temperature of the battery cell is equal to or higher than the second temperature T2, the restraint pressure of the restraint mechanism is reduced to a second restraint pressure lower than the first restraint pressure.

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