Solid-state battery system and method for recovering solid-state battery module

Abstract

This solid-state battery system (1) comprises: a solid-state battery module (10) obtained by stacking one or more battery cells (11) having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; a surface pressure measurement device (20) that measures the surface pressure distribution of the solid-state battery module (10); and a control unit (100) that controls the charging and discharging of the solid-state battery module (10). If the difference in the surface pressure between a low-surface pressure section having a low surface pressure and a high-surface pressure section having a high surface pressure in the surface pressure distribution of the solid-state battery module (10) is detected to be equal to or greater than a first threshold value when the surface pressure distribution is measured by the surface pressure measurement device (20), the control unit (100) performs discharging at a reference current value or higher.

Description

SOLID-STATE BATTERY SYSTEM AND SOLID-STATE BATTERY MODULE RECOVERY METHOD

[0001] The present invention relates to a solid-state battery system and a method for recovering a solid-state battery module.

[0002] A solid-state battery is a secondary battery made of solid materials, including an electrolyte layer, and includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. In a solid-state battery, charging and discharging are generally performed by the movement of lithium ions between the positive electrode layer and the negative electrode layer.

[0003] Patent Document 1 discloses a solid-state battery having an electrode in which the lithium diffusion coefficient in the outer edge portion of the active material-containing layer is higher than the lithium diffusion coefficient in the center portion excluding the outer edge portion of the active material-containing layer.

[0004] Japanese Patent Application Laid-Open No. 2022-20241

[0005] In the solid-state battery described in Patent Document 1, a layer with a high lithium diffusion coefficient is provided at the outer edge, promoting reaction at the outer edge and reducing in-plane pressure differences. However, if the lithium diffusion coefficient at the center is smaller than that at the outer edge, lithium diffusion at the center slows, leading to reduced performance. Furthermore, the use of materials with different lithium diffusion coefficients at the center and outer edge makes manufacturing difficult. Furthermore, in-plane SOC (State of Charge) differences do not necessarily occur radially from the center toward the lithium diffusion at the periphery. Large in-plane SOC differences can lead to problems such as reduced durability as a battery module and electrode short-circuiting during charging. Therefore, there is a need for a method to easily eliminate in-plane SOC differences in solid-state batteries.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a solid-state battery system and a method for recovering a solid-state battery module that can easily eliminate in-plane SOC differences.

[0007] In order to achieve the above object, the solid state battery system of the present invention includes a solid state battery module formed by stacking one or more battery cells, each having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; a surface pressure measuring device that measures the surface pressure distribution of the solid state battery module; and a control unit that controls charging and discharging of the solid state battery module, wherein when the surface pressure distribution is measured by the surface pressure measuring device, the control unit detects that the difference in surface pressure between a low surface pressure portion and a high surface pressure portion in the surface pressure distribution of the solid state battery module is equal to or greater than a first threshold value, and performs discharging at a reference current value or greater.

[0008] According to the present invention, it is possible to provide a solid-state battery system and a method for recovering a solid-state battery module that can easily eliminate in-plane SOC differences.

[0009] 1 is a block diagram showing an example of a functional configuration of a solid battery system according to an embodiment. FIG. 2 is a cross-sectional view showing a battery cell according to an embodiment. FIG. 3 is a cross-sectional view showing a battery cell according to an embodiment. FIG. 4 is a diagram showing an example of a hardware configuration of a control unit according to an embodiment. FIG. 5 is a cross-sectional view showing a battery cell according to an embodiment. FIG. 6 is a flowchart showing a recovery process according to an embodiment. FIG. 7 is a block diagram showing an example of a functional configuration of a solid battery system according to a modified example. FIG. 8 is a diagram showing the relationship between the restraining pressure and the internal resistance of a battery cell according to a modified example. FIG. 9 is a block diagram showing an example of a functional configuration of a solid battery system according to a modified example. FIG. 10 is a diagram showing the relationship between the SOC and the discharge DRC of a battery cell according to a modified example. FIG. 11 is a cross-sectional view showing a battery cell according to a modified example.

[0010] A solid-state battery system and a method for recovering a solid-state battery module according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent parts are designated by the same reference numerals.

[0011] (Embodiment) A fixed battery system according to an embodiment of the present invention is capable of controlling the recovery of a solid-state battery module. The solid-state battery module is formed by stacking one or more battery cells, each having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. For example, a plurality of modules of the solid-state battery system 1 constitute a vehicle drive battery, and the solid-state battery system 1 is installed in vehicles such as electric vehicles and hybrid vehicles.

[0012] Fig. 1 is a diagram showing the configuration of a solid-state battery system 1 according to this embodiment. As shown in Fig. 1, the solid-state battery system 1 includes a solid-state battery module 10, a surface pressure measuring device 20 that measures the surface pressure distribution of the solid-state battery module 10, a thermometer 30 that measures the temperature of the solid-state battery module 10, an SOC (State Of Charge) meter 40 that measures the SOC, which is the charging rate of the solid-state battery module 10, and a control unit 100 that controls charging and discharging of the solid-state battery module 10. An external power supply 200 is connected to the solid-state battery system 1. The external power supply 200 is another battery or a commercial power supply that can charge and discharge the solid-state battery system 1.

[0013] The solid-state battery module 10 includes one or more battery cells 11. Fig. 2 is a cross-sectional view showing the battery cell 11 according to the present embodiment. As shown in Fig. 2, the battery cell 11 includes a positive electrode layer 12, a negative electrode layer 13, and a solid electrolyte layer 14 disposed between the positive electrode layer 12 and the negative electrode layer 13. The battery cell 11 may be an all-solid-state battery, and the solid electrolyte layer 14 may include a liquid electrolyte, a gel, a polymer electrolyte, or the like in part.

[0014] The positive electrode layer 12 includes a positive electrode active material that releases lithium ions during charging and absorbs lithium ions during discharging. For example, a lithium metal composite oxide can be used as the positive electrode active material. For example, Li(Ni—Mn—Co)O ２ Layered rock salt compounds such as LiMn ２ O ４ spinel-type compounds such as LiFePO ４ Olivine type compounds such as Li ２ FeSiO ４ The positive electrode layer 12 is formed on a conductive positive electrode current collector layer 12A in the form of a plate or foil.

[0015] The anode layer 13 includes an anode active material that absorbs lithium (or deposits lithium) during charging and releases lithium ions during discharging. The anode active material may be, for example, metallic lithium or a lithium alloy containing lithium. Examples of lithium alloys include alloys of lithium and at least one metal selected from silicon (Si), tin (Sn), gold (Au), magnesium (Mg), aluminum (Al), calcium (Ca), zinc (Zn), and bismuth (Bi). The lithium alloy may also be an alloy of lithium and two or more of the above metals, or a compound containing silicon or tin (oxide, nitride, or alloy with other metals). The anode layer 13 is formed on a conductive plate- or foil-shaped anode current collector layer 13A. In this embodiment, the anode layer 13 contains metallic lithium as the anode active material. However, similar effects can be achieved by using a lithium alloy instead of metallic lithium.

[0016] The solid electrolyte layer 14 is disposed between the positive electrode layer 12 and the negative electrode layer 13 and is in contact with the positive electrode layer 12 and the negative electrode layer 13. The solid electrolyte layer 14 includes a sulfide solid electrolyte or an oxide solid electrolyte.

[0017] Input / output terminals are connected to the positive electrode current collector layer 12A and the negative electrode current collector layer 13A of the battery cell 11, respectively. As shown in FIG. 1 , the plurality of battery cells 11 are formed in a flat shape and are sealed in a stacked state with an exterior member. Elastic bodies 15 may be provided between the plurality of battery cells 11. Since the battery cells 11 of the solid-state battery module 10 expand when charged and contract when discharged, providing the elastic bodies 15 can absorb displacement due to charging and discharging. Note that the elastic bodies 15 do not necessarily have to be provided between all of the battery cells 11.

[0018] Cell restraint plates 16A, 16B are installed on the top and bottom surfaces of the stack, which is made by stacking multiple battery cells 11, and the position of the stack is maintained by the cell restraint plates 16A, 16B and fixing posts 17 that connect the cell restraint plates 16A and 16B, and the stack is fixed in place with a restraint pressure applied in the stacking direction.

[0019] The surface pressure measuring device 20 measures the surface pressure distribution of the solid-state battery module 10 and outputs data indicating the surface pressure distribution to the control unit 100. This allows the detection of low surface pressure regions LP and high surface pressure regions HP in the solid-state battery module 10. The surface pressure measuring device 20 is not particularly limited as long as it can measure the surface pressure distribution of the solid-state battery module 10. It may measure the surface pressure distribution using a surface pressure sensor or a strain gauge that measures the deflection of the solid-state battery module 10. Furthermore, if there is a difference in surface pressure between the low surface pressure regions LP and the high surface pressure regions HP, the cell restraint plates 16A and 16B that restrain the cells may not be parallel. Therefore, the surface pressure measuring device 20 may measure the surface pressure distribution using a sensor that measures the distance between the cell restraint plates 16A and 16B of the solid-state battery module 10. Figure 3 is a cross-sectional view of a battery cell 11 according to this embodiment. As shown in Figure 3, the negative electrode layer 13 of the battery cell 11 may have thin and thick portions. One of the causes of this is thought to be that the battery module 10 is positioned at an angle during charging and discharging of the battery module 10. When the negative electrode layer 13 of the battery cell 11 has thin and thick portions, low surface pressure portions LP and high surface pressure portions HP are generated in the battery cell 11, and these are detected as the low surface pressure portions LP and high surface pressure portions HP by the surface pressure measuring device 20. If the difference in surface pressure between the low surface pressure portions LP and the high surface pressure portions HP is large, problems such as a decrease in durability of the battery module 10 and short-circuiting of the electrodes during charging may occur.

[0020] The thermometer 30 measures the temperature of a specific battery cell 11 and outputs data indicating the measured temperature to the control unit 100 as the temperature of the solid-state battery module 10. The thermometer 30 may be provided in multiple battery cells 11.

[0021] The SOC meter 40 measures the SOC, which is the charging rate of the solid-state battery module 10, and outputs data indicating the measured SOC to the control unit 100. The SOC meter 40 is connected to the input / output terminals of the solid-state battery module 10, and includes a measuring device that measures the charging rate of the solid-state battery module 10. The SOC meter 40 may be configured to be built into the control unit 100.

[0022] The control unit 100 controls the charging and discharging of the solid-state battery module 10. When the control unit 100 detects that the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP in the surface pressure distribution of the solid-state battery module 10 measured by the surface pressure measuring device 20 is equal to or greater than a first threshold, the control unit 100 performs discharging at a reference current value or greater, thereby eliminating the in-plane pressure difference caused by the in-plane SOC difference. FIG. 4 is a diagram showing an example of the hardware configuration of the control unit 100. In the example of FIG. 4, the control unit 100 includes a processor 1011, a storage unit 1012, and a communication interface (referred to as communication I / F in the figure) 1013.

[0023] The processor 1011 includes, for example, a CPU (Central Processing Unit) and its peripheral circuits, and executes various types of arithmetic processing. The processor 1011 executes control programs stored in the storage unit 1012. The processor 1011 may include a volatile semiconductor memory such as a RAM (Random Access Memory) that functions as a working memory for the CPU. The processor 1011 may also include an arithmetic circuit such as a logical arithmetic unit or a numerical arithmetic unit.

[0024] The storage unit 1012 includes a non-volatile semiconductor memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory), a flash memory, etc. The storage unit 1012 stores the control program executed by the processor 1011 and various data used in the arithmetic processing of the processor 1011.

[0025] The communication interface 1013 is an interface for communicating with the surface pressure measuring device 20, the thermometer 30, and the SOC measuring device 40. The communication interface 1013 acquires sensor signals from the surface pressure measuring device 20, the thermometer 30, and the SOC measuring device 40 and passes them to the processor 1011, and also outputs a control signal for the external power supply 200 generated by the processor 1011.

[0026] The processor 1011 executes a control program stored in the storage unit 1012, thereby functioning as an abnormality detection unit 101, a charge / discharge control unit 102, and a determination unit 103, as shown in Fig. 1. Note that although the control unit 100 in Fig. 1 shows only the functional units according to this embodiment, the control unit 100 may also have other control or determination functions.

[0027] The abnormality detection unit 101 detects an abnormality in the solid-state battery module 10 based on data indicating the surface pressure distribution of the solid-state battery module 10. Specifically, the abnormality detection unit 101 acquires data indicating the surface pressure distribution of the solid-state battery module 10 measured by the surface pressure measurement device 20 and determines whether an abnormality exists based on whether the difference in surface pressure between the low surface pressure portion LP, which has low surface pressure, and the high surface pressure portion HP, which has high surface pressure, in the solid-state battery module 10 shown in FIG. 3 is equal to or greater than a first threshold value. The low surface pressure portion LP and the high surface pressure portion HP may be identified by quantifying the surface pressure distribution of the entire surface and using a standard deviation σ or the like. For example, a surface pressure portion equal to or less than the average surface pressure minus σ may be defined as the low surface pressure portion LP, and a surface pressure portion equal to or greater than the average surface pressure plus σ may be defined as the high surface pressure portion HP. Furthermore, if the standard deviation σ of the surface pressure distribution is equal to or greater than a certain value, it may be determined that the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP is equal to or greater than a first threshold value.

[0028] The charge / discharge control unit 102 controls the charge / discharge of the solid-state battery module 10, and when an abnormality is detected by the abnormality detection unit 101, calculates a reference current value and a maximum reference current value for recovering from the abnormality of the solid-state battery module 10. Specifically, the charge / discharge control unit 102 acquires data indicating the temperature of the solid-state battery module 10 measured by the thermometer 30 and data indicating the SOC of the solid-state battery module 10 measured by the SOC measurement meter 40, and calculates the temperature T, the SOC, and the surface pressure σ of the low surface pressure portion LP of the solid-state battery module 10. Ｌ The charge / discharge control unit 102 also calculates a maximum reference current value at which the interface between the metallic lithium at the high surface pressure portion HP in the negative electrode layer 13 of the battery cell 11 and the solid electrolyte layer 14 does not peel off. The maximum reference current value at which the interface at the high surface pressure portion HP peels off is determined by the temperature T of the solid battery module 10, the SOC, and the surface pressure σ of the high surface pressure portion HP. ＨAfter calculating the reference current value and the maximum reference current value as described above, the charge / discharge control unit 102 discharges a current from the solid-state battery module 10 at a value equal to or greater than the reference current value and equal to or less than the maximum reference current value. Furthermore, when the solid-state battery module 10 recovers, the charge / discharge control unit 102 charges the solid-state battery module 10.

[0029] The determination unit 103 acquires data indicating the surface pressure distribution of the solid-state battery module 10 measured by the surface pressure measuring device 20, and determines whether or not the solid-state battery module 10 has recovered based on the data indicating the surface pressure distribution of the solid-state battery module 10. Specifically, the determination is made based on whether or not the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP is equal to or less than a preset normal value.

[0030] Below, we will explain the principle of recovering the solid-state battery module 10 by reducing the difference in surface pressure between the low surface pressure portion LP, which has low surface pressure, and the high surface pressure portion HP, which has high surface pressure, generated in the solid-state battery module 10 and the battery cell 11.

[0031] As shown in Figure 3, an SOC difference may occur within the surface, resulting in areas with thin and thick portions in the negative electrode layer 13 of the battery cell 11. This causes a difference in surface pressure between the low surface pressure portion LP, which has low surface pressure, and the high surface pressure portion HP, which has high surface pressure, in the battery cell 11. The low surface pressure portion LP is a portion with a relatively low SOC, and the high surface pressure portion HP is a portion with a relatively high SOC. If the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP is large, problems such as a decrease in durability of the battery module 10 and short-circuiting of the electrodes during charging may occur. For this reason, it is necessary to reduce the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP to restore the solid-state battery module 10.

[0032] The recovery of the solid-state battery module 10 is achieved by discharging at a reference current value or higher at which the interface between the metallic lithium in the low contact pressure portion LP in the negative electrode layer 13 of the battery cell 11 and the solid electrolyte layer 14 separates. The reference current value at which the interface at the low contact pressure portion LP separates is determined by the creep deformation rate of the metallic lithium. In a negative electrode using metallic lithium, the metallic lithium dissolves during discharge, which tends to deteriorate contact at the interface. The creep deformation of the metallic lithium maintains contact at the interface, but the lower the contact pressure, temperature, and SOC, the smaller the amount of creep deformation, making contact more likely to deteriorate. Specifically, the reference current value is determined by the temperature T and SOC of the solid-state battery module 10, the contact pressure σ of the low contact pressure portion LP, and the Ｌ and is set based on the following equation (1): Ｌ = Aσ Ｌ exp(-B / T) x SOC (1) where j Ｌ : Current density, σ Ｌ : surface pressure of the low surface pressure portion LP, temperature: T, SOC: state of charge, A and B: constants obtained by experiment or the like for each solid-state battery module 10. Temperature T is preferably the temperature of the low surface pressure portion LP. SOC is preferably the state of charge of the low surface pressure portion LP. Discharging at a reference current value or higher causes separation between the metallic lithium and the solid electrolyte layer 14 at the low surface pressure portion LP. Creep deformation is less likely to occur in the low surface pressure portion LP, and flowing a current greater than the reference current value concentrates the discharge current at the high surface pressure portion HP, where creep deformation is more likely to occur. Figure 5 is a cross-sectional view showing a battery cell 11 after discharge according to this embodiment. By actively releasing metallic lithium from the high surface pressure portion HP, the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP is reduced, as shown in Figure 5, and the solid-state battery module 10 is restored.

[0033] If discharge is performed at a current value at which the interface between the metallic lithium at the high surface pressure portion HP in the negative electrode layer 13 of the battery cell 11 and the solid electrolyte layer 14 peels off, the interface at the high surface pressure portion HP will peel off, and the contact between the metallic lithium and the solid electrolyte layer 14 at the high surface pressure portion HP will also deteriorate, potentially making discharge impossible. For this reason, it is preferable to perform discharge at a current value below which the interface between the metallic lithium at the high surface pressure portion HP in the negative electrode layer 13 of the battery cell 11 and the solid electrolyte layer 14 will not peel off. The maximum reference current value at which the interface at the high surface pressure portion HP peels off is determined by the creep deformation rate of the metallic lithium. For example, the maximum reference current value is determined by the temperature T of the solid battery module 10, the SOC, and the surface pressure σ of the high surface pressure portion HP. Ｈ and is set based on the following equation (2): Ｈ = Aσ Ｈ exp(-B / T) x SOC (2) where j Ｈ : Current density, σ Ｈ : surface pressure of the high surface pressure portion HP, temperature: T, SOC: state of charge, A and B: constants obtained by experiments or the like for each solid-state battery module 10. Note that the temperature T is preferably the temperature of the high surface pressure portion HP. Also, the SOC is preferably the state of charge of the high surface pressure portion HP.

[0034] As described above, when the discharge current is greater than or equal to the reference current value and less than or equal to the maximum reference current value, creep deformation is likely to occur, and the discharge current is concentrated in the high pressure area HP where the SOC is relatively high, causing metallic lithium to be released from the high pressure area HP. As a result, as shown in Figure 5, the thickness of the negative electrode layer 13 in the high pressure area HP is reduced, eliminating the in-plane SOC difference, and the solid-state battery module 10 is restored.

[0035] The procedure of the method for recovering the solid-state battery module 10 by the solid-state battery system 1 configured as above will be described in detail with reference to the flowchart shown in Fig. 6. Fig. 6 is a flowchart of the recovery process executed by the processor 1011 of the control unit 100. The recovery process is executed at regular intervals while the solid-state battery system 1 is being charged in a state where it is connected to the external power source 200. Note that the recovery process may be executed at any timing to determine an abnormality in the solid-state battery module 10 and recover the solid-state battery module 10.

[0036] First, the abnormality detection unit 101 of the control unit 100 acquires data indicating the surface pressure distribution of the solid-state battery module 10 measured by the surface pressure measurement device 20 (step S101), and stores the data indicating the surface pressure distribution in the memory unit 1012.

[0037] The abnormality detection unit 101 detects an abnormality in the solid-state battery module 10 based on data indicating the surface pressure distribution of the solid-state battery module 10 (step S102). Specifically, the abnormality detection unit 101 determines whether an abnormality exists based on whether a difference in surface pressure between a low surface pressure portion LP having a low surface pressure and a high surface pressure portion HP having a high surface pressure in the solid-state battery module 10 shown in FIG. 3 is equal to or greater than a first threshold value.

[0038] If no abnormality is detected in the solid-state battery module 10 (step S102; No), the recovery process ends.

[0039] On the other hand, if an abnormality is detected in the solid-state battery module 10 (step S102; Yes), the charge / discharge control unit 102 acquires data indicating the temperature of the solid-state battery module 10 measured by the thermometer 30 (step S103).

[0040] Next, the charge / discharge control unit 102 acquires data indicating the SOC of the solid-state battery module 10 measured by the SOC meter 40 (step S104). The order of steps S103 and S104 is not limited, and step S103 may be performed after step S104.

[0041] Next, the charge / discharge control unit 102 calculates a reference current value (step S105). The reference current value is a current value at which the interface between the metallic lithium of the low surface pressure portion LP of the negative electrode layer 13 of the battery cell 11 and the solid electrolyte layer 14 separates. Specifically, the reference current value is calculated based on the temperature T of the solid battery module 10, the SOC, and the surface pressure σ of the low surface pressure portion LP. Ｌ and is calculated based on the above-mentioned formula (1).

[0042] Next, the charge / discharge control unit 102 calculates the maximum reference current value (step S106). As described above, it is preferable to discharge at a current value equal to or lower than the current value at which the interface between the metallic lithium at the high surface pressure portion HP of the negative electrode layer 13 of the battery cell 11 and the solid electrolyte layer 14 does not peel off. The maximum reference current value at which the interface at the high surface pressure portion HP peels off is determined by the temperature T of the solid battery module 10, the SOC, and the surface pressure σ of the high surface pressure portion HP. Ｈ and is calculated based on the above-mentioned formula (2). Ｈ is obtained based on the data indicating the surface pressure distribution of the solid-state battery module 10 acquired in step S101. The order of steps S105 and S106 is not limited, and step S105 may be performed after step S106.

[0043] Next, the charge / discharge control unit 102 discharges the solid-state battery module 10 at a current value equal to or greater than the reference current value and equal to or less than the maximum reference current value (step S107). For example, the charge / discharge control unit 102 may discharge at a current value equal to or greater than the reference current value and equal to the average value of the maximum reference current value, or may discharge at a current value close to the maximum reference current value in consideration of the recovery speed. An appropriate value within this range may also be determined through experiments, etc. The discharged power is supplied to the external power supply 200. By discharging at a current value equal to or greater than the reference current value and equal to or less than the maximum reference current value, the time required for recovery can be shortened, and the recovery of the solid-state battery module 10 can be efficiently performed.

[0044] Next, the determination unit 103 acquires data indicating the surface pressure distribution of the solid-state battery module 10 measured by the surface pressure measurement device 20 (step S108), and stores the acquired data indicating the surface pressure distribution in the storage unit 1012.

[0045] The determination unit 103 determines whether the solid-state battery module 10 has recovered based on the data indicating the surface pressure distribution of the solid-state battery module 10 (step S109). Specifically, the determination is made based on whether the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP is equal to or less than a preset normal value.

[0046] If it is determined that the solid-state battery module 10 has not recovered (step S109; No), steps S107 to S109 are repeated until the solid-state battery module 10 recovers.

[0047] 5, when the metallic lithium is released from the high surface pressure portion HP, the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP of the solid-state battery module 10 becomes equal to or less than a preset normal value, the difference in SOC within the surface is eliminated, and the solid-state battery module 10 recovers (step S109; Yes), the charge / discharge control unit 102 starts charging the solid-state battery module 10 (step S110). Note that if a recovery process was performed during charging, charging is resumed. Thereafter, the recovery process is terminated.

[0048] As described above, in the solid-state battery system and the method for recovering a solid-state battery module according to this embodiment, when the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP in the solid-state battery module 10 is equal to or greater than a first threshold, discharging at a current value equal to or greater than a reference current value can easily eliminate the in-plane SOC difference in the solid-state battery module 10, thereby recovering the solid-state battery module 10. Furthermore, discharging is performed at a current value equal to or less than a maximum reference current value to prevent separation of the interface between the metallic lithium in the high surface pressure portion HP in the negative electrode layer 13 of the battery cell 11 and the solid electrolyte layer 14. Furthermore, charging after the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP falls below a predetermined normal value can reduce the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP. Therefore, discharging at a current value equal to or greater than the reference current value and equal to or less than the maximum reference current value can shorten the time required for recovery of the solid-state battery module 10, thereby efficiently recovering the solid-state battery module 10.

[0049] (Modifications) The above-described embodiment can be modified in various ways, and the above-described embodiment and each modification can be combined in any way. In the above-described embodiment, the reference current value is determined based on the temperature T of the solid-state battery module 10, the SOC, the surface pressure σ of the low surface pressure portion LP, and the like. Ｌ The example in which the reference current value is set based on the above-mentioned formula (1) using the above formula has been described. The reference current value may be set in advance for each solid state battery module 10. In this case, the reference current value may be obtained experimentally. In addition, the maximum reference current value is determined based on the temperature T of the solid state battery module 10, the SOC, the surface pressure σ of the surface pressure portion HP, and the like. ＨThe example in which the maximum reference current value is set based on the above-mentioned formula (2) using the formula (1) has been described. The maximum reference current value may be set in advance for each solid state battery module 10. In this case, the maximum reference current value may be obtained experimentally.

[0050] 7 is a diagram showing a solid-state battery system 2 according to a modified example. Similar to the above embodiment, the solid-state battery system 2 according to this modified example is an all-solid-state battery module having a configuration in which a confining pressure is applied to a stack of one or more battery cells 11, each having a positive electrode layer 12, a negative electrode layer 13, and a solid electrolyte layer 14. However, it differs from the above embodiment in that it has a function of making it possible to change the average value of the confining pressure by controlling the load applied to the stack.

[0051] 7 , the solid-state battery system 2 according to this modification includes a solid-state battery module 60, a surface pressure measuring device 20, a thermometer 30, an SOC measuring device 40, and a control unit 100, as well as a surface pressure control device 90 that controls the load applied to the stack of solid-state battery modules 60. In addition to the functions of the above embodiment, the control unit 100 also includes a pressure control unit 104 that controls the average value of the binding pressure applied to the battery cells 11 by controlling the surface pressure control device 90. The hardware configuration of the control unit 100 and the functions of the abnormality detection unit 101, charge / discharge control unit 102, and determination unit 103 are the same as those of the above embodiment.

[0052] The battery module 60 is an active module in which cell restraint plates 16A to 16C, a pressure plate 18, and an elastic body 19 provided above and below the stacked battery cells 11 apply a load to the battery cells 11. The pressure plate 18 applies a load in the stacking direction of the battery cells 11 included in the solid-state battery module 60 based on a control signal transmitted from a surface pressure control device 90.

[0053] The pressure plates 18 are provided on top of the stack of battery cells 11. The pressure plates 18 are connected to an actuator (not shown) and can move up and down using power from the actuator. The actuator may move the pressure plates 18 using a servo motor, or may move the pressure plates 18 using a fluid including liquid or gas. Elastic bodies 19 are provided between the multiple pressure plates 18 and are members that transmit the load received from the pressure plates 18 to the stack of battery cells 11.

[0054] When applying confinement pressure to the battery cells 11, the position of the upper pressure plate 18 of the pair of pressure plates 18 moves down along the fixed column 17 so that the upper pressure plate 18 moves closer to the multiple battery cells 11. As the upper pressure plate 18 moves, the load from the pressure plate 18 is transmitted to the stack of multiple battery cells 11 via the elastic body 19 and the lower pressure plate 18. When reducing the confinement pressure of the battery cells 11, the position of the upper pressure plate 18 moves up along the fixed column 17 so that the upper pressure plate 18 moves away from the multiple battery cells 11.

[0055] In this way, the solid-state battery module 60 can adjust the load applied to the battery cells 11 by the control signal of the surface pressure control device 90 based on the control command output by the control unit 100. Note that the mechanism for adjusting the applied load is not limited to the mechanism shown in Fig. 7 and may be another mechanism.

[0056] The solid-state battery module 60 further includes a load sensor 50 below the stack, and by monitoring the output of the load sensor 50, the average value of the restraint pressure (surface pressure) applied to the battery cells 11 can be measured.

[0057] FIG. 8 illustrates the relationship between the confining pressure (surface pressure) and the internal resistance of the solid-state battery module 60. As shown in FIG. 8, the internal resistance of the solid-state battery module 60 is constant when the confining pressure is within the operating surface pressure range. The operating surface pressure range is the range of confining pressure applied during charging and discharging of the solid-state battery module 60. When the confining pressure is below the lower limit of the operating surface pressure range, the contact between the metallic lithium of the anode layer 13 and the solid electrolyte layer 14 weakens, resulting in increased internal resistance. Furthermore, the lower the surface pressure, the greater the degree of peeling of the metallic lithium of the anode layer 13 during discharge. This facilitates current distribution between the low surface pressure portion LP and the high surface pressure portion HP, eliminating the distribution with a small discharge amount. This allows the metallic lithium of the high surface pressure portion HP to be actively discharged more efficiently, reducing the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP, thereby enabling the solid-state battery module 60 to recover.

[0058] Specifically, when the charge / discharge control unit 102 discharges power from the solid-state battery module 60 at a current value equal to or greater than the reference current value and equal to or less than the maximum reference current value, the pressure control unit 104 controls the surface pressure control device 90 to set the constriction pressure applied to the battery cells 11 to the lower limit of the operating surface pressure range. In this case, the charge / discharge control unit 102 may set the discharge amount discharged from the solid-state battery module 60 to be less than when the constriction pressure is not controlled, between the reference current value and the maximum reference current value. In this way, the solid-state battery module 60 is restored with a small discharge amount.

[0059] 9 is a diagram showing a solid-state battery system 3 according to a modified example. Similar to the above embodiment, the solid-state battery system 3 according to this modified example is an all-solid-state battery module having a configuration in which one or more battery cells 11 are stacked, each having a positive electrode layer 12, a negative electrode layer 13, and a solid electrolyte layer 14 disposed between the positive electrode layer 12 and the negative electrode layer 13. However, it differs from the above embodiment in that it has a function of adjusting the temperature of the solid-state battery module 70.

[0060] 9 , the solid-state battery system 3 according to this modification includes a solid-state battery module 70, a surface pressure measuring device 20, a thermometer 30, an SOC measuring device 40, and a control unit 100, as well as a temperature adjusting device 80 that adjusts the temperature of the solid-state battery module 70. In addition to the functions of the above embodiment, the control unit 100 further includes a temperature control unit 105 that adjusts the temperature of the solid-state battery module 70 by controlling the temperature control device 80. The hardware configuration of the control unit 100 and the functions of the abnormality detection unit 101, the charge / discharge control unit 102, and the determination unit 103 are the same as those of the above embodiment.

[0061] The temperature control device 80 is controlled by the temperature control unit 105 and has a function of cooling the solid-state battery module 70 by water cooling or air cooling. The temperature control device 80 may also have a function of heating the solid-state battery module 70 by a heater or the like.

[0062] Since the surface pressure sensitivity is greater at low temperatures, the current distribution ratio between the low surface pressure portion LP and the high surface pressure portion HP is greater at low temperatures. On the other hand, since the internal resistance of the entire solid-state battery module 70 is greater at low temperatures, the current that can be applied is smaller. It is preferable to balance the increase in the current distribution ratio between the low surface pressure portion LP and the high surface pressure portion HP due to the low temperature with the decrease in the current that can be applied, calculate the temperature at which the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP of the solid-state battery module 70 can be reduced to a predetermined normal value or less in a short period of time, and recover the solid-state battery module 70 at that temperature.

[0063] The temperature control unit 105 calculates, based on the surface pressure and SOC, a temperature at which the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP of the solid-state battery module 70 can be reduced to a predetermined normal value or less in a short time, and controls the temperature control device 80 to set the solid-state battery module 70 to the calculated temperature. Once the solid-state battery module 70 is set to the calculated temperature, the charge / discharge control unit 102 discharges power from the solid-state battery module 70 at a current value equal to or greater than a reference current value and equal to or less than a maximum reference current value. This allows the solid-state battery module 70 to recover in a shorter time. Note that the solid-state battery system 3 may further include the surface pressure control device 90 included in the solid-state battery system 2, and the control unit 100 may include a pressure control unit 104.

[0064] In the above-described embodiment, the abnormality detection unit 101 determines an abnormality when the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP is equal to or greater than a first threshold. The abnormality detection unit 101 may also detect whether the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP in the surface pressure distribution of the solid-state battery module 10, 60, 70 measured by the surface pressure measurement device 20 is equal to or greater than a second threshold that is smaller than the first threshold. When the abnormality detection unit 101 determines that the difference in surface pressure between the surface pressure portion LP and the high surface pressure portion HP is equal to or greater than the second threshold, the charge / discharge control unit 102 performs discharge in an SOC range lower than a predetermined reference SOC. A lower SOC range provides higher surface pressure sensitivity during discharge at a higher rate, enabling more efficient recovery. Even in the case of a caution-level abnormality that does not require urgency, discharge operations can be performed in a lower SOC range with higher surface pressure sensitivity to recover the solid-state battery module 10, 60, 70.

[0065] FIG. 10 is a diagram showing the relationship between the SOC and the discharge DCR (Direct Current Resistance) of the solid-state battery modules 10, 60, and 70. As shown in FIG. 10, the discharge DCR is a downwardly convex curve, with large values ​​at SOCs of 0% and 100%. When discharging at an SOC above the minimum (local minimum) value of the discharge DCR, the discharge at the high surface pressure portion HP is small, making it difficult to reduce the difference in surface pressure between the low surface pressure portion LP and the high surface pressure portion HP. Therefore, it is preferable that the reference SOC be equal to or lower than the SOC at which the discharge DCR is minimum. This allows the solid-state battery modules 10, 60, and 70 to easily recover even in the case of an abnormality that does not require urgent attention.

[0066] FIG. 11 is a cross-sectional view showing a battery cell 11 according to a modified example. As shown in FIG. 11 , the battery cell 11 may further include an anode intermediate layer 13B between the anode layer 13 and the solid electrolyte layer 14. The anode intermediate layer 13B is a layer provided in a precipitation-type all-solid-state battery for purposes such as protecting the solid electrolyte layer 14. A precipitation-type all-solid-state battery is a secondary battery configured such that metallic lithium precipitates between the solid electrolyte layer 14 and the anode current collector layer 13A during charging. In a precipitation-type all-solid-state battery, the precipitated metallic lithium functions as the anode active material. However, direct contact of the precipitated metallic lithium with the solid electrolyte layer 14 may damage the solid electrolyte layer 14. Therefore, the anode intermediate layer 13B is provided between the solid electrolyte layer 14 and the anode current collector layer 13A. The presence of the anode intermediate layer 13B protects the solid electrolyte layer 14 from metallic lithium. The anode intermediate layer 13B used for this purpose is also included in the anode layer 13 of this embodiment. The negative electrode intermediate layer 13B can be realized by a layer containing, for example, metal particles such as silver particles, carbon particles, and a binder resin. Even when the negative electrode layer 13 includes the negative electrode intermediate layer 13B, the solid state battery module 10, 60, 70 can be recovered by discharging at a current value equal to or greater than the reference current value and equal to or less than the maximum reference current value, as in the above-described embodiment.

[0067] In addition, in the above embodiment and variant examples, examples have been described in which the processor 1011 executes a control program to realize each function, but the control unit 100 may also be configured using dedicated hardware that realizes each function.

[0068] Furthermore, the control program for executing the operations of the above-described embodiments and modifications may be stored and distributed on a computer-readable recording medium such as a CD-ROM (Compact Disc Read-Only Memory), a DVD (Digital Versatile Disc), an MO (Magneto Optical Disc), or a memory card, and the program may be installed on a computer to configure the inspection devices 10 and 11 that can realize each function. When each function is realized by sharing the work between an OS (Operating System) and an application, or by cooperation between an OS and an application, only the parts other than the OS may be stored on the recording medium.

[0069] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. In other words, the scope of the present invention is defined by the claims, not by the embodiments. Various modifications made within the scope of the claims and the meaning of the disclosure equivalent thereto are considered to be within the scope of the present invention.

[0070] 1, 2, 3 Solid-state battery system, 10, 60, 70 Solid-state battery module, 11 Battery cell, 12 Positive electrode layer, 12A Positive electrode current collector layer, 13 Negative electrode layer, 13A Negative electrode current collector layer, 13B Negative electrode intermediate layer, 14 Solid electrolyte layer, 15, 19 Elastic body, 16A to 16C Cell restraint plate, 17 Fixed column, 18 Pressure plate, 20 Surface pressure measurement device, 30 Thermometer, 40 SOC meter, 50 Load sensor, 80 Temperature adjustment device, 90 Surface pressure control device, 100 Control unit, 101 Abnormality detection unit, 102 Charge / discharge control unit, 103 Determination unit, 104 Pressure control unit, 105 Temperature control unit, 1011 Processor, 1012 Memory unit, 1013 Communication interface, 200 External power supply, LP Low surface pressure unit, HP High surface pressure unit.

Claims

1. A solid-state battery system comprising: a solid-state battery module formed by stacking one or more battery cells, each having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; a surface pressure measuring device that measures the surface pressure distribution of the solid-state battery module; and a control unit that controls charging and discharging of the solid-state battery module, wherein, when the surface pressure distribution is measured by the surface pressure measuring device, the control unit performs discharging at a reference current value or more when it detects that the difference in surface pressure between a low surface pressure portion and a high surface pressure portion in the surface pressure distribution of the solid-state battery module is equal to or greater than a first threshold value.

2. The solid-state battery system according to claim 1, wherein the reference current value is a value set in advance for each of the solid-state battery modules.

3. The solid-state battery system according to claim 1, further comprising: a thermometer that measures the temperature of the solid-state battery module; and an SOC meter that measures the SOC of the solid-state battery module, wherein the control unit calculates a reference current value based on the temperature measured by the thermometer, the SOC measured by the SOC meter, and the surface pressure measured by the surface pressure measuring device.

4. The solid state battery system according to claim 3, further comprising a temperature control device that controls the temperature of the solid state battery module, wherein the control unit controls the temperature control device to discharge at a temperature calculated based on the surface pressure and the SOC.

5. The solid-state battery system according to any one of claims 1 to 4, further comprising a surface pressure control device that controls a load applied to the solid-state battery module, wherein the control unit controls the surface pressure control device to set the surface pressure to a lower limit value of an operating surface pressure range.

6. The solid-state battery system according to any one of claims 1 to 5, wherein when the control unit detects that the difference in surface pressure between the low surface pressure portion and the high surface pressure portion in the surface pressure distribution of the solid-state battery module measured by the surface pressure measuring device is equal to or greater than a second threshold value that is smaller than the first threshold value, the control unit performs discharge in an SOC range that is lower than a predetermined reference SOC.

7. The solid-state battery system according to claim 6, wherein the reference SOC is equal to or lower than the SOC at which the discharge DCR is at a minimum value in an SOC-discharge DCR curve within an SOC range of 0% to 100% in the solid-state battery module.

8. The solid-state battery system according to claim 3, wherein the control unit calculates a maximum reference current at which discharge is possible based on the temperature measured by the thermometer, the SOC measured by the SOC meter, and the surface pressure measured by the surface pressure measuring device, and performs discharge at a current value equal to or less than the maximum reference current value.

9. The solid-state battery system according to any one of claims 1 to 7, wherein when the control unit detects that the difference in surface pressure between the low surface pressure portion and the high surface pressure portion in the surface pressure distribution of the solid-state battery module measured by the surface pressure measuring device is equal to or greater than the first threshold value, the control unit carries out discharge at or below a maximum reference current value preset for each solid-state battery module.

10. The solid-state battery system according to any one of claims 1 to 9, wherein the battery cell has an intermediate negative electrode layer disposed between the negative electrode layer and the solid electrolyte layer.

11. A solid-state battery system as claimed in any one of claims 1 to 10, wherein the control unit starts charging when the difference in surface pressure between the low surface pressure portion and the high surface pressure portion of the solid-state battery module, measured again by the surface pressure measuring device, falls below a preset normal value during discharging at a current value equal to or greater than the reference current value.

12. A method for recovering a solid-state battery module, comprising: a stack of one or more battery cells, each having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; and a surface pressure measuring device for measuring a surface pressure distribution of the solid-state battery module, wherein, when the surface pressure distribution is measured by the surface pressure measuring device, if it is detected that the difference in surface pressure between a low surface pressure portion and a high surface pressure portion in the surface pressure distribution of the solid-state battery module is equal to or greater than a first threshold value, discharging is performed at a current value equal to or greater than a reference current value.

Images