Method for controlling solid-state battery system, and solid-state battery system

Abstract

This control method is a method for controlling a solid-state battery system (1) comprising: a solid-state battery module (10) including a battery cell laminate (20) in which one or more battery cells 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 are laminated; a positive electrode tab (61) connected to the positive electrode layer and disposed on a first side of the battery cell laminate (20) in a top view viewed in the direction in which the battery cell laminate (20) is laminated; a negative electrode tab (62) connected to the negative electrode layer and disposed on a second side facing the first side in the top view; and a pressurizing device (40) that performs pressurization in the direction in which the battery cell laminate (20) is laminated. During charging or discharging, the pressurizing device (40) is used to pressurize the positive electrode tab (61) side of the battery cell laminate (20) by using a smaller surface pressure than on the negative electrode tab (62) side.

Description

Control Method and Solid-State Battery System of a Solid-State Battery System

[0001] The present invention relates to a control method and a solid-state battery system of a solid-state battery system.

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

[0003] Patent Document 1 discloses an all-solid-state battery having a first current collector, a first active material layer, a solid electrolyte layer, a second active material layer and a second current collector, a first current collecting tab connected to the first current collector, and a second current collecting tab connected to the second current collector.

[0004] Japanese Patent Application Laid-Open No. 2024-011688

[0005] In the all-solid-state battery described in Patent Document 1, when the areas of the first current collector and the second current collector increase, the electrical resistance values of the first current collector and the second current collector cannot be ignored. When lithium metal is used in the second active material layer and the areas of the first current collector and the second current collector are enlarged, the amount of lithium metal precipitation may vary in-plane depending on the distance from the first current collecting tab and the second current collecting tab. When the amount of lithium metal precipitation varies in-plane, an in-plane SOC (State Of Charge) difference occurs. When the in-plane SOC difference is large, problems such as a decrease in durability as a battery module and a short circuit of the electrodes during charge and discharge may occur. Therefore, it is required to prevent the occurrence of an in-plane SOC difference in the solid-state battery.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a control method and a solid-state battery system of a solid-state battery system that can prevent the occurrence of an in-plane SOC difference.

[0007] To achieve the above objective, the control method for a solid-state battery system according to the present invention includes a solid-state battery module including a battery cell stack in which one or more battery cells are stacked, 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 positive electrode tab connected to the positive electrode layer and located on a first edge of the battery cell stack in a top view in the orientation in which the battery cell stacks are stacked; a negative electrode tab connected to the negative electrode layer and located on a second edge opposite to the first edge in a top view; and a pressurizing device that applies pressure in the direction in which the battery cell stacks are stacked, wherein during charging or discharging, the pressurizing device is used to apply pressure to the side of the battery cell stack with the positive electrode tab with a smaller surface pressure than the side of the negative electrode tab.

[0008] According to the present invention, it is possible to provide a control method for a solid-state battery system and a solid-state battery system that can prevent the occurrence of in-plane SOC differences.

[0009] This is a block diagram showing an example of the functional configuration of a solid-state battery system according to an embodiment. This is a top view of a battery cell stack according to an embodiment. This is a side view of a battery cell stack according to an embodiment. This is a cross-sectional view showing a battery cell stack according to an embodiment. This is a diagram showing an example of the hardware configuration of a control unit according to an embodiment. This is a cross-sectional view showing a battery cell according to an embodiment. This is a flowchart showing the control process according to an embodiment. This is a flowchart showing the control process according to a modified example. This is a flowchart showing the control process according to a modified example. This is a block diagram showing an example of the functional configuration of a solid-state battery system according to a modified example. This is a flowchart showing the process according to a modified example.

[0010] The control method and solid-state battery system according to embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or equivalent parts are denoted by the same reference numerals.

[0011] (Embodiment) The solid battery system 1 according to an embodiment of the present invention is capable of controlling the solid battery module. The solid 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. The solid battery system 1, for example, can be configured as a drive battery for a vehicle using one or more modules and installed in a vehicle such as an electric vehicle or a hybrid vehicle.

[0012] Figure 1 is a diagram showing the configuration of a solid-state battery system 1 according to this embodiment. As shown in Figure 1, the solid-state battery system 1 comprises a solid-state battery module 10 and a control unit 100 that controls charging and discharging of the solid-state battery module 10. The solid-state battery module 10 comprises a battery cell stack 20, a first cell restraint plate 31, a second cell restraint plate 32, a third cell restraint plate 33, a pressurizing device 40, and a surface pressure measuring device 50. In this embodiment, an example in which five battery cell stacks 20 are stacked is described, but the number of battery cell stacks 20 is not particularly limited and may be one or multiple.

[0013] Figure 2A is a top view of the battery cell stack 20, and Figure 2B is a side view of the battery cell stack 20. As shown in Figures 2A and 2B, the battery cell stack 20 is formed in a flattened shape and comprises a positive electrode tab 61 located on the first side 20A of the battery cell stack 20 in a top view, and a negative electrode tab 62 located on the second side 20B opposite the first side 20A. Preferably, the battery cell stack 20 has a rectangular thin plate shape, with the positive electrode tab 61 and the negative electrode tab 62 located on the short side. The battery cell stack 20 is also sealed with an outer casing made of metal foil laminated with a resin film.

[0014] Figure 3 is a cross-sectional view showing a battery cell stack 20 according to this embodiment. As shown in Figure 3, the battery cell stack 20 has a monopolar structure in which battery cells 21 are connected in parallel. The battery cell 21 comprises a positive electrode layer 22 and a negative electrode layer 23, and a solid electrolyte layer 24 disposed between the positive electrode layer 22 and the negative electrode layer 23. The battery cell 21 may be an all-solid-state battery, and the solid electrolyte layer 24 may contain a liquid electrolyte, gel, or polymer electrolyte in part. In this embodiment, an example in which four sets of battery cells 21 are stacked is described, but the number of battery cells 21 stacked is not particularly limited and may be one or more. Furthermore, although an example of a monopolar structure of the battery cell stack 20 in this embodiment is described, it may also be a bipolar structure in which the battery cells 21 are connected in series.

[0015] The positive electrode layer 22 comprises a positive electrode active material that releases lithium ions during charging and absorbs lithium ions during discharge. For example, a lithium metal composite oxide can be used as the positive electrode active material. An example of a lithium metal composite oxide is Li(Ni-Mn-Co)O2. 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 Examples include Si-containing compounds such as the above. The positive electrode layer 22 is formed on a conductive plate-shaped or foil-shaped positive electrode current collector layer 22A. The positive electrode current collector layer 22A is connected to the positive electrode tab 61.

[0016] The negative electrode layer 23 comprises a negative electrode active material that intercalates (or deposits) lithium during charging and releases lithium ions during discharge. The negative electrode active material may be, for example, metallic lithium or a lithium alloy containing lithium. Examples of lithium alloys include alloys of lithium with 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 with two or more of the above-mentioned metals, or a compound containing silicon or tin (oxide, nitride, alloy with other metals), etc. The negative electrode layer 23 is formed on a conductive plate-shaped or foil-shaped negative electrode current collector layer 23A. The negative electrode current collector layer 23A is connected to the negative electrode tab 62. In this embodiment, a negative electrode layer 23 containing metallic lithium is described as the negative electrode active material, but similar effects can be obtained by using a lithium alloy instead of metallic lithium.

[0017] The solid electrolyte layer 24 is positioned between the positive electrode layer 22 and the negative electrode layer 23 and is in contact with both the positive electrode layer 22 and the negative electrode layer 23. The solid electrolyte layer 24 contains a sulfide solid electrolyte or an oxide solid electrolyte.

[0018] As shown in Figure 1, a first cell restraint plate 31 and a second cell restraint plate 32 are arranged on the upper and lower surfaces of a stack of multiple battery cell stacks 20. A third cell restraint plate 33 is placed on top of the second cell restraint plate 32. A pressurizing device 40 is placed between the second cell restraint plate 32 and the third cell restraint plate 33. The first cell restraint plate 31 and the third cell restraint plate 33 are connected to each other by fixing pillars, and are fixed in place while applying restraint pressure in the stacking direction to maintain the position of the battery cell stack 20.

[0019] The pressurizing device 40 is controlled by the control unit 100 to pressurize the battery cell stack 20 in the stacking direction, and is positioned between the second cell restraint plate 32 and the third cell restraint plate 33. It comprises a first pressurizing device 41 positioned on the positive electrode tab 61 side of the battery cell stack 20 and a second pressurizing device 42 positioned on the negative electrode tab 62 side. The first pressurizing device 41 and the second pressurizing device 42 may each have a mechanism to pressurize the battery cell stack 20 by a servo motor, or they may each have a mechanism to pressurize the battery cell stack 20 by a fluid containing liquid or gas.

[0020] The surface pressure measuring device 50 measures the surface pressure distribution of the solid battery module 10 and outputs data indicating the surface pressure distribution to the control unit 100. This allows the detection of the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side of the solid battery module 10. The surface pressure measuring device 50 is not particularly limited as long as it can measure the surface pressure distribution of the solid battery module 10, and may measure the surface pressure distribution using a surface pressure sensor, or it may use a strain gauge to measure the deflection of the solid battery module 10. In addition, if there is a difference in surface pressure, the first cell restraint plate 31 and the second cell restraint plate 32 that restrain the cells may not be parallel. For this reason, the surface pressure measuring device 50 can also measure the surface pressure distribution using a sensor that measures the distance between the first cell restraint plate 31 and the second cell restraint plate 32 of the solid battery module 10.

[0021] Elastic bodies (not shown) may be placed between the multiple battery cell stacks 20. Since the battery cell stacks 20 expand when charged and contract when discharged, the elastic bodies can absorb the displacement caused by charging and discharging. Note that elastic bodies do not necessarily need to be placed between all of the battery cell stacks 20.

[0022] Next, the solid-state battery module 10 during charging and discharging will be described. Figure 4 is a cross-sectional view showing a battery cell 21 according to this embodiment. When the area of ​​the positive electrode current collector layer 22A increases, the electrical resistance of the positive electrode current collector layer 22A becomes non-negligible. On the other hand, since the electrical resistance of the lithium metal in the negative electrode layer 23 is small, when lithium metal is deposited in the negative electrode layer 23, the influence of the electrical resistance of the negative electrode current collector layer 23A is smaller than that of the positive electrode current collector layer 22A. As shown in Figure 4, the electron movement paths in the battery cell 21 include a path R1 in which electrons move through the negative electrode current collector layer 23A and then to the negative electrode layer 23, solid electrolyte layer 24, and positive electrode layer 22, and a path R2 in which electrons move through the negative electrode layer 23, solid electrolyte layer 24, and positive electrode layer 22, and then to the positive electrode current collector layer 22A. Since the distance traveled by path R1 across the positive electrode current collector layer 22A is shorter than that of path R2, the electrical resistance of path R1 is lower than that of path R2. Consequently, the difference in electrical resistance between path R1 and path R2 affects the deposition distribution of the negative electrode layer 23, and if the surface pressure is not controlled, deposition of the negative electrode layer 23 may increase in the region close to the positive electrode tab 61. As shown in Figure 4, if the deposition of lithium metal in the negative electrode layer 23 increases in the region close to the positive electrode tab 61, the surface pressure PP on the positive electrode tab 61 side becomes greater than the surface pressure NP on the negative electrode tab 62 side, and this surface pressure difference may cause problems such as a decrease in the durability of the battery module 10 and short circuits of the electrodes during charging.

[0023] The control unit 100 is a controller that controls the charging, discharging, and surface pressure of the solid battery module 10. The control unit 100 acquires data showing the surface pressure distribution of the positive electrode tab 61 side and the negative electrode tab 62 side of the solid battery module 10, as measured by the surface pressure measuring device 50, and controls the pressurizing device 40 so that the surface pressure PP on the positive electrode tab 61 side becomes smaller than the surface pressure NP on the negative electrode tab 62 side. Figure 5 is a diagram showing an example of the hardware configuration of the control unit 100. In the example of Figure 5, the control unit 100 includes a processor 1011, a storage unit 1012, and a communication interface (indicated as communication I / F in the figure) 1013.

[0024] The processor 1011 includes, for example, a CPU (Central Processing Unit) and its peripheral circuits, and performs various arithmetic operations. The processor 1011 executes control programs stored in the memory unit 1012. The processor 1011 may also include volatile semiconductor memory such as RAM (Random Access Memory) that functions as the CPU's working memory. Furthermore, the processor 1011 may also include arithmetic circuits such as a logical operation unit and a numerical operation unit.

[0025] The storage unit 1012 includes, for example, a non-volatile semiconductor memory such as EEPROM (Electrically Erasable and Programmable Read Only Memory) or flash memory. The storage unit 1012 stores control programs executed by the processor 1011 and various data used in the arithmetic processing of the processor 1011.

[0026] The communication interface 1013 is an interface for communicating with the surface pressure measuring device 50. The communication interface 1013 acquires sensor signals from the surface pressure measuring device 50 and passes them to the processor 1011, and also outputs control signals for the pressurizing device 40 generated by the processor 1011.

[0027] The processor 1011 functions as a surface pressure detection unit 101, a pressure control unit 102, and a charge / discharge control unit 103, as shown in Figure 1, by executing the control program stored in the memory unit 1012. Although only the functional unit according to this embodiment is shown in the control unit 100 in Figure 1, the control unit 100 may have other control or determination functions.

[0028] The surface pressure detection unit 101 acquires data showing the surface pressure distribution of the solid battery module 10 measured by the surface pressure measuring device 50, and stores the data showing the surface pressure distribution in the storage unit 1012.

[0029] The pressure control unit 102 controls the pressurizing device 40 based on data showing the surface pressure distribution of the solid battery module 10 measured by the surface pressure measuring device 50, so that the surface pressure PP on the positive electrode tab 61 side becomes smaller than the surface pressure NP on the negative electrode tab 62 side. Figure 6 is a cross-sectional view showing a battery cell 21 according to this embodiment. Specifically, the first pressurizing device 41 located on the positive electrode tab 61 side and the second pressurizing device 42 located on the negative electrode tab 62 side of the battery cell stack 20 shown in Figure 1 are controlled to make the surface pressure PP on the positive electrode tab 61 side smaller than the surface pressure NP on the negative electrode tab 62 side, as shown in Figure 6. If the surface pressure PP on the positive electrode tab 61 side can be made smaller than the surface pressure NP on the negative electrode tab 62 side, the pressure control unit 102 may decrease the surface pressure of the first pressurizing device 41 located on the positive electrode tab 61 side, or increase the surface pressure of the second pressurizing device 42 located on the negative electrode tab 62 side. Furthermore, the pressure control unit 102 may reduce the surface pressure of the first pressure device 41 located on the positive electrode tab 61 side and increase the surface pressure of the second pressure device 42 located on the negative electrode tab 62 side. In this way, by making the surface pressure PP on the positive electrode tab 61 side smaller than the surface pressure NP on the negative electrode tab 62 side, the deposition rate of the negative electrode layer 23 on the positive electrode tab 61 side can be made relatively smaller than the deposition rate of the negative electrode layer 23 on the negative electrode tab 62 side, and the deposition difference between the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode tab 62 side can be reduced. In addition, if the second internal resistance value, which will be described later, is estimated multiple times by the charge / discharge control unit 103, the pressure control unit 102 will increase the surface pressure difference between the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side if the estimated second internal resistance value is less than or equal to the previously estimated second internal resistance value. The smaller the second internal resistance value, the stronger the influence of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A. Therefore, when the second internal resistance value is small, increasing the surface pressure difference allows for a faster reduction in the deposition difference between the positive electrode tab 61 side and the negative electrode tab 62 side of the negative electrode layer 23. Note that the second internal resistance value in this embodiment is just one example of an internal resistance value.

[0030] When the charge / discharge control unit 103 starts charging or discharging the solid battery module 10, it acquires the voltage and current values ​​between the positive electrode tab 61 and the negative electrode tab 62 during charging or discharging, and stores the data showing the voltage and current values ​​in the storage unit 1012. Subsequently, the charge / discharge control unit 103 estimates a first internal resistance value based on the acquired voltage and current values. The first internal resistance value can be calculated using the acquired voltage and current values ​​and the electromotive force of the battery cell 21. Alternatively, the first internal resistance value may be estimated based on a table or calculation formula that stores the relationship between the measured or estimated temperature, surface pressure, and SOC and the first internal resistance value, after measuring or estimating the cell temperature, cell surface pressure, and cell SOC (State of Charge). Next, the charge / discharge control unit 103 estimates a second internal resistance value that does not include the electrical resistance values ​​of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A. Specifically, the charge / discharge control unit 103 estimates a second internal resistance value based on a first internal resistance value and the electrical resistance values ​​of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A, which have been measured in advance.

[0031] The procedure for controlling the solid battery module 10 using the solid battery system 1 configured as described above will be explained in detail with reference to the flowchart shown in Figure 7. Figure 7 is a flowchart of the control process executed by the processor 1011 of the control unit 100. The control process is executed when the solid battery module 10 is charged or discharged.

[0032] First, the surface pressure detection unit 101 of the control unit 100 acquires data showing the surface pressure distribution of the solid battery module 10 measured by the surface pressure measuring device 50 (step S101), and stores the data showing the surface pressure distribution in the storage unit 1012.

[0033] Next, the pressure control unit 102 controls the pressure device 40 based on data showing the surface pressure distribution of the solid battery module 10 measured by the surface pressure measuring device 50, so that the surface pressure PP on the positive electrode tab 61 side becomes smaller than the surface pressure NP on the negative electrode tab 62 side (step S102). Specifically, the pressure control unit 102 controls the first pressure device 41 located on the positive electrode tab 61 side and the second pressure device 42 located on the negative electrode tab 62 side of the battery cell stack 20 shown in Figure 1, so that the surface pressure PP on the positive electrode tab 61 side becomes smaller than the surface pressure NP on the negative electrode tab 62 side, as shown in Figure 6.

[0034] Next, the charge / discharge control unit 103 starts charging or discharging the solid battery module 10 (step S103).

[0035] Next, the charge / discharge control unit 103 acquires the voltage and current values ​​between the positive electrode tab 61 and the negative electrode tab 62 during charging or discharging (step S104), and stores the data indicating the voltage and current values ​​in the storage unit 1012.

[0036] Next, the charge / discharge control unit 103 estimates a first internal resistance value based on the acquired voltage and current values ​​(step S105). The first internal resistance value can be calculated using the acquired voltage and current values ​​and the electromotive force of the battery cell 21.

[0037] Next, the charge / discharge control unit 103 estimates a second internal resistance value that does not include the electrical resistance values ​​of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A (step S106). Specifically, the charge / discharge control unit 103 estimates the second internal resistance value based on the first internal resistance value and the previously measured electrical resistance values ​​of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A.

[0038] Next, if the second internal resistance value has been estimated two or more times, the charge / discharge control unit 103 determines whether the second internal resistance value estimated this time is less than or equal to the second internal resistance value estimated last time (step S107). Note that if the control unit 100 estimates the second internal resistance value for the first time, it returns to step S104 without changing the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side.

[0039] When it is determined that the second internal resistance value estimated this time is less than or equal to the second internal resistance value estimated last time (step S107; Yes), the pressure control unit 102 increases the pressure difference between the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side (step S108). The smaller the second internal resistance value is, the stronger the influence of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A. Therefore, when the second internal resistance value is small, by increasing the pressure difference, the pressure control unit 102 can make the precipitation difference of the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode layer 23 on the negative electrode tab 62 side faster and smaller.

[0040] When it is determined that the second internal resistance value estimated this time exceeds the second internal resistance value estimated last time (step S107; No), the pressure control unit 102 does not change the pressure difference (step S109).

[0041] Next, the charge / discharge control unit 103 determines whether the charge / discharge has ended (step S110). If the charge / discharge has not ended (step S110; No), the process returns to step S104, and the control unit 100 repeats steps S104 to S109. If the charge / discharge has ended (step S110; Yes), the control process ends.

[0042] As described above, according to the control method of the solid battery system and the solid battery system 1 according to the present embodiment, since the surface pressure PP on the positive electrode tab 61 side is smaller than the surface pressure NP on the negative electrode tab 62 side, the precipitation rate of the negative electrode layer 23 on the positive electrode tab 6i side can be made relatively smaller than the precipitation rate of the negative electrode layer 23 on the negative electrode tab 62 side, and the precipitation difference between the negative electrode layers 23 on the positive electrode tab 61 side and the negative electrode tab 62 side can be reduced. Thereby, the generation of the SOC difference within the plane of the solid battery module 10 can be prevented. Further, the smaller the second internal resistance value is, the stronger the influence of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A. Therefore, the smaller the second internal resistance value becomes, the smaller the surface pressure PP on the positive electrode tab 61 side is made compared to the surface pressure NP on the negative electrode tab 62 side. By doing so, the precipitation difference between the negative electrode layers 23 on the positive electrode tab 61 side and the negative electrode tab 62 side can be made faster and smaller.

[0043] (Modified Example) The above-described embodiment can be variously modified, and the above-described embodiment and each modified example can be arbitrarily combined. In the above-described embodiment, an example in which the surface pressure PP on the positive electrode tab 61 side is made smaller than the surface pressure NP on the negative electrode tab 62 side as the second internal resistance value becomes smaller has been described. The solid battery system 1 only needs to be able to prevent the occurrence of an SOC difference within the plane of the solid battery module 10, and it is not necessary to change the surface pressure based on the second internal resistance value that does not include the electrical resistance values of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A. That is, in FIG. 7, steps S104 to S109 may be omitted. Even if it is done in this way, by making the surface pressure PP on the positive electrode tab 61 side smaller than the surface pressure NP on the negative electrode tab 62 side, the deposition rate of the negative electrode layer 23 on the positive electrode tab 61 side can be made relatively smaller than the deposition rate of the negative electrode layer 23 on the negative electrode tab 62 side, and the deposition difference of the negative electrode layer 23 between the positive electrode tab 61 side and the negative electrode tab 62 side can be made smaller. Also, by not changing the surface pressure based on the second internal resistance value, the structure of the solid battery system 1 can be further simplified.

[0044] Further, instead of changing the surface pressure based on the second internal resistance value, the solid battery system 1 may measure or estimate the SOC of the solid battery module 10, and increase the surface pressure difference between the positive electrode tab 61 side and the negative electrode tab 62 side of the battery cell laminate 20 as the SOC of the solid battery module 10 increases. FIG. 8 is a flowchart of the control process of the solid battery module 10. This example will be described in detail according to the flowchart shown in FIG. 8. Steps S201 to S204 are the same as steps S101 to S104 shown in FIG. 7.

[0045] The charge / discharge control unit 103 estimates the SOC of the solid battery module 10 based on the acquired voltage value and current value (step S205). Specifically, the charge / discharge control unit 103 estimates the SOC by calculation based on the acquired voltage value and current value, and the electromotive force of the battery cell 21. The SOC is an index representing the charge state of the solid battery module 10, with the fully charged state being 100% and the fully discharged state being 0%. The greater the SOC, the greater the thickness of the lithium metal in the negative electrode layer 23.

[0046] Next, if the SOC is estimated two or more times, the charge / discharge control unit 103 determines whether the SOC estimated this time is greater than or equal to the SOC estimated last time (step S206). Note that if the control unit 100 estimates the SOC for the first time, it returns to step S204 without changing the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side.

[0047] If it is determined that the SOC estimated this time is greater than or equal to the SOC estimated last time (step S206; Yes), the pressurization control unit 102 increases the surface pressure difference between the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side (step S207). The larger the SOC, the greater the thickness of the lithium metal in the negative electrode layer 23, and the more strongly it is affected by the difference in electrical resistance values ​​between the positive electrode current collector layer 22A and the negative electrode current collector layer 23A. Therefore, when the SOC is large, increasing the surface pressure difference can reduce the deposition difference between the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode tab 62 side more quickly.

[0048] If it is determined that the SOC estimated this time is less than the SOC estimated last time (step S206; No), the pressurization control unit 102 does not change the surface pressure difference (step S208). Step S209 is the same as step S110 shown in Figure 7.

[0049] Furthermore, the solid-state battery system 1 measures or estimates the charge or discharge electrical change dQ and the voltage change dV of the solid-state battery module 10. The smaller the voltage change dV is relative to the charge or discharge electrical change dQ of the solid-state battery module 10, the larger the surface pressure difference between the positive electrode tab 61 side and the negative electrode tab 62 side of the battery cell stack 20 may be. Figure 9 is a flowchart of the control process of the solid-state battery module 10. This example will be explained in detail following the flowchart shown in Figure 9. Steps S301 to S304 are the same as steps S101 to S104 shown in Figure 7.

[0050] The charge / discharge control unit 103 measures or estimates the charge or discharge voltage change dV / electrical change dQ of the solid battery module 10 based on the acquired voltage and current values ​​(step S305). The charge or discharge voltage change dV / electrical change dQ can be determined by measuring or estimating the charge or discharge electrical change dQ and the voltage change dV of the solid battery module 10.

[0051] Next, if dV / dQ has been estimated two or more times, the charge / discharge control unit 103 determines whether the dV / dQ estimated this time is less than or equal to the dV / dQ estimated last time (step S306). Note that if the control unit 100 has estimated dV / dQ for the first time, it returns to step S304 without changing the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side.

[0052] If it is determined that the dV / dQ estimated this time is less than or equal to the dV / dQ estimated last time (step S306; Yes), the pressurization control unit 102 increases the surface pressure difference between the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side (step S307). The larger the dV / dQ, the stronger the influence of the positive electrode current collector layer 22A and the negative electrode current collector layer 23A. Therefore, when the dV / dQ is small, increasing the surface pressure difference can reduce the deposition difference of the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode tab 62 side more quickly.

[0053] If it is determined that the dV / dQ estimated this time is greater than the dV / dQ estimated last time (step S306; No), the pressurization control unit 102 does not change the surface pressure difference (step S308). Step S309 is the same as step S110 shown in Figure 6.

[0054] The solid-state battery system 1 measures the thickness of the battery cell stack 20 on the positive electrode tab 61 side and the thickness of the battery cell stack 20 on the negative electrode tab 61 side. The greater the difference between the thickness on the positive electrode tab 61 side and the thickness on the negative electrode tab 62 side measured during charging or discharging, the greater the surface pressure difference between the positive electrode tab 61 side and the negative electrode tab 62 side of the battery cell stack 20.

[0055] Figure 10 is a block diagram showing an example of the functional configuration of a modified solid-state battery system 1. In this case, as shown in Figure 10, the solid-state battery system 1 further includes a thickness measuring device 70, which comprises a first thickness measuring device 71 for measuring the first thickness of the battery cell stack 20 on the positive electrode tab 61 side and a second thickness measuring device 72 for measuring the second thickness of the battery cell stack 20 on the negative electrode tab 62 side, in addition to the configuration of the solid-state battery system 1 shown in Figure 1. Furthermore, the control unit 100 further includes a thickness measuring unit 104 that acquires data indicating the thickness of the solid-state battery module 10 measured by the thickness measuring device 70 and measures the first thickness on the positive electrode tab 61 side and the second thickness on the negative electrode tab 62 side.

[0056] Figure 11 is a flowchart of the control process for the solid-state battery module 10. This example will be explained in detail following the flowchart shown in Figure 11.

[0057] First, the thickness measuring unit 104 of the control unit 100 acquires data indicating the first thickness of the battery cell stack 20 on the positive electrode tab 61 side and the second thickness of the battery cell stack 20 on the negative electrode tab 62 side, which are measured by the thickness measuring device 70 (step S401), and stores the acquired data in the storage unit 1012.

[0058] Next, the thickness measuring unit 104 calculates the difference between the first thickness on the positive electrode tab 61 side and the second thickness on the negative electrode tab 62 side based on the thickness data measured by the thickness measuring device 70 (step S402).

[0059] Next, the pressure control unit 102 controls the pressurizing device 40 based on the data indicating the difference in thickness estimated by the thickness measuring unit 104, so that the surface pressure PP on the positive electrode tab 61 side becomes smaller than the surface pressure NP on the negative electrode tab 62 side (step S403).

[0060] Next, the charge / discharge control unit 103 starts charging or discharging the solid battery module 10 (step S404).

[0061] Next, the thickness measuring unit 104 of the control unit 100 acquires data indicating the first thickness of the battery cell stack 20 on the positive electrode tab 61 side and the second thickness of the battery cell stack 20 on the negative electrode tab 62 side, which have been measured by the thickness measuring device 70 (step S405), and stores the acquired data in the storage unit 1012.

[0062] Next, the thickness measuring unit 104 calculates the difference between the first thickness on the positive electrode tab 61 side and the second thickness on the negative electrode tab 62 side based on the thickness data measured by the thickness measuring device 70 (step S406).

[0063] Next, the thickness measuring unit 104 determines whether the thickness difference estimated this time is greater than or equal to the thickness difference estimated last time (step S407).

[0064] If it is determined that the thickness difference estimated this time is greater than or equal to the thickness difference estimated last time (step S407; Yes), the pressure control unit 102 increases the surface pressure difference between the surface pressure PP on the positive electrode tab 61 side and the surface pressure NP on the negative electrode tab 62 side (step S408). In this example, by monitoring the thickness difference, the difference in the thickness of the lithium metal deposited in the negative electrode layer 23 can be estimated. The greater the difference in the thickness of the deposited lithium metal, the faster the difference in deposition between the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode tab 62 side can be reduced by increasing the surface pressure difference.

[0065] If it is determined that the thickness difference estimated this time is less than the thickness difference estimated last time (step S407; No), the pressure control unit 102 does not change the surface pressure difference (step S409). Step S410 is the same as step S110 shown in Figure 7.

[0066] In the solid-state battery system 1, as described above, the surface pressure PP on the positive electrode tab 61 side is smaller than the surface pressure NP on the negative electrode tab 62 side, thereby reducing the deposition difference between the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode tab 62 side. By making the temperature on the positive electrode tab 61 side of the battery cell laminate 20 lower than the temperature on the negative electrode tab 62 side, the deposition rate of the negative electrode layer 23 on the positive electrode tab 61 side can be made relatively smaller than the deposition rate of the negative electrode layer 23 on the negative electrode tab 62 side, thereby reducing the deposition difference between the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode tab 62 side. For this reason, the solid-state battery system 1 may further include a configuration that makes the temperature on the positive electrode tab 61 side lower than the temperature on the negative electrode tab 62 side. In this way, by reducing the deposition difference of the negative electrode layer 23 through surface pressure and temperature, it is possible to handle cases where the deposition difference is large.

[0067] Furthermore, the battery cell 21 may also include a negative electrode intermediate layer between the negative electrode layer 23 and the solid electrolyte layer 24. The negative electrode intermediate layer is a layer provided in a deposition-type solid battery for purposes such as protecting the solid electrolyte layer 24. A deposition-type solid battery is a secondary battery configured such that metallic lithium is deposited between the solid electrolyte layer 24 and the negative electrode current collector layer 23A during charging. However, if the deposited metallic lithium comes into direct contact with the solid electrolyte layer 24, the solid electrolyte layer 24 may be damaged. Therefore, a negative electrode intermediate layer is provided between the solid electrolyte layer 24 and the negative electrode current collector layer 23A. A negative electrode intermediate layer used for this purpose is also included in the negative electrode layer 23 in this embodiment. The negative electrode intermediate layer can be realized by a layer containing, for example, metal particles such as silver, carbon particles, and a binder resin. Furthermore, even if the negative electrode layer 23 includes a negative electrode intermediate layer, by making the surface pressure PP on the positive electrode tab 61 side smaller than the surface pressure NP on the negative electrode tab 62 side, the difference in deposition between the negative electrode layer 23 on the positive electrode tab 61 side and the negative electrode tab 62 side can be reduced.

[0068] Furthermore, in the above embodiments and modifications, examples were described in which the processor 1011 executes a control program to realize each function, but the control unit 100 may be configured with dedicated hardware to realize each function.

[0069] Furthermore, a control unit 100 capable of realizing each function may be configured by distributing a control program for executing the operations of the above embodiments and modified examples on a computer-readable recording medium such as a CD-ROM (Compact Disc Read-Only Memory), DVD (Digital Versatile Disc), MO (Magneto Optical Disc), or memory card, and installing the program on a computer. In cases where each function is realized through a division of labor between the OS (Operating System) and the application, or through cooperation between the OS and the application, only the parts other than the OS may be stored on the recording medium.

[0070] The present invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent significance of disclosure are considered to be within the scope of the invention.

[0071] 1 Solid-state battery system, 10 Solid-state battery module, 20 Battery cell stack, 20A First side, 20B Second side, 21 Battery cell, 22 Positive electrode layer, 22A Positive electrode current collector layer, 23 Negative electrode layer, 23A Negative electrode current collector layer, 24 Solid electrolyte layer, 31 First cell restraint plate, 32 Second cell restraint plate, 33 Third cell restraint plate, 40 Pressurizing device, 41 First pressurizing device, 42 Second pressurizing device, 50 Surface pressure measuring device, 61 Positive electrode tab, 62 Negative electrode tab, 70 Thickness measuring device, 71 First thickness measuring device, 72 Second thickness measuring device, 100 Control unit, 101 Surface pressure detection unit, 102 Pressurizing control unit, 103 Charge / discharge control unit, 104 Thickness measuring unit, 1011 Processor, 1012 Storage unit, 1013 Communication interface, R1, R2 path, PP, NP surface pressure.

Claims

1. A control method for a solid battery system comprising: a solid battery module including a battery cell stack in which one or more battery cells are stacked, each having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; a positive electrode tab connected to the positive electrode layer and positioned on a first edge of the battery cell stack in a top view in the orientation in which the battery cell stack is stacked; a negative electrode tab connected to the negative electrode layer and positioned on a second edge opposite to the first edge in a top view; and a pressurizing device for pressurizing the battery cell stack in the orientation in which the battery cell stack is stacked, wherein during charging or discharging, the pressurizing device is used to pressurize the side of the battery cell stack with the positive electrode tab at a smaller surface pressure than the side of the negative electrode tab.

2. A control method for a solid-state battery system according to claim 1, comprising measuring or estimating the internal resistance of the solid-state battery module, excluding the electrical resistance of the positive electrode current collector layer of the positive electrode layer and the negative electrode current collector layer of the negative electrode layer, and increasing the surface pressure difference between the positive electrode tab side and the negative electrode tab side of the battery cell stack as the internal resistance decreases.

3. A method for controlling a solid-state battery system according to claim 1, comprising measuring or estimating the State of Charge (SOC) of the solid-state battery module, and increasing the surface pressure difference between the positive electrode tab side and the negative electrode tab side of the battery cell stack as the SOC of the solid-state battery module increases.

4. A method for controlling a solid-state battery system according to claim 1, comprising measuring or estimating the charge or discharge change amount dQ and the voltage change amount dV of the solid-state battery module, and increasing the surface pressure difference between the positive electrode tab side and the negative electrode tab side of the battery cell stack as the voltage change amount dV is smaller than the charge or discharge change amount dQ.

5. A control method for a solid-state battery system according to claim 1, wherein the thickness of the battery cell stack on the positive electrode tab side and the thickness of the battery cell stack on the negative electrode tab side are measured, and the surface pressure difference between the positive electrode tab side and the negative electrode tab side of the battery cell stack is increased as the difference between the thickness on the positive electrode tab side and the thickness on the negative electrode tab side measured during charging or discharging increases.

6. A method for controlling a solid-state battery system according to any one of claims 1 to 5, wherein the negative electrode layer comprises metallic lithium or a lithium alloy containing lithium.

7. A solid battery system comprising: a solid battery module including a battery cell stack in which one or more battery cells are stacked, each having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; a positive electrode tab connected to the positive electrode layer and positioned on a first edge of the battery cell stack in a top view in the orientation in which the battery cell stack is stacked; a negative electrode tab connected to the negative electrode layer and positioned on a second edge opposite to the first edge in a top view; a pressurizing device for pressurizing the battery cell stack in the direction in which it is stacked; and a control device for controlling the pressurizing device to pressurize the side of the battery cell stack with the positive electrode tab with a smaller surface pressure than the side of the negative electrode tab during charging or discharging.

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