All-solid-state battery containment system

Abstract

To provide an all-solid-state battery containment system capable of applying uniform pressure to the all-solid-state battery from all directions.SOLUTION: An all-solid-state battery containment system 1 includes a case 21 enclosing a battery module 24 and oil O filled within the case 21 to achieve a predetermined pressure. A circulation circuit 3 connected to the case 21 is equipped with an oil pump 31c and a relief valve 32b. By adjusting the pressure inside the case 21 while circulating oil O through the circulation circuit 3 via the operation of the oil pump 31c to adjust the degree of pressure reduction via the relief valve 32b, predetermined pressure is applied uniformly to the battery module 24 from all directions, enabling the battery module 24 to fully demonstrate its performance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery housing system, and more particularly to an improvement in the housing form for fully demonstrating the performance of an all-solid-state battery. [Background technology]

[0002] Conventionally, there has been an increasing demand for the use of all-solid-state batteries as a power source in various vehicles and devices such as electric vehicles. Patent Document 1 discloses a configuration for mounting an all-solid-state battery on an electric vehicle. The mounting configuration of the all-solid-state battery disclosed in Patent Document 1 is such that a battery module is formed by stacking a plurality of unit cells in the vehicle width direction and integrating them, end plates are arranged on both ends of the stacking direction, tension plates are arranged on both the top and bottom sides of the battery module, and the end plates are fastened to both ends of the tension plates with bolts, thereby applying a restraining force in the vehicle width direction to the battery module from each end plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-147547 Summary of the Invention [Problem to be solved by the invention]

[0004] However, all-solid-state batteries have problems such as a decrease in battery capacity and deterioration in output characteristics and life characteristics when the adhesion at the interface between the electrode material and the solid electrolyte is poor. For this reason, it is necessary to form a good interface between the electrode material and the solid electrolyte.

[0005] In the mounting configuration of the all-solid-state battery disclosed in Patent Document 1, a restraining force is applied to the all-solid-state battery (battery module) only in one direction (the vehicle width direction), and therefore the above-mentioned requirements cannot be fully met.

[0006] The inventors of the present invention have focused on the fact that in order to fully satisfy the above-mentioned requirements, it is necessary to apply pressure (constraint force) to an all-solid-state battery from all directions. However, when applying pressure by fastening bolts as employed in Patent Document 1, pressure can only be applied in the direction along the bolt fastening direction, making it difficult to apply pressure from all directions. Naturally, it is also difficult to apply pressure evenly from all directions. In a situation where pressure is not applied evenly, stress may become high locally in the all-solid-state battery, which may lead to damage such as cracks.

[0007] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a system that can apply pressure uniformly from all directions to an all-solid-state battery without using means for applying pressure using fasteners such as bolts. [Means for solving the problem]

[0008] The solution of the present invention for achieving the above object is based on an all-solid-state battery housing system for housing an all-solid-state battery, and is characterized by including a case in which the all-solid-state battery is enclosed, and a liquid filled inside the case at a predetermined pressure.

[0009] The all-solid-state battery referred to here is a concept that includes both a single cell (single cell) and a battery module formed by stacking multiple cells.

[0010] Due to the above-mentioned specific features, the liquid filled inside the case applies a predetermined pressure uniformly from all directions to the all-solid-state battery sealed inside the case. This makes it possible to form a good interface (a highly adhesive interface) between the electrode material and the solid electrolyte of the all-solid-state battery, ensuring sufficient battery capacity and improving output characteristics and life characteristics. This allows the all-solid-state battery to fully demonstrate its performance. Furthermore, because pressure is applied uniformly to the all-solid-state battery, it is also possible to avoid damage caused by high local stress.

[0011] A circulation circuit that circulates the liquid between the inside and outside of the case is connected to the case.

[0012] This makes it possible to vary the pressure inside the case by adjusting the pressure of the liquid circulating in the circulation circuit. For example, it becomes possible to adjust the pressure inside the case to an optimum pressure for fully utilizing the performance of the all-solid-state battery, and to impart this optimum pressure to the all-solid-state battery.

[0013] In this case, as a specific configuration, the circulation circuit includes a pump for circulating the liquid, and a relief valve for reducing the pressure of the liquid circulating through the circulation circuit.

[0014] This makes it possible to relatively easily adjust the pressure of the liquid filled inside the case by changing the degree of pressure reduction by the relief valve, which means that the pressure applied to the all-solid-state battery can be easily adjusted to an optimum pressure that allows the all-solid-state battery to fully exhibit its performance.

[0015] Further, the liquid discharged from the pump is reduced in pressure by the relief valve on the condition that the temperature of the all-solid-state battery at the time of a request to charge or discharge the all-solid-state battery is equal to or lower than a predetermined temperature.

[0016] The "predetermined temperature" here may be a startup temperature at which the all-solid-state battery can be charged and discharged, or an optimal temperature at which the performance of the all-solid-state battery is at its highest. In other words, the condition for the energy conversion operation by decompression (the operation of converting pressure energy into thermal energy) may be a case where the temperature of the all-solid-state battery is equal to or lower than the startup temperature, or may be a case where the temperature of the all-solid-state battery is equal to or lower than the optimal temperature.

[0017] Unless a predetermined temperature is reached, an all-solid-state battery may not be charged or discharged (when the temperature of the all-solid-state battery is below the start-up temperature) or may not exhibit sufficient performance (when the temperature of the all-solid-state battery is below the optimum temperature). Therefore, if the temperature of the all-solid-state battery is below the predetermined temperature when a charge or discharge request is made to the all-solid-state battery, it is desirable to raise the temperature of the all-solid-state battery to the predetermined temperature. In this solution, when the all-solid-state battery has not reached the predetermined temperature, the circulation circuit is provided with a pump and a relief valve, and heat is generated by energy conversion (conversion of pressure energy to thermal energy) accompanying the decompression of the liquid in the relief valve, thereby raising the temperature of the liquid and also raising the temperature of the all-solid-state battery. This makes it possible to quickly raise the temperature of the all-solid-state battery to the predetermined temperature.

[0018] In this case, the all-solid-state battery has a startup temperature range in which charging and discharging are possible, and an optimal temperature range within the startup temperature range, and the liquid discharged from the pump is depressurized by the relief valve on condition that the temperature of the all-solid-state battery at the time a request to charge or discharge the all-solid-state battery is equal to or lower than the optimal temperature range, and when the temperature of the all-solid-state battery at the time a request to charge or discharge is made is lower than the startup temperature range, the degree of depressurization by the relief valve is greater than when the temperature of the all-solid-state battery at the time a request to charge or discharge is made is within the startup temperature range and lower than the optimal temperature range.

[0019] If the temperature of the all-solid-state battery at the time of a charge / discharge request is lower than the startup temperature range, the all-solid-state battery is unable to be charged or discharged, and therefore it is desirable to rapidly raise the temperature of the all-solid-state battery to the startup temperature range to make the all-solid-state battery able to be charged or discharged within a short period of time. On the other hand, if the temperature of the all-solid-state battery at the time of a charge / discharge request is within the startup temperature range but lower than the optimal temperature range, the all-solid-state battery is able to be charged or discharged, and therefore such a rapid temperature rise is not desirable. In view of this, in the present solution, the temperature rise rate of the all-solid-state battery is varied depending on the temperature of the all-solid-state battery at the time of a charge / discharge request.

[0020] Furthermore, the higher the inter-electrode voltage during charging and discharging of the all-solid-state battery, the lower the pressure of the liquid filled inside the case is set to.

[0021] The thickness of an all-solid-state battery cell changes with charging and discharging. That is, the higher the voltage during charging, the greater the thickness. In this solution, in view of the fact that the pressure inside the cell increases when the thickness of the all-solid-state battery cell increases, the target value of the internal pressure of the case is set low in such a situation to prevent the pressure inside the cell from becoming too high. Conversely, in view of the fact that the pressure inside the cell decreases when the thickness of the all-solid-state battery cell decreases, the target value of the internal pressure of the case is set high in such a situation to increase the pressure inside the cell to a certain extent, thereby ensuring adhesion at the interface between the electrode material and the solid electrolyte and allowing the all-solid-state battery to fully demonstrate its performance.

[0022] Furthermore, the pressure of the liquid filled inside the case is set to be higher as the number of times the all-solid-state battery is repeatedly charged and discharged increases.

[0023] The thickness of an all-solid-state battery cell at high voltage and at low voltage changes depending on the number of charge / discharge cycles (the degree of cell deterioration due to repeated charge / discharge cycles). Specifically, the thickness at high voltage tends to decrease as the number of charge / discharge cycles increases, and similarly, the thickness at low voltage tends to decrease as the number of charge / discharge cycles increases. In this solution, too, when the thickness of an all-solid-state battery cell is increasing, the pressure inside the cell increases. In view of this, the target value of the internal pressure of the case is set low to prevent the pressure inside the cell from becoming too high. Conversely, when the thickness of an all-solid-state battery cell is decreasing, the pressure inside the cell decreases. In view of this, the target value of the internal pressure of the case is set high to increase the pressure inside the cell to a certain extent, ensuring adhesion at the interface between the electrode material and the solid electrolyte and allowing the all-solid-state battery to fully demonstrate its performance.

[0024] The case is also provided with an opening for drawing out a power line connected to the all-solid-state battery to the outside, and a connector that seals the edge of the opening is fitted into the opening.

[0025] This makes it possible to supply power from the all-solid-state battery to an electrical load while preventing liquid from leaking from the opening in the case.

[0026] In this case, an opening is provided in the connector, and a molded portion made by molding a conductive material is provided in the opening, and a power line connected to the all-solid-state battery and a power line connected to an electrical load that receives power from the all-solid-state battery are each connected to the molded portion.

[0027] This makes it possible to realize a highly reliable configuration that enables the supply of power from the all-solid-state battery to an electrical load while preventing liquid from leaking from the opening of the case. [Effects of the Invention]

[0028] In the present invention, the inside of the case enclosing the all-solid-state battery is filled with a liquid at a predetermined pressure. This allows the predetermined pressure to be applied uniformly from all directions to the all-solid-state battery, allowing the all-solid-state battery to fully demonstrate its performance. It also makes it possible to avoid damage to the all-solid-state battery caused by high stress in localized areas. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an entire all-solid-state battery housing system according to an embodiment. [Figure 2] FIG. 1 is a perspective view showing the appearance of an all-solid-state battery pack. [Figure 3] FIG. 2 is a perspective view showing the inside of the all-solid-state battery pack. [Figure 4] FIG. 4 is a cross-sectional view showing a power line connection portion in the case. [Figure 5] FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 2 is a schematic diagram for explaining the principle of oil temperature rise. [Figure 8] FIG. 4 is a flowchart showing a procedure for controlling the startup of the battery module. [Figure 9] FIG. 10 is a diagram for explaining an example of the change characteristics of the cell thickness depending on the voltage and the number of cycles. [Figure 10] FIG. 10 is a diagram showing an example of a case internal pressure setting table. [Figure 11] FIG. 10 is a flowchart showing a procedure for controlling the setting of the case internal pressure. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where an all-solid-state battery housing system according to the present invention is mounted on a construction machine will be described as an example. Note that the all-solid-state battery housing system according to the present invention is not limited to construction machines, but can be applied to various devices such as agricultural machines and ships. In addition, this embodiment will be described as an example where pressure is applied uniformly from all directions to a battery module formed by stacking multiple cells. However, the present invention is not limited to this, and can also be applied to a configuration where pressure is applied uniformly from all directions to a single cell (single cell).

[0031] -Overall configuration of all-solid-state battery housing system- 1 is a diagram showing a schematic overall configuration of an all-solid-state battery housing system 1 according to this embodiment. As shown in this Fig. 1, the all-solid-state battery housing system 1 is configured to include an all-solid-state battery pack 2 and an oil circulation circuit (circulation circuit) 3.

[0032] (All-solid-state battery pack) The all-solid-state battery pack 2 has a configuration in which a battery module (all-solid-state battery) 24 is enclosed in a case 21. This will be specifically described below.

[0033] Fig. 2 is a perspective view showing the appearance of the all-solid-state battery pack 2. Fig. 3 is a perspective view showing the inside of the all-solid-state battery pack 2. In Fig. 3, the battery module 24 enclosed inside the case 21 is shown by a solid line, and the case 21 is shown by a virtual line.

[0034] <Case> The case 21 is formed by integrally assembling a first case 22 and a second case 23, and has a space S therein for enclosing the battery module 24 (hereinafter, sometimes referred to as the case internal space).

[0035] The first case 22 includes a cylindrical main body portion 22a, a dome portion 22b that is continuous with one end side (the upper side in the state shown in Figure 2) of the main body portion 22a and has a hemispherical outer surface, and a flange portion 22c that is continuous with the other end side (the lower side in the state shown in Figure 2) of the main body portion 22a and is provided around the entire periphery of the other end side.

[0036] The second case 23 has a shape symmetrical to the first case 22, and includes a cylindrical main body portion 23a, a dome portion 23b that is continuous with one end side (the lower side in the state shown in Figure 2) of the main body portion 23a and has a hemispherical outer surface, and a flange portion 23c that is continuous with the other end side (the upper side in the state shown in Figure 2) of the main body portion 23a and is provided around the entire periphery of the other end side.

[0037] A plurality of bolt insertion holes (not shown in FIGS. 2 and 3) are provided in the flange portions 22c, 23c of the first case 22 and the second case 23, respectively. The flange portions 22c, 23c are overlapped with each other with a packing (not shown) sandwiched therebetween, and the bolt insertion holes are aligned. Bolts B are inserted into the bolt insertion holes from one side, and nuts (not shown) are screwed onto the bolts B from the other side of the flange portions 22c, 23c, thereby fastening the flange portions 22c, 23c together. In this manner, the first case 22 and the second case 23 are assembled together, and a space (case internal space) S for enclosing the battery module 24 is formed inside the case 21. Note that welding may be used as a means for assembling the first case 22 and the second case 23 together.

[0038] Furthermore, power line connectors 25A and 25B are provided in a portion of the main body 22a of the first case 22 for connecting (electrically connecting) the power lines (positive power line 24c and negative power line 24d) extending from the battery module 24 to the power lines 4a and 4b extending from an electrical load (not shown). The configuration of these power line connectors 25A and 25B will be described later.

[0039] As will be described later, the case internal space S is filled with oil (liquid) O, and therefore the battery module 24, the power lines 24c and 24d, and the bus bar 24b, which will be described later, are covered with a covering material.

[0040] <Battery module> The battery module 24 has a configuration in which a plurality of cells 24 a, 24 a, ... are stacked in one direction (in the radial direction of the main bodies 22 a, 23 a of the cases 22, 23 in this embodiment). Each cell 24 a, 24 a, ... is an all-solid-state battery cell that uses a solid electrolyte (not shown), and includes the solid electrolyte, positive and negative electrodes (not shown) that are electrode materials sandwiching the solid electrolyte, and positive and negative terminals (not shown) electrically connected to the positive and negative electrodes, respectively. The positive terminal of one cell 24 a and the negative terminal of the other cell 24 a of adjacent cells 24 a, 24 a are connected by a bus bar 24 b, and the cells 24 a, 24 a, ... are electrically connected in series. In addition, the positive terminal of the cell 24a on one side in the connection direction (series connection direction) of the cells 24a, 24a, ... is a positive output terminal, and the negative terminal of the cell 24a on the other side is a negative output terminal. A positive power line 24c connected to the positive output terminal and a negative power line 24d connected to the negative output terminal extend toward the power line connection parts 25A, 25B, respectively, with the positive power line 24c connected to one power line connection part 25A (more specifically, connected to a molded part 25b (see FIG. 4) described later and provided on the power line connection part 25A), and the negative power line 24d connected to the other power line connection part 25B (more specifically, connected to a molded part (described later) provided on the power line connection part 25B).

[0041] Furthermore, a cell thermometer 24e (see FIG. 1) is attached to the surface of the battery module 24 (the surface of the cell 24a located on one side of the stacked cells 24a, 24a, ...). The cell thermometer 24e detects the surface temperature of the battery module 24 and outputs information on the detected cell temperature to the controller 5.

[0042] The support structure for the battery module 24 inside the case 21 is not particularly limited. For example, the battery module 24 may be supported on the inner surface of the case 21 by a support bracket (not shown).

[0043] <Power line connection part> Here, the configuration of the power line connection parts 25A and 25B will be described. The power line connection parts 25A and 25B are provided in two locations on the main body 22a of the first case 22. Since the configurations of the power line connection parts 25A and 25B are the same, only the configuration of the power line connection part 25A to which the positive electrode side power line 24c is connected will be described here.

[0044] Fig. 4 is a cross-sectional view showing the power line connection part 25A. As shown in Fig. 4, an opening 25a is provided in the main body part 22a of the first case 22. A rubber connector 26 is fitted into this opening 25a.

[0045] Fig. 5 is a perspective view of connector 26. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5. As shown in these figures, connector 26 includes boss portion 26b having opening 26a at its center, and flange portion 26c that extends radially outward from one end of boss portion 26b in a direction along the center line thereof (toward case internal space S when attached to case 21).

[0046] The outer diameter of boss portion 26b is approximately the same as or slightly larger than the inner diameter of opening 25a provided in main body portion 22a of first case 22. Flange portion 26c is approximately disk-shaped and extends in a direction perpendicular to the center line of boss portion 26b, and is shaped to abut against the inner surface of first case 22 when boss portion 26b is fitted into opening 25a of first case 22 from the case internal space S side, as shown in Fig. 4. Furthermore, the outer peripheral edge portion of flange portion 26c has an inclined surface 26d that slopes radially outward toward the inner surface of main body portion 22a of first case 22, on the surface facing the case internal space S. This is to enlarge the surface area that receives pressure from the oil O (see the arrow in Figure 4) that fills the case internal space S, thereby increasing the pressing force of the flange portion 26c against the inner surface of the first case 22 and ensuring sufficient liquid-tightness of the power line connection portion 25A.

[0047] Furthermore, the interior of opening 26a provided in the center of connector 26 is filled with molded portion 25b, which is formed by filling a molding material made of a conductive material (e.g., copper). This molded portion 25b ensures that opening 26a is liquid-tight. Furthermore, the end of molded portion 25b facing the case internal space S is located closer to the inside of case internal space S than the end face of connector 26 (the surface of flange portion 26c facing the case internal space S), and the end of molded portion 25b facing outside case 21 is located outside the outer surface of case 21. The positive power line 24c is connected (by means of soldering or the like) to the end of molded portion 25b facing the case internal space S, and the power line 4a extending from the electrical load is connected to the end of molded portion 25b facing outside case 21. As a result, the positive power line 24c and the power line 4a are electrically connected via the molded portion 25b, making it possible to supply the power stored in the battery module 24 to an electrical load. The other power line connection portion 25B to which the negative power line 24d is connected has a similar configuration.

[0048] Although not shown, the signal line pull-out structure for outputting information on the surface temperature of the battery module 24 detected by the cell thermometer 24e to the controller 5 is configured in the same manner as the power line connection parts 25A and 25B described above, making it possible to output information on the surface temperature to the controller 5.

[0049] (oil circulation circuit) The oil circulation circuit 3 is configured as a part of the hydraulic system of the construction machine. In other words, it is configured as a circuit through which a part of the oil (hydraulic oil) O for the operation of the construction machine (for travel and various operations) circulates.

[0050] As shown in FIG. 1, the oil circulation circuit 3 includes an oil supply system 31 that pumps up oil O stored in an oil pan OP and supplies it toward the case internal space S, and an oil drain system 32 that drains the oil O from the case internal space S toward the oil pan OP.

[0051] The oil supply system 31 is provided with a strainer 31b, an oil pump (pump) 31c, and an oil temperature gauge 31d, in that order from the upstream side of the oil piping 31a in the flow direction of the oil O. When the oil pump 31c is operated, the oil O is pumped up from the oil pan OP and supplied to the case internal space S. The oil pump 31c is equipped with an electric motor M and is configured as a variable pump that varies the discharge pressure of the oil O in accordance with changes in the rotation speed of the electric motor M. The strainer 31b filters the oil O pumped up from the oil pan OP. The oil temperature gauge 31d detects the temperature of the oil O discharged from the oil pump 31c.

[0052] The oil pump 31c and oil temperature gauge 31d in this oil supply system 31 are connected to a controller 5 that adjusts the pressure (oil pressure) of the oil O in the case 21. That is, information on the temperature of the oil O detected by the oil temperature gauge 31d is input to the controller 5, and a hydraulic pressure command signal is sent from the controller 5 to the oil pump 31c. The hydraulic pressure command signal sent to this oil pump 31c will be described later.

[0053] The oil drain system 32 is provided with a relief valve 32b and a cooling device 32c in this order from the upstream side in the flow direction of the oil O in an oil pipe 32a.

[0054] The relief valve 32b is configured, for example, as a well-known direct-acting relief valve, and the relief pressure can be adjusted by varying the biasing force of a built-in spring, thereby making it possible to adjust the pressure (oil pressure) in the case internal space S. The controller 5 outputs an oil pressure adjustment command signal for adjusting the relief pressure in the relief valve 32b, thereby adjusting the relief pressure and thereby adjusting the pressure in the case internal space S.

[0055] -Control of all-solid-state battery housing system- Next, a description will be given of the control of the all-solid-state battery housing system 1 configured as described above. This control includes startup control of the battery module 24 and pressure control of the case internal space S (case internal pressure setting control). These will be described in order below.

[0056] (Battery module startup control) Generally, an all-solid-state battery becomes capable of discharging when it reaches a predetermined startup temperature (for example, 25°C). For this reason, if the outside air temperature at the construction machine installation site is low and the temperature of the battery module 24 has not yet reached the startup temperature, it is desirable to rapidly raise the temperature of the battery module 24 to the startup temperature. Also, all-solid-state batteries have a temperature (for example, 40°C; hereinafter, this may also be referred to as the optimal temperature) at which they exhibit maximum performance, and even if the temperature of the all-solid-state battery exceeds the startup temperature, if it has not yet reached the optimal temperature, it is desirable to raise the temperature to this optimal temperature.

[0057] In view of this, in this embodiment, when the battery module 24 is below the startup temperature, or when the battery module 24 has reached the startup temperature but is still below the optimum temperature, startup control is performed to raise the temperature of the battery module 24. The principle of this startup control is to utilize heat generated by energy conversion (conversion of pressure energy to thermal energy) accompanying the pressure reduction of the oil O in the relief valve 32b. FIG. 7 is a schematic diagram for explaining the principle of raising the temperature of the oil O. As shown in FIG. 7, the oil O flowing out from the all-solid-state battery pack 2 flows into the relief valve 32b. The relief valve 32b is provided with a pressure reduction section 32d having a narrowed flow path for adjusting the internal pressure of the case 21, and a needle 32f is provided that is biased in a direction to close the pressure reduction section 32d by the biasing force of a spring 32e. As the pressure of the oil O is reduced in the pressure reduction section 32d, pressure energy is converted into thermal energy, and the oil O is raised in temperature. This heated oil O is temporarily collected in the oil pan OP, and then pumped up by the oil pump 31c and supplied to the all-solid-state battery pack 2 (supplied to the case internal space S). That is, the heated oil O comes into contact with the battery module 24, and can raise the temperature of the battery module 24.

[0058] 8 is a flowchart showing the procedure for controlling the startup of the battery module 24. Here, a case will be described in which the startup temperature of the battery module 24 is set to 25°C and the optimum temperature of the battery module 24 is set to 40°C.

[0059] For example, when the start switch of the construction machine is turned on, startup control is initiated for the battery module 24. When startup control for the battery module 24 is initiated, first, in step ST1, the temperature of the battery module 24 is detected by the cell thermometer 24e.

[0060] Then, in step ST2, it is determined whether or not the detected temperature Tb of the battery module 24 is 25° C. or less.

[0061] If the temperature Tb of the battery module 24 is 25°C or lower and the determination in step ST2 is YES, the process proceeds to step ST3, where the oil pump 31c is started and the discharge pressure is set to 100 MPa by the hydraulic pressure command signal. Meanwhile, the pressure of the oil O reduced by the relief valve 32b is set to 20 MPa by the hydraulic pressure adjustment command signal. In other words, the pressure of the oil O is significantly reduced from 100 MPa to 20 MPa by the relief valve 32b. Therefore, the temperature rise of the oil O per unit time due to this pressure reduction also becomes rapid, resulting in a state in which the temperature of the battery module 24 is rapidly increased. This operation corresponds to the operation in the present invention when the temperature of the all-solid-state battery at the time of a charge / discharge request is lower than the startup temperature range. In this case, discharge becomes possible when the temperature Tb of the battery module 24 reaches 25°C, and the construction machine becomes operational.

[0062] In step ST4, it is determined whether the temperature of the battery module 24 has exceeded 40° C. The temperature increase operation by decompression described above continues until the temperature of the battery module 24 exceeds 40° C. If the temperature of the battery module 24 has exceeded 40° C. and the determination in step ST4 is YES, the startup control of the battery module 24 is terminated.

[0063] When the battery module 24 is in a discharged state, the battery module 24 itself may generate heat, causing the temperature to exceed 40°C. Therefore, on the condition that the temperature of the battery module 24 exceeds 40°C, after the startup control of the battery module 24 is completed, the cooling device 32c is started and cools the oil O circulating in the oil circulation circuit 3, thereby maintaining the temperature of the battery module 24 at around 40°C.

[0064] On the other hand, if the temperature of the battery module 24 exceeds 25°C and the result of step ST2 is NO, the process proceeds to step ST5, where it is determined whether the temperature of the battery module 24 at the time when the startup control of the battery module 24 is initiated exceeds 25°C and is equal to or lower than 40°C.

[0065] If the temperature of the battery module 24 is above 25°C and below 40°C and the determination in step ST5 is YES, the process proceeds to step ST6, where the oil pump 31c is started and the discharge pressure is set to 50 MPa by the hydraulic pressure command signal. Meanwhile, the pressure of the oil O reduced by the relief valve 32b by the hydraulic pressure adjustment command signal is set to 20 MPa, as described above. That is, the pressure of the oil O is reduced from 50 MPa to 20 MPa by the relief valve 32b. Therefore, the temperature of the oil O increases per unit time in association with this pressure reduction. This operation corresponds to the operation in the present invention when the temperature of the all-solid-state battery at the time of a charge / discharge request is within the startup temperature range but lower than the optimal temperature range (optimal temperature range within the startup temperature range). The temperature increase gradient in this case is gentler than when the temperature of the battery module 24 is below 25°C. This is because the battery module 24 is already above 25°C and therefore ready for startup.

[0066] In step ST7, similarly to step ST4 described above, it is determined whether the temperature of the battery module 24 exceeds 40° C. The temperature raising operation by decompression described above continues until the temperature of the battery module 24 exceeds 40° C. Then, if the temperature of the battery module 24 exceeds 40° C. and the determination in step ST7 is YES, the startup control of the battery module is terminated.

[0067] Even in this case, after the startup control of the battery module 24 is completed, the cooling device 32c is started up and cools the battery module 24, thereby maintaining the temperature of the battery module 24 at around 40°C.

[0068] If the temperature of the battery module 24 exceeds 40°C when the startup control of the battery module 24 is initiated and the determination in step ST5 is NO, the process ends without performing the temperature increase operation by decompression described above. In this case, the cooling device 32c is started at approximately the same time as the start switch of the construction machine is turned ON, and the battery module 24 is cooled, thereby maintaining the temperature of the battery module 24 at around 40°C.

[0069] (Case internal pressure setting control) According to the all-solid-state battery housing system 1 according to this embodiment, the battery module 24 is sealed inside the case 21, and pressure can be applied uniformly from all directions to the battery module 24 by utilizing the pressure of the oil O filled inside the case 21. This makes it possible to form a good interface between the electrode material and the solid electrolyte of the all-solid-state battery, making it possible to suppress a decrease in battery capacity and a decrease in output characteristics and life characteristics.

[0070] In this case, there is an optimum value for the pressure (pressure applied evenly from all directions) to be applied to the battery module 24. Furthermore, the thickness of a cell of an all-solid-state battery changes with charging and discharging. FIG. 9 is a diagram illustrating an example of the characteristics of changes in cell thickness depending on the cell voltage (voltage between electrodes) and the number of cycles (number of times charge and discharge are repeated). As shown in FIG. 9, the thickness of a cell of an all-solid-state battery increases as the voltage increases with charging. Furthermore, the thickness of a cell at a high voltage and at a low voltage also changes depending on the number of charge and discharge cycles (degree of cell deterioration due to repeated charge and discharge). Specifically, the thickness at a high voltage tends to decrease as the number of charge and discharge cycles increases, and similarly, the thickness at a low voltage also tends to decrease as the number of charge and discharge cycles increases. Furthermore, the difference between the thickness at a high voltage and the thickness at a low voltage tends to decrease as the number of charge and discharge cycles increases.

[0071] In this embodiment, the target value of the internal pressure of the case 21 is changed in accordance with such changes in the cell thickness of the all-solid-state battery. Specifically, in a situation where the cell thickness of the all-solid-state battery is increasing, the pressure inside the cell is increasing. In view of this, the target value of the internal pressure of the case 21 is set low in such a situation to prevent the pressure inside the cell from becoming too high. On the other hand, in a situation where the cell thickness of the all-solid-state battery is decreasing, the pressure inside the cell is decreasing. In such a situation, the target value of the internal pressure of the case 21 is set high to increase the pressure inside the cell to a certain extent, thereby ensuring adhesion at the interface between the electrode material and the solid electrolyte and allowing the all-solid-state battery to fully exhibit its performance.

[0072] Fig. 10 is a diagram showing an example of a case internal pressure setting table. In Fig. 10, the setting range of the case internal pressure set in accordance with voltage changes when the number of cycles is 100 (setting range of the target value of the internal pressure) is set as setting region 1. The setting range of the case internal pressure set in accordance with voltage changes when the number of cycles is 300 (setting range of the target value of the internal pressure) is set as setting region 2. The setting range of the case internal pressure set in accordance with voltage changes when the number of cycles is 500 (setting range of the target value of the internal pressure) is set as setting region 3.

[0073] As can be seen from Fig. 10, the thicker the cell of the solid-state battery is (the fewer the number of cycles, or the higher the voltage even with the same number of cycles), the lower the target value of the internal pressure of the case 21 is set. In other words, the thinner the cell of the solid-state battery is (the more the number of cycles, or the lower the voltage even with the same number of cycles), the higher the target value of the internal pressure of the case 21 is set. The values ​​shown in Fig. 10 are merely examples and are not limited to these.

[0074] 11 is a flowchart showing the procedure for controlling the setting of the case internal pressure, which is carried out after the start-up control of the battery module 24 described above is completed.

[0075] When the case internal pressure setting control is started, first, in step ST21, information on the current number of charge / discharge cycles in the battery module 24 is acquired. This number of charge / discharge cycles is stored by incrementing a count (count of the number of charge / discharge cycles) in a memory provided in the controller 5 every time charging / discharging is performed on the battery module 24. In step ST21, this information is read from the memory.

[0076] Then, in step ST22, it is determined whether the acquired number of cycles N is 100 or less.

[0077] If the number of cycles N is 100 or less and the determination in step ST22 is YES, the process proceeds to step ST23, where the case internal pressure (the set pressure of the case internal space S) is set within the range of setting region 1 in the case internal pressure setting table shown in Fig. 10. In other words, the discharge pressure of the oil pump 31c and the degree of pressure reduction of the relief valve 32b are controlled with the case internal pressure corresponding to the voltage of the battery module 24 in setting region 1 as the target value.

[0078] If the number of cycles N exceeds 100 and the determination in step ST22 is NO, the process proceeds to step ST24, where it is determined whether the acquired number of cycles N exceeds 100 and is less than 300.

[0079] If the number of cycles N is greater than 100 and less than 300, and therefore the answer is YES in step ST24, the process proceeds to step ST25, where the case internal pressure (the set pressure of the case internal space S) is set by linearly interpolating between setting region 1 and setting region 2 in the case internal pressure setting table shown in Figure 10.

[0080] If the determination in step ST24 is NO, the process proceeds to step ST26, where it is determined whether the acquired number of cycles N is 300 or not.

[0081] If the number of cycles N is 300 and the determination in step ST26 is YES, the process proceeds to step ST27, where the case internal pressure is set within the range of setting region 2 in the case internal pressure setting table shown in Fig. 10. In other words, the discharge pressure of the oil pump 31c and the degree of pressure reduction of the relief valve 32b are controlled with the case internal pressure corresponding to the voltage of the battery module 24 in setting region 2 as the target value.

[0082] If the determination in step ST26 is NO, the process proceeds to step ST28, where it is determined whether the acquired number of cycles N is greater than 300 and less than 500.

[0083] If the number of cycles N is greater than 300 and less than 500, and therefore the answer is YES in step ST28, the process proceeds to step ST29, where the case internal pressure is set by linearly interpolating between setting region 2 and setting region 3 in the case internal pressure setting table shown in Figure 10.

[0084] If the determination in step ST28 is NO, the process proceeds to step ST30, where the case internal pressure is set within the range of setting region 3 in the case internal pressure setting table shown in Fig. 10. In other words, the discharge pressure of oil pump 31c and the degree of pressure reduction of relief valve 32b are controlled with the case internal pressure corresponding to the voltage of battery module 24 in setting region 3 as the target value.

[0085] By the above operation, it becomes possible to appropriately set the target value of the internal pressure of the case 21.

[0086] -Effects of the embodiment- As described above, in this embodiment, the case 21 enclosing the battery module 24 is configured to be filled with oil O at a predetermined pressure. This makes it possible to apply a predetermined pressure uniformly to the battery module 24 from all directions, allowing the battery module 24 to fully exhibit its performance. It also makes it possible to avoid damage to the battery module 24 due to locally high stress.

[0087] Furthermore, in this embodiment, by changing the degree of pressure reduction by the relief valve 32b, it is possible to relatively easily adjust the pressure of the oil O filled inside the case 21. Therefore, it is possible to easily adjust the pressure applied to the battery module 24 to an optimum pressure that allows the battery module 24 to fully exhibit its performance.

[0088] Furthermore, in this embodiment, when the temperature of the battery module 24 is below 40°C (optimum temperature), heat is generated by energy conversion accompanying the pressure reduction of the oil O in the relief valve 32b, raising the temperature of the oil O and also raising the temperature of the battery module 24. This allows the battery module 24 to quickly demonstrate its high performance.

[0089] In this embodiment, the edge of opening 25a provided in case 21 is sealed by fitting rubber connector 26 into opening 25a. This prevents oil O from leaking from opening 25a of case 21 while enabling power from battery module 24 to be supplied to an electrical load.

[0090] -Other embodiments- The present invention is not limited to the above-described embodiments, and all modifications and applications within the scope of the claims and equivalents thereto are possible.

[0091] For example, in the above embodiment, hydraulic oil for construction machinery is used as the liquid filled inside the case 21. The present invention is not limited to this, and a liquid dedicated to the all-solid-state battery housing system 1 may be used. In addition, the type of liquid is not limited to oil O, and various liquids can be applied.

[0092] In the above embodiment, the inside of the case 21 is filled with oil O at a predetermined pressure while the oil O is circulated through the oil circulation circuit 3. However, the present invention is not limited to this, and a configuration may be adopted in which the oil O at a predetermined pressure is sealed inside the case 21 without including the oil circulation circuit 3 (a configuration in which the oil O does not flow into or out of the case 21).

[0093] In the above embodiment, the temperature of the oil O is increased by reducing the pressure of the oil O using the relief valve 32b. However, the present invention is not limited to this. The oil circulation circuit 3 may be provided with a heater (for example, an electric heater) to increase the temperature of the oil O. [Industrial Applicability]

[0094] The present invention is applicable to an all-solid-state battery housing system that is configured to allow the all-solid-state battery to fully exhibit its performance. [Explanation of symbols]

[0095] 1. All-solid-state battery housing system 21 cases 24 Battery module (all-solid-state battery) 24c Positive side power line 24d Negative power line 25a opening 25b molded part 26 Connectors 26a opening 3 Oil circulation circuit (circulation circuit) 31c Oil pump (pump) 32b Relief valve 4a,4b power line O Oil (liquid)

Claims

1. An all-solid-state battery housing system for housing an all-solid-state battery, a case in which the all-solid-state battery is enclosed; and a liquid filled inside the case at a predetermined pressure.

2. The all-solid-state battery housing system according to claim 1, The all-solid-state battery housing system, wherein a circulation circuit that circulates the liquid between the inside and outside of the case is connected to the case.

3. The all-solid-state battery housing system according to claim 2, the circulation circuit includes a pump for circulating the liquid, and a relief valve for reducing the pressure of the liquid circulating through the circulation circuit.

4. The all-solid-state battery housing system according to claim 3, an all-solid-state battery housing system configured to reduce the pressure of the liquid discharged from the pump by the relief valve on the condition that the temperature of the all-solid-state battery at the time of a request to charge or discharge the all-solid-state battery is equal to or lower than a predetermined temperature.

5. The all-solid-state battery housing system according to claim 4, the all-solid-state battery has a start-up temperature range in which charging and discharging are possible, and an optimal temperature range within the start-up temperature range; an operation of reducing the pressure of the liquid discharged from the pump by the relief valve is performed on the condition that the temperature of the all-solid-state battery at the time of a request to charge or discharge the all-solid-state battery is equal to or lower than the optimum temperature range, an all-solid-state battery housing system configured to increase the degree of pressure reduction by the relief valve when the temperature of the all-solid-state battery at the time of the charge / discharge request is lower than the startup temperature range, compared to when the temperature of the all-solid-state battery at the time of the charge / discharge request is within the startup temperature range and lower than the optimum temperature range.

6. The all-solid-state battery housing system according to claim 2 or 3, an all-solid-state battery housing system, characterized in that the pressure of the liquid filled inside the case is set lower as the inter-electrode voltage during charging and discharging of the all-solid-state battery is higher.

7. The all-solid-state battery housing system according to claim 2 or 3, an all-solid-state battery housing system, characterized in that the pressure of the liquid filled inside the case is set higher as the number of charge / discharge cycles of the all-solid-state battery increases.

8. The all-solid-state battery housing system according to any one of claims 1 to 5, the case has an opening for drawing out a power line connected to the all-solid-state battery to the outside, and a connector that seals an opening edge of the opening is fitted into the opening.

9. The all-solid-state battery housing system according to claim 8, an opening is provided in the connector, a molded portion formed by molding a conductive material is provided in the opening, and a power line connected to the all-solid-state battery and a power line connected to an electrical load that receives power from the all-solid-state battery are each connected to the molded portion.

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