Secondary battery system

Abstract

To warm a secondary battery in a short time with reduced power consumption in such a way as to prevent deterioration of the secondary battery due to high temperature.SOLUTION: A secondary battery system comprises: a secondary battery; a housing portion which houses the secondary battery and is filled with a medium, and has a first inlet and outlet and a second inlet and outlet which communicate with the outside and inside of the housing portion; a circulation flow path which circulates the medium by supplying the medium discharged from the housing portion to the housing portion through the other of the first inlet and outlet and the second inlet and outlet; a heat exchange portion which exchanges heat between the medium circulating through the circulation flow path and outside air; a compression portion arranged between the first inlet and outlet and the heat exchange portion on the circulation flow path; an expansion portion arranged between the second inlet and outlet and the heat exchange portion on the circulation flow path; and a switching portion which switches the flow of the medium circulating through the circulation flow path to a first direction when the secondary battery is being cooled and to a second direction when the secondary battery is being warmed up.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a secondary battery system.

Background Art

[0002] Secondary batteries used as batteries for electric vehicles and the like are known (see, for example, Patent Document 1). In the secondary battery described in Patent Document 1, each of a plurality of battery modules (batteries) is connected to a heat sink via a heat pipe. Inside the heat sink, a cooling water passage through which cooling water cooled by a radiator flows is formed. Therefore, the secondary battery that heats up during charge and discharge is cooled by the heat sink through which cooling water flows inside.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Secondary batteries such as lithium-ion batteries generate heat due to the sum of heat absorption or heat generation accompanying the movement of lithium ions or the like during charge and discharge and heat generation accompanying the internal resistance of the battery and the overvoltage loss at both electrodes. The deterioration of the secondary battery starts at room temperature of about 27 degrees Celsius (°C) or higher, and the recommended operating temperature of the secondary battery is, for example, 5°C to 45°C. In winter or cold regions, charging and discharging of the secondary battery at an outside air temperature of 5°C or lower not only reduces the output and capacity but also may accelerate low-temperature deterioration and shorten the battery life. Therefore, in addition to cooling the secondary battery that heats up during charge and discharge, it is preferable to warm the secondary battery at low temperature. However, Patent Document 1 does not mention warming the secondary battery.

[0005] To suppress the decrease in output and capacity of secondary batteries and low-temperature degradation at low temperatures, a technology using a PTC (Positive Heating Coefficent) heater to heat secondary batteries is known. PTC heaters have the characteristic that their resistance increases as they approach the upper temperature limit, acting as a temperature limiter. Due to this characteristic, when the resistance increases near the upper temperature limit, the amount of power supplied to the PTC heater is restricted, and the heating time of the secondary battery increases. On the other hand, when heating a large battery pack with a small PTC heater, a heating medium is required. Therefore, in addition to the heat capacity of the battery pack, the heat capacity of the medium filled in the battery pack, the connecting pipes, and the circulation pump are also added, increasing the power required to heat the secondary battery. Therefore, there was a challenge to suppress the power required to heat the secondary battery and to heat the secondary battery in a short heating time.

[0006] This invention was made to solve at least some of the problems described above, and aims to warm a secondary battery in a low-power, short-time manner without causing degradation due to high temperatures. [Means for solving the problem]

[0007] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms. A secondary battery system comprising: a secondary battery; a housing for housing the secondary battery and filled with a medium, having a first inlet and a second inlet connecting the outside and inside of the housing; a circulation channel for circulating the medium by supplying the medium discharged from the housing through one of the first inlet and the second inlet to the housing through the other of the first inlet and the second inlet; a heat exchange section disposed on the circulation channel and performing heat exchange between the medium flowing through the circulation channel and the outside air; and a compression section disposed between the first inlet and the heat exchange section on the circulation channel, which compresses the medium discharged from the first inlet and flowing in a first direction and supplies it to the heat exchange section, or compresses the medium that has been heat-exchanged by the heat exchange section and flows in a second direction and supplies it to the first inlet. A secondary battery system comprising: a supply compression section; an expansion section disposed between the second inlet / outlet and the heat exchange section on the circulation channel, which expands the medium that flows in the first direction after heat exchange by the heat exchange section and supplies it to the second inlet / outlet, or expands the medium that is discharged from the second inlet / outlet and flows in the second direction and supplies it to the heat exchange section; a switching section that switches the flow of the medium circulating in the circulation channel to the first direction when the secondary battery is being cooled and to the second direction when the secondary battery is being warmed up; and a cooling section disposed vertically above the housing section, through which the medium can flow, wherein the medium is discharged from the expansion section and supplied to the cooling section when being cooled, discharged from the cooling section and supplied to the second inlet / outlet, and does not circulate to the cooling section when being warmed up. In addition, the present invention can also be realized in the following forms.

[0008] (1) According to one embodiment of the present invention, a secondary battery system is provided. This secondary battery system includes a secondary battery, a housing for housing the secondary battery and filled with a medium, having a first inlet and a second inlet that communicate the outside and inside of the housing, a circulation channel for circulating the medium by supplying the medium discharged from the housing through one of the first inlet and the second inlet to the housing through the other of the first inlet and the second inlet, a heat exchange section disposed on the circulation channel and performing heat exchange between the medium flowing through the circulation channel and the outside air, and a compression section disposed between the first inlet and the heat exchange section on the circulation channel, which compresses the medium discharged from the first inlet and flowing in a first direction. A secondary battery system comprising: a compression unit that supplies the medium to the heat exchange unit, or the medium that flows in a second direction after heat exchange by the heat exchange unit, and compresses it before supplying it to the first inlet / outlet; an expansion unit disposed between the second inlet / outlet and the heat exchange unit on the circulation channel, which expands the medium that flows in a first direction after heat exchange by the heat exchange unit and supplies it to the second inlet / outlet, or expands the medium that is discharged from the second inlet / outlet and flows in a second direction and supplies it to the heat exchange unit; and a switching unit that switches the flow of the medium circulating in the circulation channel to a first direction when the secondary battery is being cooled, and to a second direction when the secondary battery is being warmed up.

[0009] In this configuration, during the cooling of the secondary battery, the medium discharged from the housing flows through the circulation channel in a first direction, circulating in the order of compression, heat exchange, expansion, and housing. The medium discharged from the housing is compressed to high temperature and pressure by the compression section, and then cooled by heat exchange with the outside air in the heat exchange section. After heat exchange, the medium expands to low temperature and low pressure by the expansion section and is supplied back to the housing. The low temperature medium cools the secondary battery housed in the housing. On the other hand, during the warming of the secondary battery, the medium discharged from the housing flows through the circulation channel in a second direction, circulating in the order of expansion, heat exchange, compression, and housing. The medium discharged from the housing expands to low temperature and low pressure by the expansion section, and then heats up by obtaining cooling through heat exchange with the outside air in the heat exchanger. After heat exchange, the medium is compressed to high temperature and high pressure by the compression section and is supplied back to the housing. The high temperature medium warms the secondary battery housed in the housing. In other words, simply by switching the direction of flow of the medium in the circulation channel, the secondary battery is cooled by the medium during cooling and warmed by the medium during warming. Therefore, cooling and warming are performed with low power consumption and in a short time, without causing high-temperature degradation of the secondary battery.

[0010] (2) In the secondary battery system according to the above embodiment, a cooling unit is further provided located vertically above the housing unit and through which the medium can circulate, wherein the medium is discharged from the expansion unit and supplied to the cooling unit during cooling, discharged from the cooling unit and supplied to the second inlet / outlet, and does not need to circulate to the cooling unit during warm-up. In this configuration, during cooling of the secondary battery, the secondary battery is cooled by heat exchange between a low-temperature, low-pressure medium supplied to the cooling section and a medium filled in the housing section. Due to the temperature difference generated during heat exchange, the temperature of the medium filled in the housing section becomes higher than that of the cooling section, thus suppressing further expansion of the secondary battery caused by the pressure difference between the secondary battery, which expands during charging and discharging, and the low-pressure medium in the housing section in which it is housed. On the other hand, during warming up the secondary battery, the secondary battery is efficiently warmed by direct heat exchange between a high-temperature, high-pressure medium supplied to the housing section and the secondary battery housed in the housing section.

[0011] (3) In the secondary battery system according to the above embodiment, the medium may be a fluorocarbon-based medium having a boiling point of -30 degrees Celsius or more and 40 degrees Celsius or less at atmospheric pressure. In this configuration, since the boiling point of the fluorocarbon medium is lower than the temperature of the secondary battery, which becomes hot during charging and discharging, the fluorocarbon medium in the housing evaporates through heat exchange with the secondary battery when the secondary battery is cooled. The evaporated fluorocarbon medium is cooled and condenses through heat exchange with the fluorocarbon medium flowing through the cooling section, moves vertically downward, and evaporates again through heat exchange with the secondary battery. As a result, during cooling, the secondary battery is efficiently cooled by vapor heat transport using the latent heat of vaporization of the fluorocarbon medium in the housing.

[0012] (4) In the secondary battery system according to the above embodiment, the compression section comprises a first compression section and a second compression section disposed downstream of the first compression section in the first direction, and the secondary battery system further comprises an opening / closing section disposed between the first compression section and the second compression section on the circulation path, which opens and closes the flow of the medium between the first compression section and the second compression section, wherein the medium is discharged from the cooling section and supplied to the first compressor before being supplied to the second inlet / outlet, discharged from the first inlet / outlet and supplied to the second compression section before being supplied to the heat exchange section, and the opening / closing section is opened during warm-up, heat is exchanged by the heat exchange section and compressed by the first compression section, then further compressed by the second compression section and supplied to the first inlet / outlet. In this configuration, during the cooling of the secondary battery, a pressurized medium is supplied into the housing by the first compression section. During charging and discharging, the volume of the secondary battery expands as lithium ions, acting as active material, are inserted into the negative and positive electrodes, respectively. The expansion of the secondary battery is suppressed by the pressurized medium supplied into the housing by the first compression section. In this configuration, the compression of the medium by the first compression section and the compression of the medium by the second compression section are adjusted to suppress the expansion of the secondary battery during charging and discharging while simultaneously cooling the secondary battery. Furthermore, during the warming of the secondary battery, the two compression sections, the first and second compression sections, further increase the temperature and pressure of the medium, allowing the secondary battery to warm up rapidly.

[0013] (5) In the secondary battery system according to the above embodiment, the system further comprises: a flow rate acquisition unit for acquiring the flow rate of the liquid medium supplied to the heat exchange unit; a temperature difference acquisition unit for acquiring the temperature difference between the temperature of the heat exchange unit and the temperature of the outside air; and a control unit for controlling the compression of the medium by the compression unit, wherein the heat exchange unit has a fan for blowing outside air onto the medium flowing through the circulation channel, and the control unit may, during warm-up, control the compression of the medium by the compression unit using the flow rate of the medium supplied from the expansion unit to the heat exchange unit, the temperature difference, and the rotation speed of the fan. In this configuration, during the warm-up of the secondary battery, the compression of the medium by the compression unit is controlled using the flow rate of the liquid medium supplied to the heat exchange unit, the temperature difference between the heat exchange unit and the outside air, and the fan speed. The COP (Coefficient of Performance) changes according to the flow rate of the gaseous medium flowing through the circulation channel and the compression of the medium by the compression unit. If the flow rate of the medium supplied to the heat exchange unit is greater than the appropriate amount of cooling energy obtained in the heat exchange unit, the liquid medium that does not contribute to evaporation and condensation will circulate in the circulation channel. As a result, the power required for the compression unit to compress the medium increases due to the two-phase pressure loss in the circulation channel. On the other hand, if the flow rate of the medium supplied to the heat exchange unit is less than the appropriate amount, the amount of heat required for warm-up will be insufficient, and the time required to complete warm-up will be longer. In this configuration, the power consumption of the compression unit is controlled using the capacity of the heat exchange unit derived from the fan speed and temperature difference, and the flow rate of the liquid medium supplied to the heat exchange unit. As a result, the secondary battery is warmed up quickly without reducing the COP.

[0014] (6) In the secondary battery system according to the above embodiment, a heating unit may be further provided, which is located between the expansion unit and the heat exchange unit in the circulation channel and heats the medium during warm-up. In this configuration, during warm-up, the liquid medium heated by the heating unit evaporates, increasing the supply of steam medium to the heat exchange unit. If the supply of steam medium to the heat exchange unit is insufficient and falls below the warm-up heat of the secondary battery, the vapor pressure of the medium in the containment unit decreases due to insufficient steam. If the vapor pressure falls below the battery expansion pressure, the pressure balance is disrupted, and the secondary battery temporarily expands. This may lead to deterioration of the secondary battery and a decrease in battery safety. In this configuration, the supply of gaseous medium increases due to the heating unit, and the vapor pressure of the medium in the containment unit is maintained at a high level. Furthermore, the decrease in heat transfer coefficient due to dry-out, which is a problem with high steam quality, is avoided, and the medium evaporates with a small temperature difference due to the high heat transfer coefficient in the heating unit. In addition, the temperature difference between the wall surface of the heating unit and the fluid medium can be kept small even at high heat flux, so the liquid medium can be evaporated even if the temperature of the wall surface of the heating unit is low.

[0015] (7) In the secondary battery system according to the above embodiment, the system further includes a battery temperature acquisition unit that acquires the temperature of the secondary battery, and the control unit may use the temperature of the secondary battery to control the heating of the medium by the heating unit. In this configuration, the power consumption of the heating unit to heat the medium is controlled according to the temperature of the secondary battery, thereby adjusting the amount of vapor supplied to the heating unit for the medium to evaporate from the liquid. As a result, power equivalent to the amount of vapor that needs to be generated is supplied to the heating unit, thus suppressing the decrease in COP.

[0016] (8) In the secondary battery system according to the above embodiment, the system further includes an ambient temperature acquisition unit for acquiring the ambient temperature, and the control unit may stop the rotation of the fan when the ambient temperature is below the boiling point of the medium at atmospheric pressure during warm-up, and rotate the fan when the ambient temperature is higher than the boiling point and below the target temperature of the secondary battery after warm-up is complete. In this configuration, the fan in the heat exchange unit stops rotating when the ambient temperature is below the boiling point of the fluid. When the ambient temperature is below the boiling point of the fluid, no cooling is obtained from the ambient air by the fan's airflow, and the fluid does not evaporate. Therefore, in this case, the fluid evaporates solely through heating by the heating unit. On the other hand, when the ambient temperature is higher than the boiling point of the fluid, cooling is obtained from the ambient air by the fan's airflow, and the heat pump cycle functions. As a result, the fluid evaporates due to the cooling in addition to the heating by the heating unit, improving the COP.

[0017] Furthermore, the present invention can be realized in various forms, for example, as a secondary battery, a lithium-ion battery, a secondary battery system, a method for controlling a secondary battery, and a system comprising these devices or implementing such methods, a computer program for executing these devices or methods, a server device for distributing such computer programs, and a non-temporary storage medium storing the computer program. [Brief explanation of the drawing]

[0018] [Figure 1]It is a schematic perspective view of a secondary battery system as an embodiment of the present invention. [Figure 2] It is an explanatory diagram of an accommodation part and a cooling part. [Figure 3] It is an explanatory diagram of vapor heat transport of a medium during cooling of a battery cell. [Figure 4] It is a schematic block diagram of a secondary battery system during warm-up of a battery cell. [Figure 5] It is an explanatory diagram of vapor heat transport of a medium during warm-up of a battery cell. [Figure 6] It is an example of a P-h line of a vapor compression refrigeration cycle during warm-up of a battery cell. [Figure 7] It is a schematic block diagram of a secondary battery system of the second embodiment. [Figure 8] It is a flowchart of power control in the second embodiment. [Figure 9] It is an explanatory diagram of changes in COP during warm-up. [Figure 10] It is a schematic block diagram of a secondary battery system of the third embodiment. [Figure 11] It is an explanatory diagram of changes in battery temperature when the medium is heated. [Figure 12] It is an explanatory diagram of changes in vapor pressure when the medium is heated. [Figure 13] It is an explanatory diagram of the output ratio of heat / energy when the medium is heated. [Figure 14] It is an explanatory diagram of the energy ratio when the medium is heated. [Figure 15] It is a schematic block diagram of a secondary battery system of the fourth embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0019] <First Embodiment> Figure 1 is a schematic perspective view of a secondary battery system 100 as one embodiment of the present invention. In this embodiment, the secondary battery system 100 is mounted on a vehicle, and the battery cells 70, which are secondary batteries, function as the power source for the vehicle. In the secondary battery system 100, the battery cells 70, which generate heat during charging and discharging, are cooled by circulating a medium ME that exchanges heat with the outside air. On the other hand, when the battery cells 70 are operated at a low temperature, such as in cold regions, the medium ME is circulated in the opposite direction to when the battery cells 70 are cooled, thereby warming up the battery cells 70.

[0020] As shown in Figure 1, the secondary battery system 100 includes a battery cell 70 (not shown in Figure 1), a housing 10 that houses the battery cell 70, a cooling unit 20 positioned vertically above the housing 10, a circulation channel 50 for circulating the medium ME flowing within the secondary battery system 100, a heat exchange unit 45 for heat exchange between the outside air and the medium ME, a compression unit 30 for compressing the medium ME to high temperature and high pressure, an expansion valve (expansion unit) 40 for expanding the medium ME to low temperature and low pressure, a switching valve (switching unit) 89 and three-way valves 81-84 for switching the connection state of the circulation channel 50, and a control unit 60 for controlling the switching valve 89 and three-way valves 81-84. In Figure 1, the connection state of the circulation channel 50 and the direction of flow of the medium ME are shown by arrows when the battery cell 70 is being cooled by the medium ME during charging and discharging. The direction in which the medium ME flows along the arrows shown in Figure 1 corresponds to the first direction.

[0021] Figure 2 is an explanatory diagram of the housing section 10 and the cooling section 20. Figure 2 shows a schematic perspective view of the housing section 10 and the cooling section 20 when the battery cells 70 are cooled during charging and discharging. In Figure 2, the outlines of the housing section 10 and the cooling section 20 are shown with dashed lines, and multiple battery cells 70 etc. arranged inside the housing section 10 are illustrated. The housing section 10 and the cooling section 20 are separated as separate spaces.

[0022] As shown in Figure 2, the housing section 10 of this embodiment has a rectangular parallelepiped shape. Inside the housing section 10, a plurality of rectangular parallelepiped-shaped battery cells 70 are arranged horizontally at intervals. The battery cells 70 in this embodiment are single lithium-ion battery cells. The housing section 10 is provided with a first inlet / outlet 11 and a second inlet / outlet 12 that connect the inside of the housing section 10 to the outside. The circulation channel 50 circulates the medium ME discharged from the housing section 10 through one of the first inlet / outlet 11 and the second inlet / outlet 12, and supplies the medium ME back into the housing section 10 through the other of the first inlet / outlet 11 and the second inlet / outlet 12, thereby circulating the medium ME within the housing section 10. As a result, the battery cells 70 are cooled or heated via the medium ME.

[0023] The medium ME in this embodiment is a fluorocarbon-based medium having a low boiling point at atmospheric pressure (for example, -30°C to 40°C). The boiling point of medium ME at atmospheric pressure is -29°C. During charging and discharging of the battery cell 70, the pressure inside the housing 10 is controlled to 0.9 MPa by the control unit 60 controlling the compression unit 30.

[0024] As shown in Figure 2, the cooling unit 20 has the shape of a hollow rectangular parallelepiped. The cooling unit 20 is equipped with a third inlet / outlet 21 and a fourth inlet / outlet 22 that communicate the inside of the cooling unit 20 with the outside. The circulation channel 50 circulates the medium ME within the cooling unit 20 by supplying the medium ME discharged from the cooling unit 20 through one of the third inlet / outlet 21 and the fourth inlet / outlet 22 to the cooling unit 20 through the other of the third inlet / outlet 21 and the fourth inlet / outlet 22. In other words, the medium ME can flow within the cooling unit 20. Since the cooling unit 20 is located vertically above the housing unit 10, it can exchange heat with the housing unit 10. As will be described in detail later, when cooling the battery cell 70, a medium ME at a lower temperature than the medium ME circulating inside the housing unit 10 circulates within the cooling unit 20. As a result, the cooling unit 20 cools the battery cell 70 via the medium ME in the housing unit 10.

[0025] The heat exchange unit 45 in this embodiment, shown in Figure 1, is a radiator mounted on a vehicle. The heat exchange unit 45 has a fan FN that rotates to blow outside air into the medium ME flowing through the circulation channel 50. The fan FN rotates to take in outside air and perform heat exchange between the medium ME and the outside air. When the battery cell 70 is being cooled, high-temperature, high-pressure vaporized medium ME is supplied to the heat exchange unit 45 via the circulation channel 50. During cooling, the heat exchange unit 45 functions as a condenser, releasing the heat from the supplied medium ME to the outside air. On the other hand, when the battery cell 70 is being warmed up, low-temperature, low-pressure liquid medium ME is supplied to the heat exchange unit 45 via the circulation channel 50. During warming up, the heat exchange unit 45 functions as an evaporator, heating the supplied medium ME by obtaining cold from the outside air.

[0026] The compression unit 30 comprises two first compressors (first compression units) 31 arranged on the circulation channel 50, and a second compressor (second compression unit) 32 arranged downstream of the first compressors 31 on the circulation channel 50 in the direction in which the cooling medium ME flows as shown in Figure 1. The first compressors 31 and the second compressors 32 compress the medium ME flowing in the circulation channel 50 to high temperature and high pressure. The compression ratio of the medium ME by the first compressors 31 and the second compressors 32 changes according to the power consumption of the first compressors 31 and the second compressors 32, controlled by the control unit 60.

[0027] As shown in Figure 1, the secondary battery system 100 further includes an on-off valve (on-off unit) 85 that opens and closes the connection between the first compressor 31 and the second compressor 32 in the circulation passage 50. The on-off valve 85 is opened and closed by the control unit 60. The on-off valve 85 is closed when the battery cell 70 is cooling and opened when the battery cell 70 is warming up, as will be described later. The expansion valve 40 is located on the circulation passage 50 and expands the medium ME flowing in the circulation passage 50 to a low temperature and low pressure.

[0028] Each of the three-way valves 81 to 84 connects two of three different flow paths within the circulation flow path 50. For example, when cooling the battery cell 70 shown in Figure 1, three-way valve 81 connects the flow path located downstream of the expansion valve 40 to the fourth inlet / outlet 22 of the cooling unit 20 in the direction in which the cooling medium ME flows, but does not connect the flow path that connects three-way valve 82 and three-way valve 81.

[0029] When cooling the battery cell 70, as shown in Figure 1, the three-way valve 82 connects the first compressor 31 to the second inlet / outlet 12 of the housing 10. The three-way valve 83 connects the third inlet / outlet 21 of the cooling unit 20 to the first compressor 31 via the switching valve 89 described later. The three-way valve 84 connects the first inlet / outlet 11 of the housing 10 to the second compressor 32.

[0030] The switching valve 89 connects two of the four different circulation channels in the circulation channel 50, and also connects the remaining two channels. When the battery cell 70 shown in Figure 1 is being cooled, the three-way valve 83 is connected to the first compressor 31, and the second compressor 32 is connected to the heat exchange section 45, along the direction in which the medium ME flows.

[0031] During the cooling of the battery cell 70, the medium ME flows along the direction of the arrows shown in Figure 1. Specifically, the medium ME discharged from the first inlet / outlet 11 of the housing section 10 is compressed to high temperature and pressure (e.g., 50°C) by the second compressor 32 and supplied to the heat exchange section 45, where it dissipates heat and its temperature decreases. The medium ME discharged from the heat exchange section 45 expands to low temperature and pressure (e.g., 20°C) by the expansion valve 40 and is supplied into the cooling section 20 via the fourth inlet / outlet 22 and discharged from the third inlet / outlet 21. The medium ME discharged from the cooling section 20 is compressed to high temperature and pressure by the first compressor 31 and supplied to the housing section 10 via the second inlet / outlet 12. In other words, the medium ME discharged from the heat exchange section 45 expands by the expansion valve 40 and is supplied to the second inlet / outlet 12 of the housing section 10 via the cooling section 20. In this way, the medium ME circulates within the circulation channel 50.

[0032] The control unit 60 controls the state of the medium ME flowing through the circulation channel 50 by controlling the power consumption of the first compressor 31 and the second compressor 32. When the battery cell 70 shown in Figure 1 is being cooled, the control unit 60 controls the power consumption of the first compressor 31 and the second compressor 32 so that the temperature of the medium ME flowing through the heat exchange section 45 becomes 45°C and the temperature of the medium ME supplied to the cooling section 20 becomes 20°C.

[0033] Figure 3 is an explanatory diagram of vapor heat transport of the medium ME during the cooling of the battery cell 70. Figure 3 shows a schematic diagram in which, during charging and discharging of the battery cell 70, the medium ME in the housing 10 evaporates from liquid and the battery cell 70 is cooled by vapor heat transport. Figure 3 shows a schematic cross-sectional view of the vicinity of one battery cell 70 within the housing 10.

[0034] As shown in Figure 3, the housing 10 comprises a tube wall 17 that extends vertically in contact with the battery cell 70, and a porous body 18 that extends vertically in the same way as the tube wall 17, in contact with the tube wall 17. The tube wall 17 is connected to the cooling unit 20 vertically above. The tube wall 17 is made of a metallic material and therefore has high thermal conductivity. The porous body 18 is connected to the cooling unit 20 vertically above, in the same way as the tube wall 17. The porous body 18 is in contact with the opposite side of the tube wall 17 from the side that is not in contact with the battery cell 70. The porous body 18 is made of a metallic porous material. As shown in Figure 3, a space is formed between the two opposing porous bodies 18 through which the medium ME can flow. Since the porous body 18 is made of a porous material, the medium ME can enter into the voids within the porous body 18.

[0035] During charging and discharging, the temperature of the battery cell 70 rises to a temperature higher than the boiling point temperature of 20°C at a pressure of 0.9 MPa in the housing 10. Therefore, the liquid medium ME in the housing 10 rises to 20°C through heat exchange with the battery cell 70 and then evaporates. The evaporated medium ME moves vertically upward within the housing 10 and is cooled and condensed by the 20°C medium ME flowing through the cooling section 20. The condensed liquid medium ME quickly spreads throughout the porous body 18 due to gravity and capillary action. Subsequently, the liquid medium ME in the porous body 18 evaporates again through heat exchange with the battery cell 70 via the tube wall 17. In other words, the medium ME in the housing 10 cools the battery cell 70 using the latent heat of vaporization from repeated condensation and evaporation.

[0036] Figure 4 is a schematic block diagram of the secondary battery system 100 during the warm-up of the battery cell 70. Figure 4 shows the secondary battery system 100 when the battery cell 70 is warmed up using a medium ME when the battery cell 70 is started up, for reasons such as the ambient temperature being low (e.g., below 5°C) and the temperature of the battery cell 70 is lower than the recommended temperature (5°C to 45°C). In Figure 4, as in Figure 1, the direction of flow of the medium ME flowing through the circulation channel 50 is illustrated with arrows. The direction of flow of the medium ME in Figure 4 is opposite to the direction of flow of the medium ME during cooling shown in Figure 1, and corresponds to the second direction. The direction of flow of the medium ME through the circulation channel 50 is switched by the control unit 60.

[0037] As shown in Figure 4, of the four three-way valves 81 to 84, three-way valve 81 connects the expansion valve 40 to three-way valve 82. Three-way valve 82 connects three-way valve 81 to the second inlet / outlet 12 of the housing 10. Three-way valve 83 connects three-way valve 84 to the second compressor 32 via a switching valve 89. Three-way valve 84 connects three-way valve 83 to the first inlet / outlet 11 of the housing 10. The switching valve 89 connects the flow path connected to three-way valve 83 to the flow path connected to the second compressor 32, and also connects the flow path connected to the heat exchange section 45 to the flow path connected to the first compressor 31. When the battery cell 70 is warmed up, the on / off valve 85 opens, and the first compressor 31 and the second compressor 32 are connected in series.

[0038] During the warm-up of the battery cell 70, the medium ME flows along the direction of the arrow shown in Figure 4. Specifically, the medium ME discharged from the second inlet / outlet 12 of the housing 10 expands to a low temperature and low pressure by the expansion valve 40 and is supplied to the heat exchange unit 45, where it is heated by the supply of cold air from the outside. The medium ME discharged from the heat exchange unit 45 is compressed to a high temperature and high pressure by the first compressor 31 and the second compressor 32 and supplied to the first inlet / outlet 11 of the housing 10. During the warm-up in this embodiment, the medium ME is not supplied to the cooling unit 20.

[0039] Figure 5 is an explanatory diagram of the vapor heat transport of the medium ME during the warm-up of the battery cell 70. During the warm-up of the battery cell 70 shown in Figure 5, vapor of the medium ME, which has been changed to high temperature and high pressure (for example, 40°C, 1.02 MPa) by the first compressor 31 and the second compressor 32, is supplied into the containment section 10. The vapor medium ME cools down and condenses due to heat exchange with the battery cell 70. The condensed medium ME moves vertically downward within the porous body 18 and is discharged from the first inlet / outlet 11.

[0040] Figure 6 is an example of a Ph diagram of the vapor compression refrigeration cycle during the warm-up of the battery cell 70. As shown in Figure 6, in this embodiment, the steam medium ME is compressed to 40°C and 1.02 MPa by the power Qw supplied to the first compressor 31 and the second compressor 32. The compressed medium ME is supplied to the containment unit 10, where it exchanges heat with the battery cell 70, warming up the battery cell 70 and causing condensation. Through this heat exchange, heat Qh is transferred from the medium ME to the battery cell 70. The liquid medium ME discharged from the containment unit 10 is converted into steam at -15.6°C and 0.16 MPa by the expansion valve 40. The steam medium ME obtains heat Qc as cooling energy from the 0°C outside air by the heat exchange unit 45, and is then supplied to the first compressor 31 and the second compressor 32.

[0041] As described above, the secondary battery system 100 of this embodiment includes a housing section 10 that houses the battery cell 70 and has a first inlet / outlet 11 and a second inlet / outlet 12, and a control unit 60 that switches the direction of the medium ME flowing in the circulation channel 50. When the battery cell 70 shown in Figure 1 is being cooled, the medium ME discharged from the first inlet / outlet 11 of the housing section 10 is compressed to high temperature and high pressure by the second compressor 32 and supplied to the heat exchange section 45. The medium ME discharged from the heat exchange section 45 expands by the expansion valve 40 and is supplied to the second inlet / outlet 12 of the housing section 10 via the cooling section 20. On the other hand, when the battery cell 70 is being warmed up as shown in Figure 4, the control unit 60 switches the direction of flow in the circulation channel 50 to the opposite of the direction of flow from when the battery cell 70 is being cooled. Therefore, when the battery cell 70 is being warmed up, the medium ME discharged from the second inlet / outlet 12 of the housing section 10 expands to low temperature and low pressure by the expansion valve 40 and is supplied to the heat exchange section 45. The medium ME discharged from the heat exchange section 45 is compressed to high temperature and pressure by the first compressor 31 and the second compressor 32 and supplied to the first inlet / outlet 11 of the housing section 10. That is, in this embodiment, when the battery cell 70 is being cooled, as shown in Figure 1, the medium ME discharged from the housing section 10 circulates through the circulation channel 50 in the order of compression section 30, heat exchange section 45, expansion valve 40, and housing section 10. In this case, the medium ME discharged from the housing section 10 is compressed to high temperature and pressure by the compression section 30, and then cooled by heat exchange with the outside air in the heat exchange section 45. After heat exchange, the medium ME expands to low temperature and low pressure by the expansion valve 40 and is supplied back to the housing section 10. The low temperature medium ME cools the battery cell 70 housed in the housing section 10. On the other hand, when the battery cell 70 is warming up, as shown in Figure 4, the medium ME discharged from the housing 10 circulates through the circulation channel 50 in the order of expansion valve 40, heat exchange section 45, compression section 30, and housing 10. The medium ME discharged from the housing 10 expands to low temperature and low pressure by the expansion valve 40, and then gains heat and rises in temperature through heat exchange with the outside air in the heat exchange section 45. After heat exchange, the medium ME is compressed to high temperature and high pressure by the compression section 30 and supplied back to the housing 10. The high temperature medium ME warms the battery cell 70 housed in the housing 10.In other words, by simply switching the direction in which the medium ME flows within the circulation channel 50, the battery cell 70 is cooled by the medium ME during cooling and warmed up by the medium ME during warm-up. Therefore, cooling and warm-up are performed with low power consumption and in a short time, without causing high-temperature degradation of the battery cell 70.

[0042] Furthermore, the secondary battery system 100 of this embodiment is equipped with a cooling unit 20 located vertically above the housing unit 10, through which the medium ME can flow. When the battery cell 70 shown in Figure 1 is being cooled, the medium ME expands to a low temperature and low pressure by the expansion valve 40, is supplied into the cooling unit 20 via the fourth inlet / outlet 22, is discharged from the third inlet / outlet 21 of the cooling unit 20, and is supplied to the second inlet / outlet 12 of the housing unit 10. On the other hand, when the battery cell 70 is being warmed up as shown in Figure 4, the medium ME is not supplied into the cooling unit 20. In other words, in this embodiment, when the battery cell 70 is being cooled, the battery cell 70 is cooled by heat exchange between the medium ME supplied to the cooling unit 20, which has been reduced to a low temperature and low pressure, and the medium ME filled in the housing unit 10. Due to the temperature difference generated during heat exchange, the temperature of the medium ME filled in the housing 10 becomes higher than that of the cooling unit 20. This suppresses further expansion of the battery cells 70, which expands during charging and discharging, caused by the pressure difference between the low-pressure medium ME in the housing 10 and the battery cells 70 housed within it. On the other hand, during warm-up, the battery cells 70 are efficiently heated by direct heat exchange between the high-temperature, high-pressure medium ME supplied to the housing 10 and the battery cells 70 housed within the housing 10.

[0043] Furthermore, the medium ME in this embodiment is a fluorocarbon-based medium having a low boiling point at atmospheric pressure. In this embodiment, since the boiling point of the fluorocarbon-based medium is lower than the temperature of the battery cell 70, which is heated to a high temperature during charging and discharging, when the battery cell 70 is cooled, the medium ME in the housing 10 evaporates through heat exchange with the battery cell 70. The evaporated medium ME is cooled and condenses through heat exchange with the medium ME flowing through the cooling unit 20, moves vertically downward, and evaporates again through heat exchange with the battery cell 70. As a result, during cooling, the battery cell 70 is efficiently cooled by vapor heat transport using the latent heat of vaporization of the medium ME in the housing 10.

[0044] Furthermore, the compression unit 30 of this embodiment includes a first compressor 31 positioned on the circulation channel 50, and a second compressor 32 positioned downstream of the first compressor 31 on the circulation channel 50 in the direction in which the cooling medium ME flows as shown in Figure 1. The secondary battery system 100 also includes an on-off valve 85 that opens and closes the connection between the first compressor 31 and the second compressor 32 in the circulation channel 50, as shown in Figure 1. The on-off valve 85 is closed when the battery cell 70 is being cooled and opened when the battery cell 70 is being warmed up, as will be described later. When the battery cell 70 is being cooled, the medium ME discharged from the cooling unit 20 is compressed to high temperature and pressure by the first compressor 31 and supplied to the housing unit 10 via the second inlet / outlet 12. When the battery cell 70 is being warmed up, the medium ME discharged from the heat exchange unit 45 is compressed to high temperature and pressure by the first compressor 31 and the second compressor 32 and supplied to the first inlet / outlet 11 of the housing unit 10. In other words, in this embodiment, when the battery cell 70 is being cooled, the medium ME pressurized by the first compressor 31 is supplied into the housing 10. During charging and discharging, the volume of the battery cell 70 expands as lithium ions, acting as active material, are inserted into the negative and positive electrodes, respectively. The expansion of the battery cell 70 is suppressed by the high pressure of the medium ME vapor supplied into the housing 10 by the first compressor 31. In this embodiment, the expansion of the battery cell 70 during charging and discharging is suppressed and the battery cell 70 is cooled by adjusting the compression of the medium ME by the first compressor 31 and the second compressor 32. Furthermore, when the battery cell 70 is being warmed up, the medium ME is further heated and pressurized by the two compressors, the first compressor 31 and the second compressor 32, to rapidly warm up the battery cell 70.

[0045] <Second Embodiment> Figure 7 is a schematic block diagram of the secondary battery system 100a of the second embodiment. The secondary battery system 100a of the second embodiment differs from the secondary battery system 100 of the first embodiment in that, during the warm-up of the battery cell 70, the compression of the liquid medium ME by the compression unit 30 is controlled using detected values ​​such as the flow rate of the liquid medium ME supplied to the heat exchange unit 45. Note that the schematic block diagram in Figure 7 shows a simplified representation of the secondary battery system 100a during warm-up. Therefore, the two three-way valves 82 and 84, the switching valve 89, and the on / off valve 85 are omitted from the illustration, and the circulation flow path 50 is shown in a simplified form. Note that in Figure 7, the first compressor 31 and the second compressor 32 are shown together as the compression unit 30.

[0046] As shown in Figure 7, the secondary battery system 100a of the second embodiment includes, in addition to the configuration of the secondary battery system 100 of the first embodiment, a flow sensor (flow rate acquisition unit) 91 positioned between the expansion valve 40 and the heat exchange unit 45, a first temperature sensor 92 for detecting the temperature of the heat exchange unit 45, a second temperature sensor (outside air temperature acquisition unit) 93 for detecting the temperature of the outside air, a third temperature sensor (battery temperature acquisition unit) 94 for detecting the battery temperature Tb,t of the battery cells 70 housed in the housing unit 10, and a rotation speed sensor 95 for detecting the rotation speed N of the fan FN. The flow sensor 91 detects the liquid flow rate FRm of the medium ME supplied from the expansion valve 40 to the heat exchange unit 45.

[0047] The control unit 60a acquires the detected values ​​from each sensor. Using the detected values, the control unit 60a calculates the appropriate flow rate FRc of the medium ME discharged from the heat exchange unit 45 so that the steam quality of the medium ME becomes 1. The appropriate flow rate FRc is expressed by the following equation (1).

number

[0048] The heat transfer coefficient K is calculated by a function f, which is shown in equation (2) below, using the rotational speed N of the fan FN and the liquid flow rate FRm of the liquid medium ME detected by the flow sensor 91. In this embodiment, the function f is mapped from the relationship between the rotational speed N and the liquid flow rate FRm, which has been measured in advance.

number

[0049] The control unit 60a calculates the temperature difference ΔTe by subtracting the temperature of the heat exchange unit 45 detected by the first temperature sensor 92 from the temperature of the outside air detected by the second temperature sensor 93. The control unit 60a, the first temperature sensor 92, and the second temperature sensor 93 correspond to the temperature difference acquisition unit. The latent heat of vaporization ΔH of the medium ME is determined by the type of medium ME.

[0050] The control unit 60a controls the power consumption of the compression unit 30 so that the difference between the liquid flow rate FRm of the liquid medium ME detected by the flow sensor 91 and the calculated appropriate flow rate FRc is smaller than the absolute value of the threshold ε (>0). The change in power consumption ΔW is expressed as the absolute value of a function g corresponding to the difference ΔFR between the liquid flow rate FRm of the liquid medium ME and the calculated appropriate flow rate FRc, as shown in equation (3) below.

[0051]

number

[0052] The control unit 60a continues to warm up the battery cell 70 by circulating the medium ME until the battery temperature Tb,t detected by the third temperature sensor 94 is equal to or greater than the target temperature Tb for warm-up completion.

[0053] Figure 8 is a flowchart of the power control for supplying power to the compression section 30 during the warm-up of the battery cell 70 in the second embodiment. In the power control flow shown in Figure 8, first, the control unit 60a controls the three-way valves 81-84, the switching valve 89, and the on-off valve 85 to set the flow path connection to become the warm-up circulation flow path 50 shown in Figure 4 (simplified Figure 7) (step S1). The control unit 60a drives the fan FN (step S2). In this embodiment, the fan FN is rotated at its maximum rotational speed.

[0054] The control unit 60a drives the compression unit 30 by supplying a preset initial power W to the compression unit 30 (step S3). The control unit 60a acquires detected values ​​from each sensor (step S4). The control unit 60a calculates the temperature difference ΔTe, the heat transfer coefficient K, the appropriate flow rate FRc, and the change in power consumption ΔW using the acquired sensor values ​​and formulas (1) to (3) (step S5).

[0055] The control unit 60a determines whether the difference ΔFR between the liquid flow rate FRm of the liquid medium ME and the calculated appropriate flow rate FRc is greater than the threshold ε (step S6). If it is determined that the difference ΔFR is greater than the threshold ε (step S6: YES), the control unit 60a calculates the power by subtracting the change amount ΔW from the current power consumption of the compression unit 30 (step S7). The control unit 60a then supplies the power obtained by subtracting the change amount ΔW to the compression unit 30 (step S3) and proceeds with the processing from step S4 onward.

[0056] If it is determined that the difference ΔFR is less than or equal to the threshold ε (step S6: NO), the control unit 60a determines whether the difference ΔFR is less than -ε (step S8). If it is determined that the difference ΔFR is less than -ε (step S8: YES), the control unit 60a calculates the power by adding the change amount ΔW to the current power consumption of the compression unit 30 (step S9). The control unit 60a then supplies the power with the change amount ΔW added to it to the compression unit 30 (step S3) and performs the processing from step S4 onwards.

[0057] If it is determined that the difference ΔFR is -ε or greater (step S8: NO), the control unit 60a determines whether the temperature Tb,t of the battery cell 70 detected by the third temperature sensor 94 is less than the target temperature Tb (step S10). If it is determined that the temperature Tb,t of the battery cell 70 is less than the target temperature (step SS10: YES), the control unit 60a performs the processing from step S4 onward without changing the power consumption of the compression unit 30 at this time. If it is determined that the temperature Tb,t of the battery cell 70 is equal to or greater than the target temperature (step SS10: NO), the control unit 60a terminates the warm-up of the battery cell 70.

[0058] The COP (Coefficient of Performance) during warm-up is improved by controlling the steam quality of the medium ME discharged from the heat exchange section 45 to 1 during warm-up. Figure 9 is an explanatory diagram of the change in COP during warm-up. Figure 9 shows the Ph diagram of the steam compression refrigeration cycle when the power consumption of the compression section 30 changes. The COP in this embodiment is expressed as the value obtained by dividing the amount of heat Q used for warm-up shown in Figure 9 by the power W supplied to the compression section 30.

[0059] In Figure 9, the refrigeration cycle shown as ph1 (solid line) changes to the refrigeration cycle shown as ph2 (dotted line) when the flow rate of the medium ME circulating in the circulation channel 50 increases. As the flow rate of the medium ME increases, the power W supplied to the compression section 30 increases, and the amount of heat Q used to warm up the battery cells 70 also increases. On the other hand, as the flow rate of the circulating medium ME decreases, the refrigeration cycle changes from the ph1 shown as ph1 to the ph3 (dashed line). As the flow rate of the medium ME decreases, the power W supplied to the compression section 30 decreases, and the amount of heat Q used to warm up the battery cells 70 also decreases.

[0060] As described above, the control unit 60a of the second embodiment controls the compression of the medium ME by the compression unit 30 when the battery cell 70 is warmed up, using the liquid flow rate FRm of the liquid medium ME detected by the flow sensor 91, the temperature difference ΔTe between the ambient air temperature and the temperature of the heat exchange unit 45, and the rotational speed N of the fan FN of the heat exchange unit 45. In this embodiment, the COP changes according to the flow rate of the vapor medium ME flowing through the circulation channel 50 and the compression of the medium ME by the compression unit 30. If the flow rate of the medium ME supplied to the heat exchange unit 45 is greater than the appropriate amount of cold energy obtained from the ambient air in the heat exchange unit 45, the COP will increase for the reasons mentioned above, and liquid medium ME that does not contribute to the evaporation and condensation of the medium ME will circulate in the circulation channel 50. As a result, the power W required for the compression unit 30 to compress the medium ME increases due to the two-phase pressure loss in the circulation channel 50. On the other hand, if the liquid flow rate FRm of the medium ME supplied to the heat exchange unit 45 is less than the appropriate flow rate FRc, the amount of heat required for warming up will be insufficient, and the time required to complete warming up will be longer. In this embodiment, the power W supplied to the compression unit 30 is controlled using the capacity of the heat exchange unit 45, which is derived from the rotational speed N of the fan FN and the temperature difference ΔTe, and the liquid flow rate FRm of the liquid medium ME supplied to the heat exchange unit 45. As a result, the battery cell 70 is warmed up quickly without reducing the COP.

[0061] <Third Embodiment> Figure 10 is a schematic block diagram of the secondary battery system 100b of the third embodiment. The secondary battery system 100b of the third embodiment differs significantly from the secondary battery system 100 of the first embodiment in that the medium ME supplied to the heat exchange section 45 during warm-up is heated by the heating section 48 before being supplied. Figure 7 shows the circulation channel 50 of the secondary battery system 100b during warm-up and the direction of flow of the medium ME, represented by arrows.

[0062] The secondary battery system 100b of the third embodiment further includes a heating unit 48 positioned between the expansion valve 40 and the heat exchange unit 45 on the circulation channel 50. The heating unit 48 is a heater that receives power under the control of the control unit 60b and heats the medium ME flowing inside it. The control unit 60b controls the heating of the medium ME by the heating unit 48 using the battery temperature Tb,t of the battery cell 70 detected by the third temperature sensor 94. In this embodiment, when the ambient temperature is zero, the control unit 60b sets the temperature of the inner wall of the heating unit 48 that exchanges heat with the circulating medium ME to 5°C. The control unit 60b heats the medium ME with the heating unit 48 until the battery temperature Tb,t reaches 25°C or higher.

[0063] Figures 11 to 14 are explanatory diagrams illustrating the effect of heating the medium ME by the heating unit 48. In Figure 11, the change in battery temperature Tb,t when the medium ME is heated by the heating unit 48 is shown by the solid line Ct1. Also in Figure 11, the change in battery temperature Tb,t when heating by the heating unit 48 is not performed is shown by the dashed line Ct2. When the medium ME was heated by the heating unit 48, it took 4.5 minutes for the battery temperature Tb,t to reach the target temperature Tb of 25°C. On the other hand, when the medium ME was not heated by the heating unit 48, it took 6.8 minutes for the battery temperature Tb,t to reach 25°C. In other words, heating the medium ME by the heating unit 48 allowed the battery cell 70 to warm up more quickly.

[0064] Figure 12 shows the change in vapor pressure of the medium ME supplied to the heat exchange section 45. When the medium ME is heated by the heating section 48, the change in vapor pressure of the medium ME supplied to the containment section 10 is shown by Ps11 (thick solid line), and the change in vapor pressure of the medium ME supplied to the heat exchange section 45 is shown by Ps12 (thin solid line). Also in Figure 12, when the medium ME is not heated by the heating section 48, the change in vapor pressure of the medium ME supplied to the containment section 10 is shown by Ps21 (thick dashed line), and the change in vapor pressure of the medium ME supplied to the heat exchange section 45 is shown by Ps22 (thin dashed line). Furthermore, in Figure 12, the change in the flow rate of the medium ME, including both vapor and liquid, is shown by FL (thick dashed line). As shown in Figure 12, heating of the medium ME by the heating section 48 restores the vapor pressure Ps21 in the unheated case to a higher pressure level compared to the vapor pressure Ps11 in the heated case.

[0065] Figure 13 shows the changes in the heat-energy output ratio of the heating unit 48, the heat exchange unit 45, and the first and second compressors 31 and 32. In Figure 13, when the combined average output of the first and second compressors 31 and 32 is set to -1 (consumption), the change in the output ratio of the first and second compressors 31 and 32 is shown by Q30 (dotted line). The change in the output ratio of the heating unit 48 is shown by Q48 (double-dotted line). The change in the output ratio of the heat exchange unit 45 is shown by Q45 (dashed line). The change in the combined output ratio of the heating unit 48, the heat exchange unit 45, and the first and second compressors 31 and 32 is shown by Qs (solid line).

[0066] Figure 14 shows the ratio of power consumption of the heating unit 48, the heat exchange unit 45, and the first and second compressors 31 and 22 until the battery cell 70 is fully warmed up. Figure 14 also shows the ratio of power consumption of the heat exchange unit 45 and the first and second compressors 31 when the medium ME is not heated by the heating unit 48. Figure 14 shows the power consumption ratio when the warming heat of the battery cell 70 is set to 1. As shown in Figure 14, the heating of the medium ME by the heating unit 48 significantly reduces the power consumption of the heat exchange unit 45.

[0067] As described above, the secondary battery system 100b of the third embodiment further includes a heating unit 48 positioned between the expansion valve 40 and the heat exchange unit 45 on the circulation channel 50, which heats the medium ME supplied to the heat exchange unit 45. Therefore, in this embodiment, during warm-up, the liquid medium ME heated by the heating unit 48 evaporates, increasing the amount of steam medium ME supplied to the heat exchange unit 45. If the amount of steam medium ME supplied to the heat exchange unit 45 is insufficient and falls below the warm-up heat of the battery cell 70, the vapor pressure of the medium ME in the containment unit 10 decreases due to insufficient steam. If the vapor pressure falls below the battery expansion pressure, the pressure balance is disrupted, and the battery cell 70 temporarily expands. This may lead to deterioration of the secondary battery and a decrease in battery safety. In this embodiment, the heating unit 48 increases the supply amount of steam medium ME, and the vapor pressure of the medium ME in the containment unit 10 is maintained at a high level. Furthermore, to avoid the decrease in heat transfer coefficient caused by dry-out, which is a problem with high steam quality, the heating unit 48 evaporates the medium ME with a small temperature difference due to its high heat transfer coefficient. In addition, since the temperature difference between the inner wall of the heating unit 48 and the medium fluid can be kept small even with a high heat flux, the liquid medium ME can be evaporated even if the temperature of the inner wall of the heating unit 48 is low.

[0068] Furthermore, the control unit 60b of the third embodiment controls the heating of the medium ME by the heating unit 48 using the battery temperature Tb,t of the battery cell 70 detected by the third temperature sensor 94. In other words, in this embodiment, the power consumption of the heating unit 48 to heat the medium ME is controlled according to the battery temperature Tb,t of the battery cell 70, so the amount of vapor supplied for the medium ME to evaporate from the liquid in the heating unit 48 is adjusted. As a result, power equivalent to the amount of vapor that needs to be generated is supplied to the heating unit 48, so the decrease in COP is suppressed.

[0069] <Fourth Embodiment> Figure 15 is a schematic block diagram of the secondary battery system 100c of the fourth embodiment. The secondary battery system 100c of the fourth embodiment differs from the secondary battery system 100b of the third embodiment in that, when the ambient temperature is lower than the boiling point of the medium ME at atmospheric pressure, the heating unit 48 heats the medium ME without driving the fan FN of the heat exchange unit 45.

[0070] As shown in Figure 15, the secondary battery system 100c of the fourth embodiment further includes a first temperature sensor 92 for detecting the temperature of the heat exchange section 45 and a second temperature sensor 93 for detecting the ambient temperature, compared to the secondary battery system 100b of the third embodiment. When the battery cell 70 is warmed up, the control unit 60c obtains the temperature of the medium ME flowing through the heat exchange section 45 from the first temperature sensor 92 and the ambient temperature from the second temperature sensor 93. In the example shown in Figure 15, the ambient temperature is -30°C, which is lower than the boiling point of the medium ME at atmospheric pressure, which is -29°C. In this embodiment, if the ambient temperature is below the boiling point of the medium ME at atmospheric pressure, the control unit 60c heats the medium ME circulating in the circulation channel 50 by heating only the heating section 48 without driving the fan FN. If the ambient temperature is higher than the boiling point of the medium ME at atmospheric pressure, the control unit 60c drives the fan FN while controlling the power consumption of the compression unit 30 using the detected values, similar to the second embodiment.

[0071] As described above, the control unit 60c of the fourth embodiment does not drive the fan FN and does not execute the heat pump cycle when the ambient temperature is below the boiling point of the medium ME at atmospheric pressure. When the ambient temperature is below the boiling point of the medium ME, no cooling is obtained from the ambient air by the fan FN, and the medium ME does not evaporate. Therefore, in this case, the medium ME evaporates by heating by the heating unit 48 alone. On the other hand, when the ambient temperature is higher than the boiling point of the medium ME, cooling is obtained from the ambient air by the fan FN, and the heat pump cycle functions. As a result, the medium ME evaporates due to the cooling in addition to the heating by the heating unit 48, and the COP is improved.

[0072] <Modified examples of embodiments> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit. For example, the following modifications are possible. Furthermore, in the above embodiments, some of the configurations implemented by hardware may be replaced with software, and conversely, some of the configurations implemented by software may be replaced with hardware.

[0073] <Example 1> In the embodiments of the first to fourth embodiments described above, examples of secondary battery systems 100, 100a, 100b, and 100c were explained. However, the secondary battery system includes a heat exchange section 45, a compression section 30, and an expansion valve 40, and can be modified within a range that allows for cooling and warming of the battery cells 70 by switching the direction in which the medium ME flows in the circulation channel 50. For example, the four three-way valves 81-84, the switching valve 89, and the on / off valve 85 are configured to change a part of the flow path when the direction in which the medium ME flows is switched, and can be modified within a range that allows for cooling and warming of the battery cells 70 by switching the direction in which the medium ME flows.

[0074] In the first embodiment described above, the cooling unit 20 was positioned vertically above the housing unit 10, but the secondary battery system 100 does not necessarily have to include the cooling unit 20. In this case, the secondary battery system 100 may supply a medium ME, which has been cooled to a low temperature and low pressure by the expansion valve 40, into the housing unit 10 when cooling the battery cells 70 in the housing unit 10. Furthermore, in the secondary battery system 100 of the first embodiment, the medium flowing through the cooling unit 20 may be different from the medium ME of the fluorocarbon-based medium circulating in the housing unit 10. For example, the medium flowing through the cooling unit 20 does not necessarily have to be connected to the circulation channel 50. In this case, by switching the direction of flow of the medium ME of the fluorocarbon-based medium, cooling and warming of the battery cells 70 in the housing unit 10 can be performed, and the refrigerant flowing through the cooling unit 20 may function as a complement to the cooling of the medium ME when cooling the battery cells 70.

[0075] The medium ME flowing through the circulation channel 50 does not necessarily have to be a fluorocarbon-based medium having a boiling point within the recommended operating temperature range for the battery at atmospheric pressure; for example, it may be carbon dioxide. In order to transport vapor heat using the latent heat of vaporization, it is preferable that the medium ME is a fluorocarbon-based medium having a boiling point of -30°C to 40°C at atmospheric pressure.

[0076] In the first embodiment described above, the compression unit 30 was composed of two compressors, a first compressor 31 and a second compressor 32, but it may also be composed of a single compressor. The compression unit 30 can be deformed to the extent that it supplies the compressed medium ME to the heat exchange unit 45 when the battery cell 70 is being cooled, and supplies the compressed medium ME into the housing unit 10 when the battery cell 70 is being warmed up. Furthermore, although an expansion valve 40 was given as an example of an expansion unit that expands the medium ME flowing in the circulation channel 50, it can be deformed to the extent that it is a device capable of expanding the medium ME.

[0077] As an example of the heat exchange unit 45, a radiator mounted on a vehicle has been described. However, the heat exchange unit 45 can be deformed within a range that allows it to release heat to the outside air when cooling the battery cell 70 and to gain heat from the outside air when warming up the battery cell 70. The first inlet / outlet 11 and the second inlet / outlet 12 in the first embodiment described above are the same inlet / outlet, that is, the housing unit 10 may have only one inlet / outlet that communicates with the outside. In this case, the supply of the medium ME to the housing unit 10 and the discharge of the medium ME from the housing unit 10 may be performed alternately with a time difference.

[0078] <Modification 2> The secondary battery systems 100, 100a, 100b, and 100c may have other configurations. For example, the secondary battery system 100a of the second embodiment may be equipped with a pressure sensor for measuring the pressure inside the housing 10. In this case, the control unit 60a may acquire the pressure inside the housing 10 measured by the pressure sensor and control the power consumption of the compression unit 30 within a range where the pressure inside the housing 10 is below a threshold. This control controls the flow rate of the medium ME without circulating the medium ME, which does not contribute to evaporation and condensation, in the circulation channel 50, and without causing the battery cell 70 to exceed the upper limit temperature by the internal pressure of the housing 10 being above the threshold. As a result, even in environments with different ambient temperatures, the battery cell 70 can be warmed up in a short time while maintaining a high COP.

[0079] In the second embodiment, in the process of step S3 shown in Figure 8, a preset initial power W was supplied to the compression unit 30, but the initial power W is variable. For example, the initial power may be calculated from detected values ​​such as the ambient temperature using a map or function. The difference ΔTe between the ambient temperature and the temperature of the heat exchange unit 45 was calculated as the difference between the detected value of the first temperature sensor 92 and the detected value of the second temperature sensor 93, but the temperature difference ΔTe may be obtained directly.

[0080] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0081] The present invention can also be realized in the following forms. [Application Example 1] A secondary battery system, Rechargeable batteries and A housing section that houses the aforementioned secondary battery and is filled with a medium, the housing section having a first entrance and a second entrance that connect the outside and inside of the housing section, A circulation channel for circulating the medium by supplying the medium discharged from the containment through one of the first inlet / outlet and the second inlet / outlet to the containment through the other of the first inlet / outlet and the second inlet / outlet, A heat exchange unit is arranged on the aforementioned circulation channel and performs heat exchange between the medium flowing through the circulation channel and the outside air, A compression unit disposed between the first inlet / outlet and the heat exchange unit on the circulation flow path, the compression unit compresses the medium discharged from the first inlet / outlet and flowing in a first direction and supplies it to the heat exchange unit, or compresses the medium that has been heat-exchanged by the heat exchange unit and flows in a second direction and supplies it to the first inlet / outlet, An expansion section disposed between the second inlet / outlet and the heat exchange section on the circulation flow path, the expansion section expands the medium that flows in the first direction after heat exchange by the heat exchange section and supplies it to the second inlet / outlet, or expands the medium that is discharged from the second inlet / outlet and flows in the second direction and supplies it to the heat exchange section, A switching unit that switches the flow of the medium circulating in the circulation channel to the first direction when the secondary battery is being cooled, and to the second direction when the secondary battery is being warmed up, A secondary battery system equipped with this feature. [Application Example 2] The secondary battery system described in Application Example 1, further, A cooling unit is provided which is positioned vertically above the aforementioned housing and through which the medium can circulate. The aforementioned medium is During the aforementioned cooling, the material is discharged from the expansion section and supplied to the cooling section, and the material is discharged from the cooling section and supplied to the second inlet / outlet. A secondary battery system in which, during the warm-up period, the battery does not circulate to the cooling unit. [Application Example 3] A secondary battery system as described in Application Example 1 or Application Example 2, The aforementioned medium is a fluorocarbon-based medium having a boiling point of -30 degrees Celsius or higher and 40 degrees Celsius or lower at atmospheric pressure, in a secondary battery system. [Application Example 4] A secondary battery system described in any one of Application Examples 1 to 3, The compression section comprises a first compression section and a second compression section located downstream of the first compression section in the first direction. The aforementioned secondary battery system further, Displaced between the first compression section and the second compression section on the circulation path, the circulating flow path includes an opening / closing section that opens and closes the flow of the medium between the first compression section and the second compression section, The aforementioned medium is During the cooling process, the connection opening / closing section is closed, the material is discharged from the cooling section and supplied to the first compression section, then supplied to the second inlet / outlet, discharged from the first inlet / outlet and supplied to the second compression section, then supplied to the heat exchange section. A secondary battery system in which, during warm-up, the opening / closing section is opened, heat is exchanged by the heat exchange section, the battery is compressed by the first compression section, and then further compressed by the second compression section before being supplied to the first inlet / outlet. [Application Example 5] A secondary battery system according to any one of claims 1 to 4, further comprising: A flow rate acquisition unit that acquires the flow rate of the liquid medium supplied to the heat exchange unit, A temperature difference acquisition unit acquires the temperature difference between the temperature of the heat exchange unit and the temperature of the outside air. A control unit that controls the compression of the medium by the compression unit, Equipped with, The heat exchange section has a fan that blows outside air onto the medium flowing through the circulation channel. A secondary battery system in which the control unit controls the compression of the medium by the compression unit during warm-up using the flow rate of the medium supplied from the expansion unit to the heat exchange unit, the temperature difference, and the rotation speed of the fan. [Application Example 6] A secondary battery system described in any one of Application Examples 1 to 5, further comprising: A secondary battery system comprising a heating unit disposed between the expansion unit and the heat exchange unit in the circulation channel, which heats the medium during warm-up. [Application Example 7] A secondary battery system described in any one of Application Examples 1 to 6, further comprising: The system includes a battery temperature acquisition unit that acquires the temperature of the secondary battery, The control unit controls the heating of the medium by the heating unit using the temperature of the secondary battery, in a secondary battery system. [Application Example 8] A secondary battery system described in any one of Application Examples 1 to 7, further comprising: It is equipped with an outside air temperature acquisition unit that acquires the temperature of the outside air, The control unit, during the warm-up period, When the ambient temperature is below the boiling point of the medium at atmospheric pressure, the fan is stopped. A secondary battery system that rotates the fan when the ambient temperature is higher than the boiling point and below the target temperature of the secondary battery after warm-up is complete. [Explanation of Symbols]

[0082] 10...Detention Unit 11...1st entrance / exit 12…Second entrance / exit 17…Pipe wall 18…Porous material 20...Cooling section 21...Third entrance / exit 22…4th entrance / exit 30... Compression section 31…First compressor (first compression section) 32…Second compressor (second compression section) 40…Expansion valve (expansion part) 45...Heat exchange section 48...Heating part 50…Circulation channel 60, 60a, 60b, 60c... Control unit (temperature difference acquisition unit) 70... Battery cell (rechargeable battery) 81-84... Three-way valve 85... Shut-off valve (shut-off mechanism) 89…Diverter valve (switching part) 91…Flow sensor (flow rate acquisition unit) 92...First temperature sensor 93...Second temperature sensor (outside air temperature acquisition unit) 94...Third temperature sensor (battery temperature acquisition unit) 95... Rotation speed sensor 100, 100a, 100b, 100c… Secondary battery systems FN...fan ME…Medium Tb,t…Battery temperature Tb…Target temperature ΔTe…Temperature difference

Claims

1. A secondary battery system, Rechargeable batteries and A housing section containing the aforementioned secondary battery and filled with a medium, the housing section having a first entrance and a second entrance that connect the outside and inside of the housing section, A circulation channel that circulates the medium by supplying the medium discharged from the containment through one of the first inlet / outlet and the second inlet / outlet to the containment through the other of the first inlet / outlet and the second inlet / outlet, A heat exchange unit is arranged on the aforementioned circulation channel and performs heat exchange between the medium flowing through the circulation channel and the outside air, A compression unit disposed between the first inlet / outlet and the heat exchange unit on the circulation flow path, the compression unit compresses the medium discharged from the first inlet / outlet and flowing in a first direction and supplies it to the heat exchange unit, or compresses the medium that has been heat-exchanged by the heat exchange unit and flows in a second direction and supplies it to the first inlet / outlet, An expansion unit disposed between the second inlet / outlet and the heat exchange unit on the circulation channel, the expansion unit expands the medium that flows in the first direction after heat exchange by the heat exchange unit and supplies it to the second inlet / outlet, or expands the medium that is discharged from the second inlet / outlet and flows in the second direction and supplies it to the heat exchange unit, A switching unit that switches the flow of the medium circulating in the circulation channel to the first direction when the secondary battery is being cooled, and to the second direction when the secondary battery is being warmed up, A cooling unit is positioned vertically above the aforementioned housing and through which the medium can circulate; Equipped with, The aforementioned medium is During the aforementioned cooling, the material is discharged from the expansion section and supplied to the cooling section, and the material is discharged from the cooling section and supplied to the second inlet / outlet. A secondary battery system in which, during the warm-up period, the battery does not circulate to the cooling unit.

2. A secondary battery system according to claim 1, The aforementioned medium is a fluorocarbon-based medium having a boiling point of -30 degrees Celsius or higher and 40 degrees Celsius or lower at atmospheric pressure, in a secondary battery system.

3. A secondary battery system according to claim 1 or claim 2, The compression section comprises a first compression section and a second compression section arranged downstream of the first compression section in the first direction. The aforementioned secondary battery system further, Displaced between the first compression section and the second compression section on the circulation path, the circulation path includes an opening / closing section that opens and closes the flow of the medium between the first compression section and the second compression section, The aforementioned medium is During the aforementioned cooling, the opening / closing section is closed, the material is discharged from the cooling section and supplied to the first compression section, then supplied to the second inlet / outlet, discharged from the first inlet / outlet and supplied to the second compression section, then supplied to the heat exchange section. A secondary battery system in which, during warm-up, the opening / closing section is opened, heat is exchanged by the heat exchange section, the battery is compressed by the first compression section, and then further compressed by the second compression section before being supplied to the first inlet / outlet.

4. A secondary battery system according to claim 1, further, A flow rate acquisition unit that acquires the flow rate of the liquid medium supplied to the heat exchange unit, A temperature difference acquisition unit acquires the temperature difference between the temperature of the heat exchange unit and the temperature of the outside air. A control unit that controls the compression of the medium by the compression unit, Equipped with, The heat exchange section has a fan that blows outside air onto the medium flowing through the circulation channel. A secondary battery system in which the control unit controls the compression of the medium by the compression unit during warm-up using the flow rate of the medium supplied from the expansion unit to the heat exchange unit, the temperature difference, and the rotation speed of the fan.

5. The secondary battery system according to claim 4, further, A secondary battery system comprising a heating unit disposed between the expansion unit and the heat exchange unit in the circulation channel, which heats the medium during warm-up.

6. The secondary battery system according to claim 5, further, The system includes a battery temperature acquisition unit that acquires the temperature of the secondary battery, The control unit controls the heating of the medium by the heating unit using the temperature of the secondary battery, in a secondary battery system.

7. A secondary battery system according to claim 5 or claim 6, further comprising: It is equipped with an outside air temperature acquisition unit that acquires the temperature of the outside air, The control unit, during the warm-up period, When the ambient temperature is below the boiling point of the medium at atmospheric pressure, the fan is stopped. A secondary battery system that rotates the fan when the ambient temperature is higher than the boiling point and below the target temperature of the secondary battery after warm-up is complete.

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