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 technology]

[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. A cooling water passage is formed in the heat sink, through which coolant cooled by a radiator flows. Therefore, the secondary battery, which heats up during charging and discharging, is cooled by the heat sink through which coolant flows. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-204151 Summary of the Invention [Problem to be solved by the invention]

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

[0005] In order to suppress the decrease in output and capacity of secondary batteries at low temperatures and their degradation at low temperatures, a technology is known in which a PTC (Positive Heating Coefficient) heater is used to heat the secondary battery. The PTC heater has a feature that the resistance value increases as the temperature approaches the upper limit, and acts as a temperature limiter function. Due to this feature, when the resistance value increases near the upper limit temperature, the amount of power input to the PTC heater is restricted, and the heating time of the secondary battery increases. On the other hand, when a large battery pack is heated with a small PTC heater, a heating medium must be used. Therefore, in addition to the thermal capacity of the battery pack, the thermal capacity of the medium filled in the battery pack, the connecting pipes, and the circulation pump are also added, so the power required to heat the secondary battery increases. Therefore, there was a problem of suppressing the power required to heat the secondary battery and heating the secondary battery in a short heating time.

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to warm up a secondary battery in a short time while saving power, so as to prevent deterioration due to high temperatures. [Means for solving the problem]

[0007] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0008] (1) According to one aspect of the present invention, a secondary battery system is provided. The secondary battery system includes a secondary battery, a storage unit that stores the secondary battery and is filled with a medium, the storage unit having a first inlet and a second inlet that communicate with an outside and an inside of the storage unit, a circulation flow path that circulates the medium by supplying the medium discharged from the storage unit via one of the first inlet and the second inlet to the storage unit via the other of the first inlet and the second inlet, a heat exchange unit that is disposed on the circulation flow path and exchanges heat between the medium flowing through the circulation flow path and outside air, and a compression unit that is disposed on the circulation flow path between the first inlet and the heat exchange unit and compresses the medium discharged from the first inlet and flowing in a first direction to compress the medium. a compression unit that supplies the medium to the heat exchange unit or compresses the medium flowing in the second direction after heat exchange by the heat exchange unit and supplies it to the first inlet / outlet; an expansion unit arranged on the circulation flow path between the second inlet / outlet and the heat exchange unit, the expansion unit expanding the medium flowing in the first direction after heat exchange by the heat exchange unit and supplying it to the second inlet / outlet, or expanding the medium discharged from the second inlet / outlet and flowing in the second direction and supplying it to the heat exchange unit; and a switching unit that switches the flow of the medium circulating through the circulation flow path to the first direction when cooling the secondary battery and to the second direction when warming up the secondary battery.

[0009] According to this configuration, when the secondary battery is cooled, the medium discharged from the storage unit flows in the circulation flow path along the first direction and circulates in the order of the compression unit, heat exchange unit, expansion unit, and storage unit. The medium discharged from the storage unit is compressed to high temperature and high pressure by the compression unit, and then dissipates heat and is cooled by heat exchange with the outside air in the heat exchange unit. The medium after heat exchange is expanded to low temperature and low pressure by the expansion unit and is supplied to the storage unit again. The secondary battery stored in the storage unit is cooled by the low temperature medium. On the other hand, when the secondary battery is warmed up, the medium discharged from the storage unit flows in the circulation flow path along the second direction and circulates in the order of the expansion unit, heat exchange unit, compression unit, and storage unit. The medium discharged from the storage unit is expanded to low temperature and low pressure by the expansion unit, and then obtains cold heat by heat exchange with the outside air in the heat exchanger and is heated. The medium after heat exchange is compressed to high temperature and high pressure by the compression unit and is supplied to the storage unit again. The secondary battery stored in the storage unit is warmed by the high temperature medium. In other words, by simply switching the flow direction of the medium in the circulation flow path, the medium cools the secondary battery during cooling and warms the secondary battery during warming. Therefore, cooling and warming are performed in a short time with low power consumption so that the secondary battery does not deteriorate due to high temperature.

[0010] (2) The secondary battery system of the above aspect may further include a cooling section disposed vertically above the storage section and through which the medium can flow, and during the cooling process, the medium is discharged from the expansion section and supplied to the cooling section, and discharged from the cooling section and supplied to the second inlet / outlet, and during the warming process, the medium does not have to circulate through the cooling section. According to this configuration, when the secondary battery is cooled, the secondary battery is cooled by heat exchange between the low-temperature, low-pressure medium supplied to the cooling section and the 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 is higher than that of the cooling section, so that further expansion of the secondary battery caused by the pressure difference between the low-pressure medium in the housing section in which the secondary battery, which expands during charging and discharging, is housed can be suppressed. On the other hand, when the secondary battery is warmed up, the secondary battery is efficiently warmed by direct heat exchange between the 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 of the above aspect, the medium may be a fluorocarbon-based medium having a boiling point of -30° C. or more and 40° C. or less at atmospheric pressure. According to 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 storage unit evaporates due to heat exchange with the secondary battery when the secondary battery is cooled. The evaporated fluorocarbon medium is cooled and condensed by heat exchange with the fluorocarbon medium flowing in the cooling unit, moves vertically downward, and evaporates again due to heat exchange with the secondary battery. As a result, when cooling, the secondary battery is efficiently cooled by vapor heat transport using the latent heat of evaporation of the fluorocarbon medium in the storage unit.

[0012] (4) In the secondary battery system of the above aspect, the compression unit includes a first compression unit and a second compression unit arranged downstream of the first compression unit along the first direction, and the secondary battery system further includes an opening / closing unit arranged between the first compression unit and the second compression unit on the circulation flow path and opening and closing the flow of the medium between the first compression unit and the second compression unit, wherein the opening / closing unit is closed during the cooling, the medium is discharged from the cooling unit and supplied to the first compressor, and then supplied to the second inlet / outlet, the medium is discharged from the first inlet / outlet, supplied to the second compression unit, and then supplied to the heat exchange unit, and during the warming-up, the opening / closing unit is opened, the medium is heat exchanged by the heat exchange unit and compressed by the first compression unit, and then further compressed by the second compression unit and supplied to the first inlet / outlet. According to this configuration, when the secondary battery is cooled, the medium pressurized by the first compression unit is supplied into the storage unit. When the secondary battery is charged and discharged, lithium ions as active materials are inserted into the negative electrode and the positive electrode, respectively, and the volume of the secondary battery expands. The gas medium supplied into the storage unit by the first compression unit is pressurized, and the pressurized medium suppresses the expansion of the secondary battery. In this configuration, the compression of the medium by the first compression unit and the compression of the medium by the second compression unit are adjusted, so that the secondary battery can be cooled while suppressing the expansion of the secondary battery during charging and discharging. Furthermore, when the secondary battery is warmed up, the two compression units, the first compression unit and the second compression unit, further increase the temperature and pressure of the medium to quickly warm up the secondary battery.

[0013] (5) The secondary battery system of the above aspect may further include a flow rate acquisition unit that acquires a flow rate of the liquid medium supplied to the heat exchange unit, a temperature difference acquisition unit that acquires a temperature difference between the temperature of the heat exchange unit and an outside air temperature, and a control unit that controls compression of the medium by the compression unit, wherein the heat exchange unit has a fan that blows outside air to the medium flowing through the circulation flow path, and the control unit may control 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. According to this configuration, when the secondary battery is warmed up, 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 rotation speed of the fan. The COP (Coefficient of Performance) changes depending on the flow rate of the gas medium flowing in the circulation flow path 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 cold heat obtained in the heat exchange unit, the liquid medium that does not contribute to evaporation and condensation circulates in the circulation flow path. This increases the power required for the compression unit to compress the medium due to the two-phase pressure loss in the circulation flow path. 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 warming up is insufficient, and the time required to complete warming up is extended. In this configuration, the power consumption of the compression unit is controlled using the capacity of the heat exchange unit derived from the rotation speed and temperature difference of the fan and the flow rate of the liquid medium supplied to the heat exchange unit. As a result, the secondary battery is quickly warmed up without decreasing the COP.

[0014] (6) The secondary battery system of the above aspect may further include a heating section that is disposed on the circulation flow path between the expansion section and the heat exchange section and heats the medium during the warm-up. According to this configuration, the liquid medium heated by the heating unit evaporates during warm-up, and the supply amount of the vapor medium supplied to the heat exchange unit increases. If the supply amount of the vapor medium supplied to the heat exchange unit is small and falls below the warm-up heat amount of the secondary battery, the vapor pressure of the medium in the storage unit decreases due to a lack of vapor. If the vapor pressure falls below the battery expansion pressure, the pressure balance is lost and the secondary battery temporarily enters an expanded state. As a result, there is a risk of causing deterioration of the secondary battery and a decrease in battery safety. In this configuration, the supply amount of the gas medium is increased by the heating unit, and the vapor pressure of the medium in the storage unit is maintained high. In addition, a decrease in the heat transfer coefficient due to dry-out, which is a problem with high vapor quality, is avoided, and the medium evaporates in the heating unit with a small temperature difference due to the high heat transfer coefficient. In addition, since the temperature difference between the wall surface of the heating unit and the medium fluid can be made small even with a high heat flux, the liquid medium can be evaporated even if the temperature of the wall surface of the heating unit is low.

[0015] (7) The secondary battery system of the above aspect may further include a battery temperature acquisition unit that acquires a temperature of the secondary battery, and the control unit may use the temperature of the secondary battery to control heating of the medium by the heating unit. According to this configuration, the power consumption by the heating unit to heat the medium is controlled according to the temperature of the secondary battery, and the amount of vapor supply of the medium evaporated from the liquid in the heating unit is adjusted. Therefore, the power equivalent to the amount of vapor supply that needs to be generated is input to the heating unit, and the decrease in COP is suppressed.

[0016] (8) In the secondary battery system of the above aspect, the secondary battery system may further include an outside air temperature acquisition unit that acquires the temperature of the outside air, and the control unit may stop rotation of the fan when the temperature of the outside air is equal to or lower than the boiling point of the medium at atmospheric pressure during the warm-up, and may rotate the fan when the temperature of the outside air is higher than the boiling point and equal to or lower than a target temperature of the secondary battery after the warm-up is completed. According to this configuration, when the temperature of the outside air is equal to or lower than the boiling point of the medium, the fan of the heat exchange unit stops rotating. When the temperature of the outside air is equal to or lower than the boiling point of the medium, the cold energy from the outside air is not obtained by the blowing of the fan, and the medium does not evaporate. Therefore, in this case, the medium evaporates only by heating by the heating unit. On the other hand, when the temperature of the outside air is higher than the boiling point of the medium, the cold energy from the outside air is obtained by the blowing of the fan, and the heat pump cycle functions. As a result, the medium evaporates due to the cold energy in addition to the heating by the heating unit, improving the COP.

[0017] The present invention can be realized in various forms, for example, in the form of a secondary battery, a lithium ion battery, a secondary battery system, a control method for a secondary battery, a system including these devices or implementing these methods, a computer program for executing these devices or methods, a server device for distributing this computer program, a non-transitory storage medium on which a computer program is stored, etc. [Brief description of the drawings]

[0018] [Figure 1]1 is a schematic perspective view of a secondary battery system according to an embodiment of the present invention; [Diagram 2] FIG. 4 is an explanatory diagram of a storage section and a cooling section. [Diagram 3] FIG. 4 is an explanatory diagram of vapor heat transport of a medium when cooling a battery cell. [Figure 4] 4 is a schematic block diagram of the secondary battery system when warming up the battery cells. FIG. [Diagram 5] FIG. 4 is an explanatory diagram of vapor heat transport of a medium during warm-up of a battery cell. [Figure 6] This is an example of the Ph line of a vapor compression refrigeration cycle when a battery cell is warming up. [Figure 7] FIG. 11 is a schematic block diagram of a secondary battery system according to a second embodiment. [Figure 8] 10 is a flowchart of power control in the second embodiment. [Figure 9] FIG. 4 is a graph showing a change in COP during warm-up. [Figure 10] FIG. 11 is a schematic block diagram of a secondary battery system according to a third embodiment. [Figure 11] FIG. 4 is an explanatory diagram of a change in battery temperature when a medium is heated. [Figure 12] FIG. 4 is an explanatory diagram of a change in vapor pressure when a medium is heated. [Figure 13] FIG. 4 is a diagram illustrating the heat / energy output ratio when a medium is heated. [Figure 14] FIG. 13 is an explanatory diagram of an energy ratio when a medium is heated. [Figure 15] FIG. 11 is a schematic block diagram of a secondary battery system according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] First Embodiment 1 is a schematic perspective view of a secondary battery system 100 according to one embodiment of the present invention. The secondary battery system 100 according to this embodiment is mounted on a vehicle, and a battery cell 70, which is a secondary battery, functions as a power source for the vehicle. In the secondary battery system 100, a medium ME that exchanges heat with the outside air is circulated to cool the battery cell 70, which generates heat during charging and discharging. On the other hand, when the battery cell 70 is operated in a low temperature state in a cold region or the like, the medium ME is circulated in the opposite direction to that for cooling the battery cell 70, thereby warming up the battery cell 70.

[0020] As shown in FIG. 1, the secondary battery system 100 includes a battery cell 70 (not shown in FIG. 1), a storage unit 10 that stores the battery cell 70, a cooling unit 20 that is arranged vertically above the storage unit 10, a circulation flow path 50 that circulates the medium ME flowing in the secondary battery system 100, a heat exchange unit 45 that exchanges heat between the outside air and the medium ME, a compression unit 30 that compresses the medium ME to a high temperature and high pressure, an expansion valve (expansion unit) 40 that expands the medium ME to a low temperature and low pressure, a switching valve (switching unit) 89 and three-way valves 81 to 84 that switch the connection state of the circulation flow path 50, and a control unit 60 that controls the switching valve 89 and the three-way valves 81 to 84. Note that FIG. 1 shows the connection state of the circulation flow path 50 when the battery cell 70 is cooled by the medium ME during charging and discharging of the battery cell 70, and the flow direction of the medium ME by an arrow. The flow direction of the medium ME along the arrow shown in FIG. 1 corresponds to the first direction.

[0021] Fig. 2 is an explanatory diagram of the storage section 10 and the cooling section 20. Fig. 2 shows a schematic perspective view of the storage section 10 and the cooling section 20 when cooling the battery cell 70 during charging and discharging of the battery cell 70. In Fig. 2, the outlines of the storage section 10 and the cooling section 20 are shown by dashed lines, and a plurality of battery cells 70 and the like arranged in the storage section 10 are shown. The storage section 10 and the cooling section 20 are separated as separate spaces.

[0022] As shown in FIG. 2, the storage unit 10 of this embodiment has a rectangular parallelepiped shape. In the storage unit 10, a plurality of rectangular parallelepiped battery cells 70 are arranged side by side along the horizontal direction at intervals. The battery cells 70 of this embodiment are single cells of lithium ion batteries. The storage unit 10 has a first inlet 11 and a second inlet 12 that communicate the inside of the storage unit 10 with the outside. The circulation flow path 50 circulates the medium ME in the storage unit 10 by supplying the medium ME discharged from the storage unit 10 through one of the first inlet 11 and the second inlet 12 to the storage unit 10 through the other of the first inlet 11 and the second inlet 12. Therefore, the battery cells 70 are cooled or heated through the medium ME.

[0023] The medium ME of this embodiment is a fluorocarbon-based medium having a low boiling point (for example, −30° C. or higher and 40° C. or lower) at atmospheric pressure. The boiling point of the medium ME at atmospheric pressure is −29° C. When the battery cell 70 is charged or discharged, the pressure inside the storage section 10 is controlled to 0.9 MPa by the control section 60 controlling the compression section 30.

[0024] As shown in FIG. 2, the cooling unit 20 has a hollow rectangular parallelepiped shape. The cooling unit 20 includes a third inlet 21 and a fourth inlet 22 that communicate between the inside of the cooling unit 20 and the outside. The circulation flow path 50 supplies the medium ME discharged from the cooling unit 20 through one of the third inlet 21 and the fourth inlet 22 to the cooling unit 20 through the other of the third inlet 21 and the fourth inlet 22, thereby circulating the medium ME within the cooling unit 20. That is, the medium ME can flow within the cooling unit 20. The cooling unit 20 is disposed vertically above the storage unit 10, and therefore can exchange heat with the storage unit 10. Although details will be described later, when cooling the battery cells 70, a medium ME that is lower in temperature than the medium ME circulating within the storage unit 10 circulates within the cooling unit 20. As a result, the cooling unit 20 cools the battery cells 70 via the medium ME within the storage unit 10.

[0025] The heat exchanger 45 of the present embodiment shown in FIG. 1 is a radiator mounted on a vehicle. The heat exchanger 45 has a fan FN that rotates to blow outside air onto the medium ME flowing in the circulation flow path 50. The fan FN rotates to take in outside air and exchanges heat between the medium ME and the outside air. When cooling the battery cell 70, a high-temperature, high-pressure vapor medium ME is supplied to the heat exchanger 45 via the circulation flow path 50. The heat exchanger 45 functions as a condenser during cooling and dissipates heat from the supplied medium ME to the outside air. On the other hand, when warming up the battery cell 70, a low-temperature, low-pressure liquid medium ME is supplied to the heat exchanger 45 via the circulation flow path 50. The heat exchanger 45 functions as an evaporator during warming up and heats the supplied medium ME by obtaining cold energy from the outside air.

[0026] The compression section 30 includes two first compressors (first compression sections) 31 arranged on the circulation flow path 50, and a second compressor (second compression section) 32 arranged downstream of the first compressors 31 on the circulation flow path 50 along the direction in which the medium ME flows during cooling as shown in Fig. 1. The first compressors 31 and the second compressors 32 compress the medium ME flowing through the circulation flow path 50 to a high temperature and high pressure. The compression rate 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 under the control of the control section 60.

[0027] 1, the secondary battery system 100 further includes an on-off valve (on-off unit) 85 that opens and closes the connection of the circulation flow path 50 between the first compressor 31 and the second compressor 32. The on-off valve 85 opens and closes under the control of the control unit 60. The on-off valve 85 is closed when the battery cells 70 are being cooled, and is opened when the battery cells 70 are being warmed up, which will be described later. The expansion valve 40 is disposed on the circulation flow path 50, and expands the medium ME flowing through the circulation flow path 50 to a low temperature and low pressure.

[0028] Each of the three-way valves 81-84 connects two of the three different flow paths of the circulation flow path 50. For example, when cooling the battery cells 70 shown in FIG. 1, the three-way valve 81 connects a 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 medium ME flows during cooling, and does not connect the flow path connecting the three-way valve 82 and the three-way valve 81.

[0029] 1, when cooling the battery cells 70, the three-way valve 82 connects the first compressor 31 to the second inlet / outlet 12 of the storage unit 10. The three-way valve 83 connects the third inlet / outlet 21 of the cooling unit 20 to the first compressor 31 via a switching valve 89 described below. The three-way valve 84 connects the first inlet / outlet 11 of the storage unit 10 to the second compressor 32.

[0030] The switching valve 89 connects two of the four different flow paths in the circulation flow path 50, and also connects the remaining two flow paths. When cooling the battery cells 70 shown in Fig. 1, the three-way valve 83 and the first compressor 31 are connected along the direction in which the medium ME flows, and the second compressor 32 and the heat exchanger 45 are connected along the direction in which the medium ME flows.

[0031] When the battery cell 70 is cooled, the medium ME flows along the direction of the arrow shown in FIG. 1. Specifically, the medium ME discharged from the first inlet / outlet 11 of the storage unit 10 is compressed to high temperature and high pressure (for example, 50°C) by the second compressor 32 and supplied to the heat exchange unit 45, where the heat is released by the heat exchange unit 45 to lower the temperature. The medium ME discharged from the heat exchange unit 45 is expanded to low temperature and low pressure (for example, 20°C) by the expansion valve 40, supplied into the cooling unit 20 via the fourth inlet / outlet 22, and discharged from the third inlet / outlet 21. The medium ME discharged from the cooling unit 20 is compressed to high temperature and high pressure by the first compressor 31 and supplied to the storage unit 10 via the second inlet / outlet 12. In other words, the medium ME discharged from the heat exchange unit 45 is expanded by the expansion valve 40 and supplied to the second inlet / outlet 12 of the storage unit 10 via the cooling unit 20. In this way, the medium ME circulates in the circulation flow path 50.

[0032] The control unit 60 controls the state of the medium ME flowing through the circulation flow path 50 by controlling the power consumption of the first compressor 31 and the second compressor 32. When cooling the battery cells 70 shown in Fig. 1, 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 unit 45 becomes 45°C and the temperature of the medium ME supplied to the cooling unit 20 becomes 20°C.

[0033] Fig. 3 is an explanatory diagram of vapor heat transport of the medium ME when cooling the battery cell 70. Fig. 3 shows a schematic diagram of the medium ME in the housing 10 evaporating from a liquid and cooling the battery cell 70 by vapor heat transport when the battery cell 70 is charged or discharged. Fig. 3 shows a schematic cross-sectional view of the vicinity of one battery cell 70 in the housing 10.

[0034] As shown in FIG. 3, the storage section 10 includes a tube wall 17 that contacts the battery cell 70 and extends along the vertical direction, and a porous body 18 that contacts the tube wall 17 and extends along the vertical direction in the same manner as the tube wall 17. The tube wall 17 is connected to the cooling section 20 vertically above. The tube wall 17 is formed of a metal material and has high thermal conductivity. The porous body 18 is connected to the cooling section 20 vertically above in the same manner as the tube wall 17. The porous body 18 contacts the opposite side of the tube wall 17 that is not in contact with the battery cell 70. The porous body 18 is formed of a metallic porous material. As shown in FIG. 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 formed of a porous material, the medium ME can enter into the voids of the porous body 18.

[0035] The temperature of the battery cell 70 during charging and discharging rises to a temperature higher than the boiling point temperature of 20° C. at the pressure of 0.9 MPa in the storage section 10. Therefore, the liquid medium ME in the storage section 10 is heated to 20° C. by heat exchange with the battery cell 70 and then evaporates. The evaporated medium ME moves vertically upward in the storage section 10 and is cooled and condensed by the medium ME at 20° C. flowing in the cooling section 20. The condensed liquid medium ME quickly spreads throughout the porous body 18 due to gravity and the capillary phenomenon of the porous body 18. After that, the liquid medium ME in the porous body 18 evaporates again by heat exchange with the battery cell 70 through the tube wall 17. That is, the medium ME in the storage section 10 cools the battery cell 70 using the latent heat of evaporation by repeated condensation and evaporation.

[0036] 4 is a schematic block diagram of the secondary battery system 100 when the battery cell 70 is warmed up. FIG. 4 shows the secondary battery system 100 in the case where the battery cell 70 is warmed up using the medium ME when the temperature of the battery cell 70 is lower than the recommended temperature (5°C to 45°C) due to a low outside air temperature (for example, 5°C or lower) when starting up the battery cell 70. In FIG. 4, the direction in which the medium ME flows through the circulation flow path 50 is shown by an arrow, as in FIG. 1. The direction in which the medium ME flows in FIG. 4 is opposite to the direction in which the medium ME flows during cooling shown in FIG. 1, and corresponds to the second direction. The direction in which the medium ME flows through the circulation flow path 50 is switched by the control unit 60.

[0037] As shown in FIG. 4, among the four three-way valves 81 to 84, the three-way valve 81 connects the expansion valve 40 and the three-way valve 82. The three-way valve 82 connects the three-way valve 81 and the second inlet / outlet 12 of the storage unit 10. The three-way valve 83 connects the three-way valve 84 and the second compressor 32 via a changeover valve 89. The three-way valve 84 connects the three-way valve 83 and the first inlet / outlet 11 of the storage unit 10. The changeover valve 89 connects a flow path connected to the three-way valve 83 and a flow path connected to the second compressor 32, and also connects a flow path connected to the heat exchange unit 45 and a 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] When the battery cell 70 is warmed up, the medium ME flows in the direction of the arrow shown in Fig. 4. Specifically, the medium ME discharged from the second inlet / outlet 12 of the storage unit 10 is expanded to a low temperature and low pressure by the expansion valve 40 and supplied to the heat exchange unit 45, where cold heat is supplied from the outside air to raise the temperature. 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 storage unit 10. During warm-up in this embodiment, the medium ME is not supplied to the cooling unit 20.

[0039] 5 is an explanatory diagram of vapor heat transport of the medium ME when the battery cell 70 is warmed up. When the battery cell 70 is warmed up as shown in FIG. 5, the vapor of the medium ME that has been changed to a 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 storage section 10. The temperature of the vapor medium ME is reduced by heat exchange with the battery cell 70 and the medium ME is condensed. The condensed medium ME moves vertically downward within the porous body 18 and is discharged from the first inlet / outlet 11.

[0040] FIG. 6 is an example of a Ph diagram of a vapor compression refrigeration cycle when the battery cell 70 is warmed up. As shown in FIG. 6, in this embodiment, the vapor medium ME is compressed to 40° C. and 1.02 MPa by the power Qw input to the first compressor 31 and the second compressor 32. The compressed medium ME is supplied to the storage unit 10 and exchanges heat with the battery cell 70, warming up the battery cell 70 and condensing. This heat exchange transfers heat quantity Qh from the medium ME to the battery cell 70. The liquid medium ME discharged from the storage unit 10 is changed by the expansion valve 40 to vapor at −15.6° C. and 0.16 MPa. The vaporized medium ME obtains heat quantity Qc as cold from the outside air at 0° C. 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 the storage unit 10 that stores the battery cell 70 and has the first inlet / outlet 11 and the second inlet / outlet 12, and the control unit 60 that switches the direction of the medium ME flowing through the circulation flow path 50. When the battery cell 70 shown in FIG. 1 is cooled, the medium ME discharged from the first inlet / outlet 11 of the storage unit 10 is compressed to high temperature and high pressure by the second compressor 32 and supplied to the heat exchange unit 45. The medium ME discharged from the heat exchange unit 45 is expanded by the expansion valve 40 and supplied to the second inlet / outlet 12 of the storage unit 10 via the cooling unit 20. On the other hand, when the battery cell 70 shown in FIG. 4 is warmed up, the control unit 60 switches the direction of flow through the circulation flow path 50 to the opposite direction from when the battery cell 70 was cooled. Therefore, when the battery cell 70 is warmed up, the medium ME discharged from the second inlet / outlet 12 of the storage unit 10 is expanded to low temperature and low pressure by the expansion valve 40 and supplied to the heat exchange unit 45. The medium ME discharged from the heat exchanger 45 is compressed to high temperature and high pressure by the first compressor 31 and the second compressor 32, and is supplied to the first inlet / outlet 11 of the storage unit 10. That is, in this embodiment, when cooling the battery cells 70, as shown in FIG. 1, the medium ME discharged from the storage unit 10 circulates in the circulation flow path 50 through the compression unit 30, the heat exchanger 45, the expansion valve 40, and the storage unit 10 in that order. In this case, the medium ME discharged from the storage unit 10 is compressed to high temperature and high pressure by the compression unit 30, and then dissipates heat and is cooled by heat exchange with the outside air in the heat exchanger 45. The medium ME after the heat exchange is expanded to low temperature and low pressure by the expansion valve 40, and is supplied to the storage unit 10 again. The battery cells 70 accommodated in the storage unit 10 are cooled by the low temperature medium ME. On the other hand, when warming up the battery cells 70, as shown in Fig. 4, the medium ME discharged from the storage unit 10 circulates through the circulation flow path 50 in the order of the expansion valve 40, the heat exchange unit 45, the compression unit 30, and the storage unit 10. The medium ME discharged from the storage unit 10 is expanded to a low temperature and low pressure by the expansion valve 40, and then exchanges heat with the outside air in the heat exchange unit 45 to obtain cold heat and increase in temperature. After the heat exchange, the medium ME is compressed to a high temperature and high pressure by the compression unit 30 and is supplied again to the storage unit 10. The battery cells 70 stored in the storage unit 10 are warmed by the high-temperature medium ME.That is, simply by switching the flow direction of the medium ME in the circulation flow path 50, the battery cells 70 are cooled by the medium ME during cooling, and the battery cells 70 are warmed by the medium ME during warming. Therefore, cooling and warming are performed in a short time with low power consumption so that the battery cells 70 do not deteriorate due to high temperature.

[0042] The secondary battery system 100 of this embodiment is also provided with a cooling section 20 that is disposed vertically above the storage section 10 and through which the medium ME can flow. When cooling the battery cells 70 shown in FIG. 1, the medium ME is expanded to a low temperature and low pressure by the expansion valve 40, and then supplied into the cooling section 20 through the fourth inlet / outlet 22, discharged from the third inlet / outlet 21 of the cooling section 20, and supplied to the second inlet / outlet 12 of the storage section 10. On the other hand, when warming up the battery cells 70 shown in FIG. 4, the medium ME is not supplied into the cooling section 20. That is, in this embodiment, when cooling the battery cells 70, the battery cells 70 are cooled by heat exchange via the low-temperature and low-pressure medium ME supplied to the cooling section 20 and the medium ME filled in the storage section 10. Because the temperature difference occurring during heat exchange makes the temperature of the medium ME filled in the storage unit 10 higher than that of the cooling unit 20, it is possible to suppress further expansion of the battery cells 70 due to the pressure difference between the low-pressure medium ME in the storage unit 10 in which the battery cells 70 that expand during charging and discharging are stored. On the other hand, when warming up the battery cells 70, the battery cells 70 are efficiently warmed by direct heat exchange between the high-temperature, high-pressure medium ME supplied into the storage unit 10 and the battery cells 70 stored in the storage unit 10.

[0043] Moreover, the medium ME in this embodiment is a fluorocarbon-based medium having a low boiling point at atmospheric pressure. In this embodiment, the boiling point of the fluorocarbon-based medium is lower than the temperature of the battery cell 70, which becomes hot during charging and discharging, so that the medium ME in the storage unit 10 evaporates by heat exchange with the battery cell 70 when the battery cell 70 is cooled. The evaporated medium ME is cooled and condensed by heat exchange with the medium ME flowing through the cooling unit 20, moves vertically downward, and evaporates again by 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 evaporation of the medium ME in the storage unit 10.

[0044] The compression section 30 of this embodiment includes a first compressor 31 disposed on the circulation flow path 50, and a second compressor 32 disposed downstream of the first compressor 31 on the circulation flow path 50 along the direction in which the medium ME flows during cooling as shown in FIG. 1. As shown in FIG. 1, the secondary battery system 100 further includes an on-off valve 85 that opens and closes the connection of the circulation flow path 50 between the first compressor 31 and the second compressor 32. The on-off valve 85 is closed when the battery cell 70 is cooled, and is opened when the battery cell 70 is warmed up, which will be described later. When the battery cell 70 is cooled, the medium ME discharged from the cooling section 20 is compressed to a high temperature and high pressure by the first compressor 31, and is supplied to the storage section 10 through the second inlet / outlet 12. When the battery cell 70 is warmed up, the medium ME discharged from the heat exchange section 45 is compressed to a high temperature and high pressure by the first compressor 31 and the second compressor 32, and is supplied to the first inlet / outlet 11 of the storage section 10. That is, in this embodiment, when the battery cell 70 is cooled, the medium ME pressurized by the first compressor 31 is supplied into the storage section 10. When the battery cell 70 is charged or discharged, lithium ions as active materials are inserted into the negative and positive electrodes, so that the volume of the battery cell 70 expands. The vapor medium ME supplied into the storage section 10 by the first compressor 31 is pressurized, and the expansion of the battery cell 70 is suppressed by the pressurized medium ME. In this embodiment, the compression of the medium ME by the first compressor 31 and the compression of the medium ME by the second compressor 32 are adjusted, so that the battery cell 70 can be cooled while suppressing the expansion of the battery cell 70 during charging or discharging. In addition, when the battery cell 70 is warmed up, the two compressors, the first compressor 31 and the second compressor 32, further increase the temperature and pressure of the medium ME to quickly warm up the battery cell 70.

[0045] <Second embodiment> FIG. 7 is a schematic block diagram of a secondary battery system 100a of the second embodiment. The secondary battery system 100a of the second embodiment is significantly different from the secondary battery system 100 of the first embodiment in that the compression of the medium ME by the compression unit 30 is controlled using a detection value such as a flow rate of the liquid medium ME supplied to the heat exchange unit 45 during warm-up of the battery cell 70. Note that in the schematic block diagram of FIG. 7, the secondary battery system 100a during warm-up is shown in a simplified form. Therefore, the two three-way valves 82, 84, the switching valve 89, and the opening / closing valve 85 are omitted, and the circulation flow path 50 is shown in a simplified form. Note that in FIG. 7, the first compressor 31 and the second compressor 32 are collectively shown as the compression unit 30.

[0046] 7, the secondary battery system 100a of the second embodiment includes, in addition to the components of the secondary battery system 100 of the first embodiment, a flow rate sensor (flow rate acquisition unit) 91 arranged between the expansion valve 40 and the heat exchange unit 45, a first temperature sensor 92 that detects the temperature of the heat exchange unit 45, a second temperature sensor (outside air temperature acquisition unit) 93 that detects the outside air temperature, a third temperature sensor (battery temperature acquisition unit) 94 that detects the battery temperature Tb,t of the battery cells 70 housed in the housing unit 10, and a rotation speed sensor 95 that detects the rotation speed N of the fan FN. The flow rate 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 detection values ​​of the sensors. The control unit 60a uses the detection values ​​to calculate an appropriate flow rate FRc of the medium ME at which the vapor quality of the medium ME discharged from the heat exchange unit 45 becomes 1. The appropriate flow rate FRc is expressed by the following formula (1).

number

[0048] The overall heat transfer coefficient K is calculated by a function f shown in the following formula (2) using the rotation 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 expressed as a map function based on the relationship between the rotation speed N and the liquid flow rate FRm 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 a temperature difference acquisition unit. The latent heat of vaporization ΔH of the medium ME is determined by the type of the 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 becomes smaller than the absolute value of a threshold value ε (>0). The change in power consumption ΔW is expressed as the absolute value of a function g according 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 the following formula (3).

[0051]

number

[0052] The control unit 60a continues warming up the battery cells 70 by circulating the medium ME until the battery temperature Tb,t detected by the third temperature sensor 94 becomes equal to or higher than the target temperature Tb for completing the warm-up.

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

[0054] The control unit 60a inputs a preset initial power W to the compression unit 30 to drive the compression unit 30 (step S3). The control unit 60a acquires detection values ​​from each sensor (step S4). The control unit 60a calculates the temperature difference ΔTe, the overall heat transfer coefficient K, the optimum flow rate FRc, and the amount of change ΔW in the consumed power using the acquired sensor values ​​and formulas (1) to (3) (step S5).

[0055] The control unit 60a judges 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 a threshold value ε (step S6). If it is judged that the difference ΔFR is greater than the threshold value ε (step S6: YES), the control unit 60a calculates the power obtained by subtracting the change amount ΔW from the current power consumption of the compression unit 30 (step S7). The control unit 60a inputs the power obtained by subtracting the change amount ΔW to the compression unit 30 (step S3), and performs the processes from step S4 onward.

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

[0057] If it is determined that the difference ΔFR is -ε or more (step S8: NO), the control unit 60a determines whether or not 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 processes from step S4 onwards without changing the power consumption of the compression unit 30 at the current time. If it is determined that the temperature Tb,t of the battery cell 70 is greater than or equal to the target temperature (step SS10: NO), the control unit 60a ends the warm-up of the battery cell 70.

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

[0059] In Figure 9, when the flow rate of the medium ME circulating through the circulation flow path 50 increases, the refrigeration cycle changes from ph1 (solid line) to ph2 (dashed line). As the flow rate of the medium ME increases, the power W input to the compression section 30 increases, and the amount of heat Q warming up the battery cells 70 also increases. On the other hand, when the flow rate of the circulating medium ME decreases, the refrigeration cycle changes from ph1 to ph3 (dashed line). As the flow rate of the medium ME decreases, the power W input to the compression section 30 decreases, and the amount of heat Q warming 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 in the compression unit 30 using the liquid flow rate FRm of the liquid medium ME detected by the flow rate sensor 91, the temperature difference ΔTe between the temperature of the outside air and the temperature of the heat exchange unit 45, and the rotation speed N of the fan FN of the heat exchange unit 45 during warm-up of the battery cell 70. In this embodiment, the COP changes depending on the flow rate of the vapor medium ME flowing through the circulation flow path 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 heat obtained from the outside air in the heat exchange unit 45, not only does the COP increase for the above reason, but the liquid medium ME that does not contribute to the evaporation and condensation of the medium ME circulates through the circulation flow path 50. As a result, the power W for the compression unit 30 to compress the medium ME increases due to the two-phase pressure loss of the circulation flow path 50. On the other hand, if the liquid flow rate FRm of the medium ME supplied to the heat exchanger 45 is less than the appropriate flow rate FRc, the amount of heat required for warming up becomes insufficient, and the time required for warming up to be completed becomes longer. In this embodiment, the power W input to the compressor 30 is controlled using the capacity of the heat exchanger 45 derived from the rotation 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 exchanger 45. As a result, the battery cells 70 are quickly warmed up without reducing the COP.

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

[0062] The secondary battery system 100b of the third embodiment further includes a heating unit 48 disposed between the expansion valve 40 and the heat exchange unit 45 on the circulation flow path 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 the heating unit 48. 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 temperature of the outside air is zero, the control unit 60b sets the temperature of the inner wall that exchanges heat with the circulating medium ME by the heating unit 48 to 5°C. The control unit 60b heats the medium ME by the heating unit 48 until the battery temperature Tb,t becomes 25°C or higher.

[0063] Each of Figs. 11 to 14 is an explanatory diagram of the effect of heating the medium ME by the heating unit 48. In Fig. 11, the change in the battery temperature Tb,t when the medium ME is heated by the heating unit 48 is shown by a solid line Ct1. Also, in Fig. 11, the change in the battery temperature Tb,t when heating is not performed by the heating unit 48 is shown by a 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, the heating of the medium ME by the heating unit 48 completed the warm-up of the battery cell 70 quickly.

[0064] FIG. 12 shows the change in the vapor pressure of the medium ME supplied to the heat exchanger 45. When the medium ME is heated by the heater 48, the change in the vapor pressure of the medium ME supplied to the storage unit 10 is shown by Ps11 (thick solid line), and the change in the vapor pressure of the medium ME supplied to the heat exchanger 45 is shown by Ps12 (thin solid line). Also, in FIG. 12, when the medium ME is not heated by the heater 48, the change in the vapor pressure of the medium ME supplied to the storage unit 10 is shown by Ps21 (thick dashed line), and the change in the vapor pressure of the medium ME supplied to the heat exchanger 45 is shown by Ps22 (thin dashed line). Furthermore, in FIG. 12, the change in the flow rate of the medium ME, which is a combination of vapor and liquid, is shown by FL (thick dashed line). As shown in FIG. 12, the vapor pressure Ps21 when the medium ME is not heated is restored to a higher pressure level by heating the medium ME by the heater 48 compared to the vapor pressure Ps11 when the medium ME is heated.

[0065] FIG. 13 shows changes in the heat-energy output ratios of the heating section 48, the heat exchange section 45, the first compressor 31, and the second compressor 32. In FIG. 13, when the total average output of the first compressor 31 and the second compressor 32 is set to -1 (consumption), the change in the output ratio of the first compressor 31 and the second compressor 32 is shown by Q30 (dash line). The change in the output ratio of the heating section 48 is shown by Q48 (dash line). The change in the output ratio of the heat exchange section 45 is shown by Q45 (dashed line). The change in the total output ratio of the heating section 48, the heat exchange section 45, the first compressor 31, and the second compressor 32 is shown by Qs (solid line).

[0066] Fig. 14 shows the ratio of the power consumption of the heating unit 48, the heat exchange unit 45, the first compressor 31, and the second compressor 32 until the warm-up of the battery cell 70 is completed. Fig. 14 also shows the ratio of the power consumption of the heat exchange unit 45, the first compressor 31, and the second compressor 32 in a case where the medium ME is not heated by the heating unit 48. Fig. 14 shows the ratio of the power consumption when the warm-up heat amount of the battery cell 70 is set to 1. As shown in Fig. 14, the power consumption of the heat exchange unit 45 is greatly reduced by the heating of the medium ME by the heating unit 48.

[0067] As described above, the secondary battery system 100b of the third embodiment further includes a heating unit 48 disposed between the expansion valve 40 and the heat exchange unit 45 on the circulation flow path 50, which heats the medium ME supplied to the heat exchange unit 45. Therefore, in this embodiment, the liquid medium ME heated by the heating unit 48 evaporates during warm-up, and the supply amount of the vapor medium ME supplied to the heat exchange unit 45 increases. If the supply amount of the vapor medium ME supplied to the heat exchange unit 45 is small and falls below the warm-up heat amount of the battery cell 70, the vapor pressure of the medium ME in the storage unit 10 decreases due to a lack of vapor. If the vapor pressure falls below the battery expansion pressure, the pressure balance is lost and the battery cell 70 temporarily enters an expanded state. This may result in deterioration of the secondary battery or a decrease in battery safety. In this embodiment, the supply amount of the vapor medium ME is increased by the heating unit 48, and the vapor pressure of the medium ME in the storage unit 10 is maintained high. In addition, a decrease in heat transfer coefficient caused by dry-out, which is a problem with high vapor quality, is avoided, and the medium ME evaporates with a small temperature difference due to the high heat transfer coefficient in the heating section 48. In addition, since the temperature difference between the inner wall of the heating section 48 and the medium fluid can be made 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 section 48 is reduced.

[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. That is, in this embodiment, the power consumption by the heating unit 48 to heat the medium ME is controlled according to the battery temperature Tb,t of the battery cell 70, and therefore the vapor supply amount of the medium ME evaporated from the liquid in the heating unit 48 is adjusted. Therefore, power equivalent to the vapor supply amount that needs to be generated is input to the heating unit 48, and therefore a decrease in COP is suppressed.

[0069] <Fourth embodiment> 15 is a schematic block diagram of a secondary battery system 100c of the fourth embodiment. The secondary battery system 100c of the fourth embodiment is significantly different from the secondary battery system 100b of the third embodiment in that when the temperature of the outside air is lower than the boiling point of the medium ME at atmospheric pressure, the fan FN of the heat exchanger 45 is not driven and the medium ME is heated by the heater 48.

[0070] As shown in FIG. 15, the secondary battery system 100c of the fourth embodiment further includes a first temperature sensor 92 for detecting the temperature of the heat exchanger 45 and a second temperature sensor 93 for detecting the temperature of the outside air, in addition to the components of the secondary battery system 100b of the third embodiment. During warm-up of the battery cell 70, the control unit 60c obtains the temperature of the medium ME flowing through the heat exchanger 45 from the first temperature sensor 92 and obtains the temperature of the outside air from the second temperature sensor 93. In the example shown in FIG. 15, the temperature of the outside air is −30° C., which is lower than the boiling point of the medium ME at atmospheric pressure, that is, −29° C. In the case where the temperature of the outside air is equal to or lower than the boiling point of the medium ME at atmospheric pressure, the control unit 60c of this embodiment heats the medium ME circulating through the circulation flow path 50 only by heating the heating unit 48, without driving the fan FN. When the temperature of the outside air 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 each detection value, in the same manner as in 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 temperature of the outside air is equal to or lower than the boiling point of the medium ME at atmospheric pressure. When the temperature of the outside air is equal to or lower than the boiling point of the medium ME, the cold heat from the outside air is not obtained by the blowing of the fan FN, and the medium ME does not evaporate. Therefore, in this case, the medium ME evaporates only by heating by the heating unit 48. On the other hand, when the temperature of the outside air is higher than the boiling point of the medium ME, the cold heat from the outside air is obtained by the blowing of the fan FN, and the heat pump cycle functions. As a result, the medium ME evaporates by the cold heat in addition to the heating by the heating unit 48, improving the COP.

[0072] <Modifications of the embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the present invention, for example, the following modifications are possible: In the above-described embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware.

[0073] <Variation 1> In each of the first to fourth embodiments, an example of the secondary battery system 100, 100a, 100b, and 100c has been described. However, the secondary battery system includes a heat exchanger 45, a compressor 30, and an expansion valve 40, and can be modified within a range in which the cooling and warming of the battery cells 70 can be performed by switching the flow direction of the medium ME in the circulation flow path 50. For example, the four three-way valves 81 to 84, the switching valve 89, and the on-off valve 85 are configured to change a part of the flow path when the flow direction of the medium ME is switched, and can be modified within a range in which the cooling and warming of the battery cells 70 can be performed by switching the flow direction of the medium ME.

[0074] In the first embodiment, the cooling unit 20 is disposed vertically above the storage unit 10, but the secondary battery system 100 may not include the cooling unit 20. In this case, the secondary battery system 100 may supply the medium ME, which has been reduced in temperature and pressure by the expansion valve 40, into the storage unit 10 when cooling the battery cells 70 in the storage unit 10. In addition, 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 storage unit 10. For example, the medium flowing through the cooling unit 20 may not be connected to the circulation flow path 50. In this case, the flow direction of the medium ME of the fluorocarbon-based medium is switched, thereby cooling and warming up the battery cells 70 in the storage unit 10, 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 flow path 50 does not necessarily have to be a fluorocarbon-based medium having a boiling point in the range of the recommended temperature range for the operation of the battery at atmospheric pressure, and may be, for example, carbon dioxide. In order to transport vapor heat using latent heat of evaporation, the medium ME is preferably a fluorocarbon-based medium having a boiling point of -30°C or more and 40°C or less at atmospheric pressure.

[0076] In the first embodiment, the compression section 30 is composed of two compressors, the first compressor 31 and the second compressor 32, but may be composed of one compressor. The compression section 30 can be deformed within a range in which it supplies the compressed medium ME to the heat exchange section 45 when cooling the battery cells 70, and supplies the compressed medium ME into the storage section 10 when warming up the battery cells 70. In addition, the expansion valve 40 has been given as an example of the expansion section that expands the medium ME flowing inside the circulation flow path 50, but it can be deformed within a range of a device that can expand the medium ME.

[0077] A radiator mounted on a vehicle has been described as an example of the heat exchanger 45. However, the heat exchanger 45 can be modified to the extent that it dissipates heat to the outside air when cooling the battery cells 70 and obtains heat from the outside air when warming up the battery cells 70. The first entrance 11 and the second entrance 12 in the above first embodiment are the same entrance, that is, the storage unit 10 may have only one entrance that communicates with the outside. In this case, the supply of the medium ME to the storage unit 10 and the discharge of the medium ME from the storage unit 10 may be alternated with a time lag.

[0078] <Variation 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 have a pressure sensor that measures the pressure inside the storage unit 10. In this case, the control unit 60a may acquire the pressure inside the storage unit 10 measured by the pressure sensor and control the power consumption of the compression unit 30 within a range in which the pressure inside the storage unit 10 is less than a threshold value. With this control, the flow rate of the medium ME is controlled without circulating the medium ME that does not contribute to evaporation and condensation through the circulation flow path 50, and without causing the battery cell 70 to exceed the upper limit temperature due to the internal pressure of the storage unit 10 becoming equal to or higher than the threshold value. As a result, even in an environment with a different outside air temperature, the battery cell 70 is warmed up in a short time while maintaining a high COP.

[0079] In the second embodiment, in the process of step S3 shown in Fig. 8, a preset initial power W is input to the compression section 30, but the initial power W can be modified. For example, the initial power may be calculated from a detected value of the outside air temperature or the like using a map, a function, or the like. The difference ΔTe between the outside air temperature and the temperature of the heat exchange section 45 is 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] Although the present aspect has been described above based on the embodiment and modified examples, the above-mentioned embodiment of the aspect is intended to facilitate understanding of the present aspect and does not limit the present aspect. The present aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents are included in the present aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0081] The present invention can also be realized in the following forms. [Application example 1] A secondary battery system, A secondary battery; a storage section that stores the secondary battery and is filled with a medium, the storage section having a first inlet and a second inlet that communicate between an outside and an inside of the storage section; a circulation flow path that circulates the medium by supplying the medium discharged from the storage unit through one of the first inlet / outlet and the second inlet / outlet to the storage unit through the other of the first inlet / outlet and the second inlet / outlet; a heat exchange unit disposed on the circulation flow path and performing heat exchange between the medium flowing through the circulation flow path and outside air; a compression unit disposed between the first inlet / outlet and the heat exchange unit on the circulation flow path, the compression unit compressing the medium discharged from the first inlet / outlet and flowing in a first direction and supplying the medium to the heat exchange unit, or compressing the medium flowing in a second direction after heat exchange by the heat exchange unit and supplying the medium 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 expanding the medium flowing in the first direction after heat exchange by the heat exchange section and supplying the medium to the second inlet / outlet, or expanding the medium discharged from the second inlet / outlet and flowing in the second direction and supplying the medium to the heat exchange section; a switching unit that switches the flow of the medium circulating through the circulation flow path to the first direction when cooling the secondary battery and to the second direction when warming up the secondary battery; A secondary battery system comprising: [Application example 2] The secondary battery system according to Application Example 1, further comprising: a cooling unit disposed vertically above the storage unit and through which the medium can flow; The medium is During the cooling, the air is discharged from the expansion section and supplied to the cooling section, and is discharged from the cooling section and supplied to the second inlet / outlet, The secondary battery system does not circulate to the cooling section during the warm-up. [Application example 3] The secondary battery system according to the first or second aspect of the present invention, The medium is a fluorocarbon-based medium having a boiling point of minus 30 degrees Celsius or more and 40 degrees Celsius or less at atmospheric pressure. [Application example 4] The secondary battery system according to any one of Application Examples 1 to 3, The compression section includes a first compression section and a second compression section disposed downstream of the first compression section along the first direction, The secondary battery system further comprises: an opening / closing unit that is disposed between the first compression unit and the second compression unit on the circulation flow path and opens and closes the flow of the medium between the first compression unit and the second compression unit; The medium is During the cooling, the connection opening / closing unit is closed, the gas is discharged from the cooling unit and supplied to the first compression unit, and then supplied to the second inlet / outlet, and the gas is discharged from the first inlet / outlet, and then supplied to the second compression unit, and then supplied to the heat exchange unit, a secondary battery system in which the opening / closing section is opened during the warm-up, heat is exchanged by the heat exchange section, the fuel is compressed by the first compression section, and the fuel is further compressed by the second compression section and supplied to the first inlet / outlet. [Application example 5] The secondary battery system according to any one of claims 1 to 4, further comprising: a flow rate acquisition unit that acquires a flow rate of the liquid medium supplied to the heat exchange unit; a temperature difference acquisition unit that acquires a temperature difference between the temperature of the heat exchange unit and an outside air temperature; a control unit that controls compression of the medium by the compression unit; Equipped with the heat exchange unit has a fan that blows outside air to the medium flowing through the circulation flow path, A secondary battery system, wherein the control unit controls 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 during the warm-up, the temperature difference, and the rotation speed of the fan. [Application Example 6] The secondary battery system according to any one of Application Examples 1 to 5, further comprising: the heating section being disposed on the circulation flow path between the expansion section and the heat exchange section and configured to heat the medium during the warm-up process. [Application Example 7] The secondary battery system according to any one of Application Examples 1 to 6, further comprising: a battery temperature acquisition unit that acquires a temperature of the secondary battery; The control unit controls heating of the medium by the heating unit using a temperature of the secondary battery. [Application Example 8] The secondary battery system according to any one of Application Examples 1 to 7, further comprising: An outside air temperature acquisition unit for acquiring an outside air temperature, The control unit, during the warm-up, When the temperature of the outside air is equal to or lower than the boiling point of the medium at atmospheric pressure, the rotation of the fan is stopped; The secondary battery system rotates the fan when the temperature of the outside air is higher than the boiling point and is equal to or lower than a target temperature of the secondary battery after completion of warm-up. [Explanation of symbols]

[0082] 10. Storage section 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 section) 45...Heat exchange section 48...Heating part 50...Circulation flow path 60, 60a, 60b, 60c...Control unit (temperature difference acquisition unit) 70…Battery cell (secondary battery) 81~84…Three-way valve 85...Shutter valve (Shutter section) 89...Switching valve (switching part) 91...Flow rate 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...Rotational speed sensor 100, 100a, 100b, 100c...Secondary battery system FN…Fan ME…Medium Tb,t…Battery temperature Tb…Target temperature ΔTe…Temperature difference

Claims

1. A secondary battery system, A secondary battery; a storage section that stores the secondary battery and is filled with a medium, the storage section having a first inlet and a second inlet that communicate between an outside and an inside of the storage section; a circulation flow path that circulates the medium by supplying the medium discharged from the storage unit through one of the first inlet / outlet and the second inlet / outlet to the storage unit through the other of the first inlet / outlet and the second inlet / outlet; a heat exchange unit disposed on the circulation flow path and performing heat exchange between the medium flowing through the circulation flow path and outside air; a compression unit disposed between the first inlet / outlet and the heat exchange unit on the circulation flow path, the compression unit compressing the medium discharged from the first inlet / outlet and flowing in a first direction and supplying the medium to the heat exchange unit, or compressing the medium flowing in a second direction after heat exchange by the heat exchange unit and supplying the medium 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 expanding the medium flowing in the first direction after heat exchange by the heat exchange section and supplying the medium to the second inlet / outlet, or expanding the medium discharged from the second inlet / outlet and flowing in the second direction and supplying the medium to the heat exchange section; a switching unit that switches the flow of the medium circulating through the circulation flow path to the first direction when cooling the secondary battery and to the second direction when warming up the secondary battery; A secondary battery system comprising:

2. The secondary battery system according to claim 1 , further comprising: a cooling unit disposed vertically above the storage unit and through which the medium can flow; The medium is During the cooling, the air is discharged from the expansion section and supplied to the cooling section, and is discharged from the cooling section and supplied to the second inlet / outlet, The secondary battery system does not circulate to the cooling section during the warm-up.

3. The secondary battery system according to claim 2, The medium is a fluorocarbon-based medium having a boiling point of minus 30 degrees Celsius or more and 40 degrees Celsius or less at atmospheric pressure.

4. The secondary battery system according to claim 2 or 3, The compression section includes a first compression section and a second compression section disposed downstream of the first compression section along the first direction, The secondary battery system further comprises: an opening / closing unit that is disposed between the first compression unit and the second compression unit on the circulation flow path and opens and closes the flow of the medium between the first compression unit and the second compression unit; The medium is During the cooling, the opening / closing section is closed, the cooling gas is discharged from the cooling section and supplied to the first compression section, and then supplied to the second inlet / outlet, and the cooling gas is discharged from the first inlet / outlet, and then supplied to the second compression section, and then supplied to the heat exchange section, a secondary battery system in which the opening / closing section is opened during the warm-up, heat is exchanged by the heat exchange section, the fuel is compressed by the first compression section, and the fuel is further compressed by the second compression section and supplied to the first inlet / outlet.

5. The secondary battery system according to claim 1 , further comprising: a flow rate acquisition unit that acquires a flow rate of the liquid medium supplied to the heat exchange unit; a temperature difference acquisition unit that acquires a temperature difference between the temperature of the heat exchange unit and an outside air temperature; a control unit that controls compression of the medium by the compression unit; Equipped with the heat exchange unit has a fan that blows outside air to the medium flowing through the circulation flow path, A secondary battery system, wherein the control unit controls 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 during the warm-up, the temperature difference, and the rotation speed of the fan.

6. The secondary battery system according to claim 5, further comprising: the heating section being disposed on the circulation flow path between the expansion section and the heat exchange section and configured to heat the medium during the warm-up process.

7. The secondary battery system according to claim 6, further comprising: a battery temperature acquisition unit that acquires a temperature of the secondary battery; The control unit controls heating of the medium by the heating unit using a temperature of the secondary battery.

8. The secondary battery system according to claim 6 or 7, further comprising: An outside air temperature acquisition unit for acquiring an outside air temperature, The control unit, during the warm-up, When the temperature of the outside air is equal to or lower than the boiling point of the medium at atmospheric pressure, the rotation of the fan is stopped; The secondary battery system rotates the fan when the temperature of the outside air is higher than the boiling point and is equal to or lower than a target temperature of the secondary battery after completion of warm-up.

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