Secondary Battery System

Abstract

To evenly suppress expansions and constrictions generated when a secondary battery is discharged or charged.SOLUTION: A secondary battery system includes: a secondary battery; a storage unit for storing the secondary battery; a fluorocarbon medium filled in the storage unit; and a temperature adjusting unit for controlling the temperature of the fluorocarbon medium in the storage unit, thereby adjusting the temperature of the secondary battery by using evaporation heat of the fluorocarbon medium, as well as changing the evaporation pressure of the fluorocarbon medium in the storage unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A cooling device for cooling a secondary battery used as a battery for an electric vehicle or the like is known (see, for example, Patent Document 1). In the cooling device described in Patent Document 1, each of a plurality of battery modules 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. As a result, the heat sink is cooled via the coolant, and each battery module is cooled via the heat pipe. [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] The cooling device described in Patent Document 1 can suppress a temperature rise in a battery. However, when a secondary battery is charged or discharged, in addition to the temperature rise, the secondary battery expands and compresses due to the movement of metal ions (e.g., lithium ions in a lithium-ion battery). Specifically, when the secondary battery is charged or discharged, the volume of the secondary battery expands due to the insertion of metal ions into the active materials of the negative and positive electrodes. In particular, the higher the SOC (State of Charge), the greater the volume expansion. Furthermore, during the initial charge and discharge of a secondary battery, part of the electrolyte gasifies, or gasifies due to degradation phenomena associated with the charge and discharge cycles (such as reactions between the electrolyte and the electrodes), which may cause the secondary battery to expand due to an increase in internal pressure.

[0005] The volume expansion caused by the desorption and insertion of metal ions into the active material is converted into stress (compression) and strain depending on the internal constraints imposed by the porous electrode, the external constraints between the positive and negative electrode current collectors, and mechanical properties (elastic modulus, Poisson's ratio). Insufficient internal and external constraints can lead to the collapse of part of the active material's internal structure. Furthermore, insufficient internal and external constraints can lead to mechanical effects such as delamination or defects between the electrode and current collector, as well as ionic and electrical effects such as the disconnection of electronic conduction paths and diffusion inhibition due to reduced porosity within the electrode, resulting in a decrease in battery capacity and an increase in the battery's internal resistance (reduced conductive area).

[0006] Furthermore, when there is a distribution in the internal and external constraint conditions, a distribution in the strain and stress conditions due to volume expansion occurs. This creates areas that are susceptible to mechanical, ionic, and electrical influences and areas that are not, which may lead to non-uniform reactions throughout the secondary battery during charging and discharging. This non-uniform reaction may not only cause battery degradation to be concentrated in the susceptible areas (heat generation concentrated in the degraded areas makes the entire battery more susceptible to deterioration), but may also lead to short circuits and fires (due to metal deposition) in the reaction-concentrated areas due to the non-uniformity, thereby compromising battery safety. Attempting to uniformly constrain the surface of a secondary battery using a jig or other tool would require larger constraining components, which, in the case of secondary batteries for automotive use, would increase the vehicle weight, making uniform constraint difficult to achieve.

[0007] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to uniformly suppress expansion and contraction that occurs during charging and discharging of a secondary battery. [Means for solving the problem]

[0008] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0009] (1) According to one aspect of the present invention, there is provided a secondary battery system including a secondary battery, a housing for housing the secondary battery, a fluorocarbon medium filled in the housing, and a temperature control unit for controlling the temperature of the fluorocarbon medium in the housing to adjust the temperature of the secondary battery using the heat of evaporation of the fluorocarbon medium and for changing the vapor pressure of the fluorocarbon medium in the housing.

[0010] According to this configuration, the secondary battery, whose temperature has risen, is cooled using the heat of evaporation of the fluorocarbon-based medium, which is a low-boiling-point medium. Therefore, the temperature of the secondary battery can be controlled near the boiling point of the fluorocarbon-based medium. Furthermore, the temperature control unit can change the vapor pressure of the fluorocarbon-based medium within the housing that houses the secondary battery. Therefore, by controlling the vapor pressure of the fluorocarbon-based medium, the expansion and contraction of the secondary battery, which expands during charging and discharging, can be uniformly suppressed by the vapor pressure. Expansion of a secondary battery can cause a portion of the active material structure within the secondary battery to collapse, potentially resulting in deterioration and a decrease in safety of the secondary battery. In contrast, suppressing the expansion of a secondary battery using vapor pressure can suppress deterioration and a decrease in safety of the secondary battery. Furthermore, suppressing expansion using vapor pressure, unlike physical external constraints, can suppress expansion uniformly throughout the secondary battery. Therefore, suppressing vapor pressure does not require a large-scale external constraint. Furthermore, because vapor pressure uniformly suppresses expansion throughout the secondary battery, concentrated battery degradation caused by uneven constraints within the secondary battery can be reduced.

[0011] (2) In the secondary battery system of the above aspect, the temperature control unit may have a cooling unit that is arranged vertically above the storage unit and cools and condenses the vaporized fluorocarbon-based medium in the storage unit, and when a predetermined condition is met that indicates that the secondary battery is presumed to be expanding, the temperature of the fluorocarbon-based medium in the storage unit may be increased compared to before the predetermined condition was met, thereby increasing the vapor pressure of the fluorocarbon-based medium in the storage unit. According to this configuration, the fluorocarbon-based medium, which cools the secondary battery by evaporation heat and vaporizes, is cooled and condensed by the cooling unit located above the storage unit. The condensed fluorocarbon-based medium moves to the lower part of the storage unit, where it cools the secondary battery again and vaporizes. In this way, the secondary battery is cooled by vapor heat transport using the fluorocarbon-based medium, allowing the secondary battery to be cooled efficiently. Furthermore, when certain conditions are met that suggest the secondary battery is expanding, such as during charging and discharging of the secondary battery, the vapor pressure increases by adjusting the temperature of the fluorocarbon-based medium. This allows the vapor pressure to suppress the expansion of the secondary battery only when the secondary battery is expanding, and does not compress the secondary battery when the secondary battery is not expanding.

[0012] (3) The secondary battery system of the above aspect may further include a medium flow path that circulates the fluorocarbon-based medium within the storage unit, a first compressor that is arranged on the medium flow path and compresses the fluorocarbon-based medium supplied to the storage unit, a second compressor that is arranged on the medium flow path and compresses the fluorocarbon-based medium discharged from the storage unit, and a radiator that is arranged on the medium flow path and radiates heat from the fluorocarbon-based medium compressed by the second compressor, and the temperature adjustment unit may change the vapor pressure and temperature of the fluorocarbon-based medium within the storage unit by controlling the power allocated to the first compressor and the second compressor. With this configuration, by controlling the power allocated to the first compressor and the second compressor, an intermediate pressure between the pressure compressed by the first compressor and the pressure compressed by the second compressor can be supplied as the pressure of the fluorocarbon-based medium in the storage unit. Furthermore, by compressing the high-temperature, high-pressure fluorocarbon-based medium by the second compressor, the heat of the fluorocarbon-based medium can be released to the outside air using a radiator. Therefore, the vapor pressure of the fluorocarbon-based medium in the storage unit can be changed using the first compressor and the second compressor, and the temperature of the secondary battery can be changed by the cooling unit independently of the vapor pressure.

[0013] (4) The secondary battery system of the above aspect further comprises an expansion valve disposed on the medium flow path and expanding the fluorocarbon-based medium from which heat has been dissipated by the radiator; a refrigerant flow path for circulating the refrigerant flowing in the cooling unit; a heat exchanger disposed on the refrigerant flow path and on the medium flow path, to which the refrigerant discharged from the cooling unit and the fluorocarbon-based medium expanded by the expansion valve are supplied and which exchanges heat between the supplied refrigerant and the fluorocarbon-based medium; and a control valve disposed on the refrigerant flow path, wherein the radiator is disposed on the refrigerant flow path in parallel with the heat exchanger with respect to the cooling unit. the refrigerant discharged from the cooling unit and the fluorocarbon-based medium compressed by the second compressor are supplied, and heat is exchanged between the supplied refrigerant and the fluorocarbon-based medium; the control valve is arranged between the cooling unit, the radiator, and the heat exchanger, and controls the flow rate distribution of the refrigerant supplied from the cooling unit to the radiator and the heat exchanger, respectively; the first compressor is supplied with the fluorocarbon-based medium that has exchanged heat with the refrigerant by the heat exchanger; and the temperature adjustment unit adjusts the temperature of the refrigerant supplied to the cooling unit by controlling the control valve. According to this configuration, the temperature inside the storage unit can be adjusted by the refrigerant flowing through the refrigerant flow path, independently of the vapor pressure of the fluorocarbon-based medium inside the storage unit. Because the radiator and heat exchanger are arranged in parallel in the refrigerant flow path, the flow rate of the refrigerant supplied to the radiator and the flow rate of the refrigerant supplied to the heat exchanger are adjusted by a control valve. Because the temperature of the refrigerant passing through the radiator differs from the temperature of the refrigerant passing through the heat exchanger, the temperature of the refrigerant supplied to the cooling unit is adjusted by controlling the flow rate with the control valve. In other words, the temperature of the refrigerant supplied to the cooling unit can be easily adjusted. Furthermore, the high-temperature, high-pressure fluorocarbon-based medium compressed by the second compressor dissipates heat by the radiator. After dissipating heat, the fluorocarbon-based medium expands and cools through the expansion valve, is heated by the heat exchanger, and is pressurized by the first compressor, thereby adjusting the vapor pressure of the fluorocarbon-based medium inside the storage unit independently of its temperature.

[0014] (5) The secondary battery system of the above aspect may further include an expansion valve disposed on the medium flow path to expand the fluorocarbon-based medium from which heat has been dissipated by the radiator, the fluorocarbon-based medium expanded by the expansion valve being supplied to the cooling section, and the fluorocarbon-based medium discharged from the cooling section being supplied to the first compressor. According to this configuration, the high-temperature, high-pressure fluorocarbon medium compressed by the second compressor is dissipated by the radiator. The temperature of the fluorocarbon medium after dissipation is lowered by expansion through the expansion valve. The cooled fluorocarbon medium is supplied to the cooling unit, where it cools the secondary battery placed in the storage unit. The fluorocarbon medium discharged from the cooling unit is pressurized to an intermediate pressure by the first compressor, so that the vapor pressure of the fluorocarbon medium in the storage unit can be adjusted to be the same as the expansion pressure of the secondary battery.

[0015] (6) In the secondary battery system of the above aspect, the temperature control unit may have a shut-off valve on the medium flow path that shuts off the fluorocarbon-based medium being supplied to the storage unit, and by closing the shut-off valve when charging or discharging of the secondary battery is stopped, the fluorocarbon-based medium may be circulated within the medium flow path without being supplied into the storage unit. With this configuration, when the secondary battery expands due to charging and discharging, the shutoff valve seals the fluorocarbon-based medium in the storage compartment when charging and discharging are stopped. Even when charging and discharging are stopped, the secondary battery remains in an expanded state, so sealing the storage compartment adjusts the expansion pressure and vapor pressure of the secondary battery during charging and discharging to be the same. This prevents deterioration of the secondary battery and a decrease in safety.

[0016] (7) In the secondary battery system of the above aspect, the temperature control unit may have an acquisition unit that acquires the amount of distortion of the secondary battery, and when the secondary battery is charged or discharged under the predetermined conditions, the vapor pressure of the fluorocarbon-based medium in the storage unit may be changed to an expansion pressure of the secondary battery determined from the acquired amount of distortion. According to this configuration, the vapor pressure of the fluorocarbon medium in the storage unit is changed according to the amount of strain acquired by the acquisition unit. The expansion of the secondary battery differs between charging and discharging, and also differs depending on the SOC (State Of Charge). With this configuration, the vapor pressure of the fluorocarbon medium in the storage unit is controlled to be equal to the expansion pressure of the secondary battery determined by the amount of strain. This suppresses expansion of the secondary battery due to the vapor pressure, and further suppresses distortion of the secondary battery without excessively compressing the secondary battery.

[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 device for a secondary battery, a control method for a secondary battery, a system including these devices or realizing these methods, a computer program for executing these devices or methods, a server device for distributing this computer program, a non-transitory storage medium storing the computer program, etc. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic block diagram of a secondary battery system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic perspective view of a temperature control box. [Figure 3] FIG. 1 is an explanatory diagram illustrating the expansion of a lithium ion battery during charging. [Figure 4] FIG. 2 is an explanatory diagram showing the relationship between the boiling point temperature and vapor pressure of a fluorocarbon-based medium. [Figure 5] FIG. 4 is an explanatory diagram of the relationship between the temperature of the secondary battery and the temperature of the cooling unit, and the vapor temperature of the fluorocarbon-based medium. [Figure 6] FIG. 10 is an explanatory diagram for calculating the degree of superheat on the condensation side of a fluorocarbon-based medium. [Figure 7] FIG. 10 is an explanatory diagram for calculating the degree of superheat on the evaporation side of a fluorocarbon-based medium. [Figure 8] FIG. 10 is an explanatory diagram of the time transition of the amount of distortion of a secondary battery during charging and discharging when the vapor pressure is 0.90 MPa. [Figure 9]FIG. 1 is an explanatory diagram of the vapor pressure corresponding to the SOC when the vapor pressure is 0.90 MPa. [Figure 10] FIG. 10 is a graph showing the amount of strain corresponding to the SOC when the vapor pressure is 0.90 MPa. [Figure 11] FIG. 10 is an explanatory diagram of the time transition of the distortion amount of a secondary battery during charging and discharging when the vapor pressure is 0.48 MPa. [Figure 12] FIG. 1 is an explanatory diagram of the vapor pressure corresponding to the SOC when the vapor pressure is 0.48 MPa. [Figure 13] FIG. 10 is a graph showing the amount of strain corresponding to the SOC when the vapor pressure is 0.48 MPa. [Figure 14] FIG. 4 is a schematic block diagram of a secondary battery system according to a modified example of the first embodiment. [Figure 15] FIG. 10 is a schematic block diagram of a secondary battery system according to a second embodiment. [Figure 16] 10 is an example of a Ph diagram of a vapor compression refrigeration cycle in a second embodiment. [Figure 17] 10 is an example of a Ph diagram of a vapor compression refrigeration cycle in a second embodiment. [Figure 18] FIG. 10 is a schematic block diagram of a secondary battery system according to a modified example of the second embodiment. [Figure 19] 10 is an example of a Ph diagram of a vapor compression refrigeration cycle in a modified example of the second embodiment. [Figure 20] 10 is an example of a Ph diagram of a vapor compression refrigeration cycle in a modified example of the second embodiment. [Figure 21] FIG. 10 is a schematic block diagram of a secondary battery system according to a third embodiment. [Figure 22] 10 is a flowchart of vapor pressure control of a fluorocarbon-based medium in the third embodiment. [Figure 23] 10 is an explanatory diagram showing the time transition of the distortion amount of a secondary battery during charging and discharging in the third embodiment. FIG. [Figure 24] FIG. 2 is a diagram illustrating changes in various parameters with respect to the SOC of a secondary battery. [Figure 25] FIG. 10 is a schematic block diagram of a secondary battery system according to a fourth embodiment. [Figure 26]FIG. 10 is a schematic block diagram of the secondary battery system in a state where the accommodation section is sealed and a bypass path is formed. [Figure 27] 10 is a flowchart of control when charging / discharging is stopped in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] First Embodiment FIG. 1 is a schematic block diagram of a secondary battery system 1 according to one embodiment of the present invention. The secondary battery system 1 of this embodiment is a battery system mounted on an automobile and functions as a power source for the automobile. The secondary battery system 1 cools the secondary battery 12 by vapor heat transport of a fluorocarbon-based medium 13 filled in a storage unit 11 together with the secondary battery 12. The vapor pressure of the fluorocarbon-based medium 13 in the storage unit 11 is changed (controlled) by controlling the temperature of a cooling unit 16 that cools the fluorocarbon-based medium 13. In this embodiment, the vapor pressure of the fluorocarbon-based medium 13 is controlled to be the same as the expansion pressure of the secondary battery 12 that expands during charging, thereby suppressing expansion of the secondary battery 12 due to the vapor pressure.

[0020] As shown in FIG. 1, the secondary battery system 1 includes a temperature control box 10 having a cooling unit 16 through which a refrigerant 18 flows, a refrigerant flow path 50 through which the refrigerant 18 flows, a compressor 30 that compresses the refrigerant 18, a condenser 20 that dissipates heat from the refrigerant 18, an expansion valve 40 that expands the refrigerant 18, and a control unit (temperature control unit) 60 that controls each unit. The refrigerant flow path 50 is a flow path that circulates the refrigerant 18 between the cooling unit 16 and the condenser 20. In FIG. 1, the refrigerant flow path 50 is shown by a solid line, and the direction in which the refrigerant 18 flows is indicated by an arrow. The exchange of control signals transmitted and received by the control unit 60 is not shown. In the following description, the terms "upstream" and "downstream" are used to refer to the flow direction of the refrigerant 18.

[0021] The compressor 30 is disposed downstream of the cooling section 16 on the refrigerant flow path 50 and compresses the refrigerant 18 discharged from the cooling section 16. The condenser 20 is disposed downstream of the compressor 30 on the refrigerant flow path 50. The condenser 20 condenses the refrigerant 18, the temperature of which has increased due to compression, by dissipating heat. The expansion valve 40 is disposed downstream of the condenser 20 and upstream of the cooling section 16. The expansion valve 40 expands the refrigerant 18 from which heat has been dissipated. The temperature of the refrigerant 18 expanded by the expansion valve 40 is lowered. The lowered temperature refrigerant 18 is supplied to the cooling section 16.

[0022] Fig. 2 is a schematic perspective view of the temperature control box 10. In Fig. 2, the box-shaped outline of the temperature control box 10 that houses the cooling unit 16 is shown by a dashed line, and the interior of the temperature control box 10 is illustrated. The area of the cooling unit 16 into which the refrigerant 18 can flow is shown hatched.

[0023] As shown in FIG. 2 , the temperature control box 10 includes a storage section 11 that stores multiple secondary batteries 12 and a cooling section 16 disposed vertically above the storage section 11. The space within the storage section 11 and the space within the cooling section 16 are separated. Within the storage section 11, multiple secondary batteries 12 are arranged horizontally at predetermined intervals. In this embodiment, the secondary batteries 12 are lithium-ion batteries. The storage section 11 is filled with a fluorocarbon-based medium 13. In this embodiment, vapor heat transport of the fluorocarbon-based medium 13 within the storage section 11 is utilized to cool the secondary batteries 12 when they generate heat. Therefore, the type of fluorocarbon-based medium 13 and the amount of fluorocarbon-based medium 13 to be filled within the storage section 11 are determined so that the boiling point of the fluorocarbon-based medium 13 is the same as the desired temperature to which the secondary batteries 12 are cooled when they generate heat. As a result, the boiling point of the fluorocarbon-based medium 13 and the vapor pressure of the fluorocarbon-based medium 13 within the storage section 11 change depending on the temperature of the fluorocarbon-based medium 13 cooled by the cooling section 16. When using vapor heat transport, when the secondary battery 12 generates heat, the liquid fluorocarbon medium 13 evaporates due to the heat of the secondary battery 12. The secondary battery 12 is cooled by the heat of evaporation of the fluorocarbon medium 13. The evaporated fluorocarbon medium 13 is cooled and condensed by the cooling unit 16 arranged above the storage unit 11. The condensed liquid fluorocarbon medium 13 cools the secondary battery 12 again and evaporates. In this way, as shown by the up and down arrows in the storage unit 11 in Figure 2, the secondary battery 12 in the storage unit 11 is cooled by a cycle of evaporation and condensation of the fluorocarbon medium 13c when it generates heat.

[0024] The control unit 60 shown in FIG. 1 controls the temperature of the fluorocarbon medium 13 in the storage unit 11, thereby adjusting the temperature of the secondary battery 12 and changing the vapor pressure of the fluorocarbon medium 13 in the storage unit 11 using the heat of evaporation of the fluorocarbon medium 13. The control unit 60 controls the compressor 30 and the expansion valve 40 to adjust the temperature of the refrigerant 18 supplied to the cooling unit 16. Adjusting the temperature of the refrigerant 18 supplied to the cooling unit 16 adjusts the vapor pressure of the fluorocarbon medium 13 in the storage unit 11. That is, the control unit 60 can change the vapor pressure of the fluorocarbon medium 13 in the storage unit 11 by controlling the temperature of the fluorocarbon medium 13 in the storage unit 11. When a predetermined condition is met that indicates that the secondary battery 12 is expanding, such as during charging or discharging of the secondary battery 12, the control unit 60 increases the temperature of the fluorocarbon medium 13 in the storage unit 11 compared to before the predetermined condition was met, thereby increasing the vapor pressure of the fluorocarbon medium 13 in the storage unit 11.

[0025] FIG. 3 is an explanatory diagram of the expansion of a lithium-ion battery, which is a secondary battery 12, during charging. FIG. 3 schematically shows the size of the active mass of the negative electrode and the active mass of the positive electrode during discharging and charging of a lithium-ion battery. FIG. 3 also shows the movement of lithium ions during discharging and charging. As shown in FIG. 3, during discharging, lithium ions move from the negative electrode to the positive electrode via the separator SP. On the other hand, during charging, lithium ions move from the positive electrode to the negative electrode. During charging and discharging of a lithium-ion battery, the volume expands due to the insertion of lithium ions into the positive or negative electrode. In the case of insertion of an equivalent amount of lithium ions, as shown in FIG. 3, the negative electrode becomes larger than the positive electrode. Therefore, the volume expansion of a lithium-ion battery is greater during charging than during discharging. The higher the SOC (State of Charge), the greater the amount of expansion of a lithium-ion battery. In addition to this, during the initial charge and discharge of a lithium-ion battery, gasification of part of the electrolyte and gasification of the electrolyte due to deterioration phenomena associated with charge and discharge cycles also cause the lithium-ion battery to expand due to an increase in internal pressure.

[0026] FIG. 4 is an explanatory diagram showing the relationship between the boiling point temperature and vapor pressure of the fluorocarbon medium 13. In FIG. 4, the change in vapor pressure with respect to the change in boiling point temperature of the fluorocarbon medium 13 is shown as a curve C1. By selecting the vapor pressure of the fluorocarbon medium 13 filled in the storage section 11, the vapor pressure that compresses the secondary battery 12 relative to the temperature inside the storage section 11 can be set. In this embodiment, as shown in FIG. 4, the fluorocarbon medium 13 was selected so as to obtain a vapor pressure of 0.48 to 0.90 MPa for a boiling point control of 15.2 to 35.8 degrees Celsius (°C). Note that a vapor pressure of 0.48 MPa is the pressure that eliminates distortion of the secondary battery 12 due to expansion when the SOC of the secondary battery 12 during charging is 0.5. Furthermore, a vapor pressure of 0.90 MPa is the pressure that eliminates distortion of the secondary battery 12 due to expansion when the SOC of the secondary battery 12 during charging is 0.8.

[0027] 5 is an explanatory diagram of the relationship between the temperature of the secondary battery 12, the temperature of the cooling unit 16, and the vapor temperature of the fluorocarbon-based medium 13. The boiling point temperature T sat Once this is determined, the vapor pressure P sat is the boiling point temperature T sat The boiling point temperature T is determined as a function of sat Once this is determined, the heat generation temperature Th of the secondary battery 12 under the operating conditions of the secondary battery 12 and the cooling temperature Tc of the cooling unit 16 are calculated. Since the secondary battery 12 and the cooling unit 16 exchange heat with the fluorocarbon-based medium 13 in the storage unit 11 through the wall surface, the cooling temperature Tc on the condensation side is calculated based on the boiling point temperature T sat Superheat ΔT s,c On the other hand, the heat generation temperature Th on the evaporation side is lower than the boiling point temperature T sat Superheat ΔT s,e The degree of superheat ΔT in the cooling section 16 on the condensation side is higher by s,c is a function f of the heat flux qw as shown in the following equation (1). c -1 Similarly, the degree of superheat ΔT of the secondary battery 12 on the evaporation side can be calculated as follows: s,e is a function f of the heat flux qw as shown in the following equation (2). e -1 It can be calculated as:

[0028]

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[0029] In Fig. 5, the temperature change between the cooling unit 16 and the secondary battery 12 when the vapor pressure of the fluorocarbon medium 13 is 0.90 MPa and the boiling point is 35.8°C is shown by a line L1. Also in Fig. 5, the temperature change when the vapor pressure of the fluorocarbon medium 13 is 0.48 MPa and the boiling point is 15.2°C is shown by a line L2. Also in Fig. 5, the temperature change when the heat flux qw on the condensation side and the evaporation side is 5000 W / m 2 An example of the above is shown in a table above the graph. By substituting the value of the heat flux qw into the above formulas (1) and (2), the degree of superheat ΔT of the cooling section 16 on the condensation side can be calculated as shown in the table in FIG. s,c and the superheat degree ΔT of the secondary battery 12 on the evaporation side s,e is calculated, and the heat generation temperature Th and the cooling temperature Tc are determined. The condensation-side heat flux qw can be calculated from the flow rate and temperature of the refrigerant flowing through the cooling unit 16 and the partition wall area of the cooling unit 16. On the other hand, the evaporation-side heat flux qw can be calculated from the heat generation of the secondary battery 12 calculated from the internal resistance and current of the secondary battery 12 and the partition wall area within the accommodation unit 11.

[0030] FIG. 6 shows the degree of superheat ΔT s,c 6 is an explanatory diagram of the calculation of the degree of superheat ΔT on the condensation side for a number of experimental values. s,c The relationship between the heat flux qw and the temperature is shown in Fig. 6. c -1 The above formula (1) expressed using the formula (3) can be expressed as the following formula (3). c is the intercept in Figure 6, and nc is the slope of line L3 in Figure 6. Line L3 is a line calculated by the least squares method from multiple experimental values. Figure 6 also shows an image of fluorocarbon-based medium 13, which has evaporated due to the heat of secondary battery 12, being cooled and condensed by cooling unit 16.

[0031]

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[0032] FIG. 7 shows the degree of superheat ΔT s,e 7 is an explanatory diagram of the calculation of the degree of superheat ΔT on the evaporation side for multiple experimental values, similar to FIG. s,e The relationship between the heat flux qw and the temperature is shown in Fig. 6. e -1 The above formula (2) expressed using the formula (4) can be expressed as the following formulas (4) and (5). The following formula (4) is a relational expression when interfacial evaporation occurs at the partition wall that contacts the fluorocarbon-based medium 13 in the storage section 11. On the other hand, the following formula (5) is a relational expression when the fluorocarbon-based medium 13 evaporates in the storage section 11 and dry-out occurs at the partition wall. K in the following formulas (4) and (5) e,1 and K. e,2 is the intercept in FIG. 7. Also, ne,1 and ne,2 are the slopes of the lines L4 and L5 in FIG. 7, respectively. The lines L4 and L5 are calculated by the least squares method from multiple experimental values. The lines L4 and L5 are the intercepts in FIG. 7 at the boundary value ΔT s,e0 7 shows an image of condensed fluorocarbon medium 13 evaporating due to the heat of secondary battery 12.

[0033]

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[0034] FIG. 8 is an explanatory diagram of the time course of strain of secondary battery 12 during charge and discharge when the vapor pressure is 0.90 MPa. In FIG. 8, the graph below shows the time course of the vapor pressure and strain when secondary battery 12 is charged at 1C from a state in which the SOC of 0.5 becomes 0.8, and then discharged at 1C until the SOC becomes 0.5. The time course of the vapor pressure at 0.90 MPa is constant at 0.90 MPa, as shown by line L6. On the other hand, when secondary battery 12 of Comparative Example 1 is not constrained, the time course of the vapor pressure is approximately 10 kPa, as shown by dashed line L6x. The time course of the vapor pressure is represented by the scale "Strain (kPa)" on the left vertical axis, and the time course of the strain, which will be described later, is represented by the scale "Strain (%)" on the right vertical axis.

[0035] As shown by broken line L7, the strain in the embodiment when the vapor pressure is 0.90 MPa becomes zero when the battery is charged to an SOC of 0.8, and is negative at SOCs other than 0.8. This is because the vapor pressure of 0.90 MPa is set to be the same as the expansion pressure when the SOC of the secondary battery 12 is 0.8. On the other hand, when the secondary battery 12 of Comparative Example 1 is not restrained, the strain is always positive, as shown by broken line L7x, and peaks at approximately 0.04%.

[0036] Fig. 9 is an explanatory diagram of the vapor pressure corresponding to the SOC when the vapor pressure is 0.90 MPa. Fig. 9 shows the vapor pressure when the SOC is 0.5 and 0.8 for the embodiment and Comparative Example 1. As shown in Fig. 9, the vapor pressure of the embodiment is 894 kPa (SOC = 0.5) and 901 kPa (SOC = 0.8), which is much higher than that of Comparative Example 1.

[0037] FIG. 10 is an explanatory diagram of the amount of strain corresponding to the SOC when the vapor pressure is 0.90 MPa. FIG. 10 shows the amounts of strain for the embodiment and Comparative Example 1 when the SOC is 0.5 and 0.8. As shown in FIG. 10, the magnitude (absolute value) of the amount of strain for the embodiment when the vapor pressure is 0.90 MPa is 0.022%, which is the largest when the SOC is 0.5. On the other hand, the amount of strain for Comparative Example 1 is 0.039%, which is the largest when the SOC is 0.8. Therefore, the amount of strain for the embodiment when the vapor pressure is 0.90 MPa is suppressed to approximately 56% (0.022 / 0.039) of that for the comparative example.

[0038] 11 is an explanatory diagram of the change over time in the amount of strain of secondary battery 12 during charge and discharge when the vapor pressure is 0.48 MPa. Fig. 11 shows a graph corresponding to the case where the vapor pressure is 0.48 MPa, as compared to the case where the vapor pressure is 0.90 MPa shown in Fig. 8. The change over time at a vapor pressure of 0.48 MPa is a constant 0.48 MPa, as indicated by line L6a. Note that Fig. 11 also shows the change over time in the vapor pressure of Comparative Example 1, indicated by line L6x in Fig. 8, and the change over time in the amount of strain of Comparative Example 1, indicated by broken line L7x in Fig. 8.

[0039] As shown by broken line L7a, the amount of strain in the embodiment when the vapor pressure is 0.48 MPa is zero when the SOC is 0.5, and increases as the SOC increases from 0.5 because the vapor pressure of 0.48 MPa is set to be the same as the expansion pressure when the SOC of the secondary battery 12 is 0.5.

[0040] Fig. 12 is an explanatory diagram of the vapor pressure corresponding to the SOC when the vapor pressure is 0.48 MPa. Fig. 12 shows a bar graph corresponding to the vapor pressure of 0.48 MPa compared to the vapor pressure of 0.90 MPa shown in Fig. 9. Fig. 12 shows the vapor pressures when the SOCs are 0.5 and 0.8 for the embodiment and Comparative Example 1. As shown in Fig. 12, the vapor pressures of the embodiment are 481 kPa (SOC = 0.5) and 488 kPa (SOC = 0.8), which are significantly higher than Comparative Example 1.

[0041] FIG. 13 is an explanatory diagram of the amount of strain corresponding to the SOC when the vapor pressure is 0.48 MPa. FIG. 13 shows a bar graph corresponding to the vapor pressure of 0.48 MPa compared to the vapor pressure of 0.90 MPa shown in FIG. 10 . FIG. 13 shows the amount of strain when the SOC is 0.5 and 0.8 for the embodiment and Comparative Example 1. As shown in FIG. 13 , the magnitude of the amount of strain for the embodiment when the vapor pressure is 0.48 MPa is 0.022%, which is the largest when the SOC is 0.8. On the other hand, the maximum amount of strain for Comparative Example 1 is 0.039%, so the amount of strain for the embodiment when the vapor pressure is 0.48 MPa is suppressed to approximately 56% (0.022 / 0.039) of that for the comparative example.

[0042] As described above, in the secondary battery system 1 of this embodiment, the storage unit 11 is filled with multiple secondary batteries 12 and a fluorocarbon-based fluorocarbon medium 13. The control unit 60 controls the temperature of the fluorocarbon-based medium 13 in the storage unit 11, thereby adjusting the temperature of the secondary batteries 12 using the heat of evaporation of the fluorocarbon-based medium 13 and changing the vapor pressure of the fluorocarbon-based medium 13 in the storage unit 11. Therefore, in this embodiment, the heat of evaporation of the fluorocarbon-based medium 13, which is a low-boiling-point medium, is used to cool the heated secondary batteries 12. This allows the temperature of the secondary batteries 12 to be controlled near the boiling point of the fluorocarbon-based medium 13. The control unit 60 can also change the vapor pressure of the fluorocarbon-based medium 13 in the storage unit 11 in which the secondary batteries 12 are stored. Therefore, by controlling the vapor pressure of the fluorocarbon-based medium 13, the expansion and contraction of the secondary batteries 12, which expand during charging and discharging, can be uniformly suppressed by the vapor pressure. If the secondary battery 12 expands, there is a risk that a portion of the active material structure within the secondary battery 12 will collapse, which may result in deterioration of the secondary battery 12 or a decrease in safety. In contrast, by suppressing the expansion of the secondary battery 12 using vapor pressure, it is possible to suppress the deterioration of the secondary battery 12 or a decrease in safety. Furthermore, unlike physical external constraints, suppressing expansion using vapor pressure can suppress expansion uniformly throughout the secondary battery 12. Therefore, suppressing expansion using vapor pressure does not require large-scale external constraints. Furthermore, because vapor pressure uniformly suppresses expansion throughout the secondary battery 12, it is possible to reduce concentrated battery deterioration that occurs due to uneven constraints within the secondary battery 12.

[0043] In this embodiment, the cooling unit 16, which is disposed vertically above the storage unit 11, cools and condenses the vaporized fluorocarbon-based medium 13 that has evaporated within the storage unit 11. When a predetermined condition is met under which the secondary battery 12 is estimated to be expanding, the control unit 60 raises the temperature of the fluorocarbon-based medium 13 within the storage unit 11 compared to before the predetermined condition was met, thereby increasing the vapor pressure of the fluorocarbon-based medium 13 within the storage unit 11. In this embodiment, the fluorocarbon-based medium 13 that has condensed within the storage unit 11 moves to the lower side of the storage unit 11, where it cools the secondary battery 12 again and evaporates. The secondary battery 12 is cooled by vapor heat transport using the fluorocarbon-based medium 13, allowing the secondary battery 12 to be cooled efficiently. When a predetermined condition is met under which the secondary battery 12 is estimated to be expanding, the vapor pressure of the fluorocarbon-based medium 13 is increased by adjusting the temperature of the fluorocarbon-based medium 13. This allows the expansion of the secondary battery 12 to be suppressed by vapor pressure only when the secondary battery 12 is expanded, and the secondary battery 12 does not need to be compressed by vapor pressure when the secondary battery 12 is not expanded.

[0044] <Modification of the first embodiment> Fig. 14 is a schematic block diagram of a secondary battery system 1a according to a modification of the first embodiment. The secondary battery system 1a differs significantly from the secondary battery system 1 according to the first embodiment in that cooling water is used as the refrigerant 18a supplied to the cooling unit 16, and the temperature of the refrigerant 18a is adjusted using a heat exchange medium 56 circulating through a heat exchange medium flow path 55. Therefore, in the modification of the first embodiment, only the differences from the first embodiment will be described, and a description of the same configuration as the first embodiment will be omitted. In Fig. 14, a refrigerant flow path 50a through which the cooling water flows as the refrigerant 18a is indicated by a dashed line, and a heat exchange medium flow path 55 is indicated by a solid line.

[0045] As shown in FIG. 14, the secondary battery system 1a includes a temperature control box 10, a heat exchange medium 56, a heat exchange medium flow path 55 through which the heat exchange medium 56 flows, a compressor 30, an expansion valve 40, a refrigerant 18a, a refrigerant flow path 50a through which the refrigerant 18a flows, a pump 70 that circulates the refrigerant 18a within the refrigerant flow path 50a, a control valve 80, a condenser 21, an evaporator 22, and a control unit 60a.

[0046] In this modification, a fluorocarbon-based medium, which is a low-boiling-point medium, is used as the heat exchange medium 56. The heat exchange medium 56 flowing in the heat exchange medium flow path 55 is compressed to a high temperature and high pressure by the compressor 30, and is cooled and condensed by heat exchange with the refrigerant 18a in the condenser 21. The cooled heat exchange medium 56 is expanded by the expansion valve 40 and its temperature is lowered. The evaporated heat exchange medium 56 is heated and evaporated by heat exchange with the refrigerant 18a in the evaporator 22, and is then supplied to the compressor 30.

[0047] The refrigerant flow path 50a is a flow path that circulates the refrigerant 18a through the cooling unit 16. The condenser 21 is disposed on the refrigerant flow path 50a, and dissipates heat from the supplied refrigerant 18a, and exchanges heat between the refrigerant 18a and a heat exchange medium 56 compressed by the compressor 30. The refrigerant 18a flowing through the condenser 21 is heated by heat exchange with the high-temperature, high-pressure heat exchange medium 56, and dissipates heat into the outside air.

[0048] The evaporator 22 is disposed on the refrigerant flow path 50a, and is supplied with refrigerant 18a, which exchanges heat between the supplied refrigerant 18a and the heat exchange medium 56 expanded by the expansion valve 40. As shown in FIG. 14 , the evaporator 22 and the condenser 21 are disposed in parallel on the refrigerant flow path 50a. The refrigerant 18a flowing through the evaporator 22 is cooled by heat exchange with the low-temperature, low-pressure heat exchange medium 56. The cooled refrigerant 18a is combined with the refrigerant 18a discharged from the condenser 21 and sent to the cooling unit 16 by the pump 70. The refrigerant 18a discharged from the cooling unit 16 is supplied to the condenser 21 and the evaporator 22 at different flow rates by a control valve 80.

[0049] The control unit 60a controls the control valve 80 to adjust the refrigerant 18a supplied to the condenser 21 and the evaporator 22, thereby adjusting the temperature of the refrigerant 18a supplied to the cooling unit 16. The temperature of the refrigerant 18a passing through the condenser 21 increases (for example, to 50°C) due to heat exchange with the high-temperature heat exchange medium 56. On the other hand, the temperature of the refrigerant 18a passing through the evaporator 22 decreases (for example, to 10°C) due to heat exchange with the low-temperature heat exchange medium 56. The control unit 60a adjusts the flow rates of the refrigerant 18a supplied to the condenser 21 and the evaporator 22, thereby mixing the high-temperature refrigerant 18a that has passed through the condenser 21 and the low-temperature refrigerant 18a that has passed through the evaporator 22 and supplying the refrigerant 18a at an intermediate temperature (10°C to 50°C) to the cooling unit 16. As a result, the vapor pressure of the fluorocarbon-based medium 13 in the storage unit 11 is determined by the temperature of the cooling unit 16 adjusted by the control unit 60a.

[0050] Second Embodiment 15 is a schematic block diagram of a secondary battery system 1b of the second embodiment. The secondary battery system 1b of the second embodiment is significantly different from the secondary battery system 1 of the first embodiment in that the fluorocarbon-based medium 13b in the storage unit 11 is circulated without being sealed, and the circulating fluorocarbon-based medium 13b functions as a refrigerant supplied to the cooling unit 16. Therefore, in the second embodiment, only the differences from the first embodiment will be described, and a description of the same configuration as the first embodiment will be omitted.

[0051] As shown in FIG. 15, the secondary battery system 1b of the second embodiment includes a temperature control box 10, a condenser (heat radiator) 20b, an expansion valve (expansion valve) 40b, a fluorocarbon-based medium 13b, a refrigerant flow path (medium flow path) 50b that circulates the fluorocarbon-based medium 13b within the storage section 11, a first compressor 31, a second compressor 32, and a control section 60b.

[0052] The refrigerant flow path 50b supplies the fluorocarbon-based medium 13b discharged from the cooling unit 16 into the storage unit 11, supplies the fluorocarbon-based medium 13b discharged from the storage unit 11 to the condenser 20b, and supplies the fluorocarbon-based medium 13b discharged from the condenser 20b to the cooling unit 16. The first compressor 31 is arranged on the refrigerant flow path 50b downstream of the cooling unit 16 and upstream of the storage unit 11. The first compressor 31 compresses the fluorocarbon-based medium 13b supplied into the storage unit 11. The second compressor 32 is arranged on the refrigerant flow path 50b downstream of the storage unit 11 and upstream of the condenser 20b. The second compressor 32 compresses the fluorocarbon-based medium 13b discharged from the storage unit 11.

[0053] The condenser 20b dissipates heat from the fluorocarbon-based medium 13b compressed by the second compressor 32. The expansion valve 40b expands the fluorocarbon-based medium 13b whose temperature has been lowered by heat dissipation by the condenser 20. The fluorocarbon-based medium 13b whose temperature has been lowered by expansion is supplied to the cooling unit 16. The control unit 60b controls the power allocated to the first compressor 31 and the second compressor 32, thereby changing the vapor pressure of the fluorocarbon-based medium 13b in the storage unit 11 to the expansion pressure of the secondary battery 12 during charging and discharging.

[0054] 16 and 17 are examples of Ph diagrams of the vapor compression refrigeration cycle in the second embodiment. Fig. 16 shows a vapor compression refrigeration cycle in which the expansion pressure when the SOC of the secondary battery 12 is 0.5 is the same as the vapor pressure of the fluorocarbon medium 13b in the storage section 11. Fig. 17 shows a vapor compression refrigeration cycle in which the expansion pressure when the SOC of the secondary battery 12 is 0.8 is the same as the vapor pressure of the fluorocarbon medium 13b in the storage section 11. In Figs. 16 and 17, the first compressor 31, the second compressor 32, and the expansion valve 40b are represented by "C1," "C2," and "E," respectively.

[0055] As shown in Figure 16, the second compressor 32 increases the pressure of the fluorocarbon-based medium 13b discharged from the storage section 11 to a high temperature and high pressure (50°C, 1.32 MPa). The expansion valve 40b expands the fluorocarbon-based medium 13b, whose temperature has been reduced by the condenser 20b, to a low temperature and constant pressure (13.5°C, 0.46 MPa). The first compressor 31 increases the pressure of the fluorocarbon-based medium 13b expanded by the expansion valve 40b to a medium temperature and medium pressure (15.2°C, 0.48 MPa) so that the vapor pressure becomes the same as the expansion pressure of the secondary battery 12.

[0056] As in the vapor compression refrigeration cycle shown in Fig. 16, as shown in Fig. 17, the second compressor 32 increases the pressure of the fluorocarbon medium 13b to a high temperature and high pressure (50°C, 1.32 MPa). The expansion valve 40b expands the fluorocarbon medium 13b to a low temperature and constant pressure (34.1°C, 0.87 MPa). The first compressor 31 increases the pressure of the fluorocarbon medium 13b expanded by the expansion valve 40b to a medium temperature and medium pressure (35.8°C, 0.90 MPa) so that the vapor pressure becomes the same as the expansion pressure of the secondary battery 12.

[0057] As described above, in the secondary battery system 1b of the second embodiment, the first compressor 31 compresses the fluorocarbon-based medium 13b supplied into the storage unit 11. The second compressor 32 compresses the fluorocarbon-based medium 13b discharged from the storage unit 11. The control unit 60b controls the power allocated to the first compressor 31 and the second compressor 32 to change the vapor pressure of the fluorocarbon-based medium 13b in the storage unit 11 to the expansion pressure of the secondary battery 12 during charging and discharging. Therefore, in the second embodiment, by controlling the power allocated to the first compressor 31 and the second compressor 32, an intermediate pressure between the pressure compressed by the first compressor 31 and the pressure compressed by the second compressor 32 can be supplied as the pressure of the fluorocarbon-based medium 13b in the storage unit 11. Furthermore, by compressing the fluorocarbon-based medium 13b to a high temperature and high pressure by the second compressor 32, the heat of the fluorocarbon-based medium 13b can be released to the outside air using the condenser 21b. This allows the vapor pressure of the fluorocarbon-based medium 13b in the container 11 to be changed using the first compressor 31 and the second compressor 32, and the temperature of the secondary battery 12 to be changed by the cooling unit 16 independently of the vapor pressure.

[0058] Furthermore, the condenser 20b in the second embodiment dissipates heat from the fluorocarbon-based medium 13b compressed by the second compressor 32. The expansion valve 40b expands the fluorocarbon-based medium 13b whose temperature has been lowered by heat dissipation by the condenser 20b. In this embodiment, the high-temperature, high-pressure fluorocarbon-based medium 13b compressed by the second compressor 32 dissipates heat by the condenser 20b. The temperature of the fluorocarbon-based medium 13b after heat dissipation is lowered by expansion by the expansion valve 40b. The lowered-temperature fluorocarbon-based medium 13b is supplied to the cooling unit 16, thereby cooling the secondary batteries 12 arranged in the storage unit 11. The fluorocarbon-based medium 13b discharged from the cooling unit 16 is pressurized to an intermediate pressure by the first compressor 31, so that the vapor pressure of the fluorocarbon-based medium 13b in the storage unit 11 can be adjusted to be the same as the expansion pressure of the secondary batteries 12.

[0059] <Modification of the second embodiment> 18 is a schematic block diagram of a secondary battery system 1c according to a modification of the second embodiment. The secondary battery system 1c is significantly different from the secondary battery system 1a according to the modification of the first embodiment in that the fluorocarbon-based medium 13c in the storage unit 11 functions as a heat exchange medium without being sealed. Therefore, in the modification of the second embodiment, only the differences from the modification of the first embodiment and the second embodiment will be described, and a description of the same configuration as the modification of the first embodiment or the second embodiment will be omitted.

[0060] As shown in FIG. 18, a secondary battery system 1c of a modified example of the second embodiment includes a temperature control box 10, a condenser 21c, an evaporator 22c, an expansion valve 40c, a fluorocarbon-based medium 13c, a heat exchange medium flow path (medium flow path) 55c that circulates the fluorocarbon-based medium 13c in the storage section 11, a refrigerant 18a, a refrigerant flow path 50a, a control valve (control valve) 80, a pump 70, a first compressor 31, a second compressor 32, and a control section 60c.

[0061] In the modified secondary battery system 1c, the fluorocarbon-based medium 13c that cools the secondary battery 12 also functions as a heat exchange medium that flows through a heat exchange medium flow path 55c that connects the condenser 21c and the evaporator 22c. The heat exchange medium flow path 55c supplies the fluorocarbon-based medium 13c discharged from the storage unit 11 to the condenser 21c, supplies the fluorocarbon-based medium 13c condensed by the condenser 21c to the evaporator 22c, and supplies the fluorocarbon-based medium 13c evaporated by the evaporator 22c into the storage unit 11. The first compressor 31 is disposed on the refrigerant flow path 50b downstream of the evaporator 22c and upstream of the storage unit 11, and pressurizes the supplied fluorocarbon-based medium 13c. The second compressor 32 is disposed on the refrigerant flow path 50b downstream of the storage unit 11 and upstream of the condenser 21c. Therefore, the fluorocarbon-based medium 13c compressed to a high temperature and high pressure by the second compressor 32 is condensed by dissipating heat in the condenser 21c. The expansion valve 40c expands the fluorocarbon-based medium 13c that has been condensed by heat exchange with the refrigerant 18a in the condenser 21c. The expanded fluorocarbon-based medium 13c is heated and evaporated by heat exchange with the refrigerant 18a in the evaporator 22c. The heated fluorocarbon-based medium 13c is pressurized by the first compressor 31 to a vapor pressure that is the same as the expansion pressure of the secondary batteries 12 in the accommodation unit 11, and is supplied into the accommodation unit 11.

[0062] Figures 19 and 20 are examples of Ph diagrams of a vapor compression refrigeration cycle in a modified example of the second embodiment. Figure 19 shows a vapor compression refrigeration cycle in which the expansion pressure when the SOC of the secondary battery 12 is 0.5 is the same as the vapor pressure of the fluorocarbon medium 13c in the storage section 11. Figure 20 shows a vapor compression refrigeration cycle in which the expansion pressure when the SOC of the secondary battery 12 is 0.8 is the same as the vapor pressure of the fluorocarbon medium 13b in the storage section 11.

[0063] As shown in Figure 19, the second compressor 32 increases the pressure of the fluorocarbon medium 13c discharged from the storage unit 11 to a high temperature and high pressure (50°C, 1.32 MPa). The expansion valve 40c expands the fluorocarbon medium 13c, whose temperature has been reduced by the condenser 21c, to a low temperature and low pressure (10.0°C, 0.41 MPa). The first compressor 31 increases the pressure of the fluorocarbon medium 13c expanded by the expansion valve 40c to a medium temperature and medium pressure (15.2°C, 0.48 MPa) so that the vapor pressure becomes the same as the expansion pressure of the secondary battery 12.

[0064] As shown in Figure 20, the second compressor 32 increases the pressure of the fluorocarbon medium 13c to a high temperature and high pressure (50°C, 1.32 MPa). The expansion valve 40c expands the fluorocarbon medium 13c to a low temperature and low pressure (10.0°C, 0.41 MPa). The first compressor 31 increases the pressure of the fluorocarbon medium 13c expanded by the expansion valve 40c to a medium temperature and medium pressure (35.8°C, 0.90 MPa) so that the vapor pressure becomes the same as the expansion pressure of the secondary battery 12.

[0065] As described above, in the modified example of the second embodiment, the condenser 21 dissipates heat from the supplied refrigerant 18a and exchanges heat between the refrigerant 18a and the fluorocarbon-based medium 13c compressed by the second compressor 32. The expansion valve 40c expands the fluorocarbon-based medium 13c that has been condensed through heat exchange with the refrigerant 18a by the condenser 21c. The evaporator 22 exchanges heat between the supplied refrigerant 18a and the fluorocarbon-based medium 13c expanded by the expansion valve 40c. The evaporator 22 and the condenser 21 are arranged in parallel on the refrigerant flow path 50. Therefore, in this modified example, the refrigerant 18a flowing through the refrigerant flow path 50a can adjust the temperature inside the storage unit 11 independently of the vapor pressure of the fluorocarbon-based medium 13c inside the storage unit 11. Because the condenser 21c and the evaporator 22c are arranged in parallel in the refrigerant flow path 50a, the flow rate of the refrigerant 18a supplied to the condenser 21c and the flow rate of the refrigerant 18a supplied to the evaporator 22c are adjusted by the control valve 80. Because the temperature of the refrigerant 18a passing through the condenser 21c is different from the temperature of the refrigerant 18a passing through the evaporator 22c, the temperature of the refrigerant 18a supplied to the cooling unit 16 is adjusted by controlling the flow rate by the control valve 80. In other words, the temperature of the refrigerant 18a supplied to the cooling unit 16 can be easily adjusted. Furthermore, the high-temperature, high-pressure fluorocarbon-based medium 13c compressed by the second compressor 32 dissipates heat by the condenser 21c. After dissipating heat, the fluorocarbon-based medium 13c expands and cools by the expansion valve 40c, is heated and evaporated by the evaporator 22c, and is then pressurized by the first compressor 31. This allows the vapor pressure of the fluorocarbon-based medium 13c in the storage unit 11 to be adjusted separately from the temperature.

[0066] <Third embodiment> 21 is a schematic block diagram of a secondary battery system 1d of the third embodiment. The secondary battery system 1d of the third embodiment differs from the secondary battery system 1c (FIG. 18) of the modified example of the second embodiment in that the measured strain amount of the secondary battery 12 is used to change the vapor pressure of the fluorocarbon-based medium 13c in the storage section 11 so that it becomes equal to the expansion pressure that changes depending on the charge / discharge state of the secondary battery 12. Therefore, in the third embodiment, only the differences from the modified example of the second embodiment will be described, and a description of the same configuration as the first embodiment will be omitted.

[0067] As shown in FIG. 21, the secondary battery system 1d of the third embodiment includes a temperature control box 10, a condenser 21c, an evaporator 22c, a temperature sensor 41 that detects the temperature of the evaporator 22c, an expansion valve 40d, a fluorocarbon-based medium 13c, a heat exchange medium flow path 55c, a refrigerant 18a, a refrigerant flow path 50a, a control valve 80, a pump 70, a first compressor 31, a second compressor 32, a strain detector (acquisition unit) 90, a coulomb counter 95, a pressure sensor 96, and a control unit 60d.

[0068] The expansion valve 40d is a thermostatic expansion valve that automatically controls the degree of superheat of the fluorocarbon-based medium 13c supplied to the evaporator 22c according to the temperature detected by the temperature sensor 41. The strain detector 90 detects the strain of the secondary battery 12 that deforms due to expansion, etc. The coulomb counter 95 calculates the SOC by measuring the current flowing into and out of the secondary battery 12. The coulomb counter 95 calculates the SOC by integrating the amount of current stored during charging using a current detection resistor and determining the amount of current that flows out during discharge. The pressure sensor 96 measures the vapor pressure of the fluorocarbon-based medium 13c in the storage section 11.

[0069] The SOC, which is the value detected by the coulomb counter 95, includes an error in current measurement and also an SOC estimation error due to capacity degradation of the secondary battery 12, which increases over time. Therefore, the control unit 60d of the third embodiment corrects the SOC estimation error by the coulomb counter 95 using the amount of strain detected by the strain detector 90 and the vapor pressure in the housing unit 11 measured by the pressure sensor 96. Furthermore, during charging and discharging of the secondary battery 12, the control unit 60d changes the vapor pressure of the fluorocarbon-based medium 13c in the housing unit 11 to the expansion pressure of the secondary battery 12 determined from the amount of strain detected by the strain detector 90. In the third embodiment, the relationship between the amount of strain and the expansion pressure of the secondary battery 12 is measured in advance, and the control unit 60d uses this relationship to change the vapor pressure of the fluorocarbon-based medium 13c in the housing unit 11 to the expansion pressure determined from the amount of strain. The control unit 60d controls the power of the first compressor 31 and the second compressor 32 and the control valve 80 to change the vapor pressure of the fluorocarbon-based medium 13c in the storage unit 11.

[0070] Fig. 22 is a flowchart of vapor pressure control of the fluorocarbon-based medium 13c in the third embodiment. In the control flow shown in Fig. 22, first, charging and discharging of the secondary battery 12 is started (step S1). The control unit 60d checks the charging and discharging of the secondary battery 12 as a predetermined condition that is assumed to cause the secondary battery 12 to expand.

[0071] The coulomb counter 95 detects the SOC of the secondary battery 12 (step S2). The control unit 60d calculates the power of the first compressor 31 and the second compressor 32 and the adjustment amount of the control valve 80 according to the detected SOC (step S3). The control unit 60d calculates the power of the first compressor 31 and the second compressor 32 and the adjustment amount of the control valve 80 based on the relationship between the detected SOC and the expansion pressure of the secondary battery 12 corresponding to the SOC measured in advance, so that the vapor pressure of the fluorocarbon-based medium 13 in the storage unit 11 becomes the expansion pressure of the secondary battery 12. The first compressor 31 and the second compressor 32 are driven by the calculated power, and the control valve 80 is adjusted by the calculated adjustment amount (step S4).

[0072] The pressure sensor 96 measures the vapor pressure of the fluorocarbon-based medium 13c, and the strain detector 90 detects the secondary battery 12 (step S5). The control unit 60d determines whether the detected amount of strain is greater than a threshold value of +|ε0| (step S6). If the detected amount of strain is greater than +|ε0| (step S6: YES), the control unit 60d increases the vapor pressure of the fluorocarbon-based medium 13c in the storage unit 11 so that the amount of strain in the secondary battery 12 becomes zero (step S7), and the processes from step S5 onwards are repeated.

[0073] In the process of step S6, if the detected amount of strain is +|ε0| or less (step S6: NO), the control unit 60d determines whether the amount of strain detected by the strain detector 90 is less than a threshold value of −|ε0| (step S8). If the detected amount of strain is less than −|ε0| (step S8: YES), the control unit 60d reduces the vapor pressure of the fluorocarbon-based medium 13c in the container 11 so that the amount of strain of the secondary battery 12 becomes zero (step S9), and the processes from step S5 onwards are repeated. If the detected amount of strain is −|ε0| or more (step S9: NO), the control unit 60d corrects the coulomb counter 95 so that the SOC of the secondary battery 12 becomes equal to the SOC calculated from the detected amount of strain (step S10).

[0074] In the process of step S11, the control unit 60d determines whether or not to end the vapor pressure control flow (step S11). The control unit 60d determines whether or not to end the control flow depending on whether charging or discharging is stopped, for example, when the vehicle equipped with the secondary battery system 1d is stopped. If it is determined not to end the control flow (step S11: NO), the processes from step S2 onwards are repeated. If it is determined to end the control flow (step S11: YES), the control flow is ended. Note that in the third embodiment, if the control flow is to end, the control unit 60d stops charging or discharging the secondary battery 12. The determination to end the control flow may be made when any process is being performed.

[0075] FIG. 23 is an explanatory diagram of the time transition of the strain of the secondary battery 12 during charging and discharging in the third embodiment. FIG. 23 shows the strain of the secondary battery 12 when the vapor pressure of the fluorocarbon-based medium 13c in the storage section 11 is changed, using the strain of the secondary battery 12 detected by the strain detector 90. The time transition of the vapor pressure in the third embodiment, as shown by the broken line L6d, monotonically increases during charging and monotonically decreases during discharging, reaching a minimum when the SOC is 0.5 and a maximum when the SOC is 0.8. Note that FIG. 23 also shows the time transition of the vapor pressure of Comparative Example 1, represented by the line L6x in FIGS. 8 and 11, and the time transition of the strain of Comparative Example 1, represented by the broken line L7x in FIGS. 8 and 11. When the vapor pressure changes as shown by the line L6d, the strain of the third embodiment is nearly zero during charging and discharging, as shown by the broken line L7d.

[0076] FIG. 24 is an explanatory diagram of changes in various parameters relative to the SOC of the secondary battery 12. The upper graph in FIG. 24 shows the vapor pressure of the fluorocarbon-based medium 13c in the storage unit 11, which changes depending on the SOC of the secondary battery 12, and the saturated vapor temperature of the fluorocarbon-based medium 13c. The lower graph in FIG. 24 shows the power allocated to the first compressor 31 and the second compressor 32, which changes depending on the SOC of the secondary battery 12, and the coefficient of performance (COP). The coefficient of performance (COP) is expressed as a numerical value obtained by dividing the generated cold (kJ / kg) by the driving power of the compressor (kJ / kg). The driving power of the compressor in the third embodiment is the sum of the driving power of the first compressor 31 and the driving power of the second compressor 32.

[0077] In the upper graph of FIG. 24, vapor pressure is indicated by circles, and saturated vapor temperature is indicated by squares. As shown in the upper graph of FIG. 24, vapor pressure and saturated vapor temperature increase as the SOC of the secondary battery 12 increases. In the lower graph of FIG. 24, the driving force allocated to the first compressor 31 is indicated by circles, the driving force allocated to the second compressor 32 is indicated by triangles, and the COP is indicated by squares. As shown in the lower graph of FIG. 24, as the SOC of the secondary battery 12 increases, the driving force of the first compressor 31 increases and the driving force of the second compressor 32 decreases. Because the driving forces of the first compressor 31 and the second compressor 32 increase or decrease in response to changes in SOC in opposite ways, the COP remains almost constant and does not change much as the SOC of the secondary battery 12 increases or decreases.

[0078] As described above, the control unit 60d of the third embodiment changes the vapor pressure of the fluorocarbon medium 13c in the housing 11 to the expansion pressure of the secondary battery 12 determined from the amount of strain detected by the strain detector 90 during charging and discharging of the secondary battery 12. The expansion of the secondary battery 12 in the third embodiment differs between charging and discharging, and also differs depending on the SOC. The vapor pressure of the fluorocarbon medium 13c in the housing 11 is controlled to be the same as the expansion pressure of the secondary battery 12 determined from the amount of strain detected by the strain detector 90. This suppresses expansion of the secondary battery 12 due to the vapor pressure of the fluorocarbon medium 13c, and further suppresses distortion of the secondary battery without excessively compressing the secondary battery 12.

[0079] <Fourth embodiment> 25 is a schematic block diagram of a secondary battery system 1e of the fourth embodiment. The secondary battery system 1e of the fourth embodiment is significantly different from the secondary battery system 1b of the second embodiment (FIG. 15) in that it includes a control valve 81 and a valve 82 as shutoff valves. Therefore, in the fourth embodiment, only the differences from the second embodiment will be described, and a description of the same configuration as the second embodiment will be omitted.

[0080] As shown in FIG. 25, the secondary battery system 1e of the fourth embodiment includes a temperature control box 10, a condenser 20b, an expansion valve 40b, a fluorocarbon-based medium 13b, a refrigerant flow path (medium flow path) 50b that circulates the fluorocarbon-based medium 13b within the storage section 11, a first compressor 31, a second compressor 32, a control valve 81, a valve 82, a coulomb counter 95, a pressure sensor 96, and a control section 60e.

[0081] The control valve 81 is disposed on the refrigerant flow path 50b downstream of the first compressor 31 and upstream of the accommodating unit 11. The control valve 81 opens and closes the connection between the first compressor 31 and the accommodating unit 11 under the control of the control unit 60e. The control valve 81 is also connectable to the refrigerant flow path 50b downstream of the accommodating unit 11. In other words, the control valve 81 forms a so-called bypass path that supplies the fluorocarbon-based medium 13b supplied from the first compressor 31 to the refrigerant flow path 50b inside the accommodating unit 11 or downstream of the accommodating unit 11.

[0082] The valve 82 is disposed on the refrigerant flow path 50b downstream of the accommodating unit 11 and upstream of the second compressor 32. The valve 82 opens and closes the connection between the accommodating unit 11 and the second compressor 32 under the control of the control unit 60e. Note that FIG. 25 shows a state in which the valve 82 is open and the control valve 81 connects the first compressor 31 and the accommodating unit 11.

[0083] As in the third embodiment (FIG. 21), the coulomb counter 95 detects the SOC of the secondary battery 12. As in the third embodiment, the pressure sensor 96 measures the vapor pressure of the fluorocarbon-based medium 13b in the container 11.

[0084] When charging / discharging of the secondary battery 12 stops from a state in which the secondary battery 12 is expanding due to charging / discharging, the control unit 60e of the fourth embodiment closes the valve 82 and connects the control valve 81 to the refrigerant flow path 50b downstream of the storage unit 11 to form a bypass path. As a result, the control unit 60e seals the storage unit 11 and circulates the fluorocarbon-based medium 13b through the refrigerant flow path 50b without supplying it into the storage unit 11. FIG. 26 is a schematic block diagram of the secondary battery system 1e in a state in which the storage unit 11 is sealed and a bypass path is formed.

[0085] Fig. 27 is a flowchart of control when charging / discharging is stopped in the fourth embodiment. In the control flow shown in Fig. 27, first, the control unit 60e determines whether the secondary battery 12 that was being charged / discharged has stopped (step S21). If it is determined that the secondary battery 12 has not stopped (step S21: NO), the control unit 60e monitors whether the secondary battery 12 has stopped. If it is determined that the secondary battery 12 has stopped (step S21: YES), the control unit 60e calculates the expansion pressure Pb of the secondary battery 12 from the SOC detected by the coulomb counter 95 (step S22). The control unit 60e connects the control valve 81 to the refrigerant flow path 50b downstream of the storage unit 11 and closes the valve 82 to form a bypass path (step S23).

[0086] The pressure sensor 96 measures the vapor pressure Pm of the fluorocarbon-based medium 13b in the storage unit 11 (step S24). The control unit 60e determines whether the difference ΔP, obtained by subtracting the expansion pressure Pb of the secondary battery 12 from the measured vapor pressure Pm, is greater than a threshold value Pth (Pth>0) (step S25). If it is determined that the difference ΔP is greater than Pth (step S25: YES), the control unit 60e opens the valve 82 by a predetermined amount (step S26), and the process of step S29, described below, is performed. By the control unit 60e of the fourth embodiment opening the valve 82 very slightly as a predetermined amount, the vapor pressure Pm, which is higher than the expansion pressure Pb, is slightly reduced.

[0087] If it is determined in the process of step S25 that the difference ΔP is equal to or less than -Pth (step S25: NO), the control unit 60e determines whether the difference ΔP is smaller than -Pth (step S27). If it is determined that the difference ΔP is equal to or greater than -Pth (step S27: NO), the process of step S29, which will be described later, is performed. If it is determined that the difference ΔP is smaller than -Pth (step S27: YES), the control unit 60e connects the control valve 81 to the accommodating unit 11 to drive the first compressor 31 (step S28). This increases the vapor pressure Pm, which is smaller than the expansion pressure Pb.

[0088] Next, the control unit 60e determines whether the stopped charging / discharging of the secondary battery 12 has resumed (step S29). If it is determined that the charging / discharging of the secondary battery 12 has not resumed (step S29: NO), the processing from step S22 onwards is repeated. If it is determined that the charging / discharging of the secondary battery 12 has resumed (step S29: YES), the control unit 60e connects the control valve 81 to the housing unit 11 and opens the valve 82 to control the charging / discharging of the secondary battery 12 (step S30), and ends the control flow when charging / discharging is stopped.

[0089] As described above, when charging / discharging of the secondary battery 12 is stopped, the control unit 60e of the fourth embodiment seals the storage unit 11 and circulates the fluorocarbon-based medium 13b through the refrigerant flow path 50b without supplying it into the storage unit 11. Therefore, in the secondary battery system 1e of the fourth embodiment, when charging / discharging stops, the control valves 81 and 82 control the fluorocarbon-based medium 13b in the storage unit 11 to seal it off. Even after charging / discharging is stopped, the secondary battery 12 remains expanded. Therefore, sealing the storage unit 11 adjusts the expansion pressure and vapor pressure of the secondary battery 12 during charging / discharging to be the same. This can suppress deterioration of the secondary battery 12 and a decrease in safety.

[0090] <Modifications of the embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention, including, for example, the following modifications: In the above-described embodiment, part of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware.

[0091] The first to fourth embodiments described an example of a secondary battery system. The secondary battery system cools the secondary battery in the housing 11 with a fluorocarbon-based medium 13, and can be modified within a range that suppresses expansion of the secondary battery due to vapor pressure by adjusting the temperature of the fluorocarbon-based medium 13. For example, the secondary battery 12 may be a secondary battery other than a lithium-ion battery that expands due to charging and discharging. Furthermore, suppressing expansion of the secondary battery 12 is not limited to charging and discharging the secondary battery 12; it is sufficient if a predetermined condition is met that indicates expansion of the secondary battery 12. Examples of the predetermined condition include a SOC of 0.5 or greater or a predetermined time has elapsed since the start of charging. In the first embodiment and other embodiments, a system that controls the temperature of the refrigerant supplied to the cooling unit 16 to suppress expansion of the secondary battery 12 was described. Therefore, for example, the compressor 30, condenser 20, and expansion valve 40 shown in FIG. 1 can be modified within a range that allows the cooling unit 16 to be cooled by the refrigerant.

[0092] The secondary battery system 1d (FIG. 21) of the third embodiment described above includes a strain detector 90, a coulomb counter 95, and a pressure sensor 96, but may include at least one of these. For example, the control unit 60d may use the amount of strain of the secondary battery detected by the strain detector 90 to determine the expansion pressure of the secondary battery 12 and change the vapor pressure of the fluorocarbon-based medium 13c so that the expansion pressure is equal to the determined expansion pressure. Alternatively, instead of using the strain detector 90, the amount of strain of the secondary battery 12 may be calculated from the detected value of at least one of the coulomb counter 95 and the pressure sensor 96, and the vapor pressure of the fluorocarbon-based medium 13c may be changed. For example, the control unit 60d may change the vapor pressure based only on the SOC detected by the coulomb counter 95.

[0093] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0094] The present invention can also be realized in the following forms. [Application example 1] A secondary battery system, A secondary battery; a housing portion that houses the secondary battery; A fluorocarbon-based medium filled in the storage section; a temperature control unit that controls the temperature of the fluorocarbon medium in the storage unit to adjust the temperature of the secondary battery using the heat of evaporation of the fluorocarbon medium and change the vapor pressure of the fluorocarbon medium in the storage unit; A secondary battery system comprising: [Application example 2] The secondary battery system according to Application Example 1, The temperature control unit is a cooling unit disposed vertically above the storage unit and cooling and condensing the vaporized fluorocarbon-based medium in the storage unit; A secondary battery system in which, when a predetermined condition is met under which the secondary battery is estimated to be expanding, the temperature of the fluorocarbon-based medium in the storage unit is increased compared to before the predetermined condition was met, thereby increasing the vapor pressure of the fluorocarbon-based medium in the storage unit. [Application example 3] The secondary battery system according to Application Example 1 or Application Example 2, further comprising: a medium flow path that circulates the fluorocarbon-based medium in the storage unit; a first compressor disposed on the medium flow path and configured to compress the fluorocarbon-based medium supplied into the storage unit; a second compressor disposed on the medium flow path and configured to compress the fluorocarbon-based medium discharged from the storage section; a radiator disposed on the medium flow path and configured to radiate heat from the fluorocarbon-based medium compressed by the second compressor; Equipped with The temperature adjustment unit controls the power allocated to the first compressor and the second compressor to change the vapor pressure and temperature of the fluorocarbon-based medium in the storage unit. [Application example 4] The secondary battery system according to any one of Application Examples 1 to 3, further comprising: an expansion valve disposed on the medium flow path for expanding the fluorocarbon-based medium from which heat has been dissipated by the radiator; a refrigerant flow path that circulates a refrigerant flowing within the cooling unit; a heat exchanger that is disposed on the refrigerant flow path and on the medium flow path, that is supplied with the refrigerant discharged from the cooling unit and the fluorocarbon-based medium expanded by the expansion valve, and that exchanges heat between the supplied refrigerant and the fluorocarbon-based medium; a control valve disposed on the refrigerant flow path; Equipped with The radiator is arranged in the refrigerant flow path so as to be parallel to the heat exchanger with respect to the cooling unit, and the refrigerant discharged from the cooling unit and the fluorocarbon-based medium compressed by the second compressor are supplied to the radiator, and heat exchange occurs between the supplied refrigerant and the fluorocarbon-based medium, the control valve is disposed between the cooling unit and the radiator and the heat exchanger, and controls a flow rate distribution of the refrigerant supplied from the cooling unit to the radiator and the heat exchanger, respectively; The first compressor is supplied with the fluorocarbon-based medium that has been heat exchanged with the refrigerant by the heat exchanger, The temperature adjustment unit adjusts the temperature of the refrigerant supplied to the cooling unit by controlling the control valve. [Application example 5] The secondary battery system according to any one of Application Examples 1 to 4, further comprising: an expansion valve disposed on the medium flow path for expanding the fluorocarbon-based medium from which heat has been dissipated by the radiator; The fluorocarbon-based medium expanded by the expansion valve is supplied to the cooling section, The fluorocarbon-based medium discharged from the cooling unit is supplied to the first compressor. [Application Example 6] The secondary battery system according to any one of Application Examples 1 to 5, an expansion valve disposed on the medium flow path for expanding the fluorocarbon-based medium from which heat has been dissipated by the radiator; Equipped with The fluorocarbon-based medium expanded by the expansion valve is supplied to the cooling section, The fluorocarbon-based medium discharged from the cooling unit is supplied to the first compressor. [Application Example 7] The secondary battery system according to any one of Application Examples 1 to 6, The temperature control unit is an acquisition unit that acquires a distortion amount of the secondary battery; When the secondary battery is charged or discharged under the predetermined conditions, the vapor pressure of the fluorocarbon-based medium in the storage section is changed to an expansion pressure of the secondary battery that is specified from the acquired amount of distortion. [Explanation of symbols]

[0095] 1, 1a, 1b, 1c, 1d, 1e... Secondary battery system 10...Temperature control box 11...Storage section 12…Secondary battery 13, 13b, 13c...Fluorocarbon-based media 16…Cooling section 18, 18a...refrigerant 20...Condenser 20b, 21, 21c...Condenser (radiator) 22...Evaporator 22c...Evaporator (heat exchanger) 30...Compressor 31...First compressor 32...Second compressor 40, 40d...Expansion valve 40b, 40c...Expansion valve (expansion valve) 50, 50a, 50b... refrigerant flow path 55, 55c...heat exchange medium flow path 56...Heat exchange medium 60, 60a, 60b, 60c, 60d, 60e...Control unit (temperature control unit) 70...Pump 80...Control valve (control valve) 81...Control valve (shutoff valve) 82...Valve (Shut-off valve) 90...Distortion detector (acquisition unit) 95...Coulomb counter 96...Pressure sensor

Claims

1. A secondary battery system, A secondary battery; a housing portion that houses the secondary battery; A fluorocarbon-based medium filled in the storage section; a temperature control unit that controls the temperature of the fluorocarbon medium in the storage unit to adjust the temperature of the secondary battery using the heat of evaporation of the fluorocarbon medium and change the vapor pressure of the fluorocarbon medium in the storage unit; A secondary battery system comprising:

2. The secondary battery system according to claim 1, The temperature control unit is a cooling unit disposed vertically above the storage unit and cooling and condensing the vaporized fluorocarbon-based medium in the storage unit; A secondary battery system in which, when a predetermined condition is met under which the secondary battery is estimated to be expanding, the temperature of the fluorocarbon-based medium in the storage unit is increased compared to before the predetermined condition was met, thereby increasing the vapor pressure of the fluorocarbon-based medium in the storage unit.

3. The secondary battery system according to claim 2, further comprising: a medium flow path that circulates the fluorocarbon-based medium in the storage unit; a first compressor disposed on the medium flow path and configured to compress the fluorocarbon-based medium supplied into the storage unit; a second compressor disposed on the medium flow path and configured to compress the fluorocarbon-based medium discharged from the storage section; a radiator disposed on the medium flow path and configured to radiate heat from the fluorocarbon-based medium compressed by the second compressor; Equipped with The temperature adjustment unit controls the power allocated to the first compressor and the second compressor to change the vapor pressure and temperature of the fluorocarbon-based medium in the storage unit.

4. The secondary battery system according to claim 3, further comprising: an expansion valve disposed on the medium flow path for expanding the fluorocarbon-based medium from which heat has been dissipated by the radiator; a refrigerant flow path that circulates a refrigerant flowing within the cooling unit; a heat exchanger that is disposed on the refrigerant flow path and on the medium flow path, that is supplied with the refrigerant discharged from the cooling unit and the fluorocarbon-based medium expanded by the expansion valve, and that exchanges heat between the supplied refrigerant and the fluorocarbon-based medium; a control valve disposed on the refrigerant flow path; Equipped with The radiator is arranged in the refrigerant flow path so as to be parallel to the heat exchanger with respect to the cooling unit, and the refrigerant discharged from the cooling unit and the fluorocarbon-based medium compressed by the second compressor are supplied to the radiator, and heat exchange occurs between the supplied refrigerant and the fluorocarbon-based medium, the control valve is disposed between the cooling unit and the radiator and the heat exchanger, and controls a flow rate distribution of the refrigerant supplied from the cooling unit to the radiator and the heat exchanger, respectively; The first compressor is supplied with the fluorocarbon-based medium that has been heat exchanged with the refrigerant by the heat exchanger, The temperature adjustment unit adjusts the temperature of the refrigerant supplied to the cooling unit by controlling the control valve.

5. The secondary battery system according to claim 3, further comprising: an expansion valve disposed on the medium flow path for expanding the fluorocarbon-based medium from which heat has been dissipated by the radiator; The fluorocarbon-based medium expanded by the expansion valve is supplied to the cooling section, The fluorocarbon-based medium discharged from the cooling unit is supplied to the first compressor.

6. The secondary battery system according to claim 5, The temperature control unit is a shutoff valve for shutting off the fluorocarbon-based medium supplied to the storage section, on the medium flow path; The secondary battery system further comprises: a shutoff valve that closes when charging / discharging of the secondary battery is stopped, thereby circulating the fluorocarbon-based medium within the medium flow path without supplying the fluorocarbon-based medium to the storage portion.

7. The secondary battery system according to claim 3, The temperature control unit is an acquisition unit that acquires a distortion amount of the secondary battery; When the secondary battery is charged or discharged under the predetermined conditions, the vapor pressure of the fluorocarbon-based medium in the storage section is changed to an expansion pressure of the secondary battery that is specified from the acquired amount of distortion.

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