JP5772428B2 - Secondary battery cooling device - Google Patents

Description

  The present invention relates to a cooling device for a secondary battery.

  A secondary battery such as lithium ion may become high temperature due to overcharge and discharge, and an adjacent secondary battery may also become high temperature. Therefore, a battery module in which a plurality of lithium ion secondary batteries are stacked, It is necessary to cool to an appropriate temperature. For this reason, a lithium ion secondary battery comprising a battery element composed of a laminate of a positive electrode, a negative electrode, and a separator, and a laminate outer package enclosing the battery element and an electrolyte, and circulating cooling water between the inner layer and the outer layer of the laminate outer package. A secondary battery has been proposed (Patent Document 1).

JP 2007-66647 A

  However, in the above prior art, when the temperature of the secondary battery rises rapidly, the amount of refrigerant vapor cannot follow the rise in battery temperature because the refrigerant circulates, and the secondary battery cannot be cooled to an appropriate temperature. There's a problem.

  An object of the present invention is to provide a cooling device for a secondary battery that can be cooled to an appropriate temperature even if the temperature of the secondary battery rapidly rises.

  The present invention solves the above problem by reducing the circulation rate of the refrigerant when the temperature of the secondary battery becomes high.

  When the circulation rate of the refrigerant is reduced as in the present invention, the amount of refrigerant per unit time in contact with the secondary battery that has reached a high temperature is reduced, and thus the amount of refrigerant per unit refrigerant that is transmitted from the secondary battery to the refrigerant is reduced. The amount of heat increases. As a result, the amount of vaporization of the refrigerant increases and the latent heat of vaporization increases, so that the cooling efficiency of the secondary battery increases, and even if the temperature of the secondary battery rises rapidly, it can be cooled to an appropriate temperature.

It is a top view which shows an example of the thin battery to which one embodiment of this invention is applied. It is sectional drawing which follows the II-II line of FIG. It is a block diagram which shows the cooling device which concerns on one embodiment of this invention. It is a perspective view which shows the battery module to which the cooling device of FIG. 3 is applied. It is a front view which shows the other example of the cooling jacket shown in FIG. It is a schematic diagram which shows the battery module case of FIG. It is a schematic diagram which shows the battery pack of the assembled battery which combined the battery module of FIG.

  Hereinafter, embodiments of a cooling device according to the present invention will be described with reference to the drawings. 1 and 2 are a plan view and a cross-sectional view showing an example of a secondary battery to which a cooling device according to the present invention is applied. A thin battery 1 of this example is a lithium-based, flat plate, and laminated type thin film. It is a secondary battery. As shown in FIGS. 1 and 2, the thin battery 1 includes two positive plates 11, four separators 12, three negative plates 13, a positive terminal 14, a negative terminal 15, and an upper exterior. It is comprised from the member 16, the lower exterior member 17, and the electrolyte which is not specifically illustrated. In addition, the structure of the thin battery 1 demonstrated below is a general thing, and the cooling device of this invention is not the meaning applied to this limitedly. The cooling device of the present invention can also be applied to other secondary batteries.

  The positive electrode plate 11, the separator 12, the negative electrode plate 13 and the electrolyte constitute a power generation element 18, the positive electrode plate 11 and the negative electrode plate 13 constitute an electrode plate, and the upper exterior member 16 and the lower exterior member 17 are a pair of exterior members. Configure.

  The positive electrode plate 11 constituting the power generation element 18 includes a positive electrode side current collector 11a extending to the positive electrode terminal 14, and positive electrode layers 11b and 11c formed on both main surfaces of a part of the positive electrode side current collector 11a, respectively. Have In addition, the positive electrode layers 11b and 11c of the positive electrode plate 11 are not formed over both main surfaces of the entire positive electrode side current collector 11a, but as shown in FIG. When the power generation element 18 is configured by laminating the negative electrode plate 13, the positive electrode layers 11 b and 11 c are formed only on the portion of the positive electrode plate 11 that substantially overlaps the separator 12. Further, in this example, the positive electrode plate 11 and the positive electrode side current collector 11a are formed of a single conductor. However, the positive electrode plate 11 and the positive electrode side current collector 11a are formed separately and joined together. May be.

The positive electrode side current collector 11a of the positive electrode plate 11 is made of an electrochemically stable metal foil such as an aluminum foil, an aluminum alloy foil, a copper foil, or a nickel foil. Moreover, the positive electrode layers 11b and 11c of the positive electrode plate 11 are formed of, for example, lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), or lithium cobaltate (LiCoO ₂ ), chalcogen ( S, Se, Te) A positive electrode side current collector obtained by mixing a positive electrode active material such as a compound, a conductive agent such as carbon black, an adhesive such as an aqueous dispersion of polytetrafluoroethylene, and a solvent. It is formed by applying to both main surfaces of a part of 11a, drying and rolling.

  The negative electrode plate 13 constituting the power generation element 18 includes a negative electrode side current collector 13a extending to the negative electrode terminal 15 and negative electrode layers 13b and 13c formed on both main surfaces of a part of the negative electrode side current collector 13a, respectively. And have. The negative electrode layers 13b and 13c of the negative electrode plate 13 are not formed over both main surfaces of the entire negative electrode current collector 13a. As shown in FIG. When the power generation element 18 is configured by laminating the negative electrode plate 13, the negative electrode layers 13 b and 13 c are formed only on the portion of the negative electrode plate 13 that substantially overlaps the separator 12. Further, in this example, the negative electrode plate 13 and the negative electrode side current collector 13a are formed of a single conductor. However, the negative electrode plate 13 and the negative electrode side current collector 13a are formed as separate bodies and are joined together. May be.

  The negative electrode side current collector 13a of the negative electrode plate 13 is made of an electrochemically stable metal foil such as a nickel foil, a copper foil, a stainless steel foil, or an iron foil. The negative electrode layers 13b and 13c of the negative electrode plate 13 are negative electrodes that occlude and release lithium ions of the positive electrode active material, such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, or graphite. An active material is mixed with an aqueous dispersion of styrene butadiene rubber resin powder as a precursor material of an organic fired body, dried and then pulverized to carry carbonized styrene butadiene rubber on the carbon particle surface. A main material is formed by further mixing a binder such as an acrylic resin emulsion with this, applying this mixture to both main surfaces of a part of the negative electrode current collector 13a, and drying and rolling.

  In particular, when amorphous carbon or non-graphitizable carbon is used as the negative electrode active material, the flatness of the potential during charge / discharge is poor and the output voltage decreases with the amount of discharge. This is advantageous because there is no reduction in output.

  The separator 12 of the power generation element 18 prevents the short-circuit between the positive electrode plate 11 and the negative electrode plate 13 described above, and may have a function of holding an electrolyte. The separator 12 is a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP), for example. When an overcurrent flows, the pores of the layer are blocked by the heat generation and the current is cut off. It also has a function.

  The separator 12 according to this example is not limited to a single-layer film such as polyolefin, but a three-layer structure in which a polypropylene film is sandwiched with a polyethylene film or a laminate of a polyolefin microporous film and an organic nonwoven fabric may be used. it can. Thus, by making the separator 12 into multiple layers, various functions such as an overcurrent prevention function, an electrolyte holding function, and a separator shape maintenance (stiffness improvement) function can be provided.

  The power generation element 18 is formed by alternately stacking the positive electrode plates 11 and the negative electrode plates 13 with the separators 12 interposed therebetween. The two positive plates 11 are respectively connected to the positive terminal 14 made of metal foil via the positive current collector 11a, while the three negative plates 13 are connected to the negative current collector 13a. In the same manner, each is connected to a negative electrode terminal 15 made of metal foil.

  In addition, the positive electrode plate 11, the separator 12, and the negative electrode plate 13 of the power generation element 18 are not limited to the above number. For example, one positive electrode plate 11, two separators 12, and two negative electrode plates 13 are also included. The power generation element 18 can be configured, and the number of the positive electrode plate 11, the separator 12, and the negative electrode plate 13 can be selected and configured as necessary.

  The positive electrode terminal 14 and the negative electrode terminal 15 are not particularly limited as long as they are electrochemically stable metal materials, but the positive electrode terminal 14 has a thickness of, for example, about 0.02 mm, as in the positive electrode side current collector 11a described above. An aluminum foil, an aluminum alloy foil, a copper foil, a nickel foil, or the like can be given. Moreover, as the negative electrode terminal 15, for example, a nickel foil, a copper foil, a stainless steel foil, an iron foil, or the like having a thickness of about 0.02 mm can be used as in the negative electrode side current collector 13 a described above.

  As described above, in this example, the metal foil itself constituting the current collectors 11a and 13a of the electrode plates 11 and 13 is extended to the electrode terminals 14 and 15, in other words, a single metal foil 11a, An electrode layer (positive electrode layer 11b, 11c or negative electrode layer 13b, 13c) is formed on a part of 13a, the remaining end is used as a connecting member to the electrode terminal, and the electrode plates 11, 13 are connected to the electrode terminals 14, 15 Although it is configured to be connected, the metal foil constituting the current collectors 11a and 13a located between the positive electrode layer and the negative electrode layer and the metal foil constituting the connecting member may be connected by different materials and parts. In the following embodiment, the current collector and the connecting member located between the positive electrode layer and the negative electrode layer will be described as being constituted by a single metal foil.

  The power generation element 18 described above is housed and sealed in the upper exterior member 16 and the lower exterior member 17. Although not specifically illustrated, the upper exterior member 16 and the lower exterior member 17 of this example are both resistant from the inner side to the outer side of the thin battery 1, such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer. An inner layer composed of a resin film excellent in electrolytic solution and heat-fusibility, an intermediate layer composed of a metal foil such as aluminum, and an electrical insulating property such as a polyamide resin or a polyester resin And an outer layer made of an excellent resin film.

  Therefore, both the upper exterior member 16 and the lower exterior member 17 are made of a resin such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer on one surface of the metal foil such as aluminum foil (inner surface of the thin battery 1). It is made of a flexible material such as a resin-metal thin film laminate material obtained by laminating and laminating the other surface (the outer surface of the thin battery 1) with a polyamide resin or a polyester resin.

  As described above, when the exterior members 16 and 17 include the metal layer in addition to the resin layer, the strength of the exterior member itself can be improved. Further, the inner layers of the exterior members 16 and 17 are made of, for example, a resin such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer, so that good fusion properties with the metal electrode terminals 14 and 15 can be obtained. It can be secured.

  As shown in FIGS. 1 and 2, the positive terminal 14 is led out from one end of the sealed exterior members 16 and 17, and the negative terminal 15 is led out from the other end. Since a gap is formed in the fused portion between the upper exterior member 16 and the lower exterior member 17 by the thickness of the electrode terminals 14 and 15, the electrode terminals 14 and 15 are maintained in order to maintain the sealing performance inside the thin battery 1. For example, a seal film made of polyethylene, polypropylene, or the like may be interposed in a portion where the exterior members 16 and 17 are in contact with each other. It is preferable from the viewpoint of heat-fusibility that the seal film is made of a resin of the same system as the resin constituting the exterior members 16 and 17 in both the positive electrode terminal 14 and the negative electrode terminal 15.

  These exterior members 16, 17 enclose the power generation element 18, part of the positive electrode terminal 14 and part of the negative electrode terminal 15, so that the internal liquid space formed by the exterior members 16, 17 contains an organic liquid solvent. While injecting a liquid electrolyte having a lithium salt such as lithium chlorate, lithium borofluoride or lithium hexafluorophosphate as a solute, the space formed by the exterior members 16 and 17 is sucked into a vacuum state, The outer peripheral edges of the members 16 and 17 are heat-sealed by hot pressing and sealed.

  Examples of the organic liquid solvent that constitutes the electrolyte include ester solvents such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate. Without being limited thereto, an organic liquid solvent prepared by mixing and preparing an ether solvent or the like such as γ-butylactone (γ-BL) or dietoxyethane (DEE) in the ester solvent can also be used.

  The above is the basic structure of the thin battery 1 applied to the cooling device of this example. The cooling device of this example will be described below. FIG. 3 is a block diagram showing the cooling device 2 of this example. The cooling device 2 of this example includes a cooling jacket 21, a temperature sensor 22, a pump 23, a heat exchanger 24, a circulation pipe 25, and a controller. 26.

  The cooling jacket 21 is provided on each of the front and back surfaces of the thin battery 1 described above as indicated by a one-dot chain line in FIG. 2, and the refrigerant circulates to cool the thin battery 1. In this case, another exterior member (not shown) may be provided outside the exterior members 16 and 17 of the thin battery 1, and the cooling jacket 21 may be sandwiched therebetween. FIG. 4 is a perspective view showing a battery module 19A in which a plurality of thin batteries 1 of FIGS. 1 and 2 are stacked so that their main surfaces overlap each other. When the cooling jacket 21 is applied to the battery module 19A, for example, One cooling jacket 21 can be provided between each thin battery 1. The area of the cooling jacket 21 is preferably about the same as the area of the thin battery 1, more preferably at least the same area as the power generation element 18 and provided in a range including the power generation element 18.

  The cooling jacket 21 is made of a metal having a high thermal conductivity such as aluminum or a plastic material for reducing the weight, and is formed into a flat casing 211 so that a refrigerant flows inside. A refrigerant inlet 212 is formed at one end, and a refrigerant outlet 213 is formed at the opposite end. A partition plate 214 may be provided in the casing 211 of the cooling jacket 21 in order to prevent the refrigerant flowing from the refrigerant inlet 212 to the refrigerant outlet 213 from being unevenly distributed.

  Further, a plurality of valves 215 are provided on the surface of the casing 211 corresponding to the flow paths in the casing 211 partitioned by the partition plate 214. The valve 215 has a pressure sensing structure that opens when the pressure of the refrigerant flow path in the casing 211 reaches a predetermined value or more, and releases the refrigerant flowing in the casing 211 to the outside when the pressure reaches a predetermined value. can do.

  As the valve 215 having a pressure sensing structure, when the pressure in the casing 211 drops, the valve 215 is restored to return from the open state to the closed state. When the internal pressure is increased to a predetermined level or more, the fragile valve portion may be destroyed and the refrigerant may be discharged.

  Further, instead of the valve 215 having the pressure sensing structure described above, a seal part having a heat sensing structure including an opening and a lid for closing the valve 215 is provided in the valve 215 so that the refrigerant in the casing 211 reaches a predetermined temperature or higher. A structure may be employed in which the lid that closes the opening is peeled off or dissolved.

  The temperature sensor 22 is provided in contact with the thin battery 1 so as to directly detect the temperature of the thin battery 1, or provided at an appropriate location in the refrigerant flow path so as to detect the temperature of the refrigerant. Detect indirectly. That is, when the temperature sensor 22 is provided in the refrigerant flow path such as the refrigerant pipe 25, the relationship between the refrigerant temperature, the refrigerant flow rate, and the temperature of the thin battery 1 is acquired in advance by experiment or simulation and detected by the temperature sensor 22. The temperature of the thin battery 1 is estimated from the refrigerant temperature and the refrigerant flow rate at that time. The temperature signal of the thin battery 1 detected by the temperature sensor 22 is output to the controller 26.

  The circulation pipe 25 connects the cooling jacket 21, the pump 23, and the heat exchanger 24. By operating the pump 23, the refrigerant circulates in the order of the cooling jacket 21 → the heat exchanger 24 → the cooling jacket 21. The refrigerant flow rate by the pump 23 is controlled by the controller 26, and the refrigerant heated through the cooling jacket 21 is cooled by the heat exchanger 24. Note that another refrigerant for cooling the refrigerant circulates in the heat exchanger 24.

  The controller 26 determines whether or not the temperature of the thin battery 1 detected by the temperature sensor 22 is a predetermined threshold temperature, and outputs a signal for controlling the circulation speed of the refrigerant to the pump 23. When the temperature of the thin battery 1 is equal to or higher than a predetermined threshold temperature, the circulation of the refrigerant is suppressed, so that the refrigerant stays in the casing 211 and is transferred from the thin battery 1 per unit refrigerant amount. Therefore, the amount of refrigerant vaporized increases and the latent heat of vaporization increases. As a result, the cooling effect of the thin battery 1 is increased, and the thin battery 1 can be cooled to an appropriate temperature even when the temperature of the thin battery 1 is rapidly increased.

  As the refrigerant used in the cooling device 2 of this example, the gas when vaporized is preferably an inert gas having a low oxygen content, and in particular, a fluorinated solvent, particularly perfluoroketone, is preferred. Since these refrigerants have nonflammability or fire extinguishing properties, they also have a function of further improving the safety of the battery system as will be described later.

  The cooling jacket 21 shown in FIG. 3 has a structure in which a refrigerant inlet 212 is formed at one end of the casing 211 and a refrigerant outlet 213 is formed at the opposite end. As described above, the refrigerant inlet 212 and the refrigerant outlet 213 may be formed at one end of the casing 211, and the refrigerant flow path in the casing 211 may be formed in a U shape as illustrated. In this way, the refrigerant pipe 25 can be integrated into one of the thin batteries 1, and the battery module 19A shown in FIG. 4 or the like can be obtained by using the cooling jacket 21 shown in FIG. 3 and the cooling jacket 21 shown in FIG. In this case, the degree of freedom in the layout of the refrigerant pipe 25 is improved. In FIG. 5, members that are the same as those in the cooling jacket 21 of FIG.

Next, the operation will be described.
In a lithium ion secondary battery or the like, deterioration is suppressed by maintaining an appropriate temperature, but there is also a characteristic that heat is generated when overcharged or overdischarged. For this reason, the thin battery 1 is maintained at an appropriate temperature using the cooling device 2 of this example. That is, when the temperature of the thin battery 1 detected by the temperature sensor 22 is within a predetermined range indicating a steady state, a drive signal is output from the controller 26 to the pump 23 and the refrigerant per unit time flowing through the cooling jacket 21 is output. The flow rate (circulation speed) is controlled to be within a predetermined range. Thereby, the thin battery 1 is maintained at a suitable temperature.

  On the other hand, when the temperature of the thin battery 1 detected by the temperature sensor 22 rises to a predetermined temperature or higher, a drive signal is output from the controller 26 to the pump 23 and the unit time of the refrigerant flowing through the cooling jacket 21 is exceeded. Is set so that the flow rate is less than the steady state. In other words, the circulation speed is reduced compared to the steady state. The small flow rate in this case includes zero, that is, stopping the pump 23.

  When the circulation speed (flow rate per unit time) of the refrigerant is reduced, the amount of refrigerant per unit time that contacts the thin battery 1 that has become high temperature decreases, whereby the amount of unit refrigerant that is transmitted from the thin battery 1 to the refrigerant. The amount of heat per hit increases. As a result, the vaporization amount of the refrigerant is increased and the latent heat of vaporization is increased, so that the cooling efficiency of the thin battery 1 is increased. In particular, even when the temperature of the thin battery 1 rises rapidly, it can follow this and can be cooled to an appropriate temperature.

  In addition to the control of the refrigerant circulation speed by the pump 23, in this example, the pressure sensing structure valve 215 is provided in the casing 211 of the cooling jacket 21, so that the temperature of the refrigerant flowing through the cooling jacket 21 rises. When the pressure becomes high, the valve 215 is opened, and the refrigerant flowing in the housing 211 is discharged out of the system. Further, even when the above-described temperature sensing structure seal portion is provided in place of the valve 215, the seal portion may be peeled off or melted when the temperature of the refrigerant flowing through the cooling jacket 21 rises. The refrigerant circulating through the system is discharged out of the system.

  FIG. 6 is a diagram showing a state in which the battery module 19A shown in FIG. 4 is stored in the module case 19A1, and the temperature of the second thin battery 1 from the left rises abnormally, and the pressure sensing structure valve 215 described above. Indicates that the valve is opened or the seal of the temperature sensing structure is peeled off or melted. In this case, the refrigerant of the cooling device 2 in contact with the second thin battery 1 from the left is released into the module case 19A1. Thereby, the refrigerant | coolant which is a liquid or gas which has nonflammability and fire extinguishing property can be filled in battery module 19A1.

  FIG. 7 is a diagram showing an assembled battery 19B in which a plurality of battery modules 19A shown in FIG. 6 are stored in an assembled battery case 19B1, and the temperature of the second thin battery 1 from the left in the leftmost battery module 19A is It shows a state in which the valve 215 of the above-described pressure sensing structure is opened abnormally, or the seal part of the temperature sensing structure is peeled off or melted. In this case, after the refrigerant of the cooling device 2 in contact with the second thin battery 1 from the left is filled in the module case 19A1, it is also discharged into the assembled battery case 19B1. Thereby, the assembled battery case 19B1 can be filled with a refrigerant that is a liquid or gas having nonflammability and fire extinguishing properties.

  The temperature sensor 22 corresponds to temperature detection means according to the present invention, the controller 26 corresponds to control means according to the present invention, and the valve 215 and the seal portion correspond to discharge means according to the present invention.

DESCRIPTION OF SYMBOLS 1 ... Thin battery 11 ... Positive electrode plate 11a ... Positive electrode side collector 11b, 101c ... Positive electrode layer 12 ... Separator 13 ... Negative electrode plate 13a ... Negative electrode side collector 13b, 13c ... Negative electrode layer 14 ... Positive electrode terminal (electrode terminal)
15 ... Negative terminal (electrode terminal)
DESCRIPTION OF SYMBOLS 16 ... Upper exterior member 17 ... Lower exterior member 18 ... Power generation element 19A ... Battery module 19A1 ... Module case 19B ... Assembly battery 19B1 ... Assembly battery case 2 ... Cooling device 21 ... Cooling jacket 211 ... Housing 212 ... Refrigerant inlet 213 ... Refrigerant outlet 214 ... Partition plate 215 ... Valve (seal part)
22 ... temperature sensor 23 ... pump 24 ... heat exchanger 25 ... circulation piping 26 ... controller

Claims (6)

A cooling jacket provided on the surface of the secondary battery, in which a coolant circulates to cool the secondary battery;
Temperature detecting means for directly or indirectly detecting the temperature of the secondary battery;
A secondary battery cooling device comprising: control means for reducing a circulation speed of the refrigerant to a speed including zero when a temperature of the secondary battery is equal to or higher than a predetermined temperature.   The secondary battery cooling device according to claim 1, wherein the refrigerant is an inert gas having a low oxygen content when vaporized.   The secondary battery cooling device according to claim 2, wherein the refrigerant is a fluorinated solvent containing perfluoroketone. A cooling device provided in a secondary battery of a battery module in which a plurality of the secondary batteries are stacked,
The secondary battery cooling device according to any one of claims 1 to 3, further comprising discharge means for discharging the gas vaporized by the refrigerant into the case of the battery module. The discharge means is
The secondary battery cooling device according to claim 4, further comprising a valve that is provided in the refrigerant flow path of the refrigerant and opens when a pressure in the refrigerant flow path is equal to or higher than a predetermined value. The discharge means is
The secondary battery cooling device according to claim 4, further comprising a seal portion that is provided in the refrigerant flow path of the refrigerant and peels off or melts when a temperature in the refrigerant flow path reaches a predetermined value or more.

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