Power storage device

Abstract

To provide a power storage device capable of restraining firing, by preventing concatenation of overheat state between power storage elements.SOLUTION: A power storage device 100 includes multiple power storage elements 1, and a cooling module 30 for cooling the power storage elements 1. The cooling module 30 is placed at least between the power storage elements 1, and has a cooling part 31 incorporating a flame-resistant agent, and cooling the power storage elements 1 by endotherm of the flame-resistant agent at the time of evaporation. In the cooling part 31 in contact with the power storage element 1 that generated heat, the power storage elements 1 are cooled well by the heat of vaporization when the incorporated flame-resistant agent evaporates, and concatenation of overheat state is prevented between the power storage elements 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an energy storage device including a plurality of energy storage elements. [Background technology]

[0002] Chargeable and dischargeable energy storage elements are used in a variety of devices, including mobile phones and automobiles. In particular, electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), which use electrical energy as their power source, require large amounts of energy and are therefore equipped with large-capacity energy storage devices that comprise multiple energy storage elements.

[0003] In such an energy storage device, if the temperature of one of the energy storage elements rises excessively for some reason, even if it is not under normal use, the heat from this energy storage element will be conducted to the adjacent energy storage elements, causing the adjacent energy storage elements to heat up. If this causes the active material of the electrode of the adjacent energy storage element to heat up to or above its self-heating temperature, this adjacent energy storage element will also become overheated due to self-heating, which will further heat the adjacent energy storage element, potentially causing a chain reaction in which many energy storage elements become overheated.

[0004] When using an energy storage element with a metal case covered with a resin film, if the energy storage element becomes overheated, the resin film melts and the metal cases come into contact with each other, promoting heat conduction and resulting in a chain reaction of overheating. In particular, when the metal case is used as an electrode or when the metal case has an abnormal potential due to some abnormality, the case may come into electrical contact with the case of an adjacent energy storage element, causing an abnormal current to flow in the adjacent energy storage element, which may lead to an overheating state.

[0005] Patent Document 1 discloses a technique for suppressing the heat transfer from an energy storage element to adjacent energy storage elements.

[0006] When the energy storage element is a non-aqueous electrolyte secondary battery, a widely known non-aqueous electrolyte is one in which an electrolyte such as lithium hexafluorophosphate (LiPF6) is dissolved in a non-aqueous solvent whose main component is ethylene carbonate. These non-aqueous solvents are generally volatile and flammable. Therefore, it is necessary to suppress fires in energy storage devices. Patent Document 2 discloses that a non-aqueous electrolyte contains an acyclic fluorinated ether containing at least one -CFH group at its terminal, a cyclic carbonate compound having a carbon-carbon π bond, and a sultone, and the non-aqueous electrolyte is made flame retardant. Patent Document 3 discloses that the non-aqueous electrolyte contains a fluorinated phosphate ester and / or a fluorinated chain carbonate having a side chain with three or less carbon atoms, and the proportion of these in the solvent of the non-aqueous electrolyte is 15 to 30 mass %, making the non-aqueous electrolyte flame retardant. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-195149 [Patent Document 2] Patent No. 5092416 [Patent Document 3] Patent No. 5842873 Summary of the Invention [Problem to be solved by the invention]

[0008] In the electricity storage device of Patent Document 1, heat conduction between the electricity storage elements is suppressed by partition members made of mica aggregate material. In recent years, there has been a demand for further increases in the capacity of energy storage elements and energy storage devices. Increasing the capacity of an energy storage element results in a significant increase in the energy and heat released from the energy storage element when it becomes overheated. While increasing the thickness of the air gap or partition between the energy storage elements can improve thermal insulation, these methods result in a decrease in the energy density of the energy storage device. Therefore, new measures are needed to prevent a chain reaction of overheating between energy storage elements without decreasing the energy density. In order to ensure that the non-aqueous electrolyte of a non-aqueous electrolyte secondary battery exhibits sufficient flame retardancy in order to prevent ignition of the electricity storage device, it is necessary to mix a large amount of a fluorinated carbonate or the like. However, in order to obtain good battery characteristics, there is a limit to the amount of the fluorinated carbonate or the like that can be added.

[0009] An object of the present invention is to provide an electricity storage device that can prevent a chain reaction of overheating between electricity storage elements and suppress the occurrence of fire. [Means for solving the problem]

[0010] The energy storage device of the present invention is characterized by comprising a plurality of energy storage elements and a cooling section disposed at least between the energy storage elements, incorporating a flame retardant, and cooling the energy storage elements by the heat of vaporization of the flame retardant. [Effects of the Invention]

[0011] According to the present invention, in the cooling section that comes into contact with the heated electric storage elements, the flame retardant contained therein absorbs heat from the electric storage elements and evaporates, thereby cooling the electric storage elements effectively. Since the cooling section is disposed at least between the electric storage elements, heat conduction from the heated electric storage element to adjacent electric storage elements is suppressed. Therefore, chain heat transfer between the electric storage elements is prevented. Since the flame retardant is contained in the cooling section, after vaporizing, it is liquefied in the cooling section and reused to cool the electricity storage elements, thereby efficiently cooling the electricity storage elements. When the flame retardant vaporizes and is released from the cooling section, and flammable components are released from the energy storage element, the flammable components are made flame retardant by the flame retardant, and ignition is prevented or suppressed in the energy storage device. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. [Figure 2] 1 is a perspective view of a power storage device according to a first embodiment. [Figure 3] FIG. 2 is a perspective view of a cooling module. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. [Figure 5] 10 is an explanatory diagram illustrating cooling by a cooling module when an electric storage element generates heat; FIG. [Figure 6] FIG. 2 is an explanatory diagram illustrating the suppression of ignition by a flame retardant. [Figure 7] FIG. 10 is a perspective view of a cooling module according to a second embodiment. [Figure 8] FIG. 10 is an explanatory diagram illustrating a case where the internal spaces are connected to each other in the second embodiment. [Figure 9] FIG. 2 is an explanatory diagram illustrating the suppression of ignition by a flame retardant. [Figure 10] FIG. 10 is a perspective view of a cooling module according to a third embodiment. [Figure 11] FIG. 10 is a perspective view of a power storage device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will now be described in detail with reference to the drawings showing embodiments thereof. (First embodiment) 1 is a perspective view of the energy storage device 1. Below, a case where the energy storage device 1 is a lithium ion secondary battery will be described, but the energy storage device 1 is not limited to a lithium ion secondary battery. The energy storage element 1 includes a case 11 having a cover plate 2 and a case body 3, a positive electrode terminal 4, a negative electrode terminal 8, gaskets 6 and 10, a burst valve 20, a current collector, and an electrode assembly (not shown).

[0014] The case 11 is made of a metal such as aluminum, an aluminum alloy, or stainless steel, or a synthetic resin, has a rectangular parallelepiped shape, and contains the electrode assembly and an electrolyte (not shown). Alternatively, the case may be a pouch case made of a laminate sheet.

[0015] The positive electrode terminal 4 has a shaft portion that passes through the cover plate 2 and a plate portion provided at one end of the shaft portion. The positive electrode terminal 4 is provided so as to penetrate the cover plate 2 in an insulated state, with the inner surface of the plate portion and the shaft portion covered by the gasket 6.

[0016] The negative electrode terminal 8 has a shaft portion that penetrates the cover plate 2 and a plate portion provided at one end of the shaft portion. The inner surface of the plate portion and the shaft portion of the negative electrode terminal 8 are covered with a gasket 10, and the negative electrode terminal 8 is provided to penetrate the cover plate 2 in an insulated state.

[0017] The electrode body may be a laminated type having a main body formed into a rectangular parallelepiped shape by alternately stacking a plurality of positive and negative electrode plates with separators interposed therebetween, and a positive electrode tab and a negative electrode tab extending from the main body toward the cover plate 2. The positive electrode tab is connected to a positive electrode terminal 4 via a current collector. The negative electrode tab is connected to a negative electrode terminal 8 via a current collector. The electrode assembly may be a wound type obtained by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween in a flat shape. The electrode body is preferably a laminated type, which causes less swelling during charge-discharge cycles (swelling of the exterior body, such as a metal case like case 11 or a pouch case). Because the exterior body causes less swelling during charge-discharge cycles, the exterior body is prevented from pressing against the cooling unit 31 during normal use.

[0018] The positive electrode plate is a positive electrode substrate foil, which is a plate-shaped (sheet-shaped) or long strip-shaped metal foil made of aluminum, aluminum alloy, etc., on which a positive electrode active material layer is formed. The negative electrode plate is a negative electrode substrate foil, which is a plate-shaped (sheet-shaped) or long strip-shaped metal foil made of copper, copper alloy, etc., on which a negative electrode active material layer is formed. The separator is a microporous sheet made of synthetic resin. As the positive electrode active material used in the positive electrode active material layer or the negative electrode active material used in the negative electrode active material layer, any known material can be used as long as it is a positive electrode active material or a negative electrode active material that can absorb and release lithium ions.

[0019] Examples of the positive electrode active material that can be used include polyanion compounds such as LiMPO4, Li2MSiO4, and LiMBO3 (wherein M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), spinel compounds such as lithium titanate and lithium manganese oxide, and lithium transition metal oxides such as LiMO2 (wherein M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.).

[0020] Examples of the negative electrode active material include lithium metal, lithium alloys (lithium-aluminum, lithium-silicon, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and lithium metal-containing alloys such as Wood's alloy), alloys capable of absorbing and releasing lithium, carbon materials (e.g., graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature fired carbon, amorphous carbon, etc.), metal oxides (SiO, etc.), and lithium metal oxides (Li4Ti5O 12 etc.), polyphosphate compounds, etc.

[0021] Rupture valve 20 has a rupture portion 200 formed by partially reducing the plate thickness. When the internal pressure of energy storage element 1 increases, burst valve 20 ruptures along rupture portion 200, forming a tongue-shaped portion that springs up outward, forming an opening in cover plate 2.

[0022] FIG. 2 is a perspective view of the power storage device 100 according to this embodiment, and FIG. 3 is a perspective view of the cooling module 30. As shown in FIG. The energy storage device 100 includes a plurality of energy storage elements 1, a cooling module 30 that cools the energy storage elements 1, and a case 40 that houses the energy storage elements 1 and the cooling module 30. In Fig. 2, three energy storage elements 1 are housed, but the number of energy storage elements 1 is not limited to three. The case 40 is box-shaped and made of an insulating material such as synthetic resin. The case 40 positions the energy storage element 1, the cooling module 30, etc. in predetermined positions and protects them from impact. The case 40 is provided with external electrode terminals (not shown) for charging electricity from the outside and discharging electricity to the outside.

[0023] The cooling module 30 may be made of a metal such as aluminum that has good thermal conductivity and heat resistance, and may be subjected to an insulating treatment such as forming an insulating film on the surface. As shown in Fig. 3, the cooling module 30 includes plate-shaped cooling sections 31, connecting sections 32 and 33 that connect the cooling sections 31, and an internal pressure release valve 34. Two cooling sections 31 are interposed between the long side surfaces of adjacent energy storage elements 1, and the other two cooling sections 31 abut against the outer long side surfaces of the energy storage elements 1 on both ends. Here, the long side surfaces are provided so as to extend upward from the long sides of the bottom surface of the energy storage elements 1 in Fig. 1 and refer to the side surfaces that have the largest area among the side surfaces. An internal pressure release valve 34 is provided in the center of the top surface of each cooling section 31. The cooling units 31 may be provided in a number corresponding to the number of energy storage elements 1, or may be interposed between the energy storage elements 1 and provided so as to abut against the outer long side surfaces of the energy storage elements 1 on both ends. The installation position of the internal pressure release valve 34 is not limited to the center of the top surface of the cooling section 31 either. The internal pressure release valve 34 can be installed at a position where it can effectively prevent ignition when the flame retardant L described below is sprayed out. As shown in Fig. 2, the rupture valve 20 of the energy storage element 1 and the internal pressure release valve 34 of the cooling part 31 may face in the same direction. The internal pressure release valve 34 may face upward in the direction of gravity.

[0024] The cooling section 31 is hollow. The cooling section 31 contains a flame retardant L. The upper portions of one end of the long side surfaces of adjacent cooling sections 31 are connected by a connecting section 32. The connecting section 32 is hollow and configured so that gas inside the connecting cooling sections 31 flows inside the connecting section 32. The lower portions of one end of the long side surfaces of adjacent cooling sections 31 are connected by a connecting section 33. The connecting section 33 is hollow and configured so that the flame retardant L in the connected cooling sections 31 flows inside the connecting section 33. That is, the cooling portion 31, the connecting portion 32, and the connecting portion 33 have internal spaces that communicate with each other.

[0025] The outer cooling sections 31 can be omitted. For example, if there are five energy storage elements 1, four cooling sections 31 are arranged between the energy storage elements 1, and the four cooling sections 31 are connected by connecting sections 32, 33. The long sides of the outer energy storage elements 1 are in contact with the sides of the case 40. Providing outer cooling sections 31 provides better cooling efficiency.

[0026] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. The internal pressure release valve 34 is a circular groove, and as shown in Figure 4, the thickness of the bottom of the groove is thinner than the thickness of other parts. The internal pressure release valve 34 is formed by cutting, press working, etc. When forming the internal pressure release valve 34 by cutting, a device capable of cutting curved surfaces, such as a three-dimensional NC, is used. When forming the internal pressure release valve 34 by press working, it is formed by stamping using a mold with protrusions.

[0027] The flame retardant L exhibits flame retardancy against flammable gases by vaporizing. The flame retardant L preferably has a large heat of vaporization, is corrosion resistant, and does not generate toxic gases. The flame retardant L preferably contains at least one of acyclic fluorinated ether, fluorinated phosphate ester, and phosphazene derivative, which have high flame retardancy when vaporized.

[0028] The acyclic fluorinated ether is more preferably represented by the following formula (1): CX 3-j H j -(CF x H 2-x ) m -O-(CF y H 2-y ) n -CF 3-k H k…(1) (wherein X is F or CF3; j, k, m, n, x, and y are integers, 0≦j≦3, 0≦k≦3, 1≦m≦3, 0≦n≦1, 0≦x≦2, and 0≦y≦2, and contain at least one fluorine atom.) Specific examples include, but are not limited to, HCF2CF2CH2OCF2CF2H, HCF2CF2OCH2CF3, CF3CF2CH2OCF2CF2H, HCF2CF2CH2OCHF2, CF3CF2CH2OCF2H, (CF3)2CHCF2OCF2H, CF3CHFCF2CH2OCHF2, and the like, either alone or in mixtures of two or more thereof.

[0029] The fluorinated phosphate ester is more preferably represented by the following formula (2).

[0030] [ka]

[0031] (wherein j, k, l, m, n, o, x, y, and z are integers, 0≦j≦3, 0≦k≦3, 0≦l≦3, 0≦m≦1, 0≦n≦1, 0≦o≦1, 0≦x≦2, 0≦y≦2, and 0≦z≦2, and contain at least one fluorine atom.)

[0032] The phosphazene derivative is more preferably represented by the following formula (3).

[0033] [ka]

[0034] (In the formula, R1 to R6 are the same or different and represent a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms and substituted with a fluorine atom, an alkoxy group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms and substituted with a fluorine atom.)

[0035] The phosphazene derivative is a compound in which at least one of R1 to R6 is a fluorine atom. More preferably, the fluorine-containing phosphazene derivative is either an alkyl group substituted with a fluorine atom or an alkoxy group substituted with a fluorine atom.

[0036] Among the fluorine-containing phosphazene derivatives, monoethoxypentafluorocyclotriphosphazene represented by the following formula 3 and monophenoxypentafluorocyclotriphosphazene represented by the following formula 4 are particularly preferred.

[0037] [ka]

[0038] [ka]

[0039] The amount of flame retardant L to be stored is set based on the internal volume of the cooling section 31 and the connecting sections 32 and 33, the expected heat generation temperature of the storage element 1, the volume of the flame retardant L when vaporized, etc., so as not to damage the cooling section 31.

[0040] FIG. 5 is an explanatory diagram illustrating cooling by the cooling module 30 when the energy storage element 1 generates heat. It is assumed that the cooling module 30 contains a flame retardant L, and the central energy storage element 1 generates heat. Heat is conducted from the heated energy storage element 1 to the cooling portions 31 on both sides, and the flame retardant L in the cooling portions 31 evaporates (FIG. 5A). When the flame retardant L evaporates, heat of vaporization is taken away, and the energy storage element 1 is rapidly cooled by an endothermic reaction. The liquid amount of the flame retardant L in the cooling portions 31 decreases.

[0041] The gas in the cooling section 31 flows upward due to thermal convection and moves to the outer cooling section 31, which has a lower temperature, through the connecting sections 32, 32 (FIG. 5B). The gas condenses in the outer cooling section 31, and the liquid amount of the flame retardant L in the outer cooling section 31 increases.

[0042] The flame retardant L increases in the outer cooling section 31, and flows to the inner cooling section 31 via the connecting section 33, so that the liquid amounts of the flame retardant L in the four cooling sections 31 become equal (FIG. 5C). The circulated flame retardant L absorbs heat generated by the energy storage element 1, vaporizes, and circulates in the same manner as above.

[0043] FIG. 6 is an explanatory diagram illustrating the suppression of ignition by a flame retardant. If thermal runaway occurs, causing a sudden rise in the temperature of the energy storage element 1, the amount of heat absorbed by the energy storage element 1 increases, resulting in a large amount of evaporation of the flame retardant L. When the internal pressure of the cooling section 31 in contact with the energy storage element 1 reaches or exceeds a predetermined value, the internal pressure release valve 34 of that cooling section 31 opens, and the vaporized flame retardant L is released to the outside. Figure 6 shows a state in which the internal pressure release valves 34 of the cooling sections 31 on both sides of the energy storage element 1 are opened, releasing the flame retardant L. When the internal pressure of the outer cooling section 31 also reaches or exceeds a predetermined value, the internal pressure release valve 34 opens. When the internal pressure of the energy storage element 1 reaches a predetermined value or more, the burst valve 20 opens, and the flammable components of the evaporated electrolyte are released to the outside. The flammable components are made flame-retardant by the flame retardant L, preventing them from catching fire.

[0044] As described above, the energy storage device 100 of this embodiment comprises a plurality of energy storage elements 1 and a cooling section 31 arranged at least between the energy storage elements 1, incorporating a flame retardant L, and cooling the energy storage elements 1 by the heat of vaporization of the flame retardant L.

[0045] According to the above configuration, the flame retardant L in the cooling section 31 that comes into contact with the heated energy storage element 1 absorbs the heat of vaporization when vaporizing, thereby cooling the energy storage element 1 well. The cooling section 31 is disposed at least between the energy storage elements 1, so that heat conduction to the energy storage element 1 adjacent to the heated energy storage element 1 is suppressed. Even when heat is transferred to the adjacent energy storage element 1 without passing through the cooling section 31, the long side surface facing the heated energy storage element 1 is cooled by the cooling section 31. Therefore, heat transfer to the energy storage element 1 in a chain reaction is suppressed. The cooling structure of the cooling module 30 is simple, and can cool the energy storage elements 1 even when a small amount of heat is generated. Since the flame retardant L is contained in the cooling section 31, it is vaporized and then liquefied in the cooling section 31, and is reused for cooling the electric storage elements 1, thereby cooling the electric storage elements 1 efficiently.

[0046] In the above-described electricity storage device 100, the flame retardant L exhibits flame retardancy against flammable gases by vaporizing.

[0047] According to the above configuration, when the flame retardant L absorbs heat from the heated energy storage element 1 and vaporizes, and is released from the internal pressure release valve 34, it mixes with the flammable components released from the energy storage element 1, making the flammable components flame retardant, thereby preventing fire in the energy storage device 100.

[0048] In the above-described electricity storage device 100, the flame retardant L includes at least one of acyclic fluorinated ether, fluorinated phosphate ester, and phosphazene derivative.

[0049] According to the above configuration, the flame retardant L has high flame retardancy when vaporized.

[0050] In the above-described power storage device 100, the cooling module 30 has a connecting portion that connects the plurality of cooling portions 31 so that the internal spaces thereof communicate with each other.

[0051] According to the above configuration, the flame retardant L is vaporized in one cooling section 31 that is in contact with the heated energy storage element 1, and the resulting gas flows by thermal convection through the connecting sections 32 and 33 to the other cooling section 31. The gas is liquefied in the other cooling section 31 and flows to the one cooling section 31, and the flame retardant L circulates. Therefore, the flame retardant L is reused for cooling the electric storage elements 1, and the electric storage elements 1 are cooled efficiently. Furthermore, the heated gas flows from one cooling section 31 to the other cooling section 31 via the connecting sections 32, 33, thereby reducing the temperature difference between the long side of one energy storage element 1 that contacts one cooling section 31 and the long side that contacts the other cooling section 31, thereby reducing the temperature difference between the energy storage elements 1. The circulation of the gas and flame retardant L reduces the temperature difference between the multiple energy storage elements 1, allowing for efficient cooling. Even when a low level of heat generation occurs that is not abnormal, the cooling section 31 effectively dissipates the heat from the energy storage elements 1, reducing the temperature difference between the energy storage elements 1.

[0052] In the above-described electricity storage device 100, the cooling unit 31 has an internal pressure release valve 34 that releases the internal pressure when the internal pressure of the cooling unit 31 exceeds a predetermined pressure.

[0053] According to the above configuration, when the amount of evaporation of the flame retardant L is large and the internal pressure of the cooling part 31 exceeds a predetermined pressure, the internal pressure release valve 34 opens and the gas is released to the outside. This prevents the cooling part 31 from expanding due to the gas release and pressing against the energy storage element 1. When the temperature in the energy storage element 1 rises suddenly, the amount of heat absorbed by the energy storage element 1 increases, and the amount of evaporation of the flame retardant L increases. When the internal pressure reaches a predetermined value or higher, the cooling section 31 opens, and the vaporized flame retardant L is released to the outside. When the internal pressure of the energy storage element 1 reaches a predetermined value or higher, the energy storage element 1 opens, and the volatilized flammable components of the electrolyte are released to the outside. The flammable components are made flame retardant by the flame retardant L, and ignition is prevented.

[0054] Even if an end energy storage element 1 generates heat instead of the center, the heat is absorbed by the cooling section 31 in the same manner as above, and the energy storage element 1 is rapidly cooled. The long side of the adjacent energy storage element 1 that faces the heated energy storage element 1 is also rapidly cooled, suppressing heat transfer from the heated energy storage element 1 and preventing a chain reaction of overheating between the energy storage elements. The structure of the cooling module 30 is not limited to the structure shown in Fig. 3. A connecting portion may be provided by having a rectangular tube pass through the upper and lower portions of each of the four cooling portions 31 at one end in the longitudinal direction.

[0055] (Second embodiment) 7 is a perspective view of a cooling module 35 according to the second embodiment. In the figure, the same parts as those in FIG. 3 are denoted by the same reference numerals and detailed description thereof will be omitted. The cooling module 35 includes four cooling sections 31 and a cooling plate 36 . Unlike the first embodiment in which the four cooling sections 31 are connected by connecting sections 32 and 33, the cooling module 35 has end faces 31a of the four cooling sections 31 abutting against a cooling plate 36. As in the first embodiment, the cooling sections 31 contain a flame retardant L. The internal spaces of the cooling section 31 and the cooling plate 36 may or may not be in communication with each other.

[0056] 8 is an explanatory diagram of a case where the internal spaces are connected to each other in this embodiment. Energy storage devices 1 are inserted between cooling portions 31, and flame retardant L is contained in cooling portions 31 and cooling plates 36. When the central energy storage element 1 generates heat, as in the first embodiment, the flame retardant L in the cooling section 31 that contacts the energy storage element 1 absorbs heat of vaporization from the energy storage element 1 and evaporates, rapidly cooling the energy storage element 1. The liquid amount of flame retardant L in this cooling section 31 decreases. The generated gas flows to the other cooling sections 31 via the cooling plate 36, and the flame retardant L generated by condensation flows to the cooling section 31 where the liquid amount of flame retardant L has decreased. The flame retardant L also absorbs heat to cool the energy storage element 1, and the generated gas circulates as described above. The cooling plate 36 also cools the side surfaces of the energy storage element 1 that it contacts.

[0057] If the internal spaces are not connected, when the energy storage element 1 generates heat, the flame retardant L in the cooling portion 31 that contacts the energy storage element 1 absorbs heat of vaporization from the energy storage element 1 and evaporates, rapidly cooling the energy storage element 1. The generated gas is cooled by the cooling plate 36 and condenses into the flame retardant L. The flame retardant L absorbs heat from the energy storage element 1 and evaporates, and the energy storage element 1 is cooled.

[0058] In this embodiment, too, the cooling module 35 with a simple structure suppresses the conduction of heat to adjacent storage elements 1 from the heated storage element 1, and further suppresses the chain reaction of heat transfer to adjacent storage elements 1.

[0059] FIG. 9 is an explanatory diagram illustrating the suppression of ignition by the flame retardant L. If thermal runaway occurs, in which the temperature of the energy storage element 1 rises suddenly, the amount of heat absorbed by the energy storage element 1 increases, resulting in a large amount of evaporation of the flame retardant L. If the internal pressure of the cooling part 31 in contact with the energy storage element 1 reaches or exceeds a predetermined value, the internal pressure release valve 34 opens, and the vaporized flame retardant L is released to the outside. If the internal pressure of the energy storage element 1 reaches or exceeds a predetermined value, the burst valve 20 opens, and the flammable components of the evaporated electrolyte are released to the outside. The flammable components are made flame retardant by the flame retardant L, and ignition is prevented.

[0060] In the energy storage device of this embodiment, each of the energy storage elements 1 is formed in a rectangular parallelepiped shape, and the cooling section 31 of each of the energy storage elements 1 is in contact with a surface other than the opposing long side, and the energy storage device is provided with a cooling plate 36 that cools the multiple energy storage elements 1, and is configured to allow heat to be conducted between the cooling plate 36 and the cooling section 31.

[0061] According to the above configuration, heat is conducted between the cooling plate 36 and the cooling portion 31, and thus heat is dissipated well. The gas generated by vaporization of the flame retardant L is cooled and liquefied, and the flame retardant L absorbs heat from the energy storage elements 1 again, thereby cooling the energy storage elements 1.

[0062] In the above-described electricity storage device, the cooling plate 36 and the cooling section 31 are integrated so that the flame retardant L or the vaporized gas of the flame retardant L can circulate.

[0063] According to the above configuration, the flame retardant L is vaporized in one cooling section 31 that is in contact with the heated energy storage element 1, and the resulting gas flows by thermal convection through the cooling plate to the other cooling section 31. The gas is liquefied in the other cooling section 31 and flows to the one cooling section 31, and the flame retardant L circulates. Therefore, the flame retardant L is reused for cooling the electric storage elements 1, and the electric storage elements 1 are cooled efficiently. Furthermore, the temperature difference between one long side surface and the other long side surface of one energy storage element 1 is reduced, thereby reducing the temperature difference between the energy storage elements 1. The circulation of the gas and flame retardant L reduces the temperature difference between the multiple energy storage elements 1, allowing for efficient cooling. Even when a small amount of heat is generated that is not abnormal, the cooling unit 31 effectively dissipates the heat from the energy storage elements 1, reducing the temperature difference between the energy storage elements 1.

[0064] (Third embodiment) 10 is a perspective view of a cooling module 37 according to a third embodiment. In the figure, the same parts as those in FIG. 3 are denoted by the same reference numerals and detailed description thereof will be omitted. The cooling module 37 of the third embodiment has a configuration in which the bottom surfaces 31b of the four cooling sections 31 of the cooling module 30 of the first embodiment are in contact with a cooling plate 38. As in the first embodiment, the cooling sections 31 contain a flame retardant L (not shown). The internal spaces of the cooling section 31 and the cooling plate 38 are not in communication with each other. The cooling plate 38 may be configured to be cooled by a cooling device (not shown).

[0065] When the central energy storage element 1 generates heat, as in the first embodiment, the flame retardant L in the cooling portion 31 in contact with the energy storage element 1 evaporates, and the heat of vaporization during evaporation cools the energy storage element 1. The generated gas flows through the other cooling portions 31, and the flame retardant L generated by condensation flows to the cooling portion 31 with the least amount of flame retardant L. The cooling plate 38 cools the bottom surfaces of the energy storage elements 1 and also cools the cooling portions 31. The flame retardant L in the cooling portion 31 in contact with the energy storage element 1 absorbs heat from the energy storage element 1 and evaporates, cooling the energy storage element 1.

[0066] In this embodiment, as in the first and second embodiments, the cooling module 37 has a simple structure, which suppresses the conduction of heat to adjacent storage elements 1 from the heated storage element 1, and further suppresses the chain reaction of heat transfer to adjacent storage elements 1.

[0067] When the temperature of the energy storage element 1 rises suddenly, the amount of heat absorbed by the energy storage element 1 increases, and the amount of evaporation of the flame retardant L increases. When the internal pressure reaches a predetermined value or more, the internal pressure release valve 34 opens, and the vaporized flame retardant L is released to the outside. When the internal pressure of the energy storage element 1 reaches a predetermined value or more, the burst valve 20 opens, and the flammable components of the evaporated electrolyte are released to the outside. The flammable components are made flame retardant by the flame retardant L, and ignition is prevented.

[0068] (Fourth embodiment) 11 is a perspective view of a power storage device 101 according to a fourth embodiment. In the figure, the same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. Unlike the energy storage device 100 according to the first embodiment, the energy storage device 101 does not have connecting portions 32, 33 that connect the cooling portions 31. The cooling portions 31 are independently disposed between the energy storage elements 1 or between the energy storage elements 1 and the inner surface of the case 40. The cooling portions 31 contain a flame retardant L (not shown).

[0069] When the energy storage element 1 generates heat, the flame retardant L in the cooling portion 31 that contacts the energy storage element 1 absorbs heat of vaporization from the energy storage element 1 and evaporates, rapidly cooling the energy storage element 1. The generated gas convects and is cooled by the outside of the energy storage device 101 and / or the outside air, and is condensed into the flame retardant L. The flame retardant L absorbs heat from the energy storage element 1 and evaporates, and the energy storage element 1 is cooled.

[0070] In this embodiment, since the cooling section 31 is interposed between the energy storage elements 1, the heated energy storage element 1 is cooled by the cooling sections 31 on both sides, similarly to the first embodiment, and heat transfer to adjacent energy storage elements 1 is suppressed. Even when heat is transferred to an adjacent energy storage element 1 without passing through the cooling section 31, the long side surface facing the heated energy storage element 1 is cooled by the cooling section 31. Therefore, heat transfer to adjacent energy storage elements 1 is suppressed in a chain reaction.

[0071] When the temperature of the energy storage element 1 rises suddenly, the amount of heat absorbed by the energy storage element 1 increases, and the amount of evaporation of the flame retardant L increases. When the internal pressure reaches a predetermined value or more, the internal pressure release valve 34 opens, and the vaporized flame retardant L is released to the outside. When the internal pressure of the energy storage element 1 reaches a predetermined value or more, the burst valve 20 opens, and the flammable components of the evaporated electrolyte are released to the outside. The flammable components are made flame retardant by the flame retardant L, and ignition is prevented.

[0072] The present invention is not limited to the contents of the above-described embodiment, and various modifications are possible within the scope of the claims. In other words, embodiments obtained by combining technical means modified appropriately within the scope of the claims are also included in the technical scope of the present invention. In the first to fourth embodiments, the positive electrode terminals 4 and the negative electrode terminals 8 of the energy storage elements 1 are arranged to face upward, but the present invention is not limited to this. The cooling structure of the present invention can also be applied to cases where the positive electrode terminals 4 and the negative electrode terminals 8 are arranged to face sideways. Although the description has been given of the case where the energy storage element 1 is a lithium ion secondary battery, the energy storage element 1 is not limited to a lithium ion secondary battery. The energy storage element 1 may be another secondary battery containing an organic solvent, a primary battery, or an electrochemical cell such as a capacitor. The power storage device according to the present invention can be particularly suitably used as a power source for vehicles. The power storage device according to the present invention can also be suitably used in industrial applications such as power storage systems (large-scale power storage systems, small-scale home power storage systems), distributed power supply systems that combine natural energy such as solar power and wind power, power supply systems for railways, and power supply systems for automated guided vehicles (AGVs). [Explanation of symbols]

[0073] 1. Energy storage element 2 Lid plate 3 Case body 4 Positive terminal 8 Negative terminal 6, 10 Gasket 11 cases 20 Burst Valve 30, 35, 37 Cooling Module 31 Cooling section 32, 33 Connection part 34 Internal pressure release valve 36, 38 Cooling plate 40 cases 100, 101 Electricity storage device

Claims

[Claim 1] an electric storage element having a case having a cover plate provided with a burst valve and a case body, and an electrode body housed in the case; a cooling unit facing the case body of the energy storage element, the cooling unit cooling the energy storage element; the burst valve opens in the direction of alignment of the cover plate and the case body, the cooling unit has an internal pressure release valve that releases the internal pressure when the internal pressure of the cooling unit exceeds a predetermined pressure, The internal pressure release valve is arranged to face the same direction as the burst valve, The case body has a long side and a short side, the cooling section faces the long side surface of the case body, a connecting portion disposed so as to contact a surface different from the long side surface of the case body; The connecting portion connects the plurality of cooling portions. Energy storage device.

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