Storage battery system

Abstract

A storage battery system according to one embodiment of the present invention is provided with: a battery cell laminate in which a plurality of battery cells are laminated; constraining bodies disposed at both ends of the battery cell laminate in the lamination direction and constraining the battery cell laminate in the lamination direction; gas bags each disposed between the battery cell laminate and the restraining body and capable of accommodating a gas; a gas supply unit for supplying gas to the airbag; and a temperature information acquisition unit that acquires temperature information of the battery cell stack. The battery cell has an exterior body, a positive electrode housed in the exterior body, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution. When the temperature of the battery cell laminated body reaches a preset first temperature or more, at least one of the air bags is inflated by the gas supplied from the gas supply unit and presses the battery cell laminated body at a preset first pressure.

Description

Technical Field

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

[0002] In recent years, research and development of secondary batteries that help improve energy efficiency are being conducted to make them affordable, trustworthy, and ensure access to sustainable and advanced energy for many people. As a driving power source for vehicles such as electric vehicles and hybrid vehicles, a battery system is used, which uses a battery cell stack composed of a plurality of battery cells. In the battery system, it is envisioned that heat or gas release will occur due to a failure of a battery cell, and various countermeasures are being explored. For example, a study is being conducted to configure a heat expansion component between a plurality of battery cells, and when the battery cell generates heat, the heat expansion component is expanded to control the direction of gas release generated by the failure of the battery cell (see Patent Document 1).

[0003] [Prior Art Literature]

[0004] (Patent Document)

[0005] Patent Document 1: Japanese Patent No. 7258075 Summary of the Invention

[0006] [Problems to be solved by the invention]

[0007] In addition, in secondary batteries, safety is one of the issues to be addressed. In particular, the safety of a battery system using a battery cell stack in which a plurality of battery cells are stacked is more important. In the battery cell stack used in the battery system, in order to stabilize the charge and discharge characteristics of the battery cells, a buffer is arranged between the battery cells to apply pressure to the battery cells to make the internal resistance and other characteristics of the battery cells uniform. However, according to the research of the present inventors, it was found that if the temperature of the battery cell stack is too high, the function of the buffer is reduced, and it is difficult to apply uniform pressure to each battery cell of the battery cell stack. If the pressure applied to the battery cells is uneven, the characteristics of the battery cells become uneven, some battery cells may be overcharged or over-discharged, and the temperature of the battery cell stack may further increase.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a battery system that is less likely to cause excessive temperature rise even if a battery cell fails, and further contributes to energy efficiency.

[0009] [Technical means to solve the problem]

[0010] The inventors discovered that the aforementioned problems can be solved by placing an airbag between a battery cell stack and a restraining member. When the temperature of the battery cell stack reaches a predetermined temperature or higher, the airbag inflates and presses the battery cell stack with a predetermined pressure. This led to the completion of the present invention. Therefore, the present invention provides the following solution.

[0011] (1) A battery system comprising: a battery cell stack having a plurality of battery cells stacked thereon; a restraining body disposed at both ends of the battery cell stack in a stacking direction and restraining the battery cell stack in the stacking direction; an airbag disposed between the battery cell stack and the restraining body and capable of containing gas; a gas supply unit that supplies gas to the airbag; and a temperature information acquisition unit that acquires temperature information of the battery cell stack; wherein the battery cell comprises an outer body, a positive electrode contained in the outer body, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte; when the temperature of the battery cell stack reaches a predetermined first temperature or above, at least one of the airbags expands by the gas supplied from the gas supply unit and presses the battery cell stack with a predetermined first pressure.

[0012] According to the battery system (1), when a battery cell fails and the temperature of the battery cell stack rises to or above a predetermined first temperature, the airbag presses the battery cell stack with a first pressure, thereby applying uniform pressure to the battery cells of the battery cell stack.

[0013] (2) The battery system according to (1), further comprising a buffer material disposed between at least one set of the battery cells and the battery cells in the battery cell stack.

[0014] According to the storage battery system of (2), since uniform and constant pressure can be applied to the battery cells by the buffer members during normal operation of the battery cells, the charge and discharge characteristics are improved.

[0015] (3) The battery system according to (1) or (2), wherein the battery cell is configured to discharge the electrolyte to the outside from at least a portion of the exterior body when pressed with the first pressure.

[0016] According to the storage battery system of (3), when the battery cell is pressed with the first pressure, the electrolyte is discharged and charging and discharging cannot be performed. Therefore, the heat generation of the battery cell is suppressed.

[0017] (4) The battery system according to (3), wherein the outer casing is formed of a laminate film, and the battery cell is configured to discharge the electrolyte through at least a portion of the opening of the laminate film of the outer casing when pressed with the first pressure.

[0018] According to the battery system of (4), since the outer casing of the battery cell is formed of the laminate film, the electrolyte is discharged through at least a portion of the openings of the laminate film. Therefore, when pressing with the first pressure, the electrolyte can be discharged more reliably.

[0019] (5) The battery system according to any one of (1) to (4), wherein the melting point of the separator is a second temperature higher than the first temperature.

[0020] According to the storage battery system of (5), the battery cell stack can be pressed with the first pressure before the separator melts.

[0021] (6) The battery system according to (5), wherein the battery cell is configured to discharge the electrolyte solution of the battery cell after being pressed with the first pressure while the battery cell reaches the second temperature.

[0022] According to the battery system of (6), since the electrolyte of the battery cells is discharged before the separator melts, the separator can be uniformly melted when the second temperature is reached.

[0023] (7) The battery system according to (3), wherein the airbag has a vent portion that discharges the gas contained therein to the outside, and the vent portion discharges the gas after the battery cell discharges the electrolyte.

[0024] According to the battery system of (7), since the gas in the airbag is discharged to the outside after the electrolyte is discharged from the battery cell, the vaporized gas of the electrolyte discharged to the vicinity of the battery cell is diluted, thereby preventing the vaporized gas of the electrolyte from burning.

[0025] (8) The battery system according to (7), wherein the airbag discharges the gas when the pressure pressing the battery cell stack decreases from the first pressure.

[0026] According to the battery system of (8), since the gas in the airbag is discharged to the outside when the pressure pressing the battery cell stack decreases from the first pressure, the vaporized gas of the electrolyte discharged around the battery cell stack can be quickly diluted.

[0027] (9) The battery system according to (7) further comprises an electrolyte discharge information acquisition unit, wherein the electrolyte discharge information acquisition unit senses the discharge of the electrolyte of the battery cell, and when the electrolyte discharge information acquisition unit acquires information that the electrolyte of the battery cell is discharged, the airbag discharges the gas.

[0028] According to the battery system of (9), since the gas in the airbag is discharged to the outside when information that the electrolyte of the battery cell is discharged is obtained, the vaporized gas of the electrolyte discharged to the vicinity of the battery cell stack can be quickly diluted.

[0029] (10) The storage battery system according to any one of (1) to (9), wherein the battery cells are batteries in which the cell thickness increases with an increase in the charge rate and decreases with a decrease in the charge rate.

[0030] According to the storage battery system of (10), since a high-capacity battery cell is used, the cell thickness increases with an increase in the charging rate and decreases with a decrease in the charging rate, and thus the electric capacity is high.

[0031] (11) The battery system according to any one of (1) to (10), wherein the battery cell is a lithium ion battery, the negative electrode has a lithium metal layer, and lithium metal is deposited on the lithium metal layer during charging.

[0032] According to the battery system of (11), since a high-capacity battery cell is used, the negative electrode has a lithium metal layer, and lithium metal is deposited on the lithium metal layer during charging, so the capacity is high.

[0033] (12) The battery system according to (11), wherein the separator has a melting point lower than 180°C.

[0034] According to the battery system of (12), the separator melts at a temperature below the melting point of lithium (180°C), and the pores of the separator are blocked. As a result, even if the temperature of the battery cell stack rises above the melting point of lithium, the lithium metal layer in the battery cell is unlikely to melt and flow into the positive electrode active material layer. Therefore, the battery cell stack is unlikely to rise to a temperature above the melting point of lithium.

[0035] (13) The battery system according to any one of (1) to (12), wherein the first temperature is within a range of 130° C. to 150° C.

[0036] According to the battery system of (13), since the first temperature is within the above-mentioned range, an excessive temperature rise is unlikely to occur.

[0037] (14) The battery system according to any one of (1) to (13), wherein the gas contained in the air bag is carbon dioxide.

[0038] According to the battery system of (14), since the gas exhausted from the airbag is carbon dioxide, combustion of vaporized gas of the electrolyte can be more reliably prevented.

[0039] (Effects of the Invention)

[0040] According to the present invention, it is possible to provide a battery system in which even if a battery cell fails, an excessive temperature rise is unlikely to occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a plan view showing an example of a storage battery system according to an embodiment of the present invention.

[0042] Figure 2 yes Figure 1 Front view of the battery system shown.

[0043] Figure 3 yes Figure 1 Side view of the battery system shown.

[0044] Figure 4 yes Figure 1 A cross-sectional view of a battery cell used in the battery system shown.

[0045] Figure 5 This is a flowchart illustrating the operation of the storage battery system according to one embodiment of the present invention. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments shown below are merely illustrative of the present invention, and the present invention is not limited to the following.

[0047] Figure 1 It is a plan view showing an example of a storage battery system according to an embodiment of the present invention. Figure 2 yes Figure 1 The front view of the battery system shown, Figure 3 yes Figure 1 Side view of the battery system shown. Figure 4 yes Figure 1 A cross-sectional view of a battery cell used in the battery system shown.

[0048] like Figures 1 to 3 As shown, the battery system 100 of the present embodiment includes a battery cell stack 10 , a fixing member 40 , an airbag 50 , and a controller 60 .

[0049] The battery cell stack 10 includes a plurality of battery cells 20 and buffer members 30 disposed between the battery cells 20 .

[0050] like Figure 4 As shown, the battery cell 20 includes an outer body 21, a positive electrode 22 housed in the outer body 21, a negative electrode 25, a separator 28 disposed between the positive electrode 22 and the negative electrode 25, and an electrolyte (not shown). The battery cell 20 sequentially stacks the negative electrode 25, the positive electrode 22, the negative electrode 25, the positive electrode 22, and the negative electrode 25, with separators 28 disposed at the upper and lower ends in the stacking direction. The positive electrode 22 includes a positive electrode collector 23 and a positive electrode active material layer 24 disposed on both sides of the positive electrode collector. The negative electrode 25 includes a negative electrode collector 26 and a lithium metal layer 27 disposed on both sides of the negative electrode collector 26. In addition, the number of stacking layers of the positive electrode 22 and the negative electrode 25 is not limited to this, and the number of stacking layers can be increased or decreased according to the purpose. The battery cell 20 is a lithium metal secondary battery in which lithium metal is deposited on the lithium metal layer 27 during charging and the deposited lithium metal moves to the positive electrode active material layer 24 during discharge. The cell thickness of the battery cell 20 increases as the charge rate of lithium metal deposition due to charge increases, and decreases as the charge rate due to discharge decreases.

[0051] The outer casing 21 includes a positive electrode tab 23a and a negative electrode tab 26a. One end of the positive electrode current collector 23 is connected to the positive electrode tab 23a. One end of the negative electrode current collector 26 is connected to the negative electrode tab 26a. The outer casing 21 is formed of laminate films 21a and 21b. The ends of the laminate films 21a and 21b are heat-welded to seal the battery cell 20. The positive electrode tab 23a and the negative electrode tab 26a are arranged between the laminate films 21a and 21b. If the internal pressure of the battery cell 20 rises excessively, the laminate films 21a and 21b around the positive electrode tab 23a and the negative electrode tab 26a peel off and open. As a result, the electrolyte in the battery cell 20 is discharged to the outside.

[0052] As the laminate films 21a and 21b, for example, a laminate film in which an adhesive layer, a metal layer, and a protective layer are sequentially stacked can be used. The laminate film 21a and the laminate film 21b are heat-fused with the adhesive layers overlapping each other. As the material of the adhesive layer, a low-melting-point thermoplastic resin can be used. Examples of low-melting-point thermoplastic resins include polyethylene, polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-methacrylic acid copolymer (EMAA). Examples of the material of the metal layer include aluminum, copper, iron, nickel, and stainless steel. As the material of the protective layer, a high-melting-point thermoplastic resin or a thermosetting resin having a higher melting point than the low-melting-point thermoplastic resin can be used. Examples of the material of the protective layer include polyamide, polyethylene terephthalate, and polypropylene. In order to suppress the breakage of the metal layer caused by the extension of the laminate films 21a and 21b during the molding of the outer body 21, nylon can also be arranged between the metal layer and the protective layer for the purpose of imparting flexibility.

[0053] The material and shape of the positive electrode current collector 23 are not particularly limited as long as it can collect current from the positive electrode 22. Examples of materials for the positive electrode current collector 23 include aluminum, aluminum alloys, stainless steel, nickel, iron, and titanium. Examples of shapes for the positive electrode current collector 23 include foil and plate.

[0054] The positive electrode active material layer 24 contains at least one positive electrode active material. As the positive electrode active material, for example, a layered active material containing lithium, a spinel type active material, an olivine type active material, etc. can be used. Specific examples of positive electrode active materials include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), LiNiO2, etc. p Mn q Co r O2(p+q+r=1), LiNi p Al q Co r O2 (p + q + r = 1), lithium manganate (LiMn2O4), Li 1+x Mn 2-x-y MO4=(x+y=2, M=at least one selected from Al, Mg, Co, Fe, Ni, and Zn) represented by heteroelement substituted Li-Mn spinel, lithium titanate (an oxide containing Li and Ti), lithium metal phosphate (LiMPO4, M=at least one selected from Fe, Mn, Co, and Ni), etc.

[0055] From the perspective of improving lithium ion conductivity, the positive electrode active material layer 24 may optionally contain a solid electrolyte. Furthermore, to improve electrical conductivity, it may optionally contain a conductive additive. Furthermore, from the perspective of exhibiting flexibility, it may optionally contain a binder. The solid electrolyte, conductive additive, and binder are not particularly limited, and substances used in the positive electrode active material layer of conventional lithium metal secondary batteries may be used.

[0056] The material and shape of the negative electrode current collector 26 are not particularly limited as long as it has the function of collecting current from the negative electrode 25. Examples of materials for the negative electrode current collector 26 include nickel, copper, and stainless steel. Examples of the shape of the negative electrode current collector 26 include foil and plate.

[0057] The lithium metal layer 27 is a layer containing lithium metal. The lithium metal layer 27 may also contain a metal that forms an alloy with lithium. Examples of metals that form an alloy with lithium include Mg, Si, Au, Ag, In, Ge, Sn, Pb, Al, and Zn.

[0058] For example, a porous sheet or a nonwoven fabric sheet can be used as the separator 28. Examples of materials for the porous sheet include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polyimides, and fluororesins. Examples of materials for the nonwoven fabric sheet include glass fibers and cellulose fibers. The melting point of the separator 28 is, for example, lower than 180°C (the melting point of lithium), preferably lower than 175°C.

[0059] The electrolyte solution contains an organic solvent and an electrolyte. As the organic solvent, for example, cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, hydrofluoroethers, aromatic ethers, sulfones, cyclic esters, chain carboxylates, and nitriles can be used. Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, vinylene carbonate, and fluoroethylene carbonate. Examples of chain carbonates include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, and 4-methyl-1,3-dioxolane. Examples of chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, and diethyl ether. Examples of hydrofluoroethers include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl)ether, and 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane. Examples of aromatic ethers include anisole. Examples of sulfones include sulfolane and methyl sulfolane. Examples of cyclic esters include γ-butyrolactone. Examples of chain carboxylates include acetates, butyrates, and propionates. Examples of nitriles include acetonitrile and propionitrile. The organic solvent may be used alone or in combination of two or more.

[0060] The electrolyte contains a lithium salt. Examples of lithium salts include LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, LiN(CF3SO2)2 (LiTFSI), LiN(FSO2)2 (LiFSI), and LiBC4O8. The lithium salts may be used alone or in combination of two or more.

[0061] The buffer member 30 has the function of relieving and equalizing the pressure applied to the battery cells 20. For example, a leaf spring or rubber can be used as the buffer member 30. Alternatively, a fluid buffer member containing gas and liquid can be used as the buffer member 30.

[0062] The fixing member 40 fixes the battery cell stack 10. The fixing member 40 includes a pair of restraints 41 and fasteners 42 for fastening the restraints 41. The restraints 41 are disposed at both ends of the battery cell stack 10 in the stacking direction and restrain the battery cell stack 10 in the stacking direction.

[0063] The airbags 50 are positioned between the battery cell stack 10 and the restraining body 41. The airbags 50 are hollow containers capable of containing gas. They expand when gas is supplied to the interior, pressing against the battery cell stack 10. The airbags 50 have a vent 51 that is sealable and can be opened. The vent 51 opens when the internal pressure of the airbag 50 rises excessively. This allows the gas contained within the airbag 50 to be discharged to the outside. The vent 51 is positioned on the side of the battery cell 20 where the positive and negative tabs 23a and 26a are exposed.

[0064] The gas contained in the airbag 50 is preferably an oxygen-free gas that does not contain oxygen. The oxygen-free gas may be, for example, carbon dioxide.

[0065] The controller 60 controls the operation of the airbag 50. The controller 60 includes a gas supply unit and a temperature information acquisition unit. The gas supply unit supplies gas to the airbag 50. The temperature information acquisition unit acquires temperature information of the battery cell stack 10. The temperature information acquisition unit is, for example, a temperature sensor. Based on the temperature information of the battery cell stack 10 acquired by the temperature information acquisition unit, the controller 60 supplies gas to the airbag 50 via the gas supply unit. The controller 60 controls the amount of gas supplied to the airbag 50 and adjusts the volume and internal pressure of the airbag 50. Thus, an appropriate pressure is applied to the battery cell stack 10 according to the temperature of the battery cell stack 10.

[0066] When the temperature of the battery cell stack 10 reaches a predetermined first temperature or above, the controller 60 uses the gas supplied from the gas supply unit to inflate the airbag 50 so that the airbag 50 presses the battery cell stack 10 at a predetermined first pressure. By pressing with the first pressure, the internal pressure of the battery cell 20 rises excessively, the laminate film 21a and the laminate film 21b peel off and open, and the electrolyte is discharged to the outside. The first temperature is an abnormal temperature that exceeds the normal operating temperature of the battery cell stack 10. The first temperature is preferably a low temperature that is lower than the melting point of the diaphragm 28. The first temperature is, for example, in the range of 130°C to 150°C. It can also be set according to conditions such as the external temperature or the condition of the battery cell (for example, during discharge or charging).

[0067] After the electrolyte is discharged from the battery cells 20 , the controller 60 may further supply gas to the airbag 50 via the gas supply unit to increase the internal pressure of the airbag 50 until the exhaust port 51 opens. Thus, the gas in the airbag 50 is discharged to the outside.

[0068] The controller 60 may also include a pressure information acquisition unit that acquires the internal pressure of the airbag 50, i.e., the pressure exerted by the airbag 50 against the battery cell stack 10. The controller 60 may also determine that electrolyte is being discharged from the battery cell 20 when the pressure reaches a second pressure lower than the first pressure. Furthermore, the controller 60 may include an electrolyte discharge information acquisition unit that senses the discharge of electrolyte from the battery cell 20. The electrolyte discharge information acquisition unit may be, for example, a leakage sensor.

[0069] Next, refer to Figure 5 The operation of the battery system 100 will be described by dividing into the following cases: when the temperature of the battery cell stack 10 is (1) lower than the first temperature, (2) the first temperature, and (3) the second temperature higher than the first temperature. Figure 5 This is a flowchart illustrating the operation of the storage battery system according to one embodiment of the present invention.

[0070] (1) Lower than the first temperature

[0071] When the temperature of the battery cell stack 10 is lower than the first temperature, that is, when it is at the normal operating temperature, the airbag 50 is pressed on the battery cell stack 10 with a restraining pressure (S11). The controller 60 controls the gas supply unit so that the airbag 50 presses the battery cell stack 10 with a specified restraining pressure. When the battery cell stack 10 is pressed with a specified restraining pressure, a uniform and fixed pressure is applied to each of the plurality of battery cells 20 via the buffer member 30. By applying a uniform and fixed pressure to each of the battery cells 20, the internal resistance between the positive electrode 22 and the negative electrode 25 is reduced, and stable charging and discharging can be performed. The restraining pressure varies depending on the size of the battery cell stack 10 and the condition of the battery cell 20 (for example, during discharge or charging), but is, for example, within a range of 0.1 MPa to 3.0 MPa.

[0072] (2) First temperature

[0073] When the temperature of the battery cell stack 10 rises to the first temperature, the following operation is performed.

[0074] First, the battery cell stack 10 is pressed with a first pressure by the airbag 50 ( S21 ). The controller 60 controls the amount of gas supplied by the gas supply unit so that the airbag 50 presses the battery cell stack 10 with the first pressure.

[0075] Next, the electrolyte of the battery cell 20 is discharged (S22). The battery cell stack 10 is pressed using a first pressure when it is abnormal, i.e., at a first temperature (for example, above 130°C). By being in a high-temperature environment at the first temperature, the bonding strength of the adhesive layer of the laminate films 21a, 21b is reduced. Furthermore, by applying the first pressure to the battery cell 20, the laminate film 21a and the laminate film 21b around the positive electrode tab 23a and the negative electrode tab 26a of the battery cell 20 are peeled off and opened. As a result, the electrolyte of the battery cell 20 is discharged to the outside. The first pressure varies depending on the bonding strength of the adhesive layer of the laminate film 21a and the laminate film 21b forming the outer body 21 of the battery cell 20, for example, within a range of 0.3 MPa to 1 MPa.

[0076] Next, the airbag 50 is degassing (S23). Upon detecting the discharge of electrolyte from the battery cells 20, the controller 60 controls the gas supply from the gas supply unit, increasing the internal pressure until the vent 51 of the airbag 50 opens. With the vent 51 of the airbag 50 opening, the gas in the airbag 50 is discharged to the outside. The gas discharged from the airbag 50 dilutes the vaporized electrolyte gas in the battery cells 20 that has been discharged into the vicinity of the battery cells 20, preventing combustion of the vaporized electrolyte gas.

[0077] (3) Second temperature

[0078] When the temperature of the battery cell stack 10 rises to a second temperature higher than the first temperature, the separator 28 melts ( S31 ). The second temperature is the melting point of the separator 28 . By melting the separator 28 at the second temperature, the pores of the separator 28 are blocked. This increases the temperature of the battery cell stack 10 above the melting point of lithium. Even if the lithium metal layer 27 melts, the molten lithium is prevented from flowing into the positive electrode 22 of the battery cell 20 .

[0079] According to the battery system 100 of this embodiment configured as described above, if, for example, a battery cell 20 fails and the temperature of the battery cell stack 10 rises to or above a predetermined first temperature, the airbag 50 presses the battery cell stack 10 with a first pressure, thereby applying uniform pressure to the battery cells 20. In the battery system 100 of this embodiment, buffer members 30 are disposed between the battery cells 20. When the battery cells 20 are functioning normally, the buffer members 30 can apply uniform and constant pressure to the battery cells 20, thereby improving charge and discharge characteristics.

[0080] According to the battery system 100 of this embodiment, when the battery cell 20 is pressed with the first pressure, the laminate film 21a and the laminate film 21b around the positive electrode tab 23a and the negative electrode tab 26a are peeled off and opened, thereby discharging the electrolyte in the battery cell 20 and preventing charging and discharging. This suppresses heat generation in the battery cell 20.

[0081] According to the battery system 100 of this embodiment, since the melting point of the separators of the battery cells 20 is a second temperature higher than the first temperature, the battery cell stack 10 can be pressed with the first pressure before the separators 28 melt. Furthermore, by setting the melting point of the separators 28 below the melting point of lithium, even if the temperature of the battery cell stack 10 of the battery cells 20 rises above the melting point of lithium, the lithium metal layer 27 can be prevented from melting and flowing into the positive electrode active material layer 24. Consequently, the battery cell stack 10 is less likely to rise to a temperature above the melting point of lithium.

[0082] According to the battery system 100 of this embodiment, after the battery cells 20 discharge the electrolyte, the gas in the airbag 50 is discharged to the outside through the exhaust portion 51. This allows for rapid dilution of the vaporized electrolyte gas discharged around the positive and negative tabs 23a and 26a of the battery cells 20. This prevents the vaporized electrolyte gas from igniting. If the gas in the airbag 50 is carbon dioxide, this can further reliably prevent the vaporized electrolyte gas from igniting.

[0083] While the embodiments of the present invention have been described above, the present invention is not limited thereto. For example, in this embodiment, the outer casing 21 of the battery cell 20 is formed by thermally fusing a laminate film 21a and a laminate film 21b, but the outer casing 21 is not limited thereto. The outer casing 21 may also be a molded body. Preferably, when the battery cell stack 10 is pressed with a first pressure, at least a portion of the outer casing 21 is opened to allow the electrolyte in the battery cell 20 to be discharged to the outside.

[0084] In this embodiment, buffer members 30 are disposed between all battery cells 20 , but the arrangement of buffer members 30 is not limited thereto. Disposition of buffer members 30 is also possible. Preferably, buffer members 30 are disposed between at least one group of battery cells 20 to maintain uniform pressure applied to the battery cells 20 .

[0085] Reference numerals

[0086] 10 Battery cell stack

[0087] 20 battery cells

[0088] 21 Exterior body

[0089] 21a, 21b Laminated film

[0090] 22 positive electrode

[0091] 23. Positive electrode collector

[0092] 23a positive electrode tab

[0093] 24 Positive electrode active material layer

[0094] 25 negative electrode

[0095] 26 Negative electrode collector

[0096] 26a negative electrode tab

[0097] 27 Lithium metal layer

[0098] 28 diaphragm

[0099] 30 buffer parts

[0100] 40 Fixed parts

[0101] 41 Constraints

[0102] 42 Fasteners

[0103] 50 airbags

[0104] 100 Battery System

Claims

1. A battery system comprising: A battery cell stack having a plurality of battery cells stacked thereon; Constraints, disposed at both ends of the battery cell stack in the stacking direction, and constraining the battery cell stack in the stacking direction; airbags, each disposed between the battery cell stack and the restraining body, capable of containing gas; a gas supply unit, supplying gas to the airbag; and a temperature information acquiring unit for acquiring temperature information of the battery cell stack; and The battery cell comprises an outer casing, a positive electrode housed in the outer casing, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution; When the temperature of the battery cell stack reaches a predetermined first temperature or higher, the at least one airbag is inflated by the gas supplied from the gas supply portion and presses the battery cell stack with a predetermined first pressure.

2. The battery system according to claim 1, wherein: A buffer material is further provided, the buffer material being arranged between at least one set of the battery cells and the battery cells in the battery cell stack.

3. The battery system according to claim 1 or 2, wherein: The battery cell is configured to discharge the electrolyte to the outside from at least a portion of the exterior body when pressed with the first pressure.

4. The battery system according to claim 3, wherein: The outer body is formed of a laminated film. The battery cell is configured such that, when pressed with the first pressure, the electrolyte is discharged through at least a portion of the opening in the laminate film of the exterior body.

5. The battery system according to claim 1 or 2, wherein: The melting point of the separator is a second temperature higher than the first temperature.

6. The battery system according to claim 5, wherein: The battery cell is configured to discharge the electrolyte from the battery cell after being pressed with the first pressure while the battery cell reaches the second temperature.

7. The battery system according to claim 3, wherein: The airbag has an exhaust portion for exhausting the gas contained therein to the outside. After the electrolyte is discharged from the battery cell, the exhaust portion discharges the gas.

8. The battery system according to claim 7, wherein: The airbag discharges the gas when the pressure pressing the battery cell stack decreases from the first pressure.

9. The battery system according to claim 7, wherein: The battery further comprises an electrolyte discharge information acquisition unit that senses the discharge of the electrolyte from the battery cell. The airbag discharges the gas when the electrolyte discharge information acquisition unit acquires information that the electrolyte of the battery cell is discharged.

10. The battery system according to claim 1 or 2, wherein: The battery cell described above is a battery in which the thickness of the cell increases as the charge rate increases and the thickness of the cell decreases as the charge rate decreases.

11. The battery system according to claim 1 or 2, wherein: The battery cell is a lithium-ion battery, the negative electrode has a lithium metal layer, and lithium metal is deposited on the lithium metal layer during charging.

12. The battery system according to claim 11, wherein: The melting point of the separator is lower than 180°C.

13. The battery system according to claim 1 or 2, wherein: The first temperature is within a range of 130° C. to 150° C. inclusive.

14. The battery system according to claim 1 or 2, wherein: The gas contained in the airbag is carbon dioxide.

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