Battery

Abstract

To provide a battery from which high-temperature gas is unlikely to be released to the outside of the battery even when overcharging occurs.SOLUTION: A battery includes: an electrode body 11; a first exterior body 20 that encloses and seals the electrode body 11; and a second exterior body 30 that encloses and seals the first exterior body 20 and that has a sealing portion 30a. A part of the sealing portion 30a of the second exterior body 30 has a weak portion 30b having a lower sealing strength than the rest of the sealing portion. With the battery of the present disclosure, even if gas is generated from the electrode body under abnormal conditions and released by breaking the sealing portion of the first exterior body 20, the gas reaches an unjoined portion 30c of the second exterior body 30 and is held in the unjoined portion for a certain period of time. This cools the temperature of the released gas. Furthermore, even if the sealing portion 30a of the second exterior body 30 is broken, and the gas is released to the outside, since the temperature of the gas is lowered, it is possible to restrain the reaction of the gas with oxygen in the atmosphere and restrain the occurrence of problems caused by high-temperature gas.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a battery having an electrode assembly and an exterior body that seals the electrode assembly. [Background technology]

[0002] Patent Document 1 discloses an all-solid-state battery in which a battery cell is housed in a laminate film. Patent Document 2 discloses that an electrode laminate is covered with a soft laminate film and a hard laminate film, and also discloses an all-solid-state battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-176134 [Patent Document 2] Japanese Patent Publication No. 2020-170583 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when overcharging occurs, there is a risk that high-temperature gas will be released outside the laminate film.

[0005] Therefore, an object of the present disclosure is to provide a battery that is less likely to release high-temperature gas to the outside even when overcharging occurs. [Means for solving the problem]

[0006] The present application discloses a battery comprising an electrode body, a first exterior body that contains and seals the electrode body, and a second exterior body that has a sealing portion that contains and seals the first exterior body, wherein a portion of the sealing portion of the second exterior body has a fragile portion that has lower sealing strength than other portions of the sealing portion.

[0007] The first exterior body may be a laminate film.

[0008] The second exterior body may be a laminate film.

[0009] The second exterior housing may be rectangular in plan view, and the fragile portion may be provided in a sealing portion on a short side of the second exterior housing.

[0010] The second exterior body may have a check valve, and may be configured so that the withstand pressure of the check valve from the inside to the outside of the second exterior body is higher than the withstand pressure of the fragile portion.

[0011] The pressure between the first exterior body and the second exterior body may be reduced.

[0012] An inert gas may be contained between the first exterior body and the second exterior body.

[0013] Air may be contained between the first exterior body and the second exterior body.

[0014] The air may have a moisture content of 1000 ppm or less.

[0015] The electrode body may have a solid electrolyte, and the battery may be a solid-state battery. [Effects of the Invention]

[0016] According to the battery of the present disclosure, the gas generated from the electrode body is cooled between the two exterior bodies, so that the temperature of the gas released outside the second exterior body through the fragile portion can be kept low. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of the appearance of an all-solid-state battery 10. [Figure 2] FIG. 2 is a plan view of the all-solid-state battery 10. [Figure 3] FIG. 3 is an exploded perspective view of the all-solid-state battery 10. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1.Battery 1 to 3 show diagrams illustrating a solid-state battery (all-solid-state battery) 10 according to one embodiment. Here, an all-solid-state battery is described as a typical example, but the present disclosure does not necessarily have to be an all-solid-state battery and can be applied to any battery having an electrode body and an exterior body that seals it (for example, a battery having an electrolyte solution or a solid-state battery (semi-solid battery) that contains a solid electrolyte and an electrolyte solution). FIG. 1 is an external perspective view, FIG. 2 is a plan view (viewed from the direction of arrow II in FIG. 1), and FIG. 3 is an exploded perspective view.

[0019] 1 to 3, the all-solid-state battery 10 of this embodiment has an electrode body 11, a first exterior body 20, and a second exterior body 30. The electrode body 11, which is generally rectangular in plan view, is enclosed in the first exterior body 20, which is also generally rectangular in plan view, and the first exterior body 20 is further enclosed in the second exterior body 30, which is also rectangular in plan view. In this case, a positive electrode terminal 11a and a negative electrode terminal 11b extend from the electrode body 11, and are arranged so that their tips protrude from the first exterior body 20 and the second exterior body 30. Each component and their relationship will be described in more detail below.

[0020] 1.1. Electrode body The electrode body 11 (see FIG. 3) has a positive electrode current collecting layer, a positive electrode composite layer, a separator layer, a negative electrode composite layer, a negative electrode current collecting layer, a positive electrode terminal 11a, and a negative electrode terminal 11b. In this embodiment, the positive electrode current collecting layer, the positive electrode composite layer, the separator layer, the negative electrode composite layer, the negative electrode current collecting layer, the negative electrode composite layer, the separator layer, the positive electrode composite layer, and the positive electrode current collecting layer are stacked in this order to form unit elements, and a plurality of these are stacked (sometimes referred to as a "stack 11c"), with the positive electrode terminal 11a electrically connected to the positive electrode current collecting layer of the stack 11c, and the negative electrode terminal 11b electrically connected to the negative electrode current collecting layer of the stack 11c. In this embodiment, the laminate 11c is also rectangular in plan view.

[0021] [Positive electrode current collecting layer] The positive electrode current collecting layer is laminated on the positive electrode mixture layer to collect current from the positive electrode mixture layer. The positive electrode current collecting layer is a rectangular foil in plan view, and in this embodiment, is made up of a positive electrode current collecting foil, which is a metal foil, and a carbon layer laminated on the positive electrode current collecting foil. The carbon layer is laminated on the positive electrode mixture layer, thereby laminating the positive electrode current collecting layer on the positive electrode mixture layer. Examples of materials that can be used to form the positive electrode current collector foil include stainless steel, aluminum, nickel, iron, and titanium, and the carbon layer is made of a material containing carbon.

[0022] [Positive electrode mixture layer] The positive electrode mixture layer has the positive electrode current collecting layer on one surface and a separator layer on the other surface. The positive electrode mixture layer has a rectangular sheet shape in plan view.

[0023] The positive electrode mixture layer is a layer containing a positive electrode active material, and may further contain at least one of a solid electrolyte material, a conductive material, and a binder, as necessary. The positive electrode active material may be a known active material. Examples include cobalt-based (LiCoO2, etc.), nickel-based (LiNiO2, etc.), manganese-based (LiMn2O4, Li2Mn2O3, etc.), iron phosphate-based (LiFePO4, Li2FeP2O7, etc.), NCA-based (nickel, cobalt, aluminum compound), and NMC-based (nickel, manganese, cobalt compound). More specifically, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and others. The surface of the positive electrode active material may be coated with an oxide layer such as a lithium niobate layer, a lithium titanate layer, or a lithium phosphate layer.

[0024] The solid electrolyte is preferably an inorganic solid electrolyte, since it has higher ionic conductivity and superior heat resistance compared to organic polymer electrolytes. Examples of inorganic solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes. Examples of sulfide solid electrolyte materials having Li ion conductivity include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga, and In.) The above description of "Li2S-P2S5" means a sulfide solid electrolyte material obtained using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions.

[0025] On the other hand, examples of oxide solid electrolyte materials having Li ion conductivity include compounds having a NASICON structure. An example of a compound having a NASICON structure is a compound represented by the general formula Li 1+x AlxGe 2-x Compounds (LAGP) represented by (PO4)3 (0≦x≦2), general formula Li 1+x Al x Ti 2-x Examples of the oxide solid electrolyte material include a compound (LATP) represented by (PO4)3 (0≦x≦2). 0.34 La 0.51 TiO3), LiPON (e.g., Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (e.g., Li7La3Zr2O 12 ) etc.

[0026] The binder is not particularly limited as long as it is chemically and electrically stable, and examples thereof include fluorine-based binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), rubber-based binders such as styrene butadiene rubber (SBR), olefin-based binders such as polypropylene (PP) and polyethylene (PE), and cellulose-based binders such as carboxymethyl cellulose (CMC). As the conductive material, carbon materials such as acetylene black (AB), ketjen black, and carbon fiber, and metal materials such as nickel, aluminum, and stainless steel can be used.

[0027] The content of each component in the positive electrode mixture layer may be the same as in the past. The thickness of the positive electrode mixture layer is, for example, preferably 0.1 μm to 1 mm, more preferably 1 μm to 150 μm.

[0028] [Separator layer] The separator layer (solid electrolyte layer) is a rectangular sheet in plan view, disposed between the positive electrode composite layer and the negative electrode composite layer, and contains a solid electrolyte material. The separator layer contains at least the solid electrolyte material. The solid electrolyte material can be considered to be the same as the solid electrolyte material described for the positive electrode composite layer.

[0029] [Negative electrode composite layer] The negative electrode mixture layer is a layer containing at least a negative electrode active material. The negative electrode mixture layer may contain a binder, a conductive material, and a solid electrolyte material as needed. The binder, conductive material, and solid electrolyte material can be considered to be similar to those of the positive electrode mixture layer.

[0030] The negative electrode active material is not particularly limited, but in the case of constructing a lithium ion battery, examples of the negative electrode active material include carbon materials such as graphite and hard carbon, various oxides such as lithium titanate, Si and Si alloys, metallic lithium and lithium alloys, and the like.

[0031] The negative electrode mixture layer is in the form of a rectangular sheet in plan view, with the separator layer laminated on one surface and the negative electrode current collecting layer laminated on the other surface. The content of each component in the negative electrode mixture layer may be the same as in the past. The thickness of the negative electrode mixture layer is, for example, preferably 0.1 μm to 1 mm, more preferably 1 μm to 150 μm.

[0032] [Negative electrode current collecting layer] The negative electrode current collecting layer is laminated on the negative electrode composite layer to collect current from the negative electrode composite layer. The negative electrode current collecting layer has a rectangular foil shape in a plan view and can be made of, for example, stainless steel, copper, nickel, carbon, or the like.

[0033] [Positive terminal, negative terminal] The positive electrode terminal 11a and the negative electrode terminal 11b are electrically conductive members, and serve as terminals for electrically connecting each electrode to the outside. One end of the positive electrode terminal 11a is electrically connected to the positive electrode current collecting layer, and the other end passes through the sealing portion of the first exterior body 20 and the sealing portion 30a of the second exterior body 30 and is exposed to the outside. One end of the negative electrode terminal 11b is electrically connected to the negative electrode current collecting layer, and the other end passes through the sealing portion of the first exterior body 20 and the sealing portion 30a of the second exterior body 30 and is exposed to the outside.

[0034] 1.2. First outer casing As shown by the dashed dotted line in Fig. 2 and in the exploded perspective view in Fig. 3, in this embodiment, the first exterior body 20 is made of a rectangular sheet-like member in a plan view, and includes a first sheet 21 and a second sheet 22 (see Fig. 3). The laminate 11c of the electrode body 11 is enclosed between the first sheet 21 and the second sheet 22, and the outer peripheral edge of the first sheet 21 and the outer peripheral edge of the second sheet 22 are joined to form a sealed portion. Therefore, the first exterior body 20 is bag-shaped, and contains and seals the electrode body 11c inside.

[0035] The first sheet 21 is rectangular in plan view and has a rectangular recess 21a in plan view (the opening of the recess 21a is on the lower side of the paper in FIG. 3 and is not visible in a blind spot), and the laminate 11c of the electrode body 11 is housed inside this recess 21a. A protruding portion 21b is provided on the outer periphery edge of the recess 21a so as to protrude from the edge, and this protruding portion 21b and the outer periphery edge of the surface of the second sheet 22 are joined to form a sealing portion.

[0036] The second sheet 22 is a flat, rectangular sheet in plan view. As described above, the outer peripheral edge of the surface of the second sheet 22 facing the protruding portion 21b of the first sheet 21 is overlapped and joined to the protruding portion 21b of the first sheet 21, thereby forming a sealing portion.

[0037] In this embodiment, the first sheet 21 and the second sheet 22 are made of a laminate film. Here, the laminate film is a film having a metal layer and a sealant layer. Examples of metals used in the laminate film include aluminum and stainless steel, and examples of materials used in the sealant layer include thermoplastic resins such as polypropylene, polyethylene, polystyrene, and polyvinyl chloride. The method for forming the sealing portion between the first sheet 21 and the second sheet 22, i.e., the method for joining the laminate film, is not particularly limited, and any known method can be used. Specific examples include a method for welding the sealant material layers of the laminate film together (such as hot plate welding, ultrasonic welding, vibration welding, or laser welding) and bonding with an adhesive.

[0038] Here, the first outer casing 20 is composed of separate first and second sheets 21 and 22, but this is not limited to this, and the electrode body 11 may be arranged so as to be wrapped around a single sheet, and the overlapping ends of the sheets may be joined together due to the wrapped state. In the above-described embodiment, the recess 21a is provided only in the first sheet 21, and the second sheet 22 is flat, but this is not limited to this, and recesses may be provided in both the first sheet and the second sheet, and the electrode body stack may be placed therein.

[0039] 1.3. Second outer casing 1 to 3, in this embodiment, the second exterior body 30 is made of a rectangular sheet-like member in a plan view, and in this embodiment, includes a first sheet 31 and a second sheet 32. The first exterior body 20 (containing the laminate 11c of the electrode assembly 11) is contained between the first sheet 31 and the second sheet 32, and the outer peripheral edge of the first sheet 31 and the outer peripheral edge of the second sheet 32 ​​are joined to form the sealed portion 30a (the region outside the dashed lines in FIGS. 1 and 2). Therefore, the second exterior body 30 is bag-shaped, and contains and seals the electrode assembly 11c and the first exterior body 20 inside.

[0040] [First sheet, second sheet, sealing part] The first sheet 31 is rectangular in plan view and has a rectangular recess 31a in plan view (the opening of the recess 31a is on the lower side of the paper in FIG. 3 and is not visible in a blind spot), and the recess 21a of the first exterior body 20 and the laminate 11c of the electrode body 11 contained therein are housed inside this recess 31a. A protruding portion 31b is provided on the outer periphery edge of the recess 31a so as to protrude from the edge, and a part of this protruding portion 31b and the outer periphery edge of the surface of the second sheet 32 ​​are joined to form the sealing portion 30a.

[0041] The second sheet 32 ​​is a flat, rectangular sheet in plan view. As described above, the outer peripheral edge of the surface of the second sheet 32 ​​facing the protruding portion 31b of the first sheet 31 is overlapped and joined to the protruding portion 31b of the first sheet 31, thereby forming the sealing portion 30a.

[0042] In this embodiment, the first sheet 31 and the second sheet 32 ​​are made of a laminate film. Here, the laminate film is a film having a metal layer and a sealant layer. Examples of metals used in the laminate film include aluminum and stainless steel, and examples of materials used in the sealant layer include thermoplastic resins such as polypropylene, polyethylene, polystyrene, and polyvinyl chloride. The method for forming the sealing portion 30a by the first sheet 31 and the second sheet 32, i.e., the method for joining the laminate film, is not particularly limited, and any known method can be used. Specific examples include a method for welding the sealant material layers of the laminate film together (for example, hot plate welding, ultrasonic welding, vibration welding, or laser welding) and bonding with an adhesive.

[0043] Here, the second outer casing 30 is composed of separate first and second sheets 31 and 32, but this is not limited to this, and the first outer casing 20, in which the electrode body 11 is sealed, may be arranged in a rolled-up state with one sheet, and the ends of the overlapping sheet portions that result from the rolling may be joined together. In the above-described embodiment, the recess 31a is provided only in the first sheet 31, and the second sheet 32 ​​is flat, but this is not limited to this, and recesses may be provided in both the first sheet and the second sheet, and the electrode body stack may be placed therein.

[0044] [Weak part] 2, the sealing portion 30a has a fragile portion 30b. The fragile portion 30b belongs to the sealing portion 30a and is the portion where the first sheet 31 and the second sheet 32 ​​are joined as described above, but the fragile portion 30b is configured to have a lower joining strength (sealing strength) than the other portions of the sealing portion 30a. This allows the fragile portion 30b to be preferentially broken when the seal of the sealing portion 30a is broken. Therefore, the specific low joining strength of the fragile portion 30b is not particularly limited as long as it is configured to be preferentially broken. The scope of the fragile portion 30b is not particularly limited, as long as a part of the sealing portion 30a is made into the fragile portion 30b. In particular, it is preferable that the fragile portion 30b be provided in the sealing portion 30a provided on the short side of the second exterior body 30, which is rectangular in plan view. The fragile portion 30b can be formed by changing the bonding conditions between the fragile portion 30b and the sealing portion 30a other than the fragile portion 30b. For example, when using the above-mentioned welding method, the temperature conditions, pressing conditions, and welding time can be changed. The ratio of the fragile portion 30b to the sealing portion 30a is not particularly limited, but the fragile portion 30b preferably accounts for 5% to 80% of the total length (circumferential length) of the sealing portion 30a, more preferably 10% or more, and even more preferably 20% or more, and more preferably 60% or less, and even more preferably 50% or less.

[0045] [Non-joint part] Furthermore, in the second outer casing 30, inside the sealing portion 30a (inside the dotted line in Figure 2), a non-bonded portion 30c is provided in the area that is outside the first outer casing 20, where the first sheet 31 and the second sheet 32 ​​are not bonded. The non-bonded portion 30c is sandwiched between the first sheet 31 and the second sheet 32, but because they are not bonded to each other, it expands when a fluid flows into it. The non-bonded portion 30c may contain gas, and although there are no particular limitations, it is preferable that it contains an inert gas or air. In the case of air, it is preferable that the moisture content is low, for example, the moisture content can be 1000 ppm or less, more preferably 375 ppm or less. On the other hand, the non-jointed portion 30c may be in a decompressed state, which allows a larger amount of gas leaking from the first exterior body 20 to be received. In this case, the first sheet 31 and the second sheet 32 ​​appear to be arranged so as to be in contact with and overlap each other (but are not joined).

[0046] The size of the non-bonded portion 30c is not particularly limited, and it is sufficient as long as there is a non-bonded portion 30c, but by making the non-bonded portion 30c larger, more gas can be stored in the non-bonded portion 30c, and the effect described below will be enhanced. However, it does not need to be too large, and specifically, when the battery 10 is viewed in plan as shown in Figure 2, the area (area) surrounded by the sealed portion 30a that is occupied by the non-bonded portion 30c (sometimes referred to as the "non-bonded portion ratio") is preferably 5% or more, more preferably 10% or more, and even more preferably 30% or more.

[0047] 2. Manufacturing For example, the all-solid-state battery 10 can be fabricated as follows in a first embodiment. 2.1. First Aspect The laminate 11c of the electrode body 11 is placed in a recess 21a formed in advance in the first sheet 21 that will become the first exterior body 20. Then, the first sheet 21 and the second sheet 22 are overlapped, and the protruding portion 21b of the first sheet 21 is joined to the surface edge of the second sheet 22 to form a sealed portion. At this time, a vacuum may be drawn to evacuate the inside of the recess 21a. Next, the first exterior body 20 containing the electrode assembly 11 is placed in a recess 31a previously formed in the first sheet 31, which will become the second exterior body 30. Then, the first sheet 31 and the second sheet 32 ​​are overlapped, and the protruding portion 31b of the first sheet 31 is joined to the surface edge of the second sheet 32 ​​to form the sealed portion 30a. At this time, a vacuum is drawn to degas the inside of the non-joined portion 30c, and this is preferably carried out in a vacuum atmosphere, an inert gas atmosphere, or an atmosphere of air with an adjusted moisture content.

[0048] 2.2. Second Aspect The all-solid-state battery 10 can also be fabricated as follows, for example, as a second embodiment. The electrode body is wrapped with one sheet, and thus the laminate 11c of the electrode body 11 is arranged so as to be sandwiched between the sheets. The ends of the sheets that face each other as a result of wrapping the electrode body 11 are overlapped and joined to form the sealed portion of the first exterior body. At this time, a vacuum is drawn inside the one sheet, and the sheet deforms to fit the shape of the electrode body 11, forming a recess, which becomes the first exterior body. The first exterior housing containing the electrode assembly is wrapped with a single sheet, so that the first exterior housing is sandwiched between the sheets. The edges of the sheets that face each other as a result of wrapping the first exterior housing are overlapped and joined to form a sealed portion in the second exterior housing. At this time, a vacuum is drawn inside the single sheet, causing the sheet to deform to conform to the shape of the first exterior housing, forming a recess, which then becomes the second exterior housing. This vacuum drawing is preferably performed in a vacuum atmosphere, an inert gas atmosphere, or an air atmosphere with an adjusted moisture content.

[0049] 3. Effects etc. According to the battery of the present disclosure, even if gas is generated from the electrode assembly in the event of an abnormality and is released by breaking the sealed portion of the first exterior body 20, it reaches the non-bonded portion 30c of the second exterior body 30 and is retained there for a certain period of time. This cools the temperature of the released gas. Furthermore, even if the sealed portion 30a of the second exterior body 30 is broken and the gas is released to the outside, the temperature is lowered, so the gas is prevented from reacting with atmospheric oxygen and the occurrence of problems due to high-temperature gas is suppressed. This makes it possible to eliminate or reduce the use of insulation, which was previously necessary as a measure to prevent high-temperature gas release. Since the fragile portion 30b is formed in the sealing portion 30a, when the seal of the sealing portion 30a is broken, the fragile portion 30b is broken first, so that the direction of gas outflow can be controlled and the impact of the gas can be reduced. Also, by providing a fragile portion only in one portion, the area that breaks can be reduced in size, and the flow of gas from the inside to the outside becomes dominant, suppressing the inflow of gas (oxygen) from the outside to the inside and suppressing the occurrence of a reaction.

[0050] 4.Other The battery of the present disclosure may be configured so that a check valve is provided in the second exterior body to control the flow from inside to outside the battery. In this case, however, it is preferable that the withstand pressure of the check valve from inside to outside is also high, and the withstand pressure of the fragile portion is also high. This effectively achieves the above-mentioned effects. [Example]

[0051] 5. Working Example In the examples, tests were conducted in which the conditions of the battery configuration were changed and a severe load (overcharge) was applied to intentionally release gas. 5.1. Test specimen (battery) An electrode assembly containing a sulfide solid electrolyte was prepared and wrapped with a single laminate film, resulting in the electrode assembly stack being sandwiched between the laminate films. The space between the electrode assembly and the laminate film was then evacuated to reduce pressure, and the overlapping edges of the laminate films, which had been placed facing each other by wrapping the electrode assembly, were partially joined and sealed. The joining was performed using a hot plate welding method at a temperature of 200°C, a pressure of 0.25 MPa, and a time of 30 seconds. This resulted in a first exterior body containing the electrode assembly. Next, the first exterior body containing the electrode assembly was wrapped with a single laminate, so that the first exterior body was sandwiched between two sheets. The space between the first exterior body and the laminate film was then evacuated to reduce pressure, and the overlapping edges of the laminate film, which had been brought into contact with each other by wrapping the first exterior body, were partially joined to form a sealed portion. This joining was performed using a hot plate welding method, with the fragile portion sealed at a temperature of 200°C, a pressure of 0.20 MPa, and a time of 30 seconds. The remaining portions were sealed at a temperature of 200°C, a pressure of 0.25 MPa, and a time of 30 seconds. This formed a second exterior body, resulting in a rectangular battery (longer side 300 mm, shorter side 90 mm) in plan view. The non-bonded portion rate was set to 50%.

[0052] The different conditions for each example are shown in Table 1. In Table 1, "Sealing atmosphere" refers to the atmosphere in which the second exterior body was sealed. That is, "Vacuum" refers to sealing in a vacuum atmosphere, "Argon" refers to sealing in an argon atmosphere, which is an inert gas, and "Air" refers to sealing in an air atmosphere (dew point environment shown in °C, and moisture content shown in ppm).

[0053] Testing The battery according to each example was continuously charged at a rate of 5.5 C, and the test was carried out until the sealing portion of the second exterior body was broken. If a battery ignites, the time until ignition is also shown, and if it does not ignite, the result is recorded as "no ignition." Here, "ignition" is a result set under intentionally excessive test conditions that would not be expected under normal use in order to clearly distinguish the effect, and is purely for testing purposes. Under normal battery use, even if an abnormality occurs, such an event is not expected. Ignition in this test occurs because the released gas is at a high temperature. Therefore, if there is no ignition, the gas temperature is low, and even if it takes a long time for ignition to occur, the gas temperature is lower than if it ignites immediately. The results are shown in Table 1.

[0054] 5.3.Results The results and conditions are shown in Table 1. In Table 1, "position of the fragile part" refers to the part that was joined under the fragile part joining conditions when forming the sealing part of the second exterior body. "All sides" refers to all sides of the sealing part of the second exterior body that were joined under the fragile part joining conditions. "Long side" refers to the long side of the rectangle when viewed from above, and "short side" refers to the short side of the rectangle when viewed from above that were joined under the fragile part joining conditions.

[0055] [Table 1]

[0056] As can be seen from Table 1, when a second exterior body is provided, the temperature of the gas released from the second exterior body can be lowered by providing a weak part on one of the sides of the rectangle in plan view. Furthermore, when the atmosphere during sealing is air (air is contained in the non-bonded parts), it is preferable that the moisture content is low.

[0057] The effect is particularly pronounced when a weak part is provided on the short side in plan view. While No. 2 (vacuum seal, weak part on the long side) delayed ignition to a certain extent, it still caught fire. This is thought to be because the area of ​​the part that opens (the seal is broken) is large when the weak part is provided on the long side, making it easier for gas to enter the second outer casing from the outside, and promoting a reaction with the inflowing air (oxygen). This is most pronounced when all sides are open, as in No. 1, where the area of ​​the part that opens (the seal is broken) is the largest, making it easier for gas to enter the second outer casing from the outside, and causing the gas pressure to be greater from the outside to the inside than from the inside to the outside. On the other hand, when the fragile portion is the short side, the area of ​​the part that is opened (where the seal is broken) is smaller than in other examples, so the gas pressure from the inside to the outside inside the second outer casing is likely to be greater than the gas pressure from the outside to the inside, and it is thought that a state is maintained in which it is difficult for gas to enter from the outside to the inside, making it difficult or impossible for fire to occur. [Explanation of symbols]

[0058] REFERENCE SIGNS LIST 10... battery, 11... electrode assembly, 20... first exterior body, 30... second exterior body, 30a... sealed portion, 30b... fragile portion, 30c... non-jointed portion

Claims

1. An electrode body; a first exterior body that encloses and seals the electrode body; a second exterior body having a sealing portion that encloses and seals the first exterior body, a weak portion in a part of the sealing portion of the second exterior body, the weak portion having a sealing strength lower than that of other portions of the sealing portion; battery.

2. The battery according to claim 1 , wherein the first exterior body is a laminate film.

3. The battery according to claim 1 , wherein the second exterior body is a laminate film.

4. The battery according to claim 1 , wherein the second exterior body has a rectangular shape in a plan view, and the fragile portion is provided in a sealing portion on a short side of the second exterior body.

5. the second exterior body has a check valve; The withstand pressure from the inside to the outside of the second exterior body of the check valve is higher than the withstand pressure of the fragile portion. The battery of claim 1 .

6. The battery according to claim 1 , wherein a pressure is reduced between the first exterior body and the second exterior body.

7. The battery according to claim 1 , wherein an inert gas is contained between the first exterior body and the second exterior body.

8. The battery according to claim 1 , wherein air is contained between the first exterior body and the second exterior body.

9. 9. The battery according to claim 8, wherein the moisture content of the air is 1000 ppm or less.

10. 10. The battery of claim 1, wherein the electrode assembly has a solid electrolyte and the battery is a solid-state battery.

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