Inter-cell structure

Abstract

The present invention provides an inter-cell structure capable of durably maintaining a buffer function in which the thickness is varied with favorable followability in relation to expansion and contraction of a lithium ion battery cell to thereby relieve stress from the cell. Provided is an inter-cell structure for use in a battery module or a battery pack including a plurality of arrayed battery cells, said inter-cell structure being disposed between adjacent cells among the plurality of cells. This inter-cell structure comprises a bag body including: bag members that define a sealed space; and a fluid that contains a gas in the sealed space. The bag members are each formed from a laminated film including a metal layer and a sealant resin layer, and the bag members have a seal part that is formed by joining the sealant resin layers of the laminated films to seal the sealed space. The seal part includes: a relatively thick first seal portion that faces the sealed space; and a second seal portion that is located on the opposite side of the first seal portion from the sealed space, and that includes a relatively thin section adjacent to the first seal portion.

Description

Inter-cell structure

[0001] The present invention relates to an inter-cell structure that is disposed between a plurality of arranged lithium ion battery cells.

[0002] Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries are increasingly being used as power sources for electrically powered vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PEVs), and fuel cell vehicles (FCVs). Because these applications require extremely high output and capacity, they are used in the form of battery modules or battery packs that integrate battery cells (single cells).

[0003] It is known that cells of lithium-ion secondary batteries repeatedly expand during charging and contract during discharging, and research into the causes and solutions is ongoing. For example, Non-Patent Document 1 describes that the cause is an oxide coating formed due to a side reaction between silicon particles and the electrolyte, etc. As a countermeasure, a new antioxidant coating is used to suppress irreversible expansion of the material, thereby suppressing both electrode expansion and cycle degradation. Furthermore, for secondary batteries that experience significant expansion and contraction of battery cells during charging and discharging, Non-Patent Document 2, for example, discloses that the use of a binder with an adjusted elastic modulus suppresses electrode expansion and improves cycle characteristics.

[0004] Patent Document 1 also discloses that the elastic body that receives load from the electrode body of the secondary battery in the stacking direction of the electrode body also plays a role in absorbing pressure, and that by specifying the compressive elastic modulus of each member, it is possible to suppress an increase in resistance during high-rate charging and discharging and a decrease in capacity during charging and discharging cycles.

[0005] Japanese Patent Publication No. 2021-114361 Canadian Patent Application Publication No. 1190279

[0006] FY2015 Strategic Fundamental Technology Advancement Support Project, "Practical application of silicon-based high-capacity anode materials for lithium-ion batteries that suppress material expansion during charging", entrusted by the Kansai Bureau of Economy, Trade and Industry, entrusted to the Kyoto Advanced Technology Research Institute, a public interest incorporated foundation, development of binders for Si anodes and evaluation of electrode expansion, JSR Corporation, JSR Technical Review No. 125 (March 2018) Effect of Pressure and Mechanical Properties of Laminated Separators on Electrode Reactions of Lithium Metal Negative Electrodes, Mie University Graduate School of Engineering, Department of Molecular Materials Engineering, Energy Conversion Chemistry Course, Shogo Kanamori / Author March 2019 (March 2020) Investigation of Constant Stack Pressure on Lithium-Ion Battery Performance, High Voltage Energy Storage Group, School of Engineering, Computing, and Mathematics, Oxford Brookes University, Oxford, UK, OX33 1HX, Aiden Leonarda, Brady Plandena, Katie Lukowa / Author (2023 / 1)

[0007] As mentioned above, lithium-ion battery cells repeatedly expand due to charging and contract due to discharging, and also undergo irreversible expansion, so that in a battery pack that integrates cells or a battery module that constitutes the battery pack (hereinafter collectively referred to as a "battery module, etc."), it is necessary to consider dimensional changes in the cell integration direction, generated pressure, etc. It has also been reported that the efficiency of lithium-ion battery cells is improved when a certain amount of pressure is applied to the cell itself (for example, Patent Document 2, Non-Patent Document 3, Non-Patent Document 4).

[0008] Therefore, an object of the present invention is to provide an inter-cell structure that is placed between an array of multiple lithium-ion battery cells, and that can change in thickness with good follow-up to repeated expansion and contraction of the cells, thereby durably maintaining its buffering function of alleviating stress from the cells.

[0009] This specification provides an inter-cell structure that is disposed between adjacent cells in a battery module or battery pack including a plurality of arranged lithium-ion battery cells. The inter-cell structure includes a bag body having a bag material that defines a sealed space and a fluid containing at least a gas in the sealed space. The bag material is formed from a laminated film including a metal layer and a sealant resin layer, and has a seal portion formed by joining the sealant resin layers of the laminated film to seal the sealed space. The seal portion includes a relatively thick first seal portion facing the sealed space and a second seal portion located on the opposite side of the first seal portion from the sealed space. The second seal portion has a thin portion adjacent to the first seal portion. The thin portion is relatively thinner than the first seal portion. In an inter-cell structure having such a configuration, a fluid (including at least a gas) is contained in the sealed space within the bag body, allowing the bag body to function as a fluid spring. Such an intercellular structure can exhibit a buffering function by allowing the thickness of the bag or the like to change with good follow-up in response to repeated expansion and contraction of the cells, thereby easing stress from the cells. The intercellular structure having the above configuration can maintain such a buffering function with good durability. Specifically, it is as follows.

[0010] In the inter-cell structure having the above configuration, when a compressive load is applied to the bag body and the sealed space is pressurized, a tensile force acts on the portion of the seal portion of the bag body facing the sealed space, for example in the thickness direction of the seal portion, but the first seal portion, which is thicker than the thin portion, can ensure the seal strength between the laminate films that can resist the tensile force (the thicker the first seal portion, the greater the seal strength). When the compressive load repeatedly fluctuates up and down, the magnitude and direction of the tensile force also change dynamically accordingly, and the effective load on the seal portion tends to increase. However, in the inter-cell structure having the above configuration, the first seal portion, which is thicker than the thin portion, can ensure the seal durability between the laminate films (the thicker the first seal portion, the greater the seal durability). Additionally, in the intercellular structure having the above configuration, although the pressure difference between the inside and outside of the sealed space when the sealed space is pressurized acts as a driving force for gas permeation through the seal portion, the seal portion including not only the first seal portion but also the second seal portion (having a thin portion adjacent to the thick first seal portion) can suppress this gas permeation (the thinner and longer the thin portion, the more gas permeation tends to be suppressed). As described above, in the intercellular structure having the above configuration, the seal portion of the bag material includes the first seal portion and the second seal portion, which ensures the strength and durability of the seal portion and suppresses gas permeation through the seal portion. Therefore, the intercellular structure can durably maintain the cushioning function of reducing stress from the cells by changing its thickness with good response to repeated expansion and contraction of the cells.

[0011] In some embodiments, the second seal portion is preferably entirely made of the thin-walled portion. The second seal portion, which is located on the opposite side of the sealed space from the first seal portion, is made entirely of a thin-walled portion thinner than the first seal portion, which is advantageous from the viewpoint of suppressing gas permeation through the seal portion and suppressing gas leakage from the bag body.

[0012] In some preferred embodiments, the first seal portion has a thickness T １ In some preferred embodiments, the first seal portion has a width W of 0.7 mm or more. １These configurations are advantageous in terms of ensuring the strength and durability of the sealing portion.

[0013] In some preferred embodiments, the thickness T of the first seal portion １ The thickness T of the thin portion ２ In some preferred embodiments, the thin-walled portion has a width W of 2.0 mm or more. ２ In some preferred embodiments, the width W of the first seal portion １ The width W of the thin walled portion ２ is 0.70 or more. In some preferred embodiments, the width W of the seal portion including the first seal portion and the second seal portion is 5.0 mm or more. These configurations are advantageous from the viewpoint of suppressing gas permeation through the seal portion and suppressing gas leakage from the bag body.

[0014] In some preferred embodiments, the bag further includes a porous sheet within the sealed space, which allows the repulsive force of the porous sheet to be utilized as a mechanism for varying the thickness of the bag in response to changes in the compressive load applied to the bag, in addition to the fluid spring function exerted by the fluid.

[0015] In some preferred embodiments, the first seal extends over the entire length of the seal along the sealed space, which is suitable for ensuring strength and durability of the seal over the entire length of the seal along the sealed space.

[0016] Appropriate combinations of the elements described in this specification may also be included within the scope of the invention for which patent protection is sought by this patent application.

[0017] 1 and 2. FIG. 2 is a perspective view schematically showing an example of a battery module in which an inter-cell structure according to one embodiment is disposed between cells of a lithium ion battery. FIG. 3 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 4 is a cross-sectional view schematically showing an inter-cell structure according to one embodiment. FIG. 5 is a cross-sectional view schematically showing an example of an inter-cell structure according to another embodiment. FIG. 6 is a cross-sectional view schematically showing an example of a seal portion of the inter-cell structure shown in FIGS. 1 and 2 and its vicinity. FIG. 7 is a cross-sectional view schematically showing another example of a seal portion of the inter-cell structure shown in FIGS. 1 and 2 and its vicinity.

[0018] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0019] In this specification, unless otherwise specified, the term "to" indicating a range of values ​​means that the range includes the values ​​before and after it as the lower and upper limits.

[0020] In addition, in this specification, "weight" may be read as "mass." For example, "% by weight" may be read as "% by mass," and "parts by weight" may be read as "parts by mass."

[0021] The intercellular structure disclosed in this specification includes a bag having a bag material that defines an enclosed space and a fluid in the enclosed space. The fluid includes at least a gas. In some embodiments, the bag of the intercellular structure may further include a porous sheet in the enclosed space.

[0022] <Bag Material> The bag material is formed from a laminated film including a metal layer and a sealant resin layer, and has a seal portion formed by joining the sealant resin layers of the laminated film to seal the sealed space. The laminated film including a metal layer and a sealant resin layer makes it easy to form a bag that combines the gas barrier properties provided by the metal layer with the ease of manufacturing the bag, ease of deformation (cushion-absorbing properties), and ease of molding provided by the sealant resin layer.

[0023] The type of metal layer contained in the laminate film is not particularly limited and may be, for example, a metal layer (metal foil, metal film, etc.) such as an aluminum layer, a copper layer, or a stainless steel layer. The number of metal layers contained in the laminate film may be one layer, or two or more layers (e.g., 2 to 5 layers or 2 to 3 layers). In a laminate film containing two or more metal layers, the types of these metal layers may be the same or different. In some embodiments, a configuration in which the laminate film contains one metal layer may be preferably adopted, from the viewpoint of easily exhibiting good gas barrier properties and strength while suppressing an increase in the total thickness of the laminate film.

[0024] The thickness of the metal layer (in a laminate film including two or more metal layers, the thickness of each metal layer) may be, for example, within a range of approximately 0.1 μm to 150 μm. In some embodiments, from the viewpoint of gas barrier properties and strength, the thickness of the metal layer is suitably 1 μm or more, advantageously 3 μm or more, preferably 5 μm or more, or may be 10 μm or more, 20 μm or more, or may be 30 μm or more. In some embodiments, from the viewpoint of suppressing heat conduction through the bag, the thickness of the metal layer is suitably 100 μm or less, advantageously 80 μm or less, preferably 60 μm or less, or may be 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. The thickness of the metal layer can be determined by averaging values ​​measured at several locations (e.g., 10 locations) using a thickness gauge (e.g., a digital thickness gauge H-1A (measuring probe Φ5 mm) manufactured by Ozaki Manufacturing Co., Ltd.). If the nominal value of the thickness of the metal layer of the bag material is provided by the manufacturer or the like, that nominal value may be used.

[0025] The type of sealant resin layer contained in the laminate film is not particularly limited as long as it can be welded by heating or the like (i.e., can be sealed by heat sealing or the like). Examples include resin layers (films, coatings, etc.) such as a polypropylene (PP) layer, a polyethylene (PE) layer, an ethylene-vinyl acetate copolymer resin (EVA) layer, an ethylene-vinyl alcohol copolymer resin (EVOH), polyvinylidene chloride (PVDC), and polyethylene terephthalate (PET). Examples of the PP layer include a solid polypropylene (CPP) film and a biaxially oriented polypropylene (OPP) film. Examples of the PE layer include a linear low-density polyethylene (LLDPE) layer, a low-density polyethylene (LDPE) layer, and a high-density polyethylene (HDPE) layer. Examples of the PET layer include an amorphous polyethylene terephthalate (A-PET) film. From the standpoints of ease of heat sealing, strength, and the like, preferred sealant resin layers include a CPP layer and an LLDPE layer. In addition, preferred resin layers from the viewpoint of low gas permeability include a CPP layer, an EVOH layer, and a PVDC layer. The materials of the sealant resin layers forming the seal portion may be the same or different. Using the same material for the sealant resin layers forming the seal portion can be advantageous from the viewpoint of sealability, such as heat sealability.

[0026] The thickness of the sealant resin layer may be, for example, 40 μm or more. From the viewpoint of forming a seal portion including both the first seal portion and the second seal portion described below by joining the sealant resin layers together, in some embodiments, the thickness is preferably 50 μm or more (e.g., greater than 50 μm), more preferably 60 μm or more, 70 μm or more, 80 μm or more, 100 μm or more, or 125 μm or more. Furthermore, the thickness of the sealant resin layer of the laminated film may be, for example, 400 μm or less, preferably 300 μm or less, more preferably 250 μm or less, 200 μm or less, or 150 μm or less. It is advantageous from the viewpoint of forming the second seal portion described below that the sealant resin layer is not too thick. In some preferred embodiments, the thickness of the sealant resin layer may be, for example, 120 μm or less, 110 μm or less, 100 μm or less, or 90 μm or less. The thickness of the sealant resin layer can be determined by measuring several points (e.g., 10 points) using a thickness gauge (e.g., a digital thickness gauge H-1A (measuring probe Φ5 mm) manufactured by Ozaki Manufacturing Co., Ltd.) and using the average value of the values ​​measured at those points. If the nominal value of the thickness of the sealant resin layer of the bag material is provided by the manufacturer, that nominal value may be used (the same applies to resin layers other than the sealant resin layer, which will be described later).

[0027] The sealant resin layer of the laminated film is the innermost layer of the laminated film and may be provided over the entire area of ​​the laminated film, or may be provided in a partial area including the area where the seal portion is intended to be formed (the area to be sealed).

[0028] The laminate film may include a resin layer other than the sealant resin layer. The type of resin layer other than the sealant resin layer included in the laminate film is not particularly limited, and examples include a polyester layer (e.g., a PET layer, a polybutylene terephthalate layer, a polyethylene naphthalate layer), a polyimide layer, a polycarbonate (including flame-retardant polycarbonate) layer, a nylon layer, a PP layer, a PE layer, an EVA layer, an acrylic resin layer (typically a polymethyl methacrylate layer), an EVOH layer, and a PVDC layer. Examples of the PET layer include an oriented polyethylene terephthalate film and an A-PET film. Examples of the nylon layer include a biaxially oriented nylon (ONY) film and a non-oriented nylon film. Examples of the PP layer include a CPP film and an OPP film. Examples of the PE layer include an LLDPE layer, a LDPE layer, and a HDPE layer. The number of resin layers other than the sealant resin layer contained in the laminate film may be 1 layer, or may be 2 or more layers (for example, 2 to 7 layers, 2 to 5 layers, 2 to 4 layers, or 2 to 3 layers). In a laminate film containing two or more resin layers other than the sealant resin layer, the types of these resin layers may be the same or different.

[0029] The thickness of the resin layer other than the sealant resin layer (in a laminate film including two or more resin layers, the thickness of each resin layer) may be, for example, within a range of approximately 0.1 μm to 500 μm. In some embodiments, from the viewpoint of suppressing an increase in the total thickness of the laminate film, the thickness of the resin layer is preferably 450 μm or less, more preferably 350 μm or less, and may be 250 μm or less, 200 μm or less, 150 μm or less, or 100 μm or less. Furthermore, in some embodiments, from the viewpoint of facilitating the appropriate performance of the function of each resin layer, the thickness of the resin layer may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, or 10 μm or more. The thickness of the resin layer other than the sealant resin layer can be determined by averaging values ​​measured at several locations (e.g., 10 locations) using a thickness measuring device (e.g., a digital thickness gauge H-1A (measuring probe Φ5 mm) manufactured by Ozaki Manufacturing Co., Ltd.).

[0030] When the laminate film includes a resin layer other than the sealant resin layer, the lamination order of the metal layer and the resin layer other than the sealant resin layer included in the laminate film is not particularly limited. In some embodiments, a laminate film having a configuration in which a first resin layer, a metal layer, a second resin layer, and a sealant resin layer are laminated in this order from the outside of the bag body can be preferably used. The first resin layer can be a layer that forms the outer surface of a bag body formed using the laminate film (bag material). The first resin layer can be useful for imparting surface insulation and antifouling properties to the bag body and protecting the metal layer from deterioration and damage. The second resin layer can be useful for ensuring adhesion between the metal layer and the sealant resin layer. Non-limiting preferred examples of the first resin layer include a nylon layer (e.g., a biaxially oriented nylon (ONY) layer) and a PET layer. Non-limiting preferred examples of the second resin layer include a nylon layer (e.g., an ONY layer) and a PET layer. Although not particularly limited, the metal layer can be, for example, an aluminum layer.

[0031] The laminate film may include layers (optional layers) other than the resin layer and the metal layer as optional components. The optional layers may include, for example, fabric layers such as glass cloth, silica cloth, aramid cloth, resin-impregnated glass cloth, resin-impregnated silica cloth, and resin-impregnated aramid cloth, colored layers, antistatic layers, adhesive layers, etc. The number of optional layers included in the laminate film may be one layer, or two or more layers (for example, about 2 to 8 layers).

[0032] In some embodiments, the laminate film used as the bag material is preferably resistant to expansion and contraction deformation, has a high Young's modulus, and is highly rigid, from the viewpoint of controllability of shape change due to repeated cell expansion and contraction. For example, the Young's modulus of the bag material is preferably greater than 25 MPa, more preferably 100 MPa or more, even more preferably 500 MPa or more, and may be 800 MPa or more, 1 GPa or more, or 1.2 GPa or more. The upper limit of the Young's modulus is not particularly limited. In some embodiments, from the viewpoint of the formability and cushioning properties of the bag body, the Young's modulus of the bag material (which may be a laminate film) is suitably 5 GPa or less, preferably 3 GPa or less, more preferably 2 GPa or less, and may be 1.7 GPa or less, 1.5 GPa or less, or 1.3 GPa or less. The Young's modulus (tensile modulus) is determined by measurement in an environment of 25°C and 50% RH in accordance with JIS-K-7161. The tensile speed during measurement is set appropriately depending on the material and structure of the bag material, the size of the measurement sample, etc., and can be set to, for example, 5 mm / min. If a nominal value of Young's modulus is provided by the manufacturer, etc., this nominal value may be used.

[0033] Furthermore, from the viewpoint of the strength and durability of the bag body, the tensile strength of the bag material is suitably 10 N / 10 mm or more, preferably 30 N / 10 mm or more, more preferably 50 N / 10 mm or more, and may be 60 N / 10 mm or more, or may be 70 N / 10 mm or more. The upper limit of the tensile strength of the bag material is not particularly limited. In some embodiments, from the viewpoint of the formability and cushioning properties of the bag body, the tensile strength of the bag material may be, for example, 300 N / 10 mm or less, 200 N / 10 mm or less, or even 100 N / 10 mm or less. Tensile strength is determined by measuring in an environment of 25°C and 50% RH in accordance with JIS K 7127 or JIS C 2318-72. The pulling speed during measurement is appropriately set depending on the material and structure of the bag material, the size of the measurement sample, etc., and can be, for example, 5 mm / min. If a nominal value of tensile strength is provided by a manufacturer, etc., that nominal value may be used.

[0034] The thickness of the bag material is not particularly limited and may be, for example, within a range of approximately 60 μm to 1000 μm. In some embodiments, the thickness of the bag material is preferably 65 μm or more, more preferably 75 μm or more, and may be 85 μm or more, 95 μm or more, 100 μm or more, 105 μm or more, or 110 μm or more. In some embodiments, the thickness of the bag material is suitably, for example, 800 μm or less, preferably 600 μm or less, more preferably 500 μm or less, may be 400 μm or less, may be 300 μm or less, may be 250 μm or less, 200 μm or less, or may be 160 μm or less. When the thickness of the bag material is within the above range, it is easy to appropriately achieve both the ease of deformation (shock-absorbing properties) that can accurately absorb thickness fluctuations associated with expansion and contraction between cells and the mechanical strength of the bag body. The thickness of the bag material can be measured at several locations (for example, 10 locations) using a thickness measuring device (for example, a digital thickness gauge H-1A (measuring probe Φ5 mm) manufactured by Ozaki Manufacturing Co., Ltd.) and the average value of the values ​​measured at several locations (for example, 10 locations) can be used. If the nominal value of the thickness of the bag material is provided by the manufacturer, etc., that nominal value can be used.

[0035] <Fluid> The bag constituting the intercellular structure disclosed herein has a sealed space partitioned by the bag material. A fluid is contained in the sealed space. Here, the fluid includes at least a gas. By containing a gas in the sealed space of the bag, the bag can function as a gas spring, making it easier to realize an intercellular structure that exhibits high compliance with repeated cell expansion and contraction. Here, "a gas is contained in the sealed space" means that the sealed space contains at least one gas component under conditions of 1 atmosphere, 23°C, and a relative humidity of 50% RH. The components contained in the fluid contained in the sealed space can be determined by opening the sealed space under the above conditions, recovering the contents, and analyzing their composition. Analysis can be performed by conventional methods. For example, gas analysis can be performed using gas chromatography or infrared absorption spectroscopy (IR), and liquid chromatography can be used to analyze liquids and solids.

[0036] Here, "sealed" means that leakage of the fluid contained in the sealed space to the outside of the bag is sufficiently restricted for practical purposes. For example, in a configuration in which the fluid contains a gas, in a sealability test in which the bag is left at 40°C under atmospheric pressure for 30 days, it is appropriate that the volume of the gas contained in the sealed space decreases by 1% or less, preferably 0.5% or less, and more preferably 0.1% or less.

[0037] The gas contained in the sealed space may be one component or two or more components. The gas is not particularly limited, and any gas that exists as a gas under conditions of 1 atmosphere, 23°C, and a relative humidity of 50% RH can be appropriately selected and used. Specific examples of the gas include, but are not limited to, nitrogen, oxygen, argon, carbon monoxide, carbon dioxide, neon, helium, krypton, and xenon.

[0038] In some embodiments, it is desirable that the gas does not contain a flammable gas as a main component, from the viewpoint of ease of handling the bag, etc. For example, it is preferable that more than 50%, more preferably 70% or more of the volume of the gas (referring to the volume under conditions of 1 atmosphere, 23°C, and a relative humidity of 50% RH; the same applies hereinafter unless otherwise specified) be composed of one or more gases selected from the group consisting of nitrogen, argon, carbon dioxide, neon, helium, krypton, and xenon. An inter-cell structure in which a gas containing an inert gas as a main component is sealed within a bag has the advantage that, for example, if some cells generate abnormal heat and the bag seal is broken, the inert gas can be supplied to the surroundings from the bag.

[0039] In some embodiments, from the viewpoint of ease of sealing the gas (suppressing leakage), the volume of the Group 18 element (noble gas) in the volume of the gas is preferably 20% or less, more preferably 10% or less, even more preferably 5% or less, and may be 3% or less, 1% or less, or 0.5% or less.

[0040] In view of the ease of handling the bag and the ease of sealing the gas, particularly preferred inert gases include nitrogen and carbon dioxide. In some embodiments, the proportion of the total volume of the gas, which is the total volume of nitrogen and carbon dioxide (which may be a gas containing only one of them), is preferably more than 50%, more preferably 70% or more, and may be 80% or more, 90% or more, or even 95% or more.

[0041] In some embodiments, the sealed space may contain a liquid as the fluid together with the gas. By containing a liquid together with the gas in the sealed space, it is possible to adjust the compression characteristics (e.g., the value of compressive strain at a predetermined compressive load) of the bag body and the inter-cell structure including the bag body. The liquid may be, for example, water or an aqueous solution, but is not limited to these.

[0042] The amount of fluid such as gas contained in the sealed space is not particularly limited, and can be adjusted as appropriate to exhibit appropriate properties (e.g., cushioning properties) according to the purpose, taking into consideration the type of fluid, the size of the sealed space, the manner of use of the inter-cell structure, etc.

[0043] Although not particularly limited, in some embodiments in which at least a gas is contained as the fluid in the sealed space, the amount of gas contained in the sealed space is determined by the surface area A [m ２ ] and the volume V [L] of the gas contained in the sealed space, the amount of gas G calculated by the following formula: G = V / (A / 2); is approximately 1.0 L / m ２ or more. This makes it easier to achieve cushioning properties that allow the thickness to change with good follow-up in response to repeated cell expansion and contraction, etc. The reason why the surface area A in the denominator of the above formula is divided by 2 is to convert it into the area per side of the bag body. Note that, hereinafter, the value of A / 2 may be referred to as the surface area S per side of the bag material facing the sealed space.

[0044] The method for measuring the volume V of the gas can be selected from the well-known methods of underwater displacement, liquid phase displacement, and gas phase displacement. If the results differ depending on the measurement method, the method that gives the smallest value should be used. In the above formula, the value of the volume V of the gas is the volume at 1 atmosphere and 23°C.

[0045] In some embodiments, the gas volume G is 1.5 L / m ２ It is preferable that the amount of water used is 2.0 L / m or more. ２ More preferably, it is 5.0 L / m or more. ２ or more, and 7.0 L / m ２ or more, and 10 L / m ２ or more, and 15 L / m ２ or more, and 18 L / m ２ or more, and ２ Above, 22L / m ２ or more than 25 L / m ２ As the gas volume G increases, the amount of strain against pressure increases, and the buffering properties tend to improve. In addition, the gas volume G may be, for example, 100 L / m ２ In order to avoid increasing the size of the inter-cell structure, in some embodiments, the ２ It is appropriate that the flow rate is 60 L / m or less. ２ Preferably, the flow rate is 45 L / m or less. ２ or less, and ２ or less, 30 L / m ２ or less than 25 L / m ２ It may be the following:

[0046] <Bag> The number (number of sheets) of bag materials used to form the bag is usually 1 or more, preferably 2 or more, and usually 5 or less, preferably 4 or less, and more preferably 3 or less. The two or more bag materials may be, for example, two or more sheets of laminate film, or one sheet of laminate film may be folded over to form two sheets. When folded over in this way, the number of bag materials is considered to be two. Furthermore, when a laminate film formed into a cylindrical shape is used as the bag material, the number of bag materials is also considered to be two.

[0047] The bag body can be formed, for example, by placing two sheets of bag material (laminated film) facing each other with their sealant resin layers facing inward, and then joining the sealant resin layers along the intended sealing locations of the two bag materials to form a seal. The method for sealing the opposing surfaces of the bag material (i.e., the method for forming the seal portion) is not particularly limited, and examples include welding methods such as heat welding and ultrasonic welding. When one sheet of bag material is folded back to form two bag materials, sealing of the edges corresponding to the folded back portions can be omitted as appropriate. When a laminated film formed into a cylindrical shape is used as the bag material, an airtight space can be formed by sealing both open ends of the tube, and sealing of the edges corresponding to one or both widthwise ends of the tube can be omitted as appropriate.

[0048] In the bag material, the sealed space of the bag body is separated from the outside by a seal portion formed by joining sealant resin layers together. The seal portion has a relatively thick first seal portion facing the sealed space and a second seal portion located on the opposite side of the first seal portion from the sealed space. The second seal portion has at least a first thin portion adjacent to the first seal portion. The first thin portion is thinner than the first seal portion. Therefore, the second seal portion is the portion of the seal portion that is thinner than the first seal portion on the opposite side of the first seal portion from the sealed space (for example, the thickness T of the first seal portion described below). １The "thickness of the seal portion" refers to the portion extending from the innermost portion to the outermost portion (reaching 85% of the thickness of the seal portion). The first seal portion may extend along the entire length of the seal portion along the sealed space, or may extend along the sealed space in at least one region along the entire length of the seal portion. Here, "the entire length of the seal portion" refers to the entire length of the seal portion extending along the sealed space. From the viewpoint of ensuring the strength and durability of the seal portion along the entire length of the seal portion along the sealed space, it is preferable that the first seal portion extend along the entire length of the seal portion along the sealed space. Furthermore, from the viewpoint of suppressing gas permeation through the seal portion, it is preferable that the entire second seal portion be the first thin-walled portion in both the extension direction of the seal portion along the sealed space and the width direction (width direction of the seal portion) perpendicular to the extension direction.

[0049] In some embodiments, the second seal portion may further include a thick portion thicker than the first thin portion. In some embodiments, the second seal portion may include at least two thin portions including the first thin portion and at least one thick portion thicker than the first thin portion, and the thin portions and the thick portions may be alternately arranged in the width direction of the seal portion (the thin portion in the second seal portion other than the first thin portion is referred to as the second thin portion). The fact that the second seal portion includes the thick portion and that the thin portions and the thick portions are alternately arranged in the second seal portion is advantageous in preventing the second seal portion from also tearing if the first seal portion tears.

[0050] The thickness of the first seal portion is set, for example, in the range of 100 to 600 μm. The width of the first seal portion is set, for example, in the range of 0.7 to 10.0 mm. The thickness of the thin portion (first thin portion, second thin portion) of the second seal portion is set, for example, in the range of 10 to 150 μm. The ratio of the thickness of the thin portion to the thickness of the first seal portion is set, for example, in the range of 0.10 to 0.85. When the second seal portion has the thick portion, the thickness of the thick portion is set, for example, in the range of 100 to 600 μm. The width of the thin portion of the second seal portion (the total width of the thin portions if the second seal portion has multiple thin portions) is set, for example, in the range of 2.0 to 20.0. The ratio of the width of the thin portion to the width of the first seal portion (the total width of the thin portions if the second seal portion has multiple thin portions) is set, for example, in the range of 0.7 to 7.0. The width of the seal portion including the first seal portion and the second seal portion is set, for example, in the range of 5.0 to 20.0 mm. More specifically, the dimensions of the first seal portion and the second seal portion can be as described below with reference to Figures 5 and 6.

[0051] In the technology disclosed herein, the method for realizing a configuration in which a fluid (e.g., gas) is contained within a sealed space partitioned by a bag material is not particularly limited. For example, the sealed space may be formed in a state in which the gas is already contained therein, or the gas may be generated within the sealed space after the sealed space is formed, or an intermediate or combined method thereof may be employed. Examples of methods for generating gas within a sealed space include methods that generate gas through a chemical reaction. Specific examples include a method in which carbon dioxide gas is generated by reacting sodium bicarbonate with an aqueous citric acid solution, or a method in which carbon dioxide gas is generated by reacting an isocyanate with water. Either one of the components of the sodium bicarbonate or the aqueous citric acid solution (e.g., sodium bicarbonate) may be encapsulated, or each component may be encapsulated separately, and the capsules may be broken by pressure or the like at an appropriate time to bring the two components into contact and generate carbon dioxide gas. The same applies to a combination of isocyanate and water. With this configuration, the bag can be stored or mailed in a compact form before the two components are brought into contact, and carbon dioxide gas can be generated at the appropriate time to inflate the bag, allowing it to function as a gas spring.

[0052] The number of sealed spaces in one bag body may be one or two or more. A bag body having two sealed spaces can be formed, for example, by arranging two rectangular bag materials facing each other, sealing the bag materials in a ring shape along their outer edges to form one sealed space, and then sealing the longitudinal center portion across the width to divide the single sealed space into two. With an inter-cell structure including a bag body having two or more sealed spaces, even if the hermeticity of one sealed space is accidentally impaired, the presence of the remaining sealed spaces can suppress a decrease in the function as a fluid spring. From the standpoints of ease of manufacturing the bag body and space utilization efficiency, the number of sealed spaces in one bag body is suitably 10 or less, preferably 6 or less, and may be 4 or less, or 2 or less. In some embodiments, a configuration in which the number of sealed spaces in one bag body is one may be preferably adopted.

[0053] Furthermore, the intercell structure disclosed herein may be disposed between adjacent cells alone or in two or more. When two or more intercell structures are disposed, they are preferably disposed so that they do not overlap in the cell arrangement direction. By disposing two or more intercell structures between cells in this manner, even if the airtightness of the sealed space of the bag of one intercell structure is accidentally lost, the presence of the remaining intercell structures can suppress a decrease in the function as a fluid spring. From the viewpoint of ease of assembly of a battery module, etc., the number of intercell structures disposed between adjacent cells is suitably 10 or less, preferably 6 or less, and may be 4 or less, or 2 or less. The total number of bags possessed by those intercell structures is suitably 20 or less, preferably 12 or less, and may be 8 or less, 4 or less, or 2 or less.

[0054] The pouch constituting the inter-cell structure disclosed herein may have a thickness measured under an applied pressure of 1.00 MPa (hereinafter also referred to as the "thickness at 1.00 MPa") within a range of, for example, approximately 0.5 mm to 40 mm. When the pouch thickness is within this range, the inter-cell structure including the pouch can adequately buffer stress generated by battery expansion. From the viewpoint of easily achieving higher buffering properties, in some embodiments, the thickness of the pouch at 1.00 MPa is preferably 0.7 mm or more, more preferably 0.9 mm or more, even more preferably 1.0 mm or more, and may be 1.1 mm or more, or may be 1.2 mm or more. In some embodiments, the thickness of the pouch at 1.00 MPa is preferably 30 mm or less, more preferably 20 mm or less, even more preferably 15 mm or less, and may be 10 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, or 5 mm or less.

[0055] The thickness of the bag body when a pressure of 1.00 MPa is applied can be determined by sandwiching the bag body between two parallel metal plates having an area larger than the area S per side of the bag material facing the sealed space formed inside the bag body, and then using a precision universal testing machine to remove the load from the two metal plates and perform zero point correction. After that, a load is applied at a compression rate of 0.5 mm / min, and the testing machine is stopped when the applied pressure calculated using the area S reaches 1.00 MPa, and the cross-sectional thickness of the bag body at that time can be determined. Examples of precision universal testing machines that can be used include the Autograph AGS-10kNX manufactured by Shimadzu Corporation or an equivalent. The cross-sectional thickness of the bag body can be measured using the precision universal testing machine, or a thickness measuring instrument such as a vernier caliper.

[0056] <Porous Sheet> The sealed space of the bag constituting the intercellular structure disclosed herein may contain a porous sheet together with the fluid (e.g., gas). This configuration allows the repulsive force of the porous sheet to be utilized in addition to the gas spring function exerted by the gas contained in the sealed space of the bag as a mechanism for varying the thickness of the bag in response to changes in the compressive load applied to the bag. For example, when the bag is compressed with a predetermined applied pressure, the repulsive force of the porous sheet can counter at least a portion of the pressure. This suppresses an increase in the internal air pressure of the sealed space, reducing the load on the bag (e.g., load on the seal portion) due to the increase in internal air pressure, thereby improving the durability of the bag. As a result, the buffer function with good compliance (e.g., low hysteresis loss) can be exhibited with good durability by utilizing the gas spring function. Furthermore, by suppressing the increase in internal air pressure, the air pressure difference (pressure difference) between the inside and outside of the bag when the bag is compressed with a predetermined applied pressure can be reduced compared to a configuration in which the repulsive force of the porous sheet cannot be utilized. By reducing the pressure difference, for example, the gas in the sealed space can be better maintained (gas leakage can be suppressed) even when the inter-cell structure is used for a long period of time, so that stable cushioning properties can be exhibited for a long period of time.

[0057] As the porous sheet, for example, a porous sheet having a layer made of a fiber molded body containing fibers (hereinafter sometimes abbreviated as "fiber molded body") or a foam molded body containing a foam (hereinafter sometimes abbreviated as "foam molded body") can be preferably used. Here, "a layer made of a fiber molded body containing fibers" means a layer containing at least fibers as a constituent material, and "a layer made of a foam molded body containing a foam" means a layer containing at least foam as a constituent material. Fiber molded bodies, foam molded bodies, etc. will be described in detail below.

[0058] In some embodiments, the porous sheet is a shaped article (fiber shaped article) containing fibers. The type of fiber contained in the fiber shaped article is not particularly limited and may be inorganic fiber, organic fiber, or a combination of these. In some embodiments, non-limiting examples of materials that can be used for the fiber shaped article containing inorganic fibers include glass wool, long glass fiber, glass fiber mat, glass fiber needle mat, rock wool, alkaline earth silicate (AES) fiber, AES wool, etc. In other embodiments, non-limiting examples of materials that can be used for the fiber shaped article containing inorganic fibers include glass fiber, silica fiber, alumina fiber, silica-alumina fiber, silica-alumina-magnesia fiber, biosoluble inorganic fiber, glass fiber, zirconia fiber, alkaline earth metal silicate fiber, alkaline earth silicate (AES) fiber, glass wool, rock wool, basalt fiber, etc. Furthermore, non-limiting examples of materials that can be used for the fiber shaped article containing organic fibers include felts made of cellulose fiber, polyester, polypropylene, etc. The fiber molded product may contain one type of fiber or two or more types of fibers. The fiber assembly form is not particularly limited and may be, for example, a nonwoven fabric, a woven fabric, or a knitted fabric. In some embodiments, a fiber molded product in the form of a nonwoven fabric may be preferably used. The fibers used for the fiber molded product may be commercially available with a thermosetting resin dispersed therein as a binder (adhered to at least a portion of the fibers). Such fibers can be cut into the desired shape and then heated and compressed under appropriate conditions to form a fiber molded product.

[0059] In some embodiments, the fiber molded article used as the porous sheet may be a sheet-like molded article containing inorganic fibers (an inorganic fiber-containing sheet). A suitable example of an inorganic fiber-containing sheet is glass wool. Glass wool generally contains fibers and a thermosetting resin (e.g., a phenolic binder), with the fibers bonded together by the thermosetting resin. It also has the effect of increasing compressive stress and providing a buffering function.

[0060] The inorganic fiber-containing sheet may contain inorganic particles as described below, or may not contain inorganic particles. In some embodiments of the intercellular structure disclosed herein, the porous sheet accommodated in the sealed space of the bag preferably contains at least an inorganic fiber-containing sheet that does not contain inorganic particles (e.g., silica particles) (e.g., an inorganic fiber-containing sheet that does not contain inorganic particles and contains a binder).

[0061] The fiber content in the fiber molded product (e.g., inorganic fiber-containing sheet) is not particularly limited. In some embodiments, the fiber content in the fiber molded product is, for example, 50% by mass or more (typically 50% by mass to 99% by mass), preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more (e.g., 82% by mass or more). In some embodiments, the fiber content may be 97% by mass or less, 95% by mass or less, or 93% by mass or less. When the fiber content is within the above range, the fiber molded product is more likely to exhibit cushioning properties.

[0062] The average fiber length of the fibers in the fibrous molded product (e.g., inorganic fiber-containing sheet) is not particularly limited. In some embodiments, the average fiber length of the fibers may be, for example, 1 mm to 200 mm, preferably 5 mm or more, more preferably 10 mm or more, even more preferably 20 mm or more, and preferably 175 mm or less, more preferably 150 mm or less, even more preferably 125 mm or less. When the average fiber length of the fibers is within the above range, the fibrous molded product is more likely to exhibit cushioning properties.

[0063] The average fiber diameter of the fibers of the fibrous molded product (e.g., inorganic fiber-containing sheet) is not particularly limited. In some embodiments, the average fiber diameter of the fibers may be, for example, 3 μm to 13 μm, preferably 4 μm or more, more preferably 4.5 μm or more, even more preferably 5 μm or more, and preferably 10 μm or less, more preferably 9 μm or less, even more preferably 8 μm or less. When the average fiber diameter of the fibers is within the above range, the fibrous molded product is likely to have both cushioning properties and low thermal conductivity.

[0064] In some embodiments, the fibrous molded article preferably contains a binder in addition to the fibers. The type of binder for the fibrous molded article is not particularly limited, but can be classified into organic binders and inorganic binders.

[0065] Specific examples of organic binders include thermoplastic resins, thermoplastic elastomers, thermosetting resins, thermosetting elastomers, sugars, and water-soluble polymers. Specific examples of inorganic binders include aluminum oxide, zirconium oxide, magnesium oxide, titanium oxide, and calcium oxide. When the binder is one of the above, shape stability is improved. The fiber molded product may contain one type of binder or two or more types of binders.

[0066] In embodiments in which the fiber molding contains a binder, the content of the binder is not particularly limited. In some embodiments, the content of the binder is, for example, 1% to 50% by mass of the fiber molding, preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, or may be 10% by mass or more or 12% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, or may be 18% by mass or less or 16% by mass or less. When the binder content is within the above range, good cushioning properties are likely to be exhibited.

[0067] In some embodiments, the fiber molded article used as the porous sheet may be a sheet-like molded article containing inorganic particles and inorganic fibers (an inorganic particle / inorganic fiber-containing sheet). Examples of inorganic particles constituting the inorganic particle / inorganic fiber-containing sheet include those having the same material, shape, and / or properties as the inorganic particles that can be used in the thermal insulation layer described below. For example, an inorganic particle / inorganic fiber-containing sheet can be used as the porous sheet, in which the inorganic particles are primarily composed of at least one type of silica particles selected from the group consisting of dry silica, wet silica, and silica aerogel. The inorganic fibers constituting the inorganic particle / inorganic fiber-containing sheet may have the same material, shape, and / or properties as the inorganic fibers exemplified above as materials that can be used in the fiber molded article containing inorganic fibers, or may have the same material, shape, and / or properties as the inorganic particles that can be used in the thermal insulation layer described below. In some embodiments, an inorganic particle / inorganic fiber-containing sheet having a configuration similar to the thermal insulation layer described below can be used as at least a portion of the porous sheet contained in the sealed space of a bag. This configuration can also be recognized as an intercellular structure in which a thermal insulation layer is disposed in the sealed space of a bag. The intercellular structure disclosed herein may be configured to include both an inorganic fiber-containing sheet that does not contain inorganic particles and an inorganic particle / inorganic fiber-containing sheet as the porous sheet contained in the sealed space of the bag.

[0068] In some embodiments, the porous sheet is a molded article (foamed article) containing a foam. The material of the foam is usually a resin such as a thermoplastic resin or a thermosetting resin. The foam can be molded by appropriately adopting a known molding method and its conditions.

[0069] The type of resin of the foam of the foam molded product is not particularly limited, and specific examples include foams formed from polyolefin resins such as polyethylene and polypropylene, polyethylene terephthalate resin, polyvinyl chloride resin (PVC), styrene resins such as polystyrene, polyurethane resins such as polyurethane resin, resol-type phenolic resins such as phenolic resin (PF), melamine resins such as melamine resin (MF), epoxy resins such as epoxy resin (EP), natural rubber (NR), styrene butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), polyurethane, and the like.

[0070] The cell structure of the foamed molded product may be closed-cell or open-cell, and can be appropriately selected depending on the desired physical properties, etc. In some embodiments, a foamed molded product having an open-cell structure can be preferably used.

[0071] In the intercellular structure disclosed herein, the number of porous sheets accommodated in the sealed space of the bag may be one or two or more. From the viewpoint of ease of manufacturing the bag and thickness control, in some embodiments, the number of porous sheets is suitably 1 to 10, preferably 1 to 5, and more preferably 1 to 3 or 1 to 2. For example, by combining a first porous sheet having a relatively high compressive strength and / or weight per area with a second porous sheet having a relatively low compressive strength and / or weight per area, the total thickness of the porous sheets can be controlled while achieving a good balance of desired resilience and cushioning properties. When two or more porous sheets are used, the porous sheets may be bonded (fixed) to each other or may not be bonded. Bonding two or more porous sheets to each other can be advantageous from the viewpoint of ease of manufacturing the bag, etc. On the other hand, not bonding two or more porous sheets to each other can be advantageous from the viewpoint of improving the cushioning properties of the bag, etc.

[0072] The porous sheet may be bonded to the inner surface of the bag body with, for example, an adhesive or a pressure-sensitive adhesive, or may not be bonded with an adhesive or a pressure-sensitive adhesive, and is preferably not bonded with an adhesive or a pressure-sensitive adhesive. By not using an adhesive or a pressure-sensitive adhesive, the increase in thermal conductivity can be suppressed compared to when an adhesive or a pressure-sensitive adhesive is used.

[0073] The shape of the porous sheet is not particularly limited. In some embodiments, the shape of the porous sheet when viewed in plan may be, for example, a polygon such as a quadrangle, a circle, an ellipse, etc. Examples of quadrangles include rectangles (including squares and rectangles).

[0074] In the intercellular structure disclosed herein, the weight of the porous sheet accommodated in the sealed space of the bag body (in a configuration having two or more porous sheets, the total weight of the porous sheets) W Ｂ is 150 g / m ２ This means that when the porous sheet is viewed from above, the area of ​​the porous sheet is 1 m ２ This means that the weight per unit is 150g or more. Ｂ is 150 g / m ２ The porous sheet described above is likely to provide an appropriate repulsive force that can significantly contribute to improving the durability of the bag body. Ｂ is 250 g / m ２ Advantageously, it is equal to or greater than 200 g / m ２ It is preferable that the weight is 300 g / m or more. ２ More preferably, it is 350 g / m or more. ２ or more (for example, 360 g / m ２ or more), and ２ or more, and ２ or more, and ２ Above, 550g / m ２ Above, 600g / m ２ Above, 700g / m ２ or more than 800 g / m ２The weight W of the porous sheet may be equal to or greater than the weight W of the porous sheet. Ｂ is not particularly limited, for example, 20,000 g / m ２ or less, and ２ or less, and ２ or less, 2500 g / m ２ or less, 1500 g / m ２ It may be less than 1000 g / m ２ The weight W of the porous sheet may be less than Ｂ It is preferable that is not too large from the viewpoint of reducing the weight of the inter-cell structure.

[0075] In some embodiments, the weight of the porous sheet contained in the sealed space of the bag (in a configuration having two or more porous sheets, the total weight of those porous sheets) W Ｂ is 400 g / m from the viewpoint of facilitating reduction in the temperature dependency of the thickness. ２ It is appropriate that the weight is 450 g / m or more. ２ Advantageously, it is equal to or greater than 500 g / m ２ It is preferable that the weight is 550 g / m or more. ２ More preferably, it is 600 g / m or more. ２ More preferably, it is 650 g / m or more. ２ or more, and ２ or more, and ２ The weight W of the porous sheet may be equal to or greater than the weight W of the porous sheet. Ｂ is not particularly limited, for example, 20,000 g / m ２ or less, and ２ or less, and ２ or less, 2500 g / m ２ or less, 1500 g / m ２ It may be less than 1000 g / m ２ The weight W of the porous sheet may be less than Ｂ It is preferable that is not too large from the viewpoint of reducing the weight of the inter-cell structure.

[0076] In the technology disclosed herein, the initial thickness of the porous sheet (in a configuration having two or more porous sheets, the total thickness of those porous sheets) is not particularly limited and can be appropriately set so as to achieve the desired effect (such as the generation of a repulsive force against compression of the bag) depending on the usage mode of the intercellular structure. The initial thickness of the porous sheet may be, for example, 1 mm or more, 2 mm or more, 3 mm or more, or 4 mm or more. In some embodiments, the initial thickness of the porous sheet is suitably 5 mm or more, preferably 7 mm or more, more preferably 8 mm or more, may be 10 mm or more, may be 12 mm or more, or may be 15 mm or more. Furthermore, in some embodiments, from the viewpoint of ease of manufacturing the bag, the initial thickness of the porous sheet is suitably, for example, 100 mm or less, advantageously 75 mm or less, preferably 60 mm or less, may be 50 mm or less, may be 40 mm or less, may be 30 mm or less, 25 mm or less, or may be 20 mm or less.

[0077] As for the initial thickness of the porous sheet, similarly to the heat insulating layer described below, the thickness of the cross section of the porous sheet is measured using a thickness gauge (digital thickness gauge JAN-257, probe Φ20 mm, manufactured by Ozaki Manufacturing Co., Ltd.) when no pressure is applied (when no intentional load is applied to the porous sheet), and this measurement is further performed at any number of locations (for example, 10 locations), and the average value of the obtained values ​​can be used. That is, the initial thickness of the porous sheet means the thickness [mm] of the porous sheet when no pressure is applied. Note that the initial thickness of the porous sheet already contained in the sealed space of the bag can be estimated to be at least equal to or greater (typically, greater) than the thickness measured when the porous sheet is removed from the sealed space by disassembling the bag and similarly not pressurized.

[0078] In some embodiments of the intercellular structure disclosed herein, when a compression test is performed on the porous sheet alone at a compression rate of 0.5 mm / min, the porous sheet contained in the sealed space of the bag has a compressive strain value (applied pressure) of 1.00 MPa (hereinafter also referred to as "strain when 1.00 MPa is applied"; other similar expressions are also applicable). The compressive strain value when 1.00 MPa is applied to the porous sheet alone may be, for example, 5% or more, preferably 7% or more or 10% or more, or may be 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 50% or more, 55% or more, or 60% or more. The strain of the porous sheet when 1.00 MPa is applied may be, for example, 85% or less, preferably 80% or less, and may be 75% or less or 70% or less. A porous sheet having a strain within any of the above-mentioned ranges when a pressure of 1.00 MPa is applied is likely to stably exhibit good cushioning properties in an intercellular structure that is expected to be used in a manner in which a compressive load of around 1.00 MPa may be applied (for example, in a pressure range of about 0.03 MPa to about 1.39 MPa or a pressure range of about 0.34 MPa to about 3.45 MPa).

[0079] The thermal conductivity of the porous sheet is not particularly limited. In some embodiments, the thermal conductivity of the porous sheet at 80 ° C. and 2 MPa is preferably 0.030 W / K m or more, more preferably 0.040 W / K m or more, even more preferably 0.050 W / K m or more, and preferably 0.2 W / K m or less, more preferably 0.15 W / K m or less, and even more preferably 0.1 W / K m or less. In some embodiments, the thermal conductivity of the porous sheet at 600 ° C. and 2 MPa is preferably 0.04 W / K m or more, more preferably 0.05 W / K m or more, even more preferably 0.06 W / K m or more, and preferably 0.30 W / K m or less, more preferably 0.25 W / K m or less, and even more preferably 0.20 W / K m or less. The thermal conductivity of the porous sheet can be measured using the same method as the method for measuring the thermal conductivity of the heat insulating layer described below.

[0080] The thermal resistance of the porous sheet is not particularly limited. In some embodiments, the thermal resistance of the porous sheet at 80°C and 2 MPa is preferably 0.020 (K·m ２ ) / W or more, more preferably 0.025 (K m ２ ) / W or more, more preferably 0.03 (K m ２ ) / W or more, and preferably 0.07 (K m ２ ) / W or less, more preferably 0.06 (K m ２ ) / W or less, more preferably 0.05 (K·m ２ In some embodiments, the thermal resistance of the porous sheet at 600°C and 2 MPa is preferably 0.001 (K·m ２ ) / W or more, more preferably 0.003 (K m ２ ) / W or more, more preferably 0.005 (K·m ２ ) / W or more, and preferably 0.1 (K m ２ ) / W or less, more preferably 0.05 (K·m ２ ) / W or less, more preferably 0.01 (K m ２ ) / W or less. The thermal resistance of the porous sheet can be measured by the same method as the method for measuring the thermal conductivity of the heat insulating layer, which will be described later.

[0081] <Thermal Insulation Layer> The intercellular structure disclosed herein may be configured to include a thermal insulation layer. The thermal insulation layer may be disposed inside the bag (e.g., in a sealed space partitioned by the bag material) or outside the bag.

[0082] The insulating layer is not particularly limited, and can be appropriately selected from those having a material and configuration suitable for insulating between cells of a lithium ion battery. In some embodiments, from the viewpoint of insulating performance, etc., an insulating layer containing inorganic particles can be preferably used. The type of inorganic particles is not particularly limited, and examples thereof include silica particles (silica), titanium oxide particles, zinc oxide particles, aluminum oxide particles, silicon carbide particles, ilmenite particles (ilmenite, FeTiO), zirconium silicate particles, iron (III) oxide particles, iron (II) (wustite (FeO) particles), magnetite particles (Fe３ O ４ ), hematite particles (Fe ２ O ３ )), chromium dioxide particles, zirconium oxide particles, manganese dioxide particles, zirconia sol, titania sol, silica sol, alumina sol, bentonite particles, kaolin particles, etc. Other examples of inorganic particles include carbon-based particles such as graphite, carbon black, and carbon. Graphite with a particle diameter of 18 μm or less is preferred. Graphite may be in any shape, including flake, scale, spherical, isotropic (artificial), and anisotropic (artificial). Examples of flake graphite include BF-3AK, FBF, and BF-10AK (manufactured by Chuetsu Graphite Industries Co., Ltd.), GE-1, Z-5F, CNP7, and V-10F (manufactured by Ito Graphite Industries Co., Ltd.), examples of scaly graphite include HLP and SB-1 (manufactured by Chuetsu Graphite Industries Co., Ltd.), examples of spherical graphite include SG-BH8 (manufactured by Ito Graphite Industries Co., Ltd.), examples of isotropic graphite (artificial) include AGB-5 (manufactured by Ito Graphite Industries Co., Ltd.), and examples of anisotropic graphite (artificial) include AG-6T (manufactured by Ito Graphite Industries Co., Ltd.). Examples of carbon black include TOKABLACK #5500 (manufactured by Tokai Carbon Co., Ltd.) and Mitsubishi Carbon Black MA100 (manufactured by Mitsubishi Chemical Corporation). The heat insulating layer may contain one type of inorganic particle, or may contain two or more types of inorganic particles. The inorganic particles are preferably inorganic particles that can suppress thermal radiation, more specifically, inorganic particles that have an absorption peak in the infrared region. The absorption peak in the infrared region can be measured using an infrared spectrophotometer. The inorganic particles may also function as a binder that binds inorganic fibers together.

[0083] The content of inorganic particles in the heat insulating layer is not particularly limited, and is, for example, 50% by mass to 99.5% by mass of the heat insulating layer, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less. When the content of inorganic particles is within the above range, good heat insulating properties and mechanical strength can be easily ensured.

[0084] The heat insulating layer contains silica (SiO ２) is preferably contained. Silica particles can be classified into crystalline silica, amorphous silica, etc. based on structural characteristics, and into natural silica, synthetic silica, etc. based on the method of acquisition. Synthetic silica can also be classified into dry silica, wet silica, silica aerogel, etc. based on the production method. Dry silica can be further classified into silica obtained by a combustion method, silica obtained by an arc method, etc., and wet silica can be classified into silica obtained by a gel method, silica obtained by a precipitation method, etc. The type of silica particles is not particularly limited, but dry silica and silica aerogel are preferred, and fumed silica, as a type of dry silica, is more preferred, and hydrophilic fumed silica is particularly preferred among fumed silica. The hydrophilic fumed silica refers to fumed silica having mainly hydrophilic silanol groups (Si—OH) on the surface, and generally refers to fumed silica in which the silanol groups have not been substituted with hydrophobic groups by surface treatment or the like. Silica particles generally exist as aggregates formed by aggregation of primary particles, or as aggregates formed by further aggregation of the aggregates. The silica particles in the heat insulating layer disclosed herein may be dispersed in the form of primary particles, aggregates, aggregates, or a combination thereof.

[0085] The average primary particle diameter of the silica particles is not particularly limited, and is, for example, 1 nm to 100 nm, preferably 2 nm or more, more preferably 4 nm or more, and preferably 80 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, and particularly preferably 20 nm or less. When the silica particles are fumed silica, the average primary particle diameter is, for example, 1 nm to 40 nm, preferably 2 nm or more, more preferably 4 nm or more, and preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 18 nm or less. When the silica particles are silica aerogel, the average primary particle diameter is, for example, 1 nm to 20 nm, preferably 18 nm or less, and more preferably 10 nm or less. When the average primary particle diameter of the silica particles is within the above range, good thermal insulation properties are easily ensured. Methods for determining the average primary particle diameter of silica particles include measurements using an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, a method can be used in which silica particles are randomly selected and their particle diameters are measured under an electron microscope, and the average value of the measured values ​​is calculated. The particle size may be the diameter if the particle is spherical, the intermediate value between the minor axis and the major axis if the particle is elliptical, or the intermediate value between the minor side and the major axis if the particle is an irregular particle.

[0086] The average particle size of the secondary aggregates of silica particles (aggregates of primary particles) is not particularly limited and is, for example, 0.1 μm to 100 μm, preferably 1 μm or more, more preferably 2 μm or more, and preferably 90 μm or less, more preferably 80 μm or less. Note that, as a method for determining the average particle size of the secondary aggregates of silica particles, a method of measuring using the same method as for the primary particle size can be mentioned.

[0087] The BET specific surface area of ​​the silica particles is, for example, 90 m ２ / g or more 380m ２ / g, preferably less than 130m ２ / g or more, more preferably 175m ２ / g or more, more preferably 200m ２ / g or more, preferably 350m ２ / g or less, more preferably 320m２ / g or less, more preferably 200m ２ / g or less. When the BET specific surface area of ​​the silica particles is within the above range, it becomes easier to ensure heat insulating properties even under high temperature and high humidity conditions. The BET specific surface area can be measured by a multipoint nitrogen adsorption method (BET method) in accordance with the International Organization for Standardization ISO 5794 / 1. For example, "AEROSIL 380" manufactured by Aerosil Co., Ltd. has a nominal value of the BET specific surface area of ​​380 m. ２ / g, and taking into account the error, it is 350m ２ / g~410m ２ In this case, the nominal value of 380 m ２ / g is considered as the standard.

[0088] The apparent specific gravity of the silica particles is not particularly limited and may be, for example, 30 g / L to 130 g / L, preferably 40 g / L or more, more preferably 50 g / L or more, and preferably 100 g / L or less, more preferably 80 g / L or less, and even more preferably 60 g / L or less. The apparent specific gravity of the silica particles can be determined by filling a container capable of measuring volume, such as a 250 mL graduated cylinder, measuring the filling mass (X g) and filling volume (Y mL) of the silica particles, and then dividing the filling mass by the filling volume ([apparent specific gravity (g / L)] = X / Y × 1000). When a nominal value of the apparent specific gravity is provided by a manufacturer or the like, that nominal value can be used.

[0089] Commercially available silica particles include hydrophilic fumed silica such as AEROSIL 50, 90, 130, 200, 200V, 300, and 380 from the AEROSIL series (manufactured by Nippon Aerosil Co., Ltd.), QS-09, QS-10, QS-102, QS-20, QS-20L, QS-30, Q40, and CP-102 from the Reolosil series (manufactured by Tokuyama Corporation), and HDKV15, N20, T30, and T40 from the HDK series (manufactured by Wacker Asahi Kasei Silicone Co., Ltd.), as well as hydrophobic fumed silica such as AEROSIL R972 and R976S from the AEROSIL series (manufactured by Nippon Aerosil Co., Ltd.), and HDK from the HDK series (manufactured by Wacker Asahi Kasei Silicone Co., Ltd.). Examples of suitable silica aerogels include AIRICA (manufactured by Tokuyama Corporation), which is a silica aerogel, such as H15, H20, and H30. The heat insulating layer may contain one type of silica particles or two or more types of silica particles.

[0090] The content of silica particles in the heat insulating layer is not particularly limited, and is, for example, 50% by mass or more (typically 50% by mass to 99.5% by mass), preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. When the content of silica particles is within the above range, good heat insulating properties and mechanical strength can be easily ensured.

[0091] The heat insulating layer may contain other components in addition to inorganic particles. In some embodiments, a heat insulating layer containing inorganic particles and inorganic fibers is preferred. The type of inorganic fiber is not particularly limited, but examples include silica fiber, glass fiber, alumina fiber, silica-alumina fiber, silica-alumina-magnesia fiber, biosoluble inorganic fiber, glass fiber, zirconia fiber, alkaline earth silicate fiber, alkaline earth silicate (AES) fiber, glass wool, rock wool, and basalt fiber. When the inorganic fiber is one of the above, heat resistance is improved. The heat insulating layer may contain one type of inorganic fiber, or may contain two or more types of inorganic fibers.

[0092] The content of inorganic fibers in the heat insulating layer is not particularly limited, and is, for example, 0.5% by mass to 50% by mass, preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. When the fiber content is within the above range, it becomes easier to ensure good thermal resistance and to manufacture the heat insulating layer.

[0093] The average fiber length of the inorganic fibers contained in the heat insulating layer is not particularly limited and is, for example, 0.05 mm to 50 mm, preferably 0.5 mm or more, more preferably 1.0 mm or more, and even more preferably 2 mm or more, and is preferably 35 mm or less, more preferably 30 mm or less, more preferably 25 mm or less, more preferably 13 mm or less, and even more preferably 10 mm or less, and may be 8 mm or less, or may be 6 mm or less. When the average fiber length of the fibers is within the above range, the heat insulating layer is easy to produce.

[0094] The average fiber diameter of the inorganic fibers contained in the heat insulating layer is not particularly limited and is, for example, 0.1 μm to 50 μm, preferably 1 μm or more, more preferably 5 μm or more, even more preferably 7 μm or more, and preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. When the average fiber diameter of the fibers is within the above range, good heat insulating properties and mechanical strength can be easily ensured.

[0095] The heat insulating layer may contain organic fibers. Specific examples of organic fibers include felts made of cellulose fiber, polyester, polypropylene, etc. The content of the organic fibers in the heat insulating layer can be appropriately set so as to obtain the desired effect, and may be, for example, more than 0 parts by mass, 1 part by mass or more, 4 parts by mass or more, 8 parts by mass or more, or 16 parts by mass or more per 100 parts by mass of the inorganic fibers. On the other hand, in some embodiments, from the viewpoint of heat resistance, etc., the content of the organic fibers in the heat insulating layer is suitably less than 100 parts by mass, advantageously less than 50 parts by mass, or may be less than 20 parts by mass, less than 10 parts by mass, less than 5 parts by mass, or less than 1 part by mass, and may even be a heat insulating layer that does not contain organic fibers.

[0096] In addition to the inorganic particles, the heat insulating layer may contain a binder (binding agent) as one of the other components. The heat insulating layer may contain one type of binder, or may contain two or more types of binders. When the heat insulating layer contains a binder, shape stability tends to be improved.

[0097] When the heat insulating layer contains a binder, the type of binder is not particularly limited, but can be classified into organic binders and inorganic binders. Specific examples of organic binders include thermoplastic resins, thermoplastic elastomers, thermosetting resins, thermosetting elastomers, sugars, water-soluble polymers, etc. Specific examples of inorganic binders include aluminum oxide, zirconium oxide, magnesium oxide, titanium oxide, calcium oxide, etc. When the binder is one of the above, shape stability is effectively improved.

[0098] When the heat insulating layer contains a binder, the content of the binder is not particularly limited and is, for example, 0.01% by mass to 10% by mass of the heat insulating layer, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. When the binder content is within the above range, it becomes easier to achieve both heat insulating properties and shape stability.

[0099] The heat insulating layer is preferably a layer containing the above-mentioned inorganic particles, and more preferably a molded body formed from a mixture containing inorganic particles and inorganic fibers. When the molded body is a mixture containing inorganic particles and inorganic fibers, it is easier to achieve both heat insulating properties and mechanical strength. When the heat insulating layer is a molded body formed from a mixture containing inorganic particles and inorganic fibers, details of the mixing method of the inorganic particles, inorganic fibers, etc. will be described later.

[0100] The thickness of the insulating layer is not particularly limited and may be, for example, 0.5 mm to 10 mm, preferably 0.7 mm or more, more preferably 0.8 mm or more or 0.9 mm or more. In some embodiments, the thickness of the insulating layer may be 1.0 mm or more, 1.5 mm or more, or 2 mm or more. The thickness of the insulating layer is preferably 7 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less. When the thickness of the insulating layer is within the above range, good thermal insulation properties are easily ensured and the size of the inter-cell structure can be suppressed. In some embodiments, the thickness of the insulating layer may be less than 2 mm, less than 1.5 mm, 1.3 mm or less, or 1 mm or less, or less than 1 mm. By reducing the thickness of the insulating layer, the inter-cell structure can be made thinner and lighter. The thickness of the insulating layer can be determined by measuring the cross section of the insulating layer at several points (e.g., 10 points) using a thickness measuring device (e.g., Ozaki Seisakusho's digital thickness gauge JAN-257 (measuring probe Φ20 mm)) when no pressure is applied (when no intentional load is applied to the insulating layer).

[0101] The density of the heat insulating layer is not particularly limited, and may be, for example, 0.2 to 0.5 g / cm ３ and preferably 0.3 g / cm ３ More preferably, 0.35 g / cm ３ More preferably, 0.37 g / cm ３ or more, and preferably 0.45 g / cm ３ The following is the result.

[0102] The thermal conductivity of the insulating layer at 80°C and 0.10 MPa pressure is preferably 0.010 W / K·m or more, and preferably 0.3 W / K·m or less, more preferably 0.1 W / K·m or less, more preferably 0.08 W / K·m or less, more preferably 0.06 W / K·m or less, more preferably 0.055 W / K·m or less, more preferably 0.045 W / K·m or less, and even more preferably 0.04 W / K·m or less.

[0103] The thermal conductivity of the insulating layer at 800°C and 0.10 MPa pressure is preferably 0.010 W / K·m or more, and preferably 0.3 W / K·m or less, more preferably 0.2 W / K·m or less, more preferably 0.1 W / K·m or less, more preferably 0.08 W / K·m or less, and even more preferably 0.075 W / K·m or less.

[0104] When the thickness (initial thickness) of the heat insulating layer is adjusted to 1 mm without pressure, the heat resistance at 80°C and 0.10 MPa pressure is preferably 0.010 (K·m ２ ) / W or more, more preferably 0.015 (K·m ２ ) / W or more, more preferably 0.020 (K·m ２ ) / W or more, more preferably 0.025 (K·m ２ ) / W or more, and preferably 0.1 (K m ２ ) / W or less.

[0105] The thermal resistance of the heat insulating layer having an initial thickness of 1 mm at 800°C and a pressure of 0.10 MPa is preferably 0.005 (K·m ２ ) / W or more, more preferably 0.010 (K·m ２ ) / W or more, more preferably 0.015 (K·m ２ ) / W or more, and preferably 0.1 (K m ２ ) / W or less.

[0106] The thermal conductivity of the heat insulating layer can be measured by the method described in Japanese Industrial Standard JIS A 1412-2:1999, "Methods for measuring thermal resistance and thermal conductivity of thermal insulating materials - Part 2: Heat flow meter method (HFM method)." The heat flow meter method (HFM method) is a secondary measurement method or comparative measurement method that measures heat transfer characteristics such as thermal conductivity and thermal resistance by comparing a flat plate of heat insulating material (heat insulating layer) as a test specimen with a standard plate. The detailed measurement procedure and measurement conditions are described below.

[0107] The insulation layer is cut to a predetermined size (e.g., 20 mm x 20 mm) to prepare a test specimen, and an alumina composite material ("RS-100", manufactured by ZIRCAR Refractory Composites, Inc., thickness: 5 mm, thermal conductivity: 0.66 W / K m) or the like is prepared as a standard plate. Next, the first thermocouple, titanium plate, insulation layer, titanium plate, second thermocouple, standard plate, and third thermocouple are placed on the lower plate of a pneumatic press in this order from top to bottom, and the test specimen, standard plate, thermocouple, etc. are tightly attached between the upper and lower plates. The upper and lower plates are then heated to their respective predetermined measurement temperatures, and a load is applied to the test specimen, etc. using the pneumatic press to achieve the predetermined measurement pressure.

[0108] The measurement temperatures may be set to 80° C. for the upper plate on the first thermocouple side and 30° C. for the lower plate on the third thermocouple side. On the other hand, the measurement temperatures under high temperature conditions may be set to 800° C. for the upper plate on the first thermocouple side and 80° C. for the lower plate on the third thermocouple side, for example.

[0109] The measurement pressure can be 0.10 MPa (load: 40 N). Measurement is continued under heating and pressure until the detected temperature of each thermocouple stabilizes, and the thermal conductivity k1 of the heat insulating layer can be calculated from the detected temperature of each thermocouple after the temperature has stabilized, the thickness of the heat insulating layer when pressurized, the thermal conductivity of the standard plate, and the thickness of the standard plate when pressurized, using the following formula (I): k1 = k2 × (L1 × ΔT1) / (L2 × ΔT2) ... (I) (In the formula, k1 is the thermal conductivity of the insulating layer [W / (m·K)], k2 is the thermal conductivity of the standard plate [W / (m·K)], L1 is the thickness of the insulating layer when pressed, L2 is the thickness of the standard plate, ΔT1 is the temperature difference between the temperatures of the second thermocouple and the third thermocouple, and ΔT2 is the temperature difference between the temperatures of the first thermocouple and the second thermocouple.) Note that the detected temperature being stable means that the temperature change after about 10 minutes is within a specified range (for example, within ±0.1°C).

[0110] The thermal resistance of the heat insulating layer can be calculated from the thermal conductivity k1 and the thickness under pressure L1 using the following formula (II): R1 = L1 / k1 (II) (where R1 is the thermal resistance [(m ２·K) / W], k1 is the thermal conductivity of the heat insulating layer [W / (m ·K)], and L1 is the thickness of the heat insulating layer under pressure [m].

[0111] In some embodiments where the intercellular structure disclosed herein includes a thermal insulation layer, when a compression test is performed on the thermal insulation layer alone at a compression rate of 0.5 mm / min, the compressive strain value at a compressive stress value of 1.00 MPa (hereinafter also referred to as "1.00 MPa compression strain") is suitably, for example, 40% or less, preferably 25% or less or 20% or less, advantageously 18% or less, and may be 15% or less, 12% or less, or 10% or less. The 1.00 MPa compression strain of the thermal insulation layer is greater than 0%, and may be, for example, 4% or more, 6% or more, 8% or more, 10% or more, or 12% or more. A thermal insulation layer having a 1.00 MPa compression strain within any of the above ranges can be used as a component of any of the intercellular structures disclosed herein to easily realize an intercellular structure with good thermal insulation and cushioning properties.

[0112] The number of heat insulating layers included in the intercellular structure is usually 1 or more, and usually 10 or less, preferably 7 or less, and more preferably 5 or less. The technology disclosed herein can be preferably implemented in an embodiment in which the number of heat insulating layers is 3 or less or 2 or less (typically 1).

[0113] The insulating layer may be bonded to an adjacent layer (which may be a layer constituting the inner or outer surface of the bag material) with an adhesive or pressure-sensitive adhesive, or may not be bonded. In some embodiments, it is preferable that the insulating layer is not bonded with an adhesive or pressure-sensitive adhesive. By not using an adhesive or pressure-sensitive adhesive, the thermal conductivity can be reduced compared to when an adhesive or pressure-sensitive adhesive is used.

[0114] The shape of the heat insulating layer is not particularly limited. In some embodiments, the shape of the heat insulating layer when viewed from above may be, for example, a polygon such as a quadrangle, a circle, an ellipse, etc. Examples of quadrangles include rectangles (including squares and rectangles).

[0115] The method for producing the heat insulating layer is not particularly limited, and the layer can be produced by appropriately adopting known processes. For example, when the heat insulating layer is a layer formed from a mixture containing inorganic particles and inorganic fibers, the mixture can be prepared by adopting known mixing methods such as a wet method or a dry method. A method for producing a heat insulating layer including preparation of a mixture by a wet method can be a method including, for example, the following steps: Mixing step: a step of mixing inorganic particles and inorganic fibers in a solvent to obtain a mixed liquid; Coating step: a step of applying the mixed liquid obtained in the mixing step to obtain a coated film; Coating film forming step: a step of forming the coated film obtained in the coating step to obtain a heat insulating layer.

[0116] The mixing step is a step of mixing inorganic particles and inorganic fibers in a solvent to obtain a mixed liquid, specifically, a step of mixing inorganic particles and inorganic fibers in a solvent to prepare a mixed liquid (slurry state). The mixing in the mixing step can be performed using, for example, a Disper, a Labo Plastomill, a Trimix, a planetary mixer, a kneader, or the like.

[0117] The type of solvent is not particularly limited, and examples thereof include protic solvents such as alcohols, amides, and water, and aprotic solvents such as esters, ketones, nitriles, and ethers. The surface tension of the solvent is not particularly limited, and is, for example, 20 mN / m to 73 mN / m, preferably 21 mN / m or more, preferably 50 mN / m or less, more preferably 40 mN / m or less, and even more preferably 30 mN / m or less. When the surface tension of the solvent is within the above range, the heat insulating properties and mechanical strength are improved. The surface tension of the solvent can be measured by the ring method, for example.

[0118] The mixing temperature is not particularly limited, and is, for example, 20°C or higher and the boiling point of the solvent or lower, preferably 22°C or higher, and preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. When the mixing temperature is within the above range, the solvent (e.g., organic solvent) is less likely to volatilize, and the blending ratio is less likely to change. The mixing time is not particularly limited, and is, for example, 1 minute to 5 hours, preferably 5 minutes or longer, preferably 4 hours or shorter, more preferably 2 hours or shorter, and even more preferably 1 hour or shorter. When the mixing time is within the above range, the heat insulating layer can be easily produced efficiently.

[0119] The consistency of the mixed liquid is not particularly limited and is, for example, 50 to 200, preferably 55 or more, more preferably 60 or more, even more preferably 65 or more, and preferably 180 or less, more preferably 160 or less, and even more preferably 140 or less. When the consistency of the mixed liquid is within the above range, fiber breakage can be reduced when the fibers are uniformly dispersed. The consistency of the mixed liquid can be measured by the method described in Japanese Industrial Standards JIS K 2220:2013, "Greases - Part 7: Consistency Test Method," and in particular, can be measured as "unworked consistency." More specifically, the consistency of the mixed liquid can be measured by the method described in the Examples below.

[0120] The coating method and conditions in the coating step are not particularly limited, and any known method can be appropriately used. For example, coating can be performed using a comma coater, spin coater, die coater, dispenser, etc.

[0121] The molding method and molding conditions in the coating film molding step are not particularly limited, and known methods can be appropriately adopted. For example, compression molding can be performed using a heat press or a vacuum press, and drying can be performed using a floating oven, an IR oven, or the like. As drying conditions, a drying temperature of, for example, 60°C to 150°C is preferred. A drying time of, for example, 4 minutes to 20 minutes is preferred. The above molding method and molding conditions are determined based on the desired density (for example, a density of 0.2 to 0.5 g / cm). ３ The thickness of the insulating layer may be selected to provide a thermal barrier.

[0122] <Inter-cell structure> The inter-cell structure disclosed herein is used in a battery module or the like including a plurality of arranged cells, by being disposed between adjacent cells among the plurality of cells. The target cells are not limited to prismatic cells, and may be, for example, laminated cells or cylindrical cells. The shape of the inter-cell structure can be appropriately adopted depending on the type of cell.

[0123] In addition, target devices for the battery include electric vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs), portable electronic devices such as mobile terminals, mobile phones, and notebook computers, and wearable devices.

[0124] Fig. 1 is a perspective view schematically illustrating an example of a battery module in which inter-cell structures according to one embodiment are disposed between cells, and Fig. 2 is a cross-sectional view taken along line II-II of Fig. 1. As shown in Fig. 1, a battery module 50 includes a plurality of lithium-ion battery cells (here, prismatic cells) 51 arranged in the thickness direction, with inter-cell structures 1 disposed between each of the battery cells 51. The plurality of battery cells 51 thus arranged with the inter-cell structures 1 sandwiched between them are typically restrained by applying a pressing force (compressive force) in the thickness direction via restraint plates 52a, 52a disposed at both ends, and are housed in a battery case 53 for use.

[0125] FIG. 3 shows an enlarged view of the intercell structure 1 shown in FIG. 2 . This intercell structure 1 includes a bag body 30 in which two pieces of bag material 31A, 31B are sealed by bonding (e.g., heat sealing) at sealing edges 32 provided along their outer edges. A sealed space partitioned by the bag materials 31A, 31B is formed inside the bag body. This sealed space contains at least a gas 20 (e.g., air) and also contains a porous sheet 10. By sandwiching the intercell structure 1 having such a configuration between two adjacent battery cells 51, as shown in FIG. 2 , the intercell structure 1 can exhibit durable buffering function between the battery cells 51, 51, by utilizing the fluid spring (gas spring) and the resilience of the porous sheet to change its thickness appropriately in response to repeated expansion and contraction of the cells 51. While FIG. 3 illustrates an example of a configuration in which the intercell structure 1 has only one porous sheet 10, the number of porous sheets may be two or more. Also, as shown in FIG. 4, the intercellular structure 1 does not necessarily have to have a porous sheet housed in the sealed space.

[0126] 5 and 6 are cross-sectional views each showing a schematic example of the sealing edge 32 and its vicinity in the inter-cell structure 1 shown in FIGS. 1 and 2 . At the sealing edge 32, a seal portion S (compartmentalizing the sealed space) is formed by joining together the sealant resin layers 31a of the laminated film F forming the bag material 31 (bag materials 31A and 31B). FIGS. 5 and 6 exemplify a case in which the laminated film F has a three-layer structure including a sealant resin layer 31a, a resin layer 31b, and a metal layer 31c therebetween. The seal portion S includes a relatively thick first seal portion S1 facing the sealed space and a second seal portion S2 located on the opposite side of the sealed space from the first seal portion S1. The second seal portion S2 includes a relatively thin portion Sa (first thin portion) adjacent to the first seal portion S1. The thin portion Sa is thinner than the first seal portion S1. That is, the first seal portion S1 is thicker than the thin portion Sa.

[0127] In the sealing end 32 shown in Fig. 5, the entire second seal portion S2 is a thin portion Sa in the width direction Dw of the seal portion S. In the sealing end 32 shown in Fig. 6, the second seal portion S2 has at least two thin portions Sa, including a thin portion Sa adjacent to the first seal portion S1, and at least one thick portion Sb that is thicker than the thin portion Sa. Fig. 6 exemplarily shows a case in which the second seal portion S2 has five thin portions Sa and five thick portions Sb, with the thin portions Sa and thick portions Sb arranged alternately.

[0128] In the seal portion S, the thickness T of the first seal portion S1 １ From the viewpoint of ensuring the bonding strength between the laminated films F at the first sealed portion S1 and appropriately ensuring the strength and durability of the sealed portion S, the thickness T of the first sealed portion S1 is preferably 100 μm or more, more preferably 130 μm or more, and even more preferably 150 μm or more, and may be 200 μm or more, 250 μm or more, or 290 μm or more. １is preferably about 600 μm or less, more preferably 500 μm or less, and may be 400 μm or less, 350 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, 180 μm or less, or 160 μm or less. １ The thickness of the first seal portion S1 is the thickness in a flat region where the thickness is uniform or approximately uniform. The fact that the first seal portion S1 is not too thick is advantageous for suppressing the gas permeability of the first seal portion S1, and is therefore advantageous from the viewpoint of suppressing the permeation of the gas 20 through the seal portion S and suppressing leakage of the gas 20 from the bag body 30.

[0129] Width W of the first seal portion S1 １ From the viewpoint of appropriately ensuring the bonding strength between the laminated films F at the first sealed portion S1 and appropriately ensuring the strength and durability of the sealed portion S, the width W of the first sealed portion S1 is preferably 0.7 mm or more, more preferably 0.8 mm or more, and even more preferably 1.0 mm or more, and may be 1.5 mm or more, 2.0 mm or more, 2.5 mm or more, 3.0 mm or more, 4.0 mm or more, or 5.0 mm or more. １ is preferably 10.0 mm or less, more preferably 8.0 mm or less, and even more preferably 6.0 mm or less, and may be 5.0 mm or less, 4.0 mm or less, 3.0 mm or less, 2.0 mm or less, 1.7 mm or less, or 1.5 mm or less. １ It is advantageous that the width W of the first seal portion S1 is not too large in order to prevent the gas 20 from passing through the seal portion S and to prevent the gas 20 from leaking from the bag body 30. １ is the length of the first seal portion S1 in the width direction Dw of the seal portion S.

[0130] Thickness T of the thin portion Sa of the second seal portion S2 ２ is the thickness T of the first seal portion S1 １As long as it is smaller, it is preferably 150 μm or less, more preferably less than 100 μm, and even more preferably 80 μm or less, and may be 70 μm or less, 65 μm or less, or 60 μm or less. ２ The thickness T of the thin-walled portion Sa is the thickness of a flat region where the thickness of the thin-walled portion Sa is uniform or approximately uniform. ２ A small thickness T of the thin-walled portion Sa of the second seal portion S2 is advantageous from the viewpoint of suppressing the gas permeability of the second seal portion S2, and therefore is advantageous from the viewpoint of suppressing the permeation of the gas 20 through the seal portion S and suppressing the leakage of the gas 20 from the bag body 30. In addition, from the viewpoint of ensuring the bonding strength between the laminated films F at the second seal portion S2, the thickness T of the thin-walled portion Sa of the second seal portion S2 is ２ is the thickness T of the first seal portion S1 １ As long as it is smaller, it is preferably 10 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, and may be 60 μm or more, 70 μm or more, or 80 μm or more.

[0131] Thickness T of the first seal portion S1 １ The thickness T of the thin-walled portion Sa ２ The ratio (T ２ / T １ ) is preferably 0.85 or less, more preferably 0.65 or less, and even more preferably 0.50 or less, and may be 0.30 or less, or may be 0.20 or less. ２ / T １ ) is smaller, the gas permeability of the second seal portion S2 is more easily suppressed, and therefore the permeation of the gas 20 through the seal portion S is more easily suppressed, and the leakage of the gas 20 from the bag body 30 is more easily suppressed. １ The thickness T of the thin-walled portion Sa ２ The ratio (T ２ / T １ ) is preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.30 or more, and may be 0.35 or more, or 0.40 or more, from the viewpoint of ensuring the bonding strength between the laminated films F at the second seal portion S2.

[0132] Thickness T of the thick portion Sb of the second seal portion S2 ３ From the viewpoint of ensuring the bonding strength between the laminated films F at the second sealed portion S2, the thickness T of the thick-walled portion Sb of the second sealed portion S2 is preferably 100 μm or more, more preferably 130 μm or more, and even more preferably 150 μm or more, and may be 200 μm or more, 250 μm or more, or 290 μm or more, as long as it is thicker than the thin-walled portion Sa. ３ is preferably about 600 μm or less, more preferably 500 μm or less, and may be 400 μm or less, 350 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, 180 μm or less, or 160 μm or less. ３ It is advantageous for the thickness T of the first seal portion S1 to be not too large in order to suppress the gas permeability of the second seal portion S2, and therefore to suppress the permeation of the gas 20 through the seal portion S and to suppress the leakage of the gas 20 from the bag body 30. １ and the thickness T of the thick portion Sb of the second seal portion S2 ３ may be the same or different.

[0133] Width W of the thin-walled portion Sa of the second seal portion S2 ２ (When the second seal portion S2 has a plurality of thin portions Sa, the width W of each thin portion Sa is ３ The width W of the thin-walled portion Sa is preferably 2.0 mm or more, more preferably 3.0 mm or more, and even more preferably 4.0 mm or more, and may be 5.0 mm or more, 6.0 mm or more, 7.0 mm or more, 8.0 mm or more, or 9.0 mm or more. ２ The large width W of the thin-walled portion Sa of the second seal portion S2 is advantageous from the viewpoint of suppressing the gas permeability of the second seal portion S2, and therefore is advantageous from the viewpoint of suppressing the permeation of the gas 20 through the seal portion S and suppressing the leakage of the gas 20 from the bag body 30. ２ (When the second seal portion S2 has a plurality of thin portions Sa, the width W of each thin portion Sa is ３The width W of the thin portion Sa is preferably 20.0 mm or less, more preferably 15.0 mm or less, and even more preferably 10.0 mm or less, and may be 9.0 mm or less, or may be 8.0 mm or less. ２ is not too large is advantageous from the viewpoint of miniaturization of the inter-cell structure 1.

[0134] Width W of the first seal portion S1 １ Width W of the thin-walled portion Sa ２ (When the second seal portion S2 has a plurality of thin portions Sa, the width W of each thin portion Sa is ３ Total width of the ２ / W １ ) is preferably 0.7 or more, more preferably 0.9 or more, and even more preferably 1.5 or more, and may be 2.0 or more, 3.0 or more, or 4.0 or more. ２ / W １ ) is larger, the gas permeability of the second seal portion S2 is more easily suppressed, and therefore the permeation of the gas 20 through the seal portion S is more easily suppressed, and the leakage of the gas 20 from the bag body 30 is more easily suppressed. １ Width W of the second seal portion S2 ２ (When the second seal portion S2 has a plurality of thin portions Sa, the width W of each thin portion Sa is ３ Total width of the ２ / W １ ) is preferably 7.0 or less, more preferably 6.0 or less, and even more preferably 5.0 or less, from the viewpoint of miniaturization of the inter-cell structure 1.

[0135] The width W of the seal portion S including the first seal portion S1 and the second seal portion S2 is W １ , W ２From the viewpoint of ensuring both, the width W of the seal portion S including the first seal portion S1 and the second seal portion S2 is preferably 20.0 mm or less, more preferably 16.0 mm or less, and even more preferably 12.0 mm or less, and may be 10.0 mm or less, 11.0 mm or more, 14.0 mm or more, or 16.0 mm or more, from the viewpoint of miniaturizing the inter-cell structure 1.

[0136] In the inter-cell structure 1, when a compressive load is applied to the bag body 30 and the sealed space is pressurized, a tensile force acts on the portion of the sealed portion S of the bag body 30 facing the sealed space, for example, in the thickness direction of the sealed portion S. However, the first sealed portion S1, which is thicker than the thin portion Sa, ensures the seal strength between the laminated films to resist this tensile force. When the compressive load on the bag body 30 repeatedly fluctuates up and down, the magnitude and direction of the tensile force also dynamically change accordingly, and the effective load on the sealed portion S tends to increase. However, in the inter-cell structure 1, the first sealed portion S1, which is thicker than the thin portion Sa, ensures the seal durability between the laminated films (the thicker the first sealed portion S1, the higher the seal durability tends to be). Additionally, in the inter-cell structure 1, when the sealed space is pressurized, the pressure difference between the inside and outside of the sealed space acts as a driving force for gas permeation through the sealed portion S. However, the seal portion S, which includes the second sealed portion S2 in addition to the first sealed portion S1, can suppress this gas permeation. This is because the second sealed portion S2 has a thin-walled portion Sa adjacent to the thick first sealed portion S1. The thinner and longer the thin-walled portion Sa, the more gas permeation tends to be suppressed. As described above, in the intercellular structure 1, the sealed portion S in the bag material 31 includes the first sealed portion S1 and the second sealed portion S2, so that the strength and durability of the sealed portion S can be ensured and gas permeation through the sealed portion S can be suppressed. Therefore, the intercellular structure 1 can durably maintain the cushioning function of alleviating stress from the cells by changing its thickness with good follow-up in response to repeated expansion and contraction of the cells.

[0137] The thermal conductivity of the inter-cell structure disclosed herein is not particularly limited. In some embodiments, the thermal conductivity of the inter-cell structure under conditions of 800°C and 0.10 MPa pressure is preferably 0.04 W / K m or more, more preferably 0.05 W / K m or more, even more preferably 0.06 W / K m or more, and is preferably 200 W / K m or less, more preferably 100 W / K m or less, even more preferably 20 W / K m or less. The thermal conductivity of the inter-cell structure can be measured in the same manner as the thermal conductivity of the heat insulating layer described above.

[0138] The thermal resistance of the inter-cell structure disclosed herein is not particularly limited, and can be measured in the same manner as the thermal resistance of the heat insulating layer described above.

[0139] The matters disclosed in this specification include the following: [1] An inter-cell structure disposed between adjacent cells of an arrayed battery module or battery pack including a plurality of lithium-ion battery cells, the inter-cell structure comprising: a bag body having a bag material that defines an enclosed space and a fluid containing at least gas within the enclosed space, the bag material being formed from a laminated film including a metal layer and a sealant resin layer, and having a seal portion formed by joining the sealant resin layers of the laminated film to seal the enclosed space, the seal portion including: a relatively thick first seal portion facing the enclosed space, and a second seal portion located on the opposite side of the first seal portion from the enclosed space, the second seal portion having a relatively thin portion adjacent to the first seal portion. [2] The inter-cell structure according to [1] above, wherein the second seal portion is entirely the thin portion. [3] The inter-cell structure according to [1] or [2] above, wherein the second seal portion further has a thick portion that is thicker than the thin portion. [4] The inter-cell structure according to any one of [1] to [3] above, wherein the second seal portion has at least two thin portions including the thin portion and at least one thick portion that is thicker than the thin portion, and the thin portions and the thick portions are alternately arranged in the width direction of the seal portion. [5] The first seal portion has a thickness T１ [6] The inter-cell structure according to any one of [1] to [4] above, wherein the first seal portion has a width W of 0.7 mm or more. １ [7] The thin-walled portion has a thickness T of 150 μm or less. ２ [8] The inter-cell structure according to any one of [1] to [6] above, wherein the thickness T of the first seal portion is １ The thickness T of the thin portion ２ [9] The inter-cell structure according to any one of [1] to [7], wherein the ratio of the thickness T of the first seal portion is 0.85 or less. １ The thickness T of the thin portion ２

[10] The thin-walled portion has a width W of 2.0 mm or more, and the ratio of ２

[11] The inter-cell structure according to any one of [1] to [9] above, wherein the width W of the first seal portion is １ The width W of the thin walled portion ２

[12] The inter-cell structure according to any one of [1] to

[10] above, wherein the ratio of the width W of the first seal portion to the width W of the first seal portion is 0.70 or more. １ The width W of the thin walled portion ２

[13] The inter-cell structure according to any one of [1] to

[12] above, wherein the ratio of the first seal portion and the second seal portion to the second seal portion is 10 or less.

[14] The inter-cell structure according to any one of [1] to

[12] above, wherein the width W of the seal portion including the first seal portion and the second seal portion is 5.0 mm or more.

[15] The surface area A [m ２ ] and the amount of gas G calculated by the following formula based on the volume V [L] of the gas contained in the sealed space is 1.0 L / m ２

[15] The intercellular structure according to any one of [1] to

[14] above, wherein G=V / (A / 2).

[16] The intercellular structure according to any one of [1] to

[15] above, wherein the bag further has a porous sheet.

[16] The intercellular structure according to

[15] above, wherein the bag includes at least a sheet-like molded body containing inorganic fibers as the porous sheet.

[17] The intercellular structure according to

[16] above, wherein the sheet-like molded body containing inorganic fibers is a sheet-like molded body containing one or more selected from the group consisting of glass wool, long glass fibers, glass fiber mat, glass fiber needle mat, rock wool, alkaline earth silicate fibers, and alkaline earth silicate wool.

[18] The intercellular structure according to any one of

[15] to

[17] above, wherein the bag includes, as the porous sheet, a sheet-like molded body containing inorganic particles and inorganic fibers, and the inorganic particles comprise, as a main component, at least one type of silica particles selected from the group consisting of dry silica, wet silica, and silica aerogel.

[19] The inter-cell structure according to any one of [1] to

[18] above, wherein more than 50% (by volume) of the gas is composed of one or more gases selected from the group consisting of nitrogen, argon, carbon dioxide, neon, helium, krypton, and xenon.

[20] The inter-cell structure according to any one of [1] to

[19] above, wherein the first seal portion extends along the sealed space over the entire length of the seal portion.

[0140] Hereinafter, several examples of the present invention will be described, but it is not intended that the present invention be limited to these specific examples.

[0141] <Materials Used> The intercellular structures according to the examples described below were fabricated using the following materials.

[0142] (Film) A: Laminated film with the configuration shown in Table 1 (product of J-Film Inc.). B: Laminated film with the configuration shown in Table 1 (product of TOPPAN Co., Ltd.). C: Laminated film with the configuration shown in Table 1 (product of Toyo Seikan Co., Ltd.). The thickness of each layer and the total thickness of films A to C are the nominal values ​​provided by the manufacturer.

[0143]

[0144] (Porous sheet) Glass wool A: Glass wool manufactured by Paramount Glass Co., Ltd. (product name: Feather Glass FG, 24 kg / m ３ , thickness 25 mm) at 360 g / m ２ Glass wool B: Glass wool manufactured by Paramount Glass Industry Co., Ltd. (trade name: Feather Glass FG, 24 kg / m ３ , thickness 25 mm) at 600 g / m ２ The meat was sliced ​​to a size of 1 / 4.

[0145] Heat insulating layer A: A mixed solvent (surface tension: 23 mN / m) of 300 parts by mass of isopropyl alcohol (IPA, surface tension: 21 mN / m) as a protic solvent and 60 parts by mass of water was mixed with 100 parts by mass of hydrophilic fumed silica particles ("AEROSIL (registered trademark) 200" manufactured by Nippon Aerosil Co., Ltd.), 20 parts by mass of glass fiber ("CS 6J-888" manufactured by Nitto Boseki Co., Ltd., average fiber diameter: 11 μm, average fiber length: 6 mm), and a non-polymeric dispersant, Kotamine 24P manufactured by Kao Corporation (active ingredient: dodecyltrimethylammonium chloride (C １２ H ２５ N ＋ (CH ３ ) ３ Cl), active ingredient content: 27% by mass), 1.9 parts by mass (0.5 parts by mass as active ingredient (ammonium salt)), and 10 parts by mass of graphite ("SRN-5J", manufactured by Fuji Graphite Industries Co., Ltd., average particle size 5 μm) were added and mixed to a consistency of 70 to 140. The resulting mixture was applied to a substrate to a thickness of 2.0 mm to form a coating film (coating step). The coating film was formed to a thickness of 1.0 mm and a density of 0.3 to 0.5 g / cm ３ The mixture was compression molded in a hot press into a sheet of 1.0 mm thick (molding step), and then dried at 100°C for 10 minutes to produce a porous sheet (a sheet-like molded product containing inorganic fibers and inorganic particles) as a heat insulating layer. The thickness of the resulting heat insulating layer (heat insulating layer A) was 1.0 mm, and the density was 0.37 g / cm. ３The thermal conductivity (800°C, 0.10 MPa) of the heat insulating layer A measured according to the method described below was 0.075 (W / m·K).

[0146] Heat insulating layer B: A porous sheet (a sheet-like molded product containing inorganic fibers and inorganic particles) was prepared as heat insulating layer B in the same manner as the method for preparing heat insulating layer A, except that the thickness of the coating film formed in the coating process was 4.0 mm and the thickness of the heat insulating layer formed in the molding process was 2.0 mm.

[0147] In the manufacturing process of each of the above-mentioned thermal insulation layers, the consistency of the mixed solution was measured as "immiscible consistency" in accordance with the contents of Japanese Industrial Standard JIS K 2220:2013 "Grease - Part 7: Consistency Test Method." Specifically, a container large enough that a conical weight would not come into contact with the mixed solution when lowered was prepared, filled with the mixed solution, and placed in a PENETRO METER manufactured by Nikka Engineering Co., Ltd., to which the weight was attached. Next, the position of the weight was adjusted to a position where the weight and the mixed solution came into contact, and this position was designated as the zero point. Then, under room temperature (25°C) conditions, the weight was lowered for 5 seconds (±0.1 seconds), and the depth (mm) of the weight penetrating the mixed solution was calculated as 10. The conical weight used was a standard cone as defined in the Japanese Industrial Standards, with a total mass of 102.5 g and a weight holder with a mass of 47.5±0.05 g.

[0148] The thermal conductivity of the thermal insulation layer was measured at 800°C and 0.10 MPa in accordance with the Japanese Industrial Standards (JIS) A 1412-2:1999, "Method for measuring thermal resistance and thermal conductivity of thermal insulation materials - Part 2: Heat flow meter method (HFM method)." First, the thermal insulation layer to be measured was cut into 20 mm x 20 mm pieces to prepare samples for thermal conductivity measurement. A sample, a reference sample (alumina composite material ("RS-100," manufactured by ZIRCAR Refractory Composites, Inc., thickness: 5 mm, thermal conductivity: 0.66 W / (m·K))), and a titanium plate (thickness: 0.2 mm) were prepared. Next, on the lower plate surface of a pneumatic press (manufactured by Imoto Machinery Co., Ltd.), from the top, thermocouple 1 (sheathed thermocouple K type (SCHS1-0), φ = 0.15, class JIS1, manufactured by Chino Corporation), titanium plate, heat insulating layer (sample) as a test specimen, titanium plate, thermocouple 2 (sheathed thermocouple K type (SCHS1-0), φ = 0.15, class JIS1, manufactured by Chino Corporation), standard plate, thermocouple 3 (sheathed thermocouple K type (SCHS1-0), φ = 0.15, class JIS1, manufactured by Chino Corporation) were sandwiched in this order to closely adhere the heat insulating layer, standard plate, thermocouple, etc. Next, the upper and lower plates were heated and the load of the press was adjusted to 40 N (equivalent to 0.10 MPa), and then pressurized. In the heated and pressurized state, measurement was continued until the detected temperature of the thermocouple stabilized. The heating temperatures were 800 ° C. for the upper plate and 80 ° C. for the lower plate. The temperature was defined as being stabilized when the temperature change after 10 minutes was within ±0.1°C. After the temperature was stabilized, the thermal conductivity k1 of the thermal insulating layer was calculated from the detected temperatures of each thermocouple, the thickness of the thermal insulating layer when compressed, and the thermal conductivity and thickness of the standard sample using the following formula (I): k1 = k2 × (L1 × ΔT1) / (L2 × ΔT2) ... (I) (where k1 is the thermal conductivity of the thermal insulating layer [W / (m K)], k2 is the thermal conductivity of the standard plate [W / (m K)], L1 is the thickness of the thermal insulating layer when compressed, L2 is the thickness of the standard plate, ΔT1 is the temperature difference between the temperatures of the second thermocouple (thermocouple 2) and the third thermocouple (thermocouple 3), and ΔT2 is the temperature difference between the temperatures of the first thermocouple (thermocouple 1) and the second thermocouple (thermocouple 2).)

[0149] The density of the heat insulating layer was calculated by cutting each heat insulating layer into a size of 20 mm x 20 mm, measuring the mass and thickness, and dividing the mass by the volume.

[0150] <Preparation of Intercellular Structure> (Example 1) Two sheets of film A were prepared by cutting them into 70 mm squares. Next, the two sheets of film A were overlapped with their heat-sealed surfaces (CPP layer side) facing inward, and then the three sides of the two sheets of film A were heat-sealed (first sealing step). The heat-sealing was performed using a Fuji Impulse heat-sealing machine, model "OPL-300-10," and a pair of heat-sealing dies that sandwiched the object to be sealed. In the first sealing step, the two sheets of film A were heat-sealed at a seal width of 10.0 mm for each side at 180°C for 4 seconds. After heat-sealing one side, the film was cooled to 45°C before heat-sealing the next side. The die faces of the pair of heat-sealing dies used in this example had a surface texture for forming first and second seal portions within the seal portions, with the dimensions shown in Table 2 (the die faces of the pair of heat-sealing dies had a surface texture that was symmetrical with respect to the object to be sealed sandwiched between the die faces). Next, the remaining side (fourth side) of the film A was heat-sealed with a seal width of 10.0 mm in the same manner as in the first sealing process, ensuring that a predetermined amount of air was trapped between the two sheets of film A (second sealing process).

[0151] In this manner, an intercellular structure of Example 1 was obtained, which consisted of a bag body configured with air contained in a sealed space partitioned by two sheets of film A (bag material). The intercellular structure of Example 1 had a sealed portion including first and second sealed portions with the dimensions shown in Table 2. In Table 2, W indicates the width of the entire sealed portion, and T １ indicates the thickness of the first seal portion, and W １ indicates the width of the first seal portion, and T ２ indicates the thickness of the thin portion of the second seal portion, and W ２ indicates the width of the thin-walled portion (if there are multiple thin-walled portions, the total width of the thin-walled portions), and W ３ indicates the width of each thinned portion, the "number of lines" of the thinned portion indicates the number of thinned portions in the width direction, and T ３ indicates the thickness of the thick portion of the second seal portion, and W ４ indicates the width of the thick-walled portion (if there are multiple thick-walled portions, the total width of the thick-walled portions), and W ５indicates the width of each thick portion, and the "number of lines" of the thick portion indicates the number of thick portions in the width direction.

[0152] The initial thickness of the intercellular structure of Example 1 (unpressurized thickness measured under atmospheric pressure at 25°C) was 21.5 mm. The initial thickness was measured at the center of the intercellular structure using a digital thickness gauge J-B (measuring probe Φ50 mm, minimum scale 0.05 mm) manufactured by Ozaki Manufacturing Co., Ltd. The thicknesses of the first and second sealed portions were calculated by subtracting twice the total thickness of the layers of Film A other than the innermost layer (sealant resin layer) from the total thickness of the sealed portion measured using a dial thickness gauge H-1A manufactured by Ozaki Manufacturing Co., Ltd. The surface area (internal surface area) of the bag material constituting the bag body facing the sealed space was 50 mm × 50 mm × 2, and the volume of air accommodated in the sealed space (measured by the method described below) was 46.3 cm ３ From these values, the gas amount G of the inter-cell structure according to Example 1 was calculated as (46.3 × 10 －３ ) / (0.050 x 0.050 x 2 / 2) = 18.5 L / m ２ It is calculated as follows.

[0153] (Examples 2 to 7, Comparative Examples 1 and 3) The intercellular structures of each example were produced in the same manner as Example 1, except that the type of film used and the dimensions of the sealed portion formed by heat sealing were as shown in Table 2, and the amount of air when heat sealing the fourth side was adjusted to the gas amount G shown in Table 2. In the intercellular structure of Comparative Example 1, the sealed portion had a uniform thickness, and the dimensions of such a sealed portion are conveniently shown in the column for the first sealed portion in Table 2 (the same applies to the other Comparative Examples).

[0154] Example 8 Two sheets of film A were cut into 70 mm squares, and one sheet of porous sheet (glass wool A) was cut into a 45 mm square. The porous sheet was sandwiched between two sheets of film A with the heat-sealable surface (CPP layer side) of film A facing inward, and the two sheets were overlapped. Three sides of the two sheets of film A were heat-sealed while applying a load sufficient to compress the porous sheet (enough to enable heat sealing) (first sealing step). For the heat sealing, a Fuji Impulse heat-sealing machine, model "OPL-300-10," and a pair of heat-sealing dies sandwiching the object to be sealed were used. In the first sealing step, a seal width of 10.0 mm was applied to each side of the two sheets of film A at 180°C for 4 seconds. After heat-sealing one side, the two sheets were cooled to 45°C before heat-sealing the next side. The mold surfaces of the pair of heat-sealing molds used in this example had a surface texture for forming first and second seal portions within the seal portions, with the dimensions shown in Table 2 (the mold surfaces of the pair of heat-sealing molds had a surface texture that was line-symmetrical with respect to the object to be sealed, which was sandwiched between the mold surfaces.) Next, the load was released, allowing a predetermined amount of air to enter between the two sheets of film A, and the remaining side (the fourth side) of film A was similarly heat-sealed with a seal width of 10.0 mm (second sealing step).

[0155] In this manner, an intercellular structure of Example 8 was obtained, which consisted of a bag body configured such that air and glass wool A (porous sheet) were contained in a sealed space partitioned by two sheets of film A (bag material). The intercellular structure of Example 8 had a sealed portion including first and second sealed portions with the dimensions shown in Table 2. The initial thickness (unpressurized thickness measured under atmospheric pressure at 25°C) of the intercellular structure of Example 8 was 20.5 mm. The volume of air contained in the sealed space in Example 8 (measured by the method described below) was 45.0 cm3. ３ The gas amount G of the inter-cell structure according to Example 8 was (45.0 × 10 －３ ) / (0.050 x 0.050 x 2 / 2) = 18.0 L / m ２ It is calculated as follows.

[0156] (Examples 9 and 10, Comparative Example 2) The inter-cell structures of each example were produced in the same manner as in Example 8, except that the types of film and porous sheet used and the dimensions of the first and second sealed portions formed by heat sealing were as shown in Table 2, and the amount of air when heat sealing the fourth side was adjusted to the gas amount G shown in Table 2.

[0157] <Measurement and Evaluation> (Measurement of the Volume V of Gas Contained in the Sealed Space of the Bag) The volume V of gas contained in the sealed space partitioned by the bag material was measured by the underwater displacement method as follows. Specifically, pure water was placed in a cylindrical acrylic resin container with a bottom, an inner diameter of 50 mm, an outer diameter of 60 mm, and a depth of 80 mm. The container was then filled with pure water by placing a lid on the container, which had a diameter of 49.5 mm, a thickness of 10 mm, and a circular plate with a 2 mm diameter through-hole formed in the center and a 10 mm wide flange extending from the top end of the circular plate, to ensure that no air remained inside. The weight (W1) of the container containing pure water was measured to two decimal places. Next, the bag to be measured was placed in the container containing pure water in the same manner as above, and the lid with the through-hole was placed on top, filling the container with pure water, and the weight (W2) was measured. Furthermore, the volume (FV) of the bag material constituting the bag was calculated from the width x height x thickness x 2 sheets. Using these results, the volume V of the gas contained in the sealed space of the bag (volume at 1 atmosphere and 23°C) was calculated using the following formula. The results are shown in Table 2. Gas volume V = {(m Ｓ,Ｌ +m Ｓ,Ａ ) ÷ ρ Ｌ}-FV m Ｓ,Ｌ : Weight of container filled with pure water (W1) - Weight of container filled with pure water and containing bag (W2) m Ｓ,Ａ ρ: Weight of the bag measured by a weighing scale (i.e., the total weight of the bag material constituting the bag and the contents other than the gas contained in the bag, assuming that the weight of the gas can be ignored) Ｌ : Density of the liquid (water in this case) in the container

[0158] (Compression-release cycle test) Using a hydraulic servo fatigue endurance tester (EHF UV50kN, manufactured by Shimadzu Corporation) under an environment of 25 ° C. and 50% RH, the intercellular structure according to each example was compressed at a compression rate of 0.3 mm / sec until the compressive stress reached 3.45 MPa (zeroth compression), then released at a compression rate of 0.3 mm / sec until the compressive stress reached 0.34 MPa (first release), and then compressed at a compression rate of 0.3 mm / sec until the compressive stress reached 3.45 MPa (first compression). This compression-release operation between 3.45 MPa and 0.34 MPa was considered as one cycle, and a compression-release cycle test was performed in which this cycle was repeated 3650 times. During this time, actual measurement data of the stroke (thickness of the intercellular structure) and load were collected at 0.5 second intervals. The obtained measured data was graphed with time on the X axis and thickness change on the Y axis, and the first number at which the maximum thickness began to decrease continuously in each cycle was evaluated as the cycle durability of the inter-cell structure.

[0159] (Gas Reduction Rate) For the inter-cell structures according to each example, a first compression test, a durability test, and a second compression test were carried out in this order as described below, and the gas reduction rate due to the durability test was investigated.

[0160] In the first compression test, a precision universal testing machine (Autograph AGS-10kNX, manufactured by Shimadzu Corporation) was used to measure the compressive stress and thickness of the intercellular structure or its bag body while compressing the intercellular structure in its thickness direction at a compression rate of 0.1 mm / sec (first stress-thickness measurement). Compression was carried out until the compressive stress reached a predetermined value exceeding 1.00 MPa. In this stress-thickness measurement, the thickness of the intercellular structure when the compressive stress reached 1.00 MPa was defined as the 1 MPa initial thickness. The 1 MPa initial thickness of the intercellular structure for each example is shown in Table 2.

[0161] In the durability test, first, the intercellular structure was compressed in the thickness direction until its initial thickness became 1 MPa and restrained with a jig, and then the intercellular structure was kept restrained with the jig for 1000 hours in an environment of 1 atmosphere, 25°C, and a relative humidity of 50% RH (in this test, when gas leaks from the bag in the intercellular structure, the internal pressure in the sealed space of the bag gradually decreases, and the compressive stress decreases). Thereafter, the intercellular structure was removed from the jig.

[0162] In the second compression test, a precision universal testing machine (Autograph AGS-10kNX, manufactured by Shimadzu Corporation) was used to measure the thickness and compressive stress of the intercellular structure or its bag while compressing the intercellular structure in its thickness direction at a compression rate of 0.1 mm / sec (second stress-thickness measurement). Compression was carried out until the compressive stress reached a predetermined value exceeding 1.00 MPa. In this stress-thickness measurement, the compressive stress when the intercellular structure reached its initial thickness of 1 MPa was taken as the stress Ps (MPa) after the durability test. The stress Ps (MPa) after the durability test for each example of the intercellular structure is shown in Table 2.

[0163] The difference between the compressive stress (1.00 MPa) at an initial thickness of 1 MPa in the first compression test before the durability test and the compressive stress (Ps MPa) at an initial thickness of 1 MPa in the second compression test after the durability test reflects the difference in the amount of gas present in the sealed space of the bag body of the inter-cell structure (specifically, the change in the amount of gas lost due to the durability test). For the inter-cell structure of each example, the rate of gas loss in the sealed space due to the durability test was calculated using the following formula. The gas loss rates (%) for the inter-cell structures of each example are shown in Table 2.

[0164] Gas reduction rate (%) = {(1.00 [MPa] - Ps [MPa]) / 1.00 [MPa]} x 100

[0165]

[0166] As shown in Table 2, all of the inter-cell structures of Examples 1 to 10 (in which the sealed portion of the bag body included a first sealed portion and a second sealed portion) had excellent cycle durability and suppressed gas reduction rates. Examples 1 to 6 showed particularly low gas reduction rates. In contrast, the inter-cell structures of Comparative Examples 1 and 3, in which the sealed portion was too thick, had significantly higher gas reduction rates than the inter-cell structures of Examples 1 to 10. Furthermore, the inter-cell structure of Comparative Example 2, in which the sealed portion was too thin, had significantly lower cycle durability than the inter-cell structures of Examples 1 to 10.

[0167] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0168] The inter-cell structure of the present invention can be applied to, for example, a battery module or a battery pack, and can be particularly suitably applied to a battery module or a battery pack including a secondary battery such as a lithium-ion secondary battery.

[0169] REFERENCE SIGNS LIST 1 inter-cell structure 10 porous sheet 20 gas 30 bag body 31, 31A, 31B bag material 31a sealant resin layer 31b resin layer 31c metal layer 32 sealing edge 50 battery module 51 lithium ion battery cell F laminated film S seal portion S1 first seal portion S2 second seal portion Sa thin portion Sb thick portion

Claims

An inter-cell structure disposed between adjacent cells in a battery module or battery pack including an array of lithium ion battery cells, the inter-cell structure comprising: The device includes a bag body having a bag material that defines a sealed space and a fluid including at least a gas in the sealed space, the bag material is formed from a laminated film including a metal layer and a sealant resin layer, and has a seal portion formed by joining the sealant resin layers of the laminated film to each other and sealing the sealed space; The seal portion is an inter-cell structure including a relatively thick first seal portion facing the sealed space, and a second seal portion located on the opposite side of the first seal portion from the sealed space, the second seal portion having a relatively thin portion adjacent to the first seal portion. 　 The inter-cell structure according to claim 1 , wherein the second seal portion is entirely the thin-walled portion. 　 The first seal portion has a thickness T of 100 μm or more. １ The intercell structure of claim 1 , having: 　 The first seal portion has a width W of 0.7 mm or more. １ The intercell structure of claim 1 , having: 　 The thickness T of the first seal portion １ The thickness T of the thin-walled portion ２ The intercellular structure of claim 1 , wherein the ratio is 0.85 or less. 　 The thin-walled portion has a width W of 2.0 mm or more. ２ The intercell structure of claim 1 , having: 　 The width W of the first seal portion １ The width W of the thin portion ２ The intercellular structure of claim 1 , wherein the ratio is 0.70 or greater. 　 The inter-cell structure according to claim 1 , wherein a width W of the seal portion including the first seal portion and the second seal portion is 5.0 mm or more. 　 The intercellular structure according to claim 1 , wherein the bag further comprises a porous sheet within the sealed space. 　 The inter-cell structure according to claim 1 , wherein the first seal portion extends over the entire length of the seal portion along the sealed space.

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