Inter-cell structure

Abstract

In a battery module or a battery pack including a plurality of arranged battery cells, an inter-cell structure used by being arranged between adjacent cells among the plurality of cells is provided. The inter-cell structure includes a bag body having a bag material, and a fluid stored in a sealed space partitioned by the bag material.

Description

Inter-cell structure

[0001] The present invention relates to an inter-cell structure disposed between a plurality of arranged battery cells. This application claims priority to Japanese Patent Application No. 2024-036039, filed on March 8, 2024, the entire contents of which are incorporated herein by reference.

[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 a 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 Application 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 electrode expansion evaluation, JSR Corporation, JSR Technical Review No. 125 (March 2018) Effect of Pressure and Mechanical Properties of Stacked Separators on Electrode Reactions of Lithium Metal Anodes, 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 / Authors (January 2023)

[0007] As mentioned above, lithium-ion battery cells repeatedly expand due to charging and contract due to discharging, and also undergo irreversible expansion. Therefore, 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 stacking 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 cells themselves (e.g., Patent Document 2, Non-Patent Document 3, Non-Patent Document 4). Even in a battery module, etc. that integrates battery cells other than lithium-ion battery cells, the gap between cells may accidentally or repeatedly change due to dimensional changes in the cell stacking direction, external forces, etc., and it is desirable to buffer such changes.

[0008] Therefore, an object of the present invention is to provide an intercell structure that is disposed between a plurality of arranged battery cells and can buffer variations in the gap between adjacent cells with good adaptability. One object of the present invention is to provide an intercell structure that is disposed between a plurality of arranged lithium ion battery cells and has buffering properties that can change in thickness with good adaptability in response to repeated expansion and contraction of 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 battery cells. The inter-cell structure includes a bag having a bag material and a fluid contained in an enclosed space partitioned by the bag material. The inter-cell structure having such a configuration can buffer fluctuations in the gap between adjacent cells with good compliance by causing the bag containing the fluid in the enclosed space to function as a fluid spring. The battery cells may be cells of a non-aqueous electrolyte secondary battery, such as lithium-ion battery cells.

[0010] In some preferred embodiments, the battery cells are lithium-ion battery cells. Accordingly, this specification provides an inter-cell structure that is disposed between adjacent cells in a battery module or battery pack including an array of lithium-ion battery cells. The inter-cell structure includes a bag having a bag material and a fluid contained in an enclosed space partitioned by the bag material. An inter-cell structure having such a configuration can exhibit cushioning properties, capable of changing its thickness appropriately and flexibly in response to repeated cell expansion and contraction, by causing the bag containing the fluid in the enclosed space to function as a fluid spring.

[0011] It is preferable that at least a gas is contained as the fluid in the sealed space, which allows the bag to function as a gas spring and makes it easier to exhibit high followability to fluctuations in the gap between cells (for example, fluctuations in the gap between cells due to repeated expansion and contraction of the cells).

[0012] In some embodiments, the sealed space may contain a gas and a liquid as the fluid. By containing a liquid together with a gas in the sealed space, it is possible to adjust the compression characteristics of the bag and the inter-cell structure including the bag.

[0013] In some aspects of the intercellular structure in which at least a gas is contained in a sealed space partitioned by a bag material, the bag material has a 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 1.0 L / m ２ This makes it easier to achieve a cushioning effect that allows the thickness to change with good follow-up in response to variations in the gap between the cells (for example, variations in the gap between the cells due to repeated expansion and contraction of the cells).

[0014] The gas contained in the sealed space is preferably mainly composed of a non-flammable gas, for example, more than 50% (by volume) of the gas is preferably composed of one or more gases selected from the group consisting of nitrogen, argon, carbon dioxide, neon, helium, krypton, and xenon.

[0015] The bag material preferably includes a laminate film including a metal layer and a resin layer as a constituent material. A laminate film having such a configuration can easily form a bag body that combines the gas barrier properties provided by the metal layer with the ease of deformation (cushioning properties) and formability provided by the resin layer.

[0016] In battery packs including multiple nonaqueous electrolyte secondary batteries (e.g., lithium-ion secondary batteries), the use of components with various functions to ensure safety and other aspects has been considered. For example, insulating materials are placed between cells to prevent thermal runaway even if some cells abnormally heat up. The inter-cell structure disclosed herein can preferably function as an insulating material between cells by further including an insulating layer. This makes it possible to realize an inter-cell structure that combines buffering and insulating properties between cells. The insulating layer may be placed within a sealed space partitioned by the bag material (i.e., inside the bag) or outside the bag.

[0017] From the viewpoint of heat insulating performance, the heat insulating layer preferably contains inorganic particles. The inorganic particles preferably contain at least one type of silica particles selected from the group consisting of dry silica, wet silica, and silica aerogel as a main component. In some embodiments, a heat insulating layer containing inorganic particles and inorganic fibers can be preferably used from the viewpoint of strength, durability, etc.

[0018] 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.

[0019] 1 is a perspective view schematically showing an example of a battery module in which an inter-cell structure according to one embodiment is arranged between adjacent battery cells. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is a cross-sectional view schematically showing an inter-cell structure according to one embodiment. FIG. 4 is a cross-sectional view schematically showing an inter-cell structure according to another embodiment. FIG. 5 is a stress-strain curve (SS curve) schematically showing a loading-unloading test.

[0020] 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.

[0021] In this specification, unless otherwise specified, the use of "to" indicating a range of values ​​means that the range includes the values ​​before and after it as the lower and upper limits.

[0022] 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."

[0023] The inter-cell structure disclosed in this specification includes at least a bag having a configuration in which a fluid is contained in a sealed space. The bag includes a bag material and the fluid is contained in the sealed space defined by the bag material. In some embodiments, the inter-cell structure may further include a thermal insulating layer disposed inside or outside the bag.

[0024] <Bag Material> The bag material constituting the bag body is typically in the form of a sheet and may have a single-layer structure or a laminated structure. Non-limiting examples of layers that may be included in the bag material include metal layers (metal foils, metal films, etc.) such as aluminum layers, copper layers, and stainless steel layers; resin layers (films, coatings, etc.) such as polyester layers (polyethylene terephthalate (PET) layers, polybutylene terephthalate layers, polyethylene naphthalate layers, etc.), polyimide layers, polycarbonate (including flame-retardant polycarbonates), nylon layers, polypropylene layers, polyethylene layers, and acrylic resin layers (typically polymethyl methacrylate layers); and woven layers such as glass cloth, silica cloth, aramid cloth, resin-impregnated glass cloth, resin-impregnated silica cloth, and resin-impregnated aramid cloth. Examples of the nylon layer include biaxially oriented nylon (ONY) film and non-oriented nylon film. Examples of the polypropylene layer include non-oriented polypropylene (CPP) film and biaxially oriented polypropylene (OPP) film.

[0025] In some embodiments, a laminate film may be preferably used as the bag material. In embodiments in which the fluid contained in the bag includes a gas, a bag material including a metal layer may be preferably used from the viewpoint of gas barrier properties. Among these, a laminate film including at least one metal layer and at least one resin layer is preferred, and a laminate film configured by laminating a first resin layer, a metal layer, and a second resin layer in this order from the outside of the bag body is more preferred. Although not particularly limited, a suitable example of the metal layer is an aluminum layer. Suitable examples of the first resin layer include an ONY layer and a PET layer. Examples of the second resin layer include a CPP layer and a PE layer. A CPP layer with a high melting point is particularly preferred. The second resin layer may be a heat-seal layer that is welded when forming the bag body from the bag material.

[0026] In some embodiments, the bag material constituting the bag body is desirably resistant to expansion and contraction deformation, has a high Young's modulus, and is highly rigid, from the viewpoint of controllability of shape change associated with fluctuations in the gap between cells (e.g., fluctuations in the gap between cells 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 laminated 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 appropriately set 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.

[0027] 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.

[0028] The thickness of the bag material is not particularly limited and may be, for example, 0.03 mm to 1.00 mm, preferably 0.05 mm or more, more preferably 0.07 mm or more, even more preferably 0.08 mm or more, or 0.10 mm or more, and preferably 0.8 mm or less, more preferably 0.6 mm or less, even more preferably 0.4 mm or less, and may be 0.3 mm or less or 0.2 mm 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 (cushioning properties) of a fluid spring and the mechanical strength of the bag body. The thickness of the bag material can be measured at several locations (e.g., 10 locations) using a thickness measuring device (e.g., Ozaki Manufacturing's Digital Thickness Gauge H-1A (5 mm Φ probe)). If the nominal value of the bag material thickness is provided by the manufacturer, that nominal value may be used.

[0029] In embodiments in which the bag material includes a metal layer, the thickness of the 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, may be 10 μm or more, may be 20 μm or more, or may be 30 μm or more. Furthermore, in some embodiments, from the viewpoint of suppressing heat conduction through the bag body, the thickness of the metal layer is suitably 100 μm or less, advantageously 80 μm or less, preferably 60 μm or less, may be 50 μm or less, may be 40 μm or less, may be 30 μm or less, or may be 20 μm or less. The thickness of the metal layer can be 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.

[0030] <Fluid> The bag constituting the intercellular structure disclosed herein forms a sealed space partitioned by the bag material, and a fluid is contained in the sealed space. It is preferable that at least a gas is contained as the fluid in the sealed space. This allows the bag to function as a gas spring, making it easier to realize an intercellular structure that exhibits high compliance with variations in the gap between cells (e.g., variations in the gap between cells due to repeated expansion and contraction of the cells). Here, "containing at least a gas" as the fluid means that the fluid 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 chromatography or infrared absorption spectroscopy (IR) can be used to analyze gases, and IR, nuclear magnetic resonance spectroscopy (NMR), liquid chromatography, etc. can be used to analyze liquids and solids.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] In some embodiments, the sealed space may contain a gas and a liquid as the fluid. By containing a liquid together with a gas in the sealed space, it is possible to adjust the compressive properties (e.g., the value of compressive strain at a predetermined compressive stress) of the bag body and the intercellular structure including the bag body. The liquid may be, for example, water or an aqueous solution, but is not limited to these.

[0037] The amount of fluid contained in the sealed space is not particularly limited, and can be adjusted as appropriate, taking into consideration the type of fluid, the size of the sealed space, the manner of use of the inter-cell structure, etc., so as to exhibit appropriate properties (e.g., cushioning properties) according to the purpose.

[0038] 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 the gas contained 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 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 variations in the gap between cells (for example, variations in the gap between cells due to repeated expansion and contraction of the cells). 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.

[0039] 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.

[0040] 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 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 an increase in the size of the inter-cell structure, in some embodiments, the ２ It is appropriate that the flow rate is 30 L / m or less. ２ Preferably, the flow rate is 20 L / m or less. ２ More preferably, it is 15 L / m or less. ２ or less, and ２ It may be the following:

[0041] <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 (e.g., laminated film), or one sheet 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 cylindrical sheet is used as the bag material, the number of bag materials is also considered to be two.

[0042] The bag body can be formed, for example, by placing two sheet-like bag materials opposite each other and sealing the opposing surfaces of the bag materials in a ring shape. The method for sealing the opposing surfaces of the bag materials is not particularly limited, and examples include welding methods such as heat welding and ultrasonic welding; and bonding methods using adhesives or pressure-sensitive adhesives. The welding may be performed by directly welding the resin of the bag material, or by providing a separate resin layer for welding. When a single sheet is folded to form two bag materials, sealing the edges corresponding to the folded portions can be omitted as appropriate. When a cylindrical sheet is used as the bag material, an airtight space can be formed by sealing both open ends of the tube, and sealing the edges corresponding to one or both widthwise ends of the tube can be omitted as appropriate.

[0043] In the technology disclosed herein, the method for realizing a configuration in which a fluid is contained in 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 fluid is already contained, or the fluid (e.g., gas) may be generated in the sealed space after the sealed space is formed. An intermediate or combined method of these may also be employed. Examples of methods for generating gas in a sealed space include methods that generate gas through a chemical reaction. Specific examples include a method of generating carbon dioxide gas by reacting sodium bicarbonate with an aqueous citric acid solution, or a method of generating carbon dioxide gas by reacting an isocyanate with water. Either one of the components (e.g., sodium bicarbonate) of the sodium bicarbonate or the aqueous citric acid solution may be encapsulated, or each component may be encapsulated separately, and the capsules may be broken by pressure or other means 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.

[0044] 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.

[0045] 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.

[0046] The pouch constituting the inter-cell structure disclosed herein may have a thickness measured under an applied pressure of 0.03 MPa (hereinafter also referred to as the "thickness at 0.03 MPa") within a range of, for example, approximately 0.5 mm to 50 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 0.03 MPa is preferably 1 mm or more, more preferably 1.5 mm or more, even more preferably 2 mm or more, and may be 3 mm or more, or may be 4 mm or more. Furthermore, in some embodiments, the thickness of the pouch at 0.03 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.

[0047] The thickness of the bag body when a pressure of 0.03 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 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 0.03 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-5kNX 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.

[0048] <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.

[0049] The heat 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 secondary battery (for example, a non-aqueous electrolyte secondary battery such as a lithium ion battery). In some embodiments, a heat insulating layer containing inorganic particles can be preferably used from the viewpoint of heat insulating performance, etc. 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 (Fe ３ 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.

[0050] 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.

[0051] 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.

[0052] 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. Examples of methods for determining the average primary particle diameter of silica particles include methods using electron microscopes such as scanning electron microscopes (SEMs) and transmission electron microscopes (TEMs). 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.

[0053] 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 for measuring using the same method as for the primary particle size can be mentioned.

[0054] 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, and preferably 350m ２ / g or less, more preferably 320m ２ / 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.

[0055] 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.

[0056] 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.

[0057] 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, and even more preferably 80% by mass or more, and is 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.

[0058] 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.

[0059] 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, and even more preferably 5% by mass or more, and is 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, good thermal resistance is easily ensured and the heat insulating layer is easily manufactured.

[0060] 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 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.

[0061] 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 is preferably 25 μm or less, more preferably 20 μm or less, 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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 can be 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. Reducing the thickness of the insulating layer can reduce the thickness and weight of the inter-cell structure. The thickness of the insulating layer can be measured at several locations (e.g., 10 locations) on the cross section of the insulating layer using a thickness gauge (e.g., a digital thickness gauge JAN-257 (measuring tip Φ20 mm) manufactured by Ozaki Manufacturing Co., Ltd.).

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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).

[0077] 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].

[0078] 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 1.39 MPa (hereinafter also referred to as "1.39 MPa compression strain"; similar expressions apply) may be, for example, 45% or less or 40% or less. From the viewpoints of durability and suppression of powder generation, the compressive strain value is preferably 30% or less or 25% or less, advantageously 20% or less, and may be 18% or less, 15% or less, or 13% or less. The 1.39 MPa compression strain of the thermal insulation layer is greater than 0%, and may be, for example, 5% or more, 7% or more, 10% or more, 12% or more, or 15% or more. A thermal insulation layer having a 1.39 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.

[0079] In some embodiments in which the intercellular structure disclosed herein includes a thermal insulation layer, the thermal insulation layer's strain at 1.00 MPa compression 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 thermal insulation layer's strain at 1.00 MPa compression 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 strain at 1.00 MPa compression 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.

[0080] In some embodiments in which the intercellular structure disclosed herein includes a thermal insulation layer, the thermal insulation layer constituting the intercellular structure suitably has a strain at 0.34 MPa compression of 30% or less, preferably 20% or less, and more preferably 15% or less. The strain at 0.34 MPa compression of the thermal insulation layer is greater than 0%, and may be, for example, 3% or more, 5% or more, 7% or more, or 9% or more. A thermal insulation layer having a strain at 0.34 MPa compression within any of the above ranges is likely to realize an intercellular structure with good thermal insulation and cushioning properties (e.g., good compression characteristics in the loading-unloading test described below).

[0081] 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).

[0082] 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.

[0083] 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).

[0084] 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.

[0085] 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.

[0086] 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, and 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.

[0087] 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 also 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 more, and also preferably 4 hours or less, more preferably 2 hours or less, and even more preferably 1 hour or less. When the mixing time is within the above range, the heat insulating layer can be easily produced efficiently.

[0088] The consistency (or penetrability) 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: Penetration Test Method," and in particular, can be measured as "unmixed penetration." More specifically, the consistency of the mixed liquid can be measured by the method described in the Examples below.

[0089] 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.

[0090] 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.

[0091] <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.

[0092] 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.

[0093] 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 battery cells (here, rectangular lithium-ion battery cells) 51 arranged in the thickness direction, with an inter-cell structure 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.

[0094] FIG. 3 shows an enlarged view of the intercell structure 1 shown in FIG. 2. This intercell structure 1 has a bag body 30 in which two pieces of bag material 31A, 31B are sealed by bonding (e.g., heat sealing) at seal portions 32 provided along the outer edges of the bag materials. An enclosed space partitioned by the bag materials 31A, 31B is formed inside the bag body, and this enclosed space contains a fluid (e.g., air) 20 and also contains a thermal insulating layer 10. By sandwiching the intercell structure 1 configured in this way between two adjacent battery cells 51, 51 as shown in FIG. 2, the intercell structure 1 exerts a buffering function by the fluid spring between the battery cells 51, 51 and also exerts the effect of insulating between the opposing surfaces 51 a, 51 a.

[0095] While Figure 3 shows a configuration in which the insulating layer 10 is housed together with a fluid inside the bag body 30 (inside the sealed space), the insulating layer 10 may be disposed outside the bag body 30, for example, as shown in Figure 4. Alternatively, the inter-cell structure may be configured without an insulating layer. Also, although Figures 3 and 4 show an example of a configuration in which the inter-cell structure 1 has only one insulating layer 10, the number of insulating layers may be two or more. In a configuration including two or more insulating layers, the insulating layers may be disposed adjacent to each other, or may be disposed separately, for example, on the inside and outside of the bag body 30.

[0096] The intercell structure disclosed herein may have a thickness measured under an applied pressure of 0.03 MPa (thickness at 0.03 MPa) in the range of, for example, approximately 0.5 mm to 80 mm. When the thickness of the intercell structure is within this range, it is easy to appropriately buffer stress generated by battery expansion. From the viewpoint of easily achieving a good balance between cushioning and heat insulation, in some embodiments, the thickness of the intercell structure at 0.03 MPa is preferably 1 mm or more, more preferably 1.5 mm or more, even more preferably 2 mm or more, and may be 3 mm or more, or may be 4 mm or more. In some embodiments, the thickness of the pouch at 0.03 MPa is preferably 60 mm or less, more preferably 40 mm or less, even more preferably 30 mm or less, and may be 20 mm or less, 10 mm or less, 7 mm or less, 6 mm or less, or 5 mm or less. The thickness of the intercell structure at 0.03 MPa is measured in the same manner as the thickness of the pouch at 0.03 MPa.

[0097] In some embodiments of the intercell structure disclosed herein, the strain of the intercell structure when subjected to 0.03 MPa during loading may be, for example, 3% or more or 5% or more, preferably 10% or more, and may be 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, or 45% or more. The strain of the intercell structure when subjected to 0.03 MPa during loading is calculated using the following formula: 1 - (thickness during loading when subjected to 0.03 MPa / thickness at 0 MPa). The strain of the intercell structure when subjected to 0.03 MPa during loading may be, for example, 75% or less, preferably 70% or less, and may be 65% or less, 60% or less, 50% or less, 40% or less, 35% or less, 25% or less, or 20% or less. If the strain when 0.03 MPa is applied is within any of the above ranges, it is easy to obtain a cushioning property that allows the thickness to change with good follow-up in response to repeated expansion and contraction of the cell.

[0098] In some embodiments of the intercell structure disclosed herein, the strain of the intercell structure when subjected to 1.39 MPa may be, for example, 25% or more, advantageously 35% or more, preferably 45% or more, more preferably 50% or more or 55% or more, and may be 60% or more or 65% or more. The strain of the intercell structure when subjected to 1.39 MPa is calculated by the following formula: 1 - (thickness when subjected to 1.39 MPa / thickness at 0 MPa). The strain of the intercell structure when subjected to 1.39 MPa may be, for example, 90% or less, preferably 80% or less, and may be 75% or less. When the strain of the intercell structure when subjected to 1.39 MPa is within any of the above-mentioned ranges, cushioning properties are likely to be obtained that allow the thickness to change with good follow-up in response to repeated cell expansion and contraction, etc. In addition, in an inter-cell structure in which an insulating layer is arranged inside the bag body, it is preferable that the thickness of the insulating layer is smaller than the thickness of the inter-cell structure when a pressure of 1.39 MPa is applied (for example, the thickness of the insulating layer is 99% or less, 90% or less, or 80% or less of the thickness of the inter-cell structure when a pressure of 1.39 MPa is applied).

[0099] In some embodiments of the intercell structure disclosed herein, the strain when 0.03 MPa is applied during the unloading process of the intercell structure may be, for example, 3% or more, or 5% or more, preferably 10% or more, and may be 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, or 45% or more. The strain when 0.03 MPa is applied during the unloading process of the intercell structure is calculated using the following formula: 1 - thickness when 0.03 MPa is applied during the unloading process / thickness at 0 MPa). The strain when 0.03 MPa is applied during the unloading process of the intercell structure may be, for example, 75% or less, preferably 70% or less, and may be 65% or less, 60% or less, 50% or less, 40% or less, 35% or less, 25% or less, or 20% or less. An intercell structure having a strain when 0.03 MPa is applied within any of the above-mentioned ranges is likely to provide good cushioning properties.

[0100] In some embodiments of the intercellular structure disclosed herein, the strain of the intercellular structure during the loading process from an applied pressure of 0.03 MPa to 1.39 MPa (corresponding to the strain B / A shown in Tables 2 and 3 in the examples described below) is suitably greater than 10% (e.g., 15% or more), preferably 20% or more, more preferably 25% or more, and may be 30% or more (e.g., 35% or more), 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more. The strain (B / A) may be, for example, 95% or less, and in some embodiments, suitably 90% or less, or may be 85% or less, 80% or less, 75% or less, 70% or less, 60% or less, or 50% or less. When the strain (B / A) is within any of the above-mentioned ranges, it is easy to obtain a cushioning property that allows the thickness to change with good tracking in response to repeated cell expansion and contraction, etc.

[0101] In some embodiments of the intercellular structure disclosed herein, the strain of the intercellular structure during the unloading process from an applied pressure of 1.39 MPa to 0.03 MPa (corresponding to the strain C / A shown in Tables 2 and 3 in the examples described below) may be, for example, 10% or more, preferably 20% or more, more preferably 25% or more, 30% or more (e.g., 35% or more), 40% or more, 50% or more, 60% or more, or 70% or more. The strain (C / A) may be, for example, 95% or less, and in some embodiments, suitably 90% or less, or may be 85% or less, 80% or less, 75% or less, 70% or less, 60% or less, or 50% or less. When the strain (C / A) is within any of the above-mentioned ranges, it is easy to obtain cushioning properties that allow the thickness to change with good tracking in response to repeated cell expansion and contraction, etc.

[0102] 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.

[0103] 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.

[0104] The matters disclosed in this specification include the following. [1] An inter-cell structure used in a battery module or battery pack including a plurality of arranged battery cells, and disposed between adjacent cells of the plurality of cells, the inter-cell structure including a bag body having a bag material and a fluid contained in a sealed space partitioned by the bag material. [2] An inter-cell structure used in a battery module or battery pack including a plurality of arranged lithium ion battery cells, and disposed between adjacent cells of the plurality of cells, the inter-cell structure including a bag body having a bag material and a fluid contained in a sealed space partitioned by the bag material. [3] The inter-cell structure according to [1] or [2] above, in which the sealed space contains at least a gas as the fluid. [4] The inter-cell structure according to [1] or [2] above, in which the sealed space contains a gas and a liquid as the fluid. [5] A surface area A [m2] of the bag material facing the sealed space 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 ２The intercellular structure according to [3] or [4] above, wherein G=V / (A / 2). [6] The intercellular structure according to any of [3] to [5] 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. [7] The intercellular structure according to any of [1] to [6] above, wherein the bag material contains, as a constituent material, a laminated film including a metal layer and a resin layer. [8] The intercellular structure according to any of [1] to [7] above, further including a heat insulating layer. [9] The intercellular structure according to [8] above, wherein the heat insulating layer contains inorganic particles.

[10] The intercellular structure according to [9] above, wherein the inorganic particles contain, as a main component, at least one type of silica particles selected from the group consisting of dry silica, wet silica, and silica aerogel.

[11] The inter-cell structure according to any one of [8] to

[10] above, wherein the heat insulating layer is disposed inside the sealed space.

[12] The inter-cell structure according to any one of [8] to

[10] above, wherein the heat insulating layer is disposed outside the bag body.

[0105] 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.

[0106] <Materials Used> The intercellular structures according to the examples described below were fabricated using the following materials.

[0107] (Bag material) Film A: Aluminum laminate film manufactured by Resonac, trade name "SPALF" (a laminated film of biaxially oriented nylon (ONY, 15 μm) / aluminum (35 μm) / unstretched polypropylene (CPP, 30 μm)) was used. Film B: Aluminum laminate film high resistance packaging material type B manufactured by TOPPAN (a laminated film of PET (12 μm) / aluminum (7 μm) / biaxially oriented nylon (ONY, 15 μm) / polyethylene (PE, 150 μm)) was used.

[0108] The composition (manufacturer's nominal information), Young's modulus, and tensile strength of each film are shown in Table 1. Young's modulus (tensile elasticity) was measured in accordance with JIS-K-7161 at 25°C and 50% RH at a pulling speed of 5 mm / min. Tensile strength was measured in accordance with JIS K 7127 or JIS C 2318-72 at 25°C and 50% RH at a pulling speed of 5 mm / min.

[0109]

[0110] (Thermal insulation layer) Thermal insulation 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, to which 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 100 parts by mass of Kao Corporation's Kotamin 24P (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 then 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. The coating film was then applied to a thickness of 1.0 mm and a density of 0.3 to 0.5 g / cm ３ The mixture was compressed and molded into a sheet shape using a hot press machine, and then dried at 100°C for 10 minutes to produce a molded body (heat insulating layer A) made of a mixture containing hydrophilic fumed silica, glass fiber, graphite, and a non-polymeric dispersant. The resulting heat insulating layer A had a thickness of 1.0 mm and a density of 0.37 g / cm. ３ The thermal conductivity (800°C, 0.10 MPa) of the heat insulating layer A itself measured according to the method described below was 0.075 (W / m·K).

[0111] Heat insulating layer B: The thickness of the coating film formed from the above mixed solution was changed to 3.0 mm, and the thickness of the coating film compression molded in a hot press was changed to 1.5 mm. Except for this, the heat insulating layer B was produced in the same manner as the heat insulating layer A. The thickness of the obtained heat insulating layer B was 1.5 mm and the density was 0.37 g / cm ３ The thermal conductivity (800°C, 0.10 MPa) of the heat insulating layer B itself measured according to the method described below was 0.075 (W / m·K).

[0112] Heat insulating layer C: The thickness of the coating film formed from the above mixed solution was changed to 1.5 mm, and the thickness of the coating film compression molded in a hot press was changed to 0.75 mm. Except for this, a heat insulating layer C was produced in the same manner as the production of the heat insulating layer A. The thickness of the obtained heat insulating layer C was 0.75 mm and the density was 0.37 g / cm ３ The thermal conductivity (800° C., 0.10 MPa) of the heat insulating layer C itself measured according to the method described below was 0.075 (W / m·K).

[0113] During the manufacturing process of the thermal insulation layer, 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., with the weight 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, at room temperature (25°C), 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.

[0114] The thermal conductivity of the thermal insulation layers A to C (alone) 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).)

[0115] 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.

[0116] <Preparation of Intercellular Structure> (Example 1) Two sheets of film B were cut into rectangular shapes measuring 45 mm wide and 120 mm long, and were prepared. They were overlapped with the heat-sealed surface (PE layer side) facing inward, and the other three sides, leaving one short side, were heat-sealed. The heat-sealing was carried out using a heat-sealing machine, model "OPL-300-10," manufactured by Fuji Impulse Co., Ltd., with a seal width of 10 mm on each side, at 200°C for 4 seconds. After cooling to 45°C, one of the short sides was heat-sealed with a predetermined amount of air trapped between the two sheets of film B with the three sides heat-sealed, thereby trapping air between the two sheets of film B. The heat sealing was then carried out sequentially from one short side to the other short side, and the two films B were heat-sealed until the non-heat-sealed area was a rectangle measuring 25 mm in width and 40 mm in length. The heat-sealed area was then cut 2 mm outside the non-heat-sealed area (i.e., so that the seal width was 2 mm). In this way, an intercellular structure was obtained, consisting of a bag body in which air was contained in a sealed space partitioned by two films B (bag material). The surface area (internal surface area) of the bag material constituting the bag body facing the sealed space was 25 mm x 40 mm x 2, and the volume of air contained in the sealed space (measured by the method described below) was 11.5 cm. ３ From these values, the gas amount G of the inter-cell structure according to Example 1 was calculated as (11.5 × 10 －３ ) / (0.025 x 0.040 x 2 / 2) = 11.5 L / m ２ It is calculated as follows.

[0117] Example 2 Two rectangular sheets of film A, each 45 mm wide and 120 mm long, were prepared and stacked with the heat-sealed surface (CPP layer side) facing inward. As in Example 1, the remaining three sides were heat-sealed, leaving one short side. After cooling to 45°C, a heat insulating layer A (cut into a rectangular shape 24 mm wide and 39 mm long) was placed between the two films A with the three sides heat-sealed. One of the short sides was then heat-sealed with a predetermined amount of air inside. The heat sealing was then carried out sequentially from one short side to the other, until the unheat-sealed area was a rectangular shape 25 mm wide and 40 mm long. The heat-sealed portion was then cut 2 mm outside the unheat-sealed area. In this way, an intercellular structure was obtained, consisting of a bag body configured to contain a heat insulating layer A and air in an enclosed space partitioned by two films A (bag material). The amount of gas calculated from the surface area of ​​the bag material facing the sealed space and the volume of air contained in the sealed space is 2.0 L / m ２ It was.

[0118] (Example 3) Two sheets of film A were cut into rectangular shapes with a width of 45 mm and a length of 80 mm, and the amount of air used when heat-sealing one of the short sides was adjusted to the amount of gas shown in Table 2. The intercellular structure of this example was obtained in the same manner as in Example 2.

[0119] (Example 4) Two sheets of film A were cut into rectangular shapes with a width of 45 mm and a length of 100 mm, and the amount of air used when heat-sealing one of the short sides was adjusted to the amount of gas shown in Table 2. The intercellular structure of this example was obtained in the same manner as in Example 2.

[0120] (Example 5) The intercellular structures according to each of Examples 3 to 5 were obtained in the same manner as in Example 2, except that the amount of air used when heat-sealing one of the short sides was adjusted to the amount of gas shown in Table 2.

[0121] (Example 6) An inter-cell structure according to this example was obtained in the same manner as in Example 2, except that film B was used instead of film A and the amount of air used when heat-sealing one of the short sides was adjusted to the amount of gas shown in Table 2.

[0122] (Examples 7 and 8) The inter-cell structures of each example were obtained in the same manner as in Example 2, except that the insulating layer B or C was used instead of the insulating layer A, and the amount of air when heat-sealing one of the short sides was adjusted to the amount of gas shown in Table 2.

[0123] Example 9 Two rectangular pieces of film B, each 45 mm wide and 120 mm long, were prepared and stacked with the heat-sealed surfaces facing inward. The remaining three sides, excluding one short side, were heat-sealed in the same manner as in Example 1. After cooling to 45°C, the resulting sheet was held with one short side facing up. 1.0 g of pure water was poured between the two sheets of film B whose three sides were heat-sealed. A predetermined amount of air was then introduced, and one of the short sides was heat-sealed. The heat-sealing process was continued from one short side to the other short side until the unheat-sealed area formed a rectangular shape measuring 25 mm wide and 40 mm long. The heat-sealed area was then cut 2 mm outside the unheat-sealed area, producing a bag containing air and water in an enclosed space partitioned by two sheets of film B (bag material). Next, a heat insulating layer A (cut into a rectangular shape with a width of 25 mm and a length of 40 mm) was laminated on one outer surface of the bag body, thereby obtaining an intercellular structure including the bag body and the heat insulating layer A laminated on one outer surface thereof.

[0124] (Examples 10 and 11) The amount of pure water placed between the two sheets of film B was set as shown in Table 3, and the amount of air when heat-sealing one of the short sides was adjusted to the amount of gas shown in Table 3. Except for this, the intercellular structures of each example were obtained in the same manner as in Example 9.

[0125] Example 12 Two rectangular pieces of film B, each 45 mm wide and 80 mm long, were prepared and stacked with the heat-sealed surfaces facing inward. The remaining three sides, excluding one short side, were heat-sealed in the same manner as in Example 1. After cooling to 45°C, the bag was held with one short side facing up. A carbon dioxide gas generating agent was placed between the two pieces of film B whose three sides were heat-sealed. While removing air from the bag, a 10 mm seal was formed at a position where the unheat-sealed area was a 25 mm wide, 40 mm long rectangle. The heat-sealed portion was then cut 2 mm outside the unheat-sealed area to produce a bag. The carbon dioxide gas generating agent consisted of 0.5 g of a 5% citric acid aqueous solution and 0.035 g of sodium bicarbonate contained in a polyethylene bag so as not to come into direct contact with the 5% citric acid aqueous solution. The bag was smashed by hand to break the polyethylene bag, and then further kneaded by hand 10 times to generate carbon dioxide. After that, a heat-insulating layer A was laminated on one outer surface of the bag in the same manner as in Example 9. In this way, an intercellular structure was obtained, which included a bag body configured to contain carbon dioxide gas and remaining carbon dioxide generating agent in an airtight space partitioned by two films B (bag material), and an insulating layer A laminated on one outer surface of the bag body.

[0126] <Measurement and Evaluation> (Measurement of the Volume V of Gas Contained in the Sealed Space of the Bag) For Examples 1 to 12, the volume V of gas contained in the sealed space partitioned by the bag material was measured using 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 Tables 2 and 3. 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

[0127] (Loading-Unloading Test) A loading-unloading test was performed on the intercellular structure according to each example by the following method, and the thickness and compressive strain of the intercellular structure were measured at each of the following points. Using a precision universal testing machine (Autograph AGS-5kNX, manufactured by Shimadzu Corporation), the intercellular structure was compressed at a compression rate of 0.5 mm / min until the compressive stress reached 1.39 MPa, and then the compression was released at a compression rate of 0.5 mm / min until the compressive stress reached zero. A stress-strain curve (S-S curve) that schematically illustrates the above loading-unloading test is shown in FIG. 5. The compressive displacements at pressures of 0.03 MPa and 1.39 MPa during the compression process (when loading) of the above loading-unloading test were extracted, and the compressive displacement at a pressure of 0.03 MPa during the compression release process (when unloading) was also extracted, and the thickness and strain of the intercellular structure at each point were calculated. The results are shown in Tables 2 and 3. Tables 2 and 3 also show the value (strain B / A) obtained by dividing the difference (thickness difference B) between the thickness A at a pressure of 0.03 MPa during the compression process and the thickness at a pressure of 1.39 MPa by the thickness A, and the value (strain C / A) obtained by dividing the difference (thickness difference C) between the thickness at a pressure of 1.39 MPa and the thickness at a pressure of 0.03 MPa during the compression-release process by the thickness A. Table 2 also shows, as Reference Example 1, the results of a similar loading-unloading test on the insulating layer A itself (without the bag body).

[0128]

[0129]

[0130] As shown in Table 2, the intercellular structures of Examples 1 to 8, which were made of a bag containing a gas (air) in its internal sealed space, had large strain upon loading (B / A) and strain upon unloading (C / A), demonstrating good cushioning properties. As can be seen from a comparison between Reference Example 1 and Examples 2 to 6, the strain upon loading (B / A) and strain upon unloading (C / A) could be significantly increased by using an intercellular structure in which the insulating layer A was contained together with air in the sealed space within the bag, compared to the loading-unloading characteristics of the insulating layer A alone.

[0131] As shown in Table 3, the intercellular structures of Examples 9 to 12, which had a bag containing gas and liquid in an internal sealed space and a thermal insulating layer laminated on the outside of the bag, also had large strain upon loading (B / A) and strain upon unloading (C / A), demonstrating good cushioning properties. As can be seen from a comparison between Example 2 and Example 9, by containing a liquid (water in this case) together with gas in the sealed space within the bag, the effect of increasing strain upon loading (B / A) and strain upon unloading (C / A) was observed for the same amount of gas.

[0132] 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.

[0133] REFERENCE SIGNS LIST 1 inter-cell structure 10 heat insulating layer 20 fluid 30 bag body 31A, 31B bag material 32 seal portion 50 battery module 51 battery cell

Claims

1. An inter-cell structure that is disposed between adjacent cells in a battery module or battery pack that includes an array of multiple battery cells, the inter-cell structure including a bag having a bag material and a fluid contained in a sealed space partitioned by the bag material.

2. An inter-cell structure that is disposed between adjacent cells in a battery module or battery pack that includes an array of multiple lithium-ion battery cells, the inter-cell structure including a bag body having a bag material and a fluid contained in a sealed space partitioned by the bag material.

3. The inter-cell structure according to claim 1 or 2, wherein the sealed space contains at least a gas as the fluid.

4. The inter-cell structure according to claim 1 or 2, wherein the sealed space contains a gas and a liquid as the fluid.

5. 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 5. The inter-cell structure according to claim 3, wherein G=V / (A / 2).

6. The intercellular structure according to any one of claims 3 to 5, 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.

7. The inter-cell structure according to any one of claims 1 to 6, wherein the bag material comprises a laminated film including a metal layer and a resin layer as a constituent material.

8. The intercellular structure according to any one of claims 1 to 7, further comprising a thermal insulating layer.

9. The intercellular structure according to claim 8, wherein the heat insulating layer contains inorganic particles, and the inorganic particles contain, as a main component, at least one type of silica particles selected from the group consisting of dry silica, wet silica, and silica aerogel.

10. The intercellular structure according to claim 8 or 9, wherein the heat insulating layer is disposed within the enclosed space.

11. The intercellular structure of claim 8 or 9, wherein the insulating layer is disposed on the outside of the bag.

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