Battery pack and spacer

Abstract

Provided is a battery pack in which a spacer is arranged between unit cells, the battery pack being characterized in that the spacer includes an exterior material and an inclusion material, the exterior material includes a metal layer, and the unit cells do not come into contact with the metal layer at a temperature of 25-500°C.　This makes it possible to provide a highly safe spacer and a battery pack in which the same is incorporated.

Description

Battery pack and spacer

[0001] The present invention relates to a battery pack and a spacer.

[0002] In recent years, the use of secondary batteries as power sources for vehicles and the like has been rapidly increasing. Research is being conducted into increasing the energy density of secondary batteries for the purposes of improving the flexibility of installation in limited spaces such as vehicles and extending the range that can be traveled on a single charge. On the other hand, the safety of secondary batteries tends to be inversely related to their energy density, and the higher the energy density of secondary batteries, the lower their safety tends to be. For example, in the case of secondary batteries installed in electric vehicles with a range of several hundred kilometers, if the secondary battery is damaged due to overcharging, an internal short circuit, or the like, the battery surface temperature may exceed several hundred degrees Celsius, even reaching nearly 1000 degrees Celsius.

[0003] Since secondary batteries used as power sources for vehicles, etc. are generally used as assembled batteries consisting of multiple cells, if one of the cells constituting the assembled battery is damaged and reaches the temperature range described above, the heat generated by the damaged cell may damage the adjacent cells, leading to a chain reaction that could spread to the entire assembled battery. To prevent this chain reaction of damage between cells, various techniques have been proposed, such as providing spacers between the cells to cool the damaged cell, or providing a porous body as a spacer between the cells.

[0004] For example, a spacer has been proposed in which a metal layer with high barrier properties is used as an exterior material to hold the contained liquid (see Patent Document 1).

[0005] International Publication No. 2020 / 203646

[0006] Patent Document 1 discloses a spacer that can suppress the loss of liquid contained in the spacer even after long-term use and prevent a decline in heat transfer performance. However, in the event of an abnormality such as a battery runaway, the outermost resin layer may melt and thermally decompose, exposing the internal metal layer and potentially causing electrical conduction between the cells. Furthermore, the exposed metal layer may also transfer high-temperature heat to the casing that constitutes the battery pack, potentially causing a secondary abnormality. The present invention aims to provide a highly safe spacer and a battery pack incorporating the spacer, which reduce the possibility of this occurring in the spacer and battery pack using the spacer disclosed in Patent Document 1. That is, an object of the present invention is to provide a highly safe spacer and a battery pack incorporating the spacer.

[0007] As a result of intensive research into solving the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by providing a battery assembly in which a spacer is placed between unit cells, the spacer including an exterior material and an inner casing material, the exterior material including a metal layer, and the metal layer and the unit cells do not come into contact with each other at temperatures of 25 to 500°C, and have thus completed the present invention.

[0008] That is, the present invention includes the following aspects. [1] An assembled battery in which a spacer is disposed between unit cells, the spacer including an exterior material and an inner casing material, the exterior material including a metal layer, and the metal layer does not come into contact with the unit cells at temperatures of 25 to 500°C. [2] An assembled battery in which a spacer is disposed between unit cells, the spacer including an exterior material and an inner casing material, the exterior material including a metal layer, the exterior material including a first layer on the outer side of the metal layer relative to the inner casing material, the first layer having an area ratio of 15% or more after heat treatment in which the first layer is heated from 25°C to 500°C at a rate of 10°C / min and held at 500°C for 10 minutes relative to the area before the heat treatment. [3] The assembled battery according to [2] above, in which the first layer forms a carbonized layer under the conditions of the heat treatment. [4] The assembled battery according to [2] or [3] above, in which the first layer is a resin layer containing at least one of inorganic particles and a flame retardant. [5] The battery pack according to [4] above, wherein the flame retardant comprises a phosphate ester. [6] The battery pack according to [4] or [5] above, wherein the inorganic particles comprise at least one selected from the group consisting of metal oxides, metal hydroxides, and carbonaceous materials. [7] The battery pack according to any one of [2] to [6] above, wherein the 5% weight loss temperature of a resin composition containing the resin contained in the first layer and at least one of inorganic particles and a flame retardant is 30 to 80°C. [8] The battery pack according to any one of [2] to [7] above, wherein the first layer is a heat-resistant layer. [9] The battery pack according to [8] above, wherein the heat-resistant layer comprises a fiber.

[10] The battery pack according to any one of [1] to [9] above, wherein a heat-resistant sheet is further disposed between the spacer and the unit cells.

[11] The battery pack according to [8] or [9] above, wherein the heat-resistant layer is a fibrous sheet.

[12] The battery pack according to any one of [2] to

[11] above, wherein the thickness of the first layer is 10 to 125 μm.

[13] The battery pack according to any one of [2] to

[12] above, wherein the ratio of the thickness of the inner casing material to the thickness of the first layer is 0.002 to 0.2.

[14] The battery pack according to any one of [1] to

[13] above, wherein the spacer contains a liquid in the inner casing material.

[15] The battery pack according to any one of [1] to

[13] above, wherein the spacer contains a porous body in the inner casing material.

[16] The battery pack according to any one of [1] to

[15] above, wherein the spacer has a thermal conductivity of 0.18 W / (m·K) or more at an average surface temperature of 45° C.

[17] The battery pack according to any one of [1] to

[16] above, wherein the spacer has a thermal conductivity of less than 0.20 W / (m·K) at an average surface temperature of 180° C.

[18] A spacer including an exterior material and an inner casing material, wherein the exterior material includes a metal layer and further includes a first layer outside the metal layer with respect to the inner casing material, and wherein the area of ​​the first layer after heat treatment, which is heated from 25° C. to 500° C. at a rate of 10° C. / min and held at 500° C. for 10 minutes, has an area ratio of 15% or more to the area before the heat treatment.

[19] A method for manufacturing a spacer including an exterior material and an inner packaging material, wherein the exterior material includes a metal layer and a first layer, and the area of ​​the first layer after heat treatment, which involves heating from 25 to 500°C at 10°C / min and holding at 500°C for 10 minutes, is 15% or more of the area before heat treatment, and the method for manufacturing a spacer includes laminating the first layer on the outside of the metal layer with respect to the inner packaging material.

[20] A method for manufacturing a battery pack including a spacer including a cell and an exterior material, wherein the exterior material includes a metal layer and is configured so that the metal layer does not come into contact with the cell at temperatures of 25 to 500°C, and the method for manufacturing a battery pack includes disposing the spacer between two cell packs.

[21] A method for suppressing conduction between cell packs, wherein a spacer disposed between the cell packs inhibits contact between the metal layer and the cell at temperatures of 25 to 500°C.

[22] A method for using a spacer between batteries, the spacer including an outer casing material and an inner casing material, the outer casing material including a metal layer and a first layer located outside the metal layer with respect to the inner casing material, the first layer being heated from 25°C to 500°C at 10°C / min and held at 500°C for 10 minutes, such that the area of ​​the first layer after heat treatment has an area ratio of 15% or more to the area before heat treatment.

[0009] According to the present invention, even if a crack occurs in the encapsulating material in the spacer and liquid elutes from the outermost layer in the event of an abnormality such as battery runaway, the possibility of electrical conduction between the cells is eliminated, thereby providing a highly safe spacer and a battery pack incorporating the same.

[0010] FIG. 1 shows an example of the configuration of a spacer according to an embodiment. FIG. 2 is a cross-sectional view of the spacer shown in FIG. 1 taken along line A-A. FIG. 3 shows an example of a cell. FIG. 4 is a front view of the cell shown in FIG. 3. FIG. 5 is a side view of the cell shown in FIG. 3. FIG. 6 is a top view of an example of a battery pack. FIG. 7 is a side view schematically showing the side of the battery pack shown in FIG. 6 with the front side plate removed. FIG. 8 is a diagram illustrating a method for evaluating insulation properties.

[0011] The present invention will be described below. The following description of the embodiments shown in the drawings is for illustrative purposes only, and the present invention is not limited to the configurations shown in the drawings.

[0012] <Battery Assembly> The battery assembly of the present invention is a battery assembly in which spacers are disposed between unit cells. The battery assembly is composed of multiple unit cells, and spacers are provided between the unit cells to prevent a chain reaction of damage between the unit cells if one of the unit cells is damaged and becomes too hot. The spacers are provided with a metal layer to maintain thermal conductivity under normal conditions, but in abnormally high temperatures, the resin that makes up the battery assembly melts, exposing the metal and causing electrical conduction between the unit cells. In contrast, the battery assembly of the present invention is characterized in that the metal layer does not come into contact with the unit cells at temperatures between 25 and 500°C. In other words, because the metal layer does not come into contact with the unit cells in the range from room temperature to high temperatures, electrical conduction does not occur between the unit cells, and this prevents a chain reaction of damage between the unit cells.

[0013] One aspect of the mechanism by which the battery pack of the present invention prevents contact between the metal layer and the unit cells at temperatures between 25 and 500°C is that it has a first layer on the outside of the metal layer, and this first layer forms a coating such as a carbonized layer in the event of an abnormality, thereby preventing contact between the metal and the unit cells. A spacer with this function will be described below. Note that the numerical range "X to Y" in this specification means, for example, a temperature range of X°C or higher and Y°C or lower, and the preferred upper and lower limits can be combined arbitrarily.

[0014] <Spacer> A spacer according to one embodiment of the present invention is a spacer including an exterior material and an inner casing material, wherein the exterior material includes a metal layer and further includes a first layer outside the metal layer relative to the inner casing material, and wherein the area after a heat treatment in which the material is heated from 25°C to 500°C at 10°C / min and held at 500°C for 10 minutes is an area ratio of 15% or more to the area before the heat treatment (hereinafter simply referred to as "residual area ratio"). From the viewpoint of suppressing conduction between unit cells, the lower limit is preferably 30% or more, more preferably 50% or more, and the upper limit is preferably 100% or less, more preferably 99% or less.

[0015] When the remaining area ratio of the first layer of the exterior material constituting the spacer is 15% or more, contact between the metal layer and the unit cells is inhibited. Furthermore, even if the exterior material is carbonized, it can maintain a film state, and a carbonized layer is formed, thereby suppressing conduction between the unit cells. The remaining ratio is the ratio of the area after heat treatment at 500°C for 10 minutes to the area before heat treatment. A planar image of a square sample was divided into 10 square sections, and the percentage of the sections in which the sample remained after heat treatment was calculated. When the square is divided into four square sections, it is preferable that the first layer remain in two or more sections, more preferably that the first layer remain in three or more sections, and even more preferably that the first layer remain in four or more sections. Furthermore, when the squares are divided into 25 square sections, it is preferable that the first layer remains in 10 or more sections, it is more preferable that the first layer remains in 15 or more sections, and it is even more preferable that the first layer remains in 20 or more sections.

[0016] The thermal conductivity of the spacer at an average surface temperature of 45°C is preferably 0.18 W / (m K) or more. A thermal conductivity of 0.18 W / (m K) or more is advantageous for cooling the cells under normal conditions. From the above perspective, the thermal conductivity at an average surface temperature of 45°C is more preferably 0.20 W / (m K) or more, and even more preferably 0.25 W / (m K) or more. There is no particular limit to the upper limit of the thermal conductivity at an average surface temperature of 45°C, but it is usually preferably 1.0 W / (m K) or less.

[0017] On the other hand, the thermal conductivity of the spacer at an average surface temperature of 180°C is preferably less than 0.20 W / (m·K), and more preferably less than 0.18 W / (m·K). If the thermal conductivity is less than 0.20 W / (m·K), thermal conduction during abnormal heat generation is suppressed, and thermal runaway of the battery pack can be suppressed. From the above perspectives, the thermal conductivity at an average surface temperature of 180°C is more preferably 0.15 W / (m·K) or less, and even more preferably 0.10 W / (m·K) or less. From the same perspective, it is also preferable that the thermal conductivity be lower than the thermal conductivity at an average surface temperature of 45°C.

[0018] The spacer having the above configuration can be provided so that the outer packaging material and the inner packaging material are not bonded. Here, "the outer packaging material and the inner packaging material are not bonded" means that the interfaces between the inner surface of the outer packaging material and the surface of the inner packaging material are not substantially bonded, and the inner packaging material is free to move within the outer packaging material. "Average surface temperature" refers to the average value of temperatures measured at any three points when the entire surface of the spacer is heated at a predetermined temperature.

[0019] Fig. 1 is a diagram showing an example of the configuration of a spacer of the present invention. Fig. 1 shows a front view of a spacer 1. Fig. 2 shows a cross section of the right side of the spacer shown in Fig. 1 taken along line A-A.

[0020] 1 and 2, the spacer 1 has a flat or sheet-like overall shape having a height direction (H), a width direction (W), and a thickness direction (D). The spacer 1 has a thickness direction (D) and a plane direction (P) perpendicular to the thickness direction (D). The plane direction (P) includes the height direction (H) and width direction (D) described above, as well as multiple oblique directions between the height direction (H) and the width direction (D).

[0021] The spacer 1 is used to separate the cells constituting the battery pack or to separate the cells from components other than the cells in its thickness direction (D). The spacer 1 includes an inner casing material 110, and is preferably formed into a plate or sheet shape by enclosing the inner casing material 110 in an outer casing material 120. The thickness of the spacer 1 is preferably 0.80 to 20 mm, and more preferably 1.0 to 10 mm.

[0022] [Outer packaging material] The inner packaging material 110 of the spacer 1 may or may not be sealed by the outer packaging material 120. The spacer may have a laminated structure in which the outer packaging material is disposed on the outer side of the inner packaging material. When a liquid is used as the inner packaging material, the inner packaging material 110 is preferably sealed by the outer packaging material 120. Note that the "outer packaging material" refers to a laminated body located on the surface of the spacer and including at least a metal layer. In the example shown in FIG. 1, the outer packaging body 120 is provided with a sealing portion 120a that seals its periphery, and the insulating material 110 is contained in an internal space 111 formed in the outer packaging body 120 by sealing with the sealing portion 120a. In the example shown in FIG. 1, a gap 120b is provided between the sealing portion 120a and the insulating material 110 in the internal space 111. In other words, the internal space 111 includes, in a plan view of the front of the spacer 1, a first region S1 where the exterior body 120 and the insulating material 110 overlap, and a second region S2 where the exterior body 120 and the insulating material 110 do not overlap. However, the gap 120b is not necessarily required. The gap 120b may be in a state where the inner surfaces of the exterior body 120 are in contact with each other when no fluid (gas or liquid) is present therein. In the present invention, the volume of the internal space 111 is defined as the product of the area of ​​the internal space 111 and the thickness of the insulating material 110. Furthermore, the insulating material does not necessarily have to be located in the center of the internal space, and it does not necessarily have to be parallel to the exterior body.

[0023] One embodiment of the packaging material 120 includes a metal layer. Furthermore, one embodiment of the packaging material 120 may include multiple layers. The packaging material preferably includes at least a metal layer, and a first layer located outside the metal layer relative to the encapsulating material is a resin layer containing at least one of inorganic particles and a flame retardant (hereinafter, this may be referred to as the "first embodiment"). Furthermore, the first layer located outside the metal layer relative to the encapsulating material is preferably a heat-resistant layer (hereinafter, this may be referred to as the "second embodiment"). One embodiment of the packaging material 120 is a packaging material in which the first layer becomes a carbonized layer in a 500°C atmosphere. One embodiment of the packaging material 120 is a packaging material in which a residual area ratio in a plan view from the thickness direction in a 500°C atmosphere is 15% or more. From the viewpoint of reducing contact with the metal layer, the lower limit of the residual area ratio is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more. Furthermore, the upper limit of the residual area ratio is typically 100% or less. When the residual area ratio is 15% or more, the area of ​​the carbonized layer becomes sufficient, and conduction between the unit cells and between the metal layer and the battery can be suppressed. The exterior material preferably includes a second layer located inside the metal layer, and the second layer is preferably a sealant resin layer. Furthermore, the exterior material may include a reinforcing layer between the metal layer and the second layer.

[0024] The thickness of the exterior material 120 is not particularly limited, but taking into consideration the thickness of each of the above layers and from the viewpoint of mechanical strength, the thickness is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. Furthermore, in order to ensure flexibility, the thickness of the exterior material 120 is preferably 220 μm or less, more preferably 150 μm or less, and even more preferably 110 μm or less. The resin layer (first layer) (first embodiment), heat-resistant layer (first layer) (second embodiment), metal layer, sealant resin layer (second layer), and reinforcing layer will be described below.

[0025] [Resin Layer (First Layer)] (First Aspect) One aspect of the resin layer contains at least one of inorganic particles or a flame retardant. Examples of the resin layer include, but are not limited to, polyolefin-based resins such as homopolymers or copolymers of ethylene, propylene, butene, etc.; amorphous polyolefin-based resins such as cyclic polyolefins; polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyamide-based resins such as nylon 6, nylon 66, nylon 12, and copolymer nylon; ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide-based resins, polyetherimide-based resins, polysulfone-based resins, polyethersulfone-based resins, polyetheretherketone-based resins, polycarbonate-based resins, polyvinyl butyral-based resins, polyarylate-based resins, fluororesins, acrylic resins, and biodegradable resins. Among these, polyamide-based resins such as nylon 6 and polyester-based resins such as polyethylene terephthalate are preferred from the viewpoint of imparting heat resistance and mechanical strength as an exterior material. The resin layer may be a single layer or two or more layers laminated together. In the case of two or more layers, the resin layers may be selected from different resin layers or from the same resin layer. In the case of a multi-layer resin layer, all layers of the multi-layer resin layer are included in the resin layer.

[0026] There is no particular limitation on the thickness of the resin layer, but from the viewpoint of flexibility, the thickness of the first layer is preferably 10 to 125 μm, and more preferably 10 to 40 μm.

[0027] <Inorganic Particles> The resin layer (first layer) may contain inorganic particles from the viewpoint of improving insulation. Examples of inorganic particles include metal oxides such as silica, aluminum oxide, and titanium oxide, metal hydroxides such as potassium hydroxide and calcium hydroxide, and carbonaceous materials such as carbon black. More specific examples include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, and carbon black. Among these inorganic particles, silica, aluminum oxide, titanium oxide, and carbon black are preferred from the viewpoint of improving insulation, and silica, titanium oxide, and carbon black are particularly preferred. The inorganic particles may be used alone or in combination of two or more. Therefore, preferred particles such as silica, titanium oxide, and carbon black may be used in combination.

[0028] In addition to the inorganic particles, conventional particles may be added to impart slipperiness to the polyester film, prevent scratches during each process, and improve handleability. These particles are not particularly limited as long as they are capable of imparting slipperiness. Specific examples include the inorganic particles described above, crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles, and organic particles such as calcium oxalate and ion exchange resins. Furthermore, precipitated particles obtained by precipitating and finely dispersing a portion of a metal compound, such as a catalyst, during the polyester production process can also be used.

[0029] (Particle Shape) The shape of the particles used in the present resin layer (first layer) is not particularly limited, and any of spherical, blocky, rod-like, flat, etc. may be used. Furthermore, there are no particular limitations on the hardness, specific gravity, color, etc. Two or more types of these particles may be used in combination as needed. Here, the term "particles" includes both inorganic particles for improving the insulating properties of the present resin layer (first layer) and particles for improving the lubricity of the present resin layer (first layer).

[0030] (Average Particle Diameter) The average particle diameter of the particles used in the present resin layer (first layer) is typically 0.05 μm to 5.0 μm, preferably 0.10 μm to 4.5 μm, more preferably 0.20 μm to 4.5 μm, and particularly preferably 0.40 μm to 4.5 μm. By using particles within the above range, the desired insulating properties of the present resin layer (first layer) can be ensured. When the particles are in powder form, the average particle diameter can be determined by measuring the powder using a centrifugal sedimentation particle size distribution analyzer (e.g., the "SA-CP3" model manufactured by Shimadzu Corporation) and determining the particle diameter at 50% cumulative volume fraction (d50) in the equivalent spherical distribution. The average particle diameter of the particles in the layer or resin can be determined by observing the diameters of 10 or more particles using a scanning electron microscope (SEM) and measuring the particle diameters, and then calculating the average value. In the case of non-spherical particles, the average of the longest and shortest diameters can be measured as the diameter of each particle.

[0031] When particles are contained in this resin layer (first layer), it is preferable to provide a surface layer and an intermediate layer and contain particles in the surface layer. Also, when a three-type, three-layer structure is used, where the front and back layers are differently designed, it is possible to contain particles in only at least one of the surface layers.

[0032] The method for adding particles to the resin layer (first layer) is not particularly limited, and any conventionally known method can be used. For example, the particles can be added at any stage in the production of the polyester, but it is preferable to add them after the completion of the esterification or transesterification reaction.

[0033] <Flame Retardant> In the present invention, the flame retardant preferably contains a phosphate ester, and it is also preferable to use an organic phosphorus-based flame retardant compound. Examples of the phosphate ester include phosphate ester compounds such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and cresyl di-2,6-xylenyl phosphate, condensed phosphate ester compounds such as 1,3-phenylenebis(2,6-dimethylphenyl)phosphate, tetraphenyl(m-phenylene)bisphosphate, and bis(ditolyl)isopropylidene-di-p-phenylene phosphate, phosphate ester amide compounds such as 4,4'-bis(diphenylphosphorylamidophenyl)methane, and phosphazene compounds such as phosphonitrile acid phenyl ester. The structure of the organic phosphorus flame retardant compound is not particularly limited, and examples thereof include carboxymethyl phenyl phosphate, (2-carboxyethyl)phenyl phosphate, (2-carboxyethyl)toluyl phosphate, (2-carboxyethyl)2,5-dimethylphenyl phosphate, (2-carboxyethyl)cyclohexyl phosphate, (carboxypropyl)phenyl phosphate, (4-carboxyphenyl)phenyl phosphate, (3-carboxyphenyl)phenyl phosphate, (2-carboxyethyl)methyl phosphate, (2-carboxyethyl)ethyl phosphate, triphenyl phosphate, tributyl phosphate, t-butyldiphenyl phosphate, tris(2-ethylhexyl)phosphate, bisphenol A bis(diphenyl phosphate)-1,3-phenylbis(diphenyl phosphate), phosphonitrile acid diphenyl ester, and compounds represented by the following formula (1):

[0034]

[0035] In the above formula (1), A is a divalent or trivalent organic residue, and preferred examples thereof include lower alkylene groups such as a methylene group, an ethylene group, a 1,2-propylene group, and a 1,3-propylene group, arylene groups such as a 1,3-phenylene group and a 1,4-phenylene group, and divalent groups such as a 1,3-xylylene group and a 1,4-xylylene group.

[0036] Specific examples of the trivalent organic residue include the following:

[0037]

[0038] In the formula (1), Q is a hydrocarbon group having 1 to 18 carbon atoms, such as an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, or an aryloxy group, while Z is an ester-forming functional group, such as a carboxy group, an alkyl ester having 1 to 6 carbon atoms in the carboxy group, a cycloalkyl ester, or an aryl ester, a hydroxy group, or a hydroxylalkoxycarbonyl group having 2 to 7 carbon atoms.

[0039] As mentioned above, the structure of the organophosphorus flame-retardant compound used in the present invention is not particularly limited. However, it is preferable to use an ethylene glycol-free polycondensate of 2-(9,10-dihydro-9-oxa-10-oxide-10-phosphaphenanthrene-10-yl)methylsuccinate bis(2-hydroxyethyl) (formula (2) below). This organophosphorus compound contains a phosphorus atom in the molecule, and the lower limit of the average molecular weight measured by GPC is 1170, preferably 2290 or more, and more preferably 3410 or more. An average molecular weight of 1170 or more does not inhibit the volatilization of the organophosphorus compound and the crystallization of the polyester resin during film formation, and furthermore, bleed-out of the organophosphorus compound is suppressed, thereby maintaining the mechanical strength of the resin layer (first layer). Furthermore, while there is no particular upper limit for the average molecular weight of the organophosphorus compound, it is believed that an excessively high molecular weight would deteriorate the dispersibility of the compound in the polyester resin.

[0040]

[0041] When producing the resin layer (first layer), the method for incorporating the phosphoric acid ester and the organic phosphorus-based flame-retardant compound is not particularly limited. For example, when producing a polyester by the so-called transesterification method of a dicarboxylic acid diester and a diol, the organic phosphorus-based flame-retardant compound may be added during the transesterification reaction, or may be added before the polycondensation reaction after the transesterification reaction or at a relatively early stage of the polycondensation. Furthermore, when producing a polyester by the esterification method of a dicarboxylic acid and a diol, the organic phosphorus-based flame-retardant compound may be added at any stage of esterification.

[0042] The content of the phosphate ester and organic phosphorus-based flame-retardant compound in the resin layer (first layer) can be estimated by converting it to the amount of phosphorus element. In terms of the amount of phosphorus element, it is preferably 0.2% by mass to 3.5% by mass, more preferably 0.5% by mass to 3.0% by mass, and particularly preferably 1.0% by mass to 3.0% by mass. By satisfying this range, good flame retardancy can be imparted. The total content of the particles and flame retardant in the first layer is preferably greater than 0.1% by mass, more preferably 0.5% by mass or more. On the other hand, the upper limit is preferably 30% by mass or less, in terms of the handleability of the resin layer (first layer). Within this range, the resin layer (first layer) can exhibit good insulation properties even when used in a high-temperature atmosphere (e.g., 500°C).

[0043] <Others> In order to reduce the amount of oligomer component precipitation, the resin layer (first layer) may be produced using a polyester with a low oligomer component content as a raw material. Various known methods can be used to produce a polyester with a low oligomer component content, such as a method of solid-phase polymerization after polyester production. Furthermore, the amount of oligomer component precipitation may be reduced by configuring the resin layer (first layer) to have three or more layers, and using a polyester raw material with a low oligomer component content as the surface layer of the resin layer (first layer). Furthermore, the polyester may be obtained by esterification or transesterification, followed by melt polycondensation under reduced pressure at a higher reaction temperature.

[0044] In addition to the above-mentioned particles, conventionally known ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the resin layer (first layer) as needed.

[0045] The resin layer (first layer) may contain resins other than polyester as long as the effects of the present invention are not impaired. Other resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamideimide resins, polyamide bismaleimide resins, polyetherimide resins, polyether ether ketone resins, polyether ketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, and fluorine-based resins.

[0046] <5% Weight Loss Temperature> The 5% weight loss temperature of the resin composition containing the resin contained in the first layer and at least one of inorganic particles and a flame retardant is preferably 30 to 80°C. A 5% weight loss temperature of 30 to 80°C is advantageous in terms of forming a carbonized layer. From the above viewpoints, the 5% weight loss temperature is more preferably 30 to 70°C, and even more preferably 30 to 60°C.

[0047] [Heat-resistant layer (first layer)] (Second embodiment) In the spacer of the present invention, it is preferable that the exterior material includes multiple layers, and the first layer located outside the metal layer relative to the inner packaging material is a heat-resistant layer. A heat-resistant sheet can be used as the heat-resistant layer. In this specification, "heat-resistant" means that the weight residual rate determined by thermogravimetric differential thermal analysis is 15.0% or more. In addition, the spacer may have a form in which a heat-resistant layer is included in one layer of the exterior body, or a form in which a heat-resistant sheet independent of the spacer is used in combination with the spacer. Examples of heat-resistant sheets include fibrous sheets, thermoplastic resin sheets, and thermosetting resin sheets.

[0048] Examples of the fibrous sheet include, without particular limitation, cotton fiber sheets, polyester fiber sheets, rayon fiber sheets, linen fiber sheets, silk fiber sheets, nylon fiber sheets, acrylic fiber sheets, polypropylene fiber sheets, wool fiber sheets, glass cloth sheets, etc. Among these, glass cloth sheets are preferred from the viewpoint of suppressing decomposition and deterioration of components even at high temperatures and from the viewpoint of being able to impart heat resistance and mechanical strength required for exterior packaging materials.

[0049] Examples of thermoplastic resin sheets that can be used include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyamide resins such as nylon 6, nylon 66, nylon 12 and copolymer nylon, polyimide resins such as thermoplastic polyimide, fluorine-based resins such as tetrafluoroethylene resin and tetrafluoroethylene-hexafluoropropylene copolymer resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polycarbonate resin, polyvinyl butyral resin, polyarylate resin, acrylic resin, and biodegradable resin sheets.

[0050] Examples of thermosetting resin sheets that can be used include sheets of epoxy resins, polyimide resins, polyetherimide resins, phenolic resins, melamine resins, and polyurethane resins. These sheets may be laminated in a single layer or in two or more layers. In the case of two or more layers, the resin layers may be selected from different resin layers or from the same sheet. Among the heat-resistant layers described above, a fibrous layer containing a fibrous sheet is preferred from the viewpoint of suppressing thermal conductivity.

[0051] The thickness of the heat-resistant layer is not particularly limited, but from the viewpoint of flexibility, the thickness of the first layer is preferably 10 to 125 μm, more preferably 10 to 99 μm. When a fibrous layer is used, the fiber diameter is not particularly limited, but from the viewpoint of increasing puncture strength, it is preferably 1 to 50 μm, more preferably 20 to 50 μm.

[0052] The ratio of the thickness of the inner packaging material to the thickness of the first layer is preferably 0.002 to 0.3 (thickness of inner packaging material / thickness of first layer, hereinafter sometimes referred to as "thickness ratio 1"). A thickness ratio 1 of 0.002 or more is advantageous in terms of suppressing wrinkles at the boundary of the inner packaging material, and a thickness ratio 1 of 0.3 or less is advantageous in terms of followability to the boundary of the inner packaging material. From the above perspectives, the thickness ratio 1 is more preferably 0.005 or more. On the other hand, when the first layer is a resin layer, the thickness ratio 1 is more preferably 0.15 or less, even more preferably 0.10 or less, even more preferably 0.080 or less, particularly preferably 0.060 or less, and most preferably 0.040 or less. Furthermore, when the first layer is a heat-resistant layer, the thickness ratio 1 is more preferably 0.25 or less, even more preferably 0.20 or less, even more preferably 0.15 or less, and particularly preferably 0.10 or less.

[0053] [Metal Layer] Examples of the metal layer include aluminum foil, copper foil, tin foil, nickel foil, stainless steel foil, lead foil, tin-lead alloy foil, bronze foil, iridium foil, phosphor bronze foil, etc. In particular, aluminum foil, copper foil, and nickel foil are preferred from the viewpoints of processability and material availability, and aluminum foil is more preferred from the viewpoints of low density and easy handling.

[0054] The thickness of the metal layer is not particularly limited as long as it is 5 μm or more, but from the viewpoint of suppressing pinhole formation, it is preferably 8 μm or more, and more preferably 12 μm or more. Furthermore, from the viewpoint of ensuring flexibility, it is preferably 50 μm or less, more preferably 35 μm or less, and even more preferably 20 μm or less. The ratio of the thickness of the metal layer to the thickness of the first layer is preferably 0.01 to 6 (thickness of the inner packaging material / thickness of the first layer, hereinafter sometimes referred to as "thickness ratio 2"). A thickness ratio 2 of 0.01 or more is advantageous in terms of suppressing wrinkles at the boundary of the inner packaging material, and a thickness ratio 2 of 6 or less is advantageous in terms of conformability to the boundary of the inner packaging material. From the above viewpoints, the thickness ratio 2 is more preferably 0.05 or more, and even more preferably 0.1 or more. On the other hand, when the first layer is a resin layer, the thickness ratio 2 is more preferably 5 or less, even more preferably 4 or less, particularly preferably 3 or less, particularly preferably 2 or less, and most preferably 1 or less. Furthermore, when the first layer is a heat-resistant layer, the thickness ratio 2 is more preferably 3 or less, even more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.5 or less.

[0055] [Sealant Resin Layer (Second Layer)] Examples of sealant resins include polyolefin-based resins such as homopolymers or copolymers of ethylene, propylene, butene, etc.; amorphous polyolefin-based resins such as cyclic polyolefins; polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyvinyl butyral-based resins, acrylic resins, and biodegradable resins. Among these, from the viewpoint of low-temperature melting properties required to obtain the function of releasing liquid inside the exterior material to the outside in the event of abnormal heat generation, it is preferable to use at least one polyolefin-based resin selected from high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLPDE), polypropylene resin, etc. Furthermore, from the viewpoint of long-term storage stability within the temperature range normally used as a spacer for a battery pack and from the viewpoint of versatility, it is more preferable to use unstretched polypropylene resin.

[0056] Although there is no particular limitation on the thickness of the sealant resin layer, from the viewpoint of ensuring sealing properties, the thickness is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Furthermore, in order to ensure flexibility, the thickness of the sealant resin layer is preferably 120 μm or less, more preferably 100 μm or less, and even more preferably 80 μm or less.

[0057] [Reinforcing Layer] The exterior packaging material may further include a reinforcing layer between the metal layer and the second layer. Examples of the reinforcing layer include, but are not limited to, polyolefin-based resins such as homopolymers or copolymers of ethylene, propylene, butene, etc.; amorphous polyolefin-based resins such as cyclic polyolefins; polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyamide-based resins such as nylon 6, nylon 66, nylon 12, and copolymer nylons; ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide-based resins, polyetherimide-based resins, polysulfone-based resins, polyethersulfone-based resins, polyetheretherketone-based resins, polycarbonate-based resins, polyvinyl butyral-based resins, polyarylate-based resins, fluororesins, acrylic resins, and biodegradable resins. Among these, polyamide-based resins such as nylon 6 and polyester-based resins such as polyethylene terephthalate are preferred from the viewpoint of imparting heat resistance and mechanical strength as an exterior packaging material, and polyamide-based resins such as nylon 6 are more preferred from the viewpoint of improving the pinhole resistance of the metal layer. The reinforcing layer may be a single layer or a laminate of two or more layers. In the case of two or more layers, the reinforcing layers may be selected from different resin layers or from the same resin layer.

[0058] The thickness of the reinforcing layer is not particularly limited, but from the viewpoint of imparting mechanical strength, it is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. In order to ensure flexibility, it is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less.

[0059] [Inner casing material] One embodiment of the inner casing material 110 contains a liquid. The "inner casing material" refers to a material disposed between a pair of "external casing materials." The "liquid" is not particularly limited as long as it functions as the spacer. It refers to a substance that is in a fluid state at 100°C and 1 atm, and the fluid state is preferably a liquid state. For example, it includes substances such as gels that are not in a fluid state at 25°C but become fluid at 100°C and 1 atm. Any liquid can be used as the liquid. From a safety perspective, the liquid preferably contains water. One embodiment of the inner casing material 110 contains a porous body. The porous body includes either a powdered inorganic material or a fibrous inorganic material. In the present invention, "fibrous inorganic material" refers to an inorganic material having a shape in which the major axis is 100 times or more its minor axis, and "powdered inorganic material" refers to an inorganic material having a shape in which the major axis is less than 100 times its minor axis. In particular, in the case of a fibrous material, the "major axis" refers to the fiber length, and the "minor axis" refers to the diameter of a cross section perpendicular to the major axis direction.

[0060] The fibrous inorganic material is preferably at least one selected from the group consisting of paper, cotton sheet, polyimide fiber, aramid fiber, polytetrafluoroethylene (PTFE) fiber, glass fiber, rock wool, ceramic fiber, and biosoluble inorganic fiber, and among these, at least one selected from glass fiber, rock wool, ceramic fiber, and biosoluble inorganic fiber is particularly preferred. The ceramic fiber is a fiber mainly composed of silica and alumina (silica:alumina=40:60 to 0:100), and specifically, silica-alumina fiber, mullite fiber, and alumina fiber can be used.

[0061] Furthermore, the powdered inorganic material is preferably at least one selected from the group consisting of silica particles, alumina particles, calcium silicate, clay minerals, vermiculite, mica, cement, perlite, fumed silica, and aerogel, and among these, at least one selected from silica particles, alumina particles, calcium silicate, and vermiculite is particularly preferred. Among the types of calcium silicate, xonotlite, tobermorite, wollastonite, and gyrolite are preferred, with gyrolite being particularly preferred. Gyrolite, which has a petal-like structure, maintains its porous structure even when compressed and deformed, and therefore has excellent liquid retention properties. Clay minerals are mainly magnesium silicate (including talc and sepiolite), montmorillonite, and kaolinite.

[0062] The porous body containing a fibrous inorganic material and a powdery inorganic material can be selected from known materials that satisfy a predetermined density, for example, those described in JP-A-2003-202099.

[0063] The thermal conductivity of the porous body is usually less than 0.18 [W / (m K)], preferably less than 0.15 [W / (m K)], and more preferably less than 0.1 [W / (m K)], in order to prevent heat transfer when an abnormality occurs between the cells.

[0064] <Method for manufacturing spacers> A method for manufacturing a spacer including an inner casing material and an outer casing material includes a step of laminating a first layer on the outer side of a metal layer of the inner casing material. This method makes it possible to efficiently manufacture a spacer in which the outer casing material includes a metal layer and a first layer, and in which, after a heat treatment in which the spacer is heated from 25°C to 500°C at a rate of 10°C / min and held at 500°C for 10 minutes, the remaining area ratio of the first layer in a plan view from the thickness direction is 15% or more.

[0065] <Battery Assembly> Next, a battery assembly to which the spacer 10 is applied will be described. The battery assembly is applied to battery packs mounted in, for example, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric heavy machinery, electric motorcycles, electrically assisted bicycles, ships, aircraft, trains, uninterruptible power supplies (UPSs), home energy storage systems, and storage battery systems for stabilizing power systems that utilize renewable energy sources such as wind, solar, tidal, and geothermal power. However, the battery assembly can also be used as a power source that supplies power to devices other than the above-mentioned EVs.

[0066] In one embodiment of the present invention, a battery assembly includes a spacer disposed between unit cells, and the exterior material of the spacer includes a metal layer, which inhibits contact between the metal layer and the unit cells in an atmosphere at 500°C. One aspect of the spacer is the spacer described above. It is preferable that the spacer is configured to reduce the thermal conductivity between the two unit cells at 50 to 200°C, relative to the thermal conductivity between the unit cells at 25°C.

[0067] [Single Cell] Fig. 3 is a plan view showing an example of a single cell constituting a battery pack, Fig. 4 is a front view of the single cell shown in Fig. 3, and Fig. 5 is a right side view of the single cell. The single cell 200 is formed in a rectangular parallelepiped shape having a height direction (H), a width direction (W), and a thickness direction (D), and terminals 210 and 220 are provided on its upper surface. The single cell 200 is, for example, a lithium-ion secondary battery including a positive electrode and a negative electrode capable of absorbing and releasing lithium ions, and an electrolyte. In addition to lithium-ion secondary batteries, secondary batteries such as lithium-ion all-solid-state batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and lead-acid batteries can also be used.

[0068] [Battery Assembly] FIG. 6 shows a top view of a battery assembly 100 formed using a plurality of cells 200, and FIG. 7 is a side view schematically illustrating the battery assembly 100 shown in FIG. 6 with a side plate 300d removed. In FIGS. 6 and 7, the battery assembly 100 includes a housing 300 and a plurality of cells 200 housed within the housing 300. The housing 300 has a bottom plate 300e and side plates 300a, 300b, 300c, and 300d extending along the outer periphery of the bottom plate 300e. While FIGS. 6 and 7 illustrate five cells 200 as an example, the number of cells can be selected as appropriate. FIG. 6 illustrates a diagram in which the plane with the largest area among three planes of a rectangular parallelepiped approximating a cell is partitioned by a spacer in the thickness direction. The "between cells" where the spacer is placed means between any two cells. However, from the viewpoint of maximizing the insulating effect in the event of an abnormality, it is preferable to separate the three planes of a rectangular parallelepiped approximating a cell that have the same order of area in the thickness direction of the spacer, and it is more preferable to separate the planes with the largest area in the thickness direction of the spacer. The "rectangular parallelepiped" refers to the solid with the smallest volume in which the cells are inscribed when the shape of the cell is not a perfect rectangular parallelepiped. Furthermore, it is preferable that the area of ​​the spacer in a plan view from the thickness direction is equal to or less than the area of ​​the rectangular parallelepiped approximating the cell separated by the spacer.

[0069] Within the casing 300, the plurality of cells 200 are arranged in the thickness direction, with the spacers 10 described above disposed between the cells 200. The positive electrode terminals (e.g., terminal 210) and negative electrode terminals (e.g., terminal 220) of adjacent (opposing) cells 200 are electrically connected in series by bus bars 301 via the spacers 10, thereby allowing the battery pack 100 to output a predetermined amount of power. As shown in FIG. 7 , the battery pack 100 has spacers 1A disposed between the upper surface of the bottom plate 300e of the casing 300 and each cell 200. The spacers 1A have a similar configuration to the spacers 10.

[0070] <Heat Generation and Heat Transfer in Battery Pack> Some or all of the chemical substances constituting the electrodes, electrolyte, etc., that make up the cells 200 may undergo decomposition reactions inside the cells 200 while generating heat, causing the temperature of the cells 200 to rise, and some or all of the regions of the cells 200 to reach 200° C. or higher. In the present invention, this state is referred to as an "abnormal heat generation state."

[0071] It is generally known that the safety of the positive electrode material among the materials constituting the cell 200 is greatly affected by the stability of the crystal structure after lithium removal by charging. LiCoO ２ , Li(Ni １／３ Mn １／３ Co １／３ ) O ２ , Li(Ni ０．８ Co ０．１５ Al ０．０５ ) O ２ Materials such as these undergo crystalline collapse accompanied by oxygen release at high temperatures during charging. The oxygen released from the positive electrode causes oxidation of the electrolyte, resulting in a rapid exothermic reaction. Structural analysis using synchrotron radiation has reported that the above positive electrode materials undergo a crystalline phase transition at around 200°C. Therefore, if a part or all of the area of ​​the cell 200 reaches 200°C or higher, it means that the crystal collapse of the positive electrode is progressing, that is, the cell 200 is in a thermal runaway state (Reference 1: High Safety Technology and Materials for Lithium-Ion Batteries, CMC Publishing, p. 44 / Reference 2: J. Dahn et al., Electrochemistry Communication, 9, 2534-2540 (2007) / Reference 3: Kobayashi Hironori, "Evaluation and Analysis Techniques for Positive Electrode Materials for Lithium-Ion Secondary Batteries Using Synchrotron Radiation," Spring-8 Utilization Promotion Council, Glass and Ceramics Study Group (Second Meeting) (2011)).

[0072] Regarding the safety of the negative electrode material among the materials constituting the single battery 200, it is known that the charging negative electrode (lithium-inserted carbon negative electrode) basically exhibits strong reducing properties similar to those of lithium metal, and that a coating is formed on the negative electrode surface upon reaction with the electrolyte, thereby suppressing further reaction. Therefore, the chemical composition, structure, and thermal stability of this protective coating have a significant impact on the thermal stability of the charging negative electrode as the temperature rises. The reaction between the charging negative electrode and the electrolyte is typically explained by the formation of a protective coating followed by an explosive reductive decomposition reaction due to the destruction of the coating. It has generally been reported that the protective coating formation reaction on the negative electrode begins at around 130°C, followed by the subsequent coating decomposition reaction at around 200°C, ultimately leading to an explosive reductive decomposition reaction. Therefore, if a part or all of the area of ​​the cell 200 reaches 200°C or higher, it means that breakdown of the coating on the surface of the negative electrode is progressing, that is, the cell 200 is in a thermal runaway state (Reference 4: Battery Handbook, 1st Edition, Ohmsha, p. 591 / Reference 5: The Frontline of High Safety Technology and Evaluation Technology for Lithium-Ion Batteries, CMC Publishing, p. 90).

[0073] In the present invention, a state in which chemical substances constituting the electrodes, electrolyte, and the like constituting the cell 200 are not undergoing a decomposition reaction accompanied by a certain heat generation rate or higher inside the cell 200 is referred to as a "normal state." Here, the heat generation state of the cell 200 can be evaluated using ARC (Accelerating Rate Calorimetry), which is a means for quantitatively measuring the thermal behavior of reactive chemical substances when they self-heatingly decompose under adiabatic conditions. For example, Dahn et al. define that a self-heating reaction is progressing inside the cell when the heat generation rate observed in ARC exceeds 0.04°C / min, and this can be followed (Reference 6: J. Dahn et al., Electrochimica Acta, 49, 4599-4604 (2004)). In the present invention, a cell 200 in a normal state is referred to as a "cell maintaining a normal state," and a cell 200 that has deviated from the normal state and has not yet reached an abnormally heated state is referred to as a "cell deviating from the normal state." Heat generated inside a cell 200 is transmitted to other cells 200 via various transmission paths. For example, heat generated inside a cell 200 can be transmitted to other cells 200 via the spacer 10.

[0074] For example, the upper limit of the average surface temperature that is expected when the unit cells 200 in contact with or close to the spacer 10 deviate from the normal state but do not reach an abnormal heat generation state is set to 180°C. Here, when the general-purpose separator material is made of polyethylene or polypropylene, it is known that its meltdown temperature is 160 to 200°C. Therefore, when the average surface temperature of the unit cells 200 exceeds 180°C, there is a risk that a portion of the general-purpose separator material that constitutes the unit cells 200 will melt down, leading to an abnormal heat generation state.

[0075] As long as the average temperature of one of the two thickness-wise surfaces of the spacer 10 separating the cells 200 constituting the battery pack 100 does not exceed 100°C, the spacer 10 can transfer heat from a cell 200 (e.g., cell 200a) in the battery pack 100 in its thickness direction and to another cell 200 (cell 200b) facing the cell 200a via the spacer 10 or to a component other than the cell 200 (e.g., bottom plate 300e). In contrast, when the average temperature exceeds 100°C, the heat causes the spacer 10 to open, and the contained liquid leaks out in a gaseous or liquid state. This leak allows air (which has insulating properties) to enter the insulating material 110 within the spacer 10, increasing the insulating properties (thermal resistance) in the thickness direction. This prevents one cell 200 from falling into a state that deviates from its normal state, which in turn causes other cells 200 to fall into a state that deviates from its normal state.

[0076] <Method for manufacturing battery assembly> The battery assembly of the present invention can be manufactured efficiently by including a step of disposing a spacer between two unit cells. That is, the method for manufacturing a battery assembly includes a unit cell and a spacer including an exterior material, the exterior material including a metal layer, and the spacer is configured to inhibit contact between the metal layer and the unit cells under conditions of 25 to 500°C, and includes disposing the spacer between the two unit cells.

[0077] The above-described configuration of the spacer and battery pack of the present invention is one example, and can be appropriately changed based on design requirements and the like within the scope of the present invention.

[0078] <Method for Suppressing Conduction Between Cells> A method for suppressing conduction between cells, in which a spacer disposed between the cells inhibits contact between the metal layer and the cells under conditions of 25 to 500° C., is also one aspect of the present invention.

[0079] <Method of Use> A method of using an inter-battery spacer, in which the spacer includes an inner casing material and an outer casing material, the outer casing material includes a metal layer and a first layer that is located outside the metal layer with respect to the inner casing material, and the remaining area ratio of the first layer in a plan view from the thickness direction under conditions of 25 to 500°C is 15% or more, is also one aspect of the present invention.

[0080] In this specification, when "X to Y" or "X to Y" (X and Y are any numbers) is expressed, it means "X or more and Y or less" unless otherwise specified, and also includes the meanings "preferably greater than X" and "preferably smaller than Y." Furthermore, when "X or more" (X is any number), it means "preferably greater than X" unless otherwise specified, and when "Y or less" (Y is any number), it means "preferably smaller than Y" unless otherwise specified.

[0081] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[0082] <Evaluation Method> (1-1) Intrinsic Viscosity (IV) 1 g of polyester from which components incompatible with the polyester had been removed was precisely weighed, and dissolved in 100 mL of a mixed solvent of phenol / tetrachloroethane = 50 / 50 (mass ratio), and the intrinsic viscosity (IV) was measured at 30°C using a viscosity measuring device "VMS-022UPC-F10" (manufactured by Rigo Co., Ltd.).

[0083] (1-2) Average particle size of particles (in the case of powder) The particle size at an integrated volume fraction of 50% in the equivalent spherical distribution measured using a centrifugal sedimentation particle size distribution analyzer (SA-CP3 model) manufactured by Shimadzu Corporation was taken as the average particle size d50. (in the case of particles in a layer or resin) Ten or more particles were observed with a scanning electron microscope (SEM) to measure the particle diameters, and the average value was taken as the average particle size of the particles. In this case, in the case of non-spherical particles, the average value of the longest diameter and the shortest diameter was taken as the diameter of each particle.

[0084] (1-3) 5% Weight Loss Temperature and Weight Remaining Rate Using a TG-DTA device (model: DTG60) manufactured by Shimadzu Corporation, the temperature was raised from 25°C to 500°C at a rate of 10°C / min in a nitrogen atmosphere in accordance with JIS K7121 (2012). Then, the sample was held at 500°C for 10 minutes in a nitrogen atmosphere. From the above measurements, the 5% weight loss temperature (°C) and weight remaining rate (%) were obtained.

[0085] (1-4) Remaining Area Ratio A square sample film and a metal plate (brass, 50 x 50 mm x 5 mm thick) were placed in this order on a metal block (brass, 50 x 50 mm x 20 mm thick) with a rod heater (Watlow Fire Rod Heater G1N) inserted. The rod heater was then heated to raise the temperature of the surface of the metal plate 2 from room temperature to 500°C (at a heating rate of 10°C / min), and the surface was then held at 500°C for 10 minutes, and the remaining insulating layer ratio in a planar view was evaluated. The remaining ratio is the ratio of the area after heat treatment, which was held at 500°C for 10 minutes, to the area before heat treatment. A planar image of the square sample was divided into 10 x 10 square sections, and the percentage of the section in which the sample remained after heat treatment was calculated.

[0086] (1-5) Moldability When used as a spacer, it is effective to adhere the inner packaging material and outer packaging material together in order to maintain the thermal properties of the spacer, so the ability of the polyester film to conform to the shape of the inner packaging material was evaluated as follows. A 100 x 100 mm polyester film was layered on top of a 50 x 50 mm, 1 mm thick piece of cardboard. The layered laminate was passed through a roll laminator at room temperature. The cardboard and polyester film were then separated, and the appearance of the polyester film was confirmed, and moldability was evaluated using the following criteria: ◎: After disassembly, wrinkles that conform to the shape of the inner packaging material were clearly visible. ○: After disassembly, wrinkles that conform to the shape of the inner packaging material were slightly visible. (1-6) Insulation Properties The measurement method is explained using Figure 8. The sample film 1 and metal plate 2 (brass, 50 x 50 mm x 5 mm thick) were placed in this order on a metal block 3 (brass, 50 x 50 mm x 20 mm thick) into which a rod heater (Watlow Fire Rod Heater G1N) had been inserted, and the rod heater was heated to raise the temperature of the surface of the metal plate 2 from room temperature to 500°C (at a temperature increase rate of 10°C / min), followed by holding at 500°C for 10 minutes. The sample was then naturally cooled to room temperature, and the resistance between the surface of the metal plate 2 and the metal block 3 was measured using a tester 4 (Hioki E.E. Corporation: Model IR4054) with an applied voltage of 125 V to evaluate the insulation (presence or absence of conduction).

[0087] <Materials Used> (1) Polyester A: homopolyethylene terephthalate (intrinsic viscosity: 0.58 dL / g), dicarboxylic acid component (a-1): terephthalic acid = 100 mol%, diol component (a-2): ethylene glycol = 100 mol% (2) Polyester B: homopolyethylene terephthalate (intrinsic viscosity: 0.70 dL / g), dicarboxylic acid component (a-1): terephthalic acid = 100 mol%, diol component (a-2): ethylene glycol = 100 mol% (3) Polyester C: homopolyethylene terephthalate (intrinsic viscosity: 0.85 dL / g), dicarboxylic acid component (a-1): terephthalic acid = 100 mol%, diol component (a-2): ethylene glycol = 100 mol% (4) Polyester D: homopolyethylene terephthalate (intrinsic viscosity: 1.10 dL / g), dicarboxylic acid component (a-1): terephthalic acid = 100 mol%, diol component (a-2): ethylene glycol = 100 mol% (5) Polyester E: homopolyethylene terephthalate (intrinsic viscosity: 1.18 dL / g), dicarboxylic acid component (a-1): terephthalic acid = 100 mol%, diol component (a-2): ethylene glycol = 100 mol% (6) Polyester F: homopolyethylene terephthalate (polyester A) with 0.7 mass% silica particles having an average particle size of 2.7 μm blended masterbatch (intrinsic viscosity: 0.59 dL / g) (7) Polyester G: homopolyethylene terephthalate (polyester A) with 1.0 mass% silica particles having an average particle size of 3.2 μm blended masterbatch (intrinsic viscosity: 0.64 dL / g) (8) Polyester H: homopolyethylene terephthalate (polyester A) with 3.2 mass% silica particles having an average particle size of 3.2 μm blended masterbatch (intrinsic viscosity: 0.62 dL / g) (9) Polyester I: A masterbatch prepared by blending homopolyethylene terephthalate (polyester A) with 3.5% by mass of silica particles having an average particle size of 4.1 μm (intrinsic viscosity: 0.70 dL / g). (10) Polyester J: A masterbatch prepared by blending homopolyethylene terephthalate (polyester A) with 15.0% by mass of silica particles having an average particle size of 4.1 μm (intrinsic viscosity:(11) Polyester K: a masterbatch (intrinsic viscosity: 0.48 dL / g) prepared by blending 35% by mass (3% by mass in terms of phosphorus element amount) of a phosphorus-based flame retardant having the following structure into homopolyethylene terephthalate (polyester A);

[0088]

[0089] In the above formula (3), n is ≧ 4. The flame retardant of the above formula (3) was obtained by the manufacturing method described in

[0054] to

[0058] of JP 2015-81271 A.

[0090] (12) Polyester L: A masterbatch obtained by blending 20% ​​by mass of carbon black (oil furnace black) having an average particle size of 70 nm with homopolyethylene terephthalate (intrinsic viscosity: 0.60 dL / g). (13) Polyester M: A masterbatch obtained by blending 50% by mass of titanium oxide particles having an average particle size of 0.3 μm with homopolyethylene terephthalate (intrinsic viscosity: 0.49 dL / g). (14) Polyester N: A masterbatch obtained by blending 1.5% by mass of fluorescent whitening agent (4,4'-Bis(2-benzoxazolyl)stillbene) with homopolyethylene terephthalate (intrinsic viscosity: 0.64 dL / g).

[0091] Example 1-1 A blend of 48.8% Polyester E, 2.5% Polyester H, 44.7% Polyester K, and 4.0% Polyester L by mass was fed into a vented extruder, melt-extruded at 290°C, and then cooled and solidified on a cooling roll set at a surface temperature of 40°C using an electrostatic adhesion method to obtain an amorphous film. The resulting unstretched sheet was then stretched 3.0 times in the longitudinal direction (MD) at 85°C using a roll stretcher. Furthermore, a resin composition having the following composition was applied to the sheet so that the thickness after drying was 0.02 μm, preheated at 125°C in a tenter, and then stretched 4.0 times in the transverse direction (TD) at 130°C. Finally, a heat setting treatment was performed at 215°C to obtain a 50 μm-thick biaxially oriented polyester film having a resin layer. The evaluation results are shown in Table 1.

[0092] (Resin Layer Composition) The following compounds O to Q were mixed in a solid content ratio of O / P / Q = 80:10:10 (mass %) to obtain a resin layer composition. (15) Compound O: Aqueous dispersion of polyester resin copolymerized with the following composition: (Acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / / (Diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56 / 40 / 4 / / 70 / 20 / 10 (16) Compound P: Aqueous dispersion of polyurethane resin copolymerized with the following composition: Aqueous dispersion obtained by neutralizing a polyurethane resin consisting of isophorone diisocyanate / polyhexamethylene carbonate polyol / polyoxytetramethylene glycol / dimethylolpropanoic acid = 15 / 78 / 5 / 2 (mol %) with triethylamine. (17) Compound Q: Hexamethoxymethylolmelamine

[0093] Examples 1-2 to 1-11, Comparative Example 1-1 Polyester films were produced in the same manner as in Example 1, except that the raw material composition, film thickness, and presence or absence of a resin layer were different.

[0094]

[0095] As can be seen from the results in Table 1, the polyester films of Examples 1-1 to 1-11 had a weight residual ratio of 15.0% or more by thermogravimetric differential thermal analysis (TG-DTA), confirming their insulating properties. When a square sample film was divided into four square sections, the first layer remained in four or more of the sections. When the square sample was divided into 25 square sections, the first layer remained in 20 or more of the sections. On the other hand, in Comparative Example 1-1, the weight residual ratio by thermogravimetric differential thermal analysis (TG-DTA) was less than 15.0%, failing to confirm their insulating properties. Therefore, it is clear that the effects of the present invention can be achieved by using this polyester film as the first layer of an exterior packaging material. The polyester film of the present invention was found to be able to avoid complete vaporization of the film (resin layer) at 500°C, a temperature range where the polyester resin layer would normally melt and vaporize, leaving no residue, by using a biaxially oriented polyester film containing a specific amount of inorganic particles and / or flame retardant, allowing a portion of the film (resin layer) to remain as a carbonized layer. The present invention was completed based on a completely new idea that had not been previously conceived: carbonizing a polyester film and using it as a carbonized layer. Therefore, melting and carbonization further improve the current interruption function during a short circuit, thereby contributing to the suppression of thermal runaway reactions. Therefore, the polyester film of the present invention can be suitably used in various applications that require insulation, and the effects of the present invention can be achieved by using it as the first layer of the packaging material in the spacer of the present invention.

[0096] On the other hand, the polyester film of Comparative Example 1-1 had a weight residual rate of less than 15.0% as determined by thermogravimetric differential thermal analysis (TG-DTA), and the polyester film was completely vaporized in an atmosphere of 500°C, causing the metal plate surface to become conductive and resulting in insufficient insulation.

[0097] <Evaluation Method> (2-1) Sheet Thickness The thickness of the heat-resistant sheet was measured using a thickness gauge 547-401 manufactured by Mitutoyo Corporation.

[0098] (2-2) Fiber Diameter The fiber diameter of the heat-resistant sheet was measured using a Digimatic Caliper CD-15APX manufactured by Mitutoyo Corporation.

[0099] (2-3) Puncture Strength The puncture strength of the heat-resistant sheet was evaluated using an Instron universal testing machine, Model 5566, in accordance with JIS Z 1707 under a test environment of 23°C and 50% RH. The test conditions were a test speed of 50 mm / min, a needle shape with a diameter of 1 mm, and a tip radius of 0.5 mm.

[0100] (2-4) Thermal Conductivity at 45°C "Average surface temperature" refers to the average temperature of any three points on the spacer surface that are in contact with the heating element. Thermal conductivity at 45°C was measured as follows. The heater, brass plate, insulation plate A (Misumi Corporation, model: HIPHA, thickness 10 mm), brass plate, porous body, brass plate, insulation plate A, brass plate, and insulation plate B (Misumi Corporation, model: HIPHA, thickness 40 mm) were sandwiched in this order to bring the components into close contact, and the aforementioned insulation material was used as a spacer. A hydraulic press HYP505H (manufactured by Japan Automatic Machine Co., Ltd.) was used to apply a load of 375 kg (equivalent to 15 kgf / cm2) to the top of insulation plate B. With this load applied, the heater temperature was raised to 45°C, and after the heater temperature reached 45°C, heating at that temperature was continued for 60 minutes. After heating was completed, the thickness of the insulating material (spacer) (referred to as "film thickness") was measured, and the room temperature thermal conductivity kL of the insulating material was calculated from the temperature at each position at the end of heating, the thermal conduction resistance from the heater to the insulating material, and the film thickness of the insulating material when compressed, according to the following formula: kL = (ΔT1 × L) / (ΔT2 × R) kL: thermal conductivity of the insulating material [W / (m K)] ΔT1: temperature difference between the high temperature side and the low temperature side of insulating plate A [K] ΔT2: temperature difference between the high temperature side and the low temperature side of the insulating material [K] L: film thickness of the insulating material when compressed [m] R: thermal conduction resistance from the heater to the insulating material 6.8 × 10 －３ [m ２ ・K / W]

[0101] (2-5) Remaining Area Ratio Evaluated in the same manner as in (1-4) above.

[0102] (2-6) Insulation The measurement method is described with reference to Figure 8. The sample film 1 and metal plate 2 (brass, 50 x 50 mm x 5 mm thick) were placed in this order on a metal block 3 (brass, 50 x 50 mm x 20 mm thick) into which a rod heater (Watlow Fire Rod Heater G1N) had been inserted. The rod heater was then heated to raise the temperature of the surface of the metal plate 2 from room temperature to 500°C (at a heating rate of 10°C / min), and the temperature was then maintained at 500°C for 10 minutes. The sample was then allowed to cool naturally to room temperature, and the resistance between the surface of the metal plate 2 and the metal block 3 was measured using a tester 4 (Hioki E.E. Corporation: Model IR4054) under an applied voltage of 125 V to evaluate the insulation (presence or absence of conduction).

[0103] Example 2-1 Glass cloth sheet 1 shown in Table 1 was used. The puncture strength was 7.5 N. The evaluation results are shown in Table 1.

[0104] Example 2-2 Glass cloth sheet 2 shown in Table 1 was used. The evaluation results are shown in Table 1.

[0105] Example 2-3 Polyimide sheet 2 shown in Table 1 was used. The evaluation results are shown in Table 1.

[0106]

[0107] As can be seen from the results in Table 2, the heat-resistant sheets of Examples 2-1 to 2-3 had excellent film remaining rates under high-temperature conditions, and the remaining film hindered contact between the tester and the metal plate, resulting in a good compatibility evaluation. Furthermore, when a square sample film was divided into four square compartments, the first layer remained in four or more compartments. When the square sample was divided into 25 square compartments, the first layer remained in 20 or more compartments. Therefore, even if the resin layer, which is the main constituent material of the exterior material, melts, insulation can be maintained, making it possible to maintain high safety even if an abnormality occurs in the single cell and the temperature reaches a high level. Furthermore, the heat-resistant sheets of Examples 2-1 and 2-2 have low thermal conductivity, which can also contribute to blocking heat transfer between batteries in the event of an abnormality.

[0108] REFERENCE SIGNS LIST 1 sample film 2 metal plate 3 metal block 4 tester 10 spacer 100 assembled battery 110 inner packaging material 111 internal space 120 exterior material 120a peripheral portion, sealing portion 120b gap 200 cell 200a cell 200b cell 210 terminal 220 terminal 300 housing 300a side plate 300b side plate 300c side plate 300d side plate 300e bottom plate 301 bus bar S1 first region S2 second region

Claims

1. A battery pack in which a spacer is placed between unit cells, the spacer including an exterior material and an inner packaging material, the exterior material including a metal layer, and the metal layer and the unit cells are not in contact with each other at temperatures between 25 and 500°C.

2. A battery pack in which a spacer is disposed between single cells, the spacer including an exterior material and an inner packaging material, the exterior material including a metal layer, the exterior material including a first layer outside the metal layer with respect to the inner packaging material, the area of ​​the first layer after heat treatment in which the first layer is heated from 25°C to 500°C at 10°C / min and held at 500°C for 10 minutes has an area ratio of 15% or more to the area before the heat treatment.

3. The battery pack according to claim 2, wherein said first layer forms a carbonized layer under the conditions of said heat treatment.

4. The battery pack according to claim 2, wherein the first layer is a resin layer containing at least one of inorganic particles and a flame retardant.

5. The battery pack of claim 4, wherein the flame retardant comprises a phosphate ester.

6. The battery pack according to claim 4, wherein said inorganic particles contain at least one material selected from the group consisting of metal oxides, metal hydroxides and carbonaceous materials.

7. The battery pack according to claim 2, wherein the 5% weight loss temperature of the resin contained in the first layer and the resin composition containing at least one of inorganic particles and a flame retardant is 30 to 80°C.

8. The battery assembly according to claim 2, wherein the first layer is a heat-resistant layer.

9. The battery pack according to claim 8, wherein the heat-resistant layer comprises a fibrous material.

10. The battery pack according to claim 1 or 2, further comprising a heat-resistant sheet disposed between the spacer and the unit cells.

11. The battery pack according to claim 8, wherein the heat-resistant layer is a fibrous sheet.

12. The battery pack according to claim 2, wherein the first layer has a thickness of 10 to 125 μm.

13. The battery pack according to claim 2, wherein the ratio of the thickness of the inner packaging material to the thickness of the first layer is 0.002 to 0.

3.

14. The battery pack according to claim 1 or 2, wherein the spacer contains a liquid in an inner encapsulating material.

15. The battery pack according to claim 1 or 2, wherein the spacer includes a porous body as an inner material.

16. The battery pack according to claim 1 or 2, wherein the spacer has a thermal conductivity of 0.18 W / (m·K) or more at an average surface temperature of 45° C.

17. The battery pack according to claim 1 or 2, wherein the thermal conductivity of the spacer at an average surface temperature of 180° C. is less than 0.20 W / (m·K).

18. A spacer comprising an exterior material and an inner packaging material, wherein the exterior material comprises a metal layer and further comprises a first layer outside the metal layer relative to the inner packaging material, and the area of ​​the first layer after heat treatment in which the first layer is heated from 25°C to 500°C at 10°C / min and held at 500°C for 10 minutes has an area ratio of 15% or more to the area before the heat treatment.

19. A method for manufacturing a battery pack including a spacer containing unit cells and an exterior material, the exterior material including a metal layer and configured so that the metal layer and the unit cells do not come into contact with each other at temperatures between 25 and 500°C, the method including disposing the spacer between two unit cells.

20. A method for suppressing electrical conduction between unit cells, comprising: a spacer disposed between the unit cells that inhibits contact between the metal layer and the unit cells at temperatures between 25 and 500°C.

21. A method for using a spacer between batteries, the spacer including an exterior material and an inner packaging material, the exterior material including a metal layer and a first layer that is located outside the metal layer with respect to the inner packaging material, the first layer being heated from 25°C to 500°C at 10°C / min and held at 500°C for 10 minutes, such that the area of ​​the first layer after heat treatment has an area ratio of 15% or more relative to the area before heat treatment.

Images