JP2020161249A - Battery cell and battery - Google Patents

Abstract

To provide a battery cell capable of extinguishing a fire in a short time against ignition caused by a sudden temperature rise, etc.SOLUTION: A battery cell contains a positive electrode, a negative electrode and an electrolyte, at least part of the surface of the battery cell being covered with a fire-resistant resin composition layer. The fire-resistant resin composition layer contains an endothermic agent and a resin. A-B that is a difference between an ignition temperature A of the electrolyte and an initial endothermic temperature B of the endothermic agent is above 0°C and equal to or below 350°C.SELECTED DRAWING: None

Description

The present invention relates to battery cells and batteries.

In various batteries typified by lithium batteries, the batteries may run away due to thermal runaway due to an internal short circuit or the like, causing problems such as ignition and smoking. In order to minimize the damage caused by such a defect, a method of making it difficult to transfer the heat of the abnormally high temperature battery to the surrounding battery and the housing containing the battery is being studied. For example, around the battery cell. A method of using a protective material such as a fireproof material or a heat insulating layer can be mentioned.

For example, Patent Document 1 discloses a battery cell in which at least a part of the outside is covered with a fire-resistant coating, and the fire-resistant coating is an abrative coating, an expansion coating, or an endothermic coating. It is disclosed that polyurethane-based coatings can be used.
Further, Patent Document 2 provides a heat insulating layer containing heat-absorbing inorganic compound particles having a thermal conductivity of 0.2 W / m · K or less and having an endothermic peak at a temperature of 80 ° C. or higher, and a binder. A portable electronic device powered by a secondary battery is disclosed.

Special Table 2013-528911 Japanese Patent No. 5643648

By the way, in recent years, batteries of mobile phones and the like have a high battery capacity and are easily ignited due to a rapid temperature rise, and there is a demand for a property of extinguishing a fire in a short time after the ignition. However, although the refractory coating of Patent Document 1 has a property of protecting the battery in the event of ignition, it has not been shown to have a property of extinguishing the fire in a short time in the event of ignition. Further, although the heat insulating layer disclosed in Patent Document 2 absorbs heat generated in a battery cell, it has not been shown to have fire resistance.

Therefore, it is an object of the present invention to provide a battery cell capable of extinguishing a fire in a short time against ignition caused by, for example, a sudden temperature rise of the battery, and a battery including the battery cell.

The gist of the present invention is the following [1] to [9].
[1] A battery cell that houses a positive electrode, a negative electrode, and an electrolytic solution, and has a refractory resin composition layer covering at least a part of the surface thereof.
The refractory resin composition layer contains an endothermic agent and a resin, and contains
A battery cell in which AB, which is the difference between the ignition temperature A of the electrolytic solution and the endothermic start temperature B of the endothermic agent, is more than 0 ° C and 400 ° C or less.
[2] The battery cell according to [1], wherein the content of the endothermic agent with respect to 100 parts by mass of the resin is 10 to 1600 parts by mass.
[3] The battery cell according to [1] or [2], wherein the heat absorbing agent has an average particle size of 0.1 to 90 μm.
[4] The battery cell according to any one of [1] to [3], wherein the solubility parameter of the resin is 9 or more.
[5] The battery cell according to any one of [1] to [4], wherein the endothermic agent is a metal hydroxide.
[6] The battery cell according to [5], wherein the metal hydroxide is at least one selected from the group consisting of aluminum hydroxide, magnesium hydroxide and calcium hydroxide.
[7] The battery cell according to any one of [1] to [6], wherein the resin is a thermoplastic resin.
[8] The battery cell according to any one of [1] to [7], wherein the refractory resin composition layer has a thickness of 5 to 10000 μm.
[9] A battery including the battery cell according to any one of [1] to [8].

According to the present invention, it is possible to provide a battery cell capable of extinguishing a fire in a short time against ignition caused by a sudden temperature rise of the battery, and a battery including the battery cell.

It is the schematic sectional drawing which shows one Embodiment of the battery which has a square battery cell. FIG. 5 is a schematic cross-sectional view showing another embodiment of a battery having a square battery cell. It is a schematic sectional drawing which shows one Embodiment of the battery which has a laminated type battery cell. FIG. 5 is a schematic cross-sectional view showing an embodiment of a battery having a cylindrical battery cell.

Hereinafter, the present invention will be described in detail.
[Battery cell]
The battery cell of the present invention contains a positive electrode, a negative electrode, and an electrolytic solution, and at least a part of the surface thereof is covered with a refractory resin composition layer. Further, the fireproof resin composition layer contains a heat absorbing agent and a resin, and AB, which is the difference between the ignition temperature A of the electrolytic solution and the heat absorption starting temperature B of the heat absorbing material, is more than 0 ° C. and 400 ° C. or less.
As long as the refractory resin composition layer covers the surface of the battery cell, the form of the film and the form of the sheet are not particularly limited, but the form of the sheet is preferable.

Good fire resistance can be obtained by covering at least a part of the surface of the battery cell with the fireproof resin composition layer, and in particular, it is the difference between the ignition temperature A of the electrolytic solution and the heat absorption start temperature B of the heat absorbing material. Since AB is more than 0 ° C. and 400 ° C. or lower, the fire can be extinguished in a short time against the ignition caused by the sudden temperature rise of the battery. This is because the endothermic material starts to absorb heat before the ignition temperature A, reducing the number of ignition sources, and even if the ignition occurs at the ignition point, the endothermic agent has already generated heat, so the fire extinguishing time is further shortened. It is thought that it can be done. That is, if AB is 0 ° C. or lower, that is, if AB is 0 or negative, the fire cannot be extinguished in a short time. Further, when AB exceeds 400 ° C., it becomes difficult to obtain the heat absorbing effect of the heat absorbing material.
AB is preferably 350 ° C. or lower, more preferably 250 ° C. or lower, and even more preferably 150 ° C. or lower. Further, from the viewpoint of sufficiently obtaining the endothermic effect of the endothermic agent, AB is preferably 50 ° C. or higher, more preferably 100 ° C. or higher, and even more preferably 200 ° C. or higher.

The ignition temperature A of the electrolytic solution is a spontaneous combustion temperature based on ASTM-E659, and can be specifically measured by the method described in Examples. Further, the endothermic start temperature B of the endothermic material can be measured by a thermogravimetric differential thermal analyzer (TG-DTA), and specifically, can be measured by the method described in Examples.

Hereinafter, the battery cell of the present invention will be described in more detail.
The fire-resistant resin composition layer according to the present invention contains a heat-absorbing agent and a resin, and the fire-resistant resin composition layer is formed from a fire-resistant resin composition containing a heat-absorbing agent and a resin.
<Heat absorber>
In the present invention, it is preferable to use an endothermic agent having an endothermic start temperature of 800 ° C. or lower. Further, it is preferable to use one having a heat absorption amount of 300 J / g or more. If either the heat absorption start temperature or the heat absorption amount is out of the above range, it may be difficult to extinguish the fire promptly when the battery or the like ignites.
The heat absorbing agent preferably has an average particle size of 0.1 to 90 μm. By setting the average particle size within the above range, the heat absorbing agent can be easily dispersed in the resin, the heat absorbing agent can be uniformly dispersed in the resin, and a large amount can be blended.

The endothermic start temperature of the endothermic agent is preferably 500 ° C. or lower, more preferably 400 ° C. or lower, further preferably 300 ° C. or lower, and even more preferably 250 ° C. or lower. By setting the endothermic start temperature of the endothermic agent to these upper limit values or less, the endothermic agent is rapidly decomposed at the time of ignition, and the fire can be extinguished quickly. The endothermic start temperature of the endothermic agent is, for example, 50 ° C. or higher, preferably 100 ° C. or higher, more preferably 150 ° C. or higher, still more preferably 180 ° C. or higher.

The endothermic amount of the heat absorbing agent is preferably 500 J / g or more, more preferably 600 J / g or more, and further preferably 900 J / g or more. When the heat absorption amount of the heat absorbing agent is within the above range, the heat absorption is improved, so that the fire resistance becomes better. The endothermic amount of the endothermic agent is usually 4000 J / g or less, preferably 3000 J / g or less, and more preferably 2000 J / g or less.
The amount of heat absorbed can be measured using a thermogravimetric differential thermal analyzer (TG-DTA), and specifically, it can be measured by the method described in Examples.

The average particle size of the heat absorbing agent is more preferably 0.5 to 60 μm, further preferably 0.8 to 40 μm, and even more preferably 0.8 to 10 μm. When the average particle size of the endothermic agent is within the above range, the dispersibility of the endothermic agent in the fireproof resin composition is improved, the endothermic agent is uniformly dispersed in the resin, and the amount of the endothermic agent blended with the resin is large. Can be done.
The average particle size of the heat absorbing agent is a value of the median diameter (D50) measured by a laser diffraction / scattering type particle size distribution measuring device.

The heat absorbing agent is appropriately selected so that AB, which is the difference between the ignition temperature A of the electrolytic solution and the heat absorption starting temperature B of the heat absorbing material, is more than 0 ° C. and 400 ° C. or less. Examples thereof include oxides, boron-based compounds and hydrates of metal salts, and among them, metal hydroxides are preferable. When a metal hydroxide is used, it is preferable because water is generated by the heat generated by ignition and the fire can be extinguished quickly. Further, a combination of a metal hydroxide compound and a hydrate of a metal salt is also preferable.
Examples of the metal hydroxide include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, hydrotalcite, talc and the like, and among them, aluminum hydroxide, magnesium hydroxide and calcium hydroxide are preferable. Examples of the boron-based compound include zinc borate and the like. Zinc borate may is hydrate, e.g. _{2ZnO · 3B 2 O 5 · 3.5H} 2 O. Examples of the metal salt hydrate include calcium sulfate hydrate (for example, dihydrate), magnesium sulfate hydrate (for example, heptahydrate), kaolin clay, boehmite, and dosonite. You may.
Among these, aluminum hydroxide, magnesium hydroxide, and zinc borate are preferable, and aluminum hydroxide and magnesium hydroxide are more preferable.

The content of the heat absorbing agent in the refractory resin composition forming the refractory resin composition layer is preferably 10 to 1600 parts by mass with respect to 100 parts by mass of the resin. If it is 10 parts by mass or more, the fire can be extinguished more quickly when the battery or the like ignites. Further, when the amount is 1600 parts by mass or less, the heat absorbing agent is easily dispersed uniformly in the resin, and the moldability and the like are improved.
The content of the endothermic agent is preferably 100 parts by mass or more, more preferably 500 parts by mass or more, and even more preferably 900 parts by mass or more. Further, it is preferably 1550 parts by mass or less, more preferably 1300 parts by mass or less, and even more preferably 1150 parts by mass or less. By setting the content of the endothermic agent to these lower limit values or more, it is possible to alleviate a rapid temperature rise and to extinguish the fire promptly even if it ignites. Further, when the value is not more than these upper limit values, it becomes easy to disperse uniformly in the resin, and the moldability and the like become excellent.

<Resin>
Examples of the resin include a thermoplastic resin, a thermosetting resin, and an elastomer resin.
Examples of the thermoplastic resin include polypropylene resins, polyethylene resins, poly (1-) butene resins, polyolefin resins such as polypentene resins, polyester resins such as polyethylene terephthalate, polystyrene resins, acrylonitrile-butadiene-styrene (ABS) resins, and the like. Polyvinyl acetal resin, ethylene vinyl acetate copolymer (EVA) resin, polyvinyl alcohol resin, polycarbonate resin, polyphenylene ether resin, acrylic resin, polyamide resin, polyvinyl chloride resin (PVC), novolak resin, polyurethane resin, polyisobutylene, etc. Synthetic resin of.
Examples of the thermosetting resin include synthetic resins such as epoxy resin, urethane resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, and polyimide.

As the elastomer resin, acrylonitrile butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene block copolymer, hydrogenated styrene-butadiene block Examples thereof include copolymers, hydrogenated styrene-butadiene-styrene block copolymers, hydrogenated styrene-isoprene block copolymers, hydrogenated styrene-isoprene-styrene block copolymers and the like.
In the present invention, one of these resins may be used alone, or two or more thereof may be mixed and used.

Among the above, the resin contained in the fire-resistant resin composition is preferably a thermoplastic resin from the viewpoint of improving the dispersibility of the heat-absorbing agent in the resin and the mechanical strength of the fire-resistant resin composition layer (particularly, the fire-resistant sheet). .. Among the thermoplastic resins, a group consisting of polyvinyl acetal resin, polyvinyl alcohol resin, acrylic resin, and ethylene-vinyl acetate copolymer resin from the viewpoint of further improving the mechanical strength of the fire resistant resin composition layer (particularly, the fire resistant sheet). It is preferable that it is at least one selected from, and it is more preferable that it is at least one selected from the group consisting of polyvinyl acetal resin, polyvinyl alcohol resin, and ethylene-vinyl acetate copolymer resin. Among them, polyvinyl acetal resin is preferable. More preferable.

Further, as the resin contained in the refractory resin composition, it is preferable to use a resin having a solubility parameter (SP value) of 9 or more among the above. When a resin having an SP value of 9 or more is used, the mechanical strength of the refractory resin composition layer (particularly, the refractory sheet) formed by the refractory resin composition tends to be improved. Further, when a resin having an SP value of 9 or more is used and a hydrated metal compound is used as an endothermic agent, the mechanical strength is further increased. This is because the hydrated metal compound has a relatively high polarity, so that it has good compatibility with a resin having an SP value of 9 or more, and the dispersibility between the resin and the hydrated metal compound is increased, and as a result, the mechanical strength is improved. It is thought that it will be done.
Further, when a resin having an SP value of 9 or more is used, the dispersibility of the hydrated metal compound is enhanced, whereby the content of the endothermic agent in the refractory resin composition can be relatively increased.
The SP value of the resin contained in the refractory resin composition of the present invention is more preferably 10 or more, preferably 15 or less, and more preferably 13 or less.
The resin preferably used as the resin having an SP value of 9 or more is a thermoplastic resin, and examples thereof include polyvinyl acetal resin, polyvinyl alcohol resin, acrylic resin, and ethylene-vinyl acetate copolymer resin.
In the present invention, the SP value is a value measured by the Fedors method.

(Polyvinyl acetal resin)
The polyvinyl acetal resin is not particularly limited as long as it is a polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol with an aldehyde, but a polyvinyl butyral resin is preferable. By using polyvinyl butyral, it is possible to increase the mechanical strength even when the amount of the resin relative to the endothermic agent is relatively small. Therefore, even if the thickness of the refractory resin composition layer (particularly, the refractory sheet) is reduced, a certain level of mechanical strength can be ensured.
The amount of hydroxyl groups in the polyvinyl acetal resin is preferably 20 to 40 mol%. By setting the amount of hydroxyl groups to 20 mol% or more, the polarity of the polyvinyl acetal resin becomes high, the binding force with the endothermic agent becomes strong, and the mechanical strength becomes easy to improve. Further, by setting the amount of hydroxyl groups to 40 mol% or less, it is possible to prevent the refractory resin composition layer (particularly, the refractory sheet) from becoming too hard. The amount of the hydroxyl group is more preferably 23 mol% or more, still more preferably 26 mol% or more. The amount of hydroxyl groups is more preferably 37 mol% or less, still more preferably 35 mol% or less.

The degree of acetalization of the polyvinyl acetal resin is preferably 40 to 80 mol%. By setting the degree of acetalization within the above range, the above-mentioned amount of hydroxyl groups can be set within the desired range, and the mechanical strength of the refractory sheet can be easily improved. The degree of acetalization is more preferably 55 mol% or more, further preferably 65 mol% or more, and even more preferably 76 mol% or less.
The amount of acetyl groups in the polyvinyl acetal resin is preferably 0.1 to 30 mol%. When the amount of acetyl groups is within this range, the moisture resistance is excellent, the compatibility with the plasticizer is excellent, high flexibility is exhibited, and the handleability is improved. Further, by setting the amount of acetyl groups within these ranges, the amount of hydroxyl groups described above can be set within a desired range, and the mechanical strength of the refractory sheet can be easily improved. From these viewpoints, the amount of acetyl group is more preferably 0.2 mol% or more, further preferably 0.5 mol% or more, still more preferably 15 mol% or less, still more preferably 7 mol% or less.
The degree of acetalization, the amount of hydroxyl groups, and the amount of acetyl groups can be measured and calculated by, for example, a method based on JIS K6728 "Polyvinyl butyral test method".

The degree of polymerization of the polyvinyl acetal resin is preferably 200 to 3000. By setting the degree of polymerization within these ranges, the endothermic agent can be appropriately dispersed in the refractory resin composition layer (particularly, the refractory sheet). The degree of polymerization is more preferably 250 or more, still more preferably 300 or more.
When the degree of polymerization of the polyvinyl acetal resin is lowered, the viscosity is lowered, the endothermic agent is easily dispersed, and the mechanical strength is improved. From such a viewpoint, the degree of polymerization of the polyvinyl acetal resin is preferably 2000 or less, more preferably 1500 or less, still more preferably 1000 or less.
The degree of polymerization of the polyvinyl acetal resin refers to the degree of viscosity average polymerization measured based on the method described in JIS K6728.

The viscosity of 10% by mass ethanol / toluene of the polyvinyl acetal resin is preferably 5 mPa · s or more, more preferably 10 mPa · s or more, and further preferably 15 mPa · s or more. The viscosity of 10% by mass ethanol / toluene is preferably 500 mPa · s or less, more preferably 300 mPa · s or less, and further preferably 200 mPa · s or less. By setting the viscosity of the polyvinyl acetal resin to 10% by mass of ethanol / toluene as described above, the endothermic agent can be easily dispersed in the fire-resistant resin composition layer (particularly, the fire-resistant sheet), and the mechanical strength is improved.
The 10% by mass ethanol / toluene viscosity is a value measured as follows.
150 ml of an ethanol / toluene (1: 1 weight ratio) mixed solvent is placed in an Erlenmeyer flask, a weighed sample is added thereto, the resin concentration is adjusted to 10 wt%, and the mixture is dissolved by shaking in a thermostatic chamber at 20 ° C. The solution can be held at 20 ° C. and the viscosity can be measured using a BM type viscometer to determine the viscosity of 10% by mass ethanol / toluene.

The aldehyde is not particularly limited, but in general, an aldehyde having 1 to 10 carbon atoms is preferably used. The aldehyde having 1 to 10 carbon atoms is not particularly limited, and for example, n-butyraldehyde, isobutylaldehyde, n-barrelaldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, and n-nonylaldehyde are not particularly limited. , N-decylaldehyde, formaldehyde, acetaldehyde, benzaldehyde and the like. Of these, n-butyraldehyde, n-hexylaldehyde, and n-bareraldehyde are preferable, and n-butyraldehyde is more preferable. These aldehydes may be used alone or in combination of two or more.

(Polyvinyl alcohol resin)
The polyvinyl alcohol resin is obtained by polymerizing a vinyl ester to obtain a polymer according to a conventionally known method, and then saponifying, that is, hydrolyzing the polymer.
Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatic acid, vinyl laurate, vinyl stearate, vinyl benzoate and the like.
The degree of saponification of the polyvinyl alcohol resin is preferably 80 to 99.9 mol%, more preferably 85 to 99 mol%. When the degree of saponification is within such a range, the polarity of the polyvinyl alcohol resin is increased, so that the dispersibility with the endothermic agent is improved, and the mechanical strength of the refractory sheet formed by the refractory resin composition is likely to be improved. ..
The degree of saponification is measured according to JIS K6726. The degree of saponification indicates the ratio of the units actually saponified to vinyl alcohol units among the units converted into vinyl alcohol units by saponification.

The degree of polymerization of the polyvinyl alcohol resin is not particularly limited, but is preferably 400 or more, more preferably 500 or more, still more preferably 700 or more. Further, it is preferably 2000 or less, more preferably 1500 or less, and further preferably 1000 or less. By setting the degree of polymerization within these ranges, the endothermic agent can be appropriately dispersed in the refractory sheet, and the mechanical strength of the refractory sheet is improved. The degree of polymerization is measured according to JIS K6726.

The viscosity of the polyvinyl alcohol resin in a 4% by mass aqueous solution is preferably 8 mPa · s or more, more preferably 10 mPa · s or more, and further preferably 12 mPa · s or more. The viscosity of the 4% by mass aqueous solution is preferably 25 mPa · s or less, more preferably 20 mPa · s or less, and further preferably 16 mPa · s or less.
By adjusting the viscosity of the 4% by mass aqueous solution of the polyvinyl alcohol resin as described above, the heat absorbing agent can be easily dispersed in the fireproof resin composition layer (particularly, the fireproof sheet), and the mechanical strength is improved.
The viscosity of the 4% by mass aqueous solution can be measured at 20 ° C. according to JIS K 6726.

(Ethylene-vinyl acetate copolymer resin)
The ethylene-vinyl acetate copolymer resin may be a non-crosslinked ethylene-vinyl acetate copolymer resin or a high-temperature crosslinked ethylene-vinyl acetate copolymer resin. Further, as the ethylene-vinyl acetate copolymer resin, an ethylene-vinyl acetate modified resin such as a saponified product of the ethylene-vinyl acetate copolymer and a hydrolyzate of ethylene-vinyl acetate can also be used.
The ethylene-vinyl acetate copolymer resin preferably has a vinyl acetate content of 10 to 50% by mass, more preferably 25 to 45% by mass, as measured in accordance with JIS K 6730 “Ethylene-vinyl acetate resin test method”. .. By setting the vinyl acetate content to these lower limit values or more, the adhesiveness to the substrate, which will be described later, is improved. Further, by setting the vinyl acetate content to these upper limit values or less, the mechanical strength of the refractory resin composition layer (particularly, the refractory sheet) becomes good.
The weight average molecular weight of the ethylene-vinyl acetate copolymer resin is preferably 5000 to 20000, more preferably 1000 to 150,000. By setting the weight average molecular weight in such a range, the endothermic agent can be appropriately dispersed in the refractory resin composition layer (particularly, the refractory sheet), and the mechanical strength is improved. Here, the weight average molecular weight is a standard polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC).

(acrylic resin)
The acrylic resin is, for example, a polymer obtained by polymerizing a monomer component containing a (meth) acrylic acid alkyl ester-based monomer. In addition, in this specification, "(meth) acrylic acid alkyl ester" means "acrylic acid alkyl ester, or methacrylic acid alkyl ester". The same is true for other similar terms.
The (meth) acrylic acid alkyl ester-based monomer in the present invention is an ester of (meth) acrylic acid and an aliphatic alcohol, and the alkyl group of the aliphatic alcohol preferably has 1 to 14 carbon atoms, more preferably. Is 1-10.
Specific examples of the (meth) acrylic acid alkyl ester-based monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. , Isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl. Examples thereof include (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, and tetradecyl (meth) acrylate.
The (meth) acrylic acid alkyl ester-based monomer may be used alone or in combination of two or more.

Further, as the monomer component for obtaining the acrylic resin, a polar group-containing monomer may be contained in addition to the above-mentioned (meth) acrylic acid alkyl ester-based monomer.
Examples of the polar group-containing monomer include (meth) acrylic acid, a vinyl group-containing carboxylic acid such as itaconic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl. Vinyl monomers having hydroxyl groups such as (meth) acrylate, caprolactone-modified (meth) acrylate, polyoxyethylene (meth) acrylate, and polyoxypropylene (meth) acrylate, (meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam. , N-vinyllaurilolactam, (meth) acryloylmorpholine, (meth) acrylamide, dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, and dimethylaminomethyl (meth) acrylate. Examples thereof include nitrogen-containing vinyl monomers such as.

As the acrylic resin, a homopolymer of a (meth) acrylic acid alkyl ester-based monomer is preferable, and polymethyl (meth) acrylate and polyethyl (meth) acrylate, which are homopolymers of methyl (meth) acrylate and ethyl (meth) acrylate. Etc. are preferable, polymethyl (meth) acrylate is more preferable, and polymethyl methacrylate is further preferable.

The weight average molecular weight of the acrylic resin is preferably 1,000 to 100,000 from the viewpoint of appropriately dispersing the endothermic agent in the fire-resistant resin composition layer (particularly, the fire-resistant sheet) and improving the mechanical strength. It is more preferably 5,000 to 90,000, and even more preferably 20,000 to 80,000. Here, the weight average molecular weight is a standard polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC).
The (meth) acrylic acid alkyl ester-based monomer may be used alone or in combination of two or more.

The content of the resin in the refractory resin composition forming the refractory resin composition layer is preferably 5% by mass or more, more preferably 6% by mass or more, and further preferably 8% by mass or more. When the content of the resin in the refractory resin composition is at least these lower limit values, the moldability of the refractory resin composition is improved when it is molded into, for example, a refractory sheet. The content is preferably 85% by mass or less, more preferably 80% by mass or less, still more preferably 50% by mass or less, still more preferably 15% by mass or less. Further, in the present invention, a large amount of the endothermic agent can be blended by setting the upper limit value or less. Further, even with a small amount of resin such as 15% by mass or less, the moldability can be improved by adjusting the melt flow rate of the resin and the average particle size of the endothermic agent.

<Arbitrary ingredient>
〔Flame retardants〕
The refractory resin composition forming the refractory resin composition layer according to the present invention preferably further contains a flame retardant. When the refractory resin composition contains a flame retardant, the spread of fire can be suppressed even when the refractory resin composition layer using the flame retardant is ignited.
Examples of the flame retardant include various phosphate esters such as red phosphorus, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresil diphenyl phosphate, and xylenyl diphenyl phosphate, sodium phosphate, potassium phosphate, and the like. Examples thereof include metal phosphates such as magnesium phosphate, ammonium polyphosphate, and compounds represented by the following general formula (1).

In the general formula (1), R ¹ and R ³ represent hydrogen, a linear or branched alkyl group having 1 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms, which are the same or different. R ² represents a hydroxyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, straight-chain or branched alkoxy group having 1 to 16 carbon atoms, an aryl group having 6 to 16 carbon atoms, or carbon atoms It shows 6 to 16 aryloxy groups.

Specific examples of the compound represented by the general formula (1) include methylphosphonate, dimethyl methylphosphonate, diethyl methylphosphonate, ethylphosphonate, n-propylphosphonate, n-butylphosphonate, and 2-methylpropylphosphonate. , T-butylphosphonate, 2,3-dimethyl-butylphosphonate, octylphosphonate, phenylphosphonic acid, dioctylphenylphosphonate, dimethylphosphonate, methylethylphosphinic acid, methylpropylphosphinic acid, diethylphosphonate, dioctylphosphonate , Phosphonate, diethylphenylphosphonate, diphenylphosphonate, bis (4-methoxyphenyl) phosphonate and the like. The flame retardant may be used alone or in combination of two or more.
Among the flame retardants, red phosphorus, ammonium polyphosphate, and the compound represented by the general formula (1) are preferable from the viewpoint of improving the flame retardancy of the fire resistant resin composition layer, and flame retardant performance, safety, and so on. Ammonium polyphosphate is more preferable from the viewpoint of cost and the like.

When the refractory resin composition contains a flame retardant, the content thereof is preferably 1 to 200 parts by mass, more preferably 5 to 100 parts by mass, still more preferably 5 to 50 parts by mass with respect to 100 parts by mass of the resin component. .. When the content of the flame retardant is within the above range, the spread of fire can be suppressed when the refractory resin composition layer using the refractory resin composition ignites.

[Thermal expandable graphite]
The refractory resin composition forming the refractory resin composition layer may contain thermally expandable graphite. When the refractory resin composition contains heat-expandable graphite, the heat-expandable graphite expands when heated to form a large-capacity void and functions as a flame retardant. Therefore, the refractory resin composition is used for fire resistance. When the resin composition layer is ignited, the spread of fire can be suppressed.

The heat-expandable graphite is not particularly limited as long as it expands when heated, and powders such as natural scaly graphite, pyrolytic graphite, and kiss graphite are treated with an inorganic acid and a strong oxidizing agent to form a graphite intercalation compound. Examples include those produced, which are crystalline compounds that maintain the layered structure of carbon.
Examples of the inorganic acid include concentrated sulfuric acid, nitric acid, and selenic acid, and examples of the strong oxidizing agent include concentrated nitric acid, perchloric acid, perchlorate, permanganate, dichromate, and hydrogen peroxide. Can be mentioned.
The heat-expandable graphite may be further neutralized. Specifically, it is preferable to further neutralize the heat-expandable graphite obtained by the acid treatment with ammonia, an aliphatic lower amine, an alkali metal compound, an alkaline earth metal compound or the like.
The particle size of the heat-expandable graphite is preferably 20 to 200 mesh. When the particle size of the expandable graphite is within the above range, it expands easily to form a large-capacity void, so that the flame retardancy is improved. In addition, the dispersibility in the resin is also improved.

The average aspect ratio of the heat-expandable graphite is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. The upper limit of the average aspect ratio of the heat-expandable graphite is not particularly limited, but is preferably 1,000 or less from the viewpoint of preventing the heat-expandable graphite from cracking. When the average aspect ratio of the heat-expandable graphite is 2 or more, it expands and easily forms a large-capacity void, so that flame retardancy is improved.
The average aspect ratio of the heat-expandable graphite was measured for each of the 10 heat-expandable graphites in the maximum dimension (major axis) and the minimum dimension (minor axis), and the maximum dimension (major axis) was divided by the minimum dimension (minor axis). Let the average value be the average aspect ratio. The major axis and minor axis of the heat-expandable graphite can be measured using, for example, a field emission scanning electron microscope (FE-SEM).

When the refractory resin composition contains thermally expandable graphite, the content thereof is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, and further 30 to 100 parts by mass with respect to 100 parts by mass of the resin. preferable. When the content of the heat-expandable graphite is within the above range, it becomes easy to form a large-capacity void in the refractory resin composition, so that the flame retardancy is improved.

[Inorganic filler]
The fire-resistant resin composition forming the fire-resistant resin composition layer may further contain an inorganic filler other than the endothermic agent, the flame retardant and the expandable graphite.
The inorganic filler other than the heat absorbing agent and expansive graphite is not particularly limited, and for example, metal oxides such as alumina, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, and ferrite. Metal carbonates such as basic magnesium carbonate, calcium carbonate, magnesium carbonate, zinc oxide, strontium carbonate, and barium carbonate, silica, diatomaceous soil, dosonite, barium sulfate, clay, mica, montmorillonite, bentonite, active white clay, sepiolite, imogolite, Serisite, glass fiber, glass beads, silica-based balloon, aluminum nitride, boron nitride, silicon nitride, carbon black, graphite, carbon fiber, carbon balloon, charcoal powder, various metal powders, potassium titanate, magnesium sulfate, zinc oxide Examples thereof include lead acid acid, zinc stearate, calcium stearate, aluminum borate, molybdenum sulfide, silicon carbide, stainless fiber, zinc borate, various magnetic powders, slag fibers, fly ash, and dehydrated sludge. These inorganic fillers may be used alone or in combination of two or more.

The average particle size of the inorganic filler is preferably 0.5 to 100 μm, more preferably 1 to 50 μm. When the content of the inorganic filler is low, the particle size is preferably small from the viewpoint of improving dispersibility, and when the content is high, the viscosity of the refractory resin composition increases and the moldability becomes higher as the filling progresses. It is preferable that the particle size is large because it decreases.

When the fire-resistant resin composition contains an inorganic filler other than a heat absorbing agent and expansive graphite, the content thereof is preferably 10 to 300 parts by mass, more preferably 10 to 200 parts by mass with respect to 100 parts by mass of the resin. Is. When the content of the inorganic filler is within the above range, the mechanical properties of the refractory resin composition layer (refractory sheet) using the inorganic filler can be improved.

[Plasticizer]
The refractory resin composition forming the refractory resin composition layer may further contain a plasticizer. In particular, when the resin component is a polyvinyl chloride resin, it is preferable to include a plasticizer from the viewpoint of improving moldability.
The plasticizer is not particularly limited as long as it is a plasticizer generally used in producing a polyvinyl chloride resin molded product. Specifically, for example, phthalate ester plasticizers such as di-2-ethylhexylphthalate (DOP), dibutylphthalate (DBP), diheptylphthalate (DHP), and diisodecylphthalate (DIDP), di-2-ethylhexyl adipate (di-2-ethylhexyl adipate). DOA), diisobutyl adipate (DIBA), dibutyl adipate (DBA) and other fatty acid ester plasticizers, epoxidized soybean oil and other epoxidized ester plasticizers, adipic acid ester, adipate polyester and other adipic acid ester plasticizers Examples thereof include trimellitic acid ester plasticizers such as 2-ethylhexyl trimellitate (TOTM) and triisononyl trimellitate (TINTM), and process oils such as mineral oil. The plasticizer may be used alone or in combination of two or more.
When the refractory resin composition contains a plasticizer, the content thereof is preferably 5 to 40 parts by mass, more preferably 5 to 35 parts by mass with respect to 100 parts by mass of the resin. When the content of the plasticizer is within the above range, the extrusion moldability tends to be improved, and it is possible to prevent the molded product from becoming too soft.

<Other ingredients>
The refractory resin composition forming the refractory resin composition layer may contain various additive components as necessary, as long as the object of the present invention is not impaired.
The type of this additive component is not particularly limited, and various additives can be used. Examples of such additives include lubricants, shrinkage inhibitors, crystal nucleating agents, colorants (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, antistatic agents, fillers, reinforcing agents, and flame retardant aids. , Antistatic agents, surfactants, vulcanizing agents, surface treatment agents and the like. The amount of the additive added can be appropriately selected as long as the moldability is not impaired. The additive may be used alone or in combination of two or more.

The refractory resin composition layer is made of the above-mentioned refractory resin composition, and it is preferable that the refractory resin composition layer covers at least a part of the surface of the battery cell as a refractory sheet made of the refractory resin composition. Such a refractory sheet can be produced by molding the refractory resin composition according to the present invention. Specific examples thereof include extrusion molding, press molding, and injection molding. Among them, extrusion molding is preferable, and molding can be performed using a single-screw extruder, a twin-screw extruder, an injection molding machine, or the like.

The thickness of the refractory sheet is not particularly limited, but is preferably 5 to 10000 μm, more preferably 20 to 4000 μm, further preferably 50 to 2000 μm, further preferably 100 to 1800 μm, and even more preferably 500 to 1500 μm. When the thickness of the refractory sheet is within the above range, it can be used for a small battery cell while maintaining the mechanical strength. The "thickness" of the refractory sheet in the present specification refers to the average thickness of three points in the width direction of the refractory sheet. Further, even in the case of a refractory resin composition layer that is not a refractory sheet, the thickness is preferably in the above range.

The refractory resin composition layer may be composed of a single layer or may be composed of multiple layers.
Therefore, when the refractory resin composition layer is made of a refractory sheet, the refractory sheet may be used alone, or layers other than the refractory sheet may be laminated to form a refractory multilayer sheet. The refractory multilayer sheet has, for example, a base material and a fireproof sheet provided on at least one surface of the base material.
Here, the base material may be a combustible layer, a semi-incombustible layer, or a non-combustible layer. The thickness of the base material is not particularly limited, but is, for example, 5 μm to 1 mm. Examples of the material used for the flammable layer include one type or two or more types of cloth material, paper material, wood, resin film and the like. When the base material is a semi-incombustible layer or a non-combustible layer, examples of the material used for the semi-incombustible layer or the non-combustible layer include a metal and an inorganic material.

The refractory multilayer sheet may include a refractory sheet and an adhesive layer provided on at least one surface of the refractory sheet. The pressure-sensitive adhesive layer may be provided on the above-mentioned base material, or may be formed directly on the surface of the refractory sheet. Further, a double-sided adhesive tape provided with adhesive layers on both surfaces of the base material may be attached to at least one surface of the refractory sheet. That is, the pressure-sensitive adhesive layer, the base material, and the pressure-sensitive adhesive layer may be provided on one surface of the refractory sheet in this order.
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited, and examples thereof include, but are not limited to, an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive. The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is, for example, 3 to 500 μm, preferably 10 to 200 μm.

In the battery cell of the present invention, the positive electrode, the negative electrode, and the electrolytic solution are housed in an exterior member such as an exterior can or an exterior film, and at least a part of the surface thereof is covered with a refractory resin composition layer. Hereinafter, the positive electrode, the negative electrode, the electrolytic solution, and the like housed in the exterior member will be described.

As the electrolytic solution, for example, in the case of an electrolytic solution for a lithium ion battery, an electrolytic solution containing an organic solvent and an electrolyte salt can be exemplified. Examples of the organic solvent include non-aqueous solvents such as carbonates, esters, ethers, nitriles, sulfones, and lactones. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrohydrafuran, Polar solvents such as 2-methyltetraethane, dioxolane and methylacetamide, or mixtures of two or more of these solvents can be mentioned. Of these, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and the like are preferable.

Electrolyte salts include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₆ , LiCF ₃ CO ₂ , LiPF ₆ SO ₃ , LiN (SO ₃ CF ₃ ) ₂ , Li (SO ₂ CF ₂ CF ₃ ) ₂ , Examples thereof include lithium-containing salts such as LiN (COCF ₃ ) _2, LiN (COCF ₂ CF ₃ ) ₂ , and lithium bisoxalate boronate (LiB (C ₂ O ₄ ) ₂ ). Also, lithium organic acid salt-3 foots. Examples thereof include a boron carbonate complex, a complex such as a complex hydride such as LiBH _{4, and the} like. These salts or complexes may be used alone or as a mixture of two or more.

The concentration of the electrolyte salt in the electrolytic solution is preferably 0.05 to 10 mol / L, more preferably 0.1 to 5 mol / L.

The ignition temperature A of the electrolytic solution is preferably 300 to 600 ° C., more preferably 400 to 500 ° C., from the viewpoint of ensuring safety and ion conductivity. Further, the electrolytic solution is preferably appropriately selected so that the difference (AB) between the ignition temperature A and the heat absorption start temperature B of the heat absorbing material is more than 0 ° C. and 400 ° C. or less.
The ignition temperature of the electrolytic solution is the same as the ignition temperature of the organic solvent used, and even when the electrolyte salt is contained at, for example, about 0.05 to 10 mol / L, the ignition temperature of the electrolyte is used. It becomes the same as the ignition temperature of the organic solvent.

AB, which is the difference between the ignition temperature A of the electrolytic solution and the heat absorption start temperature B of the heat absorbing material, is selected so as to be more than 0 ° C. and 400 ° C. or less. In the present invention, the heat absorbing material is aluminum hydroxide. In the case of, the electrolytic solution is preferably a combination of ethylene carbonate or propylene carbonate. When the heat absorbing material is calcium hydroxide, the electrolytic solution is preferably a combination of dimethyl carbonate or diethyl carbonate. Further, when the heat absorbing material is zinc borate, the electrolytic solution is preferably a combination of dimethyl carbonate or propylene carbonate. When the heat absorbing material is magnesium sulfate, the electrolytic solution is preferably a combination of diethyl carbonate.

The positive electrode may be a known one, and a positive electrode active material layer formed by using a positive electrode material in which a positive electrode active material, a binder and a solvent, and, if necessary, a conductive auxiliary agent and the like are blended, is used as a current collector ( An example is provided on the positive electrode current collector). A commercially available product may be used as the positive electrode.
The negative electrode may be a known one, and a negative electrode active material layer formed by using a negative electrode material in which a negative electrode active material, a binder and a solvent, and, if necessary, a conductive auxiliary agent and the like are blended, is used as a current collector ( An example is provided on the negative electrode current collector). A commercially available product may be used as the negative electrode.
A known separator may be provided between the negative electrode and the positive electrode.

<Manufacturing method>
The method for manufacturing the battery cell of the present invention will be described below.
In producing the battery cell of the present invention, first, the refractory resin composition according to the present invention is produced. The refractory resin composition can be obtained by mixing the above-mentioned resin, heat absorber, and optional components using a known device such as a Banbury mixer, a kneader mixer, a kneading roll, a Raikai machine, and a planetary stirrer. it can.

Then, the refractory resin composition is covered with at least a part of the surface of the exterior member containing the positive electrode, the negative electrode, and the electrolytic solution to a desired thickness to form a refractory resin composition layer (coating). The battery cell of the present invention can be manufactured.
Further, when the above-mentioned refractory sheet is used as the refractory resin composition layer, the battery cell of the present invention can be manufactured by covering at least a part of the surface of the exterior member with the refractory sheet.

The refractory resin composition layer may be provided on any surface of the battery cell, but preferably covers the surface of most of the battery cell (eg, 50% or more, more preferably 70% or more of the surface area). Since the refractory resin composition layer covers most of the surface, it becomes easy to extinguish the fire quickly against the ignition of the battery cell.
Further, the battery cell often has a safety valve, but when it has a safety valve, it is preferable that the battery cell is provided so as to cover the safety valve with a refractory resin composition layer. At this time, in order to ensure the function of the safety valve, the refractory resin composition layer should be covered so as not to seal the safety valve. Further, in the case of a laminated type battery cell, it is preferable that the battery cell is provided so as to cover the heat seal portion to be crimped by the heat seal.
Since the battery cell often ignites from the safety valve or the heat seal portion, covering these with a refractory resin composition layer makes it easier to extinguish the fire more effectively than the ignition of the battery cell.
Further, when the refractory resin composition layer covers most of the surface of the battery cell and has a safety valve or a heat seal portion, it is more preferable that the refractory resin composition layer is arranged so as to cover the safety valve or the heat seal portion as well. For example, when the refractory resin composition layer is a refractory sheet, the refractory sheet may be arranged so as to be wound around the battery cell.

Battery cells are classified into cylindrical type, square type, and laminated type according to the shape of the cell.
When the battery cell has a cylindrical shape, the positive electrode, the negative electrode, the electrolytic solution, the separator, the positive electrode terminal, the negative electrode terminal, the insulating material, the safety valve, the gasket, the positive electrode cap, and the like are housed in the outer can.
When the battery cell is square, the positive electrode, the negative electrode, the electrolytic solution, the separator, the positive electrode terminal, the negative electrode terminal, the insulating material, the safety valve, and the like are housed in the outer can.
When the battery cell is a laminated type, the positive electrode, the negative electrode, the electrolytic solution, the separator, the positive electrode terminal, the negative electrode terminal and the like are housed in the exterior film. In a laminated battery, between two exterior films, or one exterior film is folded in half, for example, and between the folded exterior films, a positive electrode material, a negative electrode material, a separator, a positive electrode terminal, And the negative electrode terminal and the like are arranged, and the outer edge portion of the exterior film is crimped by heat sealing. Examples of the exterior film include an aluminum film on which a polyethylene terephthalate film is laminated.

For example, when the battery cell is square as shown in FIG. 1, the fireproof sheet 12 which is the fireproof resin composition layer is arranged so that the outer peripheral surface of the exterior member 11 can be wound around, and for example, the main surfaces 11A and 11B thereof. And, it is preferable that it is arranged on the end faces 11C and 11D. The main surfaces 11A and 11B are both sides having the largest area in the exterior member 11 of the square battery cell, and the end surfaces 11C and 11D are end surfaces connecting the main surfaces 11A and 11B. In a square cell, a safety valve (not shown) is generally provided on either of the end faces 11C and 11D. Therefore, even in the configuration of FIG. 1, the fireproof sheet 11 covers the safety valve of the battery cell.
Further, for example, when the battery cell is square as shown in FIG. 2, the fireproof sheet 12 may be provided only on both the main surfaces 11A and 11B of the exterior member 11. Further, it may be provided on only one of the main surfaces 11A and 11B.

When the battery cell is a laminated type, as shown in FIG. 3, the refractory sheet 12 may be provided so as to cover both sides 11X and 11Y of the exterior member 11, for example. At this time, the fireproof sheet 12 may be arranged so as to cover the heat seal portion 11Z as well.
Even in the laminated type, the refractory sheet 12 may be provided so as to cover only one surface 11X of the exterior member 11. Further, also in the laminated type, the refractory sheet 12 may be arranged so as to wind around the outer peripheral surface of the exterior member 11.
Further, as shown in FIG. 4, when the battery cell has a cylindrical shape, the refractory sheet 12 may be arranged so as to be wound around the outer peripheral surface of the exterior member 11.
In addition, in FIGS. 1 to 4, the refractory sheet 12 may be adhered to the exterior member 11 via an adhesive layer provided on one surface of the refractory sheet 12.
Further, the configurations shown in FIGS. 1 to 4 are merely examples of the arrangement positions of the refractory sheets, and may be arranged at positions other than these. Further, depending on the location, a portion using the refractory sheet and a portion using the refractory resin composition layer formed from the coating film of the refractory resin composition may be mixed.

The battery cell is a secondary battery such as a lithium ion battery or a lithium ion polymer battery, and among these, a lithium ion battery is preferable.

[battery]
The battery of the present invention includes the battery cell of the present invention described above. The battery usually has at least one battery cell, but it is preferable that at least one of the battery cells is the battery cell of the present invention, and it is more preferable that all of the battery cells are the battery cells of the present invention. preferable.

Batteries are used, for example, in small electronic devices such as mobile phones and smartphones, notebook computers, automobiles, and the like, but are not limited thereto.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
<Examples 1 to 3, 5 to 7, Comparative Examples 1 to 3>
A slurry liquid prepared by diluting the refractory resin composition having the composition shown in Table 1 with a mixed solvent in which ethanol / toluene was blended at a weight ratio of 50:50 to a solid content concentration of 55% by mass was prepared. The details of each component will be described later. The slurry liquid was applied to one side of a release sheet (PET film manufactured by Lintec Corporation) and dried at 80 ° C. for 30 minutes to obtain a refractory sheet formed on the release sheet. Next, the fireproof sheet was peeled off from the release sheet to obtain a single fireproof sheet.
The fireproof sheets prepared in Examples and Comparative Examples were arranged so as to be wrapped around the exterior member of the laminated lithium-ion battery used in the smartphone to prepare the battery cells of each example. As the electrolytic solution of the lithium ion battery, the one shown in Table 1 was used.

<Example 4>
The refractory resin composition having the formulations shown in Table 1 was supplied to a uniaxial extruder and extruded at 150 ° C. to obtain a refractory sheet having a thickness of 1.0 mm.
As in Example 1, a battery cell was produced by arranging the produced refractory sheet around the exterior member of a laminated lithium-ion battery used in a smartphone so as to wrap it around. As the electrolytic solution of the lithium ion battery, the electrolytic solution (4) was used.

<Resin>
The following resin was used as the resin.
PVB: Polyvinyl butyral resin, degree of polymerization 800, degree of acetalization 69 mol%, amount of acetyl group 1 mol%, amount of hydroxyl group 30 mol%, 10 mass% ethanol / toluene viscosity 142 mPa · s, SP value 10.6
PVA: Polyvinyl alcohol resin, degree of polymerization 800, degree of saponification 98 mol%, 4 mass% aqueous solution viscosity 142 mPa · s, SP value 12.4
EVA: EVAFlex EV460, Mitsui DuPont Polychemical Co., Ltd., vinyl acetate content 40% by mass, weight average molecular weight 110,000, SP value 9.1

<Heat absorber>
The following compounds were used as heat absorbers.
Heat absorbing agent (1): Aluminum hydroxide BF013, manufactured by Nippon Light Metal Co., Ltd. Heat absorbing agent (2): Calcium hydroxide CAOH-2, manufactured by Suzuki Kogyo Co., Ltd. Heat absorbing agent (3): Zinc borate Firebreak ZB, manufactured by Borax Co., Ltd. Agent (4): Magnesium sulfate heptahydrate, manufactured by Nacalai Tesque, with an average particle size of 40 μm, a thermal decomposition start temperature of 150 ° C., and an endothermic amount of 1600 J / g.
Endothermic agent (5): Calcium carbonate Whiten BF-300, Bikita Powder Co., Ltd.

<Flame retardant>
The following compounds were used as flame retardants.
Ammonium polyphosphate: AP422, Clariant AG

<Electrolytic solution>
The following composition was used as the electrolytic solution.
Electrolyte (1): Electrolyte in which LiPF ₆ was dissolved in ethylene carbonate at a ratio of 1 mol / liter Electrolytic solution (2): LiPF ₆ was dissolved in propylene carbonate at a ratio of 1 mol / liter. Electrolyte Electrolyte (3): Electrolyte in which LiPF ₆ is dissolved in diethyl carbonate at a ratio of 1 mol / liter Electrolytic solution (4): LiPF ₆ in dimethyl carbonate at a ratio of 1 mol / liter Dissolved electrolyte

<Measurement method of endothermic start temperature>
The measurement was performed using a thermogravimetric differential thermal analyzer (TG-DTA). The measurement conditions were from room temperature to 1000 ° C., a heating rate of 4 ° C./min, and an endothermic agent weight of 10 mg. The endothermic start temperature was defined as the base of the first DTA curve (endothermic peak) on the low temperature side (the point at which the inflection starts away from the baseline) that appears when the temperature rises.
<Measurement method of heat absorption>
Using a thermogravimetric differential thermal analyzer (TG-DTA), the measurement conditions were from room temperature to 1000 ° C., a heating rate of 4 ° C./min, and an endothermic agent weight of 10 mg. It was calculated from the heat absorption amount (area of the recess) from the obtained DTA curve.
<Measuring method of average particle size of heat absorber>
The average particle size of the endothermic agent was measured by laser diffraction. Specifically, the average particle size was defined as the particle size at an integrated value of 50% in the particle size distribution obtained by a particle size distribution meter such as a laser diffraction / scattering type particle size distribution meter.
<Measurement method of ignition temperature of electrolyte>
In accordance with ASTM E659, a sample was placed in a heated 500 ml round bottom flask using an ignition point measuring device manufactured by ADVANTEC, and the ignition temperature of the electrolytic solution was measured.

<Battery fire extinguishing test>
The battery cells produced in Examples and Comparative Examples were placed on a hot plate set at 300 ° C., and the time from the release of the fire to the extinguishment of the fire was evaluated.
If the fire extinguishing time is within 5 seconds, it is evaluated as "A", if the fire extinguishing time is more than 5 seconds and within 10 seconds, it is evaluated as "B", and if the fire extinguishing time is more than 10 seconds, it is evaluated as "C". , The shorter the fire extinguishing time, the better the fire extinguishing performance. The results are shown in Table 1.

As is clear from the results of the above examples, according to the present invention, it is possible to provide a battery cell capable of extinguishing a fire in a short time against ignition caused by a sudden temperature rise or the like during thermal runaway of the battery cell. ..

10 Battery 11 Exterior member 12 Fireproof sheet

Claims (9)

A battery cell that houses a positive electrode, a negative electrode, and an electrolytic solution, and has a refractory resin composition layer covering at least a part of the surface thereof.
The refractory resin composition layer contains an endothermic agent and a resin, and contains
A battery cell in which AB, which is the difference between the ignition temperature A of the electrolytic solution and the endothermic start temperature B of the endothermic agent, is more than 0 ° C and 400 ° C or less. The battery cell according to claim 1, wherein the content of the endothermic agent with respect to 100 parts by mass of the resin is 10 to 1600 parts by mass. The battery cell according to claim 1 or 2, wherein the heat absorbing agent has an average particle size of 0.1 to 90 μm. The battery cell according to any one of claims 1 to 3, wherein the resin solubility parameter is 9 or more. The battery cell according to any one of claims 1 to 4, wherein the endothermic agent is a metal hydroxide. The battery cell according to claim 5, wherein the metal hydroxide is at least one selected from the group consisting of aluminum hydroxide, magnesium hydroxide and calcium hydroxide. The battery cell according to any one of claims 1 to 6, wherein the resin is a thermoplastic resin. The battery cell according to any one of claims 1 to 7, wherein the refractory resin composition layer has a thickness of 5 to 10000 μm. A battery including the battery cell according to any one of claims 1 to 8.