WO2024122507A1

WO2024122507A1 - Battery packaging material

Info

Publication number: WO2024122507A1
Application number: PCT/JP2023/043334
Authority: WO
Inventors: 直也甲田
Original assignee: 株式会社レゾナック・パッケージング
Priority date: 2022-12-06
Filing date: 2023-12-04
Publication date: 2024-06-13
Also published as: JP2024081206A

Abstract

According to the present invention, a specific lubricant is used for a thermally fusible resin layer of a battery packaging material, thereby improving the lubricity during shaping and suppressing deterioration in the battery performance. The present invention provides a battery packaging material 1 which comprises, from the outer side toward the inner side, at least a base material layer 13, a barrier layer 11 and a thermally fusible resin layer 15. This battery packaging material is characterized in that: the thermally fusible resin layer 15 contains a polyolefin resin and one or more lubricants; and at least one lubricant is an N-substituted amide that is represented by formula (I). In the formula, R1 represents a hydrocarbon chain expressed by C_m1H_n1; and R2 represents a hydrocarbon chain expressed by C_m2H_n2.

Description

Battery packaging materials

The present invention relates to a battery packaging material that is suitable for use as a case for secondary batteries, particularly small, portable lithium-ion secondary batteries, for example, for in-vehicle, stationary, notebook computers, mobile phones, and cameras.

Electricity storage devices, such as lithium-ion batteries, can now be made into a variety of shapes and can also be made thinner and lighter by using laminated packaging materials, such as aluminum foil or metal cases, with resin film attached to both sides.

Laminate-type battery packaging materials are formed into three-dimensional shapes, such as roughly rectangular parallelepiped shapes, by deep drawing or stretch forming. By forming the battery packaging material into a three-dimensional shape, it is possible to ensure storage space for the electrodes and electrolyte.

In order to mold battery packaging materials into a three-dimensional shape in good condition without pinholes or breaks, it is necessary to improve the slipperiness of the surface of the inner heat-sealable resin layer (sealant layer). Adding a lubricant to the resin has been a method of improving the slipperiness of the heat-sealable resin layer (see Patent Documents 1 to 3).

Patent Document 1 describes how slipperiness can be improved by using a sealant film in which a specific lubricant is added to a random copolymer of α-olefins with a specific composition as the heat-sealable resin layer.

Patent Document 2 describes how the use of a sealant film containing a specified amount of saturated fatty acid amide and unsaturated fatty acid amide as a heat-sealable resin layer improves slipperiness and prevents the generation of white powder caused by bleeding out of the lubricant.

Patent Document 3 describes how using a multi-layer sealant film with three or more layers as the heat-sealable resin layer and specifying the lubricant content of each layer improves slipperiness and prevents the generation of white powder caused by bleeding out of the lubricant.

Patent No. 3774163 Patent No. 6808966 Patent Publication No. 6943547

The technology described in the above-mentioned documents focuses on the composition of the sealant film and the type and amount of lubricant added to improve slipperiness during molding. In this way, the materials for the heat-sealable resin layer of battery packaging materials have been improved solely for the purpose of improving slipperiness during molding.

The heat-sealable resin layer of battery packaging forms the inner surface of the battery case and is the layer that comes into contact with the electrodes and electrolyte, but until now, the effect of lubricants on battery performance had not been studied.

In view of the above-mentioned background technology, the present invention aims to improve the slipperiness during molding and suppress deterioration of battery performance by using a specific lubricant in the heat-sealable resin layer of battery packaging material.

In other words, the present invention has the configurations described in [1] to [7] below.

[1] A battery packaging material including, in order from the outside to the inside, at least a base layer, a barrier layer, and a heat-sealable resin layer,
The battery packaging material, wherein the heat-sealable resin layer contains a polyolefin resin and one or more lubricants, and at least one of the lubricants is an N-substituted amide represented by the following formula (I):

R1 is a hydrocarbon chain represented by C _m1 H _n1 ; and R2 is a hydrocarbon chain represented by C _m2 H _n2 . [2] The battery packaging material described in the preceding paragraph 1, wherein the N-substituted amide has 34 or more carbon atoms, and the number of carbon atoms of R1 (m1) and the number of carbon atoms of R2 (m2) satisfy the relationship |m1-m2|≦15.

[3] The battery packaging material according to

paragraph

1 or 2 above, in which the heat-sealable resin layer is a single layer or a multi-layer of two or more layers, the innermost layer contains an N-substituted amide, and the total concentration of all lubricants including the N-substituted amide in the innermost layer is 100 ppm by mass to 2500 ppm by mass.

[4] The battery packaging material according to any one of the preceding paragraphs 1 to 3, wherein the heat-sealable resin layer contains an unsaturated fatty acid amide as a lubricant.

[5] The battery packaging material according to paragraph 3 or 4 above, in which the ratio of the N-substituted amide to the total amount of lubricant in the innermost layer of the heat-sealable resin layer is 30% by mass to 100% by mass.

[6] A battery packaging material according to any one of paragraphs 1 to 5 above, in which a lubricant layer containing an N-substituted amide is formed on the surface of the heat-sealable resin layer.

[7] A battery case member, characterized in that a recess is formed by deep drawing or stretch molding in the battery packaging material described in any one of claims 1 to 6.

The battery packaging material described in [1] above contains an N-substituted amide as a lubricant added to the heat-sealable resin layer that forms the inner surface of the battery case. The lubricant precipitates on the layer surface and exhibits a slipperiness-improving effect, enabling deeper forming in deep drawing and stretch forming, thereby increasing the battery capacity. Furthermore, since the N-substituted amide has hydrocarbon chains (aliphatic hydrocarbons) R1 and R2 bonded to both ends of the amide group, even if it dissolves into the electrolyte, it does not interfere with the movement of lithium ions during charging and discharging, and the deterioration of battery performance caused by the lubricant can be suppressed.

The battery packaging material described in [2] above has a total carbon number of 34 or more in the N-substituted amide, and the carbon number of R1 (m1) and the carbon number of R2 (m2) satisfy the relationship |m1-m2|≦15. This reduces the effect of the amide group due to steric hindrance and reduces the intramolecular polarity, thereby reducing the effect of the amide group impeding the movement of lithium ions, suppressing the increase in the internal resistance of the battery, and improving the discharge rate.

The battery packaging material described in [3] above has a single or multiple heat-sealable resin layer, the innermost layer contains an N-substituted amide, and the total concentration of all lubricants including the N-substituted amide is 100 ppm by mass to 2500 ppm by mass, so that the lubricating properties are good and the amount of bleed-out is suppressed.

The battery packaging material described in [4] above has an excellent slipperiness because the heat-sealable resin layer contains an unsaturated fatty acid amide as a lubricant.

The battery packaging material described in [5] above has an N-substituted amide content of 30% to 100% by mass relative to the total amount of lubricant in the innermost layer of the heat-sealable resin layer, so that a good balance can be achieved between the effect of improving lubricity and the effect of suppressing the deterioration of battery performance.

The battery packaging material described in [6] above has an N-substituted amide-containing lubricant layer formed on the surface of the heat-sealable resin layer, which improves lubricity and inhibits deterioration of battery performance.

The battery case member described in [7] above contains an N-substituted amide as a lubricant in the heat-sealable resin layer on the inner surface of the recess, which allows for deep forming in deep drawing and stretch forming, thereby increasing the battery capacity. Moreover, even if the lubricant dissolves in the electrolyte, it does not interfere with the movement of lithium ions during charging and discharging, and the deterioration of battery performance caused by the lubricant can be suppressed.

FIG. 1 is a cross-sectional view showing an example of a battery packaging material of the present invention. FIG. 2 is a cross-sectional view showing another example of the battery packaging material of the present invention. FIG. 2 is a cross-sectional view showing still another example of the battery packaging material of the present invention. 2 is a cross-sectional view of a battery case made from the battery packaging material of FIG. 1 .

Figures 1 to 3 show an example of the battery packaging material of the present invention and its modified example.

In the following description, layers with the same reference numerals denote the same or equivalent parts, and duplicated descriptions will be omitted.
[Battery packaging material]
The battery packaging material of the present invention is basically a laminate including, from the outside to the inside, at least a base layer, a barrier layer, and a heat-sealable resin layer.

The battery packaging material 1 in FIG. 1 is a laminate in which a base layer 13 is bonded to one side of a barrier layer 11 via a first adhesive layer 12, and a heat-sealable resin layer 15 is bonded to the other side via a second adhesive layer 14.

As shown in FIG. 4, the battery packaging material 1 is processed into a main body 51 with a recess 52 formed therein and a flat lid 55, and the heat-sealable resin layers 15 of both are arranged facing each other to house a battery main body 56 in the recess 52, and the flange portion 53 around the recess 52 and the lid 55 are heat-sealed to produce a battery case 50. In the battery case 50, the base material layer 13 is on the outside and the heat-sealable resin layer 15 is on the inside. Therefore, in the present invention, when describing the positions of the layers constituting the battery packaging material in terms of direction, the direction toward the base material side is referred to as the outside and the direction toward the heat-sealable resin layer is referred to as the inside, in accordance with the direction between the inside and outside of the case.

The battery packaging material 1 of the present invention uses a specific lubricant in the heat-sealable resin layer 15 that forms the inner surface of the case 50 and comes into contact with the battery body 56, thereby improving the slipperiness during molding and preventing a decrease in battery performance.

Each layer constituting the battery packaging material 1 will be described in detail below.
(Heat-fusible resin layer)
The heat-sealable resin layer 15 provides excellent chemical resistance against highly corrosive electrolytes and the like, and also provides the battery packaging material 1 with heat sealability.

The heat-sealable resin layer 15 contains a polyolefin resin and one or more lubricants, at least one of which is an N-substituted amide represented by the following formula (I):

R1 is a _hydrocarbon chain represented by _Cm1Hn1 R2 is a hydrocarbon chain represented by _Cm2Hn2 The lubricant improves the sliding property with the mold during molding, and when the heat-fusible resin layer ₁₅ is formed from a resin composition in which a resin and a lubricant are mixed, the lubricant precipitates on the layer surface and exhibits a sliding property improving effect. Therefore, deep molding is possible in deep drawing and stretch molding, and the battery capacity can be increased.

Examples of the polyolefin resin include polyethylene resin and polypropylene resin, and propylene resin is particularly preferred. As the propylene resin, unstretched films such as cast polypropylene (CPP) and inflation polypropylene (IPP) are preferred. Examples of the propylene resin include propylene homopolymers (hPP) and ethylene-propylene copolymers containing ethylene and propylene as copolymerization components. The ethylene-propylene copolymer may be either a random copolymer (rPP) or a block copolymer (bPP).

The heat-sealable resin layer may be either a single layer or a multilayer. The heat-sealable resin layer 15 of the battery packaging material 1 in FIG. 1 is a single layer, the heat-sealable resin layer 20 of the battery packaging material 2 in FIG. 2 is a three-layer layer, and the heat-sealable resin layer 25 of the battery packaging material 3 in FIG. 3 is a two-layer layer. The multilayer film constituting the multilayer heat-sealable resin layer can be produced by co-extrusion or the like. Among the various propylene-based resin films mentioned above, a three-layer co-extruded CPP film having an hPP or bPP intermediate layer and rPP layers on both outer sides of the intermediate layer is recommended for the three-layer film, because of its excellent heat sealability, delamination resistance, and insulation properties. The heat-sealable resin layer 20 of the battery packaging material 2 in FIG. 2 is composed of a three-layer film having a laminate layer 22 bonded to the second adhesive layer 14 on one side of the intermediate layer 21 and a seal layer 23 on the other side. The heat-sealable resin layer 25 of the battery packaging material 3 in Figure 3 is a two-layer film consisting of a laminate layer 22 and a seal layer 23.

The lubricant must contain an N-substituted amide, and multiple N-substituted amides or other lubricants can be used in combination.

Examples of N-substituted amides represented by the above formula (I) include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Table 1 shows the total carbon number of these N-substituted amides, the carbon number of R1 (m1), and the carbon number of R2 (m2).

N-substituted amides have hydrocarbon chains (aliphatic hydrocarbons) R1 and R2 attached to both ends of the amide group, so even if they dissolve into the electrolyte, they do not interfere with the movement of lithium ions during charging and discharging. In particular, this can prevent performance degradation of lithium ion secondary batteries, such as an increase in internal resistance and a decrease in discharge rate. On the other hand, in the case of erucic acid amide, where the amide group is present at the end of the molecular chain, the amide group interacts with Li ions and easily forms a non-covalent bond, thus interfering with the movement of Li ions.

Among the above N-substituted amides, it is preferable to use amides having a total carbon number of 34 or more and in which the number of carbon atoms in R1 (m1) and the number of carbon atoms in R2 (m2) satisfy the relationship |m1-m2|≦15, i.e., the absolute value of m1-m2 is 15 or less. N-substituted amides that satisfy this condition have a smaller effect of the amide group due to steric hindrance and a smaller intramolecular polarity, so that the effect of the amide group impeding the movement of lithium ions can be reduced. Specifically, they are highly effective in suppressing the increase in the internal resistance of the battery and improving the discharge rate.

The heat-sealable resin layer is a single layer or multiple layers, and in order to improve the slipperiness and prevent the deterioration of the battery performance, it is preferable to include an N-substituted amide in the innermost layer and to specify the total concentration of all lubricants including the N-substituted amide in the innermost layer. The innermost layer is the layer that forms the inner surface of the battery case 50 and comes into contact with the mating material during heat sealing. The innermost layer of the three-layer heat-sealable resin layer 20 in FIG. 2 or the two-layer heat-sealable resin layer 25 in FIG. 3 is the seal layer 23. In the case of a single layer, the entire heat-sealable resin layer 15 is the innermost layer. The total concentration of all lubricants in the innermost layer is preferably 100 ppm by mass to 2500 ppm by mass. If it is less than 100 ppm by mass, good slipperiness cannot be obtained, and if it exceeds 2500 ppm by mass, the amount of bleed-out increases, and the lubricant may precipitate in the form of white powder on the surface of the innermost layer and adhere to the molding die or production line. If it is 2500 ppm by mass or less, the amount of bleed-out is suppressed. A particularly preferred total concentration of all lubricants in the innermost layer is 200 ppm by mass to 2000 ppm by mass.

The lubricant added to the innermost layer may be only N-substituted amide, or other lubricants may be used in combination. When using other lubricants in combination, it is preferable that the ratio of N-substituted amide to the total amount of lubricant in the innermost layer of the heat-sealable resin layer is 30% by mass or more in order to prevent a decrease in battery performance. If the ratio of N-substituted amide is less than 30% by mass and the ratio of other lubricants increases, the other lubricants dissolved in the electrolyte may hinder the movement of lithium ions during charging and discharging, causing a decrease in battery performance. Therefore, the preferred ratio of N-substituted amide to the total amount of lubricant in the innermost layer is 30% to 100% by mass. The particularly preferred ratio of N-substituted amide to the total amount of lubricant in the innermost layer is 40% by mass or more. The names of lubricants used in combination with N-substituted amide will be described in detail later.

In addition, when adding an N-substituted amide or other lubricant to layers other than the innermost layer in a multi-layer heat-sealable resin layer, it is preferable to increase or decrease the concentration of the other layers using the total concentration of all lubricants, including the N-substituted amide, in the innermost layer as the reference concentration.

In the three-layer heat-sealable resin layer 20 in FIG. 2, it is desirable to set the total concentration of all lubricants in the innermost sealing layer 23 as the reference concentration, the concentration in the intermediate layer 21 to 1000 ppm or more and less than twice the reference concentration, and the concentration in the laminate layer 22 to 1/2 the reference concentration or less (including 0 ppm by mass). By making the N-substituted amide concentration in the intermediate layer 21 higher than that in the sealing layer 23, it is possible to suppress the migration of the N-substituted amide in the sealing layer 26 to the intermediate layer 21 and promote the bleeding out of the N-substituted amide to the surface of the sealing layer 23. In addition, by making the N-substituted amide concentration in the laminate layer 21 lower than that in the sealing layer 23, it is possible to suppress the bleeding out of the N-substituted amide to the laminate layer/adhesive layer interface and prevent a decrease in laminate strength. In the three-layer heat-sealable resin layer 25 of FIG. 3, the total concentration of all the lubricants in the seal layer 23 is set as the reference concentration, and it is preferable that the lubricant concentration in the laminate layer 22 be 1/2 or less of the reference concentration.

Lubricants that can be used in combination with N-substituted amides include methylol amides, saturated fatty acid amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Among these lubricants, fatty acid amides, especially unsaturated fatty acid amides, are recommended as they have a greater effect on improving lubrication than N-substituted amides.

As the methylol amide, methylol stearic acid amide can be used.

As the saturated fatty acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide can be used.
As the saturated fatty acid bisamide, methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, and N,N'-distearyl sebacic acid amide can be used.

As the unsaturated fatty acid bisamide, oleic acid amide, erucic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipic acid amide, and N,N'-dioleyl sebacate amide can be used.

As the fatty acid ester amide, stearamide ethyl stearate can be used.

Aromatic bisamides that can be used include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide.

The lubricant added to the heat-fusible resin layer 15 improves the lubricity by precipitating on the layer surface. The preferred amount of lubricant precipitating on the layer surface is 0.1 μg/cm ² to 1 μg/cm ² .

In addition to the lubricant, the heat-sealable resin layer 15 may contain solid particles added as an antiblocking agent to prevent adhesion with the base layer 13, or as a surface roughening agent to improve slipperiness. Examples of the solid particles include silica, alumina, calcium carbonate, barium carbonate, titanium oxide, aluminum silicate, talc, kaolin, acrylic resin beads, and polyethylene resin beads. When using these solid particles as antiblocking agents, the preferred average particle size is 0.05 μm to 5 μm, and the preferred content is 500 ppm to 3500 ppm. When using them as surface roughening agents, the preferred average particle size is more than 5 μm and not more than 20 μm, and the preferred content is 200 ppm to 5000 ppm.

The roughening material is a component added to form irregularities on the layer surface, so in the multi-layered heat-sealable resin layers 20 and 25, it is sufficient to add it only to the innermost seal layer 23, and it is preferable not to add it to the laminate layer 22 on the barrier layer 11 side. In addition, since the preferred average particle size of the roughening material is more than 5 μm and not more than 20 μm, the thickness of the layer to which the roughening material is added is preferably in the range of 5 μm to 20 μm. If the roughening material is added to a layer with a thickness of less than 5 μm, it will easily fall off. On the other hand, if the layer thickness exceeds 20 μm, many parts of the roughening material with an average particle size of more than 5 μm and not more than 20 μm will be embedded in the resin, which may result in a loss of rigidity of the film. In addition, the roughening material will not be uniformly dispersed in the layer, which may reduce impact resistance and interlayer strength.

The coefficient of dynamic friction of the heat-resistant resin layers 15, 20, and 25 is preferably 0.02 to 0.3. If the coefficient of dynamic friction is less than 0.02, the slipperiness is too good, and the battery packaging material is likely to slip or meander on the production line. On the other hand, if the coefficient of dynamic friction exceeds 0.3, the slipperiness decreases and the effect of improving moldability cannot be expected.

The thickness of the heat-sealable resin layer 15 is preferably 20 μm to 120 μm. The same is true for the total thickness of the

multilayer films

20, 25. A particularly preferred thickness is 30 μm to 80 μm.

Furthermore, it is also preferable that a lubricant layer containing an N-substituted amide is formed on the surface of the heat-sealing

resin layer

15, 20, 25. The lubricant layer is the total amount of the lubricant layer due to precipitation from the heat-sealing resin layer and the lubricant layer due to application or transfer from the base layer 13, and this lubricant layer also provides an effect of improving the slipperiness and suppressing the deterioration of the battery performance. The lubricant layer may be a layer that completely covers the surface of the heat-sealing

resin layer

15, 20, 25, or a layer in which the lubricant is intermittently present on the surface of the heat-sealing

resin layer

15, 20, 25. The preferred amount of lubricant in the lubricant layer is 0.15 μg/cm ² to 0.6 μg/cm ² .
(Barrier Layer)
The barrier layer 11 plays a role of imparting gas barrier properties that prevent the intrusion of oxygen and moisture to the battery packaging material 1. The barrier layer 11 is not particularly limited as long as it is a metal foil, but examples thereof include aluminum foil, SUS foil (stainless steel foil), copper foil, nickel foil, titanium foil, and clad foil, and aluminum foil can be preferably used. The thickness of the barrier layer 11 is preferably 10 μm to 120 μm. By having a thickness of 10 μm or more, it is possible to prevent the occurrence of pinholes during rolling in the production of the metal foil, and by having a thickness of 120 μm or less, it is possible to reduce stress during molding such as stretch molding and drawing molding, thereby improving moldability. A particularly preferable thickness of the barrier layer 11 is 30 μm to 90 μm.

In addition, it is preferable that the barrier layer 11 is subjected to a base treatment such as a chemical conversion treatment at least on the surface of the metal foil on the side of the heat-fusible resin layer 15. By performing such a chemical conversion treatment, corrosion of the metal foil surface due to the contents (such as a battery electrolyte) can be sufficiently prevented.
(Base layer)
The base layer 13 is made of a heat-resistant resin film that does not melt at the heat-sealing temperature when the battery packaging material 1 is heat-sealed. The heat-resistant resin is a heat-resistant resin having a melting point 10° C. or higher, preferably 20° C. or higher, than the melting point of the resin constituting the heat-fusible resin layer 15. Examples of resins that satisfy this condition include polyamide films such as nylon films, polyester films, etc., and these stretched films are preferably used. Among them, it is particularly preferable to use biaxially stretched polyamide films such as biaxially stretched nylon films, biaxially stretched polybutylene terephthalate (PBT) films, biaxially stretched polyethylene terephthalate (PET) films, or biaxially stretched polyethylene naphthalate (PEN) films as the base layer 13. The nylon film is not particularly limited, but examples include 6 nylon film, 6,6 nylon film, and MXD nylon film. The base layer 13 may be formed of a single layer, or may be formed of a multilayer structure consisting of, for example, a polyester film/polyamide film (such as a multilayer structure consisting of a PET film/nylon film).

The thickness of the base material layer 13 is preferably 9 μm to 50 μm, which can ensure sufficient strength as a packaging material and can reduce stress during molding such as stretch molding and drawing, thereby improving moldability. The thickness of the base material layer 13 is more preferably 9 μm to 30 μm. When the base material layer 13 is a multi-layered layer, the total thickness is defined as the above thickness. The thickness of the adhesive that bonds the multiple layers is also included in the above thickness.
(First Adhesive Layer)
The first adhesive layer 12 is not particularly limited, and examples thereof include an adhesive layer formed by a two-liquid curing adhesive. Examples of the two-liquid curing adhesive include a two-liquid curing adhesive composed of a first liquid (base) consisting of one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols, and polyester urethane polyols, and a second liquid (curing agent) consisting of an isocyanate. Among them, it is preferable to use a two-liquid curing adhesive composed of a first liquid consisting of one or more polyols selected from the group consisting of polyester polyols and polyester urethane polyols, and a second liquid (curing agent) consisting of an isocyanate. The preferred thickness of the first adhesive layer 12 is 2 μm to 5 μm.

Furthermore, the above-mentioned adhesives are also recommended when the outer layer is made up of multiple layers (including when the base layer is made up of multiple layers).
(Second Adhesive Layer)
The second adhesive layer 14 is not particularly limited, but for example, an adhesive containing one or more of polyurethane resin, acrylic resin, epoxy resin, polyolefin resin, elastomer resin, fluorine resin, and acid-modified polypropylene resin is recommended. Among them, an adhesive made of polyurethane composite resin containing acid-modified polyolefin as a main component is preferable. The preferred thickness of the second adhesive layer 14 is 2 μm to 5 μm.

The first adhesive layer 12 and the second adhesive layer 14 are not essential layers, and the base layer 13 may be directly bonded to the barrier layer 11, or the heat-sealable resin layer 15 may be directly bonded to the barrier layer 11.

　A layer can be added to the outside of the substrate layer 13 of the battery packaging material 1 of the present invention. For example, a substrate protective layer made of a resin composition containing a resin component and solid fine particles can be formed to impart slipperiness to the outer surface, improving moldability, and imparting excellent chemical resistance, solvent resistance, and abrasion resistance.

The preferred materials for the resin composition constituting the substrate protective layer are as follows:

As the resin component, it is preferable to use at least one of the following resins: acrylic resin, epoxy resin, urethane resin, polyolefin resin, fluorine resin, and phenoxy resin. These resins have high chemical resistance and solvent resistance, so that the solid particles are less likely to fall off due to deterioration of the resin.

The resin component may be a base resin containing at least one of the above-mentioned resins and a curing agent that cures the base resin. The curing agent is not particularly limited and may be selected appropriately according to the base resin. For example, when the base resin is a mixture of a urethane resin and a phenoxy resin, it is preferable to use an isocyanate compound. As the isocyanate compound, various polyfunctional isocyanate compounds of aliphatic, alicyclic, and aromatic types can be recommended. Examples of aliphatic polyfunctional isocyanate compounds include hexamethylene diisocyanate (HDI), etc., examples of alicyclic polyfunctional isocyanate compounds include isophorone diisocyanate (IPDI), etc., and examples of aromatic polyfunctional isocyanate compounds include tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). Modified products of these polyfunctional isocyanate compounds may also be used, and examples of such modified polyfunctional isocyanates include those obtained by polymerization reactions such as isocyanuration, carbodiimide formation, and polymerization.

The hardener is preferably blended in an amount of 5 to 30 parts by weight per 100 parts by weight of the base resin. If the amount is less than 5 parts by weight, adhesion to the base layer 13 and solvent resistance may decrease. If the amount is more than 30 parts by weight, the base protection layer 30 may become hard and moldability may decrease. A particularly preferred blend amount of hardener is 10 to 20 parts by weight per 100 parts by weight of the base resin.

The substrate protective layer has a smaller shrinkage rate than the film that constitutes the substrate layer 13, so it is possible to reduce the stress caused by the expansion and contraction of the outer layer on the substrate layer 13 side. In particular, when a polyamide film is used for the substrate layer 13, polyamide has a tendency to shrink in response to moisture, but the substrate protective layer 30 blocks moisture in the air, so it is less likely to shrink and stress on the outer layer is also reduced.

It is also preferable to use urethane resins and polyester urethane resins as the base resin.

The solid fine particles may be either inorganic or organic, or may be mixed together. Examples of inorganic fine particles include silica, alumina, calcium oxide, calcium carbonate, calcium sulfate, calcium silicate, and carbon black. Examples of organic fine particles include fine particles of acrylic ester compounds, polystyrene compounds, epoxy resins, polyamide compounds, or crosslinked products thereof. One type of solid fine particle may be used, or two or more types may be used in combination.

These solid particles preferably have an average particle size of 1 μm to 10 μm, with 2 μm to 5 μm being particularly preferred. When using solid particles that are too small, less than 1 μm in particle size, they will be buried in the coating liquid, making it difficult to obtain the desired properties. On the other hand, when using solid particles that are large, more than 10 μm in particle size, their particle size will exceed the coating thickness and they will be prone to falling off the substrate protective layer.

The content of solid fine particles in the resin composition is preferably in the range of 0.1% by mass to 60% by mass, and even more preferably in the range of 5% by mass to 55% by mass.

The thickness of the base protective layer after curing is preferably 1 to 10 μm. A layer thinner than the lower limit has little effect in improving slipperiness, while a layer thicker than the upper limit increases costs. A particularly preferred thickness is in the range of 2 to 5 μm.
[Battery case components]
The battery case member of the present invention has a recess formed by deep drawing or stretch molding the battery packaging material described above. The main body 51 having the recess 52 in FIG. 4 corresponds to the battery case member of the present invention. The battery packaging material of the present invention has good slipperiness and excellent formability of the heat-sealable resin layer, which is advantageous for forming the recess 52 and is suitable for forming a deep recess. The battery capacity can be increased by forming a deep recess to expand the storage space of the battery main body. In addition, since the inner surface of the recess is a heat-sealable resin layer to which an N-substituted amide has been added, the deterioration of the battery performance can be suppressed.

[Battery packaging material]
As Examples 1, 2, and 4 to 7 and Comparative Examples 1 and 2, battery packaging material 2 was produced in the laminated form shown in Fig. 2, and as Example 3, battery packaging material 1 was produced in the laminated form shown in Fig. 1. These

battery packaging materials

1 and 2 have in common that, from the outside to the inside, a base material layer 13, a first adhesive layer 12, a barrier layer 11, and a second adhesive layer 14 are laminated, but the number of heat-sealable resin layers 15, 20 laminated on the inside of the second adhesive layer 14 is different. The heat-sealable resin layer 15 of battery packaging material 1 is a single layer, and the heat-sealable resin layer 20 of battery packaging material 2 is a three-layer structure consisting of a seal layer 23, an intermediate layer 21, and a laminate layer 22 (see Table 2).

The materials common to the

battery packaging materials

1 and 2 of each example are as follows.
(Common materials)
The barrier layer 11 was made of aluminum foil made of A8021-O specified in JIS H4160 and having a thickness of 40 μm. Both sides of the aluminum foil were coated with a chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol, and then dried at 180° C. to form a chemical conversion film. The chromium deposition amount of this chemical conversion film was 5 mg/ ^m2 per side.

A biaxially oriented nylon 6 film with a thickness of 25 μm was used as the substrate layer 13.

A two-component curing urethane adhesive was used for the first adhesive layer 12.

As the second adhesive layer 14, a two-component curing type maleic acid modified propylene adhesive was used.
(Preparation of film for heat-sealable resin layer)
As the single-layered heat-fusible resin layer 15 of Example 3, an unstretched PP film having a thickness of 30 μm was prepared by blending two types of lubricants shown in Table 3 and silica having an average particle size of 2 μm as an antiblocking material (AB material) with ethylene-propylene random copolymer (rPP). The names and concentrations of the lubricants and the content of the antiblocking material are as shown in Table 3.

Three-layer films were produced as the heat-sealable resin layer 20 for Examples 1, 2, and 4 to 7 and Comparative Examples 1 and 2.

The sealing layer 23 is made of ethylene-propylene random copolymer (rPP) blended with one or two types of lubricant shown in Table 3, silica with an average particle size of 2 μm as an antiblocking material (AB material), and HDPE beads with an average particle size of 12 μm as a roughening material. The middle layer 21 is made of ethylene-propylene block copolymer (bPP) blended with one or two types of lubricant shown in Table 3. The laminate layer 22 is made of ethylene-propylene random copolymer (rPP) blended with the lubricant shown in Table 3 and silica with an average particle size of 2 μm as an antiblocking material. The lubricant name and lubricant concentration, antiblocking material content, and roughening material content concentration of each layer are as shown in Table 3.

The mixed materials for each of the above layers were co-extruded to produce a three-layer film with a sealing layer 23 thickness of 12 μm, an intermediate layer 21 thickness of 56 μm, and a laminate layer 22 thickness of 12 μm, for a total thickness of 80 μm.

Table 2 shows the total concentration (ppm by mass) of all lubricants in the innermost layers of the heat-sealable resin layers 15 and 20, the concentration of N-substituted amide (ppm by mass), and the ratio (% by mass) of N-substituted amide to the total amount of lubricant in the innermost layer. In the single-layer heat-sealable resin layer 15, the heat-sealable resin layer 15 itself is the innermost layer, and in the three-layer heat-sealable resin layer 20, the innermost layer is the sealing layer 23.

(Preparation of battery packaging material)
The single-layer film for the heat-sealable resin layer 15 thus prepared was subjected to a corona treatment on one surface, while the three-layer film for the multi-layer heat-sealable resin layer 20 was subjected to a corona treatment on the surface of the laminate layer 22.

A 3 μm-thick first adhesive layer 12 was formed on one side of the barrier layer 11 on which the chemical conversion film was formed, and the substrate layer 13 was dry laminated. Next, a 2 μm-thick second adhesive layer 14 was formed on the other side of the barrier layer 11, and the corona-treated surface of the single-layer heat-sealable resin layer 15 or the laminate layer 22 (corona-treated surface) of the multi-layer heat-sealable resin layer 20 was superimposed on the second adhesive layer 14, and the laminate was dry laminated by sandwiching and pressing between a lamination roll heated to 100°C to produce a laminate, which was then wound up on a roll shaft.

The laminate wound around a roll shaft was aged at 40° C. for 10 days to obtain

battery packaging materials

1 and 2.
[Evaluation of Battery Packaging Materials]
The slipperiness of the

battery packaging materials

1 and 2 thus produced was evaluated by the dynamic friction coefficient measured by the following method, and the moldability was evaluated by the maximum molding depth measured by the following method. Furthermore, the performance of the batteries using the cases produced from these battery packaging materials was evaluated by the following method. The evaluation results are shown in Table 4.
(Kinematic Friction Coefficient)
The dynamic friction coefficient between the heat-sealable resin layers 15, 20 of the

battery packaging materials

1, 2 was measured using a friction tester TR model manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K7125: 1999. Those having a dynamic friction coefficient of 0.45 or less were deemed to pass.
(Moldability)
The

battery packaging materials

1 and 2 thus produced were cut into pieces of 100 mm x 150 mm to prepare molding materials. A deep drawing mold equipped with a die, a punch, and a blank holder was attached to a servo press machine, and deep drawing was performed to obtain a rectangular parallelepiped shape of 55 mm in length, 35 mm in width, and a depth D. The deep drawing was performed at a forming speed of 20 spm in a manner in which the top surface of the punch was brought into contact with the heat-sealable resin layers 15 and 20 of the molding material to protrude the base layer 13 outward, and the forming depth D was changed in increments of 0.5 mm.

Then, a light was shone on the corners of the molded product, and the presence or absence of light transmitted by pinholes or cracks was visually observed. The maximum molding depth (mm) at which good molding could be performed without any pinholes or cracks was examined, and the moldability of the maximum molding depth was evaluated based on the following criteria, with AB being deemed a pass.

A: Maximum molding depth is 7 mm or more. B: Maximum molding depth is 6 mm or more and less than 7 mm. C: Maximum molding depth is 5 mm or more and less than 6 mm. D: Maximum molding depth is less than 5 mm (battery performance).
A forming blank measuring 140 mm in length and 55 mm in width was sampled from the

battery packaging materials

1 and 2 to prepare a battery case for evaluation, and one half of the forming blank (70 mm in length and 55 mm in width) was deep-drawn to form a rectangular parallelepiped recess measuring 55 mm in length, 35 mm in width and 4 mm deep. The other part (non-formed part) of the forming blank was then folded to prepare a battery case that served as a lid part.

As materials for the battery body to be housed in the battery case, the following positive electrode sheet and negative electrode sheet were produced, and a nonaqueous electrolyte solution was prepared.
Positive electrode sheet:
90 g of LiCoO ₂ as a positive electrode active material, 5 g of carbon black (manufactured by TIMCAL) as a conductive assistant, and 5 g of polyvinylidene fluoride (PVdF) as a binder were stirred and mixed while appropriately adding N-methyl-pyrrolidone to obtain a paste-like positive electrode paste. The positive electrode paste was applied to an aluminum foil having a thickness of 20 μm with a roll coater, and dried to harden the paste. After drying, the sheet was roll pressed to make the positive electrode active material density 3.6 g/cm ³ , and a positive electrode sheet was obtained. Negative electrode sheet:
Artificial graphite particles and carbon-coated _SiO2 particles were used as the negative electrode active material, and these were mixed in a mass ratio of 4:1 to prepare a mixed negative electrode active material. Carbon black and vapor-grown carbon fiber (VGCF (registered trademark)-H, manufactured by Showa Denko K.K.) were used as the conductive assistant, and these were mixed in a mass ratio of 3:2 to prepare a mixed conductive assistant. Styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were used as the binder. The styrene butadiene rubber (SBR) was dispersed in purified water to prepare an SBR dispersion. The carboxymethyl cellulose (CMC) was mixed with purified water and stirred overnight with a stirrer to prepare a CMC solution.

90 parts by mass of the mixed negative electrode active material, 5 parts by mass of the mixed conductive assistant, an SBR dispersion containing 2.5 parts by mass as a solid content, and a CMC solution containing 2.5 parts by mass as a solid content were mixed, and an appropriate amount of water was added to adjust the viscosity, and the mixture was kneaded with a rotation/revolution mixer to obtain a negative electrode paste. The negative electrode paste was uniformly applied to a copper foil having a thickness of 20 μm with a doctor blade to a thickness of 150 μm, dried on a hot plate, and then vacuum dried. The dried sheet was pressed with a uniaxial press at a pressure of 3 ton/cm ² to obtain a negative electrode sheet.

Generally, when making a lithium-ion battery by opposing a positive electrode sheet and a negative electrode sheet, it is necessary to consider the capacity balance between the two. In other words, if there is too little negative electrode on the side that accepts lithium ions, excess Li will precipitate on the negative electrode, causing cycle deterioration, and conversely, if there is too much negative electrode, charging and discharging will occur under a small load, so the energy density will decrease but the cycle characteristics will improve.

In preparing the above-mentioned negative electrode sheet, in order to prevent the above-mentioned inconveniences, the same positive electrode sheet was used, but the discharge amount per weight of active material of the negative electrode sheet was evaluated in advance in a half cell with a Li counter electrode, and the capacity of the negative electrode sheet was fine-tuned so that the ratio of the capacity (QA) of the negative electrode sheet to the capacity (QC) of the positive electrode sheet was a constant value of 1.2.
Nonaqueous electrolyte:
A non-aqueous solvent in which ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed in a volume ratio of 3:5:2 was mixed with 1 mass% vinylene carbonate (VC) and 5 mass% fluoroethylene carbonate (FEC) as additives. An electrolyte _LiPF6 was dissolved in the non-aqueous solvent to a concentration of 1 mol/L to prepare a non-aqueous electrolyte solution.
Preparation of evaluation battery:
A battery for evaluation was fabricated in a glove box kept in a dry argon gas atmosphere with a dew point of −80° C. or less, according to the following procedure.

The positive electrode sheet and the negative electrode sheet were punched out to obtain positive electrode pieces and negative electrode pieces with an area of 20 ^cm2 . An Al tab was attached to the aluminum foil of the positive electrode piece, and a Ni tab was attached to the copper foil of the negative electrode piece. A polypropylene film microporous membrane was sandwiched between the positive electrode piece and the negative electrode piece, and the Al tab and Ni tab were pulled out from one side of the battery case and inserted into the recess of the case, and 0.5 mL of nonaqueous electrolyte was poured in. The opening of the battery case was then sealed by heat fusion to obtain a battery for evaluation.

The evaluation batteries were fabricated using Al and Ni tabs, and the internal resistance and discharge rate were measured using a HIOKI electrode resistance measurement system RM2610, and the battery performance was evaluated based on these.

The internal resistance was measured at DCR when the state of charge (SOC) was 20% and 80%, and a value of less than 6 Ω was considered to be acceptable.

The discharge rate (%) was defined as the percentage of the discharge capacity when discharging at 1C or 3C, with the discharge capacity taken as 100%. Charging conditions were CC = 0.5C, CV = 4.2V, 0.05C cut off, and discharging conditions were CC = 0.5C, EV = 2.8V. A discharge rate of 70% or more at 1C was considered acceptable, and a discharge rate of 18% or more at 3C was considered acceptable.

From Table 4, it was confirmed that the battery packaging materials of the examples have good slipperiness and formability, and that the deterioration of battery performance is suppressed in batteries using these battery packaging materials as cases.

The battery packaging material of the present invention can be suitably used as a case material for secondary batteries for in-vehicle, stationary, notebook computers, mobile phones, cameras, etc.

This application claims priority from Japanese Patent Application No. 2022-194657, filed on December 6, 2022, the disclosures of which are incorporated herein by reference in their entirety.

It should be understood that the terms and expressions used herein are used for explanatory purposes and not for limiting interpretation, and do not exclude any equivalents of the features shown and described herein, but also allow various modifications within the claimed scope of the invention.

1, 2, 3... Battery packaging material 11... Barrier layer 12... First adhesive layer 13... Base material layer 14... Second adhesive layer 15... Heat-sealable resin layer (innermost layer)
20, 25... heat-sealable resin layer 21... intermediate layer 22... laminate layer 23... seal layer (innermost layer)
50: Battery case 51: Main body (battery case member)
52...Recess

Claims

A battery packaging material including, in order from the outside to the inside, at least a base layer, a barrier layer, and a heat-sealable resin layer,
The battery packaging material, wherein the heat-sealable resin layer contains a polyolefin resin and one or more lubricants, and at least one of the lubricants is an N-substituted amide represented by the following formula (I):

R1 is a hydrocarbon chain represented by C m1 H n1. R2 is a hydrocarbon chain represented by C m2 H n2.
The battery packaging material according to claim 1, wherein the carbon number of the N-substituted amide is 34 or more, and the carbon number of R1 (m1) and the carbon number of R2 (m2) satisfy the relationship |m1-m2|≦15.
The battery packaging material according to claim 1 or 2, wherein the heat-sealable resin layer is a single layer or a multi-layer of two or more layers, the innermost layer contains an N-substituted amide, and the total concentration of all lubricants including the N-substituted amide in the innermost layer is 100 ppm by mass to 2500 ppm by mass.
The battery packaging material according to any one of claims 1 to 3, wherein the heat-sealable resin layer contains an unsaturated fatty acid amide as a lubricant.
The battery packaging material according to any one of claims 1 to 4, wherein the ratio of the N-substituted amide to the total amount of lubricant in the innermost layer of the heat-sealable resin layer is 30% by mass to 100% by mass.
The battery packaging material according to any one of claims 1 to 5, wherein a lubricant layer containing an N-substituted amide is formed on the surface of the heat-sealable resin layer.
A battery case member, characterized in that a recess is formed by deep drawing or stretch molding in the battery packaging material described in any one of claims 1 to 6.