JP6121710B2 - Battery exterior material and lithium secondary battery - Google Patents

Description

  The present invention relates to a battery case and a lithium secondary battery.

  As electronic devices such as video cameras, notebook computers, and mobile phones become more portable and smaller, there is an increasing demand for smaller and lighter batteries as driving sources, and high-performance lithium secondary batteries are widely used. Has reached. Recently, in order to apply a lithium secondary battery to an in-vehicle power source of an electric vehicle or a hybrid vehicle, an increase in the size of the lithium secondary battery has been studied.

  By the way, since the mounting space of the in-vehicle power source in the vehicle is limited and the shape of the mounting space is not constant, as in the case of electronic devices, the lithium secondary battery for in-vehicle use is lighter and free in shape. Degree is required. In addition, in-vehicle lithium secondary batteries have a large battery capacity and use current, so that better insulation (high insulation resistance value) is required to ensure higher safety.

  As an exterior material of a conventional lithium secondary battery, for example, an exterior body as disclosed in Patent Document 1 below is known. Patent Document 1 discloses an exterior body in which an exterior body made of a laminate exterior material composed of a metal layer and a synthetic resin layer is provided with an absorbent sheet containing inorganic particles having an acid-absorbing ability. Patent Document 2 discloses a lithium ion battery exterior material in which an adhesive layer, an aluminum foil layer, an aluminum protective layer, an adhesive resin layer, and a sealant layer are laminated in this order. The sealant layer has an average particle size of 200 nm or less. A packaging material for a lithium ion battery to which an elastomer composed of fine particles is added is disclosed.

JP 2008-235256 A JP 2011-216390 A

  However, the exterior body described in Patent Document 1 is one in which a resin sheet that absorbs hydrogen fluoride is enclosed together with the power generation element in order to prevent deterioration of the exterior body due to hydrogen fluoride that may be generated inside the battery. No consideration is given to insulation. Moreover, the exterior material for lithium ion batteries described in Patent Document 2 is a sealant layer in order to prevent whitening of the sealant layer during molding (micro cracks in the sealant resin) in a laminate packaging material used as an exterior material of a lithium ion battery. This is a technology that gives impact resistance to the sealant layer so as to prevent breakage and whitening due to cracks during emboss molding by adding elastomer fine particles to the insulation, and no consideration is given to insulation. As described above, the insulation performance of the conventional battery exterior material is still insufficient, and further improvement is required.

  This invention is made | formed in view of the said situation, and it aims at providing the lithium secondary battery provided with the battery exterior material excellent in insulation, and such a battery exterior material.

[1] In a battery exterior material in which an outer layer containing a heat-resistant resin film, a metal foil layer, an adhesive layer, and an inner layer containing a thermoplastic resin film are laminated,
Insulating particles are contained in the adhesive layer,
The insulating particles are any one of inorganic particles having an average particle diameter of 0.1 μm to 4 μm, organic particles having an average particle diameter of 0.1 μm to 4 μm, or a mixture thereof, and the above-mentioned in the adhesive layer The battery exterior material characterized by the addition amount of insulating particles being 1 to 30% by mass.
[2] The battery packaging material according to [1], wherein the adhesive layer is made of an adhesive for dry lamination.
[3] The adhesive layer is made of any of urethane adhesive, acid-modified polyolefin, styrene elastomer, acrylic adhesive, silicone adhesive, ether adhesive, and ethylene-vinyl acetate adhesive [2]. The battery outer packaging material according to 1.
[4] The battery outer packaging material according to any one of [1] to [3], wherein the inner layer is made of polyolefin and the outer layer is made of polyamide or polyester.
[5] The battery packaging material according to any one of [1] to [4], wherein the metal foil layer is made of any one of an aluminum foil, an iron foil, a stainless steel foil, and a copper foil.
[6] The battery outer packaging material according to any one of [1] to [5], wherein the outer layer and the metal foil layer are bonded together through an adhesive layer made of a material different from that of the adhesive layer.
[7] The battery outer packaging material according to any one of [1] to [6], wherein a concave portion is formed by deep drawing or bulging.
[8] A lithium secondary battery comprising the battery packaging material according to any one of [1] to [7].

  ADVANTAGE OF THE INVENTION According to this invention, the lithium secondary battery provided with the battery exterior material excellent in insulation and such a battery exterior material can be provided.

FIG. 1 is a schematic cross-sectional view of a lithium secondary battery including a battery exterior material according to an embodiment of the present invention. FIG. 2 is an enlarged schematic cross-sectional view of a battery exterior material according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing a deep drawing process of the battery exterior material in the example. FIG. 4 is a schematic diagram illustrating a manufacturing process of a lithium secondary battery of the battery outer package in the example. FIG. 5 is a schematic diagram showing a manufacturing process of the test cell for insulation evaluation in the example. FIG. 6 is a schematic diagram illustrating a manufacturing process of an insulation evaluation test cell in the example. FIG. 7 is a schematic diagram illustrating insulation evaluation methods of Examples 1 to 7 and Comparative Examples 2 to 5. FIG. 8 is a schematic diagram showing an insulation evaluation method of Comparative Example 1. FIG. 9 is a schematic diagram illustrating insulation evaluation methods of Examples 1 to 7 and Comparative Examples 1 to 5.

  Hereinafter, the lithium secondary battery provided with the battery exterior material and battery exterior material which are embodiments of the present invention will be described.

  As shown in FIG. 1, the lithium secondary battery 1 of the present embodiment includes, for example, at least a positive electrode 2, a negative electrode 3, an electrolyte, and a battery outer package 5 that packages the positive electrode 2, the negative electrode 3, and the electrolyte. It is configured. The battery exterior body 5 is configured by, for example, superposing sheet-shaped battery exterior materials 5a and 5b to form a bag shape. The positive electrode 2, the negative electrode 3, and the electrolyte are inserted into the battery outer package 5. In the example shown in FIG. 1, the separator 6 is disposed between the positive electrode 2 and the negative electrode 3. Instead of the separator 6, a solid electrolyte membrane may be disposed between the positive electrode 2 and the negative electrode 3.

  For example, the battery outer package 5 is formed into a bag shape by stacking two sheet-shaped battery outer packages 5a and 5b so that the inner layers face each other, and heat-sealing the outer peripheral portion 5c of the battery outer package 5a and 5b. It has been made. The battery exterior materials 5a and 5b are configured by laminating an outer layer including a heat-resistant resin film, a metal foil layer, an adhesive layer containing insulating particles, and an inner layer including a thermoplastic resin film. . Further, a concave portion 5d for accommodating the positive electrode 2, the negative electrode 3, and the electrolyte is formed in one battery outer packaging material 5a by deep drawing molding or bulging molding. In the example shown in FIG. 1, the other battery exterior material 5b is not provided with a recess, but the other battery exterior material 5b may also be provided with a recess.

  The positive electrode 2 and the negative electrode 3 are each composed of a current collector 2a, 3a made of a metal foil or a metal net, and an electrode mixture 2b, 3b laminated on the current collector 2a, 3a, respectively. it can. The electrode mixture 2b of the positive electrode 2 contains a positive electrode active material, and the electrode mixture 3b of the negative electrode 3 contains a negative electrode active material.

  Further, tab leads 2c and 3c as extraction terminals are joined to the current collectors 2a and 3a of the positive electrode 2 and the negative electrode 3, respectively. The tab leads 2c and 3c have their longitudinal base ends joined to the current collectors 2a and 3a inside the battery outer package, and the longitudinal tips penetrate through the outer peripheral portion 5c which is a heat seal portion of the battery outer package 5. It protrudes outside the lithium secondary battery 1. In the vicinity of the outer peripheral portion 5c of the tab leads 2c and 3c, the tab leads 2c and 3c are sandwiched between two sheet-shaped battery exterior materials 5a and 5b, and the inner layers of the battery exterior materials 5a and 5b are formed on the surfaces of the tab leads 2c and 3c. Is in a heat-sealed state.

  When the lithium secondary battery 1 shown in FIG. 1 is manufactured, a bag-shaped battery outer body 5 having an opening is prepared, and the positive electrode 2, the negative electrode 3, the electrolyte, and the separator 6 are inserted into the battery outer body 5. Further, after injecting an electrolyte as necessary, the opening is sealed and heat sealed so as to sandwich the tab leads 2c and 3c protruding from the opening, so that the opening is hermetically sealed. Get one.

  Next, the battery packaging material of this embodiment will be described in detail. As shown in FIG. 2, the battery exterior materials 5 a and 5 b of the present embodiment include an outer layer 51 that becomes the outer surface 51 a of the battery outer body 5, a metal foil layer 52, and an inner layer that becomes the inner surface 53 b of the battery outer body 5. 53 is laminated. As shown in FIG. 2, adhesive layers 54 and 55 are interposed between the outer layer 51 and the metal foil layer 52 and between the inner layer 53 and the metal foil layer 52.

(Outer layer 51)
The outer layer 51 constituting the battery packaging materials 5a and 5b is configured to include at least one or two or more heat resistant resin films. In the case where the outer layer 51 is composed of two or more heat-resistant resin films, the heat-resistant resin films are preferably laminated via an adhesive layer.

  The heat-resistant resin film constituting the outer layer 51 plays a role of ensuring the moldability of the battery exterior material 5a when forming the recess 5d for housing the positive electrode 2 and the negative electrode 3 in the battery exterior material 5a. A stretched film of polyamide (nylon) resin or polyester resin is preferably used. The melting point of the heat-resistant resin film constituting the outer layer 51 is preferably higher than the melting point of the thermoplastic resin film constituting the inner layer 53. Thereby, it becomes possible to perform the heat seal of the opening part at the time of manufacturing the lithium secondary battery 1 reliably.

  The thickness of the outer layer 51 is preferably about 10 to 50 μm, and more preferably about 15 to 30 μm. If the thickness is 10 μm or more, the stretch of the stretched film will not be insufficient when the battery outer packaging material 5a is molded, the metal foil layer 52 will not be necked, and molding defects will not occur. Moreover, if thickness is 50 micrometers or less, the effect of a moldability can fully be exhibited.

(Metal foil layer 52)
The metal foil layer 52 constituting the battery outer packaging material 5a, 5b serves to ensure the barrier property of the battery outer packaging material 5a, 5b. As the metal foil layer 52, aluminum foil, iron foil, stainless steel foil is used. Copper foil or the like is used, but it is preferable to use aluminum foil in consideration of formability and light weight. As the material of the aluminum foil, a pure aluminum-based or aluminum-iron-based alloy O material (soft material) is preferably used.

  The thickness of the metal foil layer 52 needs to be 20 to 80 μm in order to ensure workability and to ensure barrier properties that prevent oxygen and moisture from entering the battery. When the thickness is 20 μm or more, the metal foil layer 52 is not broken during the formation of the battery outer packaging material 5a, and no pinholes are generated, so that intrusion of oxygen and moisture can be prevented. In addition, if the thickness is 80 μm or less, the effect of improving the breakage at the time of molding and the effect of preventing the occurrence of pinholes are maintained, and the total thickness of the battery exterior materials 5a and 5b is not excessively increased, thereby preventing an increase in weight. The volume energy density of the battery 1 can be improved.

  Further, the metal foil layer 52 is subjected to undercoat treatment with a silane coupling agent or a titanium coupling agent, chromate treatment, or the like in order to improve adhesion with the outer layer 51 and the inner layer 53 or improve corrosion resistance. A chemical conversion treatment should be performed.

(Inner layer 53)
Next, the inner layer 53 constituting the battery outer packaging materials 5a and 5b is configured to include a thermoplastic resin film. As the thermoplastic resin film used for the inner layer 53, it plays a role of improving chemical resistance against electrolytes and the like of a lithium secondary battery having heat sealability and strong corrosiveness, and the metal foil layer 52 and lithium Those that can ensure insulation from the positive electrode 2 or the negative electrode 3 of the secondary battery 1 are good. For example, unstretched polyolefin films such as polypropylene and maleic acid-modified polypropylene, and unstretched ethylene-acrylate copolymers or ionomer resins. A film is preferably used. Further, the thermoplastic resin film constituting the inner layer 53 may be composed of a single thermoplastic resin layer, but may be composed of a laminate of a plurality of thermoplastic resin layers.

  The thickness of the inner layer 53 is preferably in the range of 0.1 to 200 μm, and more preferably in the range of 50 to 100 μm. When the thickness is 0.1 μm or more, preferably 50 μm or more, the heat seal strength is sufficient, the corrosion resistance against the electrolytic solution or the like is improved, and the insulation between the metal foil layer and the positive electrode or the negative electrode is enhanced. Moreover, if thickness is 200 micrometers or less, Preferably it is 100 micrometers or less, there is no trouble in heat-sealing property and chemical-resistance, and the volume energy density of a lithium secondary battery can be improved.

  Furthermore, the melting point of the thermoplastic resin film constituting the inner layer 53 is preferably in the range of 130 ° C to 170 ° C, more preferably in the range of 160 to 165 ° C. If the melting point is within this range, the heat resistance of the inner layer 53 is improved, the thickness of the inner layer 53 during heat sealing is not reduced, and the insulation of the inner layer 53 is improved.

(Adhesive layer)
The adhesive layers 54 and 55 are provided between the outer layer 51 and the metal foil layer 52 and between the inner layer 53 and the metal foil layer 52 in order to bond the outer layer 51 and the metal foil layer 52 and the inner layer 53 and the metal foil layer 52. It is arranged between.
The adhesive layers 54 and 55 are preferably an adhesive layer for dry laminate made of an adhesive for dry laminate. For example, urethane adhesive, acid-modified polyolefin, styrene elastomer, acrylic adhesive, silicone adhesive, ether adhesive One selected from ethylene-vinyl acetate adhesives can be used.

  In particular, the outer layer-side adhesive layer 54 and the inner layer-side adhesive layer 55 are preferably made of mutually different adhesive layers. As a combination of the materials of the adhesive layers 54 and 55, a urethane adhesive is preferably used as an adhesive on the outer layer side when the outer layer 51 is made of PET or nylon, and an inner layer side when the inner layer 53 is made of polypropylene. As the adhesive, an acrylic adhesive or an acid-modified olefin adhesive is preferable. By using adhesive layers made of different materials as the outer-layer-side adhesive layer 54 and the inner-layer-side adhesive layer 55, it is possible to impart adhesion strength and resistance to electrolyte solution between the respective materials.

  The adhesive layer 55 on the inner layer 53 side preferably contains insulating particles. The insulating particles contained in the adhesive layer 55 are preferably inorganic particles having an average particle diameter of 0.1 μm to 4 μm, organic particles having an average particle diameter of 0.1 μm to 4 μm, or a mixture thereof. By containing such insulating particles, the insulation between the inner layer 53 and the metal foil layer 52 can be further enhanced.

  As the inorganic particles having an average particle size of 0.1 to 4 μm or less, spherical or plate-like particles are preferable. Examples of inorganic particles include barium sulfate, barium titanate, calcite calcium carbonate, fine talc, aluminum hydroxide, silica beads, spherical fused silica, kaolin, natural calcium silicate, boron nitride, and alumina. it can. The organic particles having an average particle size of 0.1 to 4 μm or less are preferably spherical or plate-like particles, and examples thereof include plastic beads such as polyurethane, polystyrene, and polymethyl acrylate.

  If the average particle size of the insulating particles is less than 0.1 μm, it is difficult to uniformly disperse them in the adhesive, and insulative variations in the surfaces of the battery exterior materials 5a and 5b are likely to occur. In addition, when the average particle diameter exceeds 4 μm, insulating particles having a particle size larger than the thickness of the adhesive layer after applying and drying the adhesive are included, so that there are many defects in the adhesive layer. This may adversely affect the performance and increase the variation in insulation. Therefore, the insulating particles are preferably those having an average particle size of 0.1 to 4 μm.

The volume resistivity of the insulating particles is preferably 10 ⁸ Ω / cm (100 MΩ / cm) or more. Thereby, the insulation of the inner layer 53 and the metal foil layer 52 can be improved more. For example, alumina is about 10 ¹⁵ Ω / cm, and boron nitride is about 10 ¹⁴ Ω / cm.

  Furthermore, the addition amount of the insulating particles to the adhesive layer is in the range of 1 to 30% by mass, preferably in the range of 2 to 20% by mass. If the addition amount is less than 1% by mass, the addition effect of the insulating particles is hardly exhibited, and if it is added in excess of 30%, the adhesiveness may be adversely affected.

  The thickness of the adhesive layers 54 and 55 is preferably in the range of 1 to 10 μm, and more preferably in the range of 1.5 to 5 μm. If the thickness of the adhesive layers 54 and 55 is 0.1 μm or more, preferably 1.5 μm, the adhesive strength is not lowered, moisture transmission can be suppressed, and the insulation of the inner layer 53 is further enhanced on the inner layer side. be able to. Moreover, if the thickness of the adhesive layers 54 and 55 is 10 μm or less, more preferably 5 μm or less, a decrease in the adhesive strength can be prevented. Insulating particles to be added to the inner layer-side adhesive layer 55 are selected within the range of the average particle size of 0.1 to 4 μm as described above. It is desirable to select insulating particles having a maximum particle size smaller than the thickness of the material.

The insulation between the inner layer 53 of the battery outer packaging material 5a, 5b and the metal foil layer 52 can be evaluated by the following evaluation method.
First, the lithium secondary battery 1 is manufactured, and the outer layer 51 of the battery outer package 5 of the lithium secondary battery 1 is partially removed to expose the metal foil layer 52. The position where the metal foil layer 52 is exposed is preferably as far as possible from the tab leads 2c and 3c. Next, a conductive wire is connected to the exposed metal foil layer 52, and the conductive wire is also connected to the tab leads 2 c and 3 c of either the positive electrode 2 or the negative electrode 3. Instead of exposing the metal foil layer 52, a conductive tape may be attached to the metal foil layer 52 exposed on the end face, and a conductive wire may be connected to the conductive tape. And a power supply and a resistance measuring machine are inserted between these conducting wires. Then, a voltage is applied between the metal foil layer 52 and the tab leads 2c and 3c from the power source through the conductive wire, and the resistance value between the metal foil layer 52 and the tab leads 2c and 3c at this time is measured by a resistance measuring machine. Then, the insulating properties of the inner layers of the battery outer packaging materials 5a and 5b are evaluated based on the obtained resistance values.

The battery packaging materials 5a and 5b of this embodiment are preferably those having an insulation resistance value of 1 × 10 ⁸ Ω or more when a DC voltage of 5 to 50 volts or less is applied.

  In evaluating the insulation between the inner layer 53 of the battery outer package 5a, 5b and the metal foil layer 52, a tab lead is attached to the battery outer package 5 instead of the lithium secondary battery 1, and the battery outer package 5 A test cell filled with an electrolytic solution can also be used in the interior of.

In the battery exterior materials 5a and 5b of the present embodiment, a dry laminate adhesive is applied to the surface of the outer layer 51 or the metal foil layer 52, and the solvent contained in the dry laminate adhesive is volatilized.
Then, a dry laminate film is manufactured by dry laminating the outer layer 51 and the metal foil layer 52.
Next, another dry laminating adhesive containing insulating particles is applied to the surface of the metal foil layer 52 or the inner layer 53 of the dry laminating film, and the solvent contained in the dry laminating adhesive is volatilized. . Then, the dry laminate film and the inner layer 53 are dry laminated. In this way, the battery packaging materials 5a and 5b of this embodiment are manufactured.

According to the battery exterior materials 5a and 5b of this embodiment, since the insulating particles are contained in the adhesive layer 55 on the inner layer 53 side, the insulation between the inner layer 53 and the metal foil layer 52 can be improved. Specifically, when the metal foil layer 52 and the battery terminal (tab lead) are connected with a conductive wire in a state in which a lithium secondary battery is configured, an insulation resistance value is applied when a DC voltage of 5 to 50 volts or less is applied. Can be 1 × 10 ⁸ Ω or more.
The insulating particles contained in the adhesive layer 55 are either inorganic particles having an average particle diameter of 0.1 μm to 4 μm, organic particles having an average particle diameter of 0.1 μm to 4 μm, or a mixture thereof, and Since the addition amount of the insulating particles in the adhesive layer 5 is 1 to 30% by mass, the insulation between the inner layer 53 and the metal foil layer 52 can be further enhanced.

  Furthermore, the adhesive layer 55 of the battery exterior materials 5a and 5b of the present embodiment includes a urethane adhesive, an acid-modified polyolefin, a styrene elastomer, an acrylic adhesive, a silicone adhesive, an ether adhesive, and ethylene-vinyl acetate. It consists of a dry laminate adhesive made of any one of the adhesives. By using the adhesive layer 55 made of these dry laminate adhesives and using the insulating particles in combination, the insulation between the inner layer 53 and the metal foil layer 52 can be further enhanced.

The battery case materials 5a and 5b of the present embodiment are subjected to the most severe forming process at the corner part and the punch shoulder R part when forming into the shape of the battery case 5. In such a corner portion and punch shoulder R portion, the metal foil layer and the inner layer are directly and firmly bonded without using an adhesive layer in the heat laminate manufacturing method, so that the inner layer is deformed by the deformation of the metal foil layer during the molding process. Insufficient follow-up, minute defects are likely to occur at the interface between the metal foil layer and the inner layer, and the electrolyte may permeate into these minute defects, possibly reducing the insulation. On the other hand, in this embodiment, since the dry laminate manufacturing method is adopted and the metal foil layer 52 and the inner layer 53 are bonded via the adhesive layer 55, the adhesive layer 55 follows the deformation of the metal foil layer 52 during the molding process. Then, it is deformed thinly (extends), so that it is difficult for minute defects to occur at each interface of the metal foil layer 52, the adhesive layer 55, and the inner layer 53, and good insulation can be maintained. Furthermore, better insulating properties can be obtained by adding insulating particles to the adhesive layer 55.
Furthermore, according to the lithium secondary battery 1 of the present embodiment, since the battery exterior materials 5a and 5b are provided, it is possible to suppress the occurrence of an internal short circuit through the metal foil layer.

Example 1
A 12 μm thick stretched polyethylene terephthalate film (manufactured by Toray Industries, Inc., general-purpose product) and a 15 μm thick stretched polyamide film (manufactured by Kojin Co., Ltd., Bonyl RX) are combined with a 3 μm two-component curable urethane adhesive layer. The outer layer film was manufactured by dry lamination.

  Subsequently, the obtained outer layer film and an aluminum foil (JIS standard A8079H-O) having a thickness of 40 μm are passed through a 3 μm two-component curable urethane adhesive layer, speed: 80 m / min, roll temperature: 80 ° C. The outer layer / metal foil layer film was produced by dry lamination under the conditions described above.

  Next, as an inner layer, a polypropylene resin was molded by a T-die molding method to obtain an unstretched polypropylene film having a thickness of 80 μm.

  And by interposing an olefin adhesive layer having a thickness of 4.5 μm between the inner layer and the outer layer / metal foil layer film, by dry laminating under the conditions of speed: 80 m / min, roll temperature: 80 ° C., The battery packaging material of Example 1 was manufactured. The olefinic adhesive layer between the inner layer and the outer layer / metal foil layer film contained 3% by mass of boron nitride particles having an average particle size of 3.5 μm. As the olefin-based adhesive layer, an olefin-based adhesive in which maleic anhydride-modified polypropylene and hexamethylene diisocyanate are in an isocyanate / OH ratio = 5.0 was used.

(Example 2)
Example 2 is the same as Example 1 except that 20% by mass of boron nitride particles having an average particle diameter of 3.5 μm are contained in the olefin-based adhesive layer between the inner layer and the outer layer / metal foil layer film. A battery case was produced.

Example 3
The battery exterior of Example 3 is the same as Example 1 except that the olefin-based adhesive layer between the inner layer and the outer layer / metal foil layer film contains 5% by mass of alumina particles having an average particle diameter of 2 μm. The material was manufactured.

Example 4
In the same manner as in Example 1, except that 5% by mass of silica-based beads having an average particle diameter of 1.5 μm was contained in the olefin-based adhesive layer between the inner layer and the outer layer / metal foil layer film. A battery case was produced.

(Example 5)
The olefin adhesive layer between the inner layer and the outer layer / metal foil layer film contains 5% by mass of silica beads having an average particle diameter of 1.5 μm and 10% by mass of polyurethane beads having an average particle diameter of 3.5 μm. A battery exterior material of Example 5 was produced in the same manner as Example 1 except that the above was performed.

(Example 6)
Example 6 is the same as Example 1 except that 15% by mass of polyurethane beads having an average particle size of 3.5 μm are contained in the olefin-based adhesive layer between the inner layer and the outer layer / metal foil layer film. A battery case was produced.

(Example 7)
Example 7 is the same as Example 1 except that 10% by mass of silica beads having an average particle size of 0.5 μm is contained in the olefin adhesive layer between the inner layer and the outer layer / metal foil layer film. A battery case was produced.

(Comparative Example 1)
A 12 μm thick stretched polyethylene terephthalate film (manufactured by Toray Industries, Inc., general-purpose product) and a 15 μm thick stretched polyamide film (manufactured by Kojin Co., Ltd., Bonyl RX) are combined with a 3 μm two-component curable urethane adhesive layer. The outer layer film was manufactured by dry lamination.

  Subsequently, the obtained outer layer film and an aluminum foil (JIS standard A8079H-O) having a thickness of 40 μm are passed through a 3 μm two-component curable urethane adhesive layer, speed: 80 m / min, roll temperature: 80 ° C. The outer layer / metal foil layer film was produced by dry lamination under the conditions described above.

  Next, as an inner layer, a polypropylene resin was molded by a T-die molding method to obtain an unstretched polypropylene film having a thickness of 80 μm.

  And the battery exterior material of the comparative example 1 was manufactured by heat laminating the inner layer, the outer layer / metal foil layer film, and maleic anhydride-modified polypropylene under predetermined extrusion conditions.

(Comparative Example 2)
A battery outer packaging material of Comparative Example 2 was produced in the same manner as in Example 1, except that the olefin-based adhesive layer between the inner layer and the outer layer / metal foil layer film did not contain insulating particles.

(Comparative Example 3)
Comparative Example as in Example 1, except that 0.3% by mass of silica beads having an average particle size of 1.5 μm was contained in the olefin adhesive layer between the inner layer and the outer layer / metal foil layer film. 3 battery exterior materials were produced.

(Comparative Example 4)
In the same manner as in Example 1 except that 10% by mass of magnesium oxide particles having an average particle size of 0.07 μm were contained in the olefin-based adhesive layer between the inner layer and the outer layer / metal foil layer film, A battery case was produced.

(Comparative Example 5)
Comparative Example 5 was the same as Example 1 except that the olefin-based adhesive layer between the inner layer and the outer layer / metal foil layer film contained 3% by mass of boron nitride particles having an average particle diameter of 6.5 μm. A battery case was produced.

(Evaluation method)
(1) Preparation of Test Cell for Insulation Evaluation As shown in FIG. 3, a drawing process having a size of 5 cm × 3.25 cm with respect to the battery exterior material 101 of Examples 1 to 7 and Comparative Examples 1 to 5 described above. Went. The depth of the drawing process was 5.5 mm, and the surrounding trimming was performed to a size of 9.5 cm × 6.5 cm.

  Next, using the battery exterior materials 102 of Examples 1 to 7 and Comparative Examples 1 to 5 processed as described above, and the battery exterior materials of Examples 1 to 7 and Comparative Examples 1 to 5 that were not processed As shown in FIG. 4, heat sealing was performed by sandwiching a Netz tab lead 103 (length: 9 cm) to produce a battery outer package 104 as shown in FIG. 5. TP-701-A manufactured by Tester Sangyo Co., Ltd. was used as the heat sealer. The heat sealing conditions were 200 ° C., 0.2 MPa, and 6 seconds. As shown in FIG. 5, the location of the seal 105 was a location 1 cm away from the molding location.

After sealing the three sides of the battery exterior material 101 to form the battery exterior body 104, 7.5 ml of an electrolyte solution manufactured by Kishida Kagaku was injected into the container. As a component of the electrolytic solution, LiPF ₆ having a concentration of 1M was used as a solute, and a mixed solution of ethylene carbonate: diethyl carbonate = 1: 1 (volume ratio) was used as a solute. After injection of the electrolytic solution, heat sealing was performed on the fourth side, and the electrolytic solution was enclosed in the battery outer package 104 as shown in FIG.

  After the electrolytic solution was sealed, a carbon tape for SEM manufactured by Nissin EM Co., Ltd. was attached to the lower part of the test cell 106. This was performed for the purpose of increasing the contact surface with the measuring device probe in order to perform stable measurement. In the case of Examples 1 to 7 and Comparative Examples 2 to 5, as shown in FIG. 7, the internal circuit is tab lead 103 / electrolytic solution 107 / inner layer 108 / adhesive layer 109 / metal foil layer 110 / carbon. It consists of a tape 112. On the other hand, in the case of Comparative Example 1, as shown in FIG. 8, the internal circuit is tab lead 103 / electrolytic solution 107 / inner layer 108 / metal foil layer 110 / carbon tape 112. Reference numeral 113 denotes an insulation resistance tester. Insulation evaluation test cells shown in FIG. 7 and FIG. 8 were produced in units of five in Examples 1 to 7 and Comparative Examples 1 to 5, respectively.

(2) Insulation evaluation An insulation resistance tester 3154 manufactured by Hioki Electric Co., Ltd. was used for the insulation test. The measurement range was 200 MΩ to 1000 MΩ, the applied voltage was 25 V, and the application time was 10 seconds. As shown in FIG. 9, the measurement was performed with the probe in contact with the tab lead and the carbon tape, respectively. The results are shown in Table 1.

(result)
Examples 1 to 7 showed insulation resistance values of about 120 to 860 MΩ, while Comparative Examples 1 to 5 all had insulation resistance values of about 0.5 to 50 MΩ. In Comparative Example 5, the insulation resistance values of the five samples varied greatly in the range of 30 to 170 MΩ.
This difference is presumed to be due to the inclusion of various insulating particles in the adhesive layer on the inner layer side. Further, when the results of Examples 1 to 7 and Comparative Examples 3 to 5 are compared, not only the insulating particles are contained, but the average particle size and the content in the adhesive layer should be adjusted. I understand that.

  DESCRIPTION OF SYMBOLS 1 ... Lithium secondary battery, 5a, 5b ... Battery exterior material, 51 ... Outer layer, 52 ... Metal foil layer, 53 ... Inner layer, 55 ... Adhesive layer.

Claims (8)

In a battery exterior material in which an outer layer containing a heat-resistant resin film, a metal foil layer, an adhesive layer, and an inner layer containing a thermoplastic resin film are laminated,
Insulating particles are contained in the adhesive layer,
The insulating particles are any one of inorganic particles having an average particle size of 0.1 μm to 4 μm, organic particles having an average particle size of 0.1 μm to 4 μm, or a mixture thereof, and the above-mentioned in the adhesive layer the addition amount of the insulating particles Ri to 30% by mass,
The adhesive layer does not contain the insulating particles having a particle size larger than its thickness,
The insulating volume resistivity of the ^{particles, 10 8 Ω / cm (100MΩ} / cm) or more der Rukoto outer casing material for a battery according to claim.   The battery exterior material according to claim 1, wherein the adhesive layer is made of an adhesive for dry lamination.   The adhesive layer according to claim 2, wherein the adhesive layer is made of any one of a urethane adhesive, an acid-modified polyolefin, a styrene elastomer, an acrylic adhesive, a silicone adhesive, an ether adhesive, and an ethylene-vinyl acetate adhesive. Battery exterior material.   The battery outer packaging material according to any one of claims 1 to 3, wherein the inner layer is made of polyolefin, and the outer layer is made of polyamide or polyester.   The battery outer packaging material according to any one of claims 1 to 4, wherein the metal foil layer is made of any one of an aluminum foil, an iron foil, a stainless steel foil, and a copper foil.   The battery outer packaging material according to any one of claims 1 to 5, wherein the outer layer and the metal foil layer are bonded together via an adhesive layer made of a material different from that of the adhesive layer.   The battery exterior material according to any one of claims 1 to 6, wherein a concave portion is formed by deep drawing or bulging.   A lithium secondary battery comprising the battery exterior material according to any one of claims 1 to 7.

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