JP7024734B2 - Protective film, batteries, and battery manufacturing methods - Google Patents

Description

The present invention relates to a protective film, a battery, and a method for manufacturing the battery.

Conventionally, various types of batteries have been developed, and batteries with high energy density such as lithium ion batteries have been developed. In recent years, with the improvement of high performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones and the like, batteries having a higher energy density are required.

Further, as a packaging material for a battery, a metal material is often used in the past, but in recent years, various shapes are required for the battery, and thinning and weight reduction are also required. With metal packaging materials, it is difficult to keep up with the diversification of shapes, and there is a limit to weight reduction. Therefore, as a packaging material that can be easily processed into various shapes and can be made thinner and lighter, a film-like laminate in which a base material layer / barrier layer / heat-sealing resin layer is sequentially laminated is also proposed. (For example, see Patent Document 1).

In these batteries, for example, a positive electrode having a positive electrode active material coated on both sides of a positive electrode foil and a negative electrode having a negative electrode active material coated on both sides of a negative electrode foil are wound via a separator, and the wound body (electrode) thereof is wound. It is widely known that the group) is housed in a battery case. In such a battery, metal foil exposed portions in which the metal foils of the positive electrode and the negative electrode are exposed are formed at both ends of the wound body (electrode group) in the winding axis direction, and electrodes are formed on the exposed metal foil portions. The terminals and the current collector are connected by welding or the like (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2008-287971 Japanese Unexamined Patent Publication No. 2014-49311

As described in Patent Document 2, when the metal leaf exposed portion and the current collector are joined by ultrasonic welding, laser welding, friction stir welding, etc., the metal leaf exposed portion or the current collector to be joined is minutely separated. It is known that various metal pieces are scattered. When such a minute metal piece is mixed inside the electrode group, there may be a problem that a micro short circuit occurs inside the battery.

In order to solve such a problem, in Patent Document 2, at least a part of the joint portion composed of the exposed metal foil portion and the connecting plate is covered with a resin adhesive tape, a resin adhesive, or a heat-melted resin agent. The technique of covering with is disclosed.

However, as a result of repeated studies by the present inventors, even when the exposed metal foil portion is covered with a resin adhesive tape or the like, minute metal pieces generated during welding of the exposed metal foil portion are found in the electrode group. It has been found that it may not be possible to sufficiently suppress the contamination inside. In particular, due to the recent increase in the capacity of batteries, the number of laminated metal foils of electrodes has increased, and the energy during welding has increased, so that fine metal pieces are likely to be scattered during welding. For this reason, there is an increased risk that minute metal pieces generated during welding of the exposed metal foil portion are mixed inside the electrode group. In addition, since the amount of heat generated during welding also increases, in the conventional method using resin adhesive tape, the resin adhesive tape heat-shrinks due to high temperature, and the shape cannot be maintained and the surroundings of the weld cannot be protected. There is also. Further, there is a problem that the conventional resin adhesive tape or the like has insufficient insulating property.

Under such circumstances, the present invention can suitably fix the exposed metal leaf portion of the electrode around the welded portion in the battery, and further, the heat shrinkage due to high temperature during welding is small, and the insulating property is excellent. The main purpose is to provide an excellent protective film. It is also an object of the present invention to provide a battery using the protective film and a method for manufacturing the battery.

The present inventors have made diligent studies to solve the above problems. As a result, it is a protective film used for a battery having an electrode having a metal foil and an active material layer located on the surface of the metal foil, and the electrode is provided with a metal foil exposed portion where the metal foil is exposed. The protective film is used to protect at least a part around the portion where the exposed metal foil of the electrode and the metal terminal are welded, and the protective film contains at least an adhesive component (adhesiveness). A first heat-welding resin layer, a heat-resistant intermediate layer, and a second heat-welding resin layer are provided in this order, and the first heat-welding resin layer constitutes one surface of a protective film. The protective film can be suitably fixed around the portion where the exposed metal foil of the electrode is welded in the battery, and the heat shrinkage due to high temperature during welding is small, and the insulating property is also excellent. I found that. The present invention has been completed by further studies based on such findings.

That is, the present invention provides the inventions of the following aspects.
Item 1. A protective film used for a battery having an electrode having a metal foil and an active material layer located on the surface of the metal foil.
The electrode is provided with a metal foil exposed portion in which the metal foil is exposed.
The protective film is used to protect at least a part around the portion where the metal foil exposed portion of the electrode and the metal terminal are welded.
The protective film includes at least a first heat-welding resin layer having adhesiveness, a heat-resistant intermediate layer, and a second heat-welding resin layer in this order.
The first heat-welding resin layer is a protective film constituting the surface of one side of the protective film.
Item 2. Item 2. The protective film according to Item 1, wherein the heat shrinkage rate measured under the conditions of a test temperature of 200 ° C. and a heating time of 10 seconds is 10% or less.
Item 3. Item 2. The protective film according to Item 1 or 2, wherein the resin constituting the first heat-weldable resin layer has a polyolefin skeleton.
Item 4. Item 2. The protective film according to any one of Items 1 to 3, wherein the first heat-weldable resin layer contains a modified polyolefin.
Item 5. Item 2. The protective film according to any one of Items 1 to 4, wherein the first heat-welding resin layer contains an acid-modified polyolefin.
Item 6. Item 2. The protective film according to any one of Items 1 to 5, wherein a peak derived from maleic anhydride is detected when the first heat-weldable resin layer is analyzed by infrared spectroscopy.
Item 7. Item 2. The protective film according to any one of Items 1 to 6, wherein the second heat-weldable resin layer constitutes a surface opposite to the first heat-weldable resin layer.
Item 8. Item 2. The protective film according to any one of Items 1 to 7, wherein at least one of the first heat-welding resin layer, the intermediate layer, and the second heat-welding resin layer is colored.
Item 9. Item 2. The protective film according to any one of Items 1 to 8, wherein a plurality of the metal foils of the electrodes are laminated in the exposed metal foil portion.
Item 10. A battery in which at least a battery element provided with an electrode and an electrolyte is housed in a package formed of a battery packaging material.
The electrode comprises a metal foil and an active material layer located on the surface of the metal foil.
The electrode is provided with a metal foil exposed portion in which the metal foil is exposed.
A battery in which at least a part around the portion where the metal foil exposed portion of the electrode and the metal terminal are welded is covered with the protective film according to any one of Items 1 to 9.
Item 11. A method for manufacturing a battery including an electrode having a metal foil and an active material layer located on the surface of the metal foil.
The electrode is provided with a metal foil exposed portion in which the metal foil is exposed.
The step of covering at least a part of the periphery of the metal leaf exposed portion of the electrode and the metal terminal to be welded with the protective film according to any one of Items 1 to 9.
After that, the process of welding the exposed metal foil portion to the metal terminal,
A method of manufacturing a battery.

According to the present invention, the exposed metal leaf portion of the electrode can be suitably fixed around the welded portion in the battery, the heat shrinkage due to high temperature during welding is small, and the insulating property is excellent. A protective film can be provided. Further, according to the present invention, it is also possible to provide a battery using the protective film and a method for manufacturing the battery.

It is a schematic diagram of an example of the portion where the metal leaf exposed portion of an electrode is welded. It is a schematic sectional drawing of an example of the protective film of this invention. It is a schematic sectional drawing of an example of the protective film of this invention. It is a schematic sectional drawing of an example of the protective film of this invention. It is a schematic sectional drawing of an example of the protective film of this invention. It is a schematic diagram for demonstrating the method of insulation property evaluation. It is a schematic diagram for demonstrating the structure of the battery of this invention. It is a conceptual diagram of the position change of a probe in the displacement amount measurement of a probe using an atomic force microscope to which a cantilever (probe) with a heating mechanism is attached. It is a schematic diagram which shows the position of the surface of the heat-resistant intermediate layer of the cross section of a laminated film in which a probe is installed in the displacement amount measurement of a probe using an atomic force microscope to which a cantilever (probe) with a heating mechanism is attached. It is a perspective view for demonstrating the main surface of the 1st heat welding resin layer of the protective film on which a probe is installed in the measurement of the softening point of the 1st heat welding resin layer.

The protective film of the present invention is a protective film used for a battery having an electrode having a metal foil and an active material layer located on the surface of the metal foil, and the electrode has a metal foil exposed portion where the metal foil is exposed. The protective film is used to protect at least a part of the periphery of the portion where the exposed metal foil of the electrode and the metal terminal are welded, and the protective film is at least adhesive. A heat-weldable resin layer, a heat-resistant intermediate layer, and a second heat-weldable resin layer are provided in this order, and the first heat-weldable resin layer constitutes one surface of a protective film. It is characterized by that. Hereinafter, the protective film of the present invention, the battery using the protective film, and the manufacturing method thereof will be described in detail.

In this specification, the numerical range indicated by "-" means "greater than or equal to" and "less than or equal to". For example, the notation of 2 to 15 mm means 2 mm or more and 15 mm or less.

1. 1. Protective film The protective film of the present invention protects at least a part of the periphery of the portion where the exposed metal leaf of the electrode is welded (hereinafter, may be referred to as "welded portion" or "planned welded portion") in the battery. Used to do. The battery includes electrodes (positive electrode and negative electrode) in which an active material layer is formed on the surface of a metal foil. Further, the electrode is provided with a metal foil exposed portion in which the metal foil of the electrode is exposed. Specifically, the electrode is provided with a metal foil exposed portion in which the metal foil of the electrode is exposed without the presence of the active material layer. Further, the exposed metal foil portion is welded to a conductive member such as a metal terminal, and the inside and the outside of the battery are electrically connected.

FIG. 1 is a schematic diagram in which a plurality of metal leafs 20 of electrodes are laminated in a metal leaf exposed portion 21, and the metal foil exposed portions 21 and the metal terminals 30 of the plurality of metal foils 20 are welded by a welding head 40. The figure is shown. In FIG. 1, among a plurality of metal foils 20, the metal leaf exposed portion 21 of the metal leaf 20 adjacent to the metal terminal 30 is welded to the metal terminal 30, and the plurality of metal foils 20 adjacent to each other are also welded to each other. It shows how it is being welded. Note that FIG. 1 is a schematic view of an example of a portion where the metal leaf exposed portion 21 of the metal foil 20 of the electrode is welded, and the structure of the right end portion of the metal foil exposed portion 21 is omitted.

In the present invention, by covering at least a part of the periphery of the welded portion P with the protective film 10 of the present invention, the periphery of the welded portion P is effectively protected from the fine metal pieces generated during welding. Can be done. For example, FIG. 1 illustrates a case where the region R surrounded by a broken line is covered with the protective film 10 of the present invention, and when the region R is covered with the protective film 10 of the present invention, it scatters from the welded portion P. The periphery of the welded portion P can be effectively protected from fine metal pieces. At least a part around the portion to be welded (welded portion P) means, for example, the vicinity of the welded portion P, the vicinity thereof, a range in which fine metal pieces are concerned about scattering, and the like.

When at least a part of the periphery of the welded portion P is covered with the protective film 10 of the present invention, the surface of the first heat-welding resin layer 1 of the protective film 10 becomes the metal leaf exposed portion 21 side, and the second heat is generated. It is arranged so that the surface on the weldable resin layer 2 side is on the outside. By arranging the protective film 10 of the present invention in this way, the surface of the first heat-welding resin layer 1 having adhesiveness can be suitably fixed around the welded portion P. That is, the protective film of the present invention is used so that the side of the first heat-weldable resin layer 1 of the protective film is in contact with a part around the portion where the metal foil exposed portion 21 and the metal terminal 30 are welded. ..

Further, in the method of coating with a resin adhesive tape, a resin adhesive, a heat-melted resin agent, or the like as disclosed in Patent Document 2, for example, even when the periphery of the welded portion can be protected from metal pieces at the time of welding. For example, metal pieces adhering to the surface of a resin adhesive tape or the like can be easily removed. Therefore, for example, when the battery moves, the metal piece may also move and the metal piece may be mixed inside the electrode. On the other hand, as described later, in the protective film 10 of the present invention, when the second heat-weldable resin layer 2 constitutes the surface opposite to the first heat-weldable resin layer 1, at the time of welding. The generated high-temperature metal pieces can be heat-welded to the surface of the second heat-weldable resin layer 2 and captured. Since the heat-welded metal pieces do not easily separate from the surface of the second heat-weldable resin layer 2, the periphery of the welded portion P can be protected more effectively.

The welding method is not particularly limited, and conventionally known welding methods such as ultrasonic welding and laser welding can be used.

As will be described later, in the battery in which the protective film of the present invention is used, for example, as shown in the schematic diagram of FIG. 7, an electrode having at least a metal foil 20 and an active material layer 22 on the surface of the metal foil 20. The battery element including the electrolyte and the like has a structure housed in a package formed of the packaging material 50. The electrode includes a positive electrode and a negative electrode, and a separator 23 is arranged between the positive electrode and the negative electrode. In the present invention, the inside 50a of the battery means a region in which the battery element is housed by the packaging material 50, and the outside 50b of the battery means the outside of the packaging material 50. The inside 50a and the outside 50b of the battery are separated by a package.

The protective film 10 of the present invention has, for example, as shown in the schematic views of FIGS. 2 to 5, at least the first heat-welding resin layer 1 having adhesiveness, the heat-resistant intermediate layer 3, and the second heat. It is composed of a laminate provided with the weldable resin layer 2 in this order. The first heat-weldable resin layer 1 constitutes the surface of one side of the protective film 10.

As a specific example of the laminated structure of the protective film 10 of the present invention, a laminated structure having a first heat-welding resin layer 1 / heat-resistant intermediate layer 3 / second heat-welding resin layer 2 as shown in FIG. 2 is provided in this order. Configuration; Laminated configuration including the first heat-welding resin layer 1 / heat-resistant intermediate layer 3 / thermoplastic resin layer 4 / second heat-welding resin layer 2 as shown in FIG. 3 in this order; shown in FIG. A laminated structure including the first heat-welding resin layer 1 / thermoplastic resin layer 4 / heat-resistant intermediate layer 3 / second heat-welding resin layer 2 in this order; the first heat-welding property as shown in FIG. Examples thereof include a laminated structure in which the resin layer 1 / the thermoplastic resin layer 4 / the heat-resistant intermediate layer 3 / the thermoplastic resin layer 4 / the second heat-welding resin layer 2 are provided in this order. As will be described later, the second heat-weldable resin layer 2 may contain an adhesive component and have adhesiveness as in the case of the first heat-weldable resin layer 1. Further, the thermoplastic resin layer 4 may have heat-weldability like the first heat-weldable resin layer 1 and the second heat-weldable resin layer 2. The protective film of the present invention may be further laminated with other layers different from these layers.

From the viewpoint of low cost and simplification of the manufacturing process, it is preferable to make the protective film thin, and the protective film of the present invention is the first heat-welding resin layer 1 / heat-resistant intermediate layer 3 / as shown in FIG. It is preferable to have a three-layer laminated structure in which the second heat-weldable resin layer 2 is provided in this order. Further, from the viewpoint of followability to uneven shapes and the like, it is preferable to make the protective film thicker, and the protective film of the present invention is a first heat-welding resin layer 1 / heat-resistant intermediate layer 3 / second heat-welding resin. It is preferable to provide a thermoplastic resin layer between each layer of the layer 2. Specifically, a four-layer laminated structure including the first heat-welding resin layer 1 / heat-resistant intermediate layer 3 / thermoplastic resin layer 4 / second heat-welding resin layer 2 as shown in FIG. 3 in this order. A laminated structure of four layers including a first heat-welding resin layer 1 / a thermoplastic resin layer 4 / a heat-resistant intermediate layer 3 / a second heat-welding resin layer 2 as shown in FIG. 4 in this order; It has a five-layer laminated structure including the first heat-welding resin layer 1 / thermoplastic resin layer 4 / heat-resistant intermediate layer 3 / thermoplastic resin layer 4 / second heat-welding resin layer 2 as shown in this order. Is preferable. Further, the first heat-welding resin layer 1 having adhesiveness (containing an adhesive component) is laminated on the heat-resistant intermediate layer 3 via the thermoplastic resin layer 4, thereby increasing the adhesive strength between the layers. Since it can be stabilized, the protective film of the present invention preferably has a five-layer laminated structure (specifically, a first heat having adhesiveness) having adhesiveness on both sides (containing an adhesive component). Weldable resin layer 1 / thermoplastic resin layer 4 / heat-resistant intermediate layer 3 / thermoplastic resin layer 4 / second thermowelable resin layer 2 having adhesiveness in this order) and adhesiveness on one side Laminated structure of 4 layers (specifically, 1st heat-welding resin layer 1 / thermoplastic resin layer 4 / heat-resistant intermediate layer 3 / thermoplastic resin layer having adhesiveness) 4 / It is preferable to have a laminated structure in which the second heat-welding resin layer 2 having no adhesiveness (not containing an adhesive component) is provided in this order).

The protective film of the present invention may be colored. Specifically, at least one of the first heat-welding resin layer 1, the heat-resistant intermediate layer 3, and the second heat-welding resin layer 2 may be colored. By coloring at least one layer of the protective film of the present invention, it can be visually confirmed that at least a part around the portion where the exposed metal leaf of the electrode is welded is protected by the protective film of the present invention. It can be easily confirmed. The colorant is not particularly limited, and known pigments, dyes and the like can be used. Specific examples of the colorant include carbon black and the like.

The thickness of the protective film of the present invention is preferably about 50 to 200 μm, more preferably about 80 to 150 μm, from the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding and further exhibiting excellent insulating properties. Can be mentioned.

From the viewpoint of low cost and suppressing the possibility of delamination, it is preferable that the number of layers of the protective film of the present invention is small, the lower limit is 3 or more, and the preferable upper limit is 5 or less. From the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding and exhibiting excellent insulating properties, the number of layers of the protective film of the present invention is preferably about 3 to 5, more preferably 3 to 4. The degree is mentioned.

The packaging material of the battery is, for example, a film-like laminate (laminated film) in which a base material layer / a barrier layer (generally composed of a metal such as aluminum) / a heat-sealing resin layer are sequentially laminated. When the packaging material is configured as such, the peripheral portion of the packaging material is heat-sealed so that the heat-sealing resin layer sides of the packaging material face each other, so that the battery element such as an electrode is sealed by the packaging material. In such a case, a protective film is placed around the part where the exposed metal leaf of the electrode is welded, and the metal pieces scattered by welding are attached to the surface of the protective film, and the packaging material is used from above the protective film. It is sealed. Then, for example, the metal foil 20 of the electrode, the protective film 10, the metal piece, and the packaging material are located in order, and when these are sealed in this state, the metal piece becomes the protective film 10 and the packaging material. The metal foil 20 and the barrier layer of the packaging material are electrically connected to each other via the metal piece, and a short circuit may occur. From the viewpoint of avoiding such a short circuit, the protective film of the present invention having excellent insulating properties can be preferably used.

Further, the area of one surface of the protective film of the present invention can be appropriately set according to the size of the portion to be covered.

From the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding and exhibiting excellent insulating properties, the protective film of the present invention is measured for heat shrinkage under the conditions of a test temperature of 200 ° C. and a heating time of 10 seconds. The upper limit of the rate is preferably about 10% or less, more preferably about 5% or less, still more preferably about 4% or less, and the lower limit is about 0% or more and about 0.1% or more. Be done. The range of the heat shrinkage rate is preferably about 0 to 10%, about 0 to 5%, about 0 to 4%, about 0.1 to 10%, about 0.1 to 5%, and 0. About 1 to 4% can be mentioned. The heat shrinkage rate can be determined by a method according to JIS K 7133: 1999. JIS K 7133 stipulates that the size of the test piece is 120 mm × 120 mm, but if the heat shrinkage rate can be measured only with a test piece smaller than the size of the test piece, it is possible. Similarly, the heat shrinkage rate is measured for a square test piece close to the size of the test piece.

(First heat-welding resin layer 1)
In the present invention, the first heat-weldable resin layer 1 is a layer constituting one surface of the protective film. That is, the first heat-welding resin layer 1 constitutes the outermost layer on one side of the protective film 10 of the present invention.

The first heat-welding resin layer 1 has adhesiveness (specifically, contains an adhesive component). More specifically, the first heat-weldable resin layer 1 is composed of a heat-weldable resin composition containing an adhesive component.

The adhesive component is not particularly limited as long as it can impart adhesiveness to the first heat-welding resin layer 1, and is, for example, rosin or a derivative thereof such as rosin, hydrogenated rosin, polymerized rosin, and rosin ester; α-. Telpen-based resins such as pinen, β-pinene, and limonen; terpenphenol resins, kumaron-inden resins, styrene resins, xylene resins, phenolic resins, petroleum resins, hydrogenated petroleum resins, and the like can be mentioned. In addition, the hydrogenated terpene resin, rosin resin, and petroleum resin are compatible with the elastomer phase of the styrene-based block copolymer, and are highly effective in improving the adhesion to non-polar members such as polyolefins. Phenolic resins, styrene resins and the like are compatible with the styrene phase and have the effect of increasing the cohesive force. Therefore, a hydrogenated terpene resin, rosin resin, petroleum resin, xylene resin, phenol resin, styrene resin, or the like can be combined to form an adhesive component.

Amorphous polyolefin can also be used as the adhesive component. Examples of the amorphous polyolefin include amorphous polypropylene or a copolymer of amorphous propylene and another α-olefin, and specific examples thereof include propylene / ethylene copolymer, propylene / butene-1 copolymer, and propylene. Buten-1, ethylene, ternary copolymer, propylene, hexene-1, octene-1, ternary polymer, propylene, hexene-1,4-methylpentene-1,3 yuan copolymer, propylene, hexene. Examples thereof include -1,4-methylpentene-1,3 elemental copolymer and polybutene-1. Among the target amorphous alpha polyolefins, those having a large content of low molecular weight components, a number average molecular weight of 20000 or less, and a glass transition point of −20 ° C. or less are preferable.

Amorphous polyolefin is preferable as the adhesive component. Examples of commercially available products of amorphous polyolefin include REXtac2280 (manufactured by REXtac.LLC). In the first heat-weldable resin layer 1, for example, when REXtac2280 is used as an adhesive component and a modified polyolefin is used as a heat-weldable resin, the content of REXtac2280 is about 10 with respect to 100 parts by mass of the modified polyolefin. It is preferably about 20 parts by mass or about 20 parts by mass.

One type of adhesive component may be used alone, or two or more types may be used in combination.

The ratio of the adhesive component contained in the first heat-welding resin layer 1 is not particularly limited, but the lower limit is preferably about 1% by mass or more, more preferably about 5% by mass or more, and the upper limit is about 5% by mass or more. , Preferably about 30% by mass or less, more preferably about 25% by mass or less. The range of the ratio of the adhesive component is preferably about 1 to 30% by mass, about 1 to 25% by mass, about 5 to 30% by mass, and about 5 to 25% by mass. Since the ratio of the adhesive component contained in the first heat-weldable resin layer 1 has such a value, the protective film of the present invention can exhibit excellent adhesiveness, and the periphery of the welded portion can be exhibited. The protective film 10 of the present invention can be suitably fixed to the surface.

The heat-weldable resin contained in the first heat-weldable resin layer 1 is not particularly limited, but it exhibits excellent adhesiveness, reduces the heat shrinkage rate in a high-temperature environment during welding, and further provides excellent insulation. From the viewpoint of exerting the property, a modified polyolefin (that is, having a polyolefin skeleton) is preferable. The heat-weldable resin having a polyolefin skeleton is preferable as the heat-weldable resin contained in the first heat-weldable resin layer 1 because it has excellent solvent resistance to an electrolytic solution or the like. The resin constituting the first heat-weldable resin layer 1 may or may not contain a polyolefin skeleton, but from the above viewpoint, it is preferable to contain a polyolefin skeleton. The fact that the resin constituting the first heat-weldable resin layer 1 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of wave number 1760 cm ^-1 and wave number 1780 cm ^-1 .

The modified polyolefin is preferably an acid-modified polyolefin. Specific examples of the acid-modified polyolefin include unsaturated carboxylic acids and polyolefins modified with an anhydride thereof. Examples of the unsaturated carboxylic acid or its anhydride used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The modified polyethylene is not particularly limited, but is preferable from the viewpoint of exhibiting excellent adhesiveness, reducing the heat shrinkage rate in a high temperature environment during welding, and further exhibiting excellent insulating properties. Polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene; homopolyethylene, block copolymer of polypropylene (eg block copolymer of propylene and ethylene), random copolymer of polypropylene (eg propylene and ethylene) Crystalline or amorphous polypropylene such as (random copolymer); polyethylene-butene-propylene tarpolymers. Among these, polypropylene is preferable as the modified polyolefin.

From the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding while exhibiting excellent adhesiveness and further exhibiting excellent insulating properties, the heat-welding resin contained in the first heat-welding resin layer 1 Of these, modified polyolefins such as maleic anhydride-modified polypropylene and maleic anhydride-modified polyethylene are particularly preferable.

The heat-weldable resin contained in the first heat-weldable resin layer 1 may be one kind or two or more kinds.

The ratio of the heat-weldable resin contained in the first heat-weldable resin layer 1 is not particularly limited, but the lower limit is preferably about 70% by mass or more, more preferably about 80% by mass or more, and the upper limit is set. Examples include, preferably about 95% by mass or less, and more preferably about 90% by mass or less. The range of the ratio of the heat-weldable resin is preferably about 70 to 95% by mass, about 70 to 90% by mass, about 80 to 95% by mass, and about 80 to 90% by mass. Since the ratio of the heat-weldable resin contained in the first heat-weldable resin layer 1 has such a value, the protective film of the present invention exhibits more excellent adhesiveness and at the time of welding. The heat shrinkage rate in a high temperature environment can be effectively reduced, and more excellent insulation can be exhibited.

From the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding while exhibiting excellent adhesiveness and further exhibiting excellent insulating properties, it is preferable as a softening point of the first heat-welding resin layer 1. Is about 90 ° C. or lower, more preferably about 80 ° C. or lower. The lower limit of the softening point of the first heat-welding resin layer 1 is, for example, about 40 ° C. or higher, preferably 50 ° C. or higher. Preferred ranges of the softening point of the heat-welded resin layer 1 include about 40 to 90 ° C., about 40 to 80 ° C., about 50 to 90 ° C., and about 50 to 80 ° C. In the present invention, the softening point of the heat-welding resin layer 1 is a value measured in the same manner as the softening point of the heat-resistant intermediate layer described later.

The thickness of the first heat-welding resin layer 1 is not particularly limited, but from the viewpoint of exhibiting excellent adhesiveness, reducing the heat shrinkage rate in a high-temperature environment during welding, and further exhibiting excellent insulating properties. Therefore, the lower limit is preferably about 5 μm or more, more preferably about 10 μm or more, further preferably about 20 μm or more, and the upper limit is preferably about 200 μm or less, more preferably about 100 μm or less, still more preferably about. 50 μm or less can be mentioned. The thickness range of the first heat-weldable resin layer 1 is preferably about 5 to 200 μm, about 5 to 100 μm, about 5 to 50 μm, about 10 to 200 μm, about 10 to 100 μm, and about 10 to 50 μm. , About 20 to 200 μm, about 20 to 100 μm, and about 20 to 50 μm.

(Heat-resistant intermediate layer 3)
In the present invention, the heat-resistant intermediate layer 3 is located between the first heat-welding resin layer 1 and the second heat-welding resin layer 2, ensuring the excellent heat resistance of the protective film.

The material constituting the heat-resistant intermediate layer 3 is not particularly limited as long as it has excellent heat resistance, and for example, polyester, polyimide, polyamide, epoxy resin, polyvinyl alcohol, polyphenylene sulfide, polyarylate, polycarbonate, acrylic resin, etc. Examples thereof include fluororesins, silicone resins, phenolic resins, polyetherimides, and mixtures and copolymers thereof. Further, the shape of the heat-resistant intermediate layer 3 is not particularly limited, and examples thereof include a film and a non-woven fabric.

Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and ethylene terephthalate as the main constituents of the copolymerized polyester and butylene terephthalate as the main constituent of the repeating unit. Examples thereof include the copolymerized polyester. Further, as the copolymerized polyester having ethylene terephthalate as the main body of the repeating unit, specifically, a copolymer polyester having ethylene terephthalate as the main body of the repeating unit and polymerizing with ethylene isophthalate (hereinafter, polyethylene (terephthalate / isophthalate)). (Abbreviated after), polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate) , Polyethylene (terephthalate / decandicarboxylate) and the like. Further, as the copolymerized polyester having butylene terephthalate as the main body of the repeating unit, specifically, a copolymer polyester polymerizing with butylene isophthalate using butylene terephthalate as the main body of the repeating unit (hereinafter, polybutylene (terephthalate / isophthalate)). (Abbreviated after), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanticarboxylate), polybutylene naphthalate and the like. These polyesters may be used alone or in combination of two or more.

Among these, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyphenylene sulfide, etc. Examples include aramid, vinylon (polyvinyl alcohol), or polyarylate. Further, examples of the shape of the heat-resistant intermediate layer 3 include a film, a fibrous nonwoven fabric, and the like. Among these, the heat-resistant intermediate layer 3 is composed of a polyethylene terephthalate film, a polyethylene naphthalate film, a polyimide film, a polyphenylene sulfide fiber non-woven fabric, an aramid fiber non-woven fabric, a vinylon (polyvinyl alcohol) fiber non-woven fabric, or a polyarylate fiber non-woven fabric. Is preferable.

In the heat-resistant intermediate layer 3, the probe is installed on the surface of the heat-resistant intermediate layer 3 in the cross section of the protective film 10 in the measurement of the displacement amount of the probe using an atomic force microscope to which a cantilever (probe) with a heating mechanism is attached. The displacement setting value of the probe at the start of measurement is -4V, and the temperature rise rate is 5 ° C / min. When the probe is heated from 40 ° C to 220 ° C, the position of the probe does not drop from the initial value. Is desirable. Since the heat-resistant intermediate layer 3 has such characteristics, the heat shrinkage rate in a high temperature environment at the time of welding can be further reduced, and the appearance after heat welding can be improved.

In measuring the displacement of a probe using an atomic force microscope to which a cantilever (probe) with a heating mechanism can be attached, first, as shown in the conceptual diagram of FIG. 8, for example, the surface of the heat-resistant intermediate layer in the cross section of the protective film. (For example, in the case of the protective film 10 in FIG. 9, the probe 90 is installed at the position of Q) (measurement start A in FIG. 8). The cross section at this time is a portion where the cross section of the heat-resistant intermediate layer obtained by cutting in the thickness direction so as to pass through the central portion of the protective film is exposed. Cutting can be performed using a commercially available rotary microtome or the like. For example, an atomic force microscope manufactured by ANASIS INSTRUMENTS is used as an atomic force microscope to which a cantilever (probe) with a heating mechanism can be attached, and a cantilever ThermoLever AN2-200 (spring constant 0.5 to 3 N / m) is used as a probe. Can be used. The tip radius of the probe is 30 nm or less, the deflection of the probe is set to -4 V, and the temperature rise rate is 5 ° C./min. Next, when the probe is heated in this state, the surface of the heat-resistant intermediate layer 3 expands due to the heat from the probe 90, the probe 90 is pushed up, and the position of the probe 90 is the initial value. It rises above (the position when the temperature of the probe 90 is 40 ° C.). When the temperature further rises, the heat-resistant intermediate layer 3 softens, and as shown in FIG. 8C, the probe 90 may pierce the heat-resistant intermediate layer 3 and the position of the probe 90 may be lowered. In measuring the displacement of the probe 90, the protective film to be measured is in a room temperature (25 ° C.) environment, and the probe 90 heated to 40 ° C. is placed on the surface of the heat-resistant intermediate layer in the cross section of the protective film. And start the measurement.

In the protective film of the present invention, when the probe is heated from 40 ° C. to 220 ° C. under the conditions that the deflection setting value of the probe at the start of measurement is -4 V and the temperature rise rate is 5 ° C./min, the protective film is used. The position of the probe installed on the surface of the heat-resistant intermediate layer in the cross section does not drop below the initial value (the position when the probe temperature is 40 ° C), and is further protected when heated from 160 ° C to 200 ° C. It is more preferable that the position of the probe installed on the surface of the heat-resistant intermediate layer in the cross section of the film is not lowered. The heat welding step of the member using the protective film is usually performed by heating to about 160 ° C. to 200 ° C. Therefore, when the probe is heated from 160 ° C to 200 ° C, the protective film installed on the surface of the heat-resistant intermediate layer in the cross section of the protective film does not lower the position of the probe, and can exhibit particularly high heat resistance. .. From the viewpoint of further improving the heat resistance, when the probe is heated from 40 ° C to 250 ° C, the position of the probe installed on the surface of the heat resistant intermediate layer in the cross section of the protective film does not drop from the initial value, and further. It is more preferable that the position of the probe installed on the surface of the heat-resistant intermediate layer in the cross section of the protective film does not decrease when heated from 160 ° C to 200 ° C.

From the viewpoint of further enhancing the heat resistance, examples of the softening point of the heat resistant intermediate layer 3 include, for example, 90 ° C. or higher, preferably about 160 ° C. or higher, and more preferably about 200 ° C. or higher. Further, although there is no particular upper limit of the softening point of the heat-resistant intermediate layer 3, for example, about 250 ° C. or lower can be mentioned. Preferred ranges of the softening point of the heat-resistant intermediate layer 3 include about 90 to 250 ° C., about 160 to 250 ° C., and about 200 to 250 ° C. In the present invention, the softening point of the heat-resistant intermediate layer 3 is the temperature at which the deflection of the probe is maximized in the above-mentioned displacement measurement of the probe. In the measurement of the softening point of the heat-resistant intermediate layer 3, the temperature at which the deflection of the probe is maximized is read for the five samples of the heat-resistant intermediate layer to be measured, and the maximum values of the five temperatures are read. The softening point is the average value of the three temperatures excluding the minimum value.

Further, the softening point of the heat-resistant intermediate layer 3 is preferably higher than the softening point of the first heat-welding resin layer 1. Further, the softening point of the heat-resistant intermediate layer 3 is preferably higher than the softening point of the first heat-welding resin layer 1 and the softening point of the second heat-welding resin layer 2. The softening point of the heat-resistant intermediate layer 3 is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, and even more preferably 90 ° C. or higher than the softening point of the first heat-welding resin layer 1. The softening point of the heat-resistant intermediate layer 3 is preferably 8 ° C. or higher, more preferably 30 ° C. or higher, and even more preferably 90 ° C. or higher than the softening point of the second heat-welding resin layer 2. ..

The thickness of the heat-resistant intermediate layer 3 is not particularly limited, but the lower limit is preferably about 5 μm or more from the viewpoint of reducing the heat shrinkage rate in a high-temperature environment during welding and further exhibiting excellent insulating properties. More preferably, it is about 10 μm or more, and the upper limit is preferably about 200 μm or less, more preferably about 100 μm or less. The thickness range of the heat-resistant intermediate layer 3 is preferably about 5 to 200 μm, about 5 to 100 μm, about 10 to 200 μm, and about 10 to 100 μm.

When the heat-resistant intermediate layer 3 is made of a non-woven fabric, the texture of the non-woven fabric is not particularly limited, but the layer adjacent to the heat-resistant intermediate layer 3 (for example, the first heat-welding resin layer 1 and the second). From the viewpoint of sufficiently impregnating the non-woven fabric with the heat-welding resin layer 2, the thermoplastic resin layer 4, etc.) to stabilize the adhesive strength between the layers, it is preferable that the texture is small, and the lower limit is preferably about 5 g / m. ² or more can be mentioned. Further, from the viewpoint of reducing the heat shrinkage rate in a high temperature environment at the time of welding, it is preferable that the basis weight is large, and the upper limit is 30 g / m ² or less. From the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding and further exhibiting excellent insulating properties, the basis weight range is preferably about 5 to 30 g / m ² , more preferably 7 to 25 g / m. There are about ^two .

(Second heat-welding resin layer 2)
In the present invention, the second heat-welding resin layer 2 is a layer located on the opposite side of the heat-resistant intermediate layer 3 from the first heat-welding resin layer 1. The second heat-weldable resin layer 2 is made of a heat-weldable resin composition.

As described above, in the protective film 10 of the present invention, when the second heat-weldable resin layer 2 constitutes the surface opposite to the first heat-weldable resin layer 1, the high temperature generated during welding is generated. The metal piece can be supplemented by heat-welding to the surface of the second heat-weldable resin layer 2. Since the heat-welded metal pieces do not easily separate from the surface of the second heat-weldable resin layer 2, the periphery of the welded portion can be protected more effectively. Therefore, in the protective film 10 of the present invention, it is preferable that the second heat-weldable resin layer 2 constitutes a surface opposite to the first heat-weldable resin layer 1.

The heat-weldable resin contained in the second heat-weldable resin layer 2 is not particularly limited, but reduces the heat shrinkage rate in a high-temperature environment during welding, exhibits excellent insulating properties, and further causes high temperature generated during welding. From the viewpoint of preferably heat-welding the metal piece of the above to the surface of the second heat-weldable resin layer 2, modified polyolefin (that is, having a polyolefin skeleton) can be mentioned. That is, the resin constituting the second heat-weldable resin layer 2 may or may not contain a polyolefin skeleton, but from the above viewpoint, it is preferable that the resin contains a polyolefin skeleton. The heat-weldable resin having a polyolefin skeleton is preferable as the heat-weldable resin contained in the second heat-weldable resin layer 2 because it has excellent solvent resistance to an electrolytic solution or the like. The fact that the resin constituting the second heat-weldable resin layer 2 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography mass analysis, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of wave number 1760 cm ^-1 and wave number 1780 cm ^-1 .

The modified polyolefin is preferably an acid-modified polyolefin. Specific examples of the acid-modified polyolefin include unsaturated carboxylic acids and polyolefins modified with an anhydride thereof. Examples of the unsaturated carboxylic acid or its anhydride used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The modified polyethylene is not particularly limited, but the heat shrinkage rate in a high temperature environment during welding is reduced, excellent insulating properties are exhibited, and the high temperature metal pieces generated during welding are used as a second heat-welding resin. From the viewpoint of suitable heat welding to the surface of layer 2, polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene; homopolypropylene, block copolymer of polypropylene (eg, propylene and ethylene). Block copolymers of polypropylene), crystalline or amorphous polypropylenes such as random copolymers of polypropylene (eg, random copolymers of propylene and ethylene); polyethylene-butene-propylene tarpolymers. Among these, polypropylene is preferable as the modified polyolefin.

From the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding, exhibiting excellent insulating properties, and suitably heat welding the high temperature metal pieces generated during welding to the surface of the second heat weldable resin layer 2. Among the heat-weldable resins contained in the second heat-weldable resin layer 2, male anhydride-modified polypropylene and the like are particularly preferable.

The heat-weldable resin contained in the second heat-weldable resin layer 2 may be of one type or two or more types.

The ratio of the heat-weldable resin contained in the second heat-weldable resin layer 2 is not particularly limited, but the lower limit is preferably about 70% by mass or more, more preferably about 80% by mass or more, and the upper limit is set. Examples include, preferably about 95% by mass or less, and more preferably about 90% by mass or less. The range of the ratio of the heat-weldable resin is preferably about 70 to 95% by mass, about 70 to 90% by mass, about 80 to 95% by mass, and about 80 to 90% by mass. Since the ratio of the heat-weldable resin contained in the second heat-weldable resin layer 2 has such a value, the protective film of the present invention exhibits more excellent adhesiveness and at the time of welding. The heat shrinkage rate in a high temperature environment can be effectively reduced, and more excellent insulation can be exhibited.

The second heat-welding resin layer 2 may have adhesiveness (specifically, an adhesive component may be contained), if necessary. When the second heat-welding resin layer 2 contains an adhesive component, the second heat-welding resin layer 2 can exhibit adhesiveness like the first heat-welding resin layer 1. When the second heat-weldable resin layer 2 constitutes the surface opposite to the first heat-weldable resin layer 1, the second heat-weldable resin layer 2 contains an adhesive component. As a result, it is possible to impart adhesiveness to both sides of the first heat-weldable resin layer 1 and the second heat-weldable resin layer 2 of the protective film 10 to the periphery of the portion where the exposed metal foil portion of the electrode is welded. Due to the adhesive strength of the second heat-welding resin layer 2, high-temperature metal pieces generated during welding can be suitably adhered and heat-welded to be captured.

When the adhesive component is contained in the second heat-welding resin layer 2, the type of the adhesive component is not particularly limited, and the same as those exemplified in the first heat-welding resin layer 1 may be exemplified. The ratio of the adhesive component and the heat-weldable resin in the second heat-weldable resin layer 2 is not particularly limited, and examples thereof include the same ratios as those in the first heat-weldable resin layer 1.

From the viewpoint of reducing the heat shrinkage rate in a high temperature environment during welding, exhibiting excellent insulating properties, and suitably heat welding the high temperature metal pieces generated during welding to the surface of the second heat weldable resin layer 2. The softening point of the second heat-weldable resin layer 2 is preferably about 90 ° C. or lower, more preferably about 80 ° C. or lower. The lower limit of the softening point of the second heat-welding resin layer 2 is, for example, about 40 ° C. or higher, preferably 50 ° C. or higher. Preferred ranges of the softening point of the heat-welded resin layer 2 include about 40 to 90 ° C., about 40 to 80 ° C., about 50 to 90 ° C., and about 50 to 80 ° C. In the present invention, the softening point of the heat-welding resin layer 2 is a value measured in the same manner as the softening point of the heat-resistant intermediate layer described above.

The thickness of the second heat-weldable resin layer 2 is not particularly limited, but the lower limit is preferably about 5 μm or more from the viewpoint of reducing the heat shrinkage rate in a high-temperature environment during welding and exhibiting excellent insulating properties. , More preferably about 10 μm or more, still more preferably about 20 μm or more, and the upper limit is preferably about 200 μm or less, more preferably about 100 μm or less, still more preferably about 50 μm or less. The thickness range of the second heat-welding resin layer 2 is preferably about 5 to 200 μm, about 5 to 100 μm, about 5 to 50 μm, about 10 to 200 μm, about 10 to 100 μm, and about 10 to 50 μm. , About 20 to 200 μm, about 20 to 100 μm, and about 20 to 50 μm.

(Thermoplastic resin layer 4)
In the present invention, the thermoplastic resin layer 4 is a layer laminated on the protective film 10 as needed. The thermoplastic resin layer 4 is preferably laminated between the first heat-welding resin layer 1 and the heat-resistant intermediate layer 3, and between the heat-resistant intermediate layer 3 and the second heat-welding resin layer 2. .. The protective film 10 may be laminated with one thermoplastic resin layer 4 or two or more layers. The number of layers of the thermoplastic resin layer 4 in the protective film 10 is preferably about 0 to 2, more preferably about 0 to 1.

The thermoplastic resin constituting the thermoplastic resin layer 4 is not particularly limited as long as it has thermoplasticity. Examples of the thermoplastic resin include polyolefins, polyesters, polyamides, acrylic resins, fluororesins, silicone resins and the like. Among these, the thermoplastic resin layer 4 is preferably composed of polyolefin, and more preferably composed of modified polyolefin (that is, having a polyolefin skeleton). As the modified polyolefin, the same ones as exemplified in the second heat-welding resin layer 2 are preferably exemplified. That is, the resin constituting the thermoplastic resin layer 4 may or may not contain a polyolefin skeleton, but from the above viewpoint, it is preferable to contain a polyolefin skeleton. A thermoplastic resin having a polyolefin skeleton is preferable as the thermoplastic resin contained in the thermoplastic resin layer 4 because it has excellent solvent resistance to an electrolytic solution or the like. The fact that the resin constituting the thermoplastic resin layer 4 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography mass analysis, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of wave number 1760 cm ^-1 and wave number 1780 cm ^-1 .

The thermoplastic resin layer 4 may have adhesiveness (specifically, an adhesive component may be contained), if necessary. When the thermoplastic resin layer 4 contains an adhesive component, the thermoplastic resin layer 4 can exhibit adhesiveness like the first heat-welding resin layer 1. When the thermoplastic resin layer 4 contains a pressure-sensitive adhesive component, the type of the pressure-sensitive adhesive component is not particularly limited, and the same ones as exemplified in the first heat-welding resin layer 1 are exemplified. The ratio of the adhesive component in the thermoplastic resin layer 4 is not particularly limited, and examples thereof include the same ratio as in the first heat-welding resin layer 1.

The softening point of the thermoplastic resin layer 4 is preferably about 90 ° C. or lower, more preferably about 80 ° C. or lower. The lower limit of the softening point of the thermoplastic resin layer 4 is, for example, about 40 ° C. or higher, preferably about 50 ° C. or higher. Preferred ranges of the softening point of the thermoplastic resin layer 4 include about 40 to 90 ° C., about 40 to 80 ° C., about 50 to 90 ° C., and about 50 to 80 ° C. In the present invention, the softening point of the thermoplastic resin layer 4 is a value measured in the same manner as the softening point of the heat-resistant intermediate layer described above.

The thickness of the thermoplastic resin layer 4 is not particularly limited, but the lower limit is preferably about 5 μm or more from the viewpoint of reducing the heat shrinkage rate in a high temperature environment at the time of welding and further exhibiting excellent insulating properties. It is more preferably about 10 μm or more, further preferably about 20 μm or more, and the upper limit is preferably about 200 μm or less, more preferably about 100 μm or less, still more preferably about 50 μm or less. The thickness range of the thermoplastic resin layer 4 is preferably about 5 to 200 μm, about 5 to 100 μm, about 5 to 50 μm, about 10 to 200 μm, about 10 to 100 μm, about 10 to 50 μm, and about 20 to 20. Examples thereof include about 200 μm, about 20 to 100 μm, and about 20 to 50 μm. When a plurality of thermoplastic resin layers 4 are provided, these thicknesses mean the thickness of one layer of the thermoplastic resin layer 4.

(Other layers)
The protective film 10 of the present invention is further laminated with a first heat-welding resin layer 1, a second heat-welding resin layer 2, a heat-resistant intermediate layer 3, and another layer different from the thermoplastic resin layer 4. You may.

(Additive)
The protective film 10 of the present invention may contain various additives such as a lubricant, an antioxidant, an ultraviolet absorber, and a light stabilizer, if necessary. The protective film 10 may be discolored depending on the type and content of the additive.

(Manufacturing method of protective film)
The protective film 10 of the present invention comprises at least a first heat-welding resin layer 1, a heat-resistant intermediate layer 3, a second heat-welding resin layer 2, and a thermoplastic resin layer 4 provided as needed. It can be manufactured by laminating. The laminating method of these layers is not particularly limited, and for example, a thermal laminating method, a sandwich laminating method, an extruded laminating method, or the like can be used.

Further, in the protective film 10 of the present invention, when the heat-resistant intermediate layer 3 is made of a resin film, an adhesion promoter is applied to both surfaces of the heat-resistant intermediate layer 3 (that is, an adhesion promoter layer is provided). Thereby, the adhesion strength with the adjacent layer (for example, the first heat-welding resin layer 1, the second heat-welding resin layer 2, the thermoplastic resin layer 4, etc.) can be improved and the laminated structure can be stabilized. Further, on the surface of the heat-resistant intermediate layer 3, well-known easy-adhesion means such as corona discharge treatment, ozone treatment, and plasma treatment can be provided, if necessary.

As the adhesion promoter for forming the adhesion promoter layer, a well-known adhesion promoter such as isocyanate-based, polyethyleneimine-based, polyester-based, polyurethane-based, or polybutadiene-based can be used. Further, the adhesive accelerator layer can also be formed by using a known adhesive such as a two-component curable adhesive or a one-component curable adhesive. As a result of the experiment, the one composed of the isocyanate component selected from the triisocyanate monomer and the polypeptide MDI was excellent in the laminating strength and the decrease in the laminating strength was small. As the isocyanate-based adhesion accelerator, one composed of an isocyanate component selected from a triisocyanate monomer and a polypeptide MDI has excellent laminating strength and little decrease in laminating strength after immersion in an electrolytic solution. In particular, from triphenylmethane-4,4', 4 "-triisocyanate, which is a triisocyanate monomer, and polymethylenepolyphenylpolyisocyanate, which is a polypeptide MDI (NCO content is about 30%, viscosity is 200 to 700 mPa · s). It is particularly preferable to form the adhesive with a triisocyanate monomer, tris (p-isocyanate phenyl) thiophosphate, or a two-component curable adhesive containing polyethyleneimine as a main component and polycarbodiimide as a cross-linking agent. It is also preferable to form it with an accelerator.

The adhesion accelerator layer can be provided on one side or both sides of the heat resistant intermediate layer 3. The adhesion accelerator layer can be formed by applying and drying by a known coating method such as a bar coating method, a roll coating method, or a gravure coating method. The amount of the adhesion promoter applied is 20 to 100 mg / m ² , preferably 40 to 60 mg / m ² in the case of the adhesion promoter made of triisocyanate, and 40 in the case of the adhesion promoter made of polypeptide MDI. ~ 150 mg / m ² , preferably 60-100 mg / m ² , 5 to 50 mg / m ² for a two-component curable adhesion promoter with polyethyleneimine as the main ingredient and polycarbodiimide as the cross-linking agent. It is preferably 10 to 30 mg / m ² . When a known adhesive is used as the adhesion accelerator, the upper limit of the coating amount is preferably about 10 g / m ² or less, and the lower limit is preferably about 1 g / m ² . The triisocyanate monomer is a monomer having three isocyanate groups in one molecule, and the polypeptide MDI is a mixture of MDI and an MDI oligomer obtained by polymerizing MDI, and is represented by the following formula.

2. 2. Battery As shown in the schematic diagram of FIG. 7, the battery of the present invention includes at least a metal foil 20, an electrode having an active material layer 22 on the surface of the metal foil 20, and a battery element provided with an electrolyte and the like as a packaging material. It has a structure housed in a package formed by 50. The electrode includes a positive electrode and a negative electrode, and a separator 23 is arranged between the positive electrode and the negative electrode. In the present invention, the inside 50a of the battery means a region in which the battery element is housed by the packaging material 50, and the outside 50b of the battery means the outside of the packaging material 50. The inside 50a and the outside 50b of the battery are separated by a package.

The electrode is provided with a metal leaf exposed portion where the metal foil is exposed, and at least a part around the portion where the metal foil exposed portion of the electrode and the metal terminal are welded is covered with the protective film 10 of the present invention. Has been done. More specifically, the battery of the present invention includes electrodes (positive electrode and negative electrode) having an active material layer formed on the surface of a metal foil. Further, as shown in FIG. 1, the electrode is provided with a metal foil exposed portion 21 (the active material layer 22 does not exist) in which the metal foil 20 of the electrode is exposed. In the metal foil exposed portion 21, the metal foil 20 and a conductive member such as a metal terminal 30 are welded (welded portion P). As a result, the inside and outside of the battery are electrically connected. The positive electrode and the negative electrode are arranged via a separator. The electrodes are usually rolled or laminated and housed in the packaging material. The battery of the present invention usually includes a plurality of laminates in which a positive electrode and a negative electrode are laminated via a separator, and a plurality of metal foils 20 are provided in the metal leaf exposed portion 21 of the positive electrode or the negative electrode, respectively. Are laminated. Then, in a portion where a plurality of metal foils 20 of the electrodes are laminated, a conductive member such as a metal terminal 30 is welded to the metal foil 20. In the battery of the present invention, at least a part around the portion (corresponding to the welded portion P) in which the metal foil exposed portion 21 provided on the electrode and the conductive member such as the metal terminal 30 are welded is the present invention. It is covered with the protective film 10 (region R).

The packaging material for accommodating the battery element such as the electrode and the electrolytic solution may be made of metal, or may be a laminated film in which a base material layer / a barrier layer / a heat-sealing resin layer are sequentially laminated.

In the battery of the present invention, at least a part around the portion where the metal foil exposed portion 21 of the electrode and the metal terminal 30 are welded is covered with the protective film 10 of the present invention, and the metal foil exposed portion 21 is made of metal. It can be manufactured by a method including a step of welding the terminal 30. As described above, the method of coating with the protective film 10 of the present invention includes a method of adhering the surface of the first heat-weldable resin layer 1 of the protective film 10 of the present invention to at least a part around the welded portion. .. Due to the adhesive force of the first heat-welding resin layer 1, the protective film 10 of the present invention can be suitably fixed around the welded portion. Further, as described above, the welding method is not particularly limited, and ultrasonic welding, laser welding, or the like can be adopted.

The portion covered with the protective film 10 of the present invention may be a part around the portion where the metal foil exposed portion of the electrode is welded, or may be the entire portion. As the portion to be covered with the protective film 10 of the present invention, a place where fine metal pieces generated during welding can be suppressed from being mixed into the inside of the electrode may be appropriately selected.

The active material layer of the battery can be made of a known material such as an active material, a conductive auxiliary agent, and a binder, and various combinations are known.

For example, specific examples of the active material used for the positive electrode include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , Li ₄ Ti ₅ O ₁₂ , LiFePO ₄ , LiNi _1/3 Mn _1/3 Co _{1 /.} Examples include positive electrode active materials such as lithium transition metal composite oxides such as 3O ₂ , _{LiNi 0.80} Co _0.15 Al _0.05 O ₂ . As the positive electrode active material, only one kind may be used, or two or more kinds may be mixed and used.

Specific examples of the active material used for the negative electrode include natural graphite, artificial graphite, amorphous carbon, carbon black, carbon materials obtained by adding different elements to these components, metallic lithium and its alloys, tin, and silicon. And materials that can occlude and release alkali metal ions, such as alloys thereof and oxides of tin, silicon, and titanium. Only one type of negative electrode active material may be used, or two or more types may be mixed and used.

Specific examples of the conductive auxiliary agent include conductive carbon black such as graphite, furnace black, acetylene black, and Ketjen black, carbon fibers such as carbon nanotubes, and metal powder. As the conductive auxiliary agent, only one kind may be used, or two or more kinds may be mixed and used.

Specific examples of the binder include polyvinylidene fluoride, styrene-butadiene rubber, polyamide, polyimide, polyacrylic acid and the like. Only one type of binder may be used, or two or more types may be mixed and used.

The battery of the present invention may be either a primary battery or a secondary battery, but is preferably a secondary battery. The type of secondary battery is not particularly limited, and is, for example, a lithium ion battery, a lithium ion polymer battery, a lead storage battery, a nickel / hydrogen storage battery, a nickel / cadmium storage battery, a nickel / iron storage battery, a nickel / zinc storage battery, and silver oxide. Examples thereof include zinc storage batteries, metal air batteries, polyvalent cation batteries, capacitors, and capacitors. Among these secondary batteries, a lithium ion battery and a lithium ion polymer battery are preferable.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.

In Examples and Comparative Examples, the softening point of the resin is a value measured by the following method.

(Measurement of softening point)
The softening point was measured using the displacement measurement of the probe using an atomic force microscope to which a cantilever (probe) with a heating mechanism was attached. In the measurement of the softening point of the heat-resistant intermediate layer, first, a probe was installed on the surface of the heat-resistant intermediate layer in the cross section of the protective film. The cross section at this time is a portion where the cross section of the heat-resistant intermediate layer obtained by cutting in the thickness direction so as to pass through the central portion of the protective film is exposed. Cutting was performed using a commercially available rotary microtome or the like. An atomic force microscope to which a cantilever (probe) with a heating mechanism can be attached uses an afm plus system manufactured by ANASIS INSTRUMENTS, and a cantilever ThermaLever AN2-200 (spring constant 0.5 to 3 N / m) is used as a probe. did. The radius of the tip of the probe was 30 nm or less, the set value of the deflection of the probe was -4 V, and the heating rate was 5 ° C./min. Next, when the probe is heated in this state, the surface of the heat-resistant intermediate layer expands due to the heat from the probe, the probe is pushed up, and the position of the probe is the initial value (when the temperature of the probe is 40 ° C.). Position) was higher than. When the heating temperature was further increased, the heat-resistant intermediate layer was softened, the probe pierced the heat-resistant intermediate layer, and the position of the probe was lowered. In the measurement of the displacement of the probe, the protective film to be measured was in a room temperature (25 ° C.) environment, and the probe heated to 40 ° C. was placed on the surface of the heat-resistant intermediate layer to start the measurement. The softening point of the heat-resistant intermediate layer was set to the temperature at which the deflection of the probe was maximized in the measurement of the displacement amount of the probe. In the measurement of the softening point of the heat-resistant intermediate layer, the temperature at which the deflection of the probe is maximized is read for the five samples of the heat-resistant intermediate layer to be measured, and the maximum and minimum values of the five temperatures are read. The average value of the three temperatures excluding the above was taken as the softening point.

In the measurement of the softening point of the first heat-welding resin layer, what is the main surface 1a of the first heat-welding resin layer of the protective film (specifically, the heat-resistant intermediate layer side of the first heat-welding resin layer? A probe was placed on the opposite surface (see FIG. 10), and the measurement was performed in the same manner as the measurement of the softening point of the heat-resistant intermediate layer. In the measurement of the softening point of the second heat-welding resin layer, a probe is placed on the surface of the second heat-welding resin layer in the cross section of the protective film, and the measurement is performed in the same manner as the measurement of the softening point of the heat-resistant intermediate layer. Was done.

<Manufacturing of protective film>
(Example 1)
A heat-weldable resin containing an adhesive component and a maleic anhydride-modified polyethylene resin on one surface of a non-woven fabric (grain 14 g / m ² , thickness 60 μm, softening point 160 ° C or higher) made of polyarylate fiber as a heat-resistant intermediate layer. The composition was extruded and applied to a thickness of 30 μm with a T-die extruder to form a first heat-weldable resin layer (adhesive PEa, softening point 54 ° C.). Next, the maleic anhydride-modified polypropylene resin was extruded and applied to the other surface of the heat-resistant intermediate layer to a thickness of 30 μm with a T-die extruder, and a second heat-weldable resin layer (PPa, softening point 75 ° C.) was applied. First heat-welded resin layer (adhesive PEa, thickness 30 μm) / heat-resistant intermediate layer (polypropylene fiber non-woven fabric, texture 14 g / m ² , thickness 60 μm) that is formed and has adhesiveness (including adhesive components) / A protective film in which a second heat-weldable resin layer (PPa, thickness 30 μm) was laminated in this order was obtained.

(Example 2)
A second having adhesiveness (including an adhesive component) in the same manner as in Example 1 except that a polyethylene naphthalate (PEN) film (thickness 12 μm, softening point 160 ° C. or higher) was used as the heat-resistant intermediate layer. A protective film in which 1 heat-weldable resin layer (adhesive PEa, 30 μm) / heat-resistant intermediate layer (PEN, thickness 12 μm) / second heat-weldable resin layer (PPa, thickness 30 μm) is laminated in this order is obtained. rice field.

(Example 3)
A maleic anhydride-modified polypropylene resin is extruded and applied to a thickness of 30 μm on one surface of a polyethylene naphthalate (PEN) film (thickness 12 μm, softening point 160 ° C. or higher) as a heat-resistant intermediate layer using a T-die extruder. , A thermoplastic resin layer (PPa, softening point 75 ° C.) was formed. Next, a heat-weldable resin composition containing an adhesive component and maleic anhydride-modified polyethylene was extruded to a thickness of 30 μm with a T-die extruder and applied to the surface of the thermoplastic resin layer to obtain a first heat-weldable resin layer (1st heat-weldable resin layer). Adhesive PEa (softening point 54 ° C.) was formed. Next, the maleic anhydride-modified polypropylene resin was extruded and applied to the other surface of the heat-resistant intermediate layer to a thickness of 30 μm with a T-die extruder, and a second thermowelable resin layer (PPa, softening point 75 ° C.) was applied. First heat-welding resin layer (adhesive PEa, thickness 30 μm) / thermoplastic resin layer (PPa, thickness 30 μm) / heat-resistant intermediate layer (PEN, thickness) that is formed and has adhesiveness (including adhesive components) 12 μm) / A protective film in which a second thermoplastic resin layer (PPa, thickness 30 μm) was laminated in this order was obtained.

(Example 4)
Adhesiveness is the same as in Example 1 except that a non-woven fabric made of a polyphenylene sulfide (PPS) resin (grain 15 g / m ² , thickness 25 μm, softening point 160 ° C. or higher) is used as the heat-resistant intermediate layer. 1st heat-welding resin layer (adhesive PEa, 30 μm) / heat-resistant intermediate layer (PPS non-woven fabric, texture 15 g / m ² , thickness 25 μm) / second heat-welded resin layer (including adhesive component) A protective film in which PPa (thickness 30 μm) was laminated in this order was obtained.

(Example 5)
In Example 3, except that the maleic anhydride-modified polypropylene resin forming the second heat-weldable resin layer (PPa, softening point 75 ° C.) was colored black by blending a colorant (carbon black). Similar to Example 3, the first heat-weldable resin layer (adhesive PEa, thickness 30 μm) / thermoplastic resin layer (PPa, thickness 30 μm) / heat-resistant intermediate having adhesiveness (including the adhesive component). A protective film in which layers (PEN, thickness 12 μm) / second heat-weldable resin layer (PPa, black color, thickness 30 μm) were laminated in this order was obtained.

(Comparative Example 1)
As the intermediate layer, it has adhesiveness (adhesive component) as in Example 1 except that a non-woven fabric made of polyethylene fiber (PE non-woven fabric, texture 10 g / m ² , thickness 25 μm, softening point 50 ° C.) was used. 1st heat-weldable resin layer (adhesive PEa, thickness 30 μm) / intermediate layer (PE non-woven fabric, texture 10 g / m ² , thickness 25 μm) / 2nd heat-weld resin layer (PPa, thickness 30 μm) ) Was laminated in this order to obtain a protective film.

(Comparative Example 2)
A commercially available acrylic adhesive tape (Nichiban's Nystack, thickness 90 μm) was used as the protective film.

<Measurement of heat shrinkage rate>
The heat shrinkage of each protective film obtained above was measured under the conditions of a test temperature of 200 ° C. and a heating time of 10 seconds in a method according to JIS K 7133: 1999. The results are shown in Table 1.

<Evaluation of insulation>
In order to evaluate the insulating property of each protective film obtained above, first, a packaging material composed of a laminated film was manufactured by the following procedure. One surface of an aluminum foil (thickness 40 μm) and a biaxially stretched nylon film (thickness 25 μm) were laminated via a urethane adhesive (thickness 4 μm). Next, the other surface of the aluminum foil and the unstretched polypropylene film (thickness 30 μm) are sandwich-laminated with an acid-modified polypropylene resin (thickness 15 μm, polypropylene graft-modified with unsaturated carboxylic acid), and acid is applied by hot air. By heating to a temperature above the softening point of the modified polypropylene resin, biaxially stretched nylon film (25 μm) / aluminum foil (thickness 40 μm) / acid-modified polypropylene resin (thickness 15 μm) / unstretched polypropylene film (30 μm) are sequentially formed. Manufactured laminated packaging materials.

Next, the obtained packaging material was cut into a size of 150 mm in length (MD) × 60 mm in width (TD). Similarly, one protective film cut into a size of 150 mm in length (MD) × 60 mm in width (TD) was prepared. Further, a nickel terminal having a length of 100 mm, a width of 5 mm and a thickness of 0.1 mm and a nickel wire having a length of 100 mm and a diameter of 24 μm were prepared. Hereinafter, the method of evaluating the insulating property will be described with reference to the schematic diagram of FIG. First, the first heat-welding resin layer side of the protective film 10 was laminated on the surface of the packaging material 50 on the unstretched polypropylene film side so that the length direction and the width direction coincide with each other. In Comparative Example 2, the surface opposite to the adhesive surface of the acrylic adhesive tape was overlapped. Next, this was folded in half at the central portion in the length direction so that the protective film 10 was on the inside. Next, the wire 70 was placed on the nickel terminal 60 so that the length directions of the wires coincided with each other, and the end portion was fixed with tape so that the wire 70 did not move. Next, a nickel terminal 60 on which the wire 70 was placed was inserted between the protective films 10 folded in half. Next, a tester (HIOKI 3154 DIGITAL MΩ HiTESTER) was prepared, the positive electrode was connected to the nickel terminal 60, and the negative electrode was connected to the aluminum foil of the packaging material 50. At this time, the packaging material 50 was sandwiched between the crocodile clips, and the crocodile clip was passed through the aluminum foil to connect the negative electrode to the aluminum foil of the packaging material 50. In this state, as shown in FIG. 6, using a metal bar 80 having a width of 7 mm (temperature 190 ° C., gauge pressure 0.22 MPa, surface pressure 1 MPa), the packaging material of the portion where the nickel terminal 60 and the wire 70 are inserted. Thermal pressure was applied from above 50 (the side where the wire 70 of the nickel terminal 60 is located), and the time until the resistance value at 100 V became 200 MΩ or less (time until short circuit) was measured. The measurement was performed using the same sample and used as an average value (n = 5) performed 5 times. The results are shown in Table 1.

In Table 1, "adhesive PEa" means a first heat-welding resin layer composed of an anhydrous maleic acid-modified polyethylene resin composition containing an adhesive component, and "PPa" is an anhydrous maleic acid-modified polypropylene resin. It means the configured second heat-weldable resin layer. Further, "PEN" means polyethylene naphthalate, "PPS nonwoven fabric" means a nonwoven fabric made of polyphenylene sulfide (PPS) -based resin, and "PE nonwoven fabric" means a nonwoven fabric made of polyethylene.

As is clear from the results shown in Table 1, a first heat-welding resin layer having adhesiveness (containing an adhesive component), a heat-resistant intermediate layer, and a second heat-welding resin layer are provided in this order. It can be seen that the protective films of Examples 1 to 4 in which the first heat-welding resin layer constitutes the surface of one side of the protective film have small heat shrinkage in a high temperature environment and are excellent in insulating properties. .. Moreover, the heat shrinkage rate and the insulating property evaluation of the protective film of Example 5 were the same as those of Example 3. On the other hand, it can be seen that the protective film of Comparative Example 1 made of a PE non-woven fabric having a low heat resistance in the intermediate layer has a high heat shrinkage rate and a low insulating property. Further, it can be seen that Comparative Example 2 using the acrylic adhesive tape has low insulating properties.

1 1st heat-weldable resin layer having adhesiveness (including adhesive component) 1a Main surface of 1st heat-weldable resin layer 2 2nd heat-weldable resin layer 3 Heat-resistant intermediate layer 4 Thermoplastic resin layer 10 Protective film 20 Metal foil 21 Metal foil exposed part 22 Active material layer 23 Separator 30 Metal terminal 40 Welding head 50 Packaging material 50a Battery inside 50b Battery outside 60 Nickel terminal 70 Wire 80 Metal bar 90 Probe P Welded part Q Cross section of laminated film Location of the surface of the heat-resistant intermediate layer R Area covered with the protective film

Claims (11)

A protective film used for a battery having an electrode having a metal foil and an active material layer located on the surface of the metal foil.
The electrode is provided with a metal foil exposed portion in which the metal foil is exposed.
The protective film is used to protect at least a part around the portion where the metal foil exposed portion of the electrode and the metal terminal are welded.
The protective film includes at least a first heat-welding resin layer having adhesiveness, a heat-resistant intermediate layer, and a second heat-welding resin layer in this order.
The first heat-welding resin layer constitutes the surface of one side of the protective film.
The protective film is a protective film around a portion where the metal leaf exposed portion and the metal terminal of the electrode are welded, and is used to protect at least a part of the metal foil exposed portion . The protective film according to claim 1, wherein the heat shrinkage rate measured under the conditions of a test temperature of 200 ° C. and a heating time of 10 seconds is 10% or less. The protective film according to claim 1 or 2, wherein the resin constituting the first heat-weldable resin layer has a polyolefin skeleton. The protective film according to any one of claims 1 to 3, wherein the first heat-weldable resin layer contains a modified polyolefin. The protective film according to any one of claims 1 to 4, wherein the first heat-weldable resin layer contains an acid-modified polyolefin. The protective film according to any one of claims 1 to 5, wherein when the first heat-weldable resin layer is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is detected. The protective film according to any one of claims 1 to 6, wherein the second heat-weldable resin layer constitutes a surface opposite to the first heat-weldable resin layer. The protective film according to any one of claims 1 to 7, wherein at least one of the first heat-welding resin layer, the intermediate layer, and the second heat-welding resin layer is colored. The protective film according to any one of claims 1 to 8, wherein a plurality of the metal foils of the electrodes are laminated in the exposed metal foil portion. A battery in which at least a battery element provided with an electrode and an electrolyte is housed in a package formed of a battery packaging material.
The electrode comprises a metal foil and an active material layer located on the surface of the metal foil.
The electrode is provided with a metal foil exposed portion in which the metal foil is exposed.
A metal terminal is welded to the exposed metal leaf portion of the electrode.
A battery in which at least a part around a portion where the metal foil exposed portion of the electrode and a metal terminal are welded is covered with the protective film according to any one of claims 1 to 9 . A method for manufacturing a battery including an electrode having a metal foil and an active material layer located on the surface of the metal foil.
The electrode is provided with a metal foil exposed portion in which the metal foil is exposed.
The step of covering at least a part of the periphery of the metal leaf exposed portion of the electrode and the metal terminal to be welded with the protective film according to any one of claims 1 to 9 .
The process of welding the exposed metal leaf to the metal terminal,
A method of manufacturing a battery.

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