JPWO2019078155A1 - Tab lead film and tab lead using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tab lead film for preventing a decrease in adhesive force between a metal terminal and a tab lead film due to the influence of hydrogen fluoride, and contaminate a tab lead production line and a production line such as a lithium battery. To provide a film for tab lead that does not occur. SOLUTION: A surface layer (A) containing an acid-modified polyolefin resin as a main component, an inorganic filler that reacts with hydrogen fluoride and a polyolefin resin, and / or the inorganic filler that reacts with the hydrogen fluoride. In a tab lead film including a core layer (B) containing a polyolefin resin as a main component and a surface layer (C) containing an acid-modified polyolefin resin and / or a polyolefin resin as a main component, the surface layer (A). The content of the inorganic filler and the content of the inorganic filler in the surface layer (C) are 0 to 10% by weight, respectively, and 9.0 weight by weight of the inorganic filler in which the tablead film reacts with hydrogen fluoride. It is characterized by containing% or more. [Selection diagram] Fig. 1

Description

The present invention relates to a tab lead film that is heat-sealed to a tab lead for extracting electricity from the inside in a lithium ion battery, a lithium ion capacitor, or the like having a laminated film as an outer packaging material. The present invention also relates to a tab lead using the tab lead film.

In recent years, lithium-ion batteries and lithium-ion capacitors (hereinafter, simply abbreviated as "lithium batteries, etc.") have been adopted as power supplies for electronic devices such as laptop computers and mobile phones, and batteries for hybrid vehicles and electric vehicles. .. Most of these lithium batteries and the like use a laminated film in which a sealant layer made of polyolefin or the like is laminated on a metal foil such as an aluminum foil as an outer packaging material, and a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte, etc. are contained inside the outer packaging material. It is enclosed, and a tab lead for electrically connecting the inside and the outside of a lithium battery or the like is attached.

In Patent Document 1, the metal terminal (lead wire) is corroded by hydrogen fluoride (hydrofluoric acid) generated by the infiltration of water, and the tab lead film (insulating material of the lead wire) is prevented from peeling off. It is proposed to add a function of trapping acid to the tab lead film. Specifically, 100 parts by weight of a thermoplastic resin and one or more kinds selected from carboxylic acid metal salts, metal oxides, and hydrotalcites are mainly composed of 20 parts by weight or more and 100 parts by weight or less in total. It is proposed to use the resin composition to be used as a film for tab lead.

However, the tab lead film disclosed here is a single-layer film, and a large amount of filler (carboxylic acid metal salt, metal oxide, hydrotalcite, etc.) is present on the film surface. Therefore, there is a risk that the filler may fall off from the film surface and contaminate the tab lead production line and the lithium battery production line.
Further, if a large amount of the filler is present on the film surface, there is a problem that the adhesive force between the metal terminal and the tab lead film is lowered. Normally, the tab lead film is heat-sealed to the metal terminals by heat sealing, but the filler does not melt even at the heat sealing temperature (usually 150 to 250 ° C.) and does not heat-sealing with the metal terminals.

Patent Document 2 is also an invention that solves the problem that the metal terminal (lead terminal) is corroded by hydrogen fluoride and the adhesive force between the metal terminal and the tab lead film (terminal adhesive tape) is lowered.
In Patent Document 2, the tab lead film has a three-layer structure, the layer containing an inorganic filler is an intermediate layer, one of the intermediate layers is a resin layer having good adhesion to a metal terminal, and the other is an outer packaging material. It is disclosed that a resin layer having good adhesiveness to and is provided.
Since the three-layered tab lead film disclosed in Patent Document 2 does not have an inorganic filler on the film surface, it does not contaminate the tab lead production line or the production line of a lithium battery or the like. However, even with the three-layered tab lead film, there are some that have low adhesive strength with the terminals depending on the type of metal terminal.

JP-A-11-354087 JP-A-2014-120390

The present invention is a tab lead film that prevents the adhesive strength between the metal terminal and the tab lead film from being reduced by the influence of hydrogen fluoride, and can contaminate the tab lead production line and the production line of lithium batteries and the like. Furthermore, it is an object of the present invention to provide a film for tab lead in which the adhesiveness with the terminal does not deteriorate depending on the type of the metal terminal. At the same time, it is an object to provide a tab lead using the tab lead film.

The present inventors have investigated the reason why the adhesive force with terminals decreases depending on the type of metal terminal in the three-layered tab lead film disclosed in Patent Document 2. FIG. 9 is a schematic plan view (A) of a tab lead TL adopting a relatively thick metal terminal 2, an α-α cross-sectional view (B) thereof, and a β-β cross-sectional view (C) thereof. When the general three-layered tab lead film 1 is heat-sealed to a relatively thick metal terminal 2, the surface layer 11 of the tab lead film 1 is often interrupted at the corner 2a of the metal terminal 2. It was discovered that the metal terminal 2 is in contact with the core layer 12.
Since the surface layer 11 of the general tab lead film 1 is made of an acid-modified polyolefin and the core layer 12 is made of a polyolefin resin, the core layer 12 is usually more heat-sealing with the metal terminal 2 than the surface layer 11. Inferior. In particular, a film containing an inorganic filler in the core layer, such as the film for tab lead disclosed in Patent Document 2, has very poor heat-sealing property between the core layer and the metal terminal due to the influence of the inorganic filler. Therefore, it is considered that the three-layer tab lead film disclosed in Patent Document 2 does not heat-seal to the terminals at the corners of the metal terminals, and as a result, the adhesive force between the metal terminals and the tab lead film is lowered.

Therefore, the present inventors sufficiently increase the thickness or the thickness ratio of one surface layer (A) of the tab lead film so that the surface layer (A) of the tab lead film is interrupted at the corners of the metal terminals. I decided to prevent it. In this case, as the thickness or thickness ratio of the surface layer (A) increases, the thickness of the core layer (B) and the other surface layer (C) decreases, but the core layer (B) ) Is reduced, the amount of the inorganic filler contained in the layer is also reduced. Therefore, the present inventors have also studied the amount of the inorganic filler added and the effect on hydrogen fluoride, and have reached the present invention.

That is, according to the present invention, as a means for solving the above problems, a surface layer (A) containing an acid-modified polyolefin resin as a main component, an inorganic filler that reacts with hydrogen fluoride and a polyolefin resin are contained, and the fluoride A tab lead including an inorganic filler that reacts with hydrogen and / or a core layer (B) containing the polyolefin resin as a main component, and a surface layer (C) containing an acid-modified polyolefin resin and / or a polyolefin resin as a main component. The content of the inorganic filler in the surface layer (A) and the content of the inorganic filler in the surface layer (C) are 0 to 10% by weight, respectively, and the tablead film is hydrogen fluoride. Provided is a tab lead film characterized by containing 9.0% by weight or more of an inorganic filler that reacts with.
Further, there is provided a tab lead film characterized in that the tab lead film contains an inorganic filler that reacts with hydrogen fluoride in an amount of 9.6% by weight or more.
Further, there is provided a tab lead film characterized in that the median diameter of the inorganic filler that reacts with hydrogen fluoride in the tab lead film is 1.0 μm or less.
Further, a tab lead film characterized in that the thickness of the surface layer (A) is 23 μm or more is provided.
Further, there is provided a tab lead film characterized in that the thickness of the surface layer (A) is 23% or more of the thickness of the entire tab lead film.

Further, there is provided a tab lead film characterized in that the content of the inorganic filler that reacts with the hydrogen fluoride in the core layer is 13 to 60% by weight.
Further, assuming that the thickness of the surface layer (A) is t1, the thickness of the core layer (B) is t2, and the thickness of the surface layer (C) is t3, the following equations (1) and (1) A tab lead film characterized by satisfying 2) is provided.
Equation (1) t1 ≧ t3
Equation (2) t1: t2: t3 = 23-80: 15-72: 5-62
Further, a film for tab lead is provided, characterized in that the inorganic filler that reacts with hydrogen fluoride is a metal carbonate.
Further, a film for tab lead is provided in which the metal carbonate is calcium carbonate.
In addition, a tab lead film is provided in which the calcium carbonate is synthetic calcium carbonate.

Further, it is determined that the tab lead film is heat-sealed to at least one surface of the metal terminal, and the surface of the metal terminal and the surface layer (A) of the tab lead film are heat-sealed. A featured tab lead is provided.
Further, when the thickness of the metal terminal is T (mt) and the thickness of the tab lead film is T (tf), the tab lead is 0.5 T (mt) ≤ T (tf). Provided.

The tablead film of the present invention includes a surface layer (A) containing an acid-modified polyolefin resin as a main component, an inorganic filler that reacts with hydrogen fluoride and / or a core layer (B) containing a polyolefin resin as a main component. A surface layer (C) containing an acid-modified polyolefin resin and / or a polyolefin resin as a main component is provided in order, and the content of the inorganic filler in the surface layer (A) and the content of the inorganic filler in the surface layer (C). Since the amounts are 0 to 10% by weight, each of them does not contaminate the tab lead production line or the lithium battery production line.
Further, since the film contains 9.0% by weight or more of an inorganic filler that reacts with hydrogen fluoride, even if hydrogen fluoride is generated from the inside of the battery, it is caused by corrosion of metal terminals by the hydrogen fluoride and corrosion. It is possible to efficiently suppress the decrease in adhesiveness.
In addition, when the film contains 9.6% by weight or more of an inorganic filler that reacts with hydrogen fluoride, it is possible to further suppress a decrease in the adhesive force between the tab lead film and the metal terminal due to hydrogen fluoride.
In particular, since the median diameter of the inorganic filler that reacts with hydrogen fluoride is 1.0 μm or less, it is suitable for suppressing deterioration of adhesiveness due to hydrogen fluoride.

Further, since the thickness of the surface layer (A) is 23 μm or more, or 23% or more of the thickness of the entire film, the resin layer is interrupted at the corners of the terminals when heat-sealed with the metal terminals. Is suppressed.
Further, when the content of the inorganic filler that reacts with hydrogen fluoride in the core layer is 13 to 60% by weight, the corrosion of metal terminals due to hydrogen fluoride can be effectively suppressed, and the film forming property of the tab lead film can be suppressed. Is also stable.
Furthermore, when the inorganic filler that reacts with hydrogen fluoride is a metal carbonate, it is possible to particularly suppress a decrease in adhesiveness due to hydrogen fluoride without using an expensive filler.

It is a schematic cross-sectional view of the film for tab lead of this invention. It is a schematic plan view (A) of the tab lead of this invention, the α-α sectional view (B), and the β-β sectional view (C) thereof. It is a photograph of the digital microscope of the tab lead cross section of Test Example 1. It is a photograph of the digital microscope of the tab lead cross section of Test Example 2. It is a photograph of the digital microscope of the tab lead cross section of Test Example 3. It is a photograph of the digital microscope of the tab lead cross section of Test Example 4. It is a photograph of the digital microscope of the tab lead cross section of Test Example 5. 3 is a graph showing the relationship between the amount of calcium carbonate added to the tab lead films of Examples 1 to 5 and Comparative Examples 1 to 3 and the adhesive strength of the test piece after immersion in the electrolytic solution. It is a schematic plan view (A) of the tab lead using a conventional film for tab lead, the α-α sectional view (B), and the β-β sectional view (C) thereof.

Hereinafter, the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals represent the same or equivalent components. Further, the present invention is not limited to the following forms, and can take various forms.

FIG. 1 is a schematic cross-sectional view of the tab lead film 1 of the present invention. The tab lead film 1 of the present invention includes a surface layer (A) 11, a core layer (B) 12, and a surface layer (C) 13 in this order.
[Surface layer (A)]
The surface layer (A) 11 is a layer in contact with metal terminals in a tab lead described later, and contains an acid-modified polyolefin having excellent metal adhesiveness as a main component. The acid-modified polyolefin is not particularly limited as long as it is an acid-modified polyolefin, but a polyolefin graft-modified with an unsaturated carboxylic acid or an anhydride thereof is preferably used.

Examples of the acid-modified polyolefin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, polyethylene such as linear low-density polyethylene, homopolypropylene, block copolymer of propylene and ethylene, and polypropylene such as random copolymer of propylene and ethylene. Examples thereof include ethylene-butene-propylene tarpolymers. Among these polyolefins, polyethylene and polypropylene are preferably used.
Examples of the unsaturated carboxylic acid or its anhydride used for acid modification of polyolefin include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.
The surface layer (A) 11 may appropriately contain one or more acid-modified polyolefins, and if this is used as a main component, it may contain other resins such as unmodified polyolefins and thermoplastic elastomers. In the present invention, the "main component" means the component having the largest weight ratio among the components constituting the layer.

The surface layer (A) 11 has an inorganic filler content of 10% by weight or less. If the content of the inorganic filler exceeds 10% by weight, the adhesiveness between the tab lead film and the metal terminal may decrease. In addition, the inorganic filler may fall off in the process of manufacturing the tab lead and contaminate the manufacturing line. The amount of the inorganic filler in the surface layer (A) 11 is preferably 5% by weight or less, preferably 3% by weight or less, and particularly preferably 1% by weight or less.
The inorganic filler is not limited to the inorganic filler that reacts with hydrogen fluoride, which will be described later, and the inorganic filler also includes an anti-blocking agent and the like.

In the tab lead film 1 of the present invention, the thickness t1 of the surface layer (A) 11 is preferably 23 μm or more, particularly 27 μm or more, and more preferably 30 μm or more. If the thickness t1 of the surface layer (A) 11 is less than 23 μm, the surface layer (A) 11 may be interrupted at the corners of the metal terminals, and the metal terminals may come into contact with the core layer of the tab lead film.

The ratio of the thickness t1 of the surface layer (A) 11 to the entire tab lead film 1 is 23% or more (t1 ≧ 0.23 T (tf)) of the total thickness T (tf) of the tab lead film 1, 80%. The following (t1 ≦ 0.8 T (tf)) is preferable. In particular, the lower limit of 27%, 30%, 33%, 35%, 40% or 45% is preferably the upper limit of 75%, 70%, 65%, 60%, 55% or 50%. In a general tab lead, the thickness T (tf) of the tab lead film 1 and the thickness T (mt) of the metal terminal are almost the same. In this case, the thickness t1 of the surface layer (A) 11 is If it is less than 23% of the thickness T (tf) of the film 1, as described above, the surface layer (A) 11 is interrupted at the corners of the metal terminals, and the metal terminals are the core layer (B) of the tab lead film 1. There is a risk of contact with 12. Further, when the thickness t1 of the surface layer (A) 11 exceeds 80% of the film 1, the core layer (B) 12 becomes too thin and cannot contain a sufficient inorganic filler, or the other surface layer (A) C) 13 may become too thin and the adhesiveness to the outer packaging material such as a lithium battery may decrease.

[Core layer (B)]
The core layer (B) 12 in the tab lead film 1 of the present invention is composed of an inorganic filler that reacts with hydrogen fluoride and a polyolefin-based resin, and one or both of them is the main component.
The inorganic filler that reacts with hydrogen fluoride is not particularly limited, but it is particularly preferable that the inorganic filler reacts with hydrogen fluoride having a median diameter of 1.0 μm or less. The inorganic filler that reacts with hydrogen fluoride having a median diameter of 1.0 μm or less uses the same amount of inorganic filler for tab lead as compared with the inorganic filler that reacts with hydrogen fluoride having a median diameter of more than 1.0 μm. When it is contained in a film, the decrease in adhesiveness due to hydrogen fluoride can be further suppressed. In other words, an inorganic filler that reacts with hydrogen fluoride having a median diameter of 1.0 μm or less has a median diameter of more than 1.0 μm when the decrease in adhesiveness (adhesive retention rate) due to hydrogen fluoride is comparable. The amount contained in the tab lead film can be smaller than that of the inorganic filler that reacts with hydrogen fluoride. As described above, since the content in the tab lead film can be reduced to a small amount, defects during manufacturing due to the inorganic filler (resin pressure fluctuation in the extrusion process, screw wear, etc.) can be further suppressed.
Since it is difficult to produce an inorganic filler that reacts with hydrogen fluoride having an extremely small diameter, the lower limit of the median diameter is preferably 0.05 μm, 0.1 μm, or 0.2 μm. Further, it is particularly preferable that the upper limit of the median diameter is 0.8 μm, 0.6 μm or 0.5 μm from the viewpoint that the decrease in adhesiveness due to hydrogen fluoride can be further suppressed.

Examples of the inorganic filler that reacts with hydrogen fluoride include metal carbonates such as calcium carbonate and magnesium carbonate. Among the metal carbonates, calcium carbonate can be preferably used because it is inexpensive and easily available. In particular, synthetic calcium carbonate has an excellent function of catching hydrogen fluoride and can be suitably used. The synthetic calcium carbonate can be produced, for example, by reacting calcium hydroxide with carbon dioxide gas, and particles having a particle size (median diameter) smaller than that of heavy calcium carbonate can be produced.

The polyolefin-based resin used for the core layer (B) 12 is also not particularly limited, and includes, for example, polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene, homopolypropylene, and propylene. Polypropylene such as a block copolymer of ethylene, a random copolymer of propylene and ethylene, a tarpolymer of ethylene-butene-propylene and the like can be used. Among these polyolefins, polyethylene and polypropylene are preferably used. One or more of these may be selected to obtain a polyolefin-based resin that forms the core layer (B) 12.
In addition to the polyolefin-based resin described above, the core layer (B) 12 may contain other resins such as thermoplastic elastomers, colorants, and the like. However, when an acid-modified resin such as an acid-modified polyolefin is contained, the hydrophilicity is increased, the water resistance is lowered, and the generation of hydrogen fluoride may be promoted.

If the entire tab lead film 1 contains 9.0% by weight or more of an inorganic filler that reacts with hydrogen fluoride, the amount of the inorganic filler that reacts with hydrogen fluoride blended in the core layer (B) 12. Is not particularly limited. However, the content of the inorganic filler that reacts with hydrogen fluoride blended in the core layer (B) 12 is preferably 13 to 60% by weight.
When the content of the inorganic filler in the core layer (B) 12 is less than 13% by weight, the content of the inorganic filler in the tab lead film 1 is 9 while the thickness of the surface layer (A) is 23% or more. It becomes difficult to make it 0.0% by weight or more, and it becomes necessary to thin the surface layer (C) 13 or add the inorganic filler to the surface layer (A) 11 and the surface layer (C) 13.
Further, when the content of the inorganic filler in the core layer (B) 12 exceeds 60% by weight, the resin pressure tends to fluctuate when the resin composition for the core layer (B) 12 is extruded from the extruder. The thickness of the layer is difficult to stabilize. In addition, the inorganic filler wears the screw of the extruder, which may cause metal powder to be mixed into the tab lead film.

The thickness t2 of the core layer (B) 12 is preferably 15 to 72%, particularly preferably 20 to 60%, and further preferably 25 to 50% of the total thickness T (tf) of the film. When the thickness t2 of the core layer (B) 12 is less than 15% of the thickness T (tf) of the entire film, the tab lead film 1 is blended with an inorganic filler that reacts with 9.0% by weight or more of hydrogen fluoride. Becomes difficult. Further, when the thickness t2 of the core layer (B) 12 exceeds 72% of the total film thickness T (tf), the thicknesses of the surface layer (A) 11 and the surface layer (C) 13 become too thin, and the thickness of each layer becomes too thin. There is a risk that it will not function.

[Surface layer (C)]
The surface layer (C) 13 is a layer that becomes the outermost layer (surface layer that does not come into contact with metal terminals) in the tab lead described later, and is a layer that is heat-sealed with a laminate film that is an outer packaging material in a lithium battery or the like. The surface layer (C) 13 contains an acid-modified polyolefin resin and / or a polyolefin resin as a main component. When the sealant layer of the laminated film is made of a resin having poor adhesiveness to the tab lead film, it is preferable to select an acid-modified polyolefin resin as the main component of the surface layer (C) 13, and the sealant layer of the laminated film has adhesiveness. When it is abundant, it is preferable to select a polyolefin resin as the main component of the surface layer (C) 13.
As the acid-modified polyolefin resin, the same resin as the resin exemplified as the main component of the surface layer (A) 11 can be appropriately adopted, and the polyolefin resin is the resin exemplified in the core layer (B) 12. Similar resins can be used.

The thickness t3 of the surface layer (C) 13 is preferably 5 μm or more. If it is less than 5 μm, it is difficult to control the thickness in film formation, and the adhesion of the laminated film to the sealant layer may be insufficient.
The ratio of the thickness t3 of the surface layer (C) 13 to the entire tab lead film 1 is preferably 5 to 62% of the total thickness T (tf) of the film, particularly 10 to 50%, and further. It is preferably 15 to 30%. If the thickness t3 of the surface layer (C) 13 is less than 5% of the thickness T (tf) of the entire film, the adhesion of the laminated film to the sealant layer may be insufficient. When the thickness t3 of the surface layer (C) 13 exceeds 62% of the thickness T (tf) of the entire film, the thickness of the surface layer (A) 11 and the core layer (B) 12 becomes too thin, and each layer There is a risk that the function of

The surface layer (C) 13 has an inorganic filler content of 10% by weight or less, similarly to the surface layer (A) 11 described above. If the content of the inorganic filler exceeds 10% by weight, the adhesiveness between the tab lead film 1 and the laminated film may decrease. Further, in the process of manufacturing the tab lead or the process of manufacturing the lithium battery or the like, the inorganic filler may fall off and contaminate the production line. The amount of the inorganic filler in the surface layer (C) 13 is preferably 5% by weight or less, preferably 3% by weight or less, and particularly preferably 1% by weight or less.

The case where the tab lead film 1 is a three-layer film of surface layer (A) 11 / core layer 12 (B) / surface layer (C) 13 has been described above, but the film 1 is within the range in which the effect of the present invention is exhibited. May contain other resin layers.

[Tab Lead]
FIG. 2 is a plan view (A) of the tab lead TL of the present invention and an α-α cross-sectional view (B) thereof.
The tab lead TL of the present invention comprises the tab lead film 1 of the present invention and the metal terminal 2.

[Metal terminal]
The metal terminal 2 is a member electrically connected to an electrode (positive electrode or negative electrode) of a lithium battery or the like, and is made of a metal material. The metal material constituting the metal terminal 2 is not particularly limited, and examples thereof include aluminum, nickel, and copper. The metal terminal connected to the positive electrode of a lithium battery or the like is usually made of aluminum or the like. Further, the metal terminal connected to the negative electrode of a lithium battery or the like is usually made of copper, nickel or the like.
The surface of the metal terminal 2 is preferably subjected to chemical conversion treatment from the viewpoint of enhancing the electrolytic solution resistance. For example, when the metal terminal is made of aluminum, specific examples of the chemical conversion treatment include known methods for forming an acid resistant film such as a phosphate, a chromate, a fluoride, and a triazine thiol compound.

The size of the metal terminal 2 may be appropriately set according to the size of the battery used and the like. The thickness T (mt) of the metal terminal 2 is preferably 50 μm or more and 400 μm or less, and more preferably 100 μm or more and 300 μm or less. The length of the metal terminal 2 is preferably 1 mm or more and 200 mm or less, and more preferably 3 mm or more and 150 mm or less. The width of the metal terminal 2 is preferably 1 mm or more and 200 mm or less, and more preferably 3 mm or more and 150 mm or less.
When the tab lead film 1 of the present invention is used, even if the metal terminal 2 is not chamfered at the corner portion 2a, the surface layer (A) 11 is not easily interrupted at the corner portion 2a. Therefore, the present invention is particularly effective when the metal terminal 2 which is not chamfered is used.

[Tab lead film]
The resin composition, thickness, and thickness ratio of each layer constituting the tab lead film 1 are as described above.
The overall thickness T (tf) of the tab lead film 1 is not particularly limited, but it is desirable to determine the thickness of the metal terminal 2 determined by the size of the battery or the like based on T (mt). Specifically, it is desirable that 0.5T (mt) ≤ T (tf), particularly 0.7T (mt) ≤ T (tf), and further 0.8T (mt) ≤ T (tf). ) Is desirable. When the thickness T (tf) of the tab lead film 1 is less than 0.5 times the thickness T (mt) of the metal terminal 2, the tab lead film 1 is attached to the side portion 2b of the metal terminal 2 during heat fusion. The tab lead film 1 may be lifted from the terminal 2 on the side surface portion 2b without wrapping around.
If the thickness T (tf) of the tab lead film 1 is sufficiently thicker than the thickness T (mt) of the metal terminal 2, the problem that the tab lead film 1 floats from the metal terminal 2 is solved, but lithium. When heat-sealed to an outer packaging material such as a battery, the outer packaging material may be lifted from the tab lead film 1 on the side side portion 1a of the tab lead film 1. Therefore, the thickness T (tf) of the tab lead film 1 is preferably 400 μm or less, particularly 200 μm or less, and more preferably 150 μm or less.
Further, in order to sufficiently maintain the adhesion between the metal terminal 2 and the sealant layer of the laminated film, the thickness T (tf) of the tab lead film 1 must be 50 μm or more, particularly 70 μm or more, and further 75 μm or more. preferable.

[Test Example 1]
In order to confirm the problem of interruption of the surface layer (A) containing the acid-modified polyolefin as the main component shown in FIG. 9, a tab lead film in which the core layer (B) was colored gray was produced.
Specifically, the surface layer (A) is made of acid-modified polypropylene, the core layer (B) is made of polypropylene and a colorant (gray pigment), and the surface layer (C) is made of polypropylene. (Thickness 100 μm) was manufactured. The film was produced by a coextrusion molding method. The thickness of each layer was 50 μm for the surface layer (A), 30 μm for the core layer (B), and 20 μm for the surface layer (C).

[Test Examples 2-5]
As shown in Table 1, a film for tab lead was produced in the same manner as in Test Example 1 except that heavy calcium carbonate was added to the core layer (B) and the thickness of each layer was changed. The breakability was evaluated using the film.

<Evaluation of breakability>
A tab lead film is heat-sealed on both sides of a 100 μm-thick nickel terminal to prepare a tab lead. The tab lead film is arranged so that the surface layer (A) is in contact with the nickel terminals. The heat seal is performed under the conditions that the seal bar temperature is 160 ° C., the seal surface pressure is 1.0 MPa, and the seal time is 2 seconds.
The obtained tab lead is cut, and the cut surface is observed with a digital microscope. The one where the metal terminal was in contact with the gray-colored core layer (B) was ×, the one where the surface layer (A) was thin at the corner of the metal terminal was Δ, and the surface layer was also at the corner of the metal terminal. Those in which (A) remains sufficiently thick are evaluated as ◯.

Table 1 also shows the evaluation results of the breakability of the tab lead film produced in Test Examples 1 to 5. Further, a photograph of a digital microscope having a tab lead cross section using a tab lead film of Test Example 1 is shown in FIG. 3, a photograph of a digital microscope of Test Example 2 is shown in FIG. 4, and a photograph of a digital microscope of Test Example 3 is shown in FIG. A photograph of the digital microscope of Test Example 4 is shown in FIG. 6, and a photograph of the digital microscope of Test Example 5 is shown in FIG.

The tab lead using the tab lead film of Test Examples 1, 2, 4, and 5 in which the thickness of the surface layer (A) is 23% or more of the thickness of the tab lead film is acid-modified even at the corners of the metal terminals. The surface layer (A) made of polypropylene was in contact with the metal terminals. In particular, in the tab lead of Test Example 1 in which the thickness of the surface layer (A) was 50%, the surface layer (A) was hardly thinned. On the other hand, in the tab lead of Test Example 3 in which the thickness of the surface layer (A) was 20% of the whole, the corner portion of the metal terminal was in contact with the core layer (B). Since the core layer (B) contains polypropylene as a main component, it is inferior in adhesiveness.
Further, when comparing Test Example 4 in which the thickness of each layer is the same and the core layer (B) contains calcium carbonate and Test Example 5 in which calcium carbonate is not contained, the surface layer (A) is the same at the corners of the metal terminals. It was thin to some extent, and there was no difference between the presence and absence of calcium carbonate.

[Comparative Examples 1 to 3 and Examples 1 to 4]
Using the resins shown in Table 2, a tab lead film (thickness 100 μm) having the thickness shown in Table 2 was produced. The evaluation of the decrease in adhesiveness of each film due to hydrogen fluoride was performed by the following method.
In addition, the method for measuring the median diameter of calcium carbonate (CaCO ₃ ) to be used is described below.

<Evaluation of deterioration of adhesiveness due to hydrogen fluoride>
A 15 mm wide tab lead film is heat-sealed on both sides of a nickel foil having a thickness of 100 μm and a width of 20 mm to prepare a test piece. The tab lead film is arranged so that the surface layer (A) is in contact with the nickel foil. The heat seal was performed under the conditions that the seal bar temperature was 190 ° C. for the upper bar, 220 ° C. for the lower bar, the seal surface pressure was 1.0 MPa, and the seal time was 3 seconds.
Two sets of test pieces were prepared, and one set of test pieces was added to a solvent of an electrolytic solution (ethylene carbonate: dimethyl carbonate: diethyl carbonate = 1: 1: 1 (v / v%) at a ratio of LiPF ₆ at a ratio of 1 mol / L. Immerse in the product, heat to 85 ° C., and store for 2 hours.
The test piece immediately after sealing and the test piece after being immersed in the electrolytic solution for 2 hours are peeled off by 180 °, and the adhesive strength (peeling strength) is measured with a tensile tester (Autograph / manufactured by Shimadzu Corporation). To do. The tensile speed of the tensile tester is 100 mm / min, the measurement atmosphere is 23 ° C., and the humidity is 50% RH. The heat-sealed tab lead film is peeled off on the upper bar side.
From the data obtained by the measurement, the adhesive retention rate ((“ adhesive strength after being immersed in the electrolytic solution for 2 hours” ÷ “adhesive strength immediately after sealing”) × 100) was calculated. <Measurement method of median diameter of calcium carbonate>
The median diameter of calcium carbonate to be used was measured using a laser diffraction type particle size distribution measuring device, and the particle size corresponding to 10%, 50% and 90% in the cumulative distribution curve of the particle size based on the volume was calculated. The particle diameter (median diameter (D50)) to be 50% was determined.

The tab lead films of Examples 1 to 4 held an adhesive retention rate of 50% or more. It is considered that this is because calcium carbonate (CaCO ₃ ) contained in the tab lead film reacts with hydrogen fluoride (HF) and the hydrogen fluoride is confined in the tab lead film in the form of calcium fluoride (CaF ₂ ). ..

On the other hand, the tab lead films of Comparative Examples 1 to 3 had good initial adhesive strength, but the adhesive strength after immersion for 2 hours was remarkably low. It is considered that this is because the surface of the nickel foil was corroded by hydrogen fluoride contained in the electrolytic solution.

FIG. 8 shows the relationship between the amount of calcium carbonate added and the adhesive retention rate in the tab lead films of Examples 1 to 4 and Comparative Examples 1 to 3. In the region where the addition amount of calcium carbonate in the entire tab lead film was 0 to 7% by weight, the adhesive strength was 0 even if the addition amount was increased, and the tab lead film was peeled off from the metal terminal. Further, in the region of 7 to 8.9% by weight, the adhesive retention rate increased as the addition amount increased, but the adhesive retention rate was less than 50%. On the other hand, in the region of 9.0 to 11.5% by weight, the adhesive retention rate increased as the addition amount increased, and the adhesive retention rate also exceeded 50%. When the addition amount exceeds 11.5% by weight, the adhesive retention rate does not change much at 80%.

[Example 5]
Except for using calcium carbonate used in Example 4 Another calcium carbonate from _{(CaCO 3 -2) (CaCO 3} -3), to produce a similar tab lead film as in Example 4, the adhesive strength immediately after the seal The adhesive strength after being immersed in the electrolytic solution for 2 hours was measured to calculate the adhesive retention rate. A comparison of the calcium carbonate used in Example 4 (CaCO ₃ -2) as in Example 5 calcium carbonate (CaCO ₃ -3) Table 3 shows the measurement results of Example 5 in Table 4.

The relationship between the amount of calcium carbonate added and the adhesive retention rate in the tab lead film of Example 5 is added to FIG.
In the case of a tab lead film having an adhesion retention rate of about 60%, the tab lead film in Example 1 using calcium carbonate having a small median diameter is better than in Example 5 using calcium carbonate having a large median diameter. The amount of calcium carbonate added to the mixture could be reduced to two-thirds.

1 Tab lead film 11 Surface layer (A)
12 core layer (B)
13 Surface layer (C)
1a Side side 2 Metal terminal 2a Square 2b Side side TL tab lead

Claims (12)

The surface layer (A) containing an acid-modified polyolefin resin as a main component, an inorganic filler that reacts with hydrogen fluoride and a polyolefin resin, and the inorganic filler that reacts with hydrogen fluoride and / or the polyolefin resin In a tab lead film having a core layer (B) as a main component, an acid-modified polyolefin resin and / or a surface layer (C) containing a polyolefin resin as a main component in this order.
The content of the inorganic filler in the surface layer (A) and the content of the inorganic filler in the surface layer (C) are 0 to 10% by weight, respectively.
A film for tab lead, wherein the film for tab lead contains 9.0% by weight or more of an inorganic filler that reacts with hydrogen fluoride. The tab lead film according to claim 1, wherein the tab lead film contains 9.6% by weight or more of an inorganic filler that reacts with hydrogen fluoride. The film for tab lead according to claim 1 or 2, wherein the median diameter of the inorganic filler that reacts with hydrogen fluoride in the film for tab lead is 1.0 μm or less. The tab lead film according to any one of claims 1 to 3, wherein the surface layer (A) has a thickness of 23 μm or more. The tab lead film according to any one of claims 1 to 4, wherein the thickness of the surface layer (A) is 23% or more of the thickness of the entire tab lead film. The tab lead film according to any one of claims 1 to 5, wherein the content of the inorganic filler that reacts with hydrogen fluoride in the core layer (B) is 13 to 60% by weight. When the thickness of the surface layer (A) is t1, the thickness of the core layer (B) is t2, and the thickness of the surface layer (C) is t3, the following formulas (1) and (2) The tab lead film according to any one of claims 1 to 6, wherein the film is characterized by satisfying.
Equation (1) t1 ≧ t3
Equation (2) t1: t2: t3 = 23-80: 15-72: 5-62 The film for tab lead according to any one of claims 1 to 7, wherein the inorganic filler that reacts with hydrogen fluoride in the film for tab lead is a metal carbonate. The film for tab lead according to claim 8, wherein the metal carbonate is calcium carbonate. The film for tab lead according to claim 9, wherein the calcium carbonate is synthetic calcium carbonate. A tab lead in which the tab lead film according to any one of claims 1 to 10 is heat-sealed on at least one surface of the metal terminal, and the surface of the metal terminal and the surface layer of the tab lead film. A tab lead characterized by heat-sealing (A). The eleventh claim is characterized in that, when the thickness of the metal terminal is T (mt) and the thickness of the tab lead film is T (tf), 0.5 T (mt) ≤ T (tf). Tab lead.

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