Resin film for terminals of all-solid-state batteries and all-solid-state batteries

Abstract

To provide a resin film for a terminal of an all-solid-state battery and an all-solid-state battery capable of suppressing generation of air bubbles when heat-sealed to a metal terminal.SOLUTION: A resin film for a terminal of an all-solid-state battery is adhered by heat sealing to a part of the outer peripheral surface of a metal terminal electrically connected to a battery body constituting the all-solid-state battery, and has a water content of 2700 ppm by mass or less. The terminal resin film may be a multilayer film having an insulating layer and a sealant layer provided on at least one side of the insulating layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin film for a terminal of an all-solid-state battery and an all-solid-state battery. [Background technology]

[0002] In recent years, the development of all-solid-state batteries that can achieve large capacities has progressed rapidly. Unlike current lithium-ion batteries, all-solid-state batteries have a solid electrolyte, which allows them to be used at high temperatures that were previously unachievable. This eliminates the need for battery cooling equipment, and is expected to lead to improved space efficiency, reduced costs, and lower power consumption.

[0003] Such an all-solid-state battery comprises an outer bag that houses the battery body, such as the solid electrolyte and electrodes, and a metal terminal called a tab for extracting current from the battery body, and a portion of the outer surface of the metal terminal is covered with a terminal resin film (sometimes called a "tab sealant").

[0004] A known example of such a resin film for terminals is the one described in Patent Document 1 below. This document discloses a resin film for terminals that is made of a resin composition that has adhesion to a current extracting terminal, and that contains a thermoplastic resin with a melting point of 160°C or higher and does not contain a thermoplastic resin with a melting point of less than 160°C. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 004412 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the resin film for terminals of the all-solid-state battery described in Patent Document 1 has the following problems. That is, when the resin film for terminal described in Patent Document 1 is heat-sealed to a metal terminal, air bubbles are sometimes observed to be generated all over the resin film for terminal.

[0007] The present disclosure has been made in view of the above-described problems, and aims to provide a resin film for a terminal of an all-solid-state battery, and an all-solid-state battery, which can suppress the generation of bubbles when heat-sealed to a metal terminal. [Means for solving the problem]

[0008] The present inventors investigated the cause of the phenomenon of bubbles appearing throughout the entire surface of a terminal resin film. As a result, they concluded that the occurrence of bubbles throughout the entire surface of a terminal resin film may be due to the heat-sealing of the terminal resin film to a metal terminal at high temperatures. Specifically, the present inventors hypothesized that when the terminal resin film is heat-sealed to a metal terminal at high temperatures, the moisture in the terminal resin film evaporates, causing the bubbles to expand rapidly, easily combine with other bubbles, grow, and remain after cooling. Furthermore, the present inventors believed that the phenomenon may be significantly dependent on the moisture content of the terminal resin film. Therefore, the present inventors conducted further intensive research and discovered that the following disclosure can solve the above problem.

[0009] That is, the present disclosure provides a resin film for a terminal of an all-solid-state battery that is bonded by heat sealing to the outer peripheral surface of a part of a metal terminal that is electrically connected to a battery body that constitutes the all-solid-state battery, the resin film having a water content of 2700 ppm by mass or less.

[0010] The above-described terminal resin film can suppress the generation of air bubbles in the terminal resin film when the terminal resin film is heat-sealed to a portion of the outer peripheral surface of a metal terminal. This prevents the terminal resin film from having rough areas (areas with many air bubbles) and dense areas (areas with few air bubbles), which would otherwise reduce the seal strength to the metal terminal at the rough areas. Therefore, even if the battery body containing a solid electrolyte expands during use of an all-solid-state battery in a high-temperature environment, exerting a force that attempts to open the outer packaging bag, the terminal resin film can maintain the sealed state of the outer packaging bag. Therefore, even if a sulfide-based solid electrolyte is contained in the outer packaging bag of an all-solid-state battery, and gases such as hydrogen sulfide are generated by a reaction between moisture and the sulfide-based solid electrolyte within the outer packaging bag, leakage of such gases can be suppressed. Furthermore, the suppression of the generation of air bubbles in the terminal resin film, which can easily serve as a moisture passageway, suppresses the penetration of moisture into the terminal resin film from outside the packaging material. Therefore, when an all-solid-state battery contains a sulfide-based solid electrolyte as a solid electrolyte in an outer bag, it is possible to suppress the generation of hydrogen sulfide due to a reaction between water and the sulfide-based solid electrolyte.

[0011] The resin film for a terminal is preferably a multilayer film having an insulating layer and a sealant layer provided on at least one side of the insulating layer.

[0012] In this case, it is possible to separate the functions of the resin film for terminals. That is, the insulating layer ensures the thickness of the resin film for terminals, ensuring insulation during heat sealing. Meanwhile, the sealant layer can fill the gap between the resin film for terminals and the metal terminal. Furthermore, even if the sealant layer is fluidized during heat sealing of the resin film for terminals to the metal terminal, causing variations in the insulating properties of the sealant layer, the insulating layer ensures the thickness of the resin film for terminals, ensuring stable insulation.

[0013] In the resin film for a terminal, the sealant layer of the multilayer film is preferably an acid-modified polyolefin resin layer.

[0014] In this case, since the acid-modified polyolefin resin layer has excellent adhesion to metal, the adhesion between the sealant layer of the resin film for terminal and the metal terminal can be further improved.

[0015] The resin film for a terminal is preferably a polyolefin film containing a polyolefin resin or a polyester film containing a polyester resin.

[0016] In this case, the all-solid-state battery has better sealing properties for the metal terminals and the outer bag. In addition, since polyolefin films and polyester films have heat resistance, the terminal resin film can further improve the heat resistance of the all-solid-state battery.

[0017] The resin film for a terminal preferably has a melting point of 250° C. or less.

[0018] In this case, since the resin film for terminal has a melting point of 250°C or less, the heat sealing temperature can be reduced. Therefore, when the resin film for terminal is heat-sealed to a metal terminal, the generation of air bubbles in the resin film for terminal can be further suppressed. Therefore, the decrease in the seal strength and barrier properties of the resin film for terminal can be further suppressed. Therefore, the resin film for terminal can more sufficiently maintain the hermeticity of the outer bag of the all-solid-state battery. Furthermore, the resin film for terminal can also suppress the penetration of moisture through the resin film for terminal.

[0019] The resin film for a terminal preferably has a melting point of 150° C. or higher.

[0020] In this case, since the resin film for terminals has a melting point of 150° C. or higher, it is possible to prevent a decrease in the seal strength of the resin film for terminals with respect to the metal terminals even when the resin film for terminals is used in a high-temperature environment. Therefore, when an all-solid-state battery contains a sulfide-based solid electrolyte as a solid electrolyte in an outer bag, even if gases such as hydrogen sulfide are generated by a reaction between moisture and the sulfide-based solid electrolyte in the outer bag of the all-solid-state battery, leakage of such gases can be further prevented.

[0021] The present disclosure also provides an all-solid-state battery comprising: a battery body containing a solid electrolyte; a metal terminal electrically connected to the battery body; an outer bag that sandwiches the metal terminal and houses the battery body; and a terminal resin film that is bonded by heat sealing to a part of the outer peripheral surface of the metal terminal, wherein the terminal resin film is made of the above-described terminal resin film.

[0022] According to this all-solid-state battery, the terminal resin film is bonded to a portion of the outer peripheral surface of the metal terminal by heat sealing. Here, the above-described terminal resin film can suppress the generation of air bubbles in the terminal resin film when the terminal resin film is heat-sealed to the metal terminal. Therefore, the all-solid-state battery of the present disclosure suppresses the generation of rough and dense portions in the terminal resin film, which would otherwise cause the rough portions to reduce the seal strength to the metal terminal. Therefore, even if the battery body expands during use of the all-solid-state battery in a high-temperature environment, exerting a force that attempts to open the outer packaging bag, the all-solid-state battery can maintain a sealed state of the outer packaging bag thanks to the terminal resin film. Furthermore, the generation of air bubbles, which can easily become a passage for moisture, is suppressed in the terminal resin film, thereby suppressing the intrusion of moisture from outside the all-solid-state battery.

[0023] In the present disclosure, "melting point" means the "peak melting temperature" determined in accordance with the method described in JIS K7121-1987, and when two or more independent melting peaks appear, the lowest peak melting temperature is used.

[0024] In addition, in the present disclosure, when the resin film for a terminal is a multilayer film, the melting point refers to the melting point of the layer that has the lowest melting point among the layers that make up the multilayer film. [Effects of the Invention]

[0025] According to the present disclosure, there are provided a resin film for a terminal of an all-solid-state battery, which can suppress the generation of air bubbles when heat-sealed to a metal terminal, and an all-solid-state battery. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a resin film for a terminal of an all-solid-state battery according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a perspective view showing an all-solid-state battery according to an embodiment of the present disclosure. [Figure 3] 3 is a partial cross-sectional view of the resin film for terminal and the metal terminal shown in FIG. 2 taken along line AA. FIG. [Figure 4] FIG. 2 is a cross-sectional view schematically showing an example of the exterior packaging material shown in FIG. [Figure 5] FIG. 3 is a cross-sectional view schematically showing a resin film for a terminal according to another embodiment of the present disclosure. [Figure 6] FIG. 2 is a plan view showing a structure for obtaining evaluation samples in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0028] [Resin film for terminals of solid-state batteries] FIG. 1 is a cross-sectional view schematically illustrating a resin film for a terminal of an all-solid-state battery according to an embodiment of the present disclosure. As shown in FIG. 1, a resin film for a terminal of an all-solid-state battery according to this embodiment (hereinafter also simply referred to as a "resin film for terminal") 10 includes a first sealant layer 1, an insulating layer 2, and a second sealant layer 3, in this order. That is, the resin film for terminal 10 is a multilayer film. The water content of the resin film for terminal 10 is 2700 mass ppm or less. The resin film for terminal 10 may have an adhesive layer that bonds the first sealant layer 1 and the insulating layer 2 together. The resin film for terminal 10 may also have an adhesive layer that bonds the second sealant layer 3 and the insulating layer 2 together.

[0029] The resin film for terminal 10 can more effectively prevent the generation of air bubbles in the resin film for terminal 10 when heat-sealing the resin film for terminal 10 to a metal terminal, compared to when the moisture content of the resin film for terminal 10 exceeds 2700 ppm by mass. Furthermore, since the resin film for terminal 10 is a multilayer film including an insulating layer 2 and a first sealant layer 1 and a second sealant layer 3 provided on both sides of the insulating layer 2, the resin film for terminal 10 can be functionally separated. That is, the insulating layer 2 ensures the thickness of the resin film for terminal 10, thereby ensuring insulation during heat sealing. Meanwhile, the first sealant layer 1 can fill the gap between the resin film for terminal 10 and the metal terminal. Meanwhile, the second sealant layer 3 can be heat-sealed (thermally fused) to an outer packaging bag of an all-solid-state battery. Furthermore, even if the first sealant layer 1 is fluidized when the terminal resin film 10 is heat-sealed to the metal terminal, causing variations in the insulating properties of the first sealant layer 1, the thickness of the terminal resin film 10 is guaranteed by the insulating layer 2, thereby ensuring stable insulation.

[0030] The moisture content of the resin film for a terminal 10 may be 2700 ppm by mass or less, preferably 2000 ppm by mass or less, and more preferably 1500 ppm by mass or less. The moisture content of the resin film for a terminal 10 may be 0 ppm by mass.

[0031] It is sufficient that the overall moisture content of the resin film for terminal 10 is 2700 ppm by mass or less. Therefore, the moisture content may be 2700 ppm by mass or less in each of the first sealant layer 1, the insulating layer 2, and the second sealant layer 3, but it is also sufficient that the moisture content of some layers is 2700 ppm by mass or less and the moisture content of the remaining layers is greater than 2700 ppm by mass, as long as the overall moisture content is 2700 ppm by mass or less.

[0032] Each layer constituting the resin film for terminal 10 will be described in detail below.

[0033] <First sealant layer> In this embodiment, the first sealant layer 1 is a layer that is bonded to a part of the outer peripheral surface of the metal terminal 14 by heat sealing (thermal fusion).

[0034] For example, a film containing a thermoplastic resin such as a polyolefin resin, a polyamide resin, a polyester resin, a polycarbonate resin, a polyphenylene ether resin, a polyacetal resin, a polystyrene resin, a polyvinyl chloride resin, or a polyvinyl acetate resin can be used as the first sealant layer 1. By blending the various resins listed above to form a polymer alloy, it is possible to control the sealing suitability and heat resistance.

[0035] Among these, it is preferable to use a film containing a polyolefin-based resin (hereinafter also referred to as a "polyolefin film") or a film containing a polyester-based resin (hereinafter also referred to as a "polyester film"). In this case, the sealing performance for the metal terminal and the outer bag is improved. Furthermore, since polyolefin films and polyester films have heat resistance, the terminal resin film 10 can further improve the heat resistance of the all-solid-state battery.

[0036] Examples of polyolefin resins include low-, medium-, or high-density polyethylene, ethylene-α-olefin copolymer, polypropylene, block or random copolymers containing propylene as a copolymerization component, and propylene-α-olefin copolymer. The polyolefin resin may be an acid-modified polyolefin resin obtained by modifying a polyolefin resin with acid or glycidyl. In particular, the first sealant layer 1 is preferably an acid-modified polyolefin resin layer containing an acid-modified polyolefin resin. In this case, the acid-modified polyolefin resin layer has excellent adhesion to metal, which can further improve the adhesion between the resin film for terminal 10 and the metal terminal.

[0037] Examples of polyester resins include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, and copolymers thereof. These polyester resins may be used alone or in combination of two or more. Also, copolymers of any acid and glycol may be used.

[0038] The first sealant layer 1 may further contain additives such as antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, crystal nucleating agents, and plasticizers as needed to impart sealing properties, heat resistance, and other functionalities.

[0039] The melting point of the first sealant layer 1 is not particularly limited, but is preferably 150°C or higher, more preferably 155°C or higher, and even more preferably 160°C or higher. When the melting point of the first sealant layer 1 is 150°C or higher, it is possible to suppress a decrease in the seal strength of the terminal resin film 10 with respect to the metal terminal, even when the terminal resin film 10 is used in a high-temperature environment. Therefore, when an all-solid-state battery contains a sulfide-based solid electrolyte as the solid electrolyte in an outer bag, even if gases such as hydrogen sulfide are generated by a reaction between moisture and the sulfide-based solid electrolyte in the outer bag of the all-solid-state battery, leakage of such gases can be further suppressed.

[0040] The melting point of the first sealant layer 1 is preferably 250°C or lower, more preferably 240°C or lower, and even more preferably 230°C or lower. In this case, the melting point of the first sealant layer 1 being 250°C or lower allows the heat sealing temperature to be lowered. Therefore, when the resin film for terminal 10 is heat-sealed to the metal terminal, the generation of air bubbles in the first sealant layer 1 can be more effectively suppressed. Therefore, the decrease in the seal strength and barrier properties of the resin film for terminal 10 to the metal terminal is more effectively suppressed. Therefore, the resin film for terminal 10 can more adequately maintain the hermeticity of the outer bag for the all-solid-state battery. Furthermore, the resin film for terminal 10 can also suppress the penetration of moisture through the resin film for terminal 10.

[0041] The thickness of the first sealant layer 1 is not particularly limited, but is preferably 10 to 200 μm, and more preferably 20 to 150 μm. When the thickness of the first sealant layer 1 is 10 μm or more, the gap between the metal terminal and the resin film for terminal 10 is easily filled with the resin that constitutes the first sealant layer 1. Furthermore, when the thickness of the first sealant layer 1 is 200 μm or less, the amount of heat required to melt the first sealant layer 1 can be reduced, so that the resin film for terminal 10 can be sealed to the metal terminal at a low temperature in a short time, thereby shortening the takt time and further improving productivity.

[0042] The thickness of the first sealant layer 1 may be greater than or equal to the thickness of the second sealant layer 3, but is preferably greater than the thickness of the second sealant layer 3. For a given thickness of the resin film for terminal 10, a thickness of the first sealant layer 1 greater than that of the second sealant layer 3 allows a greater amount of resin to fill the gap between the first sealant layer 1 and the metal terminal when the resin film for terminal 10 is heat-sealed to the metal terminal at high temperature than the second sealant layer 3, making it easier to fill the gap. Furthermore, it is preferable that the first sealant layer 1 and the second sealant layer 3 have the same thickness and contain the same resin. In this case, the first sealant layer 1 can be used as the second sealant layer 3, and the second sealant layer 3 can be used as the first sealant layer 1. This eliminates the need to distinguish between the first sealant layer 1 and the second sealant layer 2 when fusing the resin film for terminal 10 to a metal terminal, allowing for efficient fusing. Here, it is preferable that the resin contained in the first sealant layer 1 and the second sealant layer 3 is an acid-modified polyolefin resin. In this case, even when the second sealant layer 3 is heat-sealed to the metal terminal, adhesion between the metal terminal and the resin film for terminal is improved.

[0043] <Insulating layer 2> The insulating layer 2 is a layer for preventing the resin film for terminal from becoming thin (sealing thinning) during heat sealing, and for ensuring insulation between the metal terminal and the metal layer of the exterior material.

[0044] For example, a film containing a thermoplastic resin such as a polyolefin resin, a polyamide resin, a polyester resin, a polycarbonate resin, a polyphenylene ether resin, a polyacetal resin, a polystyrene resin, a polyvinyl chloride resin, or a polyvinyl acetate resin can be used as the insulating layer 2. By blending the various resins listed above to form a polymer alloy, it is possible to control sealing suitability and heat resistance.

[0045] Among these, it is preferable to use a polyolefin film or a polyester film. In this case, since the polyolefin film or the polyester film has heat resistance, the resin film for terminal 10 can further improve the heat resistance of the all-solid-state battery.

[0046] Furthermore, the insulating layer 2 may further contain additives such as antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, nucleating agents, colorants, and plasticizers as needed to impart sealing properties, heat resistance, and other functionalities.

[0047] The melting point of the insulating layer 2 is not particularly limited, but is preferably 150°C or higher, more preferably 155°C or higher, and even more preferably 160°C or higher. When the melting point of the insulating layer 2 is 150°C or higher, it is possible to suppress a decrease in the seal strength of the resin film 10 for a terminal with respect to a metal terminal, even when the resin film 10 for a terminal is used in a high-temperature environment. Therefore, when an all-solid-state battery contains a sulfide-based solid electrolyte as a solid electrolyte in an outer bag, even if gases such as hydrogen sulfide are generated by a reaction between moisture and the sulfide-based solid electrolyte in the outer bag of the all-solid-state battery, it is possible to further suppress leakage of such gases.

[0048] The melting point of the insulating layer 2 is preferably 250°C or lower, more preferably 240°C or lower, and even more preferably 230°C or lower.

[0049] The melting point of the insulating layer 2 may be higher than the melting point of the resin contained in the first sealant layer 1 and the second sealant layer 3, or may be lower than the melting point of the resin contained in the first sealant layer 1 and the second sealant layer 3, but is preferably higher than the melting point of the resin contained in the first sealant layer 1 and the second sealant layer. In this case, when the resin film for terminal 10 is heat-sealed to an exterior material including a barrier layer made of a metal layer, seal thinning (thinning) of the insulating layer 2 can be suppressed, making it easier to ensure insulation between the barrier layer of the exterior material and the metal terminal.

[0050] The thickness of the insulating layer 2 is not particularly limited, but is preferably 10 to 200 μm, and more preferably 20 to 150 μm. When the thickness of the insulating layer 2 is 10 μm or more, sufficient insulation properties can be obtained. When the thickness of the insulating layer 2 is 100 μm or less, the amount of water vapor penetrating from the peripheral edge of the resin film for terminal 10 can be reduced.

[0051] <Second sealant layer> In this embodiment, the second sealant layer 3 is a layer that is heat-sealed (thermally fused) to the exterior bag of the all-solid-state battery.

[0052] For example, a film containing a thermoplastic resin such as a polyolefin resin, a polyamide resin, a polyester resin, a polycarbonate resin, a polyphenylene ether resin, a polyacetal resin, a polystyrene resin, a polyvinyl chloride resin, or a polyvinyl acetate resin can be used as the second sealant layer 3. By blending the various resins listed above to form a polymer alloy, it is possible to control the sealing suitability and heat resistance.

[0053] Among these, it is preferable to use a polyolefin film or a polyester film. In this case, the sealing property for the metal terminal and the outer bag is improved. Furthermore, since the polyolefin film and the polyester film have heat resistance, the terminal resin film 10 can further improve the heat resistance of the all-solid-state battery.

[0054] Examples of polyolefin resins include low-, medium-, or high-density polyethylene, ethylene-α-olefin copolymer, polypropylene, block or random copolymers containing propylene as a copolymerization component, and propylene-α-olefin copolymer. The polyolefin resin may be an acid-modified polyolefin resin obtained by modifying a polyolefin resin with acid or glycidyl.

[0055] Examples of polyester resins include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, and copolymers thereof. These polyester resins may be used alone or in combination of two or more. Also, copolymers of any acid and glycol may be used.

[0056] When the first sealant layer 1 and the insulating layer 2 are made of polyolefin films, it is preferable that the second sealant layer 3 is also made of a polyolefin film. In this case, a laminate film consisting of the first sealant layer 1, the insulating layer 2, and the second sealant layer 3 can be produced by co-extrusion, which can further increase the adhesive strength between the layers. Furthermore, when the first sealant layer 1 and the insulating layer 2 are made of polyester films, it is preferable that the second sealant layer 3 is also made of a polyester film. In this case, good adhesiveness can be obtained when the first sealant layer 1, the insulating layer 2, and the second sealant layer 3 are bonded together with a heat-resistant polyester adhesive.

[0057] Furthermore, the second sealant layer 3 may further contain additives such as antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, crystal nucleating agents, and plasticizers as needed to impart sealing properties, heat resistance, and other functionalities.

[0058] The melting point of the second sealant layer 3 is not particularly limited, but is preferably 150°C or higher, more preferably 155°C or higher, and even more preferably 160°C or higher. When the melting point of the second sealant layer 3 is 150°C or higher, it is possible to suppress a decrease in the seal strength of the terminal resin film 10 with respect to the metal terminal, even when the terminal resin film 10 is used in a high-temperature environment. Therefore, when an all-solid-state battery contains a sulfide-based solid electrolyte as the solid electrolyte in an outer bag, even if gases such as hydrogen sulfide are generated by a reaction between moisture and the sulfide-based solid electrolyte in the outer bag of the all-solid-state battery, leakage of such gases can be further suppressed.

[0059] The melting point of the second sealant layer 3 is preferably 250°C or lower, more preferably 240°C or lower, and even more preferably 230°C or lower. In this case, the melting point of the second sealant layer 3 being 250°C or lower allows the heat sealing temperature to be lowered. Therefore, when the resin film for terminal 10 is heat-sealed to an outer bag, the generation of air bubbles in the second sealant layer 1 can be more effectively suppressed. Therefore, the decrease in the seal strength and barrier properties of the resin film for terminal 10 to the metal terminal is more effectively suppressed. Therefore, the resin film for terminal 10 can more adequately maintain the hermeticity of the outer bag for the all-solid-state battery. Furthermore, the resin film for terminal 10 can also suppress the intrusion of moisture through the resin film for terminal 10.

[0060] The melting point of the second sealant layer 3 may be the same as or different from the melting point of the first sealant layer 1, but is preferably the same as the melting point of the first sealant layer 1.

[0061] The thickness of the second sealant layer 3 is not particularly limited, but is preferably 10 to 200 μm, and more preferably 20 to 150 μm. When the thickness of the second sealant layer 3 is 10 μm or more, sufficient sealing strength can be obtained. When the thickness of the second sealant layer 3 is 200 μm or less, the amount of heat required to melt the second sealant layer 3 can be reduced, so that the terminal resin film 10 can be sealed to the outer packaging bag of the all-solid-state battery at a low temperature and in a short time, thereby shortening the takt time and further improving productivity.

[0062] <Hydrogen sulfide decomposition and adsorption material> When the terminal resin film 10 is used in an all-solid-state battery having a sulfide-based solid electrolyte, at least one of the layers constituting the terminal resin film 10 of this embodiment may contain a hydrogen sulfide decomposition / adsorption material that decomposes or adsorbs hydrogen sulfide. In this case, even if hydrogen sulfide is generated in the all-solid-state battery by reaction between water and the sulfide-based solid electrolyte, the hydrogen sulfide is prevented from permeating through the terminal resin film 10. The hydrogen sulfide decomposition / adsorption material is contained in, for example, the first sealant layer 1, the insulating layer 2, the second sealant layer 3, or the adhesive layer.

[0063] Examples of hydrogen sulfide decomposition and adsorption materials include zinc oxide, amorphous metal silicates (mainly those containing copper or zinc), zirconium and tantanide hydrates, tetravalent metal phosphates (especially those containing copper), mixtures of zeolite and zinc ions, mixtures of zeolite, zinc oxide, and copper(II) oxide, potassium permanganate, sodium permanganate, silver sulfate, silver acetate, aluminum oxide, iron hydroxide, isocyanate compounds, aluminum silicate, potassium aluminum sulfate, zeolite, activated carbon, amine compounds, and ionomers. Furthermore, hydrogen sulfide decomposition and adsorption materials preferably contain zinc oxide (ZnO) and / or zinc ions, which facilitates detoxifying hydrogen sulfide and is advantageous in terms of cost and ease of handling. These hydrogen sulfide decomposition and adsorption materials can be used singly or in combination.

[0064] The hydrogen sulfide decomposition / adsorption material may be a deodorizer that has a deodorizing effect on hydrogen sulfide, such as "Daimshoo PE-M 3000-Z" (a polyethylene masterbatch product) manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., "Kesmon" manufactured by Toagosei Co., Ltd., "Shoe Cleanse" manufactured by Rasa Kogyo Co., Ltd., and "Dashlight ZU" and "Dashlight CZU" manufactured by Sinanen Zeomic Corporation.

[0065] A metal soap such as zinc stearate may be added to the layer containing the hydrogen sulfide decomposition / adsorption material to improve the dispersibility of the hydrogen sulfide decomposition / adsorption material. By using the hydrogen sulfide decomposition / adsorption material in combination with a metal soap, the dispersibility of the hydrogen sulfide decomposition / adsorption material in the layer can be improved, making it less likely that the effect of detoxifying hydrogen sulfide will be uneven, and making it easier to prevent a decrease in the functionality (e.g., adhesion strength, seal strength, etc.) of the layer containing the hydrogen sulfide decomposition / adsorption material.

[0066] The hydrogen sulfide decomposition and adsorption material may be used in the form of a masterbatch in advance. When the hydrogen sulfide decomposition-adsorbing material is blended into at least one of the first sealant layer 1, the insulating layer 2, the second sealant layer 3, and the adhesive layer, a high-concentration blend may be prepared in advance as a masterbatch, and then the masterbatch may be blended into the resin of at least one of the first sealant layer 1, the insulating layer 2, the second sealant layer 3, and the adhesive layer to achieve an appropriate concentration. The hydrogen sulfide decomposition-adsorbing material is preferably blended into the insulating layer 2. In this case, since the hydrogen sulfide decomposition-adsorbing material is not blended into the first sealant layer 1 or the second sealant layer 3, a decrease in the strength between the first sealant layer 1 of the resin film for terminal and the metal terminal can be further suppressed, and a decrease in the strength between the second sealant layer 3 of the resin film for terminal and the exterior material can be further suppressed. The hydrogen sulfide decomposition-adsorbing material may also be blended into the second sealant layer 3. Even in this case, since the hydrogen sulfide decomposition-adsorbing material is not blended into the first sealant layer 1, a decrease in the strength between the first sealant layer 1 of the resin film for terminal and the metal terminal can be further suppressed. When the hydrogen sulfide decomposition / adsorbing material is incorporated into the adhesive layer, it may be incorporated directly into the coating liquid if the adhesive layer is to be coated, or when the adhesive layer is formed by extrusion or the like, it may be incorporated by preparing a masterbatch in the same manner as the first sealant layer 1. When preparing a masterbatch, the resin that can be used may be a thermoplastic resin such as a polyolefin resin, a polyamide resin, a polyester resin, a polycarbonate resin, a polyphenylene ether resin, a polyacetal resin, a polystyrene resin, a polyvinyl chloride resin, or a polyvinyl acetate resin.

[0067] The content of the hydrogen sulfide decomposition adsorption material in the layer containing the hydrogen sulfide decomposition adsorption material may be 0.01% by mass to 30% by mass, 0.05% by mass to 20% by mass, or 0.1% by mass to 15% by mass, based on the total mass of the layer. When the content of the hydrogen sulfide decomposition adsorption material is equal to or greater than the lower limit, the effect of detoxifying hydrogen sulfide is easily achieved, and when the content is equal to or less than the upper limit, deterioration of the functionality (e.g., adhesion strength, seal strength, etc.) of the layer containing the hydrogen sulfide decomposition adsorption material can be suppressed.

[0068] [Method of manufacturing resin film for terminals] Next, a description will be given of a method for manufacturing the resin film for terminal 10. However, the method for manufacturing the resin film for terminal 10 is not limited to the following manufacturing method.

[0069] The resin film for a terminal 10 can be obtained by, for example, co-extruding the first sealant layer 1, the insulating layer 2 and the second sealant layer 3.

[0070] The resin film for terminal 10 can also be obtained by preparing the first sealant layer 1, the insulating layer 2, and the second sealant layer 3 in advance, and then layering and thermally laminating these. The temperature during the thermal lamination may be any temperature that is higher than the melting points of the first sealant layer 1 and the second sealant layer 3 .

[0071] When the resin film 10 for terminals has a first sealant layer 1, an adhesive layer, an insulating layer 2, and a second sealant layer 3, a two-layer film consisting of the insulating layer 2 and the second sealant layer 3 may be formed in advance, and then the two-layer film and the first sealant layer 1 may be laminated using an adhesive by a dry lamination method using an adhesive.

[0072] [Method for fusing resin film for terminals] The fusion process for melt-bonding the resin film for terminal 10 shown in FIG. 1 to the outer packaging bag will be described.

[0073] First, a fusion process is performed to melt and bond the resin film for terminal 10 to the metal terminal 14. At this time, the first sealant layer 1 of the resin film for terminal 10 shown in Fig. 1 is faced toward the metal terminal 14, and the resin film for terminal 10 and the metal terminal 14 are thermally fused together while simultaneously melting the first sealant layer 1 by heating and bonding the first sealant layer 1 to the metal terminal 14 by applying pressure (see Fig. 3).

[0074] In the fusion treatment, heating is preferably performed to a temperature of the melting point of the first sealant layer 1 +20° C. or higher, from the viewpoint of obtaining sufficient adhesion and sealing properties between the resin film for terminal 10 and the metal terminal 14.

[0075] The heating temperature of the resin film for terminal 10 may be, for example, 155 to 285° C. The heat-sealing time can be determined in consideration of the adhesion to the metal terminal 14 and productivity. The heat-sealing time can be appropriately set within the range of, for example, 1 to 60 seconds.

[0076] Next, a fusion process is performed to melt and bond the resin film 10 for terminals and the exterior material 13 (see FIG. 2). Specifically, the resin film 10 for terminals and the exterior material are thermally fused together while simultaneously melting the second sealant layer 3 by heating and bonding the second sealant layer 3 to the exterior material by applying pressure.

[0077] In the fusion treatment, the second sealant layer 3 of the resin film for terminals 10 and the sealant layer of the packaging material 13 are heated and melted. At this time, the heating temperature may be any temperature at which both the second sealant layer 3 of the resin film for terminals 10 and the sealant layer of the packaging material 13 melt; however, from the viewpoint of obtaining sufficient adhesion and sealing properties of the second sealant layer 3 of the resin film for terminals 10 and the sealant layer of the packaging material 13, the heating temperature is preferably set to a temperature that is 20°C or higher above the melting point of the sealant layer with a higher melting point between the second sealant layer 3 of the resin film for terminals 10 and the sealant layer of the packaging material 13.

[0078] The heating temperature of the resin film for terminal 10 may be, for example, 155 to 285° C. The heat-sealing time can be determined in consideration of the adhesion to the packaging material 13 and productivity. The heat-sealing time can be set appropriately within the range of, for example, 1 to 60 seconds.

[0079] [All-solid battery] FIG. 2 is a perspective view showing one embodiment of an all-solid-state battery produced using the above-described resin film for terminal. As shown in FIG. 2, an all-solid-state battery 50 includes a battery body 11 having a sulfide-based electrolyte as a solid electrolyte, two metal terminals (current extraction terminals) 14 for extracting current from the battery body 11 to the outside, a resin film for terminal 10, and an outer bag 54 for airtightly housing the battery body 11. The outer bag 54 is used as a container for housing the battery body 11. The resin film for terminal 10 is bonded to a portion of the outer peripheral surface of the metal terminal 14, and the metal terminal 14 is sandwiched between the outer bag 54 via the resin film for terminal 10. In the resin film for terminal 10, the first sealant layer 3 is bonded to the metal terminal 14, and the second sealant layer 3 is bonded to the outer bag 54.

[0080] In the all-solid-state battery 50, the terminal resin film 10 is bonded to the metal terminal 14 by heat sealing. Here, the terminal resin film 10 can suppress the generation of air bubbles in the terminal resin film 10 when the terminal resin film 10 is heat-sealed to the metal terminal 14. Therefore, the all-solid-state battery 50 suppresses the occurrence of rough and dense portions in the terminal resin film 10, which would cause a decrease in the seal strength to the metal terminal at the rough portions. Therefore, even if the battery body 11 expands during use of the all-solid-state battery 50 in a high-temperature environment and a force acts to open the outer bag 54, the all-solid-state battery 50 can maintain the sealed state of the outer bag 54 by the terminal resin film 10. As a result, even if hydrogen sulfide is generated within the outer bag 54, leakage of the hydrogen sulfide from the outer bag 54 is suppressed. Furthermore, the first sealant layer 1 suppresses the generation of air bubbles, which can easily serve as a passage for moisture, thereby suppressing the intrusion of moisture from the outside into the terminal resin film 10. As a result, it is possible to suppress the generation of hydrogen sulfide due to a reaction between water and the sulfide-based electrolyte.

[0081] The battery body 11, the metal terminals 14, and the outer bag 54 will be described in detail below.

[0082] <Battery body> The battery body 11 has at least one power generating element made up of a positive electrode, a solid electrolyte, and a negative electrode. The solid electrolyte is not limited to a sulfide-based solid electrolyte, and may be an oxide-based solid electrolyte or the like. <Metal terminal> 2 and 3, the pair of metal terminals 14 includes a metal terminal body 14-1 and a corrosion prevention layer 14-2. Of the pair of metal terminal bodies 14-1, one metal terminal body 14-1 is electrically connected to the positive electrode of the battery body 11, and the other metal terminal body 14-1 is electrically connected to the negative electrode of the battery body 11. The pair of metal terminal bodies 14-1 extend in a direction away from the battery body 11, and a portion thereof is exposed from the exterior material 13. The shape of the pair of metal terminal bodies 14-1 may be, for example, a flat plate shape.

[0083] The material of the metal terminal body 14-1 can be a metal, which can be determined in consideration of the structure of the battery body 11 and the materials of each component of the battery body 11.

[0084] When the all-solid-state battery 50 is a lithium-ion secondary battery, aluminum can be used as the positive electrode current collector, and copper can be used as the negative electrode current collector. When the all-solid-state battery 50 is a lithium-ion secondary battery, the material of the metal terminal body 14-1 connected to the positive electrode of the battery body 11 is preferably aluminum. The material of the metal terminal body 14-1 connected to the positive electrode of the battery body 11 may also be an aluminum material with a purity of 97% or more, such as 1N30. Furthermore, when the metal terminal body 14-1 is to be bent, an O material that has been tempered by sufficient annealing to add flexibility may be used. The material of the metal terminal body 14-1 connected to the negative electrode of the battery body 11 may be, for example, copper with a nickel plating layer formed on its surface, or nickel.

[0085] The thickness of the metal terminal body 14-1 can be determined depending on the size and capacity of the all-solid-state battery 50. When the all-solid-state battery 50 is small, the thickness of the metal terminal body 14-1 may be 50 μm or more. In the case of a large all-solid-state battery for power storage, in-vehicle use, etc., the thickness of the metal terminal body 14-1 can be appropriately set within the range of 100 to 1000 μm.

[0086] The corrosion prevention layer 14-2 is disposed so as to cover the surface of the metal terminal body 14-1. In the all-solid-state battery 50, the corrosion prevention layer 14-2 is a layer for suppressing corrosion of the metal terminal body 14-1 due to corrosive components such as hydrogen sulfide.

[0087] <Outer bag> As shown in Fig. 2, the outer bag 54 is obtained by overlapping two sheets of exterior material 13 and heat-sealing the overlapping peripheral portions. The outer bag 54 can also be obtained by folding the exterior material 13 in half and heat-sealing the overlapping peripheral portions. The exterior material 13 includes, from the battery body 11 side, a sealant layer 21, a first adhesive layer 22, a corrosion prevention treatment layer 23-1, a barrier layer 24, a corrosion prevention treatment layer 23-2, a second adhesive layer 25, and a base material layer 26, in this order (see Fig. 4).

[0088] The sealant layer 21 is a layer that provides heat-sealing properties to the exterior material 13, and is disposed on the inside and heat-sealed (thermal fusion) when assembling the all-solid-state battery 50. Examples of the base material for the sealant layer 21 include polyolefin resins and acid-modified polyolefin resins obtained by graft-modifying polyolefin resins with maleic anhydride or the like. Examples of the polyolefin resins that can be used include low-density, medium-density, and high-density polyethylenes; ethylene-α-olefin copolymers; homo-, block-, or random polypropylenes; and propylene-α-olefin copolymers. Among these, it is preferable that the polyolefin resin contains polypropylene. These polyolefin resins can be used alone or in combination of two or more.

[0089] The sealant layer 21 may be a single-layer film or a multilayer film having multiple layers laminated together depending on the required function. Specifically, it may be a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer or polymethylpentene is interposed to provide moisture resistance. The sealant layer 21 may contain various additives (such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier).

[0090] The thickness of the sealant layer 21 is preferably 10 to 150 μm, and more preferably 30 to 80 μm. When the thickness of the sealant layer 21 is 10 μm or more, the exterior packaging material 13 can have sufficient adhesion to the exterior packaging material 13 or the resin film for terminal 10. Furthermore, when the thickness of the sealant layer 21 is 150 μm or less, the cost of the exterior packaging material 13 can be reduced.

[0091] The first adhesive layer 22 can be appropriately selected from known adhesives such as dry lamination adhesives and acid-modified heat-fusible resins.

[0092] As shown in Figure 4, it is preferable from a performance standpoint to form the corrosion prevention treatment layers 23-1 and 23-2 on both sides of the barrier layer 24, but from the perspective of reducing costs, the corrosion prevention treatment layer 23-1 may be placed only on the side of the barrier layer 24 that is located on the first adhesive layer 22 side.

[0093] The barrier layer 24 may be a conductive metal layer. Examples of materials for the barrier layer 24 include aluminum and stainless steel, with aluminum being preferred from the standpoints of cost, mass (density), and the like.

[0094] The second adhesive layer 25 may be a polyurethane adhesive containing polyester polyol, polyether polyol, acrylic polyol, or the like as a main component.

[0095] The base layer 26 may be a single-layer film or a multi-layer film made of nylon, polyethylene terephthalate (PET), etc. Similar to the sealant layer 21, the base layer 26 may contain various additives (such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier).

[0096] Moreover, the packaging material 13 may further include a protective layer (not shown) for protecting the base material layer 26 on the surface of the base material layer 26 opposite to the sealant layer 21 side.

[0097] Moreover, in the exterior material 13, instead of the first adhesive layer 22, an adhesive resin layer may be used.

[0098] At least one of the layers constituting the exterior material 13 of this embodiment may contain a hydrogen sulfide decomposition-adsorbing material, similar to the terminal resin film 10. In this case, even if hydrogen sulfide is generated by reaction between water and a sulfide-based solid electrolyte in the all-solid-state battery 50, the hydrogen sulfide is prevented from permeating through the exterior material 13. The hydrogen sulfide decomposition-adsorbing material is contained in, for example, the first adhesive layer 22, the second adhesive layer 25, the sealant layer 21, or at least one of these. In particular, the hydrogen sulfide decomposition-adsorbing material is preferably contained in the sealant layer 21. In this case, the hydrogen sulfide is effectively prevented from permeating through the exterior material 13.

[0099] Although the preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments. For example, the resin film 10 for a terminal includes a first sealant layer 1, an insulating layer 2, and a second sealant layer 3, but if the outer packaging bag 54 does not have a metal layer, the resin film 10 for a terminal may not have the insulating layer 2. The resin film for a terminal may also be configured as a single-layer film, such as the resin film 110 for a terminal shown in FIG. 5. In this case, the resin film 110 for a terminal has a moisture content of 2700 mass ppm or less. The resin film 110 for a terminal may be configured as any one of the first sealant layer 1, the insulating layer 2, or the second sealant layer 3. [Example]

[0100] Hereinafter, the present disclosure will be described more specifically based on examples, but the present disclosure is not limited to the following examples.

[0101] Example 1 A film made of acid-modified polypropylene (thickness: 25 μm, melting point: 140°C), a film made of polypropylene (thickness: 50 μm, melting point: 164°C), and a film made of acid-modified polypropylene (thickness: 25 μm, melting point: 140°C) were co-extruded to obtain a 100 μm thick polyolefin film 1 (PO film 1). The water content of the obtained PO film 1 was 358 mass ppm.

[0102] Example 2 A resin film for terminals was obtained in the same manner as in Example 1, except that PO film 1 was changed to polyolefin film 2 (PO film 2) made of polypropylene-polyethylene random copolymer (manufactured by Futamura Chemical Co., Ltd., product name: FHK2, melting point: 135°C) and the thickness was changed from 100 μm to 40 μm. The moisture content of the obtained resin film for terminals was 516 ppm by mass.

[0103] Example 3 A resin film for terminals was obtained in the same manner as in Example 1, except that PO film 1 was changed to a polyester film (polyester film 1) made of polyethylene terephthalate (manufactured by Unitika Ltd., product name: Emblet, melting point: 257°C) and the thickness was changed from 100 μm to 25 μm. The moisture content of the obtained resin film for terminals was 2682 ppm by mass.

[0104] Example 4 A resin film for terminals was obtained in the same manner as in Example 1, except that the PO film 1 was changed to a polyester film (polyester film 2) made of polyethylene naphthalate (manufactured by Toyobo Co., Ltd., trade name: Teonex, melting point: 265°C) and the thickness was changed from 100 μm to 25 μm. The moisture content of the obtained resin film for terminals was 2637 ppm by mass.

[0105] Example 5 A resin film for terminals was obtained in the same manner as in Example 1, except that PO film 1 was changed to a polyester film (polyester film 3) made of a copolymer of multiple types of polyethylene terephthalate (melting point: 210°C) and the thickness was changed from 100 μm to 25 μm. The moisture content of the obtained resin film for terminals was 1648 ppm by mass.

[0106] Example 6 A resin film for terminals was obtained in the same manner as in Example 1, except that PO film 1 was changed to polyolefin film 3 (PO film 3) consisting of a laminate obtained by co-extrusion of a film made of acid-modified polypropylene (thickness: 25 μm, melting point: 165° C.), a film made of polypropylene (thickness: 50 μm, melting point: 165° C.), and a film made of acid-modified polypropylene (thickness: 25 μm, melting point: 165° C.). The moisture content of the obtained resin film for terminals was 546 ppm by mass.

[0107] (Comparative Example 1) A resin film for terminals was obtained in the same manner as in Example 1, except that the PO film 1 was changed to a polyamide film (PA film) made of nylon 6 (manufactured by Toyobo Co., Ltd., product name: Harden N1102, melting point: 225°C) and the thickness was changed from 100 μm to 25 μm. The moisture content of the obtained resin film for terminals was 23,729 ppm by mass. The moisture content was measured as follows. Specifically, a 10cm square piece of resin film for terminals was left in an environment of 23°C / 50%RH for two days, and then heated using a thermal moisture vaporizer (manufactured by Hiranuma Corporation, product name: EV-2000) set at 300°C, and the amount of moisture generated was measured using a trace moisture analyzer (Karl Fischer: Hiranuma Corporation, product name: AQ-2100). Dry N2 gas was used as the carrier gas. The moisture content measured as above was then calculated based on the following formula: Moisture content (mass ppm) = measured moisture amount (g) / mass of resin film for terminals (g)

[0108] <Evaluation of resin film for terminals> A 120 mm x 60 mm piece of resin film for terminals was cut and folded in half. Both longitudinal ends of the resin film for terminals were overlapped. These ends were heat-sealed for 10 seconds at a temperature 20°C above the melting point of the resin film for terminals while applying a pressure of 0.6 MPa. This formed a 10 mm-wide heat-sealed area (the shaded area in Figure 6 ), producing a structure. The structure was then stored at room temperature for 12 hours. A 15 mm x 30 mm piece was cut from the structure at the center of the longitudinal heat-sealed area (see Figure 6 ) to prepare an evaluation sample. This evaluation sample was then separated into two pieces at the fused portion. The fused portion of each separated piece was visually observed, and the state of bubble formation in the resin film for terminals was evaluated based on the following criteria. The results are shown in Table 1. In addition, when the resin film for the terminal is a multilayer film, the "melting point of the resin film for the terminal" is the melting point of the sealant layer, which is the layer with the lowest melting point and is arranged outermost among the layers constituting the multilayer film. (Evaluation criteria) ◎: No bubbles are observed ○: Localized bubbles are observed ×: Bubbles are observed all over the surface

[0109] [Table 1]

[0110] The results shown in Table 1 show that the resin films for terminals of Examples 1 to 6, which have a moisture content of 2700 mass ppm or less, suppress the generation of air bubbles compared to the resin film for terminals of Comparative Example 1, which has a moisture content of more than 2700 mass ppm.

[0111] Therefore, it was confirmed that the resin film for a terminal of an all-solid-state battery according to the present disclosure can suppress the generation of bubbles when heat-sealed to a metal terminal. [Explanation of symbols]

[0112] 1...first sealant layer (sealant layer), 2...insulating layer, 3...second sealant layer (sealant layer), 10,110...resin film for terminal, 11...battery body, 14...metal terminal, 50...all-solid-state battery

Claims

1. A resin film for a terminal of an all-solid-state battery that is bonded by heat sealing to a part of an outer peripheral surface of a metal terminal that is electrically connected to a battery body that constitutes the all-solid-state battery, A polyester film containing a polyester-based resin is provided, A resin film for a terminal of an all-solid-state battery, having a water content of 1648 ppm by mass or more and 2700 ppm by mass or less.

2. a multilayer film having an insulating layer and a sealant layer provided on at least one side of the insulating layer; The resin film for a terminal of an all-solid-state battery according to claim 1 , wherein the sealant layer is the polyester film.

3. The resin film for a terminal of an all-solid-state battery according to claim 1 or 2, which has a melting point of 250°C or less.

4. The resin film for a terminal of an all-solid-state battery according to any one of claims 1 to 3, having a melting point of 150 ° C. or higher.

5. a battery body including a solid electrolyte; a metal terminal electrically connected to the battery body; an outer bag that holds the metal terminals and accommodates the battery body; a terminal resin film bonded by heat sealing to a part of the outer peripheral surface of the metal terminal, The all-solid-state battery, wherein the terminal resin film is made of the terminal resin film according to any one of claims 1 to 4.

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