JP2023156753A - aluminum secondary battery - Google Patents

Abstract

To provide an aluminum secondary battery which is hard to cause the corrosion of a collector and the like, which has a cycle life of practical level, and which is advantageous in terms of cost.SOLUTION: An aluminum secondary battery comprises a negative electrode containing aluminum and/or aluminum alloy, a positive electrode collector provided to be opposite to the negative electrode, a positive electrode active material disposed on the positive electrode collector, and a separator disposed between the negative electrode and the positive electrode collector, and an electrolyte solution. In the aluminum secondary battery, the positive electrode collector is made of a material selected from a nickel-based alloy, nickel, molybdenum, glass like carbon, titanium nitride, titanium carbonitride and titanium carbide. The aluminum secondary battery further comprises an exterior material. The negative electrode, the positive electrode active material, the positive electrode collector, the separator, and the electrolyte solution are contained in the exterior material. The exterior material has an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to an aluminum secondary battery.

Conventionally, secondary batteries that can be repeatedly charged and discharged have been used for various purposes. Among them, demand for lithium ion secondary batteries has increased rapidly in recent years due to their excellent energy density. Technological innovations associated with this have also been remarkable, and while the battery capacity of recent lithium ion secondary batteries is approaching its theoretical capacity, it is becoming difficult to dramatically improve performance. Lithium-ion secondary batteries also use rare metals such as lithium and cobalt as positive electrode active materials, so there are concerns about the supply of raw materials. For these reasons, there is a need to develop secondary batteries based on materials different from lithium.

From this perspective, new secondary batteries are being considered that are made from aluminum, which has abundant reserves. Aluminum has a capacity per volume about four times that of lithium, is chemically more stable than lithium, and is less likely to generate dendrites, so it is suitable as a battery material. It has long been used as an electrode for primary batteries, and development of aluminum ion secondary batteries is also progressing (for example, Patent Documents 1 to 4, Non-Patent Document 1).

Further, aluminum-sulfur batteries using sulfur as a positive electrode are also being studied academically, although they are currently not at a practical stage (for example, Non-Patent Documents 1 and 2). Aluminum-sulfur batteries have a theoretical capacity of about 1,675 Wh/kg, which is about 7 to 8 times that of lithium-ion batteries, and are particularly promising as next-generation batteries.

Incidentally, secondary batteries are often used in the form of a laminate battery as described later for use in vehicles, personal computers, mobile terminals, and the like. A laminate battery is a battery in which a plurality of batteries (unit cells) each having a positive electrode, a negative electrode, and a separator are connected in series, if desired, and then housed in an exterior material made of a laminate film. Also called laminated electrodes, pouch batteries, etc., they have the advantages of being lightweight, high energy density, high safety, and easy to form assembled batteries.

Japanese Patent Application Publication No. 2014-222609 Japanese Patent Application Publication No. 2016-213101 Japanese Patent Application Publication No. 2021-174732 JP2017-168234A

G. A. Elia, et al. , Journal of Power Sources, 481, 228870 (2021) Jasmin Smajic, et al. , Applied Energy Materials, 3, p6805-6814 (2020)

However, aluminum secondary batteries have problems such as low discharge voltage and low charge/discharge efficiency, easy electrode deterioration, and short cycle life. Generally, in aluminum secondary batteries, salts of halogenated aluminate ions such as AlCl ₄ ^- are used as electrolytes (Patent Documents 1 to 3, Non-Patent Document 1), but as a result of AlCl ₄ ^- causing an oxidation reaction, the discharge capacity This may cause a decrease in the maintenance ratio or discharge voltage, or a reduction in the potential window.

When the halogenated aluminate ions are hydrolyzed by moisture in the electrolytic solution or in the air, they generate hydrogen halides, leading to corrosion of metal materials including current collectors. In Patent Documents 3 and 4, an electrolytic solution containing aluminum bisperfluoroalkylsulfonimide is used for the purpose of improving the discharge capacity retention rate and expanding the potential window. However, perfluoroalkylsulfonimide is also a corrosive substance and may corrode current collectors and the like.

In aluminum secondary batteries, even noble metal materials such as gold and platinum may be corroded, so extremely expensive metal materials such as niobium and tantalum must be used as current collectors. These cost issues are one of the factors preventing the practical application of aluminum secondary batteries.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an aluminum secondary battery that is resistant to corrosion of current collectors, has a cycle life at a practical level, and is advantageous in terms of cost. shall be.

As a result of extensive studies, the present inventors have found that by using a predetermined material such as a nickel-based alloy as the positive electrode current collector, corrosion of the current collector can be suppressed and physical properties such as cycle life can be improved.

That is, the present invention provides the following (1) to (5).
(1) A negative electrode containing aluminum and/or an aluminum alloy, a positive electrode current collector provided to face the negative electrode, a positive electrode active material disposed on the positive electrode current collector, and the negative electrode and the positive electrode collector. An aluminum secondary battery comprising a separator and an electrolyte disposed between electric bodies,
An aluminum secondary battery, wherein the positive electrode current collector is made of one or more selected from the group consisting of nickel alloy, nickel, molybdenum, glassy carbon, titanium nitride, titanium carbonitride, and titanium carbide.
(2) The positive electrode current collector is made of a nickel-based alloy, and the nickel-based alloy is made of HASTALLOY, INCONEL, MONEL, INCOLOY, and austenitic stainless steel (STAINLESS). The aluminum secondary battery according to (1) above, which is one or more types selected from the group.
(3) The electrolyte is selected from the group consisting of AlCl ₄ ^- , AlBr ₄ ^- , AlI ₄ ^- , Al ₂ Cl ₇ ^- , Al ₂ Br ₇ ^- , Al ₂ I ₇ ^- , and Al ₂ Cl ₆ Br ^- . The aluminum secondary battery according to (1) or (2) above, containing one or more types of ions.
(4) The aluminum secondary battery according to any one of (1) to (3) above, wherein the positive electrode active material contains sulfur.
(5) further comprising an exterior material, wherein the negative electrode, the positive electrode active material, the positive electrode current collector, the separator, and the electrolyte are housed in the exterior material;
The aluminum secondary battery according to any one of (1) to (4) above, wherein the exterior material has an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer.

The aluminum secondary battery of the present invention does not cause corrosion of the current collector, etc., has a cycle life at a practical level, and is advantageous in terms of cost.

1 is a schematic cross-sectional view of an aluminum secondary battery according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view of a laminate battery according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a laminate battery according to another embodiment of the present invention.

Hereinafter, the aluminum secondary battery of the present invention will be described in detail based on embodiments, but the present invention is not limited to these embodiments.

≪Aluminum secondary battery≫
FIG. 1 is a schematic cross-sectional view of an aluminum secondary battery according to an embodiment of the present invention. In the aluminum secondary battery 1 of this embodiment, a negative electrode 11 containing aluminum and/or an aluminum alloy, a positive electrode current collector 12 provided to face the negative electrode 11, and a negative electrode 12 disposed on the positive electrode current collector 12 are provided. A positive electrode active material 13, a separator and an electrolytic solution (for example, a separator 14 impregnated with an electrolytic solution) are provided between the negative electrode 11 and the positive electrode current collector 12, and the positive electrode current collector 12 is made of a nickel-based alloy, nickel, It consists of one or more selected from the group consisting of molybdenum, glassy carbon, titanium nitride, titanium carbonitride, and titanium carbide.

In the embodiment shown in FIG. 1, the separator 14 is in almost entire contact with the main surface of each of the negative electrode 11 and the positive electrode active material 13 layers, and the electrolyte is impregnated into the separator 14. is not limited to these embodiments. For example, a liquid, gel, or solid electrolyte may be housed inside a frame-shaped or grid-shaped separator. Further, the aluminum secondary battery may have a cylindrical shape instead of a flat plate shape as shown in FIG. 1. The area of the electrode may also be larger on the negative electrode side than on the positive electrode side. When the negative electrode is larger than the positive electrode, it becomes easier to prevent aluminum ions from being deposited at the negative end. Furthermore, unit cells as shown in FIG. 1 may be connected in series or in parallel to form an assembled battery. Below, each member constituting the aluminum secondary battery of the present invention will be explained.

<Negative electrode>
In the aluminum secondary battery 1 of this embodiment, the negative electrode 11 contains aluminum and/or an aluminum alloy. Here, aluminum and/or aluminum alloy functions as a negative electrode active material capable of releasing aluminum ions, but can also function as a current collector. For example, it is also possible to use aluminum foil or an aluminum alloy plate as a negative electrode that serves as both a negative electrode active material and a current collector.

The negative electrode 11 is also composed of a current collector and an active material, and may optionally contain a conductive aid, a binder, and/or a solid electrolyte. Although not particularly limited, for example, it may be a negative electrode with a layered structure in which a thin film or powder of aluminum and/or aluminum alloy is applied on a current collector. The negative electrode 11 may be made of any material or have any configuration as long as it is capable of precipitation/dissolution of aluminum or dealloying/alloying reaction of aluminum ions from an aluminum alloy.

There are no particular restrictions on the material of the aluminum alloy, and examples include aluminum-gold alloy, aluminum-gallium alloy, aluminum-indium alloy, aluminum-manganese alloy, aluminum-nickel alloy, aluminum-platinum alloy, aluminum-bismuth alloy, and aluminum-tin. Examples include, but are not limited to, alloys, aluminum-zinc alloys, and aluminum-silicon alloys. An alloy containing two or more types of elements other than aluminum may be used. For example, aluminum-magnesium-silicon alloy, aluminum-copper-magnesium alloy, aluminum-magnesium-zinc alloy, etc. can be used as the negative electrode material.

When the negative electrode 11 includes a current collector, the material of the current collector is not particularly limited, and for example, aluminum and/or aluminum alloy may be used as the current collector, and a negative electrode active material such as aluminum powder may be arranged on the surface thereof. It's okay. Examples of negative electrode current collector materials other than aluminum include carbon materials such as graphite and glassy carbon, stainless steel, platinum, molybdenum, nickel, and nickel alloys, as well as titanium nitride, titanium carbonitride, and titanium carbide. These include, but are not limited to: Preferably, aluminum or nickel based alloys are used.

In a more preferred embodiment, the negative electrode 11 is made of a plate, sheet, or film of aluminum and/or an aluminum alloy. If the negative electrode has such a configuration, an aluminum secondary battery can be easily produced. In particular, if a general-purpose aluminum plate or aluminum foil is used as the negative electrode 11, it is advantageous in terms of cost.

Note that the negative electrode 11 may have a reinforcing layer made of ceramics, glass, carbon material, polymer material, or the like. Such reinforcing layers are particularly useful when the anode active material and anode current collector are thin aluminum and/or aluminum alloy layers, such as aluminum foil. Further, the negative electrode 11 can be formed by vapor-depositing aluminum on these reinforcing layers.

<Positive electrode>
In the aluminum secondary battery 1 of this embodiment, the positive electrode includes a positive electrode current collector 12 provided to face the negative electrode 11 described above, and a positive electrode active material 13 disposed on the positive electrode current collector 12. The positive electrode may also optionally contain a conductive aid, a binder, a solid electrolyte, and the like. For example, it may have a layered structure in which the positive electrode active material 13 is mixed with a conductive additive or a binder and provided on the positive electrode current collector 12.

[Positive electrode current collector]
In the aluminum secondary battery 1 of the present embodiment, the positive electrode current collector 12 is one or more selected from the group consisting of nickel alloy, nickel, molybdenum, glassy carbon, titanium nitride, titanium carbonitride, and titanium carbide. Consisting of This point is the first important requirement in this embodiment. A positive electrode current collector made of these materials is resistant to corrosion even when it comes into contact with a corrosive electrolyte, and can constitute an aluminum secondary battery that has a cycle life at a practical level. Since the above-mentioned materials such as nickel and molybdenum, especially nickel-based alloys, are not as expensive as niobium and tantalum, the aluminum secondary battery 1 of this embodiment is also advantageous in terms of cost.

(Nickel alloy)
There is no particular restriction on the nickel-based alloy that can be used for the positive electrode current collector 12, and various known alloys can be used. Examples include nickel-molybdenum alloy, nickel-chromium alloy, nickel-molybdenum-chromium alloy, nickel-titanium alloy, nickel-copper alloy, nickel-copper-aluminum alloy, nickel-chromium-iron alloy, nickel-molybdenum-chromium alloy. Examples include, but are not limited to, iron alloys, nickel-molybdenum-chromium-copper alloys, nickel-tungsten alloys, nickel-manganese alloys, and nickel-containing alloys such as austenitic stainless steel. Note that stainless steel is also classified as an iron-based alloy, but since austenitic stainless steel contains nickel, it is treated as a nickel-based alloy in the present invention. The nickel-based alloy may also contain carbon, silicon, manganese, niobium, and the like. Of course, it may contain unavoidable mixtures that are mixed in during alloy production, and it is also possible to use various commercially available nickel-based alloys.

Commercially available nickel-based alloys include, for example, HASTALLOY (registered trademark), INCONEL, MONEL, INCOLOY, Udimet, Waspaloy, Nichrome, PC Permalloy, Nitinol, and Nimonic. , DASALOY (registered trademark), austenitic stainless steel (STAINLESS) (registered trademark), etc., but are not limited to these. Among these, it is particularly preferable to use one or more nickel-based alloys selected from the group consisting of Hastelloy, Inconel, Monel, Incoloy, and austenitic stainless steel.

The content of nickel in the nickel-based alloy is preferably at least 30% by mass, preferably 40% by mass or more, further preferably 50% by mass or more, particularly preferably 55 to 90% by mass, particularly 60 to 80% by mass. If the nickel content is about 30% by mass or more, the positive electrode current collector will have better corrosion resistance. However, the material of the nickel-based alloy in this embodiment is not limited to these, and especially in alloys containing corrosion-resistant metals such as chromium and molybdenum, the nickel content may be less than 30% by mass. For example, it is also possible to use SUS304, SUS304L, etc., which are general-purpose austenitic stainless steels and have a chromium content of about 18% by mass and a nickel content of about 8% by mass.

From the viewpoint of corrosion resistance, it is preferable that the austenitic stainless steel has a high nickel content. More preferably an alloy with a nickel content of 10% by mass or more, such as SUS316 or SUS316L with a chromium content of about 18% by mass and a nickel content of about 12% by mass; still more preferably an alloy with a nickel content of about 20% by mass or more , for example, SUS310S with a chromium content of about 25% by mass and a nickel content of about 20% by mass, SUH660 with a chromium content of about 15% by mass and a nickel content of about 25% by mass; particularly preferably a nickel content of about 30% by mass. It is desirable to use the above alloy, for example, Alloy 800H having a chromium content of about 21% by mass and a nickel content of about 32% by mass.

From the viewpoint of corrosion resistance, one or more alloys selected from the group consisting of Hastelloy, Inconel, Monel, Incoloy, and austenitic stainless steel as nickel-based alloys; in particular, representative nickel alloys such as Hastelloy, Inconel, One or more alloys selected from the group consisting of Monel and Incoloy are preferred.

The nickel-based alloy also preferably contains about 1 to 30% by mass of molybdenum, 10 to 25% by mass of chromium, 1 to 50% by mass of iron, and/or about 0 to 35% by mass of copper. Among them, the nickel content is 55-90% by weight, especially 60-80% by weight; the molybdenum content is 0-30% by weight, such as 2-25% by weight, especially 5-20% by weight; the chromium content is 0-25% by weight. A nickel-based alloy with an iron content of 0 to 50 mass %, particularly 10 to 20 mass %, has extremely good corrosion resistance, and therefore is used as the positive electrode current collector in this embodiment. It is suitable as a material for No. 12.

(nickel)
The positive electrode current collector 12 in this embodiment may be made of pure nickel. Since nickel itself is a metal with excellent corrosion resistance, it is suitable as a material for the current collector material 12. Note that nickel usually contains small amounts of impurities such as iron, manganese, carbon, and silicon, but in this embodiment, nickel containing these inevitable impurities is also included as pure nickel.

(molybdenum)
The positive electrode current collector 12 in this embodiment may be made of molybdenum. Molybdenum has good electrical conductivity and extremely excellent corrosion resistance, so it is suitable as a material for the positive electrode current collector 12. In this embodiment, molybdenum also includes molybdenum containing unavoidable impurities.

(glassy carbon)
Glassy carbon is non-graphitizable carbon composed of ^SP2 carbon, and has characteristics such as high hardness and low density. In addition, it has high conductivity and excellent corrosion resistance against various chemical substances, so it is suitable as a material for a current collector. Glassy carbon usually contains about 1% by mass of impurities such as silicon, but in this embodiment, any of various known glassy carbons, including those containing such unavoidable impurities, can be used. You can also do it.

(titanium nitride)
Titanium nitride is a ceramic material represented by the composition formula of TiN. It is widely used for coating various parts and as medical parts. Because it has high hardness and excellent wear resistance, it is often used as a coating material for cutting tools, etc., and because it has excellent conductivity and corrosion resistance, it is suitable as a current collector material.

(Titanium carbonitride)
Titanium carbonitride is a ceramic material represented by the composition formula of Ti(C,N). Here, there is no particular restriction on the molar ratio of carbon atoms to nitrogen atoms, and for example, titanium carbonitride with C:N=1:10 to 10:1, especially C:N=1:3 to 3:1, etc. Various known materials can be used. Because it has a hardness greater than that of titanium nitride, it is often used as a coating material for cutting tools, but it is also suitable as a current collector material because it has excellent conductivity and corrosion resistance.

(Titanium carbide)
Titanium carbide is a ceramic material represented by the composition formula of TiC. Like titanium nitride, it has high hardness and excellent wear resistance, so it is often used as a coating material for cutting tools, etc., and it is also suitable as a current collector material because it has excellent conductivity and corrosion resistance.

(Configuration of positive electrode current collector)
The positive electrode current collector 12 is made of the above-mentioned materials, but a reinforcing material made of ceramics, glass, carbon material, polymeric material, etc. may be attached to one side thereof. For example, by laminating the positive electrode current collector 12 made of a nickel-based alloy, nickel, or molybdenum film on a reinforcing plate made of ceramic or glass, the corrosion resistance around the positive electrode can be further improved. Furthermore, it is also possible to reduce the weight and cost of the aluminum secondary battery by using a structure in which a nickel-based alloy or the like is deposited on a polymer sheet as the positive electrode current collector 12. Titanium nitride, titanium carbonitride, titanium carbide, etc. are materials often used for coating as described above, and in this embodiment as well, for example, they are coated on reinforcing materials made of other metals by methods such as PVD and CVD. Depending on the method, the positive electrode current collector 12 can be obtained.

There is no particular restriction on the method of manufacturing the positive electrode current collector 12, and it can be manufactured by various known methods depending on the intended shape and the material used. From the viewpoint of ease of manufacture, metal materials, especially nickel-based alloys and nickel, particularly nickel-based alloys, are preferred. Nickel-based alloys are easier to process than molybdenum, and generally have the advantage of superior acid corrosion resistance compared to pure nickel, making them particularly excellent as current collector materials. Nickel-based alloys also have the advantage of lower cost than molybdenum, titanium nitride, and the like. Therefore, it is suitable as a material for mass-produced batteries. In particular, when the aluminum secondary battery is an aluminum ion battery, that is, when the positive electrode active material described later does not contain sulfur, the positive electrode current collector is preferably made of a nickel-based alloy.

[Cathode active material]
In the aluminum secondary battery 1 of this embodiment, the positive electrode active material 13 is arranged on the positive electrode current collector 12. There is no particular restriction on the type of positive electrode active material 13, and any material used as a positive electrode active material for aluminum secondary batteries may be used. Examples include carbon-based materials such as particulate or fibrous activated carbon, Ketjen black, acetylene black, graphite, carbon nanotubes, and graphene; manganese dioxide, lead dioxide, silver oxide, iron oxide, molybdenum oxide, vanadium oxide, Metal oxides such as titanium oxide; carbides such as titanium carbide; nitrides such as titanium nitride; coordination polymers such as ferric ferrocyanide (Prussian blue); and fluorides and sulfur of transition metals. but not limited to.

In addition to the positive electrode current collector 12 and the positive electrode active material 13, the positive electrode of the aluminum secondary battery 1 of the present embodiment may optionally contain a conductive additive, a binder, a solid electrolyte, and the like. For example, a powder of a positive electrode active material such as manganese dioxide and a conductive agent are mixed with a solution or emulsion containing a binder such as a polymer, and the mixture is applied onto the positive electrode current collector 12 and dried. It can be used as the positive electrode of the battery 1. It is also possible to form the positive electrode active material 13 by vapor-depositing graphite or the like on one side of the positive electrode current collector 12 made of the above-mentioned material such as a nickel-based alloy.

(Conductivity aid)
As the conductive aid, general-purpose conductive aids such as carbon materials such as carbon black, Ketjen black, acetylene black, and graphite, metals, metal oxides, and conductive ceramics can be used. From the viewpoint of corrosion resistance, carbon materials are particularly preferred.

(binder)
A binder plays a role in binding the positive electrode active material and conductive additive, such as polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers, polytetrafluoroethylene (PTFE), and tetrafluoroethylene. Copolymers of, fluororubber, ethylene propylene diene rubber, styrene butadiene copolymers, cellulose resins, ethylene vinyl alcohol resins, polyvinyl alcohol (PVAL), poly(meth)acrylic acid, etc. are generally used. In the present invention, any known binders including these can be used. From the viewpoint of resistance to the electrolytic solution described later, a binder mainly composed of a fluorine-based polymer, ethylene vinyl alcohol resin, or polyvinyl alcohol is preferable.

The positive electrode active material 13, the conductive aid, and the binder as described above can be applied to the positive electrode current collector by, for example, dissolving and/or dispersing them in a solvent. There are no restrictions on the solvent used here, and examples include N-methyl-2-pyrrolidone (NMP), ethylene carbonate (EC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), and ethyl propionate. , methyl propionate, propylene carbonate (PC), γ-butyrolactone (γ-BL), acetonitrile (AN), ethyl acetate (EA), tetrahydrofuran (THF), dioxane, acetone, toluene, xylene, methyl acetate (MA), etc. Any solvent used in the field of battery materials can be used. It is also possible to use a mixture of a plurality of solvents. Furthermore, additives such as viscosity modifiers, dispersants, surfactants, and antioxidants may be added.

It is also possible to use an aqueous solvent as the above solvent. When a water-based binder is used as the binder, a sufficiently thick active material layer can be formed on the current collector. There is no particular restriction on the type of aqueous binder, and any known one can be used. Examples include, but are not limited to, carboxymethyl cellulose, SBR latex, NBR latex, (meth)acrylic latex (emulsion), polyvinyl alcohol, alginic acid, gelatin, and chitosan. Note that these conductive aids, binders, solvents, etc. can also be used when producing the negative electrode 11.

<Aluminum ion battery>
An aluminum ion battery can be constituted by the positive electrode current collector 12 and positive electrode active material 13 as described above, and the negative electrode 11 that faces them and contains aluminum and/or an aluminum alloy. An aluminum ion battery is a secondary battery that is charged and discharged by moving aluminum ions between a positive electrode and a negative electrode. Compared to lithium-sulfur batteries, they have the advantages of higher capacity, higher safety, and abundant resources. The aluminum secondary battery of the present invention includes such aluminum ion batteries.

In the positive electrode of an aluminum ion battery, the above-mentioned carbon-based materials, metal oxides, carbides, nitrides, coordination polymers, transition metal fluorides, etc. are generally used as positive electrode active materials. As the current collector, it is preferable to use a nickel-based alloy. Materials such as molybdenum and titanium nitride are generally more expensive than nickel-based alloys, are harder, and are not as easily molded as nickel-based alloys, which increases the cost of producing the positive electrode current collector. From the viewpoint of maintaining high cost performance of aluminum ion batteries, it is recommended to use a nickel-based alloy as the positive electrode current collector.

<Aluminum sulfur battery>
In the aluminum secondary battery of the present invention, the positive electrode active material preferably contains sulfur. That is, the aluminum secondary battery of the present invention is preferably an aluminum sulfur battery. Aluminum-sulfur batteries have an extremely high theoretical capacity as described above, and are expected to be a next-generation battery, but they have had problems such as corrosion of the positive electrode material. In the aluminum secondary battery of the present invention, the above-mentioned materials such as nickel-based alloys and molybdenum are used as the positive electrode current collector, thereby solving the problem of corrosion and providing a sufficient cycle life.

In aluminum-sulfur batteries, the positive electrode active material contains sulfur. Examples include positive electrode active materials containing sulfur itself, positive electrode active materials containing sulfides such as copper sulfide, and the like. Here, since sulfur and sulfides generally have low electrical conductivity at room temperature, it is preferable to use a conductive additive in combination. As a conductive aid in an aluminum-sulfur battery, the above-mentioned carbon materials, copper, or a compound thereof can be used. It is also possible to use sulfur coated with carbon.

Specifically, a composite material of sulfur and a carbon material such as acetylene black, a composite material of sulfur, metallic copper, and a carbon material, or a composite material of sulfur, a copper Chevrel phase (Cu ₂ Mo ₄ S _7.8 ), and a carbon material. By dispersing it in a binder as described above, applying it onto a positive electrode current collector made of a nickel alloy, and drying it, it can be made into a positive electrode material for an aluminum-sulfur battery. A positive electrode active material, a binder, etc. of a lithium-sulfur battery or a sodium-sulfur battery may be used.

<Electrolyte>
The electrolytic solution of the aluminum secondary battery may be any solution as long as it contains ions containing aluminum element as an electrolyte. Further, the same electrolyte solution can be used in both the aluminum ion battery and the aluminum sulfur battery described above. In the present invention, the term "electrolytic solution" broadly includes colloidal solutions. That is, the "electrolytic solution" in the present invention includes gel-like and xerogel-like electrolytes.

[Electrolytes]
There are no particular limitations on the ions containing aluminum as an electrolyte. Examples include halogenated aluminate ions such as AlCl ₄ ⁻ , AlBr ₄ ⁻ , AlI ₄ ⁻ , Al ₂ Cl ₇ ⁻ , Al ₂ Br ₇ ⁻ , Al ₂ I ₇ ⁻ , and Al ₂ Cl ₆ Br ⁻ ; Perfluoroalkylsulfonimide or aluminum bis(fluorosulfone) such as (trifluoromethanesulfone)imide, aluminum bis(pentafluoroethanesulfone)imide, aluminum bis(heptafluoropropanesulfone)imide, aluminum bis(nonafluorobutanesulfone)imide Ions derived from imides; further examples include, but are not limited to, aluminum complex ions having ligands derived from urea, carboxylic acids, β-diketones, diamines, quinolines, bipyridines, catechols, and the like. Al ³⁺ ions derived from aluminum sulfate or aluminum nitrate can also be used. Moreover, a plurality of types of these ions may be contained.

Among these electrolytes, an electrolyte selected from the group consisting of AlCl ₄ ^- , AlBr ₄ ^- , AlI ₄ ^- , Al ₂ Cl ₇ ^- , Al ₂ Br ₇ ^- , Al ₂ I ₇ ^- , and Al ₂ Cl ₆ Br ^- Electrolytes containing one or more types of ions are preferred. These ions are highly stable in the electrolyte, and there are no concerns about supply. In particular, an electrolytic solution containing AlCl ₄ ⁻ (tetrachloroaluminate) and/or Al ₂ Cl ₇ ⁻ (heptachlorodialuminate) as an electrolyte is preferred.

[Solvent of electrolyte]
The solvent for the electrolytic solution is not particularly limited as long as it can generate ions containing aluminum element in the electrolytic solution. For example, nonaqueous solvents such as aromatic hydrocarbons, ethers, ketones, acetic esters, carbonic esters, sulfonic solvents, and even aqueous solvents can be used. However, from the viewpoint of suppressing the generation of hydrohalic acids and the like derived from electrolytes, it is preferable to use non-aqueous solvents such as ethers, carbonic esters, etc., especially ionic liquids and deep eutectic solvents described below.

There are no particular restrictions on the ether that can be used as a solvent for the electrolyte; examples include glyme-based solvents such as triglyme and tetraglyme, which are often used in batteries; dimethoxyethane (DME), ethoxymethoxyethane (EME), and diethoxyethane (DEE). ); cyclic ethers such as tetrahydrofuran, dioxane, dioxolane, and crown ether; fluorinated ethers such as perfluoroether and hydrofluoroether; esters such as γ-butyrolactone and methyl acetate; ) and polyalkylene oxides such as polypropylene oxide and polybutylene oxide, but are not limited thereto.

There are no particular restrictions on the carbonate ester (carbonate) that can be used as a solvent for the electrolyte, and examples include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). ), alkyl(ene) carbonates such as ethyl methyl carbonate (EMC); fluorinated carbonates such as fluoroethylene carbonate (FEC), 4,5-difluoroethylene carbonate, and 4,4-difluoroethylene carbonate; Not limited to these.

(ionic liquid)
In the aluminum secondary battery of this embodiment, it is preferable that the electrolytic solution contains an ionic liquid. An "ionic liquid" is a salt that exists as a liquid even at room temperature, and has characteristics such as high ionic conductivity, low volatility, and high thermal stability. Therefore, an aluminum secondary battery whose electrolytic solution contains an ionic liquid is less likely to have problems. In particular, an electrolytic solution in which an electrolyte and a solvent form an ionic liquid is preferred, and such an electrolyte allows the aluminum secondary battery to be used even at high temperatures of about 300°C. The ionic liquid is not particularly limited, and examples include imidazolium, pyridinium, pyrrolidinium, piperidinium, tetraalkylammonium, pyrazolium, or phosphonium, and halogen ions such as chloride ions, or ions that form electrolytes such as AlCl ₄ ^- . but not limited to.

Examples of imidazolium include 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-allyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, and 1-ethyl-3-methylimidazolium. Examples include, but are not limited to, allyl-3-ethylimidazolium, 1-allyl-3-butylimidazolium, 1,3-diallylimidazolium, and the like.

Examples of pyridinium include, but are not limited to, 1-propylpyridinium, 1-butylpyridinium, 1-ethyl-3-(hydroxymethyl)pyridinium, and 1-ethyl-3-methylpyridinium.

Examples of pyrrolidinium include, but are not limited to, N-methyl-N-propylpyrrolidinium, N-methyl-N-butylpyrrolidinium, N-methyl-N-methoxymethylpyrrolidinium, and the like.

Examples of piperidinium include N-methyl-N-propylpiperidinium; examples of tetraalkylammonium include N,N,N-trimethyl-N-propylammonium, methyltrioctylammonium, etc.; and examples of pyrazolium. , for example, 1-ethyl-2,3,5-trimethylpyrazolium, 1-propyl-2,3,5-trimethylpyrazolium, 1-butyl-2,3,5-trimethylpyrazolium, etc., respectively. These include, but are not limited to:

Among these, preferred nonionic liquids are ionic liquids containing imidazolium ions such as imidazolium chloride, and ionic liquids of imidazolium and halogenated aluminates, such as 1-ethyl-3-methylimidazolyl tetra. These include chloroaluminate, 1-ethyl-2,3-dimethylimidazolium heptachlorodialuminate, and the like. These ionic liquids have the advantage of being highly stable and easy to obtain and prepare.

(deep eutectic solvent)
In the aluminum secondary battery of this embodiment, it is also preferable that the electrolytic solution contains a deep eutectic solvent. A "deep eutectic solvent" is a solvent that is liquid at room temperature and is obtained by mixing a hydrogen bond donor compound and a hydrogen bond acceptor compound at a certain ratio. A solvent with arbitrary physical properties can be created by combining a donor compound and an acceptor compound, and various combinations have been reported.

For example, aluminum chloride, which is a strong Lewis acid, forms a deep eutectic solvent with oxygen-donating amides such as urea, methylurea, ethylurea, acetamide, or ethylpyridine. These deep eutectic solvents contain AlCl ₄ ^- caused by aluminum chloride and, for example, [AlCl ₂ (urea) ₂ ] ⁺ , etc. (see, for example, Non-Patent Document 1), so that the electrolysis in this embodiment is Suitable as a liquid.

Similar to ionic liquids, deep eutectic solvents have low vapor pressure and are flame retardant, so they are suitable as components of electrolyte solutions. Deep eutectic solvents also have the advantages of generally good thermal stability and electrochemical stability, high environmental affinity, and excellent solubility. Therefore, it is also possible to dissolve ions such as AlCl ₄ ⁻ in a deep eutectic solvent other than those mentioned above to form the electrolytic solution in this embodiment.

Examples of deep eutectic solvents that can be used as electrolyte solvents include monosaccharide/hydroxycarboxylic acid, disaccharide/hydroxycarboxylic acid, diol/hydroxycarboxylic acid, fatty acid/long chain fatty acid, urea/sulfamine, etc. Examples include, but are not limited to, acid-based ones. Among these, deep eutectic solvents consisting of hydroxycarboxylic acids and one or more compounds selected from sugars, carboxylates, and hydroxyalkylammonium salts, such as monosaccharide/hydroxycarboxylic acid systems, are derived from natural products. It is suitable as a solvent for electrolyte solution because it is excellent in terms of safety and hygiene.

Examples of hydroxycarboxylic acids include glycolic acid, lactic acid, tartronic acid, glyceric acid, hydroxybutyric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citramalic acid, citric acid, isocitric acid. , aliphatic hydroxycarboxylic acids such as leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricinelaidic acid, cerebronic acid, quinic acid, and shikimic acid; salicylic acid, vanillic acid, syringic acid, pyrocatechuic acid, resorcylic acid, protocatechuic acid, Aromatic hydroxycarboxylic acids such as gentisic acid, orceric acid, gallic acid, mandelic acid, benzylic acid, atrolactic acid, melilotic acid, fluoretic acid, coumaric acid, umbelic acid, caffeic acid, ferulic acid, and sinapinic acid, etc. but not limited to. It is also possible to use multiple hydroxycarboxylic acids in combination.

Examples of monosaccharides include aldoses such as glyceraldehyde, erythrose, threose, ribose, lyxose, xylose, arabinose, allose, talose, gulose, glucose, altrose, mannose, galactose, and idose; dihydroxyacetone, erythrulose, xylulose , ribulose, psicose, fructose, sorbose, and tagatose. Examples of disaccharides include, but are not limited to, sucrose, lactulose, lactose, maltose, trehalose, and cellobiose. It is also possible to use two or more types of sugars together, or to use monosaccharides and disaccharides together.

Examples of fatty acids and long chain fatty acids include, but are not limited to, octanoic acid, nonanoic acid, decanoic acid, lauric acid, and the like.

Deep eutectic solvents other than those mentioned above can also be used. For electrolytes of aluminum secondary batteries, a deep eutectic solvent consisting of lactic acid or citric acid, especially lactic acid, and a monosaccharide, especially glucose, is preferred.

(Additive)
The electrolyte may also optionally contain various additives. For example, negative electrode or positive electrode protective film forming agents such as vinyl group-containing compounds, γ-butyrolactone, ethylene sulfide, cyclic sulfonic acid esters, methyl benzoate, succinic anhydride, polydimethylsiloxane, AgPF ₆ , Cu(CF ₃ SO ₃ ) _2, etc. ; Overcharge preventive agent such as 2,4-difluoroanisole; Flame retardant imparting agent such as phosphoric acid ester, phosphazenes, imidazole salt, etc., about 0.01 to 5% by mass, especially 0.1 to 1 mass% % can be contained.

<Separator>
The aluminum secondary battery 1 of this embodiment includes a separator 14 installed between a positive electrode and a negative electrode to prevent short circuit between the two electrodes. There is no particular restriction on the form of the separator, and it may be, for example, frame-like or lattice-like in shape, have a certain thickness, and isolate the positive and negative electrodes. Moreover, it is also possible to use a gel electrolyte or a solid electrolyte as a separator. However, from the viewpoint of more reliably preventing a short circuit between both electrodes, as in the embodiment shown in FIG. It is preferable. Furthermore, from the viewpoint of maintaining high ionic conductivity between the positive and negative electrodes, the separator 14 preferably holds an electrolyte and is preferably in the form of a porous film, fiber, or the like.

There are no particular restrictions on the material or shape of the separator, and it may be made of porous materials such as glass, ceramics, cellulose fibers, paper such as Japanese paper, fluorine-based polymers, polyolefins such as polyethylene or polypropylene, PET, aromatic polyamides, polyacrylonitrile, polyimide, etc. Any separator can be used, such as a body, woven fabric or non-woven fabric, or gel-like separator.

<Battery type>
The aluminum secondary battery configured as described above can be used as a unit cell as it is, or a plurality of batteries can be connected in series or parallel to form a battery assembly (module). There are no particular restrictions on the size or the number of single cells in the assembled battery, and any desired size or number can be adopted depending on the purpose. For example, a positive electrode, a negative electrode, and a separator with a thickness of about 1 μm to 2 mm, especially about 10 to 500 μm, may be laminated to form a single cell, and about 1 to 1000 such cells, especially about 10 to 100 such cells may be formed. It may also be connected to form an assembled battery.

There are no particular restrictions on the type or shape of the aluminum secondary battery; for example, in addition to the flat plate type shown in FIG. 1, various types can be used, such as a cylindrical type, a coin type, a button type, and a laminate type. Here, the laminate type aluminum secondary battery is a battery in which a single cell or an assembled battery is housed in a laminate exterior material, as described above. By housing an aluminum secondary battery in such an exterior material, it becomes possible to use it as a more practical secondary battery.

≪Laminate battery≫
The present invention further includes an exterior material, and a negative electrode, a positive electrode active material, a positive electrode current collector, a separator, and an electrolytic solution are housed in the exterior material, and the exterior material is an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer. It also includes an aluminum secondary battery having a layer. If desired, members such as an insulating material, a heat insulating material, a cushioning material, etc. may be added to the exterior material.

In laminated secondary batteries, such as lithium ion batteries, thermoplastic resins such as polyolefins such as polyethylene and polypropylene, polyamides such as nylon, and polyesters such as PET are used on both sides of a metal layer made of aluminum or stainless steel (SUS). Materials in which layers are laminated are commonly used as exterior materials (laminates).

According to the findings of the present inventors, when a laminate film made of polyolefin or PET is used as an exterior material for an aluminum secondary battery, deformation such as blistering often occurs. Since such deterioration and deformation of peripheral members also pose a problem in putting aluminum secondary batteries into practical use, the inventors also investigated exterior materials for laminated batteries. The laminate battery of the present invention will be described in detail below based on embodiments, but the present invention is not limited to these embodiments.

FIG. 2 is a schematic cross-sectional view of a laminate battery according to an embodiment of the present invention. In the laminate battery 2 of this embodiment, a negative electrode 21 containing aluminum and/or an aluminum alloy, a positive electrode current collector 22 provided to face the negative electrode 21, and a positive electrode active disposed on the positive electrode current collector 22 are provided. A substance 23 and a separator 24 containing an electrolyte, which is disposed between the negative electrode 21 and the positive electrode current collector 22, are provided, and these are housed in an exterior material 25. Here, the positive electrode current collector 22 is made of one or more selected from the group consisting of a nickel-based alloy, nickel, molybdenum, glassy carbon, titanium nitride, titanium carbonitride, and titanium carbide. This is similar to the positive electrode current collector 12 in the aluminum secondary battery of the embodiment shown in FIG. The same materials as the aluminum secondary battery of the embodiment shown in FIG. 1 can also be used for the negative electrode 21, positive electrode active material 23, separator 24, and electrolyte. Moreover, the exterior material 25 has an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer.

Note that in the embodiment shown in FIG. 2, the negative electrode 21 and the positive electrode current collector 22 extend in opposite directions and constitute a negative electrode tab and a positive electrode tab, respectively, but the present invention is limited to such an embodiment. It's not a thing. For example, the negative electrode 21 and the positive electrode current collector 22 may have the same size as the separator 24, and a metal plate made of aluminum or nickel alloy may be bonded to each electrode to form an electrode tab. They may be attached in the same direction. In FIG. 2, the exterior material 25 accommodates the cell in a state separated from the negative electrode 21 and the positive electrode current collector 22, but the exterior material 25 is tightly attached to a part or the entire surface of the cell by, for example, thermal fusion. You can leave it there.

FIG. 3 is a schematic cross-sectional view of another laminate battery according to another embodiment of the present invention. In this embodiment, three single cells according to the present invention are stacked and connected in series to form an assembled battery, but the present invention is not limited to this embodiment. For example, the number of cells may be two or four or more, and each cell may be connected in parallel or directly in the horizontal direction of FIG. 3. In FIG. 3, the three cells are shown separated from each other for ease of viewing, but it is preferable that they be joined directly or via a conductor or a welded portion. A separator may be placed between the cells if desired.

Also in the embodiment shown in FIG. 3, the same materials as those of the aluminum secondary battery of the embodiment shown in FIG. can. Moreover, the exterior material 35 has an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer.

<Exterior material>
As mentioned above, the aluminum secondary battery (laminate battery) of the embodiment shown in FIGS. 2 and 3 further includes an exterior material, and the exterior material is an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer. An important requirement is to have If the exterior material has an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer as in this embodiment, even if it is applied to an aluminum secondary battery, there will be no deformation or deterioration such as swelling, and it will have a longer life. It is also possible to use it as a battery.

[Ethylene vinyl alcohol]
Ethylene vinyl alcohol is a copolymer of ethylene and vinyl alcohol having -CH ₂ CH(OH)- units, and is also written as EVOH. EVOH is generally obtained by hydrolysis (saponification) of ethylene/vinyl acetate copolymer, and various commercially available products are on the market, such as EVAL (registered trademark) by Kuraray Co., Ltd. and Soarite (registered trademark) by Mitsubishi Chemical Corporation. has been done. Since EVOH has excellent moldability and gas barrier properties, it is widely used as a food packaging material. The present inventors have now discovered that this EVOH resin is useful as one of the raw materials for the outer layer material for aluminum secondary batteries.

Although the physical properties and processability of EVOH can be controlled by the copolymerization ratio of ethylene and vinyl alcohol and the degree of polymerization, any EVOH can be used in this embodiment. For example, EVOH with an ethylene content of about 20 to 30 mol%, EVOH with an ethylene content of about 30 to 50 mol%, EVOH with an ethylene content of more than 50%; EVOH with a density of about 1.10 to 1.16 g/ ^cm3; EVOH with a melting point of about 1.16 to 1.22 g/ ^cm3 ; EVOH with a melting point of less than 170°C, EVOH with a melting point of about 170 to 185°C, and even EVOH with a melting point of over 185°C. can be used. It is also possible to use multiple types of EVOH in combination.

EVOH may be a terpolymer or the like in which a third monomer having a carboxyl group or an epoxy group is copolymerized. Such a third monomer can improve the adhesion to the metal layer when EVOH is laminated. It is also possible to further increase the resistance of EVOH by crosslinking the functional groups on the third monomer component. Hydroxy groups on EVOH may be esterified or etherified, or acetalized by reacting with an aldehyde such as formaldehyde or benzaldehyde in the presence of an acid to improve water resistance.

From the viewpoint of heat resistance of an aluminum secondary battery, EVOH with a low ethylene content is preferable, and from the viewpoint of cold resistance, an EVOH with a high ethylene content is preferable. From the viewpoint of resistance to electrolytes, completely saponified type EVOH in which about 99% or more of vinyl acetate units are saponified is preferable, and EVOH with an ethylene content of about 0.1 to 30.0 mol%, especially 1.0 About 20.0 mol % of EVOH is preferred. Even when such an exterior material having EVOH in its resin layer is used in an aluminum secondary battery, there is a low risk of deformation such as swelling or deterioration.

[Polyacrylonitrile]
Polyacrylonitrile (PAN) is a polymer of acrylonitrile, and PAN resin is a polymer containing 50 mol% or more of -CH ₂ CH(CN)- units. Various PAN resins having different acrylonitrile copolymerization ratios and molecular weights are commercially available from various companies, but any resin can be used in the present invention. Multiple types of PAN resins may be used in combination. Preferably, a PAN resin, particularly a homopolymer of acrylonitrile, having a copolymerization ratio of acrylonitrile of 80 mol % or more, particularly 90 mol % or more is used. Generally, the higher the copolymerization ratio of acrylonitrile, the better the corrosion resistance, and the more useful it is as a battery member.

[Laminate structure]
The exterior material in this embodiment preferably has a layer containing the above-mentioned ethylene vinyl alcohol resin or polyacrylonitrile resin as an inner side (battery side) layer. Embodiments are also possible in which the outer layer comprises EVOH and/or PAN resin. The exterior material basically includes an intermediate layer made of metal, an inner layer and an outer layer made of resin, and the resin of the outer layer is made of polyolefin such as polyethylene or polypropylene, polyamide such as nylon, or polyester such as PET. etc. may be used. There is no particular restriction on the material of the metal layer, and any metal used for general-purpose exterior materials (laminate materials) can be used, but aluminum or stainless steel, particularly aluminum, is preferably used. Aluminum is lightweight and flexible, and is advantageous in terms of cost, so it is suitable as a material for the middle layer of an exterior material (laminate material).

The exterior material may include an adhesive layer between the inner layer and the intermediate layer and/or between the outer layer and the intermediate layer. There are no particular restrictions on the material of the adhesive layer, and polyamides such as nylon, polyesters such as polyethylene terephthalate, fluororesins such as polyvinylidene fluoride, polyolefins or styrene polymers modified with unsaturated carboxylic acids (anhydrides), etc., or natural Various known adhesive polymers can be used, such as rubber and various synthetic rubbers. However, from the viewpoint of the durability of the exterior material, an adhesive layer is not provided between the inner layer and the intermediate layer, or an EVOH resin layer and/or PAN resin layer different from the inner layer is provided. Preferably, it is provided as an adhesive layer. For example, EVOH resin or PAN resin containing a tack agent such as phenol resin or terpene resin may be used as the adhesive layer. It is also possible to contain a tack agent in the inner surface layer and laminate it with a metal intermediate layer without using an adhesive layer.

The inner layer and/or outer layer of the exterior material, including the ethylene vinyl alcohol resin layer and the polyacrylonitrile resin layer, may contain a tack agent as described above, but may also contain other components such as a lubricant, 0.1 to 2.0 parts by mass, especially 0.2 to 1 part by mass of processing aids such as plasticizers and antistatic agents, deterioration inhibitors such as antioxidants, and coloring agents such as carbon black and pigments. It may be contained in an amount of about .0 part by mass. Polymers other than EVOH and PAN, such as polyamides such as nylon, polyesters such as polyethylene terephthalate, polyolefins or styrenic polymers modified with unsaturated carboxylic acids (anhydrides), ethylene/acrylic acid (ester) copolymers, etc. It can also be blended. It may also contain fillers such as calcium carbonate, silica, titanium oxide, barium sulfate, talc, and clay.

In addition, the metal layer that is the intermediate layer of the exterior material, such as the aluminum layer or the stainless steel layer, is subjected to treatments such as zincate treatment, chromate treatment, phosphate treatment, or sandblasting to form inner and outer layers. It is also possible to improve the adhesion of

There are no particular restrictions on the thickness of each layer or the total thickness of the exterior material, and the thickness can be set to a desired value depending on the environment in which the aluminum secondary battery is used. For example, a metal layer with a thickness of about 1 to 300 μm, especially about 10 to 100 μm, is sandwiched between an inner layer and an outer layer with a thickness of about 10 to 500 μm, especially about 30 to 300 μm, so that the total thickness is about 25 μm to 1 mm. In particular, the sheathing material may have a thickness of about 50 to 500 μm, but is not limited to this embodiment. An adhesive layer having a thickness of about 1 to 10 μm may be attached.

By accommodating, for example, the aluminum secondary battery of the above-described embodiment in the above-described exterior material, the laminate battery of this embodiment can be obtained. After accommodating the aluminum secondary battery, the exterior material is preferably pouched at least at its ends. The pouch treatment can be performed, for example, by thermocompression bonding (heat sealing). The entire laminate battery may be thermocompressed into a pouch.

The thus obtained laminate battery of this embodiment has improved cycle life by suppressing corrosion of electrodes, etc., and is resistant to deformation or deterioration of the exterior material, making it a practical product with a long life. It is a secondary battery. Furthermore, since aluminum and/or aluminum alloy is used as the negative electrode material, it is safer and lower cost than lithium ion batteries, and there is no concern about the supply of raw materials. Therefore, it is suitable as a secondary battery for vehicles such as automobiles, personal computers, mobile terminals, various home appliances, and medical equipment.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples except for what is specified above.

[Example 1]
An aluminum-sulfur battery (a single cell as shown in FIG. 1) was fabricated using a positive electrode, a negative electrode, and an electrolytic solution prepared as follows.
- Positive electrode: Sulfur, acetylene black, and polyvinylidene fluoride (PVDF) powders were mixed at a mass ratio of 2:1:1, and N-methylpyrrolidone (NMP) was added to form a slurry. Hastelloy (registered trademark) B-2 (Ni content: approximately 69% by mass, Mo content: approximately 28% by mass, and also contains approximately 1% by mass of Cr, Mn, Fe, etc.) as a positive electrode current collector. ) was coated on foil (thickness: 15 μm) and dried to produce a positive electrode.
- Negative electrode: Aluminum foil (thickness 15 μm) was used as is.
- Electrolyte solution: Ethylmethylimidazolium chloride and aluminum chloride were mixed at a mass ratio of 4:6 under an argon or nitrogen stream to prepare.
The prepared electrolytic solution was used by impregnating a glass fiber separator.

Separately, a general-purpose polyolefin three-layer laminate film consisting of a polypropylene layer (thickness: 50 μm)/aluminum layer (thickness: 50 μm)/polypropylene layer (thickness: 50 μm) was prepared as an exterior material. This film was folded at the center, the above unit cell was sandwiched therebetween, and the three ends were heat-sealed to form a pouch to produce a laminate battery as shown in FIG. 2.

The laminate battery produced as described above was charged and discharged for 100 cycles at a potential window of 2.0 to 4.5V and 0.1C. The measurement was performed using a potentiostat/galvanostat HA series manufactured by Hokuto Denko. The test results are summarized in Table 1 below.

In the laminate battery of this example, swelling of the exterior material was observed around the 30th cycle, but high battery capacity was maintained at 312 mAhg ^-1 at the 50th cycle and 156 mAhg ^-1 at the 100th cycle. When the laminate battery was disassembled after the test, no corrosion of the positive electrode current collector was observed.

[Comparative example 1]
As a positive electrode current collector, ferritic stainless steel (registered trademark) SUS430 (Cr content: about 18% by mass, and also contains about 1% by mass of Mn and Si) was used instead of Hastelloy (registered trademark) B-2. The same operation as in Example 1 was performed except for using the following.

The test results are summarized in Table 1 below, but in the case of the laminate battery of Comparative Example 1, the battery capacity decreased to 7 mAhg ^-1 at the 50th cycle, so further tests were canceled. Blisters were also observed on the exterior material, indicating significant deterioration. When the laminate battery was disassembled after the test, significant corrosion of the positive electrode current collector was observed.

[Example 2]
The same operation as in Example 1 was performed except that a three-layer laminate film in which the inner resin layer was made of EVOH was used as the exterior material.

The test results are summarized in Table 1 below, and in the laminate battery of Example 2, no deformation or deterioration such as blistering was observed in the laminate even after the 100 cycle test. Furthermore, a very high battery capacity of 376 mAhg ^-1 was achieved at the 100th cycle. When the laminate battery was disassembled after the test, no corrosion of the positive electrode current collector was observed.

[Example 3]
The same method as in Example 1 was used, except that molybdenum foil was used instead of Hastelloy (registered trademark) B-2 as the positive electrode current collector, and a three-layer laminate film whose inner resin layer was made of PAN was used as the exterior material. performed the operation.

The test results are summarized in Table 1 below, and in the laminate battery of Example 3, no deformation such as blistering or deterioration of the exterior material was observed even after the 100 cycle test. Furthermore, at the 100th cycle, a very high battery capacity of 421 mAhg ^-1 was achieved. When the laminate battery was disassembled after the test, no corrosion of the positive electrode current collector was observed.

In accordance with the present invention, in the laminate batteries of Examples 1 to 3 in which the positive electrode current collector was made of a nickel-based alloy or molybdenum, high battery capacity was maintained without corrosion of the positive electrode current collector even during 100 cycle tests. . In particular, the laminate batteries of Examples 2 and 3, which have an ethylene vinyl alcohol resin layer or a polyacrylonitrile resin layer as the inner layer of the exterior material, exhibited high battery capacity even during the 100 cycle test, and deterioration such as swelling of the exterior material occurred. It turns out there isn't.

1 Aluminum secondary battery 11 Negative electrode 12 Positive electrode current collector 13 Positive electrode active material 14 Separator 2, 3 Laminated battery 21, 31 Negative electrode 22, 32 Positive electrode current collector 23, 33 Positive electrode active material 24, 34 Separator 25, 35 Exterior material

Claims (5)

A negative electrode containing aluminum and/or an aluminum alloy, a positive electrode current collector provided to face the negative electrode, a positive electrode active material disposed on the positive electrode current collector, and a negative electrode and the positive electrode current collector. An aluminum secondary battery comprising a separator and an electrolyte disposed between,
An aluminum secondary battery, wherein the positive electrode current collector is made of one or more selected from the group consisting of nickel alloy, nickel, molybdenum, glassy carbon, titanium nitride, titanium carbonitride, and titanium carbide. The positive electrode current collector is made of a nickel-based alloy, and the nickel-based alloy is selected from the group consisting of HASTALLOY, INCONEL, MONEL, INCOLOY, and austenitic stainless steel. The aluminum secondary battery according to claim 1, wherein the aluminum secondary battery is one or more types. The electrolyte is selected from the group consisting of AlCl ₄ ^- , AlBr ₄ ^- , AlI ₄ ^- , Al ₂ Cl ₇ ^- , Al ₂ Br ₇ ^- , Al ₂ I ₇ ^- , and Al ₂ Cl ₆ Br ^- . The aluminum secondary battery according to claim 1, containing more than one type of ion. The aluminum secondary battery according to claim 1, wherein the positive electrode active material contains sulfur. further comprising an exterior material, the negative electrode, the positive electrode active material, the positive electrode current collector, the separator, and the electrolytic solution are housed in the exterior material;
The aluminum secondary battery according to any one of claims 1 to 4, wherein the exterior material has an ethylene vinyl alcohol resin layer and/or a polyacrylonitrile resin layer.

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