WO2022075287A1 - Electrolyte for aluminum secondary batteries, and aluminum secondary battery - Google Patents

Electrolyte for aluminum secondary batteries, and aluminum secondary battery Download PDF

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WO2022075287A1
WO2022075287A1 PCT/JP2021/036715 JP2021036715W WO2022075287A1 WO 2022075287 A1 WO2022075287 A1 WO 2022075287A1 JP 2021036715 W JP2021036715 W JP 2021036715W WO 2022075287 A1 WO2022075287 A1 WO 2022075287A1
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aluminum
group
electrolyte
secondary battery
ether group
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PCT/JP2021/036715
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French (fr)
Japanese (ja)
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一 松本
理恵 大藪
尚人 赤井
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国立研究開発法人産業技術総合研究所
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Publication of WO2022075287A1 publication Critical patent/WO2022075287A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
    • H01M10/39—Accumulators not provided for in groups H01M10/05-H01M10/34 working at high temperature
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to an electrolyte for an aluminum secondary battery and an aluminum secondary battery.
  • lithium secondary battery uses lithium, which is a rare metal, as an electrode raw material
  • the electrode is replaced with a general-purpose metal such as sodium, magnesium, aluminum, and zinc from the viewpoint of reducing the cost of the raw material. Batteries are also being researched.
  • aluminum secondary batteries that use trivalent ions are expected to have a high capacity density per unit volume due to their 3-electron redox characteristics.
  • aluminum secondary batteries have very high technical hurdles, and research examples are limited.
  • One of the technical issues of the aluminum secondary battery is to develop an electrolyte capable of reversibly precipitating and dissolving metallic aluminum.
  • imidazolium salts can be used to form ionic liquid electrolytes in aluminum secondary batteries.
  • the imidazolium salt when mixed with aluminum chloride, forms an ionic liquid containing redox-active chloroaluminate ions (AlCl 4- , Al 2 Cl 7- , etc.).
  • Non-Patent Document 1 reports an aluminum / chlorine storage battery using an aluminum negative electrode, a graphite positive electrode, and an AlCl 3 / 1,2-dimethyl-3-propylimidazolium chloride electrolyte.
  • Patent Document 2 reports an aluminum ion storage battery using an aluminum negative electrode, a graphite electrode, and an AlCl 3 / 1-ethyl-3-methylimidazolium chloride electrolyte.
  • the theoretical operating potential (precipitation dissolution potential) of aluminum is -1.66V.
  • the operating potential of aluminum is larger than the theoretical potential and is on the positive potential side. be. Then, if the operating potential of aluminum can be shifted to the negative potential side, it is considered that the aluminum battery can be operated at a higher voltage.
  • an object of the present invention is to provide an electrolyte capable of shifting the operating potential of aluminum to the negative potential side, and an aluminum secondary battery using the electrolyte.
  • an ionic conductive material containing a room temperature molten salt obtained by mixing an aliphatic onium halide containing an ether group and an aluminum halide shifts the working potential of aluminum to the negative potential side.
  • the ionic conductive material can shift the working potential of aluminum to a potential closer to the theoretical potential.
  • the present invention has been completed by further studies based on this finding.
  • Item 1 An electrolyte for an aluminum secondary battery, which is an ionic conductive material containing a room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide.
  • Item 2. The ether group-containing aliphatic onium halide has the following formula (I): (In formula (I), A represents nitrogen or phosphorus; R 1 and R 2 are alkyl groups having 1 to 6 carbon atoms which may be the same or different from each other, and 3 to 6 carbon atoms in which they are linked to each other.
  • the electrolyte for an aluminum secondary battery according to Item 1.
  • the ether group-containing group is an alkoxy group, an alkyl group substituted with one or more alkoxy groups, a polyoxyalkylene group, an aliphatic cyclic ether group, and an alkyl group substituted with one or more aliphatic cyclic ether groups.
  • the electrolyte for an aluminum secondary battery selected from the group consisting of. Item 4.
  • the ether group-containing group is an alkoxy group having 1 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms substituted with one or a plurality of alkoxy groups having 1 to 6 carbon atoms, and an addition number of alkylene oxides of 2 to 6 to 6.
  • Item 2. Aluminum according to Item 2 or 3, which is selected from the group consisting of an alkyl group having 1 to 6 carbon atoms substituted with a polyoxyalkylene group, an aliphatic cyclic ether group, and one or a plurality of aliphatic cyclic ether groups. Electrolyte for secondary batteries.
  • Item 6. The electrolyte for an aluminum secondary battery according to any one of Items 1 to 5, wherein the ether group-containing aliphatic onium halide contains a plurality of the ether groups.
  • the ether group-containing onium halide is N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium chloride or 2-methoxyethoxyethyltrimethylammonium chloride, and the aluminum halide is aluminum chloride.
  • Item 8. Item 2.
  • An aluminum secondary battery comprising the electrolyte for an aluminum secondary battery according to any one of Items 1 to 9.
  • an electrolyte capable of shifting the operating potential of aluminum to the negative potential side and an aluminum secondary battery using the electrolyte are provided.
  • the charge / discharge measurement result of the aluminum secondary battery using the room temperature molten salt of Comparative Example 1 is shown.
  • the charge / discharge measurement result of the aluminum secondary battery using the room temperature molten salt of Example 1 is shown.
  • the electrolyte for aluminum secondary battery of the present invention is an ionic conductive material containing a room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide.
  • Room temperature molten salt The ether group-containing aliphatic onium halide and aluminum halide are solid at room temperature by themselves. However, when these solid salts are mixed with each other, they become a liquid, that is, a room temperature molten salt.
  • the room temperature molten salt refers to a salt that is in a molten state at 100 ° C. or lower, preferably 50 ° C. or lower, more preferably 40 ° C. or lower.
  • the lower limit of the temperature at which the molten salt at room temperature exhibits a molten state is not particularly limited, and a lower temperature is preferable, and examples thereof include ⁇ 40 ° C. and higher or ⁇ 20 ° C. or higher.
  • This room temperature molten salt is capable of ion conduction at room temperature, has excellent oxidation resistance because it does not substantially generate free chloride ions in the battery, and the ether group-containing aliphatic onium cation is stable in the reduction reaction. Not only does it have a wide potential window, but it also exerts a unique electrochemical characteristic effect of shifting the aluminum working potential to the negative potential side.
  • the ether group-containing aliphatic onium halide may be a salt of an onium cation having an acyclic or cyclic non-aromatic hydrocarbon group containing an ether group and a halogen anion.
  • Aliphatic onium halides are room temperature solid salts.
  • the room temperature solid salt refers to a salt that is in a solid state at 40 ° C. or lower.
  • the ether group-containing aliphatic onium halide includes a salt represented by the following general formula (I).
  • the central element A represents nitrogen (N) or phosphorus (P), and preferably represents nitrogen.
  • R 1 and R 2 are alkyl groups having 1 to 6, preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2 carbon atoms which may be the same or different from each other; carbons in which they are linked to each other.
  • An alkylene group having a number of 3 to 6, preferably 4 to 5 that is, a divalent group represented by ⁇ R1 ⁇ R2 -is an alkylene group having 3 to 6 carbon atoms, preferably 4 to 5 carbon atoms); or ether. Represents a group-containing group.
  • an ether group-containing group is preferable from the viewpoint of shifting the working potential of the negative electrode to the negative potential side more, but among the groups other than the ether group-containing group, R 1 and R 2 may be the same or different. It is preferably an alkyl group having a good carbon number of 1 to 6, preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2.
  • R 3 represents an alkyl group having 1 to 6, preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2 carbon atoms; or an ether group-containing group.
  • R 4 represents an ether group-containing group.
  • the above-mentioned ether group-containing group was substituted with an alkoxy group, an alkyl group substituted with one or more alkoxy groups, a polyoxyalkylene group, an aliphatic cyclic ether group, and one or more aliphatic cyclic ether groups.
  • Examples thereof include alkyl groups
  • the salt represented by the general formula (I) contains one or more ether group-containing groups.
  • the ether group-containing aliphatic onium halide preferably contains a plurality of ether groups. Therefore, from the viewpoint of shifting the operating potential of the negative electrode to the negative potential side more greatly, the salt represented by the general formula (I) preferably contains a plurality of ether group-containing groups.
  • the number of carbon atoms of the alkoxy group and the alkyl group substituted with one or more alkoxy groups is not particularly limited, but for example, an alkoxy group having 1 to 6 carbon atoms and one or more carbon atoms. Examples thereof include an alkyl group having 1 to 6 carbon atoms substituted with an alkoxy group having the number 1 to 6. Specifically, these groups are represented by the following formula (II).
  • R 41 represents a sigma bond or an alkylene group having 1 to 6 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 2 to 4 carbon atoms, and further preferably 2 to 3 alkylene groups.
  • R 42 represents an alkyl group having 1 to 6, preferably 1 to 4, and more preferably 1 to 2 carbon atoms.
  • n represents an integer from 1 to 13. When n is 2 to 13, the 2 to 13 R 42s may be the same or different from each other.
  • the alkoxy group-OR 42 may be bonded to any of the carbons constituting the alkylene group, but it is represented by the following formula (II-1). As shown, it is preferred that at least one of the alkoxy groups-OR 42 is attached to the terminal carbon farthest from the central element A in the alkylene group.
  • -R 411 -R 412- corresponds to -R 41 -of the above formula (II), and R 411 has 1 to 5, more preferably 1 to 3, and even more preferably 1 to 3 carbon atoms. It represents 1 to 2 alkylene groups and R 412 represents a methylene group. m represents an integer of 1 to 3, preferably 2 to 3. R 42 and n are as described above.
  • the number of alkylene oxides added in one polyoxyalkylene group is not particularly limited, and examples thereof include 2 to 6.
  • the aliphatic cyclic ether group is not particularly limited, and for example, an unsubstituted or substituted ethylene oxide group, an oxetane group, a tetrahydrofuran group, a tetrahydropyran group, an oxepane group, a 1,4-dioxane group and the like can be used. Can be mentioned.
  • Examples of the substituent of these aliphatic cyclic ether groups include alkyl groups having 1 to 5, more preferably 1 to 3, and even more preferably 1 to 2.
  • the carbon number of the alkyl group substituted with the aliphatic cyclic ether group is not particularly limited, and examples thereof include an alkyl group having 1 to 6 carbon atoms substituted with the aliphatic cyclic ether group. .. Further, the aliphatic cyclic ether group which is a substituent of the alkyl group is the same as described above. The position of the alkyl group having 1 to 6 carbon atoms in which the aliphatic cyclic ether group is substituted is not particularly limited.
  • X represents a halogen atom, specifically, represents fluorine, chlorine, bromine, and iodine, preferably chlorine and bromine, and more preferably chlorine.
  • Examples of preferable ether group-containing aliphatic onium halides include salts represented by the following (a) to (c).
  • ether group-containing aliphatic onium halide examples include N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium chloride (DEMEL; (a) ammonium chloride), 2-.
  • DEMEL N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium chloride
  • 2- examples thereof include methoxyethoxyethyltrimethylammonium chloride (2METMACl; ammonium chloride of (b)) and N- (2-methoxyethyl) -N-methylpyrrolidinium chloride (MEMPCl; pyrrolidium chloride of (c)).
  • the ether group-containing aliphatic onium halide shown in (a) and (b) is preferable, and the ether group-containing aliphatic onium halide shown in (b) is more preferable.
  • the above-mentioned ether group-containing aliphatic onium halide may be used alone or in combination of two or more.
  • the aluminum halide is not particularly limited as long as it is a salt that is solid at room temperature.
  • examples of the aluminum halide include fluoride, chloride, bromide, and iodide of aluminum.
  • the aluminum halides used in the present invention may be used alone or in combination of two or more having different halogens. Among these halides, chloride is preferable.
  • the halogens constituting both salts may be the same or different, but are, for example, more than the ether group-containing aliphatic onium chloride. It is preferable that the halogens constituting both salts are the same so as to be combined with the valent metal chloride.
  • Particularly preferred combinations of ether group-containing aliphatic onium halides and polyvalent metal halides include a combination of DEMECl and aluminum chloride; a combination of 2METMACl and aluminum chloride.
  • the composition molar ratio (halogen atom / aluminum atom) of the halogen atom to the aluminum atom is preferably 4 or less, and the negative electrode has a negative electrode. From the viewpoint of shifting the working potential to the negative potential side more, 3.7 or less is more preferable.
  • the lower limit of the range of the constituent molar ratio of the halogen atom / aluminum atom is not particularly limited, but is, for example, 3 or more, preferably 3.3 or more, more preferably 3.4 or more, still more preferably 3.5 or more, still more preferably. 3.6 and above can be mentioned.
  • a room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide is obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide.
  • it is obtained by adding an aluminum halide to a heated molten salt of an ether group-containing aliphatic onium halide and cooling to room temperature.
  • the ether group-containing aliphatic onium halide and the aluminum halide used as raw materials can be used in an amount such that the halogen atom / aluminum atom ratio is within the above range, respectively.
  • the molten metal salt contains a complex ion represented by AlX n- ( X is a halogen and n is a number exceeding the valence of M) as a halogenated complex anion that contributes to the precipitation and dissolution reaction of aluminum.
  • the plurality of Xs contained in one halogenated complex anion are one type based on the types of halogen atoms contained in the ether group-containing aliphatic onium halide and the aluminum halide used in the molten metal salt.
  • the halogen atom may be composed of a single halogen atom, or may be composed of two or more kinds of halogen atoms.
  • the molten metal salt may contain one kind of halogenated complex anion, or may contain two or more kinds of halogenated complex anions having different halogen atoms and / or compositions.
  • examples of the halogenated complex anion include Al 3 X 10 ⁇ , Al 2 X 7 ⁇ , Al X 4 ⁇ , and the like, preferably Al 2 X 7 ⁇ .
  • the electrolyte for an aluminum secondary battery of the present invention may contain other components in addition to the above-mentioned room temperature molten salt.
  • another ionic liquid (normal temperature molten salt) may be contained for the purpose of adjusting the viscosity of the electrolyte (for example, reducing the viscosity).
  • the cation constituting the other ionic liquid is not particularly limited, but in view of the electrochemical properties, the above-mentioned ether group-containing aliphatic onium is preferable.
  • the anion constituting another ionic liquid is not particularly limited, and is appropriately selected from the viewpoint of lowering the dissolution temperature of the salt and / or promoting ion diffusion. For example, BF 4- , BF 3 CF.
  • oxygen-containing anions namely CF 3 CO 2- , CF 3 SO 3- , C 2 F 5 SO 3- , C 3 F 7 SO 3 , C 4 F 9 SO 3- , (FSO 2 ).
  • FSA- FSO 2 NSO 2 CF 3-
  • FTA- FSO 2 N
  • CF 3 SO 2 N 2 N- ( TFSA- )
  • CF 2 SO 2 NSO 2 nC 4 F 9 (C 1 C 4- )
  • the electrolyte for an aluminum secondary battery of the present invention contains other components
  • the electrolyte is prepared by mixing an ether group-containing aliphatic onium halide and an aluminum halide to prepare a room temperature molten salt, and then melting at room temperature. It is prepared by diluting the salt with the other components.
  • the room temperature molten salt obtained by mixing the above-mentioned ether group-containing aliphatic onium halide and aluminum halide shows a good molten state at a temperature under a normal battery usage environment and is extremely excellent in electrochemical properties. Therefore, the electrolyte of the present invention does not have to contain these other components. From the viewpoint of shifting the operating potential of the negative electrode to the negative potential side more, it is preferable that the electrolyte of the present invention does not contain other components.
  • the aluminum secondary battery of the present invention is configured to include the above-mentioned electrolyte for the aluminum secondary battery of the present invention.
  • the specific form of the aluminum secondary battery of the present invention includes a negative electrode and a positive electrode and the above-mentioned electrolyte of the present invention, and is a one-component type (that is, a form in which the above-mentioned electrolyte of the present invention is in contact with both electrodes). The limit is not particularly limited.
  • Negative electrode The negative electrode is not particularly limited as long as it contains aluminum and contains a negative electrode active material capable of repeating an oxidation / reduction reaction.
  • examples of the negative electrode active material of the aluminum secondary battery include metallic aluminum capable of repeating precipitation and melting of aluminum; and aluminum alloy capable of repeating dealloying and alloying reactions of aluminum ions.
  • examples of the aluminum alloy include an alloy of at least one of Si, Mn, Cr, Ni, Cu, and Mg and aluminum.
  • the negative electrode may be composed of only the above-mentioned negative electrode active material, or may be composed of the above-mentioned negative electrode active material supported on a current collector.
  • the current collector include metals such as stainless steel, aluminum foil, nickel foil, and copper foil.
  • a polarizable electrode having a high specific surface area can be used.
  • the active material of the depolarizing electrode include carbon.
  • the carbon is not particularly limited, but is preferably sp 2 type such as graphite (natural graphite / artificial graphite (KS6, KS6L, SFG6, SFG6L), etc.), graphene, fullerene (carbon nanotube, carbon nanohorn, buckminsterfullerene, etc.). Carbon is mentioned.
  • the specific form of the positive electrode is not particularly limited, and is not particularly limited as long as it contains the above-mentioned active material, and may be composed only of the above-mentioned active material. It may be composed of a mixture of a coating agent and / or a thickener, or may be composed of an active substance or a mixture supported on a current collector.
  • the form of the active material includes a woven fabric or a non-woven fabric.
  • Examples of the conductive auxiliary agent include carbons such as carbon black, acetylene black, and Ketjen black, graphite, and metals.
  • Examples of the binder include polymers such as polyvinylidene fluoride, styrene-butadiene rubber, and polytetrafluoroethylene.
  • Examples of the thickener include carboxymethyl cellulose and ethylene glycol.
  • Examples of the current collector include platinum foil, molybdenum foil, nickel foil, copper foil and the like.
  • a separator installed between the positive electrode and the negative electrode to prevent a short circuit between both electrodes, a battery container, and the like.
  • the material of the separator include glass fiber, fluoropolymer, polyethylene, polypropylene and the like.
  • a known exterior material such as a metal can or a laminated pouch can be used in a shape corresponding to the shape of the battery (cylindrical type, coin type, button type, laminated type, etc.).
  • Test Example 1 A room temperature molten salt obtained by mixing aluminum precipitation dissolution potential RCl and AlCl 3 in a room temperature molten salt at a molar ratio of 2: 3 (molar ratio of chlorine atom to aluminum atom is 11/3). And a room temperature molten salt obtained by mixing RCl and AlCl 3 at a molar ratio of 1: 2 (molar ratio of chlorine atom to aluminum atom is 7/2) were prepared.
  • iodine redox [1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide with 60 mM tetrapropylammonium iodide and 15 mM iodine dissolved] in a room temperature molten salt.
  • a reference electrode (hereinafter simply referred to as an iodine redox reference electrode) in which a platinum wire is immersed in a glass tube partitioned by porous glass is immersed, and the potential of the aluminum ribbon (E (Al vs I- / I)) 3- ) .) was measured.
  • the measured potential of the aluminum ribbon was converted into a potential with respect to the standard electrode potential of aluminum based on the following formula, and the precipitation and dissolution potential of aluminum was determined.
  • the redox potential of ferrocene is the oxidation of ferrocene obtained by dissolving ferrocene in each room temperature molten salt at about 50 mM and cyclic voltammetry using a glassy carbon electrode (reference electrode: iodine redox reference electrode, counter electrode: aluminum ribbon). Obtained from the reduction peak.
  • the redox potential of ferrocene based on the SHE (standard hydrogen electrode) is 0.400V vs. SHE (R.R.Gagne, C.A.Koval, and G.C.Lisensky, Inorg.Chem., 19, 2854. (1980)).
  • the standard electrode potential of aluminum is -1.67V vs SHE (S. Trasatti, Pure & Appl. Chem., 58 (7), 955 (1986).).
  • Table 1 shows the results of determining the precipitation and dissolution potential of aluminum in each room temperature molten salt.
  • Test Example 2 Commercially available graphite electrode (5 mm square) as the working potential acting electrode of the positive and negative electrodes in an aluminum battery , aluminum foil (5 mm square) as the counter electrode, and a glass tube whose tip is partitioned by porous bicol glass as the reference electrode.
  • a reference electrode in which an ionic liquid containing iodine redox is placed and a platinum wire is immersed in it, and an electrochemical analyzer (Bio-logic VMP3) capable of simultaneously recording the potential of counter electrode aluminum, the potential of the working electrode when a constant current is applied. The measurement was performed.
  • FIG. 1 shows the measurement result of the room temperature molten salt of Comparative Example 1
  • Example 2 shows the measurement result of the room temperature molten salt of Example 1 (both have a molar ratio of RCl and AlCl 3 of 2: 3, that is, chlorine with respect to aluminum atoms.
  • the measurement result of the room temperature molten salt prepared by mixing so that the molar ratio of atoms becomes 11/3) is shown.
  • the broken line indicates the graphite positive electrode potential
  • the solid line indicates the aluminum negative electrode potential.
  • FIGS. 1 and 2 in the room temperature molten salt of Comparative Example 1 and Example 1, the graphite positive electrode was charged and discharged at around 3.5 V based on the standard potential of aluminum, whereas FIG. 1 shows.
  • the aluminum negative electrode operates at around 1.7 V in the room temperature molten salt of Comparative Example 1
  • the aluminum negative electrode operates at around 1.2 V in the room temperature molten salt of Example 1 as shown in FIG.
  • the working potential was almost the same as the immersion potential of aluminum shown in Table 1. That is, even during battery operation, only changing the cation of the room temperature molten salt of Comparative Example 1 to an ether group-containing aliphatic onium is shown in FIG. 2 (Example 1), which is compared with FIG.
  • the precipitation and dissolution potential of aluminum can be shifted to the negative potential side by using an aliphatic cation species containing an ether group as the ionic liquid used for the electrolyte of the aluminum secondary battery.
  • the precipitation and dissolution potential of aluminum can be shifted to the negative potential side by about 0.5V, so that the operating voltage of the aluminum secondary battery combined with the graphite positive electrode using this ionic liquid as an electrolyte is improved by 0.5V or more. be able to. Therefore, it is possible to charge / discharge the aluminum secondary battery close to 3V.

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Abstract

The present invention provides: an electrolyte which is capable of shifting the operating potential of aluminum to the more negative direction; and an aluminum secondary battery which uses this electrolyte. An electrolyte for aluminum secondary batteries, said electrolyte being an ion conductive material which contains a room temperature molten salt that is obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide, is able to shift the operating potential of aluminum to the more negative direction.

Description

アルミニウム二次電池用電解質及びアルミニウム二次電池Electrolytes for aluminum secondary batteries and aluminum secondary batteries
　本発明は、アルミニウム二次電池用電解質及びアルミニウム二次電池に関する。 The present invention relates to an electrolyte for an aluminum secondary battery and an aluminum secondary battery.
　近年、エネルギーデバイスの開発はますます盛んに行われており、二次電池の分野においては、高容量、高出力、安全性、耐久性、原料の低コスト化等の観点で開発が進められている。例えば、最も普及しているリチウム二次電池がレアメタルであるリチウムを電極原料とする一方で、原料の低コスト化の観点から、電極を、ナトリウム、マグネシウム、アルミニウム、亜鉛等の汎用金属で代替する電池の研究も行われている。 In recent years, the development of energy devices has been actively carried out, and in the field of secondary batteries, development has been promoted from the viewpoints of high capacity, high output, safety, durability, cost reduction of raw materials, etc. There is. For example, while the most popular lithium secondary battery uses lithium, which is a rare metal, as an electrode raw material, the electrode is replaced with a general-purpose metal such as sodium, magnesium, aluminum, and zinc from the viewpoint of reducing the cost of the raw material. Batteries are also being researched.
　汎用金属を用いた二次電池の中でも３価イオンを利用するアルミニウム二次電池は、３電子レドックス特性による単位体積当たりの高い容量密度が期待されている。しかしながら、アルミニウム二次電池は技術的なハードルが非常に高く、研究例は限られている。アルミニウム二次電池の技術的課題の１つとして、金属アルミニウムを可逆的に析出及び溶解可能な電解質を開発することが挙げられる。 Among secondary batteries using general-purpose metals, aluminum secondary batteries that use trivalent ions are expected to have a high capacity density per unit volume due to their 3-electron redox characteristics. However, aluminum secondary batteries have very high technical hurdles, and research examples are limited. One of the technical issues of the aluminum secondary battery is to develop an electrolyte capable of reversibly precipitating and dissolving metallic aluminum.
　二次電池の電解質には揮発性及び引火性の有機溶媒を用いた電解液が用いられる一方で、安全性及び耐久性等の観点から、イオン液体やグライム錯体といった無溶媒液体に代替する研究が行われている。無溶媒液体は有機溶媒を用いた通常の電解液とは異なる電気化学的挙動を示すため、無溶媒液体中の電気化学的挙動を明らかにする研究も行われている。アルミニウム二次電池についても、電解質としてイオン液体の適用を試みる研究がなされている。 While an electrolytic solution using a volatile and flammable organic solvent is used as the electrolyte of the secondary battery, research is being conducted to replace it with a solventless liquid such as an ionic liquid or a glyme complex from the viewpoint of safety and durability. It is done. Since the solvent-free liquid exhibits an electrochemical behavior different from that of a normal electrolytic solution using an organic solvent, studies are being conducted to clarify the electrochemical behavior in the solvent-free liquid. Research is also being conducted on aluminum secondary batteries to try to apply ionic liquids as electrolytes.
　これまでの研究で、イミダゾリウム塩が、アルミニウム二次電池のイオン液体電解液を形成するために使用できることが示されてきた。イミダゾリウム塩は、塩化アルミニウムとの混合により、酸化還元活性なクロロアルミン酸イオン（ＡｌＣｌ4 -、Ａｌ2Ｃｌ7 -等）を含むイオン液体を形成する。 Previous studies have shown that imidazolium salts can be used to form ionic liquid electrolytes in aluminum secondary batteries. The imidazolium salt, when mixed with aluminum chloride, forms an ionic liquid containing redox-active chloroaluminate ions (AlCl 4- , Al 2 Cl 7- , etc.).
　具体的な研究例として、非特許文献１に、アルミニウム負極、黒鉛正極、及びＡｌＣｌ3／１，２－ジメチル－３－プロピルイミダゾリウムクロライド電解質を用いたアルミニウム／塩素蓄電池が報告されており、非特許文献２に、アルミニウム負極、黒鉛電極、及びＡｌＣｌ3／１－エチル－３－メチルイミダゾリウムクロライド電解質を用いたアルミニウムイオン蓄電池が報告されている。 As a specific research example, Non-Patent Document 1 reports an aluminum / chlorine storage battery using an aluminum negative electrode, a graphite positive electrode, and an AlCl 3 / 1,2-dimethyl-3-propylimidazolium chloride electrolyte. Patent Document 2 reports an aluminum ion storage battery using an aluminum negative electrode, a graphite electrode, and an AlCl 3 / 1-ethyl-3-methylimidazolium chloride electrolyte.
　アルミニウムの理論的な作動電位（析出溶解電位）は、－１．６６Ｖである。一方、これまで報告されているアルミニウム二次電池について、３電極式セルを用いたアルミニウム析出時の負極の電極電位の挙動を調べると、アルミニウムの作動電位は、理論電位よりも大きく正電位側にある。そうすると、アルミニウムの作動電位を負電位側にシフトさせることができれば、アルミニウム電池をより高電圧で作動させることができると考えられる。 The theoretical operating potential (precipitation dissolution potential) of aluminum is -1.66V. On the other hand, regarding the aluminum secondary batteries reported so far, when the behavior of the electrode potential of the negative electrode at the time of aluminum precipitation using a three-electrode cell is investigated, the operating potential of aluminum is larger than the theoretical potential and is on the positive potential side. be. Then, if the operating potential of aluminum can be shifted to the negative potential side, it is considered that the aluminum battery can be operated at a higher voltage.
　しかしながら、一般的に負極金属の作動電位を負電位側にシフトさせる手段についてはこれまで知られていない。また、仮に電解質の組成を変化させるとしても、それが負極金属の作動電位にどのように影響するかも知られていない。 However, generally, a means for shifting the operating potential of the negative electrode metal to the negative potential side has not been known so far. Further, even if the composition of the electrolyte is changed, it is not known how it affects the operating potential of the negative electrode metal.
　そこで、本発明は、アルミニウムの作動電位を負電位側にシフトさせることができる電解質、及び当該電解質を用いたアルミニウム二次電池を提供することを目的とする。 Therefore, an object of the present invention is to provide an electrolyte capable of shifting the operating potential of aluminum to the negative potential side, and an aluminum secondary battery using the electrolyte.
　本発明者が鋭意検討した結果、エーテル基を含有する脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との混合による常温溶融塩を含むイオン伝導材が、アルミニウムの作動電位を負電位側にシフトさせることができることを見出した。具体的には、当該イオン伝導材が、アルミニウムの作動電位を理論電位により近い電位までシフトさせることができることを見出した。本発明は、この知見に基づいてさらに検討を重ねることにより完成したものである。 As a result of diligent studies by the present inventor, it is possible that an ionic conductive material containing a room temperature molten salt obtained by mixing an aliphatic onium halide containing an ether group and an aluminum halide shifts the working potential of aluminum to the negative potential side. I found out what I could do. Specifically, it has been found that the ionic conductive material can shift the working potential of aluminum to a potential closer to the theoretical potential. The present invention has been completed by further studies based on this finding.
　即ち、本発明は、下記に掲げる態様の発明を提供する。
項１．　エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との混合による常温溶融塩を含むイオン伝導材である、アルミニウム二次電池用電解質。
項２．　前記エーテル基含有脂肪族オニウムハロゲン化物が、下記式（Ｉ）：
Figure JPOXMLDOC01-appb-I000002
（式（Ｉ）中、Ａは、窒素又はリンを表し；Ｒ1及びＲ2は、互いに同じ又は異なっていてもよい炭素数１～６のアルキル基、それらが互いに連結した炭素数３～６のアルキレン基、若しくはエーテル基含有基を表し；Ｒ3は、炭素数１～６のアルキル基又はエーテル基含有基を表し；Ｒ4は、エーテル基含有基を表し、Ｘはハロゲン原子を表す。）で表される、項１に記載のアルミニウム二次電池用電解質。
項３．　前記エーテル基含有基が、アルコキシ基、１又は複数のアルコキシ基で置換されたアルキル基、ポリオキシアルキレン基、脂肪族環状エーテル基、及び１又は複数の脂肪族環状エーテル基で置換されたアルキル基からなる群より選択される、項２に記載のアルミニウム二次電池用電解質。
項４．　前記エーテル基含有基が、炭素数１～６のアルコキシ基、１又は複数の炭素数１～６のアルコキシ基で置換された炭素数１～６のアルキル基、アルキレンオキサイドの付加数が２～６のポリオキシアルキレン基、脂肪族環状エーテル基、及び１又は複数の脂肪族環状エーテル基で置換された炭素数１～６のアルキル基からなる群より選択される、項２又は３に記載のアルミニウム二次電池用電解質。
項５．　前記アルミニウムハロゲン化物が、塩化アルミニウムである、項１～４のいずれかに記載のアルミニウム二次電池用電解質。
項６．　前記エーテル基含有脂肪族オニウムハロゲン化物が、前記エーテル基を複数含む、項１～５のいずれかに記載のアルミニウム二次電池用電解質。
項７．　前記エーテル基含有オニウムハロゲン化物が、Ｎ，Ｎ－ジエチル－Ｎ－メチル－Ｎ－（２－メトキシエチル）アンモニウムクロリド又は２－メトキシエトキシエチルトリメチルアンモニウムクロリドであり、前記アルミニウムハロゲン化物が塩化アルミニウムである、項１～５のいずれかに記載のアルミニウム二次電池用電解質。
項８．　前記常温溶融塩におけるアルミニウム原子に対するハロゲン原子の構成モル比が４以下である、項１～７のいずれかに記載のアルミニウム二次電池用電解質。
項９．　前記常温溶融塩におけるアルミニウム原子に対するハロゲン原子の構成モル比が３以上である、項１～８のいずれかに記載のアルミニウム二次電池用電解質。
項１０．　項１～９のいずれかに記載のアルミニウム二次電池用電解質を含む、アルミニウム二次電池。 That is, the present invention provides the inventions of the following aspects.
Item 1. An electrolyte for an aluminum secondary battery, which is an ionic conductive material containing a room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide.
Item 2. The ether group-containing aliphatic onium halide has the following formula (I):
Figure JPOXMLDOC01-appb-I000002
(In formula (I), A represents nitrogen or phosphorus; R 1 and R 2 are alkyl groups having 1 to 6 carbon atoms which may be the same or different from each other, and 3 to 6 carbon atoms in which they are linked to each other. Represents an alkylene group or an ether group-containing group; R 3 represents an alkyl group or an ether group-containing group having 1 to 6 carbon atoms; R 4 represents an ether group-containing group, and X represents a halogen atom. ), The electrolyte for an aluminum secondary battery according to Item 1.
Item 3. The ether group-containing group is an alkoxy group, an alkyl group substituted with one or more alkoxy groups, a polyoxyalkylene group, an aliphatic cyclic ether group, and an alkyl group substituted with one or more aliphatic cyclic ether groups. Item 2. The electrolyte for an aluminum secondary battery selected from the group consisting of.
Item 4. The ether group-containing group is an alkoxy group having 1 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms substituted with one or a plurality of alkoxy groups having 1 to 6 carbon atoms, and an addition number of alkylene oxides of 2 to 6 to 6. Item 2. Aluminum according to Item 2 or 3, which is selected from the group consisting of an alkyl group having 1 to 6 carbon atoms substituted with a polyoxyalkylene group, an aliphatic cyclic ether group, and one or a plurality of aliphatic cyclic ether groups. Electrolyte for secondary batteries.
Item 5. Item 2. The electrolyte for an aluminum secondary battery according to any one of Items 1 to 4, wherein the aluminum halide is aluminum chloride.
Item 6. Item 6. The electrolyte for an aluminum secondary battery according to any one of Items 1 to 5, wherein the ether group-containing aliphatic onium halide contains a plurality of the ether groups.
Item 7. The ether group-containing onium halide is N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium chloride or 2-methoxyethoxyethyltrimethylammonium chloride, and the aluminum halide is aluminum chloride. , The electrolyte for an aluminum secondary battery according to any one of Items 1 to 5.
Item 8. Item 2. The electrolyte for an aluminum secondary battery according to any one of Items 1 to 7, wherein the composition molar ratio of the halogen atom to the aluminum atom in the room temperature molten salt is 4 or less.
Item 9. Item 2. The electrolyte for an aluminum secondary battery according to any one of Items 1 to 8, wherein the composition molar ratio of the halogen atom to the aluminum atom in the room temperature molten salt is 3 or more.
Item 10. An aluminum secondary battery comprising the electrolyte for an aluminum secondary battery according to any one of Items 1 to 9.
　本発明によれば、アルミニウムの作動電位を負電位側にシフトさせることができる電解質、及び当該電解質を用いたアルミニウム二次電池が提供される。 According to the present invention, an electrolyte capable of shifting the operating potential of aluminum to the negative potential side and an aluminum secondary battery using the electrolyte are provided.
比較例１の常温溶融塩を用いたアルミニウム二次電池の充放電測定結果を示す。The charge / discharge measurement result of the aluminum secondary battery using the room temperature molten salt of Comparative Example 1 is shown. 実施例１の常温溶融塩を用いたアルミニウム二次電池の充放電測定結果を示す。The charge / discharge measurement result of the aluminum secondary battery using the room temperature molten salt of Example 1 is shown.
１．アルミニウム二次電池用電解質
　本発明のアルミニウム二次電池用電解質は、エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との混合による常温溶融塩を含むイオン伝導材である。 1. 1. Electrolyte for Aluminum Secondary Battery The electrolyte for aluminum secondary battery of the present invention is an ionic conductive material containing a room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide.
常温溶融塩
　エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物は、単独では常温で固体である。しかしながら、これら固体の塩を互いに混合すると液体つまり常温溶融塩になる。なお、本発明において、常温溶融塩は、１００℃以下、好ましくは５０℃以下、より好ましくは４０℃以下で溶融状態である塩をいう。常温溶融塩が溶融状態を呈する温度の下限としては特に限定されず、低いほど好ましいが、例えば-４０℃以上又は-２０℃以上が挙げられる。この常温溶融塩は、常温でイオン伝導が可能である点、電池においてフリーの塩化物イオンを実質的に生じないため酸化耐性に優れる点、及びエーテル基含有脂肪族オニウムカチオンが還元反応で安定であり電位窓が広い点だけでなく、アルミニウム作動電位を負電位側にシフトさせるという電気化学的特性上の特有の効果を発揮する。 Room temperature molten salt The ether group-containing aliphatic onium halide and aluminum halide are solid at room temperature by themselves. However, when these solid salts are mixed with each other, they become a liquid, that is, a room temperature molten salt. In the present invention, the room temperature molten salt refers to a salt that is in a molten state at 100 ° C. or lower, preferably 50 ° C. or lower, more preferably 40 ° C. or lower. The lower limit of the temperature at which the molten salt at room temperature exhibits a molten state is not particularly limited, and a lower temperature is preferable, and examples thereof include −40 ° C. and higher or −20 ° C. or higher. This room temperature molten salt is capable of ion conduction at room temperature, has excellent oxidation resistance because it does not substantially generate free chloride ions in the battery, and the ether group-containing aliphatic onium cation is stable in the reduction reaction. Not only does it have a wide potential window, but it also exerts a unique electrochemical characteristic effect of shifting the aluminum working potential to the negative potential side.
　エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物、又はエーテル基含有脂肪族オニウムハロゲン化物との混合による常温溶融塩がこのような特有の効果を発揮する理由としては定かではないが、次のように考えられる。そもそも、アルミニウムの析出溶解電位がアルミニウムの標準電位よりも正（貴）である理由は、アルミニウム析出反応が単純なＡｌ3+＋３ｅ-⇔Ａｌではなく、全く異なる反応式４Ａｌ2Ｃｌ7 -＋３ｅ-⇔Ａｌ＋７ＡｌＣｌ4 -で進行する点にある。このアルミニウム析出反応式は、実際には複数の素過程の総和となっている。その素過程で現れる中間体電極表面種については、P.K. Lai et al., Electrochimica Acta 32(10) 1443(1987)によると、Ａｌ2Ｃｌ7 -⇔［ＡｌＣｌ3・・・ＡｌＣｌ4 -］の右辺が報告されており、さらに、S. J. Ahn et al., Bull Korean Chem. Soc., 30(1)233(2009)によると、ＡｌＣｌ3が、電極上に吸着するＡｌ3+と３つのＣｌ-として存在しているモデルが報告されている。本発明で用いる常温溶融塩を構成するエーテル基含有脂肪族オニウムは、カチオンでありながらエーテル酸素が電子リッチであるため、電極表面のＡｌ3+と相互作用して安定化させることで、ＡｌＣｌ3の電極上でのＡｌ3+への解離を促進し、アルミニウムの析出溶解電位をアルミニウムの標準電位へ近づけていると考えられる。このため、エーテル基含有脂肪族オニウムに含まれているエーテル基の数の増大に応じて、電極表面のＡｌ3+がより安定化し、アルミニウム作動電位を負電位側にシフトさせる程度が大きくなる傾向となる。 The reason why the room temperature molten salt obtained by mixing the ether group-containing aliphatic onium halide and the aluminum halide or the ether group-containing aliphatic onium halide exerts such a peculiar effect is not clear, but is as follows. Can be considered. In the first place, the reason why the precipitation and dissolution potential of aluminum is more positive (noble) than the standard potential of aluminum is that the aluminum precipitation reaction is not a simple Al 3+ + 3e - ⇔Al, but a completely different reaction formula 4Al 2 Cl 7- + 3e- . ⇔ Al + 7AlCl 4 - is the point of progress. This aluminum precipitation reaction formula is actually the sum of a plurality of elementary processes. According to PK Lai et al., Electrochimica Acta 32 (10) 1443 (1987), the right side of Al 2 Cl 7 - ⇔ [AlCl 3 ... AlCl 4- ] for the intermediate electrode surface species that appear in the elementary process. Furthermore, according to S. J. Ahn et al., Bull Korean Chem. Soc., 30 (1) 233 (2009), AlCl 3 is adsorbed on the electrode as Al 3+ and three Cl- . Existing models have been reported. Although the ether group-containing aliphatic onium constituting the room temperature molten salt used in the present invention is a cation, the ether oxygen is electron-rich. Therefore, AlCl 3 is stabilized by interacting with Al 3+ on the electrode surface. It is considered that the dissociation into Al 3+ on the electrode is promoted and the precipitation and dissolution potential of aluminum is brought closer to the standard potential of aluminum. Therefore, as the number of ether groups contained in the ether group-containing aliphatic onium increases, Al 3+ on the electrode surface tends to be more stable, and the degree of shifting the aluminum working potential to the negative potential side tends to increase. Will be.
　エーテル基含有脂肪族オニウムハロゲン化物としては、エーテル基を含有する非環式又は環式の非芳香族性炭化水素基を有するオニウムカチオンとハロゲンアニオンとの塩であればよい。脂肪族オニウムハロゲン化物は常温固体塩である。なお、本発明において、常温固体塩は、４０℃以下で固体状態である塩をいう。好ましくは、エーテル基含有脂肪族オニウムハロゲン化物としては、下記一般式（I）で示される塩が挙げられる。 The ether group-containing aliphatic onium halide may be a salt of an onium cation having an acyclic or cyclic non-aromatic hydrocarbon group containing an ether group and a halogen anion. Aliphatic onium halides are room temperature solid salts. In the present invention, the room temperature solid salt refers to a salt that is in a solid state at 40 ° C. or lower. Preferably, the ether group-containing aliphatic onium halide includes a salt represented by the following general formula (I).
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
　上記式（I）中、中心元素Ａは、窒素（Ｎ）又はリン（Ｐ）を表し、好ましくは窒素を表す。Ｒ1及びＲ2は、互いに同じ又は異なっていてもよい炭素数１～６、好ましくは１～４、より好ましくは１～３、さらに好ましくは１～２のアルキル基；それらが互いに連結した炭素数３～６、好ましくは４～５のアルキレン基（つまり、－Ｒ1ーＲ2－で表される２価基が、炭素数３～６、好ましくは４～５のアルキレン基）；若しくはエーテル基含有基を表す。これらの中でも、負極の作動電位の負電位側へより大きくシフトさせる観点からはエーテル基含有基が好ましいが、エーテル基含有基以外の中では、Ｒ1及びＲ2は、同じ又は異なっていてもよい炭素数１～６、好ましくは１～４、より好ましくは１～３、さらに好ましくは１～２のアルキル基であることが好ましい。Ｒ3は、炭素数１～６、好ましくは１～４、より好ましくは１～３、さらに好ましくは１～２のアルキル基；又はエーテル基含有基を表す。Ｒ4は、エーテル基含有基を表す。 In the above formula (I), the central element A represents nitrogen (N) or phosphorus (P), and preferably represents nitrogen. R 1 and R 2 are alkyl groups having 1 to 6, preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2 carbon atoms which may be the same or different from each other; carbons in which they are linked to each other. An alkylene group having a number of 3 to 6, preferably 4 to 5 (that is, a divalent group represented by −R1 − R2 -is an alkylene group having 3 to 6 carbon atoms, preferably 4 to 5 carbon atoms); or ether. Represents a group-containing group. Among these, an ether group-containing group is preferable from the viewpoint of shifting the working potential of the negative electrode to the negative potential side more, but among the groups other than the ether group-containing group, R 1 and R 2 may be the same or different. It is preferably an alkyl group having a good carbon number of 1 to 6, preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. R 3 represents an alkyl group having 1 to 6, preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2 carbon atoms; or an ether group-containing group. R 4 represents an ether group-containing group.
　上記のエーテル基含有基としては、アルコキシ基、１又は複数のアルコキシ基で置換されたアルキル基、ポリオキシアルキレン基、脂肪族環状エーテル基、及び１又は複数の脂肪族環状エーテル基で置換されたアルキル基等が挙げられ、一般式（I）で示される塩は、これらの中から１又は複数のエーテル基含有基を含む。負極の作動電位の負電位側へより大きくシフトさせる観点からは、エーテル基含有脂肪族オニウムハロゲン化物は、複数のエーテル基を含むことが好ましい。従って、負極の作動電位の負電位側へより大きくシフトさせる観点からは、一般式（I）で示される塩は、複数のエーテル基含有基を含むことが好ましい。 The above-mentioned ether group-containing group was substituted with an alkoxy group, an alkyl group substituted with one or more alkoxy groups, a polyoxyalkylene group, an aliphatic cyclic ether group, and one or more aliphatic cyclic ether groups. Examples thereof include alkyl groups, and the salt represented by the general formula (I) contains one or more ether group-containing groups. From the viewpoint of shifting the operating potential of the negative electrode to the negative potential side more, the ether group-containing aliphatic onium halide preferably contains a plurality of ether groups. Therefore, from the viewpoint of shifting the operating potential of the negative electrode to the negative potential side more greatly, the salt represented by the general formula (I) preferably contains a plurality of ether group-containing groups.
　エーテル基含有基のうち、アルコキシ基、及び１又は複数のアルコキシ基で置換されたアルキル基の炭素数としては特に限定されないが、例えば、炭素数１～６のアルコキシ基、及び１又は複数の炭素数１～６のアルコキシ基で置換された炭素数１～６のアルキル基が挙げられる。これらの基は、具体的には下記式（II）で示される。 Among the ether group-containing groups, the number of carbon atoms of the alkoxy group and the alkyl group substituted with one or more alkoxy groups is not particularly limited, but for example, an alkoxy group having 1 to 6 carbon atoms and one or more carbon atoms. Examples thereof include an alkyl group having 1 to 6 carbon atoms substituted with an alkoxy group having the number 1 to 6. Specifically, these groups are represented by the following formula (II).
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
　上記式（II）中、Ｒ41は、シグマ結合又は炭素数１～６のアルキレン基を表し、好ましくは炭素数１～６、より好ましくは２～４、さらに好ましくは２～３のアルキレン基を表す。Ｒ42は、炭素数１～６、好ましくは１～４、より好ましくは１～２のアルキル基を表す。ｎは１～１３の整数を表す。なお、ｎが２～１３である場合、２個～１３個のＲ42は、互いに同じ又は異なっていてもよい。 In the above formula (II), R 41 represents a sigma bond or an alkylene group having 1 to 6 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 2 to 4 carbon atoms, and further preferably 2 to 3 alkylene groups. show. R 42 represents an alkyl group having 1 to 6, preferably 1 to 4, and more preferably 1 to 2 carbon atoms. n represents an integer from 1 to 13. When n is 2 to 13, the 2 to 13 R 42s may be the same or different from each other.
　Ｒ41が炭素数２以上のアルキレン基である場合、アルコキシ基－ＯＲ42は、当該アルキレン基を構成する炭素のうちいずれの炭素に結合していてもよいが、下記式（II－１）に示すように、少なくともいずれかのアルコキシ基－ＯＲ42が、当該アルキレン基において中心元素Ａから最も遠い末端の炭素に結合していることが好ましい。 When R 41 is an alkylene group having 2 or more carbon atoms, the alkoxy group-OR 42 may be bonded to any of the carbons constituting the alkylene group, but it is represented by the following formula (II-1). As shown, it is preferred that at least one of the alkoxy groups-OR 42 is attached to the terminal carbon farthest from the central element A in the alkylene group.
Figure JPOXMLDOC01-appb-C000005
Figure JPOXMLDOC01-appb-C000005
　上記式（II－１）中、－Ｒ411－Ｒ412－は上記式（II）の－Ｒ41－に該当し、Ｒ411は炭素数１～５、より好ましくは１～３、さらに好ましくは１～２のアルキレン基を表し、Ｒ412はメチレン基を表す。ｍは１～３、好ましくは２～３の整数を表す。Ｒ42及びｎについては上述した通りである。 In the above formula (II-1), -R 411 -R 412- corresponds to -R 41 -of the above formula (II), and R 411 has 1 to 5, more preferably 1 to 3, and even more preferably 1 to 3 carbon atoms. It represents 1 to 2 alkylene groups and R 412 represents a methylene group. m represents an integer of 1 to 3, preferably 2 to 3. R 42 and n are as described above.
　エーテル基含有基のうち、１個のポリオキシアルキレン基におけるアルキレンオキサイドの付加数としては特に限定されないが、例えば２～６が挙げられる。 Among the ether group-containing groups, the number of alkylene oxides added in one polyoxyalkylene group is not particularly limited, and examples thereof include 2 to 6.
　エーテル基含有基のうち、脂肪族環状エーテル基としては特に限定されないが、例えば、無置換又は置換のエチレンオキサイド基、オキセタン基、テトラヒドロフラン基、テトラヒドロピラン基、オキセパン基、１，４ージオキサン基等が挙げられる。これらの脂肪族環状エーテル基の置換基としては、炭素数１～５、より好ましくは１～３、さらに好ましくは１～２のアルキル基が挙げられる。 Among the ether group-containing groups, the aliphatic cyclic ether group is not particularly limited, and for example, an unsubstituted or substituted ethylene oxide group, an oxetane group, a tetrahydrofuran group, a tetrahydropyran group, an oxepane group, a 1,4-dioxane group and the like can be used. Can be mentioned. Examples of the substituent of these aliphatic cyclic ether groups include alkyl groups having 1 to 5, more preferably 1 to 3, and even more preferably 1 to 2.
　エーテル基含有基のうち、脂肪族環状エーテル基で置換されたアルキル基の炭素数としては特に限定されないが、例えば、脂肪族環状エーテル基で置換された炭素数１～６のアルキル基が挙げられる。また、当該アルキル基の置換基である脂肪族環状エーテル基については上述と同じである。脂肪族環状エーテル基が置換される炭素数１～６のアルキル基の位置としては特に限定されない。 Among the ether group-containing groups, the carbon number of the alkyl group substituted with the aliphatic cyclic ether group is not particularly limited, and examples thereof include an alkyl group having 1 to 6 carbon atoms substituted with the aliphatic cyclic ether group. .. Further, the aliphatic cyclic ether group which is a substituent of the alkyl group is the same as described above. The position of the alkyl group having 1 to 6 carbon atoms in which the aliphatic cyclic ether group is substituted is not particularly limited.
　上記式（I）中、Ｘは、ハロゲン原子を表し、具体的には、フッ素、塩素、臭素、ヨウ素を表し、好ましくは塩素、臭素を表し、より好ましくは塩素を表す。 In the above formula (I), X represents a halogen atom, specifically, represents fluorine, chlorine, bromine, and iodine, preferably chlorine and bromine, and more preferably chlorine.
　好ましいエーテル基含有脂肪族オニウムハロゲン化物の例としては、以下の（ａ）～（ｃ）で表される塩が挙げられる。 Examples of preferable ether group-containing aliphatic onium halides include salts represented by the following (a) to (c).
Figure JPOXMLDOC01-appb-C000006
Figure JPOXMLDOC01-appb-C000006
　エーテル基含有脂肪族オニウムハロゲン化物のより具体的な例としては、Ｎ，Ｎ－ジエチル－Ｎ－メチル－Ｎ－（２－メトキシエチル）アンモニウムクロリド（ＤＥＭＥＣｌ；（ａ）のアンモニウムクロリド）、２－メトキシエトキシエチルトリメチルアンモニウムクロリド（２ＭＥＴＭＡＣｌ；（ｂ）のアンモニウムクロリド）、Ｎ－（２－メトキシエチル）－Ｎ－メチルピロリジニウムクロリド（ＭＥＭＰＣｌ；（ｃ）のピロリジウムクロリド）が挙げられる。 More specific examples of the ether group-containing aliphatic onium halide include N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium chloride (DEMEL; (a) ammonium chloride), 2-. Examples thereof include methoxyethoxyethyltrimethylammonium chloride (2METMACl; ammonium chloride of (b)) and N- (2-methoxyethyl) -N-methylpyrrolidinium chloride (MEMPCl; pyrrolidium chloride of (c)).
　これらの中でも、好ましくは（ａ）、（ｂ）に示されるエーテル基含有脂肪族オニウムハロゲン化物が挙げられ、より好ましくは（ｂ）に示されるエーテル基含有脂肪族オニウムハロゲン化物が挙げられる。 Among these, the ether group-containing aliphatic onium halide shown in (a) and (b) is preferable, and the ether group-containing aliphatic onium halide shown in (b) is more preferable.
　常温溶融塩の調製において、上記のエーテル基含有脂肪族オニウムハロゲン化物は、１種単独で用いられてもよいし、２種以上を組み合わせて用いてもよい。 In the preparation of the molten salt at room temperature, the above-mentioned ether group-containing aliphatic onium halide may be used alone or in combination of two or more.
　アルミニウムハロゲン化物としては、常温で固体の塩であれば特に限定されない。具体的には、アルミニウムハロゲン化物としては、アルミニウムのフッ化物、塩化物、臭化物、及びヨウ化物が挙げられる。また、本発明で用いられるアルミニウムハロゲン化物は、それぞれ、単独で用いてもよいし、ハロゲンが異なる２種以上を組み合わせて用いてもよい。これらのハロゲン化物の中でも、好ましくは塩化物が挙げられる。 The aluminum halide is not particularly limited as long as it is a salt that is solid at room temperature. Specifically, examples of the aluminum halide include fluoride, chloride, bromide, and iodide of aluminum. Further, the aluminum halides used in the present invention may be used alone or in combination of two or more having different halogens. Among these halides, chloride is preferable.
　エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との組み合わせにおいて、両塩を構成するハロゲンは同じであってもよいし、異なっていてもよいが、例えばエーテル基含有脂肪族オニウム塩化物と多価金属塩化物とを組み合わせるように、両塩を構成するハロゲンが同じであることが好ましい。エーテル基含有脂肪族オニウムハロゲン化物及び多価金属ハロゲン化物の特に好ましい組み合わせとしては、ＤＥＭＥＣｌと塩化アルミニウムとの組み合わせ；２ＭＥＴＭＡＣｌと塩化アルミニウムとの組み合わせが挙げられる。 In the combination of the ether group-containing aliphatic onium halide and the aluminum halide, the halogens constituting both salts may be the same or different, but are, for example, more than the ether group-containing aliphatic onium chloride. It is preferable that the halogens constituting both salts are the same so as to be combined with the valent metal chloride. Particularly preferred combinations of ether group-containing aliphatic onium halides and polyvalent metal halides include a combination of DEMECl and aluminum chloride; a combination of 2METMACl and aluminum chloride.
　エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との混合による常温溶融塩において、アルミニウム原子に対するハロゲン原子の構成モル比（ハロゲン原子／アルミニウム原子）としては、好ましくは４以下が挙げられ、負極の作動電位の負電位側へより大きくシフトさせる観点から、より好ましくは３．７以下が挙げられる。ハロゲン原子／アルミニウム原子の構成モル比の範囲の下限としては特に限定されないが、例えば３以上、好ましくは３．３以上、より好ましくは３．４以上、さらに好ましくは３．５以上、一層好ましくは３．６以上が挙げられる。 In a room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide, the composition molar ratio (halogen atom / aluminum atom) of the halogen atom to the aluminum atom is preferably 4 or less, and the negative electrode has a negative electrode. From the viewpoint of shifting the working potential to the negative potential side more, 3.7 or less is more preferable. The lower limit of the range of the constituent molar ratio of the halogen atom / aluminum atom is not particularly limited, but is, for example, 3 or more, preferably 3.3 or more, more preferably 3.4 or more, still more preferably 3.5 or more, still more preferably. 3.6 and above can be mentioned.
　エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との混合による常温溶融塩は、エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物とを混合することで得られる。好ましくは、エーテル基含有脂肪族オニウムハロゲン化物の加熱溶融塩に、アルミニウムハロゲン化物を加え、室温に冷却することで得られる。また、原料となるエーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物は、それぞれ、ハロゲン原子／アルミニウム原子比が上記の範囲内となる量で用いることができる。 A room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide is obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide. Preferably, it is obtained by adding an aluminum halide to a heated molten salt of an ether group-containing aliphatic onium halide and cooling to room temperature. Further, the ether group-containing aliphatic onium halide and the aluminum halide used as raw materials can be used in an amount such that the halogen atom / aluminum atom ratio is within the above range, respectively.
　溶融金属塩中には、アルミニウムの析出溶解反応に寄与するハロゲン化錯アニオンとして、ＡｌＸn -（Ｘはハロゲン、ｎはＭの価数を超える数）で表される錯イオンが含まれる。なお、１個のハロゲン化錯アニオンに含まれる複数のＸとしては、溶融金属塩に用いたエーテル基含有脂肪族オニウムハロゲン化物及びアルミニウムハロゲン化物が有していたハロゲン原子の種類に基づき、１種のハロゲン原子単独で構成されていてもよいし、２種以上のハロゲン原子で構成されていてもよい。また、溶融金属塩には、１種のハロゲン化錯アニオンが含まれていてもよいし、ハロゲン原子及び／又は組成が異なる２種以上のハロゲン化錯アニオンが含まれていてもよい。 The molten metal salt contains a complex ion represented by AlX n- ( X is a halogen and n is a number exceeding the valence of M) as a halogenated complex anion that contributes to the precipitation and dissolution reaction of aluminum. The plurality of Xs contained in one halogenated complex anion are one type based on the types of halogen atoms contained in the ether group-containing aliphatic onium halide and the aluminum halide used in the molten metal salt. The halogen atom may be composed of a single halogen atom, or may be composed of two or more kinds of halogen atoms. Further, the molten metal salt may contain one kind of halogenated complex anion, or may contain two or more kinds of halogenated complex anions having different halogen atoms and / or compositions.
　具体的には、ハロゲン化錯アニオンとしては、Ａｌ3Ｘ10 -、Ａｌ2Ｘ7 -、ＡｌＸ4 -等が挙げられ、好ましくはＡｌ2Ｘ7 -が挙げられる。 Specifically, examples of the halogenated complex anion include Al 3 X 10 − , Al 2 X 7 − , Al X 4 − , and the like, preferably Al 2 X 7 − .
他の成分
　本発明のアルミニウム二次電池用電解質は、上述の常温溶融塩に加えて、他の成分を含んでいてもよい。 Other Components The electrolyte for an aluminum secondary battery of the present invention may contain other components in addition to the above-mentioned room temperature molten salt.
　例えば、他の成分として、電解質の粘度調整（例えば、粘度低下）等を目的として、他のイオン液体（常温溶融塩）を含んでいてもよい。他のイオン液体を構成するカチオンとしては特に限定されないが、電気化学的特性に鑑み、上記のエーテル基含有脂肪族オニウムであることが好ましい。また、他のイオン液体を構成するアニオンとしては特に限定されず、塩の溶解温度を下げる観点及び／又はイオン拡散を促進する観点等から適宜選択されるが、例えば、BF4 -、BF3CF3 -、BF3C2F5 -、BF3C3F7 -、BF3C4F9 -、BF3(CN)-、BF2(CN)2 -、BF(CN)3 -、B(CN)4 -、PF6 -、(C2F5)3PF3 -、CF3CO2 -、CF3SO3 -、C2F5SO3 -、C3F7SO3、C4F9SO3 -、(FSO2)2N-（ＦＳＡ-）、FSO2NSO2CF3 -（ＦＴＡ-）、(CF3SO2N)2N-（ＴＦＳＡ-）、CF3SO2NSO2C2F5 -（Ｃ1Ｃ2 -）、CF3CONSO2CF3 -（ＴＳＡＣ-）、(C2F5SO2)2N-（ＢＦＴＡ-）、CF2SO2NSO2nC4F9（Ｃ1Ｃ4 -）、環状(-CF2SO2NSO2CF2-)-（ＣＴＦＳＡ-）、環状(-CF2SO2NSO2C2F4-)-（Ｃ３ＦＳＡ-）、(CF3SO2)3C-、(FSO2)3C-、BOB-等が挙げられる。これらのアニオンの中でも、酸素を含むアニオン、つまりCF3CO2 -、CF3SO3 -、C2F5SO3 -、C3F7SO3、C4F9SO3 -、(FSO2)2N-（ＦＳＡ-）、FSO2NSO2CF3 -（ＦＴＡ-）、(CF3SO2N)2N-（ＴＦＳＡ-）、CF3SO2NSO2C2F5 -（Ｃ1Ｃ2 -）、CF3CONSO2CF3 -（ＴＳＡＣ-）、(C2F5SO2)2N-（ＢＦＴＡ-）、CF2SO2NSO2nC4F9（Ｃ1Ｃ4 -）、環状(-CF2SO2NSO2CF2-)-（ＣＴＦＳＡ-）、環状(-CF2SO2NSO2C2F4-)-（Ｃ３ＦＳＡ-）、(CF3SO2)3C-、(FSO2)3C-、BOB-が好ましく、CF3SO3 -、(CF3SO2N)2N-（ＴＦＳＡ-）がより好ましく、(CF3SO2N)2N-（ＴＦＳＡ-）がさらに好ましい。他のイオン液体の好適な具体例としては、ＤＥＭＥ－ＴＦＳＡ、２ＭＥＴＭＡ－ＴＦＳＡ、ＭＥＭＰ－ＴＦＳＡが挙げられ、より好ましくはＤＥＭＥ－ＴＦＳＡが挙げられる。 For example, as another component, another ionic liquid (normal temperature molten salt) may be contained for the purpose of adjusting the viscosity of the electrolyte (for example, reducing the viscosity). The cation constituting the other ionic liquid is not particularly limited, but in view of the electrochemical properties, the above-mentioned ether group-containing aliphatic onium is preferable. The anion constituting another ionic liquid is not particularly limited, and is appropriately selected from the viewpoint of lowering the dissolution temperature of the salt and / or promoting ion diffusion. For example, BF 4- , BF 3 CF. 3- , BF 3 C 2 F 5- , BF 3 C 3 F 7- , BF 3 C 4 F 9- , BF 3 (CN) - , BF 2 (CN) 2- , BF (CN) 3- , B (CN) 4- , PF 6- , ( C 2 F 5 ) 3 PF 3- , CF 3 CO 2- , CF 3 SO 3- , C 2 F 5 SO 3- , C 3 F 7 SO 3 , C 4 F 9 SO 3- , (FSO 2 ) 2 N- ( FSA- ), FSO 2 NSO 2 CF 3- ( FTA- ), (CF 3 SO 2 N) 2 N- ( TFSA- ), CF 3 SO 2 NSO 2 C 2 F 5- (C 1 C 2- ) , CF 3 CONSO 2 CF 3- ( TSAC- ), (C 2 F 5 SO 2 ) 2 N- ( BFTA- ), CF 2 SO 2 NSO 2 nC 4 F 9 (C 1 C 4- ) , Circular (-CF 2 SO 2 NSO 2 CF 2 - ) - (CTFSA-), Circular (-CF 2 SO 2 NSO 2 C 2 F 4 - ) - (C3FSA-), (CF 3 SO 2 ) 3 C- , (FSO 2 ) 3 C- , BOB - etc. Among these anions, oxygen-containing anions, namely CF 3 CO 2- , CF 3 SO 3- , C 2 F 5 SO 3- , C 3 F 7 SO 3 , C 4 F 9 SO 3- , (FSO 2 ). ) 2 N- ( FSA- ), FSO 2 NSO 2 CF 3- ( FTA- ), (CF 3 SO 2 N) 2 N- ( TFSA- ), CF 3 SO 2 NSO 2 C 2 F 5- ( C 1 ) C 2- ) , CF 3 CONSO 2 CF 3- ( TSAC- ), (C 2 F 5 SO 2 ) 2 N- ( BFTA- ), CF 2 SO 2 NSO 2 nC 4 F 9 (C 1 C 4- ) , Circular (-CF 2 SO 2 NSO 2 CF 2 - ) - (CTFSA-), Circular (-CF 2 SO 2 NSO 2 C 2 F 4 - ) - (C3FSA-), (CF 3 SO 2 ) 3 C- , (FSO 2 ) 3 C- , BOB - is preferred, CF 3 SO 3- , (CF 3 SO 2 N) 2 N- ( TFSA- ) is more preferred, (CF 3 SO 2 N) 2 N- ( TFSA) —— ) Is more preferable. Suitable specific examples of other ionic liquids include DEME-TFSA, 2METMA-TFSA, MEMP-TFSA, and more preferably DEME-TFSA.
　本発明のアルミニウム二次電池用電解質が他の成分を含む場合は、電解質は、エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物とを混合して常温溶融塩を調製し、その後に、常温溶融塩を当該他の成分で希釈することによって調製する。 When the electrolyte for an aluminum secondary battery of the present invention contains other components, the electrolyte is prepared by mixing an ether group-containing aliphatic onium halide and an aluminum halide to prepare a room temperature molten salt, and then melting at room temperature. It is prepared by diluting the salt with the other components.
　なお、上述のエーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との混合による常温溶融塩が、通常の電池使用環境下での温度で良好な溶融状態を示すとともに電気化学的特性に非常に優れているため、本発明の電解質には、これらの他の成分を含まなくてもよい。負極の作動電位の負電位側へより大きくシフトさせる観点から、本発明の電解質には他の成分を含まないことが好ましい。 The room temperature molten salt obtained by mixing the above-mentioned ether group-containing aliphatic onium halide and aluminum halide shows a good molten state at a temperature under a normal battery usage environment and is extremely excellent in electrochemical properties. Therefore, the electrolyte of the present invention does not have to contain these other components. From the viewpoint of shifting the operating potential of the negative electrode to the negative potential side more, it is preferable that the electrolyte of the present invention does not contain other components.
２．アルミニウム二次電池
　本発明のアルミニウム二次電池は、上述の本発明のアルミニウム二次電池用電解質を含んで構成される。本発明のアルミニウム二次電池の具体的形態は、負極及び正極と上記の本発明の電解質とを含み、一液型（つまり、上述の本発明の電解質が、両極に接している形態）である限りにおいて特に限定されない。 2. 2. Aluminum secondary battery The aluminum secondary battery of the present invention is configured to include the above-mentioned electrolyte for the aluminum secondary battery of the present invention. The specific form of the aluminum secondary battery of the present invention includes a negative electrode and a positive electrode and the above-mentioned electrolyte of the present invention, and is a one-component type (that is, a form in which the above-mentioned electrolyte of the present invention is in contact with both electrodes). The limit is not particularly limited.
負極
　負極としては、アルミニウムを含有し且つ酸化・還元反応を繰り返すことができる負極活物質を含んでいれば、特に限定されない。 Negative electrode The negative electrode is not particularly limited as long as it contains aluminum and contains a negative electrode active material capable of repeating an oxidation / reduction reaction.
　具体的には、アルミニウム二次電池の負極活物質としては、アルミニウムの析出・溶解を繰り返すことができる金属アルミニウム；アルミニウムイオンの脱合金・合金化反応を繰り返すことができるアルミニウム合金が挙げられる。アルミニウム合金としては、Ｓｉ、Ｍｎ、Ｃｒ、Ｎｉ、Ｃｕ、Ｍｇのうちの少なくとも１種とアルミニウムとの合金が挙げられる。 Specifically, examples of the negative electrode active material of the aluminum secondary battery include metallic aluminum capable of repeating precipitation and melting of aluminum; and aluminum alloy capable of repeating dealloying and alloying reactions of aluminum ions. Examples of the aluminum alloy include an alloy of at least one of Si, Mn, Cr, Ni, Cu, and Mg and aluminum.
　負極は、上記の負極活物質のみから構成されてもよいし、上記の負極活物質が集電体に担持された形態で構成されてもよい。集電体としては、ステンレス鋼、アルミニウム箔、ニッケル箔、銅箔等の金属が挙げられる。 The negative electrode may be composed of only the above-mentioned negative electrode active material, or may be composed of the above-mentioned negative electrode active material supported on a current collector. Examples of the current collector include metals such as stainless steel, aluminum foil, nickel foil, and copper foil.
正極
　正極としては、高比表面積を有する分極性電極を用いることができる。分極性電極の活物質としては、炭素が挙げられる。炭素としては特に限定されないが、好ましくは、グラファイト（天然グラファイト・人造グラファイト（ＫＳ６、ＫＳ６Ｌ、ＳＦＧ６、ＳＦＧ６Ｌ）等）、グラフェン、フラーレン（カーボンナノチューブ、カーボンナノホーン、バックミンスターフラーレン等）等のｓｐ2型炭素が挙げられる。 Positive electrode As the positive electrode, a polarizable electrode having a high specific surface area can be used. Examples of the active material of the depolarizing electrode include carbon. The carbon is not particularly limited, but is preferably sp 2 type such as graphite (natural graphite / artificial graphite (KS6, KS6L, SFG6, SFG6L), etc.), graphene, fullerene (carbon nanotube, carbon nanohorn, buckminsterfullerene, etc.). Carbon is mentioned.
　正極の具体的な形態としては特に限定されず、上記の活物質を含んでいれば特に限定されず、上記の活物質のみから構成されていてもよいし、活物質が、導電助剤、結着剤及び／又は増粘剤との合剤形態で構成されていてもよいし、活物質又は合剤が集電体に担持された形態で構成されていてもよい。 The specific form of the positive electrode is not particularly limited, and is not particularly limited as long as it contains the above-mentioned active material, and may be composed only of the above-mentioned active material. It may be composed of a mixture of a coating agent and / or a thickener, or may be composed of an active substance or a mixture supported on a current collector.
　正極が活物質のみから構成される場合、活物質の形態としては、織布又は不織布が挙げられる。 When the positive electrode is composed only of the active material, the form of the active material includes a woven fabric or a non-woven fabric.
　導電助剤としては、カーボンブラック、アセチレンブラック、ケッチェンブラック等の炭素類、黒鉛、金属類等が挙げられる。結着剤としては、ポリフッ化ビニリデン、スチレンブタジエンゴム、ポリテトラフルオロエチレン等のポリマーが挙げられる。増粘剤としては、カルボキシメチルセルロース、エチレングリコール等が挙げられる。集電体としては、白金箔、モリブデン箔、ニッケル箔、銅箔等が挙げられる。 Examples of the conductive auxiliary agent include carbons such as carbon black, acetylene black, and Ketjen black, graphite, and metals. Examples of the binder include polymers such as polyvinylidene fluoride, styrene-butadiene rubber, and polytetrafluoroethylene. Examples of the thickener include carboxymethyl cellulose and ethylene glycol. Examples of the current collector include platinum foil, molybdenum foil, nickel foil, copper foil and the like.
その他の構成
　本発明のアルミニウム二次電池における上記以外の他の構成は、電池の具体的形態等に応じて当業者が適宜設計することができる。 Other configurations Other configurations other than the above in the aluminum secondary battery of the present invention can be appropriately designed by those skilled in the art according to the specific form of the battery and the like.
　その他の構成としては、正極と負極との間に設置され両電極の短絡を防止するセパレータ、電池容器等が挙げられる。セパレータの材料としては、ガラス繊維、フッ素ポリマー、ポリエチレン、ポリプロピレン等が挙げられる。電池容器としては、金属缶、ラミネートパウチ等、公知の外装材を、電池の形状（円筒型、コイン型、ボタン型、ラミネート型等）に応じた形状で用いることができる。 Other configurations include a separator installed between the positive electrode and the negative electrode to prevent a short circuit between both electrodes, a battery container, and the like. Examples of the material of the separator include glass fiber, fluoropolymer, polyethylene, polypropylene and the like. As the battery container, a known exterior material such as a metal can or a laminated pouch can be used in a shape corresponding to the shape of the battery (cylindrical type, coin type, button type, laminated type, etc.).
　以下、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
試験例１：常温溶融塩中でのアルミニウムの析出溶解電位
　ＲＣｌとＡｌＣｌ3とを２：３のモル比（アルミニウム原子に対する塩素原子のモル比が１１／３）で混合して得た常温溶融塩と、ＲＣｌとＡｌＣｌ3とを１：２のモル比（アルミニウム原子に対する塩素原子のモル比が７／２）で混合して得た常温溶融塩とを用意した。 Test Example 1: A room temperature molten salt obtained by mixing aluminum precipitation dissolution potential RCl and AlCl 3 in a room temperature molten salt at a molar ratio of 2: 3 (molar ratio of chlorine atom to aluminum atom is 11/3). And a room temperature molten salt obtained by mixing RCl and AlCl 3 at a molar ratio of 1: 2 (molar ratio of chlorine atom to aluminum atom is 7/2) were prepared.
　常温溶融塩中に、アルミニウムリボンと、ヨウ素レドックス含有イオン液体［１－エチル－３－メチルイミダゾリウムビス（トリフルオロメチルスルホニル）イミドに６０ｍＭテトラプロピルアンモニウムヨウ化物及び１５ｍＭヨウ素を溶解させたもの］に、白金線を浸漬させたものをポーラスガラスで仕切ったガラス管に入れた参照電極（以下単にヨウ素レドックス参照電極と記す。）とを浸漬させ、アルミニウムリボンの電位（E(Al vs I-/I3 -)とする。）を測定した。測定されたアルミニウムリボンの電位を以下の式に基づいてアルミニウムの標準電極電位に対する電位に換算し、アルミニウムの析出溶解電位を求めた。 In an ionic liquid containing iodine redox [1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide with 60 mM tetrapropylammonium iodide and 15 mM iodine dissolved] in a room temperature molten salt. , A reference electrode (hereinafter simply referred to as an iodine redox reference electrode) in which a platinum wire is immersed in a glass tube partitioned by porous glass is immersed, and the potential of the aluminum ribbon (E (Al vs I- / I)) 3- ) .) Was measured. The measured potential of the aluminum ribbon was converted into a potential with respect to the standard electrode potential of aluminum based on the following formula, and the precipitation and dissolution potential of aluminum was determined.
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000007
　フェロセンの酸化還元電位は、各常温溶融塩中にフェロセンをおよそ５０ｍＭ溶解させ、グラッシーカーボン電極を用いたサイクリックボルタンメトリー（参照電極：ヨウ素レドックス参照電極、対極：アルミニウムリボン）により得られたフェロセンの酸化還元ピークから求めた。フェロセンのＳＨＥ（標準水素電極）基準での酸化還元電位は０．４００Ｖ　ｖｓ　ＳＨＥである（R. R. Gagne, C. A. Koval, and G. C. Lisensky, Inorg. Chem., 19, 2854 (1980)）。アルミニウムの標準電極電位は－１．６７Ｖ　ｖｓ　ＳＨＥである（S. Trasatti, Pure & Appl. Chem., 58(7), 955 (1986).）。 The redox potential of ferrocene is the oxidation of ferrocene obtained by dissolving ferrocene in each room temperature molten salt at about 50 mM and cyclic voltammetry using a glassy carbon electrode (reference electrode: iodine redox reference electrode, counter electrode: aluminum ribbon). Obtained from the reduction peak. The redox potential of ferrocene based on the SHE (standard hydrogen electrode) is 0.400V vs. SHE (R.R.Gagne, C.A.Koval, and G.C.Lisensky, Inorg.Chem., 19, 2854. (1980)). The standard electrode potential of aluminum is -1.67V vs SHE (S. Trasatti, Pure & Appl. Chem., 58 (7), 955 (1986).).
　それぞれの常温溶融塩中におけるアルミニウムの析出溶解電位を求めた結果を表１に示す。 Table 1 shows the results of determining the precipitation and dissolution potential of aluminum in each room temperature molten salt.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
試験例２：アルミニウム電池における正極と負極の作動電位
　作用極として市販のグラファイト電極（５ｍｍ角）、対極としてアルミニウム箔（５ｍｍ角）、及び参照電極として、先端がポーラスバイコールガラスによって仕切られたガラス管にヨウ素レドックスを含むイオン液体を入れ白金線を浸漬させた参照電極を用い、対極アルミニウムの電位を同時に記録できる電気化学アナライザー（Ｂｉｏ－ｌｏｇｉｃ　ＶＭＰ３）を用いて、定電流印加時の作用極の電位測定を行った。図１に比較例１の常温溶融塩の測定結果、図２に実施例１の常温溶融塩の測定結果（いずれも、ＲＣｌとＡｌＣｌ3とを２：３のモル比、つまり、アルミニウム原子に対する塩素原子のモル比が１１／３となるように混合して調製した常温溶融塩の測定結果）を示す。図１及び図２中、破線はグラファイト正極電位を示し、実線はアルミニウム負極電位を示す。 Test Example 2: Commercially available graphite electrode (5 mm square) as the working potential acting electrode of the positive and negative electrodes in an aluminum battery , aluminum foil (5 mm square) as the counter electrode, and a glass tube whose tip is partitioned by porous bicol glass as the reference electrode. Using a reference electrode in which an ionic liquid containing iodine redox is placed and a platinum wire is immersed in it, and an electrochemical analyzer (Bio-logic VMP3) capable of simultaneously recording the potential of counter electrode aluminum, the potential of the working electrode when a constant current is applied. The measurement was performed. FIG. 1 shows the measurement result of the room temperature molten salt of Comparative Example 1, and FIG. 2 shows the measurement result of the room temperature molten salt of Example 1 (both have a molar ratio of RCl and AlCl 3 of 2: 3, that is, chlorine with respect to aluminum atoms. The measurement result of the room temperature molten salt prepared by mixing so that the molar ratio of atoms becomes 11/3) is shown. In FIGS. 1 and 2, the broken line indicates the graphite positive electrode potential, and the solid line indicates the aluminum negative electrode potential.
　図１及び図２に示すように、比較例１及び実施例１の常温溶融塩中では、グラファイト正極はアルミニウムの標準電位基準でいずれも３．５Ｖ付近で充放電したのに対し、図１に示すように比較例１の常温溶融塩中ではアルミニウム負極は１．７Ｖ付近、図２に示すように実施例１の常温溶融塩ではアルミニウム負極は１．２Ｖ付近で作動し、これらのアルミニウム負極の作動電位は、表１で示したアルミニウムの浸漬電位とほぼ合致した。つまり、電池作動中においても、比較例１の常温溶融塩のカチオンをエーテル基含有脂肪族オニウムに変更するだけで、図１（比較例１）と対比される図２（実施例１）に示した通り、アルミニウム負極の電位が０．５Ｖ以上負電位側にシフトしたことが認められ、結果として、正負極間の電位差（電池電圧に相当）が２Ｖから２．５Ｖに大きく向上したことがわかった。 As shown in FIGS. 1 and 2, in the room temperature molten salt of Comparative Example 1 and Example 1, the graphite positive electrode was charged and discharged at around 3.5 V based on the standard potential of aluminum, whereas FIG. 1 shows. As shown, the aluminum negative electrode operates at around 1.7 V in the room temperature molten salt of Comparative Example 1, and the aluminum negative electrode operates at around 1.2 V in the room temperature molten salt of Example 1 as shown in FIG. The working potential was almost the same as the immersion potential of aluminum shown in Table 1. That is, even during battery operation, only changing the cation of the room temperature molten salt of Comparative Example 1 to an ether group-containing aliphatic onium is shown in FIG. 2 (Example 1), which is compared with FIG. 1 (Comparative Example 1). As shown above, it was confirmed that the potential of the aluminum negative electrode was shifted to the negative potential side by 0.5 V or more, and as a result, it was found that the potential difference between the positive and negative electrodes (corresponding to the battery voltage) was greatly improved from 2 V to 2.5 V. rice field.
　本発明によると、アルミニウム二次電池の電解質に用いられるイオン液体として、エーテル基を含有する脂肪族のカチオン種を用いることで、アルミニウムの析出溶解電位を負電位側にシフトさせることができる。特にアルミニウムの析出溶解電位については、負電位側に０．５Ｖ程度もシフトさせることができるため、このイオン液体を電解質としてグラファイト正極と組み合わせたアルミニウム二次電池の作動電圧を０．５Ｖ以上向上させることができる。従って、アルミニウム二次電池において３Ｖに近い充放電が可能となる。


　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 According to the present invention, the precipitation and dissolution potential of aluminum can be shifted to the negative potential side by using an aliphatic cation species containing an ether group as the ionic liquid used for the electrolyte of the aluminum secondary battery. In particular, the precipitation and dissolution potential of aluminum can be shifted to the negative potential side by about 0.5V, so that the operating voltage of the aluminum secondary battery combined with the graphite positive electrode using this ionic liquid as an electrolyte is improved by 0.5V or more. be able to. Therefore, it is possible to charge / discharge the aluminum secondary battery close to 3V.

Claims (10)

  1. 　エーテル基含有脂肪族オニウムハロゲン化物とアルミニウムハロゲン化物との混合による常温溶融塩を含むイオン伝導材である、アルミニウム二次電池用電解質。 An electrolyte for an aluminum secondary battery, which is an ionic conductive material containing a room temperature molten salt obtained by mixing an ether group-containing aliphatic onium halide and an aluminum halide.
  2. 　前記エーテル基含有脂肪族オニウムハロゲン化物が、下記式（Ｉ）：
    Figure JPOXMLDOC01-appb-I000001
    （式（Ｉ）中、Ａは、窒素又はリンを表し；Ｒ1及びＲ2は、互いに同じ又は異なっていてもよい炭素数１～６のアルキル基、それらが互いに連結した炭素数３～６のアルキレン基、若しくはエーテル基含有基を表し；Ｒ3は、炭素数１～６のアルキル基又はエーテル基含有基を表し；Ｒ4は、エーテル基含有基を表し、Ｘはハロゲン原子を表す。）で表される、請求項１に記載のアルミニウム二次電池用電解質。     The ether group-containing aliphatic onium halide has the following formula (I):
    Figure JPOXMLDOC01-appb-I000001
    (In formula (I), A represents nitrogen or phosphorus; R 1 and R 2 are alkyl groups having 1 to 6 carbon atoms which may be the same or different from each other, and 3 to 6 carbon atoms in which they are linked to each other. Represents an alkylene group or an ether group-containing group; R 3 represents an alkyl group or an ether group-containing group having 1 to 6 carbon atoms; R 4 represents an ether group-containing group, and X represents a halogen atom. ), The electrolyte for an aluminum secondary battery according to claim 1.
  3. 　前記エーテル基含有基が、アルコキシ基、１又は複数のアルコキシ基で置換されたアルキル基、ポリオキシアルキレン基、脂肪族環状エーテル基、及び１又は複数の脂肪族環状エーテル基で置換されたアルキル基からなる群より選択される、請求項２に記載のアルミニウム二次電池用電解質。 The ether group-containing group is an alkoxy group, an alkyl group substituted with one or more alkoxy groups, a polyoxyalkylene group, an aliphatic cyclic ether group, and an alkyl group substituted with one or more aliphatic cyclic ether groups. The electrolyte for an aluminum secondary battery according to claim 2, which is selected from the group consisting of.
  4. 　前記エーテル基含有基が、炭素数１～６のアルコキシ基、１又は複数の炭素数１～６のアルコキシ基で置換された炭素数１～６のアルキル基、アルキレンオキサイドの付加数が２～６のポリオキシアルキレン基、脂肪族環状エーテル基、及び１又は複数の脂肪族環状エーテル基で置換された炭素数１～６のアルキル基からなる群より選択される、請求項２又は３に記載のアルミニウム二次電池用電解質。 The ether group-containing group is an alkoxy group having 1 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms substituted with one or a plurality of alkoxy groups having 1 to 6 carbon atoms, and an addition number of alkylene oxides of 2 to 6 to 6. 2 or 3 according to claim 2 or 3, which is selected from the group consisting of a polyoxyalkylene group, an aliphatic cyclic ether group, and an alkyl group having 1 to 6 carbon atoms substituted with one or a plurality of aliphatic cyclic ether groups. Alkoxy for aluminum secondary batteries.
  5. 　前記アルミニウムハロゲン化物が、塩化アルミニウムである、請求項１～４のいずれかに記載のアルミニウム二次電池用電解質。 The electrolyte for an aluminum secondary battery according to any one of claims 1 to 4, wherein the aluminum halide is aluminum chloride.
  6. 　前記エーテル基含有脂肪族オニウムハロゲン化物が、前記エーテル基を複数含む、請求項１～５のいずれかに記載のアルミニウム二次電池用電解質。 The electrolyte for an aluminum secondary battery according to any one of claims 1 to 5, wherein the ether group-containing aliphatic onium halide contains a plurality of the ether groups.
  7. 　前記エーテル基含有オニウムハロゲン化物が、Ｎ，Ｎ－ジエチル－Ｎ－メチル－Ｎ－（２－メトキシエチル）アンモニウムクロリド又は２－メトキシエトキシエチルトリメチルアンモニウムクロリドであり、前記アルミニウムハロゲン化物が塩化アルミニウムである、請求項１～５のいずれかに記載のアルミニウム二次電池用電解質。 The ether group-containing onium halide is N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium chloride or 2-methoxyethoxyethyltrimethylammonium chloride, and the aluminum halide is aluminum chloride. , The electrolyte for an aluminum secondary battery according to any one of claims 1 to 5.
  8. 　前記常温溶融塩におけるアルミニウム原子に対するハロゲン原子の構成モル比が４以下である、請求項１～７のいずれかに記載のアルミニウム二次電池用電解質。 The electrolyte for an aluminum secondary battery according to any one of claims 1 to 7, wherein the composition molar ratio of the halogen atom to the aluminum atom in the room temperature molten salt is 4 or less.
  9. 　前記常温溶融塩におけるアルミニウム原子に対するハロゲン原子の構成モル比が３以上である、請求項１～８のいずれかに記載のアルミニウム二次電池用電解質。 The electrolyte for an aluminum secondary battery according to any one of claims 1 to 8, wherein the composition molar ratio of the halogen atom to the aluminum atom in the room temperature molten salt is 3 or more.
  10. 　請求項１～９のいずれかに記載のアルミニウム二次電池用電解質を含む、アルミニウム二次電池。 An aluminum secondary battery containing the electrolyte for the aluminum secondary battery according to any one of claims 1 to 9.
PCT/JP2021/036715 2020-10-07 2021-10-04 Electrolyte for aluminum secondary batteries, and aluminum secondary battery WO2022075287A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03238769A (en) * 1990-02-16 1991-10-24 Nisshin Steel Co Ltd Aluminum secondary battery
JP2014222609A (en) * 2013-05-13 2014-11-27 学校法人 関西大学 Aluminum secondary battery
JP2016213101A (en) * 2015-05-12 2016-12-15 株式会社テクノバ Aluminum secondary battery

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03238769A (en) * 1990-02-16 1991-10-24 Nisshin Steel Co Ltd Aluminum secondary battery
JP2014222609A (en) * 2013-05-13 2014-11-27 学校法人 関西大学 Aluminum secondary battery
JP2016213101A (en) * 2015-05-12 2016-12-15 株式会社テクノバ Aluminum secondary battery

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MATSUMOTO, HAJIME; OOYABU, RIE; AKAI, NAOTO: "1G01 Physical and Electrochemical Properties of Ambient Temperature Molten Salt Composed of Magnesium Chloride", PROCEEDINGS OF THE 86TH ELECTROCHEMICAL SOCIETY OF JAPAN (ECSJ) SPRING MEETING; KYOTO (JAPAN); MARCH 27-29, 2019, vol. 86, 13 March 2019 (2019-03-13), JP, pages 1, XP009535327 *

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