JP5786540B2 - Non-aqueous magnesium battery - Google Patents

Description

  The present invention relates to a non-aqueous magnesium battery.

  In recent years, the market for portable information devices such as mobile phones and e-mail terminals is rapidly expanding. In addition, expectations for hybrid vehicles and electric vehicles are increasing from the viewpoint of environmental problems and the energy crisis. In light of this background, there is a need for high-energy storage devices.

  For example, the standard electrode potential of magnesium is as low as -2.375 V, is relatively light among metals, is safer than lithium, and is abundant in resources (Clark number 1.93). For this reason, it can be said that magnesium is an excellent material for a negative electrode of a battery. As batteries using magnesium as a negative electrode, seawater batteries (Patent Documents 1 and 2), magnesium-air batteries (Non-Patent Documents 1 and 2), and the like have been proposed as aqueous batteries. In addition, as non-aqueous batteries, secondary batteries that utilize an intercalation reaction of magnesium ions (Non-patent Documents 3 and 6), air batteries that involve oxygen in the positive electrode reaction (Non-patent Documents 3 and 6) 7) A sulfur battery containing sulfur in the positive electrode (Patent Document 8) has been proposed. The inventors of the present invention produced a battery using a carbonate-based non-aqueous electrolyte in which magnesium was used for the negative electrode and halogen was added, and a large capacity and high output were obtained (Patent Document 9).

Japanese Patent Laid-Open No. 61-082675 JP 7-226213 A JP 2007-280627 A JP 2007-157416 A JP 2007-87938 A Japanese Patent No. 35877791 JP 2010-086924 A JP 2004-265675 A JP 2009-117126 A

Journal of Electrochemical Society Electrochemical Technology, 116, 1588 (1969) Angé Bande Chemie Internal Edition, 45, 6009 pages (2006) Nature 407, 724 (2000)

  However, although the battery described in Patent Document 9 can have a large capacity and a high output, the initial discharge voltage is low, and the discharge voltage may decrease with discharge.

  The present invention has been made to solve such problems, and it is a main object of the present invention to provide a non-aqueous magnesium battery that can maintain a high discharge voltage in an ion conductive medium containing halogen. Objective.

  In order to achieve the above-described object, the present inventors can maintain a high discharge voltage when using an ion-conducting medium containing a non-aqueous solvent that forms a molecular complex with halogen in addition to halogen. The inventors have found what can be done and have completed the present invention.

  That is, the nonaqueous magnesium battery of the present invention includes a positive electrode, a negative electrode having a negative electrode active material containing magnesium, and interposed between the positive electrode and the negative electrode, and includes magnesium ions, a halogen, and a nonaqueous solvent, A nonaqueous magnesium battery comprising an ion conducting medium that conducts magnesium ions, wherein the nonaqueous solvent forms a molecular complex with the halogen, and has at least one double bond of sulfur and oxygen One or more selected from the group consisting of a sulfur-containing organic compound having phosphorus, a phosphorus-containing organic compound having at least one double bond of phosphorus and oxygen, and a nitrogen-containing organic compound having at least one triple bond of carbon and nitrogen It is characterized by this.

  In this non-aqueous magnesium battery, a high discharge voltage can be maintained in an ion conductive medium containing halogen. That is, it is possible to increase the initial discharge voltage and to suppress the discharge voltage from being lowered due to the discharge. The reason why such an effect can be obtained is not clear, but the halogen molecule in the ion conduction medium and the non-aqueous solvent form a molecular complex, and this molecular complex decomposes magnesium oxide formed on the magnesium surface. Conceivable. Magnesium oxide formed on the magnesium surface has low conductivity and increases the resistance on the negative electrode surface, but by removing such magnesium oxide, a high discharge voltage can be maintained. Here, the molecular complex refers to a compound in which two or more kinds of stable molecules are directly bonded at a certain ratio, and can also be referred to as a molecular compound. Note that whether or not to form a molecular complex with a halogen may be determined based on whether or not a peak in a Raman spectrum due to stretching of a predetermined bond moves when a halogen is added.

It is explanatory drawing which shows typically an example of the non-aqueous magnesium battery 10 of this invention. 3 is an explanatory diagram showing an outline of a configuration of an evaluation cell 20. FIG. 2 is a discharge curve of Examples 1 and 2 and Comparative Example 1. It is a discharge curve of Examples 3-5 and Comparative Example 2. It is a discharge curve of Example 6 and Comparative Example 3. 10 is a discharge curve of Example 7. 2 is an explanatory diagram showing an outline of a configuration of an evaluation cell 30. FIG. 6 is a discharge curve of Example 8 and Comparative Example 4. It is a graph which shows the relationship between the discharge current density of Example 8 and Comparative Example 4, and a voltage. 3 is a discharge curve of Reference Example 1 and Reference Example 2. It is a surface analysis result of the negative electrode used in Reference Example 1 and Reference Example 2. It is a Raman spectrum of DMSO to which iodine is added. It is a Raman spectrum (high wave number side) of TMP which added iodine. It is a Raman spectrum (low wave number side) of TMP which added iodine. It is a Raman spectrum (high wave number side) of TMP which added bromine. It is a Raman spectrum (low wave number side) of TMP which added bromine.

  The non-aqueous magnesium battery of the present invention includes a positive electrode, a negative electrode having a negative electrode active material containing magnesium, and an ion conductive medium that is interposed between the positive electrode and the negative electrode and conducts magnesium ions. This non-aqueous magnesium battery may be, for example, a magnesium-halogen battery using halogen as a positive electrode active material, a magnesium-air battery using air as a positive electrode active material, or magnesium utilizing a magnesium intercalation reaction. An ion battery may be used.

In the nonaqueous magnesium battery of the present invention, the positive electrode is not particularly limited. For example, in the case of a magnesium-halogen battery, the positive electrode can use halogen as the positive electrode active material. This positive electrode active material may be supplied by halogen dissolved in an ion conductive medium. The positive electrode may contain a halogen redox catalyst. This is because it is considered that the halogen redox catalyst promotes the reduction reaction of the halogen that is the positive electrode active material, and the function as the positive electrode active material is improved. Examples of the halogen redox catalyst include nickel and manganese dioxide. In the case of a magnesium-air battery, the positive electrode can use oxygen from a gas as the positive electrode active material. The gas may be air or oxygen gas. The positive electrode preferably contains an oxygen redox catalyst. This is because the reaction at the positive electrode can be performed more efficiently. The oxygen redox catalyst may be a metal oxide such as manganese dioxide or tricobalt tetroxide, or may be a metal such as Pt, Pd or Co, metal porphyrin, metal phthalocyanine, or ionized fullerene. Organic and inorganic compounds such as carbon nanotubes may be used. Among these, electrolytic manganese dioxide is preferable in that it can be easily obtained. For example, in the case of a magnesium ion battery, the positive electrode may have a positive electrode active material that occludes and releases magnesium. Examples of such a positive electrode active material include vanadium pentoxide (V ₂ O ₅ ).

  The positive electrode is prepared by mixing the above-described oxidation-reduction catalyst or positive electrode active material, a conductive material and a binder, and adding a suitable solvent to form a paste-like positive electrode material on the surface of the current collector, followed by drying. If necessary, it may be compressed to increase the electrode density. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the performance of the battery. For example, graphite such as natural graphite (scale-like graphite, scale-like graphite) or artificial graphite, acetylene black, carbon black, kettle, etc. A mixture of one or more of chain black, carbon whisker, needle coke, carbon fiber, activated carbon, metal (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, as the conductive material, carbon black and acetylene black are preferable from the viewpoints of electron conductivity and coatability. The binder serves to connect the redox catalyst particles or the positive electrode active material particles and the conductive material particles. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluororubber, etc. Fluorine-containing resins, thermoplastic resins such as polypropylene and polyethylene, ethylene-propylene-dienemer (EPDM), sulfonated EPDM, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of cellulose or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used. Examples of the solvent for dispersing the oxidation-reduction catalyst, the positive electrode active material, the conductive material, and the binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N -An organic solvent such as dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran can be used. Moreover, a dispersing agent, a thickener, etc. may be added to water, and an active material may be slurried with latex, such as SBR. As the thickener, for example, polysaccharides such as carboxymethyl cellulose and methyl cellulose can be used alone or as a mixture of two or more. Examples of the application method include roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, and the like, and any of these can be used to obtain an arbitrary thickness and shape. In addition to copper, nickel, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, etc., the current collector has a surface such as copper for the purpose of improving adhesiveness, conductivity and reduction resistance. Those treated with carbon, nickel, titanium or silver can also be used. For these, the surface can be oxidized. Examples of the shape of the current collector include a foil shape, a film shape, a sheet, a net, a punched or expanded shape, a lath body, a porous body, a foamed body, and a formed body of a fiber group. The thickness of the current collector is, for example, 1 to 500 μm.

  In the non-aqueous magnesium battery of the present invention, the negative electrode contains magnesium. Examples of such a negative electrode include magnesium metal and magnesium alloys. Examples of magnesium alloys include alloys of magnesium with aluminum, silicon, gallium, zinc, manganese, and the like.

In the non-aqueous magnesium battery of the present invention, the ion conductive medium contains magnesium ions, a halogen, and a non-aqueous solvent, and conducts magnesium ions. This ion conductive medium may be a non-aqueous electrolyte solution in which halogen and a supporting salt are dissolved in a non-aqueous solvent. The halogen may be a simple substance such as iodine (I ₂ ), bromine (Br ₂ ), chlorine (Cl ₂ ), or a compound of two or more elements selected from iodine, bromine and chlorine. Of these, iodine (I ₂ ), bromine (Br ₂ ), iodinated monobromide (IBr), iodinated monochloride (ICl), iodinated trichloride (ICl ₃ ) and the like are preferred because they are easy to handle. Among these, iodinated trichloride, iodinated monochloride and bromine are preferable because they can maintain a high voltage, and among these, iodinated trichloride is preferable.

  The non-aqueous solvent in the ion conductive medium forms a molecular complex with halogen. Here, the molecular complex refers to a compound in which two or more kinds of stable molecules are directly bonded at a certain ratio, and can also be referred to as a molecular compound. Whether or not to form a molecular complex with halogen depends on whether or not a peak in a Raman spectrum due to expansion and contraction of a predetermined bond such as a bond between oxygen and another atom moves when a halogen is added. It may be determined. For example, when the halogen is iodine, the determination may be made based on whether or not the halogen moves to the low wave number side. Further, when the halogen is bromine, the determination may be made based on whether or not the halogen moves to the high wave number side.

  This non-aqueous solvent includes a sulfur-containing organic compound having one or more double bonds of sulfur and oxygen, a phosphorus-containing organic compound having one or more double bonds of phosphorus and oxygen, and a triple bond of nitrogen and carbon. It includes one or more selected from the group consisting of one or more nitrogen-containing organic compounds. Among these, the one containing a nitrogen-containing organic compound is preferable because a high discharge voltage can be maintained. Note that the sulfur-containing organic compound having two or more double bonds with oxygen may have two double bonds by bonding two oxygens to one sulfur. The phosphorus-containing organic compound having two or more double bonds with oxygen may have two double bonds by bonding two oxygens to one phosphorus. The non-aqueous solvent is preferably an aprotic solvent.

  The sulfur-containing organic compound may be one in which sulfur double-bonded to oxygen is bonded to a hydrocarbon group directly or via oxygen. Here, the hydrocarbon group is preferably a chain-like (which may be linear or branched) or a cyclic hydrocarbon group, and preferably has 1 to 20 carbon atoms. Examples of chain hydrocarbon groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decanyl, undecanyl, and dodecanyl groups. An unsaturated hydrocarbon group such as a vinyl group, a propenyl group, a butenyl group, a pentenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, and a dodecenyl group; Examples of the cyclic hydrocarbon group include cyclic saturated hydrocarbon groups such as cyclopropyl group, cyclopentyl group, cyclohexyl group, and cycloheptyl group; aromatic hydrocarbon groups such as phenyl group and naphthyl group. Moreover, these hydrocarbon groups may have a substituent. Further, the two hydrocarbon groups bonded to sulfur may be the same or different. The hydrocarbon group may form a cyclic structure containing sulfur that is double-bonded to oxygen. Each hydrocarbon group preferably has 10 or less carbon atoms, more preferably 6 or less. The sulfur-containing organic compound may have a cyclic structure. The cyclic structure may be composed of a cyclic hydrocarbon group such as a phenyl group bonded to sulfur that is double-bonded to oxygen, or may include sulfur that is double-bonded to oxygen in the cyclic structure.

  Examples of the sulfur-containing organic compound include a sulfoxide compound in which one oxygen is double-bonded to one sulfur, and a sulfone compound in which two oxygens are double-bonded to one sulfur. Examples of the sulfoxide compound include dimethyl sulfoxide (formula (1)), which is a compound in which a chain hydrocarbon group is directly bonded to sulfur, and diphenyl sulfoxide (formula, which is a compound in which a cyclic hydrocarbon group is directly bonded to sulfur). (2)), diethyl sulfite (formula (3)) which is a compound in which a chain hydrocarbon group is bonded to sulfur via oxygen, tetramethylene sulfoxide (formula (4)) which is a compound containing sulfur in a cyclic structure ) And the like. Examples of the sulfone compound include dimethyl sulfone and diethyl sulfone (formula (5)), which are compounds in which a chain hydrocarbon group is directly bonded to sulfur, and sulfolane (formula (6)), which is a compound containing sulfur in a cyclic structure. And 3-methylsulfolane (formula (7)), dimethyl sulfolane and the like.

  The phosphorus-containing organic compound may be such that phosphorus double-bonded to oxygen is bonded to a hydrocarbon group directly or via oxygen. Here, as the hydrocarbon group, the hydrocarbon groups listed in the description of the sulfur-containing organic compound can be used. The three hydrocarbon groups bonded to phosphorus double-bonded to oxygen may be the same or different. Further, the hydrocarbon group may form a cyclic structure containing phosphorus double-bonded to oxygen. Each hydrocarbon group preferably has 4 or less carbon atoms, and more preferably 2 or less.

  Examples of the phosphorus-containing organic compound include a phosphine oxide compound in which one oxygen is double-bonded to one phosphorus and a compound in which two oxygens are double-bonded to one phosphorus. In addition to the phosphine oxide compounds that do not include oxygen-mediated compounds in the bond between hydrocarbon and phosphorus, the phosphine oxide compounds described above include two phosphinic acid compounds that contain one oxygen-mediated compound, and two compounds that communicate oxygen. Also included are phosphonic acid compounds and phosphoric acid compounds in which all hydrocarbon groups are bonded via oxygen. As the phosphine oxide compound, phosphoric acid triester, more specifically, trimethyl phosphate (formula (8)) or tributyl phosphate (formula) in which a chain hydrocarbon group is bonded to phosphorus via oxygen. (9)), triethyl phosphate (formula (10)), and triphenyl phosphate which is a compound in which a cyclic hydrocarbon group is bonded to phosphorus via oxygen. Other examples of the phosphine oxide compound include triethylphosphine oxide (formula (11)), which is a compound in which a chain hydrocarbon group is directly bonded to phosphorus, and a compound in which a cyclic hydrocarbon group is directly bonded to phosphorus. Some triphenylphosphine oxides can be mentioned.

  The nitrogen-containing organic compound may be one in which carbon triple-bonded to nitrogen is bonded to a hydrocarbon group. Here, as the hydrocarbon group, the hydrocarbon groups listed in the description of the sulfur-containing organic compound can be used. Examples of the nitrogen-containing organic compound include alkyl nitriles, and more specifically acetonitrile (formula (12)), propionitrile, butyronitrile, glutaronitrile (formula (13)), and the like.

  In addition to the non-aqueous solvent that forms a molecular complex with halogen, the ion-conducting medium is, for example, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (γ-BL), diethyl carbonate (DEC), dimethyl carbonate. (DMC), dioxane, hexaethoxycyclotriphosphazene, and other organic solvents used in conventional secondary batteries and capacitors, or mixed solvents thereof may be included. For example, in addition to polymers such as polyvinylidene fluoride, polyethylene glycol, and polyacrylonitrile, saccharides such as amino acid derivatives and sorbitol derivatives may be mixed and used as a gel.

  In the ion conductive medium, the concentration of the halogen with respect to the non-aqueous solvent that forms a molecular complex with the halogen is not particularly limited, but is preferably 0.01 mol / L or more. Among these, 0.02 mol / L or more is preferable, 0.03 mol / L or more is more preferable, and 0.05 mol / L or more is more preferable. This is because it is considered that when the halogen concentration is 0.01 mol / L or more, the function as the positive electrode active material can be sufficiently exerted and a sufficient charge / discharge capacity can be obtained. In addition, the concentration of halogen contained in the ion conductive medium is preferably equal to or less than a saturation concentration (a maximum of a solvent and a halogen is up to 1: 1 in molar ratio), and more preferably 1.0 mol / L or less. This is because if the concentration is lower than the saturation concentration, it is considered that the halogen is dissolved in the ion conductive medium, so that it is difficult to inhibit the magnesium ion conduction.

In the ion conductive medium, the supporting salt is not particularly limited. For example, magnesium perchlorate (Mg (ClO ₄ ) ₂ ), magnesium bis (trifluoromethylsulfonyl) imide (Mg [N (CF ₃ SO _{3 2} ) ₂ ), magnesium trifluoromethanesulfonate (Mg (CF ₃ SO ₃ ) ₂ ), magnesium nonafluorobutane sulfonate (Mg (C ₄ F ₉ SO ₃ ) ₂ ) and the like can be used. An ion conducting medium containing such a supporting salt will contain magnesium ions. The concentration of the supporting salt is preferably 0.1 mol / L or more and 2.0 mol / L or less, and more preferably 0.8 mol / L or more and 1.2 mol / L or less.

  The nonaqueous magnesium battery of the present invention may include a separator between the positive electrode and the negative electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the non-aqueous magnesium battery. For example, the polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or a microporous olefin resin such as polyethylene or polypropylene is used. A film is mentioned. These may be used alone or in combination.

  The shape of the non-aqueous magnesium battery of the present invention is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc. FIG. 1 is an explanatory view schematically showing an example of the non-aqueous magnesium battery of the present invention. In this non-aqueous magnesium battery 10, a negative electrode 14 made of magnesium metal and a positive electrode 16 are arranged to face each other with an ion conductive medium 18 therebetween. Among these, the positive electrode 16 is produced by mixing a conductive material 16b and a binder 16c and then press-molding the current collector 16a such as a platinum mesh. The ion conductive medium 18 contains a magnesium salt such as magnesium perchlorate, a halogen, and a non-aqueous solvent. In the ion conductive medium 18, the non-aqueous solvent is a compound that forms a molecular complex with halogen.

  For example, a molecular complex of dimethyl sulfoxide and dissolved halogen is formed in a form in which halogen is coordinated to the S═O site in the solvent molecular skeleton. That is, it is considered that a complex is formed by an electrical interaction between the π bond at the S═O site and the σ bond of halogen (see Journal of American Chemical Society, Vol. 85, p. 3125, 1963). Therefore, in the present invention, the solvent contained in the ionic conduction medium is such that in the sulfur-containing organic compound, halogen is present in the solvent molecule due to an electrical interaction between the π bond at the S═O site and the σ bond of the halogen molecule. It is thought that it forms a molecular complex by coordination. Further, in the phosphorus-containing organic compound, it is considered that halogen is coordinated to the solvent molecule to form a molecular complex due to electrical interaction between the π bond at the P═O site and the σ bond of the halogen molecule.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  Hereinafter, the non-aqueous magnesium battery of the present invention will be specifically described. Here, (1) a magnesium-halogen battery using halogen as the positive electrode active material, (2) a magnesium-air battery using air as the positive electrode active material, and (3) a magnesium ion battery using intercalation of magnesium to the positive electrode Will be described in detail.

(1) Magnesium-halogen battery (1-A) Halogen: I ₂
[Example 1]
(Production of evaluation cell)
The positive electrode was produced as follows. First, 146 mg of ketjen black (ECP-6000 manufactured by Mitsubishi Chemical Corporation) as a conductive material and 20 mg of Teflon binder (manufactured by Daikin Industries, Teflon is a registered trademark) as a binder are kneaded dry using a mortar in a sheet form. A positive electrode composite was obtained. 4 mg of this positive electrode mixture was press-bonded to a Pt mesh (manufactured by Niraco) to obtain a 0.2 cm ² positive electrode. Further, a magnesium / aluminum / zinc alloy (AZ31 (Al: 3 mass%, Zn: 1 mass%) manufactured by Osaka Fuji Kogyo) having a thickness of 0.2 mm and a thickness of 10 mm × 10 mm was used for the negative electrode. An electrolytic solution as an ion conducting medium was prepared as follows. First, a solution was prepared by dissolving 0.5 mol / L of magnesium perchlorate (manufactured by Aldrich) as a supporting salt in trimethyl phosphate (manufactured by Aldrich) as an electrolyte solvent (non-aqueous solvent). 200 mg (0.066 mol / L) of iodine (manufactured by Aldrich) was dissolved in 12 mL of this solution to obtain an electrolytic solution. Using the positive electrode, negative electrode, and electrolytic solution thus obtained, an evaluation cell was produced as follows in a glove box under an argon atmosphere. First, as shown in FIG. 2, the positive electrode 22 and the negative electrode 24 were set in the evaluation cell (beaker cell) 20, and the electrolyte solution 26 was injected. Next, a plastic lid 28 was attached to the open portion of the evaluation cell 20, and the evaluation cell 20 was sealed. The space in the beaker cell is filled with argon. The capacity of the evaluation cell 20 is about 30 ml. The evaluation cell thus obtained was named Example 1.

(Charge / discharge test)
The assembled evaluation cell was connected to a charge / discharge device (HJ1001SM8A) manufactured by Hokuto Denko, and discharged at a current of 0.010 mA (0.05 mA / cm ² per positive electrode material area) between the positive electrode and the negative electrode.

[Example 2]
The evaluation cell of Example 2 was prepared through the same steps as Example 1 except that deuterated dimethyl sulfoxide (manufactured by Wako Pure Chemicals, for NMR) was used as the electrolyte solvent, and a Nilaco Mg rod was used for the negative electrode. Then, a charge / discharge test was conducted. Although deuterated dimethyl sulfoxide is used here for convenience, dimethyl sulfoxide that is not deuterated may be used.

[Comparative Example 1]
The evaluation cell of Comparative Example 1 was prepared through the same steps as Example 1 except that a mixed solvent of propylene carbonate and diethyl carbonate (volume ratio 1: 1, manufactured by Kishida Chemical Co., Ltd.) was used as the electrolyte solvent, and charge / discharge was performed. A test was conducted.

(1-B) Halogen: ICl ₃
[Example 3]
The evaluation cell of Example 3 was produced through the same process as Example 1 except that 355 mg (0.23 mol / L) of iodotrichloride (Aldrich, purity 97%) was used instead of iodine. Went.

[Comparative Example 2]
The evaluation cell of the comparative example 2 was produced through the process similar to Example 3 except having used the propylene carbonate for the electrolyte solvent, and the charge / discharge test was done.

[Examples 4 and 5]
The evaluation cell of Example 4 was produced through the same process as Example 3 except that triethyl phosphate (manufactured by Aldrich) was used as the electrolyte solvent and an Mg rod was used as the negative electrode, and a charge / discharge test was performed. Moreover, the evaluation cell of Example 5 was produced through the same process as Example 3 except that acetonitrile (made by Wako Pure Chemicals, dehydrated product) was used as the electrolyte solvent, and an Mg rod was used as the negative electrode, and the charge / discharge test was performed. went.

(1-C) Halogen: ICl
[Example 6]
The evaluation cell of Example 6 was prepared through the same steps as Example 5 except that 765 mg (0.39 mol / L) iodinated monochloride (Aldrich) was used instead of iodinated trichloride, and a charge / discharge test was performed. It was.

[Comparative Example 3]
An evaluation cell of Comparative Example 3 was prepared and subjected to a charge / discharge test through the same steps as in Example 6 except that propylene carbonate was used instead of acetonitrile as the electrolyte solvent.

(1-D) Halogen: Br ₂
[Example 7]
An evaluation cell of Example 7 was prepared through the same steps as Example 3 except that 765 mg (0.79 mol / L) bromine (manufactured by Aldrich) was used instead of trichloride iodide, and a charge / discharge test was performed.

[Experimental result]
Table 1 shows the experimental results of the magnesium-halogen batteries (Examples 1 to 7 and Comparative Examples 1 to 3). FIG. 3 is a discharge curve of Examples 1 and 2 and Comparative Example 1 using I ₂ as the halogen. 4 is a discharge curve of Examples 3 to 5 and Comparative Example 2 using ICl ₃ as the halogen. FIG. 5 is a discharge curve of Example 6 and Comparative Example 3 using ICl as the halogen. FIG. 6 is a discharge curve of Example 7 using Br ₂ as the halogen. From Table 1 and FIGS. 3-6, it turned out that Examples 1-7 can maintain a high discharge voltage compared with Comparative Examples 1-3. As the halogen, Examples 3 to 5 using ICl ₃ , Example 6 using ICl, and Example 7 using Br ₂ maintain a high discharge voltage, and those using ICl ₃ are particularly higher. It was found that the discharge voltage can be maintained. It was found that Examples 5 and 6 using acetonitrile as the electrolyte solvent can maintain a high discharge voltage. In particular, acetonitrile is particularly suitable for magnesium batteries because it reacts with lithium and cannot be applied in lithium batteries.

(2) Magnesium-air battery [Example 8]
(Production of evaluation cell)
The positive electrode was produced as follows. First, 10 mg of electrolytic manganese dioxide (made by Mitsui Mining Co., Ltd.) as a redox catalyst, 116 mg of ketjen black (ECP-600 made by Mitsubishi Chemical) as a conductive material, and Teflon binder (made by Daikin Industries, Teflon as a binder) Was registered with a dry mortar using a mortar to obtain a sheet-like positive electrode mixture. 5 mg of this positive electrode mixture was pressure-bonded to a SUS mesh (manufactured by Niraco) to obtain a positive electrode member. For the negative electrode, metal magnesium (manufactured by Wako Pure Chemical Industries, Ltd.) having a thickness of 0.2 mm and 10 mm × 10 mm was used. The electrolytic solution as the ion conduction medium was adjusted as follows. First, a solution was prepared by dissolving 0.5 mol / L of magnesium perchlorate (manufactured by Aldrich) as a supporting salt in acetonitrile as an electrolyte solvent. In 10 mL of this solution, 3 mg (0.46 mmol / L) of trichloride iodide was dissolved to obtain an electrolytic solution. An evaluation cell (F-type electrochemical cell) 30 was produced in the glove box under an argon atmosphere using the positive electrode, the negative electrode, and the electrolytic solution thus obtained as follows. First, as shown in FIG. 7, the negative electrode 34 was installed in the SUS casing 32, and the positive electrode 36 and the negative electrode 34 were set to face each other. And 5 mL of electrolyte solution 38 was inject | poured and hold | maintained for 15 hours, and the process which removes the passive film of a negative electrode surface was performed. Thereafter, a foamed nickel plate 42 was placed on the positive electrode 36, a gas reservoir 44 through which air can flow to the positive electrode 36 side was placed, and the cell was fixed to obtain an evaluation cell 30 of Example 8. The gas reservoir 44 of the evaluation cell 30 was filled with dry oxygen.

(Charge / discharge test)
The assembled evaluation cell 30 is connected to a charge / discharge device (HJ1001SM8A) manufactured by Hokuto Denko, and a current of 0.010 mA (2 mA / g per positive electrode material) is allowed to flow between the positive electrode and the negative electrode up to 300 mAh / g per positive electrode material. Discharged.

[Comparative Example 4]
An evaluation cell was prepared through the same steps as in Example 8 except that the electrolytic solution did not contain trichloride iodide, and a charge / discharge test was performed.

[Experimental result]
Table 2 shows the experimental results of the magnesium-air battery (Example 8 and Comparative Example 4). FIG. 8 is a discharge curve of Example 8 and Comparative Example 4. FIG. 9 is a graph showing the voltage 10 seconds after the start of discharge when the discharge current density is changed for Example 8 and Comparative Example 4. The discharge voltage of Example 8 using halogen was higher than that of Comparative Example 4 using no halogen. From this, it was found that the present invention can maintain a high discharge voltage even with an air battery. In Example 8, when the current density was increased, the rate at which the discharge voltage decreased was small. From this, it was found that the large current characteristics were also good in the present invention.

(3) Magnesium ion battery [Reference Example 1]
(Production of evaluation cell)
The positive electrode was produced as follows. First, 80 mg of acetylene black (made by Mitsui Mining Co., Ltd.) as a conductive material, 120 mg of vanadium pentoxide (made by Aldrich) as a positive electrode active material, and 35 mg of Teflon binder (made by Daikin Industries, Teflon is a registered trademark) as a binder. It knead | mixed using the mortar with the dry type, and obtained the sheet-like positive mix. 5 mg of this positive electrode mixture was pressure-bonded to a SUS mesh (manufactured by Niraco) to obtain a positive electrode member. Magnesium (manufactured by Wako Pure Chemical Industries) having a diameter of 16 mm and a thickness of 0.2 mm was used for the negative electrode. This negative electrode was immersed in 10 mL of trimethyl phosphate dissolved with 3 mg (0.46 mmol / L) of trichloride iodide for 30 minutes and used for the experiment after removing the passive film on the negative electrode surface. The electrolytic solution as the ion conductive medium was adjusted as follows. First, a solution was prepared by dissolving 0.5 mol / L of magnesium perchlorate (manufactured by Aldrich) as a supporting salt in 3-methoxypropionitrile (manufactured by Wako Pure Chemical Industries) as an electrolyte solvent. An evaluation cell was prepared in a glove box under an argon atmosphere using the positive electrode, the negative electrode, the electrolytic solution thus obtained, and a polyethylene separator (manufactured by Tonen Chemical). The evaluation cell thus obtained was designated as Reference Example 1.

(Charge / discharge test)
The assembled evaluation cell was connected to a charge / discharge device (HJ1001SM8A) manufactured by Hokuto Denko, and a current of 0.010 mA (2 mA / g per positive electrode material) was passed between the positive electrode and the negative electrode to discharge to 0.70 mAh.

(Surface analysis)
About the surface of the negative electrode before incorporating in an evaluation cell, the amount of MgO was measured by secondary ion mass spectrometry (IONTOF, TOFSIMS5). Specifically, it was evaluated by immersing in 10 mL of trimethyl phosphate in which 3 mg of trichloride iodide was dissolved, and then washing in the order of trimethyl phosphate and toluene.

[Reference Example 2]
An evaluation cell of Reference Example 2 was prepared through the same steps as in Reference Example 1 except that the negative electrode was used without performing treatment for removing the passive film on the negative electrode surface, and a charge / discharge test and surface analysis were performed. In the surface analysis, the negative electrode was used as it was.

[Experimental result]
Table 3 shows the experimental results of the magnesium ion batteries (Reference Examples 1 and 2). FIG. 10 is a discharge curve of Reference Examples 1 and 2. In Reference Example 1, a higher discharge voltage than in Reference Example 2 could be maintained. In Reference Example 1, the electrolyte solution does not contain a molecular complex of a non-aqueous solvent and a halogen. However, the MgO film (passive film) on the surface of the negative electrode is obtained by treating the negative electrode with a treatment liquid containing such a molecular complex in advance. Therefore, it was inferred that better results were obtained than in Reference Example 2. Here, the removal of the MgO coating on the negative electrode surface was confirmed from the results of surface analysis by secondary ion mass spectrometry shown in FIG. From FIG. 11, it was found that the treatment with the ICl ₃ solution decreased the amount of MgO on the Mg surface compared to the case where the treatment was not performed. For these reasons, the batteries of Examples 1 to 8 were assembled using the negative electrode without removing the MgO coating on the surface in advance. However, since the electrolyte contained a molecular complex, Like the battery of Reference Example 1 using the negative electrode from which the MgO film was removed, it is considered that the effect of maintaining the discharge voltage high by removing the MgO film was obtained. In other words, it can be said that the discharge voltage can be kept high if a molecular complex of a non-aqueous solvent and a halogen is included in the electrolytic solution without performing a treatment for removing the MgO film on the negative electrode surface in advance. In the magnesium ion battery, the same effect as in Reference Example 1 can be obtained if the negative electrode is used as it is without removing the MgO coating on the surface in advance and the electrolyte contains a molecular complex of a non-aqueous solvent and a halogen. It was inferred that

  In the examples described in detail above, a high discharge voltage could be maintained even when any of iodine, bromine, iodinated monochloride, and trichloride iodide was used as the halogen. Therefore, the halogen was used in the examples. It was speculated that the same effect could be obtained with other than the above. For example, it was speculated that chlorine, iodinated monobromide, iodinated tribromide and the like may be used.

(4) Passive film removal test In the present invention, the reason why a high discharge capacity can be maintained is that decomposition of MgO, which is the main component of the passive film on the surface of the Mg negative electrode, occurs due to the configuration of the present invention. Inferred. In order to confirm this, the following experiment was conducted. First, the following reference examples 3 to 7 were prepared as samples. 27 mg of MgO (manufactured by Aldrich, purity 99.99%) was placed in a 9 mL screw tube, and 3 mL of deuterated dimethyl sulfoxide in which 8.3 mg of iodine was dissolved was added as a test solution to obtain Reference Example 3. Further, Reference Example 4 was obtained in the same manner as Reference Example 3 except that iodine was not included. Reference Example 5 was obtained in the same manner as Reference Example 3 except that trimethyl phosphate was used instead of deuterated dimethyl sulfoxide. Further, Reference Example 6 was obtained in the same manner as Reference Example 5 except that iodine was not included. Further, Reference Example 7 was obtained in the same manner as Reference Example 3 except that propylene carbonate (Kishida Kagaku) was used instead of deuterated dimethyl sulfoxide. The samples of Reference Examples 3 to 7 thus obtained were left in a constant temperature bath at 80 ° C. for 3 days to examine whether MgO was decomposed. The color change of the test solution after the heating test was visually observed, and the dissolved Mg amount was quantified by ICP emission analysis.

  Table 4 shows the experimental results of Reference Examples 3 to 7. In Reference Example 3 in which iodine was added to dimethyl sulfoxide and Reference Example 5 in which iodine was added to trimethyl phosphate, the color of the test solution was decolorized from reddish brown, and the amount of Mg dissolved in the test solution was 25 μg / g or 28 μg / Therefore, it was confirmed that these test solutions had an effect of decomposing and dissolving MgO. In Reference Examples 4 and 6 in which iodine was not added, the color of the test solution remained colorless and the amount of Mg dissolved in the test solution was less than 0.2 μg / g. It was confirmed that there was almost no effect of decomposing and dissolving. From this, it was found that halogen is necessary for decomposition of MgO. Further, even in the case where iodine is added, in Reference Example 7 using propylene carbonate, the color of the test solution remains reddish brown, and the amount of Mg dissolved in the test solution is less than 0.2 μg / g, It was confirmed that there was almost no effect of decomposing and dissolving MgO. Here, it is considered that propylene carbonate has the ability to form a molecular complex with halogen, but since the ability is low, it is considered that the effect was not obtained. From this, the non-aqueous solvent not only forms a molecular complex with halogen, but also has a high ability to form a molecular complex, specifically, has one or more double bonds of sulfur and oxygen. It is understood that it should be at least one of a sulfur-containing organic compound, a phosphorus-containing organic compound having at least one double bond of phosphorus and oxygen, and a nitrogen-containing organic compound having at least one triple bond of carbon and nitrogen It was.

(5) Raman spectrum analysis In order to confirm that the electrolyte solvent formed a molecular complex with halogen, Raman spectrum analysis was performed. Specifically, with respect to dimethyl sulfoxide (DMSO) and trimethyl phosphate (TMP), those not added with iodine and those added with iodine were prepared, and Raman spectra were measured. The Raman spectrum analysis was performed with excitation light having a wavelength of 532 nm using a laser Raman spectroscopy system (manufactured by JASCO Corporation, NRS-3300). FIG. 12 shows the results of Raman spectrum measurement of DMSO. In FIG. 12, in the case of containing iodine, the signal in the vicinity of 1045 to 1055 cm ⁻¹ based on the S═O stretching of DMSO was shifted to the lower wavenumber side and the intensity was weaker than that containing no iodine. It was speculated that such a difference was caused by DMSO and iodine forming a molecular complex and weakening the double bond. 13 and 14 show the TMP Raman spectrum measurement results. In TMP, since two characteristic peaks are observed and both are separated, the high wave number side is shown in FIG. 13 and the low wave number side is shown in FIG. In FIG. 13, in the case of containing iodine, the intensity of the signal in the vicinity of 1270 to 1280 cm ⁻¹ due to the T═P stretching of TMP was weaker than that containing no iodine. In addition, in FIG. 14, in the case of containing iodine, the signal in the vicinity of 730 to 740 cm ⁻¹ caused by the TMP O—P—O symmetrical expansion and contraction is shifted to the lower wavenumber side than in the case of not containing iodine. Became weaker. It was speculated that such a difference was caused by the formation of a molecular complex between TMP and iodine.

About trimethyl phosphate (TMP), a bromine-free one and a bromine-added one were prepared, and the Raman spectrum was measured in the same manner as described above. 15 and 16 are Raman spectra of TMP. In TMP, two characteristic peaks are observed and the two are separated from each other. Therefore, the high wave number side is shown in FIG. 15, and the low wave number side is shown in FIG. In FIG. 15, in the case of containing bromine, the signal in the vicinity of 1270 to 1280 cm ⁻¹ due to the T═P stretching of TMP was shifted to the higher wavenumber side than that containing no bromine. Further, in FIG. 16, in the case of containing bromine, the signal in the vicinity of 730 to 740 cm ⁻¹ caused by the TMP O—P—O symmetrical expansion and contraction was shifted to the high wavenumber side as compared with the case of not containing bromine. Such a difference was presumed to be caused by the formation of a molecular complex between TMP and bromine.

  10 non-aqueous magnesium battery, 14 negative electrode, 16 positive electrode, 16a current collector, 16b conductive material, 16c binder, 18 ion conductive medium, 20 evaluation cell (beaker cell), 22 positive electrode, 24 negative electrode, 26 electrolyte, 28 lid, 30 evaluation cell (F type electrochemical cell), 32 casing, 34 negative electrode, 36 positive electrode, 38 electrolyte, 42 nickel foam plate, 44 gas reservoir.

Claims (3)

A positive electrode;
A negative electrode having a negative electrode active material containing magnesium;
An ion conducting medium that is interposed between the positive electrode and the negative electrode and contains magnesium ions, halogen, and a non-aqueous solvent, and conducts magnesium ions;
A non-aqueous magnesium battery comprising:
The ion conductive medium includes a compound of two or more elements selected from iodine, bromine and chlorine as the halogen,
The non-aqueous solvent forms a molecular complex with the halogen, and includes a sulfur-containing organic compound having one or more double bonds of sulfur and oxygen, or a phosphorus-containing organic having one or more double bonds of phosphorus and oxygen. A compound, one or more selected from the group consisting of nitrogen-containing organic compounds having one or more triple bonds of carbon and nitrogen,
Non-aqueous magnesium battery.   2. The non-aqueous magnesium battery according to claim 1, wherein the non-aqueous solvent includes at least one selected from the group consisting of a sulfoxide compound, a sulfone compound, a phosphine oxide compound, and a nitrile compound. The ion-conducting medium includes at least one selected from the group consisting of iodinated monobromide (IBr), iodinated monochloride (ICl), and iodinated trichloride (ICl ₃ ) as the halogen. Or the non-aqueous magnesium battery of 2.

Images