JP5929436B2 - Non-aqueous air battery - Google Patents

Description

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

  Conventionally, as a non-aqueous air battery, in a non-aqueous air battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, and a case having an air hole for supplying oxygen to the positive electrode, the positive electrode has two different compositions. It has been proposed that each layer is composed of a layer having at least oxygen reducing ability on the air hole side and a layer having at least lithium ion storage ability on the negative electrode side (see, for example, Patent Document 1). This battery has a high capacity and is capable of handling a large current discharge.

JP 2006-286414 A

  However, in the non-aqueous air battery of Patent Document 1 described above, by forming the positive electrode in two layers, it is possible to cope with high capacity and large current discharge. An improvement was desired. For example, the discharge potential of a lithium-air battery is determined by the redox potential of Li oxide generated by the discharge reaction, but is lower (about 2.5 V) than a general lithium ion battery (about 3.7 V). If this can be improved, the battery will be more convenient. However, on the other hand, as long as the combination of conducting Li and oxygen is determined, the potential is considered to be universal, and no attempt has been made to improve the potential itself.

  This invention is made | formed in view of such a subject, and it aims at providing the non-aqueous air battery which can raise a discharge voltage more while raising battery capacity more.

  As a result of diligent research to achieve the above-mentioned object, the present inventors have found that, when ions of Group 3 elements are dissolved in a non-aqueous electrolyte, the battery capacity is further increased and the discharge voltage is further increased. The inventors have found what can be done and have completed the present invention.

  That is, the non-aqueous air battery of the present invention includes a positive electrode, a negative electrode, and a non-aqueous ion conduction medium that is interposed between the positive electrode and the negative electrode and includes a Group 3 metal ion including a lanthanoid. Is.

The non-aqueous air battery of the present invention can increase the battery capacity and the discharge voltage. The reason why such an effect is obtained is not clear, but is presumed as follows. For example, the discharge potential of the air battery, oxygen (O ₂₎ is determined by the reduction potential to become oxygen ions (O ^2-). At this time, if a metal ion that strongly binds to oxygen ions is added to the ion conduction medium in advance, the oxygen ions are stabilized by the metal ions, and the reduction potential shifts to an electrochemical base. That is, it is presumed that the discharge potential as a battery increases. This effect also increases the generation rate of oxides generated during discharge (for example, Li ₂ O _{2 as} a peroxide in a lithium-air battery), so that the accumulation state becomes more uniform, that is, more It is presumed that the oxide can be deposited and accumulated on the electrode, and the discharge capacity is greatly increased.

An explanatory view of F type electrochemical cell 20. FIG. The discharge curves of Example 1 and Comparative Example 1. The discharge curves of Example 2 and Comparative Example 1. The discharge curves of Example 3 and Comparative Example 1.

  The non-aqueous air battery of the present invention is a non-aqueous air battery including a positive electrode, a negative electrode, and a group 3 metal ion containing a lanthanoid (hereinafter also simply referred to as a group 3 metal ion) interposed between the positive electrode and the negative electrode. An ion conductive medium. This non-aqueous air battery is charged and discharged with oxygen, and as an oxygen source, oxygen gas may be used, or air may be used. Further, the ion conductive medium may conduct ions of alkali metal, alkaline earth metal, and typical metal. Examples of the alkali metal include lithium, sodium, and potassium, examples of the alkaline earth metal include calcium, strontium, and barium. Examples of the typical metal include magnesium, aluminum, and zinc. Among these, lithium is preferable, and the nonaqueous lithium-air battery will be mainly described below.

In the non-aqueous air battery of the present invention, the ion conductive medium may be a non-aqueous electrolyte. This non-aqueous electrolyte may be, for example, a solution in which a supporting salt containing lithium is dissolved in a non-aqueous solvent. The supporting salt having lithium is not particularly limited. For example, hexafluorophosphate salt (LiPF ₆ ), perchlorate salt (LiClO ₄ ), tetrafluoroborate salt (LiBF ₄ ), pentafluoroarsine salt (LiAsF) ₅ ), bis (trifluoromethanesulfonyl) imide salt (Li (CF ₃ SO ₂ ) ₂ N), bis (pentafluoroethanesulfonyl) imide salt (LiN (C ₂ F ₅ SO ₂ ) ₂ ), trifluoromethanesulfonate Known supporting salts such as (Li (CF ₃ SO ₃ )), nonafluorobutane sulfonate (Li (C ₄ F ₉ SO ₃ )), and pentafluoroarsine salt (LiAsF ₅ ) can be used. Among these, a perchlorate salt, a tetrafluoroborate salt, and an imide salt are preferable, and Li (CF ₃ SO ₂ ) ₂ N is more preferable. The concentration of the supporting salt is preferably 0.1 mol / L or more and 2.0 mol / L or less, and more preferably 0.5 mol / L or more and 1.2 mol / L or less. The supporting salt having lithium may be used alone or in combination.

Non-aqueous solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate, cyclic ester carbonates such as gamma butyrolactone and gamma valerolactone, In addition to cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, chain ethers such as dimethoxyethane and ethylene glycol dimethyl ether, chloroethylene carbonate, fluoroethylene carbonate, 3-methoxypropionitrile, trimethyl phosphate, triphenyl phosphate, Known organic solvents such as sulfolane, dimethyl sulfoxide, and acetonitrile can be used. These organic solvents may be used alone or in admixture of two or more. A deuterated solvent in which all or part of hydrogen in these organic solvents is deuterium may be used. For example, a deuterated solvent of 3-methoxypropionitrile, dimethyl sulfoxide or acetonitrile, specifically, a deuterated solvent of either dimethyl sulfoxide-d ₆ or acetonitrile-d ₃ can be used. In addition, as the non-aqueous solvent, an ionic liquid, a gel electrolyte, or the like may be used. Examples of ionic liquids include N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluorosulfonyl) imide, N-methyl-N-propylpiperidinium bis (trifluorosulfonyl) imide. N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) imide, 1-methyl-3-propylimidazolium bis (trifluorosulfonyl) imide, 1-ethyl-3-butylimidazolium tetrafluoroborate, etc. Can be used. Further, it may be a mixed solvent containing one or more of the ionic liquid and the above-described organic solvent and deuterated solvent. As the gel electrolyte, a known gel electrolyte can be used. For example, an electrolyte solution containing the above-described supporting salt in a saccharide such as a polymer such as polyvinylidene fluoride, polyethylene glycol, or polyacrylonitrile, an amino acid derivative, or a sorbitol derivative is used. Examples thereof include gel electrolytes.

This non-aqueous ion conducting medium contains a Group 3 metal ion containing a lanthanoid. This group 3 metal ion is more preferable as the bond energy ΔE with the oxygen ion is higher. This bond energy ΔE (eV) is a value obtained by determining the bond energy of oxygen ion (O _2. ⁻ ) -Metal ion (Me ^{n +} ; n is 2 to 4) by electron spin resonance (ESR). And This measurement method is described in Non-Patent Document 1; (Chemistry A European Journal. 6, No. 24 4532-4535 (2000)). This binding energy is, for example, Li ⁺ is 0.53 eV, Mg ²⁺ is 0.65 eV, Ca ²⁺ is 0.58 eV, Sr ²⁺ is 0.52 eV, Sc ³⁺ is 1.00 eV, Y ^{3 +} Is 0.85 eV, La ³⁺ is 0.82 eV, Eu ³⁺ is 0.82 eV, Yb ³⁺ is 0.83 eV, and Lu ³⁺ is 0.83 eV. This Group 3 metal ion preferably has a higher binding energy (ΔE) with oxygen ions than that of lithium ions, and more preferably 0.80 eV or more. In this way, the battery capacity of the non-aqueous air battery can be further increased, and the discharge voltage can be further increased. Of these, at least one of scandium, yttrium, and lanthanum is more preferable. This is because they are relatively abundant and easy to handle. The added amount of the Group 3 metal ions is preferably in the concentration range of 0.001M to 1.0M, and more preferably in the concentration range of 0.005M to 0.5M. If the amount is less than 0.001M, the effect is not as good as the amount of oxygen ions generated, and if it is more than 1M, the transport of lithium ions is hindered.

  Although the counter anion of the Group 3 metal ion is not particularly limited, for example, the counter anion of the supporting salt contained in the ion conductive medium is preferably the same. Examples of the Group 3 metal compound added to the ion conductive medium include a hexafluorophosphate salt, a perchlorate salt, a tetrafluoroborate salt, a pentafluoroarsine salt, a bis (trifluoromethanesulfonyl) imide salt of a Group 3 metal ion, Bis (pentafluoroethanesulfonyl) imide salt, trifluoromethanesulfonate, nonafluorobutanesulfonate, pentafluoroarsine salt and the like can be used. Of these, bis (trifluoromethanesulfonyl) imide salt and the like are preferable.

Here, the relationship between the binding energy ΔE with oxygen ions and the battery performance will be described. For example, the discharge potential of the air battery, oxygen (O ₂₎ is determined by the reduction potential to become oxygen ions (O ^2-). At this time, if a Group 3 metal ion that is strongly bonded to oxygen ions is added to the ion conducting medium in advance, the oxygen ions are stabilized by the Group 3 metal ions, so that the reduction potential is electrochemical. Therefore, it is presumed that the discharge potential of the battery increases. This effect also increases the generation rate of oxides generated during discharge (for example, Li ₂ O _{2 as} a peroxide in a lithium-air battery), so that the accumulation state becomes more uniform, that is, more It is presumed that the oxide can be deposited and accumulated on the electrode, and the discharge capacity is greatly increased.

In the non-aqueous air battery of the present invention, the positive electrode uses oxygen as a positive electrode active material. The oxygen in the positive electrode active material may be oxygen contained in air or pure oxygen gas. This positive electrode is prepared by, for example, mixing a conductive material and a binder, adding an appropriate solvent to form a paste-like positive electrode mixture, applying and drying on the surface of the current collector, and if necessary, electrode density It may be formed by compression so as to increase the thickness. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance of the positive electrode. For example, graphite such as natural graphite (scale-like graphite, scale-like graphite) or artificial graphite, acetylene black, carbon black, What mixed 1 type (s) or 2 or more types, such as ketjen black, carbon whisker, needle coke, carbon fiber, 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 plays a role of binding the active material particles and the conductive material particles. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing resin such as fluorine rubber, or polypropylene, Thermoplastic resins such as polyethylene and polyacrylonitrile, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, 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) that is an aqueous binder may be used. The amount of the binder is preferably 3 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the conductive material. If it is 3 parts by mass or more, it is sufficient to maintain the strength of the positive electrode, and if it is 15 parts by mass or less, the amount of a redox catalyst and a conductive material to be described later does not decrease too much and does not inhibit the progress of the battery reaction. Because it is considered. Examples of the solvent for dispersing the conductive material and the binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N, N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. An organic solvent such as alcohol such as ethanol 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. Alternatively, the kneaded positive electrode mixture may be pressure-bonded to a mesh current collector. The current collector is preferably a porous body such as a net or mesh to allow oxygen to diffuse quickly, and may be a porous metal plate such as stainless steel, nickel, aluminum, or copper. The current collector may have a surface coated with an oxidation-resistant metal or alloy film in order to suppress oxidation. In addition, a transparent conductive material such as InSnO ₂ , SnO ₂ , ZnO, In ₂ O _3, fluorine-doped tin oxide (SnO ₂ : F), antimony-doped tin oxide (SnO ₂ : Sb), tin-doped indium oxide (In ₂ O ₃ : Sn), aluminum-doped zinc oxide (ZnO: Al), gallium-doped zinc oxide (ZnO: Ga) and other materials doped with a single layer or laminate on glass or polymer Good. The film thickness is not particularly limited, but is preferably 3 nm or more and 10 μm or less. The glass or polymer surface may be flat or may have irregularities on the surface.

  The positive electrode may contain an oxygen redox catalyst. 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. The oxidation-reduction catalyst is preferably 2% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 20% by mass or less per positive electrode mixture. If it is 2% by mass or more, it is not too little for oxidation / reduction of oxygen, and if it is 50% by mass or less, the conductive material and the binder are not too small, and electrical conductivity and strength can be ensured.

  In the nonaqueous air battery of the present invention, the negative electrode may have a negative electrode active material. The negative electrode active material is not particularly limited as long as it can store and release at least lithium, and can be used for an air battery. Examples of the negative electrode capable of occluding and releasing lithium include metal lithium and lithium alloys, metal oxides, metal sulfides, and carbonaceous materials that occlude and release lithium. Examples of the lithium alloy include alloys of lithium with aluminum, tin, magnesium, indium, calcium, silicon, and the like. Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide. Examples of the metal sulfide include tin sulfide and titanium sulfide. Examples of the carbonaceous material that occludes and releases lithium include graphite, coke, mesophase pitch-based carbon fiber, spherical carbon, and resin-fired carbon. In addition, iron phosphide may be used. If it has such a negative electrode active material, it can be set as a lithium air battery. As the conductive material, binder, solvent and the like used for the negative electrode, those exemplified for the positive electrode can be used. The negative electrode current collector includes copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as improved adhesion, conductivity and reduction resistance. For the purpose, for example, a copper surface treated with carbon, nickel, titanium, silver or the like can be used. For these, the surface can be oxidized. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded, lath, porous, foam, and formed fiber group.

  The nonaqueous air 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 can withstand the use of a non-aqueous air battery. For example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or a microporous film of an olefin resin such as polyethylene or polypropylene Is mentioned. These may be used alone or in combination.

  The shape of the non-aqueous air 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 used for an electric vehicle etc.

  The non-aqueous air battery according to the present embodiment described in detail above includes a Group 3 metal ion including a lanthanoid in addition to lithium ions in the non-aqueous ion conductive medium, and thus increases the battery capacity and increases the discharge voltage. Can be increased. This is because, for example, the Group 3 metal ions have a high binding energy ΔE with oxygen ions of 0.8 eV or more, and the oxygen ions are stabilized by the Group 3 metal ions, so that the discharge potential is increased. It is guessed. As a result, the generation rate of the oxide generated at the time of discharge is increased, and the accumulation state becomes more uniform, so that it is presumed that the battery capacity increases.

  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.

  Below, the example which produced the non-aqueous air battery of this invention concretely is shown.

[Production of evaluation cell]
FIG. 1 is a cross-sectional view of an F-type electrochemical cell 20 (made by Hokuto Denko) used in the charge / discharge test. The F-type electrochemical cell 20 was assembled as follows in a glove box under an argon atmosphere. First, the negative electrode 24 and the separator 25 were installed in the SUS casing 22, the positive electrode 26 and the negative electrode 24 were set to face each other, and 5 mL of the electrolyte solution 28 was injected. Thereafter, a foamed nickel plate 32 was placed on the positive electrode 26, and a gas reservoir 34 through which air can flow to the positive electrode 26 side was disposed thereon, and the cell was fixed to obtain an electrochemical cell of Example 1. The gas reservoir 34 of the F-type electrochemical cell 20 was filled with dry oxygen.

Example 1
The positive electrode was produced as follows. 90 parts by mass of ketjen black (ECP-600JD manufactured by Mitsubishi Chemical) as a conductive material, 10 parts by mass of polytetrafluoroethylene (manufactured by Daikin Industries) as a binder, and a solvent using ethanol as a mixture using a mortar and The kneaded mixture was rolled into a sheet shape. The obtained composite material sheet was pressure-bonded to 5 mg of a stainless steel mesh (SUS304, # 50, wire diameter 0.12 mm), and heated and dried in an oven at 100 ° C. for 120 minutes to obtain a positive electrode. As the negative electrode, metallic lithium (manufactured by Honjo Metal) having a diameter of 10 mm and a thickness of 0.4 mm was used. Next, N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) imide (manufactured by Kanto Kagaku) in which 1 mol / L lithium bis (trifluoromethanesulfonyl) imide is dissolved is prepared. Scandium trifluoromethanesulfonate (III) salt was dissolved as an additive so as to have a concentration of 05 mol / L to obtain a non-aqueous electrolyte. In a glove box under an argon atmosphere, a negative electrode, a polyethylene separator and a positive electrode were placed in an F-type electrochemical cell manufactured by Hokuto Denko as shown in FIG. 1, and the above nonaqueous electrolyte was filled between the negative electrode and the positive electrode. 1 air battery was obtained.

(Comparative Example 1)
According to the same steps as in Example 1, except that an electrolytic solution of only N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) imide in which 1 mol / L lithium bis (trifluoromethanesulfonyl) imide was dissolved was used. The produced evaluation cell was designated as Comparative Example 1.

[Charge / discharge test]
An F-type cell is connected to a charge / discharge device (HJ1001SM8A) manufactured by Hokuto Denko and discharged to 2.3 V at a current of 50 mA / g per positive electrode material between the positive electrode and the negative electrode, and then a current of 50 mA / g per positive electrode material The battery was charged to 3.85V. FIG. 2 is a discharge curve of Example 1 and Comparative Example 1. In Comparative Example 1, the initial discharge capacity was 1517 mAh / g, and the discharge voltage at the time of 1000 mAh / g was 2.46V. On the other hand, in Example 1, the initial discharge capacity was 2519 mAh / g, the discharge voltage at the time of 1000 mAh / g was 2.56 V, and it was found that the battery was excellent in both discharge capacity and discharge voltage.

(Example 2)
An evaluation cell prepared in the same manner as in Example 1 was used in Example 2 except that an electrolytic solution in which scandium (III) trifluoromethanesulfonate was replaced with yttrium (III) trifluoromethanesulfonate was used. FIG. 3 is a discharge curve of Example 2 and Comparative Example 1. In Example 2, the initial discharge capacity was 2358 mAh / g, the discharge voltage at the time of 1000 mAh / g was 2.66 V, and it was found that the battery was excellent in both discharge capacity and discharge voltage.

(Example 3)
An evaluation cell produced in the same process as in Example 1 was used in Example 3, except that an electrolyte solution in which scandium (III) trifluoromethanesulfonate was replaced with lanthanum (III) trifluoromethanesulfonate was used. 4 is a discharge curve of Example 3 and Comparative Example 1. FIG. In Example 3, the initial discharge capacity was 2823 mAh / g, the discharge voltage at the time of 1000 mAh / g was 2.65 V, and it was found that the battery was excellent in both discharge capacity and discharge voltage.

(Experimental results and discussion)
The measurement results are summarized in Table 1. As shown in Table 1, Examples 1 to 3 in which Group 3 metal ions containing lanthanoids were added to the electrolytic solution were found to have higher battery capacity and discharge voltage. The reason why such an effect can be obtained is that, for example, when a metal ion that strongly binds to oxygen ions is present in the electrolyte, the oxygen ions are stabilized by the metal ions, so that the reduction potential is electrochemical. It was inferred that the discharge potential as a battery was increased. This effect also increases the rate of generation of peroxide (Li ₂ O ₂ ) generated during discharge, making the accumulation state more uniform, that is, depositing and accumulating more oxide on the electrode. It was speculated that the discharge capacity was greatly increased. In particular, it has been found that it is preferable that a group 3 metal ion having a binding energy ΔE with oxygen ion of 0.8 eV or more and strongly binding to oxygen ion is present in the electrolyte.

  20 F type electrochemical cell, 22 casing, 24 negative electrode, 25 separator, 26 positive electrode, 28 electrolytic solution, 32 foam nickel plate, 34 gas reservoir.

Claims (1)

A positive electrode;
A negative electrode,
It is interposed between the positive electrode and the negative electrode , conducts lithium ions, contains a Group 3 metal ion that is at least one of scandium, yttrium, and lanthanum, and the concentration of the Group 3 metal ion is 0. A non-aqueous ion conducting medium that is not less than 001M and not more than 1.0M
A non-aqueous air battery.

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