JP5434062B2 - Air battery - Google Patents

Description

  The present invention relates to an air battery.

  Conventionally, an air battery using oxygen in the air as a positive electrode active material is known. In such an air battery, since oxygen in the air is used as the positive electrode active material, it is not necessary to fill the positive electrode active material in the battery. Therefore, there is an advantage that the energy density can be increased.

By the way, although an air lithium battery may use oxygen in the air at the time of discharge, moisture in the air may be taken into the battery simultaneously with oxygen and hydrolyze lithium that is a negative electrode active material. In particular, a large amount of oxygen is required at the time of large current discharge, and the amount of moisture taken in at the same time increases, so that a decrease in battery capacity due to deterioration of the negative electrode active material becomes a problem. In this regard, Patent Document 1 proposes to adopt a structure in which an air battery and a normal lithium ion secondary battery are bonded back to back. As a result, the lithium ion secondary battery, which is another battery, can supply power while reducing the amount of air supplied to the air battery and suppressing the deterioration of the negative electrode active material, thereby enabling high capacity. .
JP 2006-286414 A

  However, in the air battery described in Patent Document 1, radicals generated at the positive electrode during discharge may be combined with metal ions and deposited on the positive electrode as a solid compound such as lithium oxide. In this case, for example, when there is no region where the solid compound can be deposited, the discharge reaction of the air battery may stop. Even if the depositable region remains, if the electrical resistance of the solid compound is large, the amount of deposition increases and the resistance increases, and if it exceeds a certain amount, the discharge reaction of the air battery may stop. It was. This has been one of the problems for further increase in capacity.

  The present invention has been made to solve such a problem, and a main object of the present invention is to provide an air battery having a larger discharge capacity than the conventional one.

  In order to achieve the above-described object, the present inventors considered that it is effective to suppress the formation of a solid compound. Then, in an air battery in which an ion conductive medium is interposed between the negative electrode and a positive electrode having oxygen as a positive electrode active material, a compound that reacts with radicals and stabilizes it and an electrolyte are added to the ion conductive medium. It has been found that it contributes to the improvement of the discharge capacity, and the present invention has been completed.

That is, the air battery of the present invention is
A positive electrode using oxygen as a positive electrode active material;
A negative electrode having a negative electrode active material;
An ion-conducting medium that is interposed between the positive electrode and the negative electrode and includes a compound that reacts with a radical to stabilize it and an electrolyte;
It is equipped with.

  According to the air battery of the present invention, by using an ion conductive medium containing a compound that reacts with and stabilizes radicals (hereinafter also referred to as a radical stabilizer), the discharge capacity can be increased as compared with a conventional air battery. Can be bigger. The reason why such an effect can be obtained is not clear, but the radical stabilizer captures the radical before the radical generated at the positive electrode during the discharge combines with the metal ion to form the solid compound. This is thought to be because it suppresses the generation of. This also suppresses the deposition of the solid compound on the positive electrode, stops the discharge reaction due to the absence of the solid compound depositable region, and the discharge reaction due to the increase in resistance accompanying the increase in the amount of solid compound deposition. This is thought to be because it is possible to suppress the stoppage.

  The air battery of the present invention is a radical stabilizing compound that is interposed between a positive electrode having oxygen as a positive electrode active material, a negative electrode having a negative electrode active material, a positive electrode and a negative electrode, and reacts with a radical to stabilize it. An ionic conductive medium including an agent and an electrolyte.

  In the air battery of the present invention, the positive electrode uses oxygen from a gas as the positive electrode active material. As the gas, for example, air or oxygen gas may be used.

In the air battery of the present invention, the positive electrode may include a redox catalyst. As oxidation-reduction catalysts, electrolytic manganese dioxide, cobalt phthalocyanine, cobalt porphyrin, cerium oxide (CeO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), silver oxide (AgO), lithium tungstate (Li ₂ WO ₄ ), lithium molybdate (Li ₂ MoO ₄ ), lithium manganese cobaltate (LiMn _x Co _y O ₄ ), lanthanum calcium cobalt composite oxide (La _x Ca _y CoO ₃ -z), lanthanum strontium cobalt oxide _{(La x Sr y CoO 3-} z), sodium lanthanum manganate _{(Na x La y MnO 3)} , potassium lanthanum manganate _{(K x La y MnO 3-} z), copper-manganese composite oxide (Cu _x Mn _y O ₄ ), manganese oxide (MnO ₂ ) and the like. The oxidation-reduction catalyst may be one in which a carbon material such as ketjen black is used as a catalyst carrier and supported on the catalyst carrier.

  In the air battery of the present invention, the positive electrode may contain a conductive material. Although it will not specifically limit if it is a material which has electroconductivity as a electrically conductive material, For example, carbon is mentioned. As this carbon, carbon blacks such as ketjen black, acetylene black, channel black, furnace black, lamp black and thermal black may be used, or natural graphite such as flake graphite, graphite such as artificial graphite and expanded graphite. Alternatively, activated carbons using charcoal or coal as raw materials, or carbon fibers obtained by carbonizing synthetic fibers or petroleum pitch-based raw materials may be used. Further, conductive fibers such as metal fibers, metal powders such as nickel and aluminum, and organic conductive materials such as polyphenylene derivatives may be used. These may be used alone or in combination. The positive electrode may contain a metal oxide such as lithium oxide or a metal peroxide such as lithium peroxide.

  In the air battery of the present invention, the positive electrode may contain a binder. Although it does not specifically limit as a binder, A thermoplastic resin, a thermosetting resin, etc. are mentioned. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin) , Polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrif Examples include olefin copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and ethylene-acrylic acid copolymer. . These materials may be used alone or in combination.

  In the air battery of the present invention, the positive electrode may be formed by, for example, mixing a conductive material, a binder, or the like and rolling the sheet into a sheet shape and pressing the current collector. The mixing method may be wet mixing in the presence of a solvent such as ethanol, or may be dry mixing using a mortar or the like. The current collector is not particularly limited as long as it is formed of a conductive material, but is preferably stainless steel, nickel, aluminum, copper, or the like. In order to allow oxygen to diffuse quickly, a porous body such as a net or mesh is preferable. The current collector may have a surface coated with an oxidation-resistant metal or alloy film in order to suppress oxidation.

  In the air battery of the present invention, the negative electrode is not particularly limited, but preferably has a negative electrode active material capable of occluding and releasing lithium. Examples of such a negative electrode include metal oxides, metal sulfides, and carbonaceous materials that occlude and release lithium, in addition to metal lithium and lithium alloys. Examples of the lithium alloy include an alloy of lithium with aluminum, tin, magnesium, indium, calcium, 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 absorbs and releases lithium ions include graphite, coke, mesophase pitch-based carbon fiber, spherical carbon, and resin-fired carbon. Further, the negative electrode may be configured to include a metal, and the metal may be oxidized into metal ions at the negative electrode during discharge. Examples of such metals include lithium, sodium, potassium, magnesium, aluminum, zinc, and alloys thereof.

In the air battery of the present invention, the ion conductive medium interposed between the negative electrode and the positive electrode contains an electrolyte. As the electrolyte, but are not particularly limited, for _{example, LiPF 6, LiClO 4, LiAsF} 6, LiBF 4, Li (CF 3 SO 2) 2 N, Li (CF 3 SO 3), LiN (C 2 F A known electrolyte such as ₅ SO ₂ ) ₂ can be used. These electrolytes may be used alone or in combination of two or more. Moreover, it is preferable that an ion conduction medium is a non-aqueous ion conduction medium. As the non-aqueous ion conductive medium, for example, a non-aqueous electrolyte solution containing the above-described electrolyte can be used. The concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 to 2.0 mol / L, and more preferably 0.8 to 1.2 mol / L. As the non-aqueous electrolyte, an aprotic organic solvent can be used. Examples of such an organic solvent include cyclic carbonates, chain carbonates, cyclic esters, cyclic ethers, chain ethers, and the like. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of the cyclic ester carbonate include gamma butyrolactone and gamma valerolactone. Examples of the cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of the chain ether include dimethoxyethane and ethylene glycol dimethyl ether. These may be used alone or in combination. In addition, nitrile solvents such as acetonitrile and propyl nitrile, ionic liquids, gel electrolytes, and the like may be used as the ion conductive medium.

In the air battery of the present invention, the ion conductive medium includes a radical stabilizer. The radical stabilizer is preferably at least one selected from nitrone compounds and nitroso compounds. Specifically, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) (see formula (1)) and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M ₄ PO) (see formula (2)), N-tert-butyl-α-phenylnitrone (PBN) (see formula (3)), N-tert-butyl-α- (4-pyridyl-1-oxide) nitrone ( POBN) (see formula (4)), 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) (see formula (5)), 2- (5,5-dimethyl-2-oxo 2λ ^5- [1,3,2] dioxaphosphinan-2-yl) -2-methyl-3,4-dihydro-2H-pyrroline-1-oxide (see formula (6)), etc. Nitrosobenzene (see formula (7)), 3,5- Sodium bromo-4-nitrosobenzenesulfonate (DBNBS) (see formula (8)), 2,3,5,6-tetramethylnitrosobenzene (nitrosozulene) (see formula (9)), 2,4,6-tri Examples thereof include nitroso compounds such as -tert-butylnitrosobenzene (TTBNB) (see formula (10)) and 2-methyl-2-nitrosopropane dimer (see formula (11)). The radical stabilizer is preferably a compound that reacts with and stabilizes oxygen radicals. Since an air battery uses oxygen as a positive electrode active material, it is speculated that many of the solid compounds deposited on the positive electrode are metal oxides. Therefore, it is because it is thought that the production | generation of a solid compound can be suppressed efficiently by trapping oxygen radical. The radical stabilizer may be a polymer or a monomolecular compound. In the case of a monomolecular compound, it is preferable because it is uniformly dispersed by dissolving in an ion conductive medium (for example, an electrolytic solution) and sufficiently exhibits a redox catalyst function. Note that nitrone compounds and nitroso compounds are known as spin trapping agents in ESR (electron spin resonance analysis). The spin trapping agent captures short-lived radicals and generates stable secondary radicals called spin adducts. This is presumed to be the same mechanism as the reaction by the radical stabilizer of the present invention. Therefore, the radical stabilizer may be a spin trapping agent other than a nitrone compound or a nitroso compound. The ion conductive medium preferably contains a radical stabilizer in the range of 80% by volume or less, and more preferably in the range of 50% by volume or less. Further, the ion conductive medium preferably contains 1% by volume or more of the radical stabilizer, more preferably 5% by volume or more, and further preferably 20% by volume or more. If the volume is 80% by volume or less, it is considered that the amount of electrolyte and the like necessary for ionic conduction is not relatively reduced, and thus the capacity reduction can be further suppressed. Moreover, if it is 1 volume% or more, it is thought that the effect of addition of a radical stabilizer is fully acquired.

  The air battery of the present invention may include a separator between the negative electrode and the positive electrode. The separator is not particularly limited as long as it is a composition that can withstand the use of the air battery of the present invention. For example, the separator is a 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. A film is mentioned. These may be used alone or in combination.

  The shape of the 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 etc. which are used for an electric vehicle etc.

  The air battery of the present invention may be used as a primary battery, but may be used as a chargeable / dischargeable secondary battery.

[Example 1]
The positive electrode was produced as follows. First, 5.2 parts by weight of electrolytic manganese dioxide (made by Mitsui Mining Co., Ltd.) as a catalyst, 84.5 parts by weight of Ketjen Black (Mitsubishi Chemical, ECP600) as a catalyst carrier, and polytetrafluoro as a binder A positive electrode mixture was obtained by thoroughly mixing and kneading 10.3 parts by weight of ethylene (manufactured by Daikin) in ethanol as a solvent. The obtained positive electrode mixture was rolled, and a 1.3 mm × 1.3 mm, a thickness of 0.2 mm, and a 5 mg sheet-form positive electrode material were obtained therefrom. This positive electrode material was pressure-bonded onto a 1.3 mm × 1.3 mm stainless steel (SUS304) mesh (# 50, wire diameter 0.12 mm). This was dried in a 100 ° C. oven by vacuum heating for 120 minutes to obtain a positive electrode. Moreover, 1.5 mm x 1.5 mm, thickness 0.4mm, and 0.5g metallic lithium (made by Honjo Metal) were used for the negative electrode. As an ionic conduction medium, lithium bis (trifluoromethanesulfonyl) imide (Li (CF ₃ SO ₂ ) ₂ N) was added at 1 mol / L in a solution (manufactured by Toyama Pharmaceutical Co., Ltd.) comprising 30 parts by weight of ethylene carbonate and 70 parts by weight of diethyl carbonate. What was melt | dissolved so that it might become L was used. What added 5, 5- dimethyl- 1-pyrroline-N-oxide (refer Formula (1)) as a radical stabilizer so that it might become 20 volume% was used as this.

  The air battery 20 (F-type electrochemical cell, manufactured by Hokuto Denko) was produced as follows. First, as shown in FIG. 20, the negative electrode 25 was installed in the casing 21 made of SUS, and the positive electrode 23 was set so as to face the negative electrode through a separator 27 made of polyethylene. Next, the above-described ion conductive medium 28 was injected between the positive electrode 23 and the negative electrode 25. Thereafter, the foamed nickel plate 22 was placed on the positive electrode 23, and the cell was fixed by pressing it with a pressing member 29 that allows air to flow to the positive electrode 23 side. Thus, the air battery 20 of Example 1 was obtained. Although not shown, the casing 21 can be separated into an upper part that contacts the positive electrode 23 and a lower part that contacts the negative electrode 25, and an insulating resin is interposed between the upper part and the lower part. Thereby, the positive electrode 23 and the negative electrode 25 are electrically insulated.

  Next, the air battery 20 thus obtained was set in a charge / discharge device (model name HJ1001SM8A) manufactured by Hokuto Denko, and a current of 50 mA per 1 g of the positive electrode material was passed between the positive electrode 23 and the negative electrode 25. The battery was discharged until the open circuit voltage was 1.5V. This discharge test was performed at 25 ° C. FIG. 2 shows the change in discharge voltage at this time, and Table 1 shows the discharge capacity. In Table 1, data of Examples 2 to 4 and Comparative Examples 1 and 2 described later are also described.

[Examples 2 to 4]
An air battery of Example 2 was produced in the same manner as in Example 1 except that 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (see formula (2)) was used as the radical stabilizer. . Moreover, the air battery of Example 3 was produced similarly to Example 1 except having used N-tert- butyl-alpha-phenyl nitrone (refer Formula (3)) as a radical stabilizer. In addition, an air battery of Example 4 was produced in the same manner as in Example 1 except that sodium 3,5-dibromo-4-nitrosobenzenesulfonate (see formula (8)) was used as the radical stabilizer. A discharge test was conducted in the same manner as in Example 1 using the air battery thus obtained.

[Examples 5 and 6]
The air battery of Example 5 was prepared in the same manner as in Example 1 except that 5,5-dimethyl-1-pyrroline-N-oxide (see formula (1)) as a radical stabilizer was added to 50% by volume. Created. Further, an air battery of Example 6 was produced in the same manner as Example 1 except that 5,5-dimethyl-1-pyrroline-N-oxide as a radical stabilizer was added so as to be 80% by volume. A discharge test was conducted in the same manner as in Example 1 using the air battery thus obtained.

[Comparative Example 1]
An air battery was produced in the same manner as in Example 1 except that 5,5-dimethyl-1-pyrroline-N-oxide as a radical stabilizer was not added, and a discharge test was performed.

[Comparative Example 2]
An air battery was prepared in the same manner as in Example 1 except that 5,5-dimethyl-1-pyrroline-N-oxide as a radical stabilizer was 100% by volume and no other component was added to the ion conductive medium. A discharge test was conducted.

[Experimental result]
In Examples 1 to 4 in which the radical stabilizer was added to the ion conductive medium, it was found that the discharge capacity was increased as compared with Comparative Example 1 in which the radical stabilizer was not added. Even if it was other than the compounds used in the examples, it was speculated that the same results could be obtained if they were radical stabilizers. Further, when 5,5-dimethyl-1-pyrroline-N-oxide is used as a radical stabilizer and the proportion in the ion conductive medium is changed, the radical stabilizer is contained in an amount of 80% by volume or less. In Examples 1, 5, and 6, the discharge capacity was increased as compared with Comparative Example 2 in which the radical stabilizer was 100% by volume. In particular, it was found that the discharge capacities of Examples 1 and 5 contained in the range of 50% by volume or less were increased. It was speculated that similar results could be obtained even with radical stabilizers other than the compounds used in the examples.

2 is a cross-sectional view of the air battery 20. FIG. 3 is a graph showing a change in discharge voltage in the discharge test of Example 1.

Explanation of symbols

  20 air battery, 21 casing, 22 nickel foam plate, 23 positive electrode, 25 negative electrode, 27 separator, 28 ion conduction medium, 29 holding member.

Claims (4)

A positive electrode using oxygen as a positive electrode active material;
A negative electrode having a negative electrode active material;
An ion conductive medium that is interposed between the positive electrode and the negative electrode and includes an electrolyte and a compound that reacts with and stabilizes oxygen radicals;
With air battery.   The air battery according to claim 1, wherein the ion conductive medium contains the compound in an amount of 80% by volume or less.   The air battery according to claim 1, wherein the compound is at least one selected from a nitrone compound and a nitroso compound. The negative electrode has a negative electrode active material capable of occluding and releasing lithium,
The air battery according to any one of claims 1 to 3, wherein the ion conduction medium is a non-aqueous ion conduction medium including a compound that reacts with oxygen radicals to stabilize the ion conduction medium.

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