JP2013051091A - Metal oxygen battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal oxygen battery capable of increasing battery capacity by reducing overvoltage.SOLUTION: A metal oxygen battery 1 includes: a positive electrode 2 using oxygen as an active material and containing an oxygen storage material and a conductive material; a negative electrode 3 capable of adsorbing/desorbing lithium ions; and an electrolyte layer 4 held by the positive electrode 2 and the negative electrode 3. The positive electrode 2 includes a conductive porous body, and the oxygen storage material and the conductive material are supported on an inner surface of a pore of the conductive porous body.

Description

  The present invention relates to a metal oxygen battery.

  Conventionally, as a battery reaction, a metal oxygen battery using an oxygen redox reaction at a positive electrode is known. The metal oxygen battery includes one that performs the oxidation-reduction reaction using oxygen taken from the air, and a positive electrode provided with an oxygen storage material, and performs the oxidation-reduction reaction using oxygen released from the oxygen storage material. There is something to do.

  In a metal oxygen battery having an oxygen storage material in the positive electrode, during discharge, the metal is oxidized at the negative electrode to generate metal ions, and the metal ions move to the positive electrode side. On the other hand, in the positive electrode, oxygen released from the oxygen storage material is reduced to oxygen ions and combined with the metal ions to form a metal oxide. In the metal oxygen battery, the reverse reaction of the reaction occurs at the negative electrode and the positive electrode during charging.

  As such a metal oxygen battery, one using a manganese complex containing oxygen as the oxygen storage material (see, for example, Patent Document 1) or one using an Fe-based metal composite oxide having a perovskite structure is known. (For example, refer to Patent Document 2).

JP 2009-230985 A JP 2009-283181 A

  However, a conventional metal oxygen battery including a positive electrode using the oxygen storage material has a disadvantage that a sufficient battery capacity cannot be obtained due to a large overvoltage.

  An object of the present invention is to provide a metal oxygen battery capable of eliminating such inconvenience and reducing the overvoltage and increasing the battery capacity.

  As a result of earnestly examining the reason why the conventional metal oxygen battery has a large overvoltage and a sufficient battery capacity cannot be obtained, the present inventors have obtained the following knowledge.

  In the conventional metal oxygen battery, as described above, since the metal oxide is generated at the positive electrode during discharge, the volume of the positive electrode increases. In order to absorb the increase in volume, the positive electrode needs to have a certain thickness. However, in this case, the conductivity of electrons becomes non-uniform in the thickness direction inside the positive electrode. It seems that the internal resistance increases and the overvoltage rises.

  As a result of further investigations based on the above findings, the present inventors solved the problem by using a conductive porous body for the positive electrode and causing the battery reaction to occur on the inner surface of the pores of the conductive porous body. We have found out what we can do and have arrived at the present invention.

  Therefore, in order to achieve the above object, the present invention is sandwiched between a positive electrode containing oxygen as an active material and containing an oxygen storage material and a conductive material, a negative electrode capable of absorbing and releasing lithium ions, and the positive electrode and the negative electrode. In the metal oxygen battery comprising the electrolyte layer, the positive electrode comprises a conductive porous body, and the oxygen storage material and the conductive material are supported on the inner surfaces of the pores of the conductive porous body. It is characterized by.

  In the present application, the “oxygen storage material” means a material that can occlude and release oxygen and can adsorb and desorb oxygen on the surface thereof. Oxygen adsorbed and desorbed on the surface of the oxygen storage material does not need to diffuse into the oxygen storage material because it is occluded and released by the oxygen storage material. It will be used for the reaction and can act more preferentially.

  In the metal oxygen battery of the present invention, in the positive electrode, since the oxygen storage material and the conductive material are supported on the inner surface of the hole of the conductive porous body, the metal oxide formed during discharge is It will be accommodated in the hole. Therefore, in the metal oxygen battery of the present invention, an increase in volume due to the formation of the metal oxide can be absorbed by the conductive porous body.

  In the metal oxygen battery of the present invention, since the porous body itself has conductivity, the conduction of electrons to the oxygen storage material and the conductive material carried in the respective holes of the porous body. Can be made uniform in the thickness direction of the positive electrode. As a result, according to the metal oxygen battery of the present invention, it is possible to reduce the internal resistance, suppress an increase in overvoltage, and obtain a large battery capacity.

  In the metal oxygen battery of the present invention, it is preferable that the conductive porous body has a porosity in the range of 10 to 90% by volume. When the porosity of the conductive porous body is less than 10% by volume, it may not be possible to secure a space for accommodating the metal oxide formed during discharge, and a sufficient battery capacity may not be obtained. is there.

  Further, when the porosity of the conductive porous body exceeds 90% by volume, the structure may not be maintained when charging and discharging are repeated. If the conductive porous body cannot maintain its structure, the electron conduction path is interrupted and current collection cannot be performed, so that the function as the positive electrode is lost.

  Moreover, the metal oxygen battery of this invention WHEREIN: It is preferable that the said oxygen storage material and the said electroconductive material carry | supported by the hole inner surface of the said electroconductive porous body are provided with the thickness of the range of 1-200 micrometers. When the thickness of the oxygen storage material and the conductive material is less than 1 μm, the absolute amount of the oxygen storage material as an active material is insufficient in the positive electrode, and it may not be possible to obtain a sufficient energy density. . Further, when the thickness of the oxygen storage material and the conductive material exceeds 200 μm, the pores of the conductive porous body are buried in the oxygen storage material and the conductive material, and the metal formed during discharge It may become impossible to secure a space for accommodating the oxide.

  In the metal oxygen battery of the present invention, the oxygen storage material is preferably composed of a composite metal oxide of yttrium and manganese. According to the composite metal oxide of yttrium and manganese, an excellent oxygen storage capacity can be obtained.

  Moreover, it is preferable that the metal oxygen battery of this invention is equipped with the housing | casing which accommodates the said positive electrode, the said negative electrode, and the said electrolyte layer in the sealed state. Since the positive electrode, the negative electrode, and the electrolyte layer are hermetically sealed in the casing, it is possible to prevent water in the air, carbon dioxide, and the like from entering and deteriorating.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory sectional drawing which shows one structural example of the metal oxygen battery of this invention. Explanatory sectional drawing which expands and shows typically the state of the positive electrode of the metal oxygen battery of this invention. The graph which shows the relationship between the cell voltage at the time of discharge of the metal oxygen battery of this invention, and a capacity | capacitance.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  As shown in FIG. 1, the metal oxygen battery 1 of this embodiment is disposed between a positive electrode 2 using oxygen as an active material, a negative electrode 3 capable of absorbing and releasing lithium ions, and a positive electrode 2 and a negative electrode 3. The positive electrode 2, the negative electrode 3, and the electrolyte layer 4 are sealed and accommodated in a case 5.

  The case 5 includes a cup-shaped case body 6 and a lid body 7 that closes the case body 6, and an insulating resin 8 is interposed between the case body 6 and the lid body 7. In the metal oxygen battery 1, the case body 6 functions as a positive electrode plate and the lid body 7 functions as a cathode plate.

  In the metal oxygen battery 1, the positive electrode 2 includes a conductive porous body 21 as shown in FIG. 2, and an oxygen storage material 23 and a conductive material 24 are formed on the inner surface of the hole 22 of the conductive porous body 21. Are carried. The conductive porous body 21 also functions as a current collector in the positive electrode 2.

  As the conductive porous body 21, for example, a porous metal body made of nickel or a nickel-chromium alloy can be used. The porous metal body has, for example, pores having a pore diameter in the range of 1 to 200 μm and a porosity in the range of 10 to 90%.

The oxygen storage material 23 is made of, for example, YMnO ₃ and has a function of occluding or releasing oxygen, and can adsorb and desorb oxygen on the surface thereof. The oxygen storage material 23 has a particle diameter in the range of 0.1 to 100 μm, for example, and can be used in the range of 40 to 98% by mass with respect to the total amount of the positive electrode 2.

  As the conductive material 24, for example, carbon black such as ketjen black or vapor grown carbon fiber (VGCF) can be used.

  Further, the oxygen storage material 23 and the conductive material 24 may be supported on the inner surface of the hole 22 of the conductive porous body 21 via a binder. Examples of the binder include polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyimide (PI), and acrylic resin. Etc.

  The positive electrode 2 can be manufactured, for example, by applying a slurry in which the oxygen storage material 23, the conductive material 24, and the binder are dispersed in a medium such as water to the conductive porous body 21 and drying the slurry. . In order to apply the slurry to the conductive porous body 21, it is preferable that the slurry has a viscosity in the range of 0.01 to 100 Pa · s. When the viscosity of the slurry is less than 0.01 Pa · s, sufficient binding of the slurry to the conductive porous body 21 cannot be obtained, and it becomes difficult to uniformly apply the slurry. Moreover, when the viscosity of the slurry exceeds 100 Pa · s, the permeability of the slurry to the conductive porous body 21 becomes low, and it becomes difficult to apply the slurry uniformly in the thickness direction of the conductive porous body 21.

  Next, the negative electrode 3 is made of a material capable of absorbing and releasing lithium ions, and examples thereof include a carbonaceous material capable of absorbing and releasing lithium ions such as metallic lithium, a lithium alloy, and graphite.

  Next, the electrolyte layer 4 may be, for example, a nonaqueous electrolyte solution immersed in a separator, or may be a solid electrolyte.

  As the non-aqueous electrolyte solution, for example, a lithium salt dissolved in a non-aqueous solvent can be used. As said lithium salt, carbonate, nitrate, acetate etc. can be mentioned, for example. Examples of the non-aqueous solvent include a carbonate ester solvent, an ether solvent, and an ionic liquid.

  Examples of the carbonate solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate. Two or more of the carbonate ester solvents can be used in combination.

  Examples of the ether solvent include dimethoxyethane, dimethyl trigram, polyethylene glycol, and the like. Two or more of the ether solvents can be used in combination.

  Examples of the ionic liquid include cation such as imidazolium, ammonium, pyridinium, and peridium, bis (trifluoromethylsulfonyl) imide (TTSI), bis (pentafluoroethylsulfonyl) imide (BETI), tetrafluoroborate, park, and the like. Examples thereof include salts with anions such as lorate and halogen anions.

  Examples of the separator include glass fiber, glass paper, polypropylene nonwoven fabric, polyimide nonwoven fabric, polyphenylene sulfide nonwoven fabric, and polyethylene porous film.

  Examples of the solid electrolyte include an oxide solid electrolyte and a sulfide solid electrolyte.

Examples of the oxide solid electrolyte include Li ₇ La ₃ Zr ₂ O ₁₂ , which is a composite oxide of lithium, lanthanum, and zirconium, glass ceramics mainly composed of lithium, aluminum, silicon, titanium, germanium, and phosphorus. Can be mentioned. In Li ₇ La ₃ Zr ₂ O ₁₂ , lithium, lanthanum, and zirconium were partially substituted with other metals such as strontium, barium, silver, yttrium, lead, tin, antimony, hafnium, tantalum, and niobium. It may be a thing.

  Next, examples of the positive electrode current collector 9 include those made of a porous material such as titanium, stainless steel, nickel, aluminum, and copper.

  In the metal oxygen battery 1 of the present embodiment, at the time of discharging, as shown in the following formula, the lithium metal is oxidized in the negative electrode 3 to generate lithium ions and electrons. The generated lithium ions move to the positive electrode 2 through the electrolyte layer 4 and react with oxygen ions generated by reduction of oxygen supplied from the oxygen storage material 23 to generate lithium oxide or lithium peroxide.

(Negative electrode) 4Li → 4Li ⁺ + 4e ⁻
(Positive electrode) O ₂ + 4e ⁻ → 2O ²⁻
4Li ⁺ + 2O ²⁻ → 2Li ₂ O
2Li ⁺ + 2O ²⁻ → Li ₂ O ₂
Here, the lithium oxide or lithium peroxide precipitates in the hole 22 of the conductive porous body 21 constituting the positive electrode 2 and is accommodated in the hole 22. Therefore, in the metal oxygen battery 1 of this embodiment, the increase in volume due to the lithium oxide or lithium peroxide deposited during discharge can be absorbed by the pores 22 of the conductive porous body 21.

  Further, in the metal oxygen battery 1 of the present embodiment, the conductive porous body 21 itself has conductivity and acts as a current collector. Therefore, the electron conductivity with respect to the oxygen storage material 23 and the conductive material 24 carried in the hole 22 can be made uniform in the thickness direction of the positive electrode 2, and the individual oxygen storage materials 23 and the conductivity can be made. The distance that electrons are conducted to the material 24 can be shortened. As a result, according to the metal oxygen battery 1 of the present embodiment, the internal resistance can be reduced, an increase in overvoltage can be suppressed, and a large battery capacity can be obtained.

  On the other hand, at the time of charging, lithium ions and oxygen ions are generated from lithium oxide or lithium peroxide 24 in the positive electrode 2 as shown in the following equation. The generated lithium ions move to the negative electrode 3 through the electrolyte layer 4 and are reduced as the negative electrode 3 to be deposited as metallic lithium.

(Positive electrode) 2Li ₂ O → 4Li ⁺ + 2O ²⁻
Li ₂ O ₂ → 2Li ⁺ + 2O ²⁻
(Negative electrode) 4Li ⁺ + 4e ⁻ → 4Li
During the charging, lithium oxide or lithium peroxide 24 dissociates into lithium ions and oxygen ions and disappears. However, since lithium oxide or lithium peroxide 24 is deposited inside the hole 22 as described above, even if it disappears, the configuration of the positive electrode 2 is not affected at all.

  Next, examples and comparative examples of the present invention are shown.

〔Example〕
In this example, first, yttrium nitrate pentahydrate, manganese nitrate hexahydrate, and malic acid were pulverized and mixed in a molar ratio of 1: 1: 6 to obtain a composite metal oxide. A mixture of materials was obtained. Next, the resulting mixture of composite metal oxide materials was reacted at a temperature of 250 ° C. for 30 minutes, and further reacted at a temperature of 300 ° C. for 30 minutes and at a temperature of 350 ° C. for 1 hour. Next, the mixture of reaction products was pulverized and mixed, and then fired at a temperature of 1000 ° C. for 1 hour to obtain a composite metal oxide.

The obtained composite metal oxide was confirmed to be a composite metal oxide represented by the chemical formula YMnO ₃ and to have a hexagonal crystal structure by an X-ray diffraction pattern.

  Next, the composite metal oxide, ketjen black (manufactured by Lion Corporation), vapor-grown carbon fiber (manufactured by Showa Denko KK), and carboxymethyl cellulose (manufactured by Nippon Paper Chemical Co., Ltd.), 75: The positive electrode mixture slurry was obtained by mixing with pure water at a mass ratio of 10: 5: 10. And the obtained positive electrode mixture slurry was apply | coated to the nickel porous body (the Toyama Sumitomo Electric Co., Ltd. make, brand name: Celmet), it was made to dry, and the positive electrode 2 of diameter 15mm and thickness 1mm was formed.

  The positive electrode mixture slurry was 2.95 Pa · s as measured using a vibration viscometer (manufactured by A & I Co., Ltd.). Moreover, when the said porous porous body calculated the bulk density from the dimension and measured the porosity using the He substitution pycnometer apparatus (made by Quanta chrome.Co), the porosity was 70 volume%.

  As a result of applying and drying the positive electrode mixture slurry to the nickel porous body, the positive electrode mixture supported on the inner surface of the pores of the nickel porous body is a scanning type electron whose cross section is processed by the cross section polisher method. From the microscopic image, it had a thickness of 5 to 50 μm.

  Next, the negative electrode 3 made of a metal lithium foil (manufactured by Honjo Metal Co., Ltd.) having a diameter of 15 mm and a thickness of 0.1 mm was disposed inside a bottomed cylindrical SUS case body 6 having an inner diameter of 15 mm.

  Next, a separator made of a nonwoven fabric separator (manufactured by Tapirs Co., Ltd.) having a diameter of 15 mm and a flat film made of polyolefin (manufactured by Asahi Kasei E-Materials Co., Ltd., trade name: Hypore) was superposed on the negative electrode 3. Next, the positive electrode 2 obtained as described above was overlaid on the separator. Next, a non-aqueous electrolyte solution was injected into the separator to form an electrolyte layer 4.

As the non-aqueous electrolyte solution, a mixed solution obtained by mixing ethylene carbonate and diethyl carbonate at a mass ratio of 30:70, and lithium hexafluorophosphate (LiPF ₆ ) as a supporting salt at a concentration of 1 mol / liter. A dissolved solution (manufactured by Kishida Chemical Co., Ltd.) was used.

  Next, the laminate composed of the negative electrode 3, the electrolyte layer 4, and the positive electrode 2 housed in the case body 6 was closed with a bottomed cylindrical SUS lid 7 having an inner diameter of 15 mm. At this time, by disposing a ring-shaped insulating resin 8 made of polytetrafluoroethylene (PTFE) having an outer diameter of 32 mm, an inner diameter of 30 mm, and a thickness of 5 mm between the case body 6 and the lid body 7, FIG. A metal oxygen battery 1 shown in FIG.

Next, the discharge performance of the metal oxygen battery 1 obtained in this example was measured. In the measurement, the metal oxygen battery 1 is mounted on an electrochemical measuring device (manufactured by Toho Giken Co., Ltd.), a current of 0.05 mA / cm ² is applied between the negative electrode 3 and the positive electrode 2, and the cell voltage is 2 Discharge until 0V. The relationship between the cell voltage at this time and the discharge capacity per unit mass of the composite metal oxide is shown in FIG.

[Comparative Example]
In this comparative example, the positive electrode mixture slurry obtained in the above example was applied to a current collector made of aluminum foil and dried to form the positive electrode 2 having a diameter of 15 mm and a thickness of 0.1 mm. And a metal oxygen battery was obtained.

  Next, the discharge performance was measured in the same manner as in the above example except that the metal oxygen battery obtained in this comparative example was used. The relationship between the cell voltage at this time and the discharge capacity per unit mass of the composite metal oxide is shown in FIG.

  From FIG. 3, it is apparent that the battery oxygen (discharge capacity) superior to the comparative example can be obtained according to the metal oxygen battery 1 of the example.

  DESCRIPTION OF SYMBOLS 1 ... Metal oxygen battery, 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Electrolyte layer, 5 ... Case, 21 ... Conductive porous body, 22 ... Hole part, 23 ... Oxygen storage material, 24 ... Conductive material.

Claims (5)

In a metal oxygen battery comprising a positive electrode containing oxygen as an active material and an oxygen storage material and a conductive material, a negative electrode capable of absorbing and releasing lithium ions, and an electrolyte layer sandwiched between the positive electrode and the negative electrode.
The positive electrode includes a conductive porous body, and the oxygen storage material and the conductive material are supported on the inner surfaces of the pores of the conductive porous body.   2. The metal oxygen battery according to claim 1, wherein the conductive porous body has a porosity in a range of 10 to 90% by volume.   3. The metal oxygen battery according to claim 1, wherein the oxygen storage material and the conductive material carried on the inner surface of the hole of the conductive porous body have a thickness in the range of 1 to 200 μm. A metal oxygen battery.   4. The metal oxygen battery according to claim 1, wherein the oxygen storage material is made of a composite metal oxide of yttrium and manganese. 5.   5. The metal oxygen battery according to claim 1, further comprising a housing that accommodates the positive electrode, the negative electrode, and the electrolyte layer in a sealed state. 6.

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