JP5621416B2 - Power generation element for metal-air battery, method for producing the same, and metal-air battery - Google Patents

Description

  The present invention relates to a power generation element for a metal-air battery including a solid electrolyte layer, a manufacturing method thereof, and a metal-air battery including the power generation element.

  The metal-air battery can be charged / discharged by performing an oxidation-reduction reaction of oxygen at the air electrode and an oxidation-reduction reaction of a metal contained in the negative electrode at the negative electrode. In a metal-air battery, oxygen, which is a positive electrode active material, is supplied from the outside as air or oxygen gas during discharge. Therefore, it is possible to increase the amount of the negative electrode active material per unit volume of the battery as compared with the battery in which the positive electrode active material and the negative electrode active material are accommodated in the battery. Therefore, the electric capacity is large, and it is easy to reduce the size and weight. In addition, oxygen has the advantage that there are no resource restrictions. As described above, the metal-air battery has many advantages, and is expected to be used for a battery for portable devices, a battery for hybrid vehicles, a battery for electric vehicles, and the like. As metal-air batteries, for example, lithium-air batteries, magnesium-air batteries, zinc-air batteries, and the like are known.

Such a metal-air battery includes, for example, an air electrode layer containing a conductive material, a catalyst, and a binder, an air electrode current collector that collects the air electrode layer, and a negative electrode layer made of a metal or an alloy. And a negative electrode current collector for collecting current of the negative electrode layer, and an electrolyte interposed between the air electrode layer and the negative electrode layer.
For example, in a metal air battery in which conductive ions are monovalent metal ions, the following charge / discharge reaction is considered to proceed. In the following formula, M represents a metal species.

[During discharge]
Negative electrode: M → M ⁺ + e ⁻
Positive electrode: 2M ⁺ + O ₂ + 2e ⁻ → M ₂ O ₂
[When charging]
Negative electrode: M ⁺ + e ⁻ → M
Positive electrode: M ₂ O ₂ → 2M ⁺ + O ₂ + 2e ⁻

As the electrolyte, for example, a liquid electrolyte obtained by dissolving a supporting electrolyte salt in an organic solvent, a solid electrolyte such as an inorganic oxide, or the like is used. Since the liquid electrolyte contains a flammable organic solvent, it exhibits high ionic conductivity, and in addition to preventing liquid leakage, safety measures assuming short circuit and overcharge are indispensable. Therefore, development of a solid electrolyte material excellent in ion conductivity is desired.
For example, Patent Document 1 discloses a lithium-air secondary battery that does not contain a liquid, and includes an anode containing lithium metal, an oxygen cathode, and at least one polymer-ceramic electrolyte, glass between the anode and the cathode. Disclosed is a battery comprising a lithium ion conducting solid electrolyte selected from ceramic electrolytes and combinations thereof.
Patent Document 2 discloses an all solid-state lithium secondary battery in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are stacked, and the solid electrolyte is an ionic liquid, inorganic particles having an average particle size of less than 1 μm, And an all-solid-state lithium secondary battery, which is a gel-like composition containing a supporting electrolyte salt. In Patent Document 2, the positive electrode layer and the negative electrode layer are formed of a solid material.

JP 2010-3694 A JP 2008-146917 A

However, as a result of investigations by the present inventors, in a completely solid metal-air battery that does not contain a liquid, such as the metal-air battery described in Patent Document 1, in the oxygen reduction reaction of the air electrode, oxygen molecules are present in the air electrode. It has been found that it is difficult to be taken in, and as a result, a large overvoltage occurs, and the operating voltage (discharge voltage) decreases.
Further, the metal-air battery of Patent Document 1 needs to be at a high temperature (about 100 ° C.) in order to obtain a sufficient discharge capacity.

  On the other hand, the secondary battery described in Patent Document 2 is not an air battery. Therefore, no consideration has been given to oxygen (air) uptake in the positive electrode and the accompanying positive electrode overvoltage. Moreover, even if the secondary battery described in Patent Document 2 is applied to an air battery, the positive electrode layer is formed from a solid material, so that sufficient oxygen uptake cannot be obtained.

  As described above, in the conventional metal-air battery, it is very difficult to achieve both the leakage resistance and the operating voltage. The present invention has been achieved in view of the above circumstances, and is a metal-air battery using oxygen as a positive electrode active material, which reduces the overvoltage of the oxygen reduction reaction in the air electrode, and has excellent discharge characteristics and leakage resistance. An object is to provide a metal-air battery that combines the above.

The power generation element of the present invention is a power generation element for a metal-air battery including an air electrode and a solid electrolyte layer, wherein the air electrode includes at least a first ionic liquid and a conductive material, A metal air electrode layer made of an air electrode composite material having a content of 1 ionic liquid of 10 to 80 wt% is provided.

  Since the power generation element for metal-air battery of the present invention includes an air electrode layer containing an ionic liquid, oxygen supplied to the air electrode is easily taken into the air electrode, and the overvoltage of the oxygen reduction reaction can be reduced. it can.

In the present invention, the air electrode mixture may further contain a binder and / or inorganic particles from the viewpoint of holding the first ionic liquid in the air electrode layer.
Further, the air electrode composite material may further contain a first supporting electrolyte salt.

  As a specific form of the power generation element for a metal-air battery of the present invention, the solid electrolyte layer includes at least a liquid electrolyte containing a second ionic liquid and a second supporting electrolyte salt, and second inorganic particles. The form which consists of a solid electrolyte compound material to contain is mentioned.

A method for producing a power generation element for a metal-air battery according to the present invention is a method for producing a power generation element for a metal-air battery comprising an air electrode and a solid electrolyte layer,
Applying an air electrode mixture paste containing at least a first ionic liquid, a conductive material, and a solvent, wherein the content of the first ionic liquid with respect to the components excluding the solvent is 10 to 80 wt% , Drying step,
It is characterized by providing.
The air electrode mixture paste may further contain a binder and / or first inorganic particles.
Further, the air electrode composite paste may further contain a first supporting electrolyte salt.

The metal-air battery of the present invention is a metal-air battery comprising an air electrode, a negative electrode, and a solid electrolyte layer interposed between the air electrode and the negative electrode,
The power generation element of the present invention is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the overvoltage of the oxygen reduction reaction in an air electrode can be reduced, and the metal air battery which combines the outstanding discharge characteristic and liquid-proof property is realizable.

It is sectional drawing which shows one example of a metal air battery of this invention. It is a result of the constant current charging / discharging measurement in an Example.

The power generation element for a metal-air battery of the present invention is a power generation element for a metal-air battery comprising an air electrode and a solid electrolyte layer, wherein the air electrode includes at least a first ionic liquid and a conductive material. An air electrode layer made of an air electrode composite material is provided.
The metal battery of the present invention is a metal-air battery including an air electrode, a negative electrode, and a solid electrolyte layer interposed between the air electrode and the negative electrode, and includes the power generation element of the present invention. It is characterized by.

Hereinafter, the power generation element for metal-air batteries and the metal-air battery of the present invention will be described with reference to the drawings.
In FIG. 1, a metal-air battery 10 includes a power generation element 11 including an air electrode (positive electrode) 1 and a solid electrolyte layer 3, and a negative electrode 2 in a battery case configured by an air electrode can 6 and a negative electrode can 7. Contained. The power generation element 11 and the negative electrode 2 are laminated so that the solid electrolyte layer 3 is interposed between the air electrode 1 and the negative electrode 2. The air electrode can 6 and the negative electrode can 7 are fixed by a gasket 8 to ensure the sealing performance in the battery case.

The air electrode 1 includes an air electrode layer 5 and an air electrode current collector 4 that collects the air electrode layer 5.
The air electrode layer 5 is a redox reaction field of oxygen, and includes a conductive material (for example, carbon black), a first ionic liquid (for example, N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) amide. ) And a binder (for example, polyvinylidene fluoride).
The air electrode current collector 4 is made of a conductive material (for example, a metal mesh) having a porous structure, and the air taken in from the air holes 9 provided in the air electrode can 6 is the air current collector. 4 is supplied to the air electrode layer 5.

  The negative electrode 2 is made of metal (for example, Li metal). That is, it contains a negative electrode active material that can release and incorporate metal ions that are conductive ion species.

The electrolyte layer 3 includes a second ionic liquid (eg, N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) amide) and a second supporting electrolyte salt (eg, lithium bis (trifluoromethanesulfonyl) amide. ) Containing a liquid electrolyte, and second inorganic particles (for example, SiO ₂ ).

The power generation element for a metal-air battery of the present invention constitutes at least an air electrode and an electrolyte layer among the constituent members of the metal-air battery, and the air electrode is an ionic liquid (first ionic liquid). It has a great feature in that it has an air electrode layer containing. As a result of intensive studies by the present inventor, in a metal-air battery using oxygen as a positive electrode active material, the air electrode (positive electrode) contains an ionic liquid, thereby improving oxygen uptake in the air electrode, It has been found that the oxygen reduction reaction is promoted. That is, by using the power generation element for a metal-air battery of the present invention, the overvoltage of the air electrode of the metal-air battery can be reduced, and the operating voltage of the metal-air battery can be improved.
Further, when the air electrode contains an ionic liquid, an effect of improving the metal ion conductivity at the interface between the air electrode and the adjacent solid electrolyte layer can be expected.
Moreover, since the ionic liquid is flame retardant, the safety of the metal-air battery can be improved.

In the present invention, the metal-air battery refers to a redox reaction of oxygen as a positive electrode active material in an air electrode (positive electrode), and a redox reaction of a metal in a negative electrode. A battery in which metal ions are conducted by an electrolyte layer interposed therebetween. Examples of the metal air battery include a lithium air battery, a sodium air battery, a potassium air battery, a magnesium air battery, a calcium air battery, a zinc air battery, and an aluminum air battery.
In the present invention, the air metal battery may be a primary battery or a secondary battery.

Hereafter, each structure of the electric power generation element for metal air batteries of this invention and a metal air battery is demonstrated in detail.
(Air electrode)
The air electrode includes an air electrode layer made of an air electrode composite material including at least a first ionic liquid and a conductive material. In the air electrode layer, the supplied oxygen (oxygen radical) reacts with metal ions, and a metal oxide is generated on the surface of the conductive material. The air electrode layer usually has a porous structure and ensures the diffusibility of oxygen as an active material.

The first ionic liquid is not particularly limited. For example, N, N, N-trimethyl-N-propylammonium bis (trifluoromethanesulfonyl) amide [abbreviation: TMPA-TFSA], N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) amide [abbreviation: PP13] -TFSA], N-methyl-N-propylpyrrolidinium bis (trifluoromethanesulfonyl) amide [abbreviation: P13-TFSA], N-methyl-N-butylpyrrolidinium bis (trifluoromethanesulfonyl) amide [abbreviation: P14] -TFSA], N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) amide [abbreviation: DEME-TFSA], aliphatic quaternary ammonium salts, 1-allyl -3-Ethylimidazolium bromide [Abbreviation: AEImBr], 1- allyl-3-ethyl imidazolium tetrafluoroborate [abbreviation: AEImBF _4], 1- allyl-3-ethyl imidazolium bis (trifluoromethanesulfonyl) amide [abbreviation: AEImTFSA], 1, 3-diallylimidazolium bromide [abbreviation: AAImBr], 1,3-diallylimidazolium tetrafluoroborate [abbreviation: AAImBF ₄ ], 1,3-diallylimidazolium bis (trifluoromethanesulfonyl) amide [abbreviation: AAImTFSA], etc. And alkyl imidazolium quaternary salts.
Among the ionic liquids, since they are electrochemically stable against oxygen radicals, aliphatic quaternary ammonium salts, etc., among them, PP13-TFSA, P13-TFSA, DEME-TFSA, etc. are used for secondary batteries. Is preferable.

  From the viewpoint of retention in the air electrode layer, the ionic liquid is preferably low in volatility and preferably high in viscosity. For example, the viscosity of the ionic liquid at 25 ° C. is preferably 20 cP or more, particularly preferably 50 cP or more, and more preferably 100 cP or more.

  The content of the first ionic liquid in the air electrode layer depends on its viscosity and the conductive material to be combined, the binder, the inorganic particles, and the like, but is preferably 10 to 80% by weight, particularly 30. It is preferably -80% by weight, and more preferably 50-80% by weight. When the content of the first ionic liquid is 10% by weight or more, oxygen molecules can be effectively taken into the air electrode. On the other hand, when the content of the first ionic liquid is 80% by weight or less, the conductivity of the air electrode layer can be ensured and the air electrode layer can be formed as a solid material.

The conductive material is not particularly limited as long as it has conductivity, and examples thereof include a carbon material. Although it does not specifically limit as a carbon material, From the viewpoint of the area and space of the reaction field which a metal oxide produces | generates, the carbon material which has a high specific surface area is preferable.
Specifically, the carbon material preferably has a specific surface area of 10 m ² / g or more, particularly 100 m ² / g or more, and more preferably 600 m ² / g or more. Specific examples of the carbon material having a high specific surface area include carbon black, activated carbon, carbon carbon fiber (for example, carbon nanotube, carbon nanofiber, etc.) and the like. Here, the specific surface area of the conductive material can be measured by, for example, the BET method.

  The content of the conductive material in the air electrode layer is preferably in the range of, for example, 10% by weight to 90% by weight, although it depends on the density, specific surface area, and the like. From the viewpoint of holding the ionic liquid in the air electrode layer and from the viewpoint of producing an air electrode layer in which each component is uniformly dispersed, the content is particularly preferably 10 to 50% by weight.

  In the air battery power generation element and the air battery of the present invention, the first ionic liquid is mixed with at least a conductive material and, if necessary, further mixed with a binder and first inorganic particles described later. In general, the air electrode composite is solid.

The air electrode layer is preferably formed of an air electrode mixture containing a binder, from the viewpoint of holding the first ionic liquid and fixing the conductive material.
Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), and the like.
The content of the binder in the air electrode layer is preferably, for example, 5 to 50% by weight, and particularly preferably 10 to 30% by weight. When the binder content is 5% by weight or more, a solid air electrode composite is easily obtained, and the air electrode layer can be easily formed. On the other hand, when the binder content is 50% by weight or less, a desired reaction can be efficiently advanced without reducing the reaction field.

  Moreover, the air electrode layer may be formed from the air electrode mixture containing the 1st inorganic particle from a viewpoint of holding | maintenance of a 1st ionic liquid. By using inorganic particles, a solid air electrode composite can be easily obtained.

Examples of the first inorganic particles include insulating inorganic oxide particles such as SiO ₂ , TiO ₂ , Al ₂ O ₃ , WO ₃ , and ZrO ₂ , and dielectric inorganic oxide particles such as BaTiO ₃ .

  Moreover, inorganic solid electrolyte particles can also be used as the first inorganic particles. By using inorganic solid electrolyte particles as the first inorganic particles, metal ion conductivity in the air electrode layer can be improved. Examples of inorganic solid electrolytes include oxide solid electrolytes and sulfide solid electrolytes. Among them, oxide solid electrolytes are preferable because of their high chemical stability. Specific examples of the oxide-based solid electrolyte include NASICON type oxides, perovskite type oxides, LISICON type oxides, and garnet type oxides. The solid electrolyte may be glass, crystal, or glass ceramic.

What is necessary is just to select a specific inorganic solid electrolyte suitably according to a conductive metal ion.
For example, in the case of a lithium-air battery, as the NASICON type oxide, for example, Li _{a Xb} Y _{cP d} O _e (X is from B, Al, Ga, In, C, Si, Ge, Sn, Sb and Se) Y is at least one selected from the group consisting of Ti, Zr, Ge, In, Ga, Sn and Al, and a to e are 0.5 <a <5.0, 0 ≦ b <2.98, 0.5 ≦ c <3.0, 0.02 <d ≦ 3.0, 2.0 <b + d <4.0, 3.0 <e ≦ 12 0). In particular, in the above formula, an oxide where X = Al and Y = Ti (Li-Al-Ti-PO-based NASICON type oxide), and X = Al, Y = Ge or X = Ge, Y = An oxide that is Al (Li—Al—Ge—Ti—O-based NASICON-type oxide) is preferable.
As the perovskite-type oxide, for _example, oxide represented by Li _{x La 1-x} TiO _3, etc. (Li-La-TiO perovskite oxide) can be exemplified.

In the case of a lithium-air battery, as the LISICON-type oxide, for example, Li ₄ XO ₄ -Li ₃ YO ₄ (X is at least one selected from Si, Ge, and Ti, and Y is P, As, and Li ₄ XO ₄ —Li ₂ AO ₄ (X is at least one selected from Si, Ge, and Ti, and A is at least one selected from Mo and S). Li ₄ XO ₄ —Li ₂ ZO ₂ (X is at least one selected from Si, Ge, and Ti, Z is at least one selected from Al, Ga, and Cr), and Li ₄ XO ₄ —Li ₂ BXO ₄ (X is at least one selected from Si, Ge, and Ti, and B is at least one selected from Ca and Zn), Li ₃ DO ₃ —Li ₃ YO ₄ (D is B, Y is at least one selected from P, As and V). In particular, Li ₄ SiO ₄ —Li ₃ PO ₄ , Li ₃ BO ₃ —Li ₃ PO _{4, and the} like are preferable.

In the case of a lithium-air battery, examples of the garnet-type oxide include an oxide represented by Li _{3 + x} A _y G _z M _{2 -v} B _v O ₁₂ . Here, A, G, M and B are metal cations. A is preferably an alkaline earth metal cation such as Ca, Sr, Ba and Mg, or a transition metal cation such as Zn. G is preferably a transition metal cation such as La, Y, Pr, Nd, Sm, Lu, or Eu. Examples of M include transition metal cations such as Zr, Nb, Ta, Bi, Te, and Sb. Among these, Zr is preferable. B is preferably In, for example. x preferably satisfies 0 ≦ x ≦ 5, and more preferably satisfies 4 ≦ x ≦ 5. y preferably satisfies 0 ≦ y ≦ 3, and more preferably satisfies 0 ≦ y ≦ 2. z preferably satisfies 0 ≦ z ≦ 3, and more preferably satisfies 1 ≦ z ≦ 3. v preferably satisfies 0 ≦ v ≦ 2, and more preferably satisfies 0 ≦ v ≦ 1. O may be partially or completely exchanged with a divalent anion and / or a trivalent anion, for example, N ³⁻ . As the garnet-type oxide, Li—La—Zr—O-based oxides such as Li ₇ La ₃ Zr ₂ O ₁₂ are preferable.

  The first inorganic particles preferably have an average primary particle size in the range of 1 nm to 10 μm, particularly in the range of 1 nm to 1 μm, and further in the range of 10 nm to 100 nm. This is because when the first inorganic particles have an average particle size of primary particles within the above range, the amount of ionic liquid that can be retained can be increased. The average particle size of the first inorganic particles can be calculated by, for example, a coal counter (particle size distribution meter).

The first inorganic particles have a specific surface area of 1 m ² / g or more, preferably 10 m ² / g or more, and more preferably 100 m ² / g or more. By using the first inorganic particles having a specific surface area of 1 m ² / g or more, a solid air electrode composite can be obtained with a small amount of the first inorganic particles, and the battery capacity can be increased. is there. The specific surface area of the insulating inorganic particles can be measured using, for example, the BET method.
The content of the first inorganic particles in the air electrode layer is not particularly limited.

The air electrode layer may further be formed from an air electrode mixture containing a first supporting electrolyte salt. By forming the air electrode layer using the air electrode mixture containing the supporting electrolyte salt, the metal ion conductivity in the air electrode layer can be improved.
The first supporting electrolyte salt is not particularly limited as long as it can improve the conductivity of metal ions that are desired to be conducted between the air electrode and the negative electrode, and may be selected as appropriate. Usually, a metal salt containing a conductive metal ion can be used as the first supporting electrolyte salt.

For example, in the case of a lithium air battery, a lithium salt can be used as the supporting electrolyte salt. Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiOH, LiCl, LiNO ₃ , Li ₂ SO ₄ .
_Moreover, CH 3 _CO 2 organolithium salt such as Li, formula (1), it can also be used organic lithium salt represented by (2).
_{Li (C m F 2m + 1} SO 3) (1)
In formula (1), m is 1 or more and 8 or less, preferably 1 or more and 4 or less.
_{LiN (C n F 2n + 1} SO 2) (C p F 2p + 1 SO 2)
In formula (2), n and p are each 1 or more and 8 or less, preferably 1 or more and 4 or less, and may be the same or different from each other.
Examples of the organic lithium salt represented by the formula (1) include LiCF ₃ SO ₃ . The organic lithium salt represented by the formula (2), for _{example, LiN (CF 3 SO 2)} 2, LiN (C 2 F 5 SO 2) 2, LiC (CF 3 SO 2) 3 and the like.
The content of the first supporting electrolyte salt in the air electrode layer is not particularly limited.

The air electrode composite material may contain a catalyst that promotes the oxidation-reduction reaction of oxygen in the air electrode. The catalyst may be supported on the conductive material.
The catalyst is not particularly limited. For example, phthalocyanine compounds such as cobalt phthalocyanine, manganese phthalocyanine, nickel phthalocyanine, tin phthalocyanine oxide, titanium phthalocyanine, and dilithium phthalocyanine; naphthocyanine compounds such as cobalt naphthocyanine; iron porphyrin, etc. Porphyrin compounds; MnO ₂ , CeO ₂ , Co ₃ O ₄ , NiO, V ₂ O ₅ , Fe ₂ O ₃ , ZnO, CuO, LiMnO ₂ , Li ₂ MnO ₃ , LiMn ₂ O ₄ , Li ₄ Ti ₅ O _{12 , Li 2 TiO 3, LiNi 1/3} Co 1/3 Mn 1/3 O 2, LiNiO 2, LiVO 3, Li 5 FeO 4, LiFeO 2, LiCrO 2, LiCoO 2, LiCuO 2, LiZnO 2, Li 2 M oO ₄ , LiNbO ₃ , LiTaO ₃ , Li ₂ WO ₄ , Li ₂ ZrO ₃ , NaMnO ₂ , CaMnO ₃ , CaFeO ₃ , MgTiO ₃ , KMnO _{2 and} other metal oxides, Pt, Au, Ag, Pd, Ru, Ir And noble metals.
The catalyst content in the air electrode layer is preferably in the range of, for example, 1 wt% to 90 wt%.

In addition to the air electrode layer, the air electrode may further include an air electrode current collector that collects current from the air electrode layer.
The air electrode current collector may have a porous structure or a dense structure as long as it has a desired electronic conductivity, but it may diffuse air (oxygen). From the viewpoint of safety, those having a porous structure are preferred. Examples of the porous structure include a mesh structure in which constituent fibers are regularly arranged, a nonwoven fabric structure in which constituent fibers are randomly arranged, and a three-dimensional network structure having independent holes and connecting holes. The porosity of the current collector having a porous structure is not particularly limited, but is preferably in the range of 20 to 99%, for example.
When an air electrode current collector having a porous structure is used, unlike FIG. 1 in which the air electrode layer and the air electrode current collector are stacked (adjacent), the air electrode current collector is provided inside the air electrode layer. The body can also be placed. When the air electrode current collector is disposed inside the air electrode layer, an effect of improving the current collection efficiency of the air electrode may be expected.

Examples of the material for the air electrode current collector include metal materials such as stainless steel, nickel, aluminum, iron, titanium, and copper, carbon materials such as carbon fiber, and high electron conductive ceramic materials such as titanium nitride. Among these, from the viewpoint of corrosion resistance, a current collector using a carbon material is preferable. This is because when a strongly alkaline metal oxide is generated by a discharge reaction at the air electrode, it is possible to suppress the elution of the porous current collector, and to suppress the deterioration of the battery characteristics due to this.
Although the thickness of an air electrode electrical power collector is not specifically limited, For example, it is preferable that they are 10 micrometers-1000 micrometers, especially 20-400 micrometers.
In the metal-air battery, a battery case, which will be described later, may also have a function as a current collector for the air electrode.

  The thickness of the air electrode layer varies depending on the use of the metal-air battery, but is preferably in the range of 2 μm to 500 μm, particularly in the range of 5 μm to 300 μm.

The method for producing the air electrode is not particularly limited. For example, there is a method including a step of applying and drying an air electrode mixture paste containing a first ionic liquid, a conductive material, and a solvent. Thus, the component which comprises an air electrode layer is mixed with a solvent, and can be disperse | distributed uniformly by mixing an ionic liquid and an electroconductive material by making it into a paste form.
After the air electrode mixture paste is dried, pressure treatment or heat treatment may be further performed as necessary.
By applying and drying the air electrode mixture paste on the surface of the air electrode current collector, an air electrode in which an air electrode layer and an air electrode current collector are laminated can be produced. Alternatively, the air electrode layer obtained by applying and drying the air electrode mixture paste is superimposed on the air electrode current collector, and appropriately subjected to pressurization, heating, etc. It is also possible to produce an air electrode laminated with an electric body.

The solvent for the air electrode mixture paste is not particularly limited as long as it has volatility, and can be appropriately selected. Specific examples include acetone, N, N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and the like. A solvent having a boiling point of 200 ° C. or lower is preferable because the air electrode material mixture can be easily dried.
The method for applying the air electrode material mixture is not particularly limited, and general methods such as a doctor blade and a spray method can be used.

  In addition to the first ionic liquid, the conductive material, and the solvent, the air electrode mixture paste may further contain a binder, inorganic particles, a first supporting electrolyte salt, a catalyst, and the like as described above. .

(Solid electrolyte layer)
The solid electrolyte layer is solid and is not particularly limited as long as metal ions can conduct between the air electrode and the negative electrode, and a solid electrolyte or a liquid electrolyte may be used.

Among these, from the viewpoint of leakage resistance, operating voltage, and discharge capacity, an electrolyte layer made of a solid electrolyte mixture containing at least a liquid electrolyte and second inorganic fine particles is preferable. The electrolyte layer made of such a solid electrolyte mixture is excellent in leakage resistance because it has a solid state despite containing a liquid electrolyte, and further has an interface between the air electrode layer and the electrolyte layer and an interface between the negative electrode layer and the electrolyte layer. It is possible to improve the adhesion.
Here, examples of the liquid electrolyte include a nonaqueous electrolytic solution in which a supporting electrolyte salt (second supporting electrolyte salt) is dissolved in a nonaqueous solvent.

  The non-aqueous solvent is not particularly limited. For example, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate. , Isopropiomethyl carbonate, ethyl propionate, methyl propionate, γ-butyrolactone, ethyl acetate, methyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol didiethyl ether, acetonitrile (AcN), dimethyl sulfoxide (DMSO) ), Diethoxyethane, dimethoxyethane (DME), tetraethylene glycol dimethyl ether (TEGDME) and the like. .

An ionic liquid (second ionic liquid) can also be used as a non-aqueous solvent. Examples of the ionic liquid include N, N, N-trimethyl-N-propylammonium bis (trifluoromethanesulfonyl) amide [abbreviation: TMPA-TFSA], N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl). ) Amide [abbreviation: PP13-TFSA], N-methyl-N-propylpyrrolidinium bis (trifluoromethanesulfonyl) amide [abbreviation: P13-TFSA], N-methyl-N-butylpyrrolidinium bis (trifluoromethanesulfonyl) ) Aliphatic quaternary ammonium such as amide [abbreviation: P14-TFSA], N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) amide [abbreviation: DEME-TFSA] Salt; 1-methyl-3-ethyl ester Dazo tetrafluoroborate [abbreviation: EMIBF _4], 1- methyl-3-ethyl imidazolium bis (trifluoromethanesulfonyl) amide [abbreviation: EMITFSA], 1- allyl-3-ethyl imidazolium bromide [abbreviation: AEImBr], 1-allyl-3-ethylimidazolium tetrafluoroborate [abbreviation: AEImBF ₄ ], 1-allyl-3-ethylimidazolium bis (trifluoromethanesulfonyl) amide [abbreviation: AEImTFSA], 1,3-diallylimidazolium bromide [abbreviation: AAImBr], 1,3- diallyl tetrafluoroborate _{[abbreviation:} AAImBF 4], 1,3- diallyl imidazolium bis (trifluoromethanesulfonyl) amide [abbreviation: AAImTFSA] Include alkyl imidazolium quaternary salt of.

An ionic liquid is preferable as the non-aqueous solvent from the viewpoints that it is difficult to volatilize, liquid is difficult to leak, and the solid electrolyte layer easily maintains a solid shape.
Further, from the viewpoint of stability against oxygen radicals, AcN, DME, DMSO, PP13-TFSA, P13-TFSA, and DEME-TFSA are preferable as the non-aqueous solvent. From the viewpoint of easily maintaining the shape, PP13-TFSA, P13-TFSA, and DEME-TFSA which are ionic liquids are particularly preferable.

The second supporting electrolyte salt used in the non-aqueous electrolyte may be any one that has solubility in the non-aqueous solvent and expresses desired metal ion conductivity. Usually, a metal salt containing a metal ion to be conducted can be used. For example, the supporting electrolyte salt (first supporting electrolyte salt) exemplified in the description of the air electrode can be used as the second supporting electrolyte salt.
The content of the second supporting electrolyte salt in the nonaqueous electrolytic solution is not particularly limited, but is preferably, for example, 0.01 to 3 mol / kg, and particularly preferably 0.1 to 1.2 mol / kg. More preferably, it is 0.1 to 0.7 mol / kg.

  In the solid electrolyte mixture, for example, a polymer such as polyethylene oxide (PEO), polyacrylonitrile (PAN), or polymethyl methacrylate (PMMA) is added to the non-aqueous electrolyte to form a gel. It can also be used. However, from the viewpoint of the metal ion conductivity in the solid electrolyte layer and the ionic conductivity at the interface between the solid electrolyte layer and the air electrode layer due to the leaching of the ionic liquid and / or organic solvent into the adjacent air electrode layer, It is preferable to use the non-aqueous electrolyte in the material without gelation.

  As the second inorganic particles, the same particles as the first inorganic particles can be used. Since the material, particle size, specific surface area, and the like of the second inorganic fine particles are the same as those of the first inorganic particles, description thereof is omitted here.

  The content of the second inorganic particles in the solid electrolyte mixture is, for example, the volume ratio of the second inorganic particles to the ionic liquid, the organic solvent, or a mixture thereof in the nonaqueous electrolytic solution (second inorganic particles). / Ionic liquid, organic solvent, or a mixture thereof) is preferably 0.05 to 10, particularly preferably 0.25 to 4, particularly preferably 0.5 to 3. When the volume ratio is 0.05 or more, the solid electrolyte mixture can be powder-molded as a solid material, and when the volume ratio is 10 or less, the ionic conductivity of the solid electrolyte is kept high. Can do.

  In the metal-air battery of the present invention, the solid electrolyte layer may be made of a solid electrolyte other than the solid electrolyte mixture. Examples of the solid electrolyte other than the solid electrolyte mixture include inorganic solid electrolytes such as oxide solid electrolytes and sulfide solid electrolytes. Among inorganic solid electrolytes, oxide-based solid electrolytes are preferred because of their high chemical stability. Specific examples of the oxide-based solid electrolyte include NASICON type oxides, perovskite type oxides, LISICON type oxides, garnet type oxides and the like described in the description of the air electrode. The solid electrolyte may be glass, crystal, or glass ceramic.

The power generation element for metal-air battery of the present invention is a laminate of the air electrode and the solid electrolyte layer, and typically the air electrode and the solid electrolyte layer so that the air electrode layer and the solid electrolyte layer are adjacent to each other. An electrolyte layer is laminated.
The power generation element for a metal air battery of the present invention may include components other than the air electrode and the solid electrolyte layer.

(Negative electrode)
The negative electrode includes a negative electrode layer containing a negative electrode active material capable of releasing and capturing metal ions. Usually, in addition to the negative electrode layer, a negative electrode current collector for collecting current in the negative electrode layer is also provided.
The negative electrode active material is not particularly limited as long as it can release and capture metal ions. For example, simple metals, alloys, metal oxides, metal sulfides, and metal nitrides containing metal ions that are conductive ions Thing etc. are mentioned. A carbon material can also be used as the negative electrode active material. As the negative electrode active material, a single metal or an alloy is preferable, and a single metal is particularly preferable.
Specifically, as a negative electrode active material of a lithium air battery, for example, metal lithium; lithium alloys such as lithium aluminum alloy, lithium tin alloy, lithium lead alloy, lithium silicon alloy; tin oxide, silicon oxide, lithium titanium oxide Oxides, metal oxides such as niobium oxide and tungsten oxide; metal sulfides such as tin sulfide and titanium sulfide; metal nitrides such as lithium cobalt nitride, lithium iron nitride and lithium manganese nitride; and graphite Among them, metallic lithium and carbon materials are preferable, and metallic lithium is more preferable from the viewpoint of increasing capacity.

  Although the negative electrode layer should just contain a negative electrode active material at least, it may contain the binder which fixes a negative electrode active material as needed. For example, when a foil-like metal or alloy is used as the negative electrode active material, the negative electrode layer can be configured to contain only the negative electrode active material, but when a powdered negative electrode active material is used, the negative electrode layer Can be made into a form containing a negative electrode active material and a binder. The negative electrode layer may contain a conductive material. Since the types and usage amounts of the binder and the conductive material are the same as those of the air electrode described above, description thereof is omitted here.

  The material of the negative electrode current collector is not particularly limited as long as it has conductivity. For example, copper, stainless steel, nickel, etc. are mentioned. Examples of the shape of the negative electrode current collector include a foil shape, a plate shape, and a mesh shape. Further, the battery case may have a function as a negative electrode current collector.

  The manufacturing method of a negative electrode is not specifically limited. For example, there is a method in which a foil-like negative electrode active material and a negative electrode current collector are superposed and pressed. Another method includes preparing a negative electrode material mixture containing a negative electrode active material and a binder, and applying and drying the mixture on a negative electrode current collector.

  The metal-air battery of the present invention is provided with the power generation element for a metal-air battery of the present invention including the air electrode and the solid electrolyte layer. Specifically, a solid electrolyte layer is provided between the air electrode and the negative electrode. The power generation element and the negative electrode are laminated so as to intervene.

(Other)
A metal-air battery usually has a battery case that houses an air electrode, a negative electrode, and an electrolyte layer. The shape of the battery case is not particularly limited, and specific examples include a coin type, a flat plate type, a cylindrical type, and a laminate type. The battery case may be an open air type or a sealed type. The battery case that is open to the atmosphere has a structure in which at least the air electrode layer can sufficiently contact the atmosphere. On the other hand, a sealed battery case can be provided with an introduction pipe and an exhaust pipe for oxygen (air), which is a positive electrode active material. The oxygen concentration to be introduced is preferably high, and particularly preferably pure oxygen.

Each of the air electrode current collector and the negative electrode current collector can be provided with a terminal serving as a connection portion with the outside.
The method for producing the metal-air battery of the present invention is not particularly limited, and a general method can be adopted.
The air battery of the present invention exhibits excellent discharge characteristics even at a relatively low temperature such as 0 to 60 ° C.

[Example 1]
(Manufacture of metal-air batteries)
First, carbon black, PVDF, and PP13-TFSA were mixed at a ratio of 30:15:55 (wt%) to prepare an air electrode mixture paste. The air electrode mixture paste was applied onto carbon paper and dried to produce an air electrode.
On the other hand, a solution obtained by dissolving LiTFSA in PP13-TFSA (LiTFSA concentration 0.32 mol / kg) and SiO ₂ fine particles (BET specific surface area 215 m ² / g) in (PP13-TFSA) / (SiO ₂ ) in acetonitrile. ) = 0.7 (volume ratio). The obtained mixture was naturally dried to obtain a solid powder. The solid powder was compression molded to produce a solid electrolyte layer.
Also, a SUS foil (manufactured by SUS304) and a metal lithium foil were superposed to produce a negative electrode.
The metal air battery (lithium air battery) was produced by applying pressure with the solid electrolyte layer sandwiched between the obtained air electrode and negative electrode. At this time, the air electrode and the negative electrode were overlapped so that the carbon paper of the air electrode and the SUS foil of the negative electrode were the outermost layers, respectively.
In the obtained metal-air battery, the air electrode layer and the solid electrolyte layer contained liquid components, but it was visually confirmed that they were completely solid. That is, it was confirmed that the metal-air battery has liquid leakage resistance.

[Comparative Example 1]
(Manufacture of metal-air batteries)
A metal-air battery was produced in the same manner as in Example 1, except that the air electrode mixture paste was prepared by mixing at a ratio of carbon black: PVDF = 2: 1 (weight ratio).

(Evaluation of metal-air battery)
Using the obtained metal-air batteries of Examples and Comparative Examples, constant current charge / discharge measurements were performed in a pure oxygen (99.9%) atmosphere at 200 nA / cm ² and 60 ° C. The results of the examples are shown in FIG.
FIG. 2 shows that the metal-air battery provided with the power generation element of the present invention can be discharged near 2.6 V and has high discharge characteristics. That is, according to the present invention, it is possible to obtain a metal-air battery having both leakage resistance and high discharge characteristics. Further, in the constant current charge / discharge measurement of the conventional lithium air battery, a flat portion due to overvoltage in the air electrode is often observed in a low voltage region around 2 to 2.6 V. It can be said that the metal-air battery was able to reduce overvoltage.
On the other hand, the metal-air battery of Comparative Example 1 could not be discharged at all.

DESCRIPTION OF SYMBOLS 1 ... Air electrode 2 ... Negative electrode 3 ... Solid electrolyte layer 4 ... Air electrode collector 5 ... Air electrode layer 6 ... Air electrode can 7 ... Negative electrode can 8 ... Gasket 9 ... Air hole 10 ... Metal-air battery 11 ... Power generation element

Claims (10)

A power generation element for a metal-air battery comprising an air electrode and a solid electrolyte layer,
The air electrode includes a metal air electrode layer made of an air electrode mixture material including at least a first ionic liquid and a conductive material , wherein the content of the first ionic liquid is 10 to 80 wt%. A power generation element characterized by The power generation element according to claim 1 , wherein the air electrode composite further includes a binder . The power generating element according to claim 1 or 2 , wherein the air electrode composite further includes first inorganic particles. The power generation element according to any one of claims 1 to 3 , wherein the air electrode mixture further includes a first supporting electrolyte salt. The solid electrolyte layer, and a liquid electrolyte containing a second ionic liquid and a second supporting electrolyte salt, and a second inorganic particle, comprising at least comprises a solid electrolyte mixture material to any of claims 1 to 4 Power generation element as described in. A method for producing a power generation element for a metal-air battery comprising an air electrode and a solid electrolyte layer,
Applying an air electrode mixture paste containing at least a first ionic liquid, a conductive material, and a solvent, wherein the content of the first ionic liquid with respect to the components excluding the solvent is 10 to 80 wt% , Drying step,
A manufacturing method comprising: The manufacturing method according to claim 6 , wherein the air electrode mixture paste further includes a binder . The manufacturing method according to claim 6 or 7 , wherein the air electrode mixture paste further contains first inorganic particles. The manufacturing method according to claim 6 , wherein the air electrode mixture paste further contains a first supporting electrolyte salt. A metal-air battery comprising an air electrode, a negative electrode, and a solid electrolyte layer interposed between the air electrode and the negative electrode,
Characterized in that it comprises a power generating element according to any of claims 1 to 5, metal-air batteries.