JP2012003940A - Metal air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal air battery capable of improving cycle characteristics.SOLUTION: The metal air battery comprises: a positive electrode; a negative electrode; a first housing which houses at least an aqueous electrolyte filled between the positive electrode and the negative electrode; and a second housing which houses the aqueous electrolyte. The first housing is connected with the second housing via a junction in which the aqueous electrolyte circulates.

Description

  The present invention relates to a metal-air battery using an aqueous electrolyte.

  The air battery is a battery using oxygen as a positive electrode active material, and an oxygen-containing gas is taken in from the outside during discharge. Therefore, it is possible to increase the proportion of the negative electrode active material in the battery container as compared with other batteries having positive and negative electrode active materials in the battery. Therefore, in principle, the electric capacity that can be discharged is large, and it is easy to reduce the size and weight. Further, since the oxidizing power of oxygen used as the positive electrode active material is strong, the electromotive force of the battery is relatively high. Furthermore, since oxygen has a feature that it is a clean material without resource restrictions, the air battery has a small environmental load. As described above, the air battery having many advantages is expected to be used for a hybrid vehicle battery, a portable device battery, and the like, and in recent years, there is a demand for higher performance of the air battery.

As a technique relating to an air battery, for example, Non-Patent Document _{1, Li-Al / Li 3} -x PO 4-y N y (LiPON) / Li 1 + x + y Al x Ti 2-x Si y P 3-y O 12 (LATP ) / 1M LiCl aqueous solution / Pt indicates that the open circuit voltage is 3.64 V at room temperature of 25 ° C., and that the cell constant does not change even after standing for 1 week. Non-Patent Document 1 describes that a Li / LiPON / LATP system that is stable against water can be used for a Li-air secondary battery using an aqueous solution.

S. Hasegawa et al., "Study on lithium / air secondary batteries-Stability of NASICON-type lithium ion conducting glass-ceramics with water", J. Power Sources, (USA), 2009, 189, p.371-377

In a Li-air secondary battery using an aqueous electrolyte (hereinafter sometimes referred to as “electrolytic solution”) as disclosed in Non-Patent Document 1, discharge products (Li ⁺ and OH ⁻ ) are discharged during discharge. Is stored in the electrolyte, and the stored discharge product is consumed during charging to generate Li and oxygen. In such a battery, since the discharge product can be stored in the form of ions in the electrolytic solution, discharge is possible even if the saturation solubility of ions is exceeded. However, when the saturation solubility is exceeded, the discharge product is precipitated as ionic crystals (LiOH), and the ionic crystals are likely to be deposited with the surface of the positive electrode (air electrode) or the like as non-uniform precipitation nuclei. If an ionic crystal is deposited on the surface of the hole through which air flows, the supply of oxygen as a reactant is hindered, so that it is difficult for a discharge reaction to occur and a charge reaction may be difficult to occur. The technique disclosed in Non-Patent Document 1 has a problem in that the cycle characteristics of the battery are likely to deteriorate because no measures are taken to suppress precipitation of ion crystals on the surface of the positive electrode.

  Then, this invention makes it a subject to provide the metal air battery which can improve cycling characteristics.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention has a first casing that contains at least a positive electrode, a negative electrode, and an aqueous electrolyte filled between the positive electrode and the negative electrode, and a second casing that stores the aqueous electrolyte, and the aqueous electrolyte is distributed. The metal-air battery is characterized in that the first casing and the second casing are connected to each other through a joining portion.

  Here, “accommodating an aqueous electrolyte” is a concept including a form of accommodating an aqueous electrolyte that stores discharge products. The “first casing containing at least the positive electrode, the negative electrode, and the aqueous electrolyte filled between the positive electrode and the negative electrode” means that the first casing includes at least the positive electrode, the negative electrode, and the aqueous electrolyte. In the metal-air battery of the present invention, the first casing can also accommodate other components. When only the aqueous electrolyte is disposed between the positive electrode and the negative electrode accommodated in the first casing, the aqueous electrolyte is in contact with the positive electrode and the negative electrode. On the other hand, when the aqueous electrolyte and the other component are disposed between the positive electrode and the negative electrode housed in the first casing, the other component is interposed between the positive electrode and the negative electrode. It is accommodated in the first housing in a form that allows ions to come and go. Examples of other components that can be accommodated in the first housing include solid electrolytes, non-aqueous electrolytes, ionic liquids, anion exchange membranes, and the like. In the metal-air battery of the present invention, the portion of the first housing that contains the aqueous electrolyte and the second housing are located between the first housing and the second housing via the joint. Connected in a form that can be traversed. In the metal-air battery of the present invention, the charging reaction and the discharging reaction occur in the first casing, and the charging reaction and the discharging reaction do not occur in the second casing.

  In the present invention, it is preferable that a deposition promoting means for promoting deposition of a discharge product from the aqueous electrolyte contained in the second casing is further provided.

  Moreover, in the said invention, it is preferable that the temperature difference expansion means which expands the difference of the temperature of a 2nd housing and the temperature of a 1st housing is contained in a precipitation promotion means.

  Here, the “temperature difference widening means” that is one form of the precipitation promoting means widens the difference between the temperature of the second housing and the temperature of the first housing, which is lower than the temperature of the first housing. The form is not particularly limited. For example, a form (form A) that widens the difference between the temperature of the second casing and the temperature of the first casing by cooling the second casing, or the second casing by heating the first casing In addition to the form (form B) that widens the difference between the temperature of the first casing and the temperature of the first casing, the second casing is cooled and the first casing is heated by cooling the second casing and heating the first casing. It can be set as the form (form C) which spreads the difference with the temperature of a housing. As the form A, the form etc. which cool a 2nd housing can be illustrated by providing the 2nd housing with the cooling element represented by the Peltier device etc., and a heat sink. In addition, as the form B, the first casing is heated using an external heat source (for example, a heat source such as a mechanical friction when the metal-air battery of the present invention is installed in a hybrid vehicle or the like in addition to a heater). The form and the like can be exemplified. Examples of the form C include a form in which the second casing is cooled using a Peltier element, and the first casing is heated using waste heat generated from the Peltier element.

  Moreover, in the said invention, it is preferable that the heat insulating material arrange | positioned between the outer surface of the 1st housing and the outer surface of the 2nd housing is contained in a precipitation promotion means.

  Here, the “heat insulating material” is one form of the precipitation promoting means, and is disposed to suppress thermal diffusion between the outer surface of the first housing and the outer surface of the second housing.

  Moreover, in the said invention, it is preferable that the unevenness | corrugation provided in the inside of the 2nd casing which contacts aqueous solution electrolyte is contained in a precipitation promotion means.

Here, the “unevenness” provided inside the second casing that contacts the aqueous electrolyte is one form of the precipitation promoting means. The irregularities preferably have a surface ten-point average roughness Rz of 5.25 μm or more, an average interval Sm of 10.5 μm or more, and a surface root mean square roughness Rq of 1 to 13.5. Here, “ten-point average roughness Rz of the surface” corresponds to RzJIS described in JIS B 0601: 2001, and the maximum height of the roughness curve of the uneven surface at the reference length L (for example, 500 μm). (Height of mountain (Z _{peak, j} )) and the sum of the average of 5 points of maximum depth (depth of valley (Z _{valley, j} )) and defined by the following formula (1) . The “average interval Sm” is 4.3.1. Of JIS B 0601: 2001. Is the average length of adjacent peaks in the roughness curve of the concavo-convex surface existing between the reference length L (for example, 500 μm). The “root mean square roughness Rq” is 4.2.2. Of JIS B 0601: 2001. Is the root mean square roughness specified in.

  Moreover, in the said invention, it is preferable that the 2nd housing and the some 1st housing are connected.

  Moreover, in the said invention, it is preferable that the pressure control means which can control the pressure inside a 1st housing is connected to the 2nd housing.

  In the present invention in which the pressure control means is connected to the second housing, it is preferable that the pressure control means is a vent and the outside of the vent is humidified.

  The metal-air battery of the present invention includes a second casing that stores an aqueous electrolyte in addition to a first casing that stores each component of the metal-air battery necessary for causing a charging reaction and a discharging reaction. Yes. Therefore, it becomes possible to deposit the discharge product in the second casing having a lower temperature than that of the first casing in which the charging reaction or the discharge reaction occurs. By depositing the discharge product in the second housing, it is possible to increase the capacity of the metal-air battery while avoiding the situation where the discharge product is deposited on the surface of the positive electrode in the first housing. Become. Therefore, according to this invention, the metal air battery which can improve cycling characteristics can be provided.

  In the present invention, it is easy to improve the cycle characteristics of the metal-air battery by providing the deposition promoting means for promoting the deposition of the discharge product from the aqueous electrolyte contained in the second casing.

  In the present invention, since the temperature difference widening means is provided, the discharge product is likely to be precipitated in the second casing, so that it becomes easy to improve the cycle characteristics of the metal-air battery.

  In the present invention, since the heat insulating material is disposed between the outer surface of the first housing and the outer surface of the second housing, the temperature of the second housing is lower than the temperature of the first housing. It becomes easy to maintain the state, and as a result, the discharge product is likely to precipitate in the second casing, so that it becomes easy to improve the cycle characteristics of the metal-air battery.

  Further, in the present invention, since the unevenness is provided in the second casing that contacts the aqueous electrolyte, the discharge product is likely to be precipitated in the second casing, so that the cycle characteristics of the metal-air battery are improved. It becomes easy to improve.

  According to the present invention, there is provided a metal air battery (assembled battery) capable of improving cycle characteristics of a plurality of metal air batteries by connecting the second casing and the plurality of first casings. Can be provided.

  In the present invention, the pressure control means capable of controlling the pressure inside the first casing is connected to the second casing, thereby improving the cycle characteristics while improving the stability of the metal-air battery. Is possible.

  In the present invention, the vent functioning as the pressure control means is connected to the second casing, and the outside of the vent is humidified. In addition to the above effect, the battery withered due to electrolyte evaporation Therefore, it is easy to improve the cycle characteristics of the metal-air battery.

1 is a cross-sectional view illustrating an air battery 10. 2 is a cross-sectional view illustrating an air battery 20. FIG. It is sectional drawing explaining the 2nd housing 25. FIG. 5 is a cross-sectional view illustrating a second casing 27. FIG. 2 is a top view illustrating the air battery 30. FIG. It is a figure which shows the discharge curve of the air battery concerning an Example, and the air battery concerning a comparative example.

Among metal-air batteries in which discharge products are deposited in an aqueous electrolyte, a lithium-air battery using an aqueous electrolyte is configured as follows, for example.
Li negative electrode | non-aqueous electrolyte or ionic liquid | Li conductive solid electrolyte | aqueous solution electrolyte | air electrode The discharge reaction of the lithium air battery comprised in this way is represented by following formula (2).
_{4Li + O 2 + 2H 2 O} → 4LiOH 3.466V formula (2)
LiOH as a discharge product is dissolved in an aqueous electrolyte up to about 5.12 mol / L. When the discharge exceeds saturation, it can be precipitated as a solid using the dissolution equilibrium, thereby obtaining a high capacity.

  However, in the lithium-air battery configured as described above, the discharge product is likely to deposit using the air electrode and the Li conductive solid electrolyte as non-uniform precipitation nuclei. Since the discharge product deposited at such a location hinders ion conduction, the voltage drops and the battery may be deactivated. Therefore, in order to avoid such a situation, the interval between the Li conductive solid electrolyte and the air electrode is widened, and measures are taken to deposit discharge products in the aqueous electrolyte filled between the Li conductive solid electrolyte and the air electrode. Can be considered. However, LiOH deposited in the aqueous electrolyte is an ion conductive resistor. For this reason, when such measures are taken, the ion conduction resistance of the aqueous electrolyte increases and the performance of the air battery may deteriorate.

  As a result of earnest research, the present inventor has found that the performance of the metal-air battery due to the increase in the ionic conduction resistance of the aqueous electrolyte by precipitating the discharge product on the aqueous electrolyte disposed at a position not sandwiched between the positive electrode and the negative electrode. The inventors have found that it is possible to suppress the decrease and improve the cycle characteristics, and the present invention has been completed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the air battery in which lithium ions are occluded and released as described below is an exemplification of the present invention, and the present invention is not limited to the embodiment described below.

  FIG. 1 is a cross-sectional view illustrating an embodiment of an air battery 10 according to the first embodiment of the present invention. As shown in FIG. 1, the air battery 10 includes a first casing 11 and a second casing 12, and the first casing 11 and the second casing 12 are connected via a tubular joint portion 13. Has been. A heat insulating material 14 is disposed between the first casing 11 and the second casing 12, and the outer surface of the first casing 11 facing the second casing 12 and the first casing 11 are opposed to each other. The outer surface of the second housing 12 is connected via a heat insulating material 14.

  As shown in FIG. 1, the first casing 11 includes a negative electrode layer 1, a solid electrolyte layer 2, an aqueous electrolyte layer 3, a positive electrode (air electrode) layer 4, and an air layer 5 in order from the lower side of the drawing. And is housed. In the air battery 10, the upper surface of the negative electrode layer 1 and the lower surface of the solid electrolyte layer 2 are in contact, and an aqueous solution that conducts lithium ions in a space sandwiched between the lower surface of the positive electrode layer 4 and the upper surface of the solid electrolyte layer 2. The electrolyte 3a is filled. The air layer 5 is provided with holes (not shown) through which air to be supplied to the positive electrode layer 4 can flow.

  The second casing 12 contains the same aqueous electrolyte 3a as that filled in the aqueous electrolyte layer 3, but does not contain a positive electrode or a negative electrode. In addition, a heat radiating plate 15 that functions as a temperature difference expanding means is provided on the outer surface of the second housing 12. As shown in FIG. 1, since the second casing 12 and the aqueous electrolyte layer 3 are connected via the joint 13, the aqueous electrolyte 3 a accommodated in the second casing 12 is connected to the joint 13. The discharge product existing in the aqueous electrolyte layer 3 can move to the second casing 12 via the joint portion 13.

  During the operation of the air battery 10, a charging reaction and a discharging reaction occur inside the first housing 11. Therefore, the aqueous electrolyte 3a accommodated in the first casing 11 is heated by operating heat. On the other hand, in the second casing 12 in which the positive electrode and the negative electrode are not accommodated, no charging reaction or discharging reaction occurs. Furthermore, since the heat sink 15 is provided in the second casing 12, the temperature of the aqueous electrolyte 3a accommodated in the second casing 12 tends to decrease. In addition, in the air battery 10, thermal diffusion between the first housing 11 and the second housing 12 is suppressed by the heat insulating material 14. Therefore, when the air battery 10 is operated, the temperature of the aqueous electrolyte 3 a accommodated in the second casing 12 is lower than the temperature of the aqueous electrolyte 3 a accommodated in the first casing 11. Discharge generation in which the aqueous electrolyte 3a accommodated in the second casing 12 having a relatively low temperature is deposited as an ionic crystal is more than the aqueous electrolyte 3a accommodated in the first casing 11 having a relatively high temperature. The saturated solubility of the product (LiOH) is low. Therefore, according to the air battery 10, the discharge product (LiOH) can be deposited on the second casing 12. Here, the aqueous electrolyte 3 a accommodated in the second housing 12 is not located in a region sandwiched between the positive electrode layer 4 and the negative electrode layer 1. Therefore, according to the air battery 10, the discharge product (LiOH) can be deposited in the second housing 12 that does not hinder the charge reaction and the discharge reaction that occur in the first housing 11, and thereby the positive electrode The capacity of the air battery 10 can be increased while avoiding the situation where the discharge product (LiOH) is deposited on the surface of the layer 4 or the solid electrolyte layer 2. Therefore, according to this invention, the air battery 10 which can improve cycling characteristics can be provided.

<Negative electrode layer 1>
The negative electrode layer 1 contains an active material capable of releasing lithium ions, preferably occlude / release lithium ions (hereinafter referred to as “negative electrode active material”). A negative electrode current collector (not shown) for collecting the negative electrode layer 1 is provided in contact with the inside or the outer surface of 1. A negative electrode lead is connected to the negative electrode current collector. The negative electrode layer 1 only needs to contain at least a negative electrode active material, and may contain, in addition to the negative electrode active material, a conductive material that improves conductivity, a binder that fixes metal or the like.

As the negative electrode active material contained in the negative electrode layer 1, a known negative electrode active material that can be used as a negative electrode active material of a lithium-air battery can be appropriately used. Examples of the negative electrode active material that can be used in the air battery 10 include metal lithium, lithium alloys, and oxides such as Li ₂ TiO ₃ .

The conductive material that can be contained in the negative electrode layer 1 is not particularly limited as long as it can withstand the environment when the air battery 10 is used and has conductivity. Examples of the conductive material that can be used in the air battery 10 include carbon materials having a porous structure typified by mesoporous carbon, in addition to carbon materials such as gold, platinum, graphite, and carbon black. When the negative electrode layer 1 contains a conductive material, the content of the conductive material is preferably 10% by mass or more and 99% by mass or less from the viewpoint of suppressing a decrease in battery capacity.
Examples of the binder that can be contained in the negative electrode layer 1 include known binders that can be used for air batteries, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and styrene butadiene rubber (SBR). It can be illustrated. When the negative electrode layer 1 contains a binder, the content is not particularly limited, but is preferably 10% by mass or less, for example, and more preferably 1% by mass to 5% by mass. preferable.

  In the air battery 10, the negative electrode current collector is a member that collects the negative electrode layer 1. The negative electrode current collector is not particularly limited as long as it can withstand the environment when the air battery 10 is used and has conductivity. Examples of the constituent material of the negative electrode current collector include copper, stainless steel, and nickel. Examples of the shape of the negative electrode current collector include a foil shape, a plate shape, and a mesh (grid) shape. It can be illustrated.

  The negative electrode layer 1 configured as described above can be produced through, for example, a process of joining metallic lithium and a negative electrode current collector. The size and thickness of the negative electrode layer 1 are not particularly limited as long as the air battery 10 can function as an air battery.

<Solid electrolyte layer 2>
The solid electrolyte layer 2 contains a solid electrolyte having lithium ion conductivity. As the solid electrolyte contained in the solid electrolyte layer 2, solid electrolytes that can be used for lithium air batteries, such as various lithium-containing oxides and lithium-based solid electrolytes, are used. Examples of such solid electrolytes include NASICON type solid electrolytes, garnet type solid electrolytes, perovskite type solid electrolytes, LISICON type solid electrolytes, glass type solid electrolytes, LATP type solid electrolytes, polyethylene oxide containing lithium salts, Examples include a copolymer of polyethylene oxide and ethyl glycidyl ether containing a lithium salt. Examples of NASICON solid electrolytes include Li _1.5 Ti ₂ Si _0.4 P _2.6 O ₁₂ and Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ . Examples of the garnet-type solid electrolyte include Li ₇ La ₃ Zr ₂ O ₁₂ and Li ₆ BaLa ₂ Ta ₂ O ₁₂ . Examples of the perovskite type solid electrolyte include Li _0.5 La _0.5 TiO _3. Examples of the LISICON type solid electrolyte include Li _3.6 P _0.4 Si _0.5 O ₄ , and , Li _3.4 V _0.6 Ge _0.4 O _{4 and the} like. As the glass type solid _{electrolyte, Li 2 O-B 2 O} 3, LiCl-Li 2 O-B 2 O 3, Li 2 O-SiO 2, Li 2 SO 4 -LiPO 4, Li 2 O-Nb 2 Examples include O ₅ and Li ₂ O—Ta ₂ O ₅ . As the LATP solid _electrolyte, it can be exemplified _{Li 1 + x + y Al x} Ti 2-x Si y P 3-y O 12 and the like. Examples of the lithium salt to be contained in polyethylene oxide or a copolymer of polyethylene oxide and ethyl glycidyl ether include LiTFSA, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiFSA, and LiTfO. The solid electrolyte layer 2 containing such a solid electrolyte can be produced, for example, by mixing a powdered solid electrolyte and performing pressure molding. The size and thickness of the solid electrolyte layer 2 are not particularly limited as long as the air battery 10 can function as an air battery.

<Aqueous electrolyte layer 3>
The aqueous electrolyte layer 3 is filled with an aqueous electrolyte 3a having lithium ion conductivity. For example, the aqueous electrolyte 3a is filled in a form in which the aqueous electrolyte 3a is held in a porous separator (not shown). Yes. As the aqueous electrolyte 3a contained in the aqueous electrolyte layer 3, for example, an alkaline aqueous electrolyte in which a lithium salt is dissolved, a neutral aqueous electrolyte in which a lithium salt is dissolved, or the like can be used. In the present invention, lithium salt such as LiOH, CH ₃ COOLi, LiClO ₄ , Li ₂ SO ₄ can be dissolved in the aqueous electrolyte, and the concentration of LiOH is 0 mol / L or more and 5.12 mol / L or less. Can do. 5.12 mol / L is the saturation concentration at room temperature. However, when the electrolyte concentration is less than 0.1 mol / L, the decrease in lithium ion conductivity becomes significant. Therefore, in order to compensate for the operation in the LiOH concentration region, KOH, NaOH, or (K ⁺ , Na ⁺ , H ⁺ , NH 4 ⁺ ) and (SO 4) of 0.1 mol / L or more and 12 mol / L or less are separately provided. ₄ ²⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , F ⁻ , CH ₃ COO ⁻ , PO ₄ ³⁻ ), or seawater can be added. Note that the air battery 10 can be operated even in a state where the LiOH precipitate is present exceeding the saturation concentration of LiOH at room temperature of 5.12 mol / L. Moreover, as a separator holding the aqueous solution electrolyte 3a, in addition to porous films such as polyethylene and polypropylene, non-woven fabrics such as a resin non-woven fabric and a glass fiber non-woven fabric can be exemplified.

<Positive electrode layer 4>
If the positive electrode layer 4 can function as the positive electrode (air electrode) of an air battery, the form will not be specifically limited, It can be set as a well-known form. For example, a conductive material, a catalyst, and a binder for binding them can be contained.

As the positive electrode layer 4, the same conductive material as that used for the negative electrode layer 1 can be used. When the positive electrode layer 4 contains a conductive material, the content of the conductive material in the positive electrode layer 4 is preferably 10% by mass or more from the viewpoint of suppressing a reduction in reaction field and a decrease in battery capacity. . Moreover, from a viewpoint of making it the form which can exhibit a sufficient catalyst function, it is preferable that content of the electroconductive material in the positive electrode layer 4 shall be 99 mass% or less.
As the catalyst used for the positive electrode layer 4, MnO ₂ , perovskite type (ABO ₃ ; A is a lanthanoid such as La or Nd, which is partially substituted by alkaline earth elements such as Sr, Ba, and Ca, Is a transition metal element partially substituted by other transition metal elements such as Ni, Fe, Co, Mn, etc. As a specific example of ABO ₃ , La _x Sr _1-x Fe _y Mn _1-y O ₃ Etc.), spinel type (AB ₂ O ₄ ; A and B are transition metal elements), pyrochlore type (A ₂ B ₂ O _7, A ₂ B _2-x A _x O _7-y (A is Pb) And Bi and B are Ru and Ir)), oxides such as IrO ₂ , noble metals such as Pd, Ag, Ir, Pt, and Ru, transition metals such as Cu, Co, and Cu, and porphyrins having a polypyrrole ligand Complexes, and Pr-Ir, Pt-R It can be exemplified an alloy such as Au-Pd. In the case where the positive electrode layer 4 contains a catalyst, the content of the catalyst in the positive electrode layer 4 is preferably 1% by mass or more from the viewpoint of a form capable of exhibiting a sufficient catalytic function. Further, from the viewpoint of suppressing a decrease in reaction field and a decrease in battery capacity, the content of the catalyst in the positive electrode layer 4 is preferably 90% by mass or less.
The positive electrode 1 may be the same as the binder used for the negative electrode layer 1. When the positive electrode layer 4 contains a binder, the content of the binder is not particularly limited, but is preferably 10% by mass or less, for example, and preferably 1% by mass to 5% by mass. It is more preferable.

  The positive electrode layer 4 can be produced, for example, through steps such as applying a composition containing carbon black, a catalyst, and a binder to the surface of the positive electrode current collector described later. In addition, it can be produced through a process such as thermocompression bonding of a mixed powder containing carbon black and a catalyst. The size and thickness of the positive electrode layer 4 are not particularly limited as long as the air battery 10 can function as an air battery.

<Air layer 5>
The air layer 5 is a layer that guides air to the positive electrode layer 4. The air layer 5 has an air passage that is led to the positive electrode layer 4. For example, the air layer 5 is in contact with the inside or the outer surface of the positive electrode layer 4 and has a hole provided in the positive electrode current collector that collects the positive electrode layer 4. , Function as an air layer 5. The air layer 5 can also be expressed as the positive electrode current collector 5.

  In the air battery 10, the positive electrode current collector is a member that collects the positive electrode layer 4. The constituent material of the positive electrode current collector is not particularly limited as long as it can withstand the environment when the air battery 10 is used and has conductivity. The constituent materials of the positive electrode current collector include noble metals such as Pt, Ag, Ir, Ru, Rh, and Pd, transition metals such as Co, Ni, and Mn, carbon-based materials such as graphite and carbon, and Au such as Au—Pd. And an alloy of a noble metal and the like. Examples of the shape of the positive electrode current collector include a mesh (grid) shape. In the air battery 10, the positive electrode current collector can be produced by forming it into a mesh shape with the above constituent materials, or by compacting the fine particles of the constituent materials by thermocompression bonding. The size and thickness of the positive electrode current collector are not particularly limited as long as the air battery 10 can function as an air battery.

<First housing 11>
The shape of the first housing 11 is particularly limited as long as the substance can move between the second housing 12 and the aqueous electrolyte layer 3 via the joint 13. It is not a thing. For example, in addition to forming a hole at a position where the joint portion 13 is to be connected, a part of the first housing 11 is meshed or an opening is provided so that air taken in from the outside It can be set as the form supplied to the positive electrode layer 4. The 1st housing 11 of such a form can be produced using the well-known material which can be used for the housing | casing of a lithium air battery.

<Second housing 12>
If the second housing 12 is configured so that the substance can move between the aqueous electrolyte layer 3 accommodated in the first housing 11 and the second housing 12 via the joint portion 13. The shape is not particularly limited. For example, it can be set as the housing of the form which does not have a hole except forming a hole in the location where the junction part 13 should be connected. The 2nd housing 12 of such a form can be produced using the well-known material which can be used for the housing | casing of a lithium air battery. In the air battery 10, when the total volume of the air battery 10 is V1 and the volume of the second housing 12 is V2, V2 / V1 ≦ 0.5 from the viewpoint of not impairing the capacity density of the battery. It is preferable that

<Joint part 13>
The joint 13 is a tubular member that connects the first casing 11 and the second casing 12 so that the aqueous electrolyte 3a can move between the second casing 12 and the aqueous electrolyte layer 3. The shape of the joint 13 is not particularly limited as long as it is tubular, but considering the case where gas is generated in the battery, the shape of the cross section with the axial direction as the normal direction is circular, or A polygon such as a triangle, a quadrangle, a pentagon, or a hexagon is preferable. When bubbles are generated in the first casing 11 due to charging or the like, or when bubbles flow into the first casing 11 from the second casing 12, the aqueous electrolyte 3a (LiOH electrolyte) is highly viscous. For this reason, bubbles are clogged in the joint portion 13, and as a result, the connection between the second casing 12 and the aqueous electrolyte layer 3 is broken, and the function of the second casing 12, which is a site for inducing LiOH precipitation, is impaired. In view of preventing the above, when the cross-sectional shape of the joint portion 13 is circular, the diameter of the circle is preferably 3 mm or more. From the same viewpoint, when the cross-sectional shape of the joint portion 13 is a polygon, the length of one side of the polygon is preferably 3 mm or more. The joint portion 13 can be manufactured using, for example, the same material as the first housing 11 and the second housing 12.

<Insulation material 14>
The heat insulating material 14 is disposed in order to suppress thermal diffusion between the first housing 11 and the second housing 12 via the outer surface. In the air battery 10, the heat insulating material 14 is not particularly limited as long as it has a heat insulating function, and a known heat insulating material can be appropriately used.

<Heatsink 15>
The heat sink 15 reduces the temperature of the second casing 12 and widens the temperature difference between the first casing 11 and the second casing 12, thereby precipitating discharge products in the second casing 12. It is a member provided to make it easier. If it has the said function, the form of the heat sink 15 will not be specifically limited, A well-known heat sink may be used suitably.

  In the above description regarding the present invention, the air battery 10 including the heat radiating plate 15 that lowers the temperature of the second casing 12 has been exemplified, but the present invention is not limited to this form. In the case where the metal-air battery of the present invention is provided with a temperature difference expanding means for reducing the temperature of the second housing, a known cooling element typified by a Peltier element or the like can be used as the temperature difference expanding means. is there. In addition, it is possible to adopt a form provided with a temperature difference expanding means for increasing the temperature of the first housing. In such a form, an external heat source (for example, a heat source such as a mechanical friction in addition to a heater). Can be used to increase the temperature of the first housing. Furthermore, when reducing the temperature of the second casing using a known cooling element represented by a Peltier element or the like, by heating the first casing using waste heat generated from the cooling element, The temperature difference between the first housing and the second housing may be enlarged.

  Moreover, in the said description regarding this invention, although the form provided with the heat sink 14 and the heat sink 15 which functions as a temperature difference expansion means was illustrated, the air battery of this invention is not limited to the said form. The air battery of the present invention may be provided with only one of the heat insulating material and the heat radiating plate, or may be provided with neither the heat insulating material nor the heat radiating plate. Then, the air battery of this invention of the form provided with precipitation promotion means other than a heat insulating material and a heat sink is demonstrated below.

  FIG. 2 is a cross-sectional view for explaining the form of the air battery 20 of the present invention according to the second embodiment. In FIG. 2, description of a flow path and the like through which a fluid (for example, humidified air or the like; the same applies hereinafter) supplied to the humidifying unit 23 is omitted. In FIG. 2, components similar to those of the air battery 10 are denoted by the same reference numerals as those used in FIG. 1, and description thereof is omitted as appropriate. As shown in FIG. 2, the air battery 20 includes a first casing 11 and a second casing 21, and the first casing 11 and the second casing 21 are connected via a joint portion 13. Yes. A heat insulating material 14 is disposed between the first housing 11 and the second housing 21, and the outer surface of the first housing 11 that faces the second housing 21 and the first housing 11. The outer surface of the second casing 21 is connected via a heat insulating material 14. The air battery 20 further includes a vent 22 that functions as a pressure adjusting unit, and a humidifying unit 23 disposed outside the vent 22 (on the upper side of the vent 22 in FIG. 2). Thus, the second casing 21 and the humidifying unit 23 are connected.

  The second casing 21 is filled with the aqueous electrolyte 3a, and the surface of the second casing 21 that is in contact with the aqueous electrolyte 3a is provided with unevenness (precipitation portion 24) that functions as a precipitation promoting means. A solid surface having a large surface tension tends to behave as a crystal nucleus of a discharge product, and crystal growth is likely to occur at a site where the specific surface area is increased due to the formation of minute irregularities. Therefore, in the air battery 20, it is possible to promote the precipitation of the discharge product in the precipitation portion 24, and thereby the precipitation of the discharge product in the aqueous electrolyte layer 3 can be suppressed. That is, according to the air battery 20, the discharge product (LiOH) can be deposited on the precipitation portion 24 of the second casing 21 that does not inhibit the charging reaction and the discharge reaction that occur in the first casing 11. Thus, it is possible to increase the capacity of the air battery 20 while avoiding a situation in which discharge products (LiOH) are deposited on the surfaces of the positive electrode layer 4 and the solid electrolyte layer 2. Therefore, according to this invention, the air battery 20 which can improve cycling characteristics can be provided.

  Further, the air battery 20 has a vent 22 connected to a second housing 21. Since air is supplied to the positive electrode, the air battery basically has an open structure. Therefore, it is considered that the configuration for controlling the pressure in the housing is not essential. However, there is a risk that the internal pressure will increase due to temperature rise in the battery, etc. Further, according to the above equation 2, the air battery consumes water molecules and discharges, so the internal pressure of the battery may also decrease. If the pressure in the battery is excessively increased / decreased, the performance of the battery may be deteriorated. Therefore, the air battery preferably has a configuration for controlling the pressure in the battery. Since the air battery 20 includes the vent 22, the internal pressure of the second housing 21 and the internal pressure of the first housing 11 can be adjusted (controlled) using the vent 22.

  As described above, the second casing 21 is filled with the aqueous electrolyte 3a. If the amount of the aqueous electrolyte 3a accommodated in the second casing 21 is reduced, it may be difficult to obtain the effect of depositing a discharge product on the second casing 21. Therefore, it is preferable that the outside of the vent 22 connected to the second housing 21 has a configuration capable of humidifying the aqueous electrolyte 3a. From this point of view, in the air battery 20, a humidifying unit 23 that accommodates a fluid capable of humidifying the aqueous electrolyte 3 a is disposed outside the vent 22. Since the amount of volatilization of the aqueous electrolyte 3a can be reduced by humidifying the aqueous electrolyte 3a using the humidifying unit 23, the cycle characteristics of the air battery 20 can be easily improved.

  In the air battery 20, the precipitation part 24 can be formed by making the inner surface (inner wall) of the 2nd housing | casing 21 which contacts the aqueous solution electrolyte 3a into a rough surface, for example. The inner wall of the second casing 21 is preferably made of a resin, an inorganic inert substance, or the like. In the case where the inner wall of the second casing 21 is composed of these materials, the precipitation portion 24 can be formed in the process of generating the resin or the like and post-processing after the generation. When post-processing is performed, the precipitation portion 24 can be formed by polishing using a polishing means such as a file or by embedding inert fine particles (carbon, metal, ceramics, resin, or the like). .

  It is preferable that the surface of the precipitation portion 24 that comes into contact with the aqueous electrolyte 3a has irregularities having a point Rku of 9.96 or more as described in JIS B 0601: 2001. By having such a point, it becomes easy to preferentially deposit the discharge product on the surface of the precipitation portion 24 when the aqueous electrolyte 3a exceeds the saturation solubility.

  Moreover, it is preferable that the 10-point average roughness Rz of the surface by the unevenness | corrugation is 5.25 micrometers or more as for the surface of the precipitation part 24 which contacts the aqueous solution electrolyte 3a. Moreover, it is preferable that the average space | interval Sm of the said unevenness | corrugation is 10.5 micrometers or more. Further, the surface of the precipitation portion 24 that comes into contact with the aqueous electrolyte 3a preferably has a root mean square roughness Rq of 1 to 13.5, more preferably 4 to 12. By making the precipitation part 24 into such a form, when the aqueous electrolyte 3a exceeds the saturation solubility, it becomes easier to preferentially precipitate the discharge product on the surface of the precipitation part 24.

  In the above description of the present invention, the air battery 10 in a form not provided with a vent and the air battery 20 in a form provided with a vent 22 are exemplified, but the present invention is not limited to these forms. The metal-air battery of the present invention can be configured to include a pressure control means such as a vent together with a temperature difference widening means. The metal air battery is provided with irregularities for depositing discharge products, while the pressure control means such as a vent is provided. It is possible to adopt a form that is not provided.

  Moreover, in the said description regarding this invention, although the air battery 20 in which the precipitation part 24 was provided in the inner surface (inner wall) of the 2nd housing | casing 21 which contacts the aqueous solution electrolyte 3a was illustrated, the unevenness | corrugation which functions as a precipitation promotion means is the said The form is not limited. Therefore, with reference to FIG. 3 and FIG. 4, another embodiment of the unevenness provided in the second casing will be described.

  FIG. 3 is a cross-sectional view illustrating a second casing 25 that can be provided in the metal-air battery (for example, a lithium-air battery) of the present invention. In FIG. 3, only the joint portion 13 is shown as a component of the lithium-air battery provided outside the second casing 25, and other components are not shown. As shown in FIG. 3, the second casing 25 is filled with the aqueous electrolyte 3a, and the inner surfaces (inner walls) of the second casing 25 are structures 26, 26,. Is provided. The structures 26, 26,... Extend from one inner surface of the second housing 25 toward the inner surface facing the second housing 25, and have minute irregularities on the surface that contacts the aqueous electrolyte 3 a. It is preferable that a plurality of the structures 26 are provided inside the second casing 25 from the viewpoint of making the discharge product easily deposit. As shown in FIG. 3, when a plurality of structures 26, 26,... Are provided, the interval between the adjacent structures 26, 26 does not hinder the flow of the aqueous electrolyte 3 a and dissolved ions (the interval is an aqueous solution). It can be appropriately adjusted depending on the viscosity of the electrolyte 3a and the size of the air battery, and is preferably 5 μm to 5000 μm, for example. The structure is not particularly limited as long as the discharge product can be deposited on minute irregularities on the surface. The structures 26, 26,..., For example, polish the surface of a rod-like member or plate-like member, or embed fine particles having a large specific surface area on the surface to form minute irregularities on the surface, and then the second It can fix to the inner surface (inner wall) of the housing 25 by methods, such as welding, adhesion | attachment, or engagement. The constituent material of the structures 26, 26, ... is not particularly limited as long as it is a material that can withstand the environment during use of the air battery and can deposit discharge products on the surface. For example, a resin or an inorganic inert substance can be used. The size and shape of the structures 26, 26,... Can be appropriately selected in accordance with the object of the present invention to improve the cycle characteristics of the air battery by depositing discharge products on the surface.

  3 exemplifies a form in which only the structures 26, 26,... Are provided as the precipitation promoting means. However, from the viewpoint of facilitating precipitation of discharge products inside the second casing, the structure 26 is provided. , 26..., 26 is preferably provided with a precipitation portion 24 on the inner surface (inner wall) of the second casing 25. In the second casing configured in this manner, for example, after the precipitation portion 24 is provided on the inner surface (inner wall) of the second casing, the structures 26, 26,... Are formed on the inner surface (inner wall) of the second casing. It can be produced by a method such as fixing.

  FIG. 4 is a cross-sectional view illustrating a second casing 27 that can be provided in the metal-air battery (for example, a lithium-air battery) of the present invention. In FIG. 4, only the joint portion 13 is shown as a component of the lithium-air battery provided outside the second casing 27, and other components are not shown. As shown in FIG. 4, the aqueous electrolyte 3 a filled in the second casing 27 is impregnated in the structure 28, and the structure 28 includes crystal growth nuclei 29, 29,. .

  The structure 28 is a member such as a fiber or a film that can permeate and impregnate the aqueous electrolyte. The structure 28 can be manufactured using a material that can be used as a separator for an air battery, such as a glass material, a polymer material, an alloy, or ceramics. From the viewpoint of forming the discharge product on the surface of the structure 28, it is preferable that the surface of the structure 28 is provided with unevenness similar to that of the precipitation portion 24.

  The crystal growth nuclei 29, 29,... Function as precipitation / growth nuclei of the discharge product, and are scattered / supported in the structure 28. The inside and the surface of the structure 28 in which the crystal growth nuclei 29, 29,... Are arranged have irregularities, and these irregularities function as precipitation promoting means. From the viewpoint of making the discharge product easy to deposit, etc., it is preferable that a plurality of crystal growth nuclei 29 are provided in the structure 28, and the crystal growth nuclei 29 include fine particles and fibrous substances having a large specific surface area. , 29,... Here, “large specific surface area” means, for example, a specific surface area determined by the BET method ((particle surface area determined from the amount of gas adsorbed by BET) / (mass of particle)), It means that it is more than twice the specific surface area when assumed. The constituent material of the crystal growth nuclei 29, 29,... Is not particularly limited as long as the material can withstand the environment when the air battery is used and functions as a precipitation / growth nucleus of the discharge product. For example, a glass material, a polymer material, an alloy, ceramics, or the like can be used. Further, the size of the crystal growth nuclei 29, 29,... Is not particularly limited. For example, in the form of single particles or secondary particle aggregates, the diameter is 0.5 μm to 3000 μm. In the fibrous form, the fiber length can be 0.5 μm to 3000 μm, and the fiber diameter (width in the direction orthogonal to the fiber length direction) can be 0.01 μm to 1000 μm.

  The structure 28 provided with a plurality of crystal growth nuclei 29, 29,..., For example, prepares a plurality of fibers or films (fibers etc.) constituting the structure 28, and the crystal growth nuclei 29, .., And a step of disposing other fibers on the surface of the fiber or the like having crystal growth nuclei 29, 29,... Scattered on the surface. It can be manufactured through a process such as repeating until it reaches the same depth as the depth of the aqueous electrolyte 3a to be filled in 27. In addition, by impregnating the structure 28 with the aqueous electrolyte 3a in which the crystal growth nuclei 29, 29,... Are dispersed, a plurality of crystal growth nuclei 29, 29,. Is possible.

  In FIG. 4, the form in which only the structure 28 having a plurality of crystal growth nuclei 29, 29,... Is provided as the precipitation promoting means is illustrated, but it is easy to deposit discharge products inside the second casing. From such a viewpoint, it is preferable that a precipitation portion 24 is provided on the inner surface (inner wall) of the second casing 27 in addition to the structure 28 having a plurality of crystal growth nuclei 29, 29,. . In the second casing configured in this manner, for example, after the structure 28 is disposed on the second casing having the precipitation portion 24 provided on the inner surface (inner wall), the crystal growth nuclei 29, 29,. It can be produced by a method such as impregnating the structure 28 with the aqueous electrolyte 3a.

  In the above description regarding the air cell having the unevenness functioning as the precipitation promoting means, the form in which the unevenness and the heat insulating material 14 are provided as the precipitation promoting means is illustrated, but the present invention is not limited to the form. A cooling element (temperature difference enlarging means) typified by the heat radiating plate 15 or a Peltier element may be provided in the second casing having irregularities that function as precipitation promoting means. When the temperature of the second casing is reduced using a known cooling element typified by a Peltier element or the like, the first casing is heated by using the waste heat generated from the cooling element. You may enlarge the temperature difference of this housing and a 2nd housing.

  In the above description regarding the present invention, the air battery 20 having the heat insulating material 14, the vent 22, and the precipitation portion 24 functioning as the precipitation promoting means has been exemplified. However, the precipitation promoting means combined with the pressure control means such as the vent 22. Is not limited to the heat insulating material 14 and the unevenness provided inside the second housing represented by the precipitation portion 24. In the present invention, the pressure control means can be combined with only one of the heat insulating material 14 and the unevenness, and is combined with the temperature difference expanding means without combining with both the heat insulating material 14 and the unevenness, the temperature difference expanding means and the heat insulation. In addition to a form combined with a material, a form combined with a temperature difference widening means, a heat insulating material, and unevenness may be used.

  Moreover, in the said description regarding this invention, although the 1st housing and the 2nd housing were illustrated through the junction part, the air battery of the form was illustrated, but this invention is limited to the said form is not. Furthermore, in the said description regarding this invention, although the air battery of the form provided with the precipitation promotion means was illustrated, this invention is not limited to the said form. Accordingly, the present invention in a form in which a plurality of first casings and one second casing are connected via a joint and no precipitation promoting means is provided will be described below.

  FIG. 5 is a top view for explaining the form of the air battery 30 according to the third embodiment of the present invention. In FIG. 5, the same components as those of the air battery 10 are denoted by the same reference numerals as those used in FIG. 1, and the description thereof is omitted as appropriate. As shown in FIG. 5, the air battery 30 includes first casings 11, 11, 11 and a second casing 31, and the first casings 11, 11, 11 and the second casing 31 are tubular. Are joined via the joint portions 32, 32, and 32. The joint portions 32, 32, 32 are provided with on-off valves 33, 33, 33 that can switch the flow of the aqueous electrolyte solution 3 a in the joint portions 32, 32, 32, respectively. The housing 31 contains the aqueous electrolyte 3a, but does not contain the positive electrode or the negative electrode. In the air battery 30, the aqueous solution electrolyte layers 3, 3, 3 and the second housing 31 respectively accommodated in the first housing 11, 11, 11 are connected via the joint portions 32, 32, 32. Yes. Therefore, while the on-off valves 33, 33, 33 are open, the aqueous electrolyte 3 a accommodated in the second casing 31 is transferred to the first casings 11, 11, 11 via the joints 32, 32, 32. The discharge products present in the aqueous electrolyte layers 3, 3 and 3 of the first casings 11, 11, and 11 It is possible to move to the second housing 31 via 32, 32, 32. Note that, unlike the air battery 10 and the air battery 20, the air battery 30 does not include a deposition promoting means.

  In the first casings 11, 11, 11 where the charging reaction and the discharging reaction occur, the aqueous electrolytes 3 a, 3 a, 3 a filled in the aqueous electrolyte layers 3, 3, 3 are heated by operating heat, whereas In the second casing 31 in which the positive electrode and the negative electrode are not accommodated, no charging reaction or discharging reaction occurs. The temperature of the aqueous electrolyte 3a accommodated in the second casing 31 that is not easily heated by the operating heat is lower than the temperature of the aqueous electrolytes 3a, 3a, 3a accommodated in the first casing 11, 11, 11. Therefore, even in the air battery 30 that does not include the precipitation promoting means, the discharge product can be deposited in the second casing 31. Therefore, even if it is a form which has the 2nd housing | casing 31 connected to the some 1st housing | casing 11, 11, 11, it can be set as the air battery 30 which can improve cycling characteristics.

  In addition, open / close valves 33, 33, 33 are provided at the joints 32, 32, 32 of the air battery 30. By doing in this way, the 2nd housing 31 can be made into the form which can be attached or detached. In the air battery 30, for example, when the amount of the aqueous electrolyte 3a accommodated in the second casing 31 is reduced to a predetermined value or less, the on-off valves 33, 33, 33 are closed and the second casing 31 is removed, After the new second casing 31 filled with the aqueous electrolyte 3a is attached, the on-off valves 33, 33, 33 can be opened. And the air battery 30 can be operated in the state where the on-off valves 33, 33, 33 are opened. In the air battery 30, the second casing 31 can be made of the same material as the second casing 12, the joint portion 32 can be made of the same material as the joint portion 13, and the on-off valve 33 is made of air. A known on-off valve that can withstand the environment during use of the battery 30 can be used as appropriate.

  In the above description of the present invention, the air battery 30 in the form in which the first casing 11, 11, 11 and the second casing 31 are connected to each other but the precipitation promoting means is not provided is illustrated. The metal-air battery is not limited to this form. From the standpoint of providing a metal-air battery in a form in which the cycle characteristics are easily improved by making the discharge product easy to deposit inside the second casing, a plurality of first casings and one first casing are provided. It is preferable that the metal-air battery of the present invention in a form in which the two casings are connected is also provided with a precipitation promoting means.

  In the above description regarding the present invention, the first casing 11 containing the negative electrode layer 1, the solid electrolyte layer 2, the aqueous electrolyte layer 3, the positive electrode layer 4, and the air layer 5 in this order from the bottom side. Although the provided form was illustrated, the 1st housing | casing with which the metal air battery of this invention is equipped is not limited to the said form. The first casing only needs to contain at least a positive electrode layer and a negative electrode layer, and an aqueous electrolyte layer disposed between the positive electrode layer and the negative electrode layer so as to be in contact with the positive electrode layer. In other words, the first casing can have a form without an air layer, or can have a form in which only the aqueous electrolyte layer is disposed between the positive electrode layer and the negative electrode layer.

Below, the example of the laminated structure from the negative electrode layer to a positive electrode layer accommodated in the 1st housing in the metal air battery of this invention is demonstrated. The following structure can be illustrated as said laminated structure in the metal air battery of this invention. In the following, the aqueous electrolyte layer accommodated in the first casing is “a”, the non-aqueous electrolyte layer is “b”, the ionic liquid layer is “c”, the solid electrolyte layer is “d”, and the anion exchange membrane layer May be written as “e”.
(1) Negative electrode layer | a | Positive electrode layer (2) Negative electrode layer | d | a | Positive electrode layer (3) Negative electrode layer | b | d | a | Positive electrode layer (4) Negative electrode layer | c | d | a | (5) Negative electrode layer | d | a | e | a | Positive layer (6) Negative electrode layer | b | d | a | e | a | Positive layer (7) Negative layer | c | d | a | e | a | Positive electrode layer

  (1) is a form in which only the aqueous electrolyte layer is disposed between the positive electrode layer and the negative electrode layer, and (2) is a form corresponding to the laminated structure accommodated in the first casing 11. Further, (3) is a form in which a non-aqueous electrolyte layer is interposed between the negative electrode layer and the solid electrolyte layer of (2), and (4) is a configuration of the negative electrode layer and the solid electrolyte layer of (2). The ionic liquid layer is interposed between them. (5) is a form in which an aqueous electrolyte layer and an anion exchange membrane layer are interposed between the solid electrolyte layer and the aqueous electrolyte layer of (2). (6) is a form in which a non-aqueous electrolyte layer is interposed between the negative electrode layer and the solid electrolyte layer of (5), and (7) is a configuration of the negative electrode layer and the solid electrolyte layer of (5). The ionic liquid layer is interposed between them. When the negative electrode layer and the solid electrolyte layer (d) are in contact, they are directly joined. Hereinafter, the nonaqueous electrolyte layer, the ionic liquid layer, and the anion exchange membrane layer that can be accommodated in the first casing will be described in detail.

The non-aqueous electrolyte layer (b) is a layer filled with a non-aqueous electrolyte prepared by dissolving one or more lithium salts as a solute in a non-aqueous solvent, and the non-aqueous electrolyte layer (b) If necessary, it is also possible to adopt a form in which a non-aqueous electrolyte is held in a separator that can also be used in the aqueous electrolyte layer 3. Nonaqueous solvents used for nonaqueous electrolytes include carbonate solvents (eg, propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), etc.), and general battery solvents (eg, tetrahydrofuran, dimethyl). In addition to sulfoxide (DMSO), dioxofuran, etc.), a mixed solvent obtained by mixing a carbonate solvent and a general battery solvent can be exemplified. As the lithium salt used in the non-aqueous electrolyte _can be exemplified _{LITFSA, LiPF 6, LiBF 4,} LiClO 4, LiFSA, the LiTfO like.

The ionic liquid layer (c) is a layer filled with an ionic liquid prepared by dissolving one or more lithium salts as a solute in the ionic liquid, and the ionic liquid layer (c) is necessary Accordingly, it is possible to adopt a form in which the ionic liquid is held in a separator that can also be used in the aqueous electrolyte layer 3. Examples of the ionic liquid used in the ionic liquid layer (c) include imidazolium cations (EMIm cation, BMIm cation, etc.), alkylammonium cations (N1113 cation, etc.), alkylpyridinium cations (P13 cation, P14 cation, etc.), and alkyl piperidines. Cation such as nium cation (PP13 cation), alkylammonium cation having ether side chain (DEME cation, etc.), PF ₆ anion, BF ₄ anion, fluorosulfonylamide anion or perfluoroalkylsulfonylamide anion (FSA anion, TFSA anion) And the like, and those obtained by mixing these ionic liquids. As the lithium salt used in the ionic liquid layer _(c), it is possible to illustrate _{LITFSA, LiPF 6, LiBF 4,} LiClO 4, LiFSA, the LiTfO like.

  The anion exchange membrane layer (e) is a layer having a hydrocarbon polymer, for example, a polymer membrane containing a methylammonium group, a methylpyridinium group, and an alkyl phosphorus in the side chain (for example, A series anion type manufactured by Tokuyama Corporation). Electrolyte material) or the like.

As mentioned above, although the case where this invention is applied to a lithium air battery was illustrated in the said description regarding this invention, the metal air battery of this invention is not limited to a lithium air battery. The metal-air battery of the present invention can be applied to other types of batteries as long as a salt that is soluble in an electrolytic solution is generated during charging and discharging. The present invention is particularly effective for a battery in which the concentration of salt in the electrolytic solution varies greatly. Examples of such batteries include lithium-air batteries, other metal-air batteries having an aqueous electrolyte and having a negative electrode such as Zn, and Daniel batteries (Cu | CuSO ₄ aqueous solution | ZnSO ₄ aqueous solution | Zn). be able to. Also in the metal-air battery other than the lithium-air battery, the aqueous electrolyte is accommodated in a second casing different from the first casing that accommodates the positive electrode, the negative electrode, and the aqueous electrolyte layer disposed therebetween, and the second The effect of this invention can be show | played by setting it as the structure which connected the housing and the aqueous solution electrolyte layer so that aqueous solution electrolyte could flow.

  Hereinafter, the metal-air battery of the present invention will be described with reference to examples.

  Negative electrode | Non-aqueous electrolyte layer | Solid electrolyte layer | Aqueous electrolyte layer | A first casing containing the positive electrode layer in order, and a second casing containing the same aqueous electrolyte as the aqueous electrolyte contained in the first casing A metal-air battery (Li-air battery) of the present invention was prepared, and a tubular joint portion connecting the aqueous electrolyte layer and the second casing in a form in which the aqueous electrolyte can flow. Here, the negative electrode layer was made of metal Li, and the nonaqueous electrolyte layer was filled with a nonaqueous electrolyte prepared by dissolving 1 mol / L LiTFSA in PC. Moreover, the LATP type solid electrolyte was used for the solid electrolyte layer, and the aqueous electrolyte layer was filled with a saturated LiOH aqueous solution (1 ml) containing 5 mol / L LiOH. The air electrode layer was prepared through a process of mixing a conductive material (carbon such as Ketjen Black), a binder (PVDF, etc.) and a catalyst (Pt, perovskite catalyst, etc.). In the metal-air battery of the present invention, a total amount of 1.5 ml of LiOH aqueous solution including the amount contained in the second casing is used, the negative electrode lead is connected to the negative electrode layer via the negative electrode current collector, and the positive electrode layer is connected to the positive electrode layer. A positive electrode lead was connected via a positive electrode current collector having holes through which air can flow.

Moreover, the metal air battery of the comparative example (Li air battery) comprised similarly to the metal air battery of the said this invention except not having a coupling | bond part and a 2nd housing was also produced. And the Li air battery of this invention and the Li air battery of the comparative example were each discharged at 0.5 mA / cm < ² >, and the performance was investigated. The discharge curve (Example) of the Li air battery of the present invention and the discharge curve of the Li air battery of the comparative example are shown in FIG. The vertical axis in FIG. 6 is the discharge potential E [V], and the horizontal axis is the discharge capacity Q [mAh].

As shown in FIG. 6, in the Li-air battery of the comparative example, the discharge potential decreased rapidly after being discharged for a while at 2.7 V in the first plateau region. And it discharged further in the 2nd plateau area | region below 1.7V, and discharge end potential was 1.5V. In the Li-air battery of the comparative example, LiOH was deposited inside the positive electrode layer after the discharge was finished. This is because the discharge reaction in the first plateau region was the expected reaction represented by the following formula (2), but LiOH was precipitated in the air electrode, so that the diffusion of air in the air electrode was hindered and the oxygen reduction reaction. As a result of the decrease in the net reaction rate and the voltage drop, the discharge reaction in the second plateau region is considered to be caused by the decomposition reaction of water represented by the following formula (3).
Assumed discharge reaction: 4Li + O ₂ + 2H ₂ O → 4LiOH 3.466V Formula (2)
Water splitting reaction: 2Li + 2H ₂ O → 2OH ⁻ + H ₂ 2.127V Formula (3)

  On the other hand, in the Li air battery of the example, the discharge of 1.5 times or more of the total capacity of the air battery of the comparative example could be performed only by the potential of the first plateau region. The discharge capacity ratio between the first plateau regions in the example and the comparative example was approximately Example: Comparative Example = 3: 1. In this experiment, the Li-air battery of the example did not reach the end of discharge, and it was possible to continue the discharge.

  As described above, according to the Li air battery of the embodiment in which the second casing for depositing the discharge product is added in addition to the first casing for causing the charging reaction and the discharge reaction, the LiOH in the second casing is provided. As a result, the discharge capacity can be increased and the cycle characteristics can be improved. It was.

  The metal-air battery of the present invention can be used as a power source for electric vehicles and portable information devices.

DESCRIPTION OF SYMBOLS 1 ... Negative electrode layer 2 ... Solid electrolyte layer 3 ... Aqueous electrolyte layer 3a ... Aqueous solution electrolyte 4 ... Positive electrode layer 5 ... Air layer 10 ... Air battery (metal-air battery)
DESCRIPTION OF SYMBOLS 11 ... 1st housing 12 ... 2nd housing 13 ... Connection part 14 ... Heat insulating material 15 ... Heat sink (temperature difference expansion means)
20 ... Air battery (metal-air battery)
21 ... Second housing 22 ... Vent (pressure adjusting means)
23 ... Humidification part 24 ... Precipitation part (unevenness)
25 ... second housing 26 ... structure (unevenness)
27 ... second casing 28 ... structure 29 ... crystal growth nucleus (unevenness)
30 ... Air battery (metal-air battery)

Claims (8)

A first housing containing at least a positive electrode, a negative electrode, and an aqueous electrolyte filled between the positive electrode and the negative electrode; and a second housing containing the aqueous electrolyte, wherein the aqueous electrolyte is distributed. The metal-air battery, wherein the first casing and the second casing are connected to each other through a joining portion. 2. The metal-air battery according to claim 1, further comprising a deposition promoting means for promoting deposition of a discharge product from the aqueous electrolyte contained in the second casing. 3. The metal-air battery according to claim 2, wherein the precipitation promoting means includes temperature difference widening means for widening a difference between the temperature of the second housing and the temperature of the first housing. The metal air according to claim 2 or 3, wherein a heat insulating material disposed between an outer surface of the first casing and an outer surface of the second casing is included in the precipitation promoting means. battery. The metal-air battery according to any one of claims 2 to 4, wherein unevenness provided in the second casing in contact with the aqueous electrolyte is included in the precipitation promoting means. The metal-air battery according to any one of claims 1 to 5, wherein the second casing and the plurality of first casings are connected. The metal-air battery according to any one of claims 1 to 6, wherein a pressure control means capable of controlling a pressure inside the first casing is connected to the second casing. . The metal-air battery according to claim 7, wherein the pressure control means is a vent, and the outside of the vent is humidified.