JP2013182667A - Lithium air secondary battery and method for manufacturing lithium air secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium air secondary battery capable of solving a problem due to dendrite growing on a surface of a negative electrode and having large energy density, and a method for manufacturing the lithium air secondary battery.SOLUTION: A lithium air secondary battery 1 includes: an air electrode as a positive electrode 2; a negative electrode 3 comprising metallic lithium or a lithium alloy; a perovskite-type or garnet-type lithium conducting solid electrolyte 4 joined to a face on the positive electrode 2 side of the negative electrode 3; and an aqueous electrolytic solution 5 disposed between the lithium conducting solid electrolyte 4 and the positive electrode 2. The negative electrode 3 and the lithium conducting solid electrolyte 4 are joined so that lithium ions can be dispersed between the negative electrode 3 and the lithium conducting solid electrolyte 4.

Description

  The present invention relates to a lithium air secondary battery and a method of manufacturing a lithium air secondary battery, and more particularly to a lithium air secondary battery having a large energy density and a method of manufacturing the same.

  Conventionally, there is a lithium-air secondary battery including an air electrode as a positive electrode and a negative electrode containing lithium metal. Lithium-air secondary batteries can obtain a large energy density, and are therefore being studied for use in batteries for electric vehicles.

  As an air electrode of a lithium air secondary battery, a porous carbon carrying a catalyst made of a metal oxide is usually used. In a lithium-air secondary battery equipped with an air electrode made of porous carbon carrying a catalyst, the lithium oxide produced by the discharge reaction is clogged into the pores of the porous carbon, causing contact between lithium ions and air. There is a problem that it is impossible to discharge due to hindrance.

  As a technique for solving this problem, for example, Patent Document 1 discloses a lithium-air in which a negative electrode containing lithium metal, an organic electrolyte for a negative electrode, a separator, an aqueous electrolyte for an air electrode, and an air electrode are provided in that order. A lithium-air battery has been proposed that includes a solid electrolyte through which the separator passes only lithium ions.

  In the lithium-air battery described in Patent Document 1, a separator containing a solid electrolyte that allows only lithium ions to pass between the organic electrolyte for the negative electrode and the aqueous electrolyte for the air electrode is provided. The product becomes lithium hydroxide soluble in the water-soluble electrolyte. For this reason, it can prevent that the pore of the porous carbon which comprises an air electrode is clogged with the product produced | generated by discharge reaction.

JP 2010-176941 A

However, since the conventional lithium air secondary battery is used as a battery for an electric vehicle, it is required to further improve the energy density per battery weight and the energy density per battery volume.
Further, the conventional lithium-air secondary battery has a problem that dendrid grows on the surface of the negative electrode during charging. Specifically, in a lithium-air secondary battery including a separator between a negative electrode and a positive electrode, such as the lithium-air battery described in Patent Document 1, dendride grown from the surface of the negative electrode penetrates the separator during charging. There is a risk that the negative electrode and the positive electrode are short-circuited.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a lithium-air secondary battery having a large energy density and a method for manufacturing the same, which can solve the problems caused by dendrites growing on the surface of the negative electrode.

In order to solve the above problems and improve the energy density of the lithium-air secondary battery, the present inventor has intensively studied as described below.
In the technique described in Patent Document 1, the role of the organic electrolyte for the negative electrode is only to diffuse lithium ions. Therefore, in the technique described in Patent Document 1, if the negative electrode and the separator are arranged in contact with each other and lithium ions can be sufficiently diffused by movement of the lithium ions between the negative electrode and the separator, the battery performance is lowered. Without removing the organic electrolyte for the negative electrode.

  In the technique described in Patent Document 1, if the organic electrolyte for the negative electrode and its installation space are removed, the battery weight and the battery volume are reduced. Therefore, the energy density per battery weight and the energy density per battery volume are relatively reduced. Can be improved. Furthermore, since the organic electrolyte solution for negative electrodes becomes unnecessary, the cost of battery materials can be reduced. Further, since the organic electrolyte for the negative electrode is removed, dendride does not grow on the surface of the negative electrode.

However, when the negative electrode and the solid electrolyte having a separator function are arranged in contact with each other, the solid electrolyte may be reduced and decomposed depending on the selected solid electrolyte species (the solid electrolyte used in Patent Document 1). When the solid electrolyte is reduced and decomposed, lithium ions cannot move in the separator, and the battery performance deteriorates.
As a result of intensive studies by the inventors, when a negative electrode made of metallic lithium or a lithium alloy was used, and a perovskite-type or garnet-type lithium conductive solid electrolyte was used as the solid electrolyte, a solid was in contact with the negative electrode. It has been found that even when an electrolyte is disposed, the solid electrolyte is not likely to undergo reductive decomposition.

However, merely arranging such a negative electrode and a solid electrolyte in contact with each other results in insufficient diffusion of lithium ions between the negative electrode and the solid electrolyte, and sufficient battery performance cannot be obtained.
Therefore, the present inventor has intensively studied to make it possible to diffuse lithium ions between the negative electrode and the solid electrolyte. As a result, it was found that the negative electrode and the solid electrolyte may be joined using any one method selected from the following three methods <1> to <3>.

<1> The surface of the solid electrolyte is roughened, and a negative electrode is pressure-bonded and bonded to the surface of the roughened solid electrolyte.
<2> The negative electrode and the solid electrolyte are joined together by laminating a molten negative electrode material on the surface of the solid electrolyte and cooling and solidifying it.
<3> The negative electrode and the solid electrolyte are joined by depositing a negative electrode material on the surface of the solid electrolyte by a chemical deposition method.

  And this inventor is the lithium in which the negative electrode which consists of the material mentioned above, and the solid electrolyte which consists of the material mentioned above are joined by any one method chosen from three methods of said <1>-<3>. By making it an air secondary battery, it was confirmed that the organic electrolyte for the negative electrode can be eliminated, and the present invention was completed. That is, the present invention relates to the following.

(1) An air electrode as a positive electrode, a negative electrode made of metallic lithium or a lithium alloy, a perovskite-type or garnet-type lithium conductive solid electrolyte joined to the surface of the negative electrode on the positive electrode side, and the lithium conductive solid electrolyte An aqueous electrolyte solution disposed between the negative electrode and the lithium conductive solid electrolyte so that lithium ions can be diffused between the negative electrode and the lithium conductive solid electrolyte. And a lithium air secondary battery characterized by being joined to each other.

(2) The lithium conductive solid electrolyte is a perovskite type having a composition of (LiLa) MO ₃ (M = Ta, Zr), or Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₅ The lithium-air secondary battery according to (1), which is a garnet type composed of any composition of La ₃ Ta ₂ O ₁₂ .
(3) The lithium-air secondary battery according to (1) or (2), wherein the aqueous electrolyte solution is acidic or alkaline.
(4) The metal foil which consists of metallic lithium or a lithium alloy is affixed on the surface on the opposite side to the said lithium conductive solid electrolyte of the said negative electrode, It is characterized by the above-mentioned in any one of (1)-(3) Lithium air secondary battery.

(5) The method for producing a lithium air secondary battery according to any one of (1) to (4), wherein the lithium conductive solid electrolyte is roughened by roughening a surface of the lithium conductive solid electrolyte. A method for producing a lithium-air secondary battery, comprising the step of pressure-bonding and joining the negative electrode to the surface of the electrolyte.

(6) The method for producing a lithium-air secondary battery according to any one of (1) to (4), wherein a molten negative electrode material is stacked on the surface of the lithium conductive solid electrolyte and cooled and solidified. A method for producing a lithium air secondary battery, comprising the step of joining the negative electrode and the lithium conductive solid electrolyte.
(7) The method according to (6), further comprising a step of roughening the surface of the lithium conductive solid electrolyte before the molten negative electrode material is laminated on the surface of the lithium conductive solid electrolyte and cooled and solidified. The manufacturing method of the lithium air secondary battery of description.

(8) The method for producing a lithium-air secondary battery according to any one of (1) to (4), wherein a negative electrode material is deposited on a surface of the lithium conductive solid electrolyte by a chemical deposition method. The manufacturing method of a lithium air secondary battery characterized by including the process of joining a negative electrode and the said lithium conductive solid electrolyte.
(9) The method according to (8), further comprising a step of roughening the surface of the lithium conductive solid electrolyte before the negative electrode material is deposited on the surface of the lithium conductive solid electrolyte by a chemical deposition method. A method for producing a lithium-air secondary battery.
(10) After the step of joining the negative electrode and the lithium conductive solid electrolyte, a step of attaching a metal foil made of metallic lithium or a lithium alloy to the surface of the negative electrode opposite to the lithium conductive solid electrolyte is provided. (8) The manufacturing method of the lithium air secondary battery as described in (9) characterized by these.

  The lithium-air secondary battery of the present invention includes an air electrode as a positive electrode, a negative electrode made of metallic lithium or a lithium alloy, and a perovskite-type or garnet-type lithium conductive solid electrolyte bonded to the surface of the negative electrode on the positive electrode side. An aqueous electrolyte solution disposed between the lithium conductive solid electrolyte and the positive electrode, so that lithium ions can be diffused between the negative electrode and the lithium conductive solid electrolyte. Since the negative electrode and the lithium conductive solid electrolyte are joined, there is no need to dispose an organic electrolyte for the negative electrode between the negative electrode and the lithium conductive solid electrolyte.

  Therefore, the battery weight and the battery volume are small compared to the lithium air secondary battery including the organic electrolyte for the negative electrode, and the energy density per battery weight and the energy density per battery volume are relatively high. Become. In addition, the lithium-air secondary battery of the present invention is preferable because it does not require an organic electrolyte for the negative electrode and can reduce the cost of the battery material. Moreover, in the lithium air secondary battery of the present invention, since the negative electrode and the lithium conductive solid electrolyte are joined, dendride does not grow on the surface of the negative electrode. Further, in the lithium-air secondary battery of the present invention, since the negative electrode and the lithium conductive solid electrolyte are joined, the danger caused by the reaction of water or nitrogen in the air with the negative electrode made of metallic lithium or a lithium alloy. Sex can be avoided.

  Further, according to the method for producing a lithium-air secondary battery of the present invention, the negative electrode and the lithium conductive solid electrolyte are joined so that lithium ions can be diffused between the negative electrode and the lithium conductive solid electrolyte. The lithium air secondary battery of the present invention can be provided.

FIG. 1 is a schematic diagram for explaining an example of the lithium-air secondary battery of the present invention. FIG. 1 (a) is a diagram showing a reaction during discharge, and FIG. 1 (b) is a diagram during charging. It is the figure which showed this reaction.

Hereinafter, the lithium air secondary battery and the method for producing the lithium air secondary battery of the present invention will be described in detail.
"Lithium-air secondary battery"
FIG. 1 is a schematic diagram for explaining an example of the lithium-air secondary battery of the present invention.
A lithium air secondary battery 1 shown in FIG. 1 includes an air electrode as a positive electrode 2, a negative electrode 3, a lithium conductive solid electrolyte 4 bonded to the surface of the negative electrode 3 on the positive electrode 2 side, a lithium conductive solid electrolyte 4, and a positive electrode. 2 and an aqueous electrolyte 5 disposed between the two.

As shown in FIG. 1, the air electrode as the positive electrode 2 is one in which a porous carbon 21 or a catalyst 22 made of metal or metal oxide is supported on the porous carbon. Examples of the metal and metal oxide used for the catalyst 22 include platinum, platinum alloy, manganese oxide, cobalt oxide, nickel oxide, iron oxide, and copper oxide.
The negative electrode 3 is made of metallic lithium or a lithium alloy. Examples of the lithium alloy used for the negative electrode 3 include lithium indium, lithium aluminum, lithium copper, and lithium tin alloy.

  The negative electrode 3 may be composed of a single layer or may be composed of a plurality of layers. As the negative electrode composed of a plurality of layers, for example, a metal foil made of metal lithium or lithium alloy is attached to the surface of the negative electrode 3 opposite to the lithium conductive solid electrolyte 4 shown in FIG. Examples thereof include two layers, ie, a first layer joined to the electrolyte 4 and a second layer composed of a metal foil attached to the first layer. Such a two-layered negative electrode is formed, for example, by forming a first layer (negative electrode) by bonding a negative electrode and a lithium conductive solid electrolyte, and then removing the metal foil from which the surface anti-adhesion layer has been removed from the negative electrode lithium. It can be manufactured in a short time using the method of forming the second layer (metal foil) by pressure bonding to the surface opposite to the conductive solid electrolyte, and the adhesion between the first layer and the second layer is good. Compared with a negative electrode composed of layers, the negative electrode has a low resistance, can prevent contact failure between the lithium conductive solid electrolyte and the negative electrode, and can provide better charge / discharge characteristics.

The lithium conductive solid electrolyte 4 preferably has a perovskite type or garnet type skeleton structure. Even if the lithium conductive solid electrolyte 4 made of such a material is disposed in contact with the negative electrode 3, it is reduced and decomposed during charge and discharge. There is nothing to do.
As the lithium conductive solid electrolyte 4, a perovskite type having a composition of (LiLa) MO ₃ (M = Ta, Zr), Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₅ La ₃ A garnet type composed of any composition of Ta ₂ O ₁₂ is preferred. When the lithium conductive solid electrolyte 4 is a perovskite type having a composition of (LiLa) MO ₃ (M = Ta, Zr), the transition metal species Ta, Zr, and La are metal species that are stable with respect to Li. preferable. Further, when the lithium conductive solid electrolyte 4 is a garnet type composed of any one of Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , and Li ₅ La ₃ Ta ₂ O ₁₂ , La , Zr, Nb, and Zr are preferable metal species that are stable to Li and do not undergo reduction due to Li contact.

  The thickness of the lithium conductive solid electrolyte 4 is preferably in the range of 50 μm to 400 μm on average. When the thickness of the lithium conductive solid electrolyte 4 is within the above range, lithium ions are likely to diffuse between the negative electrode 3 joined to the surface of the lithium conductive solid electrolyte 4 and the lithium conductive solid electrolyte 4. Further, when the thickness of the lithium conductive solid electrolyte 4 is within the above range, sufficient mechanical strength can be ensured. Therefore, when the surface of the lithium conductive solid electrolyte 4 is roughened, or when the negative electrode 3 and the lithium conductive solid electrolyte 4 are used. The workability in joining is improved. Moreover, there exists a possibility that mechanical strength may become inadequate that the thickness of the lithium conductive solid electrolyte 4 is less than the said range. Further, if the thickness of the lithium conductive solid electrolyte 4 exceeds the above range, the mechanical strength can be ensured, but the resistance at the time of Li diffusion in the lithium conductive solid electrolyte 4 becomes large, and sufficient charge / discharge characteristics as battery characteristics are obtained. There is a risk that it cannot be secured.

  Moreover, in the lithium air secondary battery 1 shown in FIG. 1, the surface of the lithium conductive solid electrolyte 4 on the negative electrode 3 side is roughened. For this reason, the lithium air secondary battery 1 shown in FIG. 1 can secure a sufficient contact area between the surface of the lithium conductive solid electrolyte 4 and the negative electrode 3 and has a low contact resistance. Lithium ions easily diffuse between the joined negative electrode 3 and lithium conductive solid electrolyte 4.

The surface roughness of the roughened lithium conductive solid electrolyte 4 is preferably in the range of 1 μm to 10 μm. When the surface roughness of the lithium conductive solid electrolyte 4 is within the above range, the contact area between the surface of the lithium conductive solid electrolyte 4 and the negative electrode 3 is large and the contact resistance is further reduced. Lithium ions are more easily diffused between the solid electrolyte 4. Moreover, when the surface roughness of the lithium conductive solid electrolyte 4 is less than the above range, the lithium ion diffusion promoting effect due to the roughened surface of the lithium conductive solid electrolyte 4 may not be sufficiently obtained. Further, when the surface roughness of the lithium conductive solid electrolyte 4 exceeds the above range, the smoothness of the lithium conductive solid electrolyte 4 becomes low, so that the diffusion distance of lithium ions in the lithium conductive solid electrolyte 4 varies. It is not preferable.
In addition, the surface roughness of the lithium conductive solid electrolyte 4 in the lithium air secondary battery 1 can be measured by measurement with a microscope, a stylus, or the like. In addition, by examining the internal resistance from the battery characteristics, it is possible to derive the correlation between the roughness and the contact state qualitatively and semi-quantitatively.

The pH of the aqueous electrolyte 5 is not particularly limited, but if the pH is too high or too low, the lithium conductive solid electrolyte 4 may be corroded or dissolved. For this reason, the pH of the aqueous electrolyte 5 is preferably in the range of 3-11. Further, as the alkaline aqueous electrolyte 5, for example, a 1M aqueous solution of LiBF ₄ or lithium hydroxide can be used, and as the acidic aqueous electrolyte 5, for example, an aqueous solution of hydrochloric acid, sulfuric acid, and nitric acid is used. Can do. The aqueous electrolyte 5 is preferably weakly alkaline or weakly acidic when the lithium air secondary battery 1 is in the initial state. In the lithium air secondary battery 1 shown in FIG. 1, when discharged, OH ⁻ is generated as described later, so that the weak alkaline aqueous electrolyte 5 changes to strong alkalinity.

In the lithium-air secondary battery 1 shown in FIG. 1, the negative electrode 3 and the lithium conductive solid electrolyte 4 are joined so that lithium ions can diffuse between the negative electrode 3 and the lithium conductive solid electrolyte 4.
At the interface between the negative electrode 3 and the lithium conductive solid electrolyte 4 joined so that lithium ions can diffuse, the negative electrode 3 and the lithium conductive solid electrolyte 4 are in good contact, and the negative electrode 3 and the lithium conductive solid electrolyte 4 are in close contact. There is no large gap of 2 μm or more at the contact interface. If a large gap of 2 μm or more exists at the contact interface between the negative electrode 3 and the lithium conductive solid electrolyte 4, the adhesion between the negative electrode 3 and the lithium conductive solid electrolyte 4 becomes insufficient, and the diffusion of lithium ions is insufficient. In addition, the negative electrode 3 and the lithium conductive solid electrolyte 4 are easily peeled off.
The size of the gap existing at the contact interface between the negative electrode 3 and the lithium conductive solid electrolyte 4 can be measured using an electron microscope or the like.

  In the lithium air secondary battery 1 shown in FIG. 1, a charging positive electrode 8 is disposed in an aqueous electrolyte 5. As the positive electrode 8 for charging, for example, one made of carbon or titanium metal can be used. By using the positive electrode 8 for charging as the positive electrode during charging, when the positive electrode 2 is used during charging, adverse effects on the porous carbon 21 and the catalyst 22 of the positive electrode 2 due to oxygen generated during charging can be prevented. . In the lithium air secondary battery of the present invention, it is preferable that the charging positive electrode 8 is provided. However, the charging positive electrode 8 may not be provided, and the positive electrode 2 also serves as the charging positive electrode. Also good.

Next, reactions in charging and discharging of the lithium air secondary battery 1 shown in FIG. 1 will be described.
In the lithium air secondary battery 1 shown in FIG. 1, as shown in FIG. 1A, during discharge, a reaction of Li => Li ⁺ + e ⁻ occurs on the surface of the negative electrode 3, and lithium ions are converted into lithium conductive solid electrolyte 4. The inside moves from the negative electrode 3 side to the positive electrode 2 side, and a reaction of O ₂ + 2H ₂ O + 4e ⁻ => 4OH ⁻ occurs in the positive electrode 2.
In addition, since the discharge reaction is performed within a limited potential range, the lithium metal or lithium alloy constituting the negative electrode 3 is not completely eliminated by performing the discharge, and the interface between the negative electrode 3 and the lithium conductive solid electrolyte 4 is not lost. Is maintained in its initial state.

In the lithium-air secondary battery 1 shown in FIG. 1, as shown in FIG. 1 (b), during charging, a reaction of 4OH ⁻ => O ₂ + 2H ₂ O + 4e ⁻ occurs in the charging positive electrode 8, and lithium ions are The lithium conductive solid electrolyte 4 moves from the positive electrode 2 side to the negative electrode 3 side, and a reaction of Li ⁺ + e ⁻ => Li occurs on the surface of the negative electrode 3.
That is, at the time of charging, since lithium is deposited at the interface between the negative electrode 3 and the lithium conductive solid electrolyte 4, the interface between the negative electrode 3 and the lithium conductive solid electrolyte 4 is maintained in the initial state.

  In the lithium-air secondary battery 1 shown in FIG. 1, as described above, the interface between the negative electrode 3 and the lithium conductive solid electrolyte 4 is maintained in the initial state even when charging and discharging are performed. In order to securely hold the junction capable of diffusing lithium ions between the negative electrode 3 and the lithium conductive solid electrolyte 4, means for pressing the negative electrode 3 against the lithium conductive solid electrolyte 4 may be provided. Examples of means for pressing the negative electrode 3 against the lithium conductive solid electrolyte 4 include a spring, a surface pressure holding by a spring, and a constant surface pressure holding by a restraining plate.

"Production method of lithium air secondary battery"
Next, as an example of the manufacturing method of the lithium air secondary battery of the present invention, the manufacturing method of the lithium air secondary battery 1 shown in FIG. 1 will be described as an example.
In order to manufacture the lithium air secondary battery 1 shown in FIG. 1, first, the negative electrode 3, the lithium conductive solid electrolyte 4, and the like are selected by any one method selected from the following three methods <1> to <3>: Join.

<1> The surface of the lithium conductive solid electrolyte 4 is roughened, and the negative electrode 3 is pressed and bonded to the roughened surface of the lithium conductive solid electrolyte 4.
Examples of the method for roughening the surface of the lithium conductive solid electrolyte 4 in the method <1> include methods such as machining (cutting), etching, and substrate sintering (mesh peeling) on the mesh. .
In addition, the surface roughness of the roughened lithium conductive solid electrolyte 4 is preferably in the range of 1 μm to 10 μm. When the surface roughness of the lithium conductive solid electrolyte 4 is within the above range, the lithium ion is easily bonded between the negative electrode 3 and the lithium conductive solid electrolyte 4 by pressing the negative electrode 3 on the surface of the lithium conductive solid electrolyte 4. It becomes easy to diffuse. If the surface roughness of the lithium conductive solid electrolyte 4 is less than the above range, the effect of improving adhesion and the effect of promoting the diffusion of lithium ions due to the roughened surface of the lithium conductive solid electrolyte 4 cannot be obtained. 3 and the lithium conductive solid electrolyte 4 may be insufficiently diffused. Further, if the surface roughness of the lithium conductive solid electrolyte 4 exceeds the above range, the smoothness of the lithium conductive solid electrolyte 4 after the press bonding becomes low, and the diffusion distance of lithium ions in the lithium conductive solid electrolyte 4 varies. It is not preferable.

As a method for pressure bonding the negative electrode 3 to the surface of the roughened lithium conductive solid electrolyte 4, for example, a metal foil made of a metal lithium foil or a lithium alloy foil is disposed on the surface of the lithium conductive solid electrolyte 4, and hydraulic pressure is applied. And a method of pressing the metal foil against the lithium conductive solid electrolyte 4 with a pressure of about 1 ton using a uniaxial pressure press machine.
In addition, in order to prevent that metal foil adheres normally, the adhesion prevention layer which consists of dodecane etc. is formed in the surface of the metal foil used in the method of <1>. In the method <1>, in order to improve the adhesion between the lithium conductive solid electrolyte 4 and the negative electrode 3, the adhesion preventing layer is removed, and then the metal foil is pressure-bonded to the surface of the lithium conductive solid electrolyte 4. preferable.

  <2> The negative electrode 3 and the lithium conductive solid electrolyte 4 are joined by laminating a molten negative electrode material on the surface of the lithium conductive solid electrolyte 4 and cooling and solidifying it. In the method <2>, it is preferable to perform a step of roughening the surface of the lithium conductive solid electrolyte 4 before laminating the molten negative electrode material on the surface of the lithium conductive solid electrolyte 4 and cooling and solidifying it. As a method for roughening the surface of the lithium conductive solid electrolyte 4 in the method <2>, the same direction as the method <1> can be used. In addition, when using the method of <2>, it is preferable that the surface roughness of the lithium conductive solid electrolyte 4 is the range of 1 micrometer-10 micrometers.

  As a method of laminating a molten negative electrode material on the surface of the lithium conductive solid electrolyte 4 in the method <2>, for example, by heating metallic lithium or a lithium alloy, a molten negative electrode material is obtained. Is applied to the surface of the lithium conductive solid electrolyte 4 using a spray or the like, or the lithium conductive solid electrolyte 4 is immersed in the molten negative electrode material, so that the molten conductive electrolyte 4 is melted on the surface of the lithium conductive solid electrolyte 4. A method of laminating a negative electrode material is mentioned.

  Further, the temperature of the negative electrode material when the molten negative electrode material is laminated on the surface of the lithium conductive solid electrolyte 4 is preferably 180 ° C. to 500 ° C. Since the melting point of metallic lithium is 180 ° C., if the temperature of the negative electrode material is less than 180 ° C., the negative electrode material will not be in a molten state. Moreover, although the temperature of negative electrode material should just be below the boiling point of negative electrode material, in order to prevent that the lithium conductive solid electrolyte 4 thermally decomposes, it is preferable that it is 500 degrees C or less. Moreover, it is preferable that the cooling rate at the time of making it cool and solidify is 5-20 degrees C / min. When the temperature of the molten negative electrode material when laminating the negative electrode material is within the above range and the cooling rate at the time of cooling and solidification is within the above range, it is between the negative electrode 3 and the lithium conductive solid electrolyte 4. Therefore, lithium ions are easily diffused.

  <3> The negative electrode 3 and the lithium conductive solid electrolyte 4 are joined by depositing a negative electrode material on the surface of the lithium conductive solid electrolyte 4 by a chemical deposition method. In the method <3>, it is preferable to perform a step of roughening the surface of the lithium conductive solid electrolyte 4 before depositing the negative electrode material on the surface of the lithium conductive solid electrolyte 4 by a chemical deposition method. Also in the method <3>, the same direction as the method <1> can be used as a method for roughening the surface of the lithium conductive solid electrolyte 4. When the method <3> is used, the surface roughness of the lithium conductive solid electrolyte 4 is preferably in the range of 1 μm to 10 μm.

Examples of the chemical deposition method used in the method <3> include a vacuum vapor deposition method and a chemical vapor deposition method (CVD). When using a vacuum evaporation method, it is preferable to carry out on the vacuum conditions of 10 < ^-3 > Pa or less using the material which consists of metallic lithium or lithium alloy. Moreover, when using a chemical vapor deposition method (CVD), it is preferable to use the material which consists of metal lithium, lithium alloy, alkyl lithium, such as methyl lithium and butyl lithium.

  When the method <3> is used, a metal lithium foil or a lithium alloy foil is provided on the surface of the negative electrode 3 opposite to the lithium conductive solid electrolyte 4 after the step of bonding the negative electrode 3 and the lithium conductive solid electrolyte 4. From the metal foil attached to the first layer and the first layer bonded to the lithium conductive solid electrolyte 4, the metal foil is attached by a method of press-pressing using a hydraulic uniaxial pressing machine or the like. You may form the negative electrode which consists of two layers with the 2nd layer. Since the first layer and the second layer are made of the same or similar materials, the adhesion between the first layer and the second layer attached in this way is good.

Through the above steps, the negative electrode 3 and the lithium conductive solid electrolyte 4 are joined so that lithium ions can diffuse between the negative electrode 3 and the lithium conductive solid electrolyte 4.
Thereafter, the lithium-air secondary battery 1 shown in FIG. 1 is formed by a conventionally known method using the joined negative electrode 3 and lithium conductive solid electrolyte 4, the air electrode as the positive electrode 2, and the aqueous electrolyte 5. To manufacture.

  A lithium air secondary battery 1 shown in FIG. 1 includes an air electrode as a positive electrode 2, a negative electrode 3 made of metallic lithium or a lithium alloy, and a perovskite type or garnet type lithium bonded to the surface of the negative electrode 3 on the positive electrode 2 side. A conductive solid electrolyte 4; and an aqueous electrolyte 5 disposed between the lithium conductive solid electrolyte 4 and the positive electrode, and diffusion of lithium ions between the negative electrode 3 and the lithium conductive solid electrolyte 4 is achieved. Since the negative electrode 3 and the lithium conductive solid electrolyte 4 are joined as much as possible, there is no need to dispose an organic electrolyte for the negative electrode between the negative electrode and the lithium conductive solid electrolyte.

  Accordingly, the lithium-air secondary battery 1 shown in FIG. 1 has a smaller battery weight and battery volume than a lithium-air secondary battery provided with an organic electrolyte for the negative electrode, and relatively energy per battery weight. The density and the energy density per battery volume are high. In addition, since the lithium-air secondary battery 1 shown in FIG. 1 does not require an organic electrolyte for the negative electrode, the cost of the battery material can be reduced. Further, in the lithium air secondary battery 1 shown in FIG. 1, since the negative electrode 3 and the lithium conductive solid electrolyte 4 are joined, dendride does not grow on the surface of the negative electrode 3. Further, in the lithium air secondary battery 1 shown in FIG. 1, since the negative electrode 3 and the lithium conductive solid electrolyte 4 are joined, water, nitrogen, etc. in the air react with the negative electrode 3 made of metallic lithium or a lithium alloy. The danger caused by this can be avoided.

"Example 1 to Example 4"
A negative electrode 3 made of a lithium indium alloy and a lithium conductive solid electrolyte 4 made of Li ₇ La ₃ Zr ₂ O _12, and a catalyst 22 made of platinum particles are supported on a porous carbon 21 as the positive electrode 2. The lithium air secondary battery 1 shown in FIG. 1 was manufactured using the air electrode and the aqueous electrolyte 5 made of 1M lithium hydroxide.

"Example 1"
By machining (cutting) the surface of the lithium conductive solid electrolyte, the average surface roughness was set to 5 μm. Next, a negative electrode composed of a LiIn metal foil having a thickness of 50 μm was pressure-bonded and bonded to the roughened surface of the lithium conductive solid electrolyte having a thickness of 150 μm by the following method.
First, the adhesion preventing layer formed on the surface of the LiIn metal foil was removed. Next, a LiIn metal foil is placed on the surface of the lithium conductive solid electrolyte, and the LiIn metal foil is pressed against the lithium conductive solid electrolyte at a pressure of 1 ton / cm ² for 1 minute using a hydraulic uniaxial pressing machine. And crimped.

"Example 2"
In the same manner as in Example 1, the surface of the lithium conductive solid electrolyte was machined (cut) to obtain an average surface roughness of 5 μm. Next, by using TMIn (tri-methyl-indium) and n-butyllithium as materials and depositing LiIn metal having a thickness of 10 μm as a negative electrode on the surface of the lithium conductive solid electrolyte by chemical vapor deposition (CVD). The negative electrode and the lithium conductive solid electrolyte were joined.

"Example 3"
In the same manner as in Example 2, after joining the negative electrode and the lithium conductive solid electrolyte, a metal lithium foil having a thickness of 50 μm was placed on the surface of the negative electrode opposite to the lithium conductive solid electrolyte, and a uniaxial pressure press was used. The negative electrode which consists of two layers of the LiIn metal deposited by the chemical vapor deposition method (CVD) and the metal lithium foil stuck was formed.

Example 4
In the same manner as in Example 1, the surface of the lithium conductive solid electrolyte was machined (cut) to obtain an average surface roughness of 5 μm. Next, the LiIn metal foil was heated to 300 ° C. at 200 ° C./hour to form a molten negative electrode material, and the molten negative electrode material was sprayed on the surface of the 150 μm thick lithium conductive solid electrolyte that was roughened. By coating, a negative electrode material in a molten state is laminated on the surface of the lithium conductive solid electrolyte, and cooled and solidified at a cooling rate of 10 ° C./min, whereby a negative electrode composed of a LiIn metal foil having a thickness of 50 μm, a lithium conductive solid electrolyte, Were joined.

"Comparative Example 1"
A lithium air secondary battery was produced in the same manner as in Example 1 except that the negative electrode and the lithium conductive solid electrolyte were placed in contact with each other.
"Comparative Example 2"
A lithium air secondary battery was produced in the same manner as in Example 1 except that the organic electrolyte for the negative electrode was disposed between the negative electrode and the lithium conductive solid electrolyte.

  The lithium air secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2 thus obtained were evaluated as follows.

"Evaluation method"
A discharge test was performed at a current density of 10, 100, 500, 1000 μA / cm ² using an electrochemical measuring device.

As a result of the evaluation, in the lithium air secondary batteries of Examples 1 to 4 which are examples of the present invention, the discharge capacity of the Li-air battery could be confirmed at any current density of 10 μA / cm ² . Further, in each of the lithium air secondary batteries of Examples 1 to 4, it was confirmed that the discharge voltage was lowered due to the overvoltage due to the resistance component by increasing the current density. Example 3 was the smallest, and then Example 2 was the smallest.

  Compared with Example 1 in which the negative electrode was bonded to the surface of the lithium conductive solid electrolyte by pressure bonding, Example 2 in which the negative electrode material was deposited on the surface of the lithium conductive solid electrolyte by a chemical deposition method was used. However, the contact resistance between the negative electrode and the surface of the lithium conductive solid electrolyte is low, and compared with Example 2, the layer in which the negative electrode is bonded to the lithium conductive solid electrolyte and the metal foil attached to the layer It is presumed that Example 3, which consists of two layers consisting of the above, is due to the lower resistance of the negative electrode.

In contrast, in Comparative Example 1 in which the negative electrode and the lithium conductive solid electrolyte were not joined so that lithium ions could be diffused, the interface of the lithium conductive solid electrolyte was changed to black, and charging / discharging was impossible. It was.
In Comparative Example 2 in which the organic electrolyte for the negative electrode was disposed between the negative electrode and the lithium conductive solid electrolyte, although charge / discharge was possible, the increase in resistance due to the large number of diffusion interfaces was large, and the discharge voltage The drop in was large. Further, when the lithium air secondary battery of Comparative Example 2 after charging was disassembled, dendritic lithium was growing on the surface of the negative electrode.

  DESCRIPTION OF SYMBOLS 1 ... Lithium air secondary battery, 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Lithium conductive solid electrolyte, 5 ... Aqueous solution type electrolyte solution, 21 ... Porous carbon, 22 ... Catalyst.

Claims (10)

An air electrode as a positive electrode;
A negative electrode made of metallic lithium or a lithium alloy;
A perovskite-type or garnet-type lithium conductive solid electrolyte joined to the surface of the negative electrode on the positive electrode side;
An aqueous electrolyte solution disposed between the lithium conductive solid electrolyte and the positive electrode,
The lithium air secondary battery, wherein the negative electrode and the lithium conductive solid electrolyte are joined so that lithium ions can diffuse between the negative electrode and the lithium conductive solid electrolyte. The lithium conductive solid electrolyte is a perovskite type having a composition of (LiLa) MO ₃ (M = Ta, Zr), or Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₅ La ₃ Ta. _2. The lithium-air secondary battery according to claim 1, wherein the lithium-air secondary battery is a garnet type composed of any composition of ₂ O ₁₂ .   The lithium-air secondary battery according to claim 1 or 2, wherein the aqueous electrolyte solution is acidic or alkaline.   The metal foil which consists of metallic lithium or a lithium alloy is affixed on the surface on the opposite side to the said lithium conductive solid electrolyte of the said negative electrode, The Claim 1 characterized by the above-mentioned. Lithium air secondary battery. It is a manufacturing method of the lithium air secondary battery according to any one of claims 1 to 4,
Producing a lithium-air secondary battery comprising a step of roughening a surface of the lithium conductive solid electrolyte and bonding the negative electrode to the surface of the roughened lithium conductive solid electrolyte. Method. It is a manufacturing method of the lithium air secondary battery according to any one of claims 1 to 4,
Producing a lithium-air secondary battery comprising a step of joining the negative electrode and the lithium conductive solid electrolyte by laminating a molten negative electrode material on the surface of the lithium conductive solid electrolyte and cooling and solidifying it. Method.   7. The lithium according to claim 6, further comprising a step of roughening a surface of the lithium conductive solid electrolyte before the molten negative electrode material is laminated on the surface of the lithium conductive solid electrolyte and cooled and solidified. A method for producing an air secondary battery. It is a manufacturing method of the lithium air secondary battery according to any one of claims 1 to 4,
A method for producing a lithium-air secondary battery, comprising a step of bonding the negative electrode and the lithium conductive solid electrolyte by depositing a negative electrode material on the surface of the lithium conductive solid electrolyte by a chemical deposition method.   9. The method according to claim 8, further comprising the step of roughening the surface of the lithium conductive solid electrolyte before depositing the negative electrode material on the surface of the lithium conductive solid electrolyte by a chemical deposition method. A method for manufacturing a secondary battery.   After the step of joining the negative electrode and the lithium conductive solid electrolyte, the method includes a step of attaching a metal foil made of metallic lithium or a lithium alloy to the surface of the negative electrode opposite to the lithium conductive solid electrolyte. The manufacturing method of the lithium air secondary battery of Claim 8 or Claim 9 to do.

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