JP2022101497A - Positive electrode containing an electrolytic solution and air battery using the same, injecting method of electrolytic solution into positive electrode, and manufacturing method of air battery using the same - Google Patents

Abstract

To provide a positive electrode having a porous structure containing an electrolytic solution injected by a method different from a conventional method capable of uniformly injecting an electrolytic solution having a small amount of liquid (specifically, a liquid amount having a volume smaller than the total pore volume of the positive electrode and causing a liquid injection spot according to the conventional injection method), and a method capable of uniformly injecting such an electrolytic solution having a small amount into the positive electrode having the porous structure.SOLUTION: There is provided a positive electrode having a porous structure, which includes an electrolytic solution transferred by contact with a member containing the electrolytic solution. Further, there is provided a method of injecting the electrolytic solution into the positive electrode by bringing a member containing the electrolytic solution into contact with the positive electrode having the porous structure and transferring the electrolytic solution. Further, an air battery is provided in which the number of charge/discharge cycles (number of cycles) is 3 or more.SELECTED DRAWING: None

Description

The present invention relates to a positive electrode having a porous structure containing an electrolytic solution, an air battery containing the positive electrode, a method for injecting an electrolytic solution into the positive electrode, and a method for manufacturing an air battery using a positive electrode manufactured by the injecting method. The air battery particularly relates to a lithium air secondary battery that uses oxygen as a positive electrode active material.

An air battery (for example, a lithium air secondary battery) is a battery that uses oxygen as a positive electrode active material, and is an oxygen flow path layer for taking in oxygen, a positive electrode (sometimes referred to as an air electrode in the present application), a separator, and the like. It is composed of a negative electrode and an electrolytic solution is injected. For example, Patent Document 1 discloses a non-aqueous electrolyte battery in which a non-aqueous electrolyte is injected into a separator with respect to a four-layer laminate of an oxygen diffusion layer, a positive electrode, a separator, and a negative electrode.

Japanese Unexamined Patent Publication No. 2002-15737

It is desirable that the oxygen flow path layer does not contain the electrolytic solution because oxygen needs to diffuse in the layer and if it is wet with the electrolytic solution, it hinders the diffusion of oxygen. That is, it is desirable that the electrolytic solution is uniformly present only in the positive electrode, the separator, the negative electrode, and the periphery thereof.

The amount of electrolyte in an air battery is directly linked to the energy density of the battery. Therefore, if the amount of the electrolytic solution is reduced as much as possible within a range that does not affect the cycle characteristics, it can be expected that the energy density of the air battery will be improved accordingly.

In addition, the amount of electrolytic solution in the air battery greatly affects the diffusion of oxygen, which is the positive electrode active material, in the battery. For example, in the case of a lithium-air battery, lithium peroxide is formed in the air electrode layer constituting the air electrode of the positive electrode by the reaction between the lithium ion in the non-aqueous electrolyte solution and oxygen, which is the positive electrode active material, in the discharge process. In the charging process, lithium peroxide is oxidatively decomposed. However, since the amount of oxygen dissolved in the electrolytic solution is limited, lithium peroxide is generated in the air electrode near the oxygen flow path layer, and when the charge / discharge cycle proceeds, the vicinity of the oxygen flow path layer is reached. Lithium peroxide generated and remaining in the air electrode hinders oxygen diffusion from the oxygen flow path layer to the inside of the air electrode layer. It is understood that this will adversely affect the charge / discharge cycle characteristics. This means that as the air electrode layer becomes thicker, oxygen in the air electrode layer tends to be insufficient. Here, the volume% of the amount of the electrolytic solution when the volume of all the pores of the air electrode layer is 100% (that is, when the pore ratio of the air electrode layer is 100%) is the pore ratio (100). %) When the amount of oxygen supplied from the oxygen flow path layer is positively left in the air electrode layer as an oxygen diffusion path (so-called diffusion path), the oxygen supplied from the oxygen flow path layer becomes in the air electrode layer. It is understood that oxygen can be easily diffused to every corner of the electrolytic solution in the air electrode layer.

Therefore, for the above two reasons (improvement of the energy density of the air battery and easy diffusion of oxygen, which is the positive electrode active material, in the air battery), the amount of the electrolytic solution is reduced within a range that does not adversely affect the characteristics of the air battery. Is desirable.

Here, taking a lithium-air battery as an example of an air battery, when a porous carbon air electrode is used as a positive electrode and the pore ratio is 100%, an electrolytic solution having a smaller volume than that is applied to the air electrode. When the liquid is injected, the carbon surface of the air electrode is surely filled with the electrolytic solution, and the central portion of the hole in the air electrode (specifically, in the air electrode layer constituting the air electrode). It is desirable that a region not filled with the electric field liquid (so-called through hole) remains in the air. In such a state, by continuously connecting the electrolytic solution through the carbon surface, lithium ions can be spread over the entire air electrode (positive electrode) of the porous carbon, and the electric field solution is applied to the central portion of the pores. The presence of unfilled through holes allows oxygen supplied from the oxygen flow path layer to easily diffuse within the air electrode layer.

On the other hand, when the injection amount of the electrolytic solution is reduced, there is a problem that the electrolytic solution is easily localized in the air electrode having a porous structure (that is, liquid injection spots are likely to occur). The state in which the injected electrolytic solution is localized in the air electrode having such a porous structure is referred to as a liquid injection spot in the present application. Here, taking a lithium-air battery as an example of an air battery, oxygen peroxide, which is a positive electrode active material, reacts with lithium ions in an electrolytic solution due to a discharge reaction, and lithium peroxide is generated on the carbon surface of the air electrode of porous carbon. However, when liquid injection spots occur, a region that is not wet with the electric field liquid is generated, so that lithium ions cannot diffuse in that region and cannot function as a precipitation reaction field for lithium peroxide. .. That is, the entire air electrode, which is the positive electrode, cannot be effectively used. Further, in the region where the electrolytic solution is concentrated, lithium peroxide generated by the discharge reaction is likely to segregate, and the pores in the air electrode are likely to be locally clogged. In particular, as the amount of the electrolytic solution is reduced, the injection spots are more likely to occur, and this tendency becomes remarkable.

Further, when the injection amount of the electrolytic solution is reduced, not only the injection spots are likely to occur, but also there is a problem that the electrolytic solution is difficult to be injected into the pores inside the air electrode of the porous structure. In this case, since a region not wetted by the electric field liquid is generated inside the air electrode, lithium ions cannot diffuse in that region and cannot function as a precipitation reaction field of lithium peroxide. That is, the entire air electrode, which is the positive electrode, cannot be effectively used. As a result, the number of charge / discharge cycles (number of cycles) of the lithium-air battery may decrease or the lithium-air battery may not function.

For example, the non-aqueous electrolyte battery of Patent Document 1 has a structure of a four-layer laminate in which an oxygen diffusion layer, a positive electrode, a separator, and a negative electrode are laminated, and an electrolytic solution (specifically, specifically, an electrolytic solution) is aimed at the separator. When injecting a non-aqueous electrolyte solution) by a conventional injection method such as dropping or spraying, if the amount of the electrolytic solution is reduced, a sufficient electrolytic solution is supplied to the portion near the injection port, but the injection port is used. There is a risk of running out of electrolyte at the separator or air electrode on the opposite side. Therefore, there is a problem that liquid injection spots are likely to occur.

Therefore, it is desirable that the amount of the electrolytic solution to be injected into the positive electrode be smaller as long as the uniformity of the electrolytic solution with respect to the positive electrode after injection is maintained and the characteristics of the air battery are not adversely affected. For this reason, the amount of liquid that is smaller than the total pore volume of the air electrode layer (specifically, the volume of liquid volume that is smaller than the total volume of all pores) with respect to the positive electrode having a porous structure, in particular. According to the conventional liquid injection means, a method that can uniformly inject even a small amount of electrolytic solution that causes liquid injection spots, and further, with such a small amount of electrolytic solution. It is desired to develop a positive electrode having a porous structure in which liquid is uniformly injected.

Further, from the viewpoint of improving the number of charge / discharge cycles (number of cycles) of the air battery, the electrolytic solution is injected into the pores (pores) inside the positive electrode of the porous structure even with the above-mentioned small amount of liquid. It is desired to develop a possible method, a positive electrode having a porous structure in which an electrolytic solution is also injected into the pores, and an air battery using such a positive electrode. Examples of such pores (pores) are pores (pores) having a diameter of 10 nm or more and 100 nm or less, which can function as a reaction field of an air battery but are difficult to sufficiently wet with a conventional liquid injection method. The air.

Under such circumstances, an object of the present invention is, for example, a small amount of liquid (specifically, a liquid amount having a volume smaller than the total pore volume of the positive electrode, and a liquid injection method according to a conventional injection method. A positive electrode having a porous structure containing an electrolytic solution injected by a method different from the conventional method, which can be uniformly injected with an electrolytic solution (amount of liquid that causes spots), particularly with such a small amount of liquid. It is to provide a positive electrode having a porous structure which is uniformly injected with an electrolytic solution.
An object of the present invention is, for example, to provide an air battery including the positive electrode.
An object of the present invention is, for example, to provide a method capable of uniformly injecting an electrolytic solution into a positive electrode having a porous structure even with a small amount as described above.
An object of the present invention is, for example, to provide a method capable of injecting an electrolytic solution into pores (pores) inside a positive electrode having a porous structure even with a small amount as described above. ..
An object of the present invention is, for example, to provide a method for manufacturing an air battery using a positive electrode manufactured by the above-mentioned liquid injection method.

As a result of diligent studies to solve the above problems, the present inventors brought a positive electrode having a porous structure into contact with a member containing an electrolytic solution prepared in advance, and transferred the electrolytic solution to the positive electrode by utilizing the capillary phenomenon. By allowing the liquid to be porous, even a small amount of liquid (specifically, a liquid amount having a volume smaller than the total pore volume of the positive electrode and causing liquid injection spots according to the conventional liquid injection method) is porous. We have found that the electrolytic solution can be uniformly injected into the positive electrode of the structure, and have completed the present invention.
Specifically, various aspects of the present invention are as follows [1] to [26].

[1]
The positive electrode having a porous structure and containing the electrolytic solution transferred by contact with a member containing the electrolytic solution.
[2]
The positive electrode according to [1], wherein the electrolytic solution contains a lithium salt, and the coefficient of variation of at least one component of the lithium salt by fluorescent X-ray measurement is lower than 0.2.
[3]
The positive electrode according to [2], wherein the lithium salt is lithium bromide, and the coefficient of variation of bromine constituting the lithium bromide by Kα-ray measurement is lower than 0.2.
[4]
The positive electrode according to any one of [1] to [3], wherein 50% or more and less than 100% of the pores of the positive electrode are filled with the electrolytic solution based on the porosity.
[5]
The positive electrode according to any one of [1] to [4], wherein the member is a membrane filter made of polytetrafluoroethylene (PTFE).
[6]
The positive electrode according to any one of [1] to [5], wherein the electrolytic solution of the member is contained by dropping.
[7]
The positive electrode having a porous structure has pores moistened with a solvent of the electrolytic solution by a vacuum heat treatment before contact with a member containing the electrolytic solution, according to any one of [1] to [6]. Positive electrode.
[8]
The positive electrode according to any one of [1] to [7], wherein the pores having a diameter of 10 nm or more and 100 nm or less have a pore specific surface area after transfer of 10 m ² / g or less.
[9]
The positive electrode according to [8], wherein the pore specific surface area after transfer is 6 m ² / g or less in pores having a diameter of 10 nm or more and 100 nm or less.
[10]
The positive electrode according to any one of [1] to [9], wherein the volume after transfer is 100 μL / g or less in a pore having a diameter of 10 nm or more and 100 nm or less.
[11]
The positive electrode according to [10], wherein the volume after transfer is 60 μL / g or less in a pore having a diameter of 10 nm or more and 100 nm or less.
[12]
An air battery comprising the positive electrode according to any one of [1] to [11].
[13]
The air battery according to [12], wherein the number of charge / discharge cycles (number of cycles) before the discharge capacity or charge capacity becomes 80% or less is 3 times or more.
[14]
A method of injecting the electrolytic solution into the positive electrode by bringing a member containing the electrolytic solution into contact with a positive electrode having a porous structure and transferring the electrolytic solution.
[15]
The electrolytic solution contains a lithium salt, and the electrolytic solution is injected so that the coefficient of variation of at least one component of the lithium salt at the positive electrode by X-ray fluorescence measurement is lower than 0.2 [14. ] The method described in.
[16]
The lithium salt is lithium bromide, and the electrolytic solution is injected so that the coefficient of variation of bromine constituting the lithium bromide measured by Kα-ray at the positive electrode is lower than 0.2 [15]. The method described in.
[17]
The method according to any one of [14] to [16], wherein 50% or more and less than 100% of the pores of the positive electrode are filled with the electrolytic solution by injecting the electrolytic solution based on the porosity.
[18]
The method according to any one of [14] to [17], which uses a membrane filter made of polytetrafluoroethylene (PTFE) as the member.
[19]
The method according to any one of [14] to [18], wherein the electrolytic solution of the member is contained by dropping.
[20]
The method according to any one of [14] to [19], which comprises a step of bringing the member containing the electrolytic solution into contact and wetting the inside of the pores of the positive electrode with the solvent of the electrolytic solution before transferring the electrolytic solution. Method.
[21]
The step of wetting the inside of the pores of the positive electrode with the solvent of the electrolytic solution is to evaporate the solvent of the electrolytic solution by vacuum heat treatment and place the positive electrode having a porous structure in the solvent steam atmosphere to wet the positive electrode. 20. The method according to [20].
[22]
The method according to [21], wherein the reduced pressure heat treatment is performed under a pressure of 0.1 Pa or more and 10 Pa or less.
[23]
The method according to [21] or [22], wherein the heating of the reduced pressure heat treatment is performed at a temperature of 40 ° C. or higher and 100 ° C. or lower.
[24]
The method according to [23], wherein the heating time of the reduced pressure heat treatment is 10 minutes or more and 120 minutes or less.
[25]
With the negative electrode
Separator and
A positive electrode into which the electrolytic solution is injected by the method according to any one of [14] to [24], and a positive electrode.
A method for manufacturing an air battery by sequentially laminating an oxygen flow path layer for taking in oxygen as an active material of the positive electrode.
[26]
With the negative electrode
Separator and
A positive electrode into which the electrolytic solution is injected by the method according to any one of [14] to [24], and a positive electrode.
It is a method of manufacturing an air battery by sequentially laminating an oxygen flow path layer for taking in oxygen as an active material of the positive electrode.
A step of injecting the electrolytic solution into the positive electrode by transferring the electrolytic solution by bringing a member containing the electrolytic solution into contact with the positive electrode after stacking the positive electrodes to which the electrolytic solution has not been injected, and the member. The process of removing,
The manufacturing method.

According to the present invention, a small amount of liquid with respect to a positive electrode having a porous structure (specifically, a liquid volume having a volume smaller than the total pore volume of the positive electrode, and a liquid injection spot is formed according to the conventional liquid injection method. Even an electrolytic solution (the amount of liquid that is generated) can be injected uniformly. Therefore, for example, the following effects can be obtained.
According to the present invention, for example, it is possible to provide a positive electrode having a porous structure in which even the above-mentioned small amount of electrolytic solution is uniformly injected.
According to the present invention, for example, it is possible to provide an air electrode including the positive electrode.
According to the present invention, for example, it is possible to provide a method capable of uniformly injecting an electrolytic solution into a positive electrode having a porous structure even with the above-mentioned small amount of liquid.
According to the present invention, for example, it is possible to provide a method capable of injecting an electrolytic solution deeper into a pore inside a positive electrode having a porous structure even with the above-mentioned small amount of liquid. ..
According to the present invention, for example, it is possible to provide an air battery using a positive electrode manufactured by the above method.

It is a schematic diagram explaining the structure of the air battery which is one Embodiment of this invention (in the figure, reference numeral 100 is a lithium air battery, reference numeral 101 is an oxygen flow path layer, and reference numeral 102 is an air electrode (positive electrode of a porous structure). Reference numeral 103 indicates a separator, and reference numeral 104 indicates a negative electrode.) It is a schematic diagram explaining the structure of transferring and injecting an electrolytic solution into an air electrode in one embodiment of the present invention (reference numeral 102 in the figure is an air electrode (positive electrode having a porous structure), and reference numeral 105 is an electrolytic solution. A member (member for transferring an electrolytic solution) is shown.). It is the mapping data of the bromine Kα ray of the positive electrode after injecting the electrolytic solution, (a) is the mapping data of Example 1, and (b) is the mapping data of Comparative Example 1. It is a graph which shows the pore specific surface area in the pore (pore) which the diameter of the air electrode after the electrolytic solution injection of Example 2 and Example 1'is 10 nm or more and 100 nm or less.

One aspect of the present invention is a positive electrode having a porous structure, which contains the electrolytic solution transferred by contact with a member containing the electrolytic solution.

Further, one aspect of the present invention is a method of injecting the electrolytic solution into the positive electrode by contacting a member containing the electrolytic solution with a positive electrode having a porous structure and transferring the electrolytic solution. be.

Further, a further aspect of the present invention includes contacting a member containing the electrolytic solution and moistening the pores (pores) inside the positive electrode with the solvent of the electrolytic solution before transferring the electrolytic solution. , A method of injecting a positive electrode containing the electrolytic solution or the positive electrode.

The material used for the positive electrode having a porous structure is not particularly limited as long as it can be used for the positive electrode. For example, carbon, metals, carbides, oxides and the like are used, and carbon is particularly preferable.
Further, the positive electrode has a porous structure (that is, a porous structure).
When used as a positive electrode (air electrode) material for an air battery, a carbon material is generally preferred from the viewpoint of ease of handling, cost, weight, green environment, and recycling.
The positive electrode (air electrode) of an air battery has a porous structure in order to impart high air or oxygen permeability to the positive electrode (air electrode). For example, the positive electrode (air electrode) of a lithium-air battery needs to have a porous structure because it has conductivity and becomes a reaction field where lithium peroxide generated by a discharge reaction is deposited.

As the carbon raw material used for the positive electrode having a porous structure, it is preferable to use porous carbon particles. As the porous carbon particles, carbon black containing Ketjen black (registered trademark), carbon particles formed by the template method, or the like can be used. Among them, Ketjen Black (registered trademark) has a large total specific surface area (BET method specific surface area), and has a large pore volume and specific surface area of mesopores having a pore diameter of 2 nm or more and 50 nm or less and macropores having a pore diameter of 50 nm or more. Since it is a large material, it is preferable as a raw material used for a positive electrode for an air battery.

The member containing the electrolytic solution is a member capable of holding the electrolytic solution, and is a member capable of transferring the held electrolytic solution to the positive electrode by contact with the positive electrode. In the present application, the member containing the electrolytic solution may be referred to as an electrolytic solution transfer member.
The member containing the electrolytic solution (member for transferring the electrolytic solution) is not particularly limited as long as it is a member capable of transferring the electrolytic solution contained in the member by contact with the positive electrode. Examples of the member include a member made of PTFE (polytetrafluoroethylene) (for example, a PTFE type membrane filter). When a PTFE type membrane filter is used, it may be appropriately processed by punching or the like according to the application such as the size of the positive electrode.
The size of the member containing the electrolytic solution (member for transferring the electrolytic solution) is preferably the size of the positive electrode or larger, and is preferably larger than the size of the positive electrode.
The amount of the electrolytic solution dropped onto the member containing the electrolytic solution (member for transferring the electrolytic solution) is the amount of dropping the member containing the electrolytic solution (member for transferring the electrolytic solution) in advance and the amount of the liquid injected to the positive electrode by the transfer thereof. By creating the calibration curve of, the amount of liquid injected into the positive electrode may be set to be the desired amount.

The type of the electrolytic solution may be either an aqueous electrolytic solution or a non-aqueous electrolytic solution (non-aqueous electrolytic solution), and may be used depending on the type of the battery to be applied. Specifically, an aqueous electrolytic solution may be used for an aqueous electrolytic solution battery, and a non-aqueous electrolytic solution (non-aqueous electrolytic solution) may be used for a non-aqueous electrolytic solution battery.

Taking a lithium-air battery as an example, any non-aqueous electrolytic solution containing a lithium salt is preferable as the electrolytic solution, and an electrolytic solution containing LiBr as the lithium salt is particularly preferable. When a lithium salt is used in the non-aqueous electrolyte solution, for example, LiBr, LiNO ₃ , LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiSiF ₆ , LiAsF ₆ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li (FSO). ₂ ) ₂ N, LiCF ₃ SO ₃ (LiTfO), Li (CF ₃ SO ₂ ) ₂ N (LiTFSI), LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiB (C ₂ O ₄ ) ₂ Lithium salts such as. Each of these lithium salts may be used alone, or two or more thereof may be mixed and used. The electrolyte can be used as an electrolytic solution by dissolving it in a non-aqueous solvent. Non-aqueous solvents include glymes (monoglyme, diglyme, triglime, tetraglyme), methyl butyl ether, diethyl ether, ethyl butyl ether, dibutyl ether, polyethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, cyclohexanone, dioxane, dimethoxyethane, 2- Methyl diethyl, 2,2-dimethyltetra, 2,5-dimethyltetra, tetrahydrofuran, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, methyl formate, ethyl formate, dimethyl Carbonate, diethyl carbonate, ethylmethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, polyethylene carbonate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, acetonitrile, benzonitrile , Nitromethane, nitrobenzene, triethylamine, triphenylamine, tetraethylene glycol diamine, dimethylformamide (DMF), diethylformamide, N-methylpyrrolidone, dimethylsulfone, tetramethylenesulfone, triethylphosphinoxide, 1,3-dioxolane and sulfolane. Selected from the group, but not limited to these. Further, these solvents may be used alone or in combination of two or more.

The method of containing the electrolytic solution in the member containing the electrolytic solution (member for transferring the electrolytic solution) is not particularly limited as long as the object can be achieved. For example, the electrolytic solution may be dropped or impregnated into the member.

The injection (that is, filling) of the electrolytic solution into the positive electrode having a porous structure is performed by contacting a member containing the electrolytic solution (member for transferring the electrolytic solution) and thereby transferring the electrolytic solution to the positive electrode. In conventional liquid injection, it is common to use a micropipette or a dispenser, but in these methods, liquid injection spots are likely to occur when the amount of electrolytic solution is small. However, in the present invention, as a member containing the electrolytic solution (member for transferring the electrolytic solution), for example, a member holding the electrolytic solution is brought into contact with the positive electrode by dropping the electrolytic solution to transfer the electrolytic solution. By using a different electrolytic solution injection method, a predetermined amount (specifically, a liquid volume smaller than the total pore volume of the positive electrode) causes liquid injection spots on the positive electrode according to the conventional liquid injection method. The electrolytic solution (the amount of liquid that will be lost) is injected.

It is preferable that the electrolytic solution is uniformly injected into the positive electrode having a porous structure with respect to the positive electrode.
Specifically, when an electrolytic solution containing a lithium salt is injected and fluorescent X-rays are measured using at least one constituent element of the lithium salt as a detection probe, the coefficient of variation is lower than 0.2. preferable. For example, an electrolytic solution containing lithium bromide (LiBr) is injected into the positive electrode, and Kα-ray (in the present application, bromine (Br) of the lithium bromide is used as a detection probe at any plurality of points on the positive electrode after injection. It is preferable that the fluctuation coefficient (= standard deviation of bromine Kα ray / average value of bromine Kα ray) when measuring (sometimes referred to as bromine Kα ray) is lower than 0.2. The lower the value of this coefficient of variation, the higher the uniformity. If the value of the coefficient of variation is lower than 0.2, it can be said that the injection of the electrolytic solution into the positive electrode having a porous structure is uniform, but from the viewpoint of uniformity, a lower value is more preferable.

The upper limit of the amount of electrolytic solution to be injected into the positive electrode of the porous structure is the volume of liquid smaller than the total pore volume of the positive electrode (for example, in the case of an air battery, the total air of the air electrode layer constituting the air electrode). The volume of liquid is smaller than the volume of the pores). As described above, it is desirable that the amount of the electrolytic solution to be injected is smaller as long as the uniformity to the positive electrode is maintained and the characteristics of the air battery are not adversely affected.
Specifically, the upper limit of the amount of electrolytic solution injected (that is, filled) into the positive electrode having a porous structure is preferably less than 100% when the volume of all pores of the positive electrode is 100%. , More preferably less than 80%, even more preferably less than 70%.
The lower limit of the amount of electrolytic solution to be injected into the positive electrode of the porous structure is the amount of liquid that causes liquid injection spots according to the conventional liquid injection method, but the member (electrolyte solution transfer) containing the electrolytic solution according to the present invention. This is the minimum amount of liquid required to uniformly fill at least the entire surface of the positive electrode with the electrolytic solution by contact with the member).
Specifically, the lower limit of the amount of electrolytic solution injected into the positive electrode having a porous structure is preferably 50% or more, more preferably 60% when the volume of all pores of the positive electrode is 100%. As mentioned above, it is even more preferably 65%.
The porosity is determined, for example, by calculating the bulk density by measuring the weight of a positive electrode having a porous structure (also referred to as a porous structure in the present application) and comparing it with the true density of the porous structure. As an example, the porosity when the positive electrode is a porous structure made of a carbon material (also referred to as a porous carbon structure in the present application) is obtained by calculating the bulk density by measuring the weight of the porous carbon structure. It is determined by comparing with the true density of carbon (2.1 g / cm ³ ).
On the other hand, the maximum amount of the electrolytic solution that can be filled into the positive electrode (also referred to as the maximum amount of the electrolytic solution in the present application) is affected by the wettability of the electrolytic solution and the permeability depending on the pore size. Porosity) It may be smaller than the volume (porosity 100%). Therefore, in the present application, the maximum filling amount is defined as the amount of liquid injected (μL / cm ² ) by impregnation under reduced pressure as 100%. More specifically, the porous carbon structure itself used for the positive electrode is immersed in a chalet containing an electrolytic solution, vacuum-impregnated for 10 to 15 minutes, and then the electrolytic solution remaining on the surface is wiped off. It can be calculated from the specific gravity of the liquid.

In the positive electrode containing the electrolytic solution thus obtained (that is, after transfer), the pore specific surface area in the pores (pores) having a diameter of 10 nm or more and 100 nm or less is 10 m ² / g or less. It is preferably 1 m ² / g or more and 10 m ² / g or less, and more preferably 3 m ² / g or more and 6 m ² / g or less. Further, in the positive electrode containing the electrolytic solution (that is, after transfer), the pore volume in the pores (pores) having a diameter of 10 nm or more and 100 nm or less is 100 μL / g or less. It is preferably 10 μL / g or more and 100 μL / g or less, and more preferably 30 μL / g or more and 60 μL / g or less. Since the amount of the electrolytic solution contained in the positive electrode is small by the positive electrode or the liquid injection method of the present invention, it is difficult to moisten the pores (pores) having a diameter of 10 nm or more and 100 nm or less with the electrolytic solution by the conventional method. However, since this region can function as a reaction field of the air battery, the pores in this region are moistened with the electrolytic solution, so that the entire positive electrode can be utilized more effectively. According to the present invention, as described above, since the positive electrode containing the electrolytic solution can be obtained deep into the pores (pores) inside the positive electrode having a porous structure, the entire positive electrode can be utilized more effectively. As a result, it is possible to increase the number of charge / discharge cycles (number of cycles) of the air battery using the positive electrode.

In the injection (that is, filling) of the electrolytic solution into the positive electrode having a porous structure, the member containing the electrolytic solution (member for transferring the electrolytic solution) is brought into contact with the electrode, and the solvent of the electrolytic solution is before the transfer of the electrolytic solution. It is preferable to include a step of wetting the pores (pores) inside the positive electrode. By including this step, after wetting the pores (pores) inside the positive electrode with the solvent, a member containing the electrolytic solution (member for transferring the electrolytic solution) is brought into contact with the member to transfer the electrolytic solution. The surface of the positive electrode having a porous structure can be uniformly injected, and the electrolytic solution can be injected deeper into the pores (pores) inside the positive electrode having a porous structure.

As a specific example of the step of moistening the pores (pores) inside the positive electrode with the solvent, the solvent is evaporated by vacuum heat treatment, and the positive electrode having a porous structure is placed in the solvent vapor atmosphere. By the above step, the solvent vapor spreads to the deep part of the pores inside the positive electrode, and the inside of the pores (pores) can be wetted with the solvent to obtain a positive electrode having a porous structure. By contacting the positive electrode with a member containing the electrolytic solution (member for transferring the electrolytic solution), the positive electrode containing the electrolytic solution can be obtained deep into the pores inside the positive electrode having a porous structure. can. Further, by performing the transfer after the step of wetting the pores (pores) inside the positive electrode with the solvent, the entire surface of the positive electrode is electrolyzed with a liquid amount that causes liquid injection spots according to the conventional liquid injection method. The entire surface of the positive electrode can be uniformly filled with the liquid.

The specific surface area and volume of the pores in the pores (pores) having a diameter of 10 nm or more and 100 nm or less are BJH from the adsorption isotherm obtained by the nitrogen adsorption method using, for example, 3Flex (manufactured by Micromeritics Instrument Corp.). It can be obtained by using the (Barrett-Joiner-Hallenda) method.

The structure of the air battery, which is one embodiment of the present invention, will be described with reference to FIG. The present invention is particularly applicable to an air battery, and examples of the air battery include a lithium air battery, a magnesium air battery, a sodium air battery, and an aluminum air battery. However, the present invention is not limited to the following embodiments. Further, unless otherwise specified in the present application, there are no particular restrictions as long as the object of the present invention can be achieved.

The air battery 100 includes an oxygen flow path layer 101, and a laminated structure in which a positive electrode 102 and a negative electrode 104 are laminated via a separator 103. The electrolytic solution is injected into the positive electrode (air electrode) 102 of the air battery. This injection will be described with reference to FIG. In the description of the air battery 100, a non-aqueous electrolytic solution is injected as an electrolytic solution, but the injection method is not limited to the non-aqueous electrolytic solution, but can be applied to an aqueous electrolytic solution. May be applied.

Oxygen flow path layer 101
The oxygen flow path layer 101 includes, for example, copper (Cu), tungsten (W), aluminum (Al), nickel (Ni), titanium (Ti), gold (Au), silver (Ag), platinum (Pt), and palladium. A mesh having a metal selected from the group (Pd) can be mentioned.
That is, examples thereof include a simple substance of a metal selected from this group, an alloy containing a metal selected from this group, and a mesh composed of a metal selected from this group and a compound of carbon (C), nitrogen (N), or the like.
Further, although the metal mesh may be entirely made of metal, the polymer mesh may be metal-coated in consideration of weight reduction of the cell. In this method, the weight of the oxygen flow path layer 101 can be reduced, which in turn can contribute to increasing the energy density of the cell. The mesh can have, for example, a thickness of 0.2 mm and an opening of 1 mm.

Positive electrode (air electrode) 102
As described above, the positive electrode (air electrode) 102 needs to be conductive and have a porous structure. Examples of the material of the positive electrode include carbon, metal, carbides, oxides and the like, but carbon is preferable. For example, in the case of a lithium-air battery, the air electrode having a porous structure serves as a reaction field where lithium peroxide generated by the discharge reaction is deposited.

The positive electrode (air electrode) 102, that is, the air electrode having a porous structure can be obtained by a manufacturing method including a material mixing step, a sheet molding step, a solvent dipping step, a drying step, and a baking step.

Manufacturing method of positive electrode (air electrode) 102 In the material mixing step, for example, the porous carbon particles are 50% by weight or more and 80% by weight or less, the carbon fibers are 1% by weight or more and 15% by weight or less, and the bonding polymer material is 5% by weight. This is a step of preparing a mixture slurry using a solvent consisting of N-methylpyrrolidone in order to weigh the mixture so as to be% or more and 49% by weight or less and uniformly disperse them.
Here, as the porous carbon particles, as described above, carbon black containing Ketjen black (registered trademark), carbon particles formed by the template method, or the like can be used.
As the carbon fiber, for example, a carbon fiber having a fiber diameter of 0.1 μm or more and 20 μm or less and a length of 1 mm or more and 20 mm or less can be used.
As the polymer material to be attached, for example, polyacrylonitrile (PAN) and polyvinylidene fluoride can be used.
As the solvent, for example, N-methylpyrrolidone, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMA) and the like can be used.

The sheet molding step is a step of molding the mixture slurry. The sheet molding method is not particularly limited, and examples thereof include a wet film forming method using a known doctor blade or the like. In addition, a roll coater method, a die coater method, a spin coating method, a spray coating method and the like can also be mentioned. The shape after molding can be various shapes depending on the purpose. For example, it can be in the form of a sheet having a uniform thickness.

The solvent dipping step is a step of immersing the sample (sheet) molded in the sheet molding step in a solvent having low solubility in a binder polymer material by a non-solvent-induced phase separation method to form a porous film. Examples of the solvent used in the solvent dipping step include water, alcohols such as ethyl alcohol, methyl alcohol, and isopropyl alcohol, and a mixed solvent thereof.

The drying step is a step of volatilizing various solvents from the sample. Examples of the drying method include a method of placing in a dry air environment, a vacuum drying method, and a vacuum drying method. In this drying step, in order to increase the drying rate, heating may be performed at a temperature exceeding the boiling point of the solvent.

The firing step is a step of firing the sample (sheet) after the drying step. The firing process can be performed using, for example, an oven furnace, an infrared irradiation, an infrared irradiation furnace, a muffle furnace, a reed hammer furnace, or the like.
Here, the firing step may be a one-time heat treatment, but may also be a two-step heat treatment of infusibilization and firing. The heat treatment temperature for firing is preferably 800 ° C. or higher and 1400 ° C. or lower, and the atmosphere at that time is preferably an inert atmosphere with argon (Ar) gas, nitrogen (N ₂ ) gas or the like.
For example, when PAN is used as the binder polymer, it is heat-treated to be infusible in air at about 200 ° C. or higher and about 350 ° C. or lower, and then in an inert atmosphere with Ar gas, _N2 gas, or the like. It is preferable to perform heat treatment at 800 ° C. or higher and 1400 ° C. or lower.

By the above steps, a positive electrode 102 (air electrode) having sufficient and practical mechanical strength to have independence is manufactured. The positive electrode 102 (air electrode) has self-sustaining property, high air permeability, high ion transport efficiency, and a wide reaction field. Here, having self-sustaining means that the shape of a self-supporting film can be maintained without using a support.

The positive electrode 102 (air electrode) thus obtained has a pore volume of 2.3 cm ³ / g (2300 μL / g) to 4 cm ³ / g (4000 μL / g) occupied by pores having a diameter of 1 nm or more and 1 μm or less by the nitrogen adsorption method. ), And the pore volume occupied by pores with a diameter of 0.2 μm or more and 10 μm or less by the mercury intrusion method ranges from 0.8 cm ³ / g (800 μL / g) to 2.7 cm ³ / g (2700 μL / g). Can be in range. The pore volume can be measured by the following method.
1) Pore volume occupied by pores with a diameter of 1 nm or more and 1 μm or less
It can be obtained by the BJH method from the adsorption isotherm obtained by the nitrogen adsorption method using 3Flex (manufactured by Micromeritics Instrument Corp.).
2) Pore volume occupied by pores with a diameter of 0.2 μm or more and 10 μm or less
It can be obtained by a mercury intrusion method using AutoPore IV (manufactured by Micromeritics Instrument Corp.). For example, the pore volume in the range of the pore diameter of 10 nm (0.01 μm) to 200 μm may be measured, and the value of the pore volume of the pore diameter of 0.2 μm to 10 μm may be used.

Negative electrode 104
The negative electrode 104 may be any as long as it is usually used as the negative electrode of the battery. For example, in the case of a lithium-air battery, the negative electrode may contain a metal or alloy that absorbs and releases lithium ions, and a typical example is lithium metal.

Separator 103
A separator 103 is arranged between the positive electrode (air electrode) 102 and the negative electrode 104. The separator 103 is an insulating material having a porous structure through which metal ions can pass, and any inorganic material having no reactivity with the positive electrode (air electrode) 102, the negative electrode 104, and the electrolytic solution. Organic materials are applied. The separator 103 also serves to retain the electrolytic solution. If this condition is satisfied, there is no particular limitation, and a separator used in an existing metal battery can be used. For example, the separator 103 is selected from the group consisting of porous membranes made of synthetic resins such as polyethylene, polypropylene and polyolefin, glass fibers and non-woven fabrics.

The separator 103 is preferably made larger than each active material layer in order to prevent a short circuit between the positive electrode active material and the negative electrode active material.

Electrolyte The electrolytic solution is as described above.

Injection method The injection of the electrolytic solution into the positive electrode is performed by bringing the member containing the electrolytic solution (member for transferring the electrolytic solution) into contact with the member (member for transferring the electrolytic solution) and thereby transferring the electrolytic solution to the positive electrode. Based on FIG. 2, a structure for injecting an electrolytic solution into an air electrode by transfer in one embodiment of the present invention will be described below. However, the structure is not limited to the following.
The member containing the electrolytic solution (member for transferring the electrolytic solution) 105 is manufactured by dropping a predetermined amount of a non-aqueous electrolytic solution onto a member made of PTFE (polytetrafluoroethylene) by means such as a known micropipette or a dispenser. do. As shown in FIG. 2, the prepared electrolytic solution transfer member 105 for holding a predetermined amount of non-aqueous electrolytic solution is held in the electrolytic solution transfer member 105 by sandwiching the positive electrode (air electrode) 102 from both sides. The non-aqueous electrolytic solution is transferred to the positive electrode (air electrode) 102. By this transfer, the non-aqueous electrolytic solution held in the electrolytic solution transfer member 105 is injected into the positive electrode (air electrode) 102. The amount of the non-aqueous electrolytic solution dropped onto the electrolytic solution transfer member 105 may be a liquid amount corresponding to a desired injection amount, and this liquid amount is the amount of the electrolytic solution transfer member 105 dropped and its transfer in advance. It can be determined by creating a calibration curve of the amount of liquid injected into the positive electrode (air electrode) 102.
In FIG. 2, the structure is such that the electrolytic solution transfer member 105 is sandwiched from the upper and lower surfaces, but a predetermined amount of non-aqueous electrolytic solution may be uniformly transferred to the positive electrode (air electrode) 102, for example, electrolytic solution transfer. Only one member 105 may be used, and the non-aqueous electrolytic solution may be transferred from one side to the positive electrode (air electrode) 102.
The size of the electrolytic solution transfer member 105 is equal to or larger than the size of the positive electrode (air electrode) 102.
In this embodiment, the transfer of the non-aqueous electrolytic solution from the electrolytic solution transfer member 105 to the positive electrode (air electrode) 102 was performed at room temperature and atmospheric pressure. However, conditions other than room temperature and atmospheric pressure may be used as long as the desired amount of liquid can be injected uniformly. For example, the environmental temperature at the time of transfer may be increased. Especially in the case of a highly viscous electrolytic solution, raising the environmental temperature reduces the viscosity of the electrolytic solution, so that more uniform injection can be expected. Further, the transfer of the non-aqueous electrolytic solution from the electrolytic solution transfer member 105 in FIG. 2 to the positive electrode (air electrode) 102 may be performed under atmospheric pressure, but the environmental pressure during transfer may be reduced. However, it is necessary to match the transfer injection conditions when creating the calibration curve and the transfer injection conditions when actually injecting the transfer.

Pretreatment of positive electrode (gas phase adsorption)
The positive electrode may be pretreated before the liquid injection method. The method of pretreating the positive electrode will be specifically described below. However, the method is not limited to the following.
A positive electrode and an electrolytic solution solvent are set in the vacuum chamber, and the inside of the chamber is depressurized by a vacuum pump. Next, the inside of the chamber is heated and returned to the atmospheric pressure held for a certain period of time, and the positive electrode is taken out. At this time, the weight of the positive electrode before and after the vapor phase adsorption is measured, and the amount of the electrolyte solvent adsorbed on the positive electrode is calculated.

The upper limit of the degree of vacuum in the chamber at the time of depressurization by this method is 10 Pa or less, preferably 5 Pa or less, and more preferably 2 Pa or less. When the degree of vacuum is 10 Pa or less, the residual air in the positive electrode pores is reduced, and the solvent is easily diffused in the positive electrode pores. The lower limit of the degree of vacuum is not particularly determined, but is preferably 0.1 Pa or more, and more preferably 1 Pa or more. When the degree of vacuum is 0.1 Pa or more, it is possible to prevent a large amount of solvent volatilization and immediate exhaust.

The upper limit of the heating temperature in this method is 100 ° C. or lower, preferably 80 ° C. or lower, and more preferably 75 ° C. or lower. By setting the upper limit of the heating temperature to 100 ° C. or lower, it is possible to prevent capillary condensation of the solvent in the mesopores. The lower limit of the heating temperature is 40 ° C. or higher, preferably 50 ° C. or higher, and more preferably 60 ° C. or higher. By setting the lower limit of the heating temperature to 40 ° C. or higher, the vapor pressure of the solvent is high, and the inside of the pores of the positive electrode can be sufficiently moistened. As a result, uniform injection by transfer injection of the electrolytic solution, which is the next step, can be effectively performed.

The lower limit of the heating and holding time is 10 minutes or more, preferably 20 minutes or more, and more preferably 25 minutes or more. When the heating and holding time is 10 minutes or more, the vaporized solvent can be sufficiently diffused and permeated into the positive electrode pores, particularly deep pores. The upper limit of the heating and holding time is 120 minutes or less, preferably 60 minutes or less, and more preferably 40 minutes or less. When the heating and holding time is 120 minutes or less, it is possible to prevent the solvent from condensing the capillaries in the mesopores of the positive electrode, resulting in an amount of solvent larger than that for wetting the inner wall of the pores and closing the pores. can.

The upper limit of the solvent adsorption amount is 3 μL / cm ² or less, preferably 2 μL / cm ² or less, and more preferably 1.5 μL / cm ² or less. When the amount of solvent adsorbed is 3 μL / cm ² or less, it is possible to prevent the pores from being clogged. The lower limit of the solvent adsorption amount is 0.5 μL / cm ² or more, preferably 0.9 μL / cm ² or more, and more preferably 1.1 μL / cm ² or more. When the amount of solvent adsorbed is 0.5 μL / cm ² or more, the inside of the pores of the positive electrode can be sufficiently moistened. As a result, uniform injection by transfer injection of the electrolytic solution, which is the next step, can be effectively performed.

Manufacture of an air battery In an air battery 100, for example, a separator 103 is laminated on a negative electrode 104, a positive electrode (air electrode) 102 injected by the liquid injection method of the present invention is laminated on the separator 103, and an oxygen flow path is further formed. Manufactured by laminating layers 101.

As another method, the separator 103 is laminated on the negative electrode 104, a predetermined amount of electrolytic solution is dropped onto the separator by an arbitrary method, and then the uninjected positive electrode (air electrode) 102 is placed on the separator 103. Stack. The liquid injection method may be applied onto the positive electrode after laminating the negative electrode 104, the separator 103, and the positive electrode (air electrode) 102. After that, the air battery 100 may be manufactured by laminating the oxygen flow path layer 101 on the positive electrode (air electrode) 102 that has been injected with liquid.

The method for manufacturing the above-mentioned air battery will be described in more detail below by taking a lithium-air battery as an example, but the manufacturing method is not limited to the following.
As the negative electrode 104, for example, a lithium metal is cut out into a rectangle of 20 mm × 20 mm and prepared. A 24 mm × 24 mm separator 103 is laminated on the negative electrode 104. A predetermined amount of electrolytic solution is poured onto the separator. Any method of injecting liquid into the separator can be used.
After laminating the negative electrode 104 and the separator 103 in this order, the positive electrode (air electrode) 102 to which the non-aqueous electrolytic solution has been injected in advance according to the above-mentioned transfer injection method is laminated on the separator 103, and further oxygen flow. By stacking the road layers 101, a laminated body of a lithium-air battery is obtained.
As another method, the separator 103 is laminated on the negative electrode 104, a predetermined amount of the electrolytic solution is dropped onto the separator 103 by an arbitrary method, and then the positive electrode (air electrode) 102 which has not been injected yet is used as the separator 103. Stack on top. A predetermined amount of electrolytic solution is contained in the electrolytic solution transfer member 105, and the electrolytic solution is placed on the positive electrode (air electrode) 102 of the laminate in which the negative electrode 104, the separator 103, and the positive electrode (air electrode) 102 are laminated in this order. The electrolytic solution may be transferred to the positive electrode (air electrode) 102 by contacting the containing electrolytic solution transfer member 105. After that, the lithium-air battery 100 may be manufactured by laminating the oxygen flow path layer 101 on the positive electrode (air electrode) 102 that has been injected with liquid.

Hereinafter, the present invention will be specifically described. The present invention is not limited to the following examples in any sense.

Evaluation experiment 1
The following experiments were conducted to evaluate the uniformity of the injection of the electrolytic solution to the positive electrode.

Preparation of positive electrode First, a mixture slurry was prepared using a solvent consisting of 68% by weight of porous carbon particles, 9% by weight of carbon fibers, 23% by weight of a polymer material to be attached, and N-methylpyrrolidone that uniformly disperses them. did.
Here, as the porous carbon particles, carbon black containing 68% by weight of Ketjen Black (registered trademark) was used. As the carbon fiber, a carbon fiber having an average fiber diameter of 5 μm and an average length of 3 mm was used. Polyacrylonitrile (PAN) was used as the polymer material to be attached.
The mixture was formed into a sheet by molding it into a uniform thickness by a wet film forming method using a doctor blade. After molding, the molded sample is formed into a porous film by immersing it in methanol (poor solvent) and precipitating polyacrylonitrile (PAN) between the porous carbon particles and carbon fibers by a non-solvent-induced phase separation method. did.
Next, a drying step of removing the volatile solvent from the sheet-shaped sample at 50 to 80 ° C. for 10 hours or more was performed, followed by an infusible heat treatment at 280 ° C. for 3 hours in the air. Then, the carbon sample having a porous structure having a length of 140 mm, a width of 100 mm, and a height of 200 μm was prepared by firing at 1050 ° C. for 3 hours in a firing furnace under a nitrogen gas atmosphere after vacuum replacement.
A positive electrode was obtained by cutting out a carbon sample having a porous structure into a shape of 20 mm × 20 mm.
The porosity of the obtained positive electrode was 90%. The porosity of this positive electrode is calculated by calculating the bulk density by weight measurement of a porous carbon structure sample (analytical balance XS205 manufactured by METTLER TOLEDO) and comparing it with the true density of carbon (2.1 g / cm ³ ). The porosity was calculated.
Further, the amount of increase in the weight of the positive electrode after immersing one of the obtained positive electrodes in a petri dish having a diameter of 40 mm containing 1 ml of an electrolytic solution, impregnating with a vacuum for 15 minutes, and wiping the electrolytic solution remaining on the surface with a Kim towel is the amount. It was 16.1 mg / cm ² . The maximum filling amount (volume at which the filling amount of the electrolytic solution is 100%) was calculated from the specific gravity (1.12) of the electrolytic solution used. The calculated maximum filling amount was 18.0 μL / cm ² .

Solvent of non -aqueous electrolyte solution As the solvent of the non-aqueous electrolyte solution, tetraglyme (TEGDME) (specific gravity 1.01, boiling point 275 ° C.) was used.

Preparation of non- aqueous electrolyte solution There are three types of non-aqueous electrolyte solution: 0.5 mol / L Li (CF ₃ SO ₂ ) ₂ N (LiTFSI), 0.5 mol / L LiNO ₃ and 0.2 mol / L LiBr. The electrolyte was obtained by dissolving it in a tetraglime (TEGDME) solvent. The specific gravity of this non-aqueous electrolyte solution was 1.12.

Preparation of a member containing an electrolytic solution (member for transferring an electrolytic solution) In this embodiment, a PTFE type membrane filter (manufactured by Advancedc Toyo Co., Ltd., diameter 90 mm, hole diameter 1 μm) is used as a member containing an electrolytic solution (member for transferring an electrolytic solution). Was punched into a 22 mm square and used.

Example 1
In this example, the amount of liquid injected was 60% of the amount of pores in the positive electrode. This liquid injection amount corresponds to 10.8 μL per 1 cm ² of the positive electrode, and since the 20 mm square positive electrode is used, the liquid injection amount of the entire positive electrode is 43.2 μL.
Two members (electrolyte solution transfer members) containing an electrolytic solution are prepared for one positive electrode, and the electrolytic solution is 5.4 μL / cm ² (electrolyte solution transfer member 1) for each electrolytic solution transfer member. Each was measured with a micropipette so as to be 26.2 μL per unit, and dropped onto the electrolyte transfer member.
The transfer conditions of the electrolytic solution were the same as when the calibration curve was prepared (transfer at room temperature and atmospheric pressure for 3 minutes), and the mixture was allowed to stand as shown in FIG. After that, the electrolytic solution transfer member was removed, and the weight of the injected positive electrode was measured to confirm that the amount of the electrolytic solution at the target value was injected within an error of 3% or less.

Comparative Example 1
In this comparative example, the same positive electrode and electrolytic solution as in Example 1 are used, and an Eppendorf micropipette (product number; 4920000.059) is used to obtain an electrolytic solution amount of 10.8 μL / cm ² (that is, a 20 mm square positive electrode). A 43.2 μL electrolyte solution) was added dropwise onto the positive electrode, and the mixture was allowed to stand at room temperature and atmospheric pressure for 3 minutes.

Evaluation of Homogeneity Evaluation of uniformity in the positive electrode of the electrolytic solution injected by each of the above methods was performed using μXRF (μXRF M4 TORNADO plus manufactured by Bruker AXS). The bromine Kα ray of LiBr added as an electrolyte in the electrolytic solution was mapped to the positive electrode under the following conditions. Rh was used for the tube, the tube voltage was 50 kV, the tube current was 200 uA, the measurement speed per pixel was 12 msec / pixel, and the speed of the sample stage was 6.3 mm / sec. Of the 20 mm × 20 mm positive electrodes, 6 line analyzes were performed at 3 mm intervals, and Br (Kα) fluorescent X-rays were measured. The mean value and standard deviation of the measured 1440 bromine Kα ray data were calculated, and the coefficient of variation was calculated by dividing the standard deviation by the mean value.

FIG. 3 shows mapping data of bromine Kα rays after injection of Example 1 and Comparative Example 1.
Comparing Example 1 and Comparative Example 1, in Comparative Example 1 in which the electrolytic solution was dropped with a micropipette, bromine concentration spots were clearly seen, and it was confirmed that liquid injection spots were present. In Example 1 by transfer of the electrolytic solution of the present invention, no bromine concentration spots were observed, and it was confirmed that the liquid was uniformly injected without the presence of liquid injection spots.

Table 1 shows the mean value and standard deviation of the measured values of the bromine Kα rays at 1440 points for each of Example 1 and Comparative Example 1, and the coefficient of variation calculated from them. Comparing Comparative Example 1 and Example 1, the coefficient of variation of Example 1 is smaller than that of Comparative Example 1, and the coefficient of variation of Comparative Example 1 in which injection spots are confirmed is 0.2. It was also found that the coefficient of variation of Example 1 in which uniform injection without liquid injection spots was confirmed was smaller than 0.2.
Therefore, by applying this injection method, the uniformity of the electrolytic solution in the positive electrode of the porous structure can be improved, and the electrolytic solution is applied to the positive electrode of the porous structure, and the injection spots according to the conventional injection method. It was confirmed that the liquid can be injected uniformly even with the amount of liquid that causes the above.

Evaluation experiment 2
The following experiments were conducted to evaluate the cycle performance of the air battery and the injection of the electrolytic solution into the internal pores of the positive electrode. The method for preparing the positive electrode before injecting the solution, the method for preparing the solvent for the non-aqueous electrolytic solution and the non-aqueous electrolytic solution, and the method for producing the member containing the electrolytic solution (member for transferring the electrolytic solution) were carried out in the same manner as in Evaluation Experiment 1. ..

Example 2
In this example, the injection amount was set to 60% with respect to the maximum filling amount (volume at which the electrolytic solution filling amount is 100%). This liquid injection amount corresponds to 10.8 μL per 1 cm ² of the positive electrode, and since the 20 mm square positive electrode is used, the liquid injection amount of the entire positive electrode is 43.2 μL.
Step 1: In the vacuum chamber, place one positive electrode prepared by the above method and a chalet (φ30 mm, depth 10 mm) containing 0.2 mL of the tetraglyme (TEGDME) solvent, and use a direct-coupled oil rotary vacuum pump to perform the chamber. The inside was reduced to 1.3 Pa. Next, the inside of the chamber was heated to 70 ° C., held for 30 minutes, and then the inside of the chamber was returned to the atmosphere to take out the positive electrode. As a result of measuring the positive electrode weight before and after gas phase adsorption, the amount of the electrolytic solution solvent adsorbed on the positive electrode at this time was 1.3 mg / cm ² , and the adsorption capacity calculated from the specific gravity of the electrolytic solution solvent was 1.3 μL / cm. It was ² .
Step 2: Two members (electrolyte solution transfer members) containing an electrolytic solution are prepared for one positive electrode, and the electrolytic solution is 5.4 μL / cm ² (electrolyte solution) for each electrolytic solution transfer member. Each transfer member was measured with a micropipette so as to have a volume of 26.2 μL), and the mixture was dropped onto the electrolyte transfer member.
The transfer conditions of the electrolytic solution were the same as when the calibration curve was prepared (transfer at room temperature and atmospheric pressure for 3 minutes), and the mixture was allowed to stand as shown in FIG. After that, the electrolytic solution transfer member was removed, and the weight of the injected positive electrode was measured to confirm that the amount of the electrolytic solution at the target value was injected within an error of 3% or less.

Example 1'
In this comparative example, a positive electrode was obtained in the same manner as in Example 2 except that step 1 was not performed.

Pore injection evaluation The positive electrodes obtained in Example 2 and Example 1'were evaluated for injection into the pores by the following method.
(1) Measurement of specific surface area of pores in pores with a diameter of 10 nm or more and 100 nm or less after injection BJH (Barrett-Joiner) from the adsorption isotherm obtained by the nitrogen adsorption method using 3Flex (manufactured by Micrometrics Instrument Corp.). -It was determined using the Hallenda) method.
(2) Pore volume measurement in pores with a diameter of 10 nm or more and 100 nm or less after injection BJH (Barrett-Joiner-) from the adsorption isotherm obtained by the nitrogen adsorption method using 3Flex (manufactured by Micrometrics Instrument Corp.). It was determined using the Hallenda) method.
Table 2 and FIG. 4 show the results of pore injection evaluation.

From Table 2 and FIG. 4, although the inside of the positive electrode was moistened with the electrolytic solution in both Example 2 and Example 1', the vapor phase was adsorbed by the electrolytic solution solvent vapor before the injection by the transfer of the electrolytic solution. In Example 2, it was confirmed that the values of the specific surface area and the volume became smaller in the pores having a diameter of 10 nm or more and 100 nm or less inside the positive electrode, that is, the internal pores of the positive electrode were more effectively wetted with the electrolytic solution. rice field. Needless to say, in the conventional liquid injection method shown in Comparative Example 1, the small amount of liquid used in this Comparative Example did not reach the wetness inside the positive electrode.

Battery evaluation Example 2, Example 1', and Comparative Example 1 20 mm square positive electrode, 20 mm square Li metal leaf with a thickness of 100 μm, Toray TR-7 cut into 22 mm square as a separator, Toray as an oxygen flow path An air battery was prepared for each Example or Comparative Example by laminating as shown in FIG. 1 using the company GDL. Using this battery, first, as conditioning, discharging for 2 hours at a current density of 0.2 mA / cm ² and charging for 2 hours were repeated 3 times. Then, as an evaluation of the cycle characteristics, 10-hour discharge (discharge capacity 4 mAh / cm ² ) and 10-hour charging (charge capacity 4 mAh / cm ² ) were repeated at a current density of 0.4 mA / cm ² . At this time, the discharge limit potential was 2.0 V, and the charge limit potential was 4.8 V. The end of the cycle was defined as the time when the discharge capacity or the charge capacity became 3.2 mAh / cm ² (80%) or less, and the number of charges and discharges up to this point was defined as the number of cycles. The results of battery evaluation based on the number of cycles are shown in Table 2. Compared to the number of cycles of 14 times in Example 2 and 3 times in Example 1', the air battery using Comparative Example 1 has this Comparative Example 1. The result was that the discharge reaction did not proceed from the first time (the number of cycles was 0) with the small amount of liquid injected in.

According to Examples 2 and 1'from Table 2, even if the amount of the electrolytic solution is such that charging and discharging do not proceed by the conventional liquid injection method shown in Comparative Example 1, it can be used as an air battery, and in particular, the electrolytic solution. According to Example 2 in which the gas phase was adsorbed by the solvent vapor of the electrolytic solution before the injection by transfer, it was confirmed that an air battery having an extremely high number of cycles could be produced.

According to the present invention, a small amount of liquid (specifically, a volume smaller than the total pore volume of the positive electrode, which cannot be realized by the conventional injection method, and a liquid injection spot according to the conventional injection method). Since it is possible to inject the positive electrode uniformly even with an electrolytic solution of a liquid amount that causes It becomes possible to easily diffuse the oxygen in the air battery. Therefore, the present invention has the potential to be used for an air battery that is compact, lightweight, and suitable for increasing the capacity, and is expected to be preferably used for an air battery whose demand is expected to increase significantly in the future.

100: Air battery 101: Oxygen flow path layer 102: Positive electrode 103: Separator 104: Negative electrode 105: Member containing electrolytic solution (member for transferring electrolytic solution)

Claims (26)

The positive electrode having a porous structure and containing the electrolytic solution transferred by contact with a member containing the electrolytic solution. The positive electrode according to claim 1, wherein the electrolytic solution contains a lithium salt, and the coefficient of variation of at least one component of the lithium salt by fluorescent X-ray measurement is lower than 0.2. The positive electrode according to claim 2, wherein the lithium salt is lithium bromide, and the coefficient of variation of bromine constituting the lithium bromide by Kα-ray measurement is lower than 0.2. The positive electrode according to any one of claims 1 to 3, wherein 50% or more and less than 100% of the pores of the positive electrode are filled with the electrolytic solution based on the porosity. The positive electrode according to any one of claims 1 to 4, wherein the member is a membrane filter made of polytetrafluoroethylene (PTFE). The positive electrode according to any one of claims 1 to 5, wherein the electrolytic solution of the member is contained by dropping. The invention according to any one of claims 1 to 6, wherein the positive electrode having a porous structure has pores moistened with a solvent of the electrolytic solution by a vacuum heat treatment before contact with the member containing the electrolytic solution. Positive electrode. The positive electrode according to any one of claims 1 to 7, wherein the pore specific surface area after transfer is 10 m ² / g or less in pores having a diameter of 10 nm or more and 100 nm or less. The positive electrode according to claim 8, wherein the pores having a diameter of 10 nm or more and 100 nm or less have a pore specific surface area after transfer of 6 m ² / g or less. The positive electrode according to any one of claims 1 to 9, wherein the volume after transfer is 100 μL / g or less in the pores having a diameter of 10 nm or more and 100 nm or less. The positive electrode according to claim 10, wherein the volume after transfer is 60 μL / g or less in the pores having a diameter of 10 nm or more and 100 nm or less. An air battery comprising the positive electrode according to any one of claims 1 to 11. The air battery according to claim 12, wherein the number of charge / discharge cycles (number of cycles) before the discharge capacity or charge capacity becomes 80% or less is 3 times or more. A method of injecting the electrolytic solution into the positive electrode by bringing a member containing the electrolytic solution into contact with a positive electrode having a porous structure and transferring the electrolytic solution. The claim that the electrolytic solution contains a lithium salt, and the electrolytic solution is injected so that the fluctuation coefficient of at least one constituent element of the lithium salt at the positive electrode is lower than 0.2 by fluorescent X-ray measurement. 14. The method according to 14. 15. The electrolytic solution is injected so that the lithium salt is lithium bromide and the coefficient of variation of bromine constituting the lithium bromide measured by Kα-ray at the positive electrode is lower than 0.2. The method described in. The method according to any one of claims 14 to 16, wherein by injecting the electrolytic solution, 50% or more and less than 100% of the pores of the positive electrode are filled with the electrolytic solution based on the porosity. The method according to any one of claims 14 to 17, wherein a membrane filter made of polytetrafluoroethylene (PTFE) is used as the member. The method according to any one of claims 14 to 18, wherein the electrolytic solution of the member is contained by dropping. 13. Method. The step of wetting the inside of the pores of the positive electrode with the solvent of the electrolytic solution is to evaporate the solvent of the electrolytic solution by vacuum heat treatment and place the positive electrode having a porous structure in the solvent steam atmosphere to wet the positive electrode. 20. The method of claim 20. The method according to claim 21, wherein the reduced pressure heat treatment is performed under a pressure of 0.1 Pa or more and 10 Pa or less. The method according to claim 21 or 22, wherein the decompression heat treatment is heated at a temperature of 40 ° C. or higher and 100 ° C. or lower. The method according to claim 23, wherein the heating time of the reduced pressure heat treatment is 10 minutes or more and 120 minutes or less. With the negative electrode
Separator and
A positive electrode into which the electrolytic solution is injected by the method according to any one of claims 14 to 24,
A method for manufacturing an air battery by sequentially laminating an oxygen flow path layer for taking in oxygen as an active material of the positive electrode. With the negative electrode
Separator and
A positive electrode into which the electrolytic solution is injected by the method according to any one of claims 14 to 24,
It is a method of manufacturing an air battery by sequentially laminating an oxygen flow path layer for taking in oxygen as an active material of the positive electrode.
A step of injecting the electrolytic solution into the positive electrode by transferring the electrolytic solution by bringing a member containing the electrolytic solution into contact with the positive electrode after stacking the positive electrodes to which the electrolytic solution has not been injected, and the member. The process of removing,
The manufacturing method.

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