JP2010177036A - Air electrode layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air electrode layer which can be manufactured by a simple method and has good catalyst performance (good reduction effect of a charging voltage for example). <P>SOLUTION: The air electrode layer used for an air secondary battery has a conductive material and a metal catalyst formed on the surface of the conductive material by an electrodeposition method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an air electrode layer used for an air secondary battery, and more particularly, to an air electrode layer having a metal catalyst having a large surface area and highly dispersed.

  An air secondary battery using a non-aqueous electrolyte is a secondary battery using air (oxygen) as a positive electrode active material, and has advantages such as high energy density and easy miniaturization and weight reduction. Therefore, it has been attracting attention as a high-capacity battery that exceeds the lithium secondary battery that is currently widely used.

  Such an air secondary battery includes, for example, an air electrode layer having a conductive material (for example, carbon black), a metal catalyst (for example, manganese dioxide) and a binder (for example, polyvinylidene fluoride), and a collection of the air electrode layers. Responsible for conduction of metal ions (for example, Li ions), an air electrode current collector for performing electricity, a negative electrode layer containing a negative electrode active material (for example, metal Li), a negative electrode current collector for collecting current of the negative electrode layer, and A non-aqueous electrolyte.

  Conventionally, for example, a particulate metal catalyst (such as manganese dioxide) has been used as the metal catalyst contained in the air electrode layer. The particle diameter of such a metal catalyst is usually several tens of μm or more. On the other hand, there is an attempt to reduce the catalyst size from the viewpoint of improving the function of the catalyst. For example, Patent Document 1 describes that a manganese oxide nanostructure having a dendrite-like structure in which primary particles are aggregated is manufactured using a laser ablation method. This technique aims to obtain a manganese oxide nanostructure having excellent oxygen reduction performance by using a laser ablation method. Further, Patent Documents 2 and 3 similarly describe that a manganese oxide nanostructure is manufactured using a laser ablation method.

WO2005 / 080254 WO2005 / 019109 JP 2006-1751 A

  As described above, the catalyst performance can be expected to be improved by increasing the surface area by reducing the catalyst size. Further, since the catalyst size is small, there is an advantage that it is easy to achieve high dispersion. However, in order to perform the laser ablation method as described above, a large facility is generally required, and thus there is a problem that the production efficiency is poor.

  The present invention has been made in view of the above circumstances, and can provide an air electrode layer that can be manufactured by a simple method and that has good catalytic performance (for example, good charging voltage reduction effect). The main purpose.

  As a result of intensive studies by the present inventors in order to solve the above problems, it has been found that a metal catalyst having a large surface area and high dispersion can be formed on the surface of a conductive material by using an electrodeposition method. It was. The present invention has been made based on such knowledge.

  That is, in the present invention, it is an air electrode layer used for an air secondary battery, and has a conductive material and a metal catalyst formed on the surface of the conductive material by an electrodeposition method. Provide an air electrode layer.

  According to this invention, since it has the metal catalyst formed by the electrodeposition method on the surface of an electroconductive material, it can be set as the air electrode layer which has favorable catalyst performance. Furthermore, according to the present invention, since the metal catalyst is formed by the electrolytic method, the metal catalyst can be formed by a simple method as compared with the case where the conventional laser ablation method described above is used.

  In the above invention, the metal catalyst is preferably dispersed in a network. This is because more excellent catalyst performance can be exhibited.

In the above invention, the current caused by the metal catalyst per specific surface area of the conductive material is preferably in the range of ^{250μA / cm 2 ~800μA / cm 2} . This is because more excellent catalyst performance can be exhibited.

  In the said invention, it is preferable that the said metal catalyst is a manganese oxide. This is because, for example, the catalyst can be useful for a lithium-air secondary battery.

  Moreover, in this invention, it has an air electrode layer mentioned above, The air secondary battery characterized by the above-mentioned is provided.

  According to this invention, since it has the air electrode layer mentioned above, it can be set as the air secondary battery excellent in the charge / discharge characteristic.

  Moreover, in this invention, it is a manufacturing method of the air electrode layer used for an air secondary battery, Comprising: The electroconductive material which forms an electroconductive material content layer using the electroconductive material containing composition containing an electroconductive material A content layer forming step, and an electrodeposition step of forming an air electrode layer by forming a metal catalyst on the surface of the conductive material contained in the conductive material content layer by an electrodeposition method. An air electrode layer manufacturing method is provided.

  According to the present invention, by using the electrodeposition method, a highly dispersed metal catalyst having a large surface area can be formed, and an air electrode layer having good catalytic performance can be obtained.

  In the present invention, it is possible to produce an air electrode layer that can be produced by a simple method and that has a good catalytic performance (for example, a good charge voltage reduction effect).

It is explanatory drawing explaining the air electrode layer of this invention. It is explanatory drawing explaining the CV test in this invention. It is a schematic sectional drawing which shows an example of the air secondary battery of this invention. It is a schematic sectional drawing which shows an example of the manufacturing method of the air electrode layer of this invention. 3 is a SEM photograph of the air electrode layer of Example 1 and Comparative Example 1. 2 is a schematic cross-sectional view showing an evaluation cell used in Example 1. FIG. It is a graph which shows the relationship between the electric current accompanying the metal catalyst per specific surface area of an electroconductive material, and the reduction effect of a charging voltage.

  Hereinafter, the air electrode layer, the air secondary battery, and the air electrode layer manufacturing method of the present invention will be described.

A. Air electrode layer First, the air electrode layer of the present invention will be described. The air electrode layer of the present invention is an air electrode layer used for an air secondary battery, and has a conductive material and a metal catalyst formed on the surface of the conductive material by an electrodeposition method. It is what.

  According to this invention, since it has the metal catalyst formed by the electrodeposition method on the surface of an electroconductive material, it can be set as the air electrode layer which has favorable catalyst performance. This is because a highly dispersed metal catalyst having a large surface area can be formed by electrodeposition. In particular, the air electrode layer of the present invention has an advantage that the charging voltage can be effectively reduced as compared with the conventional air electrode layer. Furthermore, according to the present invention, since the metal catalyst is formed by the electrolytic method, the metal catalyst can be formed by a simple method as compared with the case where the conventional laser ablation method described above is used.

  FIG. 1 is an explanatory view for explaining an air electrode layer of the present invention. The air electrode layer 1 of the present invention has a conductive material 2 and a metal catalyst 3 formed on the surface of the conductive material 2 by an electrodeposition method. Although not shown, when the deposition amount of the metal catalyst by the electrodeposition method is increased, a plurality of metal catalysts are connected to each other as the catalyst grows, and a metal catalyst dispersed in a network is obtained.

  The air electrode layer of the present invention contains at least a conductive material and a metal catalyst. Furthermore, you may contain the binder as needed. Hereinafter, the air electrode layer of the present invention will be described for each configuration.

1. Conductive material Although it will not specifically limit as long as it has electroconductivity as an electroconductive material used for this invention, For example, a carbon material etc. can be mentioned. Further, the carbon material may have a porous structure or may not have a porous structure. However, in the present invention, the carbon material preferably has a porous structure. This is because the specific surface area is large and many reaction fields can be provided. Specific examples of the carbon material having a porous structure include mesoporous carbon. On the other hand, specific examples of the carbon material having no porous structure include graphite, acetylene black, carbon nanotube, and carbon fiber.

  As content of the electroconductive material in an air electrode layer, it is preferable to exist in the range of 10 weight%-99 weight%, for example. If the content of the conductive material is too small, the reaction field may be reduced and the battery capacity may be reduced. If the content of the conductive material is too large, the metal catalyst or binder may be contained relatively. This is because the amount may decrease and a desired air electrode layer may not be obtained.

2. Next, the metal catalyst used in the present invention will be described. The metal catalyst used in the present invention is formed on the surface of the conductive material by an electrodeposition method. The details of the electrodeposition method will be described later in “C. Method for producing air electrode layer”. The metal catalyst used in the present invention is not particularly limited as long as it is deposited by an electrodeposition method and has a catalytic function for promoting an electrode reaction. And the like. Furthermore, examples of the transition metal include manganese, iron, cobalt, nickel, and the like. Among these, manganese is preferable. In particular, in the present invention, the metal catalyst is preferably a manganese oxide. This is because, for example, the catalyst can be useful for a lithium-air secondary battery. Specific examples of manganese oxides include manganese dioxide, dimanganese trioxide, trimanganese tetroxide, and manganese monoxide. Among these, manganese dioxide is preferable. The composition of the manganese oxide can be adjusted by appropriately setting the composition of the electrolytic solution, the current density, and the like during the electrodeposition.

  The shape of the metal catalyst formed on the surface of the conductive material is not particularly limited as long as the desired catalyst performance can be exhibited. As an example of the shape of a metal catalyst, as shown in said FIG. 1, what was formed in the shape of a sea island on the surface of an electroconductive material can be mentioned. On the other hand, when the deposition amount of the metal catalyst by the electrodeposition method is increased, with the growth of the catalyst, a plurality of metal catalysts formed in a sea-island shape are connected to each other, and a metal catalyst dispersed in a network is obtained. Thus, in the present invention, the metal catalyst is preferably dispersed in a network. This is because even better catalyst performance can be exhibited. The shape of the metal catalyst can be observed with a scanning electron microscope (SEM).

  Further, the content of the metal catalyst in the air electrode layer is, for example, preferably in the range of 1% by weight to 60% by weight, and more preferably in the range of 1% by weight to 30% by weight.

3. Binder The air electrode layer of the present invention may contain a binder for fixing the conductive material. Examples of the binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). The binder content in the air electrode layer is, for example, preferably 40% by weight or less, and more preferably in the range of 1% by weight to 10% by weight.

4). Air electrode layer The air electrode layer of the present invention contains at least the conductive material and the metal catalyst described above. In the present invention, the current accompanying the metal catalyst per specific surface area of the conductive material is preferably in the range of 250 μA / cm ^{2 to} 800 μA / cm ² . This is because more excellent catalyst performance can be exhibited. Here, the “current associated with the metal catalyst” is a current value calculated by the following cyclic voltammetry (CV) test. Specifically, a CV test is performed on the air electrode layer before and after electrodeposition under the following conditions.
<CV condition>
-Solution: 0.1 M sodium sulfate aqueous solution + 0.05 M manganese acetate aqueous solution-Working electrode: air electrode layer-Counter electrode: Pt wire-Reference electrode: silver / silver chloride electrode-Potential range: 0-0.4 (V vs Ag / AgCl)
・ Sweep speed: 20mV / S

  By performing such a CV test, a graph as shown in FIG. 2 is usually obtained. The air electrode layer after electrodeposition has a larger current value than the air electrode layer before electrodeposition. Here, let A and B be the difference in current value at a potential of 0.22 (V vs Ag / AgCl) before and after electrodeposition. In the present invention, the sum of the absolute values of A and B is referred to as “current associated with the metal catalyst”. Furthermore, by dividing the “current associated with the metal catalyst” obtained in this way by the “specific surface area of the conductive material”, the value of “current associated with the metal catalyst per specific surface area of the conductive material” is obtained. It is done. The specific surface area of the conductive material can be measured by a nitrogen adsorption method or the like.

  In addition, the thickness of the air electrode layer in the present invention varies depending on the use of the air secondary battery, but is preferably in the range of 2 μm to 500 μm, and more preferably in the range of 5 μm to 300 μm. The method for producing the air electrode layer of the present invention will be described later in “C. Method for producing air electrode layer”.

  The air electrode layer of the present invention may be formed on an air electrode current collector. In this case, an air electrode having an air electrode current collector and the air electrode layer formed on the air electrode current collector can be provided. Thereby, an air electrode having good catalytic performance can be obtained.

  Here, the air electrode current collector performs current collection of the air electrode layer. Examples of the material for the air electrode current collector include a metal material and a carbon material. Among these, a carbon material is preferable. It is because it is excellent in corrosion resistance. As such a carbon material, it is preferable that it is a carbon fiber (carbon fiber), for example. This is because electrons can be conducted through the fiber and the electron conductivity is high. Examples of the air electrode current collector using carbon fiber include carbon cloth and carbon paper. On the other hand, examples of the metal material include stainless steel, nickel, aluminum, iron, and titanium. A metal mesh etc. can be mentioned as an air electrode electrical power collector using a metal material.

  The structure of the air electrode current collector used in the present invention is not particularly limited as long as desired electron conductivity can be ensured, and may be a porous structure having gas diffusibility, and does not have gas diffusibility. It may be a dense structure. Among them, in the present invention, the air current collector preferably has a porous structure having gas diffusibility. This is because oxygen can be diffused quickly. The porosity of the porous structure is not particularly limited, but is preferably in the range of 20% to 99%, for example. The thickness of the air electrode current collector is, for example, preferably in the range of 10 μm to 1000 μm, and more preferably in the range of 20 μm to 400 μm.

  The air electrode layer of the present invention is used for an air secondary battery. The type and the like of the air secondary battery will be described later in “B. Air secondary battery”.

B. Next, the air secondary battery of the present invention will be described. The air secondary battery of the present invention has the above-described air electrode layer.

  According to this invention, since it has the air electrode layer mentioned above, it can be set as the air secondary battery excellent in the charge / discharge characteristic.

  FIG. 3 is a schematic cross-sectional view showing an example of the air secondary battery of the present invention. The air secondary battery shown in FIG. 3 includes a negative electrode case 11a, a negative electrode current collector 12 formed on the inner bottom surface of the negative electrode case 11a, a negative electrode lead 12a connected to the negative electrode current collector 12, and a negative electrode current collector. The negative electrode layer 13 formed on the body 12 and containing a negative electrode active material, the air electrode layer 14 containing a conductive material, a metal catalyst and a binder, and the air electrode current collector for collecting the air electrode layer 14 Body 15, air electrode lead 15 a connected to air electrode current collector 15, separator 16 formed between negative electrode layer 13 and air electrode layer 14, electrolyte layer 17, and air having microporous film 18. The electrode case 11b has a packing 19 formed between the negative electrode case 11a and the air electrode case 11b. The air secondary battery of the present invention is characterized in that the air electrode layer 14 uses the one described in “A. Air electrode layer”.

  The air secondary battery of the present invention is not particularly limited as long as it has at least the air electrode layer described above, but usually has an air electrode layer, a negative electrode layer, and an electrolyte layer.

1. Air electrode layer Since the air electrode layer used in the present invention is the same as the contents described in the above-mentioned "A. Air electrode layer", description thereof is omitted here. The air secondary battery of the present invention may have an air electrode (air electrode layer and air electrode current collector).

2. Negative electrode layer The negative electrode layer used in the present invention contains at least a negative electrode active material. The negative electrode active material is not particularly limited as long as it can occlude and release metal ions, and examples thereof include simple metals, alloys, metal oxides, and metal nitrides. Examples of the metal ion include alkali metal ions such as Li ion, Na ion and K ion; alkaline earth metal ions such as Mg ion and Ca ion; amphoteric metal ions such as Al ion, among others. Alkali metal ions are preferable, and Li ions are particularly preferable. This is because a battery having a high energy density can be obtained.

  The negative electrode layer used in the present invention may contain only the negative electrode active material, or may contain at least one of a conductive material and a binder in addition to the negative electrode active material. good. For example, when the negative electrode active material is in the form of a foil, a negative electrode layer containing only the negative electrode active material can be obtained. On the other hand, when the negative electrode active material is in a powder form, for example, a negative electrode layer having a negative electrode active material, a conductive material, and a binder can be obtained. The conductive material and the binder are the same as those described in the above “A. Air electrode layer”, and thus the description thereof is omitted here. In addition, the thickness of the negative electrode layer is preferably selected as appropriate according to the configuration of the target air secondary battery.

  The negative electrode layer may be formed on the negative electrode current collector. In addition, the member which consists of a negative electrode layer and a negative electrode electrical power collector may be called a negative electrode. The material for the negative electrode current collector is not particularly limited as long as it has conductivity, and examples thereof include copper, stainless steel, and nickel. Examples of the shape of the negative electrode current collector include a foil shape, a plate shape, and a mesh (grid) shape. In addition, the thickness of the negative electrode current collector is preferably appropriately selected according to the configuration of the target air secondary battery.

  The formation method of a negative electrode will not be specifically limited if it is a method which can form the negative electrode mentioned above. As an example of a method for forming the negative electrode, a method in which a foil-like negative electrode active material is placed on a negative electrode current collector and pressurized can be exemplified. As another example of the negative electrode forming method, a negative electrode layer forming composition containing a negative electrode active material, a binder and a solvent is prepared, and then this composition is applied onto the negative electrode current collector. And a method for drying.

3. Electrolyte Layer The electrolyte layer used in the present invention is a layer formed between the air electrode layer and the negative electrode layer and responsible for conduction of metal ions. Examples of the electrolyte constituting the electrolyte layer include a liquid electrolyte (electrolyte), a gel electrolyte, a solid electrolyte, and the like. Among these, a liquid electrolyte and a gel electrolyte are preferable, and a liquid electrolyte is particularly preferable. This is because ionic conductivity is high. Further, when the electrolyte used in the present invention is a liquid electrolyte or a gel electrolyte, the solvent used may be a non-aqueous solvent or water, but in particular, it may be a non-aqueous solvent. preferable.

The type of the non-aqueous electrolyte is preferably selected as appropriate according to the type of metal ion to be conducted. For example, a non-aqueous electrolyte of a lithium air secondary battery usually contains a lithium salt and a non-aqueous solvent. Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO _4, and LiAsF ₆ ; and LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , An organic lithium salt such as LiC (CF ₃ SO ₂ ) ₃ can be used. Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), butylene carbonate, γ-butyrolactone, sulfolane, acetonitrile, Examples include 1,2-dimethoxymethane, 1,3-dimethoxypropane, diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and mixtures thereof. The nonaqueous solvent is preferably a solvent having high oxygen solubility. This is because dissolved oxygen can be used efficiently in the reaction. The concentration of the lithium salt in the non-aqueous electrolyte is, for example, in the range of 0.5 mol / L to 3 mol / L. In the present invention, a low volatile liquid such as an ionic liquid may be used as the nonaqueous electrolytic solution.

In addition, the non-aqueous gel electrolyte used in the present invention is usually a gel obtained by adding a polymer to a non-aqueous electrolyte. For example, a non-aqueous gel electrolyte of a lithium-air secondary battery is gelled by adding a polymer such as polyethylene oxide (PEO), polyacrylonitrile (PAN), or polymethyl methacrylate (PMMA) to the non-aqueous electrolyte described above. By doing so, it can be obtained. In the present _{invention, LiTFSI (LiN (CF 3 SO} 2) 2) -PEO nonaqueous gel electrolyte systems are preferred.

4). Air secondary battery The air secondary battery of the present invention preferably has a separator between the air electrode layer and the negative electrode layer. This is because a highly safe battery can be obtained. Examples of the separator include porous films such as polyethylene and polypropylene; and nonwoven fabrics such as a resin nonwoven fabric and a glass fiber nonwoven fabric.

  The air secondary battery of the present invention usually has a battery case that houses an air electrode layer, a negative electrode layer, and an electrolyte layer. Specific examples of the shape of the battery case include a coin type, a flat plate type, a cylindrical type, and a laminate type. The battery case may be an open-air battery case or a sealed battery case. As shown in FIG. 3 described above, the open-air battery case is a battery case that can come into contact with the atmosphere. On the other hand, when the battery case is a sealed battery case, it is preferable to provide a gas (air) introduction pipe and an exhaust pipe in the sealed battery case. In this case, the gas to be introduced / exhausted preferably has a high oxygen concentration, and more preferably pure oxygen. In addition, it is preferable to increase the oxygen concentration during discharging and decrease the oxygen concentration during charging.

  In addition, the type of the air secondary battery of the present invention differs depending on the type of metal ions that become conductive ions. Examples of the metal ion include alkali metal ions such as Li ion, Na ion and K ion; alkaline earth metal ions such as Mg ion and Ca ion; amphoteric metal ions such as Al ion, among others. Alkali metal ions are preferable, and Li ions are particularly preferable. This is because a battery having a high energy density can be obtained. Moreover, as an application of the air secondary battery of this invention, a vehicle mounting use, a stationary power supply use, a household power supply use etc. can be mentioned, for example.

C. Next, a method for producing an air electrode layer according to the present invention will be described. The method for producing an air electrode layer of the present invention is a method for producing an air electrode layer used in an air secondary battery, and forms a conductive material-containing layer using a conductive material-containing composition containing a conductive material. A conductive material-containing layer forming step, and an electrodeposition step of forming an air electrode layer by forming a metal catalyst on the surface of the conductive material contained in the conductive material-containing layer by an electrodeposition method. , Characterized by having.

  According to the present invention, by using the electrodeposition method, a highly dispersed metal catalyst having a large surface area can be formed, and an air electrode layer having good catalytic performance can be obtained. In particular, the air electrode layer obtained by the present invention has an advantage that the charging voltage can be effectively reduced as compared with the conventional air electrode layer. Furthermore, according to the present invention, since the metal catalyst is formed by the electrolytic method, the metal catalyst can be formed by a simple method as compared with the case where the conventional laser ablation method described above is used.

FIG. 4 is a schematic cross-sectional view showing an example of the method for producing an air electrode layer of the present invention. In FIG. 4, first, an air electrode current collector 15 is prepared (FIG. 4A). Next, a conductive material-containing layer 14a is formed by applying a conductive material-containing composition containing a conductive material and a binder to the air electrode current collector 15 and drying it (FIG. 4). (B)). Next, the air electrode layer 14 is obtained by forming a metal catalyst on the surface of the conductive material contained in the conductive material-containing layer 14a by an electrodeposition method (FIG. 4C). FIG. 4 shows a manufacturing method of the “air electrode layer”. Strictly speaking, since the air electrode layer 14 is formed on the air electrode current collector 15, the “air electrode” A manufacturing method is shown. Thus, when the board | substrate which apply | coats an electroconductive material containing composition is an air electrode electrical power collector, it can also be considered as the manufacturing method of an air electrode.
Hereafter, the manufacturing method of the air electrode layer of this invention is demonstrated for every process.

1. Conductive material-containing layer forming step The conductive material-containing layer forming step in the present invention is a step of forming a conductive material-containing layer using a conductive material-containing composition containing a conductive material.

  The conductive material-containing composition contains at least a conductive material, and further contains a binder and a solvent as necessary. The conductive material and the binder are the same as those described in “A. Air electrode layer”. On the other hand, the solvent is preferably one that disperses and dissolves a conductive material or a binder and is easily removed by drying. For example, acetone, N-methyl-2-pyrrolidone (NMP), N, Examples thereof include N-dimethylacetamide (DMA), N, N-dimethylformamide (DMF), methyl ethyl ketone (MEK), and tetrahydrofuran (THF). Further, the solid content concentration of the conductive material-containing composition is, for example, preferably in the range of 5% to 50%, and more preferably in the range of 10% to 20%.

  In the present invention, the substrate on which the conductive material-containing composition is applied is preferably an air electrode current collector. This is because the manufacturing process of the air secondary battery can be simplified. The air electrode current collector is the same as that described in “A. Air electrode layer” above. In addition, as a method for applying the conductive material-containing composition to the substrate, a general application method can be used, for example, a doctor blade method or the like.

2. Electrodeposition process Next, the electrodeposition process in the present invention will be described. The electrodeposition step in the present invention is a step of forming an air electrode layer by forming a metal catalyst on the surface of the conductive material contained in the conductive material-containing layer by an electrodeposition method.

  In the present invention, the electrodeposition is usually performed in a state where the conductive material-containing layer is immersed in an electrolytic solution. Furthermore, the electrolytic solution used for electrodeposition contains at least a metal source having the same metal element as the target metal catalyst and a solvent. When obtaining a manganese oxide as a metal catalyst, examples of the metal source include manganese acetate. On the other hand, examples of the solvent include water. The concentration of the metal source in the electrolytic solution is preferably in the range of 0.01 mol / L to 1 mol / L, for example. Moreover, when obtaining a metal oxide as a metal catalyst, it is preferable that electrolyte solution contains additives, such as sodium sulfate. The concentration of the additive in the electrolytic solution is preferably in the range of 0.01 mol / L to 1 mol / L, for example.

  In the present invention, electrodeposition may be performed with a constant current, or may be performed while changing the current. In the present invention, the metal catalyst may be deposited by cyclic voltammetry as shown in the examples described later.

  In addition, it is preferable to select the time for performing electrodeposition appropriately according to the thickness of the target metal catalyst. Moreover, the composition of the metal catalyst obtained in the electrodeposition step can be adjusted by appropriately setting the composition of the electrolytic solution, the current density, and the like at the time of electrodeposition. Furthermore, in the present invention, it is preferable to perform electrodeposition to such an extent that the air electrode layer described in “A. Air electrode layer” is obtained.

3. Others The method for producing an air electrode layer of the present invention may include a washing step and a drying step as necessary after the electrodeposition step. Moreover, in this invention, the manufacturing method of the air secondary battery characterized by using the obtained air electrode layer can be provided. Thereby, for example, an air secondary battery with a reduced charging voltage is obtained. About the formation method of members other than an air electrode layer, and the assembly method of a battery, it is the same as that of the manufacturing method of a general air secondary battery. Moreover, in this invention, the air electrode layer characterized by being obtained by the electroconductive material content layer formation process and electrodeposition process which were mentioned above can also be provided.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
First, 1 g of ketjen black (manufactured by ketjen black international) and 1.5 g of PVDF polymer (manufactured by Kureha) are mixed, and NMP (N-methylpyrrolidone, manufactured by Kanto Chemical Co., Inc.) is added thereto and kneaded. The mixture was stirred at 2000 rpm for 30 minutes with a machine to obtain a conductive material-containing composition. Thereafter, the conductive material-containing composition is formed on a carbon paper (air electrode current collector, manufactured by Toray Industries, Inc., TGP-H-090, thickness 0.28 mm) so as to have a thickness of 100 μm by a doctor blade method. Applied. Next, drying was performed at 80 ° C. for 1 hour to obtain a conductive material-containing layer.

Next, electrodeposition by CV was performed under the following conditions to form manganese dioxide on the surface of the conductive material.
<Electrodeposition conditions>
Electrolytic solution: 0.1 M sodium sulfate aqueous solution + 0.05 M manganese acetate aqueous solution Working electrode: conductive material containing layer Counter electrode: Pt wire Reference electrode: silver / silver chloride electrode Potential range: 0 to 0.4 (V vs Ag / AgCl)
・ Sweep speed: 20mV / S
・ Number of cycles: 5 cycles

  Thereafter, drying at 80 ° C. for 1 hour and vacuum drying at 60 ° C. for 1 day were performed. Finally, punching was performed at φ18 mm to obtain an air electrode having an air electrode current collector and an air electrode layer.

[Examples 2 to 6]
An air electrode was obtained in the same manner as in Example 1 except that the number of cycles of cyclic voltammetry was changed to 10 cycles, 25 cycles, 40 cycles, 45 cycles, and 50 cycles, respectively.

[Comparative Example 1]
First, 1 g of ketjen black (manufactured by ketjen black international), 1.9 g of electrolytic manganese dioxide (average particle size: 60 μm, manufactured by High Purity Chemical Laboratory), and 1.5 g of PVDF polymer (manufactured by Kureha) are mixed. NMP (N-methylpyrrolidone, manufactured by Kanto Chemical Co., Inc.) was added thereto, and the mixture was stirred with a kneader at 2000 rpm for 30 minutes to obtain a composition for forming an air electrode layer. Thereafter, the composition for forming the air electrode layer is formed on carbon paper (air electrode current collector, manufactured by Toray Industries, Inc., TGP-H-090, thickness 0.28 mm) to a thickness of 100 μm by the doctor blade method. It was applied to. Next, drying at 80 ° C. for 1 hour and vacuum drying at 60 ° C. for 1 day were performed. Finally, punching was performed at φ18 mm to obtain an air electrode having an air electrode current collector and an air electrode layer.

[Comparative Example 2]
An air electrode was obtained in the same manner as in Example 1 except that electrodeposition was not performed.

[Evaluation]
The following evaluation was performed using the air electrode obtained in Examples 1 to 6 and Comparative Examples 1 and 2.

(1) SEM Observation Using the air electrode obtained in Example 1 and Comparative Example 1, the surfaces of these air electrode layers were observed by SEM. The result is shown in FIG. 5A is an SEM photograph of the air electrode layer of Comparative Example 1, and FIG. 5B is an SEM photograph of the air electrode layer of Example 1. FIG. As shown in FIG. 5A, particulate manganese dioxide was confirmed in the air electrode layer of Comparative Example 1. On the other hand, as shown in FIG. 5B, in the air electrode layer of Example 1, manganese dioxide dispersed in a mesh shape was confirmed. Furthermore, this manganese dioxide had an acicular structure. Thus, it was confirmed that by using the electrodeposition method, a highly dispersed metal catalyst having a large surface area can be formed on the surface of the conductive material.

(2) Charging voltage reduction effect Using the air electrodes obtained in Examples 1 to 6 and Comparative Examples 1 and 2, the charging voltage reduction effect was evaluated. First, the above-described CV test was performed on the air electrode layers of Examples 1 to 6, and “the current associated with the metal catalyst per specific surface area of the conductive material” was calculated.

Next, an air secondary battery element was produced using the air electrode obtained in Examples 1 to 6 and Comparative Examples 1 and 2 (see FIG. 6). All the elements were assembled in an argon box (dew point -40 ° C. or lower). Here, the air secondary battery element 30 includes cases 21a and 21b made of Teflon (registered trademark) and a case 21c made of SUS. Note that the case 21b and the case 21c are joined by a bolt 22. Further, the case 21a has an opening for supplying oxygen, and a hollow current extraction portion 23 is provided in the opening. Further, the air electrode obtained by the above method is used for the air electrode 24, and the non-aqueous electrolyte solution obtained by dissolving LiClO ₄ in propylene carbonate (PC) at a concentration of 1M is used for the non-aqueous electrolyte solution 25. For the layer 26, metallic lithium (manufactured by Kyokuto Metals Co., Ltd., thickness 200 μm, diameter 16 mm) was used.

  Next, an evaluation cell was manufactured using the obtained air secondary battery element (see FIG. 6). The air electrode lead 33 was connected to the current extraction part 23 made of SUS, the negative electrode lead 35 was connected to the case 21c made of SUS, and the air secondary battery element 30 was housed in a glass container 31 having a capacity of 1000 cc. Thereafter, the glass container 31 was sealed, and the sealed glass container 31 was taken out from the argon box. Next, oxygen was introduced from the oxygen gas cylinder through the gas introduction part 32, and at the same time, the gas exhaust part 34 was evacuated to replace the inside of the glass container with an oxygen atmosphere at atmospheric pressure from an argon atmosphere. Thereby, the cell for evaluation was obtained.

  Next, the charging cell reduction effect was evaluated using the obtained evaluation cell. Here, the effect of reducing the charging voltage with respect to the evaluation cell of Comparative Example 2 (the cell including the air electrode layer not having manganese dioxide) was evaluated. Specifically, the voltage values when the charging voltage was stabilized were compared.

  FIG. 7 is a graph showing the relationship between the current accompanying the metal catalyst per specific surface area of the conductive material and the effect of reducing the charging voltage. As shown in FIG. 7, in Examples 1-6, it was confirmed that the charge voltage reduction effect is excellent. Although not shown, the effect of reducing the charging voltage of the evaluation cell of Comparative Example 1 (the cell provided with the air electrode layer having particulate manganese dioxide) was about 0.49V. On the other hand, it was confirmed that the evaluation cells of Examples 1 to 6 have a reduction effect equal to or higher than that of the evaluation cell of Comparative Example 1.

DESCRIPTION OF SYMBOLS 1 ... Air electrode layer 2 ... Conductive material 3 ... Metal catalyst 11a ... Negative electrode case 11b ... Air electrode case 12 ... Negative electrode current collector 12a ... Negative electrode lead 13 ... Negative electrode layer 14 ... Air electrode layer 15 ... Air electrode current collector 15a ... Air electrode lead 16 ... Separator 17 ... Electrolyte layer 18 ... Microporous film 19 ... Packing

Claims (6)

  An air electrode layer used for an air secondary battery, comprising an electroconductive material and a metal catalyst formed on the surface of the electroconductive material by an electrodeposition method.   The air electrode layer according to claim 1, wherein the metal catalyst is dispersed in a network. The current associated with the metal catalyst per specific surface area of the conductive material, 250μA / cm ² ~800μA / wherein the cm is within ² ranges claim 1 or the air electrode layer according to claim 2.   The air electrode layer according to any one of claims 1 to 3, wherein the metal catalyst is a manganese oxide.   An air secondary battery comprising the air electrode layer according to any one of claims 1 to 4. A method for producing an air electrode layer used in an air secondary battery,
A conductive material-containing layer forming step of forming a conductive material-containing layer using a conductive material-containing composition containing a conductive material;
An electrodeposition step of forming an air electrode layer by forming a metal catalyst on the surface of the conductive material contained in the conductive material-containing layer by an electrodeposition method;
The manufacturing method of the air electrode layer characterized by having.