Channel-integrated positive electrode for metal secondary battery, manufacturing method thereof, and metal secondary battery

Abstract

To provide a metal secondary battery capable of bringing out a volume energy density and a weight energy density which can be expected as a metal secondary battery, specifically as a lithium air battery stack cell, more sufficiently than conventional one.SOLUTION: According to the present invention, there is provided a channel-integrated positive electrode for a metal secondary battery, which includes: a gas diffusion channel layer of a porous layer, comprising a fibrous carbon material; and two positive electrode layers of a porous layer, comprising a fibrous carbon material that is the same as or different from the carbon material, the two positive electrode layers being provided on both surfaces of the gas diffusion channel layer, respectively. A part of the channel layer includes hollow pores that are developed by entanglement of the fibrous carbon material in the channel layer and the fibrous carbon material of the two positive electrode layers that enters the channel layer, and the channel layer and the two positive electrode layers are integrated by the pores.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a flow path-integrated positive electrode for a metal secondary battery, a method for producing the same, and a metal secondary battery including the positive electrode. [Background technology]

[0002] In recent years, the spread of renewable energy and the demand for electrified automobiles have led to a demand for the development of lightweight, large-capacity storage batteries, i.e., batteries with higher energy density. Among the storage batteries (also called secondary batteries) currently under development, the lithium-air battery, which is a metal secondary battery, has the highest theoretical energy density, and is expected to be realized as a storage battery with an energy density that significantly exceeds that of the currently popular lithium-ion batteries.

[0003] Lithium-air batteries use lithium metal as the negative electrode active material and atmospheric oxygen as the positive electrode active material. When discharging, lithium metal dissolves from the negative electrode, and reacts with oxygen absorbed from the air at the positive electrode to precipitate lithium peroxide. When charging, the reverse reaction occurs, and these steps are repeated to charge and discharge the battery. This charging and discharging process can be expressed as a chemical reaction equation: JPEG2025072802000001.jpg1137 At the positive electrode, JPEG2025072802000002.jpg1166 Here, the positive electrode is also called the air electrode because it is an electrode that has the function of absorbing and releasing atmospheric oxygen as the battery is discharged and charged.

[0004] In order to improve the discharge characteristics of a lithium-air battery in the atmosphere by improving the output and capacity of the lithium-air battery (i.e., increasing the output and capacity of the lithium-air battery), the above-mentioned oxygen reduction reaction at the positive electrode: JPEG2025072802000003.jpg1166 It is necessary to proceed with the oxygen reduction reaction at high speed and in large quantities. The speed and amount of the reaction are greatly influenced by the material constituting the positive electrode and the pore size distribution structure. Therefore, the development of a positive electrode that can accelerate the positive electrode reaction and increase the capacity is extremely important for increasing the power output and capacity of lithium-air batteries.

[0005] Therefore, in the past, positive electrodes with high porosity to facilitate oxygen gas absorption and positive electrodes with a large specific surface area that can provide a large amount of battery reaction interfaces have been developed to increase the output and capacity of lithium-air batteries.

[0006] For example, Patent Document 1 reports that it is possible to increase the output of a lithium-air battery by providing a highly porous sheet-like air battery positive electrode that uses wavy fibrous carbon.

[0007] Furthermore, Patent Document 2 reports that a gas diffusion layer (specifically, a layer that supplies air or oxygen gas) made of carbon fiber, which is lighter than a thin metal film, has been used as a gas diffusion flow path layer in a lithium-air battery stack cell (i.e., a stacked lithium-air battery), and a carbon nanotube positive electrode for metal secondary batteries has been developed in which the carbon nanotube positive electrode layer and the gas diffusion layer (i.e., the gas diffusion flow path layer) are composited and integrated.

[0008] Also, Patent Document 3 reports that a positive electrode layer using a fibrous carbon material and a gas diffusion flow path layer (specifically, a layer supplying air or oxygen gas) are integrated, thereby enabling a lithium-air battery stack cell (i.e., a laminated lithium-air battery) to have high output and large capacity. Specifically, it is reported that a positive electrode layer using a fibrous carbon material is deeply penetrated into a gas diffusion flow path layer side using the same or a different fibrous carbon material, thereby eliminating a clear boundary (i.e., discontinuous pore size distribution) between the macroscopic pore size distribution provided by the gas diffusion flow path layer and the microscopic pore size distribution provided by the positive electrode layer, thereby forming a continuous pore size distribution (specifically, a continuous pore size distribution of 10 nm to 200 μm), thereby enabling a lithium-air battery stack cell to have high output and large capacity. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2022 / 158376 [Patent Document 2] Patent Publication No. 2021-2437 [Patent Document 3] Patent application No. 2022-102125 Summary of the Invention [Problem to be solved by the invention]

[0010] Incidentally, in the present application, "integrated" or "integral type" means that, as described below, hollow pores are formed by entanglement of a fibrous carbon material in a gas diffusion flow path layer (specifically, a layer supplying air or oxygen gas) and a fibrous carbon material in a positive electrode layer that penetrates into the gas diffusion flow path layer, the pores have a continuous pore size distribution, and the flow path layer and the positive electrode layer are structurally integrated due to the continuous pore size distribution.

[0011] In this application, batteries that can be charged and used repeatedly, such as lithium-air batteries, are referred to as "storage batteries" or "secondary batteries," and among them, those that use a metal as the negative electrode active material and an external gas such as oxygen or carbon dioxide as the positive electrode active material are referred to as "metal secondary batteries."

[0012] The air battery positive electrode described in Patent Document 1 is a positive electrode sheet made by processing a highly porous positive electrode using wavy fibrous carbon into a sheet, and does not have a structure in which the positive electrode layer and the gas diffusion flow path layer are integrated. In fact, Patent Document 1 uses a positive electrode sheet in contact with a metal mesh that has a flow path function through which air or oxygen passes.

[0013] Therefore, according to the positive electrode for air batteries described in Patent Document 1, since a metal mesh, which is generally heavy, is used, there is a problem that when the positive electrode is used to fabricate a lithium-air battery stack cell (i.e., a laminated lithium-air battery), which is a metal secondary battery, the weight energy density is significantly reduced compared to the weight energy density of a non-laminated single battery (single cell). Therefore, when the positive electrode for air batteries described in Patent Document 1 is used to fabricate, for example, a lithium-air battery stack cell, there is a problem that the fabricated stack cell cannot be expected to have a high output and a large capacity. In addition, since the positive electrode layer and the gas diffusion flow path layer are not integrated, in stack design (lamination design) for metal secondary batteries, it is necessary to stack many members with high precision in the order of the gas diffusion flow path layer, the positive electrode layer, the separator, the negative electrode layer, and the current collector, which also causes a problem that the process becomes complicated.

[0014] The positive electrode for metal secondary batteries described in Patent Documents 2 and 3 is one in which a positive electrode layer is fixed to only one side of one gas diffusion flow path layer and integrated. Therefore, the positive electrode for metal secondary batteries described in Patent Documents 2 and 3 is a laminate in which one gas diffusion flow path layer and one positive electrode layer are paired and integrated. In the laminate design described in Patent Documents 2 and 3, the laminate (also referred to as a positive electrode laminate in the present application) is laminated so that the gas diffusion flow path layers face each other to form a unit (also referred to as a positive electrode unit in the present application), and a plurality of (two or more) positive electrode units are laminated to produce, for example, a lithium-air battery stack cell (i.e., a stacked lithium-air battery) as a metal secondary battery. Here, an example of the structure of the battery in the case of producing a lithium-air battery stack cell using the positive electrode for metal secondary batteries described in Patent Documents 2 and 3 is shown as a cross-sectional view in FIG. 1(A).

[0015] As shown in FIG. 1(A), when a lithium-air battery stack cell is produced using the positive electrode for a metal secondary battery described in Patent Documents 2 and 3, two positive electrode laminates are used for one positive electrode unit. In this case, two positive electrode layers and two gas diffusion flow path layers are inserted into one positive electrode unit. Therefore, in a lithium-air battery stack cell produced by stacking a plurality of such positive electrode units, the thickness and weight of the positive electrode of the cell are significantly increased, which is a factor that reduces the volumetric energy density and weight energy density of the lithium-air battery stack cell. Therefore, there is a problem that a further improvement in the volumetric energy density and weight energy density of the lithium-air battery stack cell produced using the positive electrode for a metal secondary battery described in Patent Documents 2 and 3 is desired. From this perspective, there is a current situation in which a new positive electrode for a metal secondary battery different from the conventional positive electrodes described in Patent Documents 2 and 3 is still desired as a positive electrode for a metal secondary battery.

[0016] On the other hand, if a positive electrode unit in which a gas diffusion flow layer and a positive electrode layer fixed to both sides of the gas diffusion flow layer are integrated can be produced, when the positive electrode unit is used to produce, for example, a lithium-air battery stack cell (i.e., a laminated lithium-air battery) as a metal secondary battery, the cell will have a structure showing a cross section shown in FIG. 1(B). According to the lithium-air battery stack cell shown in FIG. 1(B), one gas diffusion flow layer is reduced in the positive electrode unit compared to the lithium-air battery stack cell shown in FIG. 1(A) produced using the conventional positive electrode described in Patent Documents 2 and 3. Then, the thickness and weight of the positive electrode unit (i.e., a positive electrode in which a gas diffusion flow layer and a positive electrode layer fixed to both sides of the gas diffusion flow layer are integrated) are smaller than the thickness and weight of the conventional positive electrode unit described in Patent Documents 2 and 3. Therefore, if a positive electrode unit in which a gas diffusion flow path layer and positive electrode layers fixed to both sides of the gas diffusion flow path layer are integrated can be produced, the volumetric energy density and weight energy density of a metal secondary battery using the positive electrode unit are expected to be greater than the volumetric energy density and weight energy density of a metal secondary battery using the conventional positive electrode unit described in Patent Documents 2 and 3. In particular, when a stack cell such as a lithium-air battery stack cell is produced as a metal secondary battery by stacking a plurality of positive electrode units, the thickness and weight of the positive electrode of the metal secondary battery also increase as the number of stacked positive electrode units increases, so that the reduction in thickness and weight due to the above-mentioned positive electrode unit has a large effect on improving the volumetric energy density and weight energy density of the metal secondary battery. For example, the thickness and weight of the positive electrode of a lithium-air battery stack cell produced by stacking multiple positive electrode units each of which is an integrated positive electrode having a gas diffusion flow path layer and a positive electrode layer fixed to each side of the gas diffusion flow path layer, is significantly reduced compared to the thickness and weight of the positive electrode of a lithium-air battery stack cell produced by stacking the same number of conventional positive electrode units described in Patent Documents 2 and 3.As a result, it is possible to further improve the volumetric energy density and weight energy density of the lithium-air battery stack cell, and it is expected that the volumetric energy density and weight energy density that can be expected from the lithium-air battery stack cell can be fully achieved more than ever before. Furthermore, due to the reduction in thickness and weight caused by the above-mentioned positive electrode unit, when a stack cell such as a lithium-air battery stack cell is produced as a metal secondary battery, it is expected that the metal secondary battery can be made lighter and smaller.

[0017] However, as far as the applicant knows, there are no positive electrode units in which a gas diffusion channel layer and a positive electrode layer fixed on the gas diffusion channel layer are integrated, such as positive electrodes in which a gas diffusion channel layer and positive electrode layers fixed on both sides of the gas diffusion channel layer are integrated, or metal secondary batteries such as lithium-air battery stack cells (i.e., stacked lithium-air batteries) that can be charged and discharged using the positive electrode. In addition, as described in Patent Documents 2 and 3, the conventional method of fixing and integrating a gas diffusion channel layer and a positive electrode layer provides a positive electrode unit by stacking one gas diffusion channel layer and one gas diffusion channel layer with a positive electrode layer fixed only on one side of the gas diffusion channel layer, so that the gas diffusion channel layers face each other, which is a problem that the method cannot be applied as is. [Means for solving the problem]

[0018] As a result of intensive research into the above problems, the inventors have discovered, for the first time, a method for producing a positive electrode in which a gas diffusion flow path layer and positive electrode layers fixed to both sides of the gas diffusion flow path layer are integrated together, thereby completing the present invention.

[0019] Specifically, the present invention has the following aspects [1] to

[15] .

[0020] [1] A gas diffusion flow path layer made of a porous layer of a fibrous carbon material, and two positive electrode layers made of a porous layer of a fibrous carbon material that is the same as or different from the carbon material, The two positive electrode layers are provided on both sides of the gas diffusion flow path layer, a portion of the flow path layer includes hollow pores that are generated by entanglement of a fibrous carbon material in the flow path layer and a fibrous carbon material of each of the two positive electrode layers that penetrates into the flow path layer; The flow path layer and the two positive electrode layers are integrated by the pores. Positive electrode with integrated flow channel for metal secondary batteries. [2] The flow path-integrated positive electrode for a metal secondary battery according to [1], wherein the pores have a continuous pore size distribution of 10 nm or more and 200 μm or less. [3] The flow path-integrated positive electrode for a metal secondary battery according to [1] or [2], wherein at least a part of the fibrous carbon material of each of the two positive electrode layers penetrates into the flow path layer to a thickness of 5 μm or more from an outermost surface of the flow path layer. [4] The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to [3], wherein the hollow pores have a continuous pore size distribution of 10 μm or more and 50 μm or less. [5] The hollow pores have a pore volume of 0.5 cm per gram weight of the two positive electrode layers. 3 / g or more 5.0cm 3 / g or less. [6] The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to [5], wherein the flow path layer immediately before where the fibrous carbon material of the two positive electrode layers enters the flow path layer has a thickness of 50 μm or more and 1000 μm or less. [7] The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to [6], wherein the fibrous carbon material is a carbon fiber and / or a carbon nanotube. [8] The BET specific surface area per gram weight of the two positive electrode layers is 250 m 2 / g or more 1400m 2 The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to [7], wherein the positive electrode has a BET specific surface area of ​​0.1 μm or less; The pores having a pore size distribution of 0.1 μm to 10 μm are 1.0 cm 3 in terms of pore volume per gram weight of the two positive electrode layers.3 / g or more 10.0cm 3 / g or less. [9] The flow-path-integrated positive electrode for a metal secondary battery according to any one of [1] to [8], wherein the pore size distribution of each of the two positive electrode layers and the pore volume per gram weight of each of the two positive electrode layers are approximately the same.

[10] The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to [9], wherein the peel strength between each of the two positive electrode layers and the flow path layer is 1 mN / 5 mm or more in a 90-degree peel test.

[11] A current collector is provided in the flow path layer, The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to

[10] , wherein the current collector is a metal wire material or a metal foil material.

[12] The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to

[11] , wherein, when the contact surfaces with the two positive electrode layers on both sides of the flow path layer are defined as the surfaces of the flow path layer, the area of ​​the current collector as viewed through the surfaces is 15% or less of the area of ​​the surfaces.

[13] The flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to

[12] , wherein at least one of the two positive electrode layers has at least one slit groove.

[14] A metal secondary battery, wherein the positive electrode is the flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to

[13] .

[15] A dispersion in which a fibrous carbon material is dispersed in a solvent as a raw material for the positive electrode layer of the porous layer; a porous substrate made of a fibrous carbon material as a gas diffusion flow path layer of the porous layer; and a step of filtering the dispersion on the porous substrate, laminating the carbon material dispersed in the dispersion on one side of the flow path layer, and drying the laminated porous substrate to fix a first positive electrode layer and integrate it with the flow path layer; a step of turning over the flow path layer on which the positive electrode layer has been formed, stacking the carbon material dispersed in the dispersion liquid on the other side of the flow path layer, and drying the stacked porous substrate to fix the second positive electrode layer and integrate it with the flow path layer; Including, The method for producing a flow path-integrated positive electrode for a metal secondary battery according to any one of [1] to

[13] . Effect of the Invention

[0021] According to the present invention, a new metal secondary battery positive electrode different from conventional positive electrodes can be provided as a metal secondary battery positive electrode. Specifically, a positive electrode in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated (i.e., a flow path integrated positive electrode for a metal secondary battery) and a manufacturing method thereof can be provided. Therefore, according to the flow path integrated positive electrode for a metal secondary battery provided by the present invention, a gas diffusion flow path layer for supplying oxygen gas required as a positive electrode for a metal secondary battery and a positive electrode layer are integrated to form a positive electrode, so that a stack design in a metal secondary battery can be performed more simply and accurately than a conventional stack design in which a gas diffusion flow path layer and a positive electrode layer are individually laminated.

[0022] Alternatively, according to the present invention, in a metal secondary battery, a positive electrode in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated (i.e., a flow path integrated positive electrode for a metal secondary battery) is used as a positive electrode unit, thereby providing a new metal secondary battery different from conventional metal secondary batteries. In this case, a positive electrode in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated can be provided as a positive electrode unit (see FIG. 1(B)). Compared with the case of using a conventional positive electrode unit (see FIG. 1(A)) described in Patent Documents 2 and 3, which uses a positive electrode in which a positive electrode layer is fixed to only one side of a single gas diffusion flow path layer and integrated, one gas diffusion flow path layer can be reduced per positive electrode unit. Therefore, the volumetric energy density and weight energy density of the metal secondary battery provided by the present invention can be improved compared to the volumetric energy density and weight energy density of the metal secondary battery using the conventional positive electrode unit described in Patent Documents 2 and 3. A specific example of this point will be described below.

[0023] For example, when a metal secondary battery of a lithium-air battery stack cell (i.e., a stacked lithium-air battery) is produced by stacking a plurality (two or more) of metal secondary battery flow path integrated positive electrodes provided by the present invention as positive electrode units, the same number of positive electrode units as in the lithium-air battery stack cell produced by stacking the same number of conventional positive electrode units described in Patent Documents 2 and 3 can be provided, so that the same battery capacity can be provided. In this case, as described above, according to the metal secondary battery flow path integrated positive electrode provided by the present invention, compared with the conventional positive electrode unit, it is possible to reduce the gas diffusion flow path layer by one per positive electrode unit, so that the weight and thickness of the positive electrode unit can be reduced and discharged. As a result, according to the lithium-air battery stack cell produced by stacking a plurality of metal secondary battery flow path integrated positive electrodes provided by the present invention, the thickness and weight of the positive electrode can be greatly reduced and discharged compared with the lithium-air battery stack cell produced using the conventional positive electrode unit, so that the volumetric energy density and weight energy density of the lithium-air battery stack cell can be further improved, and the volumetric energy density and weight energy density that can be expected as a lithium-air battery stack cell can be fully brought out more than before.

[0024] Alternatively, according to the present invention, as the current collector (also referred to as "positive electrode current collector" in the present application) in the flow path integrated positive electrode for a metal secondary battery, a metal wire material (so-called metal wire wire) or a metal foil material (so-called ribbon-shaped (with width) metal foil material) having a weight smaller than that of a conventional conductive foil material (e.g., carbon paper) or a metal wire material or a metal foil material having a size (thickness, thickness, or width) smaller than that of a conventional metal wire material or metal foil material can be used, and a method for using the same can be provided. Therefore, the weight of a positive electrode having a positive electrode current collector and a metal secondary battery using the positive electrode can be further reduced. As a result, according to the present invention, the weight energy density of a metal secondary battery using a positive electrode having a positive electrode current collector can be improved to be higher than the weight energy density of a metal secondary battery using a positive electrode having a conventional conductive foil material as a positive electrode current collector.

[0025] Alternatively, according to the present invention, a method for manufacturing a positive electrode (i.e., a flow path integrated positive electrode for a metal secondary battery) in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated can be provided. In this case, it is also possible to provide a gas diffusion flow path layer including a current collector at the same time. The size of the metal material used as the current collector included in the gas diffusion flow path layer is set so that the area occupied by the surface on which the dispersion liquid of the positive electrode material made of fibrous carbon for preparing the positive electrode layer is filtered on the material made of fibrous carbon that becomes the gas diffusion flow path layer is sufficiently small, making it possible to perform a filtering operation, and the filtering operation allows the positive electrode layers to be reliably fixed to both sides of the gas diffusion flow path layer including the current collector for integration.

[0026] Alternatively, according to the present invention, a flow path-integrated positive electrode for a metal secondary battery can be provided, which has a slit-groove-shaped gas inlet. This allows gas to be introduced into the center of the positive electrode, and the discharge capacity (particularly the discharge capacity at a high discharge current) can be increased according to the area of ​​the positive electrode layer, improving the output characteristics. As a result, the weight and volumetric energy density of the metal secondary battery can be further improved. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram showing an example of the structure of a lithium-air battery stack cell (i.e., a stacked lithium-air battery) and a cross-section of the structure of a positive electrode unit constituting the cell (here, FIG. 1(A) shows an example of the structure of a lithium-air battery stack cell prepared using a positive electrode for a conventional metal secondary battery (a positive electrode integrated with a flow path for a metal secondary battery) and a cross-section of the structure of a positive electrode unit constituting the cell. FIG. 1(B) shows an example of the structure of a lithium-air battery stack cell prepared using a positive electrode integrated with a flow path for a metal secondary battery, which is one embodiment of the present invention, and a cross-section of the structure of a positive electrode unit constituting the battery). [Diagram 2] FIG. 2 is a schematic diagram showing a process for producing a flow path-integrated positive electrode for a metal secondary battery according to one embodiment of the present invention. [Diagram 3]FIG. 3 is a schematic diagram showing a manufacturing process of a flow path-integrated positive electrode for a metal secondary battery, which includes a metal wire as a positive electrode current collector, according to one embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing the cross section of the structure of various positive electrode units produced in this example (here, the positive electrode unit shown as "positive electrode unit example 1" is a simple laminate in which a gas diffusion flow path layer (carbon paper (CP)) is placed on a positive electrode layer made of CNT, and a positive electrode layer made of CNT is further placed on the carbon paper (CP). The positive electrode units shown as "positive electrode unit examples 2 and 8" are positive electrode units formed by laminating one laminate in which a positive electrode layer is fixed to only one side (one side) of one gas diffusion flow path layer and integrated, with the gas diffusion flow path layers facing each other. The positive electrode units shown as "positive electrode unit examples 3-7 and 9" are positive electrodes according to one embodiment of the present invention (i.e., flow path-integrated positive electrodes for metal secondary batteries in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated).). [Diagram 5] FIG. 5 is a diagram showing a scanning electron microscope image of a cross section of “Positive electrode unit example 3” which is a specific embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing the results of measuring the pore size distribution of "Positive electrode unit example 3", which is a specific embodiment of the present invention, and the pore size distributions of "Positive electrode unit example 1" and "Positive electrode unit example 2", which are comparative examples, by mercury porosimetry. [Figure 7] FIG. 7 shows an example of a configuration diagram of a lithium-air battery stack cell produced using a positive electrode unit that is a specific embodiment of the present invention (here, FIG. 7(A) shows a configuration diagram when current is collected from carbon paper (CP), which is a conductive gas diffusion flow path layer in the center of the positive electrode unit, and FIG. 7(B) shows a configuration diagram when current is collected from a metal wire sewn into the carbon paper (CP), which is a gas diffusion flow path layer in the center of the positive electrode unit). [Figure 8]FIG. 8 is a schematic diagram showing the configuration of each positive electrode unit used in each of the lithium-air battery stack cells of "Cell Example 17", "Cell Example 30", and "Cell Example 31" shown in Table 8 (here, the left figure is a schematic diagram showing the configuration of "Positive electrode unit example 3" which does not have a slit groove and is used in "Cell example 17". The center figure is a schematic diagram showing the configuration of "Positive electrode unit example 10" which has a slit groove and is used in "Cell example 30". The right figure is a schematic diagram showing the configuration of "Positive electrode unit example 11" which has a slit groove and is used in "Cell example 31", and in which the bottom surface of the slit groove has been removed to expose the gas diffusion flow path layer). [Figure 9] FIG. 9 is a diagram showing the relationship between the current and the discharge capacity of various lithium-air battery stack cells, namely, “Cell Example 17”, “Cell Example 30”, and “Cell Example 31” shown in Table 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, the embodiments for carrying out the present invention will be described in detail. However, it should be noted that the present invention is not limited to the following embodiments, and can be carried out in various modifications within the scope of the gist of the present invention. For example, in order to facilitate understanding of the present invention, the metal secondary battery may be described as a lithium-air battery. However, it should be noted that the use of the flow path-integrated positive electrode for a metal secondary battery of the present invention is not limited to a positive electrode for a lithium-air battery, and can also be applied as a positive electrode for a battery (so-called open-type battery) equipped with a positive electrode having a mechanism for absorbing and discharging external gas.

[0029] As described above, a "channel-integrated positive electrode for a metal secondary battery" (hereinafter also referred to as "the positive electrode of the present invention") according to one embodiment of the present invention is a channel-integrated positive electrode for a metal secondary battery, which includes a gas diffusion channel layer which is a porous layer made of a fibrous carbon material, and two positive electrode layers which are porous layers made of a fibrous carbon material that is the same as or different from the carbon material, and the two positive electrode layers are provided one on each side of the gas diffusion channel layer, and a part of the channel layer includes hollow pores which are generated by entanglement of the fibrous carbon material in the channel layer and the fibrous carbon materials of the two positive electrode layers which enter the channel layer, and the channel layer and the two positive electrode layers are integrated by the pores.

[0030] The "gas diffusion flow path layer" constituting the positive electrode of the present invention may be provided with a gas diffusion mechanism capable of absorbing and discharging external gases such as oxygen and carbon dioxide in a metal secondary battery, and the flow path layer is a porous layer made of a fibrous carbon material. The fibrous carbon material is not particularly limited as long as it is used as a material for a gas diffusion layer in a metal secondary battery (for example, an air battery such as a lithium-air battery or a fuel cell), and examples of the fibrous carbon material include carbon fiber, carbon nanotube, and graphitized carbon fiber. These may also be combined, and for example, carbon fiber and carbon nanotube may be used in combination. Typically, it is preferable to use carbon fiber and / or carbon nanotube, and it is more preferable to use carbon fiber.

[0031] Here, the gas diffusion channel layer constituting the positive electrode of the present invention is a porous layer made of a fibrous carbon material. The gas diffusion channel layer becomes a porous layer due to the voids of the fibrous carbon material. Here, the lower limit of the porosity of the fibrous carbon material is preferably 85% or more, more preferably 90% or more. From the viewpoint of ensuring the physical strength of the gas diffusion channel layer, the upper limit of the porosity is preferably 99.5% or less, more preferably 98.5% or less. However, as long as the object of the present invention can be achieved, the porosity is not limited to these values.

[0032] The density of the gas diffusion flow path layer constituting the positive electrode of the present invention is not particularly limited as long as the object of the present invention can be achieved. 3 More than 0.30g / cm 3 It is preferable that the concentration is 0.02 g / cm or less. 3 More than 0.20g / cm 3 More preferably, it is 0.05 g / cm or less. 3 More than 0.15g / cm 3 It is even more preferred that:

[0033] The thickness of the gas diffusion flow path layer constituting the positive electrode of the present invention is not particularly limited as long as the object of the present invention can be achieved, but is typically preferably in the range of 50 μm to 1000 μm, more preferably 50 μm to 500 μm, and even more preferably 120 μm to 400 μm. In particular, from the viewpoint of supplying sufficient oxygen gas to the positive electrode layer, it is preferable to set the lower limit to the above range. Here, the thickness of the gas diffusion flow path layer means the thickness immediately before the fibrous carbon material of the two positive electrode layers enters a part of the gas diffusion flow path layer in the two positive electrode layers and the gas diffusion flow path layer constituting the "metal secondary battery flow path integrated positive electrode" which is one embodiment of the present invention. It is desirable to appropriately adjust the thickness of the flow path layer in consideration of the thickness of the metal secondary battery to be designed, the thickness of the positive electrode layer, and the like.

[0034] The two "positive electrode layers" constituting the positive electrode of the present invention are provided by being disposed one on each side of the gas diffusion flow path layer (see FIG. 1(B)). The two positive electrode layers disposed one on each side of the flow path layer are both porous layers made of fibrous carbon materials in structure. In this case, the two positive electrode layers may be structurally the same or different from each other as long as the object of the present invention can be achieved, but it is preferable that they are the same from the viewpoint of ease of production and the like. In particular, it is preferable that the pore size distribution of each positive electrode layer and the pore volume per gram weight of each positive electrode layer are the same (including cases where they can be said to be roughly the same in common sense). Here, "the same as each other" means that the two positive electrode layers obtained by mechanically peeling off the two positive electrode layers fixed to the gas diffusion flow path layer and the flow path layer one on each side have the same basis weight and thickness as each other (including cases where they can be said to be roughly the same in common sense). In this case, the pore size distribution and pore volume per gram weight of the positive electrode layer (in this case, the total weight of the two positive electrode layers is 1 gram weight) of the metal secondary battery flow path integrated positive electrode of the present invention, in which the gas diffusion flow path layer and the two positive electrode layers, one each fixed to both sides of the flow path layer, are integrated, are the same as the pore size distribution and pore volume per gram weight of the positive electrode layer of the metal secondary battery flow path integrated positive electrode, which is manufactured using the same gas diffusion flow path layer and the same positive electrode layer, in which the gas diffusion flow path layer and the positive electrode layer, which is fixed to only one side (one side) of the flow path layer, are integrated (including cases where they are approximately the same in common sense). "Approximately the same in common sense" means that they are substantially the same, and for example, there can be mentioned cases where the pore size distributions of both are approximately the same, as in Example 2 and Example 3 in Figure 6, which shows the relationship between the pore volume and pore size distribution per gram weight of the positive electrode layer, which will be described later.

[0035] The fibrous carbon material constituting the two positive electrode layers constituting the positive electrode of the present invention is not particularly limited as long as it is a fibrous carbon material that can be used as a positive electrode layer in a metal secondary battery (for example, a lithium-air battery). For example, carbon fiber, carbon nanotube, graphitized carbon fiber, etc. can be mentioned, as with the fibrous carbon material used in the gas diffusion flow path layer constituting the positive electrode of the present invention. In addition, for example, carbon fiber and carbon nanotube may be used in combination. In this way, the fibrous carbon material used in the two positive electrode layers constituting the positive electrode of the present invention may be the same as or different from the fibrous carbon material used in the gas diffusion flow path layer constituting the positive electrode of the present invention. For example, with respect to the two positive electrode layers and the gas diffusion flow path layer constituting the positive electrode of the present invention, it is possible to use the same type of carbon nanotube in the two positive electrode layers and the flow path layer, and it is also possible to use carbon fiber in the two positive electrode layers and carbon nanotube different from carbon fiber in the flow path layer. Typically, it is preferable to use carbon fiber and / or carbon nanotube, and it is more preferable to use carbon nanotube. The carbon nanotubes may be single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), multi-walled carbon nanotubes (MWNTs), or a mixture thereof.

[0036] The BET specific surface area of ​​the fibrous carbon material used in the two positive electrode layers constituting the positive electrode of the present invention is 350 m 2 / g or more 1400m 2 / g or less, and 2 / g or more 1300m 2 / g or less is more preferable, and 2 / g or more 1250m 2 It is even more preferred that the .beta. / g or less.

[0037] The pore volume of the fibrous carbon material used in the two positive electrode layers constituting the positive electrode of the present invention, as determined by the BJH method, is such that the pore volume occupied by pores having a diameter of 2 nm or more and 1000 nm or less is 0.8 cm per gram weight of the two positive electrode layers. 3 / g or more 20cm 3 / g or less, and 1.2 cm 3 / g or more 15cm 3 / g or less is more preferable, and 1.5 cm 3 / g or more 12cm 3 It is even more preferred that the .beta. / g or less.

[0038] The thickness of each of the two positive electrode layers constituting the positive electrode of the present invention is not particularly limited as long as the object of the present invention can be achieved, but is typically preferably in the range of 10 μm to 500 μm, more preferably 50 μm to 300 μm, and even more preferably 100 μm to 200 μm. It is desirable to appropriately adjust the thickness of each of the two positive electrode layers in consideration of the thickness of the metal secondary battery to be designed and the thickness of the flow path layer. Specifically, it is preferable to adjust the total thickness of the two positive electrode layers and the flow path layer to be 60 μm to 1000 μm, more preferably 100 μm to 600 μm, and even more preferably 140 μm to 450 μm. The thickness of each of the two positive electrode layers means the thickness immediately before the fibrous carbon material of the two positive electrode layers enters a part of the gas diffusion flow path layer in the two positive electrode layers and the gas diffusion flow path layer constituting the positive electrode of the present invention.

[0039] The positive electrode of the present invention is the "channel-integrated positive electrode for metal secondary battery" as described above. Here, as already described, the "metal secondary battery" refers to a battery using a metal as the negative electrode active material and an external gas such as oxygen or carbon dioxide as the positive electrode active material. Examples of the metal of the negative electrode active material include, but are not limited to, lithium, zinc, sodium, aluminum, magnesium, calcium, iron, and potassium. Examples of the metal secondary battery include, but are not limited to, a metal-air battery. Specific examples of the metal-air battery include, but are not limited to, a lithium-air battery, a zinc-air battery, a sodium-air battery, an aluminum-air battery, a magnesium-air battery, a calcium-air battery, an iron-air battery, a potassium-air battery, and a lithium-carbon dioxide battery. However, the positive electrode of the present invention is preferably used as a positive electrode for a metal-air battery using oxygen as the positive electrode active material, and more preferably used as a positive electrode for a lithium-air battery. As the oxygen of the positive electrode active material, pure oxygen, atmospheric oxygen, or a gas containing any oxygen partial pressure can be used. In addition, from the viewpoint of the output characteristics during discharge of the metal secondary battery, a higher oxygen concentration is usually preferable.

[0040] In the positive electrode of the present invention, a part of the gas diffusion flow layer includes hollow pores that are generated by the entanglement of the fibrous carbon material in the flow layer and the fibrous carbon material of the two positive electrode layers that enter the flow layer, and the flow layer and the two positive electrode layers are integrated by the pores. That is, in the positive electrode of the present invention, a part of the gas diffusion flow layer (specifically, the surface parts of both sides of the gas diffusion flow layer that contact each positive electrode layer) has cavities (i.e., pores) that are generated by the entanglement of the fibrous carbon material in the flow layer and the fibrous carbon material of the two positive electrode layers that enter the flow layer. The pores have a continuous pore size distribution, and the flow layer and the two positive electrode layers are structurally integrated due to the continuous pore size distribution. This point will be described in detail below with specific examples.

[0041] For example, the flow path layer has a pore diameter of about 50 μm to 200 μm, and the two positive electrode layers have the same pore diameter of about 10 nm to 10 μm. In this case, the pores provided by the flow path layer have a pore diameter of about 50 μm to 200 μm, except for the pores corresponding to the cavities that appear in a part of the gas diffusion flow path layer. On the other hand, the pores provided by the two positive electrode layers have a pore diameter of about 10 nm to 10 μm in both positive electrode layers. Here, as described above, when the cavities (i.e., pores) appear in a part of the gas diffusion flow path layer with a pore diameter of about 10 μm to about 50 μm due to the entanglement of the fibrous carbon material in the flow path layer and the fibrous carbon material of the two positive electrode layers that enter the flow path layer, the pores provided by the flow path layer and the two positive electrode layers have a continuous pore diameter distribution of 10 nm to 200 μm. As a result, the flow path layer and the two positive electrode layers are structurally integrated due to the continuous pore size distribution, which is also referred to herein as the flow path layer and the two positive electrode layers being integrated from the viewpoint of pore size distribution.

[0042] On the other hand, when preparing a gas diffusion flow path layer and a positive electrode layer fixed on both sides of the gas diffusion flow path layer, the above-mentioned cavities (i.e., pores) are not generated by simply disposing a gas diffusion flow path layer on the positive electrode layer and further disposing a new positive electrode layer on the flow path layer. In this case, to explain using the above-mentioned specific example, the pores provided by the flow path layer and the two positive electrode layers are only the pores provided by the flow path layer (specifically, pores having a pore diameter of about 50 μm to 200 μm) and the pores provided by the two positive electrode layers (specifically, pores having a pore diameter of about 10 nm to about 10 μm). In other words, the pores provided by the flow path layer and the positive electrode layer do not have pores having a pore diameter of about 10 μm to about 50 μm, and a discontinuous pore diameter distribution appears in the pore diameter distribution of 10 nm to 200 μm. Therefore, the flow path layer and the positive electrode layer are not integrated from the viewpoint of pore size distribution.

[0043] As described above, the "integrated with flow path" in the "flow path integrated positive electrode for metal secondary battery" which is one embodiment of the present invention means that a part of the flow path layer for gas diffusion (specifically, the surface portions of both sides of the flow path layer for gas diffusion in contact with each positive electrode layer) contains hollow pores which are generated by the entanglement of the fibrous carbon material in the flow path layer with the fibrous carbon materials of the two positive electrode layers which penetrate into the flow path layer, and the flow path layer and the two positive electrode layers are integrated by the pores (in other words, the pores have a continuous pore size distribution). This is understood to be because the fibrous carbon material of the positive electrode layer component penetrates from the two positive electrode layers into the flow path layer in contact with the two positive electrode layers, and cavities appear due to entanglement with the fibrous carbon material of the flow path layer component, and a portion (so-called layer) is formed in a part of the flow path layer (specifically, the surface portions on both sides of the gas diffusion flow path layer in contact with each positive electrode layer) having cavities that appear due to the entanglement of the fibrous carbon material of the two positive electrode layer components and the fibrous carbon material of the flow path layer component, and the cavities provide pores with a pore size that connects the pores of the two positive electrode layers to the pores of the flow path layer.

[0044] In the positive electrode of the present invention, the continuous pore size distribution preferably has a continuous pore size distribution of 10 nm or more and 200 μm or less.

[0045] The pore size distribution of the positive electrode of the present invention is measured by the known mercury intrusion method, which utilizes the high surface tension of mercury to apply pressure to cause mercury to penetrate into the pores of a powder, and determines the specific surface area and pore size distribution from the pressure and the amount of intruded mercury.

[0046] According to the positive electrode of the present invention, since it has the above-mentioned "channel integrated" structure, the channel layer and the two positive electrode layers are integrated from the viewpoint of pore size distribution. In this case, the adhesion between the two positive electrode layers and the channel layer shows a significant adhesive strength (specifically, a peel strength of 1 mN / 5 mm or more in a 90-degree peel test) that allows the channel layer and the positive electrode layer to maintain their mutual adhesion even when cut with a cutting tool such as scissors or a cutter. In this application, such integration is also referred to as the channel layer and the two positive electrode layers being integrated from the viewpoint of adhesive strength. Thus, according to the positive electrode of the present invention, the channel layer and the two positive electrode layers are integrated from the viewpoint of both adhesive strength and pore size distribution.

[0047] On the other hand, it should be noted that even if the adhesion between the flow path layer and the two positive electrode layers shows a significant adhesive strength of 1 mN / 5 mm or more in a 90-degree peel test, the flow path layer and the two positive electrode layers are not necessarily integrated from the viewpoint of pore size distribution. This is because, even if the fibrous carbon material of the positive electrode layer component penetrates into the flow path layer from the two positive electrode layers to form an adhesive strength of 1 mN / 5 mm or more in a 90-degree peel test, the pore diameter of the pores made of the fibrous carbon material of the flow path layer and the pore diameter of the pores made of the fibrous carbon material of the two positive electrode layers are both small, so that the fibrous carbon material of the positive electrode layer component of the two positive electrode layers cannot penetrate deep into the flow path layer, and the entanglement with the fibrous carbon material of the flow path layer component is insufficient, and cavities may not be formed due to the entanglement of the two.

[0048] The "part of the flow path layer" constituting the positive electrode of the present invention refers to the contact surface portion with the positive electrode layer arranged on both sides of the gas diffusion flow path layer (i.e., the surface portion of both sides of the gas diffusion flow path layer in contact with each positive electrode layer), and as described above, is a portion (so-called "layer") having a cavity generated by the entanglement of the fibrous carbon material of the positive electrode layer component and the fibrous carbon material of the flow path layer component of the two positive electrode layers. In other words, the layer that is a portion having a cavity generated by the entanglement of the fibrous carbon material of the positive electrode layer component and the fibrous carbon material of the flow path layer component of the two positive electrode layers is also a portion (layer) in which at least a part of the fibrous carbon material of each positive electrode layer of the two positive electrode layers penetrates into the flow path layer. The thickness of the layer is preferably 5 μm or more from the outermost surface of the flow path layer, more preferably 10 μm, and even more preferably 20 μm. The upper limit of the thickness of the layer may be equal to or less than the thickness of the flow path layer itself.

[0049] As described above, the "hollow pores" constituting the positive electrode of the present invention refer to pores that are cavities that are generated by entanglement of the fibrous carbon material in the flow path layer and the fibrous carbon material of the two positive electrode layers that enter the flow path layer on the surface portions of both sides of the flow path layer that are in contact with the two positive electrode layers. The pore size distribution of the "hollow pores" is not particularly limited as long as the object of the present invention can be achieved, but it is preferable that the "hollow pores" have a continuous pore size distribution of 10 μm or more and 50 μm or less. This is because, if the pore size distribution is in this range, the pores are typically integrated from the viewpoint of pore size distribution.

[0050] The "hollow pores" constituting the positive electrode of the present invention are visually observed by observation with an electron microscope or an X-ray computer tomograph. For example, in the observation with an electron microscope, the hollow pores are observed as images with a scanning electron microscope device, and in the observation with an X-ray computer tomograph, the hollow pores are observed as images with an X-ray CT (X-ray computer tomograph) device.

[0051] The "hollow pores" constituting the positive electrode of the present invention have a pore volume of 0.5 cm per gram weight of the "two positive electrode layers" constituting the positive electrode. 3 / g or more 5.0cm 3 / g or less, and 3 / g or more 4.0cm 3 It is more preferred that the Cr content has a value of 0.1 to 1.0 μm / g or less.

[0052] The BET specific surface area per gram weight of the "two positive electrode layers" constituting the positive electrode of the present invention is 250 m 2 / g or more 1400m 2 / g or less, and 2 / g or more 1300m 2 / g or less is more preferable, and 2 / g or more 1250m 2 / g or less, and more preferably 800m 2 / g or more 1000m 2 It is even more preferable that the molecular weight is not more than 1 / g.

[0053] The pores in the positive electrode of the present invention have a pore size distribution of 0.1 μm or more and 10 μm or less, and the pore volume per gram weight of the two positive electrode layers is 1.0 cm 3 / g or more 10.0cm 3 / g or less, and 3 / g or more 6.0cm 3 / g or less is more preferable, and 1.5 cm 3 / g or more 5.0cm 3 It is even more preferred that the .beta. / g or less.

[0054] Of the "two positive electrode layers" constituting the positive electrode of the present invention, at least one positive electrode layer preferably has at least one slit groove. In this case, the depth of the slit groove is preferably such that the gas diffusion flow path layer in contact with the positive electrode layer does not appear from the viewpoint of discharge capacity (particularly discharge capacity at a high discharge current). In addition, the width of the slit groove is preferably 1 / 40 to 1 / 5 of the width of the positive electrode layer in which the slit is provided, and more preferably 1 / 20 to 1 / 10. For example, as shown in FIG. 8, when the surface of the positive electrode layer has a square shape of 20 mm x 20 mm, the width of the slit is preferably 0.5 mm to 4 mm, and more preferably 1 mm to 2 mm.

[0055] A "metal secondary battery" (hereinafter also referred to as "metal secondary battery of the present invention") according to one embodiment of the present invention comprises a positive electrode, a metal-containing negative electrode, and an electrolyte between the positive electrode and the negative electrode, and uses the positive electrode of the present invention as the positive electrode. Any material other than the positive electrode may be used that is used in conventional metal secondary batteries. For example, a metal-containing negative electrode uses a metal as the negative electrode active material, and specific examples of the metal that is the negative electrode active material include lithium, zinc, sodium, aluminum, magnesium, calcium, iron, and potassium. Examples of the positive electrode active material include oxygen or carbon dioxide.

[0056] As described above, the positive electrode of the present invention is preferably used as a metal-air battery positive electrode using oxygen as a positive electrode active material, and more preferably used as a positive electrode for a lithium-air battery. Therefore, it is preferable that the negative electrode containing a metal uses lithium as the metal that is the negative electrode active material. The lithium may be a lithium metal alone or a lithium alloy. Examples of elements that form a lithium alloy with lithium include, but are not limited to, magnesium, titanium, tin, lead, aluminum, indium, silicon, zinc, antimony, bismuth, gallium, germanium, and yttrium. In addition, the type of electrolyte is not particularly limited, and one used in conventional metal secondary batteries can be used, and a separator may be provided in the electrolyte.

[0057] An example of the configuration of the metal secondary battery of the present invention is shown in FIG. 7(A) and FIG. 7(B) as a configuration diagram. The "metal secondary battery" shown in FIG. 7(A) and FIG. 7(B) is a lithium-air battery that includes a lithium metal foil as a negative electrode active material, a negative electrode current collector in contact with the lithium metal foil, and uses the positive electrode of the present invention as a positive electrode unit. The negative electrode current collector is a metal material or carbon having electrical conductivity, and may have a terminal (not shown) for connecting to the outside. In the negative electrode, the negative electrode active material and the negative electrode current collector may be configured separately or may be integrated. In addition, as shown in FIG. 7(A) and FIG. 7(B), a separator may be provided between the lithium metal foil as the negative electrode active material and the positive electrode. In the positive electrode unit, the gas diffusion flow path layer and the positive electrode layers fixed to both sides of the gas diffusion flow path layer are integrated, but the positive electrode unit and the positive electrode current collector may be configured separately or may be integrated. In this case, "integrated" refers to, for example, a state in which a collector (specifically, a positive electrode collector) is fixed in a gas diffusion flow path layer constituting a positive electrode unit as shown in FIG. 7(B). Examples of the positive electrode collector include metal materials such as aluminum, copper, SUS304, nickel, and stainless steel, and aluminum, copper, and SUS304 are preferred from the viewpoints of workability and economy. The shape of the positive electrode collector is not particularly limited as long as the object of the present invention can be achieved, but a metal wire material (so-called metal wire line) or metal foil material (so-called ribbon-shaped metal foil material) having a smaller diameter, thickness, or width than a conventional metal foil material may be used. Specifically, examples of the metal wire include wires having a thickness of 10 μm or more and 200 μm or less, and ribbon-shaped foil materials having a thickness and width of 5 μm or more and 100 μm or less and 0.5 mm or more and 10 mm or less, respectively.

[0058] When the current collector (specifically, the positive electrode current collector) is fixed in a gas diffusion flow path layer, when the contact surface with the two positive electrode layers fixed and integrated onto both sides of the flow path layer is taken as the surface of the flow path layer, the area of ​​the current collector visible through the surface is preferably 15% or less of the surface.

[0059] The "manufacturing method for a flow path integrated positive electrode for a metal secondary battery" according to one embodiment of the present invention includes the steps of: preparing a dispersion liquid in which a fibrous carbon material is dispersed in a solvent as a raw material for a positive electrode layer of a porous layer; and preparing a porous substrate made of a fibrous carbon material as a gas diffusion flow path layer of the porous layer; filtering the dispersion liquid on the porous substrate, stacking the carbon material dispersed in the dispersion liquid on one side of the flow path layer, and drying the stacked porous substrate to fix a first positive electrode layer and integrate it with the flow path layer; and turning over the flow layer on which the positive electrode layer has been formed, stacking the carbon material dispersed in the dispersion liquid on the other side of the flow path layer, and drying the stacked porous substrate to fix a second positive electrode layer and integrate it with the flow path layer.

[0060] The "fibrous carbon material" used as the raw material of the positive electrode layer of the porous layer may be the "fibrous carbon material" already described in the "positive electrode layer" constituting the positive electrode of the present invention. The solvent in which the "fibrous carbon material" is dispersed is not particularly limited as long as the object of the present invention can be achieved, but typically, it is preferable to use water or 2-propanol.

[0061] Specifically, the gas diffusion flow path layer of the porous layer is as already explained in the "gas diffusion flow path layer of the porous layer" constituting the positive electrode of the present invention. As the gas diffusion flow path layer of the porous layer, a "porous substrate made of a fibrous carbon material" is used, and the porous substrate is not particularly limited as long as it is a substrate made of a fibrous carbon material used as a gas diffusion layer (i.e., a flow path layer) in a metal secondary battery (e.g., an air battery such as a lithium-air battery or a fuel cell). For example, an aggregate of carbon fibers (specifically, carbon paper, carbon cloth, or carbon felt, etc.), an aggregate of carbon nanotubes or graphitized carbon fibers (specifically, a sheet or nonwoven fabric of carbon nanotubes, etc.) can be mentioned. Preferably, it is an aggregate of carbon fibers and / or carbon nanotubes, and more preferably, it is carbon paper (sometimes simply referred to as "CP" in the present application) which is an aggregate of carbon fibers.

[0062] The filtration in the step of forming the positive electrode layer on the flow path layer by filtering the dispersion on the porous substrate may be performed by a known method, for example, a method of filtering an aqueous dispersion of carbon nanotubes on carbon paper by suction and drying the dispersion, thereby forming the positive electrode layer on the flow path layer.

[0063] The fibrous carbon material used in the dispersion has a BET specific surface area of ​​350 m 2 / g or more 1400m 2 / g or less, and 2 / g or more 1300m 2 / g or less is more preferable, and 2 / g or more 1250m 2 It is even more preferred that the .beta. / g or less.

[0064] The porous substrate preferably has a pore size of 30 μm or more, more preferably 50 μm or more, and even more preferably 70 μm or more.

[0065] The density of the porous substrate is as described above in “Density of the flow path layer” and is 0.01 g / cm 3 More than 0.30g / cm 3 It is preferable that the concentration is 0.02 g / cm or less. 3 More than 0.20g / cm 3 More preferably, it is 0.05 g / cm or less. 3 More than 0.15g / cm 3 It is even more preferred that:

[0066] In the "manufacturing method of a flow path integrated positive electrode for a metal secondary battery" which is one aspect of the present invention, in order to manufacture a positive electrode in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated (i.e., a flow path integrated positive electrode for a metal secondary battery), first, a dispersion liquid in which a fibrous carbon material is dispersed in a solvent as a raw material for the positive electrode layer of the porous layer, and a porous substrate made of a fibrous carbon material as a gas diffusion flow path layer of the porous layer are prepared. This step is also referred to as "step A" in the present application for convenience. Next, the dispersion liquid is filtered on the porous substrate, and the carbon material dispersed in the dispersion liquid is laminated on one side of the flow path layer, and the laminated porous substrate is dried to fix the first positive electrode layer and integrate it with the flow path layer. This step is also referred to as "step B" in the present application for convenience. Then, the flow path layer on which the positive electrode layer is formed is turned over, the carbon material dispersed in the dispersion liquid is laminated on the other side of the flow path layer, and the laminated porous substrate is dried to fix the second positive electrode layer and integrate it with the flow path layer. This step is also referred to as "Step C" in this application for convenience.

[0067] That is, by carrying out the drying in step B (which is also referred to as "first drying process" for convenience in this application), the first positive electrode layer is fixed to and integrated with the flow path layer. This first drying process is a process in which the integrated state between the flow path layer and the first positive electrode layer in step B is maintained as it is in step C. The reason for this is as follows.

[0068] In the "manufacturing method of a flow path integrated positive electrode for a metal secondary battery" which is one aspect of the present invention, in order to manufacture a positive electrode in which a flow path layer for gas diffusion and a positive electrode layer fixed to both sides of the flow path layer are integrated, it is required to turn over and fix a second positive electrode layer to the other side of the flow path layer and integrate them in step C after performing step B. However, if a general drying process using suction filtration (specifically, a drying process in which natural drying is performed for several tens of minutes to several hours after suction filtration) is applied as the first drying process in step B, problems occur in step C in that the flow path layer fixed and integrated in step B and the first positive electrode layer peel off, or the first positive electrode layer fixed and integrated collapses, making it impossible to manufacture a positive electrode in which a flow path layer for gas diffusion and a positive electrode layer fixed to both sides of the flow path layer for gas diffusion are integrated. Therefore, in the “manufacturing method for a flow path-integrated positive electrode for a metal secondary battery” which is one aspect of the present invention, the first drying treatment is a treatment in which the integrated state of the flow path layer and the first positive electrode layer in step B is maintained as it is in step C.

[0069] Regarding the drying process (i.e., the first drying process) in which the integrated state of the flow path layer and the first positive electrode layer in step B is maintained in step C, the inventors have intensively studied the results and found that, for example, heated vacuum drying is an effective and preferable drying method. As the first drying process, it is also possible to perform natural drying for a much longer time (specifically, several tens of hours or more) than natural drying after general suction filtration. However, from the viewpoint of production efficiency and production cost of the flow path-integrated positive electrode for metal secondary batteries of the present invention, heated vacuum drying is preferable as the first drying process.

[0070] When the first drying process is performed by heating and vacuum drying, it is preferable to perform a predetermined heating and vacuum drying process. Specifically, the heating temperature is preferably 40° C. or more and 150° C. or less, and more preferably 60° C. or more and 80° C. or less, from the viewpoint of more effectively avoiding the peeling and collapse in step C. Taking into account the manufacturing cost, etc., the degree of vacuum is preferably 10 4 Pa or less is preferable, and 10 3 From the viewpoint of more effectively avoiding the peeling or collapse in step C, the heating and vacuum drying time is preferably 12 hours or more, and more preferably 24 hours or more.

[0071] Incidentally, Patent Documents 2 and 3 state that drying is carried out in relation to the manufacture of a "channel-integrated positive electrode for a metal secondary battery in which a positive electrode layer is fixed and integrated onto only one side of a single gas diffusion channel layer," but there is no special mention of the drying process, and it is understood to be a general drying process in which natural drying is carried out for several tens of minutes to several hours after suction filtration.

[0072] In the "manufacturing method for a flow path-integrated positive electrode for a metal secondary battery" which is one aspect of the present invention, a drying process is also performed in step C (for convenience, this drying process is also referred to as a "second drying process" in this application), but the second drying process may be the same as the first drying process or may be a general drying process (i.e., a drying process in which natural drying is performed for several tens of minutes to several hours after suction filtration). However, from the viewpoint of more stabilizing the adhesion of the positive electrode layer, the first drying process is preferable.

[0073] There are no particular limitations on the conditions not specified in this application as long as the object of the present invention can be achieved. EXAMPLES

[0074] Next, the embodiment of the present invention will be described in more detail. However, the embodiment of the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0075] <Method of manufacturing a flow path-integrated positive electrode for a metal secondary battery according to one embodiment of the present invention> A flow channel integrated positive electrode for a metal secondary battery, which is an embodiment of the present invention, in which one gas diffusion channel layer and positive electrode layers fixed to both sides of the gas diffusion channel layer are integrated, was manufactured as follows. Figure 2 shows a schematic diagram of the manufacturing process of the flow channel integrated positive electrode for a metal secondary battery.

[0076] The fibrous carbon material used as the positive electrode layer raw material (hereinafter also referred to as the "positive electrode carbon material") was a single-walled carbon nanotube (CNT: ZEONANO (registered trademark) SG101, manufactured by Zeon Corporation). The single-walled carbon nanotube is hereinafter also referred to as "CNT" or "fibrous CNT".

[0077] For the gas diffusion channel layer, which is a porous layer made of a fibrous carbon material, various commercially available gas diffusion channel layers (carbon paper) shown in Table 1 were used.

[0078] First, a small amount of water was added to the CNT, which was the positive electrode carbon material, and the mixture was pre-dispersed using a mixer stirring device (SMT Corporation, High Flex Homogenizer HF93), after which pure water was added to adjust the CNT sample concentration to 0.1% by weight. The obtained CNT aqueous dispersion was ultrasonically treated at room temperature using an ultrasonic homogenizer (Branson 450D) to obtain a positive electrode carbon material dispersion (hereinafter also referred to as a positive electrode carbon material (CNT) dispersion). 80 g of the obtained positive electrode carbon material dispersion was placed in a suction filtration device (filtration area 45 cm) on which carbon paper was placed as a gas diffusion flow path layer made of sheet-shaped conductive carbon fiber (carbon fiber). 2 A suction filter (76 mm in diameter) was used to perform suction filtration on its surface (on the surface of the gas diffusion flow path layer (specifically, carbon paper)). In this example, as described above, various commercially available gas diffusion flow path layers (carbon papers) shown in Table 1 were used for the carbon paper serving as the gas diffusion flow path layer.

[0079] The above-mentioned treatment resulted in the positive electrode layer being fixed to one side of each of the carbon papers (CP) shown in Table 1 used as the gas diffusion flow path layer, which were integrated by being turned over and placed in a suction filtration device (filtration area 45 cm 2The carbon paper was placed on a carbon paper (76 mm in diameter) and the same amount (80 g) of the same type of positive electrode carbon material dispersion was again suction filtered onto the other side of the carbon paper (on the surface of the gas diffusion channel layer (specifically, the carbon paper) on the side to which the positive electrode layer was not fixed). In this way, a channel-integrated positive electrode for a metal secondary battery, which is one embodiment of the present invention, was produced, in which one gas diffusion channel layer and positive electrode layers fixed to both sides of the gas diffusion channel layer are integrated.

[0080] [Table 1]

[0081] Table 1 shows the properties of the six types of carbon paper (CP) used as the gas diffusion flow path layer. The thickness and basis weight (weight per unit area) are listed as catalog values, and the pore size was measured by mercury intrusion porosimetry. The density of the gas diffusion flow path layer was calculated by dividing the basis weight by the thickness. The porosity was calculated by taking the true density (ρ) of the carbon fiber as 2.1 g / cm 3 It was assumed that the density of the gas diffusion channel layer was 1-(density of the gas diffusion channel layer) / ρ, and it was calculated from the formula "1-(density of the gas diffusion channel layer) / ρ". It was also confirmed that, when any of the carbon papers shown in Table 1 was used as the gas diffusion channel layer, the above operation resulted in the positive electrode carbon material (i.e., CNT) being collected on the gas diffusion channel layer, and the positive electrode layer being attached (fixed) to one side of the gas diffusion channel layer, and the two layers being integrated. The integration was confirmed according to the method described later in "Evaluation and confirmation of integration of the gas diffusion channel layer and the positive electrode layer in various positive electrode units".

[0082] Here, the first positive electrode carbon material dispersion was filtered on the surface of the gas diffusion flow path layer, various drying treatments were performed, and then the gas diffusion flow path layer was turned over and the second filtration was performed on its surface. In the process, the effects on the properties of the membrane obtained by the first filtration and various drying treatments (specifically, the positive electrode layer was fixed and integrated on one side of the carbon paper that is the gas diffusion flow path layer) were investigated. The results are shown in Table 2. The first and second filtration operations in Table 2 were both performed by connecting a diaphragm type vacuum pump (KNF, N820.3FT.18) to a glass filter (Shibata Scientific, SPC filter holder, diameter 90 mm), placing CP1 described in Table 1, which is the gas diffusion flow path layer, on a filter support of SUS mesh, and suction filtering the positive electrode carbon material dispersion on the surface of the gas diffusion flow path layer.

[0083] [Table 2]

[0084] From the comparison results of No. 1 to 3 and No. 4 in Table 2, it was found that by performing a second filtration operation after the positive electrode layer applied on one side of the gas diffusion flow path layer by the first filtration operation is sufficiently and firmly fixed by performing a heating and vacuum drying process, it is possible to apply a positive electrode layer on the other side of the gas diffusion flow path layer by the second filtration operation while maintaining the fixed state of the positive electrode layer applied on one side of the gas diffusion flow path layer in the first filtration operation, thereby obtaining a positive electrode in which the positive electrode layers are fixed to both sides of the gas diffusion flow path layer and integrated. The integration was confirmed according to the method described later in "Evaluation and confirmation of integration of the gas diffusion flow path layer and the positive electrode layer in various positive electrode units".

[0085] FIG. 3 is a schematic diagram of a manufacturing process for a positive electrode having a metal wire as a positive electrode current collector (i.e., a flow path integrated positive electrode for a metal secondary battery), which is one embodiment of the present invention. Explaining with reference to FIG. 3, metal wires were sewn into various commercially available carbon papers (CP) shown in Table 1, which are used as a gas diffusion flow path layer, by parallel stitching (stitch width 20 mm) at equal intervals of 5 to 20 mm, and protruding 5 cm or more from the cross section of the carbon paper (specifically, the surface to which the positive electrode layer is applied). In this case, the intervals at which the metal wires are sewn are set so that any point is 16 mm in diameter (area 2 cm2) away from the carbon paper. 2 ) or a 2cm x 2cm square, the weight of the metal wire per unit area contained in the cut carbon paper is 1mg / cm 2 The following was adjusted. For the metal wires (wires), aluminum wires were "Al-100" with a diameter of 100 μm, aluminum foil ribbons were "Al-12-3" with a thickness of 12 μm and a width of 3 mm, copper wires were "Cu-100" with a diameter of 100 μm and "Cu-50" with a diameter of 50 μm, and SUS304 wires were "SUS-100" with a diameter of 100 μm and "SUS-50" with a diameter of 50 μm. As a result, it was confirmed that, regardless of which metal wires and which carbon paper were used, a positive electrode layer made of CNTs (also referred to as "CNT positive electrode layer" in this application) could be fixed and integrated on both sides of the carbon paper that is the gas diffusion flow path layer by filtering the positive electrode carbon material (CNT) dispersion liquid on both sides of the carbon paper that is the gas diffusion flow path layer. The integration was confirmed according to the method described later in "Evaluation and confirmation of integration between gas diffusion flow path layer and positive electrode layer in various positive electrode units."

[0086] It was also confirmed that the obtained positive electrode having the above-mentioned metal wire as a positive electrode current collector (the positive electrode is a flow path integrated positive electrode for a metal secondary battery in which one gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated) can be cut into any shape with scissors or a cutter using any of the above-mentioned metal wires and any of the carbon papers (CP) shown in Table 1. In addition, it was confirmed that the positive electrode layer made of CNTs fixed to both sides of the carbon paper as the gas diffusion flow path layer and integrated with each other was fixed with an adhesive strength of 1 mN / 5 mm or more on both sides by a 90-degree peel test. From these results, it was found that the positive electrode layer made of CNTs can be fixed in the form of a film to both sides of the various carbon papers (CP) shown in Table 1 as the gas diffusion flow path layer by filtering the positive electrode carbon material (CNT) dispersion on both sides of the gas diffusion flow path layer.

[0087] <Evaluation of the fabricated flow channel integrated positive electrode for metal secondary batteries> Table 3 shows the properties of a metal secondary battery flow path integrated positive electrode (i.e., a metal secondary battery flow path integrated positive electrode in which one gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated) which is one embodiment of the present invention manufactured by the above-mentioned manufacturing method as a positive electrode unit for use in a metal secondary battery, and two types of positive electrode units manufactured for comparison. Note that the "flow path layer" in Table 3 refers to a gas diffusion flow path layer. FIG. 4 shows a cross-sectional view of the structure of various positive electrode units in Table 3 as a schematic diagram. Therefore, the positive electrode units shown as "positive electrode unit example 3-7, 9" in FIG. 4 correspond to each of the positive electrode units of "positive electrode unit example 3" to "positive electrode unit example 7" and "positive electrode unit example 9" in the positive electrode unit examples in Table 3, and are positive electrodes (i.e., a metal secondary battery flow path integrated positive electrode in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated) which are one embodiment of the present invention. The positive electrode unit shown as "positive electrode unit example 1" in FIG. 4 corresponds to the positive electrode unit of "positive electrode unit example 1" in the positive electrode unit examples in Table 3, and is a simple laminate (comparative example) in which carbon paper (CP) as a gas diffusion flow path layer is placed on a positive electrode layer made of CNT, and a positive electrode layer made of CNT is further placed on the carbon paper. Therefore, in this simple laminate, the positive electrode layer made of CNT and the gas diffusion flow path layer (CP) placed thereon, and the gas diffusion flow path layer (CP) and the positive electrode layer made of CNT placed thereon are not fixed and integrated. In this application, the positive electrode unit of "positive electrode unit example 1" is sometimes referred to as a simple laminate. The positive electrode units shown as "positive electrode unit examples 2 and 8" in Figure 4 correspond to the positive electrode units of "positive electrode unit example 2" and "positive electrode unit example 8" in the positive electrode unit examples in Table 3, and are positive electrode units (comparative examples) obtained by simply stacking one laminate each, in which a positive electrode layer is fixed to only one side (one side) of a gas diffusion flow path layer to form an integrated laminate, with the flow path layers facing each other.

[0088] The pore volumes of the various positive electrode units shown in Table 3 are the measured values ​​of the pore volume occupied by pores with diameters of 0.1 μm to 10 μm and the pore volume occupied by pores with diameters of 10 μm to 50 μm. In measuring the pore volume occupied by pores with diameters of 0.1 μm to 10 μm, the pore volume in the pore diameter range of 10 nm to 200,000 nm (0.01 μm to 200 μm) was measured by mercury intrusion using an AutoPoreIV (Micromeritics Instrument Corp.), and the pore volume value of the pore diameters of 0.1 μm to 10 μm was used as the measured value. To measure the pore volume occupied by pores with diameters of 10 μm or more and 50 μm or less, the pore volume in the pore diameter range of 10 nm to 200,000 nm (0.01 μm to 200 μm) was measured by mercury intrusion method using an AutoPoreIV (Micromeritics Instrument Corp.), and the pore volume value of the pore diameter range of 10 μm to 50 μm was used as the measured value.

[0089] Each of the positive electrode units of "Positive Electrode Unit Example 1", "Positive Electrode Unit Example 2" and "Positive Electrode Unit Example 8" which are comparative examples shown in Table 3, was produced by the same method as in Patent Document 3. Specifically, the positive electrode unit of "Positive Electrode Unit Example 1" was produced by filtering a positive electrode carbon material (CNT) dispersion liquid on a filter paper (Omnipore™ membrane, pore size 1 μm), vacuum drying at 60°C, peeling off the filter paper, and forming a film of a positive electrode layer (CNT positive electrode layer) made of CNT (CNT basis weight 2.1 mg / cm 2) were prepared, and the two prepared positive electrode layers were simply laminated one by one on both sides of a gas diffusion flow path layer (specifically, "CP1" in Table 1) as shown in "Positive Electrode Unit Example 1" in FIG. 4. In FIG. 4, the above film is referred to as a "CNT positive electrode layer film." In addition, the positive electrode unit of "Positive Electrode Unit Example 2" is a positive electrode unit in which two laminated films are prepared by filtering and fixing a positive electrode carbon material (CNT) dispersion liquid on one side of "CP1" in Table 1 as a gas diffusion flow path layer, and then stacking them with the gas diffusion flow path layer sides of each film facing each other and the CNT positive electrode layer facing outward, as shown in "Positive Electrode Unit Examples 2 and 8" in FIG. 4. The positive electrode unit of "Positive Electrode Unit Example 8" is also a positive electrode unit prepared in the same manner as the positive electrode unit of "Positive Electrode Unit Example 2", except that "CP6" in Table 1 is used as the gas diffusion flow path layer. In other words, neither of the positive electrode units of "Positive Electrode Unit Example 2" and "Positive Electrode Unit Example 8" is formed by integrating the above-mentioned two membranes (i.e., a laminate membrane in which a positive electrode layer is fixed to only one side of a gas diffusion flow path layer and integrated) that have been produced.

[0090] [Table 3]

[0091] <Evaluation and confirmation of integration of gas diffusion flow path layer and positive electrode layer in various positive electrode units> The integration of the gas diffusion flow path layer and the positive electrode layer in each of the positive electrode units produced in this example was evaluated and confirmed using scanning electron microscope images and pore size distribution measured by mercury intrusion porosimetry. A specific example will be described below.

[0092] FIG. 5 shows a scanning electron microscope image of a cross section cut with scissors of a positive electrode unit (specifically, "Positive Electrode Unit Example 3" in Table 3) in which "CP1" is used as the carbon paper that is the gas diffusion flow path layer, and a positive electrode layer using CNT as the positive electrode carbon material is fixed in a film form on both sides of the "CP1". From FIG. 5, it was confirmed that the positive electrode layer was attached and fixed (i.e., fixed) on both sides of the "CP1" with a thickness of about 300 μm. Furthermore, it was also confirmed that on both sides where "CP1" and the positive electrode layer are in contact (i.e., the surfaces of both the top and bottom sides of "CP1"), the CNT component derived from the positive electrode layer penetrated into the hollow (pore) part of "CP1" that is the gas diffusion flow path layer, and was entangled with the carbon fiber derived from the "CP1". As a result, it was found that in a positive electrode according to one embodiment of the present invention (i.e., a flow path-integrated positive electrode for a metal secondary battery in which one gas diffusion flow path layer is integrated with positive electrode layers fixed to both sides of the gas diffusion flow path layer), a part of the gas diffusion flow path layer includes hollow pores that are generated by the entanglement of the carbon fibers in the flow path layer with the fibrous carbon material from the positive electrode layer that penetrates into the flow path layer.

[0093] FIG. 6 shows the results of measuring the pore size distribution of the positive electrode unit (specifically, "positive electrode unit example 3" in Table 3) which is one embodiment of the present invention used in FIG. 5 by mercury intrusion porosimetry. For comparison, FIG. 6 also shows the results of measuring the pore size distribution of the positive electrode units of "positive electrode unit example 1" and "positive electrode unit example 2" in Table 3 in the same manner. In FIG. 6, the pore size distribution indicated by "●" is the pore size distribution of the positive electrode unit (specifically, example 3 in Table 3) which is one embodiment of the present invention, the pore size distribution indicated by "▲" is the pore size distribution of the positive electrode unit (specifically, "positive electrode unit example 2" in Table 3) which is a comparative example, and the pore size distribution indicated by "○" is the pore size distribution of the positive electrode unit (specifically, "positive electrode unit example 1" in Table 3 (i.e., a simple laminate)) which is a comparative example. Moreover, the vertical axis in FIG. 6 shows the pore volume normalized by the weight of the positive electrode layer (CNT positive electrode layer) that uses CNT as the positive electrode carbon material (specifically, as the pore volume per gram weight of the CNT positive electrode layer).

[0094] As shown in Figure 6, in the simple laminate of "Positive Electrode Unit Example 1", a pore size distribution due to pores with diameters of 0.1 μm to 10 μm in the CNT positive electrode layer and a pore size distribution due to pores with diameters of 50 μm to 200 μm originating from the carbon paper (specifically, "CP1") which is the gas diffusion flow path layer were confirmed, but a pore size distribution due to pores with diameters of 10 μm to 50 μm was hardly observed. Therefore, it was found that in the simple laminate of "Positive Electrode Unit Example 1", the pore size distribution due to the CNT positive electrode layer and the pore size distribution due to "CP1" which is the gas diffusion flow path layer each have a clearly different pore size distribution region.

[0095] In the "Positive Electrode Unit Example 2", a positive electrode unit was prepared by simply stacking the laminates, each of which was made by fixing a CNT positive electrode layer by filtration to only one side of a carbon paper (specifically, "CP1") that was a gas diffusion flow path layer, so that the gas diffusion flow path layers faced each other. As shown in FIG. 6, it was found that the pore size distribution regions of CP1 and the CNT positive electrode layer could not be clearly distinguished from each other, and the pore size formed a continuous pore size distribution in the range of 0.01 μm to 200 μm. Although not shown, it was confirmed that the positive electrode unit of "Positive Electrode Unit Example 8", which was prepared in the same manner as the positive electrode unit of "Positive Electrode Unit Example 2", except that "CP6" in Table 1 was used as the gas diffusion flow path layer, also formed a continuous pore size distribution in the range of 0.01 μm to 200 μm, similar to "Positive Electrode Unit Example 2". As a result, it was found that in both of the positive electrode units, "Positive Electrode Unit Example 2" and "Positive Electrode Unit Example 8", in which the positive electrode layer was fixed to only one side of the gas diffusion flow path layer, the two layers were integrated.

[0096] "Positive electrode unit example 3" is a positive electrode unit according to a specific embodiment of the present invention, and is a positive electrode unit in which a CNT positive electrode layer is fixed to both sides of a carbon paper (specifically, "CP1") that is a gas diffusion flow path layer. As shown in FIG. 6, it was confirmed that a continuous pore size distribution similar to that of "positive electrode unit example 2" was formed. In addition, it was confirmed that the pore volume per gram weight of the CNT positive electrode layer was almost the same as that of "positive electrode unit example 2". Therefore, it was found that the same pore size distribution was formed on both sides of "CP1" to which the CNT positive electrode layer was fixed. In other words, it was found that the gas diffusion flow path layer and the positive electrode layers fixed and integrated to both sides of the gas diffusion flow path layer, one each, were approximately the same as each other. Although not shown, it was confirmed that in each of the positive electrode units "Positive Electrode Unit Example 4" to "Positive Electrode Unit Example 7" and "Positive Electrode Unit Example 9" in Table 3, the pore diameters were in the range of 0.01 μm to 200 μm, similar to "Positive Electrode Unit Example 3", and the pore volume per gram weight of the CNT positive electrode layer was almost the same. As a result, it was found that in each of the positive electrode units "Positive Electrode Unit Example 3" to "Positive Electrode Unit Example 7" and "Positive Electrode Unit Example 9" listed in Table 3 as the positive electrode units which are a specific embodiment of the present invention, the gas diffusion flow path layer and the positive electrode layers fixed to both sides of the gas diffusion flow path layer were integrated.

[0097] The BET specific surface areas of the positive electrode units of “Positive Electrode Unit Example 3” to “Positive Electrode Unit Example 7” and “Positive Electrode Unit Example 9” in Table 3, which are specific embodiments of the present invention, were analyzed and calculated based on the BET method from the adsorption isotherm (nitrogen adsorption isotherm) obtained by the nitrogen adsorption method using 3Flex (Micromeritics Instrument Corp.). In each positive electrode unit, the specific surface area was 800 cm per gram weight of the two positive electrode layers (specifically, the CNT positive electrode layers) constituting the positive electrode unit. 2 / g or more 1000cm 2 / g or less.

[0098] In addition, the pore volume calculated by analyzing the nitrogen adsorption isotherm by the BJH method shows that the pore volume occupied by pores with diameters of 2 nm or more and 1000 nm or less is 0.8 cm per gram weight of the two positive electrode layers (specifically, the CNT positive electrode layers) constituting the positive electrode unit in any of the positive electrode units of "Positive Electrode Unit Example 3" to "Positive Electrode Unit Example 7" and "Positive Electrode Unit Example 9" of the present invention in Table 3. 3 / g or more 1.2cm 3 / g or more.

[0099] <Fabrication of Lithium-Air Battery Stack Cell (i.e., Layered Lithium-Air Battery) and Discharge Test Results (Part 1)> Next, a lithium-air battery stack cell (i.e., a laminated lithium-air battery) was fabricated using three types of positive electrode units of the present invention, "Positive Electrode Unit Example 3," "Positive Electrode Unit Example 5," and "Positive Electrode Unit Example 6" in Table 3, and discharge characteristics were evaluated. The lithium-air battery stack cell was fabricated by the following method. The positive electrode unit was cut into a circular shape with a diameter of 16 mm, vacuum dried at 60°C for 12 hours or more, and then arranged as shown in Figures 7(A) and 7(B) to fabricate the battery. Specifically, a lithium metal foil (diameter: 16 mm) / lithium ion secondary battery separator / positive electrode unit (diameter: 16 mm, effective electrode area: 4 cm) was placed between two upper and lower negative electrode current collectors (Cu foil). 2 ) / Lithium ion secondary battery separator / Lithium metal foil (diameter: 16 mm, thickness: 200 μm) were stacked in this order, and two CNT positive electrode layers were attached to both sides of the gas diffusion flow path layer that constitutes the positive electrode unit, and integrated together. The gas diffusion flow path layer and the side not attached to the two CNT positive electrode layers were infiltrated with 24 μL of electrolyte (tetraethylene glycol dimethyl ether (TEGDME) containing 1 M lithium bistrifluoromethanesulfonylimide (LiTFSI)) solution to fabricate a lithium-air battery stack cell. Therefore, the number of stacked layers in the positive electrode unit that constitutes the fabricated lithium-air battery stack cell is one.

[0100] Current collection from the three types of positive electrode units of the present invention, "positive electrode unit example 3", "positive electrode unit example 5" and "positive electrode unit example 6" in Table 3, was carried out in two ways: from the carbon paper (CP) which is the conductive gas diffusion flow path layer in the center of the positive electrode unit (see FIG. 7(A)) and from the metal wire sewn into the carbon paper (CP) which is the gas diffusion flow path layer in the center of the positive electrode unit (see FIG. 7(B)). When collecting current from the carbon paper (CP) which is the conductive gas diffusion flow path layer in the center of the positive electrode unit shown in FIG. 7(A), both of the CNT positive electrode layers which are fixed and integrated on both sides of the carbon paper, except for the circular CNT positive electrode layer part with a diameter of 16 mm, were partially peeled off, and the carbon paper part protruding out of the positive electrode unit by about 20 mm in a strip shape with a width of 16 mm as viewed from the cross section of the lithium-air battery stack cell was clamped with an alligator clip to collect current. When collecting current from the metal wire sewn into the carbon paper (CP) that is the gas diffusion flow path layer in the center of the positive electrode unit as shown in Figure 7(B), two metal wires (one wire if an aluminum foil ribbon is used) are pulled out from the positive electrode unit as viewed from the cross section of the positive electrode unit, and the two pulled out wires are rolled up on the twisted paper, and current is collected by clamping the part about 20 mm ahead as viewed from the cross section of the lithium-air battery stack cell with an alligator clip. Discharge tests were performed using a battery charge / discharge system (Hokuto Denko, HJ1001SD8) at room temperature under constant current conditions (conditions: 0.4 mA / cm per electrode area). 2 , 1 cell (4cm 2 Discharge was performed under the following conditions: 1.6 mA per cell, 2 V cut, and dry air (~20% oxygen, dew point -60 to -50°C).

[0101] Table 4 shows 11 types of lithium-air battery stack cells (i.e., stacked lithium-air batteries) prepared using three types of positive electrode units of the present invention in Table 3, namely, "Positive Electrode Unit Example 3," "Positive Electrode Unit Example 5," and "Positive Electrode Unit Example 6," and using different current collecting materials, the configuration of the cells (positive electrode unit, gas diffusion flow path layer (simply referred to as "flow path layer" in Table 4), and each type of current collecting material), and the discharge test results of the cells (specifically, discharge capacity at a current of 1.6 mA (unit: mAh)). For convenience, the prepared lithium-air battery stack cells are referred to as "cell examples" in Table 4. Also, for convenience, the positive electrode units constituting the lithium-air battery stack cells prepared in Table 4 are referred to as "positive electrode unit examples," and the numbers correspond to the numbers of the "positive electrode unit examples" in Table 3 and FIG. 4.

[0102] In Table 4, "CP1", "CP3", and "CP4" used as current collecting materials refer to various carbon papers described as gas diffusion flow path layers in Table 1. In addition, in Table 4, used as current collecting materials, "Al-100" refers to aluminum wire (diameter 100 μm), "Al-12-3" refers to aluminum foil ribbon (thickness 12 μm, width 3 mm), "Cu-100" refers to copper wire (diameter 100 μm), "Cu-50" refers to copper wire (diameter 50 μm), "SUS-100" refers to SUS304 wire (diameter 100 μm), and "SUS-50" refers to SUS304 wire (diameter 50 μm).

[0103] [Table 4]

[0104] As shown in Table 4, in the lithium-air battery stack cell shown as "Cell Example 1", current is collected from carbon paper (specifically, "CP1"), which is a conductive gas diffusion flow path layer. In this case, since "CP1" is brittle and easily breaks, it is difficult to collect current, and a discharge test cannot be performed, and a lithium-air battery stack cell cannot be fabricated. Therefore, when providing a positive electrode having a current collector fixed in a gas diffusion flow path layer as a positive electrode in which a gas diffusion flow path layer and a positive electrode layer fixed to both sides of the gas diffusion flow path layer are integrated (i.e., a metal secondary battery flow path integrated positive electrode), it is found that it is not appropriate to use "CP1" as a material (current collector) for the current collector. On the other hand, in Table 4, in the lithium-air battery stack cell shown as "Cell Example 2", an aluminum wire (Al-100) is sewn into "CP1" of the gas diffusion flow path layer constituting the positive electrode unit in "Positive Electrode Unit Example 3" in Table 3 as a positive electrode unit. Here, the metal wire is arranged so that two metal wires are pulled out from the positive electrode unit when viewed from the cross section of the positive electrode unit, and a lithium-air battery stack cell is fabricated so that current is collected from the two pulled out wires (see FIG. 7(B)). In this case, as shown in "Cell Example 2" in Table 4, it was found that discharging can be performed. It was also confirmed that a lithium-air battery stack cell can be fabricated and discharged even when using carbon paper that is more flexible than "CP1," which is a conductive gas diffusion flow path layer (specifically, when using "CP3" or "CP4" to collect current) (see "Cell Example 3" and "Cell Example 10" in Table 4).

[0105] When providing a positive electrode having a current collector fixed in a gas diffusion flow path layer as a positive electrode in which a gas diffusion flow path layer and positive electrode layers fixed on both sides of the gas diffusion flow path layer are integrated (i.e., a flow path integrated positive electrode for a metal secondary battery), from the viewpoint of producing a lighter lithium-air battery stack cell, it is preferable to use several thin metal wires lighter than carbon paper as the material (current collector) of the current collector. In this case, from the viewpoint of reducing the weight of the lithium-air battery stack cell, it is preferable to use a thinner metal wire, but if the wire is too thin, the battery resistance increases. Therefore, it is preferable that the wire diameter is in the range of 50 μm to 100 μm, as in the metal wire used in Table 4.

[0106] Furthermore, as shown in Table 4, when a positive electrode having a current collector fixed in a gas diffusion flow path layer is provided as a positive electrode in which a gas diffusion flow path layer and a positive electrode layer, one of which is fixed to each side of the gas diffusion flow path layer, are integrated (i.e., a flow path-integrated positive electrode for a metal secondary battery), it has been confirmed that a lithium-air battery stack cell can be fabricated and discharged in the same manner as in "Cell Example 2" when an aluminum foil ribbon material (Al-12-3) is used as the material (current collector) of the current collector other than aluminum wire ("Cell Example 5"), a Cu wire is used ("Cell Example 8", "Cell Example 9", and "Cell Example 11"), or a SUS wire (SUS-100, SUS-50) is used ("Cell 6" and "Cell 7"). However, from Table 4, it was also confirmed that when metal wire is used as the current collecting material, even if the metal wire is SUS wire (SUS-100, SUS-50), it is possible to fabricate a lithium-air battery stack cell and perform discharge, but it is preferable to use aluminum wire or Cu wire, which have low resistance and specific gravity, in terms of discharge capacity.

[0107] <Fabrication of Lithium-Air Battery Stack Cell (i.e., Layered Lithium-Air Battery) and Discharge Test Results (Part 2)> Furthermore, the shape of the lithium-air battery stack cell (i.e., stacked lithium-air battery) and the positive electrode was 2 × 2 cm 2Square (effective electrode area: 8 cm 2 ), and the amount of electrolyte immersed in the positive electrode unit was 44 μl (44 × 10 -3 cm 3 ), 10 new types of lithium-air battery stack cells were fabricated in the same manner as above (i.e., in the same manner as the cell examples shown in Table 4) and discharge tests were conducted (discharge test conditions: 0.4 mA / cm per electrode area). 2 , 1 cell (8cm 2 ) was performed. In this application, the shape of the "lithium-air battery stack cell (i.e., stacked lithium-air battery) and the shape of the positive electrode" means the shape seen from directly above in the direction in which the positive electrode units are stacked as shown in FIG. 1, unless otherwise specified. The cells are shown in Table 5 as "Cell Example 12" to "Cell Example 21". For the positive electrode units constituting "Cell Example 12" to "Cell Example 21" shown in Table 5, six types of positive electrode units shown in Table 3 as specific embodiments of the present invention (specifically, "Positive Electrode Unit Example 3", "Positive Electrode Unit Example 4", "Positive Electrode Unit Example 5", "Positive Electrode Unit Example 6", "Positive Electrode Unit Example 7", and "Positive Electrode Unit Example 9"), or "Positive Electrode Unit Example 2" shown in Table 3 as a comparative example, were used. Table 5 shows the weight (unit: mg) and volume (unit: mL=cm) of each of the fabricated lithium-air battery stack cells (i.e., "Cell Example 12" to "Cell Example 21"). 3 ), the type of positive electrode unit and current collector material used, the discharge amount from the cell (unit: mAh, condition: current 3.2 mA, in air), discharge energy (unit: mWh), weight energy density (unit: Whkg -1 ), and volumetric energy density (unit: WhL -1 The "channel layer" in parentheses in the "example positive electrode unit" in Table 5 refers to the gas diffusion channel layer used in the positive electrode unit.

[0108] In "Cell Example 12" and "Cell Example 16" of the lithium-air battery stack cell using "Cathode Unit Example 2", the cathode unit constituting the cell is formed by laminating two laminated films, in which a cathode layer is fixed to only one side of a gas diffusion flow path layer and integrated, so that the flow path layers face each other, as shown in "Cathode Unit Examples 2 and 8" in Fig. 4. Here, in "Cell Example 12", one aluminum foil ribbon (Al-12-3) is used as a current collecting material between the two gas diffusion flow path layers, and in "Cell Example 16", Cu wire (Cu-50) is used as a current collecting material between the two gas diffusion flow path layers, and current is collected by protruding or drawing out the current collecting material outside the cathode unit.

[0109] [Table 5]

[0110] As shown in Table 5, when comparing "Cell Example 12" and "Cell Example 13", which use carbon paper (specifically, "CP1") as the gas diffusion flow path layer constituting the positive electrode unit, "Cell Example 13", which uses "Positive Electrode Unit Example 3" of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in FIG. 4) consisting of one sheet of "CP1" as the positive electrode unit, compared to "Cell Example 12", which uses "Positive Electrode Unit Example 2" (see "Positive Electrode Unit Examples 2, 8" in FIG. 4) of the comparative example consisting of two sheets of "CP1" as the positive electrode unit, has a larger discharge capacity and discharge energy than "Cell Example 13", which uses a lighter and smaller (or thinner) lithium-air battery stack cell, and can improve the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell. Similarly, it was confirmed that in "Cell Example 14" and "Cell Example 15," which use as positive electrode units "Positive Electrode Unit Example 5" and "Positive Electrode Unit Example 9" of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in Figure 4), which are lighter and thinner than the comparative example "Positive Electrode Unit Example 2," higher weight and volumetric energy density can be obtained as lithium-air battery stack cells.

[0111] Furthermore, as shown in Table 5, when comparing "Cell Example 16" and "Cell Example 17", which use carbon paper (specifically, "CP1") as the gas diffusion flow path layer constituting the positive electrode unit, it was confirmed that "Cell Example 17", which uses "Positive Electrode Unit Example 3" of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in Figure 4) consisting of one sheet of "CP1" has a larger discharge capacity and discharge energy than "Cell Example 16", which uses "Positive Electrode Unit Example 2" (see "Positive Electrode Unit Examples 2, 8" in Figure 4) of the comparative example consisting of two sheets of "CP1" as the positive electrode unit, despite being a lighter and smaller (or thinner) lithium-air battery stack cell, and can improve the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell. Similarly, it was confirmed that in "Cell Example 18," "Cell Example 19," "Cell Example 20," and "Cell Example 21," which use as positive electrode units "Positive Electrode Unit Example 4," "Positive Electrode Unit Example 5," "Positive Electrode Unit Example 6," and "Positive Electrode Unit Example 9" (see "Positive Electrode Unit Examples 3-7, 9" in Figure 4) of the present invention, which are lighter and thinner than "Positive Electrode Unit Example 2" of the comparative example (see "Positive Electrode Unit Examples 2, 8" in Figure 4), higher weight and volumetric energy density can be obtained as lithium-air battery stack cells. Although not shown in Table 5, when "CP5," a thin carbon paper having a thickness of 50 μm, is used as the gas diffusion flow path layer constituting the positive electrode unit (see Table 1), the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell is lower than in "Cell Example 19," which uses "CP3" having a thickness of 200 μm (see Table 1) as the gas diffusion flow path layer constituting the positive electrode unit, "CP4" having a thickness of 120 μm (see Table 1), or "Cell Example 21," which uses "CP6" having a thickness of 420 μm (see Table 1), and therefore it was confirmed that a lower limit of the thickness of the gas diffusion flow path layer is preferably 50 μm or more.

[0112] <Fabrication of Lithium-Air Battery Stack Cell (i.e., Layered Lithium-Air Battery) and Discharge Test Results (Part 3)> Furthermore, the shape of the lithium-air battery stack cell (i.e., stacked lithium-air battery) and the positive electrode was 2 × 2 cm 2 Square (effective electrode area: 8 cm 2 ) to 2×5cm 2 Rectangular shape (effective electrode area: 20 cm 2 ), four new types of lithium-air battery stack cells were fabricated in the same manner as above (i.e., in the same manner as the cell examples shown in Tables 4 and 5) and discharge tests were performed (discharge test conditions: 0.4 mA / cm per electrode area). 2 , 1 cell (20 cm 2 ) was performed. The cells are shown in Table 6 as "Cell Example 22" to "Cell Example 25". For the positive electrode units constituting "Cell Example 22" to "Cell Example 25" in Table 6, two types of positive electrode units shown in Table 3 as a specific embodiment of the present invention (specifically, "Positive Electrode Unit Example 3" and "Positive Electrode Unit Example 9"), or "Positive Electrode Unit Example 2" and "Positive Electrode Unit Example 8" shown in Table 3 as comparative examples, were used. Table 6 shows the weight (unit: mg) and volume (unit: mL=cm) of each of the fabricated lithium-air battery stack cells (i.e., "Cell Example 22" to "Cell Example 25"). 3 ), the type of positive electrode unit and current collector material used, the discharge amount from the cell (unit: mAh, condition: current 8.0 mA, in air), discharge energy (unit: mWh), and weight energy density (unit: Whkg -1 ), and volumetric energy density (unit: WhL -1 The "channel layer" in parentheses in the "example positive electrode unit" in Table 6 refers to the gas diffusion channel layer used in the positive electrode unit.

[0113] [Table 6]

[0114] As shown in Table 6, when comparing "Cell Example 22" and "Cell Example 23", which use carbon paper (specifically, "CP1") as the gas diffusion flow path layer that constitutes the positive electrode unit, "Cell Example 23", which uses positive electrode unit example 3 of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in FIG. 4) consisting of one sheet of "CP1", has a larger discharge capacity and discharge energy than "Cell Example 22", which uses the comparative example "Positive Electrode Unit Example 2" (see "Positive Electrode Unit Examples 2, 8" in FIG. 4) consisting of two sheets of "CP1" as the positive electrode unit, despite being a lighter and smaller (or thinner) lithium-air battery stack cell, and it was confirmed that this can improve the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell. Similarly, when comparing "Cell Example 24" and "Cell Example 25", which use carbon paper (specifically, "CP6") as the gas diffusion flow path layer that constitutes the positive electrode unit, it was confirmed that "Cell Example 25", which uses "Positive Electrode Unit Example 9" of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in Figure 4) consisting of a single sheet of "CP6" has a larger discharge capacity and discharge energy than "Cell Example 24", which uses "Positive Electrode Unit Example 8" (see "Positive Electrode Unit Examples 2, 8" in Figure 4) of the comparative example that consists of two sheets of "CP6" as the positive electrode unit, despite being a lighter and smaller (or thinner) lithium-air battery stack cell, and can improve the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell.

[0115] <Fabrication of Lithium-Air Battery Stack Cell (i.e., Layered Lithium-Air Battery) and Discharge Test Results (Part 4)> In addition, the shape of the lithium-air battery stack cell (i.e., stacked lithium-air battery) and the positive electrode was 2 × 5 cm 2 Rectangular shape (effective electrode area: 20 cm 2 ) to 4×4cm 2 Square (effective electrode area: 32 cm 2), except for the large change in size, four new types of lithium-air battery stack cells were fabricated in the same manner as above (i.e., in the same manner as the cell examples shown in Tables 4 to 6) and discharge tests were performed (discharge test conditions: 0.4 mA / cm per electrode area). 2 , 1 cell (32 cm 2 ) was performed. The cells are shown in Table 7 as "Cell Example 26" to "Cell Example 29". For the positive electrode units constituting "Cell Example 26" to "Cell Example 29" in Table 7, two types of positive electrode units shown in Table 3 as a specific embodiment of the present invention (specifically, "Positive Electrode Unit Example 3" and "Positive Electrode Unit Example 9"), or "Positive Electrode Unit Example 2" and "Positive Electrode Unit Example 8" shown in Table 3 as comparative examples, were used. Table 7 shows the weight (unit: mg) and volume (unit: mL=cm) of each of the fabricated lithium-air battery stack cells (i.e., "Cell Example 26" to "Cell Example 29"). 3 ), the type of positive electrode unit and current collector material used, the discharge amount from the cell (unit: mAh, condition: current 12.8 mA, in air), discharge energy (unit: mWh), weight energy density (unit: Whkg -1 ), and volumetric energy density (unit: WhL -1 The measurement results of the gas diffusion layer 14 are shown in Table 7. Note that the "channel layer" in parentheses in the "example positive electrode unit" in Table 7 refers to the gas diffusion channel layer used in the positive electrode unit.

[0116] [Table 7]

[0117] As shown in Table 7, when comparing "Cell Example 26" and "Cell Example 27", which use carbon paper (specifically, "CP1") as a gas diffusion flow path layer constituting the positive electrode unit, "Cell Example 27", which uses "Positive Electrode Unit Example 3" of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in FIG. 4) consisting of one sheet of "CP1" as a positive electrode unit, compared to "Cell Example 26", which uses "Positive Electrode Unit Example 2" (see "Positive Electrode Unit Examples 2, 8" in FIG. 4) of the comparative example consisting of two sheets of "CP1" as a positive electrode unit, has almost the same discharge capacity and discharge energy, despite being a lighter and smaller (or thinner) lithium-air battery stack cell, and it was confirmed that the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell can be improved. Similarly, when comparing "Cell Example 28" and "Cell Example 29", which use carbon paper (specifically, "CP6") as the gas diffusion flow path layer that constitutes the positive electrode unit, it was confirmed that "Cell Example 29", which uses "Positive Electrode Unit Example 9" of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in Figure 4) consisting of a single sheet of "CP6" has a larger discharge capacity and discharge energy than "Cell Example 28", which uses "Positive Electrode Unit Example 8" (see "Positive Electrode Unit Examples 2, 8" in Figure 4) of the comparative example consisting of two sheets of "CP6" as the positive electrode unit, despite being a lighter and smaller (or thinner) lithium-air battery stack cell, and can improve the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell.

[0118] <Fabrication of Lithium-Air Battery Stack Cell (i.e., Layered Lithium-Air Battery) and Discharge Test Results (Part 5)> Furthermore, the shape of the positive electrode is 2 x 2 cm 2 Square (effective electrode area: 8 cm 2 New positive electrode units ("positive electrode unit example 10" and "positive electrode unit example 11") were fabricated using positive electrode unit example 3, which is a positive electrode unit having a capacity of 100%. FIG. 8 shows schematic diagrams of "positive electrode unit example 3" and "positive electrode unit example 10" and "positive electrode unit example 11" fabricated using the positive electrode unit (see the left diagram in FIG. 8 for "positive electrode unit example 3," the center diagram for "positive electrode unit example 10," and the right diagram for "positive electrode unit example 11").

[0119] As shown in the center of FIG. 8, "Positive Electrode Unit Example 10" is a positive electrode layer constituting Positive Electrode Unit Example 3, in which slit grooves 1 mm wide and 30 μm deep are provided in the cross direction from the center on both sides to divide the positive electrode layer into four. A lithium-air battery stack cell (i.e., a stacked lithium-air battery) made using this positive electrode unit is shown in Table 8 as "Cell Example 30". The slit grooves in "Positive Electrode Unit Example 10" were provided by pressing the corresponding thickness portion of a 1 mm thick glass plate against the positive electrode layer to crush the positive electrode layer. There is no change in the weight or volume (positive electrode unit thickness) of the positive electrode unit before and after the introduction of the slit grooves.

[0120] "Positive electrode unit example 11" is obtained by peeling off (removing) the positive electrode layer of the slit groove portion of "positive electrode unit example 10" to expose the carbon paper (CP) that is the gas diffusion flow path layer. A lithium-air battery stack cell (i.e., a laminated lithium-air battery) was fabricated using this as a new positive electrode unit (see the right diagram in Figure 8). The lithium-air battery stack cell fabricated using this positive electrode unit is shown in Table 8 as "Cell example 31".

[0121] Table 8 shows the weight (unit: mg) and volume (unit: mL = cm) of a lithium-air battery stack cell prepared using "positive electrode unit 10" (i.e., "Cell Example 30") and a lithium-air battery stack cell prepared using "positive electrode unit 11" (i.e., "Cell Example 31"). 3 The discharge test was performed in the same manner as above (i.e., in the same manner as the cell examples shown in Tables 4 to 7), and the discharge test conditions were 0.4, 2.0, and 3.0 mA / cm as the current per electrode area. 2 Therefore, one cell (8 cm 2) were set to 3.2, 16, and 24 mA. For comparison, Table 8 also lists the measurement results of "Cell Example 17" in Table 5, which is a lithium-air battery stack cell (i.e., a laminated lithium-air battery) prepared using "Cathode Unit 3", together with the type of cathode unit and current collector material used. The "flow path layer" in Table 8 refers to the gas diffusion flow path layer used in the cathode unit example. Figure 9 shows the relationship (measurement results) between the current and discharge capacity of various lithium-air battery stack cells, namely "Cell Example 17" (cathode unit example: cathode unit example 3), "Cell Example 30" (cathode unit example: cathode unit example 3 with a 1 mm slit groove), and "Cell Example 31" (cathode unit example: cathode unit example 3 with a 1 mm slit groove and the bottom of the slit groove removed to expose the gas diffusion flow path layer) shown in Figure 8 and Table 8.

[0122] [Table 8]

[0123] As shown in Table 8 and Figure 9, it was confirmed that in "Cell Example 17" (see the left diagram of Figure 8), which does not have slit grooves in the positive electrode layer, the discharge capacity that can be extracted from the cell rapidly decreases when the discharge current is increased, and it is almost impossible to discharge at a discharge current of 24 mA. On the other hand, as shown in Table 8 and Figure 9, it was confirmed that in "Cell Example 30" (see the center diagram of Figure 8), which has slit grooves in the positive electrode layer, it is possible to discharge sufficiently even when the discharge current is increased to 24 mA. This is understood to be because the grooves in the positive electrode layer act as gas vents, making it easier to absorb air (specifically, oxygen gas in the air), which improves the output characteristics of the cell and allows a larger discharge capacity to be obtained even when the discharge current is increased. On the other hand, as shown in Table 8 and Figure 9, in "Cell Example 31" (see the right diagram in Figure 8), in which slit grooves were provided in the positive electrode layer and the bottom surface of the slit grooves was removed to expose the gas diffusion flow path layer, it was confirmed that the discharge capacity at high discharge currents (specifically, 16 mA or more) tended to be lower than that of "Cell Example 17." This is understood to be because, when the positive electrode layer is divided within the positive electrode layer plane, the current collection function of the positive electrode unit is reduced more than the improvement in oxygen gas absorption function due to the presence of the slit grooves, resulting in a decrease in output characteristics.

[0124] <Fabrication of Lithium-Air Battery Stack Cell (i.e., Layered Lithium-Air Battery) and Discharge Test Results (Part 6)> In addition, the shape of the lithium-air battery stack cell (i.e., stacked lithium-air battery) and the positive electrode was 2 × 5 cm 2 (Effective electrode area: 20cm 2 ) and the positive electrode unit constituting the cell is a laminate with 10 layers (effective electrode area: 200 cm 2 ) and applied a confining pressure of 80 kPa to the laminate, two new types of lithium-air battery stack cells were fabricated in the same manner as above (i.e., in the same manner as the cell examples shown in Tables 4 and 5). Discharge tests (discharge test conditions: 0.5 mA / cm per electrode area) were performed on the two types of lithium-air battery stack cells fabricated. 2 , 1 cell (200cm 2) was performed. The cells are shown in Table 9 as "Cell Example 32" and "Cell Example 33". For the positive electrode units in Table 9, two types of positive electrode units shown in Table 3 as specific embodiments of the present invention (specifically, "Positive Electrode Unit Example 8" shown as a comparative example and "Positive Electrode Unit Example 9" shown as an embodiment) were used. Table 9 shows the weight (unit: mg) and volume (unit: mL=cm) of each of the fabricated lithium-air battery stack cells (i.e., "Cell Example 32" and "Cell Example 33"). 3 ), the type of positive electrode unit and current collector material used, the discharge amount from the cell (unit: mAh, condition: current 100 mA, in air), discharge energy (unit: mWh), and weight energy density (unit: Wh kg -1 ), and volumetric energy density (unit: WhL -1 The "channel layer" in parentheses in the "example positive electrode unit" in Table 9 refers to the gas diffusion channel layer used in the positive electrode unit.

[0125] [Table 9]

[0126] As shown in Table 9, when comparing "Cell Example 32" and "Cell Example 33", which use carbon paper (specifically, "CP6") as the gas diffusion flow path layer constituting the positive electrode unit, "Cell Example 33", which uses positive electrode unit example 9 of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in FIG. 4) consisting of one sheet of "CP6", has a larger discharge capacity and discharge energy than "Cell Example 32", which uses "Positive Electrode Unit Example 8" of the comparative example (see "Positive Electrode Unit Examples 2, 8" in FIG. 4) consisting of two sheets of "CP6" as the positive electrode unit, despite being a lighter and smaller (or thinner) lithium-air battery stack cell, and it was confirmed that the amount of energy (energy density) per weight and volume of the lithium-air battery stack cell can be improved.

[0127] Furthermore, although not shown, it was confirmed that "Cell Example 33" using Positive Electrode Unit Example 9 of the present invention (see "Positive Electrode Unit Examples 3-7, 9" in FIG. 4) consisting of one sheet of "CP6" reduces the work process of stacking the positive electrode units by half and allows stacking with reduced error in the stacking position of each electrode, compared to "Cell Example 32" using "Positive Electrode Unit Example 8" (see "Positive Electrode Unit Examples 2, 8" in FIG. 4) of the comparative example consisting of two sheets of "CP6" as the positive electrode unit. For this reason, it was confirmed that the work time required to fabricate the lithium-air battery stack cell was only about 40 minutes to fabricate "Cell Example 33", compared to about 60 minutes required for a standard worker to fabricate "Cell Example 32". [Industrial Applicability]

[0128] By using the flow channel integrated positive electrode for a metal secondary battery according to the present invention, in which a gas diffusion flow channel layer and a positive electrode layer fixed to both sides of the gas diffusion flow channel layer are integrated, as a positive electrode for a metal secondary battery, it is possible to provide a lithium-air battery excellent in weight and volumetric energy density while exhibiting discharge characteristics comparable to those of a metal secondary battery flow channel integrated positive electrode in which a positive electrode layer is fixed to only one side of a single gas diffusion flow channel layer and integrated. Therefore, it can be suitably used as a positive electrode for a lightweight and small metal secondary battery, for example, a lithium-air battery (particularly, a lithium-air battery stack cell (i.e., a stacked lithium-air battery)). Furthermore, by providing a slit groove in the positive electrode layer constituting the above-mentioned flow channel integrated positive electrode for a metal secondary battery according to the present invention, it is possible to provide a metal secondary battery, for example, a lithium-air battery (particularly, a lithium-air battery stack cell) that is excellent in discharge characteristics at high current while improving output characteristics. For these reasons, the flow path-integrated positive electrode for a metal secondary battery according to the present invention can be suitably used as a positive electrode for a metal secondary battery such as a lithium-air battery (particularly, a lithium-air battery stack cell), and is highly expected to be applied to such batteries. Therefore, it has potential for use in a wide variety of industries (for example, the electrical and communication equipment industry, the energy industry, the transportation industry, the medical equipment industry, etc.).

Claims

1. The battery includes a gas diffusion flow path layer, which is a porous layer made of a fibrous carbon material, and two positive electrode layers, which are porous layers made of the same or different fibrous carbon material as the carbon material, The two positive electrode layers are provided on both sides of the gas diffusion flow path layer, a portion of the flow path layer includes hollow pores that are generated by entanglement of a fibrous carbon material in the flow path layer and a fibrous carbon material of each of the two positive electrode layers that penetrates into the flow path layer; The flow path layer and the two positive electrode layers are integrated by the pores. Positive electrode with integrated flow channel for metal secondary batteries.

2. 2. The flow path-integrated positive electrode for a metal secondary battery according to claim 1, wherein the pores have a continuous pore size distribution of 10 nm or more and 200 μm or less.

3. 3. The flow path-integrated positive electrode for a metal secondary battery according to claim 1, wherein at least a portion of the fibrous carbon material of each of the two positive electrode layers penetrates into the flow path layer to a thickness of 5 μm or more from an outermost surface of the flow path layer.

4. The flow path-integrated positive electrode for a metal secondary battery according to claim 1 , wherein the hollow pores have a continuous pore size distribution of 10 μm or more and 50 μm or less.

5. The hollow pores have a pore volume of 0.5 cm per gram weight of the two positive electrode layers. ３ / g or more 5.0cm ３ The flow path-integrated positive electrode for a metal secondary battery according to claim 1 , wherein the flow path-integrated positive electrode for a metal secondary battery has a value of not more than 1 / g.

6. 6. The flow path integrated positive electrode for a metal secondary battery according to claim 1, wherein the flow path layer immediately before the fibrous carbon material of the two positive electrode layers enters the flow path layer has a thickness of 50 μm or more and 1000 μm or less.

7. The flow path-integrated positive electrode for a metal secondary battery according to claim 1 , wherein the fibrous carbon material is a carbon fiber and / or a carbon nanotube.

8. The BET specific surface area per gram weight of the two positive electrode layers is 250 m ２ / g or more 1400m ２ The flow path-integrated positive electrode for a metal secondary battery according to any one of claims 1 to 7, wherein the positive electrode has a BET specific surface area of ​​0.1 to 0.5 μm / g or less, The pores having a pore size distribution of 0.1 μm to 10 μm have a pore volume of 1.0 cm per gram weight of the two positive electrode layers. ３ / g or more 10.0cm ３ / g or less.

9. 9. The flow path-integrated positive electrode for a metal secondary battery according to claim 1, wherein the pore size distribution of each of the two positive electrode layers and the pore volume per gram weight of each of the two positive electrode layers are approximately the same.

10. 10. The flow path-integrated positive electrode for a metal secondary battery according to claim 1, wherein a peel strength between each of the two positive electrode layers and the flow path layer is 1 mN / 5 mm or more in a 90-degree peel test.

11. A current collector is fixed in the flow path layer, The flow passage-integrated positive electrode for a metal secondary battery according to claim 1 , wherein the current collector is a metal wire material or a metal foil material.

12. 12. The flow path-integrated positive electrode for a metal secondary battery according to claim 1, wherein, when a contact surface between the flow path layer and the two positive electrode layers on both sides of the flow path layer is defined as a surface of the flow path layer, an area of ​​the current collector as viewed through the surface is 15% or less of an area of ​​the surface.

13. The flow channel-integrated positive electrode for a metal secondary battery according to claim 1 , wherein at least one of the two positive electrode layers has at least one slit groove.

14. A metal secondary battery, comprising: a positive electrode that is the flow path-integrated positive electrode for a metal secondary battery according to claim 1 .

15. a dispersion in which a fibrous carbon material is dispersed in a solvent as a raw material for the positive electrode layer of the porous layer; a porous substrate made of a fibrous carbon material as a gas diffusion flow path layer of the porous layer; and a step of filtering the dispersion liquid on the porous substrate, laminating the carbon material dispersed in the dispersion liquid on one side of the flow path layer, and drying the laminated porous substrate to fix the first positive electrode layer and integrate it with the flow path layer; a step of turning over the flow path layer on which the positive electrode layer has been formed, stacking the carbon material dispersed in the dispersion liquid on the other side of the flow path layer, and drying the stacked porous substrate to fix the second positive electrode layer and integrate it with the flow path layer; The method for producing the flow path-integrated positive electrode for a metal secondary battery according to claim 1 , comprising:

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