JP6665729B2 - Lithium-air battery cathode structure - Google Patents

Description

  The present invention relates to a positive electrode structure of a lithium air battery.

  The lithium-air battery has an energy density that is more than seven times that of the lithium-ion battery that is currently being mounted on vehicles, and can provide the energy density of 700 Wh / kg required for the spread of full-scale electric vehicles (EV). Has been actively researched. Such a lithium-air battery has a structure using metal lithium or an alloy or a compound containing metal lithium as a main component as a negative electrode active material. Depending on the type of the electrolyte, an aqueous electrolyte and a non-aqueous electrolyte may be used. It is roughly divided into two.

  As a positive electrode structure of an aqueous lithium-ion battery, an electrolytic solution is disposed between the positive electrode and the negative electrode layer, a polytetrafluoroethylene (PTFE) filter is disposed outside the positive electrode, and these are placed in a gas barrier laminate film. There is known a structure of a lithium-air battery cell that is sealed, and a window is opened only in a laminated film on the PTFE side to make contact with air (for example, Non-Patent Document 1). However, in the structure described in Non-Patent Document 1, when the lithium-air battery is placed on its side, the electrolyte may leak. Further, when a lithium air battery is used for a long time, the discharge voltage tends to be unable to be maintained at a desired value.

Report of GS Yuasa Corporation, "Current status and issues of aqueous lithium / air batteries" (June 2010)

  In view of the above problems, the present invention can prevent the electrolyte from leaking, can have a structure suitable for a vertical lithium-air battery cell or the like, improve the flexibility of layout, and stabilize for a long time. It is an object of the present invention to provide a positive electrode structure of a lithium air battery capable of performing a discharged operation.

  In order to achieve the above object, the present invention provides, in one aspect, a positive electrode structure of a lithium-air battery, the positive electrode structure of a lithium-air battery including at least a positive electrode material, a positive electrode current collector, and an exterior material, Comprises a first positive electrode material and a second positive electrode material, in plan view, the first positive electrode material surrounds the second positive electrode material over the entire circumference, the first positive electrode material and the The region formed by the difference in size from the second positive electrode material forms a contact region between the first positive electrode material and the positive electrode current collector, and the positive electrode current collector and the The exterior material is joined.

  ADVANTAGE OF THE INVENTION According to this invention, leakage of an electrolyte solution can be prevented, it can be set as the suitable structure for a lithium air battery cell of a vertical installation, etc., the degree of freedom of a layout is improved, and the stable discharge for a long time is possible. The positive electrode structure of the lithium air battery described above is provided.

FIG. 1 is a schematic cross-sectional view illustrating a basic concept of a lithium-air battery to which a positive electrode structure of a lithium-air battery according to the present invention is applied. FIG. 2A is a schematic diagram schematically showing the configuration of the positive electrode material in the first embodiment of the positive electrode structure of the lithium-air battery according to the present invention, and FIG. FIG. 2 is a schematic diagram schematically showing the configuration of the positive electrode material in a plan view when the positive electrode material is viewed from the direction of the arrow in FIG. FIG. 3 is a sectional view schematically showing the positive electrode structure of the first embodiment of the positive electrode structure of the lithium-air battery according to the present invention. FIG. 4 is a partial cross-sectional view schematically showing the structure of a lithium-air battery cell employing the positive electrode structure of the lithium-air battery according to the present invention. FIG. 5 is a partial cross-sectional view schematically showing a positive electrode structure in a second embodiment of the positive electrode structure of the lithium-air battery according to the present invention. FIG. 6 is a partial cross-sectional view schematically showing a positive electrode structure in a third embodiment of the positive electrode structure of the lithium-air battery according to the present invention. FIG. 7 is a partial sectional view schematically showing a positive electrode structure of a fourth embodiment of the positive electrode structure of the lithium-air battery according to the present invention. FIG. 8 is a schematic diagram schematically showing a part of the positive electrode structure of the example regarding the positive electrode structure of the lithium-air battery according to the present invention. FIG. 9 is a schematic diagram schematically showing the structure of a lithium-air battery cell of a comparative example, with respect to the positive electrode structure of the lithium-air battery according to the present invention. FIG. 10 is a graph showing the discharge characteristics of the example and the comparative example with respect to the positive electrode structure of the lithium-air battery cell according to the present invention.

  Hereinafter, embodiments of a positive electrode structure of a lithium-air battery according to the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited by the present embodiment. Further, the accompanying drawings are diagrams for explaining the outline of the present embodiment, and some of the attached devices are omitted.

  First, FIG. 1 schematically shows a lithium air battery 1 to which a positive electrode structure according to the present invention is applied. As shown in FIG. 1, a lithium-air battery 1 includes a positive electrode (air electrode) 2 having a positive electrode current collector supporting a catalyst, an aqueous electrolyte 3, a solid electrolyte (isolation layer) 4, and a negative electrode layer 5. ing. The buffer layer (protective layer) 6 is also referred to as a separator, and is a layer for preventing the solid electrolyte 4 and the negative electrode layer 5 from directly contacting each other. In the figure, the load 7 is schematically shown. The lithium air battery 1 is configured such that reactions represented by the following formulas (i) to (iii) occur in each of the negative electrode layer 5 and the positive electrode 2.

As shown in FIG. 1, an aqueous electrolyte 3 is disposed inside the positive electrode 2. In addition, since oxygen (O ₂ ) in the air is used as a positive electrode active material when discharging the lithium-air battery 1, it is necessary for the positive electrode 2 to take in air and secure an effective reaction field. is there.

1. First Embodiment A first embodiment of a positive electrode structure of a lithium-air battery according to the present invention will be described with reference to FIGS. The positive electrode structure of the lithium air battery according to the present embodiment includes at least a positive electrode material 10, a positive electrode current collector 20, a positive electrode exterior material 30, and a heat welding member 40.

First, FIGS. 2A and 2B illustrate only the positive electrode material 10 to facilitate understanding of the present invention.
As shown in FIG. 2A, the positive electrode material 10 has a flat plate shape, and includes a first positive electrode material 11 and a second positive electrode material 12 having the same or substantially the same shape and material. The first positive electrode material 11 has a first outer peripheral portion 11a on a side surface thereof. The second positive electrode material 12 is smaller than the first positive electrode material 11, and has a second outer peripheral portion 12a on a side surface thereof. The surface defined by the first outer peripheral portion 11a of the first positive electrode material 11 is larger than the surface defined by the second outer peripheral portion 12a of the second positive electrode material 12. Therefore, by placing the second positive electrode material 12 on the first positive electrode material 11, the first positive electrode material 11 is surrounded by the second positive electrode material 12 (outward from the second outer peripheral portion 12 a). A region (contact region 11b) for contact between the first positive electrode material 11 and the positive electrode current collector 20 is formed on the surface (1). In this specification, “the same shape” generally means a similar shape.

  Further, as shown in FIG. 2B, in plan view, the first outer peripheral portion 11 a of the first positive electrode material 11 extends over the entire outer periphery of the second outer peripheral portion 12 a of the second positive electrode material 12. Siege. In other words, the region surrounded by the first outer peripheral portion 11a includes the region surrounded by the second outer peripheral portion 12a. Further, a region formed by a difference in size between the first positive electrode material 11 and the second positive electrode material 12 forms a contact region 11b between the first positive electrode material 11 and the positive electrode current collector 20. . That is, a contact region 11b between the first positive electrode material 11 and the positive electrode current collector 20 is provided in a region other than the region surrounded by the second outer peripheral portion 12a of the first positive electrode material 11. In addition, in this specification, a plane viewed from the second positive electrode side toward the aqueous electrolyte solution is used as “plan view”.

  The shape of the first positive electrode material 11 and the second positive electrode material 12 is such that a contact region 11b is formed around the second positive electrode material 12 in plan view, and the first positive electrode material 11 is The shape may be any shape as long as the shape can surround the entire circumference, and may be the same or different. For example, the shape of the positive electrode material 10 can adopt a disk shape, a circular shape, or the like in addition to the illustrated flat plate shape. The outer dimensions and thicknesses of the first positive electrode material 11 and the second positive electrode material 12 are such that the positive electrode current collector 20, the heat welding member 40, and the exterior material 30 are arranged in this order from the aqueous electrolyte 13 side in the contact region 11b. Any external dimensions and thickness can be used.

Subsequently, the positive electrode structure of the lithium-air battery according to the present embodiment will be described with reference to FIG.
As shown in FIG. 3, the first positive electrode material 11 is located on the aqueous electrolyte 13 side with respect to the second positive electrode material 12. Further, the second positive electrode material 12 is located on the air side with respect to the first positive electrode material 11, and is configured to be exposed to the air. In this specification, the “atmosphere side” refers to the atmosphere side to which the second positive electrode material 12 is exposed.

  The positive electrode current collector 20 is in contact with the first positive electrode material 11 at least in a contact region 11b of the first positive electrode material 11. In the illustrated example, the positive electrode current collector 20 penetrates between the first positive electrode material 11 and the second positive electrode material 12 and is defined by an outer peripheral portion 11a of the first positive electrode material 11 facing each other. And the surface defined by the outer peripheral portion 12 a of the second positive electrode material 12. Since the positive electrode current collector 20 is in close contact with the first positive electrode material 11 and the second positive electrode material 12, the resistance at the positive electrode can be reduced. Such a structure can be manufactured, for example, by dividing the kneaded material of the positive electrode material 10 into the first positive electrode material 11 and the second positive electrode material 12 and sandwiching the positive electrode current collector 20 therebetween.

  The positive electrode exterior material 30 is located on the atmosphere side with respect to the positive electrode current collector 20, and has an opening 31 having the same or substantially the same shape as the second positive electrode material 12. Further, the positive electrode exterior material 30 comes into contact with the second positive electrode material 12 (or via the heat welding member 40 when the heat welding member 40 is located between the second positive electrode material 12), and Thus, the positive electrode current collector 20 and the heat welding member 40 are in contact with each other. The area of the opening 31 of the positive electrode exterior material 30 is smaller than the area of the atmosphere side surface defined by the outer peripheral portion 12a of the second positive electrode material 12 and is an area capable of taking air into the second positive electrode material 12. Good. The shape, outer dimensions, and thickness of the positive electrode exterior material 30 are such that the second positive electrode material 12 contacts the second positive electrode material 12 via the heat welding member 40 in the positive electrode structure formed by thermocompression bonding of the positive electrode, and the positive electrode current collector Any shape, external dimensions and thickness that can be joined to the substrate 20 may be used.

  The heat welding member 40 is located on the air side with respect to the positive electrode current collector 20 and on the aqueous electrolyte solution 13 side with respect to the positive electrode exterior material 30, and has an opening having the same or substantially the same shape as the second positive electrode material 12. 41. The opening 41 of the heat welding member 40 is disposed at the same or substantially the same position as the opening 31 of the positive electrode exterior material 30. Also, the heat welding member 40 joins the positive electrode current collector 20 and the positive electrode exterior material 30 by melting at the welding portion 40a. The area of the opening 41 of the heat welding member 40 is smaller than the area of the surface on the atmosphere side defined by the second outer peripheral portion 12a of the second positive electrode material 12, and the area of the positive electrode current collector 20 at the welding portion 40a Any area may be used as long as the area can be joined to the positive electrode exterior material 30 by thermal welding and air can be taken into the second positive electrode material 12. The shape, outer dimensions, and thickness of the heat welding member 40 are determined by the shape, outer dimensions, and thickness of the positive electrode structure formed by thermocompression bonding of the positive electrode, so that the positive electrode current collector 20 and the positive electrode exterior member 30 can be joined at the welded portion 40a. I just need.

  The welded portion 40a is located on the surface on the side of the contact region 11b defined by the outer peripheral portion 11a of the first positive electrode material 11, and the positive electrode is bonded to the positive electrode current collector 20 via the heat welded member 40 by thermocompression bonding. This is a portion where the positive electrode exterior body 30 is joined.

  In the positive electrode structure provided with the above configuration and thermocompression-bonding the positive electrode, the first positive electrode material 11 and the positive electrode current collector 20 contact each other in the contact area 11b of the first positive electrode material 11, and the contact area 11b At the welding portion 40 a, the positive electrode current collector 20 in contact with the positive electrode material 10 and the positive electrode exterior material 30 are joined via the heat welding member 40. As described above, the positive electrode current collector 20 is provided in the region between the large outer peripheral portion and the small outer peripheral portion of the positive electrode material 10, and the positive electrode current collector 20 and the positive electrode By joining with the exterior material 30, leakage of the aqueous electrolyte solution 13 can be prevented. Further, by making the first positive electrode material 11 large enough to surround the second positive electrode material 12 over the entire circumference in plan view, easy contact between the positive electrode current collector 20 and the positive electrode exterior material 30 is possible. Thus, the portion of the second positive electrode material 12 that is exposed to the air can be maintained large, and the portion of the first positive electrode material 11 that contacts the aqueous electrolyte 13 can be increased. Therefore, leakage of the aqueous electrolyte solution can be prevented, air required for the discharge reaction can be efficiently taken into the positive electrode from outside the lithium-air battery, and the portion of the positive electrode that contributes to the reaction of the lithium-air battery can be increased. As a result, a high discharge voltage can be maintained for a long time.

Subsequently, the material of the positive electrode structure of the lithium-air battery according to the present embodiment will be mainly described.
The positive electrode material 10 is generally composed of a conductive auxiliary, a binder (binder), and a catalyst to be supported on the positive electrode current collector 20. Examples of the catalyst include a catalyst capable of promoting an electric reaction such as manganese dioxide (MnO ₂ ), ruthenium oxide (RuO ₂ ), and iridium oxide (IrO ₂ ), and a catalyst in which a noble metal such as platinum (Pt) is supported on carbon or the like. Can be As the conductive additive, a carbon material that can be used as an electrode material such as carbon black can be used. As the binder, polytetrafluoroethylene (PTFE) having air permeability and waterproofness is preferable. By using PTFE as the binder, it is possible to impart excellent air permeability and waterproofness to the positive electrode. Therefore, air can be efficiently taken into the positive electrode, and leakage of the aqueous electrolyte solution from the positive electrode can be suitably prevented. The amount of the binder is, for example, preferably 20% by weight or more, more preferably 20% by weight or more and 50% by weight or less based on the positive electrode material. Within such a range, leakage of the aqueous electrolyte solution can be suitably prevented.

  The positive electrode current collector 20 may be any material having corrosion resistance and conductivity. Specifically, examples of the positive electrode current collector 20 include carbon paper, carbon cloth, carbon nonwoven fabric, porous metal (metal foam), and metal mesh. Of these, metal meshes are preferred. When the positive electrode current collector is a metal mesh, for example, the positive electrode current collector can be easily bonded to the heat welding member 40 and the positive electrode material 10 to facilitate the production of the positive electrode. The metal mesh may be any metal mesh having high corrosion resistance to an aqueous alkaline solution, and examples thereof include a mesh of platinum (Pt), nickel (Ni), titanium (Ti), and the like. Among these, the metal mesh is preferably a titanium mesh. The titanium mesh has high corrosion resistance to an aqueous alkali solution, is relatively lightweight and inexpensive, and can improve both the bonding property with the heat welding member 40 and the adhesion property with the positive electrode material 10. As a result, leakage of the aqueous electrolyte solution can be suitably prevented, and high strength can be imparted to the positive electrode and the lithium-air battery.

  The positive electrode casing 30 is a laminated film of at least one layer of metal foil. Examples of the metal foil include aluminum (Al) and SUS (Stainless Used Steel). Among these, the positive electrode exterior material 30 is preferably an Al foil, and more preferably has a structure of three or more layers including at least the Al foil. As the positive electrode exterior material 30 having a three-layer structure, a laminate film in which the intermediate layer is an Al foil, the outermost layer is a polyethylene terephthalate (PET) resin, and the innermost layer is a polypropylene (PP) resin is preferable. With such a layer structure, the outermost layer can impart more excellent heat resistance and strength to the cathode exterior material, and the innermost layer can impart a low melting point, excellent heat workability and heat sealability to the cathode exterior material. It should be noted that the present invention is not limited to such a layer configuration, and an outermost layer may be a film of an olefin resin such as polyethylene or polypropylene, a film of a nylon resin or the like, and an innermost layer may be a film of a PE resin or the like. Further, as the exterior material having a structure of four or more layers, a structure including one or more layers of a film such as a nylon film between three layers can be adopted.

  The heat welding member 40 may be any member that can weld the positive electrode current collector 20 and the positive electrode exterior material 30 by heat. Examples of the heat welding member 40 include a heat welding sheet, an adhesive, and the like. Specifically, the heat welding member 40 is preferably a heat welding sheet, and examples of the heat welding sheet include a sheet using an acid-modified polypropylene resin or the like as a base material. If the heat welding member 40 is a heat welding sheet, it can be easily joined to the positive electrode exterior material 30 (particularly PP), the metal of the positive electrode current collector 20, and the like. Further, the positive electrode exterior material 30 can be joined to the positive electrode current collector 20 only by welding once from the atmosphere side. Therefore, since the positive electrode and the lithium-air battery can be easily manufactured, the productivity of the positive electrode and the lithium-air battery can be improved. In addition, since the bonding strength between the positive electrode current collector 20 and the positive electrode exterior material 30 can be increased, the leakage of the aqueous electrolyte solution 13 is reliably prevented, and the positive electrode and the lithium-air battery are less likely to be damaged. When the heat-welding member 40 is used as an adhesive, it is preferable to etch the bonding surface between the positive electrode current collector 20 and the positive electrode current collector 20 before bonding.

  According to the present embodiment, the positive electrode current collector 20 and the exterior material 30 are joined using the positive electrode current collector 20 instead of the cathode material 10 and the exterior material 30 that are difficult to join, so that the aqueous solution from the positive electrode is Leakage of the system electrolyte 13 can be prevented.

  In addition, according to the present embodiment, since the positive electrode does not leak electrolyte solution, it is necessary to separately provide, for example, a polytetrafluoroethylene (PTFE) sheet having moisture resistance and gas permeability as the positive electrode structure. Disappears. Thereby, the number of parts of the positive electrode and the lithium air battery can be reduced, and the weight can be reduced. Further, since the positive electrode does not leak the electrolyte solution, a structure suitable for a vertically arranged lithium-air battery cell can be obtained, and the degree of freedom in layout can be improved. Furthermore, since the positive electrode does not leak electrolyte solution, stable discharge can be performed for a long time.

  Furthermore, according to the present embodiment, since the second positive electrode 12 can be directly exposed to the atmosphere, the air required for the discharge reaction can be efficiently supplied from outside the lithium-air battery, and can be supplied for a long time. It enables stable discharge and improves the average discharge voltage of the lithium-air battery. Furthermore, the portion where the first positive electrode material 11 comes into contact with the aqueous electrolyte 13 can be increased. Therefore, an effective reaction field can be secured in the positive electrode. As a result, stable and high-voltage discharge can be performed for a long time.

[Lithium air electric cell]
Subsequently, a lithium-air battery cell having the above-described positive electrode structure will be described with reference to FIG. FIG. 4 is a partial cross-sectional view of the first embodiment of the lithium-air battery cell according to the present invention. The lithium air battery of the present embodiment will be described as a lithium air battery using an aqueous electrolyte. The same reference numerals are given to the positive electrode structure according to the above-described first embodiment, and the description is omitted unless otherwise specified.

  In the following description, an element located in the upper direction in the drawing is expressed as “upper” or the like. However, this is only for the convenience of description, and what is described as the upper side may be the lower side depending on the state in which the metal-air battery is arranged. In addition, they may be located in a left-right relationship instead of an up-down relationship.

  As shown in FIG. 4, the lithium-air battery has a positive electrode having the positive electrode structure described in the first embodiment and a negative electrode composite opposed to each other, and an aqueous electrolyte 13 is filled between the positive electrode and the negative electrode composite. Each of the composite solid electrolytes 54 is configured to be in contact with the aqueous electrolyte 13.

  The positive electrode has a flat plate shape. One surface of the positive electrode faces one surface of the negative electrode composite (that is, the surface on the solid electrolyte 54 side). The shape, layer structure, and material of the positive electrode exterior material 30 of the positive electrode may be the same or substantially the same shape, layer structure, and material as those of the above-described positive electrode exterior material. In the illustrated example, the layer structure of the positive electrode exterior material 30 is a three-layer structure, of which the intermediate layer 30a is an Al foil, the outermost layer 30b is a PET resin, and the innermost layer 30c is a PP resin.

  The first positive electrode material 11 and the innermost layer 30c of the positive electrode exterior material 30 are sealed with the outer periphery in order to make the first positive electrode material 11 and the positive electrode current collector 20 adhere to each other and to prevent leakage of the aqueous electrolyte solution. It is sealed by a member 18. The outer peripheral sealing member 18 closes a region excluding the surface of the first positive electrode material 11 on the side of the aqueous electrolyte 13, and the first positive electrode material 11, the second positive electrode material 12, and the positive electrode It is configured to enclose a part of the electric body 20, the second positive electrode material 12, and the heat welding member 40. The outer peripheral sealing member 18 can use a heat welding sheet or an adhesive, and is preferably an adhesive. Examples of the heat welding sheet include acid-modified polypropylene. As the adhesive, those having low moisture permeability and high sealing property are suitable, and examples thereof include an epoxy-based adhesive, an olefin-based adhesive, and a synthetic rubber-based adhesive.

  The dimensions of the positive electrode current collector 20 of the positive electrode are substantially the same as those of the first positive electrode material 11. In addition, the positive electrode current collector 20 includes a tab portion extending to the outside of the lithium-air battery cell. The shape of the tab portion may be any shape as long as it can maintain the airtightness of the positive electrode and the airtightness of the lithium-air battery cell by the outer peripheral sealing member 18, and may be different from the positive electrode current collector 20. The material of the tab portion may be different from or the same as that of the positive electrode current collector 20.

  In the negative electrode composite, a laminate of the negative electrode layer 55, the buffer layer 56, and the solid electrolyte 54 is sandwiched between the upper exterior body 60 and the lower exterior body 70, and a nonaqueous electrolyte solution 80 is filled therebetween. I have. In addition, the negative electrode composite is configured by arranging, in order from the positive electrode, an upper exterior material 60, a solid electrolyte 54, a buffer layer 56, a negative electrode layer 55, and a lower exterior material 70 so as to face the positive electrode.

  The layer structure and the material of the upper exterior material 60 and the lower exterior material 70 may be the same or substantially the same as the positive electrode exterior material 30 of the first embodiment. In the illustrated example, the upper exterior material 60 and the lower exterior material 70 have a three-layer structure. Specifically, as for the materials of the upper exterior material 60 and the lower exterior material 70, of the three-layer structure, the intermediate layers 60a and 70a are made of Al foil, the outermost layers 60b and 70b are made of PET resin, and the innermost layers 60c and 70c. Is a PP resin. The shape of the upper exterior material 60 and the lower exterior material 70 may be any shape that can be joined to the positive electrode without leaking the aqueous electrolyte solution 13.

  The solid electrolyte 54 is an electrolyte that allows lithium ions to pass therethrough, and is located on a surface where the negative electrode complex contacts the aqueous electrolyte 13. Examples of the solid electrolyte include glass ceramics, which are excellent in ionic conductivity and nonflammable. As a glass ceramic, LTAP which is an oxide composed of lithium (Li), titanium (Ti), aluminum (Al), phosphorus (P), silicon (Si), oxygen (O), or the like having a NASICON-type crystal structure is used. preferable. If the solid electrolyte is LTAP, good water resistance and high strength can be imparted to the lithium-air battery.

  The buffer layer 56 is located between the solid electrolyte 54 and the negative electrode layer 55, and is configured to prevent contact between the negative electrode layer 55 and the solid electrolyte 54. The buffer layer is a layer in which an electrolyte, which is an organic electrolytic solution, is impregnated in a separator (a sheet of porous polyethylene, polypropylene, cellulose, or the like).

  The negative electrode layer 55 is configured by bonding a part of a negative electrode current collector 57 such as a copper (Cu) foil to a surface of lithium metal or the like. The remaining portion of the negative electrode current collector 57 is configured to protrude from the negative electrode composite even when both ends of the negative electrode composite are thermally welded and joined.

Examples of the non-aqueous electrolyte solution 80 include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), carbonate solvents such as ethyl methyl carbonate (EMC), tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, Ether solvents such as ethylene glycol dimethyl ether, tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane, and a mixed solution of these solvents are added to lithium hexafluorophosphate (LiPF ₆ ) and lithium perchlorate (LiClO _4). ), Lithium tetrafluoroborate (LiBF ₄ ), lithium bis (trifluoromethanesulfonyl) imide) (LiTFSI), lithium bis (fluorosulfonyl) imide (LiFSI) and other electrolytes Can be used.

  In addition, an end of the upper exterior body 60 on the solid electrolyte 54 side and the solid electrolyte 54 are sealed with an outer peripheral sealing member 58. The outer peripheral sealing member 58 closes a region excluding the surface on the positive electrode side of the solid electrolyte 54, and a part of the negative electrode current collector 57, the negative electrode layer 55, the buffer layer 56, a part of the solid electrolyte 54 and The non-aqueous electrolyte 80 is sealed. As the material of the outer peripheral sealing member 58, the same member as the outer peripheral sealing member 18 can be suitably adopted.

  The negative electrode composite having the above configuration, for example, such that the solid electrolyte and the negative electrode layer face each other, the upper exterior material, the solid electrolyte, the buffer layer, the negative electrode layer, and the lower exterior material are sequentially stacked, and the upper exterior material and The lower exterior material is joined by a heat sealer via a heat welding layer such as a heat welding sheet (not shown) so as to leave an end face opening for injecting the non-aqueous electrolyte. After the non-aqueous electrolyte is injected into the upper exterior member and the lower exterior member from the end opening, the end opening can be thermally welded and joined by a heat sealer.

  Further, the lithium-air battery cell having the above configuration, for example, the exterior body of the lower end face of the positive electrode and the exterior body of the upper end face of the negative electrode composite, leaving an end face opening for injecting the aqueous electrolyte solution. It can be manufactured by joining with a heat sealer via a heat-welding layer 90 such as a heat-welding sheet, injecting an aqueous electrolyte solution, and then heat-welding the end face opening with a heat sealer.

2. Second Embodiment FIG. 5 schematically shows a positive electrode structure of a lithium-air battery according to a second embodiment. As shown in FIG. 5, the positive electrode structure of the lithium-air battery according to the present embodiment is mainly different from the first embodiment in that it has an outer package 130 and a heat welding member 140. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The positive electrode exterior material 130 is located on the atmosphere side with respect to the positive electrode current collector 20, and has an opening 131 having the same or substantially the same shape as the second positive electrode material 12. Further, the positive electrode exterior material 130 is configured to be in contact with the positive electrode current collector 20 via the heat welding member 140 at the welding portion 140a. The area of the opening 131 of the positive electrode material 130 is larger than the area of the surface on the atmosphere side defined by the second outer peripheral portion 12 a of the second positive electrode material 12, and the first outer periphery of the first positive electrode material 11 is Any area may be used as long as it is smaller than the area of the surface on the atmosphere side defined by the portion 11a and the air can be taken into the second positive electrode material 12. The shape, outer dimensions, and thickness of the positive electrode casing 130 may be any shape, outer dimensions, and thickness that can be joined to the positive electrode current collector 20 at the welded portion 140a in the positive electrode structure formed by thermocompression of the positive electrode. The same material and layer structure as in the first embodiment can be adopted for the material and the layer structure of the positive electrode casing 130.

  The heat welding member 140 is located on the air side with respect to the positive electrode current collector 20 and on the aqueous electrolyte solution 13 side with respect to the positive electrode exterior material 130, and has an opening having the same or substantially the same shape as the second positive electrode material 12. 141. The opening 141 of the heat welding member 140 is arranged at the same or substantially the same position as the opening 131 of the positive electrode casing 130. Further, the heat welding member 140 is configured so that the positive electrode current collector 20 and the positive electrode exterior material 30 are joined by welding at the welding portion 140a. The area of the opening 141 of the heat welding member 140 is smaller than the area of the surface on the atmosphere side defined by the outer peripheral portion 11a of the first positive electrode material 11, and is defined by the outer peripheral portion 12a of the second positive electrode material 12. Any area may be used as long as it is larger than the area of the surface on the air side and can join the positive electrode current collector 20 and the positive electrode exterior material 130 by thermal welding at the welding portion 140a. The shape, outer dimensions, and thickness of the heat welding member 140 are determined by the shape, outer dimensions, and thickness of the positive electrode structure formed by thermocompression bonding of the positive electrode, so that the positive electrode current collector 20 and the positive electrode exterior member 130 can be joined at the welded portion 140a. I just need. As the material of the heat welding member 140, the same material as in the first embodiment can be adopted.

  The welded portion 140a is located on the surface of the first positive electrode material 11 on the side of the contact region 11b defined by the first outer peripheral portion 11a, and the positive electrode is heat-pressed to collect the positive electrode current via the thermal welding member 140. It is located at a portion where the body 20 and the positive electrode exterior body 130 are joined.

  According to the present embodiment, similarly to the first embodiment, leakage of the aqueous electrolyte solution can be prevented, and stable discharge can be performed for a long time. As a result, stable and high-voltage discharge can be performed for a long time. Furthermore, as compared with the first embodiment, the positive electrode casing 130 and the heat welding member 140 are not laminated on the second positive electrode 12 even when the positive electrode is thermocompression-bonded to form a multi-structure. The positive electrode can be formed thinner than that. Furthermore, by directly exposing the entire surface on the atmosphere side defined by the second outer peripheral portion 12a of the second cathode 12 to the atmosphere, the contact area between the second cathode material 12 and the atmosphere is increased. Thus, the amount of air taken into the positive electrode can be increased. Thereby, stable discharge can be performed for a longer time, and the average discharge voltage of the lithium-air battery can be improved.

  Further, the structure of the lithium-air battery cell and the structure of the negative electrode composite thereof described in the first embodiment can also be suitably used for the positive electrode structure of the lithium-air battery according to the present embodiment.

3. Third Embodiment FIG. 6 shows a third embodiment of the positive electrode structure of the lithium-air battery according to the present invention. As shown in FIG. 6, the positive electrode structure of the lithium air battery according to the present embodiment is mainly different from the second embodiment in that a positive electrode current collector 220 is provided. The same components as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The positive electrode current collector 220 has one end in the contact region 11b, the contact region 11b of the first positive electrode material 11, the first outer peripheral portion 11a of the first positive electrode material 11, and the first The surface on the side of the aqueous electrolyte 13 defined by one outer peripheral portion 11 a is in contact with the first positive electrode material 11. The positive electrode current collector 220 has a positive electrode structure formed by thermocompression bonding of the positive electrode, and is configured to be joined to the positive electrode exterior body 130 via the heat welding member 140 at the welding portion 140a. As the material of the positive electrode casing 220, the same material as in the first embodiment and the second embodiment can be adopted.

  According to the present embodiment, as in the second embodiment, the positive electrode can be formed thinner than in the first embodiment. Further, the positive electrode structure can be easily formed as compared with the first embodiment and the second embodiment. For example, the first positive electrode material 11 and the second positive electrode material 12 can be formed without cutting the kneaded material of the positive electrode material into two by cutting off the outer periphery on one side of the kneaded material of the positive electrode material. Thereby, the manufacturing cost of the positive electrode and the lithium air battery can be reduced. In addition, since the positive electrode current collector 220 is in contact with the surface of the first positive electrode material 11 on the side of the aqueous electrolyte 13 defined by the first outer peripheral portion 11a, the contact area between the positive electrode current collector and the positive electrode Can be kept large.

  Further, the structure of the lithium-air battery cell and the structure of the negative electrode composite thereof described in the first embodiment can also be suitably used for the positive electrode structure of the lithium-air battery according to the present embodiment.

4. Fourth Embodiment FIG. 7 shows a fourth embodiment of the positive electrode structure of the lithium-air battery according to the present invention. As shown in FIG. 7, the positive electrode structure of the lithium air battery according to the present embodiment is mainly different from the second embodiment in that a positive electrode current collector 320 is provided. The same components as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The positive electrode current collector 320 includes a surface on the atmosphere side defined by the second outer peripheral portion 12a of the second positive electrode material 12, a contact region 11b of the first positive electrode material 11, and a first The outer peripheral portion 11 a and the surface of the first positive electrode material 11 on the side of the aqueous electrolyte 13 are in contact with the first positive electrode material 11 and the second positive electrode material 12. Further, the positive electrode current collector 320 has a positive electrode structure formed by thermocompression bonding of the positive electrode, and is configured to be joined to the positive electrode exterior body 130 via the heat welding member 140 at the welding portion 140a. As the material of the positive electrode exterior material 320, the same material as in the first embodiment, the second embodiment, and the third embodiment can be adopted.

  According to this embodiment, as in the second and third embodiments, the positive electrode can be formed thinner than in the first embodiment. Further, similarly to the third embodiment, the positive electrode structure can be easily formed. Furthermore, as compared with the third embodiment, since the positive electrode current collector 320 is in contact with the surface on the air side defined by the second outer peripheral portion 12a of the second positive electrode material 12 and the outer peripheral portion 12a, A large contact area between the conductor and the positive electrode can be maintained.

  Further, the structure of the lithium-air battery cell and the structure of the negative electrode composite thereof described in the first embodiment can also be suitably used for the positive electrode structure of the lithium-air battery according to the present embodiment.

  In the above-described embodiment, the structure in which the positive electrode current collector is used as one member has been exemplified. The present invention is not limited to this. For example, titanium can be used for a portion requiring corrosion resistance to an aqueous electrolytic solution or the like (a portion to which a positive electrode material is pressed), and aluminum can be used for other portions to reduce the weight.

  Further, in the above-described embodiment, as a means for manufacturing a lithium-air battery cell, the lower end surface of the positive electrode and the upper end surface of the negative electrode composite are formed so as to leave an end face opening for injecting an aqueous electrolyte solution. The means for joining and directly injecting the aqueous electrolyte solution into this is exemplified. The present invention is not limited to this. For example, a material capable of absorbing an electrolytic solution may be made to absorb the aqueous solution-based electrolytic solution, and this may be used as an aqueous-based electrolytic solution (aqueous-based electrolyte layer). In this case, for example, a lithium-air battery cell can be manufactured only by disposing an aqueous electrolyte solution together with the positive electrode and the negative electrode composite, and then joining the lower end surface of the positive electrode and the upper end surface of the negative electrode composite. The material for absorbing the electrolytic solution may be any material that can absorb moisture and retain the electrolytic solution. For example, as a material for absorbing the electrolytic solution, a porous body of a resin such as cellulose, polyethylene (PE), or polypropylene (PP) can be used in a sheet shape. Alternatively, a gel body may be prepared using an aqueous electrolyte solution and used as an aqueous electrolyte layer. In this case, for example, a gel made of polyacrylamide (PAA), polyvinylidene fluoride (PVdF), or the like can be used as the electrolytic solution.

  Hereinafter, the effects of the present invention will be clarified by specifically describing the present invention with reference to examples. The positive electrode structure of the lithium-air battery according to the present invention is not limited by the following examples.

[Example 1]
1. Preparation of positive electrode A positive electrode was prepared by the following procedures i) to iii). FIG. 8 shows the structure of the positive electrode current collector and the heat-welded member manufactured in the example.
i) As a positive electrode material, 0.5 g of manganese dioxide (MnO ₂ ) as an oxygen reduction catalyst, 0.07 g of Ketjen black having a specific surface area of 800 m ² / g as a conductive aid, and polytetrafluoroethylene as a binder 0.15 g of fluoroethylene (PTFE) was weighed, transferred into a mortar, and kneaded by adding 5 ml of ethanol to obtain a kneaded product.
ii) As shown in FIG. 8, a titanium mesh having a size of 25 mm × 25 mm was formed as the positive electrode current collector 420, and a part of the titanium mesh having a width of 10 mm and a length of 60 mm was formed as a tab portion 490 of the positive electrode current collector 420. Cutting was performed so that the extension portion protruded. Further, the heat welding sheet as the heat welding member 440 was cut so that the outer frame was 35 mm × 35 mm and the inner frame was 18 mm × 18 mm. This heat-sealed sheet was arranged on one side of the positive electrode current collector 420 such that the size of the welded portion 440a was 20 mm × 20 mm in the outer frame and 18 mm × 18 mm in the inner frame.
iii) The kneaded product obtained in the procedure i) is bisected into a first positive electrode and a second positive electrode, and a positive electrode material pressing portion of titanium mesh (dimensions: 20 mm × 20 mm) using a hot press machine. Was crimped from both sides. In the welded part 440a of FIG. 8, in order to prevent the leakage of the aqueous electrolyte solution, a part of the positive electrode material was pressed on the heat-welded sheet. The kneaded material protruding from the pressure-bonded portion of the positive electrode material was removed. Then, it was air-dried in air for 24 hours to prepare a positive electrode.

2. Fabrication of Negative Electrode Composite In a glove box under an argon atmosphere, an exterior material obtained by punching a central portion of a laminated film of PP resin / Al foil / PET resin into a square of 20 mm × 20 mm, and a punched product of an acid-modified polypropylene film (outer frame) 30 mm × 30 mm, inner frame: 20 mm × 20 mm), 25 mm × 25 mm square solid electrolyte (LTAP), and an acid-modified polypropylene film punched product (outer frame: 30 mm × 30 mm, inner frame: 20 mm × 20 mm). They were stacked and heat-welded with a heat sealer to form an upper exterior material having an opening.

In order that the solid electrolyte (LTAP, LICGC manufactured by OHARA CORPORATION) and the metal Li as the negative electrode face each other, the metal Li () is added to the upper exterior material, the lithium ion battery separator (buffer layer), and the copper foil (negative electrode current collector). A joined body having dimensions: 14.5 mm × 14 mm, thickness: 200 μm) and a metal foil laminated film as a lower exterior material were sequentially stacked, and three edges of the joined portions were heat-welded using a heat sealer. Subsequently, 1 ml of a non-aqueous electrolyte (1M LiPF ₆ / EC: EMC = 1: 1) was injected into the joined body from the unjoined end. The other end of one side was heat-sealed and joined with a heat sealer to form a negative electrode composite.

3. Preparation of Lithium-Air Battery Cell As in the case of the lithium-air battery cell of FIG. 4, a 20 mm × 20 mm square hole was made in the center of an aluminum laminate film (PP resin / Al foil / PET resin) as an exterior material. This hole was arranged so as to be closed by the positive electrode material crimping portion, and the end of the positive electrode and the aluminum laminate film were welded with a heat welding sheet. Three sides of this aluminum laminated film were joined to the negative electrode composite, and 2 ml of an aqueous electrolyte solution (aqueous solution of 2M of LiCl) was injected from the remaining one side, and this one side was also joined to obtain an air battery cell.

[Comparative Example 1]
1. Production of Positive Electrode A positive electrode was produced in the same procedure as in Example 1.

2. Production of Negative Electrode Composite A positive electrode was produced in the same procedure as in Example 1.

3. Production of Lithium-Air Battery Cell As shown in FIG. 9, the lithium-air battery cell used in the comparative example was produced. 4, a 20 mm × 20 mm square hole (opening 531) is formed in the center of the aluminum laminate film (PP resin 530c / Al foil 530a / PET resin 530b), which is the exterior material 530, as described for the lithium air battery cell of FIG. The PTFE sheet 501 was placed so as to close this hole, and the end of the PTFE sheet 501 and the aluminum laminated film 530 were welded with a heat welding sheet 540. The prepared positive electrode is disposed between the aluminum laminated film 530 and the negative electrode composite, three sides of the aluminum laminated film 530 are joined to the negative electrode composite, and an aqueous electrolyte 513 (a 2M aqueous solution of LiCl) is formed from the remaining one side. After injecting 2 ml, this one side was also joined to obtain a lithium air battery cell. The aluminum laminate film and the negative electrode composite were bonded on a total of four sides, and one side of these was bonded across the tab portion of the positive electrode.

4. Discharge test The lithium-air battery cells of Example 1 and Comparative example 1 were subjected to a discharge test, and the change over time in the discharge voltage was examined. First, with respect to the lithium-air battery cell of Example 1, the current density was set to 4 mA / cm ² corresponding to a theoretical capacity of 0.05 C corresponding to 84 mAh. The same current density was used for the lithium air battery of Comparative Example 1. With respect to Example 1 and Comparative Example 1, the time course of the voltage when a 100% discharge test was performed was measured at a temperature of 25 ° C. using a battery charging / discharging device (HJ1001SD8, manufactured by Hokuto Denko Corporation). FIG. 10 shows the measurement results.

  As shown in FIG. 10, in Comparative Example 1, the discharge voltage dropped to about 2.2 V when discharged for about 10000 seconds, and dropped to about 1.7 V when discharged for about 45000 seconds. In Example 1, the discharge voltage was maintained at about 2.4 V even after discharging up to 45000 seconds.

  From the results, it was found that in Comparative Example 1, the discharge voltage was lowered at the beginning of the discharge start. On the other hand, in Example 1, it was found that the voltage did not drop at the beginning of the discharge start, and showed a stable high discharge voltage.

  ADVANTAGE OF THE INVENTION According to the positive electrode structure of the lithium air battery which concerns on this invention, leakage of electrolyte solution can be prevented with a simple structure, it can be set as a structure suitable for a lithium air battery cell of a vertical installation, etc., and the flexibility of a layout is improved. And stable discharge over a long period of time is enabled.

1 Lithium-air battery 2 Positive electrode (air electrode)
3, 13, 513 Aqueous electrolyte 4, 54, 554 Solid electrolyte (isolation layer)
5, 55, 555 Negative electrode layer 6, 56, 556 Buffer layer (protective layer)
7 Load 10 Positive electrode material 11, 511 First positive electrode material 12, 512 Second positive electrode material 11a First outer peripheral portion 11b Joining area 12a Second outer peripheral portion 18, 58, 558 Outer peripheral sealing members 20, 220, 320 , 420, 520 Positive electrode current collector 30, 130, 530 Positive exterior material 30a, 530a Positive exterior material middle layer 30b, 530b Positive exterior material outer layer 30c, 530c Positive exterior material inner layer 31, 41, 131, 141 , 531 Opening portions 40, 140, 440, 540 Heat welding members 40a, 140a, 440a, 540a Welding portions 57, 557 Negative electrode current collector 60, 560 Upper exterior material 60a, 560a Outermost layers 60c, 560c of the materials Innermost layers 70, 570 of the upper exterior materials 70a, 570a Lower intermediate materials 70b of the lower exterior materials The outermost layer 70c of 570b lower exterior member, the tab portion 501 PTFE sheets innermost 80,580 nonaqueous electrolyte 90,590 thermocompression layer 490 positive electrode current collector of 570c lower exterior member

Claims (5)

A positive electrode structure of a lithium air battery including at least a positive electrode material, a positive electrode current collector, and an exterior material,
The positive electrode material includes a first positive electrode material and a second positive electrode material,
In a plan view, the first positive electrode material surrounds the second positive electrode material over the entire circumference, and is formed by a difference in size between the first positive electrode material and the second positive electrode material. Forming a contact area between the first positive electrode material and the positive electrode current collector,
The positive electrode structure of a lithium-air battery, wherein the positive electrode current collector and the exterior material are joined at the contact area.   The positive electrode structure of a lithium air battery according to claim 1, wherein the positive electrode current collector penetrates between the first positive electrode material and the second positive electrode material.   The positive electrode structure of a lithium air battery according to claim 1 or 2, further comprising a heat welding member that is welded by heat between the positive electrode current collector and the exterior material.   The positive electrode structure of a lithium air battery according to any one of claims 1 to 3, wherein the positive electrode material is exposed to the atmosphere.   The lithium-air battery according to any one of claims 1 to 4, wherein the electrolyte of the lithium-air battery is an aqueous electrolyte, and at least a portion of the positive electrode current collector that contacts the electrolyte is made of titanium. Positive electrode structure.

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