Lithium-containing composition, positive electrode material for closed-type lithium oxygen battery using same, positive electrode for closed-type lithium oxygen battery, and closed-type lithium oxygen battery

Abstract

The present disclosure provides a means capable of improving capacitance characteristics of a closed-type lithium oxygen battery. Disclosed is a lithium-containing composition including a lithium oxide, a catalyst, and a conductive polymer. The composition is useful as a positive electrode material for a closed-type lithium oxygen battery.

Description

Lithium-containing composition, and positive electrode material for closed-type lithium-oxygen battery, positive electrode for closed-type lithium-oxygen battery, and closed-type lithium-oxygen battery using the same

[0001] The present invention relates to a lithium-containing composition, and a positive electrode material for a closed-type lithium-oxygen battery, a positive electrode for a closed-type lithium-oxygen battery, and a closed-type lithium-oxygen battery, which use the same.

[0002] In recent years, the widespread use of various electric vehicles is expected to help solve environmental and energy problems. Secondary batteries have been actively developed as on-board power sources for driving motors and other applications, which are key to the widespread use of these electric vehicles. Non-aqueous electrolyte secondary batteries, such as lithium-ion secondary batteries, have been attracting attention as they are expected to have high energy density and high output.

[0003] Lithium-oxygen batteries (lithium-oxygen secondary batteries) are known as one type of non-aqueous electrolyte secondary battery. These lithium-oxygen batteries have the highest theoretical energy density of all secondary batteries, including next-generation batteries, and are expected to offer battery performance with a high energy density that far exceeds that of current lithium-ion secondary batteries. However, sufficient capacity characteristics have yet to be achieved, and further improvements are currently required.

[0004] Lithium-oxygen batteries use gaseous molecular oxygen (O ２ ) is used, and O ２ When charging, ２ and a lithium-air battery that generates ２ The latter is a battery that does not consume or generate oxygen (lithium-oxygen battery in the narrow sense). ２ Since there is no exchange of electricity, the battery can be constructed as a sealed cell and can be called a "closed-type lithium-oxygen battery."

[0005] JP 2015-159098 A discloses the above-mentioned closed-type lithium-oxygen battery. This document describes a closed-type lithium-oxygen battery that prevents atmospheric moisture and carbon dioxide from entering the cell while retaining lithium oxide (LiO) as an electrode active material. ２ O) and a catalyst containing a transition metal atom (Co ３ O ４ They are attempting to achieve high capacity electrode active materials by pulverizing raw material compositions containing these materials through mechanochemical treatment.

[0006] According to the investigations of the present inventors, it has been found that even when a closed-type lithium-oxygen battery is fabricated using the technology disclosed in JP 2015-159098 A, it may still not be possible to achieve sufficient capacity characteristics.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a means for improving the capacity characteristics of a closed-type lithium-oxygen battery.

[0008] One aspect of the invention is a lithium-containing composition comprising a lithium oxide, a catalyst, and a conductive polymer.

[0009] 1 is a cross-sectional view schematically illustrating a stacked (flat) closed-type lithium oxygen battery according to one embodiment of the present invention.

[0010] One aspect of the invention is a lithium-containing composition comprising a lithium oxide, a catalyst, and a conductive polymer. The lithium-containing composition according to this aspect is useful as a positive electrode material for a closed-type lithium-oxygen battery.

[0011] The present inventors, while searching for a positive electrode material that can improve the capacity characteristics of closed-type lithium-oxygen batteries, discovered lithium oxide (Li ２ It has been found that using a lithium-containing composition further containing a conductive polymer in addition to the lithium-containing compound (C10) and a catalyst as the positive electrode material is useful for improving capacity characteristics. Hereinafter, an example will be described in which the lithium-containing composition according to this embodiment is used as a positive electrode material for a closed-type lithium-oxygen battery, but the lithium-containing composition can also be used for other purposes.

[0012] The above-mentioned embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention should be defined based on the claims and is not limited to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios. In this specification, the range "X to Y" means "X or more and Y or less." Furthermore, unless otherwise specified, operations and measurements of physical properties, etc. are performed at room temperature (20 to 25°C) and a relative humidity of 40 to 50% RH.

[0013] FIG. 1 is a cross-sectional view showing a schematic representation of a stacked (flat) closed-type lithium-oxygen battery (hereinafter also simply referred to as a "stacked-type lithium-oxygen battery") according to one embodiment of the present invention. In this specification, the term "closed-type lithium-oxygen battery" refers to a battery in which charge and discharge reactions proceed in a sealed cell (i.e., the battery is free from the exchange of molecular oxygen (O ２ This "closed-type lithium-oxygen battery" is disclosed in the above-mentioned JP 2015-159098 A, as well as in a document such as Wang, J. et al., "Reversible Conversion between Lithium Superoxide and Lithium Peroxide: A Closed "Lithium-Oxygen" Battery. Inorganics 2023, 11, 69."

[0014] As shown in FIG. 1 , the stacked lithium-oxygen battery 10a of this embodiment has a structure in which a substantially rectangular power-generating element 21, where charge and discharge reactions actually proceed, is sealed inside a laminate film 29. Here, the power-generating element 21 has a configuration in which a positive electrode, in which a positive electrode active material layer 13 is disposed on both sides of a positive electrode current collector 11′, an electrolyte layer 17 made of a separator containing an electrolytic solution, and a negative electrode, in which a negative electrode active material layer 15 is disposed on both sides of a negative electrode current collector 12, are laminated. Specifically, the positive electrode, the electrolyte layer, and the negative electrode are laminated in this order, with one positive electrode active material layer 13 and the adjacent negative electrode active material layer 15 facing each other with the electrolyte layer 17 interposed therebetween. As a result, the positive electrode, the electrolyte layer, and the negative electrode constitute one unit cell layer 19. Therefore, the stacked lithium-oxygen battery 10a shown in FIG. 1 can also be said to have a configuration in which a plurality of unit cell layers 19 are stacked and electrically connected in parallel. Although the positive electrode active material layer 13 is disposed on only one side of each of the outermost positive electrode current collectors located on both outermost layers of the power-generating element 21, active material layers may be disposed on both sides. That is, instead of using a current collector exclusively for the outermost layer with an active material layer disposed on only one side, a current collector with active material layers on both sides may be used as the outermost current collector. Furthermore, by reversing the arrangement of the positive electrode and negative electrode from that shown in FIG. 1 , the outermost negative electrode current collectors may be located on both outermost layers of the power-generating element 21, and negative electrode active material layers may be disposed on one or both sides of the outermost negative electrode current collectors.

[0015] A positive electrode current collector 25 and a negative electrode current collector 27 that are electrically connected to the electrodes (positive and negative electrodes) are attached to the positive electrode current collector 11′ and the negative electrode current collector 12, respectively, and are configured to be sandwiched between the ends of the laminate film 29 and led out of the laminate film 29. The positive electrode current collector 25 and the negative electrode current collector 27 may be attached to the positive electrode current collector 11′ and the negative electrode current collector 12 of the electrodes by ultrasonic welding, resistance welding, or the like, via a positive electrode terminal lead and a negative electrode terminal lead (not shown), respectively, as needed.

[0016] The main components of the stacked lithium-oxygen battery according to this embodiment will be described below.

[0017] [Current Collector] The current collector has a function of mediating the movement of electrons from the positive electrode active material layer and the negative electrode active material layer described later. There are no particular limitations on the material constituting the current collector. For example, metals and conductive resins can be used as the material constituting the current collector.

[0018] Specifically, examples of metals include aluminum, nickel, iron, stainless steel, titanium, and copper. Other examples include clad materials of nickel and aluminum, and clad materials of copper and aluminum. A foil having a metal surface coated with aluminum may also be used. Among these, aluminum, stainless steel, copper, and nickel are preferred from the viewpoints of electronic conductivity, battery operating potential, and adhesion of the negative electrode active material to the current collector by sputtering. Examples of conductive resins include resins containing a conductive filler added to a non-conductive polymer material.

[0019] The current collector may have a single layer structure made of a single material, or may have a laminate structure made of an appropriate combination of layers made of these materials. From the viewpoint of reducing the weight of the current collector, it is preferable that the current collector includes at least a conductive resin layer made of a resin having electrical conductivity. Furthermore, from the viewpoint of blocking the movement of lithium ions between the cell layers, a metal layer may be provided on a part of the current collector. Furthermore, if the positive electrode active material layer and the negative electrode active material layer described later are electrically conductive and can perform a current collecting function, it is not necessary to use a current collector as a separate member from these electrode active material layers. In such a configuration, the positive electrode active material layer described later constitutes the positive electrode, and the negative electrode active material layer described later constitutes the negative electrode.

[0020] [Positive Electrode Active Material Layer] In this embodiment, the positive electrode active material layer contains the lithium-containing composition according to one embodiment of the present invention as a positive electrode material.

[0021] <Lithium-containing composition (positive electrode material)> As described above, the lithium-containing composition according to one embodiment of the present invention contains a lithium oxide, a catalyst, and a conductive polymer. Hereinafter, the configuration of the lithium-containing composition according to this embodiment will be described.

[0022] (Lithium oxide) Lithium oxide is a compound in which lithium is covalently bonded to oxygen, and there are several compounds depending on the atomic ratio. Specifically, lithium oxide is Li ２ O, LiO, Li ２ O ２ and LiO ２ It is preferable that the lithium oxide contains one or more selected from the group consisting of Li ２ O, Li ２ O ２ or LiO ２ In particular, from the viewpoint of having a higher theoretical capacity and being chemically stable (hard to decompose and low in reactivity with moisture in the air and carbon dioxide) compared to other lithium oxides, it is more preferable to include Li ２ It is particularly preferred that the lithium oxide contains O. These lithium oxides have the functions of either releasing lithium ions (reacting in a direction that decreases the atomic ratio of lithium to oxygen) when the lithium-oxygen battery is charged, or absorbing lithium ions (reacting in a direction that increases the atomic ratio of lithium to oxygen) when the lithium-oxygen battery is discharged. From the above, it can be said that lithium oxides function as positive electrode active materials for lithium-oxygen batteries.

[0023] (Catalyst) A catalyst is a substance that has the function of promoting the bonding / dissociation reaction between the lithium oxide and oxygen by reducing the activation energy of these reactions. Any conventionally known compound can be used as a catalyst as long as it can exhibit this function. As an example, the catalyst is preferably a compound containing a transition metal (a transition metal-containing compound). This transition metal-containing compound is preferably in the form of, for example, an oxide (including composite oxides), sulfide, halide, nitride, carbide, or the like containing the transition metal. Among these, from the viewpoint of excellent catalytic activity, the catalyst preferably contains a transition metal-containing oxide. When the catalyst contains a transition metal-containing compound, there are no particular limitations on the type of transition metal contained in the compound, and the atom may be any metal classified as a transition metal, and one or more types may be used. Among these, from the viewpoint of catalytic activity, the transition metal is preferably at least one transition metal belonging to Groups 6 to 11 of the periodic table, more preferably one or more selected from the group consisting of cobalt, manganese, iron, nickel, molybdenum, iridium, and rhodium, particularly preferably one or more selected from the group consisting of cobalt, manganese, and iron, and most preferably cobalt. Examples of transition metal-containing compounds include transition metal-containing oxides such as cobalt oxide, manganese oxide, iron oxide, nickel oxide, molybdenum oxide, iridium oxide, and rhodium oxide. Among these, cobalt oxide, manganese oxide, and iron oxide are preferred, and cobalt oxide (e.g., Co ３ O ４ ) is particularly preferred.

[0024] The content of the catalyst in the lithium-containing composition is not particularly limited, and although it depends on the types of lithium oxide and catalyst, it is preferably 50 to 500 mass%, more preferably 100 to 450 mass%, still more preferably 200 to 400 mass%, and particularly preferably 250 to 350 mass%, relative to 100 mass% of the total amount of the lithium oxide when the battery is fully discharged.

[0025] (Conductive Polymer) A conductive polymer is a polymer compound having electron conductivity. There are no particular limitations on the specific structure as long as it satisfies this definition. Preferably, the conductive polymer is a π-electron conjugated polymer compound having a structure in which double bonds and single bonds are alternately arranged in the molecular structure and having a main chain with developed π-conjugation. The conductive polymer may be one that generates carriers by doping the polymer compound with an acceptor molecule or donor molecule called a dopant, thereby exhibiting electron conductivity. Examples of dopants include Li ＋ , Na ＋ , K. ＋ , Cs ＋ Examples of the conductive polymer include alkali metal ions such as tetraethylammonium ions, alkyl ammonium ions such as tetraethylammonium ions, halogens, Lewis acids, protons, and transition metal halides. The conductive polymer used in the present invention is not particularly limited, but it is preferable that the electronic conductivity of a film of the conductive polymer measured by the four-probe method is, for example, 10 −３ The viscosity is 0.01 S / cm or more, preferably 0.01 S / cm or more, and more preferably 0.1 S / cm or more.

[0026] The conductive polymer may be, for example, a polymer having one or more structural units selected from the group consisting of structural units derived from substituted or unsubstituted aniline, pyrrole, thiophene, furan, benzene, phenylene vinylene, thienylene vinylene, fluorene, naphthalene, and 3,4-ethylenedioxythiophene. The substituent is not particularly limited, but may include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an acyl group, an alkoxycarbonyl group, a nitro group, an amino group, a sulfo group, an alkylsulfo group, a carboxy group, an alkylcarboxy group, and a hydroxy group.

[0027] The conductive polymer is not particularly limited, but from the viewpoint of excellent conductivity, polyaniline (PANI), polypyrrole (PPy), polythiophene, polyfuran, poly(p-phenylene), poly(p-phenylenevinylene), poly(thienylenevinylene), polyfluorene, polynaphthylene, poly(3,4-ethylenedioxythiophene), and derivatives thereof can be preferably used. These derivatives include those having a substituent in the monomer constituting these polymer compounds. The substituent is not particularly limited, but includes a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an acyl group, an alkoxycarbonyl group, a nitro group, an amino group, a sulfo group, an alkylsulfo group, a carboxy group, an alkylcarboxy group, a hydroxy group, and the like.

[0028] Among these, the conductive polymer preferably contains one or more selected from the group consisting of polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene) (PEDOT), and even more preferably contains one or more selected from the group consisting of polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid (PEDOT:PSS). These conductive polymers are likely to provide high electronic conductivity. They are also suitable because they are resistant to the high potential region (oxidative environment) used in high-capacity positive electrodes and to active oxygen species generated from the positive electrode active material.

[0029] Polyaniline (PANI), polypyrrole (PPy), polythiophene, and PEDOT:PSS are polymers that have repeating structures represented by the following chemical formulas and exhibit electrical conductivity.

[0030]

[0031] In the lithium-containing composition according to the present embodiment, the average molecular weight of the conductive polymer is not particularly limited, and conventionally known knowledge can be appropriately referred to. For example, the weight average molecular weight (in terms of polystyrene) measured by gel permeation chromatography is 1,000 to 1,000,000, preferably 5,000 to 50,000, and more preferably 10,000 to 30,000.

[0032] The content of the conductive polymer in the lithium-containing composition according to the present embodiment is not particularly limited, and depends on the types of lithium oxide, catalyst, and conductive polymer. Here, from the viewpoint of being highly effective in improving the capacity characteristics of a closed-type lithium-oxygen battery when used as a positive electrode material, for example, the content is preferably 0.5 to 5.0 mass%, more preferably 1.0 to 5.0 mass%, and even more preferably 1.0 to 2.0 mass% relative to the total amount of the lithium oxide and catalyst when the battery is fully discharged.

[0033] While there are no particular limitations on the form in which each component (lithium oxide, catalyst, and conductive polymer) in the lithium-containing composition exists, it is preferable that these components are present so that the lithium oxide and catalyst involved in the battery reaction are in contact with each other. In particular, it is more preferable that the lithium oxide and catalyst are in the form of composite particles combined with a conductive polymer. Here, the lithium-containing compound being "in the form of composite particles" means that when the lithium-containing composition is used as a positive electrode material for a closed-type lithium-oxygen battery and charge / discharge reactions are carried out, the particles do not collapse and maintain their particle shape even if the lithium oxide expands and contracts during charge / discharge. This configuration allows the charge / discharge reaction to proceed more smoothly when the lithium oxide is used as a positive electrode material, which can effectively contribute to further improving the capacity characteristics of the battery.

[0034] As described above, it has been found that the lithium-containing composition according to this embodiment is useful as a positive electrode material for closed-type lithium-oxygen batteries, and that using the composition as a positive electrode material in closed-type lithium-oxygen batteries can improve capacity characteristics. While the mechanism by which this effect is achieved is not fully understood, the following mechanism is presumed. Specifically, the inclusion of a conductive polymer in a lithium-containing composition maintains more contact points between the lithium oxide (positive electrode active material) and the catalyst than in a battery that does not contain the conductive polymer. As a result, sufficient electron traffic between the lithium oxide and the catalyst occurs during the charge / discharge reactions of a closed-type lithium-oxygen battery, which is believed to effectively contribute to improving the capacity characteristics of the battery. Furthermore, since the conductive polymer also functions to bind the lithium oxide and the catalyst, maintaining the shape of the lithium-containing composition as a positive electrode material and minimizing its collapse is also believed to contribute to improving the capacity characteristics. However, these mechanisms are based on speculation, and their correctness does not affect the technical scope of the present invention.

[0035] The lithium-containing composition having the above-described structure can be obtained, for example, as described in the Examples section below, by dry-mixing a lithium oxide and a catalyst by a mechanical mixing method such as a mechanochemical method, then mixing the mixture with a conductive polymer solution, and volatilizing the solvent. The lithium-containing composition obtained in this manner is usually in the form of composite particles.

[0036] The content of the positive electrode material according to one embodiment of the present invention contained in the positive electrode active material layer (the total amount when two or more types are contained) is not particularly limited, but is preferably 60 to 99 mass % and more preferably 80 to 95 mass % relative to 100 mass % of the total solid content of the positive electrode active material layer.

[0037] <Additive Components> In addition to the above-described positive electrode material, the positive electrode active material layer preferably further contains a conductive additive and / or a binder as additive components.

[0038] (Conductive additive) The conductive additive has a function of forming an electron conduction path (conductive passage) in the positive electrode active material layer. When such an electron conduction path is formed in the positive electrode active material layer, the internal resistance of the battery can be reduced and the rate characteristics can be improved.

[0039] Examples of the conductive aid include particulate carbon materials such as acetylene black, carbon black, channel black, thermal black, and Ketjen Black (registered trademark), and fibrous carbon materials such as carbon nanotubes (single-walled carbon nanotubes and multi-walled carbon nanotubes), carbon nanofibers, vapor-grown carbon fibers, electrospun carbon fibers, polyacrylonitrile-based carbon fibers, and pitch-based carbon fibers. One type of conductive aid may be used alone, or two or more types may be used in combination.

[0040] The content of the conductive additive that can be contained in the positive electrode active material layer (the total amount when two or more kinds are contained) is not particularly limited, but is preferably 0.5 to 10 mass % and more preferably 1 to 5 mass % relative to 100 mass % of the total solid content of the positive electrode active material layer.

[0041] (Binder) The optional binder used in the positive electrode active material layer is not particularly limited, and examples thereof include the following materials: polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyether nitrile, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, thermoplastic polymers such as styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and hydrogenated products thereof, styrene-isoprene-styrene block copolymer and hydrogenated products thereof, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene Fluorine resins such as ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), etc., vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP-TFE fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), Examples of the fluororubber include vinylidene fluoride-based fluororubbers such as vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene-based fluororubber (VDF-PFMVE-TFE-based fluororubber), and vinylidene fluoride-chlorotrifluoroethylene-based fluororubber (VDF-CTFE-based fluororubber), and epoxy resins. Among these, polyvinylidene fluoride (PVDF), polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are preferred.

[0042] The content of the binder that can be contained in the positive electrode active material layer (the total amount when two or more types are contained) is not particularly limited, but is preferably 0.5 to 10 mass % and more preferably 1 to 5 mass % with respect to the total solid content of the positive electrode active material layer.

[0043] The thickness of the positive electrode active material layer is not particularly limited, and conventionally known knowledge about batteries can be appropriately referenced. For example, the thickness of the positive electrode active material layer is usually about 1 to 1000 μm, preferably 20 to 800 μm, more preferably 30 to 500 μm, and even more preferably 40 to 200 μm. The thicker the positive electrode active material layer, the more positive electrode active material can be retained to achieve sufficient capacity (energy density). On the other hand, the thinner the positive electrode active material layer, the more the discharge rate characteristics can be improved.

[0044] [Negative Electrode Active Material Layer] (Negative Electrode Active Material) The negative electrode active material layer contains a negative electrode active material. The type of negative electrode active material is not particularly limited, but includes carbon materials, metal oxides, and metal active materials. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of metal oxides include Nb ２ O ５ , Li ４ Ti ５ O １２ and the like. Furthermore, silicon-based negative electrode active materials and tin-based negative electrode active materials may be used. Here, silicon and tin belong to Group 14 elements and are known to be negative electrode active materials that can greatly improve the capacity of secondary batteries. These simple substances can absorb and release a large number of charge carriers (lithium ions, etc.) per unit volume (mass), and therefore become high-capacity negative electrode active materials. Here, it is preferable to use Si simple substance as the silicon-based negative electrode active material. Similarly, SiO disproportionated into two phases, a Si phase and a silicon oxide phase, is also used. ｘIt is also preferable to use silicon oxides such as (0.3≦x≦1.6). In this case, the range of x is more preferably 0.5≦x≦1.5, and even more preferably 0.7≦x≦1.2. Furthermore, an alloy containing silicon (silicon-containing alloy-based negative electrode active material) may be used. On the other hand, examples of negative electrode active materials containing tin (tin-based negative electrode active materials) include simple Sn, tin alloys (Cu—Sn alloys, Co—Sn alloys), amorphous tin oxides, tin silicon oxides, etc. Among these, examples of amorphous tin oxides include SnB ０．４ P ０．６ O ３．１ Examples of tin silicon oxide include SnSiO ３ Examples include: a lithium-containing metal; and a lithium-containing alloy may be used as the negative electrode active material. Such a negative electrode active material is not particularly limited as long as it is a lithium-containing active material, and examples thereof include lithium metal and lithium-containing alloys. Examples of lithium-containing alloys include, but are not limited to, alloys of Li with at least one of In, Al, Si, Sn, Mg, Au, Ag, and Zn. In some cases, two or more negative electrode active materials may be used in combination. Of course, negative electrode active materials other than those described above may also be used. The negative electrode active material preferably includes lithium metal, a lithium-containing alloy, a silicon-based negative electrode active material, or a tin-based negative electrode active material, and particularly preferably includes lithium metal or a lithium-containing alloy. When the negative electrode active material includes lithium metal or a lithium-containing alloy, the lithium-oxygen battery according to this embodiment may be a so-called lithium deposition type battery in which lithium metal or a lithium-containing alloy is deposited on the negative electrode current collector during charging. In this case, a layer of lithium metal or a lithium-containing alloy deposited on the negative electrode current collector during charging serves as the negative electrode active material layer of the lithium-oxygen battery according to this embodiment. Therefore, the thickness of the negative electrode active material layer increases as the charging process progresses, and decreases as the discharging process progresses. The negative electrode active material layer need not be present during full discharge, but in some cases, a certain amount of the negative electrode active material layer made of lithium metal or a lithium-containing alloy may be present during full discharge.

[0045] The shape of the negative electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. When the negative electrode active material is particulate, the average particle diameter is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm.

[0046] The content of the negative electrode active material in the negative electrode active material layer is, for example, 60% by mass or more and less than 100% by mass, preferably 80% by mass or more and 99.5% by mass or less, more preferably more than 95% by mass and 99.0% by mass or less, and even more preferably 97% by mass or more and 98.5% by mass or less, relative to 100% by mass of the total solid content. When the content of the negative electrode active material is within the above range, both battery capacity and output characteristics can be achieved.

[0047] Furthermore, the negative electrode active material layer may further contain other additives such as a conductive aid and a binder, as described above for the positive electrode active material layer, if necessary.

[0048] The thickness of the negative electrode active material layer (in the case of a lithium deposition type secondary battery, the thickness when fully charged) differs depending on the configuration of the intended stacked battery, but is preferably within the range of 0.1 to 1000 μm, for example.

[0049] [Electrolyte Layer] The electrolyte layer contains an electrolytic solution (liquid electrolyte) and preferably has a configuration in which a separator is impregnated with the electrolytic solution.

[0050] (Electrolyte) The electrolyte functions as a carrier of lithium ions. The electrolyte has a form in which a lithium salt is dissolved in a non-aqueous solvent. Preferably, the electrolyte is obtained by further adding a fluorine-containing carbonate to the non-aqueous solvent in which the lithium salt is dissolved.

[0051] The non-aqueous solvent is preferably one that can easily dissolve lithium salts, and examples thereof include chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and methyl ethyl carbonate (MEC); fluorine-containing chain carbonates in which some of the hydrogen atoms of these chain carbonates have been substituted with fluorine atoms; ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (MC). fluorine-containing cyclic carbonates in which some of the hydrogen atoms of these cyclic carbonates have been substituted with fluorine atoms; methyl propionate (MP), methyl acetate (MA), methyl formate (MF), 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL).

[0052] In particular, from the viewpoint of further improving the rapid charging characteristics and output characteristics, the non-aqueous solvent preferably contains a chain carbonate, and more preferably contains at least one selected from the group consisting of diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0053] The lithium salt is Li(FSO ２ ) ２ N(lithium bis(fluorosulfonyl)imide; LiFSI), Li(C ２ F ５ SO ２ ) ２ N, LiPF ６ , LiBF ４ , LiClO ４ , LiAsF ６ , LiCF ３ SO ３ etc.

[0054] The concentration of the lithium salt in the non-aqueous solvent is preferably 0.1 to 3.0 mol / L, and more preferably 0.8 to 2.2 mol / L.

[0055] In addition, it is preferable that the electrolyte solution further contains a fluorine-containing carbonate such as a fluorine-containing cyclic carbonate or a fluorine-containing linear carbonate. This allows the battery to have excellent durability even when operated at high voltage. Furthermore, these fluorine-containing carbonates form a protective film on the surface of the positive electrode active material, thereby improving the voltage resistance of the positive electrode active material. In this case, preferred fluorine-containing carbonates include fluorine-containing cyclic carbonates such as fluoroethylene carbonate (FEC), difluoroethylene carbonate, and 4-fluoropropylene carbonate; and fluorine-containing linear carbonates such as ethyl trifluoromethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, and bis(2,2,2-trifluoroethyl) carbonate. The content of the fluorine-containing carbonate is not particularly limited. In a preferred embodiment, the electrolyte solution contains 0.5 to 10 mass% of a fluorine-containing carbonate, particularly fluoroethylene carbonate, based on the total amount of the finally obtained electrolyte solution. This allows the above-mentioned effects to be obtained more significantly. When the electrolytic solution contains two or more kinds of fluorine-containing carbonates, the total amount thereof is preferably within the above range.

[0056] The electrolyte may further contain additives other than the above-mentioned components. Specific examples of such compounds include vinylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate, phenyl vinylene carbonate, diphenyl vinylene carbonate, ethyl vinylene carbonate, diethyl vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1-methyl-1-vinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, 1-ethyl-1-vinyl ethylene carbonate, and 1-ethyl-2-vinyl ethylene carbonate. ester, vinyl vinylene carbonate, allyl ethylene carbonate, vinyloxymethyl ethylene carbonate, allyloxymethyl ethylene carbonate, acryloxymethyl ethylene carbonate, methacryloxymethyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, ethynyloxymethyl ethylene carbonate, propargyloxyethylene carbonate, methylene ethylene carbonate, 1,1-dimethyl-2-methylene ethylene carbonate, etc. These additives may be used alone or in combination of two or more. In addition, when an additive is used in the electrolytic solution, the amount used can be appropriately adjusted.

[0057] (Separator) The separator constituting the electrolyte layer has the function of retaining the electrolyte to ensure lithium ion conductivity between the positive electrode and the negative electrode, and also functions as a partition wall between the positive electrode and the negative electrode.

[0058] Examples of the form of the separator include a porous sheet separator made of polymer or fiber that absorbs and retains the electrolyte, and a nonwoven fabric separator.

[0059] As a separator made of a porous sheet of polymer or fiber, for example, a microporous material (microporous membrane) can be used. Specific forms of the porous sheet made of polymer or fiber include microporous (microporous membrane) separators made of polyolefins such as polyethylene (PE) and polypropylene (PP), laminates of multiple layers of these (for example, a laminate with a three-layer structure of PP / PE / PP), hydrocarbon resins such as polyimide, aramid, and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and glass fibers.

[0060] As the nonwoven fabric separator, conventionally known materials such as cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; polyimide, aramid, etc. may be used alone or in combination.

[0061] The thickness of the separator may be the same as that of the electrolyte layer, and is preferably 5 to 200 μm, and particularly preferably 10 to 100 μm.

[0062] Furthermore, a separator having a heat-resistant insulating layer laminated on a porous substrate (a separator with a heat-resistant insulating layer) can be used. The heat-resistant insulating layer is a ceramic layer containing inorganic particles and a binder. A separator with a heat-resistant insulating layer is used that has high heat resistance, with a melting point or thermal softening point of 150°C or higher, preferably 200°C or higher. The presence of a heat-resistant insulating layer can mitigate the internal stress of the separator that increases with temperature rise, thereby suppressing thermal shrinkage. As a result, short circuits between battery electrodes can be prevented, resulting in a battery configuration that is less susceptible to performance degradation due to temperature rise. Furthermore, the presence of a heat-resistant insulating layer improves the mechanical strength of the separator with a heat-resistant insulating layer, making it less likely to rupture. Furthermore, the heat-shrinkage suppression effect and high mechanical strength make the separator less likely to curl during the battery manufacturing process.

[0063] [Positive electrode current collector plate and negative electrode current collector plate] The material constituting the current collector plate (25, 27) is not particularly limited, and known highly conductive materials conventionally used as current collector plates for lithium ion secondary batteries can be used. Metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferred as constituent materials of the current collector plate. From the viewpoints of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be made of the same material or different materials.

[0064] A closed-type lithium-oxygen battery using the positive electrode material for a closed-type lithium-oxygen battery according to the present invention has excellent rate characteristics even after repeated charge-discharge cycles, and is therefore suitable for use as a power source for EVs and HEVs.

[0065] One embodiment of the lithium-containing composition according to one aspect of the present invention (a positive electrode material for a closed-type lithium-oxygen battery) has been described above. However, the present invention is not limited to the configurations described in the above-described embodiment, and can be modified as appropriate based on the claims.

[0066] The following embodiments are also included within the scope of the present invention: the lithium-containing composition according to claim 1 having the characteristics of claim 2; the lithium-containing composition according to claim 1 or 2 having the characteristics of claim 3; the lithium-containing composition according to any one of claims 1 to 3 having the characteristics of claim 4; the lithium-containing composition according to any one of claims 1 to 4 having the characteristics of claim 5; the lithium-containing composition according to any one of claims 1 to 5 having the characteristics of claim 6; the lithium-containing composition according to any one of claims 1 to 6 having the characteristics of claim 7; the lithium-containing composition according to any one of claims 1 to 7 having the characteristics of claim 8; the lithium-containing composition according to any one of claims 1 to 8 having the characteristics of claim 9; the positive electrode for a closed-type lithium-oxygen battery according to claim 11, which contains the lithium-containing composition according to any one of claims 1 to 10; the positive electrode for a closed-type lithium-oxygen battery according to claim 12, which has the characteristics of claim 11; and the closed-type lithium-oxygen battery according to claim 13, which contains the positive electrode according to claim 11 or 12.

[0067] According to another aspect of the present invention, there is also provided use of a lithium-containing composition comprising a lithium oxide, a catalyst, and a conductive polymer (preferably in the form of composite particles in which the lithium oxide and the catalyst are composited with the conductive polymer) as a positive electrode material for a closed-type lithium-oxygen battery.

[0068] According to yet another aspect of the present invention, there is also provided a method for improving the capacity characteristics of a closed-type lithium-oxygen battery, comprising using a lithium-containing composition containing lithium oxide, a catalyst, and a conductive polymer (preferably in the form of composite particles in which the lithium oxide and the catalyst are combined with the conductive polymer) as a positive electrode material for the closed-type lithium-oxygen battery. In this specification, "improved capacity characteristics" means that when a closed-type lithium-oxygen battery is constructed using the lithium-containing composition according to this aspect as a positive electrode material, at least one of the initial charge capacity and discharge capacity (e.g., charge capacity and discharge capacity per mass of lithium oxide) is improved compared to a battery constructed using a comparative positive electrode material having the same configuration except that it does not contain a conductive polymer.

[0069] The present invention will be described in more detail below with reference to examples, although the technical scope of the present invention is not limited to the following examples.

[0070] <<Fabrication of Closed-Type Lithium-Oxygen Battery>> [Example 1] (Preparation of Positive Electrode Material) Lithium oxide (Li) was used as the positive electrode active material (lithium oxide). ２ O, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and cobalt oxide (Co ３ O ４ , manufactured by Kojundo Chemical Laboratory Co., Ltd.) and another 70 mL pot for a planetary ball mill were placed in each pot and crushed in a planetary ball mill (crushing conditions: treatment for 1 hour at 400 rpm using 40 g of 3 mmφ zirconia balls and 15 g of 15 mmφ zirconia balls).

[0071] Next, 5 g of the crushed lithium oxide and 15 g of cobalt oxide were placed in a 70 mL planetary ball mill pot and mixed in a planetary ball mill (mixing conditions: treatment for 30 minutes at 400 rpm using 40 g of 3 mmφ zirconia balls and 15 15 mmφ zirconia balls).

[0072] Meanwhile, 0.0125 g of conductive polymer polyaniline (PANI, manufactured by Sigma-Aldrick Co. LLC) and 11 g of solvent N-methyl-2-pyrrolidone (NMP, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed (mixing conditions: 2000 rpm for 5 minutes) using a planetary stirring mixer / kneader "Awatori Rentaro" (ARE-310, manufactured by Thinky Corporation) to dissolve the polyaniline in NMP. 2.5 g of the mixture of lithium oxide and cobalt oxide mixed in the ball mill described above was added to the NMP solution of polyaniline obtained in this way, and further mixed (mixing conditions: 2000 rpm for 5 minutes) using the mixer / kneader. The resulting mixture was transferred to a metal tray and placed on a hot plate heated to 120°C to volatilize the NMP. The remaining powder was collected and mixed by hand in an agate mortar for 5 minutes to prepare the positive electrode material (in the form of composite particles) of Example 1. In the positive electrode material of this example, the content of the conductive polymer (PANI) was 100% of that of the lithium oxide (Li ２ O) and catalyst (Co ３ O ４ ) was 0.5% by mass relative to the total amount of

[0073] (Preparation of Positive Electrode) A solid content consisting of 80% by mass of the positive electrode material prepared above, 10% by mass of acetylene black (abbreviation: AB, Li-400, manufactured by Denka, average primary particle diameter: 48 nm, aspect ratio: 1) as a conductive additive, and 10% by mass of PVDF (Kureha KF Polymer W #9700, manufactured by Kureha) as a binder was prepared. First, the positive electrode material (total amount) and the conductive additive (total amount of acetylene black) were kneaded. N-methyl-2-pyrrolidone (NMP) was added to this so that the solid content concentration was 85%, and the mixture was mixed at 2000 rpm for 5 minutes using the above-mentioned mixer / kneader. N-methyl-2-pyrrolidone (NMP) was added to this so that the solid content concentration was 35% by mass, and the mixture was mixed at 2000 rpm for 2 minutes using the above-mentioned mixer / kneader. The binder (total amount of PVDF) was added to this, and mixed for 4 minutes at 2000 rpm using the above-mentioned mixing and kneading device. N-methyl-2-pyrrolidone (NMP) was added to this so that the solid content concentration was 25% by mass, and the viscosity was adjusted to prepare a positive electrode slurry. The positive electrode slurry was uniformly applied to aluminum foil placed on a smooth plate using a doctor blade so that the thickness of the positive electrode active material layer was 20 μm. Then, the positive electrode of this example was prepared by drying for 30 minutes on a hot plate heated to 80 ° C., transferring it to a vacuum dryer, and drying it at 130 ° C. for 8 hours under vacuum.

[0074] (Fabrication of Closed-Type Lithium-Oxygen Battery (Coin Cell)) The positive electrode and lithium counter electrode fabricated above were placed opposite each other, and a separator (polyolefin, thickness: 20 μm) was placed between them. Next, the laminate of the positive electrode, separator, and lithium counter electrode was placed in a coin cell (CR2032, material: stainless steel (SUS316)), and the following electrolyte solution was injected using a syringe and sealed to fabricate the closed-type lithium-oxygen battery (coin cell) of this example. The electrolyte solution was a mixture of an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a ratio of EC:DEC = 3:7 (volume ratio), and lithium hexafluorophosphate (LiPF ６ ) dissolved at a concentration of 1 mol / L was used.

[0075] [Example 2] A closed-type lithium-oxygen battery (coin cell) of this example was fabricated in the same manner as in Example 1, except that the amount of polyaniline (PANI) used in preparing the positive electrode material was changed to 0.025 g. In the positive electrode material of this example, the content of the conductive polymer (PANI) was 0.025 g. ２ O) and catalyst (Co ３ O ４ ) was 1.0 mass % relative to the total amount of

[0076] [Example 3] A closed-type lithium-oxygen battery (coin cell) of this example was fabricated in the same manner as in Example 1, except that the amount of polyaniline (PANI) used in preparing the positive electrode material was changed to 0.05 g. In the positive electrode material of this example, the content of the conductive polymer (PANI) was 0.05 g, and the content of the lithium oxide (Li ２ O) and catalyst (Co ３ O ４ ) was 2.0 mass % relative to the total amount of

[0077] [Example 4] A closed-type lithium-oxygen battery (coin cell) of this example was fabricated in the same manner as in Example 1, except that the amount of polyaniline (PANI) used in preparing the positive electrode material was changed to 0.125 g. In the positive electrode material of this example, the content of the conductive polymer (PANI) was 0.125 g. ２ O) and catalyst (Co ３ O ４ ) was 5.0 mass % relative to the total amount of

[0078] Comparative Example 1 A closed-type lithium-oxygen battery (coin cell) of this comparative example was fabricated in the same manner as in Example 1, except that polyaniline (PANI) was not added when preparing the positive electrode material.

[0079] The closed-type lithium-oxygen battery (coin cell) fabricated above was subjected to the following charge-discharge test (initial charge-discharge), and the charge capacity and discharge capacity were measured. The experiment was carried out in a thermostatic chamber at 300 K (27° C.).

[0080] (Charge / Discharge Test Conditions) Charge / Discharge Tester: TOSCAT-3000, Model TYS-30TU10 (manufactured by Toyo Systems Co., Ltd.) Charge / Discharge Conditions: [Charge process] 0.02 C (current density 18 mA / g), 1.8 V → 4.6 V (CCCV) [Discharge process] 0.02 C (current density 18 mA / g), 4.6 V → 1.8 V (CC) Rest time between charge and discharge processes: 30 minutes.

[0081] The results of the charge / discharge capacity measured by the above charge / discharge test are shown in Table 1 below. The charge / discharge capacity values ​​shown in Table 1 are relative values ​​when the measured value of Comparative Example 1 is set to 1. After the charge / discharge test was completed, the coin cells were disassembled to check the state of the positive electrode materials of Examples 1 to 4. It was confirmed that the particles of the positive electrode material made of the lithium-containing composition in all cases did not disintegrate and maintained their particle shape.

[0082]

[0083] From the results shown in Table 1, according to the present invention, lithium oxide (Li ２ It can be seen that by using a composition containing a conductive polymer in addition to the catalyst and the conductive polymer as a positive electrode material for a closed-type lithium-oxygen battery, the capacity characteristics of the closed-type lithium-oxygen battery can be improved.

[0084] 10a: laminated lithium-oxygen battery; 11': positive electrode current collector; 12: negative electrode current collector; 13: positive electrode active material layer; 15: negative electrode active material layer; 17: electrolyte layer; 19: single cell layer; 21: power generating element; 25: positive electrode current collector (positive electrode tab); 27: negative electrode current collector (negative electrode tab); 29: laminate film.

Claims

A lithium oxide, a catalyst, and a conductive polymer, A lithium-containing composition comprising the same. 　 The lithium-containing composition according to claim 1, wherein the lithium oxide and the catalyst are in the form of composite particles complexed by the conductive polymer. 　 The lithium-containing composition according to claim 1, which is used as a positive electrode material for a closed-type lithium oxygen battery. 　 The lithium-containing composition according to claim 1 or 3, wherein the content of the conductive polymer in the composition is 0.5 to 5.0% by mass based on the total amount of the lithium oxide and the catalyst. 　 The lithium-containing composition according to claim 1 or 3, wherein the content of the conductive polymer in the composition is 1.0 to 5.0% by mass based on the total amount of the lithium oxide and the catalyst. 　 The lithium-containing composition according to claim 1 or 3, wherein the content of the conductive polymer in the composition is 1.0 to 2.0% by mass based on the total amount of the lithium oxide and the catalyst. 　 wherein the lithium oxide contains one or more selected from the group consisting of Li ２ O, LiO, Li ２ O ２ and LiO ２ The lithium-containing composition according to claim 1 or 3. 　 The lithium-containing composition according to claim 1 or 3, wherein the conductive polymer contains one or more selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyfuran, poly(p-phenylene), poly(p-phenylene vinylene), poly(thienylene vinylene), polyfluorene, polynaphthalene, poly(3,4-ethylenedioxythiophene) and derivatives thereof. 　 The lithium-containing composition according to claim 1 or 3, wherein the catalyst contains a transition metal-containing oxide. 　 The lithium-containing composition according to claim 9, wherein the transition metal contained in the transition metal-containing oxide contains one or more selected from the group consisting of cobalt, manganese, iron, nickel, molybdenum, iridium and rhodium. 　 A positive electrode for a closed-type lithium oxygen battery, wherein the positive electrode active material layer contains the lithium-containing composition according to claim 1 or 3 as a positive electrode material. 　 The positive electrode for a closed-type lithium oxygen battery according to claim 11, wherein the positive electrode active material layer further contains a conductive assistant and / or a binder as an additive component. 　 A closed-type lithium oxygen battery comprising the positive electrode according to claim 11.

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