Electrode mixture and battery

Abstract

To provide an electrode mixture capable of improving capacity of a battery, and a battery containing such an electrode mixture.SOLUTION: An electrode mixture contains hard carbons. The electrode mixture contains a metal oxide, a metal element constituting the metal oxide is a d-block element of the fourth period, and a ratio of a mass of the metal oxide with respect to a total mass of the hard carbons and the metal oxide is less than 10 mass%. A battery 1 successively includes an anode collector layer 10, an anode active material layer 20, an electrolyte layer 30, a cathode active material layer 40 and a cathode collector layer 50 and any one of the anode active material layer and the cathode active material layer contains the electrode mixture.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electrode mixture and a battery. [Background technology]

[0002] Lithium-ion batteries are used as power sources for mobile devices and automobiles, taking advantage of their high capacity and light weight characteristics. However, in recent years, sodium-ion batteries, which use sodium as an alternative to lithium, have been attracting attention from the perspective of resource conservation.

[0003] As disclosed in Patent Document 1, a technology has been developed that uses hard carbon as a negative electrode active material for secondary batteries such as lithium ion batteries and sodium ion batteries. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-050148 Summary of the Invention [Problem to be solved by the invention]

[0005] There is room for improvement in the battery capacity of batteries that use hard carbon as the negative electrode active material.

[0006] The present disclosure aims to provide an electrode mix that can improve battery capacity, and a battery containing such an electrode mix. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> An electrode mixture containing hard carbon, Contains a metal oxide, The metal element constituting the metal oxide is a d-block element of the fourth period, and the ratio of the mass of the metal oxide to the total mass of the hard carbon and the metal oxide is less than 10 mass%; Electrode composite material. <Aspect 2> 2. The electrode composite of embodiment 1, wherein the metal element oxide comprises at least one of an iron element, a titanium element, a manganese element, a zinc element, a nickel element, and a copper element. <Aspect 3> 3. The electrode composite of claim 2, wherein the metal oxide is Fe2O3, TiO, TiO2, MnO, Mn2O3, MnO2, NiO, CuO, or ZnO. <Aspect 4> 3. The electrode composite of embodiment 2, wherein the metal oxide comprises at least one of elemental iron, elemental titanium, and elemental manganese. <Aspect 5> 3. The electrode composite of claim 2, wherein the metal oxide is Fe2O3, TiO, TiO2, MnO, Mn2O3, or MnO2. <Aspect 6> 6. The electrode composite of claim 5, wherein the metal oxide is Fe2O3, TiO, MnO, or Mn2O3. <Aspect 7> 5. The electrode composite of embodiment 4, wherein the metal oxide comprises elemental iron. <Aspect 8> 8. The electrode composite of claim 7, wherein the metal oxide is Fe2O3. <Aspect 9> a negative electrode current collector layer, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order; One of the negative electrode active material layer and the positive electrode active material layer contains the electrode mixture according to any one of aspects 1 to 8. battery. <Aspect 10> A battery according to aspect 9, wherein the negative electrode active material layer contains the electrode mixture according to any one of aspects 1 to 8. <Aspect 11> 11. The battery of embodiment 10, wherein the electrolyte layer is a sodium ion battery having sodium ions. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an electrode mixture that can improve battery capacity, and a battery containing such an electrode mixture. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a battery according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0011] 《Electrode composite material》 The electrode mixture of the present disclosure includes hard carbon and a metal oxide, the metal element constituting the metal oxide is a d-block element of the fourth period, and the ratio of the mass of the metal oxide to the total mass of the hard carbon and the metal oxide is less than 10 mass%.

[0012] The present inventors unexpectedly discovered that an electrode composite containing a predetermined amount of a metal oxide composed of hard carbon and a metal element that is a d-block element in Period 4 can improve the battery capacity of a battery containing the electrode composite. Without intending to be bound by any theory, the reason for this is presumed to be as follows: Metal oxides composed of metal elements that are d-block elements in Period 4 have relatively high electrical conductivity. It is believed that the inclusion of a predetermined amount of such a metal oxide in an electrode composite changes the electronic conductivity of the battery, thereby improving the battery capacity.

[0013] In the present disclosure, an "electrode mixture" refers to a composition that can constitute an electrode active material layer either as is or by further containing other components. Also, in the present disclosure, an "electrode mixture slurry" refers to a slurry that contains an "electrode mixture" and a dispersion medium and that can be applied and dried to form an electrode active material layer.

[0014] The electrode mixture of the present disclosure includes hard carbon. The electrode mixture of the present disclosure includes a metal oxide composed of a metal element that is a d-block element of the fourth period. The electrode mixture of the present disclosure may optionally include a conductive additive and a binder. When a battery containing the electrode mixture of the present disclosure is a solid-state battery, the electrode mixture of the present disclosure may optionally include a solid electrolyte.

[0015] <Hard carbon> The electrode mixture of the present disclosure contains hard carbon, which can function as an electrode active material.

[0016] In the present disclosure, the "electrode active material" can be used as either a "positive electrode active material" or a "negative electrode active material", and is particularly used as a "negative electrode active material".

[0017] The content of hard carbon may be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, and may be less than 100% by mass, 99% by mass or less, 95% by mass or less, or 90% by mass or less.

[0018] The average particle size of the hard carbon is not particularly limited, but may be, for example, 50 nm to 100 μm.

[0019] The hard carbon may be a commercially available product or may be produced by a conventional method. Hard carbon can be produced, for example, by carbonizing a raw material containing carbon element. The carbonization temperature may be, for example, about 1000 to 2000°C. Carbonization can be carried out in an inert atmosphere. The raw material for hard carbon is not particularly limited as long as it can be used to produce hard carbon. For example, organic compounds such as alcohols (e.g., ethanol), phenols, and aldehydes (e.g., formaldehyde) can be used as raw materials. Other resins that can be used as raw materials include phenolic resins, polyacrylonitrile, and polyimides. These raw materials may be used alone or in combination.

[0020] <Metal oxides> The electrode composite of the present disclosure contains a metal oxide. The metal element constituting the metal oxide is a d-block element of the fourth period. The ratio of the mass of the metal oxide to the total mass of the hard carbon and the metal oxide is less than 10 mass%. This configuration can improve the battery capacity, particularly the discharge capacity.

[0021] Examples of metal elements that are d-block elements of the fourth period include iron, titanium, manganese, nickel, copper, zinc, scandium, vanadium, and chromium. Examples of metal oxides composed of such metal elements include FeO, Fe3O4, Fe2O3, TiO, TiO2, MnO, Mn3O4, Mn2O3, MnO2, MnO3, Mn2O7, NiO, NiO2, Ni2O3, Cu2O, CuO, ZnO, Sc2O3, VO, VO2, VO2, CrO, Cr2O3, CrO2, and CrO3.

[0022] The metal oxide preferably contains at least one of iron, titanium, manganese, nickel, copper, and zinc. The metal oxide may contain any one of these elements. That is, the metal oxide may contain iron, titanium, manganese, nickel, copper, or zinc. In this case, the metal oxide may be Fe2O3, TiO, TiO2, MnO, Mn2O3, MnO2, NiO, CuO, or ZnO.

[0023] The metal oxide preferably contains at least one of iron, titanium, and manganese. The metal oxide may contain any one of these elements. That is, the metal oxide may contain iron, titanium, or manganese. In this case, the metal oxide may be Fe2O3, TiO, TiO2, MnO, Mn2O3, or MnO2. This configuration can improve not only the battery capacity but also the charge / discharge efficiency of the battery at a standard C rate (e.g., 0.3 C) for secondary batteries. Note that, in the context of the present disclosure, charge / discharge efficiency refers to the ratio of discharge capacity to charge capacity. From the viewpoint of more effectively improving battery capacity and charge / discharge efficiency, the metal oxide is more preferably Fe2O3, TiO, MnO, or Mn2O3.

[0024] When the metal oxide contains titanium element or manganese element, and particularly when the metal oxide in this case is TiO, TiO2, MnO, or MnO2, the charge / discharge efficiency of the battery can be improved at a C rate (e.g., 0.1 C) lower than the standard C rate in secondary batteries.

[0025] From the viewpoint of being able to particularly effectively improve not only the battery capacity but also the capacity retention rate of the battery, the metal oxide may contain iron. In this case, the metal oxide may be Fe2O3. Note that, in the context of the present disclosure, the capacity retention rate refers to the ratio of the discharge capacity at a standard C rate (e.g., 0.3 C) of a secondary battery to the discharge capacity at a lower C rate (e.g., 0.1 C).

[0026] The ratio of the mass of the metal oxide to the total mass of the hard carbon and the metal oxide is less than 10% by mass, and may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 1.5% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or less, and may be 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, 5% by mass or less, 4% by mass or less, or 3% by mass or less.

[0027] <Conductive additive> The conductive additive may be, for example, a carbon material, a metal material, or the like. Specific examples of carbon materials include carbon black such as acetylene black, ketjen black, furnace black, and thermal black; carbon fiber such as VGCF; graphite; hard carbon; and coke. Specific examples of metal materials include Fe, Cu, Ni, and Al. These may be used alone or in combination. The content of the conductive additive in the electrode mixture is not particularly limited and may be determined appropriately depending on the desired conductivity.

[0028] <binder> The binder may be one that is chemically and electrically stable. Specific examples of binders include fluorine-based binders such as polyvinylidene fluoride (PVdF) binders and polytetrafluoroethylene (PTFE) binders; rubber-based binders such as styrene butadiene rubber (SBR) binders; olefin-based binders such as polypropylene (PP) binders and polyethylene (PE) binders; cellulose-based binders such as carboxymethyl cellulose (CMC) binders; and polyacrylic acid (PAA) binders. These binders may be used alone or in combination. The content of the binder in the electrode mixture is not particularly limited and may be determined appropriately depending on the desired binding properties.

[0029] <Solid electrolyte> The solid electrolyte may be an inorganic solid electrolyte. Examples of inorganic solid electrolytes include oxide solid electrolytes and sulfide solid electrolytes. Examples of oxide solid electrolytes include Na3Zr2Si2PO 12 and β-alumina (Na2O-11Al2O3). Examples of sulfide solid electrolytes include Na2S-P2S5. The solid electrolyte may be in the form of particles, for example.

[0030] <Other ingredients> The electrode mixture of the present disclosure may contain an electrode active material other than hard carbon. The content of the negative electrode active material other than hard carbon may be less than 50 mass%, less than 30 mass%, less than 10 mass%, less than 5 mass%, or less than 1 mass%. In addition, the electrode mixture of the present disclosure may contain additives other than the above-mentioned conductive aid, binder, and solid electrolyte.

[0031] Examples of a method for preparing the electrode mixture of the present disclosure include a method of mixing an electrode active material, and an optional solid electrolyte, a conductive additive, a binder, etc. At this time, the mixture may be mixed together with a dispersion medium to prepare an electrode mixture slurry.

[0032] "battery" As illustrated in FIG. 1 , a battery 1 according to the present disclosure includes an anode current collector layer 10, an anode active material layer 20, an electrolyte layer 30, a cathode active material layer 40, and a cathode current collector layer 50, in this order, and either the anode active material layer or the cathode active material layer contains the electrode composite according to the present disclosure.

[0033] The battery of the present disclosure may be a primary battery or a secondary battery such as a lithium ion battery or a sodium ion battery. In particular, the battery of the present disclosure may be a sodium ion battery in which the electrolyte layer contains sodium ions.

[0034] The battery of the present disclosure may be a liquid-based battery or a solid-state battery. In the present disclosure, a "solid-state battery" refers to a battery that uses at least a solid electrolyte as an electrolyte. Therefore, a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as an electrolyte. Alternatively, the solid-state battery of the present disclosure may be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as an electrolyte.

[0035] Hereinafter, as an example, elements constituting the battery of the present disclosure will be described in the case where the battery of the present disclosure is a sodium ion battery.

[0036] <Negative electrode current collector layer> Examples of materials for the negative electrode current collector layer include SUS, aluminum, copper, nickel, and carbon.

[0037] The negative electrode current collector layer may be, for example, in the form of a foil, a mesh, a porous material, or the like.

[0038] <Negative electrode active material layer> The negative electrode active material layer contains a negative electrode mixture including a negative electrode active material and, optionally, a solid electrolyte, a conductive additive, a binder, and the like. In particular, the negative electrode mixture may be the electrode mixture of the present disclosure. That is, the negative electrode active material layer may contain the electrode mixture of the present disclosure. For the electrode mixture of the present disclosure, reference may be made to the above description of the electrode mixture of the present disclosure.

[0039] The negative electrode active material layer may have a certain thickness. The thickness of the negative electrode active material layer is not particularly limited, but may be, for example, 0.1 μm or more and 1 mm or less.

[0040] <Electrolyte layer> When the battery of the present disclosure is a liquid battery, the separator may be impregnated with an electrolytic solution to form an electrolyte layer.

[0041] (separator) The separator material is not particularly limited as long as it has the function of electrically separating the negative electrode active material layer and the positive electrode active material layer, and examples thereof include porous sheets made of resins such as polyethylene (PE), polypropylene (PP), polyester, cellulose, polyamide, etc., and porous insulating materials such as nonwoven fabrics and glass fiber nonwoven fabrics, or combinations thereof. The thickness of the separator is not particularly limited, and may be, for example, 5 μm or more and 1 mm or less.

[0042] (electrolyte) The electrolyte may contain a sodium salt and a non-aqueous solvent. Examples of the sodium salt include inorganic sodium salts such as NaPF, NaBF, NaClO, and NaAsF; and organic sodium salts such as NaCF, NaN(CF, SO), NaN(C, F, SO), NaN(FSO), and NaC(CF, SO).

[0043] The non-aqueous solvent is not particularly limited as long as it dissolves sodium salts. Examples of non-aqueous solvents include high-dielectric-constant solvents and low-dielectric-constant solvents. Examples of high-dielectric-constant solvents include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), γ-butyrolactone, sulfolane, N-methyl-2-pyrrolidone (NMP), and 1,3-dimethyl-2-imidazolidinone (DMI). Examples of low-viscosity solvents include chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), acetates such as methyl acetate and ethyl acetate, and ethers such as 2-methyltetrahydrofuran. A mixed solvent of a high-dielectric-constant solvent and a low-viscosity solvent may also be used.

[0044] When the battery of the present disclosure is a solid-state battery, the electrolyte layer includes a solid electrolyte and may optionally include a conductive additive, a binder, and the like.

[0045] For the solid electrolyte, conductive assistant, and binder, reference can be made to the above description regarding the electrode composite material of the present disclosure.

[0046] 〈Positive electrode active material layer〉 The positive electrode active material layer contains a positive electrode active material and may optionally contain a conductive assistant, a binder, etc. When the battery of the present disclosure is a solid battery, the positive electrode active material layer may optionally contain a solid electrolyte.

[0047] When the negative electrode active material layer contains the electrode composite material of the present disclosure, that is, when hard carbon is used as the negative electrode active material, as the positive electrode active material, a material showing a noble potential with respect to the negative electrode active material can be used. Examples of such positive electrode active materials include Na-containing oxides such as layered active materials, spinel-type active materials, olivine-type active materials, etc. Specifically, NaFeO2, NaNiO2, NaCoO2, NaMnO2, NaVO2, Na(Ni X Mn 1-X )O2 (0 < X < 1), Na(Fe X Mn 1-X )O2 (0 < X < 1), NaVPO4F, Na2FePO4F, Na3V2(PO4)3, etc. can be mentioned.

[0048] The content of the positive electrode active material may be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, and may be less than 100% by mass, 99% by mass or less, 95% by mass or less, or 90% by mass or less.

[0049] The shape of the positive electrode active material is not particularly limited, and for example, it may be particulate. In this case, its average particle size may be, for example, 1 nm or more or 10 nm or more, and may be 100 μm or less or 30 μm or less.

[0050] For the conductive assistant, binder, and solid electrolyte, reference can be made to the above description regarding the electrode composite material of the present disclosure.

[0051] The positive electrode active material layer may have a certain thickness. The thickness of the positive electrode active material layer is not particularly limited, but may be, for example, 0.1 μm or more and 1 mm or less.

[0052] <Positive electrode current collector layer> Examples of materials for the positive electrode current collector layer include SUS, aluminum, nickel, iron, titanium, and carbon.

[0053] The positive electrode current collector layer may be, for example, in the form of a foil, a mesh, a porous material, or the like.

[0054] For example, when the battery of the present disclosure is a battery other than a sodium ion battery, various materials commonly used in such batteries can be used.

[0055] <Other components> The battery of the present disclosure may include a battery case that houses each layer of the battery, and terminals connected to current collectors, etc. The battery of the present disclosure may also include a restraining member that restrains each layer in the stacking direction to reduce contact resistance. Conventional restraining members may be used for these.

[0056] Examples of the shape of the battery of the present disclosure include coin type, laminate type, cylindrical type, and prismatic type.

[0057] A method of manufacturing a battery of the present disclosure may include forming an electrode active material layer containing an electrode mix of the present disclosure.

[0058] The electrode active material layer may be formed by a wet method or a dry method.

[0059] A method for forming an electrode active material layer by a wet process may include providing an electrode mixture slurry containing the electrode mixture of the present disclosure and a dispersion medium, applying the electrode mixture slurry to a substrate, and drying and removing the dispersion medium.

[0060] The dispersion medium is not particularly limited, and examples thereof include alcohols, glycols, cellosolves, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, phosphoric acid esters, ethers, nitriles, etc. Specific examples include ethanol, 2-propanol, methyl ethyl ketone, and N-2-methylpyrrolidone.

[0061] The drying temperature, drying time, etc. can be appropriately determined depending on the boiling point, amount used, etc. of the dispersion medium.

[0062] A method for forming an electrode active material layer by a dry process may include forming a compact of an electrode mixture on a substrate.

[0063] For the electrode mixture in the method for forming an electrode active material layer, reference can be made to the above description of the electrode mixture of the present disclosure.

[0064] The substrate is not particularly limited, but may be, for example, a negative electrode current collector layer when the negative electrode active material layer contains the electrode mixture of the present disclosure. [Example]

[0065] Example 1 <Production of evaluation cells> (Preparation of electrode mixture) Hard carbon (HC) and diiron trioxide (Fe2O3) were mixed as electrode active materials at a mass ratio of 0.49:0.01. That is, the ratio of the mass of Fe2O3 to the total mass of HC and Fe2O3 was 2 mass%. The resulting mixture and polyvinylidene fluoride (PVdF) as a binder were weighed out at a mass ratio of 95:5, dispersed in N-methyl-2-pyrrolidone (NMP), and stirred at 2000 rpm for 10 minutes. This resulted in a slurry-like electrode mixture (electrode mixture slurry).

[0066] (Formation of electrode active material layer) The obtained electrode mixture slurry was coated onto an aluminum (Al) current collector foil using a 75 μm bar coater. The obtained coating film was dried, punched out to a diameter of 16 mm, and then molded using a press. This resulted in an electrode active material layer being formed on the Al current collector foil. The electrode active material layer thus obtained was used as a negative electrode active material layer.

[0067] (Cell preparation) A 2032-type coin cell was fabricated using a laminate of Al current collecting foil and an electrode active material layer as the working electrode, metallic sodium (Na) as the counter electrode, a 25 μm polypropylene / polyethylene / polypropylene (PP / PE / PP) three-layer separator, and 1 M NaPF6EC:DMC = 1:1 (volume ratio) as the electrolyte.

[0068] "evaluation" <Battery capacity evaluation> A charge-discharge test was carried out at a voltage range of 0.01-1.5 V and a current value of 0.3 C in an environment of 25°C, and the sodium insertion capacity (charge capacity) and sodium desorption capacity (discharge capacity) of the coin cell were evaluated. The ratio of the discharge capacity to the charge capacity was taken as the charge-discharge efficiency.

[0069] Examples 2 to 18 and Comparative Examples 1 to 35 Cells of Examples 2 to 18 and Comparative Examples 1 to 35 were produced and evaluated in the same manner as in Example 1, except that the metal oxide (MO) and the ratio of the mass of the metal oxide to the total mass of the hard carbon and the metal oxide (MO / (HC+MO)) were changed as shown in Tables 1 to 3. Comparative Example 1 is an example relating to an electrode mixture that does not contain a metal oxide. The evaluation results of the charge capacity, discharge capacity, and charge / discharge efficiency of the cells of each example are shown in Tables 1 to 3.

[0070] For the cells of Comparative Example 1 and Examples 1 to 18, charge / discharge tests were carried out under the same conditions as above, except that the current value was set to 0.1 C. The ratio of the discharge capacity at 0.3 C to the discharge capacity at 0.1 C was taken as the capacity retention rate, and the evaluation results are shown in Table 1. The results of the evaluation carried out at a current value of 0.1 C corresponding to Comparative Example 1 and Examples 1 to 18 are shown in Table 4 as Comparative Reference Example 1 and Reference Examples 1 to 18.

[0071] [Table 1]

[0072] As shown in Table 1, the batteries of the examples, which contained an electrode composite containing a predetermined amount of a metal oxide composed of a metal element that is a d-block element of the fourth period in addition to hard carbon, exhibited improved battery capacity, particularly discharge capacity, compared to the battery of Comparative Example 1, which contained an electrode composite that did not contain such a metal oxide. In particular, the batteries of the examples, in which the metal oxide contained iron, titanium, or manganese, also exhibited improved charge / discharge efficiency. Among these, the batteries of the examples, in which the metal oxide was Fe2O3, TiO, MnO, or Mn2O3, exhibited particularly high discharge capacity. Furthermore, the batteries of the examples, in which the metal oxide contained iron, exhibited particularly high capacity retention.

[0073] [Table 2]

[0074] As shown in Table 2, the batteries of Comparative Examples 2 to 13, in which the electrode composite contained a metal oxide composed of a metal element that is a d-block element of the fourth period but the MO / (HC+MO) was outside the range of the present disclosure, did not have improved battery capacity, particularly discharge capacity, compared to the battery of Comparative Example 1.

[0075] [Table 3]

[0076] As shown in Table 3, when the electrode composite contained a metal oxide composed of a metal element that was not a d-block element of the fourth period, the battery capacity, particularly the discharge capacity, was not improved compared to the battery of Comparative Example 1, even when MO / (HC+MO) was within the range of the present disclosure.

[0077] [Table 4]

[0078] As shown in Table 4, when the metal oxide contained titanium or manganese, the charge-discharge efficiency at 0.1 C was improved. [Explanation of symbols]

[0079] 1 battery 10 Negative electrode current collector layer 20 Negative electrode active material layer 30 Electrolyte layer 40 Cathode active material layer 50 Positive electrode current collector layer

Claims

1. An electrode mixture containing hard carbon, Contains a metal oxide, The metal element constituting the metal oxide is a d-block element of the fourth period, and the ratio of the mass of the metal oxide to the total mass of the hard carbon and the metal oxide is less than 10 mass%; Electrode composite material.

2. The electrode mixture according to claim 1 , wherein the metal element oxide contains at least one of an iron element, a titanium element, a manganese element, a zinc element, a nickel element, and a copper element.

3. The metal oxide is Fe ２ O ３ , TiO, TiO ２ , MnO, Mn ２ O ３ , MnO ２ , NiO, CuO, or ZnO.

4. The electrode mix according to claim 2 , wherein the metal oxide comprises at least one of an iron element, a titanium element, and a manganese element.

5. The metal oxide is Fe ２ O ３ , TiO, TiO ２ , MnO, Mn ２ O ３ , or MnO ２ The electrode mixture according to claim 4,

6. The metal oxide is Fe ２ O ３ , TiO, MnO, or Mn ２ O ３ The electrode mixture according to claim 5 ,

7. The electrode mixture according to claim 4 , wherein the metal oxide comprises elemental iron.

8. The metal oxide is Fe ２ O ３ The electrode mixture according to claim 7,

9. a negative electrode current collector layer, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order; One of the negative electrode active material layer and the positive electrode active material layer contains the electrode mixture according to any one of claims 1 to 8. battery.

10. The battery according to claim 9, wherein the negative electrode active material layer contains the electrode mixture according to any one of claims 1 to 8.

11. The battery of claim 10 , wherein the electrolyte layer is a sodium ion battery having sodium ions.

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