A negative electrode active material for alkaline-ion batteries, a negative electrode material, an alkaline-ion battery comprising the negative electrode material, and a method for manufacturing a negative electrode active material for alkaline-ion batteries.

Abstract

To provide a negative electrode active material, a negative electrode material, an alkali ion battery having the negative electrode material, and a manufacturing method of the negative electrode active material, capable of realizing an excellent capacity characteristic and a cycle characteristic in the alkali ion battery.SOLUTION: A negative electrode active material for an alkali ion battery of the present invention, contains a composite material containing metal sulfide and carbon. The metal sulfide includes zinc, and at least one kind of transition metal element other than zinc. A manufacturing method of the negative electrode active material for the alkali ion battery of the present invention, comprises: a step 1 of obtaining a precursor by mixing a zinc source, a transition metal element source, and an organic ligand into a solvent; a step 2 of obtaining the sulfide by performing a heating treatment on the precursor in the presence of a sulfur source; and a step 3 of obtaining the composite material by performing an etching treatment on the sulfide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a negative electrode active material for alkaline-ion batteries, a negative electrode material, an alkaline-ion battery equipped with the negative electrode material, and a method for producing a negative electrode active material for alkaline-ion batteries. [Background technology]

[0002] Metal sulfides have recently attracted considerable attention as anode materials for high-performance sodium-ion batteries (SIBs) due to their high ionic / electron conductivity, theoretical capacity, excellent thermal stability, reversible sodium ion storage capacity, and high electrochemical activity.

[0003] For example, Non-Patent Document 1 discloses hollow nanoparticles of transition metal sulfide embedded in carbonaceous fibers as an anode material. Non-Patent Document 2 proposes an anode material in which coral-like ZnS is embedded in carbon co-doped with N and S. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] ACS Applied Materials Interfaces 10(2018):40531-40539 [Non-Patent Document 2] Applied Surface Science 535 (2021) 147748 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, conventional metal sulfides exhibit significant volume fluctuations and slowed ion diffusion during charge / discharge cycles, leading to reduced cycle performance and rate capability, thus limiting their application in sodium-ion batteries. Furthermore, the anode materials disclosed in Non-Patent Documents 1 and 2 both require complex synthesis processes, leaving room for improvement in terms of ease of manufacture.

[0006] In recent years, there has been a strong demand in the battery field for further improvements in capacity and cycle characteristics compared to conventional batteries. Accordingly, there is a need for the development of battery materials capable of providing excellent capacity and cycle characteristics. From this perspective, developing anode active materials that can provide excellent capacity and cycle characteristics when applied to the anode material of alkaline-ion batteries has been of extremely important importance in the battery field.

[0007] The present invention has been made in view of the above, and aims to provide a negative electrode active material, a negative electrode material, an alkaline ion battery equipped with the negative electrode material, and a method for producing a negative electrode active material, which can provide excellent capacity characteristics and cycle characteristics to an alkaline ion battery. [Means for solving the problem]

[0008] As a result of diligent research to achieve the above objective, the inventors of this invention discovered that the above objective can be achieved by a composite material comprising a metal sulfide containing a specific metal and a carbon material, and thus completed the present invention.

[0009] In other words, the present invention encompasses, for example, the subject matter described in the following sections. Item 1 A negative electrode active material for alkaline ion batteries, It includes a composite material containing metal sulfides and carbon, The metal sulfide is a negative electrode active material for an alkaline ion battery, comprising zinc and at least one transition metal element other than zinc. Section 2 The negative electrode active material for an alkali ion battery according to item 1, wherein the transition metal element is at least one selected from the group consisting of Ni, Co, Mn, Fe, Cu, and Mo. Item 3 The negative electrode active material for an alkali ion battery according to item 1 or 2, wherein the composite material is formed in a microsphere structure. Item 4 A negative electrode material containing the negative electrode active material for an alkali ion battery according to any one of items 1 to 3. Item 5 An alkali ion battery including the negative electrode material for an alkali ion battery according to item 4. Item 6 A method for manufacturing a negative electrode active material for an alkali ion battery according to any one of items 1 to 3, Step 1 of obtaining a precursor by mixing a zinc source, a transition metal element source, and an organic ligand in a solvent, Step 2 of obtaining a sulfide by heat-treating the precursor in the presence of a sulfur source, and Step 3 of obtaining the composite material by etching the sulfide A method for manufacturing a negative electrode active material for an alkali ion battery, comprising:

Effects of the Invention

[0010] The negative electrode active material of the present invention can provide excellent capacity characteristics and cycle characteristics to an alkali ion battery.

Brief Description of the Drawings

[0011] [Figure 1] SEM images of the negative electrode active materials obtained in each example and comparative example are shown. [Figure 2] X-ray diffraction measurement (XRD) results of the negative electrode active materials obtained in each example and comparative example are shown. [Figure 3] Results of constant current charge and discharge tests of the batteries assembled in each production example are shown.

Modes for Carrying Out the Invention

[0012] Embodiments of the present invention will be described in detail below. In this specification, the expressions "containing" and "including" include the concepts of "containing," "including," "substantially consisting of," and "consisting only of."

[0013] 1.Negative electrode active material The negative electrode active material for alkaline-ion batteries of the present invention (hereinafter sometimes simply referred to as "negative electrode active material") comprises a composite material containing a metal sulfide and carbon, wherein the metal sulfide comprises zinc and at least one transition metal element other than zinc. Such a negative electrode active material can be used as a negative electrode material for constructing an alkaline-ion battery (for example, a sodium-ion battery), and can provide the alkaline-ion battery with excellent capacity characteristics and cycle characteristics. Specifically, the negative electrode active material of the present invention has high initial discharge capacity and charge capacity, and can maintain a high capacity even after repeated charging and discharging.

[0014] The negative electrode active material of the present invention contains the aforementioned composite material as its main component. The aforementioned composite material is composed of a metal sulfide and carbon.

[0015] The aforementioned metal sulfide is a composite sulfide comprising zinc and at least one transition metal element other than zinc. Hereinafter, the at least one transition metal element other than zinc will be referred to as "transition metal element M".

[0016] In the aforementioned metal sulfide, it is preferable that the at least one transition metal element M other than zinc is selected from the group consisting of Ni, Co, Mn, Fe, Cu, and Mo. In this case, the negative electrode active material of the present invention is more likely to provide excellent capacity characteristics and cycle characteristics to alkaline ion batteries. It is more preferable that the transition metal element M contains Ni. Therefore, it is more preferable that the metal sulfide is a sulfide containing zinc and nickel.

[0017] The metal contained in the metal sulfide may include metal elements other than zinc and the transition metal element M, or it may consist only of zinc and the transition metal element M. The metal contained in the metal sulfide may consist of two or more types of metals, or only two types. For example, the metal contained in the metal sulfide may consist only of zinc and one transition metal element M.

[0018] The composite material contains carbon. The carbon may exist in an amorphous state in the composite material, for example. The composite material has an amorphous carbon framework, and the metal sulfide may be encapsulated within this carbon framework.

[0019] The composite material may contain elements and components other than metal sulfides and carbon, as long as they do not impede the effects of the present invention. Preferably, the total proportion of metal sulfides and carbon in the composite material is 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The composite material may be formed of only the metal sulfides and carbon.

[0020] In the composite material, the content ratio of each element is not particularly limited. For example, the molar ratio (Zn:M) of zinc and the transition metal element M in the composite material can be, for example, 1:0.5 to 1:10, preferably 1:0.5 to 1:5, and more preferably 1:0.8 to 1:3.

[0021] Furthermore, the content ratio of sulfur atoms relative to the total mass of the metal sulfide can be 10 to 50% by mass, preferably 15 to 45% by mass, and more preferably 20 to 40% by mass.

[0022] In the composite material, the carbon content is, for example, 20 to 80% by mass, preferably 50 to 70% by mass.

[0023] In the composite material, the content of the ZnS component is preferably 1 to 30% by mass, more preferably 2 to 25% by mass, even more preferably 3 to 15% by mass, and particularly preferably 4 to 10% by mass. By having the content of the ZnS component within a specific range, the negative electrode active material of the present invention tends to provide particularly excellent capacity characteristics and cycle characteristics in alkaline ion batteries.

[0024] The form of the composite material is not particularly limited and can take various forms such as powder, lump, granule, or fibrous form. When the composite material is in powder form, for example, it can be porous particles such as microspheres, and may also have various other shapes such as hollow particles, amorphous particles, or spherical particles. The composite material is preferably porous particles, and more preferably has a microsphere structure, in that it can provide excellent capacity characteristics and cycle characteristics to alkaline ion batteries.

[0025] When the composite material is particulate, its average particle diameter is not particularly limited and can be, for example, 100 nm to 100 μm. In this case, the negative electrode active material tends to provide excellent cycle characteristics to alkaline ion batteries. When the composite material is particulate, its average particle diameter is preferably 1 to 80 μm, and more preferably 2 to 50 μm. The average particle diameter referred to here is the value obtained by arithmetic mean by randomly selecting 50 particles by direct observation of the composite material with a scanning electron microscope and measuring their equivalent circle diameters.

[0026] The BET specific surface area of ​​the composite material is not particularly limited; for example, 85 m². 2 It is preferable that the value is 1 / g or more. In this case, alkaline ion batteries tend to provide superior capacity characteristics and cycle characteristics. The BET specific surface area of ​​the composite material is 90 m². 2 It is more preferable that it be 100m or more per gram. 2 It is even more preferable that it be 110m or more per gram. 2 It is particularly preferable that the BET specific surface area of ​​the composite material be 5000 m² or more. 2Preferably 3000 m / g or less, more preferably 1000 m / g or less, still more preferably 500 m / g or less, particularly preferably 300 m / g or less. 2 Preferably 1000 m / g or less, more preferably 500 m / g or less, still more preferably 300 m / g or less, particularly preferably 100 m / g or less. 2 Preferably 500 m / g or less, more preferably 300 m / g or less, still more preferably 100 m / g or less, particularly preferably 50 m / g or less. 2 Preferably 300 m / g or less, more preferably 100 m / g or less, still more preferably 50 m / g or less, particularly preferably 30 m / g or less. 2 is 30 m / g or less.

[0027] In addition to the carbon material, the negative electrode active material of the present invention can contain other components as long as the effects of the present invention are not inhibited, or the negative electrode active material can be composed only of the carbon material. The content ratio of the carbon material contained in the negative electrode active material is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 99% by mass or more. Whether the carbon material is present in the negative electrode active material can be determined from the XRD spectrum of the negative electrode active material.

[0028] Conventional materials containing metal sulfides have severe volume fluctuations and sluggish ion diffusion during the charge / discharge cycle, resulting in a decrease in cycle performance and rate capability. Therefore, their application to sodium-ion batteries and the like is likely to be limited. In contrast, the negative electrode active material of the present invention contains the composite material in which the metal sulfide is compounded with the carbon material as a constituent component, thereby improving conductivity, buffering volume fluctuations, and providing higher rate capability and cycle stability.

[0029] 2. Method for producing the negative electrode active material The method for producing the negative electrode active material is not particularly limited. For example, the negative electrode active material of the present invention can be produced by a production method including the following steps 1, 2, and 3. Step 1: A step of obtaining a precursor by mixing a zinc source, a transition metal element source, and an organic ligand in a solvent. Step 2: A step of obtaining a sulfide by heat-treating the precursor in the presence of a sulfur source. Step 3: A step of obtaining the composite material by etching the sulfide.

[0030] (Step 1) Step 1 is a process for obtaining a precursor by mixing a zinc source, a transition metal element source, and an organic ligand in a solvent.

[0031] The zinc source may be pure zinc, a zinc compound, or a mixture thereof, and is preferably a zinc compound.

[0032] The types of zinc compounds are not particularly limited and include, for example, inorganic zinc compounds, chlorides, and organic zinc compounds. Examples of inorganic zinc compounds include zinc nitrates, sulfates, chlorides, oxides, chlorates, perchlorates, chloride complexes, carbonates, bicarbonates, phosphates and hydrogen phosphates, cyanide compounds, cyanide compound salts, and compounds containing oxoanions (zinc salts). Examples of organic zinc compounds include acetates, oxalates, formates and succinates.

[0033] In particular, the zinc source is preferably an inorganic compound of zinc, and preferably a zinc nitrate (for example, Zn(NO3)2).

[0034] The transition metal element source may be a single transition metal element, a compound of a transition metal element, or a mixture thereof, and is preferably a compound of a transition metal element. The transition metal element is the aforementioned transition metal element M, and Ni is more preferably used.

[0035] The types of transition metal element compounds are not particularly limited; for example, inorganic compounds, chlorides, and organic compounds of transition metal elements can be cited. Examples of inorganic compounds of transition metal elements include nitrates, sulfates, chlorides, oxides, chlorates, perchlorates, chloride complexes, carbonates, bicarbonates, phosphates, and hydrogen phosphates of transition metal elements, cyanide compounds, cyanide compound salts, and compounds containing oxoanions (zincates). Examples of organic compounds of transition metal elements include acetates, oxalates, formates, and succinates.

[0036] In particular, the transition metal element source is preferably an inorganic compound of a transition metal element, and more preferably a nitrate of a transition metal element. An example of a transition metal element source is the nitrate of Ni (for example, Ni(NO3)2).

[0037] The organic ligand used in step 1 is a raw material that serves as a carbon source in the composite material. The type of organic ligand is not particularly limited, and a wide range of organic ligands that can coordinate to various transition metals can be mentioned. For example, aromatic carboxylic acid compounds, imidazole compounds, amino compounds, etc., which are known to function as ligands can be mentioned.

[0038] Specifically, the organic ligands include p-benzenedicarboxylic acid (H2BDC), o-benzenedicarboxylic acid, m-benzenedicarboxylic acid, 2,5-dihydroxyterephthalic acid (H4DOBDC), 1,3,5-benzenetricarboxylic acid (H3BTC), 1,4-benzenedicarboxylate, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (H3TATB), 2-aminoterephthalic acid (NH2BDC), 2-methylimidazole (2-MIM), 1- Examples include methylimidazole (1-MIM), 1,4-bis(imidazole-1-yl)benzene (1,4-BIB), 4-(imidazole-1-yl)phthalic acid (H2IPC), 4,4'-dimethyl-2,2'-bipyridyl, 4,4'-oxybisbenzoic acid, fumaric acid, oxalic acid, succinic acid, biphenyl-3,4',5-tricarboxylic acid (BPTC), 4,4'-biphenyl dicarboxylate (BPDC), and 2,5-dioxide terephthalate (DOT).

[0039] The solvent used in step 1 is not particularly limited and can be appropriately selected depending on the raw materials used. Examples of such solvents include water; alcohol-based solvents such as ethanol, isopropanol, and n-butyl alcohol; amide-based solvents such as N-dimethylformamide (DMF) and N,N-diethylformamide (DEF); and others such as glycerol, ethylene glycol, N-methyl-2-pyrrolidone (NMP), acetonitrile, triethylamine, and tetrahydrofuran (THF). The solvent used in step 1 may also be a mixture of two or more solvents.

[0040] In step 1, the method of mixing the zinc source, the transition metal element source, and the organic ligand in a solvent is not particularly limited. One form of mixing is to mix a solvent containing the zinc source and the transition metal element source with a solvent containing the organic ligand. In this case, the former solvent and the latter solvent may be the same or different.

[0041] In step 1, the proportions of the zinc source, the transition metal element source, and the organic ligand are not particularly limited, and these raw materials can be used in appropriate proportions to obtain the desired composite material. For example, conditions similar to those for obtaining known metal-organic frameworks (MOFs) can be adopted. As an example, the reaction can be carried out by mixing solutions in which the concentrations of the zinc source and the transition metal element source are 0.1 to 1000 mM (preferably 0.5 to 500 mM, more preferably 1 to 100 mM) and solutions in which the concentration of the organic ligand is 0.1 to 1000 mM (preferably 0.5 to 500 mM, more preferably 1 to 100 mM).

[0042] In step 1, when mixing the zinc source, the transition metal element source, and the organic ligand in a solvent, the mixing temperature is, for example, 80 to 400°C, preferably 100 to 200°C, and the mixing time is appropriately selected according to the temperature.

[0043] In step 1, a precursor is generated by mixing a zinc source, a transition metal element source, and an organic ligand in a solvent. Such a precursor is a metal-organic framework (MOF).

[0044] The precursor obtained in step 1 is, for example, a solid, and can be separated by an appropriate method to obtain the product. Such product can be further purified and dried by an appropriate method.

[0045] (Process 2) Step 2 is a step to obtain a sulfide by heating the precursor obtained in Step 1 in the presence of a sulfur source.

[0046] The sulfur source used in step 2 may be elemental sulfur (sulfur powder or sublimated sulfur) or a sulfur-containing compound, but a sulfur-containing compound is preferable.

[0047] Examples of sulfur-containing compounds include a wide range of known sulfur compounds, such as thioacetamide (CH3CSNH2), thiourea (SC(NH2)2), cysteine ​​(C3H7NO2S), sodium thiosulfate (Na2S2O3), ammonium sulfide ((NH4)2S), and sodium sulfide (Na2S). In addition, in sulfur-containing compounds, some of the sulfur element may be replaced with Se and / or Te. A single sulfur source may be used, or two or more may be used in combination.

[0048] In step 2, the method for heat-treating the precursor obtained in step 1 in the presence of a sulfur source is not particularly limited. For example, a method can be used in which the solid precursor and the sulfur source are placed in a reactor and heat-treated at a predetermined temperature. This heat treatment can be carried out in an air atmosphere, an inert gas atmosphere, etc. For example, a known heating device such as a commercially available heating furnace can be used for the heat treatment.

[0049] In step 2, the heat treatment temperature is not particularly limited and can be, for example, 200 to 2000°C, preferably 250 to 1000°C, and more preferably 300 to 800°C. The heat treatment time is appropriately selected according to the temperature, for example, 1 to 10 hours.

[0050] The proportions of the precursor and sulfur source used in step 2 are not particularly limited. For example, in order to facilitate the formation of metal sulfides and to obtain the desired negative electrode active material, it is preferable to use 10 to 1000 parts by mass of sulfur source per 100 parts by mass of precursor, more preferably 30 to 800 parts by mass, and even more preferably 50 to 600 parts by mass.

[0051] The heat treatment in step 2 yields metal sulfides as a product. This heat treatment also causes carbonization, generating a carbon source. In other words, the heat treatment in step 2 forms an amorphous carbon framework, and the metal sulfides can be encapsulated within this carbon framework. The product obtained from the heat treatment in step 2 can also be processed by an appropriate method to obtain purified metal sulfides.

[0052] (Step 3) Step 3 is a process for obtaining the composite material by etching the sulfide obtained in Step 2.

[0053] The etching method is not particularly limited, and for example, a method of contacting the sulfide obtained in step 2 with an etching agent can be cited. The etching agent is not particularly limited, and for example, a wide range of known etching agents can be used. For example, acids or alkalis such as hydrochloric acid, sulfuric acid, nitric acid, aqueous sodium hydroxide solution, and aqueous potassium hydroxide solution can be used as etching agents. When the etching agent is an acid or alkali, its concentration is, for example, 0.1 to 5 M, preferably 0.5 to 3 M.

[0054] The etching agent may also contain a metal salt such as iron chloride (FeCl3). For example, an acid or alkali containing a metal salt such as iron chloride (FeCl3) can be used as the etching agent. When the etching agent contains a metal salt such as iron chloride (FeCl3), the concentration of the metal salt is, for example, 0.1 to 5 M, preferably 0.2 to 3 M.

[0055] The etching process in step 3 can be carried out, for example, by immersing the sulfide obtained in step 2 in an etching agent and stirring. The etching temperature is, for example, 10 to 90°C, preferably 30 to 80°C, more preferably 40 to 70°C, and most preferably 50 to 65°C. The etching time (contact time between the etching agent and the sulfide) is, for example, 1 to 60 minutes. When the etching temperature is 50 to 65°C, the etching time is preferably 15 minutes or more, and more preferably 18 minutes or more.

[0056] The etching process in step 3 allows for the acquisition of the desired composite material. Unwanted components can be removed through the etching process. Furthermore, excess ZnS is removed through the etching process, which leads to the formation of defects in the composite material, making it easier to adjust the specific surface area to an appropriate range. As a result, the resulting negative electrode active material tends to exhibit particularly excellent capacity and cycle characteristics for alkaline-ion batteries.

[0057] After etching, the composite material may be cleaned as needed. In this case, for example, carbon disulfide can be used as the cleaning solution.

[0058] The composite material obtained in step 3 (a composite material containing metal sulfide and carbon) can be obtained as the anode active material of the present invention, or it can be obtained as the anode active material of the present invention by blending in other components as needed.

[0059] According to the manufacturing method comprising steps 1, 2, and 3 described above, the anode active material of the present invention can be easily obtained through a simple process, and the manufacturing method is low-energy. Furthermore, the raw materials used in the manufacturing process are inexpensive and can be obtained from abundant resources.

[0060] 3. Anode material The negative electrode material of the present invention may contain other components as long as it contains the above-mentioned negative electrode active material. For example, known components used in the negative electrode material of alkaline-ion batteries (e.g., sodium-ion batteries) can be cited. For example, the negative electrode material of the present invention may contain a conductive additive and a binder in addition to the above-mentioned negative electrode active material.

[0061] Conductive additives can broadly include known conductive additives used, for example, to form electrode materials for various types of batteries. Examples of conductive additives include various carbon materials, such as hard carbon, soft carbon, graphene, reduced graphene oxide, natural graphite, artificial graphite, conductive carbon black, and carbon fibers. Examples of carbon fibers include carbon nanofibers and carbon nanotubes. Other conductive additives that can be used include metal powders such as copper and nickel, metal fibers, and conductive ceramic materials.

[0062] Binders can be broadly categorized into known binders used to form electrode materials for various types of batteries. Examples of binders include various resin materials, specifically polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyethylene terephthalate, polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyethylene, polypropylene, and the like.

[0063] In the negative electrode material, the content ratio of the negative electrode active material is not particularly limited. For example, it is preferable that the negative electrode active material is contained in an amount of 50 to 95% by mass, and more preferably 60 to 90% by mass, relative to the total mass of the negative electrode active material, conductive additive, and binder contained in the negative electrode material.

[0064] In the negative electrode material, the proportion of the conductive additive is not particularly limited. For example, it is preferable that the conductive additive is present in an amount of 3 to 30% by mass, and more preferably 5 to 20% by mass, relative to the total mass of the negative electrode active material, conductive additive, and binder contained in the negative electrode material.

[0065] In the negative electrode material, the binder content is not particularly limited. For example, it is preferable that the binder be present in an amount of 3 to 30% by mass, and more preferably 5 to 20% by mass, relative to the total mass of the negative electrode active material, conductive additive, and binder contained in the negative electrode material.

[0066] The negative electrode material may consist only of a negative electrode active material, a conductive additive, and a binder, or it may contain other components.

[0067] The method for preparing the negative electrode material is not particularly limited, and for example, known methods for preparing negative electrode materials can be widely employed. For example, the negative electrode material can be prepared by mixing a negative electrode active material, a conductive additive, and a binder in predetermined proportions using an appropriate method. When preparing the negative electrode material, a solvent can also be used to disperse the negative electrode active material, conductive additive, and binder. Examples of solvents include water and various organic solvents, such as lower alcohol compounds with 1 to 3 carbon atoms, and NMP (N-methyl-2-pyrrolidone). When the negative electrode material contains a solvent, it may be in the form of a slurry or paste.

[0068] 4. Alkaline ion batteries The alkaline-ion battery of the present invention is not particularly limited in its other configurations, as long as it includes the aforementioned negative electrode material, and can have a configuration similar to that of a known alkaline-ion battery, for example. The type of alkaline-ion battery is not particularly limited, and examples include sodium secondary batteries, lithium-ion batteries, potassium secondary batteries, etc. The alkaline-ion battery of the present invention is preferably a sodium battery, and more preferably a sodium-ion secondary battery.

[0069] Alkaline ion batteries may, for example, comprise a positive electrode, a negative electrode, an electrolyte, and a separator. The size and shape of the battery can be appropriately determined according to its application.

[0070] The positive electrode can have a structure composed of, for example, a metal foil and a positive electrode material. Examples of metals for forming the metal foil include aluminum, titanium, platinum, molybdenum, stainless steel, and copper. The positive electrode material can be a wide range of known positive electrode materials; for example, materials constituting the positive electrode material include sodium metal, lithium metal, NaFePO4, Na3V2(PO4)3, and Na x MO4(M=Co, Mn, V, Fe), LiTiS2, LiCoO2, LiNiO2, LiMnO2, LiNi 0.33 Mn 0.33 Co 0.33 O2, LiLiLi 0.8 Mn 0.15 Al 0.05 Examples include O2, LiMn2O4, and LiFePO4. The positive electrode can be manufactured by known methods, such as coating a positive electrode material onto a metal foil.

[0071] The negative electrode may have a structure in which the negative electrode active material of the present invention is supported on a metal foil, for example. Examples of metal foils include aluminum, titanium, platinum, molybdenum, stainless steel, and copper. The negative electrode can be manufactured by known methods.

[0072] In alkaline-ion batteries, the type of electrolyte is not particularly limited; for example, any known electrolyte can be used. The electrolyte may be either a solid electrolyte or a liquid electrolyte.

[0073] Liquid electrolytes include solutions in which the electrolyte is dissolved in a solvent. Depending on the type of battery, various alkali salts can be used as electrolytes, such as NaPF6, NaClO4, NaCF3SO3, NaFSI, NaTFSI, LiPF6, LiClO4, LiBF4, LiBOB, LiAsF6, LiCF3SO3, LiTFSI, LiFSI, KPF6, KFSI, KTFSI, KBF4, etc. Other examples include known magnesium salts, aluminum salts, zinc salts, etc. Examples of solvents include water, diglyme, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, propyl acetate, fluoroethylene carbonate, propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, etc.

[0074] Examples of solid electrolytes include inorganic materials such as sulfides and oxides, and polymer materials such as PEO (polyethylene oxide).

[0075] As the separator, known separators used in secondary batteries can be used, such as polyolefin resins such as polyethylene and polypropylene; polyimide; polyvinyl alcohol; fluororesins such as terminally aminated polyethylene oxide polytetrafluoroethylene; acrylic resin; nylon; aromatic aramid; inorganic glass; ceramics, etc. The separator can be in the form of a porous membrane, nonwoven fabric, woven fabric, etc. Other separators include various polymer membranes and inorganic electrolytes. Examples of inorganic electrolytes include LiLaTiO3 and Li7La3Zr2O 12 (LLZO), Na3Zr2Si2PO 12 na 11 Sn2PS 12 Examples include Na3PSe4. [Examples]

[0076] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to the embodiments of these examples.

[0077] (Example 1) Raw material 1 was prepared by dispersing 150 mg of Ni(NO3)2 hexahydrate and 150 mg of Zn(NO3)2 hexahydrate in 15 mL of ethylene glycol. Raw material 2 was prepared by dispersing 90 mg of p-benzenedicarboxylic acid (H2BDC) in 24 mL of N,N-dimethylformamide (DMF) by sonication. Next, raw materials 1 and 2 were mixed and stirred at room temperature for 1 hour. Then, the mixture was transferred to a Teflon-lined sealed autoclave (50 ml capacity) and heated at 150 °C for 6 hours. The resulting pale green precursor (Ni-ZnMOF) was collected by centrifugation, washed several times with DMF and ethanol, and then dried in a vacuum oven at 60 °C for 12 hours (Step 1). The dried precursor was heated with thioacetamide (TAA) in a mass ratio of 1:5 in an argon atmosphere at 500 °C for 2 hours to obtain a black sulfide as the product (Step 2). Finally, the sulfide was placed in 13 mL of 1 MH2SO4 solution containing 0.5 MFeCl3 and subjected to etching by stirring at 60°C for 15 minutes. After washing three times each with distilled water and carbon disulfide, a composite material (Ni-Zn-S@C-2) was obtained (Step 3). The BET specific surface area of ​​the composite material was measured based on nitrogen adsorption / desorption isotherms and was found to be 114.86 cm². 2 The concentration was found to be / g. Furthermore, the amount of ZnS in the obtained composite material was quantified by elemental analysis to be approximately 5.6% by mass.

[0078] (Comparative Example 1) Raw material 1 was prepared by dispersing 150 mg of Ni(NO3)2 hexahydrate and 150 mg of Zn(NO3)2 hexahydrate in 15 mL of ethylene glycol. Raw material 2 was prepared by dispersing 90 mg of p-benzenedicarboxylic acid (H2BDC) in 24 mL of N,N-dimethylformamide (DMF) by sonication. Next, raw materials 1 and 2 were mixed and stirred at room temperature for 1 hour. Then, the mixture was transferred to a Teflon-lined sealed autoclave (50 ml capacity) and heated at 150 °C for 6 hours. The resulting pale green precursor (Ni-ZnMOF) was collected by centrifugation, washed several times with DMF and ethanol, and then dried in a vacuum oven at 60 °C for 12 hours. The dried precursor was heated with thioacetamide (TAA) in a mass ratio of 1:5 in an argon atmosphere at 500°C for 2 hours to obtain a black sulfide product (Ni-Zn-S@C-1). The BET specific surface area of ​​the product was measured based on nitrogen adsorption / desorption isotherms and was found to be 82.20 cm². 2 The value was / g. Furthermore, the amount of ZnS in the obtained product (Ni-Zn-S@C-1) was quantified by elemental analysis and found to be approximately 37 mass%.

[0079] (Example 1) The composite materials obtained in the examples and comparative examples were used as negative electrode active materials, and batteries were fabricated using each negative electrode active material. Specifically, a slurry for negative electrode materials was prepared consisting of the negative electrode active material, superP (conductive carbon black) as a conductive additive, and polyvinylidene fluoride (PVDF) dissolved in methylpyrrolidinone as a binder. In this slurry, the ratio of negative electrode active material:superP:PVDF was 7.5:1.5:1 (mass ratio). The slurry was coated onto copper foil, and the negative electrode was fabricated by drying it in a vacuum at 120°C for 12 hours. The battery was assembled using this negative electrode, a positive electrode (sodium metal with aluminum foil), a liquid electrolyte, and a separator ("Whatman GF / C glass fiber filter paper" provided by Cytiva) impregnated with this liquid electrolyte, by a known method. The electrolyte was a 1M sodium trifluoromethanesulfonate solution, and the solvent for this solution was diglyme.

[0080] (Evaluation results) Figure 1 shows SEM images of the negative electrode active materials obtained in Example 1 (Figure 1(b)) and Comparative Example 1 (Figure 1(a)). It was found that both negative electrode active materials possess a microsphere structure.

[0081] Figure 2 shows the X-ray diffraction (XRD) results of the negative electrode active materials obtained in the examples and comparative examples. X-ray diffraction measurements were performed using Rigaku's "SmartLab" and a Cu-Kα (λ=1.540Å) radiation source in the range of 2θ=10 to 100°.

[0082] From the XRD patterns in Figure 2, it was observed that the negative electrode active material made of the composite material obtained in Example 1 all closely matched the diffraction peaks of NiS (JCPDS card number 02-1280) and ZnS (JCPDS card number 05-0566), and no other diffraction peaks appeared. Therefore, it was found that the negative electrode active material made of the composite material in Example 1 was formed of a composite material containing zinc and nickel metal sulfides and carbon. The negative electrode active material made of the composite material in Comparative Example 1 only matched the NiS (JCPDS card number 02-1280) sample, and no other diffraction peaks appeared.

[0083] Figure 3 shows the results of a constant current charge-discharge test of the battery assembled in Fabrication Example 1. This measurement was performed using the LAND Battery Test System "CT2001A" (Wuhan LAND electronics Co., Ltd.). d. Measurement was performed using a Chinese (Chinese) device. Here, the measurement temperature was 30°C and the applied voltage was 1.5~3.5V (1Ag). -1 ) was used. Note that in Figure 3, the first axis of the Y axis is capacity (mAhg -1 The second axis of the Y-axis shows the Coulomb efficiency (%).

[0084] After 200 cycles, the electrode fabricated from the composite material of Example 1 was 1Ag -1 With a high current density of 415.1 mAhg -1It shows a specific capacity of 404.5 mAhg even after 1900 cycles. -1 The specific capacity was shown. In contrast, the electrode made from the composite material of Comparative Example 1 had a specific capacity of 1Ag -1 With a high current density of 297.9mAhg -1 It remained at the specific capacity level.

[0085] Therefore, it was found that a battery equipped with a negative electrode material containing the negative electrode active material obtained in Example 1 can provide better capacity characteristics and cycle characteristics than a battery equipped with the negative electrode active material of Comparative Example 1.

Claims

1. A negative electrode active material for alkaline ion batteries, It includes a composite material containing metal sulfides and carbon, The aforementioned metal sulfide is a sulfide containing zinc and nickel. The aforementioned metal sulfide is a negative electrode active material for alkaline ion batteries, having a ZnS component content of 1 to 30% by mass.

2. The composite material is formed into porous particles, as described in claim 1, for a negative electrode active material for an alkaline ion battery.

3. A negative electrode material for an alkaline-ion battery, comprising the negative electrode active material for an alkaline-ion battery described in claim 1 or 2.

4. An alkaline-ion battery comprising the negative electrode material for alkaline-ion batteries described in claim 3.

5. A method for producing a negative electrode active material for an alkaline ion battery according to claim 1 or 2, Step 1 involves mixing a zinc source, a nickel source, and an organic ligand in a solvent to obtain a precursor; Step 2 involves heating the precursor in the presence of a sulfur source to obtain a sulfide; and Step 3: Etching the sulfide to obtain the composite material. A method for producing a negative electrode active material for alkaline ion batteries, comprising the same components.

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