JP2020084208A - Ally, electricity storage device, and manufacturing method of alloy - Google Patents

Abstract

To provide an alloy with a novel composition.SOLUTION: An alloy is represented by MLi, where M is one or more of Si, Ge, Sn, Sb, Bi and Al, when M is Si, Ge and Sn, 4<x≤9 is satisfied, when M is Sb and Bi, 3<x≤6 is satisfied, and when M is Al, 1<x≤3 is satisfied.SELECTED DRAWING: None

Description

The present specification discloses an alloy, a power storage device, and a method for manufacturing the alloy.

Conventionally, as a negative electrode of an electricity storage device, a binder and a solvent are added to a negative electrode material containing silicon to prepare a slurry, the slurry is applied to a conductive metal foil, the solvent is removed, and then the slurry is baked in a non-oxidizing atmosphere. A material integrated with a material has been proposed (for example, see Patent Document 1). It is said that this negative electrode can reduce the contact resistance between the sintered body containing silicon as an active material and the current collector.

JP, 11-339777, A

By the way, in a metal material such as silicon that occludes and releases Li, the amount of occluded Li per unit volume or unit mass is limited to a fixed value, and the amount of occluded Li cannot be exceeded. As described above, there has been a demand for a technique that realizes a Li storage amount that exceeds the conventional limit.

The present disclosure has been made in view of such problems, and a main object of the present disclosure is to provide an alloy having a novel composition, a method for producing the alloy, and an electricity storage device using the alloy.

As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that when a metal material that absorbs and releases Li is treated at a high pressure within a predetermined composition range in which Li is an excessive amount, Li metal becomes It has been found that an alloy that does not exist in isolation can be manufactured, and the alloy, the electricity storage device, and the method for manufacturing the alloy of the present disclosure have been completed.

That is, the alloys disclosed herein are
MLi _x (where M is one of Si, Ge, Sn, Sb, Bi and Al, and when M is Si, Ge and Sn, 4<x<12 is satisfied, and when M is Sb and Bi, 3 <x<8 is satisfied, and when M is Al, 1<x<5 is satisfied).

The power storage device disclosed in the present specification is
A positive electrode having a positive electrode active material,
A negative electrode having the above alloy as a negative electrode active material,
An ion conductive medium that is interposed between the positive electrode and the negative electrode and conducts Li ions,
It is equipped with.

The method of making the alloys disclosed herein comprises
MLi _x (where M is one of Si, Ge, Sn, Sb, Bi and Al, and when M is Si, Ge and Sn, 4<x<12 is satisfied, and when M is Sb and Bi, 3 An alloying step of mixing M metal and Li metal so that the composition represented by <x<8 is satisfied and 1<x<5 is satisfied when M is Al, and a pressure treatment exceeding 6 MPa is performed, Is included.

The present disclosure can provide an alloy having a novel composition, a method for producing the alloy, and an electricity storage device using the alloy. For example, in a conventional manufacturing method, it is common to electrochemically insert Li into a metal material. For example, a general formula MLi _x (where M is Si, Ge, Sn, Sb, Bi or Al) is used. When M is Si, Ge, and Sn, x is 4 or less, when M is Sb and Bi, x is 3 or less, and when M is Al, x is 1 or less. , Each was the upper limit. On the other hand, in the present disclosure, it is speculated that by performing pressure treatment in a state in which an excessive amount of Li metal is added to M metal, Li is sufficiently introduced, Li metal is unlikely to remain, and an MLi _x alloy is obtained. .. The limit value of this Li excess depends on the M metal, and the upper limit of x is less than 12 when M is Si, Ge and Sn, the upper limit of x is less than 8 when M is Sb and Bi, and M is Al. When, the upper limit of x is presumed to be less than 5.

The schematic diagram which shows an example of the electrical storage device 20. 3 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 1. 3 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 1. The electrochemical evaluation and the differential scanning calorimetry measurement result of Example 2. 5 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 2. The electrochemical evaluation of Example 3 and a differential scanning calorimetry result. 7 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 3. The electrochemical evaluation and the differential scanning calorimetry result of Example 4. 8 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 4. 5 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 5. 5 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 5. 7 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 6. 7 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 6. 7 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 7.

(alloy)
The alloy disclosed in the present specification is MLi _x (where M is one of Si, Ge, Sn, Sb, Bi and Al, and when M is Si, Ge and Sn, 4<x<12 is satisfied. , M is Sb and Bi, 3<x<8 is satisfied, and when M is Al, 1<x<5 is satisfied). This alloy can occlude more Li than the alloy composition in which Li is electrochemically inserted at room temperature and atmospheric pressure. M is more preferably Si, Ge, Sn, or the like, which has a large amount of absorbed Li. When M is Si, Ge and Sn, it is preferable that x is larger in view of the Li storage amount, preferably 4.2 or more, more preferably 4.5 or more, still more preferably 5 or more. Further, when M is Si, Ge and Sn, x is preferably 11 or less, more preferably 10 or less, and further preferably 9 or less from the viewpoint of the presence of Li metal. When M is Si, Ge and Sn, and x is 9 or less, Li metal is not present, which is preferable. In addition, when M is Sb and Bi, it is preferable that x is larger in view of the Li storage amount, 3.2 or more is preferable, 3.5 or more is more preferable, and 4 or more is further preferable. Further, when M is Sb and Bi, x is preferably 7.5 or less, more preferably 7 or less, and further preferably 6 or less, from the viewpoint of the presence of Li metal. When M is Sb and Bi, and x is 6 or less, Li metal is not present, which is preferable. Further, when M is Al, it is preferable that x is larger, from the viewpoint of the amount of stored Li, preferably 1.2 or more, more preferably 1.5 or more, still more preferably 2 or more. In addition, when M is Al, x is preferably 4.5 or less, more preferably 4 or less, and further preferably 3 or less, from the viewpoint of the presence of Li metal. When M is Al and x is 3 or less, Li metal does not exist, which is preferable.

This alloy appears in a temperature range of 175° C. or higher and 225° C. or lower when the alloy and the electrolytic solution are put into a closed stainless steel measuring container having an internal withstand pressure of 5 MPa in a differential scanning calorimeter (DSC) measurement and the container is sealed. The heat generation intensity may be 1 W/g or less. In this DSC measurement, the heat generation intensity that appears in the temperature range of 175° C. to 225° C. is the heat of reaction between the Li metal and the electrolytic solution. Therefore, it can be said that the smaller the exothermic strength in this temperature range, the less Li metal contained in the alloy. Therefore, this DSC measurement can be used as a method for quantifying the Li metal contained in the alloy. In this DSC measurement, the electrolytic solution is assumed to have LiPF ₆ dissolved at 1 mol/L in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1. Further, in this DSC measurement, the closed measurement container, the alloy 1mol of MLi _x, and that adds 0.52μL the electrolyte solution. Then, in this DSC measurement, the heat flow rate is measured at a scanning speed of 5° C./min. In this measurement result, if the exothermic intensity appearing in the temperature range of 175° C. or higher and 225° C. or lower is 1 W/g or less, it can be said that the Li metal is an alloy of MLi _x that does not exist alone. The heat generation intensity is preferably smaller, preferably 0.8 W/g or less, and more preferably 0.5 W/g or less.

The alloy of MLi _x (where M is Bi) may have a superconducting transition temperature Tc in the range of 2.2 K or more and 6 K or less when the magnetic susceptibility is measured. The superconducting transition temperature Tc may be in the range of 4K or more and 5.5K or less. The superconducting transition temperature Tc of Bi alone at room temperature is 0.53 mK. Further, this Bi simple substance has a superconducting transition temperature Tc of 8.9 K under a high pressure of 9 GPa. Therefore, it can be said that this BiLi _x alloy is a novel substance.

(Method of manufacturing alloy)
The method for producing an alloy disclosed in the present specification may include an alloying step in which M metal (referring to a simple substance of M) and Li metal are mixed in a composition within a predetermined range and a pressure treatment exceeding 6 MPa is performed. Good.

(Alloying process)
In this step, MLi _x (where M is one of Si, Ge, Sn, Sb, Bi and Al, and when M is Si, Ge and Sn, 4<x<12 is satisfied, and M is Sb and A mixing treatment is performed in which M metal and Li metal are mixed so as to have a composition represented by 3<x<8 when Bi and 1<x<5 when M is Al. In this mixing treatment, M metal and Li metal may be mixed so as to have any of the above alloy compositions. In particular, in this step, when M is Si, Ge and Sn, x≦9 is satisfied, when M is Sb and Bi, x≦6 is satisfied, and when M is Al, x metal is satisfied so that x≦3. It is more preferable to mix Li metal with Li metal. This mixing process is preferably performed in an inert atmosphere, for example. The inert atmosphere may be, for example, nitrogen or a rare gas atmosphere such as He or Ar. This mixing process can be performed by, for example, a ball mill, a planetary mill, an automatic mortar mixing device, or the like. Further, in this step, pressure treatment exceeding 6 MPa is performed on the mixed mixture, but pressure treatment at a higher pressure is preferable, 8 MPa or more is preferable, 10 MPa or more is more preferable, and 12 MPa or more is further preferable. preferable. By processing at a higher pressure, Li can be diffused into M uniformly. This pressure treatment may be performed at 20 GPa or less in consideration of the restrictions of the manufacturing apparatus. In this step, the pressure treatment may be performed in the range of 150° C. or higher and 300° C. or lower. By heating, Li can be uniformly diffused in M. In this heat treatment, heating may be performed after reaching a predetermined pressure value (for example, a set pressure of 12 GPa). By going through such a step, the above-described MLi _x alloy in which no Li metal is present alone can be obtained.

(Power storage device)
The electricity storage device disclosed in the present specification includes a positive electrode having a positive electrode active material, a negative electrode having the above-described alloy as a negative electrode active material, and an ion conductive medium interposed between the positive electrode and the negative electrode to conduct Li ions. I have it. This electricity storage device may be, for example, an electric double layer capacitor, a hybrid capacitor, a pseudo electric double layer capacitor, a lithium ion battery, or the like. The positive electrode may include a positive electrode active material that absorbs and releases carrier ions.

In this electricity storage device, the positive electrode may be a positive electrode used in a general lithium ion battery. In this case, a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like can be used as the positive electrode active material. Specifically, transition metal sulfides such as TiS ₂ , TiS ₃ , MoS ₃ , and FeS _2, whose basic composition formulas are Li _(1-y) MnO ₂ (0 <y <1, etc., the same applies hereinafter) and Li _{(1 -y)} Lithium manganese composite oxide such as Mn ₂ O _4, lithium cobalt composite oxide whose basic composition formula is Li _(1-y) CoO _2, etc., basic composition formula Li _(1-y) NiO _2, etc. Lithium nickel composite oxide having a basic composition formula of Li _(1-y) Ni _a Co _b Mn _c O ₂ (a+b+c=1) and the like, a basic composition formula of LiV ₂ O ₃ For example, a lithium vanadium composite oxide having a basic composition formula such as V ₂ O ₅ can be used. Further, the positive electrode active material may be lithium iron phosphate or the like. Of these, lithium transition metal composite oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , and LiV ₂ O ₃ are preferable. The "basic composition formula" means that other elements may be included.

Alternatively, the positive electrode may be a known positive electrode used in lithium ion capacitors and the like. The positive electrode may include, for example, a carbon material as a positive electrode active material. The carbon material is not particularly limited, for example, activated carbons, cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, Examples thereof include polyacenes. Of these, activated carbons having a high specific surface area are preferable. The activated carbon as the carbon material preferably has a specific surface area of 1000 m ² /g or more, more preferably 1500 m ² /g or more. When the specific surface area is 1000 m ² /g or more, the discharge capacity can be further increased. The specific surface area of this activated carbon is preferably 3000 m ² /g or less, more preferably 2000 m ² /g or less, from the viewpoint of easy production. It is considered that at the positive electrode, at least one of an anion and a cation contained in the ion-conducting medium is adsorbed and desorbed to store electricity. It may be charged and discharged.

The positive electrode is prepared by, for example, mixing the positive electrode active material, the conductive material, and the binder, and adding a suitable solvent to form a paste-like positive electrode mixture, which is applied to the surface of the current collector and dried. Accordingly, it may be formed by compression so as to increase the electrode density. The conductive material is, for example, graphite such as natural graphite (scaly graphite, flake graphite) or artificial graphite, acetylene black, carbon black, Ketjen black, carbon whiskers, needle coke, carbon fiber, metal (copper, nickel, aluminum, It is possible to use one kind or a mixture of two or more kinds such as silver and gold). Among these, carbon black and acetylene black are preferable as the conductive material from the viewpoint of electron conductivity and coatability. The binder plays a role of binding the active material particles and the conductive material particles together, and includes, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), fluororubber, and the like. Fluorine resins, thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more kinds. Further, it is also possible to use an aqueous dispersion of cellulose-based or styrene-butadiene rubber (SBR), which is an aqueous binder. Examples of the application method include roller coating using an applicator roll or the like, screen coating, doctor blade method, spin coating, bar coater, and the like, and any of these can be used to obtain an arbitrary thickness and shape. As the current collector, aluminum, titanium, stainless steel, nickel, iron, baked carbon, conductive polymer, conductive glass, or the like can be used. Examples of the shape of the current collector include a foil shape, a film shape, a sheet shape, a net shape, a punched or expanded shape, a lath body, a porous body, a foamed body, and a fiber group formed body. The thickness of the current collector is, for example, 1 to 500 μm.

The negative electrode is MLi _x (where M is one of Si, Ge, Sn, Sb, Bi and Al, and when M is Si, Ge and Sn, 4<x<12 is satisfied, and M is Sb and Bi. Is satisfied, and 3<x<8 is satisfied, and when M is Al, 1<x<5 is satisfied). The negative electrode may be, for example, one in which the above-mentioned negative electrode active material is pressure-bonded to a current collector. As the current collector used for the negative electrode, for example, those exemplified for the positive electrode can be appropriately used.

In this electricity storage device, the ion conductive medium may be, for example, a non-aqueous electrolytic solution containing a supporting salt and an organic solvent. As the supporting salt, for example, when the carrier is lithium ion, a known lithium salt may be included. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li(CF ₃ SO ₂ ) ₂ N, LiN(C ₂ F ₅ SO ₂ ) _{2 and the} like. Of these, LiPF ₆ and LiBF _{4 and the} like are preferable. The concentration of this supporting salt in the non-aqueous electrolytic solution is preferably 0.1 mol/L or more and 5 mol/L or less, and more preferably 0.5 mol/L or more and 2 mol/L or less. When the concentration for dissolving the supporting salt is 0.1 mol/L or more, a sufficient current density can be obtained, and when the concentration is 5 mol/L or less, the electrolytic solution can be more stabilized. A flame retardant such as phosphorus or halogen may be added to this non-aqueous electrolyte. As the organic solvent, for example, an aprotic organic solvent can be used. Examples of such organic solvents include cyclic carbonates, chain carbonates, cyclic esters, cyclic ethers, chain ethers, and the like. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate. Examples of cyclic ester carbonates include gamma butyrolactone and gamma valerolactone. Examples of the cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of chain ethers include dimethoxyethane and ethylene glycol dimethyl ether. These may be used alone or in combination of two or more. This electrolytic solution may be, for example, a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1 and LiPF ₆ is dissolved at 1 mol/L. In addition, as the non-aqueous electrolyte solution, a nitrile solvent such as acetonitrile or propyl nitrile, an ionic liquid, a gel electrolyte, or the like may be used.

Further, the ion conductive medium may be a solid electrolyte. Examples of solid electrolytes include inorganic solid electrolytes and polymer solid electrolytes. The solid electrolyte is not limited to the following composition and structure, and may be any one as long as Li ions can move. As long as the compounds exemplified below have a basic skeleton, they can be used even if they are partially substituted or have different composition ratios. Examples of the inorganic solid electrolyte include Li ₃ N, Li ₁₄ Zn(GeO ₄ ) ₄ called LISON, sulfide Li _3.25 Ge _0.25 P _0.75 S ₄ , perovskite type La _0.5 Li _0.5 TiO ₃ , and (La _{2 / 3} Li _3x □ _1/3-2x )TiO ₃ (□: atomic vacancies), garnet type Li ₇ La ₃ Zr ₂ O ₁₂ , LiTi ₂ (PO ₄ ) ₃ called NASICON type, Li _1.3 M _0.3 Ti _1.7 (PO ₃ ) ₄ (M=Sc, Al), Li ₇ P ₃ S ₁₁ obtained from glass having a composition of 80Li ₂ S·20P ₂ S ₅ (mol%), which is a glass ceramic, and a sulfide-based compound having high conductivity. Li ₁₀ Ge ₂ PS ₂ is a material having a rate, Li ₂ S-SiS ₂ is a glass-based inorganic solid _{electrolyte, Li 2 S-SiS 2 -LiI} , Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S _{-SiS 2 -Li 4 SiO 4, Li} 2 S-P 2 S 5, Li 3 PO 4 -Li 4 SiO 4, Li 3 BO 4 -Li 4 SiO 4, and _{SiO 2, GeO 2, B 2} O 3, Examples thereof include P ₂ O ₅ as a glass-based material and Li ₂ O as a network modifier, and thiolysicon solid electrolytes such as Li ₂ S—GeS ₂ system, Li ₂ S—GeS ₂ —ZnS system, Li ₂ S—. Ga ₂ S _{2 system, Li 2 S-GeS 2 -Ga} 2 S 3 _{system, Li 2 S-GeS 2 -P} 2 S 5 _{based, Li 2 S-GeS 2 -SbS} 5 system, Li ₂ S-GeS ₂ - Al ₂ S ₃ system, Li ₂ S-SiS _{2 system, Li 2 S-P 2 S} 5 _{based, Li 2 S-Al 2 S} 3 _{system, LiS-SiS 2 -Al 2 S} 3 system, Li ₂ S-SiS such as ₂ -P ₂ S ₅ systems.

The solid polymer electrolyte includes, for example, a complex of polyethylene oxide (PEO) and an alkali metal, and is not limited to PEO as long as it is a polymer, and a unit structure of a polymer material that dissolves a lithium salt is exemplified. PEO: PPO: poly(propylene oxide), Polyamine-based PEI: poly(ethylene imine), PAN: poly(acrylonitrile), Polysulfide-based PAS: poly(conjugate sulfide), and the like. Examples of lithium salts include LiTFSI:(LiN(SO ₂ CF ₃ ) ₂ ), LiPEI:(COCF ₂ SO ₂ NLi) _n , and LiPPI:(COCF(CF ₃ OCF ₂ CF ₂ SO ₂ NLi)) _n . Further, gel polymer electrolytes using PVdF (PolyVinylidene DiFluoride), PAN, HFP (Hexafluoropropylene) and the like can be mentioned. Further, examples of the organic ionic plastic electrolyte include those having a plastic crystal phase. Typical molecules of the plastic crystal phase include Tetrachloromethane, Cyclohexane, Succinonitrile, etc., and Tf ₂ N: (trifluoromethylsulfonyl)amide, LiBF ₄ is added to these plastic crystal phases, or an aliphatic quaternary ammonium is added. And a salt having a plastic crystal phase composed of perfluoroanion. Organic-inorganic hybrid ionic gel, which is a mixture of ionic liquid and glass component at the molecular level, namely, organoboron ionic gel electrolyte using cellulose, organoboron ionic gel electrolyte using amylose, and boron polysubstitution macrocycle derived from cyclodextrin And so on.

This electricity storage device may include a separator between the positive electrode and the negative electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the electricity storage device, for example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or an olefin resin such as polyethylene or polypropylene. Examples include microporous films. These may be used alone or in combination.

The shape of the electricity storage device is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Further, it may be applied to a large one used for an electric vehicle or the like. FIG. 1 is a schematic diagram showing an example of the electricity storage device 20. The electricity storage device 20 includes a cup-shaped cell case 21, a positive electrode 22 having a positive electrode active material and provided below the cell case 21, and a positive electrode 22 having a negative electrode active material via a separator 24. A negative electrode 23 provided at a position facing each other, a gasket 25 formed of an insulating material, and a sealing plate 26 disposed in an opening of the cell case 21 for sealing the cell case 21 via the gasket 25 are provided. There is. In this electricity storage device 20, the space between the positive electrode 22 and the negative electrode 23 is filled with the ion conductive medium 27. Further, the negative electrode 23 has the above-described MLi _x alloy as a negative electrode active material.

The present disclosure described in detail above can provide an alloy having a novel composition, a method for producing the alloy, and an electricity storage device using the alloy. For example, in a conventional manufacturing method, it is common to electrochemically insert Li into a metal material. For example, a general formula MLi _x (where M is Si, Ge, Sn, Sb, Bi or Al) is used. When M is Si, Ge, and Sn, x is 4 or less, when M is Sb and Bi, x is 3 or less, and when M is Al, x is 1 or less. , Each was the upper limit value. On the other hand, in the present disclosure, it is speculated that by performing pressure treatment in a state in which an excessive amount of Li metal is added to M metal, Li is sufficiently introduced, Li metal is unlikely to remain, and an MLi _x alloy is obtained. .. The limit value of this Li excess depends on the M metal, and the upper limit of x is less than 12 when M is Si, Ge and Sn, the upper limit of x is less than 8 when M is Sb and Bi, and M is Al. When, the upper limit of x is presumed to be less than 5.

It is needless to say that the present disclosure is not limited to the above-described embodiments and can be implemented in various modes as long as they are within the technical scope of the present disclosure.

Hereinafter, examples in which the alloy of the present disclosure is specifically manufactured will be described as examples. It is needless to say that the present disclosure is not limited to this embodiment and can be implemented in various modes within the technical scope of the present disclosure.

(Example 1)
Si and Li were mixed at a molar ratio of 1:9 in a mortar in a glove box in an inert atmosphere to obtain a mixture of SiLi ₉ . The mixture was sealed and subjected to a pressure treatment at a pressure of 12 GPa and a temperature of 300° C. for 30 minutes. SiLi ₉ after this treatment was recovered in the above glove box and used as Example 1.

(Comparative Example 1)
Si and Li were mixed at a molar ratio of 1:12 in a mortar in a glove box in an inert atmosphere to obtain a mixture of SiLi ₁₂ , and the same treatment as in Example 1 was performed. The thing was set as the comparative example 1.

(Reference example 1)
LiPF ₆ was dissolved at a ratio of 1 mol/L in a solvent in which Si was used as a working electrode, Li metal was used as a counter electrode, and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed as a electrolyte in a volume ratio of 1:1. A bipolar cell using the non-aqueous electrolyte solution (1M-LiPF ₆ EC/DEC) was prepared. This bipolar cell was reduced to 5 mV with a constant current of 300 μA. As a result, a reducing capacity of 3740 mAh/g was obtained. Since about 15 mAh/g is consumed by the initial film formation, SiLi ₄ in which Li was occluded up to a theoretical capacity of 3817 mAh/g was obtained, and this was referred to as Reference Example 1. The reference example 1 is a SiLi alloy in which the maximum Li is occluded in Si by inserting Li in a bipolar cell.

(Example 2)
Ge and Li were mixed at a molar ratio of 1:9 in a mortar in a glove box in an inert atmosphere to obtain a mixture of GeLi ₉ , and the same treatment as in Example 1 was performed. The thing was set as Example 2.

(Comparative example 2)
Ge and Li were mixed at a molar ratio of 1:12 in a mortar in a glove box in an inert atmosphere to obtain a mixture of GeLi ₁₂ , and the same treatment as in Example 1 was performed. It was designated as Comparative Example 2.

(Reference example 2)
A bipolar cell was prepared using Ge as a working electrode and Li metal as a counter electrode and using a nonaqueous electrolytic solution (1M-LiPF ₆ EC/DEC). This bipolar cell was reduced to 5 mV with a constant current of 300 μA. As a result, a reduction capacity of 1428 mAh/g was obtained. Taking into consideration the consumption amount of the initial film formation, GeLi ₄ in which Li was occluded up to a theoretical capacity of 1475 mAh/g was obtained, and this was referred to as Reference Example 2. The reference example 2 is a GeLi alloy in which the maximum Li is occluded in Ge by inserting Li in the bipolar cell.

(Example 3)
Sn and Li were mixed at a molar ratio of 1:9 in a mortar in a glove box in an inert atmosphere to obtain a mixture of SnLi ₉ , and the same treatment as in Example 1 was performed. The thing was set to Example 3.

(Comparative example 3)
Sn and Li were mixed at a molar ratio of 1:12 in a mortar in a glove box in an inert atmosphere to obtain a mixture of SnLi ₁₂ , and the same treatment as in Example 1 was performed. The thing was set as the comparative example 3.

(Reference example 3)
A bipolar cell was prepared using Sn as a working electrode and Li metal as a counter electrode and using a nonaqueous electrolytic solution (1M-LiPF ₆ EC/DEC). This bipolar cell was reduced to 5 mV with a constant current of 300 μA. As a result, a reducing capacity of 886 mAh/g was obtained. Considering the consumption amount of the initial film formation, SnLi ₄ in which Li was occluded up to a theoretical capacity of 903 mAh/g was obtained, and this was referred to as Reference Example 3. The reference example 3 is a SnLi alloy in which the maximum Li is occluded in Sn by inserting Li in the bipolar cell.

(Example 4)
Sb and Li were mixed at a molar ratio of 1:6 in a mortar in a glove box in an inert atmosphere to obtain a mixture of SbLi ₆ , and the same treatment as in Example 1 was performed. The thing was set to Example 4.

(Comparative example 4)
Sb and Li were mixed at a molar ratio of 1:8 in a mortar in a glove box in an inert atmosphere to obtain a mixture of SbLi ₈ and the same treatment as in Example 1 was performed. It was designated as Comparative Example 4.

(Reference example 4)
A bipolar cell was prepared using Sb as a working electrode and Li metal as a counter electrode and using a nonaqueous electrolytic solution (1M-LiPF ₆ EC/DEC). This bipolar cell was reduced to 5 mV with a constant current of 300 μA. As a result, a reducing capacity of 620 mAh/g was obtained. Considering the amount of consumption of the initial film formation, SbLi ₃ in which Li was occluded up to a theoretical capacity of 660 mAh/g was obtained, and this was referred to as Reference Example 4. Reference Example 4 is an SbLi alloy in which the maximum Li was occluded in Sb by inserting Li in the bipolar cell.

(Example 5)
Bi and Li were mixed at a molar ratio of 1:6 in a mortar in a glove box in an inert atmosphere to obtain a mixture of BiLi ₆ , and the same treatment as in Example 1 was performed. The product is referred to as Example 5.

(Comparative example 5)
Bi and Li were mixed at a molar ratio of 1:8 in a mortar in a glove box in an inert atmosphere to obtain a mixture of BiLi ₈ , and the same treatment as in Example 1 was performed. It was designated as Comparative Example 5.

(Reference example 5)
A bipolar cell was prepared using Bi as a working electrode and Li metal as a counter electrode and using a nonaqueous electrolytic solution (1M-LiPF ₆ EC/DEC). This bipolar cell was reduced to 5 mV with a constant current of 300 μA. As a result, a reducing capacity of 365 mAh/g was obtained. Considering the consumption amount of the initial film formation, BiLi ₃ having Li occluded up to about 384 mAh/g which is the theoretical capacity was obtained, and this was referred to as Reference Example 5. The reference example 5 is a BiLi alloy in which the maximum Li was occluded in Bi by inserting Li in the bipolar cell.

(Example 6)
Al and Li were mixed at a molar ratio of 1:3 in a mortar in a glove box in an inert atmosphere to obtain a mixture of AlLi ₃ , and the same treatment as in Example 1 was performed. The product is referred to as Example 6.

(Comparative example 6)
Al and Li were mixed at a molar ratio of 1:5 in a mortar in a glove box in an inert atmosphere to obtain a mixture of AlLi ₅ , and the same treatment as in Example 1 was performed. It was designated as Comparative Example 6.

(Reference example 6)
A bipolar cell was prepared using Al as a working electrode and Li metal as a counter electrode and using a nonaqueous electrolytic solution (1M-LiPF ₆ EC/DEC). This bipolar cell was reduced to 5 mV with a constant current of 300 μA. As a result, a reduction capacity of 843 mAh/g was obtained. Considering the consumption amount of the initial film formation, AlLi in which Li was occluded up to a theoretical capacity of 993 mAh/g was obtained, and this was referred to as Reference Example 6. This reference example 6 is an AlLi alloy in which the maximum Li was occluded in Al by inserting Li in a bipolar cell.

(Comparative Example 7)
Zn and Li were mixed at a molar ratio of 1:3 in a mortar in a glove box in an inert atmosphere to obtain a ZnLi ₃ mixture, and the same treatment as in Example 1 was performed. It was designated as Comparative Example 7.

(Reference example 7)
A bipolar cell was prepared using Zn as a working electrode and Li metal as a counter electrode and using a non-aqueous electrolyte solution (1M-LiPF ₆ EC/DEC). This bipolar cell was reduced to 5 mV with a constant current of 300 μA. As a result, a reduction capacity of 348 mAh/g was obtained. Considering the consumption of the initial film formation, ZnLi in which Li was occluded up to a theoretical capacity of 409 mAh/g was obtained, and this was referred to as Reference Example 7. This reference example 7 is a ZnLi alloy in which the maximum Li was occluded in Zn by inserting Li in the bipolar cell.

[Electrochemical evaluation]
An electrochemical cell was prepared and electrochemical evaluation was performed. Using the prepared sample as a working electrode, the counter electrode was made of Li metal, and a cell using a non-aqueous electrolyte (1M-LiPF ₆ EC/DEC) was prepared. The produced cell was oxidized and reduced at a current value of 50 hours within a range of 3V to 0.01V.

[Differential scanning calorimetry]
The differential scanning calorimetry is performed by using a differential scanning calorimeter (Thermo plus2 manufactured by Rigaku Co.) to seal the sample and the non-aqueous electrolyte solution prepared in a stainless steel closed measuring container having an internal pressure of 5 MPa, and a scanning speed of 5°C. It was performed by measuring the heat flow rate from room temperature to 485° C./min. The measurement sample was prepared by adding 0.52 μL of a non-aqueous electrolyte solution (1M-LiPF ₆ EC/DEC) to 1 mol of the above sample.

[Measurement of superconducting transition temperature Tc]
The superconducting transition temperature Tc of the obtained sample was determined using a magnetization measuring device (MPMS manufactured by Quantum Design). First, 10 mg of the sample was sealed with aluminum foil, and the temperature was set to 100 K and the magnetic field was set to zero. Then, the temperature was rapidly cooled to 2.2 K, and a magnetic field of 30 (Oe) was applied. The magnetization was measured while increasing the temperature to 20 K at a temperature interval of 0.1 K. Finally, the magnetic susceptibility was measured while lowering the temperature from 20K to 2.2K. When the sample transitions to the superconducting phase, the Meissner effect causes the transition from weak paramagnetism to diamagnetism, and the magnetization shows a large negative value. The temperature at which this diamagnetic transition occurs was defined as the superconducting transition temperature Tc.

(Results and discussion)
The composition of each sample, the oxidation capacity and the theoretical capacity (mAh/g) at the time of Li desorption in the first cycle, and the maximum value (W/g) of the exothermic intensity in the range of 175°C to 225°C by differential scanning calorimetry are summarized Showed. 2 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 1, where FIG. 2A is a redox curve, FIG. 2B is a DSC measurement result, and FIG. 2C is a reduction oxidation curve of Si metal. As shown in Table 1 and FIG. 2A, in Example 1, it was found that the oxidation capacity associated with the oxidation releasing Li was 8156 mAh/g, which was close to the theoretical capacity of 8588 mAh/g. Further, as shown in FIG. 2B, the exothermic intensity showing the reaction between the Li metal and the non-aqueous electrolyte was not confirmed in the measurement temperature range of 175° C. to 225° C. That is, it was found that in Example 1, the alloy was a SiLi ₉ alloy with almost no excess Li metal. Further, as shown in FIG. 2C, since Si metal shows a capacity of only up to about 4000 mAh/g, it was clarified that the oxidation capacity increased in Example 1, which proves that it is a SiLi ₉ alloy. Was given. In addition, in Example 1, when X-ray diffraction measurement was performed, it was presumed that the peak was broad and that it did not show crystallinity and was amorphous.

FIG. 3 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 1, FIG. 3A is a redox curve, FIG. 3B is a DSC measurement result, and FIG. 3C is an enlarged view of the oxidation curves of SiLi ₉ and SiLi ₁₂ . .. As shown in Table 1 and FIG. 3A, in Comparative Example 1, the oxidation capacity associated with the oxidation releasing Li was 9535 mAh/g, which was increased by about 1000 mAh/g from Example 1, but the theoretical capacity was 11451 mAh/g. I realized that it wouldn't come. In addition, as shown in FIG. 3B, the exothermic intensity showed a maximum of 6.6 W/g in the measurement temperature range of 175° C. to 225° C., suggesting the reaction between the Li metal and the non-aqueous electrolyte solution. That is, in Comparative Example 1, it was found that excess Li metal was present. Further, as shown in FIG. 3C, it was found that the oxidation potential of SiLi ₁₂ remained at a potential lower than that of SiLi _{9 up} to about 1000 mAh/g. It was speculated that this was because the Li metal remained without being absorbed by Si and the Li metal was oxidized. As described above, it was found that the SiLi alloy can occlude Li at least up to the alloy composition of SiLi ₉ by the pressure treatment.

4 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 2, where FIG. 4A is the oxidation-reduction curve, FIG. 4B is the DSC measurement result, and FIG. 4C is the reduction oxidation curve of Ge metal. As shown in Table 1 and FIG. 4A, in Example 2, it was found that the oxidation capacity associated with the oxidation releasing Li was 3269 mAh/g, which was close to the theoretical capacity of 3320 mAh/g. Further, as shown in FIG. 4B, the exothermic intensity showing the reaction between the Li metal and the nonaqueous electrolytic solution was not confirmed in the measurement temperature range of 175° C. to 225° C. That is, it was found that in Example 2, the alloy was a GeLi ₉ alloy with no excess Li metal. Further, as shown in FIG. 4C, Ge metal exhibits a capacity of only up to about 1545 mAh/g. Therefore, in Example 2, it was clarified that the oxidation capacity increased, which proves that the material is GeLi ₉ alloy. Was given. In addition, in Example 2, when the X-ray diffraction measurement was performed, it was assumed that the peak was broad and was amorphous without showing crystallinity.

5 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 2, FIG. 5A shows the redox curve, and FIG. 5B shows the DSC measurement results. As shown in Table 1 and FIG. 5A, in Comparative Example 2, the oxidation capacity associated with the oxidation releasing Li was 4554 mAh/g, which was close to the theoretical capacity of 4427 mAh/g. On the other hand, as shown in FIG. 5B, the exothermic intensity showed a maximum of 0.66 W/g in the measurement temperature range of 175° C. to 225° C., suggesting the reaction between the Li metal and the non-aqueous electrolyte solution. That is, it was found that in Comparative Example 2, excess Li metal was present. Thus, it was found that in the GeLi alloy, it is possible to occlude Li at least up to the alloy composition of GeLi ₉ by the pressure treatment.

6 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 3, where FIG. 6A is the oxidation-reduction curve, FIG. 6B is the DSC measurement result, and FIG. 6C is the reduction oxidation curve of Sn metal. As shown in Table 1 and FIG. 6A, in Example 3, it was found that the oxidation capacity accompanying Li-releasing oxidation was 1984 mAh/g, which was close to the theoretical capacity of 2031 mAh/g. Further, as shown in FIG. 6B, the exothermic intensity showing the reaction between the Li metal and the nonaqueous electrolytic solution was not confirmed in the measurement temperature range of 175° C. to 225° C. That is, in Example 3, it was found that the alloy was a SnLi ₉ alloy with no excess Li metal. Further, as shown in FIG. 3C, Sn metal exhibits a capacity of only up to about 942 mAh/g. Therefore, in Example 3, it was clarified that the oxidation capacity increased, and it was confirmed that the SnLi ₉ alloy was used. Was given. In addition, in Example 3, when the X-ray diffraction measurement was performed, it was assumed that the peak was broad and was amorphous without showing crystallinity.

7 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 3, FIG. 7A shows the oxidation-reduction curve, and FIG. 7B shows the DSC measurement results. As shown in Table 1 and FIG. 7A, in Comparative Example 3, it was found that the oxidation capacity associated with the oxidation releasing Li was 2569 mAh/g, and did not reach the theoretical capacity of 2708 mAh/g. Further, as shown in FIG. 7B, the exothermic intensity was 0.90 W/g at the maximum in the measurement temperature range of 175° C. to 225° C., suggesting the reaction between the Li metal and the non-aqueous electrolyte solution. That is, in Comparative Example 3, it was found that excess Li metal was present. As described above, in the SnLi alloy, it was found that the pressure treatment can occlude Li up to at least the alloy composition of SnLi ₉ .

8 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 4, where FIG. 8A is a redox curve, FIG. 8B is a DSC measurement result, and FIG. 8C is a reduction oxidation curve of Sb metal. As shown in Table 1 and FIG. 8A, in Example 4, it was found that the oxidation capacity associated with the oxidation releasing Li was 1250 mAh/g, which was close to the theoretical capacity of 1320 mAh/g. Moreover, as shown in FIG. 8B, the exothermic intensity showing the reaction between the Li metal and the non-aqueous electrolyte was not confirmed in the measurement temperature range of 175° C. to 225° C. That is, it was found that in Example 4, the alloy was an SbLi ₆ alloy with no excess Li metal. Further, as shown in FIG. 8C, Sb metal exhibits a capacity of only up to about 502 mAh/g. Therefore, in Example 4, it was clarified that the oxidation capacity was increased, and it was confirmed that the SbLi ₆ alloy was used. Was given. In addition, in Example 4, when X-ray diffraction measurement was performed, it was assumed that the peak was broad and was amorphous without showing crystallinity.

9 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 4, FIG. 9A shows the redox curve, and FIG. 9B shows the DSC measurement results. As shown in Table 1 and FIG. 9A, in Comparative Example 4, it was found that the oxidation capacity accompanying the oxidation that releases Li was 1603 mAh/g, and did not reach the theoretical capacity of 1760 mAh/g. Further, as shown in FIG. 9B, the exothermic intensity showed a maximum of 1.9 W/g in the measurement temperature range of 175° C. to 225° C., suggesting the reaction between the Li metal and the non-aqueous electrolyte solution. That is, it was found that in Comparative Example 4, excess Li metal was present. As described above, in the SbLi alloy, it was found that the pressure treatment can occlude Li up to at least the alloy composition of SbLi ₆ .

10 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 5, where FIG. 10A is a redox curve, FIG. 10B is a DSC measurement result, FIG. 10C is a reduction oxidation curve of Bi metal, and FIG. 10D is a magnetic susceptibility measurement. The result. As shown in Table 1 and FIG. 10A, in Example 5, it was found that the oxidation capacity accompanying the oxidation that releases Li was 773 mAh/g, which was a value close to the theoretical capacity of 769 mAh/g. Moreover, as shown in FIG. 10B, the exothermic intensity showing the reaction between the Li metal and the nonaqueous electrolytic solution was not confirmed in the measurement temperature range of 175° C. to 225° C. That is, it was found that in Example 5, it was a BiLi ₆ alloy with no excess Li metal. Further, as shown in FIG. 10C, since Bi metal exhibits a capacity of only up to about 380 mAh/g, it was revealed that the oxidation capacity was increased in Example 5, and it was confirmed that BiLi ₆ alloy was used. Was given. Further, as shown in FIG. 10D, in Example 5, it was found that the superconducting transition temperature Tc appears near 5K. For example, it has been reported in Non-Patent Document 1 (Science, 355, 52 (2017).) that the superconducting transition temperature Tc of Bi alone at room temperature is 0.53 mK. Further, it has been reported in Non-Patent Document 2 (Nature Reviwes Materials 2, Article number;17005 (2017).) that this Bi has a superconducting transition temperature Tc of 8.9 K under a high pressure of 9 GPa. Therefore, the BiLi ₆ alloy of Example 5 was presumed to be a novel substance. In addition, in Example 5, when the X-ray diffraction measurement was performed, it was assumed that the peak was broad and that it did not show crystallinity and was amorphous.

11 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 5, FIG. 11A shows the redox curve, and FIG. 11B shows the DSC measurement results. As shown in Table 1 and FIG. 11A, in Comparative Example 5, the oxidation capacity associated with the oxidation that releases Li was 1029 mAh/g, which was close to the theoretical capacity of 1025 mAh/g. On the other hand, as shown in FIG. 11B, the exothermic intensity showed a maximum of 5.9 W/g in the measurement temperature range of 175° C. to 225° C., suggesting the reaction between the Li metal and the non-aqueous electrolyte solution. That is, in Comparative Example 5, it was found that excess Li metal was present. As described above, in the BiLi alloy, it was found that the pressure treatment can occlude Li at least up to the alloy composition of BiLi ₆ .

12 shows the results of electrochemical evaluation and differential scanning calorimetry of Example 6, where FIG. 12A is the oxidation-reduction curve, FIG. 12B is the DSC measurement result, and FIG. 12C is the reduction oxidation curve of Al metal. As shown in Table 1 and FIG. 12A, in Example 6, it was found that the oxidation capacity associated with the oxidation releasing Li was 2916 mAh/g, which was a value close to the theoretical capacity of 2980 mAh/g. Moreover, as shown in FIG. 12B, the exothermic intensity showing the reaction between the Li metal and the non-aqueous electrolyte was not confirmed in the measurement temperature range of 175° C. to 225° C. That is, it was found that in Example 6, the alloy was an AlLi ₃ alloy with no excess Li metal. Further, as shown in FIG. 12C, Al metal exhibits a capacity of only up to about 787 mAh/g. Therefore, in Example 6, it was clarified that the oxidation capacity increased, and it was confirmed that the alloy was an AlLi ₃ alloy. Was given. In addition, in Example 6, when the X-ray diffraction measurement was performed, it was assumed that the peak was broad and that it did not exhibit crystallinity and was amorphous.

13 shows the results of electrochemical evaluation and differential scanning calorimetry of Comparative Example 6, FIG. 13A shows the redox curve, and FIG. 13B shows the DSC measurement results. As shown in Table 1 and FIG. 13A, in Comparative Example 6, it was found that the oxidation capacity associated with the oxidation that releases Li was 1029 mAh/g, and did not reach the theoretical capacity of 4966 mAh/g. Further, as shown in FIG. 13B, the exothermic intensity was 3.5 W/g at the maximum in the measurement temperature range of 175° C. to 225° C., suggesting the reaction between the Li metal and the non-aqueous electrolyte solution. That is, in Comparative Example 6, it was found that excess Li metal was present. As described above, in the AlLi alloy, it was found that the pressure treatment can occlude Li up to at least the alloy composition of AlLi ₃ .

Figure 14 is an electrochemical evaluation and differential scanning calorimetry results of Comparative Example 7, the redox curve in Fig. 14A is ZnLi _3, DSC measurement result of FIG. 14B is ZnLi _3, reduction-oxidation curve of FIG. 14C is Zn metal, FIG. 14D is the DSC measurement result of ZnLi prepared by reduction of Zn metal. As shown in Table 1 and FIG. 14A, in Comparative Example 7, the oxidation capacity associated with the oxidation releasing Li was 1203 mAh/g, which was close to the theoretical capacity of 1229 mAh/g. On the other hand, as shown in FIG. 14B, the exothermic intensity was 3.7 W/g at maximum in the measurement temperature range of 175° C. to 225° C., suggesting the reaction between the Li metal and the non-aqueous electrolyte solution. That is, in Comparative Example 7, it was found that excess Li metal was present. Further, as shown in FIG. 14C, Zn metal showed a capacity of about 391 mAh/g. On the other hand, as shown in FIG. 14D, the exothermic intensity showing the reaction between the Li metal and the non-aqueous electrolyte was not confirmed in the measurement temperature range of 175° C. to 225° C. That is, it was found that the Zn metal in FIG. 14C is a ZnLi alloy in which excess Li metal does not exist. From the above, it has been clarified that in Comparative Example 7, even if the pressure treatment is performed, even if Li is inserted into Zn at room temperature and normal pressure, Li cannot be inserted beyond the composition of ZnLi.

INDUSTRIAL APPLICABILITY The alloy, the electricity storage device, and the method for manufacturing the alloy according to the present disclosure can be used in the battery industry.

20 electricity storage device, 21 cell case, 22 positive electrode, 23 negative electrode, 24 separator, 25 gasket, 26 sealing plate, 27 ion conductive medium.

Claims (9)

MLi _x (where M is one of Si, Ge, Sn, Sb, Bi and Al, and when M is Si, Ge and Sn, 4<x<12 is satisfied, and when M is Sb and Bi, 3 <the alloy satisfying <x<8 and satisfying 1<x<5 when M is Al). The alloy according to claim 1, wherein when M is Si, Ge and Sn, x≦9 is satisfied, when M is Sb and Bi, x≦6 is satisfied, and when M is Al, x≦3 is satisfied. The alloy 1mol of the MLi _x stainless steel closed measurement container having an internal breakdown voltage of 5MPa in differential scanning calorimetry, were mixed in a 1: 1 ratio of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio 0.52 μL of an electrolyte solution in which LiPF ₆ was dissolved at 1 mol/L was added to the solvent, the mixture was sealed, and the heat flow rate was measured at a scanning rate of 5° C./min. The alloy according to claim 1 or 2, which is 1 W/g or less. The superconducting transition temperature Tc is in the range of 2.2 K or more and 6 K or less when the magnetic susceptibility of the alloy of MLi _x (where M is Bi) is measured. Alloy of. A positive electrode having a positive electrode active material,
A negative electrode having the alloy according to any one of claims 1 to 4 as a negative electrode active material,
An ion conductive medium that is interposed between the positive electrode and the negative electrode and conducts Li ions,
An electricity storage device including. MLi _x (where M is one of Si, Ge, Sn, Sb, Bi and Al, and when M is Si, Ge and Sn, 4<x<12 is satisfied, and when M is Sb and Bi, 3 An alloying step of mixing M metal and Li metal so that the composition represented by <x<8 is satisfied and 1<x<5 is satisfied when M is Al, and a pressure treatment exceeding 6 MPa is performed, A method for producing an alloy containing. In the alloying step, when M is Si, Ge and Sn, x≦9 is satisfied, when M is Sb and Bi, x≦6 is satisfied, and when M is Al, x metal is satisfied so that x≦3. The method for producing an alloy according to claim 6, wherein Li and Li metal are mixed. The method for producing an alloy according to claim 6, wherein the pressure treatment is performed at 10 MPa or more in the alloying step. The method for producing an alloy according to claim 6, wherein in the alloying step, the pressure treatment is performed in a range of 150° C. or higher and 300° C. or lower.