Negative electrode active material for fluoride ion battery, negative electrode active material layer for fluoride ion battery, composition for forming negative electrode active material layer for fluoride ion battery, fluoride ion battery, method for manufacturing negative electrode active material for fluoride ion battery, and method for manufacturing fluoride ion battery

Abstract

To provide a negative electrode active material for a fluoride ion battery that can be formed from readily available materials, a fluoride ion battery having such a negative electrode active material, a method for manufacturing such a negative electrode active material for a fluoride ion battery, and a method for manufacturing a fluoride ion battery having such a negative electrode active material.SOLUTION: A negative electrode active material for a fluoride ion battery according to the present disclosure is aluminum carbide.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a negative electrode active material for a fluoride ion battery, a negative electrode active material layer for a fluoride ion battery, a composition for forming a negative electrode active material layer for a fluoride ion battery, a fluoride ion battery, a method for manufacturing a negative electrode active material for a fluoride ion battery, and a method for manufacturing a fluoride ion battery.

Background Art

[0002] Various materials have been proposed as a negative electrode active material (anode active material) for a fluoride ion battery.

[0003] For example, Patent Document 1 discloses a fluoride ion battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, wherein the negative electrode active material layer contains a negative electrode active material containing Si element and La element, and a solid electrolyte containing La element, Ba element, and F element.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although various materials have been proposed as a negative electrode active material for a fluoride ion battery, there is a demand for a novel negative electrode active material for a fluoride ion battery that can be formed from easily available materials.

[0006] An object of the present disclosure is to provide a negative electrode active material for a fluoride ion battery that can be formed from easily available materials, a fluoride ion battery having such a negative electrode active material, a method for manufacturing such a negative electrode active material for a fluoride ion battery, and a method for manufacturing a fluoride ion battery having such a negative electrode active material.

Means for Solving the Problem

[0007] The present inventors have found that the above problems can be solved by the following means.

[0008] <Aspect 1> A negative electrode active material for a fluoride ion battery, which is aluminum carbide. <Aspect 2> The negative electrode active material according to Aspect 1, wherein the aluminum carbide has been pretreated by fluorination up to 3V (vs. Pb / PbF2). <Aspect 3> A negative electrode active material layer for a fluoride ion battery, which has the negative electrode active material according to Aspect 1 or 2. <Aspect 4> A composition for forming a negative electrode active material layer for a fluoride ion battery, which has the negative electrode active material according to Aspect 1 or 2. <Aspect 5> A fluoride ion battery, which has the negative electrode active material layer according to Aspect 3. <Aspect 6> A method for producing the negative electrode active material according to Aspect 2, which includes performing a pretreatment of fluorinating aluminum carbide up to 3V (vs. Pb / PbF2). <Aspect 7> A method for producing the fluoride ion battery according to Aspect 5, which includes performing a pretreatment of discharging an untreated fluoride ion battery having aluminum carbide as a negative electrode active material while applying a voltage up to 3V (vs. Pb / PbF2) to the aluminum carbide.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to provide a negative electrode active material for a fluoride ion battery that can be formed of an easily available material, a fluoride ion battery having such a negative electrode active material, a method for producing such a negative electrode active material for a fluoride ion battery, and a method for producing a fluoride ion battery having such a negative electrode active material.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the disclosure.

[0012] 《Negative Electrode Active Material for Fluoride Ion Battery》 The present disclosure provides a negative electrode active material for a fluoride ion battery, which is aluminum carbide.

[0013] The present inventors unexpectedly found that aluminum carbide (especially represented by Al4C3) functions as a negative electrode active material for a fluoride ion battery.

[0014] The negative electrode active material may be one that has been pretreated by fluorinating aluminum carbide up to 3V (vs. Pb / PbF2). This pretreatment can further improve the charge-discharge capacity of a fluoride ion battery having aluminum carbide as a negative electrode active material. Although not intending to be bound by any theory, the reason is presumed as follows. That is, by applying a large voltage in advance for fluorination, the aluminum-carbon bond constituting aluminum carbide is broken, and the diffusibility of fluoride ions (F - ) into aluminum carbide is improved, it is considered.

[0015] In the present disclosure, aluminum carbide may be manufactured by a conventional method or may be commercially available.

[0016] The shape of the negative electrode active material is not particularly limited, and may be, for example, particulate.

[0017] The average particle diameter of the negative electrode active material is, for example, from 10 nm to 100 μm, preferably from 50 nm to 20 μm, and more preferably from 100 nm to 10 μm.

[0018] 《Method for Producing Negative Electrode Active Material for Fluoride Ion Battery》 The method of the present disclosure for producing a negative electrode active material for a fluoride ion battery includes performing a pretreatment of fluorinating aluminum carbide up to 3 V (vs. Pb / PbF2).

[0019] Note that the negative electrode active material in a fluoride ion battery releases fluoride ions during charging and receives fluoride ions during discharging.

[0020] Regarding the aluminum carbide used as a raw material in the method of this disclosure, reference can be made to the above description regarding the negative electrode active material of this disclosure.

[0021] 《Negative Electrode Active Material Layer for Fluoride Ion Battery》 The negative electrode active material layer for a fluoride ion battery of the present disclosure has the negative electrode active material of the present disclosure.

[0022] When the fluoride ion battery is a liquid fluoride ion battery using a liquid electrolyte, the negative electrode active material layer for a fluoride ion battery of the present disclosure can have the negative electrode active material of the present disclosure and optionally a conductive assistant. Further, when the fluoride ion battery is a solid fluoride ion battery using a solid electrolyte, the negative electrode active material layer for a fluoride ion battery of the present disclosure can have the negative electrode active material of the present disclosure and a solid electrolyte. The negative electrode active material layer for a fluoride ion battery of the present disclosure can optionally have a binder and a conductive assistant.

[0023] Incidentally, from the viewpoint of capacity, it is preferable that the content of the negative electrode active material in the negative active material layer is larger. The ratio of the mass of the negative electrode active material to the mass of the negative active material layer may be from 10% by mass to 90% by mass, preferably from 20% by mass to 80% by mass. The ratio of the mass of the negative electrode active material to the mass of the negative active material layer may be 40% by mass or more, 50% by mass or more, 60% by mass or more, and more preferably 60 to 70% by mass.

[0024] From the viewpoint of capacity, it is preferable that the content of the solid electrolyte in the negative active material layer is smaller, and from the viewpoint of fluoride ion conductivity, it is preferable that the content is larger. The ratio of the mass of the solid electrolyte to the mass of the negative active material layer may be from 15% by mass to 75% by mass, preferably from 30% by mass to 60% by mass.

[0025] From the viewpoint of capacity, it is preferable that the content of the conductive assistant in the negative active material layer is smaller, and from the viewpoint of electron conductivity, it is preferable that the content is larger. The ratio of the mass of the conductive assistant to the mass of the negative active material layer may be from 1% by mass to 40% by mass, preferably from 2% by mass to 20% by mass.

[0026] Hereinafter, the materials constituting the negative active material layer for the fluoride ion battery of the present disclosure will be described.

[0027] (Solid electrolyte) The solid electrolyte may be any solid electrolyte that can be used in a fluoride ion battery.

[0028] Examples of the solid electrolyte include fluorides of lanthanoid elements such as La and Ce, fluorides of alkali metal elements such as Li, Na, K, Rb, and Cs, or fluorides of alkaline earth elements such as Ca, Sr, and Ba. Further, the solid electrolyte may be a fluoride containing a plurality of types of lanthanoid elements, alkali metal elements, and alkaline earth elements.

[0029] Specific examples of the solid electrolyte include, for example, La (1-x) Ba x F (3-x)(0 ≦ x ≦ 1), Pb (1-x) Sn x F2(0 ≦ x ≦ 1), Ca (1-x) Ba x F2(0 ≦ x ≦ 1) and Ce (1-x) Ba x F (3-x) (0 ≦ x ≦ 1) are included. Each of the above x may be greater than 0, may be 0.1 or more, may be 0.2 or more, and may be 0.3 or more. Also, each of the above x may be less than 1, may be 0.9 or less, may be 0.8 or less, and may be 0.7 or less.

[0030] The shape of the solid electrolyte is not particularly limited, and may be, for example, particulate.

[0031] (Binder) The binder is not particularly limited as long as it is chemically and electrically stable, and examples thereof include fluorine-based binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0032] (Conductive aid) The conductive aid is not particularly limited as long as it has a desired electron conductivity, and examples thereof include carbon materials. Examples of the carbon material include carbon blacks such as acetylene black, ketjen black, furnace black, and thermal black, and carbon nanotubes.

[0033] 《Composition for forming negative electrode active material layer for fluoride ion battery》 The composition for forming a negative electrode active material layer for a fluoride ion battery of the present disclosure has the negative electrode active material of the present disclosure.

[0034] When the fluoride ion battery is a liquid fluoride ion battery using a liquid electrolyte, the composition for forming the negative electrode active material layer of the fluoride ion battery of the present disclosure can have the negative electrode active material of the present disclosure and optionally a conductive assistant. Further, when the fluoride ion battery is a solid fluoride ion battery using a solid electrolyte, the composition for forming the negative electrode active material layer of the fluoride ion battery of the present disclosure can have the negative electrode active material of the present disclosure and a solid electrolyte. The composition for forming the negative electrode active material layer of the fluoride ion battery of the present disclosure can optionally have a binder and a conductive assistant.

[0035] The composition for forming the negative electrode active material layer of the fluoride ion battery of the present disclosure may be in a slurry or paste state for forming the negative electrode active material layer. In this case, the composition can contain a dispersion medium for dispersing the negative electrode active material of the present disclosure. Further, the composition for forming the negative electrode active material layer of the fluoride ion battery of the present disclosure may be in a powder state without containing a dispersion medium.

[0036] Regarding the conductive assistant when the fluoride ion battery is a liquid fluoride ion battery, and the solid electrolyte, binder, and conductive assistant when the fluoride ion battery is a solid fluoride ion battery, reference can be made to the above description regarding the negative electrode active material layer of the fluoride ion battery of the present disclosure.

[0037] 《Fluoride Ion Battery》 The fluoride ion battery of the present disclosure has the negative electrode active material layer of the present disclosure.

[0038] The fluoride ion battery of the present disclosure may be a liquid battery or a solid battery, particularly a all-solid-state battery. Further, the fluoride ion battery in the present disclosure may be a primary battery or a secondary battery. Examples of the shape of the fluoride ion battery in the present disclosure include coin type, laminate type, cylindrical type, and square type.

[0039] When the fluoride ion battery of the present disclosure is a liquid fluoride ion battery using a liquid electrolyte, the fluoride ion battery of the present disclosure can have a negative electrode active material layer, a separator layer, and a positive electrode active material layer in this order. In particular, in this case, the fluoride ion battery of the present disclosure can have a negative electrode current collector layer, a negative electrode active material layer, a separator layer, a positive electrode active material layer, and a positive electrode current collector layer in this order.

[0040] When the fluoride ion battery of the present disclosure is a solid fluoride ion battery using a solid electrolyte, the fluoride ion battery of the present disclosure can have a negative electrode active material layer, a solid electrolyte layer, and a positive electrode active material layer in this order. In particular, in this case, the fluoride ion battery of the present disclosure can have a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order.

[0041] For example, as shown in FIG. 1, the solid fluoride ion battery 1 of the present disclosure has a structure in which a positive electrode current collector layer 10, a positive electrode active material layer 20, an electrolyte layer 30, a negative electrode active material layer 40, and a negative electrode current collector layer 50 are laminated in this order.

[0042] The fluoride ion battery of the present disclosure may have a battery case for housing its components. The battery case may be of any shape capable of accommodating the members of the fluoride ion battery, and a battery case used for a general battery can be adopted.

[0043] Hereinafter, each layer constituting the fluoride ion battery of the present disclosure will be described.

[0044] (Negative electrode current collector layer) Examples of the material of the negative electrode current collector layer include stainless steel (SUS), copper, nickel, iron, titanium, platinum, and carbon. Examples of the shape of the negative electrode current collector layer include foil shape, mesh shape, and porous shape.

[0045] (Negative electrode active material layer) Regarding the negative electrode active material layer, reference can be made to the above description of the negative electrode active material layer of the present disclosure.

[0046] (Solid electrolyte layer and separator layer) When the fluoride ion battery of the present disclosure is a liquid battery, the fluoride ion battery of the present disclosure can have a separator layer as an electrolyte layer, and this separator layer may hold an electrolyte solution.

[0047] The electrolyte solution can contain, for example, a fluoride salt and an organic solvent. Examples of the fluoride salt include inorganic fluoride salts, organic fluoride salts, and ionic liquids. An example of the inorganic fluoride salt is XF (X is Li, Na, K, Rb, or Cs). An example of the cation of the organic fluoride salt is an alkylammonium cation such as a tetramethylammonium cation. The concentration of the fluoride salt in the electrolyte solution is, for example, 0.1 mol% or more and 40 mol% or less, and preferably 1 mol% or more and 10 mol% or less.

[0048] The organic solvent of the electrolyte solution is usually a solvent that dissolves the fluoride salt. Examples of the organic solvent include glymes such as triethylene glycol dimethyl ether (G3) and tetraethylene glycol dimethyl ether (G4), cyclic carbonates such as ethylene carbonate (EC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), propylene carbonate (PC), and butylene carbonate (BC), and chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). Also, an ionic liquid may be used as the organic solvent.

[0049] The separator is not particularly limited as long as it has a composition that can withstand the use range of the fluoride ion battery. Examples of the separator include polymer non-woven fabrics such as polypropylene non-woven fabric and polyphenylene sulfide non-woven fabric, and microporous films of olefin resins such as polyethylene and polypropylene.

[0050] When the fluoride ion battery of the present disclosure is a solid battery, the fluoride ion battery of the present disclosure can have a solid electrolyte layer as an electrolyte layer. Regarding the solid electrolyte constituting the solid electrolyte layer, reference can be made to the above description regarding the negative electrode active material layer of the present disclosure.

[0051] (Positive electrode active material layer) The positive electrode active material layer in the present disclosure contains a positive electrode active material.

[0052] When the fluoride ion battery of the present disclosure is a liquid fluoride ion battery using a liquid electrolyte, the positive electrode active material layer of the fluoride ion battery of the present disclosure can have a positive electrode active material. Further, when the fluoride ion battery of the present disclosure is a solid fluoride ion battery using a solid electrolyte, the positive electrode active material layer for the fluoride ion battery of the present disclosure can have the positive electrode active material and the solid electrolyte of the present disclosure. The positive electrode active material layer for the fluoride ion battery of the present disclosure can optionally have a binder and a conductive assistant.

[0053] The positive electrode active material is an active material that undergoes defluorination during discharge. Examples of the positive electrode active material include a simple metal, an alloy, a metal oxide, and fluorides thereof. Examples of the metal element contained in the positive electrode active material include Cu, Ag, Ni, Co, Pb, Ce, Mn, Au, Pt, Rh, V, Os, Ru, Fe, Cr, Bi, Nb, Sb, Ti, Sn, Zn, etc. Among them, the positive electrode active material is preferably PbF2, FeF3, CuF2, BiF3, or AgF.

[0054] Regarding the solid electrolyte, binder, and conductive assistant constituting the positive electrode active material layer, reference can be made to the above description regarding the negative electrode active material layer of the present disclosure.

[0055] In addition, from the perspective of capacity, it is preferable that the content of the positive electrode active material in the positive active material layer is larger. The ratio of the mass of the positive electrode active material to the mass of the positive electrode active material layer may be 10% by mass to 90% by mass, and preferably 20% by mass to 80% by mass. Regarding the content of the solid electrolyte and the conductive assistant in the positive active material layer, reference can be made to the above description regarding the negative electrode active material layer of the present disclosure.

[0056] (Positive electrode current collector layer) Examples of the material of the positive electrode current collector layer include lead, stainless steel (SUS), aluminum, nickel, iron, titanium, platinum, and carbon. Examples of the shape of the positive electrode current collector layer include foil shape, mesh shape, and porous shape.

[0057] 《Method for manufacturing a fluoride ion battery》 The method of the present disclosure for manufacturing a fluoride ion battery includes performing a pretreatment of discharging Al4C3 as a negative electrode active material up to 3 V (vs. Pb / PbF2).

[0058] Regarding the method of the pretreatment, reference can be made to the above description regarding the method for manufacturing a negative electrode active material for a fluoride ion battery.

Example

[0059] 《Fabrication of a fluoride ion battery》 〈Example 1〉 Negative electrode active material (Al4C3 powder, high-purity chemical product), solid electrolyte (Ca 0.5 Ba 0.5 F2: Calcium fluoride (CaF2, high-purity chemical product) and barium fluoride (BaF2, high-purity chemical product) are synthesized by mixing with a ball mill at 600 rpm for 20 hours), and vapor-grown carbon fiber (VGCF (registered trademark), manufactured by Showa Denko) as a conductive assistant is mixed using a ball mill (rotation speed: 200 rpm) at a mass ratio of 19:19:2 to obtain a negative electrode composite material. The counter electrode is obtained by mixing an active material (PbF2) and a conductive assistant (acetylene black) at a mass ratio of 95:5 to obtain a counter electrode composite material. The above negative electrode composite material, the solid electrolyte (Ca 0.5 Ba 0.5(F2) An evaluation battery was fabricated by laminating the above-mentioned counter electrode composite material and Pb foil in this order and subjecting them to pressure molding.

[0060] <Example 2> An evaluation battery was fabricated in the same manner as in Example 1, except that Al4C3 as the negative electrode active material was pretreated by fluorination up to 3V (vs. Pb / PbF2) before the charge-discharge test described below.

[0061] <Reference Example 1> An evaluation battery was fabricated in the same manner as in Example 1, except that LaF3 was used as the negative electrode active material.

[0062] <Reference Example 2> An evaluation battery was fabricated in the same manner as in Example 1, except that LaSi was used as the negative electrode active material.

[0063] <<Charge-Discharge Test>> The fabricated evaluation battery was subjected to a charge-discharge test. The conditions of the charge-discharge test were a temperature of 200°C, a cut-off potential of the negative electrode of -2.5V (vs. Pb / PbF2) to 0V (vs. Pb / PbF2), and a current of 50 μA / cm 2 .

[0064] <<Results>> As shown in Fig. 2, in Example 1 using Al4C3 as the negative electrode active material, the discharge capacity was larger than that in Reference Example 1 using LaF3 and Reference Example 2 using LaSi. Further, as shown in Figs. 2 to 4, in Example 2 where Al4C3 was pretreated by fluorination up to 3V (vs. Pb / PbF2), the discharge capacity was further improved compared to Example 1. [[Description of Reference Numerals]]

[0065] 1 Fluoride ion battery 10 Positive electrode current collector layer 20 Positive electrode active material layer 30 Electrolyte layer 40 Negative electrode active material layer 50 Negative electrode current collector layer

Claims

1. A negative electrode active material for a fluoride ion battery, which is aluminum carbide.

2. The pretreatment is carried out to fluorinate the aluminum carbide up to 3 V (vs. Pb / PbF ２ ), and the negative electrode active material according to claim 1.

3. A negative electrode active material layer for a fluoride ion battery, which has the negative electrode active material according to Claim 1 or 2.

4. A composition for forming a negative electrode active material layer for a fluoride ion battery, which has the negative electrode active material according to Claim 1 or 2.

5. A fluoride ion battery, which has the negative electrode active material layer according to Claim 3.

6. The method for producing a negative electrode active material according to claim 2, comprising performing a pretreatment of fluorinating aluminum carbide up to 3 V (vs. Pb / PbF ２ ).

7. The method for manufacturing a fluoride ion battery according to claim 5, comprising performing a pretreatment of discharging an untreated fluoride ion battery having aluminum carbide as a negative electrode active material until a voltage is applied up to 3 V (vs. Pb / PbF ２ ).

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