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

Abstract

To provide a negative electrode active material for fluoride ion batteries capable of achieving high charge / discharge capacity, a fluoride-ion battery having such a negative electrode active material, and a manufacturing method a negative electrode active material for fluoride ion batteries.SOLUTION: A disclosed negative electrode active material for fluoride ion batteries contains non-layered transition metal carbide. A disclosed method of producing negative electrode active material for fluoride ion batteries includes a step of converting the same into a non-layered transition metal carbide by subjecting the layered transition metal carbide to mechanical shock.SELECTED DRAWING: Figure 2

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 fluoride ion battery, and a method for manufacturing a negative electrode active material for a fluoride ion battery. [Background technology]

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

[0003] For example, Patent Document 1 discloses an anode containing a layered material selected from the group consisting of hard carbon, nitrogen-doped graphite, boron-doped graphite, TiS2, MoS2, TiSe2, MoSe2, VS2, VSe2, an electride of an alkaline earth metal nitride, an electride of a metal carbide, and a combination thereof.

[0004] Patent Document 2 discloses negative and positive electrode active materials containing a transition metal oxide having a rock salt type crystal structure.

[0005] Patent Document 3 discloses an active material for a fluoride ion secondary battery containing a metal composite fluoride, and the metal composite fluoride is said to contain at least one metal selected from the group consisting of alkali metals, alkaline earth metals, scandium, yttrium, and lanthanoids, a first transition metal, a second transition metal different from the first transition metal, and fluorine. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2020-534652 [Patent Document 2] Japanese Patent Application Publication No. 2020-194697 [Patent Document 3] Japanese Patent Application Publication No. 2019-204775 Summary of the Invention [Problem to be solved by the invention]

[0007] Although various materials have been proposed as negative electrode active materials for fluoride ion batteries, there is a demand for novel negative electrode active materials for fluoride ion batteries having improved properties.

[0008] An object of the present disclosure is to provide a negative electrode active material for a fluoride ion battery that can achieve high charge / discharge capacity, a method for producing such a negative electrode active material for a fluoride ion battery, and a fluoride ion battery having such a negative electrode active material. [Means for solving the problem]

[0009] The present inventors have found that the above object can be achieved by the following means: <<Aspect 1>> A negative electrode active material for a fluoride ion battery, comprising a transition metal carbide with a non-layered structure. <<Aspect 2>> The negative electrode active material according to aspect 1, wherein the transition metal carbide satisfies the following condition: A / B≦0.05 During the ceremony, A is the maximum peak intensity between 10° and 20° in the X-ray diffraction analysis, and B is the maximum peak intensity between 25° and 35° in X-ray diffraction analysis. Aspect 3 2. The negative electrode active material of embodiment 1, wherein the transition metal carbide is selected from the group consisting of scandium carbide, yttrium carbide, dysprosium carbide, and titanium carbide. Aspect 4 The negative electrode active material according to aspect 1, wherein the transition metal carbide is represented by the following formula: M x C (1-x) In the formula, 0.25 <x<0.78。 Aspect 5 A negative electrode active material layer for a fluoride ion battery, comprising the negative electrode active material according to any one of aspects 1 to 4. Aspect 6 6. The negative electrode active material layer according to embodiment 5, comprising the negative electrode active material, a solid electrolyte, and a conductive additive. Aspect 7 A fluoride ion battery having the negative electrode active material layer according to embodiment 5. Aspect 8 A method for producing a negative electrode active material according to any one of aspects 1 to 4, comprising applying a mechanical impact to a layered transition metal carbide to convert it into the non-layered transition metal carbide. Aspect 9 The method of embodiment 8, wherein the layered transition metal carbide satisfies the following conditions: 0.05≦A / B During the ceremony, A is the maximum peak intensity between 10° and 20° in the X-ray diffraction analysis, and B is the maximum peak intensity between 25° and 35° in X-ray diffraction analysis. Aspect 10 9. The method of embodiment 8, wherein the mechanical impact is applied by a ball mill. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a negative electrode active material for a fluoride ion battery that can achieve high charge / discharge capacity, a method for producing such a negative electrode active material for a fluoride ion battery, and a fluoride ion battery having such a negative electrode active material. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a fluoride ion battery of the present disclosure. [Figure 2] FIG. 2 is a graph showing the XRD results of the negative electrode active material (Y0.67C0.33 (layered structure)) used in the fluoride ion battery of Reference Example 1. [Figure 3] FIG. 3 is a graph showing the XRD results of the negative electrode active material (Y0.67C0.33 (non-layered structure)) used in the fluoride ion battery of Example 1. [Figure 4]FIG. 4 is a graph showing the XRD results of the negative electrode active material (Dy0.67C0.33 (non-layered structure)) used in the fluoride ion battery of Example 2. [Figure 5] FIG. 5 is a graph showing the XRD results of the negative electrode active material (Sc0.67C0.33 (non-layered structure)) used in the fluoride ion battery of Example 3. [Figure 6] FIG. 6 is a graph showing the charge / discharge curves of the fluoride ion battery of Reference Example 1. [Figure 7] FIG. 7 is a graph showing the charge / discharge curves of the fluoride ion battery of Example 1. [Figure 8] FIG. 8 is a graph showing the charge / discharge curves of the fluoride ion battery of Example 2. [Figure 9] FIG. 9 is a graph showing the charge / discharge curves of the fluoride ion battery of Example 3. [Figure 10] FIG. 10 is a graph showing the charge / discharge curves of the fluoride ion battery of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0013] <Negative electrode active material for fluoride ion batteries> The negative electrode active material for a fluoride ion battery of the present disclosure has a transition metal carbide with a non-layered structure, particularly a transition metal carbide with a rock salt structure.

[0014] In lithium-ion batteries, metal oxides having a layered rock salt structure, such as lithium cobalt oxide and lithium cobalt-nickel-manganese oxide, are used as positive electrode active materials. Specifically, in lithium-ion batteries, the battery reaction occurs by inserting and extracting lithium ions between the layers of the layered structure of these compounds.

[0015] Similarly, in fluoride ion batteries, it has been theoretically shown that metal carbides with a layered rock salt structure can be used as negative electrode active materials to cause a battery reaction, and that fluorine ions can be inserted and released between the layers of the layered structure of these compounds.

[0016] However, the present inventors have found that when such a metal carbide having a layered rock salt structure is used as a negative electrode active material for a fluoride ion battery, i.e., when a metal carbide having a significant XRD peak at around 15° due to the layered structure is used as a negative electrode active material for a fluoride ion battery, no substantial battery reaction occurs. Without being limited by theory, the present inventors believe that the reason for this lack of substantial battery reaction is that the diffusion process of fluoride ions into the metal carbide having the layered rock salt structure is very slow.

[0017] In response to this, the present inventors came up with the idea of ​​distorting the layered structure of the transition metal carbide to form a disordered crystal structure, thereby forming vacancies through which fluorine ions can diffuse, thereby enabling three-dimensional diffusion instead of the two-dimensional diffusion that occurs in a layered structure.

[0018] In the present disclosure, the transition metal carbide having a non-layered structure means that in an XRD diffraction analysis of the transition metal carbide, the peaks attributable to the layered structure are small, and in particular, there are no significant peaks attributable to the layered structure. Specifically, for example, in the present disclosure, the transition metal carbide having a non-layered structure means that the transition metal carbide satisfies the following conditions: A / B≦0.05, especially 0.03, more especially 0.01 During the ceremony, A is the maximum peak intensity between 10° and 20° in the X-ray diffraction analysis, and B is the maximum peak intensity between 25° and 35° in X-ray diffraction analysis.

[0019] In X-ray diffraction analysis, the maximum peak at 10° to 20° represents a peak derived from a layered structure, and the maximum peak at 25° to 35° in X-ray diffraction analysis represents a peak derived from a rock salt structure. Regarding the present disclosure, XRD measurement can be performed, for example, using a Miniflex (manufactured by Rigaku) with a Cu-Kα ray source, and the composite material for the negative electrode active material layer can be measured under an argon (Ar) atmosphere under the conditions of a measurement range of 10° to 80°, a scan speed of 2° / min, and a measurement interval of 0.02°.

[0020] In the present disclosure, the transition metal carbide may be, for example, a Group 3 element carbide, zirconium carbide, niobium carbide, molybdenum carbide, titanium carbide, vanadium carbide, or tantalum carbide. Here, the Group 3 element carbide can be selected from the group consisting of dysprosium carbide, scandium carbide, samarium carbide, gadolinium carbide, terbium carbide, holmium carbide, europium carbide, thulium carbide, ytterbium carbide, lutetium carbide, and erbium carbide.

[0021] In the present disclosure, the transition metal carbide can be particularly selected from the group consisting of scandium carbide, yttrium carbide, dysprosium carbide, and titanium carbide.

[0022] In the present disclosure, the transition metal carbide may be represented by the following formula: M x C (1-x) In the formula, M represents a transition metal element, and 0.25 < x < 0.78, particularly 0.50 < x < 0.70, more particularly 0.60 < x < 0.70, and even more particularly x = about 0.67.

[0023] M x C (1-x) In the transition metal carbide represented by MxCy, when x is in the above range, a rock salt structure containing defects in the carbon (C) site is formed, and vacancies through which fluoride ions can diffuse are likely to be formed.

[0024] The negative electrode active material in a fluoride ion battery releases fluoride ions (fluorine ions) during charging and receives fluoride ions during discharging. In other words, the negative electrode active material for a fluoride ion battery of the present disclosure may further contain fluorine depending on the charge / discharge state of the fluoride ion battery.

[0025] The shape of the negative electrode active material is not particularly limited, but may be, for example, particulate.

[0026] <<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 applying a mechanical impact to a transition metal carbide having a layered structure to convert it into a transition metal carbide having a non-layered structure. Thus, in the method of the present disclosure, the mechanical impact converts the transition metal carbide having a layered structure into a transition metal carbide having a non-layered structure, thereby obtaining the negative electrode active material for a fluoride ion battery of the present disclosure.

[0027] The layered transition metal carbide used as a raw material in the method of the present disclosure can satisfy the following conditions. 0.05, especially 0.08, and more especially 0.10 During the ceremony, A is the maximum peak intensity between 10° and 20° in the X-ray diffraction analysis, and B is the maximum peak intensity between 25° and 35° in X-ray diffraction analysis.

[0028] For the type and composition of the layered transition metal carbide used as a raw material in the method of the present disclosure, reference can be made to the description of the negative electrode active material for a fluoride ion battery of the present disclosure.

[0029] ​The method of the present disclosure can be carried out in any device capable of applying a mechanical impact at an intensity sufficient to convert a layered transition metal carbide to a non-layered transition metal carbide. For example, the mechanical impact can be applied by a ball mill, and the rotation speed of the ball mill can be adjusted to control the intensity of the mechanical impact. The mechanical impact can be applied for a period of time required to convert the layered transition metal carbide to a non-layered transition metal carbide, such as 1 hour or more, 3 hours or more, 5 hours or more, or 10 hours or more.

[0030] <Negative electrode active material layer for fluoride ion batteries> 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.

[0031] When the fluoride ion battery is a liquid-based fluoride ion battery using a liquid electrolyte, the negative electrode active material layer for the fluoride ion battery of the present disclosure can include the negative electrode active material of the present disclosure and a conductive additive. When the fluoride ion battery is a solid-state fluoride ion battery using a solid electrolyte, the negative electrode active material layer for the fluoride ion battery of the present disclosure can include the negative electrode active material of the present disclosure, a solid electrolyte, and a conductive additive. The negative electrode active material layer for the fluoride ion battery of the present disclosure can optionally include a binder.

[0032] From the viewpoint of capacity, the content of the negative electrode active material in the negative active material electrode layer is preferably as high as possible. The ratio of the mass of the negative electrode active material to the mass of the negative electrode active material layer may be 10% by mass to 90% by mass, and preferably 20% by mass to 80% by mass.

[0033] The content of the conductive additive in the negative active material electrode layer is preferably as low as possible from the viewpoint of capacity, and is preferably as high as possible from the viewpoint of electronic conductivity. The mass ratio of the conductive additive to the mass of the negative active material layer may be 1% by mass to 40% by mass, and preferably 2% by mass to 20% by mass.

[0034] The content of the solid electrolyte in the negative active material electrode layer is preferably smaller from the viewpoint of capacity, and is preferably larger from the viewpoint of fluoride ion conductivity. The mass ratio of the solid electrolyte to the mass of the negative active material layer may be 5% by mass to 70% by mass, and preferably 10% by mass to 40% by mass.

[0035] The materials constituting the negative electrode active material layer for a fluoride ion battery according to the present disclosure will be described below.

[0036] (Conductive additive) The conductive additive is not particularly limited as long as it has the desired electronic conductivity, and examples of the conductive additive include carbon materials, such as carbon blacks such as acetylene black, ketjen black, furnace black, and thermal black, and carbon nanotubes.

[0037] (solid electrolyte) The solid electrolyte can be any solid electrolyte that can be used in a fluoride ion battery.

[0038] 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, and fluorides of alkaline earth elements such as Ca, Sr, and Ba. The solid electrolyte may also be a fluoride containing multiple lanthanoid elements, alkali metal elements, and alkaline earth elements.

[0039] Specific examples of solid electrolytes include La (1-y) Ba y F (3-y) (0≦y≦1), Pb (2-y) Sn y F4(0≦y≦2), Ca (2-y) Ba y F4(0≦y≦2) and Ce (1-y) Ba y F (3-y)(0≦y≦1). The above y may be greater than 0, 0.3 or greater, 0.5 or greater, or 0.9 or greater. Also, the above y may be smaller than 1, 0.9 or less, 0.5 or less, or 0.3 or less.

[0040] The shape of the solid electrolyte is not particularly limited, but may be, for example, particulate.

[0041] (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).

[0042] Fluoride-ion battery The fluoride ion battery of the present disclosure has the negative electrode active material layer of the present disclosure.

[0043] The fluoride ion battery of the present disclosure may be a liquid battery or a solid-state battery, and particularly may be an all-solid-state battery. The fluoride ion battery of the present disclosure may be a primary battery or a secondary battery. The shape of the fluoride ion battery of the present disclosure may be, for example, a coin type, a laminate type, a cylindrical type, or a prismatic type.

[0044] When the fluoride ion battery of the present disclosure is a liquid-based 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.

[0045] Furthermore, 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 an anode active material layer, a solid electrolyte layer, and a cathode active material layer in this order. In particular, in this case, the fluoride ion battery of the present disclosure can have an anode current collector layer, an anode active material layer, a solid electrolyte layer, a cathode active material layer, and a cathode current collector layer in this order.

[0046] For example, as shown in FIG. 1, a solid fluoride ion battery 100 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 stacked in this order.

[0047] The fluoride ion battery of the present disclosure may have a battery case for housing its components. The battery case may have any shape that can house the components of the fluoride ion battery, and a battery case used for a general battery may be adopted.

[0048] Each layer constituting the fluoride ion battery of the present disclosure will be described below.

[0049] (negative electrode current collector layer) Examples of materials for 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, mesh, and porous shapes.

[0050] (Negative electrode active material layer) For the negative electrode active material layer, reference can be made to the above description regarding the negative electrode active material layer of the present disclosure.

[0051] (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 may have a separator layer as an electrolyte layer, and this separator layer may hold an electrolytic solution.

[0052] The electrolyte solution may 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 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.

[0053] The organic solvent of the electrolyte is usually a solvent that dissolves a 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). An ionic liquid may also be used as the organic solvent.

[0054] The separator is not particularly limited as long as it has a composition that can withstand the range of uses of a fluoride ion battery, and examples of the separator include polymer nonwoven fabrics such as polypropylene nonwoven fabrics and polyphenylene sulfide nonwoven fabrics, and microporous fillers of olefin resins such as polyethylene and polypropylene.

[0055] When the fluoride ion battery of the present disclosure is a solid-state battery, the fluoride ion battery of the present disclosure can have a solid electrolyte layer as an electrolyte layer. For 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.

[0056] (Cathode active material layer) The positive electrode active material layer in the present disclosure contains a positive electrode active material.

[0057] When the fluoride ion battery of the present disclosure is a liquid-based fluoride ion battery using a liquid electrolyte, the positive electrode active material layer of the fluoride ion battery of the present disclosure can include a positive electrode active material. Also, 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 include the positive electrode active material of the present disclosure and the solid electrolyte. The positive electrode active material layer for the fluoride ion battery of the present disclosure can optionally include a binder and a conductive additive.

[0058] The positive electrode active material is an active material that defluorinates during discharge. Examples of the positive electrode active material include simple metals, alloys, metal oxides, and fluorides thereof. Examples of metal elements 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, and Zn. Among these, the positive electrode active material is preferably PbF2, FeF3, CuF2, BiF3, or AgF.

[0059] For the conductive additive, solid electrolyte, and binder 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.

[0060] From the viewpoint of capacity, the content of the positive electrode active material in the positive active material electrode layer is preferably as high as possible. The mass ratio 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. For the contents of the solid electrolyte and the conductive additive in the positive active material electrode layer, the above description regarding the negative electrode active material layer of the present disclosure can be referred to.

[0061] (Positive electrode current collector layer) Examples of materials for the positive electrode current collector layer include stainless steel (SUS), aluminum, nickel, iron, titanium, platinum, and carbon. Examples of the shape of the positive electrode current collector layer include foil, mesh, and porous shapes. [Example]

[0062] <Reference example 1> (Mixture material for negative electrode active material layer) Yttrium (Y) (manufactured by Alfa Aeser) and carbon (C) (manufactured by Kojundo Chemical) were weighed to have a molar composition of Y:C = 0.67:0.33, and then arc melted to obtain a layered rock salt structure yttrium carbide (Y) as the negative electrode active material. 0.67 C 0.33 The synthesized yttrium carbide as the negative electrode active material was pulverized in a mortar until it could pass through a 100 μm sieve.

[0063] Calcium fluoride (CaF2) (manufactured by Kojundo Chemical Co., Ltd.) and barium fluoride (BaF2) (manufactured by Kojundo Chemical Co., Ltd.) were mixed in a ball mill at 600 rpm for 20 hours to prepare calcium barium fluoride (CaF2) as a solid electrolyte. 0.5 Ba 0.5 F2) was prepared.

[0064] Yttrium carbide as the negative electrode active material, calcium barium fluoride as the solid electrolyte, and vapor grown carbon fiber (VGCF) (manufactured by Showa Denko) as the conductive additive were provided in a weight ratio of 47.5:47.5:5, and mixed in a ball mill at 100 rpm for 10 hours to prepare a composite for the negative electrode active material layer.

[0065] (Mixture material for electrolyte layer) The composite material for the electrolyte layer was the calcium barium fluoride prepared as described above.

[0066] (Cathode active material layer composite material) Lead fluoride (PbF2) (manufactured by Kojundo Chemical Co., Ltd.) and acetylene black (manufactured by Denka Co., Ltd.) were weighed out to a weight ratio of 95:5 and mixed in a ball mill at 600 rpm for 3 hours to prepare a composite material for the positive electrode active material layer.

[0067] (XRD measurement) Using a Miniflex Cu-Kα radiation source (manufactured by Rigaku), the composite for the negative electrode active material layer was measured in an argon (Ar) atmosphere under conditions of a measurement range of 10° to 80°, a scan rate of 2° / min, and a measurement interval of 0.02°. The results are shown in Figure 2. As shown in Figure 2, the yttrium carbide after ball milling has a relatively large peak between 10° and 20°, which is due to its layered structure, and therefore it is understood to have a layered structure.

[0068] (Preparation of evaluation battery) A platinum (Pt) foil as a negative electrode current collector, a composite for a negative electrode active material layer, a composite for an electrolyte layer, a composite for a positive electrode active material layer, and a lead (Pb) foil as a positive electrode current collector were laminated in this order and compacted to prepare a fluoride ion battery for evaluation.

[0069] (Charge / discharge evaluation) A charge-discharge test was carried out in the voltage range of 0 V to -2.5 V (vs. Pb / PbF2) at 50 μA and 200° C. The evaluation results are shown in Figure 6. As shown in Figure 6, no substantial charge-discharge reaction occurred in the evaluation battery of Reference Example 1.

[0070] Example 1 The fluoride ion battery of Example 1 was produced and evaluated in the same manner as in Reference Example 1, except that in preparing the composite for the negative electrode active material layer, the treatment with a ball mill was carried out at 200 rpm for 10 hours instead of 100 rpm. The evaluation results are shown in Figs. 3 and 7.

[0071] As shown in the XRD results in Figure 3, the yttrium carbide, which was the negative electrode active material of Example 1, was converted from a layered structure to a non-layered structure by the ball mill treatment. Also, as shown in Figure 7, the evaluation battery of Example 1 was able to undergo good charge-discharge reactions.

[0072] Example 2 Dysprosium carbide (Dy) is used as the negative electrode active material. 0.67 C 0.33 ) was used, the fluoride ion battery of Example 2 was produced and evaluated in the same manner as in Example 1. The evaluation results are shown in FIGS.

[0073] As shown in the XRD results in Figure 4, the dysprosium carbide used as the negative electrode active material in Example 2 had a non-layered structure. Furthermore, as shown in Figure 8, the evaluation battery of Example 2 was able to undergo a good charge-discharge reaction.

[0074] Example 3 Scandium carbide (Sc) was used as the negative electrode active material. 0.67 C 0.33 ) was used, the fluoride ion battery of Example 3 was produced and evaluated in the same manner as in Example 1. The evaluation results are shown in FIGS.

[0075] As shown in the XRD results in Figure 5, the scandium carbide used as the negative electrode active material in Example 3 had a non-layered structure. Furthermore, as shown in Figure 9, the evaluation battery of Example 3 was able to undergo a good charge-discharge reaction.

[0076] Example 4 Titanium carbide (Ti) was used as the negative electrode active material. 0.67 C 0.33 ) was used, the fluoride ion battery of Example 4 was produced and evaluated in the same manner as in Example 1. The evaluation results are shown in FIG.

[0077] As shown in FIG. 10, the test battery of Example 4 was able to undergo a good charge-discharge reaction.

[0078] (Battery overview and evaluation results) The outline and evaluation results of the batteries of the Examples and Reference Examples are shown in Table 1 below.

[0079] [Table 1] *1 A is the maximum peak intensity between 10° and 20° in X-ray diffraction analysis (an index of layered structure). *2 B is the maximum peak intensity between 25° and 35° in X-ray diffraction analysis (an indicator of rock salt structure). *3 The solid line indicates the first cycle, and the dotted line indicates the second cycle. [Explanation of symbols]

[0080] 1. Fluoride-ion battery 10 Positive electrode current collector layer 20 Cathode active material layer 30 Electrolyte layer 40 Negative electrode active material layer 50 Negative electrode current collector layer

Claims

1. The transition metal carbide has a non-layered structure, The transition metal carbide satisfies the following conditions: A / B≦0.05 During the ceremony, A is the maximum peak intensity between 10° and 20° in the X-ray diffraction analysis, and B is the maximum peak intensity between 25° and 35° in X-ray diffraction analysis; the transition metal carbide is selected from the group consisting of scandium carbide, yttrium carbide, dysprosium carbide, and titanium carbide; Negative electrode active material for fluoride ion batteries.

2. The negative electrode active material according to claim 1 , wherein the transition metal carbide is represented by the following formula: MxC(1-x) In the formula, 0.25<x<0.

78.

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

4. The negative electrode active material layer according to claim 3 , comprising the negative electrode active material, a solid electrolyte, and a conductive additive.

5. A fluoride ion battery having a negative electrode active material layer according to claim 3.

6. 3. The method for producing a negative electrode active material according to claim 1, comprising applying a mechanical impact to a layered transition metal carbide to convert it into the non-layered transition metal carbide.

7. The method according to claim 6, wherein the layered structure transition metal carbide satisfies the following conditions: 0.05≦A / B During the ceremony, A is the maximum peak intensity between 10° and 20° in the X-ray diffraction analysis, and B is the maximum peak intensity between 25° and 35° in X-ray diffraction analysis.

8. The method of claim 6 , wherein the mechanical impact is applied by a ball mill.

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