Hydride ion conductor, method for producing same, and all-solid-state battery

Abstract

To provide a hydride ion conductor that has high conduction properties at room temperature and a method for producing the same, and an all-solid-state battery that includes the hydride ion conductor and can operate at room temperature.SOLUTION: A hydride ion conductor has a composition represented by the general formula M1xM2yM3zHαOβ (where M1 represents a trivalent rare earth element, M2 represents at least one Group 2 element selected from the group consisting of Mg, Ca, Sr and Ba, and M3 represents at least one Group 1 element selected from alkali metals, with 0.4≤x<1, 0≤y≤0.6, 0≤z≤0.5, 0.7<x+y+z≤1, 0<y+z≤0.6, 2<α<3, 0≤β<0.3, 3x+2y+z=α+2β).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a hydride ion conductor, a method for producing the same, and a all-solid-state battery.

Background Art

[0002] Protons and oxygen ions are used as mobile ions in energy conversion devices such as fuel cells and air batteries. On the other hand, hydride ions are monovalent and have an appropriate ionic radius of about 1.2 angstroms and a large polarizability, so they have characteristics more suitable as mobile ions than protons and oxygen ions. Furthermore, since the redox potential of H2 + 2e 1 , 2 , α →2H - is as high as -2.25 V (vs. SHE), it has the potential to create a new energy conversion device with a high potential.

[0003] Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-204632) describes "a hydride ion conductor having a composition represented by the general formula Ln 2-X M X AH y O3 (where Ln is a trivalent rare earth element, M is tetravalent Ce or an alkaline earth metal element, and A represents Li or Na. When M is tetravalent Ce, 0 < x < 0.2 and y = 1 + x, and when M is an alkaline earth metal element, 0 < x < 1 and y = 1 - x).)

[0004] Patent Document 2 (Japanese Patent Application Laid-Open No. 2017-098067) describes "a general formula M 1 X M 2 y AH z O α (where M 1 is a trivalent rare earth element, M 2 is an alkaline earth metal element or Mg, and A represents Li, Na, Sc, Co, Ni, Cu, Mn or Fe. 0 ≦ x ≦ 2; 0 ≦ y ≦ 2; x + y = 2; 0 < z < 4; and 1 ≦ α < 3 or 3 < α < 4).) A hydride ion conductor having the composition represented by [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-204632 [Patent Document 2] Japanese Patent Application Publication No. 2017-098067 Summary of the Invention [Problem to be solved by the invention]

[0006] The hydride ion conductors described in Patent Documents 1 and 2 exhibit high hydride ion conductivity in the medium temperature range of 300° C. to 350° C. There is a demand for hydride ion conductors that exhibit hydride ion conductivity at lower temperatures, preferably around room temperature from room temperature to about 100° C.

[0007] An object of the present disclosure is to provide a hydride ion conductor having high conductivity at room temperature, a method for producing the same, and an all-solid-state battery that includes the hydride ion conductor and can operate at room temperature. [Means for solving the problem]

[0008] Lanthanum hydride LaH3 not only has a fluorite-type framework that is suitable for the diffusion of anions, but also has a hydride ion (H - ) occupy interstitial octahedral sites, which is thought to result in fast hydride ion conductivity via a quasi-interstitial mechanism. However, LaH3 exhibits high-speed hydride ion conductivity due to the H - This leads to the formation of donor levels, which results in electronic conductivity, making it difficult to use the material as a solid electrolyte.

[0009] The present inventors have 3+ The ionic bond between LaH3 and alkali metal ions or alkaline earth metal ions is stronger than that of LaH3. 3+By replacing a part thereof, it has been found that the introduction of voids can be suppressed or the band gap can be expanded, thereby suppressing the expression of electronic conductivity caused by hydride ion deficiency in LaH3. Further, the present inventors have found that the above alkali metal ion or alkaline earth metal ion substituent has a hydride ion conductivity at a level that can function as a solid electrolyte at room temperature, and that a all-solid-state battery operable at room temperature can be fabricated using the above alkali metal ion or alkaline earth metal ion substituent.

[0010] This disclosure includes the following aspects. [Aspect 1] General formula M 1 x M 2 y M 3 z H α O β (In the formula, M 1 is a trivalent rare earth element, M 2 is at least one Group 2 element, M 3 is at least one Group 1 element selected from alkali metals, 0.4 ≦ x < 1, 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 0.5, 0.7 < x + y + z ≦ 1, 0 < y + z ≦ 0.6, 2 < α < 3, 0 ≦ β < 0.3, and 3x + 2y + z = α + 2β.) A hydride ion conductor having the composition represented by [Aspect 2] The hydride ion conductor according to Aspect 1, wherein the trivalent rare earth element is at least one selected from the group consisting of La, Ce, Nd, Sc, and Y. [Aspect 3] The hydride ion conductor according to Aspect 1 or 2, wherein the Group 2 element is at least one selected from the group consisting of Mg, Ca, Sr, and Ba. [Aspect 4] The hydride ion conductor according to any one of Aspects 1 to 3, wherein the Group 1 element is at least one selected from the group consisting of Na, K, Rb, and Cs. [Aspect 5] General formula M 1 x M 2y M 3 z H α O β (where M 1 is a trivalent rare earth element, M 2 is at least one Group 2 element, M 3 is at least one Group 1 element selected from alkali metals, 0.4 ≦ x < 1, 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 0.5, 0.7 < x + y + z ≦ 1, 0 < y + z ≦ 0.6, 2 < α < 3, 0 ≦ β < 0.3, and 3x + 2y + z = α + 2β.) A method for producing a hydride ion conductor having a composition represented by M 1 with a hydride containing M 2 a hydride containing, M 3 a hydride containing or a combination thereof and reacting, a method for producing a hydride ion conductor. [Aspect 6] The method for producing a hydride ion conductor according to Aspect 5, wherein the reaction is carried out by a high-pressure synthesis method in the presence of a hydrogen gas generating agent. [Aspect 7] The method for producing a hydride ion conductor according to Aspect 5, wherein the reaction is carried out by a mechanochemical method. [Aspect 8] The method for producing a hydride ion conductor according to Aspect 7, further comprising performing hydrogen annealing treatment [Aspect 9] The method for producing a hydride ion conductor according to any one of Aspects 5 to 8, wherein the trivalent rare earth element is at least one selected from the group consisting of La, Ce, Nd, Sc, and Y. [Aspect 10] The method for producing a hydride ion conductor according to any one of Aspects 5 to 9, wherein the Group 2 element is at least one selected from the group consisting of Mg, Ca, Sr, and Ba. [Aspect 11] The method for producing a hydride ion conductor according to any one of Aspects 5 to 10, wherein the Group 1 element is at least one selected from the group consisting of Na, K, Rb, and Cs. [Aspect 12] An all-solid-state battery comprising: a positive electrode containing a hydride ion donor; a negative electrode containing a hydrogen storage metal or a hydrogen storage alloy; and the hydride ion conductor according to any one of aspects 1 to 4, disposed between the positive electrode and the negative electrode. [Aspect 13] 13. The all-solid-state battery according to embodiment 12, wherein the hydride ion donor is a metal hydride. [Aspect 14] 14. The all-solid-state battery according to aspect 12 or 13, wherein the negative electrode contains a Ti-containing composite active material. [Effects of the Invention]

[0011] According to the present disclosure, a hydride ion conductor having high conductivity at room temperature is provided, and an all-solid-state battery including the hydride ion conductor can operate at room temperature.

[0012] It should be noted that the above description should not be considered as a disclosure of all embodiments of the present invention and all advantages associated with the present invention. [Brief explanation of the drawings]

[0013] [Figure 1] This is a powder X-ray diffraction pattern of the hydride ion conductor synthesized by the high-pressure synthesis method and the raw material LaH3-δ. [Figure 2] These are powder X-ray diffraction patterns of the hydride ion conductor synthesized by the mechanochemical method and the raw materials LaH3-δ and SrH2. [Figure 3] 1 shows the results of crystal structure analysis of the hydride ion conductor of Example 8 by the Rietveld method using powder X-ray diffraction. [Figure 4] FIG. 1 shows the crystal structure of La0.8Sr0.2H2.482O0.159. [Figure 5] 1 shows the diffuse reflectance spectra of the hydride ion conductors of Examples 7 to 11. [Figure 6] This is a plot of the band gap versus the amount of Sr solid solution. [Figure 7]1 is a photograph of the hydride ion conductors of Examples 7 to 11 and the raw material LaH3-δ. [Figure 8] 1 is an impedance spectrum at 25° C. of the hydride ion conductor of Example 8. [Figure 9] 1 shows Arrhenius plots of hydride ion conductors of Examples 7 to 11 and activation energies of hydride ion diffusion (boxed). [Figure 10] 1 shows discharge curves of all-solid-state batteries using the hydride ion conductors of Examples 7 to 11 as solid electrolytes. [Figure 11] 1 shows powder X-ray diffraction patterns of a Ti-containing composite active material before and after discharge. [Figure 12] These are powder X-ray diffraction patterns of the hydride ion conductor synthesized by the mechanochemical method and the raw materials LaH3-δ and NaH. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the present invention will be described in more detail with reference to the drawings for the purpose of illustrating typical embodiments thereof, but the present invention is not limited to these embodiments.

[0015] [Hydride ion conductors] In one embodiment, the hydride ion conductor has the general formula M 1 x M 2 y M 3 z H α O β It has a composition shown below.

[0016] M 1 is a trivalent rare earth element. M 1 Examples of the trivalent rare earth element include at least one selected from the group consisting of La, Ce, Nd, Sc, Y, Sm, Eu, and Gd. From the viewpoints of ionic radius and cost, the trivalent rare earth element is preferably at least one selected from the group consisting of La, Ce, Nd, Sc, and Y, and more preferably La.

[0017] M 2 is at least one Group 2 element. From the viewpoint of ionic radius, the Group 2 element is preferably at least one selected from the group consisting of Mg, Ca, Sr and Ba, and more preferably at least one selected from the group consisting of Sr and Ba.

[0018] M 3 is at least one Group 1 element selected from alkali metals. From the viewpoint of ionic radius, the Group 1 element is preferably at least one element selected from the group consisting of Na, K, Rb, and Cs, and from the viewpoint of cost, it is more preferably at least one element selected from the group consisting of Na and K.

[0019] x is an essential constituent atom of the hydride ion conductor, M 1 where x is a composition ratio of 0.4≦x<1. x is preferably 0.5 to 0.9, and more preferably 0.7 to 0.8.

[0020] y is the M in the hydride ion conductor 2 where 0≦y≦0.6. y is preferably 0.1 to 0.4, and more preferably 0.15 to 0.3.

[0021] When y is 0, the hydride ion conductor has the general formula M 1 x M 3 z H α O β In this embodiment, z is preferably 0.15 to 0.4, and more preferably 0.2 to 0.3.

[0022] z is M in the hydride ion conductor 3 where 0≦z≦0.5. z is preferably 0 to 0.3, and more preferably 0 to 0.1.

[0023] When z is 0, the hydride ion conductor has the general formula M 1 x M 2 y H α O β In this embodiment, y is preferably 0.15 to 0.4, and more preferably 0.2 to 0.3.

[0024] x, y, and z are expressed by the following formulas (1) and (2): 0.7 <x+y+z≦1 (1) 0 <y+z≦0.6 (2) For formula (1), it is preferable that 0.8≦x+y+z≦1, and more preferable that 0.9≦x+y+z≦1. For formula (2), it is preferable that 0.1≦y+z≦0.4, and more preferable that 0.15≦y+z≦0.3.

[0025] α represents the composition ratio of hydrogen atoms (H) which are the hydride ion source of the hydride ion conductor, and is 2<α<3. α is preferably 2.5 to 2.98, and more preferably 2.7 to 2.95.

[0026] β represents the composition ratio of oxygen atoms (O) in the hydride ion conductor, and is 0≦β<0.3. Oxygen atoms (O) are atoms that can be mixed into the hydride ion conductor due to the raw materials used in synthesizing the hydride ion conductor or the production conditions. β is preferably 0.2 or less, and more preferably 0.1 or less.

[0027] x, y, z, α, and β represent the charge compensation of the hydride ion conductor as shown in the following formula (3): 3x+2y+z=α+2β (3) Satisfy the following.

[0028] [Method for producing hydride ion conductor] The hydride ion conductor is M 1 and hydrides containing M 2 Hydrides containing M 3or a combination thereof.

[0029] M 1 Examples of hydrides containing M include LaH3, CeH3, NdH3, ScH3, YH3, SmH3, EuH3, and GdH3. 1 The hydride may be deficient in a hydride containing M 1 H 3-δ (For example, LaH 3-δ ) is written as

[0030] M 2 Examples of hydrides containing MgH2 include MgH2, CaH2, SrH2, and BaH2.

[0031] M 3 Hydrides containing include, for example, NaH, KH, RbH, and CsH.

[0032] M 1 Hydrides containing M 2 hydrides containing M 3 When used as a raw material for synthesizing a hydride ion conductor, for example, in a powder state, a hydride containing the above may contain oxygen atoms (O) as impurities, and the oxygen atoms may be introduced into the hydride ion conductor.

[0033] The charging ratio of the hydrides can be adjusted appropriately depending on the composition of the desired hydride ion conductor. 1 , M 2 and M 3 The hydrides are used in a stoichiometric ratio corresponding to the composition of the above. Before reacting the hydrides, they may be mixed using an agate mortar, a ball mill, or the like to obtain a precursor. The mixing is preferably carried out in an inert gas atmosphere such as argon gas to prevent the inclusion of oxygen from the air. The precursor may be used in powder form or may be formed into pellets before use.

[0034] In one embodiment, the reaction is carried out by high-pressure synthesis in the presence of a hydrogen gas generating agent. The reactor used for high-pressure synthesis is not particularly limited. For example, the hydride ion conductor can be synthesized by mixing the hydride or precursor with the hydrogen gas generating agent, encapsulating the mixture in a capsule made of Au, Pt, or rock salt in a cubic anvil-type high-pressure apparatus, and baking the mixture at a pressure of 1 GPa to 10 GPa and a temperature of 600°C to 1200°C for 10 minutes to 24 hours.

[0035] The hydrogen gas generating agent may be, for example, a metal hydride such as NaBH4 or LiAlH4, a metal hydroxide such as Ca(OH)2, or a mixture thereof. In one embodiment, the hydrogen gas generating agent is a mixture of NaBH4 and Ca(OH)2, or LiAlH4. The hydrogen gas generating agent may be formed into pellets.

[0036] In another embodiment, the reaction is carried out by a mechanochemical method. The reactor used in the mechanochemical method is not particularly limited. For example, the hydride or precursor is sealed in a tungsten carbide pot together with tungsten carbide balls, and mixed and pulverized in a planetary ball mill at a temperature of 15°C to 100°C and a rotation speed of 100 rpm to 1000 rpm for 30 minutes to 24 hours, thereby synthesizing a hydride ion conductor.

[0037] After synthesizing a hydride ion conductor by the mechanochemical method, a hydrogen annealing treatment may be performed. The hydrogen annealing treatment reduces the hydride ion deficiency in the hydride ion conductor, thereby increasing its hydride ion conductivity. The reactor used for the hydrogen annealing treatment is not particularly limited, and the hydrogen annealing treatment can be performed in the reactor used for the mechanochemical method. For example, the hydrogen annealing treatment can be performed for 1 to 24 hours in a hydrogen gas atmosphere at a temperature of 250°C to 600°C and a pressure of 0.1 to 5 MPa.

[0038] The hydride ion conductor of the present disclosure can be suitably used in solid-state batteries such as hydride ion secondary batteries and ammonia fuel cells, particularly in all-solid-state batteries.

[0039] In one embodiment, there is provided an all-solid-state battery comprising: a positive electrode including a hydride ion donor; a negative electrode including a hydrogen storage metal or a hydrogen storage alloy; and the above-described hydride ion conductor disposed between the positive electrode and the negative electrode.

[0040] The hydride ion donor contained in the positive electrode may be a material itself that is a hydride ion source, or may be a permeable membrane made of Pd, a PdCu alloy, or the like that can convert hydrogen gas supplied from the outside into hydride ions and supply them to the hydride ion conductor.

[0041] In one embodiment, the hydride ion donor is a metal hydride. Examples of metal hydrides include, for example, M 1 Metal hydrides include LaH 3-δ (wherein δ represents the amount of hydride ion deficiency, and 0≦δ<0.5) is preferred.

[0042] Examples of hydrogen storage metals or alloys contained in the negative electrode include metals with high hydrogen affinity, such as Ti, Zr, Mg, V, and rare earth elements (e.g., La), and alloys containing these metals with high hydrogen affinity and metals with low hydrogen affinity, such as Fe, Ni, Co, Cr, and Cu. Examples of hydrogen storage alloys include rare earth alloys such as LaNi5, magnesium alloys such as MgNi and MgCu, and titanium alloys such as Ti-Fe, Ti-Mn, Ti-Ni, and Ti-Cu. The hydrogen storage metal is preferably metallic titanium. The hydrogen storage alloy is preferably a titanium alloy.

[0043] In one embodiment, the negative electrode comprises a Ti-containing composite active material. The Ti-containing composite active material may comprise metallic titanium or the titanium-based alloy described above and the hydride ion conductor described above. The hydride ion conductor contained in the Ti-containing composite active material may have the same composition as or a different composition from the hydride ion conductor that functions as a solid electrolyte between the positive electrode and the negative electrode.

[0044] In this embodiment, the Ti-containing composite active material may further contain additives such as a conductive additive and a binder. Examples of conductive additives include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include acetylene black, ketjen black, carbon fiber, carbon nanotubes, and carbon nanofibers. Examples of binders include rubber-based binders such as styrene butadiene rubber (SBR), and fluorine-based binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0045] The all-solid-state battery may have a current collector containing SUS, Al, Ni, Ti, carbon, or the like on the positive electrode, and may have a current collector containing SUS, Cu, Ni, carbon, or the like on the negative electrode. [Example]

[0046] The following examples illustrate specific embodiments of the present disclosure, but the invention is not limited thereto. All parts and percentages are by weight unless otherwise specified.

[0047] 1. Synthesis of hydride ion conductors 1 The raw material hydride is lanthanum hydride (LaH 3-δ ), strontium hydride (SrH2), and barium hydride (BaH2). 3-δ was obtained by firing a block of metallic lanthanum at 400°C under a hydrogen gas atmosphere at a pressure of 0.5 MPa for 10 minutes.

[0048] Example 1 to Example 2 General formula M 1 x M 2 y H α O β (M 1 =La, M 2 A hydride ion conductor with the composition (x = Sr) was synthesized by high-pressure synthesis. x and y are shown in Table 1.

[0049] [Table 1]

[0050] Stoichiometric LaH under argon gas atmosphere 3-δ and SrH2 were weighed. These hydrides were mixed by hand in an agate mortar for 30 minutes to obtain a powdered precursor. The powdered precursor was pelletized and sealed in a gold tube of a cubic anvil-type high-pressure apparatus together with a mixed pellet containing sodium borohydride (NaBH4) and calcium hydroxide (Ca(OH)2) as hydrogen gas generating agents. The pellets were then sintered at a pressure of 3 GPa and a temperature of 1000°C for 30 minutes to obtain a polycrystalline powdered hydride ion conductor.

[0051] The obtained hydride ion conductor and the raw material LaH 3-δ The powder X-ray diffraction pattern of this is shown in the upper part of Figure 1. The measurement range of X-ray diffraction was 10°≦2θ≦80°. It was observed that the peak shifted to lower angles as the amount of Sr in solid solution increased.

[0052] Examples 3 to 6 General formula M 1 x M 2 y H α O β (M 1 =La, M 2 A hydride ion conductor having a composition represented by the formula (x = Ba) was synthesized by high-pressure synthesis in the same manner as in Example 1. x and y are shown in Table 2.

[0053] [Table 2]

[0054] The obtained hydride ion conductor and the raw material LaH 3-δ The powder X-ray diffraction pattern of this is shown in the lower part of Figure 1. The measurement range of X-ray diffraction was 10°≦2θ≦80°. It was observed that the peak shifted to lower angles as the amount of Br in solid solution increased.

[0055] Examples 7 to 12 and Comparative Examples 1 to 3 General formula M 1 x M 2 y H α O β (M 1 =La, M 2 A hydride ion conductor with the composition (x = Sr) was synthesized by a mechanochemical method. x and y are shown in Table 3.

[0056] [Table 3]

[0057] Stoichiometric LaH under argon gas atmosphere 3-δ and SrH2 were weighed. These hydrides were placed in a tungsten carbide pot together with 10 mm diameter tungsten carbide balls and mixed and ground using a planetary ball mill at room temperature (25°C) and 800 rpm for 3 hours. The mixture was then hydrogen annealed for 12 hours in a hydrogen gas atmosphere at 400°C and 1 MPa pressure, yielding a polycrystalline powder of hydride ion conductor.

[0058] The obtained hydride ion conductor and the raw material LaH 3-δ The powder X-ray diffraction patterns of SrH2 and SrH2 are shown in Figure 2. The measurement range of X-ray diffraction was 10°≦2θ≦80°. Sr solid solution was formed at least up to y=0.6 (Example 12).

[0059] 2.Crystal structure analysis The crystal structure of the hydride ion conductor was determined by the Rietveld method using powder X-ray diffraction. The results of the crystal structure analysis of the hydride ion conductor of Example 8 are shown in Figure 3. 3-δ Since it is thought that a small amount of oxygen mixed in the inert gas is adsorbed on the surface of the hydride ion conductor, a previously reported crystal structure model containing oxygen was used for analysis. Since the oxygen occupancy rate is 0.159(4) and charge compensation is established, the composition of the hydride ion conductor in Example 8 is La. 0.8Sr 0.2 H 2.482 O 0.159 (x=0.8, y=0.2, α=2.482, β=0.159). The composition of La and Sr was determined as the ratio of the hydride used as the raw material. 0.8 Sr 0.2 H 2.482 O 0.159 The crystal structure of is shown in Figure 4. It is expected that the oxygen content in the hydride ion conductor will change depending on the synthesis environment.

[0060] The results of powder X-ray diffraction Rietveld analysis are shown in Table 4.

[0061] [Table 4]

[0062] 3. Bandgap Measurement The band gaps of the hydride ion conductors of Examples 7 to 11 were calculated using ultraviolet-visible-near-infrared absorption spectroscopy. Measurement conditions were room temperature (25°C) and a wavelength range of 175 to 3300 nm. The resulting diffuse reflectance spectra are shown in Figure 5. A plot of the band gap versus the amount of Sr in solid solution is shown in Figure 6. It was confirmed that the lower limit of the energy of absorbed light shifts to the higher energy side with increasing amount of Sr in solid solution. The band gap was 2.14 eV at y = 0.1 and expanded to 2.78 eV at y = 0.5.

[0063] Hydride ion conductors of Examples 7 to 11 and the raw material LaH 3-δ A photograph of the raw material LaH 3-δ In Examples 7 to 11, the color of the hydride ion conductor changed due to the widening of the band gap and the reduction of the hydride ion deficiency.

[0064] 4. Hydride ion conductivity measurement The hydride ion conductivities of the hydride ion conductors of Examples 7 to 11 were measured using an electrochemical AC impedance method. Symmetrical cells were fabricated by sputtering Pt films as hydrogen-blocking electrodes on both sides of a pelletized hydride ion conductor with a diameter of 6 mm and a thickness of 1.1 mm. The diameter of the Pt films was 5 mm. Measurement conditions were an argon atmosphere, an applied voltage of 10 mV, a frequency range of 0.1 Hz to 35 MHz, and a temperature range of 0 to 100°C. Figure 8 shows the impedance spectrum at 25°C of the hydride ion conductor of Example 8. The impedance spectrum consisted of a semicircle on the high-frequency side due to the diffusion of hydride ions within the hydride ion conductor and a rising edge on the low-frequency side due to the electrode blocking hydrogen. Because the bulk and grain boundary components could not be separated, the hydride ion conductivity of the hydride ion conductor was calculated from the combined resistance of the bulk and grain boundary.

[0065] The Arrhenius plots and activation energies (in boxes) for hydride ion diffusion of the hydride ion conductors of Examples 7 to 11 are shown in Figure 9. The smaller the amount of Sr in solid solution, the higher the conductivity and the smaller the activation energy for hydride ion diffusion.

[0066] 5. Battery reactions using hydride ion conductors The hydride ion conductors of Examples 7 to 11 were used as solid electrolytes, LaH 3-δ A solid-state battery was fabricated using the positive electrode active material and the Ti-containing composite active material as the negative electrode active material, and a constant current discharge test was performed. 150 mg of a hydride ion conductor was used as the solid electrolyte. 70 mg of LaH was used as the positive electrode active material. 3-δ The Ti-containing composite active material was prepared by manually mixing 30 parts by mass of metallic titanium, 60 parts by mass of the same hydride ion conductor as the solid electrolyte, and 10 parts by mass of a carbon conductive additive VGCF (registered trademark) (manufactured by Showa Denko K.K.) in an agate mortar. 10 mg of the Ti-containing composite active material was used as the negative electrode active material. The discharge conditions were room temperature (25°C), under an argon atmosphere, with a discharge current value of 50 μA and a 1 / 67.2 C rate. The theoretical capacity of Ti was approximately 1120 mAhg. -1As a result of the discharge test, the voltage reached the theoretical capacity. Figure 10 shows the discharge curve together with the assumed reaction formula.

[0067] FIG. 11 shows the powder X-ray diffraction patterns of the Ti-containing composite active material before and after discharge when the hydride ion conductor of Example 8 was used as the solid electrolyte. The Ti peak observed before discharge at 33° to 42° was not observed after discharge. In addition, a new titanium hydride TiH2 peak was observed around 58° after discharge. From the powder X-ray diffraction pattern, it was clear that the TiH2 in the positive electrode was LaH 3-δ From these results, it can be seen that the discharge reaction in which the hydride ions released from the negative electrode pass through the hydride ion conductor, which is a solid electrolyte, and are absorbed by the Ti anode, has progressed completely. 3-δ It was demonstrated that the hydride ion conductor in which Sr was dissolved as a solid solution exhibited virtually no electronic conductivity and functioned as a hydride ion solid electrolyte at room temperature.

[0068] 6. Synthesis of hydride ion conductors 2 The lanthanum hydride (LaH) used in Example 1 was used as the raw material hydride. 3-δ ), and sodium hydride (NaH) were used.

[0069] Example 13 General formula M 1 x M 3 z H α O β (M 1 =La, M 3 = Na, x = 0.7, z = 0.3) was synthesized by mechanochemical method.

[0070] Stoichiometric LaH under argon gas atmosphere 3-δand NaH were weighed. These hydrides were placed in a tungsten carbide pot together with 10 mm diameter tungsten carbide balls and mixed and ground using a planetary ball mill at room temperature (25°C) and 800 rpm for 3 hours. The mixture was then hydrogen annealed for 12 hours in a hydrogen gas atmosphere at 400°C and 1 MPa pressure, yielding a polycrystalline powder of hydride ion conductor.

[0071] The obtained hydride ion conductor (x = 0.7, z = 0.3) and the raw material LaH 3-δ The powder X-ray diffraction patterns of NaH and LaH are shown in Figure 12. The measurement range of X-ray diffraction was 10° ≤ 2θ ≤ 80°. No peaks due to NaH were observed in the powder X-ray diffraction pattern of the synthesized hydride ion conductor, and a peak shift to the lower angle side due to lattice expansion was observed. This indicates that Na is LaH 3-δ This suggests that the solid solution was formed.

[0072] It will be apparent to those skilled in the art that the above-described embodiments and examples may be modified in various ways without departing from the basic principles of the present invention, and that various improvements and modifications of the present invention may be made without departing from the spirit and scope of the present invention. [Industrial Applicability]

[0073] The hydride ion conductors of the present disclosure are useful as solid electrolytes in all-solid-state batteries, etc. Furthermore, the hydride ion conductors of the present disclosure have the potential to create new energy devices that utilize hydride ions as charge carriers.

Claims

1. General formula M １ ｘ M ２ ｙ M ３ ｚ H α O β (In the formula, M １ is a trivalent rare earth element, and M ２ is at least one Group 2 element, M ３ is at least one Group 1 element selected from alkali metals, 0.4≦x<1, 0≦y≦0.6, 0≦z≦0.5, 0.7<x+y+z≦1, 0<y+z≦0.6, 2<α<3, 0≦β<0.3, and 3x+2y+z=α+2β.

2. 2. The hydride ion conductor according to claim 1, wherein the trivalent rare earth element is at least one selected from the group consisting of La, Ce, Nd, Sc, and Y.

3. 3. The hydride ion conductor according to claim 1, wherein the Group 2 element is at least one selected from the group consisting of Mg, Ca, Sr, and Ba.

4. 4. The hydride ion conductor according to claim 1, wherein the Group 1 element is at least one selected from the group consisting of Na, K, Rb, and Cs.

5. General formula M １ ｘ M ２ ｙ M ３ ｚ H α O β (In the formula, M １ is a trivalent rare earth element, and M ２ is at least one Group 2 element, M ３ is at least one Group 1 element selected from alkali metals, 0.4≦x<1, 0≦y≦0.6, 0≦z≦0.5, 0.7<x+y+z≦1, 0<y+z≦0.6, 2<α<3, 0≦β<0.3, and 3x+2y+z=α+2β, M １ and a hydride comprising M ２ hydrides including M ３ or a combination thereof, A method for producing a hydride ion conductor, comprising reacting

6. 6. The method for producing a hydride ion conductor according to claim 5, wherein the reaction is carried out by a high-pressure synthesis method in the presence of a hydrogen gas generating agent.

7. 6. The method for producing a hydride ion conductor according to claim 5, wherein the reaction is carried out by a mechanochemical method.

8. The method for producing a hydride ion conductor according to claim 7, further comprising performing a hydrogen annealing treatment.

9. 9. The method for producing a hydride ion conductor according to claim 5, wherein the trivalent rare earth element is at least one selected from the group consisting of La, Ce, Nd, Sc, and Y.

10. 10. The method for producing a hydride ion conductor according to claim 5, wherein the Group 2 element is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

11. 11. The method for producing a hydride ion conductor according to claim 5, wherein the Group 1 element is at least one selected from the group consisting of Na, K, Rb, and Cs.

12. An all-solid-state battery comprising: a positive electrode containing a hydride ion donor; a negative electrode containing a hydrogen storage metal or a hydrogen storage alloy; and the hydride ion conductor according to any one of claims 1 to 4, disposed between the positive electrode and the negative electrode.

13. The all-solid-state battery according to claim 12, wherein the hydride ion donor is a metal hydride.

14. The all-solid-state battery according to claim 12 or 13, wherein the negative electrode contains a Ti-containing composite active material.

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