Hydride conductor

Abstract

A hydride ion conductor, the general formula of which is represented by formula (1), MAMBH 4－x F x (1), wherein MA is selected from Ca, Sr and Ba, MB is selected from Mg and Ca and is different from MA, and 0 < x < 4.

Description

Technical Field

[0001] This invention relates to a hydrogen anion conductor. Background Technology

[0002] Hydrogen ions (H+) are composed of a hydrogen atom and two electrons. － It is lighter than lithium ions and has a similar ionic radius to fluoride ions (F). － With many of the same characteristics, it is a very attractive charge carrier in electrochemistry.

[0003] For example, in electrochemical devices such as fuel cells and secondary batteries, hydrogen anion conductors are used as alternatives to protons (H+). + ) and lithium ions (Li + When ions are used as conductors, it is possible to realize a new type of energy device.

[0004] To date, several hydrogen anion conductors exhibiting high ionic conductivity have been reported (e.g., non-patent literature 1, 2).

[0005] Existing technical documents

[0006] Non-patent literature

[0007] Non-patent document 1: Keiga Fukui, et al., "Characteristic fast H-ion conductionin oxygen-substituted lanthanum hysride", nature communications, (2019) 10: 2578

[0008] Non-patent literature 2: Maarten C. Verbraeken, et al., “High H-ionic conductivity inbarium hydride”, Nature Materials, vol. 14, p. 95–p. 100, January, 2015 Summary of the Invention

[0009] Previous hydrogen anion conductors had stability issues. Specifically, they tended to decompose rapidly when exposed to the atmosphere.

[0010] Therefore, it is predicted that an atmospherically stable hydrogen anion conductor is needed in order to practically apply hydrogen anion conductors to electrochemical devices.

[0011] The present invention was made in view of the following background, and the object of the present invention is to provide a hydrogen negative ion conductor that is more stable in an atmospheric environment.

[0012] In this invention, a hydrogen anion conductor is provided, the general formula of which is represented by formula (1).

[0013] MAMBH 4－x F x (1)

[0014] here,

[0015] MA is selected from Ca, Sr, and Ba.

[0016] MB is selected from Mg and Ca, and is different from MA.

[0017] 0 < x < 4.

[0018] In addition, this invention provides a hydrogen anion conductor with a BaZnF4 type structure and a conductivity of 10 at 300°C. －5 S / cm or higher.

[0019] This invention provides a hydrogen anion conductor that is more stable in an atmospheric environment. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the crystal structure of a hydrogen anion conductor according to one embodiment of the present invention.

[0021] Figure 2 It focuses on showing BaH2 and LaH 1.92 O 0.54 La 0.6 Sr 1.4 LiH 1.6 Reference plot of temperature dependence of O2 and SrMgH4 conductivity.

[0022] Figure 3 This is a hydrogen anion conductor, namely SrMgH, which is shown as one embodiment of the present invention. 4－x F x A graph showing the temperature dependence of the conductivity of the material.

[0023] Figure 4 This is a schematic diagram illustrating the process of manufacturing a hydrogen anion conductor according to one embodiment of the present invention.

[0024] Figure 5 This is a graph showing the X-ray diffraction results of an atmospheric exposure of a hydrogen anion conductor (sample 1) according to one embodiment of the present invention.

[0025] Figure 6 This is a diagram showing the X-ray diffraction results of a hydrogen negative ion conductor (sample 2) according to one embodiment of the present invention before and after atmospheric exposure.

[0026] Figure 7 This is a diagram showing the X-ray diffraction results of a hydrogen anion conductor (sample 3) according to one embodiment of the present invention before and after atmospheric exposure.

[0027] Figure 8 This is a graph showing the temperature dependence of the conductivity of a hydrogen anion conductor (sample 2) according to one embodiment of the present invention.

[0028] Figure 9 This is a graph showing the temperature dependence of the conductivity of a hydrogen anion conductor (sample 3) according to one embodiment of the present invention. Detailed Implementation

[0029] Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

[0030] (A hydrogen anion conductor according to one embodiment of the present invention)

[0031] In one embodiment of the present invention, a hydrogen anion conductor is provided, the general formula of which is represented by formula (1).

[0032] MAMBH 4－x F x (1)

[0033] here,

[0034] MA is selected from Ca, Sr, and Ba.

[0035] MB is selected from Mg and Ca, and is different from MA.

[0036] 0 < x < 4.

[0037] In another embodiment of the present invention, a hydrogen anion conductor is provided, having a BaZnF4 type structure, and a conductivity of 10 at 300°C. －5 S / cm or higher.

[0038] One embodiment of the present invention provides a hydrogen anion conductor having a BaZnF4 type structure.

[0039] Figure 1 The diagram schematically illustrates the structure of a hydrogen anion conductor according to one embodiment of the present invention, namely the crystal structure of BaZnF4.

[0040] The hydrogen negative ion conductor of one embodiment of the present invention exhibits significantly higher stability in atmospheric conditions compared to conventional hydrogen negative ion conductors.

[0041] For example, the conductivity of the hydrogen anion conductor of one embodiment of the present invention does not decrease even after being placed in the atmosphere for one week at 300°C.

[0042] It should be noted that the reasons for the stability of the hydrogen anion conductor in the atmosphere according to one embodiment of the present invention are not yet fully understood.

[0043] However, F atoms are typically bonded to cations with high bonding strength. Therefore, it is believed that in the hydride anion conductor of one embodiment of the present invention, which has a structure in which a portion of the hydrogen (H) atom is replaced by a fluorine (F) atom, the increased bonding strength between such cations and anions contributes to stability.

[0044] Thus, in one embodiment of the present invention, a hydrogen anion conductor that is easily processed in the atmosphere can be provided, making it easier to apply to electrochemical devices compared to the past.

[0045] (A specific example of a hydrogen anion conductor according to one embodiment of the present invention)

[0046] Next, a specific example of a hydrogen negative ion conductor of one embodiment of the present invention having the features described above will be described.

[0047] (SrMgH 4－x F x Tie)

[0048] SrMgH4 is obtained by replacing a portion of the hydrogen atoms (H) with fluorine atoms (F) in the material SrMgH4 having a BaZnF4 type structure. 4－x F x system material. htK 4－x F x The material is equivalent to the case where MA = Sr and MB = Mg in the aforementioned equation (1).

[0049] Here, as mentioned before, 0 < x < 4. If the value of x increases, the atmospheric stability of the material improves. Therefore, x is preferably 1 or higher. Furthermore, if the value of x is 3 or lower, SrMgH is obtained. 4－x F x The material has good conductivity.

[0050] Figure 2 The temperature dependence of conductivity for various hydrogen anion conductors is shown in the figure for reference.

[0051] Figure 2 BaH2 and LaH2 are shown in the figure. 1.92 O 0.54 La 0.6 Sr 1.4 LiH 1.6 Temperature dependence of O2 and SrMgH4.

[0052] in addition, Figure 3 SrMgH is concentrated in the middle.4－x F x The temperature dependence of the conductivity of the system material. Figure 3 In the diagram, (i) represents the behavior of SrMgH4 material, (ii) represents the behavior of SrMgH3F1 material, (iii) represents the behavior of SrMgH2F2 material, (iv) represents the behavior of SrMgH1F3 material, and (v) represents the behavior of SrMgF4 material.

[0053] according to Figure 3 It can be seen that in SrMgH 4－x F x In the system of materials, if the value of x decreases, then SrMgH exists. 4－x F x The trend is towards increased conductivity of the system material.

[0054] In one embodiment of the present invention, SrMgH is preferably used at 300°C. 4－x F x The conductivity of the material is 10. －5 S / cm or higher.

[0055] (BaMgH 4－x F x Tie)

[0056] BaMgH4 is obtained by replacing a portion of the hydrogen atoms (H) with fluorine atoms (F) in the material BaMgH4, which has a BaZnF4-type structure. 4－x F x System materials. BaMgH 4－x F x The material is equivalent to the case where MA = Ba and MB = Mg in the aforementioned equation (1).

[0057] As mentioned before, 0 < x < 4. If the value of x is less than or equal to 3, then BaMgH is obtained. 4－x F x The material exhibits good conductivity. Furthermore, increasing the value of x improves the material's atmospheric stability. Preferably, x is in the range of 1 to 3.

[0058] (A method for manufacturing a hydrogen anion conductor according to one embodiment of the present invention)

[0059] The following is for reference Figure 4 A method for manufacturing a hydrogen negative ion conductor according to one embodiment of the present invention will be briefly described.

[0060] Figure 4 The diagram schematically illustrates a process for manufacturing a hydrogen anion conductor according to one embodiment of the present invention.

[0061] like Figure 4As shown, a method for manufacturing a hydrogen anion conductor according to one embodiment of the present invention includes:

[0062] (i) The process of mixing the specified raw materials to prepare a mixed powder (process S110), and

[0063] (ii) The process of heat-treating the mixed powder (process S120).

[0064] It should be noted that in the method for manufacturing a hydrogen negative ion conductor according to one embodiment of the present invention, each step is carried out in a non-atmospheric atmosphere such as an inactive gas atmosphere or a hydrogen atmosphere.

[0065] The following is a description of each process.

[0066] (Process S110)

[0067] First, prepare the ingredients.

[0068] As raw materials, for example, hydrides of metal MA and metal MB, and fluorides of metal MA and metal MB can be used.

[0069] For example, manufacturing SrMgH 4－x F x When constructing a hydride anion conductor, SrH2 powder, MgH2 powder, SrF2 powder, and MgF2 powder can be used. Alternatively, BaMgH2 can be manufactured. 4－x F x When using a system of hydrogen anion conductors, BaH2 powder, MgH2 powder, BaF2 powder, and MgF2 powder can be used.

[0070] The raw materials can be thoroughly mixed using a ball mill or similar equipment.

[0071] The resulting mixed powder can also be molded. In this case, the hydrogen anion conductor can be provided in the form of a molded body.

[0072] (Process S120)

[0073] Next, the resulting mixed powder is heat-treated at high temperature to manufacture a hydrogen anion conductor.

[0074] This process can utilize a cubic multi-anvil high-pressure device. When using this device, a cube called a pyrophyllite block is used, and a mixture of powders is filled into the interior of this block. Then, the cubic multi-anvil high-pressure device generates ultra-high hydrostatic pressure, thereby isotropically pressurizing the six faces of the pyrophyllite block located inside.

[0075] The pressure applied to the pyrophyllite briquettes is, for example, in the range of 1 GPa to 6 GPa.

[0076] The processing temperature is, for example, in the range of 500℃ to 1000℃.

[0077] Through the above processes, a hydrogen negative ion conductor according to one embodiment of the present invention can be manufactured.

[0078] It should be noted that step S120 is not necessarily required in the above manufacturing method. That is, the hydrogen anion conductor of one embodiment of the present invention can also be provided in the form of a mixed powder.

[0079] Furthermore, the above manufacturing method is merely an example, and the hydrogen negative ion conductor of one embodiment of the present invention can also be manufactured using other manufacturing methods.

[0080] Example

[0081] Samples of hydrogen anion conductors were prepared using the following method. Furthermore, the properties of the prepared samples were evaluated. It should be noted that in the following description, Examples 1 to 3 are exemplary cases, and Examples 11 and 12 are comparative examples.

[0082] (Example 1)

[0083] The following methods are used to prepare evaluation samples.

[0084] (SrMgH 4－x F x (Sample preparation)

[0085] A mixed powder was prepared by weighing and mixing 1.338 g of SrH2 powder (manufactured by Mitsutsu Kagaku Co., Ltd.), 0.197 g of MgH2 powder (manufactured by Wako Pure Chemical Co., Ltd.), and 0.465 g of MgF2 powder (manufactured by Mitsutsu Kagaku Co., Ltd.) under an Ar atmosphere.

[0086] The particle size of SrH2 powder is 0.1–200 μm, the particle size of MgH2 powder is 0.1–200 μm, and the particle size of MgF2 powder is 0.1–200 μm.

[0087] In the mixed powder, H:F = 3:1 (molar ratio).

[0088] The resulting mixed powder was fed into a planetary ball mill (with zirconia ball milling) and pulverized and mixed at room temperature. The rotation speed was 600 rpm, and the processing time was 48 hours.

[0089] Thus, a hydrogen negative ion conductor (hereinafter referred to as "Sample 1") was produced.

[0090] (Example 2)

[0091] Hydrogen anion conductors were prepared using the same method as in Example 1. In this Example 2, the H:F ratio in the mixed powder was 2:2 (molar ratio). Other conditions were the same as in Example 1.

[0092] Thus, a hydrogen negative ion conductor (hereinafter referred to as "sample 2") was produced.

[0093] (Example 3)

[0094] Hydrogen anion conductors were prepared using the same method as in Example 1. In Example 3, the H:F ratio in the mixed powder was 1:3 (molar ratio). Other conditions were the same as in Example 1.

[0095] Thus, a hydrogen negative ion conductor (hereinafter referred to as "sample 3") was produced.

[0096] (Example 11)

[0097] Hydrogen anion conductors were prepared using the same method as in Example 1. However, in Example 11, a mixed powder was prepared without adding MgF2 powder. The mixed powder consisted of stoichiometric amounts of SrMgH4. Other conditions were the same as in Example 1.

[0098] Thus, a hydrogen negative ion conductor (hereinafter referred to as "sample 11") was produced.

[0099] (Example 12)

[0100] The sample was prepared using the same method as in Example 1. In Example 11, 1.337 g of SrF2 powder and 0.663 g of MgF2 powder were weighed and mixed under an Ar atmosphere to prepare a mixed powder. No hydrides were added to the raw materials. The mixed powder consisted of stoichiometric amounts of SrMgF4. Other conditions were the same as in Example 1.

[0101] Therefore, a sample (hereinafter referred to as "sample 12") is made.

[0102] (evaluate)

[0103] (Atmospheric Exposure Test)

[0104] Each manufactured sample was exposed to an atmospheric environment with a relative humidity of 50-60%, and the condition of the samples was observed.

[0105] In addition, the following evaluation was carried out using samples taken before and after atmospheric exposure.

[0106] (X-ray diffraction analysis)

[0107] X-ray diffraction analysis of each sample was performed using a benchtop X-ray diffraction analyzer (MiniFlex 600; manufactured by RIGAKU). It should be noted that measurements prior to atmospheric exposure were performed under an argon atmosphere, while measurements after atmospheric exposure were performed under an atmospheric atmosphere.

[0108] (AC impedance measurement)

[0109] Each sample was molded to create a molded body with a diameter of approximately 6 mmφ and a thickness of approximately 2 mm. Gold electrodes were then brought into contact with the two bottom surfaces of the molded body, and an atmosphere-controlled measurement unit was used to perform AC impedance measurements.

[0110] The measuring apparatus used was a VSP-300 (Bio-Logic). The measurement frequency was 1 Hz to 7 MHz, and the applied AC voltage was 50 to 500 mV. The measurements were conducted in a hydrogen atmosphere. The conductivity was calculated based on the measurement results (cole-cole-plot).

[0111] (result)

[0112] The evaluation results obtained from each sample are summarized in Table 1 below.

[0113] [Table 1]

[0114]

[0115] In the atmospheric exposure test, Sample 11 began to decompose immediately after atmospheric release, deteriorating very rapidly. On the other hand, Samples 1 through 3 deteriorated later and were more stable compared to Sample 11. In particular, in Samples 2 and 3, almost no deterioration was observed even one week after atmospheric release.

[0116] Figure 5 The X-ray diffraction analysis results for sample 1 are shown below. Additionally, Figure 6 and Figure 7 The X-ray diffraction analysis results for samples 2 and 3 are shown in the figure.

[0117] Here, the X-ray diffraction analysis results for Sample 1 were obtained 1 hour after atmospheric release. In contrast, the X-ray diffraction analysis results for Samples 2 and 3 were obtained 1 week after atmospheric release. It should be noted that Sample 11 could not be analyzed by X-ray diffraction because it began to decompose immediately after atmospheric release.

[0118] Figure 6 and Figure 7 The X-ray diffraction analysis results before atmospheric release are shown simultaneously in the image.

[0119] according to Figure 6 and Figure 7It can be seen that, in the cases of samples 2 and 3, almost no phase change occurred before and after atmospheric exposure.

[0120] The aforementioned Figure 3 (ii) shows the temperature dependence of conductivity obtained in sample 1 before atmospheric release. Additionally, the aforementioned... Figure 3 (iii) shows the temperature dependence of conductivity obtained in sample 2 before atmospheric release, as described above. Figure 3 (iv) shows the temperature dependence of conductivity obtained in sample 3 before atmospheric release. Furthermore, Figure 3 (i) shows the temperature dependence of conductivity obtained in sample 11 before atmospheric release. Figure 3 (v) shows the temperature dependence of conductivity obtained in sample 12 before atmospheric release.

[0121] like Figure 3 As shown, the conductivity at each temperature is lowest in sample 12, and increases sequentially for samples 3, 2, 1 and 11.

[0122] Figure 8 The temperature dependence of conductivity of sample 2 after atmospheric release is shown in the figure. Figure 8 The results of pre-exposure atmospheric measurements are also shown (i.e. Figure 3 The curve (iii) in the figure is used for comparison.

[0123] Based on this result, it can be seen that Sample 2 maintained high conductivity even after atmospheric exposure. For example, in Sample 2, the conductivity at 300°C after atmospheric exposure was approximately 10. －7.0 S / cm.

[0124] Figure 9 The temperature dependence of conductivity of sample 3 after atmospheric release is shown in the figure. Figure 9 The results of pre-exposure atmospheric measurements are also shown (i.e. Figure 3 The curve (iv) in the figure is used for comparison.

[0125] Based on this result, it can be seen that Sample 3 maintained high conductivity even after atmospheric exposure. For example, in Sample 3, the conductivity at 300°C after atmospheric exposure was approximately 10. －4.5 S / cm.

[0126] It should be noted that in sample 3, the conductivity at 300°C after atmospheric exposure increased compared to the conductivity at 300°C before atmospheric exposure.

[0127] Thus, samples 1 through 3 were confirmed to have better atmospheric stability than sample 11.

[0128] This application claims priority to Japanese Patent Application No. 2021-130271, filed on August 6, 2021, the entire contents of which are incorporated herein by reference.

Claims

1. A hydrogen anion conductor, represented by general formula (1), MAMBH 4－x F x (1) in, MA is selected from Ca, Sr, and Ba. MB is selected from Mg and Ca, and is different from MA. 0＜x＜4。 2. The hydrogen anion conductor according to claim 1, having a BaZnF4 crystal structure, has a conductivity of 10 at 300°C. －5 S / cm or higher.

3. The hydrogen anion conductor according to claim 1 or 2, which is composed of the general formula SrMgH 4－x F x or BaMgH 4－x F x express.

Images