Lithium diboride sheet-containing substance, manufacturing method of lithium diboride sheet-containing substance

Abstract

To provide a lithium diboride sheet-containing substance having a large amount of introduced metal and not comprising hydrogen, and a manufacturing method of the lithium diboride sheet-containing substance.SOLUTION: A lithium diboride sheet-containing substance has a two-dimensional network consisting of (LiB2)n (n≥12), wherein the two-dimensional network has a mesh shape in which boron atoms are arranged in a hexagonal ring and hexagons formed by the boron atoms are connected, and comprises a site where two lithium atoms sandwich a central part of a hexagon of boron.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lithium diboride sheet-containing material and a method for producing the lithium diboride sheet-containing material. [Background technology]

[0002] In recent years, new functional phenomena have been discovered in materials in which atoms form two-dimensional networks (hereinafter referred to as "atomic network materials"), and atomic network materials have attracted attention for their potential as functional materials.

[0003] Two-dimensional boron sheet-containing materials, a type of atomic network material, have been reported by theoretical calculations to exhibit excellent performance as electrodes for batteries using alkali metals (see, for example, Non-Patent Documents 1 to 3). Theoretical calculations show that two-dimensional boron sheet-containing materials are flat materials with no edges that extend to infinity. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Monolayer Honeycomb Borophene: A Promising Anode Material with a Record Capacity for Lithium-Ion and , Sodium-Ion Batteries, J. Electrochem. Soc. 167 (2020) 090527. [Non-patent document 2] Xiaoming Zhang, Junping Hu, Yingchun Cheng, Hui Ying Yang, Yugui Yao, Shengyuan A. Yang, “Borophene as an extremely high capacity electrode material for Li-ion and Na-ion batteries”, Nanoscale, 2016, 8, 15340. [Non-patent document 3] Lele Li, Hong Zhang, Xinlu Cheng, “The high hydrogen storage capacities of Li-decorated borophene”, Computational Materials Science 137(2017)119-124. Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional techniques have not been able to introduce metals into two-dimensional boron sheet-containing materials. Furthermore, methods for introducing metal ions into two-dimensional boron sheet-containing materials always resulted in the inclusion of hydrogen in the product. This is thought to be due to a problem with the preparation method of ion exchange resins for the metals to be introduced into two-dimensional boron sheet-containing materials.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a lithium diboride sheet-containing material that has a large amount of metal incorporated and does not contain hydrogen, and a method for producing the lithium diboride sheet-containing material. [Means for solving the problem]

[0007] The present invention has the following aspects. [1](LiB2) n (n≧12) The two-dimensional network is a lithium diboride sheet-containing material in which boron atoms are arranged in a hexagonal ring, the hexagons formed by the boron atoms are connected to form a mesh, and two lithium atoms have a portion where the center of the boron hexagon is sandwiched between them. [2] Step A of stirring a cation exchange resin and lithium carbonate in water; a step B of recovering a precursor ion exchange resin in which lithium ions are coordinated with the cation exchange resin from the aqueous solution containing the cation exchange resin and the lithium carbonate after stirring; Step C of washing the precursor ion exchange resin with water; a step D of stirring the precursor ion exchange resin and magnesium diboride in an aqueous solution containing a polar organic solvent to form a first dispersion; a step E of, after completing the stirring in the step D, filtering and extracting a first supernatant of the first dispersion, and concentrating and drying the first supernatant to obtain a first product; a step F of mixing the first product with a polar organic solvent to prepare a second dispersion, and centrifuging the second dispersion to obtain a second supernatant and a second precipitate; and step G of concentrating and drying the second supernatant and the second precipitate, respectively, to obtain a second product. [3] The method for producing a lithium diboride sheet-containing material according to [2], wherein the polar organic solvent is acetonitrile. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a lithium diboride sheet-containing material that has a large amount of metal incorporated and does not contain hydrogen, and a method for producing the lithium diboride sheet-containing material. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing the molecular structure of a lithium diboride sheet-containing material according to one embodiment of the present invention. FIG. [Figure 2] FIG. 1 shows the results of infrared spectroscopic analysis of the products obtained in the examples. [Figure 3] FIG. 1 shows the results of infrared spectroscopic analysis of the products obtained in the examples. [Figure 4] FIG. 1 is a diagram showing the results of thermal desorption gas analysis of the products obtained in the examples. [Figure 5] FIG. 1 is a diagram showing the results of thermal desorption gas analysis of the products obtained in the examples. [Figure 6] FIG. 1 shows the results of X-ray diffraction measurement of the product obtained in the example. [Figure 7] FIG. 1 shows the results of X-ray diffraction measurement of the product obtained in the example. [Figure 8] FIG. 1 shows the results of ultraviolet-visible absorption spectroscopy of a two-dimensional borohydride sheet for comparison and the product obtained in the example. [Figure 9] FIG. 1 is a diagram showing the results of observation of a product obtained in an example using a transmission electron microscope. [Figure 10] FIG. 1 is a diagram showing the results of observation of a product obtained in an example using a transmission electron microscope. [Figure 11] FIG. 1 is a diagram showing the results of observation of a product obtained in an example using a transmission electron microscope. [Figure 12] FIG. 1 shows the results of electron energy loss spectroscopy analysis of the products obtained in the examples. [Figure 13] FIG. 1 shows the results of ultraviolet-visible absorption spectroscopy of the product obtained in the example. [Figure 14] FIG. 1 is a diagram showing the results of measuring the molar absorption coefficient of the product obtained in the example. [Figure 15] FIG. 1 shows the results of 1H-NMR measurement of the product obtained in the example. [Figure 16] FIG. 1 shows the results of 11B-NMR measurement of the product obtained in the example. [Figure 17] FIG. 1 shows the results of 7Li-NMR measurement of LiB2. [Figure 18] FIG. 1 shows the results of 7Li-NMR measurement of LiB2. [Figure 19] FIG. 1 shows the results of 7Li-NMR measurement of LiCl. [Figure 20] FIG. 1 shows the results of 7Li-NMR measurement of LiOH. [Figure 21] FIG. 1 shows the results of X-ray photoelectron spectroscopy of the products obtained in the examples. [Figure 22] FIG. 1 shows the results of X-ray photoelectron spectroscopy of the products obtained in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the lithium diboride sheet-containing material and the method for producing the lithium diboride sheet-containing material of the present invention will be described. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0011] [Lithium diboride sheet-containing material] The lithium diboride sheet-containing material according to one embodiment of the present invention is (LiB2) n (n≧12), in which boron atoms (B) are arranged in a hexagonal ring, forming a mesh of interconnected hexagons formed by boron atoms (B), and there is a region where two lithium atoms sandwich the center of a boron hexagon.

[0012] As shown in FIG. 1, in the lithium diboride sheet-containing material of this embodiment, boron atoms (B) are arranged in a hexagonal ring like a benzene ring, and are present at the vertices of the hexagons. The hexagons formed by the boron atoms (B) are connected without gaps to form a mesh-like surface structure (two-dimensional network). In the lithium diboride sheet-containing material of this embodiment, the hexagonal network formed by boron atoms (B) refers to, for example, a honeycomb structure.

[0013] As shown in FIG. 1, the lithium diboride sheet-containing material of this embodiment has a region in which two lithium atoms (Li) sandwich the center of a hexagon of boron (B).

[0014] The lithium diboride sheet-containing material of this embodiment is a thin film-like material having a two-dimensional network made up of boron atoms (B) and lithium atoms (Li). In the lithium diboride sheet-containing material of this embodiment, the total number of boron atoms (B) and lithium atoms (Li) forming the mesh-like plane structure is 1000 or more.

[0015] 1, the bond distance d1 between two adjacent boron atoms (B) is 0.17 nm to 0.18 nm, and the bond distance d2 between two boron atoms (B) sandwiching a lithium atom (Li) is 0.31 nm to 0.33 nm.

[0016] The thickness of the lithium diboride sheet-containing material of this embodiment is 0.31 nm to 1000 nm. In the lithium diboride sheet-containing material of this embodiment, the length in at least one direction (for example, the length in the X direction or Y direction in FIG. 1) is preferably 100 nm or more. Furthermore, the lithium diboride sheet-containing material of this embodiment preferably includes a crystalline or amorphous body having a length in at least one direction of 100 nm or more. In the lithium diboride sheet-containing material of this embodiment, if the length in at least one direction is 10 nm or more, the lithium diboride sheet-containing material of this embodiment can be effectively used as a hydrogen storage material, a battery electrode material, etc. The size (area) of the lithium diboride sheet-containing material of this embodiment is not particularly limited, and can be formed to any size by the method for producing the lithium diboride sheet-containing material of this embodiment described below.

[0017] The lithium diboride sheet-containing material of this embodiment is a two-dimensional material that has edges and wrinkles that can be seen with a transmission electron microscope.

[0018] The lithium diboride sheet-containing material of this embodiment is a material having a crystalline structure. In addition, in the lithium diboride sheet-containing material of this embodiment, the bonding strength between the boron atoms (B) forming the hexagonal ring and between the boron atoms (B) and the lithium atoms (Li) is strong. Therefore, even if the lithium diboride sheet-containing material of this embodiment forms a crystal (aggregate) consisting of multiple stacks during production, it can be easily cleaved along the crystal plane like graphite and separated (recovered) as a single layer of two-dimensional sheet.

[0019] The lithium diboride sheet-containing material of this embodiment makes it possible to provide a hydrogen storage material composed of light elements, unlike conventional hydrogen storage materials that use heavy metals. The lithium diboride sheet-containing material of this embodiment can provide a battery material that has excellent performance, different from that of carbon.

[0020] It has been reported that modifying a boron monolayer with lithium ions can store 13.7% by mass of hydrogen per 100% by mass of the total mass of the boron monolayer (see Lele Li, Hong Zhang, Xinlu Cheng, "The high hydrogen storage capacities of Li-decorated borophene", Computational Materials Science 137 (2017) 119-124). Therefore, the lithium diboride sheet-containing material of this embodiment is expected to be used as a new hydrogen storage material that exceeds this. In addition, it is expected to be used as a solid acid catalyst material, a reducing agent functional material, etc.

[0021] A monolayer of boron with a honeycomb atomic arrangement provides 5268mAhg of charge per lithium ion. -1 It has been reported that lithium has a battery capacity of 372mAhg. -1It has been reported that the capacity is about 14 times higher than that of conventional lithium diboride sheets (see Jingzhen Li, Georgios A. Tritsaris, Xiuying Zhang, Bowen Shi, Chen Yang, Shiqi Liu, Jie Yang, Linqiang Xu, Jinbo Yang, Feng Pan, Efthimios Kaxiras, Jing Lu, "Monolayer Honeycomb Borophene: A Promising Anode Material with a Record Capacity for Lithium-Ion and Sodium-Ion Batteries", Journal of the Electrochemical Society, 2020 167 090527). Therefore, the lithium diboride sheet-containing material of this embodiment is expected to be used as a new electrode material that exceeds this capacity.

[0022] Boron monolayers with a structure called β12 and X 3 A boron monolayer with a structure called -1 (See Xiaoming Zhang, Junping Hu, Yingchun Cheng, Hui Ying Yang, Yugui Yao, Shengyuan A. Yang, "Borophene as an extremely high capacity electrode material for Li-ion and Na-ion batteries", Nanoscale, 2016, 8, 15340.) Therefore, the lithium diboride sheet-containing material of this embodiment is expected to be used as a new electrode material that exceeds this.

[0023] [Method for producing lithium diboride sheet-containing material] A method for producing a lithium diboride sheet-containing material according to one embodiment of the present invention includes the steps of: A) stirring a cation exchange resin and lithium carbonate in water; B) recovering a precursor ion exchange resin in which lithium ions are coordinated to the cation exchange resin from the aqueous solution containing the cation exchange resin and the lithium carbonate after stirring; C) washing the precursor ion exchange resin with water; D) stirring the precursor ion exchange resin and magnesium diboride in an aqueous solution containing a polar organic solvent to obtain a first dispersion; E) filtering and extracting a first supernatant of the first dispersion after the stirring in step D, concentrating and drying the first supernatant to obtain a first product; F) mixing the first product with a polar organic solvent to prepare a second dispersion, centrifuging the second dispersion to obtain a second supernatant and a second precipitate; and G) concentrating and drying the second supernatant and the second precipitate to obtain a second product.

[0024] "Process A" In step A, cation exchange resin and lithium carbonate (Li2CO3) are stirred in water.

[0025] The cation exchange resin in which an ion-exchangeable ion is coordinated with a lithium ion constituting lithium carbonate is not particularly limited, and examples thereof include a polymer of styrene having a functional group (hereinafter referred to as a "functional group α") in which an ion-exchangeable ion is coordinated with a lithium ion constituting lithium carbonate, a polymer of divinylbenzene having the functional group α, and a copolymer of styrene having the functional group α and divinylbenzene having the functional group α. Examples of the functional group α include a sulfo group, a carboxyl group, etc. Among these, a sulfo group is preferred because it can easily undergo ion exchange with lithium ions constituting lithium carbonate in a polar organic solvent.

[0026] The water is not particularly limited, and tap water or distilled water may be used.

[0027] In step A, a cation exchange resin and lithium carbonate are added to water, and the mixed solution containing water, the cation exchange resin, and lithium carbonate is stirred to bring the lithium carbonate and the cation exchange resin into sufficient contact with each other. This causes ion exchange between the lithium ions constituting the lithium carbonate and the ions of the functional group α of the cation exchange resin, producing a precursor ion exchange resin in which lithium ions are coordinated with the cation exchange resin.

[0028] The concentration of the cation exchange resin in the mixed solution is preferably 200 mL / L (0.4 mol / L as ion exchange capacity) to 600 mL / L (1.2 mol / L as ion exchange capacity), more preferably 300 mL / L (0.6 mol / L as ion exchange capacity). However, the concentration is not necessarily limited as long as stirring is possible.

[0029] The concentration of lithium carbonate in the mixed solution is preferably such that the ion exchange capacity of the cation exchange resin is equivalent to the lithium ion concentration in the lithium carbonate. If the amounts are less than this, the second supernatant-derived components of the second product increase and the precipitate components decrease. If the amounts are more than this, unreacted lithium carbonate remains.

[0030] In the step A, it is preferable to gently proceed with the ion exchange reaction between the lithium ions constituting the lithium carbonate and the ions of the functional group α of the cation exchange resin without applying ultrasonic waves or the like to the mixed solution.

[0031] When the mixed solution is stirred, the temperature of the mixed solution is preferably 15°C to 35°C. The time for stirring the mixed solution is not particularly limited, but is set to, for example, 3 to 24 hours until the generation of bubbles subsides.

[0032] Step A can be carried out under an atmospheric air atmosphere. However, since a large amount of carbon dioxide is generated in Step A, it is preferable to carry out Step A in an open system.

[0033] "Process B" In step B, a precursor ion exchange resin in which lithium ions are coordinated with the cation exchange resin is recovered from the aqueous solution containing the cation exchange resin and lithium carbonate after stirring.

[0034] "Process C" In step C, the precursor ion exchange resin recovered in step B is washed with water.

[0035] The water is not particularly limited, and tap water or distilled water may be used.

[0036] The number of times the precursor ion exchange resin is washed with water is not particularly limited, but is preferably 10 times or more.

[0037] "Process D" In step D, the precursor ion exchange resin and magnesium diboride are stirred and mixed in an aqueous solution containing a polar organic solvent to disperse the precursor ion exchange resin and magnesium diboride in the polar organic solvent, thereby preparing a first dispersion.

[0038] The polar organic solvent is not particularly limited, and examples thereof include acetonitrile, N,N-dimethylformamide, etc. Among these, acetonitrile is preferred because it does not contain oxygen.

[0039] The concentration of the polar organic solvent in the aqueous solution is preferably 50% to 70%, more preferably 60%. If the concentration is below the lower limit, components derived from the second supernatant of the second product will precipitate and will not be able to be recovered as a filtrate, whereas if the concentration is above the upper limit, the ion exchange efficiency will decrease.

[0040] The concentration of the precursor ion exchange resin in the mixed solution is preferably 200 mL / L (0.4 mol / L as ion exchange capacity) to 600 mL / L (1.2 mol / L as ion exchange capacity), more preferably 300 mL / L (0.6 mol / L as ion exchange capacity). However, the concentration is not necessarily limited as long as stirring is possible.

[0041] The concentration of magnesium diboride in the aqueous solution is preferably such that the ion exchange capacity of the precursor ion exchange resin and the magnesium ion concentration in the magnesium diboride are equivalent. Note that Mg is divalent. Since lithium is monovalent, twice the amount of Mg is required. If the amount is less than equivalent, the yield will decrease, but if the amount is more than equivalent, unreacted magnesium diboride will remain, reducing the amount of second precipitate in the second product.

[0042] In step D, the precursor ion exchange resin and magnesium diboride are introduced into an aqueous solution containing a polar organic solvent, and the first dispersion containing the aqueous solution containing a polar organic solvent, the precursor ion exchange resin, and magnesium diboride is stirred to thoroughly contact the precursor ion exchange resin and magnesium diboride. This causes ion exchange between the magnesium ions constituting the magnesium diboride and the lithium ions of the functional group α of the precursor ion exchange resin, producing a lithium diboride sheet-containing material having a two-dimensional network formed by boron atoms and lithium atoms derived from the functional group α of the ion exchange resin.

[0043] In step D, it is preferable to gently proceed with the ion exchange reaction between the magnesium ions constituting magnesium diboride and the lithium ions of the functional group α of the precursor ion exchange resin without applying ultrasound or the like to the first dispersion.

[0044] When the first dispersion is stirred, the temperature of the first dispersion is preferably 15°C to 35°C. The time for stirring the first dispersion is not particularly limited, but is preferably, for example, 3 hours or more and 168 hours or less, and particularly preferably 72 hours.

[0045] Step D is preferably carried out under an inert atmosphere of an inert gas such as nitrogen (N2) or argon (Ar).

[0046] "Process E" In step E, after the stirring in step D is completed, the first dispersion is filtered using a membrane filter or the like, a first supernatant is extracted, and the first supernatant is concentrated and dried to obtain a first product.

[0047] "Process F" In step F, the first product is mixed with a polar organic solvent to prepare a second dispersion, and the second dispersion is centrifuged to obtain a second supernatant and a second precipitate.

[0048] The polar organic solvent is not particularly limited, and examples thereof include acetonitrile, N,N-dimethylformamide, etc. Among these, acetonitrile is preferred because it does not contain oxygen.

[0049] The second dispersion may be centrifuged by a general centrifugal separator.

[0050] "Process G" In step G, the second supernatant and the second precipitate are each concentrated and dried to obtain a second product.

[0051] The resulting second product is the lithium diboride sheet-containing material of the above-described embodiment.

[0052] The obtained lithium diboride sheet-containing material contains the by-product LiH2B6 and the main component LiB2.

[0053] Examples of methods for analyzing the product obtained by the method for producing a lithium diboride sheet-containing material of this embodiment include X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and observation by energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) performed within a transmission electron microscope.

[0054] In X-ray photoelectron spectroscopy (XPS), for example, an X-ray photoelectron spectrometer (product name: JPS9010TR) manufactured by JEOL is used to irradiate the surface of the product with X-rays and measure the energy of the photoelectrons generated, thereby analyzing the constituent elements of the product and their electronic states. In this analysis, if photoelectrons with the energy of photoelectrons originating from magnesium, which constitutes the raw material magnesium diboride, are hardly detected, and only photoelectrons with the energy of photoelectrons originating from boron are detected, then it can be said that the product is composed of boron.

[0055] In observations using a transmission electron microscope (TEM), for example, a JEOL transmission electron microscope (product name: JEM-2100F TEM / STEM) is used to observe the product and analyze its shape (appearance). If a film-like (sheet-like) substance is observed in this analysis, the product can be said to be a two-dimensional sheet-like substance. By performing energy dispersive X-ray analysis (EDS) in the transmission electron microscope, the presence or absence of metal elements can be observed in the TEM-observed portion of the product. Furthermore, by performing electron energy loss spectroscopy (EELS) in the transmission electron microscope, the constituent elements can be observed in the TEM-observed portion of the product. If only X-ray energy attributable to boron is detected in this analysis, the product can be said to be composed of boron.

[0056] In inductively coupled plasma (ICP) emission spectrometer inductively coupled plasma mass spectrometry (ICP-MS), for example, an Agilent inductively coupled plasma mass spectrometer (trade name: Agilent 5800, and trade name: Ion Chromatograph ICS-1600, manufactured by Dionex) is used. An inductively coupled plasma (hereinafter referred to as ICP) generated by applying high-frequency power to argon (Ar) gas is used as the ion source. A liquid sample is atomized and introduced into the ICP, and the elements in the sample ionized by the plasma are separated and detected by a mass spectrometer (MS). If only lithium ions and boron ions are detected in this analysis, it can be said that the product is composed of boron and lithium.

[0057] In nuclear magnetic resonance (NMR) analysis, for example, an Oxford Instruments tabletop nuclear magnetic resonance analyzer (product name: X-Pluse) is used to apply a magnetic field to a sample solution dissolved in a heavy solvent, and when external electromagnetic waves are irradiated, the phenomenon in which atomic nuclei absorb specific electromagnetic waves according to their respective chemical environments (resonance phenomenon) is observed. In this analysis, if signals from Li and B nuclei are observed but no signal from H nuclei is observed, it can be said that the product is composed of boron and lithium.

[0058] According to the method for producing a lithium diboride sheet-containing material of this embodiment, the above-mentioned lithium diboride sheet-containing material can be easily produced. [Example]

[0059] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0060] [Example] 60 mL of cation exchange resin was washed with distilled water. In an air atmosphere, 60 mL of cation exchange resin and 4.4 g (equivalent to 0.06 mol) of lithium carbonate (Li2CO3) were stirred in 200 mL of distilled water in a flask for 24 hours at 25°C. Because a large amount of carbon dioxide gas was generated during this process, the stopcock of the flask was left open. After stirring, only the solution containing the cation exchange resin and lithium carbonate was discarded, and the cation exchange resin was washed with water at least 10 times to recover the precursor ion exchange resin in which lithium ions were coordinated to the cation exchange resin. The precursor ion exchange resin and 1.0055 g of magnesium diboride (MgB2) were stirred and mixed in 200 mL of a 60% aqueous acetonitrile solution to disperse the precursor ion exchange resin and MgB2 in the aqueous acetonitrile solution, and the mixture was stirred at 310 rpm for 3 days to prepare a first dispersion. The first supernatant of the first dispersion was filtered through a 0.2 μm membrane filter for extraction, and the first supernatant was concentrated and dried to obtain a first product. The first product was mixed with 10 mL of acetonitrile to prepare a second dispersion. The second dispersion was centrifuged at 5000 rpm for 5 minutes using a centrifuge to obtain a second supernatant and a second precipitate. The second supernatant and the second precipitate were concentrated to give 118.8 mg of LiH2B6 (dark yellow powder) and 241.2 mg of LiB2 (white powder), respectively.

[0061] [evaluation] "Infrared spectroscopy" The resulting product was analyzed using an infrared spectrometer (product name: FTIR ALPHA II, manufactured by Bruker). The analytical results for the white powder are shown in Figure 2. The analytical results for the dark yellow powder are shown in Figure 3. From the results shown in Figure 2, although B-O stretching vibrations were also detected, B-B stretching vibrations were mainly detected. From the results shown in Figure 3, B-H stretching vibrations and B-B stretching vibrations were mainly detected.

[0062] "Thermal desorption gas analysis" The resulting product was subjected to thermal desorption spectrometry (TDS). The resulting product was heated from 25°C to 1200°C at a rate of 10°C / min, and the released gas was sampled and subjected to mass analysis using a quadrupole mass analyzer. The amount of released hydrogen (mass number 2) was measured. The analysis results for the white powder are shown in Figure 4. The analysis results for the dark yellow powder are shown in Figure 5. The results shown in Figure 4 indicate that hydrogen was not released from the white powder, and that the white powder does not contain hydrogen. The results shown in Figure 5 indicate that hydrogen was released from the dark yellow powder, and that the dark yellow powder contained hydrogen.

[0063] "X-ray diffraction" The obtained product was analyzed using an X-ray diffraction device (product name: MINI FLEX, manufactured by Rigaku Corporation). The analysis results for the white powder are shown in Figure 6. The analysis results for the dark yellow powder are shown in Figure 7. From the results shown in Figure 6, it was found that the white powder was a substance composed of an amorphous structure. From the results shown in Figure 7, it was found that the dark yellow powder was a substance composed of an amorphous structure.

[0064] "Ultraviolet-visible absorption spectroscopy" The obtained product was subjected to ultraviolet-visible absorption spectroscopy using an ultraviolet-visible absorption spectrometer (product name: Duett, manufactured by HORIBA). Acetonitrile was used as the solvent. The concentration of the product in the solution dissolved in acetonitrile was set to 1 mg / mL. The results are shown in Figure 8. The results shown in Figure 8 show that the white powder has lower absorption around 320 nm than the dark yellow powder and magnesium diboride. This indicates that the introduction of lithium has changed the light absorption characteristics.

[0065] "Transmission electron microscope observation" The obtained white powder was observed using a transmission electron microscope (product name: JEM-2100F TEM / STEM) manufactured by JEOL Ltd. The observation results are shown in FIGS. From the results shown in Figure 9, wrinkles characteristic of two-dimensional sheets can be observed in the obtained white powder, which suggests that the obtained white powder forms a two-dimensional sheet. From the results shown in Figure 10, wrinkles characteristic of two-dimensional sheets can be observed in the obtained white powder, which suggests that the obtained white powder forms a two-dimensional sheet. From the results shown in Figure 11, it was found that boron is distributed throughout the white powder.

[0066] "Electron Energy Loss Spectroscopy" The obtained white powder was subjected to electron energy loss spectroscopy analysis using a transmission electron microscope (product name: JEM-2100F TEM / STEM) manufactured by JEOL Ltd. The results are shown in FIG. From the results shown in Figure 12, the obtained white powder detected X-ray energy due to boron (B), slightly detected X-ray energy due to oxygen (O), and did not detect X-ray energy due to carbon (C).

[0067] "Ultraviolet-visible absorption spectroscopy" The obtained white powder was subjected to UV-visible absorption spectroscopy using a UV-visible absorption spectrometer (product name: Duett, manufactured by HORIBA). Acetonitrile was used as the solvent. The concentrations of the white powder in the solution prepared by dissolving the product in acetonitrile were 1.0 mg / mL, 2.5 mg / mL, 5 mg / mL, 10 mg / mL, 25 mg / mL, 50 mg / mL, 75 mg / mL, 100 mg / mL, and 150 mg / mL. The results are shown in Figure 13. The results shown in FIG. 13 show that the absorption wavelength increases as the concentration of the white powder increases.

[0068] "Measurement of molar extinction coefficient" The molar absorption coefficient of the obtained white powder was measured using an Excitation-Emission Matrix Spectroscopy (EEM) device (trade name: Duetta, manufactured by Horiba). The results are shown in Figure 14. The results shown in Figure 14 show that the luminescence characteristics are different from those of the borohydride sheet.

[0069] "Elemental analysis" The resulting product was subjected to elemental analysis using a high-frequency inductively coupled plasma (ICP) emission spectrometer (trade name: Agilent 5800, manufactured by Agilent, and trade name: Ion Chromatograph ICS-1600, manufactured by Dionex). The results are shown in Table 1.

[0070] [Table 1]

[0071] From the results shown in Table 1, it was confirmed that LiB2 (white powder) contained Li and B in a molar ratio of 1:2.

[0072] "NMR measurement" The obtained white powder was analyzed using a Nuclear Magnetic Resonance apparatus (trade name: X-Pulse, manufactured by Oxford Instruments). 1 H-NMR and 11 B-NMR measurements were performed on the white powder in 50 mg / mL of deuterium oxide (DO). 1 The results of H-NMR measurement are shown in FIG. 11 The results of B-NMR measurement are shown in Figure 16. From the results shown in Figure 15, no hydrogen was observed in the white powder. From the results shown in Figure 16, it was found that the white powder contained boron.

[0073] "NMR measurement" The obtained white powder was analyzed using a Nuclear Magnetic Resonance apparatus (trade name: X-Pulse, manufactured by Oxford Instruments). 7 Li-NMR measurements were performed on the white powder in 50 mg / mL of heavy water (DO). LiB2 7 The results of Li-NMR measurements are shown in Figure 17. 7 The results of Li-NMR are shown in Figure 18.7 The results of Li-NMR are shown in Figure 19. 7 The results of Li-NMR measurements are shown in FIG. From the results shown in Figures 17 to 20, the 7 Since peaks are observed at almost the same shift values ​​in the Li-NMR and Li-NMR of LiB2, it is believed that all lithium exists as ions.

[0074] "X-ray photoelectron spectroscopy" The bond energy of the obtained product was measured using an X-ray photoelectron spectrometer (product name: JPS 9010 TR, manufactured by JEOL Ltd.). The measurement results for the white powder are shown in Figure 21. The measurement results for the dark yellow powder are shown in Figure 22. From the results shown in Figure 21, it was confirmed that the material other than the surface oxide was negatively charged boron. From the results shown in Figure 22, it was confirmed that the boron was negatively charged. [Industrial Applicability]

[0075] The lithium diboride sheet-containing material of the present invention can be used as a hydrogen storage material, an electrode material, etc.

Claims

1. (Lib ２ ) ｎ (n≧12), The two-dimensional network is a lithium diboride sheet-containing material in which boron atoms are arranged in a hexagonal ring, the hexagons formed by the boron atoms are connected to form a mesh, and two lithium atoms have a portion where the center of the boron hexagon is sandwiched between them.

2. Step A: stirring a cation exchange resin and lithium carbonate in water; a step B of recovering a precursor ion exchange resin in which lithium ions are coordinated with the cation exchange resin from the aqueous solution containing the cation exchange resin and the lithium carbonate after stirring; Step C of washing the precursor ion exchange resin with water; a step D of stirring the precursor ion exchange resin and magnesium diboride in an aqueous solution containing a polar organic solvent to form a first dispersion; a step E of, after completing the stirring in the step D, filtering and extracting a first supernatant of the first dispersion, and concentrating and drying the first supernatant to obtain a first product; a step F of mixing the first product with a polar organic solvent to prepare a second dispersion, and centrifuging the second dispersion to obtain a second supernatant and a second precipitate; and a step G of concentrating and drying the second supernatant and the second precipitate, respectively, to obtain a second product.

3. 3. The method for producing a lithium diboride sheet-containing material according to claim 2, wherein the polar organic solvent is acetonitrile.

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