2D particles, conductive films, conductive pastes and composite materials

Abstract

The purpose of the present invention is to provide a two-dimensional particle which exhibits high electrical-conductivity and which enables an electrically-conductive film that exhibits moisture resistance to be realized. This two-dimensional particle has one or more layers and contains Li atoms. Said layers include: a layer main body represented by formula MmXn (in the formula, M is at least one type of metal belonging to groups 3, 4, 5, 6 and 7, X is a carbon atom, a nitrogen atom or a combination of these, n is 1-4, and the value of m is greater than the value of n and is 5 or less); and a modification or terminal T present at the surface of the layer main body (T is at least one type selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom). The Li atoms include a first component and a second component having a higher chemical shift, as measured using 7Li NMR, than the first component. The proportion of the first component is 17-70 atom% relative to the total amount of the first component and the second component.

Description

[Technical Field]

[0001] The present disclosure relates to two-dimensional particles, conductive films, conductive pastes and composite materials. [Background technology]

[0002] In recent years, MXene has attracted attention as a novel electrically conductive material. MXene is a type of so-called two-dimensional material, and as described below, it is a layered material having the form of one or more layers. Generally, MXene has the form of particles of such layered materials (which may include powders, flakes, nanosheets, etc.).

[0003] Currently, various research efforts are being conducted to apply MXene to various electrical devices. Toward these applications, it is necessary to further improve the conductivity and moisture resistance of materials containing MXene. As part of this research, cleaning methods for MXene are being investigated.

[0004] In Non-Patent Document 1, Li was obtained by washing MXene in the presence of an acid. + It is stated that it can be removed. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Hongwu Chen, et al., "Pristine Titanium Carbide MXene Films with Environmentally Stable Conductivity and Superior Mechanical Strength" Adv. Mater. 2020, 30, 1906996 Summary of the Invention [Problem to be solved by the invention]

[0006] In the MXene described in Non-Patent Document 1, Li + Although moisture is removed, the conductivity decreases by about 20% due to moisture absorption. Furthermore, the conductivity of the film of MXene described in Non-Patent Document 1 is not fully satisfactory.

[0007] The present disclosure aims to provide two-dimensional particles that can realize conductive films having high conductivity and moisture resistance, as well as conductive films, conductive pastes, and conductive composite materials that use such two-dimensional particles. [Means for solving the problem]

[0008] The present disclosure includes the following. [1] A two-dimensional particle having one or more layers, Contains Li atoms, The layer may comprise a compound having the following formula: M m X n (wherein M is at least one Group 3, 4, 5, 6, or 7 metal; X is a carbon atom, a nitrogen atom, or a combination thereof; n is between 1 and 4, m is greater than n and less than or equal to 5) and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, The Li atom is a first component and 7 and a second component having a larger chemical shift as measured by Li NMR, Two-dimensional particles, wherein a ratio of the first component to a total of the first component and the second component is 17 atomic % or more and 70 atomic % or less. [2] Ibid. 7 The chemical shift of the first component measured by Li NMR is less than 0.6 ppm, 7 The two-dimensional particle according to [1], wherein the chemical shift of the second component measured by Li NMR is 0.6 ppm or more and 2.0 ppm or less. [3] The two-dimensional particle according to [1] or [2], which contains phosphorus atoms. [4] The two-dimensional particle according to any one of [1] to [3], wherein the content of the phosphorus atoms is 0.1% by mass or more and 14% by mass or less. [5] The phosphorus atom is PO4 3- The two-dimensional particle according to any one of [1] to [4], which has the form: [6] The two-dimensional particle according to any one of [1] to [5], which has an average thickness of 1 nm or more and 10 nm or less. [7] A conductive film comprising the two-dimensional particles according to any one of [1] to [6]. [8] A conductive paste containing the two-dimensional particles according to any one of [1] to [6]. [9] A conductive composite material comprising the two-dimensional particle according to any one of [1] to [6] and a resin. [Effects of the Invention]

[0009] The present disclosure can provide two-dimensional particles that can realize conductive films having high conductivity and moisture resistance. The present disclosure can also provide conductive films, conductive pastes, and conductive composite materials that use such two-dimensional particles. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are schematic cross-sectional views showing MXene particles of layered material in one embodiment of the present disclosure, where (a) shows a single-layer MXene particle and (b) shows a multi-layer (exemplarily two-layer) MXene particle. [Figure 2] 1 is a schematic cross-sectional view showing a conductive film according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Embodiment 1: Two-dimensional particles) Two-dimensional particles according to one embodiment of the present disclosure will be described in detail below, but the present disclosure is not limited to such an embodiment.

[0012] The two-dimensional particles in this embodiment are two-dimensional particles of a layered material having one or more layers and containing Li atoms.

[0013] The layer has the following formula: M m X n (wherein M is at least one Group 3, 4, 5, 6, or 7 metal; X is a carbon atom, a nitrogen atom, or a combination thereof; n is between 1 and 4, m is greater than n and less than or equal to 5) and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on a surface of the layer body (more specifically, on at least one of two opposing surfaces of the layer body), The Li atom is the first component, 7 a second component whose chemical shift measured by Li NMR (nuclear magnetic resonance) is larger than that of the first component; The proportion of the first component in the total of the first component and the second component is 17 atomic % or more and 70 atomic % or less.

[0014] As a result, a conductive film obtained using the two-dimensional particles of the present disclosure has high conductivity and good moisture resistance. In the present disclosure, moisture resistance means that the conductivity can be maintained even when left under high humidity conditions for a long period of time. Furthermore, an electrode including such a conductive film can be used in applications requiring high conductivity and high moisture resistance, such as an antenna electrode, particularly an electrode for an RFID (radio frequency identifier).

[0015] In the present disclosure, when an "atom" refers to a certain element, the oxidation number of the element is not limited to 0, but may be any number within the range of oxidation numbers that the element can take.

[0016] The layered material may be understood as a layered compound and is referred to as "M m X n T s ", where s is any number, and conventionally, x or z may be used instead of s. Typically, n can be 1, 2, 3, or 4, but is not limited thereto.

[0017] In the above formula for MXene, M is preferably at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn, and more preferably at least one selected from the group consisting of Ti, V, Cr, and Mo.

[0018] MXene is a compound represented by the formula: M m X n However, it is known that it can be expressed as follows: Sc2C, Ti2C, Ti2N, Zr2C, Zr2N, Hf2C, Hf2N, V2C, V2N, Nb2C, Ta2C, Cr2C, Cr2N, Mo2C, Mo 1.3 C, Cr 1.3 C, (Ti,V)2C, (Ti,Nb)2C, W2C, W 1.3 C, Mo2N, Nb 1.3 C, Mo 1.3 Y 0.6 C (in the above formula, "1.3" and "0.6" mean approximately 1.3 (= 4 / 3) and approximately 0.6 (= 2 / 3), respectively), Ti3C2, Ti3N2, Ti3(CN), Zr3C2, (Ti,V)3C2, (Ti2Nb)C2, (Ti2Ta)C2, (Ti2Mn)C2, Hf3C2, (Hf2V)C2, (Hf2Mn)C2, (V2Ti)C2, (Cr2Ti)C2, (Cr2V)C 2, (Cr2Nb)C2, (Cr2Ta)C2, (Mo2Sc)C2, (Mo2Ti)C2, (Mo2Zr)C2, (Mo2Hf)C2, (Mo2V)C2, (Mo2Nb)C2, (Mo2Ta)C2, (W2Ti)C2, (W2Zr)C2, (W2Hf)C2, Ti4N3, V4C3, Nb4C3, Ta4C3, (Ti,Nb)4C3, (Nb,Zr)4C3, (Ti2Nb2)C3, (Ti2Ta2)C3, (V2Ti2)C3, (V2Nb2)C3, (V2Ta2)C3, (Nb2Ta2)C3, (Cr2Ti2)C3, (Cr2V 2)C3, (Cr2Nb2)C3, (Cr2Ta2)C3, (Mo2Ti2)C3, (Mo2Zr2)C3, (Mo2Hf2)C3, (Mo2V2)C3, (Mo2Nb2)C3, (Mo2Ta2)C3, (W2Ti2)C3, (W2Zr2)C3, (W2Hf2)C3, (Mo 2.7 V 1.3 ) C3 (In the above formula, "2.7" and "1.3" mean approximately 2.7 (= 8 / 3) and approximately 1.3 (= 4 / 3), respectively.)

[0019] Typically, in the above formula, M can be titanium or vanadium, and X can be a carbon atom or a nitrogen atom. For example, the MAX phase is Ti3AlC2, and MXene is Ti3C2T s (In other words, M is Ti, X is C, n is 2, and m is 3).

[0020] In the present disclosure, MXene may contain a relatively small amount of A atoms derived from the MAX phase of the precursor, for example, 10% by mass or less of the original A atoms. The amount of residual A atoms is preferably 8% by mass or less, more preferably 6% by mass or less. However, even if the amount of residual A atoms exceeds 10% by mass, this may not be a problem depending on the application and use conditions of the two-dimensional particles.

[0021] In this disclosure, the layer may be referred to as an MXene layer, and the two-dimensional particles may be referred to as MXene two-dimensional particles or MXene particles.

[0022] The two-dimensional particle of this embodiment is an aggregate including one layer of MXene particles (hereinafter simply referred to as "MXene particles") 10a (single-layer MXene particles) as shown in FIG. 1(a). More specifically, the MXene particles 10a are m X nThe layer body (M m X n The MXene layer 7a has a main layer 1a and modifications or terminations T3a, 5a present on the surface of the main layer 1a (more specifically, on at least one of the two surfaces facing each other in each layer). m X n T s ", where s is an arbitrary number.

[0023] The two-dimensional particles of this embodiment may contain one or more layers. Examples of MXene particles with multiple layers (multilayer MXene particles) include, but are not limited to, two-layer MXene particles 10b, as shown schematically in FIG. 1(b). Elements 1b, 3b, 5b, and 7b in FIG. 1(b) are the same as elements 1a, 3a, 5a, and 7a in FIG. 1(a). Two adjacent MXene layers (e.g., 7a and 7b) in a multilayer MXene particle do not necessarily need to be completely separated and may be partially in contact. The MXene particle 10a may be a single layer in which the multilayer MXene particles 10b are individually separated, or may contain unseparated multilayer MXene particles 10b, forming a mixture of the single-layer MXene particles 10a and the multilayer MXene particles 10b.

[0024] Although this embodiment is not limited thereto, the thickness of each layer (corresponding to the above-mentioned MXene layers 7a and 7b) contained in the MXene particle is, for example, 0.8 to 5 nm, particularly 0.8 to 3 nm (this can vary mainly depending on the number of M atomic layers contained in each layer). The interlayer distance (or gap dimension, shown as Δd in FIG. 1(b)) for each individual stack of the multilayer MXene particle that may be contained may be, for example, 0.8 to 10 nm, particularly 0.8 to 5 nm, more particularly about 1 nm, and the total number of layers may be 2 to 20,000.

[0025] The two-dimensional particles of this embodiment preferably contain multilayer MXene particles with a small number of layers obtained through a delamination process. The term "small number of layers" refers to, for example, six or fewer MXene layers. Furthermore, the thickness of the multilayer MXene particles with a small number of layers in the stacking direction is preferably 15 nm or less, and more preferably 10 nm or less. Hereinafter, these "multilayer MXene particles with a small number of layers" may be referred to as "small-layer MXene particles." Furthermore, single-layer MXene particles and small-layer MXene particles may be collectively referred to as "single-layer / small-layer MXene particles."

[0026] The two-dimensional particles of this embodiment preferably contain single-walled MXene particles and few-walled MXene particles, i.e., single-walled and few-walled MXene particles. In the two-dimensional particles of this embodiment, the proportion of single-walled and few-walled MXene particles with a thickness of 15 nm or less is preferably 90% by volume or more, more preferably 95% by volume or more.

[0027] The Li atom is a first component, 7 The composition further comprises a second component having a larger chemical shift as measured by Li NMR than the first component, and the proportion of the first component in the total of the first and second components is 17 atomic % or more and 70 atomic % or less, thereby achieving a conductive film having high conductivity and moisture resistance.

[0028] The ratio of the first component to the total of the first and second components is: 7 It can be measured by Li NMR. For example, 7 In the Li NMR spectrum, when the relative area of ​​the peak attributed to the first component is S1 and the relative area of ​​the peak attributed to the second component is S2, the ratio of the first component to the total of the first and second components can be calculated as S1 / (S1+S2). 7 The cumulative delay time for Li NMR measurement is 4 seconds.

[0029] Without being bound by any particular theory, it is believed that the first component is bound by water and exists in a state with a low degree of freedom, while the second component is loosely adsorbed to the layer surface of the two-dimensional particle and exists in a state with a relatively high degree of freedom. The coexistence of the first and second components in a specific abundance ratio is believed to achieve a single layer and a small number of layers while preventing water adsorption, thereby demonstrating high electrical conductivity and high moisture resistance.

[0030] The degree of freedom of the first and second components can be confirmed, for example, by comparing the T2 relaxation times (spin-spin relaxation times). Without being bound by any particular theory, it is believed that the T2 relaxation time is related to the mobility of each component, and the shorter the T2 relaxation time, the stronger the interaction with the substance. In one embodiment, the T2 relaxation time of the first component is shorter than the T2 relaxation time of the second component; for example, the T2 relaxation time of the first component is 0.6 ms or less, and the T2 relaxation time of the second component is 1.2 ms or more. From the comparison of the T2 relaxation times of the first and second components, it is believed that the first component interacts more strongly with the substance than the second component.

[0031] In one aspect, 7 The chemical shift of the first component measured by Li NMR can be, for example, less than 0.6 ppm, furthermore, from −0.2 ppm to 0.55 ppm, particularly from −0.15 ppm to 0.5 ppm. 7 The chemical shift of the second component measured by Li NMR can be, for example, from 0.6 ppm to 2.0 ppm, and even from 0.7 ppm to 1.7 ppm. 7 The reference substance for Li NMR measurements is Li in a 1 mol / L LiCl aqueous solution.

[0032] In the present disclosure, 7 The chemical shift of the first component measured by Li NMR is 7 In the Li NMR spectrum, the chemical shift value of the peak assigned to the first component is shown. 7 The chemical shift of the second component measured by Li NMR is 7This represents the chemical shift value of the peak assigned to the second component in the Li NMR spectrum. The chemical shift of the second component is 7 The chemical shift of the peak attributed to the second component is larger than that of the first component measured by Li NMR, and the peak attributed to the second component is larger than that of the first component. 7 Located on the downfield side of the Li NMR spectrum. 7 In Li NMR, when a peak attributed to the first component and a peak attributed to the second component overlap, the peaks may be separated by regression using a Lorentz curve.

[0033] The Li atoms are typically present on the layer, i.e., they may be in contact with the layer or may be present on the layer via another element.

[0034] The content of Li atoms in the two-dimensional particles (e.g., the sum of the layer and the metal cations) may be, for example, 0.1% by mass or more and 20% by mass or less, further 0.1% by mass or more and 10% by mass or less, particularly 0.2% by mass or more and 5% by mass or less, and particularly 0.2% by mass or more and 3% by mass or less.

[0035] The Li atom content can be measured by, for example, inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0036] In one embodiment, the two-dimensional particles contain phosphorus atoms. The presence of phosphorus atoms is believed to facilitate the presence of Li atoms, the second component, which contributes to high electrical conductivity and moisture resistance. The phosphorus atom content may be, for example, 0.1% by mass to 14% by mass, preferably 0.15% by mass to 5% by mass, and particularly preferably 0.15% by mass to 1% by mass.

[0037] The phosphorus atom may be present, for example, in the form of an anion containing a phosphorus atom, in particular PO4 3- The anion containing a phosphorus atom may be bonded to M in the layer. Furthermore, without being bound to a particular theory, it is believed that the Li atom loosely adsorbed on the anion containing a phosphorus atom corresponds to the second component.

[0038] In one embodiment, the ratio of (average major axis length of the two-dimensional surfaces of the two-dimensional particles) / (average thickness length of the two-dimensional particles) is 1.2 or more, preferably 1.5 or more, and more preferably 2 or more. The average major axis length of the two-dimensional surfaces of the two-dimensional particles and the average thickness length of the two-dimensional particles may be determined by the method described below.

[0039] (Average value of the longest diameter of the two-dimensional surface of a two-dimensional particle) The two-dimensional particles of this embodiment have an average major axis of the two-dimensional surface of 1 μm to 20 μm. Hereinafter, the average major axis of the two-dimensional surface may be referred to as the "average flake size."

[0040] The larger the average flake size, the higher the conductivity of the conductive film. The two-dimensional particles of this embodiment have a large average flake size of 1.0 μm or more. Therefore, a film formed using these two-dimensional particles, for example, a film obtained by laminating these two-dimensional particles, can achieve a conductivity of 2,000 S / cm or more. The average long diameter of the two-dimensional surface is preferably 1.5 μm or more, more preferably 2.5 μm or more. When MXene is delaminate-treated by ultrasonic treatment, the majority of the MXene is reduced in diameter to approximately several hundred nanometers in the long diameter. Therefore, a film formed from the single-layer MXene delaminated by ultrasonic treatment is thought to have low conductivity.

[0041] The average value of the major axis of the two-dimensional surface is 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less, from the viewpoint of dispersibility in the dispersion medium.

[0042] The longest diameter of the two-dimensional plane refers to the longest diameter when each MXene particle is approximated to an ellipse in an electron microscope photograph, as shown in the Examples below, and the average longest diameter of the two-dimensional plane refers to the number average of the longest diameters of 80 or more particles. As the electron microscope, a scanning electron microscope (SEM) or a transmission electron microscope (TEM) can be used.

[0043] The average major axis of the two-dimensional particles of this embodiment may be measured by dissolving the conductive film containing the two-dimensional particles in a solvent and dispersing the two-dimensional particles in the solvent, or by measuring the average major axis of the conductive film from an SEM image.

[0044] (average thickness of two-dimensional particles) The average thickness of the two-dimensional particles of this embodiment is preferably 1 nm or more and 15 nm or less. The thickness is preferably 10 nm or less, more preferably 7 nm or less, and even more preferably 5 nm or less. On the other hand, considering the thickness of single-layer MXene particles, the lower limit of the thickness of the two-dimensional particles can be 1 nm.

[0045] The average thickness of the two-dimensional particles is determined as a number-average size (for example, a number-average of at least 40 particles) based on atomic force microscope (AFM) or transmission electron microscope (TEM) photographs.

[0046] (Embodiment 2: Method for producing two-dimensional particles) Hereinafter, a method for producing two-dimensional particles according to one embodiment of the present disclosure will be described in detail, but the present disclosure is not limited to this embodiment.

[0047] The method for producing two-dimensional particles of this embodiment includes: (a) providing a predetermined precursor; (b) performing an etching treatment using an etching solution to remove at least some of the A atoms from the precursor; (c) performing a water washing treatment, which includes a step of washing the etched product obtained by the etching treatment with water; (d) performing an intercalation treatment, which includes a step of mixing the water-washed product obtained by the water washing with a metal-containing compound; (e) performing a delamination treatment, which includes a step of stirring the intercalation treatment product obtained by the intercalation treatment, to obtain two-dimensional particles; The etching solution contains phosphorus atoms, The metal-containing compound contains at least a Li atom.

[0048] Each step will be described in detail below.

[0049] ·Process (a) First, a predetermined precursor is prepared. The predetermined precursor that can be used in this embodiment is a MAX phase, which is a precursor of MXene. The following formula: M m AX n (wherein M is at least one Group 3, 4, 5, 6, or 7 metal; X is a carbon atom, a nitrogen atom, or a combination thereof; A is at least one element of Groups 12, 13, 14, 15, or 16; n is between 1 and 4, m is greater than n and less than or equal to 5) It is expressed as:

[0050] The above M, X, n, and m are as described in the first embodiment. A is at least one element of Groups 12, 13, 14, 15, and 16, and is usually an element of Group A, typically Group IIIA and Group IVA, and more specifically, can include at least one element selected from the group consisting of Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, S, and Cd, and is preferably Al.

[0051] The MAX phase is M m X n (each X may have a crystal lattice in which it is located in an octahedral array of M) and a layer composed of A atoms is located between them. In the MAX phase, typically when m=n+1, one layer of X atoms is arranged between each of the n+1 layers of M atoms (these are collectively referred to as "M m X n The repeating unit may have a layer of A atoms (also referred to as an "A atom layer") arranged as the next layer after the n+1th layer of M atoms, but is not limited thereto.

[0052] The MAX phase can be produced by a known method. For example, TiC powder, Ti powder, and Al powder are mixed in a ball mill, and the resulting mixed powder is sintered in an Ar atmosphere to obtain a sintered body (a block of MAX phase). The sintered body is then pulverized with an end mill to obtain a powdered MAX phase for the next step.

[0053] ·Process (b) In step (b), an etching treatment is carried out using an etching solution to remove at least some of the A atoms from the precursor.

[0054] The etching solution contains phosphorus atoms, particularly anions containing phosphorus atoms. This allows phosphorus atoms, for example, phosphorus atoms, particularly anions containing phosphorus atoms, to be bonded to M atoms. Furthermore, without being bound by a particular theory, it is believed that the inclusion of phosphorus atoms in the etching solution makes it easier for Li atoms, the second component, to exist. Furthermore, sufficient etching processing is possible, and in the subsequent intercalation processing, Li atoms are more easily intercalated. The form of the anions containing phosphorus atoms is not particularly limited, and they may exist as ions, such as H + It may be combined with a cation to exist as an acid, or may be combined with a cation to exist as a salt.

[0055] Anions containing phosphorus atoms include PO4 3- Examples include:

[0056] The etching solution preferably contains H3PO4 and may further contain HF. A specific example of the etching solution is a mixture of an aqueous solution of HF and an aqueous solution of H3PO4. The etching solution may further contain HCl and LiF.

[0057] In the above etching solution, anions containing phosphorus atoms, especially PO4 3- The concentration can be, for example, from 2 mol / L to 20 mol / L, further from 2.5 mol / L to 18 mol / L, and particularly from 3 mol / L to 15 mol / L.

[0058] In the etching solution, the concentration of HF can be, for example, from 2 mol / L to 20 mol / L, further from 2.5 mol / L to 18 mol / L, particularly from 2.5 mol / L to 15 mol / L.

[0059] In the etching solution, the sum of the concentration of the anion containing a phosphorus atom and the concentration of HF can be, for example, 7 mol / L or more and 30 mol / L or less, further 7.5 mol / L or more and 27 mol / L or less, particularly 8 mol / L or more and 25 mol / L or less.

[0060] The etching procedure and other conditions using the etching solution may be those conventionally used.

[0061] ·Process (c) The etched product obtained by the etching treatment is washed with water. Washing with water can sufficiently remove the acid used in the etching treatment. The amount of water to be mixed with the etched product and the washing method are not particularly limited. For example, adding water and stirring, centrifuging, etc. can be performed. Stirring methods include stirring using a hand shake, an automatic shaker, a shear mixer, a pot mill, etc. The degree of stirring, such as the stirring speed and stirring time, can be adjusted depending on the amount and concentration of the acid-treated product to be treated. The water washing can be performed one or more times. Preferably, water washing is performed multiple times. For example, steps (i) to (iii) of (i) adding water (to the etched product or the remaining precipitate obtained in (iii) below) and stirring, (ii) centrifuging the stirred product, and (iii) discarding the supernatant after centrifugation can be performed two or more times, for example, 15 or less times.

[0062] ·Process (d) An intercalation treatment is carried out, which includes a step of mixing the water-washed product obtained by the water washing with a metal-containing compound containing metal ions, thereby intercalating the metal ions between the layers.

[0063] Examples of the metal ions include monovalent metal ions, specifically alkali metal ions such as lithium ions, sodium ions, and potassium ions, copper ions, silver ions, and gold ions. Examples of metal-containing compounds containing the metal ions include iodides, phosphates, sulfide salts including sulfates, nitrates, acetates, and carboxylates of the metal ions.

[0064] The metal ions include at least lithium ions. The metal-containing compound preferably includes a metal compound containing lithium ions, more preferably an ionic compound of lithium ions, and even more preferably one or more of iodides, phosphates, and sulfides of lithium ions, and particularly preferably a phosphate of lithium ions. By using lithium ions as the metal ions, the resulting two-dimensional particles can contain Li atoms.

[0065] In the mixture for intercalation treatment obtained by mixing the water-washed product with a metal-containing compound, the content of the metal-containing compound can be, for example, from 0.001% to 10% by mass, more preferably from 0.01% to 1% by mass, and even more preferably from 0.1% to 1% by mass. When the content of the metal-containing compound is within the above range, the dispersibility in the mixture for intercalation treatment is good.

[0066] The specific method of intercalation treatment is not particularly limited, and for example, the water-washed product may be mixed with a metal-containing compound and stirred or left to stand. For example, stirring at room temperature may be used. Examples of the stirring method include a method using a stirring bar such as a stirrer, a method using a stirring blade, a method using a mixer, and a method using a centrifugal device. The stirring time can be set depending on the production scale of the single-walled / few-walled MXene particles, and can be set, for example, between 12 and 24 hours.

[0067] ·Process (e) In step (e), a delamination treatment is performed, which includes a step of stirring the intercalation product obtained by the intercalation treatment. The delamination treatment can result in a single layer or a few layers of MXene particles.

[0068] The conditions for the delamination treatment are not particularly limited, and can be performed by any known method. Examples of agitation methods include ultrasonic treatment, hand shaking, and stirring using an automatic shaker. The degree of agitation, such as the agitation speed and agitation time, can be adjusted depending on the amount and concentration of the material to be treated. For example, the above-mentioned intercalated slurry can be centrifuged to discard the supernatant, and then pure water can be added to the remaining precipitate, followed by stirring using, for example, hand shaking or an automatic shaker, to separate the layers. Removal of unexfoliated material can be achieved by centrifuging the slurry, discarding the supernatant, and then washing the remaining precipitate with water. For example, (i) pure water can be added to the remaining precipitate after discarding the supernatant, followed by stirring, (ii) centrifugation, and (iii) recovery of the supernatant. These steps (i) to (iii) can be repeated at least once, preferably at least twice, but not more than 10 times, to obtain a supernatant containing the single-layered or single-layered MXene particles before acid treatment as the delamination-treated product. Alternatively, the supernatant may be centrifuged, and the supernatant after centrifugation may be discarded to obtain clay containing single-layer and few-layer MXene particles before acid treatment as a delamination treatment product.

[0069] In the manufacturing method of this embodiment, phosphorus atoms may be present during delamination. Such phosphorus atoms may be present in the form of anions containing phosphorus atoms, such as PO4 3- In this case, the pure water added to the precipitate may be an aqueous phosphoric acid solution. The pH of such an aqueous phosphoric acid solution may be, for example, 2 to 5, or 2.5 to 4.5.

[0070] In one embodiment, phosphorus atoms may be present only during layer separation, and not during washing. For example, after centrifuging the slurry after intercalation and discarding the supernatant, a phosphoric acid aqueous solution may be used instead of the pure water added to the remaining precipitate, and pure water may be added in operation (i). In another embodiment, phosphorus atoms may be present during layer separation and washing. For example, after centrifuging the slurry after intercalation and discarding the supernatant, a phosphoric acid aqueous solution may be used instead of the pure water added to the remaining precipitate, and pure water may be added in operation (i).

[0071] In the manufacturing method of this embodiment, ultrasonic treatment is not required during the delamination treatment. If ultrasonic treatment is not performed, particle destruction is unlikely to occur, and it is easy to obtain single-layered or few-layered MXene particles with large planes parallel to the particle layers, i.e., large two-dimensional surfaces.

[0072] The delamination product obtained by stirring can be used as is as two-dimensional particles containing single-layer and few-layer MXene particles, and may be washed with water if necessary.

[0073] (Embodiment 3: Conductive film) The two-dimensional particles of this embodiment can be used in conductive films containing the two-dimensional particles. Such conductive films have high conductivity, high moisture resistance, and high smoothness. The conductive film of this embodiment will be described with reference to FIG. 2. While FIG. 2 illustrates a conductive film 30 obtained by laminating only two-dimensional particles 10, the conductive film is not limited to this. If necessary, the conductive film may contain additives such as binders that are added during film formation. The additives preferably account for 30% by volume or less of the conductive film (when dried), more preferably 10% by volume or less, even more preferably 5% by volume or less, and most preferably 0% by volume.

[0074] A conductive film can be produced without using a binder or the like by suction filtering the supernatant containing the two-dimensional particles obtained by the delamination, or by spraying the two-dimensional particles mixed with a dispersion medium to form a slurry of an appropriate concentration, followed by removing the dispersion medium by drying or the like, once or multiple times. The spraying method can be, for example, an airless spray method or an air spray method. Specific examples include spraying using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush. Examples of dispersion media that can be contained in the slurry include water; organic media such as N-methylpyrrolidone, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, dimethyl sulfoxide, ethylene glycol, and acetic acid.

[0075] Examples of the binder include acrylic resin, polyester resin, polyamide resin, polyolefin resin, polycarbonate resin, polyurethane resin, polystyrene resin, polyether resin, and polylactic acid.

[0076] The conductivity of the conductive film is preferably 2,000 S / cm or more, more preferably 5,000 S / m or more, and even more preferably 10,000 S / cm or more, and may be, for example, 100,000 S / cm or less, or even 50,000 S / cm or less.

[0077] The conductivity of the conductive film of this embodiment can be determined by substituting the thickness of the conductive film and the surface resistivity of the conductive film measured by the four-probe method into the following formula. Conductivity [S / cm] = 1 / (thickness of conductive film [cm] x surface resistivity of conductive film [Ω / sq.])

[0078] (Embodiment 4: Conductive paste and conductive composite material) Other applications of the two-dimensional particles of this embodiment include conductive pastes containing the two-dimensional particles and, if necessary, resins and additives (dispersion media, viscosity modifiers, etc.), and conductive composite materials containing the two-dimensional particles and resins. These are also suitable for applications that require high conductivity even under high humidity conditions.

[0079] Resins that can be contained in the conductive paste and conductive composite material include the same resins that can be contained in the conductive film. Dispersion media that can be contained in the conductive paste include water, and organic media such as N-methylpyrrolidone, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, dimethyl sulfoxide, ethylene glycol, and acetic acid.

[0080] (Embodiment 5: Electrode) The electrode according to this embodiment includes the conductive film. Such an electrode may be formed only from the conductive film, or may include the conductive film and, for example, a substrate.

[0081] The electrode of this embodiment is not limited to a specific form as long as it includes the conductive film. Examples of the electrode include those in a solid state and those in a flexible, soft state.

[0082] In the electrode of this embodiment, the conductive film may be exposed to the outside air so as to be in direct contact with the object to be measured, or may be covered with a substrate or the like.

[0083] When the electrode of this embodiment has a substrate, the conductive film and the substrate may be in direct contact. The material of the substrate is not particularly limited and may be, for example, an inorganic material such as ceramic or glass, or an organic material. Examples of such organic materials include flexible organic materials, specifically thermoplastic polyurethane elastomer (TPU), PET film, polyimide film, etc. Furthermore, the material of the substrate may be a fibrous material such as paper or cloth (for example, a sheet-like fibrous material).

[0084] (Electrode applications) The electrode of this embodiment can be used for any appropriate application. Examples include a counter electrode or reference electrode in electrochemical measurements, an electrode for an electrochemical capacitor, an electrode for a battery, an electrode for a biological body, an electrode for a sensor, and an electrode for an antenna. It can also be used for applications that require maintaining high conductivity (reducing the decrease in initial conductivity and preventing oxidation), such as electromagnetic shielding (EMI shielding). Details of these applications are described below.

[0085] The electrodes are not particularly limited, and may be, for example, capacitor electrodes, battery electrodes, biosignal sensing electrodes, sensor electrodes, antenna electrodes, etc. By using the conductive film, it is possible to obtain large-capacity capacitors and batteries, low-impedance biosignal sensing electrodes, and highly sensitive sensors and antennas even in a smaller volume (volume occupied by the device).

[0086] The capacitor may be an electrochemical capacitor. An electrochemical capacitor is a capacitor that utilizes a capacitance generated by a physicochemical reaction between an electrode (electrode active material) and ions (electrolyte ions) in an electrolyte solution, and can be used as a device for storing electrical energy (electricity storage device). The battery may be a chemical battery that can be repeatedly charged and discharged. The battery may be, for example, a lithium ion battery, a magnesium ion battery, a lithium sulfur battery, a sodium ion battery, or the like, but is not limited to these.

[0087] The biosignal sensing electrode is an electrode for acquiring a biosignal, and may be, for example, but not limited to, an electrode for measuring EEG (electroencephalogram), ECG (electrocardiogram), EMG (electromyogram), or EIT (electrical impedance tomography).

[0088] A sensor electrode is an electrode for detecting a target substance, state, abnormality, etc. The sensor may be, for example, a gas sensor, a biosensor (a chemical sensor that utilizes a molecular recognition mechanism of biological origin), etc., but is not limited to these.

[0089] The antenna electrode is an electrode for emitting electromagnetic waves into space and / or receiving electromagnetic waves in space. The antenna formed by the antenna electrode is not particularly limited to an antenna for mobile communication such as a mobile phone (so-called 3G, 4G, or 5G antenna), an antenna for RFID, or an antenna for NFC (Near Field Communication).

[0090] The electrode of this embodiment is preferably used as an antenna electrode. The electrode including the conductive film has high conductivity and high moisture resistance, and also has high smoothness as a conductive film. An electrode having such properties can be advantageously used to extend communication distances.

[0091] Although the two-dimensional particles according to one embodiment of the present disclosure have been described in detail above, various modifications are possible. Note that the two-dimensional particles according to the present disclosure may be produced by a method different from the production method according to the above embodiment, and that the production method of the two-dimensional particles according to the present disclosure is not limited to the method for producing the two-dimensional particles according to the above embodiment. [Example]

[0092] The present disclosure will be explained in more detail below with reference to examples, but the present disclosure is not limited thereto.

[0093] [Examples 1 to 8, Comparative Examples 1 and 2] [Creation of two-dimensional particles] In Examples 1 to 8 and Comparative Examples 1 and 2, two-dimensional particles were produced by sequentially carrying out the following steps, as detailed below: (1) preparation of precursor (MAX), (2) etching of the precursor, (3) washing, (4) intercalation, (5) delamination, and (6) washing with water.

[0094] (1) Preparation of precursor (MAX) TiC powder, Ti powder, and Al powder (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed in a 2:1:1 molar ratio in a ball mill containing zirconia balls for 24 hours. The resulting mixed powder was sintered at 1,350°C for 2 hours in an Ar atmosphere. The resulting sintered body (block) was then pulverized with an end mill to a maximum size of 40 μm or less. This yielded Ti3AlC2 particles as the precursor (MAX).

[0095] (2) Etching of precursor Using the Ti3AlC2 particles (powder) prepared by the above method, etching was carried out under the following etching conditions to obtain a solid-liquid mixture (slurry) containing solid components derived from the Ti3AlC2 powder. (Etching conditions) Precursor: Ti3AlC2 (passed through a 45 μm sieve) See Table 1 for the etching solution composition. Precursor input: 3.0g Etching container: 100mL Eye Boy Etching temperature: 35℃ Etching time: 24 hours Stirrer rotation speed: 400 rpm

[0096] (3) Cleaning The slurry was divided into two parts and placed in two 50 mL centrifuge tubes. The tubes were centrifuged at 3500 G for 5 minutes, and the supernatant was discarded. 35 mL of pure water was added to each tube, and the tubes were centrifuged again at 3500 G for 5 minutes, and the supernatant was removed. This procedure was repeated 11 times. After the final centrifugation, the supernatant was discarded, and the Ti3C2T s -Water medium clay was obtained.

[0097] (4) Intercalation Ti3C2T prepared by the above method s- 5.3g of 85% by mass phosphoric acid aqueous solution, 0.68g of Li3PO4, and 31.9g of pure water were added to the water medium clay, and the mixture was stirred at 20°C to 25°C for 24 hours to perform intercalation using lithium ions as the intercalator. The detailed conditions for intercalation are as follows: (Intercalation conditions) Ti3C2T s -Water medium clay (MXene after washing): 0.5g solids ·Metal-containing compound: Li3PO40.68g Intercalation vessel: 100mL Eye Boy ·Temperature: 20℃ or higher and 25℃ or lower (room temperature) Hours: 24 hours Stirrer rotation speed: 700 rpm

[0098] (5) Delamination The resulting slurry was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then recovered. 35 mL of a phosphoric acid solution adjusted to pH 3.5 was added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing monolayer MXene particles. This procedure was repeated four times to obtain a solution containing monolayer MXene particles. The resulting supernatant was then centrifuged at 4,300 G for 2 hours. The supernatant was then discarded, yielding a clay containing two-dimensional particles (monolayer MXene particles).

[0099] [Example 9] After the preparation of the precursor (MAX), the etching process, the cleaning process, and the delamination process were carried out in the same manner as in Example 1, the following step (5) was carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Examples 1 to 8 (2) Etching of precursor: same as in Examples 1 to 8 (3) Washing: Same as in Example 1 (4) Intercalation: Same as in Examples 1 to 8 (5) Delamination The slurry obtained after intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes, after which the supernatant was obtained. This supernatant was then centrifuged at 4,300 G for 2 hours, after which the supernatant was discarded, and clay containing two-dimensional particles (single-layer MXene particles) was obtained.

[0100] [Example 10] After the preparation of the precursor (MAX), the etching process, the cleaning process, and the delamination process were carried out in the same manner as in Example 1, the following step (5) was carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Examples 1 to 8 (2) Etching of precursor: same as in Examples 1 to 8 (3) Washing: Same as in Example 1 (4) Intercalation: Same as in Examples 1 to 8 (5) Delamination The resulting slurry was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then collected to yield a clay containing two-dimensional particles (single-layer MXene particles). 35 mL of pure water was then added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing single-layer MXene particles. This supernatant was then centrifuged at 4,300 G for 2 hours. The supernatant was then discarded to yield a clay containing two-dimensional particles (single-layer MXene particles).

[0101] [Example 11] After the preparation of the precursor (MAX), the etching process, the cleaning process, and the delamination process were carried out in the same manner as in Example 1, the following step (5) was carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Examples 1 to 8 (2) Etching of precursor: same as in Examples 1 to 8 (3) Washing: Same as in Example 1 (4) Intercalation: Same as in Examples 1 to 8 (5) Delamination The slurry obtained after intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then collected to yield clay containing two-dimensional particles (single-layer MXene particles). 35 mL of pure water was then added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing single-layer MXene particles. This process was repeated twice to obtain a single-layer MXene particle-containing supernatant. The supernatant was then centrifuged at 4,300 G for 2 hours, after which the supernatant was discarded to yield clay containing two-dimensional particles (single-layer MXene particles).

[0102] [Example 12] After the preparation of the precursor (MAX), the etching process, the cleaning process, and the delamination process were carried out in the same manner as in Example 1, the following step (5) was carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Examples 1 to 8 (2) Etching of precursor: same as in Examples 1 to 8 (3) Washing: Same as in Example 1 (4) Intercalation: Same as in Examples 1 to 8 (5) Delamination The resulting slurry was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then collected to yield a clay containing two-dimensional particles (single-layer MXene particles). 35 mL of pure water was then added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing single-layer MXene particles. This process was repeated three times to yield a single-layer MXene particle-containing supernatant. The resulting supernatant was then centrifuged at 4,300 G for 2 hours. The supernatant was then discarded, yielding a clay containing two-dimensional particles (single-layer MXene particles).

[0103] [Example 13] After the preparation of the precursor (MAX), the etching process, the cleaning process, and the delamination process were carried out in the same manner as in Example 1, the following step (5) was carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Examples 1 to 8 (2) Etching of precursor: same as in Examples 1 to 8 (3) Washing: Same as in Example 1 (4) Intercalation: Same as in Examples 1 to 8 (5) Delamination The slurry obtained after intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then collected to yield a clay containing two-dimensional particles (single-layer MXene particles). 35 mL of pure water was then added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing single-layer MXene particles. This process was repeated four times to yield a single-layer MXene particle-containing supernatant. The supernatant was then centrifuged at 4,300 G for 2 hours, after which the supernatant was discarded to yield a clay containing two-dimensional particles (single-layer MXene particles).

[0104] Comparative Example 3 After preparing the precursor (MAX) in the same manner as in Example 1, the following step (2) was carried out, the washing step was carried out in the same manner as in Example 1, and then the following steps (4) and (5) were carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Example 1 (2) Etching of precursor Using the Ti3AlC2 particles (powder) prepared in the above step (1), etching was carried out under the following etching conditions to obtain a solid-liquid mixture (slurry) containing solid components derived from the Ti3AlC2 powder. (Etching conditions) Precursor: Ti3AlC2 (passed through a 45 μm sieve) Etching solution composition: 49% HF 6mL 18mL of H2O HCl (12M) 36mL Precursor input: 3.0g Etching container: 100mL Eye Boy Etching temperature: 35℃ Etching time: 24 hours Stirrer rotation speed: 400 rpm (3) Washing: Same as in Example 1 (4) Intercalation Ti3C2T prepared by the above method s 0.75g of LiCl and 37.2g of pure water were added to the aqueous clay medium, and the mixture was stirred at 20℃ to 25℃ for 24 hours to perform intercalation using lithium ions as the intercalator. The detailed intercalation conditions are as follows: (Intercalation conditions) Ti3C2T s -Water medium clay (MXene after washing): 0.5g solids ·Metal-containing compound: LiCl 0.75g Intercalation vessel: 100mL Eye Boy ·Temperature: 20℃ or higher and 25℃ or lower (room temperature) Hours: 24 hours Stirrer rotation speed: 700 rpm (5) Delamination The slurry obtained after intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then collected to yield a clay containing two-dimensional particles (single-layer MXene particles). 35 mL of pure water was then added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing single-layer MXene particles. This process was repeated four times to yield a single-layer MXene particle-containing supernatant. The supernatant was then centrifuged at 4,300 G for 2 hours, after which the supernatant was discarded to yield a clay containing two-dimensional particles (single-layer MXene particles).

[0105] Comparative Example 4 The precursor (MAX) was prepared in the same manner as in Example 1, and then the following step (2) was carried out. After a washing step was carried out, the following step (5) was carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Example 1 (2) Precursor etching and intercalation Using the Ti3AlC2 particles (powder) prepared in the above step (1), etching was carried out under the following etching conditions to obtain a solid-liquid mixture (slurry) containing solid components derived from the Ti3AlC2 powder. (Etching and intercalation conditions) Precursor: Ti3AlC2 (passed through a 45 μm sieve) Etching solution composition: LiF 3g HCl (9M) 30mL Precursor input: 3.0g Etching container: 100mL Eye Boy Etching temperature: 35℃ Etching time: 24 hours Stirrer rotation speed: 400 rpm (3) Washing: Same as in Example 1 (5) Delamination The slurry obtained after intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then collected to yield a clay containing two-dimensional particles (single-layer MXene particles). 35 mL of pure water was then added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing single-layer MXene particles. This process was repeated four times to yield a single-layer MXene particle-containing supernatant. The supernatant was then centrifuged at 4,300 G for 2 hours, after which the supernatant was discarded to yield a clay containing two-dimensional particles (single-layer MXene particles).

[0106] [Comparative Examples 5 and 6] After the preparation of the precursor (MAX), the etching process, the cleaning process, and the delamination process were carried out in the same manner as in Example 1, the following step (5) was carried out to produce clay containing two-dimensional particles (single-layer MXene particles). (1) Preparation of precursor (MAX): Same as in Examples 1 to 8 (2) Etching of precursor: same as in Examples 1 to 8 (3) Washing: Same as in Example 1 (4) Intercalation: Same as in Examples 1 to 8 (5) Delamination The slurry obtained after intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes. The supernatant was then collected to yield a clay containing two-dimensional particles (single-layer MXene particles). 35 mL of pure water was then added, followed by 15 minutes of stirring on a shaker. The tube was then centrifuged at 3,500 G for 5 minutes, and the supernatant was collected as a solution containing single-layer MXene particles. This process was repeated four times to yield a single-layer MXene particle-containing supernatant. The supernatant was then centrifuged at 4,300 G for 2 hours, after which the supernatant was discarded to yield a clay containing two-dimensional particles (single-layer MXene particles).

[0107] (Method for measuring phosphorus atom content) The clay containing two-dimensional particles (single-layer MXene particles) obtained in Examples 1 to 13 and Comparative Examples 1 to 6 was subjected to suction filtration. After filtration, the clay was vacuum dried at 80°C for 24 hours to produce a conductive film containing two-dimensional particles. A membrane filter (Merck, Durapore, pore size 0.45 μm) was used for the suction filtration. The supernatant contained 0.05 g of two-dimensional particle solids and 40 mL of pure water.

[0108] The conductive film containing the obtained two-dimensional particles was measured by X-ray photoelectron spectroscopy (XPS) to determine the phosphorus atom content in the two-dimensional particles. For the XPS measurement, a Quantum 2000 manufactured by ULVAC-PHI, Inc. was used.

[0109] The content of phosphorus atoms contained in the two-dimensional particles was 0.20 mass% in Example 1, 0.25 mass% in Example 2, 0.32 mass% in Example 3, 0.34 mass% in Example 4, 0.14 mass% in Comparative Example 1, 0.18 mass% in Comparative Example 2, 0.20 mass% in Comparative Example 5, and 0.34 mass% in Comparative Example 6.

[0110] (Method for measuring Li atom content) The two-dimensional particles (single-layer MXene particles) obtained in Examples 1 to 13 and Comparative Examples 1 to 6 were dissolved by the alkali fusion method, and the resulting solutions were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to detect the metal cations contained in the two-dimensional particles. For the ICP-AES analysis, an iCAP7400 manufactured by Thermo Fisher Scientific was used.

[0111] The content of Li atoms contained in the two-dimensional particles in Example 1 was 0.30 mass %.

[0112] [Table 1]

[0113] ( 7 Li NMR measurement method: Quantitative determination of the first and second components In a glove box with an Ar atmosphere (dew point below -60°C), two-dimensional particles (single-layer MXene particles) and dried Al2O3 powder were mixed in a mass ratio of 1:9 and ground in an agate mortar to obtain a mixed powder. The mixed powder was then loaded into a zirconia sample tube for solid-state NMR with an outer diameter of 4 mm in the glove box, and a Kel-F cap was placed on top to prepare the NMR measurement sample. The combined weight of the two-dimensional particles (single-layer MXene particles) and Al2O3 powder sample was 200 mg.

[0114] 7 The Li NMR spectrometer (spectrometer) was a Bruker AVANCE III 400 (magnetic field strength 9.4 T, 7 The resonance frequency of the Li nucleus was 155.455 MHz. The probe used was a Bruker PH MAS 400S1 BL4 NP / H VTN.

[0115] Under the following conditions 7 Li NMR measurements were performed to obtain one-dimensional 7 Li NMR spectra were obtained. Measurement method: Magic angle rotation + single pulse method Magic angle rotation speed: 15kHz Pulse intensity: 28-56kHz (output fixed at 100W) Pulse flip angle: 90° Accumulated delay time: 4 seconds Accumulation count: 1,024 times

[0116] obtained 7The Li NMR spectrum was regressed with a Lorentzian curve for the two components to determine the chemical shift and relative area of ​​each peak. The reference substance was Li in a 1 mol / L LiCl aqueous solution. The regression calculations for Li and the calculation of chemical shift and relative area were performed using the spectrum fitting function included in the Bruker NMR console software. Peaks assigned to the first and second components were identified from the chemical shift values, and the proportion of the first component (atomic basis) was calculated as S1 / (S1+S2) from the relative area S1 of the peak assigned to the first component and the relative area S2 of the peak assigned to the second component. The results are shown in Table 2.

[0117] [Table 2]

[0118] In the two-dimensional particles of the examples, the proportion of the first component in the total of the first and second components was in the range of 17 atomic % to 70 atomic %. In particular, in Examples 4 and 5, a phosphoric acid aqueous solution was used during delamination, while in Examples 9 to 13, pure water alone was used during delamination without a phosphoric acid aqueous solution. Because the etching conditions were different between Examples 4 and 5 and Examples 9 to 13, the state of the surface groups of the MXene layer was different. It is believed that in Examples 9 to 13, delamination using only pure water resulted in two-dimensional particles in which the proportion of the first component in the total of the first and second components was 17 atomic % to 70 atomic %. On the other hand, in the two-dimensional particles of Comparative Examples 3 and 4, the proportion of the first component in the total of the first and second components exceeded 70 atomic %, while the first component was not detected in the two-dimensional particles of Comparative Examples 5 and 6.

[0119] ( 7 Li NMR measurement method: T2 relaxation time measurement For the two-dimensional particles of Example 5 and Comparative Examples 2 to 4, NMR measurement samples were prepared in the same manner as in the quantification of the first and second components. 7 A Li NMR instrument was used.

[0120] Under the following conditions 7 Li NMR measurements were performed to obtain one-dimensional 7 Li NMR spectra were obtained. Measurement method: Magic angle spinning + CPMG method Magic angle rotation speed: 12.5kHz Pulse intensity: 28-56kHz (output fixed at 100W) Echo time: 160 μsec Number of echoes: 48 Accumulated delay time: 4 seconds Accumulation count: 1,024 times

[0121] The time-domain data were phase-corrected and the relative area of ​​each echo was plotted against the refocusing time. This echo decay profile was regressed with the sum of exponential functions, with the relative areas of the first and second components obtained by the quantitative measurement above as fixed coefficients, to determine the time constants (T2 relaxation times) of each.

[0122] In the two-dimensional particles of Example 5, the T2 relaxation time of the first component was 0.47 ms, and the T2 relaxation time of the second component was 1.7 ms. In the two-dimensional particles of Comparative Example 2, the T2 relaxation time of the first component was 0.36 ms, and the T2 relaxation time of the second component was 2 ms. In the two-dimensional particles of Comparative Example 3, the T2 relaxation time of the first component was 0.56 ms, and the T2 relaxation time of the second component was 1.5 ms. In the two-dimensional particles of Comparative Example 4, the T2 relaxation time of the first component was 0.44 ms, and the T2 relaxation time of the second component was 1.2 ms. In these two-dimensional particles, the T2 relaxation time of the first component was shorter than the T2 relaxation time of the first component, and it is believed that the first component interacts more strongly with the substance.

[0123] (Conductive composite film manufacturing method 1) To 50 g of the dispersion of the two-dimensional particles of Example 5 (two-dimensional particle (MXene solids) concentration: 6.4% by mass), 52.750 g of a solution prepared by diluting a polyurethane solution (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., nonvolatile content concentration: 35% by mass) 100 times with pure water was added to prepare a composite. The composite was then stirred for 15 minutes using an automatic shaker (SK550 manufactured by F&FM). A polyimide film (Kapton film manufactured by Toray DuPont Co., Ltd.) was prepared, and the surface of the polyimide film was hydrophilized using oxygen plasma treatment (PC-1000 manufactured by Samco Inc.). The composite was then spray-coated 30 times onto the film. Each spray was dried for 2 minutes using a dryer. A spray nozzle manufactured by ATOMAX was used.

[0124] After application, the film was dried in a normal pressure oven at 80°C for 2 hours, and then dried overnight in a vacuum oven at 150°C to obtain a spray film. The resulting composite spray film had a thickness of 4.4 μm, and its initial conductivity, measured using the conductivity measurement method described below, was 17,668 S / cm. Furthermore, after a humidity resistance test was conducted for 14 days at room temperature and 99% humidity, the conductivity, measured in the same manner, was 8,127 S / cm, a change of 46% from the initial conductivity.

[0125] A composite was prepared by adding 14.779 g of a solution prepared by diluting a polyurethane solution (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., non-volatile content concentration 35% by mass) 100 times with pure water to 25.221 g of the two-dimensional particle dispersion of Comparative Example 3 (two-dimensional particle (MXene solids) concentration: 3.25% by mass). The composite was then stirred for 15 minutes using an automatic shaker (SK550, manufactured by F&FM). A polyimide film (Kapton film, manufactured by Toray DuPont Co., Ltd.) was prepared, and the surface of the polyimide film was hydrophilized using oxygen plasma treatment (PC-1000, manufactured by Samco Inc.). The composite was then spray-coated 30 times onto the film. Each spray was dried for 2 minutes using a dryer. A spray nozzle manufactured by ATOMAX was used.

[0126] After application, the composite was dried in a normal pressure oven at 80°C for 2 hours, and then dried overnight in a vacuum oven at 150°C to obtain a spray film. The resulting composite spray film had a thickness of 3.2 μm, and the initial conductivity measured using the conductivity measurement method described below was 10,269 S / cm, a lower result than when the two-dimensional particles of Example 5 were used. Furthermore, after a moisture resistance test was conducted for 14 days at room temperature and 99% humidity, the conductivity measured in the same manner was 3,081 S / cm, a change of 30% from the initial conductivity.

[0127] From the above, it was confirmed that the conductive composite film containing the two-dimensional particles of Example 5 had high initial conductivity and good moisture resistance. On the other hand, in the two-dimensional particles of Comparative Example 3, the proportion of the first component in the total of the first component and the second component exceeded 70 atomic %, and the initial conductivity and moisture resistance were not fully satisfactory.

[0128] (Conductive film manufacturing method 1) 15 mL of pure water was added to 0.5 g of clay containing two-dimensional particles (single-layer MXene particles) obtained in Examples 4, 6, and 7, and Comparative Examples 3 and 4, and then the mixture was suction filtered using a Nutsche funnel. After filtration, the mixture was vacuum dried at 80°C for 24 hours to produce a conductive film containing two-dimensional particles. A membrane filter (pore size 0.22 μm) was used for the suction filtration.

[0129] The film density of the conductive film containing two-dimensional particles obtained in Example 4 was 3.6 g / cm 3 The film density of the conductive film containing two-dimensional particles obtained in Example 6 was 3.7 g / cm. 3 The conductivity was 15,700 S / cm, and the rate of change in conductivity was 95%. The film density of the conductive film containing two-dimensional particles obtained in Example 7 was 3.2 g / cm. 3 The conductivity was 13,600 S / cm, and the rate of change in conductivity was 94%. The film density of the conductive film containing two-dimensional particles obtained in Comparative Example 3 was 2 g / cm 3The conductivity was 9,000 S / cm, and the rate of change in conductivity was 78%. The film density of the conductive film containing two-dimensional particles obtained in Comparative Example 4 was 2 g / cm 3 The conductivity was 6,000 S / cm, and the rate of change in conductivity was 23%.

[0130] From the above, it was confirmed that the conductive films containing two-dimensional particles obtained in the examples had high conductivity and good moisture resistance. On the other hand, in Comparative Examples 3 and 4, the proportion of the first component in the total of the first and second components exceeded 70 atomic %, and the conductivity and rate of change of the conductivity of the obtained conductive films were not fully satisfactory.

[0131] (Conductive film manufacturing method 2) The clay containing two-dimensional particles (single-layer MXene particles) obtained in Examples 1 to 13 was coated onto a polyethylene terephthalate film (Lumirror, manufactured by Toray Industries, Inc.) to a thickness of 120 μm or less. The film was then air-dried to obtain a conductive film by coating. The thickness of the resulting conductive film was 1 μm.

[0132] (Conductive film manufacturing method 3) 4 mL of pure water was added to 0.5 g of clay containing two-dimensional particles (single-layer MXene particles) obtained in Examples 1 to 13. The mixture was then sprayed onto a polyethylene terephthalate film (Lumirror, Toray Industries, Inc.) 1 to 30 times using a spray gun (Tamiya airbrush). Each spray application was followed by drying for 2 minutes in a dryer. After application, the mixture was dried in a normal pressure oven at 80°C for 2 hours, and then dried overnight in a vacuum oven at 150°C to obtain a spray film.

[0133] The film density, conductivity, and rate of change in conductivity of the conductive film were measured by the following methods.

[0134] (Film density measurement method) The film was punched out to a diameter of 12 mm, and the weight was measured with an electronic balance and the thickness was measured with a height gauge. The film density was calculated from the obtained values.

[0135] (Method for measuring the conductivity of conductive films) The conductivity of the resulting conductive film containing two-dimensional particles was determined. Resistivity (Ω) and thickness (μm) were measured at three locations per sample. The conductivity (S / cm) was calculated from these measurements, and the average of the three resulting conductivities was used. Resistivity was measured using a simple low-resistivity meter (Loresta AX MCP-T370, manufactured by Mitsubishi Chemical Analytical Co., Ltd.) to measure the surface resistance of the conductive film using the four-terminal method. Thickness was measured using a micrometer (MDH-25MB, manufactured by Mitutoyo Corporation). The volume resistivity was then calculated from the measured surface resistance and the thickness of the conductive film, and the conductivity was calculated as E0 by taking the reciprocal of this value.

[0136] (Conductivity change rate measurement method) The conductive film was placed in a thermo-hygrostat chamber at a relative humidity of 99% and a temperature of 25°C. After leaving it for 7 days, the conductivity was measured and designated as E. E was divided by E0 to determine the rate of change in conductivity. [Explanation of symbols]

[0137] 1a, 1b layer body (M m X n layer) 3a, 5a, 3b, 5b Modified or terminal T 7a, 7b MXene layers 10, 10a, 10b MXene particles (two-dimensional particles of layered materials)

Claims

1. A two-dimensional particle having one or more layers, Contains Li atoms, The layer comprises a compound of the formula: M m X n wherein M is at least one Group 3, 4, 5, 6, or 7 metal; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 or more and 4 or less, m is greater than n and is equal to or less than 5. and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, The Li atom is a first component and 7 a second component having a larger chemical shift as measured by Li NMR; Two-dimensional particles, wherein a ratio of the first component to a total of the first component and the second component is 17 atomic % or more and 70 atomic % or less.

2. The aforementioned 7 The chemical shift of the first component measured by Li NMR is less than 0.6 ppm, 7 The two-dimensional particle according to claim 1 , wherein the chemical shift of the second component measured by Li NMR is 0.6 ppm or more and 2.0 ppm or less.

3. The two-dimensional particle of claim 1 , comprising phosphorus atoms.

4. The two-dimensional particle according to claim 1 , wherein the content of the phosphorus atoms is 0.1% by mass or more and 14% by mass or less.

5. The phosphorus atom is PO 4 3- 2. The two-dimensional particle of claim 1, which is in the form of:

6. The two-dimensional particle according to claim 1 , wherein the average thickness is 1 nm or more and 10 nm or less.

7. A conductive film comprising the two-dimensional particles according to any one of claims 1 to 6.

8. A conductive paste comprising the two-dimensional particles according to any one of claims 1 to 6.

9. A conductive composite material comprising the two-dimensional particles according to any one of claims 1 to 6 and a resin.

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