Electrode and method for manufacturing electrode

Abstract

The purpose of the present disclosure is to provide an electrode having low impedance, preferably an electrode having low surface impedance.　The electrode according to the present disclosure comprises a film containing two-dimensional particles. The two-dimensional particles have at least a metal cation, and one or more layers. The layer includes a layer body represented by the formula MmXn (where: M is at least one metal belonging to group 3, 4, 5, 6, or 7, and contains at least a Ti atom; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1-4 inclusive; and m is greater than n and 5 or less), and a modification or terminal T existing on the surface of the layer body (where T is at least one option selected from the group consisting of hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms, and hydrogen atoms). The metal cations include Li cations, and the content of the Li cations in the two-dimensional particles is 5.4 moles or more per 100 moles of Ti atoms.

Description

Electrode and method for manufacturing the electrode

[0001] The present disclosure relates to electrodes and methods for manufacturing electrodes.

[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. MXene generally has the form of particles of such layered materials (which may include powders, flakes, nanosheets, etc.).

[0003] Currently, various studies are being conducted to apply MXene to various electrical devices. For example, Patent Documents 1 and 2 describe that MXene, in the form of a film, can be used as an electrode for measuring neural signals (Patent Document 1).

[0004] Nicolette Driscoll, et al., "Two-Dimensional Ti3C2 MXene for High Resolution Neural Interfaces," ACS Nano, 2018, Vol. 12, Issue 10, pp. 10419-10429Nicolette Driscoll, et al., "MXene-infused bioelectronic interfaces for multiscale electrophysiology and stimulation," Science Translational Medicine, 2021, Vol. 13, Issue 612, article abf8629

[0005] The present disclosure aims to provide an electrode with low impedance, preferably an electrode with low surface impedance, and also aims to provide a method for manufacturing such an electrode.

[0006] The electrode of the present disclosure comprises a membrane comprising two-dimensional particles, the two-dimensional particles having at least a metal cation and one or more layers, the layers having a metal cation represented by the following formula: M ｍ X ｎ(wherein M is at least one metal of Group 3, 4, 5, 6, or 7 and contains at least a Ti atom; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and modified or terminated 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, wherein the metal cation contains a Li cation, and the content of Li cations in the two-dimensional particles is 5.4 mol or more per 100 mol of Ti atoms.

[0007] The method for manufacturing an electrode of the present disclosure also includes forming a film using two-dimensional particles, the two-dimensional particles being: (a) a polymer having a structure represented by the following formula: M ｍ AX ｎ (wherein M is at least one metal of Groups 3, 4, 5, 6, and 7 and contains at least a Ti atom; X is a carbon atom, a nitrogen atom, or a combination thereof; A is at least one element of Groups 12, 13, 14, 15, and 16; n is 1 or more and 4 or less; and m is greater than n and 5 or less); (b) removing at least a portion of the A atoms from the precursor using an etching solution to obtain an etched product; (c) washing the etched product to obtain an etched-washed product; and (d) mixing the etched-washed product with a metal compound containing a metal cation to obtain an intercalation product in which the metal cation is intercalated into the etched-washed product, wherein the metal cation contains a Li cation.

[0008] According to the present disclosure, it is possible to provide an electrode having low impedance, preferably an electrode having low surface impedance, and it is also possible to provide a method for manufacturing such an electrode.

[0009] 1A and 1B are schematic cross-sectional views of layered MXene particles according to 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.

[0010] An electrode and a method for manufacturing the same according to one embodiment of the present disclosure will be described below.

[0011] The electrode of the present disclosure comprises a film including two-dimensional particles, the two-dimensional particles having at least metal cations and one or more layers, the layer including a layer body represented by the following formula: (wherein M is at least one Group 3, 4, 5, 6, or 7 metal and includes at least a Ti atom; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and a modified or terminated 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 metal cations including Li cations, and the content of the Li cations is 5.4 mol or more per 100 mol of Ti atoms.

[0012] The electrode of the present disclosure can exhibit low impedance by having the above-mentioned configuration. Although it should not be interpreted as being limited to a particular theory, the two-dimensional particles contained in the film are layered materials, but contain a certain amount of Li cations, which is thought to facilitate charge transfer and high conductivity. Therefore, it is thought that by providing such a film to the electrode, the impedance is kept low, and in particular the surface impedance is kept low.

[0013] The two-dimensional particles can be understood as layered materials or layered compounds, and are 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.

[0014] In addition, 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.

[0015] In the above formula for MXene, M is at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn, and preferably contains at least Ti, and more preferably at least one selected from the group consisting of Ti, V, Cr, and Mo, and contains at least Ti.

[0016] The proportion of Ti atoms in M ​​may be preferably 50 atomic % or more and 100 atomic % or less, more preferably 70 atomic % or more and 100 atomic % or less, and even more preferably 90 atomic % or more and 100 atomic % or less.

[0017] MXene is a compound represented by the formula: M ｍ X ｎ However, it is known that it can be expressed as follows: Sc ２ C, Ti ２ C, Ti ２ N, Zr ２ C, Zr ２ N, Hf ２ C, Hf ２ N.V. ２ C.V. ２ N, Nb ２ C, Ta ２ C, Cr ２ C, Cr ２ N, Mo ２ C, Mo １．３ C, Cr １．３ C, (Ti, V) ２ C, (Ti, Nb) ２ C.W. ２ C.W. １．３ C, Mo ２ N, 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), Ti ３ C ２ , Ti ３ N ２ , Ti ３ (CN), Zr３ C ２ 、(Ti,V) ３ C ２ 、(Ti ２ Nb)C ２ 、(Ti ２ Ta)C ２ 、(Ti ２ Mn)C ２ 、Hf ３ C ２ 、(Hf ２ V)C ２ 、(Hf ２ Mn)C ２ 、(V ２ Ti)C ２ 、(Cr ２ Ti)C ２ 、(Cr ２ V)C ２ 、(Cr ２ Nb)C ２ 、(Cr ２ Ta)C ２ 、(Mo ２ Sc)C ２ 、(Mo ２ Ti)C ２ 、(Mo ２ Zr)C ２ 、(Mo ２ Hf)C ２ 、(Mo ２ V)C ２ 、(Mo ２ Nb)C ２ 、(Mo ２ Ta)C ２ 、(W ２ Ti)C ２ 、(W ２ Zr)C ２ 、(W ２ Hf)C ２ 、 Ti ４ N ３ 、V ４ C ３ 、Nb ４ C ３ 、Ta ４ C ３ 、(Ti,Nb) ４ C ３ 、(Nb,Zr) ４ C ３ 、(Ti ２ Nb ２ )C ３, (Ti ２ Ta ２ ) C ３ , (V ２ Ti ２ ) C ３ , (V ２ Nb ２ ) C ３ , (V ２ Ta ２ ) C ３ , (Nb ２ Ta ２ ) C ３ , (Cr ２ Ti ２ ) C ３ , (Cr ２ V ２ ) C ３ , (Cr ２ Nb ２ ) C ３ , (Cr ２ Ta ２ ) C ３ , (Mo ２ Ti ２ ) C ３ , (Mo ２ Zr ２ ) C ３ , (Mo ２ Hf ２ ) C ３ , (Mo ２ V ２ ) C ３ , (Mo ２ Nb ２ ) C ３ , (Mo ２ Ta ２ ) C ３ , (W ２ Ti ２ ) C ３ , (W ２ Zr ２ ) C ３ , (W ２ Hf ２ ) C ３ , (Mo ２．７ V １．３ ) C ３ (In the above formula, "2.7" and "1.3" mean approximately 2.7 (= 8 / 3) and approximately 1.3 (= 4 / 3), respectively.)

[0018] Typically, in the above formula, M may contain Ti and X may be a carbon atom or a nitrogen atom, and preferably M may be Ti and X may be a carbon atom. For example, the MAX phase may contain Ti ３ AlC ２ and MXene is Ti ３ C ２ T ｓ (in other words, M is Ti, X is C, n is 2, and m is 3).

[0019] 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 residual amount of A atoms may be preferably 8% by mass or less, more preferably 6% by mass or less. However, even if the residual amount of A atoms exceeds 10% by mass, this may not be a problem depending on the application and use conditions of the two-dimensional particles.

[0020] The two-dimensional particle 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 ｎ The 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 opposing surfaces of each layer). ｍ X ｎ T ｓ ", where s is an arbitrary number.

[0021] The two-dimensional particles may contain one or more layers. Examples of multi-layered MXene particles (multilayered MXene particles) include, but are not limited to, two-layered MXene particles 10b, as shown schematically in FIG. 1(b). 1b, 3b, 5b, and 7b in FIG. 1(b) are the same as 1a, 3a, 5a, and 7a in FIG. 1(a). Two adjacent MXene layers (e.g., 7a and 7b) in a multilayered MXene particle do not necessarily need to be completely separated and may be partially in contact. The MXene particle 10a may be a mixture of the single-layered MXene particles 10a and the multilayered MXene particles 10b, with some unseparated multilayered MXene particles 10b remaining.

[0022] Although not limiting this embodiment, the thickness of each layer (corresponding to the above-mentioned MXene layers 7a and 7b) contained in the MXene particle can be, for example, 0.8 nm to 5 nm, particularly 0.8 nm 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 stack of the multilayer MXene particle can be, for example, 0.8 nm to 10 nm, particularly 0.8 nm to 5 nm, more particularly about 1 nm, and the total number of layers can be 2 to 20,000.

[0023] 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.

[0024] The two-dimensional particles of this embodiment preferably contain MXene particles with a large number of layers. The term "large number of layers" refers to, for example, seven or more MXene layers. The thickness of the MXene particles with a large number of layers in the stacking direction is preferably greater than 15 nm, more preferably 18 to 50 nm, and even more preferably 18 to 30 nm. In the MXene particles with a large number of layers, the ratio of (average major axis of the two-dimensional surface of the two-dimensional particle) to (average thickness of the two-dimensional particle) is, for example, greater than 5 to 50, preferably 10 to 30, and more preferably 11 to 20. This makes it easier to incorporate a large amount of metal cations by including MXene particles with a large number of layers. Examples of the MXene particles with a large number of layers include two-dimensional particles obtained without undergoing a delamination process.

[0025] The two-dimensional particles of this embodiment preferably include multilayer MXene particles with a small number of layers. The term "small number of layers" refers to, for example, six or fewer MXene layers. The thickness of the multilayer MXene particles with a small number of layers in the stacking direction is preferably 15 nm or less, more preferably 10 nm or less. Furthermore, in multilayer MXene particles with a small number of layers, the ratio of (average major axis of the two-dimensional surface of the two-dimensional particle) to (average thickness of the two-dimensional particle) is 1.2 or more, preferably 1.5 to 10, and more preferably 2 to 5. Hereinafter, these "MXene particles with a small number of layers" may be referred to as "few-layer MXene particles." Furthermore, single-layer MXene particles and few-layer MXene particles may be collectively referred to as "single-layer / few-layer MXene particles." This may improve the film-forming properties of films containing the two-dimensional particles. Examples of the single-layer / few-layer MXene particles include two-dimensional particles obtained through a delamination process.

[0026] In one aspect, the two-dimensional particles of this embodiment preferably contain the multi-layered MXene particles and the single-layered or single-layered MXene particles. The proportion of multi-layered MXene particles in the two-dimensional particles of this embodiment can be preferably 20% by volume to 100% by volume, more preferably 30% by volume to 100% by volume, and even more preferably 60% by volume to 100% by volume. This can facilitate the production of two-dimensional particles containing a large amount of metal cations.

[0027] In one aspect, the two-dimensional particles of this embodiment preferably contain single-layer MXene particles and few-layer MXene particles, i.e., single-layer and few-layer MXene particles. The proportion of single-layer and few-layer MXene particles with a thickness of 15 nm or less in the two-dimensional particles of this embodiment can be preferably 0% to 70% by volume, more preferably 0% to 60% by volume, and even more preferably 0% to 25% by volume. This can improve the film-forming properties of films containing the two-dimensional particles.

[0028] (Average value of major axis of two-dimensional surface of two-dimensional particle) The average value of major axis of two-dimensional surface of the two-dimensional particle of this embodiment is preferably 1 μm or more and 20 μm or less. Hereinafter, the average value of major axis of two-dimensional surface may be referred to as "average flake size".

[0029] The larger the average flake size, the better the orientation of the two-dimensional particles in the material containing the two-dimensional particles. The orientation of the two-dimensional particles can be evaluated, for example, by the electrical conductivity of the material containing the two-dimensional particles. The average value of the major axis of the two-dimensional surface is preferably 1.5 μm or more, more preferably 2.5 μm or more. When MXene is delaminated by ultrasonic treatment, the majority of the MXene is reduced in diameter to approximately several hundred nanometers in major axis by the ultrasonic treatment, and therefore the film formed from the single-layer MXene delaminated by ultrasonic treatment is thought to have low orientation of the two-dimensional particles.

[0030] The average value of the major axis of the two-dimensional surface is, for example, 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.

[0031] 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 micrograph, 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.

[0032] The average major axis of the two-dimensional particles of this embodiment may be measured by dissolving a material containing the two-dimensional particles in a solvent and dispersing the two-dimensional particles in the solvent, or by measuring the average major axis from an SEM image of the material.

[0033] (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 the monolayer MXene particles, the lower limit of the thickness of the two-dimensional particles can be 1 nm.

[0034] 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.

[0035] The two-dimensional particles preferably contain voids, which makes it easier to contain a large amount of metal cations and to obtain an electrode with high conductivity and low impedance.

[0036] The metal cations include monovalent Li cations and may further include other metal cations, provided that the metal of the metal cations is different from the M atom, and the metal of the metal cations is different from the A atom contained in the precursor described below.

[0037] In one embodiment, the content of Li cations in the two-dimensional particles is 5.4 mol or more, preferably 5.4 mol or more to 67 mol or less, more preferably 5.4 mol or more to 20 mol or less, and even more preferably 5.4 mol or more to 9.7 mol or less, per 100 mol of Ti atoms. This can increase the conductivity of the film containing the two-dimensional particles, making it easier to obtain an electrode with low impedance.

[0038] The content of Li atoms in the two-dimensional particles may be, for example, 0.1% by mass to 20% by mass, further 0.1% by mass to 10% by mass, particularly 0.2% by mass to 3% by mass, and particularly 0.2% by mass to 0.5% by mass. This can further increase the conductivity of the film containing the two-dimensional particles, making it easier to obtain an electrode with low impedance. The content of Ti atoms, Li atoms, metal cations, and Li cations in the two-dimensional particles can be measured, for example, by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0039] The content of Li cations in the metal cations may be, for example, 1 mol% or more and 100 mol% or less, preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, and even more preferably 90 mol% or more and 100 mol% or less.

[0040] The metal cations 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.

[0041] In one aspect, the two-dimensional particles preferably contain a first component having a large number of layers and a Li cation content of 5.4 moles or more per 100 moles of Ti atoms. By including two-dimensional particles of the first component, it is possible to easily form a film containing a large amount of metal cations while maintaining film-forming properties. The thickness of such two-dimensional particles of the first component may be preferably greater than 15 nm, more preferably 18 nm to 50 nm, and even more preferably 18 nm to 30 nm. The number of layers may be preferably greater than 5 and less than 50, preferably greater than 10 and less than 30, and more preferably 11 to 20. Furthermore, in the two-dimensional particles of the first component, the Li cation content may be preferably 5.4 moles to 69 moles, more preferably 5.4 moles to 9.7 moles, and even more preferably 6 moles to 9.7 moles per 100 moles of Ti atoms. Furthermore, the two-dimensional particles of the first component preferably contain voids.

[0042] The content of the first component in the two-dimensional particles may be preferably 20% by volume or more and 100% by volume or less, more preferably 30% by volume or more and 100% by volume or less, and even more preferably 60% by volume or more and 100% by volume or less, which may facilitate the formation of a film containing a large amount of metal cations while maintaining film-forming properties.

[0043] Such a first component can typically be produced as an intercalation treatment product, which will be described later, but is not limited to those produced by such a production method.

[0044] In one aspect, the two-dimensional particles preferably contain a second component having a small number of layers and a Li cation content of more than 0 mol and less than 5.4 mol per 100 mol of Ti atoms. This can improve the film-forming properties of a film containing the two-dimensional particles. The thickness of the two-dimensional particles of the second component is preferably 15 nm or less, more preferably 10 nm or less, and the number of layers is preferably 1 to 6. Furthermore, in the two-dimensional particles of the second component, the Li cation content is preferably 1 mol or more and less than 5.4 mol, particularly 5.3 mol or less, per 100 mol of Ti atoms.

[0045] In the above two-dimensional particles, the content of the second component may be preferably 0% by volume or more and 70% by volume or less, more preferably 0% by volume or more and 60% by volume or less, and even more preferably 0% by volume or more and 25% by volume or less, relative to 100 parts by volume of the first component.

[0046] Such a second component can typically be produced as a delamination-treated product as described below, but is not limited to products produced by such a production method.

[0047] In the electrode of the present disclosure, the content of the two-dimensional particles in the film may be preferably 70% by volume or more and 100% by volume or less, more preferably 80% by volume or more and 100% by volume or less, and even more preferably 90% by volume or more and 100% by volume or less, which may facilitate obtaining an electrode with high conductivity and low impedance.

[0048] The method for producing two-dimensional particles will be described in detail below, but the present disclosure is not limited to such an embodiment.

[0049] The method for producing the two-dimensional particles includes: (a) forming a compound having the following formula: M ｍ AX ｎ(wherein M is at least one metal of Groups 3, 4, 5, 6, and 7, including at least Ti; X is a carbon atom, a nitrogen atom, or a combination thereof; A is at least one element of Groups 12, 13, 14, 15, and 16; n is 1 or more and 4 or less; and m is greater than n and 5 or less); and (b) removing at least some A atoms from the precursor using an etching solution to obtain an etched product; (c) washing the etched product to obtain an etched-cleaned product; (d) mixing the etched-cleaned product with a metal compound containing a metal cation to obtain an intercalation product in which the metal cation is intercalated into the etched-cleaned product; (e) stirring the intercalation product to obtain a delamination product in which the intercalation product is delaminated; and (f) washing the delamination product to obtain a delamination-cleaned product. The metal cations in step (d) may further include Li cations.

[0050] In the present disclosure, etching products, etching-cleaning products, intercalation products, delamination products, and delamination-cleaning products may all be included in the technical scope of two-dimensional particles.

[0051] Each step will be described in detail below.

[0052] Step (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, and is represented by the following formula: M ｍ AX ｎ (wherein M is at least one metal of Groups 3, 4, 5, 6, and 7, including at least Ti; X is a carbon atom, a nitrogen atom, or a combination thereof; A is at least one element of Groups 12, 13, 14, 15, and 16; n is 1 or more and 4 or less; and m is greater than n and 5 or less).

[0053] The above M, X, n and m are as described above.

[0054] A is at least one Group 12, 13, 14, 15, or 16 element, and is usually a Group A element, typically Group IIIA or Group IVA, and more particularly may 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.

[0055] 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 has 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.

[0056] 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 the MAX phase). The sintered body is then pulverized with an end mill to obtain the powdered MAX phase for the next step.

[0057] Step (b) In step (b), the M of the precursor is removed using an etching solution. ｍ AX ｎ An etching treatment is performed to remove at least a part of the A atoms from the precursor by etching. ｍ X ｎ The treated product is obtained in which at least a part of the layer constituted by A atoms has been removed while the layer represented by the formula (I) is maintained.

[0058] The etching solution may contain an acid such as HF, HCl, HBr, HI, sulfuric acid, phosphoric acid, or nitric acid, and typically, an etching solution containing F atoms can be used. Examples of such etching solutions include a mixture of LiF and hydrochloric acid, a mixture of hydrofluoric acid and hydrochloric acid, and a mixture containing hydrofluoric acid, and these mixtures may further contain phosphoric acid or the like. Typically, the etching solution may be an aqueous solution.

[0059] As the etching procedure and other conditions using the above etching solution, conditions conventionally used can be adopted.

[0060] Step (c) In step (c), the treated product obtained by the etching treatment is washed to obtain an etching-washed product. By performing washing, the acid used in the etching treatment and the like can be sufficiently removed.

[0061] The cleaning can be performed using a cleaning solution, typically by mixing the etched material with the cleaning solution. Such a cleaning solution typically contains water, preferably pure water. Alternatively, a small amount of hydrochloric acid or the like may be further contained in addition to pure water. The amount of cleaning solution to be mixed with the etched material and the method for mixing the etched material with the cleaning solution are not particularly limited. For example, such a mixing method may involve coexisting the etched material with the cleaning solution and then stirring, centrifuging, or the like. Examples of the stirring method include stirring using a hand shake, an automatic shaker, a shear mixer, a pot mill, or the like. The degree of stirring, such as the stirring speed and stirring time, may be adjusted depending on the amount and concentration of the etched material to be treated. Washing with the above cleaning solution may be performed one or more times, and it is preferable to perform washing with the cleaning solution multiple times. Specifically, for example, washing with the washing solution may be carried out by sequentially carrying out the following steps: step (i) adding the washing solution (to the treated product or the remaining precipitate obtained in (iii) below) and stirring; step (ii) centrifuging the stirred product; and step (iii) discarding the supernatant after centrifugation. Steps (i) to (iii) may be repeated two or more times, for example, 15 or less times.

[0062] Step (d): In step (d), an intercalation treatment is performed using a metal compound containing a metal cation to intercalate the metal cation into the etching and cleaning treatment product, thereby obtaining an intercalation treatment product. As a result, the metal cation is intercalated into two adjacent M ｍ X ｎ An intercalated product is obtained in which the intercalation is carried out between the layers. Such an intercalation process may be carried out in a dispersion medium.

[0063] The metal cation may be the same as the metal cation contained in the two-dimensional particle, including Li cations, and may also contain other metal cations, provided that the metal of the metal cation is different from the M atom, and the metal of the metal cation is different from the A atom contained in the precursor.

[0064] Examples of the metal compound include ionic compounds in which the metal cation and anion are bonded. Examples include iodides, phosphates, sulfides including sulfates, nitrates, acetates, and carboxylates of the metal cations. The metal cation is preferably a lithium ion, and the metal compound is preferably a metal compound containing a lithium ion, more preferably an ionic compound of a lithium ion, and even more preferably one or more of an iodide, a phosphate, and a sulfide salt of a lithium ion. If a lithium ion is used as the metal ion, it is thought that the water hydrated with the lithium ion has the most negative dielectric constant, making it easier to form a monolayer.

[0065] The specific method for the intercalation treatment is not particularly limited, and for example, the etched and washed product may be mixed with a metal compound and stirred or allowed 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-layer / few-layer MXene particles, and can be set, for example, between 12 and 24 hours.

[0066] The intercalation treatment may be carried out in the presence of a dispersion medium, such as water, or an organic medium such as N-methylpyrrolidone, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, dimethyl sulfoxide, ethylene glycol, or acetic acid.

[0067] The order of mixing the dispersion medium, the etching-cleaned product, and the metal compound is not particularly limited, but in one embodiment, the dispersion medium and the etching-cleaned product may be mixed together, and then the metal compound may be mixed in. Typically, the etching liquid after the etching treatment may be used as the dispersion medium.

[0068] The intercalation treatment is typically carried out on the etching-cleaned product, but in another embodiment, it may be carried out on the precursor simultaneously with the etching treatment. Specifically, the etching and intercalation treatment include mixing the precursor, an etching solution, and a metal compound containing a metal cation to remove at least a part of the A atoms from the precursor, and intercalating the metal cation into the precursor from which the A atoms have been removed, thereby obtaining an intercalation-treated product. As a result, at least a part of the A atoms are removed from the precursor (MAX), and the M in the precursor is removed. ｍ X ｎ The layer remains, and multiple adjacent M ｍ X ｎ An intercalation product is obtained in which metal cations are intercalated between the layers.

[0069] The etching solution and metal compound used in the etching and intercalation treatment may be the same as the etching solution and metal compound used in step (b), respectively.

[0070] The intercalation-treated product may be washed before being used in the production of an electrode to form an intercalation-washed product, and such an intercalation-washed product is also included in the scope of the intercalation-treated product. By washing the intercalation-treated product, excess metal compounds can be removed.

[0071] The intercalation-treated product can be washed using a washing solution, typically by mixing the intercalation-treated product with the washing solution. The washing solution can be the same as the washing solution used in step (c), and mixing can be performed using the same method as in step (c). For example, water can be used as the washing solution. Washing with the washing solution can be performed by sequentially performing steps (i) (to the treated product or the remaining precipitate obtained in (iii) below) and stirring, step (ii) centrifuging the stirred product, and step (iii) discarding the supernatant after centrifugation. Steps (i) to (iii) can be repeated two or more times, for example, up to 15 times.

[0072] Step (e): In step (e), the intercalation-treated product is stirred to perform a delamination process for delaminating the intercalation-treated product, thereby obtaining a delamination-treated product. By this stirring, shear stress is applied to the intercalation-treated product, and two adjacent M ｍ X ｎ At least a portion of the space between the layers can be peeled off, and the MXene particles can be divided into a single layer or a few layers.

[0073] The conditions for the delamination treatment are not particularly limited and can be performed by known methods. For example, a method of applying shear stress to the intercalation-treated product includes dispersing the intercalation-treated product in a dispersion medium and stirring the mixture. Examples of stirring methods include stirring using a mechanical shaker, vortex mixer, homogenizer, ultrasonic treatment, hand shake, automatic shaker, etc. The degree of stirring, such as the stirring speed and stirring time, can be adjusted depending on the amount and concentration of the product to be treated. For example, the above-mentioned intercalation-treated 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, a hand shake or automatic shaker to separate the layers. Removal of unexfoliated material can be achieved by centrifuging the mixture, 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) centrifuging, and (iii) recovering the supernatant. The 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 single-layer and few-layer MXene particles as a delamination-treated product. Alternatively, the supernatant can be centrifuged and discarded to obtain a clay containing single-layer and few-layer MXene particles as a delamination-treated product.

[0074] Step (f): In step (f), the delamination product is washed to obtain a washed delamination product. By this washing, impurities and the like can be removed.

[0075] In one embodiment, the cleaning can be performed using a cleaning solution, typically by mixing the delamination-treated product with the cleaning solution. In another embodiment, the cleaning can be performed by acid-treating the delamination-treated product and then mixing the acid-treated product with the cleaning solution. Examples of such acids include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, hydroiodic acid, hydrobromic acid, and hydrofluoric acid; and organic acids such as acetic acid, citric acid, oxalic acid, benzoic acid, and sorbic acid. The acid concentration in the acid solution can be adjusted appropriately depending on the delamination-treated product. The cleaning with the cleaning solution can be performed sequentially by: step (i) adding the cleaning solution to the treated product or the remaining precipitate obtained in (iii) below and stirring; step (ii) centrifuging the stirred product; and step (iii) discarding the supernatant after centrifugation. Steps (i) to (iii) can be repeated two or more times, for example, up to 15 times. The stirring can be carried out using a handshake, an automatic shaker, a shear mixer, a pot mill, or the like. The acid treatment may be carried out at least once, and if necessary, the operation of mixing with a fresh acid solution (an acid solution not used in the acid treatment) and stirring may be carried out at least twice, for example, at most 10 times. The cleaning solution used in step (c) can be the same as the cleaning solution used in step (c), and the mixing can be carried out by the same method as the mixing method used in step (c). For example, water can be used as the cleaning solution.

[0076] The intermediates and final products in the above-described production methods, for example, the intercalation-treated product and the delamination-treated product, may be dried by suction filtration, heat drying, freeze drying, vacuum drying, or the like.

[0077] In one embodiment, the film may be binderless. In another embodiment, the film may further include a resin in addition to the two-dimensional particles. Examples of such resins include acrylic resin, polyester resin, polyamide resin, polyimide resin, polyamideimide resin, polyolefin resin, polycarbonate resin, polyurethane resin, polystyrene resin, polyether resin, polylactic acid, and polyvinyl alcohol.

[0078] The film may further contain other additives.

[0079] In one embodiment, the electrode of the present disclosure may be formed solely from the film. In another embodiment, the electrode of the present disclosure may include the film and one or more selected from a substrate and a protective layer. The electrode may be in a solid state or in a flexible, soft state.

[0080] When the electrode of the present embodiment includes one or more selected from a substrate and a protective layer, the film and the one or more selected from the substrate and the protective layer may be in direct contact with each other.

[0081] The substrate may be an inorganic material such as ceramic or glass, or an organic material. Examples of such organic materials include flexible organic materials, specifically thermoplastic polyurethane elastomers (TPU), PET films, polyimide films, etc. The substrate may also be a fibrous material such as paper or cloth (e.g., a sheet-like fibrous material).

[0082] The protective layer may be a layer that covers at least a part or all of the film, and preferably a layer that covers at least a part of the film. The protective layer may be made of an organic material, specifically, a resin such as an acrylic resin, a polyester resin, a polyamide resin, a polyimide resin, a polyamideimide resin, a polyolefin resin, a polycarbonate resin, a polyurethane resin, a polystyrene resin, a polyether resin, polylactic acid, or polyvinyl alcohol.

[0083] In the electrode of this embodiment, the membrane 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, a protective layer, or the like.

[0084] The method for manufacturing an electrode of the present disclosure includes forming a film using the two-dimensional particles, and the two-dimensional particles include at least the intercalation-treated product, and may include the intercalation-treated product and the delamination-treated product and / or the delamination-washed product. In one aspect, the film may preferably include the intercalation-treated product and the delamination-treated product, and in another aspect, the film may preferably include the intercalation-treated product and the delamination-washed product.

[0085] Although not intended to be limited to a particular theory, it is believed that the intercalation-treated product contains metal cations and that interlayer adhesion is moderately suppressed compared to the etching-treated product or the etching-cleaning-treated product. Furthermore, the intercalation-treated product contains more metal cations than the delamination-treated product or the delamination-cleaning-treated product. Therefore, it is believed that using two-dimensional particles containing an intercalation-treated product can produce a film that contains metal cations and has good film-forming properties. Furthermore, the two-dimensional particles used in the electrode manufacturing method of the present disclosure contain the intercalation-treated product, and it is believed that the intercalation-treated product can undergo some degree of interlayer delamination due to shear stress during the film formation process. Therefore, film formation is possible even when the two-dimensional particles do not contain the delamination-treated product or the delamination-cleaning-treated product.

[0086] The film can be formed, for example, by suction filtering a mixture containing two-dimensional particles, a dispersion medium, and the resin used as needed, or by coating a mixture containing two-dimensional particles, a dispersion medium, and the resin used as needed and drying the dispersion medium once or twice or more times. For example, the supernatant containing the two-dimensional particles (delamination-treated product) obtained by the delamination treatment can be mixed with the intercalation-treated product to be used as the mixture.

[0087] Examples of methods for applying the mixed liquid include spray coating. The spray method may be, for example, an airless spray method or an air spray method, and specific examples include methods of spraying using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush. The dispersion medium can be the same as the dispersion medium described above, and examples include water; organic media such as N-methylpyrrolidone, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, dimethyl sulfoxide, ethylene glycol, and acetic acid.

[0088] The ratio of the intercalation product in the two-dimensional particles is preferably 20% by volume or more and 100% by volume or less, more preferably 30% by volume or more and 100% by volume or less, and even more preferably 60% by volume or more and 100% by volume or less, based on 100% by volume of the two-dimensional particles. This makes it easy to form a film containing a large amount of metal cations while maintaining film-forming properties.

[0089] Furthermore, the total proportion of the intercalation-treated product, delamination-treated product, and delamination-washed product in the two-dimensional particles is preferably 0% by volume or more and 70% by volume or less, more preferably 0% by volume or more and 60% by volume or less, and even more preferably 0% by volume or more and 25% by volume or less, based on 100% by volume of the two-dimensional particles.

[0090] The intercalation-treated product, the delamination-treated product, and the delamination-washed product can be produced by the above-mentioned production methods, but are not limited to these.

[0091] (Uses of Electrode) The electrode of this embodiment can be used for any appropriate purpose. For example, it can be used as a counter electrode or reference electrode when performing electrochemical measurements, an electrode for an electrochemical capacitor, an electrode for a battery, a bioelectrode, an electrode for a sensor, an electrode for an antenna, an electrode for electrical stimulation, etc. It can also be used for purposes requiring high moisture resistance (for example, reducing the decrease in initial conductivity and preventing oxidation), such as electromagnetic shielding (EMI shielding). Details of these uses will be described below.

[0092] The electrodes are not particularly limited, and may be, for example, capacitor electrodes, battery electrodes, biosignal sensing electrodes, sensor electrodes, antenna electrodes, electrical stimulation electrodes, etc. The electrodes disclosed herein make it 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).

[0093] The capacitor may be an electrochemical capacitor. An electrochemical capacitor is a capacitor that utilizes 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 (electrical 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.

[0094] The biosignal sensing electrode is an electrode for acquiring a biosignal, and may be, for example, an electrode for measuring EEG (electroencephalogram), ECG (electrocardiogram), EMG (electromyogram), or EIT (electrical impedance tomography), but is not limited to these.

[0095] 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.

[0096] 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).

[0097] An electrical stimulation electrode is an electrode for applying electrical stimulation to a living body, and such electrical stimulation can be applied to a living body, particularly to biological tissues such as, but not limited to, the spinal cord, brain, nerve tissue, muscle tissue, etc.

[0098] Preferably, the electrode of the present embodiment can be used as a biosignal sensing electrode. Because the electrode of the present disclosure has low impedance, it is expected to contribute to sensing with higher spatial resolution, and can be advantageously used to measure biosignals such as EEG (electroencephalogram), ECG (electrocardiogram), EMG (electromyogram), and EIT (electrical impedance tomography).

[0099] Although the electrode and the two-dimensional particles used in such an electrode according to one embodiment of the present disclosure have been described in detail above, various modifications are possible. Note that the electrode and the two-dimensional particles according to the present disclosure may be manufactured by a method different from the manufacturing method according to the above embodiment, and that the manufacturing method of the electrode and the two-dimensional particles according to the present disclosure is not limited to only those that provide the electrode and the two-dimensional particles according to the above embodiment.

[0100] The present disclosure includes the following: [1] A film comprising two-dimensional particles, the two-dimensional particles having at least metal cations and one or more layers, the layers having a structure represented by the following formula: M ｍ X ｎ(wherein M is at least one Group 3, 4, 5, 6, or 7 metal and includes at least a Ti atom; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and modified or terminated 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, wherein the metal cation includes a Li cation, and the content of the Li cation in the two-dimensional particle is 5.4 mol or more per 100 mol of Ti atoms. [2] The electrode according to [1], wherein the content of the Li cation in the two-dimensional particle is 5.4 mol or more and 9.7 mol or less per 100 mol of Ti atoms. [3] The electrode according to [1] or [2], which is a biosignal sensing electrode. [4] A method for forming a film using two-dimensional particles, the two-dimensional particles having the following formula: M ｍ AX ｎ(wherein M is at least one metal of Group 3, 4, 5, 6, or 7 and contains at least a Ti atom; X is a carbon atom, a nitrogen atom, or a combination thereof; A is at least one element of Group 12, 13, 14, 15, or 16; n is 1 or more and 4 or less; and m is greater than n and 5 or less); (b) obtaining an etched product by removing at least a portion of the A atoms from the precursor using an etching solution; (c) washing the etched product to obtain an etched-washed product; and (d) mixing the etched-washed product with a metal compound containing a metal cation to obtain an intercalation product in which the metal cation is intercalated into the etched-washed product, wherein the metal cation contains a Li cation. [5] The method for manufacturing an electrode according to [4], wherein the two-dimensional particles further include a delamination-treated product manufactured by a manufacturing method comprising: (e) stirring the intercalation-treated product to perform a delamination treatment to delaminate the intercalation-treated product, thereby obtaining a delamination-treated product. [6] The method for manufacturing an electrode according to [4] or [5], wherein the two-dimensional particles further include a delamination-washed product manufactured by a manufacturing method comprising: (e) stirring the intercalation-treated product to obtain a delamination-treated product in which the intercalation-treated product is delaminated, and (f) washing the delamination-treated product to obtain a delamination-washed product. [7] The two-dimensional particles at least have the metal cation and one or more layers, wherein the layers are represented by the following formula: M ｍ X ｎ(wherein M, X, n, and m are as defined above), and modified or terminated 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 metal cations include Li cations, and the content of Li cations in the two-dimensional particles is 5.4 mol or more per 100 mol of Ti atoms.

[0101] The present disclosure will be explained in more detail below with reference to examples, but the present disclosure is not limited thereto.

[0102] [Experimental Examples 1 to 6] [Preparation of Two-Dimensional Particles] In Experimental Examples 1 to 6, the following steps were carried out in order to prepare intercalation-treated products and delamination-treated products: (1) preparation of precursor (MAX), (2) etching of the precursor, (3) washing, (4) intercalation, and (5) delamination and washing, as detailed below.

[0103] (1) Preparation of Precursor TiC powder, Ti powder, and Al powder (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed in a molar ratio of 2:1:1 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 pulverized with an end mill to a maximum dimension of 40 μm or less. This resulted in TiC powder as a precursor (MAX). ３ AlC ２ particles were obtained.

[0104] (2) Etching of the precursor Ti prepared by the above method ３ AlC ２ Using particles (powder), etching was performed under the following etching conditions to remove Ti ３ AlC ２ A solid-liquid mixture (slurry) containing a solid component (etched product) derived from the powder was obtained. (Etching conditions) Precursor: Ti ３ AlC ２ (Sieved through a 45 μm mesh) Etching solution composition: 49% HF 6 mL H ２O 18 mL HCl (12 M) 36 mL Precursor input amount: 3.0 g Etching container: 100 mL Eye Boy Etching temperature: 35°C Etching time: 24 h Stirrer rotation speed: 400 rpm

[0105] (3) Washing The above slurry was divided into two parts and placed in two 50 mL centrifuge tubes, respectively. After centrifugation at 3500 G for 5 minutes using a centrifuge, the supernatant was discarded. 35 mL of pure water was added to each centrifuge tube, and the tubes were centrifuged again at 3500 G for 5 minutes to separate and remove the supernatant. This procedure was repeated 11 times. After the final centrifugation, the supernatant was discarded, and Ti ３ C ２ T ｓ A clay containing the etched and washed particles (hereinafter also referred to as "two-dimensional particles (c)") and a water medium was obtained.

[0106] (4) Intercalation The above Ti ３ C ２ T ｓ To the clay (etched and washed) and the water medium, 0.75 g of LiCl and 37.2 g of pure water were added, and the mixture was stirred at 20°C to 25°C for 24 hours to perform intercalation using lithium ions as an intercalator, thereby obtaining an intercalation-treated product (hereinafter also referred to as "two-dimensional particles (d)"). The detailed conditions for intercalation are as follows. (Intercalation conditions) Ti ３ C ２ T ｓ - Water medium clay (etching and cleaning treatment product): solid content 0.5 g Metal compound: LiCl 0.75 g Intercalation container: 100 mL Eye Boy Temperature: 20 ° C or higher and 25 ° C or lower (room temperature) Time: 24 hours Stirrer rotation speed: 700 rpm

[0107] (5) Delamination and Washing The slurry obtained by intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3,500 G for 5 minutes using a centrifuge. The supernatant was then collected to obtain a clay containing two-dimensional particles (delamination-treated product). 35 mL of pure water was then added, followed by stirring with a shaker for 15 minutes, followed by centrifugation at 3,500 G for 5 minutes. The supernatant was then collected as a solution containing single-layered MXene particles. This procedure was repeated four times to obtain a single-layered MXene particle-containing supernatant. The supernatant was then centrifuged at 4,300 G for 2 hours using a centrifuge, after which the supernatant was discarded to obtain a clay containing delamination-washed material (hereinafter also referred to as "two-dimensional particles (f)").

[0108] [Preparation of Slurry] The etching-cleaned product, intercalation-cleaned product, and delamination-cleaned product were placed in a 50 mL centrifuge tube in the proportions shown in Table 1, and pure water was added so that the proportion of two-dimensional particles, including the intercalation-cleaned product and the delamination-cleaned product combined, was 1.5 mass %. The mixture was then stirred with a shaker for 15 minutes to obtain a slurry.

[0109] [Fabrication of Electrode] The above slurry was placed in a 25 mL syringe, and the syringe was set in a spray coater. Next, a 3 cm square polyimide substrate was set on the suction stage of the spray coater, and the above slurry was applied 15 times to form a film, thereby obtaining a laminate comprising a polyimide substrate and an undried film disposed on the polyimide substrate. The spray coating conditions were as follows. (Spray coating conditions) Atomization pressure: 0.5 MPa Distance between nozzle tip and substrate: 15 cm Liquid delivery rate: 5 mL / s Sweep speed: 150 mm / s Stage heater: 45°C

[0110] The laminate was dried in an atmospheric pressure oven at 80°C for 2 hours and then at 150°C overnight in a vacuum to form an electrode comprising a polyimide substrate and a film disposed on the polyimide substrate.

[0111] (Method of measuring impedance) The electrode was covered with Kapton (registered trademark) tape, and an opening of 10 mm diameter was formed to serve as a working electrode. A beaker cell was assembled using a platinum electrode as a counter electrode and a silver-silver chloride electrode as a reference electrode. The counter electrode had an area larger than the opening of the working electrode.

[0112] Next, electrochemical measurements were performed in potentiostat mode with a frequency in the range of 10 Hz, a voltage set to 1 mVrms to 20 mVrms relative to the open circuit voltage or reference electrode, 71 plots, and an N number per plot of 1 to 10. Bio-Logic Science Instruments' VMP-300 high-performance electrochemical measurement system (16-channel advanced model) was used as the electrochemical measurement device.

[0113] (Measurement of Li atom content by inductively coupled plasma atomic emission spectroscopy (ICP)) The electrode was dissolved by an alkali fusion method, and the resulting solution was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to detect metal cations contained in the two-dimensional particles. For the ICP-AES measurement, an iCAP6300 (manufactured by Thermo Fisher Scientific) was used.

[0114] The results are shown in Table 1. Those that correspond to comparative examples of the present disclosure are marked with the symbol "*", and the rest correspond to examples of the present disclosure.

[0115]

[0116] Experimental Examples 1 to 3 are examples of the present disclosure, and electrodes with low impedance were obtained. Experimental Examples 4 to 6 are examples in which the content of metal cations was less than 5.4 moles per 100 moles of Ti atoms, and the impedance was not fully satisfactory.

[0117] 1a, 1b Layer body (M ｍ X ｎ Layer) 3a, 5a, 3b, 5b Modified or terminated T 7a, 7b MXene layer 10, 10a, 10b MXene particle (2D particle of layered material)

Claims

1. A membrane including two-dimensional particles, The two-dimensional particle has at least a metal cation and one or more layers; The layer has the following formula: M ｍ X ｎ (wherein M is at least one Group 3, 4, 5, 6, 7 metal, including at least a Ti atom; 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 terminal 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 metal cations include Li cations; The content of Li cations in the two-dimensional particles is 5.4 moles or more per 100 moles of Ti atoms.

2. The electrode of claim 1 , wherein the content of the Li cations in the two-dimensional particles is 5.4 moles to 9.7 moles per 100 moles of Ti atoms.

3. The electrode according to claim 1 or 2, which is a biosignal sensing electrode.

4. forming a film using two-dimensional particles; The two-dimensional particle is (a) a compound of the formula: M ｍ AX ｎ (wherein M is at least one Group 3, 4, 5, 6, 7 metal, including at least a Ti atom; X is a carbon atom, a nitrogen atom, or a combination thereof; A is at least one Group 12, 13, 14, 15, or 16 element; n is 1 or more and 4 or less, m is greater than n and is equal to or less than 5. providing a precursor represented by (b) removing at least a portion of the A atoms from the precursor using an etching solution to obtain an etched product; (c) cleaning the etched product to obtain an etch-cleaned product; and (d) mixing the etching and cleaning product with a metal compound containing a metal cation to obtain an intercalation product in which the metal cation is intercalated into the etching and cleaning product; The metal cation is produced by a production method including Li cation. At least one intercalation product is included, The method for producing an electrode, wherein the content of Li cations in the two-dimensional particles is 5.4 moles or more per 100 moles of Ti atoms.

5. The two-dimensional particle is (e) stirring the intercalation-treated product to perform a delamination process to delaminate the intercalation-treated product, thereby obtaining a delamination-treated product. The method for producing an electrode according to claim 4, further comprising a delamination treatment.

6. The two-dimensional particle is (e) stirring the intercalation-treated product to obtain a delamination-treated product in which the intercalation-treated product is delaminated; (f) washing the delamination-treated product to obtain a delamination-washed product; The method for producing an electrode according to claim 4 or 5, further comprising the step of subjecting the electrode to delamination cleaning treatment.

7. The two-dimensional particle has at least the metal cation and one or more layers, The layer has the following formula: M ｍ X ｎ (In the formula, M, X, n, and m are defined as above.) and a modification or terminal 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 method for producing an electrode according to claim 4 or 5, wherein the metal cations include Li cations.