Electrode and manufacturing method thereof

Abstract

The conductive film includes one or more layers and includes particles of a layered material having a π-electron conjugated compound attached thereto, the one or more layers being represented by the following formula: m X n (wherein M is at least one kind of 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; and m is greater than n and 5 or less), and a modification or termination T (T is at least one kind 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, and the π-electron conjugated compound has one or more of an aromatic ring, a heteroaromatic ring, a conjugated diene unit, an allyl group, and a vinyl group.

Description

[Technical field]

[0001] The present disclosure relates to electrodes and methods for making the same. [Background technology]

[0002] In recent years, MXene has been attracting attention as a new material having electrical conductivity. 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. In general, MXene has the form of particles of such layered material (which may include powder, flakes, nanosheets, etc.).

[0003] Currently, various researches are being conducted on the application of MXene to various electric devices. For example, Patent Document 1 discloses an electrode having a contact material containing MXene as an electric device and exhibiting a lower impedance than Au. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 055784 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the conductivity of MXene can decrease over time (for example, within a few days to a month), there is a need to maintain excellent electrode properties such as high conductivity for a long period of time. The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide an electrode capable of maintaining excellent electrode properties for a long period of time and a method for producing the same. [Means for solving the problem]

[0006] According to one aspect of the present invention, a conductive film comprising one or more layers and including particles of a layered material having a π-electron conjugated compound attached thereto; The one or more layers may have 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 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 π-electron conjugated compound has at least one of an aromatic ring, a heteroaromatic ring, a conjugated diene unit, an allyl group, and a vinyl group.

[0007] According to another aspect of the present invention, (a) the 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 Group 12, 13, 14, 15, or 16 element; n is 1 or more and 4 or less, m is greater than n and less than or equal to 5) preparing a precursor of a conductive film represented by (b) removing at least a portion of the A atoms from the precursor using an etching solution; (c) washing the first intermediate obtained by (b) with water; (d) performing intercalation, which includes mixing the second intermediate obtained by (c) with an intercalation compound for the second intermediate; (e) stirring the third intermediate obtained by (d) in a liquid; (f) washing the fourth intermediate obtained by (e) with water to obtain particles of a layered material; (g) mixing the particles of the layered material obtained by (f) with a π-electron conjugated compound having one or more of an aromatic ring, a heteroaromatic ring, a conjugated diene unit, an allyl group, and a vinyl group to form particles of a layered material having a π-electron conjugated compound attached thereto; (h) supplying particles of a layered material having a π-electron conjugated compound attached thereto onto a substrate to form a conductive film; A method for manufacturing an electrode is provided, comprising: Effect of the Invention

[0008] In accordance with the present invention, an electrode comprises one or more layers and comprises particles of a defined layered material (also referred to herein as "MXene") having a defined π-electron conjugated compound attached thereto, thereby providing an electrode comprising MXene and capable of maintaining stable electrode properties over time. [Brief description of the drawings]

[0009] [Figure 1] 1A and 1B are schematic cross-sectional views showing MXene, a layered material that can be used for the conductive film of the electrode of this embodiment, in which (a) shows a single-layer MXene and (b) shows a multi-layer (exemplarily two-layer) MXene. [Diagram 2] FIG. 2 is a schematic cross-sectional view for explaining the operation and effect of one embodiment of the electrode of the present embodiment. [Diagram 3] FIG. 2 is another schematic cross-sectional view for explaining the operation and effect of one embodiment of the electrode of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1: Electrode) An electrode according to one embodiment of the present invention will be described in detail below, but the present invention is not limited to this embodiment.

[0011] The electrode in this embodiment is a conductive film comprising one or more layers and including particles of a layered material having a π-electron conjugated compound attached thereto; The one or more layers may have 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 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 π-electron conjugated compound has at least one of an aromatic ring, a heteroaromatic ring, a conjugated diene unit, an allyl group, and a vinyl group. The electrode has the conductive film, and thus can maintain stable electrode characteristics for a long period of time. For example, the electrode can ensure low impedance as an electrode characteristic. More specifically, for example, in a biological environment, the electrode can suppress an increase in initial impedance and also suppress an increase in impedance over time.

[0012] The layered material may be understood as a layered compound, and may be 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.

[0013] 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.

[0014] MXene is a compound represented by the above formula: 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.)

[0015] 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, which is a precursor of MXene, is Ti3AlC2, and MXene is Ti3C2T s(In other words, M is Ti, X is C, n is 2, and m is 3).

[0016] In this embodiment, MXene may contain a relatively small amount of residual A atoms, for example, 10 mass% or less of the original A atoms. The amount of residual A atoms may be preferably 8 mass% or less, more preferably 6 mass% or less. However, even if the amount of residual A atoms exceeds 10 mass%, there may be cases where there is no problem depending on the application and use conditions of the electrode.

[0017] Hereinafter, the layered material particles (also referred to as "MXene particles") constituting the conductive film in the electrode according to this embodiment will be described with reference to Fig. 1. In Fig. 1, the layered material particles for adhering the π-electron conjugated compound will be described, and therefore the π-electron conjugated compound is not shown.

[0018] The particles of the layered material constituting the conductive film of this embodiment are aggregates containing one layer of MXene10a (single-layer MXene) as illustrated in FIG. 1(a). More specifically, MXene10a is m X n The layer body (M m X n The MXene layer 7a has a layer body 1a and a modification or termination T3a, 5a present on the surface of the layer body 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 any number.

[0019] The layered material particles according to the present embodiment may include multiple layers as well as one layer. As an example of multiple layer MXene (multilayer MXene), as shown in FIG. 1(b), two layers of MXene 10b are included, but are not limited to these examples. In FIG. 1(b), 1b, 3b, 5b, and 7b are the same as 1a, 3a, 5a, and 7a in FIG. 1(a). The two adjacent MXene layers (e.g., 7a and 7b) of the multilayer MXene do not necessarily have to be completely separated, and may be partially in contact. The MXene 10a is a single layer in which the multilayer MXene 10b is individually separated, and the unseparated multilayer MXene 10b may remain, resulting in a mixture of the single layer MXene 10a and the multilayer MXene 10b. Even when the multilayer MXene is included, the multilayer MXene is preferably an MXene with a small number of layers obtained through a delamination process. The "small number of layers" refers to, for example, 10 or less layers of MXene. Hereinafter, this "multilayer MXene with a small number of layers" may be referred to as "few-layer MXene." The thickness of the few-layer MXene in the stacking direction is preferably 10 nm or less. Furthermore, the single-layer MXene and few-layer MXene may be collectively referred to as "single-layer / few-layer MXene."

[0020] It is preferable that the particles of the layered material according to this embodiment contain a large amount of single-layered and few-layered MXene. By containing a large amount of single-layered and few-layered MXene, the specific surface area of ​​MXene can be made larger than that of multi-layered MXene, and as a result, as shown in the examples described later, the deterioration of electrode properties over time can be further suppressed. For example, in the particles of the layered material according to this embodiment, the number of stacked layers of MXene is 10 or less and the thickness is preferably 10 nm or less, and the ratio of single-layered and few-layered MXene to the total MXene is preferably 80% by volume or more, more preferably 90% by volume or more, and even more preferably 95% by volume or more. It is also more preferable that the volume of single-layered MXene is larger than the volume of few-layered MXene. Since the true density of these MXenes does not vary greatly depending on the form of existence, it can be said that it is more preferable that the mass of single-layered MXene is larger than the mass of few-layered MXene. When these relationships are satisfied, the specific surface area can be further increased and the deterioration of electrode properties over time can be further suppressed. Most preferably, the particles of the layered material according to this embodiment are formed only of single-layered MXene.

[0021] Although this embodiment is not limited thereto, the thickness of each layer of MXene (corresponding to the above-mentioned MXene layers 7a and 7b) can be, for example, 1 nm or more and 30 μm or less, and may be, for example, 1 nm or more and 5 nm or less, or even 1 nm or more and 3 nm or less (which can vary mainly depending on the number of M atomic layers contained in each layer). For each stack of multilayer MXene that can be included, the interlayer distance (or gap dimension, shown as Δd in FIG. 1(b)) can be, for example, 0.8 nm or more and 10 nm or less, particularly 0.8 nm or more and 5 nm or less, and more particularly about 1 nm, and the total number of layers can be 2 or more and 20,000 or less.

[0022] In the electrode of this embodiment, the particles of the layered material, which is included in the conductive film and includes one or more layers, have a π-electron conjugated compound (also called a "sacrificial oxidant") attached thereto. FIG. 2 is a schematic cross-sectional view of an embodiment of the electrode of the present embodiment, in which a substrate 31 is included and a biological tissue 30 is used as a test subject. Examples of measurement targets in the biological tissue 30 include the skin of a human body, blood vessels, muscles, the brain, and other organs under the skin. Measurement may be performed by directly contacting the electrode with the measurement target, or, for example, a measurement target under the skin may be indirectly measured by contacting the electrode with the skin. FIG. 2 is a schematic cross-sectional view of a conductive film 32 composed of π-electron conjugated compound-attached particles 33, that is, layered material particles (MXene particles) 34 to which π-electron conjugated compounds 35 are attached. FIG. 3 is an enlarged view of one of the layered material particles (MXene particles) 34 to which π-electron conjugated compounds 35 are attached. 2 and 3, the entire circumference of the cross section of the layered material particle (MXene particle) 34 is covered with the π-electron conjugated compound 35, but the present invention is not limited thereto, and it is sufficient that the π-electron conjugated compound 35 is attached to at least a part of the layered material particle (MXene particle) 34. In addition, in Fig. 3, the junction 36 formed by the π electrons of the layered material particle (MXene particle) 34 constituting the conductive film 32 and the π electrons of the π-electron conjugated compound 35 is exaggerated for the purpose of explaining the action and effect, and essentially, there is no gap formed by the junction 36 in Fig. 3 between the layered material particle (MXene particle) 34 and the π-electron conjugated compound 35, and the layered material particle (MXene particle) 34 and the π-electron conjugated compound 35 are substantially in contact with each other.

[0023] As shown in Fig. 2 and Fig. 3, the π-electron conjugated compound adheres to the layered material particles (MXene particles), covering the oxidation sites (mainly edges) 37 of the MXene particles 34 to prevent oxidation. Furthermore, a conductive path can be secured by bonding between the MXene particles 34 and the π-electron conjugated compound 35 by π electrons. Furthermore, the π-electron conjugated compound reacts with water, oxygen, etc. from the outside, i.e., is sacrificially oxidized, thereby preventing oxidation of the MXene by water, oxygen, etc. from the outside. As a result, excellent electrode characteristics such as maintaining high conductivity, suppressing an increase in initial impedance, and suppressing an increase in impedance over time can be realized. The biological tissue 30, for example, human skin, and the electrode 38 are in direct contact as shown in Fig. 2, and a film including a gel or porous membrane that is permeable to ions (not shown) may be present between the biological tissue 30 and the electrode 38.

[0024] The π-electron conjugated compound according to this embodiment has one or more of an aromatic ring, a heteroaromatic ring, a conjugated diene unit, an allyl group, and a vinyl group. The π-electron conjugated compound is preferably one or more compounds selected from the group consisting of ascorbic acid, erythorbic acid, dibutylhydroxytoluene, tocopherol, butylhydroxyanisole, catechin, and catechin derivatives. These compounds can be attached to almost every one of the MXene particles according to this embodiment, and all of them are sacrificially oxidized and form a bond with the MXene particles through π electrons.

[0025] Examples of the catechin derivative include catechin gallate, epicatechin, epicatechin gallate, gallocatechin, gallocatechin gallate, epigallocatechin, and epigallocatechin gallate. From the viewpoint of suppressing aggregation of MXene particles in a liquid and easily forming the conductive film according to the present embodiment, it is not preferable to use ascorbic acid or erythorbic acid, which are prone to losing the charge balance of MXene particles due to the presence of metal ions, as the compound, and it is preferable to use ascorbic acid having a proton or erythorbic acid having a proton. The π-electron conjugated compound is more preferably ascorbic acid (L-ascorbic acid).

[0026] In order to fully exert the effect of the π-electron conjugated compound, the ratio of the total amount of the π-electron conjugated compound to the total amount of the particles of the layered material is preferably in the range of 0.001% by mass or more and 10% by mass or less. The ratio can be, for example, 0.01% by mass or more, and further 0.1% by mass or more. In order to fully exert the inherent conductivity of the conductive film, the ratio is preferably 5% by mass or less.

[0027] The layered material particles to which the π-electron conjugated compound is attached preferably have a thickness of 1 nm or more and 30 μm or less, and the layered material particles to which the π-electron conjugated compound is attached preferably have a thickness of 1 nm or more and 1 μm or less.

[0028] The surface of the layered material particles does not have to be completely covered with the π-electron conjugated compound, and the π-electron conjugated compound is preferably attached to 20% or more of the surface of the layered material particles, more preferably 50% or more, and even more preferably 80% or more of the surface of the layered material particles. The layered material particles including one or more layers are preferably coated with the π-electron conjugated compound, for example, at the above ratio.

[0029] The number average Feret diameter of the particles of the layered material contained in the conductive film according to this embodiment is preferably 3 μm or more. As described above, the shape of the particles of the layered material has a plane, and the larger the plane area, the relatively smaller the number of end faces (edges) of the particles of the layered material that are likely to become oxidation sites, and the improved in-plane orientation of the coating film as a whole can be expected. As a result, the π-electron conjugated compound also becomes more likely to adhere, and many π-junctions between the MXene particles and the π-electron conjugated compound are easily formed, the conductivity becomes higher, and for example, the deterioration of electrode characteristics over time, such as an increase in impedance over time, can be further suppressed. In this specification, the size of the plane part of the particles of the layered material is defined by the number average Feret diameter. The number average Feret diameter is more preferably 4 μm or more. The number average Feret diameter is preferably as large as possible from the viewpoint of maintaining excellent electrode characteristics over a long period of time, but the upper limit of the number average Feret diameter is approximately 50 μm in consideration of production efficiency, etc. The Feret diameter can be measured at the stage of producing MXene particles, i.e., by using an MXene slurry, or by removing the π-electron conjugated compound from MXene particles to which the π-electron conjugated compound is attached, and then measuring the Feret diameter of the MXene particles. The number-average Feret diameter can be determined using a SEM (scanning electron microscope) or an AFM (atomic force microscope) as shown in the examples described later.

[0030] The electrode of this embodiment is not limited to a specific form as long as it includes a conductive film containing particles of a layered material containing one or more layers to which a π-electron conjugated compound is attached. The electrode may be in a solid state or a flexible soft state. The thickness of the layered material particles and the thickness of the π-electron conjugated compound in the electrode can be measured by, for example, measurement with a micrometer, or cross-sectional observation using a scanning electron microscope (SEM), a microscope, or a laser microscope.

[0031] One of the characteristics of the electrode of this embodiment is impedance. The smaller the initial impedance, the more preferable it is. According to the measurement conditions shown in the examples below, for example, at 10 Hz, it is 80 kΩ cm2 Below, 10 kΩ cm at 1 kHz 2 The smaller of the following ranges is preferred:

[0032] 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 a film including a gel or a porous film that is permeable to ions may be formed as another laminate. The porous film may be a film that has a large number of fine pores and selectively transmits ions or molecules smaller than the diameter of the pores. The material of these other laminates is not particularly limited and may be formed of an organic material, an inorganic material, or a mixture thereof. For example, the organic material may be a polymer such as a hydrophilic polymer, and the inorganic material may be ceramics or a combination thereof. The film thickness of these other laminates may be, for example, 0.1 μm or more and 300 μm or less. The porous film may have an average pore size of, for example, 1 nm or more and 1 μm or less. The porous film may be, for example, an aggregated particulate porous film, a mesh-like porous film, a fibrous porous film, a porous film having a plurality of isolated and / or connected tubular pores, a honeycomb-structured porous film, etc., according to the pore shape.

[0033] In the case where the electrode of the present embodiment has a substrate, the conductive film and the substrate are in direct contact with each other. The material of the substrate is not particularly limited. The substrate is formed of a conductive material. The conductive material may be at least one of metal materials such as gold, silver, copper, platinum, nickel, titanium, tin, iron, zinc, magnesium, aluminum, tungsten, and molybdenum, and conductive polymers. The substrate may have a conductive film, such as a metal film, other than the conductive film of the present embodiment on the contact surface with the conductive film of the present embodiment. Alternatively, the substrate may be formed of an organic material. The organic material may be, for example, a flexible organic material, such as a thermoplastic polyurethane elastomer (TPU), a PET film, or a polyimide film.

[0034] (Electrode Use) The electrode of the present embodiment may be used in any suitable application, such as an electrode in any suitable electric device, an electromagnetic shield (EMI shield), or the like, where maintaining high electrical conductivity (reducing the decrease in initial electrical conductivity and preventing oxidation) is required.

[0035] 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 of the present embodiment, it is possible to obtain a large-capacity capacitor and battery, a low-impedance biosignal sensing electrode, and a highly sensitive sensor and antenna even in a smaller volume (volume occupied by the device).

[0036] The capacitor may be an electrochemical capacitor. The electrochemical capacitor is a capacitor that utilizes a capacity generated due to a physicochemical reaction between an electrode (electrode active material) and an ion (electrolyte ion) in an electrolyte, and can be used as a device that stores electric 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 thereto.

[0037] The biosignal sensing electrode is an electrode for acquiring a biosignal. The biosignal sensing electrode may be, for example, but is not limited to, an electrode for measuring EEG (electroencephalogram), ECG (electrocardiogram), EMG (electromyogram), and EIT (electrical impedance tomography).

[0038] The 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.

[0039] The antenna electrode is an electrode for emitting electromagnetic waves into space and / or receiving electromagnetic waves in space.

[0040] The electrode of this embodiment is preferably used as a biosignal sensing electrode having the π-electron conjugated compound film on the surface that comes into contact with a subject.

[0041] (Embodiment 2: Electrode manufacturing method) Hereinafter, a method for producing an electrode according to an embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment.

[0042] The method for producing an electrode according to the present embodiment includes the steps of: (a) the 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 Group 12, 13, 14, 15, or 16 element; n is 1 or more and 4 or less, m is greater than n and less than or equal to 5) preparing a precursor of a conductive film represented by (b) removing at least a portion of the A atoms from the precursor using an etching solution; (c) washing the first intermediate obtained by (b) with water; (d) performing intercalation, which includes mixing the second intermediate obtained by (c) with an intercalation compound for the second intermediate; (e) stirring the third intermediate obtained by (d) in a liquid; (f) washing the fourth intermediate obtained by (e) with water to obtain particles of a layered material; (g) mixing the particles of the layered material obtained by (f) with a π-electron conjugated compound having one or more of an aromatic ring, a heteroaromatic ring, a conjugated diene unit, an allyl group, and a vinyl group to form particles of a layered material having a π-electron conjugated compound attached thereto; (h) forming a conductive film by supplying particles of a layered material having a π-electron conjugated compound attached thereto onto a substrate. This manufacturing method makes it possible to manufacture an electrode that can maintain excellent electrode properties for a long period of time.

[0043] Each step of the above manufacturing method will now be described in detail. ·Process (a) First, a predetermined precursor is prepared. The predetermined precursor that can be used in this embodiment is the 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 Group 12, 13, 14, 15, or 16 element; n is 1 to 4, m is greater than n and less than or equal to 5) It is expressed as:

[0044] The above M, X, n, and m are as described for MXene. A is at least one element of Groups 12, 13, 14, 15, and 16, and is usually an A group element, typically Groups IIIA and IVA, and more specifically 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.

[0045] The MAX phase is M m X n (each X may have a crystal lattice in which it is located in the octahedral array of M) between which a layer composed of A atoms is located. 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 (collectively referred to as "M m X nand a layer of A atoms (also referred to as an "A atom layer") arranged as a layer next to the n+1th layer of M atoms, but is not limited thereto.

[0046] 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-shaped MAX phase). The sintered body is then pulverized with an end mill to obtain a powdered MAX phase for the next process.

[0047] ·Process (b) Etching is performed by using an etching solution to remove at least some of the A atoms from the precursor. The etching solution may contain, for example, one or more of HF, H3PO4, HCl, HI, and H2SO4. The etching solution preferably contains at least one of HF (hydrofluoric acid) and H3PO4 (phosphoric acid). For example, etching can be performed by the so-called MILD method in which HCl and LiF contained in the etching solution are reacted in the system to generate HF, but it is preferable to perform etching by the so-called ACID method in which etching is performed with an etching solution containing HF (hydrofluoric acid) or an etching solution containing phosphoric acid. These methods are preferable because they can easily obtain flake-shaped layered material particles (MXene particles) with a large planar area and a number average Feret diameter of preferably 3 μm or more compared to the MILD method. Other conditions for etching are not particularly limited, and known conditions can be adopted. As the etching solution, a mixture of the above-mentioned acid and, for example, pure water as a solvent can be used. The etching solution may be one that satisfies at least one of the following: HF concentration 1.5M or more, H3PO4 concentration 5.5M or more, HCl concentration 6.0M or more, H3PO4 concentration 5.5M or more, HI concentration 5.0M or more, and H2SO4 concentration 5.0M or more. In the etching of the A atoms, in addition to the A atoms, some of the M atoms may also be selectively etched. An example of the etched product obtained by the above etching is a slurry.

[0048] ·Process (c) The etched product (first intermediate) obtained by the etching is washed with water. By washing with water, the acid used in the etching can be sufficiently removed. The amount of water to be mixed with the etched product and the washing method are not particularly limited. For example, water may be added and stirred, centrifuged, etc. may be added. 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, may be adjusted according to the amount and concentration of the object to be treated. The washing with water may be performed one or more times. Preferably, the washing with water is performed multiple times. For example, the 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 and recovering the remaining precipitate may be performed two or more times, for example, 15 times or less.

[0049] ·Process (d) The treated product (second intermediate) obtained by the water washing is mixed with an intercalation compound for the second intermediate to carry out intercalation.

[0050] The intercalation compound of the second intermediate may be of any type, so long as it can be inserted between the layers of the second intermediate and separated into each layer by the delamination in the next step (e). The intercalation compound is preferably an alkali metal compound or an alkaline earth metal compound. More preferably, it is a Li-containing compound. As the Li-containing compound, an ionic compound in which Li ions and cations are bonded can be used. For example, halides including iodides, chlorides, and fluorides, phosphates, sulfides including sulfates, nitrates, acetates, and carboxylates of Li ions can be mentioned.

[0051] The content of the intercalation compound in the intercalation blend is preferably 0.001% by mass or more. The content is more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more. On the other hand, from the viewpoint of dispersibility in the solution, the content of the intercalation compound is preferably 10% by mass or less, and more preferably 1% by mass or less.

[0052] The specific method of intercalation is not particularly limited, and for example, the intercalation compound may be mixed with the water medium clay of the MXene, 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 stirrer or other stirring bar, a method using a stirring blade, a method using a mixer, and a method using a centrifugal device. The stirring time can be set according to the manufacturing scale of the electrode, and may be set, for example, between 12 and 24 hours.

[0053] ·Process (e) The treated product (third intermediate) obtained by the intercalation in step (d) is subjected to delamination, which includes stirring in a liquid such as water. This delamination can separate MXene into a single layer or a few layers. The conditions for delamination are not particularly limited, and can be performed by a known method. For example, stirring using a hand shake or an automatic shaker can be used as a stirring method. The degree of stirring, such as the stirring speed and stirring time, can be adjusted according to the amount and concentration of the treated product to be treated. For example, the above-mentioned slurry after intercalation is centrifuged to discard the supernatant, and then pure water is added to the remaining precipitate, and then stirring using a hand shake or an automatic shaker is performed to separate the layers.

[0054] In the manufacturing method of the present embodiment, ultrasonic treatment is not performed as delamination. As described above, since ultrasonic treatment is not performed, particle destruction is unlikely to occur, and as a result, single-layered or few-layered MXene having a large number average Feret diameter and a large plane parallel to the particle layer, i.e., a large two-dimensional surface, can be obtained as the particles of the layered material.

[0055] ·Process (f) The treated product (fourth intermediate) obtained by delamination is washed with water to obtain particles of layered material. The amount of water and the washing method are not particularly limited. For example, water is added and stirring and centrifugation are 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 may be adjusted according to the amount and concentration of the material to be treated. The washing with water may be performed one or more times. Preferably, the washing with water is performed multiple times. For example, the steps (i) to (iii) of (i) adding water and stirring, (ii) centrifuging the stirred product, and (iii) recovering the supernatant after centrifugation are performed two or more times, for example, within a range of 10 times or less, to obtain a MXene-containing supernatant. Then, the MXene-containing supernatant is centrifuged to obtain a MXene-containing clay.

[0056] ·Process (g) The layered material particles obtained by (f) are mixed with the π-electron conjugated compound to form layered material particles to which the π-electron conjugated compound is attached (π-electron conjugated compound-attached particles). The π-electron conjugated compound may be any of the compounds described in the description of the electrodes. The mixing method is not particularly limited. For example, a solution containing a π-electron conjugated compound and an aqueous dispersion containing layered material particles are prepared and mixed. The solution containing the π-electron conjugated compound is preferably a solution in which the molar concentration of the π-electron conjugated compound is 0.001M or more and 5M or less. In addition, the aqueous dispersion containing the layered material particles is preferably a layered material particle-containing slurry in which the solid content concentration of the layered material particles is 10mg / mL or more and 250mg / mL or less. By mixing these, layered material particles to which the π-electron conjugated compound is attached can be easily formed. The mixing method is not particularly limited, and examples include hand shaking or stirring with a device such as a magnetic stirrer, a mechanical stirrer, a homomixer, or a homogenizer. The speed and time of stirring may be appropriately determined depending on the amount of processing, etc. After mixing, the mixture is left for about 3 hours as shown in the examples, for example, so that the π-electron conjugated compound can be sufficiently attached to the particles of the layered material. Then, the formed particles with the π-electron conjugated compound attached thereto can be collected by centrifugation, filtration, etc. The mixing and the subsequent leaving can be carried out at room temperature. The leaving after mixing is preferably at 0°C or higher and 10°C or lower, for example, preferably in a refrigerator.

[0057] ·Process (h) A conductive film is formed by supplying particles of a layered material to which a π-electron conjugated compound is attached onto a substrate. The method of supplying particles of a layered material to which a π-electron conjugated compound is attached onto a substrate is not limited, and examples of the method include coating, immersion, and filtration. For example, when a slurry containing particles to which a π-electron conjugated compound is attached is applied to a substrate (e.g., a substrate), the coating method is not limited. For example, examples of the coating method include spray coating using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush, slit coating using a table coater, a comma coater, or a bar coater, screen printing, metal mask printing, spin coating, immersion, brushing, and dripping.

[0058] The above coating and drying steps may be repeated several times as necessary until a conductive film of the desired thickness is obtained. Drying and curing may be performed at a temperature of 400° C. or less using, for example, a normal pressure oven or a vacuum oven.

[0059] As described above, the electrode according to this embodiment may or may not have a substrate. In the case of an electrode having a substrate, the substrate made of the above-mentioned material can be used. For example, when a flexible organic material substrate is used, as shown in the examples described later, a plasma treatment may be performed before coating to improve the hydrophilicity of the surface, and a pretreatment may be performed. In the case of an electrode without a substrate, the substrate used in this step may be any substrate for forming a conductive film, and the material is not important. For example, when a conductive film is formed by suction filtration, a polymer film such as a membrane filter can be used as the substrate.

[0060] Although the electrode and the manufacturing method thereof according to the embodiment of the present invention have been described in detail above, various modifications are possible. Note that the electrode according to this embodiment may be manufactured by a method different from the manufacturing method according to the above-mentioned embodiment, and that the manufacturing method of the electrode according to this embodiment is not limited to only the method of providing the electrode according to the above-mentioned embodiment. EXAMPLES

[0061] [Example 1] In Example 1, an experiment was conducted to compare the change in impedance over time between a conductive film formed from MXene particles to which ascorbic acid was attached as a π-electron conjugated compound (an MXene film with ascorbic acid attached) and a conductive film formed from MXene particles not attached to a π-electron conjugated compound (MXene particles only) (an MXene film without ascorbic acid attached).

[0062] (Preparation of layered material particles (MXene particles)) MXene was prepared by the method shown below (the ACID method was used as the etching method for MAX). The details are as follows.

[0063] (Preparation of MXene particles using the ACID method as the MAX etching method) (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 mixed powder was sintered at 1350°C for 2 hours in an Ar atmosphere. The sintered body (block-shaped MAX) was pulverized with an end mill to a maximum dimension of 40 μm or less. As a result, Ti3AlC2 particles were obtained as a precursor (powder-shaped MAX).

[0064] (2) Etching of Precursor Using the Ti3AlC2 particles (powder) prepared by the above method, etching was carried out under the following etching conditions (ACID method) to obtain a solid-liquid mixture (slurry) containing solid components derived from the Ti3AlC2 powder. (Etching conditions) Precursor: Ti3AlC2 (passed through a 45μm sieve) Etching solution composition: 49% HF 6mL, H2O 18mL HCl (12M) 36mL Precursor input: 3.0g Etching container: 100mL Eyeboy Etching temperature: 35℃ Etching time: 24h Stirrer speed: 400 rpm (3) Cleaning after etching The above slurry was divided into two, inserted into two 50 mL centrifuge tubes, and centrifuged at 3500 G using a centrifuge, after which the supernatant was discarded. 40 mL of pure water was added to each centrifuge tube, and the centrifuge was again performed at 3500 G to separate and remove the supernatant. This operation was repeated 11 times. After the final centrifugation, the supernatant was discarded to obtain Ti3C2Ts-water medium clay. (4) Lithium intercalation Ti3C2T prepared by the above method s - For the water medium clay, Li intercalation was performed by using LiCl as a Li-containing compound and stirring for 12 hours at 20°C to 25°C according to the Li intercalation conditions below. The detailed conditions for Li intercalation are as follows. (Li intercalation conditions) · Ti3C2T s - Moisture medium clay (MXene after washing): 0.75g solids LiCl: 0.75g Intercalation vessel: 100mL Eye Boy ·Temperature: 20℃ or higher and 25℃ or lower (room temperature) ·Time: 10h Stirrer speed: 800 rpm (5) Delamination The slurry obtained by Li intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3500 G using a centrifuge, after which the supernatant was discarded. Next, (i) 40 mL of pure water was added to the remaining precipitate and stirred for 15 minutes using a shaker, (ii) centrifuged at 3500 G, and (iii) the supernatant was collected as a single-layer / sparse-layer MXene-containing solution. These steps (i) to (iii) were repeated a total of four times to obtain a single-layer / sparse-layer MXene-containing supernatant. This supernatant was then centrifuged at 4300 G for 2 hours using a centrifuge, after which the supernatant was discarded to obtain a single-layer / sparse-layer MXene-containing clay.

[0065] (Formation of electrode sample) Ascorbic acid was dissolved in pure water to obtain an aqueous solution with a concentration of 10 mM. Pure water was added to the above single-layer and few-layer MXene-containing clay to obtain an aqueous dispersion slurry of MXene with a solid concentration of 10 mg / mL or less. The mixture obtained by mixing the above aqueous solution of ascorbic acid and the aqueous dispersion slurry of MXene was stirred by hand for 5 minutes and then left for 3 hours. Then, centrifugation was performed to separate the ascorbic acid-attached MXene from the solution. After centrifugation, the supernatant was separated and removed, and the remaining ascorbic acid-attached MXene slurry was washed three times, and then the obtained ascorbic acid-attached MXene slurry was redispersed in DI water. The ascorbic acid-attached MXene slurry was spray-coated on a flexible organic material substrate (polyimide film, size: circular shape with a diameter of 10 cm) that had been plasma-treated in advance to improve the hydrophilicity of the substrate surface. Then, it was dried in an oven to obtain an electrode sample with an ascorbic acid-attached MXene film formed on the flexible organic material substrate.

[0066] (Measurement of the ratio of the total amount of π-electron conjugated compounds to the total amount of layered material particles) The ascorbic acid-attached MXene film was scraped off from the electrode sample, and the weight loss was measured using a TG-DTA (manufacturer: a thermal analyzer (instrument name: STA7300) manufactured by Hitachi High-Tech Science Corporation). From the measurement results, the ratio of the total amount of the π-electron conjugated compound to the total amount of the layered material particles was calculated, and was within the range of 0.05% by mass or more and 5% by mass or less.

[0067] (Measurement of initial impedance value and rate of change) The impedance of the above electrode sample was measured in a three-electrode system using a Gamry Reference 600 Potentiostat / Galvanostat / ZRA. Natus disposable adhesive electrodes were used as the reference electrodes, and Conmed ECG electrodes were used as the counter electrodes. The instantaneous overvoltage was 10 mV. Values ​​at frequencies of 10 Hz and 1 kHz were recorded. The electrodes were placed on the skin of the inside of the forearm and measurements were performed. The electrodes were fixed with an elastic band or the like. Before the measurements, the area where the electrodes were to be attached was wiped with cotton soaked in disinfectant ethanol and allowed to dry, then wiped with cotton soaked in PBS (product name: 1X PBS, pH 7.4, manufacturer: Quality Biological), and excess PBS was gently removed with dry cotton.

[0068] In order to obtain a reference value, an MXene membrane without ascorbic acid was prepared instead of the MXene membrane with ascorbic acid attached, and similar measurements were performed. The initial impedance (day 0) of the MXene membrane without ascorbic acid attached was set to 1.00, and the ratio of each impedance measurement value to the initial impedance of the MXene membrane without ascorbic acid attached was calculated as the impedance change rate to evaluate the change in impedance over time. The initial impedance of the MXene membrane without ascorbic acid attached and the MXene membrane with ascorbic acid attached are shown in Table 1. In Table 1, the impedance change rate relative to the initial impedance of the MXene membrane without ascorbic acid attached is also shown in parentheses for the measurement value of the MXene membrane with ascorbic acid attached. In addition, as the change in impedance over time, the results of measuring the impedance every day after wearing for 4 days are shown in Table 2 for 10 Hz and Table 3 for 1 kHz, respectively. In Tables 2 and 3, the numbers in parentheses are the change rate of each impedance relative to the initial impedance of the MXene membrane with ascorbic acid attached.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] As shown in Table 1, the increase in initial impedance of the MXene membrane with ascorbic acid was suppressed to less than 10% compared to the MXene membrane with no ascorbic acid attached. Furthermore, as shown in Tables 2 and 3, in the case of the MXene membrane with no ascorbic acid attached, the impedance after 3 days (4th day) was more than 30 times the initial impedance at 10 Hz and more than 16 times the initial impedance at 1 kHz. In contrast, the impedance of the MXene membrane with ascorbic acid attached remained about 20 times at 10 Hz and about 15 times at 1 kHz. In particular, when the initial impedance of the MXene membrane with no ascorbic acid attached and the MXene membrane with ascorbic acid was set to 1.00, at 10 Hz, the impedance of the MXene membrane with no ascorbic acid attached increased to about 33 times on the 4th day (3 days), whereas the impedance of the MXene membrane with ascorbic acid attached was about 20 times, a reduction of -30%.

[0073] From the above results, it is believed that oxidation is suppressed in the MXene film with ascorbic acid attached. The reason why the above effect was obtained by the attachment of ascorbic acid is thought to be as follows. That is, ascorbic acid behaves like a vinyl carboxylic acid in an acidic solution, and the π electrons of the double bond are transferred between the hydroxyl group and the carbonyl group to form a stable conjugate base O - In other words, in the weakly acidic MXene aqueous dispersion, -The MXene groups are strongly adsorbed to the edges of the MXene sheets, which are positively charged and are the oxidation sites of MXene, and to the carbon defects of the MXene sheets. Therefore, it is thought that it plays a role in protecting MXene itself from oxygen in the air. In addition, since ascorbic acid also has a carbon double bond and has many π electrons, it is thought that the metal atoms of MXene interact with the π electrons of ascorbic acid, creating a phenomenon called π junction, which increases electrical conductivity. In addition, ascorbic acid acts as a reducing agent and sacrificially oxidizes, which is thought to prevent the oxidation of MXene particles by external water, oxygen, etc.

[0074] [Example 2] In Example 2, the effect of the particle shape of the layered material on the change in impedance over time was examined.

[0075] A water-dispersed MXene clay (10 mM) was prepared in the same manner as in Example 1. Pure water was added to this single-layer / few-layer MXene-containing clay (10 mM) to obtain a water-dispersed MXene slurry (ACID method) with a solid concentration of 10 mg / mL or less.

[0076] In addition to the above-mentioned MXene water-borne clay (ACID method), MXene water-borne clay was prepared by the method described below (the MILD method was used as the MAX etching method).

[0077] (Preparation of MXene particles using the MILD method as the etching method for MAX) (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 mixed powder was sintered at 1350°C for 2 hours in an Ar atmosphere. The sintered body (block-shaped MAX) was pulverized with an end mill to a maximum dimension of 40 μm or less. As a result, Ti3AlC2 particles were obtained as a precursor (powder-shaped MAX). (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 45μm sieve) Etching solution composition: LiF 3.0g 7.5mL H2O HCl (12M) 22.5mL Precursor input: 3.0g Etching container: 100mL Eyeboy Etching temperature: 35℃ Etching time: 72h Stirrer speed: 400 rpm (3) Cleaning after etching The above slurry was divided into two, inserted into two 50 mL centrifuge tubes, and centrifuged at 3500 G using a centrifuge, after which the supernatant was discarded. 40 mL of pure water was added to each centrifuge tube, and the centrifuge was again performed at 3500 G to separate and remove the supernatant. This operation was repeated 11 times. After the final centrifugation, the supernatant was discarded to obtain Ti3C2Ts-water medium clay. (4) Delamination 40 mL of pure water was added to the Ti3C2Ts-water medium clay, which was then stirred on a shaker for 15 minutes, (ii) centrifuged at 3500G, and (iii) the supernatant was collected as a single-layer / several-layer MXene-containing solution. These steps (i) to (iii) were repeated a total of four times to obtain a single-layer / several-layer MXene-containing supernatant. This supernatant was then centrifuged at 4300G for two hours using a centrifuge, after which the supernatant was discarded to obtain a single-layer / several-layer MXene-containing clay.

[0078] Pure water was added to 10 mM of the above single-layer and few-layer MXene-containing clay (MILD method) to prepare an MXene aqueous dispersion slurry (MILD method) with a solid concentration of 10 mg / mL or less.

[0079] The above MXene aqueous dispersion slurry (ACID method) and the above MXene aqueous dispersion slurry (MILD method) were each spray-coated onto a glass slide and dried to prepare single-layer and few-layer MXene films (ACID method) and single-layer and few-layer MXene films (MILD method).

[0080] (Measurement of the initial impedance of each MXene thin film) Using electrodes formed with each of the above single-layer and few-layer MXene films, the initial impedance and the impedance after standing for 2 weeks were measured at room temperature in air. Other impedance measurement conditions were as follows. That is, measurements were performed in a standard three-electrode system using a Gamry Reference 600 Potentiostat / Galvanostat / ZRA, a saturated Ag / AgCl reference electrode (Sigma-Aldrich; 3 M potassium chloride) and a carbon counter electrode. Electrochemical impedance spectroscopy (EIS) was performed in the range of 0.1 to 105 Hz and a driving voltage of 10 mV (peak-to-peak amplitude, sine wave). Impedance was evaluated at 10 Hz and 1 kHz.

[0081] (Measurement of the number-average Feret diameter of the particles of the layered materials that compose each MXene thin film) For both the particles of the layered material obtained by etching MAX using the ACID method and the particles of the layered material obtained by the MILD method, the number average Feret diameter was measured after removing ascorbic acid from the MXene film with ascorbic acid attached. In detail, the MXene film with ascorbic acid attached was ultrasonically cleaned in pure water, and MXene flakes without ascorbic acid attached were dispersed in the pure water. An arbitrary amount of the pure water in which the MXene flakes were dispersed was dropped onto a Si substrate. The mixture was left to stand at room temperature for 8 hours, and the water was removed to obtain a Si substrate carrying MXene flakes. The MXene flakes carried on the Si substrate were visually observed and confirmed using a scanning electron microscope (product name S-4800) manufactured by Hitachi High-Technologies Corporation, which was used to take a picture at a magnification of 2000 times. The number average Feret diameter was determined by randomly extracting 50 or more particles from the photograph, determining the Feret tangential diameter in a specific direction of each particle, and averaging the above numbers to obtain the number average Feret diameter.

[0082] As a result of calculating the number average Feret diameter, when MAX etching was performed by the MILD method, it was less than 3.00 μm, and when MAX etching was performed by the ACID method, it was 3.00 μm or more.

[0083] In addition, even if the etching of MAX is performed by the phosphoric acid etching described below instead of the ACID method shown in Example 1, it is believed that MXene having a number average Feret diameter of 3.00 μm or more can be obtained and the impedance increase suppression effect can be obtained.

[0084] (MAX method includes phosphoric acid etching) [Sample preparation] MXene particles were fabricated by sequentially carrying out five steps: (1) preparation of precursor (MAX), (2) etching of the precursor, (3) washing, (4) intercalation, and (5) delamination, as detailed below. (1) Preparation of precursor (MAX) 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 mixed powder was sintered at 1350°C for 2 hours in an Ar atmosphere. The sintered body (block) was pulverized with an end mill to a maximum dimension of 40 μm or less. As a result, Ti3AlC2 particles were obtained as the precursor (MAX). (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 45μm sieve) Etching solution composition: Aqueous solution with HF concentration of 1.5M or more and H3PO4 concentration of 5.5M or more Precursor input: 3.0g Etching container: 100mL Eyeboy Etching temperature: 35℃ Etching time: 24h Stirrer speed: 400 rpm (3) Cleaning The above slurry was divided into two and placed in two 50 mL centrifuge tubes, respectively, and centrifuged at 3500 G using a centrifuge, after which the supernatant was discarded. (i) In each centrifuge tube, 40 mL of pure water was added to the clay that had settled by centrifugation, and the mixture was mixed to form a slurry. (ii) The process of centrifuging again at 3500G and separating and removing the supernatant was repeated 11 times. After the final centrifugation, the supernatant was discarded and the remaining precipitate was Ti3C2T s - Moisture medium clay was obtained. (4) Intercalation Ti3C2T prepared by the above method s -Li3PO4, H3PO4 and pure water were added to the clay as a water medium, and the mixture was stirred at 20°C to 25°C for 15 hours to perform Li intercalation. The detailed conditions for Li intercalation are as follows: (Li intercalation conditions) · Ti3C2T s - Moisture medium clay (MXene after washing): 0.75g solids Li3PO4: 0.68g ·85 mass% H3PO4: 3.1mL H2O: 31.9mL Intercalation vessel: 100mL Eye Boy ·Temperature: 20℃ or higher and 25℃ or lower (room temperature) ·Time: 15h Stirrer speed: 800 rpm (5) Delamination The slurry after Li intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3500 G using a centrifuge, after which the supernatant was discarded. Next, 40 mL of pure water was added to the remaining precipitate after removing the supernatant, and the mixture was stirred for 15 minutes on a shaker, centrifuged at 3500 G, and the supernatant was collected as a solution containing single and few layers of MXene. This procedure was repeated four times to obtain a sample containing single and few layers of MXene.

[0085] The results of measuring the initial impedance at 10 Hz and 1 kHz for each number average Feret diameter are shown in Table 4. The rate of change in parentheses in Table 4 indicates the reduction rate of the initial impedance due to the increase of the Feret diameter from less than 3.00 μm to 3.00 μm or more, as a negative value. Furthermore, the change in impedance over time when left in the atmosphere for two weeks is shown in Table 5 for 10 Hz and in Table 6 for 1 kHz for number average Feret diameters of less than 3.00 μm and 3.00 μm or more.

[0086] [Table 4]

[0087] [Table 5]

[0088] [Table 6]

[0089] As shown in Table 5, it can be seen that the initial impedance can be reduced by approximately -10% to -5% by applying MXene having a number average Feret diameter of 3.00 μm or more. This is thought to be due to the fact that when produced by the ACID method, a single MXene sheet is large, which contributes to the improvement of in-plane conductivity. In addition, as shown in Table 6, it can be seen that the increase in impedance after 2 weeks is also gradual when the number average Feret diameter is 3.00 μm or more. This is thought to be due to the effect of reducing the oxidation sites (number of edges) per unit area by having a number average Feret diameter of 3.00 μm or more. From the ratio of the impedance change rate after 2 weeks, it can be said that this suppression effect is about a reduction in the impedance increase rate of -25%.

[0090] Moreover, the MXene shown in Tables 1 and 2 above was obtained by etching using the ACID method, and the number average Feret diameter of the particles is 3 μm or more. It can be seen from Tables 1 and 2 that the impedance change rate can be sufficiently suppressed by using MXene particles with a large number average Feret diameter and by attaching ascorbic acid to the MXene particles.

[0091] From these results, the following can be said. In MXene particles (particles of a layered material), π junctions can be formed only in the XY plane of the MXene particle, so it is believed that particles with a large Feret diameter form more π junctions. By forming a conductive film using layered material particles (MXene particles) with a large Feret diameter, preferably a number-average Feret diameter of 3 μm or more, which are more likely to form π junctions, in addition to the effect of ascorbic acid adhering to the MXene particles described in Example 1, it can be said that an additional effect was obtained in that the in-plane orientation of the MXene film was improved, π junctions with the attached ascorbic acid were easily formed, and the effect of suppressing the increase in impedance was more remarkable. [Industrial Applicability]

[0092] The electrode according to this embodiment may be used for any appropriate purpose, and may be preferably used, for example, as a biosignal sensing electrode.

[0093] This application is based on and claims priority to U.S. Provisional Patent Application No. 63 / 223,292, filed with the U.S. Patent and Trademark Office on July 19, 2021, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0094] 1a, 1b layer body (M m X n layer) 3a, 5a, 3b, 5b Modified or terminal T 7a, 7b MXene layers 10a, 10b, 34 MXene particles (particles of layered materials) 30 Biological Tissue 31 Base material 32 Conductive Film 33 Particles with π-electron conjugated compounds 35 π-electron conjugated compounds 36 Bonding between π electrons of MXene particles and π electrons of π-electron conjugated compounds 37 Edges of MXene particles 38 electrodes

Claims

1. A conductive film comprising particles of a layered material having one or more layers with a π - electron conjugated compound attached thereto, wherein the one or more layers comprise a layer body represented by the following formula: M ｍ X ｎ (wherein M is at least one metal of Groups 3, 4, 5, 6, 7; 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 5 or less), 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, and the π - electron conjugated compound has one or more of a conjugated diene unit, an allyl group, and a vinyl group, an electrode.

2. A conductive film comprising particles of a layered material having one or more layers with a π - electron conjugated compound attached thereto, wherein the one or more layers comprise a layer body represented by the following formula: MmXn (wherein M is at least one metal of Groups 3, 4, 5, 6, 7; 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 5 or less), 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, and the π - electron conjugated compound is one or more compounds selected from the group consisting of ascorbic acid, erythorbic acid, dibutylhydroxytoluene, tocopherol, butylhydroxyanisole, catechin, and catechin derivatives, an electrode.

3. The electrode according to claim 1 or 2, wherein the particles of the layered material comprising the one or more layers are coated with a π - electron conjugated compound.

4. The electrode according to claim 1 or 2, wherein the ratio of the total amount of the π - electron conjugated compound to the total amount of the particles of the layered material is 0.001 mass% or more and 10 mass% or less.

5. The thickness of the particles of the layered material to which the π - electron conjugated compound is attached is 1 nm or more and 30 μm or less, and the thickness of the π - electron conjugated compound attached to the particles of the layered material is 1 nm or more and 1 μm or less, the electrode according to claim 1 or 2.

6. The electrode according to claim 1 or 2, wherein the number - average Feret diameter of the particles of the layered material is 3 μm or more.

7. The electrode according to claim 1 or 2, which is used as a biological signal sensing electrode.

8. (a) Prepare a precursor of a conductive film represented by the following formula: M ｍ AX ｎ (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7; 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; m is greater than n and 5 or less) (b) Remove at least some of the A atoms from the precursor using an etching solution; (c) Wash the first intermediate obtained in (b) with water; (d) Perform intercalation, including mixing the second intermediate obtained in (c) with a compound for intercalation between the layers of the second intermediate; (e) Stir the third intermediate obtained in (d) in a liquid; (f) Wash the fourth intermediate obtained in (e) with water to obtain particles of a layered material; (g) Mix the particles of the layered material obtained in (f) with a π - electron conjugated system compound having one or more of a conjugated diene unit, an allyl group, and a vinyl group to form particles of a layered material with the π - electron conjugated system compound attached; (h) Form a conductive film by supplying the particles of the layered material with the π - electron conjugated system compound attached onto a substrate. A method for manufacturing an electrode, comprising:

9. (a) Prepare a precursor of a conductive film represented by the following formula: M m AX n (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7; 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; m is greater than n and 5 or less) (b) Remove at least some of the A atoms from the precursor using an etching solution; (c) Wash the first intermediate obtained in (b) with water; (d) Perform intercalation, including mixing the second intermediate obtained in (c) with a compound for intercalation between the layers of the second intermediate; (e) Stir the third intermediate obtained in (d) in a liquid; (f) Wash the fourth intermediate obtained in (e) with water to obtain particles of a layered material; ​ (g) Mixing the particles of the layered material obtained in (f) with one or more compounds selected from the group consisting of ascorbic acid, erythorbic acid, dibutylhydroxytoluene, tocopherol, butylhydroxyanisole, catechin, and catechin derivatives, which are π-electron conjugated compounds, to form particles of the layered material to which the π-electron conjugated compound is attached. (h) Supplying the particles of the layered material to which the π-electron conjugated compound is attached onto a substrate to form a conductive film. A method for manufacturing an electrode, comprising the steps of: **Claim 10** The method for manufacturing an electrode according to claim 8 or 9, wherein particles of a layered material coated with the π-electron conjugated compound are formed. **Claim 11** The method for manufacturing an electrode according to claim 8 or 9, wherein the etching solution contains at least one of hydrofluoric acid and phosphoric acid. **Claim 12** (a) The following formula: MmAXn (In the formula, M is at least one metal of Groups 3, 4, 5, 6, and 7; 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; m is greater than n and 5 or less). Prepare a precursor of the conductive film represented by the formula. (b) Using an etching solution, remove at least some of the A atoms from the precursor. (c) Wash the first intermediate obtained in (b) with water. (d) Perform intercalation, including mixing the second intermediate obtained in (c) with a compound for intercalating into the layers of the second intermediate. (e) Stir the third intermediate obtained in (d) in a liquid. (f) Wash the fourth intermediate obtained in (e) with water to obtain particles of the layered material. (g) Mixing a solution containing a π-electron conjugated compound having one or more of an aromatic ring, a heteroaromatic ring, a conjugated diene unit, an allyl group, and a vinyl group at a molar concentration of 0.001 M or more and 5 M or less with a slurry containing the particles of the layered material obtained in (f) at a solid content concentration of 10 mg / mL or more and 250 mg / mL or less to form particles of the layered material to which the π-electron conjugated compound is attached. (h) Supplying the particles of the layered material to which the π-electron conjugated compound is attached onto a substrate to form a conductive film. A method for manufacturing an electrode, comprising the steps of:

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