Electrode and manufacturing method thereof

Abstract

The present invention comprises a laminate of a conductive film including particles of a layered material including one or more layers and a π-electron conjugated compound film, wherein the one or more layers are 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, wherein the π-electron conjugated compound film contains a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond.

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, The present invention includes a lamination of a conductive film including particles of a layered material including one or more layers and a π-electron conjugated compound film, 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 to 4, m is greater than n and less than or equal to 5) and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, The π-electron conjugated compound film includes a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond.

[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 to 4, 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) forming a conductive film containing particles of the layered material on a substrate; (h) forming a π-electron conjugated compound film on the conductive film, the π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond; A method for manufacturing an electrode is provided, comprising: Effect of the Invention

[0008] According to the present invention, the electrode comprises a laminate of a conductive film containing particles of a predetermined layered material (also referred to in this specification as "MXene") having one or more layers and a π-electron conjugated compound film, thereby providing an electrode that contains MXene and can maintain stable electrode properties over the long term. [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. 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 The present invention includes a lamination of a conductive film including particles of a layered material including one or more layers and a π-electron conjugated compound film, The one or more layers may have the formula: M mX 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 film includes a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond. The electrode has the conductive film, and thus can maintain stable electrode characteristics for a long period of time. For example, low impedance can be ensured as an electrode characteristic. More specifically, for example, in a biological environment, an increase in the initial impedance of the electrode can be suppressed, and an increase in impedance over time can also be suppressed.

[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 particles of the layered material (also referred to as "MXene particles") that constitute the conductive film in the electrode according to this embodiment will be described with reference to FIG.

[0018] The electrode of this embodiment is an assembly including 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 conductive film according to the present embodiment may include multiple layers as well as one layer. As a multiple layer MXene (multilayer MXene), as shown in FIG. 1(b), there may be mentioned two layers of MXene 10b, but the present invention is 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). In the multilayer MXene, two adjacent MXene layers (e.g., 7a and 7b) may not necessarily be completely separated, and may be partially in contact with each other. The MXene 10a may be 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 having a small number of layers obtained through a delamination process. The "small number of layers" means, for example, that the number of stacked layers of MXene is 10 or less. 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] The conductive film according to the present embodiment preferably contains 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, deterioration of electrode properties over time can be further suppressed. For example, in the conductive film according to the present embodiment, the single-layered and few-layered MXene, which has 10 or less MXene layers and a thickness of preferably 10 nm or less, preferably accounts for 80% or more by volume of the total MXene, more preferably 90% or more by volume, and even more preferably 95% or more by volume. It is more preferable that the volume of the single-layered MXene is larger than the volume of the few-layered MXene. Since the true density of these MXenes does not vary significantly depending on the form of existence, it can be said that it is more preferable that the mass of the single-layered MXene is larger than the mass of the few-layered MXene. When these relationships are satisfied, the specific surface area can be further increased, and deterioration of electrode properties over time can be further suppressed. Most preferably, the conductive film according to the present embodiment is formed only of single-layered MXene.

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

[0022] In the electrode of this embodiment, the conductive film and the π-electron conjugated compound film are laminated to form a laminated film. FIG. 2 is a schematic cross-sectional view of an embodiment of the electrode of this embodiment, which has a substrate 21 and is a biological tissue 25 as a test subject. The measurement target in the biological tissue 25 may be, for example, the skin of a human body or the like, as well as blood vessels, muscles, the brain, and other organs under the skin. The measurement may be performed by directly contacting the electrode with the measurement target, or, for example, the measurement target under the skin may be indirectly measured by contacting the electrode with the skin. In particular, in FIG. 2, the bond 24 between the π electrons of the MXene particles constituting the conductive film 22 and the π electrons of the π-electron conjugated compound film 23 is exaggerated for the purpose of explaining the action and effect, and the gap formed by the bond 24 in FIG. 2 is not formed between the conductive film 22 and the π-electron conjugated compound film 23, and the conductive film 22 and the π-electron conjugated compound film 23 are substantially in contact with each other. 2, by providing the π-electron conjugated compound film 23 so as to be in contact with and covering the conductive film 22, a conductive path can be secured by bonding between the π-electron conjugated compound film 23 and the conductive film 22 by π-electrons, and oxidation of the conductive film 22 can be prevented, resulting in excellent electrode characteristics such as maintaining high conductivity, suppressing an increase in initial impedance, and suppressing an increase in impedance over time. The biological tissue 25, for example, human skin, and the electrode 26 are in direct contact as shown in FIG. 2, and a gel or film that is permeable to ions (not shown) may be present between the biological tissue 25 and the electrode 26.

[0023] The π-electron conjugated compound film includes a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond. The compound has a molecular structure in which π electrons are delocalized, and is bonded to the π electrons of the MXene particles constituting the conductive film to exert the above-mentioned action and effect. The heteroaromatic ring has a heteroatom such as nitrogen, oxygen, sulfur, phosphorus, chlorine, iodine, or bromine as a ring constituent element. The π-electron conjugated compound film may be a continuous form of the compound on a microscopic level, or may be an aggregate of the compound having a plate-like, granular, powdery, columnar, or cylindrical shape.

[0024] The π-electron conjugated compound is preferably one or more compounds selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, polyacetylene, polyparaphenylene, polyparaphenylenevinylene, polypyrrole, polythiophene, polyethylenedioxythiophene, polyaniline, and polythienylenevinylene. More preferably, the π-electron conjugated compound is one or more compounds selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, and carbon nanotubes.

[0025] The thickness of the π-electron conjugated compound film can be, for example, in the range of 0.03 μm or more and 30 μm or less.

[0026] In order to enhance the effect of laminating the conductive film and the π-electron conjugated compound film, it is preferable that the surface of the conductive film facing the π-electron conjugated compound film is covered with the π-electron conjugated compound film by 80% or more of the area, more preferably 90% or more of the area, and most preferably 100% or more of the area. The side surface of the conductive film may be covered with the π-electron conjugated compound film. The oxidation of the conductive film generally tends to progress from the end of the conductive film (the portion near the outer shape of the conductive film). Therefore, it is preferable that the π-electron conjugated compound film also covers the end and side surface of the conductive film.

[0027] In addition, in order to reliably secure the electrode characteristics inherent to the conductive film, for example, as shown in the examples described later, from the viewpoint of sufficiently suppressing an increase in initial impedance and an increase in impedance over time, the ratio of the amount of the π-electron conjugated compound film to the total amount of the conductive film and the π-electron conjugated compound film is preferably 80 mass% or less. The ratio is more preferably 75 mass% or less, and even more preferably 70 mass% or less. On the other hand, in order to fully exert the above-mentioned effects due to the formation of the π-electron conjugated compound film, the ratio is preferably 5 mass% or more, more preferably 15 mass% or more, and even more preferably 30 mass% or more.

[0028] 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. The shape of the particles of the layered material has a plane as described above, and the larger the plane area, the 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 contact area with the π-electron conjugated compound film becomes larger, and many π-junctions between the conductive film and the π-electron conjugated compound film are easily formed, the conductivity becomes higher, and 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 preparing MXene particles, i.e., by using an MXene slurry, or by removing the π-electron conjugated compound film from the laminated film with the π-electron conjugated compound film and measuring the Feret diameter of the MXene particles constituting the conductive film of the electrode. 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.

[0029] The electrode of this embodiment is not limited to a specific form as long as the conductive film and the π-electron conjugated compound film are at least laminated. The electrode may be in a solid state or a flexible soft state. The thickness of the conductive film and the π-electron conjugated compound film can be measured by, for example, measurement with a micrometer, or by cross-sectional observation using a scanning electron microscope (SEM), a microscope, or a laser microscope.

[0030] 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 cm 2Below, 10 kΩ cm at 1 kHz 2 The smaller of the following ranges is preferred:

[0031] In the electrode of this embodiment, the conductive film is in direct contact with the π-electron conjugated compound film. In the electrode of this embodiment, the surface of the π-electron conjugated compound film opposite to the conductive film side may be exposed to the outside air so as to be in direct contact with the object to be measured, or a gel that can permeate ions or a film including a porous film may be formed as another laminate. The porous film may be a film that has a large number of fine pores and selectively permeates ions or molecules with a size 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, the inorganic material may be ceramics, or a combination of these. 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 membrane may be classified according to the pore shape, and may be, for example, an aggregated particulate porous membrane, a mesh-like porous membrane, a fibrous porous membrane, a porous membrane having a plurality of isolated and / or interconnected pores, or a honeycomb-structured porous membrane.

[0032] 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.

[0033] (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.

[0034] 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).

[0035] 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.

[0036] 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).

[0037] 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.

[0038] The antenna electrode is an electrode for emitting electromagnetic waves into space and / or receiving electromagnetic waves in space.

[0039] 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.

[0040] (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.

[0041] 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) forming a conductive film containing particles of the layered material on a substrate; (h) forming a π-electron conjugated compound film on the conductive film, the π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond; This manufacturing method makes it possible to manufacture an electrode that can maintain excellent electrode properties for a long period of time.

[0042] 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:

[0043] 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.

[0044] 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 n and 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.

[0045] 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.

[0046] ·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 preferably, the so-called ACID method in which etching is performed with an etching solution containing HF (hydrofluoric acid) or a method in which etching is performed with an etching solution containing phosphoric acid is preferred. 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.

[0047] ·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.

[0048] ·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.

[0049] 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 process 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.

[0050] 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.

[0051] 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.

[0052] ·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.

[0053] 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.

[0054] ·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.

[0055] ·Process (g) A conductive film containing particles of the layered material is formed on a substrate. The method of forming the conductive film on the substrate is not limited, and examples of the method include coating, filtration such as suction filtration, and the like. For example, when a first slurry (a slurry containing layered material particles) containing particles of the layered material 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.

[0056] 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.

[0057] 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, a plasma treatment may be performed before coating to perform a pretreatment to improve the hydrophilicity of the surface. In the case of an electrode without a substrate, the substrate used in this step may be any material as long as it is a substrate for forming a conductive film. 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.

[0058] ·Process (h) A π-electron conjugated compound film containing a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond is formed on the conductive film. The π-electron conjugated compound may be the compound described in the description of the electrode above. The π-electron conjugated compound may be dispersed in water, for example, to form a second slurry (a slurry containing a π-electron conjugated compound, or an aqueous dispersion of a π-electron conjugated compound) which is applied onto the conductive film.

[0059] When a first slurry (slurry containing layered material particles) is used to form the conductive film and a second slurry (slurry containing a π-electron conjugated compound) is used to form the π-electron conjugated compound film, it is preferable that the conductive film is formed by applying a first slurry containing layered material particles at a solid concentration of 10 mg / mL or more and 250 mg / mL or less to the base material, and the π-electron conjugated compound film is formed by applying a second slurry containing a π-electron conjugated compound at a solid concentration of 10 mg / mL or more and 250 mg / mL or less to the surface of the conductive film.

[0060] In addition, when using the first slurry (slurry containing layered material particles) and the second slurry (slurry containing a π-electron conjugated compound) having the above-mentioned concentrations for the manufacture of an electrode, the ratio of the coating amount of the second slurry to the total coating amount of the first slurry and the second slurry is preferably 5% by volume or more and 80% by volume or less. If the first slurry and the second slurry satisfy the above-mentioned solid content concentration range and the above-mentioned ratio, it is preferable because a laminated film of a conductive film and a π-electron conjugated compound film that can maintain excellent electrode properties is easily obtained.

[0061] The method for applying the π-electron conjugated compound-containing slurry is not limited, and examples thereof include spray coating, which is performed by spray coating using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush; slit coating, which is performed using a table coater, a comma coater, or a bar coater; screen printing, metal mask printing, spin coating, immersion, brushing, and dropping.

[0062] In addition, in the formation of the π-electron conjugated compound film, the above coating and drying may be repeated several times as necessary until a π-electron conjugated compound film of a 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.

[0063] 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 for providing the electrode according to the above-mentioned embodiment. EXAMPLES

[0064] [Example 1] In Example 1, an experiment was conducted to compare the change in impedance over time between an rGO-MXene laminate (layered composite) in which rGO (reduced graphene oxide) was laminated as a π-electron conjugated compound film, and an MXene layer not laminated with rGO.

[0065] (Preparation of particles of layered material) MXene was prepared by the method shown below (the ACID method was used as the etching method for MAX). The details are as follows.

[0066] (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).

[0067] (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: 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, and Ti3C2Ts-water medium clay was obtained as the remaining precipitate. (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 and water washing 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 solution containing single and few layers of MXene. These steps (i) to (iii) were repeated a total of four times to obtain a supernatant containing single and few layers of MXene. Furthermore, this supernatant was centrifuged at 4300G for 2 hours using a centrifuge, after which the supernatant was discarded and single-layer and few-layer MXene-containing clay was obtained as the remaining precipitate.

[0068] (Formation of electrode sample) Pure water was added to the single-layer and few-layer MXene-containing clay to obtain an MXene slurry (MXene water dispersion) with a solid concentration of the layered material particles of about 10 mg / mL. The MXene slurry was spray-coated once onto a glass slide and dried to prepare an MXene thin film with a thickness of 0.1 μm.

[0069] Next, an aqueous dispersion of reduced graphene oxide (rGO) with a solid concentration of approximately 15 mg / mL was spray-coated twice onto the MXene thin film and then dried to form a 0.2 μm-thick rGO film as a π-electron conjugated compound film, and an rGO-MXene laminated film was prepared as an electrode sample.

[0070] (Measurement of initial impedance and rate of change) The electrode formed with the above rGO-MXene laminated film was immersed in PBS (phosphate buffered saline) heated to 73 °C in a beaker for 24 days, and the impedance was measured periodically. The impedance was measured at the time of immersion (day 0) and on the immersion days shown in Tables 2 and 3. The impedance was measured using a Gamry Reference 600 Potentiostat / Galvanostat / ZRA in a standard three-electrode system using 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, with a driving voltage of 10 mV (peak-to-peak amplitude, sinusoidal wave). The impedance was measured at 10 Hz and 1 kHz, respectively.

[0071] To obtain a reference value, a sample was prepared in which only the MXene layer, i.e., the non-rGO laminated MXene layer, was formed as described above instead of the rGO-MXene laminated film, and similar measurements were performed. The initial impedance (day 0) of the non-rGO laminated MXene layer was set to 1.00, and the ratio of each impedance measurement value to the initial impedance of the non-rGO laminated MXene layer was calculated as the impedance change rate to evaluate the change in impedance over time. The initial impedance values ​​of the non-rGO laminated MXene layer and the rGO-MXene laminated film are shown in Table 1. In Table 1, the impedance change rate relative to the initial impedance of the non-rGO laminated MXene layer is also shown in parentheses for the measurement value of the rGO-MXene laminated film. In addition, the results of measuring the impedance over time on the elapsed days shown in Tables 2 and 3 are shown in Tables 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 rGO-MXene laminated film.

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] As shown in Table 1, the initial impedance of the rGO-MXene laminated film was about twice as high as that of the non-rGO-laminated MXene layer, but as time passed, the impedance of the non-rGO-laminated MXene layer increased more rapidly than that of the rGO-MXene laminated film. As a result, at 10 Hz, the impedance after 24 days was more than 12 times the initial impedance of the non-rGO-laminated MXene layer, while it was about 8 times for the rGO-MXene laminated film, showing a smaller increase than that of the non-rGO-laminated MXene layer. In addition, at 1 kHz, the impedance of the non-rGO-laminated MXene layer increased about 4 times the initial impedance, while it was less than 4 times for the rGO-MXene laminated film, showing a smaller increase than that of the non-rGO-laminated MXene layer. Furthermore, when the initial impedance of the non-rGO MXene layer and the rGO-MXene laminated film was taken as 1.00, at 10 Hz, the impedance change rate after 24 days was about 12 times that of the non-rGO MXene layer, while it was about 4 times that of the rGO-MXene laminated film, which was suppressed to about one-third. Similarly, at 1 kHz, the impedance change rate of the rGO-MXene laminated film was suppressed to less than half that of the non-rGO MXene layer. These results show that the change in impedance over time is sufficiently suppressed in the rGO-MXene laminated film.

[0076] The reason why the rGO-MXene laminated film showed less change in impedance over time than the MXene layer without rGO is thought to be that rGO has many π electrons, so the metal atoms of MXene interact with the π electrons of the rGO, creating a phenomenon known as π junctions that increase the electrical conductivity. It is also thought that the oxidation resistance of rGO prevents the MXene coated by rGO from oxidizing, and a conductive path is secured through π junctions with the MXene, thereby maintaining the electrical conductivity.

[0077] [Example 2] In Example 2, the effect of the particle size of the layered material on the change in impedance over time was examined.

[0078] MXene water-borne clay was prepared in the same manner as in Example 1. Separately, MXene water-borne clay was prepared by the method described below (production of MXene particles using the MILD method as the MAX etching method).

[0079] (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 22.5 mL HCl (12M) 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, and Ti3C2Ts-water medium clay was obtained as the remaining precipitate. (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 / 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 4300G for two hours using a centrifuge, after which the supernatant was discarded and the remaining precipitate was used to obtain a single-layer / sparse-layer MXene-containing clay.

[0080] Pure water was added to 10 mM of the above single-layered and few-layered MXene-containing clay to prepare MXene-water medium clay (MILD method) with a solid concentration of less than 10 mg / mL.

[0081] The above two types of MXene water medium clay were diluted with pure water to obtain an MXene slurry, which was spray-coated onto a glass slide and dried to produce an MXene thin film.

[0082] (Measurement of the initial impedance of each MXene thin film) The electrodes formed with the MXene thin film produced by each method were left in the air at room temperature for 12 weeks, and the impedance was measured at the 2nd, 4th, 6th, 7th, 10th, and 12th weeks. The impedance was measured at the 2nd, 4th, 6th, 7th, 10th, and 12th weeks shown in Table 5. The impedance measurement conditions were the same as in Example 1.

[0083] (Measurement of the number-average Feret diameter of the particles of the layered materials that compose each MXene thin film) The number-average Feret diameters of 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 were measured by removing the rGO layer from the rGO-MXene laminated film. In detail, the rGO layer was destroyed by polishing from the rGO-MXene laminated film, and the remaining film was ultrasonically cleaned in pure water to disperse MXene flakes 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 substrate 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 photograph 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.

[0084] 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.

[0085] In addition, even if MAX etching is performed by the phosphoric acid etching method described below instead of the ACID method shown in Example 1, MXene particles having a number average Feret diameter of 3.00 μm or more can be obtained, and it is believed that the effect of suppressing impedance increase can be obtained.

[0086] (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.

[0087] 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 Feret diameter increasing from less than 3.00 μm to 3.00 μm or more, as a negative value. Furthermore, the change in impedance over time 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.

[0088] [Table 4]

[0089] [Table 5]

[0090] [Table 6]

[0091] As shown in Table 4, it can be seen that the initial impedance can be reduced by about -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, one MXene sheet is large, which contributes to the improvement of in-plane conductivity. In addition, as shown in Table 5, the impedance after 12 weeks (at 10 Hz) also increased more slowly when the number average Feret diameter of the particles was 3.00 μm or more. In detail, the impedance change rate after 12 weeks in Table 5 when the number average Feret diameter was 3.00 μm or more and when it was less than 3.00 μm was compared, and it was found that the impedance change rate was reduced by about half. This effect is thought to be due to the reduction in the number of oxidation sites (number of edges) per unit area of ​​the particles due to the number average Feret diameter being 3.00 μm or more.

[0092] In addition, the MXene shown in Tables 1 and 2 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 Feret diameter and laminating an rGO layer.

[0093] From these results, the following can be said. In MXene particles (particles of a layered material), π junctions can only be formed 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 stacking rGO 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 stacked rGO were easily formed, and the effect of suppressing the increase in impedance was more remarkable.

[0094] [Example 3] In Example 3, the influence of the difference in the existence form of rGO on the initial impedance was examined.

[0095] (Preparation of rGO-MXene laminated film) An rGO-MXene laminate film was obtained in the same manner as in Example 1, except that an rGO aqueous dispersion with a solid concentration of rGO of approximately 10 mg / mL was used and the MXene slurry (MXene aqueous dispersion) and the rGO aqueous dispersion were spray-coated three times each.

[0096] (Preparation of rGO-MXene blend film) A mixed film of rGO and MXene was prepared as follows. 10 mL of MXene water medium clay with a solid concentration of MXene of approximately 10 mg / mL and rGO water dispersion with a solid concentration of rGO of approximately 10 mg / mL were each measured and mixed to prepare a mixed solution. This was spray-coated six times to prepare an rGO-MXene mixed film. Unlike the rGO-MXene laminated film described above, the rGO-MXene mixed film is a film in which rGO and MXene are randomly mixed.

[0097] (Initial impedance measurement) The electrodes formed with each structure of the rGO-MXene laminated film and the rGO-MXene mixed film were immersed in PBS at room temperature to measure the initial impedance. The other impedance measurement conditions were the same as in Example 1. The initial impedance of each structure in PBS is shown in Table 7.

[0098] [Table 7]

[0099] As shown in Table 7, the initial impedance of the rGO-MXene blend film increased up to 1.7 times that of the rGO-MXene laminate film. This is thought to be because, in the case of the rGO-MXene laminate film (coated type), the ionic conduction between the layers specific to MXene is not inhibited, the conductivity of MXene is maintained, and degradation over time due to oxidation is suppressed, whereas in the case of the rGO-MXene blend film, the ionic conduction between the layers specific to MXene is greatly inhibited, resulting in an increase in the initial impedance.

[0100] [Example 4] In Example 4, the effect of the ratio of the rGO layer to the MXene layer on the initial impedance was examined.

[0101] (Preparation of rGO-MXene laminated films with different rGO volume ratios) First, an rGO-MXene laminate film was obtained by spray-coating the rGO aqueous dispersion twice in the same manner as in Example 1. In addition, an rGO-MXene laminate film was also obtained by fabricating the same manner as in Example 1, except that the rGO aqueous dispersion was spray-coated six times.

[0102] (Initial impedance measurement) The electrodes formed with the rGO-MXene laminated films spray-coated with the rGO aqueous dispersion two times and six times were immersed in PBS at room temperature in a beaker, and the initial impedance was measured at 10 Hz and 1 kHz. The other impedance measurement conditions were the same as in Example 1. The measurement results using each rGO-MXene laminated film are shown in Table 8.

[0103] [Table 8]

[0104] As shown in Table 8, the initial impedance of the rGO-MXene laminate with an rGO ratio of 67 mass% was significantly lower than that of the rGO-MXene laminate with an rGO ratio of 85 mass%. This result suggests that by setting the rGO ratio in the rGO-MXene laminate to preferably 80 mass% or less, excellent electrical conductivity due to MXene is exhibited, and the increase in initial impedance and degradation over time due to oxidation of MXene can be suppressed. [Industrial Applicability]

[0105] 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.

[0106] This application is based on and claims priority to U.S. Provisional Patent Application No. 63 / 223,306, 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]

[0107] 1a, 1b layer body (M m X n layer) 3a, 5a, 3b, 5b Modified or terminal T 7a, 7b MXene layers 10a, 10b MXene particles (particles of layered materials) 21 Base material 22 Conductive film (film containing MXene particles) 23 π-electron conjugated compound film 24 Bonding between π electrons of MXene particles and π electrons of π-electron conjugated compound films 25 Biological Tissue 26 electrodes

Claims

1. A laminate including a conductive film containing particles of a layered material including one or more layers, and a π-electron conjugated compound film, wherein the one or more layers include the following formula: M ｍ X ｎ (wherein 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, n is 1 or more and 4 or less, m is greater than n and 5 or less), including a layer main body represented by the formula 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 main body, wherein the π-electron conjugated compound film includes a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond, wherein the ratio of the amount of the π-electron conjugated compound film in the total amount of the conductive film and the π-electron conjugated compound film is 5% by mass or more and 80% by mass or less. An electrode.

2. A laminate including a conductive film containing particles of a layered material including one or more layers, and a π-electron conjugated compound film, wherein the one or more layers include the following formula: MmXn (wherein 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, n is 1 or more and 4 or less, m is greater than n and 5 or less), including a layer main body represented by the formula 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 main body, wherein the π-electron conjugated compound film includes a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond, wherein the number average Feret diameter of the particles of the layered material is 3 μm or more. An electrode.

3. A laminate including a conductive film containing particles of a layered material including one or more layers, and a π-electron conjugated compound film, wherein the one or more layers include the following formula: MmXn (wherein 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, n is 1 or more and 4 or less, m is greater than n and 5 or less), A layer body represented by 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, wherein the π-electron conjugated compound film of the conductive film contains a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond, the surface of the conductive film on the π-electron conjugated compound film side is coated with the π-electron conjugated compound film by 80 area% or more, an electrode. **Claim 4** The electrode according to any one of claims 1 to 3, which is used as a biosignal sensing electrode. **Claim 6** The electrode according to claim 4, which is used as a biosignal sensing electrode. **Claim 7** (a) 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) Prepare a precursor of the conductive film represented by (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 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 the layered material, (g) Form a conductive film containing the particles of the layered material on a substrate by applying a first slurry containing the particles of the layered material at a solid content concentration of 10 mg / mL or more and 250 mg / mL or less to the substrate. (h) A π-electron conjugated compound film containing a π-electron conjugated compound having one or more selected from the group consisting of an aromatic ring, a heteroaromatic ring, a carbon-carbon double bond, a carbon-carbon triple bond, and a carbon-phosphorus double bond is formed by applying a second slurry containing the π-electron conjugated compound at a solid content concentration of 10 mg / mL or more and 250 mg / mL or less to the surface of the conductive film. A method for manufacturing an electrode, comprising the above.

8. The method for manufacturing an electrode according to claim 7, wherein the etching solution contains at least one of hydrofluoric acid and phosphoric acid.

9. The method for manufacturing an electrode according to claim 7 or 8, wherein the π-electron conjugated compound is one or more compounds selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, polyacetylene, polyparaphenylene, polyparaphenylene vinylene, polypyrrole, polythiophene, polyethylene dioxythiophene, polyaniline, and polythienylene vinylene.

10. The method for manufacturing an electrode according to claim 7 or 8, wherein the ratio of the coating amount of the second slurry to the total coating amount of the first slurry and the second slurry is 5% by volume or more and 80% by volume or less.

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