Film and electrode

Abstract

Provided is a novel film that contains MXene and a polymer and that has high strength and low impedance.　A film (20) contains a polymer (11) and two-dimensional material particles (10, 10a, 10b) containing at least one layer (7a, 7b), wherein: each of the layers (7a, 7b) contains a layer body (1a, 1b) represented by formula MmXn (in the formula, M represents at least one metal belonging to group 3, 4, 5, 6 or 7, X represents a carbon atom, a nitrogen atom or a combination thereof, n represents a number of 1 to 4, and m represents a number that is greater than n but is not greater than 5) and a modification or a terminal T (3a, 3b, 5a, 5b) (T represents at least one group or atom selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) that is present on the surface of the layer body; the polymer (11) has an anionic functional group and a cationic functional group; and the proportion of the polymer in the film relative to the total amount of the two-dimensional material particles and the polymer is 5 to 70 vol%.

Description

Membranes and electrodes

[0001] The present disclosure relates to a membrane and an electrode using the membrane.

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

[0003] Composite materials of MXene and polymers have been known for some time. For example, Patent Document 1 describes a method for applying the principle of polyurethane foaming to a reaction between a mixture containing MXene and polyisocyanate and a mixture containing other materials (such as other MXenes, graphene, carbon nanotubes, or oxide particles) and polyether in a mold to obtain an MXene composite foam in which MXene and the other materials are combined in a polyurethane foam.

[0004] Chinese Patent Application Publication No. 112300363

[0005] (Films containing MXene and a polymer can exhibit electrical conductivity, and the use of such conductive films as electrodes is being considered.) Electrodes, such as biosignal sensing electrodes, are required to have sufficient strength and as low an impedance as possible. However, the MXene composite foam described in Patent Document 1 has the drawback of low strength. Furthermore, Patent Document 1 makes no mention of the impedance of the MXene composite foam.

[0006] An object of the present disclosure is to provide a novel membrane comprising MXene and a polymer, which membrane has high strength and low impedance. A further object of the present disclosure is to provide an electrode using such a membrane.

[0007] According to one aspect of the present disclosure, there is provided a membrane comprising particles of a two-dimensional material comprising one or more layers and a polymer, wherein the layers are represented by the following formula: M ｍ X ｎ(wherein M is at least one Group 3, 4, 5, 6, or 7 metal; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and a modified or terminated T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, wherein the polymer has an anionic functional group and a cationic functional group, and the ratio of the polymer to the total of the particles of the two-dimensional material and the polymer in the film is 5% by volume or more and 70% by volume or less.

[0008] According to another aspect of the present disclosure, there is provided an electrode including the membrane described above.

[0009] The present disclosure provides novel membranes that include particles of a predetermined two-dimensional material (also referred to herein as "MXene") and a polymer, which membranes have high strength and low impedance. The present disclosure also provides electrodes using such membranes.

[0010] 1A and 1B are schematic cross-sectional views of a membrane according to one embodiment of the present disclosure, and are schematic cross-sectional views of particles of a two-dimensional material (MXene) that can be used in one embodiment of the present disclosure, where (a) shows a single-layer MXene particle and (b) shows a multi-layer (exemplarily two-layer) MXene particle.

[0011] A film (more specifically, a conductive film) in one embodiment of the present disclosure will be described in detail below, but the present disclosure is not limited to such an embodiment.

[0012] 1 , the film 20 of this embodiment includes particles 10 of a predetermined two-dimensional material (layered material) and a polymer having anionic functional groups and cationic functional groups (hereinafter also referred to as an "ampholytic polymer" in the present disclosure) 11, and the proportion of the ampholytic polymer 11 to the total of the particles 10 of the predetermined two-dimensional material and the ampholytic polymer 11 in the film 20 is 5% by volume or more and 70% by volume or less. By using such ampholytic polymer 11 in combination with the particles 10 of the predetermined two-dimensional material (layered material), a film 20 with high strength and low impedance can be realized.

[0013] The membrane 20 of this embodiment will be described in detail below through its manufacturing method. Unless otherwise specified, the description of the membrane manufacturing method can also be applied to the membrane itself.

[0014] The method for producing a membrane of the present embodiment includes: (a) preparing a liquid composition containing particles of a predetermined two-dimensional material (layered material), a polymer having anionic functional groups and cationic functional groups, and a liquid medium; and (b) forming a precursor membrane on a substrate using the liquid composition, and at least drying the precursor membrane to obtain a membrane.

[0015] Step (a) <MXene Particles> First, particles of a predetermined two-dimensional material (layered material) are prepared. The predetermined two-dimensional material that can be used in this embodiment is MXene, which is defined as follows: A two-dimensional material (layered material) comprising one or more layers, wherein the layers are represented by the following formula: M ｍ X ｎ a two-dimensional material (which may be understood as a layered compound and referred to as "M") comprising a layer body (which may have a crystal lattice in which each X is located in an octahedral array of M) represented by the formula (wherein M is at least one metal of Groups 3, 4, 5, 6, 7, and may include at least one so-called early transition metal, for example, Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn); 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 selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on a surface of the layer body (more specifically, on at least one of two mutually opposing surfaces of the layer body). ｍ X ｎ T ｓ ", where s is any number, and conventionally, x is sometimes used in place of s.) Typically, n can be 1, 2, 3, or 4, but is not limited thereto.

[0016] 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.

[0017] MXene is a compound represented by the formula: M ｍ X ｎ However, it is known that it can be expressed as follows: Sc ２ C, Ti ２ C, Ti ２ N, Zr ２ C, Zr ２ N, Hf ２ C, Hf ２ N.V. ２ C.V. ２ N, Nb ２ C, Ta ２ C, Cr ２ C, Cr ２ N, Mo ２ C, Mo １．３ C, Cr １．３ C, (Ti, V) ２ C, (Ti, Nb) ２ C.W. ２ C.W. １．３ C, Mo ２ N, Nb １．３ C, Mo １．３ Y ０．６ C (in the above formula, "1.3" and "0.6" mean approximately 1.3 (= 4 / 3) and approximately 0.6 (= 2 / 3), respectively), Ti ３ C ２ , Ti ３ N ２ , Ti ３ (CN), Zr ３ C ２ , (Ti, V) ３ C ２ , (Ti ２ Nb)C ２ , (Ti ２ Ta) C ２ , (Ti ２ Mn)C ２ , Hf ３ C ２ , (Hf ２ V) C ２ , (Hf ２Mn)C ２ 、(V ２ Ti)C ２ 、(Cr ２ Ti)C ２ 、(Cr ２ V)C ２ 、(Cr ２ Nb)C ２ 、(Cr ２ Ta)C ２ 、(Mo ２ Sc)C ２ 、(Mo ２ Ti)C ２ 、(Mo ２ Zr)C ２ 、(Mo ２ Hf)C ２ 、(Mo ２ V)C ２ 、(Mo ２ Nb)C ２ 、(Mo ２ Ta)C ２ 、(W ２ Ti)C ２ 、(W ２ Zr)C ２ 、(W ２ Hf)C ２ 、 Ti ４ N ３ 、V ４ C ３ 、Nb ４ C ３ 、Ta ４ C ３ 、(Ti,Nb) ４ C ３ 、(Nb,Zr) ４ C ３ 、(Ti ２ Nb ２ )C ３ 、(Ti ２ Ta ２ )C ３ 、(V ２ Ti ２ )C ３ 、(V ２ Nb ２ )C ３ 、(V ２ Ta ２ )C ３ 、(Nb ２ Ta ２ )C ３ 、(Cr２ Ti ２ ) C ３ , (Cr ２ V ２ ) C ３ , (Cr ２ Nb ２ ) C ３ , (Cr ２ Ta ２ ) C ３ , (Mo ２ Ti ２ ) C ３ , (Mo ２ Zr ２ ) C ３ , (Mo ２ Hf ２ ) C ３ , (Mo ２ V ２ ) C ３ , (Mo ２ Nb ２ ) C ３ , (Mo ２ Ta ２ ) C ３ , (W ２ Ti ２ ) C ３ , (W ２ Zr ２ ) C ３ , (W ２ Hf ２ ) C ３ , (Mo ２．７ V １．３ ) C ３ (In the above formula, "2.7" and "1.3" mean approximately 2.7 (= 8 / 3) and approximately 1.3 (= 4 / 3), respectively.)

[0018] Representatively, M ｍ X ｎ But Ti ２ C, Ti ３ C ２ , Ti ３ (CN), (Cr ２ Ti)C ２ , (Mo ２ Ti)C ２ , (Mo ２ Ti ２ ) C ３ , and (Mo ２．７ V １．３ ) C ３The compound is represented by at least one selected from the group consisting of:

[0019] In particular, M ｍ X ｎ is Ti ３ C ２ It could be.

[0020] Such MXene particles (hereinafter simply referred to as "MXene particles") can be synthesized by selectively etching (removing and optionally separating) A atoms (and optionally some M atoms) from the raw material MAX phase.

[0021] In other words, the film manufacturing method of this embodiment may further include a step of obtaining MXene particles before step (a), and the step of obtaining MXene particles includes etching the raw material MAX phase with an etching solution (etching treatment).

[0022] The MAX phase (hereinafter simply referred to as "MAX raw material") used as the raw material has the following formula: ｍ AX ｎ (wherein M, X, n and m are as defined above, and A is at least one element of Groups 12, 13, 14, 15 and 16, and is usually an element of Group A, typically Group IIIA and Group IVA, and more particularly may contain 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). The MAX phase is represented by M ｍ X ｎ (each X may have a crystal lattice in which it is located in an octahedral array of M) and a layer composed of A atoms is located between them. In the MAX phase, typically when m=n+1, one layer of X atoms is arranged between each of the n+1 layers of M atoms (these are collectively referred to as "M ｍ X ｎ The MAX phase has a repeating unit in which a layer of A atoms (also referred to as an "A layer") is arranged as a layer next to the n+1th layer of M atoms, but is not limited to this. By selectively etching (removing and optionally separating) the A atoms (and optionally a part of the M atoms) from the MAX phase, the A atom layer (and optionally a part of the M atoms) is removed to expose the M atoms.ｍ X ｎ The surface of the layer is modified with hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms, hydrogen atoms, etc. present in the etching solution (usually, an aqueous solution containing hydrofluoric acid is used, but this is not limited to this) to terminate the surface.

[0023] The etchant may include any suitable acid (HF, HCl, HBr, HI, sulfuric acid, phosphoric acid, nitric acid, etc.).

[0024] For example, the MAX raw material may be etched with an etching solution containing hydrofluoric acid. By using hydrofluoric acid as the etching solution, hydrofluoric acid (HF) is present in the etching solution. Etching treatment using an etching solution containing hydrofluoric acid may also be referred to as an ACID method. In addition to hydrofluoric acid, the etching solution may further contain other acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, sulfuric acid, acetic acid, formic acid, hypochlorous acid, and fluorosulfonic acid.

[0025] Alternatively, for example, the MAX raw material may be etched with an etching solution containing fluoride and an acid (excluding hydrofluoric acid). By using fluoride and an acid (excluding hydrofluoric acid) in the etching solution, hydrofluoric acid (HF) is present in situ in the etching solution. The etching process using an etching solution containing fluoride and an acid (excluding hydrofluoric acid) may also be referred to as the MILD method. The fluoride may be a metal fluoride, such as lithium fluoride, sodium fluoride, or potassium fluoride, and may particularly be lithium fluoride. When a metal fluoride is used, the etching process may involve intercalating a metal (metal ion) into the MXene particles while etching the MAX raw material. The acid (excluding hydrofluoric acid) may be, for example, hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, sulfuric acid, acetic acid, formic acid, hypochlorous acid, or fluorosulfonic acid, and may particularly be hydrochloric acid. Ammonium hydrogen difluoride may be used as the fluoride and acid (except hydrofluoric acid).

[0026] The process for obtaining MXene particles may include any suitable treatment after the etching treatment, as appropriate. Such treatments include, for example, washing, intercalation, delamination, etc. Washing may involve the application of any suitable washing medium, such as water or dilute hydrochloric acid, followed by centrifugation / decantation. Intercalation may involve the intercalation of metals (metal ions) into the MXene particles. Delamination may involve the application of impacts, such as vibration and / or ultrasound, to promote delamination of the MXene particles (reducing multilayered MXene particles into MXene particles with fewer layers, e.g., single-layered MXene particles). For example, the delamination treatment may be carried out for a predetermined period of time using a hand shake, an automatic shaker, a mechanical shaker, a vortex mixer, a homogenizer, an ultrasonic bath, etc.

[0027] In the present disclosure, the MXene particles may contain a relatively small amount of residual A atoms, for example, 10% by weight or less of the original A atoms. The amount of residual A atoms may be preferably 8% by weight or less, more preferably 6% by weight or less. However, even if the amount of residual A atoms exceeds 10% by weight, this may not be a problem depending on the application and conditions of use of the film.

[0028] The MXene particles 10 thus synthesized may be layered material particles containing one or more MXene layers 7a, 7b, as shown schematically in Figure 2 (examples of the MXene particles 10 include, but are not limited to, a single-layer MXene particle 10a in Figure 2(a) and a two-layer MXene particle 10b in Figure 2(b)). More specifically, the MXene layers 7a, 7b may be composed of MXene particles 10a, 10b, and 7b, respectively. ｍ X ｎ The layer body (M ｍ X ｎ The MXene layers 7a and 7b have the "MXene" (MXene-containing) polymerizable polymers 1a and 1b, and the modified or terminated T 3a, 5a, 3b, and 5b present on the surfaces of the layer bodies 1a and 1b (more specifically, on at least one of the two surfaces facing each other in each layer). ｍ X ｎ T ｓ", where s is an arbitrary number. MXene particle 10 may be one in which the MXene layers are individually separated and present as a single layer (single-layer structure shown in FIG. 2(a), so-called single-layer MXene particle 10a), or a laminate in which multiple MXene layers are stacked and spaced apart (multilayer structure shown in FIG. 2(b), so-called multilayer MXene particle 10b), or a mixture thereof. MXene particle 10 may be an aggregate particle (which may also be referred to as powder or flake) composed of single-layer MXene particles 10a and / or multilayer MXene particles 10b. In the case of a multilayer MXene particle, two adjacent MXene layers (e.g., 7a and 7b) do not necessarily have to be completely separated and may be partially in contact.

[0029] Although this embodiment is not limited to this, the thickness of each MXene layer (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 (this may vary mainly depending on the number of M atomic layers contained in each layer), and the maximum dimension in a plane parallel to the layer (two-dimensional sheet surface) (which may correspond to the "in-plane dimension" of the particle) is, for example, 0.1 μm or more, particularly 1 μm or more, for example, 200 μm or less, particularly 40 μm or less.

[0030] When the MXene particles are stacked (multilayered MXene) particles, the interlayer distance (or gap dimension, shown as Δd in Figure 2(b)) within each stacked particle is not particularly limited, and may be, for example, 0.8 nm or more and less than 10 nm (i.e., 8 Å or more and less than 100 Å), particularly 0.8 nm or more and 5 nm or less, more particularly about 1 nm, and the maximum dimension in a plane perpendicular to the stacking direction (two-dimensional sheet surface) (which may correspond to the "in-plane dimension" of the particle) is, for example, 0.1 μm or more, particularly 1 μm or more, for example, 100 μm or less, particularly 20 μm or less.

[0031] The total number of layers in an MXene particle may be one or more, for example, from 1 to 20, and the thickness in the stacking direction (which may correspond to the "thickness" of the particle) is, for example, from 0.8 nm to 20 nm.

[0032] When the MXene particles are laminated (multilayered MXene) particles, they may be MXene with a small number of layers. The term "small number of layers" refers to, for example, MXene having six or fewer stacked layers. Furthermore, the thickness of multilayered MXene with a small number of layers in the stacking direction may be less than 10 nm. In this specification, this "multilayered MXene with a small number of layers" is also referred to as "few-layered MXene."

[0033] Although not limiting to this embodiment, the MXene particles may be particles (which may also be referred to as nanosheets) composed mostly of monolayered MXene and / or few-layered MXene. In this specification, monolayered MXene and few-layered MXene may be collectively referred to as "monolayered / few-layered MXene."

[0034] Each of the above dimensions can be determined as a number-average dimension (e.g., a number-average of at least 40 dimensions) based on a photograph taken with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an atomic force microscope (AFM), or as a distance in real space calculated from the position of the (002) plane in reciprocal lattice space measured by X-ray diffraction (XRD).

[0035] <Amphoteric Polymer> An amphoteric polymer is prepared separately. In the present disclosure, an "amphoteric polymer" is a polymer having an anionic functional group and a cationic functional group. The polymer may be composed of one or more types of monomer units. A monomer unit refers to a structural unit derived from a monomer that is a raw material for the polymer. The anionic functional group and the cationic functional group may be present in the same monomer unit or in separate monomer units.

[0036] The anionic functional group refers to a moiety that exhibits anionic properties (carries a negative charge) in a liquid medium. The anionic functional group may be, for example, at least one selected from the group consisting of a carboxylic acid group, a carboxylate group, a sulfonic acid group, a sulfonate group, a phosphate group, and a phosphate group (or a portion of any of these). One or more types of anionic functional groups may be present in the amphoteric polymer.

[0037] The cationic functional group refers to a moiety that exhibits cationic properties (carries a positive charge) in a liquid medium. The cationic functional group may be, for example, at least one selected from the group consisting of amines, phosphoniums, and salts thereof (or any part thereof), more specifically, at least one selected from the group consisting of primary amines, secondary amines, tertiary amines, acid salts thereof, and quaternary ammonium salts, as well as primary phosphoniums, secondary phosphoniums, tertiary phosphoniums, acid salts thereof, and quaternary phosphonium salts. One or more types of cationic functional groups may be present in the amphoteric polymer.

[0038] For example, the amphoteric polymer may include a first monomer unit having an anionic functional group and a cationic functional group, in other words, the first monomer unit may have an anionic functional group and a cationic functional group.

[0039] Typically, the first monomer unit may have a phosphorylcholine group. The phosphorylcholine group is represented by -OP(=O)(-O - )OCH2CH2N + The moiety that functions as an anionic functional group is represented by (-CH3)(-CH3)CH3 (-OP(=O)(-O - )O-) and a moiety that functions as a cationic functional group (-CH2CH2N + (-CH3)(-CH3)CH3) and can therefore be understood as a bipolar functional group.

[0040] The amphoteric polymer may further contain, in addition to the first monomer unit, a second monomer unit having another anionic functional group.

[0041] Alternatively, the amphoteric polymer may include a third monomer unit having an anionic functional group and a fourth monomer unit having a cationic functional group, i.e., the third monomer unit may have an anionic functional group but no cationic functional group, and the fourth monomer unit may have a cationic functional group but no anionic functional group.

[0042] In any case, the bond between the monomer units constituting the amphoteric polymer is not particularly limited and may be any appropriate bond. For example, the amphoteric polymer may be an acrylic polymer. The acrylic polymer means a polymer containing a monomer unit derived from a (meth)acryloyl group as a main component. The "(meth)acryloyl group" means an acryloyl group and / or a methacryloyl group. The main component means a component that accounts for 50% by mass or more of the polymer. The monomer unit derived from a (meth)acryloyl group is, for example, a monomer unit represented by the formula: -CH2-C(-R 1 )(-COOR 2 )-(wherein, R １ is a hydrogen atom or a methyl group, and R ２ can be represented by an organic group having an anionic functional group and / or a cationic functional group, which may optionally be a metal cation, a nonionic organic group, etc.

[0043] Commercially available resin materials containing amphoteric polymers include the Lipidure (registered trademark) series (manufactured by NOF Corporation). For example, Lipidure (registered trademark)-HM contains, as a polymer component, a homopolymer of a first monomer unit having a phosphorylcholine group, and Lipidure (registered trademark)-A contains, as a polymer component, a copolymer of a first monomer unit having a phosphorylcholine group, a second monomer unit having a carboxylate group, and another nonionic monomer unit.

[0044] Commercially available resin materials may contain amphoteric polymers as well as any suitable additives, including, but not limited to, liquid media, surfactants, curing and / or crosslinking agents, viscosity modifiers (e.g., thickeners), and the like.

[0045] <Liquid Composition> A liquid composition containing the MXene particles and amphoteric polymer prepared above in a liquid medium is prepared.

[0046] The liquid medium may be either an aqueous medium or an organic medium, but an aqueous medium is preferred. The aqueous medium is typically water, and may optionally contain a relatively small amount of other liquid substance in addition to water (for example, 30% by mass or less, preferably 20% by mass or less, based on the total amount of the aqueous medium). The organic medium is not particularly limited, but may be, for example, a protic solvent such as an alcohol, an aprotic solvent, or a mixed solvent of two or more of these.

[0047] The resulting liquid composition allows the MXene particles to be well dispersed in the liquid medium due to the amphoteric polymer. As described below, by using a liquid composition with improved MXene particle dispersibility, the final film can achieve high strength and low impedance.

[0048] The ratio of the amphoteric polymer to the total of the MXene particles and amphoteric polymer in the liquid composition is 5 to 70 volume %, and within this range, high strength and low impedance can be achieved. This ratio in the liquid composition is considered to be substantially the same as the ratio of amphoteric polymer 11 to the total of the MXene particles 10 and amphoteric polymer 11 in the final film 20.

[0049] The liquid composition may be in the form of a slurry or a paste, depending on the total solids concentration including the MXene particles and the amphoteric polymer.

[0050] Step (b) <Precursor Film> Then, a precursor film is formed on a substrate using the liquid composition prepared above, and the precursor film is at least dried to obtain a film (more specifically, a conductive film).

[0051] The substrate is not particularly limited and may be made of any suitable material and may have any suitable structure and / or form. The region of the substrate surface on which the precursor film is formed may be flat or uneven, and may have a surface shape such as a curved, uneven, or irregular shape. The substrate may typically be a substrate, a film, or the like, but is not limited thereto. The material of the substrate is not particularly limited. The substrate may be made of a conductive material. Examples of conductive materials include 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, separate from the film of this embodiment, on the surface that contacts the film (conductive film) of this embodiment. Alternatively, the substrate may be made of an organic material. Examples of the organic material include flexible organic materials, such as thermoplastic polyurethane elastomer (TPU), PET film, polyimide film, and liquid crystal polymer film.

[0052] When high adhesion between the final film and the substrate is required, the surface of the substrate (the surface on which the precursor film is formed) preferably has functional groups (e.g., OH groups) capable of hydrogen bonding with the MXene particles. Such functional groups may be inherent to the substrate or may be developed by pretreatment (e.g., plasma treatment). The pretreatment may be performed for purposes such as cleaning or hydrophilization.

[0053] However, the film of this embodiment may be in the form of a free-standing film finally separated from the substrate, in which case adhesion between the film and the substrate is not necessary.

[0054] The method for forming the precursor film on the substrate is not particularly limited, and may be, for example, spraying the liquid composition onto the substrate. However, a precursor film may also be formed on the porous member by a method other than spraying, such as using a porous member (e.g., a membrane filter) as the substrate and passing the liquid composition through the porous member (filtration). Spraying can orient the MXene particles on the substrate (aligning the two-dimensional sheet surface of the MXene particles so that it is approximately parallel (e.g., within ±20°) to the surface of the substrate), resulting in a denser membrane than a filtration membrane and thus higher environmental resistance (moisture resistance). Other methods, such as bar coating, spin coating, and dipping, can also be used.

[0055] The precursor film is dried to remove the unnecessary liquid medium (not all of the liquid medium is necessarily removed, and some may remain), and a film is formed. The spraying and drying process may be repeated to obtain a film of the desired thickness.

[0056] The membrane obtained as described above is produced using a liquid composition in which the dispersibility of MXene particles is improved by the amphoteric polymer, and therefore can achieve both high strength and low impedance. Because the membrane of this embodiment has high strength, a free-standing membrane can be easily obtained by removing the substrate, if desired.

[0057] Although the present disclosure is not bound by any theory, the following is believed to be the reason why the amphoteric polymer allows a liquid composition with good dispersibility of MXene particles to be obtained, improving the strength of the final film and reducing the impedance.

[0058] MXene particles are M ｍ X ｎThe surface of the MXene particle body is modified or terminated with T (where T is at least one selected from the group consisting of hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms, and hydrogen atoms), resulting in the presence of charged sites. The two-dimensional sheet surface (a plane parallel to the MXene particle layer) that occupies the majority of the surface of the MXene particle is typically negatively charged. When MXene particles are mixed with a liquid medium (typically water), the MXene particles can disperse in the liquid medium due to the repulsion of their negative charges, but some of them can aggregate due to intermolecular forces or hydrogen bonding. For this reason, films prepared using a liquid composition in which MXene particles are mixed alone in a liquid medium have low strength. To uniformly mix MXene particles and a polymer in a liquid medium, it is considered to use a polar polymer that has a high affinity for MXene particles, rather than a polymer with low polarity. However, for example, although polyurethane (see Patent Document 1) has high polarity, a liquid composition in which MXene particles and polyurethane are mixed in a liquid medium can cause the MXene particles to aggregate, making it difficult to obtain a membrane with high strength and low impedance.

[0059] In this embodiment, in addition to MXene particles and a liquid medium, an amphoteric polymer (a polymer having anionic and cationic functional groups) is used in a predetermined ratio. The use of the amphoteric polymer effectively utilizes the electrostatic repulsion dispersion mechanism, allowing the MXene particles and amphoteric polymer to be mixed with each other in the liquid medium while maintaining a good dispersion state. More specifically, the cationic functional groups of the amphoteric polymer adsorb the negatively charged MXene particles, while the anionic functional groups of the amphoteric polymer electrostatically repel each other. This adsorption and electrostatic repulsion are thought to be well balanced, effectively preventing aggregation of the MXene particles through the steric hindrance of the amphoteric polymer, resulting in good dispersion of the MXene particles. In a film prepared using a liquid composition in which MXene particles and an amphoteric polymer are mixed in a liquid medium in a predetermined ratio, the MXene particles are well dispersed in the amphoteric polymer, enabling both high strength and low impedance to be achieved.

[0060] In the final film 20, the ratio of amphoteric polymer 11 to the total of MXene particles 10 and amphoteric polymer 11 is 5% by volume or more and 70% by volume or less, the same as the ratio in the liquid composition used, and within this range, the effects of high strength and low impedance can be achieved.

[0061] The strength of the film can be determined, for example, by the presence or absence of cohesive failure. Films made of MXene alone are easily cohesively peeled off by tape peeling (based on the cross-cut method specified in JIS K5600-5-6:1999). In contrast, the film of this embodiment contains MXene particles and amphoteric polymer in a specified ratio, preventing cohesive peeling and achieving high film strength.

[0062] A film made of a composite material containing MXene particles and a polymer can be judged to have low impedance if its impedance is equal to or less than that of a film made of MXene alone (e.g., Reference Example 1, described later). According to the measurement conditions shown in the Examples, the impedance at 10 Hz is preferably 340 Ohms or less, and more preferably 330 Ohms or less.

[0063] There is no particular limitation on the ratio of anionic functional groups to cationic functional groups in the amphoteric polymer 11. In some examples, it is preferable that the amphoteric polymer 11 as a whole is not too cationic and is neutral or anionic. In other examples, it is preferable that the amphoteric polymer 11 as a whole is hydrophilic.

[0064] The film 20 of this embodiment is a conductive film and can be used for any suitable application, such as an electrode in any suitable electrical device or an electromagnetic shield (EMI shield) that requires electrical conductivity.

[0065] The electrodes are not particularly limited, and may be, for example, biosignal sensing electrodes, capacitor electrodes, battery electrodes, sensor electrodes, antenna electrodes, electrical stimulation electrodes, etc. By using the membrane of this embodiment, it is possible to obtain low-impedance, highly sensitive biosignal sensing electrodes, large-capacity capacitors and batteries, and highly sensitive sensors and antennas, even in a smaller volume (volume occupied by the device).

[0066] The biosignal sensing electrode is an electrode for sensing (acquiring) a biosignal, and may be, for example, an electrode for measuring EEG (electroencephalogram), ECG (electrocardiogram), EMG (electromyogram), or EIT (electrical impedance tomography), but is not limited to these.

[0067] The capacitor may be an electrochemical capacitor. An electrochemical capacitor is a capacitor that utilizes capacitance generated by a physicochemical reaction between an electrode (electrode active material) and ions (electrolyte ions) in an electrolyte solution, and can be used as a device for storing electrical energy (electrical storage device). The battery may be a chemical battery that can be repeatedly charged and discharged. The battery may be, for example, a lithium-ion battery, a magnesium-ion battery, a lithium-sulfur battery, a sodium-ion battery, or the like, but is not limited to these.

[0068] The sensor electrode is an electrode for detecting a target substance, condition, 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. The antenna electrode is an electrode for emitting electromagnetic waves into space and / or receiving electromagnetic waves in space.

[0069] An electrical stimulation electrode is an electrode for applying electrical stimulation to a living body, and such electrical stimulation can be applied to a living body, particularly to biological tissues such as, but not limited to, the spinal cord, brain, nerve tissue, muscle tissue, etc.

[0070] By using the film of this embodiment, an electromagnetic shield with a high shielding rate (EMI shielding property) can be obtained.

[0071] Although the membrane according to one embodiment of the present disclosure has been described in detail above, various modifications of the present disclosure are possible. Note that the membrane according to the present disclosure may be manufactured by a method different from the manufacturing method in the above-described embodiment.

[0072] Example 1 1. Preparation of Layered Material Particles MXene particles were first obtained by sequentially carrying out the following steps, as detailed below: (1) preparation of a precursor (MAX), (2) etching of the precursor, (3) cleaning after etching, (4) intercalation of Li, and (5) delamination.

[0073] (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 resulting mixed powder was sintered at 1350°C for 2 hours in an Ar atmosphere. The resulting sintered body (block-shaped MAX) was pulverized with an end mill to a maximum size of 40 μm or less. This resulted in the preparation of TiC powder as a precursor (powder-shaped MAX). ３ AlC ２ particles were obtained.

[0074] (2) Etching of precursor (MAX) Ti prepared by the above method ３ AlC ２ Using particles (powder), etching was performed under the following etching conditions to remove Ti ３ AlC ２ A solid-liquid mixture (slurry) containing solid components derived from the powder was obtained. (Etching conditions) Precursor: Ti ３ AlC ２ (Sieved through a 45 μm mesh) Etching solution composition: 49% HF 6 mL, H ２ O 18 mL HCl (12 M) 36 mL Precursor input amount: 3.0 g Etching container: 100 mL Eye Boy Etching temperature: 35°C Etching time: 24 h Stirrer rotation speed: 400 rpm

[0075] (3) Post-etching cleaning The above slurry was divided into two equal parts and placed in two 50 mL centrifuge tubes. Then, after centrifuging at 3500 G for 5 minutes using a centrifuge, the supernatant was discarded. Then, (i) 35 mL of pure water was added to the remaining precipitate in each centrifuge tube, (ii) stirring by hand shaking, (iii) centrifuging at 3500 G for 5 minutes, and (iv) removing the supernatant. These steps (i) to (iv) were repeated 10 times. Finally, centrifugation at 3500 G for 5 minutes was performed to remove Ti. ３ C ２ T ｓ - Water medium clay was obtained.

[0076] (4) Li intercalation Ti prepared by the above method ３ C ２ T ｓ Li intercalation was carried out on the clay using a water medium, using LiCl as the Li-containing compound, and stirring at 20°C to 25°C for 12 hours according to the Li intercalation conditions below. The detailed conditions for Li intercalation are as follows: (Li intercalation conditions) Ti ３ C ２ T ｓ - Water medium clay (MXene after washing): solid content 0.75 g LiCl: 0.75 g Intercalation container: 100 mL Eye Boy Temperature: 20 ° C or higher and 25 ° C or lower (room temperature) Time: 12 hours Stirrer rotation speed: 800 rpm

[0077] (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, followed by stirring for 15 minutes on a shaker, (ii) centrifuging at 3500 G, and (iii) recovering the supernatant 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. Furthermore, this supernatant was centrifuged at 4300 G for 2 hours using a centrifuge, after which the supernatant was discarded, and MXene clay containing single and plural layers of MXene was obtained as the remaining precipitate.

[0078] 2A. Preparation of Slurry of MXene Single Material (Reference Example 1) A predetermined amount of the MXene clay obtained in 1 above was placed in a 50 mL centrifuge tube, and pure water was added. The amount of pure water added was adjusted so that the MXene concentration in the mixture was 1.5 mass%. The mixture was then stirred for 15 minutes with a shaker to obtain an MXene slurry as a liquid composition.

[0079] 2B. Preparation of MXene / Polymer Composite Slurry (Examples 1-5 and Comparative Examples 1-4) A predetermined amount of the MXene clay obtained in 1 above was placed in a 50 mL centrifuge tube. Subsequently, one of the polymer dispersions P1-P3 and polymers P4-P5 listed in Table 1 was added according to the indication in the "Polymer / Polymer Dispersion" column of Table 2 for Examples 1-5 and Comparative Examples 1-4, and purified water was added as needed. The amounts of P1-P5 and purified water added were adjusted so that the MXene concentration in the mixture was 1.5% by mass and the ratio of polymer to the total of MXene (MXene particles) and polymer in the dried film was the "Polymer Ratio" value listed in Table 2. The mixture was then stirred for 15 minutes on a shaker to obtain a MXene / polymer composite slurry as a liquid composition.

[0080]

[0081] In Table 2, the symbol "-" indicates that evaluation was not possible because a free-standing film could not be produced.

[0082] 3. Preparation of Film Samples Using each of the slurries obtained in 2A and 2B, film samples were prepared in the following order: (a) The slurry was placed in a 25 mL syringe. (b) The syringe (a) was set in a spray coater. (c) A polyimide substrate was set on the suction stage of the spray coater. (d) The atomization pressure was set to 0.5 MPa, the distance between the nozzle tip and the substrate was set to 15 cm, the liquid delivery rate was set to 5 mL / s, the sweep speed was set to 150 mm / s, and the stage heater was set to 45°C. (e) A precursor film was formed by applying the solution 15 times to the substrate. (f) The film was dried in a normal pressure oven at 80°C for 2 hours, and then further dried in a vacuum oven at 150°C for 16 hours to obtain a film (dried film) sample.

[0083] 4. Evaluation of Samples (1) Impedance Impedance was measured as follows. (a) The polyimide substrate was removed from the film sample prepared on the polyimide substrate in 3 above to obtain a free-standing film, and a beaker cell was assembled using this free-standing film as the working electrode, a platinum electrode as the counter electrode, and a silver-silver chloride electrode as the reference electrode. The working electrode had a diameter of 1.5 mm, and the counter electrode was larger than the working electrode. (b) Measurement conditions were a frequency of 0.1 Hz to 10 ５ Measurements were performed in potentiostat mode, with the voltage set to 10 mVrms relative to the open circuit voltage, the number of plots across the entire measurement frequency range set to 61, and the number of plots set to 1 to 10. The equipment used was a Bio-Logic Science Instruments VMP-300 high-performance electrochemical measurement system (16-channel advanced model). The measurement results, impedance at 10 Hz, are shown in Table 2.

[0084] (2) Strength (Tape Peel Test) The strength (bonding strength) of the film samples prepared on the polyimide substrate in step 3 above was evaluated in accordance with the cross-cut method specified in JIS K5600-5-6:1999. The evaluation results were classified as follows. The results are shown in Table 2. 0: The edges of the cuts were completely smooth, and there was no peeling at any of the grid squares. 1: There was minor peeling of the coating at the intersections of the cuts. The affected area in the cross-cuts did not clearly exceed 5%. 2: The coating peeled along the edges of the cuts and / or at the intersections. The affected area in the cross-cuts clearly exceeded 5% but did not exceed 15%. 3: There was partial or complete major peeling of the coating along the edges of the cuts, and / or various parts of the squares were partially or completely peeled. The affected area in the cross-cuts clearly exceeded 15% but did not exceed 35%. 4: The coating has peeled partially or completely along the edges of the cuts and / or partially or completely in several places. The cross-cut area is not affected by more than 65%. 5: Peeling that cannot be classified as Category 4.

[0085] (3) Interlayer distance (d ００２ ) as follows: Interlayer distance (d ００２ ) was measured. (a) The film sample prepared on the polyimide substrate in 3 above was cut into 2 cm squares and subjected to XRD measurement (characteristic X-rays: CuKα 1.541 Å) using an X-ray diffractometer (manufactured by Rigaku Corporation, SmartLab3 and SmartLab Studio II software) to obtain an XRD profile of the θ-axis scan in the range of 2θ = 2 degrees to 50 degrees. The step was set to 0.02 degrees, and the scan rate was set to 5 degrees / min. (b) At around 2θ = 7 degrees, MXene (Ti ３ C ２ T ｓ ) appears, so by applying the θ of the peak, n = 1, and λ = 1.541 Å (wavelength of CuKα radiation) to Bragg's equation (2d sin θ = nλ), the interplanar spacing d of the (002) plane is calculated. ００２ The values ​​were calculated as the interlayer distance. The results are shown in Table 2.

[0086] Referring to Table 2, Examples 1 to 5, which were membrane samples made by mixing MXene particles with an amphoteric polymer at a polymer ratio of 5 to 70% by volume, exhibited lower impedance and higher membrane strength than Reference Example 1, which was a membrane sample made of MXene particles only (no polymer). On the other hand, Comparative Example 1, which was a membrane sample made of MXene particles with an amphoteric polymer at a polymer ratio of 75% by volume, had high membrane strength but significantly higher impedance than Reference Example 1. The higher the polymer ratio in the membrane, the shorter the MXene interlayer distance d ００２ It is understood that when the polymer ratio in the film exceeds 70 vol%, for example, 75 vol%, the interlayer distance d ００２ It is believed that this occurs when the value of the MXene particles exceeds a certain threshold, causing a significant decrease in the conductivity of the membrane and an excessively high impedance. In contrast to Examples 1 to 5 and Comparative Example 1, which used an amphoteric polymer, Comparative Example 2, which used a polyethylene-methacrylic acid copolymer ionomer, Comparative Example 3, which used hydrophobic paraffin, and Comparative Example 4, which used a cationic PVOH without anionic functional groups, the dispersibility of the MXene particles and polymer in the slurry was poor, and the MXene particles and polymer were not well mixed (separated) in the resulting membrane (dried membrane), had low strength (easily coagulated and peeled off), and it was not possible to obtain a free-standing membrane.

[0087] The membrane of the present disclosure may be used for any suitable purpose, and may be preferably used, for example, as an electrode, particularly as a biosignal sensing electrode.

[0088] <1> A film comprising particles of a two-dimensional material including one or more layers and a polymer, wherein the layer is represented by the following formula: M ｍ X ｎ(wherein M is at least one Group 3, 4, 5, 6, or 7 metal, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, and m is greater than n and 5 or less), and a modified or terminated T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, wherein the polymer has an anionic functional group and a cationic functional group, and the proportion of the polymer to the total of the particles of the two-dimensional material and the polymer in the film is 5% by volume or more and 70% by volume or less. <2> The film according to <1>, wherein the polymer comprises a first monomer unit having the anionic functional group and the cationic functional group. <3> The film according to <2>, wherein the first monomer unit has a phosphorylcholine group. <4> The film according to <2> or <3>, wherein the polymer further comprises a second monomer unit having another anionic functional group. <5> The membrane according to any one of <1> to <4>, wherein the polymer comprises a third monomer unit having the anionic functional group and a fourth monomer unit having the cationic functional group. <6> An electrode comprising the membrane according to any one of <1> to <5>. <7> The electrode according to <6>, which is a biosignal sensing electrode. <8> The electrode according to <6>, which is an electrical stimulation electrode.

[0089] 1a, 1b Layer body (M ｍ X ｎ Layer) 3a, 5a, 3b, 5b Modified or terminated T 7a, 7b MXene layer 10, 10a, 10b MXene particle (particle of two-dimensional material) 11 Amphoteric polymer (polymer with anionic and cationic functional groups) 20 Membrane

Claims

1. A membrane comprising particles of a two-dimensional material comprising one or more layers and a polymer, The layer comprises a compound having the following formula: M ｍ X ｎ wherein M is at least one Group 3, 4, 5, 6, or 7 metal; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 or more and 4 or less, m is greater than n and is equal to or less than 5. and a modification or terminal T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, The polymer has anionic functional groups and cationic functional groups, A film, wherein the ratio of the polymer to the total of the particles of the two-dimensional material and the polymer in the film is 5 volume % or more and 70 volume % or less.

2. The membrane of claim 1 , wherein the polymer comprises a first monomer unit having the anionic functional group and the cationic functional group.

3. The membrane of claim 2 , wherein the first monomer unit has a phosphorylcholine group.

4. The membrane of claim 2 , wherein the polymer further comprises a second monomer unit having another anionic functional group.

5. The membrane of claim 1 , wherein the polymer comprises a third monomeric unit having the anionic functional group and a fourth monomeric unit having the cationic functional group.

6. An electrode comprising the membrane according to any one of claims 1 to 5.

7. The electrode of claim 6 which is a biosignal sensing electrode.

8. 7. The electrode of claim 6 which is an electrical stimulation electrode.